Crane control means employing load sensing devices

Abstract

A large mobile tower crane comprises a vertical multi-section lattice-type tower having its lower end fixedly mounted on the rotatable upper section of a self-propelled vehicle and a load-supporting multi-section lattice-type crane boom having its base end pivotally mounted on the upper end of the tower. A load to be lifted, swung and lowered, is attachable to a load line suspended from a pulley at the point end of the boom. The tower is selectively rotatable to swing the boom and the boom is selectively pivotable vertically to desired boom (luffing) angles. A crane control system employs strain gauge-type electronic sensing devices mounted on opposite lateral sides of the crane boom and on a side of the crane tower to provide electric signals pertaining to applied loads. A transducer provides an electric signal pertaining to boom angle. A programmable electronic computer, which processes these signals to calculate down load and side load moments in the boom and torque loads in the tower, provides output signals related thereto which are usable to operate the crane within safe limits. The output signals are usable to operate visual display devices which inform the crane operator of safe operating limits, or to effect automatic operation (subject to manual override) of certain crane functions (swinging, luffing, lifting) within safe limits. The sensing devices in the boom comprise strain gauges which are embodied in clevis bolts or pins which are located on opposite sides of the boom and which mechanically secure together certain sections of the multi-section boom. The strain gauge signals, which pertain to load magnitude in the boom, are added to determine load weight suspended from the boom, and are substracted to determine side load magnitude and direction.