| 摘要 |
A pilot operated diaphragm valve (10) having a diaphragm (12) that biases itself normally to a position that positively closes the valve. The diaphragm has either a peripheral ridge (48) or convolution (50) in its flexible portion intermediate its stiffened centre and its marginal edge where it is clamped between a body (14) and a cover (16). The diaphragm may be independently self-biasing or the ridge or convolution may be shaped so as to co-operate with an inside surface of the cover. The diaphragm may be stiffened in the central seat-engaging portion by thickening or encapsulation of a plastics plate. |
