| 摘要 |
PURPOSE:To accelerate the manufacturing speed, produce in uniform wall thickness and enhance the fatigue resistance of a tube by a method wherein a corrugated tube, which is made of composition or mixture of polyolefin, polyvinyl chloride and rubber and has large pitch of waves and shallow groove, is formed under semi-molten state and, after that, shaped so as to produced grooves having the desired pitch. CONSTITUTION:Resin 5, which is continuously extruded smoothly with an extruder, is pressed against the inner surfaces of molds 2 so as to form the outer surface of a tube into wavy shape having large pitch of waves and shallow groove as the same shape as that of the inner surface of the mold 2. In the neighborhood of the outlet of a forming section 4, which consists of a train of the molds 2, of synthetic resin corrugated tube 6, a deep groove forming device 7, which consists of two cylinders located at opposed positions or a cylinder 8 providing with a rib 11 thereon and a cylinder 9 providing with a rib 12 thereon, is provided. By rotating the ribs 11 and 12, the pitch of waves of the synthetic resin corrugated tube 6, which is carried under semi-molten state from the mold forming section 4 and formed so as to have large pitch of waves the shallow groove as the same shape as that of the inner surface of the mold 2, is contracted and shaped so as to become equal to the pitch of the ribs 11 and 12. |
