CN1459805A

CN1459805A - Coaxial cable

Info

Publication number: CN1459805A
Application number: CN 02117922
Authority: CN
Inventors: 张兴武
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-23
Filing date: 2002-05-23
Publication date: 2003-12-03

Abstract

A coaxial cable is sequentially composed of a central conductor, a dielectric polymer layer, a shielding film layer, an external conductor layer and a protecting and insulating layer. The said external conductor layer consists of a non-woven conductor and a woven conductor. The said non-woven conductor is extending axially in straight line or spiral mode. Its making method is also disclosed.

Description

A kind of coaxial cable

The present invention relates to a kind of coaxial cable, coaxial cable a kind of flexibility, that be used for radio signal transmission, for given demarcation size, coaxial cable of the present invention has decay and the distorted characteristic that good bending, shielding properties have significantly improved simultaneously.

One of main application of coaxial cable is a radio signal transmission, for example TV signal, vision signal, broadcast singal, mobile telephone signal etc., the lower limit of its operating frequency is generally 25000 hertz, and the upper limit reaches thousands of megahertzes, and often works in the frequency up to hundreds of megahertzes.Owing to the good flexibility that has of coaxial cable, can bear more high-power, cheap cost, carry with advantage such as easy to use it is used widely, as the main flow kind of Zhi Gan, branch and terminal use's incoming end.

The design of coaxial cable often obtains compromise between electrical property and mechanical performance, on the one hand, in order to improve the electrical property of coaxial cable, realize preferably transmission quality and reach good shielding properties, the scientists and engineers of various countries has been developed the structure and the dimensions of multiple coaxial cable, and various quality materials have been used, to obtain good performance, as use closed metal pipe metal armouring (comprising smooth straight inner wall tube and bellows) to obtain best electrical characteristics, use the silver-plated conductor material of copper to obtain better high frequency characteristics, use the physical blowing polymer as dielectric reducing dielectric loss, use multilayer screen to obtain better shield effectiveness etc. when constituting the coaxial cable of outer conductor making by many conductors.But above technology all has serious limitation separately, as use metal tube then to lack flexibility as armouring, use and install inconvenience, and it is with high costs, the general outer conductor diameter that only is applied to is greater than one inch high-power large bore coaxial cable, if use the metal light wall pipe, then bending all causes damage to outer conductor each time, reliability is lower, and price is also higher, generally also only is applied to the occasion of larger caliber, so the coaxial cable of metal tube outer conductor can only use as main line, and above technology all causes price high.

Because the product for civilian use is to convenience, requirement cheaply, the coaxial cable that uses many strip conductors to constitute outer conductor becomes the kind of use amount maximum, this coaxial cable softness, with low cost, through repeatedly still keeping good electrical properties after the bending, can make the coaxial cable of different nominal apertures, comprise from larger caliber to an inch so that more small-bore to one millimeter.For longer Distance Transmission radiofrequency signal, the shielding properties of cable is very important, so each major industrial country of the world all issues industrial standard, with shielded film and the metallic conductor mesh grid outer conductor (armouring) as the cable TV signal coaxial cable.The common coaxial cable of present most popular flexibility such as wired TV signal cable comprise that inner wire, dielectric (the main at present physical blowing dielectric that uses), metal-plastic laminated film screen and braided metal net metal armouring are as outer conductor.Though the coaxial cable of this technical specification has good shielding properties, flexibility, easy to use, the coaxial cable of the metal tube outer conductor that its electrical property and same specification are aforementioned still has big gap, shows as that through-put power is little, decay is big etc.The phenomenon that braided outer conductor has increased signal attenuation is considered to " weave effect " in association area.In addition, the inventor thinks, only also produce the linear deterioration of spontaneous beat interference, signal, the problems such as news are big of making an uproar as the coaxial cable of outer conductor with netted knitted conductor armouring, especially when transmission high peaks level, will produce serious modulation distortion and compression, signal attenuation sharply increases with the decay of operating frequency rising signals, and the operating frequency upper limit is low.

The inventor thinks, design a kind of easily manufactured, cost is cheap relatively, coaxial cable with good electric property, shielding properties and flexibility has tangible economic implications and industrial significance undoubtedly, the purpose of this invention promptly is this.The inventor thinks, after the outer conductor of coaxial cable has comprised the specific metallic conductor that does not participate in weaving, reduced weave effect, the electrical property of cable is significantly improved, makes signal attenuation obviously reduce, more make the dynamic range index of nonlinear distortion index and transmission signals to obtain greatly improving.Use the present invention program coaxial cable electrical property and equal specification, material with the metal tube armouring as the electrical property of the coaxial cable of outer conductor relatively near and surmount at present general far away with the coaxial cable of netted knitted conductor as armouring.

Because the skin effect and the proximity effect of high-frequency current, should be the inboard that is positioned at knitted conductor as the optimum position of the non-braided outer conductor of the part of the compound outer conductor of feature of the present invention, the outside of optional screened film; If non-knitted conductor comprises many strip conductors, then its optimum arrangementing mode is parallel with inner wire separately, extends vertically.In order to improve the pliability of coaxial cable, the spiral that also can make non-knitted conductor center on screened film advances.Experimental results show that, as long as the diameter sum of the non-knitted conductor of each bar reaches 1/10th of inner wire girth, its electrical property promptly is significantly improved, during practical application in industry, the diameter sum of all non-knitted conductor should reach more than 1/4th of inner wire girth, when the diameter sum of all non-knitted conductor reaches to three times of inner wire girth, reach the optimum value of industrial design.When the diameter sum of non-knitted conductor surpasses three times of inner wire girth, its electrical property no longer obviously (for example improves, nominal impedance is 75 ohm a coaxial cable, and the maximum of its effective non-establishment conductor diameter sum is 4.5 times to 7 times that the girth of outer conductor is about the inner wire girth).

The inventor thinks, the coaxial cable of this invention, by suitable manufacture technology, its electrical property can reach equal specification with the level of metal tube as the coaxial cable of outer conductor.The present invention program is mainly used in outer conductor (conductor mesh tubulose armouring) the less occasion of diameter, as less than 0.038 meter, and promptly 1.5 inches.

The inventor thinks, if outer conductor only uses non-braided outer conductor, when short-range applications, its distortion index is compared with the present invention does not have tangible gap, but, because simple non-knitted conductor is not tight with contacting of screened film, with the shielding action that lacks knitted conductor, make its shadow loss serious, and consistency of product is difficult to ensure, when coaxial cable is crooked, more may cause serious signal leakage, and through after the several times bending, the conductive capability of coaxial cable and various electrical property will seriously descend, thereby only be applicable to more short-range radio signal transmission, so, in order to ensure length apart from the radio signal transmission quality, it is essential that knitted conductor remains, and its effect reduces the signal attenuation except the screen that strengthens, the electric conductivity of each non-knitted conductor be can also significantly improve, and the pliability and the reliability of coaxial cable improved.

For digital signal communication and digital television signal, use the present invention program's coaxial cable to compare also with the coaxial cable of present standard and can improve laser propagation effect significantly, effective propagation path is obviously prolonged, and save the investment of line amplifier greatly.

Accompanying drawing 1 has represented to embody the coaxial cable of the present invention program's feature, in this figure, this coaxial cable comprises an inner wire 2, this inner wire 2 is in the drawings for having the sub-thread conductor of smooth surface, but also can be the multiply conductor, or surround the metal light wall pipe of an insulator, (as shown in this figure) to use more be sub-thread round conductor or multiply round conductor in the less coaxial cable product of nominal diameter.Inner wire uses ordinary metallic material or its alloys such as copper, aluminium usually, or silver etc. has no particular limits than the composite material of expensive metal on a kind of metal-plated.Around the inner wire 2 is cylindrical dielectric 3, its cross section is generally circle, but it is oval also not getting rid of, and column polyhedron, cylindrical dielectric 3 is used cellular expanded material at present usually, also can be than using solid in the early production or the vertical hole of lotus root shape material, the material of selecting has no particular limits, usually should have less dielectric coefficient, as the vinyl esters resin, the polyurethane kind resin, resins such as epoxy resin, organic fiber, or the inorganic fibre made of inorganic substances etc., they can be used alone or in combination, the diameter of cylindrical dielectric and inner wire diameter ratio meet the desired ratio of impedance according to the industrial standard regulation.Shielded film 4 plays an important role for the shielding properties that improves coaxial cable, used quite at large when the industry is made like product, but it does not constitute core content of the present invention, neither the requisite content of the present invention.Barrier film layer 4 is coated on one deck tape base 6 by layer of metal paper tinsel layer 5 and constitutes, and shielded film 4 is parcel cylindrical dielectric 3 vertically, and mutual part is superimposed at two ends, and superimposed ratio is about cylindrical dielectric girth 1/10th.The mode that shielded film 4 coats column dielectric medium 3 is that tape base 6 is connected with column dielectric layer 3, metal foil layer 5 is positioned at the outside of tape base 6 to be close to following non-braided outer conductor 8, tape base 6 mainly plays the effect of supporting and adsorbing metal foil layer 5, usually by having certain flexible polymer manufacturing, but have no particular limits, it also can be the material beyond the polymer, metal foil layer 5 is aluminium normally, the metal or alloy that also can be other is by airless spraying or chemicalpiston or additive method manufacturing, metal foil layer 5 is thinner, and its thickness is usually greater than 1.5 microns.Outer conductor (metal armouring) 7 comprises non-knitted conductor 8 and knitted conductor 9, wherein non-knitted conductor 8 can be a strip conductor, also can be many strip conductors, if many strip conductors, then can be evenly distributed, also can be to be divided into some groups, and each organizes evenly distributed, or the week that otherwise is arranged in screen 4 is upwards, knitted conductor 9 with two groups mutually in the other direction the conductors of helical arrangement weave mutually and with non-knitted conductor 8 further screened film 4 metal foil layer 5 and make its tight connection.The weaving manner of knitted conductor 9 is current modes that satisfy industrial requirements that the technical staff of the industry can both understand, and it is not proposed special requirement among the present invention.The material of knitted

conductor

9 and 8 uses of non-knitted conductor can be the lead that copper, aluminium, almag or surface are coated with tin, magnesium or silver or other corrosion-resistant oxidation resistant material, and the principle of selecting for use is that cost still has good electric property than hanging down.In economical material commonly used, fine copper is the excellence conductor that electric property is only second to silver under the nature, but shortcoming be cost than aluminium height, erosion-resisting ability is not as aluminium, uses the rear surface may oxidation for a long time, and the conductive capability on surface is descended; In lower-cost conductor material, aluminium also has good electric property, but its tensile strength a little less than, erosion-resisting ability also a little less than; Zinc-plated or the zinc of conductive surface can make the anticorrosive oxidation resistance of conductor improve, but electric conductivity especially the high frequency electric conductivity decrease; Silver-plated resistance to corrosion and the electric property of making of conductive surface all improves, and is applied to the high high price product of quality requirement.Manufacturing outer conductor 7 uses the most generally, and the cross section is the lead of the thin diameter of circle, its diameter generally should be less than 1/2nd of center conductor diameter, what often use in the industry is the thin round conductor of diameter as the 0.15-0.35 millimeter, but also can be that the cross section is the flat thin wire of square, or narrower metallic foil (narrower be meant less than the cylindrical dielectric girth 1/10th), the reason of using thin wire is because the skin effect and the proximity effect of the high-frequency current that those skilled in the art know altogether, the electric current that passes through in inner conductor 2 and outer conductor 7 is equivalent reciprocal, current concentration in the inner wire 2 is in the outer surface thin layer of inner wire 2, current concentration in the outer conductor 7 can obviously be saved cost so use thin wire to make outer conductor 7 in the inboard thin layer of tubulose (or pipe network shape) outer conductor 7.It is in order to obtain better shield effectiveness that outer conductor 7 uses the mode of braiding, make knitted conductor 9 cover more than 90% of coaxial cable surfaces so can use tight braiding for better shield effectiveness knitted conductor, in order to save cost, also can use and dredge the net braiding, make the coverage rate less than 50% of 7 pairs of coaxial cable surface areas of outer conductor.Coaxial cable must comprise barrier film layer 4 when use dredging the net braiding, and non-knitted conductor 8 and screened film 4 are combined closely to realize under the lower cost shielding properties and electric property preferably when dredging the net braiding.The usage quantity of non-knitted conductor 8 should aforesaid to require consistent, best consumption be to make 1-3 that the diameter of the non-knitted conductor of its each bar amounts to the inner wire girth doubly with this specification.Insulating sleeve 10 normally is expressed on the coaxial cable body by insulating material of polymer, and the thickness that reaches common industrial standard requirement gets final product, and this thickness calibration is relevant with the nominal diameter of coaxial cable usually.

Though accompanying drawing 1 can illustrate coaxial cable involved in the present invention, according to claims of the present patent application, coaxial cable of the present invention also can have changing form of other, is positioned at the scheme in the outside of knitted conductor as accompanying drawing 2 described non-knitted conductor.The technical staff of any industry may make amendment based on this and be out of shape, but these modifications and distortion is included in the spirit and scope of the present patent application appending claims through after the reading narration of the present invention.

Accompanying drawing 3 and accompanying drawing 4 are with the process of a kind of manufacturing of picture specification coaxial cable of the present invention (being applicable to the preferred version that the inventor thinks, i.e. accompanying drawing 1 scheme).As shown in Figure 3, from suitable source of supply, for example cable hank 21 for inner wire 11 (being generally the plastic tube or the metal tube of solid copper wire, hollow copper tubing or outer copper-clad, also can be the multiply conductor).Then, inside conductor 11 is eliminated bending by straightening.In illustrated embodiment, the realization of this point is by straightening wheel 22, and draws mould 23 by one., by warp let-off extruder assembly 24 this extruder assembly is applied in order to form the foamable polymer of foamed insulation material 12 by the inner wire 11 of straightening.In extruder assembly 24, the composition that is used to form foamed insulation material 12 is in conjunction with forming polymer melt, after these polymer melts are melted, spray the foamable polymer of formation with nitrogen or similar blowing agent immediately, these polymer melts are applied in pressure to prevent its foaming and intumescing in extruder assembly 24.The inner wire 11 that advances in the extruder assembly 24 is the squeeze polymer melt with one heart, foamable polymer leaves extruder 24 backs and reduces foaming and intumescing because of pressure, around the cylindrical wall of inner wire 11 formation foamed insulation materials 12, inner wire 11 becomes an initial cable axle core 13 with column foamed insulation material 12.Initial cable axle core 13 is admitted to vertical chartered plane device 30, vertical chartered plane device 30 provides screened film 31 vertically to surround initial cable axle core 13 and makes the circumferentially mutually part superimposition of screened film 31 along cable axle core, when screened film 31 vertically surrounds initial cable axle core 13, the metal level 32 of screened film 31 is positioned at the outside, and tape base layer 33 is positioned at the inboard.Initial cable axle core 13 advances with screened film 31, the initial cable axle core 13 that leaves vertical chartered plane device 30 all is coated with forms complete cable axle core 14.Arrive this, accompanying drawing 3 indicated work are finished substantially, and complete cable axle core 14 can be collected on suitable packing material such as the cable hank 25, and complete cable axle core 14 is moved on, and directly finish remaining manufacture process such as Fig. 4.

As shown in Figure 4, complete cable axle core 14 is drawn out with further processing, to form coaxial cable.Complete cable axle core 14 is admitted to establishment machine 40, braiding machine device 40 has an axle center 41, around this axle center 41 a non-braided wire axle framework 42 that is circular distribution is arranged, with the circular braiding frame 44 of circular braiding frame 43 in upper strata and lower floor around it is outer, the plane at three annulus places of circular braiding frame 43 in non-braided wire pedestal 42 and upper strata and the circular braiding frame 44 of lower floor is all perpendicular to the axle center 41 of braiding machine device.Non-braided wire axle framework 42 can be fixed, also can be in a clockwise direction (or counterclockwise) folk prescription to slow rotation, on the circumference of non-braided wire axle framework 42, be mounted with a plurality of coil of wire 45 equidistantly, be used to provide the non-braid that forms described coaxial cable outer conductor (described in Fig. 1 7) required thin wire 46.Be mounted with a plurality of coil of wire 47 separately equidistantly on the circular braiding frame 44 of circular braiding frame 43 in upper strata and lower floor, 44 1 on the circular braiding frame of circular braiding frame 43 in upper strata and lower floor turns clockwise during braiding, one is rotated counterclockwise, be used to form the knitted conductor layer 49 (Fig. 1 described 8) in the outer conductor, the traverse shaft of braiding on the frame 43 and 44 constantly entad carries out and centrifugal back and forth movement along the diametric(al) of annulus on frame repeatedly with the air catapult-launching gear, and the reciprocating direction of any adjacent two traverse shafts is opposite on the annulus braiding frame.After complete cable axle core 14 sent into braiding machine device 40, complete cable axle core 14 arrives the position in axle center 41, coil of wire 45 on the non-braided wire axle framework 42 provides many non-ground that twine of non-knitted conductor 46 separate non-braidings around complete cable axle core 14, and the coil of wire 47 on the coil of wire 47 on the upper strata annulus braiding frame 43 and the lower floor's annulus braiding frame 44 also provides many strip conductors 48 around complete cable axle core 14.Complete cable axle core 14 and many non-knitted conductor 46 are advanced, upper strata annulus braiding frame 43 and lower floor's annulus braiding frame 44 mutual opposite spins, drive is by 41 rotations around the axle center of its many thin wires that send 48, the a plurality of conductors volumes 47 that meanwhile are installed on upper strata annulus 43 and the lower floor's annulus 44 weave many thin conductors 48 by carrying out back and forth movement centrifugal and entad repeatedly along the diametric(al) of annulus in predetermined each comfortable banded annulus of order mutually, finish the manufacturing work of knitted conductor layer 49 (knitted conductor 8 among Fig. 1), and knitted conductor layer 49 closely is bound on the complete cable axle core 14.Along with the braiding of knitted conductor layer 49 with tighten the cable axle center, many non-knitted conductor 46 be bound to the cable axle core 14 that covers screened film around and closely paste and finished the manufacturing of the cable body of coaxial cable with screened film 31.In order to improve the pliability of coaxial cable, can make non-braided wire pedestal 42 with suitable speed rotation, make many non-knitted conductor of sending by non-braided wire pedestal 42 46 be wound into complete cable axle core 14.The cable body of coaxial cable moves on, enter extruder assembly 50 to form the insulating sleeve (Fig. 1 described 9) of coaxial cable, insulating material 51 is housed in the extruder assembly 50, the material that insulating material 51 uses is generally polymer, should have good pliability and higher insulation resistance, and anticorrosion, anti-aging and fire-retardant.Insulating material 51 becomes melt in extruder assembly 50, the coaxial cable body be extruded to when the extruder assembly coaxial cable body around.Insulating material solidifies the formation insulation sheath when cooling off rapidly when coaxial cable leaves extruder assembly 50.At last the coaxial cable 53 that completes is collected on the cable hank 52.

Claims

1, a kind of coaxial cable, it is characterized in that, comprising: an axle center, comprise at least one inner wire and coat this inner wire cylindrical dielectric on every side and the metal forming-polymer shield film of this cylindrical dielectric of coating, a compound outer conductor that constitutes and surround described axle center by many thin conductors, with one surround the described insulating material crust that meets outer conductor, described compound outer conductor is by non-knitted conductor and knitted conductor layer two parts compound composition.

According to the described coaxial cable of claim 1, it is characterized in that 2, described compound outer conductor is by non-knitted conductor and the knitted conductor layer is compound forms, two parts become physics and electric tight the connection, extend axially around described axle center.

According to claim 1 and the described coaxial cable of claim 2, it is characterized in that 3, knitted conductor becomes pipe network shape conductor by the many strip conductors of helical arrangement that are divided into two groups mutual opposite spin around the mutual interlacing in described axle center; Non-knitted conductor comprises at least one, normally many strip conductors, with linear fashion or in a spiral manner the surface of the netted knitted conductor of close neighbour extend vertically.

According to claim 1, claim 2, the described coaxial cable of claim 3, it is characterized in that 4, its diameter is usually less than 0.038 meter, promptly 1.5 inches.

According to claim 1, claim 2, claim 3, the described coaxial cable of claim 4, it is characterized in that 5, the diameter sum of each conductor that constitutes the non-knitted parts of described outer conductor is not less than 5% of inner wire girth.

6, according to claim 1, claim 2, claim 3, claim 4, the described coaxial cable of claim 5, it is characterized in that, the many strip conductors that constitute compound outer conductor usually its diameter separately all be significantly less than inner wire diameter 1/2nd, many strip conductors of the promptly described compound outer conductor of formation are thin wire.

7, a kind of manufacture method of coaxial cable is characterized in that, comprises the steps:

One lead (having smooth outer surface usually) is advanced along a predetermined stroke; But be expressed to foaming and intumescing insulating polymer composition on the described inner wire and form tubular articles and make inner wire be positioned at the center of tubular polymer; One insulating polymer film that is coated with metal foil layer is wrapped up this tubular articles and part is superimposed to form barrier film layer mutually along above-mentioned tubular articles longitudinal extension and along its circumferencial direction, and the insulating film layer of this composite film partly is close to tubular articles and is made metal film be positioned at the outside to form the axle center of coaxial cable; Make many thin conductors be positioned at the periphery of the aforementioned columnar object that is coated with barrier film layer, make many thin conductors be divided into internal layer and outer to construct compound outer conductor; The extruding insulation polymer forms insulating sleeve around aforementioned coaxial cable outer conductor.

8, method according to claim 7, it is characterized in that, many strip conductors of making its outer conductor are divided into the inner conductor and the outer contact of outer conductor, the inner conductor of conductor keeps lax inactive state (also can rotate with suitable speed) outside described, the outer contact of outer conductor be divided into two groups of conductors weave mutually become netted and the tension, its metal foil surfaces of being close to the aforementioned barrier film layer outside is wrapped and made to described inner conductor, and the inner conductor that makes outer conductor and aforesaid metal forming form physics and electric tight the contact.