Abstract: Apparatus for extrusion of a plastics pipe, comprising a plurality of different layers is disclosed, including an extrusion die having a base-plate with a mandrel extending therefrom, a stack of five annular die plates secured to the base plate and defining with the mandrel an annular extrusion passage leading to an annular extrusion outlet. Three annular plenum chambers defined respectively between the mandrel and the rearwardmost plate and between adjoining said plates lead into the annular extrusion passage upstream of the extrusion opening. Equalization rings and a front die member are adjustable diametrally with respect to the mandrel to adjust the concentricity of the different layers in the pipe produced.

Abstract: There is disclosed a pipe joint comprising a first pipe having an end portion engaged as a snug fit in a concentric end portion of a second pipe. The pipes have, at positions spaced from their adjacent ends, external annular ribs with corresponding internal annular grooves, an annular seal being accommodated in the annular groove of the outer pipe between the outer pipe and the inner pipe.A clamping ring which spans the annular ribs of the two pipes comprises two arcuate parts connected end to end by a hinge and having at their ends remote from the hinge outwardly turned edge formations which are received in a wedge-shaped channel member and engage relatively inclined opposing side walls of the channel member. The clamping ring can simply be closed around the pipe joint by relative pivoting of the two arcuate parts and can be retained by sliding the wedging member, in a direction parallel with the axis of the pipe joint, over the edge formations at the ends of the arcuate parts remote from the hinge.

Abstract: Apparatus for moulding articles of synthetic plastics. Plasticized plastics material is fed by a screw within a cylinder, along the cylinder to a nozzle from whence the material is injected into the mould cavity. The feeding of the material into the mould cavity is however effected by rotation of the screw almost in its forwardmost position instead of by longitudinal movement of the screw from its rearwardmost to its forwardmost position. The longitudinal position of the screw is adjusted during filling of the mould cavity by biasing apparatus acting axially on the screw and controlled by means sensing the position of the screw.The temperature distribution throughout the cylinder, the nozzle, the screw and the screw tip is controlled by separate cooling circuits for the various zones, the various cooling circuits coming into operation at various times during a moulding cycle, as determined by timing apparatus.

Abstract: A pipe coupling is disclosed in which two identical tubular parts, to receive pipe ends, each have a flange at one end thereof and are held together, via their flanges, by a clamping ring which has a radially inwardly facing groove which receives the flanges. Each flange on its side remote from the other flange slopes outwardly from the periphery of the tubular part towards said one end thereof providing a ramp surface engaged by the free edge of a respective one of the two side walls of the inwardly facing groove of the clamping ring so that a circumferential tension in the clamping ring produces a wedging action urging the flanges into engagement with each other. In a variant each of the two tubular parts is angled with respect to its end flange so that by adjusting the tubular parts relative to each other about the common axes of their flanges, the angle between the axes of the main portions of the tubular parts can be adjusted, thus providing a pipe bend of adjustable angle.