| 摘要 |
PURPOSE:To provide torsional rigidity efficiently to synthetic resin lid by projecting a circumferential rib and folded ribs coupling between the center of one long side of lid and the opposite ends of the other long side from the inner face of bonnet. CONSTITUTION:Single or plural circumferential ribs 7 extending along four sides of bonnet 2 are provided on the upper face of bonnet 2. First folded rib 8 coupling between the center of long side at the front of bonnet 2 and the opposite ends of rear long side and second folded rib 9 coupling between the center of the rear long side and the opposite ends of the front long side are further projected. Said ribs 7, 8, 9 will cooperate to improve the torsional rigidity of bonnet 2. |
