Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-06-24
2001-04-10
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S446000, C313S447000, C313S438000
Reexamination Certificate
active
06215238
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for manufacturing an electron gun, in which method a number of electrodes is stacked and secured to a number of insulating support rods by securing means.
The invention also relates to a cathode ray tube having an electron gun for generating an electron beam, the electron gun having a number of electrodes secured to a number of insulating support rods by means of securing means.
The invention also relates to an electron gun for use in a cathode ray tube, the electron gun having a number of electrodes secured to a number of insulating support rods by means of securing means.
Such cathode ray tubes are known and are used in for instance television apparatuses and computer monitors.
Conventional electron guns of cathode ray tubes comprise a number of electrodes, which are positioned one after the other, starting from one cathode (for monochromic cathode ray tubes) or from three cathodes (for colour cathode ray tubes). The electrodes have at their outer circumference securing means secured to electrically insulating support rods. Usually the securing means comprise parts such as protrusions, hooks or brackets which are secured to a number of insulating support rods, for instance by being partly embedded in or attached to a number, usually two, beading rods. The insulating support rods, e.g. beading rods, are usually made of glass and form the back-bone of the electron gun to which the electrodes are attached. In order to attach the electrodes to the beading rods, the electrodes are stacked on each other, for instance in a jig, the beading rods are heated to a temperature at which the glass of the beading rods softens, and the beading rods are pressed against the securing means. Thereby the securing means are at least partly embedded in or attached to the softened material of the beading rods, i.e. secured to the insulating support rods. Thereupon the temperature is lowered, and the material of the rods solidifies, trapping part of the securing means in the beading rods.
Although the conventional design and method for manufacturing have been used with some success, the inventor has realized that the ever higher demands that are placed on the performance of the electron gun and the strive for cost reduction have made the disadvantages of the conventional design ever more relevant. It is very difficult in the conventional design to maintain an accurate positioning of the electrodes with respect to each other. Any change of the positions of the electrodes introduces an error in the position and/or shape of the electron beams on the display screen and/or on the relative positions of the electron beams. Such errors have a detrimental effect on the quality of the image on the display screen. Furthermore the number of parts necessary for the manufacturing of the electron gun increases as the number of electrodes increases. This adds to the cost of manufacturing and furthermore increases the risk that the electron gun comprises a flaw.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for manufacturing an electron gun in which one or more of the above mentioned problems are decreased or alleviated.
To this end the method for manufacturing the electron gun is characterized in that it comprises the following method steps:
in a planar element a pattern of openings is made, thereby forming a number of securing means attached to the remainder of the plate,
parts of said securing means are bend out of the plane of the planar element,
a number of said bend parts are secured to an insulating support rod,
the insulating support rod-securing means assembly is disconnected from the remainder of the planar element,
a number of insulating support rods are made to engage a stack of electrodes via said securing means and
said securing means and the stack of electrodes are interconnected.
The method according to the invention uses a planar element, e.g. a flat plate or strip of material in which a number of securing means are made, which, further in the method of manufacturing, will interconnect the electrodes and the insulating support rods. In conventional designs and manufacturing method each electrode is secured to a pair or a number of pairs of securing means, each pair comprising a securing means at opposite sides of the electrode. For flat electrodes the securing means are usually protrusions at the periphery of the electrode, for tubular or cylindrical electrodes hooks or brackets are used which are attached to the electrodes. The number of different elements is large and the number of attachment steps is also large. Because the securing means in the invention are no separate elements, but either form part of the planar element, or part of the insulating support rod-securing means assembly, the effective number of different elements, i.e. the number of elements that have to be dealt with separately is strongly reduced. The reduction of the effective number of elements effects a substantially reduction of the cost of manufacturing. Furthermore, there is no need to exert pressure on the electrodes during interconnecting the electrodes and the beading rods as in the conventional method. This reduces the risk that the electrodes change position, thereby increasing the average quality of the electron guns and reducing the manufacturing loss. The electrodes are also not subjected to high temperatures which reduces the thermal stresses in the electron gun. This results in an improved average quality of the electron gun.
The securing means can be secured in various ways to the insulating support rod, for instance by clamping. In preferred embodiments bend parts of the securing means are made to engage an insulating support rod, which is at a high temperature, and embedded at least partly in the support rod. This process is usually called “beading”, and the insulating support rods are called “beading rods”. The method can be used very advantageously in such beading processes because the invention make it possible to control much more accurately the temperature of the beading rod and the force, speed and direction with which the securing means are embedded in the beading rod. In the conventional method all beading rods (usually two or four) are simultaneously heated by differing heating devices (usually some type of flame torches) and simultaneously forced against the securing means. It is however very difficult in such conventional method to ensure that all beading rods have throughout the length of the beading rod the same temperature and that all beading rods are, throughout the length of the beading rod forced against the securing means with the same force (in strength and direction). In the method according to the preferred embodiment of the invention, however, the securing means attached to the plate are secured to the beading rods in a method step separate from the method steps in which the electrodes are stacked. This enables a greater control on important parameters such as the temperature of the beading rod, the force with which the securing means and beading rod are pressed to each other, the rate of cooling, and the separation between the securing means. As a result better and better controllable connections between the securing means and the beading rods can be made.
In a preferred embodiment of the invention the pattern of openings is made by means of etching the openings in the planar element.
Etching the openings can be done with a great accuracy and does not introduce mechanical stresses in the material of the planar element. Mechanical stresses can lead to shifts in the positions of the electrodes.
Alternatively, other methods for making the patterns of openings can be used for instance laser cutting or stamping.
A preferred embodiment is characterized in that the first and second mentioned method steps (making a pattern of openings and bending parts of the elements out of the plate) are performed simultaneously. This can be achieved for instance by a combined stamping/bending method. Doi
Leemans Martinus J. J. M.
Van Der Horst Michiel G. A. M.
Verheggen Petrus J. M.
Kraus Robert J.
Patel Nimeshkumar D.
U.S. Philips Corporation
Williams Joseph
LandOfFree
Cathode ray tube, electron gun for a cathode ray tube,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cathode ray tube, electron gun for a cathode ray tube,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cathode ray tube, electron gun for a cathode ray tube,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2550743