Patent GB-431381-A (GB)
Title: Improvements in inner tubes for tyres and like collapsible and distensible articles and their manufacture
IPC: B29C67/00
Filed: 1933-12-06
Abstract: <PICT:0431381/III/1> <PICT:0431381/III/2> <PICT:0431381/III/3> <PICT:0431381/III/4> <PICT:0431381/III/5> For improving the gas-retaining qualities of inner tubes for tyres and like hollow and distensible articles, the collapsed article prior to vulcanization is inserted within a chamber of an internal diameter equal to the external diameter of the unvulcanized article, the pressure between the article and the chamber is reduced so that the tube is positioned without deformation against the wall of the chamber under atmospheric pressure, and the tube is subjected on its internal surface to a coating operation.  The space between the tube and the casing is sealed from the external atmosphere and a fluid seal may be obtained by folding back one or both ends of the tube over the end of the casing.  The casing is connected to a vacuum pump and in order to avoid local distortion of the tube, a spring seal or flexible disc may be provided in the pipe of the pump where it is connected to the casing.  The flexible disc may have an adjusting rod or wire.  The casing may have an inner permeable wall and an outer continuous and impermeable wall.  In order to use the casing for articles of different length it may be provided at one end with a plug for closing the end of the tube and a distance block of varying length. The coating may be effected by immersion or spraying, the spraying device moving longitudinally relative to the casing or about an axis within it, or a yielding body coated with the liquid or plastic composition may be drawn through the tube. Clips of steel or other material may be inserted in the tube to prevent certain portions from being coated.  After the coating operation, the tube is dried, if desired, in the same apparatus and is then vulcanized, the ends being joined together if desired. As shown in Fig. 1, a tube 3 is placed inside a tubular mandrel 1 and the ends of the tube are folded over the ends of the mandrel and secured by bands of rubber 6.  The interior of the mandrel is provided with a connection 2 to a vacuum pump, and to prevent local distortion of the tube, a flexible disc 4 with an adjusting rod 5 is provided.  Clips 7 are placed in the tube to cover parts which are not to be coated.  As shown in Fig. 2, the mandrel is connected at one end to a pump by the pipe 8.  As shown in Fig. 3, the mandrel has an inner wall 9 of permeable material and an outer casing 6 of impermeable material.  To prevent longitudinal distortion of tubes shorter than the mandrel, a plug 10 as shown in Figs. 4 and 5, is used to close one end of the tube, and a distance piece 11 with air channel 14 is placed at the end of the mandrel which is connected to the pump.  The distance piece 11 slides in the mandrel and its surface may be slotted to allow air to be removed from the mandrel.  The Provisional Specification describes also the use of a spraying head for the coating solution which has jets inclined to radii from the axis, the flow of solution causing automatic rotation of the feed pipe.