US2944173A - Cathode-ray tube scanning apparatus - Google Patents

Description

July 5, 1960 A. HAZELTINE 2,944,173

CATHODE-RAY TUBE SCANNING APPARATUS Filed July 17, 1958 2 Sheets-Sheet 1 15, I A. HAZELTINE 2,944,173

I CATHODE-RAY TUBE scmmmc APPARATUS Filed July 17, 1958 z Sheets-Sheet 2 I I I l I I I I I I I l I I I I I I FIG. 4 I I I l I l I I I I I I l l I I l I J I I v I 23 I l I E I l z l 5E o I I I |ao I360 0 I I 2 a 20 30 z I ANGULAR DISTANCE FIG.5

United States Patent ice CATHODE-RAY TUBE SCANNING APPARATUS Alan Hazeltlne, Maplewood, N.J., assignor to Hazeltine Research, Inc., Chicago, 111., a corporation of Illinois Filed July 17, 1958, Ser. No. 749,275

4 Claims. (Cl. 313-77) flection in one direction and which enables the use of deflection circuit components with lower power ratings.

In supplying scanning currents to the horizontal and vertical deflection yoke windings of a cathode-ray tube, it is sometimes found to be more diflicult to secure suflicient power for producing deflection in one direction than for producing deflection in the other. This is particularly true in television receiver systems where approximately ten times as much power is required to produce horizontal deflection as compared to that necessary to produce vertical deflection. This increase in power is required due to increased losses occurring at the higher horizontal scanning frequencies. It is a serious problem even when vacuum tube deflection circuits are utilized. In the case of vacuum tube circuits the problem is overcome by using components with suitably high power ratings. However, in some applications such as transistor television receivers,

it becomes important to provide some solution tof this problem which will allow the use of circuit components which are smaller in size and thereforeh-ave lower power ratings. p i p An early solution is to be found inUnited States Patent 2,177,688, issued to MadisonCawein on October 31,

1939, wherein there is disclosed an arrangement or" permanent magnets located around and abutting the neck of a television tube between the deflecting yoke and the tube bell for augmenting the horizontal deflection. However, such an arrangement is difficult to apply to cathode-ray tubes favored in present-day practice, especially those found in portable receivers, since the tracks of such tubes are short and the available space around them is fully occupied by the yoke windings, the magnetic core around these windings, the ion trap, and perhaps the focusing and centering arrangements. Moreover, this magnetic core would tend to short-circuit the magnetic field of permanent magnets placed close to it. Furthermore, it is ditficult to arrange permanent magnets in such a way as to to prevent their field from producing a certain amount of undesirable picture. distortion. I i It is an object of the present invention to provide new and improved scanning apparatus to augment the electron-beam deflection and which avoids the disadvantages of prior such apparatus.

It is another object of the present invention to provide scanning apparatus which produces a constant magnetic field so distributed across the cross-section of the electron beam that substantially no distortion of the picture results.

It is a further object of the present invention to provide scanning apparatus which may be utilized in conjunction with small short-necked, wide deflection angle cathoderay tubes without substantially increasing the size of such apparatus. 1

In accordance with the present invention, cathode-ray Patented July 5, 1960 tube scanning apparatus for providing augmented beam deflection comprises deflection winding means for scanning the beam, magnetic core means encompassing the deflection means, means for supplying a direct current and means including a four-pole auxiliary winding responsive to the direct-current supply means and disposed between the core means and the tube for providing a uniformly changing magnetic field across the beam-deflection area. In one form of the invention the auxiliary winding has its longitudinal sides distributed substantially sinusoidally about the tube. In another form, the sides are distributed uniformly through four angular regions about the tube. a

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with'the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring to the drawings:

Fig. 1 is a diagrammatic cross-sectional side view of a portion of a cathode-ray tube showing a preferred embodiment of the present invention;

Fig. 2 is a diagrammatic cross-sectional view through the neckof the cathode-ray tube of Fig. 1;

Fig. 3 shows components of magnetic intensity produced by the auxiliary winding;

Fig. 4 shows diagrammatically the manner in which the auxiliary winding is wound, and

Fig. 5 is a graph of magnetic potential over the inner surface of the auxiliary winding of Fig. 2 plotted against the angular distance around the circumference.

Referring to Figs. 1 and 2 there is shown cathode-ray tube scanning apparatus for providingaugmented beam deflection which comprises in part deflection winding windings might alternatively be of the saddleyoke construction described at pages 610 of Television Engineering Handbook, edited by Donald G. Fink, McGraw-Hill Book 'Co., Incl, 1957. These windings are preferably placed directly over the glass neck of the tube 10.

The cathode-ray tube scanning apparatus further comprises a magnetic core means encompassing the deflection means. As shown in Fig.2 the magnetic core 13 sur rounds the horizontal andvertical deflection windings 11, 11 and 12, 12 and auxiliary winding 15, in accordance with the present invention. The windin g 15 is more fully described hereinafter. The core serves" as a return path for the magnetic flux of all three windings.

In addition to the conventional deflection windings and the magnetic'core, the apparatus further comprises means for supplying a direct current and means including a four-pole auxiliary winding responsive to the directcurrent supply means and disposed between the core means and thetube for providing a uniformly changing magnetic field across the beam deflection area. In one form of the invention the auxiliary winding has its longitudinal sides distributed substantially sinusoidally about the tube. In another form the auxiliary winding is symmetrical and has its longitudinal sides distributed uniformly through four angular regions being substantially equal to 60. These means include in Figs. 1 and 2 the direct-current voltage supply 16 and the auxiliary winding 15, which is a single layer winding disposed between the magnetic core 13 and the horizontal and vertical defleconly in the flat portion of the deflection windings, are

the axis.

current of the auxiliary winding. .lscribed, for the ideal condition .of. no distortion, the sides iof the coils comprising thelwinding arehhbstantially sinusoidally distributed about the neck of the tube. In

preferably wound to conform to the configuration of the deflection windings. In winding the auxiliary winding the four coils comprising the winding are spirally wound in reverse sequence and serially connected so that the adjacent sides of any two neighboring coils produce a magnetic field in the same relative direction.

Referring to Fig. 4, the auxiliary winding is shown in 7 developed form, namely, before being wrapped around the neck of the cathode-ray tube 10. The winding comprises four coils 18, 19, 20, and 21, each coil having the conductors in its longitudinal side preferably parallel and straight. For the case of sinusoidal distribution of the coil sides the densest portions of the windings are arranged at the horizontal and vertical axes relative to the desired direction of increased beam deflection. The direction of direct-current flow through the winding then determines the axis of increased beam deflection. For reasons to be explained hereinafter, it may be more practical to wind the coils without adhering to the rigorous sinusoidal distribution. In Fig. 4, one such preferred form of a winding is shown wherein each longitudinal coil side has a width which covers an angular distance of on thereby producing an angular distance of 20: when adjacent coils are placed in abutting relation. The angle, a, is preferably substantially equal to 30. When wound in this fashion the magnetic pole, which is the center of the coil, has a width equal to the width of one longitudinal side of the coil.

In describing the operation of the apparatus, reference is made to Fig. 3 wherein the ideal magnetic field, developed by a sinusoidal distribution of coil sides of the auxiliary winding 15, is shown as having a vertical component intensity H directly proportional to the horizontal distance x from the longitudinal axis 17 of the tube 19 and reversing in direction with a reversal in x. In a television receiver in which it is desired to augment the horizontal deflection, the x axis would lie along the horizontal plane and would preferably orthogonally intersect the axis-of-rotation 17 of the tube 10. The linearly in creasing magnetic field increases the horizontal deflection by a constant factor. While the vertical component H is produced there is unavoidably present, at the same time, the horizontal component intensity I-I which ideally isrdirectly proportional to the vertical distance y from Such a field will then decrease the vertical deflection by a constant factor in the same manner in which the horizontal deflection was increased. Thus, less power is required of the horizontal deflection wind ings 11, 11 and correspondingly more power is required of the vertical deflection windings 12, 12.

Due to the ideal uniformly changing field developed, the picture is not'distorted. By uniformly changing is meant linear variation with respect to distance from the ,tube axis. The reason for this lack of distortion can be where r and 0 are the polar coordinates of any point within the field and distant from its ends. With a symmetrical fourpole field the solution of this equation becomes; I

r r 1 V=a sin 26+ a sin 66+c sin 106+ .where R is the inner radius of the auxiliary winding and the as are constants determined by, the distribution and As previously de- 25. this case all the as of Equation 2 are at zero except a;, in which case the equation simplifies to:

r r V= or S111 20=2a sin 0 cos 0 Thus H is independent of x and directly proportional to y. H is independent of y and directly proportional to x. These are the desired relations illustrated in Fig. 3. The corresponding additional deflections d and d are indicated by the dotted arrows, the current of the auxiliary winding having such direction as to increase horizontal deflections at the expense of decreased vertical deflections.

In place of a sinusoidal distribution, it may be more convenient to use an auxiliary symmetrical windinguniformly distributed over portions of the circumference, as illustrated in Fig. 2. The magnetic potential just inside the auxiliary winding (r=R) is then as represented in Fig. Sand as expressed by the Fourier series:

V= k sin 2a sin 28+ sin 60: sin 69 Sin Sn; 100+ sin 6na= sin n=0 (n=1, 3, s, (6)

Equation 5 then reduces to sin 220+ At any point r, 0 in the field, the magnetic potentiahby 1 l sin 146 112 Equation 2, is then V=k sin 60 R2 S111 To obtain an estimate of the distortion due to the departure of this magnetic potential from the ideal sinusoidal distribution, the radial and tangential components of magnetic intensity may be found from Equation 8:

th k sin 60- Z sin 20 Using the maximum values 1 of the sines and cosines, the values of the second terms relative to the first are each equal to 1 l i 5 R 5-2 l280 at a radial distance r==R/2 within which practically all of the electrons of the beam will be confined. This value, 1/1280, is so small that the departure from the ideal condition is unimportant; and the values for higher terms are smaller still. So distortion due to the departure of V in Fig. 5 from the ideal sinusoidal distribution is quite tolerable with a=30.

When used in conjunction with a television-receiver scanning system the auxiliary winding need comprise merely a single layer. Since the voltage of this winding is low it requires no insulation other than the ordinary type of wire insulation.

It can be seen that the desired increase in beam deflection and a simultaneous decrease in component power rating may be produced by the present invention without occupying space about the tube already necessary for conventional image-reproducing apparatus. Since only a single layer, lightly insulated winding is necessary to practice this invention, the very small extra space required may be provided by slightly increasing the diameter oi the magnetic core 13 or alternatively by decreasing the size of windings 11, 11 and 12, 12 or both.

While there has been described what is at present considered to be the preferred embodiment of this invention, it Will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. Cathode-ray tube scanning apparatus for providing augmented beam deflection, comprising: deflection winding means for scanning the beam; magnetic core means encompassing the deflection means; means for supplying a direct current; and means including a four-pole auxiliary winding responsive to the direct-current supply means and disposed between the core means and the tube for providing a uniformly changing magnetic field across the beam-deflection area, said auxiliary winding having its longitudinal sides distributed substantially sinusoidally about the tube.

2. Cathode-ray tube scanning apparatus for providing augmented beam deflection, comprising: deflection Winding means for scanning the beam; magnetic core means encompassing the deflection means; means for supplying a direct current; and means including a four-pole auxiliary winding responsive to the direct-current supply means and disposed between the core means and the deflection means for providing a uniformly changing magnetic field across the beam-deflection area, said auxiliary Winding having its longitudinal sides distributed substantially sinusoidally about the tube.

3. Cathode-ray tube scanning apparatus for providing augmented beam deflection, comprising: deflection winding means for scanning the beam; magnetic core means encompassing the deflection means; means for supplying a direct current; and means including a fourpole symmetrical auxiliary winding responsive to the direct-current supply means and disposed between the core means and the tube for providing a uniformly changing magnetic field across the beam-deflection area, said auxiliary winding having its longitudinal sides distributed through four angular regions about the tube, said regions being substantially equal to 4. Cathode-ray tube scanning apparatus for providing augmented beam deflection, comprising: deflection winding means for scanning the beam; magnetic core means encompassing the deflection means; means for supplying a direct current; and means including a four-pole symmetrical auxiliary Winding responsive to the direct-current supply means and disposed between the core means and the deflection means for providing a uniformly changing magnetic field across the beam-deflection area, said auxiliary winding having its longitudinal sides distributed through four angular regions about the tube, said regions being substantially equal to 60.

References Cited in the file of this patent UNITED STATES PATENTS 2,177,688 Cawein Oct. 31, 1939 2,414,925 Buckbee Jan. 28, 1947 2,455,977 Bocciarelli Dec. 14, 1948 2,467,009 Bull et al. Apr. 12, 1949 2,498,354 Bocciarelii Feb. 21, 1950 2,578,343 Ekvall Dec. 11, 1951 2,846,606 Jones et al. Aug. 5, 1958 2,855,530 Hamann Oct. 7, 1958 FOREIGN PATENTS 739,068 Great Britain Oct. 26, 1955

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