GB2322664A

GB2322664A - Variable configuration stepladder

Info

Publication number: GB2322664A
Application number: GB9803394A
Authority: GB
Inventors: Mark Redsell
Original assignee: ABRU Ltd
Current assignee: ABRU Ltd
Priority date: 1997-02-28
Filing date: 1998-02-19
Publication date: 1998-09-02
Anticipated expiration: 2018-02-19
Also published as: GB9704155D0; GB2322664B; GB9803394D0

Abstract

A variable configuration stepladder (11) may be used as a stepladder, a asymmetric stepladder for use on interrupted or inclined surfaces, or as a extension ladder. The stepladder (11) is characterised by the provision of a slide bracket (14) pivotally attached at or adjacent an end of the first of a pair of ladder sections (13), the second ladder section (12) being slidably mounted in the slide bracket (14). The slide bracket (14) allows the second ladder section (12) to slide longitudinally with respect to the first (13). There may be provided a locking means (31) pivotally connected to the slide bracket (14) engagable over a rung(17), to prevent relative sliding movement of the second ladder section (12) with respect to the slide bracket (14). There may alternatively or additionally be provided an elongate tie member (52) pivotally connected to one ladder section, and releasably to the other, which restrains against spreading of the two ladder sections.

Description

A VARIABLE CONFIGURATION STEPLADDER The present invention relates generally to variable configuration stepladders, and in particular to stepladders of the type comprising two ladder sections of stiles and rungs, one forming a base section and having a slide bracket pivotally connected thereto, and the other comprising a slide or fly section which is slidably engaged in the slide bracket. Such variable configuration stepladders can be used as a conventional stepladder, as an asymmetric stepladder for use on interrupted or inclined surfaces, and as an extension ladder by suitably varying the configuration.

One known variable configuration stepladder of this type is described in the Applicant's own earlier British Patent No. 1 497 253. That patent described a ladder which comprises two ladder members made of stiles and treads, a hinge plate and a locking link system, the hinge plate being pivotally mounted on one ladder member as well as being connected to the said one ladder member by a locking link system and being in slidable engagement with one of the stiles of the other ladder member. The locking link system described in this earlier patent comprised two link members pivoted together at respective adjacent ends and to the hinge plate and the said one ladder member at opposite respective ends. Other locking link systems for variable configuration stepladders have been devised, the most common including an arcuate slot in a member carried by one of the ladder sections and a peg or spigot trapped in the slot and carried by the other ladder section. The length of the arcuate slot defines the maximum extent by which the two ladder sections can be spread apart in the stepladder configuration. Although this has been found to be largely satisfactory in practice, new regulations in contemplation are likely to impose a more stringent requirement on the form of a stepladder spreader tie, and in particular require that it should span directly between two ladder sections. A locking link between a ladder section and a slide plate is quite likely to fail to meet these new regulations.

In addition, many prior art variable configuration ladders are made with one section narrower than the other so that the narrower section can be "nested" within the other in the exterior ladder configuration and when stowed. This adds certain constraints which it is sought to overcome. For example, in known variable configuration stepladders the interlock between the slide plate and the fly section of the ladder, which prevents the fly section from sliding through the slide plate during use, is achieved by forming the base section of the ladder with a shaped notch at or adjacent its end, which engages a corresponding portion of a rung of the fly section. In order to erect a variable configuration stepladder of this type, therefore, care must be taken to ensure that the notch is properly aligned with the appropriate rung as the stepladder is opened otherwise the notch may be located between two rungs and the fly section not locked within the slide plate. Misuse of or carelessness with such a system can cause damage to the rungs as the mechanical advantage from the very short lever arm between the pivot and the notch is very great.

Moreover, known variable configuration stepladders are not readily separable into two components, which limits their use. It has also been found necessary to make the fly section one rung longer than the base section.

The present invention seeks to provide a variable configuration stepladder which will be easier and more secure in use, which will be adapted to meet the new regulations by allowing a direct spreader tie connection between the two pivoted ladder sections, and which will allow the fly section to be separated from the base section easily and quickly. It is also a feature of the present invention that the two ladder sections can be made to almost equal lengths.

According to one aspect of the present invention, therefore, a variable configuration stepladder suitable for use as a stepladder, as an asymmetric stepladder for use on interrupted or inclined surfaces and as an extension ladder, comprises first and second ladder sections each having stiles and rungs the first of which sections carries a slide bracket pivotally connected thereto at or adjacent an end of at least one stile thereof and the second of which is slidably engaged to the slide bracket for relative movement along the length of the stiles, in which the slide bracket carries locking means pivotally connected thereto and turnable between an engaged position in which it engages over a rung to prevent relative sliding movement of the said second ladder section with respect to the slide bracket and a release position in which it does not obstruct the said relative sliding movement.

It is a particular feature of the present invention that there is no restraining link between the slide bracket and the first ladder section to limit the turning movement between end positions otherwise defined by abutment of the slide bracket itself against cooperating components or parts of the first ladder section.

Preferably there is provided an intermediate element between contacting faces of the slide bracket and the stile to which it is pivotally connected whereby to determine the frictional resistance to relative turning movement between the bracket and the stile. Such frictional resistance is preferably not so great as seriously to affect the force which must be applied in order to turn the bracket, but sufficiently great that the bracket will remain in a selected position against the gravitational force exerted by its own weight.

The said locking means preferably comprise a rung lock pivotally mounted to the slide bracket and having two arms with oppositely directed rung-contact faces substantially perpendicular to a line joining the said faces to the pivot centre. The two arms with rungcontact faces are preferably defined in one limb of a channel-section element the other limb of which is pivotally connected to the slide bracket.

The slide bracket preferably has an abutment face which contacts the stile of the said first ladder section to act as a limit stop determining the end point of the relative rotation of the slide bracket and the said first ladder section in a first direction of relative rotation corresponding to the maximum spread position of the two ladder sections in the stepladder configuration.

The spreader restraints provided for directly interconnecting the ladder sections may be removably connectable to at least one ladder section.

The said one ladder section may be the said second ladder section, that is the fly section.

The rung locks are preferably provided with abutment means limiting their turning motion with respect to respective said slide brackets. Typically, such abutment means may be formed as a tab bent out of the plane of the lock wall.

Like the interconnection between the slide brackets and the base section of the stepladder the said rung locks are preferably pivotally interconnected to the said slide brackets themselves with a light frictional resistance such that, when not loaded, the rung locks will remain in any selected position.

In order to ensure that the rung locks engage in the locked position securely they are preferably provided with detent means engageable with a rung or a stile (or both) whereby to retain the rung lock in its locked position. Such detent means may be formed, for example, as a pressed boss or stud on a lock wall.

The rung locks may have a channel-section form with two limbs which lie on opposite sides of a stile when the rung lock is in the locked position.

The present invention also comprehends a variable configuration stepladder suitable for use as a stepladder, an asymmetric stepladder for use on interrupted or inclined surfaces, and as an extension ladder, comprising a base ladder section carrying a slide bracket pivotally connected to its stiles at or adjacent an upper end thereof and a fly section the stiles of which are slidably engaged in respective slide brackets, in which restraint against spreading of the two ladder sections is provided by at least one elongate tie member pivotally connected to one ladder section and releasably connectable to the other.

In a preferred embodiment of the invention the ladder sections comprise stiles to which hollow rungs are secured in a way which leaves the open ends of the rungs exposed, and the releasable connection of the tie member includes means for locating a projection thereof within an end of a selected rung.

The stiles may have an outwardly facing channel-section form with facing flanges and the releasable tie member connector preferably has a component with lugs engageable under the flanges to fix the connector in position. Such lugs preferably project in opposite directions from a connector body and have a rectangular plan form with two diagonally opposite corners rounded such that the body of the tie member connector can be turned from an engaged to a disengaged position through substantially 90".

It is preferred that the releasable tie member connector includes a plug component which can be introduced into the exposed open end of a rung to locate the tie member connector in position along a stile.

There may also be provided resilient means urging the body and the plug of the tie member connector apart whereby each contacts an opposing face of the flange of the channel-section of the stile when the tie connector member is fitted thereto. Such resilient means may be a corrugated spring washer located between the said two components.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a variable configuration ladder formed as a first embodiment of the present invention shown in one configuration; Figure 2 is a side view of the embodiment of Figure 1 shown in its extension ladder configuration; Figure 3 is a side view of the embodiment of Figure 1 shown in its asymmetric stepladder configuration; Figure 4 is an enlarged perspective view of the embodiment of Figure 1 in its stepladder configuration; Figure 5 is a plan view from above of the rung lock forming a component of the embodiment of Figure 1; Figure 6 is a side view of the rung lock illustrated in Figure 5; Figure 7 is a cross-sectional view taken through the line A-A of Figure 1 showing the spreader tie lock in an unlocked position; Figure 8 is a sectional view similar to that of Figure 7, showing the spreader tie lock in its locked position; Figure 9 is an enlarged schematic side view of the spreader tie lock shown in Figure 7; Figure 10 is a side view of the spreader tie lock illustrated in Figure 8; Figure 11 is a side view of a slide bracket forming part of the embodiment of Figure 1; and Figure 12 is a plan view from above of the slide bracket illustrated in Figure 11.

Referring now to the drawings, Figure 1 illustrates a variable configuration stepladder generally indicated 11 comprising a first or base stepladder section 13 and a second or fly stepladder section 12 pivotally connected together at their upper ends by a slide bracket generally indicated 14 and which will be described in more detail hereinbelow. Each ladder section 12, 13 is composed of respective stiles 15, 16 and rungs 17, 18 secured to the stiles by double clenching on either side of a central web 19 (see Figure 4) of the stile in a known way. This, as can be seen in Figure 4, leaves an open end of the rung exposed on each side of the ladder section.

At their upper ends the two stiles 16 of the base section 12 carry respective slide brackets 14 which are identical to one another although "handed" in that they are respectively a left hand and right hand bracket. As can be seen in Figures 11 and 12, each slide bracket comprises a generally U-shape main body portion 20 having two parallel limbs 21, 22 having aligned holes 23 through which passes the pivot pin 24 by which the slide bracket 14 is pivotally mounted to the upper end of the respective stile 16 of the base ladder section 12 as can be seen in Figure 4. Generally coplanar with the limb 22, and extending away from the base body portion is a channel-section slide guide 25 having a transverse end wall 26 and a flange 27 which defines an internal guide space 28 within which slides a stile 15 of a fly or slide section 13 of the variable configuration ladder. A central hole 29 in the main wall 25 of the slide guide receives a pivot pin 30 by which a rung lock generally indicated 31 is pivotally connected to the slide bracket 14.

The parallel limbs 21, 22 of the slide bracket 14 have chamfered corners 33, 34 for a purpose which will be described in more detail hereinbelow, and likewise the limbs 21, 22 have an offset aligned hole 35 for receiving a stop pin the function of which, again, will be described in more detail below.

The rung lock 31 illustrated in Figures 5 and 6 comprises a main arm 36 through one end of which the opening 30 is pierced for receiving the pivot pin by which the rung lock 31 is pivotally connected to the slide bracket 14.

Surrounding the opening 30 is an embossed annular region 37 the function of which is to maintain the arm 36 slightly spaced from the face of the limb 25 of the slide bracket. A dimple or boss 38 is pressed into a central portion of the arm 36 to act as a frictional contact between the arm 36 and the slide bracket 14 such that the rung lock 31 will be frictionally restrained to remain, against the action of its own weight, in any position in which it is located. A tab 39 is pressed out of one edge of the arm 36, to act as a limit stop to prevent upward rotation of the rung lock 31 beyond the position illustrated in Figure 4. In this position the tab 39 engages the lower edge of the slide bracket 14. A cranked portion 40 of the arm 36 joins it to a generally U-section clip body 41 having a bottom wall 42 and two parallel side walls 43, 44 the latter of which has a central lateral slot 45 defining two parallel arms 46, 47 the tips 48, 49 of which are bent outwardly slightly to act as a guide for engagement on the stile. The recess 45 has an internal curved edge 50 the shape of which substantially corresponds with that of the rungs 17 (which in the embodiment illustrated are circular although other shapes may be used) whilst two facing inward edges of the arms 46, 47, identified 46a, 47a are parallel to one another and perpendicular to a line passing through these edges and the pivot opening 30. In other words these edges 46a, 47a are each tangential to the arc travelled by the channel-section body portion 41 as the arm 36 turns about the pivot 30 so that, when contacting a rung 17, there is no tendency for the clip to be worked loose by cam action.

As can be seen in Figure 4, the rung clip 31 can be turned about the pivot 30 to a released position (in which position it is illustrated in Figure 4) or can be turned to a rung-engaged position, as shown in Figures 1 to 3, in which the two parallel limbs 44, 45 of the channel-section body 41 clip over the stile 15 whilst the two arms 46, 47 which define the opening 45 pass to either side of the rung 17, the boss 38 ensuring that the rung clip 31 is held firmly in its locked position.

In the locked position of the rung clips 31 the two ladder sections 12, 13 can be pivoted about the main pivotal interconnection defined by the pivots 24 between a parallel, extension ladder, configuration as shown in Figure 2 to an inclined stepladder configuration as shown in Figures 1 and 3. With the rung locks 31 snapped to their engaged position the stepladder behaves entirely as a fixedly pivoted ladder. If it is desired to move from the configuration illustrated in Figure 1 to that illustrated in Figure 3, for example, the rung locks 31 are moved manually to the release position illustrated in Figure 4 and the fly section 13 of the ladder can then (after preliminary release of the spreader stays which will be described in more detail below) displaced longitudinally sliding through the slide brackets 14 to a desired position at which the rung locks 31 are again snapped to the locked position. It will be appreciated that the adjustment increments are defined by the rung spacing.

In its stepladder configuration illustrated in Figure 1 or the asymmetric stepladder configuration illustrated in Figure 3 the ladder of the invention is retained with the two ladder sections spread apart by a pair of spreader stays or ties 52, only one of which can be seen in Figures 1 and 3. The spreader stays 52 are pivotally connected to a fixed point 53 on the base section 12 and are releasably connected by a stay lock 54 to the fly section 13. The length of the spreader stay 52 is chosen to be of such a length that, when released from the fly section 13, the spreader stay 52 can be moved to a position parallel to the base section 12 and the spreader stay lock 54 reengaged on the base section as will be described in more detail below.

Referring first to Figures 7 and 8 the cross-sectional shape of the stile 15 can be seen, this comprising the central web 19 referred to above and two lateral channel limbs 55, 56 each of which has a transverse flange 57, 58 defining a channel-like cavity within the ladder stile 15 itself.

The spreader stay connector comprises two main body parts, namely a plug part 59 having a projecting circular boss 60 the diameter of which is such as to fit snugly into the exposed opening at the end of a rung 17 or 18 and having a radial flange 61 with an axially extending rim 62 which fits over the circular clenched bead 83 by which each rung 17, 18 is fixed to the web 19 of the ladder stile 15. The plug member 59 has a central aperture 63 housing a pivot pin which pivotally connects the plug member 59 to a lug member generally indicated 66 and to the spreader stay 52.

Figures 9 and 10 illustrate the shape of the pivotable lug member in further detail. This comprises a generally rectangular plate-like body having two rounded diagonally opposite corners 67, 68. This defines two projecting lobes at the other two diagonal corners 69, 70. The lug body 66 has a projecting handle 71 by which it can be gripped and turned between its release and its locking position. As shown in Figure 9 the longer edges 72, 73 of the rectangular plate-like lug body 66 lie parallel to the flanges 57, 58 of the stile 15 so that the lug body 66 can pass between them in positioning the plug 59 into the open end of the selected rung 17 or 18. Once the plug body 60 has been fully inserted, so that the axial flange 62 is in contact with the web 19, the handle 71 is gripped and the lug body 66 turned (clockwise as viewed in Figures 9 and 10) from the position shown in Figure 9 to that shown in Figure 10 where the longer edges 72, 73 of the lug body 66 now lie perpendicular to the length of the flanges 57, 58 and beneath them, as shown in figure 8, thereby retaining the spreader stay connector 54 in position. The dimensions of the lug body 66 are carefully chosen such that the curved corners 67, 68 just frictionally engage the inner faces of the side walls 55, 56 of the ladder stile 15 so that, in the position illustrated in Figure 10, the lug body is securely held by this frictional engagement. Frictional resistance is also assisted by the presence of a corrugated washer 75 between the plug body 60 and the lug body 66.

Positioning and repositioning the spreader stays 52 is therefore a simple one-handed operation effected by contacting the handle 71, with the finger or thumb, pressing this to turn the lug body 66 through 90" and then gripping it between finger and thumb to withdraw the plug body 60 from the open end of the rung 17 or 18 into which it had been locked, and acting similarly on the other spreader stay. The stepladder may then be opened or closed, and the fly section 13 slid in relation to the slide brackets 14 (after having released the rung locks 31 as described above) to select the desired configuration where upon, after snapping the rung locks 31 into their locked position the spreader stays 52 can be repositioned easily by introducing the plug body 60 into a selected open end of a rung 17 or 18, turning the lug body 66 by pressure against the handle 71 until the lug body is turned through 90" to its locking position.

The variable configuration stepladder of the present invention has a further advantage in that, having released the spreader stays 52 and the rung locks 31, the two ladder sections can be separated entirely simply by withdrawing the fly section 13 through the slide guides 14 there being no terminal enlargements to prevent such separation. The two independent ladder sections can then be used in a range of other functions unavailable to a permanently hinged stepladder whether of standard symmetrical or variable configuration type.

It will be noted in Figure 1 that the fly section 13 has a hook (in practice a pair of hooks 76 although only one is visible in Figure 1) for engaging a selected rung 18 of the base section 12 in the extension ladder configuration as illustrated in Figure 2. When this hook 76 is engaged on the selected rung 18 the rung locks 31 can be snapped into their locking position thereby giving the extension ladder an even more secure interconnection than has hitherto for been available.

Claims

1. A variable configuration stepladder suitable for use as a stepladder, an asymmetric stepladder for use on interrupted or inclined surface and as an extension ladder, which comprises first and second ladder sections each comprising stiles and rungs the first of which sections carries a slide bracket pivotally connected thereto at or adjacent an end of at least one stile thereof and the second of which is slidably engaged to the slide bracket for relative movement along the length of the stiles, in which the slide bracket carries locking means pivotally connected thereto and turnable between an engaged position in which it engages over a rung to prevent relative sliding movement of the said second ladder section with respect to the slide bracket and a release position in which it does not obstruct the said relative sliding movement.

2. A variable configuration stepladder as claimed in Claim 1, in which there is provided an intermediate element between contacting faces of the slide bracket and the stile to which it is pivotally connected whereby to determine the frictional resistance to relative turning movement between the bracket and the stile.

3. A variable configuration stepladder as claimed in Claim 1 or Claim 2, in which the said locking means comprise a rung lock pivotally mounted to the slide bracket and having two arms with oppositely directed rung-contact faces substantially perpendicular to a line joining the said faces to the pivot centre.

4. A variable configuration stepladder as claimed in Claim 3, in which the two arms with rung-contact faces are defined in one limb of a channel-section element the other limb of which is pivotally connected to the slide bracket.

5. A variable configuration stepladder as claimed in any preceding claim, in which the slide bracket has an abutment face which contacts the stile of the said first ladder section to act as a limit stop determining the end point of the relative rotation of the slide bracket and the said first ladder section in a first direction of relative rotation corresponding to the maximum spread position of the two ladder sections in the stepladder configuration.

6. A variable configuration stepladder as claimed in any preceding claim, in which there are further provided spreader restraints directly interconnecting the ladder sections and being removably connectable to at least one ladder section.

7. A variable configuration stepladder as claimed in Claim 6, in which the said one ladder section is the said second ladder section.

8. A variable configuration stepladder as claimed in any preceding claim, in which the rung locks have abutment means limiting their turning motion with respect to the respective said slide brackets.

9. A variable configuration stepladder as claimed in any preceding claim, in which the said rung locks are pivotally interconnected to the said slide brackets with a light frictional resistance such that, when not loaded, the rung locks remain in any selected position.

10. A variable configuration stepladder as claimed in any preceding claim, in which the rung locks are provided with detent means engageable with a rung or a stile to retain the rung lock in its locked position.

11. A variable configuration stepladder as claimed in any preceding claim, in which the rung locks have a channel-section form with two limbs which lie on opposite sides of a stile when in the locked position.

12. A variable configuration stepladder substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

12. A variable configuration stepladder suitable for use as a stepladder, an asymmetric stepladder for use on interrupted or inclined surfaces, and an extension ladder, comprising a base ladder section carrying a slide bracket pivotally connected to its stiles at or adjacent an upper end thereof and a fly section the stiles of which are slidably engaged in respective slide brackets, in which restraint against spreading of the two ladder sections is provided by at least one elongate tie member pivotally connected to one ladder section and releasably connectable to the other.

13. A variable configuration stepladder as claimed in Claim 12, in which the ladder sections comprise stiles to which hollow rungs are secured in a way which leaves the open ends of the rungs exposed, and the releasable connection of the tie member includes means for locating within an end of a selected rung.

14. A variable configuration stepladder as claimed in Claim 13, in which the stiles have an outwardly facing channel-section form with facing flanges and the releasable tie member connector has a component with lugs engageable under the flanges to fix the connector in position.

15. A variable configuration stepladder as claimed in Claim 14, in which the lugs have a rectangular plan form with two diagonally opposite corners rounded such that the said component of the tie member connector can be turned from an engaged to a disengaged position through substantially 90".

16. A variable configuration stepladder as claimed in any of Claims 12 to 15, in which the said releasable tie member connector includes a plug component which can be introduced into the exposed open end of a rung to locate the tie member connector in position along a stile.

17. A variable configuration stepladder as claimed in Claim 16, in which there are provided resilient means urging the body component and the plug components of the tie member connector apart whereby each contacts an opposing face of the flanged channel-section of the stile when the tie connector member is fitted thereto.

18. A variable configuration stepladder as claimed in Claim 17, in which the said resilient means is a corrugated spring washer located between the said two components.

19. A variable configuration stepladder substantially as hereinbefore described with reference to and as shown in the accompanying drawings Amendments to the claims have been filed as follows CLAIMS 1. A variable configuration stepladder suitable for use as a stepladder, an asymmetric stepladder for use on interrupted or inclined surface and as an extension ladder, which comprises first and second ladder sections each comprising stiles and rungs the first of which sections carries a slide bracket pivotally connected thereto at or adjacent an end of at least one stile thereof and the second of which is slidably engaged to the slide bracket for relative movement along the length of the stiles, in which the slide bracket carries locking means pivotally connected thereto and turnable between an engaged position in which it engages over a rung to prevent relative sliding movement of the said second ladder section with respect to the slide bracket and a release position in which it does not obstruct the said relative sliding movement.

4. A variable configuration stepladder as claimed in Claim 3, in which the two arms with rung-contact faces are defined in one limb of a channel-section element the other limb of which is pivotally connected to the slide bracket 5. A variable configuration stepladder as claimed in any preceding claim, in which the slide bracket has an abutment face which contacts the stile of the said first ladder section to act as a limit stop determining the end point of the relative rotation of the slide bracket and the said first ladder section in a first direction of relative rotation corresponding to the maximum spread position of the two ladder sections in the stepladder configuration.