Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-10-07
2001-08-07
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S1020SP, C174S1020SP
Reexamination Certificate
active
06271466
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of preventing a high-frequency noise on a grounding cable for the purpose of reducing damages caused by a high-frequency noise generated in electronics such as OA (office automation) equipment used in office buildings, and to a cable used for this end.
BACKGROUND OF THE INVENTION
In modern office buildings, networking is predominant and internet has been actively used. Inevitably, electronic instruments such as personal computers and the like are used in numbers. High frequency noise is generated not only from these electronic instruments but also from other equipment generally referred to as electronics. Since this high-frequency noise causes various types of damage to the above-mentioned precision electronic devices, countermeasures have been recently taken such as attaching a shield against radiation noise of the electronic device itself and installing a noise cut transformer against a conduction noise. In general, connection to a grounding cable of a grounding electrode having a low impedance to a high-frequency wave, from among the grounding electrodes set in office buildings at the time of construction, is considered to be sufficient for the removal of high-frequency noise.
This high-frequency noise does not disappear into the earth through a grounding cable, but in fact remains in the grounding cable as a standing wave of a high-frequency noise having various frequencies and greater amplitude than the initial amplitude, due to repeat reflection between the grounding electrode side and the electronic instrument side of the grounding cable.
A high-frequency noise remaining on a grounding cable as such standing wave flows into electronic devices to cause malfunction of or damage to the devices, thereby causing serious problems in offices.
The present invention provides a method for easily reducing or eliminating a standing wave generated on a grounding cable by modifying the grounding cable such that a high-frequency noise does not remain as a standing wave on the grounding cable, and a cable constitution therefor.
SUMMARY OF THE INVENTION
In general terms, when the current flows in a metal conductor, a low-frequency wave at a commercial frequency and the like flows in the metal conductor, whereas a high-frequency noise tends to flow on the surface of a metal conductor by virtue of a skin effect phenomenon.
It has been known that, of the aforementioned high-frequency noises having various frequencies, a high-frequency noise having a maximum amplitude called resonance causes substantial damages to electronic devices.
In the present invention, therefore, the resonance of the high-frequency noise is reduced by forming a resistor having a small electric resistance on the surface of a metal conductor of a grounding cable such that, of the high-frequency noises flowing on the surface of the metal conductor, particularly the high-frequency noise, which produces resonance, is consumed when flowing through the electric resistor. The constitution of the present invention is explained in detail in the following.
A first aspect of the invention is a method of preventing a high-frequency noise that is generated in an electronic device, remains in a grounding cable as a standing wave, and is transmitted to electric devices, the method comprises disposing, directly or via an insulating layer, a non-metallic conductive material having a slight electric resistance on a conductor of the above-mentioned grounding cable, and making the electric resistance of the non-metallic conductive material consume the high-frequency noise flowing on a surface of the conductor of the grounding cable by virtue of a skin effect, whereby resonance of the high-frequency noise is reduced.
A second aspect of the invention is the method according to the first aspect wherein an electric resistance R of the non-metallic conductive material and an inductance L of the conductor of the grounding cable having the conductive material satisfy the formula: 2&pgr;fL/R≦1 wherein f is a resonance frequency of the high-frequency noise.
A third aspect of the invention is the method according to the first aspect, wherein the non-metallic conductive material is disposed by coating a periphery of the conductor of the grounding cable with the non-metallic conductive material or disposing a tape-like non-metallic conductive material in the longitudinal direction of the conductor of the grounding cable.
A forth aspect of the invention is the method according to the first aspect, wherein the non-metallic conductive material is disposed by applying an insulating layer to the outside of the non-metallic conductive material.
A fifth aspect of the invention is a grounding cable for preventing a high-frequency noise that is generated in an electronic device, which remains in the grounding cable as a standing wave, and is transmitted to electric devices. The cable comprises a non-metallic conductive material, that consumes the high-frequency noise flowing on a surface of a conductor of the grounding cable with its small electric resistance by virtue of a skin effect. The non-metallic conductive material is disposed, directly or via an insulating layer, on the conductor, wherein two points spaced apart in a longitudinal direction of the conductor, the conductor and the non-metallic conductive material are electrically in contact with each other.
A sixth aspect of the invention is the cable according to the fifth aspect, wherein an electric resistance R of the non-metallic conductive material and an inductance L of the conductor satisfy the formula: 2&pgr;fL/R=1 wherein f is a resonance frequency of the high-frequency noise.
A seventh aspect of the invention is the cable according to the fifth aspect, wherein the non-metallic conductive material is applied to a periphery of the conductor or disposed in a longitudinal direction of the conductor in the form of a tape.
In addition, an eighth aspect of the invention is the cable according to the fifth aspect, wherein the non-metallic conductive material comprises an insulating layer formed on the outside of the material.
REFERENCES:
patent: 3643007 (1972-02-01), Roberts et al.
patent: 4301428 (1981-11-01), Mayer
patent: 4383225 (1983-05-01), Mayer
patent: 4408089 (1983-10-01), Nixon
patent: 4822950 (1989-04-01), Schmitt
patent: 4960965 (1990-10-01), Redmon et al.
patent: 5008488 (1991-04-01), Nakagawa
patent: 5171938 (1992-12-01), Katsumata et al.
patent: 5394507 (1995-02-01), Okamoto
Electrical Engineering Pocketbook, ed. The Institute of Electrical Engineers of Japan, 1987, p. 148.
Hans C. Ohanian, Physics, Union College and Rensselaer Polytechnic Institute, W. W. Norton & Company, 1985, p. 763.
Murano Yoshihiro
Okada Ken'ichi
Okawa Yoshinao
Tsuneoka Masaki
Japan Atomic Energy Research Institute
Mayo, III William H
Reichard Dean A.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Grounding cable does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grounding cable, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grounding cable will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2447370