GB1116097A - Method and means for forming hollow articles out of a sheet of thermoplastic material - Google Patents

Abstract

<PICT:1116097/C1/1> <PICT:1116097/C1/2> A hollow article is formed from thermoplastic sheet material, which may be of glass, by clamping the sheet in a frame comprising two pivoted halves, heating the sheet and then vacuum or blow forming the sheet on to a mould or former, the frame being pivoted to fold the sheet prior to or during the forming. In one embodiment, illustrated in Figs. 1-5, a sheet 1 is clamped in a split frame 2, heat softened, and then drawn by a male member 4. The member carries a V-shaped bead 6 against which the clamp is folded at a certain point in the drawing operation, the sheet then being vacuum drawn against the member, recesses 7 and 8 being formed. The article may be released by disassembling the mould or by re-opening the clamping frame a certain amount (see Fig. 5, not shown). In an alternative embodiment, see Figs. 6-13, the sheet is clamped in a lower split frame and mould halves M, M1 are carried by an upper split frame, the pivotal axes of the frames being vertically aligned. The clamped sheet is first heated from both sides, after which the lower split frame is pivoted by upward movement of the axis relative to fixed rollers 43, the sheet being pre-inflated by hot air from 47. After a predetermined movement of the lower split frame, the upper split frame is similarly pivoted by upward movement of the pivotal axis relative to rollers 17 so that the mould halves are pivoted on the sheet, the sheet being welded and cut along the line of contact of the mould halves. The enclosed pre-inflated body is then sucked or blown into contact with the mould halves to form a completely closed article.