AU613456B2 - Optical cable joint - Google Patents

Description

7/' 613456 ORIfNlw COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1969 0 a. S ~0 cc.

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S6 S 0 0 S S COMPLETE SPECIFICATION FOR THE IN1VENTION ENTITLED "OPTICAL CABLE JOINT" 040 The following statement is a full description of this invention, including the best method of performing it known to us:- BY Signature of Applicant To: The Commissioner of Patents This invention refers to a joint and a method for restoring the mechanical continuity of cables, particularly optical cables, having essentially at least an optical fibre, a strength member made of KEVLAR (trademark) or the like and an outer sheath.

Such a joint is of the kind in which the end of each of the two cables to be jointed is provided with an outer sleeve shell having a substantially tubular shape, at an end of which there is provided a grommet, projecting outwardly, in which the cable outer sheath fits slidingly, said sleeve shell being adapted to be screwed or otherwise connected with the corresponding sleeve shell on the other cable, after having restored the optical continuity.

0: When a failure or breakage in a field cable occurs, it is necessary to restore both the optical and mechanical continuity of the cable under field conditions.

g In particular, the mechanical continuity to give the cable resistance to tensile stress is usually ensured by a sleeve made of metal or any rigid material. This sleeve is designed to transmit the tensile stress between the two jointed cables without stressing the optical fibres and particularly the optical junction.

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The critical step in restoring the mechanical continuity of cables (problems concerned with the optical continuity restoration are not taken into consideration here, being not object of the invention) is the clamping of the cable ends to be jointed to the sleeve. In fact, should this clamping be not secure enough, the cable, when under compressive or tensile stress, tends to slip so causing the breakage of the optical junction.

Various types of field optical cables joints are already known in the prior art. For some of them, in order to clamp the cable to the sleeve, the use of high temperature curing epoxy resins is customary. This type of joint, apart from being unsuitable under field conditions where dirt, moisture and other factors limit its use, especially when it has to be done Signature of Declarant To: The Commissioner of Patents.

by unskilled workers, is time consuming (it is necessary to wait for the curing of the resin) and, further, it does not allow the re-use of the joint parts e.g. should the optical junction be made again.

Other types of joint mount a clamping body provided with holes, clamping slots and screws, but they are not very reliable.

An object of the present invention is to provide a joint and a method for restoring the mechanical continuity of cables, particularly optical cables, which is reliable and of easy and speedy realisation even under field conditions.

Another object of this invention is to provide a joint as mentioned above, which allows an easy disassembly and reassembly and, therefore, to re-use the joint itself.

0" *According to the invention this is provided by a joint arrangement for jointing a cable of the type having at least one conductive element, at least one strength element and an outer sheath, said arrangement comprising two hollow cup-shaped cylindrical sleeve members each comprising a bottom wall, a side wall and an open side defined by a rim, said bottom wall containing a central cable entrance hole, said sleeve members adapted to be releasably joined together proximate the rim to form a closed sleeve for enclosing a joint of said at least one conductive element, wherein each said sleeve member slidably contains a first cylindrical cable locking member having a bottom wall a top wall and a side wall, said bottom wall and said side wall being respectively contiguous with the bottom wall and part of the side wall of its associated sleeve member, and a first cable hole coaxial with said cable entrance hole, each said sleeve member further slidably containing a second cylindrical locking member comprising a wall having at least one surface for mating with the said surface of said top wall of the first cylindrical cable locking member and a second cable hole coaxial with said first cable hole, the said surfaces of the cable locking members forming a space therebetween adapted to receive a length of exposed

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strength member of a cable end received in said cable entrance and passed through said first and second cable holes, said length of strength member being gripped therein by said locking members when axial tension is applied to the cable to cause said second cylindrical locking member to be urged against the first cylindrical locking member.

In order that the invention may be fully understood, embodiments thereof will now be described with reference to the accompanying drawings, in which: fig. i shows schematically a longitudinal cross-sectional view of the joint according to the invention, 00: fig. 2 shows schematically a detail of the arrangment of the joint fee: parts assembled before the cable is subjected to tensile stress, 0*4 fig. 3 shows the parts of fig. 2 after the tensile stress is applied to the jointed cables, 0 S figs. 4a) to 4d) show schematically the various steps concerning the cable preparation, and "0 -fig. 5 shows a spacer mounted in the joint of fig. 1.

Like parts in both the sleeve shells are labelled with like numerals, S* with the addition of an apex to those on the right.

Referring now more particularly to fig. 1, the outer sleeve consists of two parts or shells, a male part 7 and a female part 10, which are screwed together by virtue of screw threads (fig. 4).

Both the shells 7, 10 are provided at their opposite ends with an entrance hole with a gromet 2,2' arranged therein and through which the respective cable 1,1' to be jointed is passed in a sliding dust-tight manner.

Inside each shell, from the entrance end, there are housed respectively: a first locking member 3,3' in the form of a funnel-shaped clamp element, consisting of a cylinder with an axial bore housing the cable 1,1' i

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0S and having an abutting surface 13, at the entrance end of the shell and an opposite surface provided with a countersink; a second locking member in the form of a cone having an axial bore housing the cable 1,1' and consisting of a frusto-conical shaped portion nesting in said countersink surface and overlapped by a cylindrical portion 14,14' facing the centre of the junction and having its outer diameter smaller than the inner diameter of the shell, so as to form therebetween a first hollow space which communicates with a second hollow space (see fig. 2) formed by the countersink in the first locking member LO 3,3' and the fitting conical portion of the cone said second hollow space varying as a function of the axial position of the cone 4,4' with respect to the first locking member Preferably, the diameter of the axial bore of the first locking member 3,3' is greater than the diameter of the cable sheath so as to form therebetween a third hollow space which communicates with the second one (see fig. 2).

Advantageously, the first locking member 3,3' may be constructed in two sections symmetrical sections with respect to an axial plane and held together by screws in order to simplify the assembly operations (see fig. 1, 4c, 4d).

20 The hollow spaces are adapted to receive a length 12,12,' of the strength member released from the outer sheath and folded back over the cylindrical portion 14,14' of the cone.

A spacer 6, in the form of a shaped plate (see fig. located between the two sleeve shells, is rigidly connected at its ends to the respective first locking members by means of screws The plate ends are bifurcated and adapted to receive in abutment each of the respective cones.

The spacer 6 has two functions: on the one hand it is used to prevent compressive stress applied to the cable from being transmitted to the optical fibre junction 11 and, on the other hand, it acts as a supporting w'j *T~----nasiiuPr i member for the optical fibre junction ii, which is protected by the plastic material housing 9.

Between the two shells 7, 10 an 0 ring 8 is inserted in a sealed manner.

Having described the structure of the joint, the steps for performing the junction will now be described.

They include: 1) Preparation of the cable to be jointed (fig. 4a, 4b). After removalof the damaged length of the cable, the two free ends are inserted each in the respective shell (fig. 4a), then a length of outer sheath is removed from the ends of the cables to be jointed (fig. 4b) so stripping the optical Sfibres and the kevlar yam.

2) Pre-arrangement of the mechanical junction (fig. 4c). The cone is slipped on the cable and the stripped kevlar yarn length is folded back S• over it.

3) Completion of the mechanical junction (fig. 4d, 4e). The first locking •member is located and the screws are tightened. The cable is ready to be optically jointed in a way known per se.

Ultimately, the two shells are screwed together after which tensile stress, applied on the cable, causes the engagement of the cone into the countersink thus strongly gripping the kevlar yarn and causing the instantaneous and secure automatic locking of the cable.

It is necessary to emphasise that the above engagement involves a displacement of a few tenths of millimeter and, being the optical fibres provided with some stress relief, this will cause no problem to the fibres themselves.

The present invention, therefore, fully achieves all intended objects of the invention.

From the above description, the joint and the method according to the present invention provide a reliable locking system. In fact, this solution provides a junction structure which operates in a self-locking fashion, i.e. the higher the tensile stress applied on the cables, the stronger the instantaneous locking action of the system.

Moreover, the junction and the method according to the invention are easy and quick to realise, even in the field (it is not necessary to wait for any resin curing).

As a result of its simplicity and the absence of resins, it is possible to disassemble and re-use the joint.

Finally, the joint according to the present invention features versatility of use. Although it is typically used in military, optical transmission systems, the joint can be used in any transmission system including cables with strength members made of kevlar yam or the like.

While the present invention has been described with regard to many o: particulars, it is to be understood that equivalents may be substituted without departing from the scope of the invention.

Claims (11)

1. An optical fibre cable connector for connecting cables including at least one conductive element having a strength member disposed around the conductive ele- ment or elements, the connector comprising first and second connector shells, the first and second shells being rigidly connectable, each shell being a substantially hollow cylindrical wih a first end being partially closed to allow the passage of a cable, each shell containing a first substantially frusto-conical member, an axial bore to permit the cable to be passed theretlhrough, the first. member having a maximum diameter less than the inner diameter of the shell whereby, when the strength member is folded back over the first member, the first member can slide in the shell, each connector further having a collar including a frusto-conical recess to receive the first member, the collar having a bore through which the cable can pass, the shell having an internal annular protrusion at its first end against which the collar abuts, wherein, in the as- first member. S

2. Ae connector as claimed inp clai r wtheirn the base of the fusto-conical member comprises an annular section of the st memgreater the siametrength mean tis folded bac over- eter of its conical portion.

3. A connector as claimed in claim l or claim 2 wherein the collar is split in an Saxial planbe to form tewo halves connected by transverse screws.

4. A connector as claimed in any one of claims t to 3 wherein the collars of each shelfare held in a fixed longitudinal rlationsmberip by a spacer member joined to the two collars. .2

5. A connector as claimed in claim 4, wherein the spacer supports the connection "between the conductive element of the cable passing through each shell.

6. me A connector as claimed in any one of claims I to whereinn the apex of the first member points away from the end of te cable.

7. A connector as claimed in a one or claims to 6 wherein the strength memberi acomprises a kevlart mesh e tube. ct ansv e ses

8. An optical fibre conector s ijbst antially as herein described with reference to 25 sthell are haeld in a fixed longludinal relationship by a spacermember joine to the l5. A connector as caismed in cain 4, wherein the spacer supports the connection between the conuctive element of the cable passingaccompanyi throughng drawingseach shell 6. connector as claimed in any one of clais to 5, whereinthe apex o the t0 first member paints away from the end of the cable. 7. A connector as claimed in an one of claims i to 6 werein the strength me ber comprises a kevlar mesh tube. :I 3. An optical fibreconnector sujbsa.ntially as herein descrilbed with ieftence to the accompanying drawings. .catt ewe h odcie lmn ftecbepssn hog ahsel 6.7 A onco scamdi ayoeo lisIt hri h pxo h 9

9. A method of joining an optical fibre cable having at least one conducutive el- ement and a strength member by the use of a connector as claimed in any one of claims 1 to 8, the method comprising for each shell, inserting the cable through the first end of the shell and through the axial bore of the first member, exposing the strength member and folding it back over the first member so that it lies along the cable, applying the collar on the cable adjacent to the first member to clamp the strength member between the cable and the collar, joining the conductive elements of the cables in the first and second shells, moving each shell relative to the cable and joining the first and second shells.

10. The method claimed in claim 9 as appcnded to claim 4 or claim 5 including the step of joining the collar in the first shell to the collar in the second shell by the spacer member before joining the conductive element.

11. A method olf joining optical fibre cables substantially as herein described with reference to the accompanying drawings. see* DATED THIIS SEVENTEENTH DAY OF MAY 1991. ALCATEL N.V. 0 S. IL i I -I