US2501516A

US2501516A - Deflecting and focusing device for cathode-ray apparatus

Info

Publication number: US2501516A
Application number: US795080A
Authority: US
Inventors: Harold C Holden
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1947-12-31
Filing date: 1947-12-31
Publication date: 1950-03-21
Anticipated expiration: 1967-03-21

Description

March 21, 1950 H. c. HOLDEN 2,501,516 DEFLECTING AND FOCUSING DEVICE FOR CATHODE RAY APPARATUS Filed Dec. 31, 1947 2 Sheets-Sheet 1 Inventor: Harold C. H olden,

His Attorney.

March 21, 1950 H. c. HOLDEN DEFLECTING AND FOCUSING DEVICE FOR CATHODE RAY APPARATUS Filed Dec. 31, 1947 VII/1 VIIIIIIIIII$ 2 Sheets-Sheet 2 lhvehtor: Harold C. Holden,

by m%- Wm His Attorney.

Patented Mar. 21, 1950 UNITED STATES PATENT 'QFFHCE DEFLECTING AND FOCUSING DEVICE FOR CATHODE-RAY APPARATUS Harold C. Holden, Bridgeport, Conn., assignor to General Electric Company, a corporation of New York 4 Claims.

My invention relates to devices for deflecting and focusing cathode ray beams in electron discharge devices of the cathode ray type and has particular application to cathode ray tubes for television receivers.

In television receivers and similar apparatus it is desirable to provide some arrangement for centering and adjusting the cathode ray beam in the picture tube and for aligning the horizontal and vertical axes of the picture. Such adjustment makes it possible to replace the tube and adjust the new tube satisfactorily without the necessity of providing a new tube which is so constructed that it produces its cathode ray beam in the exact location of that produced by the replaced tube. Relatively complicated mountings have been provided for this purpose heretofore. Accordingly it is an object of my invention to provide an improved adjustable beam deflecting and focusing arrangement for electron discharge devices of the cathode ray type.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is a side elevation view, partly illustrated in Fig. 1 includes an electron dis charge device I which is of the cathode ray type commonly used for the reproduction of pictures in television receivers. The device is provided with a glass envelope comprising a bowl portion 2, only; a part of which is shown in the drawing, and an;

elongated cylindrical neck 3. The envelope is supported on suitable brackets 4 and 5, the bracket 5 being provided with an adjustable collar 5 clamped about the neck 3. The device I may have as an additional support a clamping arrangement (not shown) which is positioned aboutthe edge portion of the bowl 2 adjacent the usual,

fluorescent screen on which the picture is reproduced. Within the neck 3 near the end remote from the bowl 2 there is provided the usual cathode ray beam forming device commonly called an electron gun an anode portion of which is indicated generally at I. The construction and arrangement of the electron gun to produce a cathode ray beam is well known and a detailed description is not necessary to an understanding of the present invention. The electron beam is projected along the axis of the neck 3 onto the fluorescent screen and produces a spot of light at the point at which it impinges on the screen. In order to focus the spot of light upon the screen, a focusing yoke 8 is mounted about the envelope 3 near the source of the electron beam. The yoke 8 produces a magnetic field which constitutes a magnetostatic lens for concentrating the beam of electrons. As illustrated, the yoke 8 comprises a coil 9 arranged within a hollow ring of magnetic material comprising an inner cylinder l0, an outer cylinder It and an end member I 2, the outer cylinder ll being formed to provide the opposite end member. The inner cylinder in is spaced from the outer cylinder H at its inner periphery to provide an annular air gap 13, the magnetost-atic lens being formed generally in the plane of the air gap so that the center of the lens coincides with the longitudinal axis of the coil 9. The focusing of the beam is effected by adjusting the excitation of the coil 9 which is supplied with direct current from a suitable source (not shown).

In order to produce the television picture which requires horizontal and vertical deflection of the cathode ray beam in a manner which is well understood in the art, a deflecting coil assembly I4 is mounted about the neck 3 between the bowl 2 and the focusing yoke 8. The television picture is produced by modulating the intensity of the beam while it is being deflected over the surface of the screen so that the intensity of any given area of the screen corresponds with that of the transmitted picture of that area. The yoke 8 is supported within the bracket 4 and is rotatable about theneck 3 on a nonmagnetic sleeve l5 which is rotatably fitted in an opening [5 in the bracket 4 and is retained in place by a plurality of spring clips l1; one of which is shown. The deflecting coil assembly I4 is rotatably mounted with respect to the bracket 4 on a circular plate 18 held in an annular retaining shoulder 19 formed on the bracket and retained in place frictionally by a plurality of spring clamps 20 only one of which has been illustrated on the drawing. The plate l8 and the endportion of the assembly M are spaced from the sleeve l5 so that the sleeve 3 and the assembly may each be rotated in the bracket 4 independently.

It is impractical to provide television receivers which are so adjusted at the factory that no further adjustment or servicing is necessary in order to center the picture on the screen. Furthermore, the cathode ray tubes employed for television receivers are not identical so that when it becomes necessary to replace a tube it is also necessary to readjust the focusing and deflecting devices to secure the desired position of the picture. In the apparatus illustrated, this adjustment can be accomplished by first rotating the reflecting coils l4 about the envelope 3 until the edges of the rectangular picture are parallel to their desired final positions. The spring clamps then retain the deflecting coils in their required positions. The next step in adjusting the picture is to move the center of the picture until it coincides with its required center position. This is accomplished by rotating and tilting the focusing yoke 8 in a manner to be described.

The yoke 8 is mounted on the sleeve 15 on two spring arms 21 attached by screws 22 to opposite sides of the yoke. The arms 2i extend axially of the yoke within the cylinder H3 and are provided with pivots 23 which engage diametrically opposite holes 25 in the sleeve l5, as clearly shown in Fig. 2. The spring arms take up any slack or endplay in the pivot members and, since the pivots 23 are located so that the pivotal axis passes substantially through the center of the magnetostatic lens, tilting of the yoke produces little shifting of the lens center and maintains the center of the lens substantially on the axis of the electron gun regardless of the tilt of the yoke. After the electron beam has been focused by adjusting the strength of the magnetic field as determined by the excitation of the focusing coil El, and after correct alignment of the picture by adjustment of the deflecting-coils l 4, the focusing yoke 8 is rotated on the collar 15 about the neck 3 until the axis of the pivots 23 is at right angles to a line passing through the centers of the picture in its incorrect position and in its desired position. It will now be apparent that the picture can be centered merely by tilting the yoke until the center points coincide. The tilting is accomplished by adjusting a wing nut 25 threaded on a stud 26 which is attached to an extension 27 on the sleeve l5 and passes through a lug 28 attached to the outer cylinder ll of the yoke 8. bracket 4 is prevented by a compression spring 28 arranged about the stud 26 between the bracket and lug 28. It is thus apparent that the entire adiustinent necessary may be made simply by rotation of the deflecting assembly l4 about the envelope 3, rotation of the yoke 8 with the sleeve [5, and tilting of the yoke by adjustment of the wing nut 25.

Referring now to Fig. 3, I have illustrated a deflecting and focusing assembly embodying my invention and in which a permanent magnet focusing yoke an is employed. The yoke and a deflecting coil assembly 3! are rotatably mounted on a neck 32 of a cathode raytube 33 of the same type as the tube I of Fig. 1. The yoke 53! is secured directly to a sleeve 34 by screws 35 and the sleeve 34 fits about the neck 32, a suitable intermediate or spacing sleeve 36 of felt or other suitable material being provided so that the sleeve 34 may readily be rotated about the glass envelope. The yoke 3| includes a casing or shell 31 and the focusing and deflecting assembly'is Lost motion between the lug 28 and rotatably secured within a support 38 which is provided with a circular opening 39 rotatably engaging a boss 40 on the shell 37. A flange M on the sleeve 34 prevents axial movement of the deflecting and focusing assembly in the opening 39. lhis flange may be resilient to provide spring pressure for retaining the assembly in position on the support. The deflecting coil assembly 3|, as shown in Fig. l, comprises a square magnetic core 42 on which are arranged two sets of deflecting coils 43, a: for providing deflecting fields at right angles to one another. The casing 37 is of square cross section and is closed by a cap 45 having a circular opening provided with a suitable resilient gasket 46 engaging the neck 32 of the tube adjacent the bowl indicated at 41. The cap 45 thus encloses the yoke and coils within the casing 31. The yoke 42 is secured within the casing 31 on four corner pieces 48 which are welded or otherwise secured in position and are provided with rectangular openings for receiving the corners of the yoke, as clearly indicated in Fig. 6, which illustrates one of the corner pieces 45% showing the opening .at 39 and the position of the core 42, as indicated in .dot and dash lines. It will thus be seen that the deflecting coil assembly 3i may readily be rotated within the support 38 about the envelope 32 so that the cathode ray beam generated by the usual electron gun, the anode of which is indicated at 58, may be defiected along the desired paths.

The permanent magnet focusing yoke 36 comprises a permanent magnet in the form of a cylinder or ring 5| and two

pole pieces

52 and 53 forming with the magnet 5! a hollow ring provided with an annular air gap 55 between the

pole pieces

52 and 53. The yoke 30 is pivotally mounted on a sleeve 55 which is slidably mounted on the sleeve 36 so that it may be rotated and moved axially along the sleeve 13%. The yoke fill is provided with two diagonally opposite spring arms 56 secured to the yoke by screws 57 remote from the air gap 54. The spring arms 56 extend axially of the yoke 30 and cross the air gap 54, and pivot members or trunnions 58 are secured in the ends of the spring arms and are J'ournaled in bearings 59 in the sleeve 55. It will thus be apparent that the yoke '30 can be moved axially of the sleeve 32, rotated thereon, and tilted with respect thereto along the axis of the pivots 58. The axial movement of the yoke is necessary in order to adjust the effect of the magnetostatic lens on the cathode ray beam since it is not possible to adjust the strength of the permanent magnet in a manner similar to the adjustment of the field strength by changing the excitation of the coil 9 of the yoke in Fig. 1. Except for the different method for focusing the beam, the adjust ment of the deflecting and focusing yoke of the apparatus shown in Fig. 3 is the same as that of the apparatus shown in Fig. 1, the edges of the picture first being made parallel with their required positions and the yoke thereafter being tilted to bring the center of the aligned picture into coincidence with the required center for the picture.

The positioning of the yoke pivots in the plane of the air gap so that the pivotal axis passes substantially through the center of the magnetostatic lens insuring minimum shifting of the center of the lens when focusing yoke is tilted to center the picture. The mounting of the yokes on spring arms provides an arrangement for taking up end-play in the pivots and facilitates the as- 76 sembly of the yoke.

From the foregoing it is readily apparent that I have provided a simple-and easily adjusted arrangement for securin the proper positioning of the deflecting coils and focusing yoke so that the picture presented on the screen of an electron discharge device of the cathode ray type may be made to appear in its required position. Although I have illustrated and described specific arrangements embodying m invention, modifications will occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the particular constructions illustrated and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray beam onto the screen, a support, .a magnetic deflecting coil attached to said support and mounted about said envelope between said gun and said screen, a magnetic focusing yoke for providing a, magnetostatic lens in the path of said beam, said yoke being attached to said support and mounted about said envelope near the origin of said beam, said coil and said yoke both being rotatable relative to each other and to said support and said envelope about the axis of said beam, the mounting for said yoke including pivot members positioned in the plane of said lens whereby the direction of said beam may be adjusted.

2. In an electron discharge apparatus of the cathode ray type including an envelope having a screen and an electron gun for projecting a cathode ray beam onto the screen, a support, a sleeve rotatably mounted about said envelope and rotatably secured to said support, a magnetic deflecting coil mounted on said support for rotation about the axis of said beam and arranged about said envelope between said gun and said screen, a magnetic focusing yoke for providing a magnetostatic lens in the path of said beam, said yoke being mounted about said envelope near the neticideflecting' coil mounted about said envelope bet en said gun and said screen, a magnetic ing yoke comprising a magnetic shell in the "of a hollow ring having an annular air gap the inner wall thereof for providing a magestatic lens in the path of said beam, a sleeve atably fitted about said envelope, and means hiding axially extending spring arms secured id shell remote from said air gap and having pivot members engaging said sleeve in the plane pfsaid air gap for mounting said yoke on said sleeve to aiford tilting of the central axis of said lens with respect to the central axis of said envelope whereby the direction of said beam may 5b adjusted.

In an electron discharge apparatus of the cathode ray type including an envelope having therein'a screen and an electron gun for projectng a cathode ray beam onto the screen, a sleeve netic deflecting coil mounted on said sleeve and arranged about said envelope between said gun ro atably mounted about said envelope, a ma and said screen, a second sleeve rotatably and slidably mounted on said first sleeve, a magnetic focusing yoke for providing a, magnetostatic lens in the path of said beam, said yoke being mounted about said envelope near the origin of said beam and being secured pivotally to said second sleeve Q for rotation about said envelope with respect to located on a transverse axis passing substantially said coil, the pivotal mountin for said yoke being through the center of said lens normal to the central axis thereof.

HAROLD C. HOLDEN.

, file of this patent:

origin of said beam and being secured pivotally therein a screen and an electron gun for project- I ing a cathode ray beam onto the screen, a mag- UNITED STATES PATENTS Number Name Date 2,234,720 Detar Mar. 11, 1941 2,416,687 Fry Mar. 4, 1947 2,418,487 Sproul Apr. 8, 1947 2,428,928 Cain Oct. 14, 1947 2,431,077 Jackson Nov. 18, 1947 2,435,613 Sproul Feb. 10, 1948 2,440,403 Pooh Apr. 27, 1948 2,456,399 Gethmann Dec. 14, 1948 FOREIGN PATENTS Number Country Date 472,165 Great Britain Sept. 13, 1937 523,439 Great Britain July 15, 1940