US Patent 8690171 Individually steered rear axle for dual path steered vehicles

A caster wheel assembly selectively providing steering assist includes a pivoting shaft coupled with a caster wheel with an engagement lug connected to the shaft in a fixed manner. A steering arm selectively engages the engagement lug to couple the steering arm and engagement lug so that pivoting motion of the steering arm is transferred to the engagement lug. A turn assist cylinder connects to an outward end of the steering arm and an engagement mechanism acting upon the steering arm for engaging the steering arm with the engagement lug. When engaged, the steering arm is coupled with the engagement lug such that the turn assist cylinder pivots the shaft and caster wheel. When disengaged, the steering arm is uncoupled with the engagement lug such that the shaft and caster wheel are free to pivot independent of the turn assist cylinder.