GB1045143A - Method for covering tubular articles with synthetic organic plastics materials - Google Patents

Abstract

1,045,143. Applying flexible tubing, e.g. to metal pipes. ENFIELD-STANDARD POWER CABLES Ltd. May 3, 1963 [May 4, 1962], No. 17196/62. Headings F2G, F2P and F2S. ) A covering of synthetic organic plastics material having an interference fit with a tubular article is applied over that article whilst being distorted by reducing the surrounding pressure and is subsequently pressed against the surface of the article by bringing the surrounding pressure to above atmospheric pressure. The article to be covered, for example, a metal tube 8, is placed inside the covering, for example a polythene tube 1, in a tube 2 forming part of an exhaust chamber. The ends of the polythene tube are warmed and stretched and are sealed inside holes in the end walls 5, 6 of the chamber. The polythene tube is shown enlarged due to vacuum applied through a pipe 7. The metal tube normally has an interference fit with the polythene tube and therefore the polythene tube shrinks on the metal tube when vacuum is released and the pressure raised above that of the atmosphere. To guard against misalignment due to deflection, the metal tube may be supported internally, or the covering may be applied with the tube vertical. Fig. 4 (not shown), shows an arrangement which allows the polythene tube to contract in length as it expands in diameter, because the outer tube 2 of the exhaust chamber is made telescopic at its end 13 and a bellows 14 is incorporated. To cover a pipe joint between two such tubes, a polythene tube 17, Fig. 6 (not shown), may be prepared by radially expanding an undersize tube whilst it is softened by heat and cooling it to freeze it at the larger diameter. The expanded tube is then placed over the joint and reheated, when it shrinks into position. Collars may be placed around the tube 8 under the ends of the tube 17.