GB574639A - Improvements in or relating to injection moulding machines - Google Patents

Abstract

574,639. Injection-moulding machines. GOLDHARD, F. K., and PRENN, D. D. June 29, 1944. No. 12419. [Class 87 (ii)] In an injection-moulding machine for thermosetting and/or thermoplastic material, a movable die plate is connected with a movable thrust plate, both plates being adapted to be together quickly approached to and retracted from an adjustably set position in which the thrust plate is locked at the end of the quick approach stroke and held stationary for the purpose of taking up the thrust during the subsequent slow closing movement of the movable die plate. In the machine shown, a movable die plate 6 is connected to a thrust plate 9 by toggle-lever mechanism 10, which is actuated by an hydraulic piston 11 in a cylinder 13 fixed to the plate 9. Alternatively, instead of toggle mechanism, an hydraulic or other equivalent arrangement may be used. Tie rods 15 are attached to the fixed die plate 1, and form guides for the plates 9 and 10, the rods 15 having threaded portions 16 on which are drive nuts 17 mounted in housings 18 fixed to the thrust plate 9. The nuts are driven by worm &c. gearing from a motor 20, the plates 6, 9 with the cylinder 13 and driving arrangement forming a single unit which is mounted on a carriage 21. The die plate 6 is movable on the carriage. The cylinder 13 is connected to a stationary control valve and pump (not shown), preferably through two parallel tubes, one of which is shown at 26, slidable in bores 28 of the cylinder ; one of the tubes communicates with the front space and one with the back space of the cylinder. The die plate 6 carries a cam or dog 31, adapted to operate a limit switch 32 for the motor ; the switch, or an associated relay, may also operate other circuits, e.g. for controlling the working of the piston 11 and that of the injection cylinder, for heating or cooling, or for an automatic timer by which the reversal of the motor 20 after the moulding operation may be controlled. Adjustment of the position of the switch 32 or the dog 31 determines the point at which the piston 11 operates to effect the slow closing of the mould. A limit switch 35, adapted to be actuated by the carriage 21 when it has returned to its initial position, may be provided to effect a succeeding reversal of the motor, either immediately or with timed delay. Another limit switch 33, fixed on the thrust plate 9 and adapted to be operated by a dog 34 on the toggle-actuating piston-rod 12, is also provided in the motor circuit to ensure that the motor can only be started to drive the carriage through the screw and nut devices when the toggle mechanism has retracted the die plate 6.