Patent GB-815660-A (GB)
Title: Improvements in or relating to a molding machine
IPC: B29C45/53
Filed: 1956-10-16
Abstract: 815,660. Injection-moulding machines. NATIONAL AUTOMATIC TOOL CO. Inc. Oct. 16, 1956 [Nov. 21, 1955], No. 31449/56. Class 87(2). An injection - moulding machine comprises a frame having a mould and three movable units mounted thereon, the first unit forming with the second unit an injection cylinder, plunger and actuating means therefore, the third unit forming with the first unit a feed cylinder, plunger and actuating means therefore, said third unit upon movement thereof relative to the first unit effecting operation of the feed plunger, the first unit having a chamber .located between the feed and injection plungers for the moulding material fed by the feed plunger and cylinder. The machine has a base 10 with a fixed mould carrying platen 14, movable heads 20, 22 rigidly joined by tie rods 26, and a movable head 52 rigidly connected to piston rods 58 with pistons 59 movable in hydraulic cylinders 34 carried by the head 22 and a combined injection plunger and nozzle 50 held in abutting engagement with the mould 16 by U bars 76 on piston rods 74 of pistons 70 in cylinders 19 of the fixed head 14. The heads 20, 22 are movable on the base 10 by a piston 21 and piston rod 23, attached to the head 20, in a cylinder 18 attached to the base 10. The head 20 carries a chamber 38, with electric heating elements 48, having at one end an injection cylinder 40, slidable over the injection plunger 50, in its centre a torpedo 46 formed by a series of holes 47 and at its other end a feed cylinder 42 with an inlet shoot 43. A feed plunger 62, attached to a piston and rod 61, 60 movable in a cylinder 30 attached to the head 22, is movable in the feed cylinder 42 of the chamber 38. The rate of flow of hydraulic fluid to and from the cylinders 34 is controlled by a hydraulic circuit Fig. 6. In operation, at the end of a moulding cycle, with the moulded article still in the mould and the machine as shown in Fig. 5, with the piston 60 and the feed plunger 62 in the chain dot positions 60a, 62a, a measured amount of plastic material is fed into the feed shoot 43 and allowed to fall on top of the plunger 62. Fluid is then admitted to the left of the piston 60, causing the plunger 62 to move to the right and the plastic material (or part of it) to fall into the feed cylinder 42. Reciprocation of the piston 60 then causes the material to be forced through the passages 47 into the injection cylinder 40, tending to enlarge it thus moving the chamber 38 and hence the heads 20, 22 to the right. This movement is resisted by the hydraulic pressure to the left of the pistons 59 and controlled by the hydraulic circuit to maintain a predetermined pressure in the injection cylinder 40. The feed plunger 62 may be reciprocated a part of or any number of strokes and the machine at the end of this "stuffing" operation takes up the position shown in Fig. 6. The previously moulded article is then removed from the mould and the mould closed. Hydraulic fluid is then admitted to the left of the pistons 59 causing the beads 22, 20 to move. to the left and thus forcing the injection cylinder 40 over the nozzle 50 and injecting the material into the mould. The cycle of operations may then recommence. To clean the injection sprue, pistons 70 may be moved to the right, U bars 76 removed, fluid admitted to the left of piston 21 causing the beads 52, 20, 22 to move to the right to give access to the mould, Fig. 8 (not shown). To purge the chamber 38, fluid is admitted to the left of piston 21, with head 52 secured stationary by U bars 76, causing the heads 20, 22 to move to the right until the injection cylinder 40 is clear of the injection plunger 50, Fig. 7 (not shown), reciprocation of the plunger 62 then purges the chamber 38.