Patent GB-733821-A (GB)
Title: Improvements relating to impregnated tubes of fibrous material
IPC: B32B27/00
Filed: 1953-02-02
Abstract: 733,821. Making tubes of fibrous material. FLEURY, M. Feb. 2, 1953 [Aug. 13, 1952], No. 2874/53. Class 99 (2). A sheath 4, of threads, fibres or fabrics, combined with fillings, backings or cores of natural or syntehtic material such as cotton, glass, asbestos or nylon, or metallic material, forming the basic layer of a multi-layer tube is prepared on the front part of and advanced along a hollow mandrel 1 by an actuating device such as driven rollers 6. The sheath is impregnated with a resin in the cold state within a fluid-tight chamber 8 which is preferably under a partial vacuum, the resin being hardened and polymerized at a low pressure and the sheath being optionally used as a second mandrel for preparing thereon other layers by the same method. As shown in Fig. 1, the mandrel 1, filled with resin through a connection 2, has holes 16 situated within the chamber 8 and through which the resin is discharged to impregnate the sheath. A perforated ring 18 surrounds and projects resin on to the outside of the sheath and the chamber 8 is rendered fluid-tight by toroidal joints 10, 11 comprising rubber tubes of circular or oval cross-section inflated by compressed air and lodged in recesses 14, 15 forming part of the chamber. The vacuum in the chamber 8 eliminates any air carried therein by the sheath or resin. Directly above the level at which impregnation of the sheath is carried out a cooling chamber 22 is located within the mandrel and supplied through tubes 23, 24 with a cooling liquid to prevent premature polymerization of the resin. Subsequent to impregnation, the sheath 4 passes into a polymerization chamber 25 enclosing ring-like heating elements 26 surrounding the sheath. The exit of the chamber 25 is provided with a toroidal joint 29 and there is a collar 30 for further drying and cooling operations, and a device 31 for providing constant motion of the sheath along the mandrel; after leaving the device 31 the sheath is cut into lengths, wound on to drums or passed through identical apparatus to be provided with further layers. The hollow construction of the mandrel is continued beyond the joint 11 and fluid supplied to that part of the mandrel fills the sheath to maintain a certain temperature or pressure, or both, therein, the fluid leaving the sheath at the'free end thereof. In a modification, the sheath is formed by two helically wound and tensioned ribbons drawn from bobbins 32, 33, Fig. 2, the ribbons being offset in relation to one another by a distance equal to half the width of the ribbons and impregnated with resin by devices 37, 38, longitudinally and transversely acting pressure rollers 34, 35, some of which are heated to start polymerization of the resin, compressing one ribbon on to the other. A second sheath 4 is woven over the ribbons and impregnation is carried out in a chamber 8, the holes 16 in the mandrel 1 being used to supply a lubricant between the mandrel and sheath. For accelerating polymerization of the resin a chamber 39 is provided, the accelerating product supplied to the chamber being in the form of a suspension or mist. Prior to final polymerization of the resin in the chamber 25 the sheathing may be bound with a ribbon of glass fabric or a sheet of parallel threads of glass drawn from a bobbin 43, or, where a temporary binding is desired, a ribbon of " Cellophane " (Registered Trade Mark), a film of polyvinyl alcohol, or a metal band through which an electric current is passed. In further modifications: (a) the sheathing is formed by applying resin-impregnated ribbons on to the mandrel in the longitudinal direction thereof, the longitudinal joint of the second ribbon being displaced 180 degrees in relation to the joint of the first ribbon; and (b) an impregnated ribbon is applied to the mandrel .and has a longitudinal overlapping joint, and the second layer comprises a helically-wound ribbon having the turns thereof in contact.