Fire escape – ladder – or scaffold – Unitary foldable – rigid scaffold or ladder – Collapsible ladder
Patent
1997-06-12
1999-08-31
Chin-Shue, Alvin
Fire escape, ladder, or scaffold
Unitary foldable, rigid scaffold or ladder
Collapsible ladder
182159, E06C 152
Patent
active
059441410
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a ladder and, in particular, to a ladder which can be folded for storage.
BACKGROUND OF THE INVENTION
Foldable ladders are known which can be folded for storage in small spaces such as trunks of cars or closets. These ladders generally allow a ladder to be folded to about 36 inches in length. Such ladders are extended into straight, rigid form for use. Foldable ladders are often dangerous in that they can move between a rigid position and a collapsible position relatively easily. In addition, the folding nature of the ladders can render them of insufficient strength, when extended, to support the weight of a person.
Any ladder construction should be as simple as possible, to cause the cost of the ladder to be reasonable.
SUMMARY OF THE INVENTION
A ladder is provided which can be folded for storage and extended into rigid form for use. The inventive ladder is resistant to inadvertent collapse during use and is of sufficient strength to maintain its rigid form while supporting weight.
According to a broad aspect of the present invention there is provided a ladder comprising a pair of side rails and a plurality of rungs, a pivotal attachment being positioned between each rung and each of the side rails such that the side rails are free to rotate from positions substantially coplanar with the rungs to positions defining a plane substantially normal to the rungs to support the rungs, the pivotal attachment between the rungs and side rails being disposed to permit relative rotation of the side rails not more than 90.degree. from the position substantially coplanar to the rungs, and the side rails being formed in segments pivotally attached at their ends such that the side rails can be folded into an accordion arrangement.
DESCRIPTION OF THE INVENTION
The present inventive ladder can be folded into an accordion arrangement by having side rails formed as segments which collapse about pivotal connections disposed along the side rails. The pivotal connections are spaced longitudinally along the side rails and in corresponding locations on each side rail so that the two side rails can fold simultaneously. The pivotal connections are of any suitable type. Preferably, pivotal connections are provided having a suitable tolerance to accommodate weight placed on the ladder. In one embodiment the pivotal connections are in the form of double hinges. Double hinges allow ease of manufacture and strengthen the ladder. The double hinges can be formed by placing a u-shaped member between abutting ends of the side rails. The double hinges can alternatively be formed by placing a pair of links between the ends. Where the rail segments are hollow, plate or block inserts formed of suitable material, such as for example, steel or plastic, can be used to reinforce the pivotal connections. It has been found that a plastic insert acts to retain the tightness of the pivotal connection over a greater period of time, as compared to steel, and is therefore preferred.
In a preferred embodiment, the side rails are formed as two foot long sections with a single hinge at each end. The sections are manufactured in one piece by molding a high strength material such as plastic, fibre reinforced plastic or injectable metals. A preferred length for the side rail segments is twenty four (24) inches, however a twelve (12) inch length can be used in some embodiments. The hinges at the ends of the side rails in this preferred embodiment are formed to join the abutting ends of the rails directly. In a preferred embodiment, the hinges are formed as a plurality of ribs extending outwardly and upwardly from the ends of the segments. Apertures are disposed through the ribs for accepting a pin about which the segments can pivot.
The segments of the side rails are free to collapse about the pivotal connections when the ladder is disposed in a flat position wherein the rungs and side rails are in a single plane. When the ladder is prepared for use, the side rails are rotated about 90.degree. to each de
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Kochan Brian
Thorpe George W.
Chin-Shue Alvin
Gerald R. Kendall and Edward J. Green
Jones Bennett
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