Note: Descriptions are shown in the official language in which they were submitted.
CA 02514026 2005-07-28
LADDER LEVELLER
Field of the Invention
This invention relates to extension ladder attachments comprising a movable
and adjustable stile extension that engages the ladder via hollow ladder
rungs, for the purpose
of using a ladder on uneven surfaces.
Background of the Invention
Ladders are used extensively in construction and maintenance tasks on
construction sites and in buildings by a variety of trades and home do it
yourself people. Used
both indoors and out, ladders are often needed in locations and positions
where the footing
upon which they rest is uneven. indoor stairwells present a particular problem
for painters,
electricians, etc. for accessing walls and ceilings_ Out of doors uneven
ground around a
building or structure upon which work is to be performed poses a significant
challenge in
terms of safe ladder use. Many solutions to this problem have been devised
including ladders
with independently telescoping legs of various design, and ladder attachments
that incorporate
telescoping legs for the purpose of leveling a ladder on uneven surfaces.
Applicant is aware of patents regarding adjustable ladders and ladder
attachments that provide support to the ladder so that each leg may adequately
engage the
supporting uneven surfaces:
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CA 02514026 2005-07-28
Patent Country Inventor Patented
1.609,257 IUS.A .Lazear 25-May-26
3,998,293 USA Rai.a 21-Dec-76
4.852,689 USA Erion 01-Aug-89
4,984,655 IUSA !Scherer, et al, 15-Jan-91
5,476153 USA Dickerson, 19-Dec-95
,et al.
1,790,732 Canada Veness 15-Oct-91
2,274,330 Canada Batten App June 3,
1999
1.499,300 USA. Hayes 24-Jun-24
1.862.171 USA Baker 07-Jun-32
2,517,771 USA Stefano 08-Aug-50
3.447.631 USA Smith 03-Jun-69
4.607.726 USA Davis, et al. 26-Aug-86
5.094.320 USA Deitz, et al, 10-Mar-92
5.121.813 USA 'Fun.ston 16-Jun-92
5.232,067 USA Griffith 03-Aug-93
5.542.497 USA Macyszyn 06-Aug-96
5,553.,93 USA by, etal. 10-Sep-96
6.293367 USA Gul.seth 25-Sep-01
6,374.947 USA Nurkiewicz 23-Apr-02
6.435,306 USA Stoneburg 20-Aug-02
4.014,406 IUSA Easton March 29, 1977
The fore-mentioned patents teach a variety of methods to make ladder legs
adjustable in order to compensate for uneven supporting surfaces. Some require
tools to attach
the ladder leveling device, while others can be applied without tools. Some
are mounted
through the rung of a hollow rung ladder, while others are affixed to the
outside of the rung or
the main ladder frame or stiles. Some are easily removed while others are not.
Some insulate
the ladder primarily by means of a rubber foot pad, while others are not. Some
are adjustable
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and positively secured, with some being easily quick and easy to adjust, while
most are not.
Many require permanent modification of the ladder being attached to.
Summary of the Invention.
The present invention provides the means to use a hollow rung ladder on
uneven surfaces by attachment of one or more extendible legs to the ladder
stiles. One
common application where the invention may be used on uneven surfaces is in
painting a
hallway with a set of stairs in it. The present invention is readily attached
to or removed from
a ladder without the use of tools or modification of the ladder in any manner.
Further the
present invention once installed does not interfere with the operation of the
ladder where the
ladder is an extension ladder or a step ladder. The present invention attaches
to a ladder by
passing threaded rods centrally through two adjacent hollow rungs on the
lowest extent of the
ladder stiles, and securely affixing the rod therein by insulated ladder
collars that locate and
seat in the ladder rung port, and on the surface of the stile at the ladder
rung port. The
insulated ladder collar is surfaced with grooves in a manner that provides an
interlocking
surface with a similarly surfaced extendible leg in the form of u shaped
channel. The -channel
is mated against the ladder collars so as to attain the desired leg extension,
and secured thereon
by means of a quick-release locking bar, which is guided into position by a
cylindrical groove
on a locking bar guide. The quick release locking bar eases adjustment of the
extendible leg,
without the use of tools, while providing a secure means of attaching the
ladder leveller to the
ladder. This also allows for quick relocation of a single leveller leg from
one side, that is stile,
of the ladder to the other.
Thus in summary, the present invention may be summarized as a ladder leveller
for mounting onto at least one stile of a hollow lunged ladder, the leveller
including, an
elongate stile extension member at least one cross bar sized for mounting
journalled through a
hollow rung of the ladder, a locking pin extending from the at least one cross
bar and
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cooperating locking bar. The extension member has a spaced array of apertures
fbrrned
therealong, each aperture of the array extending through, the stile extension
member.
Cross bar mounts are mountable onto an end of the cross bars in mating
engagement with an end of the hollow rung so as to secure the cross bars
journalled in the
hollow rungs. The cross bars and cross bar mounts extend co-axially from the
cross bars and
through any one of the apertures in the stile extension member so that the
locking pin is
exposed outwardly of the stile extension member oppositely disposed relative
to the ladder
when the stile extension member is abutted against, so as to lie along, the
corresponding stile.
The locking bar is releasably mounted onto the locking pin when extending
through an
aperture in the stile extension member. The locking pin has locking grooves
for interlocking
with the locking bar.
Thus, with the cross bars mounted through corresponding hollow rungs, and
with the cross bar mounts mounting the cross bars securely in the rungs, and
with the locking
pin or pins protruding outwardly of the stile, and with the stile extension
member mounted
along and adjacent the stile with the locking pin protruding through one of
the apertures in the
stile extension member so as to expose the locking grooves on the locking pin
outwardly of the
stile extension member, and with the locking bar mated onto the locking
grooves on the
locking pin, the stile extension member is releasably mounted to and along the
stile so as to
adjustably extend from a lower end of the stile.
= Advantageously, the cross bars extend to opposite ends of the
corresponding
hollow rungs, and the cross bar mounts mount to opposite ends of each cross
bar and
corresponding rung, and the locking pins are mounted to, so as to extend
oppositely from, the
opposite ends of the each cross bar and corresponding rung.
The locking bar may be an elongate rigid member having slotted apertures
therein spaced apart so as to coincide with spacing between at least two of
the locking pins
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extending from the corresponding cross bars. The slotted apertures in the
locking bar mount
simultaneously over the two locking pins so as to engage the locking bar into
releasable
locking engagement with corresponding the locking grooves in the locking pins.
At least one stop may be mounted on. the stile extension member and
engageable with the locking bar to limit travel of the locking bar along the
stile extension
member as the locking bar is mounted into engagement with the locking pins.
Further advantageously, the cross bar mounts are electrically insulating and
are
mounted onto exposed ends of the cross bars, and the cross bars are of
sufficient length to
extend outwardly of the corresponding rung so as to expose ends thereof for
mounting of the
mounts thereto. The mounts mount between the stile extension member and
corresponding
stile to insulate one from the other. The mounts have outwardly disposed
surfaces, disposed
outwardly of the corresponding stile. The outwardly disposed surfaces are
contoured for inter-
locking engagement with a correspondingly contoured surface on the stile
extension member
so as to inhibit slipping of the stile extension member along the
corresponding stile when the
stile extension member is mounted thereto. For example, the contoured surfaces
may be
corrugated such as forming interlocking teeth.
The stile extension member may be a channel member, u-shaped in cross
section, so as to form an elongate channel along the length of the member. The
locking bar
when mounted onto the locking pin is contained within the elongate channel.
In one embodiment, an elongate resilient latch bar is mounted at one end
thereof onto the locking bar. The locking bar includes an aperture
therethrough disposed
underneath a free end of the latch bar. The aperture in the locking bar is
sized to mate over the
locking pin so as to allow the locking pin to extend therethrough. The latch
bar has a mating
aperture in the free end thereof fig mating over the exposed locking pin
exposed through the
aperture in the locking bar. The free end of the latch bar is biased by a user
lifting it away
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from the locking bar against a return biasing resiliency of the locking bar so
as to mount the
mating aperture onto the locking pin. The free end of the latch bar, once
released, is resiliently
biased so as to return towards the locking bar to thereby releasably lock the
locking pin in the
mating aperture, thereby mating the locking bar in a locked position relative
to the stile
extension member and thereby releasably locking the stile extension member
onto the
corresponding stile of the ladder.
In one embodiment, the aperture in the mating bar is a key slot, and the
mating
.aperture in the latch bar is positioned over a narrow end of the key slot.
The narrow end of the
key slot engages the locking grooves in the locking pin.
A handle may be formed on the free end of the latch bar adjacent the mating
aperture, for gasping by a user so as to bias the free end of the latch bar
away from the
locking bar.
Brief Description of the Drawings
Figure I is, in front perspective view, an exploded assembly for the ladder
leveller in alignment of the ladder ports used to attach to the ladder body.
Figure 2 is, in front perspective view, and exploded assembly of the ladder
leveller without a ladder present.
Figure 3 is, in front perspective view, a partially exploded assembly of the
ladder leveller without a ladder present.
Figure 4 is, in perspective view, the locking components of the ladder
leveller.
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Figure 5 is, in side cut-away view, the mounting interface between ladder
stile,
rung port and ladder leveller.
Figure 5a is, in top cut-away view, the mounting interface between ladder
stile,
rung port and ladder leveller.
Figure 6 is, in perspective view, a ladder with a ladder leveller attached to
one
stile in a extended position with the locking bar engaged.
'Figure 7 is, in perspective view, a ladder with a ladder leveller attached to
one
stile in a retracted or stowed position with the locking bar engaged.
Figure 8, is in perspective view, a ladder with a ladder leveller installed
and
extended to support the ladder on a set of stairs.
Figure 9, is in top cross sectional view, the ladder locking bar guides.
Figure 10 is, in perspective view, an alternative embodiment of the channel
and locking bar according to the present invention.
Figure 10a is, in exploded view, the channel and locking bar of Figure 10.
Figure 11 is an enlarged view of a portion of Figure 10.
Figure 12 is an enlarged view of a portion of Figure 10.
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Detailed Description of Embodiments of the Invention
The present invention is a ladder leveling device that attaches to various
stile
designs of hollow rung ladders and is described with reference to the
accompanying drawings
wherein similar characters of reference denote corresponding parts in each
view. One
embodiment of the present invention as seen in Figures 1-9 is attached to a
ladder 12 by first
passing threaded rods 6 centrally through the hollow rungs 13 and securing
them in place
using insulated ladder collar 5 which has locking pin 11 press fit into it,
and together are
retained on rod 6 by hand threading the collar and locking pin assembly onto
rod 6, and seated
by locating ring 19 in the ladder port 10 against the ladder stile 20, with
the locking grooves 21
on the collar being positioned normal to the longitudinal axis of the ladder
stile 20.
The leg assembly as shown in Figure 2, complete with channel 2, and locking
bar guides 4 secured by rivets 16, and locking bar 1 is attached to the ladder
by bringing the
assembly of Figure 2 to a ladder stile as shown in Figure 1 so that the
locking pins 11 pass
through the channel slots 3 or holes 15 and the locking bar slots 8 and 9
until the grooves 17 in
the channel web 14 engage with the grooves 21 in the collars. The locking bar
1 is then
moved towards the foot of the ladder engaging the locking bar slots 8 and 9 in
the locking pin
11 slots 18. Similarly a second ladder leveling device may be optionally
attached to the
opposite stile.
To adjust the ladder leveling device one lifts the locking bar 1 until the
locking
bar slots 8 and 9 disengage the locking pin grooves 18 allowing the leg
assembly to move
away from the ladder stile 20 enough for the channel grooves 17 and the collar
grooves 21 to
clear. The leg assembly is then moved towards or away from the foot of the
ladder to the
desired position, the leg assembly is moved towards the ladder style 20 until
the channel
grooves 17 and collar grooves 21 are once again engaged. The locking bar 1 is
then moved
towards the foot of the ladder stile 20 engaging the locking pin 11 in groove
18 by the locking
bar slots 8 and 9. Once the locking bar 1 is fully engaged in the locking pin
grooves 18, the
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ladder can be positioned and used as shown for example in figure 8 where the
swivel foot 22
of the channel 2 extended to contact a lower step 23a is in contact with the
lower step 23a, and
the swivel foot 22 of the channel 2 extended to contact an upper step 23b,
separated from
lower step 23a by rise 24, is in contact with upper step 23b.
The combination of the cylindrical grooves 25 on the locking bar guides as
shown in figure 9, and the key hole slot 8 and 9 on the locking bar enables
the key hole slots 8
and 9 to engage the groove 18 of the locking pin 11. The locking bar 1 is
pushed down
through the locking bar guides 4 until the top end of the key hole slot 8 and
9 slide until the bar
fully engages the top half circumference of pin slot 18. The locking bar 1
will not engage the
collar pin 11 if the grooves between the collar 21 and the channel 17 are
misaligned, signaling
to the user that the ladder leveller is not locked in position and is not safe
to use.
The ladder collar 5 may be made of insulating material so as to provide an
extra
measure of protection against unintentional grounding of the ladder when used
in servicing
electrical devices, which may be energized at the time. The combination of the
insulated
collar and centrally locating this steel threaded rod inhibits an electrical
charge passing
through the attachment to the ladder body. The locking pin 11 is shown as a
separate
component from the collar 5, and can be metallic in nature adding strength to
the locking
mechanism. An alternative embodiment may have the collar 5 and locking pin 11
combined
as a single component that could be made of a high strength electrically
insulating material
such as plastic, or it could be made of a metallic material which may simplify
the design while
possibly forgoing the electrical insulating properties of the collar 5.
Figures 5 and 5a show the ladder collar 5 securely engaging the ladder port 10
and stile 20 by means of the protrusion or locating ring 19 on the collar 5
seating within the
ladder port 10, while the shoulder portion of the collar engages the surface
of the stile 20, and
is held in contact with the stile 20 by the pressure resulting from two such
collars 5 being
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turned onto the threaded rod 6 until they both actively engage the opposing
rung ports 10 with
the collar locating ring 19, and the stile 20 with the shoulder portion of the
collar.
Figures 5 and 5a also show by top view cutaway section the channel 2 grooves
17 and 21 engaged, and the locking bar 1 slot 8 engaged with the locking pin
11 groove 18.
The locking bar 1 is also shown entrapped by the locking bar guides 4 which
are riveted 16 to
the channel 2.
Non-slip rubber pads on the swivel feet 22 are typically installed at the foot
of
the ladder levellers by bolting through hole 7 on the channel 2, providing the
ladder leveller
additional safety through both non-slip and electrical insulation properties
of the feet. The
rotational degree of freedom in the mounting of the feet 22 enhances the
ladder safety when
used on different ladder slopes.
The u-shaped channel 2 is used for legs in the present invention due to its
improved strength and weight characteristics when compared with much of the
prior art. The
present invention may be installed onto a conventional hollow rung ladder
without the use of
tools, modification of the ladder, or interference with the ladder operation.
It is may be
adjusted without tools by simply lifting and lowering the locking bar 1. The
ladder leveller
may be moved from one side of the ladder frame to the other side with out the
use of tools, and
is not restricted to specific ladder widths making it a flexible add on to
most existing ladder
designs.
The insulated ladder collar separates the ladder leveller from the main ladder
frame and is non-conductive, adding a measure of safety when used around
energized
electrical circuits. The ladder leveller has two connecting points to the
ladder, spreading the
stress over a greater area than some of the prior art. There is no contact
between the ladder
frame and the ladder leveller leg, other than through the insulated collar,
which distributes the
load through the rung port. The grooves on the insulated collar and the
grooves on the ladder
CA 02514026 2013-03-20
leveller channel positively lock into each other to provide very secure
support. The locking
bar prevents unintended unlocking as it has to be lifted up in a vertical
direction and is
generally held in place through friction and gravity. The ladder leveller does
not interfere with
the clear operation of the ladder at any time. No tools are required for
installation or removal
of the ladder leveller, making it easy to move from one ladder to another.
The tightening and the precise alignment of the two insulated collar grooves
on
the ladder to engage the locking bar 1 is done without tools using the
following method. The
ladder attachments lower slot and grooves are engaged on the lower collar and
the locking bar
in slid into place. The attachment is rotated around in a circular arc
securing the insulated
collar against the face of the ladder style. The attachment is rotated again
till the upper
insulated pin aligns with the upper corresponding slot and passes through. The
process is
followed for the upper insulated collar and when complete the ladder grooves
are now aligned
exactly and the locking bar and corresponding grooves can be engaged properly.
In an alternative embodiment seen in Figures 10-12, the lower end of locking
bar I is planar and slides along channel 2 under an opposed facing pair of
channel rails 2a so
that locking bar 1 is held snugly flush against the web 2b of channel 2 as the
locking bar is slid
along channel 2 in direction A. Locking bar 1 has key slot 8 so as to engage a
locking pin 11
extending from collar 5 through channel slots 3 in channel web 2b. The
narrowed slot 8b of
key slot 8 engages corresponding slots 18 in locking pins 11.
A flexible latch bar la is mounted by fastener lb to channel web 2b at one end
of the latch bar so as to flexibly dispose the free end of the latch bar over
the lower of the key
slots 8. Latch bar la has an aperture l c in the free end thereof sized to fit
snugly over the
exposed end of locking pin 11. Thus, once the exposed end of locking pin 11 is
inserted
through the large opening 8a in key slot 8, and with the free end of latch bar
la elevated away
from locking bar 1 in direction B, locking pin 11 may be slid along the narrow
slot 8b of key
slot 8 until aligned with aperture lc in latch bar la. Latch bar la may then
be lowered so as to
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journal the exposed end of locking pin II through aperture lc. This locks
locking pin 11 into
key slot 8 until such time as it is desired to remove locking bar 1 from
engagement with
locking pin 11. When it is desired to remove locking bar 1, the free end of
latch bar 1 a is
elevated in direction B to allow locking pin 11 to be removed from aperture I
c, thereby
allowing locking pin 11 to be slid along locking bar 1 into the opening 8a of
key slot 8 for
removal of locking pin 11 through opening 8a. This allows dis-engaging of
locking bar I from
locking pin 11 thereby allowing the removal of channel 2 from engagement with
the
corresponding stile 20 of ladder 12.
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