| 摘要 |
<p>PURPOSE:To make a projection conventionally provided in the end of the bulb unnecessary by forming at least one U-shaped protruding piece for restricting the rotation of bases on their inner surface and fitting said protruding piece in at least one of circular constricted parts formed on both end portions of the bulb. CONSTITUTION:At least one of bases 2 and 3 has a U-shaped protruding piece 7 for restricting the rotation of the base on its inner surface. Both end portions 1a and 1b of a bulb 1 have circular constricted parts 8. The base-rotation-restricting protruding piece 7 is attached to the constricted part 8 in such a manner that the piece 7 is fitted in the constricted part 8. When the bases 2 and 3 rotate, the protruding piece 7 moves in the direction indicated by arrow (c) until the side surface 7a of the piece 7 touches the sealing area 1c of the bulb 1 in such a manner as indicated by the dotted line thereby restricting the range of the rotation. As a result, it is not necessary to provide a projection inside the constricted area 8, thereby preventing any generation of cracks.</p> |
