US2881341A - Deflection yoke - Google Patents

Description

K. SCHLESINGER A ril 7, 1959 DEFLECTION YOKE 3 Sheets-Sheet 1 Filed April 12. 1955 INVENTOR. ff L Z J'Z 50/21861' er B M Z K. SCHLESINGER April 7, 1 959 DEFLECTION YOKE',

3 Sheets-Sheet 2 Filed April 12. 1955 a? a5 a6 [f 127i Sc/zlesi INVENTOR.

April 7, 1959 v K. SCHLESINGER DEFLECTION YOKE 3 Sheets-Sheet 5 Filed April 12. 1-955 INVNTOR. KZLTZ' Sc/zlesz United States Patent DEFLE'CTION YOKE Kurt Schlesinger, La Grange, 111., assignor to Motorola, Inc., Chicago, 111., a corporation of Illinois Application April 12, 1955, Serial No. 500,870

16 Claims. (Cl. 313--76) This invention relates generally to the deflection of the beam in cathode ray tubes, and more particularly to a magnetic toroid deflection yoke for providing highly accurate beam deflection.

For displaying an image on a cathode ray tube, the beam thereof is deflected to form a raster on the screen. Such deflection may be provided by either electromagnetic or electrostatic deflection fields positioned along the neck of the tube through which the beam passes. For television use, electromagnetic deflection is generally used because it has been found more satisfactory to provide the wide deflecting angles required on modern television picture tubes. However, to provide such wide angle deflection, considerable power is required in yokes now being used. Further, for precise deflection, such as is required in color television receivers, it is necessary that the yokes be very accurately constructed so that the various beams in the tube will register on the mask to eliminate color fringing. Accordingly, the yokes now in use must have wide apertures to minimize distortion, and this in turn reduces efliciency and increases size and weight.

It is, therefore, an object of the present invention to provide a highly eflicient magnetic deflection yoke for a cathode ray tube.

A further object of the invention is to provide a magnetic deflection yoke of simple construction, which is small and compact and of relatively light weight.

A further object of the invention is to provide a magnetic deflection yoke which produces highly accurate deflection in two directions so that accurate registry of a plurality of beams may be provided, as in a three gun color television tube.

A feature of the invention is the provision of a deflection yoke for a cathode ray tube which is of the toroid type with an annular magnetic structure having pole pieces of such configuration to produce linear fields.

A further feature of the invention is the provision of a toroid deflection yoke wherein the magnetic structure includes front pole pieces positioned about the flared portion of the cathode ray tube to move the center of deflection in the direction of the tube bulb portion.

Another feature of the invention is the provision of a toroid deflecting yoke in which the core is formed of a plurality of rings of magnetic material with the intermediate rings having larger inner diameters than the outer rings to control the distribution of the field produced so that it is substantially linear.

Still another feature of the invention is the provision of a toroid yoke in which the core is formed by a pair of rings interconnected by runners extending longitudinally of the neck of the tube and extending radially inwardly from the rings to a position closely adjacent the tube neck, with the coils being positioned on the rings intermediate the runners.

A still further feature of the invention is the provision of a toroid yoke in which the deflection in each direction is produced by a plurality of coil sections wound on the same annular core structure, with the winding turns so distributed to produce a field which corrects for pincushion effect generally present in yokes of the saddle wound type.

Further objects, features and the attending advantages of the invention will be apparent from a consideration of the following description when taken in conjunction with the accompanying drawings, wherein:

Fig. 1 illustrates a toroid yoke in accordance with the invention positioned on a cathode ray tube;

Figs. 2 and 3 illustrate one construction of the toroid yoke;

Fig. 4 shows the position and connection of the windings on the toroid yoke;

Fig. 5 is a chart showing the flux distribution produced by the toroid yoke in accordance with the invention;

Figs. 6 and 7 show other embodiments of the yoke, including cores formed by ferrite rings; and

Figs. 8 to 10 illustrate still another embodiment in which the core includes rings and longitudinal runners forming pole pieces.

In practicing the invention, there is provided a toroid deflection yoke which includes a magnetic core structure having pole pieces which extend radially inward from the annular body of the core to a position closely adjacent the neck of a cathode ray tube on which the yoke is positioned. The core structure also includes front pole pieces extending axially from the core proper, which are of tapered configuration to fit closely about the flared portion of the tube at the junction thereof with the neck portion. The pole pieces are spaced angularly about the annular structure and toroid coil sections are positioned in the space between the pole pieces. In order to provide symmetry, the number of pole pieces must be a multiple of 4 and may preferably be a multiple of 8 to provide symmetry of both horizontal and vertical fields. To provide the desired accuracy of the fields, 24 pole pieces may be required. The core is made of magnetic material and may be formed of a plurality of rings with the end rings having an inside diameter of fit closely to the tube neck and the intermediate rings having a larger diameter. The rings have slots therein for receiving the coil sections, with the slots defining the inner pole pieces as previously mentioned. The front ring may have projections extending therefrom to form the front pole pieces which embrace the flared portion of the tube.

The core may also be of a squirrel cage type including a pair of rings interconnected by longitudinally extending runners which extend close to the tube neck and have portions embracing the flared tube portion. Although the use of ferrite material for the core may be preferable in most applications because of the low losses involved, laminated constructions may also be used, such as, thin laminations of silicon iron with insulating sheets positioned therebetween. The distribution of the turns of the toroidal coil sections may be selected to provide substantially uniform flux distribution with some deviation from a cosine distribution of turns being effective to prevent pincushion distortion.

Referring now to the drawings, in Fig. 1 there is illustrated a cathode ray tube 10 on which the toroid yoke 11 is positioned. The tube includes a neck 12 and a flared portion 13 extending from the tube neck. The body of the yoke is positioned around the neck with front pole pieces 14 embracing the flared portion for producing a field therein so that the center of deflection of the yoke is moved toward the flared bulb portion of the tube.

Figs. 2 and 3 illustrate one construction of the tube wherein the core is formed of annular laminations or rings which may be formed of silicon iron or the like. The core proper is divided into A and B sections with the B section being positioned between 2 A sections. The A section rings have an internal diameter to fit close to the neck 12 of the tube and the B section rings have a somewhat larger diameter. The toroidal coil sections 15 are wound around the stacked A and B sections, being positioned in slots 16 which are provided in both the A and B rings. The slots, in effect, provide inner pole pieces or teeth 17 and 18 in the A and B rings respectively. The teeth 17 extend all of the way to the tube neck and the teeth 18 extend only part of the way to the tube neck.

As previously stated, front pole pieces 14 are provided which may include extensions 20 positioned in slots 21 in the outer edge of the front A rings. This causes the pole pieces 14 to have the same magnetic potential as the portions of the rings to which they are connected The insulating rings 22 and 23 are provided at the outer extremity of the A rings to provide a form on which the toroid coil sections are wound. As previously stated, thin insulating sheets such as paper are provided between the laminations or rings when the laminated structure is used.

By providing A rings having a smaller internal diameter than the B rings, the magnetic field produced by the core has a more uniform distribution. That is, the tendency of the field to be crowded in the center is alleviated by providing the center sections of larger diameter, so that the reluctance of the path therebetween is greater. The use of the front pole pieces 14 causes the magnetic field to be moved forward so that the center of deflection is also moved forward and this has been found to provide more precise deflection so that better registry is provided when the yoke is used on a tube having a plurality of beams.

Fig. shows the field distribution resulting from the toroidal yoke, as has been described. This chart shows the pattern of the flux lines, and it is apparent that the lines through the tube neck are substantially straight. The dotted curve C shows the field strength at various points along the yoke which would be provided by use of a core without the front pole pieces 14. The solid curve D shows the field strength pattern when the pole pieces 14 are used. It will be noted that the pole pieces are effective to move the field forward so that the center of deflection is moved from point E to point F. This forward movement of the center of deflection has the advantage of avoiding neck shadow, and is also essential in special types of tubes having a plurality of beams as presently used in color television receivers.

Fig. 4 shows the manner in which the toroid winding sections are provided on the core. The field for producing horizontal deflection is provided by the coil sections 25, and the field for producing vertical deflection is provided by the coil sections 26. In the structure shown, 24 teeth and 24 coil sections are used so that three types of coil sections are provided for each direction of deflection. It will be noted that these coils are interspersed with each other, but for each direction of deflection, coil sections are directly adjacent each other on opposite sides of the diameter which is in the direction of deflection. These coil sections adjacent the diameters are designated a coils and the coils spaced therefrom are designated b and c coils, respectively. It will be obvious that it would be possible to make a symmetrical distribution wherein the a coils for one field are spaced by two slots into which the c coils for the other field could be placed. It has been found, however, that a better distribution may be provided by positioning the a coils adjacent to each other. The distribution of the turns in the various coils may be selected to provide linear fields and to coorrect pincushion distortion, as will be described more-in detail.

In Fig. 6, there is illustrated a toroid yoke generally similar to that shown in Figs. 2 and 3, except that the magnetic core is formed of rings of ferrite material. The

4 rings may have substantial thickness such as one-quarter inch, for example. The outer rings 30 have teeth or pole pieces 31 which extend closely adjacent the tube neck 12. The inner rings 31 have teeth which extend only part way to the tube neck so the field is not concentrated in the center to provide crowding of the flux lines and nonlinearity thereof. The front pole pieces 32 may be cast interconnected by an annular ring 33, which is included within the toroid coil sections 34 so that the proper field potential is applied to the front pole pieces 32. The operation of this structure is exactly the same as that previously described, and the structure has the advantage that the losses in the ferrite core will be somewhat less than the losses in a laminated core previously mentioned.

Fig. 7 shows another core construction formed of ferrite rings. In this case, the back ring 30 and the intermediate rings 29 may be identical to the corresponding rings in Fig. 6. The front ring 35 is of the same inner diameter as the rings 29, and has the front pole pieces 36 provided integrally therewith. This somewhat simplifies the construction by requiring one less element. The toroidal coil portions 37 circle the end rings 34 and 35 and the intermediate rings 29, as in Fig. 6.

Figs. 8, 9 and 10 show a different construction for the toroid deflection yoke. In this construction, two spaced annular rings 40 and 41 are provided about the neck 12 of the cathode ray tube. Angularly positioned about the rings are a plurality of magnetic pole pieces or runners 43. These runners extend longitudinally along the neck of the cathode ray tube with forward ends 44, which are tapered so that they will fit up against the flared or enlarged end of the tube. The configuration of runners 43 is shown in Fig. 10. As shown in Fig. 9, 24 runners 43 are provided, spaced angularly at 15 intervals. Positioned on the rings between the runners are toroid winding sections 45, which provide electromagnetic fields between the runners 43.

In the construction of Figs. 8 to 10, the annular rings 40 and 41 may be identical, and the toroid core sections 45 may be provided on these rings before assembly of the pole pieces or runners thereon. The rings may be formed of a pair of semicircular sections so that preformed coils may he slid thereon. The runners may then be positioned with the notches 42 thereof receiving the rings, and an inner insulating cylindrical form 46 may then be positioned to hold the parts assembled. This construction simplifies the Winding of the coil sections and the assembly of the components into a yoke structure. Further, the amount of magnetic material required is held to a minimum, and the coils are small to thereby reduce the amount of copper required. This structure is highly eflicient, especially when using ferrite material to form the magnetic rings and pole pieces. Although the low loss provided by such ferrite material is particularly advantageous for use in the pole pieces, it may be less important in the rings, and rings formed of thin lamdinations of a ttnaterial such as silicon iron may be use The structure of Figs. 8 to 10 has the advantage that the greatest field strength is provided directly under the magnetic rings 40 and 41, so that the field intermediate the rings is reduced to give generally the same eifect as the graded-diameter structure in the embodiments previously described. It is to be pointed out, however, that additional magnetic rings can be provided about the pole pieces, if this is desired for any particular application. The rings may be notched to receive the runners, if desired. It is also to be pointed out that, although separate soil sections are shown positioned about the individual magnetic rings 40 and 41, the structure could. operate satisfactorily if long coil sections linking all rings are used.

Considering now the turns distribution of the coil sections, reference is again made to Fig.4. As previously stated, the a coils may be placed adjacent each other or spaced by two slots to receive the c coils of the other windings. When placed close together as shown, the a coils encompass a 15 are extending from the diameter in the direction of deflection, the b coils encompass 45, and the c coils 75. The turns distribution to provide a uniform field would require a cosine distribution with the a coils including 26.8% of the turns in either the horizontal or vertical windings, the b coils 46.4%, and the c coils 26.8%. Although such a turns distribution should theoretically produce a uniform field through the yoke, it has been found that by somewhat increasing the proportion of the turns in the a coil section with a corresponding decrease in the b and sections, the pincushion effect which is customarily produced by magnetic deflection yokes may be corrected. As an example, in one particular construction used highly accurate deflection is produced by placing 33% of the turns in the a section, 42% in the b section, and 25% in the c section. It is to be pointed out, however, that other turns distributions may be satisfactory with somewhat different core constructions and with tubes of different constructions.

The total number of turns in the horizontal and vertical coil sections depends, of course, upon the inductance desired. To provide horizontal deflection windings having an inductance of 12 millihenries, 912 turns are required. Similarly, to provide vertical deflection windings of 100 millihenries, 1300 turns in the vertical sections are required. The turns distribution of the horizontal and vertical windings may be substantially the same as the winding sections are placed in exactly the same manner for both horizontal and vertical deflection.

The coil sections on the two halves of the core can be connected in parallel or in series with parallel connection being better in some applications. The coil sections on the different exciter rings in a structure as shown in Figs. 8-10 may also be connected in series or in parallel.

As has been previously stated, the number of pole pieces or teeth and winding sections need not be 24, as shown, but may be any number divisible by 4, and structures with 12, 16 or 20 pole pieces may be used. As stated above, to provide a structure which is symmetrical with respect to both horizontal and vertical coil sections, the number must be divisible by 8. The use of three coil sections for each direction of deflection in each quadrant has been found to provide highly accurate deflection as required for use with a color television receiver tube having a plurality of guns, the beams from which must be accurately converged to provide color registry. For monochrome receivers, a yoke with 16 poles is entirely adequate.

Although the dimensions of the yoke and the specific configuration thereof will vary with the tube dimensions, a yoke structure as shown in Figs. 1 to 4 for use on a three gun color television tube has been constructed with the following dimensions:

Outside diameter of rings 3% inches. Inside diameter of A rings 2% inches. Inside diameter of B rings 2 /8 inches. Axial length of each A ring section inch.

Axial length of B ring section 1 inch. Thickness of Bakelite end plates 22---. inch.

A and B ring laminations 4 mil silicon iron. Length of front pole pieces inch.

By using such a core construction, the Q of the yoke has been found to be slightly less than 3. Substantially, the same dimensions can be used when using toroid rings as illustrated in Fig. 6. In such case, the Q of the yoke will be increased to approximately 8.

In the structure of Figs. 8 to 10, the rings 40 and 41 may have an outside diameter of 4 inches and an inside diameter of 3 inches, and a thickness of A inch. The runners may have a width of inch, a thickness of A3 inch, and an over-all length of 3% inches. The notches 42 may have a depth of inch, and the front portion 44 may have alength of 1 inch.

The deflection yoke so provided is much more eflicient than saddle wound yokes commonly used. Also, the copper required may be reduced to less than one-sixth of that required in a saddle wound yoke, and the over-all size and weight are greatly reduced. Further, the precise positioning of the field with respect to the tube neck can be very accurately controlled to provide highly accurate deflection. As previously stated, compensation can be provided in the yoke itself for the pincushion effect normally produced.

What is claimed is:

1. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, an annular magnetic core structure having radial teeth extending inwardly and adapted to surround the cathode ray tube neck portion, and coil sections mounted on said core structure in the spaces between said teeth, said core structure having projecting pole pieces extending axially from one end thereof, said pole pieces having tapered pole faces shaped to receive the flared portion of the cathode ray tube, said tapered pole faces of said pole pieces being adapted to be positioned adjacent the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion of the cathode ray tube by action of said pole pieces.

2. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, an annular magnetic core structure having radial teeth extending inwardly and adapted to surround the cathode ray tube neck portion, said core structure having projecting pole pieces extending axially from one end thereof, said pole pieces having tapered pole faces shaped to receive the flared portion of the cathode ray tube, said tapered pole faces of said pole pieces being adapted to be positioned adjacent the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion of the cathode ray tube by action of said pole pieces, said teeth and said pole pieces being angularly spaced about the axis of said core structure with said teeth and said pole pieces having corresponding angular positions, and coils mounted on said core structure in the spaces between said teeth and said polepieces.

3. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, an annular core structure including a plurality of annular magnetic laminations having inward projections, a plurality of annular insulating laminations, said magnetic laminations and said insulating laminations being stacked to form a cylidrical structure, said projections of the end laminations being longer than the projections of the intermediate laminations, and coils wound about said cylindrical structure in the spaces between said projections, said core structure including tapered magnetic pole pieces extending axially from one end thereof and magnetically coupled to said magnetic rings, said pole pieces being shaped to fit closely against the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion by action of said pole pieces.

4. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, an annular core structure including a plurality of magnetic annular rings having inward projections, said rings being stacked to form a cylindrical structure, said projections of the end rings being longer than the projections of the intermediate rings, and coils wound about said 7 cylindrical structure in the spaces between said projections, said core structure including tapered magnetic pole pieces extending axially from one end thereof and magnetically coupled to said magnetic rings, said pole pieces being shaped to fit closely against the flared portion of the cathode ray tube so that the field produced by the yoke is elfectively shifted toward the flared portion by action of said pole pieces.

5. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom said yoke including in combination, an annular core structure including a plurality of magnetic annular rings having inward projections, said rings being stacked to form a cylindrical structure, said ring at one end of said cylindrical structure including tapered magnetic pole pieces projecting axially from one end thereof and having tapered pole faces shaped to receive the flared portion of the cathode ray tube, said tapered pole faces of said magnetic pole pieces being adapted to be positioned against the flared portion of the cathode ray tube that the field produced by the yoke is effectively shifted toward the flared portion by action of said pole pieces, said inward projections and said pole pieces being angularly spaced about the axis of said cylindrical structure at corresponding angular positions, and coils wound about said cylindrical structure in the space between said projections.

6. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure including an annular portion, angularly spaced radial portions extending inwardly from said annular portion, and angularly spaced axial portions projecting from one end of said annular portion, and coils mounted on said annular portion in the space between said radial portions, said axial portions having tapered pole faces shaped to receive the flared portion of the cathode ray tube, so that the field produced by the yoke is effectively moved toward the flared portion of the cathode ray tube by action of said axially extending parts.

7. A toroid deflection yoke for a cathode ray tube having a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure including a cylindrical portion formed of a plurality of rings of magnetic material, longitudinal portions extending radially inward from said cylindrical portion, and projecting portions extending axially from one end of said cylindrical portion and having pole faces tapered outwardly to receive the flared portion of the cathode ray tube, said longitudinal portions and said projecting portions being spaced angularly with respect to the axis of said cylindrical portion, said longitudinal portions having a smaller inner diameter at the ends of said cylindrical portion than intermediate the ends thereof, and coils wound about said cylindrical portion in the spaces between said longitudinal portions.

8. A toroid deflection yoke for a cathode ray tube having a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure including a cylindrical portion, radial portions extending inward from said cylindrical portion, and axial portions projecting from one end of said cylindrical portion and having pole faces tapered outwardly to receive the flared portion of the cathode ray tube, said radial portions and said axial portions being spaced angularly with respect to the axis of said cylindrical portion at corresponding angular positions, and coils wound about said cylindrical portion in the spaces between said radial portions and between said axial portions.

9. A toroid deflection yoke for a cathode ray tube having a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure including annular portions and longitudinal portions connected to said annular portions, said longitudinal portions extending radially inward from annular portions and coil sections wound about said annular portions in the spaces between said longitudinal portions, said longitudinal portions having ends extending axially beyond said annular portions and having tapered pole faces shaped to correspond to the flared portion of the cathode ray tube, so that the field produced by the yoke is eifectively moved toward the flared portion of the cathode ray tube by action of said ends of said longitudinal portions.

10. A toroid deflection yoke for a cathode ray tube, which tube has a neck and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure adapted to fit about the neck of the cathode ray tube including, annular portions positioned about the tube neck, longitudinal portions within said annular portions extending parallel to the axis of said annular portions and extending radially inward to positions adjacent the neck of the tube, at least part of said core portions having notches therein to receive other core portions, and coil sections about said annular portions in the spaces between said longitudinal portions, said longitudinal portions having ends extending axially beyond said annular portions and having tapered pole faces shaped to fit about the flared portion of the cathode ray tube, so that the field produced by the yoke is effectively moved toward the flared portion by action of said ends of said longitudinal portions.

11. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure including first and second annular portions and longitudinal portions connected to said annular portions and extending radially inward therefrom said longitudinal portions being adapted to extend along the neck of the cathode ray tube and being spaced angularly with respect to the axis thereof, and coils about said annular portions in the space between said longitudinal portions, said longitudinal portions having ends extending axially beyond said annular portions and having tapered pole faces shaped to receive the flared portion of the cathode ray tube, said pole faces of said longitudinal portions being adapted to be positioned adjacent the flared portion of the cathode ray tube so that the field produced by the yoke is effectively moved toward the enlarged portion of the cathode ray tube by action of said ends of said longitudinal portions.

12. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke providing linear horizontal and vertical deflecting fields extending substantially at right angles with respect to each other and including in combination, an annular magnetic core structure having radial teeth extending inwardly and adapted to surround the cathode ray tube neck portion, said core structure having projecting pole pieces extending axially from one end thereof, said pole pieces having tapered pole faces shaped to receive the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion of the cathode ray tube by action of said pole pieces, and horizontal and vertical windings including sections wound about said core structure in the spaces between said teeth and said pole pieces, each of said windings including first pairs of coil sections positioned adjacent each other on each side of the diameter of said annular core structure which is in the direction of deflection produced by such winding and second pairs of coil sections spaced from said diameter, with each winding including coil sections spaced between coil sections of the other winding.

13. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke providing linear horizontal and vertical deflecting fields extending substantially at right angles with respect to each other and includingin combination, an annular magnetic core structure having radial teeth extending inwardly and adapted to surround the cathode ray tube neck portion, said core structure having projecting pole pieces extending axially from one end thereof, said pole pieces having tapered pole faces shaped to receive the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion of the cathode ray tube by action of said pole pieces, and horizontal and vertical wind ings including sections wound about said core structure in the spaces between said teeth and said pole pieces, each of said windings including first, second and third coil sections positioned on each side of the diameter of said annular core structure which is in the direction of deflection produced by such winding, with each winding including coil sections interspersed between coil sections of the other winding, each of said windings having the turns thereof distributed among the coil sections thereof in a substantial cosine distribution about said annular core structure.

14. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke providing linear horizontal and vertical deflecting fields extending substantially at right angles with respect to each other and including in combination, an annular magnetic core structure having radial teeth extending inwardly and adapted to surround the cathode ray tube neck portion, said core structure having projecting pole pieces extending axially from one end thereof, said pole pieces having tapered pole faces shaped to receive the flared portion of the cathode ray tube so that the field produced by the yoke is effectively shifted toward the flared portion of the cathode ray tube by action of said pole pieces, and horizontal and vertical windings including sections wound about said core structure in the spaces between said teeth and said pole pieces, each of said windings including first second and third coil sections positioned in the order named on each side of the diameter of said annular core structure which is in the direction of deflection produced by such winding, with each winding including coil sections spaced between coil sections of the other winding, each of said windings having the turns thereof distributed among the sections thereof in a modified cosine distribution with the first sections having a greater proportion of turns than that resulting from a cosine distribution and the second and third sections having smaller proportions.

15. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure adapted to fiit about the neck portion of the cathode ray tube including, first and second annular portions each formed of a plurality of core parts, longitudinal portions extending parallel to the axis of said annular portions and extending radially inward to positions adjacent the neck portion of the tube, a part of said core portions having notches therein for receiving other portions to facilitate assembly thereof into a core structure, and coil section positioned about said parts of said annular portions in the spaces between said longitudinal portions, said longitudinal portions having ends extending axially beyond said annular portions and having tapered pole faces shaped to fit about the flared portion of the cathode ray tube, so that the field produced by the yoke is effectively moved toward the flared portion by action of said ends of said longitudinal portions.

16. A toroid deflection yoke for a cathode ray tube, which tube has a neck portion and a flared portion extending therefrom, said yoke including in combination, a magnetic core structure adapted to fit about the neck portion of the cathode ray tube including, annular portions positioned about the tube neck portion, longitudinal portions having notches therein for receiving said annular portions, said longitudinal portions extending parallel to the axis of said annular portions and extending radially mward to positions adjacent the neck portion of the tube, and coil sections positioned about said annular portions in the spaces between said longitudinal portions, said longitudinal portions having ends extending axially beyond said annular portions and having tapered pole faces shaped to fit about the flared portion of the cathode ray tube, so that the field produced by the yoke is effectively moved toward the flared portion by action of said ends of said longitudinal portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,234,038 Redford et a1. Mar. 4, 1941 2,437,513 Gethmann Mar. 9, 1948 2,664,522 Page Dec. 29, 1953 2,771,563 Reinhard Nov. 20, 1956 2,800,615 Stubbins July 23, 1957

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