| 摘要 |
A cage 1 sliding inside a vertical slideway 2 is suspended from one end 4 of the endless chain controlling the tilting of the door panel. A cradle 5 stressed upwards by a spring 12 is secured to a vertical spindle 10 passing through the base 9 of the cage 1 and to which the other end 11 of the endless chain is fixed. A pivoting locking member 15 is articulated to the upper part of the cage 1. In normal operation, the spindle 7 is at the bottom of the opening 13 and the member 15 which bears on this spindle is in an inclined position. In the event of the endless chain breaking, the spring 12 relaxes and the spindle 7 comes into abutment at the top of the slot 13, placing the immobilising member 15 in a substantially horizontal position in which it engages the slideway 2. The invention applies to doors of great weight such as carpark or garage doors. <IMAGE>
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