US3302049A

US3302049A - Magnet means for correction of blue beam lateral deflection for color television receiver tubes

Info

Publication number: US3302049A
Application number: US277800A
Authority: US
Inventors: Lemke Eugene
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1963-05-03
Filing date: 1963-05-03
Publication date: 1967-01-31
Anticipated expiration: 1984-01-31
Also published as: BE647490A; NL146683B; NL6404843A; DE1219967B; GB1031187A

Description

Y' E. LEMIKE 3302,04

MAGNET MEANS FOR CORRECTION OF BLUE BEAM LATERAL DEFLECTION FOR COLOR TELEVISION RECEIVER TUBES Filed May 3, 1965 I N VENTOR. fYJGE'A/F [iMA P United States Patent G 3,302,049 MAGNET MEANS FOR CORRECTION OF BLUE BEAM LATERAL DEFLECTION FOR COLOR TELEVISION RECEIVER TUBES Eugene Lemke, Indianapolis, Ind., assignor to Radio Corporation of America, a corporation of Delaware Filed May 3, 1963, Ser. No. 277,800 4 Claims. (Cl. 313-75) The present invention relates to color television receivers. More particularly the present invention relates to a blue lateral deflection arrangement for a multi-beam cathode ray tube of a color television receiver.

Many color television receivers today utilize shadow mask color cathode ray tubes. The shadow mask tube has three electron guns and the screen of the cathode ray tube is arranged in a pattern of red, blue and green emitting phosphors. The electron beams from the three electron guns impinge respectively on only one of the red, green or blue phosphors. The three beams, hereinafter referred to as the red, green and blue beams respectively, are made to converge at the shadow mask. The particular phosphor which each beam contacts depends on the angle the beam makes with the shadow mask at the convergence point.

A number of different beam convergence arrangements have been tried to bring about the desired meeting of the three beams at a single point. By adjusting the beams in a radial direction it has been found that the intersection of two (such as, for example, the red and green) beams at the desired point can be accomplished. However, it is not always possible to make the third (such as, for example, the blue) beam converge at the intersection of the red and green beams by radially adjusting the blue beam. Therefore means have been provided for adjustng the blue beam in a lateral direction which permits the intersection of all three beams at a desired point.

One of the difficulties of the blue beam deflecting devices has been their rather large size. The convergence assembly is mounted exteriorly of the neck of the cathode ray tube and is arranged close to the end of the tube. The blue lateral deflection magnet is generally the closest component to the socket end of the tube and therefore, during servicing of the television receiver it may inadvertently be moved out of adjustment when the back cover of the receiver is replaced. By using the present invention it is possible to have a very small blue beam lateral deflection device positioned about the neck of the cathode ray tube to prevent inadvertent movement thereof and yet to permit accurate lateral adjustment of the blue beam for convergence purposes.

It is accordingly an object of the present invention to overcome the disadvantages of blue lateral deflection devices used in color television receivers today.

A second object of the present invention is to provide a blue lateral deflection device for the cathode ray tube of a color television receiver which is very small in size and yet permits accurate adjustment.

With the above objects in view the present invention contemplates a blue lateral deflection magnet arrangement for cathode ray tubes. The tube includes an envelope within which is mounted at least three electron guns one for each of the red, blue green beams, respectively. A pair of internal pole pieces made of magnetic material are arranged in the tube envelope spaced on opposite sides of the electron gun for the blue beam. A blue lateral deflecting member made of magnetic material is movably mounted exteriorly of the cathode ray tube envelope adjacent the internal pole pieces. The blue lateral deflecting member provides a magnetic flux at least part of which extends into the interior of the tube envelope. The member is movable between a first position wherein substantially all of the magnetic flux produced thereby and extending into the tube envelope passes through only one of the pair of pole pieces without affecting any of the beams produced by the electron guns and at least a second position. In the second position, the magnetic flux produced by the deflection member and reaching inside the tube envelope passes through the pair of pole pieces and affects only the blue beam.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof will best be understood from the following description of an illustrative embodiment when read in connection with the accompanying drawings in which:

FIGURE 1 is a schematic diagram of the deflection portion of a color television receiver partially in block form showing a sectional view of a cathode ray tube utilizing the present invention;

FIGURE 2 is a schematic showing of a method of magnetizing a blue lateral deflection member constructed in accordance with the principles of the present invention;

FIGURE 3 is a sectional view taken along the lines 33 of FIGURE 1 showing the blue lateral deflection member in its central position; and

FIGURES 4 and 5 are similar to FIGURE 3 showing the blue lateral deflection member in its two extreme positions on the cathode ray tube.

Referring to the drawings and more particularly to FIGURE 1, the cathode ray tube 10 has a glass cone portion 11 to which is attached a glass faceplate 12. A ranged on the inner surface of faceplate 12 is a luminescent screen 13 made up of dots of phosphors respective ly producing light of the different primary colors in which the image is to be reproduced upon impingement thereon of respective electron beams. Spaced from the luminescent area 13 is an aperture mask 14 containing an aperture for each of the primary color clusters used. For example if the primary colors are red, blue and green, each cluster would contain three phosphor dots respectively emitting red, blue and green light upon excitation.

Sshown converging at an aperture of the shadow mask 14 are three electron beams 16, 1'7 and 18. In order to obtain an accurate reproduction of the televised image it is desirable to have the three electron beams all converge at one point at the centers of the respective apertures.

The electron beams are produced at the opposite end of the cathode ray tube 10 in the neck portion 19. The neck 19 has a nonmagnetic envelope 21 made of glass, for example. Arranged within the glass envelope are three substantially similar electron guns for the cathode ray tube 10, one for each of the primary colors blue, red and green, respectively. The cathode for the electron beam, which is aimed at the blue emitting phosphor, is identified by the numeral 22 having an associated control grid 23, an accelerating electrode 24, a focussing electrode 26 and an ultor (or final accelerating) electrode 27. Except for the blue lateral deflect-ion member which will be described subsequently, the red and green electron guns are identical to the blue structure. There may also be a conductive coating inside the funnel or cone portion 11 electrically connected to the ultor 27 and to the phoshpors 12, 13, 14.

The video signals to be reproduced as an image are applied from the video amplifier (not illustrated) to the control grid 23 by means including a coupling capacitor 28. In order to avoid unnecessarily complicating the drawing the components of the television receiver which need not be described for an understanding of this invention have not been illustrated with the exception of the blocks 29 and 31, which represent respectively the vertical and horizontal deflection wave generators for the beams in the cathode ray tube. The complete details of a color television receiver in which the present invention may be embodied is shown in Color Television Service Data-File 1962 No. T6published by RCA Sales Corporation, 600 North Sherman Drive, Indianapolis, 1, Indiana.

The outputs of generators 29 and 31 are applied respectively by means of conductors 32 and 33 to the yoke 34 surrounding the neck of the cathode ray tube 10. The yoke 34 contains the conventional horizontal and vertical deflection coils to which the deflecting currents are applied to produce the deflecting magnetic fields for the electron beams passing therethrough.

Arranged about the neck of the cathode ray tube just behind the yoke 34 with respect to the screen is the static and dynamic beam convergence member 36. The purpose of member 36 is to deflect the electron beams passing therethrough in differing amounts depending upon the point of impingement of the electron beams on the luminescent screen. This corrects for any beam convergence errors that may be introduced due to such known factors as the flatness of the screen 13, for example, in accordance with the principles disclosed in such patents as No. 2,751,519 granted to A. \V. Friend on June 19, 1956.

As a general rule the assembly 36 includes both static and dynamic convergence magnets in a known manner. The static convergence magnet is generally a small permanent magnet mounted exteriorly of the tube envelope close- 1y adjacent to the beam it is to control. A typical static convergence magnet structure and arrangement on the cathode ray tube is shown in FIGURES 8 and 13 of the reference Service Data-File 1962 No. T6.

The dynamic convergence member generally includes an electromagnet for each electron beam. These electromagnets are mounted externally of the tube neck and are supplied with energizing current that vary with the different positions of the beams during the horizontal and vertical scanning periods. To increase the effectiveness of the electromagnets each one usually is provided with a pair of pole pieces mounted on opposite sides of the associated beam on the inside of the tube neck. A structure of this nature is shown in Patent No. 2,707,248 granted to H. C. Goodrich on April 26, 1955. These dynamic convergence electromagnets are energized from the vertical and horizontal deflection wave generators 29 and 31 as, for example, shown in FIGURE 47 of the reference Service DataFile 1962 No. T6.

Also mounted exterior-1y of the neck portion 19 of the tube 10 is a blue lateral deflection magnet 37. This arrangement may best be seen in FIGURE 3. The magnet 37 is shown arranged in the central portion of, and atop, the glass envelope 21 and supported in a nonmagnetic holder 38 which, together with the magnet 37, is urged against the enevolep 21 by means of a tension spring 39. The spring 39 and the holder 38 encircle the neck 19 of the tube 10. It can be seen in FIGURE 3 that the blue focussing electrode 26 is arranged between two radially spaced internal pole pieces 41 and 42 which are made of a magnetic material.

The magnetic member 37 is a rectangular parallelopiped which is permanently magnetized, by an apparatus such as partially shown in FIGURE 2, to have a magnetization geometry with the north and south poles at the opposite ends of the longitudinal dimension. This is indicated schematically in FIGURE 2 wherein only the north pole 35 and the south pole 45 of the magnetizing magnet are shown. The poles 35 and 45 may be the pole pieces of an electromagnet. To appreciate the actual size of the member 37 one such magnet which was found to operate satisfactorily was made of barium ferrite 0.4 long, 0.25" wide and 0.125" thick. The magnetic member 37 is arranged as shown in FIGURE 3 to produce a flux which cooperates with the internal pole pieces 41 and 42.

In operation, the accelerating potentials generally associated with the cathode ray tube of a color television receiver are applied to the cathode raytube 10 for generating electron beams in the electron gun structures thereof and directing the same along their respective path towards the screen 13. The video signals applied through coupling condenser 28 vary the intensity of the respective electron beams and the beams are deflected across the face of the screen 13 in synchronism with the transmitted image by the magnetic fields set up by the deflection yoke 34.

In the original installation of the cathode ray tube in the television receiver and possibly in subsequent servicing the static convergence magnets contained in the assembly 36 are generally moved radially towards and away from the aixs of the cathode ray tube to provide radial movement of the beam affected by its respective magnetic field. In this manner the red and green beams are caused to converge at the proper aperture of the shadow mask. If the blue beam also converges at the same point the blue lateral deflection magnet 37 may remain in the central position illustrated in FIGURE 3.

In this position it may be seen that substantially all of the flux entering the envelope 21 indicated by the lines 40 will be prevented by the pole piece 41 from reaching the path of the electron beam passing through the electrode 26. That is, substantially all of such magnetic flux flows from the north pole of the member 37 in the direction of the arrows through the pole piece 41 back to the south pole of member 37. Therefore the blue beam is not affected by the magnetic field set up by magnetic member 37.

In the event it is found that lateral adjustment of the blue beam is necessary or desirable, the member 37 may be moved through any intermediate position to either of the extreme positions shown in FIGURES 4 and 5.

In FIGURE 4, the magnetic member 37 has been moved to its extreme counterclockwise position. It can be seen that in this position the magnetic flux entering the envelope 21 of the cathode ray tube will flow from the north pole of member 37 through the internal pole piece 42 and upwardly in the direction of the arrows to the pole piece 41, back to the south pole of member 37.

In FIGURE 4 the electron beam for exciting the blue phosphor passes through the electrode 26 in a direction perpendicular to the plane of the drawing coming out of the drawing. The lines of magnetic flux 46 are shown to be substantially perpendicular to the path of movement of the blue electron beam. Therefore, the blue beam will be deflected to the left in the direction of the arrow 47. How much the beam is deflected will of course depend upon the intensity of the magnetic field and the velocity of the electrons passing therethrough. The intensity of the magnetic field may be adjusted even though the lines of flux are still maintained in the illustrated direction by moving the magnetic member 37 between its central position shown in FIGURE 3 and its counterclockwise extreme position shown in FIGURE 4.

Similarly in FIGURE 5 the magnetic member 37 is shown moved to its extreme clockwise position. The resulting lines of flux are directed out of phase with the arrangement shown in FIGURE 4 but are still perpendicular to the path of the electron beam passing through the electrode 36. The electron beam will therefore be laterally deflected to the right in the direction of the arrow 48. As before, different intensity fields may be obtained by shifting the member 37 between the central position and the clockwise extreme position shown in FIGURE 5.

In the central position of FIGURE 3 and the two extreme positions of FIGURES 4 and 5, as well as all the intermediate positions, substantially none of the lines of flux entering the envelope 21 are able to affect the electron beams'passing through the red or green beam focussing electrodes 51 and 52 respectively. That is, the pole pieces 41 and 42 cooperate to prevent any of the magnetic flux produced by the magnetic member 37 from affecting the electron beams which are not to be laterally displaced.

By use of the magnetic member 37 in cooperation with the internal pole pieces 41 and 42 it is possible to deflect the electron beam used for excitation of the blue phosphor laterally in either direction by varying amounts. It has been found for example that with the illustrated arrangement it is possible to obtain a total beam deflection on the face of a 70 color kinescope of $0.4. This is generally sufficient to meet most such color kinescope requirements.

If desired, of course, an arrangement such as has been described for the blue beam may be used for the red or green beams to produce the proper intersection of the three beams.

It can also be seen that, because of the relatively small size of the magnetic member 37, it is possible to prevent, or at least minimize, inadvertent movement of this device due to the removal and replacement of the socket of the cathode ray tube and the manipulation of other apparatus such as the static convergence magnets, for example, during servicing of the color television receiver.

What is claimed is:

1. For use in a color television receiver, in combination,

a cathode ray tube having an envelope, a screen and a neck portion, at least part of said neck portion being made of a nonmagnetic material, said cathode ray tube further including at least three electron guns mounted within said neck portion, each of said electron guns respectively emitting an electron beam along a path towards said screen;

a pair of substantially parallel internal pole pieces made of magnetic material and arranged transversely within said tube envelope on opposite sides of one of said electron guns;

a nonmagnetic holder mounted exteriorly of said nonmagnetic neck portion of said envelope adjacent said pole pieces and movable circumferentially about said neck portion; and

a lateral beam deflecting member made of magnetic material mounted in said nonmagnetic holder for producing a magnetic flux extending into said cathode ray tube envelope, said nonmagnetic holder bein movable into a first circumferential position in which said lateral beam deflecting member is substantially parallel to said pole pieces wherein substantially all of the magnetic flux emitted thereby and extending into said tube envelope passes through only one of said pair of pole pieces and does not extend into the path of any of the electron beams and being further movable to at least a second circumferential position wherein said magnetic flux extending into said tube envelope passes through both of said internal pole pieces and into the path of only said electron beam emitted by said one of said electron guns.

2. For use in a color television receiver, in combination,

a cathode ray tube having an envelope, a screen and a neck portion, at least part of said neck portion being made of a nonmagnetic material, said cathode ray tube further including at least three electron guns mounted within said neck portion, each of said electron guns respectively emitting an electron beam alon" a path towards said screen thereof;

a pair of substantially parallel internal pole pieces made of magnetic material and arranged transversely within said tube envelope on opposite sides of one of said electron guns so as to effectively isolate magnetically the electron beam produced by said one electron gun from the electron beams produced by the others of said electron guns;

a lateral beam deflecting member made of magnetic material mounted in said nonmagnetic holder for producing a magnetic flux extending into said oath ode ray tube envelope, said nonmagnetic holder being movable between a first circumferential position in which said lateral beam deflecting member is substantially parallel to said pole pieces and at least two extreme non-parallel circumferential positions whereby in said first circumferential position substantially all of said magnetic flux extending into said tube envelope passes through only one of said pair of pole pieces and does not intersect the paths of any of said electron beams and in each of said two extreme circumferential positions, said magnetic flux passes through both of said internal pole pieces and intersects the path of only one of said electron beams.

3-. Apparatus as claimed in claim 2 wherein the direction of the magnetic fiux intersecting said path of said electron beam in one of said extreme circumferential positions is opposite to the direction of the magnetic flux intersecting said electron beam path in the other of said extreme circumferential positions.

4. In a blue lateral beam deflecting arrangement for cathode ray tubes used in a color television receiver wherein the cathode ray tube has at least three electron guns respectively emitting red, blue and green phosphor exciting electron beams, the improvement comprising, a pair of internal pole pieces made of magnetic material and mounted on opposite sides of the electron gun producing the blue phosphor exciting beam, one of said pole pieces being radially outwardly of said blue beam producing electron gun and the other of said pole pieces being disposed radially inwardly of said blue beam producing electron gun;

a rectangular parallelopiped blue lateral beam-deflecting member having its longest dimension smaller than the diameter of the neck portion of the cathode ray tube, said member being made of magnetic material and mounted in said nonmagnetic holder, said member being magnetized to produce magnetic flux extending into the neck portion of the cathode ray tube, said nonmagnetic holder being movable between a first circumferential position in which said lateral beam deflecting member is substantially parallel to said pole pieces wherein substantially all of the magnetic flux produced by said lateral beam deflecting member and extending into the neck portion of the cathode ray tube cooperates with and passes through one of said pair of pole pieces without affecting the direction of movement of the red, blue or green phosphor exciting electron beams, said nonmagnetic holder being movable into at least a second circumferential position wherein substantially all of the magnetic flux produced by said lateral beam deflecting member and extending into the neck portion of the cathode ray tube passes through both of said pair of pole pieces and affects the path of movement of only the blue one of said red, blue or green phosphor exciting electron beams.

References Cited by the Examiner UNITED STATES PATENTS 2,752,520 6/1956 Morrell 3 l3-70 2,769,110 10/1956 Obert 313 2,806,164 9/1957 Clay et al. 3l3--75 3,192,452 6/1965 Rennick 317-200 JAMES W. LAWRENCE, Primary Examiner.

V. LA FRANCHI, Assistant Examiner.

Claims

1. FOR USE IN A COLOR TELEVISION RECEIVER, IN COMBINATION, A CATHODE RAY TUBE HAVING AN ENVELOPE, A SCREEN AND A NECK PORTION, AT LEAST PART OF SAID NECK PORTION BEING MADE OF A NONMAGNETIC MATERIAL, SAID CATHODE RAY TUBE FURTHER INCLUDING AT LEAST THREE ELECTRON GUNS MOUNTED WITHIN SAID NECK PORTION, EACH OF SAID ELECTRON GUNS RESPECTIVELY EMITTING AN ELECTRON BEAM ALONG A PATH TOWARDS SAID SCREEN; A PAIR OF SUBSTANTIALLY PARALLEL INTERNAL POLE PIECES MADE OF MAGNETIC MATERIAL AND ARRANGED TRANSVERSELY WITHIN SAID TUBE ENVELOPE ON OPPOSITE SIDES OF ONE OF SAID ELECTRON GUNS; A NONMAGNETIC HOLDER MOUNTED EXTERIORLY OF SAID NONMAGNETIC NECK PORTION OF SAID ENVELOPE ADJACENT SAID POLE PIECES AND MOVABLE CIRCUMFERENTIALLY ABOUT SAID NECK PORTION; AND A LATERAL BEAM DEFLECTING MEMBER MADE OF MAGNETIC MATERIAL MOUNTED IN SAID NONMAGNETIC HOLDER FOR PRODUCING A MAGNETIC FLUX EXTENDING INTO SAID CATHODE RAY TUBE ENVELOPE, SAID NONMAGNETIC HOLDER BEING MOVABLE INTO A FIRST CIRCUMFERENTIAL POSITION IN WHICH SAID LATERAL BEAM DEFLECTING MEMBER IS SUBSTANTIALLY PARALLEL TO SAID POLE PIECES WHEREIN SUBSTANTIALLY ALL OF THE MAGNETIC FLUX EMITTED THEREBY AND EXTENDING INTO SAID TUBE ENVELOPE PASSES THROUGH ONLY ONE OF SAID PAIR OF POLE PIECES AND DOES NOT EXTEND INTO THE PATH OF ANY OF THE ELECTRON BEAMS AND BEING FURTHER MOVABLE TO AT LEAST A SECOND CIRCUMFERENTIAL POSITION WHEREIN SAID MAGNETIC FLUX EXTENDING INTO SAID TUBE ENVELOPE PASSES THROUGH BOTH OF SAID INTERNAL POLE PIECES AND INTO THE PATH OF ONLY SAID ELECTRON BEAM EMITTED BY SAID ONE OF SAID ELECTRON GUNS.