| 摘要 |
<p>A guillotine damper for a duct of large cross sectional dimensions has a thrust frame (58) movable into and out of an operative position in sealing engagement with a blade (48) when positioned to block flow through the duct or a downstream seat (28B) exposed when the blade is retracted. A series of devices (68) are spaced about the flow path with each consisting of a unit in which fluid pressure operated means (67) and resilient means (66) are combined in opposition to each other, a series of toggle joints (63) each connected to the thrust frame (58) and to upstream structure (33) and a connection (83), (72) between the knee pivot (63C) of each toggle joint and the unit to be operated by whichever of the opposing means (67), (68) is dominant. The resilient means (68) yieldably holds the thrust frame (58) operatively positioned and the fluid pressure operated means (67) is utilized to retract the frame (58) when the blade (48) is to be moved from one position to the other. The forces exerted by both opposing means (67), (68) in a plane parallel to the path of the blade (48). </p> |
