| 摘要 |
The retractable-gasket ball valve includes sealing means fixed on the valve body, and including, in particular, a gasket for providing sealing between the shutter member and the valve body when the shutter member is in a closed position, and further including a slide for causing said sealing means to move between a retracted position which is also a rest position in which the sealing means is spaced spart from the spherical shutter member, and a contact position in which the gasket is pressed against the shutter member. The valve includes a first resilient element of low stiffness which tends to separate the sealing means from the shutter member when the valve is brought to its open position, and a second resilient element of relatively greater stiffness which is put under tension by the slide a few degrees before the mechanical closure position of the valve when thegasket is in contact with the shutter member, and which exerts control pressure on said gasket in contact with the shutter member.
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