Foldable extension ladder

作者: S Deese

DOI:

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摘要: This invention relates to a foldable extension ladder of channel shaped or tubular metal comprising plurality side rail sections hinged together at their end portions so that when the is assembled into operating position, one section will project sleeve portion hinge connected an adjoining as be reinforced and guided thereby. The rungs have pivoted struck out sections, which hollow directly supported by main panels such sections.

参考文章(1)
William R. Hire, Foldable extension ladder ,(1963)