Fire escape – ladder – or scaffold – Ladder with pivoted prop – Hinged to top-step rear flange
Reexamination Certificate
1996-10-17
2001-03-27
Lev, Bruce A. (Department: 3634)
Fire escape, ladder, or scaffold
Ladder with pivoted prop
Hinged to top-step rear flange
C182S096000, C182S166000, C182S170000
Reexamination Certificate
active
06206139
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of foldable ladders, and, more particularly, to foldable ladders having a tripod configuration with extendable legs.
BACKGROUND OF THE INVENTION
Various types of foldable ladders are well known in art. Such ladders provide a means for an individual to climb to or reach heights using a free standing ladder in contrast to extension ladders which are braced against a structure when is use.
Ensuring the stability of such a ladder is critical for safety purposes. When the center of gravity of the ladder and user combination falls outside the ladder footprint, any ladder will topple. Thus, the large triangular footprint of a tripod configuration is desirable. However, even tripod configurations can be unstable when used on an uneven flat terrain. This is particularly true when the tripod is not a true tripod in that the legs which bracket the steps both engage the ground as one ridged unit. Such an arrangement means unevenness in any of four points and will cause instability in the ladder.
Various solutions have been devised in attempts to overcome the problem. WIPO Patent Application PCT/US90/07498 entitled IMPROVED TRIPOD LADDER to Baker which published on Jul. 9, 1992 discloses a tripod ladder having legs that rotate about a pivot pin held between rear leg extensions. The legs are maintained in a 120 degrees orientation from one another by lips which form alignment channels.
U.S. Pat. No. 4,524,849 entitled TRIPOD issued on Jun. 25, 1985 to Riddle discloses a tripod ladder for use on uneven ground. The second or third leg portions can be provided in a telescoping or shortening manner on at least one of the legs.
U.S. Pat. No. 3,165,169 entitled LADDER HOLDER issued on Jan. 12, 1965 to Machen discloses a tripod type ladder holder having adjustable leg portions composed of upper tubular leg portions which telescope for adjustment into lower leg portions.
U.S. Pat. No. 3,189,124 entitled LADDER issued on Jun. 15, 1965 to Rateau shows a ladder having a sole which engages the ground.
None of the known prior art disclose the combination set forth herein.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a stable ladder for use on all terrain, whether even or uneven.
It is a further object of this invention to provide a tripod ladder having legs oriented at 120 degrees from one another for maximum stability.
It is still another object of this invention to provide a tripod ladder having extendable legs.
Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
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Lev Bruce A.
McGue Frank J.
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