US3002047A - Coaxial cable - Google Patents

Description

sept. 26, 1961 o. A. MANNELLA 3,002,047

coAxIAL CABLE Filed Oct. l5, 1959 ,United Scare Patent 3,002,047 COAXIAL CABLE Orlando A. Mannella, Forest Park, Ill., assignor to Amphenol-Borg Electronics Corporation, Broadview, Ill f a corporation ofDelaware` Filed Oct. 15, 1959, Ser.No. 846,696 4 Claims. (Cl. 174-124) 1 This invention relates to radio Yfrequency transmission lines. More specifically, it relates to an improved type of coaxial cable capable of continuous dependable service at extreme temperatures or under conditions of intense nuclear radiation, yet quite exible and with a high degree of flexing endurance.

The specific form of cable here disclosed has been demonstrated, by actual test, to be capable of continuous operation at 1000 F. ambient temperature with satisfactory attenuation and VSWR characteristics; with no perceptible deterioration or change in insulation resistance even after 20,000 cycles of bending over a mandrel ten times the diameter of the cable under test. No other cablepresently available to the industry accomplishes comparable performance.

It is thus the primary object of the present Iinvention to provide aunique and improved coaxial line capable of continuous operation under ambient temperatures in the 1000 F. range and also cabable of withstanding thousands, of cyclesfof bending'without undue deterioration, particularly as to the breakdown voltage or insulation resistance of the cable dielectric. The manner in which the foregoing objects are accomplished will be described in greater detail in connection with the drawing attached to and vforming a part of the present specification wherein:

FIGURE 1 is a detail side elevational view of a portion of the transmission system described hereinafter, with the outer jacket and the successive layers of which the line is formed shown cut back to illustrate the details of construction thereof; and

FIGURE 2 is a sketch of a sealed radio frequency transmission system consisting of a length of the unique line shown in FIGURE l, extending between a pair of connector ttings.

As will be observed fromFIGURE l, the basic parts of the line are the central conductor 10, which is surrounded by a semi-solid silica dielectric 11 andra tubular outer conductor 12. The dielectric 11 preferably consists of plural layers 13, y14, 15, 16 and 17 of berglass, eachV in the -form of a continuous coaxial sheath around the central conductor. 'Ihe parts 10 and 11 thus comprise a core closely encased in the outer conductor 12 of braided wire and surrounded by a jacket 18 consisting of a flexible hose of stainless steel. The opposite ends of the stainless steel jacket 18 are brazed to terminal connector fittings 19 and 20, each of which have dielectric inserts hermetically sealed in the connector shells so that the entire unit functions as a sealed radio frequency transmission system.

In the present preferred commercial embodiment of the cable, which is'designed to have a characteristic impedance of 50 ohms, the central conductor 10 consists of seven strands of American wire gauge size 21, silver covered copper wire. The nominal diameter of each strand of this Wire is .0285 inch, whereby the inside conductor has a nominal diameter of .085 inch with a lay of .7 to 1.3 inches. The fiberglass core is made up of a major portion (substantially 55% of the strands) of yarn formed of fiberglass bonded staple sliver 22 (identied in the industry as ESD-E-lO), with a minor portion (45%) of continuous filament berglass yarn. In the preferred construction, this includes about 18% of the strands 23 of filament identified as ECG-150-4/4 and about 27% of the strands 24 identified as ECG-150 1/10, 8 ends. For

Patented Sept. 26, 1961 2 optimum results, the inside layers 13, 14, 15 and 16 of the dielectric are each woven with twelve strands 22 of the staple berglass, interwoven with four strands 23 of the continuous filament fiberglass to give a major portion of 75% staple iiberglass and 25% continuous lament fiberglass in the innermost layers, while the outer layer 17 is formed of twenty-four strands 24 of continuous` filament ber. This results in tive coaxial sheaths of progressively thinner layers of braided dielectric, with the wall thickness of the inside sheath 13 being greatest and the sheaths 14, 15, lloand 17 progressively less.

VAftertheV sheaths 13-17 are braided, the line is subjected to high temperature baking, preferably for a period of at least an hour, and at a sustained temperature of at least 900 F. The outer tubular conductor 12 off the line is then applied. Y As illustrated, the outer conductor consists of a laye' ofmetallic braid formed of 168 strands of No. 32 American wire gauge silver-plated copper wire, in 24 carriers 'of seven strands each. The wire of both theinner and outer conductors should preferably be of oxygen-free, high conductivity copper and free of oil or other Aforeign matter. The line is then drawn through a sizing die and dried overnight at a temperature of 300 or 400 F., after which indivdual lengths of the cable are mechanically pulled through corresponding lengths ofstainless steel hose 18. End connector ttngs 19 and 20 are brazed t the hose to close the ends of the sealed system..

'- .f As lindica-ted in. the introduction to the present dis-v closure, there are many and varied instances in which extremely high temperature coaxial cables are needed in connection with jet aircraft, guided missiles, rockets and many variations of nuclear'installations, yet there has not heretofore been developed a transmission line capable of satisfactorily withstanding such temperatures and still possessing the degree of flexibility and mechanical endurance necessary to withstand repeated cycles of iiexing or extreme vibration. It has been learned, however, that coaxial transmission line constructed as described above is superior in high temperature perform-ance to any ilexible line heretofore available to the industry and that, when constructed according to the specifications here given, it is quite practical to achieve a high degree of ilexibility and flexing endurance greatly exceeding normal requirements, yet to also maintain satisfactory insulation resistance and breakdown voltage characteristics even after continued ilexing at these elevated temperatures. This is accomplished, moreover, with a cable construction having very satisfactory characteristics as to voltage standing wave ratio and attenuation. Further, it has been discovered that while neither staple filament ii-berglass nor continuous filament iiberglass have shown themselves to be capable of forming a cable dielectric achievingthe desired results, yet the combination of these two types of glass iibers, in Ithe proportions and placement here discharacteristics without a compromise of electrical, physiv cal or mechanical requirements, and thus results in a gable having properties not obtainable with either fiber one.

Having thus described my invention, what l claim as new and desire to secure by United States Letters Patent l. A high temperature radio frequency transmission system comprising an airtight iiexible metallic jacket of corrugated stainless steel hose extending between a pair of terminal connectors and hermetically sealed thereto, together with a exible coaxial transmission line interconnecting said connectors and housed within said jacket; the coaxial line consisting of a central conductor of stranded flexible wire, an outer tubular conductor of high conductivity woven metallic wire braid, with the central V andsouter conductors .heldin coaxial-spaced relation to each other by a semi-solid silica dielectric resistant to temperaturesof l000 F. and resistant to repeated bendingfsaid dielectric consisting of aplura1ity'of-continnous Asheaths fof braided fiberglass: yam surroundingreach other andatiording plural dielectricvlayers betweenthewcentral f Vandsouter conductorsgfwithseach of theinteriolsheaths composed substantially? 5%k of yarn consisting of bonded `staple sliver berglass and 25% -ofyarnconsisting ofgconi v`tinuous Vfilament: vfiber-glass, vand the 011terlsheath consist ingorf' continuous filament ber-glass.

t CS2. Ahightemperature radiofrequency transmission system comprising an airtight flexible jacketextendingbetween a pair fof terminal connectors @and ihermetically .sealed thereto; 'together with a vflexibleY coaxial transmission-:line interconnecting said :connectors andfhousedl withinrsaidrjaclget; the coaxial lineconsistlng of azcentral conv. dnctor of flexible wire and'4 an' outer 'tubular conductor held incoaxial spaced relationtoeaclrotherby assomisolid vsilica dielectric resistant totemperatures .of-.1000 F. `and resistant to repeated bending;fsaid'.dielectric-consiso `ing 1 of braided fiberglass yarn icomposed substantially 5.5%.,01? yarnv consisting ofstaple fberglass and 45% of yarn consisting of filament berglass.

3.` A ii-exible high' temperature vcoaxial'fradio:frequency transmission ,line consisting of alcentralv conductorfof stranded exible wire and anoutertubular conductor di highjconductiyity Wovenmetallicwirebraid, `with the central and outer conductors heldgincoaxialfspaced res lation to each other by asemi-solidsi-licadielectric re.-

sistant to temperatures of 41.(l0(}".`r"`. andresistant tore- Ypeated bending; said dielectric consisting offs-aiplnralityof continuous sheaths of Abraidedviberglass yarn surrounding each other and affording plural dielectric layers bel Itween the central and outer conductors; with each of the interior sheaths composed substantially 75% of yarny .consisting of ybonded staplefsliver iberglass and 25% of yarn consisting of continuousilament fiberglass, and the sheaths composed substantially 75% of yarn consisting l of staplev berglass and-25% of yarn consisting of lament fiberglass, land lthe Vouter` sheathv vconsisting of fila-` ment berglass. Y

References Cited in the-leofthispatent' ,Y

UNITEDl STATES vvPA'EIKFS 2334560 t Keyes ivntrx1:1.'1941Y '=2,6s9,695 Birdv -Feb.v1'6, '1954 A FOREIGN PATENTS slaan; Netherlands s jnec. v15,1934 .'OTHERIREFERENCES l v 'Wire and Wire Products (publication), November 19.46, {pages`f885-'888 Zandt-9110.

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