Patent GB-836407-A (GB)
Title: Improvements relating to flexible tubing
Inventor: LANGFORD ARTHUR
IPC: B29D23/18
Filed: 1956-01-19
Abstract: 836,407. Corrugated flexible tubing. HOOVER Ltd. Jan. 18, 1957 [Jan. 19, 1956 ; May 18, 1956], Nos. 1835/57 and 15664/56. Divided out of 836,406. Class 99(2). In a flexible extensible reinforced hose comprising a resilient helical reinforcing coil and a deeply corrugated tube composed solely of thin elastomeric material and formed with inwardly and outwardly opening helical corrugations whereof the latter is unoccupied whilst the former contains the filament of the reinforcing coil over at least a part of the hose the reinforcement is bonded to the tube along an area at the crest of the corrugation where the surfaces would be in any event in contact in an extended position but the surfaces are free to separate in adjacent areas where they are in contact in the normal position but not in the extended position. The tube of elastomeric material has an initial diameter less than that of the coil and the method of making the hose includes stretching the coil longitudinally, radially expanding a,length of the tube having a free length substantially greater than the free length of the coil and passing it over the coil when so extended, allowing the tube to contract radially and embrace the coil and allowing the coil to contract longitudinally and initiate corrugations in the tube between the convolutions of the coil. The elastomeric material may be a synthetic rubber-like material such as polyvinyl chloride. The reinforcing coil may be formed of spring wire sheathed or coated in a covering of thermoplastic elastomeric material 14 preferably the same material as that of the tube 11. In the normal position the corrugation snugly embraces the filament over at least half its circumference. The wire is coated with the sheath 14 either before or after the wire is wound into a helical coil. The corrugations may be fused to the coating of the reinforcement over a crest area representing an arc of approximately 60 degrees. Various ways of bonding the reinforcement to the tube are described in detail. Bonding may be effected by applying solvent or cement to appropriate areas of the reinforcement. Alternatively the bonding may be effected by a solvent or cement which is allowed to evaporate or dry with the hose in the extended position. In one method solvent is applied to the interior of the tube to soften the material of the tube. Warm air under pressure is then supplied to the interior of the tube. Warm air is supplied until the corrugations are fused to the coating of the reinforcement. The tube is then placed in warm water to allow the reinforcement to contract. In another method of bonding the reinforcement is heated by passing either direct current or alternating current through the reinforcing coil. In an alternative method the bonding is achieved by dielective heating. In this case the bonding is confined to the ends of the hose. In another method the reinforcing wire itself serves as the inner electrode for dielectric heating. In yet another method of bonding induction heating is employed and both ends of the hose are treated simultaneously. Alternatively the full length of the hose may be heated by travelling induction coil. Specifications 784,060, 800,371 and 836,408 are referred to.