Abstract:
The disclosure describes an improved apparatus for converting a manually-powered wheelchair into an electrically powered wheelchair. The apparatus comprises a frame, at least one powered drive wheel, at least one motor powering said drive wheel, and at least one power base axle receiver capable of connecting with an existing axle receiver of a manually powered wheelchair. The apparatus further includes an anti-tip/counterbalance mechanism to prevent a user from losing control and falling backward when the power base attachment is connected. The apparatus uses the existing axle receiver of a manual wheelchair as a universal connection point and to maintain the center of gravity for a user.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/121,856, filed on Mar. 17, 2014, which claims the benefit of U.S. Provisional Application Ser. No. 61/800,782 filed Mar. 15, 2013. The contents of these applications are incorporated by reference herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of wheelchairs. Specifically, this invention relates to a wheeled power attachment that converts a manually powered wheelchair into an electrically powered wheelchair. 
     2. Description of the Related Art 
     Manually powered wheelchairs come in a variety of sizes for a variety of purposes. Two of the most common are the standard folding wheelchair and the non-folding rigid frame wheelchair  1  (as seen in  FIG. 1 ) designed for more active and mobile individuals. Manually powered wheelchairs, regardless of the type of frame, generally include a frame  2 , seating portion  3 , backrest  4 , front castor wheels  5 , and rear wheels  6  having push rims  7 . Each rear wheel  6  has an axle receiver  8  that is aligned with an axle receiver  9  that is connected, directly or indirectly, to the frame  2 . A pin  10  locks each rear wheel  6 , through its axle receiver  8 , to the frame  2  through axle receiver  9 . The wheelchairs are powered by the operator gripping the push rims  7  and pushing clockwise or counterclockwise for the specified direction and speed. However, there are some times when manual wheelchairs are not beneficial, such as propelling long distances, managing uneven terrain, or when the user&#39;s deficits are of such degree that manual propulsion becomes painful, exhaustive, or relatively impossible given time or circumstances. In these situations, electrically powered wheelchairs are desired to ease the burden and stress on the operator. 
     Electrically powered wheelchairs have several drawbacks including the expense, size and weight. Financial, storage, and transportation concerns often make it not practical, or possible, for a user to have both an electric powered and manually powered wheelchair. It is especially inconvenient when traveling to take both types of wheel chairs. Additionally, insurance carriers generally will not pay for a user to have both types of chairs. 
     As a result, there is a need for a wheeled power base attachment that can convert a manual wheelchair into an electric powered wheelchair. While power attachments for manual wheelchairs exist, those in the prior art do not replace the large rear push wheels, are not controlled by a joystick, do not keep the same height as the manual wheelchair, do not support the necessary posture and positioning of the user, and/or do not have an anti-tip/counterbalance mechanism. None of the prior art power attachments provide for connection through the axle receivers of the standard wheelchair. The failure to attach at the axle receiver makes the prior art attachments more difficult to attach to all types of manual wheelchairs as it generally results in a changed center of gravity for the user. Additionally, the failure of the prior art to allow for removal of the rear wheels complicates operation of the electric powered wheelchair by making maneuverability difficult by retaining the cumbersome large rear wheels despite no longer serving a purpose. 
     SUMMARY OF THE INVENTION 
     The present invention converts a manually powered wheelchair into a powered wheelchair by replacing the rear wheels with a power base attachment. The power base attachment consists of drive wheels powered by an electric motor that are operably controlled by a user-controlled joystick. The power base attaches to the manually powered wheelchair frame through the existing axle receivers used to connect the rear wheels. The power base attachment is adjustable to fit manually powered wheelchairs of different heights and widths. Utilization of the existing axle receivers for attachment of the power base maintains the user&#39;s center of gravity necessary for balance and function. The power base attachment also includes an anti-tip/counterbalance mechanism that connects between the manually powered wheelchair frame and the frame of the power base attachment. As a user leans backwards in the converted manually powered wheelchair, the anti-tip/counterbalance mechanism slows the backward rotation of the user by resisting the rotational force and then biasing the backrest toward the normal position for safety and stability. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a profile view of a standard rigid frame manually powered wheelchair. 
         FIG. 2  is a profile front view of the disclosed embodiment. 
         FIG. 3  is a profile front view of the disclosed embodiment attached to a standard rigid frame manually powered wheelchair. 
         FIG. 4  is a profile rear view of the disclosed embodiment attached to a standard rigid frame manually powered wheelchair. 
         FIG. 5  is a profile front view of the frame of the disclosed embodiment. 
         FIG. 6  is a profile rear view of the frame of the disclosed embodiment. 
         FIG. 7  is a top view of the frame of the disclosed embodiment with one mounting sleeve removed. 
         FIG. 8  is a cross section of line  8 - 8  in  FIG. 7   
         FIG. 9  is the exterior view of the frame mounted axle plate and axle receiver of the disclosed embodiment. 
         FIG. 10  is the interior view of the frame mounted axle plate and axle receiver of the disclosed embodiment. 
         FIG. 11  is a front view of the disclosed embodiment. 
         FIG. 12  is a rear view of the disclosed embodiment. 
         FIG. 13  is a top down view of the disclosed embodiment without the housing cover. 
         FIG. 14  is a cross section of line  14 - 14  in  FIG. 11 . 
         FIG. 15  is close up view of the disclosed embodiment attached to a manual wheelchair. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  discloses the power base attachment  20  which comprises a frame  30 , powered drive wheels  91 , rear castor wheels  94 , hand rails  69 , axle receiver  76 , electrically powered motors  90  in electrical communication with a joystick module  95 , and an anti-tip/counterbalance mechanism  100 .  FIGS. 3 and 4  disclose a front and rear side profile views, respectively, of the power base attachment  20  connected to the frame  2  of a manually powered wheelchair  1 . The power base attachment  20  is positioned underneath the seating portion  3  of the manually powered wheelchair  1  where the front end  21  is positioned proximal to the front castor wheels  5  and the back end  22  extends beyond the backrest portion  4 . 
       FIGS. 5 and 6  further disclose the frame  30  of power base attachment  20 . The frame  30  consists of a rigid portion  31  and an adjustable portion  55 . The rigid portion  31  consists of a support frame  32  and a housing  45 . The support frame  32  comprises a front lateral member  33 , wide longitudinal members  34 , first elbow members,  35 , narrow longitudinal members  36 , second elbow members  37 , rear side members  38 , and a rear lateral member  39 . The front lateral member  33  is positioned at the front end  21  of the power base attachment  20  and is perpendicular to the longitudinal axis  23  of the power base attachment  20 . Wide longitudinal members  34  extend from the lateral ends of the front lateral member  33  towards the back end  22  of the power base attachment  20 . First elbow members  35  are positioned between each wide longitudinal member  34  and the narrowed longitudinal member  36 . The first elbow member  35  is angled perpendicularly toward the longitudinal axis  23  of the power base attachment  20  such that the distance between the narrowed longitudinal members  36  is smaller than the distance between the wide longitudinal members  34 . Second elbow members  37  are positioned between each of the narrowed longitudinal members  36  and each of the rear side members  34 . Each wide longitudinal member  34 , first elbow member  35 , narrowed longitudinal member  36 , second elbow member  37 , and short lateral member  38  are mirrored across the longitudinal axis  23  of the power base attachment  20 . The rear lateral member  39  is positioned between the two second elbow members  37  and is parallel to the front lateral member  33 . A rear lateral bracket  40  is positioned at the approximate midpoint of the rear lateral member  39 . Preferably, the front lateral member  33 , wide longitudinal members  34 , first elbow members  35 , narrowed longitudinal members  36 , second elbow members  37 , rear side members  38 , and rear lateral member  39  are positioned in the same plane. The front lateral member  33  and wide longitudinal members  34  have a first flange  41  extending into the interior space defined by the support frame  32 . Each wide longitudinal members  34  have a second flange  42  extending outwardly from the support frame  32  opposite from the first flange  41 . Two mounting sleeves  43  are mounted on the front lateral member  33  with mounting brackets  52 . The longitudinal axes of the mounting sleeves  43  are aligned and parallel to the front lateral member  33 . Each mounting sleeve  43  is positioned on either side of the longitudinal axis  23  of the power base attachment  20 . 
     The housing  45  of the rigid portion  31  of the frame  30  comprises a bottom panel  46 , two longitudinal side panels  47 , front panel  48 , middle panel  49  and rear panel  50 . The bottom panel  46  is parallel to the support frame  32  and is connected to the support frame  32  by the front panel  48 , middle panel  49  and rear panel  50 . The front panel  48  is connected to the flange  41  and extends at an angle to the bottom panel  46 . The middle panel  49  is attached to the support frame  32  between the first elbow members  35  and narrow longitudinal members  36  and extends perpendicular relative to the longitudinal axis  23 . The middle panel  49  also connects to the bottom panel  46  and longitudinal side panels  47  and end extends slightly above the support frame  32 . The rear panel  50  is attached to the support frame  32  between the narrow longitudinal members  36  and second elbow members  37  and is positioned perpendicular relative to the longitudinal axis  23 . The rear panel  50  connects to the bottom panel  46 , longitudinal side panels  47 , and rear lateral member  39  and extends above the support frame  32 . 
     Referring to  FIGS. 5 ,  6 , and  7 , the adjustable portion  55  consists of a generally U-shaped swing arm  56  having a middle member  57  and two extending side arms  58 . The middle member  57  is positioned parallel and pivotally mounted to the front lateral member  33  through the mounting sleeves  43 . Each of the two extending side arms  58  of the swing arm  56  generally extend from the middle member  57  towards the back end  22  of the power base attachment  20 . Each of the side arms  58  have telescoping portions  61  which extend outwardly from each lateral end of the middle member  57  in a direction parallel to the middle member  57 . The telescoping portions  61  have a smaller circumference than the middle member  57  and telescopically insert within the middle member  57 . Each telescoping portion  61  also has a series of holes  59  equally spaced along the length of the telescoping portion  61 . The side arms  58  may be pulled out of the middle member  57  or pushed into the middle member  57  depending on the width needed. Once the proper width is determined, a specific hole  59  on the telescoping portion  61  is aligned with a hole  60  on the middle member  57 . A bolt or locking pin is inserted into the hole  60  on the middle member  57  and into the hole  59  of the telescoping portion  61  which secures the side arms  58  to the middle member  57  and prevents further lateral movement. The side arms  58 , through the telescoping portions  61 , extend laterally from the middle member  57  then angle towards the rear end  22  of the power base attachment  20 . The angled portion extends upwards over the drive wheels  91  relative to the support frame  32  before becoming parallel and bend at approximately the centerpoint of their length to extend generally parallel to the longitudinal axis  23  of the power base attachment  20 . 
     Referring to  FIGS. 5 ,  6 ,  9  and  10 , a sleeve  65  is positioned proximal to each rear terminal end of the side arms  58  of the swing arm  56 . Attached to each sleeve  65  is an axle plate  66  having a lateral slot  67  positioned below the sleeve  65  and an adjustment slot  68  positioned above the sleeve  65 . Each axle plate  66  is positioned on the exterior of the sleeve  65  on the side that faces the longitudinal axis  23 . A hand rail  69 , having a frame member  70  and hand rail member  71 , is attached to the axle plate  66 . Frame member  70  forms a “V” shape with a bore hole  72  positioned proximal to the apex. Frame member  70  is secured to the axle plate  66  through bolts or pins  73  which extend through the adjustment slot  68  of the axle plate  66  and holes  74  in the frame member  70 . Extending from one of the frame members  70  is a joystick module bracket  75  (as seen in  FIG. 11 ). Hand rail  69  is designed to mimic the push rim  7  of the rear wheel  6  of an industry standard manually powered wheelchair  1 . Each sleeve  65  with the hand rail  69  and axle plate  66  may rotate towards the longitudinal axis  23  of the power base attachment  20  for convenient storage when not in use. 
     A power base axle receiver  76 , having an axle bore (not shown) there through, is mounted to each axle plate  66  within the lateral slot  67 . The axle bore (not shown) is aligned with the bore hole  72  of the frame member  70 . The power base axle receiver  76  may be adjusted for and aft in a direction parallel to the longitudinal axis  23  of the power base attachment  20  by moving the hand rail  69  through the adjustment slot  68 . This allows the axle receiver  76  to slide in the for/aft position within the lateral slot  67 . Preferably, each axle receiver  76  is adjusted to the same forward/aft position. 
     The axle bore of the power base axle receiver has a diameter that is equal, or similar, to the diameter of the axle bore of the axle receiver  9  of the manually powered wheelchair  1 . A pin  77 , having industry standard locking mechanisms, including deployment of recessed bearings or a latching pin, is positioned in the axle bore (not shown) of the power base axle receiver  76 . It is industry standard for the axle bore to fit a 0.5 inch pin. The axle plate  66  may be made in a variety of different shapes so long as an axle receiver  76  is mounted proximal the terminal end of the swing arm  56 . 
     Referring to  FIG. 8 , a shock absorber  80  or dampener is positioned in alignment with the longitudinal axis  23  of the power base attachment  20 . The shock absorber  80  is attached at its lower end to the bottom panel  46  of the rigid portion  31  of the frame  30  through a lower shock mount  81  connected to a lower bracket  86  extending from the bottom panel  46 . The shock absorber  80  is attached at its upper end to an upper bracket  82  extending from the middle member  57  of the swing arm  56  through an upper shock mount  83 . The upper bracket  82  is positioned along the midpoint of the middle member  57  and extends away from the middle member  57  towards the back end  22  of the power base attachment  20 . The lower bracket  86  is connected to the bottom panel  46  with a bolt or pin  87  through one of a series of holes  84  in the bottom of panel  46 . The position of the lower bracket  86  on the bottom panel  46  may move toward the front or rear end of the bottom panel  46  by connecting the lower bracket  86  through a different hole  84 . 
     The height of the terminal ends of the side arms  58  of the swing arm  56  may be adjusted through movement of the shock absorber  80 . As the lower bracket  86  and lower shock mount  81  are moved toward the front of bottom panel  46 , the shock absorber  80  becomes more perpendicular in relation to the longitudinal axis  23 , effectively raising the upper end of shock absorber  80 . As a result, the upper shock mount  83  is raised causing the upper bracket  82 , and resulting swing arm  56 , to rotate upwards within the mounting sleeves  43 . As the swing arm  56  rotates up, the side arms  58  and the power base axle receivers  76  correspondingly rotate upwards effectively raising the position of the power base axle receivers  76  relative to the rigid portion  31  of the frame  30 . Consequently, lower bracket  86  may be adjusted along the longitudinal axis  23  to accommodate varying rear wheel sizes of the manually powered wheelchair such as 24, 25, and 26 inch diameters. Additionally, the attachment point of the upper shock mount  83  to the upper bracket  82 , may be similarly adjusted to various positions on the upper bracket  82  and effectively change the height of the power base axle receiver. 
     Referring to  FIGS. 11 ,  12 , and  13 , an electric motor  90  is attached to each wide longitudinal member  34  through attachment to the flange  41  and mirrored flange  42 . Each electric motor  90  is positioned between the drive wheel  91  and a longitudinal side panel  47  of the housing and powers one of the drive wheels  91 . In the preferred embodiment, two batteries  92  and a controller  93  are positioned within the housing  45 . A removable housing cover  51  is placed over the housing  45  and secured over the middle panel  49  and rear panel  50  (as seen in  FIG. 2 ). 
     Still referring to  FIGS. 12 and 13 , two castor wheels  94  are mounted to the terminal ends of each rear side member  38  of the support frame  32 . Each castor wheel  94  is able to rotate freely 360 degrees around a vertical axis. A joystick module  95  is attached to the joystick module bracket  75 . A wire or cable  96  extends from the joystick module  95 , along the swing arm  56 , into the housing  45  and to the controller  93 . The controller  93  is electrically connected to each battery  92  and to the respective electric motors  90 . 
     Referring to  FIGS. 4 and 14 , an anti-tip/counterbalance mechanism  100  is attached to the rear lateral bracket  40  of the rear lateral member  39 . The anti-tip/counterbalance mechanism  100  is comprised of a latch  101 , rod  102 , spring  105 , sleeve  109 , base cap  110  and an adjustable pivot joint  111 . The latch  101  is positioned at to the upper end  103  of the rod  102 . The lower end  104  of the rod  102  is positioned within the sleeve  109  and arranged for engagement with a spring  105 . The lower end  104  of the rod  102  has a smaller circumference than the remainder of the rod  102 . The upper end  106  of the spring  105  coils around the lower end  104  of the rod  102  and engages a shoulder created by the smaller circumference of the lower end  104 . The lower end  107  of the spring  105  abuts the base cap  110 . The base cap  110  encapsulates the lower end of the sleeve  109 . A spring adjustment screw  108  is attached to the base cap  110  and may be used to increase or reduce the base line compression of the spring  105  to allow a user a stiffer anti-tip support or a looser anti-tip support. The rod  102  is telescopically arranged with the sleeve  109  in that as the rod  102  is compressed, the rod  102  slides within the sleeve  109 . The spring  105  allows for resilient compression and returns the rod  102  to a static position when no compressive force is applied. An adjustable pivot joint  111  attaches the sleeve  109  to the rear lateral bracket  40 . This pivot joint  111  allows the anti-tip/counterbalance mechanism  100  to rotate around a pivot point on the rear lateral bracket  40 . The sleeve  109  may be adjusted up or down in relation to the rear lateral member  39  by changing the pivot point that attaches the sleeve  109  to the rear lateral bracket  40 . 
     The latch  101  attaches to an upper frame member  11  located behind the backrest portion  4  of a standard manually powered wheelchair  1 . In the disclosed embodiment the latch  101  is a clamp but other standard latching mechanisms are anticipated so long as the clamping system allows the latch to rotate slightly in relation to the upper frame member during compression. For wheelchairs that do not have an upper frame member for the anti-tip/counter balance mechanism  100  to attach to, an upper cross beam is added (not shown). The upper cross beam connects to the latch as described above and the upper cross beam (not shown) attaches to upper vertical frame members of the standard wheelchair with a similar latching mechanism. In the disclosed embodiment, the pin  77  and axle receiver  76  may be integrally connected. In this embodiment, the pin is not removable from the axle receiver  76 . 
     To connect the power base attachment  20  to a standard manually powered wheelchair  1 , the pin  10  is removed from the axle receiver  9  of the industry standard manually powered wheelchair  1  and the two rear wheels are removed  6 . The power base attachment  20  is positioned under the seating portion  3  such that the front end  21  of the power base attachment  20  is positioned behind the wheelchair&#39;s front castor wheels  5 . The power base axle receivers  76  are adjusted for height as described supra through movement of the shock absorber  80 . The distance between the power base axle receivers  76  is adjusted as described supra through adjustment of the telescoping portions  61  of the side arms  58 . Once fully adjusted, the longitudinal axis of each power base axle receiver  76  is aligned with the longitudinal axis of the corresponding wheelchair axle receiver  9 . As seen in  FIG. 15 , the pin  77  is positioned in the axle bore (not shown) of the power base axle receiver  76  and inserted into the axle bore of wheelchair axle receiver  9  of the manually powered wheelchair  1 . In other embodiments the pin  77  may slide within the axle bore of the power base axle receiver, may be removed com completely from the axle bore of the power base axle receiver, or completely remain stationary within the axle bore of the power base axle receiver. Once positioned in the axle bore of the wheelchair axle receiver  9 , the pin is secured through industry standard means including deployment of recessed bearings, latching pin, spring loaded pin, or other suitable means. The process is repeated for the remaining axle pin and axle receiver. In this manner, the front castor wheels  5 , two drive wheels  91 , and two rear castor wheels  94  are all in contact with level ground. 
     The anti-tip/counterbalance mechanism  100  is positioned so that the latch  101  attaches to the upper frame member  11  of the manually powered wheelchair  1 . The pivot joint  111  is adjusted up or down to ensure the latch  101  is of the appropriate height to latch to the upper frame member  11 . The latch  101  is clamped to the upper frame member  11 . When secured, the latch  9  is located proximal to the center point of the upper frame member  11 . The rear castor wheels also assist in stabilizing the wheelchair and provide added safety as an anti-tip/counterbalance mechanism. In some embodiments the two castor wheels may be replaced with a single castor wheel mounted along the longitudinal axis  23  of the power base attachment  20 . In this embodiment, it is anticipated the rear castor wheel would be located further back from where the anti-tip/counterbalance mechanism  100  attaches to the rear lateral member  39 . 
     Once the power base attachment  20  is secured, the distance from wheelchair axle receiver and the ground is identical to the height of the manually powered wheelchair with rear wheels. The hand rails  69  are in the approximately the same position as the push rims  7  of the preexisting rear wheels. 
     In operation, the user manipulates the joystick module  95  to control the direction and speed of the now electrically powered wheelchair. The joystick module  95  sends a signal to the controller  93  via a cable  96 . The controller  93  processes the information and determines the direction and speed of each motor  90 . The controller  93  sends this information to each respective electric motor  90  via a cable. The electric motor  90 , powered by the battery  92 , then operates the drive wheel  91  in a manner to correspond with the user&#39;s instructions from the joystick module  95 . The controller and joystick provide for industry standard operation of an electrically powered wheelchair which allow for variable drive speed and direction control. Each electric motor is powered by a rechargeable battery. Typically, each electric motor runs on 24 volts and is a conventional motor used in the electric powered wheelchair industry. In the preferred embodiment there is at least 24 volts of battery powered either through a single battery or a combination of batteries. The controller  93  is electrically connected to the batteries  92  and supplies power to both electric motors  90  and the joystick module  95  through cables. As in standard operation for electrically powered wheel chairs, when the joystick is placed in neutral from a directional position, the electric motor decelerates to allow for a smooth stop. Once stopped and when the joystick is in neutral the drive wheels are locked to prevent movement of the wheelchair when positioned on inclines or uneven terrains. 
     When the converted wheelchair is in motion, the swing arm  56  and shock absorber  80  assist to dampen the movement of the power base attachment  20  in relation to the manual wheelchair frame  2 . The user&#39;s center of gravity remains unchanged due to the power base attachment  20  having the same height and as the rear wheels of the standard wheelchair. The hand rail&#39;s  69  identical location to and conformity with the standard push rim, makes the user more comfortable as the hand rail is a familiar point of stability. A user may use the hand rail for transferring, positioning, lifting up for pressure management and for leaning forward. 
     The anti-tip/counterbalance mechanism  100  enables the wheelchair attached to the power base attachment  20 , to respond as if the manually operated wheels were still attached. The anti-tip/counter balance mechanism  100  allows the user to lean back to reduce pressure on lower extremities and to raise the front end castor wheels  5  several inches off the ground to overcome obstacles. The leaning back and raising of the front castor wheels  5  are accomplished by the user without changing the user&#39;s center of gravity. As the chair tilts back, the rod  102  compresses the spring  105 , allowing the user to raise the front castors  5  or to lean back. After compression of the spring  105  during the tilting process, the spring  105  decompresses to push the rod  102 , and resulting back rest and chair, towards the normal position. It is envisioned other anti-tip/counter balance mechanisms may be used to achieve the compression/decompression affect. A hydraulic cylinder, elastic, spring powered telescoping rod or other materials may be suitable to accomplish the compression and decompression mechanism. The anti-tip/counterbalance mechanism  100  assists user&#39;s ability to maintain balance as they overcome obstacles without having to adjust for the additional weight of the power drive attachment. 
     The present disclosure is described above in terms of a preferred illustrative embodiment of a power base attachment. Those skilled in the art will recognize that alternative constructions of such an apparatus can be used in carrying out the present invention. Other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.