Abstract: A regenerative hydraulic cylinder has a piston dividing its interior into a pair of chambers. A rod extends from the piston through a cylinder end wall. Several axial passages in the piston extend between opposite piston faces. A valve member is mounted over one piston face and has a sleeve that slides axially in a recess formed in the one piston face. Springs urge the valve member to a flow-impeding orientation against the piston face. A hydraulic pilot line in the rod, accessible at an external rod end, permits the valve member to be displaced away from the piston face to a flow-enabling orientation. The valve state is controlled to permit fluid flow directly between chambers during extension or contraction of the cylinder.

Abstract: A hydraulic press is adapted to permit adjustment of the clearance between upper and lower platens and to permit the press to be divided into distinct upper and lower sections for purposes of transport. The press has four vertical posts which extend upwardly from the lower platen. Each post has a lower section which slides in the lower platen, an upper section is fitted into and slides relative to the upper platen, and a releasable joining structure which connects the post sections to define a unitary post structure. Light-duty hydraulic cylinders permit gross positioning of the upper platen on the posts. The upper platen is then locked to the upper post sections in a predetermined relative position, and heavy-duty hydraulic cylinders acting on the posts serve to draw the upper platen towards the lower platen to compress a work piece.

Abstract: A hydraulic press has a frame including a crosshead formed with a vertical passage. A lower platen is fixed to the base of the frame, and an upper movable platen is located between the crosshead and lower platen. Light-duty hydraulic cylinders move the upper platen between an operating position proximate to the lower platen and a retracted position relatively distant from the lower platen. A short-stroke, large-bore hydraulic ram extends vertically from the upper platen and travels with the upper platen is positioned by the light-duty cylinders. An upper free end of the ram locates in the vertical passage of the crosshead when the upper platen is in its retracted position but clears the passage when the upper platen is in its operating position. A hydraulic mechanism then closes the passage so that the ram can drive the upper platen towards the lower platen.

Abstract: A 2000 ton hydraulic press is designed to eliminate the side slabs and substantial cross-head associated with conventional presses. The press simply has a base that includes a lower platen and bolster plate. Four vertical posts extend upwardly through the lower platen bolster plate, and guide structure beneath the lower platen bolster plate constrains the posts to move vertically while bearing horizontal forces and bending moments which may be applied to posts for example during compression of a mold containing a molding charge. Four large-bore, short-stroke hydraulic cylinders are attached to the base below the lower platen bolster plate, and serve to raise and lower the posts during compression phases of operation.

Abstract: A 2000 ton hydraulic press which can be conveniently retrofitted for platen parallelism control has a conventional support structure which includes a base, a pair of side slabs and a cross-head. A lower platen is fixed to the base structure, and an upper platen is guided on the side slabs for vertical movement towards and away from the lower platen. Short-stroke, large bore compression-phase hydraulic cylinders are mounted within the lower platen, and have piston rods extending vertically through an upper surface of the lower platen. A vertical post is supported from each piston rod, and travels through an aligned vertical passage provided in the upper platen. A pair of long-stroke, narrow bore hydraulic cylinders permit the upper platen to be advanced quickly towards the lower platen to close the gap between the platens.