Patent GB-540324-A (GB)
Title: Improvements relating to the coating and manufacture of pipes and similar hollow bodies from cementitious or similar plastic materials
IPC: B28B21/58
Filed: 1939-08-02
Abstract: 540,324. Coating, lining and making pipes. HUME, W. R. Aug. 2, 1939, Nos. 22444, 22445, 22446 and 22447. Convention dates, Aug. 2, 1938, Sept. 2, 1938, Sept. 3, 1938 and Sept. 14, 1938. [Class 87 (ii)] A method for coating or manufacturing pipes and the like for cementitious, bituminous or other suitable plastic materials comprises attaching a flexible sleeve of foraminous material such as hessian to one end of a pipe or mandrel, arranging the sleeve to extend loosely around the pipe or mandrel so as to provide in association therewith an annular space, introducing the plastic material under the force of gravity or applied pressure into the annular space so that it travels towards that end of the pipe or mandrel to which the sleeve is attached, moving the pipe or mandrel in the same direction as the feed of the plastic material, and restraining free movement of the flexible sleeve so that it is progressively placed under tension from its attached end by and during movement of the pipe or mandrel whereby an annular body of the plastic material is progressively built up in a lengthwise direction within the annular space and is compressed or moulded between the sleeve and the adjacent surface of the pipe or mandrel. As shown in Fig. 1, apparatus for carrying out the method comprises an extruding machine 3 provided with a hopper 11 for the plastic material 7 and a discharge nozzle 4 through which the pipe or mandrel 2 is traversed, a foraminous sleeve 6 adapted to be attached to the end 6b of the pipe or mandrel, and a tension device comprising a frame 8 carrying a rubber or like yielding ring 9 the inner end of which presses against the sleeve 6. The warp and weft strands of the sleeve 6 preferably extend diagonally in relation to the length of the pipe or mandrel which may be effected by forming the sleeve from a strip of material cut on the bias and wound spirally on a former. The hopper 11 is provided with a tubular guide 17 through which the pipe or mandrel 2 is fed by suitable means, e.g. a wheeled carriage actuated by screw and nut gear on an endless chain, the pipe or mandrel being centralized in the guide by spring fingers 19 and the guide 17 being centralized, in the nozzle 4 by projections 21. Heating jackets 16 may be provided around the hopper 11 and the inner part 4a of the nozzle 4. Pressure means, e.g. compressed air, a feed screw, or a plunger 13 are provided for forcing the plastic material from the hopper to the space between the sleeve 6 and the pipe or mandrel as the latter is moved forward carrying the sleeve with it. In a modification, the hopper is provided with a depending tubular extension forming the nozzle through which the pipe or mandrel is passed in a vertical direction, the plastic material being supplied under gravity or pressure, and the tension device comprising either an inverted conical shaped member or a series of rings of resilient material secured between rings of non-resilient material, the apertures of the rings decreasing in diameter in the direction of movement of the pipe or mandrel. A metal reinforcement, e.g. a wire cage, may be positioned around the pipe or mandrel and embedded within the plastic material during the extrusion. The Specification as open to inspection under Sect. 91 includes a modification in which a pipe is lined internally by supplying the plastic material to the space between a foraminous sleeve positioned inside the tube and the internal surface of the pipe, the pipe being moved relatively to a tension device consisting of alternate rings of rubber and wood which progressively increase in diameter in the direction of movement of the pipe. This subject-matter does not appear in the Specification as accepted.