Wheelchair with lever drivetrain
A manually powered wheelchair includes a first lever associated with a first rear wheel and demountably coupled to a first drivetrain, the first lever having a first brake thereon. The wheelchair also includes a second lever associated with a second rear wheel and demountably coupled to a second drivetrain, the second lever having a second brake thereon. Each drivetrain includes a chainring, a chain, and a freewheel, and each drivetrain has a fixed gear ratio. The freewheel of each drivetrain is actuated by manual pivoting of the lever associated therewith. In use, the wheelchair achieves changes in mechanical advantage when a user shifts the user's hands up and down the first and second levers.
1. A manually powered wheelchair comprising:
a first lever associated with a first wheel and a second lever associated with a second wheel;
a first brake positioned on the first lever for engaging the first wheel and a second brake positioned on the second lever for engaging the second wheel; and
a first drivetrain to which the first lever is demountably coupled and a second drivetrain to which the second lever is demountably coupled, each drivetrain providing its respective lever with pivotal movement to propel the wheelchair only when the levers are pushed forward and to permit the brake on each lever to come in contact with the respective wheel when each lever is pulled backward beyond a predetermined angle;
wherein each of the first and second drivetrains include a chainring, a chain, and a freewheel, and each drivetrain has a fixed gear ratio; and
wherein the freewheel of each of the first and second drivetrains is actuated by manual pivoting of the lever associated therewith.
2. The wheelchair of claim 1 , further comprising a single front wheel.
3. The wheelchair of claim 1 , wherein the first lever when pivoting backwards within the predetermined angle permits a resetting of the first drivetrain for a next power stroke; and the second lever when pivoting backwards within the predetermined angle permits a resetting of the second drivetrain for a next power stroke.
4. The wheelchair of claim 1 , further including a separate axle for each of the first and second wheels.
5. The wheelchair of claim 1 , wherein the freewheel has 20 teeth.
6. The wheelchair of claim 5 , wherein the chainring has 36 teeth.
7. The wheelchair of claim 1 , wherein the freewheel has 18 teeth.
8. The wheelchair of claim 7 , wherein the chainring has 28 teeth.
9. The wheelchair of claim 1 , wherein the drivetrains permit a 4:1 change in mechanical advantage.
10. The wheelchair of claim 1 , wherein the drivetrains permit a 3:1 change in mechanical advantage.
11. The wheelchair of claim 1 , further comprising a footrest.
12. The wheelchair of claim 1 , wherein the first and second wheels are disposed parallel to one another.
13. The wheelchair of claim 1 , wherein a wheelbase of between about 60 cm and about 80 cm is provided between a front wheel and the first and second wheels.
14. The wheelchair of claim 1 , further comprising a back pad configured and dimensioned for being disposed between shoulder blades of a user of the wheelchair.
15. The wheelchair of claim 1 , further comprising a seat frame that is tapered such that the seat frame is wider proximate a user's hips than proximate the user's legs.
16. A manually powered wheelchair comprising:
a first lever associated with a first wheel and demountably coupled to a first drivetrain, the first lever having a first brake thereon;
a second lever associated with a second wheel and demountably coupled to a second drivetrain, the second lever having a second brake thereon;
a pair of drivetrains, each drivetrain having a chainring, a chain, and a freewheel, and each drivetrain has a fixed gear ratio; and
wherein the freewheel of each drivetrain is actuated by manual pivoting of the lever associated therewith;
a first cylinder for receiving the first brake and a first bracket for supporting a first main body of the first lever; and a second cylinder for receiving the second brake and a second bracket for supporting a second main body of the second lever.
17. A method of operating a wheelchair, the method comprising:
providing a wheelchair having a first lever associated with a first wheel a second lever associated with a second wheel, a first brake positioned on the first lever for engaging the first wheel and a second brake positioned on the second lever for engaging the second wheel, and a first drivetrain to which the first lever is demountably coupled and a second drivetrain to which the second lever is demountably coupled, each drivetrain providing its respective lever with pivotal movement to propel the wheelchair only when the levers are pushed forward and to permit the brake on each lever to come in contact with the respective wheel when each lever is pulled backward beyond a predetermined angle, the method further comprising:
changing hand position on the levers to change mechanical advantage.
18. The method of claim 17 , further comprising: moving hand position closer to a pivot point associated with the first lever to increase speed achieved by a power stroke.
19. The method of claim 17 , further comprising: moving hand position away from a pivot point associated with the first lever to increase torque at the first wheel.
20. The method of claim 17 , wherein hand position may be set over lever lengths between about 20 cm and about 86 cm.
21. The method of claim 17 , wherein hand position may be set over lever lengths between about 20 cm and about 60 cm.
22. The method of claim 17 , wherein a wheelbase of between about 50 cm and about 80 cm is provided between a front wheel and the first and second wheels.
23. The method of claim 17 , wherein the drivetrains permit a 4:1 change in mechanical advantage.
24. The method of claim 17 , wherein the drivetrains permit a 3:1 change in mechanical advantage.
25. The method of claim 17 , wherein each drivetrain has a fixed gear ratio.
26. The method of claim 17 , wherein a freewheel is actuated by manual pivoting of the first lever.
27. The method of claim 17 , wherein the wheelchair is moved by differentially powering at least one of the levers or applying at least one of the brakes.
28. A manually powered wheelchair comprising:
a first lever associated with a first wheel and demountably coupled to a first drivetrain, the first lever having a first brake thereon, and is pivotally movable to permit the first brake to come in contact with the first wheel when the first lever pivots backward beyond a predetermined angle;
a second lever associated with a second wheel and demountably coupled to a second drivetrain, the second lever having a second brake thereon, and is pivotably movable to permit the second brake to come in contact with the second wheel when the second lever pivots backward beyond a predetermined angle; and
a first cylinder for receiving the first brake and a first bracket for supporting a first main body of the first lever; and a second cylinder for receiving the second brake and a second bracket for supporting a second main body of the second lever;
wherein each of the first and second drivetrains include a chainring, a chain, and a freewheel, and each drivetrain has a fixed gear ratio; and
wherein the freewheel of each of the first and second drivetrains is actuated by manual pivoting of the lever associated therewith.
29. A manually powered wheelchair comprising:
a first lever associated with a first wheel and a second lever associated with a second wheel;
a first drive train to which the first lever is demountably coupled and a second drivetrain to which the second lever is demountably coupled, each drivetrain providing its respective lever with pivotal movement to propel the wheelchair only when the levers are pushed forward;
a first brake fixedly positioned on the first lever and a second brake fixedly positioned on the second lever, such that each brake moves along with its respective lever when each lever is pivotally pulled backward beyond a predetermined angle to permit the brake on each lever to frictionally engage the respective wheel.