| 摘要 |
Insertable ladder staircase is for folding up into an attic, or similar, with articulated shear-legs type side stringers and a trap door with its open end hinged to each of these. At least one piston-and-cylinder unit (7) and electrically driven pump assembly (8) are provided for powered operation of the staircase. One end of the former engages one or two guide rods (6) close to the hinge point (10) on the trap door (4), the other end being hinged to a fixed point (9) above the flap's axis of rotation (5). There may be a piston-and-cylinder unit on each side. The staircase may be lowered under its own weight. The cylinder may be hinged to the fixed point, and the open end of the piston-rod to the guide-rod. |
