Fire escape – ladder – or scaffold – Unitary foldable – rigid scaffold or ladder – Trestle
Reexamination Certificate
2002-12-04
2004-07-13
Thompson, II, Hugh B. (Department: 3634)
Fire escape, ladder, or scaffold
Unitary foldable, rigid scaffold or ladder
Trestle
C182S225000
Reexamination Certificate
active
06761249
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a support comprising at least two pivoting legs, these legs being adapted to pivot between a folded position and an unfolded position.
This support can in particular be a trestle or a table with four pivoting legs, a trestle comprising, at one longitudinal end, one or two fixed legs and, at its other longitudinal end, two pivoting legs, or a stepladder comprising two fixed legs on one lateral side and two pivoting legs on another lateral side.
A support of this type should comprise a foldable leg so as to be able to be stored in a small size. A conventional trestle is thus formed by two structures in the form of a frame, pivotally connected to each other at their upper portions, and adapted to be disposed either in a closed, folded position or in a spaced, unfolded position.
DESCRIPTION OF THE RELATED ART
A trestle of this type has the drawback of being unstable when the surface on which the trestle is disposed is not perfectly flat. This problem arises particularly for trestles for professional use such as those used at worksites.
Moreover, a conventional trestle is not perfectly adapted to receive relatively heavy loads.
The patent GB-A-2 020 545 discloses a tripod comprising a structure on which three legs are pivotally mounted; the structure has a vertical upright and each leg is bent at its upper portion, above the region by which it is connected to this upright, this bend being such that the upper bent portion of the leg comes to rest against said upright when the leg is unfolded.
The tripod according to this document is not adapted to be emplaced on an irregular surface nor to receive relatively heavy loads.
SUMMARY OF THE INVENTION
The present invention seeks to overcome these drawbacks, hence to provide a support which can be disposed stably on an irregular surface whilst being adapted to receive relatively heavy loads.
The support in question comprises, in a manner known per se, a structure on which at least two legs are pivotally mounted; the structure has at least one vertical upright and each leg comprises an upper portion located above the region by which it is connected to this upright, this upper portion being such that it bears against said upright when the leg is unfolded.
According to the invention:
said upper portion of at least one of the pivoting legs has a portion of circular transverse cross-section, or the upright to which this leg is connected has a portion of circular transverse cross-section facing said upper portion of the pivoting leg;
said upright comprises a piece of U shaped transverse cross-section fixed to it, or, respectively, said upper portion of the pivoting leg comprises this piece of U shaped cross-section; the two sidewalls of this piece of U shaped cross-section are disposed at a distance from each other less than the diameter of said circular transverse cross-section portion, the assembly being so shaped that, in the unfolded position of the leg, said portion of circular transverse cross-section will be bearing against said sidewalls of the U shaped piece, by being laterally wedged relative to this letter; and
at least one other of the pivoting legs has, at its upper portion, a screw perpendicular to the longitudinal axis of this upper portion, this screw being adapted, when it is screwed in, to come to bear against the upright to which this leg is connected and thereby to define a fixed angular position of pivoting of the leg relative to this upright.
Said U shaped piece thus permits perfectly wedging the pivoting leg or legs cited above, in a maximum unfolded position, whilst the screw or screws of the other pivoting leg or legs permit fixing this or these other pivoting legs in angular positions adapted to the irregularities of the surface of the ground on which the support is disposed, so as to carry out the perfect wedging of this support.
The support according to the invention thus comprises:
“bearing” legs which can be fixed and which include at least one pivoting leg adapted to be perfectly wedged laterally relative to the structure thanks to said U shaped member; said “bearing” legs forming a perfectly rigid structure;
at least one “wedging” leg, adapted to be pivoted angularly relative to the structure, to permit, in coaction with the “bearing”, a perfect wedging of the support, in a horizontal position of said structure.
According to one embodiment of the invention, said at least one pivoting leg has said portion of circular cross-section on its upper portion, and the upright to which this leg is connected comprises said piece of U shaped transverse cross-section.
According to another embodiment of the invention, said at least one pivoting leg comprises said piece of U shaped transverse cross-section on its upper portion, and the upright to which this leg is connected has said portion of circular transverse cross-section.
Preferably, each upright has a squared transverse section, and comprises at least one pair of tongues fixed to it, which form a stirrup for reception of a leg, said U shaped member being fixed to the upright by its intermediate wall, between the tongues.
Preferably, the two lateral walls of each U shaped member are positioned relative to each other such that their external surfaces come into immediate proximity with the internal surfaces of the tongues of the corresponding pair of tongues.
According to another characteristic of the invention, each leg has a tubular structure.
The upper portion of each leg provided with a screw can have, at this upper portion, a screw-threaded bore which passes through it, receiving said screw.
This screw can be a wing screw.
Moreover, each pivoting leg can have a pivoting foot at its internal end.
REFERENCES:
patent: 3139951 (1964-07-01), Clayton
patent: 3175642 (1965-03-01), Neeley
patent: 3583676 (1971-06-01), Yamakawa
patent: 3978943 (1976-09-01), Greenman et al.
patent: 4823913 (1989-04-01), Riegel, Jr.
patent: 4836332 (1989-06-01), Henson
patent: 5954156 (1999-09-01), Cooke
patent: 6419048 (2002-07-01), Robinson et al.
patent: 1 149 669 (2001-10-01), None
patent: 2 376 356 (1978-07-01), None
patent: 2 754 877 (1998-04-01), None
patent: 2 020 545 (1979-11-01), None
patent: 2 337 692 (1999-12-01), None
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