Patent Publication Number: US-10322048-B2

Title: Systems and methods for powered wheelchair personal transfer

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/452,542 filed Jan. 31, 2017, entitled “Systems and Methods for Powered Wheelchair Personal Transfer,” the contents of which are hereby incorporated herein by reference in their entirety. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with government support under Contract Nos. B9269-L and B9250C, awarded by the U.S. Dept. of Veterans Affairs, and Contract No. EEC-1560174S, awarded by the National Science Foundation. The U.S. Government may have certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to devices, apparatuses, systems and methods for patient transfer. More specifically, the invention relates to patient transfer from a rollable powered wheelchair to a bed and back. 
     BACKGROUND 
     Transferring a person with a disability (PwD) between a bed and a wheelchair—or standing position, commode, chair, walker, and/or toilet—can be a labor intensive and time consuming task. In some cases, it can take multiple people to perform the transfer and can cause injury (both acute and cumulative) to the PwD, the caregiver, and/or the transfer equipment, particularly if errors are made during transfer (e.g., if the chair is mis-positioned or the brakes are not engaged). Other risks of PwD transfer include fear, loss of dignity, and increased dependence on others. 
     For PwDs who need assistance with transfers, there are not a lot of good options. The most commonly used lift technologies include the overhead ceiling lift, the floor-based sling lift, and the Gantry lift. While these devices allow for safer transfer of PwDs, they do so with shortcomings. For example, overhead sling lifts require extensive installation that may not be suitable for homes or buildings with structural deficiencies or low ceilings; floor-based sling lifts have issues with caregiver manipulation and ease of use; and gantry lifts are difficult to move and store due to their size. 
     Research and experience suggest that caregivers and PwDs are unsatisfied with current patient transfer technology, and are concerned that their lifestyle is impaired by the lack of appropriate technologies or that it will negatively affect them and their caregivers in their futures. Typically, wheelchairs and beds have been regarded as separate technologies, with the designers of one technology not working in tandem with designers of the other to coordinate movement between the two. What is needed is a solution that makes patient transfer more streamlined, convenient, and safe, both for the patient and the caregivers involved. 
     SUMMARY OF THE INVENTION 
     The present invention includes improved systems and methods for patient transfer, such as enabling autonomous transfers of an occupant of a rollable chair (e.g., a powered wheel chair or “PWC”) to and from a bed. In some embodiments, the invention includes a powered, pedestal-mount wheelchair that works in tandem with a hospital bed having a built-in conveyor. In some embodiments, the invention provides powered, coordinated and synchronized motion of the wheelchair seat and the bed to allow for independent transfers from one to the other while minimizing the physical effort needed by the patient and/or the caregiver(s) during transfer. In some embodiments, the invention includes a new transfer device for users of electric powered wheelchairs (“EPWs”) that is designed to reduce environmental and equipment complications that can lead to progressive inactivity of persons with disabilities, as well as frustration and injury risks experienced by users and their assistants. In some embodiments, the invention automates EPW-to-bed transfers, saving time, minimizing staff involvement, and decreasing caregiver risk. 
     In some embodiments, the seat frame of the chair travels rearward and rotates to move the seated occupant onto or proximal to the foot end of the bed. For context, in certain prior manual chair configurations, these motions have been handled with separate frames (a sliding frame and a rotating seat frame) and were separately powered by actuators in a docking module of the bed. In the present invention, these motions can be produced by a single seat frame powered by just one actuator. For example, the seat frame can be drawn along a “J”-shaped path or track. In some embodiments, the actuator initially draws a rearward edge of the seat frame horizontally along a straight section of the track. This movement begins to position the occupant proximal to the moving bed conveyor by closing the gap between the seat frame and the bed. Once in position for transfer, the powered wheelchair backrest rotates or translates laterally and the PwD leans against the mattress of the bed, which has been positioned near vertically. The actuator continues to draw the rear edge of the seat frame down along the arced path, causing the front edge of the seat frame to tip upward toward the bed, further pushing and/or lifting the occupant&#39;s legs up onto the moving bed conveyor. The bed rotates synchronously as the conveyor moves to minimize shear by matching the kinematics and rate of motion. 
     In some embodiments, the chair has a leg ramp with a foot rest that is hinged at the front edge of the seat frame, and linkage connecting the leg ramp to the seat frame can control the angle between the two. In some embodiments, the nominal angle is potentially adjustable to allow an elevated position to support the occupant&#39;s legs while the chair is in the “normal” position. The linkage can control and synchronize the angle of the ramp/leg rest to minimize shear forces on the occupant&#39;s legs during transfers and when the chair is in the “tilt” position. The linkage can also control leg ramp position without the need for another actuator. 
     In some embodiments, a powered back helps to enable autonomous or independent transfers. The powered back can be configurable, for example, to rotate or slide to the left or right and can be field-adjustable. The system can control the point in the transfer when the back unlocks and pivots out from behind the chair occupant. Sensors can ensure correct back position and locking. Motor current may be monitored to detect collisions of the back into objects or to cause a prompt to the occupant to lean forward off the chair back. An armrest opposite the side of the back that pivots can be moved out of the way by the occupant. In some embodiments, sensing of this position and powered locking may be used. 
     In some embodiments, actuators and mechanisms for seat and back frames occupy space to the rear and sides of the chair, leaving the volume directly under the seat relatively open. This arrangement can provide a single, centered mounting point that fits to a post of the PWC. In some embodiments, this design can be adapted to pedestal-mount chairs from several manufacturers. In some embodiments, the design can be revised to work with wheelchairs with base designs other than the pedestal-mount designs. In some embodiments, as the chair translates for transfer the seat frame tilts backward. This feature can provide a powered tilt option. In this mode the chair back can be left locked in place and rearward translation can provide an adjustable amount of tilt. In some embodiments, movement of the chair back can be limited, e.g., to prevent a center of gravity from moving to an unstable point or tipping point. 
     In some embodiments, the chair connects to and communicates with the bed electronically, e.g., by umbilical cable or wirelessly. The actuators in the chair may be powered directly from the bed if connected by umbilical or from the chair&#39;s own controller or power supply. Whether powered from the bed or self-powered, command of chair movements and/or actuators can be controlled and coordinated by a controller (located, e.g., in the bed, or anywhere within wireless communication range if connected wirelessly). In some embodiments, the motions of both can be synchronized for safe and comfortable transfers. In some embodiments, both the chair and the bed can have absolute sensing of actuators positions, speed and current draw, and separate IO to ensure correct frame positions and frame locking. In some embodiments, chair and bed use actions are logged by the bed and stored electronically. 
     In some embodiments, the chair is positioned at the foot of the bed (and/or couples to the bed, e.g., mechanically and/or electronically) for transfer. One approach is to use a docking assembly or docking platform. In such embodiments, an operator can drive the chair up onto the docking platform from almost any angle within a ground plane. In some embodiments, the docking assembly can sense the approach angle of the chair and rotate or otherwise move to align with it. Once the chair is properly positioned on the platform, the docking assembly can rotate the chair to be square to the foot end of the bed and draw a platform back for transfer. Command of the docking assembly can reside, e.g., in the bed controller. In some embodiments, the chair positions itself using a drive system. In some embodiments, the docking assembly includes electronic docking options based on user ability. 
     In some embodiments, the rollable chair is an EPW and/or a Group- 2  wheelchair. In some embodiments, the patient transfer system allows a patient to transfer from the chair to the bed and back with minimal or no assistance from a caregiver. In some embodiments, the movements of the bed and custom wheelchair seating system are electrically powered and synchronized through computer control. In some embodiments, the patient transfer system is particularly suitable for patients with a primary diagnosis of obesity, cardiovascular disease, cardiopulmonary disease, paraplegia with upper extremity pain or overuse injury, or metabolic diseases, at least because they often use powered wheelchairs and have the ability to operate their powered wheelchair and to control the interface for the transfer device. 
     In one aspect, the invention features a rollable chair. The rollable chair includes a first frame including a seat. The rollable chair also includes a second frame coupled to the first frame, the second frame including a backrest configured to move relative to the first frame. The rollable chair also includes a third frame coupled to the first frame, the third frame including a track having a curvilinear length configured to allow the first frame to rotate and/or to translate relative to the third frame. 
     In some embodiments, the track further includes a linear length configured to allow the first frame to translate relative to the third frame, the linear length adjoining the curvilinear length. In some embodiments, the track includes a J-shape. In some embodiments, the first frame is powered by a first actuator that is mechanically coupled to the first frame. In some embodiments, the rollable chair includes at least one sensor, connected to the rollable chair, for determining a position of the rollable chair relative to a bed. In some embodiments, the second frame is configured to rotate about a pivot point to permit the backrest to be removed from a path of patient transfer between the rollable chair and a bed. In some embodiments, the second frame is powered by a second actuator that is mechanically coupled to the second frame. 
     In some embodiments, the second frame includes a latching mechanism configured to engage with a corresponding latching mechanism of the third frame. In some embodiments, the corresponding latching mechanism on the third frame includes a taper configured to proper alignment of the rollable chair. In some embodiments, the rollable chair includes a quick-release feature for aiding an assistant with disengaging the rollable chair from a bed. In some embodiments, the rollable chair further includes a fourth frame that is mechanically coupled to the first frame, the fourth frame including a leg rest. In some embodiments, the first and fourth frames are rigidly coupled, the fourth frame configured to guide a patient&#39;s legs during a patient transfer operation. In some embodiments, the rollable chair is configured to couple to a bed having a chair receiving frame. In some embodiments, the seat has a posterior tilt with respect to the rollable chair. 
     In another aspect, the invention includes a patient transfer system. The patient transfer system includes a rollable chair having a first frame including a seat; a second frame coupled to the first frame, the second frame including a backrest configured to move relative to the first frame; and a third frame coupled to the first frame, the third frame including a track having a curvilinear length configured to allow the first frame to rotate and/or to translate relative to the third frame. The patient transfer system also includes a bed including a chair receiving frame configured to couple to the first frame of the rollable chair. 
     In some embodiments, the patient transfer system further includes a first microprocessor coupled to the rollable chair and a second microprocessor coupled to the bed, the first microprocessor in direct or indirect electronic communication with the second microprocessor. In some embodiments, the patient transfer system further includes a computing device in electronic communication with the first and second microprocessors, the computing device configured to execute instructions to coordinate kinematics between the rollable chair and the bed during a patient transfer operation. In some embodiments, a motion path of the seat is determined by the computing device and includes both translational and rotational components. 
     In some embodiments, the bed is configured to fold during a patient transfer operation between the rollable chair and the bed, the bed configured to work in tandem with the rollable chair to receive the patient during a patient transfer operation. In some embodiments, the patient transfer system further includes a docking assembly configured to receive the rollable chair and to facilitate transfer of a patient from the rollable chair to the bed. In some embodiments, the docking assembly is configured to receive the rollable chair from any (or nearly any) angle of approach within a ground plane. In some embodiments, the docking assembly includes a third microprocessor, the third microprocessor in direct or indirect electronic communication with the first and second microprocessors. In some embodiments, the bed includes a sensor configured to ensure that the rollable chair is properly positioned with respect to the bed. In some embodiments, the rollable chair is a retrofitted Group 2 Electric Powered Wheelchair. 
     In another aspect, the invention features a method of transferring a patient between a rollable chair and a bed. The method includes positioning the rollable chair at or near a proximal end of the bed. The method also includes translating a distal end of the bed toward the proximal end of the bed, the bed folding into a first section and a second section, wherein the first section becomes positioned behind a chair back of the rollable chair and the second section forms an angle with the first section. The method also includes moving the chair back of the rollable chair, via at least one of a rotational or a translational motion, such that the patient contacts the first section of the bed. The method also includes moving a seat frame of the rollable chair along a guide rail disposed relative to the seat frame, via at least one of a translational or a rotational motion, to position the patient at least substantially on the bed. 
     In some embodiments, the guide rail is a track having a curvilinear length. In some embodiments, moving the chair back is accomplished using a powered actuator. In some embodiments, moving the seat frame is coordinated with a simultaneous or near-simultaneous moving of the bed. In some embodiments, positioning the rollable chair at or near a proximal end of the bed is achieved using a docking assembly positioned proximate the bed and the rollable chair. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1A  is an isometric view of a patient transfer system including a rollable chair and a bed, according to an illustrative embodiment of the invention. 
         FIG. 1B  is a side view of the patient transfer system of  FIG. 1A  showing a seat and a frame having a “J” shape track, according to an illustrative embodiment of the invention. 
         FIG. 1C  is a side view of the patient transfer system of  FIG. 1A  with the seat removed, according to an illustrative embodiment of the invention. 
         FIG. 1D  is a top view of the patient transfer system of  FIG. 1A  showing a rollable chair interacting with dock sensors, according to an illustrative embodiment of the invention. 
         FIG. 1E  is a side view of the patient transfer system of  FIG. 1A  showing a rollable chair interacting with dock sensors, according to an illustrative embodiment of the invention. 
         FIG. 1F  is a side view a rollable chair, according to an illustrative embodiment of the invention. 
         FIG. 1G  is a close-up view of a seat actuator of a rollable chair, according to an illustrative embodiment of the invention. 
         FIG. 1H  is a close-up view of a backrest actuator of a rollable chair, according to an illustrative embodiment of the invention. 
         FIG. 2A  is a perspective view of a latching mechanism of a rollable chair, in the unlatched position, for capturing a backrest, according to an illustrative embodiment of the invention. 
         FIG. 2B  is a perspective view of a latching mechanism of a rollable chair, in the latched position, for capturing a backrest, according to an illustrative embodiment of the invention. 
         FIG. 3A  is a perspective view of a docking assembly for a patient transfer system in which the docking assembly is in a closed position, according to an illustrative embodiment of the invention. 
         FIG. 3B  is a perspective view of a docking assembly for a patient transfer system in which the docking assembly is in an open position, according to an illustrative embodiment of the invention. 
         FIGS. 4A-4H  is are depictions of a patient transfer mechanism having a rollable chair, a bed, and a docking assembly in various stages of operation during a patient transfer operation, according to an illustrative embodiment of the invention. 
         FIG. 5  is a flowchart of a method of transferring a patient from a rollable chair to a bed, according to an illustrative embodiment of the invention. 
         FIG. 6  is a schematic diagram of an electronic architecture for a patient transfer system, according to an illustrative embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is an isometric view of a patient transfer system  100  including a rollable chair  104  (also depicted separately in  FIG. 1F ) and a bed  108 , according to an illustrative embodiment of the invention. The rollable chair  104  includes a first frame  112 , a second frame  116  coupled to the first frame  112 , and a third frame  120  coupled to the first frame  112 . The frames  112 ,  116 ,  120  can be made of, for example, steel, aluminum, another metal or metal alloy, or a composite material such as carbon fiber. The rollable chair  104  also includes several wheels (e.g., wheels  122 A-F as shown in  FIGS. 1A-1E ). The base unit  110  can be a commercially available pedestal seat powered wheelchair base. In some embodiments, the wheels  122 A,  122 F (rear wheels) help to guide the rollable chair  104  toward the bed  108 . In some embodiments, the wheels  122 B,  122 E (drive wheels) are larger and help to power the rollable chair  104 . In some embodiments, the wheels  122 C and  122 D (front wheels) help to guide the rollable chair  104  with forward motion. 
     The first frame  112  includes a seat  124 , which can be a square cushion capable of supporting a patient. The seat  124  can assume a posterior tilt with respect to the rollable chair  104  during a patient transfer operation, as shown and described in greater detail below. The second frame  116  includes a backrest  128 , which can include a section of canvas, cloth, or another material capable of supporting a patient&#39;s back and/or matching the size and medical needs of the user. The backrest  128  can be configured to move relative to the first frame  112 , e.g., to rotate about a pivot point or to translate, such that the backrest  128  is removable from a patient transfer path between the rollable chair  104  and the bed  108  during a patient transfer operation. For example, in  FIG. 1A , the second frame  116 , and correspondingly the backrest  128 , are shown rotated 90 degrees from the upright position, such that the backrest is fully removed from the patient&#39;s path from the seat  124  to the bed  108 . 
     The third frame  120  includes a track  148  (e.g., having a curvilinear length  148 A) configured to allow the first frame  112  to rotate and to translate relative to the third frame  120 , for example, during a patient transfer operation as shown and described in greater detail below. In some embodiments (e.g., as shown in  FIG. 1A ), the track  148  also includes a linear length  148 B configured to allow the first frame to translate relative to the third frame. In some embodiments, the linear length  148 B adjoins the curvilinear length  148 A. In some embodiments, the two lengths  148 A,  148 B collectively form a “J-shape”. In some embodiments, the first frame  112  is powered by a first actuator (e.g., the actuator  190  as shown in  FIG. 1G ) that is mechanically coupled to the first frame  112 . In some embodiments, the second frame  116  is powered by a second actuator (e.g., the actuator  192  as shown in  FIG. 1H ) that is mechanically coupled to the second frame  116 . In some embodiments, the rollable chair  104  includes a latching mechanism  152  that is configured to engage with a corresponding latching mechanism of the first frame  112 , e.g., such that when the latching mechanism  152  is engaged with the corresponding latching mechanism, the first frame  112  is secured to the second frame  116  (e.g., as shown and described in  FIGS. 2A and 2B ). 
     The bed  108  includes a first frame  132  (e.g., a main frame), a second frame  136  (e.g., a chair receiving frame), and a third frame  140  (e.g., a movable frame). The first frame  132  includes wheels (e.g., wheels  134 A,  134 B). The second frame  136  interfaces with sensors of the rollable chair  104  (as shown and described below). The third frame  140  includes a mattress  144  and can be powered by a bed actuator. The bed  108  (e.g., the mattress  144 ) is configured to fold during a patient transfer operation between the rollable chair  104  and the bed  108 , the bed  108  configured to work in tandem with the rollable chair  104  to receive the patient during a patient transfer operation. The bed has a proximal end  154 A (e.g., a foot end) and a distal end  154 B (e.g., a head end), the distal end  154 B configured to translate toward the proximal end  154 A during a patient transfer operation. 
     In some embodiments, the rollable chair  104  includes a fourth frame  156  that is mechanically coupled to the first frame  112 . In some embodiments, the fourth frame  156  includes a leg rest  160  (e.g., is rigidly coupled to the leg rest  160 ). In some embodiments, the leg rest  160  includes two separate shoe prints  162 A,  162 B for separately accommodating a patient&#39;s two feet. In some embodiments, the leg rest  160  is made of molded plastic or another lightweight material suitable for supporting a patient&#39;s feet. In some embodiments, the fourth frame  156  is configured to guide a patient&#39;s legs during a patient transfer operation (e.g., as shown and described below in  FIG. 4 ). In some embodiments, the leg rest  160  uses a cam follower driven with the seat actuator. 
     In some embodiments, the patient transfer system  100  includes a computing device  164  configured to execute instructions to coordinate movements between the rollable chair  104  and the bed  108  during a patient transfer operation. The computing device  164  can be in direct or indirect electronic communication with a first microprocessor  168  coupled to the rollable chair  104 , and/or a second microprocessor  172  is coupled to the bed  108 . In some embodiments, the computing device  164  is included the bed  108 . In some embodiments, electronic communication is hard-wired and/or wireless. In some embodiments, the computing device  164  sends instructions to microprocessors  168 ,  172 , which in turn trigger movements of first and second actuators and determine a motion path of the first frame  112  relative to the bed  108  (as shown and described in greater detail below). In some embodiments, a master/slave approach is used for the computing operations (e.g., as shown and described below in  FIG. 6 ), where the master is equivalent to the computing device  164 . In some embodiments, the master can be anywhere within hard-wired or wireless electronic communication distance, as applicable. 
     Referring now to  FIG. 1D , in some embodiments, the bed  108  includes two sensors  173 A,  173 B, connected by a bar  175 , collectively forming a “bumper” (e.g., the second frame  136 ) connected to the bed  108  for determining a position of the rollable chair  104  with respect to the bed  108 . The sensors  173 A,  173 B can be in electronic communication with the microprocessor  164 . The sensors  173 A,  173 B can detect a physical indication that the bed  108  has come into proper alignment with the rollable chair  104  (e.g., is at the right orientation or distance). The sensors  173 A,  173 B can relay a sensed signal to the microprocessor  164 , which can cause the computing device  164  to cut power to the drive wheels  122 B,  122 E of the rollable chair  104 . In some embodiments, the sensors  173 A,  173 B are attached to a bar  175  (e.g., the second bed frame  136  shown and described above) to form a dock that is bolted to the bed  108 . When the rollable chair  104  is backed into the dock (e.g., as shown below but not depicted here separately), in the correct orientation, the rollable chair  104  can collapse both bump sensors  173 A,  173 B, closing an electronic switch that is normally open, indicating to the computing device  164  that the rollable chair  104  is in the correct position for transfer. The geometry can be such that no other position of the chair will allow both sensors to activate. 
       FIG. 2A  is a perspective view of a latching mechanism  204  of a rollable chair, in the unlatched position, for capturing a backrest, according to an illustrative embodiment of the invention. In some embodiments, the second frame  116  of the rollable chair  104  shown and described in  FIG. 1  includes the latching mechanism  204 , and the third frame  120  of the rollable chair  104  includes a corresponding latching mechanism  208 . The corresponding latching mechanism  208  on the third frame  120  includes a taper. As the second frame  116  is pushed into the corresponding latching mechanism  208 , the tapered surface on the corresponding latching mechanism  208  pushes  116  tightly against the third frame  120 , which secures it to be used as a backrest without excessive “wobbling” or “play”. In this embodiment, there is no “positive latching”, which eliminates the need for an additional actuator to “latch” or positively constrain the backrest. The latching mechanism  204  can be a bore in the second frame  116 , i.e., resembling a half-cylindrical shape. The corresponding latching mechanism  208  can be made of plastic or another suitable material.  FIG. 2B  is a perspective view of a latching mechanism of a rollable chair, in the latched position, for capturing a backrest, according to an illustrative embodiment of the invention. Fully engaged, the latching mechanism  204  is no longer visible, but is tightly and flushly secured within the corresponding latching mechanism  208 . 
       FIG. 3A  is a perspective view of a docking assembly  300  for a patient transfer system in which the docking assembly  300  is in a closed position, according to an illustrative embodiment of the invention. The docking assembly  300  has a platform  304  and a base  308 . The platform  304  is configured to receive a rollable chair (e.g., the rollable chair  104  shown and described in  FIG. 1A ) and to facilitate transfer of a patient from the rollable chair to a bed (e.g., the bed  108  shown and described in  FIG. 1A ). The platform  304  and/or the base  308  can be made of, for example, aluminum, steel, or a composite material. The platform  304  can include a ramp feature  312  for allowing the rollable chair to roll onto the assembly with ease. The platform  304  can include a pivot feature  316  to allow the platform  304  to rotate with respect to the base  308 . The platform  304  can include depressions  320 A,  320 B for receiving specific wheels of the rollable chair (e.g., drive wheels  122 C,  122 D of the rollable chair shown and described in  FIG. 1 ). The platform  304  can include a rotation marker  324  for aligning to a corresponding rotation marker  328  of the base  308  to signify when the rollable chair is in the proper position for a patient transfer operation. 
     In some embodiments, the docking assembly  300  has two degrees of freedom (e.g., a first degree including a linear dimension of fore and aft translation, and a second degree including rotation about the pivot feature  316 ). In some embodiments, the entire docking assembly  300  can roll or slide toward the bed  108  (or a top component of the docking assembly can roll or slide over the base). In some embodiments, the platform  304  can rotate 360 degrees and be accessible to the chair from any approaching direction. In some embodiments, the docking assembly  300  is short enough in height to be able to fit under the bed when it is not in use, e.g., about 50 millimeters. 
     In some embodiments, the docking assembly  300  is configured to receive the rollable chair from any angle of approach within a ground plane. For example,  FIG. 3B  shows the docking assembly  300  in an “open” position in which the platform is rotated 90 degrees from the closed position (shown in  FIG. 3A ) with respect to the base. In some embodiments, the docking assembly  300  includes a third microprocessor  328  in direct or indirect electronic communication with the computing device and/or the first and second microprocessors (e.g., as shown above). In some embodiments, the third microprocessor  328  causes one or more actuators connected to the docking assembly  300  to effect the translational and the rotational movements required or desirable for a patient transfer operation. In some embodiments, the docking assembly  300  includes four panels to allow it to break down more easily, e.g., to allow it to be assembled inside a room that has tight doorways and/or passageways. 
       FIGS. 4A-4H  is are depictions of a patient transfer mechanism  400  having a rollable chair  404 , a bed  408 , and a docking assembly  412  in various stages of operation during a patient transfer operation, according to an illustrative embodiment of the invention. The rollable chair  404  has a first frame  416  including a seat  420 . The rollable chair  404  also has a second frame  424  coupled to the first frame  416 . The second frame  424  includes a chair back  428  configured to move relative to the first frame  416 . The rollable chair  404  also includes a third frame  432  coupled to the first frame  416 . The third frame  432  includes a track having a curvilinear length  432 A configured to allow the first frame  416  to rotate and to translate relative to the third frame  432 . A patient  436  occupies the rollable chair  404  at the start of an exemplary patient transfer operation. 
     Referring to  FIG. 4A , the rollable chair  404  is first positioned at or near a proximal end (e.g., a foot end)  408 A of the bed  408  (the proximal end  408 A opposite a distal end  408 B). For example, a caregiver or the patient  436  can back the rollable chair  404  to the foot end  408 A of the bed  408 , e.g., sufficiently close so that the bed  408  can eventually support a backside of the patient  436 . The distal end  408 B of the bed  408  is then translated toward the proximal end  408 A of the bed  408 , the bed thereby folding into a first section  408 C and a second section  408 D, as shown in  FIG. 4B . The first section  408 C becomes positioned behind a chair back or chair back  428  of the rollable chair  404 , and the second section  408 D forms an angle  408 E with the first section  408 C. 
     Referring to  FIG. 4C , the chair back  428  of the rollable chair  404  is then moved, via at least one of a rotational or a translational motion (a rotational motion about a pivot point on the right of the chair, from the perspective of the patient  436 , as shown in  FIG. 4C ), such that the patient  436  contacts (or now may contact) the first section  408 C of the bed  408 . In some embodiments, an operator is further prompted to confirm electronically that the chair back  428  should in fact swing away, clearing the path from the patient  436  to the first section  408 C of the bed  408 . 
     With a back of the patient  436  now leaning against the first section  408 C of the bed  408 , referring now to  FIG. 4D , a seat frame or first frame  416  of the rollable chair  404  is moved along a guide rail or third frame  432  disposed relative to the seat frame  416  (e.g., in mechanical communication with or interlocking with), via at least one of a translational or a rotational motion, to position the patient  436  at least substantially on the bed  408 , e.g., as shown in  FIG. 4E . As shown, the first section  408 C of the bed  408  begins to recline and convey the patient  436  onto the bed. Referring to  FIG. 4F , the first frame  416  follows the curvilinear portion  432 A of the guide rail/third frame  432 , such that the first frame  416  is translated and rotated with respect to the third frame  432 . A fourth frame/leg rest  440 , rigidly coupled to the first frame  416 , aids in transporting the legs of the patient  436  closer to the bed  408 . 
     Meanwhile, referring to  FIG. 4G , the first frame  416  continues moving along the first frame  416  while a roller mechanism (e.g., two powered spools with a “transfer sheet” or “conveyor sheet”, not depicted for neatness) moves the patient  436  toward the distal end  408 B of the bed  408 . In some embodiments, the transfer sheet that moves the patient to and from the bed is moved up and over a surface of the bed mattress by two powered spools at the head end and foot end of the bed  408 . In this embodiment, the fourth frame  440  can pivot along a pivot point  444  to remain out of the way of the patient  436  transferring to the bed  408 . The roller mechanism can continue to move the patient  436  further toward the distal end  408 B of the bed  408 , positioning the patient  436  in a final resting position on the bed as shown in  FIG. 4H . In some embodiments, the transfer to bed is completed when a through-beam emitter sensor and receiver sensor located at the foot end of the bed senses the patient&#39;s feet passing. The motions shown in  FIGS. 4A-4H  can be reversed, e.g., exactly or substantially, to effect a transfer in the opposite direction from the bed  408  to the rollable chair  404 . 
     In some embodiments, the patient transfer system  400  includes a user interface on a computing device that provides a series of verbal prompts during the course of operation. For example, the computing device can verbally prompt the operator (e.g., the patient or the caregiver) to remove sheets and blankets from the bed before beginning the transfer process. In some embodiments, after transferring the patient  436  to the bed, the bed automatically resets itself into a position to start the “to chair” transfer. In some embodiments, when ready to transfer back to the rollable chair  408 , the conveyor sheet moves the patient  436  toward the foot end of the bed  408 . As the patient&#39;s feet (or lower extremity) pass through the through-beam sensor at the foot end of the bed  408 , software on the computing device can command the actuator controlling the first frame (e.g., seat rotation frame) to begin rotating as defined in the software parameters. 
     Once the seat is fully rotated, the head deck portion and foot deck portion of the bed frame are commanded by software on the computing device to rotate so that a foot deck portion of the mattress is moved to assist in moving the patient  436  into a seated position within the rollable chair  408 . After the foot deck portion of the mattress has moved the person into the maximum seated position, the operator is prompted to activate the powered backrest into the locked upright position. After the backrest is locked in place, the seat translates and/or rotates away from the bed to further position the patient into a fully seated position. After the seat frame has translated forward to its maximum forward position, the operator is prompted to activate the rollable chair drive system, and the patient can drive the rollable chair  408 . 
     In some embodiments, the timing and angle of chair movement is adjustable to accommodate height, weight and other attributes of individual patients. In some embodiments, the timing of the custom seat and bed functions are coordinated via software commands. In some embodiments, a transfer to or from a bed takes approximately two minutes. In some embodiments, there is an emergency pull switch that flattens the bed and cuts the power. In some embodiments, there is a battery backup that allows for five complete transfer cycles in two days. 
     In some embodiments, the conveyor sheet can be a 70 Denier Nylon, PVC coated material per IEC  60601  fire safety guidelines. In some embodiments, the conveyor sheet and can be 94″L×34″W×0.024″ H. In some embodiments, the conveyor sheet is very thin, e.g., if used with a pressure-relieving mattress, so as not to interfere with the goals of a such a mattress. In some embodiments, a fabric, 96″×35″, 60/40 poly/cotton bed sheet, is attached to the conveyer sheet with Velcro™ tabs and is used as the sleeping surface. The presence of the sheet does not need to interfere with the transfer into and out of the bed. The bed sheet can also be removed for regular washing as necessary. In some embodiments, the conveyor sheet remains in place and can be spot cleaned using disinfectant wipes. Periodic removal for more extensive cleaning and servicing is recommended and scheduled with the customer. Unless there is tearing or damage caused by misuse, the conveyor sheet can be replaced with a new or reconditioned sheet at the time of servicing. Changing the conveyor sheet can be a simple process, which takes approximately 15 minutes. 
     In some embodiments, when the patient transfer system  400  is active (input to the UI and/or system motion), every 100 ms a main controller (e.g., the computing device  164  shown and described above) communicates to a data logger the state of all electrical components (discrete input devices, motor currents/voltages, power supply input/output and batteries). In some embodiments, the data logger records these data to the USB memory device. For example, every 24 hours the data logger can write the day&#39;s data to a compressed file archive. In such embodiments, a 8 GB USB memory device can handle one day of continuous system operation and the archived data from the previous 30 days. In some embodiments, electronic components are located under the center of the bed. 
     In some embodiments, the invention incorporates an array of sensors to stop the operation of the patient transfer system if unsafe behavior is detected (e.g., clothing or parts of the body near moving parts, attempting to move the “patient” to far up the bed where they may hit the headboard). In some embodiments, the software prohibits moving from one step to the next without the sensors indicating that each step is completed. In some embodiments, the microprocessors are hardwired or wireless. In some embodiments, the microprocessors are in direct communication with one another or indirect communication, e.g., via a central processing hub. 
     In some embodiments, the bed interfaces with a Group 2 EPW equipped with a custom seating system. In some embodiments, the invention accommodates a wide variety of mattresses commonly used with hospital beds for acute care, long-term care, and homecare. In some embodiments, the bed incorporates one or more features of current “high-end” hospital beds, e.g., the ability to integrate several therapeutic pressure redistribution mattresses. In some embodiments, the custom wheelchair seating systems is compatible with a wide variety of seat cushions, such as foam, gel, air-flotation. 
     In some embodiments, the “J” track permits one continuous motion of the first frame along the third frame to provide seamless transfer of a patient from a rollable chair to a bed and back. In some embodiments, the track is mechanical or virtual (e.g., a set of actuators can be used to program the kinematics of motion that mimic a mechanical track). In some embodiments, a gap space  438  between patient and bed is minimized (e.g., minimized to a smallest practical length in view of competing constraints) at one or more points in the transfer, e.g., at the point shown in  FIG. 4D , or at any given point in the transfer. 
       FIG. 5  is a flowchart of a method  500  of transferring a patient from a rollable chair to a bed, according to an illustrative embodiment of the invention. In a first step  505 , the rollable chair is positioned at or near a proximal end of the bed (e.g., by a patient or a caregiver). In a second step  510 , a distal end of the bed is translated toward a proximal end of the bed, the bed folding into a first section and a second section, wherein the first section becomes positioned behind a chair back of the rollable chair and the second section forms an angle with the first section. In a third step  515 , the chair back of the rollable chair is moved, via at least one of a rotational or a translational motion, such that the patient contacts the first section of the bed. In a fourth step  520 , a seat frame of the rollable chair is moved along a guide rail disposed relative to the seat frame, via at least one of a translational or a rotational motion, to position the patient at least substantially on the bed. In some embodiments, the guide rail is a track having a curvilinear length. In some embodiments, moving the chair back is accomplished using a powered actuator. In some embodiments, moving the seat frame is coordinated with a simultaneous or near-simultaneous moving of the bed. In some embodiments, moving the seat frame is coordinated with a simultaneous or near-simultaneous moving of a leg rest coupled to the seatframe. In some embodiments, positioning the rollable chair at or near a proximal end of the bed is achieved using a docking assembly positioned proximate the bed and the rollable chair. 
       FIG. 6  is a schematic diagram of an electronic architecture for a patient transfer system, according to an illustrative embodiment of the invention. In one exemplary sequence of events, a rollable chair as described above is driven against one or more switches in contact with the bumper. By this action, the rollable chair can activate one or more physical switches, e.g., “SW6 Chair Present R” and “SW7 Chair Present L”. When the “Main Controller” (e.g., the computing device  164  shown and described above) detects that “SW6 Chair Present R” and “SW7 Chair Present L” are activated, it communicates to the “Seat Slide Motor Controller” to activate the “Seatback Actuator” through the “Chair Connect Harness” cable, which initiates movement of backrest (e.g., the backrest  116  shown and described above) to its transfer position. Once the backrest  116  strikes the switch “Seatback Remove Limit Switch,” a signal is sent through port “OS1 Back Lowered” and to the “Main Controller.” 
     The “Main Controller” then sends a signal to the “Seat Slide Motor Controller” to stop the “Seatback Actuator”, hence stopping the motion of the backrest. Completion of backrest removal initiates rotation of the seat (e.g., the seat  112  shown and described above) by the “Main Controller”. The “Main Controller” then sends a signal to the “Seat Rotate Motor Controller” telling it to turn on the “Seat Rotate Actuator”, which rotates the seat toward the bed. As the Seat rotates, the potentiometer sensor “Seat Rotate Position” sends signals to the “Main Controller” that state its current position. This information is used to coordinate the movements of the bed. When the seat physically contacts “SW11 Chair Rotate Present,” a signal is sent to the “Main Controller” indicating that seat has rotated to its maximum extent. The “Main Controller” sends a signal to the “Seat Rotate Motor Controller,” telling it to stop the motion of the “Seat Rotate Actuator”, which stops the rotation of the seat. The bed continues its own to position the person using the sheet and spool (not depicted), as in the manual chair product. 
     To return the patient to the rollable chair, the above steps can be executed substantially in reverse, with some exceptions. First, for the backrest striking the switch “Seatback Remove Limit Switch,” the “Seatback Restore Limit Switch” is physically contacted and port “OS2 Patient Bed Exit”, indicating the backrest is in its driving configuration. Second, for the seat physically contacting “SW11 Chair Rotate Present”, the motion of the seat rotation physically contacts the “SW10 Chair Rotate Latch” indicating the seat ( 112 ) is it drive position. The “Chair Connect Harness” is the physical connector that when connected tethers the bed wires to the wheelchair. “SW8 Chair Slide Latch” and “SW9 Chair Slide Latch” are legacy switches that are still physically present of the bed from the manual chair version but are not used in the power chair version. 
     While the invention has been particularly shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the following claims.