| 摘要 |
<p>A roller shutter door limit sensing means comprising a screw member for rotation in response to rotation of the drum onto which the curtain of the roller shutter door is wound, a limit switch actuator means threadably carried by the screw member to advance or retreat therealong in response to its rotation operates a corresponding opposite limit switch means, whereby the switch means can be activated for the curtain fully closed or the curtain fully opened positions whereby to switch off an electric drive means which opens or closes said roller shutter door. A roller shutter door sensing means is also provided for sensing increased pressure on closing of the door and to open the door in response to detecting such increased pressure which is representative of an object under the door comprising: said motor being mounted on a swingable arm and biased to drive engage with the drum, the swinging being such that if increased driving pressure is required, then the motor tends to move out of drive engagement by swinging on the arm, thereby activating a sensing means which does not swing which reverses direction of rotation of the motor to open the door curtain.</p> |
