US3581143A

US3581143A - Ontracking wire spark gap component

Info

Publication number: US3581143A
Application number: US791683*A
Authority: US
Inventors: John E Dornfeld
Original assignee: Sprague Electric Co
Current assignee: Sprague Electric Co
Priority date: 1969-01-16
Filing date: 1969-01-16
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

Each of two noncontacting wire leads has a face of one extremity in registration a predetermined fixed distance from its counterpart to form a spark gap therebetween. Each lead is bent so that the extensions of the leads are oppositely disposed and spaced from each other by a distance substantially greater than the spark gap. A mass of nonconducting material covers both of the bends, and bridges the lead extensions near the bends so as to fix the spacing of the spark gap. The mass is also set back on both sides of the spark gap a distance at least sufficient to assure avoidance of exposure of the mass to carbonizing temperatures during sparking within the voltage rating range of the unit.

Description

United States Patent 2,378,893 6/l945 Berkey et al 31 3/35X 3,045,143 7/1962 Shickel 313/325 3,322,995 5/1967 Hansen et al. 3l5/35X ABSTRACT: Each of two noncontacting wire leads has a face of one extremity in registration a predetermined fixed distance from its counterpart to form a spark gap therebetween. Each lead is bent so that the extensions of the leads are oppositely disposed and spaced from each other by a distance substantially greater than the spark gap. A mass of nonconducting material covers both of the bends, and bridges the lead extensions near the bends so as to fix the spacing of the spark gap. The mass is also set back on both sides of the spark gap at distance at least sufficient to assure avoidance of exposure of the mass to carbonizing temperatures during sparking within the voltage rating range of the unit.

NONTRACKING WIRE SPARK GAP COMPONENT BACKGROUND OF THE INVENTION The present invention relates to a spark gap component and more particularly to a nonwire spark gap component.

In one prior art method of forming a spark gap component, an insulating material, such as an epoxy resin, is formed over the closed end of a U-shaped wire so that a web of the material covers the closed end and bridges the more or less parallel leads near the bend in the unit. To form the spark gap, a saw cut of predetermined thickness is made into the insulating coating and through the lead wire. Depending mainly upon the width of the spark gap, the unit is then given a particular voltage rating range and the unit can be employed in a circuit which is likely to see surge voltages within this voltage rating range.

The function of the spark gap component in a particular circuit is to protect individual components or groups of components from overvoltages that these components may see from periodic transient voltages which may be caused by lightning, momentary arcing or shorting of other elements in the circuit, etc. ln a relatively short space of time the spark gap component might actually function a large number of times. When this happens, the overvoltage, or the brunt of the overvoltage, jumps the gap and directs the overvoltage to ground until the'voltage drops back below the voltage rating of the spark gap. After this the circuit continues to operate in its designed manner. It has been determined, on careful inspection of these prior art spark gap components after they have been subjected to a number of overvoltages, that a condition known in the art as tracking occurs in the region of the spark gap. Tracking is a condition caused by the temperature produced at the spark gap. The high temperature causes a decomposition and carbonization of the organic insulating material or electrostatically attracted dust, dirt, etc. in the region of the electrode faces which constitute the spark gap. Eventually this carbonization from one side of the spark gap meets that of the other side and a low impedance current path is formed. As a result, the prior art spark gap component falls far below its voltage rating range and the component will arc at very low voltages and may eventually become a continual short.

An object of this invention is to present a new and novel spark gap component.

lt is another object of the invention to present a spark gap component not subject to a tracking condition.

These and other objects of the invention will become obvious upon reading the following specification and claims.

SUMMARY OF THE INVENTION The present invention broadly is concerned with a spark gap component having two noncontacting wire leads each having the face of one extremity in registration a predetermined fixed distance from its counterpart to form a spark gap therebetween. Each of the leads has a bend therein so that extensions of the leads are oppositely disposed and spaced from each other by a distance substantially greater than the spark gap. A mass of rigid, flame-resistant, nonconducting material covers each of the bends, and bridges that portion of the lead extensions near the bends so as to maintain the predetermined fixed distance between the faces of the lead extremities. The mass is also set back remote from the faces of said extremities by a distance at least sufficient to assure avoidance of exposure of the mass to carbonizing temperatures during sparking within the voltage rating range of the unit. The mass is also thick enough so that no other component or body can be brought within sparking distance of one of the wire leads. In a narrower aspect of the invention, the mass of nonconducting material is molded in place and the lead extensions, where they emerge from said mass at a point remote from said spark gap, are accurately spaced a predetermined distance apart.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a front view in elevation of a unit of the present invention.

The drawing shows a spark gap component 10 having

metal lead wires

12 and 14. The face 16 of one extremity of lead 12 is shown spaced from the face 18 of one extremity of lead 14. A molded jacket 20 of insulation material is shown molded about the lead wires so that the molding material is set back from the spark gap to point 22 on lead wire 12 and point 24 on lead wire 14.

DETAILED DESCRlPTlON OF THE INVENTION EXAMPLE A spark gap component of the present invention is formed in the following manner: A U-shaped tinned copper wire of approximately one sixty-fourth of an inch in diameter is inserted into a mold. The mold is so designed that when an insulating material is inserted into it, the U-shaped end of the wire will be covered with the insulating material except for the central or bridging portion of the U-shaped wire. In other words, insulating material will cover the two, more or less, right-angle bends in the lead wires and part of the lead extensions which are oppositely disposed to one another and a web of insulating material will bridge across these lead extensions. In the molding operation a suitable commercial insulating material Plaskon is employed. This material is an alkyl-type resin derived from the reaction of phthalic anhydride, plus maleic anhydrides and glycol. It is selected because of its rigidity, nonconductivity and flame resistance. Other materials with similar physical and electrical characteristics can be employed. The length of uninsulated wire that is the bridging portion of the U-shaped wire will be determined by the voltage rating range of the unit. The smaller the actual spark gap, the smaller will be the uninsulatedportion. The larger thespark gap, the greater will be the length of uninsulated lead wire. After the insulating jacket has been molded about the bent lead wire, the uninsulated portion of the lead wire is severed by cutting through the wire to form a precise, fixed spark gap.

The insulating molding material must be set back from this spark gap by a distance which is at least sufiicient to assure avoidance of exposure of the molding material to carbonizing'temperatures during sparking within the voltage range of the spark gap unit. In the present example, employing a spark gap of approximately 0.020 inch, a mold is employed which insures that the insulating material is set back from the spark gap a distance of approximately 0.050 inch. The insulating material should be about 0.100 inch thick. This will insure that no other component or body can be brought closer than about 0.050 inch to either of the electrodes at the spark gap.

The distance from the spark gap that the insulating material should be set back will vary somewhat depending not only upon the size of the spark gap but upon the particular insulating material employed. One skilled in the art can readily determine the temperature range which the sparking condition will produce and this information can be compared to the known carbonization temperature of the particular insulation material employed. The insulating material will then be set back from the spark gap a distance which is at least sufficient to assure that the insulating material will not be exposed to carbonizing temperatures.

A wide variety of insulating materials can be employed and the use of particular ones will be dictated by consideration of economy, rigidity, nonconductivity, moisture penetration resistance, flame resistance and its electrical insulation characteristics. Usefulmaterials will be found in the broad class of epoxy, phenol formaldehyde resins, etc. Tracking can and does occur in prior art units even if the insulating material is noncarbonizing. Foreign material, such as dust, dirt,organic matter, etc., becomes deposited near the spark gap due to electrostatic attraction or other phenomena and .this material causes the tracking condition. The insulating material, therefore, also can be inorganic in nature, e.g. ceramic, since the structure of the device of the present invention overcomes the tracking problem no matter what type of insulator is employed. The lead wire material likewise can be selected from a large variety of metals. In addition to tinned copper, one can employ copper wire, tin wire, steel wire, nickel wire, etc.

Since it is obvious that many changes and modifications can be made in the above described details without departing from the nature and spirit of the invention it is to be understood that the invention is not limited to said details except as set forth in the appended claims.

l claim:

l. A spark gap component comprising two noncontacting wire leads each having the face of one extremity in registration a predetermined fixed distance from its counterpart to form a spark gap therebetween, each of said leads having a bend therein so that extensions of said leads are oppositely disposed and spaced from each other by a distance substantially greater than said spark gap; a mass of rigid, flame-resistant, nonconducting material covering each of the bends and bridging said extensions near said bends so as to maintain said spark gap, said mass being set back remote from said spark gap a distance at least sufficient to assure avoidance of exposure of said mass to carbonizing temperatures during sparking within the voltage rating range of the unit.

2. The component of claim 1 wherein said mass is molded in place and said lead extensions, where they emerge from said mass, are accurately spaced from each other a predetermined distance.

3. The component of claim 2 wherein said lead extensions are substantially parallel and extending from said bends in the same direction, and said mass encases a substantial length of said extensions thereby maintaining said predetermined distance.

4. The component of claim 1 wherein said mass around said set back has a thickness greater than said spark gap thereby insuring spacing from adjacent bodies a greater distance than said spark gap.

Claims

1. A spark gap component comprising two noncontacting wire leads each having the face of one extremity in registration a predetermined fixed distance from its counterpart to form a spark gap therebetween, each of said leads having a bend therein so that extensions of said leads are oppositely disposed and spaced from each other by a distance substantially greater than said spark gap; a mass of rigid, flame-resistant, nonconducting material covering each of the bends and bridging said extensions near said bends so as to maintain said spark gap, said mass being set back remote from said spark gap a distance at least sufficient to assure avoidance of exposure of said mass to carbonizing temperatures during sparking within the voltage rating range of the unit.