| 摘要 |
PROBLEM TO BE SOLVED: To continuously cover many steel tubes with resin without using a core by supporting a support bar and a mandrel mounted at the end and brought into contact with the contact parts of the tubes by a support bar holding unit. SOLUTION: A support bar 1a having a length from the inlet of a connecting zone 12 to this side of a coating zone 14 and a mandrel 1b mounted at the bar 1a and having a length from this side of the zone 14 to the front half of a cooling zone 15 are so provided as to be disposed in a steel tube. The mandrel 1b and the bar 1a are supported by two or more support bar holding units 2a, 2b provided at a suitable interval in the longitudinal direction of the region of the zone 12. In this case, the mandrel 1b mounted at the end of the bar 1a is so provided as not to cause a tongue and a groove at the contact parts of the preceding tube to the following tube with the requirement that the outer periphery is disposed along the inner periphery of the tube. |
