AU480570B2 - Magnetic beam adjusting arrangements - Google Patents

Description

3 65 n2 This invention relates generally to magnetic

arrangements for beam position adjustment in a multiple-

beam cathode ray tube, and particularly to magnetic

arrangements of such character which may be employed,

for example, to effect static convergence of the plurality.

of electron beams in an in-line, tri-beam, shadow-mask

color kinescope.

In a tri-beam color kinescope employing an in-

line configuration, the electron beam sources are aligned

to originate beam paths having axes lying essentially in

a common plane, with a central beam path oriented in

registry with the tube neck axis and with respective

outer beam paths symmetrically disposed on opposite

sides of the central beam.

For proper picture reproduction, it is desired

that the three beams strike coincident regions of the

phosphor screen of the kinescope. While the gun structures

of the kinescope ideally are designed to effect such

convergence of the beams at the screen center in the

absence of beam deflection, practical tolerances in the

manufacture of the kinescope and associated components

dictate the need for associating with the kinescope

suitable means for correcting a range of center-of-screen

misconvergence errors that may be encountered in actual

practice.

Adjustable magnetic fields are usually employed

in effecting the requisite static convergence adjustments,

and the typical commercially employed arrangement, for

both in-line and delta gun configurations, has involved

the use of adjustable magnets in association with field-

48 0,570

365 n2 directing pole piece structures outside and within the

neck of the kinescope. The presence of magnetic

pole piece structures for convergence purposes in

close proximity to the neck region enclosed by the

deflection yoke poses a problem of undesired inter-

actions between the fields associated with the respect-

ive structures.

According to the present invention there

is provided the combination comprising:

tri-beam color kinescqpe having a

cylindrical neck enclosing a trio of in-line beam

paths, a cerral one of said in-line beam paths

substantially coinciding with the longitudinal axis

of said neck with the remaining outer ones of said

in-line beam paths being substantially symmetrically all disposed on opposite sides of said axis, and with the of said in-line beam paths traversing a region of

interior of said neck which is free of magnetizable

structure; eoomprig

a first adjustable magnetic field producing

means mounted on said neck forcausing mutually opposing

shifts of said outer beam paths in said region without and substantially disturbing said central beam path;

a second adjustable magnetic field

producing means mounted on said neck for causing

shifts of said outer beam paths in the same direction

in said region without substantially disturbing said

central beam path.

The preferred embodiment is directed the to an adjustable magnet arrangement facilitating

48 0,570

50,365 n2 achievement of static convergence of in-line beams

without the use of internal field-directing pole

piece structures. Provision is made for the establish-

ment of adjustable magnetic fields of two different

characters in axially spaced regions of the tube neck,

one field character being such that it oppositely

intersects the respective outer beam paths while

having negligible magnitude in the central beam

vicinity, and the other field character being such that

it intersects with similar direction the respective

outer beam paths while also having negligible magnitude

in the central beam vicinity. By appropriate adjust-

ment of the orientation, polarity and magnitude of the

respective fields,opposite-direction shifts of the

positions of the outer beams, and/or like-direction

shifts of the positions of tle outer beams, may be

carried out, as required, to bring the outer beams

in registry with the central beam at the center of

the screen.

In accordance with illustrative

embodiments of the present invention, quadripolar

(4-pole) magnet structures are employed for field

establishment of the first-named (differential effect

on outer beams) character, while

48 0,570

3 6 5 n2 sextipolar (6-pole) magnet structures are employed for field outer establishment of the second-named (common effect on

beams) character. Adjustably positioned PM (permanent (electromagnet) magnet) structures and adjustably energized EM the 4-pole structures are both feasible for realization of

and 6-pole magnet systems.

In an illustrative PM arrangement, a pair of

juxtaposed 4-pole magnet rings and a pair of juxtaposed axially 6-pole magnet rings are rotatably mounted about presence spaced regions of the tube neck (free of the

of internal magnetizable structures). Each of the 4-pole

about the rings has four poles symmetrically positioned

ring periphery and alternating in polarity; i.e.,

with reference to a given north pole location thereon, 0 0 0 N-180 and S-270 the remaining pole locations are: S-90 symmetrically Each of the 6-pole rings has six poles in positioned about the ring periphery and alternating

polarity; with reference to a given north pole location 0 0 S-60 N-120 thereon, the remaining pole locations are: 0 S-180 0 N-240 0 and S-300 Conjoint rotation of the

rings of a pair alters the direction of the resultant of beam shifts, while differential rotation of the rings

a pair alters the beam shift magnitude.

In use of the above-described PM arrangement,

an additional pair of rotatable magnet rings, of a bipolar

(2-pole) form, may conveniently be supported on a common

mount with the other ring pairs, the additional ring

pair providing a facility for commonly shifting all three

beams for conventional purity correction purposes. While

the precise locations of the respective ring pairs along 480,570

365 n2 the tube neck axis to the rear of the deflection yoke

does not appear to be critical, an order of locations

which places the 6-pole ring pair centrally, with the 4-pole rings to the fore and the 2-pole rings to the rear,

appears advantageous for readily obtaining adequate

adjustment sensitivity for all of the desired fields other location orders, however, are recognized as being

feasible.

Desirably, in the above-described PM magnet arrangement, realization of the desired 4-pole and 6-pole

magnet systems is effected by employment of low permeability

magnetic material (such as barium ferrite) to minimize

disturbance of, or other interaction with, the deflection

yoke field. This may be of particular concern in one contemplated application of the present invention where the

design of the color kinescope and associated deflection

yoke are such as to substantially maintain within tolerances acceptable to an average viewer) the center-of-

screen convergence conditions throughout the scanning of a

raster. The described arrangementsZIf tiy present invention

are particularly suitable for such application by providing

means for readily obtaining accurate center-of-screen conver-

gence with structures suffering little or no interference

from fringe yoke fields, and, in turn, causing little or

no disturbance to the formation of precision yoke fields

suitable for convergence maintenance.

In the aforementioned application,lf the prcnt invention, the array of 2 -pole, 6-pole and 4-pole magnet ring pairs constitute the only neck components (exclusive

of the deflection yoke apparatus) required in set-up and

6 48 0,5 u

50.3 65 n2 operation of the color kinescope.

r1 f t h .7h oboto.vnnp -A-,2Argp g e present

in invention will be (e description the art upn a reading of the following detailed which: and an inspection of the accompanying drawings, in FIGURE 1 is a side elevation view of a color position kinescope assembly incorporating PM-type beam of adjusting apparatus in accordance with an embodiment

the present invention; FIGURE 2 is a sectional view along the line 2-2

of FIGURE 1, simplified to omit a showing of structure

within the kinescope neck; FIGURE 3 is an exploded perspective view of adjusting several magnet ring elements of the beam position

apparatus of FIGURE 1; FIGURES 4a, 4b and 4c are diagrammatic showings

illustrating various directions of beam position shifts 4-pole obtainable with various rotational positions of

magnet ring elements of the FIGURE 1 apparatus; FIGURES 5a, 5b and 5c are diagrammatic showings shifts illustrating various directions of beam position 6-pole obtainable with various rotational positions of

magnet ring elements of the FIGURE 1 apparatus;

FIGURES 6a, 6b and 6c are diagrammatic showings shifts illustrating various directions of beam position of 2-pole obtainable with various rotational positions

magnet ring elements of the FIGURE 1 apparatus; 7 48 0,570

3 65 n72 FIGURES 7a and 7b are further diagrammatic

showings, illustrating how differential rotation of

4-pole magnet ring elements from their FIGURE 4a

positions affects beam shift magnitude;

FIGURES 8a and 8b diagrammatically illustrate

4-pole electromagnet structures that may be employed

pursuant to an EM modification of the FIGURE 1 embodiment

of the present invention.

In the side elevation view of FIGURE 1, an

in-line, tri-beam, shadow-mask color kinescope

having at its base end a cylindrical neck section 21

and at its viewing end a funnel portion 23, is illustrated

in assembly with associated external neck components.

The latter include deflection yoke apparatus 27 (not

shown in detail) encircling the forward end of the

kinescope neck 21 an and adjoining flared portion of

the funnel section 23.

To the rear of the deflection yoke 27 are

the remaining neck components, in the form of six rotatable

magnet rings 30A, 30B, 40A, 40B, 50A and 50B mounted

on a common (non-magnetic) cylindrical support 70 encircling

the neck 21. As better indicated in the sectional view of

FIGURE 2, which shows the front face of the forwardmost

ring 50B, each ring is formed with a pair of projecting

tabs 51B, 52B) to facilitate manual adjustment of

the rotational position of the ring about the support

Details of the internal structure of the kinescope neck

480,570

50.365/ 2 have not been shown in the sectional view of FIGURE 2 to

simplify the drawing, but nominal beam axis locations I,

II and III have been shown within the tube neck to indicate

the in-line configuration of the beam paths; the central

beam axis II is shown as substantially coincident with the

tube neck axis. The interior of the tube neck 21 encircled

by the magnet rings is free of magnetic pole pieces or other

magnetizable structures.

The inner diameter of support 70 is of sufficient

width to permit the support to slide over the tube neck 21.

A clamping strap 80 provides means for securing the support

in a desired fixed position on the neck 21. Axially

spaced (nonmagnetic) positioning rings 60, suitably secured

to the support 70, establish a trio of appropriately spaced

gaps along the length of the support 70 for occupancy by

the rotatable rings in respective pairs (30A 30B; and 50A, 50B). Thin washers (not illustrated) of

suitable material paper) may be provided between the

rings of each pair to facilitate independent ring rotation.

In the simplified exploded view of FIGURE 3,"

only the magnet rings (minus their tabs) are shown in order

to illustrate the magnetization pattern associated with

each of the rings. Each of the rings 30A, 30B of the rear-

most pair has a two-pole magnetization pattern in which

a north pole location is diametrically opposed to a south

pole location. Each of the rings 40A, 40B of the central

pair has a six-pole magnetization pattern, with the poles

equally spaced (at 600 intervals) about the ring periphery

and alternating in polarity. Each of the rings 50A,

of the forwardmost pair has a four-pole magnetization 9 480.570

50,365 /72 pattern, with the poles equally spaced (at 900 intervals)

about the ring periphery and alternating in polarity.

The diagrammatic showing of FIGURE 4a illustrates

the nature of the beam position shifts that result from the

fields of the 4-pole ring pair (50A, 50B) for a particular

orientation thereof. In the orientation of FIGURE 4a, ring

is positioned with its north poles directly above and

below the axial beam location II; ring 50B is similarly

positioned (whereby the fields of the two rings are

similarly directed, and are fully aiding). With the indicated orientation, the field at beam location I is

laterally directed with a polarity producing a downward

shift of the electron beam at location I (electron motion

being into the plane of the paper in the views of FIGURES 4a,

et seq.). The field at beam location III is also laterally

directed but with opposite polarity, producing an upward

shift of the electron beam at location III.

In the orientation of FIGURE 4b, rings 50A and

have both been rotated 450 counterclockwise from their

FIGURE 4a positions. In the FIGURE 4b positions, the field

direction at location I is vertically downward while

the field direction at location III is vertically upward;

the resultant beam position shifts are laterally leftward

at location I and laterally rightward at location III.

FIGURE 4c illustrates that a further counterclockwise

rotation (of approximately 22.50) of both rings results

in opposite diagonally directed beam position shifts

(upward and rightward at location I, and downward and left-

ward at location III)..

It will be noted that no beam position shift is

480.570

365n2 indicated for the electron beam at the axial location II

in any of FIGURES 4a, 4b or 4c. This follows from the fact

that the central region of the aperture of the 4-pole rings

is substantially field free, whereby a beam at the axial

location II is substantially unaffected by the 4-pole

rings no matter what their orientation may be. The

quadripolar field provided by rings 50A, 50B thus constitutes

a facility for introducing, in any required direction,

equal-but-opposite shifts of the outer beams of an in-line

trio without disturbing the central, axial beam (which

may thus serve as a reference for the desired spot registry

at the kinescope screen).

The diagrammatic showing of FIGURE 5a illustrates

the nature of the beam position shifts that result from

the fields of the 6-pole ring pair (40A, 40B) for a

particular orientation thereof. In the orientation of

FIGURE 5a, ring 40A is positioned with a pair of diametrically

opposed poles in horizontal alignment with in-line

locations I, II and III, the north pole of the pair being

adjacent location I;ring 40B is similarly positioned. With

the indicated orientation, the field direction at location

I is lateral with a polarity producing an upward shift

of an electron beam at location I; the field direction at

location III is also lateral and with like polarity, this

also producing an upward shift of an electron beam at

location III. FIGURE 5b illustrates that a 300 counterclock-

wise rotation of rings 40A and 40B from their FIGURE

positions results in laterally leftward shifts at both of

the locations I and III. FIGURE 5c illustrates that a

smaller degree of counterclockwise rotation 11 480,570

3 65 7n2 results in like diagonally directed shifts at locations I

and III.

As in the previous 4-pole ring case, no motion

is shown for a beam at the axial location II; again,

the reason is that the central region of the apertures of

the 6-pole rings is substantially field free. The sextipolar field provided by rings 40A, 40B thus constitutes

a facility for introducing, in any required direction,

equal-and-common shifts of the outer beams of an in-line

trio without disturbing the central, reference beam.

In contrast with the previously described effects

of the 4-pole and 6-pole rings, the 2-pole rings 30A and

have an effect on all three beams. This is illustrated

in FIGURE 6a where common lateral shifts of all three

beams result from a vertical orientation of the poles of 2 the -pole rings, in FIGURE 6b where common vertical

shifts of all three beams result from a lateral orientation

of the poles of the 2-pole rings, and in FIGURE 6c where

common diagonal shifts of all three beams result from a

diagonal orientation of the poles of the 2-pole rings.

With the noted common shift effect for all three

beams, the bipolar field provided by the 2 -pole rings

and 30B constitutes a facility for adjusting the angles

of approach of the trio to the kinescope's shadow-mask

to ensure landing of each on the appropriate phosphor

area to establish optimum "purity").

In all of the illustrations of FIGURES 4, 5 and 6,

like positioning of each ring of a pair has been assumed.

Such relationship provides maximum magnitude for the

associated beam shift effects. FIGURES 7a and 7b illustrate

12 480,570

3 6 5 7n2 from how relative rotation of the rings of a pair away

direct alignment introduces a reduction of the magnitude

of the associated beam shift effects. Chosen for illustration

purposes are the 4-pole rings 50A and 50B. In FIGURE 7a,

from the 4-pole ring 50A has been rotated 150 clockwise has been its FIGURE 4a position, while the 4-pole ring 50B position. rotated 150 counterclockwise from its FIGURE 4a in FIGURE As suggested by the arrow directions and lengths III are 7a, the beam shift directions at locations I and

the same as in FIGURE 4a but the beam shift magnitudes

are both reduced. This magnitude reduction effect of a accompanying the "spreading" of the magnet rings the like pair will be familiar to those acquainted with

use of prior art purity ring pairs or centering ring herein. pairs, and should not require further explanation

While PM structures have been described above be for producing the desired field patterns, it will with appreciated that such patterns may also be produced

EM structures. FIGURES 8a and 8b respectively illustrate

a pair of four-pole EM ring structures, 50A' and

each having four coils-symmetrically positioned about Ring its periphery, with adjacent coils oppositely wound.

as shown in FIGURE 8a, is fixedly positioned with

its poles in the orientation of FIGURE 4a to introduce I and III. oppositely directed vertical shifts at locations

Ring 50B', as shown in FIGURE 8b, is fixedly positioned

with its poles in the orientation of FIGURE 4b to introduce

oppositely directed lateral shifts at locations I and III.

By adjusting the polarity and magnitude of the current

flowing serially in the coils of the respective rings 13 480,570

3 6 5 n2 (through tap adjustments of the respective potentiometers

and 100), one may duplicate any of the effects provided

by the rotations of the PM rings 50A, 50B. It will be

recognized that comparable techniques may be employed with

six-pole EM ring structures to duplicate the effects provided

by the rotation of the PM rings 40A,

As previously indicated, the illustrated order

for the respective bipolar, sextipolar and quadripolar

fields is preferred, placing the sextipolar field centrally

to maximize its effectiveness. It may also be noted that

there is a concomitant preferred order of field adjustment

to minimize retouching requirements. Preferably the

bipolar field is adjusted first to optimize purity, estab-

lishing the position of the reference beam. Thereafter,

the sextipolar field is adjusted to provide the required

common shifts of the outer beams relative to the axial

beam. Finally, the quadripolar field is adjusted to provide

the required opposing shifts of the outer beams, necessary

to achieve final registry. Such order of adjustment (in

the order of location along the beam path) has the

advantage that a given field adjustment does not alter

the beam locations in the region of a previously adjusted

field.

Illustratively, a low permeability material, such

as barium ferrite, may be used in forming the several

magnet rings of the FIGURE 1 assembly to minimize undesired

interactions between the deflection field and the

convergence and purity fields. However, for the illustrated

order of ring pairs, which places the purity rings

and 30B in a remote location relative to the yoke 27, this

14 48 0.570

3 6 5 n2 of the precaution may readily be omitted in the case

purity rings; a more inexpensive material, such as rings a suitable steel, may be used for the purity

with little adverse consequence.

It will be appreciated that conditions may be

encountered in practice where no quadripolar field correction

and/or sextipolar field correction is required. Reduction

of the shift effect of any of the ring pairs may readily be

eliminated by aligning the rings of a pair in cancelling

relationship, as shown, for example, in FIGURE 7b.

480,570

Claims (1)

1. 50,365/7n2 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1. The combination comprising:

   a tri-beam color kinescope having a cylindrical

   neck enclosing a trio of in-line beam paths,

   a central one of said in-line beam paths substantially

   coinciding with the longitudinal axis of said neck with

   the remaining outer ones of said in-line beam paths

   being substantially symmetrically disposed on opposite

   sides of said axis, and with all of said in-line beam

   paths traversing a region of the interia of said neck

   which is free of magnetizable structures,

   a first adjustable magnetic field producing means

   mounted on said neck for causing mutually opposing

   shifts of said outer beam paths in said region without

   substantially disturbing said central beam path.; and

   a second adjustable magnetic field producing means

   mounted on said neck for causing shifts of said outer

   beam paths in the same direction in said region without

   substantially disturbing said central beam path.

   2. The combination as claimed in claim I, wherein

   said first field producing means comprises means for

   developing a quadripo;lar field pattern in said region;

   and

   said second field producing means comprises

   means for developing a sextipolar field pattern in said

   region.

   48 0,570

   50,365 n2 3. The combination as claimed in claim 2,

   wherein said quadripolar field pattern developing means

   comprises a pair of four-pole magnet rings encircling

   a portion of said region; and

   said sextipolar field pattern developing

   means comprises a pair of six-pole magnet rings encircling

   a second portion of said region axially spaced from

   said-first-named region.

   4. The combination as claimed in claim 3,

   characterized in that all of said magnet rings comprise

   individually rotatable permanent magnet rings.

   The combination as claimed in claim 3 or 4

   comprising:

   a cylindrical support encircling said neck

   of said kinescope, a pair of two-pole magnet rings, each

   magnetized across a ring diameter;

   said pair of four-pole magnet rings, each

   having poles, alternating in polarity, at 900 intervals

   about the ring periphery; and

   a pair of six-pole magnet rings., each

   having poles, alternating in polarity, at 600 intervals

   about the ring periphery;

   said ring pairs being mounted for rotation

   concentrically about said support at respective longitud-

   inally spaced locations on said support.

   48 0,570

   50,365 n2 6. The combination as claimed in claim

   comprising a deflection yoke mounted on said neck,

   said four-pole magnet rings being mounted on said

   support in a location adjacent to said deflection

   yoke, said two-pole magnet rings being mounted on

   said support in a location remote from said deflection

   yoke, and said six-pole magnet rings being mounted

   on said support in a location intermediate the locations

   of said two-pole and four-pole magnet rings.

   7. Magnetic beam adjusting arrangement substan-

   tially as hereinbefore described with reference to the

   accompanying drawings.

   DATED THIS 17th Day of JANUARY 1977.

   RCA CORPORATION By its Patent Attorneys:

   CLEMENT RACK CO.

   Fellows Institute of Patent Attorneys of Australia.

   480.570

   50.3 65 n2

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   48 0.570