Field of the Invention

The present invention relates to a multiduct or flatliner assembly for guiding and protecting optical fibre cables in which multiduct or flatliner assembly is adapted to have increased tensile strength by incorporating a tensile strength unit. The tensile strength unit enables the entire multiduct or flatliner assembly to be pulled through channels below infrastructure with an increased pull force without breaking, i.e. the multi duct or flatliner assembly has a higher pull force tolerance.

Background of the Invention

The ever-increasing demand for higher internet bandwidth means that thousands of kilometres of multi duct assemblies for guiding and protecting optical fibre cables are being laid into the ground along infrastructure such as roads and buildings.

In many cases it is preferable to just dig a channel below this infrastructure and then pull the multiduct or flatliner assembly through it. Activity on a road for instance would thereby be disrupted to a much lesser degree, compared to shutting down said road entirely to facilitate a dig. In the latter example, vehicles would require redirection and the road must be repaired afterwards. This increase both time costs and operation costs.

Thus, there is a need for a multiduct or flatliner assembly with increased tensile strength enabling pulling with a higher force.

Object of the Invention

It is an object of the invention to provide a multi duct or flatliner assembly for guiding and protecting optical fibre cables or optical waveguides, wherein the multiduct or flatliner assembly have increased tensile strength. Description of the Invention

An object of the invention is achieved by a multi duct or flatliner assembly for guiding and protecting optical fibre cables or optical waveguides. The multiduct or flatliner assembly comprises an outer sheath supporting a plurality of first longitudinal guides being in parallel relationship with said outer sheath and

- at least one tensile strength unit extending inside the outer sheath, and/or

- at least one longitudinal fibre rod extending inside the outer sheath, and/or

- at least one metal rod extending inside the outer sheath, and/or

- aramid fibres extending inside the outer sheath, and/or

- fiberglass extending inside the outer sheath.

The plurality of first longitudinal guides is adapted for receiving optical fibre cable.

The least one longitudinal fibre rod extend along the outer sheath and increases the tensile strength of the multiduct or flatliner assembly as a function of diameter of the fibre rod and a small increase in diameter of the fibre rod will significantly increase the tensile strength. The at least one longitudinal fibre rod will move within the multiduct or flatliner assembly as a function of temperature changes since the friction with the other components is not great enough to prevent the at least one longitudinal fibre rod from moving.

The least one longitudinal metal rod extend along the outer sheath and increases the tensile strength of the multiduct or flatliner assembly as a function of diameter of the metal rod and a small increase in diameter of the metal rod will significantly increase the tensile strength. The at least one longitudinal metal rod will move within the multiduct or flatliner assembly as a function of temperature changes since the friction with the other components is not great enough to prevent the at least one longitudinal metal rod from moving.

The aramid fibres extend along the outer sheath and increases the tensile strength of the multiduct or flatliner assembly as a function of the combined diameter of the aramid fibres. The aramid fibres may extend loosely inside the outer sheet. The aramid fibres will significantly increase the tensile strength. The aramid fibres will move within the multiduct or flatliner assembly move as a function of temperature changes since the friction with the other components is not great enough to prevent the aramid fibres from moving.

The fiberglass extends along the outer sheath and increases the tensile strength of the multiduct or flatliner assembly as a function of the combined diameter of the fiberglass. The fiberglass may extend loosely inside the outer sheet. The fiberglass will significantly increase the tensile strength. The fiberglass will move within the multiduct or flatliner assembly move as a function of temperature changes since the friction with the other components is not great enough to prevent the fiberglass from moving.

In an aspect, the at least one tensile strength unit may comprise

- a second longitudinal guide adapted for receiving optical fibre cable,

- at least one longitudinal fibre rod external to the second longitudinal guide or at least one metal rod external to the second longitudinal guide, or loose aramid fibres external to the second longitudinal guide, or loose glass fibres external to the second longitudinal guide, and

- an inner sheath supporting the second longitudinal guide and the at least one longitudinal fibre rod or the at least one metal rod or the loose glass fibres or the loose aramid fibres.

The longitudinal fibre rod increases the tensile strength of the multiduct or flatliner assembly as a function of diameter of the fibre rod and a small increase in diameter of the fibre rod will significantly increase the tensile strength.

For example, in the case where the sum of first and second longitudinal guides are 12 and the longitudinal guides have an outer diameter of 10 mm and an inner diameter of 6 mm then the maximum pull force will be roughly 12x400N = 4800 N. The addition of a fibre rod being a fiberglass rod having a diameter of 2 mm will increase the maximum pull force by 3000 N which is an increase of 62,5 % compared to an multiduct or flatliner assembly with no tensile strength unit. Thus, the multiduct or flatliner assembly being reinforced with a tensile strength unit can be pulled over longer distances. The at least one tensile strength unit establishes an interference fitting between the second longitudinal guide, at least one longitudinal fibre rod or the at least one metal rod or the loose fiberglass or the fiberglass

, and the inner sheath meaning that the at least one tensile strength unit becomes a single unit. In addition, an interference fitting is established between the at least one tensile strength unit, the first longitudinal guides, and the outer sheath. Thereby, the at least one longitudinal fibre rod or the at least one metal rod or the loose fiberglass or the fiberglass is prevented from moving due to changes in temperature.

The outer sheath and the inner sheath may be made using the same materials and using similar methods such as extrusion.

The first and second longitudinal guides may be identical or similar guides, where the only difference is whether they form part of the tensile strength unit or not.

The first and second longitudinal guides may be guide tubes having a substantially tubular cross-section.

The first longitudinal guides and the second longitudinal guide may be packed to form an overall hexagonal packing in a cross-section perpendicular to the longitudinal direction of the multiduct assembly, since a hexagonal packing has the highest packing density.

Thus, multiduct assembly will compared to the flatliner assembly have less perturbation of the overall structure due to overall hexagonal packing in a cross-section perpendicular to the longitudinal direction of the multiduct assembly.

However, there are spaces between the longitudinal guides and the least one longitudinal fibre rod can be fitted into said space between the longitudinal guides with little to no perturbation of the overall hexagonal structure. The at least one tensile strength unit could have two or more longitudinal guides. This can in some cases however make it more difficult to keep an overall hexagonal structure. Furthermore, the purpose of the second longitudinal guides is to keep the longitudinal fibre rod in place relative to the other components.

The multiduct or flatliner assembly may comprise two, three, five or more tensile strength units.

The at least one tensile strength unit may comprise two, three, five or more longitudinal fibre rods.

The longitudinal fibre rod may comprise a diameter of 0.5 mm or 0.8 mm or 1.5 mm or 2.0 mm or 2.5 mm or larger depending on the required tensile strength.

In the case wherein the longitudinal fibre rod is a glass fibre rod with the diameters mentioned above, the maximum pull force will increase by 200 N (for 0.5 mm) or 500 N (for 0.8 mm) or 1500 N (for 1.5 mm) or 3000 (for 2.0 mm) or 4500 N (for 2.5 mm).

The metal rod may be iron rod or a steel rod.

The longitudinal metal rod may comprise a diameter of 0.5 mm or 0.8 mm or 1.5 mm or 2.0 mm or 2.5 mm or larger depending on the required tensile strength.

The loose aramid fibres will be kept in place by the inner sheath such that the aramid fibres will not move as function of temperature due to a higher friction compared to an embodiment without the inner sheath.

The loose fibreglass will be kept in place by the inner sheath such that the aramid fibres will not move as function of temperature due to a higher friction compared to an embodiment without the inner sheath.

In an aspect, the outer sheath may originate from an extrusion process establishing an interference fitting between the outer sheath and the plurality of first longitudinal guides and the at least one tensile strength unit. Thereby, the multiduct or flatliner assembly becomes more stable as drift between components is prevented.

In an aspect, the inner sheath may originate from an extrusion process establishing an interference fitting between the inner sheath and the second longitudinal guide and the at least one longitudinal fibre rod. Thereby, the at least one tensile strength unit becomes more stable as drift between components is prevented.

The inner sheath may comprise a thickness between 0.5-1.1 mm or 0.7-0.9 mm. The inner sheath may be thinner than the outer sheath since the inner sheath is impart protected from impact by the outer sheath.

In an aspect the plurality of first longitudinal guides may comprise at least 2-5, 6-9, 10- 16, 17-25 microducts.

The microducts being defined by an inner diameter and outer diameter, wherein the inner diameter defines a volume for pulling optical fibre cables or optical waveguides.

The microducts may have longitudinal grooves along an inner side.

The plurality of first longitudinal guides may be arranged in a hexagonal packing.

The second longitudinal guide may also be a microduct having one, more or all the features discussed for the first longitudinal guides in the application.

In an aspect the microducts may comprise an outer diameter between 5-20 mm.

The microducts may comprise an inner diameter between 2-16 mm.

The microduct outer/inner diameter may be 4 mm / 2 mm or 5 mm /3.5 mm or 8 mm /4 mm or 10 mm /6 mm or 10 mm /8 mm or 12 mm /8 mm or 12 mm /10 mm or 14 mm /10 mm or 14 mm /12 mm or 16 mm /14 mm or 20 mm /15 mm or 20 mm /16 mm. In the list above the first value is the outer diameter and the second value is the inner diameter.

In an aspect the outer sheath comprises a thickness between 0.5-1.3 mm or 0.7-1.1 mm.

The thickness enables the outer sheath to withstand impacts and wear during the pulling of the multiduct or flatliner assembly.

In an aspect the plurality of first longitudinal guides may comprise a central-positioned longitudinal guide with an outer diameter of at least 20 mm and wherein the central- positioned longitudinal guide being surrounded by the other first longitudinal guides and the at least one tensile strength unit.

Thereby, a different configuration than the hexagonal packing is possible while achieving an increased tensile strength. An embodiment is shown in figure 3 A.

The other first longitudinal guides have a smaller outer diameter than the central-positioned longitudinal guide.

In an embodiment, the at least one tensile strength unit has a central-positioned and the second longitudinal guide comprise an outer diameter of at least 20 mm.

In an aspect at least one of the at least one longitudinal fibre rod comprises a fibre reinforced polymer such as fiberglass or aramid fibre or Kevlar yarn, nylon yarn.

Thereby, the at least one longitudinal fibre rod has a high tensile strength.

An object of the invention is achieved by a method of producing a multi duct or flatliner assembly with a tensile strength unit. The method comprises

- a step of providing a second longitudinal guide adapted for receiving optical fibre cable, and at least one longitudinal fibre rod, or at least one metal rod or loose aramid fibres, or loose fiberglass; and - a step of orienting the at least one longitudinal fibre rod or the at least one metal rod or the loose aramid fibres, or the loose fiberglass external to and in parallel with the second longitudinal guide;

- a step of extruding an inner sheath around the second longitudinal guide and the at least one longitudinal fibre rod or the at least one metal rod or the loose aramid fibres, or the loose fiberglass; thereby forming a tensile strength unit;

- a step of providing plurality of first longitudinal guides;

- a step of orienting the tensile strength unit and the plurality of first longitudinal guides in parallel; and

- a step of extruding an outer sheath around the tensile strength unit and the plurality of first longitudinal guides.

The method enables production of a multiduct or flatliner assembly along a single process line. In the case where more than a single tensile strength unit is desired, the first three steps are simply repeated.

An object of the invention is achieved by use of the multi duct or flatliner assembly according to the invention to pull through channels below infrastructure.

The infrastructure may be a road or a building.

An object of the invention is achieved by use of a tensile strength unit for increasing tensile of a multiduct or flatliner assembly comprising outer sheath supporting a plurality of first longitudinal guides being in parallel relationship with said outer sheath. The tensile strength unit comprises

- a second longitudinal guide adapted for receiving optical fibre cable,

- at least one longitudinal fibre rod or at least one metal rod or loose aramid fibres or loose fibreglass extending along and external to the second longitudinal guide, and

- an inner sheath supporting the second longitudinal guide and the at least one longitudinal fibre rod or the at least one metal rod or the loose aramid fibres or the loose fibreglass. As previously described the use of the tensile strength unit with a longitudinal fibre rod can in some cases increase the maximum pull force with 62.5 %.

The inner sheath is extruded onto the second longitudinal guide and the at least one longitudinal fibre rod or at least one metal rod or loose aramid fibres or loose fibreglass to achieve an interference fitting.

Description of the Drawing

Fig. 1 illustrates three different tensile strength units;

Fig. 2 illustrates an embodiment of a multiduct assembly;

Fig. 3 illustrates two embodiments of a multiduct assembly; and

Fig. 4 illustrates infrastructure and a channel.

Detailed Description of the Invention

Fig. 1 illustrates three different tensile strength units 40. The three different tensile strength units 40 are denoted A, B and C.

Each of the shown tensile strength units 40 comprise a second longitudinal guide 42 adapted for receiving optical fibre cable, and at least one longitudinal fibre rod 44 external to the second longitudinal guide 42, and an inner sheath 46 supporting the second longitudinal guide 42 and the at least one longitudinal fibre rod 44. The tensile strength units 40 denoted B and C have two longitudinal fibre rods 441, 4411 and the difference between the two embodiments is the positioning of the fibre rods 441, 4411. The fibre rods 441, 4411 in B are positioned on opposite sides of the second longitudinal guide while the fibre rods 441, 4411 in C are positioned next to each other. The tensile strength in B and C will be the same if identical fibre rods 441, 4411 are used.

The two fibre rods 441, 4411 may be placed anywhere between the two extremes B and C.

Fig. 2 illustrates an embodiment of a multi duct assembly 10. The multi duct assembly 10 comprises an outer sheath 20 supporting a plurality of first longitudinal guides 22 being in parallel relationship with said outer sheath 20 and at a tensile strength unit 40. The plurality of first longitudinal guides 22 are adapted for receiving optical fibre cables. The first longitudinal guides 22 are in a hexagonal configuration.

The tensile strength unit 40 comprises a second longitudinal guide 42 adapted for receiving optical fibre cable and a longitudinal fibre rod 44 external to the second longitudinal guide 42 and an inner sheath 46 supporting the second longitudinal guide 42 and the longitudinal fibre rod 44.

The tensile strength unit 40 is similar to the tensile strength unit 40 shown in figure 1 A, however one could substitute the shown tensile strength unit 40 for the tensile strength unit 40 in either of figure IB or 1C.

The first longitudinal guides 22 are shown having different levels of grey scale this is due to the first longitudinal guides 22 typically having different colours. This is however not relevant for the present invention. This is also the reason why the white first longitudinal guide 22 has been drawn using stippled lines.

Fig. 3 illustrates two embodiments of a multi duct assembly 10 denoted A and B. The multi duct assembly 10 in figure 3 A comprises an outer sheath 20 supporting a plurality of first longitudinal guides 22 being in parallel relationship with said outer sheath 20 and at a tensile strength unit 40.

The plurality of first longitudinal guides 22 are adapted for receiving optical fibre cables. The plurality of first longitudinal guides 22 comprises a central-positioned longitudinal guide 24 with an outer diameter being larger than the other first longitudinal guides 22 and wherein the central-positioned longitudinal guide 24 being surrounded by the other first longitudinal guides and the at least one tensile strength unit 40.

The tensile strength unit 40 comprises a second longitudinal guide 42 adapted for receiving optical fibre cable and a longitudinal fibre rod 44 external to the second longitudinal guide 42 and an inner sheath 46 supporting the second longitudinal guide 42 and the longitudinal fibre rod 44.

The tensile strength unit 40 is similar to the tensile strength unit 40 shown in figure 1 A, however one could substitute the shown tensile strength unit 40 for the tensile strength unit 40 in either of figure IB or 1C.

The multi duct assembly 10 in figure 3B comprises an outer sheath 20 supporting a plurality of first longitudinal guides 22 being in parallel relationship with said outer sheath 20 and at two tensile strength units 401, 4011.

The plurality of first longitudinal guides 22 are adapted for receiving optical fibre cables. The first longitudinal guides 22 are in a hexagonal configuration.

The tensile strength unit 401 comprises a second longitudinal guide 42 adapted for receiving optical fibre cable and a longitudinal fibre rod 44 external to the second longitudinal guide 42 and an inner sheath 46 supporting the second longitudinal guide 42 and the longitudinal fibre rod 44.

The tensile strength unit 401 is similar to the tensile strength unit 40 shown in figure 1A, however one could substitute the shown tensile strength unit 401 for the tensile strength unit 40 in either of figure IB or 1C. The tensile strength unit 4011 comprises a second longitudinal guide 42 adapted for receiving optical fibre cable and two longitudinal fibre rods 441, 4411 external to the second longitudinal guide 42 and an inner sheath 46 supporting the second longitudinal guide 42 and the longitudinal fibre rod 44.

The tensile strength unit 401 is similar to the tensile strength unit 40 shown in figure 1A, however one could substitute the shown tensile strength unit 401 for the tensile strength unit 40 in either of figure IB or 1C. Fig. 4 illustrates infrastructure 80 and a channel 82. The multi duct assembly 10 according to the invention can be pulled with a larger force and thus can be pulled over larger distances without damaging the infrastructure 80.

In the example the infrastructure 80 is a road.