WO1999051848A1

WO1999051848A1 - Collapsible stepladder

Info

Publication number: WO1999051848A1
Application number: PCT/GB1999/001012
Authority: WO
Inventors: James Thomas Weston; Richard Weston
Original assignee: Eriksson, Per-Olof; Johansson, Christer
Priority date: 1998-04-04
Filing date: 1999-04-01
Publication date: 1999-10-14
Also published as: GB2336174A; AU3161499A; GB9807195D0

Abstract

A telescopically collapsible stepladder comprises two legs (12 and 14) that are hinged to one another. Each leg is formed of telescopically collapsible sections having latch mechanisms in each of the rungs for automatically locking the sections relative to one another when the leg is extended. The latch mechanisms in each rung are designed to release the next higher section when the rung is collapsed against the next lower rung. The separation of the rungs (14b, 14c, 14d) of one of the legs when the stepladder is extended is greater than the separation of the rungs (12b, 12c, 12d) in the other leg (12).

Description

Collapsible Stepladder

The present invention relates to a collapsible stepladder .

Background of the invention

It is already known, for example from US-A-5, 495, 915, to form a ladder of telescopically collapsible sections and to provide latch mechanisms in each of the rungs for automatically locking the sections relative to one another when the sections are extended. In the latter prior art patent, the latch mechanisms are arranged to release the sections when a rung is collapsed against the next lower rung.

Object of the invention

The present invention seeks to provide a stepladder made up of telescopically collapsible sections that is safe during use and that is simple to extend and to collapse.

Summary of the invention

According to the present invention, there is provided a stepladder comprising two legs that are hinged to one another, wherein each leg is formed of telescopically collapsible sections having latch mechanisms in each of the rungs for automatically locking the sections relative to one another when the leg is extended, the latch mechanisms in each rung being operative to release the next higher section when the rung is collapsed against the next lower rung, and wherein the separation of the rungs of one of the legs when the stepladder is extended is greater than the separation of the rungs in the other leg. - 2 -

Each of the legs of the stepladder of the present invention is constructed in the same manner as the telescopically collapsible ladder of US-A-5, 95, 915. As a result, it benefits from the same sturdiness and safety. Each leg is designed to collapse from the bottom upwards (not from the top downwards) and as a result, the stepladder cannot accidentally be collapsed by a person standing on the stepladder inadvertently tripping the latch mechanism on one of the rungs .

It is advantageous to provide the leg with the smaller separation between the rungs with a collapsible extension that projects above the hinge between the two legs. The extension may comprise one or more telescopically collapsible sections similar to the sections of the leg.

A tray may conveniently be fitted to the top of the extension to hold tools, paint or other working materials. If the tray is pivotably mounted on the extension, then it can lie flat against the stepladder when collapsed and be pivoted to a horizontal operating position when the stepladder is extended.

It is advantageous to form the leading edge of the tray with a ramped lip so that it should not interfere with the collapsing of the stepladder. If the tray should come into contact with a lower rung as the extension is collapsed, the ramped lip would automatically deflect it out of the way of the rung.

It is important to prevent the legs of the stepladder from splaying apart when in use and while this can be achieved by suitable design of the hinge between the two legs it is preferred to provide a cord, cable or chain connected to the lower ends of the two legs. The same flexible link can also be used to keep legs of the - 3 -

stepladder together when the stepladder is collapsed to ease its transportation.

The two legs will in use serve different functions and accordingly the treads on the rungs of the two legs may be shaped differently. In particular, the leg with the smaller separation between the rungs is the one on which the user will stand and its rungs may be shaped to provide a wide area tread for comfort. The other leg on the other hand is intended primarily as a stay but also as a trestle-like support for a scaffold board and its treads may be shaped for improved anchoring of scaffold boards .

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which :

Figure 1 shows a stepladder of the invention in its fully extended position,

Figure 2 is a perspective view of a detail of the stepladder in Figure 1,

Figure 3 shows the stepladder after its legs have been folded together in preparation for its collapse, Figure 4 shows the stepladder fully collapsed but with its extension projecting above the hinge still extended,

Figure 5 shows the stepladder fully collapsed but prior to the tray being folded down into its storage position, and

Figure 6 shows an alternative design of the hinge between the two legs of the stepladder.

Detailed description of the preferred embodiment

The stepladder 10 in the accompanying drawings comprises two telescopically collapsible legs 12 and 14 each of which is constructed in the manner described in US Patent - 4 -

No. 5,495,915 and will not therefore need to be described herein in detail.

In the case of the leg 12, it comprises a lowermost section formed of the two rungs designated 12a and 12b and two upright wide diameter tubes 30a and 30b that form part of the stiles. The next higher section comprises the rung 12c and two tubes 30c and 30d of slightly smaller diameter that are slidably within the tubes 30a and 30b, respectively. The stiles are held in their extended positions by latch mechanism that comprise resiliently biased pins within the rungs that engage in holes in the tubes of the stiles. These pins are retractable by means of release levers 20 (best seen in Figure 3) that project from the underside of each of the rungs. If the release levers

20 on the underside of the rung 12b are raised manually, the next higher section can collapse downwards, narrowing the distance between the rungs 12c and 12b. As these rungs touch, the release levers 20 of the rung 12c are raised and in turn allow the next higher section to collapse, and so on .

Each of the telescoped tubes 30 forming a stile, with the possible of the exception of the uppermost tube, is preferably at its upper end with a plastics bush to allow the tubes to slide relative to one another more smoothly and to prevent wear and scuffing of the surfaces of the tubes with prolonged used.

The two legs 12 and 14 of the stepladder in the illustrated embodiment are hinged to one another by means of two conventional door-type hinges 16 and they are prevented from splaying apart by means of a flexible link 18, which can be a cord, cable or chain.

Instead of door-type hinges, it is preferred, as shown in section in Figure 6, to form the rungs 12, 14 that are to - 5 -

be pivotably joined to one another as special extrusions each having a C-shaped socket 40, 42 protruding from one side. The rungs are joined to one another by a separately formed hinge plate 44 having a part-cylindrical bead 46, 48 on each side received in the respective sockets 40, 42 protruding from the two rungs 12, 14. Such a construction is more sturdy, less costly and more easily assembled. The hinge can be assembled by simply sliding the hinge plate 44 into the sockets 40, 42 and crimping the ends of the sockets to prevent the hinge plate 44 from sliding out.

The leg 12 has an extension 22 which comprised only one section in the illustrated embodiment but may alternatively comprise a number of sections. At the top of the extension 22, which can itself be collapsed in a similar manner to the remaining sections of the leg 12, there is mounted a tray 24, better seen in Figure 2. The tray is pivotably mounted on the section 22 by means of pivot pins 26 and is shown pivoted anti-clockwise, as viewed, to its operative position. When rotated clockwise to its other end position, the tray lies flat against the stiles for convenient storage. The leading edge 28 of the tray has a lip to retain tools and materials resting on it and the edge of this lip can catch on the rungs while the extension 22 is being collapsed, This can be avoided however by providing a further ramped portion inclined in the opposite direct to deflect the tray 24 out of the way of the rungs as the extension 22 is being collapsed.

The leg 12 is the leg on which the user will stand when the stepladder is in use and its rungs can be formed with flat treads that lie horizontally when the stepladder is extended in a plane angles relative to the plane normal to the stiles. The rungs of the other leg 14, on the other hand, need not be shaped for comport but may be shaped as the rungs of a trestle. - 6 -

While the lengths of the legs 12 and 14, measured from the hinge 16 to the floor, are substantially equal, the leg 12 has four sections while the leg 14 has only three. There are several advantages associated with this difference which will now be described.

The separation of the rungs and therefore the length of the sections of the leg 12 is dictated by the need to ensure that the stepladder can be climbed and descended comfortably and safely, even by a shorter person. On the other hand, the leg 14 is not used for climbing and it functions only as a stay or support for the other leg. It does not therefore need to have as many rungs and sections and reducing the number of sections in the leg 14 reduces manufacturing cost.

A second advantage is concerned with the ease of collapsing the stepladder that will be evident from a study of Figure 3. When the stepladder is folded to allow the stepladder to be collapsed, it is necessary to release the latch mechanisms of the rungs 12b and 14b of the two legs and to push down on the upper sections at the same time. The difference in length of the sections in the two legs results in easy access to the release levers of the rungs 12b and 14b because they are staggered from one another.

If the stepladder is inclined backward slightly, the feet of the leg 12 will be raised off the ground. When the release levers on the rung 14b are released, then the leg can start to be collapsed until the feet of the leg 12 touch the ground. At this time, the release levers 20 on the rung 12b can be released allowing both legs to be collapsed at the same time. Thus the difference in the lengths of the sections of the two legs allows the legs to be collapsed sequentially while allowing easy access to both sets of release lever. - 7 -

As the legs are collapsed, some resistance is met as the latch mechanisms are released. The difference in section lengths also ensures that the legs are collapsed one section, rather than two sections, at a time so that less resistance is met.

The different sections lengths also result in the rungs of the two legs being at different heights when the stepladder is in use as is clearly seen from Figure 3. As a result, it is possible to rest a trestle board at many different heights from the ground with small increments between the available positions.

A final important advantage of the difference in section lengths between the two legs is that when the legs are fully collapsed below the hinge, as shown in Figure 4, the top rung 12e will still be spaced from the rung 12d and its latch mechanisms will not be released automatically. Consequently, it is possible to collapse and raise the extension 22 independently of the collapse of the legs 12 and 14. If the stepladder is collapsed by pressing down on the top rung of the extension 22, it will reach the position shown in Figure 4 then stop, thereby avoiding the risk of the user trapping his fingers beneath the top rung as it collapses .

Figure 5 shows that when the stepladder is fully collapsed, the cord 18 can be used to keep the sections of the stepladder together by clipping the cord to a catch on the top rung of the stepladder. The tray 24 can be pivoted by a further 180° from the position illustrated in Figure 5 to lie flat against the stiles of the stepladder for compact storage and transportation.

It is possible to provide the lowermost section of one or both of the legs with means for improving lateral stability, that is to say for preventing the stepladder from swaying from side to side. Such a stabiliser may have the form of two short arms mounted on the upright tubes of the lowermost sections and pivotable between laterally extended positions and retracted positions. Alternatively, a telescopic bar resting directly on the ground may be attached to the feet of the legs. When extended, such a bar will improve lateral stability but when its sections are retracted it will not interfere with the portability of the stepladder .

Claims

- 9 -CLAIMS

1. A stepladder comprising two legs (12,14) that are hinged to one another, wherein each leg (12,14) is formed of telescopically collapsible sections having latch mechanisms (20) in each of the rungs ( 12a-12e, 14a-14c) for automatically locking the sections relative to one another when the leg is extended, the latch mechanisms in each rung being operative to release the next higher section when the rung is collapsed against the next lower rung, characterised in that the separation of the rungs (14a-14c) of one of the legs (14) when the stepladder is extended is greater than the separation of the rungs (12a-12e) in the other leg (12) .

2. A stepladder as claimed in claim 1, wherein the leg (12) with the smaller separation between the rungs is provided with a collapsible extension (22) that projects above the hinge (16) between the two legs.

3. A stepladder as claimed in claim 2, wherein the extension (22) comprise only one telescopically collapsible section similar to the sections of the leg (12) .

4. A stepladder as claimed in claim 2 or 3, wherein a tray (24) is fitted to the top of the extension (22) to hold tools, paint or other working materials.

5. A stepladder as claimed in claim 4, wherein the tray (24) is pivotably mounted on the extension so that it can lie flat against the stepladder when collapsed and be pivoted to a horizontal operating position when the stepladder is extended.

6. A stepladder as claimed in claim 5, wherein the leading edge of the tray (24) is formed with a ramped lip

(28) so that it should not interfere with the collapsing of the stepladder. - 10 -

7. A stepladder as claimed in any preceding claim, wherein a flexible link (18) is provided between the lower ends of the two legs (12,14) to prevent the legs of the stepladder from splaying apart during use.

8. A stepladder as claimed in claim 1, wherein the flexible link (18) can clipped to the top rung of the stepladder when the stepladder is collapsed.

9. A stepladder as claimed in any preceding claim, wherein the treads on the rungs (12a-12e and 14a to 14c) of the two legs are shaped differently from one another.

10. A stepladder as claimed in any preceding claim, wherein at least one of the legs of the stepladder is provided with means for improving lateral stability.

11. A stepladder as claimed in claim 10, wherein the means for improving lateral stability comprise arms mounted on the lowermost sections of the legs of the stepladder and pivotable between a laterally extended position and a retracted position.

12. A stepladder as claimed in claim 10, wherein the means for improving lateral stability comprise a telescopic bar secured to the feet of a leg of the stepladder.