| 摘要 |
1,124,930. Moulding grooves in pipes. CHEMIDUS PLASTICS Ltd. 2 May, 1967 [25 May, 1966], No. 23282/66. Heading B5A. [Also in Division F2] An internal annular groove or recess 17 e.g. for the reception of a sealing ring at a pipe joint, is formed in the heat softened end of a thermoplastic pipe 1, e.g. a cold water or rainwater pipe of P.V.C., or of an enlarged socket end 2 thereof around the exterior whereof is clamped a split cavity mould 3, having an internal annular cavity corresponding to the external profile of the desired groove 17, and the interior whereof is blocked by a mandrel 6 comprising bolted together members 8, 10 which define an annular space 7 therebetween housing an expandable moulding ring 14 e.g. of natural rubber or neoprene. The ring is radially expanded to deform and mould the pipe wall into the annular cavity by the thrust from the inclined surface 12a of a frusto-conical member 12 which is displaced axially upon an internal cylindrical portion of mandrel 6 by rods 13, and which member 12 either acts directly upon the interior of moulding ring 14 or upon the mating internal surface 15 of a thrust ring. The latter comprises a plurality of separate rigid thrust sections (15b) (Figs. 3 and 4, not shown), each secured by bonding or mechanical engagement at the circumference thereof to the inner edge of ring 14 which is expanded by their radial movement. The edges 3a of the cavity are rounded to reduce strain at the corners 17a of the groove 17. Localized thinning of the pipe wall may be reduced by swaging to increase the socket 2 thickness after forming the socket or by the heat shrink fitting thereon of a thermoplastic sleeve prior to formation of the groove 17 and which operation may be followed by heating of the mould and combined pipe and sleeve and forming a plain socket 2 and the groove 17 either immediately thereafter, or after further heating of the pipe and sleeve. The external surface of the ring 14 is cylindrical. In an alternative embodiment (Figs. 5-8, not shown), the thrust ring (15) is provided with a concentric passage (18) extending through each section (15b) thereof and wherein is located a coil spring (19) which acts to contract the thrust ring (15), which may or may not be attached to the moulding ring 14. |
