Robert B Macgregor

US Patent:

41701240, Oct 9, 1979

Filed:

Dec 13, 1977

Appl. No.:

5/860235

Inventors:

Robert MacGregor - Blue Island IL

Assignee:

Dreis & Krump Manufacturing Company - Chicago IL

International Classification:

B21D 706

US Classification:

72389

Abstract:

A control and actuator system for a press brake having a frame, a bed, a ram, and a pair of hydraulic cylinders for reciprocating the ram, utilizes a jackscrew arrangement in conjunction with positive mechanical stops on the ram pistons to support the ram beneath the cylinders to enable the bottom travel limit of the ram to be preset. The top travel limit of the ram is preset by means of vertically adjustable actuator rods on the ram, which engage actuator stems on valves associated with each cylinder to stop upward travel and hold the ram in position. Tilt compensation is provided at the top and bottom ram limits by independent adjustment of the jackscrews and actuator rods, obviating the need for a complex tape and pulley driven differential valve arrangement. The novel hydraulic circuit provided for powering the cylinders utilizes pilot-driven control valves, and provides for direct venting of the system high-volume hydraulic pump when not in use to maximize system efficiency.