Patent ID: 6032506
Filing Date: 2000-03-07
Classification: B21D

Abstract:
Stamping press comprising a ram (1) mounted so as to move relative to the cushion (4) of the press, a die (2) being fixed to the ram and able to press a sheet (11) resting on a blank holder (3), the blank holder resting on the cushion, the press being characterised in that one or more fluid-operated compensating cylinders (5) are distributed around the blank holder (3), the said compensating cylinders resting on the cushion (4) and are provided to exert their force against the ram (1) of the press, in that the compensating cylinders (5) come into contact with the ram (1) before the die touches the sheet (11) during the descent of the ram (1) and in that the compensating cylinders receive a pressurized fluid from at least one control valve which receives a pressure control signal so that the total force (B) developed by the compensating cylinders (5) varies during the stamping operation while always remaining at the most equal to the force (A) exerted by the cushion (4) so that the blank-holder force which is applied to the sheet (11) between the die and the blank holder and which is equal to the difference between the forces (A) and (B) varies during stamping, even if the force (A) exerted by the cushion is constant.