| 摘要 |
PROBLEM TO BE SOLVED: To lessen deformation of a lid body by increase or decrease of internal pressure of a container and to improve tightness in sealing and external appearance for the container by a method wherein the top plate of the lid body tightly sealing the container by means of heat welding and fitting is formed in a shape protruding downward with a step formed at a place near the circumferential wall. SOLUTION: For a lid body 100 made of thermoplastic resin for tightly sealing a container with a heat welding part 131 and a fitting part 121 that are applied to the container body, the top plate 110 of the lid body 100 is formed in a shape protruding downward with a step provided at a place near the circumferential wall 120 while a groove part having a groove at the upside of its periphery and protruding downward is formed. A reinforcement rib may be provided at the surface facing the inside of the container of the top plate 110. Furthermore, an openable spouting hole 114 may be provided at the top plate 110, and the spouting hole 114 is normally sealed up with a seal-up film 140 stuck separably to the exterior side of the container by means of insert injection molding or the like. Then, a energy director is provided at the heat welding part 131 wherewith the lid body 100 is welded to the container body, and the energy director is used when ultrasonic welding is applied. |
