Self-contained steering guidance means

Abstract

A mechanical guidance mechanism is associated with each steerable wheel of a vehicle such as a fork lift truck. The guidance mechanism has a roller guidance member positioned to contact the guide surface laterally adjacent the vehicle. The roller is rotatably mounted on a slidable C-shaped channel member which is slidably disposed over a square bar. The square bar is rigidly, pivotally affixed to the vehicle. The other free end of the bar is pivotally fixed to the first lever at one end, which first lever has a fixed axis about which it pivots substantially midway between one end and an elongated slot on the other end. A second lever having a fixed pivot substantially midway between the ends thereof has a pin rigidly fixed to a first end which traverses the slot in the first lever. The other end of said second lever has a spring rigidly mounted thereon which is mechanically linked to a third lever pivotally fixed to the vehicle intermediate the ends thereof and having a free end thereof fixed to a wheel king pin so as to transmit turning motion to a wheel. A control valve is provided for rendering the hydraulic power system normally controlling the turning motion of the wheel into an inoperative condition whereby the mechanical guidance mechanism fully controls the turning of the wheel. Thus, the mechanical guidance mechanism provides for automatic guided steering of the vehicle in narrow aisle environments which is easily converted to operator control by means of a control valve when the vehicle is taken from a narrow aisle environment.