Forklift apparatus for unloading articles from an elevated surface

Abstract

An improved forklift device for unloading palletized articles from the bed of a flatbed truck may be removably carried in 'piggyback' fashion on the rear end of the truck. The device has a fork structure adapted to liftingly engage one of the pallets, a wheeled, ground-supportable frame, and an articulated linkage structure which interconnects the frame and the fork structure and is movable between a fully lowered and rearwardly retracted position and a fully raised and forwardly extended position. The forklife may be propelled along the ground by an engine-driven hydraulic drive system, and is also provided with a hydraulic actuating system for pivoting gantry and boom portions of the linkage, and pivoting the fork structure relative to the linkage. In unloading the articles the fork structure may be moved a substantial distance laterally across the truck bed to liftingly engage the pallet of an article on the far side of the bed. The removed load may be lowered using an automatic mode portion of the actuation system which moves the articulated linkage to its fully lowered and retracted position while maintaining the fork structure in a fixed pivotal orientation relative to the ground. The forklift is provided with a variety of safety features including an anti-tipping system which senses a tipping load moment and responsively prevents the actuating system from moving the articulated linkage in a manner appreciably increasing such load moment, and preventing movement of the forklift away from the truck during unloading of an article.