| 摘要 |
PURPOSE:To simplify the structure of the titled apparatus, while making it stable and prolonging the lifetime thereof, by a method wherein the compression of a flexible gas container wherein a gas is held is utilized for protection from excessive pressure. CONSTITUTION:When an outside pressure P applied to a protecting diaphragm 22 is lower than a lower-limit pressure Pc for protection, the pressure P is transmitted to a liquid L held hermetically in a fluctuating-pressure chamber 20, and it is detected by a liquid-pressure detector 1. When P exceeds Pc, the capacity of a gas container 25 is contracted, and when a change DELTAV in the capacity becomes equal to the capacity of a small chamber 23, a liquid L enclosed in the small chamber 23 is transferred entirely into the fluctuating-pressure chamber 20. Accordingly, the protecting diaphragm 22 is in close contact with the pressure-receiving surface 211A of the upper cover 211 of a housing 21, and thus the outside pressure is applied only on the rigid wall 21 of the housing 21 even when P rises further. Therefore, the pressure of the liquid L held hermetically in the fluctuating-pressure chamber 20 is maintained at the sum of an increase in pressure equivalent to the change DELTAV in the capacity, and Pc, and thus a pressure detecting unit 10 is protected from excessive pressure. By this constitution, the structure of the apparatus is simplified, while it is stablized and the lifetime thereof is prolonged. |
