METHOD AND APPARATUS FOR SERVICING COUNTERBALANCED LIFTING DEVICE

摘要

A counterbalanced lifting apparatus includes two weighted members suspended from cables which are trained over sheaves supported in an elevated position on a framework. One of the weighted members may be a bridge span and the other a counterweight. The first weighted member (bridge span) normally seats against a terminal surface while the second weighted member (counterweight) is normally suspended. During operational cycles, the relative positions of the weighted members reverse, and the counterweight may seat on cylinder-type buffers affixed to its underside. Some servicing operations require slack in the cables and this is achieved by seating the first weighted member against its terminal surface and then supporting jacking beams on a temporary support system installed directly beneath the cylinder-type buffers of the second weighted member. Thereafter, a hydraulic pump is connected with the barrels of the cylinder-type buffers and hydraulic fluid is pumped into these barrels to cause the piston rods therein to extend against the jacking beams. This raises the second weighted member and thereby loosens the cables.