US1262305A - Insulating material and body composed thereof. - Google Patents

Description

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UNITED STATES PATENT OFFICE,

ALBERT CHAMPION AND TAINE G. MODOUGAL, OF FLINT, MICHIGAN, ASSIGNORS TO CHAMPION IGNITION COMPANY, OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN.

INSULATING MATERIAL ANDQBODY COMPOSED THEREOF.

To all whom it may concern:

Be it known that we, ALBERT CHAMPION and TAINE G. MCDOUGAL, citizens of the Republic of France and the United States of America, respectively, and residents of Flint, county of Genesee, State of Michigan, have invented certain new and useful Improvements in Insulatin Material and 'Body Composed Thereof, f which the fol lowing 1s a specification.

Our invention relates to the manufacture of spark plugs designed for use with internal combustion engines, and particularly to the insulating members used in and forming a part of such devices. One object of our invention is to provide an insulating member which will have improved dielectric strength, under the high temperature condi tions present in internal combustion engines and will possess a structure which will enable it to better resist sudden changes in temperature Without cracking.

With the above and other objects in view, our invention consists: First: in an insulating member for the purpose stated in which the proportion of clay to the other ingredi ents used in the finished member and upon which its i nsulating properties depend, is increased, and in which the proportion of those substances which have to be mixed with the clay in the practical manufacture of insulators (and which ordinarily have a deleterious efiect thereupon so far as concerns' the insulating properties, when used at higher temperatures, of the finished prod not), is reduced to a minimum. Second: in i an insulating member which, during the,

manufacture thereof is subjected to a higher firing temperature than has heretofore been usual, made necessary bythe new prop'or-, tioning of the ingredients used in order to maintain a vitrified structure. Third: in such other improvements in and relating to insulating members for spark plugs as will hereinafter appear.

Our inventionnot only includes an insulating member for 'a spark plug as a new article of manufacture, the same being made from a plastic composition made up of certain materials hereinafter enumerated, but

, it also includes the porcelain material per se made from the composition or mixture disclosed, which material is capable of use Patented Apr. 9, 1918.

Wherever high insulating qualities at high temperatures are desirable in an article or device to be made therefrom, and the method or process of making insulating members for spark plugs from a composition made up of the ingredients specified, by subjecting the same to suitable operations during and as steps in the manufacture of the said members from the composition disclosed.

The insulating members of spark plugs for use in internal combustion engines are ordinarily formed from a composition comprising plastic clay or kaolin mixed with a certain portion of non-plastic and more or less fusible materials and molded or shaped into proper form, and then dried, and finally subjected to a high temperature, or fired, to Vitrify the mass. The plasticity of the mass is made possible on account of its raw clay content.

The non-plastic material (ordinarily reduce and control the shrinkage of the molded members and to prevent the formation of cracks therein during the drying thereof at a comparatively low temperature, and before they are subjected to the firing process, during which the uncombined water is driven oif (but not the water heldin chemical combination in the clay) also to prevent abnormal shrinkage and distortion during the vitrifying process. Fusible material (ordinarily feldspar) is used to promote vitrification of the mass during the firing process, thus producing a hard, strong and compact finished product, the feldspar being melted at a lower temperature than any of the other ingredients.

The less the quantity of' the morefusible material present in the mixture from which the insulating members are formed, the

plugs because it reduces the insulating properties thereof at the higher temperatures.

It therefore follows that a minimum vper cent. referred to above.

amount-of feldspar is desirable, because of its direct effect in reducing the insulating qualities at higher temperaturesof the finished insulator, due to its mere presence, and because vitrified bodies obtained (usually at lower heats) through high feldspar content have been found to poorly resist breakage under suddenly varymg temperatures.

It is found in practice that a quantity of raw clay equal to about sixty per cent. of the composition or mixture employed should be used in order to secure the requisite plasticity to permit the various molding, lathing, kneading and other operations necessary to give the proper shape and form to the insulators, while a quantity of feldspar equal to about ten per cent. or as little as five per cent. of the composition will be suflicient to secure a proper vitrification thereof when they are subjected to the correct firing process and will at the same time not seriousl lower the insulating qualities of the insu ators. This'quantit has been found to secure the best balance between an unavoidable impairment of insulating qualities in the finished product'due to the presence of feldspar therein on the one hand, and the necessity for an excessivel high firing temperature due to an inor inate reductitliln of, the quantity of feldspar used on the ot er.

From the above it will be appreciated that there remains an unassigned quantity equal to 40% of the composition from which the insulators are made, which deficiency is su plied by the non-plastic materials here in efore referred to, as it has been found in practice that non-plastic material to the extent of about 40% of the composition is necessary to prevent crackin and undue shrinkage of the molded an shaped insulating members during the drying operation or step to which they are subjected before firing. If flint, alone, is used to' make up 30% or 35% of this 40% then the fired insulators would not be uniform or homogeneous in structure, the flint being present in much the same condition as when introduced, because the flint is but slowly soluble in the molten feldspar during the firing operation.

Our invention, therefore, contemplates the use of calcined clay as the non-plastic ingredient of the composition employed for making the insulating members, either alone or in. connection with a much smaller quantity of flint than the thirty or thirty-five It follows that the amount of flint in the finished product is greatly reduced and the amount of clay upon which substitution the insulating qualities at increased temperatures of the members is dependent is proportionately increased. For example, and still assuinin the 60% proportion of raw or uncalcin clay and 10% of feldspar, then if 20% of calcined clay is used the amount of flint is reduced to 10%; and if calcined clay and feldspar alone are'used as the non-plastic constituents of the composition, then the flint is eliminated altogether.

It will be appreciated that the calcined clay is produced by heating raw or ordinary plastic clay to such a temperature that the chemically combined water held there- 15 in is driven off. This heattreatment of the cla causes it to lose its plastic qualities and to ecome an inert or non-plastic substance. As this clay will not thereafter combine with water, the uncombined water, which is ordinarily contained in the uncalcined clay, and is therefore present in the ingredients employed, will facilitate the operations necessary to give the proper form to Ehe insulating members before drying and Finally both the raw or uncalcined clay and the calcined clay are in precisely the same condition, and are in all respects alike after the firing process has been performed, so that the finished insulating members made in accordance with our invention are made up entirely of clay vitrified by the use of say 10% or less each of feldspar and flint, if flint is used at all.

In making an insulator for spark plugs in accordance with our invention the proper quantities of raw or uncalcined clay, calcincd clay (and flint or other non-plastic material if any such is used) and feldspar, are mixed and ground together in any suitable grinding mill until the proper degree of fineness is obtained and an intimate mixture has been secured. After grinding the insulating members are properly formed from the mixture by any suitable molding, shaping, forming or similar operations. The sa1d members are next dried at a comparatively low temperature to eliminate the water held in mechanical suspension in the composition from which they are formed, and which was either present in the raw clay or was added during the operations anterior to the final production of the formed insulating members in order to facilitate the working of the composition.

- The body is then fired at the required temperature which exceeds by 40 centi grade or more that used in common porcelain manufacture.

Having thus described and explained our invention, we claim and desire to secure by Letters Patent:

1, As a new article of manufacture, an insulating member for a spark plug made from porcelain, and in which calcined clay is used aszanon-plastic ingredient of the composition from which the said member is formed.

2. As a new article of manufacture, an insulating member for a spark plug formed from a mixture containing plastic uncalcined clay, non-plastic calcined clay, and a fusible vitrifying material.

3. As a new article of manufacture, an insulating member for a spark plug formed from a mixture containing plastic uncalcined clay, non-plastic calcined clay, and feldspar.

4. As a new article of manufacture, an insulating member for a spark plug formed from a mixture comprising plastic uncalcined clay, a non-plastic material made up of calcined clay and flint, and a fusible Vitrifying material.

5. As a new article of manufacture, an insulating member for a spark plug formed from a -mixture comprising plastic uncalcined clay, a non-plastic material made up of calcined clay and'flint, and feldspar.

6. As anew article of manufacture, an insulating member for a spark plug formed from a mixture comprising approximately 60% of plastic uncalcined clay, approximately 10% of a fusible vitrifying material, and approximately of non-plastic ma terial some of which is calcined clay.

7. As a new article of manufacture, an insulating member for a spark plug fdrmed from a mixture comprising approximately 60% of plastic uncalcined clay, approximately 10% of feldspar, and approximately 30% of non-plastic material some of which is calcined clay.

8. The insulating material herein described and made from a mixture comprising approximately 60% of plastic uncalcined clay, approximately 10% of fusible vitrifying material, and approximately 30% of non-plastic material some of which is calcined clay.

. 9. The insulating material herein described and made from a mixture comprising approximately 60% of plastic uncalcined clay, approximately 10% of a fusible vitrifying material, and approximately 30% of non-plastic material made up of calcined clay and flint.

10. The insulating material herein described and made from a mixture comprisingapproximately 60% of plastic uncalcined clay, approximately 10% of feldspar, and approximately 30% of n0n-plastic material some of which is calcined clay.

11. The insulating material herein described and made from a mixture comprising approximately 60% of plastic uncalcined clay, approximately 10% of feldspar, and approximately 30% of non-plastic material made up of calcined clay and flint.

In witness whereof we have hereunto set our hands at Flint, county of Genesee, State of Michigan, this 17th day of August, 1917 ALBERT CHAMPION. TAINE G. MGDOUGAL.