GB2489009A

GB2489009A - Levelling device for a ladder

Info

Publication number: GB2489009A
Application number: GB1104340.3A
Authority: GB
Inventors: Christina Marie Valentine
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-03-15
Filing date: 2011-03-15
Publication date: 2012-09-19
Anticipated expiration: 2031-03-15
Also published as: GB2489009A8; GB201104340D0; GB2489009B; GB2489009B8

Abstract

A levelling device 7 for a ladder comprises a telescopic leg having nested outer and inner sleeves (13, 15, fig 3) connected to either a side rail 3 and/or rungs 5 of the ladder. The inner sleeve moves relative to the outer sleeve between a number of discreet positions, possibly defined by a rack of teeth 17 selected by a locking pawl. A drive rod (35, fig 3) is positioned within the inner sleeve and is moveable linearly relative thereto for fine adjustment. The drive rod is rotated with respect to the inner sleeve, preferably by a threaded coupling, to impart this extension. Preferably, the drive rod is adjusted from an ergonomically placed handle (33, fig 3) at the top of the device. In a further aspect, a levelling device is adapted to be secured to a ladder side rail and imparts linear movement between the inner sleeve and the drive rod to move a foot towards a support surface. In a further aspect, a removable locking device is provided.

Description

Levelling Device for Ladders

Field of the Invention

This invention relates to levelling devices for ladders.

Background of the Invention

It is well known that, for safety reasons, a ladder should in use be level. In other words, the ladder rungs should be horizontal. This is achieved on many occasions by ensuring that the ladder is placed on level ground. There are occasions, however, when this is not possible. One such occasion is when work is being carried out on a wall alongside a staircase. Here, a ladder can only safely be used if the effective length of one side rail (also known as a stile) can be increased by the height of one or more treads of the staircase. It is, of course, essential on such occasions that the ladder is truly level.

is Levelling devices for adjusting the effective length of a side rail of a ladder are well known.

Examples of such devices are to be found in US patents 4209078, 4423797 and 4606432. In the first of these patents, a sleeve attached to a ladder side rail houses a threaded rod which can be rotated through a handle to move a plate attached to the base of the rod into contact with the ground. On occasions where the distance to be travelled by the rod to achieve levelling is significant, the time taken in doing so is also significant.

Both of the other patents disclose levelling devices similar to that described above except that the extendable leg is movable to a position coincident with a selected one of several discrete holes set in a side of the sleeve. Such a device enables relatively rapid incremental increases or reductions in the effective length of a side rail but lacks the fine linear tuning achieved by using a threaded rod as disclosed in US4209078.

It is an aim of this invention to provide a levelling device for ladders which provides relatively rapid changes in the effective length of one or each side rail followed by an accurate linear adjustment to achieve accurate and reliable levelling of a ladder.

Summary of the Invention

According to the present invention in one aspect there is provided a levelling device for a ladder, the device comprising an elongate telescopic leg attachable to one side rail and/or one or more rungs of a ladder, the elongate leg including an outer sleeve, an inner sleeve mounted for sliding movement within the outer sleeve between two of a plurality of predetermined discrete positions, locking means for selectively enabling and preventing relative movement between the sleeves, and a drive member positioned within and partially protruding from one end of the inner sleeve, and means for imparting rotational movement to the drive member relative to the inner sleeve to move the protruding end of the drive member into contact with a support surface.

The outer sleeve may include at least one sideways projecting arm for connection to a side rail or one or more rungs of the ladder.

In a preferred arrangement, the inner and outer sleeves are rectangular in cross section and at least one side wall of the inner sleeve includes or is formed with a lengthwise extending rack comprising a succession of discrete teeth which cooperate with a pawl of a locking sleeve located about the periphery of the outer sleeve to permit or prevent relative movement between the inner and outer sleeves.

The pawl is preferably movable through a ratchet arm into and out of contact with any pair of the teeth of the rack.

The drive member preferably includes a rod having a threaded length which passes through a bore of an end cap of the inner sleeve, the bore including internal threads complementary to those of the rod whereby rotation of the drive member imparts linear movement to the rod. Preferably, the drive member has slots formed in its sides into which project the ends of a laterally extending pin of the rod.

A spirit level may be positioned on a horizontal surface of the levelling device or the ladder (e.g. on the uppermost rung) for accurate levelling of the ladder.

In another aspect, the invention provides a ladder including side rails separated by a plurality of rungs, and an elongate levelling device comprising an outer sleeve connected to one side rail and/or one or more rungs of the ladder, an inner sleeve mounted for relative sliding movement within the outer sleeve, a plurality of spaced openings or recesses or the like formed in or carried by a lengthwise extending surface of the inner sleeve, a locking member carried by the outer sleeve and movable into or out of the openings or recesses or the like selectively to prevent or permit relative movement between the inner and outer sleeves, a partially threaded drive rod positioned within the inner sleeve and moveable linearly relative thereto, a closure member for the lower end of the inner tube formed with a threaded bore through which a threaded length of the drive rod passes, and means for imparting is rotational movement to the drive rod to move a foot of the drive rod into contact with a surface on which the ladder is supported.

One or more rungs of the ladder may be open-ended and hollow and the outer sleeve may include at least one arm which projects outwardly from the outer sleeve and generally parallel to the rungs of the ladder, the or each arm being shaped and dimensioned to enable it to locate as a relatively close fit within a hollow rung of the ladder.

In a further aspect, the invention provides a levelling device adapted to be secured to a side rail of a ladder, the levelling device comprising an outer sleeve, an inner sleeve mounted within the outer sleeve, a drive rod mounted within the inner sleeve, means for imparting incremental relative movement between the outer and inner sleeves, and means for imparting linear relative movement between the inner sleeve and the drive rod to move the foot of the drive rod towards or away from a support surface.

Brief Description of the Drawings

The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:-Figure 1 shows a levelling device in accordance with the invention projecting from one side rail of a ladder; Figure 2 shows the levelling device illustrated in Figure 1 projecting from each side rail of a ladder; Figure 3 is a section taken along the length of the levelling device illustrated in Figures 1 and 2; Figure 4 is a view of the illustrated levelling device taken in the direction of arrow A of Figure 2; Figure 5 shows a ladder incorporating a levelling device in accordance with the invention supported on two different stair treads of a stairwell; Figure 6 is a perspective view of a bubble-type two-dimensional spirit level incorporated onto a rung of the ladder; Figure 7 is a schematic diagram of a ladder viewed from one side which shows the is preferred angle of slope of a ladder for safe use; and Figure 8 is a partial perspective view of a system for attaching the levelling device to the ladder.

Detailed Description of a Preferred Embodiment

The ladder illustrated in the drawings is typically produced from aluminium or galvanised steel and comprises spaced side rails 1, 3 connected together by a plurality of open ended hollow rungs 5. Connected to the side rail 3 is a levelling device 7 which is used to vary the effective length of the rail 3 in the event that the ladder is positioned on a surface which slopes or is stepped.

The levelling device 7 comprises an elongate telescopic leg 9 which lies parallel or substantially parallel to the rail 3 and is connected to the ladder through horizontally extending arms 11. Each arm 11 is formed with a series of spaced holes and is shaped and dimensioned to slide as a relatively close fit within an adjacent hollow rung of the ladder.

The arms 11 may be permanently retained within these rungs or may be removed for separate storage. In either case, the exposed arm lengths are selected simply by varying the position of each arm within the respective rung. Thus, the distance between the side rail 3 and the telescopic leg 9 can be varied by movement of the arms 11 within the rungs 5. Preferably, the length of each arm 11 approaches, or is substantially the same as, the length of each rung 5. This means that the engagement between the levelling device 7 and the ladder is stable. Where two levelling devices 7 are provided for use with a single ladder, the arms 11 may be staggered, as shown in Figure 2, so that the arms of the left hand device are in use connected to different rungs than the arms of the right hand device. By making the horizontal arms 11 the same diameter and staggering the respective rung locations, this enables otherwise identical extensible levelling devices to be used on either side of the ladder. Alternatively, the horizontal arms 11 may be of different diameters or cross sections (if not round sections) such that in use they may be nested one inside the other inside the rungs when mounted onto the ladder whilst still extending the full rung width and thus providing substantial support and rigidity when extended width-ways.

As described, each ladder rung is open ended and internally dimensioned to receive one of the arms 11 in a relatively firm grip. This need not be the case, only a selected few rungs being so dimensioned.

Referring to Figure 8, the arms 11 can be securely attached to the rungs 5 by means of a pin 60 which is in use located through a hole 61 in a circumferential collar extending from the side of each rung 5. A row of holes 62 are also provided in the arms 11 defining discrete positions through which the pin 60 passes when the user selects the required lateral distance.

Other ways of attaching the levelling device to the rungs or side rails of the ladder may be adopted. Thus, the levelling device may simply be clamped to one or each side rail of the ladder.

As illustrated in Figure 2 of the drawings, a levelling device 7 is positioned alongside each side rail 1, 3 of the ladder. In this embodiment, either or both side rails can be lengthened to level the ladder. Also, the distance between the levelling devices 7 can readily be changed by movement of the arms 11 within the rungs 5.

As will be seen more clearly from Figure 3, the levelling device comprises an outer sleeve 13 which is rectangular in cross section and is positioned about the periphery of an inner sleeve 15 also of rectangular cross section. The opposed narrower outer surfaces of the inner sleeve 15 are each formed with a linear rack of teeth 17 which cooperates with one of a pair of pawls in the form of ridges 19 which protrude from the inner face of each of a pair of ratchet arms 21. As will be seen more clearly from Figure 4, a tensioned locking sleeve 23 encompasses the ratchet arms and the outer sleeve 13 to urge the pawl ridges between neighbouring teeth of the rack 17.

The ratchet arms 21 protrude outwardly from the narrow sides of the outer sleeve 13 and are movable against the loading imposed by the locking sleeve 23 from a rest position in which the two pawl ridges 19 are trapped between neighbouring teeth 17 of the rack to prevent movement of the inner sleeve 15 relative to the outer sleeve 13, and an active position in which each pawl ridge 19 is released from its trapped position to enable the inner sleeve to slide within the outer sleeve thereby changing the effective length of the levelling device 7. The locking sleeve 23 is a separate component to the ratchet arms 21 and in use ensures the ratchet pawl ridges 19 do not jump out of engagement with the teeth 17. The locking sleeve 23 is preferably formed of resilient material, for example a plastic or rubber material.

On release of the ratchet arms 21, the pawl ridges 19 are once more trapped between neighbouring teeth 17 to prevent further relative movement between the inner and outer sleeves. Thus, movement of the inner sleeve relative to the outer sleeve between initial and final positions defined by a multiple of the gaps between neighbouring teeth can be achieved simply by movement of the ratchet arms away from the narrow sides of the outer sleeve.

Such incremental changes in side rail length provide speedy and relatively coarse changes in the length of the telescopic leg 9 but do not ensure that small differences between the effective lengths of both side rails no longer exist. To achieve accurate levelling, a second fine levelling function is provided.

This second levelling function will now be described.

As will be seen from Figure 3, a slotted drive tube 25 is positioned within the inner sleeve 15. At its upper end, the drive tube is connected by a pin 27 to a shaft 29 of a rotatable knob 31 operated by handle 33. The handle 33 and knob 31 can best be seen from Figures 3 and 4. Thus rotation of the handle 33 imparts like rotation to the drive tube 25.

At its lower end, the drive tube 25 is connected to a rod 35 through a drive pin 37 whose ends project outwardly from the rod 35. The projecting ends of the drive pin 37 locate within the slotted sides of the drive tube 25. Rotation of the drive tube 25 therefore imparts rotational movement to the rod 35. The lower end 39 of the rod 35 is threaded. The drive pin 37 extends telescopically within the slotted drive tube 25 with the ends of the pin 37 tracking within the slots of the drive tube to accommodate increases or decreases in the overall length of the levelling device 7 occasioned by operation of the ratchet arms 23.

The lower end of the outer sleeve 13 is closed by an end cap 41. Within the end cap 41 a bore 43 is provided through which the threaded end 39 of the rod 35 extends.

The bore 43 is formed with threads which complement and engage with those of the rod end 39. A locking ring 45 holds the end cap 41 in place. The rod 35 terminates in a swivel foot 47.

In use, rotation imparted to the drive tube 25 by operation of the handle 33 causes the rod 35 to rotate to raise or lower the foot 47 depending on the direction of rotation imparted to the handle 33. The slots formed in the sides of the drive tube 25 enable translational movement to be imparted to the rod and, therefore, the swivel foot 47.

Ladder levelling devices in accordance with the invention provide a rapid incremental change to the effective length of one or both side rails of a ladder through operation of the ratchet arms followed by a final linear adjustment through rotation of the handle 33.

The operation of the levelling device will now be explained with reference to Figure 5 of the accompanying drawings. As shown, the side rails of the ladder are supported on different treads of a staircase. To achieve a level and therefore stable ladder, the ratchet arms 21 are operated to enable the inner sleeve 15 to travel swiftly downwardly to a position where the swivel foot 43 lies just above the lower stair. The ratchet arms are then released to prevent further downward movement of the inner sleeve 15, the rod 35 and swivel foot 47. Fine tuning of position of the swivel foot, and therefore the effective length of the side rail 1 is achieved by turning the handle 33 to drive the swivel foot linearly and firmly into contact with the lower stair. This is important because a ladder can in use become unstable if it leans over to one side even to a small extent.

It is also important that the angle subtended to a ladder supporting wall is neither too great nor too small. Referring to Figure 7, preferably, the ratio of the height at which the upper end of the ladder 1 rests against a wall 57 and the distance of the foot of the ladder from the wall is between 3.5:1 and 4:1. To this end, a two-dimensional spirit level 49 may be positioned on the top of the outer sleeve as shown in Figure 4.

Alternatively, a level gauge 51 may be supported on one of the ladder rungs 5 as shown in Figure 6. Preferably, this spirit level is a bubble-type spirit level one having cross hairs, one showing the actual level of the ladder and the other being biased to show when the angle subtended by the ladder to the supporting wall surface corresponds to a 4:1 lean ratio.

It will be appreciated that the following description of levelling devices in accordance with the invention is by way of example only and that modifications can be readily made to the devices as described without departing from the scope of the invention as set out in the appended claims.

The use of one or more of the levelling devices described previously can be used to create a wider base support for taller ladders or any application where side-to-side or lateral stability is compromised by the relatively narrow width between siderails of a conventional ladder.

Claims

CLAIMS1. A levelling device for a ladder, the device comprising an elongate telescopic leg attachable to one side rail and/or one or more rungs of a ladder, the elongate leg including an outer sleeve, an inner sleeve mounted for sliding movement within the outer sleeve between two of a plurality of predetermined discrete positions, locking means for selectively enabling and preventing relative movement between the sleeves, and a drive member positioned within and partially protruding from one end of the inner sleeve, and means for imparting rotational movement to the drive member relative to the inner sleeve to move the protruding end of the drive member into contact with a support surface.
2. A device as claimed in claim 1 wherein the outer sleeve includes at least one is arm which projects substantially normal to the longitudinal axis of the outer sleeve for connection to a side rail or one or more rungs of the ladder.
3. A device as claimed in claim 1 or claim 2 wherein the inner and outer sleeves are rectangular in cross section and at least one side wall of the inner sleeve includes or is formed with a lengthwise extending rack comprising a succession of discrete teeth which cooperate with a pawl carried by the outer sleeve to permit or prevent relative movement between the inner and outer sleeves.
4. A device as claimed in claim 3 wherein the pawl is movable through a ratchet arm into and out of contact with any pair of rack teeth.
5. A device as claimed in claim 3 or claim 4, wherein the pawl or ratchet arm carried by the outer sleeve is movable against loading imposed by a locking sleeve arranged to hold the pawl in a first position in which it is engaged or trapped between neighbouring teeth, the pawl being releasable from the first position by user action against said loading.
6. A device as claimed in claim 5, wherein the locking sleeve is a separate component to the pawl or ratcher arm.
7. A device as claimed in claim 5 or claim 6, wherein the locking sleeve is formed of resilient material.
8. A device as claimed in any one of the preceding claims wherein the drive member is connected to a rod having a threaded length which passes through a bore of an end cap of the inner sleeve, the bore including internal threads complementary to those of the rod whereby rotation of the drive member imparts linear movement to the rod.
9. A device as claimed in claim 5 wherein the drive member has slots formed in its sides into which project the ends of a laterally extending pin of the rod.
1O.A device as claimed in claim 6 wherein a spirit level is positioned on a horizontal surface of the levelling device.
11.A ladder including side rails separated by a plurality of rungs and an elongate levelling device comprising an outer sleeve connected to one side rail and/or one or more rungs of the ladder, an inner sleeve mounted for relative sliding movement within the outer sleeve, a plurality of spaced openings or recesses or the like formed in or carried by a lengthwise extending surface of the inner sleeve, a locking member carried by the outer sleeve and movable into or out of the openings or recesses or the like selectively to prevent or permit relative movement between the inner and outer sleeves, a partially threaded drive rod positioned within the inner sleeve and moveable linearly relative thereto, a closure member for the lower end of the inner tube formed with a threaded bore through which a threaded length of the drive rod passes, and means for imparting rotational movement to the drive rod to move a foot of the drive rod into contact with a surface on which the ladder is supported.
12.A ladder as claimed in claim 8 wherein one or more rungs of the ladder are open ended and hollow and the levelling device includes at least one arm which projects outwardly from the outer sleeve of the device and generally parallel to the rungs of the ladder, the or each arm being shaped and dimensioned to enable it to locate as a relatively close fit within a hollow rung of the ladder
13.A ladder as claimed in claim 8 or claim 9 wherein the longitudinal surface of the inner sleeve carries or is formed with an array of discrete openings or recesses which cooperate with a pawl carried by the outer sleeve to permit or prevent relative movement between the two sleeves.
14.A ladder as claimed in any one of claims 8 to 10 wherein the inner and outer sleeves are rectangular in cross section and at least one side wall of the inner sleeve includes or is formed with a lengthwise extending rack comprising a succession of discrete teeth which cooperate with a pawl carried by the outer is sleeve to permit or prevent relative movement between the inner and outer sleeves.
15.A ladder as claimed in claim 11 wherein the pawl is movable through a ratchet arm into and out of contact with any pair of rack teeth.
1 6.A device as claimed in any one of claims 13 to 15, wherein the pawl or ratchet arm carried by the outer sleeve is movable against loading imposed by a locking sleeve arranged to hold the pawl in a first position in which it is engaged with the inner sleeve or rack teeth thereof, the pawl being releasable from the first position by user action against said loading.
17.A device as claimed in claim 5, wherein the locking sleeve is a separate component to the pawl or ratcher arm.
18.A device as claimed in claim 5 or claim 6, wherein the locking sleeve is formed of resilient material.
19.A ladder as claimed in any one of claims 8 to 12 wherein the drive member includes a rod having a threaded length which passes through a bore of an end cap of the inner sleeve, the bore including internal threads complementary to those of the rod whereby rotation of the drive member imparts linear movement to the rod.
20.A ladder as claimed in claim 13 wherein the drive member has slots formed in its sides into which project the ends of a laterally extending pin of the rod.
21.A ladder as claimed in any one of claims 8 to 14 which includes a levelling device attached to each of its side rails.
22.A levelling device adapted to be secured to a side rail of a ladder, the levelling device comprising an outer sleeve, an inner sleeve mounted within the outer sleeve, a drive rod mounted within the inner sleeve, means for imparting incremental relative movement between the outer and inner sleeves, and is means for imparting linear relative movement between the inner sleeve and the drive rod to move the foot of the drive rod towards or away from a support surface.
23.A levelling device as herein described with reference to the accompanying diagrammatic drawings.
24.A ladder including a levelling device substantially as herein described with reference to the accompanying drawings.
25.A removeable locking device applied to the pawl and ratchet adjustment mechanism decribed in any one of the previous claims to prevent accidental disengagement.