Field of the invention

The present invention relates to a method for removal of a cable core out of a cable sheath. Also, the invention relates to a system for performing such a method.

Background

In recent years, the constant advances in technology, the proliferation on the internet and the constant demand for faster data transfer speeds, lower latency, and greater reliability have forged the requirement for network upgrades. The migration from traditional copper based networks to fiber optical alternatives in

telecommunications and data networks left many telecommunication cables based upon a copper core unused. Different approaches are known for removal of these cables or cable cores due to the importance of recycling or fiber upgrade.

When these cables are located in an underground environment a conventional way to remove them would be to dig out the cable, if the purpose is purely for copper recovery, or either dig out and replace with fiber in an upgrade scenario. Since we are speaking of very long conduits of cable this would be a time- consuming and expensive operation.

In the prior art, many methods for removal of a cable core from a cable sheath are known. From methods that just apply pushing and pulling on a cable core to methods that introduce a flow medium and then apply a tensile force.

A method for removal of a cable core is known from WO 2011/037445 that discloses a method that comprises an introduction of a flow medium into the cable sheath to reduce friction and pulling at least a fraction of the core out from the sheath.

A method for removal of a cable core is known from WO 02/067397 that discloses a method which comprises an introduction of a flowing medium under pressure into the cable to reduce friction and a step of exerting a tension force at the other end of the cable. The medium is only introduced into the space between the sheath and the casing of the cable core. These conditions make it difficult to apply this method over longer lengths of cable. A method for removal of a cable core is known from WO 82/00388 that discloses a method that comprises an introduction of a flow medium into the cable sheath to at least partially dissolve the internal insulation and thereafter apply a force to draw the conductors from the cable.

The object of the present invention is to overcome the disadvantages from the prior art.

Summary of the invention

The object is achieved by a method which comprises an introduction of a rehydration liquid after the dissolution reaction process has been done. The introduction is at the same time or starts a predetermined time before the step of the drawing of the conductors from the cable sheath.

This step has the effect that the dissolved reaction product is rehydrated which improves its lubricating properties. Additionally the introduction of a rehydration liquid allows the reaction product to flow along with the conductors. In such a flow simultaneously with the movement of the conductors, the dissolved and rehydrated reaction product can provide additional lubrication.

As an advantage the method allows to extract longer lengths of the cable at the same time and have the ability to work on wet and damaged cables.

The present invention relates to a method for removing a cable core from a cable sheath comprising a cable having a cable sheath and a cable core between an introduction end and an extraction end, in which the cable core comprises a core wrapping and a bundle of conductors; a liquid compound is introduced in the cable at the introduction end, the liquid component being an agent that reacts with the core wrapping; holding the liquid compound (L) inside the cable during a predetermined reaction time, in which the core wrapping (3) releases a lubricant; after the reaction time ends, the inside of the cable is flushed with a rehydration liquid introduced at the introduction end of the cable and the cable core is removed from the cable sheath at the extraction end.

Advantageously, the method provides an improved extraction of the cable core from the cable sheath. Moreover, the method according to the present invention is applicable to cables buried underground or installed in a ducted environment. According to an embodiment, the present invention relates to the method as described above, wherein an end cap is placed on the extraction end of the cable before or during the introduction of the liquid compound.

According to an embodiment, the present invention relates to the method as described above, wherein the end cap is only placed when the liquid compound has reached the extraction end of the cable.

According to an embodiment, the present invention relates to the method as described above, wherein the core wrapping consists of paper or a paper compound, or a paper based material.

According to an embodiment, the present invention relates to the method as described above, wherein the wrapping of the conductors consists of paper or a paper compound or a paper based material.

According to an embodiment, the present invention relates to the method as described above, wherein the liquid compound is pumped under pressure into the cable core.

According to an embodiment, the present invention relates to the method as described above, wherein the rehydration liquid is pumped under pressure into the cable core.

According to an embodiment, the present invention relates to the method as described above, wherein the rehydration liquid is an aqueous liquid, preferably water.

According to an embodiment, the present invention relates to the method as described above, wherein the cable core is removed from the cable sheath by exerting a tensile force on the cable core.

According to an embodiment, the present invention relates to the method as described above, wherein the tensile force is exerted on the extraction end of the cable core.

According to an embodiment, the present invention relates to the method as described above, wherein, in principle, the tensile force is exerted in a longitudinal direction of the cable.

According to an embodiment, the present invention relates to the method as described above, wherein the tensile force is initiated prior to the introduction of the rehydration liquid and maintained thereafter during extraction. According to an embodiment, the present invention relates to the method as described above, wherein the tensile force is initiated simultaneously with the introduction of the rehydration liquid and maintained thereafter during extraction.

According to an embodiment, the present invention relates to the method as described above, wherein the tensile force is initiated after the introduction of the rehydration liquid and maintained thereafter during extraction.

According to an embodiment, the present invention relates to the method as described above, wherein a time delay exists between the introduction of the rehydration liquid and the initiation of the tensile force.

The time delay can be selected as minimally about a second.

Moreover, the present invention relates to a system for removing a cable core from a cable sheath according to a method as described above comprising a liquid compound pump for supplying a liquid compound into the cable at an introduction end of the cable, a rehydration liquid source for supplying a rehydration liquid into the cable at the introduction end of the cable and an actuation device for generating a tensile force on the cable core on an extraction end of the cable.

According to an embodiment, the present invention relates to the system as described above, wherein the actuation device comprises a winch.

According to an embodiment, the present invention relates to the system as described above, wherein the rehydration liquid source is pressurized by a pump.

According to an embodiment, the present invention relates to the system as described above, wherein the actuation device comprises a rope, preferably a metal rope, coupled to the cable core at the extraction end of the cable.

According to an embodiment, the present invention relates to the system as described above, wherein the actuation device comprises a roller structure for guiding the rope between the cable core at the extraction end and the winch.

Advantageous embodiments are further defined by the dependent claims.

Brief description of drawings

The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. They are intended exclusively for illustrative purposes and not to restrict the inventive concept, which is defined by the appended claims. Figure la shows a cross-sectional view of a cable during a first step of a method in accordance with an embodiment of the invention;

Figure lb shows a cable core during a second step of a method in accordance with an embodiment of the invention;

Figure 2 shows a schematic view of a system according to a first step of a method in accordance with an embodiment of the invention;

Figure 3 a shows a schematic view of a system according to a second step of a method in accordance with an embodiment of the invention;

Figure 3b shows a schematic view of a system according to a second step of a method in accordance with an embodiment of the invention;

Figure 4 shows a system according to an embodiment of the invention.

Detailed description of embodiments

Figure la shows a cross-sectional view of an electrical cable, for example for telecommunication applications. The electrical cable has a first and second end, hereafter respectively referred to as 'introduction end' 10a and 'extraction end' 10b. The introduction end 10a and the extraction end 10b can be chosen

independent of the wrapping direction of the core wrapping 3.

The electrical cable further comprises a cable sheath 1 and a cable core 2. The cable core 2 comprises a core wrapping 3 and a bundle of conductors 4 each one covered by a wrapping 5. The core wrapping 3 is located around the bundle of conductors 4. Typically in telecommunication applications the core wrapping 3 of the cable consists of paper or a paper compound or a paper based material.

The method aims to remove the bundle of conductors 4 from the cable sheath 1. In a first step of a method in accordance with an embodiment of the invention, the interior of the cable is soaked with a liquid compound L. The liquid compound L is introduced at the introduction end 10a into the cable core 2 to react with the core wrapping 3, and optionally with the wrapping of the conductors 5. In this reaction process the liquid compound L reacts with the paper of the core wrapping 3 and forms a paper reaction product 3a. The liquid compound L will only break down the paper very slightly, but release as reaction product one or more (natural) lubricants, such as Lignin and Cellulose from the paper. According to an embodiment of the invention, the liquid compound is based on an acetate solution in water. The liquid compound may comprise about 80-90 %wt water and about 10-20 %wt acetic acid (concentration about 5 - 10 % in water).

According to an alternative embodiment, the liquid compound is based on an hydroxide solution in water. The liquid compound may comprise about 95-99 %wt water and about 1-5 %wt solid sodium hydroxide.

According to yet a further embodiment, the liquid compound L comprises a mixture of acetic acid and sodium hydroxide in water. The liquid compound may comprise about 80-82 %wt water, about 14-18 %wt acetic acid (concentration about 5-10 % in water) and as remainder about 1-4 %wt sodium hydroxide (solid).

Alternatively, the liquid compound L is based on a liquid comprising enzymes that are capable of breaking down the paper wrapping of the core, i.e., that catalyze a reaction to break down the paper wrapping of the core. The liquid compound L may comprise up to about 80 %wt- about 90 %wt water and about 10 %wt enzymes. Optionally, the liquid compound L may comprise other components or additives such as an acidic or alkaline component or a lubricating supplement.

In an embodiment, the core wrapping 3 of the cable may consist of or may comprise a cellophane, a jelly or a foam or a plastic material such as polypropylene or polyethylene. According to the invention , the composition of the liquid compound L allows to break down such cable core wrappings material made out of cellophane, jelly or a foam or plastic into washable reaction products by using specific components that react with such cable core wrappings material. The person skilled in the art will realize that such components may comprise enzymes that catalyze a reaction to break down cellophane, jelly or foam or plastic.

Figure lb shows a cable core 2 during a second step of a method in accordance with an embodiment of the invention. In the second step, after a predetermined time chosen normally 0.5-24 h after the first step, a rehydration liquid FFis pumped under pressure into the cable, i.e. between the cable sheath 1 and the bundle of conductors 4 but also in-between the conductors. Other ranges for the predetermined time are also possible up to a few days. The introduction of the rehydration liquid FFis essential in that it mixes with the lubricants from the paper out of the reaction step, rehydrates them which enhances the lubrication properties and increases the volume of the lubricants. Besides this the flow of rehydration liquid provides a pressure for at least assisting the extraction of the cable core 2 out of the cable sheath 1. During or after the rehydration liquid Wis introduced, a tensile force F is applied on the extraction end 10b. The rehydration liquid W is typically water-based.

Figure 2 shows a schematic view of a system, for removing the cable core 2 from the cable sheath 1, according to the first step of a method. The system for removal of the cable core 2 comprises a reaction liquid pump 6, an input connector 9 and an end cap 11.

The input connector 9 is arranged to connect the introduction end 10a, via a conduit 8, to the reaction liquid pump 6.

Once the input connector 9 has been attached to the cable, and the reaction liquid pump 6 has been connected to the input connector 9 the liquid compound L enters into and around the cable core 2. The end cap 11 is arranged to hinder outflow of the liquid compound L, and to enable the monitoring of the fluid level, ensuring saturation of the cable core whilst minimizing fluid spillage at the extraction end 10b. The end cap 11 can be attached on the cable prior to pumping commences, or it can be attached during pumping.

Then the liquid compound L is pumped under pressure into the cable core 2 over substantially the length between the introduction 10a end and extraction end 10b, soaking the core wrapping 3 and the interior space in the bundle of conductors 4. Optionally, when the wrapping of the conductors 5 consist of a paper or a paper compound, the liquid compound L will soak this wrapping of the conductors 5 as well.

According to an embodiment, the reaction liquid pump 6 operates continuous until the cable core 2 is at least partly submerged.

According to an embodiment of the invention, the reaction liquid pump 6 is arranged with a heating system 17 for heating of the liquid compound L before entering the cable core 2.

The reaction process now commences whereby the paper wrapping around the cable core 2 if left exposed to the liquid compound L for a predetermined time, for example between 0.5-24 h or for example up to a few days, releases a reaction product comprising (natural) lubricants. After the reaction process, the end cap 11 is removed, the liquid compound L is optionally removed. Next, the extraction step commences.

Figure 3 a shows the system of fig 2 during a next step of the extraction process. In this next step, at the introduction end 10a, a rehydration liquid W typically an aqueous liquid is flushed under pressure into the cable core 2. At substantially the same time, at the extraction end 10b of the cable, a tensile force F is applied on the cable core 2 to extract the cable core 2 from the cable sheath 1. An extraction clamp 12 is attached to the cable core 2 at the extraction end 10b, while a rehydration liquid source 7 is connected with the input connector 9. The extraction force F is applied in a longitudinal direction at the extraction end 10b of the cable core 2, at a same time as or shortly after the flushing process starts at the other end.

The flushing provides that the lubricants that were released during the reaction of the liquid compound with the paper wrapping are rehydrated so as to increase the lubricating properties of these lubricants. Additionally, the pressurized flow of the rehydration fluid assists the extraction process by transporting the natural lubricants towards the extraction end 10b while the cable core 2 moves in the same direction inside the cable sheath 1.

According to an embodiment of the invention, the rehydration liquid source 7 comprises a heating system 18 for heating of the rehydration liquid ^before it enters the cable core 2.

Figure 3b shows the system of figure 2 during an extraction step. According to an embodiment there is a time delay provided between the start of rehydration liquid ^flushing at one end, and the actuation of the tensile force F being applied at the extraction end 10b.

The purpose of the time delay is to be able to start flushing rehydration liquid W before the tensile force F is applied. The time delay has the effect that the lubricants from the reaction process are enhanced in terms of both volume and lubrication capabilities. This time delay can be selected from about 1 s to 60 s or more.

Figure 4 shows a system according to an embodiment of the invention, wherein the cable is located in an underground environment. In practical situations, the cable is usually buried below a surface layer, such as a brick or asphalt pavement, or soft verge. Removal of the cable is adversely affected by the need to open the surface layer. According to an embodiment of the invention, the removal is facilitated by the formation of two cavities 13 to expose the cable, this cavity can for example be a pit or manhole, and in both cavities 13 the cable is cut to reveal the cable core 2. Above ground the reaction liquid pump 6 is provided at one end to provide liquid compound L for the reaction process. For the extraction process a water source 7 to provide rehydration liquid Wand a pulling system 14 is installed.

On the introduction end 10a of the cable the input connector 9 is installed and connected with the pump 6, via a conduit 8. In the reaction step the liquid compound L is pumped under pressure into the cable core 2, until the cable core 2 is fully soaked.

The end cap 11 is usually attached to the cable at the same time as the input connector 9 is attached, or during the entry of the liquid compound L into the cable before the compound has reached the extraction end 10b.

According to an embodiment, the cable core 2 is left in this state for a predetermined time, minimally equal to the time for soaking the cable core or for example between about 0.5 h and about 24 h, after which the end cap 11 is removed and the extraction process commences. The predetermined time delay can be selected based on various practical circumstances, such as the cable type, amount or type of paper wrapping, cable length.

The extraction step starts by connecting the cable core 2 with an extraction clamp 12 at the extraction end 10b. A rehydration liquid source 7 supplies rehydration liquid ^through the input connector 9 into the cable at the introduction end 10a. Here the rehydration liquid FFis introduced into the cable core 2 to flush the inside of the cable. At the same time, or after a time delay, an extraction force F is applied in a longitudinal direction on the cable core 2. The extraction force F forces the cable core 2 out of the cable sheath 1, whilst leaving the cable sheath 1 in place. Once the cable core 2 is partially out of the cable sheath 1 the direction of the extraction force F is shifted, to extract the cable core 2 out of the cavity 13.

According to an embodiment, the actuation device that generates the tensile force to pull the cable, comprises a winch 14. A preferably metal rope 16 is coupled to the winch and to the extraction end 10b of the cable. Optionally the metal rope 16 is guided over rollers 15 between the winch 14 and the extraction end 10b. Other alternatives and equivalent embodiments of the present invention are conceivable within the idea of the invention, as will be clear to the person skilled the art. The scope of the invention is limited only by the appended claims.