| 摘要 |
PURPOSE:To form approximately uniform roughness over the inner surface to avoid concentration of stresses by inserting a spring mandrel into an unvulcanized hose in which a resin layer, inner rubber layer, reinforcing string layer, and outer rubber layer are stacked from the innermost layer successively and withdrawing said mandrel after vulcanization. CONSTITUTION:Reinforcing strings constituting a reinforcing string layer 13 which have dry thermal contraction ratio of 0.5-5.0% at 150 deg.C and for 30 minutes are used so that an inner rubber layer 12 and a resin layer 11 bite into the outer periphery of a mandrel 15 during vulcanization. The spring mandrel 15 is inserted into an unvulcanized hose 10 cut to a predetermined length. Next, a rigid mandrel 16 is inserted into the mandrel 15 to form it into a specified shape and then vulcanization is effected. Since the layers 12, 11 bite into the outer periphery of the mandrel 15, approximately uniform roughness 17 is formed over the inner wall surface of the layer 11. Thereafter, if the mandrel 16 is pulled out and further the mandrel 15 is pulled, its outer diameter becomes smaller, so that it is easily pulled out. |
