Hydraulic overload control system for power presses

Abstract

A hydraulic overload control system for a mechanical power press having a flywheel driven eccentric shaft and one or more pitmen drivingly coupled to the eccentric shaft. The press has a slide drivingly coupled to the pitmen by corresponding hydraulic piston and cylinder connections. The overload control system includes means for generating a first electrical signal having a value proportional to the force exerted on the die by the slide throughout the work stroke thereof; means for generating a second electrical signal having a value proportional to the position of the slide throughout the work stroke; means for storing the maximum tonnage capacity values of the press at a multiplicity of slide positions throughout the work stroke; control means responsive to the second electrical signal for retrieving the stored value representing the maximum tonnage capacity of the press at the slide position represented by the second signal; means for comparing the retrieved value corresponding to the second signal with the value of the first signal to determine whether the press is in an overload condition; and means responsive to the determination of an overload condition at any point in the work stroke for actuating the clutch and break interlock mechanism of the press to stop movement of the slide.