GB2385213A

GB2385213A - Device for fixing a self-supporting cable on a support with vertical overload limiter

Info

Publication number: GB2385213A
Application number: GB0300055A
Authority: GB
Inventors: Jean-Claude Libert
Original assignee: TELENCO Telecommunication Engineering Company SAS
Current assignee: TELENCO Networks SAS
Priority date: 2002-01-10
Filing date: 2003-01-03
Publication date: 2003-08-13
Anticipated expiration: 2023-01-03
Also published as: IE20030003A1; FR2834590A1; FR2834590B1; GB2385213B; GB0300055D0

Abstract

This device comprises two metal jaws (M1, M2) which can be brought closer together by transverse bolts (1) and bearing, near at least one of their longitudinal edges, an asymmetric C-shaped longitudinal groove (7, 8) delimiting a channel for housing the carrier cable (C2), the said channel opening to the side via a slot (10) for accommodating the connecting strap (9b) of the self-supporting cable (C). In each jaw (M1, M2), the groove or each of the longitudinal grooves (7, 8) is formed in an overload-limiting piece (G1, G2) consisting of a lining made of plastic and connected to the corresponding jaw (M1, M2), the material defining this groove (7 or 8) being connected to the body of the lining (G1, G2) by a longitudinal region (Zr) that can rupture in the event of vertical overload and comprising, for example, recesses (26).

Description

The invention relates to a device for fixing a self-supporting cable to a support. It relates more particularly, although not exclusively, to selfsupporting cables made up, on the one hand, of a functional bundle or cable, for example for transmitting electrical or optical signals, this cable being arranged in an insulating jacket and, on the other hand, of a carrier cable, parallel to the first and arranged in an insulating jacket separate from the other jacket but connected to it by a strap.

At the present time, a self-supporting cable is fixed to a support, for example to a post, by a device made up of two metal jaws each comprising: near each of its longitudinal edges, an asymmetric C-shaped longitudinal groove defining, with the groove of the opposite jaw, a channel opening to the outside via a slot for accommodating the strap, at their middle, a hole for the passage either of a bolt for fixing to a support piece that can be fixed by a strip, or a screw or bolt for fixing to a post made of wood or cement, and, on each side of this central hole, two bores, one plain, in the case of one of the jaws, and the other threaded, in the case of the other, for fitting two screws for clamping the two jaws together.

In general, the joining plane of these two jaws is a circular segment, which means that one of them is convex and the other is concave.

Furthermore, the two channels formed by the jaws have different diameters so that, by turning the jaw over, two carrier cables of different diameters chosen from those most often encountered can be hung and fixed.

The fixing device is very widespread in various forms defined by each manufacturer. It holds the

carrier cable in all directions of loading and, for example : - holds the cable under a vertical load because of the C-shape of the grooves, - holds the cable under a longitudinal load because of the clamping and the curved shape of the jaws, - holds the cable under a horizontal load, for example in an angle, because the carrier cable bears against the curved face of the groove.

As a result, if there is a point overload on the self-supporting cable, the reactions are different.

Thus: - a vertical overload causes the carrier cable to leave the groove of the device, sometimes causing damage to the insulation of the carrier cable, - a unilateral longitudinal overload causes the carrier cable to slip in the groove, - a horizontal overload is borne well by the carrier cable and by the device.

A careful examination of the various causes leading to overloads reveals that the one that causes the greatest damage to the self-supporting cable is the vertical overload which, in some instances, can lead to rupture of the strap connecting the insulating jackets of the functional cable and of the carrier cable and can even lead to damage to the fixing device.

It is an object of the present invention to provide a fixing device with overload limiter preventing damage to the self-supporting cable and, in particular, to its connecting strap connecting the jackets of the two cables, functional and carrier respectively, and also preventing damage to this device.

The device according to the invention comprises, like the known devices, two metal jaws which can be

brought closer together by transverse bolts and bearing edges, near at least one of their longitudinal bearing edges, an asymmetric C-shaped longitudinal groove delimiting a channel for housing the carrier cable, the said channel opening to the side via a slot for accommodating the connecting strap connecting the two jackets of the self-supporting cable.

According to the invention, in each jaw, the groove or each of the longitudinal grooves is formed in an overload-limiting piece consisting of a lining made of plastic and connected to the corresponding jaw, the material defining this groove being connected to the body of the lining by a longitudinal region that can rupture in the event of vertical overload and comprising, locally, recesses which may or may not go all the way through, and/or a thin web of material of lesser thickness than the said piece.

This device is therefore made up of two metal jaws bearing plastic linings, comprising grooves for retaining the carrier cable of a self-supporting cable.

With this device, when the vertical overload reaches a threshold value determined by the characteristics of the material of which the linings or overload-limiting pieces are made and the value of the cross section of material in the rupture region of these pieces, the region of these pieces clamping the carrier cable ruptures and allows this clamping region and the bodies of the pieces to separate, leading to release of this clamping region and of the carrier cable. What this means is that, in the vertical overload region, the carrier cable escapes from its hanging and fixing device, preventing it from becoming damaged.

The line or network can be repaired all the more quickly since neither the cable or the jaws are

deformed and since, in order to reattach the selfsupporting cable to a support, all that is required is replacement of the linings, something which is far easier than replacing a length of self-supporting cable.

In one embodiment, the two overload-limiting pieces or linings have the general shape of ring segments, concave and convex respectively, while the jaws are made of pressed sheet metal and each comprises a central part in the shape of a W the legs of which have bent returns shaped to serve as support for the. dorsal faces, concave and convex respectively, of the pieces or linings, each of these bent returns having, passing through it, a hole for the passage of the bolt used to clamp the jaws together.

In this configuration, the elements which give the device mechanical strength, namely the jaws, are made by pressing a sheet metal and are far less expensive than the current jaws which are produced by casting aluminium alloy, while the rupture pieces are produced by moulding plastic and are themselves less expensive than the pieces obtained by casting an aluminium alloy.

Advantageously, each of the overload-limiting pieces or linings comprises clip-fastening means connecting it to the corresponding jaw.

This arrangement is particularly beneficial because it avoids each lining separating from the jaw which bears it, particularly when the device is being fitted at the top of a post.

As a preference, each of the jaws comprises, on the one hand, in the bottom of its central part, a cylindrical hole for the passage of any possible fixing bolt or tie bolt, also passing through the cylindrical holes formed in the pieces or linings, and on the other

hand, in the legs of its central part, a vertical recess for the passage of any fixing strip there might be, and, in addition, in the continuation of one of its bent returns, a perforated lug for the attachment of a stringing pulley.

This construction allows the device to be fixed to a support either by a screw, a tie bolt or bolt, or by a strip and, when it is place, makes it easier for the self-supporting cable to be fitted by facilitating the attachment of a stringing pulley to one of its perforated lugs.

Other characteristics and advantages will become apparent from the description which follows, with reference to the appended diagrammatic drawing, which, by way of example, depicts several embodiments of this fixing device.

Figure 1 is an exploded perspective view showing the essential elements of a first embodiment of this device, Figures 2 and 3 are views, respectively, in perspective and in plan view from above the device when it is in a position of use, Figures 4 and 5 are views in section on IV-IV of Figure 3 when the device supports the self-supporting cable and yields when subjected to a vertical overload, Figure 6 is a view in section similar to Figure 4, showing an alternative form of the embodiment of the linings, Figure 7 is a perspective view of another embodiment of the linings, Figure 8 is a view in section on VIIIMVIII of Figure 7.

The invention relates to the fixing of a self-

supporting cable c comprising a functional bundle or cable Cl and a carrier cable C2 which are arranged in

separate insulating jackets 9a and 9c respectively, which jackets are connected by a strap 9b.

This fixing device is essentially made up of two metal jaws Ml and M2 respectively, each bearing a lining or overload-limiting piece G1 and G2 respectively, and of two clamping bolts each made up of a screw 1 and of a nut 2.

In the embodiments depicted, the two linings Gl, G2 are made of plastic and have the general shape of ring segments, the piece Gl having, facing the piece G2, a convex face 3 and a concave back 4 while the piece G2 has, facing the piece Gl, a concave face 5 and a convex back 6.

As shown in greater detail in Figures 4 and 5, each of the pieces Gl and G2 comprises, near each of its longitudinal edges, an asymmetric C-shaped groove, 7 and 8 respectively. When the two pieces are clamped together, these grooves delimit a channel able to accommodate the jacket 9a of the carrier cable C2. The channel thus formed communicates with the outside via a slot 10 for the passage of the connecting strap 9b making the connection with the jacket 9c of the functional bundle or cable Cl.

In the known way, the grooves 7 and 8 have different diameters corresponding to the outside diameters of two of the most common carrier cables.

As shown in Figures 1 to 3, each of the jaws Ml and M2 is made of sheet metal, pressed and treated against corrosion, and have a W-shaped central part 12 bordered by two outwardly bent returns, 13a, 13b in the case of the jaw Ml and 14a, 14b in the case of the jaw M2. The central parts of the two jaws are identical, but their bent returns are bent differently, so that they can be pressed, 13a, 13b against the concave face

4a of the jaw Gl, and 14a, 14b against the convex face 6 of the jaw G2, as shown in Figures 2 and 3. In each jaw, the bottom 12a of the central part 12 has, passing through it, a cylindrical hole 15 for the passage of a bolt, tie bolt or equivalent, while each of the legs 12b has, passing through it, a vertical recess 16 for the passage of a strip.

Finally, each of the bent returns 13a, 13b of the jaw Ml has, passing through it, a square hole 17. intended to collaborate with the square collar la of the screw 1, while the bent returns 14a, 14b, have, passing through them, a round hole 17a for the passage of the shank of the screw 1. In each jaw, the bent return 13b and 14b is continued by a lug 18 through which there passes a cut-out 19, for example for the attachment of the hook of a stringing pulley.

Each of the lining pieces Gl, G2 comprises, projecting from its dorsal face, at least one positioning peg 20 and 21 respectively, visible in Figure 3. This peg is inserted between the legs 12a, 12b of the central part of the corresponding jaw Ml or M2, to position the lining with respect to the jaw and prevent it from moving in horizontal translation.

Furthermore, each lining Gl, G2 is equipped with clipfastening means connecting it to its jaw to form a captive assembly.

In the case of the piece Gl, captive status is afforded by the screws 1 which comprise, as shown in greater detail in Figures 4 and 5, between their square collars la and their threaded parts lb collaborating with the nut 2, a cylindrical bearing surface ic of a smaller diameter than the said threaded part lb.

Connection is afforded by a tongue 22 formed, on one of the edges of each of the two square openings formed in the piece Gl for the passage of the collars la of the screws 1. Each tongue is rendered elastically

deformable by the formation of a groove 24 visible in Figures 4 and 5.

Thus, when the screw 1 is engaged through one of the holes 17 of the jaw Ml and through the corresponding hole 23 of the piece Gl, its threaded end lb moves the tongue 22 elastically away. As soon as its cylindrical central part lc comes level with this tongue, it allows the latter to return to its initial position, opposing the withdrawal of the screw and securing this screw to the jaw Ml and also to the piece

Gl.

The lining G2 is secured to jaw M2 by clipfastening tongues 25 formed at its ends and able to clip elastically over the edges of the bent returns 14a, 14b of the jaw, as shown in Figure 3.

By virtue of this arrangement, each jaw/lining assembly Ml/Gl and M2/G2 is captive and can very easily be fitted onto a support high up.

The grooves 7 and 8 of the overload-limiting pieces Gl, G2 are connected to the bodies of these pieces by a rupture region which, in the embodiment depicted in Figures 4 and 5, is defined by the dot/dash line Zr and is embodied by longitudinal furrows 26 back to back with the corresponding grooves to which they are connected by a mere thin web of material 27.

With this arrangement, when the vertical load F exerted on the self-supporting cable C and transmitted to the resisting cross section of the pieces Gl, G2 leads to a stress which exceeds the breaking stress of the material of which the pieces Gl, G2 are made, the sections concerned rupture and release the functional cable Cl from the carrier cable C2 as shown in Figure 5.

In the embodiment depicted in Figures 4 and 5, the rupture region Zr is more or less in the diametral plane of the channel formed by the grooves but it may, of course, lie in some other region, and, for example, as shown in Figure 6, between the carrier cable clamping region and the horizontal mid-plane of the device. In this Figure 6, the furrows 26a form a thin web of material 27a which is thicker than the web 27 in the previous embodiment, for example because of the use of a material which has a lower rupture strength.

In the embodiment depicted in Figures 7 and 8, the rupture region Zr embodied by the plane of section VIII-VIII of Figure 7, consists of two thin webs of material 30 bordering a recess 32 that passes all the way through and does so in each of the two linings Gl, G2. Each thin web of material 30 is associated with a transverse groove 31 initiating rupture in the region Zr.

Evidently, this rupture region may, according to the characteristics of the material of which the linings Gl and G3 [sic] are made, be defined by any localized thinning of the thickness of the corresponding piece, this thinning being used alone or in combination with recesses that go all the way through, or equally by simple recesses that go all the way through and locally define small bridges connecting the carrier cable clamping regions and the bodies of the linings attached to the jaws.

As in the current devices, turning the jaws over allows the clamping channel to be replaced with channel of a different diameter but, unlike the current devices, the same jaws can be used with linings that differ in the diameter of their longitudinal grooves 7 and 8.

This fixing device can be fixed, for example, to a wooden post, by a tie bolt passing through a cylindrical hole 15 of the Jaws and holes 11 made in the pieces Gl and G2, to a concrete post by a bolt passing through the same holes, and to a metal post, or any other support, by a strip 33 passing through the recesses 16 of the jaw Ml or M2, pressed against the supporting face of the support, and for example the jaw Ml, as shown in Figure 3.

It is evident from the foregoing that, by comparison with fixing devices involving cast metal jaws, the device according to the invention has the advantage of an overload limit for various types of self-supporting cable simply by replacing the overloadlimiting pieces Gl, G2, while at the same time providing a hanging and fixing means that is far less expensive, practically universal, and can serve as a substitute, without difficulty, for devices of the prior art.

Claims

CLAIMS 1. Device for fixing, with an overload limiter, a self-supporting cable (C) made up of a carrier cable (C2) arranged in an insulating jacket (9a) and of a functional cable (Cl) arranged in another insulating jacket (9b) connected to the first by a connecting strap (9B), the device comprising two metal jaws (Ml, M2) which can be brought closer together by transverse bolts (1) and bearing, near at least one of their longitudinal edges, an asymmetric C-shaped longitudinal groove (7,8) delimiting a channel for housing the carrier cable (C2), the said channel opening to the side via a slot (10) for accommodating the connecting strap (9b) of the self-supporting cable (C), characterized in that, in each jaw (Ml, M2), the groove or each of the longitudinal grooves (7,8) is formed in an overload-limiting piece (Gl, G2) consisting of a lining made of plastic and connected to the corresponding jaw (Ml, M2), the material defining this groove (7 or B) being connected to the body of the lining (Gl, G2) by a longitudinal region (Zr) that can rupture in the event of vertical overload and comprising, locally, recesses (26,32) which may or may not go all the way through, and/or a thin web (27) of material of lesser thickness than the said piece.
2. Fixing device according to Claim 1, characterized in that the two lining pieces (Gl, G2) have the general shape of ring segments, while the jaws (Ml, M2) are made of pressed sheet metal and each comprises a central part (12) in the shape of a W the legs (12b) of which have bent returns (13a, 13b) shaped to serve as support for the dorsal faces (4 and 6), concave and convex respectively of the two lining pieces (Gl, G2), each of these bent returns having, passing through it, a hole (17) for the passage of the bolt (1) used to clamp the jaws together.

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3. Fixing device according to Claim 1, characterized in that each of the overload-limiting pieces (Gl, G2) comprises, projecting from its dorsal face, at least one positioning peg (20,21) which engages in a part (12) of complementary shape formed in the corresponding Jaw (MI, M2).
4. Fixing device according to Claim 1, characterized in that each of the overload-limiting pieces (Gl, G2) comprises clip-fastening means (22,25) connecting it to the corresponding jaw (Ml, M2).
5. Fixing device according to Claim 1, characterized in that, in each of the overload-limiting pieces (Gl, G2), the rupture region (Zr) between the body of the piece and the clamping region of the carrier cable (C2) is formed more or less in the horizontal mid-plane of the groove (7,8) collaborating in the clamping of this carrier cable (C2).
6. Fixing device according to Claim 1, characterized in that, in each of the overload-limiting pieces, the rupture region (Zr) between the body of the piece and the carrier cable clamping region is formed between the groove (7,8) and the horizontal mid-plane of the device.
7. Fixing device according to Claim 1, characterized in that each of the bolts (1) used to clamp the two jaws (Ml, M2) together comprises, starting from its free end, a threaded part (lb), an unthreaded part (lc) of smaller diameter, and a square collar (la) passing through a square hole (17) formed in one of the jaws (Ml, M2) and a square hole (23) formed in the corresponding lining piece, while each of the two square holes (23) formed in the lining piece (Cl) for the passage of the two clamping bolts is bordered by an elastic tongue (22) able to move away as the threaded part (lb) of the screw (1) is engaged and to return

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elastically against its unthreaded part (1c) to provide the connection of the screw (1) and of the piece (Gl) with the jaw (Ml). e. Fixing device according to Claim 3, characterized in that each of the jaws (Ml, M2) comprises, on the one hand, in the bottom of its W-shaped central part (12), a cylindrical hole (11) [sic] for the passage of any possible fixing bolt or tie bolt, also passing through the cylindrical holes (11) formed in the overload limiting pieces (Gl, G2), and on the other hand, in the legs (12b) of its central part, a vertical recess (16) for the passage of any fixing strip (31) there might be, and, in addition, in the continuation of one of its bent returns (13b), a perforated lug (18) for the attachment of a stringing pulley.