Patent ID: 7827843

Claim:
A device for controlling a drawing process in a transfer press, with two tool parts which act in opposition to one another and between which a workpiece to be deformed is held and of which one tool part, in particular a negative mold, can be moved between two reversal points, of which tool parts the first is assigned to the commencement of a work cycle, by a mechanical crank mechanism driven at a constant rotational speed, and of which the second tool part, in particular a drawing cushion, is connected via a piston rod to the piston of a hydraulic differential cylinder, wherein the movement of the piston is controlled by the supply of pressure medium into a first chamber and by the discharge of pressure medium out of a second chamber of the differential cylinder, and in which, during a first time segment which extends within a range delimited by the first and the second reversal point, the rod-side face of the piston is acted upon by a pressure which is sufficiently high to accelerate the second tool part in such a way that, when the first tool part and the second tool part impinge one onto the other, both tool parts move at virtually the same speed, and in which a controllable throttle arranged between a bottom-slide chamber of the differential cylinder and a tank determines the pressure in the bottom-side chamber, wherein, in a second time segment (Δt 3 ) which follows the first time segment (Δt 2 ) and extends until the second reversal point (UT) is reached, the rod-side face (A r ) of the piston ( 16 ; 56 ) is acted upon by a second pressure (p sN ) which is lower than the pressure (p sH ) during the first time segment (Δt 2 ), further comprising two pressure accumulators ( 27 , 31 ), of which one ( 27 ) is charged to the first pressure (p sH ) and the second ( 31 ) is charged to the second pressure (p sN ), and wherein the pressure accumulators are selectively and alternatively connected to a common port of the differential cylinder so that the action of pressure medium upon the rod-side chamber ( 15 s ; 55 s ) at the differential cylinder ( 15 ; 55 ) takes place from the same pressure accumulator ( 27 , 31 ) which is charged to the pressure (p sH , p sN ) provided for the respective time segment (Δt 2 , Δt 3 , Δt 4 +Δt 5 ).