PURPOSE: To form a socket and seal an opening at the top end of a perforated plastic tube simultaneously, by making the expanded diameter-forming cavity of a metal die, provided with a socket-forming cavity, gradually thinner toward its top end, and forcedly inserting one end of the perforated tube, being heated, into the socket-forming cavity.
CONSTITUTION: One end of a perforated tube 1, being heated, is forcedly inserted into the socket-forming cavity 20 of a metal die 2. The cavity 20 is narrower at its innermost end, so that the clearance at the top end 11 of the perforated tube 1 is formed in a thinner thickness corresponding to the cavity. When the perforated tube 1 is further pushed into the cavity 20, the top end part 11 of the perforated tube 1 is affected by a reaction force from the innermost end 23 of the socket-forming cavity. Consequently, the opening at the top end of the perforated tube is ruptured by pressures from the outside surface of a core 21 and the inside surface of an outside die 22. In this case, the amount of the perforated tube 1 to be forced in can be reduced, because the top end of the perforated tube is already formed in a small diameter. As a result, the pressure can be lowered, and the buckling of the tube 1 can be avoided.
ITOU TAKEHIRO
ISHIHARA KATSUROU
YOSHIKAWA ATSUSHI
