| 摘要 |
PURPOSE:To cause no deformation nor damage on the inner tube by fixing the thermal plastic and flexible outer shell tube in which the inner tube is inserted inside the spiral groove of the inner and outer dies of the die for spiral forming and by heating and cooling it. CONSTITUTION:The outer shell tube 1 is formed in tubular shape with a flexible thermal plastic resin and six pieces of copper made inner tubes 2 for instance which are slightly longer than the outer shell tube 1 are inserted therein. This outer shell tube 1 is wound so as to closely fit to the die groove 11a of the inner die 11 coating a release agent, the 1st and 2nd outer die pieces 12a, 12b coating a release agent from thereon are fitted to the tube 1 inside its die grooves 13a, 13b and pinched so as to fix the spiral state of the tube 1. The tube 1 is in succession plasticized by heating to the prescribed temp. with a electric heater, thereafter it is cooled by a water cooling and so on together with the die 10. The outer die pieces 12a and 12b are removed at the stage of the tube 1 being hardened in spiral shape, in succession the inner die 13 is drawn from between the spiraled tubes 1 and the spiral tube 1 is obtd. Since there is no sand packing stage in this way no deformation nor damage on the inner tube are caused and the service life can be extended.
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