US816270A - Refractory material for electric insulation and other purposes. - Google Patents

Description

UNITED STATES Parana orrron.

DEMETRIUS M. STEWARD, OF CHATTANOOGA, TENNESSEE.

REFRACTORY MATERIAL FOR ELECTRIC INSULATION AND OTHER PURPOSES.

Specification of Letters Patent.

Patented March 27, 1906.

To all whom if may concern:

non-conductivity afford insulation equally against heat as against electricity.

Generally speaking, the substance of my present invention is a compound, a refractory material of high electrical resistance and of practically perfect homogeneity that is absolutely fireproof and that is unaffected by cold or moisture. Its hardness, its stressresisting qualities, and its resistance to moisture and to the effects of heat and cold render my material superior to any vitreous or amorphous insulating substance, such as rubher or the like, and render it available in many instances under conditions which would absolutely prohibit the employment of many, if not all, substances which have been under favorable conditions employed for insulating purposes.

The compound or material, by either of which terms my invention is herein. designated, is the product of a process which constitutes the subject-,matter of a separate application for patent made by me filed May 25, 1905, Serial No. 262,262.

The substance, which may be regarded as constituting the basis of my inventionthat is, the indispensable ingredient of itis magnesium silicate or aluminium silicate or a substantial equivalent of either. In their most familiar forms the silicates referred to have close resemblance one to another and are found in nature in the form of soapstone, steatite, talc, or the like. For convenience I shall hereinafter employ the term steatite to designate conventionally all substances of the general description above specified or their substantial equivalents, including pyrophillite.

In the manufacture of my material or compound, as herein described, I utilize the steatite or its equivalent, as s ecified, preferably in finely comminuted or pu verulent form, and

having reduced that component by mixture with other ingredients to a plastic mass impart to such plastic mixture any desired shape. The molding, as it maybe termed, of the plastic mixture, although, perhaps, more accurately described as shaping or modeling, is preferably effected under great pressure. The molding feature of the invention is particularly important, because asidefrom and in addition to the characteristic qualities it imparts to the product or compound, particularly that of uniform homogeneity when it is practiced under great pressure, which is, as specified, always preferred, it affords an important and valuable aid or contribution to the manufacture in general of certain articles from steatite. The known deposits of native steatite are not only limited, but the value of that substance in workable bulk is at present considerable and is increasing. My invention renders equally serviceable all raw material and much which ordinarily would be esteemed waste or at any rate of inferior value. Besides that the employment of the steatite in plastic form alone renders it possible to produce at diminished cost articles of a shape and configuration different from that in which they could be produced by the formerly universal practice of cutting or carving the massive steatite it makes it possible in very many instances to produce shapes which could not in anywise be produced from the native material, as by cutting or carving or any other of the usual methods of working it. In respect to the former suggestion contained in the last sentence specific reference may be had to the manufacture of steatite gas-burner tips, which although they may be made and have been made of native steatite may be better made and cheaper from the mixture subsequently converted, which con stitutes my present invention herein specified/ In respect to the latter suggestion contained in the aforesaid sentence reference may be had not only to the production of minute tubes of any desired lengths and possessing certain characteristic qualities specified herein as belongjn to my material, which is rendered practicable by the use of my invention and which cannot be arrived at in manufacture from native steatite, but also to the manufacture of insulators of exact dimensions, which from the nature of the compound can be produced in my material, owing to its homogeneity and quality ofresistanc-e without warping upon application f heatqualities not possessed by the native steatite to the same degree or, generally speaking, to-a reliable degree In specifying the proportions of compo nents employed in my mixture I desire to have it understood that while magnesium silicate or aluminium silicate is the basis as aforesaid of the compound, and therefore always introduced into the mixture considerably in excess of any other component, some latitude of variation is permissible without departing from the principle of my invention, the object aimed at by change of the proportionate quantity of water-glass, as hereinafterspecified, being to vary the composition of the material, compound, or finished product, so as to obtain the degree of hardness and density or compactness sought.

In the manufacture of my com ound the proportions of the components 0 the mixture I prefer by reason of the comparative width of range of utility in the resultant product to use one hundred parts of finelycomminuted steatite or its equivalent, as specified, and twenty parts of water-glass t at is, sodium silicate or potassium silicate I in fluid form-the said partsbeing proportioned by weight.

The components specified are thoroughly .mixed in any suitable manner by machinery or otherwise to a plastic or semi lastic mass of about the consistency of wor able putty.

. The first'step in the treatment of the mixture is to expel or partially expel the water it contains, "which may be accomplished by drying it in a drying-kiln for example, one heated by steam. f

The mixture may be formed into blanks and shaped, as by cutting, after they are steam dried, or it may be molded or shaped while the'mixture is in the plastic state and steam dried in any desired form imparted to it.

In preparing the mixture above specified for thedryi'ng-kiln it is preferably, as specified, reduced to a closely-compacted mass of uniform density throughout. This effect may be produced by subjecting the lastic f mixture to heavy pressure, as in a hy raulic press, and that treatment is preferably resorted to whether the mixture be presented tothe drying-kiln in the form of a blank or native or massive steatite.

ual or mechanical operation necessary or desirable for the completion or finishing of the article.

The mixture undergoes inthefinal step of the process by which the compound is produced a radical change from its green state, and becomes exceedingly hardhard enough, it may be, by way of illustration, to scratch glass and to resistthe action of any ordinary cutting-tool. In assing to that state the mixture ceases to e a mixture having steatite for its basic component, andbecomes a compound. That final step of the rocess is to subject the mixture, preferaby kilndried, as above specified, to a sufiiciently high temperature to convert it into the finished product, material, or compound,'which is distinguishable by a variety of characteristic qualities. From among such qualities there may be selected for enumeration the following, to, wit: The compound possesses the quality of resistance to moisture, it is unaffected by heat, and it may not be carbonized or ignited by intense heat,it is believed, even in that of any electric arc. Articles produced therefrom are durable, being incomparably stronger than porcelain or any vitreous or other similar material, and of an electrical resistance that is practically infinite, and may be manufactured at reason able cost.

The temperature at. which the change in the character of the mixture to that of a compound occurs ma be varied somewhat. The reaction by Whic the mixture is converted begins at about 700 centigrade and it appears to depend upon an elevated temperature rather than upon the length of time of exposure. Experience has shown the reaction to be complete and the best results in the manufacture of minute articles to be obtainable at about 1,500 centigrade. 'The time of exposure may be varied and is dependent in part upon the bulk of the mass that is being treated. In actual manufacture I employ a temperature of from 1,500 to 2,000 centigrade for aperiod dependent upon tests repeated during the firing, but usually of from five to eight hours. Laboratory tests upon minute articles have shown the best results to be obtainable by a fiveminutes exposure to a temperature of about 1,500 centigrade.

While in the foregoing specification I have indicated a choice of materials as available in the preparation of the mixture from which my compound is produced, yet I wish it to be distinctlyunderstood that I regard magnesium silicate and sodium silicate as the unquestionably available components of the,

mixture. Whatever is predicated of the of the same in the manufacture of my product for commercial purposes. Said mixture constitutes, therefore, the standard with Which proposed substitutions in the reparation of my mixture must be compared in order to determine their equivalency or non-equivalency to the said components.

Articles made of my finished material may be, ifpreferred, supplied with a surface glaze by the use of magnesium or other suitable enamelsuch, for example, as that used on porcelain or kaolin Ware.

What I claim is 1. An insulating and refractory material comprising the combination of water-glass and steatite or their substantial equivalents, chemically converted practically to a complete extent by heat.

2. An insulating and refractory material comprising the combination of steatite and water-glass or theirsubstantial equivalents, converted by ractically complete reaction.

3. An insulating and refractory material comprising the combination of powdered steatite and Water-glass or their substantial equivalents, substantially in the roportions specified, converted by practical y complete reaction.

4. An insulating and refractory material I Luna. 4. 4