Double actuator hydraulic lifting device - has simple and sequential type non return valves

摘要

The lifting device has two hydraulic rams (2a,2b), each with a non return valve (25,26), a feed, return pipes and a pump-selector unit. The first ram (2a) is the leading one and has a sequential non return valve with closing spheres (255). The valves equalise pressure between main ram chambers via a pipe (3) joining the two valves and also establishing communication with a second pipe (19), connected to a high pressure source. The valve (25) closure of the first ram (2a) is a ball (250) moving under the action of a piloting piston (20a) joined to a third high pressure pipe (15).