Patent ID: 7264272

Claim:
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.