| 摘要 |
According to the invention there is provided a control valve having casing having an inlet port, an outlet part and an opening having a nominal opening area bordered by a seat and being disposed between the inlet and outlet ports to provide communication therebetween. A flexible diaphragm is secured to the casing to define with the casing a control chamber and a pressure chamber on either side of the diaphragm. A diaphragm connector is mounted on the diaphragm for movement therewith between an open position clear of the seat and a closed position against the seat. The diaphragm is urged into the closed position. A flexible bellows extends between the diaphragm connecter and the casing within the upper chamber. The bellows has an interior isolated from the upper chamber and encloses an area of the diaphragm generally equal to the size of the nominal opening area so as to isolate a portion of the diaphragm enclosed by the bellows from pressure within the control chamber.
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