Patent GB-540207-A (GB)
Title: Improvements in or relating to hydraulic machinery
IPC: B30B15/16
Filed: 1939-11-03
Abstract: 540,207. Hydraulic presses. ERNST, W. Nov. 3, 1939, No. 29366. [Class 69 (ii)] A press-circuit comprises a pump for supplying a hydraulic motor for reciprocating the pressplaten, and an automatically operable dischargecontrolling member for varying the supply, the member being adapted, at the end of the pressing stroke, to initiate reverse movement of the pressplaten, and to byepass the pump - discharge during the interval between forward and reverse movement of the press-platen. The press-circuit shown in Fig. 2 includes a main cylinder 26, pull-back cylinders 39, a surge-tank 45, a surge-valve, a pump 3, and a valve 2. The pump is of the kind comprising a rotary cylinder provided with pistons co-operating with controlling-member comprising a ring arranged in another ring which is adjustable in eccentricity to vary the delivery. Adjustment is effected manually by a hand-wheel 113 or automatically by means of a piston arranged in a chamber 127 which communicates through a pipe 131 with the pump. The piston is provided with a spring-pin 142, Fig. 9, for opening a switch 154 referred to below. The valve 2 comprises rods 166 and 198, Fig. 10, formed with heads 171 ... 174, and 199, 200 and mounted in a casing 160 which is formed with ports and ducts referred to below, and choked apertures 184, 189 having adjusting-screws 183, 188. The rod 166 is connected by linkage 80 ... 75 to a spring-urged lever 65 which abuts on a collar 63 on a rod 53 operated by a handlever 56 or an arm 54 on the platen 31 carried by the press-plunger 27. The linkage 80 ... 75 is provided also with automatic control-devices described below. When the rods 166, 198 are in the position shown in Fig. 10, the pump delivers oil through a pipe 81, intake port 206, Fig. 2, ducts 179, 178, port 207, and pipe 87 to the cylinder 26, and the platen 31 is depressed. The pull-back cylinders 39 deliver oil to the surgetank 45 through the pipes 41, 86, port 208, duct 180, choked aperture 189, exhaust port 186 and pipe 90. The speed of the platen is regulated by means of the screw 188. When the platen engages the work, the rod 198 is forced towards the right in opposition to a spring 203, and a duct 181 is opened to provide an additional passage for the oil delivered by the pull-back cylinders. When the work has been pressed, the rod 166 is moved towards the right by means of the hand-lever 56, or automatically as described below. Thereupon, the pump is byepassed, oil being delivered to the surge-tank through the port 206, ducts 179, 180, 181, choked aperture 187, and pipe 90. Simultaneously, pressure is released gradually from the cylinder 29, oil being delivered to the surge-tank through the pipe 87, port 207, ducts 178, 179, choked aperture 184, and pipe 90. When the pressure has been released, the spring 203 returns the rod 198, the pump delivers into the pull-back cylinders through the port 206, ducts 179, 180, port 208, and pipes 86, 41, and the platen is returned. At the end of the return-stroke, the arm 54 raises the rod 53, and the rod 166 is moved towards the left to bring the heads 173, 172 into register with the ducts 180, 178. Thereupon the pump is again by-passed, oil being delivered to the surge-tank through the port 206, passages 175, 176 in the head 172, ducts 178, 177, aperture 184, and pipe 90. The head 173 prevents escape of oil from the pull-back cylinders and thereby causes the platen to remain in raised position. If the platen slips downwards, the rod 166 moves towards the right, oil is delivered to the pull-back cylinders, and the platen is returned. The automatic or semi-automatic control of the press is effected by the circuit-arrangement shown in Fig. 9 and comprising an electromagnet 71 having an armature 70, Fig. 2, connected to the lever 65. The circuit includes also a magnetic switch 72 having blades 212, 213, 214, switches 217 ... 220, the pump-controlled switch 154, and a contact 62 operated by a tappet 61 on the rod 53. For fully automatic operation, the switches 219, 220 are closed. On depression of the switch 217, the switch 72 is energized, the blades 212, 213 close the circuit of the solenoid 71, and the blade 214 closes a holding-circuit for the switch 72 to permit release of the switch 217. Thereupon, the armature 70 moves the rod 166 into the position shown in Fig. 10 and the platen is moved downwards and pressing is performed. When the hydraulic pressure rises to a pre-determined amount, the switch 154 is opened by the pumpcontrolling member, the blades 212, 213, 214 disengage from their contacts, the solenoid 71 is de-energized, the valve moves into position for releasing pressure from the cylinder 29 and bypassing the pump, and then moves into position for causing the platen to return. At the end of the return movement, a tappet 61 closes the switch 62, the switch 72 is re-energized, and the platen is again moved downwards. For semiautomatic operation, the switch 220 is opened, and the switch 217 is depressed. The platen is moved downwards and returned in the abovedescribed manner, but the switch 62 fails to re-energize the switch 72, and the platen is thereby caused to rest in the upper position. For causing the platen to halt at an intermediate point, and then return, the normally closed switch 218 is depressed to de-energize the switch 72. The automatic and semi-automatic control arrangement can be disabled by opening the switch 219. Specification 540,242 is referred to.