Apparatus with a hydraulic ram

摘要

A hydraulic ram has, in a push chamber (3), a spring-loaded push valve (7) on the outflow side and a pressure-side non-return valve (14) leading to an air vessel (1) provided with a rising connection (19). In its closed position, the push valve (7) is supported on a coaxial, freely movable auxiliary valve piston (21) which on one of its sides can be exposed to a control pressure applied to a control connection (22) and on its other side is connected to an outlet space (6) of the push valve (7). The stroke of the auxiliary valve piston (21) is smaller than that of the push valve (7) so that, when the control pressure is applied, the auxiliary valve piston (21) acts as an auxiliary cushion for the push valve (7) for the automatic pushing of the ram and for maintaining the pushing operation. After the control pressure drops away, the auxiliary valve piston (21) is uncoupled from the push valve (7). For the most simple control, a driving tank (28) is provided with an overflow (32) connected to the control connection (22) of the auxiliary valve piston (21). To automatically stop the ram when the push valve (7) is closed, air pockets can be carried into a driving line (31), e.g. by means of a snifting hole (30) in a driving tube (29) lying in the driving tank (28). <IMAGE>