US2684455A

US2684455A - Symmetrical magnetic deflection system

Info

Publication number: US2684455A
Application number: US293479A
Authority: US
Inventors: Jr Arthur D Mccomas
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1952-06-13
Filing date: 1952-06-13
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20
Also published as: DE963262C; GB735259A; FR1080841A

Description

y 1954 A. D. M COMAS, JR 2,684,455

SYMMETRICAL MAGNETIC DEFLECTION SYSTEM Filed June 13, 1952 4 Sheets-Sheet 1 FIG. I

INVENTOR. ARTHUR D. MCCOMAS JR.

A TTOR July 20, 1954 A. D. M coMAs, JR 2,684,455

METRICAL MAGNETIC DEFLECTION SYSTEM 5- A glv s y 1954 A. D. M coMAs, JR 2,684,

SYMMETRICAL MAGNETIC DEFLECTION SYSTEM Filed June 13, 1952 4 heets-Sheet 4 INVENTOR. ARTHUR D. MCCOMAS JR.

MW, QZIZLZMG ATTORNE S Patented July 20, 1954 UNITED STATE SYMMETRICAL MAGNETIC REFLECTION SYSTEM Arthur D. McComas, J12, Cockeysville, M11, as-

signor to Bendix Aviation Corporation, Towson, Md, a corporation of Delaware Application June 13, 1952, Serial No. 293,479

13 Claims.

This invention relates generally to electromagnetic deflection systems for cathode ray tubes and more particularly to improved arrangements of such systems which provide novel disposition of the deflection coils around the neck of a cathode ray tube to provide improved deflection characteristics.

Prior art electromagnetic deflection systems have been arranged in various ways to provide uniformity of operation between the pairs of coils making up the orthogonal deflection system. The coils of these prior art systems have usually taken the form of cylindrical coil pairs orthogonally disposed or have been similar to a progressive lap winding in the manner used in the stators of rotating machines. In all such prior art arrangements, however, eflicient deflection has required that the coils providing the magnetic deflecting field in one direction be placed closer to the ments of the stationary coils the coupled impedance to the rotating coil is not independent of the rotational position thereof. The resultant variation of the relative impedance of the orthogonal deflection coils introduces nonlinearities in the deflection of the cathode ray which detracts from the utility of the display. rotating and stationary yoke combinations made in accordance with the present invention overcome this limitation and provide coupled impedance efiects which are independent of the relative position of the two yokes. Furthermore, the symmetry of the stationary yokes herein described provide improved deflection systems generally, due to the simplified driver circuits which may be used with such identical load devices and the improved deflection characteristics resulting from identical deflection force generating means for both deflection axes. With the methods of the present invention a high order accuracy of the magnetic axis of the coil pairs and of the angle between the axes of the deflection coordinates may be obtained by spiral adjustment of individual coils in both deflection pairs inwardly or outwardly as required.

Accordingly, it is the primary object of the present invention to provide an orthogonal electromagnetic deflection system having both pairs of coils symmetrically arranged with respect to the cathode ray tube upon which they are placed.

Another object is to tem employing deflection coils which are arranged with ccrresponding portions underlapping and overlapping adjacent coils in the deflection system.

A further object is to provide a deflection system having a closed spiral coil arrangement for equalizing the effective winding diameters of the coils of the system.

Another object is to provide multiple sets of spirally arranged coils for use in balanced driving systems and the like.

Another object is to provide spirally arranged coils in a deflection yoke with the windings thereof distributed to obtain magnetic fields having desired characteristics.

A further object is to provide sets of spirally arranged deflection coils which are oppositely directed for obtaining desired control of the magnetic field produced thereby.

Another object of the present invention is to provide a closed spiral fixed deflection coil system in combination with a concentric rotating coil deflection system for equalizing the coupled impedance therebetween.

A further object is to provide a combination rotating and fixed deflection coil system capable of producing a desired deflection irrespective of the rotational position of the movable coil for high sweep speeds.

A further object is to provide a new and improved method of sub-assembly for individual coils from an orthogonal pair deflection system such that the criticality of the final assembly of the orthogonal pair is greatly reduced.

Still another object is to provide an improved method of aligning the spiral coils of a plural axes deflection yoke for a predetermined relation.

These and other objects of the present invention are accomplished with a deflection yoke made up of orthogonal deflection coil pairs which are approximately semi-cylindrical in shape and which are mounted ofi-set with respect to the axis of the cathode ray tube with which they are used with a substantially equal amount of underlap and overlap between adjacent coils of the two pairs. Yokes constructed in this manner may be employed as stationary orthogonal deflection systems or combined with concentric rotating yokes for combined signal displays. 7

The invention may be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a perspective View of four adjacent coils formed into a deflection system of the present invention;

Fig. 2 is a sectional view taken in the vertical plane through the line 2-2 of Fig. 1;

provide a deflection sys- Fig. 3 is an end elevational view for a balanced pair deflection system in accordance with the invention;

Fig. 4 is a View in the natiu'e of a developed winding diagram showing the coils of Fig. 3 laid flat to illustrate the connections therebctween and including an enlarged view of one coil;

Fig. 5 is an end elevation showing a double deflection yoke in accordance with the present invention with oppositely directed spirals;

Fig. 6 is an end view of one pair of coils from each deflection system shown in Fig. 5 with representation of the component and resultant magnetic fields produced thereby;

Fig. 7 is an end elevation view of a fixed spiral deflection system with a rotating concentric pair of deflection coils;

Fig. 3 is a plan view of an arrangement for practicing the method of orthogonal sub-assembly of the invention;

Fig. 9 is a diagram useful in explaining the method of Fig. 8;

Fig. 10 is a plan view of an arrangement for practicing the method of aligning all of the coils of a spiral yoke; and

Fig. 11 is a sectional view of a pair of deflection coils with a modified winding distribution.

Referring now to Fig. 1, there is shown a pair of vertical deflection coils H, l2 and a pair of horizontal deflection coils l'3', I l. The individual coils H-M may be wound in any of the well known distributed arrangements for producing a desired distribution of the field therebetween. For simplicity of manufacture the individual coils may be wound and formed with a true semi-cylindrical inner contour, although it will be apparent that a true or approximate spiral inner contour may be employed, if desired. With the cylindrical construction of the coils H-i-4, the assembly, in accordance with the present invention, is made layoff-setting the coils of a pair by an equal amount in opposite directions with respect to the axis of the cathode ray tube upon which they are to be placed. A cylindrical container IE! or other suitable provision for supporting the coils in this manner is provided and the coils may then be secured thereto by suitable means with approximately an equal amount of underlap and overlap between adjacent coils. As is shown in Fig. 1, coil is underlaps coil H and overlaps coil I2, coil H underlaps coil l4 and overlaps coil 1-3, coil 14 underlaps coil 12 and overlaps coil II, and coil l2 under-laps coil [3 and overlaps coil f4.

Referring to Fig. 2' the arrangement of the coils IIM with respect to the neck of a cathode ray tube [5 will be apparent. With this arrangement the coil pairs H, H and 13, Himay be energized in any conventional manner to pro" vide an orthogonal deflection system, the performance of which will be that of one having equal effective winding diameters for each pair of coils; The substantially complete encirclement of the tube [5 by each pair of coilspermitsmaximum deflection sensitivity without introducing dissymmetry of the coil arrangement.

In Fig. 3, there is shown a deflection system which is essentially a double set of windings arranged in spiral relation, generally similar to the single set shown in Fig. 2. The vertical deflection system has inner windings t6, IT and outer windings I8, i9 and the horizontal deflection system has inner windings 2|. 22 and

outer windings

23, 24, all having the underl'ap and overlap relation of the present invention with respect to adjacent coils and the inner and outer sets being arranged to spiral in the same direction. This multiple set of windings is useful, for example, in obtaining push-pull operation of the deflection system, the connections for which may be best seen in Fig. 4. The whole assembly may be impregnated between the outer container I0 and an inner container 26* with a setable compound to provide a rugged structure and maintain the relative orientation of the coils.

Fig. 4 shows a yoke similar to that of Fig. 3 as it would appear if the various windings were peeled away from their assembled positions and laid fiat along the deflection axes with the outer set of coils placed farthest from the cathode ray tube 15. One connection which is suitable for using the windings iii-24 in push-pull operation is shown. All of the winding pairs are returned to a common supply source terminal 25. From the supply terminal 25. the coils i5, {'1 are serially connected to provide a north deflection pair, and coils ['8 I9 are serially connected to provide a south deflection pair. In like manner, coils 21, 22 are serially connected from the source 25 to provide an east deflection pair and coils 23, 24 are serially connected fora west. deflection pair. In the operation of the system. of Fig. l, the terminals N, S may be driven in push-pull to provide a north-south deflection and the terminals E. W may likewise be driven in push-pull to provide the east-west deflection. In such a system the deflection sensitivities of the outer coils may be adjusted to equal that of the corresponding inner pair of coils to obtain equal deflection sensitivities in opposite directions. The sensitivity adjustment could be achieved, for example, by providing an increased number of turns on the outer pair of coils l6, l9 relative to the inner pair i6, t1 and a corresponding adjustment for the E, VJ axis coils. The coil i8 is shown enlarged with a cosine distribution of the: separate hanks 3d of the coil: winding for providing a uniform. field distribution: and is representative of the construction which. is preferably used for the coils l"l--24.

In Fig. 5 a deflection yoke construction is shown having orthogonal pairs 26 which spiral outward in a clockwise direction surrounded by a set of orthogonal deflection coils 2'5 which spiral outward in a counterclockwise direction. The orthogonal deflection axes individual to the two sets are substantially symmetrical and the resultant field from the two sets is such as to produce cancellation of undesired components, as will be more fully described with reference to Fig. 6.

In Fig. 6 one pair of coils 26 and one pair 2'! of the oppositely spiraling deflection coil sets of Fig. 5 are shown. The oil-set or spiral arrangements of the coils 26 is such as to produce a magnetic field represented, for purposes of illustration with exaggerated curvature, by flux lines 28. The magnetic field produced by the coils 27 has oppositely directed flux lines 29. The resultant field from these two-components has flux lines 3 l which may be had with any desired degree of uniformity or' other desired field configuration by properly positioning and proportioning the coil pairs 26, '21. Localized magnetic flux 32 due to the end effect of the configuration of the coils 26 is substantially eliminated by a like opposite end effect flux 32" produced by the coils 21. In practice, it will generally be found possible to arrange the single direction spiral coil configuration of the present invention to produce satisfactory results without noticeable distortion due to the end effect flux 32. For example, for uniform fields the distribution of windings in the individual coils may be proportioned with the turns in the outward half slightly compressed with respect to the geometrical axis of the coil, as hereafter described with reference to Fig. 11. For extremely precise displays, however, or in special applications where some particular oleflecting fields are desired, the oppositely spiraling correction of end effect flux may be employed. When so used, the four

windings

26, 21 of Fig. 6 may be all serially connected and the number of turns in the windings 21 increased relative to the number in the windings 26 to provide equal deflection sensitivities or such ratio as is desired.

Referring now to Fig. '7, there is shown a stationary closed spiral yoke comprising a horizontal deflection pair 33 and a vertical deflection pair 34, together with a conventional rotating concentric pair of deflection coils 35, all positioned around the cathode ray tube IS. The rotating coils 35 may be energized, for example, by slip rings. Rotating and fixed deflection coil combinations are useful for ofl center sector displays or, for example, in combined automatic direction finder radar displays, wherein a directional indication of a particular aircraft is combined with a rotatable indication such as a planposition indication. In such displays used heretofore, it has been found that the impedance coupled between the rotating coil from the stationary coils varies with the relative position thereof.

For indications which are produced from a resultant deflection of the rotating and the orthogonal stationary coils, this condition produces nonlinearities because of the different impedances in the stationary pairs caused by the unsymmetrical coupling of impedance between these circuits and the coils 35. These unequal impedances cause the currents in coil pairs 33, 34 to be unequal, thus producing the undesired non-linearity. This effect is especially objectionable for fast sweeps. With the arrangement as shown in Fig. 7 however it has been found that the impedance coupling between the coils 35 and each of the pairs 33, as is substantially constant and independent of the rotational position of the coils 35 and hence the aforementioned non-linear deflection is eliminated.

The method of sub-assembly of coils will be described with reference to Fig. 8, where a schematic arrangement for the sub-assembly of adjacent coils 35, 3? is shown for use with a corresponding pair, not shown, to make an orthogonal yoke. The

coils

36, 31 are movably arranged upon a cam cylinder All which supports them in a manner identical with a final four coil assembly. Obviously, an assembly of four coils, two of which would be dummy coils, similar to that ofFig. 10 could be used to practice the method. of adjacent coil alignment to eliminate the need for the specially shaped cam cylinder 4%. The coils 36, 3? are positioned around a pair of crossed

loops

38, 39 which have previously been fixed in accurate orthogonal relation by well known null signal methods. Upon energization of the coil 38 from a signal generator 45 the coil 36 is moved until a null signal appears at the terminals thereof as measured by a high impedance voltmeter 46. The signal generator 45 is removed from the coil 38 and connected to the coil 39, whereupon the coil 31 is moved until a null signal is measured by the meter 46 at the thereof are perpendicular to each other.

terminals thereof. Ganged switching means 41 may be provided to facilitate the required changes in circuit connections. These adjustments may be repeated if desired and the coils 3B, 3! are then permanently secured in the relative position thus established, according to any of the well known coil manufacturing techniques. The method just described provides sub-assembly pairs of

coils

36, 37 which may be combined. with a similar pair adjusted in the same manner to form any of the deflection yokes of the present invention. The final assembly of these pairs will produce an orthogonal deflection system without extremely accurate alignment of the opposite fixed sub-assembly pairs, as will be ap parent from the description of Fig. 9.

In Fig. 9 the sub-assembly of coils 36, 3'1 is positioned upon a cylindrical support 20. The coil 3% will produce a magnetic field having axis 35 and the coil 3'! will produce a field having a magnetic axis 31 and these axes 36, 3'! are perpendicular as a result of the previously performed sub-assembly method described in connection with Fig. 8. Another fixed sub-assembly of coils 4!. 42 located approximately opposite the coils 36, 3'1 on the support 29 will produce magnetic fields having orthogonal axes 4i and 42. Upon energizing the

coils

38 and 42 in series, the magnetic fields 36 and d2 combine to produce a magnetic field axis t3. Similarly energizing coils 3i and 4! in series combines the magnetic field axes 3i and M to produce a magnetic field having an axis 54. These resultant magnetic fields l3 and M are orthogonal and provide orthogonal deflection forces for the oathode ray tube with which the yoke, comprising coils 35, 37, M, 42 mounted on the support 20, is used.

In Fig. 10 an arrangement is shown which is similar to that of Fig. 8, except that it is arranged for adjustment of both sets of coils of a deflection yoke. For this purpose the

perpendicular loops

38, 39 are positioned inside a cylindrical shell t8. Upon the outer surface of the shell 48, a set of coil pairs d9, 56 is arranged in interleaved relation as herein described. Connections are provided for selectively connecting the signal generator 45 to the loops 38, 3E and voltmeters 46, 45' to the individual coils of the

pairs

50, 48 by means of ganged switches iii. With this arrangement and with the switches 55 in the positions shown, the loop 39 is energized and the voltages induced in the coils 323 are measured by the voltmeters 46, t5. The coils 49 are both adjusted spirally to obtain null readings on the

voltmeters

46, 45 and the switches 5! are reversed. The loop 33 is then energized and the coils 56 are adjusted to obtain null voltages. These steps may be repeated, if required, until null conditions obtain in the respective coils for either switch position without further adjustment. The coils are then secured in their adjusted relative positions with a suitable binder or adhesive and assembled into a finished yoke of the type shown in Fig. 2. Yokes adjusted by this method, in addition to having the magnetic axes of the

pairs

49, 58 orthogonal, achieve a high order of colinearity of the fields of the individual coils of the pairs. In other words, the fields of the coils 49 approach colinearity as do the field of the coils 50 and the resultant fields The optimum adjustment of both of these characteristics is thus readily accomplished. I

As hereinbefore described, uniform turn distributions in individual coils may be employed or such variants as the cosine distribution or the like. For compensating the different spacing from the axis of the cathode ray tube E5 of the turns on the inner and outer portions of a spiral coil, the distribution of such turns may be varied in any desired manner. In Fig. 11, for example, there is shown a tube [5 with a pair of spiral coils 52, 53 disposed in accordance with the present invention. The hanks 5 55, 55 (groups of turns) make up coil 52 and the hanks 5'5, 58, 59 make up coil 53 and the distribution thereof is approximately cosinusoidal with respect to the center of the coils. The departure from a true cosine distribution is shown by the displaced positions of the portions of

hanks

55, 55 and 58, 59 on the outer portion of the

respective coils

52 and 53 with respect to the indicated positions 55', 55 and 58', 53' thereof for a true cosine distribution. The distribution in this case locates the hanks on the coils 52, E3 in the positions corresponding to symmetrical angular projections from the center of the tube i5. This shaped distribution of the outer hanks constitutes an effective cosine distribution with respect to the tube 55 for the spiral coil arrangement.

Many variations and modifications will be apparent to those skilled in the art in the light of the above teachings and are to be understood as being within the scope of the present invention.

What is claimed is:

1. An electromagnetic deflection yoke for a cathode ray tube comprising, a first pair of deflec-tion coils arranged for positioning on opposite sides of said tube, and a second pair of coils similarly arranged for positioning on opposite sides of said tube, the magnetic axes of said pairs being substantially perpendicular and each of the coils in a pair respectively overlapping one and underlapping the other or the coils of the other of said pairs.

2. A cathode ray tube deflection system comprising, a coil assembly having pairs of essentially diametrically opposed windings, each of said windings overlying a portion of one underlying a portion of the other of the windings peripherally adjacent thereto, and means for supplying deflection currents to said pairs.

3. A deflection coil assembly comprising, two pairs of essentially diametrically opposed wind-- ings, the magnetic axes of said pairs being substantially perpendicular and each of said windings overlyiir a portion of one and underlying a portion of the other of the windings forming the one of said pairs diverse from said each Winding.

4. A deflection system comprising, a coil assembly accordance with claim 3 encircled by a similar assembly in accordance with claim 3, the magnetic axes of said assemblies being substantially aligned, and means for energizing corresponding pairs of coils in said assemblies in pushpull signal relation, the outward progression of all coils in said assemblies having the same sense,

5. The system according to claim 4 in which the coils of the outside assembly have a greater number of turns than the corresponding coils of the inside assembly, whereby the deflection sensitivities of corresponding coil pairs is equalized.

6. A deflection coil assembly in accordance with claim 3 encircled by a similar assembly in accordance with claim 3, the magnetic axes of said assemblies being in approximate alignment and the outward progression of the coils in. one assembly being of opposite sense to that of the. other assembly.

'2. A deflection system comprising, a coil assembly in accordance with claim 6, and meansfor serially energizing corresponding pairs of coils in said assemblies.

8. A deflection assembly comprising, an assem-- bly in accordance with claim 3, and a pair of diametrically opposed deflection coilsmounted for rotation about the longitudinal axis of said windings.

9. A deflection coil assembly comprising, first and second pairs of approximately semi-cyclindrical coils, the coils of each pair being in concave opposition with said opposition being slightly ofi-set, and means positioning said pairs with the magnetic axes thereof substantially perpendicular and the coils of said pairs interleaved such that any coil of a given pair is partially inside of one coil and partially outside of the other coil of the pair diverse to said given pair and the remaining coil of said given pair is partially inside said other coil and partially outside said one coil.

10. A deflection assembly comprising, an assembly in accordance with claim 9 and a pair of diametrically opposed coils mounted for rotation about the approximate mean longitudinal axis of said semi-cylindrical coils.

11. The assembly according to claim 10 and including sliding contact means for energizing said rotating coils.

12. A deflection coil assembly comprising, first and second pairs of approximately semi-cylindrical coils of substantially equal size, the coils of each pair being in concave opposition with said opposition slightly oii-set, and means positioning said pairs with the magnetic axes thereof substantially perpendicular and the coils of said pairs interleaved such that any coil of a given pair is partially inside of one coil and partially outside of the other coil of the pair diverse to said given pair and the remaining coil of said given pair is partially inside said other coil and partially inside said other cell and partially outside said one coil.

13. A cathode ray tube deflection system comprising, stationary flrst and second pairs of essentially semi-cylindrical coils, the coils of each pair being in concave opposition on opposite sides of the central beam axis of said tube and slightly off-set in opposite directions with respect to said beam axis, said pairs being positioned with the magnetic axes thereof. substantially perpendicw lar and the coils of said pairs interleaved such that any coil of a given pair is partially inside of one coil and partially outside of the other coil of the pair diverse to said given pair and the remaining coil of said given pair is partially inside said other coil and partially outside said one coil, a pair of coils in concave opposition concentric with said axis and rotatable thereabout, and means for supplying deflection currents to said stationary and said rotatable coil pairs.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,155,514 Tolson et a1 Apr. 25, 1939 2,243,893 Blumlein June 3, 1941 2,395,736 Grundmann Feb. 26, 1946 2,420,156 Suchtelen May 6, 1947