WO2005031420A1

WO2005031420A1 - Method for manufacturing aluminum spray-coated anti-corrosive optical unit

Info

Publication number: WO2005031420A1
Application number: PCT/KR2004/002493
Authority: WO
Inventors: Sung-Wook Kim; Sung-Ik Shim
Original assignee: Lg Cable Ltd.
Priority date: 2003-09-29
Filing date: 2004-09-24
Publication date: 2005-04-07
Also published as: PT2005031420W; RU2006115572A; RU2319181C9; RU2319181C1; KR100571147B1; KR20050031294A

Abstract

Disclosed herein is a manufacturing method of an optical unit having an aluminum coating layer formed on the surface of a stainless-steel loose-tube. The method improves productivity and price competitiveness of products through spray-coating of aluminum using arc heat. That is, such a method comprises the step of producing fine aluminum powder by liquefying an aluminum preform using arc heat, and spray-coating the fine aluminum powder on the surface of the stainless-steel loose-tube by using high-pressure air.

Description

Description METHOD FOR MANUFACTURING ALUMINUM SPRAY- COATED ANTI-CORROSIVE OPTICAL UNIT Technical Field

[1] The present invention relates to a method of manufacturing an optical unit having an aluminum coating layer, and more particularly to a method of manufacturing an aliminim spray-coated anti-corrosive optical unit which can improve productivity and price competitiveness of products through spray-coating of aliminim using arc heat, can improve corrosion resistance by reducing porosity of a resultant aluminum spray- coating layer, and can reduce optical loss due to micro-bending, etc. by reducing thickness deflection.

[2] Background Art

[3] As well known, an optical fiber composite overhead ground wire (OPGW), having stainless-steel loose-tubes is a cable installed at the top of a power-transmission tower, and as shown in Figs. 1 and 2, comprises one or more optical units 2 incorporating optical fibers 6, one or more tension members 1 for bearing the load caused by gravitational force and external forces acting on the wire, and conductors. In this case, the respective optical units 2 are fabricated by similtaneously drawing the optical fibers 6 and a stainless-steel tape and applying jelly 5 thereon, and then rolling the stainless- steel tape using a guide roller, and laser welding the rolled stainless-steel tape to take the form of a tube. Along with the tension members 1 and the conductors, the optical units 2, fabricated as stated above, are alternately twisted in a spiral direction, thereby forming the OPGW in the form of a cable.

[4] In this case, since the optical fibers 6 tend to generate micro-bending loss due to lateral pressure, etc., the optical units 2 have to be formed to have a diameter smaller than diameters of the tension members 1 and the conductors, such that a prescribed gap is produced around the respective optical units 2 during twisting. In this way, it is possible to prevent external stress from being transmitted to the optical units 2, thereby reducing optical loss.

[5] Here, the surface of the tension member 1 is coated with aluminum, whereas the surface of the optical unit 2 is surrounded by a -stainless-steel tube. This may cause a risk of galvanic corrosion due to a potential difference between aliminim and stainless steel. Therefore, in order to prevent such a galvanic corrosion problem, the surface of the optical unit 2 trust also be coated with aliminim. Examples of methods for coating the optical unit 2 with aliminim include aluminum taping, electroplating, vapor deposition methods, and the like. Further, as occasion demands, grease is filled between strands for preventing corrosion.

[6] However, in the case of the aliminim taping method, aliminim tape 7 may be torn or loosened during twisting or installation, or may be completely separated from the optical unit 2 as the adhesive strength thereof is reduced due to degradation of an adhesive after a prolonged time-lapse. As a result, the invasion of moisture or impurities may be generated through the loosened tape 7, thus inducing galvanic corrosion, etc. This results in a considerable deterioration of corrosion resistance.

[7] Further, in the case of the aluminim extrusion coating method, since aliminim is preliminary heated up to approximately 500 degrees centigrade, and is coated through a high-pressure extrusion manner, it presents various problems including degradation of the jelly 5, optical fibers 6 and binder yarns inside the stainless-steel loose-tube 4, and deformation and tearing of the stainless-steel loose-tube 4 due to high pressure during extrusion.

[8] Such an aluminum extrusion coating method also has a problem in that it is difficult to reduce the thickness of a resultant aluminim coating layer below 0.35mm. As a result, both the size and weight of the optical unit 2 increase, and thus the overall size and weight of the cable proportionally increase, thereby inevitably raising manufacturing costs, transportation expenses, and processing costs, and resulting in earth fault and short-circuit phenomena.

[9] Furthermore, in the case of the aliminim electroplating method, it requires the use of special solutions since it is impossible to perform such a plating in aqueous solutions, thereby disadvantageously increasing processing costs, and causing a danger of explosion during plating. In addition, such an electroplating method requires a considerably long time to plate aliminim to a desired thickness, resulting in a reduction in productivity of products.

[10] Finally, considering the grease-filling method, the grease may be hardened as a result of gradual degradation over a long time, or may leak to the outside by heavy rains, thereby deteriorating corrosion resistance and delaying an optical connection operating time.

[11] Disclosure of Invention Technical Problem

[12] Therefore, the present invention has been made in view of the above problems, and it is a first object of the present invention to provide a method of manufacturing an aliminim spray-coated anti-corrosive optical unit in which aluminim is applied onto the surface of a stainless-steel loose-tube through spray-coating using arc heat, thereby improving productivity of products and reducing manufacturing costs thereof.

[13] It is a second object of the present invention to provide a method of manufacturing an aluminum spray-coated anti-corrosive optical unit in which aluminim is spray- coated, and then is heated and rolled, such that thickness deflection and porosity of a resultant aluminum coating layer can be reduced, thereby preventing corrosion of the aluminim coating layer.

[14] Technical Solution

[15] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a method of manufacturing an aluminim spray-coated anti-corrosive optical unit, having an aluminim coating layer formed on a surface of a stainless-steelloose-tube, comprising the steps of spray-coating a fine aliminim powder on the surface of the stainless-steel loose-tube by liquefying an aluminim preform using arc heat and blowing the liquefied aluminum with high- pressure air.

[16] Preferably, in the spray -coating step, the resultant aluminum coating layer may have a thickness of 5 to 100 micrometers.

[17] Preferably, in the spray-coating step, the resultant aluminum coating layer may have a thickness of 80 to 90 micrometers.

[18] Preferably, before the spray -coating step, the method may further comprise the step of preheating the stainless-steelloose-tube to a temperature of 50 to 100 degrees centigrade.

[19] Preferably, before the preheating step, the method may further comprise the step of blasting the surface of the stainless-steel loose-tube to form convex and concave portions.

[20] Preferably, in the spray-coating step, the stainless-steel loose-tube may be recirculated along a predetermined course, such that the aluminim powder is repeatedly spray-coated thereon more than two times.

[21] Preferably, after the spray -coating step, the method may further comprise the steps of: heating the aliminim coating layer to a temperature of 100 to 700 degrees centigrade; rolling the heated aluminim coating layer in order to reduce porosity and thickness deflection of the aluminum coating layer; and quenching the rolled optical unit in order to prevent degradation inside the optical unit. [22] Preferably, in the rolling step, the aluminum coating layer may be press-rolled such that the thickness thereof is reduced by 15 to 20%. [23] In accordance with another aspect of the present invention, there is provided an OCGW comprising one or more optical units manufactured according to the method as set forth in claim 1. [24] Advantageous Effects

[25] According to a manufacturing method of an aluminim spray-coated anti-corrosive optical unit, liquefied aluminum is spray-coated onto the surface of a stainless-steel loose-tube, such that the aluminum can adhere to the stainless-steel loose-tube with improved adherence and can show high density, thereby improving corrosion resistance. Further, as the aluminim can be coated in the form of a thin film having a thickness of 80 to 90 micrometers, it is possible to reduce the size and weight of products, and to simplify optical connection thereof.

[26] Further, as the stainless-steelloose-tube is re-circulated along a predetermined course, such that the surface of the stainless-steel loose-tube can be repeatedly coated with the aluminim a plurality of times, it is possible to improve productivity of products and to reduce the amount of coating material required.

[27] Furthermore, since the resultant aluminim coating layer, obtained from the spray- coating of the present invention, is rolled such that the thickness thereof can be reduced by 15 to 20%, and pores existing in the aluminim coating layer can be removed, the corrosion resistance property of the aliminim coating layer can be improved. In addition, according to the present invention, through quenching of the aluminim coating layer, which was heated and rolled, it is possible to prevent jelly, binders and optical fibers incorporated in the optical unit from being degraded.

[28] In addition to the above-described various effects, the aluminim coating layer of the present invention has a uniform thickness as a result of heating and rolling thereof, thereby producing a predetermined gap around the optical unit during twisting. This has the effect of reducing optical loss due to micro-bending etc., caused by external loads acting upon the aluminim coating layer. While passing through the heating and rolling steps, furthermore, the aluminim coating layer can be adhered more closely to the surface of the stainless-steel loose-tube, resulting in a reduction in surface peeling.

[29] Brief Description of the Drawings

[30] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[31] Fig. 1 is a sectional view illustrating an optical fiber composite overhead ground wire (OPGW) having conventional aliminim taped optical units;

[32] Fig. 2 is a sectional view illustrating an optical fiber composite overhead ground wire (OPGW) having conventional aliminim extrusion coated optical units;

[33] Fig. 3 is a sectional view illustrating an optical fiber composite overhead ground wire (OPGW) in accordance with the present invention; and

[34] Fig. 4 is a f ow chart illustrating a manufacturing procedure of an optical unit in accordance with the present invention.

[35] Best Mode for Carrying Out the Invention

[36] Now, a preferred embodiment of the present invention will be explained with reference to the accompanying drawings.

[37] Fig. 3 is a sectional view illustrating an optical fiber composite overhead ground wire (OPGW) in accordance with the present invention. Fig. 4 is a flowchart illustrating a manufacturing procedure of an optical unit in accordance with the present invention.

[38] Referring to Figs. 3 and 4, an OPGW basically comprises one or more optical units 2 incorporating optical fibers, one or more tension members 1 for bearing load caused by gravitational force and external forces acting upon the wire, and conductors. Further, around of the respective optical units 2 are formed the aluminim coating layer 3, in order to prevent galvanic corrosion, which may be generated between stainless steel and aluminim materials constituting the wire.

[39] In this case, the optical unit 2 is manufactured by sinultaneously drawing the one or more optical fibers 6 and a stainless-steel tape, applying jelly 5 thereon, rolling the stainless-steel tape using a guide roller, and welding the rolled stainless-steel tape to take the form of a tube.

[40] More particularly, as shown in Fig. 4, a manufacturing method of the optical unit 2 according to the present invention comprises a pre-treatment step (S9), a blasting step (S10), a pre-heating step (Sl l), a spray-coating step (S12), a heating step (S13), a rolling step (S14), and a quenching step (S15). [41] Considering first the spray-coating step (S12), it is a step of spray -coating a fine aliminim powder on the surface of the stainless-steel loose-tube by liquefying an aluminim preform using arc heat and blowing the liquefied aluminum with high- pressure air.. That is, the aluminim preform, taking the form of a pair of wires having a diameter of 1.2mm to 2.0mm, is liquefied using arc heat of 3000 to 4000 degrees centigrade upon receiving electric power, and sinultaneously is blown using high- pressure air, such that the resultant fine aluminim powder is spray-coated onto the surface of the stainless-steel loose-tube 4. In this case, the high-pressure air, used in 2 the spray -coating of the aliminim powder, is injected at a pressure of 3 to 10 kgf/cm .

[42] The maximm thickness of the aliminim coating layer 3, obtainable from the spray-coating step (S12), can be changed according to conditions, warranty length, and corrosion environment, and the minimm thickness thereof is appropriately determined to prevent the aliminim coating layer 3 from being peeled from the stainless-steel loose-tube 4 due to friction between strands and external load acting upon the aluminim coating layer 3 during manufacture. The aliminim coating layer 3, preferably has a thickness of 5 to 100 micrometers, and more preferably has a thickness of 80 to 90 micrometers. If the thickness of the aliminim coating layer 3 is below 5 micrometers, the aliminim coating layer 3 may be peeled from the stainless- steel loose-tube 4 due to friction, etc., thereby raising the risk of galvanic corrosion. On the contrary, if the thickness of the aluminum coating layer 3 is above 100 micrometers, both the size and weight of the optical unit 2 increase, and thus the overall size and weight of the wire proportionally increase, thereby disadvantageously raising manufacturing costs, transportation expenses, processing costs, etc.

[43] In the present invention, prior to the spray-coating step (S12), it is preferable that the stainless-steel loose-tube 4 is pre-heated to a temperature of 50 to 100 degrees centigrade in the pre-heating step (Sl l). Such a pre-heating step (Sl l) is requiredsince in the spray-coating step (S12), the spray-coating material, namely, the fine aliminim powder, is adhered to the surface of the stainless-steel loose-tube 4 at a temperature of approximately 50 to 100 degrees centigrade. That is, pre-heating the stainless-steel loose-tube 4 reduces a temperature difference between the stainless-steel loose-tube 4 and the aluminum powder to be attached thereto, thereby preventing the aluminim powder from being unintentionally detached from the stainless-steel loose-tube 4 due to heat shrinkage. Further, the above mentioned pre-heating temperature of 50 to 100 degrees centigrade is effective to prevent degradation of the jelly 5, optical fibers 6, and binder yarns incorporated in the optical unit 2. [44] Preferably, prior to the pre-heating step (Sl l) and the spray-coating step (S12), the optical unit 2 passes through the pre-treatment step (S9). In the pre-treatment step (S9), the surface of the optical unit 2 is washed in order to remove wire drawing oil smeared thereon when the optical unit 2 is manufactured. After that, the surface of the stainless- 2 steel loose-tube 4 is preferably blasted with a pneumatic pressure of 5 to 7 kgf/αn in the blasting step (S10), in order to produce concave and convex portions on the surface of the stainless-steel loose-tube 4. Such concave and convex portions serve to allow the fine aluminim powder to easily adhere to the surface of the stainless-steel loose- tube 4.

[45] Considering again the spray-coating step (S12), in order to reduce loss of the spray- coating material, namely, the aliminim powder, and to achieve a target thickness of the aliminim coating layer 3 within a short time, preferably, the stainless-steel loose- tube 4, having passed through a spray gun, is adapted to also pass through a capstan, such that it can be returned and repeatedly spray-coated with the aliminim powder more than two times. The number of repetitions of the spray-coating depends on the linear velocity of the stainless-steel loose-tube 4 and the target thickness of the aluminim coating layer 3. For example, if the linear velocity is 20mpm, and the target thickness is 80 micrometers, if the aliminim powder is spray-coated three times, the loss of the aliminim powder can be reduced by more than 63%).

[46] After the stainless-steel loose-tube 4 is preheated, and the aluminim powder is spray-coated on the surface of the stainless-steel loose-tube 4 as stated above, in order to reduce thickness deflection and porosity of the aluminim coating layer 3, it is preferable to successively perform the heating step (S13), rolling step (S14), and quenching step (S15) on the aluminum coating layer 3. In general, the aluminim coating layer 3 shows a porosity of approximately 13%), and such a degree of porosity is in danger of causing corrosion. Therefore, in order to prevent corrosion of the aluminim coating layer 3, the aluminum coating layer 3 has to be heated and rolled in order to increase the density thereof, thereby removing pores and preventing corrosion.

[47] The heating step (SI 3) is a step of instantaneously heating the stainless-steel loose- tube 4, formed with the aliminim coating layer 3, to a temperature of 100 to 700 degrees centigrade, thereby allowing the aluminim coating layer 3 to be kept in an easily deformable state. That is, in order to secure smooth movement of aliminim particles, and to effectively reduce the porosity and thickness deflection of the aliminim coating layer 3, the aluminum coating layer 3 has to be press rolled in a state wherein it is heated to a temperature of 100 to 700 degrees centigrade so that it is softened. In this case, although it is easier to roll the aluminim coating layer 3 as the heating temperature increases, if the heating temperature rises above 700 degrees centigrade, exceeding the melting point of aluminum, it may deteriorate processing ability of the aliminim coating layer 3 and result in degradation in the jelly 5, optical fibers 6, and binder yarns incorporated in the optical unit 2. Further, it is preferable to perform the heating step (S13) at an acceptable maxinum temperature only for a short time, such that degradation of the jelly 5, binder yarns and optical fibers 6 incorporated in the optical unit 2 can be minimized.

[48] The rolling step (S14) is a step of press-rolling the aliminim coating layer 3, which was heated to the temperature of 100 to 700 degrees centigrade in the above- described heating step (S13), such that the thickness of the aluminim coating layer 3 is reduced by 15 to 20%, thereby reducing the porosity and thickness deflection existing in the aliminim coating layer 3. If the thickness deflection of 10 to 15 micrometers is present in the aluminim coating layer 3, it is difficult to produce a gap of approximately 0.05mm between the optical units 2, tension members 1, and conductors in the later quenching step (S15), and thus optical loss due to micro-bending may be generated when external load is applied to the aliminim coating layer 3. Therefore, in order to prevent generation of optical loss, it is necessary to provide the aliminim coating layer 3 with a uniform thickness. In this way, the thickness of the aliminim coating layer 3, which was in a range of 5 to 100 micrometers in the spray -coating step (S12), is reduced to 4 to 85 micrometers, and has a uniform thickness value in the rolling step (S 14).

[49] As the aluminum coating layer 3 is heated to a temperature of 100 to 700 degrees centigrade and then rolled, in the quenching step (SI 5) performed right after the rolling step (S14), the aluminum coating layer 3 has to be quenched before such a high- temperature heat of the aluminim coating layer 3 is transferred to the interior of the optical unit 2, thereby preventing the jelly 5, binder yarns and optical fibers 6 inside the optical unit 2 from being degraded.

[50] The one or more optical units 2, fabricated as stated above, are alternately twisted in an SZ direction, along with the tension members 1 and conductors, to form an optical cable. In order to prevent external stress from being transmitted to the optical units 2 during twisting and installation, and even after installation, the optical units 2 are formed such that the diameter thereof is smaller than diameters of the tension members 1 and conductors, thereby producing a gap of approximately 0.05mm around the respective optical units 2.

[51] As the one or more optical units 2 manufactured according to the method of the present invention as stated above are incorporated, an optical fiber composite overhead ground wire can be achieved.

[52] Industrial Applicability

[53] As apparent from the above description, the present invention provides a method of manufacturing an aliminim spray-coated anti-corrosive optical unit in which liquefied aluminim is spray-coated onto the surface of a stainless-steel loose-tube, such that the aluminim can be adhered to the stainless-steel loose-tube with improved adherence and can show high density, thereby improving corrosion resistance. Further, as the aluminim can be coated in the form of a thin film having a thickness of 80 to 90 micrometers, it is possible to reduce the size and weight of products, and to simplify optical connection thereof.

[54] Further, according to the present invention, as the stainless-steel loose-tube is recirculated along a predetermined course, such that the surface of the stainless-steel loose-tube can be repeatedly coated with the aluminim a plurality of times, it is possible to improve productivity of products and to reduce the amount of coating material required.

[55] Furthermore, since the resultant aluminim coating layer, obtained from the spray- coating of the present invention, is rolled such that the thickness thereof can be reduced by 15 to 20%, and pores existing in the aluminim coating layer can be removed, the corrosion resistance property of the aliminim coating layer can be improved. In addition, according to the present invention, through quenching of the aluminim coating layer, which was heated and rolled, it is possible to prevent jelly, binders and optical fibers incorporated in the optical unit from being degraded.

[56] In addition to the above-described various effects, the aluminim coating layer of the present invention can have a uniform thickness as a result of heating and rolling thereof, thereby producing a predetermined gap around the optical unit during twisting. This has the effect of reducing optical loss due to micro-bending etc., caused by external loads acting upon the aluminim coating layer. While passing through the heating and rolling steps, furthermore, the aliminim coating layer can be adhered more closely to the surface of the stainless-steel loose-tube, resulting in a reduction in surface peeling. [57] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[58]

Claims

[1] A method for manufacturing an aliminim spray-coated anti-corrosive optical unit, having an aluminim coating layer formed on a surface of a stainless-steel loose-tube, comprising the steps of: spray-coating a fine aluminum powder on the surface of the stainless-steel loose-tube by liquefying an aluminim preform using arc heat and blowing the liquefied aluminim with high-pressure air. [2] The method as set forth in claim 1, wherein, in the spray -coating step, the resultant aluminum coating layer has a thickness of 5 to 100 micrometers. [3] The method as set forth in claim 2, wherein in the spray-coating step, the resultant aluminum coating layer has a thickness of 80 to 90 micrometers. [4] The method as set forth in claim 1, before the spray-coating step, further comprising the step of: preheating the stainless-steel loose-tube to a temperature of 50 to 100 degrees centigrade. [5] The method as set forth in claim 4, before the preheating step, further comprising the step of: blasting the surface of the stainless-steel loose-tube to form convex and concave portions. [6] The method as set forth in claim 1, wherein, in the spray -coating step, the stainless-steel loose-tube is re-circulated along a predetermined course, such that the aluminum powder is repeatedly spray -coated thereupon more than two times. [7] The method as set forth in claim 1, after the spray-coating step, further comprising the steps of: heating the aliminim coating layer to a temperature of 100 to 700 degrees centigrade; rolling the heated aluminum coating layer in order to reduce porosity and thickness deflection of the aluminim coating layer; and quenching the rolled optical unit in order to prevent degradation inside the optical unit. [8] The method as set forth in claim 7, wherein, in the rolling step, the aliminim coating layer is press-rolled such that the thickness thereof is reduced by 15 to 20%. [9] An optical fiber composite overhead ground wire comprising one or more optical units manufactured according to the method as set forth in claim 1.