US1308878A - John thomson - Google Patents

Description

J. THOMSONI METHOD FOR PREVENTIYG ELECTRIC CARBON RESISTERS FROM OXIDIZING.

APPLiCATlON FILED OCT.7, 1918.

1,308,878. Patented July 8, 1919.

Z INVENTOR BY UNITED STATES PATENT OFFICE.

' 101m THOMSON, or new roux, N. i.

Application flled October 7, 1918. Serial No. 257,213.

To all whom it may concern:

ing.

Be it known that I, JOHN THOMSON, a citizen of the United States, and a resident of the borough of Manhattan, city of New York, county and State of New York, have invented certain new and useful Improvements in Methods for Preventing Electric CarbonResisters from Oxidizing, of which the following is a specification.

This invention relates to electric furnaces and consists in a method for pr'eventin carbon 'resisters from oxidizing, or airurn- The accompanying drawing is a-diagrammatic sectional view of an electric furnace comprising the essential elements necessary to illustrate the present method. In said dra-Win in whic A is the base, B the side-walls, and

C the arched roof that together provide the furnace chamber D. Mounted in the sidewalls, and passing through the chamber, is a carbon resister E whose type is commonly designated as the zig-zag, its terminals being empirically shown in a power-circuit F,

Hitherto, the chief difficulty, and to a large extent the limiting factor, in the use of electric carbon resisters, irrespective of their type or form, is their liabilit to attack and disintegration when air or ot er active gases are present in the resistor-chamber. A method has hitherto been employed to avoid the destruction of carbon resisters, as by the introduction of an inert gas. For an example of such method see U. S. patent to F. A. J. FitzGerald, No. 950,905, dated March 1, 1910. Said method has proven fairly successful; but the method now to be described is more generally applicable in present practice and possesses certain impontant advantages.

Thus, the method now to be described consists of locating within a resister-chamber a charge composed of a mixture of oxid of zinc (ZnO) and carbon '(C), which, when sufiiciently heated, reacts according to the classical. formula,

If or when any oxygen is present in the resister-chamber, it combines with the zincfume and produces ZnO, whereby the resister itself is made wholly immune to pernicious attack; or, as expressed in common parlance,-is immune to air-burning.

Specification of Letters Patent.

a furnace construction is shown- Patented Ju y s, 1919.

The mixed charge, as h, may be convenlently introduced to the resister-chamber,

from time-to-time, through an opening or. tube, as m, to be received by a pan, as n resting upon the resistor, or it may be dropped upon the bottom of the chamber, as at 1-. The tube may also be utilized as a vent, as at s,wherea t to burn a flame of mixed or intermingled Znfume and CO, thereby indieating to an operator thatthe chamber contains an adequate supply of thebenign vapor and gas.

It is preferable, for the present purpose,"

that both the zinc oxid ZnO and the carbon C which compose the charge shall be of a high degree of purity, whereby the residuum of the reaction shall be a merely nominal amount; and also in that there shall be practically no other development of vapor and gas than pure zinc-fume and monoxid of carbon. v

Obviously, the charge needs not be located precisely within the confines of the resistorchamber; for, if desirable, it might be placed in a communicating side-chamber, or niche, or wherever sufficient heat could be directed thereon to produce the reaction; which becomes active at or about 1,000 C.

The following controlling advantages reside in the production of zinc-fume by'means of the aforesaid reaction rather than by merely vaporizing metallic zinc: Firstly, the CO performs the function of an active carrier for the denser Zn vapor or fume and serves to convey 'the latter into any crevices in the furnace-walls'whereat, if air is present, it will burn to ZnO, thus automatically closing the vents and excluding a further entrance of oxygen. Secondly, the expansion of the fume and gas, particularly when the resister chamber is wholly inclosed, produces pressure, of which but a nominal amount is necessary to cause the reaction. to cease. Consequently, when there are no vents to permit escape of the fume and gas, or when no oxygen is present to consume the fume, the reduction of the charge is automatically suspended; and, per contra, if vents develop, and if air again enters, the benign reaction is automatically resumed. In these circumstances, a merely nominal quantity of reacting charge serves to protect-the resister for a relatively long period of time. In fact, carbon resisters have been thus continuously operated, at high temperatures, for periods of months, without the slightest deterioration; the conditions of service being such that, without the utilization of this' method, they would not have endured but a few hours. 4 p

While the foregoing matter has preferably dealt specifically with the metallic vapor produced from oxid of zinc and the gas resulting from its reagent, monoxid of carbon, the method, broadly, is not necessarily confined to these specific substances,; in that the oxid of any metal, when combined with any suitable reagent whose reaction will produce a metallic vapor which combines with oxygen, and a gas which will'not attack carbon, may. be utilized. c

What I claim is:

1. In electric furnaces, the method of preventing a carbon resistor from oxidizing which consists in locating a charge of oxid of zinc and carbon (ZnO and 0) within the resistor-chamber and heating the said charge until it reacts and produces zinc fumes and carbon monoxid (Zn and CO.) v

2. In electric furnaces, the method of preventing a carbon resister from destructive G0), which method consists in so situatin a charge of oxid of zinc and carbon (Zn and 0) within a resistor-chamber, that the ingredients of the charge will be caused to react until the developed pressure is sufiicient to automatically sus nd the reaction.

4. In electric furnaces, t e method of preventing a carbon resistor from oxidizing which method consists of envelopin the resister in an atmosphere comp of the fumes or vapors from a vaporized metallic oxid and its gaseous reducing reagent.

This specification signed and witnessed this 13th day of September, A. D. 1918.

, JOHN THOMSON.

Signed in the presence of RALPH M. THOMSON, H. O. Wain).

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