EP0652582A1

EP0652582A1 - Cathode-ray tube having ARC supressing means therein

Info

Publication number: EP0652582A1
Application number: EP93117917A
Authority: EP
Inventors: Baek-Young Choi
Original assignee: Orion Electric Co Ltd Korea
Current assignee: Orion Electric Co Ltd Korea
Priority date: 1993-11-04
Filing date: 1993-11-04
Publication date: 1995-05-10

Abstract

The present invention is direct to a cathode-ray tube having arc suppressing means therein. An electron gun mount assembly comprises the cathode electrode (3) to emit thermions, a control grid electrode to adjust the amount of the thermions emitted from the cathode electrode and to form the beam of electrons, a focusing electrode to focus the beam of electrons formed in the control grid electrode, and an accelerating electrode to accelerate the beam of electrons focused in the electrode. To remove the thermions leaking from the cathode electrode a metal piece (12) is positioned between any one of the metal wires located horizontally farthest away from the cathode electrode (3) and an inner wall of a neck glass (11), with one end of the metal piece being electrically connected to an extra stem pin grounded at any one of ground terminals outside the cathode-ray tube.

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

This invention relates to a cathode-ray tube having arc suppressing means therein, more particularly to a cathode-ray tube having arc suppressing means to make thermions leaking from a cathode electrode of an electron gun mount assembly flow out of a cathode ray tube by positioning a metal piece to an extra stem pin, thereby using the extra stem pin for grounding.

INFORMATION DISCLOSURE STATEMENT

Generally, a cathode-ray tube comprises a neck accommodating an electron gun mount assembly and a deflection plate assembly, and a viewing window having a fluorescent viewing screen. The electron gun mount assembly comprises the cathode electrode to emit thermions; a control grid electrode to adjust the amount of the emitted thermions and form the beam of electrons; a focusing electrode to focus the beam of electrons formed in the control grid electrode; and an accelerating electrode to accelerate the beam of electrons. The electron gun mount assembly is enveloped by a neck glass. Most of the thermions emitted from the cathode electrode reach the viewing screen passing through the control grid electrode, the focusing electrode and the accelerating electrode. However, a few of the thermions emitted from the cathode electrode leak toward the neck glass. The leaked thermions collide with the neck glass and generate secondary electrons, thereby causing the avalanches. The charged electrons due to the avalanches are moved toward the accelerating electrode in high voltage, thereby causing arcing phenomena.
To suppress such arcing,an inner wall of the neck glass have been coated, or a metal ring has been mounted to surround the accelerating electrode. However, the formed prevents only a part of the arcing, while the inner coating is burned by the arcing. The latter also partially reduce the arcing around the metal ring. That is, the prior art of the inner wall coating or the metal ring mounting is only partially effective in preventing arcing, but cannot eliminate the avalanches that cause the arcing.
Therefore, the object of the present invention is to provide the cathode-ray tube having arc suppressing means by positioning a metal piece between the inner wall of the neck glass and the electron gun mount assembly and connecting the metal piece to an extra stem pin so that the leaked thermions from the cathode electrode flow through the metal piece and the stem pin, and be released out of the cathode-ray tube.
The above function is only of the various, useful features of the invention. The invention can achieve other advantages when applied in a different manner or modified within the scope of the disclosure. The summary of the invention and the detailed description of the invention below describe the preferred embodiment of the invention within the scope of its claims.

SUMMARY OF THE INVENTION

To achieve the above-mentioned purposes, the invention connects an extra stem pin that is unused among these fixed in a stem to the ground terminal outside the cathode-ray tube. A metal piece is positioned between a metal wire located horizontally farthest away from a cathode electrode and an inner wall of a neck glass, and one end of the metal piece is connected to the extra stem pin. The metal piece is non-magnetic and is bent to contact the inner wall of the neck glass.
The pertinent and important features of the present invention have been outlined above in order to provide better understanding of the invention. Additional features of the invention described hereinafter further elaborate the claims of the invention. Those skilled in the art can appreciate that the conception and the specific embodiment disclosed herein may be readily utilized as a basis for modifying or designing structures to carry out the same purpose of the present invention. Furthermore, those skilled in the art can realize that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

To better understand the nature and object of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a sectional view, partly in cross-section of a neck for a cathode-ray tube according to the prior art; and
FIG. 2 is a sectional view, partly in cross-section of a neck for a cathode-ray tube according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a sectional view, partly in cross-section of a neck for cathode-ray tube according to the prior art. As being shown in FIG. 1, a neck 1 comprises an electron gun mount assembly 2. The electron gun mount assembly 2 comprises a cathode electrode 3 to emit the thermions, a control grid electrode 4 to adjust the mount of the thermions emitted from the cathode electrode 3 and to form the beam of electrons, a focusing electrode 5 to focus the beam formed in the control grid electrode 4, and an accelerating electrode 6 to accelerate the beam of electrons focused in the focusing electrode 5. The cathode electrode 3, the control grid electrode 4, the focusing electrode 4 and the accelerating electrode 6 are connected respectively to a plurality of stem pins 9a to 9f which are fixed in stem 8 by a plurality of metal wires 7a, 7b, 7c, 7d. An extra stem pin 10 is generally not used for electrode connections. The control grid electrode 4 is applied with negative voltage, while the focusing electrode and the accelerating electrode are applied with positive high voltage.
The operation of the electron gun mount assembly as shown FIG. 1 are as follows.
The thermions, emitted by the cathode electrode, form the beam of electrons through the control grid electrode 4. Increase of negative voltage applied to the control grid electrode 4 reduce the beam current. Also, the beam of electrons is focused by the focusing electrode 5. Increase of positive voltage applied to the focusing electrode 5 narrows the width of the beam of electrons. The beam of electrons passed through the focusing electrode 5 are accelerated by the accelerating electrode 6.
On the other hand, a few of the thermions, emitted from the cathode electrode 3, collides with an inner wall of a neck glass 11. Secondary electrons is generated by the collision and causes the avalanches. Charged electrons due to the avalanches move toward the accelerating electrode 6 which is applied with high voltage, thereby causing arcing between metal wire and the inner wall.
FIG. 2 is a sectional view, partly in cross-section of a neck for a cathode-ray tube according to the present invention. As shown in FIG. 2 a metal piece 12 which is bent toward the inner wall of the neck glass 11 is positioned between the metal wire 7d located farthest away from the cathode electrode 3 and an extra stem pin 10. The extra stem pin 10 is used for grounding, connected to a ground terminal in a printed circuit board placed in a monitor or a television set.
Accordingly, the thermions which leaking from the cathode electrode does not cause any arcing because they flow through the metal piece 12 and the extra stem pin 10 to the ground terminal of the printed circuit board.
Meanwhile, the metal piece 12 is made of non-magnetic metal and is bent to contact the inner wall of the neck glass 11 so that the metal piece 12 should not be shorted with the metal wire 7d.
As mentioned above, the cathode-ray tube having arc suppressing means therein according to the present invention makes the thermions leaking from the cathode electrode be released out of the cathode-ray tube and thus eliminate the arcing generated in the neck by the leaked thermions.
Although this invention has been described in its preferred embodiment with a certain degree of particularity, one skilled in the art would know that the preferred embodiment disclosed here is only an example and that the construction, combination and arrangement of its parts may be changed variously without departing from the spirit and scope of the invention.

Claims

A cathode-ray tube comprising a cathode electrode to emit thermions;
a control grid electrode to adjust the amount of the thermions emitted from said cathode electrode and to form the beam;
a focusing electrode to focus the beam of electrons formed in said control grid electrode;
an accelerating electrode to accelerate the beam of electrons focused in said focusing electrode;
a plurality of stem pins which are electrically connected to said cathode electrode, said control grid electrode, said focusing electrode and said accelerating electrode through a plurality of metal wires, respectively;
an extra stem pin;
a stem to fix said stem pins and said extra stem pin; and
a neck glass to envelope said cathode electrode, said control grid electrode, said focusing electrode and said accelerating electrode, characterized in that a metal piece is placed between one of said metal wires that are located horizontally farthest away from said cathode electrode and an inner wall of the neck glass, with one end of said metal piece being electrically connected to said extra stem pin which is grounded at any one of ground terminals outside said cathode-ray tube.
The cathode-ray tube as claimed in claim 1, wherein said metal piece is made of non-magnetic metal.
The cathode-ray tube as claimed in claim 1, wherein said metal piece is bent to contact an inner wall of said neck glass.