RELATIONSHIP TO PRIOR INVENTION
This application constitutes a continuation-in-part of
provisional U.S. patent application serial No. 60/017,679, filed on May 21, 1996.
FIELD OF THE INVENTION
This invention relates to an improved suspension system
for a powered wheelchair or similar self-propelled vehicle wherein the vehicle frame
may be conveniently lowered relative to the powered wheels and all wheels of the
vehicle are vertically movable relative to the vehicle frame to permit the wheels
to follow the contour of the ground or road on which the vehicle is operated.
BACKGROUND OF THE INVENTION
Powered wheelchairs and similar vehicles available on the
market are generally characterized by a pair of power driven wheels and one or more
caster wheels which are non-adjustably mounted on the vehicle frame. Thus, in the
case of the wheelchair, the combined height of the occupant of the wheelchair and
the chair structure exceeds the clearance available in conventional side loading
passenger vans, thereby requiring that the wheelchair be loaded into the van without
the occupant and the occupant then manually lifted into the van and placed in the
The prior solutions to this problem include an expensive
modification of the van to lower the van floor so that the occupant can drive the
wheelchair directly into the van, with the aid of a small ramp.
Another approach is to raise the roof of the van and install
a powered lifting platform, which projects through the side door of the van. Such
modifications of conventional passenger vans having side loading doors generally
involve expenditures on the order of $10,000 over and above the cost of the van.
Another problem encountered with conventional wheelchairs
and similar self-propelled vehicles is that the wheel mountings do not permit any
of the wheels, whether power driven or caster wheels, to move independently in a
vertical plane to follow the ground or road contour on which the vehicle is operated.
Cushioning the frame of the vehicle and the occupant from
road shocks is also greatly desired.
United States Patent, No. 4,469,188 describes an articulated
tricycle in which either the drive sprocket or the driven sprocket is positioned
about a constant velocity universal joint which is in turn positioned about a transverse
shaft or the transverse rear axle.
It is the object of this invention to overcome the above
listed problems that are encountered with conventional suspension systems for power
wheelchairs and similar self-propelled vehicles.
SUMMARY OF INVENTION
According to the present invention there is provided a
suspension system for a powered wheelchair having an elongated frame (2) supporting
an occupant seat (2b) comprising;
a transaxle housing (5) having a pair of power driven wheels (3) mounted on opposite
ends of said transaxle housing;
linkage means (6) for connecting said transaxle housing in transverse relation to
said elongated frame with said transaxle housing being freely tiltable in a vertical
plane transverse to said elongated frame, whereby said power driven wheels may follow
the contour of the ground traversed by said power driven wheels;
fluid pressure cylinder means (13) operatively connected between said linkage means
and said frame for vertically positioning said frame relative to said ground engaging
operator controlled means for supplying and withdrawing fluid from said fluid pressure
cylinder means, and wherein
the suspension system further comprises:
- a pair of caster wheels (4) for said powered wheel chair;
- a subframe (8) supporting said caster wheels in laterally spaced relationship
to said elongated frame;
- a second linkage means (10) for supporting said subframe in transverse relationship
to said elongated frame to permit tilting movement of said subframe in a vertical
transverse plane relative to said elongated frame, whereby said caster wheels may
follow the contour of the ground traversed by said caster wheels;
- a second fluid pressure cylinder means (12) operatively connected between said
second linkage means and said elongated frame for vertically positioning said elongated
frame relative to said caster wheels; and
- means connecting said second fluid pressure cylinder means to said operator
controlled means for supplying and withdrawing fluid from said second fluid pressure
A powered wheelchair, or similar self-propelled vehicle,
embodying this invention preferably employs two powered ground engaging wheels which
are rotatably mounted on opposite ends of a transaxle housing which contains a dual
planetary transmission. The transaxle housing and the enclosed dual planetary transmission
is preferably of the constructions disclosed in issued U.S. Patent No. 5,275,248
and our pending application Serial No. 08/652,975, filed May 25, 1996.
An elongated frame for the wheelchair is provided which
mounts an occupant seat, driving and steering motors, and a battery compartment
in conventional fashion. The battery compartment is preferably located beneath the
vehicle seat. In accordance with this invention, the transaxle housing is mounted
to a first vertically depending frame portion by three links. Two of the links are
identical and one end of such links is respectively mounted in a pair of universal
pivot mountings, such as a ball joint or elastometric bushing, respectively provided
in horizontally spaced relation on the aforementioned depending frame portion. The
other ends of such links are respectively mounted to two universal pivot mountings
provided on the transaxle housing in horizontally spaced relation. Thus the powered
wheels are free to move vertically relative to each other by tilting of the transaxle
housing to follow the ground or road contour.
To prevent lateral displacement of the powered wheels relative
to the frame, a third link of generally triangular configuration is provided. Such
link has horizontal pivots on each end of its triangular base and two horizontally
spaced, single axis pivot mountings for said horizontal pivots are provided on the
aforementioned first depending frame portion in vertically spaced relation to the
universal pivot mountings. The vertex portion of the triangular link, which is hereinafter
referred to as the stabilizing link, is pivotally secured to a universal pivot mounting
on the transaxle housing at a position centrally intermediate the aforementioned
two universal pivot mountings.
Thus the transaxle housing, and hence the powered wheels,
is prevented from horizontal displacement relative to the vehicle frame.
Two caster wheels for the vehicle are conventionally mounted
on an inverted L-shaped subframe having a horizontal leg that supports the caster
wheels and a vertical leg which is mounted to a second depending frame portion that
is longitudinally spaced relative to the first depending frame portion. For example,
the one depending frame portion may also provide a front wall for the battery compartment,
while the other depending frame portion provides a rear wall for the battery compartment.
The mounting of the caster wheel subframe to the second
depending frame portion is accomplished by the same arrangement of three links,
two of the links having universal pivot connections to the second depending frame
portion and the vertical leg of the caster wheel subframe, plus a triangular stabilizing
link having two horizontal axis pivot connections to the second depending frame
portion and a single universal pivot connection to the caster wheel subframe. Thus
the caster wheels have the same mountings as described for the powered wheels and
can move independently of each other and the vehicle frame to conform to the ground
or road contour.
To selectively position the height of the frame relative
to the caster wheels, a pair of hydraulic or pneumatic cylinders are respectively
mounted between the stabilizing link and said vehicle frame. The axes of such cylinders
are generally vertical. A motor driven fluid pump is mounted at any convenient location
on the vehicle frame. An operator actuator fluid control circuit is provided to
selectively effect the elongation or contraction of both the fluid cylinders.
Alternatively, and in the preferred embodiment of the invention,
two fluid cylinders can be utilized to respectively connect the two links connecting
the transaxle to separate locations provided on the frame. These two cylinders would
be substituted for the single cylinder connecting the stabilizing link to the vehicle
frame as discussed above. Such two cylinders would be connected in parallel in the
fluid control circuit, hence would be concurrently controlled.
Thus the operator can raise, lower or tilt the vehicle
frame in a vertical plane relative to the ground engaging powered wheels and caster
wheels. The overall height of the vehicle plus the operator can be reduced to permit
direct entry into the side loading door of a conventional van by merely providing
a ramp from the ground or road to the floor of the van.
The two fluid cylinders can also function to cushion the
frame of the vehicle from road shocks, and still permit the wheels of the vehicle,
both powered and caster wheels, to move vertically to follow the contour of the
ground or road over which the vehicle travels.
The advantages of the aforedescribed suspension system
for wheel chairs and similar vehicles will be readily apparent to those skilled
in the art.
BRIEF DESCRIPTION OF DRAWINGS
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
- Figure 1 is a schematic side elevational view of this invention as applied to
a powered wheelchair, showing the frame and seat of the wheelchair in their normal
elevated position relative to the ground engaging wheels.
- Figure 2 is a view similar to Figure 1 but showing the frame and seat of the
wheelchair in a lower position relative to the ground engaging wheels.
- Figure 3 is a schematic perspective view of a suspension system embodying this
invention as applied to the powered wheels of a wheelchair.
- Figure 4 is an enlarged schematic perspective view of a suspension system embodying
this invention as applied to the caster wheels of a wheelchair.
- Figure 5 is a detailed pressured fluid control circuit for effecting changes
in elevation of the frame and seat of the wheelchair relative to the ground engaging
- Figure 6 is a front elevational view of the wheelchair of Figure 1, illustrating
the conformity of the powered wheels to the ground contour.
- Figure 7 is a rear elevational view of the wheelchair of Figure 1, illustrating
the conformity of the caster wheels to the ground contour.
- Figure 8 is a schematic side elevational view of a powered wheelchair incorporating
a modification of this invention.
Referring to Figure 1, a powered wheelchair 1 of the type
described in detail in U.S. Patent No. 5,275,248 and our pending application Serial
No. 08/652,975, filed May 24, 1996 is schematically illustrated. Such wheelchair
comprises an elongated articulated frame 2, which, at its forward end, defines a
leg rest portion 2a while the medial portion of the elongated frame defines a conventional
mounting for an occupant seat 2b above the frame 2 and a battery compartment 2c
beneath the frame 2 having a forward vertical wall 2g and a rearward vertical wall
2e. The frame 2 is supported and powered by two ground engaging wheels 3 shown at
the forward end of the elongated frame 2, and a pair of caster wheels 4 at the rearward
end of the frame 2. Those skilled in the art will understand the terms "forward"
and "rearward" are relative terms and the positions of the powered wheels 3 and
the caster wheels 4 relative to the frame 2 may be reversed.
The two powered wheels are mounted on opposite ends of
a transaxle housing 5 which is described in detail in the above referred to issued
patent and pending application. For clarity of the drawings, the transaxle housing
is deliberately shown in greatly reduced size, but such housing will be understood
to contain a dual planetary transmission for applying driving and steering power
to the powered wheels 3 as controlled by the occupant, as is fully described in
the aforementioned issued patent and pending application. Steering of the wheelchair
1 is accomplished by providing a differential in direction or speed of rotation
of the two powered wheels 3.
The mounting of the transaxle housing 5 to the frame 2
thus controls the vertical position of power wheels 3 relative to frame 2, while
the mounting of the subframe 8 to the frame 2 controls the vertical position of
caster wheels 4 relative to the frame 2.
In accordance with this invention, the mountings for the
powered wheels 3 and the caster wheels 4 are functionally identical. A pair of mounting
links 6 respectively have their one end connected in horizontally spaced relation
to the depending front wall 2g of the battery compartment 2c by universal pivot
bearings 2f. The other ends of mounting links 6 are connected by universal pivot
bearings 5a provided on the bottom wall of the transaxle housing 5, or any other
convenient location which disposes the mounting links in generally parallel relationship.
Due to the universal pivot mountings of both ends of the mounting links 6, the powered
wheels 3 may assume a plurality of vertical positions relative to the frame 2 as
they follow the contour of the ground or road traversed by such wheels.
To prevent lateral shifting of the transaxle housing 5,
hence lateral shifting of the powered wheels 3 relative to frame 2, a stabilizing
link 7 is provided which is of a generally triangular or T shaped configuration,
having a wide base portion 7a and a vertex portion 7b, as best shown in Figure 3.
A pair of horizontally spaced, horizontal axis pivot mountings 2d are provided on
the forward battery compartment vertical wall 2g to respectively receive pivot pins
traversing pivot holes 7c provided at the lateral end of stabilizing link 7. Thus
stabilizing link 7 can only move in a vertical plane about a horizontal axis defined
by the pivot bearings 2d, and can be either above the universal pivot bearings 2f,
as shown in Figure 3, or below.
The vertex end 7b of stabilizing link 7 is secured to the
transaxle housing 5 by a universal pivot 5c, thus permitting the transaxle housing
5 to tilt in a vertical plane, due to the powered wheels 3 following ground contours,
but there is no significant lateral displacement of the transaxle housing 5 relative
to the elongated frame 2.
To similarly mount the caster wheels 4 to the frame 2,
a subframe 8 (best shown in Figure 4) is provided having a generally inverted L
shaped configuration with a horizontal caster wheel mounting leg 8a and a generally
vertical link mounting leg 8b. One or preferably two caster wheels 4 are conventionally
swivelly mounted on horizontal leg 8a of subframe 8.
To secure the subframe 8 to the elongated frame 2, a pair
of mounting links 9 are respectively connected to a pair of universal pivot mountings
8c provided in horizontally spaced relation on the horizontal leg 8a of subframe
8. The other ends of mounting links 9 are respectively connected to a pair of horizontally
spaced, universal pivot mountings 2j provided on the rearward vertical wall 2e of
the battery compartment 2c. Thus the subframe 8 may freely pivot in a vertical plane
as the caster wheels follow the road or ground contours.
To prevent lateral movement of the subframe 8 relative
to the elongated frame 2, a generally triangular or T shaped stabilizing link 10
is provided. Link 10 has a wide base portion 10a terminating in two horizontally
spaced single axis pivot bores 10b which are respectively secured to two horizontally
spaced, horizontal axis pivot mountings 2k provided on the rearward wall 2e of the
battery compartment. The vertex portion 10c of stabilizing link 10 is universally
pivotally secured to a pivot bearing 8d on subframe 8. Thus no significant lateral
movement of the caster wheels 4 can occur as the wheelchair moves over an uneven
surface. Stabilizing link 10 may be either below (as shown in Figure 4) or above
the mounting links 9.
Preferably a torsion rod 14 is connected between mounting
links 6 and also between mounting links 9 to maintain the parallelity of the mounting
links 6 and 9 relative to each other.
While the aforedescribed mounting structures for the powered
and caster wheels of a powered wheelchair will permit such wheels to follow the
road or ground contours, such mounting structures also provide for effecting occupant
controlled vertical raising and lowering of the frame and seat relative to the wheels.
This highly desirable feature is accomplished by providing a pair of fluid pressure
cylinders 12 operating between the stabilizing link 10 and the vertical frame 2,
as shown in Figure 4, or by utilizing a pair of fluid pressure cylinders 13 respectively
operating between the mounting links 6 and the frame 2, as shown in Figure 3.
In either modification, the supply of pressured fluid,
either air or hydraulic, to the fluid pressure cylinders will cause such cylinder(s)
to expand and elevate the entire frame 2 and the seat occupant relative to the wheels
as shown in Figure 1. Removal of fluid from such cylinder(s) will cause the frame
to lower relative to the ground engaging wheels to permit the wheelchair with an
occupant to enter the side door of a conventional van, as shown in Figure 2.
The occupant controlled fluid circuit is fully illustrated
in Figure 5. The applied legends on Figure 5 make such circuit self-explanatory.
It should be particularly noted that separate control of the vertical positions
of the powered wheels 3 and the caster wheels 4 relative to the frame 2 may be effected
by appropriate movement of the control stick 20 which is mechanically connected
to switch blades 20a and 20b.
The frame elevating and lowering fluid pressure cylinders
perform another desirable feature, particularly when such cylinders contain air
as the activating fluid. A conventional air bag can be employed. Since the fluid
pressure cylinders are respectively connected between the wheel mounting links 6
and 9 and the frame 2, the vertical movements of such links caused by a powered
wheel or a caster wheel encountering a ridge or depression are cushioned by the
fluid pressure cylinders, thus reducing shock forces imparted to the frame, hence
to the occupant of the wheelchair. Figure 6 illustrates the manner in which the
powered wheels 3 conform to a ridge in the road or ground surface by tilting of
the transaxle housing in a vertical plane. Obviously, the caster wheels 4 will equally
conform by tilting of the subframe 8 in a vertical plane. All of the wheels will
also ride through depressions with minimum shock to the occupant, as illustrated
in Figure 7.
Referring now to Figure 8 of the drawings, there is shown
a modification of this invention which is particularly suited for powered wheelchairs
having large transaxle housings 5. Such large transaxle housings would interfere
with the location of the fluid cylinders 12 as shown in Figure 1. Instead, the links
6 are extended forwardly as shown at 6a, and an airbag-type fluid cylinder 15 is
mounted between the frame 2 and a ledge 5m formed on the transaxle housing 5.
The functioning of this embodiment is the same as previously
described. Pressured air is supplied to, or withdrawn from airbags 15 which function
to raise or lower frame 2 relative to the power wheels 3 by pivoting the mounting
links 6 and stabilizing link 7. A similar airbag 15 is applied between stabilizing
link 10 and a projection 2m on frame 2 to control the vertical position of frame
2 relative to caster wheels 4. Such airbags thus function to reduce rough road shocks
transmitted to frame 2, without interfering with the vertical movements of powered
wheels 3 to follow the road or ground contours.