PURPOSE: To obtain the more economical manufacturing method of a propulsion tube by a method wherein a stock tube having thin-walled tube ends is produced by extrusion molding and, after that, thin-walled parts are formed on inner surface side or outer surfacr side of the tube by forming the ends of the stock tube.
CONSTITUTION: The haul-off speed of a haul-off machine 22 is increased or the extrusion rate of an extruder 18 is decreased or the like at every certain period relative to the extrusion speed of the extruder 18 so as to produce thin-walled parts 26 at fixed intervals to the long direction of a pipe 24. By cutting apart the pipe 24 nearly at the middle part (a) of each thin-walled part 26, stock tubles 10 are obtained. Next, a mold 12, the inner surface form of which is nearly the same form as the end part form of a propulsion tube 28 to be manufactured, is prepared. After that, the thermally softened thin-walled part 26 of the stock tube 10 is forced in the mold 12 SO as to be formed. By forming both the end parts of the stock tube 10 as just mentioned above, a propulsion tube having thin-walled parts 14 on the inner surface side at both the end parts. By means of a collar 30 installed on the outer surface of the thin-walled part 14, the propulsion tube 28 is joined with another propulsion tube 28. As no cutting work is necessary in the above-mentioned method, economical efficiency is improved.
HIRUMA NOBUHIKO
NAKANISHI YOSHIHIKO
