WO2006112566A1

WO2006112566A1 - Cable crosslinking apparatus using infrared

Info

Publication number: WO2006112566A1
Application number: PCT/KR2005/001158
Authority: WO
Inventors: Byeong-Kwan Chung
Original assignee: LS Cable Ltd
Current assignee: LS Cable and Systems Ltd
Priority date: 2005-04-21
Filing date: 2005-04-21
Publication date: 2006-10-26
Anticipated expiration: 2007-10-21
Also published as: CN101167144A

Abstract

A cable crosslinking apparatus using infrared prevents a surface of polymer acting as an insulator from being damaged due to heating, and also improving a thermal efficiency in an infrared irradiating process. This cable crosslinking apparatus using infrared includes a heating unit for heating a wire to a predetermined temperature; an extruding unit for coating polymer on the heated wire to make a cable; an IR (infrared) irradiating unit for irradiating infrared to the cable; and a cooling unit for cooling the wire passing through the IR irradiating unit.

Description

CABLE CROSSLINKING APPARATUS USING INFRARED

Technical Field

[1] The present invention relates to a cable crosslinking apparatus using infrared, and more particularly to a cable crosslinking apparatus capable of preventing a surface of polymer acting as an insulator from being damaged due to heating, and also improving a thermal efficiency in an infrared irradiating process. Background Art

[2] Generally, a cable includes a wire allowing flow of current, and a polymer coated on the wire for insulation. The wire is made of metal with good electric conductivity such as copper and aluminum.

[3] The polymer is coated on the wire by means of an extruder. At this time, crosslinking is executed for enhancing chemical, electrical and mechanical properties of the polymer. The crosslinking is classified into three kinds, in general.

[4] The three kinds of crosslinking are a silane method using trismethoxy vinyl silane, an irradiating crosslinking for applying an irradiation energy to a polymer chain using electron beams or UV irradiating rays to cause crosslinking, and a chemical crosslinking for causing crosslink by means of radicals formed by additive or crosslinking agent such as organic peroxide.

[5] In the chemical crosslinking method, a crosslinking reaction is generally caused by heat. In order to effectively transfer heat to the polymer acting as an insulator and thus react the additive or crosslinking agent, CCV (Continuous Catenary Vulcanization) has been proposed. CCV transfers heat using steam or heated nitrogen. However, CCV takes a significant time to transfer heat to inside since the heat is transferred by means of conduction from the surface of the polymer. In particular, since the polymer is a nonconductor with a very low conduction coefficient, a rate of transferring heat is low, so much time is required for crosslinking.

[6] In order to solve the problems of CCV, a device for heating polymer by irradiating a radiant light thereto has been proposed. This device is disclosed in US Pat. No. 4,234,624. As shown in FIG. 1, this device 10 has a radiation means 13 for auxiliarily irradiating a radiant light to an outside of a crosslinking tube 12 so as to heat polymer.

[7] First, an extruder 14 is used to coat polymer 3 on a wire 1. Subsequently, with moving the wire 1 through a crosslinking tube 12, the polymer 3 is heated using steam or heated nitrogen. At the same time, a radiant light is irradiated to the crosslinking tube 12 using the radiation means 13 so that a radiant heat is emitted from the crosslinking tube 12, thereby transferring the radiant heat to the polymer 3. [8] This device 10 shows an excellent heat transfer efficiency in comparison to CCV, since it uses a radiant heat. However, after the radiant heat reaches the surface of the polymer 3, it should be transferred to the inside of the polymer using conduction. Thus, it is still difficult to perform crosslinking in a short time. In particular, if an intensity of the radiant heat is increased in order to perform crosslinking in a short time, the surface of the polymer 3 is apt to be damaged.

[9] In order to solve the problems of the above device 10, a device for crosslinking polymer by irradiating a radiant light in a specific wavelength range has been proposed. This device is disclosed in EP0921921. As shown in FIG. 2, this device 20 crosslinks polymer using an IR (Infrared) irradiating member 23 mounted in a crosslinking oven 22. That is to say, a tube 7 with a predetermined shape is extruded in an extruder 26 by using a compound in which polyethylene 24 and crosslinking agent 25 are mixed. The tube 7 is crosslinked by means of the IR irradiating member 23 with passing through the crosslinking oven 22, and the crosslinked tube 7 is cooled with passing through a cooling reservoir 27. The cooled tube 7 is pulled by a capstan 28 and then taken up by a take-up 29.

[10] The IR irradiating member 23 irradiates infrared of a wavelength different from an absorption wavelength of polymer. It prevents the surface of polymer from being excessively heated. In addition, it is possible to use an absorption peak wavelength of additive or crosslinking agent so that only the additive or the crosslinking agent is reacted to enhance a crosslinking efficiency.

[11] However, the device 20 requires a special filter in order to filter the absorption wavelength range of the polymer, and shows a deteriorated thermal efficiency since an absorption peak of the polymer is not used. Disclosure of Invention Technical Problem

[12] The present invention is designed in consideration of the above problems, and therefore it is an object of the invention to provide a cable crosslinking apparatus using infrared, which is capable of preventing a surface of polymer from being damaged by heating.

[13] Another object of the present invention is to provide a cable crosslinking apparatus using infrared, which is capable of improving a thermal efficiency in an IR irradiating process. Technical Solution

[14] In order to accomplish the above object, the present invention provides a cable crosslinking apparatus using infrared, which includes a heating unit for heating a wire to a predetermined temperature; an extruding unit for coating polymer on the heated wire to make a cable; an IR (infrared) irradiating unit for irradiating infrared to the cable; and a cooling unit for cooling the wire passing through the IR irradiating unit. [15] Preferably, the heating unit heats the wire over a reaction temperature of a cros slinking agent. [16] Preferably, there are provided at least one pair of the IR irradiating units in opposite directions based on the cable. [17] Preferably, the IR irradiating unit includes an emitter for generating infrared; and a reflective plate mounted at a side opposite to the emitter for reflecting the infrared in order to enhance an IR emitting efficiency of the emitter. [18] In addition, the IR irradiating unit preferably includes an emitter for generating infrared; and a reflective plate mounted at the rear of each emitter. [19] Moreover, the IR irradiating unit includes emitters installed to both sides of the cable respectively for generating infrared; and reflective plates mounted at the rear of each emitter.

[20] Preferably, the cooling unit includes a cooling tube mounted at the rear of the IR irradiating unit and receiving a coolant therein; and a cooling reservoir mounted at the rear of the cooling tube. [21] More preferably, the cooling unit further includes a direction-changing wheel mounted between the cooling tube and the cooling reservoir to support the cable and also changing a moving direction of the cable, and the IR irradiating unit, the cooling tube and the direction-changing wheel are arranged so that the cable forms a catenary with a predetermined curvature. [22] Preferably, the IR irradiating unit irradiates infrared of the entire wavelength ranges to the cable.

Brief Description of the Drawings [23] These and other features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description, taken accompanying drawings. In the drawings: [24] FIGs. 1 and 2 shows essential parts of cable crosslinking devices according to the prior art; [25] FIG. 3 shows essential parts of a cable crosslinking apparatus using infrared according to a preferred embodiment of the present invention;

[26] FIG. 4 shows an IR irradiating unit of the cable crosslinking apparatus of FIG. 3;

[27] FIG. 5 shows an IR irradiating unit of a cable crosslinking apparatus using infrared according to another embodiment of the present invention; and [28] FIG. 6 shows an IR irradiating unit of a cable crosslinking apparatus using infrared according to still another embodiment of the present invention. Best Mode for Carrying Out the Invention

[29] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

[30] FIG. 3 shows essential parts of a cable crosslinking apparatus using infrared according to a preferred embodiment of the present invention, and FIG. 4 shows an IR (Infrared) irradiating unit of the cable crosslinking apparatus.

[31] Referring to FIGs. 3 and 4, the cable crosslinking apparatus 100 includes a heating unit 30 for heating a wire 1, an extruding unit 40 for coating polymer 3 on the heated wire 1 to make a cable, an IR irradiating unit 50 for irradiating infrared to the cable 5, and a cooling unit 60 for cooling the cable 5 passing through the IR irradiating unit 50.

[32] The heating unit 30 heats the wire 1 supplied from a supply roll 32 to a predetermined temperature. The heating unit 30 may adopt a high frequency induction heater or a heating furnace, commonly used for heating a wire 1. Reference numeral 34 designates a guide roller for guiding movement of the wire 1.

[33] The wire 1 is preferably heated over a reaction temperature of a crosslinking agent

4. In this case, though the heated wire 1 is cooled by the cooling unit 60 via the extruding unit 40 and the IR irradiating unit 50, the wire 1 may keep its temperature over the reaction temperature of the crosslinking agent 4, thereby promoting reaction of the crosslinking agent 4.

[34] The wire 1 heated in the heating unit 30 is carried to the extruding unit 40.

[35] The extruding unit 40 coats the polymer 3 on the wire 1 to make a cable 5. The extruding unit 40 coats the wire 1 using a compound in which an additive or a crosslinking agent 4 is added to the polymer 3, and has a common configuration.

[36] Preferably, in case the cable crosslinking apparatus 100 is used for crosslinking a small cable, an extruding head of the extruding unit 40 has a temperature higher than a reaction temperature of the crosslinking agent 4 as much as about 5⁰C.

[37] Generally, in case a polymer 3 including a crosslinking agent 4 is extruded and then crosslinked using heat, the polymer 3 is extruded while an extruding head has a lower temperature than a reaction temperature of the crosslinking agent 4. If the extruding process is conducted over a reaction temperature of the crosslinking agent 4, the polymer is crosslinked in a barrel of the extruding unit 40 or at the extruding die, and the crosslinked polymer 3 will not be extruded.

[38] However, in case the cable crosslinking apparatus 100 is used for crosslinking a small cable, an extruding rate may be set faster, so a time for the polymer 3 being stagnated in the extruding unit 40 is very short. Thus, though a temperature of the extruding head of the extruding unit 40 is raised over a reaction temperature of the crosslinking agent 4, a time is needed for transferring heat to the polymer 3, so the temperature of the crosslinking agent 4 is not raised over the reaction temperature.

[39] In addition, in case the polymer 3 is extruded while the extruding head has a temperature higher than a reaction temperature of the crosslinking agent 4, the heat of the extruding head is gradually transferred to the polymer 3, thereby advantageously promoting reaction of the crosslinking agent 4 included in the extruded polymer 3.

[40] The cable 5 coated with the polymer 3 is carried to the IR irradiating unit 50.

[41] The IR irradiating unit 50 irradiates infrared to crosslink the polymer 3 coated on the wire 1. The IR irradiating unit 50 includes an emitter 52 for irradiating infrared, and a reflective plate 54 for reflecting the infrared generated in the emitter 52.

[42] Preferably, the emitter 52 irradiates infrared in the entire wavelength range. Here, the infrared in the entire wavelength range is defined as infrared including all wavelengths generated from an IR lamp, without installing any filter for making a specific wavelength range to the IR lamp. That is to say, the emitter 52 has no need to be equipped with a separate device for intercepting a polymer absorption wavelength in order to prevent overheating of the surface of the polymer 3 coated on the surface of the wire 1.

[43] Since the wire 1 is previously heated prior to the IR irradiating process, the infrared of the entire wavelength range may be used to crosslink the polymer 3. That is to say, though the surface of the polymer 3 is heated using the infrared below a temperature at which any problem such as burning is caused thereon, it gives no effect on the crosslinking reaction of the polymer 3 due to the heated wire 1.

[44] As shown in FIG. 4, among the infrared emitted from the emitter 52, an infrared having an absorption wavelength of the polymer 3 is absorbed in the polymer 3 to promote crosslinking, and an infrared with an absorption wavelength of the crosslinking agent 4 is absorbed in the crosslinking agent 4 to promote crosslinking.

[45] Among the infrared emitted from the emitter 52, an infrared passing through the polymer 3 is reflected on the reflective plate 54 and then irradiated to the polymer 3 or the crosslinking agent 4 again.

[46] Meanwhile, among the infrared emitted from the emitter 52, an infrared reflected by the wire 1 is also irradiated to the polymer 3 or the crosslinking agent 4 again. A device 20 (see FIG. 2) disclosed in EP0921921 irradiated infrared to the tube 7 and reflected the infrared passing through the tube 7 by means of a reflective plate, thereby promoting crosslinking. That is to say, the above device 20 cannot use the infrared reflected by the wire 1.

[47] To the contrary, the cable crosslinking apparatus 100 of the present invention may use the infrared reflected by the wire 1, thereby capable of improving a crosslinking efficiency.

[48] The cooling unit 60 includes a cooling tube 62 and a cooling reservoir 66 mounted at the rear of the IR irradiating unit 50 to cool the cable 5.

[49] Preferably, in case the cooling tube 62 and the cooling reservoir 66 may not easily installed in a line, a direction-changing wheel 64 is preferably mounted between the cooling tube 62 and the cooling reservoir 66.

[50] A coolant is received in the cooling tube 62. Since the cable 5 passing through the

IR irradiating unit 50 has a very high temperature and the polymer 3 is in a glassified state, the cable 5 cannot keep its original shape if it contacts with the direction- changing wheel 64 before being cooled. Thus, the cable 5 is cooled using the cooling tube 62 in advance before it contacts with the direction-changing wheel 64.

[51] The coolant gives a cooling action from the surface of the polymer 3. Meanwhile, since the wire 1 positioned at the center of the cable 5 keeps a high temperature during the cooling process, a crosslinking reaction is continued due to the heat transferred from the wire 1.

[52] The cable 5 whose surface is cooled with passing through the cooling tube 62 is carried to the cooling reservoir 66 via the direction-changing wheel 64.

[53] The cooling reservoir 66 has turn wheels 67 provided to both sides thereof. As shown in FIG. 3, the cable 5 passes through the cooling reservoir 66 via the turn wheels 67. In order to lower a temperature of the cable 5 to a desired level, the number of turns passing the turn wheels 67 may be increased. The completely crosslinked cable 5 is drawn using a capstan 70 and then taken up by means of a take-up 80.

[54] Preferably, the IR irradiating unit 50, the cooling tube 62 and the direction- changing wheel 64 are arranged so that the cable 5 forms a catenary with a predetermined curvature. As mentioned above, since the polymer 3 of the cable 5 passing through the IR irradiating unit 50 is in a glassified state, a support member such as the direction-changing wheel 64 cannot be used. Thus, if the cable 5 is arranged horizontally, the cable 5 is drooped down, which makes it difficult to keep an original shape of the extruded polymer 3 and also to set concentricity of the polymer 3 and the wire 1. Meanwhile, if the cable 5 forms a catenary with a predetermined curvature, it is possible to prevent the original shape of the cable 5 from being deformed and also to set exact concentricity of the polymer 3 and the wire 1. [55] More preferably, a sensor 72 for detecting a drooping amount of the cable 5 is mounted between the extruding unit 40 and the direction-changing wheel 64. The sensor 72 measures a drooping amount of the cable 5 and then transmits its signal to the capstan 70. The capstan 70 controls a drawing rate of the cable 5 according to the signal, thereby controlling a drooping amount of the cable 5.

[56] FIG. 5 shows an IR irradiating unit of a cable crosslinking apparatus using infrared according to another embodiment of the present invention. This IR irradiating unit 50a includes an emitter 52 for generating infrared, and a reflective plate 54 installed at the r ear of the emitter 52. Among the infrared emitted from emitter 52, an infrared advancing backward is reflected by the reflective plate 54 and then heats the polymer 3 of the cable 5.

[57] FIG. 6 shows an IR irradiating unit of a cable crosslinking apparatus using infrared according to still another embodiment of the present invention. This IR irradiating unit 50b includes emitters 52 mounted to both sides of the cable 5 to generate infrared, and reflective plates 54 installed at the rear of each emitter 52.

[58] Among the infrared emitted from each emitter 52, an infrared advancing backward is reflected by the reflective plate 52 and heats the polymer 3 of the cable 5.

[59] Preferably, at least one pair of such IR irradiating units 50b is provided in an opposite direction based on the cable 5.

[60] Now, an operation of the cable crosslinking apparatus 100 using infrared according to the preferred embodiment of the present invention will be described.

[61] First, a wire 1 supplied from the supply roll 32 is heated in the heating unit 30 to a predetermined temperature. At this time, the wire 1 is preferably heated over a reaction temperature of the crosslinking agent 4. This allows the wire 1 to be kept over the reaction temperature of the crosslinking agent 4 and thus promotes reaction of the crosslinking agent 4 though the heated wire 1 is cooled by the cooling unit 60 via the extruding unit 40 and the IR irradiating unit 50.

[62] The heated wire 1 is carried to the extruding unit 40. The extruding unit 40 coats a polymer 3 on the wire 1 to make a cable 5. A cable 5 to be made has a small size, the extruding head of the extruding unit 40 keeps a temperature higher than a reaction temperature of the crosslinking agent 4 as much as about 5⁰C. In case of crosslinking a small cable, the extruding rate may be set fast, so a time during which the polymer is stagnated in the extruding unit 40 is very short. Thus, though a temperature of the extruding head is raised over the reaction temperature of the crosslinking agent 4, a time is taken for transferring heat to the polymer 3, so the temperature of the crosslinking agent 4 is not increased over the reaction temperature.

[63] The cable 5 coated with the polymer is carried to the IR irradiating unit 50. Infrared of the entire wavelength range is irradiated from the emitter 52, and the infrared passing through the polymer 3 is reflected by the reflective plate 54 and then irradiated again to the polymer 3. In addition, the infrared reflected by the wire 1 is also irradiated again to the polymer 3 or the crosslinking agent 4.

[64] The cable 5 passing through the IR irradiating unit 50 is carried to the cooling tube

62 via the sensor 72. The sensor 72 measures a drooping amount of the cable 5 and then transmits its signal to the capstan 70. The capstan 70 adjusts a drawing rate of the cable 5 according to the signal so as to control a drooping amount of the cable 5.

[65] A coolant is received in the cooling tube 62. The cable 5 passing through the IR irradiating unit 50 has a very high temperature and the polymer 3 is in a glassified state, so the original shape of the cable 5 cannot be maintained if it contacts with the direction-changing wheel 64 before being cooled. Thus, the cable 5 is cooled in advance using the cooling tube 62 before being contacted with the direction-changing wheel 64.

[66] Meanwhile, while a cooling process using the coolant is progressed, the wire 1 positioned at the center of the cable 5 keeps a high temperature, so the crosslinking reaction is continuously executed by means of the heat transferred from the wire 1.

[67] The cable 5 whose surface is cooled with passing through the cooling tube 62 is carried to the cooling reservoir 66 via the direction-changing wheel 64. The cable 5 is cooled with moving between the turn wheels 67 in the cooling reservoir 66 predetermined times. In order to lower the temperature of the cable 5 to a desired level, the number of turns moving via the turn wheels 67 may be increased. The completely crosslinked cable 5 is drawn by the capstan 70 and then taken up by means of the take- up 80.

[68] In the above cable making process, the IR irradiating unit 50, the cooling tube 62 and the direction-changing wheel 64 are arranged so that the cable 5 forms a catenary with a predetermined curvature. If the cable 5 forms a catenary with a predetermined curvature, it is possible to prevent deformation of the original shape of the cable 5 and also to set exact concentricity of the polymer 3 and the wire 1.

[69] The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Industrial Applicability

[70] As described above, the cable crosslinking apparatus using infrared according to the present invention gives the following effects.

[71] First, it is possible to prevent the surface of polymer from being damaged by heating.

[72] Second, it is possible to improve a thermal efficiency in the IR irradiating process.

[73] Third, since the wire is previously heated and then an internal polymer is heated using the heat conducted from the wire, it is possible to crosslink the polymer efficiently.

[74] Fourth, since the cable is moved with forming a catenary having a predetermined curvature, it is possible to keep an original shape of the cable and exactly set concentricity of the cable.

Claims

[1] A cable crosslinking apparatus using infrared, comprising: a heating unit for heating a wire to a predetermined temperature; an extruding unit for coating polymer on the heated wire to make a cable; an IR (infrared) irradiating unit for irradiating infrared to the cable; and a cooling unit for cooling the wire passing through the IR irradiating unit. [2] The cable crosslinking apparatus using infrared according to claim 1, wherein the heating unit heats the wire over a reaction temperature of a crosslinking agent. [3] The cable crosslinking apparatus using infrared according to claim 1, wherein the

IR irradiating unit includes: an emitter for generating infrared; and a reflective plate for reflecting the infrared in order to enhance an IR emitting efficiency of the emitter. [4] The cable crosslinking apparatus using infrared according to claim 3, wherein there are provided at least one pair of the IR irradiating units in opposite directions based on the cable. [5] The cable crosslinking apparatus using infrared according to claim 1, wherein the cooling unit includes: a cooling tube mounted at the rear of the IR irradiating unit and receiving a coolant therein; and a cooling reservoir mounted at the rear of the cooling tube. [6] The cable crosslinking apparatus using infrared according to claim 5, wherein the cooling unit further includes a direction-changing wheel mounted between the cooling tube and the cooling reservoir to support the cable and also changing a moving direction of the cable, and wherein the IR irradiating unit, the cooling tube and the direction-changing wheel are arranged so that the cable forms a catenary with a predetermined curvature. [7] The cable crosslinking apparatus using infrared according to any of claims 1 to 6, wherein the IR irradiating unit irradiates infrared of the entire wavelength ranges to the cable.