| 摘要 |
PURPOSE: To prevent occurrence of pin holes at a thin wall part at the time of ultrasonic welding by a method wherein the rear face of a predetermined opening part is provided with a recess part depressed toward the base part of a tab means in a position matching with the base part thereof to avoid the entrapment of air bubbles in the thin wall part at the time of forming a top. CONSTITUTION: A recess part 8 is provided immediately below the base part 7 of a tab means 6 and on the rear face of a predetermined opening part 5 in such a way that it is depressed toward the base part 7. Therefore, the thickness of a part of the predetermined opening part 5 in which the base part 7 is positioned does not become large noticeably as compared with that of the other part thereof. That is, in a cavity for forming a top 1, since a raised part for forming the recess part exists in the portion shifting from the location at which the predetermined opening part is formed to the location at which the base part of the tab means 6 is formed, at the time of forming the top, the pressure of resins will not be lowered sharply in the portion at which the raised part for forming the recess part exists, avoiding the occurrence of air bubbles. Therefore, no pin hole is produced even if the top is attached by the vibration of ultrasonic welding. |
