Patent Publication Number: US-11026853-B2

Title: Patient repositioning system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/593,228 filed Oct. 4, 2019 (pending) which is a continuation of U.S. patent application Ser. No. 16/154,274 filed Oct. 8, 2018, (now U.S. Pat. No. 10,463,555) which is a continuation of U.S. patent application Ser. No. 14/942,380 filed Nov. 16, 2015, (now U.S. Pat. No. 10,137,045) which is a continuation of U.S. patent application Ser. No. 13/837,185 filed Mar. 15, 2013, (now U.S. Pat. No. 9,205,012), the disclosures of which are expressly incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system and method for patient repositioning and, more particularly, to a safe, efficient and user-friendly system and method for repositioning a patient by moving the patient toward a head end of a bed. 
     SUMMARY OF THE DISCLOSURE 
     Since at least the 1950&#39;s, it has been recognized that a person supported on an articulating bed, such as a hospital bed or other type of conventional health care bed, tends to migrate from the head end of the bed toward the foot end of the bed when the head end of the bed is raised. Generally, this problem has been addressed by moving the patient back toward the head end of the bed, either by manually lifting and pulling the patient or by using a lifting device to move the patient. 
     The problems associated with manually pulling a patient are well-recognized, and include potential injury to the puller, i.e., the caregiver(s), often one or more nurses. And certain factors can further aggravate this problem, such as a shortage of nurses and/or an obese or uncooperative patient. 
     In addition to manual repositioning of a patient, a significant number of prior devices have been devised in an effort to solve this problem. For instance, U.S. Pat. Nos. 2,827,642; 4,796,313; 4,799,273; 4,819,283; 5,020,171; 5,697,109; 5,737,781; 6,615,423; 6,722,456; 2005/0217,023; U.S. Pat. Nos. 7,003,819; 7,293,303; 7,487,558; 7,725,964; and 2012/0144581 show and describe some examples of such prior structures. Some of these devices use a hand crank to manually wind a bed sheet toward the head end of a bed, with the patient supported thereon. Some use the bed frame and/or the headboard of the bed. Some use pulleys and/or suspension devices. But despite the relatively high number of devices which purport to resolve the above-described problem, applicants are unaware of any commercially viable product on the U.S. market which adequately addresses this problem. In other words, despite the seemingly simple nature of this problem, and the multiple and well-documented prior efforts at solving this problem, this problem has not been adequately solved. 
     Prior U.S. Pat. No. 8,087,109, entitled “Patient Positioning Device,” which is expressly incorporated by reference herein, in its entirety, represents a significant step toward solving this problem. The &#39;109 patent discloses, in general, a device which pulls a sheet and a patient supported thereon toward the head end of the bed, with the sheet guided on opposite sides by a pair of spaced tracks which hold opposite side edges of the sheet. The owner of this present application also owns the &#39;109 patent. 
     The present application represents a further advance in this field, with a safe, practical, robust, yet user-friendly solution to the above-described problem. Generally, the present invention achieves the solution to this problem by the cooperative interaction of three main components, namely, a mattress, a sheet, and a sheet receiver for pulling the sheet toward a head end of the mattress. Generally, in the context of this specification, the sheet receiver encompasses a housing and a drive mechanism. The mattress has a movable head end piece, i.e., preferably foldable about a fold line, which moves to enable access to the housing and the drive mechanism contained therein. The housing includes an access door to enable a user to readily access a sheet chamber within the housing. 
     With this arrangement, by folding the head end piece of the mattress and by opening the access door to the housing, a user may readily access the sheet chamber without any accompanying need to articulate a deck on which the mattress and the housing reside. This structure greatly facilitates cleaning and maintenance of the components located within the housing. In the hospital environment, over the past few years infection control has become increasingly more important. By providing simple and easy access to these components, this system and method help the user to take steps to fight against instances of infection. But at the same time, the housing protects the components located therein, and does so within a volume that does not interfere with a standard bed deck, to which the housing is preferably secured. 
     This system and method also facilitate the simple and repeatable attachment of the sheet to be pulled with the pulling device, which is located in the housing. In fact, this system and method eliminate the need to raise the head end of the mattress, or to articulate the bed, in order to change the sheet, to disinfect the housing and the components located within the housing for infection control. 
     More specifically, the housing includes a slot through which at least one connector extends, to connect to a head end of the sheet, and thereby enable the sheet to be pulled into the housing when attached to the connector. The connector may include one or more straps. The slot is preferably defined in part by the access door of the housing, to facilitate routing of the connector to the sheet for attachment. The housing also includes one or more contoured surfaces located adjacent the slot, to facilitate movement of the sheet by reducing the friction on the sheet and compression of the mattress as the sheet moves toward and into the slot. Also, the top head end surface of the mattress, at the corner, may have reduced elasticity to facilitate slidability of the sheet thereover as it is pulled toward the slot. 
     The sheet has a length that is significantly longer than the mattress, to enable multiple repositioning operations with the same sheet. Also, the sheet has a width that is greater than that of the mattress, and has opposing beaded edges, with each beaded edge retained along one outer side of the mattress by a plurality of spaced retainers secured to the mattress. Each of the retainers has an open position to enable placement of the beaded edge of the sheet therein, and a closed position to retain the beaded edge therein. In the closed position, the retainers permit the sheet to be pulled toward the head end of the mattress. In this preferred embodiment, by locating the retainers on the outer sides of the mattress, the entire top surface of the mattress is available for use by the patient, without obstruction. In addition, with this embodiment there are no obstructions along the perimeter of the top surface of the mattress. The retainers also manage the sheet&#39;s longitudinal perimeter, by preventing the upper ticking from becoming exposed. This management also creates a stable surface for the patient during ingress, egress and transfer. 
     The sheet includes at least one reinforced slit, to which a T-shaped tab is removably attachable, the T-shaped tab located at an outer end of a connector. The T-shaped tab quickly and easily slides within the reinforced slit, to enable pulling of the connector toward the head end of the mattress to also pull the sheet toward the head end. The other end of the connector is secured inside the housing, for instance, to a roller mounted therein, whereby rotation of the roller pulls the connector and the sheet attached thereto into the housing via the slot. The connector and the sheet wrap around the roller within the housing. Each repositioning of the patient causes more of the sheet length to wrap around the roller located in the housing. 
     By collecting the used sheet within the housing, this system and method accommodates multiple repositionings of the patient, without any commensurate entanglement of that portion of the sheet that has already been used. At the same time, the location and the shape of the housing, relative to the top surface of the mattress, eliminate the need for the sheet to span between various bed structures, and thereby create the potential for interference between the sheet and surrounding bed structures. 
     According to one aspect of the invention, the attachment structure between the connector and the sheet, i.e., the T-shaped tab and the reinforced slit, is designed so as to have a very small profile. This small profile facilitates movement of the attachment structure into the slot of the housing, to enable the connector and a head end of the sheet to sufficiently wrap around the roller so that, upon further rotation of the roller, the sheet is pulled toward the head end of the bed with enough pulling force to also pull a patient supported on the sheet. For example, the structure that is shown and described herein, i.e., two pairs of reinforced slits oriented longitudinal to the length of the sheet, and each of two T-shaped tabs located at the outer ends of two straps which are secured to the roller, is capable of pulling a patient in excess of 500 pounds. According to this aspect of the invention, the initial attachment of the connector to the sheet and the initial pulling of the sheet into the housing essentially “loads” the system, for subsequent pulling of the sheet in a weighted condition, i.e., with a patient supported thereon. 
     Still further, in association with this aspect of the invention, the sheet includes “loaded” indicia, to indicate (for instance, to visibly indicate) to the user when the sheet has been sufficiently pulled into the housing to achieve adequate “loading.” The sheet loading indicia can be located on either side of the sheet, and preferably is discernable through the sheet, so that the sheet can be used with either side facing upwardly. In addition, the sheet loaded indicia can be arranged or located so as to match up with, or become aligned with, corresponding mattress indicia located on the mattress. The alignment of these two corresponding sheet and mattress indicia serves to indicate when the sheet has been loaded. The Figures of this application show visible indicia, for both the sheet loaded indicia and the mattress indicia. The sheet may also include additional sheet usage indicia, to indicate the amount of sheet remaining at the foot end of the bed, and when the excess length of sheet at the foot end has been exhausted, such that it is time to replace the existing sheet with a new sheet. The sheet usage indicia may be numerical, color coded, or symbolic, as examples. 
     Alternatively, the controller included with the drive mechanism may include a counter which counts the number of times the sheet has been repositioned, i.e., for instance, by the number of rotations of the roller, thereby to provide an indication when the sheet needs to be replaced after a predetermined number of rotations. Still further, the housing may include a sensor, operatively connected to the controller, which is adapted to sense and to convey to the controller one or more of: the sheet loaded indicia, the sheet usage indicia, or perhaps other indicia, such as indicia to assure that a properly sized sheet, i.e., a compatible sheet, has been attached. 
     The mattress includes two rows of spaced retainers, for holding opposite sides of the sheet as the sheet is moved toward the head end of the mattress to reposition the patient. The use of a plurality of spaced retainers provides a significant advantage in everyday use. More specifically, in a hospital setting, there are a significant and consistent number of situations wherein a sheet must be replaced while the patient remains on the mattress of the bed. Applicants are aware of studies which state that this occurs frequently. With the system and method described in this specification, a caregiver can secure one edge of the sheet to one side of the mattress via the retainers, then tuck the sheet underneath the patient for subsequent securement of the other edge of the sheet to the retainers on the opposite side of the mattress. When the sheet is secured in this manner, enough “slack” can be left at the head end of the sheet, as indicated by the sheet loading indicia, to enable the system to become loaded without having to pull any portion of the sheet which is supporting the patient. In other words, only the slack at the head end of the sheet is pulled. Thus, this system and method can readily accommodate the repositioning of a patient in those situations where a sheet must be replaced while the patient remains on the bed. In other words, with this system and method it is not necessary to connect both sides of the sheet at the foot end of the mattress, and to then simultaneously move both connected sides of the sheet toward the head end, along parallel continuous tracks. 
     According to another aspect of the invention, the retainers have a base piece secured to the mattress (or to a ticking which comprises the outer cover and surface for the mattress) and a movable piece which connects to the base piece and moves relative thereto. The movable piece moves between a closed position which defines a channel for retaining the beaded edge of the sheet, and an open position which opens the channel to allow the sheet to be released. In the closed position, the channel allows movement of the sheet toward the head end of the bed. According to yet another aspect of this invention, the pieces of the retainers have a detented position to identify when the movable piece is properly located in the closed position. The spaced retainers are located along the sides of the mattress, preferably in locations that are displaced from the rails of a conventional health care bed. 
     Although it is contemplated that various types of drive mechanisms would work with this system and method, one suitable drive mechanism includes a power supply, a controller, a drive train, and gears located entirely within the housing, and operable to cause the driven components, in this case a roller and two connector straps, to rotate so as to pull the sheet into the housing. The controller operatively connects to inputs mounted on the external surface of the housing, to enable a user to operate the system. Preferably, an arrestor, which could be a clutch, holds the roller in a fixed position, to thereby prevent the sheet from being pulled downwardly toward the foot end of the bed, i.e., to prevent unwinding of the sheet from the roller. With this structure, to reposition the patient the controller is enabled, as by depressing an enabling (or “start”) pushbutton, and then a reposition button is depressed to activate the drive mechanism to rotate the roller. Because of the need for a user to actively interface with two separate controls, this system and method provide a significant degree of safety in repositioning the patient. Further, to reposition the sheet towards the foot end of the mattress, or to remove the sheet, the arrestor is released which enables the roller to freewheel in a direction to allow the sheet to be pulled from the housing. 
     Nonetheless, other structures or components could be used, in the alternative, to supply the degree of safety needed. Still further, a safety stop device, such as a disabling sensor and/or switch, can be incorporated into the system to prevent inadvertent movement of the patient too close to the head end of the mattress, or to the headboard. It may also be desirable to incorporate a separate sensor into the system, to disable the drive mechanism unless the head end of the mattress is oriented horizontally, or at least below a predetermined angle relative to horizontal. 
     Regardless of the particular drive mechanism used, when movement of the sheet toward the head end stops, the system permits reversal of the drive mechanism to permit the sheet to pull back toward the foot end of the bed. This reversal releases the tension in the sheet and enhances patient comfort. 
     According to another aspect of the invention, it would be possible to reduce the overall cost of the system by reducing the number of components located within the housing itself, perhaps by locating only the passive driven components within the housing and perhaps one or more components which couple to the driven components. In this respect, a separate hand held unit could be used from outside the housing to interface with the passive components, i.e., a roller, or other pulling device or sheet take-up structure located inside the housing, thereby to drive the passive components located in the housing so as to reposition the sheet and the patient residing thereon. Thus, multiple products could be operated by a single hand held unit. And for a facility with a significant number of beds, this option would reduce overall costs by eliminating the need to locate some or all of the active drive components in each housing. 
     At the foot end of the mattress, a barrier may be used to support and isolate the unused and remaining part of the sheet. This barrier may be connected to the mattress, the bed frame, and/or the footboard. This barrier can also serve as a spacer between the foot end of the mattress and the bed frame, typically the footboard, to provide unobstructed movement of the sheet. Alternatively, the barrier and the spacer can be separate structures. 
     As shown and described herein, the sheet is wider than the mattress and also wider than the housing. Nevertheless, the drive mechanism pulls the extra sheet width, on both sides, around the corners of the mattress at the head end thereof and into the housing via the slot. The contours of the housing, at the head end and at the corners, facilitate movement of the sheet toward the slot. To achieve this contoured effect, the head end of the housing may include a curved extension that extends slightly beyond the head end of the mattress. This creates a “waterfall” effect to prevent against the entry of foreign objects into the slot. This extension can also serve as the head end boundary for the head end of the mattress, and also reduces compression of the head end of the mattress. 
     The transverse dimension of the slot needs to be able to accommodate some amount of sheet overlap, or doubling over of the sheet, near the outer ends. Moreover, within the housing itself, the roller may have a reduced diameter at its outer ends, thereby to provide additional internal clearance within the housing to accommodate this extra sheet width. Nonetheless, the width of the slot is still sufficiently small, i.e., preferably about 8 mm, to prevent the accidental ingress into the housing of a user&#39;s finger or medical tubes or wires. Additionally, a safety cut-off switch may be incorporated into the system, particularly to disable the drive mechanism, so as to discontinue rotation of the roller upon detection of a higher than normal resistance. 
     The mattress has a head end section of reduced thickness, and is complementary in shape with the housing, at least with respect to a central longitudinal vertical plane. The head end section may contain a foldable head end piece defined by a fold line, and foldable about the fold line to access the housing. Alternatively, the head end piece could be removably connected to the mattress along the “fold line.” The head end section of the mattress may be firmer than the rest of the mattress, to further protect a patient from the housing residing therebelow. An increased firmness of the head section may also increase the wear resistance of the head end section as the sheet is pulled over the edge of the mattress. To further protect against mattress head section wear, a portion of the housing is adjacent the head end of the mattress to limit the compressibility of the mattress as the sheet is advanced. In an alternative embodiment, the mattress head section does not have a reduced thickness. Instead, the housing is integrated into the head section of the bed deck. In this embodiment, the access door of the housing may be incorporated into the bed deck. 
     With this patient repositioning system, according to the preferred embodiments, the structure which pulls the sheet does not contact or interact with the bed frame or the headboard of the bed. Instead, because of the complementary shape of the mattress and the housing, the system primarily operates within the space envelope of the mattress. Preferably, the housing is removably mounted to the deck of the bed, thereby to assure its physical position relative to the mattress during articulation of the bed into various positions. Regardless of the position of the deck, the housing can be accessed by moving the head end piece of the mattress. Additionally, because the hinged access door partially defines the slot in this embodiment, this structure simplifies the proper routing and/or orienting of the connectors, namely the straps, prior to their releasable attachment to the sheet. Overall, this structure helps to assure a safe, simple, efficient, user-friendly, and repeatable attachment of the sheet to the drive mechanism. This structure also facilitates the user&#39;s ability to practice effective infection control. 
     The system and method disclosed herein are not limited to use with a conventional health care bed having a flat deck. Rather, this invention may be readily adaptable for use in combination with a type of hospital bed known as a “step-deck” bed, as shown in U.S. Pat. No. 5,692,256, a birthing bed which is specifically adapted for use when a mother gives birth to an infant, or even with a bariatric bed. For these variations of the invention, the mattress and the housing are reoriented and/or reconfigured to accommodate the different bed shapes, and particularly the different shapes of the deck and/or the mattress. With these various bed designs, the patient repositioning system may be integrated at least partially into the bed deck. 
     Those skilled in the art will more readily understand the scope and content of this specification in view of the following drawings and the detailed description of those drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a side view of a patient repositioning system for use with a health care bed, according to one exemplary, preferred embodiment of the invention. 
         FIG. 1B  is the side view of the patient repositioning system shown in  FIG. 1A , with a patient residing on the health care bed near the foot end. 
         FIG. 1C  is the side view similar to  FIG. 1B , but with the patient residing near the head end. 
         FIG. 2  is a perspective view of a mattress complementarily positioned against a sheet receiver, and more particularly the housing, according to the embodiment shown in  FIG. 1A . 
         FIG. 3A  is an enlarged perspective view of the mattress and the sheet receiver shown in  FIG. 2 , at the head end of the mattress. 
         FIG. 3B  is an enlarged perspective view which shows the mattress complementarily positioned against the sheet receiver, with the sheet receiver attached to the health care bed as shown in  FIG. 1A , with a sheet on the mattress, and with connecting structure extending out of the sheet receiver. 
         FIG. 3C  is an enlarged perspective view, similar to  FIG. 3B , showing the connecting structure positioned adjacent the sheet. 
         FIG. 3D  is an enlarged perspective view, generally similar to  FIGS. 3B and 3C , but directed to one corner of the overall system, and showing the connecting structure releasably attached to the sheet. 
         FIG. 3E  is an enlarged perspective view, similar to  FIG. 3D , showing the sheet as it is pulled into the sheet receiver. 
         FIG. 4A  is a perspective view of a retainer used for retaining a longitudinal edge of the sheet, with the retainer in an open position. 
         FIG. 4B  is a perspective view, similar to  FIG. 4A , with the retainer in a closed position. 
         FIG. 5  is a schematic cross sectional view taken along line  5 - 5  of  FIG. 4B . 
         FIG. 6  is the enlarged perspective view, similar to  FIGS. 3A and 3B , showing a head end piece of the mattress folded and an access door of the sheet receiver in an open position. 
         FIG. 7A  is a schematic cross sectional view of the sheet receiver and the head end piece of the mattress shown in  FIG. 6 , with the connecting structure extending out of the sheet receiver and the access door open. 
         FIG. 7B  is a schematic cross sectional view, similar to  FIG. 7A , with the access door of the sheet receiver in a closed position, the connecting structure extending upwardly, and a sheet located above the surface of the mattress. 
         FIG. 7C  is a schematic cross sectional view, similar to  FIG. 7B , with the sheet attached and ready to be pulled into the housing. 
         FIG. 8  is a schematic cross sectional view, similar to  FIG. 7A , showing another embodiment of a portion of a suitable drive mechanism that may be used with the patient repositioning system of this invention. 
         FIG. 9  is an exploded view of the sheet receiver shown in  FIG. 1A . 
         FIG. 10  is a perspective view of the sheet receiver shown in  FIG. 9 . 
         FIG. 11  is a top view of the sheet receiver that is shown in  FIGS. 9 and 10 , with the top panel removed. 
         FIG. 12  is a top view of a sheet according to the embodiment shown in  FIG. 1A . 
         FIG. 13A  is a schematic cross sectional view of an alternative embodiment of the retainer, namely a slide retainer in an open position. 
         FIG. 13B  is a schematic cross sectional view of the slide retainer shown in  FIG. 13A , in a closed position. 
         FIG. 14A  is a schematic cross sectional view of yet another embodiment of a retainer, namely a pivot retainer, in an open position. 
         FIG. 14B  is a schematic cross sectional view of the pivot retainer shown in  FIG. 14A , in a closed position. 
         FIGS. 15A and 15B  are schematic cross sectional views of still another embodiment of a retainer, in this case a clip retainer. 
         FIGS. 16A, 16B, and 16C  are schematic cross sectional views of yet another embodiment of a retainer, in this case a rigid retainer which retains a compressible bead located at the edge of a sheet. 
         FIG. 17  is an enlarged perspective view which shows another aspect of the patient repositioning system of this invention, namely a hand held unit capable of driving the pulling device from outside the sheet receiver. 
         FIG. 18  is a side view of a first preferred embodiment of the sheet receiver. 
         FIG. 19  is a perspective view, from the inside of the sheet receiver and looking outwardly, which shows some details of a latch mechanism for the access door. 
         FIG. 20  is an enlarged perspective view that is analogous to the views of  FIGS. 3B and 3C , but showing an alternative embodiment, with the sheet receiver integrated with a portion of a bed deck, so that the top of the sheet receiver is contiguous with the top of the bed deck. 
         FIG. 21  is a block diagram which schematically shows a control system for communicating with the various components of a patient repositioning system of the type shown and described herein. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     With reference to  FIG. 1A , an embodiment of a patient repositioning system  10  for use with a health care bed  12 , such as a hospital bed, includes a mattress  14 , a sheet  16 , and a sheet receiver  18 . As noted previously, the sheet receiver generally encompasses a housing and a drive mechanism. The exemplary health care bed  12  is more particularly an articulating bed commonly used in hospitals, nursing homes, private homes, or any other environment where patient care is enhanced through the use of the articulating bed. Common articulating beds, such as the health care bed  12 , include a frame  20  for supporting a bed deck  22  above a floor  24 . According to the exemplary embodiment, the frame  20  also includes a plurality of wheels  26  to more easily move the health care bed  12  in preparation of or during patient care. The health care bed  12  also includes a headboard  28  and footboard  29  each removably attached to a respective head end  30  and foot end  31  of the health care bed  12 . With respect to the use of the terms “head” or “head end” and “foot” or “foot end,” it will be appreciated that such directions are intended to describe relative locations along exemplary embodiments of the patient repositioning system  10  positioned along the health care bed  12 . It is not intended that the terms “head end” and “proximal end” limit the invention to any of the exemplary embodiments described herein. 
     The sheet receiver  18 , mattress  14 , and sheet  16  are each positioned adjacent to the bed deck  22  as shown in  FIG. 1A . More particularly, the bed deck  22  includes a head deck portion  32 , a central deck portion  34 , and a foot deck portion  36 . Each of the head deck, central deck, and foot deck portions  32 ,  34 ,  36  is pivotably connected together for use as the articulating bed. The mattress  14  rests directly upon the bed deck  22  similar to a traditional mattress. However, unlike a traditional mattress, the sheet receiver  18  is secured to the head deck portion  32  below a portion of the mattress  14 , while the sheet  16  may be partially stowed between the mattress  14  and the footboard  29 .  FIG. 1A  shows the sheet receiver  16  entirely below a top surface of the mattress  14 . But in the context of this specification “below” means at least in part below, as in at least in part below the top surface of the mattress. The sheet receiver  18  also releasably attaches to the mattress  14  for reducing the likelihood of inadvertent relative movement therebetween. For example, the sheet receiver mattress  14  may attach to the mattress  14  via cooperating structures such as hook and loop fasteners, snaps, magnets or any other structure for releasably attaching one surface to another. According to the exemplary embodiment, a barrier  38  attaches to the frame  20  below the foot deck portion  36  and extends toward the footboard  29 . Accordingly, the barrier  38  supports at least a portion of the sheet  16  resting between the mattress  14  and the footboard  29 . While the health care bed  12  may be the articulating bed shown in the exemplary embodiment, it will be appreciated that the patient repositioning system  10  may also be used with other beds, such as stepped deck beds and birthing beds, which will be described below in further detail. 
     As indicated by arrow  40  in  FIG. 1A , the sheet  16  is pulled onto an upper surface  110  of the mattress  14  from a mattress foot end  112  to a mattress head end  114 , where the sheet  16  feeds into the sheet receiver  18 . More particularly with respect to  FIG. 1B , a beaded edge  510   a  on a sheet longitudinal side  512   a  is slidably positioned within a row of retainers  116 . The row of retainers  116  is located along a mattress longitudinal side  118   a  for guiding the sheet  16  between the mattress foot and head ends  112 ,  114 . The retainers  116 , described further below, may be spaced along the mattress  14  in generally any orientation that both holds the sheet  16  and allows for operator access to the retainers around various components of the health care bed  12 . The sheet  16  is similarly received by another row of retainers (not shown) on an opposing mattress longitudinal side  118   b  (see  FIG. 2 ). 
     A patient is shown in  FIG. 1B  resting on the sheet  16  in a foot end position after having migrated from a head end position. Generally, the term “head end position” refers to a preferred patient position closer to the mattress head end  114  than the mattress foot end  112 . Similarly, the term “foot end position” generally refers to any position of the patient after migrating from the mattress head end  114  toward the mattress foot end  112 . It will be appreciated, however, that the terms head end position and foot end position are merely exemplary and intended to show distinguishing positions in which to move the patient. As such, the invention is not intended to be limited to the head and foot end positions shown. 
     An operator, such as a caregiver or an attendant, may desire to return the patient to the head end position. Frequently, moving the patient from the foot end position to the head end position may require manually gripping and pulling a sheet, on which the patient rests, toward the headboard  28 . However, the patient repositioning system  10  automatically repositions the patient to the head end position under direction by the operator. According to the exemplary embodiment, the operator enables the patient repositioning device  10  by activating an enabling switch  210  operatively connected to the sheet receiver  18 . Once enabled, the operator then activates a drive switch  212  operatively connected to the sheet receiver  18 . With both the enabling switch  210  and drive switch  212  activating, the sheet receiver  18  pulls the sheet along the upper surface  110  toward the head board  28 , as indicated by arrows  42 . Because the patient is resting on the sheet  16  as it moves, the patient similarly moves away from the footboard  29  and toward the headboard  28 , as indicated by arrow  42 . The patient is moved toward the headboard  28  until reaching the desired head end position shown in  FIG. 1C . Of course, in the event that the patient again migrates toward the foot end position, the operator may repeat the operation of repositioning the patient with the patient repositioning system  10  as desired. 
     With respect to  FIG. 2 , the mattress  14  for repositioning the patient generally includes the mattress foot end  112 , the mattress head end  114 , the upper surface  110 , and the pair of longitudinal sides  118   a ,  118   b  as described above. Generally, the pair of longitudinal sides  118   a ,  118   b  is symmetric with a generally uniform thickness, while the upper surface  110  has a substantially uniform width and length. The mattress  14  is also covered in an outer ticking  120  for effectively improving the life and comfort of the mattress  14 . In addition, each of the retainers  116  is attached to the outer ticking  120  of the mattress  14  in spaced relation along the length of the mattress longitudinal sides  118   a ,  118   b . However, the mattress head end  114  also includes a head end section  122  of reduced thickness relative to the generally uniform thickness of the remaining mattress  14 . In this respect, the head end section  122  is a relatively thin portion of the mattress  14  and further includes a head end piece  124 . The head end piece  124  folds about a fold line  126  relative to the rest of the mattress  14  for improving access to the sheet receiver  18  below the upper surface  110  of the mattress head end  114 . Further details concerning access to the sheet receiver  18  will be further discussed below with respect to  FIG. 6 . However, it will be appreciated that other respective portions of the mattress  14  may be otherwise movable for accessing the sheet receiver  18 . 
     Furthermore, at least a portion of the sheet receiver  18  is positioned within a volume envelope  128  (see  FIG. 7B ) of the mattress  14  for effectively reducing an overall footprint of the mattress  14  and sheet receiver  18 . The reduced thickness of the head end section  122  has a lower surface  130  and a forward surface  131  that collectively define the volume envelope  128  that would otherwise be occupied by the mattress  14  if not for the head end section  122  of reduced thickness. Thereby, the head end section  122  is complementary in shape to a housing  214  of the sheet receiver  18 . 
     As best shown in  FIGS. 7A-7C  and according to an exemplary embodiment of the invention, the housing  214  at least partially fits within the volume envelope  128  against the lower surface  130  and the forward surface  131  of the head end section  122 . The housing  214  has a length substantially the same as the width of the mattress  14  and includes a slot  216  extending horizontally along the length of the housing  214 . Additionally, the housing  214  includes an extension  218  protruding horizontally along the length of the housing  214  and above the slot  216 . According to an exemplary embodiment of the invention, the extension  218  defines a lip  220  against which the head end piece  124  abuts when the sheet receiver  18  is positioned within the volume envelope  128 . 
       FIG. 3A  shows additional detail of the relative positions between the mattress  14  and the housing  214  and greater detail of the outer ticking  120 . Specifically, the outer ticking  120  is formed from a comfort material  132 , a durable material  134 , and a stiff material  136 . In this respect the comfort material  132  forms a portion of the outer ticking  120  suitable for comfortably supporting and contacting the patient, directly or indirectly. Meanwhile, the durable material  134  and the stiff material  136  form respective portions of the outer ticking  120  that increase life and durability of the mattress  14  where patient comfort is of less concern. On one hand, the durable material  134  also provides sufficient structure for attaching the retainers  116 . The exemplary retainers  116  are welded to the durable material  134 , but other structures and methods, such as adhesive, snaps, fasteners, or stitching, may similarly be used to attach the retainers  116  to the durable material  134 . On the other hand, the stiff material  136  also provides reduced elasticity and reduced friction where components of the sheet  16  and/or sheet receiver  18  may frictionally engage the mattress  14 . In this respect, the head end section  122  is relatively firmer than the rest of the mattress to support pulling the sheet  16  about the head end edge  140  as shown in  FIGS. 3A-3D . While the nomenclature “comfort,” “durable,” and “firm” each relatively describe various features of the outer ticking  120 , it will be appreciated that these features are not intended to be limited solely to these material types. Rather, the exemplary embodiment merely shows one combination of known materials for producing an outer ticking  120  with properties sufficient for use with the patient repositioning system  10 . 
     With respect to  FIGS. 3A and 3B , the durable material  134  is stitched to the comfort material  132  at a seam  138  extending along the mattress longitudinal sides  118   a ,  118   b . Also, a head end edge  140  of the mattress head end  114  includes the stiff material  136  that extends along at least a portion of the head end piece  124 . The stiff material  136  is attached directly onto the comfort material  132  and provides a surface of reduced elasticity about which the sheet receiver  18  may pull the sheet  16 . In the alternative to stitching and/or gluing the outer ticking  120  together, the comfort, durable, and stiff materials  132 ,  134 ,  136  may be similarly welded to improve sealing and reduce the likelihood of fluids, such as bodily contaminates, from permeating into the mattress  14 . However, it will be appreciated that any known method of connecting materials together to form the outer ticking  120  may be used in accordance with the invention. 
     The sheet receiver  18  has a slot  216 , and also includes a connecting structure  222  for releasably attaching to the sheet  16  adjacent to the mattress head end  114 . The connecting structure  222  is generally of a sufficiently small dimension so as to pass through the slot  216  and toward the sheet  16 , which may also be referred to herein as a “low-profile” connecting structure  222 . According to the exemplary embodiment of the invention, the connecting structure  222  is a pair of straps  224   a ,  224   b . Each of the straps  224   a ,  224   b  includes a first end  226  secured within the housing  214  and a second end  228  for releasably attaching to the sheet  16 . Accordingly, the operator extends the pair of straps  224   a ,  224   b  about the head end edge  140  and pulls the sheet  16  along the upper surface  110  of the mattress  14 , as indicated by arrow  44 . The sheet head end  516  and the second end  228  each move adjacent to the mattress head end  114  as shown in  FIG. 3C . Thus, in order to releasably attach the pair of straps  224   a ,  224   b , each of the second ends  228  includes a T-shaped tab  230  that cooperates with at least one of a pair of reinforced slits  514   a ,  514   b  formed in a sheet head end  516 . Notably, the width of the sheet  16  is generally wider than the upper surface  110  such that the beaded edge  510   a  rests along the mattress longitudinal side  118   a  and adjacent to the row of retainers  116 . While an exemplary embodiment of the invention includes the connecting structure  222  as a pair of straps  224   a ,  224   b , it will be appreciated that other forms of connecting structures for connecting the sheet  16  to the remainder of the sheet receiver  18  may also be used. By way of example, the connecting structure  222  may be any number of straps, such as one strap, that may be separate or unitary for pulling the sheet  16 . 
       FIG. 3C  and  FIG. 3D  show that each of the pair of slits  514   a ,  514   b  is spaced apart from one another and generally parallel for receiving the T-shaped tab  230 . In addition, each of the retainers  116  operatively holds the beaded edge  510   a  for guiding movement of the sheet  16 . More particularly, each of the straps  124   a ,  124   b  withdraws through the slot  216  and into the housing  214 , as indicated by arrow  46 , to simultaneously pull the sheet  16  along the upper surface  110 , as indicated by arrow  48 . However, in the event that an external force halts, or otherwise impedes the movement  46  of the sheet  16 , the tab  230  releases from the pair of slits  514   a ,  514   b  for preventing damage to the sheet  16  and/or sheet receiver  18 . 
     As can be more clearly seen in  FIG. 3D  and  FIG. 3E , the sheet  16  continues to move toward the mattress head end  114 , about the head end edge  140 , and toward the sheet receiver  18  until being pulled into the slot  216  and within the housing  214 , as indicated respectively by arrows  48 ,  50 , and  52 . The sheet receiver  18  generally pulls the sheet  16  until a sufficient amount of sheet  16  collects within the housing  214  to fixedly attach the sheet  16  to the sheet receiver  18 . According to an exemplary embodiment, the mattress longitudinal side  118   a  includes an alignment sheet indicia  144 , and the sheet  16  includes a sheet loaded indicia  518 . Once sheet loaded indicia  518  moves into alignment with the alignment sheet indicia  144 , the pair of indicia  144 ,  518  cooperatively indicate to the operator, for instance by visual alignment, that the sheet  16  is engagingly attached to the sheet receiver  18 , i.e. it is “loaded.” Because the sheet  16  is engagingly attached, the sheet  16  may be used to pull both the sheet  16  and the patient (see  FIG. 1B ). To brace the sheet receiver  18  while pulling the patient, the sheet receiver  18  also includes a pair of mounting brackets  232   a ,  232   b  for mounting the sheet receiver directly to the head deck portion  32  below the head end section  122 . However, it will be appreciated that the sheet receiver  18  may be attached to the bed via one of any number of different structures. 
       FIG. 3D  and  FIGS. 4A-5  show an exemplary embodiment of the retainer  116  having a base piece  410  and a movable piece  412 . The retainer  116  secures to the mattress  14  by welding the base piece  410  directly to the durable material  134  of the outer ticking  120 . In contrast, the movable piece  412  connects to the base piece  410  or otherwise projects from the base piece  410 . Notably, the movable piece  412  moves relative to the base piece  410  between an open position and a closed position for defining a channel  414  therebetween. The base piece  410  is generally planar and relatively thin for providing sufficient surface area to both weld to the outer ticking  120  and connect the movable piece  412 . However, the base piece  410  also includes a horizontally extending base projection  416  having a base curved portion  418  and a base planar portion  420 . The movable piece  412  similarly includes a horizontally extending projection  422  having a curved portion  424  and a planar portion  426 . Thus, while in the closed position, the base curved portion  418  of the base piece  410  aligns with the curved portion  424  of the movable piece  412  to define the channel  414  for retaining the beaded edge  510   a . Also, the base planar portion  420  aligns with the planar portion  426  to define a gap  428  therebetween for allowing the remaining sheet longitudinal side  512   a  to extend toward the upper surface  110  of the mattress  14 . 
     In the open position shown in  FIG. 4A , the open channel  414  facilitates the insertion of the beaded edge  510   a  into the channel  414  and/or the removal of the beaded edge  510   a  from the channel  414 . To retain the sheet  16 , the movable piece  412  is rotated, or otherwise moved, as indicated by arrow  54 , to the closed position. The closed position retainer  116  is shown in  FIG. 4B  and  FIG. 5 . On one hand, the closed channel  414  has a diameter generally larger than the beaded edge  510   a  for allowing the beaded edge  510   a  to slide along the channel while being pulled, as indicated by arrow  56 . On the other hand, the gap  428  has a width that is generally smaller than the beaded edge  510   a  for retaining the beaded edge  510   a  within the channel  414 . 
     Furthermore, the base and movable pieces  410 ,  412  each cooperate together with a detented surface relationship to affirmatively indicate when the movable piece is in the closed position. More particularly, the base piece  410  includes a horizontally extending detent  430 , and the movable piece  412  includes a horizontally extending groove  432  adapted to receive the detent  430 . For example, the movable piece  412  rotates against the direction of the pull  56  to open the channel  414 . The movable piece  412  may then be rotated back  54  along the direction of the pull  56 , as seen in  FIG. 4A , to “snap” the detent  430  into the groove  432  to achieve the closed position in  FIG. 4B . However, according to the exemplary embodiment, the movable piece  412  ceases to rotate  54  beyond the snap of the detent  430  and the groove  432 . As such, foreseeable drag of the sheet  16  within the retainer  116  during the pull  54  will not unintentionally open the retainer  116  and release the sheet  16 . 
     Greater detail of the rotational mounting of the movable piece  412  to the base piece  410  is shown in  FIG. 5 . First, the base piece  410  includes a face plate  434  for welding to the durable material  134  of the mattress  14  and abutting the movable piece  412 . Second, the base piece  410  also includes a back plate  436  within a mattress foam  146  for mounting a fastener  438 . A hole  440  extends through the back plate  436 , the face plate  434 , and into the movable piece  412 . The hole  440  receives the fastener  438  for assembly of the retainer  116  and for rotatably mounting the movable piece  412  to the base piece  410 . Thus, if the movable piece  412  requires any repair, the movable piece  412  may simply be removed from against the base piece  410  and a replacement movable piece  412  threaded back onto the fastener  438 . However, it will be appreciated that the movable piece  412  and the base piece  410  may be movable relative to each other via a living hinge extending therebetween, or similar unitary structure. 
     While the exemplary embodiment of the retainer  116  is configured for retaining the sheet  16  as described above, it will be appreciated that other retainers in accordance with the invention may also be used. For exemplary purposes, additional retainers  116  for retaining the sheet  16  are described below with respect to  FIGS. 13A-15E . In any case, the retainer  116  is not intended to be limited to these exemplary embodiments described herein. 
     After the unused sheet  16  has been exhausted, the sheet  16  may be removed from the retainers  116  and sheet receiver  18  for cleaning the patient repositioning system  10  as shown in  FIG. 1C  and  FIG. 6 . Each of the retainers  116  opens at the operator&#39;s discretion for removing the sheet  16  therefrom. The sheet receiver  18  includes a sheet release  234  that may be operatively activated by the operator so that the sheet  16  may be removed from the housing  214 . During patient use, the sheet  16  may become contaminated and advance into the sheet receiver  18 , which, in turn, contaminates the sheet receiver  18 . Thus, the sheet receiver  18  opens to provide cleaning access during and/or between patient uses as shown in  FIG. 6 . 
     With respect to  FIG. 6 , the housing  214  of sheet receiver  18  includes an access door  236  adjacent a top panel  238 . The head end piece  124  folds back at the fold line  126  to expose the access door  236  that hingedly connects to the housing  214 . As such, the operator may move the access door  236  by pivoting it up and against the mattress  14  to open the sheet receiver  18  as shown in  FIG. 6 . However, it will be appreciated that the access door  236  may be movable in any way relative to the remainder of the sheet receiver  18  to open the sheet receiver. For example, the access door  236  may be unitary with or connected to the head end piece  124  such that folding back the head end piece  124  simultaneously opens the access door  236 . The access door  236  opens at the slot  216  for reducing the number of openings into the housing  214 . The open sheet receiver  18  exposes each of the components within a sheet chamber  240  defined by the housing  214 . The sheet chamber  240  includes a portion of the sheet receiver  18  that may interact with the sheet  16  (see  FIG. 1C ), and thus, may require periodic cleaning by the operator. It will be appreciated that maintaining cleanliness within patient care environments, such as hospitals, nursing homes, and even private homes, critically enhances patient outcomes. For this reason, accessibility within the sheet chamber  240  provides an opportunity for the operator to simply and completely clean the sheet receiver  18  and proves particularly beneficial over the prior art described above. For example, portions of the sheet receiver  18  within the sheet chamber  240  are positioned relative to each other in order to provide enough clearance for operator cleaning and hand access for maintenance. According to an exemplary embodiment, the portions of the sheet receiver  18  within the chamber  240  provide at least generally 12 mm of clearance space therebetween. 
     In this respect, the sheet receiver  18  further includes a pulling device  242  operatively connected to the connecting structure  222  that operatively pulls the sheet  16  into the sheet chamber  240 . More specifically, the pulling device  242  includes a roller  244  rotatably and removably supported within the sheet chamber  240  and generally parallel to the slot  216 . The roller  244  includes a central portion  246  and opposing outer portions  248 . Each first end  228  of the pair of straps  224   a ,  224   b  is secured to the central portion  246  of the roller  244  via at least one fastener  245 . According to the exemplary embodiment of the invention, the fastener  245  is threaded and extends through the first end  228  and into the roller  244 . Of course, it will be appreciated that any structure or method of securing the straps  224   a ,  224   b  to the roller  244  may be similarly used. 
     With respect to  FIG. 1B ,  FIG. 3E , and  FIG. 6 , as the pulling device  242  pulls the sheet  16  into the sheet chamber  240 , the sheet  16  is pulled to wrap about the roller  244 . According to the exemplary embodiment of the invention, engaged attachment of the sheet  16  to the sheet receiver  18  occurs when the sheet  16  sufficiently wraps around the roller  244  to transmit enough torque from the roller  244  to the sheet  16  with enough force to pull the patient. More particularly, the central portion  246  is generally larger in diameter than the opposing outer portions  248 . On one hand, the larger diameter of the central portion  246  transmits torque to the sheet  16  while pulling both the sheet  16  and the patient resting thereon. On the other hand, the reduced diameter of the opposing outer portions  248  accommodates the excess width of the sheet  16  for both the sheet longitudinal sides  512   a ,  512   b  and the beaded edges  510   a ,  510   b  during use. As such, most of the force required to pull the patient transmits through the portion of the sheet  16  on the upper surface  110  and about the head end section  122  of the mattress  14 , while less force transmits through the sheet longitudinal sides  512   a ,  512   b.    
     While the sheet  16  may be pulled by and wrapped about the roller  244  shown in  FIG. 6 , the sheet  16  may alternatively be pulled by other mechanisms for pulling sheets. Another exemplary embodiment may use two or more abutting rollers in the form of a roller press (not shown) for engaging and pulling a sheet. According to yet another exemplary embodiment, one or more rollers may also be placed against another type of surface for engaging and pulling the sheet. Thus, the pulling device  242  is not necessarily intended to be limited to the roller  244  wrapping the sheet  16  as described herein. 
     In any case, a drive mechanism  252  operatively drives the pulling device  242  for pulling the sheet  16  along the upper surface  110  of the mattress  14 .  FIGS. 7A and 7B  show a gear drive portion  253  of the drive mechanism  252  including a drive gear  254 , an idler gear  256 , and a driven gear  258 . The drive gear  254  is actively rotated by the remaining portion of the drive mechanism  252  described below in further detail with respect to  FIG. 11 . The drive gear  254  engages the idler gear  256 , which, in turn, engages the driven gear  258 . Thus, as the drive gear  254  actively rotates, the idler gear  256  and driven gear  258  passively rotate in response. Finally, the driven gear  258  connects to the roller  244  such that, as the driven gear  258  rotates, the roller  244  rotates in turn. 
     According to an exemplary embodiment of the invention shown in  FIG. 3E  and  FIGS. 7A-7C , the driven gear  258  in conjunction with the sheet release  234  also functions as an arrestor  260  for both restricting rotation of the roller  244  and releasing the rotation of the roller  244 . Restricting rotation of the roller  244  operatively holds the sheet  16  in place so as to prevent movement of the sheet  16  toward the mattress foot end  112  (see  FIG. 1B ), while releasing the roller  244  enables repositioning or unwrapping of the sheet  16  from the roller  244 . To restrict rotation of the roller  244 , the remaining portion of the drive mechanism  252  engages the drive gear  254  rigidly against the idler gear  256  when not actively rotating the driven gear  258 . However, the drive gear  254  selectively moves via the sheet release  234  to disengage the idler gear  256  and release the rotation of the roller  244 , as indicated by arrow  262 . Thus, the driven gear  258 , the idler gear  256 , and the roller  244  may freely rotate, or “freewheel,” when the drive gear  254  disengages from the idler gear  256 . In the alternative, the drive mechanism  252  may actively reverse under power to release the sheet  16 . In another alternative, the arrestor  260  may be a brake or similar mechanism for halting the drive mechanism  252  and/or roller  244 . 
       FIGS. 7A-7C  show the access door  236  in both an open and closed position, respectively. The housing  214  further includes a hinge  264  attached between the access door  236  and the remainder of the top panel  238  for pivoting, or otherwise moving, the access door  236  between open and closed positions. The hinge  264  may also include damping or drive-assisted movement for enhanced performance between the open and closed positions. 
     In the closed position of  FIGS. 7B-7C , the head end piece  124  of the mattress  14  conforms to both the hinge  264  and the lip  220  of the extension  218 . The access door  236  opens and closes at the slot  216 , which is defined by the extension  218  of the access door  236  and a front panel  272  of the housing  214 . Notably, the slot  216  essentially expands into the open sheet chamber  240  when the access door  236  pivots upward toward the head end section  122  of the mattress  14  so that slot  216  and the sheet chamber  240  share a common opening. By reducing the number of openings through the housing  214  and into the sheet chamber  240 , the pair of straps  224   a ,  224   b  may only extend through the housing  214  at the slot  216 . In turn, the likelihood of the operator inadvertently extending the pair of straps  224   a ,  224   b  through an incorrect opening is similarly reduced while still providing ample access for the operator to clean within the sheet chamber  240 . 
     With the access door  236  closed, the slot  216  has a transverse dimension large enough for receiving the pair of straps  224   a ,  224   b  and sheet  16 , but small enough for inhibiting a human finger or other foreign object from extending therethrough. Particularly, the transverse dimension may be from about 4 millimeters to about 12 millimeters. More particularly, the transverse dimension may be less than about 8 millimeters. Furthermore, the extension  218  of the access door  236  preferably includes a “waterfall” lip  274  secured to the remaining portion of the access door  236 .  FIG. 7  and  FIG. 3D  taken together more clearly show that the waterfall lip  274  is curved for smoothly guiding the pair of straps  224   a ,  224   b  and sheet  16  into the slot  216 . Similarly, the extension  218  includes a pair of contoured corners  275   a ,  275   b  further defining the slot  216  for smoothly guiding the sheet longitudinal sides  512   a ,  512   b  into the slot  216 . Together, the waterfall lip  274  and contoured corners  275   a ,  275   b  reduce the likelihood of sheet stress and sheet snags while helping to maintain the sheet longitudinal sides  512   a ,  512   b  along the mattress longitudinal sides  118   a ,  118   b  by retaining the head end position of the beaded edges  510   a ,  510   b  being pulled into the slot  216 , respectively. On the other hand, the waterfall lip  274  also projects outward beyond the front panel  272  for inhibiting foreign matter that lays or falls nearby from entering the slot  216  unintentionally. For example and with respect to both  FIG. 1C  and  FIG. 7B , contaminates from the patient or tubing required for patient care may fall over the mattress head end  114  and against the sheet receiver  18  near the slot  216 . However, the waterfall lip  274  decreases the likelihood of the tubing or contaminates from entering the slot  216  by directing such foreign matter outward from both the slot  216  and the front panel  272 . 
     Furthermore, the term “low-profile” with respect to the connecting structure  222  may be further defined as having the sufficiently small dimension generally less than the transverse dimension of the slot  216  to pass therethrough. Preferably, the “low-profile” connecting structure  222  has the sufficiently small dimension configured for also reducing the amount of sheet  16  deformation resulting from wrapping the sheet  16  over the connecting structure  222  on the roller  244 . After all, localized deformation of the sheet  16  tends to create wear patterns that may prematurely tear portions of the sheet  16 . However, the “low-profile” connecting structure  222 , such as the straps  224   a ,  224   b , serves to enhance and extend the useful life of the sheet  16 . 
     With respect to  FIG. 7C , the extension  218  rigidly guides the sheet  16  and the straps  224   a ,  224   b  about the extension  218  and into the slot  216 . In contrast, the head end piece  124  is relatively softer than the extension  218  for enhancing patient comfort. As such, the straps  224   a ,  224   b  and sheet  16  tend to compress the head end piece  124  while being pulled into the sheet receiver  18  and, in turn, hold the sheet  16  in excess tension. In response, once the roller  244  rotates to reposition the patient, the driven gear  258  reverses for a predetermined period time to reverse the wrapping of the sheet  16  about the roller  244 . The predetermined period of time is generally long enough to release the excess tension in the sheet head end  516 , but short enough to prevent the sheet  16  from becoming loosely held by the sheet receiver  16 . As such, the sheet  16  remains slightly taut while allowing the head end piece  124  to return to form as shown in  FIG. 7C . Alternatively, the roller  244  may operatively disengage from the drive unit, such as via a clutch  276   a  (see  FIG. 8 ), to allow the roller  244  to freewheel for the predetermined period of time. 
       FIG. 8  shows an alternative chain drive portion  277  driven by a motor  276   b  connected to a clutch  276  for rotating the roller  244  in which like numbers indicate like features described above. The chain drive portion  277  includes a chain drive gear  278  operatively connected to the clutch  276  and chain driven gear  280 . Rather than pivot the chain drive gear  278  for operatively disengaging the roller  244  as described above, the clutch  276  selectively engages the chain driven gear  280 . In this way, the motor  276   b  may either rotate the roller  244  or allow the roller  244  to freewheel as described above so that the clutch  276   a  acts as the arrestor  260  (see  FIG. 7C ). In addition, a chain  281  simultaneously wraps about the chain drive gear  278  and the chain drive gear  280  such that the actively driven chain drive gear  278  drives the chain driven gear  280  via the moving chain  281 . Accordingly, the roller  244  may rotate for pulling the sheet  16  as described above. However, it will be appreciated that the other combination of drive components, such as gears, chains, sprockets, and/or belts, may be used to operatively rotate the roller  244 . 
       FIGS. 9-11  show further details of the sheet receiver  18  removed from the volume envelope  128  (see  FIG. 7C ) of the mattress  14 . The housing  214  includes the top and front panels  238 ,  272  described above and also a pair of side panels  282   a ,  282   b , a rear panel  284 , and a bottom panel  286 . Furthermore, the housing  214  has a housing frame  288  that includes a pair of lateral support members  290   a ,  290   b  and a central cross member  291 . The central cross member  291  extends perpendicularly between the pair of lateral support member  290   a ,  290   b  and divides space within the housing  214  into the sheet chamber  240  and a drive chamber  292 . The members  290   a ,  290   b ,  291 ,  290   a ,  290   b  may also be rounded to facilitate cleaning within the sheet chamber  292 . More particularly, the sheet chamber  240  is defined by the top panel  236 , the support members  290   a ,  290   b , the bottom panel  286 , and the front panel  272 . Also, the drive chamber  292  is defined by the top panel  238 , the support members  290   a ,  290   b , the bottom panel  286 , and the rear panel  284 . 
     The drive chamber  292  generally includes the remaining portion of the drive mechanism  252 . According to the exemplary embodiment, the drive mechanism  252  also includes a power source  294 , a controller  294   a , a sheet release sensor  296 , a door sensor  298 , and a motor  300 . The motor  300  directly connects to the drive gear  254  for selectively rotating the drive gear  254 . In addition, the pair of lateral support members  290   a ,  290   b  rotatably supports a sheet release rod  302  within the drive chamber  292 . The motor  300  connects to the rotatable sheet release rod  302 , which extends through the side panels  282   a ,  282   b  to each of the sheet releases  234 . At the operator&#39;s discretion, movement of the sheet release  234  pivots the motor  300  about the sheet release rod  302 . In turn, the drive gear  254  directly connected to the motor  300  pivots, as indicated by arrow  262  in  FIG. 7A , for operating the sheet release  234 . 
     With respect to  FIG. 11  and  FIG. 1B , the controller  294   a  electrically connects to the motor  300 , the sheet release sensor  296 , the door sensor  298 , the enabling switch  210 , and the drive switch  212  for operating the sheet receiver  18 . The controller  294   a  also connects to a power source  294  via a power cord  306  for powering the drive mechanism  252 . As described above, the enabling switch  210  and drive switch  212  cooperate for directing the controller  294   a  to power the motor  300 , rotate the drive gear  254 , and effectively pull the sheet  16 . However, the sheet release sensor  296  and door sensor  298  are configured for preventing powering the motor  300  for movement while either sheet release  234  is active or the access door  236  is open, respectively. For example, rotating the sheet release rod  302  via the sheet release  234  moves a sheet release cam  304  that operatively engages the sheet release sensor  296 . The engaged sheet release sensor  296  then operatively prevents the controller  294   a  from operating the motor  300 . Similarly, the door sensor  298  is configured to selectively engage a door projection  308  attached to the access door  236  (see  FIG. 6 ). On one hand, when the access door  236  closes, the door projection  308  engages the door sensor  298  for indicating the closed access door  236  to the controller  294   a . On the other hand, when the access door  236  opens, the door projection  308  (see  FIG. 6 ) disengages from the door sensor  298  for indicating the open access door  236  to the controller  294   a . Accordingly, the controller  294   a  recognizes this engagement or disengagement with the door sensor  298  and only permits the motor  300  to operate when the access door is closed. The controller  294   a  may also monitor the rotation of the roller  244  by directly counting revolutions of the roller  244  or indirectly counting revolutions of the roller  244  by timing the amount that the motor  300  advanced the roller  244 . In either case, the controller  294   a  correlates the number of roller  244  revolutions to the length of sheet  16  wrapped about the roller  244 . Finally, the controller  294   a  may indicate the status of the sheet  16  to the operator as described below. 
     According to the exemplary embodiment of the invention, the drive mechanism  252  is contained entirely within the housing  214  of the sheet receiver  18 . However, in the alternative, portions of the drive mechanism  252  may be exterior of the housing  214 . The portions of the drive mechanism  252  may be similar portions of the pulling device  242  that connect, directly or indirectly, to the portions of the drive mechanisms  252  for rotating the roller  244 . An exemplary embodiment of a portion of the drive mechanism  252  exterior of the housing  214  will be described below in further detail. 
       FIG. 12  shows an exemplary embodiment of the sheet  16  for use with the sheet receiver  18  of  FIG. 11 . The sheet  16  includes the sheet head end  516  and an opposing sheet foot end  520 . Furthermore, the sheet longitudinal sides  512   a ,  512   b  and beaded edges  510   a ,  510   b  extend from the sheet head end  516  to the sheet foot end  520 . The sheet head end  516  also preferably includes a reinforced sheet portion  521  into which the slits  514   a ,  514   b  are sown. Examples of reinforced sheet portions  520  may comprise multiple layers of material and/or additional stitching. Additionally, the sheet  16  may include a reinforced sheet portion  521  and slits  514   a ,  514   b  at both the head and foot ends  516 ,  520  of the sheet  16 . As such, the sheet  16  is generally symmetrical and may be operatively connected to the sheet receiver  18  at either the sheet head end  516  or the sheet foot end  520 . 
     The sheet  16  also includes the sheet loaded indicia  518  and a sheet usage indicia  522 . In contrast to the sheet loaded indicia  518  described above, the sheet usage indicia  522  aligned with the alignment sheet indicia  144  of the mattress  14  (see  FIG. 3A ) indicates to the operator that a sufficient length of the sheet  16  is within the sheet receiver  18  and, thus, should be replaced with another sheet  16 . According to the exemplary embodiment, the sheet loaded indicia  518  is a green circle, and the sheet usage indicia  522  is a red octagon, similar to a traditional traffic “stop sign.” The sheet  16  may also include a sheet remaining indicia (not shown) or a coded section  524 . The sheet remaining indicia may be positioned along the length of the sheet  16  and indicate to the operator the length of the sheet remaining before reaching the sheet usage indicia  522 . The coded section  524  may communicate with the sheet receiver  18  for verifying any information related to the sheet  16  and/or indicating such information to the operator. For example, the coded section  524  may communicate to the sheet receiver  18  the type of sheet, engaged attachment, length of sheet remaining, or any other relevant status information concerning the sheet  16  to the operator. The sheet  16  may also include a measured indicia  530  for communicating to the operator the amount of sheet  16  used, remaining, or the number of pulls remaining with respect to the present position of the sheet  16 . An exemplary embodiment of the measured indicia  530  indicates the number of pulls remaining via numerical indicators; however, it will be appreciated that any visual indication may be used in accordance with the invention.  FIGS. 13A-15B  show alternative embodiments of retainers according to the invention. In this respect, like numbers indicate like features of the retainers.  FIG. 13A  and  FIG. 13B  show a slide retainer  610  including a base piece  612  and a movable piece  614 . The movable piece  614  connects to the base piece  612  or otherwise projects from the base piece  612 . In addition, the movable piece  614  moves relative to the base piece  612  between the open position and the closed position for defining the channel  414  and retaining the sheet  16 , as described above. 
     More particularly, the base piece  612  and movable piece  614  each include cooperating tracks  616 . The track  616  of the movable piece  614  slides into the track  616  of the base piece  612  for connecting the base piece  612  and the movable piece  614  together. In addition, the movable piece slides along the track  616  of the base piece  614  to open and close the channel  414 , as indicated by arrow  618 . Because the movable piece  614  slides against the base piece  612 , a stopper  620  protrudes from the movable piece  614  toward the base piece  612  to engage the detent  430  and inhibit movement of the movable piece. Of course, the operator may simply snap the stopper  620  beyond the detent  430  in either direction such that the detent  430  is received in either the track  616  of the movable piece  614  or the closed channel  414 . However, it will be appreciated that any base piece  612  and movable piece  614  slidably attached may open and close the channel  414  as described above. Accordingly, the slide retainer  610  is not intended to be limited to the exemplary embodiment described herein. 
       FIG. 14A  and  FIG. 14B  show a pivot retainer  630  including a base piece  632  and a movable piece  634 . The movable piece  634  connects to the base piece  632  or otherwise projects from the base piece  632 . In addition, the movable piece  634  moves relative to the base piece  632  between the open position and the closed position for defining the channel  414  and retaining the sheet  16 , as described above. 
     More particularly, the base piece  632  and movable piece  634  include a pair of holes  636  and a pair of dowels  638  respectively. The holes of the base piece  632  receive the dowels  638  of the movable piece  634  such that the movable piece  634  pivots between open and closed positions, as indicated by arrow  640 . In addition, the base piece  632  includes a tab portion  642  that extends toward a collar  644  defined by an opening  646  in the movable piece  634 . As the movable piece  634  pivots to the closed position, the tab portion  642  snaps against the collar  644  for holding the movable piece closed. Thereby, the operator may simply snap the tab portion  642  into the opening  646  and out of the opening  646  to respectively open or close the channel  414 . However, it will be appreciated that any base piece  632  and movable piece  634  pivotably attached may open and close the channel  414  as described above. Accordingly, the pivot retainer  630  is not intended to be limited to the exemplary embodiment described herein. 
       FIG. 15A  and  FIG. 15B  show a clip retainer  650  including a base piece  652  and a movable piece  654 . The movable piece  654  connects to the base piece  652  or otherwise projects from the base piece  410 . In addition, the movable piece  654  moves relative to the base piece  652  between the open position and the closed position for defining the channel  414  and retaining the sheet  16 , as described above. More particularly, the base piece  652  is generally rigid and includes the lip projection  416 . The movable piece  654  is generally flexible and resiliently extends from the base piece  652  against the lip projection  416 . The movable piece  654  also includes the planar portion  426  resiliently held against the lip projection  416  to define the channel  414  of the clip retainer  650  in the closed position. However, the movable piece  654  may resiliently bend toward the open channel  414  to receive the sheet  16 , but resiliently bends back to again close the channel  414 . As such, the operator may simply snap the beaded edge  510   a  of the sheet  16  into the channel  414 . However, it will be appreciated that any base piece  652  and movable piece  654  may resiliently bend to open and close the channel  414  as described above. Accordingly, the clip retainer  650  is not intended to be limited to the exemplary embodiment described herein. 
       FIGS. 16A-16C  show a rigid retainer  660  having a body portion  662  and a base portion  664 . The base portion  664  is generally planar and configured for attaching or welding as described herein. The body portion  662  defines a channel  666  and includes an opening  668  that extends through the body portion  662  and into the channel  666 . Generally, the sheet  16  includes the beaded edge  510   a , which is received within the channel  666 . However, the beaded edge  510   a , according to an exemplary embodiment, is generally compressible for insertion through the opening  668  and into the channel  666 . In addition, the opening  668  may be tapered such that the opening  668  narrows into the channel  666 . Accordingly, the beaded edge  510  and the opening  668  mate such that the insertion force needed to position the beaded edge  510   a  into the channel  666  is less than the removal force needed to withdraw the beaded edge  510   a  from the channel  666 . 
     With respect to  FIG. 17 , an alternative embodiment of a drive mechanism  670  includes an external portion  672  of the drive mechanism  670  and an internal portion  674  of the drive mechanism  670  contained within the housing  214 . By splitting the drive mechanism  670  into external and internal portions  672 ,  674 , patient care environments with multiple health care beds may purchase less external portions  672  for use with any number of internal portions  674 . Specifically, the external portion  672  is hand held and includes an external motor  676  operably driven by an external controller  678 . The operator may direct the external controller  678  to rotate the external motor  676  and, in turn, operate the internal portion  674  of the drive mechanism  670  as described above to pull the sheet  16 . For instance, a nursing home with a plurality of health care beds  12  may reduce costs by only purchasing one external portion  672  for use with multiple health care beds equipped with a patient repositioning system  10   a . In other words,  FIG. 17  shows an embodiment wherein only a part of the drive mechanism  670  is contained within the housing  214 . The other part may be hand held, and driven by AC or a battery. 
     According to an exemplary embodiment, the hand held external portion  672  inserts through a coupling  680  in the housing  214  for operatively connecting to the roller  244  shown in  FIG. 6  and  FIG. 9 . Preferably, the coupling  680  also includes a key member  682  received within a key slot  684  while connected to the internal portion  674  for preventing backlash of the hand held external portion  672 . For example, if the external motor  676  suddenly encounters substantial force during use, the external portion  672  may suddenly twist in hand. However, in the event that the key slot  684  receives the key member  682 , the sheet receiver  18  will bear the backlash of the twisting force in hand. It will be appreciated that any portions of the drive mechanism  670  may be internal or external of the housing  214  in accordance with the invention described herein. 
       FIG. 18  is an alternative embodiment of a sheet receiver  18 ′ having an optional digital and graphic display module  350 . The display module  350  is positioned within the side panel  282   a  and operatively connected to the controller  294  (see  FIG. 21 ) for displaying any information discussed herein that may be communicated via the controller  294  and indicated to the operator. The sheet receiver  18 ′ also includes the enabling switch  210  and drive switch  212 . According to one embodiment, the drive switch  212  may be the only input needed to operate the sheet receiver  18 . Alternatively, the enabling switch  210  and the drive switch  212  inputs both are needed to operate the sheet receiver  18 , either concurrently or sequentially. 
     Furthermore, the sheet receiver  18 ′ includes a plurality of light emitting diodes (LEDs) acting as a power indicator  352 , a leveling indicator  354 , and an open access door indicator  356 . The power indicator  352  emits light to indicate that the sheet receiver  16  is enabled for operation. The leveling indicator  354  emits light to indicate that the sheet receiver  18 ′ is too unlevel for operation. The open access door indicator  356  emits light to indicate that the access door  236  is open and, as such, not ready for operation until the access door  236  is sufficiently closed. 
     The sheet receiver  18 ′ also includes a sheet release  234 ′ and a door release  358 . The sheet release  234 ′ is operatively connected to the clutch  276  (see  FIG. 8 ) for disengagement and releasing of the sheet  16  (see  FIG. 7A-7C ) as described above. The door release  358  operatively slides to the right, with respect to  FIG. 18 , in order to release the latch  360 . Specifically, as the door release  358  translates, the latch  360  rotates out of a cooperating door slot  362  within the access door  236  for allowing the access door  236  to move as described herein. The latch  360  is biased with a torsion spring  364  for returning the latch  360  and insertion into the door slot  362 . As such, the latch  360  locks the access door  236  in the closed position for preventing the taut sheet  16  similar to  FIG. 3E  from lifting the access door  236  open while being pulled. Furthermore, another latch (not shown) is connected to the latch  360  via the extended bar  366 . In this respect, the sheet receiver  18 ′ has two symmetrically positioned latches  360  for locking the access door  236  closed. 
       FIG. 20  shows another alternative sheet receiver  18 ″ for use with a mattress  14 ″. Notably, the sheet receiver  18 ″ is integrated into the head deck portion  32 ″. Accordingly, the sheet receiver  18 ″ may be used with the mattress  14 ″, which includes a head end section  122 ″ with a substantially uniform thickness throughout. Furthermore, the head end section  122 ″ is substantially the same thickness as the remainder of the mattress  14 ″. While the exemplary embodiment of the sheet receiver  18 ″ is integrated with the head deck portion  32 ″, it will be appreciated that the sheet receiver  18 ″ may alternatively be mounted below the head deck portion  32 ″ for use with the mattress  14 ″ of substantially uniform thickness throughout. In other respects, like numbers indicate like features described above. 
     With respect to  FIG. 21 , the controller  294  may be connected to one or more switches for preventing the patient from contacting the headboard  28  during use. According to an exemplary embodiment, a pressure pad  684  senses pressure of patient contact while a light curtain  686  senses the patient breaking the light passing therethrough. Alternatively, the controller  294  may be operatively connected to a trip switch  688  operably mounted to the sheet receiver  18 . Similar to the pressure pad  684 , in the event that the patient passes too close to the head end, the patient contacts the trip switch  688  for communicating the patient&#39;s presence to the controller  294 . The controller  294  may also maintain the amount of time the sheet receiver  16  operates with an operation timer  690  and the amount of electrical current or rate of electrical current being used by the drive mechanism  252  at any given time. 
     In any case, the controller  294  is operatively connected to a status indicator, such as the display  350  described above with respect to  FIG. 18 , the drive mechanism  252 , and the pulling device  242 . As such, if the operation time  690  reaches a predetermined maximum amount of time, the maximum electrical current peaks via a motor shunt control  692 , or the pressure pad  684 , light curtain  686 , or trip switch  688  communicates with the controller  294 , the controller  294  may remove power from the drive mechanism  252  to stop the patient from moving toward the headboard  28 . The controller  294  may also communicate visually via the status indicator  350  or audibly via an operatively connected alarm generator  694   
     Another option of an exemplary embodiment shows a sheet receiver  18  having a UV disinfection module  694  contained therein for selective operation. Specifically, the module  694  is connected to a UV control interface that also connects to the controller  294 . As such, the operator may selectively operate the UV disinfection module  694 , or the controller  294  may maintain the operation time  690  for periodic disinfection. 
     According to another exemplary embodiment, the patient repositioning device  10  may be used as substantially described above with respect to other types of beds. For example, the patient repositioning device  10  may be used with a birthing bed described within U.S. Pat. No. 6,757,924, the disclosure of which is hereby incorporated by reference herein. In this respect, the mattress is sized and shaped so as to accommodate the removal of the foot section of the birthing bed. By way of another example, the patient repositioning device  10  may also be used with a bed described within U.S. Pat. No. 5,692,256, the disclosure of which is hereby incorporated by reference herein. In this respect, the mattress has a non-uniform thickness with respect to a central lateral vertical plane. Of course, the patient repositioning device  10  may be configured to accommodate a conventional bed or any other bed for which repositioning the patient provides increased comfort and performance to both the operator and the patient. 
     In use, with a patient supported on the sheet  16  and the sheet  16  located on the mattress  14 , this patient repositioning system  10  enables an attendant to cause the sheet  16  and the patient supported thereon to move toward the head end  30  of the mattress  14 , as the sheet  16  is pulled into the slot  216  formed in the housing  214 . Because the sheet  16  has a width that is greater than that of the mattress  14 , and that additional width is retained along opposing longitudinal sides of the mattress  14 , as the sheet  16  moves and the patient is repositioned the outer portions of the sheet  16 , i.e. the sheet longitudinal sides  412   a ,  512   b  move from a substantially vertical orientation to a substantially horizontal orientation as the sheet  16  is pulled into the slot  216 . For each sheet  16 , a number of such patient repositionings may occur, until the system  10  indicates via the sheet usage indicia  522  that it is time to replace the sheet  16 . Generally, the attendant causes the sheet  16  to move via operation of the inputs to the drive mechanism  252 , as described above. 
     To initiate patient repositioning using this system, an attendant places a sheet  16  on the mattress  14 , connects the sheet  16  to the mattress  14 , and also operatively couples the sheet  16  to the drive mechanism  252 . Typically, this connecting of the sheet  16  to the mattress  14  involves securing opposite sheet longitudinal sides  512   a ,  512   b  of the sheet  16  to oppositely located rows of retainers  116  spaced along the length of the mattress  14 , and the sheet  16  has beaded edges  510 ,  510   b  along its longitudinal sides  512   a ,  512   b  which allow for longitudinal movement of the sheet  16  along the retainers  116 . To operatively couple the sheet  16  to the drive mechanism  252 , the attendant who may also be referred to as an operator, releasably attaches the sheet  16  to the drive mechanism  252 , and the drive mechanism  252  is then used to pull the sheet  16  toward the head end  30  of the mattress  14 , to “load” the sheet  16  in preparation for subsequent pulling of the sheet  16  toward the head end  30  of the mattress  14  with a patient residing thereon. 
     In some situations, it may be necessary to replace a sheet  16  on a mattress  14  while a patient remains thereon, perhaps due to soiling of the sheet  16 , or other reasons. In this situation, after removal of the old sheet  16 , the attendant retains a first beaded edge  510   a  of a first longitudinal side  512   a  of the new sheet  16  to the row of spaced retainers located on one side of the mattress  14 . Thereafter, the patient and the sheet  16  are maneuvered so as to place the sheet  16  between the patient and the mattress  14 , and then the attendant retains the second beaded edge  510   a  of the opposite, second longitudinal side  510   b  of the new sheet  16  to the second row of spaced retainers  116  located on the second side of the mattress  14 . Once the sheet  16  has been retained on both sides of the mattress  14 , the sheet  16  is then releasably attached to a drive mechanism  252  located adjacent the head end  30  of the mattress  14 , and the sheet  16  is thereafter pulled toward the head end  30  of the mattress  14  to “load” the system. Typically, during this initial pulling, the head end of the sheet  16  is not weight bearing, i.e., the patient is not residing thereon. Stated alternatively, the new sheet  16  is retained on the mattress  14  with some amount of slack at the head end  30  thereof, as indicated by indicia on the new sheet  16 , to facilitate unweighted pulling of the sheet  16  to the loaded position. 
     In addition to these methods as described above, this patient repositioning system  10  also facilitates infection control, or even retrieval of the sheet  16 , by facilitating access to the housing  214  into which the sheet  16  is pulled. More particularly, to access the inside of the housing  214 , the attendant merely needs to open the access door  236  to the housing  214 . There is no need to raise any portion of the bed. Depending on the configuration of the patient repositioning system  10  and the structure of the bed, this opening of the access door  236  may occur after moving the head end piece  124  of the mattress  14 , as by folding. Moreover, this opening the access door  236  may involve manipulation of the bottom of the mattress  14 , or the top of the bed deck  22 , depending on how the housing  214  is configured with respect to the mattress  14  and/or the bed deck  22 . 
     This specification shows and describes several preferred embodiments of the invention. However, those skilled in the art will appreciate that the disclosed embodiments are susceptible to a reasonable amount of modification and/or permutation, without departing from the overall scope of the invention. For instance, the dimensions of the components shown and described, and/or the relationships of those dimensions to other components may vary, as needed, in order to apply the general principles of the present invention to the actual circumstances at hand. 
     Moreover, it is to be understood that the recitation of “objects of the invention” in this specification, or referenced problems recognized in the prior art, are not intended to be construed as an admission that others have also recognized the same problems or perceived the same limitations in the state of the art, as recognized by the present inventors. Moreover, any reference to objects of the invention is not intended to require each of the following claims to achieve all of the above-stated objects or advantage. Rather, the recitation of the objects of the invention in this specification is intended merely to help explain the story behind the present invention, and to explain why the present invention represents an advance in the state of the art over existing technology. Accordingly, the inventors intend that the scope of the appended claims is not to be limited by the specific details shown or described in this specification.