GB547654A - Improvements in hydraulically operated presses - Google Patents

Abstract

547,654. Hydraulic presses. VICKERS, Inc. Nov. 28, 1941, No. 15322. Convention date, Oct. 14, 1940. [Class 69 (ii)] A hydraulic press is constructed with a pre-fill valve 22 forming part of a unitary self-contained assembly to provide for pre-fill valve operation and to control the application of pressure to the main ram 12. The platen 10 of the press is advanced to working position by the aid of booster cylinders 20 with pistons 18 connected by rods 16 to the platen, and the pistons also act to return the platen. The operating liquid is supplied by a pump 26 driven by a motor 28, and an auxiliary pump 68 supplies liquid for actuating control valves 80, 56, which are also capable of actuation by electromagnets 82, 60, 58 under control of switches 184, 196, 192 and 194, of which the latter is a limit switch which is opened when the platen 10 has returned to its upper position and causes the pressure liquid to be byepassed to tank. On operation of the starting switch 184 the solenoids 60, 82 are energized, and as soon as the platen 10 starts downwardly switch 194 closes and holds the solenoid 82 energized. Release of switch 184 de-energizes solenoid 60 without shifting valve 56. The moving of valves 56, 88 to the right causes operation of a four-way valve 34 to the right and the liquid from pump 26 passes via pipe 40 to the cylinders 20, and also to a port 44 of the pre-fill valve. The actual pre-fill valve 124, Fig. 2, is open while the platen descends under the action of the pistons 18. The discharge from cylinders 20 passes to the tank 24 via a valve 48 which opens under pressure. When the platen meets the work the pressure builds up in the cylinders 20 and in port 44. At a particular pressure a valve 148 of the kind described in Specification 393,761, opens to admit pressure to a recess 132 of the pre-fill valve and so a piston 138 is moved to the right to close the valve 124 and cut off connection with the tank, and also to open connection between recesses 132, 134 of the valve. Pressure liquid now flows to the main cylinder 14 through passage 166 and port 114, and also passes to valve 48 so as to open this valve further and so reduce the resistance to the return liquid. At the completion of the operation stored up energy is released gradually by bleeding the pressure liquid from cylinder 14 through port 114, passage 166, recesses 134, 132, cheek valve 162, Fig. 3, restrictor 164, chamber 146, port 44 and thence to the left-hand cylinder port of valve 34, and tank conduit 36. The returning liquid also acts upon the small area of piston 138 tending to open the valve 124, but this can only take place when the pressure on the large area of the piston is reduced to a fraction of that on the small area. When this occurs the valve 124 opens. Finally the limit switch 194 is operated to de-energize the solenoid 82 and the parts then return to normal inoperative. position. An indicator 144 is fitted to the spindle of the pre-fill valve to indicate the extent of opening.