OA12591A

OA12591A - Method for removing a cable core from a cable sheath.

Info

Publication number: OA12591A
Application number: OA1200300194A
Authority: OA
Inventors: Alois Pichler
Original assignee: Alois Pichler
Priority date: 2001-02-20
Filing date: 2002-02-20
Publication date: 2006-06-08
Also published as: AT410611B; BG65266B1; ATA10102001A; MA27541A1; ECSP034736A; BG108028A; TR200401953T4; CZ293812B6; PT1362398E; CZ20032494A3

Abstract

A cable core has a sheath (8). At one end of the cable (1), a liquid medium (22) is introduced under pressure in the cable conduit (9) in order to reduce friction, and a pulling force is exerted at one cable (1) end (5) on the cable core. To accomplish a method, by means of which the existing cables are freed of the cores it is proposed to introduce the liquid medium into an annular space extending between the cable sheath inner side and the cable core sheath (8).

Description

X 012591 C · - 1 - A Method for Removing a Cable Core from a Cable Sbeath

The invention relates to a method for removing a cable corefrom a cable sheath of a cable, which cable core comprises anenvelope, wherein at one end of the cable - the so-calledproximal cable end - a flowable medium is introduced underpressure into the cable tube so as to reduce friction, and atensile force is applied to the cable core at an end of thecable.

The présent invention particularly relates to undergroundcables for télécommunication purposes, which usually comprise acable core with a plurality of leads and at least on envelopesurrounding them altogether and provided e.g. by a paperwinding. Moreover, such cables mostly hâve a rigid cable sheathwhich may often be formed by a layer of lead (Pb) over which aSteel layer and, in addition, a fabric or synthetic materialenvelope may be arranged. Yet, the invention also relates toaerially supported cables, e.g. télécommunication cables guidedon high voltage towers.

The term flowable medium includes gaseous, liquid or pastymedia or mixed forms thereof.

The rapid technical development in the field oftélécommunications requires the use of new data transmissionlines via which higher data rates can be transmitted. In thisconnection, particularly optical waveguides with low atténuationare used, via which a very high band width can be transmittedwith little loss. At présent, in particular following thelibéralisation of télécommunication, there exist efforts toreplace the old cable networks by new networks of highercapacity.

The laying of new cables in the ground by means of costlyearthwork is also very expensive and time-consuming. With theprevailing compétition in the field of télécommunications, thisis not tolerable.

One method of renewing old cables consists in that tubes arefastened to the cables laid in the ground or the like, whichtubes are pulled in when the existing cables are pulled out and - thus take their place. Subsequently, optical waveguides, e.g.,are laid in the tubes. What is disadvantageous is that thesurrounding soil poses an enormous résistance to the cable or 012591 Γ - 2 - tube, respectively, to be inserted, so that always only shortdistances can be renewed without earthwork.

One method of removing inner conductors front cables is knowne.g. front WO 82/00388 Al. In this known method, a fluid isintroduced under pressure in the cable in coaxial mode ofconstruction so as to break and remove the insulating materialbetween the inner conductor and the shield. Subséquently, theinner conductor can easily be pulled out of the cable. Intélécommunication cables comprising a plurality of innerconductors, the insulation is disintegrated by using appropriatesubstances, whereby the extraction of the inner conductors isfacilitated. Moreover, also the use of milling cutters orcutting tools is provided for, which disintegrate the innerconductors of the cable and remove them appropriately. Thisknown technique is very costly and time-consuming and notgenerally useful for télécommunication cables. A method of the présent type is known from US 4,197,628 A,wherein the ends of a piece of cable are exposed and a sleeve isfastened around one end of the cable. The sleeve is tightlysealed by a cap, and a lubricant is introduced under pressureinto the cable core via a connecting piece on the cap. At theopposite end of the cable, the emergence of the lubricant iswaited for, and subsequently further introduction of lubricantis stopped. After an envelope usually provided externally on thecable core has been soaked with lubricant, the cable core ispulled out. In practice, this method has not prevailed, sincehere apparently only relatively short cable sections can bepulled out.

Therefore, the présent invention has as its object toprovide a method of the initially defined type, by whichexisting cables can be freed from their cable cores as quicklyand cost-effectively as possible so as to be able to use thecable sheath then présent as a tube for the laying of, e.g., newdata transmission cables, such as optic waveguides or the like,and, on the other hand, be able to re-use the raw materials ofthe cable core, in particular copper. The removal of the cablecore shall be possible over as long cable lengths as possible.

The object of the invention is achieved in that the flowablemedium is introduced precisely targeted into an annular spacebetween the inner side of the cable sheath and the envelope of 012591 r the cable core 012591 PREFERABLY, AT LEAST DURING PART OP THE STEP OF INTRODUCING THE FLOKASLEMEDIUMr THE ANNULAR SPACE OR THE ENTIRE CABLE IS NOT PRESSURE-SEALED AT THE OTHERCABLE END (THE SO-CALLED DISTAL CABLE END) SO THAT LIQUID MEDIUM UNDER THE ACTIONOF PRESSURE FLOWS SUBSTANTIALLY IN THE ANNULAR SPACE TO THE DISTAL CABLE END. THIS PARTIAL STEP THEREFORE KILL ALSO BE TERMED “FLOK STEP” IN THE FOLLOWING.

Preferably, at least during part of the step of introducingthe flowable medium, the annular space or the entire cable ispressure-sealed at the distal end so that the liquid mediumunder the action of pressure compresses the cable core and/orexpands the cable sheath. This partial step therefore will alsobe termed “compression step” in the following, wherein it must benoted that also during the flow step an (i.a. even higher)compression will occur.

Particularly preferably, i.n the scope of the présent method,both mentioned partial steps are carried out, i.e. at first theflow step and subsequently the compression step. Advantageously,the flow step will be terminated and the compression step willbe started when the flowable medium emerges at the distal cableend.

The flow step primarily serves to transport the flowablemedium through the entire cable. A doser look shows that herethe flowable medium mainly moves in longitudinally extendingdépréssions of the cable core, which are derived from the leadsstructure of the cable core. A wetting of the interface betweenenvelope and inner side of the cable sheath need not necessarilyoccur overthe entire periphèry, but only in smaller partialrégions of the periphery corresponding to the aforementioneddépréssions. In the subséquent compression step, however, thehigher lubricant pressure which builds up causes a (continuing)compression of the cable core (and, in cables with an elasticsheath, possibly also an expansion of the sheath), whereby theannular space will be widened over the entire periphery and bythis, the entire interface over the entire periphery will bewetted by lubricant.

In embodiments of the method in which the envelope of thecable core to be pulled out is designed as a winding, it hasproven to be particularly advantageous to use that cable end asthe proximal· cable end towards which the winding proceeds. Inother words, in this instance the flowable medium is to be movedforwards in the annular space in counter-direction to the 012591 5 winding direction. The precisely targeted introduction of theflowable medium into the annular space between the inner side ofthe cable sheath and the envelope will be assisted by the factthat the flowable medium is introduced against a possiblyprésent winding direction of the envelope of the leads. Oftenthe envelope of the leads of a cable consists of a strip, inparticular of paper, which is wound around the leads inoverlapping fashion. By introducing the flowable medium incounter-direction to the winding direction of this envelope, apénétration of the flowable medium into the interior of thecable core is effectively prevented. The method is facilitatedby the fact that the flowable medium is introduced at the sameend of the cable as that end of the- cable at which the cablecore is pulled out (i.e., at the proximal end). Thereby, most ofthe installations required for the method need only be providedat one end of the cable. At the opposite end of the cable (i.e.at the distal end), only the core sealing as well as a closureof the cable end are effected. If, however, a wound envelope ofthe core, e.g. in case of a helically arranged paper envelope,is présent, the extraction of the core in the winding directionwill be assisted, since the overlapped portions of the woundenvelope are not opened in fan-like manner. When pulling out thecore in the winding direction of the envelope, tearing open ofthe envelope will be prevented and the extraction procedure willnot be rendered more difficult. Alternatively, however, theflowable medium may also be introduced at the end of the cableother than that end of the cable at which the core is pulledout.

Besides, in such wound cable core envelopes, it has provenparticularly advantageous to pull out the cable core at thatcable end, towards which the winding proceeds, i.e. to allow thepulling movement to be effected in the winding direction. Inother words, it is particularly advantageous to use that cableend as the proximal end, towards which the winding proceeds, andnot only to effect the introduction of the flowable medium, butalso the extraction of the cable at this proximal end.

In a preferred embodiment, at least during part of the stepof introducing the flowable medium,'a compressed gas, inparticular compressed air, is introduced into the interior ofthe cable core surrounded by the envelope. In this manner, a 012591 6 force acting from the inside towards the outside onto theenvelope is effected, whereby the entry of the flowable mediuminto the cable core can effectively be prevented. In thismanner, a counter-pressure acting on the envelope from within isproduced against the flowable medium that is introduced underpressure, improving the sealing of the envelope towards itsinner side. Basically, this measure can be effected during theflow step and/or the compression step or parts thereof.Preferably, however, this measure will be taken only during thecompression step so as not to impede the spreading of theflowable medium in the longitudinal direction of the cableduring the flow step, on the one hand and to assist in a highpressure build-up during the compression step, on the otherhand. The pressure of the pressure gas is, i.a., markedly lowerthan that with which the flowable medium is introduced so as notto excessively impede both, the flow of the latter in thelongitudinal direction of the cable and the compression of thecable core.

In the aforementioned embodiments which hâve an envelopedesigned as a winding, e.g. a helically arranged paper envelope,it is, moreover, advantageous to allow the compressed gas,preferably the compressed air, to flow in the interior of thecable core in the winding direction of the envelope. Thisfavorably assiste in a sealing of the overlapped portions of thewinding and prevents tearing up of the overlapped portions ofthe envelope by the compressed air, which might resuit in a moredifficult extraction of the cable core from the cable tube.

It is advantageous to admix a liquid medium, in particularan adhesive, to the compressed gas, in particular to thecompressed air, which thereby is introduced into the interior ofthe cable core. Depending on the construction of the cable, theadmixture of a liquid medium to the compressed gas, orcompressed air, respectively, may lead to a kind of gluingtogether of the overlapped portions of the envelope, so thatpénétration of the flowable medium into the cable core will bemade even more difficult. To humidify the compressed gas, water,oil or certain adhesives may be used which are admixed to thepressurized gàs to a slight degree. Such additions shall notbuild up a hydraulic pressure, by which the annular space wouldbe reduced, but a mutual gluing together of the overlapping 012591 Γ - 7 - portions of the winding shall be attained. The volume defined bythe cable core shall still remain compressable so that aréduction of the volume will remain feasible by the introducedflowable medium and, consequently, an enlargement of the annularspace between the envelope and the inner side of the cablesheath can be attained. As the glue, component glues withretarded hardening which should be as low-viscous as possible,can be employed.

The precisely targeted introduction of the flowable mediuminto the annular space may advantageously be effected in thatthe interior of the cable core at the proximal cable end isclosed pressure-sealed relative to the flowable medium to beintroduced under pressure into the annular space, so thatflowable medium cannot penetrate into the interior of the cablecore at the proximal cable end. The flowable medium can then bepressed in at the end side of the cable; pressing in is,however, also possible through rearwardly offset radial bores inthe cable sheath.

If the distal cable end were simply to be closed withoutavoiding a communication between the open end of the annularspace and the open end of the interior of the cable core,flowable medium emerging from the annular space could enter intothe interior of the cable core and flow back therein to theproximal end. To prevent this, preferably the interior of thecable core also at the distal cable end is closed pressure-sealed relative to the annular space so that flowable mediumemerging from the annular space cannot enter there into theinterior of the cable core.

In both instances, the pressure-sealed closure of theinterior of the cable core relative to the annular space canadvantageously be achieved by sealing attachment of a core sealto the respective end of the cable core. The core sealing ispreferably effected by an elastic envelope which is applied overthe exposed leads. In doing so, a vulcanisation band may, e.g.,be used which causes an automatic gluing after its applicationand thus an impervious envelope of the leads.

If it shall be possible to introduce compressed air or tovent the interior of the cable core àt the respective end, thecore sealing preferably is equipped with a venting tube.

By the fact that the cable core, at least at the proximal 012591 r - » - cable end, is enveloped, flowable medium cannot enter into theinterior of the cable core at the front side thereof. Incontrast, the flowable medium is introduced precisely targetedinto the annular space between the inner side of the cablesheath and the envelope, whereby a force acts from the outsideon the cable core, which force will lead to the compression ofthe cable core, whereby the annular space is enlarged, acomplété wetting of the annular space is assisted and thefriction during the extraction is reduced. Thereby, greaterlengths of old cable can be freed from the cable core présenttherein in one procedure. The lengths obtainable will dépend,i.a. on the type and diameter of the cable, the number of leadsin the core, the pressure with which the flowable medium isintroduced, the flowable medium used as well as the course ofthe curves of the cable. By removing the core from the cables,the material thereof, mostly copper, can be re-used, or theempty cable tube formed thereby may be used for laying newwires, e.g.. In addition, environmental risks posed by the oldcable are reduced.

The flowable medium preferably is introduced into the cabletube before the cable core is pulled out.

In addition, the flowable medium may also be introduced intothe cable while the cable core is being pulled out.

If the cable core is equipped at both ends of the cable witha core sealing before the flowable medium is introduced, anentry of the flowable medium can also be prevented at the distalcable end.

To check the tightness and the permeability of the cable,compressed air can be introduced into the interior of the cablecore before the flowable medium is introduced. To check thetightness, the pressure on the side of introduction of thecompressed air is measured while the compressed air is beingintroduced. From the measured pressure values, a pressure losswhich is caused by a leaking site of the cable can be determined. In such an instance, the cable can be eut apart infront of the leaking site, and the procedure for removing thecore from the cable can be carried out for the new cable piece.

To check the permeability of the cable, the pressure ismeasured on the side other than that of the introduction of thecompressed air, while the compressed air is being introduced. In 01259 1 ( 9 this manner, possible squeezed locations of the cable can befound. If, due to a very pronounced squeezing, for once anextraction were no longer possible, the cable can be eut off infront of this squeezed location and then the method for removingthe core can be carried out for the new cable piece.

During the introduction of the flowable medium, the distalend preferably is open so that the air displaced by the flowablemedium can escape.

While the flowable medium is being introduced, the cablecore preferably is tensioned so as to prevent an axialdisplacement of the latter during the introduction of theflowable medium. This bias may, e.g., be effected via a tubewhich serves to introduce the compressed air into the cablecore, the tube being glued together with the leads of the cablecore and a tensile force of a certain extent being exerted onthe tube.

Introduction of the flowable medium is preferablyinterrupted if the latter emerges at the other end of the cable.In this manner, the amount of the flowable medium is limited tothe volume required.

According to a further embodiment, it is provided that afterthe introduction of the flowable medium, the two ends of thecable are closed in an air-tight and pressure-sealed manner, thecable is provided with a venting tube and that furthermore apressure is exerted on the flowable medium. By this method step,due to the compression already occurring in the flow step,airprésent in the interior of the cable core is pressed out throughthe venting tube, whereby the diameter of the cable core isreduced and thus a wetting of the annular space and, thereby, anextraction of the core is substantially facilitated. In thecompression step, on the other hand, it is rather advantageousnot to permit venting of the cable core and even to introducecompressed air into the latter, since here the amount of the airvolume to be displaced is relatively small.

To prevent the cable core from rotating during theextraction procedure and thus, from possibly enlarging itsdiameter, the cable core preferably is secured against rotation during theextraction procedure. This may be effected e.g. by cantileveringmeans on a commonly used collar, via which the cable core is 012591 Ç - ίο - pulled out of the cable tube, the cantïlevering means preventinga rotation of the core.

Alternatively, during the extraction procedure, the corepreferably could also be rotated into a possibly existinghelical direction of the leads présent in the cable core, sinceby this the diameter of the core will be reduced and thus aneffect blocking the extraction procedure will not occur.

To allow for a further use of the flowable medium followingthe extraction procedure, it is provided that at that end of thecable at which the cable core is being pulled out, the flowablemedium is stripped off and collected. Stripping off is effectedin a simple manner, e.g. by an elastic ring which grazes on theenvelope and thus strips off the flowable medium, whereupon itflows into a collecting funnel, e.g., and from there onwardsinto a container.

To be able to re-use a particularly large portion of theflowable medium, it is provided that at the distal end of thecable, during the extraction procedure of the core, the flowablemedium is entrained by the cable. This may be effected e.g. bymeans of a piston-like element connected to the end of the core,which element transports the flowable medium through the cablesheath to the proximal end of the cable, where, as mentionedabove, it is collected by a collecting funnel, e.g., and isguided onwards into a container.

To prevent a damage of the cable sheath during theextraction procedure, the cable sheath preferably is securedagainst rotation at that end at which the cable core is pulledout. This securing against rotation may, e.g. be effected by acollar with cantïlevering means présent therein.

The procedure for removing the core from the sheath may beassisted in that during the extraction of the core, a pressureforce is exerted on the distal end of the core. In this manner,the tensile force can be reduced to a slight extent, thusreducing the risk of the core being torn. Moreover, the lengthof the cable which can be reached, which can be freed from itscore in one procedure, can be increased by assisting theextraction procedure.

The supporting pressure force may be applied via a flowablemedium introduced under pressure to the end of the cable otherthan that from which the core is pulled out. In this instance, 012591 11 however, a relatively large amount of flowable medium isrequired.

According to a further embodiment, the tensile force istransmitted to the core via a clamp which is fastened to thecore. This constitutes a simple method for carrying out themethod according to the invention.

Just as well, the tensile force can be applied to the corevia a motor-driven shaft around which the core is wound severaltimes. In this instance, a sufficient length of the core isexposed and wound several times about the motor-driven shaft,drum or the like, resulting in a sufficient friction so that. therotating movement of the shaft, drum or the like can betransmitted as a tensile force on the core.

To further facilitate extraction of the core, and to obtainlarger lengths of the core to be extracted, according to afurther feature of the method, the introduced gas and/or theintroduced liquid may contain an admixed lubricant, or theflowable medium itself may be formed by a lubricant. Thelubricant may be provided in liquid or solid form. When using agas introduced into the cable under pressure, the introductionof a powderized lubricant has proven suitable.

If a thixotropic liquid is used as the lubricant, theundesired entry of the flowable medium into the core canadditionally be prevented or reduced, respectively. Thixotropicliquids hâve a viscosity that is dépendent on the shearingstress, whereby depositing of the flowable medium can beprevented. Thixotropic properties are to be found e.g. inpotassium soaps or oils with certain admixtures. Besides thethixotropic properties, the lubricants or the liquid media,respectively, should be as inexpensive as possible and, ideally,also biologically degradable.

The changing of old cores for e.g., optical datatransmission cables can be further facilitated and acceleratedif at least one new cable or the like is pulled into the cabletube while the core is being pulled out.

The présent invention will be explained by more detail byway of embodiments and figures illustrating the same. Therein,

Fig. 1 shows the usé of one embodiment of the methodaccording to the invention at an underground cable, seen in sideview; 012591 12

Fig. 2a shows the end of the cable according to detail II inFig. 1 during a first method step;

Fig. 2b shows the end of the cable during the introductionof the flowable medium;

Fig. 2c shows the end of the cable according to detail II ofFig. 1 before the pulling out or extraction of the core isstarted;

Fig. 2d shows a side view onto the end of the cableaccording to Fig. 2c;

Fig. 3a shows the other end of the cable according to detailIII of Fig. 1 at the point of time of the method shown in Fig. 2a;

Fig. 3b shows the end of the cable according to detail IIIof Fig. 1 during the introduction of the flowable medium;

Fig. 3c shows the end of the cable according to detail IIIof Fig. 1 before the core is pulled out;

Fig. 4 shows a perspective view of a clip for pulling outthe core with a means for protecting the core from beingrotated;

Fig. 5 shows a longitudinal section through a cable with awound convoluted covering.

Fig. 1 shows a cable 1 as has been used, or is still beingused, respectively, e.g. in télécommunication, which usually islaid in the ground 2. To employ the method according to theinvention, the cable 1 is exposed and severed at a certainlocation, the so-called starting pit 3. At a certain distancefrom the starting pit 3, e.g. 100 or 200m, a so-called targetpit 4 is made, and the cable 1 is also exposed and severed.

Thus, there results a piece of cable 1 of a certain length withan end 5 located in the starting pit 3 as well as with an end 6located in the target pit 4.

By way of Figs. 2a to 2d, and 3a to 3c, respectively, whichshow details II and III, respectively, of Fig. 1 in enlargedillustrations during different method steps, an embodiment ofthe method according to the invention will be explained in moredetail in the following. Usually the cable comprises a pluralityof leads 7 made of massive copper or of copper strands and aleads insulation, e.g/ made of pàper or of a synthetic material.Moreover, groups of leads 7 may be surrounded by furtherinsulations made of paper or synthetic material. Finally, the 012591 ( - 13 - entirety of the leads 7 is surrounded by an envelope 8,preferably made of paper or synthetic material. The leads Ί, theenvelope 8 and optionally additional, further inwardly locatedenvelopes, longitudinal fibers etc. together form the cablecore. To protect the cable core from external mechanical andChemical influences, an inner sheath 9 is arranged which mayconsist of lead (Pb). Usually a further sheath layer 10, mostlyof steel, in particular of a helically applied Steel sheet, isarranged over the inner sheath 9, which sheath layer 10additionally protects the cable 1 from mechanical influences.Externally on the steel layer 10, a further insulation 11, e.g.of oil-soaked fabric or synthetic material, may be providedwhich protects the steel sheath 10 from environmentalinfluences. Ail together, the sheath layers 9 to 11 form thecable sheath. The cable core with its envelope 8 contacts theinterior of the cable sheath substantially over its entireperiphery, the cable sheath partially even encloses the cablecore with a certain tension. By the “annular space” between cablecore and cable sheath thus a space located between twointerfaces (the outside of the cable core and the inside of thecable sheath) is to be understood, wherein the radial extensionof the annular space may be as small as desired because of thedirect contact of the interfaces. The end of the cable 1 in thestarting pit 3 constitutes the so-called proximal cable end 5,the end of the cable 1 in the target pit 4, on the other hand,constitutes the so-called distal cable end 6. At the end of themethod described in the following, a tensile force is applied tothe cable core at the proximal cable end 5 in the starting pit 3for extracting the cable core.

To start the method, the proximal cable end 5 from which thecore is to be pulled out, is peeled by removing the cablesheath, i.e. the insulation 11, the steel sheath 10 as well asthe lead (Pb) sheath 9, over a certain length, so that the cablecore, i.e. the leads 7 and the envelope 8 project from the cable1 for a certain length. As the following method step which ismore clearly visible in Fig. 2a, an aerating and venting tube 12is inserted into the cable core and there preferably is gluedtogether with the latter. Subsequently, the end of the cablecore plus its envelope 8 is enveloped by a core seal 13, e.g. aself-vulcanising rubber band, resulting in a preferably air- 012591 14 tight and pressure-sealed closure of the cable core at theproximal cable end 5. A vulcanisation band has the advantagethat the latter will automatically glue to the envelope 8 and tothe aerating and venting tube 12, respectively, whereby a tight -closure can be realised. Subsequently, a sleeve 14 made ofmétal, e.g., is pushed over the proximal cable end 5. The sleeve14 may be provided with a bore 15 via which glue can be pressedin so that the annular space between the inner side of sleeve 14and the outer side of the cable sheath is filled with the glueand a reliable connection of the sleeve 14 with the cable sheathis obtained. As glue, e.g. a two-component glue may be usedwhich causes a rapid and reliable .connection. The sleeve 14serves to stabilize' and secure the cable sheath to avoid damageby excessive axial forces when inserting the flowable mediumunder pressure, and during the later extraction of the cablecore from the cable sheath, respectively.

According to Fig. 3a, the distal cable end 6 in target pit 4just as the proximal cable end 5 are eut off, peeled, providedwith an aerating and venting tube 12 and, finally, the cablecore is provided with a core sealing 13. Finally, also a sleeve14 is laid around the cable sheath and glued together with thelatter.

In other (not illustrated) embodiments, no aerating andventing tube is arranged at the proximal cable end 5. Yet alsothere the core sealing 13 closes the interior of the cable corepressure-sealed against the entry of flowable medium.

According to Fig. 2b, finally, at the proximal cable end 5of cable 1, a lid 17 is arranged over sleeve 14 and tightlyconnected with the former. This connection preferably iseffected via a thread 18 at the outer side of sleeve 14 to whichthe lid 17 is screwed. If necessary, additional sealing materialmay be used. The lid 17 optionally has an opening 19 in themiddle of its end side, through which the aerating and ventingtube 12 can be put. On the sheath of the cylindrical part of lid17, a further opening 20 is provided via which the feed line 21for the flowable medium or lubricant 22, respectively, isconnected. As is schematically visible in Fig. 1, the feed line21 is connected to a pump 23 which in turn is connected to acontainer 24 for the lubricant 22. In case of an envelope 8helically wound around the leads 7, the flowable medium or 012591 C - 15 - lubricant 22, respectively, is preferably introduced in counter-direction to the winding direction of envelope 8 (to define thewinding direction: cf. Fig. 5), so that there is a tendency forthe overlapping portions of the winding to be closed by the flowdirection of the lubricant 22, whereby an entry of the flowablemedium or lubricant 22 from the annular space into the cablecore is reduced. In case of a wound envelope 8, the cable core,moreover, preferably is pulled out in the winding direction,because in this way the overlapping portions of the envelope 8will not be opened like a fan during the extraction process andwill not straddle against the extraction movement.

The flowable medium or lubricant 22, respectively,preferably has a lower density than the volume enclosed by theenvelope 8. As has already been mentioned, gaseous, liquid orpasty media or mixed forms thereof are used as the flowablemedium. The aerating and venting tube 12 is fixed with the lid17 via appropriate union nuts 27, wherein a tensile force can beexerted on the aerating and venting tube 12 prior to fixing sothat the core will be pre-stressed. Instead of being provided inlid 17, the opening 20 in theory can also be provided in sleeve14 or in a corresponding extension of sleeve 14, and from therealso the lubricant 22 can be introduced. However, sleeve 14 isdesigned as an expendable part, and therefore also thestructural means preferably are arranged on lid 17 which can beused several times. When the cable core has been removed fromcable 1, sleeve 14 may serve as connecting piece for re-connecting the cable pièces, if cable 1 again is being used as atube for an optical waveguide, e.g., or the like.

As can be seen from Fig. 3b for the distal cable end 6, alsothere a lid 17 is arranged over the cable end 6, and theaerating and venting tube 12 is fixed to the lid 17 bycorresponding union nuts 24. Opening 20 on lid 17 and theaerating and venting tube 12 at first are kept clear. Ifcompressed air is to be admitted to the interior of the cablecore, the aerating and venting tube 12 may be connected via aduct 25 to a compressor 26 for producing the compressed air(Fig. 1).

Before carrying oüt the method proper, compressed air can beblown into the interior of the cable core via the aerating andventing tube 12, and the pressure can be monitored at the other 012591 C - 16 - end of the cable with the help of a manometer 28. By thismeasurement, the cable 1 is checked for it permeability. Withthe assistance of the pressure gauge usually provided on thecompressed air compressor or on a compressed air connection 25,it can furthermore be checked whether or not cable 1 is tight,since a possible site of a break could be located by aninsufficient pressure increase. When the cable has been checkedfor its tightness and permeability, finally, the end of theaerating and venting tube 12 will be closed (not illustrated) atthe proximal cable end 5, e.g. by means of a rotatable closingmeans which is screwed onto the aerating and venting tube 12..

Now the method as such will start, i.e. the so-called flowstep. For this purpose, via feed line 21 lubricant 22 isintroduced under pressure via opening 20, the annular gap at thedistal cable end 6 being open. The lubricant 22 enters theannular space between the lead (Pb) sheath 9 and the envelope 8precisely targeted and there flows in the longitudinal directionof the cable to the distal cable end 6, without the risk of thelubricant 22 penetrating into the câble core. Compressed air mayalready be admitted to the interior of the cable core during theflow step. Preferably, in case of a wound around envelope 7, thecompressed air will be introduced from the distal cable end 6,so that there will be a tendency of the flow of compressed airclosing the overlapped portions of the winding, instead ofopening them in fan-like manner. The pressure within the cablecore presses the overlapped portions onto each other and thusmakes it difficult for the lubricant 22 to penetrate into theinterior of the cable core. By adding a liquid medium to theintroduced compressed air, the overlapped portions of theenvelope 8 can be caused to glue together. The liquid medium maybe water, oil, or certain adhesives admixed to a particularlyslight degree to the compressed air. Finally, the lubricant 22makes its way through the annular space between the lead (Pb)sheath 9 and the envelope 8 as far as to the distal cable end 6.As soon as the lubricant 22 emerges from the opening 20 on lid17 at the distal cable end 6, the annular space at the distalcable end 6 is sealed, this being done by closing the opening20. Now the so-called compression step.will start. The continuedpressing in of the lubricant now does not mainly serve totransport the lubricant 22 through the annular space along cable 012591 17 1 (naturally resulting already in a compression of the cablecore), but it serves to build up pressure in the annular space,since the distal end of the annular space has now been closed.Whereas in the preceding flow step the lubricant 22 preferably ·only has moved along in longitudinal dépréssions of the envelope8 (caused by the leads structure of the cable core) andtherefore has not wetted the interface between envelope 8 andthe inner side of the cable sheath over its entire periphery,there is now a (continuing) compression of the cable core (andpossibly, an expansion of the cable sheath, if the latter is notcompletely rigid), whereby the lubricant 22 now will wet the.said interface over its entire periphery. When a sufficientpressure has been built up, the press-in procedure of thelubricant will be stopped. The pressure application on lubricant22 will be terminated when the pressure remains substantiallystable and a further compression of the cable core is no longerpossible. The lubricant 22 can be admixed to the flowablemedium, or the flowable medium itself can be formed by thelubricant 22. The pressure applied to the lubricant 22 willdépend on the structure of cable 1, the length of cable 1 aswell as on various other factors. Finally, also flowable mediaare suitable, in which the lubricant is combined with a solventthat evaporates after some time. This facilitâtes the introduction of the liquid medium by dilution with the solvent,and finally, after évaporation of the solvent, there results animproved sliding action on account of the more viscous lubricantremaining.

Finally, according to Fig. 2c, the lid 17 is screwed off theproximal cable end 5, and the aerating and venting tube 12 isremoved. Subsequently, a stripping means 29 for the lubricant 22is fastened over the proximal cable end 5, which may be donee.g. by utilizing the thread 18 on sleeve 14. The strippingmeans 29 may be substantially annularly designed and hâve anelastic edge grazing on the envelope 8 so that the lubricant 22is stripped off the envelope 8 when the cable core is pulled outand will flow downwards on account of gravity, where it can becollected by an appropriate funnel and an appropriate container(not illustrated) and re-used to a great ext'eht. Finally, aclamp.30 is tightly connected over the core sealing 13, and atensile force in the direction of arrow F is exerted on this 012591 18 clamp 30.

At the distal end 6 of cable 1, the lid 17 is also removed.With the core sealing 13 at the distal cable end 6, one or morepiston-like éléments, e.g. dises 32 maintained in spacedrelationship by spacer éléments 31 can be arranged which entrainthe lubricant 22 when the cable core is pulled out of cable 1 sothat the lubricant emerges at the end 5 of cable 1 and isstripped off by the stripping means 29, where it can becollected and re-used. During the extraction of the cable corefrom the cable sheath, it is suitable to secure the cable coreagainst rotation. This can be effected in various ways, e.g. byarms 33 or cantilevering means which are fastened to the clamp30 and thus make a rotation impossible. In addition, slidingskids 34 can be fastened to the arms 33, which skids will slideon the ground while the core is being extracted (cf. Fig. 4).Furthermore, it is suitable also to secure cable 1 againstrotation, which can be realized by arms or cantilevering meansarranged on the sleeve 14 in a similar manner as illustrated inFig. 4. Simultaneously with the extraction of the cable core, anew cable, e.g. a modem optical waveguide or the like, can beconnected to the end of the cable core at the distal end 6 andthus can be pulled into the cable sheath that now forms a tube,simultaneously with the pulling-out procedure.

To avoid a damage to the envelope 8 at the proximal cableend 5, the cable core preferably is pulled out of the cablesheath straight over a certain length, before an intentionalchange of direction is made,'e.g. so as to get the cable corefrom the starting pit 3 onto an appropriate reeling means (notillustrated).

Fig. 5 illustrâtes the définition of the “winding direction”of the envelope 8 by way of a longitudinal section. When a stripis wound around the bundle of leads 7, there resuit scale-likeoverlaps in longitudinal section, wherein always the first laidwinding is partially covered by’ the subséquent winding. Thewinding direction extends along the cable 1 and is thatdirection in which the winding proceeds while it is being made.In Fig. 5, the winding direction is indicated by arrow W. The -preferred direction for introducing thé lubricant is in counter-direction to the direction of arrow W so that the overlappingportions of the strip-type envelope 8 will be closed by the flow c 19 012591 of the lubricant. The preferred direction for introducing thecompressed air into the interior of the cable core surrounded bythe envelope 8 is in the winding direction, in the direction ofarrow W, since by this the overlaps of the strip-shaped envelope8 will be rather closed than opened. Finally, the preferreddirection for pulling out the cable core again is in thedirection of the arrow W of the winding, since by this theoverlapping portions of the strip-shaped envelope 8 will beclosed during the extraction movement.

The Figures only show an exemplary embodiment of theinvention. Structural changes and différences in the methodcoursé are possible within the scope of the daims.

Claims

012591 r 20 Claims:

1. A method for removing a cable core from a cable sheath of acable, which cable core comprises an envelope, wherein, at anend of the cable - the so-called proximal cable end - a flowablemedium is introduced under pressure into the cable tube so as toreduce friction, and a tensile force is exerted on the cablecore at an end of the cable, characterised in that the flowablemedium is introduced precisely targeted into an annular spacebetween the inner side of the cable sheath and the envelope ofthe cable core.
2. A method according to claim 1, characterised in that atleast'during part of the step of introducing the flowablemedium, the annular space or the entire cable is not pressure-sealed at the distal cable end, so that liquid medium under theaction of pressure flows substantially in the annular space tothe distal cable end, whereby a so-called flow step is formed.
3. A method according to claim 1 or 2, characterised in thatat least during part of the step of introducing the flowablemedium, the annular space or the entire cable is pressure-sealedat the distal end so that the liquid medium under the action ofpressure compresses the cable core and/or expands the cablesheath, whereby a so-called compression step is formed.
4. A method according to claim 2 or 3, characterised in thatat first the flow step and subsequently the compression step iscarried out.
5. A method according to claim 4, characterised in that afterthe emergence of the flowable medium at the distal cable end,the flow step is terminated and the compression step is started.
6. A method according to any,one of claims 1 to 5, characterised in that in a cable in which the envelope of thecable core is designed as a winding, that cable end is used asthe proximal cable end towards which the winding proceeds, sothat the flowable medium is moved forwards in the annular spacein counter-direction to the winding direction. 012591 ç 21
7. A method according to any one of daims 1 to 6, characterised in that in a cable in which the envelope of thecable core is designed as a winding, the cable core is pulledout at that cable end towards which the winding proceeds, i.e.that the pulling movement is effected in the winding direction.
8. A method according to any one of daims 1 to 7, characterised in that at least during part of the step of theintroduction of the flowable medium, in particular during acompression step, a compressed gas, in particular compressedair, is introduced into the interior of the cable coresurrounded by the envelope,. whereby a counter-pressure acting onthe envelope from within is produced against the flowable mediumthat is introduced under press.ure.
9. A method according to daim 8, characterised in that in acable in which the envelope of the cable core is designed as awinding, the compressed gas is introduced at that cable end fromwhich the winding extends so that the compressed gas flows inthe interior of the cable core in the winding direction.
10. A method according to daim 8 or 9, characterised in thata liquid medium, in particular an adhesive, is admixed to thecompressed gas and thus is introduced into the interior of thecable core.
11. A method according to any one of daims 1 to 10, characterised in that the interior of the cable core at theproximal cable end is closed pressure-sealed relative to theflowable medium to be introduced under pressure into the annularspace, so that flowable medium cannot penetrate into theinterior of the cable core at the proximal cable end.
12. A method according to any one of daims 1 to 11, characterised in that the interior of the cable core at thedistal cable end is closed pressure-sealed relative to theannular space so that at the distal cable'end flowable mediumemerging from the annular space cannot enter into the interiorof the cable core. 012591 22
13. A method according to daim 11 or 12, characterised inthat the pressure-sealed closure of the interior of the cablecore relative to the annular space is achieved by sealing byattaching a core sealing to the end of the cable core.
14. A method according to claim 13, characterised in that thecore sealing is equipped with a venting tube for venting theinterior of the cable core.
15.. A method according to any one of daims 1 to 14, characterised in that the flowable medium is introduced into thecable tube before the core is pulled out-.
16. A method according to claim 15, characterised in that theflowable medium is introduced into the cable while the cablecore is being pulled out.
17. A method according to any one of daims 1 to 16, characterised in that the interior of the cable core at bothends of the cable is closed in a pressure-sealed manner relativeto the annular space before the flowable medium is introduced.
18. A method according to any one of daims 1 to 17, characterised in that the tightness of the cable is checked withcompressed air before the flowable medium is introduced.
19. A method according to any one of daims 1 to 18, characterised in that the permeability of the cable is checkedwith compressed air before the flowable medium is introduced.
20. A method according to any one of daims 1 to 19, characterised in that the cable core is tensioned while theflowable medium is being introduced.
21. A method according to any one of daims 1 to 20, characterised in that the cable core is secured against rotationduring the extraction procedure.
22. A method according to any one of daims 1 to 21, 012591 - 23 - characterised in that during the extraction procedure, the cablecore preferably is rotated into a possibly existing helicaldirection of wires présent in the cable core.
23. A method according to any one of daims 1 to 22, characterised in that at that end of the cable at which thecable core is being pulled out, the flowable medium is strippedoff during the pull-out procedure and collected.
24. A method according to any one of daims 1 to 23, characterised in that at the other end of the cable than thatend at which the cable core is being pulled out, the flowablemedium is entrained by the cable core during the extractionprocedure, e.g. by a piston-like element connected to the end ofthe cable core.
25. A method according to any one of daims 1 to 24, characterised in that during the extraction procedure, the cablesheath is secured against rotation at that end at which thecable core is pulled out.
26. A method according to any one of daims 1 to 25, characterised in that during the extraction procedure, to assistthe extraction of the cable core, a pressure force is exerted onthat end of the cable core which faces away from the pullingside.
27. A method according to daim 26, characterised in that thepressure force is applied via a flowable pressing-out mediumintroduced under pressure to the end of the cable core thatfaces away from the pull side.
28. A method according to any one of daims 1 to 27, characterised in that the pulling force is transmitted to thecable core via a clamp which is fastened to the cable core.
29. A method according to any one of daims 1 to 28, characterised in that the pulling force is applied to the cablecore via a motor-driven shaft about which the cable core iswound several times. 012591 24
30. A method according to any one of daims 1 to 29, characterised in that the introduced, flowable medium containsan admixed lubricant.
31. A method according to any one of daims 1 to 30, characterised in that the flowable medium itself is formed by alubricant.
32. A method according to daim 30 or 31, characterised inthat the lubricant is formed by a thixotropic liquid.
33. A method according to any one of daims 1 to 32, characterised in that at least one new cable or the like ispulled into the cable sheath simultaneously-with the extractionof the core.