GB561978A - Control valve for hydraulic presses - Google Patents

Abstract

561,978. Valves. TOWLER, J. M., and TOWLER, F. H. Dec. 8, 1942, No. 17444. [Class 135] A valve device adapted to be interposed between a control valve and an hydraulic press or hydraulic power cylinder is arranged to restrict the release of pressure to exhaust until such time as the pressure of liquid in the press cylinder has fallen to a predetermined minimum. In the form shown in the Figure, a valve piston f with a tapered flat o is slidably mounted on the reduced part e of a plunger a and is normally held against a shoulder on the plunger by a light spring n. A piston h detachably secured to the plunger is formed with a flat m to provide a restricted passage connecting a chamber l on the outer side of the piston with a chamber k provided with a connection d leading to the press. The plunger is loaded by a spring p and an adjustable stop q is provided to limit the movement of the valve f so that the flat o forms a restricted passage connecting the chamber k to a connection c leading to the control valve. When the control valve is operated to admit fluid pressure, the valve f opens againstthe action of the spring to permit a free flow to the pressure. As pressure builds up in the press cylinder, pressure seeps into the chamber l, moving the plunger against the action of the spring, When the control valve is put to exhaust the valve f immediately closes and exhaust takes place through the restricted passage o. As the cylinder pressure falls, the plunger gradually moves back to its original position gradually increasing the area or decreasing the length of the passage o until finally the valve is opened fully to allow a free exhaust. Specification 547,172 is referred to