US3438793A - Thermofluid screen-color piece - Google Patents

Description

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April 15, 1969 e. D. MARTIN A THERMOFLUID SCREEN-COLOR PIECE Filed Nov. 22, 1966 United States Patent 3,438,793 THERMOFLUID SCREEN-COLOR PIECE George D. Martin, Baltimore, Md., assignor, by mesne assignments, to SCM Corporation, New York, N.Y., a corporation of New York Continuation-impart of application Ser. No. 289,564,

June 21, 1963. This application Nov. 22, 1966, Ser.

Int. Cl. C03c 9/ 00, 9/02 US. Cl. 106-19 2 Claims ABSTRACT OF THE DISCLOSURE This patent application is a continuation-in-part of my copending patent application Ser. No. 289,564, filed June 21, 1963, now abandoned, and entitled Thermofiuid Screen-Color Casting Apparatus and Process, and Resulting Cast Piece.

This invention relates to a cast small piece of thermofluid color such as is used in decorating glass and ceramic ware. Such colors are mixtures of glass frit, color and thermoplastic organic vehicle, and are sometimes called hot-oil and/ or hot-melt screening colors because of the way they are used.

For example, in decorating glassware such as beverage bottles, two or more different colors (i.e., frit plus color, or colored frit) may be desired, and to apply all the colors, separately and in a short time period, the separate decorating materials are carried in a meltable thermoplastic organic vehicle. By melting such colored vehicle in a container (melting-pot) disposed close to a frame having a heated wire screen in its bottom, the bottle can be placed against the underside of the screen and a small quantity of molten colored vehicle can be metered from the melting pot to the screen and squeegeed onto a portion of the bottles surface. See US. Patent 2,061,679. The color so applied to the bottle cools quickly and in so doing hardens to a strong, adherent and abrasion resistant form. Hence the partially decorated bottle can again be placed under a different screen from which molten vehicle of a different color can be squeegeed onto its surface. Additional colors can be added similarly by stepwise application with or Without intermediate firings. The various wire screens can, of course, be blocked out so as to leave only a desired pat-tern open. See US. Patent 2,064,764. Squeegeeing then applies the molten color in conformance with the pattern.

By having different patterns in the screens through which the different molten colored vehicles are squeegeed, and by indexing a particular bottle through a planned sequence of squeegeeing operations, with or without intermediate firings, the bottle can end up having a variety of different colors applied to it in conformance with predetermined designs. In such procedure, the final and any intermediate firings heat the bottle and applied colorsto temperatures which cause the glass frits of the colored vehicle(s) to fuse to the surface of the bottle. Meanwhile the thermoplastic vehicle has been burned away. When the bottle emerges from the firing operation(s), it carries the desired colored design, in glass, fused to the bottle.

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In the past, the therrnofluid screen colors have been distributed to the users in the form of chunks, the latter representing rather coarse fragments of an antecedant slab. That is, the thermofiuid screen color manufacturer has mixed up preformed glass frit with a suitable molten thermoplastic material, and then has poured the mixture into a flat pan or tray where the molten mass is allowed to cool and harden. When hard, the slab is broken up by hammering it with mallets. The resulting chunks of thermofluid screen color, and the described manner of preparing them possess various shortcomings, here itemized:

(1) When a chunk is dropped into a melting pot (disposed adjacent to a screening frame), the heat requirement of the chunk is usually so great that the whole mass of colored vehicle in the melting pot thickens or solidifies. Moreover, it stays thick-to-solid for many minutes, due to said heat requirement and to the poor thermal conductivity of the material. This means that molten colored vehicle needed for squeegeeing operations is not available during this time and only becomes available again when most of the colored vehicle in the melting pot has been melted.

(2) The chunks are irregular in shape, present rough and matte surfaces toward each other, and do not pack well against each other for shipment. The result is that during transit the chunks are jostled against each other, edges, faces, and corners become abraded, and dust is formed. Later, when the package is opened, the dust creates some handling difficulties and loss of expensive material.

(3) The casting of slabs of colored vehicle, the waiting period entailed in allowing the slabs to cool, and the subsequent manual hammering operations constitute an intermittant, laborious, and time-consuming program. Moreover, the hammering of the slabs to break them into chunks creates considerable powder of colored vehicle. Portions of this powder get air-borne and create loss as well as a dust-type health hazard.

In accordance with the present invention the foregoing and other difficulties are avoided while at the same time valuable advantages are gained, by casting the molten colored vehicle in the form of small drops on a forcecooled metal conveyor belt. Under such circumstances the castings become cold and hard within a few minutes, and can be delivered from the conveyor directly into storage or shipping containers. The castings formed in this way are generally disc-shaped, have a flat bottom and a nearly-flat-toshallowly-convex upper surface as illustrated in FIGURE 5. Such pieces can be formed in large quantities in short periods of time by using suitable casting equipment. Hence the overall time and labor required to produce a given weight of thermofiuid screen color is materially lower than by the old method, while losses are practically eliminated. Moreover, the resulting cast piece cooled in this manner is produced with a comparatively smooth and glossy top as contrasted with the irregular and matte surface of a fractured face. Hence, the pieces pack snugly in a shipping container and resist dusting from abrasion in handling and transit. Furthermore, in the customers plant, the pieces can be added to a melting pot a few at a time at spaced time intervals without freezing up the whole mass of molten screen color in the pot. Hence, squeegeeing can be carried on continuously even though said pieces of cold screen color are being added to the melting pot as needed.

Accordingly, the novel thermofiuid screening color of my invention is a small, hard, flat-bottom having a generally convex and somewhat glossy top, said piece being a viscous drop of said color that has been deformed and solidified by contact with a cooling surface in motion transverse to the path of fall of the drop, said piece being substantially free of sharply angular profiles.

In the drawings FIGURE 1 is a vertical elevational view of apparatus suitable for casting and forming the thermofluid color pieces of my invention in a continuous manner. FIGURE 2 is a sectional view taken on the line 2-2 of FIGURE 1. FIGURE 3 is a sectional view taken on line 33 of FIGURE 2. FIGURE 4 is an enlarged sectional view taken along the line 44 of FIGURE 1. FIG- URE depicts a cast piece of my thermofluid screening color in about its natural size.

My typical thermofluid screening color is a mixture of about 70*90% by Weight particulate inorganic solids for firing (to yield the permanent decoration) bound together with 30% by weight thermofluid organic vehicle in the form of the wafers described. The proportion of such vehicle can vary rather widely, but for most purposes it is kept as low as feasible consistent with the securing a freeflowing mass having desired viscosity at screening temperatures. Advantageously, the composition of the Wafer will be from about 12-30% of vehicle by weight. Sub stantially less than about 10% of vehicle yields products which are difficult to form and to use. Conversely, use of substantially more than about 30% vehicle is wasteful as this material is decomposed when the screening color is used.

Usually the inorganic particulate solids material of the mass is a mixture of frit plus tfinely divided ceramic color. As will be understood, the :frit is a finely-divided glass product or mixture having a melting or softening range below that of the body to which the colored vehicle is to be applied, and serves to bind the accompanying ceramic color to the body upon firing. Thus, the proportions between ceramic color and frit can vary widely, e.g. 0-25% of color, by weight, and preferably less than about 10%. Thus the ceramic color can sometimes be at very low levels, or even absent completely. In other instances the color constitutes a substantial amount. In all instances, frit is at a complementing level, e.g., 75100%. Choice of color/frit ratios depends on the strength and hue of the color(s), on the size of the color particles, on the amount of hiding needed to conceal the color or appearance of the body, and on the kind of color etfect which the fired screen-color is to achieve in a chosen decorating scheme. Moreover, the kind of effect secured to can also be varied somewhat by raising or lowering the amount of vehicle, thereby to control viscosity and hence applied thickness or thinness of the thermofluid color(s).

The frit-plus-color component of the thermofluid screen color, must, for most purposes, be finely-divided; that is, it should be sufficiently fine that less than 1% and preferably less than 0.1% by weight will remain on a standard 325 mesh sieve. The frit(s) in said component can have any melttng or softening ranges appropriate to the work which is to be decorated. That is, for decorating glass, the frit or frit mixture will usually be chosen so as to mature at 8501200 F. If pottery or porcelain enamel is to be decorated, then, of course, frits maturing at much higher temperatures can be used. Thus the chemical composition, softening range, maturing temperature, and other characterizing properties of a frit are here of no real significance, since the invention can be readily practiced with any frit or frit mixtures selected in accordance with practices which are well understood by persons skilled in the art.

The thermoplastic vehicle component of the thermofluid screen colors likewise is neither a feature of novelty nor a feature of unobviousness in the invention. Thermoplastic organic materials having a wide variety of chemical compositions have long been used as or in vehicles of thermofluid screen colors. Any of such and of any analogous materials having the needed qualities can be used in practicing the present invention. The following US. patents disclose a wide variety of such organic thermoplastic materials: 3,084,129; 2,748,093; 2,682,480; 2,617,740; 2,607,702; 2,607,701; and 2,505,740.

Thus, from what has been said above it will be apparent that there is nothing novel about the compositional elements of thermofluid screen colors used in the casting process and apparatus. To better understand the preparation of my thermofluid screening color pieces reference is now made to the drawings. in FIGURE 1 there is illustrated, in elevation, a feeding hopper 1 mounted on a frame 2, 2 so as to be disposed above a sheet metal conveyor belt 3 operating around drums 4, 4' journalled at 5 and 5' on a welded plate-and-channel-iron frame 6. The drum 4 is driven by a belt 7 operating on a small pulley 8 on jackshaft 9. A large pulley 10 on said jackshaft is driven by a belt 11 operated by electric motor 12 carried on a frame 13 bridging the path of the bottom side of conveyor belt 3. The upper side of the conveyor belt 3 passes over a cooling box 14 which is shown in FIGURE 4 to consist of two longitudinal and two terminal Webs 15, 15 which define an open-topped chamber kept full of water brought in under pressure through pipes 16, 16. Water overflows the webs 15, 15 to fall into a peripheral launder 17, 17 from which the water can be pumped to a cooler and then recirculated, if desired. It will be understood that the cooling box keeps cooling water in contact with the undersurface of conveyor belt 3 and thereby assists in cooling cast material dropped from hopper 1 onto the dry upper surface of the conveyor belt. The structure and operation of the cooling box is described in more detail in US. Patent 2,437,492.

Returning now to the feeding hopper 1, its structure is apparent from FIGURES 2 and 3. The hopper consists of four side walls 18, 18, a rigid bottom plate 19, a reciprocable feeder (cutting) plate 20, and angle iron frame 21 and an air-motor 22. One end of motor 22 drives plate 20 and the other end is stationarily fixed to frame 21. Action of the air-motor causes plate 20 to slide longitudinally back and fourth under plate 19, its movement with respect thereto being guided and constrained by spring-pressed guides 25, 25 associated with plate 20. The rigid bottom plate 19 and the reciprocating feeder plate 20 have a plurality of aligned and matching apertures, preferably circular holes 23, 23', respectively. Thus it will be understood that when the position of feeder plate 20 is adjusted so that its holes 23' are not in overlapping alignment with the holes 23 in bottom plate 19, then the feeding hopper 1 is sufiiciently fluid-tight so that melted screen color can be poured into it. External elec tric heaters 24, 24 on the hopper can be turned on to keep the screen color in a molten and fluid condition. Next the conveyor belt 3 can be brought into motion so that its upper surface will mave continuously at a predetermined speed to the left under the hopper. Now the air-motor 22 can be started in operation, whereby plate 20 is caused to reciprocate under bottom plate 19. Once or twice in each cycle of reciprocation, (depending on adjustment) its holes 23' will line up momentarily with the holes 23 in the bottom plate 19, and in each brief period of time some molten screen color will flow through the aligned holes, be cut oif by plate 20, and drop onto the moving conveyor belt. By adjusting (a) the speed of air-motor 22; (b) its stroke; and (c) the speed of travel of conveyor belt 3, the apparatus can be made to operate so that whenever molten screen color drops from the holes of the feeder plate, the molten portions will fall onto unoccupied areas of the conveyor belt, thereby making good contact with the cold metal of said belt. In this way the heat contained in said molten portions resting on the belt will be dissipated quite rapidly by the cooling Water which contacts the under surface of the belt. Accordingly, the molten portions soon lose enough heat to being to harden, and by the time they arrive at the terminal drum 4' of the belt, they will be thoroughly hard and ready for packaging in a container 26, if so desired.

EXAMPLE 1 Atypical frit used for decorating glassware is described herein as illustrative of the many frit compositions which can be used in practicing the invention. Another typical frit (flux) for glass decoration is disclosed in a publication entitled Leadin the Ceramic Industries (Lead Industries Association, New York 17, N.Y., November 1956) of which Section 6 is entitled Glass Decorating Colors. Ten more typical frits are disclosed in the companion publication Supplement to Lead in the Ceramic Industries (ibid, December 1957) of which Section 6 is entitled Enamels for Application to Glass.

Fritz lbs. (oxide basis) Milled zircon 5.4 Silica 24.7 Litharge 58.6 Boric acid 4.4 Sodium carbonate 8.7 Titanium dioxide 3.7

These materials are carefully mixed, charged into a suitable melting furnace, e.g., a rotary smelter, and fused at a temperature of about 1,900 P. until completely glassy, following which the molten flux is discharged into a suitable quenching medium (e.g., a water bath or watercooled rolls). The resulting mass is then dried and charged into a suitable grinding mill wherein it is preferably milled until less than 0.1 wt. percent of powdered frit is retained on a 325 mesh US. Standard Sieve.

Thermoplastic Vehicle lbs. Cetyl alcohol 35.41 Ethyl cellulose 6.22 Stearyl alcohol 58.37

These materials are melted and mixed together in a heated dispersion mixer of any suitable type. Heating can be by steam, hot water or other means capable of heating the batch to approximately 225 F. When thoroughly mixed, the batch can be discharged, allowed to cool, and then stored until a screen color is to be made up, at which time it is remelted in the mixer. However, for the present purpose, the batch is left in the mixer, and it is colored by adding 57 lbs. titanium dioxide. Frit, as de scribed above is also added in the amount of 413 lbs. Mixing of the resulting molten slurry is continued until it is quite homogeneous and smooth. The batch is then discharged into the preheated hopper of FIGURE 1. The conveyor is started, and then the air-motor is started so as to cause the feeder plate to reciprocate under the bottom plate. With holes one-half inch in diameter in both plates as compared to other embodiments wherein the holes can be up to 1" in diameter, the molten mixture forms drops which fall onto the conveyor belt so as to form solidified thin wafers or pieces such as are shown in FIGURE 5, which have diameters ranging from about /2" to A, and a count of about 120 per pound. The molten drops solidify promptly after landing on the conveyor belt, and are thoroughly hard and ready for packaging by the time they fall off the belt as the latter passes over drum 4'.

EXAMPLE 2 The following table illustrates various frit formulations which are suited to various uses in the ceramic, pottery, and porcelain enamel fields. Such frits are typical of the higher melting frits which can be used in practicing the present invention.

It will be understood that such and other frits can be used along with other ceramic materials to form glazes, and that such mixtures ofmaterials can include appropriate coloring agents and appropriate amount(s) of thermoplastic vehicle(s), whereby the thermofluid color can be screened (squeegeed) onto any ceramic or porcelain objects which are to be deco-rated through a subsequent firing operation.

From the foregoing description of the invention it will be apparent that the principles can be practiced by employing various departures from the particular embodiments described above. For instance, the apertures in plates 19 and 20 of the drawings can have a wide variety of desired geometrical shape and area. Moreover, while an air-motor 22 has been illustrated in the drawings, any other pneumatic, hydraulic, mechanical, electrical, manual, or magnetic means for reciprocating plate 20 over a stroke of desired length can be substituted. Furthermore, instead of having a single row of apertures in each of plates 19 and 20, a plurality of rows can be used to increase the rate of casting. The force-cooled conveyor belt can be cooled in manners other than that shown in the drawings. For example, the pipes 16, 16 can be made to spray water or air on the underside of the belt, or can be replaced with refrigeration coils making good thermal contact with said belt. Any other kinds of force-cooling can be used equally well.

Furthermore, while Example 1 describes the formation of cast pieces having an average diameter of about /8 and a count of about 120 per pound, the count per pound can be varied considerably, e.g., from 50 to 300 if desired, by changing the areas of the apertures in plates 19 and 20 and by varying the oscillations per minute of the reciprocating plate 20. The pieces should have a diameter between about and 2". In all of such diameters and counts per pound the advantages of the invention accrue mainly from the fact that the cast pieces are relatively thin and hence can be melted fairly rapidly in the conventional melting-pots of conventional screening-frame devices.

I claim:

1. Thermofluid screening color in the form of a small hard piece having a generally smooth convex top, said piece being a viscous drop of said color that has been deformed and solidified by contact with a cooling surface in motion transverse to the path of fall of the drop; said piece being substantially free of sharply angular profiles; said screening color being a composition comprising:

(a) from about to about by weight particulate inorganic solids bound together with (b) from about 10 to about 30% by weight thermofluid organic vehicle;

said particulate inorganic solids comprising a finely divided mixture of frit and ceramic color having a particle size such that less than 1% will remain on a standard 325 mesh sieve, said frit being a finely divided glass product having a softening range below that of the body to which the compositions is to be applied; said thermofluid organic vehicle being selected from the group consisting of cetyl alcohol, ethyl cellulose, stearyl alcohol and mixtures thereof.

2. The thermofluid screening color piece of claim 1 having broadest dimension between about and 2" and weight between about 3 and 20 grams.

(References on following page) TABLE.-FRIT COMPOSITIONS (WT. PERCENT) NazO CaO MgO BaO ZnO A1203 B203 8102 F 7 References Cited UNITED STATES PATENTS 2,268,888 1/1942 Mericola 264-13 2,318,803 5/1943 Schneider et a1 106-193 2,682,480 6/1954 Andrews 106-193 8 2,872,326 2/1959 Morris 106-19 3,208,101 9/1965 Kaiser et a1. 264-13 ALLAN LIEBERMAN, Primal Examiner.

US. Cl. X.R.

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