Fluid operated drive for machine tools - has control valve with switch and spring engaging on operating rod

摘要

The drive is for shears where there is a double-acting piston-cylinder arrangement with a sealed piston rod and with connections for the feed or takeoff of the fluid as well as a control valve to control the fluid action. The control valve is a conventional four way/three position valve (9) with double-ended spring loading which attempts to move the valve out of its two end positions into its neutral centre position. A switch and a spring (27) engage on the operating rod (10). The spring element adjusts to different forces according to the two end positions of the piston rod (24). One of these forces corresponds to the disengagement force of the valve from its end position and its transfer into its neutral middle position while the other is less than the resetting force of the valve from its other end position and transfer into its neutral centre position.