Wheel chair abstract
This invention relates to push rod apparatus for propelling wheel
chairs. Several different embodiments of the invention are disclosed.
All the embodiments include a plurality of push rod mechanisms that
provide the occupant with a means to propel a wheel chair in a forward
and reverse direction. In addition, the push rod mechanisms of the
various embodiments all include means to move the push rods away
from and toward the center of the rear wheels of the wheel chair
to which the push rods have been added. The push rods are extended
away from the rear wheels of the wheel chair when in their uppermost
position to place the push rods in a better position to be engaged
by the occupant of the wheel chair and retract toward the center
of the rear wheels in their lowermost position so that the push
rods will not contact the surface on which the wheel chair is moving.
Wheel chair claims
What is claimed is:
1. On a wheel chair having a first rear wheel and a first push
rim located on one side of said wheel chair and a second rear wheel
and a second push rim located on the other side of said wheel chair,
a push rod system used by the occupant of said wheel chair to propel
said wheel chair, said push rod system comprising:
a first plurality of push rods equally spaced around said first
push rim;
a second plurality of push rods equally spaced around said second
push rim, said second plurality of push rods being equal in number
to said first plurality of push rods;
a first cam located on said one side of said wheel chair and secured
to said wheel chair;
a second cam located on said other side of said wheel chair and
secured to said wheel chair;
separate cam followers operatively associated with each of said
first and second plurality of push rods, each of said separate cam
followers operatively associated with said first plurality of push
rods being guided by said first cam and each of said separate cam
followers associated with said second plurality of cam followers
being guided by said second cam, said first and second cams being
so designed that each of said first plurality of push rods extends
in a direction away from said first push rim when in its uppermost
position and retracts in a direction toward said first push rim
when in its lowermost position and said second cam being so designed
that each of said second plurality of push rods extends in a direction
away from said second push rim when in its uppermost position and
retracts in a direction toward said push rim when in its lowermost
position.
2. The push rod system as defined in claim 1 wherein each of said
plurality of first and second push rods comprises: an L-shaped rod
having a fork formed at the end of one leg of said L-shape, said
fork forming said separate cam follower, said fork of each of said
first plurality of push rods mating with said first cam and said
fork of each of said second plurality of push rods mating with said
second cam; a knob secured to the end of the other leg of said L-shape;
and wherein said first and second push rims each have a plurality
of holes drilled therethrough equal in number to said first and
second plurality of push rods, said other leg of said L-shape of
each of said first plurality of push rods passing through a different
one of said plurality of holes drilled in said first push rim and
said other leg of said L-shape of each of said second plurality
of push rods passing through a different one of said plurality of
holes drilled in said second push rim.
3. The push rod system as defined in claim 1 wherein said first
and second plurality of push rods each comprises:
a cylindrical rod;
a knob secured to one end of said cylindrical rod;
a collar slipped over said cylindrical rod, a keeper secured to
the other end of said cylindrical rod and a spring surrounding said
rod and being located between said collar and said keeper.
4. The push rod system as defined in claim 3 wherein each collar
of said first plurality of push rods is secured to said first push
rim and each collar of said second plurality of push rods is secured
to said second push rim.
5. The push rod system as defined in claim 4 wherein said separate
cam follower operatively associated with each of said first and
second plurality of push rods comprises a U-shaped member with a
bearing secured to the end of each leg of said U-shaped member,
each cam follower of said first plurality of push rods mating with
said first cam and each cam follower of said second plurality of
push rods mating with said second cam and wherein each cam follower
mating with said first cam is coupled to a different one of said
first plurality by means of a separate cable and each said cam follower
mating with said second cam is coupled to a different one of said
second plurality of push rods by a separate cable.
6. The push rod system as defined in claim 1 wherein said first
and second plurality of push rods each comprise:
a cylindrical rod;
a knob secured to one end of said cylindrical rod;
a keeper surrounding said cylindrical rod and being located adjacent
the other end of said cylindrical rod; and
a spring surrounding said cylindrical rod and being located between
said collar and said knob, said collar of each of said first plurality
of push rods being secured to said first push rim and said collar
of each of said second plurality of push rods being secured to said
second push rim.
7. The push rod system as defined in claim 6 wherein said separate
cam followers operatively associated with each of said plurality
of first and second push rods each comprises a U-shaped member having
a separate bearing secured to the end of each leg of said U-shape,
said separate cam followers operatively associated with said first
plurality of push rods mating with said first cam and said separate
cam followers operatively associated with said second plurality
of push rods mating with said second cam follower.
8. The push rod system as defined in claim 7 wherein each of said
separate cam followers mating with said first cam is coupled to
a different one of said first plurality of push rods by a separate
cable and each of said separate cam followers mating with said second
cam is coupled to a different one of said second plurality of push
rods by a separate cable.
9. The push rod system as defined in claim 1 wherein said first
push rim has a plurality of holes equal in number to said first
plurality of push rods and said second push rim has a plurality
of holes equal in number to said second plurality of push rods.
10. The push rod system as defined in claim 9 wherein each push
rod of said first plurality of push rods comprises:
a cylindrical rod passing through one of said holes in said first
push rim;
a knob secured to one end of said cylindrical rod;
a keeper secured at approximately the mid-point of the length of
said cylindrical rod; and
a spring surrounding said cylindrical rod and being located between
said first push rim and said keeper; and
wherein each push rod of said second plurality of push rods comprises:
a cylindrical rod passing through one of the holes of said second
push rim;
a knob secured to one end of said cylindrical rod;
a keeper secured at approximately the mid-point of the length of
said cylindrical rod; and
a spring surrounding said cylindrical rod and being located between
said second push rim and said keeper.
11. The push rod system as defined in claim 10 wherein each separate
cam follower associated with said first plurality of push rods is
secured to the other end of said cylindrical rod of a different
one of said first plurality of push rods and each separate cam follower
associated with said second plurality of push rods is secured to
the other end of said cylindrical rod of a different one of said
second plurality of push rods; said separate cam followers associated
with said first plurality of push rods mating with said second cam
and said separate cam followers associated with said second plurality
of push rods mating with said second cam.
Wheel chair description
BACKGROUND OF THE INVENTION
This invention relates to wheel chairs and, more particularly,
to push rod mechanisms for propelling wheel chairs by the occupant
of the wheel chair.
Conventional wheel chairs, foldable type or rigid frame type, are
generally provided with hand rims that are attached to the rear
wheels of the chair. These hand rims are used by the occupant of
the wheel chair to propel the chair. If the occupant of the wheel
chair has full use of his hands and arms, these hand rims provide
a satisfactory means of propelling a wheel chair. However, if the
occupant of the wheel chair has restricted or little or no use of
his hands, the conventional push rim does not provide a satisfactory
means even though such a person may be able to use his arms and/or
his shoulder muscles to provide a force sufficient to propel a wheel
chair. On many wheel chairs the hand rims do carry short push rods
to help the occupant propel the wheel chair. However, these rods
are short and not optimumly positioned.
Various other different propelling mechanisms have been devised
to provide occupants of wheel chairs who have little or no use of
their hands but do have use of their arm and/or shoulder muscles
with a means to propel their wheel chairs. Most of these prior art
mechanisms known to the applicant use large single levers and many
have relatively complicated mechanical linkages to provide the proper
motion for the lever.
This invention provides occupant operated push rod apparatus to
propel a wheel chair. The various embodiments of this invention
provide mechanical advantages over the conventional push rims or
push with the short fixed knobs and, in addition, the occupant of
the wheel chair does not have to grasp the push rods to propel the
wheel chair. All the occupant of a wheel chair needs to do to use
the push rod apparatus of this invention is to apply a forward or
reverse force on the push rods to move the wheel chair in the forward
or reverse direction, respectively.
SUMMARY OF THE INVENTION
This invention relates to push rod apparatus for propelling a wheel
chair. While several different embodiments of the invention are
disclosed, all of the embodiments include a plurality of push rods
operatively associated with the push rims on each side of the wheel
chair. If the occupant of the wheel chair applies a force on the
push rods in a forward direction, the wheel chair moves in the forward
direction and conversely, if the occupant applies a force on the
push rods in a backward direction, the wheel chair will move backwards.
In each embodiment of this invention means are provided to move
each push rod away from or toward the axis of the push rim associated
with that push rod so that each push rod is retracted toward its
associated push rim when the push rod is in its lowermost position
and each push rod is moved in a direction away from the outer edge
of its associated push rim when that push rod is in its uppermost
position. Each push rod is retracted toward the center of its associated
push rim when it is in its lowermost position so that the push rods
will not contact the surface upon which the wheel chair is moving
and is extended away from its associated push rim when in the uppermost
position to place the push rod in a better position for engagement
by the occupant of the wheel chair.
BRIEF DESCRIPTION OF THE DRAWING
A full and complete understanding of the invention can be obtained
from the following detailed description of the invention when read
in conjunction with the annexed drawing in which:
FIG. 1 is a side view of a conventional wheel chair with a first
embodiment of the push rod apparatus of this invention added to
the wheel chair;
FIG. 2 is a fragmented view of the wheel chair and push rod apparatus
of FIG. 1 taken along the line 2--2 of FIG. 1;
FIG. 3 is a detailed view of a segment of the push rod apparatus
of FIGS. 1 and 2;
FIG. 4 shows a second embodiment of the push rod apparatus of the
invention;
FIG. 5 is a view of the second embodiment of the invention taken
along the line 5--5 of FIG. 4;
FIG. 6 shows a third embodiment of the push rod apparatus of the
invention;
FIG. 7 is a view of the third embodiment taken along the line 7--7
of FIG. 6;
FIG. 8 shows a fourth embodiment of the push rod apparatus of the
invention; and
FIG. 9 is a view of the fourth embodiment of the invention taken
along the line 9--9 of FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1, 2 and 3, the wheel chair 1 is any conventional
wheel chair, either of the rigid frame type or the collapsible frame
type. Note that as shown in FIGS. 1 and 2, wheel chair 1 is not
collapsable. However, the precise structure of the basic wheel chair
does not form a part of this invention; therefore, it is to be understood
that the various embodiments of this invention can be added to any
conventional wheel chair. Such conventional wheel chairs have a
pair of large rear wheels 2, one located on each side of the wheel
chair. These rear wheels 2 usually have rubber tires. These conventional
wheel chairs also usually have a pair of push rims 3, one associated
with each of the rear wheels 2 and extending beyond its associated
rear wheel as shown in FIGS. 1 and 2. To propel the wheel chair,
the occupant grasps the push rims and provides a forward or backward
force to move the wheel chair forward or in reverse, respectively.
Instead of using the push rims 3 to propel wheel chair 1, the push
rod apparatus of this invention is utilized. As shown in FIGS. 1,
2 and 3, the push rod apparatus of the first embodiment of this
invention includes a plurality of push rods 4 equally spaced around
each of the push rims 3. While FIG. 1 shows eight push rods equally
spaced around one of the push rims 3, any number of such push rods
can be provided with, of course, the same number of push rods being
provided on each side of the wheel chair. While any number of push
rods can be provided, from a practical standpoint, the number of
push rods provided should probably not be less than four or more
than sixteen. If less than four push rods are provided, the spacing
between rods becomes too great and if more than sixteen push rods
are provided, the spacing between rods will be so small that the
next rods in line may interfere with the occupant as he propels
the wheel chair by pushing on one of the rods.
As shown more clearly in FIG. 3, each of the push rods 4 is generally
L-shaped and has a fork 5 formed at one end thereof. Evenly spaced
holes are drilled through each of the push rims 3 and the straight
end, the end not having the fork 5, of each of the push rods 4 is
slipped through a different one of the holes drilled in the push
rims 3. A suitable knob 6 is then secured to each of the push rods
4. The knobs 6 may be made of any suitable material and are secured
to push rods 4 by any suitable means. Conveniently, the end of each
of the push rods 4 can be threaded and each of the knobs 6 will
then have a threaded hole so that the knobs 6 can be screwed onto
the push rods 4. In this manner, a knob 6 can be conveniently replaced
if a knob breaks or wears out.
A separate cam 7 is secured to each side of the frame of wheel
chair 1 between the chair frame and the rear wheel 2 on that side
of wheel chair 1. In FIG. 2, the rods or elements 8 are shown as
securing the cams 7 to the chair frame. These rods or elements 8
may be welded to the cams 7 and the chair frame or may be secured
to cams 7 and the chair frame by any other suitable means. Further,
any other suitable means can be used to secure cams 7 to the chair
frame. As shown in FIG. 2, the cams 7 are so secured to the chair
frame that the top of each of the cams 7 is closer to associated
rear wheel 2 than at the bottom. That is, each of the cams 7 is
slightly tilted so that the top of each cam 7 is closer to the associated
rear wheel 2 and the bottom is closer to the chair frame. The reason
for so tilting the cams 7 will be described later. Also, the cams
7 are not concentric with the rear wheels 2 as is shown in FIG.
1. That is, each of the cams 7 is off-set such that the distance
between the edge of each of the rear wheels 2 and the outside surface
of the associated cam 7 is greater at the bottom then at the top.
The reason for this off-set will become apparent.
As is shown in FIGS. 2 and 3, the forks 5 of the push rods 4 slip
over the cams 7 such that one tine of each fork 5 rides on the inside
edge of its associated cam 7 while the other tine rides on the outside
edge. Note that while the cams 7 are shown as being generally ring-shaped
with the tines of the forks 5 riding on the narrow edges, the cams
7 could be generally ringshaped but with the wide surfaces of the
cams 7 being horizontal rather than verticle. If the cams 7 are
so shaped, the tines of the forks 5 would ride on the wide surfaces
rather than the narrow edges as shown. In fact, as will become evident,
the cams 7 can have any suitable design that will provide the proper
motion to the push rods 4.
The push rods 4 are used by the occupant of the wheel chair to
propel the wheel chair in either a forward or backward direction
in the following manner: The occupant of the wheel chair pushes
on the knob 6 of the uppermost push rod 4. This can be done without
tightly grasping the knob 6. Assuming he wishes to move the chair
forward, he pushes in a forward direction. The chair then moves
forward and this push rod 4 moves away from the occupant while the
following push rod 4 moves into its uppermost position so that this
following push rod 4 can now be used to propel the chair. Thus,
push rod 4 after push rod 4 moves into the uppermost position rod
after rod as the chair moves forward and the occupant pushes on
each rod as it moves through this uppermost position to keep the
chair moving. Of course, the same procedure is used in reverse to
move the chair in a backward direction and if the occupant wishes
to turn the chair he merely pushes the push rods 4 on one side in
one direction while pushing the push rods 4 on the other side in
the opposite direction.
As a push rod 4 reaches its lowermost position it must obviously
be so positioned relative to its associated rear wheel 2 that it
can clear the floor. The cams 7 and the fork 5 of each push rod
4 provides the required movement of the push rods 4 relative to
the rear wheels 2 to enable the push rods 4 to clear the floor when
in their lowermost position. As a push rod 4 rotates, its fork 5
is guided by its associated cam 7. Any movement of a fork 5 away
from or toward the axis of its associated push rim 3 is translated
to its push rod 4 and causes that portion of push rod 4 that passes
through the associated hole in push rim 3 and thus the knob 6 to
move in the same direction. This portion of each of the push rods
4 is smaller in diameter than the diameter of the associated hole
in push rim 3 and is therefore free to slide in its hole in push
rim 3. The push rims 3 are concentric with their associated rear
wheels 2 but the cams 7 are off-set from the axes of their associated
rear wheels 2 such that the distance between the outer edge of a
rear wheel 2 and the outer edge of its associated cam 7 is greater
at the bottom of each cam 7 than at the top. Thus, as each push
rod 4 rotates toward the bottom of its cam 7, its fork 5 is drawn
toward the center of the push rim 3 by cam 7 and is closest to the
center of its push rim 3 when at the bottom of its cam 7. Since
the knob 6 of each push rod 4 moves in the same direction as its
fork 5, the knob 6 will be retracted toward the axis of its associated
rim 3 when the push rod 4 is in its lowest position. Each cam 7
is off-set a sufficient amount to cause knobs 6 of each push rod
4 to move inward a sufficient amount to provide clearance between
each knob 6 and the surface upon which the wheel chair is moving
when a push rod 4 approaches and is at its lowest point. As each
push rod 4 passes through its lowest point and then begins to rotate
to its highest point, its fork 5 riding in its cam 7 begins to move
away from the axis of the associated push rim 3 and is at its furtherest
point away from the axis of its push rim 3 when it is at the top
of its cam 7; therefore, knob 6 of each push rod 4 will be at its
furtherest point away from its associated push rim 3. This extending
of knob 6 of each push rod 4 away from its push rim 3 moves the
knob 6 into a convenient position for the occupant of the wheel
chair to push on that knob 6. In summary, then the occupant of the
wheel chair 1 applies a force to each knob 6 as each knob 6 moves
into its uppermost position. At this point cam 7 has moved the knob
6 away from its push rim 3 and toward the occupant and as each push
rod 4 moves through its lowest point its knob 6 is retracted toward
its push rim 3 so that knob 6 clears the surface upon which the
wheel chair is moving. Thus, the occupant propels wheel chair 1
by pushing on knobs 6 of push rods 4 one at a time as each knob
6 is brought into position by its push rim 3 and its cam 7 and each
push rod 4 is retracted at the lowest point of travel and extended
at its highest point of travel by the interaction of each cam 7
and the forks 5 of the push rods 4.
FIGS. 4 and 5 show a second embodiment of the invention. In these
Figures only a portion of a single rear wheel 10 and the associated
push rim 3 of a wheel chair 1 are shown. In addition, only three
push rods, the push rods 12, are shown in FIG. 4 and only one of
the push rods 12 is shown in FIG. 5. In practice, a plurality of
push rods 12 (preferably no less than 4 or more than 16) will be
equally spaced around push rim 11 as in the case in the embodiment
of FIGS. 1, 2 and 3 and such push rods 12 will be provided on each
side of the wheel chair. Each push rod 12 includes a rod 13, a knob
14 secured to one end of rod 13, a spring 16 and a keeper 17. A
separate collar 15 surrounds each rod 13 between its knob 14 and
its spring 16. Each support collar 15 has a hole drilled therethrough
of sufficient diameter to permit the associated rod 13 to move up
and down freely in the hole in the support collar 15. Each support
collar 15 is secured to the push rim 11. A cable 17 is secured at
one end to keeper 17, passes over a retainer 18 secured to rim 11
and is secured to fork arrangement 20 at its other end. Each fork
arrangement 20 has a pair of rollers or bearings 21 that ride in
a cam 22. One of the push rods 12, the push rod 12 on the right
in FIG. 4, is broken away to show rollers 21. Each fork 20 is tied
to the next fork by means of a section of cable 3 and to a trailing
and a leading spoke 25 by means of the separate cables 24. Not all
of the forks 20 need to be tied to the spokes 25. The tying of every
other fork 20 to the spokes 25 should be sufficient.
Spring 16 of each push rod 12 operates to urge the push rod 12
toward keeper 17. Cam 22 is off-set from the axis of the push rim
11 and thus from the axis of the wheel 10. However, in this case
the off-set is exactly opposite the off-set of cam 7 of FIGS. 1,
2 and 3. That is, the outer surface of cam 22 is closer to the edge
of wheel 10 at its bottom than at its top. In addition, cam 22 has
a lip to retain the rollers or bearings 21 while cam 7 of FIGS.
1, 2 and 3 does not have a lip.
The operation of the embodiment is similar to the operation of
the embodiment of FIGS. 1, 2 and 3 in that the occupant of the wheel
chair pushes on push rods 12 one at a time to propel the wheel chair;
however, in this embodiment spring 16 in conjunction with cam 22
and the cam followers comprised of forks 20 and rollers or bearings
21 of each push rod 12 cooperate to retract the rods at their lowermost
position and extend them at their uppermost position. When a push
rod 12 is at the top, the outer surface of cam 22 is at its furtherest
distance from the surface of push rim 11; therefore, its cable 18
is pulled downward and thus push rod 12 is urged upward away from
the push rim 11 against its spring 16. When a push rod 12 is at
its lowest position cable 18 moves in the direction away from cam
22 since the outer surface of cam 22 is at its closest distance
from the surface of push rim 11. When cable 18 of a push rod 12
moves in thus, this push rod 12 is urged inward by its spring 16
and will therefore clear the surface upon which the wheel chair
is moving.
FIGS. 6 and 7 show a third embodiment of the invention. This third
embodiment is a variation of the second embodiment. FIGS. 6 and
7 show only a part of one of the rear wheels, the wheel 30, a part
of the associated push rim 32 and a few of the push rods 33, In
practice, a plurality of push rods 33 (peferably not less than 6
nor more than 10) are equally spaced around push rim 31 and, of
course, such a plurality of push rods are provided on both sides
of the wheel chair.
As shown in FIGS. 6 and 7, each push rod 33 includes a rod 34,
a knob 35 secured to one end of rod 34, a keeper 37 and a spring
36 surrounding rod 34 and located between keeper 37 and and knob
35. Keeper 37 of each push rod 33 is secured to rim 31 by any suitable
means.
Rod 34 of each push rod 33 passes through a hole drilled in its
keeper 37. The hole drilled in each keeper 37 is of a sufficient
diameter to permit its rod 34 to freely slide up and down in keeper
37. The end of each rod 34 that extends beyond its keeper 37 is
formed into an eyelet. Each rod 34 has a cable 38 secured at one
end to its eyelet. Each cable 38 extends away from its rod 34 and
passes through a separate hole drilled in the hub plate 39. After
passing through its hole in hub plate 38, each cable 38 is brought
up toward its associated push rod 33 and secured to a separate fork
40. Each fork 40 has a pair of rollers or bearings 41 that ride
on the cam 42. The configuration of cam 42 is identical to the configuration
of cam 22 of FIGS. 4 and 5; however, cam 42 is off-set in the opposite
direction from cam 22 of FIGS. 4 and 5. That is, the outer surface
of cam 42 is closer to the outer surface of push rim 31 at the top
than at the bottom. This off-set of cam 42 is identical to the off-set
of cam 7 of FIGS. 1, 2 and 3.
As is the case with the first two embodiments, the occupant of
a wheel chair merely pushes on push rods 33 one at a time to propel
the wheel chair. It is noted that while not shown in FIGS. 6 and
7, a cable arrangement identical to the cables 3 and 24 of FIGS.
4 and 5 is provided in the embodiment of FIGS. 6 and 7 to tie one
fork 40 to the next fork 40 and to tie each fork 40 or a number
of the forks 40 to the spokes. These cables are not shown in FIGS.
6 and 7 in order to avoid cluttering. Spring 36 of each push rod
33 urges the knob 35 of each push rod 33 away from its keeper 37.
When a push rod 33 is in its uppermost position, its fork 40 is
at its closest distance from the surface of push rim 31 and its
spring 36 is free to move its knob 35 away from its keeper 37. When
a push rod 33 moves to its lowest position, its cable 38 is pulled
toward cam 42 due to the off-set of cam 42. This motion of cable
38 causes its associated rod 34 to move toward hub 39 thereby retracting
knob 35 of that push rod 33 toward its keeper 37 thereby allowing
that push rod 33 to clear the surface upon which the wheel chair
is moving. Thus, as each push knob rotates, it is retracted against
its spring 36 by the action of its cable 38, cam follower consisting
of its fork 40 and bearings or rollers 41, and cam 42 and as this
push rod moves to its uppermost position, it is extended to its
fullest away from its keeper 37 under the action of its spring 36
and the action of its cam follower and cam 42.
FIGS. 8 and 9 show still another embodiment of the invention. Again,
only a part of one rear wheel, the wheel 50 of a wheel chair and
its associated push rim 51 is shown. This embodiment also includes
a plurality of push rods 53, only four of which are fully shown.
FIG. 4 does, however, show that eight push rods 53 are equally spaced
around push rim 51. Again, the exact number of push rods 53 provided
is not critical but for obvious reasons, the number of push rods
provided should not be less than six nor more than ten and, of course,
a plurality of push rods 53, equal in number, are provided on both
sides of the wheel chair.
As shown in FIGS. 8 and 9, push rods 53 each comprise a rod 54,
a spring 55, a keeper 56, a knob 57 secured to one end of rod 54
and a roller bearing 58 secured to the other end of rod 54.
Push rim 51 has a plurality of holes, equal in number to the number
of push rods 53. The rods 54 of push rods 53 each pass through a
different one of the holes in push rim 51 as shown in FIGS. 8 and
9. The holes in push rim 51 are of sufficient diameter to permit
rods 54 to freely move up and down in the holes and spring 55 of
each push rod 53 is retained in place by push rim 51 and the associated
keeper 56. Roller bearings 58 ride on a cam 52 secured to the axle
59. Cam 52 is not concentric with axle 59. That is, the distance
between the center of axle 59 and the top of cam 52 is greater than
the distance between the bottom of cam 52 and the center of axle
59. Cam 52, of course, does not rotate with wheel 50 and push rim
51.
As is the case in the other three embodiments, the occupant of
a wheel chair propels the chair by merely pushing on the push rods
53 one at a time as a rod comes into position. As a push rod approaches
its uppermost level, the push rod 53 will be pushed upward by the
action of cam 52 and roller bearing 58. This upward movement of
the push rod causes its spring 55 to be compressed. As this push
rod approaches its lowermost point, it moves inward toward axle
59 under the influence of its spring 55 and the action of cam 52
and roller bearing 58 of that push rod. Thus, as the occupant of
the wheel chair pushes on push rods 53, one at a time, push rods
53 rotate around cam 52 and move inward and outward as they pass
from their lowest position to their highest position, respectively.
While the invention has been described with reference to four specific
embodiments, it will be apparent to those skilled in the art that
various changes and modifications can be made to these specific
embodiments without departing from the spirit and scope of this
invention as set forth in the claims. |