Patent GB-707530-A (GB)
Title: Construction and arrangement of hydraulic presses
Inventor: ERNST WALTER
IPC: B30B15/16
Filed: 1951-10-19
Abstract: 707,530. Hydraulic presses. COMMONWEALTH ENGINEERING CO. OF OHIO. Oct. 19, 1951, No. 22517/53. Divided out of 707,475. Class 69 (2) In a hydraulic press comprising a frame having a head 12 and a bed 10 and uprights 14 therebetween with strain rods 16 extending through the uprights connecting the head and bed and with a hydraulic motor (cylinder 26 and ram 34) in the head having a platen 36 connected thereto movable between the head and bed, the hydraulic unit for supplying the hydraulic motor in the press head comprises a reservoir 60 on top of the press head, a pump tank 256 on the back of the press head below the reservoir and hydraulically connected therewith, and a pump 254 mounted on top of the pump tank connected to draw fluid therefrom and also connected to supply fluid to the hydraulic motor. The press frame detachably supports die cushion and blank holder assemblies 132 and 170 respectively. 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, valves in the hydraulic circuit being so positioned that the pump draws in fluid from the back of the ram 34, port 70, past valve 68, conduits 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 thereon actuates a switch, a valve 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 a relief valve. 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, downward movement of the plunger 130 is resisted by the setting of a relief valve which controls the flow from the cylinder 128 past a check valve into a conduit 146 leading to fitting 148 and conduit 262. Prior to the completion of the pressing stroke a cam on the platen 36 actuates a switch, and upward movement of the plunger 130 is prevented. When the cam and switch disengage fluid pressure acts on both the unequal faces of plunger 130 which is then urged upwards. The blank holder platen 170 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 on the platen 36 engages a switch to actuate a valve member 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. The pump tank 256 comprises two compartments, viz. 266 and 274, the former being directly under the reservoir 60 with which it communicates via a conduit 268 having a manually operated shut-off valve 270, whereas the latter forms an exhaust tank under atmospheric pressure, fluid delivered to this tank being conveyed back to the reservoir by a pump 280. Specifications 707,475 and 707,531 are referred to.