Slide valve for pipelines

Claim 1

A slide valve for gas pipelines comprising an upstream and a downsteam pipeline section, said sections being spaced apart and rigidly connected by stays, a valve plate that is movable into a valve-closing position between said sections, and a floating annular sealing member connected to the upstream section by a flexible sleeve-like seal, wherein the improvement comprises a plurality of springs which are distributed around the annular sealing member and which act between the upstream section and the annular sealing member, and a plurality of pressure-medium actuated bellows which are distributed around the annular sealing member and are separate from the springs, each bellows having one end connected to the upstream section and having its other end more remote from the annular sealing member and connected to the annular sealing member by at least one pull-rod, both the valve plate and the downstream section having an annular seating surface for sealing engagement with the annular sealing member, and both the bellows and the springs having a stroke sufficient so that the bellows, when actuated by the pressure medium, move the annular sealing member clear of the valve plate, and so that when the valve plate is then removed from between the sections and the pressure in the bellows is relieved, the springs move the annular sealing member into sealing engagement with the annular seating surface on the downstream section.