| 摘要 |
<p>The device comprises a housing with a circular passage orifice, a pivoting closing element in the form of a spherical dome and a circular gasket surrounding the said orifice and mounted on an annular support axially displacable towards the closing element under the action of a pneumatic fluid, the said annular support possessing for this purpose a passive annular surface exposed to the pressure in the said housing, the active surface of the support being larger than its passive surface.</p> |
