GB813700A - Flexible conduit - Google Patents

Abstract

813,700. Flexible conduits. DAYTON RUBBER CO. March 20, 9156 [March 24, 1955], No. 8594/56. Class 99(2) In a flexible, radially non-collapsible, conduit having circumferential reinforcing means with axially spaced turns and a yieldable, deformable surface layer, the reinforcing means, formed by a helix 12, is surrounded by a plastic and deformable tube 14 having corrugations formed therein, which corrugations depend between the turns of the helix so as to straddle the turns and extend to the plane of the innermost surface portion of the helix. The inner surfaces at the crests of the corrugations are bonded to the peripheries of the turns of the helix over a portion only of the embraced areas of the turns whereby on the application of tension, as by bending or stretching, the portion of the tube normally embracing but not bonded to the turns of the helix will pull away therefrom and return to embracing position on release of that tension. As shown, the reinforcing helix 12 is of synthetic plastic or of wire coated with synthetic plastic and has a flat, inner surface 11a. The inner peripheries of the corrugations may be flat. The coating is deposited on the wire by immersion in, spraying on or extrusion of the plastic. The tube 14 may be of natural rubber or synthetic rubber-like composition such as the polychloroprenes known as Neoprene the butadiene-styrene copolymers known as Buna-S or GR-S (Registered Trade Mark), the butadiene-acrylic nitrile copolymers known as Buna-N or GR-A, the polysulphides known under the Registered Trade Mark "Thiokol", butyl rubber, vinyl copolymers, cellulose acetate, cellulose acetate butyrate and polyethylene. In making the conduit, a preformed tube 14 is distended by the application of air pressure and passed over the helix which has previously been positioned on a hollow, perforated mandrel, the convolutions of the helix being spaced apart and placed under tension to bear against the surface of the mandrel. The latter together with the hose assembly is then placed in a pressurized vulcaniser or oven and a differential pressure is applied between the exterior of the tube and the interior of the mandrel so that the tube becomes corrugated and embraces the convolutions of the coil. The softened condition of the plastic material used for the tube and coating of the coil is such as to cause fusion or coalescence; alternatively, bonding between these parts is effected by a solvent or adhesive.