NL2004158C2

NL2004158C2 - Coupling plate for cable ducts.

Info

Publication number: NL2004158C2
Application number: NL2004158A
Authority: NL
Inventors: Henricus Antonius Maria Ligthart
Original assignee: Stago Bv
Priority date: 2010-01-27
Filing date: 2010-01-27
Publication date: 2011-07-28

Description

P90551NL00

Title: Coupling plate for cable ducts

The invention relates to a coupling plate for cable ducts, and to a system of coupled cable ducts.

Typical cable ducts are elongated structures with U-shaped cross-section, wherein the bottom is at right angles to sidewalls corresponding to the 5 rising legs of the U. In buildings, lengths of cable ducts are joined to each other to form longer cable paths. Coupling plates may be used to join meeting cable ducts, each coupling plate being engaged against the sidewalls of the meeting cable ducts.

EP 520583 discloses a coupling plate that can be attached by hand to 10 a meeting cable ducts, without requiring bolts or other additional connections. The coupling plate is used in combination with cable ducts that each have a sidewall of which the top is bent to form an inwardly curled edge, with an initial edge part that bends off from the surface of the sidewall at a 120 degree angle and continues into a final part that curls so that its tip is directed 15 slightly back into the direction of the sidewall. When the coupling plate is inserted, locking lugs of the coupling plate are engaged in the curl of the tip of the curled edge of the sidewalls of the meeting cable ducts, while the coupling plate is held at an angle to the sidewalls. Then the coupling plate is rotated around the contact of the locking lug and the curled edge of the sidewalls, until 20 the coupling plate is parallel to the sidewall and guiding tabs on top of the coupling plate engages the top of the curled edge, where the initial part bends from the surface. The locking lugs and guiding tabs are formed by bending different parts of the top edge of the coupling plate along bending axes that extend along the length of the coupling plate.

25 NL 8005563 discloses a coupling plate that can be snapped into place between the bottoms of the cable ducts and bent over edges of the sidewalls. The coupling plate has a series of slots along its length, to make it possible to straighten a bend in the plate by hand when the plate is positioned 2 against the sidewalls of a pair of cable ducts. The top end of this coupling plate is bent along the entire length of the coupling plate, to fit under the folded edge of the sidewalls of the meeting cable ducts. This coupling plate additionally has lips that are inserted into slots in the bottom walls of the 5 meeting cable ducts.

This type of coupling plate makes it possible, in principle, to provide for a reliable coupling between meeting ends of cable ducts without using bolts. The reliability is partly realized by the coupling plate itself, because it clamped in a fixed relation to the cable ducts, reinforced by lips that extend into slots in 10 the walls of the cable ducts, if present, and partly because the coupling plate forces the meeting ends of the sidewalls of the cable ducts into alignment. However, this type of coupling plate has the disadvantage that it works well only when the height of the coupling plate and the side walls of the cable duct are accurately matched. If the side wall is not high enough excessive force is 15 needed to insert the coupling plate, so that the coupling plate or the cable duct may be deformed. If the side wall is too high, the coupling plate can come loose. For cable duct with different nominal sidewall heights different coupling plates are needed, which gives rise to errors and increased inventory costs.

20 Among others it is an object to provide for a coupling plate for cable ducts that can reliably kept in place without relying on accurate height matching.

A coupling plate according to claim 1 is provided. This coupling plate has a main surface with a depressible element on top, and preferably at least 25 two depressible elements. Upon coupling cable ducts, the depressible element or elements may be fitted under curled edges of aligned side walls of meeting cable ducts for example, to be depressed towards the bottom wall. The depressible element compensates for height differences. Typically at least two such depressible elements are provided on the coupling plate, for use on 3 respective ones of the meeting cable ducts, but in principle one such depressible element could be used for one of the meeting cable ducts only.

The depressible element is connected to the main surface of the coupling plate only through a first end of the depressible element and the 5 depressible element extends from said first end at least partly along the direction of the top edge of the coupling plate. The longest distance from the connected first end of the depressible element to any point on the depressible element preferably lies substantially in parallel to the plane of the coupling plate. The top of the depressible element is located beyond the top edge of the 10 main surface of the coupling plate. Thus, the top of the depressible element can be pressed towards the top edge by pressure on the depressible element. It has been found that this provides for sufficient depressibility and strength to provide a reliable form of coupling that compensates for practical height variations, in contrast to curls or other depressible elements that extend from 15 the main surface perpendicularly to the plane of the coupling plate. These perpendicular extensions do not provide for sufficient depressibility, so that the cable ducts deform when the coupling plate is inserted.

In an embodiment the first end of the depressible element is located at the top edge of the main surface, for example in contact with the top edge or 20 with substantially only solid material between it and the top edge. In this embodiment the depressible element has an arched shape, such as a circle part or a part with discrete folds, leaving a gap in the second planar direction between the top of the depressible element and the top edge of the main surface. In this way the depressibility can be realized in a compact way.

25 Preferably, at least part of the arched shape lies in the plane of the main surface, so depression will be stopped by contact between the top edge of the main surface and parts of the arch.

In an embodiment the depressible element has a curved top, curved at least according to a curve in a cross section with a plane perpendicular to 30 the top edge direction. The curved top may be realized by subjecting material 4 of the coupling plate to pressure in a mould for example. The curved top makes it possible to realize a lateral force pressing the coupling plate against the side wall of the cable duct independent of the amount of depression. In an embodiment the curved top rounded at least according to a curve in a cross 5 section with a plane perpendicular to said top edge direction at least from perpendicular to the main surface on top, to a downward inclination on a side away from the aligned side wall of the cable duct.

In an embodiment the depressible element has an extension that acts as a stop to prevent excessive deformation of the depressible element 10 under influence of the lateral force. This extension extends from the depressible element adjacent the main surface of the coupling plate, on the side of the coupling plate opposite the aligned side wall of the cable duct, so that it stops against the main surface in the case of lateral movement of the depressible element.

15 The coupling plate may be manufactured by folding plate material.

The plate material may be distinguished into a first part and a second part. The first part is used to form the main surface. The plate material is folded between the first part and the second part at the top edge of the main surface. As a result at least part of the surface of the second part is directed along a 20 direction transverse to the main surface to form a flange, the depressible element being formed by a protrusion from said at least part of the second part. Thus a coupling plate is provided that can easily be manufactured.

In a further embodiment said second part comprises a first fold between the main surface and the second part that folds the second part back 25 against the main surface, a second fold that folds the second part back against itself in parallel with the main surface and a third fold that folds the second part towards said direction transverse to the main surface. Thus a thickening can be provided on the side of the coupling plate that faces the aligned side wall of the cable duct, leaving room for part of the depressible element to 30 extend over the top edge of the main surface of the coupling plate in that 5 direction without affecting the coupling action of the coupling plate. In an embodiment additional folds are provided to make part of the second part form a back protrusion, protruding from the main surface of the coupling plate for insertion into a corresponding slot in the wall of the cable duct. Thus, the same 5 second part can be used to realize a plurality of functions. In an embodiment, the plate material is additionally folded at the bottom to form a bottom protrusion for insertion into a corresponding slot in the cable duct.

In an embodiment the main surface comprises a stop protrusion extending from the top edge adjacent the depressible element. The stop 10 protrusion can be used to prevent excessive depression of the depressible element, for example when the cable ducts are temporarily subjected to an imbalanced load during installation. Preferably, the stop protrusion is lower than the depressible element in its least depressed position.

The coupling plate may be designed to be inserted with a slight 15 bend along its length, so that it can easily be fitted between the curled edge of the side walls of the cable ducts and their bottom edges or other extensions from the side walls. After insertion this bend may be straightened to clamp the coupling plate. In an embodiment the main surface of the coupling plate may have a series of opening that define a weakening line at which the coupling 20 plate will bend most easily. The main surface may have a thinned portion adjacent at least part of this bending line, for example on the side of the main surface that is made concave by the bend. This provides for a threshold action, snapping the main surface into its straightened state when it is pushed.

25 These and other objects and advantageous aspects will become apparent from a description of exemplary embodiments using the following figures.

Figure 1 shows a system of meeting cable ducts

Figure la shows part of a cable duct 30 Figure 2 shows a coupling plate for cable ducts 6

Figure 2a shows part of a coupling plate

Figure 3 shows a top view of a coupling plate

Figure 4 shows a pre-form of a coupling plate

Figure 5a,b illustrates insertion of a coupling plate 5

Figure 1 shows a system with a pair of meeting cable ducts 10, 12 and a coupling plate 14. Cable ducts 10, 12 may be several meters long: only the meeting ends of the cable ducts 10, 12 are shown. Each cable duct 10, 12 has a bottom 100, 120 and a pair of sidewalls 102a, b, 122a, b extending 10 perpendicularly from the bottom of the cable duct. Coupling plate 14 is engaged against aligned side walls 102a, 122a of the meeting cable ducts 10, 12. Coupling plates may be provided on sidewalls 102a,b, 122a,b on both sides of bottom 100, 120.

Figure la schematically shows part of a cable duct 10 and coupling 15 plate 14 in projection onto a plane transverse to the length of cable duct 10. The top of the sidewall 102a ends in a curled edge 104, at least near the meeting ends of cable ducts 10, 12. In the coupled state, the top of a depressible element of coupling plate 14 fits under this curled edge 104. A sidewall protrusion 140 on coupling plate extends through an opening in 20 sidewall 102a and a bottom protrusion 142 extends through an opening in bottom 100.

Figure 2 shows a front view of coupling plate 14. The term “front” is used here to refer to the surface of the coupling plate that is visible when the coupling plate is mounted against the sidewalls of the meeting cable ducts, i.e. 25 the surface that does not face the sidewalls. On the top of coupling plate 14 there is a flange 20 and stops 22. Flange 20 extends into resilient extensions 24 with further stops 26. Resilient extensions 24 form depressible elements that can be pressed toward the top edge of the main surface of coupling plate 14 by curled edge 104. The main surface extends between the top and bottom 30 of the coupling plate, although not necessarily fully from the top to the bottom, 7 for example because resilient extensions 24 are present between the main surface and the top of the coupling plate. Resilient extensions 24 are arched, so that their top points define the highest point of coupling plate 14, with a gap between the resilient extension and the top edge of the main surface. The tip 5 ends of resilient extensions 14 away from flange 20 are only connected to coupling plate 14 through the resilient extensions and flange 20.

A series of bottom protrusions 142 extends from the bottom of coupling plate 14. Coupling plate 14 is provided with elongated bolt openings 28a 28b and a series of elongated slots 29 that extend horizontally, 10 successively between bolt openings 28a 28b. Bolt openings 28a 28b and slots 29 nearly separate coupling plate 14 into an upper part and a lower part.

Material of coupling plate 14 is present in narrow vertical connections located between slots 29 to connect the upper and lower parts. Material of coupling plate 14 is also present in narrow vertical connections at the edges of coupling 15 plates, adjacent bolt openings 28a,b.

Figure 2a shows part of coupling plate 14 in cross-section in a plane transverse to coupling plate 14. The intersection of this place and the plane parallel to the main surface of coupling plate 14 is shown by line A-A in figure 2. As shown in figure 2a the surface of resilient extension 24 is free from the 20 top of the main surface of coupling plate 14 and resilient extension 24 is rounded along a curve transverse to the main surface of coupling plate 14 (from the back to the front of coupling plate 14). The tangent direction of the rounding curve varies from perpendicular to the main surface of coupling plate 14 at a virtual extension plane of the main surface at the front side of coupling 25 plate 14 to an angle of about forty five degrees at a position in front of the virtual extension plane. The offset of this position relative to the virtual extension plane is selected in correspondence with the internal width of the curled edges 104 of the cable ducts 10, 12. The width of resilient extension 24 corresponds to the width of curled edges 104.

8

In operation the front to back rounding of resilient extension 24 ensures that curled edge 104 will always push resilient extension 24 towards the plane of the sidewalls of cable ducts 10, 12 when coupling plate 14 couples the ends of cable ducts 10, 12. In this way the top of coupling plate 14 is kept 5 in contact with the sidewalls of cable ducts 10, 12 and the sidewalls of the different cable ducts 10, 12 are kept in alignment. Thus, resilient extension 24 absorbs height differences due to manufacturing tolerances and even differences due to use of cable ducts with different nominal plate thickness. Curled edge 104 presses down resilient extension 24 to a greater or smaller 10 extent, dependent on the relative height of coupling plate 14 and the sidewall of the cable duct 10, while the rounded surface of resilient extension 24 ensures that a lateral force will be exerted no matter how much resilient extension 24 is depressed.

It may be noted that in theory this effect could also be achieved with 15 a curved resilient extension that extends from the main surface of the coupling plate towards the front, .e. in a direction perpendicular to the main surface, but it has been found that such extensions require to high forces and allow for too little height variation to produce practical reliability in cable duct connections. The use of a resilient extension 24 that extends freely in the 20 direction along the length of coupling plate 14 makes it possible to allow for much larger height variations with more practical forces.

Figure 3 shows a top view of coupling plate 14. The term “top” is used to refer to the edge of the coupling plate in the direction of the curled edge 104 of the sidewalls of the cable ducts. The figure shows flange 20, stops 25 22, resilient extensions 24 and further stop 26. Sidewall protrusions 140 are also visible. Stops 22 comprise protrusions from the main surface of coupling plate, and in the illustrated embodiment they have been thickened by folding back the material of the plate. Further stops 26 extend perpendicularly to the plane of the drawing. They are located adjacent the front side of coupling plate. 30 Sidewall protrusions 140 protrude from the back side of coupling plate.

9

Figure 4 shows a pre-form of coupling plate 14. During manufacture a sheet of material, such as a metal, is cut into the shape of the preform and folded along folds indicated by dashed lines, to form the coupling plate. A metal plate may be used for example. Flange 20, resilient extensions 24, 5 further stop 26 and sidewall protrusions 140 are formed by five folds in an upper part. The upper part is folded back onto the back surface of the back plate by a first fold. A second fold folds a part that forms the sidewall protrusions 140 transversely to the back surface and a third fold at the tip of the sidewall protrusions folds this part. A fourth fold at the base of the 10 sidewall protrusions 140 folds the upper part upward along the back surface of the coupling plats. A fifth fold at the top of the coupling plate results in a flange 20 and resilient extensions 24. Further folds (not indicated) at the tip of resilient extensions 24 results in further stops 26.

The arch shape and the rounding curve of resilient extensions 24 15 may be formed by pressing the extensions in a mould. Preferably the thickness of the resilient extensions 24 decreases from the highest point towards flange 20 and further stop 26. This provides for a minimum of deformation. By providing a folded part against the main surface before realizing flange 20, it is made possible that the width resilient extensions 24 extends to the front and 20 to the back outside the main surface of the coupling plate, so that they will be securely pressed against the top edge of the coupling plate when resilient extensions 24 are depressed.

Stops 22 are formed by folding extensions of the top of the coupling plate. Bottom protrusions 142 are formed by folding extensions of the bottom of 25 the coupling plate. Optionally, at least part of bottom protrusions have a widened base section resting against the main surface of the coupling plate. This may be realized by using a widened tip at the end of the extension and folding back at least part of the tip against the main surface. This provides for increased support to counteract lateral forces. In an embodiment, optional 30 guiding surfaces 40 are formed between pairs of bottom protrusions 142 by 10 material between bottom protrusions 142 over an angle of about a hundred and twenty degrees.

Optional side surfaces 42 may be formed by folding edge parts at the left and right of the coupling plate. Folding over a small angle of, say less than 5 thirty degrees, suffices. Side surfaces 42 may be used to protect cables in the cable duct from damage due to coupling plate 14.

Furthermore the coupling plate is folded prior to use over a small angle (e.g. less than thirty degrees) along its length at the height of slots 29. Optional side surfaces 42 are absent at the height of slots 29 to facilitate 10 folding.

In an embodiment, the thickness of the coupling plate is locally reduced between bolt openings 28 above slots 29, for example in shaded region 290. This can be done for example by locally removing material, for instance on the back side of the coupling plate (the side facing the side wall). The reduction 15 of the thickness provides for bistable behaviour, when the fold at the height of slots 29 is straightened. That is, as long as the angle of this fold exceeds a threshold angle, the structure opposes reduction of the angle, so that one has to exert a pushing force to reduce the angle, but when the angle of the fold is reduced to a value below the threshold (by pushing) the structure itself exerts 20 a force to reduce the angle even further and to create an overshoot from the straightened position.

In other words, the structure snaps into a state with a slight bend, so that the convex side of this bend points towards the side wall (cf. figure 5b). A slight reduction of thickness of the coupling plate between bolt openings 28 25 above slots 29 suffices for this, for instance on the back side of the coupling plate. A suitable amount of reduction may depend on circumstances, but can easily be determined for a specific type of coupling plate by testing successively increasing reductions and determining whether the bistable behaviour occurs. The overshoot from the straightened position has the advantage that the back 11 protrusions a placed more reliably in corresponding slots in the side wall, making the coupling more robust.

Figure 5a illustrates insertion of coupling plate 14. Coupling plate is inserted folded over small angle at the height of slots 29. When meeting ends 5 of a pair of cable ducts 10, 12 are coupled, bottom protrusions 142 are inserted in slots in the bottom walls of the cable ducts 10, 12 and the top of coupling plate 14 is moved underneath resilient extensions. Because of the fold in the coupling plate at the height of slots 29 the top of coupling plate 14 fits underneath curled edge 104 at the meeting ends of the cable ducts 10, 12.

10 Next, one pushes in the middle of coupling plate 14 to straighten the fold at the height of slots 29. This causes the top of coupling plate 14 to rise into curled edge 104 and sidewall protrusions to move into corresponding slots in the side walls of respective ones of the meeting cable ducts 10, 12.

This results in the state shown in figure 5b. As a result coupling 15 plate 14 is locked into position. In the locked state the resilient extensions 24 are depressed by the inside of curled edge 104. Due to the curved shape of resilient extensions 24 this results in a lateral force exerted by the inside of curled edge 104 pushing the top edge of coupling plate into contact with the side walls of the meeting cable ducts 10, 12. Further stops 26 prevent resilient 20 extensions 24 from being pushed beyond coupling plate 14. As a result the meeting ends of the sidewall of cable ducts 10,12 will be accurately aligned, contacting each other at facing edges of the sidewalls. This prevents relative movements of the ends of the cable ducts 10, 12.

In the locked state stops 22 act as an optional additional protection 25 against incidental forces that force down one cable duct relative to the other. The top height of stops 22 lies below the normal top height of resilient extensions 24 absent such forces. In the presence of such forces resilient extensions 24 may be depressed. In this case downward movement of curled edge 104 will be stopped by stops 22. This prevents coupling plate 14 from 30 coming loose under influence of such incidental forces. Preferably, there is a 12 gap between the tips of resilient extensions 24 and stops 22, to allow resilient extensions 24 to stretch under pressure.

In the locked state sidewall protrusions 140 act together with the bottom of coupling plate as an optional protection that prevents formation of a 5 non zero angle between the bottom walls of the meeting cable ducts 10, 12.

The slots in the bottom wall are located offset from the fold between the side wall and the bottom wall of the cable ducts 10, 12. Optional guiding surfaces 40 assist in inserting bottom protrusions 142 into these slots. Guiding surfaces 40 preferably extend from the main surface of coupling plate 14 10 corresponding to the offset between the bottom wall and the fold between the side wall and the bottom wall of the cable ducts. Preferably, optional side surfaces 42, if present, do not extend further than the distance to sidewall defined by the offset of the slots in the bottom of cable ducts.

Although an embodiment has been shown wherein coupling plate 14 15 is located inside cable ducts 10, 12 against a sidewall, it should be appreciated that alternatively coupling plate 14 could be located outside cable duct 14, for example if the top edge of the sidewall curves outwardly and there is an extension on the cable duct from the side wall at the level of the bottom wall. Also, a coupling plate could be provided against the bottom wall, clamped 20 between the sidewalls. In each of these cases, resilient extension 24 may be used to ensure clamping independent of tolerances. But of course, the use against the side wall is the most relevant application.

Although an embodiment has been shown wherein a depressible element is realized by means of resilient extension 24 that is connected to the 25 main surface of the coupling plate at the top edge, it should be appreciated that other solutions may be used. For example, a solution may be used wherein plate material is folded from the main surface along a fold at a distance from the top edge, so that the folded material extends beyond the top edge to form a depressible element.

13

Although embodiments have been shown with two depressible elements in the form of resilient extensions, it should be appreciated that one such depressible element, or more than two such elements may be used. For example, if one of the meeting cable ducts has accurately controlled 5 dimensions and the other has not, or the coupling plate can be fixed to the one cable duct by bolts or otherwise, a depressible element on the side of the other cable duct may suffice. On the other hand, two or more depressible elements may be used in the curled edge on the side wall of one cable duct, so that more than two depressible elements may be provided for two cable ducts.

10 Although embodiments have been shown wherein the sidewalls of both cable ducts have the same height, so that a rectangular coupling plate could be used with depressible elements at the same height, it should be appreciated that the sidewalls may have different heights, in which case the coupling plate may have different heights at different ends.

15 Walls of meeting cable ducts are coupled by means of a coupling plate that is clamped in a position against aligned walls of the cable ducts. The coupling plate is inserted between extensions from the aligned walls and pushed into a clamped position. The top edge of the coupling plate is provided with for example arch shaped depressible elements that extend freely along 20 the direction of the top edge, from a connection where they are connected to the coupling plate. When the coupling plate is inserted, a force exerted by the extensions from the walls of the cable duct to depress the arch shape by straightening the depressible element along the edge, which allows the coupling elements to be depressed towards the coupling plate to an extent 25 needed to compensate for height tolerances. The coupling plate including the depressible elements may be realized from plate material by folding part of the material to realize a strip at the top edge, perpendicular to the main surface of the coupling plate and realizing the depressible elements as extensions from that strip. As part of the folding a spacer between the main surface of the 30 coupling plate and the walls of the cable ducts may be realized, as well as 14 protrusions from the coupling plate for insertion in slots in the walls of the cable ducts.

Claims

A coupling plate for coupling aligned walls of connecting cable ducts, with a top and bottom of the coupling plate clamped against protrusions from the aligned walls, which coupling plate is provided with a main surface that extends between the top and bottom, said main surface having an upper edge, the main surface defining a first and second plane direction at the upper edge, parallel to and perpendicular to the upper edge, respectively; - an compressible element which extends at least in the first plane direction, and which is at least partly located in the second plane direction beyond the upper edge, which compressible element has a first end which is coupled to the main surface, wherein the compressible element only with the main surface is connected via said first end, so that compressibility is provided from a top of the compressible element to the main surface in the second plane direction.

2. A coupling plate according to claim 2, wherein the first end extends in an arc shape at the top edge and the compressible element, leaving a space open in the second plane direction between the top edge and the compressible element at the top of the top. impressive element.

A coupling plate according to any one of the preceding claims, wherein the top of the compressible element is curved with a cross-sectional curve with a plane perpendicular to the main surface at the top edge.

4. A coupling plate according to any one of the preceding claims, wherein the compressible element comprises a stop extending alongside the main surface, whereby movement of the compressible element in a perpendicular direction perpendicular to the main surface is at least partially blocked.

5. A coupling plate according to claim 4, wherein the compressible element has a round top, curved with a cross-sectional curvature with a plane perpendicular to the main surface, the top having tangents in this plane from at least tangent perpendicular to the main surface to a second tangent line with the perpendicular direction on the side of the main surface next to the stop is located.

6. A coupling plate according to any one of claims 3 to 5, comprising a rear protrusion extending transversely to the main surface, for insertion into a corresponding slot in the wall of the cable duct, said stop and rear protrusion being situated on mutually opposite sides of the cable duct. main surface.

7. A coupling plate according to any one of the preceding claims, which comprises plate material, which plate material has a first, second and third part, the first part forming the main surface, the plate material being folded between the first and second part at the upper edge of the main surface, wherein at least a portion of the second portion is directed transversely to the main surface and wherein the compressible element is formed by the third portion protruding from said portion of the second portion.

A coupling plate according to claim 7, wherein said second portion comprises a first fold between the first and second portions that fold back the second portion against the first portion, a second fold that folds the second portion against itself and parallel to the first portion and a third fold covering the second portion to said direction transversely of the main surface.

A coupling plate according to claim 8, wherein said second portion comprises a fourth and fifth fold between the first and second fold, folding at least a further portion of the second portion into a rear protrusion that extends in a direction transverse to the main surface, for 30 insert into a corresponding slot in the wall of the cable duct.

10. A coupling plate as claimed in any of the foregoing claims, wherein the main surface comprises a stop projection which extends in the second plane direction from the top edge next to the depressable element to a distance from the top edge that is smaller than a distance from the top edge to the top of the impressive element.

11. A coupling plate according to any one of claims 7 to 9, wherein the plate material comprises a folded part and a further fold at a lower edge of the main surface, between the first part and the folded part which folds the folded part back against the main surface around a lower protrusion. for insertion into a corresponding slot in the cable duct.

12. A coupling plate according to any one of the preceding claims, wherein the main surface comprises a series of openings along a line parallel to the top and bottom, wherein the series of openings define a bending line to extend the main surface from a curved state, the main surface made thinner part has in addition to at least a part of the bending line.

13. A coupling plate according to any one of the preceding claims, wherein a thickness of the thinned portion is chosen such that the coupling plate 20 has respective stable states on bending angles on which the coupling plate is respectively bent along said bending line in mutually opposite directions relative to a stretched state of the coupling plate, with a range of unstable bending angles between the bending angles of said states.

A coupling plate according to any one of the preceding claims, provided with a side surface connected to the main surface at an angle non-zero with the main surface in the direction of the wall of the cable duct at least a part of a side edge of the main surface of the top to bottom of the coupling plate, for protecting cables against damage by the side edge of the main surface.

A coupling plate according to any one of the preceding claims, with a further compressible element with the claimed properties of the compressible element.

A system of cable trays provided with a coupling plate according to any one of the preceding claims, a first and second cable tray coupled by the coupling plate, with an upper and lower side of the coupling plate against protrusions of aligned walls of the first and second cable tray, with the compressible element pressed against one of the protrusions.

A cable duct system according to claim 16, wherein the first and second cable ducts each have a bottom wall, said aligned walls extending from the bottom walls of the first and second cable ducts, wherein the aligned walls have bead edges and the bead edges and corners between the aligned walls and the bottom walls form the protrusions of the aligned walls between which coupling plate 15 is clamped.

A cable duct system according to claim 17, wherein the compressible element is located in said bead edge of the aligned wall of the first cable duct.

19. A cable duct system as claimed in claim 18, wherein the coupling plate is provided with at least two compressible elements which are located in said bead edges of the aligned walls, the first and second cable duct, respectively.

20. A cable duct system according to any one of claims 16 to 19, wherein the bottom walls are provided with bottom slots and wherein the coupling plate has bottom protrusions located in the bottom slots.

A cable duct system according to any of claims 16 to 19, wherein the aligned walls are provided with wall slots and wherein the coupling plate has rear protrusions located in said wall slots.

A method of manufacturing a coupling plate for coupling aligned walls of connecting cable trays with an upper bottom of the coupling plate clamped against protrusion of the aligned walls, which method comprises forming sheet material in a form that forms a first, second and a third portion, wherein the first portion defines a circumference of a main surface and has an upper edge, the second portion protruding from a line defined by the upper edge and being narrower than the first portion, and wherein the third portion is parallel to said line protrudes from the second portion; - deforming the third part from the plane of the plate material; - folding the second portion relative to the first portion so that the plane in said second portion where the third portion protrudes from the second portion perpendicular to the plane in said first portion is directed beyond the main surface, the deformation of the third portion portion a space between the top of the distortion and the top edge of the main surface.

A method for joining walls of connecting cable trays, comprising 20. aligning said walls; - placing a coupling plate between protrusions from the aligned walls, - impressions of compressible elements on top of the coupling plate by stretching the compressible elements in a direction parallel to an upper edge of the coupling plate, under pressure of the protrusions from the aligned walls of the cable ducts .