| 摘要 |
A safety device is proposed for closable openings (10) in which there is a risk of jamming. An acoustic sensor which contains a sound generator (16), an acoustic section (15) and a sound receiver (17) is provided as jamming sensor. Means (21, 23, 26, 41) which output an output signal (25) which is compared to a threshold (32) are provided for the purpose of detecting the propagation time (T12, T13, T21, T22, T33, T34, T35) or the change in the propagation time of the sound. In the event of overshooting of the threshold, the electric motor drive (13) of the closing part (12) is shut down or its direction of movement is reversed. <IMAGE> |
