| 摘要 |
861,254. Ladders. WAGNER, J. Oct. 23, 1957 [Oct. 23, 1956], No. 33146/57. Class 20(2) A folding trap door ladder comprises steps 3 joining lazy tong sides 1 each pivoted to the trap door 9 by a lever 7 to which is pivoted a tension spring 5 secured at its other end to a fixed standard 6. As the trap door 9 is closed, the ladder contracts under tension of the springs 5 acting on the levers 7 which pivot on the trap door 9 to face the hinge 12 of the trap and lock the ladder. The trap door is then secured by a bolt 17. During contraction, rollers 15 move over the upper side of the trap door 9. The lazy tongs 1 comprise aluminium I sections and have rubber floor buffers 13. Springs 5 in telescopic tubes securable to different heights of the standard 6 are described. |
