Apparatus and method for attaching a motorized wheel to a wheelchair

An apparatus and method for attaching a motorized wheel to a wheelchair including a mounting frame operatively connected to the motorized wheel, the frame having a laterally-extending cylindrical member, and a mounting bracket operatively connected to a frame of the wheelchair, the bracket having an open slot for receiving the cylindrical member of the mounting frame, the slot defining an interior cam surface which is open on the front side thereof and enclosed on the bottom, back and top sides thereof. The frame has means for adjusting the width thereof to accommodate a variety of different wheelchairs. The mounting frame has a second laterally-extending cylindrical member which is a slidable pin for selective engagement with the mounting bracket to attach the motorized wheel to the wheelchair.

The invention relates to motorized wheelchairs and more particularly to an 
apparatus and method for attaching a motorized driven wheel to a 
manually-operated wheelchair. 
BACKGROUND OF THE INVENTION 
There are a variety of types of motorized wheelchairs which are known. 
These include three-wheel wheelchairs having a pair of rear wheels and a 
front wheel. With this arrangement, there are examples of both 
rear-wheel-drive and front-wheel-drive chairs. Alternatively, four-wheel 
motorized wheelchairs are also available. With this arrangement, the 
larger rear wheels are normally the driven wheels and the smaller front 
wheels are normally idler wheels. One major drawback of most three-wheeled 
and four-wheeled wheelchair arrangements is the fact that the motor and 
drive apparatus are permanently installed on the wheelchair. This results 
in high cost, excessive weight and a wheelchair which cannot be easily 
collapsed to be transported. 
For these and other reasons, motorized attachments for standard wheelchairs 
have been developed. However, these attachments have suffered from the 
drawbacks of being overly complex and heavy so that the occupant or user 
of the wheelchair cannot easily connect and disconnect the motorized 
attachment to the wheelchair while in the chair. 
For example, U.S. Pat. No. 5,016,720 issued to Coker, discloses a 
battery-powered steerable electric drive unit for detachable connection to 
a conventional wheelchair. The unit includes a clamp for receiving and 
being connected to a bolt extending from the frame underneath the 
wheelchair in a position inaccessible to the user. 
U.S. Pat. No. 3,921,744 issued to Benoit et al. discloses a detachable 
drive means for a wheelchair that is manipulable by the occupant but is 
heavy and complex. The connecting means includes ramps that guide 
laterally-sliding pins toward their sockets and rotatable cams received in 
vertical slots at the forward ends of the wheelchair arm rests. 
U.S. Pat. No. 4,503,925 issued to Palmer et al. discloses a steerable 
motorized power unit constructed for detachable coupling to a wheelchair. 
Coupling pins are provided with mounting plates which can be fixably 
clamped to the chair frame to engage with a downwardly opening recess 
formed in a member of the detachable power unit. However, this arrangement 
is also heavy and cumbersome. 
In order to address these and other problems and to achieve an improved 
method and apparatus for attaching a motorized wheel to a wheelchair, the 
following invention has been developed. 
SUMMARY OF THE INVENTION 
The apparatus for attaching a motorized wheel to a wheelchair includes a 
mounting frame operatively connected to the motorized wheel and a mounting 
bracket operatively connected to the frame of the wheelchair, wherein the 
bracket defines an open slot for receiving a laterally-extending 
cylindrical member of the mounting frame. The slot defines an interior cam 
surface and is open on the front side thereof and enclosed on the bottom, 
back and top sides thereof. The mounting frame and motorized wheel can be 
rotated so that the cylindrical member bears against the interior cam 
surface of the mounting bracket and lifts a front wheel of the wheelchair 
off the ground. 
Another aspect of the present invention includes a method for mounting a 
motorized wheel to a frame of a wheelchair including the first step of 
positioning the motorized wheel relative to the wheelchair so that a first 
laterally-extending cylindrical member of a mounting frame attached to the 
motorized wheel engages with an interior cam surface of a mounting bracket 
attached to the wheelchair. The motorized wheel and mounting frame are 
then pivoted about the first cylindrical member until a second cylindrical 
member of the mounting frame is aligned with and is in position to engage 
with a receptacle of the mounting bracket on the wheelchair frame. The 
mounting frame is then engaged with the mounting bracket to attach the 
motorized wheel to the wheelchair. 
Other aspects of the present invention include the open slot in the 
mounting bracket having a C-shape, a width adjusting means in the mounting 
frame for selectively varying and adjusting the width of the frame to 
accommodate a variety of differently-sized wheelchairs, and the second 
cylindrical member being a selectively slidable pin within the mounting 
frame. 
Other aspects, features and details of the present invention can be more 
completely understood by reference to the following detailed description 
of the preferred embodiment, taken in conjunction with the drawings, and 
from the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The apparatus 20 of the present invention as best seen in FIGS. 2 and 3 is 
employed to attach a detachable motorized unit 22 to a wheelchair 24. The 
apparatus includes a mounting frame 26 detachably connected to the 
motorized unit and a pair of mounting brackets 30 attached to the 
wheelchair for supporting the mounting frame on the wheelchair. A first 
embodiment of the apparatus 20 is used for collapsible wheelchairs. A 
second embodiment of the apparatus, described later, is used for 
attachment of the detachable motorized unit to rigid, non-collapsible 
wheelchairs. 
The collapsible wheelchair 24 (FIGS. 1 and 4) includes a frame 32 composed 
of a plurality of hollow tubular members 34. The frame supports a seat 36 
and a seat back 40. The wheelchair frame 32 is supported by a pair of 
relatively large rear wheels 42 and a pair of relatively smaller front 
caster or idler wheels 44. For supporting the arms and legs of the 
occupant, a pair of arm rests 46 and foot rests 50 are conventionally 
mounted on the frame. An exemplary wheelchair is sold under the product 
designation QUICKIE II by Motion Design, Inc. of Fresno, Calif. 
The pair of mounting brackets 30 (FIGS. 2, 3, 12 and 13) are mounted on the 
tubular frame 32 of the wheelchair 24. Each bracket 30 is preferably 
composed of a sturdy material such as aluminum, metal or plastic and is 
formed to define a plurality of openings therein. A circular opening 52 
best seen in FIG. 3 and an oval or slot-shaped opening 54 receive mounting 
bolts 56 which are part of the mounting hardware for the front caster 
wheels 44 on the wheelchair 24. Each of the mounting brackets are held in 
place against the frame 32 of the wheelchair by a pair of nuts 60 threaded 
onto the bolts 56. The variability provided by the oval-shaped opening 
allows the mounting brackets to be used on a variety of differently-sized 
and configured collapsible wheelchairs. 
For support of the mounting frame 26 of the apparatus 20, the mounting 
brackets 30 each include a slotted or C-shaped opening 62 defined in a 
front edge 64 of the brackets by an interior cam surface, as shown in FIG. 
2. In addition, a second circular opening 66 is defined in each of the 
brackets 30 adjacent to a top edge 70 for further support of the mounting 
frame (FIG. 13). To facilitate support of the mounting frame 26, a 
laterally and inwardly extending lip 72 is formed on an inner side 74 of 
each of the mounting brackets 30 adjacent to the second circular opening. 
The lip 72 extends along approximately one-quarter of the periphery of the 
second circular opening 66. 
The detachable motorized unit 22 (FIG. 3) includes a steering or control 
handle 76, a steering control rod assembly 80, and a power head 82 with a 
motor 84 (FIG. 17) and drive wheel 86. The motor 84 receives command 
signals from the control handle 76. As best seen in FIG. 17, the motor is 
linked to a gear assembly 90 by a timing drive belt 92. In turn, the gear 
assembly 90 is linked to the drive wheel 86 by a drive chain 94. Thus, 
activation of the motor results in rotation of the drive wheel in a 
conventional manner. Each of these drive components is mounted to and 
housed within a power head housing 96. A pair of battery lead wires 100 
(FIG. 3), having battery connectors 102 at an end thereof, extend from the 
motor 84 through the housing 96 for connection to a battery as discussed 
below. 
The control handle 76 is connected to the power head 82 by the steering 
control rod assembly 80. The control rod assembly 80 includes an upper 
tube 104 and a lower tube 106. The lower tube 106 is connected to the 
power head housing 96. The upper tube 104 is connected to the control 
handle 76 at its upper end 110. A lower end 111 of the upper tube 104 is 
bifurcated to form a key slot 113 for engagement with a complementary 
member (not shown) in the lower tube 106 so that the upper and lower tubes 
are pivotable in unison about their longitudinal axes. The upper tube is 
telescopically received in the open upper end 114 of the lower tube 106 
and retained in position by a collar 112 and a set screw 117. Thus, by 
tightening or loosening the retaining collar 112, the upper tube can be 
connected to or disconnected from the lower tube. 
The T-shaped control handle 76, connected to the upper end 110 of the upper 
tube 104 of the steering control rod assembly 80, is provided so that the 
operator can control the direction and speed of the detachable motorized 
unit 22 and thus of the wheelchair 24, when motorized. The control handle 
76 includes a pair of hand grips 115 and a forward/reverse rocker switch 
116. This switch 116 serves in a conventional way to control the 
activation and direction of rotation of the motor 84 discussed above. The 
detachable motorized unit 22 is available as part of a motorized 
wheelchair sold under the product designation AMIGO by Amigo Sales Inc. of 
Bridgeport, Mich. 
The mounting frame 26 (FIGS. 3 and 11) includes a hollow, vertical center 
support tube 120 for rotatably receiving the steering control rod assembly 
80 of the detachable motorized unit 22. The center support tube 120 is 
connected to a pair of transverse lower and upper horizontal support tubes 
122 and 124. Attached to as by welding and depending from the transverse 
support tubes 122 and 124 is a battery frame assembly 126. The battery 
frame assembly includes a base plate 127 supported by a plurality of 
extension arms 128 depending from the support tubes 122 and 124. For 
retaining a battery 129 within the frame assembly 126, a retaining strap 
is attached to the base plate 127. The battery connectors 102 on the ends 
of the battery lead wires 100 can be attached to a pair of terminals 132 
on the battery 129. 
For adjusting the width of the mounting frame 26 to allow the apparatus to 
be mounted on a variety of wheelchairs of various widths, a pair of 
support collars 134 are slidably received on each open end of the 
transverse support tubes 122 and 124. The support collars are adjustably 
affixed to the transverse support tubes by set screws 136. The screws 136 
protrude through the support collar and associated transverse support tube 
122 or 124 so as to be engagable with laterally adjustable sleeves 140 and 
142 slidably received within the upper and lower support tubes 
respectively. There are a pair of the sleeves 140 associated with the 
support tube 124 and a pair of the sleeves 142 associated with the support 
tube 122 with the sleeves projecting out of the opposite open ends of the 
support tubes. 
The adjustable sleeves 140 and 142 can be repositioned to different 
longitudinal positions as desired by loosening and tightening the set 
screws 136. Thus, the overall width of the mounting frame 26 can be 
adjusted while leaving the center support tube 120 centered between the 
sides of the wheelchair. 
For engagement with and support by the mounting bracket 30, a fixed pin 144 
is received within opposite open ends of the lower adjustable sleeve 142. 
The fixed pin includes a shaft 150 and an enlarged integral head 156 at a 
free end of the shaft. The fixed pin has a blind threaded radial hole 146 
in its shaft 150 for receiving an attachment screw 152 protruding through 
an unthreaded hole 154 in the associated lower adjustable sleeve 142. 
For selective engagement with the mounting bracket 30, a slide pin 160 
protrudes from and is slidably received in each open end of the upper 
adjustable sleeve 140. Each slide pin includes a shaft 162 and a rounded 
head 164 on its free end. Each upper adjustable sleeve 140 has a 
longitudinal slot 166 along a top surface for receiving an adjustment 
screw 170 with a knob 172 on an end thereof. The screw 170 protrudes 
slidably through the longitudinal slot 166 and is threadedly received in a 
radial blind hole 174 in the slide pin 160. By tightening the screw 170, 
the slide pin can be longitudinally fixed within the upper adjustable 
sleeve. Conversely, upon loosening the screw 170, the slide pin can be 
repositioned longitudinally within the adjustable sleeve 140. Thus, the 
slide pin can be selectively moved into and out of operative engagement 
with the mounting bracket 30. Alternatively, the screw 170 could be 
replaced with a spring-biased locking device (not shown). 
For facilitating the connection of the detachable motorized unit 22 to the 
wheelchair 24, an installation handle 176 is provided (FIGS. 6-10). The 
L-shaped installation handle 176 can be inserted into the open upper end 
114 of the lower tube 106 of the steering control rod assembly 80, after 
the upper tube 104 has been removed. A grip portion 180 of the 
installation handle is provided as a lever arm for installation of the 
detachable motorized unit 22. 
As shown sequentially in FIGS. 6-10, the detachable motorized unit 22, with 
the installation handle 176 inserted, is brought into proximity with the 
front of the wheel chair 24. The slide pins 160 in each of the upper width 
adjustable sleeves 140 are first placed in the retracted position. The 
fixed pins 144 of the lower width adjustable sleeves 142 are placed in the 
C-shaped opening 62 of the mounting brackets 30 (FIG. 6). The motorized 
unit 22 is thus supported by its drive wheel 86 with the fixed pins 144 
bearing against a bottom surface 182 of the C-shaped opening 62. This 
operation can be easily accomplished by the occupant in the wheelchair. 
Next, the occupant pivots the detachable motorized unit 22 by applying a 
downward and forward force to the grip portion 180 of the installation 
handle 176. As the unit is pivoted clockwise as viewed in FIGS. 6-10, the 
fixed pin slides along the cam surface from the bottom surface 182 of the 
opening 62 along a side surface 184 and into engagement with a top surface 
186 of the C-shaped opening (FIGS. 7 and 8). As the operator continues to 
pivot the motorized unit by applying downward force on the grip portion 
180, the front caster wheels 44 of the wheelchair 24 are lifted off the 
supporting surface (FIG. 9). The wheelchair is now supported by the rear 
wheels 42 and the drive wheel 86 of the detachable motorized unit 22, 
through the cooperative action of the mounting bracket 30 and the mounting 
frame 26. The operator continues to pivot the motorized unit until the 
rounded end 164 of the retracted slide pin 160 contacts the protruding lip 
72 formed on the inner side 74 of the mounting brackets 30 (FIGS. 10 and 
13). At this point, the retracted slide pins can be repositioned 
longitudinally and locked in position with knobs 172 so that the pins 
protrude through and engage with the second circular openings 66 formed in 
the mounting brackets 30. Thus, the mounting frame 26 is now securely 
attached to the mounting brackets 30 and in turn to the wheelchair 24. 
Before or after the motorized unit is positioned and attached to the 
wheelchair as described above, the occupant can slide the battery 129 into 
the battery frame assembly 126 (FIG. 3) so that the battery connectors 102 
of the battery lead wires 100 can be attached to the battery terminals 
132. Once the installation handle 176 is removed from the lower tube 106, 
the upper tube 104 of the steering control rod assembly 80 can be 
inserted. The motorized wheelchair is then ready for operation. 
To disconnect the motorized unit 22 from the wheelchair 24, the occupant 
reverses the above-described procedure (FIGS. 6-10). The upper tube 104 of 
the steering control rod assembly 80 is removed from the lower tube 106 
and replaced with the installation handle 176. After loosening the knobs 
172, the slide pins 160 are retracted out of engagement with the second 
circular opening 66 of the mounting brackets 30. The operator then applies 
an upward force to the grip portion 180 of the installation handle 176 so 
as to pivot the motorized unit and return the front caster wheels 44 of 
the wheelchair 24 into engagement with the support surface. As the 
motorized unit continues to be pivoted, the fixed pins 144 of the mounting 
frame 26 slide along the side surface 184 of the C-shaped opening 62 and 
into engagement with the bottom surface 182 thereof. The fixed pins can 
then be lifted out of the C-shaped opening to completely disconnect the 
motorized unit from the wheelchair. 
A second embodiment 188 of the mounting frame and mounting brackets for use 
with a rigid, non-collapsible wheelchair is shown in FIGS. 14-16. Similar 
components from the first embodiment are shown with a prime (') 
denotation. Mounting brackets 190 affixed to the wheelchair frame at 
laterally spaced locations include a C-shaped opening 62', an intermediate 
slot-shaped opening 54' and upper and lower circular openings 66' and 52', 
respectively Each of the mounting brackets 190 is attached to the 
wheelchair 24 via a frame clamp 194. The frame clamp 194 includes a pair 
of confronting U-shaped members 196 clamped to a hollow tubular portion of 
the frame 32 of the wheelchair 24. Bolts 56' extend through the U-shaped 
members 196 and through the lower and intermediate openings 52' and 54' of 
the mounting bracket 190. The bolts are retained in place by a pair of 
nuts 60'. The mounting bracket includes a protruding lip 72' formed 
adjacent to the upper circular opening 66'. 
The second embodiment 200 of the mounting frame includes a center support 
tube 120' and a pair of transverse support tubes 122' and 124'. The 
support tubes are supported on the rear side of the center support tube 
120' by a bracket 202. Other than this opposite mounting of the support 
tubes to the center support tube, the mounting frame 200 is substantially 
identical to the first embodiment 26 of the mounting frame. Connection and 
disconnection of the motorized unit 22 to the wheelchair 24 using the 
mounting frame 200 and mounting bracket 190 is identical to that of the 
mounting frame 26 and mounting brackets 30 described above. 
A presently preferred embodiment of the present invention has been 
described above with a degree of specificity. It should be understood, 
however, that this degree of specificity is directed toward the preferred 
embodiment. The invention itself, however, is defined by the scope of the 
appended claims.