Hydraulic overload control system for power presses

In a mechanical press having a flywheel driven shaft, a pitman drivingly connected with said driven shaft, a slide coupled to said pitman, a die actuated by said slide, and a clutch and brake interlock mechanism for restricting movement of said slide, the improvement comprising, in combination

• a hydraulic piston and cylinder disposed between said slide and said pitman,
• an overload control valve in communication with said cylinder, said valve having a pressure transducer associated with it, said pressure transducer generating an electrical signal representing the fluid pressure generated inside said cylinder due to the motion of said slide,
• a rotational transducer in rotational communication with said driven shaft, said rotational transducer generating an electrical signal representing the position of said 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 said position indicating signal for retrieving the stored values representing the maximum tonnage capacity of the press at the slide position represented by said position signal,
• means for comparing said retrieved value with said value of said pressure 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 said clutch and brake interlock mechanism to stop movement of said slide.