Wheelchair suspension

Abstract

A wheelchair suspension includes a frame, a pivoting assembly, at least one front caster, and at least one rear caster. The pivoting assembly has a first link pivotally coupled to the frame member, a second link pivotally coupled to the frame member, a drive assembly fixedly connected to a first end of the first link, and a third link pivotally connected to the first link and pivotally connected to the second link. The drive assembly causes downward pivotal movement of the first end of the first link and upward pivotal movement of a second end of the first link. The upward pivotal movement of the second end of the first link causes the second link and the caster assembly to undergo upward movement.

1 . A wheelchair suspension defining a forward direction and a rearward direction of the wheelchair, the suspension comprising:
 a frame;   at least one main drive wheel for engaging the ground;   at least one front caster for engaging the ground forward of the main drive wheel; and   a pivoting assembly mounting the front caster to the frame so that the front caster can move upwardly and rearwardly when encountering an object, the pivoting assembly comprising an upper link and a lower link, the upper link being pivotally mounted to the front caster and to the frame at respective upper pivot axes, the lower link being pivotally mounted to the front caster and to the frame at respective lower pivot axes, the distance between the upper pivot axes being different than the distance between the lower pivot axes.   
     
     
         2 . The wheelchair suspension of  claim 1 , further comprising at least one rear caster for engaging the ground rearward of the main drive wheel, the front caster and rear caster being mounted with respect to the frame so that the front caster, the main drive wheel and the rear caster can all engage level ground at the same time, and further wherein the front caster is biased to normally remain in contact with the ground. 
     
     
         3 . The wheelchair suspension of  claim 1 , wherein the front caster is biased to remain in contact with the ground.