US3152291A

US3152291A - Magnetic deflection yoke

Info

Publication number: US3152291A
Application number: US93121A
Authority: US
Inventors: Kratochvil Friedrich
Original assignee: Telefunken AG
Current assignee: Telefunken AG
Priority date: 1960-03-10
Filing date: 1961-03-03
Publication date: 1964-10-06
Anticipated expiration: 1981-10-06
Also published as: BE600152A; DE1144406B; GB983149A

Description

Oct. 6-, 1964 F. KRATOCHVIL 3,152,291

MAGNETIC DEFLECTION yoxs Filed March 3. 1961 Fig. I

PRIOR ART 1. 4 y 4 m 5' i0 15 mm 2'0 iNVENTOR Friedrich Kraiochvii ATTORNEY United States Patent 3,152,291 MAGNETIC DEFLECTION YOKE Friedrich Kratochvii, Hannover-Ricklingen, Germany,

assignor to Telefunken Aktiengeseilschaft, Berlin, Germany Filed Mar. 3, 1%1, Ser. No. 93,121 Claims priority, application Germany Mar. 10, 1960 4 Claims. (Cl. 311-200) The present invention relates to improvements in magnetic deflection yokes for deflecting the beams of cathode ray tubes, the yokes comprising a ring of ferromagnetic material and sets of deflecting coils thereon respectively for horizontal deflection and for vertical deflection.

Prior art means for magnetic deflection of the electron beam of a cathode ray tube for television purposes include deflection devices wherein two saddle coils diametrically oppose one another and have cosine-shaped winding distributions for the deflection of the beam in the horizontal direction. These coils are arranged within a ring-shaped yoke of ferromagnetic material surrounding the electron beam. For deflection of the beam in the vertical direction, two continuously wound toroidal coils are used which are either wound on the yoke or are slipped thereon after winding. Such a prior-art device is shown in FIGURE 1, wherein the neck 1 of a cathode ray tube is enclosed by a ring-shaped yoke 2 of ferromagnetic material on which are arranged two diametrically opposed continuously wound toroidal coils 3 of such a length that each of these coils overlaps the longitudinal conductor groups of one saddle coil 4, each respectively, wound with a cosine-shaped coil distribution. The longitudinal conductor groups 5 in this device are shown in cross-section. In this known device, the toroidal coils 3 are either previously wound on a straight winding core and subsequently slipped onto the yoke core or are directly wound on the yoke core 2 by means of a winding machine, the feed of the winding machine being adjusted in such a way that the core is turned continuously and the wound wire always runs radially with respect to the center of the ring-shaped yoke. It is also known in such a device to wind the toroidal coil in a so-called saw-tooth step wherein the wire after each completed turn is brought back to the beginning of the coil. It is further known to design the distribution of the coils of the toroidal winding non-uniformly so as to vary the field distribution of this winding.

The invention is based on the problem of improving by simple means the sharpness of the image point when using such windings. Broadly, this invention teaches the winding of the toroidal coils in such a way that the parts of the coil outside the ring-shaped yoke extend over a smaller circumferential angle than the parts of the coil on the inside of the ring-shaped yoke. In a preferred embodiment, the turns of the coil on the outside of the ring-shaped yoke are bunched together by a U-shaped support form.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is, as described above, an end view, partly in section, of a deflection yoke according to the prior art.

FIGURE 2 is an illustration of a portion of a deflection yoke according to the present invention showing the cross section of one winding thereof.

FIGURES 3 and 4 are graphical illustrations which will be referred to in order to facilitate an understanding of the following discussion.

Referring now to the drawings, FIGURE 2 shows one half of a ring-shaped yoke core 6, on which there is ion wound a toroidal coil '7. This toroidal coil is so dimensioned that the portions 8 of the windings located on the outside of the ring-shaped yoke subtend a considerably smaller circumferential angle 11' than the angle a of portions 3a of the winding on the inside of the ring-shaped yoke. In the embodiment shown in the drawings, this is accomplished by using a U-shaped form 9 on the outside of the ring-shaped yoke core 6, between the yoke and the coil 7. In the case where the coil is slipped onto the yoke core 6, it may be advisable to arrange, at the inside of the winding, a strip of adhesive tape 10 whose ends 11 are wrapped around the sides of the winding to keep it from spreading. The legs 12 of the U-shaped form 9 may also serve as finger levers for the displace ment of the toroidal coils around the circumference of the yoke core 6. By this means trapezoidal distortion, for example, may be compensated for and adjusted. After the correct adjustment, the coils may be fixed, for example, by spraying with a synthetic resin.

These measures achieve a considerable improvement in the sharpness of the image points on the screen, and this improvement can be illustrated with reference to the diagrams shown in FIGURES 3 and 4.

The point focus b is plotted over a vertical or a horizontal pincushion pattern (S or W) both for the case of a toroidal coil wound according to FIGURE 1 and for a toroidal coil wound according to the invention. Herein, b is understood to be the width of the image point, which in the most favorable case (image point in the center of the screen) is assumed to be Stated as the value for the pincushion distortion is the distance of the picture raster, measured at the margin, from the shape of a rectangle given by the picture corners. A is the curve for a prior-art toroidal coil according to FIGURE 1; B is a curve for the coil according to the invention. With the same point focus, the pincushion distortion for the known coil is 2 to 3 times as large as that for the coil according to the invention (measured under the same electrical conditions). It has been found that the point focus of the luminous spot produced on the fluorescent screen by the cathode beam gives more favorable values with circularly-distorting coils than with non-distorting or cylindrically-distorting coils. Such circular distortions, however, are intolerable, from the standpoint of the viewer. Up to now, therefore, a compromise always had to be made between point focus and distortion. As shown by the diagrams in FIGURE 3, the teaching according to the invention makes it possible to improve the point focus without thereby affecting the circular distortion in an unfavorable manner. With a coil according to the invention, therefore, the compromise between point focus and distortion may be made considerably more favorable.

If the ratio of circumferential angles 0L and a is chosen in such a way that the windings all run parallel, the production process may be simplified for making such a coil, and still provide the present improvement in the point focus. Because in such a case it is possible to wind the coil directly onto the core without having to turn the core for feeding, production can thereby be rntade considerably more economical.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. A magnetic deflection yoke for deflecting the beam of a cathode ray tube, comprising, in combination: a ring of ferromagnetic material for surrounding said beam; at least one set of magnetic deflection windings compris ing toroidal windings symmetrically spaced and Wound through and on said ring so that the portion of the Winding disposed outside of said ring subtends a smaller circumferential angle as measured from the center of the ring than the portion of the Winding passing inside of the ring.

2. In a deflection yoke as set forth in claim 1, the ratio of the angle subtended by the portion of the Winding lying outside the ring-to the angle subtended by the portion of the winding lying inside the ring not exceeding 1:2.

3. In a deflection yoke as set forth in claim 1, a U- shaped form interposed between the ring and the portion of the winding lying outside of the ring and having its two legs extending outwardly away from the ring and confining the turns of the winding therebetween.

4. In a deflection yoke as set forth in claim 3, said U-shaped form being slidable on said ring and said legs serving as hand grips for positioning the associated wind ing circumferentially of the ring.

References Cited in the file of this patent UNITED STATES PATENTS Janssen Dec. 15, 1959 2,926,273 Haupt et al Feb. 23, 1960

Claims

1. A MAGNETIC DEFLECTION YOKE FOR DEFLECTING THE BEAM OF A CATHODE RAY TUBE, COMPRISING, IN COMBINATION: A RING OF FERROMAGNETIC MATERIAL FOR SURROUNDING SAID BEAM; AT LEAST ONE SET OF MAGNETIC DEFLECTION WINDINGS COMPRISING TOROIDAL WINDINGS SYMMETRICALLY SPACED AND WOUND THROUGH AND ON SAID RING SO THAT THE PORTION OF THE WINDING DISPOSED OUTSIDE OF SAID RING SUBSTENDS A SMALLE CIRCUMFERENTIAL ANGLE AS MEASURED FROM THE CENTER OF THE RING THAN THE PORTION OF THE WINDING PASSING INSIDE OF THE RING.