Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/788,147, filed on May 26, 2010 (entitled “Power Add-On Device For Manual Wheelchair”), which claims the benefit under 35 U.S.C. §119 of U.S. Provisional Patent Application No. 61/181,602 filed by Patrick Tallino on May 27, 2009 and entitled “Power Add-On Device For Manual Wheelchair”, the entirety of each of which is hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an auxiliary power add-on attachment for a manual rigid-framed wheelchair. 
     2. Description of the Related Art 
     Most spinal cord-injured individuals with injury levels from the five cervical vertebrate down to the lumbar vertebrates use a lightweight rigid framed manual wheelchair for everyday use. However, lengthy outings or ones that require traversing uneven or sloped terrain are unrealistic and often impossible for many using manual chairs. Although electric-powered wheelchairs exist that can be used for those situations, they are not generally prescribed unless the user lacks the ability to use a manual wheelchair. Moreover, electric-powered wheelchairs tend to be expensive, heavy, and cumbersome. 
     Several patents disclose devices which can be attached to a manual wheelchair to electrically power the chair. For example, U.S. Pat. No. 5,494,126 to Meeker, entitled “Apparatus and Method For Attaching a Motorized Wheel to a Wheelchair”, discloses a motorized wheel that can be attached to the front of a wheelchair. As another example, U.S. Pat. No. 5,496,904 to Zwaan, entitled “Wheelchair Power System”, discloses a power system that can be added to a manual wheelchair to convert it to an electric-powered wheelchair. 
     Although such devices are somewhat useful and beneficial, the existing technology fails to provide an easy way to attach/detach a power add-on device to a conventional manual wheelchair. Furthermore, such devices fail to provide for traversal over rough terrain and adequate stability. Additionally, many such devices require modification to the manual wheelchair. Accordingly, it would be desirable and highly advantageous for there to be an auxiliary power add-on attachment for a manual wheelchair that overcomes these and other deficiencies. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, a power add-on device for powering a manual wheelchair includes a motorized component including dual electric motors and a power source electrically coupled to the electric motors, wherein each of the motors is configured to turn a respective one of a set of drive wheels. The power add-on device includes a latching mechanism adapted to attach the power add-on device to the camber tube of the manual wheelchair; and a controller, reachable by a person sitting in the manual wheelchair, that controls the latching mechanism, the motors, and a swing arm that allows the rear wheels of the manual wheelchair to be lifted off the ground. 
     Attachment of the wheelchair to the power add-on device is accomplished simply by backing up the wheelchair into the device. To reduce tipping, the power add-on device features a front anti-tip castor wheel and a back anti-tip castor wheel. When the power add-on device is attached to the wheelchair, the front wheels can be lifted several inches off the ground when encountering obstacles or by the user leaning back. A notable design feature of the present invention is that the latching mechanism is not tightly clamped down on the camber tube; instead, it rather surrounds the camber tube, allowing the camber tube to rotate slightly as the wheelchair tilts to allow the front wheels of the manual wheelchair to be lifted. Advantageously, the power add-on device can be detached from the manual wheelchair and loaded into the trunk of a car when travelling or may be checked in as baggage when flying. 
     In an embodiment of the present invention, the latching mechanism includes a clamshell latching mechanism. In this embodiment, the clamshell latching mechanism includes an upper clamshell portion and a bottom clamshell portion, the upper clamshell portion and the bottom clamshell portion attached by a hinge. When the clamshell latching mechanism is in a closed position, the clamshell latching mechanism surrounds the camber tube of the manual wheelchair. 
     These and other aspects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary power add-on device for a manual wheelchair, in accordance with a preferred embodiment of the present invention; 
         FIG. 2A  shows a conventional manual wheelchair having a camber tube; 
         FIG. 2B  shows the power add-on device of  FIG. 1  attached to a conventional manual wheelchair; 
         FIG. 3  shows the frame structure of the power add-on device of  FIG. 1 ; 
         FIGS. 4 to 6  show an exemplary power add-on device for a manual wheelchair, in accordance with another preferred embodiment of the present invention; 
         FIGS. 7 and 8  show the frame structure of the power add-on device of  FIG. 4 ; and 
         FIG. 9  shows a schematic view of the electrical components for the power add-on device. 
         FIG. 10  shows an embodiment of a power add-on device having an embodiment of a rotation resistance element. 
         FIG. 11  shows another view of the embodiment of the power add-on device shown in  FIG. 10 . 
         FIG. 12  shows an embodiment of a bracket assembly and roller member of the rotation resistance element of the embodiment of the power add-on device shown in  FIG. 10 . 
         FIG. 13  shows the embodiment of the rotation resistance element of the embodiment of the power add-on device shown in  FIG. 10 , illustrating an embodiment of a gas spring component secured to the bracket assembly of the rotation resistance element. 
         FIG. 14  shows another view of the embodiment of the rotation resistance element of  FIG. 13 . 
         FIG. 15  shows another view of the embodiment of the rotation resistance element shown in  FIG. 13 . 
         FIG. 16  shows an enlarged view of the embodiment of the power add-on device shown in  FIG. 10 , showing the embodiment of the rotation resistance element of  FIG. 13 . 
         FIG. 17  shows a portion of the bracket assembly of the rotation resistance element attached to the power add-on device. 
         FIG. 18  shows a portion of the bracket assembly of the rotation resistance element attached to the power add-on device. 
         FIG. 19  shows a rear view of a portion of the rotation resistance element in a first or relaxed position relative to a wheelchair. 
         FIG. 20  shows a side view of a portion of the rotation resistance element in a first or relaxed position relative to a wheelchair. 
         FIG. 21  shows a side view of a portion of the rotation resistance element in a second or rotated position relative to a wheelchair. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates an exemplary power add-on device  100  useable for powering a manual wheelchair, in accordance with a preferred embodiment of the present invention.  FIG. 2B  illustrates the power add-on device  100  attached to a manual wheelchair  201  having a camber tube  202 . The power add-on device  100  includes a housing  102 . The housing  102  includes, therein, two conventional electric wheel-chair motors that are electrically coupled to a power source, and are arranged so that each drives a wheel  104 . The manual wheelchair  201  can be attached to the power add-on device  100  simply by backing up the manual wheelchair  201  until a pair of latches  103  holds the camber tube of the manual wheelchair  201 . Advantageously, no modification is required to the manual wheelchair  201 . 
     Preferably, the latches  103  can be activated by an electric actuator so that when a user wants to de-couple the power add-on device  100  from the manual wheelchair  250 , the user employs remote control  108  to activate the electric actuator so that the latches  103  assume an open position, releasing the manual wheelchair  250 . Preferably, the remote control  108  is a conventional joystick or other such user-friendly remote control device. 
     Preferably, the power add-on device  100  can also be released manually, for example, by pulling a lever. 
     Preferably, the power add-on device  100  has built in recline and anti-tip features so the user can recline and relieve pressure from their seat cushion safely which is very important in order to avoid pressure sores. Preferably, the anti-tip feature is at least in part accomplished by employing front anti-tip castor wheel  107  and rear anti-tip castor wheel  106 . 
     When the power add-on device  100  is attached to the manual wheelchair  250 , the front anti-tip castor wheel  107  can be lifted several inches off the ground when encountering obstacles (preferably, as much as three inches). A notable design feature of the present invention is that the latches  103  are not tightly clamped down on the camber tube; instead, the latches  103  rather surround the camber tube, allowing the camber tube to rotate slightly as the manual wheelchair  250  tilts to allow the front wheels of the manual wheelchair to lift of the ground when encountering obstacles or when the user wishes to recline. 
     Preferably, the power add-on device  100  includes built-in armrests  109  on which the remote control  108  is mounted which operates the device. Preferably, the armrests  109  are mounted to the housing  102  using brackets  111 , as shown. 
     Referring to  FIG. 3 , the framing structure  400  of the power add-on device  100  is shown. As depicted in  FIG. 4 , the framing structure  400  includes body frame  401 , motor mount  402  (for securely holding the electric motors), coil-over shock absorber  403 , rear anti-tip castor wheel  106  and front anti-tip castor wheel  107  (to prevent tipping, as discussed above), combination electric actuator  404  and latches  103  (to open the latching system and release the manual wheelchair  201 , as discussed above), armrest mounts  111  (to secure the pair of armrests  109 ), and combination electric actuator  406 /swing arm  408  (to allow the swing arm  408  to pivot upwardly, thereby raising the rear wheels of the manual wheelchair  250  off the ground and transferring the weight of the user from the rear wheels of the manual wheelchair through the shock-absorbed swing arm to provide traction to the power add-on&#39;s drive wheels). However, even when the rear wheels of the manual wheelchair  250  are positioned on the ground, relatively level terrain may still be traversed easily because the powered drive wheels  104  are lined up with the wheels of the manual wheelchair  250 . In general, the higher the rear wheels of the manual wheelchair  250  are raised, the larger the obstacles that can be traversed. An additional benefit of this design is that it enables the user the advantage of additional height and reach capabilities for different everyday tasks. 
       FIG. 4  Shows an alternate and preferred latching mechanism wherein the user backs up to an upper clamshell  201  of the latch  203  and then employs the remote control  108  to activate an electric actuator to close the latch  204  by lifting a lower clamshell  204 , thereby securing the camber tube of the manual wheelchair to the power add-on device  100 . As illustrated, the upper clamshell  201  and a bottom clamshell  204  are attached by at least one hinge. As shown in  FIG. 4 , the latch  203  is in an open position.  FIG. 5  illustrates the latch  203  in a closed position.  FIG. 6  illustrates that the front castor wheel  107  can be lifted off the ground by this mechanism as well to provide extra clearance of obstacles. 
       FIG. 7  illustrates the framing structure  400  of the power add-on device  100  with the alternate preferred latching mechanism discussed above. As depicted in  FIG. 7 , the electric actuator  404  is coupled to a pivot member  405 , and the pivot member  405  is coupled to the coil-over shock absorber  403 . In operation, as shown in  FIG. 8 , when the electric actuator  404  is activated, the electric actuator  404  applies force to the pivot member  405 , and the pivot member  405  changes the direction of the force to upwardly apply the force to the coil-over shock absorber  403 . As shown, the coil-over shock absorber  403  is coupled to the bottom clamshell  204 , and the coil-over shock absorber  403  pushes the bottom clamshell  204  so as to close the latch  204 . 
       FIG. 9  shows a schematic view of the electrical components for the power add-on device  100 . As depicted in  FIG. 5 , the electrical system includes power source  501 , motors  502 , brakes  503 , linear actuators  504 ,  505 , controller  506 , and charger  507 . 
     The power source  501  comprises energy storage via batteries with charging and current limiting elements. The batteries are electrically connected in series, as shown, and provide all power for all functions. This configuration of battery power allows for use of standard batteries while providing the total output voltage needed for proper operation of the motors  502 , actuators  503 ,  504 , and brakes  503 . 
     Since it is possible that either the motors  502  or the actuators  503 ,  504  can experience states of operation, such as short circuiting during a failure mode, which draw excessive power from the batteries, the batteries are each protected with current limiting elements. These current limiting elements comprise left battery fuse  515 , right battery fuse  516 , and circuit breaker  518 . The circuit-opening characteristics of these current limiting elements preferably are selected based on allowing the circuit breaker first open-circuit followed by the fuses open-circuiting as the total current sourced from the batteries exceed the rated current discharge rate of the batteries. 
     The motors  502  are preferably direct current motors, sized preferably for propelling the manual wheelchair  201  and an adult user up at least a twenty degree grade. Similarly, the brakes are preferably direct-current-activated at the voltage of the two batteries when connected in series. 
     The actuator  504  is preferably a direct-current-powered actuator sized and preferably mounted under the frame so as to raise the swing arm  408 , and thus lifting the rear of the manual wheelchair  201 . 
     The actuator  505  is preferably a direct-current-powered actuator sized and preferably mounted so as to operate the latches  103 , thereby releasing the wheelchair  201 . 
     The controller  506  preferably includes wired or wireless remote actuator switches attached to a joystick/controller. Alternately, preferably, the actuator switches can be built into the joystick/controller. In either preferred configuration the actuator switches allow the operator to control the raising of the swing arm  408  (thus lifting the rear of the manual wheelchair  201 ), and operating the release lever (opening the latches  103  and releasing the manual chair  201 ), as shown. 
     Some embodiments of the power add-on device can be configured to minimize, dampen, and/or slow the rotation of the power add-on device relative to a manual chair coupled with the power add-on device. For example, with reference to  FIGS. 10 and 11 , in some embodiments, the power add-on device  600  can be configured to have a rotation limiting or dampening element or mechanism  602  (also referred to herein as an anti-tilt mechanism or a rotation resistance element) configured to minimize, dampen, and/or slow rotation between the power add-on device  600  and a manual wheelchair coupled with the power add-on device. Note that the manual wheelchair is not illustrated in either of  FIG. 10  or  11 . 
     As discussed above, at least some of the power add-on device embodiments disclosed herein can be coupled with a camber tube or similar component of the wheelchair, for example, by engaging the camber tube of the wheelchair with the engagement mechanism (which can be a clamshell engagement mechanism, latch mechanism, or other similar or suitable mechanism). Engaging the camber tube of the wheelchair can permit a desirable amount of rotation of the manual chair relative to the power add-on device. Such relative rotation can be beneficial, for example, for traversing changes in the slope or height of the ground surface. For example, when the power add-on device and wheelchair advance up or down a ramp, whether an upward sloping ramp or downward sloping ramp, there will likely be a point when the drive wheels of the power add-on device are at a different height or level than the front wheels of the wheelchair. Without permitting the rotation of the wheelchair relative to the power add-on device, such mismatch in the height of the drive wheels of the power add-on device relative to the front and/or the rear wheels of wheelchair can result in decreased stability and control of the wheelchair, and increased stress on the connection between the power add-on device and the wheelchair. Permitting such relative rotation therefore increases the stability, comfort, and overall performance of the power add-on device and wheelchair (i.e., the powered wheelchair system) and the ability of the powered wheelchair system to traverse uneven ground surfaces, bumps, and other changes in the ground surface. 
     However, there are also advantages to softening or resisting the amount of rotation between the power add-on device and the wheelchair, as too much relative rotation or quick rotation between the power add-on device and the wheelchair can affect the comfort level of the user, the control of the power add-on device, and the control of the remote control, such as the remote control  108 . For example, in embodiments where the armrests  109  are secured to the power add-on device, and where the remote control is secured to the armrests, such as armrests  109 , rapid or sudden, undampened rotation between the power add-on device and the wheelchair can cause relative rotation and movement between a user seated in the wheelchair and the armrests and remote control. This can reduce the comfort level of the user and the level of control the user has over the remote control. 
     In some embodiments, softening or dampening the amount of rotation between the power add-on device and the wheelchair can be achieved with the rotation resisting element  602  that can engage a rear facing surface of the wheelchair and prevent the power add-on device from over-tipping or over-tilting in a forward direction relative to the wheelchair and/or prevent the wheelchair from over-tipping or over-tilting in a rearward direction relative to the power add-on device. 
     With reference to  FIG. 12 , some embodiments of the rotation resistance element  602  can have a bracket assembly  606  and roller member  610  secured to a distal end portion  606   a  of the bracket assembly. As will be discussed, the roller member  610  can contact a rear portion of the wheelchair and provide at least one of the contact points between the rotation resistance element  602  and the wheelchair. The roller member  610  can rotate in response to the contact between the wheelchair and the rotation resistance element  602 , as the wheelchair rotates relative to the rotation resistance element and/or the rotation resistance element rotates relative to the wheelchair. In some embodiments, the bracket assembly  606  can have a first bracket element  612  and a second bracket element  614 . The first bracket element  612  can support the roller member  610 . As will be discussed, the first and second bracket elements  612 ,  614  can be fastened to one another and/or to the power add-on device using any suitable fastening mechanisms, including without limitation threaded fasteners such as bolts and nuts. For example, a fastener can be used to fasten the first bracket member  612  to the second bracket member  614  through opening  616 . One example of a fastener that can be used to attach the first bracket member  612  to the second bracket member  614  through opening  616  is the threaded fastener  618  shown in  FIG. 18 . A similar threaded fastener  618  can be used to fasten the first end  620   a  of the spring member  620  to the first bracket member  612 , as illustrated in  FIG. 18 . Similarly, similar fasteners such as threaded fasteners  619  can be used to secure the bracket assembly  606  to the power add-on device, as shown in  FIG. 17 . 
     With reference to  FIG. 13 , some embodiments of the rotation resistance element can have a spring mechanism  620 , such as but not limited to a gas spring component, secured to the bracket assembly  606 . For example and without limitation, a first end portion of the spring mechanism  620   a  can be secured to the first bracket member  612 , and a second end portion of the spring mechanism  620   b  can be secured to the second bracket mechanism  614 . Openings  622  can be used to secure the bracket assembly  606  to a frame portion or other support member on the power add-on device. 
     Any embodiments of the power add-on device disclosed herein can have one or more rotation resistance elements  602  to resist the relative rotation of the power add-on device relative to the wheelchair. In some embodiments, as in the embodiments illustrated in  FIGS. 10 ,  11 , and  16 , inter alia, the power add-on device can have two rotation resistance elements  602 , one on each lateral side of the power add-on device. Additionally, though not required, the first rotation resistance element  602   a  and the second rotation resistance element  602   b  can be interconnected with a lateral support member  630  that can be, but is not required to be, secured to the bracket assembly  606  of each of the first rotation resistance element  602   a  and the second rotation resistance element  602   b.    
     As shown in  FIG. 19 , some embodiments of the power add-on device can be configured such that the rotation resistance element  602  can be aligned with a frame portion of the wheelchair, designated with “W” in  FIG. 19 . For example, the rotation resistance element  602  can be positioned such that a centerline  634  of the roller member  610  can be approximately aligned with a centerline  634  of a vertical tube member of the wheelchair. In some embodiments, the roller member  610  can be aligned with any suitable member or surface on the wheelchair, whether it be the frame or otherwise. 
       FIG. 20  shows a side view of a portion of the rotation resistance element  602  in a first or relaxed position relative to a wheelchair.  FIG. 21  shows a side view of a portion of the rotation resistance element  602  in a second or rotated position relative to a wheelchair. As can be seen with reference to  FIGS. 20 and 21 , rotating the wheelchair  610  in the direction designated by arrow A 1  relative to the power add-on device can cause the first bracket  612  of the rotation resistance element  602  to rotate in the direction A 1  about the fastener or axle positioned in opening  616  relative to the second bracket  614 . As a result, the second bracket  612  can compress the spring member  620 , which can be configured to resist the rotation of the first bracket member  612  about the fastener or axle positioned in opening  616 . In this arrangement, the rotation resistance element  602  can resist and slow the rotation of the wheelchair relative to the power add-on device  600 . Any of the features of the power add-on device  600  and/or the rotation resistance element  602  can be used with any of the other features or components of any of the other power add-on device embodiments disclosed herein. 
     While this invention has been described in conjunction with the various exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.

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