US Patent 7780145 Load compensating device, especially for lifting appliance

A load compensating device, especially one for lifting appliances, includes a detector for detecting an overload or an underload and designed to cause actuation of the compensating device. The device comprises an actuator attached to one of ends of a rope or ropes that support the load for producing positive or negative displacement of the rope or ropes over a short distance compared with the length of the rope or ropes. The actuator is operated by a brushless electric motor connected to an infinitely variable-speed transmission. The transmission is connected to the detector.