Driving device for vertically movable shutters

A driving device for shutters, especially roller shutters, movable between a closed position and an open position, said driving device including:

• a motor generating a rotational movement and a drive, which motor and drive, by means of driving elements act on the shutter by setting it to the open position, having means to automatically transfer the shutter into the closed position without assistance of the motor;
• a braking element, which decelerates the automatic movement of the shutter into the closed position under its dead weight;
• a viscous coupling, said viscous coupling acts as a braking element and comprises a coupling housing and a coupling hub as coupling parts which, between them, form an operating chamber, said operating chamber has the shape of an annular cylinder, said viscous coupling, furthermore, between the coupling housing and the coupling hub, comprises annular plates which are arranged in a predetermined sequence, which partially overlap in a radial direction and are arranged in the operating chamber, and which, furthermore, comprises a filling of a highly viscous medium which fills a part of the operating chamber not occupied by the plates and is subjected to a permanent pre-pressure which is higher than atmospheric pressure;
• one of the two coupling parts is held non-rotatably;
• the plates apply a braking moment increasing as a function of speed to the coupling part of the viscous coupling which participates in a rotational direction and rotational movement corresponding to movement of the shutter into the closed position;
• and
• that the plates, in a counter clockwise rotational direction opposed thereto corresponding to the movement of the shutter into the open position, said plates exert a minimum braking effect on the coupling part having rotational movement.