Abstract: A conduit closure apparatus, e.g.

Abstract: A sliding blade damper is provided with an improved seal arrangement around the blade withdrawal aperture. Two pairs of flexible sealing strips are used, mounted on either side of the aperture and pressing against the opposite sides of the blade. The unattached edges of the sealing strips are curled and bent away from the blade. The curled edges of one pair of strips hook the curled edges of the other pair, so that when the blade is inserted into the damper, the spreading apart of the first pair of strips serves to partially spread apart the second pair as well. In this manner the leading edge of the blade penetrates between the second pair of strips rather easily, lessening the chances that those strips will be bent or torn.

Abstract: A conduit closure apparatus comprising a main 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, a slot-like port through which the blade slides when it is moved between its open and closed positions, and an inflatable sealing ring 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, is improved by having the main frame define a channel which holds the edges of the blade when in the closed position, and having the inflatable ring being carried by a second frame, smaller than the main frame, which slidably fits in the channel of the main frane and which can be withdrawn from the main frame through the blade port