APPARATUS HAVING MULTISTEP OPERATION STAGE FOR FORMING STABLE AND INTERNALLY NORMAL BELL-SHAPED MOUTH SHAPE IN END JOINING PORTION OF THERMOPLASTIC RESIN PIPE

摘要

PROBLEM TO BE SOLVED: To obtain an apparatus having a multistep operation stage for forming a stable and internally normal bell-shaped mouth shape in the end joining part of a thermolastic resin pipe. SOLUTION: An initial inclusion part 13 having a hollow rubber element expansible until preforming a first bell-shaped mouth part and capable of being freely guided into an end part 2, a first part 11 for forming a maximaly expanded temporary bell-shaped mouth part movable from a first contraction position becoming an outer diameter of a degree capable of being freely guided into a the end part 2 to a second expansion position and having an outer diameter larger than the inner diameter of the first bell-shaped mouth part at the expansion position and a second part 12 capable of being introduced into the temporary bell-shaped mouth part expanded to the max. degree after becoming a contracted state upon the completion of the interposition of the first part and naturally contracted after the preceding expansion process to reach a final prescribed inner diameter in its inner diameter are provided.