US3028214A - Process for the manufacture of continuous refractory fibers - Google Patents

Description

Apnl 3, 1962 H. s. SCHWARTZ 3,028,214

PROCESS FOR THE MANUFACTURE OF CONTINUOUS REFRACTORY FIBERS Filed March 3, 1961 2 Sheets-Sheet 1 INVENTOR. HERBERT S. CHWARTZ.

ATTORN EYS H. s. SCHWARTZ 3,028,214 PROCESS FOR THE MANUFACTURE OF CONTINUOUS REFRACTORY FIBERS Filed March 6, 1961 2 Sheets-Sheet 2 April 3, 1962 INVENTOR. HERBERT s. SCHWARTZ ATTORNEYS United States Patent 3,028,214 PROCESS FOR THE MANUFACTURE OF CONTINUOUS REFRACTORY FIBERS Herbert S. Schwartz, 800 Eppington Drive, Trotwood, Ohio Filed Mar. 3, 1961, Ser. No. 93,277 6 Claims. (CI. 18-54) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be'manufactured and used by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a new and improved process for making refractory fibers.

Past practices in making refractory fibers of silica, aluminosilicate and the like have been by heating the end of a rod of the refractory material and drawing a filament away from the rod; by blowing molten material into filaments; and for refractories with lower melting points by melting the refractory material in a multiple orifice crucible and drawing fibers from the crucible orifices; and the like. For materials with high melting points, such as silica and aluminosilicate, there are no completely satisfactory materials for crucibles.

Filaments made by the first two of the above mentioned processes have the limitations of being of non-uniform diameter, of random lengths, of varying flexibilities, and of non-uniform tensile strength when used in fabrics for high strength, high temperature resistant structural laminates and the like. Filaments with these limitations are poorly applied when used with automatic machinery and result in low grade articles when used in fabrics of protective types such as in fire fighting costumes and the like, whether they ar woven, matted, felted, made into thread, cables or otherwise converted into equipment.

Silica softens at temperatures above 1470 C. which corresponds to 2678 F. Aluminosilicate softens at about 1372" C. or 2500 F. Alumina melts at about 2050" C. or 3722 F. Tantalum melts at about 3000" C. or 5432 F. Tungsten melts at 3370 C. or 6098" F. An acetylene-oxygen flame has a flame temperature of about 2632" C. or 4770 F.

The subject matter of this invention and its general object is the provision of an improved process for making refractory fibers or filaments. The fibers that are produced by the method described herein structurally are more nearly of uniform diameter than those previously produced and are of uniform tensile strength and quality.

The invention also has for an object the provision of a compact and simply operated and controlled battery of filament producing units.

Apparatus that is used in practicing the present invention is illustrated in the accompanying drawing wherein:

FIG. 1 is a perspective view of an apparatus that is used in following the process that is disclosed herein;

FIG. 2 is a view taken from the line 2-2 in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line 3 3 of FIG. 2; and

FIGS. 4, 5 and 6 are plan views of doctor blades that work the molten refractory material preparatory to its being drawn as a filament or thread.

In FIG. 1 of the accompanying drawing is illustrated a battery of discs of refractory material from which a plurality of filaments are drawn in the practice of the present invention.

The process that is contemplated hereby is the drawing of a filament from a slowly rotated and peripherally heated refractory disc 1 made of silica, aluminosilicate, mixtures thereof or the like, and using a doctor blade for hot working the refractory in its molten state.

The disc 1 illustratively is mounted on a core 2 and has "icea flame 3 applied substantially tangentially to its periphery in the direction of the rotary motion of the disc. The flame 3 liquefies the refractory material of silica, aluminosilicate or the like, which it contacts. A doctor blade 4 is applied to the periphery of the disc 1 and adjacent the tip of the flame 3, such that it acts as a baflle around which the slowly moving fluid refractory must flow. The doctor blade imparts a puddling or a mixing action into the molten silica, aluminum silicate or the like refractory material of which the peripheral edge of the disc 1 is made as the disc 1 is rotated through a gear train by a motor 10. The doctor blade 4 works and mixes the molten refractory to remove seeds, air bubbles, undesirable variations in viscosities from abrupt temperature gradients and the like for the purpose of imparting uniformity in composition, texture and structure to a filament 5 that is drawn from the periphery of the disc 1 just after it passes the doctor blade 4.

In drawing a filament of glass from a pool of molten glass, it is common practice to touch the surface of the molten glass with the tip of a solid glass rod and draw the glass rod away from the pool of molten glass, carrying the end of the glass filament to a desired destination. This technique is used in initiating the withdrawal of a filament from the pool of molten refractory material on the edge of or on the periphery of the disc 1 after the molten refractory material has been puddled by the doctor blade while the disc 1 is rotating or after the doctor blade has worked or has mixed the liquid refractory material that continues to be carried along by the circumferential travel of the disc 1 as it is rotated by the motor 10.

The doctor blade 4 illustratively is made of tungsten or tantalum at the tip, welded to a support of steel, brass or the like that is positively mounted to maintain a firm and predetermined position with respect to the flame 3.

The tungsten or tantalum tipped doctor blade terminates at its distal or unattached end in a preferred contour, of which those shown in FIGS. 4, 5 and 6 are illustrative.

The doctor blade tip 4' in FIG. 4 is laterally flat from a projection midway between its edges and engages the molten refractory material under the flame 3 at the periphery of the disc 1 in a laterally spreading flow starting midway between the lateral edges of the disc.

The docotor blade tip 4" is wedged or tapered to converge toward its tip and engages the molten refractory material under the flame 3 an optimum spreading amount intermediate the lateral edges of the disc.

The doctor blade tip 4" is tapered from its lateral edges and is slotted at its tip to preform the filament midway between the lateral edges of the disc 1.

All of the doctor blade mountings preferably are adjustable, such as by the hinge 9 in FIG. 2 or the like, so that at the beginning of operations the refractory material may be brought to its melting point before the tip of the doctor blade is depressed into the material and so that at the end of operations the doctor blade may be lifted up out of the molten refractory material before it returns to its solid state.

The discs 1 are rotated at a sufiiciently slow and uniform rate beneath the flames 3 to impart continuously a substantially uniform diameter to the filaments 5. The flames 3 illustratively are of acetylene emitted from bumer nozzles 6 that are fed from a gas supply pipe 7. The nozzles 6 preferably are adjustable with respect to the gas pipe 7.

The core 2 has a plurality of refractory discs I mounted thereon in a desired manner, such as by the drum being grooved axially along its periphery at both ends of a common diameter, with each of the axial grooves opening into short circumferential grooves to provide bayonet slot mounts for the discs.

Each disc 1 has projecting from its radially inner edge a pair of diametrically opposed keys 8 and 8' that are caused to enter the axial grooves and lodge in the bayonet slots in mounting the discs on the core 2 or in disassembling the structure when the refractory has been used up.

The process is followed simultaneously for each disc I mounted on the drum 2 to provide a steady flow of a bank of filaments 5. The bank of filaments 5 may be woven directly into fire resistant fabrics, cords, cables and the like, or may be passed continuously through a mixture of lubricating oil and starch or the like and stored on spools or bobbins for future use.

The disc 1 is made of a refractory such as silica, aluminosilicate, mixtures of silica with alumina, or the like. A representative mixture of refractory out of which the discs 1 are made consists of by weight, 55 percent silica, 41 percent alumina and 4 percent zirconia. The refractory is mixed and ground to a uniform and homogeneous composition and then is cast to a desired shape.

In making a representative disc 1 under laboratory conditions of temperature and pressure pure silica is ground to about 100 mesh and is mixed with a water dispersion of celloidal silica gel as binder to make a slurry. The slurry is poured into the disclike cavity of a mold made of a plastic, silicon rubber, graphite, a ceramic, metal or the like. The silica slip molded disc is dried at 230 F. for from 30 minutes to one hour and then is removed from the mold and is fired in an oven at 1800" F. for one-half hour. The resulting fired disc is then ready for use and is of a preferred contour, mounting and operation.

The illustrative installation shown in the accompanying drawing comprises a plurality of the refractory discs I mounted on the core 2. The discs 1 are rotated in a desired manner, such as from an electric motor and speed reduction gear train 11 from which the drive shaft 12 is journalled in a bearing 13 and ends in a hexagonal or square tip 14 that fits snugly in a correspondingly shaped socket centrally of the right hand face of the core 2 in FIG. 3. The left hand face of the core 2 in FIG. 3 bears a cylindrical aperture in which a stub shaft 15 seats.

The refractory discs 1 on the core 2 are borne by supports 16 and 17 with the support 17 provided with suitable means such as the spring loaded or lockable hinge 18 for accomplishing the assembly and disassembly of the refractory discs 1 and the core 2 between their supports when the refractory material of the discs 1 has been converted into filaments and the discs are to be replaced.

The drive shaft 12 is connected by a chain 20 to a driven shaft 21 that is journalled in the supports 22 and 23 that are back of the supports 16 and 17. The driven shaft 21 is connected by chains 24 and 25 to a second driven shaft 26 on which drums 27 and 28 are mounted. Cords 29 and 30 wind on the drums 27 and 28 to lower a bar 31 against the yielding resistance of coil springs 32 and 33 housed in the upper ends of the supports 22 and 23. The bar 31 carries the gas line 7 and doctor blades 4 that are lowered to follow the decreasing diameter of the discs l as the filaments 5 carry away the refractory material of which the discs are made. The motor 10 and gear train 11 are mounted on the supports 34, 35, 36 and 37.

In lieu of the acetylene flame 3 a plasma flame may be used. A plasma flame is obtained by passing a gas, such as argon, helium or nitrogen through an electric are 4 nozzle. The Encyclopedia of Chemistry (Supplement) by G. L. Clark and G. G. Hawley published in 1958 by the Reinhold Publishing Corporation, New York City, New York, on page 226, elaborates on the term plasma.

It is to be understood that the method that is disclosed herein for the production of filaments of refractory material may be modified somewhat within the scope of the present invention and with apparatus other than that shown in the accompanying drawing.

I claim:

1. The process of drawing a filament from a disc of solid refractory material having a peripheral edge, by imparting rotary motion to the disc of solid refractory material, applying heat to the refractory material peripheral edge from a source of heat as the refractory material peripheral edge continuously moves past the heat source at a rate that permits the part of the refractory material to which the heat source is applied to change locally from the solid state to the liquid state, maintaining a liquid refractory material working stationary doctor blade with its tip in the liquid state portion of the refractory material disc as the molten refractory material is carried past the stationary doctor blade, and withdrawing a filament of refractory material from the worked area of molten material at the peripheral edge of the disc while the disc is rotating.

2. The process defined by the above claim 1 applied to silica as the refractory material.

3. The process defined by the above claim 1 applied to aluminosilicate as the refractory material.

4. The process defined by the above claim 1 applied to a refractory material having the composition by weight of 55% silica, 41% alumina, and 4% zirconia.

. 5. The process defined by the above claim 1 for producing filaments of refractory material, inclusive of the step of passing the filaments through a mixture of starch in lubricating oil as a surface conditioner thereof.

6. The process of drawing a refractory fiber from a continuously moving molten pool of refractory material in a groove on the peripheral edge of a continuously rotating disc of the refractory material by continuously rotating a disc of solid refractory material having a peripheral edge, applying a flame from a fixed flame source to a limited area on the continuously moving peripheral edge of the disc of solid refractory material that is moving at a sufiiciently slow rate to permit the flame to form a puddle of liquid refractory material in the groove on the peripheral edge of the disc of solid refractory material, continuously working the puddle of liquid refractory material as it leaves contact with the flame by the curved tip of a fixed doctor blade that extends into the groove on the peripheral edge of the continuously rotating disc, and continuously withdrawing a fiber of the refractory material from the disc groove after the material has moved past the doctor blade.

References Cited in the file of this patent UNITED STATES PATENTS 1,580,199 Hering Apr. 13, 1926 2,313,296 Lamesch Mar. 9, 1943 2,514,627 Cook July 11, 1950 2,780,890 Russell Feb. 12, 1957

Claims (1)

1. 6. THE PROCESS OF DRAWING A REFRACTORY FIBER FROM A CONTINUOUSLY MOVING MOLTEN POOL OF REFRACTORY MATERIAL IN A GROOVE ON THE PERIPHERAL EDGE OF A CONTINUOUSLY ROTATING DISC OF THE REFRACTORY MATERIAL BY CONTINUOUSLY ROTATING A DISC OF SOLID REFRACTORY MATERIAL HAVING A PERIPHERAL

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