Patent GB-761208-A (GB)
Title: Improvements in pipes
Inventor: DECK PHILIP RONALD
IPC: B29C53/66
Filed: 1954-11-12
Abstract: 761,208. Composite pipes; pipe-making machines. SHARP, JONES & CO., Ltd. Nov. 7, 1955 [Nov. 12, 1954; Feb. 16, 1955], Nos. 32785/54 and 4589/55. Class 99(2) [Also in Group X] A composite pipe comprises an external layer of synthetic resin bonded material and an internal layer of concrete which may be reinforced. The material may be glass or asebstos fibres in the form of rovings, mat, tape or cloth, and be bonded with a thermoplastic or thermosetting synthetic resin, e.g. allyl compounds, polyester, phenolic, silicone, melamine, expoxide or furane resins. Preferably, the material is helically wound and has a helix angle of 30 degrees. The concrete may have a composition, by volume, of Portland cement 1 part, sand 1¢ parts and granite chippings 2¢ parts; the Portland cement may be replaced by sulphate resisting or aluminous cement. A pipe of synthetic resin bonded material may first be made and then provided with a cast-in concrete lining or the latter may be centrifugally spun into the pipe, or a concrete core pipe may first be made by centrifugal spinning, tamping or vibration casting and then after the concrete has matured the synthetic resin impregnated material is applied by winding to the outside of the pipe, the resin being allowed to set. It is stated that, after hardening of the resin, the layer of synthetic resin bonded material serves to seal the concrete pipe against the seepage o thigh-pressure fluid from inside the pipe, pre-stress the concrete pipe by virtue of the contraction of the resin on setting and the tension applied to the material during application thereof, and increases the bursting strength of the concrete pipe. The concrete pipe may project from one end of and terminate short of the other end of the synthetic resin bonded pipe. Apparatus for applying the synthetic resin bonded material. A lathe bed 1 provided with a headstock and tailstock of normal construction has recesses 5, 6 along the sides thereof parallel to the axis of rotation of the faceplate 3 of the headstock and housing roller chains 7, 8 mounted on sprockets 9, one pair of the latter being driven through gearing and reversing mechanism at a speed proportional to the speed of rotation of the faceplate. Wheeled carriages 12, 13 which move along tracks 10, 11, have sprockets 15, 16 mounted thereon engageable with the chains 7, 8, those sprockets being either locked or free to rotate as desired. Each carriage supports a number of shafts 17 carrying totatably mounted bobbins 18 of. for example, glass fibre rovings, a number of polished guide rods 19, two alignment combs 20, 21, a vessel 22 filled with liquid synthetic resin, a fixed die block 23 containing ceramic dies, and an angularly adjustable die block 24 also containing- ceramic dies, mounted on an adjustablearm 25. Mounting the concrete core pipe. Thepipe 26 is fitted with end rings 27.'Fig 3, held in position by a tie bolt 28, An assembly 29, comprising circular discs. 30, 31 spaced apart by a cylindrical member 32 of a length a little greater than the winding pitch X of the rovings, is: bolted to the tailstock 4 and the face-plate 3; the disc 30 has a peripheral flange 33 and a ring 34 of friction material, and a sleeve- 35 is slidably mounted on the discs. The pipe 26 is lifted into position and clamped against the rings 34 of the assemblies 29, the lifting eyebolts 36 being removed, and the sleeves 35 being slid towards the pipe ends leaving narrow gaps 37, Fig. 1. Operation of apparatus. The required number of rovings 38 are threaded around the guides 19, through the combs 20, 21 around polished guides 39 in the vessels 22 and through the dies in the blocks 23, 24, one carriage being respectively located adjacent the headstock and tailstock of the lathe bed. The ends of the rovings are led from the blocks 24 and tied to the sleeves 35. After locking the sprockets 15. 16, against rotation the face plate 3 and sprockets 9 are set in motion so that the carriages 12, 13 travel in opposite directions, rotation of the pipe 26 causing the rovings to be drawn from the bobbins 18; two layers of rovings are applied to the pipe. The ceramic dies in the blocks 23, 24 remove surplus resin. The sprockets 15, 16 are unlocked when the carriages reach the opposite ends of the pipe and a layer of rovings is wound with a zero helix angle on each sleeve 35, the sprockets then being locked and the carriages caused to move back along the pipe to apply two further layers of rovings at opposite helix angles. After the desired number of layers of rovings have been applied to the pipe the latter is freed from the sleeves 35 by cutting of the rovings at the gaps 37 whereupon the pipe is removed from the apparatus and the resin cured in an oven. A wooden or rubber scraper 40 equal in length to that of the pipe removes surplus resin and smooths the finished product. In modified apparatus, the concrete core pipe 26 may be rotated and moved laterally with respect to a stationary carriage or carriages, or the pipe may be disposed vertically and rotated, there being relative vertical movement between the pipe and the means for applying the rovings. Two or more lengths of core pipe may be joined by rebated joints and the latter covered by helically wound rovings while in the apparatus. According to the second Provisional Specification tapered wooden plugs are lightly driven into the ends of the concrete pipe and the pipe is then mounted in a lathe. at least one tensioned, continuous glass fibre thread drawn from a storage reel, over glazed porcelain pulleys and then through a bath of polyester resin, being then wound on to the pipe.