US608685A - kelly - Google Patents

Description

Patented Aug. 9, |898.

J.F.KELLY.

LIGHTNING ARRESTER.

(Application filed Dec. 16, 1895.)

2 Sheets-Sheet l.

(No Model.)

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No. 608,685. Patented Aug. 9, |898. J. F. KELLY.

LIGHTNING ARRESTER.

(Application filed Dec. 16, 1895.)

(No Model.) 2 Sheets-Sheet 2.

Fig. 5.

WITNESSES: v VENTOR 7M @if UNITED STATES PATENT OFFICE.

JOHN Fa KELLY, OF IITTSFIELD, MASSACHUSETS, ASSIGNOR OF ONE-HALF TO CUMMINGS C. CHESNEY, OF SAME PLACE.

LIGHTNING-ARRESTER.

SPECIFICATION forming part of Letters Patent No. 608,685, dated August 9, 1898.

Application tiled December 16, 1895. Serial No. 572,228. (No model.)

To @ZZ whom zit may concern:

De it known that I, JOHN F. KELLY, a citizen of the United States, residing at Pittsfield, in the county of Berkshire and State of Massachusetts, have invented a new and useful Lightning-Arrester, ot' which the following is a speciiication.

My invention belongs to that class of instruments used in electrical systems, whether for alterna-ting' or continuous currents, for permitting the passage to the earth of any currents of abnormally high difference of potential which may be dueto static discharges, such as lightning or other causes, and which if not provided for are liable to injure the system or parts thereof. Such instruments are commonly known as lightning-arresters.

My invention has for its object to provide an arrester which, while offering practically infinite resistance to ordinary electromotive forces, shall be readily permeable to hightension static discharges, and incidentally in my preferred form to provide an arrester which is in itself at the same time a safetyfuse. I attain these objects by the use of a device hereinafter described, reference being had to the accompanying drawings,in which- Figure l represent-s a perspective View of a device embodying my invention. Fig. 2 represents a side view of the same with the parts cutaway so as to show the details more clearly, and Fig. 3 represents the generator and line of a system of electrical distribution with my arrester applied.

To lightning-arresters such as are at present used there are various objections. For instance, they either oifer an objectionably high resistance to the passage of the current of abnormallyhigh difference of potential or an objectionably low resistance to the passage of the normal current or are too costly or too bulky for ordinary use. In the first case they cannot be relied upon to operate in all cases of necessity, In the second case if they do operate when needed the normal current will follow the abnormal discharge and continue to follow it until interrupted by some outside means, thereby becoming in itself a source of danger. My invention avoids all these objections, being of reasonable cost and of small bulk and eifel-ing a resistance to static discharges and the like neither too high, so

to impair its usefulness as an arrester, nor too low, so as to interfere with the system under normal conditions. Aside from these 55 advantages the particular device hereinafter shown and described as being an embodiment of my invention in its preferred form may act as a safety-fuse, so that if the normal current should follow the static discharge the circuit would be automatically opened.

The drawings represent an arrester enibodying my invention in its preferred form. This device consists of a non-conducting body or cylinder C, mounted upon a suitable support S by bands T T and containing a series of conducting or semieonducting pieces I I in bad electrical contact with one another. The cylinder C has metallic end pieces or caps D E, having binding-posts F G, to which the conductors L L to the line and to the earth are connected, respectively. The cap D has a pressure-screw I), which bears upon one end of the series I I, so as to insure lgoed contact between the ends of the series and the caps D E. By using a sufficient number of pieces in the series the bad contacts practically open the circuit for ordinary electronictive forces and yet are very readily traversed by high-tension discharges. One of the simplest ways of making the series of conducting or semiconducting bodies is to form a column of lead pellets, such as shot more or less oxidized. I have found that an arrester constructed with an eighteen-inch column of oxidized shot, as above described, the shot being about eighteen-hundredths of an inch in diaineter and only slightly and superficially oxidized and being arranged in a single scries, as shown in the drawings, will withstand with safety two thousand volts pressure and yet at the same time be easily traversed by a spari; from a small Holtz machine. One great dilticulty with the present type of lightningarresters of this class seems te be that they offer toc great a resistance to the q uiclr pas-- sage therethrough of a current of abnormally high tension and toe low a resistance to prevent the passage of an appreciable amount of current at normal tension, as a consequence of which latter some of the normal current is certain to leak away. My device offers substantially no passage for currents of normal tension, but a comparatively low resistance to currents of very high or abnormal tension. When lightning strikes the line, the enormous tension of the current resulting therefrom changes the condition of the particles and reduces the resistance of the arrester, so that the charge passes off at once.

In Fig. 3 I have shown my arrester in connection with a portion of a system in which it is so located as to protect a generator K. The arrester consists of the device described above and is connected to the line in the same manner as the ordinary spark gap arresterthat is, the line is directly connected to one terminal by the conductor L, While a conductor L, leading to the earth, is connected to the other.

Although it is not necessary to use pellets of lead or a similar fusible metal in making up the series I I in arresters embodying my invention, broadly considered, their use presents a distinct advantage-namely, that arresters when so constructed, if arranged with the column in a vertical position, will themselves act perfectly as safety-fuses, since when such an arrester is so used, if the current should follow the path of the lightning discharge, the pieces making up the series will fuse and fall together, thus opening the circuit. The arrester as thus constructed is an almost perfect safeguard against static discharges reaching the machine or instrument to be protected and also against the shortcircuiting of such a machine or instrument itself when it is a current-generator. The arrester is connected with the system in the usual manner, so as to form a shunt to the earth for the static discharge. Y

What I claim as my invention, and desire to secure by Letters Patent, is-

1. A lightning-arrester consisting of a column of conducting or semiconducting bodies in bad contact With one another, as a Whole practically nonconducting under ordinary electric stress, but under high stresses conducting, in combination with suitable terminals for the line, in contact with the column respectively, substantially as described.

2. A lightning-arrester consisting of a nonconducting containing vessel, in combination With a column of conducting or semiconducting bodies in bad contact with one another, Within said vessel, and suitable terminals in contact With the ends of the column respectively, substantially as described.

3. A lightning-arrester consisting of a column of fusible conducting or semiconducting bodies held in position in bad contact with one another, in combination With suitable terminals in contact With the ends of the column respectively, substantially as described.

4. A lightning-arrester consisting of a column of pieces of fusible metal partially oxidized, held in position in combination With suitableterminals in contact with the ends of the column respectively, substantially as described.

In testimony whereof I have hereunto set my hand this 11th day of December, 1895.

JOHN F. KELLY.

Vitnesses:

C. C. CHEsNEY, A. C. BUNKER.

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