| 摘要 |
<p>An exhaust air valve for placement in a ventilation conduit through which air is exhausted from a space to be ventilated. The valve has a casing with a concave seat surface facing upstream of the flow through the conduit and having a central valve orifice. A convex valve element cooperates with the seat surface and when the valve is closed engages the seat surface along a line of contact surrounding the seat. The curvature of the respective surfaces is the same, at least along the line of contact to ensure a tight closure of the orifice by the valve body. When opening, the valve body slides along the curved surface and the upstream surface of the valve body exposed to the flow is also convex to guide the flow toward the center of the orifice. Several embodiments are illustrated including valves with cords for remotely controlling the valve and heat-sensitive tripping mechanisms which automatically close the valve in the event of a rise in temperature above a preset level. The closing movement may be pivotal about a pivotal connection maintaining the valve element in sliding contact with the valve seat or may be a sliding displacement longitudinally of a slot in one of the elements.</p> |
