| 摘要 |
A device for automatically turning down a shutter with a certain delay from a turned-up position comprises an elastically deformable envelope (12), the interior of which communicates with a passage (19) for air. Said passage is delimited by an elastically deformable piece of material which permits that it is powerfully widened when the envelope is compressed and which reduces the air-passing ability of the passage to a minimum when the envelope strives to widen to an expanded state and, in that connection, sucks in air in the interior thereof. The envelope has the purpose of bringing the shutter, during expansion, to pass an unstable state of equilibrium after which it is automatically turned to a turned down position. |
