GB568873A - Improvements in hydraulically operated die casting machines of the pressure type - Google Patents

Abstract

568,873. Casting- machines. PETERBOROUGH DIE CASTING & MACHINE CO., Ltd., and STOCK, H. A. Dec. 8,1943, No. 20484. [Class 83 (i)] In a die-casting machine having hydraulic means for closing the die and for forcing in the molten metal, electromechanical means are provided for locking the dies in closed position, these means being rendered operative by limit switches, operated by full closure of the dies, and become operative despite failure of the hydraulic system. The operator initiates a casting cycle by starting a motor-driven pump 21, which draws oil from a tank 22 and forces it into the system 28, 39, &c., and then pressing a switch to energize a solenoid 23, Fig. 2, and move a valve 24 into the position shown in Fig. 1, thus supplying pressure below the valve plunger 34 and moving it up. This causes the pressure oil in pipe 38 to be supplied through a plunger 56, fixed in a cylinder 3, to urge a plunger 4, connecting-rods 8, Figs. 2, 3, and die part 15 to the right, pressure in the pipe 73 being checked by a one-way. valve 101 and a valve 69. The plunger 4 is also connected to a lever 12 pivoted to the frame at 13 so that this is rotated and, as the die 15 presses the spring- mounted die 16 against the nozzle 58, it operates a switch 67 to energize a solenoid 68 and rotate the plug 70 of the valve 69 into the position shown. This admits pressure oil to a cylinder 47 and moves its plunger 75 and a wedge 48 to the right, thus passing below the member 66 of the lever 12 and locking the die in closed position. At the same time the wedge 48 operates a switch 77 to energize a pump-solenoid which moves a valve plug 79 into the position shown, thus admitting pressure oil to a cylinder 84 above its piston 85 which forces a plunger P, Fig. 3, down and molten metal into the die. When the die is full, pressure builds up in the pipe 83 and causes a plunger 88 to operate a switch 90 which de-energizes the pumpsolenoid to reverse the valve plug 79 and return the piston 85. This carries an arm 95, Fig. 3, which, during the return movement, operates switches to reset all the electrical controls ready for a new cycle and de-energizes the solenoids 23, 68, whereby the valves 25, 70 are reversed, Fig. 1A. This also reverses the position of the valve 30 to admit pressure oil to a pipe 46 and the front of the cylinder 47 and withdraw the wedge 48 and, as soon as the plunger 75 uncovers a port 147, pressure is admitted to the front of piston 53 to withdraw die 15, a one-way valve 102 preventing flow from pipe 45 to 100 direct. As the die 15 moves to the left, a bracket 103, Fig. 3, engages an ejector plate 104 thereof to eject the casting, and finally a cam 105 on the die carriage 10 depresses the piston of a byepass valve 107 to short-circuit the pump 20. If, however, the machine is to operate continuously, the cam 105 is made inoperative and another cam on the carriage 10 operates a switch to energize the solenoid 23 and initiate a new cycle.