| 摘要 |
PURPOSE:To simplify cutting-off of a cullet part without thinning thickness of the sealing part of a glass valve by detecting the time when the flare periph eral part of a stem and the softend and contracted part of an envelope by heating which is expected to be sealed are deposited ranging over the whole periphery in catching a pressure change caused by thermal expansion of the gas inside the envelope. CONSTITUTION:A minute pressure detection device 302, which detects gas pressure, for example, by a diaphragm and gives an electric signal, is connected to an opening of a rotary joint 301. thermally expanded air, exhausted from the inside of an envelope 1, passes through a space A inside a mount shaft 104 and the rotary joint 301 and raises pressure inside the minute pressure detection device 302. In this way, the minute pressure detection device 302 automatically detect pressure rise of air inside the envelope 1. Thus the time is automatically detected when the part 109a, an expected, part for the sealing of the envelope 1, is sealed to the flare periphery 2a of the stem 2 by a contraction process actuated by heating with burners 108.
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