PURPOSE: To reduce the usage amount of Mo lead by arranging the sealing surface between an Mo lead and a stem ceramics to be on an inner end surface of a bulb of a stem ceramics, and the sealing surface between a sealing part and the stem ceramics to be on an outer end surface of a bulb of the stem ceramics.
CONSTITUTION: A thermoelectron emitting filament 1 is placed between an upper end shield 2 and a lower end shield 3 to prevent deviation of thermoelectrons into an axial direction of a bulb, and a center lead 4 and a side lead 5 made of Mo are connected to the upper end shield 2 and the lower end shield 3, respectively. While the two leads 4 and 5 are brazed to an inner end surface of the bulb of a stem ceramics 6, a sealing part 7 is brazed to an outer end surface of the bulb of the stem ceramics 6. Accordingly, length of both leads 4 and 5 become substantially short and a distance between a fixed spot of the two leads 4 and 5 and the filament 1 is made short. By this method, vibration-proof and shock-proof characteristics of the filament 1 are substantially improved, which makes it possible to reduce wire diameters of the center lead 4 and the side lead 5.
JPS56132747A | 1981-10-17 |