Hydraulic ram for lifting heavy workpieces

摘要

The ram has a base plate (12) on which is mounted a piston (54). The cylinder (18) has a movable fitting over the piston and inside the housing and lifts an upper thrust plate (22) to which the cylinder is attached. Hydraulic ducts lead from the inlet/outlet to either side of the piston to provide different amounts of lift. Three different piston chambers are obtained; one (46a) above the top of the piston, a second (46b) below the piston and a third (46c) below the moving cylinder. The housing has a number of sensors to monitor the displacement of the ram.