Abstract:
A manual wheelchair including a frame, a drive wheel connected to the frame, having a first axis of rotation and configured to rotate relative to the frame, a push rim connected to the frame, having a second axis of rotation extending substantially parallel to the first axis of rotation of the drive wheel and configured to rotate relative to the frame, wherein the second axis of rotation of the push rim is offset from the first axis of rotation of the drive wheel in a direction orthogonal to the first axis of rotation of the drive wheel, and a transmission configured to transmit rotation of the push rim to rotation of the drive wheel. Additionally, the wheelchair may also include multispeed fixed-gear hubs for propulsion on different terrain and removable or rotatable push rims for easier transfers.

Description:
BACKGROUND 
     1. Field of the Invention 
     The purpose of the invention is to provide a wheelchair system that allows for independent positioning of the push rims and drive wheels, allowing for improved stability and improved shoulder biomechanics. The approach also allows for the addition of multispeed fixed-gear hubs for improved propulsion on sloped surfaces and allows for removal or repositioning of the push rims out of the way for easier transfers in and out of the wheelchair. 
     2. Related Art 
     The most common form of a manual wheelchair  100  utilizes a push rim  110  connected directly to the drive wheels  120  as shown in  FIG. 1 . The wheelchair user is able to propel the wheelchair  100  by pushing the push rims  110  with their hands, thereby rotating the wheel an equal angle and translating the chair forward. The common wheelchair is elegant in its simplicity. However, the inherent mechanical coupling of the push rim  110  and the wheel  120  require that they be placed in the same fore-aft position, which may lead to reduced stability of the wheelchair and/or shoulder problems. In setup of the common wheelchair, the clinician must balance concerns of shoulder biomechanics and stability of the wheelchair. On one hand, the clinician would like to move the push rims forward to promote a better positioning of the shoulders for propulsion. On the other hand, the axle of the wheels  120  must remain behind the center of gravity  130  to reduce the likelihood the wheelchair  100  will tip over backward. A common approach is to move the push rim/wheel combination  110 / 120  as far forward as possible while still maintaining a stable base  150  of support of the wheelchair by positioning the drive wheel  120  and front casters  140  to frame the center of gravity  130  in fore/aft directions. 
     The positioning of the push-rim/wheel  110 / 120  combination in common wheelchairs leads to difficulties in transfers (transferring in and out of the wheelchair  100 ). For example, the user must position the wheelchair at an angle with a bed  200  or other transfer surface in order to use a transfer board  210  (see  FIG. 2 ). Without a transfer board, the person must elevate their body a significant distance to clear the wheel of the wheelchair ( FIGS. 3A, 3B ). 
     Therefore, what is needed is a system and method that overcomes these significant problems found in the conventional systems as described above. 
     SUMMARY 
     Described herein is a new manual wheelchair system that decouples the push rims from the drive wheels of the wheelchair and reconnects the push rims to the drive wheels using a belt drive or chain drive, thus allowing for optimal stability and better shoulder positioning for propulsion. The push rims are also removable or rotatable for easier transfers. The wheelchair can also include multispeed fixed-gear hubs for easier propulsion on different terrain. The wheelchair advantageously reduces shoulder problems that are common in persons who use manual wheelchairs while maintaining optimal stability. 
     Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure and operation of the present invention will be understood from a review of the following detailed description and the accompanying drawings in which like reference numerals refer to like parts and in which: 
         FIG. 1  is a diagram illustrating an example related art wheelchair; 
         FIG. 2  is a diagram illustrating an example related art wheelchair transfer with a transfer board; 
         FIGS. 3A and 3B  are diagrams illustrating an example related art wheelchair transfer without a transfer board; 
         FIGS. 4A-4D  are diagrams illustrating an example wheelchair with a push rim capable of being rotated backward and out of the way for transfers according to a first implementation of the present application; 
         FIGS. 5A-5D  are diagrams illustrating an example wheelchair with a push rim capable of being removed and placed out of the way for transfers according to a second implementation of the present application; 
         FIG. 6  is a block diagram illustrating an example transfer of a patient from a bed to a wheelchair according to an embodiment of the invention. 
         FIGS. 7A-7B  are diagrams illustrating an example wheelchair with a push rim capable of being translated backward and out of the way for transfers according to a third implementation of the present application; 
         FIG. 8  is a diagram illustrating a user&#39;s range of motion laid over a diagram of an example related art wheelchair; 
         FIG. 9  is a diagram illustrating a user&#39;s range of motion laid over a diagram of a wheelchair according to an implementation of the present application; 
         FIGS. 10A-10C  are diagrams illustrating placement of a push rim at different positions along a wheelchair according to an implementation of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     Certain implementations disclosed herein provide for a manual wheelchair that allows for optimization of stability and shoulder biomechanics for individual wheelchair users. For example, one apparatus disclosed herein provides a wheelchair having a drive wheel rotatable about a first axis of rotation, a push rim rotatable about a second axis of rotation, which is offset from the first axis of rotation, and a transmission coupling the push rim to the drive wheel. 
     Additionally, some implementations disclosed herein provide for a manual wheelchair that allows for the positioning of the push rim to allow transfer into and out of the wheelchair. For example, one apparatus disclosed herein provides a wheelchair having a push rim repositioning mechanism that allows the push rim to be rotated between a propulsion position and a transfer position. 
     After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention as set forth in the appended claims. 
       FIGS. 4A-4D  are diagrams illustrating an example wheelchair with a push rim capable of being rotated backward and out of the way for transfers according to a first implementation of the present application. More specifically,  FIG. 4A  illustrates the wheelchair with the push rim rotated forward into a propulsion position. Further,  FIG. 4B  illustrates an enlarged view of the push rim relocation mechanism in the propulsion position. Further,  FIG. 4C  illustrates the wheelchair with the push rim rotated backward into a transfer position. Further,  FIG. 4D  illustrates an enlarged view of the push rim relocation mechanism in the transfer position. 
     In this implementation, the wheelchair  400  includes a frame  405 , a rotatable push rim  410  connected to the frame  405  and a drive wheel  420  connected to the frame  405 . The wheelchair  400  may also include caster wheels  440  located in front of the drive wheel  420 . The caster wheels  440  and the drive wheels  420  collectively form the base of support  435  of the wheelchair. In order to provide a stable ride for the user, it may be preferable that caster wheels  440  and the drive wheels be positioned such that the user&#39;s center of gravity  430  is located directly above the base of support  435 , rather than in front of or behind the base of support  435 . 
     As shown in  FIGS. 4A-4D , the axis of rotation  425  of the drive wheel  420  is offset from the axis of rotation  415  of the push rim. Thus, instead of being directly coupled to each other, the push rim  410  and drive wheel  420  are connected by a transmission  460 . The transmission  460  may include a drive gear/hub  450  coupled to drive wheel  420 , a push rim gear/hub  470  coupled to the push rim  410 , and a chain or belt  490  connected to the drive gear/hub  450  and the push rim gear/hub  470 . 
     Thus, de-coupling the fore-aft position of the push rims  410  and drive wheels  420  may allow a clinician to place the drive wheels  420  in their optimal position to provide a stable base of support  435  while still allowing the person to do “wheelies” if needed (to go over curbs and other thresholds). Also, the position of the push rims  410  can be set to promote the best positioning of the wheelchair  400  user&#39;s shoulders. A potential aspect of this more forward positioning of the push rims  410  is a reduction in shoulder pain resulting from manual propulsion of the wheelchair. In other words, de-coupling of the push rims  410  and drive wheels  420  may allow the clinician to place the push rims  420  in front of the user&#39;s center of gravity  430  as shown in  FIGS. 4A-4D , potentially improving mechanical efficiency without sacrificing wheelchair stability. 
     Additionally, the use of the transmission  460  with the belts or chains  490  may allow the wheelchair to also incorporate into one or both of the drive gear/hub  450  and the push rim gear/hub  470  a multispeed fixed-gear hub such as the Sturmey-Archer S3X fixed-gear hub. In such implementations, the ability to switch to higher or lower speeds may allow the wheelchair user to go faster on smooth even terrain and to require less torque and forces on the shoulders to go up inclined terrain. 
     Additionally, in some implementations, the wheelchair  400  also includes a push rim repositioning member  480  that allows the push rim  410  to be repositioned to allow a user to transfer into and out of wheelchair  400  without having to lift himself over the push rim as shown in  FIGS. 3A and 3B  above. In  FIGS. 4A-4D , the repositioning member  480  is a swing arm rotatably mounted to the frame  405  and configured to rotate about the axis of rotation  425  of the drive train. As shown, the push rim gear/hub  470  and push rim  410  are located at a first end of the swing arm  480  and the drive wheel gear/hub  450  is located at a second end of the swing arm  480  and the belt/chain  490  extends along the length of the swing arm. As shown in  FIGS. 4A and 4B , the swing arm  480  can be rotated forward to position the push rim  410  forward of a user&#39;s shoulders to allow the propulsion of the wheel chair by the user (known as the propulsion position). As shown in  FIGS. 4C and 4D , the swing arm  480  can be rotated backward to position the push rim  410  behind a user&#39;s shoulders to allow the user to transfer into and out of the wheelchair. 
     Additionally, in some embodiment, a locking mechanism  483  may be provided to releasably hold the push rim repositioning member  480  (swing arm) in the propulsion position shown in  FIGS. 4A and 48 . Further, a second locking mechanism  487  or hard stop may also be provided to releasably hold or limit the rearward rotation of the push rim repositioning member  480  (swing arm) in the transfer position shown in  FIGS. 4C and 40 . 
     Though various aspects of this embodiment are shown in the figures and discussed above, implementations of this application are not limited to these aspects and alternative implementations are discussed below. 
       FIGS. 5A-5D  are diagrams illustrating an example wheelchair with a push rim capable of being removed and placed out of the way for transfers according to a second implementation of the present application. More specifically,  FIG. 5A  illustrates the wheelchair with the push rim attached to the wheelchair in a propulsion position. Further,  FIG. 5B  illustrates an enlarged view of the push rim relocation mechanism with the push rim attached in the propulsion position. Further,  FIG. 5C  illustrates the wheelchair with the push rim disconnected from the wheelchair and repositioned for a transfer. Further,  FIG. 5D  illustrates an enlarged view of the push rim removed for a transfer. 
     As with the implementation discussed above, in this implementation the wheelchair  500  includes a frame  505 , a rotatable push rim  510  connected to the frame  505  and a drive wheel  520  connected to the frame  505 . The wheelchair  500  may also include caster wheels  540  located in front of the drive wheel  520 . Again, the caster wheels  540  and the drive wheels  520  collectively form the base of support  535  of the wheelchair. In order to provide a stable ride for the user, it may be preferable that caster wheels  540  and the drive wheels be positioned such that the user&#39;s center of gravity  530  is located directly above the base of support  535 , rather than in front of or behind the base of support  535 . 
     As shown in  FIGS. 5A-5D , the axis of rotation  525  of the drive wheel  520  is offset from the axis of rotation  515  of the push rim  510 . Thus, instead of being directly coupled to each other, the push rim  510  and drive wheel  520  are connected by a transmission  560 . The transmission  560  may include a drive gear/hub  550  coupled to drive wheel  520 , a push rim gear/hub  570  coupled to the push rim  510 , and a chain or belt  590  connected to the drive gear/hub  550  and the push rim gear/hub  570 . 
     Again, de-coupling the fore-aft position of the push rims  510  and drive wheels  520  may allow a clinician to place the drive wheels  520  in their optimal position to provide a stable base of support  535  while still allowing the person to do “wheelies” if needed (to go over curbs and other thresholds). Also, the position of the push rims  510  can be set to promote the best positioning of the wheelchair  500  user&#39;s shoulders. A potential aspect of this more forward positioning of the push rims  510  is a reduction in shoulder pain resulting from manual propulsion of the wheelchair. In other words, de-coupling of the push rims  510  and drive wheels  520  may allow the clinician to place the push rims  520  in front of the user&#39;s center of gravity  530  as shown in  FIGS. 5A-5D , potentially improving mechanical efficiency without sacrificing wheelchair stability. 
     Again, the use of the transmission  560  with the belts or chains  590  may allow the wheelchair to also incorporate into either one or both of the drive gear/hub  550  and the push rim gear/hub  570  a multi-speed fixed-gear hub such as the Sturmey-Archer S3X fixed-gear hub, for example. In such implementations, the ability to switch to higher or lower speeds may allow the wheelchair user to go faster on smooth even terrain and to require less torque and forces on the shoulders to go up inclined terrain. 
     Additionally, in some implementations, the wheelchair  500  also includes a push rim repositioning member  580  that allows the push rim  510  to be repositioned to allow a user to transfer into and out of wheelchair  500  without having to lift himself over the push rim as shown in  FIGS. 3A and 3B  above. In the implementation shown in  FIGS. 5A-5D , the repositioning member  580  is release mechanism that allows the push rim  510  to be disconnected from the frame  505 . For example, a quick release mechanism could be used to allow the push rim  510  to be removably attached to the frame  505 . As shown in  FIGS. 5A and 5B , the release mechanism (push rim repositioning member  580 ) holds the push rim  510  forward of a user&#39;s shoulders to allow propulsion of the wheelchair by the user (known as the propulsion position). As shown in  FIGS. 5C and 5D , the release mechanism (push rim repositioning member  580 ) allows the push rim  510  to be disconnected from the frame  505 , and once disconnected, the push rim  510  can be placed behind a user&#39;s shoulders to allow the user to transfer into and out of the wheelchair. 
     Though various aspects of this embodiment are shown in the figures and discussed above, implementations of this application are not limited to these aspects and alternative implementations are discussed below. 
       FIG. 6  is a block diagram illustrating an example transfer of a patient from a bed to a wheelchair according to an embodiment of the invention. 
     By incorporating a push rim reposition member, such as shown in the implementations of  FIGS. 4A-4D  and  FIGS. 5A-5D , the wheelchair  500  can now be placed directly next to the bed  600  or other transfer surface, reducing the distance to transfer and also reducing the height to elevate the body since the user no longer needs to clear the wheel  520  or the push rim  510  or the combination. 
       FIGS. 7A-7B  are diagrams illustrating an example wheelchair with a push rim capable of being rotated backward and out of the way for transfers according to a third implementation of the present application. More specifically,  FIG. 7A  illustrates the wheelchair with the push rim to the wheelchair located in a propulsion position. Further,  FIG. 7B  illustrates the wheelchair with the push rim repositioned into a transfer position. 
     This implementation shown in  FIGS. 7A and 7B  may include features and elements similar to those discussed above with respect to the first and second implementations. Thus redundant descriptions thereof may be omitted. As with the implementations discussed above, in this implementation the wheelchair  700  includes a frame  705 , a rotatable push rim  710  connected to the frame  705  and a drive wheel  720  connected to the frame  705 . The wheelchair  700  may also include caster wheels  740  located in front of the drive wheel  720 . 
     As shown in  FIGS. 7A-7B , the axis of rotation  725  of the drive wheel  720  is offset from the axis of rotation  715  of the push rim. Thus, instead of being directly coupled to each other, the push rim  710  and drive wheel  720  are connected by a transmission (not specifically labeled in  FIGS. 7A and 7B ; individual components labeled). The transmission may include a drive gear/hub  750  coupled to drive wheel  720 , a push rim gear/hub  770  coupled to the push rim  710 , and a chain or belt  790  connected to the drive gear/hub  750  and the push rim gear/hub  770 . 
     Again, de-coupling the fore-aft position of the push rims  710  and drive wheels  720  may allow a clinician to place the drive wheels  720  in their optimal position to provide a stable base of support while still allowing the person to do “wheelies” if needed (to go over curbs and other thresholds). Also, the position of the push rims  710  can be set to promote the best positioning of the wheelchair  700  user&#39;s shoulders. A potential aspect of this more forward positioning of the push rims  710  is a reduction in shoulder pain resulting from manual propulsion of the wheelchair. In other words, de-coupling of the push rims  710  and drive wheels  720  may allow the clinician to place the push rims  720  in front of the user&#39;s center of gravity as shown in  FIGS. 5A-5D , potentially improving mechanical efficiency without sacrificing wheelchair stability. 
     Again, the use of the transmission with the belts or chains  790  may allow the wheelchair to also incorporate a multi-speed fixed-gear hub to provide the ability to switch to higher or lower speeds and thereby allow the wheelchair user to go faster on smooth even terrain and to require less torque and forces on the shoulders to go up inclined terrain. 
     Additionally, in some implementations, the wheelchair  700  also includes a push rim repositioning member  780  that allows the push rim  710  to be repositioned to allow a user to transfer into and out of wheelchair  700  without having to lift himself over the push rim as shown in  FIGS. 3A and 3B  above. In  FIGS. 7A-7B , the repositioning member  580  is a guide rail extending along the frame  705  that the push rim  710  can be slid along. Thus, the push rim  710  may be slidingly mounted to the guide rail (push rim repositioning mechanism  780 ) and repositioned at different portions along the length of the guide rail (push rim repositioning mechanism  780 ). As shown in  FIG. 7A , the push rim  710  has been slid forward along the guide rail (push rim repositioning mechanism  780 ) to be located forward of a user&#39;s shoulders to allow the propulsion of the wheel chair by the user (known as the propulsion position). As shown in  FIG. 7B , the push rim  710  has been slid backward along the guide rail (push rim repositioning mechanism  780 ) to be located behind or even with a user&#39;s shoulders to allow the user to transfer into and out of the wheelchair. 
     Additionally, in some implementations, a locking mechanism (not shown) may be provided to releasably hold the push rim  710  (swing arm) in the propulsion position located in front of the user&#39;s shoulders as shown in  FIG. 7A . Further, a second locking mechanism (not shown) or hard stop may also be provided to releasably hold or limit the rearward movement of the push rim  710  in the transfer position shown in  FIG. 7B . Additionally, in some embodiments, the transmission of the wheel chair may also include an idler sprocket (not shown), which can be used to maintain a fixed tension in the belt or chain  790 . 
     Though various aspects of this embodiment are shown in the figures and discussed above, implementations of this application are not limited to these aspects and alternative implementations are discussed below. 
       FIG. 8  illustrates the reachable workspace of a user&#39;s wrist for different shoulder ranges of motion laid over a diagram of an example related art wheelchair  800  and  FIG. 9  illustrates the reachable workspace of a user&#39;s wrist for different shoulder ranges of motion laid over a diagram of a wheelchair  900  according to an implementation of the present application. As discussed above, a problem with conventional wheelchairs relates to the positioning of the drive wheel/push rim assembly relative to the user&#39;s shoulders. Rearward placement of the drive wheel/push rim assembly can improve stability, but such placement can require a user to continually reach backward with shoulder extension and sometimes shoulder abduction. Use of the shoulders in excessive extension and in abduction are thought to be damaging for repeated use. Also, some users may have experienced reduced range of motion that can limit the propulsive force that can be generated by the user.  FIGS. 8 and 9  illustrate a hypothetical user&#39;s range of motion laid over diagrams of a related art wheelchair  800  and a wheelchair  900  according to an implementation of the present application. Specifically, in  FIGS. 8 and 9 , regions  810 ,  910  represent a user with a full range of motion, regions  820 ,  920  represent a user with a slightly reduced range of motion, and regions  830 ,  930  represent a reduced range of motion. As shown in  FIG. 8 , in order to achieve and maximize the arc of propulsion by starting the application of torque at the upper surface of the push rim of the conventional wheel chair, the user needs to take his shoulders into large angles of extension (i.e. into region  810 ). However, by moving the push rims forward in an implementation according to the present application, the user may be able to apply a maximum arc of propulsion with less shoulder extension (i.e. outside region  910 , and into regions  920 ,  930 ). 
     In the implementations discussed above, the push rim was shown being movable between a propulsion position and a transfer position. However, implementations of the present invention need not have only two positions. Instead, a wheelchair according to the present application may include a push rim repositioning mechanism configured to allow customizable placement of the push rim based on a user&#39;s specific physical dimensions and/or physical capabilities and/or the activities that the patient is involved in.  FIGS. 10A-10C  illustrate placement of a push rim at various positions along a wheelchair according to an implementation of the present application based on a user&#39;s range of motion.  FIG. 10A  illustrates the push rim  1010  of the wheelchair  1000  in position even with the user&#39;s shoulders  1015 .  FIG. 10B  illustrates the push rim  1010  of the wheelchair  1000  rotated forward by 15 degrees with respect to the user&#39;s shoulders  1015 .  FIG. 100  illustrates the push rim  1010  of the wheelchair  1000  rotated forward by 15 degrees with respect to the user&#39;s shoulders  1015 . 
     Those of skill in the art will appreciate that skilled persons can implement the described functionality in varying ways for particular applications, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. Also, in the various embodiments described above, the improvements to the push rim and drive wheels can be implements for a single side of the wheelchair or on both sides of the wheelchair. 
     The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.