US2879421A - Cathode ray tube electrode structure - Google Patents

Description

March 24, 1.959 B. G. BRQADBENT ET AL 2,879,421

' CATHODE RAY TUBE ELECTRODE STRUCTURE Filed Jan. so, 1956 ATTORNEY United States Patent 2,879,421 I CATHODE RAY TUBE ELECTRODE STRUCTURE Bernard G. Broadbent, Seneca Falls, and Frederick A.

Hemphill, Waterloo, N.Y., assignors to Sylvania Electric Products Inc'., a corporation of Massachusetts Application January 30, 1956, Serial No. 562,149

Claims. oasis-s2 This invention relates to image reproduction devices and more particularly to picture-tubes employed in such devices as, for example, television apparatus.

The source of electrons for the writing beam utilized to form the imageon a picture tube viewing panel is provided by a cathode which is assembled on an electron gun mount along with electron'accelerating and beam modulating electrodes. In an electrostatic focusing type picture tube, the electron beam focusing electrodes are also mounted as an integral part of the gun structure.

Generally these gun mount electrodes are positioned and aligned relative to one another by means of several straight ceramic rods cooperatingwith integral pins or bands connected to or around the electrodes. The ceramic rods are disposed about the periphery of the electrodes and extend longitudinally along the gun mount. Due to the necessity of centering the electron beam after removing the ions from the electron beam, the electrode assembly is positioned at a small angle with the longitudinal axis of the neck portion of the tube. An electrostatic lens and an ion trap magnet causes the ions to be removed from the writing beam in a manner well understood in the art.

Since some of the electrode'ssuch as 'thelens ring electrode usedjn uni-potential electrostatic focusing type picture tubes has a diameter greater than the diameters of the other electrodes, the straight ceramic rods holding the mount together must be positioned exteriorly of the larger-electrodes and therefore further away from the smaller diameter electrodes. In effect, this makes the entire gun mount correspondingly as large along its entire length as is necessitated by the largest diameter electrode. Due to the small diameter of the tube neck and the angle in which the gun structure is positioned, the ends of these ceramic rods adjacent the first grid electrode are very often touching the inside surface of the tube neck.

Since the wafer of the stem used to seal the neck portion of the tube must be heated to make a glass to glass hermetic seal, and since the ends of the ceramic rods often touch the glass neck very close to the sealing position, a strain is created in the glass due to uneven heat conduction during the sealing operation. This strain results in numerous cracks which extend longitudinally along the glass neck portion of the tube after the glass has cooled.

Another inherent disadvantage in conventional electrode mount structures using straight ceramic rods is the inability of the rods to effectively support the electrodes which have only one mounting pin longitudinally disposed along the electrode. Such electrodes tend to be very loosely supported on the rods, and can be easily dislodged by vibration. Due to the critical distance tolerances between the electrodes, it is important that the electrode positions be maintained after they have been mounted in the gun structure assembly.

Accordingly, it is an object of the invention to reduce .2 p the aforementioned disadvantages, and to provide an improved cathode ray tube electrode assembly.

A further object is the provision of an electron gun structure which reduces the number of cathoderay tube rejects due to cracks in the glass neck portion. ofthe tube caused by uneven heat conduction during the tube fabricating process.

A further object is the provision of a cathode ray tube mount wherein the electrodes are rigidly and permanently aflixed in spaced relationship with one another.

The foregoing objects are achieved in one aspect of the invention by the provision of a gun mount electrode assembly employing support members formed generally to conform to the profile of the peripheral surfaces of the electrode. assembly.

For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a sectioned view of a portion of a cathode ray tube employing an electrode gun mount formed in accordance with one aspect of the invention; and t Fig. 2 is a perspective view of the gun mount shown in Fig. 1.

Referring to the drawings, a cathode ray tube. 11 is provided with a face plate 13, and a neck portion 17. The cathode ray tube is hermetically sealed by wafer 19 and exhaust tubulation 21. Disposed on the internal surface of face plate 13 is an electron responsive fluorescent material 23. Mounted in neck portion 17 is the electron gun structure 25 which provides the source, ac.- celeration, modulation, and focusing of the electron beam. An electrically conductive coating 27 is applied to the internal surface of the neck and flared portion (not shown) of the tube to form an electrode which carries a high potential for accelerating the electrons toward the fluorescent material layer 23. 1

The electrode gun structure assembly 25 is mounte within neck portion 17 by means of support tabs 29 and snubbers '31. The axis of the gun assembly is disposed at an angle of approximately 3 degrees with the longitudinal axis of the tube so that the electron beam will be directed generally towards an extended portion of the tube neck. This directed beam is operated on by the slashed lens formed by the trailing edge of second grid 33 and the leading edge of first anode 35, and by an ion trap magnet 37 positioned outside the tube neck to remove the heavy ions from the electron beam and to return the beam to its operative position along the axis of the tube.

The modulating voltages for the writing beam are normally applied to a circuit including the cathode and grid 31, while grid 33 and anode 35 serve to accelerate the electrons during the scanning period in addition to providing the beam deflection field for removing the ions as described above. In an electrostatic focus type picture tube such as the embodiment illustrated in the drawings, the terminal section 39 of anode 35, along with lens ring 41 and lens cup 43 serve to accelerate the electrons and to focus the electron beam. Horizontal and vertical deflection coils 45 provide the means for scanning the focused and modulated writing beam over fluorescent panel 23 to reproduce the transmitted image.

The electrodes employed in the tube are atfixed to one another by elongated ceramic beads 47 and integral electrode studs 49. A preferred embodiment uses 3 beads disposed around the periphery of the electrodes approximately apart. Beads 47 are formed along their longitudinal lengths to substantially conform to the profile of the longitudinal peripheral configuration of the electrode assembly 25. This configuration allows the beads to be positioned correspondingly close to all of the electrodes. Therefore, the studs 49 will have substantially equal lengths, which, with the aid of the closely 3 spaced beads-"causes the efiectiveness andrigidity of the electrode mounting to be enhanced.

The ceramic beads 47 have an oiI-set portion formed in the region of lens ring-'41, which in the illustrated embodimentis the largest diameter electrode. lnother types of gun structures the ofi-set portions will correspond to the=lateral dimensions of the electrodes disposed' 'along the longitudinal length of the electrode as- 'se'mbly.

During the processing of cathode ray tube 11, the neck portion 17 is hermetically sealed to water 19 prior to-the' exhaust and tip-olf of the exhaust tubulation 21. The wafer to neck sealing operation is made along the edge ofneck 17 and at the rim of wafer 19, and requires a'heating operation so that these portions of both of the glass members become plastic. if one of these beads 47 positioned-near the sealing region touches the glass duringthe-sealing operation, the neck portion 17 will tend to crack upon cooling from a strain created in the glass due to uneven heat conduction through the bead'trom thatlportion where the bead and-neck were touching. With the beads47 formed inaccordance with the longitudinal profile of the gun structure, the beads can be positioned close to grid 31, and thereby'greatly reduce the possibility of touching neck portion 17.

Gun structures formed inaccordauce with the invention are compact and rigid and their critical dimensional tolerances can be more easily maintained. In addition, due to the small diameter of the electrode assembly including the support beads, less cathode ray tube rejects occur from cracked glass neck portions.

Although one embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that variations and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. An electrode structure for an'electron discharge device having a neck portion comprising an electron emitter, electrodes for accelerating and modifying the electron beam arranged within said neck portion, and common support members for said electrodes extending longitudinally along substantially the entire length of said electrodes, said support members having'a form substantially conforming to the longitudinal profile of said electrode structure.

2. An electrode structure for an electron discharge 4 device having a neck portioncoinp'rising an electron emitter, electrodes for accelerating and modifying the electron beam arranged within said neck portion, some of said electrodes having a lateral dimension greater than other electrodes, and common support members for said electrodes extending longitudinally along substantially the entire length of said electrodes said support members having a form substantially conforming to the longitudinal profile or said electrode structure.

3. An electrode structure for an electron discharge device having an'eckp'o'rtion comprising'ianelectron emitter, an accelerating electro'de,"fociising electrodes, one of said focusing electrodes having a lateral dimension greater than other focusing electrodes,-and common support members for said electrodes within said neck portion extending longitudinally along said electrodes, said support members having a form substantially conforming to the longitudinal profile of said electrode structure.

"4. -An electrode structure for anelectron discharge device having a neck portion comprising'an electron emitter, an acceleratingelectrode, firstand-second lens electrodes, an electrostatic ring electrode, said ring electrode having a larger lateral dimension-that said lens electrodes, and common support members for said electrodes extending longitudinally along said electrodes Within said neck portion, said support-members.having a form substantially conforming to the longitudinal profile of said electrode structure.

'5. In an electrode structure .for-an electron discharge device having a neck portion comprising an electron emitter, an accelerating electrode, an electrostatic focusing assembly comprising a first lens electrode, an elongated ring electrode, and a second lens electrode arranged sequentially in the direction of electron travel, the ring electrode having a larger lateral dimension than said lens electrodes, and insulating support members extending longitudinally along said focusing assembly electrodes within the neck portion, said support members having a form substantially conforming to the profile of said focusing assembly.

References Cited'in the file-of this patent UNITED STATES PATENTS 2,053,537 Schlesinger Sept. 8, 1936 2,289,906 Epstein July 14, 1942 2,719,243 Hoagland Sept. 27, 1955

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