US1338294A - Electrical-heater resistance element - Google Patents

Description

UNITED sTAT PATENT DFFICE.

WILLIAM E. GARDNER, or PITTSBURGH, PENNSYLVANIA, ASSIGNOR 0E ONE-THIRD To .HENBY oLAY BLACK, or BEN AVON, PENNSYLVANIA, ANI) ONE-THIRD TO JULIUS JACOB, OF rrrrsnunen, PENNSYLVANIA.

' ELECTRICAL-HEATER RESISTANCE ELEMENT.

No Drawing.

long used, and which nevertheless is cheap' to produce and economical to. use.

In general the invention consists in a re sistance unit composed of non-metallic, nonfusible and non-combustible substances under the heating current. More specifically, it comprises an electrical resistance element formed of a mixture of finely divided nonmetallic conducting and non-conducting substances, which will not fuse and therefore remain. in their original condition no matter how long used.

Various substances can be used for the two elements of the compound. As the conducting element of the compound I prefer to use carbon, and preferably that form of carbon found in substantially pure coke. For the non-conducting element of the compound various substances can be used, preferably bone ash or bone earth, such as can be obtained on the market in various grades,--that which is best for my purposes being the white bone ash; or commercial carborundum may be used as the non-conducting element. These ingredients will be mixed in a finely divided state, either granulated, but preferably in powdered form.

The finer the in redients the better, as it obviates any slig t arcs which might form between the grains of granulated material. Satisfactory results are secured by reducing the ingredients to a size to pass through a sixty-mesh sieve or finer.

These ingredients reduced to a fine state are then very thoroughly mixed, so that all.

the particles of the conducting material (carbon) are divided or separated by particles of non-conducting material (bone ash Specification of Letters Patent.

Applicationfiled July 7, 1919. Serial No. 309,133.

or carborundum, orboth). The more intimate the mixture the better the result.

The proportions of the ingredients may be varied, depending upon the particular use to which the heater is to be applied, and to the voltage and amperage of the current to which itis to be subjected. NVithhigh voltage currents obviously the proportion of the non-conductingor insulating ingredient must be greater than for a low voltage current. Likewise the higher the resistance of the non-conducting ingredient the less the amount that need be used. In general I have found that carborundum must be used in a .slightly larger proportion than bone ash, as carborundumis not as good an insulator as bone ash. For ordinary purposes .I have found that a mixture consisting of three parts of carbon to one part of bone ash (or a slightly greater amount of carborundum when the latter is used in place of bone ash) gives satisfactory results.

This composition can be used either in a loose dry form or can be formed into a solid by the use of asuitable binder. It can be used in loose dry form by merely placing it in a tube composed. of electrically nonconducting but heat conducting material, or

in a metallic tube provided with a suitable electric insulating lining and having the two terminals ofthe electric circuit inserted into the ends of the tube and into the powdered material; orsuch dry material may merely be placed in an electric non-conducting pan or trough, such as one composed of porcelain or earthern ware, with the terminals of the circuit inserted into the powdered material at opposite ends of said pan or trough.

t can also be molded into solid form of any desired size or shape by the use of a binder which is non-fusible under the heating cur rent and'which does not form too high a conductor of electric current. I have found that if these dry ingredients are mixed with a very small quantity of molasses and then molded and carbonized at a high heat in a closed receptacle a very solid and durable resistance element is formed.

These resistance elements can be connected in the circuit either in multiple are or in series or in any other well known way of connecting elements in an electric circuit. They can be made of any desired size or? element between the electrical terminal) the larger should bethe' percentage of conducting material relative to the non-conducting material.

A resistance element composed of the ingredients specified is cheap to produce, is highly efficient in use, does not burn out as do metallic resistance elements, and furthermore is practically unaffected by the electric current due to the fact that the elements do not fuse together under a heating current but always remain in the condition of original mixture.

l lhis resistanceelement can be used for any purpose or in any place Where an electrical resistance element for heating purposes can be used.

' Obviously various kinds of ingredients suitable for the purpose stated will suggest themselves to those skilled in' the art. ikewise the proportions of these ingredients can be varied within quite wide-limits, depending upon the characteristics of the specific ingredients used, the value of. the current of the circuit in which 'the same is to be inserted, and the particular "use to which the heating element is to be put.

I claim: s

1. An electrical resistance element con sisting of an intimatemixture of finely divided dry carbon, and finely divided bone ash.

2. An electrical resistance element consisting of an intimate mixture of finely divided coke, and finely divided bone ash.

In testimony whereof I have hereunto set my hand.

WILLIAM GARDNER.

Witness v G. G. TRILL.