Hydraulic lifting machine with three telescoping pistons - has cylinders with flanges forming annular gaps and pressure control valves connecting annular chambers formed

摘要

The drive cylinder contains three nested telescopic pistons and the nesting cylinders formed have flanges with circumferential seals so that annular chambers are formed between cylindrical pistons. The annular chambers formed are connected by valves. The maximum excess pressure acting on smallest piston ensures that no damage occurs within the telescopic system. Between the presurised cylinder chamber (7) and annular chamber (6) is arranged pressure difference actuated valve which is opened only if normal operating pressure is exceeded for admitting liquid from annular chamber to cylinder. A non-return valve between the chamber (13) of middle telescopic piston (8) and cylinder chamber (9) is opened shortly before maximum extension of the inner telescopic piston 12). This valve is actuated by a contact stop (21) and liquid flows into cylinder chamber (9).