Wheelchair with lever drivetrain

Abstract

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 rear wheel and demountably coupled to a first drivetrain, the first lever having a first brake thereon;   a second lever associated with a second rear wheel and demountably coupled to a second drivetrain, the second lever having a second brake thereon;   wherein each drivetrain comprises 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.   
     
     
         2 . The wheelchair of  claim 1 , further comprising a single front wheel. 
     
     
         3 . The wheelchair of  claim 1 , wherein:
 the first lever is pivotable so that the first brake may contact the first wheel; and   the second lever is pivotable so that the second brake may contact the second wheel.   
     
     
         4 . The wheelchair of  claim 1 , further including a separate axle for each of the first and second rear 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 rear 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 rear 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 . The wheelchair of  claim 1 , further comprising:
 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 comprising 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 further comprising a second lever associated with a second rear wheel and demountably coupled to a second drivetrain, the second lever having a second brake thereon, the method 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 rear 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.