Patent GB-1355040-A (GB)
Title: Apparatus for and method of manufacturing reinforced tubes of plastics or elastomeric material
IPC: B29C48/09
Filed: 1970-05-21
Abstract: 1355040 Delivering reinforcing mesh to extrusion coating head CREATORS Ltd 17 May 1971 [21 May 1970 11 Dec 1970 4 March 1971] 24761/70 59201/70 and 6052/71 Heading B5A [Also in Division F2] In the extrusion of a circular or elliptical section plastics or rubber tube reinforced by a woven tubular mesh, an extrusion crosshead mandrel 3 extends rearwardly of the extrusion head to be supported between an opposed plastics or rubber roller pair 27, which are adjustably mounted for centring of the mandrel 3 within the die, and which support the mandrel by locating within axial grooves 29 thereof at a sufficient clearance to permit the delivery, around the mandrel 3, of a woven reinforcing tube 12 to which a coating of polyvinyl chloride, polyurethane, neoprene or butyl rubber is applied during passage through the die. Within the extrusion head, the coating is applied to the exterior of the reinforcing tube 12, and to the interior thereof via a reduced diameter portion 16 of the mandrel and passages (19), Fig. 2 (not shown), and an annular passage 15 of a sleeve 14 mounted to the mandrel. The tube drawn from the die may be cooled in passage through a water bath, and may also pass through a sizing device. A mandrel vent passage 44 avoids collapse of the extruded tube. The upper roller 27 is flanged to restrain transverse movement of the mandrel 3 and the rollers 27 may be driven, but in the Figs. 1 and 4 embodiment are each freely rotatable about pins 37, extending between one bifurcated end of an arm 36, the other bifurcated end whereof is pivotally mounted, at pins 38 engaging with a "snap action", at a yoke 28 through upper and lower arms of which extend adjusting screws 39 to effect the transverse adjustment of the rollers 27, by abutment with the arms 36. The yoke 28 is mounted for free pivoting movement in the vertical plane, to permit self centring of the mandrel within the extrusion die, about pins 35 extending from blocks 30 which are adjustably mounted, for positioning in the direction of the die head (for balancing of the axial extrusion pressures on the mandrel within the die), by screws 43 abutting the ends of pillars to which the blocks 30 are secured by grub screws and which are carried by a plate 32, screwed to the die head against heat insulant 34. In the Fig. 8 embodiment, sequential vertical and horizontal idler roller pairs 27a, 27b, are provided, which may be mounted as in the Fig. 4 embodiment, or to non-pivotable supports when the rollers of each pair are adjustable both in their common plane and at right angles thereto. In the Fig. 8 embodiment, the coated reinforcement 11 drawn from the extrusion die 1 has applied thereto at least one layer of overlapping helically wound reinforcing tape 50, e.g. to which may be applied a further oppositely wound tape layer, to which is applied a further coating 51 from an extrusion head 113. The tapes are applied from a plurality of spools 119, freely rotatably mounted in diametrically opposed pairs to arms 121 of a tubular member 124 which is rotated to wind the tapes 50 around the coated reinforcement, by a pulley and belt drive 129, 128, 130 from a motor 127. The spools 119 are angularly adjustably mounted to the arms 121 to which they are also replaceably mounted, about pins 120 by nuts 122. The woven tubular reinforcement may comprise twisted yarns permitting transverse stretching of the tube, or may comprise nylon, glass, polyester, or metal wire serving also to dissipate electrostatic charges in use and which function may alternatively be performed by incorporating, during extrusion, a metal wire strand, or a strip which, if incorporated in transparent plastics, may carry advertising matter. The woven tubular reinforcement and the helical reinforcing tape may be coated with the same plastics materials, e.g. polyvinylchloride, or respectively coated with different materials. The helically wound reinforcing tape 50 may comprise textile material, synthetic fibres, paper, metal, or plastics strip, and is bonded to the coatings on either side thereof by fibrous or roughened surfaces of the tape, or by a heat sensitive adhesive heated by hot air jets as the tape 50 is applied. Where the tape 50 is of open mesh structure, the extruded coating penetrates therethrough to bond with the coating of the woven tubular reinforcement where this is uncooled, or has been additionally softened by hot air. In the Fig. 11 embodiment, the tubular woven reinforcement 12 coated with plastics 11, has applied thereto sequential helically wound tape and plastics coatings 50, 51. The woven tubular reinforcement 12 may be coated with polyurethane by the crosshead 1, and may have applied thereto a coating of polyvinyl chloride from a further die, prior to application of the helical tape 50. The tapes 50 may also be applied to the coated reinforcement 11 heated by hot air jets in delivery from a storage reel, instead of directly from the crosshead 1. Where the helical tapes 50 are not applied, the woven tubular reinforcement may be completely or partially embedded in the coating 11 applied thereto, e.g. polyurethane, to which a further extrusion coating of a different plastics, e.g. polyvinylchloride, may be applied. The coating of the woven tubular reinforcement may also comprise neoprene or butyl rubber, when curing is effected by passage through a salt bath at 80 C.