| 摘要 |
<p>Apparatus for use as a stairway, stepladder and the like has a pair of upper stringers and a pair of lower stringers, all connected at one end to a top structure; and a series of treads, each of which is pivoted to the upper and lower stringers. The axes of articulation associated with the upper stringers are offset vertically from those associated with the lower stringers so that the stringers may be swung about their points of connection with the top structure without the treads deviating from the horizontal. In the horizontal position of the stringers, the upper stringers rest on the lower stringers.</p> |
