WO2006024832A1

WO2006024832A1 - A ladder for a manhole

Info

Publication number: WO2006024832A1
Application number: PCT/GB2005/003328
Authority: WO
Inventors: Philip Knight
Original assignee: Caswick Limited
Priority date: 2004-08-28
Filing date: 2005-08-26
Publication date: 2006-03-09
Also published as: GB0419219D0; GB2417751A

Abstract

A manhole ladder is described, having steps which are each pivotable between a position allowing the ladder to be ascended or descended and a folded-away position.

Description

A LADDER FOR A MANHOLE

This invention relates to ladders. Specifically, but not exclusively, it relates to a ladder for use in a manhole, access shaft or similar enclosed space.

Figures 4 and 5 show previously proposed manhole ladder attached to a shaft wall of a manhole.

Such a ladder 50 comprises lateral support members 51 (or 'stringers') and a plurality of rungs 56 arranged in succession between the stringers. Where necessary, a plurality of stringers are joined together, for example, by a plate and bolt arrangement 55.

As shown in Figures 4 and 5, the ladder is secured to a wall surface 20 of a manhole via stay elements 52. These stay elements are secured to the stringers at regular intervals and secured to the access shaft wall via mounting bolts 54.

Many manholes or access shafts offer a limited amount of access space, and the conventional ladder arrangement further reduces the amount of available space in the shaft by virtue of the stay elements 52 that are necessitated by the need for sufficient foot space behind each ladder rung 56; the rungs are positioned at a distance C from the shaft wall. Furthermore, in the event of an accident (such as a person falling into the shaft), the pronounced profile of a conventional ladder arrangement presents a potential barrier to snag-free deployment and operation of rescue equipment and the like, and to the subsequent winching up of an injured person.

Alternatively, a series of individual steps maybe set rigidly into the wall of a manhole. Again, these permanently protrude a distance from the wall.

The present invention arose from an attempt to solve the aforementioned problems associated with conventional ladder arrangements, and to provide an improved ladder.

According to the present inventor there is provided a ladder for a manhole comprising a plurality of step members mounted on a support means, wherein the step members are adapted to pivot into and out of a usable position.

Preferably, the support means is mounted adjacent to an interior wall of a manhole or access shaft.

Preferably, at the usable position the step members lie in a plane substantially orthogonal to the longitudinal direction of the ladder and at a second position they lie in a plane substantially parallel with the longitudinal direction of the ladder.

Preferably, the support means comprises a pair of lateral support members with at least one cross-member interposed between the lateral support members. Advantageously, the ladder may include a fastening member for attaching the cross-member to the interior wall of a manhole or access shaft. Preferably, the step members consist of two arm portions interconnected by a tread

portion, and has a generally u-shaped form.

The step members may be pivotally attached to the lateral support members via a pivot arm and the movement of the step members is limited by a stop.

The pivot arm and the stop form opposing arms of a U-shaped pin.

Alternatively, the pivot arm and the stop are provided as individual, separate items.

The location of the pivot arm and the stop are offset from one another in both horizontal and vertical directions relative to the longitudinal direction of the ladder, whereby the stop serves to limit both extremes of the step member's movement.

The ladder may comprise a plurality of lateral support members that are adapted to be connected end to end to form a ladder of a desired length.

In contrast with a conventional ladder, the ladder according to the present invention can be placed and secured in close proximity to the wall surface of the access shaft since the need for foot space behind each step is negated by the use of retractable steps. Consequently, there is no need for stay elements that increase the overall profile of the ladder arrangement. Embodiment of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 shows a ladder in situ;

Figure 2 is a side view of part of the ladder;

Figure 3 is a plan view of the ladder in situ;

Figure 4 shows a previously proposed ladder;

Figure 5 is a top view of the ladder of Figure 4;

Figure 6 shows a second embodiment of the ladder of the present invention;

Figure 7 is a plan view of the ladder of Figure 6;

Figure 8 shows a ladder of the present invention incorporating an interconnecting member;

Figure 9 shows the interconnecting member of Figure 8 connecting adjacent stringers;

Figure 10 shows a ladder of the present invention held in place with an alternative fixture;

Figure 11 is a plan view of the ladder of Figure 10;

Figure 12 shows a ladder of the present invention held in place with a second alternative fixture; and

Figure 13 is apian view of the ladder of Figure 12.

Referring to Figures 1 to 3, a ladder comprises two lateral support members (or 'stringers') 2 disposed generally parallel to one another as shown. Located between the stringers at regular intervals are step members 3. The step members 3 are of a generally U-shaped construction and are pivotally mounted so as to be movable between position A and position B, as shown in Figure 2. They comprise two arm portions 4 disposed at substantially 90° to, and interconnected by, a tread portion 5. However, the arm portions may extend at other angles.

Generally, each step member will be a single, integrally formed body, and may be of a plastics material, a plastics-coated metal or otherwise.

In general use the step members will be in position A to allow a user to ascend and descend the ladder 1. However, in other situations, especially when it is desirable to maximise the available space in the shaft, the step members can be folded back into position B, where they lie generally parallel to, and within the plane of stringers 2, ie parallel to a shaft wall 20 to which the ladder is mounted.

The step members are pivotally attached to the stringers via the pivot arms 7 of an opposing pair of U-pins 6. The U-pins 6 also provide a stop for preventing the step member from moving beyond positions A and B.

In a first embodiment, the stop means comprises a corresponding pair of stop arms 8. In use, raising a step member to position B (ie in the 'folded away' position), brings face F of the arm portion 4 into abutment with the stop arm 8, thus preventing any further movement passed this position. When the step member is lowered to position A, face F abuts the underside of stop arm 8, and so preventing any further movement passed this position also, and defining the relative angle of position A.

Of course, instead of a U-shaped pin, two separate pins, or a separate stop and pivot point may be provided, disposed so that the step member pivots about a pivot point and is stopped by the stop point.

Other means of defining the stop and limiting position A and B may be used.

Advantageously, by offsetting the pivot point horizontally and vertically from the stop, the stop can act to limit the movement of the step member at both ends of its movement, and the pivot point is positioned so that when the step is vertical (ie at position B) it abuts pin 8. hi a preferred embodiment, a line joining the pivot point and the stop makes an angle of 45° relative to the longitudinal direction of the stringers (and therefore with the wall of the shaft also) and so the step member can move between extreme positions generally perpendicular and parallel to the stringers. However, by altering this angle, and/or the relative position of the pivot point to the top of the step, other desired limiting positions can be achieved if required.

Cross-members 9 are located at periodic intervals along the length of the stringers. The cross-members form a support bridge between the inner surface of the stringers, and may be attached to the stringers via a nut and bolt arrangement, via welded joints, or any other such suitable affixing method. A fastening member 10 is disposed midway along the length of the cross-member between opposing stringers. The fastening member, which is preferably a bolt, secures the ladder 1, via the cross-member 9, to a shaft wall 20. Therefore, the ladder is attached to a shaft wall (eg the wall of a manhole or access shaft) by the cross-members. Since these can abut the wall, the ladder can be more strongly attached than with previously proposed ladders, where since the ladder is spaced from the wall, there is a turning effect which must be overcome.

hi practice, the stringers 2 are provided in predetermined lengths, and are joined end to end to form a ladder of a desired length for the specific situation, hi the example shown in Figures 1 to 3, the ladder (of which only a small section is shown) is secured in place to the interior wall of an access shaft.

The ladder of the present invention is not restricted to use within a manhole or access shaft, it may be utilised in many situations: as a fire escape ladder affixed to the outer wall of a building; as a ladder providing access to a loft, etc.

The configuration shown enables each step member to be pivoted generally upward and out of the way. This is useful for emergency situations where if a person is unconscious or injured at the bottom of a shaft, they can be winched upwards and then- body will push each step out of the way as it is pulled upwards.

In an alternative embodiment of the present invention, and as shown in Figures 6 to 8, the ladder may be affixed in place within an access shaft, or other structure, via brackets 11. These brackets may be generally L-shaped, V-shaped or any other shape, depending upon the particular situation or structure to which the ladder is to be affixed.

As shown, the brackets are secured to the surface of the access shaft 20 via securing bolts 12. It should be understood however, that any type of securing device may be used, for example, in certain situations a screw or heavy-duty staple may be the more appropriate choice.

The stringers 2 are secured to opposing pairs of brackets 11 via locking-nut 14 that are threaded to end portions of each cross-member 9 that extend through opposing stringers. Each step member 3 is attached to the stringers by a pair of opposing securing bolts 13, about which each step member is adapted to pivot.

The securing bolts 13 extend through each stringer and continue through a sleeve portion (not shown) of each arm portion 4 of the step member 3. In this embodiment, the combination of securing bolts 13 and cross-members 9 are provided to function in a similar manner to the aforementioned U-pins 6; the cross-member 9 acts as a stop in analogous fashion to that of the stop arm 8 described above.

In an alternative embodiment of the present invention, the ladder is modular, and comprises a plurality of stringer sections that interconnect with one another via an interconnecting member 17 (see Figures 8 and 9). hi the example shown, the interconnecting member 17 comprises a diamond- like shaped plate that is secured to adjacent stringer sections via bolt fixings 18. The interconnecting member 17 may slot into an interior cavity of each stringer (Figure 8), or may be secured to an outside surface of the periphery of each stringer (Figure 9). An advantage of this embodiment is that stringer sections can be prefabricated to predefined lengths (as dictated by each particular situation) and constructed in situ, or assembled prior to deployment, depending upon the given circumstances. It is also envisaged that a user would be available to choose a desired number of stringers from a range of predetermined, commercially available lengths, and to also select various add-ons as require: cross-members, step members, etc. In this way, a user would be able to construct their own modular ladder to meet with their own specific requirements.

With reference to Figures 10 and 11, as an alternative to either fastening member 10 (Figure 10 or brackets 11, the ladder (either in modular or single-piece form) may be affixed to an access shaft 20 via fixing 21. The fixing comprises a substantially U-shaped member 22, constructed form steel plate or the like, a lengthwise slot 23 and a transverse slot 24. The slot 23 accommodates a bolt 25 for adjustably securing the fixing 21 to a surface of the access shaft 20, and the slot 24 accommodates a cross-member 9 a shown. In this embodiment, the ladder is hung from the fixing 21 as shown, and in order to strengthen the ladder at the hanging point, and to align the depending sections, a spacer plate 19 is provided that is secured to the outside peripheral surface of the uppermost stringers.

In a still further embodiment of the ladder of the present invention, and as shown in Figures 12 and 13, a hook-type fixing 26 is provided. Here, the fixing 26 includes a lengthwise slot 23', but instead of a transverse slot, the fixing includes opposing V-shaped slots 28 adapted so as to supportively receive an uppermost cross-member 9. The ladder may therefore be hung from the fixing when needed, and when not required it can be removed and stored in appropriate location. An advantage of this particular embodiment is that it provides an ideal solution to situations where the security of the access shaft is important: access to the shaft is prevented when the ladder is not in place.

In another embodiment of the present invention, and as shown in Figures 14 and 15, the ladder includes an interconnecting means 30 adapted to pivotally attach to each step member 3 via attachment tabs 31, and to a lever 33, either directly or via attachment tab 32.

In operation, the step members 3 can be simultaneously moved from a usable position A', where ascent and descent of the ladder is possible, to position B', in which the step members are disposed in an essentially unusable position, by simple operation of the lever 33.

Since attachment tabs 31 may be present on both left and right sides of each step member (as shown in the figures), the lever 33 and interconnecting means 30 maybe positioned for operation on either side of the ladder also.

In the above described embodiment, the interconnecting means 30 may be rigid or flexible. For example, it might comprise a metal or plastics rod, or a number of links forming a chain.

Interconnecting means, as shown in Figures 14 or 15, or any other type of interconnecting means, enabling all the steps to be moved together, may be used with any embodiment of the invention.

Claims

1. A ladder for a manhole, comprising a plurality of step members mounted on a support means, wherein the step members are adapted to pivot into and out of a usable position.

2. A ladder as claimed in claim 1, wherein the support means is mounted adjacent to an interior wall of a manhole or access shaft.

3. A ladder as claimed in claim 1 or 2, wherein at the usable position the step members lie in a plane substantially orthogonal to the longitudinal direction of the ladder and at a second position they lie in a plane substantially parallel with the longitudinal direction of the ladder.

4. A ladder as claimed in claim 1, 2 or 3, wherein the support means comprises a pair of lateral support members and at least one cross-member interposed between the lateral support members.

5. A ladder as claimed in claim 4, wherein the ladder includes a fastening member for attaching the cross-member to the interior wall of a manhole or access shaft.

6. A ladder as claimed in Claim 5, wherein the fastening member comprises a bracket including a slot for receiving and supporting a cross-member.

7. A ladder as claimed in Claim 5, wherein the fastening member comprises a bracket including a slot adapted to removably receive and support a cross-member in the manner of a hook.

8. A ladder as claimed in any preceding claim, wherein the step members have a generally U-shaped form and consist of two arm portions interconnected by a tread portion.

9. A ladder as claimed in any preceding claim, wherein the step members are pivotally attached to the support means via a pivot arm and the movement of the step members is limited by a stop.

10. A ladder as claimed in Claim 9, wherein the stop is formed by the cross- member.

11. A ladder as claimed in Claim 9, wherein the pivot arm and the stop form opposing arms of a U-shaped pin.

12. A ladder as claimed in any of Claims 9 to 11 , wherein the position of the pivot arm and the stop are offset from one another in both horizontal and vertical directions relative to the longitudinal direction of the ladder, whereby the stop serves to limit both extremes of the step member's movement.

13. A ladder as claimed in Claim 12, wherein a line joining the pivot arm and the stop makes an angle of 45° relative to the longitudinal direction of the ladder.

14. A ladder as claimed in any preceding claim, including a plurality of lateral support means that are adapted to be connected end to end to form a ladder of a desired length.

15. A ladder as claimed in Claim 14, wherein the ladder includes an intercomiecting member adapted to articulate adjacent lateral support members.

16. A ladder as claimed in any preceding claim, wherein the step members pivot upwards, when moved out of the usable position.

17. A ladder as claimed in any of Claims 4 to 16, wherein an uppermost lateral support member includes a spacer plate.

18. A ladder as claimed in any preceding claim, including an interconnecting means adapted to pivotally attach to each of the plurality of step members so as to articulate the movement of each step member.

19. A ladder as claimed in Claim 18, wherein articulated movement of the step member is activated by a lever.

20. A ladder as hereinbefore described, with reference to Figures 1 to 3 and 6 to

15, of the accompanying drawings.