초록 ▼

A bi-directional anti-tip system for a wheelchair includes a pair of anti-tip system subassemblies actively lifting a leading anti-tip wheel when traveling in either forward or reverse directions. The anti-tip system subassemblies operate to couple a leading anti-tip wheel to the drive assembly such

A bi-directional anti-tip system for a wheelchair includes a pair of anti-tip system subassemblies actively lifting a leading anti-tip wheel when traveling in either forward or reverse directions. The anti-tip system subassemblies operate to couple a leading anti-tip wheel to the drive assembly such that pivot motion thereof effects vertical displacement of the leading anti-tip wheel and to decouple a trailing anti-tip wheel from the drive assembly to null pivot motion inputs therefrom. In one embodiment, rheonetic links actively couple and decouple the anti-tip system subassemblies. The system may also include compliant bearings or extensible links for inward displacement of the anti-tip wheel upon impact with a curb.

대표청구항 ▼

What is claimed is: 1. A wheelchair comprising: a seat; a frame supporting the seat; a pair of drive wheels supporting and mobilizing the frame; a drive system capable of propelling the wheelchair forwardly and rearwardly, the drive system including a pair of drive assemblies pivotally mounted to t

What is claimed is: 1. A wheelchair comprising: a seat; a frame supporting the seat; a pair of drive wheels supporting and mobilizing the frame; a drive system capable of propelling the wheelchair forwardly and rearwardly, the drive system including a pair of drive assemblies pivotally mounted to the frame at a pivot axis, each said drive assembly applying input torque to one of the drive wheels; at least one bi-directional anti-tip system including a pair of anti-tip assemblies mounted to the frame and disposed on opposite sides of the drive pivot axis, each of the anti-tip assemblies including an anti-tip wheel, each anti-tip wheel alternately being a leading anti-tip wheel or a trailing anti-tip wheel depending on the direction in which the drive system is propelling the wheelchair, the bi-directional anti-tip system operative to (i) couple the leading anti-tip wheel to one of the drive assemblies such that a pivoting motion thereof effects vertical displacement of the leading anti-tip wheel, and to simultaneously (ii) decouple the trailing anti-tip wheel from the drive assembly to null pivot motion inputs therefrom, and a suspension assembly biasing the anti-tip wheels to a predetermined operating position. 2. The wheelchair according to claim 1, wherein each of the anti-tip assemblies includes a wheel mount rotatably supporting the associated wheel and a bell-crank link pivotably connected to the frame at a pivot axis, the bell-crank link having a first portion connected to the wheel mount and a second portion connected to the first portion at the bell-crank pivot axis, and wherein the anti-tip system includes an actuator link connected to the one of the drive assemblies, the actuator link also connected to the bell-crank link of each anti-tip assembly, the bell-crank link of each anti-tip assembly carrying a pin received in a slot formed in the actuator link to provide sliding motion between the actuator link and the anti-tip assembly when the anti-tip assembly is decoupled. 3. The wheelchair according to claim 1, wherein each anti-tip assembly includes a wheel mount rotatably supporting the associated wheel and a bell-crank link pivotably connected to the frame at a pivot axis, the bell-crank link having a first portion connected to the wheel mount and a second portion connected to the first portion at the bell-crank pivot axis, and wherein the anti-tip system includes an actuator link connected to the one of the drive assemblies, the actuator link having first and second portions each connected to the bell-crank link of one of the anti-tip assemblies, and wherein at least one of the portions of the actuator link comprises a rheonetic device including a cylinder and a piston slidingly received by the cylinder, the rheonetic device having first and second operating states respectively permitting and preventing relative motion between the piston and cylinder to either couple or decouple one of the anti-tip assemblies depending on the operating state of the rheonetic device. 4. The wheelchair according to claim 1, wherein each anti-tip assembly includes a wheel mount rotatably supporting the associated wheel and a link pivotably connected to the wheel mount and to the frame at a link pivot axis, and wherein the anti-tip system includes at least one rotary rheonetic device connected to the link of one of the anti-tip assemblies and supported by the frame at the link pivot axis, the at least one rotary rheonetic device having first and second portions pivotably connected to each other, the at least one rotary rheonetic device having first and second operation states respectively permitting and preventing relative pivot between the first and second portions to either couple or decouple the associated anti-tip assembly depending on the operating state of the at least one rotary rheonetic device. 5. A bi-directional anti-tip system for a power wheelchair having a frame, the wheelchair having a drive system capable of propelling the wheelchair forwardly and rearwardly, the drive system pivotably mounted to the frame, the bi-directional anti-tip system comprising: a pair of anti-tip assemblies mounted to the frame, each anti-tip assembly including an anti-tip wheel rotatably supported by a wheel mount, the anti-tip wheel of one of the anti-tip assemblies located forwardly of the frame and the anti-tip wheel of the other one of the anti-tip assemblies located rearwardly of the frame, each anti-tip wheel being a leading anti-tip wheel or a trailing anti-tip wheel depending on the direction in which the drive system is propelling the wheelchair, each anti-tip assembly including at least one link pivotably connected to the wheel mount and to the frame for elevating the anti-tip wheel from a normal wheel position; and an actuator assembly connected to each anti-tip assembly and to the drive system, the actuator assembly adapted to simultaneously (i) couple the leading anti-tip wheel to the drive system such that a pivoting motion thereof effects vertical displacement of the leading anti-tip wheel, and (ii) decouple the trailing anti-tip wheel from the drive system to null pivot motion inputs therefrom. 6. A wheelchair comprising: a frame; a drive system including a motor capable of propelling the wheelchair forwardly and rearwardly, the drive system mounted to the frame for pivot about a pivot axis in response to a torque generated by the motor, the drive system respectively pivoting in opposite first and second pivot directions from a neutral motor position during forward and rearward propulsion of the wheelchair; and a bi-directional anti-tip system having front and rear anti-tip assemblies each including a wheel rotatably supported by a wheel mount and a linkage including at least one link pivotably connected to the frame and to the wheel mount to elevate the wheel from a normal wheel position when the linkage is pivoted, the front and rear wheels respectively located forwardly and rearwardly of the frame, the anti-tip system also having a linkage actuator pivotably connected to each of the front and rear anti-tip assemblies and to the drive system, the anti-tip system adapted to couple the linkage actuator and the front linkage during pivot of the drive system in the first direction for pivot of the front linkage while simultaneously nulling pivot motion of the rear linkage, the anti-tip system further adapted to couple the linkage actuator and the rear linkage during pivot of the drive system in the second direction for pivot of the rear linkage while simultaneously nulling pivot motion of the front linkage. 7. The wheelchair according to claim 6, wherein the linkage actuator comprises an elongated bar and wherein at least one of the front and rear anti-tip assemblies includes a pin received in a slot of the bar to provide for sliding translation between the linkage actuator and the anti-tip assembly. 8. The wheelchair according to claim 6 further comprising a suspension system supported by the frame to bias the drive system towards the neutral motor position. 9. The wheelchair according to claim 6, wherein the linkage of each of the front and rear anti-tip assemblies includes a pair of substantially parallel links, each pivotably connected at one end to the frame and pivotably connected at an opposite end to a wheel mount member of the anti-tip assembly. 10. The wheelchair according to claim 6, wherein each of the front and rear linkages of the bi-directional anti-tip system includes a bell crank link having a first portion pivotably connected to the frame at one end at a link pivot location and pivotably connected to a wheel mount member at an opposite end, the bell crank link further including a second portion connected to the first portion at the link pivot location, the second portion of the bell crank link connected to the linkage actuator to pivot the linkage when drivingly engaged by the linkage actuator. 11. The wheelchair according to claim 9, wherein the wheel mount member of at least one of the front and rear anti-tip assemblies comprises an elastic bearing including a housing defining an interior, an inner shaft located within the housing interior and at least one elastic element disposed between the shaft and an inner surface of the housing, the associated wheel operably connected to the inner shaft of the elastic bearing. 12. The wheelchair according to claim 9, wherein one of the substantially parallel links is extensible to provide for pivoting of the wheel mount member with respect to the parallel links without pivot of the parallel links with respect to the frame. 13. The wheelchair according to claim 12, wherein the extensible link includes first and second portions and a connecting mechanism, the connecting mechanism including a rod slidingly received in openings defined by each of the first and second link portions, the connecting mechanism also including a spring engaging the rod such that the first and second link portions are biased towards each other. 14. The wheelchair according to claim 6, wherein the normal wheel position for the wheel of each of the front and rear anti-tip assemblies results in contact between the wheel and a substantially level ground surface on which the wheelchair is supported. 15. The wheelchair according to claim 6, wherein the anti-tip system includes at least one rheonetic device having first and second portions connected to each other, the at least one rheonetic device having first and second operating states respectively permitting and preventing relative motion between the first and second portions of the at least one rheonetic device, the at least one rheonetic device arranged to either provide for driving pivot of the linkage of one of the anti-tip assemblies or null pivot movement of the linkage depending on the operating state of the at least one rheonetic device. 16. The wheelchair according to claim 15, wherein the at least one rheonetic device is included in the linkage actuator and wherein each of the at least one rheonetic device is a linear device including a cylinder and a piston slidingly received by the cylinder. 17. The wheelchair according to claim 16, wherein each of the at least one rheonetic device is a rotary rheonetic device having first and second portions arranged for relative pivot between the portions when the at least one rheonetic device is in the first operating state, and wherein the at least one rheonetic device is supported by the frame at a location where a link of one of the front and rear linkages is pivotably connected to the frame.