US Patent 9320661 Electric mid-wheel drive wheelchair

A wheelchair of the mid-wheel drive type has a chassis frame (10), a pair of front link arms (30) and a pair of rear link arms. The link arms are pivotally connected to the chassis frame. Front caster wheels (32) and drive wheels (53) are fixed to the front link arms. Rear caster wheels (42) are fixed to the rear link arms. Each front link arm (30) is operatively connected to an adjacent rear link arm (40) by a respective coupling (70), which is arranged to transmit pivotal movement of one of the front (30) and rear (40) link arm to an opposite pivotal movement of the other of the front (30) and rear (40) link arm.