Automatically extending and retracting ladder - has prestressing spring for latch, and swivelling lock release arm eliminating manual operation

摘要

The extensible ladder has two standing side bars and two sliding side bars, and one or more locking pawls. The pawl (22) is fitted near the standing bar (10) top, or sliding bar bottom. It is prestressed with a spring (28) in the locked position, gripping below or above a rung (20) on the adjoining bar. An unlocking arm (32) is held by a spring (34) in a position where it engages the rung movement track. It swings against spring force into an inactive position permitting the rung to slide past when the bars are being extended. On retraction, the arm works in conjunction with the pawl, pressing it out of the rung movement track. Manual pawl operation for extension or retraction is not required.