Abstract:
A height adjustable patient support has a frame, a pair of motor powered leg assemblies operable to vertically raise and lower the frame between a lowermost position and an uppermost position, a guide structure for longitudinally guiding an end of at least one of the pair of leg assemblies along the frame as the at least one of the pair of leg assemblies operates to vertically raise and lower the frame, and a non-motorized structure operable to longitudinally bias the end of the at least one of the pair of leg assemblies when the frame is in the lowermost position, the non-motorized structure mounted on the patient support by a mounting structure non-rigidly secured to the patient support. The non-motorized structure may assist with raising the frame from the lowermost position until motors operating the motor powered legs are able to continue with raising the frame.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/073,952, filed on Oct. 31, 2014 which is incorporated herein by reference in its entirety and is commonly owned by Stryker Corporation, Kalamazoo, Mich. 
     
    
     FIELD 
       [0002]    This application relates to vertically adjustable furniture, in particular to vertically adjustable patient supports. 
       BACKGROUND 
       [0003]    Vertically adjustable or height adjustable patient supports, for example beds, are of great utility in hospital and extended care settings. Such beds are used in a lowered position to minimize the risk of injury to persons who may through inattention or infirmity fall out of the bed. The beds are used in an upper position to enable personnel to perform their functions with respect to the bed or its occupant without bending down or having to work in an awkward physical position. 
         [0004]    Patient support decks of height adjustable beds may be raised or lowered by way of actuators, for example linear actuators. The actuators may be motor driven and may be attached to pivoting legs and a bed frame, while the legs are pivotally attached to the bed frame. When raising the patient support deck of such a bed from a lowermost position, one problem that arises is the greater motor power required to initiate the raising sequence action. Greater motor power at the lowermost position is required because the leg is tucked under the bed frame and virtually parallel thereto resulting in almost no effective angle between the leg and the bed frame. 
         [0005]    One arrangement for overcoming this problem is disclosed in U.S. Pat. No. 7,185,377 issued Mar. 6, 2007. This arrangement comprises linear guide rods rigidly attached at both ends to the bed frame. Bearing blocks are rigidly connected to linear actuators and movably mounted on the linear guide rods. Spring members are mounted circumferentially on the linear guide rods. When the bed frame is in the lowermost position, the bearing blocks attached to the linear actuators longitudinally compress the springs between the bearing blocks and transverse cross-members of the bed frame. When the bed frame is sought to be raised the energy in the compressed springs act on the bearing blocks to assist the actuators during the first or initial movement along the linear guide rods. Once movement has been started and an effective angle established, the actuators alone are then capable of raising the bed frame the rest of the way. 
         [0006]    Despite the improvements described in U.S. Pat. No. 7,185,377, there remains a need for more robust assemblies that assist motorized actuators in raising the patient support deck of a height adjustable bed from a lowermost position. 
       SUMMARY 
       [0007]    In one aspect, there is provided a height adjustable patient support comprising: a frame; a pair of motor powered leg assemblies operable to vertically raise and lower the frame between a lowermost position and an uppermost position; a guide structure for longitudinally guiding an end of at least one of the pair of leg assemblies along the frame as the at least one of the pair of leg assemblies operates to vertically raise and lower the frame; and, a non-motorized structure operable to longitudinally bias the end of the at least one of the pair of leg assemblies when the frame is in substantially the lowermost position, the non-motorized structure mounted on the patient support by a mounting structure non-rigidly secured to the patient support. 
         [0008]    In another aspect, there is provided a height adjustable patient support comprising: a frame; a pair of leg assemblies powered by linear actuators, the leg assemblies operable to vertically raise and lower the frame between a lowermost position and an uppermost position; tracks mounted on the frame for longitudinally guiding ends of the leg assemblies along the frame as the leg assemblies operate to vertically raise and lower the frame, the leg assemblies comprising rotating elements mounted thereon, the rotating elements riding in the tracks as the frame is raised and lowered; and, springs operable to longitudinally bias the ends of the leg assemblies when the frame is in substantially the lowermost position, the springs mounted on the patient support by mounting structures non-rigidly secured to the patient support. 
         [0009]    The patient support may be, for example, a bed, a chair, a stretcher or the like. Preferably, the patient support is a bed, particularly a hospital bed or an extended care bed. The motor powered leg assemblies may be powered by actuators, for example linear actuators, mounted on the patient support. The actuators may be connected to the leg assemblies and the patient support, for example the frame. While only one of the leg assemblies may be provided with a guide structure and a non-motorized structure to longitudinally bias the end of the leg assembly, preferably both of the leg assemblies have a guide structure and a non-motorized structure to longitudinally bias the ends of the leg assemblies. 
         [0010]    The non-motorized structure may be any mechanical device not powered by a motor, which can apply force to effect movement. Preferably, the non-motorized structure comprises a resiliently deformable element, such as an elastomeric element or a spring (e.g. helical spring, gas spring or the like), preferably a compression spring, more preferably a helical compression spring. The non-motorized structure may apply a longitudinal biasing force to the end of the leg assembly when the frame is in substantially the lowermost position (i.e. at or near the shortest vertical distance from the floor), where the longitudinal biasing force is capable of longitudinally translating the end of the leg assembly to assist in raising the frame from the substantially lowermost position. 
         [0011]    The non-motorized structure may be mounted on the patient support by a mounting structure non-rigidly secured to the patient support. The mounting structure may comprise an elongated element slidingly supported in an aperture through an end plate secured to the frame. In addition to the elongated element, the mounting structure may comprise a ball and socket arrangement to which the elongated element is connected. Connection of the elongated element to the ball may be releasable or non-releasable. The mounting structure is free to translate longitudinally. 
         [0012]    The non-motorized structure may cooperate with the mounting structure to bias the mounting structure toward an end of the leg. The elongated element may be permitted to slide through the aperture upon raising and lowering of the leg. The non-motorized structure may be coaxially mounted around the elongated element. The non-motorized structure may engage a surface of the mounting structure, for example a surface of the socket, whereby the forces applied by the non-motorized structure act on the surface of the mounting structure to bias the mounting structure longitudinally with respect to the frame. The biasing of the mounting structure may occur when the frame is in substantially the lowermost position. 
         [0013]    The leg assemblies may comprise engagement structures, preferably rigidly mounted thereon, configured to engage the non-motorized structures, or the mounting structures, when the frame is in substantially the lowermost position. The non-motorized structures may apply longitudinal biasing forces to the engagement structures when the frame is in substantially the lowermost position, the longitudinal biasing forces capable of longitudinally translating the ends of the leg assemblies to assist in raising the frame from the lowermost position. The actuators powering the leg assemblies may be connected to the leg assemblies proximate the engagement structures. The engagement structures may be configured, for example with abutment plates, to engage the mounting structure to compress the springs when the frame is in the lowermost position. 
         [0014]    The guide structures may comprise one or more tracks longitudinally mounted on the frame. The tracks engage with one or more elements on the leg assemblies to guide the ends of the leg assemblies longitudinally when the frame is being raised and lowered. The elements on the leg assemblies that engage the tracks may comprise one or more rotating elements rotationally mounted thereon that cooperate with the guide structure to assist with longitudinal translation of the ends of the leg assemblies. The rotating elements may be rollers, for example wheels, wherein the one or more rotating elements are configured to roll in the one or more tracks. The one or more tracks may comprise, for example, two spaced apart tracks. The one or more rollers may comprise, for example, two rollers configured to ride in the tracks. 
         [0015]    The arrangement described herein assists the actuators in raising the frame from a lowermost position for a sufficient distance to permit the formation of an effective angle between the frame and the longitudinal elements of the leg assemblies so that the motors do not require greater motor power to initiate the raising sequence action. The arrangement described herein allows both the motorized and non-motorized elements to act directly on the leg, rather than an intermediate structure connected to the leg, leading to improved transfer of force to the leg, reduced friction in raising and lowering the bed, and less tendency towards binding during movement of the leg. In addition, the pivotal connection of the leg to the frame is able to be located proximal the deck, which increases the effective angle between the leg and the frame when the bed is in the lowermost position. This increases the load lifting capability of the motorized structure, allowing larger patients to be raised and lowered by the bed. 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 
         [0016]    For clearer understanding, preferred embodiments will now be described in detail by way of example, with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is an isometric view of a topside of a height adjustable bed in a lowermost position. 
           [0018]      FIG. 2  is an isometric view of a topside of the height adjustable bed of  FIG. 1  in an uppermost position. 
           [0019]      FIG. 3  is an isometric view of an underside of the height adjustable bed of  FIG. 1  in a lowermost position. 
           [0020]      FIG. 4  is an isometric view of an underside of the height adjustable bed of  FIG. 1  in an uppermost position. 
           [0021]      FIG. 5  is a side sectional view of a spring-loaded assist mechanism in a compressed configuration when the height adjustable bed of  FIG. 1  is in the lowermost position. 
           [0022]      FIG. 6  is a side sectional view of the spring-loaded assist mechanism in an uncompressed configuration when the height adjustable bed of  FIG. 1  is in the uppermost position. 
           [0023]      FIG. 7  is a magnified view of the spring-loaded assist mechanism of  FIG. 5 . 
           [0024]      FIG. 8  is a magnified view of the spring-loaded assist mechanism of  FIG. 6 . 
           [0025]      FIG. 9  is an isometric view from the topside of the height adjustable bed depicting the spring-loaded assist mechanism in a compressed configuration. 
           [0026]      FIG. 10  is an isometric view from the topside of the height adjustable bed depicting the spring-loaded assist mechanism in an uncompressed configuration. 
           [0027]      FIG. 11  is an isometric sectional view from the underside of the height adjustable bed depicting the spring-loaded assist mechanism in an uncompressed configuration 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    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 or extended care beds for use in supporting patients in a hospital or extended care environment. Other embodiments may be conceived by those skilled in the art. The exemplary term “bed” may be used interchangeably with “patient support” herein without limiting the generality of the disclosure. 
         [0029]    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. 
         [0030]    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 line segment 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. 
         [0031]    Referring to  FIGS. 1-11 , a height adjustable bed  1  is shown comprising a bed frame  2 . The bed frame  2  is supported on a surface (e.g. the floor or ground) by opposed head end and foot end leg assemblies  5 . In the illustrated embodiment, head end and foot end leg assemblies  5  comprise substantially U-shaped leg frame members  6  pivotally supported by the bed frame  2  and pivotally connected to caster assemblies  7 . As will be more described below in reference to  FIG. 9 , U-shaped leg frame members  6  are pivotally supported by frame on rollers  17 , which are guided along tracks  18  mounted to bed frame  2 . 
         [0032]    Referring to  FIG. 2 , the leg assemblies  5  each further comprise linkage arms  10  pivotally attached to the leg frame members  6 . The linkage arms  10  are rigidly attached to a cross tube  3  that is pivotally connected to the bed frame  2 . The caster assemblies  7  comprise casters  8 , which rest on the surface and permit the bed  1  to be moved readily from place to place. Brake pedals  9  on the caster assembles  7  permit locking the casters  8  in any one of a number of modes including a freely swiveling mode in which the casters  8  are fully free to swivel and rotate, a fully locked mode in which the casters  8  cannot swivel or rotate, and a steer mode in which the casters  8  are free to rotate but not swivel. The head end and foot end leg assemblies  5  are substantially identical and the description of one applies to the other, although they are coupled to the bed frame  2  in an opposing orientation. 
         [0033]    As best seen in  FIGS. 9 and 11 , the U-shaped leg frame members  6  further comprise actuator mounting brackets  11  rigidly mounted thereon to which actuator rods  13  of actuators  12  are pivotally connected via actuator mounting pins  15 . When the bed  1  is in the lowermost position (see  FIG. 1  and  FIG. 3 ), the U-shaped leg frame members  6  and linkage arms  10  are nested within the frame  2 . Extending the actuator rods  13  in barrels  14  of actuators  12  causes the actuator mounting brackets  11  to translate along tracks  18  on rollers  17  causing pin  15  to pivot in bracket  11 , which in turn causes the U-shaped leg frame members  6  and linkage arms  10  to pivot about their respective pivot points resulting in raising of the bed frame  2  as the U-shaped leg frame members  6  and linkage arms  10  unfold (see  FIG. 2  and  FIG. 4 ). Raising and lowering of the bed frame  2  is effected in a manner similar to the one described in U.S. Pat. No. 7,185,377, which is herein incorporated by reference. 
         [0034]    As seen most clearly in  FIG. 6 , and as noted above, the actuator rod  13  is pivotally connected by actuator mounting pin  15  to the actuator mounting bracket  11 , which is rigidly mounted on the U-shaped leg frame member  6 . When the actuator  12  is switched on to extend, the actuator rod  13  extends pushing the actuator mounting bracket  11  longitudinally (to the right when comparing  FIG. 5  to  FIG. 6 ). As the actuator extends, actuator mounting bracket  11  translates along tracks  18  on rollers  17 , and actuator mounting pin  15  pivots about bracket  11 . As actuator mounting bracket  11  translates along track  18 , actuator mounting bracket  11 , which forces the U-shaped leg frame member  6  to pivot (in a clockwise direction as viewed in  FIG. 11 ) so that a lower end of the U-shaped leg frame member  6  is forced downward, thereby raising the bed frame  2 . To ensure stability of the leg assemblies  5  and the bed  1  as a whole while the bed frame  2  is being raised or lowered, tracks  18  and rollers  17  are laterally spaced apart, and rollers  17  are guided between upper and lower flanges  18   a  and  18   b  of tracks  18  so that rollers  17  resist rotational moments that may occur about an axis transverse to the longitudinal axis of bed  1  in U-shaped leg frame members  6 . For example, rollers  17  may be mounted to spaced apart flanges  11   a ,  11   b  of bracket  11  by a shaft (not shown) that extends through both flanges  11   a ,  11   b . Bracket  11  also may include a spacer  16  (for example, in the form of a cylindrical collar that extends around the shaft that supports the rollers) to support flanges  11   a ,  11   b  in their spaced relationship. 
         [0035]    As the bed frame  2  is raised and lowered, the actuator mounting bracket  11  moves longitudinally along frame as guided by the rollers  17  riding in the tracks  18 . Thus, the U-shaped leg frame member  6  is able to, as noted above, resist movement transverse to the longitudinal axis of bed  1 . The rollers  17  may be confined entirely by the upper and lower flanges  18   a ,  18   b  of tracks  18 , or the rollers  17  may be confined between lower flanges  18   b  of track  18   s  and a frame element, such as plate  18   c  ( FIG. 9 ) and thus upper flanges  18   a  of tracks  18  may be eliminated. Thus, the rollers  17  riding in the tracks  18  also provide lateral support for the leg assembly  5 , which stabilizes the entire bed  1  when the bed frame  2  is being raised and lowered. 
         [0036]    The actuator mounting bracket  11  further comprises an abutment plate  19  ( FIG. 10 ), Abutment plate  19  is configured to provide a bearing surface for a non-motorized assist structure  20 , as described below. The non-motorized assist structure  20  is designed to provide an initial force on the leg assemblies  5  when the bed frame  2  is to be raised from the lowermost position. As described above, when raising the bed frame  2  from the lowermost position, one problem that arises is greater actuator motor power required to initiate a raising sequence action. Greater actuator motor power at the lowermost position is required because the leg assembly  5  is tucked under the bed frame  2  at a highly acute angle thereto, resulting in relatively little mechanical advantage. 
         [0037]    With specific reference to  FIG. 5 ,  FIG. 6 ,  FIG. 7  and  FIG. 8 , the non-motorized assist structure  20  comprises a helical compression spring  21  and a mounting structure  23 , which mounts compression spring  21  to an end plate  29 , which is secured to frame  2 . An optional spring shield  22  is provided over the spring  21  for safety. A first end of the compression spring  21  is seated on a second face  29   b  of end plate  29 , and a second end of the compression spring  21  abuts the mounting structure  23 . The mounting structure  23  comprises a socket  24 , which extends over the end of spring  21  and forms an abutment face  25  for bearing on abutment plate  19 , and a ball  26  in the socket  24 . The ball  26  is secured to a first end of a longitudinally moveable longitudinal element  27 , which extends from the ball  26  though an aperture in a bushing  28  provided and supported in end plate  29 . The longitudinal element  27  is releasably secured to the ball  26 , for example by mating screw threads. Proximate a second end of the longitudinal element  27 , the longitudinal element  27  comprises a stop  30  that prevents the second end from passing through the bushing  28 . The compression spring  21  is mounted coaxially with the longitudinal element  27 , and longitudinal extension of the compression spring  21  causes the longitudinal element  27 , the ball  26  and the socket  24  to move longitudinally. The mounting structure  23  comprising the longitudinal element  27 , the ball  26  and the socket  24  is not rigidly attached anywhere on the bed frame  2  and is free to move longitudinally. 
         [0038]    As seen in  FIG. 5 ,  FIG. 7  and  FIG. 9 , the non-motorized assist structure  20  is provided on the bed frame  2  proximate the linear actuator  12  such that the abutment plate  19  of the actuator mounting bracket  11  engages the abutment face  25  of the socket  24  when the actuator rod  13  is fully retracted, i.e. when the bed frame  2  is in the lowermost position. Thus, when the bed frame  2  is in the lowermost position, the compression spring  21  is biasing the mounting structure  23  towards the actuator mounting bracket  11 . While the actuator  12  is switched off, the spring cannot move the mounting structure  23 , because the actuator  12  resists the force of the compression spring  21 . Under these conditions, the longitudinal element  27  extends a relatively long way out of the bushing  28 . 
         [0039]      FIG. 6 ,  FIG. 8 ,  FIG. 10  and  FIG. 11  illustrate relative positions of the non-motorized assist structure  20  and the actuator mounting bracket  11  when the bed frame  2  has been raised from the lowermost position. With the bed frame  2  in the lowermost position, switching on the actuator  12  to extend causes the actuator rod  13  to move longitudinally. Although the motor of the actuator  12  initially has difficulty moving the U-shaped leg frame member  6  as described above, it is assisted by the force provided by extension of the compression spring  21 . Along with the force of actuator  12 , extension of the compression spring  21  can provide enough initial force to move the U-shaped leg frame member  6  a sufficient distance to change the effective angle between the leg assembly  5  and the bed frame  2 , so that the motor of the actuator  12  can eventually take over movement of the leg assembly  5  once the spring  21  is fully extended. As seen in  FIG. 6 ,  FIG. 8 ,  FIG. 10  and  FIG. 11 , once the compression spring  21  is extended, the abutment plate  19  of the actuator mounting bracket  11  disengages from the abutment face  25  of the socket  24  of the mounting structure  23 . The spring  21  is then once again retained on end plate  29  by the mounting structure  23  by way of the stop  30  of the longitudinal element  27 , which abuts the bushing  28  proximal the first face  29   a  of end plate  29 , preventing the mounting structure  23  from falling off of the bed  1 . As the bed frame  2  is once again lowered to the lowermost position, the abutment plate  19  of the actuator mounting bracket  11  causes compression of the compression spring  21  by pushing on the abutment face  25  of the socket  24  of the mounting structure  23 . 
         [0040]    The arrangement described herein allows the pivotal attachment of the leg assembly  5  to the frame  2  to be located on an upper portion of the frame  2  proximal the bed deck (not shown). This increases the effective angle between the leg frame members  6  and the bed frame  2  when the bed is in the lowermost position, allowing the actuator  12  greater mechanical advantage. This allows heavier patients to be lifted with the same actuator force. However, during longitudinal movement of the rollers  17  and pivoting of the leg assembly  5 , the abutment plate  19  moves arcuately relative to the abutment face  25 . The socket  24  is rotatable about the ball  26  through three degrees of freedom and is able to compensate for lateral forces applied to the mounting structure  23 . The ball  26  and socket  24  therefore allow the abutment face  25  to remain substantially tangential to the curved surface of the abutment plate  19  during relative arcuate movement and reduces the tendency for side loads to be applied to the spring  21 . This in turn improves smoothness of operation of the non-motorized assist structure  20 . To prevent side loads from being applied to the leg assembly  5  during operation, the rollers  17  are engaged with the track  18  and prevent the leg assembly  5  from twisting. It should be noted that the rollers  17  are not connected to the mounting structure  23  on which the compression spring  21  is coaxially mounted around the longitudinal element  27 . 
         [0041]    The novel features will become apparent to those of skill in the art upon examination of the description. It should be understood, however, that the scope of the claims should not be limited by the embodiments, but should be given the broadest interpretation consistent with the wording of the claims and the specification as a whole.