| 摘要 |
PROBLEM TO BE SOLVED: To obtain the structure of a pipe which is conveniently used when different load is added and the load is different depending to a direction by having the structure of a double pipe in which a special shaped pipe having a special cross-sectional shape is lightly press-fitted into a hollow pipe and allowing the special shaped pipe to be provided with plural projected line parts projected in the radial direction as the cross- sectional shape so that the top part of the projected line parts is brought into contact with the inside surface of a hollow pipe and lightly press-fitted. SOLUTION: The special shaped pipe is a flat pipe crushed flatly, whose top part is brought into contact with the insider surface of the hollow pipe and which is lightly press-fitted, or it may be partially charged in the longitudinal direction. As the hollow pipe, a circular pipe 1 such as a steel pipe is applied and, by lightly press-fitting the special shaped pipe 2 in the inside of this hollow pipe and fixing arbitrary joining parts (s) by arc welding or the like, they are composed as a integrated combined pipe. In the fixing method of the special shaped pipe 2 to the circular pipe 1, it is preferable that hole parts are previously formed on the circular pipe 1, the special shaped pipe 2 is inserted so that the top parts of the special shaped pipe 2 are made to coincide with these hole parts and the special shaped pipe 2 is fixed by executing the arc welding of the hole parts.
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