VIDEO PRESENTATION INSTRUMENT THAT INCLUDES A DEVICE TO ELIMINATE ELECTRICAL FIELD ISSUED FROM A
CRT
BACKGROUND OF THE INVENTION 1. Field of the invention The present invention relates to an apparatus for presenting video, such as a television receiver, a computer monitor, etc., and more particularly, to a video presentation apparatus. which includes a device for eliminating the electric field emitted by a cathode ray tube. 2. Description of the Prior Art A common video display apparatus contains a cathode ray tube (CAT), a cabinet and a back cover. The cabinet and the back cover are made of a thermoplastic material and are coupled together to accommodate a TAC between them. The TAC has a high vacuum space and consists of a funnel-shaped glass ampule that has a cover plate or face plate and a neck, an electron gun installed in the neck to irradiate the electron beams, and a yoke deflector installed on the outside of the neck. In this cathode ray tube that was described above, the electron beams radiating from the cathode of the electron gun are controlled, accelerated and directed by conventional means, and then irradiated on a fluorescent screen that is formed on the back side of the cover or front plate. During these processes, the horizontal return pulses that are generated by means of a horizontal output transformer are applied to a deflecting yoke coil, and the high voltage of a section to generate high voltage is applied to an anode, by means of which electric fields are generated. In the TAC as it is used in a video display apparatus, a measurable electric field can be generated by means of the return voltage pulses from the horizontal deflection circuit. With the present use of monitors with TAC in many companies and recreational activities, interest has also grown about the danger of electric fields emitted to users. The manufacturers of the TACs are continuously trying acceptable radiation levels according to the known measurement protocols. Various methods of canceling the electric field in front of a TAC are known. An example is illustrated in Figure 1. With respect to Figure 1, a TAC consists of a deflecting yoke 2 for deflecting the electron beams radiating from an electron gun 1, a fluorescent screen 4 radiating by means of the collision of the electron beams through a shadow mask 3, a high voltage generating section 5 for generating a voltage, an anode 6 for charging the high voltage that is generated in the high voltage generating section 5 (e.g. , 24 KV more or less), and a protective panel 7 installed in the TAC coating plate. In a manufacturing TAC as in the above, the electron beams radiating from the electron gun 1 are deflected in the vertical or horizontal direction by the deflecting yoke 2. The diverted electron beams collide with the fluorescent screen 4 through the shadow mask 3. > The fluorescent screen 4 radiates from this collision, and, as a result, an image is displayed on the CT scan. In this step, the horizontal return pulses generated by the horizontal output transformer (not shown) are applied to the coil of the deflector yoke 2 and the high voltages that are generated in the high voltage generation section 5 are applied to the anode 6, by means of which the generation of the electric fields (E) is made expressed by: VE = - [V / m equation (II)} d where E is an electric field strength, V is a voltage that is applied to the defector coil, and d is a distance from the coil. According to the previous equation, the electric field (E) is produced in proportion to the current applied to it. Many countries have established regulatory restrictions on electric waves, and those skilled in the art have suggested methods for eliminating electric waves. A suggested method is to provide an electric field eliminator for eliminating the electric fields that are generated from the deflecting coil at the top of the deflecting yoke, and a coil for displacing or balancing the electric fields at the front of the deflecting yoke. To eliminate the electric fields, metal protective plates are placed on the image board attached to the back of the neck and on the main board placed on the lower part of the neck. Also, to eliminate any electric field in front of a CT, a protective panel 7, as shown in figure 1, is provided on the cover plate of the TAC. This panel 7 is a conductive transparent glass panel, coated by means of tin-indium oxide. A conventional CT like the one illustrated in figure 1 can protect from electric fields with a panel attached to the TAC coating plate. However, these panels require a special expensive treatment. Therefore it is difficult to produce panels in large quantities. Likewise, the transmissivity of the TAC monitor is reduced by this protective panel, by means of which the deterioration of the brightness of the monitor is achieved. In addition, since the protective panel is made of glass, it is very likely that the operator will feel eye fatigue due to the reflection of the panel when the panel is attached to the front of the TAC.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an apparatus for presenting video, which contains a device for removing radiation from the front of a cathode ray tube. To achieve this object * one embodiment of the present invention provides a video display apparatus consisting of a beveled section formed in a cover plate of a cathode ray tube, a composite coil having a demagnetization coil and a shielded wire wound along a periphery of the demagnetizing coil, and a horizontal output transformer having a primary winding section to which a predetermined voltage is applied, a secondary winding section which induces high voltage pulses in response to the voltage pulses applied to the primary winding section to provide the high voltage pulses to an anode of the TAC, and a third winding section which induces in it the reverse high voltage pulses for the high voltage pulses applied to the voltage section. primary winding. It is desirable to introduce the composite coil into a cabinet having a plurality of projections and guides on one side thereof. The shielded wire is preferably made with a non-magnetic material having excellent electrical conductivity and permeability, and wound one to several times, in an open loop fashion. The induced voltage pulses in the tertiary winding section, which are inversed to the high voltage pulses, are applied to the shielded wire. For mode of the present invention, it provides a device for eliminating the electric field that is produced in proportion to the voltage pulses that are applied to the deflection coil of the TAC and then emitted from the TAC.
BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned object and other features and advantages of the present invention will be apparent by describing the preferred embodiments thereof with respect to the accompanying drawings, in which:
Figure 1 is a view illustrating a conventional device for eliminating the electric field emitted from a video presentation apparatus. Figure 2 is a demagnetized view of a video display apparatus having a device for removing an electric field in accordance with the present invention. Figure 3 is a view illustrating the structure of a composite coil according to the present invention. Figure 4 is a view illustrating the structure of a composite coil in an assembled state according to the present invention. Figure 5 is a diagram of a circuit for protecting against radiation waves according to the present invention. Figure 6A and 6 & they are diagrams of the waveform that illustrates the waveform of the electric field radiated from the TAC and the waveform of the pulses that are applied to an armored wire, respectively.
DETAILED DESCRIPTION OF THE INVENTION Figure 2 illustrates a CRT 11 presenting an image applying a high voltage from a horizontal output transformer to an anode 19 thereof. The CRT 11 includes in its cover plate an HA beveled section with a composite coil 13 installed therein. The composite coil 13 is fixed to a concave section 12C (shown in Figure 4), which is formed between a projection 12A and a guide 12B provided on the side of the cabinet 12 connected to the CRT 11. The composite coil 13 illustrated more specifically in Figure 3 it contains a degaussing coil 14 for the elements of the CRT 11 and a shielded wire 15, wound one to several times in the form of an open loop along the periphery of the degaussing coil. Demagnetization coil 14 and shielded wire 15 are surrounded by a coating 16 for the purpose of insulating from the outside. The lead wires 17, 18 are connected to the demagnetization coil 14 and the shielded wire 15, and the negative voltage pulses induced in the tertiary winding of the horizontal output transformer (TSH) are supplied through the lead wires 17, 18. Figure 5 shows a circuit of a device for removing the electric field in accordance with the present invention. The circuit consists of a primary winding section Ll to produce an AC return voltage by means of the voltage of the power supply B +, a secondary winding section L2 to induce a high AC voltage in response to the voltage applied to the power section. primary winding Ll and the application to an anode of the CRT a high voltage obtained by the AC rectification induced through the DI diode, and a tertiary winding section L3 to induce the inverse pulses towards the high voltage pulses applied to the section of primary winding and the application of the induced reverse pulses towards a shielded wire 15. By the above construction, an AC current is applied through (unreadable) fixed in the concave section formed on the inner surface of the cabinet 12, concurrently with the operation of the TRC 11. In an initial stage, when the current of the AC component is applied the demagnetization coil 14 of the composite coil 13, a large amount of current required for the demagnetization of the TRC is applied to the degaussing coil 14. At a predetermined time, for example, about 3 seconds, the resistance of the demagnetization circuit (not shown in the drawings) ) connected to the degaussing coil 14 is increased by means of this the current flow through the degaussing coil 14 is decreased. Accordingly, the degaussing of the CRT 11 is achieved. Also, as shown in Fig. 11, if a predetermined horizontal voltage pulse HP is applied to the primary winding section Ll of the high voltage induced in the secondary winding section 12 of the horizontal output transformer (TSH) in proportion to the transformation ratio thereof, and then supplied to the anode 19 of the TAC 11 after being rectified by a diode D2. Inverse voltage pulses of, for example, around -16 to -32 V, are induced to the tertiary winding section L3 of the horizontal output transformer (TSH), and then supplied to the shielded wire 15 wound around the coil of demagnetization 14 by a conductive wire 18. As shown in Figures 6A and 6B, voltage pulses supplied to the shielded wire 15 have the same level and phase as those of the electric field emitted from the TRC 11, but have an inverse polarity to these. Therefore, since the pulses having the same level and phase, but inversed in polarity to the radiation wave of the TRC 11 are supplied to the shielded wire 15, it is possible to balance the wave radiated by the electric field generated by the protective wire 15. A person skilled in the art could expect that the loop type protective wire 15 is made of non-magnetic material having excellent electrical conductivity and high permeability and that can be manufactured in a solid or twisted line, or in the form of a tube regardless of its diameter. The various modifications and changes that do not depart from the scope of the appended claims will be apparent to those skilled in the art. The illustration is not unduly limited to the illustrative modalities shown therein.