Wheelchair suspension
View Patent ↗A wheelchair suspension includes a frame, a drive assembly pivot arm, a drive assembly, a front caster pivot arm, a front caster, and a spring and shock absorbing assembly. The drive assembly pivot arm is pivotally connected to the frame. The drive assembly includes a drive wheel and is mounted to the drive assembly pivot arm. The front caster pivot arm is pivotally mounted to the frame and coupled to the drive assembly pivot arm. The front caster is coupled to the at least one front caster pivot arm. The spring and shock absorbing assembly is pivotally connected to the drive assembly pivot arm at a first pivotal connection and pivotally connected to the front caster pivot arm at a second pivotal connection. The first and second pivotal connections are positioned such that a majority of the force applied by the spring and shock absorbing assembly is applied to the drive wheel when the suspension is on a flat, horizontal support surface.
1. A wheelchair suspension comprising:
a frame;
a drive assembly pivot arm pivotally connected to the frame;
a drive assembly including a drive wheel, wherein the drive assembly is mounted to the drive assembly pivot arm;
a front caster pivot arm pivotally mounted to the frame and coupled to the drive assembly pivot arm;
a front caster coupled to the at least one front caster pivot arm;
a spring and shock absorbing assembly pivotally connected to the drive assembly pivot arm at a first pivotal connection and pivotally connected to the at least one front caster pivot arm at a second pivotal connection;
wherein the first and second pivotal connections are positioned such that a majority of the force applied by the spring and shock absorbing assembly is applied to the drive wheel when the suspension is on a flat, horizontal support surface.
2. The wheelchair suspension of claim 1 wherein the drive assembly pivot arm and the front caster pivot arm are disposed in a crossed configuration such that the drive assembly pivot aim intersects the front caster pivot arm when viewed from the side when the wheelchair suspension is on the flat, horizontal support surface.
3. The wheelchair suspension of claim 1 wherein said majority of the force applied to the drive wheel is between 60% and 90% of the force.
4. The wheelchair suspension of claim 1 wherein said majority of the force applied to the drive wheel is between 60% and 70% of the force.
5. The wheelchair suspension of claim 1 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface.
6. The wheelchair suspension of claim 1 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 70 and 110 degrees when the suspension is on a flat, horizontal support surface.
7. The wheelchair suspension of claim 1 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
8. The wheelchair suspension of claim 1 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 10 degrees when the suspension is on a flat, horizontal support surface.
9. The wheelchair suspension of claim 1 wherein:
a. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface; and
b. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
10. The wheelchair suspension of claim 1 wherein:
a. a distance D 1 is defined from the first pivotal connection to a third pivotal connection where the drive assembly pivot arm is pivotally connected to the frame;
b. a distance D 2 is defined from the second pivotal connection to a fourth pivotal connection where the front caster pivot arm is pivotally connected to the frame; and
c. a ratio of D 1 /D 2 is 0.5 to 1.5.
11. The wheelchair suspension of claim 10 wherein said ratio is 0.75 to 1.25.
12. The wheelchair suspension of claim 10 wherein said ratio is 0.9 to 1.1.
13. The wheelchair suspension of claim 10 wherein:
a. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and the third pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface; and
b. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and the fourth pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
14. The wheelchair suspension of claim 1 further comprising at least one rear caster coupled to the frame.
15. The wheelchair suspension of claim 1 wherein the spring and shock absorbing assembly has a maximum length and is compressible from the maximum length to a shorter length.
16. The wheelchair suspension of claim 15 wherein pulling of the variable length motion transfer member when the variable length motion transfer member is at the maximum length pulls the front caster pivot arm to move the front caster away from the support surface.
17. A wheelchair comprising:
a frame;
a seat supported by the frame;
a pair of suspension assemblies disposed on opposite sides of the frame, each suspension assembly comprising:
a drive assembly including a drive wheel, wherein the drive assembly is mounted to the drive assembly pivot arm;
a front caster pivot arm pivotally mounted to the frame and coupled to the drive assembly pivot arm;
a front caster coupled to the at least one front caster pivot arm;
a spring and shock absorbing assembly pivotally connected to the drive assembly pivot aim at a first pivotal connection and pivotally connected to the at least one front caster pivot arm at a second pivotal connection;
wherein the first and second pivotal connections are positioned such that a majority of the force applied by the spring and shock absorbing assembly is applied to the drive wheel when the suspension is on a flat, horizontal support surface.
18. The wheelchair of claim 17 wherein the drive assembly pivot arm and the front caster pivot arm are disposed in a crossed configuration such that the drive assembly pivot arm intersects the front caster pivot arm when viewed from the side when the wheelchair suspension is on the flat, horizontal support surface.
19. The wheelchair of claim 17 wherein said majority of the force applied to the drive wheel is between 60% and 90% of the force.
20. The wheelchair of claim 17 wherein said majority of the force applied to the drive wheel is between 60% and 70% of the force.
21. The wheelchair of claim 17 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface.
22. The wheelchair of claim 17 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 70 and 110 degrees when the suspension is on a flat, horizontal support surface.
23. The wheelchair of claim 17 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
24. The wheelchair of claim 17 wherein an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 10 degrees when the suspension is on a flat, horizontal support surface.
25. The wheelchair of claim 17 wherein:
a. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface; and
b. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and a pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
26. The wheelchair of claim 17 wherein:
a. a distance D 1 is defined from the first pivotal connection to a third pivotal connection where the drive assembly pivot arm is pivotally connected to the frame;
b. a distance D 2 is defined from the second pivotal connection to a fourth pivotal connection where the front caster pivot arm is pivotally connected to the frame; and
c. a ratio of D 1 /D 2 is 0.5 to 1.5.
27. The wheelchair of claim 26 wherein said ratio is 0.75 to 1.25.
28. The wheelchair of claim 26 wherein said ratio is 0.9 to 1.1.
29. The wheelchair of claim 26 wherein:
a. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and the third pivotal connection where the drive assembly pivot arm is pivotally connected to the frame is between 60 and 120 degrees when the suspension is on a flat, horizontal support surface; and
b. an angle between a line that connects the first and second pivotal connections and line that connects the first pivotal connection and the fourth pivotal connection where the front caster pivot arm is pivotally connected to the frame is between 0 and 30 degrees when the suspension is on a flat, horizontal support surface.
30. The wheelchair of claim 17 further comprising at least one rear caster coupled to the frame.
31. The wheelchair of claim 17 wherein the spring and shock absorbing assembly has a maximum length and is compressible from the maximum length to a shorter length.
32. The wheelchair of claim 31 wherein pulling of the spring and shock absorber assembly when the spring and shock absorber assembly is at the maximum length pulls the front caster pivot arm to move the front caster away from the support surface.