US2793311A

US2793311A - Deflection yoke

Info

Publication number: US2793311A
Application number: US221590A
Authority: US
Inventors: Thomas Harry
Original assignee: Allen B du Mont Laboratories Inc
Current assignee: Allen B du Mont Laboratories Inc
Priority date: 1951-04-18
Filing date: 1951-04-18
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

May 2l, 195,7 H. THOMAS DEFLECTION YoxE 2 Sheets-Sheet l Filed April 18 1951 Fig. 4

. INVEN TOR. HARR Y THOMAS A TTORNEY May 21, 1957 vH. THOMAS DEFLECTION Yoxa 2 shears-sheet 2 Filed April 18 .1.951-

INVENTUR. HARRY THOMAS United States Patent O DEFLECTION YOKE Harry Thomas, Glen Rock, N. J., assgnor to Allen B.

Du Mont Laboratories, Inc., Passaic, N. J., a corporation of Delaware Application April 18, 1951, Serial No. 221,590

3 Claims. (Cl. 313-76) This invention relates to electron-beam deflection means adaptable for use with cathode-ray tubes, and particularly to magnetic deflection yokes capable of producing wide-angle deflection of an electron beam.

It is desirable to produce a wide angle of electronbeam deflection in certain devices, such -as in certain television cathode-ray picture tubes of the larger sizes. For example, a thirty-inch diameter television picture tube such as the type 3013134 requires a deflection angle of 90 degrees whereas prior tubes of smaller sizes have been designed to operate with a beam-deflection angle of only 70 degrees or thereabouts. Larger deflection angles are required in the larger television picture tubes in order to reduce `the overall tube length. Accordingly, it is an object of the present invention to provide a deflection means which will enable cathode-ray tubes to have relatively larger diameters and shorter lengths than heretofore.

Another object is to provide a wide-angle magnetic de flection means for cathode-ray tubes.

A further object is to `avoid neck cut-off of an electron beam in a cathode-ray tube.

An additional object is to incorporate means in a magnetic deflection yoke which will cooperate to effect a displacement of the magnetic field.

A nal object is yto accomplish the above-recited objects with a minimum of distortion effects and with a maximum optimum sensitivity of deflection.

Still other objects will become apparent from the following disclosure and claims.

In accordance with the invention, the above-recited objects are realized by a combination of magnetic fieldshaping devices which are incorporated in the design of a magnetic deflection yoke. The said devices cooperate to displace the effective concentration of magnetic flux in a forward direction toward the screen of a cathoderay tube on the neck of which the yoke is placed in the customary manner. The magnetic field is caused to bulge from the yoke in the forward direction in which the electron beam moves toward the viewing screen.

The invention will be understood in greater detail by reference to the drawing, in which Fig. l is a perspective view of a deflection yoke constructed yaccording to the invention,

Fig. 2 is a longitudinal sectional view of the invention applied to a cathode-ray tube,

Figs. 3 and 4 are cross-sectional views of the device.

Fig. 5 shows a partial wiring diagram of the invention,

Figs. 6 and 7 show a feature of the invention, and

Figs. 8-12 show representative magnetic iiux patterns produced with and without a deflection yoke embodying the present invention.

As shown in the drawing, a deflection yoke 11 is positioned on the neck 12 of a cathode-ray tube 13 which contains an electron gun 14 that provides an electron beam 16 which impinges upon a viewing screen 17. The yoke 11 comprises an arrangement 1S of deflection ycoils 2,793,311 Patented May 21, 1957 having front flares 19 and rear flares 2), a tapered liner 21 positioned between the coils 18 and the tube neck 12, a tapered core 22 surrounding the outer periphery of the coils 18, a clamp 23 surrounding the outer periphery of the core 22, and a rear fringe ilux compensating device 24 positioned adjacent the rear ares 20. The front flares 19 of the coils 18 are extended to conform with the shape of the bulb 25 of the cathode-ray tube 13. The coil structure 18 preferably comprises two pairs of coils for obtaining horizontal and vertical deections of the beam 16, each coil being of a semi-cylindrical shape and the horizontal and vertical pairs being oriented to produce magnetic fluxes at right angles to each other, in a well-known manner. The cathode-ray tube 13 is shown as comprising Va metal cone 26, and a face plate 2'7 and neck 12 and bulb 25 of glass.

The liner 21 may be formed from fibre or other suitable material, and is shaped and arranged to produce an enlarged diameter of the coil arrangement 18 at the front end, i. e. the end nearest the screen 17. The core 22 is made of a permeable material having the usually desirable magnetic characteristics, and is tapered or shaped and arranged to have a relatively greater mass or volume at the front end of the yoke. The front surface 28 of the core 22 is beveled to closely conform with the shape of the front flare 19 of the coil structure 1S. A shoulder 29 may be provided to obtain better seating of the clamp 23 against the core 22. The core 22 may be split longitudinally into two or more sections in order to facilitate assembly of the yoke.

The rear fringe flux compensating device 24 is a magnetic device which functions to compensate or reduce the rear fringe flux produced by the rear flares 20 of the coiis 18.

Fig. 8 shows diagramtnatically the magnetic flux configuration produced by the yoke 11 without the cornpensating device 24; magnetic flux 31 includes a front fringe flux 32 and a rear fringe flut 33 which are produced in part by the front are 19 and the rear flare 20, respectively.

A preferred form of `the rear fringe flux compensating device 24 is shown sectionally in Fig. 4 and schematically in Fig. 5. The compensating device 24 comprises a compensating coil 36 positioned adjacent each rear flare 2t) of each of the coils of the coil assembly 18. Each compensating coil 36 is preferably connected electrically to its corresponding deflection coil 13 with a polarity such that the magnetic flux produced by each com pensating coil 36 will oppose and compensate and reduce or eliminate the rear fringe iiux 33. Alternatively, the coils 36 can be connected to a separate source of current which fluctuates in accordance with any fluctuations of the magnetic eld produced by the rear flares 2G. Fig. 9 illustrates now the rear fringe flux 33 of Fig. 8 has been eliminated by the action of the rear fringe flux compensating device 24 having compensating coils 36. Al` though the schematic diagram of Fig. 5 shows a series electrical connection between the compensating coils 36 and the pair of deilecting coils 18, it is obvious that parallel connections or a series-parallel combination of connections may be employed.

As an `alternative to the rear fringe iiux compensating device 24 having compensating coils 35, said device 24 may comprise an annular ring 37 or cylinder of magneticresponsive material. Referring to Fig. l0, the annular ring 37 compensating device 24 reduces and confines and displaces the rear fringe ux 33 from its normal position shown in Fig. 8. The annular ring 37 reduces the magnitude of the fringe flux 33 in the neck 12 by short-cir cuiting or shunting and deviating the iiux, from its normal path through the neck 12 of the tube 13, to a new path of circular configuration through the contines of 3 said annular ring 37. Any remaining fringe flux 33 within the neck 12 of the tube 13 is displaced in a forward direction toward the screen 17, by the action of the annular ring 37. (Refer to Fig. l0.) The annular ring 37 is preferably formed from powdered or laminated magnetic-responsive material such as iron.

Although the rear fringe ux compensating device 24 is shown in a preferable position behind and adjacent the rear flares 20, it is to be understood that said device 24 may also be positioned in a manner to surround the periphery of said flares 20, and in certain situations it may be positioned immediately in front of the rear ares 20.

The coils comprising the coil structure 18 are formed in a certain shape as shown in Figs. 6 and 7. Fig. 6 shows an individual deflection coil 41 positioned on the neck 12 of the cathode-ray tube 13. The remaining coils comprising the coil structure 1S are not shown. The coil 41 may be wound in the usual manner with a continuous piece of conductive wire looped to form

side portions

42 and 43 and end portions of front and

rear flares

19 and 20. A feature of the present invention is the distribution and spacing of the

side portions

42 and 43 to form a wedge-shaped window 44 having a greater width at its end near Ithe front flare 19. Fig. 7 shows the ux pattern produced by a deflecting coil shaped in this manner. The magnetic ilux 31 is displaced and made to curve and bulge outwardly from the coil 41 at its front end where the greatest width of the tapered window 44 is located.

In accordance with the present invention, a deflection yoke is produced having several features which cooperate to produce a magnetic ilux 46 (Fig. l2) which has an etfective center Y that is displaced toward the front of the yoke from its normal position X (Fig. 1l). For cxample, a yoke without the features of the present invention will have a center of deection, denoted by X in Figs. 2 and ll, somewhat near the geometrical center of the yoke; the maximum deection angle of a normallydeflected electron beam 47 is limited by the neck cut-off point 48 at the juncture of the neck 12 and bulb 25. When a yoke is employed which utilizes the present invention, the center of deflection is shifted forward to a position indicated by Y in Figs. 2 and 12; the maximum deflection angle of a wide-angle-deected electron beam 49 -isvnot so severely limited by the neck cut-off point 48 a-s is the normally-dellected electron beam 47. The center of deecton, such as X or Y, is found by extending rearwardly the axis of the deflected beam, such as 47 or 49, until it intersects the axis of the undeected beam 16. For simplicity, the electron beam is shown deflected in only one direction from its original axis.

As is illustrated in Fig. l2, the invention causes an active magnetic flux to be produced in front of and beyond the contines of the yoke, the term active distinguishing this ilux from a relatively weak fringe flux that normally exists beyond the confines of the yoke.

The tapered liner 21 effects a forward iux displacement due to the accompanying physical tapered configuration of the coils 18. The relatively long front flare 19 causes a forward llux displacement by effecting a forward extension of the coils 18. It has been found that the combined effects of the tapered liner 21 and front flare 19 produce a greater forward displacement of the center of deection than would be obtained from a summation of the displacements produced individually by these factors. The reason for this desirable effect is, it is believed, in part due to the fact that the tapered liner causes a less acute angle between the front flare 19 and body portion of the coils 18. The front are thus becomes more nearly in line with the body portion and operates more eciently and produces a stronger magnetic field having greater lateral vector components at the forward part of the yoke than can be obtained if the front are isformed at the normally more acute angle. Also,

the tapering of the coil 18 permits the rear flare 20 to have a more acute angle with respect to the body portions of said coils 1S, thereby reducing the rear fringe ux.

The tapered magnetic core 22 provides a greater magnetic permeance at the front of the yoke where the fluxproducing elds have been increased and aids in obtaining more fully the effects of increased magnetic flux in and beyond the front portion of the yoke. The Itapered core 22 also -serves to distribute the ux produced along the coils 18 so as to produce a concentration of flux toward the thick end of the core at the front end 0f Ithe yoke. r[hese effects result in a wider angle of deflection due to a forward displacement of the center of deection. it has been found that, for a typical yoke, a twentythousandths of an inch forward displacement of the center of deliection resulted in a one-degree increase in deflection angle.

While the present invention has been particularly described with respect to a preferred embodiment, it is realized that modications may be made within the scope and teachings disclosed herein; also, subcombinations may sometimes be employed when the full effect of the invention is not required. The scope of the invention is defined by the following claims.

What is claimed is:

1. A deection coil comprising a plurality of turns of an electrical conductor, said turns shaped to form a pair of side portions and front and rear are portions; a window area bounded by said side portions and both said are portions; said pair of side portions being unequally spaced from each other along their inner edges, said unequal spacing being smallest at said rear are portion and greatest at said front are portions; said side portions being narrowest at said front flare portion and widest at said rear flare portions; the outer edges of each of said side portions being equally spaced along the length thereof.

2. A deflection yoke comprising a cylindrical structure of deflection coils, each of said coils being made from an electrical conductor shaped to form a pair of side portions and flare portions which define and bound a window area, the side portions of each said pair thereof being unequally spaced from each other along their inner edges, said unequal spacing being the greatest at one end of said coil structure and said side portions being narrowest at said one end of the coil structure, the outer edges of said side portions of each pair thereof being equally spaced apart along the length thereof, a core formed of material having magnetic permeance positioned around the periphery of said coil structure and having its greatest magnetic permeance at said one end of said coil structure, means to energize said coils to produce magnetic fields, and a flux compensating device positioned adjacent said are portions at the remaining end of said coil structure whereby said flux mass is effectively shifted away from said remaining end and toward said one end.

3. A deflection yoke comprising a cylindrical structure of deflection coils, said coils having laterally extending flares at an end of said cylindrical structure, a core formed of material having magnetic permeance positioned around the periphery of said coil structure and having its greatest magnetic permeance at the end thereof remote from said flares, means to energize said coils to produce magnetic fields, and a ux compensating device positioned adjacent said flares.

References Cited in the le of this patent UNlTED STATES PATENTS 2,151,530 Ruska Mar. 2l, 1939 2,172,733 Frederrnann et al Sept. 12, 1939 2,186,595 Fuska Ian. 9, 1940 2,207,777 Blain July 16, 1940 21,227,080 Goldsmith Dec. 31, 1940 (Other references on following page) 5 Gunther I an. 7, 1941 Bruche Apr. 8, 1941 Gunther Sept. 29, 1942 Flechsig June 1, 1943 Bedford Dec. 14, 1943 De Tar June 8, 1948 Haantjes Nov. 30, 1948 Bocciarelli Dec. 14, 1948 6 Torsch Jan. 10, 1950 Bocciarelli Oct. 9, 1951 Neeteson Nov. 4, 1952 Lawrence Nov. 25, 1952 OTHER REFERENCES July 17, 1951.