US2476854A

US2476854A - Transformer

Info

Publication number: US2476854A
Application number: US619871A
Authority: US
Inventors: Albert W Friend
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1945-10-02
Filing date: 1945-10-02
Publication date: 1949-07-19
Anticipated expiration: 1966-07-19

Description

July 19, 1949.

' A. hw. FRIEND TRANSFQRMER Filed Oct. 2, 1945 'Patented July H19, 1949 HTED TRANSFORMER of Delaware Application Cctober 2, 1945, Serial No. 619,871

1 2 Claims. i'Ihe present invention relates to electrical transformers, especially coupling o1' output transformers of the type employed in television receiving systems which include a cathode ray image-reproducing tube. More particularly, the invention relates to means whereby a television coupling or output transformer may be utilized to regulate the size of the image raster scanned by the electron beam of such a cathode ray image-reproducing tube.

The invention herein disclosed constitutes a further development of the inventions set forth in my copending applications for U. S. Letters Patent, Serial No. 619,869, now Patent Nol 2,451,- 026, and Serial No. 619,870, led concurrently herewith, and entitled Television system and Transformer respectively.

Television receiving systems utilizing the principle of electromagnetic deflection of a cathode ray scanning beam normally include a power output tube which is adapted to deliver cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time, through a coupling transformer to a pair of cathode ray beam deflection coils incircling the neck of an image-reproducing cathode ray tube. Since the instantaneous angle of deflection of the cathode ray scanning beam is a function of the instantaneous strength of the magnetic deiiecting field in the vicinity of the deflection coils, and since this deecting field is, in turn, dependent upon the amplitude of the current flowing through the deflection coils at such time, it follows that a change in the peak amplitude of the current flowing through the deiiection coils will produce a change in the size of the image raster scanned by the cathode ray beam.

In my two copending applications referred to above, there is Set forth means for eliminating the necessity for the separate variable inductor which is normally shunted across several turns of the secondary winding of the coupling transformer to thereby control the peak amplitude of the deection current for the purpose of image size regulation. In one of these disclosures, this may be achieved by forming in the transformer core an aperture which is adapted selectively to receive a slug of magnetic material. This slug, by varying the permeability of the core as it enters the aperture, changes the overall impedance of the transformer, and hence the peak amplitude of the cyclically Varying current flowing through the cathode ray beam deflection coils. In the disclosure of the Vother mentioned application, the center leg of the transformer core (that is, the leg around which the' coils are wound) is separated into two portions, one of which is arranged to be movable. By an actuation of this movable leg portion, a change in the overall impedance of the transformer is brought about. y

In this last-mentioned application, three tubular transformer coil windings of different diameters are utilized, consisting of one primary winding and two separate secondary windings. These elements are arranged so that one of the secondary windings surrounds the center leg of the transformer core. The primary winding overlies, and is insulated from, this secondary winding, while the other of the two secondary windings overlies, and is insulated from, the primary winding. As a result of such a construction, any change in the impedance of the transformer due to variations in the position of the movable core leg portion will have an influence upon the currents produced in each of the separate secondary windings which ls approximately proportional to the turns ratio therebetween.

When a transformer such as described above is employed in a television system, the primary winding is customarily connected in theanodecathode circuit of the power output tube. One secondary winding may be connected across the cathode rai7 beam deflection coils, while the other secondary Winding may be used to step up the surge voltage developed across the transformer during the retrace periods of the cathode ray beam, so that this voltage may be rectified and employed as the second anode potential for the kinescope, either directly or through a voltage doubling or multiplying" circuit.

This step-up secondary winding, mentioned above, must consist of a relatively large number of turns in order to develop the high second anode potential required. In such a case, however, it will be appreciated that any change in the impedance of the transformer due to an adjustment of the movable core leg section for the purpose of image size control will have al very appreciable effect on the voltage developed across this step-up secondary winding, or, in other words, such an adjustment of the transformer for the purpose of size control will cause undesirable variations in the accelerating potential applied to the cathode -ray image reproducing tube which is commonly termedV a-kinescopef One object ofthe present invention, therefore, is to provide, in a television receiving system in which the accelerating potentials for the imagereproducing cathode ray tube are obtained by provide an improved form of image size control for television receivers. U

A still further object of theinvention is toprovide a multi-winding transformer in which variations in theV electromagnetic coupling between certain of the windings will @fiest to La much lesser degree the electromagnetic coupling between certain other of the windings.

Other objects and advantages will be apparent .from )the .following :description :of vpreferred forms .of vthe 1invention and vfrom the drawings, i-n-which:

Fig. 1 is a:sectionalview'offaitransformerconstructed fin accordance :with Ather 4present vinvention; Y

Fig. zaisatopsfplan wiewfofther-transformer of Fig. .1;

Fig. '3 tis :a :diagramioffon'e fpossible Acircuit in which fthe transformer .-ofdFig, 1 -might be employed; Y y

fFig. 41is a simplified:circuit/equivalent from an;impedaneefstandpoint:tothat of Fig. 3; and

'.Fig.t5. is fa :perspective :.VleW, in section, of a modicationfof the transformery of Fig. ,1.

i'In Ei'gs. '.1 l and Y2;'isfshownr :a coupling or cutpnt-:transformen 1- general-ly indicated by the reference characteril -The'core:(if-transformer I isxcomposeidrofgtwo*matchingframe pieces I2 and 14,:bestfzshown=in':Fig;i2,:and-i two lcentral leg sections, .or;slugs, h6-.Band A28. #Eachvof these core components 121, :If6- and "I8 is preferably molded v-cf fsome :suitable ffinely Vdivided ferromagnetic rmaterial, :such :as ipowdered or comminuted firon, in rcombi-nation iwth a binder. Theematehing frameupieces- I-'2..and I 4 are each preferablyrrectangular-lnfshape,:with the central iliortion-:of:theitwoglongasides.ofy each frame piece being ;curved;;a ayzfromithe plane of the frame piece-l in such'agmwnner :i that the inner surface of veach ofi thesfctirve-dggportionsis .approximately semi-cylindrical in ishape..Y 4The curved central portions of; onegsideeofreaohpf:the frame vpieces 12e-andi# ire-respecti lit:designated,asr Iza and I 4a..in-,1i'ig- 11,2 heycur. zcentralfportions of the other, or lowergsidefo `eachnof-'the frame pieces being respectlvely-.videntiealto these portions Iza and.14a.:butnot-beinawisibleinnig. 2 -due to the .manner ofetak-ing thegpltn lliew. However, when the-matching framepiecesfflkand I '4 are, in faceto-face.relatiom-.as shownf-infFig. 2, vthen the inner, surfacesofcluYQdfgpQrtions I2a and Illa together define y.an r:aperture- ;of :substantially cylindrical.,outlinajasfdo also; the inner surfaces oftheu eurvedportions `(11011;,shown) ofthe other, orlowendong sidesgofrthefframe-pieces- Iz and I4.

The` central .v leg usection, ,ore slug, I 8 'is cylindrical in.shape,..andiis..so..dimensioned as to t securelybut moi/ably` in-theaperture ,of cylindrical. outline` .defined Ebyathe Vcurved -core portions ;Zlza ...ar 1;i. Ma. -..Sirnfllarlyl Y the lcylindrical eentralljeg seetion..or.sliig-I 6in-is so dimensioned as.V to lit. securelyintheaaperture defined by' the Vis intended to be movable relative both to the slugV I6 and to the frame pieces I2 and I4, so that the dimensions of the .air gap .2 3 between slugs I6 and L8 may be varied..

The means for moving the slug I8 relative to the slug it are shown in Figs. 1 and 2. A screw 22 is embedded in, or otherwise securely afiixed to, the slug I 8. This screw 22 passes through a threaded opening a support 24, the latter being positionedapart from the core frame pieces I2 and 'Id by two

spacers

26 and 28. A plurality of screws 30 secure support 24 to the spacers 26 and 23.

The core frame pieces I2 and le are held in face-to-face relation, as well as against the

spacers

26 and 28, by means including two pairs of brackets 32 andi'34 respectively. ,Two .pairs of screws 35 and v33 v-respectiwely .pass ythrough the two pairs of-brackets32 and 34. Whenthe'screws Se and 33 are tightened, 'theytiethe--variouscore elements and slug-adjusting means into a unitary transformer structure," as shown in Eig-s.' -1 and 2.

Three disk-.shaped coil windings -P, Siand S2 (representing the primary and-the assumed two secondary windings, respectively) -arepositioned so that their planes are insubstantially-parallel relation with .respect-to each other, and so Vthat they are approximately normal to ltlielo'ngiti'1 dinal axis of theeyli-nd-rical c oreleg sections 16 and I8, as best showninFig. 11. :All'fthree coils are preferably lwound .on an -insulating support or tube 39, which is Aslightlylarger vindia'rn'eter than the slugs Y-I'S and I8,- andso-disposedasfto be substantiallycoaxial` withtheslu'gs. As a-result ofthis arrangement, Athe-slug` I8-isfree to move axially within the.tube-39inresponse-to an actuationof ad'justingscrew-22.

The coil P,comprising.the-primary-,-or input, coil winding of'. the transformer IvD; Jis disposed intermediate the .-two VVcoils :Si and-S2, .vas shown in Fig. 1. vCoils/S1.andS2eachcomprisea secondary, or output, -coil ...winding .of transformer s s.

The coils P, S1-andSz-arepositionedrelative to the slugs VI6l ,andIlsoathattlieair" gapflZ formed by the slugs/vlies between-the primary coil P and one `ofthe secondary' coils, orAS'e in the example illustratedf has tlf`1e` "effect, when current is:iiowinginlthepr-iinarycoil P, 'of varying the electromagnetic coupling between the coils lP and :'Sz. (in .response-to ar-"ariatio'nI in the dimensions ofl thegairvgapwas a--resultlof an actuation of screw 22) without affecting, -toan' appreciable degree,A -theel'ectromagnetie coupling between thefcoils1-:P-yandds1- `This'n action isde primarily ,A to the luxzzleakage; between .fthe -coils P and S2 and willabemoreiully Vdiscusseddreiriafter in connection withthel circuitpf-:Fig 34.

Fig. 3 showsI oneifpossiblegcircuitin. which-1the transformer .ofigsf 1 and..2;;ri;iigl;it..ln r employed, although it willbe.- clearly-.understooda,that this particular circuit is 'beingy .given merelyasfanaexample, and thatf:thertransformemof:the .present invention is suitableforzusedmnumerous. systems where it is desired. to: vary;the-.couplingrbetween two portions of a A circuit...withoutnappreciably varyingY the; QOllplI-lgheltweeir .ones of.. theseli'lftions andafthird portion.

Fig. 3 showsl a ,cathode-raybeamidefiection. circuit including a` -powerpoutput.tubefmhaving at least an anode, a cathode, and a control electrode. Power tube 40 ls adapted to deliver, when voltage variations having a waveform such as indicated by the reference character 42 are applied between the cathode and control electrode thereof, cyclically varying current, a portion of each cycle of which varies in a substantially linear manner with respect to time as shown by the sawtooth current waveform 44, to a pair of cathode ray beam deflection coils 45 through the output or coupling' transformer I5 (shown schematically in Fig. 3)

The primary winding P oi transformer I5 is connected in the output, or anode-cathode, circuit of power tube 4i?. The secondary winding S1 steps up the voltage developed across the primary winding P for application to a high-voltage surge-type rectier 45 which may, for example, be of the type set forth in a copending application of Otto H. Schade, Serial No. 578,678, filed February 19, 1945, now Patent No. 2,439,223. The output of rectifier 48 is applied to the accelerating electrode of an image-reproducing cathode ray tube of kinescope 50.

The secondary winding S2 of transformer I5 is wound in a direction opposite to that of both windings P and S1. A damper tube 52, in series with a parallel resistance-condenser combination 54, in connected across the secondary winding S2. Damper tube 52, together with the resistance-condenser combination 54, prevents oscillations in the circuit by acting as a switch which closes at the end of the return, or snapback, portion of each cycle of the sawtooth current wave 44, or, in other words, at the beginning of each deectlon cycle. The switching operation of tube 52 causes a current to flow therethrough which is of such waveform as to assist the power tube 40 in producing the desired linear current variation through the deflection coi1s 45. The operation of such a damper tube is set forth in U. S. Patent No. 2,309,672 granted February 2, 1943, to Otto H. Schade, and hence will not herein be described in detail.

The horizontal cathode ray beam deflection coils 46 preferably form part of a yoke assembly (not shown) encircling the neck of the conventionally represented kinescope 5G. As illustrated in Fig. 3, the series combination of damper tube 52 and resistance-condenser combination 54, as well as the horizontal deflection coils 45, are connected in parallel inter-relation across the secondary winding S2 of transformer I0.

By varying the dimensions of the air gap 25 through adjustment of screw 22, the electromagnetic coupling between the two coi1s P and S2, on opposite sides of the gap 20, is altered. This results in a change in the peak amplitude of the sawtooth current wave 44 flowing through the horizontal deection coils 46. Since the instantaneous angle of deflection of the cathode ray scanning beam of kinescope 55 is a function of the instantaneous strength of the magnetic deectlon eld which, in turn, depends upon the amplitude of current wave 44, such a change in peak amplitude of current wave 44 produces a change in the size of the image raster scanned by the cathode ray beam.

However, such a variation in the dimensions of the air gap 20 as a result of adjustment of screw 22 does not change to any appreciable degree the electromagnetic coupling between the two coils P and S1, since the air gap 20 lies on the opposite side of coil P from the coll S1. The flux linkage between coils P and S1 is, therefore,

6 relatively constant for such variations in the width of the air gap 25 as would be made under operating conditions.

As one example of the above operation, it hasbeen found in practice that an increase in thef width of the air gap 2 5 which decreases the elec-v tromagnetic coupling between coils P and S2 to1 such an extent as to decrease the size of theJ image raster scanned by the cathode ray beam of kinescope 55 by 32%, changes the electromag-A netic coupling between coi1s P and S1 to such al small degree that the second anode voltage ap-f' plied to kinescope 5) decreases by only 2%.v This!l approximately constant second anode voltage isi also somewhat influenced by the reduction in'v transformer inductances decreasing the beam return time slightly, which likewise tends to maintain a high voltage value for the pulse generated by the sudden magnetic ilux decay.

The eiiiciency of the powdered iron core transiormer of the present invention is at a maximum when the horizontal deflection coi1s 46 form part of a yoke assembly provided with a core structure of approximately the same or an equivalent type of powdered iron material. In such cases, the circuit of Fie. 3 may be represented schematically by the equivalent circuit of Fig. 4, where Using the above terms, it can be shown that:

L1=L2= (l-C) -Lp t L3=C'L1 and L L4=Z3BLU By a positioning of coils P, S1 and S2 relative to the air gap 25 in the manner illustrated in Figs. 1 and 2, it can be shown that an increase in the width of the gap 20 will produce a decrease in the value of Ls (Fig. 4) and a simultaneous increase in the values of L1 and L2, or at least an increase in the ratios L 1 LL Lp L.. In other words, the coupling coeiiicient k between the coils P and S2 is decreased to correspondingly decrease the peak amplitude of the current wavel and A modified form of the transformer of Figs. 11 and 2 is shown in Fig. 5. A pair of matching`

core portions

56 and 58 of hollow cylindrical con-` uration are each formed with one open end. The open ends of the cylindrical core portions 56,;v and 58 are then tted together as shown so as to substantially completely enclose the interior of the core portions.

The closed end oi each of the core portions 55 and 58 has a centrally located aperture therein to receive the core leg sections, or slugs, IB and I6 respectively. The slugs I8 and I6, the former being movable, extend toward one another so as to form an air gap 2i) therebetween in the same manner as do the slugs I8 and I6 in Fig. 1.

The three coil windings P, S1 and Sz have the same positions relative to One another and to the.

theiseleeimeprevdee aSubstantially;heiteren.

melreieslielete path. fer. the; slfefeeetie-tf1exefeh-. 'i

tra f rmeli windings.

it: will, The apparent that I, thefeieefedmstina. means of Figs. 1l andl k2,.,-incljt-iling;'the'. screw 12215,

nieuwe??? 2i meY-IeediIWe; reeel, ,t beenipieyed te very the `pesitien, ef; ue...

' fthe inventienjillils etedin 1 APPefPeSQ-:fee regulating-,i e1f1efSiZe-v imeee--1eeierfeeeneeel lei/fre @moderar-'bea television systern of the typefln Whig output tube is adapted to deliyer cylially` vary` ing current, a portiori of each `cyle f of Iwhich varis inea substantially 1inear manner Withre.- spect to time, throughl a ouplingqtransforrner Ato at least one cathode ray beam deflection1 coil associated withnanimagereproducing cathoderay tube, said couplinge'transformerbeing'prgjvided cuit of said power outputtube, a s econdlwnding connected to said cathode-ray'beam deflection coil, anda-third stepup Winding designed to pro:` vide a source of potential lforhapplioation to one or more of the accelerating:electrodes of said image-reproducing cathode ray tube, said appa-y ratus including a core for said coupling transformer having a portiongthegposition of which is variable, and means for Varying the position of Seeeer-efpertiee Se, es, teeeet e eheneefinmhe ode ray beam deection coils is Valtered to result in a change in the size of the image raster scanned by the cathode ray beam, While the po- Number .Y Name 1 Date 1,727,2241 Waters SeptfB,y 1929 1,815,380` S Porteret al: July-21, 1931-' 2,158,613'.v Loughlin Maygl-B; 1939` 2,180,413v i Harvey Nov; 21, 1939- 2,218,764 Moller i Oct'.-;22,v 1940 Y 2,280,733 Toison Apr.- 21, 1942 2,318,271v Weiche Maye, 1943- 2,361'5187- i Foster Oct. 24,- 1944 e 2,439,277#` Walker Alain-6, 1948 l 24411116; Mackey V May 4, 1948 FGREEGN Pry-TENTS-l Number Country Date 23,524/35 Australia July -16, 1936;-A '792,130 France Dec.- 23,` 1935 tential applied to .the cne-` ory moreaccelerating1 8 i, @ieaidimagefrepreduenecathode'ray f intermedi; substantially constant f in.;`

"1 an image producingzcathode-ray 171110851y It ,transfer-.mer including a pltnrlarsri Winsinezeonneeted mbe energized bythe, outrnlt r tube, at a secondary Winding electromagnetically, Coupled@geant-primary Winding andpconneeted rgyyto theV A deecting colafrorn the.:

adapted, o proyidea so urce of 1t otentialforzeat;y n pi the-accelerating electrodes of,v the., redire' feathode rays::tube:.sadf;trans. including. a imagnetic core a portion. of;- is ac :lj11s-table in positonrelative to the ref;

wi'relnes-r1eeine fsueh; that Whentheimsitmn;.of the adjustable portion of the coreis'alteredthe outgapprecablyaltering the potential appledto;

thec a tlg-logie-4 raygtube accelerating electrode- ALBERT WLFFR-IEND,

REEERENCES CETED i Tl1e1i`ol1owngreferences are of vreeord'in the file' of this patent:

UNITED- STATES VPATENIS