Patent GB-742075-A (GB)
Title: Improvements in or relating to the production of reinforced tubes
IPC: B29C48/09
Filed: 1953-04-25
Abstract: 742,075. Making tubes of fibrous material; flexible tubes. YARSLEY, V. E. July 26, 1954 [April 25, 1953 ; April 30, 1953], Nos. 11490/53 and 11934/53. Class 99(2). [Also in Group V] A fibrous rope-like material treated with a resinous bonding composition is helically coiled with adjacent turns substantially in contact and passed through an axially elongated space between the inner surface of a sleeve and the outer surface of a mandrel, the resin composition then being set or allowed to set to the solid coherent state. The passage of the coiled material through the annular space is obtained by the rotation relative thereto of a thread formed on the sleeve or the mandrel, and the dimensions of the sleeve or mandrel, or both, is or are such as to produce mechanical reaction upon the coiled material while the latter passes through the annular space thereby maintaining the coiled diameter of the material substantially constant. The material may be of cotton, hemp, sisal, jute, hair, rayon, wool or nylon fibres spun into a thread and used as such ; alternatively, the fibres are spun to form a multicored material, woven to a form resembling a conventional sash cord, or plaited, or otherwise formed, e.g. by binding or stitching bundles of fibes together. Also, the rope-like material may have a metallic reinforcement such as a wire core or external binding. The bonding material may consist of thermosetting or thermoplastic natural or synthetic materials such as natural rubber, synthetic elastomers, phenol-formaldehyde, melamine-formaldehyde and urea-formaldehyde condensation products and polymers of ethylenic monomers such as styrene, vinyl chloride or acrylonitrile ; these substances may be used as such or in conjunction with plasticisers, solvents or other liquid media according to the properties required of the finished tube. As shown in Fig. 1, a mandrel A rotatably located in a bearing block and formed with a continuous thread having a pitch equal to the diameter of the rope-like material B and a depth slightly less than the radius of that material, passes through a cross-head D attached to the extruder head F of a conventional extrusion machine, the material B being wound onto the mandrel from a spool the axis of which is arranged to orbit the axis of the mandrel at twice the rotational speed of the mandrel. Under the action of the thread rotating relatively thereto, the coiled material passes through the cross-head D and is coated with a resinous bonding composition forced from the head F and through passages H. A cartridge heater inserted at E maintains the resin under optimum conditions of temperature depending upon whether the resin is thermoplastic or thermosetting. The coiled and coated material emerges from the cross-head and passes off the mandrel when the resin cools rapidly or is cooled rapidly by quenching in water. A portion of the mandrel lying beyond the cross-head supports the tube during the cooling stage and has a slight taper to accommodate shrinkage of the tube. Adjustable bushes C serve for restraining, by friction, the coiled material against rotation and for locating by reaction with the coiled material, the mandrel with the cross-head, and spring- loaded guide bearings bear on the tube as the latter passes over the tapered portion of the mandrel to provide further restraint against rotation. The material B may be impregnated with a resinous material in solution before passing to the extrusion head, and the impregnated tubing may pass through an infra-red oven beyond the spring-guide bearings. In a modification, an apparatus for use with a resin of relatively low viscosity, e.g. a polyamide or a vinyl paste or latex comprises a mandrel 2, Fig. 2, rotatably mounted in and defining with a vertical tube 1 an annular space 3, the radial width of the space being slightly greater than the diameter of the rope-like material 4, and the mandrel being formed over half the length thereof with a thread 5 having a depth equal to half the diameter of the material and a pitch at a region 7 substantially equal to the diameter of the material. Below the region 7 the pitch of the thread is increased so that the material is wound onto the portion of the mandrel projecting below the lower end 8 of the tube 1 without danger of adjacent turns being formed in overlapping relationship. Above the region 7 the mandrel has tapered and parallel portions or is wholly tapered. Heated bonding composition is passed through an axial hole 9 in the mandrel and flows from an undercut 10 to effect impregnation of the material 4 which is fed onto the mandrel as the latter rotates continuously. To maintain a continuous feed two spring- loaded bearing faces situated above the mandrel engage the resulting impregnated and cured section of tubing and also prevent rotation of the tubing so that the screwing action of the mandrel continuously feeds the material 4 in an upward direction between the mandrel and the inner face of the tube 1. An electrically-heated band positioned around the upper end of the tube may be used to facilitate curing when a thermosetting resin is used. In an alternative form, the thread is formed on the inner surface of the tube 1.