US460140A

US460140A - Electric safety-catch

Info

Publication number: US460140A
Authority: US
Publication date: 1891-09-29
Anticipated expiration: 1908-09-29

Description

(No Model.)

J. W. HOWELL. ELECTRIC SAFETY CATCH No. 460,140. Patented Sept. 29, 1891.

I WWI/wow .Xonniia UNITED STATES PATENT OFFICE.

JOHN \V. HOW ELL, OE NEVARK, NEW JERSEY.

ELECTRIC SAFETY-CATCH.

SPECIFICATION forming part of Letters Patent No. 460,140, dated September 29, 1891.

Application filed January 6, 1891. Serial No. 376,831. (No model.)

To aZZ whom it may concern:

Be it known that-I, JOHN V. HOWELL, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in Electric Safety-Catches, of which the following is a specification.

The object I have in view is to produce a practical and effective form of safety-catch for the protection of electrical instruments which are wound with fine wire, such as comparative indicators, telephones, telegraphs, electric clocks, (to. These instruments are liable to be burned out when their circuits become crossed with a circuit, which causes an abnormal flow of current through them. A difficulty has heretofore been experienced in the protection of theseinstruments by safety-catches, since with metal wire of sizes which can be practically made and handled the instruments will be destroyed or injured before the safety-catch wire is fused, due to the fact that the heat is conserved in the closelycompacted coils of the instruments. By my invention I employ for a safety-catch a material which is a conductor of electricity and has a high specific resistance compared with the metals, and which material is destroyed by chemical action (as distinguished from fusion) when an abnormally large current passes through it. The material may be one which when abnormally heated will combine with the oxygen of the air with which it is surrounded or will combine with a particular gas with which the chamber containing the safety-catch is filled, or the material may be one which contains in itself elements which will combine and effect its destruction upon a rise in temperature. I prefer to employ a carbon for the purpose, the carbon being used in the form of a filament or wire. An abnormal current heats the carbon safetycatch, and it is oxidized by the surrounding air. Many other materials or compositions can be used having the characteristics before pointed out. For illustration, a wire or filament of an explosive mixture, such as gunpowder, can be employed. I11 fact, many materials and compositions which are high-resistance conductors of electricity and which can be destroyed by chemical action when heated abnormally by the electric current can be used, theimportant feature being that the cut-out conductor, containing carbon or other high-resistance material, is heated and destroyed chemically, as described, to interrupt the circuit, rather than being destroyed by a mere fusion of the cutout conductor or by a fusion of wax orother binding agent in which carbon or other conducting powder is incorporated. A safetycatch made of material of this character, by reason of the high specific resistance of the material, can be constructed of a large size, compared with a metal safety-catch which would respond to the same current. I have found that these safety-catches can easily be made to open the circuit when a current of onetenth of an ampere, or even less,is flowing, and still be of an entirely practical size for handling. The wire, of carbon or other material, may be held between clamps which clamp its ends directly, or any of the wellknoWn methods for making good contacts with carbon may be employed, such as electroplating the ends of the safety-catch wire where they enter the clamps or by securing short lengths of metallic wire to the ends of the safetycatch wire by any of the methods known in the construction of incandescent electric lamps for securing carbon filaments to leading-wires, the metal and pieces being received by sockets or clamps of any suitable construction. lVhen carbon is employed for the safety-catch, it should be located in the air, so as to be oxidized when raised to a red heat by the current. It may be inclosed in any suitable safetycatch box which will have or admit sufficient air to oxidize the carbon wire. The carbon wire may be produced in any of the ways well known in the manufacture of carbon filaments for incandescent lamps. A great advantage in using a carbon wire for the safety-catch is that the carbon becomes rapidlythinner and increases its resistance until finally broken. This has the same effect as rapidly inserting a resist ance into the circuit, the final rupture of the circuit taking place with a much smaller cur rent than it would with a metallic-wire safetycatch and the tendency to form an are being greatly reduced.

In the accompanying drawing, forming a part hereof, the figure represents a side elevation of one form of safety-catch and clamping-holders, a supporting-base and inclosinging-cover being shown in dotted lines.

A B are two spring-clamps, to which are connected the wires 1 and 2 of the circuit to be protected. The safety-catch 0, held by the clamps A B, is a wire or filament of car- 'bon, gunpowder, or other material which is infusible or practically infusible, and is destroyed by chemical action when an abnormally large current passes through it. The material of the safety-catch is one which has, as before explained, a high specific resistance compared with the metals. The clamps may be mounted upon a suitable base and the whole inclosed by a suit-able cover, as shown in dotted lines. The clamps, or other equivalent mode of fastening permits the safety'catch to be readily replaced when burned out.

hat I claim is- 1. A safety-catch for electric circuits, composed of a conductorof electricity which is destroyed by chemical action (as distinguished from fusion) when an abnormally large current passes through it, substantially as set forth.

2. A safety-catch for electric circuits, composed of a conductor of electricity having a high specific resistance compared with the metals, and which is destroyed by chemical action (as distinguished from fusion) when an abnormally large current passes through it, substantially as set forth.

3. A safety-catch for electric circuits, composed of carbon, substantially as set forth.

This specification signed and witnessed this 2&th day of December, 1890.

JOHN V. HOWELL.

lVitnesses:

WILSON S. HOWELL, HALSEY M. BARRETT.