An impregnated pellet for a cathode structure according to the present invention is produced by forming a plurality of voids by arranging a plurality of metal rods within a cylinder of heat-resisting metal open at both ends thereof, impregnating the voids with electron emission material, thereby to prepare a rod-shaped pellet base, cutting the rod-shaped pellet base into respective impregnated pellets of a predetermined thickness, and finishing the cut surfaces of the pellets by vibration and tilting operation of working plate. The impregrate pellets can be extensively applied to a cathode-ray tube, an electron tube and the like, which require high current density.
1. An impregnated pellet for a cathode structure comprising:
a metallic cylinder made of heat-resisting metal and open at both ends thereof;
a plurality of metal rods arranged vertically within said metallic cylinder to form a plurality of voids between said metal rods; and
electron emission material in each of said voids.
2. A method of producing an impregnated pellet for a cathode structure, comprising the steps of:
preparing a metallic cylinder open at both ends thereof;
forming a plurality of voids by arranging a plurality of metal rods within said metallic cylinder;
impregnating said voids with electron emission material thereby to prepare a rod-shaped pellet base;
cutting said rod-shaped pellet base into respective impregnated pellets of a predetermined thickness; and
finishing the surface of said cut pellets by vibration and tilting operation of a working plate on which a working material of fine powder is distributed.
3. A method of producing an impregnated pellet for a cathode structure as claimed in claim 2, wherein said step of impregnating said voids with electron emission material is carried out after said step of cutting said rod-shaped pellet base.
4. A method of producing an impregnated pellet for a cathode structure as claimed in claim 2, wherein said working material of fine powder is one or more powder material selected from alumina (Al2 O3) and tungsten(W).
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cathode structure mounted in an electron gun of a picture tube to emit thermions, and more particularly an impregnated pellet for a cathode structure, which is impregnated with electron emission material, and a method of producing the pellet.
2. Description of the Prior Art
Generally, a cathode structure comprises an impregnated pellet 11 composed of heat-resisting metal and thermion emission material and disposed on the top of a cathode sleeve 12 with a cathode heater 13 mounted therein, as shown in FIG. 1 of the accompanying drawings. The impregnated pellets have been used in the past in an oscilloscope and the like requiring a cathode current and at present are also applied to electron tubes such as picture tubes which tend to be large-sized and require high precision and minuteness. Particularly, the impregnated pellet applied to the cathode structure of the picture tube is an important component having a great influence upon the quality and service life of a product.
As shown in FIGS. 2a and 2b, a prior method of producing the impregnated pellet 11 applied to the cathode structure of the picture tube comprises the steps of preparing a heat-resisting, porous sintered body 11a having a plurality of internal and external voids 15,16 by pressing and sintering high temperature and heat-resisting metal powder such as tungsten (W); impregnating the voids 15,16 of the porous sintered body 11a with a molten working material such as copper, plastics, etc., and then shaping the impregnated sintered body into an element in the form of a coin having an outer diameter of about 1.5 mm and a thickness of 0.4 mm by machining the sintered body to conform to the area of the top of the cathode sleeve 12(FIG. 1); clearing the voids 15,16 of the copper or plastic material through evaporation of the material by high temperature heating, or dissolution of the material by a chemical treatment; removing the remaining metal fragments on the surface of the pellet produced during the machining work by using fine power and high pressure gas; and impregnating the voids 15,16 of the pellet with molten electron emission material such as barium oxide(BaO), calcium oxide(CaO), alumina(Al2 O3), etc., at a high temperature atmosphere. Then, after the impregnated pellet 11 thus produced is subjected to a surface treatment and bonded porous pellet is coated with metal such as osmium(Os), ruthenium(Ru), etc., to lower the work function of the cathode structure.
The impregnated pellet must have a smooth surface so as to facilitate emission of the electrons from the electron emission material 14 in the voids 15,16 of the pellet during the operation. the prior impregnated pellet produced through the steps as set forth above is however disadvantageous in that since fine powder and high pressure gas are used to remove the melts which remain on the surface of the pellet after the impregnation of the voids 15,16 with the molten electron emission material to deteriorate the smoothness of the surface, the manufacturing process is increased, resulting in lower productivity and higher manufacturing cost. In addition, since the internal voids 15 of the porous sintered body 11a are isolated from the exterior, only the external voids 16 open to the exterior are impregnated with the electron emission material in the external void is shallow and the distribution of the impregnation areas on the surface of the pellet and the size of each impregnation area are irregular and ununiform. As a result, during the heating operation of the heater of the cathode structure, emission of the thermions from the surface of the pellet may be effected ununiformly and the electron emission material may be exhausted rapidly, thereby to shorten the service life of the product.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art in view, it is an object of the present invention to provide an impregnated pellet for a cathode structure, which comprises a regular array of heat-resisting metal rods to form voids, which are in turn impregnated with electron emission material, so that uniform emission of thermions can be effected and plastic impregnating and removing steps can be eliminated, thereby to reduce the manufacturing process, resulting in increased productivity and lowered manufacturing cost.
To achieve the above object, there is provided according to one aspect of the present invention an impregnated pellet for a cathode structure comprising a metallic cylinder made of heat-resisting metal and open at both ends thereof, a plurality of metal rods arranged vertically within the metallic cylinder to form a plurality of voids between the metal rods, and electron emission material impregnated the voids.
According to another aspect of the present invention, there is provided a method of producing an impregnated pellet for da cathode structure, comprising the steps of preparing a metallic cylinder open at both ends thereof; forming a plurality of voids by arranging a plurality of metal rods within the metallic cylinder; impregnating the voids with electron emission material thereby to prepare a rod-shaped pellet base; cutting the rod-shaped pellet base into respective impregnated pellets of a predetermined thickness; and finishing the surfaces of the cut pellets by vibration and tiling operation of a working a plate on which a working material of fine powder is distributed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings;
FIG. 1 is a vertical cross-sectional view of a conventional cathode structure;
FIGS. 2a and 2b are vertical cross-sectional and plan views of a prior art impregnated pellet, respectively;
FIGS. 3a and 3b are vertical cross-sectional and plan views of an impregnated pellet according to the present invention, respectively;
FIG. 4a is a perspective view showing a rod-shaped pellet base before being cut into the respective impregnated pellets according to the present invention;
FIG. 4b is a perspective view showing one of the impregnated pellets cut from the rod-shaped pellet base; and
FIG. 5 is a perspective view explaining the operation of a working plate used for a surface treatment of the cut surfaces of the impregnated pellets according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention will now be described in detail, by way of example, with reference to the accompanying drawings.
Referring to FIGS. 3a and 3b showing vertical cross-sectional and plan views of an impregnated pellet for a cathode structure according to the present invention, the impregnated pellet 1 of the present invention comprises a metallic cylinder 2 made of heat-resisting metal and open at both ends thereof, a plurality of heat-resisting metal rods 3 disposed vertically in a given array within the metallic cylinder 2 to form a plurality of voids 5 in the form of a tunnel between the metal rods, and electron emission material 4 molten and impregnated voids 5.
A method of producing the impregnated pellet of the present invention will now be described with reference to FIGS. 4a, 4b and 5.
As shown, the method comprises the steps of preparing the metallic cylinder 2 having open opposite ends from high temperature and heat-resisting metal such as molybdenum(Mo) by means of deep drawing, welding, pressing or piping operation; forming the voids 5 by arranging a plurality of the rods 3 of high temperature and heat-resisting metal such as tungsten (W) in a given array within the metallic cylinder 2; impregnating the voids 5 formed by the array of the metal rods 3 with the molten electron emission material 4 of oxides such as barium oxide(BaO), calcium oxide(CaO), alumina(Al2 O3), etc., at a high temperature atmosphere, thereby to prepare a rod-shaped pellet base 1a, as shown in FIG. 4a; cutting the rod-shaped pellet base 1a containing the electron emission material 4 into the respective impregnated pellets 1 in the form of a coin having a predetermined thickness (about 0.4 mm), as shown in FIG. 4b, by laser or mechanical means; and removing the metal fragments remaining on the cut surfaces of the impregnated pellets 1 through a surface treatment process of the pellets, which comprises placing the pellets i on the surface of a working plate 7 on which a working material 6 comprising fine powder of alumina, tungsten or the like is distributed, and then vibrating and tilting through a predetermined angle(θ) the working plate 7, as shown in FIG.5.
Then, the impregnated pellet 1 thus produced is bonded to the top surface of the cathode sleeve 12 with the cathode heater 13 mounted therein, as shown in FIG. 1, and thereafter metal such as osmium(Os), ruthenium(Ru) or the like is coated on the upper surface of the bonded pellet so as to lower the work function of the cathode structure. Thus, assembly of the cathode structure is completed.
Alternatively, the step of impregnating the voids 5 with the electron emission material 4 may be carried out after the step of cutting the pellet base 1a into the respective impregnated pellets 1.
Further, in the step of forming the voids 5, although the porosity of the impregnated pellet 1 of more than 9% can be obtained, the size of each void is determined depending upon the shape and size of each metal rod 3. Therefore, it is possible to obtain a desired porosity by varying the configurations of the voids through changes of the arrangement distance and shape of the metal rods. For example, when the pellet is made by arranging the metal rods having a diameter of 0.5 mm, the voids 5 having a diameter of about 0.012 mm are provided in the pellet, so that the porosity of about 10% is achieved. That is, the greater the diameter of the metal rod, the lower the porosity of the pellet. On the contrary, the less the diameter of the metal rod, the higher the porosity of the pellet. Therefore, the diameter of the metal rod 3 can be chosen to obtain an optimum porosity. In addition, the configuration of the void and the porosity of the pellet can be varied with a change of the shape of the metal rod.
As discussed above, since the impregnated pellet 1 of the present invention is made by impregnating a plurality of the voids 5 in the form of a tunnel, which are formed by an array of the metal road 3 and each o
pen at both ends thereof, with the molten electron emission material, uniform emission of electrons form the surface of the impregnated pellet can be induced and exhaustion of the electron emission material due to emission of the electrons therefrom during operation of the cathode heater does not proceed rapidly. Further, since a working material for shaping of a sintered body, as in the prior art, is not necessitated and the impregnated pellets 1 are cut from the rod-shaped pallet base 1a, and then subjected at only the cut surfaces to a surface treatment, the manufacturing process is shortened, resulting in lowered manufacturing cost and increased productivity.
While the invention has been shown and described with particular reference to a preferred embodiment thereof, it will be understood that variations and modifications in form and detail may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
US Patent References:
4916356 High emissivity cold cathode ultrastructure 1990-04-10 Ahern et al. 313/346R
4310603 Dispenser cathode 1982-01-12 Falce 313/346R
4031425 Dispenser cathode for a grid-controlled electron tube and method of manufacturing same 1977-06-21 Ziegler et al. 313/346DC
3753025 INDIRECTLY HEATED SUPPLY CATHODE 1973-08-14 Van Stratum et al. 313/270
2958798 Electron emitter 1960-11-01 Anton 313/310
Foreign References:
JP5834540 March, 1983
JPS5834540A 1983-03-01.
Method of forming a phosphor layer on the screen panel of a cathode-ray tube
A method of forming a phosphor layer on the screen panel of a cathode-ray tube include the steps of charging phosphor slurry on the inside of the screen panel, rotating the screen panel to spread the phosphor slurry forming the phosphor layer, and exposing the screen panel to a light disposed in front of the inside of the screen panel and a plurality of lights disposed in front of the outside of the screen.
1. A method of forming a phosphor layer on a screen panel of a cathode-ray tube, consisting of the steps:
charging phosphor slurry on the inside of said screen panel;
rotating said screen panel to spread said phosphor slurry forming said phosphor layer; and
exposing said screen panel and said phosphor layer to a light disposed in front of the inside of said screen panel and a plurality of lights disposed in front of the outside of said screen panel,
wherein said plurality of lights disposed in the front of the outside of said screen panel are respectively disposed in front of a central portion and four corners of said screen panels.
Description:
FIELD OF THE INVENTION
The present invention concerns a method of forming a phosphor layer on the screen panel of a color picture tube, and more particularly a method of exposing the peripheral portions of the phosphor layer.
BACKGROUND OF THE INVENTION
Generally, the screen forming process of a color picture tube is to form a three-color phosphor layer, comprising the steps of black coating and screen coating.
The black coating is to spread a non-reflective black paint on the inside of the screen panel to absorb unwanted light emission caused by scattered electrons generated between phosphor stripes or external light in order to enhance the contrast, while the screen coating is to spread the phosphors of three colors (Green, Blue, Red) in the holes between the black stripes formed by the black coating.
In order to form the phosphor layer, after a plurality of light-absorbing black stripes 6 are formed on the inside of the screen panel 2 as shown in FIG. 2, a green phosphor slurry comprising a phosphor powder, salt of chromic acid that is light-sensitive, polyvinyl alcohol and surfactant is loaded on the inside of the screen panel 2 rotated with a high speed to spread the phosphor slurry over the whole surface of the panel.
The phosphor slurry layer on the inside of the panel is dried, and then exposed to light developing into the holes of green, blue and red. If the panel and shadow mask are connected and exposed to an infrared light source 4 as shown in FIG. 3, the portions of the phosphor layer illuminated with the infrared ray become insoluble by light coupling reaction between the polyvinyl alcohol (PVA) and salt of chromic acid firmly adhered to the panel. Further the outer side of the panel is exposed to a light source 5 in order to enhance the effect of the infrared light source 4. Likewise the blue and red phosphor layers are sequentially formed.
In this conventional method of forming the phosphor layer on the screen panel, when the panel 2 is rotated with a high speed to spread the phosphor slurry over the whole surface, the central portion of the panel 2 hardly receives the centrifugal force, and the phosphor slurry disposed in the corners is hindered from spreading by the skirt portions 2a. Consequently, the phosphor layer 1 comes to have thicker portions in the central and corner regions than in the other regions, as shown in FIG. 1.
The thicker central and corner portions of the phosphor layer 1 do not receive the light of the infrared light source 4 enough to influence the depth, so that the phosphor layer 1 may be separated during development. Furthermore, in order to resolve this problem if the light intensity of the infrared light source is increased, the relatively thinned portions of the phosphor layer are excessively exposed to the light, and the width of the stripe 7 is widened to the positions of the phosphor layers of different colors so as to impair the clearness of the screen colors of images. In addition, the light source 5 such as incandescent lamp disposed in front of the central portion of the outer side of the panel 2 may prevent the separation of the central portion of the phosphor layer, but there is not resolved the problem caused by inadequacy of the exposing light in the corner portions.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method of forming a phosphor layer comprising uniform stripes on the screen panel of a cathode-ray tube, which realizes clear screen images.
According to the present invention, there is provided a method of forming a phosphor layer on the screen panel of a cathode-ray tube comprising the steps of charging phosphor slurry on the inside of the screen panel, rotating the screen panel to spread the phosphor slurry forming the phosphor layer, and exposing the screen panel to a light disposed in front of the inside of the screen panel and a plurality of lights disposed in front of the outside of the screen.
The present invention will now be described more specifically with reference to the drawings attached only by way of example.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
FIG. 1 is a schematic diagram for illustrating the cross section of a phosphor layer formed according to a conventional method;
FIG. 2 is an enlarged view of the stripes of the phosphor layer formed according to the conventional method;
FIG. 3 illustrates the light exposing arrangement of the conventional method;
FIG. 4 illustrates the light exposing arrangement of the inventive method; and
FIG. 5 illustrates the variation of the width (u) of the phosphor stripe with the luminosity of the lights disposed in front of the corners of the outer side of the panel according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized by a plurality of lights for exposing the outer side of the screen panel together with a infrared light source 4 for directly exposing the phosphor slurry spread on the inner side of the panel.
Referring to FIG. 4, there are shown a plurality of back lights 5 and 5a for exposing the outer side of the panel in order to improve the light exposition of the thickened portions in the central and corner regions of the phosphor slurry layer spread over the inside of the panel. An infrared light source 4 is disposed in front of the inside of the panel, while the back central light 5 is disposed in front of the central portion of the outer side of the panel with the back corner lights 5a disposed in front of the corners. The infrared light source and back lights are simultaneously turned on.
The panel coated with the phosphor slurry layer is mounted on a light exposing apparatus to expose the phosphor slurry layer to light. The infrared light source 4 and back lights 5 and 5a may be automatically turned on and off by an optical sensor.
It is preferable that the luminosity of the corner lights 5a have about 20-70% of that of the central light 5.
If the panel coated with a green, blue and red phosphor slurries is covered with the shadow mask, and mounted on the light exposing apparatus, the shutter of the light exposing apparatus is opened by the operation of the optical sensor, so that the inside of the panel is exposed to the infrared light source 4. Then the portions of the phosphor layer exposed to the infrared light through the slots of the shadow mask 3 are firmly adhered to the panel by the light coupling reaction between the PVA and salt of chromic acid.
The thicker central and corner portions of the phosphor layer also undergo sufficient light coupling reaction with the help of the central and corner lights 5 and 5a, thus providing uniform stripes 7a over the whole surface of the panel.
FIG. 5 is a graph for illustrating the changes of the width of the stripe with variation of the luminosity of the back corner lights 5a provided the luminosity of the infrared light source 4 and back central light 5 is fixed to 100W for obtaining the optimum stripe of the phosphor layer 1. As shown by the graph, the luminosity of the back corner lights 5a must be in the range of 20-70W in order to obtain a desired stripe of the phosphor layer.
As stated above, the back central and corner lights provided in front of the outer side of the panel help the whole surface of the panel be uniformly exposed to the light, thus providing desired phosphor layer stripes. Thus the corner portions of the phosphor layer are not separated from the panel so as to improve the quality of the cathode-ray tube, and even if the portions of the phosphor layer is separated during manufacturing, the back lights may be promptly and properly adjusted so as to prevent the separation. Moreover, the whole surface of the phosphor layer may be uniformly exposed to the light within a short time, which improves the productivity.
Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims.
US Patent References:
3954470 Process for fabricating a color cathode ray tube 1976-05-04 Barczynski et al. 430/24
Foreign References:
JP62076132 April, 1987 MANUFACTURE OF FLUORESCENT SCREEN FOR COLOR PICTURE TUBE
KR79-3493 March, 1983
JPS6276132A 1987-04-08
KR790003493B1.
Cathode heater structure of an electric gun for a cathode-ray tube and method of assembling the heaters
This invention provides a method of positioning and assembling in place cathode heaters of an electron gun for a cathode-ray tube, thereby resulting in improvements in assembling workability and in the white balance characteristic on the screen of the tube. A cathode heater structure includes a cathode heater and a heater supporter. The cathode heater includes a heat generating portion and a pair of leg portions extending from the heat generating portion. Each leg portion is formed with a bent engaging portion at its end. The heater supporter has guide grooves for receiving the engaging portions of the cathode heater to guide and position them. According to the method of the present invention, the cathode heaters are shot in sequence into the guide grooves of the heater supporter by means of
shooters, and then the leg portions of the heaters caught and positioned in the guide grooves are welded to the guide grooves.
1. A cathode heater structure disposed in a respective cathode assembly of an electron gun for a color picture tube and secured to opposite bead glasses together with electrodes, the heater structure comprising:
a cathode heater comprising a heat generating portion having two ends and a pair of leg portions extending from one end of said heat generating portion, each leg portion formed with a bent engaging portion at its end; and
a heater supporter having a plurality of guide grooves for receiving said engaging portions of said cathode heater to guide and position them,
wherein said engaging portions of said cathode heater are formed by bending said leg portions in conformity with the distance between the other end of the heat generating portion and each of said guide grooves of said heater supporter.
2. A cathode heater structure disposed in a respective cathode assembly of an electron gun for a color picture tube and secured to Opposite bead glasses together with electrodes, the heater structure comprising:
a cathode heater comprising a heat generating portion having two ends and a pair of leg portions extending from one end of said heat generating portion, each leg portion formed with a bent engaging portion at its end; and
a heater supporter having a plurality of guide grooves for receiving said engaging portions of said cathode heater to guide and position them,
wherein said guide grooves of said heater supporter are formed at predetermined intervals to correspond to the number of R, G, and B electron beam passage apertures of each of said electrodes and each of said guide grooves have a deepest bottom at its central portion.
3. A cathode heater structure disposed in a respective cathode assembly of an electron gun for a color picture tube and secured to opposite bead glasses together with electrodes, the heater structure comprising:
a cathode heater comprising a heat generating portion having two ends and a pair of leg portions extending from one end of said heat generating portion, each leg portion formed with a bent engaging portion at its end; and
a heater supporter having a plurality of guide grooves for receiving said engaging portions of said cathode heater to guide and position them,
wherein said guide grooves of said heater supporter have shapes including a triangular shape, a circular arc shape and a combined shape of circular arcs to provide smooth sliding and guiding of said leg portions of said heater.
4. A method of assembling cathode heaters of an electron gun for a color picture tube, comprising the steps of:
providing heater feeding means for feeding said cathode heaters each having a heat generating portion and a pair of leg portions;
shooting in sequence said heaters into guide grooves of a heater supporter by using said heater feeding means; and
securing said leg portions of said heaters caught in said guide grooves of said heater supporter,
wherein said heater feeding means has an outlet portion having a progressively decreasing cross-section and provided with an outlet opening comprising a central opening portion of a larger diameter through which said heat generating portion of each said heater passes during the shooting, and two side opening portions of a smaller diameter which are provided at the opposite sides of the periphery of said central opening portion to be in communication with said central portion and through which said leg portions of each said heater pass.
5. A method of assembling cathode heaters of an electron gun for a color picture tube, comprising the steps of:
providing heater feeding means for feeding said cathode heaters each having a heat generating portion and a pair of leg portions;
shooting in sequence said heaters into guide grooves of a heater supporter by using said heater feeding means; and
securing said leg portions of said heaters caught in said guide grooves of said heater supporter,
wherein said step of securing said leg portions comprises welding said leg portions to said heater supporter.
Description:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a cathode heater structure of an electron gun for a cathode-ray tube and a method of assembling the cathode heaters, and particularly a method of automatically positioning and assembling the cathode heaters of an electron gun.
DESCRIPTION OF THE PRIOR ART
Generally, an electron gun for a color picture tube comprises a stem 1 for applyi
ng voltage from the exterior of the gun, three cathode heaters 3 mounted in a row adjacently to the stem 1 and transversely of the gun through a heater supporter 2, three cathode assemblies 5 containing the respective cathode heaters 3 and supported in a row on bead glasses 12 through a cathode supporter 4, and first, second, third, fourth, fifth and sixth electrodes 6,7,8,9,19,11 disposed in order ahead of the cathode assemblies 5 and secured to the opposed bead glasses 12, as shown in FIG. 1 of the accompanying drawings.
Here, as shown in FIG. 2, each cathode assembly 5 comprises a t
ubular cathode sleeve 5a within which the cathode heater 3 is disposed to generate heat, and a cathode cap 5b having on its top thermion emission material such as barium carbonate. Each cathode heater 3 comprises a coiled heat generating portion 3a located in the cathode sleeve 5a of each cathode assembly 5, and a pair of leg portions 3b extending divergently from both sides of one end of the heat generating portion 3a.
With this construction, when voltage from the exterior of the electron gun is applied to the stem 1, the cathode heaters 3 in the cathode assemblies 5 generate heat, which is in turn transferred to the cathode caps 5b mounted at the upper ends of the cathode sleeves 5a of the cathode assemblies 5, so that thermions are emitted from the cathode caps having barium carbonate. Then, as the thermions pass through a plurality of the electrodes 6-11, they are accelerated, controlled and converged to form electron beams of a given shape. The electron beams land on a fluorescent screen coated with color phosphors, thereby developing a picture image. Thus, in order to obtain a picture image of good quality on the screen it is required to accurately secure the cathode heaters 3 in the respective cathode assemblies 5 to the bead glasses 12 in consideration of the pitch S of the R,G, and B electron beam passage apertures of each electrode of the color picture tube.
A process of assembling the cathode heaters of the electron gun for the color picture tube according to a prior art will now be described with reference to FIGS. 2 to 4 of the accompanying drawings.
First, as shown in FIGS. 2 and 3, the heat generating portions 3a of the three cathode heaters 3 are each inserted into each of the three cathode assemblies 5 arranged in a row at one side of the electron gun. Then, after the distance L between the leading end of the heat generating portion 3a of each cathode heater 3 and a welding point P on each leg portion 3b of the heater, which will be hereinafter referred to as a "welding point distance", and the pitch S of the electron beam passage apertures of each elec
trode have been set manually by the aid of a microscope, the leg portions 3b of the cathode heaters 3 are welded to longitudinally extending ridges 2a formed on the thin plate type heater supporter 2.
This prior assembling process however has a drawback in that since the cathode heaters 3 are manually assembled to the heater supporter 2, it is difficult to accurately set the welding point distance L shown in FIG. 3, and thereby deviation of the welding points P on the leg portions 3b of the heater from the horizontal line perpendicular to the center line of the electron beam passage aperture, may occur as indicated by the distance R in FIG. 4, causing adverse effects on the development of a picture image on the screen. More specifically, when the cathode caps 5b disposed at the Upper ends of the cathode assemblies 5 are heated by the cathode heaters 3 to emit thermions, the variation of the welding point distance L or existence of the deviation distance R may lead to temperature differences at the upper ends of the cathode assemblies. Then, the temperature differences influence the amount of electron beams emitted, resulting in an adverse effect on a picture image, such as white unbalance phenomenon of a color picture tube. Further, the manual assemblage is fairly labor-intensive and consequently time-consuming task, resulting in lower productivity.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art in view, the present invention is able to automatically, accurately position and assemble the cathode heater to a heater supporter at predetermined positions.
According to one aspect of the present invention a cathode heater structure disposed in a respective cathode assembly of an electron gun for a color picture tube and secured to opposite bead glasses together with electrodes comprises a cathode heater including a heat generating portion and a pair of leg portions extending from the heat generating portion and each formed at its end with a bent engaging portion; and a heater supporter having a plurality of guide grooves which position the leg portions.
According to another aspect of the present invention, a method of assembling cathode heaters comprises the use of heater shooters each having an interior cavity for containing the cathode heater and an opening for discharging the heater shot against a heater supporter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a schematic view of a conventional electron gun for a color picture tube;
FIG. 2 is an enlarged cross-sectional view of three cathode assemblies of the gun of FIG. 1, showing a cathode heater disposed one in each cathode assembly and welded to a heater supporter;
FIG. 3 is a side view illustrating one of the cathode heaters of FIG. 2, with the cathode assembly shown in section;
FIG. 4 is a plan view of the cathode heater shown in FIG. 3;
FIG. 5 is an enlarged cross-sectional view similar to FIG. 2, but showing three cathode heaters according to the present invention assembled in a row to a heater supporter;
FIG. 6 is a side view showing the cathode heater of the present invention assembled to the heater supporter;
FIG. 7 is a plan view of the cathode heater shown in FIG. 6;
FIGS. 8a and 8b are views showing different shapes of a guide groove formed in the heater supporter according to the present invention;
FIG. 9 is a view explaining the operation of assembling the cathode heater to the heater supporter in accordance with the present invention;
FIGS. 10a and 10b are front and side views of a heater shooter used in the present invention; and
FIG. 11 is a bottom view of the heater shooter used in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described in detail, by way of example, with references to FIGS. 5 to 10 of the accompanying drawings.
Referring to FIGS. 5 and 6, the present invention provides a method of assembling in place three cathode heaters 3, which are disposed on in each of three cathode assemblies 5 arranged in a row transversely of an electron gun, by using a heater supporter 2 having a plurality of pairs of guide grooves 2b formed therein to correspond in number to the number of the cathode assemblies 5 and the guide and position leg portions 3b of the cathode heaters 3. The guide grooves 2b of the heater supporter 2 are disposed at predetermined intervals corresponding to the distances S between the longitudinally extending lines passing through the centers of the R, G and B electron beam passage apertures of electrodes (not shown). Each guide groove has a deepest bottom at its central portion. The shape of each guide groove is not restricted to a triangular shape as shown in FIG. 5, but may be any of various shapes including a single circular arc 2c as shown in FIG. 8a and a multiple arc 2d comprised of a plurality of circular arcs as shown in FIG. 8b.
The cathode heater 3 on the present invention has engaging portions 3c formed by bending the ends of the leg portions 3b to be engaged with the guide groove 2b of the heater supporter 2. At this time, the bending positions of the leg portions of the cathode heater are determined in design in consideration of the distance G between the leading of a heat generating portion 3a of the heater and the deepest central bottom of each guide groove 2b of the heater supporter.
Referring to FIGS. 10a, 10b and 11 which respectively show front, side and bottom views of a heater shooter for feeding the cathode heaters to the heater supporter, the heater shooter 40 according to the present invention is made of a tubular member comprising a hollow cylindrical body 40a and an outlet portion 40b formed at one end of the cylindrical body 40a to have a progressively decreasing cross-section. As shown in FIG. 11, an outlet opening 41 of the outlet portion 40b is comprised of a central opening portion 41a of a larger diameter through which the heat generating portion 3a of the cathode heater 3 passes during feeding operation, and two side opening portions 41b of a smaller diameter which are provided at the opposite sides of the periphery of the central opening portion 41a to be in communication with the central portion and through which the leg portions 3b of the cathode heater pass during the feeding operation. In cathode heater assembling operation, the shooters 40 are used with three shooters joined together to make a set.
A process of assembling the cathode heaters for the electron gun according to the present invention will now be explained with reference to the drawings.
First, the cathode heaters 3 are put into the heater shooters 40 with the heat generating portion 3a of each heater positioned within the larger central opening portion 41a of each shooter and with the leg portions 3b of each heater positioned within the smaller side opening portions 41b of each shooter. At this time, the heater is loaded into the shooter 40 with the heat generating portion 3a thereof facing forwardly.
Then, as shown in FIG.9, the heaters 3 contained in the shooters 40 are shot in the direction of the arrow (downwardly as viewed in the drawing) through the outlet openings 41 of the shooters such the engaging portions 3c of the leg portions 3b of the heaters are inserted into the guide grooves 2b of the heater supporter 2. Then, as the heaters 3 caught in the guide groove 2b of heater supporter are slid down by their own gravity to rest on the deepest central bottoms of the guide grooves, each of the heaters is disposed accurately symmetrically with respect to each of the longitudinally extending lines passing through the centers of the R, G and B electron beam passage apertures of the electrodes, as shown in 
FIG. 7. At this time, since the engaging portions 3c of each cathode heater 3 are bent at the points corresponding to the predetermined distance G between the leading end of the heat generating portion 3a of the heater and the deepest bottom of each guide groove 2b of the heater supporter 2, the welding point distance L between welding point P1 of each leg portion 3b of the heater and the leading end of the heat generating portion 3a can be always kept constant.
Finally, assembly is completed by welding the thus aligned leg portions 3b of the heater 3 to ridges 2a of the heater supporter 2 at the welding points P1.
From the foregoing it will be appreciated that according to the present invention, since the cathode heaters can be automatically supplied by means of the shooters, and then guided and secured in place by the suitably shaped guide grooves of the heater to be accurately assembled to the supporter, an improvement in assembling workability and a reduction in assembling tolerance can be achieved. As a result, white unbalance occurring on the screen of the color picture tube is reduced, resulting in enhanced product quality.
While the invention has been shown and described with particular reference to an embodiment thereof, it will be understood that variations and modifications may be made therein without departing from spirit and scope of the invention as defined in the appended claims.
Foreign References:
DE2654554A1 1978-06-08 313/446
JP0017535 January, 1982 313/337
JPS5717535A
Electron gun for color picture cathode-ray tube with hexagonal cross-section
An electron gun for a color picture cathode-ray tube which includes a main focusing lens of a large diameter for reducing deterioration of the focusing property caused by the spherical aberration of the main focusing lens, shortening the distances among three electron beams to minimize the deflection aberration from deflection yoke and making feasible a design for effective enlargement of the lens diameter even with the shortening of the distances among the three electron beams in the color picture cathode-ray tube requiring a good focusing property of the three beams.
1. An electron gun for a color picture cathode-ray tube, which comprises:
an electron beam formative region for emitting three electron beams, said electron beam formative region including cathode emitting electrons fixed on a cathode support wherein the electrons are emitted from a heater located in the cathode, and a first grid electrode and a second grid electrode for controlling the amount of actuate function of said electrons, and
an electrostatic focusing lens for focusing said three electron beams, said electrostatic focusing lens including a first accelerating, focusing electrode and a second accelerating, focusing electrode for reducing the spherical aberration and the magnification of the said electrostatic focusing lens, said first accelerating, focusing electrode and said second accelerating, focusing electrode having their openings facing each other and containing a rim extended from an outer wall and having an oblong hole, a slanting enlarging aperture electrode located in said outer wall, said slanting enlarging aperture electrode having a longitudinally oblong center hole of a longitudinal cross section larger than a lateral cross section, two longitudinally elongated semi-hexagonal outer end portions of the longitudinal cross section being larger than the lateral cross section of said semi-hexagonal outer end portions, two electrode connecting portions in parallel to said outer wall, and two side slant portions narrowing down to a bottom portion extended from two head portions and said two electrode connecting portions, whereby a laterally oblong hole is formed by said rim and three longitudinally oblong holes, and said electron beam formative region and said electrostatic focusing lens are fixed on the head glass, respectively.
2. The electron gun of claim 1, wherein the slanting enlarging aperture electrode further has oblong hole portions disposed at side slant portions extended from the bottom portion.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron gun for a color picture cathode-ray tube (hereinafter "CRT") for reducing deterioration of focusing property, minimizing deflection aberration from deflection yoke, and improving focusing property.
2. Description of the Prior Art
Generally, conventional electron guns are utilized in an electrostatic focusing system. An electrostatic focusing lens of the electrostatic focusing system placed between a first accelerating and focusing electrode and a second accelerating and focusing electrode closely focuses the beams from the electron beam forming region consisting of cathodes and a number of electrodes in front of the cathodes. The performance of such electrostatic lens depends on the difference of focusing force between the near-axis region and the maximum outer angle region, causing the spherical aberration of the lens. The larger the lens diameter is, the lesser the spherical aberration becomes.
In order to obtain a good electron beam focusing property for an electron gun for the color picture CRT, the electron beam through-holes of the first and second accelerating and focusing electrodes are preferred to be as large as possible.
FIGS. 1, 2(A), 2(B), and 3 show a conventional electron gun for a color picture cathode-ray tube. Such conventional electrode gun includes a first accelerating and focusing electrode 8 and a second accelerating and focusing electrodes.
The first accelerating and focusing electrode 8 and the second accelerating and focusing electrodes 9 form an electrostatic lens. Each of the electrodes 8 and 9 has an open end on one side and a oblong-shaped closed end and the two closed ends face each other. The closed end 13 of the electrode 8 and the closed end 14 of the electrode 9 connected to respective end walls 11 and 12, respectively are provided with three through-holes 11a and 12a, 11b and 12b, and 11c and 12c for passing electron beams. The through-holes have a rimmed lip extending from the closed end faces, respectively.
In the focusing electrodes 8 and 9, the upper walls 11 and 12 have 6 mm in height (hereinafter "H"), the lips 15 and 16 have 1.2-3.5 mm h, the electron beam holes have 5.5-5.9 mm in diameter (hereinafter "D"), and the distance between the adjacent holes is 6.6-6.9 mm. However, the above measurements are subject to the limitation of the optimum diameter 29.1 mm of the tube neck in a conventional color picture CRT.
The first and second focusing electrodes 8 and 9 are also arranged, as shown in FIG. 1, for the first focusing electrode 8 to be connected with its open end to a third grid electrode 7. The electron gun for the color CRT basically includes a cathode 4 fixed to a cathode support 2, first, second and third grid electrodes 5, 6, and 7, and the first and second accelerating and focusing electrodes 8 and 9 wherein they are arranged in a pile in the above mentioned order and fixed to a pair of bead glass 10.
In a conventional color picture CRT shown in FIG. 1, a heater 3 welded to a support 1 and inserted into the cathode 4, heats the cathode 4 and make it emit heated electrons. The third grid electrode 7 having an elongated cylindrical configuration and positioned in front of the first and second grid electrodes 5 and 6 connects to the first accelerating and focusing electrode. The first and second accelerating and focusing electrodes 8 and 9 constitute an electrostatic focusing lens, that is a bi-potential focus (hereinafter "BPF").
The first and second accelerating and focusing electrodes 8 and 9 may be utilized in an electron gun including a plurality of additional electrodes disposed in the third grid electrode 7.
According to the conventional electron gun for the CRT, the electrons emitted from the cathode 4 by the heating of the heater 3 form an electron beam. The electron beam passes through the first grid electrode 5, the second grid electrode 6 and the third grid electrode 7 and enters the electrostatic focusing lens formed between the first and the second focusing electrodes 8 and 9. The received electron beams are closely focused to reach the fluorescent screen of the CRT and form a beam spot. The beam spot formed on the screen should have a high density in a round form in the least possible area.
However, in the first and second accelerating and focusing electrodes 8 and 9 for forming an electrostatic focusing lens of the electron gun shown in FIG. 2, the beam spot is distorted into a laterally oblong shape under the influence of the electrostatic focusing lens diameter. The diameter is restricted by the limited holes 11a-11c and 12a-12c for passing electron beams. Furthermore, the beam spot is distorted the deflection aberration caused by a deflection yoke. Therefore, the beam spot has a low density which deteriorates the resolution of the color picture CRT as a disadvantage.
For example, as shown in FIG. 3, the electrodes 8 and 9 for constituting an electrostatic focusing lens are housed in a tube neck 17 having an optimum diameter of 29 mm for the CRT. The thickness (b) of the rims respectively surrounding three beam through-holes in the closed end face of the first focusing electrode 8 has to be 1 mm in actual structure. Therefore, their relation is expressed by the following formula (I): D≤S-1 (I)
Furthermore, the distance (a) between the inner wall of the tube neck 17 and the outer end walls 11 and 12 of the focusing electrodes requires to be 1 mm, their relationship being expressed by the following formula (II): D≤R-(2a)-2(S+b) (II)
wherein R is the inner diameter of the tube neck, approximately 24 mm.
Therefore, the diameter is represented by the following formula (III): D≤20-2S (III), and
Dmax=6 mm and Smax=7 mm result from the formulas (I) and (III).
The conventional first and second focusing electrodes 8 and 9 form merely an electrostatic focusing lens of 6 mm at the maximum in diameter. Therefore, the small diameter of the focusing lens increases the spherical aberration, that is, the difference in focusing force between the near-axis region and the maximum outer angle region in the lens forms beam spots with a low density on the screen.
Also, because of the round shape of the electrostatic focusing lens, the beam spot with a low beam density distorts into a laterally oblong shape by the deflection aberration of deflection yoke to and further deteriorates the resolution of the color picture CRT. The known art concerning the lateral distortion of electron beams by the deflection aberration of deflection yoke will be omitted.
Besides, in order to obtain a better concentration of three electron beams for focusing three beam spots to gather a small converging area on the image screen, the distance S between adjacent beam holes is required to be smaller, but the conventional art gives 7 mm of S at the maximum under the limitation of the maximum lens diameter of 6 mm from the formulas (I) and (III). Accordingly, it is an disadvantage that the large distance S between the holes brings deterioration of the concentrating property of the CRT.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved electron gun for a color picture CRT, which can be shortened the distance among electron beams and yet effectively enlarge the lens diameter without changing the distance among the beams even when the first and second focusing electrodes for the electrostatic focusing lens are housed in a restricted tube neck so as to eliminate the disadvantages of the conventional art.
Another object of the present invention is to provide an electron gun construction which includes a slanted enlarging electrode provided with a laterally oblong hole having openings through which three beams jointly pass together. The openings are formed at the opposite faces of the first and second focusing electrodes and surrounded by respective rims extending from the end walls. A longitudinally oblong hole through which three beams pass, has a distance from the end rim so that the laterally oblong hole and the longitudinally oblong hole form a perpendicularly oblong hole.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Briefly described, the present invention relates to an electron gun for a color picture cathode-ray tube, which includes a main focusing lens having a large diameter for reducing deterioration of the focusing property, short distances among three electron beams for minimizing the deflection aberration from deflection yoke and a feasible design for effective enlargement of the lens diameter disposed in the color picture cathode-ray tube so as to achieve a better focusing property of the three beams.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
FIG. 1 is an elevational view of the conventional electron gun for the color picture CRT containing cut away portions in order to illustrate the construction of basic components thereof;
FIG. 2(A) is an sectional view of FIG. 1 showing the main electrostatic focusing lens including a first accelerating and focusing electrode and a second accelerating and focusing electrode;
FIG. 2(B) is a top plan view of the first accelerating and focusing electrode of FIG. 1;
FIG. 3 is a sectional view of the electrode of FIG. 2(B) showing the electrode placed within the tube neck of the color picture CRT;
FIG. 4(A) is a front elevational view of the electron gun for the color picture CRT according to the present invention containing cut away portions in order to illustrate the construction of basic components of the present invention;
FIG. 4(B) is a sectional view of FIG. 4(A), taken along line A--A;
FIG. 5(A) is a top plan view of the first accelerating and focusing electrode for the electrostatic lens according to the present invention;
FIG. 5(B) is a sectional view of FIG. 5(A), taken along line B--B;
FIG. 5(C) is a sectional view of FIG. 5(A), taken along line C--C;
FIG. 6(A) is a top plan view of the slanted enlarging electrode disposed on the side of the first accelerating and focusing electrode according to the present invention; and
FIG. 6(B) is a sectional view of FIG. 6(A), taken along line B--B.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, the electron gun for the color picture cathode-ray tube as shown in FIGS. 4(A) and 4(B), includes a cathode 4 fixed to a support 2, a first grid electrode 5a, a second grid electrode 6a, a third grid electrode 7a, a first accelerating and focusing electrode 18 and a second accelerating and focusing electrode 19 wherein they are arranged in a pile in the above-mentioned order and fixed to a pair of bead glasses 10.
The first and second accelerating and focusing electrodes 18 and 19 are shown in FIG. 5(A). That is, the first accelerating and focusing electrode 18 is fully open at one side thereof and is provided at the other side thereof, with a slanted enlarging electrode 20 disposed on the interior of an oblong cylindrical electrode 24 which has an opening surrounded by an upper rim 23 extending from an outer end wall 22.
Also, as shown in FIGS. 6(A) and 6(B), the slanted enlarging electrode 20 is provided with connecting parts 26 formed at both ends thereof with same angle. The connection parts 26 extend to a head 27 and bend inward and form slopes 29 connected to a bottom portion 28. Three oblong holes 30a, 30b, and 30c are disposed from the bottom to the slopes 29 for passing beams through the holes.
The slanted enlarging electrode 20 as shown in FIG. 5(A) has the electron beam holes 30a, 30b, and 30c wherein the distance S between the hole centers of the beam holes is in the range of 5.1 mm-6.6 mm. The angle θ of inclination from the head 27 to the bottom portion 28 is in the range of 100-140 degree as shown in FIG. 6(B). The electrode 20 is disposed on the inner end wall 22 of the oblong shaped electrode 24 wherein the distance from the rim 23 of the electrode 24 to the bottom of the electrode 20 is in the range of 1.5-3 mm as shown in FIG. 5(C).
Also, referring to the oblong electron beam holes 30a, 30b, and 30c as shown in FIG. 5(A), the central hole 30b has a ratio 2:1 for the longitudinal length to the lateral width, and the holes 30a and 30c respectively having an approximate ratio 4:3 for the same directional measurements.
Furthermore, due to optimum limitation of the tube neck of 29.1 mm, for the lateral width of the open end surrounded by the upper rims 23 of the focusing electrodes 18 and 19 determines approximately 8 mm and the longitudinal diameters of the oblong holes 30a, 30b, and 30c of the electrode 20 also is set approximately at 8 mm.
In the arrangement of the focusing electrodes 18 and 19, the open end of the electrode 18 connects to the third grid electrode 7a, and the space disposed at the opposite rim 23 plays the function of an electrostatic focusing lens. Although the above description was made concerning solely an electron gun having a BPF lens, the present invention may be employed for an electron gun having multistaged connections with addition of a plurality of electrodes disposed at the position of the third grid electrode 7a.
According to the present invention, the electron gun operates as follows:
The oblong opening surrounded by the upper rim 23 extending from the outer end wall 22 of the oblong cylindrical electrode 24 of the first and second acceleration and focusing electrodes 18 and 19 forms a common beam hole for passing three electron beams therethrough as a common electrostatic focusing lens.
The above arrangement means that even through the shortest width of the oblong opening is about 8 mm due to the limitation of the tube neck, the size thereof shows an expansion of 1.45 times based on the diameter of 5.5 m of the conventional electron beam hole. It is to indicate the reduction of the spherical aberration by an approximate factor of 0.33 and the reduction of the lens force by an approximate factor of 0.69.
If the dimension of the electrostatic lens enlarges by a ratio of M, the derivative of the second order to the dislocation potential in the electrostatic lens reduces by 1/M2, because results are the lens force A=1/M . . . (4) and the lens spherical aberration C=1/M3 . . . (5).
Consequently, the electrostatic focusing lens formed by the first and second focusing electrodes 18 and 19 according to the present invention not only greatly reduces the spherical aberration of the lens but also reduces the magnification of the lens by its weak function such that small beam spots of high density beams form on the fluorescent screen of the color CRT.
Thus, according to the common electrostatic focusing lens formed by the common oblong opening surrounded by the upper rim 23, the lens has a short length in the longitudinal direction and a long length in the lateral direction such that the lens action in the longitudinal direction is strong. On the other hand, the lens action in the lateral direction is weak such that the beam after passing the lens comes to have a different ratio of lengths between longitudinal and lateral directions and have a more laterally elongated shape. The electron beam further distorts into a most laterally elongated shape due the deflection aberration of deflection yoke. Thus, the arrangement of slanted enlarging electrodes 20 and 21 to the first and second accelerating and focusing electrodes 18 and 19 brings the function of a supplementary electrostatic lens for compensating the lateral elongation of the electron beam.
As shown in FIGS. 5(A) and 6(A), the three oblong electron beam holes of the slanted enlarging electrode 20 have a ratio of the longitudinal length and the lateral width of 2:1 about the central hole 30b and 4:3 about the outer holes 30a and 30c, so that the electron beams passing the longitudinally oblong holes of the electrode 20 are subject to a weak focusing action in the longitudinal direction and a strong focusing action in the lateral direction to form a longitudinally oblong form of beams.
Thus, the laterally elongating action of the common electrostatic focusing lens formed by the common oblong opening surrounded by the upper rim 23 and the laterally elongating action from the deflection aberration are compensated to form screen small round beam spots of high density electron beams on the CRT and improves the resolution of the color picture CRT.
Besides, according to the electron gun of the present invention, the longitudinally oblong holes 30a, 30b, and 30c of the slanted electrode 20 perform solely the function of the supplementary electrostatic lens at the focusing electrodes 18 and 19 such that the shortening of the distance S among the three beams still gives enough action as the supplementary lens without influencing the function of the three electron beams from the action of the common electrostatic focusing lens regardless of the variation of the distance S.
The present invention therefore obtains a better concentration for three electron beams due to deflection by shortening the distance S among the beams and also greatly improves the focusing property of the electron gun by the electrostatic focusing lens enlarged to the bottom portion 28 of the slanted electrode 20 regardless of any variation of the distance S among the beams.
Furthermore, the supplementary electrostatic lens formed by the longitudinally oblong holes 30a, 30b, and 30c which are perforated across the bottom 28 to the slant portion 29 of the slanted electrode 20 are controlled for their accurate function by a longitudinal and lateral ratio and the difference in electrostatic lens action between the openings in the slant portion 29 and the bottom portion 28. For the electron gun of the present, the distance S among the electron beams of the slanted enlarging electrode 20 disposes at the first focusing electrode 18 and the second focusing electrode 19, and the dimension of the electron beam holes are determined from the action of the common electrostatic focusing lens of three beams enlarged from the rim 23 to the bottom 28.
For example, if an electron gun is placed in a tube neck of 29 mm diameter with the longitudinal opening of the upper rim 23 determined to have 8 mm in diameter, the distance S is set at 5 mm, the longitudinal direction diameter of the oblong hole of the electrode 20 is set at 8 mm, and the lateral direction diameters and set 4 mm for the central hole and 6 mm for the outer holes, respectively.
According to the present invention, the first and second accelerating and focusing electrodes 18 and 19 with the electrostatic focusing lens include an improved supplementary electrostatic lens construction such that the focusing of electron beams improves and the housing of the first and second focusing electrodes 18 and 19 within the restricted tube neck rather shortens the distance among the electron beams and effectively enlarges the diameter of the lens. Thus, the present invention provides a high quality electron gun.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included in the scope of the following claims
US Patent References:
4887009 Color display system 1989-12-12 Bloom et al. 313/414
4766344 In-line electron gun structure for color cathode ray tube having oblong apertures 1988-08-23 Say 313/414
4626738 Color display tube with electrostatic focusing lens 1986-12-02 Gerlach 313/414
4622491 Electron gun for color picture tube with electrostatic focussing lens 1986-11-11 Izumida et al. 313/414
4535266 In-line electron gun structure for color cathode ray tube having tapered walls and elongated apertures for beam spot-shaping 1985-08-13 Say 313/414
4370592 Color picture tube having an improved inline electron gun with an expanded focus lens 1983-01-25 Hughes et al. 313/414
4370592 Color picture tube having an improved inline electron gun with an expanded focus lens January, 1983 Hughes et al. 313/414
Deflection yoke mounting apparatus for a color picture tube
A deflection yoke mounting apparatus for a color picture tube having a deflection yoke for deflecting electron beams generated by an electron gun to be securely fixed to a neck portion of a funnel of the picture tube to prevent deterioration of convergence and purity characteristics of the picture tube due to displacement of the yoke by an external shock. The apparatus includes a thermal shrinkage tube inserted over the outer periphery of the neck portion and thermally contracted into close contact with the neck portion, a neck contact member of the deflection yoke having a plurality of protrusions formed on its inner surface and engaged with the outer periphery of the thermal shrinkage tube, and a metallic band engaged with the outer periphery of the thermal shrinkage tube, the metallic band being engaged with the outer periphery of the neck contact member to press the contact member and the thermal shrinkage tube, thus fixing the yoke to the neck portion.
1. A deflection yoke mounting apparatus for a picture tube having a deflection yoke and a funnel with a neck portion comprising:
a thermal shrinkage tube inserted over an outer periphery of said neck portion and thermally contracted into close contact with said neck portion;
a neck contact member having a plurality of protrusions formed on its inner surface, said neck contact member being engaged with an outer periphery of said thermal shrinkage tube;
means engaged with an outer periphery of said neck contact member for fastening said neck contact member to said thermal shrinkage tube, said fastening means fixing said yoke to said neck portion; and
said thermal shrinkage tube further contracting onto the neck portion when the neck portion is heated by an electron gun during operation of the color picture tube.
2. A deflection yoke mounting apparatus for a picture tube according to claim 1, wherein said thermal shrinkage tube has an inside diameter approximately in the range of 0.2.about.0.4 mm greater than an outside diameter of said neck portion of said funnel.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a deflection yoke mounting apparatus for a color picture tube, and more particularly to a deflection yoke mounting apparatus for a color picture tube, that allows a deflection yoke to be securely fixed to a neck portion of a funnel of the picture tube to prevent deterioration of convergence and purity characteristics of the picture tube due to displacement of the yoke by an external shock.
2. Description of the Prior Art
Generally, a color picture tube has a form of a cone-shaped vacuum bulb comprising a panel (not shown) having phosphor applied in forms of dots or strips to its inner surface, and a funnel 2 integrated with the panel and having a neck portion 2a' of a reduced cross-section, as shown in FIG. 1 of the accompanying drawings. In addition, the picture tube includes an electron gun mounted internally in the neck portion 2a' to generate and direct electron beams to the phosphor of the panel, and a deflection yoke 3 fixedly mounted externally on the neck portion to deflect the electron beams.
With the color picture tube thus constructed, the electron beams emitted from the electron gun and passed through grids are deflected by the deflection yoke 3. The electron beams pass through small through-holes of a shadow mask for color selection, and then land on the phosphor of the panel to cause the luminescence of the phosphor. Thus, a picture image is formed on the screen. At this time, if a displacement of the deflection yoke occurs, convergence and purity characteristics of the picture tube may deteriorate, so that an image of good quality may not be produced. Therefore, in order to obtain an image of good quality, it is necessary to securely fix the deflection yoke 3 to the neck portion 2a' of the funnel to prevent displacement.
An example of a deflection yoke mounting apparatus for a color picture tube according to the prior art is shown in FIGS. 1, 2A, and 2B of the accompanying drawings. The deflecting yoke 3 of FIGS. 1, 2A and 2B comprises horizontal deflection coils(not shown) for correction of horizontal convergence wound into a saddle shape and disposed internally in a separator 8 of an insulating material and vertical deflection coils 7 for correction of vertical convergence round into a toroidal shape and disposed externally on the separator. The deflection yoke 3 is mounted on the neck portion 2a of the funnel through an adhesive tape 10 having on one side surface an adhesive material 9 bonded to the outer surface of the glass neck portion 2a'. More particularly, as shown in FIG. 2B, the adhesive tape 10 is first bonded around the outer periphery of the neck portion, and then a neck contact member 4 of the deflection yoke having protrusions 4a formed on its inner surface is inserted over the bonded adhesive tape and tightly clamped by a metallic band 5 wrapped around its outer periphery. The metallic band 5 is fastened by a bolt 6 which is threadedly engaged in threaded through-holes 5a formed at opposite ends of the band. As a result, the deflection yoke is fixed to the neck portion 2a' of the funnel to act against displacement.
This prior apparatus, however, has a drawback in that although the deflection yoke has been accurately assembled to the neck portion taking into consideration the convergence and purity characteristic in the manufacturing process, the yoke 3 exhibits a tendency to be displaced relative to the glass neck portion 2a' during transportation or use of the product, so that a picture image of good quality may not be obtained. In addition, during operation of the color picture tube, the temperature of the neck portion rises up to 60° C..about.80° C. due to heat generated by a heater of the electron gun disposed in the neck portion. As a result, the adhesive force the adhesive tape bonded to the neck portion is weakened. Thus, even a minute shock is applied to the picture tube may displace the deflection yoke thereby deteriorating the convergence or purity characteristics of the picture tube.
SUMMARY OF THE INVENTION
In view of the aforesaid problem of the prior apparatus, it is an object of the present invention to provide a deflection yoke mounting apparatus for a color picture tube, that prevents deterioration of convergence or purity characteristics of the picture tube, resulting from a displacement of the deflection yoke by an external force.
To achieve the above object and according to one embodiment of the present invention a deflection yoke mounting apparatus for a color picture tube is provided comprising a thermal shrinkage tube inserted over a neck portion of a funnel of the picture tube and thermally contracted into close contact with the neck portion, a neck contact member of a deflection yoke having a plurality of protrusions formed on its inner surface and engaged with the outer periphery of the thermal shrinkage tube, and fastening means engaged with the outer periphery of the neck contact member to press the contact member and the thermal shrinkage tube, thereby fixing the deflection yoke to the neck portion.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a schematic side view illustrating a neck portion of a funnel of a color picture tube with a deflection yoke mounted thereon according to the prior art;
FIG. 2A is a cross-sectional view of line 2A--2A of FIG. 1;
FIG. 2B is an enlarged schematic view illustrating (1 section of FIG. 2A.
FIG. 3 is an enlarged schematic, view illustrating the neck portion of the funnel with the deflection yoke mounted thereon according to the present invention; and
FIG. 4 is a cross-sectional view of line 4B--4B of FIG. 3, showing the deflection yoke mounting apparatus according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention will now be described in more detail, by way of example, with reference to FIGS. 3 and 4 of the accompanying drawings.
FIG. 3 shows a deflection yoke being mounted on a neck portion of a funnel of a color picture tube according to a preferred embodiment of the present invention. FIG. 4 shows a cross-sectional view of the deflection yoke mounting apparatus according to the present invention, taken along line 4B--4B of FIG. 3. The apparatus according to the present invention is similar to the prior art in that the deflection yoke 3 comprises a separator 8 having horizontal deflection coils (not shown) and vertical deflection coils 7 wound internally and externally thereof, respectively, and is mounted around the neck portion 2a' of the funnel 2. However, the present invention utilizes a hollow, thermal shrinkage tube 1 inserted over the neck portion 2a', thereby preventing displacement of the yoke. Therefore, elements similar to those of the prior art are indicated by the same reference numbers and not explained in detail here to avoid the duplication of explanation.
The thermal shrinkage tube 1 preferably has an inside diameter of about 0.2.about.0.4 mm greater than the outside diameter of the neck portion 2a', and more preferably, 0.3 mm greater than the outside diameter of the neck portion 2a. For example, a color picture tube having a neck portion with an outside diameter of 29.1 mm should have a thermal shrinkage tube 1 with an inside diameter in the range of 29.3.about.29.5 mm.
The reason for defining the inside diameter of the thermal shrinkage tube to be 0.2.about.0.4 mm greater than the outside diameter of the neck portion is to take into consideration the workability in the manufacturing process of the picture tube. If the inside diameter of the tube 1 is less than the outside diameter of the neck portion 2a', it would be difficult to place the tube on the neck portion. To the contrary, if the inside diameter of the tube is far greater than the diameter of the neck portion, i.e., exceeding the range of 0.2.about.0.4 mm, the tube may not be accurately mounted at a predetermined position due to a shift in position which may occur when mounting the tube on the outer periphery of the neck portion and heating the tube by a heater (not shown).
The process of mounting the deflection yoke 3 on the neck portion 2a' of the funnel 2 by using the thermal shrinkage tube 1 will now be explained.
First, the thermal shrinkage tube 1 is placed at a predetermined position on the neck portion 2a', and then heated uniformly along its outer circumference by a separate heater, thus contracting the shrinking tube to tightly engage the neck portion. Then, the deflection yoke 3 is inserted over the tube 1 such that a metallic band 5 wrapped around a neck contact member 4 of the yoke is in register with the thermal shrinkage tube. Thereafter, the yoke position is adjusted to provide optimum convergence and purity of the color picture tube, and then a bolt 6 threadedly engaged in threaded through-holes 5a formed at opposite ends of the band 5 is slowly tightened such that protrusions 4a formed on the inner surface of the contact member 4 press the thermal shrinkage tube 1 into close contact with the neck portion.
With the color picture tube thus constructed, as the temperature of the neck portion 2a' rises due to heat generated by a heater of an electron gun in the neck portion during operation of the picture tube,the thermal shrinkage tube 1 is further contracted into more close contact with the neck portion, whereby the deflection yoke 3 is more securely fixed to the neck portion.
The present invention is advantageous in that since the deflection yoke is securely fixed to the neck portion through the thermal shrinkage tube firmly engaged with the neck portion of the funnel, the yoke is not displaced even when subjected to an external shock. Therefore, convergence and purity adjusted in the manufacturing process of the picture tube are kept constant during use of the picture tube, resulting in an enhanced reliability of the product.
While the invention has been shown and described with particular reference to the preferred embodiment thereof, it will be understood that variations and modifications in form and detail may be made therein without departing from the spirit and scope of the invention as defined in the appended claims
US Patent References:
5172877 Pipe fixing structure using clamp member 1992-12-22 Hattori et al.
5169176 Heat shrinkable clamping, connecting, repair, and reinforcing sleeve and method of use 1992-12-08 Brossard 156/84
5129608 Snap fit clamp 1992-07-14 Goldman
4207364 Heat-shrinkable laminate 1980-06-10 Nyberg 156/84
Elastic support device for a shadow mask of a color picture tube
This invention relates to an elastic support device for a shadow mask of a color picture tube which is able to minimize stress of elastic members resulting from thermal expansion of the shadow mask during operation of the color picture tube. Thus, the compensation for mislanding of an electron beam emitted to a screen is improved. The device includes a first elastic member having a first end thereof fixed to the frame and coupled at a second end thereof to a panel pin, wherein the panel pin is secured to the panel, thereby exerting elastic force upon the frame and a second elastic member having a first end thereof slidably coupled with the frame and a second end thereof to the first elastic member, thereby exerting auxiliary elastic force upon the frame.
1. An elastic support device for a shadow mask of a color picture tube, which cooperates with a frame to elastically support said shadow mask on a panel, said device comprising:
a first elastic member having a first end fixed to said frame and a second end coupled to a panel pin, wherein said panel pin is secured to said panel, thereby exerting elastic force upon said frame, said panel pin having a front side and a back side; and
a second elastic member having a first end slidably coupled with said frame and a second end fixed to said first elastic member, thereby exerting auxiliary elastic force upon said frame,
wherein said second end of said second elastic member which is fixed to said first elastic member is located on said back side of said panel pin.
2. An elastic support device for a shadow mask of a color picture tube as claimed in claim 1, wherein said first and second elastic members are made of stainless steel.
3. An elastic support device for a shadow mask of a color picture tube, which cooperates with a frame to elastically support said shadow mask on a panel, said device comprising:
a first elastic member having a first end fixed to said frame and a second end coupled to a panel pin, wherein said panel pin is secured to said panel, thereby exerting elastic force upon said frame, said panel pin having a front side and a back side; and
a second elastic member having a first end slidably coupled with said frame and a second end fixed to said first elastic member, thereby exerting auxiliary elastic force upon said frame,
wherein said second end of said second elastic member which is fixed to said first elastic member is fixedly secured to a portion of said first elastic member which is located on said front side of said panel pin.
4. An elastic support device for a shadow mask of a color picture tube as claimed in claim 3, wherein said first and second elastic members are made of stainless steel.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an elastic support device for a shadow mask of a color picture tube, and more particularly an elastic support device for a shadow mask of a color picture tube, which is able to minimize stress of elastic members resulting from thermal expansion of the shadow mask during operation of the color picture tube, thereby improving compensation for mislanding of an electron beam emitted to a screen.
2. Description of Related Art
Generally, a color picture tube has, as shown if FIG. 1 of the accompanying drawings, a bulbiform exterior configuration comprising a panel 1, and a funnel 2 formed with a neck portion 2a having a reduced cross-section. An electron gun 3 is mounted within the neck portion 2a of the color picture tube to emit an electron beam 4, and a shadow mask 6 formed with small through-holes each having a diameter of the order of 0.3 mm is disposed within the enlarged portion of the funnel 2 opposite the neck portion 2a in spaced-apart relationship to the inner surface of the panel 1 so that the electron beam 4 emitted from the electron gun 3 passes through respective through-holes of the shadow mask.
In addition, a screen 5 having luminous fluroescent materials for red, green and blue colors coated thereon in a given pattern is attached to the inner surface of the panel 1 in parallel, spaced-apart relationship to the shadow mask 6, whereby the electron beam passed through the shadow mask lands on the luminous fluorescent materials coated on the screen to cause luminescence of the fluroescent materials coated on the screen, thereby forming a picture image on the screen. At this time, the interior of the color picture tube is maintained in a high vacuum state (of approximately 10 Torr) in order to enable the electron beam 4 to be accelerated and effectively land on the screen 5 coated with the luminous fluorescent materials.
With the color picture tube thus constructed, about 20% of the electron beam 4 emitted from the electron gun 3 mounted within the neck portion 2a passes through the small through-holes of the shadow mask 6, while the remaining 80% of the beam collides against the shadow mask, resulting in thermal expansion of the shadow mask made of a thin sheet having thickness of appoximately 0.2 mm. Such thermal expansion of the shadow mask due to the collisin of the electrom beam causes variation of the relative positions between the through-holes of the shadow mask 6 and the fluorescent materials for red, green, and blue colors coated on the screen 5, thereby giving rise to a scanning error and thus lowering color purity of the color picture tube. In order to eliminate such a phenomenon, therefore, elastic members(referred to as "corner springs") are disposed at a frame supporting the shadow mask, so that correction of the position variation as set forth above may be accomplished.
A prior art elastic member performing the function as described above is of the type shown in FIG. 2. The elastic member 8 is attached at one end thereof to the frame 7 supporting the shadow mask 6 and coupled at another end thereof to a panel pin 10 provided on the inner surface of the horizontally extending peripherey portion of the panel 1, so that it exerts elastic force upon the frame and cooperates with the frame to elastically support the shadow mask which is secured to the panel by means of the frame and the elastic member.
In this prior art, when heat is transmitted to the shadow mask 6 during operation of the color picture tube, the frame 7 supporting the shadow mask deforms due to thermal expansion of the shadow mask to exert compressive force upon the elastic member 8 secured to the lower portion of the frame.
As a result, the elastic member undergoes stress caused by the compressive force and is shifted along with the shadow mask and the frame from the position as indicated by the solid line in FIG. 2 to the position indicated by the dotted lines. At this time, if the relative positions between the mask and the frame deviate from the given allowable limits necessary for the design of the color picture tube, color purity of the picture tube is greatly lowered. Therefore, it is desired to meet the requirements that the relative positions must be maintained within the given allowable limits.
This prior elastic member is however disadvantageous in that when the member is thick so as to meet the requirements as set forth above, good elastic supportability may be obtained, but a spring-back phenomenon takes place during the forming operation, thereby making it difficult to carry out the forming operation, and to the contrary, when the elastic member is thin, the forming operation may be easily carried out, but the desired elastic supportability is not obtained.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art elastic member in view, it is an object of the present invention to provide an elastic support device for a shadow mask of a color picture tube, which is able to minimize stress of elastic members resulting from thermal expansion of the shadow mask during operation of the color picture tube, thereby improving compensation for mislanding of an electron beam emitted to a screen.
To achieve the above object, there is provided according to one form of the present invention an elastic support device for a shadow mask of a color picture tube, which cooperates with a frame to elastically support the shadow mask on a panel, the device comprising a first elastic member fixed at one end thereof to the frame and coupled at another end thereof to a panel pin secured to the panel, thereby exerting elastic force upon the frame; and a second elastic member disposed at one end thereof in slidable contact with the frame and fixed at another end thereof to the first elastic member, thereby exerting auxiliary elastic force upon the frame.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagramatic cross-sectional view of a common color picture tube;
FIG. 2 is an enlarged cross-sectional view showing an elastic member for a shadow mask of the color picture tube shown in FIG. 1;
FIG. 3 is an enlarged cross-sectional view showing an elastic support device for a shadow mask of a color picture tube, according to one embodiment of the present invention; and
FIG. 4 is an enlarged cross-sectional view showing an elastic support device for a shadow mask of a color picture tube, according to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 3 showing an elastic support device for a shadow mask of a color picture tube according to one embodiment of the present invention, the elastic support device which cooperates with a frame 7 to elastically support the shadow mask 6 on a panel 1, comprises a first elastic member 8a fixed at one end thereof to the frame 7 and coupled at another end thereof to a panel pin 10 secured to the panel 1, thereby acting to exert elastic force upon the frame, and a second elastic member 8b disposed at one end thereof in slidable contact with the lower surface of the frame and fixed at another end thereof to the first elastic member, thereby acting to exert auxiliary elastic force upon the frame 7.
Here, the end of the second elastic member 8b held in slidable contact with the frame is smoothly finished to reduce friction resistance during its sliding movement on the frame 7, and the opposite end thereof is fixedly secured to the end portion of the first elastic member 8a located on the back side of the panel pin 10, so that the frame is elastically supported by the first and second elastic members on the both sides of the panel pin. In this instance, preferably, the first elastic member 8a is thin in order to reduce a stress concentration on the joint thereof secured to the frame 7, and made of material having good elasticity, more preferably stainless seel. The second elastic member 8b is preferably made in the form of a thin leaf spring of good elastic material such as stainless steel (SUS631) to increase the auxiliary elastic force exerted upon the frame 7.
In operation of the support device thus constructed, when heat is transmitted to the shadow mask 6 during operation of the color picture tube, as shown in FIG. 3, the frame 7 supporting the shadow mask deforms due to thermal expansion of the mask, thereby exerting compressive force upon the first elastic member 8a fixedly secured to the lower surface of the frame, as a result of which stress is concentrated on the joint of the first elastic member attached to the frame 7. At this time, as the first elastic member undergoes the compressive force slowly applied by the frame 7, the second elastic member 8b is pivotally moved about its one end fixed to the first elastic member 8a, while sliding at its another end being in slidable contact with the lower surface of the frame. Therefore, the shadow mask 6, the frame 7, and the first and second elastic members 8a, 8b are shifted toward the screen 5 from the position as indicated by the solid line in FIG. 3 to the position indicated by the dotted lines.
At this time, the second elastic member 8b functions to increase the elastic supportability of the thin first elastic member 8a and reduce the stress concentration on the joint between the frame and the first elastic member as the frame is displaced toward the screen 5 due to the thermal expansion of the shadow mask 6. Therefore, the shadow mask can be moved uniformly toward the screen without undue deformation of the first elastic member. In addition, since the shadow mask 6 may be elastically supported with the relative positions between the luminous fluorescent materials coated on the screen 5 and the small through-holes of the shadow mask 6 maintained within the given allowable limits, a lowering of color purity of the color picture tube may be prevented.
Referring to FIG. 4 showing another embodiment of the present invention, the elastic support device according to this embodiment is identical in general construction and operation with that of the preceding embodiment in that it comprises a first elastic member 81a fixed at one end thereof to the frame 7 and coupled at another end thereof to the panel pin 10, thereby acting to exert the elastic force upon the frame and cooperating with the frame to elastically support the shadow mask 6 on the panel 1, and a second elastic member 81b disposed at one end thereof in slidable contact with the frame 7 and fixed at another end thereof to the first elastic member 81a, thereby acting to exert the auxiliary elastic force upon the frame. However, according to this embodiment, the position at which one end of the second elastic member is fixed to the first elastic member is differently from that in the first embodiment. More specifically, differently from the first embodiment, the second elastic member 81b exerting the auxiliary elastic force upon the frame 7 is fixedly secured to the portion of the first elastic member 81a located on the front side of the panel pin 10.
As can be seen from the foregoing, the present invention provides advantages over the prior art in that the first and second elastic members are thin, which results in excellent formability, and the separate second elastic member disposed in addition to the thin first elastic member compensates for reduction of the elastic supportability of such a first elastic member, whereby the excellent elastic support for the frame and hence the shadow mask can be provided. Furtheremore, the device according to the present invention minimizes the stress of the elastic members resulting from the compressive force applied by the frame during the operation of the color picture tube, whereby the relative positions between the through-holes of the shadow mask and the fluorescent materials of the screen can be maintained within the given allowable limits, resulting in enhanced compensation for the mislanding of the electron beam emitted to the screen.
While the invention has been shown and described with particular reference to preferred embodiments thereof, it will be understood that variations and modifications may be made therein without departing from the spirit and scope of the invention as defined in appended claims.
US Patent References:
4950943 Support for shadow mask in a cathode ray tube 1990-08-21 Ito 313/404
4358702 Color tube shadow mask mount 1982-11-09 Gijrath et al. 313/402
4335329 Mask support for shadow mask assembly 1982-06-15 Fukuzawa et al. 313/406
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