Method of forming hollow articles

1,126,421. Moulding hollow articles. RUBBER & PLASTICS RESEARCH ASSOCIATION OF GREAT BRITAIN. 27 Sept., 1965 [26 Sept., 1964], No. 39311/64. Heading B5A. In a method of forming a hollow article, the hollow article is heat softened in a fluidized bed, after which it is subjected to one or more formative operations, and then cooled to harden it. As described, a P.V.C. pipe is heated in either a vertical or horizontal fluidized bed, e.g. of alumina, silica, ballotini or aluminium and is then placed on a jig and bent; alternatively the heated end of the pipe may be formed into a socket. The pipe may be fed vertically into the bed so that the fluidizable medium is present inside and outside the pipe, or it may be fed horizontally into the bed and over a mandrel via an unfluidized section of the bed. Alternatively, the pipe is supported horizontally in apertures in opposed end walls of the bed, which walls are vertically adjustable to allow the pipe to be lowered into the bed. During the bending operation over a lower jig portion, a mandrel is located in the pipe and comprises a flexible metal tube surrounded by a rubber tube which is inflated to engage the pipe interior. After the bending operation, an upper part of the jig is applied and the pressure within the rubber tube increased to remove any wrinkles in the pipe.