An improved method and apparatus for blow molding or vacuum molding hollow articles the material of which is oriented along two axes.

摘要

1,156,185. Blow-moulding; stretching. PHILLIPS PETROLEUM CO. 23 Sept., 1966 [24 Sept., 1965], No. 42624/66. Heading B5A. Blow-moulded articles are produced from synthetic plastics material, e.g. polypropylene, and given longitudinal molecular orientation by stretching the parison prior to or during expansion thereof. The circumferential expansion ratio is preferably 2 : 1 to 10 : 1 and the axial stretching ratio is preferably from 1 : 1 to 8 : 1. The apparatus, Fig. 2, comprises a hollow split mould 18, 19, air inlet channel 41, vertically reciprocable grippers 3, 4 cut away at 13, 14, pivoted at 9, 10 and having cams 11, 12, cam-tube 15 which is vertically reciprocable, and foot 66 on rod 63. Firstly, grippers 3, 4 are lowered and opened by cam tube 15, and parison 40 is introduced from below. The neck portion is then compression-moulded by die pieces 5, 6, pressed together by lowering of cam tube 15 on grippers 3, 4, compression ring 50 and washer 51. The parison is then pinched off either by mould halves (18, 19, Fig. 4, not shown) or separate means (53, 54, Figs. 6-8, not shown). Foot 66 is lowered to seal the seam while grippers 3, 4 are raised by cam tube 15 to stretch the parison longitudinally (Fig. 4, not shown). The parison is then expanded (Fig. 5, not shown) by differential pressure and may be ejected by foot 66. In one embodiment (Figs. 6-8, not shown), the parison is pinched off by six members (53-58) reciprocable by toggle arrangements on rotation of inner ring (77) by arm (76).