Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Reexamination Certificate
1999-05-10
2001-06-19
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
C361S103000, C361S119000, C361S213000
Reexamination Certificate
active
06249415
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to surge protection in communications systems. More particularly, the present invention relates to a surge protector and a method for protecting against electrical surges in coaxial and other cables.
BACKGROUND OF THE INVENTION
Surge protectors are in use to protect electronic components from the deleterious effects of electrical surges. Generally, surge protectors function to shunt abnormal surges of electricity away from electronic components. There are three major causes of electrical surges: lightning pulses, ground surges, and power crosses. Lightning pulses are a relatively brief surge of electricity stemming from a strike of lightning on or near an electrical conduit, such as a power line or a communications line. Ground surges are caused when excess voltage, which follows the path of least resistance, does not entirely travel to ground, but instead strays off to another line which is itself connected to ground. Ground surges may be caused by a shorted circuit, a faulty connection to ground, the intensity of the abnormal voltage level, or the duration of an abnormal voltage level.
A power cross is potentially the most devastating type of electrical surge. A power cross comes when a pole carrying power lines is toppled, such as by high wind, a tree falling against it, or a car running into it, and falls into another line, for example, a telecommunications cable or line. Upon the pole falling, the various lines may become dislodged and crossed. Crossed lines may remain so for a lengthy time, thus subjecting a line or cable and any electrical components in connection with it to abnormal voltage conditions for a lengthy period of time. Depending upon the intensity of the power cross, as well as its duration, the line or cable may be melted. If the line or cable is running in from an industrial site, such as, for example, a phone company, the amount of line or cable melted may be miles long. The replacement cost, as well as the cost of running new line or cable, is high.
Devices have been utilized on so called “twisted pair” telephone lines to protect against electrical surges since the 1920 s. One such device, described in U.S. Pat. No. 4,161,762 (Scheithauer), acts as a fuse. Specifically, the device operates if an excess current flows through the line. Devices such as the one described in Scheithauer are impractical for coaxial communications lines. In particular, placing a fuse in a coaxial communications line changes the characteristics of the coaxial cable by adding impedance to the center conductor. Changing the characteristics alters the signals being transmitted.
Surge protectors for cables have been described in U.S. Pat. No. 5,835,326 (Callaway), U.S. Pat. No. 5,751,534 (DeBalko), U.S. Pat. No. 5,726,851 (Knapp), and U.S. Pat. No. 5,508,873 (Knapp et al.).
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for protecting electronic components and signal carrying cables from damage due to electrical line surges. The apparatus has first and second conductors respectively connectable to electrical signal paths, and a first line protection device electrically connected between the first and second conductors. The first line protection device includes a third conductor interconnecting the first and second conductors and being electrically connected to at least one of the first and second conductors through a meltable conductive fixing material, e.g., a solder. The conductive fixing material disrupts electrical connection between the third conductor and at least one of the first and second conductors when predetermined overload electrical signals are present. In one aspect of the invention, the cables are coaxial cables.
In a preferred embodiment of the invention, the third conductor is a lead which is soldered to the first conductor at a first point, the lead being further connected to the second conductor, with the solder melting under predetermined electrical overload conditions. The invention may also employ a second line protection device formed by connecting the lead to one electrical side of gas breakdown device, the other electrical side of the gas breakdown device being groundable.
These and other features and advantages of the invention will become more apparent from the following detailed description of preferred embodiments of the invention.
REFERENCES:
patent: 3936785 (1976-02-01), Novak
patent: 4086648 (1978-04-01), Hines et al.
patent: 4161762 (1979-07-01), Scheithauer
patent: 4277812 (1981-07-01), Jones
patent: 4394704 (1983-07-01), Jones
patent: 4603368 (1986-07-01), Pagliuca
patent: 5101180 (1992-03-01), Frey
patent: 5384679 (1995-01-01), Smith
patent: 5508873 (1996-04-01), Knapp et al.
patent: 5726851 (1998-03-01), Knapp
patent: 5751534 (1998-05-01), Debalko
patent: 5835326 (1998-11-01), Callaway
patent: 6023403 (2000-02-01), McGuire et al.
Daoud Bassel Hage
DeBalko George Andrew
Eckhardt Peter F.
Figueiredo Antonio Albino
Kane Adam Stuart
Avaya Technology Corp.
DeBeradinis Robert L.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Fleming Fritz
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