GB443851A - Improvements in and relating to valve mechanism for hydraulic presses - Google Patents

Abstract

443,851. Valves for hydraulic presses. SHAW & SONS (SALFORD), Ltd., J., and SHAW, J. B., Wellington Street, Salford, Lancashire. Sept. 15, 1934, No. 26509. [Classes 69 (ii) and 135] Valve mechanism for a hydraulic press comprises a pair of inlet and exhaust valves c, d for the main cylinder interconnected by a lever h so that one opens after the other has closed, and vice versa, and a double - acting pressure - influenced piston in a control cylinder i for operating the lever h, the piston being controlled by a pilot valve o. The inlet and exhaust valves e, f for the " jack cylinder are similarly operated by the same piston. The mechanism is combined with a valve l for changing over from low to high pressure, the said valve being operated by the building up of pressure in the low pressure ports. In Figs. 2, 3, the two pairs of valves c, d and f, e are loaded by springs g and operated by parallel levers h, the valves c, f when closed, acting as abutments for the fulcra of the levers whilst the valves d, e are opened, and valves d, e acting similarly when the valves f, c are opened. The levers h are loosely connected to a rod k pivoted to the piston rod of the piston which is constantly exposed on its smaller side to the low pressure fluid entering at a<2>. The larger side of the piston is also exposed to the low pressure when the pilot valve o is raised against its weight or hydraulic load by manual or electric means. The latter may comprise a solenoid o operated by a relay under the control of a hand- or time-controlled switch. The solenoid may be replaced by a motor and gearing. High pressure fluid entering at a<1> is under the control of the valve l operated against a spring by a lever m carrying a roller m<3>. The latter rests on a piston n, Fig. 4, exposed on its underside to the low pressure. The levers h, m have guides h<1>, m<2> respectively. High pressure fluid has constant access to the jack feed valve e by means of passages u, u<1>. Connections a<3>, a<4> a5 lead to the main and jack cylinders and to waste respectively. In operation, after the pilot valve o has been raised to allow low pressure fluid to pass to the under side of the piston j, the main cylinder feed valve c and the jack cylinder exhaust valve f open. When the press meets the work, the pressure builds up beneath the piston n which finally opens the valve l so that high pressure fluid may pass to the main cylinder by the valve c or through a separate port. The admission of high pressure fluid closes a non-return valve p which cuts off the low pressure supply. If desired, a single pilot valve may be arranged to control the valve mechanism of several presses. The valve l may be replaced by an independent valve operated electrically or by an independent pilot valve. The piston j may be operated by compressed air instead of the hydraulic fluid.