Quickly switchable pressure cushion for hot-forging presses, in particular, crank and eccentric presses

摘要

The pressure cushion (52) for presses with a hydraulically operated piston (2) supported on an oil cushion (4) is characterised by the following facts: (a) a control ring (6) surrounds and seals the oil cushion (4); and (b) by operation of the control ring the connection between the oil cushion and a tank or an intermediate container located outside the pressure cushion (52) is unblocked. The control ring (6) is held down against its seating with a predetermined pressure. Via the non-return valve (61), the same pressure fills the oil cushion (4). During a working stroke, when the pressure on the oil cushion exceeds the holding-down pressure, the ring is lifted automatically this excess pressure. The control ring is provided with top and bottom sealing surfaces (60, 59) blocking respectively the holding-down side (63) and the oil cushion against the tank connection (18). The sealing effect of the surface (59) is increased by an elastic radial spreading of the control ring. Alternatively, the opening motion of the control ring is initiated by means of a control valve. Oil leaking into the clearance between the piston (2) and the control ring is led into the tank. The motion of the control ring close to its final position is slowed down by means of a damper space. Alternatively, the motion of the ring is controlled by means of damping dependent on displacement in such a way that force relief in the press takes place smoothly and quickly. In another variant of the invention, damping decreases with a decrease in the residual press force.