PURPOSE: To satisfy both sealing strength and easily unsealable properties of a lid, and reduce irregularity of the sealing strength in a method of welding the lid to a double container with a heating/pressing body.
CONSTITUTION: A heating/pressing body 1 provided with a planar pressing part 3 and a pressing part 4 having an annular protrusion at an intermediate part in the radial direction of the pressing part is used as a seal type, and a lid 11 is pressed at the same time by these pressing parts to be welded to a flange part 26 of a double container 21. The pressing part of the annular protrusion is provided circularly and annularly in the heating/pressing body, and a position where the annular pressing part is disposed is set so that, when the inner diameter of the annular pressing part is denoted by (d), and the outer diameter thereof, by D and, when the inner diameter of an annular part of the easily openable lid, which is pressed and welded by the heating/pressing body, is denoted by (r), and the outer diameter thereof, by R, an inequality of (d+D)/2<(r+R)/2 is set.
OSE YASUHIRO
SEKINE SHINICHI
TAKAHASHI KATSUMI
