Patent Publication Number: US-2022218543-A1

Title: Patient support usable with bariatric patients

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/916,994 (P462D), filed Jun. 30, 2020, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, which is a continuation of U.S. application Ser. No. 16/194,636 (P462C), filed Nov. 19, 2018, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, now U.S. Pat. No. 10,716,722, which is a continuation of U.S. application Ser. No. 14/916,335 (P462A), filed Mar. 3, 2016, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, now U.S. Pat. No. 10,130,536, which is a national stage application of PCT/CA2014/050850, filed on Sep. 8, 2014, by Richard Roussy, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, which claims the benefit of U.S. Provisional Pat. Application Ser. No. 61/874,959, filed Sep. 6, 2013, by Richard Roussy, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, which are incorporated herein by reference in their entireties and are commonly owned by Stryker Corporation of Kalamazoo, Mich. Application Ser. No. 16/194,636 (P462C), filed Nov. 19, 2018, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, now U.S. Pat. No. 10,716,722, is also a continuation of U.S. application Ser. No. 15/394,111, filed Dec. 29, 2016, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, now U.S. Pat. No. 10,188,569, which is a continuation-in-part application of U.S. application Ser. No. 14/916,335 (P462A), filed Mar. 3, 2016, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, now U.S. Pat. No. 10,130,536, which is a national stage application of PCT/CA2014/050850, filed on Sep. 8, 2014, by Richard Roussy, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, which claims the benefit of U.S. Provisional Pat. Application Ser. No. 61/874,959, filed Sep. 6, 2013, by Richard Roussy, entitled PATIENT SUPPORT USABLE WITH BARIATRIC PATIENTS, which are incorporated herein by reference in their entireties and are commonly owned by Stryker Corporation of Kalamazoo, Mich. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to patient supports, such as hospital beds, and more specifically, patient supports for bariatric patients. More particularly, this disclosure relates to patient supports with features for use with morbidly overweight patients. 
     BACKGROUND 
     Typical hospital beds are designed with numerous functionalities to facilitate patient comfort and safety and to facilitate the ability of caregivers to provide efficient and effective care. However, most hospital beds are designed to accommodate patients of average size and weight. For bariatric patients, i.e. morbidly obese patients having extremely large sizes and whose weights can be as high as 1000 pounds or greater, normal hospital beds are generally too small and lack sufficient structural strength to withstand the load of a bariatric patient. Special bariatric beds have been designed to accommodate bariatric patients, but these beds generally lack the functionalities of regular hospital bed. Further, bariatric beds are generally specialized only for bariatric patients, limiting their use for general patient care, which ultimately increases hospital costs to have such bariatric beds in stock without seeing regular usage. 
     There is a need in the art for a hospital bed that possesses the same functionalities as regular hospital beds but can be converted between a regularly sized hospital bed and one that can accommodate bariatric patients. 
     SUMMARY OF THE DESCRIPTION 
     There is provided a patient support that may be adjustable in height, width, length or a combination thereof. The patient support may be usable with normal sized patients or with bariatric patients. 
     A height adjustable patient support may comprise one or more frames and a patient support deck supported on at least one of the one or more frames by at least one height adjustable leg assembly. The height adjustable patient support may comprise two or more frames, for example three frames. The patient support deck may be supported on one of the one or more frames. The height adjustable patient support may comprise at least two height adjustable leg assemblies, for example two height adjustable leg assemblies. At least one of the frames may comprise one or more casters, for example four casters, for supporting the patient support on a surface. 
     A height adjustable patient support may comprise a patient support deck supported on a first frame, the first frame supported on a second frame by at least two linearly extendible leg assemblies, the linearly extendible leg assemblies configured to adjust a height of the first frame relative to the second frame. 
     A patient support may comprise a patient support deck supported on a first frame, the first frame supported on a caster frame, one or both of the patient support deck and caster frame having an adjustable width. 
     A height adjustable patient support may comprise a patient support deck supported on a first frame, the first frame supported on a second frame by at least one leg assembly configured to raise and lower the first frame, wherein a touch sensitive obstruction sensor is provided on the patient support under the first frame, the touch sensitive obstruction sensor configured to detect an obstruction under the patient support and to stop lowering of the first frame when an obstruction is detected. 
     A height adjustable patient support may comprise: a patient support deck supported on a frame by one or more leg assemblies configured to raise and lower the patient support deck, the patient support deck having an adjustable width, the patient support deck configured to articulate into a plurality of positions; sensors configured to detect deck height and deck width and/or position; and, a controller in electrical communication with the sensors and patient support functions, the controller configured to enable and/or disable actions of the patient support in response to sensed combinations of the deck height and deck width and/or position. 
     In one aspect, leg assemblies of a patient support may be telescoping. Each leg assembly may comprise lower and upper legs in a telescoping arrangement. The lower leg may be pivotally mounted on the second frame. The lower leg may be longitudinally immovable on the second frame. The upper leg may be pivotally mounted on the first frame. The upper leg may be longitudinally immovable on the first frame. A lift actuator may be pivotally connected to the upper leg and the first frame. The lift actuator may be configured to rotate the upper leg causing the leg assembly to telescope. Each leg assembly may comprise a variable speed control mechanism configured to vary the speed at which the upper leg moves. Varying the speed at which the upper leg moves may compensate for a non-linear relationship between the speed at which the upper leg moves and a rotational speed of the lift actuator at the pivotal connection between the lift actuator and the upper leg. The variable speed control mechanism may comprise a leg actuator connecting the lower leg to the upper leg. The leg actuator may comprise cam arm. The cam arm may comprise a cam configured to ride in a cam track mounted on the lower leg. The cam arm and cam track may be configured to vary the speed at which the upper leg moves as the lift actuator raises and lowers the upper leg. 
     In one aspect, at least a patient support deck of a patient support may have an adjustable width. The width of the patient support deck may be adjustable manually. The width may be adjustable from either side of the patient support. Manually adjusting the width may be accomplished by pulling or pushing the patient support deck in a direction lateral to a longitudinal axis of the patient support, the longitudinal axis extending between a head end and a foot end of the patient support. The patient support deck may comprise a rack and pinion mechanism configured to permit manually adjusting the width of the patient support deck. The patient support deck may comprise at least two deck extension pans. The rack and pinion mechanism may connect the at least two deck extension pans. The rack and pinion mechanism may comprise a latch releasable from either side of the patient support. Releasing the latch may permit manually adjusting the width of the patient support deck. Manually adjusting the width of the patient support deck may be accomplished by simultaneously sliding the at least two deck extension pans by pulling or pushing one of the deck extension pans. 
     In one aspect, a patient support may comprise a guard structure positioned at a side of the patient support. The guard structure may be movable between a guard position above a plane of a patient support deck and an ultralow position fully below a plane of the patient support deck. The guard structure may be configured to swing longitudinally but not laterally while the guard structure is moved between the guard position and the ultralow position. The guard structure may comprise at least one pivotal arm configured to be pivotally mounted on the patient support. Pivoting of the at least one pivotal arm on the patient support may cause the guard structure to raise and lower. The at least one pivotal arm may have a pinion gear mounted thereon. The pinion gear may be meshed with a toothed rack of the guard structure. The toothed rack may be configured to translate longitudinally as the at least one pivotal arm pivots and the guard structure is raised and lowered. The at least one pivotal arm may be two pivotal arms. The guard structure may be configured to translate laterally in the ultralow position to be tuckable under the patient support deck. The guard structure may be lockable in the guard position. The guard structure may be electronically unlockable and releasable to permit unassisted lowering of the guard structure. The guard structure may be in electronic communication with a cardiopulmonary resuscitation feature, and actuation of the cardiopulmonary resuscitation feature may cause the guard structure to unlock and release. 
     In one aspect, a patient support may comprise a touch sensitive obstruction sensor provided on one or more surfaces of the patient support, for example on the extendible leg assemblies and/or one or more frames. The touch sensitive obstruction sensor may be configured to detect an obstruction under the patient support and to stop lowering of a movable frame when an obstruction is detected. The touch sensitive obstruction sensor may be configured to at least partially raise the frame when the touch sensitive obstruction sensor detects the obstruction. A touch sensitive obstruction sensor may be provided on all of the leg assemblies. 
     In one aspect, a patient support may comprise an electrical connection assembly for mounting an endboard on the patient support. The electrical connection assembly may comprise first and second electrical mating halves. The first electrical mating half may comprise at least one electrically conducting leaf spring. The second electrical mating half may comprise at least one electrically conducting tab. The at least one leaf spring and at least one tab may be in electrical contact when the mating halves are mated. The at least one electrically conducting leaf spring may be longer and/or wider than the at least one electrically conducting tab. One of the mating halves may be on the endboard. The other of the mating halves may be in a mounting bracket on the patient support. The mounting bracket may comprise a retractable cover over the mating half in the mounting bracket. The retractable cover may be configured to be retracted as the endboard is being mounted on the mounting bracket and the mating half on the endboard contacts the retractable cover. 
     In one aspect, sensors for a patient support may be configured to detect position of a guard structure. A controller may be configured to enable and/or disable actions of the patient support in response to sensed combinations of patient support deck height, patient support deck width and/or position and guard structure position. The sensors may be configured to detect both patient support deck width and patient support deck position. Enabling and/or disabling actions of the patient support in response to the sensed combinations may involve raising or lowering the patient support deck, preferably enabling and/or disabling raising and/or lowering the patient support deck beyond pre-determined set points. 
     A width adjustable headboard for a patient support may comprise a first headboard section and a second headboard section, the first headboard section having at least one mount configured for removable installation on a headboard supporting base, the first headboard section movable between at least two different positions on the headboard supporting base, the first and second headboard sections configured to leave no gap therebetween when the first headboard section is at any of the at least two different positions. The width adjustable headboard may comprise downwardly extending mounting posts. The mounting posts may be configured to remove ably and selectively engage different post sockets in a headboard supporting base at different positions along the headboard supporting base. 
     In one aspect, a width adjustable headboard for a patient support may comprise a first headboard section and a second headboard section linked by a length extendible actuator, extension of the actuator driving the first and second headboard sections laterally in opposite directions, the first headboard section comprising a first side laterally off-set to the second headboard section, and the first headboard section comprising a second side substantially laterally aligned with the second headboard section when the actuator is fully retracted. 
     In one aspect, there is provided a method of operating a hospital bed comprising a height adjustable patient support deck, the method comprising: determining a weight applied to the bed; and, adjusting an allowable minimum height, an allowable maximum height or a combination thereof in response to the weight applied to the bed. 
     In one aspect, there is provided a method of operating a hospital bed comprising a height adjustable patient support deck and a frame having a pair of caster wheels mounted thereto at each end thereof, a width between each pair of caster wheels being adjustable, the method comprising: determining the width between at least one pair of caster wheels; and, adjusting an allowable minimum height, an allowable maximum height or a combination thereof in response to the width between the pair of caster wheels. 
     In one aspect, there is provided a method of operating a hospital bed comprising a frame having a pair of caster wheels mounted thereto at each end thereof, a width between each pair of caster wheels being adjustable, the method comprising: determining a weight applied to the bed; determining the width between at least one pair of caster wheels; and, indicating that an increase or decrease in width between the pair of caster wheels is desirable based upon the weight applied to the bed. The method may further comprise increasing or decreasing the width based upon the weight applied to the bed. 
     In one aspect, there is provided a method of operating a hospital bed comprising a variable width patient support deck and a frame having a pair of caster wheels mounted thereto at each end thereof, a width between each pair of caster wheels being adjustable, the method comprising: determining the width of the patient support deck; determining the width between at least one pair of caster wheels; and, indicating that an increase or decrease in width between the pair of caster wheels is desirable based upon the width of the patient support deck. The method may further comprise increasing or decreasing the width based upon the width of the patient support deck. The method may further comprise determining a weight applied to the bed; and, indicating that an increase or decrease in width between the pair of caster wheels is desirable based upon both the width of the patient support deck and the weight applied to the bed. In this case, the method may yet further comprise increasing or decreasing the width based upon both the width of the patient support deck and the weight applied to the bed. 
     In one aspect, there is provided a method of operating a hospital bed comprising a height adjustable patient support deck that is optionally variable in width mounted to an upper frame of the bed and comprising at least one guard structure mounted to either the patient support deck or the upper frame along a side of the bed, the guard structure movable both vertically and laterally along a width of the bed, the guard structure locatable beneath at least the patient support deck, the method comprising: determining whether the guard structure is located beneath the patient support deck; and, adjusting an allowable minimum height of the bed in response to the guard structure being located beneath the patient support deck. In a particular embodiment, the patient support deck is variable in width and the guard structure is mounted to the patient support deck. 
     In one aspect, there is provided a method of operating a hospital bed comprising a height adjustable patient support deck that is variable in width mounted to an upper frame of the bed and comprising at least one guard structure mounted to the patient support deck along a side of the bed, the guard structure movable both vertically and laterally along a width of the bed, the guard structure locatable beneath at least the patient support deck, the method comprising: determining whether a width of the patient support deck is too wide to fit through a doorway of the hospital; decreasing the width of the patient support deck to fit through the doorway; and, moving the guard structure to a position located beneath the patient support deck. 
     In one aspect, there is provided a method of operating a hospital bed comprising a plurality of vertically movable guard structures each comprising a locking structure that is an electronically actuatable between a locked and unlocked state, the method comprising: electronically actuating the locking structure of each guard structure simultaneously to the unlocked state; and, allowing each guard structure to move vertically downwardly under the influence of gravity when in the unlocked state. The locking structure may be electronically actuated using a single electronic signal provided to all guard structures simultaneously. The single electronic signal may be transmitted when the CPR release is activated. 
     In one aspect, there is provided a method of operating a hospital bed having a bed condition monitoring system comprising: monitoring a plurality of signals associated with a plurality of bed conditions; automatically obtaining setpoints for the conditions based on a current configuration of the bed after a first pre-determined time period has elapsed; and, generating an alarm in the event that the monitored signals indicate that the conditions have varied from the setpoints. The method may further comprise providing a visual indication of the alarm that is able to be switched off, irrespective of ongoing monitoring of the plurality of signals. In this case, the method may still further comprise switching off the visual indication for a second pre-determined time period followed by automatically obtaining new setpoints for the conditions based on a new current configuration of the bed. It is therefore possible to change a configuration of the bed within the second pre-determined time period. 
     Further features will be described or will become apparent in the course of the following detailed description. It should be understood that each feature described herein may be utilized in any combination with any one or more of the other described features, and that each feature does not necessarily rely on the presence of another feature except where evident to one of skill in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be more clearly understood, embodiments thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1A  is a perspective view of a patient support. 
         FIG. 1B  is a perspective view of the patient support of  1 A with side rails on one side of the patient support tucked under the patient support deck. 
         FIG. 2A  is a perspective view of one embodiment of a lift mechanism of an adjustable patient support in an ultralow position shown in context with an upper frame, lower frame and caster frame of the patient support. 
         FIG. 2B  the adjustable patient support of  FIG. 2A  in a low position including upper leg lift actuators. 
         FIG. 3A  is a perspective view of a leg assembly of the adjustable patient support of  FIG. 2A . 
         FIG. 3B  is a perspective view of frames of the adjustable patient support of  FIG. 2A  showing mounting features for the leg assembly of  FIG. 3A . 
         FIG. 4  depicts a magnified view of a leg assembly mounted in the frames with the leg assembly in the ultralow position. 
         FIG. 5  depicts a magnified view of the leg assembly of  FIG. 4  in the high position. 
         FIG. 6  is a perspective view of an adjustable patient support deck of the patient support of  FIG. 1A  shown in a horizontal prone position. 
         FIG. 7  is a perspective view of an adjustable patient support deck of the patient support of  FIG. 1A  shown in an articulating position with a head deck tilted up to form a backrest. 
         FIG. 8  is a perspective view of an adjustable patient support deck of the patient support of  FIG. 1A  shown in a position with a head deck tilted up to form a backrest and a knee deck raised to form a knee support. 
         FIG. 9  is a view of the adjustable patient support deck of  FIG. 8  without deck panels. 
         FIG. 10  is a side view of  FIG. 9 . 
         FIG. 11  is a bottom view of  FIG. 9 . 
         FIG. 12  is a head end perspective view of  FIG. 9 . 
         FIG. 13A  is a perspective view of an auto-regression mechanism with a head deck in a flat position. 
         FIG. 13B  is a perspective view of an auto-regression mechanism with a head deck in a raised position. 
         FIG. 14  is a perspective view of an adjustable patient support deck of the patient support of  FIG. 1A  shown in a vascular or bail position. 
         FIG. 15A  is a side view of knee- and foot decks of the adjustable patient support shown in  FIG. 8 . 
         FIG. 15B  is a perspective view showing the foot deck depicted in  FIG. 15A  mounted on a footboard mounting bracket mount. 
         FIG. 16A  is a foot end perspective view of details of how the foot deck depicted in  FIG. 15B  is mounted on the footboard mounting bracket mount with a bail assembly for placing the foot deck in a vascular position. 
         FIG. 16B  is a side view of details of how the foot deck depicted in  FIG. 15B  is mounted on the footboard mounting bracket mount a bail assembly for placing the foot deck in a vascular position. 
         FIG. 16C  is a side perspective view of details of how the foot deck depicted in  FIG. 15B  is mounted on the footboard mounting bracket mount a bail assembly for placing the foot deck in a vascular position. 
         FIG. 17  is a perspective view of an adjustable patient support deck of the patient support of  FIG. 1A  shown in a horizontal prone position without deck panels at a standard first width. 
         FIG. 18  shows the patient support deck of  FIG. 17  expanded to a second intermediate width. 
         FIG. 19  shows the patient support deck of  FIG. 17  expanded to a more expanded third width. 
         FIG. 20  shows a bottom view of the expanded patient support deck of  FIG. 19 . 
         FIG. 21  is a plan perspective view of a head deck of the patient support deck of  FIG. 17  showing elements for expanding and latching the head deck of the adjustable deck. 
         FIG. 22  is a bottom view of the  FIG. 21 . 
         FIG. 23  shows the head deck of  FIG. 21  expanded to a more expanded third width. 
         FIG. 24  is a magnified view of a rack and pinion mechanism and latching mechanism for expanding the head deck shown in  FIG. 21 . 
         FIG. 25  is a magnified view of the latching mechanism shown in  FIG. 24  illustrating a latch mount for the latching mechanism. 
         FIG. 26  is perspective view of a deck extension handle for releasing the latching mechanism shown in  FIG. 25 . 
         FIG. 27A  is a perspective view of an underside of a head deck panel showing protruding ball studs. 
         FIG. 27B  is a sectional view of a ball and socket connection for connecting deck panels to a deck. 
         FIG. 28A  is a perspective view of a caster frame in a fully retracted position for a standard first width deck. 
         FIG. 28B  is a perspective view of the caster frame of  FIG. 28A  in an expanded position. 
         FIG. 29A  and  FIG. 29B  are close-up views of one end of the caster frames of  FIG. 28A  and  FIG. 28B , respectively. 
         FIG. 30A  and  FIG. 30B  are close-up views of one end of the caster frames of  FIG. 28A  and  FIG. 28B , respectively, specifically showing how inner caster extension slide tubes are disposed in relation to an actuator that drives the inner caster extension slide tubes. 
         FIG. 31A  is a foot end perspective view of an extendible headboard at a standard first width supported on a headboard mounting bracket. 
         FIG. 31B  is a head end view of an extendible headboard at a standard first width supported on a headboard mounting bracket. 
         FIG. 31C  and  FIG. 31D  are perspective views the headboard depicted in  FIG. 31A  separated from the headboard mounting bracket, where  FIG. 31C  depicts the headboard and  FIG. 31D  depicts the headboard mounting bracket. 
         FIG. 32  is a perspective view of the extendible headboard shown in  FIG. 31  split apart into two headboard sections. 
         FIG. 33A ,  FIG. 33B  and  FIG. 33C  are perspective views showing an extendible headboard separate from a headboard mounting bracket at a standard first width ( FIG. 33A ), at an intermediate second width ( FIG. 33B ) and at a third more expanded width ( FIG. 33C ). 
         FIG. 34A  is a perspective view of an alternate embodiment of an extendible headboard in which the headboard sections sit in a headboard tray, the headboard being shown at a narrowest width. 
         FIG. 34B  is a magnified view of  34 A showing detail of the tray. 
         FIG. 34C  is a perspective view of the extendible headboard of  FIG. 34A  at an intermediate width. 
         FIG. 34D  is a magnified view of  34 C showing detail of the tray. 
         FIG. 34E  is a perspective view of the extendible headboard of  FIG. 34A  at a widest width. 
         FIG. 34F  is a magnified view of  34 E showing detail of the tray. 
         FIG. 35A  and  FIG. 35B  are end views of an alternate embodiment of an extendible headboard in which headboard extension is driven by an actuator, where  FIG. 35A  shows the headboard at a standard first width and  FIG. 35B  shows the headboard at a more expanded width. 
         FIG. 36A  and  FIG. 36B  are perspective views of a first embodiment of an extendible footboard mountable on a patient support in a retracted position ( FIG. 36A ) and an extended position ( FIG. 36B ). 
         FIG. 37A ,  FIG. 37B ,  FIG. 37C  and  FIG. 37D  are front and back views of the extendible footboard shown in  FIG. 36A  and  FIG. 37B  illustrating a locking feature. 
         FIG. 38A ,  FIG. 38B  and  FIG. 38C  are perspective views of a second embodiment of an extendible footboard in a standard 84 inch position ( FIG. 38A ), an 88 inch position ( FIG. 38B ) and a 92 inch position ( FIG. 38C ). 
         FIG. 39A ,  FIG. 39B  and  FIG. 39C  are bottom views of the three perspective views shown in  FIG. 38 . 
         FIG. 40A  is a perspective view of a locking mechanism for an endboard shown with mounting posts and post sockets. 
         FIG. 40B  depicts  FIG. 40A  with the mounting posts and some of the post sockets removed. 
         FIG. 40C  is a top view of a locking plate for the endboard locking mechanism of  FIG. 40A . 
         FIG. 40D  is a top view of a second embodiment of a locking plate in a locked configuration for an endboard locking mechanism. 
         FIG. 40E  is a top view of the locking plate depicted in  40 D in an unlocked configuration. 
         FIG. 41A  is a perspective view of an endboard mounting bracket within showing a lock knob associated with the locking mechanism of  FIG. 40A . 
         FIG. 41B  is a perspective view depicting a bottom surface of the endboard mounting bracket shown in  FIG. 41A  with the lock knob removed. 
         FIG. 42A  is a side view of an endboard mounting post above a post socket showing slots for receiving a post engaging portion of the locking plate of  FIG. 40C . 
         FIG. 42B  is a perspective view of an endboard mounting post above a post socket showing slots for receiving a post engaging portion of the locking plate of  FIG. 40C . 
         FIG. 42C  is a side view of a lock knob engaged with a locking plate for the endboard locking mechanism of  FIG. 40A . 
         FIG. 42D  is a magnified perspective view of the lock knob engaged with the locking plate depicted in  FIG. 42C . 
         FIG. 43  is a perspective view of a lower frame of a patient support. 
         FIG. 44  is a magnified perspective view of one end of the lower frame of  FIG. 43  together with caster frame elements. 
         FIG. 45A  is a magnified perspective view of one corner of the end of the lower frame of  FIG. 43 . 
         FIG. 45B  is a foot end view of  FIG. 45A  through a cross-section taken at A-A. 
         FIG. 45C  is a bottom view of  FIG. 45B  through a cross-section taken at B-B. 
         FIG. 45D  is a perspective view of a load cell with annular bushings and bolt. 
         FIG. 45E  is a perspective view of a load cell. 
         FIG. 45F  is a perspective view of one bushing in the load cell depicted in  FIG. 45D . 
         FIG. 46A  is a perspective view of an alternative caster frame. 
         FIG. 46B  is a perspective view of an alternative lower frame with load cell for cooperation with the alternative caster frame of  FIG. 46A . 
         FIG. 46C  is a perspective view of a bushing-less load cell for use with the alternative lower frame and caster frame. 
         FIG. 46D  is a side cross-sectional view of the bushing-less load cell of  FIG. 46C  resting on a mounting flange of the caster frame. 
         FIG. 46E  is a perspective view of a bushing-less load cell for use with the alternative lower frame and caster frame, where the load cell has a swivel instead of a stud. 
         FIG. 46F  is a side view of the bushing-less load cell of  FIG. 46D . 
         FIG. 46G  is a longitudinal cross-sectional view of the side view depicted in  FIG. 46F . 
         FIG. 47  is a perspective view of head end and a foot end caster assemblies depicting central lock and steer. 
         FIG. 48A  is a magnified perspective view of the head end caster assembly shown in  FIG. 47  as viewed from the foot end. 
         FIG. 48B  is a back side perspective view of  FIG. 48A . 
         FIG. 49  is a further magnified view of the head end caster assembly shown in  FIG. 47 . 
         FIG. 50  is a magnified view of a head end of a rack and pinion mechanism connecting head end and foot end caster assemblies. 
         FIG. 51  is a perspective view of a patient support deck having guard structures mounted on deck extension pans thereof. 
         FIG. 52A  is a perspective view of a foot rail mounted on a seat deck extension pan. 
         FIG. 52B  is a bottom view of  FIG. 52A . 
         FIG. 52C  shows  FIG. 52A  without an outer shell of the seat deck extension pan illustrating how the foot rail is mounted to the seat deck extension pan. 
         FIG. 53A  is a side perspective view of a foot rail in a raised or guard position. 
         FIG. 53B  is a side perspective view of a foot rail in a low position. 
         FIG. 53C  is a side perspective view of a foot rail in an ultralow position. 
         FIG. 54A  is a side view of the foot rail shown in  FIG. 53A  without foot rail panel. 
         FIG. 54B  is a side view of the foot rail shown in  FIG. 53B  without foot rail panel. 
         FIG. 54C  is a side view of the foot rail shown in  FIG. 53C  without foot rail panel. 
         FIG. 55A  is a magnified view of  FIG. 54A  showing details of the foot rail mechanism. 
         FIG. 55B  is a magnified view of  FIG. 54B  showing details of the foot rail mechanism. 
         FIG. 55C  is a magnified view of  FIG. 54C  showing details of the foot rail mechanism. 
         FIG. 56  is a magnified view of  FIG. 55A  showing more details of the foot rail mechanism. 
         FIG. 57A  is a perspective view of a latch lever of the latching mechanism of Fig. “RailsLatchPerspective” together with a foot rail release handle. 
         FIG. 57B  is a side view of  FIG. 57A . 
         FIG. 57C  is a perspective view of the latch lever of  FIG. 57A  without the foot rail release handle. 
         FIG. 57D  is a front view of  FIG. 57C . 
         FIG. 58A  is a perspective view of a footboard at a foot end of a patient support. 
         FIG. 58B  is a perspective view of a footboard mounting bracket with mating components for mating with the footboard of  FIG. 58A . 
         FIG. 59A ,  FIG. 59B ,  FIG. 59C ,  FIG. 59D  and  FIG. 59E  depicts magnified views of electrical connection components in the footboard and footboard mounting bracket of  FIGS. 58A-B , where  FIG. 59A  is a perspective view of electrical mating contacts in the footboard mounting bracket,  FIG. 59B  is a foot end view of electrical mating contacts in the footboard mounting bracket,  FIG. 59C  is a perspective view of electrical mating contacts in the footboard,  FIG. 59D  is a head end view of electrical mating contacts in the footboard and  FIG. 59E  is a perspective view of the electrical connection components mated together. 
         FIG. 60A ,  FIG. 60B  and  FIG. 60C  depicts magnified views of the electrical mating contacts in the footboard mounting bracket depicted in  FIGS. 59A-B  in association with a spring-loaded sliding cover, where  FIG. 60A  is a perspective view of the electrical mating contacts in the footboard mounting bracket covered by the cover,  FIG. 60B  is a perspective cross-sectional view showing more detail of how the cover covers the electrical contacts, and  FIG. 60C  is a side view of the cross-section in  FIG. 60B . 
         FIGS. 61A and 61B  show side views of the electrical mating half in the footboard mounting bracket with a retractable cover in a gap covering position ( FIG. 61A ) and in a retracted position ( FIG. 61B ) to expose leaf spring electrical contacts. 
         FIGS. 62A, 62B and 62C  depict a first embodiment of a device for permitting a patient support to automatically detect whether a nurse call system is connected to the patient support. 
         FIGS. 63A and 63B  depict a second embodiment of a device for permitting a patient support to automatically detect whether a nurse call system is connected to the patient support. 
         FIG. 64  depicts a multi-angle reading light integrated into a head rail of a patient support. 
         FIG. 65A  depicts a magnified view of the multi-angle reading light of  FIG. 64  showing a light ray directed forward (toward the foot of the patient support) and inward at a fixed angle between about 15° and 20° in relation to an axis parallel to the length of the patient support. 
         FIG. 65B  depicts a magnified view of the multi-angle reading light of  FIG. 64  showing a light ray directed forward (toward the foot of the patient support) and inward at a fixed angle between about 30° and 40° in relation to an axis parallel to the length of the patient support. 
         FIG. 65C  depicts a magnified view of the multi-angle reading light of  FIG. 64  showing a light ray directed forward (toward the foot of the patient support) and inward at a fixed angle between about 45° and 60° in relation to an axis parallel to the length of the patient support. 
         FIG. 65D  depicts a magnified view of the multi-angle reading light of  FIG. 64  showing three light rays directed forward (toward the foot of the patient support) and inward at different angles. 
         FIG. 66A  is a perspective view of a patient support showing location of obstruction sensors on caster assembly covers. 
         FIG. 66B  is the same view as  FIG. 66A  with a base frame assembly cover removed to show location of an obstruction sensor on a base frame assembly. 
         FIG. 66C  is a bottom view of a patient support showing location of obstruction sensors on leg assemblies. 
         FIG. 66D  is a bottom perspective view of the patient support depicted in  FIG. 66C . 
         FIG. 67A  is an exploded perspective view of a leg assembly including an obstruction sensor and a cover. 
         FIG. 67B  is an exploded perspective view of a skid plate including an obstruction sensor and a cover. 
         FIG. 68  depicts a block diagram of an embodiment of a control system for a patient support whereby data communication occurs through a port interconnected with a controller via an I/O interface of the controller. 
         FIG. 69  depicts a block diagram of an embodiment of a control system for a patient support whereby a port is used to provide required information for encryption and/or authentication, but data communication occurs through a separate communication interface. 
         FIG. 70  depicts a flow chart depicting how a program of a patient support may synchronize time stored at the patient support with the time at an external device. 
         FIG. 71  depicts another block diagram of the control system of  FIG. 68  for controlling the patient support. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “patient support” refers to an apparatus for supporting a patient in an elevated position relative to a support surface for the apparatus, such as a floor. One embodiment of a patient support includes beds, for example hospital beds for use in supporting patients in a hospital environment. Other embodiments may be conceived by those skilled in the art. The exemplary term “hospital bed” or simply “bed” may be used interchangeably with “patient support” herein without limiting the generality of the disclosure. 
     As used herein, the term “guard structure” refers to an apparatus mountable to or integral with a patient support that prevents or interferes with egress of an occupant of the patient support from the patient support, particularly egress in an unintended manner. Guard structures are often movable to selectively permit egress of an occupant of the patient support and are usually located about the periphery of the patient support, for example on a side of the patient support. One embodiment of a guard structure includes side rails, mountable to a side of a patient support, such as a hospital bed. Other embodiments may be conceived by those skilled in the art. The exemplary terms “guard rail”, “side rail”, or “rail structure” may be used interchangeably with “guard structure” herein without limiting the generality of the disclosure. 
     As used herein, the term “longitudinal” refers to a direction parallel to an axis between a head end of the patient support and a foot end of the patient support, where a head-to-foot distance is parallel to a longitudinal axis and is referred to as the length of the patient support. The terms “transverse” or “lateral” refer to a direction perpendicular to the longitudinal direction and parallel to a surface on which the patient support rests, where a side-to-side distance is parallel to a transverse or lateral axis and is referred to as the width of the patient support. 
     As used herein, the term “control circuit” refers to an analog or digital electronic circuit with inputs corresponding to a patient support status or sensed condition and outputs effective to cause changes in the patient support status or a patient support condition. For example, a control circuit may comprise an input comprising an actuator position sensor and an output effective to change actuator position. One embodiment of a control circuit may comprise a programmable digital controller, optionally comprising or interfaced with an electronic memory module and an input/output (I/O) interface. Other embodiments may be conceived by those skilled in the art. The exemplary terms  68 , “control system”, “control structure” and the like may be used interchangeably with “control circuit” herein without limiting the generality of the disclosure. 
     As used herein, the term “actuator” refers to a device for moving or controlling a mechanism or system and may be frequently used to introduce motion, or to clamp an object so as to prevent motion. Actuators include, for example, motors, hydraulic actuators, pneumatic actuators, electric actuators (e.g. linear actuators), mechanical actuators and electromechanical actuators. 
       FIG. 1A  and  FIG. 1B  illustrate an embodiment of a height-adjustable patient support  100  capable of supporting overweight patients. The patient support  100  may include a substantially horizontal upper frame  102  that may support an adjustable patient support deck  104  (or simply “deck”) positioned thereon to receive a patient support surface (or “mattress”) for supporting a patient thereon. For clarity, the mattress is not illustrated. The patient support deck  104  may have a head deck  105  capable of tilting up to form a backrest and tilting down to a prone position (prone position shown). At a head end of the patient support  100  may be a headboard  106 , while a footboard  108  may be attached to the upper frame  102  at a foot end of the patient support  100 . The headboard  106  and footboard  108  may be collectively known as endboards. Guard structures may comprise side rails including head rails  110  and foot rails  113  and may be positioned on each side of the patient support  100 . Such side rails  110 ,  113  may be movable so as to facilitate entry and exit of a patient. In  FIG. 1A , the side rails  110 ,  113  are all in the raised or guard position, while in  FIG. 1B , the side rails  110 ,  113  on the patient right side of the patient support are in the tucked position whereby the rails  110 ,  113  are in ultra-low positions and tucked under the patient support deck  104 . In this embodiment, the patient support  100  is a bed. The term “patient” is intended to refer to any person, such as a hospital patient, long-term care facility resident, or any other occupant of the patient support  100 . 
     The patient support  100  may include a lift mechanism comprising two leg assemblies  112 ,  114 . The head end leg assembly  112  may be connected at the head end of the patient support  100  and the foot end leg assembly  114  may be connected at the foot end of the patient support  100 . The leg assemblies  112 ,  114  may be connected to one or more actuators in a manner whereby the actuators may raise and lower the upper frame  102 . Articulation of the patient support deck  104  may be controlled by actuators (not shown) that adjust the tilt of the head deck  105  of the patient support deck  104  as well as the height of a knee deck  107  of the patient support deck  104 . 
     The lower ends of the leg assemblies  112 ,  114  may be connected to a lower frame  132 . The lower frame  132  may be large enough so that when the upper frame  102  is at its lowest position, the upper frame  102  may be nested within the lower frame  132 . The lower frame  132  may be nested within and suspended by a caster frame  142 , the lower frame comprising four load cells (not shown) resting on the caster frame  142 . Connected to the caster frame  142  at the foot end and head end may be two caster assemblies  118  each assembly comprising two casters  119  that allow the patient support  100  to be moved to different locations. Brake pedals  117  at the head end and foot end (the head end one not shown) may permit locking the foot end, head end or both the foot end and head end casters in full stop or tracking straight positions, in addition to permitting the casters to rotate and travel freely when needed. 
     A manual cardiopulmonary resuscitation (CPR) quick release handle  124  may be provided on each side of the patient support  100  to rapidly lower the head deck  105  of the patient support deck  104  and place the patient support into an emergency state wherein the patient support deck  104  is flat and optionally the side rails are unlocked, the side rails permitted to fall under the influence of gravity to a low position. 
     The patient support  100  may further include control circuitry and an attendant&#39;s control panel  120  located, for example, at the footboard  108 . The attendant&#39;s control panel  120  may, among other things, control the height of the upper frame  102 , as well as the articulation of the patient support deck  104 . To allow for similar adjustment, an occupant&#39;s control panel may be provided, for example, on a side rail. 
     Control panels may include user interfaces, for example buttons. The buttons may be keypad style buttons that operate as momentary contact switches (also known as “hold-to-run” switches). Buttons may be provided to raise and lower the upper frame  102 , articulate the patient support deck  104 , set/pause/reset an exit alarm, zero an occupant weight reading, lockout controls, and to enable other functions. The control panels may have different sets of buttons for different sets of functions, with the attendant&#39;s control panel  120  typically having a wider array of functions available than any occupant&#39;s control panel that may be provided on the patient support. Other styles of user interface and buttons, such as touch-screen buttons, are also suitable. The user interface of the control panels may include indicators, such as printed graphics or graphics on a display, for describing the functions of the buttons or other interface and as well as indicating data related to the patient support  100 . A pico-projector  2309  may be mounted in any suitable location on the patient support  100 , for example the headboard  106 , and electronically connected to the control circuitry for projecting images on a surface. 
     A lift mechanism for a height adjustable patient support should be sufficiently robust to raise and lower the patient support deck with a patient supported thereon. Lift mechanisms typically raise and lower the patient support between at least two pre-defined positions, an uppermost position and a lowermost position, although there are many examples in the prior art where the patient support can be raised and lowered to intermediate positions. In many height adjustable patient supports, the deck may be raised and lowered to three distinct positions, each position having a different purpose in patient care. These positions are the high (or raised) position, the low position and the ultralow position. A fourth position, called the tuck position, is also often noted, but in terms of the height of the deck off the ground or floor, the tuck position is usually the same as the low position, except that guard structures are tucked under the deck instead of being beside the deck. 
     In the context of hospitals, it has become increasingly desirable to be able to lower the patient support deck to as low a height as possible (i.e. the ultralow position) off the surface on which the patient support rests (e.g. a floor). This has been difficult to achieve because the frames on which the patient support deck are supported often limit the extent of downward travel of the deck. Further, to lift the deck from a very low height requires an extremely strong and robust lift mechanism, which is exacerbated in the context of a bariatric patient support where loads on the patient support are even more extreme. 
     Lift mechanisms may comprise legs at the head end and foot end of the patient support. The legs are generally attached at one end to the deck or a frame on which the deck is supported and at the other end to a frame supported on the ground. In order to raise and lower the deck, the legs must either change length or one or both of the ends of the legs must travel longitudinally on the patient support. Variations in the prior art include articulating legs, legs connected by pivoting linkages and legs having upper ends that travel longitudinally along the deck or frame on which the deck is supported. Movement of the legs is generally driven by actuators attached to the legs and one or more frames. However, prior art lift mechanisms experience many of the difficulties previously described. 
     In the present patient support, to overcome one or more of these difficulties while maintaining the ability to achieve various height positions, a lift mechanism may be provided having extendible length legs, particularly legs that extend linearly. In one embodiment, the extendible legs may comprise telescoping legs. Linearly extending legs, particularly telescoping legs, provide a mechanical advantage for lifting heavy weights. Further, extending legs, particularly telescoping legs, provide the opportunity for a more compact leg design in lower positions ultimately permitting the deck to achieve lower height positions. One or the combination of these features may be advantageous for bariatric patient supports. 
     Referring to  FIG. 2A  and  FIG. 2B , one embodiment of a lift mechanism is shown in context with the upper frame  102 , the lower frame  132  and the caster frame  142  of the patient support  100 . Upper ends of the head end leg assembly  112  and foot end leg assembly  114  may be pivotally mounted to the upper fame  102  at upper frame leg hangers  1003 . Lower ends of the head end leg assembly  112  and foot end leg assembly  114  may be pivotally mounted to the lower frame  132  at lower frame leg hangers  1004 . The leg hangers  1003 ,  1004  are fixed positions on the frames  102 ,  132 , respectively. The upper and lower ends of the leg assemblies  112 ,  114  do not translate along the frames  102 ,  132 . The leg assemblies  112 ,  114  may comprise no intermediate pivot points between the pivot points on the fixed leg hangers  1003 ,  1004  of the upper and lower frames  102 ,  132 , respectively. 
     Head end upper leg lift actuator  1001  may be pivotally mounted at a rod end of the actuator  1001  on a mounting bracket  1005  at the upper end of the head end leg assembly  112  and pivotally mounted at a base end of the actuator  1001  on another mounting bracket (not shown) on a cross-member  1010  of the upper frame  102 . The pivoting mounting points at each end of the actuator  1001  may be longitudinally off-set from each other. Likewise, foot end upper leg lift actuator  1002  may be pivotally mounted at a rod end of the actuator  1002  on a mounting bracket  1006  at the upper end of the foot end leg assembly  114  and pivotally mounted at a base end of the actuator  1002  on another mounting bracket  1008  on a cross-member  1011  of the upper frame  102 . The leg assemblies  112 ,  114  may be arranged as mirror images of each other through a vertical plane laterally bisecting the patient support so that the upper frame  102  moves vertically and not laterally. Otherwise the two leg assemblies  112 ,  114  may be the same, functioning in the same manner. 
       FIG. 3A  illustrates the head end leg assembly  112  and  FIG. 3B  illustrates the upper frame  102  and the lower frame  132  showing upper frame leg hangers  1003  and lower frame leg hangers  1004 . The head end leg assembly  112  may comprise a lower leg  1015  housed inside an upper leg  1016  in telescoping cooperation in a tube-in-tube manner. The lower leg  1015  may comprise leg support pins  1017  (only one shown) that may be pivotally mounted on the lower frame  132 . The upper leg  1016  may comprise leg support pins  1018  (only one shown) that may be pivotally mounted on the upper frame  102 . As previously mention, mounting bracket  1005  at the upper end of the head end leg assembly  112  may be provided for pivotally mounting the rod end of the head end upper leg lift actuator  1001 . The lower frame leg hangers  1004  may be fixed to the lower frame  132  proximate the corners of the lower frame  132 . The lower frame leg hangers  1004  may be fixed to prevent longitudinal translation of the head end leg assembly  112  along the lower frame  132 . Supported in each lower frame leg hanger  1004  may be a leg bearing block  1012  having a cylindrical bore  1013  in which the leg support pin  1017  may be received. The leg support pin  1017  may pivot within the cylindrical bore  1013 . The upper frame leg hangers  1003  may be fixed to the upper frame  102  to prevent longitudinal translation of the head end leg assembly  112  along the upper frame  102 . The upper frame leg hangers  1003  may comprise cylindrical bore  1014  (only one shown) that receive the leg support pins  1018  of the upper leg  1016 . The leg support pins  1018  may pivot within the cylindrical bores  1014  of the upper frame leg hangers  1003 . Thus, the head end leg assembly  112  may be pivotally mounted between the upper frame  102  and the lower frame  132  by seating the leg support pins  1017  of the lower leg  1015  in the cylindrical bore  1013  of the leg bearing blocks  1012  of the lower frame  132  and seating the leg support pins  1018  of the upper leg  1016  in the cylindrical bore  1014  of the upper frame leg hangers  1003  of the upper frame  102 . The preceding description is equally applicable to the foot end leg assembly  114 . 
     When the upper frame  102  is in the ultralow position ( FIG. 2A ), the head end upper leg lift actuator  1001  and foot end upper leg lift actuator  1002  may be fully retracted. To raise the upper frame  102  (and the deck supported thereon) from the ultralow position ( FIG. 2A ) to the low position ( FIG. 2B ), the head end upper leg lift actuator  1001  and foot end upper leg lift actuator  1002  may be actuated to extend by a signal from the control circuit. Simultaneous extension of the two actuators  1001 ,  1002  may apply a vertical force at the upper ends of the head end and foot end leg assemblies  112 ,  114 . Because the leg hangers  1003 ,  1004  are immovable on the upper and lower frames  102 ,  132 , respectively, the leg assemblies  112 ,  114  may be prevented from moving longitudinally along the frames. This may force the leg assemblies  112 ,  114  to extend. With reference to  FIG. 3A , the lower leg  1015  and upper leg  1016  must slide with respect to each other. Because the lower leg  1015  is mounted on the lower frame  132 , and the lower frame  132  is mounted on the caster frame  142 , and the caster frame  142  rests on immovable ground, the upper leg  1016  must slide upward in relation to the lower leg  1015 . Since the upper leg  1016  is connected to the head end upper leg lift actuator  1001  and the head end upper leg lift actuator  1001  is also mounted on the upper frame  102 , extension of the head end upper leg lift actuator  1001  must then force the upper frame  102  upward, thereby raising the deck supported on the upper frame  102 . As the head end upper leg lift actuator  1001  extends, the lower leg  1015  of the head end leg assembly  112  may pivot on the leg support pins  1017  and the upper leg  1016  of the head end leg assembly  112  may pivot on the leg support pins  1018 , thereby permitting the upper frame  102  to rise as the upper leg  1016  slides on the lower leg  1015  contained therein. The operation of the foot end leg assembly  114  is similar. 
     The upper frame  102  may be similarly raised to the high or raised position from the low position, and retracting the lift actuators  1001 ,  1002  may lower the upper frame  102 . 
     While the telescoping arrangement of the leg assemblies  112 ,  114  together with leg assembly fixed pivot points on the upper and lower frames  102 ,  132  and the pivoting lift actuators  1001 ,  1002  coupling the upper frame  102  to the upper legs of the leg assemblies permits raising the upper frame  102  in relation to the lower frame  132 , there may be two issues to overcome. 
     First, the arrangement of the telescoping leg assemblies should be sufficiently rigid to permit only (or primarily) linear relative motion of the upper leg on the lower leg and of sufficiently low friction, both of which may be useful to mitigate against binding of the lower leg in the upper leg during relative motion. It may be noted here that instead of the lower leg being contained in the upper leg, the upper leg could be contained in the lower leg. 
     Second, uneven loading between the head end and foot end of the patient support results in uneven lift requirements at the head end and foot end of the patient support. Thus, even though both lift actuators still extend, the leg assembly under greater load may have a tendency not to extend while the leg assembly under lesser load does extend but more quickly than it should. This arises because the legs are free to telescope, the leg assembles are allowed to pivot at both the upper and lower legs, the lift actuators are allowed to pivot at both ends, and as long as the angle between the leg assemblies  112 ,  114  remains the same, one end may be raised while the other end does not, resulting in the upper frame tilting away from horizontal. When the end with the greater load reaches maximum height, the end with the lighter load then rises and rises extremely quickly to maintain the angle between the leg assemblies. However, it is desirable for the upper frame to remain parallel to the lower frame while the upper frame is being raised. This so-called “teeter-totter” effect may be accommodated in several ways. 
     Rotational speed of the pivot point where the upper leg lift actuator connects to the upper leg of a given leg assembly is related non-linearly to extension speed of the leg assembly. To avoid the “teeter-totter” effect, the upper leg of the leg assembly may be fixed to the lower leg of the leg assembly by an extension control mechanism that accounts for the non-linearity between the rotation and extension of the leg assembly. This may be accomplished by: (a) having a constant rotational speed at the pivot point (e.g. a constant speed actuator) and a non-linear (variable) speed control mechanism in the leg assembly; (b) having a variable rotational speed at the pivot point (e.g. a variable speed actuator) and a constant speed control mechanism in the leg assembly; or, (c) having variable rotational speed at the pivot point (e.g. a variable speed actuator) and a non-linear (variable) speed control mechanism in the leg assembly. Non-linear (variable) speed control mechanisms in the leg assemblies may comprise any suitable device or combinations of devices, for example variable speed actuators and/or cam in track devices. 
     Referring to  FIG. 4  and  FIG. 5 , one embodiment of a telescoping leg arrangement is a tube-in-tube arrangement shown in relation to the head end leg assembly  112  of the patient support of  FIG. 2A ,B. The same description may apply to the foot end leg assembly  114 . The lower leg  1015  may comprise parallel rectangular inner tubes  1021   a,    1021   b  that are free to slide in corresponding rectangular outer tubes  1022   a,    1022   b  of the upper leg  1016 . To reduce friction between the tubes  1021   a,    1021   b  and  1022   a,    1022   b,  and to reduce the possibility of the tubes binding while sliding, the inner tubes  1021   a,    1021   b  may comprise low friction side pads that both take up side-to-side tolerance and reduce friction between the inner tubes  1021   a,    1021   b  and outer tubes  1022   a,    1022   b.  Further, rollers  1023   a,    1023   b  on the outer tubes  1022   a,    1022   b  may engage an upper outer surface of the inner tubes  1021   a,    1021   b,  while similar rollers (not shown) on the inner tubes  1021   a,    1021   b  may engage a lower inside surface of the outer tubes  1022   a,    1022   b  to permit rolling engagement between the upper leg  1016  and lower leg  1015 . In another embodiment, low friction slide blocks could replace one or more of the rollers. Furthermore, outer surfaces of the lower leg may be plated to lower friction between the upper leg  1016  and the lower leg  1015 . Since the inner tubes  1021   a,    1021   b  are constrained in two dimensions in the outer tubes  1022   a,    1022   b,  the legs  1015  and  1016  may be only free to extend or retract in one direction in relation to each other. 
     The head end leg assembly  112  may further comprise a leg extension control mechanism  1020  comprising a lower leg actuator  1025  having a base mounted to the lower leg  1015  at a lower end of the lower leg  1015  and a rod  1026  mounted at pivot point  1031  to an arcuate cam arm  1030 . The arcuate cam arm  1030  may be pivotally mounted to the upper leg  1016  at pivot point  1032 . The arcuate cam arm  1030  may comprise a cam roller (not visible) next to a spacer  1033 , the cam roller riding in a cam track  1035  fixed to the lower leg  1015 . As seen in  FIG. 4 , when the upper leg lift actuator  1001  pivotally connected to the upper leg  1016  on the mounting bracket  1005  is fully retracted, the inner tubes  1021   a,    1021   b  of the lower leg  1015  may be fully inserted in the outer tubes  1022   a,    1022   b  of the upper leg  1016 . Further, the lower leg actuator  1025  may be fully retracted and the cam roller may be located at a lower portion of the cam track  1035 . When the upper leg lift actuator  1001  is activated to extend, the lower leg actuator  1025  may be activated to extend simultaneously. 
     In this embodiment, the two actuators  1001  and  1025  are variable speed actuators. As previously described, extension of the upper leg lift actuator  1001  may cause the upper leg  1016  to telescope away from the lower leg  1015 . However, the speed of rotation of the pivot point where the upper leg lift actuator  1001  is connected to the mounting bracket  1005  varies in comparison to the speed of extension of the leg assembly  112 . If the lower leg actuator  1025  was connected directly to the upper leg  1016  the variable difference in the speed of rotation and the speed of leg extension would damage the mechanism and cause the leg assembly  112  to fail. However, the lower leg actuator  1025  is indirectly connected to the upper leg  1016  through the arcuate cam arm  1030 . As the lower leg actuator  1025  extends, the arcuate cam arm  1030  pivotally connected to the upper leg at pivot point  1032  may also be pushed along with the extending actuator rod  1026  thereby pushing the upper leg  1016  along the lower leg  1015 . In addition, the arcuate cam arm  1030  also pivots at pivot point  1032 , which may be laterally off-set from the pivot point  1031 . Pivoting of the arcuate cam arm  1030  may permit the cam roller to travel within the cam track  1035 . The shape and length of the cam track  1035  is designed to make the arcuate cam arm  1030  pivot about pivot point  1032  and to vary the longitudinal position of the pivot point  1032  with respect to the lower leg  1015  non-linearly in relation to the speed of the actuators  1001 ,  1025 . This variation in position of pivot point  1032  correspondingly varies the speed of extension of the upper leg  1016  on which the pivot point  1032  exists. Since the pivot point  1032  always travels in a straight line when the legs  1015 ,  1016  telescope, the shape of the cam track  1035  only varies the speed at which the pivot point  1032  moves in the direction of motion of the upper leg  1016 . The speed at which the pivot point  1032  moves, and therefore the speed at which the upper leg  1016  moves, is generally slower in the beginning and faster by the end. This arrangement ensures that the upper leg  1016  actually moves under load. Since both the head end leg assembly  112  and foot end leg assembly  114  may comprise such a leg extension control mechanism, both ends are forced to move under load and the “teeter totter” effect is eliminated. 
     With reference to  FIG. 5 , once the lower leg actuator rod  1026  (and the upper leg lift actuator  1001  (not seen in  FIG. 5 ) is fully extended, cam roller on the arcuate cam arm  1030  has traveled to the other end of the cam track  1035  and the upper leg  1016  has traveled its full course along the lower leg  1015 . The leg assembly  112  may now be fully extended. Reversing the actuators  1001 ,  1025  may reverse the motions of the arcuate cam arm  1030  and the upper leg  1016  to bring the upper frame  102  back to a lower position. 
     The arcuate cam arm  1030  may comprise a second cam roller  1034  on the other side of the pivot point  1032  and the other side of the pivot point  1031 , the second cam roller  1034  riding in a second cam track (not shown) on the lower leg  1015 . While a second cam roller  1034  in a second cam track may be unnecessary to control the speed of extension of the upper leg  1016 , the second cam roller  1034  in the second cam track does help stabilize the motion of the upper leg  1016 . 
     Thus, with the variable speed two actuators  1001 ,  1025  working in unison, the pivoting arcuate cam arm  1030  linking the lower leg actuator  1025  to the upper leg  1016  works together with the cam roller in the cam track  1035  to slow down or speed up the extension of the upper leg  1016  to compensate for the non-linear difference in speed between the leg extension and the rotation of the upper leg lift actuator  1001  in the mounting bracket  1005 . It should be noted that the primary work involved in raising and lowering the upper frame  102  is done by the upper leg lift actuators  1001 ,  1002 , while the lower leg actuators  1025  are responsible, in part, for eliminating the “teeter totter” effect. 
     While the embodiment described in detail herein involves the use of two variable speed actuators and a cam in track mechanism, there are other ways of synching the rotational speed of the upper leg lift actuator at the upper leg linkage point to the extension speed of the upper leg and eliminating the “teeter totter” effect. In another embodiment, constant speed actuators are used with a cam in track mechanism that alone synchronizes the rotational speed of the upper leg lift actuator at the upper leg linkage point to the extension speed of the upper leg. In another embodiment, no track may be used and the upper leg lift actuator and lower leg actuator may be configured to obtain a greater variable speed, where the lower leg actuator is run at a speed to match the extension speed of the upper leg. This would permit direct connection of the lower leg to the upper leg through the lower leg actuator. In another embodiment, no track is used and the upper leg lift actuator may be a constant speed actuator while the lower leg actuator may be a variable speed actuator to match the leg extension speed of the upper leg. The cam in track mechanism permits the use of less powerful and smaller lower leg actuators. 
     To provide flexibility in patient care and comfort, patient supports should be able to support patients in a number of different positions. The patient support described herein has such capability. Referring to  FIG. 6 , the patient support deck  104  may be in a horizontal prone position. Referring to  FIG. 7 , the patient support deck  104  may be in an articulating position with the head deck  105  tilted up relative to the upper frame  102  to form a backrest and the other portions remaining horizontal. Referring to  FIG. 8 , the patient support deck  104  may be in a head-up, knees-up position with the head deck  105  tilted up relative to the upper frame  102  to form a backrest and the knee deck  107  and the foot deck  2002  tilted up relative to the upper frame  102  to form an inverted “V”. Referring to  FIG. 14  the patient support deck  104  may be in a vascular position with the head deck  105  tilted up relative to the upper frame  102  to form a backrest, the knee deck  107  tilted up relative to the upper frame  102  at the foot end to raise the knees the and foot deck  2002  raised but horizontal. In all of the aforementioned positions, a seat deck  2001  remains horizontal. The deck  104  may also be moved to the Trendelenburg position (head lower than foot) or the reverse Trendelenburg position (head higher than foot). 
     Each of the deck pans  105 ,  2001 ,  107  and  2002  of the deck  104  may comprise a deck panel for supporting a portion of a patient&#39;s body. The head deck  105  may comprise a head deck panel  2005 . The seat deck  2001  may comprise a seat deck panel  2011 . The knee deck  107  may comprise a knee deck panel  2007 . The foot deck  2002  may comprise a foot deck panel  2012 . The deck  104  may be supported on the upper frame  102 . The deck  104  may further comprise mattress keepers  2003  for keeping a mattress (not shown) from sliding sideways off the deck and the manual cardiopulmonary resuscitation (CPR) quick release handle  124 . The upper frame  102  may further support an upper frame footboard mount  2015  and an upper frame headboard mount  2016 . 
     Further possible features of the deck  104  supported on the upper frame  102  are shown in  FIG. 9 ,  FIG. 10 ,  FIG. 11  and  FIG. 12  in which the deck panels are removed. 
     To move the head deck  105  between the horizontal and raised positions, a head deck actuator  201  may be employed whereby one end of the head deck actuator  201  may be pivotally linked to the head deck  105  at pivot  2017  proximate a head end of the head deck  105 , and the other end of the actuator  201  may be pivotally linked at pivot  2020  to the upper frame  102  at a position proximate a foot end of the head deck  105 . The head deck  105  comprises support struts  2021 , which may be pivotally linked to the upper frame  102 . Linear movement of the actuator  201  may cause the support struts  2021  to pivot thereby raising or lowering the head deck  105 . 
     The head deck  105  may also comprise a mechanism whereby movement of a patient longitudinally toward the foot end of the patient support is reduced or eliminated while the head deck is being raised. This movement occurs because while the head deck is being raised, the upper part of the head deck moves longitudinally toward the foot end of the patient support. An auto-regression mechanism to reduce or eliminate this movement may be accomplished by permitting the lower end of the head deck  105  to move toward the head end of the patient support while the head deck is being raised. This compensates for the movement of the upper part of the head deck toward the foot end of the patient support. 
     With reference to  FIG. 9 ,  FIG. 10 ,  FIG. 11 ,  FIG. 12  and  FIG. 13A-13B , an autoregression mechanism may comprise upwardly depending arcuately-shaped auto-regression linkages  2029  pivotally linked to the head deck  105  at pivots  2027  proximate upper ends of the linkages  2029  and toward the upper part of the head deck  105 . The auto-regression linkages  2029  may further comprise track rollers  2026  proximate the lower end of the auto-regression linkages  2029 , the track rollers  2026  riding in auto-regression cam tracks  2023  situated in mounting plates  2009 . The mounting plates  2009  may be mounted (e.g. bolted, welded, etc.) on the upper frame  102 , for example on to the longitudinal main rails of the upper frame  102 . The auto-regression linkages  2029  may also be pivotally linked to the mounting plates  2009  at pivots  2022 . 
     With specific reference to  FIG. 13A-13B , as the head deck  105  is raised and the upper part of the head deck moves toward the foot end of the patient support, the lower part of the head deck may move towards the head end of the patient support as the track rollers  2026  move longitudinally in and ride within the cam tracks  2023  towards the head end of the patient support. The ability of the lower part of the head deck  105  to move in such a manner is a result of the presence of the auto-regression linkages  2029 . Thus, the longitudinal position of the head deck  105  may not be as far toward the foot end of the patient support as the position that the head deck  105  would have taken had there been only a pivoting linkage at the lower part of the head deck  105 . When the head deck moves from the raised position to the lowered position, the track rollers  2026  may move longitudinally in and ride within the cam tracks  2023  towards the foot end of the patient support. The auto-regression linkages  2029  may be further connected by an auto-regression cross-member  2028  attached to and extending between the linkages  2029  below the arc of the auto-regression linkages  2029  to reduce torsional distortions and to force the auto-regression linkages  2029  to act in concert without binding the motion of the head deck  105 . In this manner, patient movement toward the foot end may be reduced or eliminated without the aid of an additional actuator. 
     To move the knee deck  107  and foot deck  2002  between the horizontal and raised positions, a knee deck actuator  202  may be employed whereby one end of the knee deck actuator  202  may be pivotally linked to the knee deck  107  at pivot  2018  proximate a foot end of the knee deck, and the other end of the knee deck actuator  202  may be pivotally linked to the upper frame  102  at pivot  2014  proximate a head end of the knee deck  107 . The foot end of the knee deck  107  may be pivotally linked at pivot  2019  to a head end of the foot deck  2002  so that movement upward or downward of the foot end of the knee deck  107  may also cause movement upward or downward of the head end of the foot deck  2002 . 
     Adjustment of the angle of the foot deck  2002  may be accomplished without the use of a variable length actuator. The head end of the foot deck  2002  may be pivotally linked to the foot end of the knee deck  107 . Actuation of the knee deck actuator  202  raises and lowers the foot end of the knee deck  107  and consequently raises and lowers the head end of the foot deck  2002 . To accommodate the resulting requirement for the foot end of the foot deck  2002  to move longitudinally in response to the raising and lowering of the head end of the foot deck  2002 , the foot end of the foot deck  2002  may be configured with an engagement structure that slidingly engages a corresponding structure on the upper frame  102  that permits the foot end of the foot deck  2002  to translate longitudinally while retaining the foot end of the foot deck  2002  in the same horizontal plane. Thus, raising the foot end of the knee deck  107  using an actuator would also raise the head end of the foot deck  2002  while keeping the foot end of the foot deck  2002  down, all without using a variable length actuator mounted directly to the foot deck  2002 . 
     In one embodiment, the foot end of the foot deck  2002  may comprise a bail assembly  2013  comprising a bail cross-member  2025  extending from one side to the other of the foot deck  2002 . The bail cross-member  2025  may be slidably engaged in bail cam tracks  2024  in the upper frame footboard mount  2015  supported on the upper frame  102 . Movement up or down of the head end of the foot deck  2002  may cause the bail cross-member  2025  to slide longitudinally within the bail cam tracks  2024 . The bail cross-member  2025  may be longitudinally closest to the foot end of the deck  104  when the foot deck  2002  is in the horizontal position, for example in the articulating position shown in  FIG. 6  or  FIG. 7 . Moving the head end of the foot deck up to the knees up (comfort) position may cause the bail cross-member  2025  to slide in the bail cam tracks  2024  toward the head end of the deck  104  as shown in  FIG. 8 . This mechanism of adjusting the foot deck does not require a variable-length mechanism, such as a variable-length actuator, between the knee deck  107  and the foot deck  2002 . The bail cross-member  2025  in the bail cam tracks  2024  may pivot and slide but does not change in length, and is therefore not a variable length actuator. 
     To achieve the vascular position (to  FIG. 14 ), the angle of the foot deck  2002  may be changed independently of the angle of the knee deck  107 . Further, an actuator is not required to change the angle of the foot deck  2002 . With reference to  FIG. 15A , B and  FIG. 16A-C , a mechanism for changing the angle of the foot deck  2002  of the deck on the upper frame  102  to achieve the vascular position is shown. The foot deck  2002  may comprise longitudinal supporting struts  2095 ,  2096  from which bail linkages  2240 ,  2241  extend longitudinally. The upper frame footboard mount  2015  may comprise the two bail cam tracks  2024  within which two track rollers  2243  mounted proximate opposite ends of the bail cross-member  2025  may roll. The upper frame footboard mount  2015  may be mounted on the bail linkages  2240 ,  2241  by virtue of the track rollers  2243  in the bail cross-member  2025 . As the head end of the footboard portion  2002  moves up and down, the track rollers  2243  may roll in the bail cam tracks  2024  causing the bail cross-member  2025  to slide longitudinally. 
     Lobed cams  2242  (only one shown) may also be pivotally mounted on the bail cross-member  2025  between the upper frame footboard mount  2015  containing the bail cam tracks  2024  and the bail linkages  2240 ,  2241 . With reference to the lobed cam  2242  between the upper frame footboard mount  2015  and the bail linkage  2240 , the lobed cam  2242  may comprise a spring holder  2244  and a catch  2245 . One end of a coiled spring  2246  may be attached to the spring holder  2244  and another end of the coiled spring  2246  may be attached to a spring holding pin  2247  mounted on the bail linkage  2240 . A catch stop  2248  may be mounted on the upper frame footboard mount  2015 , an upper surface of the catch stop  2248  comprising a groove  2249  in which the catch  2245  of the lobed cam may be retained. There may be a similar arrangement on the other side of the upper frame footboard mount  2015 . 
     To achieve the vascular position ( FIG. 14 ) from the normal knees-up position  FIG. 8 ), the longitudinal supporting struts  2095 ,  2096  may be physically lifted by lifting on the foot end of the foot deck  2002 , which causes the bail cross-member  2025  to move toward the head end. When the catch  2245  of the lobed cam  2242  contacts the foot end of the catch stop  2248  the lobed cam  2242  rotates in a first direction to bring the catch  2245  up and over the foot end of the catch stop  2248  until the catch  2245  is over the groove  2249  whereupon the spring  2246  rotates the lobed cam  2242  in a second direction to engage the catch  2245  in the groove  2249  of the catch stop  2248 . With the catch  2245  retained in the groove  2249  of the catch stop  2248 , the bail cross-member  2025  may be prevented from moving longitudinally foot-ward, thereby locking the foot end of the foot deck  2002 . With the foot deck  2002  thus locked, lowering the knee-supporting section  107  with the knee deck actuator  202  may cause the head end of the foot deck  2002  to lower without also moving the foot end of the foot deck  2002 . At some point, the knee deck  107  will reach a position where the knees are up but the foot deck  2002  is horizontal or almost horizontal with the head end of the foot deck down slightly, i.e. the vascular position ( FIG. 14 ). 
     To unlock the foot deck  2002 , the longitudinal supporting struts  2095 ,  2096  may be physically lifted again by lifting on the foot end of the foot deck  2002 , which lifts the catch  2245  over the head end side of the catch stop  2248 . Lowering the longitudinal struts  2095 ,  2096  causes the bail cross-member  2025  to move longitudinally toward the foot end. When the catch  2245  contacts the head end side of the catch stop  2248 , the spring  2246  bends allowing the lobed cam  2242  to rotate in the second direction which lifts the catch  2245  above the catch stop  2248 . Because of the shape of the catch  2245 , the catch  2245  does not engage in the groove  2249  of the catch stop  2248  as the bail cross-member  2025  moves toward the foot end. With the catch  2245  now foot-ward of the catch stop  2248 , the bail cross-member  2025  is free to move longitudinally foot-ward in the bail cam track  2024  to return to the foot deck  2002  to non-vascular position. 
     Thus, the patient support described herein is able to achieve vascular and non-vascular positions without a variable length mechanism, for example without the use of another actuator on the foot deck of the deck. 
     Most patient supports are designed to accommodate patients of average size and weight. For bariatric patients, normal patient supports are generally too small and lack sufficient structural strength to withstand the load of the patient. The patient support disclosed herein is structurally strong enough to accommodate greatly overweight patients and comprises features for extending the length and/or width of the caster frame, deck, headboard and footboard to accommodate average-sized patients on the one hand and bariatric patients on the other hand. The width may be adjusted sideways in any increments, for example between a first width such as for a standard patient support, a second intermediate width and a third more expanded width for large bariatric patients. Notionally, the first standard width may be considered a 36 inch width, the second intermediate width may be considered a 42 inch width and the third more expanded width may be considered a 48 inch width, although these numerical widths are not actual widths but are descriptors that may be used in the art. 
     Referring to  FIG. 17 ,  FIG. 18 ,  FIG. 19  and  FIG. 20 , a patient support deck  104  is shown in a horizontal prone position without deck panels at a standard first width, an intermediate second width and a more expanded third width. 
     The head deck  105  may comprise two head deck extension pans  2031  on either side of the deck  104 , which are normally under the head deck panel when the deck  104  is at standard width. The seat deck  2001  may comprise two seat deck extension pans  2032  on either side of the deck  104 , which are normally under the seat deck panel when the deck  104  is at standard width. The knee deck  107  may comprise two knee deck extension pans  2033  on either side of the deck  104 , which are normally under the knee deck panel when the deck  104  is at standard width. The foot deck  2002  may comprise two foot deck extension pans  2034  on either side of the deck  104 , which are normally under the foot deck panel when the deck  104  is at standard width. The deck extension pans may be made as thin as possible to provide more space under the deck extension pans to tuck the guard structures. 
     As seen in  FIG. 18  and  FIG. 19 , when the deck  104  is expanded, the deck extension pans  2031 ,  2032 ,  2033 ,  2034  supported on deck extension pan cross-members may be pulled laterally away to provide a wider surface. The deck extension pans that are normally under the deck panels may now be exposed to provide an extended surface on which a larger mattress may rest. The upper frame  102 , which supports the deck  104 , may not expand with the deck. 
     The width of head deck  105  and foot deck  2002  may be adjusted (expanded or contracted) independently. The seat deck  2001  and knee deck  107  may be adjusted together. The deck extension pans may be moved manually or movement may be powered. In a manual embodiment, on each side of the deck  104  may be head deck extension handles  2041 , seat/knee deck extension handles  2042  and foot deck extension handles  2044 . With these handles, the deck extension pans may be unlatched and then moved laterally by pulling or pushing. The head deck extension handles, seat/knee deck extension handles and foot deck extension handles may be operationally connected to head deck extension latch mechanism  2051 , seat/knee deck extension latch mechanism  2052  and foot deck extension latch mechanism  2054 , respectively. The handles may be configured with a structure, for example a lever, for leasing the latch mechanisms. The latch mechanisms may immobilize the deck extension pans with a pin-in-hole structure. 
     To expand each portion, at least two rack and pinion mechanisms in each portion may be employed. The head deck  105  may have two head rack and pinion mechanisms housed in head deck rack and pinion mechanism housing tubes  2061 . The two head rack and pinion mechanisms may be linked by pinion gear shaft  2071  so that the two head rack and pinion mechanisms operate in unison to expand the head deck  105 . The seat deck  2001  and knee deck  107  may have two rack and pinion mechanisms each housed in seat and knee deck rack and pinion mechanism housing tubes  2062 ,  2063 , respectively. The seat and knee deck rack and pinion mechanisms may be linked by pinion gear shafts  2072 ,  2073 , respectively. The rack and pinion mechanisms of seat deck may be linked by pinion gear shaft  2075  to the rack and pinion mechanisms of the knee deck so that the four rack and pinion mechanisms operate in unison to expand the seat-supporting and knee decks together. In an alternative embodiment, one of the rack and pinion mechanisms in the knee deck may be replaced by a simple slide mechanism, for example a tube-in-tube arrangement. The foot deck  2002  may have two foot deck rack and pinion mechanisms housed in foot deck rack and pinion mechanism housing tubes  2064 . The two foot deck rack and pinion mechanisms may be linked by pinion gear shaft  2074  so that the two foot deck rack and pinion mechanisms operate in unison to expand the foot deck  2002 . 
     To illustrate more clearly the operation of the rack and pinion mechanisms and the deck extension latch mechanisms, reference is made to  FIG. 21 ,  FIG. 22 ,  FIG. 23 ,  FIG. 24  and  FIG. 25 , which illustrate a rack and pinion mechanism  2065  and the deck extension latch mechanism  2051  of the head deck  105 . The rack and pinion mechanisms and the deck extension latch mechanisms of the other deck portions may be similar. 
     As discussed above, the head deck  105  may comprise two head deck extension pans  2031 , one on each side of the head deck, on which may be mounted mattress keepers  2003 . Head deck extension handles  2041  and manual cardiopulmonary resuscitation (CPR) quick release handles  124  may be mounted on the under-surface of the head deck extension pans  2031 . The CPR handles  124  may be cabled to the decks articulating features so that pulling on the handle releases the deck to return automatically to the prone position under the force of gravity more quickly than is achieved by driving the actuator normally. The head deck extension handles  2041  may be cabled or electronically connected to the head deck extension latch mechanism  2051  so that pulling on the handle disengages the head deck extension latch mechanism  2051  so that the head deck  105  may be expanded. 
     Each rack and pinion mechanism  2065  may comprise two extension cross-members for a total of four extension cross-members  2081 ,  2082 ,  2083 ,  2084 . Extension cross-members  2081  and  2083  may be fixed to and support the head deck extension pan on one side of the head deck and extension cross-members  2082  and  2084  may be fixed to and support the head deck extension pan on the other side of the head deck. The extension cross-members may be configured so that the extension cross-members supporting one deck extension pan may be directly adjacent corresponding extension cross-members supporting the other deck extension pan. Thus, extension cross-member  2083  may be adjacent to and to the inside of extension cross-member  2084 , while extension cross-member  2081 , which supports the same deck extension pan as extension cross-member  2083 , may be beside and to the outside of extension cross-member  2082 . The extension cross-members may be slidably supported in head deck rack and pinion mechanism housing tube  2061  attached to the head deck  105 , the head deck rack and pinion mechanism housing tube  2061  comprising tube cap  2070 . 
     The extension cross-members  2081 ,  2082 ,  2083 ,  2084  may comprise toothed racks  2076 ,  2077 ,  2080 ,  2089 , respectively. The extension cross-members  2081 ,  2082 ,  2083 ,  2084  may comprise a toothed profile as shown, which serves as the toothed racks, or toothed racks may be machined and attached to the extensions cross-members  2081 ,  2082 ,  2083 ,  2084 . The elongated through-apertures and toothed racks on neighboring extension cross-members may be aligned in the same horizontal plane so that pinion gear  2068  can mesh with and rest on toothed tracks  2076  and  2077  simultaneously and pinion gear  2069  can mesh with and rest on toothed tracks  2086  and  2089  simultaneously. Each of the pinion gears  2068  and  2069  may alternatively be two separate gears for a total of four pinion gears each associate with one of the four toothed tracks. The pinion gears  2068 ,  2069  may be mounted on and fixedly connected to pinion gear shaft  2071 , the pinion gear shaft  2071  capable of rotating with the pinion gears. The pinion gears  2068 ,  2069  and pinion gear shaft  2071  may be secured by pinion retainers  2078 ,  2079 . The pinion retainers  2078  and  2079  may be fixedly mounted on the deck (mount not shown) to prevent longitudinal and lateral motion of the pinion gear shaft  2071 , thereby keeping the pinion gears  2068 ,  2069  captured in their respective toothed tracks and on the same longitudinal axis while the gears and pinion gear shaft rotate. 
     In operation, activating the latch release structure of one of the head deck extension handles  2041  may disengage the head deck extension latch mechanism  2051 , which permits lateral movement of the extension cross-members  2081 ,  2082 ,  2083 ,  2084  and hence the head deck extension pans  2031 . If the head deck extension handle  2041  on the head deck extension pan  2031  supported on extension cross-members  2082  and  2084  is pulled, the extension cross-members  2082  and  2084  will be pulled laterally. The lateral motion of the extension cross-members  2082  and  2084  may cause the pinion gears  2068 ,  2069  to rotate due to the action of the teeth in toothed tracks  2077 ,  2089  with which the pinion gears  2068 ,  2069  are meshed. Because the pinion gears  2068 ,  2069  are restricted from moving laterally, rotation of the pinion gears  2068 ,  2069  also may cause the extension cross-members  2081 ,  2083  to begin lateral movement since the two pinion gears  2068 ,  2069  may be also meshed with the toothed tracks  2076 ,  2080  in extension cross-members  2083 ,  2081 , respectively. The extension cross-members  2081  and  2083  will move on the opposite direction of the extension cross-members  2082  and  2084  because they are on opposite sides of the head deck  105 . Because the two pinion gears  2068 ,  2069  may be fixedly connected to the pinion gear shaft  2071 , the rotational speeds of both gears may be the same, which prevents the extension cross-members at one end of the head deck  105  from getting ahead of or behind the extension cross-members at the other end of the head deck. In this way, the head deck  105  may expand uniformly without jamming of the extension cross-members. Further, because the extension cross-members supporting the head deck extension pan on one side may be linked through the pinion gears  2068 ,  2069  to the extension cross-members supporting the head deck extension pan on the other side, it is only necessary for one operator to operate the expanding feature from one side of the patient support. Once the head deck extension pans  2031  and the extension cross-members  2081 ,  2082 ,  2083 ,  2084  have moved laterally to the desired position (e.g. second width or third width), the head deck extension latch mechanism  2051  re-engages. To return the head deck  105  to a narrower width, the latch release structure of one of the head deck extension handles  2041  may be activated again and the extension cross-members together with the head deck extension pan  2031  on one side pushed laterally back toward the middle. 
     Alternatively or additionally, rotation of the pinion gears  2068 ,  2069  may be motorized by connecting the pinion gear shaft  2071  to an actuator. The actuator should be bi-directional. The actuator may be a multi-speed actuator. 
     Wheels  2085 ,  2086 ,  2087 ,  2088  protruding from upper surfaces of the extension cross-members  2081 ,  2082 ,  2083 ,  2084 , respectively, may be provided to reduce friction between the extension cross-members and the tubes  2061  housing the extension cross-members. Corresponding wheels  2085 ′,  2086 ′,  2087 ′,  2088 ′ protruding from the bottom surfaces of the extension cross-members may provide the same function below the extension cross-members. 
     Comparison of  FIG. 21  to  FIG. 23  illustrates the difference in configuration of the extension cross-members  2081 ,  2082 ,  2083 ,  2084  between the standard first width and the expanded third width of the head deck  105 . At the standard first width ( FIG. 21 ), the through-apertures of adjacent extension cross-members may be nearly aligned laterally, whereas at the expanded third width ( FIG. 23 ) the through-apertures may be substantially less aligned than at the standard first width. 
       FIG. 24  and  FIG. 25  provide more detail of the head deck extension latch mechanism  2051 . The head deck extension latch mechanism  2051  may comprise a spring-loaded pin  2090  loaded in a wrap spring  2091  housed in extension latch housing  2035 , the pin  2090  biased by the spring  2091  toward the extension cross-member  2083  through an aperture (not shown) in the latch housing  2035 . When the spring-loaded pin  2090  is aligned with an aperture  2092  in the extension cross-member  2083 , the pin  2090  is forced into the aperture  2092  by the spring  2091 . Because the latch housing  2035  may be fixedly mounted to longitudinal supporting strut  2095  and the housing tube  2061  (not shown in  FIG. 24  and  FIG. 25 ), which do not move with the extension cross-member  2083 , the extension cross-member  2083  may be prevented from moving when the pin  2090  is engaged in the aperture  2092 . The head deck extension latch mechanism  2051  may further comprise a lever  2093  connected to the pin  2090  by a linking pin  2099  through an arcuate slot  2039  in the lever  2093 . A cable (not shown) attached to aperture  2038  of the lever  2093  and threaded through cable groove  2036  and cable guide  2098  may be attached at the other end to the head deck extension handle  2041 . Another cable (not shown) also attached to the aperture  2038  of the lever  2093  may be threaded through cable groove  2037  and another cable guide on longitudinal supporting strut  2096  terminating at the head deck extension handle on the other side of the head deck. Activating the latch release structure on the head deck extension handle  2041  pulls the cable causing the lever  2093  to pivot in turn pulling the spring-loaded pin  2090  out of the aperture  2092 . The extension cross-member  2083  may now be permitted to move and lateral movement of the extension cross-member  2083  brings the spring-loaded pin  2090  into alignment first with aperture  2094  in the extension cross-member  2083 . Releasing the pin  2090  into the aperture  2094  locks the extension cross-member  2083  into place at the second width position. If the extension cross-member  2083  was allowed to move until the spring-loaded pin  2090  aligned with aperture  2097 , releasing the pin  2090  into the aperture  2097  locks the extension cross-member  2083  into place at the expanded third width position. Holding the deck extension handle  2041  keeps the spring-loaded pin  2090  retracted, while releasing the deck extension handle  2041  allows the spring  2091  to bias the pin  2090  toward the cross-member apertures  2092 ,  2094  or  2097 . 
     With reference to  FIG. 26 , the head deck extension handle  2041  is shown comprising manual latch release structure  2045  having an aperture to which the cable (not shown) is connected, the cable being fed through aperture  2046  in the deck extension handle  2041 . Pulling up on handle portion  2047  pulls the cable and releases the head deck extension latch mechanism by pulling the spring-loaded pin out of the aperture in the extension cross-member. Alternatively or additionally, the head deck extension handle  2041  may provide an electric switch for electrically locking/unlocking the extension latch mechanism. The electric switch may comprise a spring-leaf electrical contact  2048  and a button electrical contact  2049 . Pushing down on handle portion  2047  brings the spring-leaf electrical contact  2048  into electrical contact with the button electrical contact  2049 , which completes a circuit and sends a signal to a solenoid associated with the spring-loaded pin to pull the pin out of the aperture in the extension cross-member. The signal may be sent through wires or wirelessly. 
     To facilitate access to under-components of the patient support, easily removable and remountable deck panels are desirable. Such access may be required for servicing under-components of the patient support or to retrieve debris or other items that have become lodged under the deck panels. Further, in combination with the extending deck features described above, it may be desirable to use a larger deck panel when the width of the deck is adjusted to wider positions. Therefore, deck panels that may be readily interchanged are desirable. 
     With reference to  FIG. 27A  and  FIG. 27B , easily removable and remountable deck panels may be achieved with the use of ball and socket connectors. An underside of the head deck panel  2005  as shown in  FIG. 27A  may comprise protruding ball studs  2160  secured in the deck panel  2005 . Securing the ball stud may be accomplished, for example, by gluing a stud  2161  of the ball stud  2160  in an aperture in the underside of the deck panel  2005  or by threadably engaging a threaded stud with mating threads in an aperture in the deck panel  2005 . A similar arrangement may be employed with the other deck panels of the patient support. Corresponding sockets  2163  for receiving balls  2162  of the ball studs  2160  may be mounted on or in apertures on longitudinal or transverse supporting struts of the deck. The sockets  2163  may be mounted in such a way that the deck panel can only be secured in place when it is in the correct orientation on the deck. 
     With specific reference to  FIG. 27B , when mounting the deck panel on the deck, the ball  2162  of the ball stud  2160  may be aligned with an aperture  2164  in the corresponding socket  2163  and then pressed into an annular ball receiver  2165 . The annular ball receiver  2165  may be arcuately-shaped to conform to the shape of the ball  2162 . The diameter of the ball  2162  may be slightly larger than the diameter of the aperture  2164  and deformation of the ball  2162 , the annular ball receiver  2165  or both permits ingress of the ball  2162  into the annular ball receiver  2165 . Engagement of the ball  2162  within the arcuately-shaped annular ball receiver  2165  frictionally secures the ball  2162  in the ball receiver  2165 . The lower part of the socket  2163  including the ball receiver  2165  may be disposed on one side of an aperture in a supporting strut of the deck, while an upper lip  2166  engages with the surface of the supporting strut on the other side of the aperture to prevent the socket  2163  from sliding completely through the aperture in the supporting strut. An outer bulge in the ball receiver  2165  together with the upper lip  2166  may secure the socket  2163  in the aperture in the supporting strut. To remove the deck panel from the deck, sufficient upward force may be applied to the deck panel to force the ball  2162  out of the ball receiver  2165 , which is permitted by deformation of the ball  2162 , the annular ball receiver  2165  or both. One or both of the ball  2162  or ball receiver  2165  may be made of resilient material (e.g. an elastomer) that permits some deformation. Preferably, the entire socket  2163  is made of a resilient material. 
     In order to accommodate the extending deck features and to distribute the patient load more evenly over the casters when the deck is in a wider position, it would be desirable to have the casters farther apart laterally when the deck is in wider positions. Referring to  FIG. 28A  and  FIG. 28B , perspective views of the caster frame  142  in a fully retracted position for a standard first width deck ( FIG. 28A ) and in an expanded position ( FIG. 28B ) are shown. The caster frame  142  may comprise caster frame main rails  2171  extending longitudinally between and linking two caster assemblies  118 . The caster assemblies  118  may comprise caster frame cross-members  2172 , which may be rectangular tubes that house caster extension slide tubes  2173   a,b,  which are best seen in  FIG. 28B . Near the four intersections of the caster frame main rails  2171  and caster frame cross members  2172  are four lower frame support brackets  2183  that support the lower frame (not shown) on the caster frame  142 . Each caster frame cross-member  2172  may house left and right caster extension slide tubes  2173   a,b,  the slide tubes  2173   a,b  slidable laterally within the caster frame cross-member  2172 . Connecting the left and right caster extension slide tubes  2173   a,b  of each caster assembly  118  may be caster extension actuators  2174 . The caster assemblies  118  may be equipped with brake pedals  117  that may be connected to brake lever mechanisms  2175  that may actuate brake control rods  2181  connecting the brake lever mechanisms  2175  to the casters  119 . The brake control rods  2181  may extend between the casters  119 , the brake control rods  2181  comprising two separate portions to permit expansion with the caster frame as shown in  FIG. 30A  and  FIG. 30B , inside the caster extension slide tubes  2173   a,b.  The caster frame  142  may be mounted on the casters  119  proximate each corner of the caster frame  142 . 
       FIG. 29A  and  FIG. 29B  show close-up views of the caster assembly  118  at one end of the caster frame  142  depicted in  FIG. 28A  and  FIG. 28B , respectively. Lateral extension of the casters  119  of a caster assembly  118  may be controlled by the caster extension actuator  2174 , which may be an actuator comprising a housing  2176  and a rod  2178 . The rod  2178  may be attached to first caster extension slide tube  2173   a,  while the housing  2176  may be attached to second caster extension slide tube  2173   b.  The ends of the caster extension actuator  2174  are attached to the caster extension slide tubes  2173   a,b  through slots  2179  in a side of the caster frame cross-member  2172 . The casters  119  are mounted on the caster extension slide tubes  2173   a,b  proximate the ends of the slide tubes  2173   a,b.    
       FIG. 30A  and  FIG. 30B  show close-up views of the caster assembly  118  of  FIG. 29A  and  FIG. 29B , respectively, with the caster frame cross-member removed to more clearly show how the caster extension slide tubes  2173   a,b  may be disposed in relation to caster extension actuator  2174  that drives the caster extension slide tubes  2173   a,b.  It can be seen that the end of rod  2178  may be secured to the first caster extension slide tube  2173   a  and the end of the housing  2176  may be secured to the second caster extension slide tube  2173   b  through linkages  2180 . It would be evident that the caster extension actuator  2174  may have the reverse orientation whereby the rod  2178  may be secured to the second caster extension slide tube  2173   b  and the end of the housing  2176  may be secured to the first caster extension slide tube  2173   a.    
     Starting in the retracted position ( FIG. 29A ), when the rod  2178  of the caster extension actuator  2174  starts extending one or both of the caster extension slide tubes  2173   a,b  may start to move laterally outwardly because the two caster extension slide tubes  2173   a,b  may be attached to the caster extension actuator  2174 , the caster extension slide tubes  2173   a,b  may be slidable within the caster frame cross-member  2172 , and the caster extension slide tubes  2173   a,b  may not be attached to each other. It may not be necessary, and may often not be the situation due to unbalanced load, that both caster extension slide tubes  2173   a  and  2173   b  slide in tandem. If the frictional forces on one of the slide tubes are greater than the other, then the slide tube experiencing less frictional first would move laterally before the other slide tube. The other slide tube may move laterally once the first slide tube reached its stop position. The linkages  2180  between the caster extension actuator  2174  and the caster extension slide tubes  2173   a,b  may move within the slots  2179  of the caster frame cross-member  2172  as the caster extension slide tubes  2173   a,b  slide within the caster frame cross-member  2172 . The position of the casters  119  in the expanded position is shown in  FIG. 29B . As may be seen by the above description, only the caster extension slide tubes  2173   a,b  carrying the casters  119  and the ends of the caster extension actuator  2174  may move when the caster frame is extended laterally. Reversing the direction of the caster extension actuator  2174  reduces the lateral distance between the caste wheels  119 . To reduce the chance of binding the mechanism, the casters  119  may be unlocked during width adjustment so that the casters  119  may pivot in order to align the direction of roll in the lateral direction. Software associated with the control circuitry may be used to ensure that the casters  119  are unlocked during movement of the caster extension actuator  2174  when the caster frame is extending or retracting. 
     Width extension of the deck of the patient support, for example from the first to the second and third widths, creates the potential for entrapment zones between the headboard and the head rails of the patient support. It is therefore desirable to fill-in entrapment zone spaces created when the deck is extended to larger widths, preferably in an easy to use and adjust manner. An indexable, two-piece, split headboard may be provided that can be manually adjusted and/or positioned as required depending on the width of the deck. Each headboard may have two sections, each section having at least one mount that installs on a headboard supporting base. Each section can be removed, adjusted, and replaced as required to suit selected deck width and to maintain required entrapment spacing. Thus, in one embodiment, the width of the extending headboard may be adjusted manually by utilizing two movable pieces having downwardly extending mounting posts that may be selectively engaged in different post sockets at different positions along a headboard supporting base. No extra gap filler and no sliding parts may be required, making the extendible headboard simpler, safer and/or more robust. In another embodiment, the headboard may be driven by an actuator in which the two-pieces do slide. 
       FIG. 31A  and  FIG. 31B  depict an extendible headboard  106  at a standard first width supported on a headboard mounting bracket  2101 . The headboard mounting bracket  2101  may be supported on headboard insert  2114 , which may be supported in the upper frame headboard mount on the upper frame (not shown) at the head end of the patient support. The headboard  106  may have two sections, a first headboard section  2106   a  and a second headboard section  2106   b,  the headboard sections comprising headboard openings  2107 , which may be used as handgrips for handling the headboard  106 . First and second headboard support clips  2112   a,    2112   b  may be employed to help secure the sections together at the top and a headboard lock knob  2113  at the bottom may be used to lock the headboard sections  2106   a,    2106   b  in place. 
     As shown in  FIG. 31C , the headboard  106  may further comprise downwardly depending mounting posts. Any suitable number of mounting posts may be utilized. For example, there may be two laterally spaced-apart mounting posts  2108   a,    2108   b  depending downwardly from the first headboard section  2106   a  and two laterally spaced-apart mounting posts  2109   a,    2109   b  depending downwardly from the second headboard section  2106   b.  Referring to  FIG. 31D , a trapeze  2105  may be mounted on the headboard mounting bracket  2101  to provide a mount for accessories such as oxygen tanks, IV bags and others. 
     Still referring to  FIG. 31D , the headboard mounting bracket  2101  may also comprise two or more post sockets for receiving the mounting posts. As shown in  FIG. 31D , the headboard mounting bracket  2101  may comprise ten post sockets  2110   a - e,    2111   a - e,  five posts sockets  2110   a - e  on one side of the headboard mounting bracket for receiving mounting posts  2108   a,    2108   b  and five posts sockets  2110   a - e  on the other side of the headboard mounting bracket for receiving mounting posts  2109   a,    2109   b.  On a given side of the headboard mounting bracket  2101 , the post sockets may be spaced apart so that the distance from one post socket to the post socket two over may be substantially the same as the distance between the mounting posts. For example, the distance between posts sockets  2111   e  and  2111   c  may be substantially the same as the distance between the mounting posts  2109   a,    2109   b.  The headboard  106  may be mounted on the headboard mounting bracket  2101  by aligning the mounting posts with the post sockets and sliding the mounting posts into the post sockets. The headboard  106  may be removed from the headboard mounting bracket  2101  by pulling headboard  106  up so that the mounting posts slide out of the post sockets. 
     As further illustrated in  FIG. 32 , the headboard  106  may be physically separated into two parts, the first headboard section  2106   a  and the second headboard section  2106   b.  The first headboard section  2106   a  may be monolithic having first and second sides where the second side may be of smaller dimensions than the first side. The second headboard section  2106   b  may be monolithic having first and second sides both of which are of smaller dimension that the first side of the first headboard section  2106   a,  where the second side of the second headboard section  2106   b  may comprise the second headboard support clip  2112   b  having an opening  2102  in which the second side of the first headboard section  2106   a  may be retained. The dimensions of the second side of the first headboard section  2106   a  may permit the second side of the first headboard section  2106   a  to fit through the opening in  2102  to thereby engage with the second headboard support clip  2112   b.  The second side of the first headboard section  2106   a  may be thus retained within the second headboard support clip  2112   b  at any lateral position along the second side of the first headboard section  2106   a,  thereby effectively permitting adjustment of the width of the entire headboard  106  depending on the lateral distance between the edge of the second side of the second headboard section  2106   b  and the edge of the first side of the first headboard section  2106   a.  Alternatively, the features of the first and second headboard sections  2106   a,    2106   b  may be reversed. One or both of the headboard sections  2106   a,    2106   b  may be hollow. 
       FIG. 33  illustrates the headboard  106  at three different widths: the first standard width ( FIG. 33A ); the second intermediate width ( FIG. 33B ); and, the third more expanded width ( FIG. 33C ). At the first width, the mounting posts  2108   a  and  2108   b  of the first headboard section  2106   a  may be aligned with, slid into and retained in post sockets  2110   c  and  2110   e  toward the middle of the headboard mounting bracket  2101 , while the mounting posts  2109   a  and  2109   b  of the second headboard section  2106   b  may be aligned with, slid into and retained in post sockets  2111   e  and  2111   c  toward the middle of the headboard mounting bracket  2101 . At the first width, the second side of the first headboard section  2106   a  may not be visible from the foot end. To adjust the headboard  106  to the second or third widths, the two sections  2106   a,    2106   b  of the headboard may be lifted out of the sockets and the mounting posts  2108   a,b  and  2109   a,b  may be slid into sockets towards the outer sides of the headboard mounting bracket  2101 . Thus, at the second position ( FIG. 33B ), the mounting posts  2108   a  and  2108   b  of the first headboard section  2106   a  may be aligned with, slid into and retained in post sockets  2110   b  and  2110   d,  respectively, while the mounting posts  2109   a  and  2109   b  of the second headboard section  2106   b  may be aligned with, slid into and retained in post sockets  2111   d  and  2111   b,  respectively. At the third position ( FIG. 33B ), the mounting posts  2108   a  and  2108   b  of the first headboard section  2106   a  may be aligned with, slid into and retained in post sockets  2110   a  and  2110   c,  respectively, while the mounting posts  2109   a  and  2109   b  of the second headboard section  2106   b  may be aligned with, slid into and retained in post sockets  2111   c  and  2111   a,  respectively. The second side of the first headboard section  2106   a  becomes visible from the foot end of the patient support at the second and third widths. The two headboard sections  2106   a,    2106   b  therefore always provide an effective block at every width effectively eliminating any entrapment zone. The two headboard sections  2106   a,    2106   b  provide a blocking structure which is as effective as a similar single-piece blocking structure of the same dimension. Because the horizontal channel  2102  in the second headboard section  2106   b  covers and retains the upper edge of the second side of the first headboard section  2106   a,  it may be more effective to remove the second headboard section  2106   b  first and replace it last when adjusting the width of the headboard  106 . 
     With reference to  FIG. 34A ,  FIG. 34B ,  FIG. 34C ,  FIG. 34D ,  FIG. 34E  and  FIG. 34F , in an alternate embodiment of an extendible headboard  106 , a headboard tray  2119  is provided in which the headboard  106  sits and that spans both headboard sections. The downwardly depending mounting posts  2108   a,    2108   b,    2109   a  and  2109   b  protrude through a slot  2103  in the tray  2119 . Each downwardly depending mounting post  2108   a,    2108   b,    2109   a  and  2109   b  are provided with slots in which an inner edge of the tray  2119  may engage. The slot  2103  comprises an enlarged opening  2104  that provides a post-install position at which the mounting posts  2108   a,    2108   b,    2109   a  and  2109   b  may be inserted through the tray  2119 . Expanding the headboard  106  from the narrowest width ( FIG. 34A-B ) to the widest width ( FIG. 34E-F ) is accomplished by simply sliding the headboard sections apart while the sections are in the tray  2119 . The tray serves to keep the headboard sections together during width adjustment to facilitate handling the headboard  106 . Otherwise, the operation of the headboard  106  is as described in the previous embodiment. 
     With reference to  FIG. 35A  and  FIG. 35B , in an alternate embodiment of an extendible headboard  106 , the first headboard section  2106   a  and the second headboard section  2106   b  may be driven apart or together by a length extendible headboard actuator  2115 . A base  2116  of the headboard actuator  2115  may be secured to a head end side of the first headboard section  2106   a  and a rod  2117  of the headboard actuator  2115  may be secured to a head end side of the second headboard section  2106   b.  It is evident that the base  2116  and rod  2117  of the headboard actuator  2115  may be secured to the other headboard sections if desired. Extension and retraction of the headboard actuator  2115  may cause the headboard sections  2106   a,    2106   b  to move laterally in opposite directions with respect to each other in a headboard track  2118  in a top surface of the headboard mounting bracket  2101 . First and second headboard support clips  2112   a,    2112   b  may still be employed to help secure the sections together at the top. 
     Many patient supports have a mattress length of about 84 inches (7 feet), the mattress extending from the headboard to the footboard. Sometimes it is desirable to extend the length of the patient support to accommodate extra tall patients. Prior art methods of extending patient support length generally involve extending the length of the deck, particularly the foot deck. Extending the length of the deck can involve complicated mechanical arrangements, often requiring actuator driven features. Less complicated and less mechanically intensive arrangements for extending the length of the patient support are therefore desirable. 
     Rather than extending the length of the patient support by changing the length of the deck platform, the length of the patient support from headboard to footboard may be integrated into a removable footboard. By extending the length of the patient support without having to extend the deck, no installation of accessory pieces may be required. Extending the length of the patient support with features associated with a removable footboard permit extending the length by any desired increment. For example, the removable footboard may be indexable into two or more length positions. In practice, it is often sufficient to be able to accommodate the standard 84 inch length and additional lengths of 88 inches and 92 inches. 
     Length extension of the patient support may involve moving the footboard longitudinally further away from the headboard. The footboard may be mounted on the patient support through pivoting linkage arms, whereby pivoting of the linkage arms may result in longitudinal movement of the footboard either toward or away from the foot end of the patient support. The pivoting linkage arms may or may not be indexed to certain positions. The pivoting linkage arms may or may not be lockable into place at certain positions. The pivoting linkage arms permit folding allowing for compact design. 
       FIG. 36A ,  FIG. 36B ,  FIG. 37A ,  FIG. 37B ,  FIG. 37C  and  FIG. 37D  depict perspective views of a first embodiment of an extendible footboard. Extendible footboard  2120  may comprise mounting posts  2121  mounted on a footboard mounting bracket  2123  of the patient support. Each mounting post  2121  may comprise a lower half, which may be mounted on the patient support, and an upper half  2122 , which may be secured to footboard panel  2124 . The upper and lower halves of the mounting posts may be separate pieces linked together by linkage arms  2125 ,  2126 . The lower halves of the mounting posts  2121  may be supported by a transverse support plate  2154  in order to keep the mounting posts  2121  aligned with receiving apertures  2155  in the footboard mounting bracket  2123 . First linkage arms  2125  may be pivotally mounted on the upper halves  2122  of the mounting posts. Second linkage arms  2126  may be pivotally mounted on the lower halves of the mounting posts  2121 . Pivotal mounting of the linkage arms to the mounting posts may be accomplished by having the mounting posts journaled in apertures in the linkage arms with sufficient tolerance between the mounting posts and an edge of the apertures to permit rotation of the linkage arms around the mounting posts. The first and second linkage arms may be pivotally connected to each other by linking pins at pivot points  2127 . 
     When the footboard  2120  is in the standard length fully retracted position as seen in  FIG. 36A , the linkage arms  2125 ,  2126  may point substantially laterally and may be folded together and occupy compartments  2129  in the footboard panel  2124  in such a configuration that the upper halves  2122  and lower halves of the mounting posts  2121  are vertically aligned. Spring-loaded locking pins  2128  housed inside the upper halves  2122  of the mounting posts may be biased into hollow portions of the lower halves of the mounting posts  2121  as best seen in  FIG. 37B  and  FIG. 37D . The locking pins  2128  may prevent the footboard  2120  from moving when the footboard is in the fully retracted position. The locking pins  2128  may be connected to a lift bar  2130 , for example a mattress pump hanger bracket, such that lifting the lift bar  2130  may lift the locking pins  2128  out of the lower halves of the mounting posts  2121  thereby permitting the footboard panel  2124  to move away from the patient support to a fully extended position as seen in  36 B. As the footboard panel  2124  moves, the first and second linkage arms  2125 ,  2126  unfold pivoting around the upper and lower halves of the mounting posts  2121  and around the linking pins at pivot points  2127  until the linkage arms  2125  and  2126  both point substantially longitudinally.  FIG. 37A  (back view) and  FIG. 37B  (front view) show the footboard  2120  with the lift bar  2130  and the locking pin  2128  attached thereto both in a down position, therefore the footboard  2120  in the fully retracted position is locked.  FIG. 37C  (back view) and  FIG. 37D  (front view) show the footboard  2120  with the lift bar  2130  and the locking pin  2128  attached thereto both in an up position, therefore the footboard  2120  is unlocked and free to extend. 
     A locking mechanism, for example a lock bolt at the pivot point  2127 , may be employed to prevent the linkage arms  2125 ,  2126  from pivoting when it is desired to keep the footboard  2120  in the fully extended position, or in any other position intermediate between the standard fully retracted position and the fully extended position. Moving the footboard panel  2124  back toward the foot end of the deck of the patient support may return the linkage arms  2125 ,  2126  to compartment  2129 , thereby aligning the upper and lower halves of the mounting posts  2121  permitting the locking pin  2128  to once again secure the footboard  2120  in the fully retracted position. 
       FIG. 38A ,  FIG. 38B ,  FIG. 38C ,  FIG. 39A ,  FIG. 39B  and  FIG. 39C  depict a second embodiment of an extendible footboard. Extendible footboard  2140  may comprise footboard mounting bracket  2143  and footboard panel  2144 . The footboard mounting bracket  2143  may be mounted on a footboard insert (not shown) of the patient support. The footboard panel  2144  may be linked to the footboard mounting bracket  2143  by pivoting linkage arms  2145 ,  2146 ,  2147 . First linkage arms  2145  may be pivotally connected to panel mounting posts  2142  secured to the footboard panel  2144  and to central mounting posts  2148  external to and between the footboard mounting bracket  2143  and footboard panel  2144 . Second linkage arms  2146  may be pivotally connected to the footboard mounting posts  2141  secured inside the footboard mounting bracket  2143  and to the central mounting posts  2148 . Third linkage arms  2147  may be pivotally connected to indexable mounting posts  2149  inside the footboard mounting bracket  2143  and to the central mounting posts  2148 . Pivotal mounting of the linkage arms to all of the mounting posts may be accomplished by having the mounting posts journaled in through channels in the linkage arms with sufficient tolerance between the mounting posts and an edge of the through channels to permit rotation of the linkage arms around the mounting posts. Linkage arms  2146  and  2147  may extend from the central mounting posts  2148  to the footboard mounting posts  2141  and the indexable mounting posts  2149 , respectively, through an aperture  2150  in a foot end face of the footboard mounting bracket  2143 , because both the footboard mounting posts  2141  and the indexable mounting posts  2149  may be inside the footboard mounting bracket  2143 . 
     Indexable mounting posts  2149  may be movable laterally inside the footboard mounting bracket  2143 . The footboard mounting bracket  2143  may comprise two or more index apertures in upper and/or lower surfaces of the footboard mounting bracket  2143 , which are configured to receive index pins to lock the indexable mounting posts  2149  in position. In this embodiment, there are three sets of index apertures  2151 ,  2152 ,  2153 , each set of index apertures comprising vertically aligned apertures in the upper and lower surfaces of the footboard mounting bracket  2143 . Each set of index apertures corresponds to a position of the footboard, where index apertures  2151  correspond to the standard 84 inch fully retracted position as shown in  FIG. 38A  and  FIG. 39A , index apertures  2152  correspond to the 88 inch position as shown in  FIG. 38B  and  FIG. 39B , and index apertures  2153  correspond to the 92 inch position as shown in  FIG. 38C  and  FIG. 39C . To secure the footboard  2140  in a position, the indexable mounting posts  2149  may be aligned with one of the sets of index apertures by moving the footboard panel  2144  longitudinally toward or away from the patient support, and then locking pins may be inserted through the index apertures in the upper surface of the footboard mounting bracket  2143 , through a hollow interior of the indexable mounting posts  2149  and out through the index apertures in the lower surface of the footboard mounting bracket  2143 . Removing the locking pins may permit adjustment of the footboard panel  2144  to achieve a different position for the footboard. 
     Endboards (headboard and footboard) often need to be removed to facilitate greater access to a patient. Further, with the extending headboard and/or footboard features, endboards may need to be removed to permit expansion or contraction of endboard width when the patient support deck is expanded or contracted. However, it is also desirable to be able to prevent removal of the endboards when removal is undesired. Since the endboards, especially the headboard, are often used by care givers to guide the patient support when the patient support is being moved on its casters, it may be especially important to have a mechanism for locking the endboards in place. It is therefore desirable to have a simple mechanism for locking and unlocking the endboards in order to facilitate endboard removal and replacement, while preventing removal of the endboard when removal is undesired. 
     With reference to  FIG. 40A ,  FIG. 40B ,  FIG. 40C ,  FIG. 41A ,  FIG. 41B ,  FIG. 42A ,  FIG. 42B ,  FIG. 42C  and  FIG. 42D , a mechanism for locking and unlocking a headboard is described.  FIG. 40A  and  FIG. 40B  show the locking and unlocking mechanism in a locked position. The description herein may be equally applicable to footboards. 
     The locking and unlocking mechanism may comprise a locking plate  2320  extending laterally from proximate one side of the headboard mounting bracket  2101  to proximate the other side. The locking plate  2320  may be mounted within the headboard mounting bracket  2101 , the headboard mounting bracket being mounted on the headboard insert  2114  as described above. The headboard mounting bracket  2101  may be a rectangular tube having socket apertures through upper and lower surfaces thereof through which post sockets  2110   a - e,    2111   a - e  may be inserted. The post sockets  2110   a - e,    2111   a - e  may be retained within the headboard mounting bracket  2101  by capturing an inner edge of the socket apertures between an upper lip  2335  and outwardly flaring retainer tabs  2336  of the post sockets as best seen in  FIG. 42C . More or less than the ten post sockets shown in the figures may be used. The downwardly depending mounting posts  2108   a,b,    2109   a,b  of the headboard may be inserted into four post sockets, in this case  2110   c,    2110   e,    2111   e  and  2111   c  representing the headboard being in the standard width has described above. More or less than the four mounting posts shown in the figures may be used. 
     The locking plate  2320  may comprise a series of locking plate through apertures  2321  (only one labeled) that align with the post sockets  2110   a - e,    2111   a - e.  The locking plate through apertures  2321  may be bounded by inner edges of the locking plate  2320 . The inner edges of the locking plate  2320  that define the boundaries of the locking plate through apertures  2321  may comprise post disengaging portions  2322  and post engaging portions  2323  (only one each labeled). The post disengaging portions  2322  may be shaped and sized such that when the post disengaging portions  2322  are aligned with the post sockets  2110   c,    2110   e,    2111   e,    2111   c  and the downwardly depending mounting posts  2108   a,b,    2109   a,b  therein, the downwardly depending mounting posts  2108   a,b,    2109   a,b  may be removed from the post sockets  2110   c,    2110   e,    2111   e,    2111   c.  The post engaging portions  2323  may be shaped and sized such that when the post engaging portions  2323  are aligned with the post sockets  2110   c,    2110   e,    2111   e,    2111   c  and the downwardly depending mounting posts  2108   a,b,    2109   a,b  therein, the downwardly depending mounting posts  2108   a,b,    2109   a,b  may not be removed from the post sockets  2110   c,    2110   e,    2111   e,    2111   c  because the post engaging portions  2323  of the locking plate  2320  may be engaged within locking slots  2324  proximate a bottom of the downwardly depending mounting posts  2108   a,b,    2109   a,b  and within corresponding slots  2325  proximate a bottom of the post sockets  2110   c,    2110   e,    2111   e,    2111   c.  Lateral movement of the locking plate  2320  in one direction may cause alignment of the post disengaging portions  2322  with the post sockets  2110   c,    2110   e,    2111   e,    2111   c  and the downwardly depending mounting posts  2108   a,b,    2109   a,b  therein, while lateral movement of the locking plate  2320  in the other direction may cause the post engaging portions  2322  to engage within the locking slots  2324  in the downwardly depending mounting posts  2108   a,b,    2109   a,b  and within the corresponding slots  2325  in the post sockets  2110   c,    2110   e,    2111   e,    2111   c.  Each downwardly depending mounting post  2108   a,b,    2109   a,b  and each post socket  2110   a - e,    2111   a - e  has two slots, one for engagement with each inner edge of the post engaging portion  2323  of the locking plate  2320 . While the post engaging portions  2322  are engaged within the locking slots  2324 , the downwardly depending mounting posts  2108   a,b,    2109   a,b  may not be removed from the post sockets  2110   c,    2110   e,    2111   e,    2111   c  thereby locking the headboard in place. When the post disengaging portions  2322  are aligned with the downwardly depending mounting posts  2108   a,b,    2109   a,b  and the post sockets  2110   c,    2110   e,    2111   e,    2111   c,  the headboard is unlocked. 
     Lateral movement of the locking plate  2320  may be effected by a single lock knob  2113 . The lock knob  2113  may comprise a rotation hub  2327  mountable in a lock knob mounting aperture  2330  through the lower surface of the headboard mounting bracket  2101 . The lock knob  2113  may be rotatable about a vertical rotation axis A through the rotation hub  2327 . The lock knob  2113  may also comprise a plate engagement pin  2326  depending vertically the lock knob  2113 , the plate engagement pin  2326  configured to engage within pin engagement slot  2329  in an outer edge  2328  of the locking plate  2320 . The plate engagement pin  2326  is located off the vertical rotation axis A so that rotation of the lock knob  2113  will cause the plate engagement pin  2326  to describe an arcuate path. Rotation of the lock knob  2113  in one direction may cause the plate engagement pin  2326  to describe an arcuate path in one direction, this arcuate motion being translated into a lateral motion of the locking plate  2320  in one lateral direction since the plate engagement pin  2326  of the lock knob  2113  is engaged within the pin engagement slot  2329  in the outer edge  2328  of the locking plate  2320 . Rotation of the lock knob  2113  in the opposite direction may cause the plate engagement pin  2326  to describe an arcuate path in the opposite direction, this arcuate motion being translated into a lateral motion of the locking plate  2320  in the other lateral direction. Thus, rotation of the lock knob  2113  may cause the post engaging portions  2323  of the locking plate  2320  to slide in or out of the locking slots  2324  of the downwardly depending mounting posts  2108   a,b,    2109   a,b  resulting in locking or unlocking of the downwardly depending mounting posts  2108   a,b,    2109   a,  and  b.    
     When the lock knob  2113  is in a locked position and the downwardly depending mounting posts  2108   a,b,    2109   a,b  are not in the post sockets, it is not possible to fully insert the downwardly depending mounting posts  2108   a,b,    2109   a,b  into the post sockets because the post engaging portions  2323  of the locking plate  2320  block the post sockets. The lock knob  2113  should be in an unlocked position before inserting the downwardly depending mounting posts  2108   a,b,    2109   a,b  into the post sockets so that the post engaging portions  2323  of the locking plate  2320  may then be engaged within the locking slots  2324  of the downwardly depending mounting posts  2108   a,b,    2109   a,b  by turning the lock knob  2113  to the locked position. 
     Because the locking plate  2320  is inside the headboard mounting bracket  2101  and the lock knob  2113  is outside the headboard mounting bracket  2101 , an arcuate slot  2331  is provided in the lower surface of the headboard mounting bracket  2101  so that the plate engagement pin  2326  may be allowed to travel through its arcuate path when the lock knob  2113  is rotated. The arcuate slot  2331  also provides some support against play in the lock knob  2113  by forcing the plate engagement pin  2326  to follow a particular path. Additionally, index protrusion  2332  on lock knob  2113  may be engaged in one of two index depressions  2333   a,    2333   b  in the lower surface of the headboard mounting bracket  2101  when the lock knob  2113  is in the locked or unlocked positions. Engagement of the index protrusion  2332  in the index depressions  2333   a,    2333   b  ensures that some minimum force is required to be able rotate the lock knob  2113  between the locked (index depression  2333   a ) and unlocked (index depression  2333   b ) positions so that the lock knob  2113  cannot rotate without user intervention once in the locked or unlocked position. Furthermore, decals  2334   a,    2334   b  may be fixed to the headboard mounting bracket  2101  in appropriate locations to provide an indication of whether the headboard is locked (decal  2334   a ) or unlocked (decal  2334   b ). It would be apparent to one skilled in the art that by reversing the directionality of the through apertures  2321  in the locking plate  2320 , the directionality of locking and unlocking would be reversed. 
     With reference to  FIG. 40A  and  FIG. 40B , a second embodiment of a locking plate  2337  for an endboard locking mechanism is illustrated. This embodiment is particularly suited for footboards and a first connection housing  2210  of a blind mate connector is shown for context. The second embodiment operates in a similar fashion as the locking plate  2320  described above, however the locking plate  2337  utilizes only a single exterior edge  2338  to engage a slot in post socket  2111 , and a slot in a mounting post  2121  in the post socket  2111 . The exterior edge  2338  of the locking plate  2337  has an arcuate indentation  2339  that matches the circumference of an inner circular (or elliptical) wall of the post socket  2111 . When the arcuate indentation  2339  is aligned with the inner wall of the post socket  2111 , the footboard is unlocked as shown in  FIG. 40B . Rotating lock knob  2113  shifts the locking plate  2337  so that the arcuate indentation  2339  is misaligned with the inner wall of the post socket  2111  and the exterior edge  2338  of the locking plate  2337  partially occludes the post socket as shown in  FIG. 40A . With the post  2121  in the post socket  2111 , the exterior edge  2338  would also engage within a corresponding slot in the post  2121 , thereby locking the post in place. 
     As described above, a patient support may comprise a caster frame, a lower frame and an upper frame. The upper frame may support the patient support deck, which may support the patient, and the upper frame may also support the footboard and headboard. The upper frame may in turn be supported on the lift mechanism, which may be supported entirely by the lower frame. Thus, the entire load of the patient and the upper frame may be supported by the lower frame through the lift mechanism. The lower frame may be supported by the caster frame on four load cells proximate the corners of the lower frame. 
     Referring to  FIG. 43 , the lower frame  132  of a patient support may comprise lower frame main rails  2190  connected proximate the ends of the main rails  2190  by lower frame cross-members  2191  to form a rectangular frame. The lower frame cross-members  2191  may comprise lower frame hangers  2192  on which may be supported four lower frame bearing blocks  2193  (only a bottom half shown), one proximate each corner of the lower frame  132 . The lower frame bearing blocks  2193  may support the legs of the lift mechanism of the patient support. 
     The lower frame  132  may be supported by the caster frame as shown in  FIG. 44 . As described above, the caster frame  142  may comprise generally longitudinally oriented parallel caster frame main rails  2171  connected at one end by the generally transversely oriented caster frame cross-member  2172 . The lower frame support brackets  2183  may be located proximate the intersections of the caster frame main rails  2171  and the caster frame cross-member  2172 . The lower frame  132  may be positioned underneath the lower frame support brackets  2183  and within the caster frame main rails  2171  and the caster frame cross-member  2172 , whereby the lower frame main rails  2190  may be generally parallel to the caster frame main rails  2171  and the lower frame cross-member  2191  may be generally parallel to the caster frame cross-member  2172 . The lower frame  132  and the caster frame  142  may generally occupy the same transversely oriented plane parallel to the surface on which the casters  119  travel. This feature contributes to permitting the entire patient support structure to be as close to the traveling surface as possible when the patient support is in a low position. 
     The lower frame  132  may be supported by the caster frame  142  by suspending the lower frame  132  from the caster frame  142  beneath the lower frame support brackets  2183 . As can be seen in  FIG. 45A ,  FIG. 45B ,  FIG. 45C ,  FIG. 45D ,  FIG. 45E  and  FIG. 45F , the lower frame support brackets  2183  may comprise downwardly extending flanges  2184 ,  2185  having apertures through which a bolt  2194  may be passed. The bolt  2194  may pass through annular bushings  2195  positioned within an aperture  2196  of a load cell  2197  extending longitudinally out a hollow interior of the lower frame main rail  2190 . The load cell  2197  may be housed in the lower frame main rail  2190  and held in position by a screw  2198  through a top of the lower frame main rail  2190  and the load cell  2197 . The load cell  2197  may be electronically connected to the control circuitry through electrical contact  2199 . 
     Within the aperture  2196  of the load cell  2197  may be annular bushings  2195 , one labeled as  2195   a  and the other labeled as  2195   b  in  FIG. 45D . As shown in  FIG. 45F , each annular bushings  2195   a,    2195   b  may comprise a larger outer portion  2189   a  that is positioned outside of the aperture  2196  of the load cell  2197  and a smaller diameter inner portion  2189   b  that rests inside the aperture  2196  of the load cell  2197 . The faces of the inner portions  2189   b  of the two annular bushing  2195   a,    2195   b  may touch each other or very nearly touch each other inside the aperture  2196 . The annular bushings  2195   a,    2195   b  may comprise a central through aperture  2188  through which the bolt  2194  is inserted. The annular bushings  2195   a,    2195   b  may be designed to compensate for non-axial loading. To this end, the inner portions  2189   b  of the annular bushings  2195   a,    2195   b  may comprise hollows  2187 , which are off a vertical axis, while comprising a thicker region  2186  directly on the vertical axis. The vertical axis is perpendicular to a central lateral axis through the annular bushings  2195   a,    2195   b.  The thicker region  2186  provides rigid support for axial loads. When a non-axial loading is experienced, the hollows  2187  may deform thereby compensating for the non-axial loading so that the entire load remains vertically axial. 
     A similar configuration may be used at each corner of the lower frame  132 ; therefore, the lower frame  132 , the lift mechanism, the upper frame, the patient support deck, the headboard, the footboard, the mattress and the patient may be all supported only on four load cells. The only connection between the lower frame  132  and the caster frame  142  may be through the four load cells. By measuring the load on the four load cells, an accurate measurement of the load on the patient support may be obtained at any given time. By knowing the mass of the components of the patient support, or by taring the scale before the patient enters the patient support, a measurement of the mass of the patient may be obtained from the load cells. 
     Referring to  FIG. 46A ,  FIG. 46B ,  FIG. 46C  and  FIG. 46D , an alternative load cell and an alternative load cell mount are depicted in which a load cell  2340  is bushing-less. Instead, the load cell  2340  may comprise a cylindrical stud  2341  having a flattened or slightly convex (spherical) face  2342  that rests on a horizontal surface  2345  of a lower frame mounting flange  2346  fixedly mounted on the caster frame cross-member  2172  and/or the caster frame main rails  2171  of the caster frame  142 . The lower frame mounting flange  2346  may be U-shaped to prevent the stud  2341  from slipping off the horizontal surface  2345 , and may comprise a cross-bolt  2347  to prevent the lower frame  132  from being lifted off the caster frame  142  when the lower frame  132  is resting on the caster frame  142 . The bolt  2347  does not normally touch the lower frame  132 . The stud  2341  may comprise a mounting post  2344 , the mounting post  2344  rigidly mounted on the load cell  2340 . In one embodiment, the mounting post  2344  may be a bolt threadingly engaged with mating threads machined into the load cell  2340 . The load cells  2340  may be mounted within the lower frame main rails  2190  of the lower frame  132 . The studs  2341  mounted thereon depend downward and the entire lower frame  132  and everything else supported on the lower frame  132  may be supported by the studs  2341  resting on the horizontal surfaces  2345  of the lower frame mounting flanges  2346  proximate the four corners of the caster frame  142 . The only contact between the lower frame  132  and the caster frame  142  is between the face  2342  of the stud  2341  and the horizontal surface  2345  of the mounting flange  2346 . 
     Referring additionally to  FIG. 46E ,  FIG. 46F  and  FIG. 46G , the load cell  2340  may comprise a swivel  2348  instead of a stud. The swivel  2348  comprises a flat face  2349  that contacts the horizontal surface  2345  of the mounting flange  2346 . The swivel  2348  may comprise a swivel ball  2343  engaged in a socket of a mounting post  2344   a,  the mounting post  2344   a  rigidly mounted on the load cell  2340  in a manner as described above. Under load, the flat face  2349  of the swivel  2348  may always be flat against the horizontal surface  2345  because the swivel ball  2343  will swivel in the socket of the mounting post  2344   a  when the lower frame  132  experiences off-axis loading. In this manner, compensating for off-axis loading may be accomplished without the use of bushings, while gaining the simplicity and robustness of the stud design described above. 
     In order to transport a patient support from one location to another, it may be useful to equip the patient support with casters or other types of wheels to permit moving the patient support on surfaces. Casters may be mounted on a caster frame, typically having one caster proximate each corner of the caster frame. Further, it may be useful to be able to lock casters in one of several conditions including a locked condition, a neutral condition and/or a steer condition. 
     In the locked condition, the caster is unable to either rotate or swivel. The locked condition may be useful when the patient support is to remain stationary in a fixed position and no movement of the patient support is desired. In the neutral condition, the caster is free to rotate and swivel. The neutral condition may be useful when the patient support is to be moved from one location to another since freedom to rotate permits translation of the patient support across a surface and swiveling of the caster permits turning the patient support as the patient support is being translated. In the steer condition, the caster is able to rotate but swiveling is only permitted until the caster is in a position where the caster must rotate in a plane parallel to the longitudinal axis of the patient support, at which the time the caster becomes locked in this plane. This may be useful during translation of the bed to help with proper tracking of the patient support as it is being moved across the surface. For example, moving the patient support typically involves pushing the patient support from either the head end or the foot end, usually the head end. When pushing the patient support from one end, the casters at the end being pushed may be in the neutral condition while the casters at the other end may be in the steer condition. The casters in the neutral condition permits an operator to freely move the one end in any direction, for example when turning a corner, while the casters at the other end in the steer condition help keep the patient support tracking straight. If all of the casters were in the neutral condition during movement of the patient support, the patient support would be difficult to steer as the other end of the bed would have a tendency to wander. In the case when the patient support is moved by pushing from the head end, the casters at the foot end may be settable to the locked, neutral and steer conditions, while the casters at the head end may be settable only in the locked and neutral conditions. Casters having functionality to be set in locked, neutral and steer conditions are known in the art and are commercially available. Such casters may be useful at the foot end of the patient support. Casters that are settable in three conditions where one of the conditions is the locked condition and the other two are the neutral condition are also known in the art and are commercially available. Such casters may be useful at the head end of the patient support. 
     While casters with the requisite functionality for locking and steering are known in the art, it would be time consuming and inconvenient to have to set each of the casters each time the patient support is to be moved or locked in place. For this reason, it is generally desirable to have a central lock and steer arrangement whereby one operator can set all of the casters in the desired configuration with one control action. Therefore, it is useful to be able to coordinate the head end and foot end casters so that the two sets of casters are always coordinated to be in the proper condition. In one embodiment, the central lock and steer arrangement may be electronic, whereby electronic casters are utilized and the casters are in electronic communication with the control circuit. Electronically controllable casters are also available commercially. 
     In another embodiment, and with reference to  FIG. 28A ,  FIG. 47 ,  FIG. 48A ,  FIG. 48B ,  FIG. 49  and  FIG. 50 , the patient support may be provided with a mechanical central lock and steer arrangement. The casters and the central lock and steer mechanism therefor may be associated with the caster frame  142  as shown in  FIG. 28A . The casters  119  may be mounted on the caster frame cross-members  2172  and the caster frame cross-members  2172  connected with caster frame main rails  2171  to form the caster frame  142  with the casters  119  proximate the corners of the caster frame  142 . As seen in  FIG. 47 , the central lock and steer mechanism may comprise brake pedals  117  mounted at each end of the caster frame and mechanically linked through pedal pins  2273  to brake lever mechanisms  2175 . The brake lever mechanisms  2175  may be mechanically linked to brake control rods  2181 . The brake control rods  2181  may be mechanically linked to the casters  119 . As shown in  FIG. 30B , each brake control rod  2181  may be two separate portions to permit width expansion and contraction of the brake control rods  2181  when the caster frame  142  expands and contracts in width. Alternatively or additionally, the brake control rods  2181  may comprise a core portion and two end extension portions to accommodate width change. As seen in  FIG. 47 ,  FIG. 48A ,  FIG. 48B  and  FIG. 49 , brake control rod brackets  2271  may support the brake control rods  2181  keeping the two portions of each brake control rod  2181  mated together throughout expansion and contraction of the caster frame. The brake control rods  2181 , brake control rod brackets  2271  and at least some portions of the brake lever mechanisms  2175  may be housed in the caster frame cross-members  2172 , the caster frame cross-members  2172  being hollow tubes. The central lock and steer arrangement may further comprise a control rod connector  2272  to mechanically link the brake control rods  2181  at each end of the patient support. The control rod connector  2272  may comprise an elongated rack as shown, which may be housed within one of the caster frame main rails  2171 . Alternatively or additionally, the control rod connector may comprise a cable (not shown) linking the brake lever mechanisms  2175  at each end of the patient support. 
     The function of the brake lever mechanism  2175  is to translate rotational motion of the brake pedal  117  to rotational motion of the brake control rod  2181 . The brake lever mechanism  2175  may comprise any suitable combination of linkages to effect this function. In one embodiment, with specific reference to  FIG. 48A ,  FIG. 48B  and  FIG. 49 , the central lock and steer mechanism at the head end of the patient support operates as follows. With the brake pedal  117  in a horizontal position as shown, the casters  119  are set in the neutral condition so the casters are free to rotate and swivel. To set the casters  119  in the locked condition, an operator may apply force on a locking side  2274  of the brake pedal  117 . Applying force the locking side  2274  may cause the pedal pin  2273  to rotate. The rotation is clockwise with respect to the arrangements as shown in  FIG. 48A ,  FIG. 48B  and  FIG. 49 . The pedal pin  2273  may be fixedly mounted in pin bearing block  2276  of the brake lever mechanism  2175 , therefore clockwise rotation of the pedal pin  2273  may cause clockwise rotation of the pin bearing block  2276 . Clockwise rotation of the pin bearing block  2276  may then further create a cascade of movement through various linkages that comprise a remainder of the brake lever mechanism  2175 . Thus, clockwise rotation of the pin bearing block  2276  may cause a first brake lever linkage  2277  to translate upwardly through an arcuate path as the first brake lever linkage  2277  is fixedly mounted to the pin bearing block  2276  perpendicular to the pedal pin  2273 . Upward translation of the first brake lever linkage  2277  may cause a second brake lever linkage  2278  to translate vertically upward as the second brake lever linkage  2278  is pivotally connected to the first brake lever linkage  2277  by first pivot pin  2279 . Upward translation of the second brake lever linkage  2278  may cause upward translation of third brake lever linkage arm  2280  as the third brake lever linkage arm  2280  is pivotally connected to the second brake lever linkage  2278  by second pivot pin  2281 . The third brake lever linkage arm  2280  may form part of a third brake lever linkage, the third brake lever linkage further comprising a brake control rod bushing  2282  having a through aperture through which the brake control rod  2181  extends. Upward movement of the third brake lever linkage arm  2280  may cause the brake control rod bushing  2282  to rotate counter-clockwise. The brake control rod  2181  and the through aperture of the brake control rod bushing  2282  have mated shapes (e.g. hexagonal, rectangular, square, triangular, etc.) so that counter-clockwise rotation of the brake control rod bushing  2282  may cause counter-clockwise rotation of the brake control rod  2181 . The brake control rod  2181  is mechanically connected to the casters  119  by a similar rod-through-aperture mounting, therefore counter-clockwise rotation of the brake control rod  2181  rotates mechanisms within the casters thereby setting the casters to the locked condition from the neutral condition. The brake pedal  117  may now no longer be horizontal as the locking side  2274  has rotated down. 
     The casters may be returned to the neutral condition by applying force on a steering side  2275  of the brake pedal  117  until the brake pedal  117  returns to the horizontal position. Counter-clockwise rotation of the brake pedal  117  reverses all of the motions described above thereby setting the casters in the neutral condition from the locked condition. To set the casters  119  in the steer condition from the neutral condition, an operator may apply force on the steering side  2275  of the brake pedal  117 . Applying force the steering side  2275  may cause the pedal pin  2273  to rotate. The rotation is counter-clockwise with respect to the arrangements as shown in  FIG. 48A ,  FIG. 48B  and  FIG. 49 . Counter-clockwise rotation of the pedal pin  2273  may cause counter-clockwise rotation of the pin bearing block  2276 , causing the first brake lever linkage  2277  to translate downwardly through an arcuate path, causing the second brake lever linkage  2278  to translate vertically downward causing downward translation of third brake lever linkage arm  2280 , causing the brake control rod bushing  2282  to rotate clockwise, thereby causing counter-clockwise rotation of the brake control rod  2181 . Counter-clockwise rotation of the brake control rod  2181  rotates mechanisms within the casters in a direction opposite to the rotation caused by applying force to the locking side  2274  of the brake pedal  117 , thereby setting the casters  119  to the steer condition from the neutral condition. The brake pedal  117  may now no longer be horizontal as the steering side  2275  has rotated down and the locking side  2274  has rotated up. The casters  119  may be returned to the neutral condition by applying force on the locking side  2274  of the brake pedal  117  to return the brake pedal  117  to the horizontal position. As would be evident to one skilled in the art, the central lock and steer mechanism may be configured so that the locking side and steering side of the brake pedal  117  may be reversed if desired. 
     The central lock and steer mechanism would not be complete unless actuation of the brake pedal  117  at one end of the patient support also caused the casters  119  at the other end of the bed to change setting. As previously stated, this could be accomplished by connecting the brake lever mechanism on opposite of the patient support by a cable so that motion of a linkage in one brake lever mechanism would cause a mirror motion of a corresponding linkage in the other brake lever mechanism. However, such a cable would need to run longitudinally approximately down a central longitudinal axis of the patient support. Such a cable could potentially interfere with the lift mechanism of the patient support. To mitigate against this potential problem, instead of using a cable to link the brake lever mechanisms, the control rod connector  2272  may be provided connecting the brake control rods  2181  at opposite ends of the patient support. Since the brake control rods  2181  extend laterally across the width of the patient support, the control rod connector  2272  may be placed on any longitudinal axis of the patient support. For convenience, protection and esthetics, the control rod connector  2272  may be mounted within one of the caster frame main rails  2171 . In another embodiment, there may be two control rod connectors, one on each side of the patient support, preferably housed in the two caster frame main rails  2171 . 
     With reference to  FIG. 50 , the control rod connector  2272  may comprise an elongated rack  2285 . A toothed portion  2286  may be provided on the rack  2285  at least proximate one end of the rack  2285 . Teeth of the toothed portion  2286  may be mated with teeth of a pinion gear  2287 , the pinion gear  2287  being connected to the brake control rod  2181 . When the brake control rod  2181  rotates, the pinion gear  2287  connected to the brake control rod  2181  may also rotate and the rack  2285  may then translate longitudinally by virtue of the toothed connection between the pinion gear  2287  and the toothed portion  2286  of the rack  2285 . Relative to  FIG. 50 , counter-clockwise rotation of the brake control rod  2181  may cause the pinion gear  2287  to rotate counter-clockwise, which may then cause the rack  2285  to translate longitudinally toward the other end of the patient support. Rotation of the brake control rod  2181  clockwise may cause the rack  2285  to translate in the opposite direction. There may be a similar rack and pinion arrangement at the other end of the patient support. Translation of the rack  2285  may cause the pinion gear at the other end to rotate, thereby causing the brake control rod at the other end to rotate, thereby setting the condition of the casters at the other end. Thus, rotation of the brake control rod  2181  at one end of the patient support due to actuation of the brake pedal  117  may also cause rotation of the brake control rod at the other end of the patient support simultaneously setting the caster conditions at both ends of the patient support. Furthermore, since the brake control rod at the other end of the patient support is also linked to a corresponding brake lever mechanism, pedal pin and brake pedal, actuation of the brake pedal  117  may also cause corresponding motions in the brake lever mechanism, pedal pin and brake pedal at the other end. 
       FIG. 50  shows the pinion gear  2287  fixedly mounted on the brake control rod  2181  whereby the brake control rod  2181  is seated in a complementary shaped aperture in the pinion gear  2287 . A set screw  2288  ensures that the brake control rod  2181  and the pinion gear  2287  are secured together. However, it is evident that other arrangements for connecting the pinion gear to the brake control rod may be used and other styles of pinion gears used. Further, while one control rod connector is all that may be required, two or more control rod connectors at various location along the width of the patient support may be provided if desired. 
     Furthermore, the control rod connector  2272  is shown in the figures in three parts, the elongated rack  2285  with toothed portions  2286  secured to the ends of the rack  2285 . However, the control rod connector may be constructed from one, two, three or more pieces as desired. The teeth of the rack may be on a separate piece (as shown) or may be machined directly onto the elongated rack. Only one or more portions of the rack may comprise teeth, or the entire rack may comprise teeth. 
     Because the movement of the patient support is most likely to be effected by pushing the patient support from one end (e.g. the head end), different types of casters may be used at the head end as opposed to the foot end. For example, the casters at the head end may have three distinct conditions—locked, neutral and steering. The casters at the foot end may have only two distinct conditions—locked and neutral. However, since the central lock and steer mechanism may provide a direct 1:1 correlation between three pedal positions and the three distinct caster conditions, and the pedal at one end of the patient support is directly correlated with the pedal at the other end, the casters at the foot end could also have three conditions where two of the conditions are indistinct, i.e. two of the conditions are the neutral condition. Thus, when the casters at the head end of the patient support are in the steer condition, the casters at the foot end would be in the neutral condition. 
     Guard structures at the sides of a patient support are useful for reducing the possibility that a patient may fall out of the patient support causing injury to himself or herself. Conversely, when a patient may deliberately enter or exit the patient support, it may be useful for the guard structures to be in positions that do not block ingress and egress of a patient. Therefore, guard structures that are movable between a guard position and an open position may be useful. In addition, the open position for a guard structure may still obstruct patient ingress and egress from the patient support unless the guard structure may be moved to a position that is completely out of the path of a patient entering or exiting the patient support. Such a completely out of the path position may be under the patient support deck of the patient support. 
     On patient supports, guard structures may occupy several positions. For example, a raised or guard position may be above the patient support deck blocking entrance to and exit from the patient support. A low position may be alongside the patient support deck. An ultralow position may be below a horizontal plane of the patient support deck but laterally outward of the patient support deck. A tuck position may be below a horizontal plane of the patient support deck and under a lower surface of the patient support deck such that the guard structure has been moved laterally toward a centerline of the patient support relative to the ultralow position. The tuck position is especially useful for permitting the patient to enter and exit the patient support unobstructed and for assisted patient transfers from one patient support to another. The tuck position also reduces the effective width of the patient support to facilitate transport, especially through doors. 
     In a height and width adjustable patient support, the provision of width expandability together with low patient support deck height and tuckability of the guard structures was a problem. The guard structures ideally have a narrow enough profile to completely tuck under the patient support deck at all patient support deck widths. However, to permit the patient support to achieve a low position and then be raiseable back to a high position while supporting the extreme weight of a bariatric patient, a variety of frames and a robust lift mechanism need to be placed under the patient support deck, thereby limiting the space available for tucking a guard structure. To overcome this problem, the guard structures may be mounted on the deck extension pans with a pin in slide mechanism that is slim enough to fit the guard structure under the deck extension pans when the patient support is at the narrowest width, and a rack and pinion mechanism may be employed to reduce the space required by linkages for pivoting the guard structures from position to position. These features especially coupled with height controls for preventing the guard structures in the tuck position from accidentally being crushed under the patient support in the low position help overcome the limitations imposed by such a height and width adjustable patient support. 
     In addition, on a width adjustable patient support it may be desirable for the guard structures to be adjustable laterally along with the patient support deck. While guard structures at the head end of the patient support have been mounted on the patient support deck in order to be raised together with the deck when the deck is articulated, guard structures nearer the foot end of the patient support have been typically mounted on the frame supporting the deck. In contradistinction, the present patient support may have the foot end guard structures mounted on the deck itself in order to allow the foot end guard structures to adjust with the deck. 
     Referring to  FIG. 51  a patient support deck  104  having head rails  110  and foot rails  113  mounted on head deck extension pans  2031  and seat deck extension pans  2032 , respectively, is shown, in which one of the head deck extension pans is not shown to illustrate head rail slide bracket  2401  slidably engaged with head rail bracket support pins  2402 . The head rail  110  may be rotatably supported on the head rail slide bracket  2401  and the head rail bracket support pins  2402  may be fixedly secured to the head deck extension pan (not shown). All of the head rails  110  and foot rails  113  may be slidably mounted to respective deck extension pans  2031  and  2032  in a similar manner. Further detail is provided below in connection with  FIG. 52A ,  FIG. 52B  and  FIG. 52C . Mounting the head rails  110  and foot rails  113  to respective deck extension pans  2031  and  2032  may permit the rails  110 ,  113  to move with the extension pans  2031 ,  2032  when the width of the patient support deck is adjusted between the various widths. Because the foot rails  113  do not need to be mounted on the frame of the patient support, an independent mechanism for foot rail expansion may not be required. 
       FIG. 52A ,  FIG. 52B  and  FIG. 52C  show a foot rail  113  mounted on a seat deck extension pan  2032 . The following description of the foot rail  113  analogously applies to all of the guard structures (e.g. head rails and foot rails). The seat deck extension pan  2032  may comprise an outer shell  2403  housing a foot rail mounting bracket  2404 . The foot rail mounting bracket  2404  may be fixedly secured to the seat deck (not shown) at seat deck rail mounts  2405 , which may be part of the extending deck mechanism described above, as best seen in  FIG. 23 . The foot rail mounting bracket  2404  may also comprise foot rail bracket support pins  2406  fixedly attached thereto and extending laterally therefrom. The foot rail bracket support pins  2406  may be slidably engaged in through apertures  2407  of foot rail slide bracket  2408 . The foot rail slide bracket  2408  may be free to slide laterally on the foot rail bracket support pins  2406 . However, when the foot rail  113  is in a raised position or a low position (see  FIG. 53A  and  FIG. 53B ), the foot rail slide bracket  2408  may be prevented from sliding the full distance towards the foot rail mounting bracket  2404  because foot rail arms  2409 , which may be pivotally attached to the foot rail slide bracket  2408  through foot rail arm weldments in foot rail arms  2409 , hit the seat deck extension pan  2032 . Only when the foot rail  113  is in an ultralow position (see  FIG. 53C ) with the foot rail arms  2409  fully beneath the seat deck extension pan  2032  can the foot rail slide bracket  2408  slide the full distance towards the foot rail mounting bracket  2404 , thereby tucking the foot rail  113  under the seat deck extension pan  2032 . To facilitate smooth tucking no matter where on the foot rail  113  a user pushes, one of the foot rail bracket support pins  2406  may be rigidly fixed to the foot rail mounting bracket  2404 , while the other of the foot rail bracket support pins  2406  may have some movement tolerance. Thus, even if the force used to tuck the foot rail  113  is off center, the foot rail  113  may tuck smoothly without binding on the foot rail bracket support pins  2406 . 
       FIG. 53A ,  FIG. 53B  and  FIG. 53C  show the foot rail  113  in the raised or guard position, the low position and the ultralow positions, respectively. The foot rail arms  2409  may be pivotally attached to the foot rail slide bracket  2408  and as the two foot rail arms  2409  pivot on the foot rail slide bracket  2408  the foot rail may travel through an arcuate path with the foot rail arms  2409  pointing vertically in the raised and ultralow positions and horizontally in the low position. Throughout the arcuate path, the foot rail  113  may remain oriented in the same direction. As can be seen in  FIG. 53C , the foot rail  113  may be at or below the level of the foot rail slide bracket  2408  in the ultralow position, which may be below the level of the seat deck extension pan. In the ultralow position, the foot rail  113  may be tucked under the seat deck extension pan in a tuck position. The foot rail may further comprise a foot rail panel  2410  and a foot rail panel overlay  2411  to cover internal workings of the foot rail  113 . A foot rail release panel  2412  may also house a foot rail release overlay  2413  and cover a foot rail release mechanism inside the foot rail  113 . 
       FIG. 54A ,  FIG. 54B  and  FIG. 54C  show side views of the foot rails shown in  FIG. 53A ,  FIG. 53B  and  FIG. 53C  without covering panels. Foot rail arm weldments  2414  may pivotally connect the foot rail mechanism housing  2417  to the foot rail slide bracket  2408  at pivot pins  2415  between the foot rail arm weldments  2414  and the foot rail slide bracket  2408  and pivot pins  2418  between the foot rail arm weldments  2414  and the foot rail mechanism housing  2417 . The two foot rail weldments  2414 , the foot rail slide bracket  2408  and the foot rail mechanism housing  2417  may form a pivoting parallelogram linkage with pivot points at the two pivot pins  2415  and the two pivot pins  2418 . As the foot rail mechanism housing  2417  pivots, the parallelogram linkage may maintain the foot rail mechanism housing  2417  in the same orientation. The pivot pins  2415  may be hollow in the center to permit passage of a foot rail electronic release wire  2416  that may connect an electronic foot rail release mechanism to the control circuitry of the patient support. 
     Within the foot rail mechanism housing  2417  there may be a rack and pinion system comprising two pinion gears  2420  and a toothed linear rack  2421 . The pinion gears  2420  may be fixedly mounted on the pivot pins  2418  located at pivot points of the foot rail, rotation of the pivot pins  2418  resulting in rotation of the pinion gears  2420 . Teeth of the pinion gears  2420  may be meshed with teeth of the toothed linear rack  2421 . The toothed linear rack  2421  may be above or below the pinion gears  2420 . Clockwise rotation of the pinion gears  2420  as the foot rail is pivoted from a higher position to a lower position moves the rack  2421  toward the left, while counter-clockwise rotation of the pinion gears  2420  as the foot rail is pivoted from a lower position to a higher position moves the rack  2421  toward the right. Because the two pinion gears  2420  are longitudinally aligned along an axis parallel to the linear rack  2421 , the rack and pinion system may keep the foot rail arm weldments  2414  parallel throughout the pivoting of the foot rail, even when all of the pivot points (at the pivot pins  2415  and  2418 ) longitudinally align. The rack and pinion system may require less space permitting construction of a foot rail with a narrower profile. A foot rail damper  2425  (e.g. a gas cylinder) connected to the linear rack  2421  may be used to control fall rate of the foot rail. A foot rail release handle  2419  may actuated to manually release a lock on the foot rail to permit pivoting of the rail. 
       FIG. 55A ,  FIG. 55B  and  FIG. 55C  show details of the foot rail mechanism. The toothed rack  2421  may be free-floating for unimpeded movement left or right depending on which way the foot rail is being pivoted. When the foot rail is in the raised position ( FIG. 55A ) with the foot rail arm weldments  2414  pointing downward, the rack  2421  may be as far right as possible in the foot rail mechanism housing  2417 . When the foot rail is in the ultralow position ( FIG. 55C ) with the foot rail arm weldments  2414  pointing upward, the rack  2421  may be as far left as possible in the foot rail mechanism housing  2417 . 
     However, if the rack is completely free, pivoting action of the foot rail becomes labored when the foot rail arm weldments  2414  pass through a longitudinally aligned position. The lack of smooth action is uncomfortable and annoying. To smooth out the pivoting action of the foot rail, the rack  2421  may be pre-loaded with a load to permit flexing of the rack  2421 , which controls manufacturing tolerances. Without a load on the rack  2421 , the foot rail weldments  2414  may not be able to pivot past the pivot pins  2418  causing the foot rail to bind when the foot rail weldments  2414  are longitudinally aligned. Any suitable means for applying a load to the rack  2421  may be used. For example, as shown in  FIG. 55A ,  FIG. 55B  and  FIG. 55C , slings  2422  may be bolted over the rack  2421  with bolts  2424  to apply the load. Although the load may be applied in any suitable location close to a vertical axis through the pivot pins  2418 , the load may be preferably applied at a location that is not vertically aligned with the pivot pins  2418  in order to provide a slight bow in the rack  2421 . For space considerations, the load may be applied just to the inside of the vertical axis through the pivot pins  2418 , for example with the bolts  2424  as shown in  FIGS. 55A-C . The load should not be applied too far from the vertical axis through the pivot pins  2418 , otherwise the pinion gears  2420  may skip a tooth on the rack  2421 . In addition, rotational bearings may be placed under the under the rack  2421  to support the rack  2421  and to provide for smooth linear travel of the rack  2421 . The rotational bearings may be placed anywhere along the rack  2421 , however, for convenience rotational bearings  2423  may be placed around the bolts  2424  and held in place by the sling  2422 . 
     Thus, by pre-loading the rack  2421  at points off the vertical axis through the pivot pins  2418 , the foot rail may be pivoted smoothly without binding. By placing all the parts in the foot rail mechanism housing  2417 , the lower part of the foot rail arm weldments  2414  may be as short as possible improving tuckability of the foot rail. 
     More details of the foot rail mechanism are shown in  FIG. 56 , where the foot rail mechanism housing  2417  may house the pinion gears  2420  meshed with the toothed linear rack  2421  loaded by the slings  2422  (only one shown) bolted to the foot rail mechanism housing  2417  over the rack  2421  with the bolt  2424 , the rack  2421  free to move longitudinally and riding on rotational bearings  2423 . The foot rail mechanism may further comprise a latching mechanism. The latching mechanism may comprise a two-position latch piece  2430  having a raised position catch retainer  2431  and a low position catch retainer  2432 . A catch retainer for the ultralow position is unnecessary as the foot rail cannot pivot any lower than the ultralow position. The latch piece  2430  may be secured to the rack  2421  so that the latch piece  2430  moves with the rack  2421  when the foot rail is pivoted. Over travel adjustment screws  2433  may prevent further longitudinal motion of the rack when the adjustment screws  2433  abut travel stops  2434  attached to the housing  2417 . The over travel adjustment screws  2433  control play and position of the foot rail in the raised and ultralow positions. The foot rail damper may comprise a gas cylinder having a body  2426   a  and a rod  2426   b,  the body  2426   a  attached to the housing  2417  by bolt  2427  and the rod  2426   b  attached to the latch piece  2430  by bolt  2428 . 
     The latching mechanism may further comprise spring-loaded latch lever  2435  having a raised catch  2436  proximate one end. When the raised catch  2436  is aligned with one of the catch retainers  2431  or  2432 , a pivot spring  2437  on pivot rod  2438  forces the raised catch  2436  into the catch retainer  2431  or  2432 , thereby locking further movement of the rack  2421  and hence preventing further movement of the foot rail. Releasing the latching mechanism may be accomplished manually or electronically. 
     To manually release the catch  2436  from the catch retainer  2431  or  2432 , the foot rail release handle  2419  (see  FIG. 54A ,  FIG. 54B  and  FIG. 54C ) may be depressed since the foot rail release handle  2419  is configured to apply force to latch interface pins  2439  rigidly connected to the latch lever  2435  (see  FIG. 57A  and  FIG. 57B ). The applied force pushes the catch  2436  out of the catch retainer  2431  or  2432  permitting the rack  2421  to move longitudinally. A small amount of travel by the rack  2421  misaligns the catch  2436  and the catch retainer  2431  or  2432  so that when the foot rail release handle  2419  is no longer depressed, the catch  2436  presses against the latch piece  2430  but is not an impediment to movement of the rack  2421 . A coiled spring (not shown) under the foot rail release handle  2419  may be used for tension and to return the release handle  2419  to an undepressed state, but the coiled spring should be configured to not interfere with longitudinal movement of the latch piece  2430  and rack  2421 . 
     Referring to  FIG. 57A ,  FIG. 57B ,  FIG. 57C  and  FIG. 57D , details of the latch lever  2435  together with the foot rail release handle  2419  are shown. The latch lever  2435  may comprise the raised catch  2436 , the latch interface pins  2439  and the pivot spring  2437  on the pivot rod  2438  as previously described. The foot rail release handle  2419  may comprise release handle pivot arms  2441  and release handle pivot pins  2442 , the release handle pivot pins  2442  pivotally mounted to a latch lever cover (not shown) secured to the foot rail mechanism housing. The release handle pivot arms  2441  may contact the latch interface pins  2439 , for example at shoulders in the release handle pivot arms  2441 . Depressing the foot rail release handle  2419  may cause the release handle pivot arms  2441  to pivot on the release handle pivot pins  2442 , the release handle pivot arms  2441  thereby applying a force to the latch interface pins  2439 , which may cause the latch lever  2435  to pivot on the pivot rod  2438  against the bias of the pivot spring  2437  resulting in disengagement of the raised catch  2436  from the catch retainer (not shown). 
     Referring to  FIG. 56 ,  FIG. 57A ,  FIG. 57B ,  FIG. 57C  and  FIG. 57D , to electronically release the catch  2436  from the catch retainer  2431  or  2432 , a servo  2443  may be employed. A drive shaft of the servo  2443  is connected to a lever arm  2444  that abuts one of the latch interface pins  2439 . A signal to the servo  2443  from the control circuit of the patient support rotates the drive arm which rotates the lever arm  2444  thereby applying a force to the latch interface pin  2439 , which in turn pushes the catch  2436  out of the catch retainer  2431  or  2432  permitting the rack  2421  to move longitudinally. The servo  2443  may be small as not much power is required to push the catch  2436 , although the servo  2443  may be larger if desired or one or more extra servos may be employed if more power is desired. To reduce the need for more power from the servo  2443 , the raised catch  2436  may comprise a bevel  2446  that mates with a matching bevel on the catch retainers  2431  or  2432  ( FIG. 56 ). The matching bevels may reduce friction between the raised catch  2436  and the catch retainers  2431 ,  2432  thereby reducing the power requirement for disengaging the catch  2436  from the catch retainers  2431 ,  2432 . The bevel may be any suitable angle, for example 5°, that reduces friction while not compromising the latching function of the catch  2436  in the catch retainers  2431 ,  2432 . 
     The foot rail may be equipped with a mechanism for automatically determining rail position. This may be accomplished in any number of ways including, for example, using accelerometers or inclinometers attached to the foot rail, using rotary encoders on the pinion gears or using switches that switch on and off when the foot rail reaches certain positions. The use of switches may be one of the simpler solutions. 
     Referring to  FIG. 56 ,  FIG. 57A ,  FIG. 57B ,  FIG. 57C  and  FIG. 57D , the foot rail mechanism may further comprise first and second foot rail position switches  2447 ,  2448  to determine electronically whether the latching mechanism is open or closed. The first foot rail position switch  2447  is positioned with the latch lever  2435  under a switch arm  2449  of the latch lever  2435 . With the foot rail in the raised position and the raised catch  2436  engaged in the raised position catch retainer  2431 , the switch arm  2449  may activate the first foot rail position switch  2447  because the latch lever  2435  is up at the end comprising the catch  2436  and down at the end comprising the switch arm  2449  by virtue of a fulcrum at the spring-loaded pivot rod  2438 . The second foot rail position switch  2448  may be inactivated, as seen in  FIG. 56 . Therefore, a first switch on/second switch off state may indicate that the foot rail is locked in the raised position. When the catch  2436  is released from the raised position catch retainer  2431 , the latch lever  2435  may pivot so that the switch arm  2449  moves away from the first switch  2447  thereby switching off the first switch  2447 . Therefore, a first switch off/second switch off state may indicate that the foot rail is unlocked and free to pivot away from the raised position. 
     As the foot rail pivots toward the low position from the raised position, the toothed linear rack  2421  may move longitudinally toward the second foot rail position switch  2448  (see  FIG. 55B ). When the foot rail reaches the low position, the catch  2436  may engage with the low position catch retainer  2432 , which may once again cause the switch arm  2449  to switch on the first switch. In addition, the rack  2421  may pass over the second switch  2448  causing the second switch  2448  to switch on as well (see  FIG. 55B  for the position of the rack in relation to the second switch in the low position). Therefore, a first switch on/second switch on state may indicate that the foot rail is locked in the low position. When the catch  2436  is released from the low position catch retainer  2432 , the latch lever  2435  may pivot so that the switch arm  2449  moves away from the first switch  2447  thereby switching off the first switch  2447 . Therefore, a first switch off/second switch on state may indicate that the foot rail is unlocked and free to pivot away from the low position. 
     As the foot rail pivots toward the ultralow position from the low position, the toothed linear rack  2421  may continue to move longitudinally over the second foot rail position switch  2448  (see  FIG. 55C ). When the foot rail reaches the ultralow position, there is no catch retainer to engage the catch  2436 , therefore the switch arm  2449  does not activate the first switch  2447 . However, the rack  2421  is still over the second switch  2448  causing the second switch  2448  to remain on as well (see  FIG. 55C  for the position of the rack in relation to the second switch in the ultralow position). Therefore, a first switch off/second switch on state may also indicate that the foot rail is in the ultralow position and free to pivot away from the ultralow position. To determine whether the foot rail is in the tuck position may require a further switch or other position sensing device. However, the second switch  2448  may be included in a circuit connected to the height adjustability of the patient support such that when the second switch  2448  is on and the first switch  2447  is off, the patient support cannot be lowered below a fixed height. Such an arrangement reduces the likelihood of crushing the foot rail beneath the patient support deck when the foot rail is in the tuck position. 
     In addition, permutations of switch states for the first and second switches  2447 ,  2448  may also be linked to predetermined height adjustability parameters of the patient support. Also, any additional or alternative ways of determining guard structure position may be linked to predetermined height adjustability parameters of the patient support. 
     Pivoting of the foot rail back to the raised position from the ultralow position reverses the switching order. Thus, the interaction of the switch arm  2449  with the first foot rail position switch  2447  may be an indicator of whether the rail is locked in the raised or low positions, while the interaction of the toothed linear rack  2421  with the second foot rail position switch  2448  may be an indicator of the position of the foot rail. Information from both switched may provide an indication of both the position and lock state of the foot rail. While the latching mechanism may lock the foot rail in the raised and low positions to prevent further downward pivoting of the foot rail, the latching mechanism, even when engaged, does not prevent the foot rail from being raised. As seen in  FIG. 57C  and  FIG. 57D , the raised catch  2436  may comprise a second bevel  2445  on the opposite side of the catch  2436  as the smaller bevel  2446 . Unlike the bevel  2446 , the second bevel  2445  may be much larger and affords no abutment surface to catch within the catch retainers  2431 ,  2432 . Thus, upward pivoting of the foot rail may be unrestricted by the latch mechanism. Upward pivoting of the foot rail is halted at the raised position because that is as far as the foot rail can travel. Downwards pivoting may be halted at the raised and low positions by the latch mechanism and at the ultralow position because that is as low as the foot rail can travel. Therefore, in the raised position the foot rail is not free to pivot either up or down, while in the low and ultralow positions the foot rail is free to pivot up but not down. 
     In addition, the first and second foot rail position switches  2447 ,  2448  may be slightly asynchronous, with one switch turning on or off, depending on the direction of travel of the foot rail, before the other switch. This affords the opportunity to determine whether the foot rail is pivoting up or down. Other devices, for example accelerometers, may provide the same information and can be used in conjunction with or instead of the asynchronicity of the first and second foot rail position switches  2447 ,  2448 . 
     In another aspect, instead of a rack and pinion mechanism, an endless member (e.g. a belt of a chain) may connect the two pinion gears  2420  allowing the pinion gears  2420  to rotate synchronously. The pinion gears could be replaced with other rotational elements, for example toothless wheels. 
     One feature that is useful on patient supports is the ability to remove the footboard. Because the footboard may contain a control panel for electrical and electronic functionalities of the patient support, it may become necessary to electrically connect the footboard to the rest of the patient support in a reversible manner that does not require a great deal of time and labour to connect and disconnect. Ideally, the acts of removing and replacing the footboard automatically result in the disconnection and connection of the electrical components. One problem faced in such an operation is to ensure that electrical connection between the footboard and the rest of the patient support are properly aligned when replacing the footboard. The prior art uses circular plug-in connections and the half of the connection in the foot board is a so-called floating connection that moves into the correct position as the footboard is replaced on the patient support. Such an arrangement suffers from the possibility jamming when the footboard is being replaced and component wear due to the moving parts. An alternate type of connection assembly is therefore desired. 
     Referring to  FIG. 58A ,  FIG. 58B ,  FIG. 59A ,  FIG. 59B ,  FIG. 59C ,  FIG. 59D ,  FIG. 59E ,  FIG. 60A ,  FIG. 60B  and  FIG. 60C , an electrical connection assembly usable in conjunction with a footboard at the foot of a patient support is illustrated.  FIG. 58A  shows a footboard mounting bracket  2200  on a footboard insert  2217  mountable on the upper frame footboard mount (not shown) at a foot end of a patient support. The footboard mounting bracket  2200  may comprise a pair of post sockets  2202 . A first electrical mating half  2204  may be housed in the footboard mounting bracket  2200  and covered by a retractable cover  2213  over gap  2206  to keep dust, fingers and other detritus out of the electrical connection when the footboard is not in place.  FIG. 58B  shows a corresponding footboard  108  to be mated with the footboard mounting bracket  2200 . The footboard may comprise a pair of tubular posts  2205  secured within tubular post engagement elements  2201 . A second electrical mating half  2203  may be housed in the footboard and configured to mate electrically with the first electrical mating half  2204  of the footboard mounting bracket  2200 . In operation a caregiver may simply lift the footboard  108  out of the post sockets  2202  automatically disengaging the second electrical mating half  2203  from the first electrical mating half  2204 . Sliding the tubular posts  2205  of the footboard  108  back into the post sockets  2202  of the footboard mounting bracket  2200  results in automatic re-engagement of the second electrical mating half  2203  with the first electrical mating half  2204 . 
       FIG. 59A ,  FIG. 59B ,  FIG. 59C ,  FIG. 59D  and  FIG. 59E  depicts magnified views of the first and second electrical mating halves depicted in  FIG. 58A  and  FIG. 58B .  FIG. 59A  and  FIG. 59B  show the first electrical mating half  2204 , which may comprise a plurality of leaf spring electrical contacts  2208  (e.g. six leaf springs) extending outwardly from a first connection housing  2210  on which the leaf springs are attached. The housing  2210  may also house other electrical components (not shown) electrically connected to the leaf springs for transmitting electrical signals to other parts of the patient support. The leaf springs  2208  may be arcuately-shaped, flexible and made of an electrically conductive material, for example stainless steel. A pair of coiled compression springs  2212  attached to the housing  2210  and placed proximate the ends of the plurality of leaf springs  2208  may be configured to compress when the retractable cover  2213  is forced to move laterally when the footboard is replaced on the footboard mounting bracket  2200 . Details of the cover are provided in  FIG. 60  discussed below.  FIG. 59C  and  FIG. 59D  show the second electrical mating half  2203 , which may comprise a plurality of electrically conducting tabs  2207  (e.g. six tabs) configured to align with the leaf springs when the footboard is in place. The tabs  2207  may be longer and wider than the leaf springs  2208  thereby accommodating movement tolerance of the footboard without the tabs themselves having to move. Electrical contact between the leaf springs  2208  and the tabs  2207  may be maintained by virtue of the springiness of the leaf springs and the size of the tabs, both of which may assist in accommodating misalignments in all three coordinates between the contacts of the first and second electrical mating halves. The tabs  2207  may be attached to a second connection housing  2209  and electrically connected to other electrical components  2211  attached to the housing  2209  for transmitting electrical signals in the footboard. 
       FIG. 59E  shows the first and second electrical mating halves mated together with most of the first and second connection housings  2210 ,  2209  removed for clarity. When the posts  2205  of the footboard are completely slid into the post sockets  2202  of the footboard mounting bracket  2200 , the tabs  2207  (only one labeled) may come into mating contact with the leaf springs  2208  (only one labeled) at such close proximity that the torque in the leaf springs maintains electrical contact of the leaf springs with the tabs. The larger length and width of the tabs allows for misalignment with the leaf springs without requiring floating components. 
       FIG. 60A ,  FIG. 60B  and  FIG. 60C  depict magnified views of the first electrical mating half  2204  in association with the retractable cover  2213 . The retractable cover  2213  may sit slidably atop the housing  2210  of the first electrical mating half  2204  such that downwardly extending portion  2214  of the retractable cover  2213  shelters the leaf springs  2208  (only one labeled) when the footboard  108  is not in place on the footboard mounting bracket  2200 . The coiled compression springs  2212  attached to the first connection housing  2210  may be engaged with the under surface of the retractable cover  2213  at the downwardly extending portion  2214 . Biasing from the coiled springs prevents the retractable cover  2213  from sliding back along the top of the first connection housing  2210  without applying significant force to the cover. The downwardly extending portion  2214  of the retractable cover  2213  may comprise two cover interface element engagement surfaces  2216 , the function of which is described below. 
     The following description of the operation for putting on and taking off the footboard  108  from the patient support is made with reference to  FIG. 58A ,  FIG. 58B ,  FIG. 59A ,  FIG. 59B ,  FIG. 59C ,  FIG. 59D ,  FIG. 59E ,  FIG. 60A ,  FIG. 60B ,  FIG. 60C ,  FIG. 61A  and  FIG. 61B . To put the footboard  108  on the end of the patient support, the footboard  108  may be slid into place on the footboard mounting bracket  2200  by first aligning the tubular posts  2205  of the footboard with the post sockets  2202  in the footboard mounting bracket  2200 . As the posts slide into the sockets, the second electrical mating half  2203  aligns with the first electrical mating half  2204  and enters the gap  2206  above the first electrical mating half  2204 . Since the retractable cover  2213  is covering the gap  2206 , the second mating half  2203  first engages the retractable cover  2213  whereby cover interface elements  2215  of the second connection housing  2209  engage the cover interface element engagement surfaces  2216  of the retractable cover  2213  causing the retractable cover  2213  to begin sliding across the top of the first connection housing  2210  of the first mating half  2204  in the direction of the arrow in  FIG. 60C  with sufficient force to overcome the bias of the compression springs  2212  to expose the leaf springs  2208 . The second mating half  2203  continues to push into the gap  2206  until the retractable cover  2213  is pushed entirely out of the way and the electrically conducting tabs  2207  are mated with the leaf spring electrical contacts  2208 . When the footboard  108  is removed from the end of the patient support, the tubular posts  2205  begin to slide up and out of the sockets  2202  and the second electrical mating half  2203  begins to slide up and away from the first electrical mating half  2204 . As the second electrical mating half  2203  is pulled away, the cover interface elements  2215  begin to disengage from the cover interface element engagement surfaces  2216  of the retractable cover  2213  and the compression springs  2212 , having been compressed when the footboard was put in place, bias the retractable cover  2213  back over the gap  2206  when the second electrical mating connection  2203  finally clears the gap  2206 .  FIGS. 61A-B  show side views of the first electrical mating half  2204  with the retractable cover  2213  in the gap covering position ( FIG. 61A ), and in the retracted position ( FIG. 61B ) to expose the leaf spring electrical contacts  2208 . 
     The electrical connection assembly for the removable footboard may thus be a blind-mate connector that provides sufficient clearances and electrical contact surface areas to allow for and accommodate: installation of the footboard even during misalignment; manufacturing tolerances; easy installation and removal of the footboard; and, hands-free electrical mating connection. Both halves of the connection assembly are fixed (no floating components) and the retractable cover protects the electrical contacts in the patient support when the footboard is not on the patient support. Removal and replacement of the footboard may be done quickly and easily while minimizing damage to electrical connections between the footboard and patient support. 
     It will be apparent to one skilled in the art that the first electrical mating half  2204  may comprise electrically conductive tabs instead of leaf spring contacts, while the second electrical mating half  2203  may comprise leaf spring contacts instead of electrically conducting tabs. Equally apparent is that both electrical mating halves  2203 ,  2204  may comprise leaf spring contacts. 
     Most nurse call (NC) systems associated with patient supports have the ability to monitor and detect whether the patient support is connected to the NC system. However, the reverse is often not the case as patient supports are often not equipped to determine whether the patient support is connected to the nurse call system. This can be detrimental to patient safety, particularly in connection with exit alarm features of the patient support. In an effort to improve the safety of the exit alarm feature, there is a need to allow the control circuitry of the patient support to detect whether a nurse call interconnect cable (e.g. a DB37 interconnect cable) is connected to the patient support. By doing so, the patient support may auto-adjust to ensure that Bed Exit Priority Call signaling is subsequently enabled. Conversely, if the DB37 cable is disconnected the patient support can auto-adjust and revert the exit alarm to an audible alarm signal and a visual warning message. Further, it would be beneficial if this may be accomplished without the use of embedded ‘interlock’ circuits, i.e. custom/modified DB37 interconnect cables. 
     Referring to  FIG. 62 , a first embodiment of a device for permitting a patient support to automatically detect whether a nurse call system is connected to the patient support is shown. The device may comprise a floating faceplate  2221  and a switch  2222 . The floating faceplate  2221  may be a monolithic molded metal gasket having a central aperture  2223  through which a DB37 port  2224  mounted in a mounting plate  2225  may protrude when the faceplate  2221  is mounted on an outside surface of the mounting plate  2225  around the DB37 port  2224 . The faceplate  2221  may further comprise spring tabs  2227 , which bias the faceplate  2221  away from the outside surface of the mounting plate  2225  when the faceplate  2221  is mounted thereon. The faceplate  2221  may further comprise a faceplate plunger  2228 , which protrudes through an aperture in the mounting plate to extend outwardly from an inner surface of the mounting plate  2225  as best seen in  FIG. 62B . The switch  2222  may be mounted proximate the inner surface of the mounting plate  2225  and configured so that a spring-leaf contact  2229  of the switch  2222  is proximate a distal end of the faceplate plunger  2228  protruding through the mounting plate  2225 . 
     As seen in  FIG. 62A , when a DB37 cable plug  2226  is not plugged into the DB37 port  2224 , the faceplate  2221  is kept away from the outside surface of the mounting plate  2225  and the distal end of the faceplate plunger  2228  is disengaged from the spring-leaf contact  2229  of the switch  2222 . Control circuitry connected to the switch  2222  recognizes that the circuit in the switch  2222  is not closed and determines that the DB37 cable plug  2226  is not plugged into the DB37 port  2224 . As seen in  FIG. 62B , when the DB37 cable plug  2226  is plugged into the DB37 port  2224 , the faceplate  2221  is pushed against the outer surface of the mounting plate  2225 , which forces the faceplate plunger  2228  into engagement with the spring-leaf contact  2229  of the switch  2222 , which closes the circuit in the switch  2222 . Control circuitry connected to the switch  2222  recognizes that the circuit in the switch  2222  is closed and determines that the DB37 cable plug  2226  is plugged into the DB37 port  2224 . In each case, the control circuitry takes appropriate action in resetting the exit alarm features of the patient support. 
     Referring to  FIG. 63 , a second embodiment of a device for permitting a patient support to automatically detect whether a nurse call system is connected to the patient support is shown. The device may comprise a proximity sensor transmitter  2231  and a proximity sensor receiver  2232  facing each other and mounted on opposed inner surfaces of a closed aperture  2237  in a mounting plate  2235 . The transmitter  2231  and receiver  2232  may be electronically connected to control circuitry of the patient support. A DB37 port  2234  may be mounted on the mounting plate  2235  in the aperture  2237 . An invisible electromagnetic beam  2238  may be transmitted from the transmitter  2231  to the receiver  2232 . As shown in  FIG. 63A , as long as DB37 cable plug  2236  is not plugged into the DB37 port  2234 , the invisible electromagnetic beam  2238  remains uninterrupted, which is recognized by the control circuit as a state in which the DB37 cable plug  2236  is not plugged in. As seen in  FIG. 63B , when the DB37 cable plug  2236  is plugged into the DB37 port  2234 , the invisible electromagnetic beam  2238  is interrupted, which is recognized by the control circuit as a state in which the DB37 cable plug  2236  is plugged in. In each case, the control circuitry takes appropriate action in resetting the exit alarm features of the patient support. 
     Because patient supports may be occupied for a long time by a patient, keeping a patient entertained to alleviate boredom is important. One activity performed my many patients while occupying the patient support is reading. Therefore, many patient supports are equipped with reading lights. However, the reading light is preferably sufficiently versatile to provide lighting in a number of different directions. In the art, reading lights may be generally mounted on patient supports and configured to swivel or otherwise move to change the angle of incidence of the light. Such reading lights may suffer from drawbacks, for example they may be a safety hazard as they are not integrated into the patient support and/or they may possess moving parts that regularly wear out. An integrated reading light that permits multi-angle directional positioning without moving parts is generally desirable. 
     Referring to  FIG. 64 ,  FIG. 65A ,  FIG. 65B ,  FIG. 65C  and  FIG. 65D , a reading light  2300  integrated into the patient support is disclosed that allows for multi-angle directional positioning without moving parts. The reading light may comprise a lens  2301  covering rows and columns of lights, for example light emitting diode (LED) lights and a bezel  2302  with a control button  2303 . Each light may be integrated into the structure of the patient support and fixed in place to provide light at a certain fixed angle. There may be no external mountings protruding from the patient support and no moving parts. The lens, LED lights, bezel and control button may be in a self-contained module, which makes manufacturing and replacement simpler. 
     There may be any number of lights and rows and columns of lights. For example, there may be a single light and no rows or columns. There may be two or more lights. There may be one or more rows of lights. There may be one or more columns of lights. There may be obliquely oriented rows of lights. Any pattern of lights and rows of lights may be used to achieve the desired lighting effect. Any color or colors of light may be used, although white or yellow light may be preferred for reading. Lights may be integrated into any convenient location on the patient support, for example the head board or one or more side rails, for example head rails or foot rails. Preferably, reading lights may be located in both left and right head rails. 
     In the embodiment illustrated in  FIG. 64 ,  FIG. 65A ,  FIG. 65B ,  FIG. 65C  and  FIG. 65D , the reading light  2300  may be integrated into head rail  110 . The reading light  2300  may comprise three rows and three columns of LED lights  2304  for a total of nine lights (only one labeled). The lights may be mounted along a curved surface  2305  of rail opening  2306 . Although the reading light is shown mounted on the headward inner surface of the rail opening, the light may be mounted on another of the curved surfaces of the rail opening, for example underneath the top side of the rail opening. The curvature of the mounting surface in conjunction with a selected column of LED lights permits adjustment of reading light angle and hence light direction. Thus, the LED lights in a given column may be fixed to direct light in one direction, for example, the rightmost column of three lights in  FIG. 64  may direct light forward (toward the foot of the patient support) and inward at a fixed angle between about 15° and 20° ( FIG. 65A ) in relation to an axis parallel to the length of the patient support, the middle column of three lights may direct light forward and inward at a fixed angle between about 30° and 40° ( FIG. 65B ) and the leftmost column of three lights may direct light forward and inward at a fixed angle between about 45° and 60° ( FIG. 65C ). All three columns of LED lights may be on as shown in  FIG. 65D . 
     The lights may be controlled with any suitable controllers, e.g. buttons, knobs, toggle switches and the like, and any number of suitable controllers. Controllers may be on-off switches and/or may provide variable brightness control. In the embodiment illustrated in  FIG. 64 , one control button  2303  mounted in the bezel  2302  may be employed to control all the lights. The control may be programmed so that successive pressing of the button selectively switches on different combinations of lights. Any on/off pattern may be employed. For example, in this embodiment, pressing the button once turns on the leftmost column of lights. Pressing the button a second time turns off the leftmost column and turns on the middle column. Pressing the button a third time turns off the center column and turns on the rightmost column. Pressing the button a fourth time turns on all the columns of lights. And, pressing the button a fifth time turns off all the lights. Pressing and holding the button may be used to adjust the brightness of the light until the desired level of brightness is achieved, at which time the button may be released. 
     It is sometimes necessary or useful in a healthcare setting to display images of such things as patient information (e.g. patient name, attending nurse, allergies, etc.), dynamic information (e.g. scheduled reminders, countdown timers, bed information, etc.), instructional programs or other information of interest to the patient or caregivers (e.g. television signals, videos, JPEG files, etc.). Prior art methods, for example white boards and other static displays, cannot be efficiently updated and are often difficult to see and adjust. 
     To overcome such problems, a pico-projector may be positioned and installed on the patient support in any convenient location (e.g. the headboard as shown for a pico-protector  2309  in  FIG. 1A ) and electronically connected to the control circuitry of the patient support or some external control circuitry. The pico-projector may be controlled to swivel and position to any angle allowing for the projection and display of any screen image onto any nearby surface (e.g. a wall (side, back or front), a ceiling, a screen, etc.). Firmware driving the projector image may adjust, skew or otherwise correct the image shape to compensate for the display angle and direction. Pico-projectors and modules for driving them are known in the art, for example the Forever Plus™ pico projector turn-key module. Alternatively or additionally, the attendant&#39;s control panel  120  may comprise a graphical display for displaying any images. 
     Patient supports are often equipped with one or more holders for holding accessories, for example fluid drainage bags, intravenous (I.V.) bags, diagnostic equipment, etc. In some cases, especially for drainage bags, the accessory bags needs to be positioned below the patient and below the mattress surface level of the patient support in order to ensure proper operation of the accessory. Accessories also need to be positioned so as to not be damaged by the articulation and up/down motion of the patient support, and they should generally not be allowed to contact or drag on the floor (for health/hygiene reasons). 
     Accessories are often held to or supported on the patient support by simple static and mechanical elements, for example hooks, shelves, brackets and the like. Such elements may be generally incapable of detecting the presence or measuring the weight of the accessory. It would be useful to have an accessory holder capable of detecting the installation and presence of an accessory, and subsequently monitoring and/or measuring any ‘weight change’ of the accessory. This would be particularly useful for fluid drainage bags where monitoring the weight is a direct indication of whether the bag is full, or if the bag has become supported on an object external to the patient support. 
     Thus, there is provided an accessory holder for a patient support, the accessory holder comprising a sensor configured to measure mechanical load, pressure or weight on the holder. The sensor may include, for example, a load cell, strain gauge or the like. The sensor may be in communication with a signaling device (e.g. a sound alarm, a visual indicator and the like) that simply provides an indication of holder status, i.e. simply detecting if or when an accessory is installed. The sensor may be in communication with a control circuit that is configured to interpret data from the sensor to make a decision based on measured values. The decision may result in any one or more operations being automatically performed, for example giving an alarm, sending information to a nurse&#39;s station, restricting height of the patient support, etc.). For example, when a drainage bag hanging from a holder is being measured and monitored and the weight reaches a pre-determined weight, the sensor would send a signal that sounds an alarm, displays a visual message, sends a nurse call or a priority call signal to a nurse&#39;s station, or any combination thereof. 
     On low patient supports, the support platform is often allowed to collapse down so that the patient support can be lowered very close to the floor. This can limit positions and or ability to hang accessories, especially fluid drainage bags, for fear that lowering of the patient support might crush the accessory. Detecting the presence of and monitoring the status of the accessory installed on the patient support in the aforementioned manner permits a control system to automatically limit patient support height accordingly, thereby reducing the risk that the accessory would be crushed and reducing the risk of the accessory contacting the floor. 
     The height adjustable patient support may be provided with one or more obstruction sensors located at one or more key places on the patient support to increase safety by sensing when an object, for example a part of a person&#39;s body, may be obstructing one or more movements of the patient support, particularly the height adjustable movement. Obstruction sensors may reduce the likelihood of something being crushed under the patient support deck when the deck is lowered. 
     Obstruction sensors may take the form of touch sensitive sensors (e.g. sheet switches) that are very sensitive to pressure. A variety of types of sheet switches are available and the obstruction sensors may be one or more of these types. Types of sheet sensors may include those having printed ink circuits printed on a first sheet of plastic and a second sheet of plastic having a conductive layer laminated thereon laminated on top of the first sheet with the printed ink circuit and the conductive layer between the plastic sheets. Plastic separators may normally keep the printed ink circuit and the conductive layer sufficiently separated to permit no electrical contact between the layers until pressure is applied forcing the conductive layer to contact the printed ink circuit thereby completing the circuit. The printed ink circuit may be electrically connected to the control circuitry so completion of the circuit may send a signal to the controllers to stop motion of the patient support deck. In another type, the printed ink circuit may be replaced by another conductive layer, the two conductive layers each forming half of a circuit. Otherwise, this type of sheet switch works similarly to the printed ink type. Useful obstruction sensors are described in more detail in U.S. Pat. No. 8,134,473 issued Mar. 13, 2012, the entire content of which is herein incorporated by reference. 
     Referring to  FIG. 66A  and  FIG. 66B , a patient support is depicted showing the patient support deck  104  supported on the upper frame  102 . The upper frame  102  may be connected to and supported on the head end leg assembly  112  and foot end leg assembly  114 , the leg assemblies  112 ,  114  connected to and supported on the lower frame  132 . The leg assemblies  112 ,  114  may be raised and lowered by actuators in relation to the lower frame  132 , thereby raising and lowering the upper frame  102  and patient support deck  104 . The lower frame  132  may be suspended from the caster frame  142 . The caster frame may comprise caster assemblies  118  at the head end and foot end of the patient support. The caster assemblies may be covered by caster assembly covers  2311 . The lower frame  132  and caster frame  142  together may be collectively known as a base frame assembly  152 , and longitudinal rails of the base frame assembly  152  may be covered by a base frame assembly cover  2310 . Only one side of the base frame assembly  152  is depicted, but there may be another base frame assembly cover on the other side of the base frame assembly. 
     In lowering the patient support deck  104 , an obstruction located between the deck  104  and the base frame assembly cover  2310  or the caster assembly cover  2311  may be crushed unless some warning or control is provided in response to the presence of the obstruction. Caster assembly obstruction sensors  2313  in the form of sheet sensors may be fixed, for example with an adhesive, to an upper surface of the caster assembly covers  2311 . Further, as best seen in  FIG. 66B , base frame assembly obstruction sensors  2312  in the form of sheet sensors may be fixed to an upper surface of the caster frame  142 , for example with an adhesive, and may be wide enough to also cover the lower frame  132  so that the base frame assembly obstruction sensors  2312  cover the width of the base frame assembly  152  along the length of the base frame assembly  152  on both sides of the patient support. The base frame assembly obstruction sensors  2312  are also covered by the base frame assembly covers  2310  on both sides of the base frame assembly  152 . If there is an obstruction between the patient support deck  104  and the caster assembly covers  2311  and/or base frame assembly covers  2310 , when the obstruction contacts a caster assembly obstruction sensor  2313  or a base frame assembly cover  2310 , the weight of the object may trigger the caster assembly obstruction sensor  2313  or may push the base frame assembly cover  2310  into contact with the base frame assembly obstruction sensor  2312  thereby triggering the base frame assembly obstruction sensor  2312 . Triggering one of the obstruction sensors  2312 ,  2313  may send a signal to the control circuitry to stop the lowering of the deck  104 . In some embodiments, triggering one of the obstruction sensors  2312 ,  2313  may also include sending a signal to at least partially raise the deck  104  when the touch sensitive obstruction sensor detects the obstruction. The obstruction may then be removed and lowering of the deck  104  recommenced. 
     In another aspect, the base frame assembly obstruction sensor may comprise a more conventional switch rather than a sheet switch between the base frame assembly  152  and the base frame assembly cover  2310 . Since the base frame assembly cover  2310  is normally fairly rigid, a force applied to one part of the base frame assembly cover  2310  may depress the entire length of the base frame assembly cover  2310  so that the more conventional switch may be located anywhere along a longitudinal rail of the base frame assembly  152 . 
     Referring to  FIG. 66C  and  FIG. 66D , an obstruction located beneath the patient support but within the area bounded by the base frame assembly  152  and the caster frame assemblies  118  may not trigger either the base frame assembly obstruction sensors  2312  or the caster assembly obstruction sensors  2313  when the deck  104  is lowered. Therefore, upper leg assembly obstruction sensors  2314  in the form of sheet switches may be fixed, for example by an adhesive, on a lower surface of the upper parts of the head end and foot end leg assemblies  112 ,  114 . Obstructions beneath the upper parts of the head end and foot end leg assemblies  112 ,  114  may trigger one or both of the upper leg assembly obstruction sensors  2314 , thereby sending a signal to the control circuitry to stop the lowering of the deck  104 . In some embodiments, triggering one of the obstruction sensors  2314  may also include sending a signal to at least partially raise the deck  104  when the touch sensitive obstruction sensor detects the obstruction. The obstruction may then be removed and lowering of the deck  104  recommenced. 
     Referring to  FIG. 67A , an alternate embodiment is shown in which the leg assembly  112  has the obstruction sensor  2314  in the form of a sheet switch floating between the leg assembly  112  and a leg assembly cover  2315 . The cover  2315  form fits over the leg assembly  112  and the obstruction sensor  2314  floats between the leg assembly  112  and the cover  2315 . 
     Referring to  FIG. 67B , a skid plate  2316  is depicted which is secured to the caster frame of the patient support to protect the actuators on the underside of the patient support in the middle region of the patient support. An obstruction sensor  2317  in the form of a sheet switch floats between a skid plate cover  2318  and the underside of the skid plate  2316 . The cover  2318  form fits over the skid plate  2316  and the obstruction sensor  2317  floats between the skid plate  2316  and the cover  2318 . In the event an obstruction is directly under the middle of the bed out of range of the obstruction sensors on the leg assemblies, the obstruction sensor  2317  will be activated if the patient support is lowered on to the obstruction. The sensor  2317  would stop the lowering of the patient support and send a signal to raise the patient support a little to free the skid plate from the obstruction. 
     Superhydrophobic surfaces are highly hydrophobic, i.e., extremely difficult to wet with water or other aqueous-based fluid. The contact angles of a water droplet on the surface exceeds 150° and the roll-off angle/contact angle hysteresis is less than 10°. Likewise, superoleophobic surfaces are highly oleophobic, i.e., extremely difficult to wet with oil or another organic solvent-based fluid. The contact angles of an oil droplet on the surface exceeds 150° and the roll-off angle/contact angle hysteresis is less than 10°. Any one or more, including all, surfaces of the patient support may be coated with a superhydrophobic coating, a superoleophobic coating or a coating that is both superhydrophobic and superoleophobic. Superhydrophobic surfaces would be highly resistant to fluid spills, including beverages, medical fluids and excretions of body fluids. In addition, if the surfaces were superoleophobic, the surfaces would be highly resistant to oily secretions such as those from the hands of patients and/or caregivers. Superhydrophobic and/or superoleophobic surfaces would be more resistant to contamination, reducing the likelihood of spreading diseases. Due to the coating&#39;s hydrophobic and self-cleaning properties, it makes it more difficult for a treated surface to harbor bacteria. This allows surfaces to remain sterile, even after contact with contaminating fluids. With bacteria unable to cling to the surface, the surface remains sterile for much longer without needing to constantly be cleaned or replaced. Such coatings are particular useful on textiles, for example on mattresses, but any surface of the patient support may benefit from such coatings. 
       FIG. 68  shows a block diagram of a system  3300  for controlling the patient support  100 . Each of the components of the system  3300  may be attached to the patient support  100  at a suitable location. 
     The system  3300  includes a control circuit that comprises a controller  3302  that includes a processor  3304  electrically coupled to an input/output interface  3306  and memory  3308 . The controller  3302  may be situated in a control box that is attached or otherwise coupled to the patient support  100 . The controller  3302  may be physically integrated with another component of the system  3300 , such as the attendant&#39;s control panel  120 . 
     The processor  3304  may be a microprocessor, such as the kind commercially available from Freescale™ Semiconductor. The processor  3304  may be a single processor or a group of processors that cooperate. The processor  3304  may be a multicore processor. The processor  3304  is capable of executing instructions obtained from the memory  3308  and communicating with an input/output interface  3306 . 
     The memory  3308  may include one or more of flash memory, dynamic random-access memory, read-only memory, and the like. In addition, the memory  3308  may include a hard drive. The memory  3308  is capable of storing data and instructions for the processor  3304 . Examples of instructions include compiled program code, such as a binary executable, that is directly executable by the processor  3304  and interpreted program code, such as Java® bytecode, that is compiled by the processor  3304  into directly executable instructions. Instructions may take the form programmatic entities such as programs, routines, subroutines, classes, objects, modules, and the like, and such entities will be referred to herein as programs, for the sake of simplicity. The memory  308  may retain at least some of the instructions stored therein without power. 
     The memory  3308  stores a program  3310  executable by the processor  3304  to control operations of the patient support  100 . The controller  3302  comprising the processor  3304  executing the program  3310 , which configures the processor  3304  to perform actions described with reference to the program  3310 , may control, for example, the height of the upper frame  102 , articulation of the patient support deck  104  (e.g., upper-body tilt and knee height), exit alarm settings, and the like. The controller  3302  may also be configured to obtain operational data from the patient support  100 , as will be discussed below. Operational data obtained by the controller  3302  may be used by the processor  3304  and program  3310  to determine control limits for the patient support  100 . 
     The memory  3308  also stores data  3312  accessible by the processor  3304 . The data  3312  may include data related to the execution of the program  3310 , such as temporary working data. The data  3312  may additionally or alternatively include data related to properties of the patient support  100 , such as a patient support serial number, model number, MAC address, IP address, feature set, current configuration, and the like. The data  3312  may additionally or alternatively include operational data obtained from components, such as sensors and actuators, of the patient support  100 . Operational data may include the height of the upper frame  102 , an articulated state of the patient support deck  104 , a status of the side rails  110 ,  113 , an exit alarm setting or status, and an occupant weight. The data  3312  may include historic data, which may be time-stamped. For example, the occupant&#39;s weight may be recorded several times a day in association with a timestamp. The data  3312  may be stored in variables, data structures, files, data tables, databases, or the like. Any or all of the data mentioned above may be considered as being related to the patient support  100 . 
     The input/output (I/O) interface  3306  is configured to communicate information between the processor  3304  and components of the system  3300  outside the controller  3302 . The communication may be in the form of a discrete signal, an analog signal, a serial communication signal, or the like. The I/O interface  3306  may include a bus, multiplexed port, or similar device. The input/output interface  3306  may include one or more analog-to-digital converters. The I/O interface  3306  allows the processor  3304  to send control signals to the other components of the system  3300  and to receive data signals from these components in what may be known as a master-slave arrangement. 
     The system  3300  further includes components located on any suitable portion of the patient support  100  to achieve their intended function. The components may be interfaced directly to the controller  3302 , or interfaced to sub-controllers that act as slaves to the controller  3302 , but as masters to their respective components. For example, the controller  3302  is interfaced with: one or more support actuator sub-controllers  3316  configured to communicate with actuators of the patient support in order to control the articulation of the patient support deck  104 ; one or more load sensor sub-controllers  3318  configured to communicate with load cells positioned to measure the weight of the occupant of the patient support  100 ; one or more side-rail lock sub-controllers  3320  and/or side-rail position sub-controllers  3321 , configured to communicate with sensors configured to indicate the position and/or lock state of a side rail  110 ,  113 ; one or more frame-height actuator sub-controllers  3200  configured to communicate with actuators of the patient support  100  in order to control the height of the patient support  100 ; an occupant&#39;s control panel sub-controller  3122  that includes an interface for the occupant to adjust various features of the patient support  100 ; and/or an attendant&#39;s control panel sub-controller  3120  that includes an interface for an attendant to adjust various features of the patient support  100 . Each of the sub-controllers may receive control signals from the controller  3302 , send data signals to the controller  3302 , or both. 
     The controller  3302  is interconnected with one or more ports  3322  via the I/O interface  3306  of the controller  3302 . The port may be physical, such as a universal serial bus (USB) port, a memory card slot, a serial port, etc., or comprise structure for implementing short-range wireless communications using, for example, Bluetooth™, near field communications (NFC), optical/infra-red, or similar communication protocol. The port  3322  may be provided in any suitable location on the patient support. The I/O interface  3306  is configured to implement an appropriate data transfer protocol to allow transfer of data between a connected external device and the controller  3302 , either uni-directionally from the device to the controller  3302  or bi-directionally, via the port  3322 . Examples of suitable external devices include a data storage device, such as a flash drive, memory stick, memory card, etc. or a portable computer, such as a laptop, tablet, smartphone, or the like. 
     When the port  3322  comprises structure for implementing short-range wireless communications, the range may be limited to within, for example, 1-3 m. This is advantageous in that the connected device is constrained to be proximate to the patient support  100  when communicating, thereby increasing the security of such communication. That is, an unauthorized person would first have to gain physical access to the patient support  100  in order to communicate with it via the port  3322 , either by physical connection or wireless connection in close proximity to the patient support  100 . 
     The port  3322  may be used to communicate data between the patient support  100  and a connected device in a secure manner. The port  3322  may be used in the encryption of data and/or in the authentication of the connected device as one which has been previously authorized to communicate with the patient support  100  by personnel having physical access to the patient support. An encryption key  3314  may be uploaded via the port  3322  to facilitate the transfer of encrypted data  3332 , for example via a portable memory device  3324 .  FIG. 68  describes an embodiment whereby data communication occurs through the port  3322  itself, whereas  FIG. 69  describes an embodiment whereby the port  3322  is used to provide the required information for encryption and/or authentication, but data communication occurs through a separate communication interface  3609  (e.g. via Ethernet). Further details on secure data communication using the port  3322  and/or interface  3609  may be found in co-pending application PCT/CA2013/000495, filed May 22, 2013, which is incorporated herein by reference. 
       FIG. 69  shows a block diagram of a system  3600  for transferring data between a patient support  100  and an external device  3326 , such as a computer. Differences between the system  3600  and the system  3300  will be discussed in detail below. For further description of features and aspects of the system  3600 , the description of the system  3300  may be referenced. Features and aspects of the system  3300  may be used with the system  3600 . 
     The system  3600  includes a controller  3602  that is similar to the controller  3302  described above. The controller  3602  further includes a communication interface  3609  coupled to the I/O interface  3306 . The communication interface  3609  may include a network adaptor, such as a wired Ethernet adapter or an adapter for radio frequency communication. A radio frequency communication adapter may include a wireless bridge connected to a wired Ethernet jack. The communication interface  3609  uses standard network communication protocols, such as TCP/IP or a similar protocol, and allows the processor  3304  to communicate over a network (signified in this figure by a dashed line). 
     An external device  3326  connected to the network may then make requests for, and obtain data  3332  from, the patient support  100  via the communication interface  3609 . The external device  3326  may be a portable computer, a computer located in a facility, such as a hospital, that houses the patient support  100 , or a computer located remote from the facility. 
     In one embodiment, the external device  3326  may operate as a client in relation to the controller  3602  of the patient support operating as the server. The processor  3304  may execute a server process so that the controller  3602  operates as a server. In another embodiment, the external device  3326  is configured as a server and the controller  3602  of the patient support is configured as a client. In yet another embodiment, the external device  3326  and controller  3602  are peers. 
     When first connected to the facility network, the communication interface  3609  is assigned a temporary lease with a unique IP address via the facility&#39;s DHCP server. Alternatively the DHCP server could be set up to issue a permanent lease of the same IP address for a patient support  100  each time it is connected to the network. For example, a unique MAC address associated with the communication interface  3609  of the patient support  100  might always be provided with the same IP address by the facility&#39;s DHCP server. The choice of which method to use depends upon the facility&#39;s network configuration. 
     However, the patient support, once connected to the network, is unaware of the IP address of the external device  3326  with which it needs to communicate. It needs a mechanism to find this address, otherwise it cannot participate in data communications via the communication interface  3609 . 
     In one embodiment, in order to find the IP address of the external device  3326 , an entry is made under a specific field in the facility&#39;s DNS server. The processor  3304  is configured to check for this field and, if present, retrieves the IP address of the external device  3326 . In another embodiment, the external device  3326  periodically sends a message with the device&#39;s IP address. For example, the IP address may be encoded along with each data request or sent on a regular schedule so that each patient support is regularly updated with an IP address that is stored in memory  3308 . The choice of method depends upon the facility&#39;s network configuration and whether there is a desire for communication to only be initiated in response to a request from the remote device  3326  or self-initiated by the patient support  100 . 
     As mentioned above, data stored at the patient support  100  may be time-stamped. This is particularly useful when the patient support  100  is configured to periodically record data, such as patient weight or alarm triggering history. When the patient support  100  is connected to an external device  3326 , such as a computer, a program of the patient support  100 , such as the program  3310 , may synchronize the time stored at the patient support  100  with the time at the external device. The time at the patient support may be tracked by a local clock of the controller  3302 , for example. The local clock may be a hardware component of the controller or may be part of the program  3310 . 
     Synchronizing time in this manner is depicted in the flowchart of  FIG. 70  as method  3700 . At step  3702 , the controller of the patient support detects an external device  3326 , such as a computer, connected to the patient support  100 . The external device may be, for example, a portable computer directly connected to the patient support, a remote client or server computer connected via a network to the patient support, or similar clock-bearing electronic device. 
     Then, at step  3704 , the controller synchronizes the local clock of the patient support  100  to the clock of the external device. This may be achieved by the controller requesting a time from the external device and then setting the time at the patient support upon receiving the time from the external device. 
     The method  3700  is advantageous in that data output by the patient support  100  is time-stamped by a local clock that is synchronized to a reference clock external to the patient support  100 . Drift or error in the local clock of the patient support  100  is corrected each time the external device is connected to the patient support  100 . 
       FIG. 71  shows another block diagram of the system  3300  for controlling the patient support  100 . Electrical couplings are shown by solid connecting lines and mechanical couplings are shown by dashed ones. In this embodiment, the system  3300  further includes electromechanical actuators, for example side-rail unlocking servo  2443 , for unlocking the side rail  110 ,  113 . Each side rail  110 ,  113  is generally provided with one servo  2443 , and a side-rail release button  3609  for activating the servo  2443  may be provided on the patient support remote from the side rail  110 ,  113 . A single side-rail release button  3609  may be configured to actuate the release mechanism of a plurality of side rails  110 ,  113 . 
     The servo  2443  and/or side-rail release button  3609  may be electrically coupled to the side rail locking sensor sub-controller  3320 , which in turn is interfaced with the controller  3302  via I/O interface  3306 . The servo  2443  may be double acting, spring biased in one direction, or of other design. The servo  2443  is configured to electrically actuate and unlock the locking structure  3510  comprising the raised catch  2436  upon activation of a switch via side-rail release button  3609 . Alternative embodiments of electromechanical actuators may be used in place of the servo  2443 , for example linear actuators, etc. 
     The side-rail release button  3609  may form part of the occupant&#39;s control panel and may be connected to the occupant&#39;s control panel sub-controller  3122 . In some embodiments, the side-rail release button  3609  is positioned on an inside surface of the side rail  110 ,  113  at a location that is readily accessible to the occupant of the patient support  100 . In other embodiments, a handle, lever, or other device may be used to activate the switch instead of the button  3609 . This may be provided in a location that is inaccessible to the occupant of the patient support  100 . A side rail release button similar to the button  3609  may be provided in additional or alternative locations, for example on the outside of the side rail, the attendant&#39;s control panel  120 , etc. 
     The side-rail locking structure  3510  is configured to unlock upon electrical actuation of the release via button  3609 . The side-rail locking structure  3510  is configured to mechanically unlock, as mentioned, upon mechanical actuation of the release via rail release handle  2419 . Therefore, the button  3609  is part of an electrical release and the rail release handle  2419  is part of a mechanical release. The electrical and mechanical releases together form a combined release that electrically and mechanically controls the locking structure  3510 . That is, in order to lower the side rail  110 ,  113 , an attendant (or sometimes an occupant) may unlock the side rail  110 ,  113  by pressing rail release handle  2419  or may unlock the side rail  110 ,  113  by pressing the button  3609 . The mechanical release may override the electrical release and permit the rail to be unlocked. It is advantageous that the same side-rail locking structure may be unlocked both mechanically and electrically; for example, in the event of power failure. 
     Side-rail release buttons  3609  may be provided elsewhere on the patient support  100  to facilitate electrical unlocking of the side rails  110 ,  113 . For example, four side-rail release buttons  3609 , one for each side rail  110 ,  113 , may be provided at the attendant&#39;s control panel  120  and interfaced with the attendant&#39;s control panel sub-controller  3120 . A side rail release button  3609  may be accessible to an occupant of the bed to electrically actuate the release and unlock the side rail to permit egress from the bed. This may be in addition to or as an alternative to buttons  3609  provided for use by the caregiver or attendant. 
     The program  3310  may be configured to control side-rail unlocking as follows. 
     The program  3310  responds to predetermined input at the side-rail release button  3609  in order to unlock the side rails  110 ,  113 . In one embodiment, three presses of the side-rail release button  3609  by an occupant of the bed in quick succession electrically actuates the release and unlocks the respective side rail  110 ,  113 . If the program  3310  detects fewer than three presses in an allotted time, then the side rail  110 ,  113  is not unlocked, while detection of three or more presses in the allotted time unlocks the side rail  110 ,  113 . This may advantageously prevent inadvertent unlocking of the side rails  110 ,  113  by the occupant of the patient support  100 . 
     The program  3310  may be configured to lock out the side-rail release button  3609 . That is, the program  3310  may ignore input at the side-rail release button  3609  under certain circumstances. For example, the attendant&#39;s control panel sub-controller  3120  may include a control lockout option that configures the program  3310  to ignore commands received from the occupant of the patient support  100 . This may be used when the safety of the occupant is a concern. Additional lockout states may include when the bed is in an unacceptable configuration, for example a Trendelenburg or reverse Trendelenburg orientation, when the backrest or knee is raised above an acceptable level, when a height of the bed is above or below an acceptable level, when a patient support surface or mattress is in an unacceptable orientation, when the caster wheels or brakes are unlocked, etc. 
     The program  3310  may be configured to automatically electrically actuate the release and unlock any or all of the side-rail locking structures  3510  using the respective servos  2443  in the event that the CPR handle  124  is pulled, thereby putting the patient support in an emergency state. Each CPR handle  124  includes a switch  3606  that indicates to the controller  3302  that the CPR handle  124  has been pulled. Among other things, the switch  3606  may provide the controller  3302  with information on the state of the CPR handle  124 , which the controller  3302  may use, for example, to reset the emergency CPR mechanism. However, regarding the side rails  110 ,  113  the program  3310  may reference the state of each CPR handle switch  3606  and accordingly control the servos  2443  to unlock the side-rail locking structures  3510  after one of the CPR handles  124  has been pulled. Which of the side rails  110 ,  113  are to be so unlocked or the sequence in which they are unlocked may be predetermined. In one embodiment, only the two head-end side rails  110 ,  113  are unlocked in an emergency state. In another embodiment, all of the side rails  110 ,  113  are unlocked in this way. Electrically unlocking the side rails  110 ,  113  during an emergency may advantageously allow the side rails to lower automatically, thereby permitting quicker and less complicated access to the occupant of the patient support  100 . That is, emergency personnel do not need to first manually lower the side rails  110 ,  113  before performing procedures, such as chest compressions, that require unobstructed access to the occupant. Other actions may be taken by the controller  3302  in an emergency state, for example flattening the patient support surface, triggering lights or alarms indicative of an emergency state, etc. 
     The program  3310  may be configured to automatically electrically actuate the release and unlock any or all of the side-rail locking structures  3510  using the respective servos  2443  in other circumstances. For example, the occupant&#39;s control panel may be provided with a switch for unlocking the side-rails. This is particularly useful for mothers breast feeding an infant because the mother does not need to call for an attendant to lower the side rails to return the infant to a bassinet once breast feeding is over. The mother is able to lower the rails easily without needing to disturb the infant and then is able to exit the patient support without assistance of an attendant. 
     The program  3310  may be configured to generate an alarm signal in response to unlocking of a side rail  110 ,  113 . In one embodiment, the alarm signal is generated when the release is electrically actuated. In another embodiment, a side rail  110 ,  113  is provided with a side rail locking sensor interfaced with a side-rail locking sensor sub-controller  3320  that senses the locked/unlocked state of the side rail  110 ,  113 . The side-rail locking sensor may comprise a limit switch or similar device. When the program  3310  determines that a side rail  110 ,  113  has been unlocked, the program  3310  outputs the alarm signal to a device, such as an alarm device  3608  on the patient support  100  or a remote monitoring device located at a nurse call station. The alarm device  3608  may include one or more of an audible device, such as a speaker, and a visible device, such as a light or display. The alarm device  3608  may further indicate which of the side rails  110 ,  113  has been unlocked. For example, each side rail  110 ,  113  may include a light-emitting diode (LED) that flashes when the side rail  110 ,  113  is unlocked. 
     In another embodiment, still with reference to  FIG. 71 , the program  3310  may be configured to adjust an allowable height of the upper frame  102  of the patient support  100  with reference to the side rails  110 ,  113 . Adjusting an allowable height based on the side rails  110 ,  113  may reduce a patient falling hazard and/or may reduce the likelihood of damage to the patient support  100 . 
     The program  3310  constrains the height-adjusting actuator sub-controller  3200  to operate according to at least one actuation limit and provides an alarm signal to the alarm device  3608  when the actuation limit is violated. The program  3310  may establish one or more actuation limits corresponding to one or more of a maximum allowable height of the upper frame  102  and a minimum allowable height of the upper frame  102 . An actuation limit corresponds to a position of a height adjusting actuator connected to the sub-controller  3200  and may be stored and compared in terms, such as rotary encoder pulse count, that are different from terms (e.g., cm or inches) in which the corresponding allowable height is expressed. An allowable height is enforced by the program  3310  ignoring commands that would cause the height-adjusting actuator sub-controller  3200  to violate an actuation limit. Default maximum and minimum allowable heights may be used to stop the height-adjusting actuator sub-controller  3200  during normal raising and lowering of the patient support  100 . 
     The system  3300  may additionally or alternatively include side-rail position sensors, for example first and second rail position switches  2447 ,  2448  (see  FIG. 56 ) that are electrically coupled to a side-rail position sensor sub-controller  3321  that is connected with the input/output interface  2306 . The side-rail position sensor sub-controller  3321  is configured to detect a position of the side rail  110 ,  113  for example whether the respective side rail  110 ,  113  is in the raised position, the lowered position, or optionally another position. The side-rail position sensors may be limit switches, proximity sensors, optical sensors or similar devices. 
     The program  3310  may reference one or more of the side-rail locking sensor sub-controller  3320  and side-rail position sensor sub-controller  3321  to determine whether an allowable height of the patient support  100  is to be adjusted. Each sub-controller  3320 ,  3321  may indicate to the program  3310  that the patient support  100  should not be raised or lowered beyond an allowable height. Other features of the patient support  100 , such as configuration, may be controlled based on input from the sub-controllers  3320  and/or  3321 ; for example the patient support  100  may be prevented from entering a Trendelenburg or reverse Trendelenburg orientation, the backrest or knee may be prevented from being raised above an acceptable level, a height of the patient support  100  may be prevented from being adjusted outside of an acceptable range, the patient support deck  104  may be prevented from entering an unacceptable orientation, the caster wheels or brakes may be prevented from being unlocked, etc. 
     The program  3310  may be configured to lower the maximum allowable height of the upper frame  102  when a side rail  110 ,  113  is unlocked, as determined by the side-rail locking sensor sub-controller  3320 , or when a side rail  110 ,  113  is lowered, as determined by the respective side-rail position sensor sub-controller  3321 . When a side rail  110 ,  113  is unlocked or lowered, the program  3310  ignores commands that would cause the upper frame  102  to be raised higher than the maximum allowable height. When the program  3310  determines that the upper frame  102  is higher than the maximum allowable height, as may be the case when a side rail  110 ,  113  is unlocked or lowered after the upper frame  102  has been raised, then the program  3310  outputs an alarm via the alarm device  3608 . This advantageously helps reduce injury caused by the occupant falling from the patient support  100 . 
     In a numerical example, the default maximum allowable height is 91 cm (or 36 inches) and the maximum allowable height with an unlocked or lowered side rail  110 ,  113  is 61 cm (or 24 inches). The patient support  100  may be raised and lowered below 61 cm irrespective of the side rails  110 ,  113  being locked/unlocked or raised/lowered. If a side rail  110 ,  113  is unlocked or lowered and an attempt is made to raise the patient support  100  above 61 cm, then the program  3310  ignores the raise command. If the patient support is already above 61 cm when a side rail  110 ,  113  is unlocked or lowered, then the program  3310  issues an alarm and also ignores raise commands. 
     The program  3310  may be configured to raise the minimum allowable height of the upper frame  102  when a side rail  110 ,  113  is unlocked, as determined by the respective side-rail locking sensor sub-controller  3320 , or when a side rail  110 ,  113  is lowered, as determined by the respective side-rail position sensor sub-controller  3321 . When a side rail  110 ,  113  is unlocked or lowered, the program  3310  ignores commands that would cause the upper frame  102  to be lowered lower than the minimum allowable height. When the program  3310  determines that the upper frame  102  is lower than the minimum allowable height, as may be the case when a side rail  110 ,  113  is unlocked or lowered after the upper frame  102  has been lowered, then the program  3310  outputs an alarm via the alarm device  3608 . This may advantageously help prevent damage to the side rails  110 ,  113  or objects on the floor underneath the side rails  110 ,  113 . 
     In a numerical example, the default minimum allowable height is 15 cm (or 6 inches) and the minimum allowable height with an unlocked or lowered side rail  110 ,  113  is 20 cm (or 8 inches) or other increased amount sufficient to prevent interference between the side rails  110 ,  113  and the floor. The patient support  100  may be raised and lowered above 20 cm irrespective of the side rails  110 ,  113  being locked/unlocked or raised/lowered. If a side rail  110 ,  113  is unlocked or lowered and an attempt is made to lower the patient support  100  below 20 cm, then the program  3310  ignores the lower command. If the patient support is already below 20 cm when a side rail  110 ,  113  is unlocked or lowered, then the program  3310  issues an alarm and also ignores lower commands. 
     The features of the program  3310  described in the embodiments above, and specifically the features regarding electrical unlocking of side rails  110 ,  113 , such as control lock out, CPR unlocking, alarms, and allowable height adjustments, may be used independently of each other and may be used together in any suitable combination. 
     The mechanical release action of the side-rail locking structure  3510  may override the electrical release action of the locking structure  3510 . That is, in some situations, such as power failure, the side rail locking servo  2443  may not be used to unlock the side rail  110 ,  113 . However, in such situations, the rail release handle  2419  may always be pushed to unlock the side rail  110 ,  113 . Another example of such a situation is provided when a control lock out is enabled via the attendant control panel sub-controller  3120  that disables the side-rail release button  3609  and thus disables electrical unlocking of the side rail  110 ,  113 . Again, the rail release handle  2419  may be pushed/pulled to unlock the side rail  110 ,  113 . This is advantageous in that the side rails  110 ,  113  may always be lowered during an emergency, regardless of the state of electrical power at the patient support  100 , while still providing convenience via electrical side rail unlocking when power is available. 
     The bed may be equipped with the bed condition monitoring system, otherwise known as a “watchdog” system, which permits a user to define a number of bed conditions for monitoring, data logging, and/or alarm generation. Data collected in conjunction with the monitored bed conditions may be stored locally, indicated locally with or without storage, output locally to an electronic storage device, and/or transmitted over a TCP/IP network. Transmission of data over a TCP/IP network may be dependent on the presence of an encryption key, as previously described. Examples of bed conditions that may be monitored include one or more of the following: height of the bed frame, angle of bed frame, angle of one or more portions of the mattress support deck (e.g., head portion of mattress support deck), contour of the mattress support deck, with of the mattress support deck or bed frame, position of one or more side rails, lock state of one or more side rails, headboard width, lock state of one or more casters, width between two casters at the head or foot end of the bed, actuation of a CPR release, weight applied to the bed, movement of the bed (especially movement of the bed along the floor), electrical power provided to the bed (especially connection or disconnection of AC power), mattress conditions of the bed (especially inflation status of a mattress), and other bed related conditions. The conditions to be monitored are pre-set or selectable by an attendant or other authorized person using, for example, an attendant control panel on the footboard of the bed. Alternatively, all conditions are monitored by default, with either all conditions or only selected conditions available for storage and/or local indication. 
     In one embodiment, the conditions are monitored in relation to a setpoint; deviation of the condition from the setpoint (outside of optional tolerance limits) triggers an alarm. The setpoint is obtained by taking a momentary snapshot of the monitored conditions when the bed is in a desired configuration. The momentary snapshot is obtained by an attendant using, for example, a button on the attendant control panel at the footboard of the bed. Alternatively, the snapshot is obtained automatically after expiry of a predetermined reconfiguration time limit (e.g. 30 seconds), following the clearing of an alarm generated by deviation of the monitored condition from the previous setpoint and/or following the cancellation of a monitoring pause initiated by an attendant. The pre-determined time limit may be fixed or may be modified by the attendant within certain limits. The monitoring pause is initiated by the attendant by pressing a button on the attendant control panel at the footboard of the bed. The monitoring pause may have a predetermined or user adjustable monitoring pause time limit, after which the monitoring pause is canceled. Alternatively, the monitoring pause may be canceled by the attendant by pressing a button on the attendant control panel. The monitoring pause may suspend monitoring during the monitoring pause time limit. Alternatively, the monitoring pause may simply inhibit visual and audible indications of alarms during the monitoring pause time limit and the reconfiguration time limit. 
     The alarm is locally indicated by a visual indicator, an audible alert or a combination thereof. The visual indicator may be provided at 1, 2, 3, 4 or more positions about the bed. In one embodiment, the visual indicator is provided as a light at a foot end of the bed, for example, on the footboard. In another embodiment, the visual indicator is provided as two lights at the foot end of the bed, for example, as illuminated bumper lights provided beneath a frame or footboard of the bed. In yet another embodiment, the visual indicator is provided as three lights at the foot end of the bed, for example, a light on the footboard and two illuminated bumper lights provided beneath a frame or footboard of the bed. In still another embodiment, the visual indicators is provided as four lights at four corners of the bed, for example, four illuminated bumper lights provided beneath a frame of the bed and/or with two of the four lights provided beneath a footboard of the bed. In other embodiments, the visual indicators are provided by LCD screen or by non-illuminated indicators, such as mechanical flags. The visual indicator comprises a color that would not be confused by persons of skill in the art with colors designated for other bed functions. For example, a purple light may be chosen rather than green or red lights, which are reserved for other conditions that are not necessarily monitored by the bed condition monitoring system. The visual indicator may be provided in more than one color and/or in more than one pattern, for example, a short flash, a long flash, a combination of short and long flashes, a fade in, a fade out, etc. The visual indicator and/or audible alert may be varied in brightness and/or switched off independently of monitoring of bed conditions, for example at night in order to prevent disturbing sleeping patients nearby, without interrupting the monitoring of bed conditions. In this manner, bed condition data and/or alarms can continue to be logged, or output via TCP/IP or nurse call system, without a local visual or audible indication. 
     It should be noted that, independently of the bed condition monitoring system, beds are equipped with monitoring for certain critical safety parameters. These parameters include a lock state of the caster wheels, activation of the CPR release and optionally interference between a component of the bed and a person. A different audible alert and/or visual indicator is used for these conditions to allow them to be readily distinguished from alarms generated by the bed condition monitoring system, which may be less critical in nature. For example, in the event that the caster wheels are unlocked, one or more visual indicators is provided in a solid red color. In the event that the CPR release is activated, one or more visual indicators is illuminated in a flashing red color. In the event that there is interference between a component of the bed and a person, one or more visual indicators is illuminated in a different color or a flash pattern, optionally in combination with an audible alert. In this way, violation of critical safety parameters is readily recognizable by attendants. 
     The bed may be equipped with a patient condition monitoring system, sometimes known as a “bed exit” monitoring system, which permits a user to define a number of patient conditions for monitoring, data logging, and/or alarm generation. Data collected in conjunction with the monitored patient conditions may be stored locally, indicated locally with or without storage, output locally to an electronic storage device, and/or transmitted over a TCP/IP network. Transmission of data over a TCP/IP network may be dependent on the presence of an encryption key, as previously described. Examples of patient conditions that may be monitored include one or more of the following: movement on the bed, movement from one location on the bed to another location, exit from the bed, weight, restlessness, heart rate, blood oxygen level, respiration rate, etc. The conditions to be monitored are pre-set or selectable by an attendant or other authorized person using, for example, an attendant control panel on the footboard of the bed. Alternatively, all conditions are monitored by default, with either all conditions or only selected conditions available for storage and/or local indication. 
     In one embodiment, the conditions are monitored in relation to a setpoint; deviation of the condition from the setpoint (outside of optional tolerance limits) triggers an alarm. The setpoint is obtained by taking a momentary snapshot of the monitored conditions when the patient is in a desired position, condition or configuration on the bed. The momentary snapshot is obtained by an attendant using, for example, a button on the attendant control panel at the footboard of the bed. Alternatively, the snapshot is obtained automatically after expiry of a predetermined reconfiguration time limit (e.g. 30 seconds), following the clearing of an alarm generated by deviation of the monitored condition from the previous setpoint and/or following the cancellation of a monitoring pause initiated by an attendant. The pre-determined time limit may be fixed or may be modified by the attendant within certain limits. The monitoring pause is initiated by the attendant by pressing a button on the attendant control panel at the footboard of the bed. The monitoring pause may have a predetermined or user adjustable monitoring pause time limit, after which the monitoring pause is canceled. Alternatively, the monitoring pause may be canceled by the attendant by pressing a button on the attendant control panel. The monitoring pause may suspend monitoring during the monitoring pause time limit. Alternatively, the monitoring pause may simply inhibit visual and audible indications of alarms during the monitoring pause time limit and the reconfiguration time limit. 
     The alarm is locally indicated by a visual indicator, an audible alert or a combination thereof. The visual indicator may be provided at 1, 2, 3, 4 or more positions about the bed. In one embodiment, the visual indicator is provided as a light at a foot end of the bed, for example, on the footboard. In another embodiment, the visual indicator is provided as two lights at the foot end of the bed, for example, as illuminated bumper lights provided beneath a frame or footboard of the bed. In yet another embodiment, the visual indicator is provided as three lights at the foot end of the bed, for example, a light on the footboard and two illuminated bumper lights provided beneath a frame or footboard of the bed. In still another embodiment, the visual indicators is provided as four lights at four corners of the bed, for example, four illuminated bumper lights provided beneath a frame of the bed and/or with two of the four lights provided beneath a footboard of the bed. In other embodiments, the visual indicators are provided by LCD screen or by non-illuminated indicators, such as mechanical flags. The visual indicator comprises a color that would not be confused by persons of skill in the art with colors designated for other bed functions. For example, a blue light may be chosen rather than green or red lights, which are reserved for other conditions that are not necessarily monitored by the patient condition monitoring system. The visual indicator may be provided in more than one color and/or in more than one pattern, for example, a short flash, a long flash, a combination of short and long flashes, a fade in, a fade out, etc. The visual indicator and/or audible alert may be varied in brightness and/or switched off independently of monitoring of patient conditions, for example at night in order to prevent disturbing sleeping patients nearby, without interrupting the monitoring of bed conditions. In this manner, bed condition data and/or alarms can continue to be logged, or output via TCP/IP or nurse call system. 
     When the patient condition monitoring system is used to monitor patient movement on the bed, movement from one location on the bed to another location, or exit from the bed, load cells are employed. 1, 2, 3, 4 or more load cells may be used, depending upon the sensitivity of the monitoring desired. Input from the load cells, either calibrated for patient weight or merely indicative of patient wait, may be provided to a controller and used in performing calculations. The results of these calculations may be used to determine whether the monitored condition is outside of allowable parameters, thus generating an alarm. 
     In one embodiment, in a first mode, the sum of a pair of load cells at the head end of the bed and the sum of a pair of load cells at the foot end of the bed is calculated. When the sum of either pair of load cells differs from the sum obtained when a snapshot of the bed is taken by a predetermined percentage, an alarm is generated. For example, when the sum of load cells at the foot end of the bed increases by more than 10% from the value obtained for the sum when the snapshot is taken, or the value for the sum of load cells at the head end of the bed decreases by more than 10% from the value obtained for the sum when the snapshot is taken, an alarm indicative of the raising of the patient&#39;s head (thereby transferring weight from the head end of the bed to the foot end of the bed) is generated. In a second mode, the sum of a pair of load cells on the right side of the bed and the sum of a pair of load cells on the left side of the bed is calculated. When the sum of either pair of load cells differs from the sum obtained when a snapshot of the bed is taken by a predetermined percentage, an alarm is generated. For example, when the sum of load cells at the right side of the bed increases by more than 25% from the value obtained for the sum when the snapshot is taken, or the value for the sum of load cells at the left side of the bed decreases by more than 25% from the value obtained for the sum when the snapshot is taken, an alarm indicative of the patient rolling towards the right side of the bed (thereby transferring weight from the left side of the bed to the right side of the bed) is generated. By increasing the percentage value chosen, for example to more than 35%, this mode may also be used to indicate when a patient is seated on the right edge of the bed and about to exit from the right side of the bed. In a third mode, the sum of at least two load cells (preferably all load cells) is calculated. When the sum differs from the sum obtained when the snapshot is taken by a predetermined percentage, an alarm is generated. For example, when the sum of the load cells decreases by more than 90% from the value obtained for the sum when the snapshot is taken, an alarm indicative of the patient having exited the bed (thereby transferring the majority of his or her weight from the bed to the floor) is generated. Persons of skill in the art will understand that these percentages are provided for illustrative purposes only and may be varied to adjust the sensitivity of each mode. The bed may be provided with any combination of the above modes, including one, two or three modes. The number of modes and the sensitivity of the modes may be preset or may be adjusted by an attendant or other authorized person using the attendant control panel. 
     In a second embodiment, the location of a center of gravity of the patient on the bed is calculated. This calculation is performed using at least two load cells, preferably three load cells, more preferably four load cells. In a first mode, a first region for the location of the center of gravity on the bed is defined. Movement of the center of gravity outside of the first region generates an alarm indicative of a small amount of patient movement. For example, the first region may be defined such that raising of a patient&#39;s head causes the center of gravity to move outside of the first region and generate an alarm. In a second mode, a second region for location of the center of gravity on the bed is defined. The second region is larger than the first region and includes all, or at least a portion of, the first region. Movement of the center of gravity outside of the second region generates an alarm indicative of a larger amount of patient movement. For example, the second region may be defined such that movement of a patient towards the right side or left side of the bed causes the center of gravity to move outside of the second region and generate an alarm. In a third mode, a third region for location of the center of gravity on the bed is defined. The third region is larger than the first and second regions and includes all, or at least a portion of, the first and second regions. Movement of the center of gravity outside of the third region generates an alarm indicative of an even larger amount of patient movement. For example, the third region may be defined such that movement of a patient off of the bed causes the center of gravity to move outside of the third region and generate an alarm. Although a variety of methods may be used, one particular method of calculating a center of gravity of the patient is further described in U.S. Pat. No. 5,276,432, which is hereby incorporated herein by reference. 
     Independently of the bed or patient condition monitoring systems, the bed may include an attendant information system configurable to generate an audible and/or visual indicator in response to certain attendant specified conditions. In one embodiment, a button on the attendant control panel of the footboard of the bed is used to activate a nurse reminder function that illuminates one or more visual indicators in response to the attendant specified condition. The specified condition may comprise expiry of a certain time limit; this can be advantageous to serve as a timer for blood pressure monitoring, taking a patient&#39;s pulse, or simply serving as a reminder to return and perform a certain function at a certain time. Other specified conditions may include patient related conditions, such as patient weight, or bed related conditions, such as position or lock state of one or more side rails. 
     The alarm is locally indicated by a visual indicator, an audible alert or a combination thereof. The visual indicator may be provided at 1, 2, 3, 4 or more positions about the bed. In one embodiment, the visual indicator is provided as a light at a foot end of the bed, for example, on the footboard. In another embodiment, the visual indicator is provided as two lights at the foot end of the bed, for example, as illuminated bumper lights provided beneath a frame or footboard of the bed. In yet another embodiment, the visual indicator is provided as three lights at the foot end of the bed, for example, a light on the footboard and two illuminated bumper lights provided beneath a frame or footboard of the bed. In still another embodiment, the visual indicators is provided as four lights at four corners of the bed, for example, four illuminated bumper lights provided beneath a frame of the bed and/or with two of the four lights provided beneath a footboard of the bed. In other embodiments, the visual indicators are provided by LCD screen or by non-illuminated indicators, such as mechanical flags. The visual indicator comprises a suitable color (e.g. pink) that would not be confused by a person of skill in the art with colors designated for other bed functions. The visual indicator may be provided in more than one color and/or in more than one pattern, for example, a short flash, a long flash, a combination of short and long flashes, a fade in, a fade out, etc. to further distinguish it from other bed indicators. The visual indicator for the nurse reminder function may be co-located with other visual indicators, for example visual indicators relating to the bed condition monitoring system and/or patient condition monitoring system. 
     Programs detailed herein are described in terms of software, hardware, or firmware for sake of convenience. Software, hardware, firmware, or various combinations of such may be used to realize any of the programs described herein. 
     Novel features will become apparent to those of skill in the art upon examination of the detailed description. It should be understood, however, that the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the specification as a whole. 
     Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s). 
     The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular. Any reference to claim elements as “at least one of X, Y and Z” is meant to include any one of X, Y or Z individually, and any combination of X, Y and Z, for example, X, Y, Z; X, Y; X, Z ; and Y, Z.