WO2007139369A2 - Coaxial cable having a surface with low coefficient of friction and method of manufacture thereof - Google Patents

Coaxial cable having a surface with low coefficient of friction and method of manufacture thereof Download PDF

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Publication number
WO2007139369A2
WO2007139369A2 PCT/MX2007/000065 MX2007000065W WO2007139369A2 WO 2007139369 A2 WO2007139369 A2 WO 2007139369A2 MX 2007000065 W MX2007000065 W MX 2007000065W WO 2007139369 A2 WO2007139369 A2 WO 2007139369A2
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WO
WIPO (PCT)
Prior art keywords
cover
coaxial cable
lubricating agent
shield
insulation
Prior art date
Application number
PCT/MX2007/000065
Other languages
Spanish (es)
French (fr)
Other versions
WO2007139369A3 (en
Inventor
Patricio Gerardo MURGA GONZÁLEZ
Sergio Arturo Montes Valdez
José RANC GÓMEZ
Héctor Ricardo LÓPEZ GONZÁLEZ
Walter Hugh Reeker Martinez
Original Assignee
Conductores Monterrey, S.A. De C.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Conductores Monterrey, S.A. De C.V. filed Critical Conductores Monterrey, S.A. De C.V.
Publication of WO2007139369A2 publication Critical patent/WO2007139369A2/en
Publication of WO2007139369A3 publication Critical patent/WO2007139369A3/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1878—Special measures in order to improve the flexibility
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/016—Apparatus or processes specially adapted for manufacturing conductors or cables for manufacturing co-axial cables
    • H01B13/0165—Apparatus or processes specially adapted for manufacturing conductors or cables for manufacturing co-axial cables of the layers outside the outer conductor

Definitions

  • This invention relates to the field of coaxial cables and more precisely, to a coaxial cable of low coefficient of surface friction that has a cover that incorporates at least one lubricating agent that migrates to its outer surface, and likewise refers to a method of manufacturing said coaxial cable.
  • coaxial cable is used to transmit high frequency signals, such as data, voice and television signals, the latter commonly known as cable television (CATV).
  • CATV cable television
  • the coaxial cable is generally formed by a central conductor, an insulation, an outer shield or conductor and an outer cover.
  • the central conductor can be formed by a wire or cable, commonly made of copper, aluminum, steel coated with aluminum or copper; and which in turn is coated with an insulation, generally made of one or more dielectric layers of polyethylene-based plastic material, or mixtures of polyethylene, solid or foamed.
  • the insulation is surrounded by an outer shield or conductor commonly formed by a metallic tape and a metal mesh.
  • the metallized tape is applied in a helical or longitudinal manner and is substantially formed by a thin aluminum foil adhered to a layer of polymer; while the metal mesh is normally formed by a plurality of thin metal wires of copper, aluminum or tinned applied helically or as a braided mesh.
  • the shield or outer conductor in addition to serving as an electric conductor, also serves as a protective shield of coaxial cable against the loss or dispersion of radiation from the transmitted radio frequency.
  • the outer cover fulfills the functions of mechanical protection against the external environment.
  • covers based on polyvinyl chloride (PVC) are used due to their excellent properties of resistance to the environment, sunlight, chemical agents, the propagation of the flame and moisture.
  • PVC polyvinyl chloride
  • the outer shell in addition to providing mechanical protection to the coaxial cable against the outside environment, also provides mechanical rigidity to the outer shield or conductor in order to maintain the metal wires of the metal mesh, as well as the same metal mesh and the metallic cover in electrical contact uniformly along the length of the coaxial cable.
  • the outer sheath generally has a high coefficient of friction that causes problems during the installation of the coaxial cable.
  • the shape and composition of the outer surface of the coaxial cable cover determines the ease with which the coaxial cable can be pushed or pulled through and in contact with another surface, such as, for example, the outer surface of the cover of another cable or the surface of the internal wall of a conduit in which the coaxial cable is or will be installed.
  • a coaxial cable is installed in a conduit, such as a tube, which may or may not contain other cables, such as coaxial cables, fiber optic cables or electrical power cables.
  • the friction between a coaxial cable and another surface that the coaxial cable contacts resists the movement of the coaxial cable and holds the coaxial cable, or its internal components, to tension when moving the coaxial cable with respect to the surface.
  • the value of the tension that is imposed on the coaxial cable increases as the length of the cable that is subjected to friction increases.
  • the tension on the coaxial cable generated by the friction can cause damage to the rigidity and mechanical integrity of the cable or damage the components of the coaxial cable damaging its electrical-dielectric qualities thereof. For example, if a pulling force that is too large is applied to a coaxial cable during its installation as a result of the friction that occurs over a long section of the coaxial cable that stretches over another surface, the coaxial cable can be stretched further. beyond an allowable extension. This undue elongation can cause breakage or fractures, both in the central conductor, insulation, shielding or external conductor and in the same external cover that severely damage the electrical, dielectric and mechanical capacity thereof.
  • a lubricant composition for electric cable that includes an aqueous solution of 1% to 4% of a water soluble cellulose derivative, such as carboxymethyl cellulose, and 0.5% to 2% polyacrylamide.
  • the lubricant may be presented in liquid or gel form.
  • Nobuhiro Fujio and Akihiro Ishihara in Japanese patent JP-9251811, describe a resin composition for cable sheath that has excellent flexibility and low coefficient of friction.
  • the resin composition includes from 0.2 parts by weight to 3 parts by weight of an aliphatic amide and from 55 parts by weight to 90 parts by weight of a liquid plasticizer with respect to 100 parts by weight of any resin, for example PVC.
  • any resin for example PVC.
  • erucilamide is used.
  • Henry Williamson Harcourt Robinson in British patents GB-1175059, GB-1175060 and GB-1230189, describes a low friction electric cable having a cover composed of at least one polyolefin and a lubricating agent, such that the polyolefin can be a polymer or copolymer of ethylene, propylene or butylene, while the lubricating agent can be an amide of fatty acid such as, for example, caprilamide, capramide, lauramide, myristamide, palmitamide, estereamide, oleamide, linoleamide and erucamide.
  • the polyolefin can be a polymer or copolymer of ethylene, propylene or butylene
  • the lubricating agent can be an amide of fatty acid such as, for example, caprilamide, capramide, lauramide, myristamide, palmitamide, estereamide, oleamide, linoleamide and erucamide.
  • KyIe Cope and Tareq Hanque in European Patent Publication EP-0949635, describe a pre-lubricated cable and its manufacturing process.
  • the cable is provided with an external coating and has a layer of non-adhesive lubricating coating that adheres to the outermost surface of the outer shell.
  • the lubricating coating layer is of an organo-polysiloxane release agent, such as polyalkylsiloxane.
  • a coaxial cable in particular a coaxial cable for CATV, with a low coefficient of surface friction that has an outer sheath that incorporates at least one lubricating agent that migrates to its surface, and that has an intermediate cover that prevents said agent lubricant migrates towards the internal components of the coaxial cable, in such a way that the lubricating composition of the external cover maintains a high degree of lubrication, without excessive residues, on the surface of the external cover for a long period of time, including the period of time after the installation of the coaxial cable inside a conduit; that allows the application of connectors; a cover that can withstand the wear associated with abrasive loads ordinarily experienced by a coaxial cable; that is not flammable; that allows printing on the surface of the outer cover of a code pattern and that I continue to have the above qualities after being subjected to a wide range of temperatures and humidity conditions.
  • a coaxial cable with a low coefficient of surface friction said coaxial cable has a central conductor; an insulation that envelops the central conductor; a shield surrounding the insulation; a first cover that wraps around the shield; and a second cover that envelops the first cover; such that the second cover incorporates at least one lubricating agent that migrates towards the external surface of the coaxial cable; and the first cover prevents the lubricating agent from migrating towards the shield.
  • the object of the invention to offer a method of manufacturing a coaxial cable with a low coefficient of surface friction, the method has the steps of extruding an insulation around a central conductor; wrap the insulation with a shield; extrude a first cover around the shield; and co-extrude a second cover around the first cover; such that the second cover incorporates at least one lubricating agent that migrates towards the external surface of the coaxial cable; and the first cover prevents the lubricating agent from migrating towards the shield.
  • Figure 1 illustrates a perspective view in section of a coaxial cable according to the invention.
  • Figure 2 illustrates a block diagram of a method of manufacturing a coaxial cable according to the invention.
  • a coaxial cable 10 generally formed by a central conductor 20, an insulation 30, a shield 40 (also known as an external conductor), a first cover 70 and a second cover 80.
  • the central conductor 20 is formed by a metal wire or cable which in turn is surrounded by the envelope insulation 30, generally made of one or more dielectric layers of one or more plastic materials based on polyethylene or other dielectric material.
  • the insulation 30 is surrounded by the shield 40 which is generally formed by one or more metalized tapes 50 and by one or more metal meshes 60.
  • the metallic tape 50 is applied helically or longitudinally and is substantially formed by a lamella thin aluminum bonded to a polymer layer; while the metal mesh 60 is normally formed by a plurality of thin metal wires applied helically or as a braided mesh.
  • the first cover 70 which surrounds the shield 40, mechanically protects the coaxial cable 10 against the outside environment and maintains the mechanical rigidity thereof and serves as a protective barrier that prevents the lubricating composition, which is described later, from migrating into the interior of the coaxial cable 10 in order to avoid damage to the electrical, dielectric and mechanical qualities thereof.
  • the first cover 70 is generally made of one or more layers of polymer-based plastic material such as, for example, polyethylene, polypropylene, polyvinylchloride, vinyl chloride copolymers with vinyl acetate, ethylene copolymers with an alpha-olefin or with a saturated ester, fluoropolymers, chlorinated polymers, vinylidene polychloride, polyamides, acrylic polymers, polyesters, ionic hydrocarbon polymers and mixtures thereof.
  • polymer-based plastic material such as, for example, polyethylene, polypropylene, polyvinylchloride, vinyl chloride copolymers with vinyl acetate, ethylene copolymers with an alpha-olefin or with a saturated ester, fluoropolymers, chlorinated polymers, vinylidene polychloride, polyamides, acrylic polymers, polyesters, ionic hydrocarbon polymers and mixtures thereof.
  • Envelope in the first outer cover 70 is a second cover 80 that has a low coefficient of friction by incorporating a lubricating agent that migrates towards the surface of said cover.
  • Said lubricating agent is incorporated into the polymer-based plastic material such as, for example, polyethylene, polypropylene, polyvinylchloride, vinyl chloride copolymers with vinyl acetate, ethylene copolymers with an alpha-olefin or with a saturated ester, fluoropolymers, chlorinated polymers, vinylidene polychloride, polyamides, acrylic polymers, polyesters ,. ionic hydrocarbon polymers and mixtures thereof.
  • the low coefficient of friction on the surface of the second cover 80 is the result of the migration of the lubricating agent towards the surface of said cover due to the incompatibility defined between the lubricating agent and the polymer used in the composition of the cover.
  • the migration rate of the lubricating agent towards the surface of said cover is the result of the migration of the lubricating agent towards the surface of said cover due to the incompatibility defined between the lubricating agent and the polymer used in the composition of the cover.
  • the surface is generally defined by the length of the chain of the lubricating agents (compatibility with the polymer) and by the characteristics of the polymer, including their crystallinity. The larger the chain of the lubricating agent is
  • lubricating agents preferably employed in the invention, we have those based on fatty acid amides such as, for example, oleamide, erucamide, caprilamide, capramide, lauramide, palmitamide, stearamide, linoleamide, myristamide and mixtures thereof. More preferably oleamide and erucamide within a range of 0.25% by weight to 1.0% by weight in relation to the final composition to form said second cover 80.
  • a characteristic of the second cover 80 is. which must have a thickness much less than the thickness of the first cover 70, so that the greater amount of lubricating agent incorporated in the second cover 80 only tends to migrate towards the external surface and that that amount of lubricating agent that arrives to migrate towards the internal surface in contact with the first cover 70 is dissipated in this cover, without subsequently migrating to the shield.
  • the first cover preferably has a thickness in a range of 0.5 mm to 1.1 mm; while the second cover has a thickness preferably in a range of 0.05 mm to 0.25 mm.
  • the second cover 80 may have on its surface a first printed code pattern (not shown), formed by a sequence based on characters, symbols, numbers, visual patterns based on colors and / or combinations of all of these and that together they serve to identify, for example, the type of coaxial cable, its physical and electrical characteristics, the manufacturing company thereof, the company that owns and provides CATV signals, among other data.
  • This pattern of printed code is not affected by the lubricating agent that migrates to the surface of the cover 80.
  • samples of coaxial cable for CATV type RG-59 were first manufactured having a single cover made of PVC, to which increasing amounts of oleamide were added.
  • the tensile force exerted on each of the samples of said cable that was passed, at a speed of 600 mm / min was measured through a commercial polyethylene conduit of 0.8 m long and with a 90 ° elbow placed at half of said length. It should be mentioned that the tensile force, measured for each sample, corresponds to the force necessary to pull the coaxial cable in order to pass it through the polyethylene conduit.
  • Table 1 shows the characteristics and results obtained from the samples of coaxial cable type RG-59 with a single cover, in which it is observed that when the amount of oleamide is increased, the tensile strength decreases, for example, when the concentration of oleamide is 0.5% by weight of the cover, the effect is only marginal; while when the concentration is 1% the friction is considerably reduced.
  • the coaxial cable of the sample, with the cover containing 1% by weight of oleamide could not be connected satisfactorily to the connector, since it was found that the cover did not show any adhesion with the shield because the oleamide had migrated towards it.
  • a series of coaxial cable samples were manufactured with a first cover consisting of a flexible polyvinyl chloride compound suitable for use in covers of the coaxial cables of the invention.
  • a second cover was placed on top of the first cover, consisting of the same material as the first cover, but containing several concentrations of at least one lubricating agent.
  • the lubricating agents contemplated in the study are oleamide and erucamide.
  • the thickness of the second roof was also systematically varied. The results obtained from these samples are illustrated in Table 2.
  • Table 3 illustrates the results of the average tensile strength and standard deviation obtained for each sample for the 25 determinations.
  • the erucamide is more effective in reducing the tension force while a higher concentration of it tends to reduce even more the friction between the external surface of the second cable sheath and the internal surface of the polyethylene duct.
  • storage simulation studies were carried out under various temperature conditions. Samples E, H and J were stored in a cold room, whose temperature was maintained at 15 0 C, at room temperature (23 0 C) and in a hot room with a controlled temperature of 36 0 C. After 2 months in these conditions, the samples were removed, conditioned at room temperature for 24 hours to subsequently test the tensile strength.
  • samples D, F, G, H were selected and J to carry out a study of tension and connection force after 2 months of storage at room temperature.
  • the results, shown in Table 5, indicate that the measurements of the tensile force at 0 and 2 months of storage are comparable. It should be mentioned that these samples were successfully connected after 2 months of being manufactured and conditioned at room temperature. This means that the ease of sliding of the second cover remains stable over time regardless of the lubricating agent and thickness of the second cover.
  • step 1OO by applying insulation on a conductor by means of extrusion; proceeding, in step 110, to wrap the insulation with a shield, such that the shield consists of first wrapping the insulation with a metallized tape, then wrapping the metallized tape with a metal mesh; in step 120, for extrusion medium, the shield is wrapped with a first cover; immediately step 140 a second cover is applied by means of a co-extrusion stage on the first cover, such that the second cover incorporates a lubricating agent that was previously mixed, in step 130, with the plastic composition to form it .
  • the second cover is co-extruded to the first cover with a thickness much smaller than the thickness of the first cover.
  • code 150 a code pattern is applied on the surface of the second cover.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Insulated Conductors (AREA)
  • Manufacturing Of Electric Cables (AREA)
  • Communication Cables (AREA)

Abstract

A coaxial cable (10) having a central conductor (20), an insulation (30) surrounding the central conductor (20), a shield (40) surrounding the insulation (30), a first covering (70) surrounding the shield (40), and a second cover (80) surrounding the first co (70), wherein the second cover (80) contains at least one lubricating agent based on amide of fatty acids, such as oleamide and erucamide, which move towards the external surface of the second cover (80).

Description

CABLE COAXIAL DE BAJO COEFICIENTE DE FRICCIÓN SUPERFICIAL Y MÉTODO DE FABRICACIÓN DEL MISMO COAXIAL CABLE OF LOW COEFFICIENT OF SURFACE FRICTION AND MANUFACTURING METHOD OF THE SAME
CAMPO TÉCNICO DE LA INVENCIÓNTECHNICAL FIELD OF THE INVENTION
Esta invención se refiere al campo de los cables coaxiales y de una manera más precisa, a un cable coaxial de bajo coeficiente de fricción superficial que cuenta con una cubierta que incorpora al menos un agente lubricante que migra a su superficie externa, y así mismo se refiere a un método de fabricación de dicho cable coaxial.This invention relates to the field of coaxial cables and more precisely, to a coaxial cable of low coefficient of surface friction that has a cover that incorporates at least one lubricating agent that migrates to its outer surface, and likewise refers to a method of manufacturing said coaxial cable.
ANTECEDENTES DE LA INVENCIÓNBACKGROUND OF THE INVENTION
Actualmente un típico cable coaxial es usado para transmitir señales de alta frecuencia, tales como señales de datos, voz y televisión, ésta última comúnmente conocida como televisión por cable (CATV). El cable coaxial está formado generalmente por un conductor central, un aislamiento, un blindaje o conductor exterior y por una cubierta exterior.Currently a typical coaxial cable is used to transmit high frequency signals, such as data, voice and television signals, the latter commonly known as cable television (CATV). The coaxial cable is generally formed by a central conductor, an insulation, an outer shield or conductor and an outer cover.
El conductor central puede estar formado por un alambre o cable, hecho comúnmente de cobre, aluminio, acero recubierto con aluminio o cobre; y que a su vez está recubierto con un aislamiento, hecho generalmente de una o varias capas dieléctricas de material plástico a base de polietileno, o mezclas de polietilenos, sólido o espumado.The central conductor can be formed by a wire or cable, commonly made of copper, aluminum, steel coated with aluminum or copper; and which in turn is coated with an insulation, generally made of one or more dielectric layers of polyethylene-based plastic material, or mixtures of polyethylene, solid or foamed.
A su vez el aislamiento está rodeado por un blindaje o conductor exterior formado comúnmente por una cinta metalizada y por una malla metálica. La cinta metalizada es aplicada en forma helicoidal o longitudinal y está formada substancialmente por una laminilla delgada de aluminio adherida a una capa de polímero; mientras que Ia malla metálica está formada normalmente por una pluralidad de hilos metálicos delgados de cobre, aluminio o estañados aplicados en forma helicoidal o como malla trenzada. El blindaje o conductor exterior además de servir como un conductor eléctrico, también sirve como una pantalla protectora de cable coaxial contra Ia pérdida o dispersión de radiación de Ia radio frecuencia transmitida.In turn, the insulation is surrounded by an outer shield or conductor commonly formed by a metallic tape and a metal mesh. The metallized tape is applied in a helical or longitudinal manner and is substantially formed by a thin aluminum foil adhered to a layer of polymer; while the metal mesh is normally formed by a plurality of thin metal wires of copper, aluminum or tinned applied helically or as a braided mesh. The shield or outer conductor, in addition to serving as an electric conductor, also serves as a protective shield of coaxial cable against the loss or dispersion of radiation from the transmitted radio frequency.
La cubierta exterior cumple las funciones de protección mecánica contra el medio exterior. Generalmente se utilizan cubiertas a base de policloruro de vinilo (PVC) debido a sus excelentes propiedades de resistencia al medio ambiente, luz solar, agentes químicos, a Ia propagación de Ia flama y a Ia humedad. También es bien reconocido que Ia cubierta exterior además de proporcionar protección mecánica al cable coaxial contra el medio exterior, también proporciona rigidez mecánica al blindaje o conductor exterior con el objeto de mantener a los hilos metálicos de Ia malla metálica, así como Ia misma malla metálica y Ia cubierta metalizada en contacto eléctrico en forma uniforme a Io largo de Ia longitud del cable coaxial.The outer cover fulfills the functions of mechanical protection against the external environment. Generally covers based on polyvinyl chloride (PVC) are used due to their excellent properties of resistance to the environment, sunlight, chemical agents, the propagation of the flame and moisture. It is also well recognized that the outer shell, in addition to providing mechanical protection to the coaxial cable against the outside environment, also provides mechanical rigidity to the outer shield or conductor in order to maintain the metal wires of the metal mesh, as well as the same metal mesh and the metallic cover in electrical contact uniformly along the length of the coaxial cable.
Sin embargo, Ia cubierta exterior cuenta, por Io general, con un alto coeficiente de fricción que provoca problemas durante la instalación del cable coaxial. La forma y Ia composición de Ia superficie externa de Ia cubierta del cable coaxial determina Ia facilidad con Ia que el cable coaxial se puede empujar o jalar a través y en contacto con otra superficie, tal como, por ejemplo, Ia superficie externa de Ia cubierta de otro cable o Ia superficie de Ia pared interna de un conducto en el que está o estará instalado el cable coaxial. Frecuentemente, un cable coaxial está instalado en un conducto, tal como un tubo, que puede contener o no otros cables, tales como cables coaxiales, cables de fibra óptica o cables de energía eléctrica. La fricción entre un cable coaxial y otra superficie que el cable coaxial contacta se resiste al movimiento del cable coaxial y sujeta el cable coaxial, o sus componentes internos, para tensarse al mover el cable coaxial respecto a Ia superficie. El valor de Ia tensión que se impone sobre el cable coaxial aumenta al aumentar Ia longitud del cable que esté sometido a fricción. La tensión sobre el cable coaxial generada por Ia fricción puede provocar daños a Ia rigidez e integridad mecánica del cable o perjudicar los componentes del cable coaxial perjudicando sus cualidades eléctrico-dieléctricas del mismo. Por ejemplo, si se aplica una fuerza de tracción demasiado grande a un cable coaxial durante su instalación como resultado de Ia fricción que se produce a Io largo de un largo tramo del cable coaxial que se estira sobre otra superficie, el cable coaxial puede estirarse más allá de una extensión permisible. Esta elongación indebida puede provocar roturas o fracturas, tanto en el conductor central, aislamientos, blindaje o conductor externo y en Ia misma cubierta externa que dañan de manera severa Ia capacidad eléctrica, dieléctrica y mecánica del mismo.However, the outer sheath generally has a high coefficient of friction that causes problems during the installation of the coaxial cable. The shape and composition of the outer surface of the coaxial cable cover determines the ease with which the coaxial cable can be pushed or pulled through and in contact with another surface, such as, for example, the outer surface of the cover of another cable or the surface of the internal wall of a conduit in which the coaxial cable is or will be installed. Frequently, a coaxial cable is installed in a conduit, such as a tube, which may or may not contain other cables, such as coaxial cables, fiber optic cables or electrical power cables. The friction between a coaxial cable and another surface that the coaxial cable contacts resists the movement of the coaxial cable and holds the coaxial cable, or its internal components, to tension when moving the coaxial cable with respect to the surface. The value of the tension that is imposed on the coaxial cable increases as the length of the cable that is subjected to friction increases. The tension on the coaxial cable generated by the friction can cause damage to the rigidity and mechanical integrity of the cable or damage the components of the coaxial cable damaging its electrical-dielectric qualities thereof. For example, if a pulling force that is too large is applied to a coaxial cable during its installation as a result of the friction that occurs over a long section of the coaxial cable that stretches over another surface, the coaxial cable can be stretched further. beyond an allowable extension. This undue elongation can cause breakage or fractures, both in the central conductor, insulation, shielding or external conductor and in the same external cover that severely damage the electrical, dielectric and mechanical capacity thereof.
A fin de superar el inconveniente antes descrito, es común que el cable coaxial, antes de su instalación, sea impregnado de vaselina o algún otro lubricante con el propósito de disminuir el coeficiente de fricción del mismo y por ende facilitar su instalación dentro de conductos o secciones internas. Ver, por ejemplo, las patentes estadounidenses US-3, 565,213 y US-4,063,617, que describen procedimientos de lubricación de un cable al estirar del cable en un conducto. Una lubricación impropia o inadecuada del cable o del tubo puede producir daños en el cable cuando se estira del cable contra Ia superficie más interna del tubo durante o después de Ia instalación.In order to overcome the inconvenience described above, it is common for the coaxial cable, before its installation, to be impregnated with petroleum jelly or some other lubricant in order to reduce the coefficient of friction thereof and therefore facilitate its installation within conduits or internal sections See, for example, US patents US-3, 565,213 and US-4,063,617, which describe lubrication procedures of a cable when stretching the cable in a conduit. Improper or inadequate lubrication of the cable or tube can cause damage to the cable when the cable is stretched against the innermost surface of the tube during or after the installation.
Otro ejemplo de esta aplicación, Io encontramos descrito por William Alexander en Ia patente estadounidense US-4,378,299, en Ia que se describe una composición de lubricante para cable eléctrico que incluye una solución acuosa de 1 % a 4 % de un derivado de celulosa soluble en agua, tal como carboximetil celulosa, y de 0.5 % a 2 % de poliacrilamida. El lubricante puede estar presentado en forma líquida o en gel.Another example of this application, we find described by William Alexander in US Pat. No. 4,378,299, which describes a lubricant composition for electric cable that includes an aqueous solution of 1% to 4% of a water soluble cellulose derivative, such as carboxymethyl cellulose, and 0.5% to 2% polyacrylamide. The lubricant may be presented in liquid or gel form.
La aplicación de un lubricante sobre un cable o un tubo en el que se va a instalar el cable coaxial, en el momento de Ia instalación, no es siempre, sin embargo, un procedimiento simple, barato y conveniente. Por ejemplo, las condiciones ambientales presentes en Ia instalación pueden ser severas. Además, Ia mano de obra y el equipo adicional requeridos para aplicar el lubricante pueden ser costosos. Aunado a que todo el procedimiento de lubricación puede consumir mucho tiempo.The application of a lubricant on a cable or a tube in which the coaxial cable is to be installed, at the time of installation, is not always, however, a simple, cheap and convenient procedure. For example, the environmental conditions present in the installation can be severe. In addition, the labor and additional equipment required to apply the lubricant can be expensive. In addition to that the entire lubrication procedure can be time consuming.
Actualmente, muchos de los lubricantes conocidos que se aplican a un cable en un lugar de instalación están hechos de grasa, aceite o un material similar al gel, cuya aplicación en exceso puede provocar que permanezca un residuo sucio y pesado de lubricante sobre Ia cubierta del cable. Este residuo sucio puede impedir Ia posterior manipulación, y las operaciones para obtener acceso a los componentes internos del cable, así como propiciar fallas en las cualidades eléctricas, dieléctricas y mecánicas del mismo.Currently, many of the known lubricants that are applied to a cable at an installation site are made of grease, oil or a gel-like material, whose excessive application can cause a dirty and heavy residue of lubricant to remain on the cover of the cable. This dirty residue can prevent subsequent manipulation, and the operations to obtain access to the internal components of the cable, as well as cause failures in the electrical, dielectric and mechanical qualities thereof.
De una manera complementaria, también se usan guías de pequeño diámetro, un extremo de los cuales se inserta a través del conducto a través de Ia que ha de pasar el cable, y el otro se fija al extremo del cable que se ha de insertar en el conducto. De esta manera una vez que ha salido Ia guía en el lugar deseado, se estira hasta que el extremo del cable aparece otra vez después de haber pasado a través de toda Ia sección. La desventaja en el uso de esta guía es que si el cable coaxial llega tensarse en Ia superficie interna del conducto, durante un tirón fuerte, es posible que se pueda provocar roturas o fracturas, tanto en el conductor central, aislamientos, blindaje o conductor externo y en Ia misma cubierta externa que dañan de manera severa Ia capacidad eléctrica, dieléctrica y mecánica del mismo. Otra solución actual es proveer un cable cuya cubierta externa tenga un bajo coeficiente de fricción al agregar aditivos o agentes lubricantes en su composición. Ejemplos de estas aplicaciones las encontramos descritas en los siguientes documentos de patente:In a complementary manner, small diameter guides are also used, one end of which is inserted through the conduit through which the cable is to pass, and the other is fixed to the end of the cable to be inserted into the duct In this way once the guide has left in the desired place, it is stretched until the end of the cable appears again after having passed through the entire section. The disadvantage in the use of this guide is that if the coaxial cable becomes tensioned on the internal surface of the conduit, during a strong pull, it is possible that it can cause breakage or fractures, both in the central conductor, insulation, shielding or external conductor and in the same external cover that severely damage the electrical, dielectric and mechanical capacity thereof. Another current solution is to provide a cable whose outer sheath has a low coefficient of friction by adding additives or lubricating agents in its composition. Examples of these applications are described in the following patent documents:
Nobuhiro Fujio y Akihiro Ishihara, en Ia patente japonesa JP-9251811, describen una composición de resina para cubierta de cable que tiene excelente flexibilidad y bajo coeficiente de fricción. La composición de resina incluye de 0.2 partes por peso a 3 partes por peso de una amida alifática y de 55 partes por peso a 90 partes por peso de un plastificante liquido con respecto a 100 partes por peso de cualquier resina, por ejemplo PVC. En un caso en particular se emplea erucilamida.Nobuhiro Fujio and Akihiro Ishihara, in Japanese patent JP-9251811, describe a resin composition for cable sheath that has excellent flexibility and low coefficient of friction. The resin composition includes from 0.2 parts by weight to 3 parts by weight of an aliphatic amide and from 55 parts by weight to 90 parts by weight of a liquid plasticizer with respect to 100 parts by weight of any resin, for example PVC. In a particular case, erucilamide is used.
Henry Williamson Harcourt Robinson, en las patentes británicas GB-1175059, GB-1175060 y GB-1230189, describe un cable eléctrico de baja fricción que tiene una cubierta compuesta de al menos una poliolefina y un agente lubricante, tal que Ia poliolefina puede ser un polímero o copolímero de etileno, propileno o butileno, mientras que el agente lubricante puede ser una amida de ácido graso como, por ejemplo, caprilamida, capramida, lauramida, miristamida, palmitamida, estereamida, oleamida, linoleamida y erucamida.Henry Williamson Harcourt Robinson, in British patents GB-1175059, GB-1175060 and GB-1230189, describes a low friction electric cable having a cover composed of at least one polyolefin and a lubricating agent, such that the polyolefin can be a polymer or copolymer of ethylene, propylene or butylene, while the lubricating agent can be an amide of fatty acid such as, for example, caprilamide, capramide, lauramide, myristamide, palmitamide, estereamide, oleamide, linoleamide and erucamide.
Jean Pierre BoniceL y Olver Tatat, en Ia publicación de patente europea EP- 0905717, describen un dispositivo para recubrir un cable con un lubricante sólido, en el que una película de lubricante se deposita sobre una cubierta extrudida mediante pulverización en Ia fase de plasma (rociado).Jean Pierre BoniceL and Olver Tatat, in the European patent publication EP-0905717, describe a device for coating a cable with a solid lubricant, in which a film of lubricant is deposited on an extruded cover by means of spraying in the plasma phase ( sprayed).
KyIe Cope y Tareq Hanque, en Ia publicación de patente europea EP-0949635, describen un cable prelubricado y su procedimiento de fabricación. El cable está provisto de un recubrimiento externo y tiene una capa de recubrimiento lubricante no adhesiva que se adhiere a Ia superficie más externa de Ia cubierta extema. La capa de recubrimiento lubricante es de una agente de desmoldeo organo-polisiloxano, tal como el polialquilsiloxano.KyIe Cope and Tareq Hanque, in European Patent Publication EP-0949635, describe a pre-lubricated cable and its manufacturing process. The cable is provided with an external coating and has a layer of non-adhesive lubricating coating that adheres to the outermost surface of the outer shell. The lubricating coating layer is of an organo-polysiloxane release agent, such as polyalkylsiloxane.
Randy D. Kummer y otros, en las publicaciones de solicitudes de patente estadounidenses US-20060065427, US-20060065428, US-20060065430, US- 20060068085, US-20060068086 y US-20060088657, describen el uso de agentes lubricantes, como Ia oleamida y erucamida, en Ia composición de las cubiertas para cable y sus procedimientos de aplicación durante el proceso de fabricación del cable, ya sea en mezcla con los demás componentes de Ia cubierta o por medio de su aplicación a través de las etapas de conformación de Ia cubierta o por medio de rociado.Randy D. Kummer and others, in U.S. Patent Application Publications US-20060065427, US-20060065428, US-20060065430, US- 20060068085, US-20060068086 and US-20060088657, describe the use of lubricating agents, such as oleamide and erucamida, in the composition of the cable covers and their application procedures during the cable manufacturing process, either in admixture with the other components of the cover or through its application through the stages of forming the cover or by spraying.
Las propuestas anteriormente descritas de contar con un cable cuya cubierta externa incorpore en su composición algún tipo lubricante implica una desventaja para el caso de un cable coaxial, pues dicho lubricante puede migrar hacia los componentes internos del cable coaxial y por tanto propiciar fallas en las cualidades eléctricas, dieléctricas y mecánicas del mismo. Por ejemplo, en el caso que el lubricante migre de Ia cubierta exterior al blindaje o conductor externo, implica que Ia rigidez mecánica entre ambas capas se pierda propiciando que dicho blindaje pierda contacto eléctrico y que Ia misma cubierta externa tienda a corrugarse o a deslizarse del mismo cable, dificultando Ia aplicación del conector.The previously described proposals to have a cable whose external cover incorporates some type of lubricant in its composition implies a disadvantage in the case of a coaxial cable, since said lubricant can migrate towards the internal components of the coaxial cable and therefore lead to flaws in the qualities electrical, dielectric and mechanical thereof. For example, in the case that the lubricant migrates from the outer shell to the shield or external conductor, it implies that the mechanical stiffness between both layers is lost, causing said shield to lose electrical contact and that the same outer shell tends to corrugate or slide from it. cable, hindering the application of the connector.
Por Io tanto, existe Ia necesidad de ofrecer un cable coaxial, en particular un cable coaxial para CATV, de bajo coeficiente de fricción superficial que cuente con una cubierta externa que incorpore al menos un agente lubricante que migre a su superficie, y que cuente con una cubierta intermedia que impida que dicho agente lubricante migre hacia los componentes interiores del cable coaxial, de tal manera que Ia composición lubricante de Ia cubierta externa mantenga un alto grado de lubricación, sin residuos excesivos, en Ia superficie de Ia cubierta externa durante un largo periodo de tiempo, incluyendo el periodo de tiempo posterior a Ia instalación del cable coaxial en el interior de un conducto; que permita Ia aplicación de conectores; que sea una cubierta que pueda soportar el desgaste asociado con las cargas abrasivas experimentadas de manera ordinaria por un cable coaxial; que no sea inflamable; que permita Ia impresión sobra Ia superficie de Ia cubierta externa de un patrón de código y que continué teniendo las cualidades anteriores después de someterse a un amplio alcance de temperaturas y a condiciones de humedad.Therefore, there is a need to offer a coaxial cable, in particular a coaxial cable for CATV, with a low coefficient of surface friction that has an outer sheath that incorporates at least one lubricating agent that migrates to its surface, and that has an intermediate cover that prevents said agent lubricant migrates towards the internal components of the coaxial cable, in such a way that the lubricating composition of the external cover maintains a high degree of lubrication, without excessive residues, on the surface of the external cover for a long period of time, including the period of time after the installation of the coaxial cable inside a conduit; that allows the application of connectors; a cover that can withstand the wear associated with abrasive loads ordinarily experienced by a coaxial cable; that is not flammable; that allows printing on the surface of the outer cover of a code pattern and that I continue to have the above qualities after being subjected to a wide range of temperatures and humidity conditions.
SUMARIO DE LA INVENCIÓNSUMMARY OF THE INVENTION
En vista de Io anteriormente descrito y con el propósito de dar solución a las limitantes encontradas, es objeto de Ia invención ofrecer un cable coaxial de bajo coeficiente de fricción superficial, dicho cable coaxial cuenta con un conductor central; un aislamiento que envuelve al conductor central; un blindaje que rodea al aislamiento; una primera cubierta que envuelve al blindaje; y una segunda cubierta que envuelve a Ia primera cubierta; tal que Ia segunda cubierta incorpora al menos un agente lubricante que migra hacia Ia superficie externa del cable coaxial; y Ia primera cubierta impide que el agente lubricante migre hacia el blindaje.In view of the previously described and with the purpose of solving the limitations found, it is the object of the invention to offer a coaxial cable with a low coefficient of surface friction, said coaxial cable has a central conductor; an insulation that envelops the central conductor; a shield surrounding the insulation; a first cover that wraps around the shield; and a second cover that envelops the first cover; such that the second cover incorporates at least one lubricating agent that migrates towards the external surface of the coaxial cable; and the first cover prevents the lubricating agent from migrating towards the shield.
Finalmente es objeto de Ia invención ofrecer un método de fabricación de un cable coaxial de bajo coeficiente de fricción superficial, el método cuenta con los pasos de extrudir un aislamiento alrededor de un conductor central; envolver el aislamiento con un blindaje; extrudir una primera cubierta alrededor del blindaje; y co-extrudir una segunda cubierta alrededor de Ia primera cubierta; tal que Ia segunda cubierta incorpora al menos un agente lubricante que migra hacia Ia superficie externa del cable coaxial; y Ia primera cubierta impide que el agente lubricante migre hacia el blindaje.Finally, it is the object of the invention to offer a method of manufacturing a coaxial cable with a low coefficient of surface friction, the method has the steps of extruding an insulation around a central conductor; wrap the insulation with a shield; extrude a first cover around the shield; and co-extrude a second cover around the first cover; such that the second cover incorporates at least one lubricating agent that migrates towards the external surface of the coaxial cable; and the first cover prevents the lubricating agent from migrating towards the shield.
DESCRIPCIÓN BREVE DE LAS FIGURASBRIEF DESCRIPTION OF THE FIGURES
Los detalles característicos de Ia invención, se describen en los siguientes párrafos en conjunto con las figuras que Io acompañan, los cuales son con el propósito de definir al invento pero sin limitar el alcance de éste.The characteristic details of the invention are described in the following paragraphs in conjunction with the accompanying figures, which are for the purpose of defining the invention but without limiting its scope.
Figura 1 ilustra una vista en perspectiva en corte de un cable coaxial de acuerdo al invento.Figure 1 illustrates a perspective view in section of a coaxial cable according to the invention.
Figura 2 ilustra un diagrama de bloques de un método de fabricación de un cable coaxial de acuerdo al invento.Figure 2 illustrates a block diagram of a method of manufacturing a coaxial cable according to the invention.
DESCRIPCIÓN DETALLADA DE LA INVENCIÓNDETAILED DESCRIPTION OF THE INVENTION
Con referencia a Ia Figura 1, se muestra un cable coaxial 10 formado generalmente por un conductor central 20, un aislamiento 30, un blindaje 40 (también conocido como conductor exterior), una primera cubierta 70 y una segunda cubierta 80.With reference to Figure 1, there is shown a coaxial cable 10 generally formed by a central conductor 20, an insulation 30, a shield 40 (also known as an external conductor), a first cover 70 and a second cover 80.
El conductor central 20 está formado por un alambre o cable metálico que a su vez está rodeado por el aislamiento 30 envolvente, hecho generalmente de una o más capas dieléctricas de uno o más materiales plásticos a base de polietileno u otro material dieléctrico. A su vez el aislamiento 30 está rodeado por el blindaje 40 que está formado generalmente por una o más cintas metalizadas 50 y por una o más mallas metálicas 60. La cinta metalizada 50 está aplicada en forma helicoidal o longitudinal y está formada substancialmente por una laminilla delgada de aluminio adherida a una capa de polímero; mientras que Ia malla metálica 60 está formada normalmente por una pluralidad de hilos metálicos delgados aplicados en forma helicoidal o como malla trenzada.The central conductor 20 is formed by a metal wire or cable which in turn is surrounded by the envelope insulation 30, generally made of one or more dielectric layers of one or more plastic materials based on polyethylene or other dielectric material. In turn, the insulation 30 is surrounded by the shield 40 which is generally formed by one or more metalized tapes 50 and by one or more metal meshes 60. The metallic tape 50 is applied helically or longitudinally and is substantially formed by a lamella thin aluminum bonded to a polymer layer; while the metal mesh 60 is normally formed by a plurality of thin metal wires applied helically or as a braided mesh.
La primera cubierta 70, que envuelve al blindaje 40, protege mecánicamente al cable coaxial 10 contra el medio exterior y mantiene Ia rigidez mecánica del mismo y sirve como barrera protectora que impide que Ia composición lubricante, que más adelante se describe, migre al interior del cable coaxial 10 a fin de evitar daños en las cualidades eléctricas, dieléctricas y mecánicas en el mismo. La primera cubierta 70 está generalmente hecha de una o más capas de material plástico a base de polímeros como, por ejemplo, polietileno, polipropileno, policloruro de vinilo, copolímeros de cloruro de vinilo con vinil acetato, copolímeros de etileno con una alfa-olefina o con un éster saturado, fluoropolímeros, polímeros clorados, policloruro de vinilideno, poliamidas, polímeros acrílicos, poliésteres, polímeros hidrocarbonados iónicos y sus mezclas.The first cover 70, which surrounds the shield 40, mechanically protects the coaxial cable 10 against the outside environment and maintains the mechanical rigidity thereof and serves as a protective barrier that prevents the lubricating composition, which is described later, from migrating into the interior of the coaxial cable 10 in order to avoid damage to the electrical, dielectric and mechanical qualities thereof. The first cover 70 is generally made of one or more layers of polymer-based plastic material such as, for example, polyethylene, polypropylene, polyvinylchloride, vinyl chloride copolymers with vinyl acetate, ethylene copolymers with an alpha-olefin or with a saturated ester, fluoropolymers, chlorinated polymers, vinylidene polychloride, polyamides, acrylic polymers, polyesters, ionic hydrocarbon polymers and mixtures thereof.
En forma envolvente a Ia primera cubierta exterior 70 se encuentra una segunda cubierta 80 que cuenta con un bajo coeficiente de fricción al incorporar una agente lubricante que migra hacia Ia superficie de dicha cubierta. Dicho agente lubricante está incorporado al material plástico a base de polímeros como, por ejemplo, polietileno, polipropileno, policloruro de vinilo, copolímeros de cloruro de vinilo con vinil acetato, copolímeros de etileno con una alfa-olefina o con un éster saturado, fluoropolímeros, polímeros clorados, policloruro de vinilideno, poliamidas, polímeros acrílicos, poliésteres,. polímeros hidrocarbonados iónicos y sus mezclas. EI bajo coeficiente de fricción en Ia superficie de Ia segunda cubierta 80 es el resultado de Ia migración del agente lubricante hacia Ia superficie de dicha cubierta debido a Ia incompatibilidad definida entre el agente lubricante y el polímero empleado en Ia composición de Ia cubierta. La velocidad de migración del agente lubricante haciaEnvelope in the first outer cover 70 is a second cover 80 that has a low coefficient of friction by incorporating a lubricating agent that migrates towards the surface of said cover. Said lubricating agent is incorporated into the polymer-based plastic material such as, for example, polyethylene, polypropylene, polyvinylchloride, vinyl chloride copolymers with vinyl acetate, ethylene copolymers with an alpha-olefin or with a saturated ester, fluoropolymers, chlorinated polymers, vinylidene polychloride, polyamides, acrylic polymers, polyesters ,. ionic hydrocarbon polymers and mixtures thereof. The low coefficient of friction on the surface of the second cover 80 is the result of the migration of the lubricating agent towards the surface of said cover due to the incompatibility defined between the lubricating agent and the polymer used in the composition of the cover. The migration rate of the lubricating agent towards
Ia superficie es por Io general definida por Ia longitud de Ia cadena de los agentes lubricantes (compatibilidad con el polímero) y por las características del polímero, entre ellas su cristalinidad. Entre más grande es Ia cadena del agente lubricanteThe surface is generally defined by the length of the chain of the lubricating agents (compatibility with the polymer) and by the characteristics of the polymer, including their crystallinity. The larger the chain of the lubricating agent is
(mayor número de átomos de carbono) más compatible es con el polímero y más lenta es Ia migración hacia Ia superficie.(greater number of carbon atoms) more compatible is with the polymer and slower is the migration towards the surface.
Entre los agentes lubricantes preferentemente empleados en el invento, tenemos aquellos a base de amidas de ácido graso como, por ejemplo, oleamida, erucamida, caprilamida, capramida, lauramida, palmitamida, estearamida, linoleamida, miristamida y sus mezclas. Más preferentemente oleamida y erucamida dentro de un alcance de 0.25 % en peso a 1.0 % en peso en relación a Ia composición final para formar dicha segunda cubierta 80. Está reportado en Ia literatura que Ia oleamida migra más rápido que Ia erucamida, pero ésta última resulta ser térmicamente más estable y más resistente a Ia oxidación y crea pocos residuos volátiles durante su procesamiento, Io que significa que Ia erucamida resulta ser más adecuada para procesos cuyas etapas incluyan el manejo de altas temperaturas.Among the lubricating agents preferably employed in the invention, we have those based on fatty acid amides such as, for example, oleamide, erucamide, caprilamide, capramide, lauramide, palmitamide, stearamide, linoleamide, myristamide and mixtures thereof. More preferably oleamide and erucamide within a range of 0.25% by weight to 1.0% by weight in relation to the final composition to form said second cover 80. It is reported in the literature that oleamide migrates faster than erucamide, but the latter It turns out to be thermally more stable and more resistant to oxidation and creates few volatile residues during its processing, which means that the erucamide turns out to be more suitable for processes whose stages include the handling of high temperatures.
Una característica de Ia segunda cubierta 80 es. que debe contar con un espesor mucho menor que el espesor de Ia primera cubierta 70, a fin de que Ia mayor cantidad de agente lubricante incorporado en Ia segunda cubierta 80 sólo tienda a migrar hacia Ia superficie externa y que aquella cantidad de agente lubricante que llegue a migrar hacia Ia superficie interna en contacto con Ia primera cubierta 70 se disipe en esta cubierta, sin que llegue a migrar posteriormente hacia el blindaje. La primera cubierta tiene un espesor preferentemente en un alcance de 0.5 mm a 1.1 mm; mientras que Ia segunda cubierta cuenta con un espesor preferentemente en un alcance de 0.05 mm a 0.25 mm.A characteristic of the second cover 80 is. which must have a thickness much less than the thickness of the first cover 70, so that the greater amount of lubricating agent incorporated in the second cover 80 only tends to migrate towards the external surface and that that amount of lubricating agent that arrives to migrate towards the internal surface in contact with the first cover 70 is dissipated in this cover, without subsequently migrating to the shield. The first cover preferably has a thickness in a range of 0.5 mm to 1.1 mm; while the second cover has a thickness preferably in a range of 0.05 mm to 0.25 mm.
La segunda cubierta 80 puede tener sobre su superficie un primer patrón de código (no mostrado) impreso, formado por una secuencia a base de caracteres, símbolos, números, patrones visuales a base de colores y/o combinaciones de todos estos y que en conjunto sirven para identificar, por ejemplo, el tipo de cable coaxial, sus características físicas y eléctricas, Ia compañía manufacturera del mismo, Ia compañía propietaria y proveedora de señales de CATV, entre otros datos. Este patrón de código impreso no sé ve afectado por el agente lubricante que migra hacia Ia superficie de Ia cubierta 80.The second cover 80 may have on its surface a first printed code pattern (not shown), formed by a sequence based on characters, symbols, numbers, visual patterns based on colors and / or combinations of all of these and that together they serve to identify, for example, the type of coaxial cable, its physical and electrical characteristics, the manufacturing company thereof, the company that owns and provides CATV signals, among other data. This pattern of printed code is not affected by the lubricating agent that migrates to the surface of the cover 80.
A fin de corroborar las realizaciones del invento, se fabricaron, primeramente muestras de cable coaxial para CATV tipo RG-59 teniendo una sola cubierta hecha a base de PVC, a Ia cual se adicionaron cantidades crecientes de oleamida. Para determinar Ia facilidad de instalación de dicho cable coaxial, se midió Ia fuerza de tensión ejercida sobre cada una de las muestras de dicho cable que se hicieron pasar, a una velocidad de 600 mm/min, a través de un conducto de polietileno comercial de 0.8 m de longitud y con un codo de 90° colocado a Ia mitad de dicha longitud. Cabe mencionar que Ia fuerza de tensión, medida para cada muestra, corresponde a Ia fuerza necesaria para jalar al cable coaxial a fin de hacerlo pasar a través del conducto de polietileno. Estas mediciones se hicieron por medio de una máquina de tensión universal provista de una celda de carga. Para cada muestra, se realizaron un total de 25 determinaciones.In order to corroborate the embodiments of the invention, samples of coaxial cable for CATV type RG-59 were first manufactured having a single cover made of PVC, to which increasing amounts of oleamide were added. To determine the ease of installation of said coaxial cable, the tensile force exerted on each of the samples of said cable that was passed, at a speed of 600 mm / min, was measured through a commercial polyethylene conduit of 0.8 m long and with a 90 ° elbow placed at half of said length. It should be mentioned that the tensile force, measured for each sample, corresponds to the force necessary to pull the coaxial cable in order to pass it through the polyethylene conduit. These measurements were made by means of a universal tension machine equipped with a load cell. For each sample, a total of 25 determinations were made.
En Ia Tabla 1 se ilustran las características y resultado obtenidos de las muestras de cable coaxial tipo RG-59 con una sola cubierta, en Ia cual se observa que al incrementarse Ia cantidad de oleamida, Ia fuerza de tensión disminuye, por ejemplo, cuando Ia concentración de oleamida es de 0.5 % en peso de Ia cubierta el efecto es sólo marginal; mientras que cuando Ia concentración es del 1 % Ia fricción se reduce considerablemente. Sin embargo, se encontró que cuando se trató de instalar un conector, de aquellos utilizados para unir el cable coaxial a un aparato de televisión, el cable coaxial de Ia muestra, con Ia cubierta conteniendo el 1 % en peso de oleamida, no pudo conectarse satisfactoriamente al conector, pues se encontró que Ia cubierta no mostró adherencia alguna con el blindaje debido a que Ia oleamida había migrado hacia éste.Table 1 shows the characteristics and results obtained from the samples of coaxial cable type RG-59 with a single cover, in which it is observed that when the amount of oleamide is increased, the tensile strength decreases, for example, when the concentration of oleamide is 0.5% by weight of the cover, the effect is only marginal; while when the concentration is 1% the friction is considerably reduced. However, it was found that when trying to install a connector, of those used to connect the coaxial cable to a television set, the coaxial cable of the sample, with the cover containing 1% by weight of oleamide, could not be connected satisfactorily to the connector, since it was found that the cover did not show any adhesion with the shield because the oleamide had migrated towards it.
Figure imgf000014_0001
Figure imgf000014_0001
Tabla 1Table 1
En base a los resultados anteriormente descritos, se procedió a fabricar una serie de muestras de cable coaxial con una primera cubierta consistente en un compuesto de cloruro de polivinilo flexible apropiado para el uso en cubiertas de los cables coaxiales de Ia invención. Encima de Ia primera cubierta se colocó una segunda cubierta, consistente en el mismo material de Ia primera cubierta, pero que contenía varias concentraciones de al menos un agente lubricante. Los agentes lubricantes contemplados en el estudio son oleamida y erucamida. Aunado a esto, también se varió sistemáticamente el espesor de Ia segunda cubierta. Las resultados obtenidos de las estas muestras se ilustran en Ia Tabla 2. Based on the results described above, a series of coaxial cable samples were manufactured with a first cover consisting of a flexible polyvinyl chloride compound suitable for use in covers of the coaxial cables of the invention. A second cover was placed on top of the first cover, consisting of the same material as the first cover, but containing several concentrations of at least one lubricating agent. The lubricating agents contemplated in the study are oleamide and erucamide. In addition to this, the thickness of the second roof was also systematically varied. The results obtained from these samples are illustrated in Table 2.
Figure imgf000015_0001
Figure imgf000015_0001
(a) Oleamida, (b) Erucamida(a) Oleamide, (b) Erucamide
Tabla 2Table 2
Dentro de los primeros siete días transcurridos desde Ia fabricación de las muestras de Ia Tabla 2, se procedió a medir Ia fuerza de tensión, usando el procedimiento descrito anteriormente. La Tabla 3 ilustra los resultados de Ia fuerza de tensión promedio y desviación estándar obtenida para cada muestra para las 25 determinaciones.Within the first seven days after the manufacture of the samples in Table 2, the tensile force was measured, using the procedure described above. Table 3 illustrates the results of the average tensile strength and standard deviation obtained for each sample for the 25 determinations.
Figure imgf000015_0002
Figure imgf000015_0002
Tabla 3Table 3
Como puede observarse en Ia Tabla 3, Ia erucamida es más efectiva en Ia reducción de Ia fuerza de tensión a Ia vez que una concentración mayor de Ia misma tiende a reducir más aun Ia fricción entre Ia superficie externa de Ia segunda cubierta del cable y Ia superficie interna del conducto de polietileno. Con el objeto de determinar Ia velocidad de migración de los agentes lubricantes contemplados, se procedió a realizar estudios de simulación de almacenamiento en varias condiciones de temperatura. Las muestras E, H y J fueron almacenadas en un cuarto frío, cuya temperatura se mantuvo a 15 0C, a temperatura ambiente (23 0C) y en un cuarto caliente con una temperatura controlada de 36 0C. Después de 2 meses en estas condiciones, las muestras fueron retiradas, acondicionadas a temperatura ambiente por 24 horas para posteriormente probar Ia fuerza de tensión.As can be seen in Table 3, the erucamide is more effective in reducing the tension force while a higher concentration of it tends to reduce even more the friction between the external surface of the second cable sheath and the internal surface of the polyethylene duct. In order to determine the migration rate of the lubricating agents contemplated, storage simulation studies were carried out under various temperature conditions. Samples E, H and J were stored in a cold room, whose temperature was maintained at 15 0 C, at room temperature (23 0 C) and in a hot room with a controlled temperature of 36 0 C. After 2 months in these conditions, the samples were removed, conditioned at room temperature for 24 hours to subsequently test the tensile strength.
Los resultados de las muestras E, H y J, en las condiciones mencionadas, son ilustrados en Ia Tabla 4, los cuales indican que después de dos meses en condiciones muy variadas de temperatura, las muestras reflejan muy poca variación en su fuerza de tensión. Hay una pequeña tendencia de Ia fuerza de tensión a aumentar con Ia temperatura de almacenamiento Io que indicaría que a condiciones de temperaturas bajas tendrían una pequeña influencia en reducir el coeficiente de fricción del material de Ia segunda cubierta, mientras que el efecto contrario, también pequeño en magnitud, se presentaría a temperaturas mayores a Ia ambiente. Esto pudiera explicarse como sigue, a temperaturas mayores Ia solubilidad de los agentes lubricantes aumenta y por tanto Ia velocidad de migración disminuye; mientras que a temperaturas menores Ia velocidad de migración aumenta como resultado de una falta de solubilidad. Además, las muestras de Ia Tabla 4 se conectaron satisfactoriamente después de 2 meses de acondicionamiento.The results of samples E, H and J, under the conditions mentioned, are illustrated in Table 4, which indicate that after two months under very varied temperature conditions, the samples reflect very little variation in their tensile strength. There is a small tendency of the tension force to increase with the storage temperature which would indicate that at low temperature conditions they would have a small influence on reducing the friction coefficient of the material of the second cover, while the opposite effect, also small in magnitude, it would be presented at temperatures higher than the ambient. This could be explained as follows, at higher temperatures the solubility of the lubricating agents increases and therefore the migration rate decreases; while at lower temperatures the migration rate increases as a result of a lack of solubility. In addition, the samples in Table 4 were successfully connected after 2 months of conditioning.
Figure imgf000016_0001
Tabla 4
Figure imgf000016_0001
Table 4
Para demostrar que el cable coaxial de Ia invención tiene propiedades de deslizamiento estables y que Ia migración de Ia segunda cubierta no provoca problemas de adherencia de Ia superficie interior de Ia primera cubierta con el blindaje, se seleccionaron las muestras D, F, G, H y J para realizar un estudio de fuerza de tensión y de conexión después de 2 meses de almacenaje a temperatura ambiente. Los resultados, mostrados en Ia Tabla 5, indican que las mediciones de Ia fuerza de tensión a 0 y 2 meses de almacenamiento son comparables. Cabe mencionar que dichas muestras se conectaron satisfactoriamente después de 2 meses de fabricadas y acondicionadas a temperatura ambiente. Esto significa que Ia facilidad de deslizamiento de Ia segunda cubierta permanece estable con el tiempo independientemente del agente lubricante y espesor de Ia segunda cubierta.To demonstrate that the coaxial cable of the invention has stable sliding properties and that the migration of the second cover does not cause problems of adhesion of the inner surface of the first cover with the shield, samples D, F, G, H were selected and J to carry out a study of tension and connection force after 2 months of storage at room temperature. The results, shown in Table 5, indicate that the measurements of the tensile force at 0 and 2 months of storage are comparable. It should be mentioned that these samples were successfully connected after 2 months of being manufactured and conditioned at room temperature. This means that the ease of sliding of the second cover remains stable over time regardless of the lubricating agent and thickness of the second cover.
Figure imgf000017_0001
Figure imgf000017_0001
Tabla 5Table 5
Cambiando ahora a Ia Figura 2, se muestra un diagrama de bloques de un método de fabricación del cable coaxial de acuerdo al invento. El método inicia en el paso 1OO al aplicar un aislamiento sobre un conductor por medio de extrusión; procediéndose, en el paso 110, a envolver al aislamiento con un blindaje, tal que el blindaje consiste en envolver primeramente el aislamiento con una cinta metalizada, para luego envolver Ia cinta metalizada con una malla metálica; en el paso 120, por medio de extrusión, el blindaje es envuelto con un primera cubierta; inmediatamente el paso 140 se aplica una segunda cubierta por medio de una etapa de co-extrusión sobre Ia primera cubierta, de tal manera que Ia segunda cubierta incorpora un agente lubricante que previamente fue mezclado, en el paso 130, con Ia composición plástica para formarla. La segunda cubierta es co-extrudida a Ia primera cubierta con un espesor mucho menor que el espesor de Ia primera cubierta. Finalmente y de manera opcional se aplica, por un proceso de impresión, en el paso 150, un patrón de código sobre Ia superficie de Ia segunda cubierta.Changing now to Figure 2, a block diagram of a method of manufacturing the coaxial cable according to the invention is shown. The method starts in step 1OO by applying insulation on a conductor by means of extrusion; proceeding, in step 110, to wrap the insulation with a shield, such that the shield consists of first wrapping the insulation with a metallized tape, then wrapping the metallized tape with a metal mesh; in step 120, for extrusion medium, the shield is wrapped with a first cover; immediately step 140 a second cover is applied by means of a co-extrusion stage on the first cover, such that the second cover incorporates a lubricating agent that was previously mixed, in step 130, with the plastic composition to form it . The second cover is co-extruded to the first cover with a thickness much smaller than the thickness of the first cover. Finally, and optionally, by a printing process, in code 150, a code pattern is applied on the surface of the second cover.
Basado en las realizaciones descritas anteriormente, se contempla que las modificaciones a estas realizaciones descritas, así como las realizaciones alternativas serán considerados evidentes para una persona experta en el arte de Ia técnica bajo Ia presente descripción. Es por Io tanto, contemplado que las reivindicaciones abarcan dichas modificaciones y alternativas que estén dentro del alcance del presente invento o sus equivalentes. Based on the embodiments described above, it is contemplated that the modifications to these described embodiments, as well as the alternative embodiments will be considered evident to a person skilled in the art of the technique under this description. It is therefore contemplated that the claims encompass such modifications and alternatives that are within the scope of the present invention or its equivalents.

Claims

REIVIN DICACION ES REIVIN DICATION EN
1. Un cable coaxial de bajo coeficiente de fricción superficial, dicho cable coaxial comprende: un conductor central; un aislamiento que envuelve a dicho conductor central; un blindaje que rodea a dicho aislamiento; una primera cubierta que envuelve a dicho blindaje; y una segunda cubierta que envuelve a dicha primera cubierta; en donde dicho cable coaxial se caracteriza porque dicha segunda cubierta incorpora al menos un agente lubricante que migra hacia Ia superficie externa de dicho cable coaxial; y porque dicha primera cubierta impide que dicho agente lubricante migre hacia dicho blindaje.1. A coaxial cable of low surface friction coefficient, said coaxial cable comprises: a central conductor; an insulation that surrounds said central conductor; a shield surrounding said insulation; a first cover that envelops said shield; and a second cover that envelops said first cover; wherein said coaxial cable is characterized in that said second cover incorporates at least one lubricating agent that migrates towards the external surface of said coaxial cable; and because said first cover prevents said lubricating agent from migrating towards said shield.
2. El cable coaxial de Ia reivindicación 1, en donde dicho conductor central se caracteriza por estar formado por uno o más conductores.2. The coaxial cable of claim 1, wherein said central conductor is characterized by being formed by one or more conductors.
3. El cable coaxial de Ia reivindicación 1, en donde dicho aislamiento se caracteriza por comprender una o más capas dieléctricas de materiales plásticos.3. The coaxial cable of claim 1, wherein said insulation is characterized by comprising one or more dielectric layers of plastic materials.
4. El cable coaxial de Ia reivindicación 1, en donde dicho blindaje se caracteriza por incluir una o más cintas metalizadas y/o una o más mallas metálicas.4. The coaxial cable of claim 1, wherein said shielding is characterized by including one or more metallic tapes and / or one or more metal meshes.
5. El cable coaxial de Ia reivindicación 1, en donde dicha primera cubierta además se caracteriza por comprender una o más capas de materiales plásticos. 5. The coaxial cable of claim 1, wherein said first cover is further characterized by comprising one or more layers of plastic materials.
6. El cable coaxial de Ia reivindicación 1, en donde dicha segunda cubierta además se caracteriza por tener un espesor mucho menor que el espesor de dicha primera cubierta.6. The coaxial cable of claim 1, wherein said second cover is further characterized by having a thickness much less than the thickness of said first cover.
7. El cable coaxial de Ia reivindicación 6, en donde el espesor de dicha primera cubierta tiene un alcance de 0.5 mm a 1.1 mm.7. The coaxial cable of claim 6, wherein the thickness of said first cover has a range of 0.5 mm to 1.1 mm.
8. El cable coaxial de Ia reivindicación 6, en donde el espesor de dicha segunda cubierta tiene un alcance de 0.05 mm a 0.25 mm.8. The coaxial cable of claim 6, wherein the thickness of said second cover has a range of 0.05 mm to 0.25 mm.
9. El cable coaxial de Ia reivindicación 1, en donde dicha segunda cubierta además se caracteriza por comprender material plástico mezclado con dicho agente lubricante.9. The coaxial cable of claim 1, wherein said second cover is further characterized by comprising plastic material mixed with said lubricating agent.
10. El cable coaxial de Ia reivindicación 1, en donde dicho agente lubricante es una o más amidas de ácido graso seleccionada del grupo que consiste de oleamida, erucamida, caprilamida, capramida, lauramida, palmitamida, estearamida, linoleamida, miristamida y sus mezclas.10. The coaxial cable of claim 1, wherein said lubricating agent is one or more fatty acid amides selected from the group consisting of oleamide, erucamide, caprilamide, capramide, lauramide, palmitamide, stearamide, linoleamide, myristamide and mixtures thereof.
11. El cable coaxial de Ia reivindicación 1, en donde dicho agente lubricante tiene un alcance de 0.25 % en peso a 1.0 % en peso en relación a Ia composición final para formar dicha segunda cubierta.11. The coaxial cable of claim 1, wherein said lubricating agent has a range of 0.25% by weight to 1.0% by weight in relation to the final composition to form said second cover.
12. Un método de fabricación de un cable coaxial de bajo coeficiente de fricción superficial, el método comprende los pasos de: extrudir un aislamiento alrededor de un conductor central; envolver a dicho aislamiento con un blindaje; extrudir una primera cubierta alrededor de dicho blindaje; y co-extrudir una segunda cubierta alrededor de dicha primera cubierta; en donde dicho método se caracteriza porque dicha segunda cubierta incorpora al menos un agente lubricante que migra hacia Ia superficie externa de dicho cable coaxial; y porque dicha primera cubierta impide que dicho agente lubricante migre hacia dicho blindaje.12. A method of manufacturing a coaxial cable with a low coefficient of surface friction, the method comprises the steps of: extruding an insulation around a central conductor; wrap said insulation with a shield; extrude a first cover around said shield; and co-extruding a second cover around said first cover; wherein said method is characterized in that said second cover incorporates at least one lubricating agent that migrates towards the external surface of said coaxial cable; and because said first cover prevents said lubricating agent from migrating towards said shield.
13. El método de Ia reivindicación 12, en donde dicho conductor central se caracteriza por estar formado por uno o más conductores.13. The method of claim 12, wherein said central conductor is characterized by being formed by one or more conductors.
14. El método de Ia reivindicación 12, en donde dicho aislamiento se caracteriza por comprender una o más capas dieléctricas de materiales plásticos.14. The method of claim 12, wherein said insulation is characterized by comprising one or more dielectric layers of plastic materials.
15. El método de Ia reivindicación 12, en donde dicho blindaje se caracteriza por incluir una o más cintas metalizadas y/o una o más mallas metálicas.15. The method of claim 12, wherein said shielding is characterized by including one or more metallic tapes and / or one or more metal meshes.
16. El método de Ia reivindicación 12, en donde dicha primera cubierta además se caracteriza por comprender una o más capas de materiales plásticos.16. The method of claim 12, wherein said first cover is further characterized by comprising one or more layers of plastic materials.
17. El método de Ia reivindicación 12, en donde el paso de co-extrudir una segunda cubierta alrededor dicha primera cubierta se caracteriza porque dicha segunda cubierta es extrudida con un espesor mucho menor que el espesor de dicha primera cubierta.17. The method of claim 12, wherein the step of co-extruding a second cover around said first cover is characterized in that said second cover is extruded with a thickness much less than the thickness of said first cover.
18. El método de Ia reivindicación 17, en donde el espesor de dicha primera cubierta tiene un alcance de 0.5 mm a 1.1 mm.18. The method of claim 17, wherein the thickness of said first cover has a range of 0.5 mm to 1.1 mm.
19. El método de Ia reivindicación 17, en donde el espesor de dicha segunda cubierta tiene un alcance de 0.05 mm a 0.25 mm. 19. The method of claim 17, wherein the thickness of said second cover has a range of 0.05 mm to 0.25 mm.
20. El método de Ia reivindicación 12, en donde dicha segunda cubierta además se caracteriza por comprender al menos un material plástico mezclado con el dicho agente lubricante.20. The method of claim 12, wherein said second cover is further characterized by comprising at least one plastic material mixed with said lubricating agent.
21. El método de Ia reivindicación 12, en donde dicho agente lubricante es una o más amidas de ácido graso seleccionada del grupo que consiste de oleamida, erucamida, caprilamida, capramida, lauramida, palmitamida, estearamida, linoleamida, miristamida y sus mezclas.21. The method of claim 12, wherein said lubricating agent is one or more fatty acid amides selected from the group consisting of oleamide, erucamide, caprilamide, capramide, lauramide, palmitamide, stearamide, linoleamide, myristamide and mixtures thereof.
22. El método de Ia reivindicación 12, en donde dicho agente lubricante tiene un alcance de 0.25 % en peso a 1.0 % en peso en relación a Ia composición final para formar dicha segunda cubierta. 22. The method of claim 12, wherein said lubricating agent has a range of 0.25% by weight to 1.0% by weight in relation to the final composition to form said second cover.
PCT/MX2007/000065 2006-05-26 2007-05-25 Coaxial cable having a surface with low coefficient of friction and method of manufacture thereof WO2007139369A2 (en)

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