| 摘要 |
1383434 Controlling extrusion temperature distribution B F GOODRICH CO 19 Jan 1972 [20 Jan 1971] 2617/72 Heading B5A In a blow moulding process, thermoplastic material is downwardly extruded as a circular tubular parison from each of a pair of die heads 19, each supplied with heat plasticized material from separate circular section adaptor passages 39, 29, and 38, 30, which branch from a single circular section passage 28 connecting to an extrusion source. The symmetrical temperature and velocity profiles of material within the passage 28, e.g. as in Fig. 5, produces non- symmetrical profiles within each of the passages 29, 30, e.g. as in Fig. 7, for the passage 29, which are changed to a more symmetrical profile to avoid uneven thickness in the blown parison; by cooling of the mandrel 45 of each die and of the portion of the surface of each of the passages 29, 30 in the region of higher material temperature and velocity. The cooling is effected by compressed air which, to cool the surface portions of the passages 29, 30, is delivered along adaptor passages 33, 32, respectively parallel to the passages 29, 30, via an inlet 31 and outlets 34 to atmosphere. To cool each mandrel 45, the air from an inlet conduit 54 is delivered in the opposite direction to that of extrusion into a mandrel chamber 47, from which it exhausts at an outlet conduit 57, and also through a throttle 61 when functioning to blow the extruded parison. The conduits 54, 57 connected to the mandrel 45 through mandrel supports 53a and 53b, at which locations they are heat insulated by air filled spaces 64, or an insulating sleeve. Two blow mould pairs 20 are reciprocated by an actuating cylinder, for each die alternately to extrude into one of a pair. |
