Automatic counterbalance for load on crane boom - has balanced operation switch to detect deflections and move counterweight to compensate

摘要

The load on the crane boom is automatically counterbalanced as it travels along the rails, the counterweight being moved to compensate the deflections. It comprises a switch (1) fitted in a suitable position at the top of the crane, this having contacts on a balance beam. The beam operates in an oil bath (6) to dampen its movements and prevent oscillation and the unbalance caused by the boom deflection closes selected contacts to energise a motor. This has a reversible action and is connected to the counterweight by a cable, its direction depending on the contacts closed. Limit switches control counterweight travel.