US2553039A

US2553039A - Cathode-ray tube combined beam centering and deflection device

Info

Publication number: US2553039A
Application number: US89698A
Authority: US
Inventors: Richard O Gray
Original assignee: Zenith Radio Corp
Current assignee: Zenith Electronics LLC
Priority date: 1949-04-26
Filing date: 1949-04-26
Publication date: 1951-05-15
Anticipated expiration: 1968-05-15

Description

May 15, 1951 GRAY CATHODE-RAY TUBE ONBINED BEAM CENTERING AND DEFLECTION DEVICE Filed April 26, 1949 @9 5 w wEmwm 522 mcoEE l v w E E W N. N 29 :8

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RICHARD GRAY 'INVENTOR.

HIS AGENT Patented May 15, 1951 THODE-R Y TUBE C M INE BEAM oENTnnINo AND DEFLno'r o ev ce" Richard 0. Gray, Broadview, 111., assignor to Zenith Radio Corporation, a, corporation of Application April 26, 1943, Serial No. 89.69? 4 Qlaims. (Cl. 250-15 (5) This invention relates to devices for use in conjunction with electron-discharge devices of the cathode-ray .tube type for deflecting and also for centering the electron beam in such discharge devices.

Present-day cathode-ray tubes usually include a source of electrons situated in an elongated, or neck portion of the tube, anda screen situated in an enlarged, or bulbous, portion thereof at the opposite extremity from the electron source. The tube also includes suitable electrodes for forming the electrons from the source into an electron beam and for directing the beam to impinge on the screen. The cathode-ray tube has associated therewith an electro;,-static .or electro-magnetic arrangement for deflecting the beam in a predetermined fashion to scan the screen so that im es repr sen e y a re e y d t levi ionsie a may be reproduced thereon. Furthermore, the tu e a so u u l y s assoc ated h r wi h electro-static, an electro-magnetic, or a perman n m n ti a ra em o f u in t e c ro am tha the ma on t reen may be reproduced clearly and distinctly.

It has been found necessary to provide some means for centering the electron beamin oath ode-ray tubes in order that images maybe reproduced correctly centered on the iscree'n areaidespite slight misalignments of the elements asso: ciatfedwith thetube. Various systems havebeen proposed for providing an adjustable centering control over the electron beam to center it properly on the screen. One method of accomplishing this consists in providing some-means for adjusting the angularposition of the magnetic focusing arrangement relative to the cathode-ray tube. The chief disadvantage of this, apart from its inherentawlrwardness,is the fact that it isefiective only when the beam is off center by a very small amount. This is'because the focusing arrangement is mounted about the neck portion of the cathode-ray tube at a considerable distance from the enlarged portion thereof, since thedeflection. elements are placed between this focusing arrangement and the enlarged portion. Therefore, when the angular position of the focusing arrangement is adjusted to attempt to compensate for appreciable misalignment of the electron beam, shadows appear in the reproduced image due to the beam being intercepted the neck portion of the cathode-raytube upon deflection by the deflection elements.

Another method of providing a centering adjustment for the electron beamef an electromagnetically deflected type of tube consists in passing i n bee in aw de Pe m nent .rately centered ,on Tth eiscr Ii of the tube.

therewith, and

a controllable unidirectional current through the vertical and horizontaldeflectionwindings. :Ihe amount of current passing through the respective deflection windings maybe adjusted by any suit able control means, and thesecontrol means be vvaried until the electron beam is accur ely centered ,on the screen. Since the deflect n .coils are mounted a u he neck PO K iQ of 1 cathode-ray tube in a position adjacent the larged portion of the tube, the previously cussed shadow effect is not as critical as it was in the first-mentioned centering arrangement method. Therefore, accurate centering may be provided for appreciable misalignment of the electron beam. However, this methodentails the need r e t and elat vel ae e v fe zntbr anents, n those c m onent ad mater al y i the manufacturing costof theapparatus.

-It is ageneral objectofthe present invention to provide an improved magnetic structure deflecting and centering theelectron team cathode-ray tube by means of which the a described disadvantages are overcome. It is a further objectof this invention to pro vide a magneticstru urefor e r eetinggtneeiee electron beam in y.

Anotherobje'ct'nf this intention is to provide such a. structure in which the permanent 'fma'gne t means is readily and conveniently adjus tabl .does not require complicated awkward justment mechanism."

" e a i thQ b bt this inv t n i is p evide such .structure in which the perm n nt ma net means i-se'ffective for centering the eo b. ,.inaceihqd gayiab ,wiihb fi sl tiously ffecting the images reproducedon :the

screen ofthe tube, even though" the beam may normally be misaligned to'a'n app ieciab'leextent. The features of this invention whicharebelieved tube neivar set forth with particularity the lappended cla'irns'f The invention itself,

however, together with further objects and ad vantages thereof may best" beund'ers'tood by reference'to the following description when taken in conjunction with the accompanying" drawing, in wh h:

{Figure 1 shows a cathode-ray tube havingone embodiment of the cathode-ray beam deflecting and centering device of the-invention associated of this device.

3 In Figure 1, a cathode-ray tube is designated I0, and includes an electron gun structure I I for developing a beam of electrons therein. The tube II) has a deflection yoke I2 associated therewith for deflecting the electron beam over a fluorescent screen |3. The deflection yoke I2 is shown in a particular form, but it is to be understood that any of the well known types of deflection yokes, when modified in accordance with the present invention, may be used. The illustrated deflection yoke I2 is shown partially in section and comprises a pair of horizontal-deflection coils I4 and a pair of vertical-deflection coils I5. The leads I6 and I! may be connected to suitable deflection generators, not shown, to supply the deflection currents to the respective coils. The yoke |2 has a core I8 for intensifying the deflection fields of the deflection coils, and this core is shown as comprising an iron wire wound about the coils I4 and I5, although other types of core members may be used. The core winding I8 is enclosed by a cylindrical tube I9 having a smooth external surface, and which may be composed of fibre, Bakelite, or other appropriate material. In accordance with the invention, an air gap is formed in the core winding, for reasons to become -apparent. The annular member 2| is mounted about the smooth outer surface of the tube I9 in such a fashion that it may be conveniently rotated or moved longitudinally on this surface. The member 2| is shown in detail in Figure 2 and comprises two or more permanent magnets '22, 23 fixed to an annular mount 24 composed of Bakelite, fibre, or other material. The

permanent magnets

22, 23 are magnetized as shown, to produce a magnetic field substantially perpendicular to the longitudinal axis of the yoke |2. The direction of this field may be rotated by rotation of the annular member 2|, and the magnitude of the field may be varied by movement of the member 2| along the longitudinal axis of the deflection yoke I2. When the member 2| is centered over the air gap 20, the field due to the

permanent magnets

22 and 23 is a maximum, and when the member is centered over the core l8 this lfield is a minimum due to the fact that the major portion of the field flux produced by the

magnets

22 and 23 is confined in the core l8. .When desired, instead of providing an air gap 20 in the core I8, the core may be constructed with varying thickness and hence with varying magnetic reluctance from one end to the other. This provides a gradual increase or decrease in the beam-centering field due to the magnets 22 =and 23 as the member 2| is moved along the longitudinal axis of the deflection yoke I2. Furthermore, the annular member 2| may take the form of a simple, properly magnetized, an- ;nular ring, when for reasons of economy it is desired to reduce the cost of the permanent magnet device to an absolute minimum.

- It can be seen that by manipulation of the annular member 2|, control can be exercised on the electron beam in the cathode-ray tube ID to center the beam. The member 20 is rotated until -the field due to the

magnets

22 and 23 is in the proper position to direct the electron beam to the center of the cathode-ray tube screen, and the member is then moved longitudinally until this field is of the proper magnitude to bring the electron beam back to the exact center point.

The illustrated embodiment of the combined cathode-ray beam deflecting and centering device comprises a usual deflection yoke having an air gap formed therein, and a magnetic member rotatably and slidably mounted on the yoke. Centering of the electron beam may be effected with a high degree of accuracy with this simple device, and the need for complicated physical adjusting means to vary the angular position of the focusing arrangement of the cathode-ray tube, or for costly circuit components to supply adjustable unidirectional currents to the deflection yokes, to obtain this centering control, is thereby obviated. Furthermore, since the centering field is produced by means within the deflection yoke, which is adjacent the enlarged portion of the cathode-ray tube, the shadow effect that arises when it is attempted to center the beam by movement of the focussing coil, which is dis placed from this enlarged portion, is greatly reduced. It has been found that this invention can be used for accurately centering the electron beam in a cathode-ray tube, without deleteriously aifecting the images reproduced on the screen thereof, even when the beam i normally misaligned from the longitudinal axis of the tube to a substantial degree.

While a particular embodiment of the invention has been shown and described, modifications may be made, and it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. A magnetic structure for deflecting and centering an electron beam in a cathode-ray tube havin an elongated neck portion comprising: at least one pair of beam-deflection windings having a portion circumscribing said neck for producing a magnetic field within said tube to deflect said beam; a tubular-shaped core member of magnetic material surrounding said portion of said beam-deflection windings in concentric relation with respect thereto and having a vary ing magnetic reluctance along its length; and an annular permanent magnet member mounted on said core member in concentric relation with respect thereto for longitudinal and rotational movement relative to said core for producing a transverse magnetic field in said tube to center said electron beam.

2. A magnetic structure for deflecting and centering an electron beam in a cathode-ray tube having an elongated neck portion com rising: at least one pair of beam-deflection windings having a portion circumscribing said neck for producin a magnetic field within said tube to deflect said beam; a tubular-shaped core member of magetic material surrounding said portion of said beam-deflection windings in concentric relation with respect thereto and having an air gap extending therethrough; and an annular permanent magnet member mounted on said core member in concentric relation with respect thereto for longitudinal and rotational movement relative to said core for producing a transverse magnetic field through said air gap to center said electron beam.

3. A magnetic structure for deflecting and centering an electronc beam in a cathode-ray tube having an elongated neck portion comprising: two pairs of beam-deflection windings forming a yoke circumscribing said neck portion for producing magnetic fields within said tube to deflect said beam; a tubular-shaped core member of magnetic material surrounding said yoke in concentric relation with respect thereto and having an annular peripheral air gap extending therethrough; and a ring member, including a pair of oppositely disposed permanent magnet segments, mounted on said core member in concentric relation with respect thereto for longitudinal and rotational movement relative to said core, said segments being magnetized to produce a transverse magnetic field through said air gap for centering said electron beam.

4. A magnetic structure for deflecting and centering an electron beam in a cathode-ray tube having an elongated neck portion comprising: two pairs of beam-deflection windings forming a yoke circumscribing said neck portion for producing magnetic fields within said tube for deflecting said beam; a pair of tubular-shaped core members of magnetic material mounted on said yoke in concentric relation with respect thereto and spaced apart to define an annular air gap with a longitudinal dimension small compared with the overall length of said cores; a cylindrical tube of insulating material mounted coaxially on said core members; and an annular permanent magnet member mounted on said cylindrical tube in concentric relation with respect thereto for longitudinal and rotational movement relative to said cylindrical tube for producing a transverse magnetic field through said air gap to center said electron beam.

RICHARD O. GRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,004,099 Bedford June 11, 1935 2,102,421 Kuehni Dec. 14, 1937 2,157,182 Malofi May 9, 1939 2,177,688 Cawein Oct. 31, 1939 2,188,579 Schlesinger Jan. 30, 1940 2,200,039 Nicoll May 7, 1940 2,207,777 Blain July 16, 1940 2,211,613 Bowie Aug. 13, 1940 2,456,474 Wainwright Dec. 14, 1948 2,499,065 Heppner Feb. 28, 1950 FOREIGN PATENTS Number Country Date 464,637 Great Britain Apr. 21, 1937