Abstract: The invention relates to a process for the production of coupling pieces which possess an undercut annular groove optionally provided with a sealing ring, in which process a sleeve, having an internal diameter which increases in steps towards the open end, is initially preformed, the terminal part of the sleeve is postformed in order to form the annular groove, after having optionally introduced a sealing ring into the preformed sleeve, and, during preforming, only the terminal part of the preformed sleeve is kept at the deformation temperature and the remainder of the preformed sleeve is cooled, the terminal part of the preformed sleeve being cooled after postforming.

Abstract: Process and device for the forming, on the end of a pipe made of a thermoplastic, of a coupling piece possessing an undercut annular groove intended for receiving an annular seal, according to which process and device the coupling piece is initially preformed by means of a forming core which possesses an annular rib for forming the annular groove, the core then being withdrawn from the partially cooled coupling piece by virtue of an elastic deformation of the part possessing the groove, by means of the rib of the forming core, and this part being kept at the elastic deformation temperature, and according to which this part is subjected to a postforming operation, before it has completely cooled, by means of a postforming ring.

Abstract: An apparatus for forming a bell end having a thickened portion on a pipe composed of thermoplastic material, in which an annular shaping space is established between a shaping sleeve and a mandril having an elastic shaping ring, the height of the shaping space increasing along transition portions of the surfaces of the sleeve and the mandril to a region defining a sealing chamber and then decreasing again.

Abstract: A bell end on a pipe of thermoplastic material has variable wall thickness in the axial direction, the maximum being where the inner wall acts as a sealing face. The bell end can be formed by upsetting the pipe wall into the cavity between a mandril and a shaping sleeve.