Method and apparatus for producing radially-expanded socket ends on thermoplastic pipe lengths


1356765 Expanding pipe ends RIEBER & SON PLASTIO-IKDUSTBI AS 24 April 1972 [26 April 1971 24 June 1971 27 Sept 1971] 18914/72 Heading B5A [Also in Division F2] The end of a thermoplastic pipe 18 (Fig. 2) is expanded and grooved by engaging the heated pipe end over a mandrel 1, mould element 2 and support member 3, the latter serving to position the mould element 2 to form the pipe groove. In a first embodiment, an internally reinforced mould element 2 and hot pipe end 18 are pushed on to the steel mandrel 1 and support member 3 until the mould element abuts the end of the support member, and the pipe end encloses the mould element and abuts a shoulder 15. The mould element seats against a similarly shaped surface 11 (Fig. 4) of the support member 3, and adjacent one or more slots 9 that allow free air circulation about the element. The support member 3 is retracted and a vacuum applied internal to the mandrel 1 sealed by 0-rings 3a. After water cooling with sprays 14, the support member 3 pushes the pipe and moulding element, serving as a seal, off the mandrel 1. The pipe comprises polyethylene or P.V.C., and the mould element 2 rubber, nylon, polyacetal or spring steel of trapezoidal or semicircular shape, and may be removed from the pipe or left as a sealing element. A heating band 16 (Fig. 2) is provided. Second embodiment.-A mandrel 20 (Fig. 5) is slidably supported on a hollow shaft 29 and is surrounded by a support member 44 fixed to a holder 40. The holder slidably supports a spring returned support 55. Vacuum and compressed air are supplied via nipples 38, 60 respectively. The whole is mounted in a partitioned housing (63) (see Fig. 7, not reproduced), the front end 21 (Fig. 5) of the mandrel being movable through a chamber (67) (Fig. 7) of the housing to project from the housing. A mould element 82 (Fig. 10) is pushed on to the mandrel by a heated pipe end 83. Simultaneously, air at 170‹ C. is circulated through the housing (63) (Fig. 7), and compressed air admitted via nipple 60 (Fig. 5) to push the mandrel 20 to the left in Fig. 5 (right in Fig. 10) into the pipe. The compressed air is cut off and the pipe pushed further to force the mandrel 20 back to its starting position within the housing, and push the mould element 82 (Fig. 10) over a projection 53a of the support member 44 to seat between the supports 44 and 55, until the pipe end abuts a projection 45 and encloses the element 82. The pushing-on of the pipe is arrested, and compressed air again supplied to push support 55 to the right (in Fig. 10) and force the mould element 82 back over projection 53a and into a desired position in the pipe. Mandrel 20 also moves to the right (in Fig. 10) to pull the pipe off supports 44, 45; the pipe is sucked around the element 82 and on to the mandrel 20 by a vacuum applied to nipple 39 (Fig. 5). The hot air is cut off from the housing (63) (Fig. 7) and the pipe end water cooled in the chamber (67). The compressed air is disconnected, and the vacuum draws the mandrel 20 back to starting position within the housing, while hinged flaps defining chamber (67) push the pipe off. Third embodiment.-A single, non-movable support member (144) (Fig. 16, not reproduced) is provided, and the mould element comprises a split ring (182).




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