GB2437332A

GB2437332A - Tube

Info

Publication number: GB2437332A
Application number: GB0607842A
Authority: GB
Inventors: Peter David Jenkins; Daniel Owen Jenkins; Roger John Bates
Original assignee: Miniflex Ltd
Current assignee: Miniflex Ltd
Priority date: 2006-04-21
Filing date: 2006-04-21
Publication date: 2007-10-24
Anticipated expiration: 2026-04-21
Also published as: GB2437332B; GB0607842D0

Abstract

A tube 20 for use in blown fibre (or blown cable installations), the tube 20 comprising a hard inner coating 22. The inner coating 22 may alternatively or additionally comprise carbon nanotubes. The inner coating 22 has a shore hardness of at least 60.

Description

TUBE

BACKGROUND

a. Field of the Invention

The present invention relates to a tube for use in the installation of optical fibres and optical fibre cables, and in particular to the installation of optical fibres and optical fibre cables by pushing and sometimes additionally using a lubricating air flow.

b. Related Art It is well known in the field of cable installation to use the viscous drag generated by a turbulent air flow to install an optical fibre into a tube, and this is frequently referred to as blown fibre or blown cable. EP-B-0108 590 discloses the basis method in which an optical fibre cable was pushed into a tube containing an air flow until the viscous drag of the air flow became sufficient to overcome frictional forces between the cable and the interior of the tube. Many developments have been made subsequently to improve the installation technique, for example the development of special blown cables that generate reduced friction (see, for example, EP-B-0 521 710) and more advanced blowing equipment that reduces the risk of damage to the cable being blown into the tube (see, for example, EP-B- 1 015 928).

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a tubular linear member comprising an outer layer and an inner coating formed on the interior of the outer layer, wherein the inner coating comprises a material comprising a Shore hardness of at least 60.

* * * * S * * S * S * S S S S * S S S S *S* * S S *5 * S 55 S S S * * S * S S S S ** S tes S *SS The tubular linear member may be adapted to receive a cable installed into the tubular linear member. Preferably the outer layer and/or the inner coating comprise a plastics material. Furthermore, the inner coating preferably comprises a plurality of carbon nanotubes. The inner coating may comprise between 0.1% and 5% of carbon nanotubes and in particular the inner coating comprises 2% of carbon nanotubes.

According to a second aspect of the present invention there is provided a tubular linear member comprising an outer layer and an inner coating formed on the interior of the outer layer, wherein the inner coating comprises a plurality of carbon nanotubes.

Preferably, the inner coating comprises between 0.1% and 5% of carbon nanotubes and in particular the inner coating comprises 2% carbon nanotubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the following Figures in which: Figure 1 shows a schematic depiction of cross-section of a tube 10 according to the present invention; and Figures 2 and 3 show a graphical depiction of the installation performance of a tube made in accordance with the teaching of the present invention with a conventional tube.

DETAILED DESCRIPTION

Figure 1 shows a schematic depiction of cross-section of a tube 10 according to the present invention. The tube may be used in a blown fibre or blown cable installation, and is also suitable for use in an installation where the fibre (or cable) is pushed into the duct with no, or negligible, viscous drag acting on the cable.

* S * * S * * . S S * S S * S * * * S S **S S * * S. S S 55 S S S S S S S S * * S ** S 555 * 555 The tube 10 comprises an outer layer 20 which defines a bore formed within the interior of the tube 10. An inner coating 22 is formed on the inner surface of the outer layer to improve the installation performance of a fibre (or cable) being installed into the tube.

It has been observed that the installation distances and speeds obtained were chiefly limited by two factors: the friction between the cable and the tube and build up of static electricity which was generated by the motion of the cable relative to the tube. The standard approach to the friction problem, as exemplified by, EP-B- 0 521 710 was to process the cable to reduce the physical interaction in between the tube and the cable. For example, this was achieved by the incorporation of glass microspheres in the outermost layer of the cable such that there was a reduced surface contact area between the cable and the tube. EP-B-0 432 171 discloses a tube for blown installation in which the inner layer comprises a proportion of anti-static grade carbon black, which acts to mitigate the build-up of static electricity in the tube. Without this additive, the accumulated static electricity would cause the tube to be attracted to the cable and thus limit the installation of the tube.

The inner coating 22 is formed from a hard plastics material, typically having a minimum Shore hardness of 60. It is the insight of the present invention that when a fibre is blown or pushed into a tube, the cable repeatedly bounces and rebounds off the internal wall of the tube. If the internal wall is elastic then some of the kinetic energy of the cable will be absorbed by the internal wall during these interactions. It is believed that this mechanism is a significant limiting factor in the distance that a cable can be blown (or pushed) into a tube (viewed in an alternative manner, this mechanism may be seen to significantly increase the time that is required to install a cable into a tube of a given length and configuration).

By using a hard inner layer to the tube, when the cable bounces off the tube there is a greater conservation of the kinetic energy of the cable, leading to improved cable installation performance (see below).

* S S * * * * S * S * * S * S * S * S S *S* S S S S. S S *S * * * S * S S S * * * S. S *e* S **S It will be readily understood that the material that is used to form the inner coating 22 of the tube must be compatible with the material(s) and the processes used in the manufacture of the tube. An example of a suitably hard polymer is a high density polyethylene (HDPE) with a with Shore (D) value of 60 or greater (an HDPE having a D value of 68 has been achieved). Alternatively, a polymeric alloy may be used; an alloy of polyethylene and a polyamide having a Shore value of 72 has been shown to be compatible with the tube manufacturing process (for example, OrgalIoyTM, which is a polyamide resin produced by Atofina). It will be understood that other polymers that meet the hardness requirement and that can be used with the tube manufacturing process are suitable for use in the present invention. It is believed that the greater the hardness of the inner coating the greater the increase in installation performance.

It will be understood that further materials may be included in the inner coating of the tube to provide one or more desired characteristics, for example friction reduction, fire retardant properties, etc. The outer layer 20 of the tube is made from conventional materials, for example polypropylene, nylon-6, nylon-I I, nylon- 12, polybutylene terephthalate (PBT) or Orgalloy TM Additives may be added to the outer layer to provide the desired performance characteristics. The outer layer may comprise a single material or may be formed from a plurality of layers of different materials.

The use of anti-static grade carbon black in the tubing to reduce the build-up of static electricity, as disclosed in EP-B-0 432 171, has been demonstrated to be successful. However, if the levels of static electricity can be reduced further then it is believed that installation can be increased still further. The anti-static grade carbon black is added to the tubing material and thus if too much carbon is added then the tubing material will no longer meet other requirements (tensile strength, flexibility, etc.). Commercially available tubes comprise approximately 20% carbon black and it is believed that this is near to the maximum that can be used in a tube.

It has been found that the addition of a small amount of carbon nanotubes into the * * * * * * S S * S S S S S S * S S S S *5* S S S S* S S *S * S S S * S 5 0 S S S S* * S.. * .5* inner coating transforms the coating from an insulating material into a conductive (or semi-conductive) material. This allows any build up of static electricity to be discharged via the carbon nanotubes, leading to an improved cable installation performance. It has been found that the addition of approximately 2% carbon nanotubes provides superior ant-static performance that the use of 20% carbon black. Depending on the tube size and installation performance required, the carbon nanotubes may comprise between 0.1 and 5% of the inner coating.

Suitable nanotubes are the Fibril TM nanotubes produced by Hyperion Catalysis International, of Cambridge, Massachusetts.

It should be understood that the use of carbon nanotubes may be used in a conventional tubing structure, such as those disclosed in EP-B- 0 432 171, in place of the ant-static carbon black. Alternatively, it could be used with the hard inner coating disclosed in the present application. Due to the cost of carbon nanotubes, it is commercially preferable to add the nanotubes to a thin coating layer rather than to the entire tubing material. Typically the inner coating will have a thickness of 0.1 mm, but this thickness may be varied depending on the inner diameter of the tube and the cable to be installed into the tube. Furthermore, the hard inner coating disclosed in the present application may also be used without the carbon nanotubes.

Figures 2 and 3 show a graphical depiction of the performance of a tube made in accordance with the teaching of the present invention with a conventional tube.

The tube made according to the present invention has an inner coating comprising a polymeric alloy with a Shore hardness value of 72, the polymer additionally comprising 2% silicone and 2% carbon nanotubes. The inner diameter of the tube (including the coating) was 2.5mm and the outer diameter was 6 mm. The total length of tube was 488m. The conventional tube had the same inner and outer diameters and was installed over the same 488m route, which was representative of a typical external plant telecommunications infrastructure. The tube was made according to the teaching of EP-B-0 432 171. A fibre cable, made * S S * * * S S * * * * S S * * S S S S **S * S ** S * SI S * S S * S S S S S S *S S 555 S *** according to the teaching of EP-B-0 521 710, was installed using the blown fibre' installation method disclosed in EP-B-01 08 590.

Figure 2 shows the time taken to install the cable into each of the tubes; the dashed line shows the installation of the cable into the tube made according to the present invention and the solid line shows the installation of the cable into the conventional tube. Figure 2 shows that the tube according to the present invention provides significantly improved blowing performance, with the time taken to fully install the cable into the 488m length of tube being reduced by approximately 25% compared to a conventional tube.

Figure 3 shows the variation of installation speed for the cable installations discussed above with reference to Figure 2. Again, the dashed line shows the installation of the cable into the tube made according to the present invention and the solid line shows the installation of the cable into the conventional tube. For the tube according to the present invention, the cable is installed at a constant speed of 37 metres per minute. For the conventional tube, the installation speed was approximately 37 metres per minute for the first 250m of the tube. After this point, the speed of the cable decreases significantly until at the end of the 488m tube route the cable speed is only 15 metres/minute. Figure 3 indicates that the use of the tube according to the present invention enables cables to be installed into longer and/or more tortuous routes than with conventional tubing. A corollary of this is that it may be possible to push a cable into a route comprising the tubing of the present invention whereas it may be necessary to blow a cable into a route of conventional tubing.

It has been found that it is possible to push a 3 mm silica fibre jumper' cable into a complex route of approximately 100 m of tubing according to the present invention. The jumper cable had a hard nylon sheath. The tube had an outer diameter of 10 mm and an inner diameter of 7 mm. The installation route comprised sixteen 90 degree bends of 300mm radius and the installation was completed in under 3 minutes. If a route can not be installed into using pushing * S * * a * * S * S * S S 0 S * 0 * S * *S0 I) S. 0 * *s S * * S a I S 0 0 0 0 S. I **S a *** only, for instance when the sheath of the cable has a soft' PVC sheath, then it has been found that installation ranges can be increased through the limited supply of compressed air to act as a lubricant', effectively reducing the friction by reducing the contact between the cable and the tube. Clearly, installation ranges can be extended further by providing sufficient air flow to cause viscous drag forces to propel the cable.

It will be understood that the present invention is applicable to tubes of all sizes.

Typically, the outer diameter of the tube will be 2-10 mm, but it may be smaller than this, for example down to a diameter of several hundred microns, or greater than this range for specific applications. The tube may be used with any optical fibre, whether formed from plastic (for example, POF MOST, POF 1DB, PCS, etc.) or silica (either multi-mode or single-mode), or cable (for example, single fibre, or a cable comprising 4, 7 or more fibres). It will be readily understood that the inner and outer diameters of the tube will be determined by the diameter of the optical fibre or cable that is to be installed into the linear member. The outer surface of the tube may comprise a series of annular grooves to provide enhanced bend resistance to the tube.

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Claims

CLAIMS

1. A tubular linear member comprising an outer layer and an inner coating formed on the interior of the outer layer, wherein the inner coating comprises a material comprising a Shore hardness of at least 60.

2. A tubular linear member according to claim 1, wherein the tubular linear member is adapted to receive a cable installed into the tubular linear member.

3. A tubular linear member according to claim I or claim 2, wherein the outer layer and the inner coating comprise a plastics material.

4. A tubular linear member according to any preceding claim wherein the inner coating comprises a plurality of carbon nanotubes.

5. A tubular linear member according to claim 4, wherein the inner coating comprises between 0.1 % and 5% of carbon nanotubes.

6. A tubular linear member according to claim 5, wherein the inner coating comprises 2% of carbon nanotubes.

7. A tubular linear member comprising an outer layer and an inner coating formed on the interior of the outer layer, wherein the inner coating comprises a plurality of carbon nanotubes.

8. A tubular linear member according to claim 7, wherein the inner coating comprises between 0.1% and 5% of carbon nanotubes.

9. A tubular linear member according to claim 8, wherein the inner coating comprises 2% of carbon nanotubes.

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Amendments to the claims have been filed as follows

CLAIMS

1. A tubular linear member for use in the installation of cables, the tubular linear member comprising an outer layer and an inner coating formed on the interior of the outer layer, wherein the inner coating comprises i) a material comprising a Shore (D) hardness of at least 60; and ii) between 0.1% and 5% of carbon nanotubes.

2. A tubular linear member according to claim 1, wherein the outer layer and the inner coating comprise a plastics material.

3. A tubular linear member according to claim 1 or claim 2, wherein the inner coating comprises substantially 2% of carbon nanotubes.

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