Means to reduce oscillatory deflection of vehicle

Abstract

A rough terrain vehicle comprises a vehicle chassis, resilient terrain-engaging wheel assemblies connected to the chassis and enabling vertical and angular deflection of the chassis relative to the terrain during vehicle movement, a telescopic crane boom carried by the chassis, a pivot pin for connecting the boom to the chassis and enabling limited reciprocable angular deflection of the boom relative to the chassis as the vehicle moves across supporting terrain and a hydraulic boom hoist cylinder to raise and lower the boom. A deflection reduction system is connected between the chassis and the boom to reduce or eliminate vertical and angular deflection (bouncing and porpoising) of the chassis relative to the terrain which tends to occur in response to dynamic loads imposed on the vehicle axles by movement across uneven terrain or by acceleration or deceleration of the vehicle. The deflection reduction system includes a resiliently compressible and expandable spring connected between the chassis and the boom and enables limited angular deflection of the boom relative to the chassis. The deflection reduction system further comprises a damping system connected between the chassis and the boom and to the spring to reduce the speed of spring motion as rapidly as possible to thereby dissipate the dynamic load. Preferably, the deflection reduction system is embodied in the boom hoist cylinder.