Apparatus for suppressing field radiation from display device

• US 5,260,626 A
• Filed: 02/19/1992
• Issued: 11/09/1993
• Est. Priority Date: 02/20/1991
• Status: Expired due to Term

• Current Assignee: Dr. Ing. Roberto Dini Societa' Italiana Per Lo Sviluppo Dell'Elettronica S.A.S.V.E.L. S.p.A., Nanao Corporation
• Original Assignee: Nanao Corporation
• Inventors: Terada, Masakazu, Michihata, Masatoshi, Sakai, Yoshikazu, Nakashima, Yoshiyuki, Takase, Katsuhisa
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US07/837,756
• Time in Patent Office: 629 Days
• Field of Search: 315/85, 315/8, 313/313, 358/245, 361/424
• US Class Current: 315/85
• CPC Class Codes: H01J 2229/0015 Preventing or cancelling fields leaving the enclosure
• CPC Class Codes: H01J 2229/0053 Demagnetisation
• CPC Class Codes: H01J 29/003 Arrangements for eliminating unwanted electromagnetic effects, e.g. demagnetisation arrangements, shielding coils H01J29/06, H01J29/867 take precedence; demagnetisation in general H01F13/00; circuit arrangements therefor H04N9/29; screening of apparatus against electric or magnetic fields H05K9/00
• CPC Class Codes: H04N 9/29 using demagnetisation or compensation of external magnetic fields

Abstract

In order to eliminate any harmful influence due to electric field radiation on the human body, electric field radiation from a front surface of a cathode ray tube is reduced. A degaussing coil arranged in proximity to a peripheral edge of a front surface of a cathode ray tube is employed advantageously. The degaussing coil is supplied with a voltage which is opposite in polarity to an electric field radiated from the front surface of the cathode ray tube. The reverse polarity voltage is derived from an output signal obtained from an output signal of a horizontal deflection circuit by a flyback transformer and/or derived from a voltage obtained by phase-inverting an anode voltage fluctuating in vertical synchronization. After a degaussing operation is completed, relay contacts are opened on the basis of a timer-controlled relay switch, thereby completely cutting the connection between the degaussing coil and a degaussing power source generating an alternating current which is supplied to the degaussing coil for the degaussing operation.

Claims

1. An apparatus for suppressing electric field radiation from a display device, comprising:

an electrode arranged in proximity to the peripheral edge of a display surface of a display device; and

means for supplying said electrode with a voltage of reverse polarity relative to an electric field radiated from said display surface of said display device.

2. An apparatus for suppressing electric field radiation from a display device in accordance with claim 1, wherein said display device includes a cathode ray tube, said electrode is arranged in proximity to the peripheral edge of said front surface of said cathode ray tube, and said electric field includes an electric field radiated from said front surface of said cathode ray tube.

3. An apparatus for suppressing electric field radiation from a display device in accordance with claim 2, wherein a degaussing coil is provided in relation to said cathode ray tube, said electrode being provided by said degaussing coil.

4. An apparatus for suppressing electric field radiation from a display device in accordance with claim 3, wherein said degaussing coil is connected to a degaussing power source for generating an alternating current which is attenuated with a lapse of time, said apparatus further comprising means for completely cutting connection between said degaussing coil and said degaussing power source.

5. An apparatus for suppressing electric field radiation from a display device in accordance with claim 4, wherein said means for cutting connection includes a timer-controlled switch.

6. An apparatus for suppressing electric field radiation from a display device in accordance with claim 2, wherein said means for supplying said electrode with said voltage of reverse polarity includes means for adjusting the phase and regulating the amplitude of said voltage of reverse polarity.

7. An apparatus for suppressing electric field radiation from a display device in accordance with claim 2, wherein said voltage of reverse polarity is provided by a signal of reverse in polarity relative to a flyback pulse signal of a horizontal deflection circuit, said signal being derived from said flyback pulse signal.

8. An apparatus for suppressing electric field radiation from a display device in accordance with claim 2, wherein said voltage of reverse polarity includes a voltage obtained by phase-inverting a voltage, fluctuating in vertical synchronization, which is applied to an anode of said cathode ray tube.

9. An apparatus for suppressing electric field radiation from a display device in accordance with claim 2, wherein said voltage of reverse polarity includes a voltage provided by a signal which is reverse in polarity to a flyback signal of a horizontal deflection circuit, said signal being derived from said flyback pulse signal, and a voltage obtained by phase-inverting a voltage, fluctuating in vertical synchronization, which is applied to an anode of said cathode ray tube.

10. An apparatus for suppressing field radiation from a display device in accordance with claim 2, further comprising a plurality of stop members arranged around said cathode ray tube, and said electrode comprises a conductive member provided with a conductive wire of a prescribed length having both end portions being tied up toward the same direction, said conductive member engaging with said plurality of stop members, and a slider being movable along said tied end portions of said wire while receiving said end portions in common.

11. An apparatus for suppressing electric field radiation from a display device in accordance with claim 10, wherein said plurality of stop members are located on a front panel which is arranged to cover the periphery of said front surface of said cathode ray tube.

12. An apparatus for suppressing electric field radiation from a display device in accordance with claim 10, wherein said conductive wire is insulation-coated.

13. An apparatus for suppressing electric field radiation from a display device in accordance with claim 10, wherein said slider has a tubular configuration.

14. An apparatus for suppressing electric field radiation from a display device in accordance with claim 13, wherein said slider is formed of an insulating material.

15. An apparatus for suppressing electric field radiation from a display device in accordance with claim 1, wherein said display device includes a display panel of an alternatingly driven flat display device, said electrode is arranged in a peripheral portion of said display panel, and said electric field includes an electric field radiated from said display panel.

16. An apparatus for suppressing electric field radiation from a display device in accordance with claim 15, wherein said means for supplying said electrode with said voltage of reverse polarity includes means for amplitude-regulating said voltage of reverse polarity.

17. An apparatus for suppressing electric field radiation from a display device in accordance with claim 15, wherein said display panel comprises a liquid crystal display panel having a common electrode which is supplied with an alternating voltage.

18. An apparatus for suppressing electric field radiation from a display device in accordance with claim 17, wherein said means for supplying said electrode with said voltage of reverse polarity includes means for phase-inverting said alternating voltage.

19. An apparatus for suppressing field radiation from a display device in accordance with claim 15, further including a chassis frame for holding said display panel, said electrode being arranged on said chassis frame.

20. An apparatus for suppressing field radiation om a display device in accordance with claim 15, further including a front panel which is arranged to cover the periphery of said display panel, said electrode being arranged on said front panel.