PHILIPS 20CT4426 /08Z SEGANTINI CHASSIS KT4 CRT TUBE PHILIPS A51-570X

 

 

 

 

 

Hi-bri COLOUR PICTURE TUBE
• goo deflection
• In-line gun, electrostatic bi-potential focus
• 2g, 1 mm neck diameter
• Hi-Bri screen with pigmented phosphors featuring high brightness and increased contrast performance
• Soft-Flash technology offering improved set reliability
• Slotted shadow mask optimized for minimum moire
• Fine pitch over entire screen
• Phosphor lines follow glass contour
• Quick-heating cathodes
• Internal magnetic shield
• Reinforced envelope for push-through mounting
• When combined with an appropriate hybrid saddle toroidal deflection unit (e.g. A T1237), it forms a
self-converging assembly; dynamic convergence is not required.

Notes
1. Absolute maximum rating system.
2. The X-ray dose rate remains below the acceptable value of 0,5 mR/h, measured with ionization
chamber when the tube is used within its limiting values.
3. During adjustment on the production line this value is likely to be surpassed considerably. It is
therefore strongly recommended to first make the necessary adjustments for normal operation with-
out picture tube.
4. Operation of the tube at lower voltages impairs the luminance and resolution.
5. The short-term average anode current should be limited by circuitry to 1500 μA.
6. For maximum cathode life and optimum performance, it is recommended that the heater supply be
designed for 6,3 V at zero beam current.

FLASHOVER PROTECTION
With the high voltage used with this tube (max. 27,5 kV) internal flashovers may occur. As a result of
the Soft-Flash technology these flashover currents are limited to approx. 60 A offering higher set
reliability, optimum circuit protection and component savings.
Primary protective circuitry using properly grounded spark gaps and series isolation resistors (preferably
carbon composition) is still necessary to prevent tube damage. The spark gaps should be connected to
all picture tube electrodes at the socket according to the figure below; they are not required on the
heater pins. No other connections between the outer conductive coating and the chassis are permissible.
The spark gaps should be designed for a breakdown voltage at the focusing electrode (g3) of 8,5 kV
(1,5 x Vg3 max. at Va,g4 = 25 kV), and at the other electrodes of 1,5 to 2 kV.
The values of the series isolation resistors should be as high as possible (min. 1,5 kn) without causing
deterioration of the circuit performance. The resistors should be able to withstand an instantaneous
surge of 20 kV for the focusing circuit and 12 kV for the remaining circuits without arcing.

DEGAUSSING
The picture tube is provided with an internal magnetic shield. This shield and the shadow mask with its
suspension system may be provided with an automatic, degaussing system, consisting of two coils
covering top and bottom cone parts, or one large coil shaped in the form of a figure eight, with one
half on the top and the other half on the bottom cone part.
For proper degaussing an initial magnetomotive force (m.m.f.) of 300 ampere-turns is required in each
of the coils. This m.m.f. has to be gradually decreased by appropriate degaussing circuitry. In the steady
state, no significant m.m.f. should remain in the coils (.;;; 0,3 ampere-turns).
If single-phase power rectification is employed in the t.v. circuitry, provision should be included to
prevent asymmetric distortion of the a.c. voltage applied to the degaussing circuit due to high d.c.
inrush currents.

 

 

 

 

 

Strengthening means for a CRT in-line electrode component:

 The invention relates to improved strengthening means for a substantially planar one-piece electrode component utilized in an in-line multi-beam CRT electron gun assembly. Advantageous ruggedizing properties are achieved by discretely formed longitudinal channels oriented along the sides of the component with defined ledge portions extending outward therefrom; beneficially dimensioned supporting projections are formed as integral extensions thereof. A plurality of cooperating mini-channels are included as transversals in the component to provide a markedly improved structure.

1. Improved strengthening means for a substantially planar one-piece electrode component in a plural electrode in-line multi-beam cathode ray tube electron gun assembly integrated by a plurality of longitudinal insulative support members, said electrode component evidencing alpha and beta surfaces and having opposed side and end regions with defining L--L' and W--W' axes thereacross; said component having a center and two side-related spatially positioned apertures therethrough located in an in-line relationship substantially coinciding with said L--L' axis, the center aperture being located at the intersection of said L and W axes, with said side-related apertures oriented equidistantly therefrom along said L--L' axis on either side of said W--W' axis; said strengthening means comprising: at least one longitudinal channel located in each of the side regions of said component in parallel relationship with said L--L' axis, each of said channels being indented inward from said beta surface of said component for the full length of said region to form a longitudinal rib projecting from said alpha surface, each of said channels being an open-ended trough formation having width and depth dimensions formed by three adjoining longitudinal surfaces defining an outer wall portion, an inner wall portion and a bottom portion therebetween, each of said channels displaced inwardly from either side of said component to form ledges in the beta surface between the channels and the side edges of the component, the ledge edges being substantially parallel with said L--L' axis and extending along the full length of said side region; each of the channel-related ledges having an outstanding dimension at least substantially equal to the thickness of the component material and supporting projections extending from either side of said component; the supporting projections being integral planar extensions of said ledge formations.


2. An improved electrode component of the in-line CRT electron gun assembly according to claim 1 wherein each of said channels evidences two longitudinal and parallel strengthening bends therein, said bends being separated to define the bottom width dimension of said channel.

3. An improved electrode component of the in-line CRT electron gun assembly according to claim 1 wherein each channel evidences a substantially uniform depth dimension that is at least substantially equal to the thickness of said component material.

4. An improved electrode component of the in-line CRT electron gun assembly according to claim 1 wherein each channel has a substantially uniform width dimension that is at least substantially equal to the thickness of said component material.

5. An improved electrode component of the in-line CRT electron gun assembly according to claim 1 wherein each of said channel-related ledges extends in a substantially right-angle relationship with the outer wall of said channel.

6. An improved electrode component of the in-line CRT electron gun assembly according to claim 1 wherein at least two mini-channels are formed as elongated lateral indentations in the beta surface of said electrode component, said mini-indentations transversing the area between said side longitudinal channels and being located substantially midway between said apertures in parallel relationship with said W--W' axis.

7. An improved electrode component of the in-line CRT electron gun assembly according to claim 6 wherein each mini-indentation forms an elongated protrusion from the alpha surface of said electrode component, the height of said protrusion being less than the thickness of said component material.

8. An improved electrode component of the in-line CRT electron gun assembly according to claim 6 wherein each of said apertures is oriented in an individual spaced-apart dish-like depression formed in said alpha surface to project as a separate protuberance from said beta surface, and wherein said mini-channel indentations are located in the spacings between said aperture protuberances.

Description:

TECHNICAL FIELD
This invention relates to a substantially planar one-piece electrode component in a multi-beam in-line cathode ray tube electron gun assembly, and more particularly to improved strengthening means incorporated into the structure of a substantially planar electrode member.

BACKGROUND OF THE INVENTION
Cathode ray tubes (CRT's) commonly used in color television and related display applications conventionally utilize unitized electron gun assemblies which direct a plurality of controlled electron beams to the display screen of the tube. In certain gun assembly constructions, the first and second grid electrode components, such being normally control and screen grid electrodes, are often formed as substantially planar members oriented in substantially parallel planes in spaced apart superposed relationship. In multi-beam guns each of these first and/or second planar electrodes contains several spatially related apertures to accommodate the respective electron beams generated within the assembly. It is very important that these several apertures be accurately and consistently spaced relative to the related apertures in the adjacent electrode components, and, in the case of the first electrode component, with the respective cathode surfaces from which the specific electron beams emanate. These and associated electrodes are conventionally affixed to at least two longitudinal insulative support members of the integrated gun assembly by supporting projections extending from the respective electrode components.
Fabrication of the gun assembly involves embedment of the supporting projections of the related electrode components into the temporarily heat-softened longitudinal insulative support members. In this operation, which is commonly referred to as "beading", the softened support members on opposed sides of the assembly are pressured inward toward the several electrode components thereby forcing the supporting projections thereof into the support members. The opposing compressive pressures tend to exert a distorting force upon the electrode components, this being especially critical to the planar components wherein a bowing or arcuate bending effect sometimes results. Such bowing, however slight, changes the aperture locations relative to those in the adjacent electrode components, thereby producing deleterious inter-electrode spacing relationships within the gun structure. These uncontrollable changes in the related aperture spacings are particularly troublesome in in-line gun constructions wherein the first and the second grid electrodes usually have related apertures of small diameter and close spacings.
Two serious manufacturing control problems are caused by the bowing or warping of the first (G1) and/or second (G2) electrode components. The first of these is variation of cutoff and associated cutoff ratio. Cutoff is defined as the positive cathode (K) voltage at which the electrons cease to flow through the G1 aperture. Cutoff ratio is the ratio of the highest cutoff voltage to the lowest cutoff voltage of the three guns in a given tube. Cathode cutoff ratio is now commonly specified at 1.25, a condition which requires precise G1, G2, and K-G1 spacing control. This has proven to be one of the more difficult manufacturing control problems.
The second control problem relating to bowed G1 and G2 electrodes is variation of focus quality. This is largely determined by gun design, but for the gun construction to be successful, three factors are essential: (a) high quality parts must be used, (b) parts alignment must be accurately maintained, and (c) K-G1 and G1-G2 spacings must be precisely controlled at or near design center for optimum focus performance. This factor is directly related to bow-free electrodes. The most difficult production control parameter is the endeavor to achieve consistent K-G1 spacings for the three associated beams.
There are disclosures in the prior art to ruggedize in-line planar type electrodes by incorporating strengthening ribs such as those taught by Floyd K. Collins in U.S. Pat. Nos. 4,049,990 and 4,049,991.
A second grid electrode having channels therein is also shown in the gun structure disclosed by Allen P. Blacker and James W. Schwartz in U.S. Pat. No. 4,058,753.
While teachings of incorporating strengthening ribs fulfilled the existing needs at the time of disclosure, the state of the CRT art has advanced to stages of greater constructional sophistication wherein gun assemblies are made smaller and more compact, and tube operating requirements more stringent and exacting. In view thereof, improved strengthening of planar type electrodes, to prevent bowing during tube fabrication, is essential to achieving the desired tube performance characteristics required in the present state of the art.

DISCLOSURE OF THE INVENTION
It is therefore an object of the invention to provide a substantially planar CRT in-line electrode component having improved ruggedizing structural means incorporated therein to counteract the distorting forces encountered during the electron gun assembly fabrication procedure.
Another object of the invention is to provide an improved in-line ruggedized electrode component that is formed in a manner to optimize the maintenance of initial shaping when incorporated in a plural beam gun assembly thereby providing the desired subsequent inter-electrode spacings within the gun structure.
These and other objects and advantages are achieved in one aspect of the invention wherein improved strengthening means are provided for a substantially planar one-piece electrode component in a plural electrode in-line multiple beam CRT gun assembly integrated by a plurality of longitudinal insulative support members. The substantially planar component evidences alpha and beta surfaces wherein there are opposed side and end regions having L--L' and W--W' axes thereacross. The component contains a center and two side-related spatially positioned apertures located in an in-line relationship substantially coinciding with the L--L' axis. The center aperture is positioned at the intersection of the L and W axes, while the side-related apertures are located equidistantly therefrom along the L--L' axis on either side of the W--W' axis.
The invention relates to electrode component strengthening means in the form of at least one longitudinal channel located in each of the side regions thereof in parallel relationship with the L--L' axis. Each of these channels is indented inward from the beta surface to extend the full length of the respective side region to form a longitudinal rib projecting from the alpha surface. Extending outward from each channel, for the full length thereof, in the plane of the side region, is a defined ledge having a leading edge substantially parallel with the L--L' axis. Additionally, at least a pair of spatially-related supporting projections are extended outward equally from either side of the component as integral planar extensions of the respective ledge formations. The facing edges of each pair of projections are beneficially spaced from the W--W' axis by dimensions in the order of substantially half the separation distance between apertures.
Each of the ruggedizing longitudinal channels is further defined as an open-ended trough formation having width and depth dimensions formed by three adjoining longitudinal surfaces comprising an outer wall, an inner wall and a substantially planar bottom therebetween. As such, each channel evidences two separated longitudinal and parallel strengthening bends therein, the distance therebetween defining the bottom width dimension of the channel.
Each channel evidences a substantially uniform width dimension being in the order of at least twice the thickness of the component material. In like manner, a substantially uniform depth dimension is also evidenced, such being at least substantially equal to the thickness of the component material. Each of the channel-related ledges, which extends in a substantially right-angle relationship with the outer wall of each channel, has an outstanding dimension that is also at least substantially equal to the thickness of the component material.

The electrode component preferably also evidences at least two mini-channels formed as elongated lateral indentations in a surface thereof, preferably the beta surface, being located substantially midway between the center and side-related apertures in parallel relationship with the W--W' axis thereby transersing the area between the longitudinal side channels. Each of these mini-indentations forms an elongated protrusion from the opposite surface of the component, the height of this protrusion being less than the thickness of the component material.
The electrode component may be further defined as being fabricated in a manner wherein each of the apertures is oriented in an individual spaced-apart dish-like depression formed in the alpha surface in a manner to project as a separate protuberance from the beta surface. In keeping therewith, the aforedescribed mini-channel indentations are located in the spacings between the aperture protuberances.
The aforedescribed strengthening features incorporated in the structural configuration of a substantially planar electrode component effects the beneficial desired ruggedization thereof in a manner not heretofore achieved.