Extensible ladder
US5927434A · kind A · utility
Inventor
Key dates
| Filing date | Dec 15, 1998 |
| Grant date | Jul 27, 1999 |
| Priority date | — |
| Expiry date | Dec 15, 2018 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE06C9/14
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
An extensible ladder includes an upper frame, an up and down transmitting unit and a first and a second extensible frame. The first and the second extensible frame each have a plurality of pairs of crisscrossing rods pivotally connected with each other. Plural ladder steps and connecting rods are pivotally connected between the first and the second extensible frame. The connecting rods are pivotally connected to guide blocks, which have a vertical threaded hole for each of two threaded rods of the up and down transmitting unit to fit in and engage. Then each threaded rod has a clockwise threaded portion and counterclockwise threaded portion engaging the vertical threaded holes of the guide blocks. When an active rod with two worm sections is rotated by two worm gears combined with splines with an upper spline shaft portion of the two threaded rods, the active rod rotates the threaded rods, forcing the two extensible frames to extend down or shrink up.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.