GB698721A - Improvements in injection moulding and die-casting methods and moulds for use therewith - Google Patents

Abstract

698,721. Moulds ; composite casting. MEJLSO, G. M., and HEIMANN, E. S. March 19, 1952 [Feb. 1, 1952], No. 2736/52. Class 83 (i). [Also in Groups V and XV] A method of die-casting employing complemental mould elements comprises feeding a mould cavity in one mould element via a gate having an outlet overhanging the lip of the cavity, the gate being formed in a gate-unit removably mounted between the mould elements, separating the latter, then removing the gate-unit and simultaneously breaking away the gate waste therein from the exposed surface of the casting at a severing-point within the confines of the lip of the cavity. The object is to enable castings to be produced, e.g. of lead alloy, in which the junction of the break-off gate waste is inside the confines of the periphery of the casting and thus to obviate the need for re-fashioning the edge by a subsequent process. A recess 16 is made in the moulding face 15 of the upper mould element 1 opening at its front face 17 to receive a removable gate unit, Fig. 8, the upper face of which has a central gate 22 which registers with a complemental gate 24 in the bottom of the recess 16. The central gate 22 is intersected by a crossgate 25 so that three feeding branches are formed for the three moulding cavities 4 ... 6 in the mould as described, and the size of the recess 16 is such that the edges of the gate-unit which fits it form chords across the cavities whereby metal fed into the entrance hole at the face 17 is delivered to the cavities 4 ... 6 at points inside their peripheries. In the example described the cavity 4 is for a toy fly-wheel, or it may be for the core and boss of a structure of metal discs which are inserted before the casting operation. The upper mould half has a cavity 7 to form a boss and pinion on the fly-wheel and the cavities 4, 7 carry core pins 8. The cavity 5 is for a toy driving pinion and has a central hole for an axle pin 10 around which the driving pinion is cast. The cavity 6 is for a toy intermediate gear and has two recesses for casting a pair of integral pinions and a fixed core-pin 12. On separating the mould halves the gate-unit is left on top of the lower half, being lightly held by the cast metal in the gates attached at spots on top of the three castings from which it may be separated by a light tap. A plate 26 in the lower mould half carries pins 27 which eject the castings from the cavities when the plate is pushed inwards against spring pressure. Specification 656,956 is referred to.