1310396 Cutting waste during blow-moulding SIDEL 20 Oct 1970 [24 Oct 1969] 49776/70 Heading B5A A wall portion of a hollow article is removed during blow-moulding by providing a cutting edge projecting into the mould cavity and increasing the volume of that part of the cavity corresponding to the wall portion to be removed so that the blowing pressure cuts the article against the cutting edge. As shown in Fig. 3, an article 5 is formed by blow-moulding an extruded tube against the walls of mould halves 1, 2 and against cutting edges 6e, 7e by air supplied from blowing head 17. The mould halves have recesses 8, 9 containing slidable members 6, 7 held in their forward position against the blowing pressure by cylinders 11, 12 and by stops 13 against the ends of further recesses 14. After blowing to the shape of Fig. 3, the pressure in cylinders 11, 12 is reduced so that members 6, 7 are pushed back by the blowing pressure, slicing off the waste portion 5b and communicating recesses 8, 9 with the atmosphere via ducts 15, 16. The members 6, 7 may contain ducts 28, 29 for circulation of cooling- water.
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