| 摘要 |
A butterfly valve has a disc which is pivotally mounted inside the passage through the housing and movable between open and closed positions. In its closed position, a seal is established between the valve housing and the disc with a seal ring that has a flat portion clamped to the housing with an axially movable pressure ring and an inwardly extending, resilient seal ring portion that engages a conical periphery of the disc. A plurality of threaded, circumferentially spaced-apart locking bolts in a segmented retainer ring attached to the valve housing are tightened against the pressure ring to secure the seal ring to the housing. The locking bolts are disposed in through holes in the support ring. Each through hole includes a threaded portion, which is contiguous with the side of the support ring facing the pressure ring, and an unthreaded section which terminates at the outer side of the pressure ring. The ends of the bolts disposed in the threaded portion of the through holes and facing away from the pressure ring have Allen-head (or the like) recesses so that they can be tightened with an Allen-head wrench (or the like) extending through the unthreaded section of the holes. A locking bolt which becomes loose over time cannot unthread itself past the unthreaded section of the through hole and, therefore, cannot accidentally fall into the medium flow through the valve. If needed, a set screw can be used to prevent an accidental loosening of the locking bolt. The set screw has a through opening of a sufficient cross-section so that the Allen-head wrench can pass through it. The through bore of the counter screw further has a cross-section so that it too can be engaged and tightened with a wrench. Like the locking bolt, the unthreaded section of the through hole prevents the set screw from dropping into the medium flow through the valve.
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