Patent GB-812133-A (GB)
Title: Improvements in and relating to control valves for hydraulic presses
IPC: B21J9/12
Filed: 1956-03-23
Abstract: 812,133. Forging presses. ELECTRAULIC PRESSES Ltd., and TOWLER, F. H. [Representative of TOWLER, J. M.]. March 23, 1956 [March 30, 1955], No. 9221/55. Class 83 (4). [Also in Group XXIX] An hydraulic forging press which can make a series of planishing strokes in addition to normal forging strokes, has a manually-operated valve U controlling the operation of a distributing valve E which controls flow of servo-pressure from a pump W to valves J, K for loading primary pressure pumps Y, Z and to valves F, H for directing primary pressure to a main press cylinder A and to return cylinders B, the distributing valve E also controlling flow of primary pressure controlling a prefill-exhaust valve C. Neutral.-When the hand-operated valve U is in the neutral position shown, pressure from the servopump W holds the distributing valve E in its left-hand position; servo-pressure is not directed to valves J, K which open to unload primary pumps Y, Z and valve H is closed which locks the liquid in the return cylinders B so that the press ram is held in position. Forge.-When the valve U is moved part way to the left to the forge position, the valve E is held in its left-hand position and servopressure is applied to the valves J, K to load all the primary pressure pumps. Servo-pressure is not applied to valve F, which is opened by pressure from the pumps Z which then deliver to the main cylinder. Valve H is opened against its spring loading by pressure from the pumps Y which then deliver to the main cylinder, and the press moves down. Return cylinders B discharge through valve H into the main cylinder. When the pressure in the main cylinder exceeds the setting of an adjustable relief valve T, pressure is applied via valve T to a connection 11 of valve E so moving the spindle of valve E to the right. In this position of the valve E pressure from the pumps Y is supplied to open the decompression valve 26 of the prefill-exhaust valve C, and servopressure is supplied to a connection 4 of valve H, which closes, and the pumps Y are thus cut off from the main cylinder A and deliver to the return cylinders B. When the pressure has fallen sufficiently the main valve 25 of the prefill-exhaust valve opens, valve F is closed by servo-pressure and all the primary pumps deliver to the cylinders B to return the press ram. The extent of the return stroke is controlled (a) by returning valve U to neutral or (b) by contacting a top stop N, which results in the opening of valves J, K to unload the pumps Automatic planishing.-Valve U is held in its extreme left-hand position in contact with a reversing valve c. In this position a valve S is opened by servo-pressure and servo-pressure is supplied, through valve S, to a connection 3 of valve H which is thereby opened and return cylinders R are thus opened to the main cylinder A. The press ram falls freely under gravity at the rate controlled by the setting of valve H. The prefix-exhaust valve C is open and the primary pressure pumps are loaded. On contacting the work the valve C closes and pressure builds up in the main cylinder, this pressure being applied by a plunger j to the reversing valve c. When the load applied. by plunger j exceeds that applied by hand through the valve U, the reversing valve c is moved slightly to the right and servo-pressure is applied through connection 11 of valve E to move the valve to its return position. On the return stroke oil displaced from a control cylinder D moves a piston 19 in a valve V to the right until the piston covers exhaust ports 13 and pressure in the line from valve V to cylinder D builds up; this pressure acts on a plunger o1 of valve E and eventually overcomes the force applied to servo-pressure at the lefthand end of valve E and valve E is returned to its forge position. The length of the return stroke is determined by the setting of valve V. Hand reversal is obtained by moving valve U to the right of the neutral position. Overstroke.-Should an overstroke of the press ram occur, a valve O is contacted and valves J, K thereby opened to unload the primary pumps. The Provisional Specification refers to Specification 784,933. Specifications 727,976, 732,775, 773,142 and 783,413, [all in Group XXIX], also are referred to.