Patent GB-850562-A (GB)
Title: Improvements in and relating to a pipe element composed of thermoplastic material and method and apparatus for its production
IPC: B29D1/00
Filed: 1959-02-16
Abstract: 850,562. Moulding thermoplastic pipes. COMPAGNIE DE PONT-A-MOUSSON. Feb. 16, 1959 [Feb. 20, 1958; Jan. 20, 1959], No. 5256/59. Class 87(2). [Also in Group XXVIII] A moulded thermoplastic pipe element T, Fig. 1, e.g. of polyvinyl chloride, comprises at at least one end of a cylindrical body, male or female screw-threading 3, 5 of unsymmetrical form. In Fig. 4 the moulding apparatus comprises a supporting and gripping device S, a two-part metal mould M, a closing device B having a sealing ring 25, a piston P and a fluid-pressure supply device F. The end 2 is first heated to a softening temperature over a length L 3  and then gripped in the device S which are vice jaws which serve also to grip the mould M. The piston P is introduced into pipe T until the sealing ring 25 is compressed against the end 12 and there is maintained in ram 23 a pressure which seals but does not buckle the end 12 and simultaneously compressed air is admitted into the end of the pipe by opening the tap 31. The compressed air expands the softened end of the pipe until it contacts the mould cavity where it commences to cool and stabilize. In a modification, Fig. 6, the plate 21a constitutes a piston which is slidable in the cylindrical portion 33 so that simultaneously with the admission of compressed air the piston 21a is displaced at a constant speed by the rod 22 of the ram so as to exert a buckling force in the wall of the pipe. A further embodiment, Fig. 9, comprises a fixed support and clamping device S 2 , an axially-movable two part metal mould M 2 , a fixed abutment N 2 , an axial thrust device R 2  co-operating with a piston P 2 , Fig. 11, and a compressed-air supply device F 2 . Electrical heating sleeves 51 and 40 are provided in the thrust device R 2  and the mould M 2  respectively. With the mould M 2  heated to 60-160‹C. and the punch heated to 160‹C., the end T 3  of the pipe is heated to 160‹C. and then held stationary in S 2  with the heated end in the mould M 2 . The punch 45 is advanced until the shoulder 50 abuts the mould M 2  and the compressed air is admitted through pipe 30 whilst further movement of punch 45 moves the mould M 2  on rollers 38 along the pipe T 3  until stopped by the fixed abutment N 2  and the pipe end is formed as shown in Fig. 11 where it cools and stabilizes by contact with the mould and the compressed air. In Fig. 13 the apparatus comprises a clamping device S 3  which is movable and mounted on rollers 54 within a fixed housing 55, a fixed mould M 3  and a double acting axial thrust device R3. The device R3 comprises a ram V3 with pistons 56, 77 which move in opposite directions when fluid is supplied through a pipe 58. The piston 56 is connected via rod 58 to the clamping device S 3 . When acted on by fluid under pressure the piston 56 causes axial compression of the pipe in the direction of the arrow # 1  and the piston 57 moves the device S 3  in the direction of the arrow f 2  to cause axial compression of the other end of the pipe.