GB2163011A - Cable ladders - Google Patents

Abstract

A cable ladder system comprises cable ladders with abutting stringers 1 and secured together by connecting members 20. Longitudinally extending marginal portions 31, 32 of each connecting member 20 are of such a shape that they interengage with longitudinally extending marginal portions of the adjacent end portions of a pair of aligned stringers 1 to effect a snap fit between the connecting member and the end portions of the stringers and parts 29 and 30 of protrude through holes 21 and 22 to prevent relative lengthwise movement between the stringers and the connecting member. No separately formed bolts or rivets are employed and the connecting members 20 are of such a construction that they can be readily hot dipped galvanised without risk that the galvanising will hamper securing of the connecting members to the stringer 1. <IMAGE>

Description

SPECIFICATION An improved cable ladder This invention relates to ladder-like structures for supporting electric cables and/or service pipes, which structures comprise a pair of elongate side members (generally and hereinafter referred to as "stringers") and, extending transversely between and secured to the stringers at spaced positions along their lengths, a plurality of elongate support members (generally and hereinafter referred to as "rungs"). Such ladder-like structures may also include coupling components such as bends for supporting electric cables and/or service pipes as the direction and/or plane in which they extend gradually changes, tee-connectors and cross-connectors, all such coupling components having, as common features, at least one pair of stringers interconnected by mutually spaced transversely extending rungs.For convenience, all such ladder-like structures and coupling components therefore will hereinafter be included in the generic expression "cable ladder".

In the construction of ladder-like support systems built up of cable ladders, it is the general practice to secure adjacent cable ladders end-to-end by interconnecting the stringers of the cable ladders. This is usually done either by arranging forthe stringers of one cable ladderto overlap the stringers of an adjacent cable ladder and to secure the overlapping parts ofthe cable stringers together by one or more than one bolt or by arranging forthe stringers of adjacent cable ladders to abut or be closely spaced apart and to secure them together by a separately formed connecting member or "fish plate" which overlaps adjacent end portions of both stringers and is secured to these parts by bolts.In both methods of securing adjacent cable ladders together, an operative has to insert and tighten a number of bolts by means of a spanner and, under difficult conditions, the spannerand/orthe nuts and bolts are liable to be dropped. Such methods of securing adjacent cable ladders together are both tedious and time-consuming and can add to the cost of erection of a ladder-like support system.

In the specification of our Patent No: 210591 9B, there is described and claimed a cable ladder system comprising at leasttwo cable ladders so arranged end-to-end that their stringers abut or a closely spaced apart and, securing the stringers together, separately formed connecting members each overlapping and being secured to adjacent end portions of a pair of aligned stringers.Parts of each connecting member and/orof said adjacent end portions ofthe stringers protrude through holes in said adjacent end portions ofthe stringers and/or in the connecting members and each connecting member is locked to the stringers by at least one separate elongate member extending lengthwise between said protruding parts of the connecting member and/or of said adjacent end portions of the aligned stringers and surfaces of said end portions ofthe aligned stringers and/ora surface oftheconnecting member.

It is an object ofthe present invention to provide an improved cable ladder system in which pairs of aligned stringers of cable ladders arranged end-toend are secured together by separatelyformed connecting members, which connecting members and stringers are of such a construction that they can be readily hotdipped galvanisedwithout riskthatthe galvanising will prevent or hamper secu ring of the connecting memberstothestringers.

According to the invention we provide an improved cable ladder system comprising at leasttwo cable ladders so arranged end-to-end thattheir stringers abut or are closely spaced apart and, securing the stringers together, separately formed connecting members each overlapping and being secured to adjacent end portions of a pair of aligned stringers, wherein longitudinally extending marginal portions of each connecting member are of such a shape that they inter-engagewith longitudinally extending marginal portions of the adjacent end portions ofthe pair of aligned stringers to effect a snap fit between the connecting member and the end portions of the stringers and wherein parts of each connecting member and/or of said adjacent end portions ofthe stringers protrude through holes in said adjacent end portions of the stringers and/or in the connecting members to prevent relative lengthwise movement between the stringers and the connecting member.

By virtue ofthe fact that securing together of stringers by separatelyformed connecting members does not involve the use of bolts, rivets or other securing means which require to befitted in aligned holes in a connecting member and the associated end portions ofthe stringers, the connecting members and stringers can be hot dipped galvanised because the riskthatgalvanisingwill prevent or hamper introduction of bolts or other securing means into such aligned holes no longer arises.

Preferably, parts of each connecting member protrude through holes in said adjacent end portions ofthe stringers at positions close to one longitudinally extending edge ofthe aligned stringers and parts of each connecting member protrude through holes in said adjacent end portions of the stringers at positions adjacentthe other longitudinally extending edge of the aligned stringers.

Preferably, also, parts of each connecting member protruding through holes in said adjacent end portions ofthe stringers adjacent at least one ofthe longitudinal edges of the aligned stringers are in the form of lugs orearswhich are folded or otherwise distorted to clamp the stringers against a surface of the connecting member.

Where, as is preferred, each stringer has a longitudi nallyoxtending surface that is inclined atan obtuse angie to an adjoining longitudinally extending surface ofthe stringer and has, at each of a plurality of longitudinally spaced positions along the length of the stringer, two longitudinally spaced, transversely extending slots in said inclined surface th rough which parts ofthe side walls of a channel-shaped rung protrude, said protruding parts ofthe side walls of the rung and/orthe adjacent parts ofthe stringer being so deformed thatthe rung is permanently locked to the stringer, preferablythe oreach hole in the end portion of each stringerthrough which a partoftheconnecting member protrudes and is folded or otherwise deformed to clamp the stringer against a surface of the connecting member extends through that part ofthe stringer having said inclined surface.

The parts of each connecting member protruding through holes in said adjacent end portions ofthe stringers at positions adjacentthe other longitudinally extending side edge ofthe aligned stringers are each preferably bounded bytwo longitudinally spaced, transversely extending slots in the connecting member and pressed out ofthe plane or planes ofthe member to form, in effect, a staple which is integral with the connecting member and which protrudes through its associated hole in the stringer.

In a preferred embodiment, each stringer has two adjoining longitudinally extending surfaces that are so inclined to one another and to adjoining surfaces of the stringer as to form in one side face ofthe stringer a longitudinally extending groove in which liethe deformed protruding parts of the side walls ofthe rungs and has integral with one of said two adjoining longitudinally extending surfacesasubstantiallyflat flange and has, extending along the other of its longitudinally extending edges, a folded-over flange, and each connecting member has one longitudinally extending marginal portion which engages underthe folded overflanges ofthe aligned stringers and, adjacent its other longitudinally extending edge, a marginal portion which is shaped to form a channel in which the substantiallyflatflanges ofthe aligned stringers makeasnapfitand are positively held bythe folded or otherwise deformed protruding parts ofthe connecting member.

Preferably,throughout its length and over at least a substantial part of its width, each connecting member has a transverse cross-section that is substantially identical to that ofthe aligned end portions ofthe stringers so that, when the connecting member is locked to said end portions ofthe stringers, the connecting member is in inter-facial contact with the end portions over the whole of its length and over at least a substantial part of its width.

The invention is further illustrated by a description, by way of example, of a preferred form of cable ladder system with reference to the accompanying drawings, in which: Figure lisa fragmental pictorial view ofthe cable ladder of the system; Figure 2 is a fragmental pictorial view of a stringer and one ofthe rungs of the cable ladder shown in Figurel; Figure 3 is an enlarged view of detail of Figure 2; and Figures 4 and 5 are fragmental perspective views of a connection between stringers oftwo cable ladders asshown in Figure 1.

Referring to Figures 1 to 3, the cable ladder comprises two steel stringers 1 of substantially channel-shaped cross-section arranged substantially parallel to one anotherwith the flanges ofthe stringers pointing inwardly and, extending transversely between and secured to the stringers at spaced positions along their lengths a plurality of steel rungs 2 each of channel-shaped cross-section. Each stringer 1 in cludes a base 3, a folded-overflange 9 and a flange 6 interconnected bytwo adjoining longitudinally ex tending surfaces4and 5which are inclined at obtuse angles to the base 3 and flange 6, respectively, to form, in the outer side face ofthe stringer, a longitudinally extending groove 7.The part of each stringer 1 having longitudinally extending surfaces 4 and 5 has at each of a plurality of longitudinally spaced positions along its length a pair of longitudinally spaced, transversely extending slots 8. End parts 18 ofthe sidewall 17 of a rung 2 protrude through a pair of slots 8 and are folded, as shown in Figures 2 and 3, to lie in the groove 7 and to lock the rung permanently to the stringer. The end faces of the rungs 2 abut the bases 3 of the channel-shaped stringers 1.

Referring to Figures 4 and 5, two cable ladders of the kind shown in Figure 1 are joined end-to-end by arranging fortheir stringers 1 to abut and by securing together the abutting end portions of each pairof aligned stringers by means of a separate connecting member 20. Each end portion of each stringer 1 has a hole 21 extending through the inclined surface 5 and also has a hole 22 in its base 3 adjacentthe folded-over flange 9. The connecting member 20 includes a base 23, a flange 26 and, interconnecting the base and the flange a longitudinally extending part 25which is inclined at obtuse angles to the base and flange.

Extending along the free edge of the flange 26 throughout its length is an upstanding lip 27, the longitudinally extending part 25, the flange 26 and the lip 27forming a marginal portion 31 in the shape of a channel in which the flanges 6 of the aligned stringers 1 are a snap fit. At each of two longitudinally spaced positions along the longitudinally extending part 25 is a window out of which is folded an ear 29. The ears 29 protrude through the holes 21 in the end portions of the stringers 1 and are folded to bear against a surface oftheflanges 6 to clamp the flanges in the channelshaped marginal portion 31. Integral with the base 23 remote from the channel-shaped marginal portion 31 is a marginal portion 32 which is inclined at an obtuse angle to the base. At each oftwo longitudinally spaced positions adjacent the marginal portion 32 are two longitudinally spaced, transversely extending slots which extend through the connecting memberand bound a part30 which is pressed out ofthe plane ofthe base 23to form, in effect, a staple integral with the base. The marginal portion 32 of the connecting member engages underthe folded-overflanges 9 of the aligned stringers 1 and the parts 30 engage in the holes 22 in the stringers to prevent relative lengthwise movement between the stringers and the connecting member 20.

Claims (8)

1. A cable ladder system comprising at leasttwo cable ladders so arranged end-to-endthattheir stringers abut or are closely spaced apart and, securing the stringers together, separately formed connecting members each overlapping and being secured to adjacent end portions of a pair of aligned stringers, wherein longitudinally extending marginal portions of each connecting member are of such a shapethatthey inter-engage with longitudinally extending marginal portions of the adjacent end portions ofthe pair of aligned stringers to effect a snap fit between the connecting member and the end portions ofthe stringers and wherein parts of each connecting member and/or of said adjacent end portions ofthe stringers protrude through holes in said adjacent end portions ofthe stringers and/or in the connecting members to prevent relative lengthwise movement between the stringers and the connecting member.

2. Acable ladder system as claimed in Claim 1, wherein parts of each connecting member protrude through holes in said adjacent end portions of the stringers at positions close to one longitudinally extending edge ofthe aligned stringers and parts of each connecting member protrude through holes in said adjacent end portions ofthe stringers at positions adjacent the other longitudinally extending edge of the aligned stringers.

3. A cable ladder system as claimed in Claim 2, wherein parts of each connecting member protruding through holes in said adjacent end portions of the stringers adjacent at least one of the longitudinal edges ofthe aligned stringers are in the form of lugs or ears which are folded or otherwise distorted to clamp the stringers against a surface ofthe connecting member.

4. A cable ladder system as claimed in Claim 3 in which each stringer has a longitudinally extending surface that is inclined at an obtuse angle to an adjoining longitudinally extending surface ofthe stringer and has, at each of a plurality of longitudinally spaced positions along the length of the stringer, two longitudinally spaced, transversely extending slots in said inclined surface through which parts of the side walls of a channel-shaped rung protrude, said protruding parts ofthe side walls ofthe rung and/orthe adjacent parts ofthe stringer being so deformed that the rung is permanently locked to the stringer, wherein the or each hole in the end portion of each stringerthrough which a part ofthe connecting member protrudes and is folded or otherwise deformed to clamp the stringer against a surface ofthe connecting member extends through that part of the stringer having said inclined surface.

5. A cable ladder system as claimed in Claim 3 or4, wherein the parts of each connecting member protruding through holes in said adjacent end portions of the stringers at positions adjacent the other longitudi nally extending side edge ofthe aligned stringers are each bounded bytwo longitudinally spaced, trans- versely extending slots in the connecting member and pressed out ofthe plane or planes ofthe memberto form, in effect, a staple which is integral with the connecting member and which protrudes through its associated hole in the stringer.

6. A cable ladder system as claimed in Claim 4 or 5, in which each stringer has two adjoining longitudinally extending surfaces that are so inclined to one another and to adjoining surfaces ofthe stringer as to form in one side face ofthe stringer a longitudinally extending groove inwhich liethedeformedprotrud- ing parts ofthe side walls of the rungs, wherein each stringer has integral with one of said two adjoining longitudinally extending surfaces a substantially flat flange and has, extending along the other of its longitudinally extending edges, a folded-overflange, each connecting member has one longitudinally extending marginal portion which engages underthe folded-overflanges of the aligned stringers and, adjacent its other longitudinally extending edge, a marginal portion which is shaped to form a channel in which the substantiallyflatflanges ofthe aligned stringers make a snap fit and are positively held by the folded or otherwise deformed protruding parts of the connecting member.

7. Acableladdersystem as claimed in any one of the preceding Claims, wherein, throughout its length and over at least a substantial part of its width, each connecting member has a transverse cross-section that is substantially identical to that ofthe aligned end portions ofthe stringers so that, when the connecting member is locked to said end portions of the stringers, the connecting member is in inter-facial contact with the end portions overthewhole of its length and over at least a substantial part of its width.

8. A cable ladder system substantially as herebefore described with reference to and as shown in the accompanying drawings.