US2696834A

US2696834A - Flexible wave guide

Info

Publication number: US2696834A
Application number: US92640A
Authority: US
Inventors: Robert S Carr
Original assignee: Airtron Inc
Current assignee: Airtron Inc
Priority date: 1949-05-11
Filing date: 1949-05-11
Publication date: 1954-12-14
Anticipated expiration: 1971-12-14

Description

DEC. 14, 1954 R s, vvCARR 2,696,834

` FLEXIBLE WAVE GUIDE Filed May ll, 1949 INVENTOR ATTORNEYS United States Patent O .FLEXIBLE WAVE GUIDE Roberts. (Carr, 'Maplewood, N. J., assigner to Airtron, Inc.,'Linden, N. J., acorporation of New Jersey Application May `11, 1949, :Serial No. 92,640

-Claims. Cl. 13S-56) 'This *invention relates lto improvements `in lfiex'ib'le waveguides .and 1more particularly to waveguides which are :suitable for being subjected internally to fluid pressure --andtotcontain such pressure to enhance `the conduction characteristics of :the waveguide.

Waveguides, as :referred to fherein, are ordinarilyem- -ployed :for the purpose of transmitting micro-waves in radar and ftelevision equipment and in :other equipment in which electrical impulses, usually of high frequency, 4are prcsentand :require conduction between `various components of the apparatus. Under many `conditions Eit :.is necessary or vdesirable to provide waveguides which are iflexible, :to -perrnit limited vmovement or vibration :of .various parts of such apparatus relatively to eachother `or rto Ypermit `contortion of the waveguide to facilitate its .installation inthe apparatus.

It has 'been lfound that waveguides should perefabht be :hollow `and rectangular in cross section, and `to meet ythese Arequirements while `nevertheless providing 'for vilexibility'in'the waveguide,'it has become more or less conventional practice to form Vthe :guiding or cond ating portionfofthe waveguide of hollow, thin metal tubing of rectangular -cross section vhaving yperipherally extending .corrugations to impart flexibility to the tubing. {Such ,flexible tubing can be produced in various ways as, for example, by -merelv ypressing such corrugations iinto a previously formed more or less rigid tubingor by winding Ia llongitudinally convoluted strip of thin, .lilexible `metal spirally-upon a rectangular mandrel insuch a way that the convolutions of each turn of thestrip -aboutthe ,mandrel interlock with each preceding and succeeding turn, thereby forming a continuous tube. in forming the guidingor-conducting core of the waveguide inlhealatter .mannen it is desirable to solder Lthe-spiralseam sothat thereris `no airleakage through/or slippage in `said seam; l.the Vflexibility of the metal in -the convolutions being .relied upon .to rvgive the requisiteexibility to the hollow,

.tubularvcore 'Sometimes the solder is zomitted yfrom 4the seam vso .that ,ma ycertain amount of slippage vis present therein. While this may enhance `the flexibility -of ythe waveguide to some extent, it has been found that itdoes .not Iyield best `results from `the standpoint ,of microvwave guidance or conduction.

A .complete waveguide includes suitable `connecting iilangesor ecuivalent connecting means ixed ,tothe oppo- `site ends 'of a length of such a hollow, trnetal, 'tubular core and commonly is provided with an `outerjacliet of rubber, synthetic rubber .or other rubber-.like material.

It ,has .been found that waveguides :are much ymore .efficient for .micro-wave guiding `and `conduction purposes, yif .the waveguides and `other parts of a wave .conduction system are maintained Vwith y.duid pressure `there- "in substantially ygreater than atmospheric pressure. lpresent .invention comorehends :improvements inflexible waveguides which enable them to .contain `ailuid suchas air .under pressure, thereby ,rendering them suitable for use in such pressurized systems.

`lt an important'obiect of the present {invention to provide waveguides which yare adequately vilexible 'but which `nevertl'ieless have the capacity of ,containing yair `under substantial `pressure without material leakage.

.Another important obiect of this invention'is vthe .provision of,.a llexible waveguide in which ,connecting danger at one xor both endsthereof are adapted .forlirm aixar-.tiou ,to the metal conductingcore ofthe waveguide and are grooved peripheraliy `to afford a uidiight interlock lwith a rubberlikeiaclret which covers the said core.

.Another .important ,object Lis .the Lprovision, in a ilexible waveguide, .of -means 1to1-preventing material outice ward fdistortion for bulging rof `the metal conducting core as a result t of rsubstant'ial fair pressure therewithin, Awhile nevertheless ipreserving substantial ilexibility yin the core.

Another object of .this :invention is the yprovision of a;lexible .waveguidehaving means `for preventing material :outwardtdistortion or Vbulgingof the metal conducting core in the tpresence of substantial ypressure therewitlinand having connecting `flanges or their equivalent Lrrnly.andfluicbtightly fixed atopposite ends of the said core, .and :improved `means aifording an interlocking, fluid-tight connection ,between lsuch `flanges -and a -frubberlike `jacket providedias 1a covering forthe core.

The foregoing :and ,other .objects of this `invention should .be apparent from the ,following description ,and `the Aaccompanying drawing rin which:

vFigure vl is aside .elevational view, partly in central axial isection, of a tllexible waveguide according to .the 4present invention;

Fig. 2 .is a cross-sectional view atfone hanged end of the said waveguide,ithesection.being-substantially on the .line ',2-2 `of .-Fig. q1.;

.Fig. ,3 isa.cros s sectional viewatone flanged end of the said waveguide, .the t section lbeing lsubstantially on t the -lineSw-.S of g'Fig. .1;

Fig. `4 is a view toward `one send -of .a Amodified form of waveguide according to this invention, the said View beingtpartly in `side elevation and partly in central axial section, `and fbeingrbroken `away inlayers to show certain interior `parts `in .side elevation;

Fig. 5:is a vieu/.substantially like-thefleft side of Fig. l, .showing :a -further Amodified `form of vflexible waveguide .accordingto .this `invention;` and .16 ,isa view substantially like Fig 4 4but `showing uthermoditication within the present invention. to Figs. .l-.3, inclusive, the .flexible waveguide illustrated therein fcomprises .a flexible, metal, tubular `core .11, `which fis `rectangular in `cross section and is :shown ashavingplural peripheral .corrugations or con- ,volutions 12 suitableQforimparting.exibility to said core. As .the Iparticular.conformation o'f `the convolutions and Vthemanncr of 'forming them do notion-a any essential ,part ,of this invention, such convolutions are shown Vin thefdrawing onlydiagrammatically rather Vthan in detail. flthoughlit is considered preferable that themetal, tubular corefbe convoluted, nevertheless it should he under fstocd that ,the @present invention valso comprehends .flexjible 'waveguides which may have other structural ,provisions -for yielding exibility as, for example, an .unsoldered tslip joint or seam between turns of interlocking, non-.convoluted strip metal.

Connectionelementsin the form of connecting anges 13 `preferably areuid-tightly fixed upon the core 11 at ,the `ends ,of ,theilatter as by soldering at 14, yto afford means forconnecting the waveguides to other pieces of equipment; and a ljacket 15 of relatively soft rubber, ,syntheticrubber or other rubber-like ilexible material is :suitably lmolded in place `to completely surround the `portion ,of Vthe core'between the `said connecting flanges. The 'liacket V`1'5 conforms in outer shape to the core l2.

having a wall .of substantially uniform thickness except ,as noted hereafter.

The connectinganges 13, 4as illustrated, have a main or 'bodyportion 16 with bolt holes 17 therein to receive bolts `for `inter-ccnnecting the lwaveguide between other pieces of equipment. Although similar `flanges are illustrated at Aopposite ends of the waveguide, 'it is, of course, Within thepresent "inventionto provide diferent 'flanges or equivalent connecting means at opposite ends yof the waveguide, ,andmeans otherthan boltsmay be employed -to effect connection with other pieces ,of equipment. For this reason such `.connecting flanges or other suitable means 'for .inter-connecting the waveguide with other V,equipment l,are :sometimes referred to herein ,and 4in the claims `as connection-,elements.

Asbest seen in lFig. l, the ,connection element .13 has .anfinterlockingportion .1.5, integral with the bodylportion .316, and extending therefrom in a ,generallyrlongitudinal or axial direction. .The :interlocking portion 18 vis formed with a .continuous .inner :peripheral groove 19 :adjacent to ...the fbody portion .51,6, .and a continuous .outer peripheral gtoovetoward .the..free.end of said.interlockingportiou 'I'he provision of the mentioned grooves gives the interlocking portion 18 a somewhat zigzag or convoluted shape as viewed in axial section as it appears in Fig. 1. The interlocking portion thus consists of an outer longitudinally extending web 21, a transverse or radial web 22 which connects the web 21 to an inner longitudinally extending web 23, and a transverse or radial flange 24 which extends outwardly from the web 23.

It may be observed that the inner diameters of the web 23 are greater than the corresponding outer diameters of the flexible metal core 11, so that when the jacket 15 is molded to constitute a part of the device, the rubberlike material of that jacket extends between the web 23 and the core 11 and extends into and completely fills the inner peripheral groove 19. Also, it may be observed that the outer diameters of the radial flanges 24 are less than the corresponding outer diameters of the web 21, so that when the jacket 15 is molded in place, the rubber-like material thereof completely encases the flange 24 and extends into and completely fills the outer peripheral groove 2l). Under the last mentioned conditions the rubber-like material of the jacket may be formed to give it outer diameters at the connection element which are the same as the corresponding outer diameters of the web 21, so that the adjacent outer surfaces of the said web and of the jacket are in effect continuous uninterrupted surfaces; the rubber-like material of the jacket being smoothly graduated from the connection element into the main body portion of the jacket without any undesirable lumps or ridges.

It may be seen that under the above described arrangement there exists a lrm mechanical and fluid-tight interlock between the jacket 15 and the connection element 13. It should be appreciated that, although the flexible metal core may be made to be air-tight, it may nevertheless develop slight leaks which would enable fluid pressure to escape from within the core. If this occurs and if the pressure within the waveguide is not extremely high, the jacket 15 should prevent the escape of air and thus maintain the pressure within the waveguide. In this condition, however, the described interlocking arrangement between the jacket 15 and the connection elements 13 is of considerable importance; for without it, air leaking from within the core 11 would pass longitudinally between the latter and the jacket 15 and would eventually find avenues of escape at the ends of the jacket. However, with an interlocking arrangement as herein described, air attempting to escape would have to pass completely around the rubber-like material within the groove 19, thence completely around the web 23 and the radial flange 24, and thence around the rubber-like material within the groove 2t).

There are several features about the described interlocking arrangement which operate to prevent such escape of fluid under pressure. For example, the molding of the jacket 15 to the remainder of the waveguide causes the rubber-like material of the jacket to extend within the inner groove 19 and in the space between the web 23 and the core 11 and causes those spaces to be completely filled with the rubber-like material to thereby oppose the escape of air therethrough. In addition, if air should find its way to a point between the interlocking portion 18 and the convolutions of the metal core 11 underlying that interlocking portion, the air pressure at that point would deform the rubber-like material outwardly, thus urging it very tightly into the groove 19 and into an enhanced sealing engagement with the outer surface of the web 23, so that the pressure of the air itself aids in preventing the escape of the air at the end of the jacket.

Aside from the effect of air pressure as just described for preventing the escape of air, it is obvious that for air to escape at the end of the jacket, it must pursue a circuitous and lengthy path, and this in itself presents very substantial opposition to its possible escape.

The embodiment of this invention shown in Fig. 4 differs from that illustrated in Figs. 1-3, inclusive, only in the addition of a sheath 2S of braided metal wire or braided thin metal strip material which preferably is braided upon and extends entirely about the metal core 11. The metal of which this sheath is formed preferably is somewhat flexible and of suflicient tensile strength to permit flexing of the core 11 while nevertheless preventing any material outward bulging thereof in the presence of fluid pressure therewithin. The soldering at 14, to fix the connection element 13 upon the core, permeates the braided sheath in the vicinity of the said element so that the solder, in addition to serving as a means of aflixing the flange to the core, also serves, as in the first described embodiment, to prevent the escape of fluid pressure between the element 13 and the core 11. In the structure illustrated in Fig. 4, the interlocking portion 18 functions similarly to its counterpart, as previously described with reference to Figs. 1-3.

The structure illustrated in Fig. 5 differs from that illustrated in Figs. 1 3 only in that its connection element, instead of having both inner and outer grooves such as grooves l@ and 20 of Fig. l, is provided with only an outer groove 20a. In this arrangement, the soldering at 14 prevents the escape of fluid pressure between the connecting flange 13a and the metal core 11, and fluid pressure attempting to escape at the end of the jacket 15 would have to find its way around the radial flange 24 and thence around the rubber-like material of the jacket which fills the outer groove 20a. However, if air pressure should find its way around the radial flange 24 and to the inner radial face of said flange, the pressure of the air at that point would tend to urge the rubber-like material in the groove Zita leftwardly as viewed in Fig. 5, thereby enhancing its sealing contact with the left radial surface which defines the said groove; thus in this structure, as in that of Figs. 1 4, the air pressure itself aids in sealing against its escape.

The structure illustrated in Fig. 6 is similar to that illustrated in Fig. 5, except that it includes also a braided metal sheath 25. This sheath is like its counterpart in the structure in Fig. 4, and functions similarly thereto, and the connecting flange 13a is similar to and functions similarly to its counterpart illustrated in Fig. 5.

it should be apparent from the foregoing that by providing connection element or flange structures and a fluidtight rubber-like jacket having its end portions interlocked with such elements or flanges according to this invention, a very effective means is provided for preventing the escape of fluid pressure from a flexible waveguide; and that flexible waveguides according to this invention may be pressurized to contain fluid pressures substantially above atmospheric pressure and thereby be rendered more efflcient for the conduction of micro-wave energy. It should also be apparent that the provision of the braided metal sheath, as hereinbefore described, affords suitable means for preventing any material radial distortion of the flexible metal core which might undesirably alter the conduction characteristics of the waveguide.

Although the capacity of the herein disclosed waveguides to contain fluid pressure is limited to pressures which are not sufficiently high to cause ballooning or bursting of the rubber-like jacket, it should nevertheless be obvious that waveguides according to this invention may be adapted for containing higher fluid pressures by the simple expedient of providing a jacket which is sufficiently stronger to enable it to withstand the higher pressures.

It should be understood that the present inventive concept may be embodied in various structures other than those hereinbefore described and illustrated in the accompanying drawings, without, however, departing from the invention as set forth in the following claims.

What I claim is:

l. A flexible waveguide comprising an approximately rectangular, flexible, tubular, conductive inner core which is substantially resistant to the passage of fluid from the interior to the exterior thereof; a connection element fluid-tightly fixed to said core toward one end thereof and having an approximately rectangular inner-end portion with a substantially continuous, peripherally extending, radially opening groove therein having approximately parallel sidewalls; and a flexible, fluid impervious, tubular jacket, which is approximately rectangular throughout its length, surrounding said core and extending into lapping relationship relatively to said inner-end portion of the connection element with the material of said jacket extending into and substantially filling said groove to oppose passage of fluid between the connection element and the jacket; the jacket material in and bordering said groove being in substantially non-flexed condition, whereby such material in said groove is free of any flexing influence from such bordering material tending to loosen the said material from its filling position in the groove, said connection element further having a second such groove with the jacket material extending therento and filling it, one of said grooves opening radially outwardly and the other of said grooves opening radially inwardly.

2. A exible waveguide comprising an approximately rectangular, flexible, tubular, conductive inner core which is substantially resistant to the passage of fluid from the interior to the exterior thereof; a connection element Huid-tightly fixed to said core toward one end thereof and having an approximately rectangular inner-end portion with a substantially continuous, peripherally extending, radially opening groove therein having approximately parallel sidewalls; and a exible, fluid impervious, tubular jacket, which is approximately rectangular throughout its length, surrounding said core and extending into lapping relationship relatively to said inner-end portion of the connection element with the material of said jacket extending into and substantially filling said groove to oppose passage of uid between the connection element and the jacket; the jacket material in and bordering said groove being in substantially non-flexed condition, whereby such material in said groove is free of any flexing influence from such bordering material tending to loosen the said material from its filling position in the groove, said core further being formed with peripherally extending corrugations and the material of said jacket extending into and lling said corrugations.

3. A exible waveguide comprising the combination of a substantially rectangular, flexible, tubular, fluidtight metallic inner core, a metallic, rigid connection element having a longitudinal opening therethrough to receive said core, an end of said core being inserted in said opening and said core being fluid-tightly connected to said connection element, said connection element further comprising integrally an outer web extending longitudinally inwardly of said core, a web integral with said outer web and extending radially inwardly therefrom, an inner web integral with said radial web and extending therefrom longitudinally inwardly of said core and in spaced relation thereto, and a flange integral with said inner web and extending radially outwardly therefrom and terminating radially inwardly of said outer web, said webs and flange defining a radially inwardly open groove and a radially outwardly open groove, and said waveguide further comprising a flexible, fluid impervious tubular jacket molded around said core and in said grooves and filling the latter, said jacket further comprising a body portion having a wall of substantially uniform thickness and conforming in outer diameter to said outer web and being smoothly graduated therefrom into said body portion.

4. A exible waveguide according to claim 2, further including a exible sheath which is substantially nonexpansible peripherally, intimately surrounding the said core and restraining the latter against peripheral expansion in the presence of fluid pressure therewithin.

5. A iiexible waveguide according to claim 1, further characterized in that the said connection element has a body portion extending around the core toward one end thereof and an integral, peripherally continuous web, of S-shape in longitudinal section, extending longitudinally inwardly and being embedded within said jacket material with the reversely extending parts of the S deining the mentioned grooves; the said web, longitudinally inwardly of the mentioned inwardly-opening groove being of greater internal diameter than the corresponding outer diameter of the said core to provide space for accommodating the jacket material uninterruptedly from the body portion of the jacket to and into the said inwardly-opening groove, and said jacket material extending uninterruptedly from the body portion of the jacket to and into the said outwardly-opening groove.

6. A flexible waveguide according to claim 1, further including a exible sheath of relatively high tensile strength, intimately surrounding the said core and restraining the latter against peripheral enlargement in the presence of fluid pressure therewithin.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,461,130 Loughead July 10, 1923 1,630,895` Herbst May 31, 1927 1,684,717 Sherbino Sept. 18, 1928 1,847,218 Lamb Mar. 1, 1932 2,085,563 Aime June 29, 1937 2,257,355 Vohrer Sept. 30, 1941 2,261,948 Beach Nov. 11, 1941 2,308,073 Hagerty Jan. 12, 1943 2,467,036 Iftiger Apr. 12, 1949 2,479,288 Allen Aug. 16, 1949 OTHER REFERENCES Microwave Transmission Circuits, Radiation Laboratory SerieS-Ragan-Published May 28, 1948.

C. Q. Magazine-The Radio Amateurs Journal-November 1946 issue- Page 25.