| 摘要 |
PURPOSE:To realize low prime cost by forming a bottom-fitted center lead insertion hole, which is equal in its diameter to a center lead and has a prescribed depth, in the center of a circular board-shaped part which is fitted to a filament end part on a lower side of an upper end shield, and next by inserting a center lead end part into this hole so as to be junctioned with the upper end shield. CONSTITUTION:A bottom-fitted center lead insertion hole, which is equal in its diameter to a center lead 4 and has a prescribed depth, is formed in the center of a circular board-shaped part which is fitted to a filament end part on a lower side of an upper end shield 2, and a center lead 4 end part is inserted into this hole so that it is junctioned with the upper end shield 2 by welding or brazing or the like. Namely, since the center lead insertion hole of the upper end shield 2 is provided with a bottom, the center lead 4 enters the upper end shield 2 by a constant length even if the center lead 4 is inserted into this hole, and own weight of the upper end shield 2 is supported by the center lead. The center lead 4 does not enter the upper end shield 2 in excess of the prescribed length accordingly, and also the upper end shield 2 does not enter the filament end part in excess of the prescribed length. A high-melting-point and expensive material can be hence prevented from being wasted.
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