| 摘要 |
PURPOSE:To improve reliability by arranging a pressure receiving diaphragm, an overpressure preventing mechanism, and an annular diaphragm coaxially while aligning them to the center of a body. CONSTITUTION:When pressure PH to be measured becomes excessive, the pressure PH is impressed to the outside of a bellows 22 through the pressure receiving diaphragm 21a and a pressure transmission medium 28a. When this excessive pressure is received, the bellows 22 moves to right and a valve rod 24 and valve parts 23a and 23b also move to right reacting to the motion. Then, the valve part 23a contacts the valve seat 29 of the body 20 to inhibit the medium 28a from moving. Namely, the movement of the medium 28a is inhibited to stop subsequent pressure transmission and the excessive pressure is never transmitted to a pressure sensitive element part 27. Further, if the temperature varies while the movement of the medium 28a is inhibited, differential pressure is generated owing to the thermal expansion of the media 28a and 28b, but this differential pressure is absorbed by an annular diaphragm 30. Differential pressure generated by thermal expansion while over pressure is prevented is not supplied to the element part 27 either. |
