Surge-gap end plug

• US 6,473,285 B1
• Filed: 09/13/2000
• Issued: 10/29/2002
• Est. Priority Date: 09/13/2000
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Wallis, David, Schlenz, Alan J.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/660,653
• Time in Patent Office: 776 Days
• Field of Search: 361/111, 361/112, 361/117, 361/118, 361/119
• US Class Current: 361/112
• CPC Class Codes: H01T 4/08 structurally associated with protected apparatus with switches H01H9/14; with fuses H01H85/44
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/104 Switchers or splitters

Abstract

A surge-gap device (300) includes two electrodes (310, 315), having an inside portion and an outside portion, and an insulator material (320), which secures the two electrodes (310, 315). The insulator material (320) has an opening through the material to expose an open-air gap (325) that is defined by the space between the two inside portions of the electrodes (310, 315). In cases of a voltage surge, the surge-gap device permits an arc to pass between the proximate inside portions of the electrodes (310, 315) across the open-air gap (325), which gives a current surge a low impedance path to ground. Also included is a fastener (305) for electrically coupling the surge-gap device (300) to a ground plane (220) of an external electrical device (300) for suppressing the voltage and current surges.

Claims

1. A surge-gap device, comprising:

two electrodes each having an inner portion and an outer portion;

an insulator for partially surrounding the two electrodes, the insulator having an open-air gap that is formed in a central region thereof and that separates the inner portions of the electrodes, wherein the insulator has an opening formed therethrough and into which the inner portions of the electrodes extend; and

a fastener for electrically coupling the surge-gap device to a ground plane of an external electrical device for directing excess current to the ground plane and thereby suppressing voltage surge.

2. The surge-gap device of claim 1, wherein the two electrodes and the insulator comprise a subassembly of the surge-gap device.

3. The surge-gap device of claim 1, wherein the open-air gap has a length L that is defined by a space between the inner portions of the two electrodes allowing, in the event of a voltage surge, an arc path for excess current.

4. The surge-gap device of claim 2, wherein the fastener is configured to define a cavity therein, and wherein the fastener further comprises:

threads formed on its exterior;

an opening at one end of the fastener for inserting the subassembly into the cavity; and

an end plug at a second end of the fastener that defines a boundary of the cavity to secure the subassembly therein.

5. The surge-gap device of claim 4, further comprising a spring, wherein the spring is positioned in the cavity between the end plug and the outside portion of one electrode of the subassembly.

6. The surge-gap device of claim 1, wherein:

the inner portions of the electrodes each have a first diameter selected to minimize inherent capacitance and to allow the current surge to pass between the two electrodes; and

the outer portions of the electrodes each have a second diameter larger than the first diameter, wherein the second diameter is sized to secure the two electrodes in the insulator and to form a connection point between the outer portion and the spring.

7. A tap for splitting signals, the tap comprising:

a tap housing having at least one access port, wherein the access port is configured to have a cavity therein, and wherein the access port comprises;

conducting means for contacting tap circuitry; and

a surge-gap device coupled to the access port to protect the tap against voltage and current surges, the surge-gap device comprising;

two electrodes each having an inner portion and an outer portion;

an insulator for partially surrounding the two electrodes, the insulator having an open-air gap that is formed in a central region thereof and that separates the inner portions of the electrodes, wherein the insulator has an opening formed therethrough and into which the inner portions of the electrodes extend; and

a fastener for electrically coupling the surge-gap device to the tap housing and for directing excess current, during voltage surges, from the tap circuitry to the tap housing via the surge-gap device and the conducting means.

8. The tap of claim 7, wherein the open-air gap has a length L that is defined by a space between the inner portions of the two electrodes allowing, in the event of a voltage surge, an arc path for excess current surge.

9. The tap of claim 7, wherein the two electrodes and the insulator comprise a subassembly of the surge-gap device.

10. The tap of claim 7, wherein the fastener is configured to define a cavity therein, and wherein the fastener further comprises:

threads formed on its exterior to mate with corresponding threads of the access port;

an opening at one end of the fastener for inserting the subassembly; and

an end plug at a second end of the fastener that defines a boundary of the cavity to secure the subassembly therein.

11. The tap of claim 7, further comprising a spring, wherein the spring is positioned in the cavity between the end plug and the outside portion of one electrode of the subassembly.

12. The spring of claim 11, wherein the spring exerts pressure onto the subassembly, forcing contact between the outside portion of the second electrode and the conducting means.

13. The tap of claim 7, wherein:

the inner portions of the electrodes each have a first diameter selected to minimize inherent capacitance and to allow the current surge to pass between the two electrodes; and

the outer portions of the electrodes each have a second diameter larger than the first diameter, wherein the second diameter is sized to secure the two electrodes in the insulator, and wherein the second diameters of the two electrodes are sized to form a connection point to the spring and sized to form a connection point to the conducting means.

14. A tap for splitting signals, the tap comprising:

a tap housing having at least one access port, wherein the access port is configured to define a cavity therein, and wherein the access port further comprises;

conducting means for contacting tap circuitry; and

a surge-gap device coupled to the access port to protect the tap against excess voltage and current surges, the surge-gap device comprising;

a fastener configured to define a cavity therein and to mate with the access port;

a subassembly situated within the cavity of the fastener, wherein the subassembly comprises;

two electrodes each having an inner portion and an outer portion; and

an insulator for securing the two electrodes and to center the two electrodes about the same longitudinal axis, the insulator having an open-air gap that is formed in a central region thereof and that separates the inner portions of the two electrodes, and wherein the insulator has an opening formed therethrough into which the inner portions of the electrodes extend; and

a spring situated within the cavity of the fastener between a bottom surface of the cavity and the subassembly for forcing the subassembly into contact with the conducting means of the access port when the fastener is mated with the access port.

15. The tap of claim 14, wherein:

the inner portions of the two electrodes each have a diameter of 0.065 inches and a length of 0.325 inches; and

the outer portions of the two electrodes each have a diameter of 0.375 inches and a length of 0.7 inches.

16. The tap of claim 15, wherein the insulator is formed from teflon.

17. The tap of claim 15, wherein the opening formed in the insulator has a diameter of 0.2 inches.

18. The tap of claim 15, wherein the cavity formed within the fastener has a diameter of 0.375 inches and a length measured within the cavity to the bottom surface of 0.50 inches.