US2926273A - Arrangement for the magnetic deflection of the electron beam in cathode ray tubes, particularly for television purposes - Google Patents

Description

Feb. 23, 1960 G. HAUPT ETAL 2,926,273

ARRANG NT R THE NETI EFLECTION OF THE ELECTRON EA u CATHO RAY ass, PARTICULARLY FOR TELEVISION PURPOSES Filed Feb. 20, 1958 3 Sheets-Sheet 1 lR/OR ART PRIOR ART Fla. 3 PRIOR ART 1960 G. HAUPT ETAL 2,926,273

ARRANGEMENT FOR T MAGNETIC DEFLECTION THE ELECTRON BEAM IN C RAY TUBES, PARTI ARLX FOR EVISION PURPOSES Filed Feb. 20, 1958 3 Sheets-Sheet 2 """iiiiiiiiiiiiiii"""""" PRIOR 'ART Feb. 33, 1960 HAUPT ETA ,926,273

ARRANGEMENT FOR THE MAGNETIC DEFLEC OF THE TRON BEAM IN CATH CULARLY ODE RAY TUBES, PARTI FOR TELEVISION PURPOSES Filed Feb. 20, 1958 3 Sheets-Sheet 3 x 1WWW;

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FlG 8 Inventons G.Hau 1 fl,F'c'z;L1ie1 ARRANGEMENT FOR THE MAGNETIC DEFLEC- TION OF THE ELECTRON BEAM IN CATHODE RAY TUBES, PARTICULARLY FOR TELEVISION PURPOSES Giinter Haunt and Rndo Fiilker, Altena (Westphalia), Germany, assignors to Graetz Komrnanditgesellschaft, Altena (Westphalia), Germany Application February 20, 1958, Serial No. 716,341

Claims priority, application Germany February 23, 1957 Claims. (Cl. 313-76) In order to deflect the electron beam of cathode ray tubes used in television, deflection arrangements are often used nowadays in which two diametrically opposed saddle coils are arranged inside a ferromagnetic ring yoke of circular shape surrounding the electron beam, for the deflection of the beam in horizontal direction, whereas toroidal coils wound or slipped on the ring yoke are used in order to deflect the beam in vertical direction.

The toroidal coils of this invention are an improvement over the conventional toroidal coils in that the windings thereof are not only distributed in accordance with a cosine function to provide a high marginal definition of the raster and a satisfactory raster geometry, but will also avoid the generation of partial oscillations therein due to coupling with the magnetic field of the horizontal deflection coils. To this end, the toroidal coil of this invention comprises at least three layers of windings in which each of the layers covers an azimuthal angle smaller than the azimuthal angle covered by the entire coil and the arithmetic mean of all the values of azimuthal angles occupied by the odd layers is different from the arithmetic mean of all the values of azimuthal angles occupied by the even layers. The coils of the invention can be machine-wound in one operation without the winding process having to be interrupted.

Fig. 1 shows a conventional magnetic deflection yoke with part of the horizontal saddle winding in crosssection,

Fig. 2 shows a part of a yoke with one conventional toroidal coil in cross-section,

Fig. 3 is a section through a conventional toroidal coil in cross-section in which the turns are distributed in approximation to a cross-section,

Fig. 4 shows another form of a conventional toroidal coil,

Fig. 5 is a cross-sectional view of a toroidal coil wound on a ring yoke in accordance with this invention,

Fig. 6 shows the winding plan of a coil according to Fig. 5,

Fig. 7 illustrates another winding plan of a coil according to this invention, and

Fig. 8 shows the toroidal coils of this invention wound on a ring yoke for both the horizontal and vertical deflections of a cathode ray beam.

A well-known example for the construction of such a deflection arrangement is shown in Figure 1. The neck 15 of the cathode ray tube, indicatedby a dotted line, is surrounded by the circular ring yoke 16 of ferromagnetic material. Between the ring yoke 16 and the tube neck 15 are two saddle coils 18 and 19, employed for the horizontal deflections, which lie diametrically opposed to one another in the vertical axis 17 of the drawing, their longitudinal wire bundles which extend parallel to the electron-optical axis being here illustrated in cross section. The frontally situated Wire bundles which face the beholder are not shown whereas the frontal wire bundles facing away from the beholder are visible out- 2,926,273 Patented Feb. 23, 1960 "ice side the ring yoke. Also arranged on the ring yoke 16 are two toroidal coils 20 and 21 diametrically opposed to one another in the vertical axis 17 of the drawing which coils are used for the purpose of vertical deflection.

As is apparent from the sectional faces of the longitudinal wire bundles of the saddle coils, so-called cosine saddle coils are shown in this illustration the particular feature of which it is that the total number of turns in each longitudinal wire bundle is distributed over the azimuthal angle covered by the longitudinal wire bundle in accordance with a cosine function. These cosine coils are now widely used because they achieve a particularly high marginal definition of the raster and, at the same time, a satisfactory raster geometry. Since the longitudinal wire bundles of these cosine saddle coils are spread over an azimuthal angle of nearly the necessity arises, in order to attain a sufliciently ample winding space for the toroidal coils, for the latter to overlap the longitudinal wire bundles of the saddle coils to a certain angular degree.

Basically, the above-described deflection arrangement can also be constructed with ordinary saddle coils in which the turns of the longitudinal wire bundles are not distributed according to a cosine function. As the longitudinal wire bundles of such ordinary saddle coils generally cover a much smaller azimuthal angle than is the case with cosine saddle coils a sufficient space is left vacant between the two longitudinal wire bundles by the ordinary saddle coils to accommodate a suitable toroidal coil so that in this case the overlapping of the toroidal coils and the longitudinal wire bundles of the saddle coils is unnecessary.

Irrespective of the kind of saddle coil used for the horizontal deflection, there are two known forms of construction regarding the toroidal coils which are used for the vertical deflection. One of these is shown diagrammatically in Figure 2. This drawing shows a section through a toroidal coil of the same shape as is also indicated in Figure 1 and figures only one half of the ring yoke 16 and only one toroidal coil 20. As may be gathered from the sectional plane, the coil consists of several layers and all layers extend over the azimuthal angle occupied by the entire coil. The diameter of the coil winding is therefore constant.

The second known form of toroidal coil construction is diagrammatically represented in Figure 3. Here, too, is shown a section through a coil 20 which is wound on the yoke 16. The various layers of this coil however do not extend over the same azimuthal angle and only the first layer closest to the ring yoke occupies the entire angle of the coil whereas each additional layer is symmetrically shortened relatively to the preceding layer so that the last layer occupies only a comparatively smallangle. The diameter of the coil winding is therefore not constant and decreases symmetrically on both sides, relatively to the azimuthal centre. By suitably dimensioning the amounts by which the various layers are shortened, a distribution of the turns approximately in accordance with a cosine function can be achieved. This kind of toroidal coil shaped in approximation to a cosine function offers the same advantage as the cosine saddle coil, namely an improvement in the marginal raster definition and, at the same time, a satisfactory raster geometry.

'In the successful construction of the vertical deflection coils it is a factor of decisiveimportance that the magnetic field of the horizontal deflection coils which permeates at least partially also the vertical deflection coils, will excite parts of the vertical deflection coil windings so as to generate partial oscillations.

In order to avoid these partial oscillations whose interference becomes noticeable as an undesirable vertical deflection of the electron beam, a well-known method of winding the toroidal coils is used whereby the wire is led back from the end of each layer ina straight line to the beginning of the next layer. This winding method is shown in Figure 4. The drawing gives the perspective view of a ring yoke half 16 on which the first layer of a toroidal coil is arranged. From the beginning of this layer, indicated by A l, the progresses constantly (from left to right in the drawing) to the end of the layer, indicated by Ei. From this point the wire is led back to the left in a straight line up to the point denoted by A2 where the second layer commences. This layer and all further layers which for reasons of clarity have not been shown in Figure 4, progress in the same azimuthal sense as the first layer, and the wire is turned back from the end of each layer in a straight line to the beginning ofthe next layer. In this way this winding method is distinct from an ordinary layered Winding in which,as is known the end of one layer represents also the beginning of the next layer for which reason the layers progress alternately in opposite directions. This ordinary type of layered winding is useless for the abovedescribed toroidal coils because it leads to partial oscillations of too great a magnitude.

The above-described winding method using a straightline return of the wire after each layer whichas is knownis widely employed in the manufacture of toroidal deflection coils, suffers from the disadvantage that the wire must be fastened both at the beginning and at the end of each layer, for instance by being tied with thread. This makes it necessary to stop the machine on which the coil is wound upon completion of each layer. Following this, the required manipulations must be carried out and only then can the machine be restarted to wind the following layer. As this procedure repeats itself after every layer the time required for carrying out all the manual operations for one coil amounts to far more than half of the time required for completing the whole coil. For the purpose of rationalized mass production therefore, a coil seems desirable which can be machine-wound throughout without any manual operation and which is, at the same time, free from partial oscillations. Such a toroidal coil is the subject matter of the present invention which will now be described as follows.

According to the invention it is proposed to build up the toroidal coil from a number of layers every one of which extends over an azimuthal angle smaller than the azimuthal angle occupied by the entire coil, and at the same time so to choose the values ofthe azimuthal angles over which the various layers extend that the arithmetic means of all angles occupied by the first, third and any further odd layer is different from the arithmetic mean of all those azimuthal angles which are occupied by the second, fourth and any further even layer. At the same time, the layers are to be wound without interruption throughout in such a way that, as with the ordinary type of layered coil, the even layers progress in the opposite azimuthal direction to the odd layers, the end of any one layer thus representing also the beginning of the next layer. In order to explain the principle of the invention in more detail, various examples of constructing toroidal coils according to the concept of the invention are described hereafter.

One of these examples is diagrammatically, illustrated inFigure 5. The drawing shows a section through a toroidal coil which is wound on a ring yoke half-16. To facilitate the understanding all sectionalfaces belonging to one and the same layerhave here been connected by a line. The layers are numbered in their order of Winding. According to the invention, all layers extend over an azimuthal angle smaller, thanf tl1e,azi-

muthal angle covered by the entire coil. Besides, the layers'starting from the beginning (A) of the coil are so arranged that the odd layers progress in the opposite azimuthal direction to the even layers, the former from left to right and the latter from right to left in the drawing.

Another essential feature of the invention, namely the fact that the arithmetic means of all azimuthal angles occuplied by the odd layers dilfers from the arithmetic mean of all azimuthal angles occupied by the even layers, is materialized in the example of Figure 5 in a particularly simple way in that all azimuthal angi'esoceup'iea by the odd layers are equal to one another and, at the same time, greater than the azimuthal angles occupied by the even layers, the latter also being equal to one another.

In Figure 6 is shown the winding plan of a coil according to Figure 5. plotted the azimuthal angle occupied by the entire coil, the angle bisector being indicated 0. In accordance with the angular data of Figure 5 therefore, the coil extends from --60 to +60". All odd layers which progress from the beginning (A) towards the end (E) occupy an azimuthal angle of 30 and all even layers which progress backwardly towards the beginning (A) cover an angle of 15". The result is a coil with an approximately constant winding diameter which corresponds to the known type of coil shown in Figure 2 as far as its electrical properties are concerned.

The determination of the number of layers and of the values of azimuthal angles covered by the respective layers is in practice carried out empirically, i.e. in such a way that the coil will not give rise to undesirable partial oscillations. The'numerical values in Figures 5 and 6 have a merely explanatory meaning.

A further example of the toroidal coil carried out according to the invention is illustrated by the winding scheme according to Figure 7. The winding shown here ditfers from that in Figures 5 and 6 only in that, near the azimuthal coil centre indicated by 0", the ratio of the values of azimuthal angles occupied by two consecutive layers is not the same as near the beginning (A) and the end (E) of the coil. For instance, in the example according to Figure 7 the azimuthal angle of an odd layer near the beginning and near the end 'of the coil is 20 and that of an adjacent even layer 10. The ratio of these two angles is therefore 2:1 or 1:2. But near the azimuthal coil centre an odd layer covers an angle of 30 and an adjacent even layer an angle of 20 so that the ratio of these two angles amounts to 3:2 or 2:3.

This results in more layers overlapping one another near the coil centre than in the marginal coil portions. Thus the straight line 22 for instance, drawn in Figure 7 near the beginning, intersects three layers whereas the line 23 drawn near the coil centre intersects five layers.

In a toroidal coil according to the invention, the varied ratio of the azimuthal angles for two consecutive layers will therefore result in a variation of the coil diameter. In this way it has become possible to distribute the turns over the azimuthal angle of the entire coil in approximation toa cosine function and thus to produce toroidal .coilswwhic'hin regard to their electrical properties correspond to the'known type of coil shown in Figure 3.

The empirical determination of the number of layers required for a toroidal coil according to the invention in which the distribution of turns approximately comiplie's withfacosinefunction, and the determination of 70.

the. valu'esof azimuthal angles required for the respective layers which values are given in' Figure 7 merely by .way. of, example, takes place with the following two eomenmnd n the other hand, the coil should On the horizontal scale has been 7 not generate undesirable partial oscillations. A satisfactory solution from both points of view is here attainable for every case of any practical importance, thanks to the manifold possibilities of variation.

A further modification of the toroidal coil according to the invention may be obtained if in the even layers the wire is wound with a pitch diflerent from that used in the odd layers. In the embodiments heretofore described an identical pitch was assumed for all layers because this usually applies to ordinary layered windings. If in the case of coils as proposed by the invention the odd and the even layers are wound with a diiferent pitch, a procedure applicable to every modification of a coil built according to the invention then greater freedom in the establishment of the best winding scheme for any given requirement will result.

Employment of the toroidal coils according to the invention is not confined to deflection arrangements in which the horizontal deflection is effected by saddle coils although in practice the main emphasis is to be laid on their application to this kind of arrangement. Toroidal coils according to the invention may for instance also be employed in deflection arrangements which effect the deflection in both directions by means of toroidal coils. A system of this kind is diagrammatically illustrated in Figure 8. On the ring yoke 16 are arranged two toroidal coils 18 and 19 for horizontal deflection and another two toroidal coils 20 and 21 for vertical deflection. A deflection system of this kind may be equipped, as indicated by the practical requirements of the case, either with coils according to the invention for deflection in one sense and with conventional coils for deflection in the other sense, or coils according to the invention may be employled for deflection in both senses.

In every case a toroidal coil constructed according to the inventive concept differs from the conventional coils in that each of its layers covers an azimuthal angle smaller than the azimuthal angle occupied by the entire coil and in that the arithmetic mean of all the values of azimuthal angles occupied by the odd layers is different from the arithmetic mean of all the values of azimuthal angles occupied by the even layers. By exploiting this principle of the invention it is possible to wind toroidal deflection coils which are free from partial oscillations and yet do not contain any wire leaps wherefore such coils can be machine-wound in one operation without the winding process having to be interrupted for the carrying out of manual operations.

We claim:

1. An arrangement for the magnetic deflection of the electron beam in cathode ray tubes, particularly for television purposes, which comprises a circular ring yoke of ferromagnetic material, a set of coils effecting the horizontal deflection and a set of coils effecting the vertical deflection and in which at least the set of coils effecting the deflection in one direction consists of toroidal coils all of which are wound in a continuous process on said yoke and consist of several layers, characterized in that each of the layers of a toroidal coil extends over an azimuthal angle smaller than the angle covered by the entire coil, and also in that the arithmetic mean of all azimuthal angles occupied by the first, third and any further odd layer is different from the arithmetic mean of all azimuthal angles occupied by the second, fourth and any further even layer.

2. A deflection arrangement as claimed in claim 1, characterized in that all azimuthal angles occupied by the odd layers of a toroidal coil are equal to one another and that all azimuthal angles occupied by the even layers are equal to one another.

3. A deflection arrangement as claimed in claim 1, characterized in that the ratio of the azimuthal angles occupied by two consecutive layers in a toroidal coil is not constant throughout the azimuthal angle covered by the entire coil.

4. A deflection arrangement as claimed in claim 1, characterized in that the ratio of the azimuthal angles occupied by two consecutive layers in a toroidal coil is so varied throughout the azimuthal angle covered by the entire coil that the resulting distribution of turns in the coil progresses approximately in accordance with n cosine function.

5. A deflection arrangement as claimed in the claim 1, characterized in that the even layers of a toroidal coil are wound with a pitch diflerent from that used in the odd layers.

References Cited in the file of this patent UNITED STATES PATENTS 2,155,514 Tolson Apr. 25, 1939 2,406,740 Buckbee Sept. 3, 1946 2,831,997 Marley Apr. 22, 1958

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