Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02228083 1998-O1-28
TITLE OF THE INVENTION
Plastic ladder
FIELD OF THE INVENTION
The present invention pertains to ladders and, more
specifically, to a ladder entirely made of plastic material.
BACKGROUND OF THE INVENTION
Plastic ladders are known, such as the hollow plastic ladder
described in U.S. patent 5,131,495 issued July 21, 1992 to Bartnicki et al.
The front and rear sections of the ladder described in this patent are folded
towards and away each other through a linkage arrangement that consists
of legs pivotally connected to one another by means of hinges. However, in
order to be structurally reliable, such linkage component must be made of
metallic material.
STATE=MENT OF THE INVENTION
It is an object of the present invention to provide a ladder which
is entirely made of plastic material and which has a particular construction
so
as to give to the ladder the required stability, rigidity and strength when it
is
in a free standing position with a user mounted on one of its steps as well as
neat compactness when it is in a folded position.
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Essentially, the ladder comprises three plastic components
which are pivotally connected to one another to move between closed and
opened standing positions.
The present invention therefore relates to a plastic ladder which
comprises:
a first plastic component defining an inverted U-shaped body
having opposite first and second front side rails integral with a top part;
a second plastic component having opposite first and second
rear side rails extending coplanar with the first and second front side rails
respectively; the upper end of each rear side rail being hingedly mounted to
a respE~ctive front side rail; and
a third plastic component connected to the first and second
plastic components; the third plastic component defining an intermediate
step plate having a top wall and opposite side walls;
the first, second and third components having inter-engaging
means allowing pivotal movement of the second component to contact the
first component whereby the rear side rails bear in coplanar arrangement
against the front side rails and whereby the intermediate step plate lies
substantially vertically in an area included within the first and second front
and rear side rails bearing against each other.
In one form of the invention, the top part of the body defines a
tray.
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In a further embodiment of the invention, a plastic tray is
mountf:d to the top part of the body and is pivotable between a horizontal
plane and a plane coincident with the parallel plane of the first and second
front side rails.
Yet, in a further embodiment, a plastic tray is pivotally mounted
to the first and second front side rails and is pivotable between a horizontal
plane and a plane coincident with the parallel plane of a first and second
front side rails.
Other objects and further scope of applicability of the present
invention will become apparent from the detailed description given
hereinafter. It should be understood, however, that this detailed description,
while indicating preferred embodiments of the invention, is given by way of
illustration only, since various changes and modifications within the spirit
and
scope of the invention will become apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a first embodiment of a plastic
ladder made in accordance with the present invention;
Figure 2 is a side elevation thereof;
Figure 3 is a perspective view of the intermediate step plate;
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Figure 4 is a perspective view of the second plastic component
of the ladder;
Figure 5 is a front elevation view of the ladder shown in figure
1;
Figure 6 is a cross sectional view taken along lines 6-6 of figure
5;
Figure 7 is a cross sectional view, similar to that of figure 6,
showing the ladder in the folded position;
Figure 8 is a perspective view of a second embodiment of the
present invention; and
Figure 9 is a perspective view of a third embodiment of the
present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings wherein like reference numerals refer
to similar or identical parts throughout the several views, there is shown, in
figures 1-7, a first embodiment 10 of a ladder which is made entirely of
plastic material. It comprises a first plastic component, generally denoted
11,
defining an inverted U-shaped body consisting of a plastic front side rail 12,
havirng a bottom end 16, of a second plastic front side rail 18 having a
bottom
end 22 and of an integral top part 23. A plastic step 24 is integrally formed
to thE~ inner walls of the side rails 12 and 18; additional steps may be
provided, if required.
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The ladder also comprises a second plastic component,
generally denoted 25, consisting of a first rear side rail 26 having its upper
end 28 hingedly connected to the side rail 12 and of a second rear side rail
30 which has its upper end 32 hingedly connected to the side rail 18. A
plastic X-shaped brace structure 34 extends between and is integral with the
two rE~ar side rails 26 and 30 to provide reinforcement.
The ladder comprises a third plastic component, generally
denoi:ed 36, defining an intermediate step plate which is connected to the
front pair of side rails and to the rear pair of side rails. Referring more
particularly to figure 3, the step plate 36 comprises a flat top face 38,
having
anti-skid means 39, and opposite side walls 40 and 42, each displaying a
projecaion 41, 43 for pivotal connection to respective side rails 12 and 18.
The projections 41 and 43 are C-shaped to enable a snap engagement with
corre:>ponding pins (one of which is shown as 44 in figures 6 and 7)
integrally
formed with the side rails 12 and 18. On each side wall of the step plate an
elongated curved recess 45, 45' is provided to receive a pin 46, 47 (see
figure 4) integral formed with an associated rear side rail 26, 30.
Referring to figures 6 and 7, the particular construction of the
plate 36 is such that, from the standing open position of figure 6, pivotal
movement of rear rails 26 and 30 about hinges 28 and 32 causes also the
pivotal movement of plate 36 about pivots 44 whereby pins 46 and 47
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slidably follow the curved path of recesses 45, 45' in the opposite side walls
of the plate until they reach the position shown in figure 7 where the rear
side
rails c'.6 and 30 come to lie in a substantially coplanar arrangement with and
to beer against their associated front side rails 12 and 18. As can be seen
also in figure 7, the cross plate 36 reaches an almost vertical position in an
area included between the pair of front and rear side rails to form a neat
compact folded condition.
In the embodiment illustrated in figures 1 to 7, the top part 23
of the first plastic component is shaped to define an integral tray 64. This
upper part of the ladder described above with respect to a first embodiment
of the invention may have various arrangements. For example, in figure 8,
the inverted U-shaped body 11' has a top portion 23' with a pivotal tray 66.
This bray may be moved from a horizontal position (for use) to a substantially
vertical position (for storing) in a plane coincident with the plane of the
front
side rails 12' and 18'. No structural changes are required for components 25
and 36 of the ladder.
Figure 9 shows an inverted U-shaped structure 11 " with a tray
68 pivotally mounted to the inner walls of two side rails 12" and 18". Tray
68 is mounted so that it may be moved from a horizontal position (for use)
to a plane (for storing) which is coincident with the plane of side rails 12"
and
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18", changes are required for the components 25 and 36 to provide a
compact storing arrangement.
Although the invention has been described above with respect
to three specific forms, it will be evident to a person skilled in the art
that it
may be modified and refined in various ways. For example, the inter-
engaging means between the three plastic components may be varied. It is
therefore wished to have it understood that the present invention should not
be limited in scope, except by the terms of the following claims.
