Hydraulic presses, notably for shearing and cutting materials

In a hydraulic press for performing shearing or cutting operations, of the type comprising a press piston mounted for reciprocating motion in opposite directions in a hydraulic space divided into one chamber for the piston operating at the working pressure and another chamber for the return stroke of said piston, a reservoir for the working fluid, and a pressure-fluid accumulator for supplying fluid to the piston working chamber, the piston rod being rigid with a slide arm adapted to slide along a linkage terminating at one end with an adjustment nut, the accumulator communicates with the working chamber of the piston via a hydraulic circuit comprising essentially a normally closed spring-loaded valve and a chamber in which a spool valve is adapted to move transversely to the piston axis, said spool valve having a stem extension projecting axially outside the press control device, the outer end of this spool valve stem engaging one arm of a bell-crank lever fulcrumed to a fixed pivot pin and having its other arm rigid with said linkage.