| 摘要 |
<p>An opening flap ventilator for buildings has pneumatic opening springs (13) and electric motor-gear drive mechanism (14) operable to close the ventilation flap (11). The mechanism has an electrically energised clutch (54) interposed in the gear drive chain (24, 26, 28, 48, 46) (see Fig. 2). On de-energisation of the clutch (54), which may be automatic in response to the detection of a fire condition occuring, the ventilation flap (11) is automatically opened. The flap (11) is subsequently closed by operation of the motor which drives a winch pulley (20) for winding in a single operating cable (76) in opposite directions from a location between its ends. A fused fire prop is provided to prop the flap (11) open in the event of a fire as a safety measure.</p> |
