US2155514A

US2155514A - Deflecting coil for cathode ray tubes

Info

Publication number: US2155514A
Application number: US52318A
Authority: US
Inventors: William A Tolson; Ioury G Maloff
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1935-11-30
Filing date: 1935-11-30
Publication date: 1939-04-25
Anticipated expiration: 1956-04-25
Also published as: DE767800C

Description

FIN/5H 2 Sheets-Sheet 2 I FIN/J ll HOE/Z WINDING I w. A. TOLSON in" AL DEFLECTING COIL FOR CATHODE RAY TUBES Filed Nov. :50, 19:55

50b 61b 6'21) 40a 41a 42a. 60a, 61a 52a 40b 41b 42115011516 April 25, 1939.

VENT/GIL WINDING 3 INVENTOHJ Vl illiam A. Tol-son/ H'I'TOHNEY Ioury G. Mal off .1:

Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE DEFLECTING COIL FOR CATHODE RAY TUBES aware Application November 30, 1935, Serial No. 52,318

11 Claims.

Our invention relates to cathode ray deflecting devices and particularly to deflecting devices of the electromagnetic type.

Progressive advancements in the art of television have imposed rather stringent requirements upon deflecting devices and deflecting circuits used for deflecting a cathode ray beam at both the television transmitter and the television receiver as regards linearity of deflection, em-

ciency of the deflecting devices and circuits, and defocusing of the electron beam. Deflecting coils have certain advantages over electrostatic defleeting plates, one advantage being that it permits a cheaper cathode ray tube construction since the cost of adding deflecting plates'to the tube is avoided. However, considerable difficulty was encountered in designing an electro-magnetic deflecting device which was eflicient and which i did not defocus the electron beam a considerable amount. It was finally discovered that the major portion of the defocusing of the electron beam was caused by the non-uniform flux distribution in the plane perpendicular to the electron beam. 28 An object of our-invention is to provide an improved deflecting device for a cathode ray tube. A further object of our invention is to provide a deflecting device which causes minimum defocusing of the electron beam. 30 A further object of our invention is to provide improved deflecting coils for a cathode ray tube. A still further object of our invention is to pro-- vide improved deflecting coils which produce a magnetic fleld having substantially uniform flux distribution in a plane perpendicular to the cathode ray.

In practicing our invention, we employ a distributed form of winding for the deflecting coils.

- In one embodiment of the invention, a laminated 40 iron core or yoke is employed, the core having slots therein in which the coils of the winding are placed. The distributed winding may be applied to the yoke by methods commonly employed in winding motors, but, as will be explained later, it is generally preferred to have the winding skip a slot, that is, have it non-uniformly distributed, in order to obtain a more uniform flux distribution.

Other objects, features and advantages of our invention will appear from the following description in which Figure 1 is a side view of a cathode ray tube having mounted thereon a set of deflecting coils 5 constructed in accordance with our invention;

Fig. 2 is an end view on an enlarged scale of the deflecting coils shown in Fig. 1;

Fig. 3 is a winding diagram of the deflecting coils shown in Fig. 2;

Fig. 4 is an end view of a set of deflecting co 5 wound in accordance with another embodiment of our invention;

Fig. 5 is a winding diagram of the deflecting coils shown in Fig. 4;

Fig. 6 is both a diagram of the flux distribution 10 mounted on a cathode ray tube of well known 20 design. The cathode ray tube comprises a highly evacuated envelope 60 having therein an electron gun 6! which includes a first anode 62. A second anode 63 is provided, which'consists of a metallic coating on the inner surface of the en- 25 -velope 60. The cathode ray. indicated by the dash-dot line 64, is focused electro-statically by means of the electro-static fleld between the first and second anodes. The electro-static focusing causes the electron beam to be concentrated to 30 a beam of very small diameter at the fluorescent screen 65 located at the end of the cathode ray tube. As previously stated, it is one of the objects of our invention to provide deflecting coils which do not disturb this focusing of the electron beam. 35 It will be understood that magnetic focusing may be substituted for the electro-static focusing.

Referring to Figs. 1 and 2, a laminated iron core or yoke 66 is provided, each lamination being a thin sheet of soft iron and having a plurality of slots cut therein. These laminations are stacked to form a core having a plurality of longitudinal slots therein which extend parallel to the longitudinal axis of the cathode ray tube.

In the specific embodiment being described, the 5 core has twelve slots which are indicated by the reference numerals I to I2. It will be understood that a more uniform magnetic fleld may be obtained by employing more slots with a corresponding increase in the number of coils. In Fig. 2, there are illustrated both a horizontal deflecting winding and a vertical deflecting winding, the horizontal deflecting winding consisting of coils 20a, Ila and no on the top side of the core 66 and the coils 26b, 2| b and 22b on the bottom side of the core. The vertical deflecting windings consist of the coils a, Ila and 324 on the right hand side of the core and the coils 80b, lib and 32b on the left hand side of the core. In Fig. 1, only the ends of the coil 32a can be seen.

The winding shown in Fig. 2. and more clearly shown in Fig. 3, is of the concentric coll type. Referring to the horizontal winding, it will be noted that there is no horizontal winding condoctor in the slots 4 and It. The conductors of the coil 20a are located in slots 3 and I, the slot 4 being skipped. The conductors of the coil Zia are in slots 2 and i, and the conductors of the coil 22a are in the slots l and 1. It will be noted that the three coils 200, Ma and 221; are located symmetrically with respect to the slot 4. Each coil preferably includes a plurality of turns, the number of turns depending upon the character of the circuit supplying the defleeting current and upon the frequency of occurrence of the deflecting cycle.

Referring to the lower portion of the horizontal deflecting winding, the conductors of the coil 20b are located in slots 9 and ii, the slot Ill being skipped. The conductors of the coil 2Ib are located in slots 8 and I! while the conductors of the coil 22b are located in slots 1 and i. It will be understood that the lower portion of the horizontal deflecting winding is a, duplicate of the upper portion, the

coils

20a and 20b containing the same number of turns, and, similarly, the coils 2m and 2| b containing the same number of turns. In the speciflc example here described, all the coils contain the same number of turns, anywhere from ten to several hundred, depending upon operating conditions, but it should be understood that in some instances the uniformity of flux distribution may be improved by having a diflerent number of turns in one coil than in another. For example, the coil 20a might have fifty turns and the coil 22a flfty-flve turns.

The way in which the coils are connected is shown in Fig. 3 where the horizontal deflecting winding is represented by the light lines and the vertical deflecting winding by the heavy lines. The winding diagram in Fig. 3 is in the form of a conventional motor winding diagram, it being assumed that the core and windings have been cut at the slot l2 and then flattened out. In order to simplify the diagram, only one turn per coil is shown. In Figs. 2 and 3, like parts are indicated by the same reference characters.

The vertical deflecting winding is the same, except, perhaps, for the number of turns per coil, as the horizontal deflecting winding and is located at right angles to it. On the right hand side,.the conductors of the coil 30a are located in the slots 6 and 1, the slot 1 being skipped. The conductors of the coil lla are located in the slots 5 and 9, while the conductors of the coil 32a are located in the slots 4 and ill.

On the left hand side, the conductors of the coil 30b are located in the slots 2 and II, the slot I being skipped. The conductors of the coil Slb are located in the slots 3 and II and the conductors of the coil 32b are located in the slots 4 and Ill.

The way in which the coils of the vertical deflecting winding are connected is shown in Fig. 3, where the ends of the conductors which are connected together are indicated by like reference characters.

Instead of employing the concentric coll winding described above, the deflecting coils may belap wound, as shown in Figs. 4 and 5. In the structure shown in these figures, the horizontal deflecting winding and the vertical deflecting winding are wound on a core similar to the one described above. The horizontal deflecting winding consists of the coils 40a, Ma and 42a at the top of the core and the coils 4.1:, Nb and 42b at the bottom of the core. The conductors of the coil a are located in slots 1 and I, the conductors of coil 4ia are located in slots 2 and I and the conductors of 42s are located in slots 3 and I. It will be apparent from the drawings that in slot 4 there are no conductors of the horizontal deflecting coils and that these coils are located symmetrically with respect to the slot 4. Likewise, the lower coils 40b, 4lb and 425 are located symmetrically about the slot I I which has no horizontal deflecting coil conductors located therein.

The winding diagram in Fig. 5 shows how the coils are connected, like parts in Figures 4 and 5 being indicated by the same reference characters. The ends of the windings which are connected together are indicated by the same reference characters in Fig. 5.

The vertical deflecting winding consists of the coils 500, Sin, and "a on the right handside of the core and'the coils 50b, Slb and 52b on the left hand side of the core. It will be evident upon inspection of Fig. 4 that the coils on the right hand side of the core skip the slot 1 while the coils on the left hand side of the core skip the slot I.

In Fig. 4, the connections for the vertical deflecting coils are indicated by the winding in heavy lines. The ends of the windings which are'to be connected together are indicated by the same reference characters; For example, the conductor end marked at the right hand side of Fig. connects to the conductor end marked c at the left hand side of Fig. 5.

Instead of employing laminations having open slots, as shown in Figs. 2 and 3, laminations having slots which are partially closed, as shown in Fig. 6,.may be employed. In some instances, this may aid in obtaining a more uniformly distributed flux.

Either of the distributed windings described above will produce a magnetic fleld which is substantially uniform in a plane at right angles to the longitudinal axis of the cathode ray tube,

that is, in the plane of the paper in Figs. 2 and 3. 'As a result. the deflecting coils do not disturb the focusing of the electron beam and the Y In Fig. 6 the flgures indicate the flux distribution in a plane taken through the center of the deflecting yoke or core 6, this plane being at right angles to the axis of the electron gun. The amount of flux is indicated in arbitrary units, each point at which a measurement was taken being marked by an x. The dotted rectangle ll indicates the region through which the cathode ray is deflected. In this region the variation in the amount of flux at different points does not exceed 5% of the minimum value.

It has been found that if the flux variation is of the order of 5% or less in a plane at right anglm to the beam, as shown in Fig. 6, the defocusing of the beam is so slight that a very high quality picture may be obtained. Even if the value of the flux varies as much as 10%, there will be only a small amount of defocusing of the beam as compared with that produced by conventional deflecting coils.

In Fig. 7 the dotted circle Ii represents the inner periphery of the core 66 and the dotted rectangle 12 represents the region through which the cathode ray is deflected. The flgures next to each point marked by an a: show the flux distribution for uniformly distributed windings. That is, this flux diagram shows the flux distribution of deflecting coils wound as shown in either Fig. 2 or Fig. 4 without skipping a slot. It will be noted that the flux varies from the value 44 in the center to the value 30 next to the inner periphery of the core. A variation of this magnitude will cause serious defocusing.

The flux diagrams in Figs. 6 and 7 are for the horizontal deflecting windings only which produce a" flux in the direction from the top to the bottom of the drawings, as indicated by the letters ings which are distributed. Also,- a fairly uniform flux distribution may be obtained by resorting to expedients other than that of distributing the windings.

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

We claim as our invention:

1. In combination with a cathode ray tube, electro-magnetic deflecting means, said means comprising a pair of diametrically opposed distributed windings which are concentrically wound.

2. In combination with a cathode ray tube having an electron gun, electro-magnetic deflecting means, said means comprising a pair of diametrically opposed distributed windings which are so distributed that their magnetic fleld is substantially uniform in a plane at right angles to the axis of said gun whereby defocusing of the oathode ray is minimized.

3. The invention according to claim 2, char acterised in that the said windings are concentrically wound.

4. The invention according to claim 2, characterised in that the said windings are lap wound.

5. In combination with a cathode ray tube having an electron gun, means including deflecting coils comprising distributed windings which are so distributed as to produce a magnetic deflecting field which, from point to point in a plane at right anglestotheaxisofsaidgunandintheregion through which the cathode ray is deflected, does not vary in value more than of the minimum value.

6. In combination with a cathode ray tube having an electron gun, means comprising diametrically opposed distributed windings which are so distributed as to produce a magnetic deflecting field which, from point to point in a plane at right angles to the axis of said gun and in the region through which the cathode ray is deflected, does not vary in value more than 10% of the minimum value.

'7. In combination with a cathode ray tube, electro-magnetic deflecting means, said means comprising a pair of non-uniformly distributed windings, each winding consisting of a plurality of coils, and each coil having a plurality of turns, certain coils having a different number of turns than other coils.

8. In combination with a cathode ray tube, a pair of deflecting coils, supporting means for said coils, said supporting means having an opening therein through which a portion of said tube may be passed, one coil of said pair comprising a plurality of distributed windings which are distributed about said supporting means on one side of said opening and the other coil of said pair also comprising a plurality of distributed windings which are distributed about the opposite side of said supporting means.

9. In combination, a cathode ray tube having therein means for producing an electron beam, and deflecting means for deflecting said electron beam, said deflecting means comprising a pair of diametrically opposed distributed windings.

10. In combination with a cathode ray tube, a deflecting yoke comprising a pair of deflecting coils, supporting means for said coils, said supporting means having an opening therein through which a portion of a cathode ray tube may be passed, one coil of said pair comprising a plurality of distributed windings which are distributed about said supporting means on one side of said opening and the other coil of said pair also comprising a plurality of distributed windings which are distributed about said supporting means on the opposite side of said opening, said windings being so distributed that in a plane at right angles to the longitudinal axis of said opening and within said opening their magnetic fleld is approximately uniform whereby defocusing of a cathode ray during deflection is minimised.

11. In combination with a cathode ray tube, a deflecting yoke comprising two pairs of deflecting coils, one of said pairs comprising two diametrically opposed distributed windings and the other of said pairs comprising two diametrically Opposed distributed windings located at right angles to said flrst pair whereby the flelds of said two pairs of coils are substantially at right angles to each other.

WILLIAM A. 101.808. IOURY G. MALOI'I'.