| 摘要 |
A controlled valve comprising a substantially hollow and elongate body fitted at its longitudinal ends with means for coupling to a pipe that is to be closed, the body including a transverse partition with a central channel formed therethrough, and also including a closure element that is movable parallel to the fluid flow between a closed position in which a zone of said element is in contact with a stationary bearing surface formed on the transverse partition and an open position in which said zone is at a distance from said bearing surface, in which the closure element is in the form of a piston having two end heads slidably mounted in two respective chambers that are coaxial with the channel and that are situated inside the body on opposite sides of the transverse partition, and the sum of the projections in a transverse plane of the surface areas of the element exposed to the pressure that exists in the pipe upstream from the zone of contact between the closure element and the bearing surface and that face downstream is equal to the sum of the same projections of the surface areas that are similarly exposed to said pressure and that face upstream.
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