| 摘要 |
<p>For use in a ventilation flue or the like, a damper positioning mechanism comprising a yieldable means biasing said damper toward a first position, motive means for opposing the bias of said yieldable means to drive said damper to a second position and thermally responsive means modulating the return of said damper from said second position to said first position, said thermally responsive means being strong in relation to said yieldable means. In one embodiment the thermally responsive means resists closure of said damper until exposed to a sufficiently low temperature. In another embodiment the thermally responsive means resists opening of said damper until exposed to a sufficiently high temperature.</p> |
