MXPA00000226A - Color picture tube having an inline electron gun - Google Patents

Abstract

The present invention relates to a color picture tube (10) having a viewing screen (22), and an electrode gun (26) within a neck (14) of the tube for generating and directing three in line electron beams, a center beam and two side beams, toward the screen. The electron gun includes a plurality of electrodes including a focus electrode (G5). The tube neck is adapted for receipt of a surrounding scan velocity modulation coil (54, 56) at a location thereon. The focus electrode includes two spaced parts (44, 46) that are electrically connected and adapted for connection to the same focus voltage (VFOCUS). The space (45) between the parts is surrounded by the neck location for the coil.

Description

COLOR IMAGE PIPE WHICH HAS AN ONLINE ELECTRON CANYON The present invention relates to improved color image tubes having in-line electron guns, and particularly to a tube having an in-line electron gun that includes an electrode of divided focus. For a tube of color images, the resolution of an image depends on having small electron beam spot sizes on the tube viewing screen. In a tube of this type, an electron gun generates three electron beams, which must be focused simultaneously on small points on the screen. It is known to use coils in the neck of a tube to provide scanning speed modulation (SVM). A scanning speed modulation coil is a two-pole device aligned to produce vertical magnetic fields, which induce horizontal deflection of the electron beams. These berets improve the quality of the image of a tube by modulating the horizontal deflection speed of the electron beams. The scanning speed modulation coil is activated as a function of the video signal. As the video speed increases, such as the NTSC speed at VGA and SVGA speeds, the scanning speed modulation coil must be operated at corresponding higher frequencies. These higher frequencies cause magnetic fields that change rapidly. In accordance with Faraday's law of induction, the changing magnetic flux will generate internal closed-loop current paths in any conductor. Additionally, Lenz's law says that induced eddy currents will produce a magnetic induction flux that opposes the change in the incident field, thus reducing the magnitude of the magnetic field that reaches the electron beams. The magnitude of these currents depends on the rate of change of the flow, that is, frequency. This reduction of the magnetic field requires higher energy circuits or coils of higher sensitivity, and therefore produces a higher undesirable cost. The present invention relates to a color image tube having a viewing screen and an electron gun in a tube neck to generate and direct three in-line electron beams, one central beam and two side beams, towards the screen . The electron gun includes a plurality of electrodes including a focus electrode. The neck of the tube is adapted to receive surrounding scanning speed modulation coils at a location thereof. The focus electrode includes two separate parts that are electrically connected and are adapted for connection to the same focus voltage. The space between the parts is surrounded by the neck location for the coils. This space provides a free region of parasitic current, thus increasing the resulting magnetic field seen by the electron beams. In the pictures: Figure 1 is a plan view, partially in axial section, of a tube of color images including the invention. Figure 2 is a side view, partly in axial section, of the electron gun of Figure 1, placed on the neck of the tube with scanning speed modulation coils placed on the neck. Figure 3 is a schematic view of the electron gun of Figure 2, showing the electrical connections of the electrodes of the electron gun. Figure 4 is a front view of the side of a part of the electrode G5B opposing a part of the electrode G5T in the electron gun of Figure 2. Figure 5 is a front view of the side of the electrode part G5B which opposes the part of the G5T electrode in an alternative electron gun. Figure 1 shows a rectangular color image tube 10 having a glass envelope 11 comprising a rectangular faceplate panel 12 and a tubular neck 14 connected by a rectangular funnel 15. The funnel 15 has an internal conductive coating ( not shown) extending from an anode button 16 to neck 14. Panel 12 comprises an observation front plate 18 and a side wall or peripheral flange 20, which is sealed to the funnel 15 by a glass frit 17. A three-color phosphor screen 22 is supported by the internal surface of the faceplate 18. The screen 22 is preferably a line screen with the phosphor lines arranged at triads, each triad includes a match line of each of the three colors. Alternatively, the screen may be a dot screen. A multi-aperture color selection electrode or shade mask 24 is removably mounted, by conventional means, in a predetermined spaced relation to the screen 22. An electron gun 26, shown schematically by broken lines in Figure 1, it is mounted centrally in the neck 14 to generate and direct three electron beams along converging paths through the mask 24 to the screen 22. The tube of Figure 1 is designed to be used with a magnetic deflection yoke external (not shown) that is attached to the tube in the vicinity of the funnel-to-neck junction. When activated, the yoke subjects the three beams to magnetic fields that cause the beams to scan horizontally and vertically in a rectangular frame on the screen 22. The details of the electron gun 26 are shown in Figures 2, 3, and 4. The barrel 26 comprises three separate in-line cathodes 34 (only one of which is shown), a control grid electrode 36 (G1), a screen grid electrode 38 (G2), an acceleration electrode 40 ( G3), a plate-shaped electrode 42 (G4), a focus electrode (G5) divided into two parts, 44 (G5B) and 46 (G5T). and a final electrode 48 (G6), separated in the order named.

Each of the electrodes G1 to G6 has openings in it to allow the passage of the three electron beams. The electrostatic main focusing lens in the barrel 26 is formed by the front portions of the electrode part G5T 46 and the electrode G6 48. The electrode G5B 44 and the electrode G5T are each formed by two pieces, 44B and 44T, and 46B and 46T, respectively. All electrodes of the electron gun 26 are directly or indirectly connected to two insulating support rods 50 and 52. Preferably, the support rods are made of glass that has been heated and pressed into hooks extending from the electrodes, to insert the electrodes. hooks on the rods. Shown in the neck 14 of Figure 2, there are two scanning speed modulation coils 54 and 56. Each coil is somewhat rectangular and is contoured to conform to the cylindrical shape of the neck. Each coil also includes a large central window which are positioned opposite each other at the top and bottom of the neck. Although the scanning speed modulation coils of this type have been used in tubes having electron guns with fixed focus voltages, the present invention has found that the effect on the scanning speed modulation coils in these tubes can be increasing by incorporating an additional space 45 in the electron gun to allow the scanning speed modulation field to act on the electron beams in an obstruction-free manner.

The space 45 allows the rapidly changing flow created by the scanning speed modulation coils to reach the electron beams without suffering the losses caused by the generation of eddy currents at the electrodes. This additional space 45 is formed by longitudinally spacing the focus electrode G5 into two parts, the electrode part G5B 44 and the electrode part G5T 46. The coils must surround the space between the parts 44 and 46, but preferably, the space it should be placed closer to the longitudinal center of the coils than near their ends, as shown in Figure 2. The electrical connections of the electrodes of the electron gun 26 are shown in Figure 3. The electrode G 1 is connected to Earth. The electrode G2 and the electrode G4 are connected to each other and at the voltage G2 VG2, the electrode G3, the electrode G5B and the electrode G5T are connected to each other and at a fixed focus voltage VFOco > and the electrode G6 is connected to the anode voltage VANDUS- In the electron gun 26, the front pieces 44T and 46B of the two electrode parts 44 and 46, respectively, each include a single elongated opening 47, as shown the part 44T in Figure 4. The remote parts 44B and 46T of the two electrode parts 44 and 46, respectively, include three openings 60, 62 and 64 therein, for the passage of the three electron beams, as shown in FIG. sample for part 44T in Figure 4. Figure 5 shows an alternative embodiment of parts 44T and 46B, designated with prime numbers of the same items, respectively. This alternative embodiment shows how the shapes and sizes of all openings in the electrode portions 44 and 46 can be altered to obtain a particular level of performance. In the portion of the alternative embodiment shown in Figure 5, a larger elongated opening 47 'is included in part 44T' and three larger openings 60 '62' and 64 'are included in part 44B'. A set of the separations for the electron gun 26 is provided in the following table. TABLE I Separation between the cathode and G1 = 0.076 mm * Separation between G1 and G2 = 0.229 mm Separation between G2 and G3 = 0.762 mm Separation between G3 and G4 = 1.270 mm Separation between G4 and G5B = 1.270 mm Separation between G5B and G5T = 1,778 mm Separation between G5T and G6 = 1,270 mm * at operating temperature.

Claims (3)

1. CLAIMS 1. A color image tube (10) having an observation screen (22) and an electron gun (26) in a neck (14) of said tube to generate and direct three in-line electron beams, a central beam and two side beams, towards said screen, said electron gun includes a plurality of electrodes including a focus electrode (G5), such focus electrode includes two separate parts (44, 46, 44 ') that are connected electrically and adapted for connection to the same focus voltage (VFocus), wherein front portions (44T, 46B) of said two separate parts of said focus electrode each include three openings (60, 62, 64, 60 ', 62' 64 ') therein for the passage of the three electron beams, and in at least one of said two separate parts, such three apertures are supported by an edge portion (43, 43') forming a single aperture. elongated (47, 47 ') in the same for the passage of the three hac it's electrons.
2. 2. A color image tube (10) having an observation screen (22) and an electron gun (26) in a neck (14) of such a tube to generate and direct three in-line electron beams, one beam central and two side beams, towards said screen, such electron gun includes a plurality of electrodes including a focus electrode (G5) said tube neck is surrounded by a scanning speed modulation coil (54, 56) in a location of the focus electrode, and said focus electrode includes two separate parts (44, 46, 44 ') which are electrically connected and adapted for connection to the same focus voltage (VFocus) -
3. 3. The tube as defined in FIG. claim 2, wherein the front portions of said two separate portions (44, 46, 44 ') of such focus electrode (G5) each include three openings (60, 62, 64, 60', 62 ', 64' ) in it for the passage of the three electron beams, and in at least one of the d Said separate parts, said three openings are supported from an edge portion (43, 43 ') forming a single elongated opening (47, 47') therein for the passage of the three electron beams.