Note: Descriptions are shown in the official language in which they were submitted.
CA 02418581 2003-04-01
CONVERTIBLE LADDER
FIELD OF THE INVENTION
The present invention relates generally to a ladder. More particularly,
the present invention relates to a convertible ladder that is positionable in
a variety of
configurations.
BACKGROUND OF THE INVENTIO]I~i
For some time it has been known that constructing ladders with two
sections that are slidably mounted with respect to each other enables the
overall
length of the extension ladder to be varied depending upon the desired use of
the
extension ladder. This feature is particularly useful for transporting the
ladder to a
desired use location.
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CA 02418581 2003-04-01
Conventional extension ladders do not have the ability to stand up
without being leaned against another obj ect. In certain circumstances it is
not
possible to lean the extension ladder against other objects. To overcome this
limitation, KunnYaerlin et al., U.S. Patent No. 3,692,143, pivotally attaches
two
extension ladders together. This ladder retained the benefits of being able to
adjust
the height of the ladder while adding the benefit that the ladder could remain
erect
without leaning against other objects.
Boothe, U.S. Patent Nos. 4,407,045 and 4,566,150, are both directed to
a hinge for an articulating ladder. The hinge includes two hinge plates -that
are
pivotally attached with a central hub. Pivoting of the hinge plates is
controlled with a
locking handle that extends through apertures in the hinge plates. The locking
handle
is biased to a loclcing position where the -egs on the locking handle extend
into the
hinge plate apertures.
SUMMARY OF THE INVENTION
The present invention is a convertible ladder that includes a first ladder
portion, a second ladder portion and an adjustable binge mechanism, The first
ladder
portion and the second ladder portion each include a first section and a
second
section.
The first and second sections of the first ladder portion are slidably
attached to each other. The first and second sections of the second ladder
portion are
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slidably attached to each other. The first sections of the first and second
ladder portions
are pivotally attached to each other.
The present invention also includes two alternative fixed hinge mechanisms and
an
alternative adjustable hinge mechanism that are attachable to the second
sections of the
first and second ladder portions to maintain the second sections in an erect
or linear
position with respect to each other.
In a broad aspect, the present invention relates to a ladder comprising: a
first ladder
section; a second ladder section removably attachable to the first ladder
section by
means of a hinge; and an adjustable hinge mechanism and a non-adjustable
static hinge
mechanism, both hinge mechanisms being selectively attachable to the ladder
sections for
affixing first and second ladder sections together at an angle in selectably
varying
configurations, the adjustable hinge mechanism being angularly adjustable,
the static hinge mechanism presenting a fixed angle, wherein the adjustable
hinge
mechanism comprises a first adjustable hinge plate and a second adjustable
hinge plate, the
first adjustable hinge plate being pivotably attached to the second adiustable
hinge plate,
and wherein the static hinge mechanism comprises a first static hinge plate
and
a second static hinge plate and a substantially inelastic intermediate plate
generally parallel
to and intermediate to the first static hinge plate and the second static
hinge plate.
In another broad aspect, the present invention relates to a ladder having a
first
ladder section and a second ladder section removably attachable to the first
ladder section,
comprising: a non-adjustable static hinge mechanism, the hinge mechanism being
selectively attachable to the first and second ladder sections for affixing
first and second
ladder sections together at an angle, the static hinge mechanism presenting a
fixed angle,
wherein the static hinge mechanism comprises a first static hinge plate and a
second static
hinge plate and an intermediate plate generally parallel to and intermediate
to the first
static hinge plate and the second static hinge plate.
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In another broad aspect, the present invention relates to a method of forming
a
ladder comprising: removably attaching a first ladder section to a second
ladder section by
a selected hinge; and selecting the hinge from an adjustable hinge mechanism
and a non-
adjustable static hinge mechanism, selectively attaching either hinge
mechanism to the
ladder sections for affixing first and second ladder sections together at an
angle in
selectably varying configurations, forming the adjustable hinge mechanism to
be angularly
adjustable and having a first adjustable hinge plate and a second adjustable
hinge plate, the
first adjustable hinge plate being pivotably attached to the second adjustable
hinge
plate, and forming the static hinge mechanism to present a fixed angle and
having a
first plate and a second plate, the first and second plates being spaced apart
by an
intermediate plate.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a photograph of a convertible ladder of the present invention in a
first
orientation.
Fig. 2 is a photograph of the convertible ladder in a second orientation.
Fig. 3 is a photograph of the convertible ladder in a third orientation.
Fig. 4 is a photograph of the convertible ladder in a fourth orientation.
Fig. 5 is an enlarged view of a lower end of the convertible ladder.
Fig. 6 is a photograph of the locking mechanism in an engaged position.
Fig. 7 is a photograph of a locking mechanism of the convertible ladder in a
disengaged orientation.
Fig. 8 is a top view of an adjustable hinge mechanism in an assembled
configuration.
Fig. 9 is a bottom view of the adjustable hinge mechanism in the assembled
configuration.
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Fig. 10 is a side view of the adjustal-le hinge mechanism in the
assembled configuration.
Fig. 11 is a top view of the adjustable hinge mechanism in an
unassembled configuration.
Fig. 12 is a bottom view of the adjustable hinge mechanism in the
unassembled configuration.
Fig. 13 is a photograph of the adjustable hinge mechanism in a
disengaged orientation.
Fig. 14 is a photograph of the adjustable hinge mechanism in an
engaged orientation.
Fig. 15 is a photograph of the adjustable hinge mechanism in a first
position.
Fig. 16 is photograph of the adjustable hinge mechanism in a second
position.
Fig. 17 is a photograph of the adjustable hinge mechanism in a third
position.
Fig. 18 is a photograph of a static hinge rnechanism partially attached
to the convertible ladder with the locking mechanism.
Fig. 19 is a front view of a fixed hinge mechanism for use with the
convertible ladder.
Fig. 20 is a top view of the fixed hinge mechanism.
Fig. 21 is a side view of tlie fixed hinge mechanism.
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Fig. 22 is a side view of an alternative fixed hinge mechanism.
Fig. 23 is a top view of the alternative fixed hinge mechanism.
Fig. 24 is a top view of the alternative adjustable hinge mechanism in
an assembled configuration.
Fig. 25 is a photograph of a case for use with the convertible ladder.
DETAEC,ED DESC.RIPTION OF THE 1'REFERREP- EMBODIMENTS
The present invention is a convertible ladder, as most clearly
illustrated at 10 in Figs. 1-4. The convertible ladder 10 includes a first
ladder portion
12 and a second ladder portion 14 tha't are intercoavnected with an adjustable
hinge
mechanism 16.
The convertible ladder 10 is convertible between four different
configurations. In a first configuration, the convertible ladder 10 is an
extension
ladder, as most clearly illustrated in Fig. 1. In a second configuration, the
convertible
ladder 10 is an upright standing, 2-sided step ladder, as inost clearly
illustrated in Fig.
2. In a third configuration, the convertible ladder 10 separates into two
ladder
portions 10a, lOb that may be used independently or with a scaffold 20, as
most
clearly illustrated in Fig. 3. In a fourth configuration, the convertible
ladder 10 is
adjusted so that the first ladder portion 12 and the second ladder portion 14
have
different lengths to facilitate using the convertible ladder on uneven
surfaces such as
stairs 22, as most clearly illustrated in Fig. 4.
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CA 02418581 2003-04-01
As a result of the various configurations in which the convertible
ladder 10 may be positioned, the convertible ladder 10 of the present
invention takes
the place of several different prior art ladders. The convertible ladder 10
thereby
reduces the number of ladders that a person must own 'to do a variety of
tasks.
The first ladder portion 12 and the second ladder portion 14 each
include a first section 30 and a second section 32 that are slidably attached
together,
as most clearly illustrated in Fig. 1. The first section 30 includes a pair of
first side
rails 34 and a plurality of first rungs 36 that are mounted to extend between
the first
side rails 34 at selected intervals. The first side rails 34 preferably have a
rectangularly shaped configuration. A person o#` ordinary skill in the art
will
appreciate that the size of the first side rails 34 and the first rungs 36 is
selected based
upon the intended use of the convertible ladder 10.
The second section 32 includes a pair of second side rails 40 and a
plurality of second rungs 42 that are mounted to extend between the second
side rails
40 at selected intervals. The second side rails 40 preferably have a C-shaped
configuration that permits the first side rails 34 to at least partially seat
with the
second side rails 40. A person of ordinary skill in the art will appreciate
that the size
of the second side rails 40 and the second rungs 42 is selected based upon the
intended use of the convertible ladder 10.
The second section 32 also preferably includes a Y-shaped brace 44
proximate a lower end thereof, as illustrated in Figs. 2 and S. Lower ends 45
of the
brace 44 are attached to the front and back of each C -shaped side rai140. The
upper
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end 47 of the brace 44 is attached to the lowest rung 42. The brace 44 thereby
enhances the ability of the ends of the second sections 32 to resist
defor,mation when
forces are applied thereto.
The second section 32 fwRher preferably includes at least one brace 46
that extends between the second side rails 40 opposite the rungs 42, as
illustrated in
Fig. 2. Preferably one of the braces 46 is located proximate a lower end of
the second
section 32 and one of the braces 46 is located proximate an upper end of the
second
section 32. The at least one brace 46 further enhances the structural rigidity
of the
second section 32.
Proximate lower ends of the second side rails 40, feet 48 are attached
thereto, as illustrated in Figs. 2 and S. The feet 48 enhance the ability of
the
convertible ladder 10 to remain in a stationary position. The feet 48 are
preferably
removably attached to the second side rails 40 with a bolt. The bolt enables
the feet
48 to be readily replaced when damaged.
The lower ends of the second side rails 40 are flared apart from each
other so that a distance between the second side rails 40 proximate the lower
end is
greater than or equal to a distance between the second side rails 40 proximate
the
upper end. Using this configuration enhances the lateral stability of the
convertible
ladder 10.
The second sections 32 each have a pair of locking mechanisms 51.
The locking mechanisms 51 are attached to the second side rails 40 proximate
an
upper end thereof. The locking mechanism 51 prefexably includes a lock handle
53.
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The lock handle 53 is movable between in an engaged position and a disengaged
position. The lock handle 53 is preferably biased to the engaged position.
When in
the engaged position, the lock handle 53 engages the first section 30 and
thereby
maintains the first section 30 in a fixed position with respect to the second
section 32,
as illustrated in Fig. 6. When in the disengaged position, the lock handle 53
permits
the first section :30 to slide with respect to the second section 32, as
illustrated in
Fig. 7.
The adjustable hinge mechanism 16 includes a handle 50, a first hinge
plate 52 and a second hinge plate 54, as most clearly illustrated in Figs. 8-
11. The
first hinge plate 52 is pivotally mounted with respect to the second hinge
plate 54.
The first hinge plate 52 and the second hinge plate 54 each include a
pivot aperture 56 formed therein. The pivot apertures 56 are aligned when the
first
hinge plate 52 is pivotally attached to the second hinge piate 54.
The first hinge plate 52 has a pair of first positioning apertures 60
formed therein, as most clearly illustrated in Fig. i 1. The first positioning
apertures
60 are located on opposite sides of the pivot aperture 56.
The second hinge plate 54 preferably has three pair of second
positioning aperkures 62 formed therein (two pairs are shown in phantom and
one pair
is aligned with the first positioning apertures 60). The second positioning
apertures
62 are located on opposite sides of the pivot aperture 56 so that each pair of
second
positioning apertures 62 may be selectively aligned with the first positioning
apertures 60.
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CA 02418581 2007-12-10
{
A hub 70 extends through the pivot apertures 56 to pivotally attach the
first hinge plate 52 to the second hinge plate 54, as illustrated in Figs. 11
and 12.
Proximate a first end of the hub 70 an outwardly extending flange 72 is
provided. A
channel 73 is provided at an intermediate location on the hub 70. A locking
clip
seats in the channel 73 to retain the first hinge portion 52 and the second
hinge
portion 54 on the hub 70.
The hub 70 has a bore 76 extending therethrough. The bore 76 is
adapted to receive a hinge shaft 78. The hinge shaft 78 has a first shaft
section 80 and
a second shaft section 82 that are substantially adjacent to each other. The
second
shaft section 82 has a diameter that is smaller than the first shaft section
80 so as to
define a shoulder 84.
The first shaft section 80 has at least one recess 85 formed therein that
is adapted to receive an outwardly biased ball bearing (not shown). An
additional
recess (not shown) may be formed on an opposite side of the first shaft
section 80 to
receive another outwardly biased ball bearing. The ball bearing is adapted to
engage
a corresponding recess 87 formed in the hub 70.
Seating of the ball bearing in the recess 87 maintains the adjustable
hinge mechanism 16 in the disengaged position so that the hinge plates 52, 54
may be
pivoted with respect to each other. Once the lringe plates 52, 54 are
positioned at a
desired orientation, a modest force on the handle 50 causes the adjustable
hinge
mechanism 16 to return to the engaged position.
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A diameter of the hub bore 76 is approximately the same as the
diameter of the first shaft section 80. The hub 70 also preferably includes an
end
plate 88 proximate the second end. The end plate 88 has an aperture formed
therein.
A diameter of the end plate aperture is approximately the same as a diameter
of the
second shaft section 82.
A safety sleeve 86 extends at least a portion of the second shaft section
82. The safety sleeve 86 is preferably fabricated from a material with a color
that
contrasts from a color of the other portions of the convertible ladder 10 so
that the
safety sleeve 86 is readily visible when exposed. A person of ordinary skill
in the art
will appreciate that, as an aiternative to placing a safety sleeve 86 over the
second
shafft section 82, the safety sleeve 86 may be formed by applying paint to the
second
shaft section 82.
When in the disengaged position, as iilustrated in Fig. 13, the safety
sleeve 86 is visible on either side of'the convertible ladder 10. When in the
engaged
position, as illustrated in Fig. 14, the safety sleeve 86 is not visible on
either side of
the convertible ladder 10. 'The safety sleeve 86 thereby indicates to the
person that
the person should not step on the convertible ladder 10, as the adjustable
hinge
mechanism 16 is not in the engaged position.
The handle 50 has a first portion 100 and a second portion 102 that are
attached on opposite sides of the hinge shaft 78, as illustrated in Figs. 8-
10. The fnst
portion 100 preferably has a substantially elongated shape with a pair of
locking pins
104 extending therefrom. The locking pixis 104 are preferably selected with a
width
CA 02418581 2003-04-01
that is approximately the same as the diameter of the first positioning
apertures 60
and the second positioning apertures 62.
Moving the first portion 100 towards the first hinge plate 52 causes the
locking pins 104 to extend through the first positioning apertures 60 and the
second
positioning apertures 62 to thereby maintain the first hinge plate 52 in a
rotational
position with respect to the second hinge plate 54.
The adjustable hinge mechanism 16 preferably includes a spring 110
that biases the first portion 100 towards the first hinge plate 52 to maintain
the
adjustable hinge mechanism 16 in a loclced position. Urging the second portion
102
towards the first hinge plate 52 causes the locking pins 104 to be withdrawn
:&om the
first positioning apertures 60 and the second positioning apertures 62 to
thereby
permit the first hinge plate 52 to rotate with respect to the second hinge
plate 54.
The second portion 102 preferably has a substantially cylindrical shape
that includes a top section 112 and a side section 114 that extends from the
top
section 112. The top section 112 provides a substantially flat surface that is
depressed for urging the adjustable hange mechanism 16 from the engaged
position to
the disengaged position. The side section 114 extends towards the first hinge
section
52 and thereby reduces the potential for a person's fingers to become pinched
between the second portion 102 and the lirst hinge section 52.
Usitig the three pairs of second positioning apertures 62 enables the
first hinge plate 52 to be locked at three different angular positions with
respect to the
second hinge plate 54. In a first orientation of the adjustable hinge
mechanism 16,
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the first ladder portion 12 is positioned adjacent to the second ladder
portion 14 for
storage or transportation, as most clearly illustrated in Fig. 15.
In a second orientation of the adjustable hinge mechanism 16, the first
ladder portion 12 is oriented at an angle with respect to the second ladder
portion 14
for use as a step ladder, as most clearly illustrated in Fig. 16. In a third
orientation of
the adjustable hinge mechanism 16, the first ladder portion 12 is parallel to
and
aligned with the second ladder portion 14 for use as an extension ladder, as
most
clearly illustrated in Fig. 17. A person of ordinary skill in the art will
appreciate that
varying the number of second positioning apertures 62 allows the number of
angular
orientations to be varied.
Two of the static hinge mechanisms 140 are preferably attached to one
of the second sections 32, as illustrated in Fig. 18. Another second section
32 is then
aligned with the static hinge mechanism 140 to assemble the erect step ladder.
The convertible ladder 10 also includes a fixed hinge mechanism 140
is most clearly illustrated in Figs. 19-21. The fixed hinge mechanism 140
iricludes a
first plate 142 and a second plate 144 that are attached together in a spaced-
apart
configuration.
The first plate 142 and the second plate 144 each preferably have a
generally U-shaped configuration. An angle a between hinge legs 146 is less
than 90
degrees, preferably between 20 and 50 degrees and most preferably about 35
degrees.
A person of ordinary skill in the art will appreciate that the angle a is
selected based
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CA 02418581 2003-04-01
upon the desired use conditions such as the weight that is to be placed on the
second
sections 32.
A length of the hinge legs 146 is selected so that the hinge legs 146
extend sufficiently into the second sections 32 to prevent the second sections
32 from
rotating with respect to each other.
Proximate the end of the hinge legs 146, cach of the hinge legs 146 has
an aperture 148 formed therein. The aperture 148 is adapted to receive either
the lock
handle 53 to thereby retain the fixed hinge mechanism 140 in a fixed position
with
respect to the second sections 32.
Positioned between the first plate 142 and the second plate 144 is an
intermediate plate 145. The intermediate plate 145 maintains the first plate
142 and
the second plate 144 in a spaced apart relationship. The intermediate plate
145 also
limits the extent to which the second sections 32 can be inserted into the
fixed hinge
mechanism 140.
The first plate 142, the second plate 144 and the intermediate plate 145
are attached to each other with a plurality of reinforcing members 150. The
number
and size of the reinforcing members 150 is selected based upon the anticipated
load
that is to be placed on the convertible ladder 10.
An alternative fixed hinge mechanism 240, which has a generally
linear configuration, is illustrated in Fig. 22. The fixed hinge mechanism 240
enables
second sections 32 to be attached to each other in a substantially aligned
orientation.
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The fixed hinge mechanism 240 includes a first plate 242, a second
plate 244, and an intermediate plate 245. Proximate opposite ends of the fixed
hinge
mechanism 240 are hinge legs 246.
A length of hinge legs 246 is selected so that the hinge legs 246 extend
sufficiently into the second sections 32 to prevent the second sections 32
from
rotating with respect to each other.
Proximate the end of the hinge legs 246, each of the hinge legs 246 has
an aperture 248 formed therein. The aperture 248 is adapted to receive either
the lock
handle 53 to thereby retain the fixed hinge mechanism 240 in a fixed position
with
respect to the second sections 32.
The intermediate plate 245 maintains the t"irst plate 242 and the second
plate 244 in a spaced apart relationship. The intermediate plate 245 also
limits the
extent to which the second sections 32 can be inserted into the fixed hinge
mechanism
240.
The first plate 242, the second plate 244, and the intermediate plate
245 are attached to each other with a plurality of reinforcing members 250.
The
number and size of the reinforcing members 250 is selected based upon the
anticipated load that is to be placed on the convertible ladder 10.
The convertible ladder also includes an alternative adjustable hinge
mechanism 116 for use with each portion of the second ladder section 32, as
most
clearly illustrated in Fig. 24. The adjustable hinge mechanism 116 enables the
second
sections 32 to be pivotally attached to each other.
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The adjustable hinge mechanism 116 includes a handle 350, a first
hinge plate 352, and a second hinge plate 354. The alternative hinge mechanism
116
also has two hinge legs 356. The first hinge plate 352 is pivotally mounted
with
respect to the second hinge plate 354.
Proximate the end of the alternative adjustable hinge tegs 356, each of
the hinge legs 356 has an aperture 358 formed therein. "1"he aperture 358 is
adapted to
receive either lock handle 53 to thereby retain the altemative adjustable
hinge
mechanism 116 in a fixed position with respect to the second sections 32.
The configuration of the adjustable hinge mechanism 116 is preferably
similar to the adjustable hinge mechanism 16. A difference between adjustable
hinge
mechanism 16 and the alternative hinge mechanism 116 is the ends of the hinge
legs
356, which enables the adjustable hinge mechanism 116 to be removably attached
to
the second sections 32.
The components of the convertible ladder 10 are preferably fabricated
1.5 from a lightweight aluminum material. However, a person of ordinary skill
in the art
will appreciate that it is possible to fabricate the convercible ladder 10
from alternate
materials such as steel and fiberglass using the concepts of the present
invention.
Since the fixed hinge rnechanism 140 is not used in three of' the four
configurations of the convertible ladder 10, there is the potential that the
fixed hinge
mechanism 140 will be misplaced when not in use. To minimize the potential of
the
fixed hinge mechanism 140 being lost, the fixed hinge mechanism 140 is
preferably
stored in a case 160. The case 160 is preferably injection molded plastic and
includes
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a handle, as illustrated in Fig. 25. The case may also be used to store other
items such as
instructions on the use of the convertible ladder 10.
It is contemplated that the features disclosed in this application, as well as
those
described in the above applications, can be mixed and matched to suit
particular
circumstances. Various other modifications and changes will be apparent to
those of ordinary
skill.
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