Ring-shaped glass bulb and lamp assembly using the same

摘要

A ring-shaped glass bulb includes a ring-shaped light permeable hollow body having opposite ends each disposed at a prescribed distance from one to the other, and a filament arranged in the hollow body of the bulb. The outer-most edge portion of the outer ring edge of one of the ends of the bulb is disposed at at least the intersecting point between an outer circumferential line extending from the outer-most edge portion of the outer ring edge of the other end of the bulb and a tangent line extending from the inner-most edge portion of the inner ring edge of the other end of the bulb. A desirable prescribed distance between the opposite ends of the bulb is equal to or greater than 30 mm.