Drawing device for drawing presses

Abstract

A drawing device for drawing presses has a sheet holding ring which travels along the entire drawing path during the drawing operation. For admitting a corresponding sheet holding force to the sheet holding ring, a pneumatic force generating device is provided whose pressure cylinders generating the force are permanently or statically acted upon by compressed air with a defined pressure volume. For adjusting the sheet holding force, the corresponding pistons of the force generating device can be acted upon on their opposite side with counterpressure of a defined pressure level. Thus, the course of the sheet holding force can be adjusted by way of the drawing depth. For local adjustment of the distribution of the sheet holding force along the sheet holding ring, hydraulic cylinders are arranged between the sheet holding ring and the pressure box, and are combined into groups. Communicating by way of switch-over valves 46, these hydraulic cylinders can be switched to a first reservoir and, communicating alternatively, can be switched to a second reservoir. In conjunction with the pneumatic force generating device, the hydraulic cylinders supply a certain buffer or damping effect which becomes effective when the pressure surface is placed on the sheet bar situated on the sheet holding ring.

Dependencies are inferred from the claim text.