US 3007222 A
Description (OCR text may contain errors)
R. c. RAGAN 3,007,222
METHOD FOR CONTINUOUS MANUFACTURE OF CERAMIC SHEETS Nov. 7, 1961 Filed Jan. 2, 1955 A; A, a??? 7 A, 2 1;;
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United States Patent 3,007,222 METHOD FOR CONTINUOUS MANUFACTURE OF CERAMIC SHEETS Randall C. Ragan, Glendale, Califi, assignor to Gladding McBean & Co., Los Angeles, Calif., a corporation of California Filed Jan. 2, 1953, Ser. No. 329,265 1 Claim. (Cl. 25156) This invention pertains to methods for continuously manufacturing very thin ceramic objects, such as light and thin plates of insulating material for use in electrical and electronic equipment, light, thin tile, ceramic veneer and ceramic sheathing, heat-resistant carriers for catalysts, etc. The invention also pertains to methods whereby the various thin ceramic articles may be provided with glazed or otherwise decorated surfaces and to the use of compositions, materials and devices whereby the various products hereinbefore referred to may be manufactured economically and efiiciently.
Ceramic tile are ordinarily made by dry-pressing a body composition in a press which compresses a substantially dry mixture of finely divided body composition to the ultimate size and shape of the tile. Definite limitation's as to minimum thickness of tile so pressed have been found to exist and it is virtually impossible to compress and process normal bodies of finished tile with a shape and size where the width or face dimension of the tile is more than twenty times the thickness of the tile. Ordinary methods of compression such as are used in tile presses (including single-acting and double-acting types of presses) cannot be employed in the preparation of extremely thin wafers of ceramic material for use as separators, insulators, etc. As a result, fioor and decorative wall tile made heretofore were relatively thick and heavy, could not be shipped great distances because of the excessive costs of transportation, had to be installed individually, and required large expenditures of time and money in order to be properly installed.
The present invention is based upon the discovery of methods, means and conditions whereby ceramic articles such as tile, thin insulating wafers, etc. may be made in a continuous manner, such tile having a face dimension or width from 30 to 3,000 times the thickness thereof. Differently expressed, ceramic objects in the form of sheets or plates and having a thicknesses of from about 0.001 to 0.150 in. may be made, the objects having any desired width from, say 1 in. to 6 in. or more. Moreover, the present inventionis directed to the production of thin, wafer-like tile provided with glazed or otherwise decorated surfaces and to methods whereby such tile or ceramic veneer may be supplied to the architect and builder in the form of large sheets capable of being readily applied to the external and internal surfaces of buildings and other structures, each sheet bearing a plurality of tile units, thereby obviating the necessity of installing the tile in the form of separate and discrete, small elements or units.
An object of the present invention, therefore, is to disclose and provide means, methods and conditions whereby'ver'y thin ceramic objects may be rapidly and economically manufactured.
A still further object of the invention is to disclose and provide novel, continuous methods of making thin ceramic objects.
Again, an object of the invention is to disclose and provide a method whereby ceramic compositions may be converted into long, continuous, leathery strips capable of being die-punched or otherwise divided into units.
These and various other advantages, adaptations, characteristics and uses of the invention will become apparent 3,007,222 Patented Nov. 7, 1961 from the following description, in which exemplary modes of procedure and products made thereby will be described. For purposes of example and illustration, reference will be had to the appended drawings, in which:
FIG. 1 is a perspective view of a portion of a sheet of ceramic veneer of sheathing made in accordance with the present invention.
FIG. 2 is an enlarged section taken along the plane 11-11 of FIG. 1.
FIG. 3 is a transverse section taken through a portion of a thin ceramic veneer made in accordance with the present invention.
FIG. 4 is a perspective view of a portion of a continuous strip of unburned ceramic material showing one method of dividing such strip into units.
FIG. 5 is a diagrammatic representation, inside elevation, of an arrangement of elements adapted for use in the manufacture of thin ceramic objects pursuant to this invention.
FIG. 6 is an enlarged plan view of a pair of cooperating rollers employed in the arrangement illustrated in FIG. 5.
Generally stated, the method of the present invention comprises forming a thin coherent, continuous strip of compressed ceramic composition, the width of said strip being more than thirty times the thickness thereof. This strip, in its unburned condition is somewhat pliable and leathery and is provided with a smooth, dense surface which retains its calendered, smooth character even after firing. In the event the finished product is not to be glazed, the leathery strip may be divided into units of a desired size and shape and then subjected to firing at a temperature sufficient to mature the ceramic composition. If, however, the final product is to be provided with a glazed or decorated surface, then a layer of glazeforming composition is applied to a surface of such strip before it is subjected to firing, although glaze can also be applied to a surface of the previously burned strip. The latter procedure involves both a bisque and a glost firing and is not as economical.
It will be noted that in contradistinction to previous methods of procedure, wherein individual units were separately made by dry-pressing or the like, the present method is concerned with the continuous production of a long or continuous strip or ribbon of a desired finished thickness, which ribbon is then subdivided into units in a continuous or semi-continuous manner. The method of the present invention is therefore eminently suited for use with continuous kilns and greatly shortens the time required to produce a given number of tile and reduces labor costs to a minimum. at this time that the method of the present invention insures the production of finished tile more closely adherent to established, predetermined size limitations and does not produce the relatively large proportion of warped or off-size tile.
By referring to FIG. 5, an exemplary method of procedure will become apparent. The apparatus there illustrated may be used in the production of very thin, glazed tile sheathing or veneer. The apparatus may consist of apair of ribbon-forming rolls 10 and 10 to which a suitable body composition 12 is supplied. These rolls 10 and 10' are preferably mounted on parallel axes, both rolls being driven at the same peripheral speed.
A similar pair of rolls 11 and 11' may be positioned pressed, coherent, leathery strip 14 which may be dis- -It may also be noted charged upon a continuous conveyor belt 16. A suitably prepared glaze-forming composition 13 is compressed between the rolls 11 and 11 into a continuous, leathery strip 15 which is deposited upon the body composition strip or ribbon 14 and moves therewith. These two strips 14 and 15 may then be slightly compressed together by a pair of rolls 17 and 17, these rolls being driven by a variable speed drive, the surfaces of the rolls moving at substantially the same linear speed as the two ribobns 14 and 15. Such combined strips may then be fed into a die punching machine 18 wherein th strip is subdivided into a plurality of tile units of a desired size and shape. Since the die punch operates intermittently, the combined strips may be first cut into relatively long sections 19 and such sections then intermittently fed into the punch 18. From the punch 18 the cut-out tile units may be discharged either directionally or laterally onto a continuous conveyor and fed into a kiln wherein they are burned to a temperature and for a sufficient length of time to mature both the body and the glaze.
FIG. 6 illustrates one form of rolls which have been used effectively in the method. In order to prevent the development of cracks in the continuous ribbon or strip, it has been found desirable to subject the composition to lateral and transverse compression. Moreover, it has been found desirable to feed the composition to the rolls without the application of substantial pressure to the uncompacted material in the direction of movement of the two surfaces between which the composition is compressed. As diagramamtically illustrated therefore, the body composition 12 is fed by gravity, as by a hopper, in uncompacted form into position between the pair of converging surfaces of the two rolls and 10, these two surfaces moving at substantially the same linear speed and in the same direction. One of the surfaces, such as for example, the surface 22, is provided with tapering edge areas 23 and 24 which tend to compress the material laterally and prevent the material from flowing laterally beyond the edges of the rolls.
Moreover, it may be noted that the width of the tapered flanges 23 and 24 appears to bear a relationship to the width of the surface 22 between such flanges or to the total width of the surface of the opposing roll 10'. In practice, it has been found that a ratio of between about 1:8 and 1:16 between the width of the tapered flanges and the width of the smooth central portion of the roll 10 gives good results. Moreover, the diameter of the roll bears a relationship to the maximum thickness of the compressed strip; the larger the diameter of rolls, the thicker is the strip which can be successfully formed. When rolls 8 in. in diameter are employed, sheets or strips of thicknesses from as low as 0.004" and up to at least 0.090" can be made. Again, it appears that for any given roll diameter, the thinner the sheet being made, the greater the compression to which the body composition is subjected.
Although the method of the present invention may be carried out with any customary ceramic body, it is desirable that the uncompacted body composition have non-bridging, free-flowing characteristics, so that it is not necessary to force-feed the body composition into the converging surfaces of the rolls. Such free-flowing characteristics may be imparted to the composition by fine grinding and by granulation. Granulation may be attained in various Ways, as for example, by spray-drying in accordance with the process of the character described in Patent No. 2,251,454 or the like, or by the use of a Simpson mixer (an arrastra type of muller) or any other suitable method. Furthermore, the moisture content of the material should be maintained within a relatively narrow range, ordinarily from between about 8% and by weight. The particle size of the material subjected to the pressure in the manner indicated may vary considerably; a very finely divided material consisting of particles passing a 200 mesh may be used; if the material has been granulated or pelletized, the agglomerates may pass a 4 mesh sieve and remain on a 100, or mesh sieve.
In order to impart a desired strength to the body in its compacted, ribbon-like form, it has been found desirable to use an organic binder in the composition, particularly when the clay content of the composition is relatively low. The organic binder may be introduced in the form of an aqueous emulsion and thereby introduce a portion, at least, of the necessary water. Emulsions of various microcnystalline waxes, paraffin, stearic acid, or thermoplastic materials such as a methacrylate, may be used. When emulsions are incorporated, it is desirable to first introduce water in quantity sufiicient to slightly moisten the ceramic material and then add the emulsion in quantity adequate to introduce from 1% to as high as 10% of the organic binder by weight of the total mixture. Not only do these organic binders appear to impart wet strength and flexibility but they also appear to reduce sticking of the ceramic composition to the rolls. It may be noted at this point that the surfaces of the rolls should be polished and plating with chromium is desirable, but not essential.
The comments made hereinabove with respect to the ceramic composition are also applicable to the glazeforming composition; in most instances better wet strength and freedom from cracks are attained in the ribbon 15 when an organic binder is incorporated in the glazeforming composition. In some instances it may be desirable to form long strips of glaze-forming composition and to keep such strips available in storage for subsequent use. For example, such strips may be used as a stock from which letters or numerals may be die-punched, such die-punched numerals of glaze-forming composition being subsequently applied to the surface of tile, brick, panels or other ceramic objects being burned for special purposes. These previously dried strips of glaze-forming composition need only be moistened, as with a wet sponge, in order to reinvest such strip with suflicient leathery characteristics to permit die punching into desired shape without shattering.
As previously indicated, the method of this invention is applicable to any ceramic composition. The following examples illustrate the wide range of body compositions which may be successfully manipulated in the manner stated. Objects can be made from bodies compounded of from 25% to 45% of clay, 5% to 40% of a fusible matrix material such as ground glass, volcanic glass or highly alkaline materials of similar properties, 0% to 25 of raw, unburned talc and 20% to 65% of calcined talc or talc bisque. An exemplary body within this group may contain 37% clay, 16% ground glass, 10% raw talc and 37% talc bisque. Objects can also be made, by the methods of this invention, from bodies of a sewerpipe composition type, for example, one composed of clay and grog, such as one containing 33% filler clay, 10% low grade refractory clay, 15% plastic red burning clay, 32% semiplastic red burning clay and 10% grog. China bodies can also be used, such as one composed of 15% ball clay, 30% kaolin, 35% of nepheline syenite and 20% silica.
It is to be understood that the glaze composition need not be applied to the strip 14 in the form of a compressed leathery strip 15. Instead, the glaze composition, in the form of a slurrymay be spread upon the strip 14 by means. of a doctor blade, or the glaze composition may be sprayed or dusted upon the strip 14. Any other form of decoration such as the application of glaze by the silk screen process or the application of underglaze decorations, over-glaze decals, and the like, may be had.
Furthermore, the very thin tile or other ceramic objects formed need not be provided with plane, parallel upper and lower surfaces. By suitably lateral'ly grooving the forming rolls and gearing them together, the strip of body composition may be caused to produce a strip of body (and a finished ceramic object) having a corrugated surface of the character illustrated in FIG. 3. Moreover, one of the Surfaces of the strip 14 may be provided with minor indentations or a texture, such as one imparted thereto by lightly knurling that roll surface which forms the roll surface of the finished strip. By imparting a slight irregularity or knurled or textured effect to the lower surface of the thin tile, subsequent cementing, ancho-ring and adhesion of the tile to a supporting wall surface is facilitated.
The continuous strip of ceramic composition (with or without its superimposed glaze forrning coating) may either be die-cut as previously indicated, or such continuous strip may be scored along longitudinal edges and transversely as indicated in FIG. 4, the score lines being preferably formed by the use of rotating cutting wheels which form the score lines or grooves such as 26 and 27, these lines extending partly through the entire thickness of the strip. Relatively long strips can then be burned and after burning separated into individual tile units by breaking the tile along the score lines. Scoring may also be done on the bottom side or on both sides to develop a cleaner break.
Moreover, it is to be understood that instead of employing the rolls such as the rolls --10, a continuous leathery strip of ceramic composition may be obtained by feeding the ceramic composition into position between flexible metal bands, the inner lays of such bands moving at the set speed and in the same direction and converging to a desired minimum. One or both of the bands may be provided with tapered or thickened edge portions to provide the flanges, similar to 23 and 24, and thereby subject the material to lateral pressure and prevent cracking.
When the product of the present invention is in the form of thin decorative tile or ceramic veneer, such tile need not be cemented into position on a Wall in the form of separate and discrete units as is customary but instead may be applied in the form of large sheets. FIGURES 1 and 2 are particularly directed to a new article of commerce consisting essentially of a carrier sheet which is preferably flexible, porous and has considerable tensile strength. A suitable carrier sheet may comprise a coarsely woven open-mesh fabric 28 (having openings between the individual threads of from about in. to A2 in.). Such a fabric may be made of cotton, synthetic monofilaments, jute or even metal wires. A fabric of the desired character may be first coated or impregnated with a thermoplastic adhesive (as by spraying the adhesive thereon or dipping the fabric therein) and before such adhesive has set, the thin tile or ceramic plates such as the plates 30, 30', 30", etc., may be properly arranged upon the surface of the fabric with uniform spacing between the various tile or plates. Preferably the plates or tile are provided with rectilinear edges. Instead of dipping or impregnating the fabric with a thermoplastic adhesive, the rear face of the tile may be sprayed with such adhesive and the fabric then applied to a multiplicity of tile with their edges in proper spaced relation. At all events, the resulting product consists of a carrier sheet carrying on one face a large number of thin ceramic plates, tiles or veneer elements. The carrier sheet may be slightly smaller than the total area of the tile units carried thereby, or may extend beyond the margins of the tile along one or two sides of the assembly. It will be understood that the application of the tile to the fabric or vice versa is preferably carried out by the aid of mechanical devices and fixtures so as to insure uniform alignment and spacing between the tile.
As a result, carrier sheets of a size comparable with or equal to Wall board or paneling of customary size (such as 4' x 6' or 4 x 8') can be shipped in flat bundles, boxes or crates and such sheets can then be applied to walls of buildings by spreading quick-setting cements on the supporting surface and cementing the entire sheet, carrying 50 to 300 tile, to such surface. The cementing composition used may be suitably colored, and excess cement exuding through the spaces between adjacent tile may be smoothed down to give the effect of conventional joints between the tile. It will be appreciated that this newform of decorative material greatly enlarges the scope of utility of ceramic tile and materially reduces the cost.
It is to be understood that not all of the tile carried by a sheet need be of the same color or design; instead the tile may be arranged to produce bands, large designs and other decorative effects.
A continuous method of making thin, continuous bands of ceramicbody composition comprising: compounding a ceramic body composition material containing a water compatible binder to impart non-bridging and free-flowing characteristics thereto; regulating the moisture content of said composition to between 8% and 15% by weight; feeding said compounded ceramic body material in granular uncompacted free-flowing form into position between a pair of hard, convex surfaces of equal radius moving at substantially the same linear speed and in the same direction, compressing said material transversely in a zone of compression and maximum convergence of said surfaces while restraining the material from lateral movement in such zone, to continuously discharge a continuous, compressed, coherent, leathery strip of ceramic composition provided with a calendered surface and adapted to be dried and burned to maturity.
References Cited in the file of this patent UNITED STATES PATENTS 1,342,192 Trevillian June 1, 1920 1,445,204 Dunstan Feb. 13, 1923 1,511,458 Gibson Oct. 14, 1924 1,702,730 Hite Feb. 19, 1929 1,964,177 Rosner June 26, 1934 2,067,012 Loetscher Jan. 5, 1937 2,126,191 Hubbell Aug. 9, 1938 2,348,829 MacArthur et al. May 16, 1944 2,540,354 Selden Feb. 6, 1951 2,552,937 Cohen May 15, 1951 2,582,993 Howatt June 22, 1952