US2165803A - Cathode ray deflecting device - Google Patents

Description

July 11, 1939. L G MALOFF 2,165,803

CATHODE RAY DEFLECTING DEVICE Filed April 25, 1936 ECE/ VER Hanze/vm:

sc r/Ms WERT/GOL Inventor Gttorneg Patented July 11, 1939 UNITED STATES PATENT OFFICE Radio Corporation of America,

of Delaware a corporation Application April 25, 1936, Serial No. '76,377

5 Claims.

My invention relates to cathode ray deflecting devices and particularly to deflecting devices of the electro-magnetic type.

In television receivers employing cathode ray tubes and in cathode ray oscillographs it is necessary to provide means for deflecting a cathode ray simultaneously in two directions which are substantially at right angles to each other. In the past, when electro-magnetic deflection Was employed, two pairs of deflecting coils were employed, one pair for horizontal deflection andone pair for vertical deflection. It was found that, in television receivers, especially, this was not altogether satisfactory for two reasons. In the rst place, the cathode ray did not scan a truly rectangular pattern even though deflected by perfect saw-'tooth waves, and, in the second place, the deflecting eld tended to defocus the cathode ray.

Accordingly, it is an object of my invention to provide an improved deflecting device of the above-mentioned type.

It is a further object of my invention to provide an improved deilecting device which causes a cathode ray to scan a substantially rectangular pattern when supplied with saw-tooth deflecting current.

It is a still further object of my invention to provide an electro-magnetic deflecting device which deects a cathode ray with a minimum of defocusing.

In a preferred embodiment of my invention the deflecting yoke includes a magnetic core having eight pole pieces instead of the usual four pole pieces. The horizontal and Vertical deflecting windings may be wound on these pole pieces in several different ways. One way is to wind the deflecting coils on the eight pole pieces as a continuous winding, the vertical deiiecting current being supplied to the continuous winding at diametrically opposite points and the horizontal deflecting current being supplied to the winding at diametrically opposite points located 90 away from the first mentioned points. With this arrangement, the vertical deflecting current and the horizontal deflecting current flow through the same deflecting windings to provide the desired resultant deflecting fields,

Another way of applying the deecting windings to the pole pieces is to provide six windings (three pairs of coils) for the vertical deflection, these windings being placed on diametrically opposite pole pieces and being connected with the three pairs of coils in parallel. Similarly six deflecting coils are Vprovided for horizontal de- (Cl. Z50- 157) flection, these coils being placed on six diametrically opposed pole pieces and being connected the same as the vertical deflecting coils.

With this arrangement, there is a single deflecting coil on each of two diametrically opposed pole pieces which may be referred to as the main vertical deecting pole pieces and likewise there is a single horizontal defiecting winding on each of two diametrically opposed pole pieces which may be referred to as the main horizontal deecting pole pieces. The remaining four pole pieces, which may be referred to as the shading or correcting pole pieces each have two windings thereon, one winding being a vertical delecting winding, the other winding being a horizontal deflecting winding.

Other objects, features and advantages of my invention will appear from the following description taken in connection with the accompanying drawing of which Figure 1 is a schematic diagram of a television receiver embodying my invention;

Figs. 2 and 3 are views showing two different embodiments of my invention and Figs. 4a and 4b indicate the shapes of two scanning patterns which are referred to in explaining the invention.

Referring to Fig. 1, one embodiment of my invention is shown applied to Va television receiver of the type comprising a radio receiver I for the reception of a carrier wave modulated by picture and synchronizing signals. The carrier wave is demodulated in the receiver l and the picture signals are supplied to the control grid 2 of a cathode ray tube 3. The horizontal synchronizing impulses are supplied to a horizontal deflecting circuit 4 while the vertical synchronizing impulses are supplied to a vertical deflecting circuit (i.V

The cathode ray tube 3 preferably is of a well known type comprising an evacuated envelope having therein an indirectly heated cathode 1, the control grid 2, a first anode 8, a second anode 9 and a fluorescent screen Il. In this type of cathode ray tube the cathode ray is electrostatically focused by means of the electrostatic eld between the first anode 3 and the second anode 9.

Referring to Figs. l and 2 the deflecting yoke for the tube 3 comprises a laminated iron core l2 having eight pole pieces spaced 45, degrees apart. As shown in Fig. 2 these pole pieces are provided with a continuous winding, i. e., there is a winding on each pole piece and all the windings are connected in series to form a closed circuit. The horizontal deflecting current is supplied to the continuous winding I3 at diametrically opposite points through the leads I4 and I6. The vertical deflecting current is supplied to the continuous winding I3 at diametrically opposite points through the leads I'l and I8.

As indicated by the letters N and S at the inner ends of' the pole pieces, the windings are wound in such direction that current flowing from the lead I4 through the winding to the lead I6 will make the inner ends of the four lower pole pieces north and the inner ends of the four opposing pole pieces south, assuming there is no flow of vertical defiecting current. 'Ihe corresponding polarities at the outer ends of the pole pieces, i. e., at the ring of the core I2, are south and north as indicated by the letters SH and NH.

Vertical deflecting current flowing from the lead I1 through the deecting coils and out the lead I8 will cause the inner ends of the four right hand pole pieces to be of south polarity and the inner ends of the four left hand pole pieces to be oi' north polarity, assuming there is no flow of horizontal deiiecting current. The corresponding north and south polarities of the pole pieces at their outer ends are indicated by the letters Nv and Sv. If the vertical and horizontal deiiecting currents are flowing simultaneously and ii' the magnetic fluxes produced by these currents are equal, the resultant deflecting flux will be in the plane indicated by the dotted arrow, and the polarity at the ring of the core will be that indicated by the letters NR and SR.

The vertical and horizontal defiecting circuits preferably are of such design that they will produce a ow of saw-tooth current through the delecting coils.

As shown in Fig. l, the defiecting coils preferably are coupled to the deflecting circuits 4 and 6 through transformers I9 and 2|, respectively. This is almost a necessity when a winding of the character shown in Fig. 2 is employed, since the comparatively low frequency vertical deflecting current flows through the same coils as the comparatively high frequency horizontal deflecting current. it follows that if the impedance of the deflecting winding is correct for the horizontal defiecting circuit it will be much too low for the vertical deflecting circuit. The impedance of the coils, therefore is effectively increased by means of the transformer 2|. The transformer I9 for the horizontal deflecting circuit may be omitted, if desired, or the deflecting coils may be given the proper impedance for the vertical deflecting circuit and a transformer employed only for coupling the horizontal defiecting circuit to the deflecting coils.

In the particular embodiment of my invention being described, all of the deflecting coils have the same number of turns. As will be explained later, however, it may be desirable to have fewer turns on certain coils than on others.

It may be noted that as a modification of the deecting yoke shown in Fig. 2, the direction of winding of the coils in two opposing quadrants of the yoke may be reversed. For example, the coils on the two poles adjacent to the character SR and the coils on the two poles adjacent to the character NR may have their direction of winding reversed. In that case the deflecting fields (horizontal and vertical) will be rotated 90 degrees from their position illustrated in Fig. 2.

The eight-pole deflecting yoke illustrated in Fig. 2 will give a much more uniform deecting field in the plane of the yoke than will the conventional four-pole deflecting yoke. This is apparent from an inspection of the polarity marking of the pole pieces at their inner ends, this marking being for the condition, of horizontal deflecting current flowing in the direction indicated by the arrows when there is no flow of vertical deecting current.

The effect of this increase in uniformity of the deecting field will be seen by a comparison of the deflecting patterns shown in Figs. 4a and 4b. These patterns are those produced on the fluorescent screen II of the cathode ray tube as the screen is scanned by the cathode ray. The pattern indicated in Fig. la is a type of pattern which is obtained by defiecting the cathode ray With the conventional four-pole defiecting yoke. The deilecting pattern indicated in Fig. 4b in solid lines is the pattern which is obtained when deflecting the cathode ray with the deflecting yoke shown in Fig. 2. It will be noted that this pattern, which is one that was actually obtained in practice, corresponds very closely to the perfect rectangle indicated by the dotted lines. While there was a certain amount of over-correction which reversed the curvature of the sides of the pattern, it was not great enough to be very objectionable.

What is perhaps an even more important benefit derived from my multi-pole defiecting yoke is that there is less defocusing of the cathode ray at the fluorescent screen during deflection.

If desired, my ring or closed type of winding illustrated in Fig. 2 may be applied to a deflecting yoke having only four pole pieces. Obviously, however, the yoke structure illustrated is preferable because of the great increase in the uniformity of the defiecting field.

Referring to Fig. 3, this embodiment of the invention includes a magnetic core 22 which may be identical with the core employed in the modication shown in Fig. 2. In this embodiment of the invention the pole pieces 23 and 24 will be referred to as the main vertical defiecting pole pieces, the pole pieces 26 and 28 will be referred to as the main horizontal deilecting pole pieces and the pole pieces 29, 3|, 32 and 33 will be referred to as the correcting or shading pole pieces.

The main vertical deflecting coils 34 and 36 may be wound on the pole pieces 23 and 24 and connected in series in the usual manner. Likewise, the main horizontal deilecting coils 3l and 38 may be wound on the horizontal delecting pole pieces 26 and 28 and connected in series in the usual manner. The letters N and S at the inner ends of the pole pieces indicate their polarity as the time deflecting current is flowing in the direction indicated by the arrows.

Each shading pole has two windings thereon, one winding being connected in the vertical deecting circuit and the other winding being connected in the horizontal delecting circuit. Thus it will be seen that the windings 39 and 4| on the two upper shading poles 3| and 32 are connected in series with each other and in parallel with the main vertical defiecting windings 34 and 36. Likewise, the windings 42 and 43 on the two lower shading poles 26 and 33 are connected in series with each other and in parallel with the main vertical deflecting coils 34 and 36. The direction of winding of the coils 39 and 4I is the same as that of the main deflecting coils 34 and 36, respectively. Likewise, the direction of winding of the coils 42 and 43 on the lower shading poles is the same as that of the main deflecting coils 34 and 36, respectively.

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Referring now to the auxiliary windings in the horizontal deecting circuit, the coils 44 and 46 on the right hand shading poles 32 and 33 are connected in series with each other and in parallel with the main horizontal deiiecting windings 3l' and 38. Likewise, the coils 4l and 48 on the left hand shading poles 29 and 3l are connected in series with each other and in parallel with the main horizontal deecting windings 31 and 38. As in the case of the windings in the vertical deflecting circuit, the windings 44 and 48 on the two upper shading poles 3| and 32 are wound in the same direction as the horizontal deecting winding 3l and the windings 45 and 4l on the other shading poles are wound in the same direction as the horizontal deflecting coils 38.

In one preferred embodiment of the invention, each coil contains the same number of turns. Therefore, each shading pole has thereon twice as many turns as the main deflecting poles. It has been found that this embodiment of my multi-pole delecting yoke gives the same improved results as to the shape of the deecting pattern and as to reduction in defocusing of the cathode beam as does the deflecting yoke previously described.

It will be understood that although I have described two embodiments of my invention in which each winding contains the same number of turns, it may be preferred to employ a different number of turns on certain pole pieces in order to obtain a deflecting pattern which approaches a rectangle still more closely and which still further reduces defocusing of the cathode ray. Furthermore, it will be apparent that still more satisfactory results may be obtained by utilizing a deflecting yoke with more than eight pole pieces.

From the foregoing description it will be apparent that various modifications may be made in my invention without departing from the spirit and scope thereof and I desire therefore that only such limitations shall be imposed thereon as are necessitated by the prior art and set forth in the appended claims.

I claim as my invention:

l. A deecting device for a cathode ray tube, said device comprising a pair of diametrically opposed deflecting coils so connected that their opposing poles are of unlike polarity, and a second pair of diametrically opposed deflectng coils so connected that their opposing poles are of unlike polarity, adjacent poles of said pairs being of like polarity, said coils being so located that the axis of one pair of coils and the axis of the other pair of coils intersect at an angle which is substantially greater than zero degrees and less than 9) degrees.

2. A deilecting device for a cathode ray tube, said device comprising a pair of diametrically opposed deflecting coils so connected that their opposing poles are of unlike polarity, and a second pair of diametrically opposed deflecting coils so connected that their opposing poles are of unlike polarity, adjacent poles of said pairs being of like polarity, said coils being so located that the axis of one pair of coils and the axis of the other pair or coils intersect at an angle which is substantially greater than zero degrees but which is not greater than 45 degrees.

3. A deflecting device for a cathode ray tube, said device comprising a pair of diametrically opposed deecting coils, a second pair of diametrically opposed deflecting coils, the axes of said pairs of coils intersecting at an angle of substantially 90 degrees, said coils being connected in series, vertical deflecting input leads connected to said series connected coils at diametrically opposed points whereby two adjacent coils are in parallel with the other two adjacent coils with respect to said leads, and horizontal deflecting input leads connected to said series connected coils at diametrically opposed points substantially 90 degrees from said rst-mentioned points whereby two adjacent coils are in parallel with the other two adjacent coils with respect to said horizontal deilecting leads, said coils being wound in such direction that current supplied through either said vertical deiiecting input leads or through said horizontal deiiecting input leads causes opposing poles of diametrically opposed coils to be of opposite polarity.

4. A deflecting device for a cathode ray tube, said device comprising a magnetic core having at least eight pole-pieces located in four diametrically opposed pairs, a deflecting coil on each of said pole-pieces, said coils being connected in series to form a closed ring circuit, vertical deflecting input leads connected at diametrically opposed points on said ring circuit, and horizontal deflecting input leads connected at diametrically opposed points on said ring circuit which are substantially 90 degrees from said first-mentioned points, said coils being wound in such direction that current supplied through either said vertical deflecting input leads or through said horizontal deflecting input leads causes opposing poles of diametrically opposed coils to be of opposite polarity.

5. A deecting device for a cathode ray tube, said device comprising a magnetic core having at least eight pole-pieces located in four diametrically opposed pairs, one pair of diametrically opposed pole-pieces being the main vertical deflecting pole-pieces, another pair of diametrically opposed pole-pieces being substantially 90 degrees from said main Vertical deflecting pole-pieces and being the main horizontal defiecting pole-pieces, the remaining pole-pieces being correcting or shading pole-pieces, vertical delecting coils on said main vertical deecting pole-pieces and on said shading pole-pieces, said vertical deflecting coils being connected to produce a vertical deflecting eld in response to vertical deecting current supplied thereto through a pair of leads, and horizontal deflecting coils on said main horizontal deflecting pole-pieces and on said shading pole-pieces, said horizontal deflecting coils being connected to produce a horizontal deflecting eld in response to horizontal delecting current supplied thereto through a second pair of leads.

IOU'RY G. MALOFF.

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