ANORDNING FOR AAPNING OG STENGNING AV EN HEV- OG SENKBAR PORT

摘要

A reversible motor operates a vertically movable door through transmission means including a friction clutch. Control means receiving the output of a tachometer generator driven by the driven member of the friction clutch are arranged to switch off the motor automatically in response to a predetermined deviation downwards of the rate of rotation caused by an obstruction in the path of the door. The system may include means for automatically re-starting the motor in the opposite direction subsequent to a switching-off caused by an obstruction to the travel downwards of the door.