| 摘要 |
This invention relates to a shut-off valve, and primarily to a valve for shutting-off the flow of a fluid such as a mains water supply to commercial premises or a domestic dwelling. The shut-off valve (10) comprises a diaphragm valve and a pilot valve (30). The diaphragm valve has an inlet (14) and an outlet (16), a valve member (26) and a valve seat (22), the valve member having a closed position in which it engages the seat and prevents the flow of fluid from the inlet to the outlet, and an open position in which the valve member does not engage the seat and fluid can flow from the inlet to the outlet. A first fluid conduit (36) connects the inlet of the diaphragm valve to the inlet of the pilot valve, and a second fluid conduit (40) connects the outlet of the pilot valve to the outlet of the diaphragm valve. The pilot valve has an open position in which fluid can flow from the first fluid conduit to the second fluid conduit and a closed position in which fluid cannot flow from the first fluid conduit to the second fluid conduit. The invention is characterised in that the diaphragm valve has a control member (42, 44, 46) which is adapted to hold the valve member against the valve seat, whereby the diaphragm valve remains closed even if the pressure at its outlet equals or perhaps exceeds the pressure at its inlet. |
