Importance

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Abstract

A conduit closure apparatus, e.g., a damper, comprising a frame adapted for connection to a conduit in a position generally in registry with the conduit, a movable blade slidably mounted in the frame, means for moving the blade back and forth between an open position in which the blade is outside the conduit and a closed position in which the blade blocks the conduit, an opening in the frame through which the blade slides when it is moved between its open and closed positions, an inflatable sealing ring mounted in the frame that is operable, when inflated, to press against the face of the blade at the blade's periphery when the blade is in the closed position, thereby creating a seal between the blade and the frame, and means for inflating said sealing ring, is improved by including means for pulling a sufficient vacuum on the interior of the sealing ring to cause the ring to collapse and recede from contact with the blade, thereby creating a wider separation between the ring and the blade than if the interior of the ring were at atmospheric pressure. This lessens the chances of the sealing ring being abraded and damaged during movement of the blade, for example by encrustation on the side of the blade.

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First Claim