HK1069304B - Wheelchair suspension having pivotal motor mount - Google Patents

Description

FIELD OF THE INVENTION

The invention relates generally to conveyances and, more particularly, to wheelchair suspensions capable of traversing an obstacle or rough terrain.

BACKGROUND OF THE INVENTION

Wheelchairs are an important means of transportation for a significant portion of society. Whether manual or powered, wheelchairs provide an important degree of independence for those they assist. However, this degree of independence can be limited if the wheelchair is required to traverse obstacles such as, for example, curbs that are commonly present at sidewalks, driveways, and other paved surface interfaces.

In this regard, most wheelchairs have front and rear casters to stabilize the chair from tipping forward or backward and to ensure that the drive wheels are always in contact with the ground. One such wheelchair is disclosed in US-A-5,435, 404 . On such wheelchairs, the caster wheels are typically much smaller than the driving wheels and located both forward and rear of the drive wheels. Though this configuration provided the wheelchair with greater stability, it made it difficult for such wheelchairs to climb over obstacles such as, for example, curbs or the like, because the front casters could not be driven over the obstacle due to their small size and constant contact with the ground.

US A-5,964,473 describes a wheelchair having front and rear casters similar and a pair of additional forward lift wheels. The lift wheels are positioned off the ground and slightly forward of the front caster. Configured as such, the lift wheels first engage a curb and cause the wheelchair to tip backwards. As the wheelchair tips backwards, the front caster raises off the ground to a height so that it either clears the curb or can be driven over the curb.

US A6,196,343 also describes a wheelchair having front and rear casters. The front casters are each connected to a pivot arm that is pivotally attached to the sides of the wheelchair frame. Springs bias each pivot arm to limit the vertical movement thereof. So constructed, each front caster can undergo vertical movement when driven over an obstacle.

While the above-mentioned art provides various wheelchair configurations for traversing obstacles, a need still exists for a more complete wheelchair suspension.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a wheelchair suspension according to claim 1.

According to another aspect of the present invention, there is provided a wheelchair suspension according to claim 11.

The present invention provides a suspension for a conveyance such as, for example, a wheelchair, that is capable of traversing obstacles and rough terrain. In this regard, the suspension has a frame member and a pivoting assembly. The pivoting assembly has a pivot arm and a drive assembly. The pivot arm is pivotally coupled to the frame and has a first engagement surface. The drive assembly is pivotally coupled to the frame and has a second engagement surface configured to engage the first engagement surface. The second engagement surface is further configured to disengage from the first engagement surface upon pivotal movement of the drive assembly in a first direction and to re-engage the first engagement surface upon pivotal movement of the drive assembly in a second direction. Configured as such, pivotal motion of the drive assembly in a first direction causes pivotal motion of the pivot arm, while pivotal motion of the drive assembly in a second direction does not cause any pivotal motion of the pivot arm.

Therefore, it is an advantage of the present invention to provide a suspension system having a pivotal drive assembly.

It is yet another advantage of the present invention to provide a suspension system having a pivot arm and a pivoting drive assembly wherein pivotal movement of the drive assembly engages the pivot arm during pivotal motion in a first direction and disengages from the pivot arm during pivotal motion in a second direction.

It is still further an advantage of the present invention to provide a wheelchair suspension that maintains all of its wheels in contact with the ground when traversing rough terrain. In a preferred embodiment of the invention, the first engagement surface comprises a shoulder and the second engagement surface comprises a cylindrical shape. The first engagement surface comprises at least a partially undulating surface and the cylindrical shape is received by the undulating surface. Advantageously, the second engagement surface comprises a shape configured to be at least partially seated within the at least partially undulating surface. The pivot arm and the drive assembly are pivotally coupled to the frame at a common location on the frame, and the pivoting assembly further comprises a resilient member for regulating the disengagement of the second engagement surface from the first engagement surface. The pivot arm further comprises first and second ends, the first end has a castor assembly coupled thereto and the second end comprises the first engagement surface, and the common pivot location is between the first and second ends.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly and completely disclosed, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a perspective view of a wheelchair incorporating a suspension in accordance with the present invention.

Figure 2 is an exploded perspective view of, certain components of the wheelchair of Figure 1.

Figure 3 is an exploded detail view of certain components of a frame and pivot assembly in accordance with the present invention.

Figures 4A and 4B are side elevational views of the frame and pivot assembly under static conditions.

Figure 5 is a side elevational view of the frame and pivot assembly traversing an obstacle by ascending an obstacle.

Figures 6A and 6B are further side elevational views of the frame and pivot assembly traversing an obstacle by ascending the obstacle.

Figures 7,8, and 9 are side elevational views of a second embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The present invention provides a suspension system having a pivot arm and a pivoting drive assembly wherein pivotal movement of the drive assembly engages the pivot arm during pivotal motion in one direction and disengages from the pivot arm during pivotal motion in a second direction. When the drive assembly is engaged with the pivot arm, moment arms generated by the drive assembly facilitate upward pivotal movement of the pivot arm to traverse obstacles and rough terrain. In this scenario, the drive assembly and pivot arm pivot act together thereby raising the front castor attached to the pivot arm. Disengagement of the drive assembly from the pivot arm facilitates a smoother ride because the drive assembly can pivot independently of the pivot arm. In this scenario, the drive assembly and pivot arm have independent pivotal motion and function as two separate components.

Referring now to Figure 1, a wheelchair 100 of the present invention is shown. Wheelchair 100 has a seat 102, drive wheels 104 and 106, front casters 108 and 110, and rear casters 112 and 114 (caster 114 shown in Figure 2). Wheelchair 100 further has one or more footrests 116 and control circuitry for driving and steering the wheelchair. Wheelchair 100 is preferably configured as a mid-wheel drive wheelchair although other configurations are also possible.

Illustrated in Figure 2 is an exploded prospective view of wheelchair 100. In this regard, wheelchair 100 further has a frame 206 to which seat 102, front casters 108 and 110, and rear casters 112 and 114 are coupled. As will be described in more detail with reference to Figure 3, wheelchair 100 has drive assemblies 202 and 204 and pivot arms 208 and 210 pivotally coupled to frame 206. Springs 212 and 214 are provided between pivot arms 208 and 210 and frame 206 to limit the amount of pivotal motion the arms can undergo. Additionally, a tension bar 216 is attached to and between pivot arms 208 and 210 to limit the amount of independent pivotal motion each arm can undergo before the other arm is influenced. The tension bar 216 is preferably made of a resilient spring-like metal that can undergo a limited amount of deformation or twisting and still return to its original shape or configuration. Batteries 218 are also provided and fit within frame 206 for providing power to drive assemblies 202 and 204.

Referring now to Figure 3, an exploded prospective view of frame 206, pivot arm 208, and drive assembly 202 is provided. In this regard, frame 206 has a plurality of sub-members 302, 304, 306, and 308 coupled together as shown. In the preferred embodiment, frame sub-members 302, 304, 306, and 308 are preferably made of metal and welded together. Frame 206 further has a bracket 303 coupled to frame sub-member 302. Bracket 303 can be U-shaped having two spaced apart longitudinal extensions joined by a mid-section wherein the longitudinal extensions each have co-centered apertures therein for pivotally securing pivot arm 208 and drive assembly 202. Alternatively, bracket 303 can have two spaced apart longitudinal extensions that are welded or otherwise affixed to the bottom portion of frame sub-member 302 and include co-centered apertures for once again pivotally securing pivot arm 208 and drive assembly 202. Frame sub-member 304 has a similar bracket coupled thereto, but not shown.

Pivot arm 208 is preferably formed of tubular metal construction and has a head tube 316 for coupling a front caster thereto and a pivot arm engagement interface 314 for engaging drive assembly 202. As shown, head tube 316 is at the forward portion of pivot arm 208 and engagement interface 314 is to the rear portion thereof. Pivot arm 208 further has a pivotal mounting 310 that is between head tube 316 and engagement interface 314. Pivotal mounting 310 is preferably in the form of a cylindrical member that is either formed or attached to the body of pivot arm 208. Pivot arm 208 further has a spring seat 312 that aligns with a spring seat 307 for receiving and retaining compression spring 212 (compression spring 212 shown in Figure 2). Pivot arm 210 is of similar construction.

Drive assembly 202 preferably has a motor/gearbox sub-assembly for driving one of the drive wheels and a pivotal mounting bracket 318. Alternately, the motor/gearbox assembly can be replaced with a brushless gearless motor drive. Pivotal mounting bracket 318 is in the form of a U-shaped bracket having spaced apart longitudinal members 319 joined by a mid-section at one of their ends. The mid-section is preferably used for mechanically attaching the motor/gearbox sub-assembly. The spaced apart longitudinal members 319 have projecting ear portions with co-centered apertures 320. Pivotal mounting bracket 318 further has a seat 328 for receiving a vertically-oriented compression spring 326 and its lower seat member 332. The upper portion of compression spring 326 along with upper seat member 330 are received within engagement interface 314 by a similar seat. In this regard, engagement interface 314 has a hollow space portion (not shown) for providing this configuration.

Drive assembly 202 further has a drive assembly engagement interface for engaging pivot arm 208. The drive assembly engagement interface has a pin or bolt 324 and co-centered apertures 322 in the longitudinal extensions 319 of pivotal mounting bracket 318. As will be presently described, the engagement interfaces of the drive assembly 202 and pivot arm 208 engage and disengage from each other under certain operating conditions.

Configured as such, pivot arm 208 and its pivotal mounting 310 are received within the longitudinal extensions 319 of pivotal mounting bracket 318 of drive assembly 202 with spring 326 seated in place. This sub-assembly is then received within the longitudinal extensions of mounting bracket 303 and the co-centered apertures therein. This entire assembly is then pivotally secured with a pin or bolt 334 that passes through the mounting bracket 303, drive assembly 202 bracket 318, and pivot arm 208 mounting tube 310. So formed, wheelchair 100 is provided with a suspension system wherein the drive assembly and pivot arm have a common pivotal coupling to the frame.

Referring now to Figures 4A and 4B, an elevational view of the suspension of wheelchair 100 under static conditions (i.e., no acceleration or deceleration) is shown. In this regard, all of the caster and drive wheels are in contact with the wheelchair supporting or driving surface. More specifically, the summation of the moment arms around pivot P is zero and, therefore, neither pivot arm 208 or drive assembly 202 undergo pivotal motion. Furthermore, spring 326 (shown in Figure 3) urges the drive assembly engagement interface 324 into physical engagement with pivot arm engagement interface 314. More specifically, the force generated by spring 326 causes a surface of drive assembly engagement interface 324 to bear down upon engagement surface 402.

As shown more clearly in the enlarged detail 404 of Figure 4B, pivot arm engagement interface 314 has an engagement surface 402 that is undulating in character and at least partially configured to receive drive assembly engagement interface 324. In this regard, engagement surface 402 is in the form a shoulder. However, any physical configuration that allows for the engagement and disengagement of drive assembly engagement surface 324 is contemplated.

Illustrated in Figure 5 is an elevational view of the suspension of wheelchair 100 traversing over an obstacle 500 by ascending the obstacle. This operating condition is accomplished by either rapidly accelerating wheelchair 100 in the forward direction or directly driving front caster 108 over obstacle 500. In this scenario, the moment arm generated by drive wheel 104 is greater then all other moment arms around pivot P. This causes drive assembly 202 to pivot counter-clockwise around pivot P. As such, drive assembly engagement interface 324 also pivots counter-clockwise around pivot P. In this scenario, drive assembly engagement interface 324 comes into engagement or already is in engagement with pivot arm engagement interface 314, thereby causing pivot arm 208 to also pivot counter-clockwise around pivot P. During this engagement, drive assembly engagement interface 324 is in physical contact with pivot arm engagement interface 314, as shown in Figure 4B. This causes front caster 108 to rise above obstacle 500 or to be driven over obstacle 500. Hence, engagement interfaces 314 and 324 translate the pivotal motion of drive assembly 202 to pivot arm 208 to thereby raise front caster 108 to traverse obstacle 500.

Referring now to Figures 6A and 6B, a side elevational view of the suspension of wheelchair 100 with drive wheel 104 traversing obstacle 500 is shown. In this regard, when drive wheel 104 comes into contact with obstacle 500, drive assembly 202 pivots in a clockwise direction around pivot P to soften the impact from obstacle 500. In Figure 6A, the dashed outline 602 of drive assembly 202 represents the drive assembly's position prior to encountering obstacle 500 and the solid representation of drive assembly 202 represents its position after pivotal movement caused by encountering obstacle 500. During such pivotal movement, the drive assembly engagement interface 324 and the pivot arm engagement interface 314 physically disengage from each other. This state is more clearly shown in Figure 6B wherein drive assembly engagement interface 324 is spaced apart from pivot arm engagement surface 402. The pivotal movement of drive assembly 202 is limited by spring 326 (shown in Figure 3), which dampens the impact caused by the obstacle 500. After traversing obstacle 500, spring 326 causes drive assembly 202 to pivot counter-clockwise back to its position prior to encountering obstacle 500. This position includes the physical engagement between drive assembly engagement interface 324 and pivot arm engagement interface 314.

Illustrated in Figure 7 is a side elevational view of a second embodiment of the present invention. The second embodiment differs from the first in that the drive assembly 202 and the pivot arm 208 are rigidly coupled together. That is, the drive assembly 202 does not pivot independently of pivot arm 208. As a matter of design choice, springs 326 and 327 may or may not be used with this embodiment. This arrangement is facilitated by providing a latching mechanism between drive assembly 202 and pivot arm 208. The latching assembly is in the form of a permanently welded or fastened pin 702. More specifically, pivotal mounting bracket 318 and pivot arm engagement interface 314 have co-centered apertures therein for receiving pin 702, which is then permanently affixed to either pivotal mounting bracket 318 and/or pivot arm engagement interface 314. In alternate embodiments, pin 702 can be a quick-release pin, threaded bolt, or screw allowing for a less permanent coupling. This would allow a user to determine whether the drive motor assembly is pivotal or rigid with respect to the pivot arm 208 and frame 206.

Figure 8 illustrates the second embodiment when traversing obstacle 500 by ascending the obstacle. This operating condition is accomplished by either rapidly accelerating wheelchair 100 in the forward direction or directly driving front caster 108 over obstacle 500. In this scenario, the moment arm generated by drive wheel 104 is greater then all other moment arms around pivot P. This causes drive assembly 202 to pivot counter clockwise around pivot P. Since drive assembly 202 is rigidly coupled to pivot arm 208 by pin 702, pivot arm 208 also pivots counter-clockwise around pivot P so as to lift front caster 108 to traverse obstacle 500.

Illustrated in Figure 9 is a side elevational view of the suspension of wheelchair 100 with drive wheel 104 traversing obstacle 500. In this regard, when drive wheel 104 comes into contact with obstacle 500, drive assembly 202 pivots in a clockwise direction around pivot P and causes pivot arm 208 and caster 208 to be brought down onto the lower driving surface elevation. Drive assembly 202 and pivot arm 208 act in unison owing to their rigid coupling via pin 702, as described above. Springs 212 assist in this scenario by also urging pivot arm 208 to rotate about pivot P in clockwise direction. By causing pivot arm 208 and caster 108 to be brought down onto the lower driving surface elevation, the second embodiment provides the wheelchair with greater stability when traversing obstacle 500 and ensures that all of the wheelchair's wheels stay in constant contact with the wheelchair driving surface.

While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, a plurality of casters can be used instead of one caster, one well-known latching means can be substituted for another, and the wheelchair component geometry can deviate from that shown without departing from the operative teaching herein. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures can be made from such details without departing from the scope of the invention as defined by the followings Claims.

Claims (20)

1. A wheelchair suspension comprising:

   a frame (206)

   a front caster (108) coupled to the frame (206);

   a rear caster (112) coupled to the frame (206);

   a drive wheel (104) coupled to the frame (206) between the front caster (108) and the rear caster (112); and a pivoting assembly having:

   a pivot arm (208) having the front caster (108) coupled thereto, wherein the pivot arm (208) is pivotally coupled to the frame (206); and

   a drive assembly (202) for driving the drive wheel (104) and pivotally coupled to the frame (206);

   wherein said pivot arm (208) and said drive assembly (202) have respective first and second engagement surfaces of which the second is configured to engage the first; and

   wherein the second engagement surface is configured to disengage from the first engagement surface upon pivotal movement of the drive assembly (202) in a first direction, such that upward pivotal movement of the pivot arm (208) is facilitated when the drive assembly is engaged.
2. A suspension according to claim 1, wherein the first engagement surface is undulating.
3. A suspension according to claim 1 or 2, wherein the first engagement surface comprises a shoulder.
4. A suspension according to any preceding claim, wherein the second engagement surface (324) comprises a cylindrical shape.
5. A suspension according to claim 4 as appended to claim 2, wherein the cylindrical shape is received by the undulating surface.
6. A suspension according to any preceding claim, wherein the pivot arm (208) and the drive assembly (202) are pivotally coupled to the frame (206) at a common location on the frame (206).
7. A suspension according to any preceding claim, and further comprising a resilient member (326) for regulating the disengagement of the second engagement surface from the first engagement surface.
8. A suspension according to any preceding claim, wherein one end of the pivot arm (208) has a castor assembly that includes the front caster (108) coupled thereto and wherein the other end thereof comprises the first engagement surface.
9. A suspension according to claim 8 as appended to claim 6, wherein said common location is between said one end and said other end.
10. A suspension according to any preceding claim and further comprising means enabling said drive assembly (202) and said pivot arm (208) to be rigidly coupled together.
11. A wheelchair suspension comprising:

    a frame (206)

    first and second front casters (108,110) coupled to the frame (206) and at respective first and second opposite sides of the frame (206);

    first and second rear casters (112,114) coupled to the frame (206) and at said respective first and second opposite sides;

    first and second drive wheels (104,106) coupled to the frame (206) between the first and second front casters (108,110) and the first and second rear casters (112,114); and first and second pivoting assemblies having:

    respective pivot arms (208,210) having the front casters (108,110) coupled thereto, wherein the pivot arms (208,210) are pivotally coupled to the frame (206); and

    respective drive assemblies (202,204) for driving the respective drive wheels (104,106) and pivotally coupled to the frame (206);

    wherein each pivot arm (208,210) and its associated drive assembly (202,204) have respective first and second engagement surfaces of which the second is configured to engage the first; and

    wherein each second engagement surface is configured to disengage from its associated first engagement surface upon pivotal movement of its associated drive assembly (202,204) in a first direction, such that upward pivotal movement of the pivot arms (208,210) is facilitated when the drive assembly is engaged.
12. A suspension according to claim 11, wherein each first engagement surface is undulating .
13. A suspension according to claim 11 or 12, wherein each first engagement surface comprises a shoulder.
14. A suspension according to any one of claims 11 to 13, wherein each second engagement surface comprises a cylindrical shape.
15. A suspension according to claim 14 as appended to claim 12, wherein each cylindrical shape is received by its associated undulating surface.
16. A suspension according to any one of claims 11 to 15, wherein each pivot arm (208,210) and its associated drive assembly (202,204) are pivotally coupled to the frame (206) at a common location on the frame (206).
17. A suspension according to any one of claims 11 to 16 and further comprising, in each pivoting assembly, a resilient member (326,327) for regulating the disengagement of its associated second engagement surface from its associated first engagement surface.
18. A suspension according to any one of claims 11 to 17, wherein one end of each pivot arm (208, 210) has a castor assembly that includes its associated front caster (108,110) coupled thereto and wherein the other end thereof comprises the associated first engagement surface.
19. A suspension according to claim 18 as appended to claim 16, wherein, for each pivoting assembly, said common location is between said one end and said other end of the associated pivot arm (208,210).
20. A suspension according to any preceding claim and further comprising, for each pivoting assembly, means enabling its associated drive assembly (202) and its associated pivot arm (208) to be rigidly coupled together.