Anti-tip system for wheelchairs

An anti-tip system for a powered wheelchair (2, 202) for curb-climbing and ride stability includes at least one anti-tip wheel (16, 216), a suspension arm (24, 224) for mounting the anti-tip wheel and a pair of links (30, 34; 230, 234) coupling the suspension arm to the main structural frame (3, 203) of the wheelchair (2, 202). Each link (30, 34; 230, 234) is pivotally mounted to a main frame (3, 203) of the wheelchair (2, 202) about a first pivot point (P1A) and to the suspension arm (24) about a second pivot point (P2A, L1, L2). A lower link (34, 234) is connected by a third link (44, 244) to the drive wheel (6, 206) suspension (9, 209) and drive train (7, 207) so that the anti-tip wheel moves in response to forces on the drive wheel (6, 206) without being rigidly linked to the drive train (7, 207). In one embodiment an upper link (30) is extensible to facilitate angular displacement of the suspension arm (24) to permit rearward displacement of the anti-tip wheel (16) in response to an externally applied load.