| 摘要 |
1,070,020. Moulding hollow thermoplastic articles. ILLINOIS TOOL WORKS Inc. Dec. 31, 1963 [Dec. 31, 1962], No. 51401/63. Addition to 1,010,603. Heading B5A. In a method of forming a beaded article from thermoplastic sheet material as described in the parent Specification, after severing, the peripheral portion of the sheet material 36 is compressed between opposed surfaces 72 and (120), (Fig. 4, not shown) of two members 66 and 102 and caused to flow in a direction transverse to the direction of movement of the member 66 and so form a bead 34 (Figs. 1, 1A, not shown). Preheated sheet material 36, e.g. polystyrene is supported between two mould sections 38, 40. The upper mould 40 is connected to an air pressure source 54, and consists of an upper annular clamp 56 engageable with the top side of sheet 36, a ring 60 having a necked-down lower portion 62, a mandrel portion 66 having a side wall 68, and a sheet shearing edge defined by wall 68 and a lower mandrel surface 72. The mandrel portion 66 has a central bore 74 in which is mounted an insert 76 supporting a heat-insulating plug 80 having a bore 82. The bottom of the lower mould cavity is formed by the enlarged head of a knockout plug 96 which is slidable in a mould base insert 94 and movable independently of the mould 40 to eject the finished article. A substantially cylindrical mould member 102 has a shoulder 107 and threaded portion 108 adapted to receive an external ring 110. The ring 110 has a necked-down upper portion 112 which is operable to protrude between part 62 and side wall 68 of the mandrel 66. The top surface 114 of the portion 112 defines a cut-off corner (116) which co-operates with the corner 70 of the mandrel portion. An inner mould insert 104 is disposed inside member 102. A lower annular clamp 86 cooperating with clamp 56 is operable independently of the mould 40. In operation, the sheet 36 is firmly clamped between members 56 and 86, and is mechanically prestretched by movement of plug 80 relative to the clamps. The lower mould is actuated so that the parts assume the position seen in Fig. 3 (not shown) and air under pressure is admitted from source 54 to force the sheet against the female lower mould. With the air pressure still on, the mandrel is actuated to sever the material between corners 70 and (116) and then moved to the position seen in Fig. 4 (not shown). Thus a bead 34 is formed by compression between the surfaces 72 and 120, and the air pressure forces the material of the bead into intimate engagement with the portion 112 at the outer periphery of the bead. By modifying the shapes of surfaces 120, 118 and 112 beads of various crosssection may be obtained (see Figs. 5, 6C, 7C, 8, 9, not shown). The surface may be made of irregular cross-section to provide a series of projections on the bead. Instead of using an air pressure source, the container may be vacuum formed.
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