Patent GB-901278-A (GB)
Title: Hydraulic press
IPC: B21D22/12
Filed: 1961-05-10
Abstract: 901,278. Cupping. CINCINNATI MILLING MACHINE CO. May 10, 1961 [Sept. 1, 1960], No. 16976/61. Class 83 (4). [Also in Group XXIX] An hydraulic press comprises a pressure chamber 23 connected with a source of fluid pressure 40 and enclosed by a flexible die member 22, a die plunger 35 connected with an hydraulic motor 36 and diverting means 70 to allow fluid to flow from the pressure chamber to the motor when a desired pressure is reached in the pressure chamber. The die plunger is housed in a rest ring 15 on a base member 10 connected by rods 13 to an intermediate member 12 secured to the head 11. The member 12 houses a sleeve 21 which is movable by hydraulic motors 25 disposed in the head 11, the flexible die member, which is in the form of a diaphragm, being secured to the sleeve so that as the sleeve is moved downwardly over a tubular extension 18 depending from the head 11, the volume of the pressure chamber 23 is increased until the diaphragm engages a workpiece 16 disposed on the ring 15. The extension 18 houses a poppet valve 20 which is urged to a closed position wherein it engages a seat 26a by a spring 27, the valve opening as a result of suction during downward movement of the sleeve to enable fluid from a tank 16 on the head to enter the chamber; the valve also opens when fluid pressure is supplied to a chamber 28 when the sleeve is raised after a forming operation. The die plunger is movable by the hydraulic motor 36 which has a piston 36a slidable on a fixed piston 36c secured to the base 10. The die plunger is connected by a rack-and-pinion mechanism 80, 81 to a shaft 85 on which is mounted a pair of cams 83, 84, the cam 84 controlling a valve 73 in turn controlling a relief valve 70 which regulates the pressure in the chamber 23 of the press and diverts excess fluid through a port 79 to a line 92 leading to the motor 36. Cam 83 actuates a valve 62 to connect a supply line 59 leading to the chamber 23 to a tank 49 during raising of the sleeve. The operation of the press to form a workpiece is automatic, limit switches operating solenoids controlling the valves in the hydraulic circuit. Upon operating a push button, a pilot valve 51 connects a pump 53 to one end of a valve 43 to direct the flow from the pump 40 to the line 59 leading to the motor 25 to lower the sleeve 21 and expand the chamber 23, the valve 20 opening to permit fluid in the tank 16 to enter the chamber 23. The movement of the sleeve actuates a limit switch shortly before the diaphragm engages the workpiece to operate a valve 61 and connect the supply line 59 to a line 59b and line 69 leading to the chamber 23 to increase the pressure therein. The pressure in line 69 acts in a chamber 71 of the relief valve 70 which has a second chamber 72 connected to the valve 73 controlled by the cam 84. The chambers 71, 72 are interconnected by a throttle 77 and as the pressure differential across the throttle varies depending on the condition of the valve 73 as determined by the cam 84, the pressure in line 69 and hence in chamber 23, is varied, the excess fluid passing through the port 79 to the line 92 leading to the motor 36 to raise the plunger so that the pressure in the chamber corresponds with the position of the die plunger. When the initial forming pressure is reached, a pressure switch may actuate a valve 93 to connect line 92 by way of a line 90 directly to line 41 from the pump 40 and the cam 84 may be programmed so that the valve 73 is closed, preventing flow from the pressure chamber in which case the pressure in the chamber increases as a result of the reduction in its volume effected by the extension of the plunger, the pressure of the fluid from the pump acting in motor 36 and on the plunger preventing fluid being supplied to the chamber. The pressure in the chamber may be increased further by not actuating valve 93 so that the pump 40 continues to supply fluid through lines 41, 59, 69, the fluid above that required to maintain the desired pressure being discharged through port 79 of the relief valve 70 to the motor 36, the movement of the plunger rotating cam 84 to adjust valve 73 and thus valve 70 to control the pressure in chamber 23. At the end of the forming operation, the cam 84 actuates the valve 62 connecting the pressure chamber to the tank and operates a limit switch controlling a valve which directs fluid to the opposite ends of the motors 25, 36 to return the press to its initial position. A source 120 of air pressure is connected by a valve 119 to the pressure chamber to assist removal of the diaphragm.