| 摘要 |
The invention relates to an extension ladder for a room with a central access shaft composed of a fixed ladder placed against one of the walls of the access shaft, of a movable ladder sliding along the fixed ladder and of a locking device holding the movable ladder in its raised position. The movable ladder is characterised in that the locking device 20 is located only on the movable ladder 3 and in that it comprises automatic unlocking means 22 actuated by additionally slightly raising the raised movable ladder 3. The invention relates to extension ladders which must be kept in the extended position. <IMAGE>
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