EP0669677B1 - Electrical connection device for conductive cable shields and method for its implementation - Google Patents

Abstract

The connection system for providing connection to the metal screen (7) around the cable (6) includes a connector (1) with a rigid body (2) which is intended to applied to the side of the cable. A flexible wire conductor element (3) is provided to surround the cable lying in a transverse peripheral groove (21). The rigid body includes a tensioning mechanism for the flexible wire so that the wire may be pulled tightly around the main cable ensuring a good electrical connection. The wire may cut through an outer insulating sleeve which surrounds the conducting metal screen with which contact is to be made.

Description

The present invention relates to an electrical connection device for screens conductive cables, in particular telecommunication cables. This invention applies more particularly to cables provided with a very low protection screen thickness, consisting of a metallic layer, in particular of aluminum, covered with a insulating protective layer, such as polyethylene. Such a screen with its device connection protects the cable it surrounds against radio interference and electromagnetic, and ensure grounding or grounding, for example by connecting a cable, belonging to an installation, to a structure receiving this installation, or ensure continuity between two screens.

We know, more particularly, realizations with protective screen in aluminum with a thickness between 80 and 200 microns, covered with a film polyethylene protector a few microns thick, held by adhesion (plasticization of aluminum). The screen thus formed is interposed between the beam of electrical conductors of the cable and an insulating outer sheath, the installation of this screen and outer sheath being achievable by extrusion.

Considering this kind of realization of cables with protective screen, we is currently experiencing difficulties in performing a reliable electrical connection with the screen, with a view to earthing or resuming the potential or continuity of this screen. These difficulties in making a connection result from the adhesion of the screen to the outer sheath, and the small thickness of said screen. Connection is usually made on site, at the end of the cable, and it consists of cutting more or less conveniently a window or other interruption in the outer sheath, then put in places a connecting claw with another cable to ensure electrical continuity of the screen or its earthing (see document US-A-4051323 or its equivalent FR-A-2368156). When cutting the window and installing the link claw, there is a risk damage the screen and / or damage the cable conductors.

We also know, from documents US-A-1935085 and GB-A-2245772, electrical connection devices for earthing, comprising a body connector rigid capable of being supported in a zone of the periphery of a cylindrical object, and an element flexible filiform conductor provided for entangling said cylindrical object, means being provided on these devices for securing one end of the flexible conductive element to the body of the connector, and to immobilize, with controlled mechanical tensioning, the part of this flexible conductive element embracing said cylindrical object. However, these connection devices are only intended for earthing metallic objects rigid, in particular of tubes, the flexible conducting element in the form of a small cable or tape being applied and clamped on the exterior surface of the rigid object such as tube. The known devices mentioned here are neither intended nor adapted to the grounding of a screen very thin protection, located under the insulating sheath of a cable telecommunications. In particular, these devices have parts which would injure the cable, and in particular would damage its screen, in an irreversible manner.

The invention aims to avoid these drawbacks by providing a device allowing to make an electrical connection with the screen at any point along the cable length, on a small part of the periphery thereof, quickly and easily, without risk of damage to the screen or to the conductors belonging to the cable.

To this end, the invention essentially relates to a connection device electric for screens of conductive cables of the type concerned, the device being of the type comprising a rigid body connector capable of being supported in a region of the periphery of the cable, and a flexible filiform conductive element intended to entrap the cable, means being provided for securing one end of the flexible filiform conductive element to the connector body, and for a immobilization with controlled mechanical tensioning of the part of this element flexible conductor embracing the cable, the device being characterized in that the element flexible filiform conductor is produced in the form of a conductive braid or a flexible cable, forming a loop intended to be positioned in a groove transverse hollowed out in the outer insulating sheath of the cable over at least a fraction of its circumference, and reaching the screen, in that one end of the filiform conducting element flexible is secured to the connector body by means of a threaded tensioning member mechanically controlled, axially traversed by this end and in that, the body of the connector comprises a housing such as a channel or notch receiving the strand of the element flexible conductor forming the end of the loop embracing the cable, a locking screw being provided for immobilizing this strand of the flexible conductive element in said housing.

The flexible conductive element thus forms a loop which takes place in a groove cut into the thickness of the outer insulating sheath of the cable and covering preferably an arc less than a full circumference, while the rigid body of the connector is supported on the part of the outer insulating sheath which has remained intact.

In an advantageous embodiment, the threaded tensioning member mechanically controlled is an internally threaded sleeve, rotatably mounted but immobilized axially on the connector body, while the end of the element flexible conductor is provided with an externally threaded driver cooperating with the internal thread of the sleeve.

Advantageously, the mechanical tensioning screw and the locking screw are fuse head screws, allowing easy control of their tightening torque, therefore control of the tension of the flexible conducting element embracing the cable, and of its contact force on the screen, therefore optimal contact between this flexible conductive element and the screen belonging to the cable.

According to a particular embodiment, the connector is provided with a braid conductive, one end of which is integral with the body of this connector and intended to ensure the envisaged electrical connection: earthing of the cable screen, continuity, equipotentiality, flow of electromagnetic disturbances. In this case, the free strand of the flexible conductive element can be cut as close as possible to the body of the connector, after immobilization and tensioning of this element around the cable.

According to another possibility, removing the aforementioned braid, the free strand of the element flexible, uncut, thread-like conductor is used to directly bond electrical, such as grounding the cable screen.

For this purpose, as appropriate, the free end of the connecting braid or the free end of the flexible filiform conductive element is advantageously provided with a terminal, for crimping or to be fixed by any other means, such as screwing, for example on a ground plane.

In its final state, the connection device object of the invention can still include sealing and insulating means surrounding the connector and the cable.

The invention also relates to a method of making a connection electric for screens of conductive cables of the type concerned, with implementation of the connection device defined above.

• à creuser dans la gaine extérieure isolante du câble, sur au moins une fraction de sa circonférence, une saignée dont le fond atteint l'écran, la saignée étant creusée par utilisation d'un élément souple filiforme du genre corde, ceinturant le câble et soumis à un mouvement de va-et-vient, formant cette saignée par un effet mécanique et/ou par un effet thermique,
• à engager dans la saignée l'élément conducteur filiforme flexible du dispositif précité, en formant une boucle, tandis que le corps du connecteur est appliqué en une zone de la périphérie du câble,
• à immobiliser et mettre en tension mécaniquement et de façon contrôlée l'élément conducteur flexible, et
• à réaliser la liaison électrique envisagée entre le connecteur et un élément extérieur.

This process essentially consists of:

• to dig into the insulating outer sheath of the cable, over at least a fraction of its circumference, a groove whose bottom reaches the screen, the groove being dug by the use of a flexible, threadlike element of the rope type, encircling the cable and subjected to a back and forth movement, forming this bleeding by a mechanical effect and / or by a thermal effect,
• in engaging the flexible filiform conductive element of the aforementioned device into the groove, by forming a loop, while the body of the connector is applied in an area of the periphery of the cable,
• immobilizing and tensioning the flexible conductive element mechanically and in a controlled manner, and
• to make the envisaged electrical connection between the connector and an external element.

Preferably, the bleeding is carried out on a fraction of the circumference complete of the cable, for example in an arc of approximately 300 °, so as to leave remain a part of integral outer sheath on which is applied the body of the connector.

According to one embodiment of the method, the bleeding is dug in the insulating outer sheath of the cable by using a flexible threadlike element of the rope type, encircling the cable and subjected to a back and forth movement. The bleeding is thus easily formed, at the desired point on the cable, by a mechanical abrasion effect or by an effect thermal (local fusion of the cable insulating sheath), or by the combination of these two effects. The operator, printing the rope back and forth preferably thanks to gripping means such as handles equipping the two ends of the rope, easily perceives the contact of this rope with the screen; the back and forth movement can even be chased on the screen without limit, because the risk of damage to the screen is here practically zero, whatever the nature of this screen. Once released from the rope, the groove formed in the insulating sheath can immediately receive the conductive element flexible connector, then brought to the cable. Note that the establishment of the connector does not require engaging the conductive element around the cable by one end of it. On the contrary, the connector can be installed on a cable without accessibility at the ends, the flexible filiform conductive element being wound, on a lathe, around the cable, before being brought back and blocked on the connector body.

Figure 1 est une vue en perspective du dispositif objet de l'invention, dans une première forme d'exécution,

Figure 2 est une vue de face du dispositif de figure 1, mis en place autour d'un câble,

Figure 3 est une vue en plan par dessus correspondant à figure 2,

Figure 4 est une vue en perspective montrant une deuxième forme d'exécution du dispositif de connexion selon l'invention,

Figure 5 est une autre vue en perspective du dispositif de figure 4,

Figures 6 et 7 sont des vues en coupe d'une troisième forme d'exécution de ce dispositif de connexion, avant et après mise en tension de l'élément conducteur flexible,

Figures 8 et 9 sont des schémas illustrant le mode de creusement de la saignée sur le câble recevant le dispositif de connexion.

The invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of examples, three embodiments of this electrical connection device for screens of conductive cables, and illustrating the method of implementation of this device.

FIG. 1 is a perspective view of the device which is the subject of the invention, in a first embodiment,

FIG. 2 is a front view of the device in FIG. 1, placed around a cable,

FIG. 3 is a plan view from above corresponding to FIG. 2,

FIG. 4 is a perspective view showing a second embodiment of the connection device according to the invention,

FIG. 5 is another perspective view of the device of FIG. 4,

FIGS. 6 and 7 are sectional views of a third embodiment of this connection device, before and after tensioning of the flexible conductive element,

Figures 8 and 9 are diagrams illustrating the method of digging the groove on the cable receiving the connection device.

As shown in Figures 1 to 3, relating to a first form of embodiment, the device comprises a connector, generally designated by the reference 1, in which there is mainly a rigid body 2 made of electrically material conductive, such as a copper alloy, and a flexible filiform conductive element 3, is having like a conductive braid or a flexible cable, for example of steel stainless. In this first embodiment, the device also comprises a connecting braid 4, mechanically and electrically connected to the rigid body 2 of the connector 1.

This rigid body 2 comprises a base 5 of curved profile, designed to take support in a zone of the periphery of a cable 6 with protective screen 7. In the part massive body 2, are formed transversely a threaded hole 8 and a channel 9, which one and the other cross this massive part on both sides, in different planes.

In the threaded hole 8 of the body 2 is introduced a tensioning screw 10, provided with an axial bore 11 and a fuse head 12. A first end of the cable 3 passes through the axial bore 11 of the screw 10, and is provided with an enlarged head 13 which takes pressing on an internal retaining shoulder formed in the axial bore 11 of the screw 10.

The flexible cable 3 is provided to form, in the position of use of the connector 1, a loop embracing the cable 6, the strand of cable 3 which forms the end of the loop being introduced through the transverse channel 9 of the body 2. In this body 2 is formed another tapped hole, opening into the channel 9 and receiving a locking screw 14 to fuse head 15.

The loop formed by the cable 3 embracing the cable 6 is engaged in a transverse groove, hollowed out in the insulating outer sheath 16 of the cable 6 (in a way described in detail below) over at least a fraction of its circumference, the bottom of the groove reaching the protective screen 7. The locking of the cable 3 by tightening the screw 14, followed of its controlled mechanical tensioning around the cable 6 by tightening the screw 10, ensures the mechanical connection and the electrical contact between the screen 7 belonging to the cable 6, on the one hand, and the cable 3, therefore the body 2 of the connector 1, on the other hand.

Braid 4, which can be made of copper like a bare braid, or coated with a like a small cable, here provides the desired electrical connection between connector 1 and a external element not shown, such as ground network. The first end of the braid 4 is crimped at 17 onto the rigid body 2 of the connector 1. The other end, initially free, braid 4 is provided with a terminal 18, designed to be crimped, screwed, welded or fixed by any other means on said external element, so as to ensure electrical continuity.

Due to the presence of the connecting braid 4, the free strand 19 of the cable 3, that is to say the part not forming the loop and situated beyond the body 2 of the connector 1, can here be cut as close as possible to the body 2 and eliminated, as illustrated in FIG. 3.

FIGS. 4 and 5 represent a second embodiment of the invention, in which the rigid body 2 of the connector 1 comprises, in addition to a solid part with hole threaded receiving the tensioning screw 10 of the cable 3, a tab in which is formed a notch 20. A tapped hole, opening into the notch 20, receives a screw blocking 14 with fuse head 15, of axis parallel to the tensioning screw 10, and located in the same transverse plane.

Thus the cable 3, forming in a transverse plane a loop which embraces the cable 6, has a part locked in the notch 20 by the screw 14 and, beyond this part, a free strand 19 which is here bent at a right angle and brought in a direction parallel to the axis of the cable 6. The free strand 19 of the cable 3 serves here as a connecting element (replacing the braid 4 of the first embodiment). A terminal 18 to be crimped or screwed is provided for the end of the free strand 19 of the cable 3. As before, the loop formed by this cable 3 is engaged in a groove 21, hollowed out in the outer sheath insulating 16 of the cable 6 and reaching the protective screen 7 of this cable 6.

Figures 6 and 7 show a third embodiment, which is different from the previous ones by the constitution of the mechanical tensioning means controlled part of the flexible cable 3 embracing the cable 6.

The body 2 of the connector 1 here has a smooth hole 8A receiving a socket 10A smooth on the outside and internally threaded, mounted revolving but immobilized axially on the body 2, the sleeve 10A comprising for this purpose an annular groove 26 cooperating with a complementary part belonging to the body 2. This socket 10A is provided with a 12A fuse operating head allowing mechanical tensioning controlled.

The end of the cable 3 is provided with a driver 13a, produced in the form an externally threaded ring, and secured to this end. Coach 13A takes place inside the socket 10A, the external thread of the driver 13A being complementary to the internal thread of the socket 10A.

Before tightening, as shown in Figure 6, the coach 13A is located towards the end of the socket 10A remote from the operating head 12A. Manual operation of this operating head 12A, rotating the socket 10A, causes it to be screwed onto the coach 13A and, consequently, an advance of the coach 13A in the direction of said operating head 12A, until desired tightening - see Figure 7 showing the configuration obtained at the end of controlled mechanical tensioning of the cable 3 after breaking of the fuse head.

The latter solution leads to a reduced bulk, the socket 10A not being not moved axially with respect to the body 2 and finally making only a slight projection on the body 2. In addition, an anti-vibration O-ring 27 can here be mounted and compressed between the operating head 12A of the socket 10A and the entry of the smooth hole 8A of the body 2.

The method of implementing the device described above comprises, in a first step, the digging of the groove 21 in the insulating outer sheath 16 of the cable 6. As illustrated in FIG. 8, the digging of this groove 21 can be carried out using of a material constituted by a cord 22, or other flexible filiform member of the same kind, both ends of which are advantageously provided with respective grips 23 and 24. The rope 22 is brought so as to encircle the cable 6, the two free strands formed by the end regions of this intersecting cord 22. A back and forth movement is printed on cord 22, along arrow F, by the operator entering this cord by its ends, in particular by the two handles 23 and 24. Thus, the cord 22 hollow gradually, by mechanical and / or thermal effect, in the insulating outer sheath 16 of the cable 6, a groove 21 which extends over an arc of a circle less than one complete revolution, covering for example around 300 °, an integral zone 25 remaining between the two ends of the groove 21 - see figure 9.

Once the groove 21 has been dug, the operator removes the cord 22 and proceeds with the setting in place of connector 1, applying body 2 of connector to zone 25 and engaging the cable 3 in the groove 21, to form a loop before returning to the body 2 where the locking of the cable 3 is effected by means of the screw 14 with a fuse head 15 forming torque limiter. Then, there is manual mechanical tensioning controlled loop on the screen 7 by tightening the screw 10, whose fuse head 12 plays also the role of torque limiter.

Then, as the case may be, the electrical connection is made with an external element either at using the free end 19 of the cable 3, or using the braid 4.

After immobilization and controlled mechanical tensioning of cable 3, engaged in the groove 21, it is further possible to provide sealing and insulation around of connector 1 and cable 6 in the region of the connector, by various means complementary such as: installation of a self-sealing tape, installation of a shell suitable and filling it with an insulating resin, fitting accessories adapted with flexible parts (for example elastomer rubber), fitting of a sheath heat shrinkable or mechanically shrinkable.

The connection device can be placed at the end of the cable, at a point through a cable with no accessibility at the ends, around an accessible cable only on a short length, or on an accessible cable only on a reduced angle. Although the invention is applicable in particular to the connection of screens belonging to telecommunication cables, the connection device in question is also adaptable to cables for transporting electrical energy, for video network cables, for coaxial cables, as well as insulated sheaths or guides, the constitution and geometry of these cables or analogs can be various. In particular, the same connection device is adaptable, without modification, to cables of various diameters, forming with the cable a loop of varying length wrapping the cable.

Claims (9)

1. Electrical connection device, for protective conducting cable screens, the screen (7) consisting of a metal layer of very small thickness, inserted between the electrical conductor or conductors of the cable (6) and an insulating outer jacket (16) of the cable (6), the device being of the kind comprising a connector (1) having a rigid body (2) capable of bearing on a region (25) of the periphery of the cable (6), and a flexible filiform conducting element (3) provided for encircling the cable (6), means (8 to 12, 14, 15, 20) being provided for securing an end (13) of the flexible conducting element (3) to the body (2) of the connector (1) and for immobilizing, with controlled mechanical tensioning, of the part of this flexible conducting element (3) encircling the cable (6), characterized in that the flexible filiform conducting element is made in the form of a conducting braid or of a flexible cablet (3), forming a loop intented to be positioned in a transverse groove (21), hollowed out in the insulating outer jacket (16) of the cable (6) , over at least a fraction of its circumference, and reaching the screen (7), and that one end (13, 13A) of the flexible filiform conducting element (3) is secured to the body (2) of the connector (1) by means of a threaded controlled-mechanical-tensioning member (10, 10A) through which this end (13) passes axially, and in that the body (2) of the connector (1) includes a housing, such as a channel (9) or notch (20), receiving the strand of the flexible conducting element (3), forming the end of the loop encircling the cable (6), a lock screw (14, 15) being provided for immobilizing this strand of the flexible conducting element (3) in the said housing (9; 20).
2. Electrical connection device according to Claim 1, characterized in that the threaded controlled-mechanical-tensioning member is an internally threaded bush (10A) mounted so as to rotate, but axially immobilized (at 26) on the body (2) of the connector (1), while the end of the flexible conducting element (3) is provided with an externally threaded driver (13A) interacting with the internal thread of the bush (10A).
3. Electrical connection device according to Claim 1 or 2, characterized in that the threaded mechanical-tensioning member (10, 10A) and the lock screw (14) are screws or bushes with a shear head (12; 15) permitting control of their tightening torque, and therefore control of the contact force of the said flexible conducting element (3) on the screen (7).
4. Electrical connection device according to any one of Claims 1 to 3, characterized in that the connector (1) is provided with a conducting braid (4), one end of which is fastened to the body (2) of this connector (1) and which is designed to provide the envisaged electrical bonding, such as earthing of the screen (7) of the cable (6).
5. Electrical connection device according to any one of Claims 1 to 3, characterized in that the free strand (19) of the flexible filiform conducting element (3) is used to provide directly the envisaged electrical bonding, such as earthing the screen (7) of the cable (6).
6. Electrical connection device according to Claim 4 or 5, characterized in that the free end of the bonding braid (4) of the flexible filiform element (3) is equipped with a lug (18).
7. Method of making an electrical connection for conducting cable screens by employing the connection device according to any one of Claims 1 to 6, characterized in that it essentially consists in:

   hollowing out, in the insulating outer jacket (16) of the cable (6), over at least a fraction of its circumference, a groove (21) whose bottom reaches the screen (7), the groove (21) being hollowed out by using a filiform flexible element (22) of the cord kind, surrounding the cable (6) and subjected to a to-and-fro movement (F), forming the groove (21) by a mechanical effect and/or by a thermal effect ;

   engaging the flexible filifom conducting element (3) of the aforementioned device in the groove (21), forming a loop, while the body (2) of the connector (1) is applied on a region (25) of the periphery of the cable (6);

   immobilizing and mechanically tensioning, in a controlled manner, the flexible conducting element (3); and

   making the envisaged electrical bonding between the connector (1) and an external element.
8. Method of making an electrical connection according to Claim 7, characterized in that the groove (21) is made over a fraction of the complete circumference of the cable (6), so as to leave a part (25) of the outer jacket intact, on which part the body (2) of the connector (1) is applied.
9. Method of making an electrical connection according to Claim 8, characterized in that the groove (21) is made in the form of a circular arc of approximately 300°.

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