Step ladder
US4754845A · kind A · utility
Inventor
Key dates
| Filing date | Oct 29, 1987 |
| Grant date | Jul 5, 1988 |
| Priority date | — |
| Expiry date | Oct 29, 2007 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE06C1/16
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A step ladder is shown, having a rigidified step section, a strengthened upper platform, two independently articulated angled rear legs, supported by a pair of rigid, pivoting supports. The angle of extension of the rear legs creates, in conjunction with the front step section of the step ladder, an essentially equilateral, triangular footprint of increased stability. The individual legs, in cooperation with a strengthened, rigid top plate structure, and the single member rigid support strut produces a decreased likelihood that the ladder will "walk" or move under the shifting weight of a user. The triangular footprint creates increased static stability, and also reduces the likelihood of toppling as a result of movement of a person standing on or near the upper step. The support leg actuation linkage is vertically fixed along a linkage support shaft. By fixing the linkage in three dimensions, torsional rigidity is maintained between the independent legs and walking motion is eliminated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.