GB726551A - Improvements in or relating to die-casting methods and machines - Google Patents

Abstract

726,551. Casting-machines; moulds. HODLER, F. Feb. 3, 1953 [Feb. 7, 1952; Dec. 29, 1952], No. 3013/53. Class 83 ( 1 ). A process for die-casting comprises injecting molten metal into a die by a plunger in two main phases, the first phase being carried out at a lower speed than the second, evacuating the major part of the air entrapped in the injection cylinder during the first phase and filling the die completely with molten metal during the second phase. Mould parts 62, 63, Fig. 7, are forced together by a hydraulic piston 64 acting through toggle joints 66. The injection cylinder 70 has a plunger 71 connected to a hydraulic piston 72 moving in a cylinder 73 forming part of the machine frame. The pistons 64, 72 are supplied with liquid from a pump and motor 78, 77. The liquid is delivered to a pipe 80 and a control valve 81 which is operated by a hand lever 86. On moving the control from positions 1-4 switch contacts 112a are temporarily closed, causing a valve 89 to open and a similar valve 98 to close. These valves are operated by auxiliary pistons fed with compressed air from valves 93 which are electromagnetically controlled. Valves 82, 83 remain closed until position 3 is reached, when valve 82 opens to admit fluid to the piston 64 which clamps the mould parts 62, 63 together. When the control lever reaches position 4 valves 82, 83 are both open and a contact-piece 110 engages a contact 112b. Liquid enters pipe 88 and passes through valve 89 and also around a smaller by-pass 94 joining again prior to passing through adjusting valve 96 to cause a slow injection movement of the pistons 71, 72. A stop 120 on the connecting-rod between these pistons strikes a switch 118 which closes the valve 89 and opens a valve 107 to start suction of air out of the mould through the pipe 106. The by-pass 94 allows a small flow of fluid to the piston 72 which thus moves the injection piston 71 slowly forward. As soon as the pressure inside the mould cavity has been reduced to the desired point a manometer 108 connected therewith allows current to pass through a circuit 114, this circuit is, however, additionally controlled by a switch 116 in the form of a detecting device which is closed only when the level of casting metal in the mould reaches it. Cement flowing through circuit 114 operates a relay 115 and, through further switches and relays, opens the valve 98 to start the stage of rapid injection of molten metal into the mould. As soon as the metal reaches the level of a piston valve 129, Fig. 8, extending into the mould cavity, this is moved and through lever connections closes the.valve 125 through which air has been withdrawn and prevents any metal particles passing into the suction line 106. The machine is subsequently opened by returning the control lever 86 to position 1 when, after removing the casting, a fresh operation may begin. Modifications are described including a simplified mechanical operating device for obtaining the two injection movements, with omission of the suction pump.