| 摘要 |
The invention concerns a vertical flexible roller shutter door 1 held at its upper end on the frame 3 of the door and having straps 5 for raising it by rolling it around a roller 7. A safety device raises the door partially in the event of a power cut. It comprises a spiral spring 10 rolled around the axis of the roller 7, fixed on the one hand to the frame 3 and on the other hand to the roller 7. The spring produces a restoring force opposite to that of the weight of the shutter, and the characteristic of this spring during the opening of the door is linear. <IMAGE>
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