US2592242A

US2592242A - Electron gun and mounting therefor

Info

Publication number: US2592242A
Application number: US174769A
Authority: US
Inventors: Von C Campbell
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-07-02
Filing date: 1950-07-19
Publication date: 1952-04-08
Anticipated expiration: 1969-04-08

Description

1 April 1952 v. c. CAMPBELL ELECTRON GUN AND MOUNTING THEREFOR Filed July 19, 1950 Fig.1.

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Patented Apr. 8, 1952 2,592,242 ELECTRON GUN AND MOUNTING THEREFOR Von C. Campbell, Syracune, N. Y., minor to General Electric Company, a corporation of New York Application July 19, 1950, Serial No. 174,769

v 4 Claims.

The present invention relates to an improved electron gun structure and mounting therefor and more particularly to a simplified gun structure of the ion trap type.

Cathode ray tubes employing an ion trap for separating unwanted ions from the electron stream have been widely used commercially. In one form of tubes of this type the electron gun is designed to impart to both the ions and elec-' trons a transverse deflection by subjecting them to a transverse component of electrostatic field. The electrons only are returned to the axis of the cathode ray tube by means of an electromagnetic field and the ions suitably collected on a surface lying off the axis of the tube.

It is an important object of the present invention to provide an improved and simplified gun structure for use in an ion trap type of tube and including a simplified mounting therefor.

My invention will be better understood by reference to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing Fig. 1 is an elevational view partially in section of a cathode ray tube embodying my invention. Fig. 2 is an enlarged sectional view of the neck of the tube of Fig. 1 showing the details of construction of the electron gun and Fig. 3 illustrates a modified gun structure embodying my invention.

Referring now to the drawing I have shown my invention embodied in a cathode ray tube of the metal envelope type including a generally conical metal part I having a glass face plate 2 sealed A glass neck -3 including a flare or funnel 4 is sealed to the smaller end of the metal cone I. The neck is closed at the lower end thereof by a stem 5 of conventional construction through which the various lead-in conductors are sealed and which is provided with an exhaust tubulation I through which the device is evacuated.

The inner surface of the face plate 2 is provided with a fluorescent coating 8 and the neck 3 is provided with a conducting inner surface 9 which extends from the metal cone to the upper end of the gun structure designated generally by the numeral II]. The coating may be applied in any suitable manner and in accordance with a method well known in the art, a graphite suspension is painted on the interior surface of the neck.

The gun structure I0 in accordance with my invention includes a generally cylindrical grid cylinder II. The end of the cylinder ll toward the screen is cut at an angle with respect to the axis of the tube and is effective in cooperation with the conducting surface 9, when a direct current voltage difference is applied therebetween to impart a transverse deflection to electrons and ions emanating from the gun. The cylinder II supports a transverse metal disc I2 having a central grid aperture I3 and a cylindrical cathode I4 having a closed end located directly behind the rid aperture and coated with a suitable electron emissive coating designated by the numeral I5. The cathode cylinder I 4 is suitably supported from the grid cylinder II by an insulating disc I6 which is spaced from the disc I 2 by a collar II. The cathode assembly also includes a suitable filamentary heater member I8 received within the cathode cylinder. The gun assembly thus far described is supported from the stem by means of a. plurality of lead-in conductors of which two are visible in Fig. 2, and designated by numerals I9 and 20. The conductors are directed outwardly at their upper ends and bonded to a collar 2| which is welded to the lower end of the grid cylinder II. The grid cylinder I I is further supported and positioned within the neck 3 of the cathode ray tube by a pair of spaced insulating discs such as

mica discs

22 and 23. The lower disc 22 bears against the flange of collar 2| and the upper disc 23 is supported by a plurality of hollow rivets 24 carried by conductors 25 and 26. These latter conductors are sealed into the stem 5 but preferably do not extend to the exterior side thereof.

A metal ring 21 having a plurality of pellets of getter material 21' positioned on either surface thereof and preferably on the outer surface thereof is positioned between the

insulating discs

22 and 23 and secured, as illustrated, to the conductors 25 and 2B. This construction largely confines the getter material to a localized area of the envelope wall. As is well understood, the getter may be flashed by suitable application of high frequency energy to the tube during processing of the tube.

The connections with the heater element III are made with two suitable lead-in conductors 28 and 29, the cathode cylinder is connected with a lead-in conductor 30, and the grid cylinder as previously indicated is connected with conductors I9 and 20. All of the lead-in conductors which are needed for energizing the various elements are connected to suitable terminal prongs 3| secured to a conventional insulating tube base 32 which is bonded to the base of the tube by basing cement 33.

As is well understood by those skilled in the art, in the operation of the device described above, electrons are emitted from the cathode surface I5. when it attains a suitable operating temperature. These electrons move in the form of a beam toward the screen 8 of the tube under the control of the grid including the transverse disc I2, and the anode potential which is impressed on the cone I and the conductive coating 9. The control or signal voltage is impressed on the grid cylinder I I to vary the intensity of the beam in accordance with the received signal. With the bias cut 01' the grid cylinder II, the beam is givena deflection in a transverse direction and this deflection is substantially equal for both electrons and any ions that may be present 3 in the beam. The electrons only are returned to the axis of the tube by the action of a magnetic field transverse to the axis of the tube and produced by a suitably magnetized ring 34 supported on the outside of the tube on a resilient sleeve 36. A smaller and weaker permanent magnet member 35 located in spaced relationship to the ring 34 provides a suitable means for just bringing the electron beam back to the center of the screen. It may be moved longitudinally of the tube and also rotated with respect to the tube to produce the final adjustment. The arrangement of magnets described is more fully described and claimed in Wainwright Patent 2,456,474 dated December 14, 1948. It will be well understood that the beam is focused and deflected to scan the screen by means of suitable magnetic means which are associated with the exterior of the tube in use and which are not shown in the drawing.

It has been found that in spite of the voltage variations on the grid cylinder l l due to the grid signal, it cooperates effectively with the conductive coating of the wall 9 to provide the necessary transverse component of electrostatic field to deflect both the ions and electrons toward the wall of the tube so that the magnetic field returns only the electrons to the axis of the tube leaving the ions to be collected by the conducting surface 9. In a preferred embodiment of my invention the angle of the bias cut grid cylinder is approximately 16 as illustrated in the drawing.

In some cases it may be desirable to collect the ions on a metal surface and in that case a tubular metal member may be supported from the gun structure and electrically connected with the conductive coating 9 and in this way form effectively an extension of that coating. Such a modification is shown in Fig. 3 in which the gun structure is the same as that shown and described in Figs. land 2. The additional' cylinder is illustrated at 31 and is supported from the gun structure by means of suitable glass stalks 38 which are sealed to suitable lugs 39 welded to the cylinder ll of the grid and to the cylinder 31. A suitable disc is mounted on the upper end of the cylinder 31 and provided with a beam-limiting aperture 40. Suitable spring contact fingers ll carried by this disc and engage the conductive surface of the inner wall of the envelope. Electrically, the operation of the modification described in connection with Fig. 3 is identical with that described in connection with Figs. 1 and 2.

While I have described particular embodiments of my invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I intend, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. A cathode ray tube comprising an envelope including a cylindrical neck, an electron gun supported within said neck comprising a generally cylindrical control grid member, a cathode supported from and within said grid member, said grid member terminating in a plane making an acute angle with the axis thereof at one end and provided with an outwardly extending flange at the other end thereof, a pair of spaced insulating disks interposed between said cylindrical control grid member and the neck of said envelope, one of said insulating disks engaging said flange and a getter ring surrounding said grid member and supported in the space between said insulating disks.

2. A cathode ray tube comprising an envelope including a cylindrical neck, an electronic gun supported within said neck comprising a generally cylindrical control grid member, a cathode supported from and within said grid member, said grid member being provided at one end with an outwardly extending flange, a pair of spaced insulating disks interposed between said electrical control grid member and the neck of said envelope, one of said insulating disks engaging said flange and a getter ring surrounding said grid member and supported in the space between said insulating supports.

3. A cathode ray tube comprising an envelope including a fluorescent screen at one end, an elongated cylindrical neck at the other end, a conductive surface within said envelope extending down the inner wall of said neck portion, an electron gun supported within said neck and including a control grid cylinder, a cathode supported within said grid cylinder, an apertured transverse wall supported from and conductively connected to said control grid cylinder on the side of said cathode nearer said screen, said grid cylinder having the end toward said screen terminating in a plane extending at an acute angle with respect to the axis of said grid cylinder and operable in response to a voltage difference between said grid and said conductive surface to subject electrons emanating from said gun to a component of electrostatic field transverse with respect to the axis of said grid cylinder.

4. A cathode ray tube comprising an envelope having a tubular portion, a conductive surface on the inner wall of said tubular portion, an electron gun supported within said tubular portion and including a control grid cylinder, a cathode supported within said cylinder, an apertured transverse wall supported from and conductively connected to said control grid cylinder intermediate the ends thereof, said grid cylinder having the end away from said cathode terminating in a plane extending at an acute angle with respect to the axis of said grid cylinder and cooperating with the conductive surface on said tubular portion to subject electrons emanating from said gun to a component of electrostatic field transverse with respect to the axis of said grid cylinder in response to a voltage difference between said grid cylinder and said conductive coating.

VON C. CAMPBELL.

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

UNITED STATES PATENTS Number Name Date 2,185,378 Maloif et a1. Jan. 2, 1940 2,225,901 Bruche Dec. 24, 1940 2,264,274 Broadway Dec. 2, 1941 2,268,194 Glass Dec. 30, 1941 2,295,038 Hergnrother Sept. 8, 1942 2,297,429 Paehr Sept. 29, 1942 2,443,916 Kelar June 22, 1948 2,456,474 Wainwright Dec. 14, 1948 2,496,127 Kelar Jan. 31, 1950 2,515,305 Kelar July 18, 1950