This invention relates to die casting machines having relatively movable die members associated with a movable ejector die assembly, and more particularly to an improved oblique core locking mechanism for use with die casting machines of the type disclosed in U.S. Pat. No. 3,433,292, issued Mar. 18, 1969 in the name of J. W. McDonald.
In the die casting of articles of complex shape, such as engine blocks, a plurality of movable die sections are registered in a die-closed position to form a die cavity, and are subsequently retracted to permit removal of the cast part from the die. These die sections must be held in place in the closed position against extremely high molten metal injection forces, sometimes up to 500,000 to 1,000,000 pounds. Those die parts which are movable in a direction coinciding with the principal or longitudinal direction of movement of the die casting machine are locked in place by the normal opening and closing mechanism of the machine itself. Those die parts which move in a direction parallel to the parting plane, which is perpendicular to the principal axis of the machine, are locked in place during the injection step by wedges or the like protruding from the cover die. Even though substantial force builds up during the metal injection step in die casting, movable die members can be satisfactorily locked in a die-closed position when they move only in these two directions. However, die members which are movable at an acute angle with respect to the longitudinal axis of the die casting machine have been locked in die-closed positions by engagement of a backup plate with the piston rods of the hydraulic cylinder means used for moving the die members, as disclosed in the above U.S. Pat. No. 3,433,292. This locking mechanism has not been satisfactory because the great angular forces acting on the piston rods deleteriously affect the packing of the hydraulic cylinders, and cause rapid wear in the area of contact between the piston ends and the backup plate because of sliding action and relatively small contact area. It has also been unsatisfactory because of limited access to the hydraulic cylinders.