HOOK-MOUNTED VERTICAL MOTION COMPENSATION APPARATUS

HOOK-MOUNTED VERTICAL MOTION COMPENSATION APPARATUS Disclosed is a self-contained vertical motion compensation unit adapted to be carried by a crane hook between the crane hook and the load. The unit includes a cylinder and piston assembly which supports the load on a compensated hook and automatically varies the distance between the crane hook and the compensated hook to compensate for relative vertical movement of the platform supporting the crane and the platform to or from which the load is to be transferred. Sensors which generate a signal in response to be vertical movement are associated with each platform which is movable with respect to a fixed horizontal position. Signals from the sensors are used to control the position of the piston in the cylinder and thereby vary the vertical separation between the compensated hook and the crane hook in relation to relative vertical movement between the crane boom and the landing platform.