Cathode ray tube apparatus and method of manufacturing the same

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a cathode ray tube apparatus wherein a phosphor screen is dividedly scanned by a plurality of electron beams, and a method of manufacturing the cathode ray tube apparatus.

2. Description of the Related Art

In recent years, considerable research has been conducted regarding the development of a standard-format or a wide-screen type high-resolution cathode ray tube suitable for high-quality broadcasting. In general, in order to achieve a cathode ray tube of high resolution, the spot diameter of an electron beam on a phosphor screen must be reduced. To this end, in the prior art, the structure of an electrode of an electron gun assembly was improved, or the caliber and/or length of the electron gun assembly was increased. However, the results obtained so far have not been fully satisfactory, the main reason for this being that the distance between the electron gun assembly and the phosphor screen increases in accordance with an increase in the size of the cathode ray tube, with the result that the magnification of the electron lens increases excessively. Accordingly, in order to achieve high resolution, it is most important that the distance (depth) between the electron gun assembly and the phosphor screen be reduced. In addition, if the deflection angle of an electron beam is increased, the difference in magnification between the center area and peripheral area of the phosphor screen increases. Thus, wide-angle deflection is not advantageous for achieving high resolution.

To overcome the above-described disadvantage, EP 0 471 359 A3 discloses a cathode-ray tube in which a flat face plate is employed and a phosphor screen is continuously formed on the inner surface of the face plate and comprises a plurality of regions which are simultaneously and independently scanned by electron beams emitted from a plurality of electron gun assembles. It is necessary to provided support means in the cathoderay tube for supporting the face plate against the atmospheric pressure applied thereto.

However, even if the screen is formed integrally and the support means is provided in the cathode-ray tube, a practical problem still remains. Specifically, where scanning is performed simultaneously in plural regions of the screen, it is necessary to employ a simple structure and/or method so as to make connecting portions between adjacent pictures reproduced on the screen invisible.

The above-described cathode ray tube has a plurality of independent electron gun assemblies, and a plurality of deflection units (elemental deflection units) for deflecting plural electron beams emitted from the electron gun assemblies to scan a predetermined number of regions of the phosphor screen dividedly. The number of the deflection units is equal to that of the electron gun assemblies. To hide the connecting portions of adjacent regions scanned independent of one another, it is necessary to adjust the deflection units individually. This can be performed in the case where a small number of deflection units are employed, or where a monochrome image cathode ray tube which can be adjusted in a comparatively simple manner is used. However, an increase in the number of the deflection units will make it difficult to perform such adjustment. Further, in the case of a color image cathode ray tube, it is necessary to perform adjustment for color purity or beam-converging, in addition to such adjustment as moving a reproduced image in the vertical direction and horizontal direction, and/or rotating the same. Thus, it is extremely difficult to adjust all the deflection units appropriately.

SUMMARY OF THE INVENTION

The present invention is contrived in consideration of the above circumstances and its object is to provide a cathode ray tube apparatus of a type wherein a phosphor screen is dividedly scanned in a plurality of regions by a plurality of electron beams, and wherein a deflection device for respectively deflecting the electron beams to the predetermined regions can easily be adjusted in position relative to the cathode ray tube, and also to provide a method of manufacturing the apparatus.

To attain the above object, the cathode ray tube apparatus according to the invention comprises: a phosphor screen; a plurality of electron gun assemblies, each for emitting at least one electron beam to the phosphor screen; and deflection means for deflecting the electron beams emitted from the electron gun assemblies, the deflection means having a plurality of elemental deflection units corresponding to the respective electron gun assemblies, for deflecting the electron beams to scan the phosphor screen dividedly, and coupling means for coupling at least two of the elemental deflection units to one another.

Preferably, the deflection means has a plurality of adjusting means for adjusting the positions of the elemental deflection units in relation to the coupling means.

According to another aspect of the invention, the cathode ray tube apparatus has a vacuum envelope having the phosphor screen and electron gun assemblies, and adjusting means for adjusting the position of the coupling means in relation to the vacuum envelope.

With the cathode ray tube apparatus, a plurality of elemental deflection units are coupled with one another into one body by means of the coupling means, so that they can simultaneously be arranged in predetermined positions. When it is necessary to adjust the position of each elemental deflection unit to align a corresponding electron gun assembly, this adjustment can be performed by an adjusting means.

Further, since a plurality of elemental deflection units are arranged in predetermined positions by means of coupling means before attaching them to the cathode ray tube, it is not necessary to individually adjust the positions of the elemental deflection units relative to the electron gun assemblies. However, if adjustment of each deflection unit is necessary, the positions of the deflection units can simultaneously be adjusted by adjusting the position of the coupling means relative to the cathode ray tube by use of the adjusting means. Thus, adjustment of the deflection means to the cathode ray tube is significantly simplified.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.

FIGS. 1 to 3 show a cathode ray tube apparatus according to an embodiment of the invention, in which:

FIG. 1 is a perspective view showing the appearance of the apparatus,

FIG. 2 is a cross sectional view taken along line II--II of FIG. 1, and

FIG. 3 is a perspective view showing a deflection device of the apparatus;

FIGS. 4 to 7 show a cathode ray tube apparatus according to another embodiment of the invention, in which:

FIG. 4 is a cross sectional view of the apparatus,

FIG. 5 is a perspective view showing a deflection device of the apparatus,

FIG. 6 is a perspective view showing an adjusting/fixing mechanism, and

FIG. 7 is an exploded perspective view showing the adjusting/fixing mechanism;

FIGS. 8 and 9 show a cathode ray tube apparatus according to a further embodiment of the invention, in which:

FIG. 8 is a cross sectional view of the apparatus, and

FIG. 9 is a perspective view showing an adjusting fixing mechanism of the apparatus;

FIG. 10 is an exploded perspective view useful in explaining a method for manufacturing the cathode ray tube apparatuses according to the invention;

FIG. 11 is a perspective view showing a state in which two deflection units are attached to a standard jig; and

FIG. 12 is a perspective view showing a state in which two deflection units are fitted in a coupling member by use of the standard jig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the invention will be explained in detail with reference to the accompanying drawings.

FIGS. 1 and 2 show a cathode ray tube apparatus according to an embodiment of the invention. As is shown in the figures, the cathode ray tube apparatus has a vacuum envelope 30, which comprises a face plate (first plate) 1 formed by a substantially-rectangular flat glass, side walls 2 fixed to the peripheral portion of the face plate 1 and extending substantially perpendicular to the face plate 1, a rear plate (second plate) 3 formed by a substantially-rectangular flat glass and coupled to the face plate 1 through the side walls 2 in parallel to the face plate, and a plurality (e.g. 5 rows.times.4 columns=20) of funnels 4 fixed to the rear plate 3. The rear plate 3 has 20 (=5 rows.times.4 columns) openings 23 formed therein at predetermined intervals, and the funnels 4 are secured to the plate 3 to cover the openings 23, respectively.

A phosphor screen 5 is continuously formed on substantially the overall inner surface of the face plate 1. An electron gun assembly 7 is located in the neck 6 of each funnel 4 for emitting three electron beams to the screen 5. A plurality of support rods 8 serving as support means are provided between the face plate 1 and the rear plate 3. The support rods 8 are provided for supporting the face plate 1 of the vacuum envelope 30 against the atmospheric pressure applied thereto, and each has a wedge-shaped end close to the phosphor screen 5. An elemental deflection unit 10 is provided around each funnel 4 for deflecting the electron beams emitted from a corresponding electron gun assembly 7 located in the corresponding neck 6. Further, the cathode ray tube apparatus includes a shadow mask (not shown) arranged in the vacuum envelope 30 to face the phosphor screen 5.

As is shown in FIGS. 2 and 3, the elemental deflection units 10 are secured to a single plate-like coupling member 11 by means of adjusting mechanisms 19 as individual adjusting means. The coupling member 11 and the elemental deflection units 10, which correspond to the individual electron gun assemblies 7 located in the necks 6 of the funnels 4, constitute in combination a deflection device 12 serving as deflection means.

Each deflection unit 10 has two pairs of deflection coils 13 for deflecting the electron beams, emitted from the corresponding electron gun assembly 7, in the vertical and horizontal directions, a core 14 formed of a magnetic material, and a mold 15 holding the deflection coils 13 and core 14 in predetermined positions, respectively. The mold 15 is of a truncated cone shape, and has a terminal table 16 provided on an outside portion for supplying deflection current to the deflection coils 13.

The coupling member 11 is rectangular and has substantially the same size as the rear plate 3 of the vacuum envelope 30, and has 20 (=5 rows.times.4 columns) circular openings 32 formed therein and accurately aligned with the funnels 4. Three threaded holes 34 are formed in the coupling member 11 around each opening 32. The coupling member 11 is formed of an electrically insulating material so as to restrain interference in magnetic field between adjacent deflection units 10 or loss due to eddy current.

Each adjusting mechanism 19 has an annular holding member 36, in which a large-diameter end of the mold 15 of a corresponding deflection unit 10 is inserted. The holding member 36 has a plurality (e.g. 3) of threaded holes 38 formed therein with regular intervals in the circumferential direction of the holding member and extending radially. First adjusting screws 40 are screwed in the threaded holes 38, thereby securing the deflection units 10 to the holding member 36.

The holding member 36 further has a plurality (e.g. 3) of through holes 42 formed at regular intervals in the circumferential direction and extending in the axial direction of the holding member. Second adjusting screws 44 are passed through the through holes 42 and screwed in the threaded holes 34 of the coupling member 11 through coil springs 46, respectively. Thus, each elemental deflection unit 10 is secured to the coupling member 11 by means of the corresponding holding member 36, opposed to the corresponding opening 32. The holding members 36, first and second adjusting screws 40 and 44 are formed of an electrically insulating material so as not to affect the operation of the elemental deflection units 10.

The deflection device 12 having the coupling member 11 and the elemental deflection units 10 attached thereto is secured to the rear plate 3 of the vacuum envelope 30, and the neck 6 of each funnel 4 is inserted in the corresponding elemental deflection unit 10 through the corresponding opening 32 of the coupling member 11. The mold 15 of each elemental deflection unit 10 has a small-diameter end portion mounted on the outer periphery of the inserted neck 6. The end portion has an inner diameter slightly larger than an outer diameter of the neck 6 so that the deflection unit 10 can be adjusted in position relative to the neck 6 as described later.

In the cathode ray tube apparatus constructed as mentioned above, electron beams emitted from the individual electron gun assemblies 7 are deflected in the horizontal and vertical directions by magnetic fields generated by two pairs of deflection coils 13 located outside the funnels 4, thereby scanning corresponding regions of the phosphor screen 5, respectively. Thus, the continuous phosphor screen 5 is dividedly scanned in a plurality of regions R1, R2, . . . , R20 by the electron beams. Screen images obtained by respective scanning of the electron beams are coupled with one another by means of signals supplied to the electron gun assemblies 7 and deflection units 10, thus forming a single large reproduced image R, without discontinuity, on the phosphor screen 5.

In a cathode ray tube apparatus capable of displaying a single large screen image without discontinuity obtained by deflecting electron beams, emitted from the individual electron gun assemblies 7, by means of magnetic fields generated from the elemental deflection units 10 corresponding to the gun assemblies 7 so that the electron beams from each gun assembly can scan a corresponding region of the phosphor screen 5, the degree of pincushion-shaped deflecting distortion of the image in each region which may occur at the time of deflecting electron beams must be made equal to that of deflecting distortion of the image in the adjacent region, and further must be minimized. Therefore, the deflection magnetic field of each elemental deflection unit 10 must be accurately adjusted.

As in the conventional cathode ray tube apparatus, an ununiform magnetic distribution is necessary in order to eliminate the pincushion-shaped deflecting distortion. An ununiform magnetic field component is necessary in the case where correction (i.e., elimination of deflecting distortion) is performed by use of a deflecting current with a correction component, or by additionally using the correction component.

Moreover, in the case where predetermined deflection without deflecting distortion is performed by a deflection device for generating a deflection magnetic field with an ununiform distribution, each electron beam must be passed through the symmetry axis (center) of a corresponding deflection magnetic field, and through the center of a corresponding divisional screen region. In other words, in order to display a screen image without deflecting distortion, the axis of the electron beam, the center of the deflection magnetic field, and the center of the corresponding screen region must completely be aligned with one another, and the center axis of the electron beam be perpendicular to the phosphor screen.

In addition, in order to display a screen image without discontinuity, it is necessary to adjust the deflection device such that the rotational positions of the deflection magnetic fields of adjacent elemental deflection units 10 are identical to each other, and that the horizontal and vertical components of the deflection magnetic fields are aligned in rows and columns, respectively.

In the above embodiment, when it is necessary to adjust the positions of the elemental deflection units in relation to the electron gun assemblies 7, the units 10 can be adjusted individually by the respective adjusting mechanisms 19. In the specification, the adjusting the elemental deflection units "in relation to the electron gun assembly" means adjusting the elemental deflection units in relation to the electron beams emitted from the electron gun assemblies, more concretely to the electron beams which pass the center of the corresponding screen region. Specifically, adjusting the first adjusting screws 40 can displace the elemental deflection unit 10 relative to the electron gun assembly 7 in the horizontal direction, i.e., in a direction parallel with the surface of the coupling member 11. Further, simultaneously rotating the three second adjusting screws 44 can displace the elemental deflection unit 10 in a direction perpendicular to the surface of the coupling member 11, i.e., in a direction of the beam axis, together with the holding member 36. By selectively rotating the adjusting screws 44, the angle between the center axis of the elemental deflection unit 10 and that of the electron gun assembly 7 can be changed.

According to the cathode ray tube apparatus constructed as described above, the elemental deflection units 10 are coupled to one another by the coupling member 11, and thus constitute the deflection device 12, so that all elemental deflection units 10 can be fitted to the respective funnels 4 only by attaching the coupling member 11 to the vacuum envelope 30. Moreover, since the elemental deflection units 10 are secured to predetermined portions of the coupling member 11, they can be arranged in predetermined positions with respect to the respective electron gun assemblies 7 only by attaching the deflection device 12 to the vacuum envelope 30. This makes the attaching/adjusting work easier than in the case of individually attaching the elemental deflection units 10 to the respective funnels of the cathode ray tube. If necessary, the adjusting mechanism 19 is used to adjust with ease the position of the elemental deflection unit 10 in relation to the electron gun assembly 7. Thus, it is possible to provide a cathode ray tube apparatus which can be manufactured in a simple manner and has a deflection device 12 whose position can be easily adjusted.

Then, a second embodiment according to the invention will be explained. In this embodiment, the same elements as those in the first embodiment are denoted by corresponding reference numerals, and their detailed explanation will be omitted.

As is shown in FIGS. 4 and 5, elemental deflection units 10 are attached directly to a rectangular plate-like coupling member 11 with no adjusting mechanisms interposed therebetween, thus constituting a single deflection device 12. Specifically, each elemental deflection unit 10 has two pair of deflection coils 13 for deflecting electron beams, emitted from a corresponding electron gun assembly 7, in the vertical and horizontal directions, a core 14 formed of a magnetic material, and a mold 15 holding the deflection coils 13 and core 14 in predetermined positions, respectively. The mold 15 is of a truncated cone shape, and has a terminal table 16 provided on an outside portion thereof for supplying deflection current to the deflection coils 13. Each elemental deflection unit 10 is attached to the coupling member 11 with the large-diameter end of the mold 15 fitted in a corresponding circular opening 32 of the coupling member 11.

In the second embodiment, the deflection device 12 is secured to a rear plate 3 of a vacuum envelope 30 by means of a plurality of adjusting/fixing mechanisms 21. The mechanisms 21 are provided at the four corners of the coupling member 11, thereby adjusting the relative position between the coupling member 11 and the vacuum envelope 30 and fixing the deflection device 12 to the vacuum envelope 30.

As is shown in FIGS. 6 and 7, each adjusting/fixing mechanism 21 has vertical walls 50 and 52 extending perpendicular to each other and projecting from each corner of the coupling member 11, and a prismatic fixing portion 54 projecting from a corresponding corner of the rear plate 3. The vertical walls 50 and 52 are engaged with the fixing portion 54, serving as an engaging portion in the invention. In a state where the deflection device 12 is fitted to the rear plate 3, the vertical walls 50 and 52 oppose side surfaces of the fixing portion 54, and the upper surface of the fixing portion 54 faces the lower surface of the coupling member 11.

Each of the vertical walls 50 and 52 has a threaded hole 55, into which a first adjusting screw 58 is screwed. The tip of the screw 58 abuts against the side surface of the fixing portion 54. Thus, by rotating the first adjusting screws 58, the deflection device 12 can be displaced in the horizontal direction, i.e., in a direction parallel with the surface of the rear plate 3. A threaded hole 60 is formed in the upper surface of the fixing portion 54 such that it extends perpendicular to the surface of the rear plate 3. A second adjusting screw 64 is screwed in the threaded hole 60 through a through hole 62, formed in the coupling member 11, and a coil spring 63. Rotating the second adjusting screws 64 by the same tunes or selectively rotating the screws 64 can adjust the distance between the rear plate 3 and the coupling member 11, or the angle therebetween. The diameters of the through hole 62 and the coil spring 63 are set larger than that of the shaft of the second adjusting screw 64 so as to allow the coupling member 11 to move in the horizontal direction.

The components of the adjusting/fixing mechanism 21 such as the vertical walls 50 and 52, screws 58 and 64, etc. are formed of an electrically insulating material. A desired number of adjusting/fixing mechanisms can be provided at desired locations, if they are arranged between the coupling member 11 and the rear plate 3 at locations where they do not interfere with other components.

FIGS. 8 and 9 show a simplified structure of the adjusting/fixing mechanism 21. This mechanism 21 has a support bar 26 perpendicularly extending from the rear plate 3 to the coupling member 11. The coupling member 11 has a through hole 27 larger than the diameter of the bar 26, through which the bar 26 extends. Circular plates 25 made of an elastic resin are secured to the upper and lower surfaces of the coupling member 11 and close the upper and lower openings of the through hole 27. The support bar 26 extends through the plates 25. Thus, the deflection device 12 is secured to a predetermined portion of the vacuum envelope 30 by means of frictional contact between the support bars 26 and the plates 25.

With the adjusting/fixing mechanism 21 constructed as described above, horizontal adjustment of the deflection device 12 is performed by moving the coupling member 11 within a range in which the support bars 26 are held by the plates 25. Further, vertical adjustment of the deflection device 12 is performed by vertically moving the coupling member 11 along the support bars 26. Adjusting some of the adjusting/fixing mechanisms 21 in combination can adjust the inclination of the deflection device 12 in relation to the vacuum envelope 30. These adjusting/fixing mechanisms 21 can be arranged as in the second embodiment, and an appropriate maximum adjustment amount can be obtained by use of a support bar 26 of a desired size and a plate 25 of a desired size.

In the case of the cathode ray tube apparatus according to the second embodim