Patent ID: 6974044

Claim:
A system for controlling a load lifting apparatus ( 1 ), comprising a controllable drive ( 2 ); a load-bearing element ( 5 ) connected to the drive ( 2 ) and aligned at least in a vertical path (Z—Z) as a result of gravitational force in a rest position of the load-bearing element; a load-receiving device ( 7 ) connected to the load-bearing element ( 5 ); and a regulating circuit operatively associated with the controllable drive ( 2 ) for load-balancing purposes, the regulating circuit comprising: a device ( 11 ) responsive to movement of the load-receiving device on the vertical path (Z—Z) for generating a signal (S) for balancing the load ( 9 ) in the vertical path without presetting the weight of the load; the regulating circuit operating, after the load ( 9 ) is received by means of the load-receiving device ( 7 ), to automatically increase the torque of the drive ( 2 ) until a substantially vertical (Z—Z) movement of the load bearing element ( 5 ) out of the rest position begins, thereby causing the device ( 11 ) to generate the signal (S), which contains information dependent on and corresponding to an incremental course of movement covered during the beginning of the substantially vertical (Z—Z) movement of the load bearing element ( 5 ), and which provides an input signal for controlling the drive ( 2 ) so as to balance the load in the vertical path (Z—Z); and the regulating circuit operating to constant-switch the drive ( 2 ) in response to a zero deviation (ΔS) of said signal (S) from a predetermined value (W), so as to maintain the load-receiving device ( 7 ) and the load balanced in the substantially vertical path.