GB684611A - Improvements in or relating to a method of and means for blow-moulding plastic material - Google Patents

Abstract

684,611. Blow-moulding hollow articles. T.H.P. (LONDON), Ltd. Nov. 28, 1950 [Nov. 29,1949], No. 30557/49. Class 87 (ii). A method comprises three stages. In the first stage a bag-like preform is injection-moulded about a core; in the second stage the core with the preform thereon is transferred to a blowmoulding die; and in the third stage the preform is blown to the final shape in the blowmoulding die. The stages of preform-moulding and blowing occur simultaneously on separate articles, and the three stages occur in repeating sequence. Figs. 1 and 2 show a hydraulic press comprising a stationary crosshead 1 and a vertically-reciprocable platen 2. The crosshead carries a slide 3 which can be moved horizontally, from right to left and left to right, Fig. 1, on rollers 11, Fig. 2. Fig. 2 is a section at right-angles to Fig. 1. Depending from the slide 3 are two pairs of upper injection-mould parts 4, 4a having cores 5, 5a, and two mechanisms 15 which de-gate and deliver blown articles. Upstanding from the platen 2 are two central moulds 7 which co-operate with the cores 5 to produce preforms, two' pairs of blowing moulds 8, 8a which co-operate with the cores to blow the preforms into article shape, and two pairs of standards 28. The moulds 7, 8, 8a are of the split wedge type, and are opened and closed, as the platen descends and ascends, by fluid pressure means 9. Operation.-Platen 2 is raised to the closed position, as shown, and an injection-moulding means 12 is brought down. Plastic material is injected through a sprue bush 16 and gates 17 to make a pair of preforms 13. The injection means 12 is then raised and the platen 2 lowered. As the platen descends, the dies 7 open and the preforms are left clinging to the cores. The slide 3 is then moved to the left to register the preforms with the blowing moulds 8 and the cores 5a with the injection dies 7. The platen ascends and then, simultaneously, a second pair of preforms are injected between dies 7 and cores 5a whilst the first-moulded pair 13* are blown in moulds 8. The blowing is effected by air from pipe 6 passing through the separated parts A, B, of cores 5 (as shown on the right in Fig. 1), these parts having been separated when the platen ascended by means of bolts 19. The platen descends, the blown mouldings 13* remaining in mould 8 and the second pair of preforms clinging to cores 5a. Slide 3 moves back to the right, the second pair of preforms being transferred to a position over blowing mould 8a ; at the same time, mechanism 15 (at the left of Fig. 1) is brought to the position shown. The platen ascends, a third pair of preforms is injected between 5 and 7, the second pair of preforms 13a are blown between 5a and 8a, and the first pair 13* are acted upon by cutter 15 which is urged downwardly by spring 22 to de-gate and trim the blown moulding. The cut-off gate is gripped by spring-pressed arms 26. Suction cups 14 on the cutter engage the two blown articles. From the Fig. 1 position the platen descends, the blown and de-gated articles 13* being sucked out of the moulds, the preforms 13 remaining on their cores 5, and the blown articles 13a remaining in the moulds. The slide then moves to the left and the platen ascends, whereupon the standards 28 on the platen act on the arms 26 and cause them to drop the gate and runners; at the same time suction to cups 14 is cut off and blowing air supplied to the cups to blow the articles away for delivery. During these operations the preforms 13 are being blown in moulds 8, other preforms are being made in moulds 7, and the blown articles 13a are being de-gated in moulds 8a. Fig. 3 shows a modified core, which is porous and may be made from powdered metal, the pores being indicated diagrammatically at 24. The cores and the blowing fluid may be heated. The dies may be temperature-controlled. In modifications (not illustrated) (a) the slide may have a circular or arcuate path and may move reciprocally or in steps all in the same direction; (b) the press may operate in a direction other than vertical; (c) a set of articles may be moulded in one piece and subsequently parted simultaneously with preform-moulding, blowing, &c. ; (d) a heating station may be disposed between the preform-moulding station and the blowing station.