Patent GB-707475-A (GB)
Title: Construction and arrangement of hydraulic presses
Inventor: ERNST WALTER
IPC: B30B15/04
Filed: 1951-10-19
Abstract: 707,475. Hydraulic presses. COMMONWEALTH ENGINEERING CO. OF OHIO. Oct. 19, 1951, No. 24471/51. Class 69 (2) In a hydraulic press having a head 12 and a bed 10 and uprights 14 between the head and bed with strain rods 16 extending through the uprights and connecting the head and bed and with a hydraulic motor comprising a cylinder 26 and ram 34 in the head having a platen 36 connected thereto movable between the head and bed, the press frame, particularly the bed thereof, is adapted for detachably supporting die cushion and blank holder assemblies 132 and 170 respectively for selective assembly therewith or disassembly therefrom. The unit for supplying hydraulic fluid comprises a reservoir 60 connected with a tank 256 having a pump 254 mounted thereon for supplying fluid from the tank to the cylinder 26. Rails 312 extending between the uprights carry switches 308 for controlling the operation of the press and include means for illuminating the working space of the press. To advance the platen 36 the motor 250 is energized to drive the variable delivery pump 254, a valve 82, Fig. 15, being so positioned as to drain fluid from above the piston 76 in a valve 74 and permit the piston to rise to connect conduits 72 and 78, so that the pump draws in fluid from the back of the ram 34, port 70, past valve 68, conduits 72, 78, 66, 64, fitting 148, Fig. 3, and conduit 262, and discharges fluid through conduit 260, fitting 264, conduit 44 and passage 46 to the top of the ram, surge valves 54 opening to admit fluid from the reservoir 60. When the platen 36 has advanced to a position where a cam 86, Fig. 15, thereon actuates a switch LS1 thereby closing the valve 82 and interrupting exhaust from above the piston 76, the valve 74 closes and entraps fluid in the push back side of the ram. The pump now delivers fluid through the conduit 260, Fig. 1, and passage 46 through hollow ram 40 to act on that part of the upper surface of the ram 34 directly beneath ram 40, fluid being expelled from the push back side of the ram 34 when the pressure reaches a value to open relief valve 80. A pressure shift-over valve 50 opens and connects passage 46 with the upper surface of the press ram. When the work is engaged by the platen 36 and moves the die cushion platen 132, Fig. 10, downward movement of the plunger 130 is resisted by the setting of a relief valve 144 which controls the flow from the cylinder 128 past a check valve 142 into a passage 140 and a conduit 146 leading to the fitting 148 and conduit 262. Prior to the completion of the pressing stroke a cam 162 on the platen 36 actuates a switch LS2 thereby moving a valve 158 to connect conduit .146 with a conduit 152 so that when fluid is supplied to the conduit 262 to move the platen 36 upward, pressure fluid from conduit 146 flows into passage 140 and also into conduit 152 to hold check valve 142 closed, and upward movement of the plunger 130 is prevented. When the cam 162 and switch LS2 disengage, the valve 158 shifts to exhaust conduit 152 releasing check valve 142 so that pressure in passage 140 acts on both the unequal faces of plunger 130 which is then urged upwards. The'blank holder platen 170, Fig. 3, is suspended by rods 172 from the main platen 36 and descends with it until sleeves 194 adjustably threaded on the rods 188 connecting the platen 170 to the piston rod 184, bottom against caps 202. Thereafter a cam 234, Fig. 18, on the platen 36 engages a switch LS3 to actuate a valve member 231 to connect a fluid supply unit, comprising a tank 232, pump 230, accumulator 235 and conduit 224, with a conduit 220. The hollow rod 184 is connected to a piston 180 having another rod 182 of equal diameter. The piston has a central bore from which lead passages communicating with the spaces in the cylinder 178 above and below the piston, a valve member in the bore being normally in an open position to permit flow of liquid through the piston when the platen 170 is moving with the main platen. Pressure fluid in conduit 220 moves the valve member to permit flow to the upper surface only of the piston 180, thus causing a downward thrust on the rods 188 and blank holder platen. The main press ram 34 is retracted by reversing the pump 254. Specifications 707,530 and 707,531 are referred to.