GB2144115A - Method of forming fibers from glass and apparatus therefor - Google Patents

Abstract

A method of economically producing large quantities of glass fibres from hard glass uses a cylindrical rotary body 2 provided in its peripheral wall with a number of orifices 4 for discharge of molten glass into the inner flame 12 of a blast flame flow 14 of a burner 7. The lower portion of the circumferential wall 5 contacts an outer flame 13 of said flow 14, whose velocity is lowered to an extent that it does not destroy the discharge cone of molten glass from each orifice. The temperature distribution at the circumferential wall 5 is such that the centre portion of the circumferential wall is maintained at a higher temperature than the upper region of said wall and the lower region of said wall is maintained at a temperature which is lower than that of the upper region of said wall. Fibre entanglement is prevented by varying the diameters of orifices 4 and/or the thickness of the circumferential wall 5 as illustrated in Figures 3 and 7. <IMAGE>

Description

SPECIFICATION Method of forming fibers from glass and apparatus therefor The present invention relates to an improved method of forming fibers put of glass by using a cylindrical hollow body of revolution, by utilizing centrifugal force and blast flame flow, and also relates to an apparatus therefor.

In a known method and apparatus for forming fibers out of glass by using a cylindrical hollow body of revolution by utilizing centrifugal force and blast flame flow, which is adopted for manufacturing glass fibers, melted glass is discharged by centrifugal force out of a number of orifices bored through the circumferential wall of a cylindrical hollow body of revolution or rotor.

The discharged melted glass is formed at the outer surface of the circumferential wall into a small circular cone having a bottom surface of a small circle corresponding to the area of the opening of each of the orifices, and a primary filament is formed at a position on the top of the smalled circular cone. The primary filament is advanced by centrifugal force towards the blast flame flow for secondarily extending the primary filament, and the primary filament is secondarily extended in the blast flame flow and formed into a secondary filament which is a component fiber of glass wool. There are, however, disadvantages in this method.As shown in Fig. 8, a glass fiber of a secondary filament G is obtained in the manner such that after being discharged out of a orifice D of an upper region C of the circumferential wall B of the cylindrical hollow body of revolution A, the melted glass is formed into a primary filament E which is then extended by blast flame flow F to be formed into the secondary filament G. Another glass fiber of a secondary filament K is obtained in the manner such that after being discharged out of an orifice I of a center region H of the circumferential wall, the melted glass if formed into a primary filament J which is then extended by blast flame flow F to be formed into the secondary filament K.Still another glass fiber of a secondary filament 0 is obtained in the manner such that after being discharged out of a orifice M of a lower region L of the circumferential wall, the melted glass is formed into a primary filament N which is then extended by blast flame flow F to be formed into the secondary filament 0. The disadvantages are that these filaments tangle with each other and variations are caused in the diameter of the produced glass fibers, resulting in deterioration in adiabatic performance, compression stability coefficient tension strength, or the like.

In order to prevent the above-mentioned entanglement and obtain high quality glass fibers, it has been proposed to discharge a relatively large quantity of melted glass out of the orifice D at the upper region C of the circumferential wall B and form it into a relatively thick primary filament E. This is then injected out of an extension burner and transversely advanced through the blow flame F, which is not reduced in velocity or temperature, so as to be extended to be formed into the secondary filament G in an inner flame Q of the blow flame flow F composed of an outer flame P of a lowered velocity and the inner flame Q of a high velocity.Melted glass of a quantity slightly less than that at the upper region C is discharged out of the orifice I at the center region H of the circumferential wall B to be formed into a primary filament J slightly thinner than the primary filament E and then transversely advanced through the blow flame F to be extended into the secondary filament K in the middle of the inner flame Q, and a relatively small quantity of melted glass is discharged out of the small aperture M at the lower region L of the circumferential wall B to be formed into a relatively thin primary filament N and then transversely advanced through the blow flame F to be extended into the secondary filament as soon as it has reached the inner flame Q of a largely lowered velocity.

In order to increase the quantity of production, on the other hand, the height of the abovementioned circumferential wall B and the number of small apertures can be increased. With this arrangement, however, the quantity of heat radiation at the lower region of the circumferential wall B increases thereby to decrease the temperature thereat.

As a first prior art proposal to prevent the above-mentioned entanglement of glass fibers as well as the temperature reduction at the lower region of the circumferential wall, there is a technique disclosed by Japanese Patent Publication No. 13748/1967.

According to this first prior art proposal, high frequency induction heating is applied to the lower region of the circumferential wall of a cylindrical hollow body of revolution to maintain the temperature of the circumferential wall substantially uniform and, in order to prevent the abovementioned entanglement of glass fiber, the diameter of the orifices is varied from small to large through a middle value as the position of the orifice changes from the lower region to the upper region through the center region, respectively, so that the quantity of discharged melted glass is largest, smaller and smallest at the upper, center and lower regions respectively.

As a similar second prior art proposal, there is a technique disclosed in the publication of Japanese Patent Application Laid-open No. 113638/1980.

According to this second prior art proposal, the supplied high temperature melted glass is passed through the inside upper portion of the circumferential wall of a cylindrical hollow body of revolution and then distributed over the entire inner surface of the circumferential wall, the lower region of the circumferential wall being strongly heated by high frequency means. Thus, the temperature distribution of the circumferential wall is such that the temperature is the highest of all, relatively low and at a middle value between the former two, at the lower, center and upper regions, respectively, of the circumferential wall of the cylindrical hollow body of revolution.

That is, it is believed that the upper region of the circumferential wall is maintained at the middle temperature as mentioned above by the heat provided by the high temperature melted glass, in spite of the fact that the region is far from the high frequency heating coil, because the total quantity of the high temperature melted glass supplied to the cylindrical hollow body of revolution is brought into contact with the inside upper portion of the circumferential wall and then distributed over the entire inner surface of the circumferential wall. The lower region of the circumferential wall is maintained at the highest temperature by the induction heating of the high frequency coil.It is considered that the temperature at the center region of the cirumferential wall will be low in comparison with that at the upper and lower regions, because the center region of the circumferential wall is not far from the high frequency coil and the melted glass is distributed to this region after it has been divested of a large quantity of heat.

According to this second prior art proposal, in order to prevent the above-mentioned fiber entanglement, the following arrangement is adopted.

That is, in the lower region of the circumferential wall of the cylindrical hollow body of revolution, the temperature of the circumferential wall is the highest of all as described above, and therefore the melted glass passing through the orifices in this region has the lowest viscosity. In this lower region of the circumferential wall, however, since it is necessary to form the primary filament out of glass discharged out of the orifice into the secondary filament immediately after the primary filament has reached the inner flame of the blow flame, the quantity of the melted glass discharged out of each of the orifices in the lower region of the circumferential wall has to be so small as to enable the primary filament to be formed into the secondary fibrous filament as soon as the primary filament reaches the inner flame of the blow flame.In order to attain this, the thickness of the circumferential wall is made to be the largest of all to elongate the path of the orifice thereby to increase the fluid resistance when the melted glss passes through the orifice such that only a small quantity of melted glass can be discharged out of it.

In the center region of circumferential wall of the cylindrical hollow body of revolution, the temperature of the circumferential wall is the lowest of all as described above and therefore the melted glass passing through the orifices in the center region has the highest viscoity. In this center region of the circumferential wall, however, since it is necessary to form the primary filament out of glass discharged out of the orifice into the secondary filament in the middle of the inner flame of the blow flame, the quantity 6f the melted glass discharged out of each of the orifices in the center region of the circumferential wall has to be larger than the quantity of the melted glass discharged out of the orifice in the lower region so as to enable the primary filament to be formed into the secondary fibrous filament when the primary filament reaches the intermediate part of the inner flame of the blow flame. In order to attain this, the thickness of the circumferential wall is made to be the smallest of all to shorten the path of the orifice to thereby decrease the fluid resistance when the melted glass passes through the orifice such that such an intermediate quantity of melted glass can be discharged out of the orifice.

In the upper region of the circumferential wall of the cylindrical hollow body of revolution, the temperature of the circumferential wall is the intermediate one as described above and therefore the melted glass passing through the orifices in the upper region has an intermediate viscosity In this upper region of the circumferential well. ho@@aver@ th@ p@@@@a@y fila@@ent formed ou@ of glass disch@@ @@@@@ut of the orifice @@ required is be former fro@@ a @@rge quar@ity of melted glass so as to onab@@ @@@ primary liemment@@ bo formed into the secondary @@ement immedia@ely bofore the primary f@@@nen@comc@ cuis@@e the inner flame of the blow flame offer passage therethrough @@ @@ce@@@ attain this, the thickne@s on the circumferential wail is set to an intermedi@te val@@ b@t voen the this@messes in the @@v@@ and cen@@@ @egi@n@ of the circumfeien tial wall so as to @ause the p@th of the onfice to l@@@@ en i@termediete l@ngth and bence an intermediate fluid resis@ance when the meke@ gla@@ @sser @h@ough the path@@ as to discha@ge @ large quantity o@ molted glass.

Although the above-mentioned first and second prio@ art te@hniques can attain the object of prevonting @ibor entanglement from occurring and of increasing the quantity of product by incrensing the height of the ci@cumferential wall of the cylindri@al hollow body of revolution, they have drawbacks that not only it is required to provide induction heating means such as a high frequency coil.Such means requiring a large capacity high frequency heating energy generator, but it is also necessary to provide electromagnetic shideling for the prevention of danger in the vicinity of the glass fiber forming apparatus provided with the high frequency coil, resulting in the complication of the glass fiber forming apparatus as well as the deterioration of the workability in operation.

In order to eliminate the above-mentioned drawbacks, there is a third prior art proposal disclosed in Japanese Patent Publication No. 20612/1975.

According to the technique of this third prior art proposal, a burner is provided for the exclusive purpose of heating the circumferential wall of the cylindrical hollow body of revolution by bringing a flame into contact with the entire circumferential wall from the outside of the cylidrical hollow body of revolution. It is, however, necessary to provide, separately from the burner for the exclusive purpose of heating, an extension apparatus for injecting a flow of high pressure and high temperature steam for forming the primary filament out of the melted glass discharged out of the circumferential wall into the secondary fibrous filament, and this thereby makes the glass fiber forming apparatus complicated, resulting in disadvantages in the viewpoint of effective use of heat.

In each of the above-mentioned three prior art techniques, a large capacity of heat source for heating the circumferential wall is required separately from the injection flow heat source for forming the primary filament out of the melted glass discharged out of the circumferential wall into the secondary fibrous filament, and therefore such techniques are not suitable in the present day circumstances where the necessity of energy saving is strongly required.

As a fourth prior art technique, for the purpose of maintaining the high quality of produced glass fibers with a main object of saving fuel, there is a technique disclosed by the Japanese Patent Application Laid-Open No. 106532/1982.

This fourth prior art technique has the arrangement which can be understood from Figs. 1 and 2, in which a cylindrical hollow body of revolution 2 is fixed to a lower portion of a rotary shaft 1, the body of revolution body 2 having a bottom wall 3, a circumferential wall 5 provided with a number of small, melted-glass discharging orifices 4 extending therethrough and an upper annular flange 6 formed at the inside upper end of the circumferential wall 5, and in which an extension burner 7 is disposed surrounding the body of revolution 2 and the rotary shaft 1 is disposed in an annular space 8 at the centre of the extension burner 7, so that melted glass 9 is supplied from a nozzle 10 into the body of revolution 2 through the space 8.

The extension burner 7 emits from its fire nozzle 11 a blow flame flow 14 composed of a high-velocity inner flame 1 2 and a relatively low velocity outer flame 1 3. This blow flame flow 14 is for forming the primary filament, formed at a tip end of a small circular cone of melted glass discharged out of each of the orifices 4, into the secondary fibrous filament, and the inner flame 1 2 has a sufficient velocity to be able to form the primary filament into the secondary fibrous filament, the outer flame 1 3 having a velocity which is lowered to the extent so as not to destroy the small circular cone of melted glass and the primary filament following the small circular cone.

The first nozzle 11 of the extension burner 7 is positioned where the outer flame 1 3 portion contacts the lower portion of the outer surface of the circumferential wall 5 of the body of revolution 2.

A heating burner 1 5 is provided inside the upper annular flange 6 of the body of revolution 2, a flame 1 6 of which is directed onto the extended plane of the flange 6 and in the direction parallel with the surface of the flange 6. The extent of heating is such that the flame 16 passes by the upper surface or upper and lower surfaces of the annular flange while contacting the surface/surfaces, whereby the heat can reach at least the connection portion between the upper annular flange 6 and the circumferential wall 5.

According to this fourth prior art technique having the arrangement as described above, upon reaching the bottom wall 3 of the body of revolution 2, which is rotated at a high velocity by the rotary shaft 1, the melted glass 9, flowing down out of the nozzle 1 9 from a glass melting furnace (not shown) with a controlled constant flow rate, is distributed to the inside of the circumferential wall 5 by the action of centrifugal force and discharged by centrifugal force to the outside of the circumferential wall 5 through the orifices 4, being formed into a small circular cone of melted glass having a bottom surface of a small circle corresponding to the opening area of each of the orifices 4, extended at the position of the tip end of the small circular cone to form a primary filament, which is itself extended to the portion of the inner flame 1 2 having a capability of extension of the blow flame flow emitted from the fire nozzle 11 of the extension burner 7, and extended secondarily to form a secondary fibrous filament.

The width and the velocity of the blow flame flow 1 4 becomes wider and lower, respectively, as it advances down from the fire nozzle 11 of the extension burner 7, and it is preferable to cause the outer flame 1 3 with its broadened width to approach the lower portion of the outer surface of the circumferential wall 5 as close as possible so as not adversely to affect formation of the small circular cone and the primary filament.However, if the inner flame 1 2 having a velocity capable of forming the primary filament into the secondary fibrous filament, contacts the outer surface of the circumferentialwall 5, the melted glass discharged out of each orifice 4 of the circumferential wall 5 is applied to the outer surface of the circumferential wall 5 by the inner flame 1 2 with no sufficient time to form the small circular cone and the primary filament, and when the thickness of the adhered melted glass becomes a certain value by the application of successively discharged melted glass, the adhered melted glass is then discharged in the form of random particles or in the form of fibers of a non-controlled thickness, so that it becomes impossible to attain normal fiber formation.

If the temperature of the circumferential wall 5 is maintained high by causing the outer flame 13, which is reduced in velocity to the extent so as not adversely to affect the formation of the small circular cone and the primary filament, to approach the lower portion of the outer surface of the circumferential wall 5 as close as possible as described above, the decrease in temperature of the melted glass, which is passing through the orifice 4, can be avoided thereby to enable the melted glass to be discharged out of the orifice by a sufficient quantity for the predetermined formation of fibers.

According to this fourth prior art technique, the outer flame 1 3 of the blow flame flow 1 4 the lower portion of the outer surface of the circumferential wall 5, and the upper portion of the circumferential wall 5 is also heated by the heating burner 15, so as to maintain the te-.ioernture of the circumferential wall 5 high. However, if the height of the circumferential wall 5 is raised to increase the quantity of glass fibers produced, the position of the lower end of the circumferentual wall 5 becomes distant from the fire nozzle 11 of the extension burner 7, so that the outer flame 1 3 of the blow flame flow 14 used for raising the temperature of the lower end becomes so wide at said lower end as to be insufficiently hot to provide the required heating there.

Of course, although the outer flame 1 3 can be maintained at a temperature sufficient to raise the temperature of the circumferential wall 5 at its lower portion if the width of the fire nozzle 11 is increased and a large quantity of fuel is supplied, this solution is not adoptable in view of the purpose of energy saving.

In this fourth prior art technique intended to attain fuel saving and to produce high quality glass fiber, it has been proved through measurement that the temperature distribution in the direction of the height of the circumferential wall 5 is different from that in the direction of the height of the circumferential wall 5 of the cylindrical hollow body of revolution 2 in each of the first, second and third prior art techniques, when the height of the circumferential wall 5 of the cylindrical hollow body of revolution 2 is raised to increase the quantity of production of glass fibers.

That is, the temperature of the circumferential wall 5 was the highest of all in its center region, the lowest of all in its lower region and intermediate or lower in its upper region than in the center region.

It is considered that this phenomenon is such because the distance from the fire nozzle 11 of the extension burner 7 to the lower end of the circumferential wall 5 is elongated to diffuse the outer flame 1 3 of the blow flame flow 14, so that the outer flame 1 3 has an insufficient quantity of heat to raise the temperature of the lower end of the circumferential wall 5 to a required value and the temperature at the portion from the lower region of the circumferential wall 5 to the bottom wall 3 thus becomes low.

Further it is considered that, when the high temperature melted glass 9 flowing down out of the nozzle 10 contacts the low temperature bottom wall 3, the viscosity of the melted glass becomes large due to the decrease in temperature thereof, so that a boundary film of high viscosity is formed between the bottom wall and the high temperature melted glass successively flowing down. The high temperature and small viscosity melted glass successively flowing down reaches the center region of the circumferential wall 5 without having lost a large quantity of heat to the bottom wall 3 and the lower region of the circumferential wall 5, even though it contacts the above-mentioned boundary film, so that the temperature of the circumferential wall in the center region becomes the highest of all.

It is considered that the temperature takes an intermediate value as described above at the portion of the upper end of the circumferential wall 5 and the upper annular flange 6, because the upper portion of the body of revolution 2 is covered by the extension burner 6 and the melted glass 9 flowing down out of the nozzle 10 is distributed into the upper region of the circumferential wall 5 while contacting the above-mentioned boundary film with its temperature maintained high, even though some of its heat is taken off in the central region of the circumferential wall 5.

As described above, if it was intended to raise the height of the circumferential wall 5 to increase the quantity of production of glass fibers and to reduce the cost of fuel consumption according to the forth prior art technique, it has been proved that the temperature distribution in the direction of the height of the circumferential wall 5 would be different from each of the first, second and third prior art techniques, that is the temperature of the circumferential wall 5 would be the highest of all in its center region, the lowest of all in its lower region and intermediate in its upper region.

This phenomenon appears in the case where glass fibers are produced by using so-called hard glass which contains only small amount of alkali oxide such as Na2O, K20 or the like and BaO or not contains BaO, which shows higher viscosity at the same temperature in comparison with the glass oridinarily used for glass fiber formation.

An object of the invention is to provide a method and apparatus intended to produce high quality glass fibers or to form so-called hard glass into fibers, while preventing the increase of energy consumption, the entanglement of produced fibers, etc., from occurring.

The present invention relates to a method and an apparatus for performing the method, in which the quantity of production of glass fibers can be increased, while avoiding energy increase and while maintaining the unique temperature distribution which occurs at the circumferential wall when the height of the circumferential wall is raised to increase the quantity of glass fiber production or when glass fibers are produced out of so-called hard glass, namely such a temperature distribution that the temperature in the center region of the circumferential wall is the highest of all, the temperature in the upper region of the circumferential wall is lower than the center region, and the temperature in the lower region is lower than the upper region.

The invention will be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section schematically showing an example of a glass fiber formng apparatus; Figure 2 is a fragmentary enlarged cross-sectional view showing a main part of the apparatus of Fig. 1, Figure 3 is an enlarged cross-sectional view schematically showing a main part of the apparatus of Fig. 1 incorporating a first embodiment of the invention; Figure 4 is a diagram showing the relation between the temperature and viscosity of glass; Figure 5 is an enlarged cross-sectional view schematically showing a main part of a second embodiment of apparatus of the invention; Figure 6 is a view similar to Fig. 5 showing a main part of a fifth embodiment; Figure 7 is a view similar to Figs. 5 and 6 showing a main part of a sixth embodiment;; and Figure 8 is an enlarged cross-sectional view schematically showing a main part of conventional apparatus.

As described already, in producing glass fibers, the diameters of the orifices 4 and/or the thickness of the circumferential wall 5 are selected in accordance with the viscosity of the melted glass used, to make it possible to obtain glass fibers of the desired diameter in the manner such that the melted glass distributed in the upper region of the circumferential wall 5, and having an intermediate temperature and an intermediate viscosity which are slightly lower and slightly higher than the temperature and the viscosity, respectively, of the melted glass distributed in the center region of the circumferential wall 5, is discharged in large quantity out of the small apertures 4 in the upper region of the circumferential wall 5 to form a thick primary filament which is then extended to the farthest position from the outer surface of the circumferential wall 5 through the inner flame 1 2 of the blow flame flow 14, which is near the fire nozzle 11 of the burner 7 and the velocity of which is not yet lowered, to obtain a secondary fibrous filament.

The diameters of the small apertures 4 and/or the thickness of the circumferential wall 5 are selected in accordance with the viscosity of melted glass used, to make it possible to obtain glass fibers of the desired diameter in the manner such that the melted glass distributed in the center region of the circumferential wall 5, and having the highest temperature and low viscosity is discharged in an intermediate quantity, which is smaller than that in the upper region, out of the orifices 4 in the center region of the circumferential wall 5 to form a primary filament, having an intermediate thickness thinner than the primary filment in the upper region, which is then extended to the intermediate position between the farthest and the nearest positions respectively from the outer surface of the circumferential wall 5 through the inner flame 1 2 of the blow flame flow 14, which is somewhat separated from the fire nozzle 11 of the burner 7 and the velocity of which is somewhat lowered, thereby to obtain a secondary fibrous filament.

Lastly, the diameters of the orifices 4 and/or the thickness of the circumferential wall 5 are selected in accordance with the viscosity of melted glass used, to make it possible to obtain glass fibers of the desired diameter in the manner such that the melted glass distributed in the lower region of the circumferential wall 5, and having the lowest temperature and the highest viscosity, due to contact with the low temperature lower region and the bottom wall, is discharged out of the orifices 4 in the lower region of the circumferential wall 5 to form a relatively thin primary filament which is then extended to the position adjacent to the circumferential wall 5 through the inner flame 1 2 of the blow flame flow 14, which is separated to the farthest position from the fire nozle 11 of the burner 7 and the velocity of which is relatively reduced, thereby to obtain a secondary fibrous filament.

In accordance with the invention, the selection of the diameters of the orifices 4 and the thickness of the circumferential wall 5 in the upper, center and lower regions of the circumferential wall 5 is determined depending on the viscosity of glass used, and, in general, selection is made such that in the upper region the diameters of the orifices 4 are large while the thickness of the circumferential wall 5 is thin, in the center region the diameters of the orifices are small while the thickness of the circumferential wall 5 is large, and in the lower region the diameters of the orifices 4 are large while the thickness of the circumferential wall 5 is thin.

Referring to Figs. 3 to 7 some embodiments of the invention will now be described.

The invention relates to changing the circumferential wall 5 in the apparatus according to the fourth prior art technique described above with reference to Figs. 1 and 2, and in one embodiment has an arrangement as shown in Fig. 3, in which the diameters of orifices 25 in a center region 24 of a circumferential wall 1 9 of a cylindrical hollow body of revolution 1 8 are made smaller than the diameters of each of orifices 22 and 23 in upper and lower regions 20 and 21 respectively.

Fig. 4 is a diagram showing the relation between the temperature and the viscosity with respect to three kinds of glass, R, S and T, R being an example of soft glass used for ordinary glass fiber production, S and T being examples of so-called hard glass as described above.

Fmbodirnents of the invention will now be described in comparison with the comparing examples of the above-mentioned fourth prior art technique.

(COMPARING EXAMPLE 1) According to the fourth prior art technique having such an arrangement as shown in Figs. 1 and 2, glass fibers were produced by using the glass R shown in Fig. 4 with 1 mm diameter orifices under the following conditions: 1) The height of the circumferential wall 5 from the center of the orifices 4 in the uppermost row to the center of the orifices 4 in the lowermost row was 30 mm; 2) The number of rows of the orifices 4 was 30 and the total number of the orifices was 7710; 3) The glass R was supplied at 330 kg/h; 4) The diameter of the body of revolution 2 was 300 mm; 5) The thickness of the circumferential wall 5 was 4 mm; and 6) The extension burner 7 was adjusted such that the average diameter of the obtained glass fibers was 7 um.

As a result, respective temperatures at various portions of the circumferential wall 5 and the estimated temperature and the estimated viscosity of the melted glass pasing through each of the orifices 4 were as shown in Table 1 and the standard deviation of the diameter distribution of the obtained glass fibers was 3.77 um. The formation manner of the secondary fibrous filament in the blow flame flow 14 was as shown in Fig. 8 and some glass fiber entanglement was observed.

Table 1.

Distribution of Temp. Temp. of Rotor When passing through Diameter and Orifice Dia. in circumferantial Orifice, Glass' of Rotor Circumferential Wall Estimated Estimated Orifice Wall C Temp. C Visc. Poise @m- Uppermost Part 3 Rows 915 945 5500 1.0 Center Part 24 Rlows 955 985 2550 1.0 Lowermost Part 3 Rows 915 945 5500 1.0 (EMBODIMENT 1) According to the above-mentioned arrangement of the invention glass fibers were produced by using the glass R shown in Fig. 4 under the same energy using condition as the abovementioned comparing example 1 and under the following condition for the distribution of diameter of the small apertures in Table 2: : 1) The height of the circumferential wall 1 9 from the center of the orifices in the uppermost row to the center of the orifices in the lowermost row was 50 mm; 2) The number of rows of the orifices was 50 and the total number of the orifices was 12850; 3) The glass R was supplied at 560 kg/h; 4} The diameter of the body of revolution 18 was 300 mm; 5) The thickness of the circumferential wall 1 9 was 4 mm; and 6) The extension burner 26 was adjusted such that the average diameter of the obtained glass fibers was 7 um.

As the result, respective temperatures at various portions of the circumferential wall 19 and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 2 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.61 um, whereby high quality glass fibers could be obtained.

The formation manner of the secondary fibrous filament 28 in the blow flame flow 27 was as shown in Fig. 3 and glass fiber entanglement was scarcely observed.

Table 2

Distribution of Tesp. Teap. of Rotor When passing through | Diameter and Orifice Oia. in Circuaferential orifice, Glass' @ of Rotor Circusferential Wall Fsti3atd Estiaat~d ~ Orifice Wall C Temp. C Visc. Poise mm Uppermost Part 3 Rows 923 953 4690 1.2 Upper Part 3 Rows 939 969 3430 1.1 Center Part 30 Rows 955 985 2550 1.0 Lower Part II Rows | 9 3 1 96 1 | 40 3 0 I . 1 Lowermost Part 3 Rows 911 941 5880 1.2 As apparent from the comparison between the above-mentioned embodiment 1 and the comparing example 1, it is possible to attain mass-production of high quality glass fibers without requiring additional energy consumption.

(COMPARING EXAMPLE 2) According to the fourth prior art technique having such an arrangement as shown in Figs. 1 and 2, glass fibers were produced by using the so-called hard glass S shown in Fig. 4 with 1 mm diameter orifices under the following conditions: 1) The height of the circumferential wall from the center of the orifices in the uppermost row to the center of the orifices in the lowermost two was 30 mm; 2) The number of rows of the orifices was 30 and the total number of the orifices was 7710; 3) The glass S was supplied at 330 kg/h; 4) The diameter of the body of revolution was 300 mm; 5) The thickness of the circumferential wall was 4 mm; 6) The extension burner 7 was adjusted such that the average diameter of the obtained glass fibers was 7 um; and 7) Since the glass S was so-called hard glass, a quantity of fuel larger than in the case of obtaining glass fibers by using the glass R of Fig. 4 was supplied to the extension burner as well as the heating burner so as to increase the load of the burners.

As the result, respective temperatures at various portions of the circumferential wall and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 3 and the standard deviation of the diameter distribution of the obtained glass fibers was 4.69 um, which was an undesirable value.

The formation manner of the secondary fibrous filament in the blow flame flow was substantially the same as that shown in Fig. 8 and some glass fiber entanglement was observed.

Table 3

Distribution of Temp. Temp. of Rotor When passing through Diametar and Orifice Dia. in Cirumfe@ential Orifice, Glass' of Rotor Citcum@erential Wall Esticated Istimated Orifice Wall C Temp. C Visc. Poise mm Uppe@most Part 3 Rows | 1 1 0 S | L 1 3 5 | 2 4 2 0 1 . 0 Cante@ Part 13 Rows 1110 1140 229.0 1.0 Lover Part 5 Rows 1100 1130 2580 1.0 Lawerzast Part 4 Raws 1 0 9 0 1 1 2 0 2 9 1 0 1 . 0 In this comparing example 2, since a large quantity of fuel is used to make the temperature high at the circumferential wall of the cylindrical hollow body of revolution, the nominal life of the cylindrical hollow body of revolution becomes shorter, and this example is not preferable in view of energy saving, in view of the nominal life of the cylindrical hollow body of revolution and also in view of the industrial operation due to increase in the number of times of replacement of the cylindrical hollow body of revolution. Further, the quality of the obtained glass fibers is low.

(EMBODIMENT 2) According to the above-mentioned arrangement of the invention, glass fibers were produced by using the glass S shown in Fig. 4 under the energy using condition in which the quantity of fuel supply was decreased from the case of the comparing example 2 and under the following condition for the distribution of diameter of the orifices in Table 4: 1) The height of the circumferential wall 30 of the body of revolution 29 as shown in Fig. 5 from the center of the orifices in the uppermost row to the center of the small apertures in the lowermost row was 30 mm; 2) The number of rows of the orifices was 30 and the total number of the orifices was 7710; 3) The glass S was supplied at 330 kg/h; 4) The diameter of the body of revolution 29 was 300 mm; 5) The thickness of the circumferential wall 30 was 4 mm; and 6) The extension burner 31 was adjusted such that the average diameter of obtained glass fibers was 7.0 um.

As the result, respective temperatures at various portions of the circumferential wall 30 and the estimated temperature and the estimated viscosity of the melted glass pass through each of the orifices were as shown in Table 4 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.58 um. Thus high quality glass fibers could be obtained without accompanying increased fuel consumption in comparison with the comparing example 2.

The formation manner of the secondary fibrous filament 33 in the blow flame flow 32 was as shown in Fig. 5 and glass fiber entanglement was scarcely observed.

Table 4

Distribution or. Tesp. Tesp. or Rotor When passing through Diameter and Orifice Dia. in @itcumferential | Orifice, Glass' of Rotor Circumferential Wall Estimate Estimated Orifice Wall C Temp. C Visc. Paise mm Uppermost Part 3 Rows 1060 1090 4350 1.2 Center Part 18 Rows 1090 1120 2910 1.0 Low Part 5 Rows 1057 1087 4570 1.1 Lowermost Part 4 Rows 1032 1062 6650 1.2 (EMBODIMENT 3) In the above-mentioned embodiment 2, when the fuel for the extension burner 31 was slightly reduced and glass fibers were produced, the respective temperatures at various portions of the circumferential wall 30 and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 5 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.60 um.

The formation manner of the secondary fibrous filament in the blow flame flow was substantially the same as that shown in Fig. 5.

Table 5

Distribution of Temp. Temp. of Rotor When passing through Diameter and Orifice Dia. in Circumferential Orifice, Glass' | of Rotor Circumferential Wall Estimated Estimated Orifice Wall C Temp. C Visc. Paise mm Upparmost Part 3 Rows 1034 1064 6540 1.2 Cater Part 18 Rows 1080 1110 3300 1.0 Low Part 5 Rows 1050 1080 5130 1.1 Lowermost Part 4 Rows 1023 1053 7450 1.2 (EMBODIMENT 4) When glass fibers were produced by using the glass T shown in Fig. 4 with the distribution of orifice diameter as shown in Fig. 6 and under other conditions which were the same as in the embodiment 2, the respective temperatures at various portions of the circumferential wall and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 6 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.63 um. The formation manner of the secondary fibrous filament in the blow flame flow was substantially the same as that shown in Fig. 5.

Table 6

Distribution of Temp. Temp. of Rotor When passing through Diameter and Orifice Dia. in Circumferential Orifice, Glass' of Rotor Circumferential Wall Estimated Estimated Orifice Wall C Temp. C Visc. Poise mm Uppermast Part 3 Rows 1055 1085 6620 1.3 Upper Part 3 Rows 1072 1102 4900 1.2 Center Part 15 Rows 1090 1120 3700 1.1 Lower Part 5 Rows 1064 1094 5540 1.2 Lowermost Part 4 Rows 1048 1078 7800 1.3 (EMBODIMENT 5) Glass fibers were produced by using the glass S shown in Fig. 4, with the 1.1 mm diameter orifices under the same fuel using conditions as in the comparising example 1 and under the following conditions:: 1) The height of the circumferential wall 35 of the body of revolution 34 as shown in Fig. 6 from the center of the orifices in the uppermost row to the center of the orifices in the lowermost row was 30 mm; 2) The number of rows of the orifices was 30 and the total number of the orifices was 7710; 3) The glass S was supplied at 330 kg/h; 4) The diameter of the body of revolution 34 was 300 mm; 5) The thickness of the circumferential wall 35 was made thin in its upper region, thick in its center region, and intermediate in its lower region, in accordance with the numerical values as shown in Table 7; and 6) The extension burner 36 was adjusted such that the average diameter of obtained glass fibers was 7.0 um.

As the result, the respective temperatures at various portions of the circumferential wall 35 and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 7 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.57 um. The formation manner of the secondary fibrous filament in the blow flame flow 37 was as shown in Fig. 6 and glass fiber entanglement was scarcely observed.

Table 7

Distribution of Temp. Temp. of Rotor When passing through Diametar and Orifice Dia. in Circumferential Orifice, Glass' of Rotor Circumferenhtial Wall Estimated Estimated Orifice Wall C Temp. C Visc. P. mm Uppermost Part 1st Row 1060 1090 4350 3.0 Center Part 12th Row 1090 1120 2910 6.2 Low Part 23rd Row 1058 1088 4570 4.8 Lowermost Part 30th Row 1034 1064 5650 4.0 (EMBODIMENT 6) Glass fibers were produced by using the glass T shown in Fig. 4, with the orifice diameter distribution as shown in Table 8 under the same energy using conditions as in embodiment 4, that is as in embodiment 2, and under the following conditions:: 1) The height of the circumferential wall 39 of the body of revolution 38 as shown in Fig. 7 from the center of the orifices in the uppermost row to the center of the orifices in the lowermost row was 30 mm; 2) The number of rows of the orifices was 30 and the total number of the orifices was 7710; 3) The glass T was supplied at 330 kg/h; 4) The diameter of the body of revolution 38 was 300 mm; 5) The thickness of the circumferential wall 39 was made thin in its upper region, thick in its center region, and intermediate between the former two in its lower region, in accordance with the numerical values as shown in Table 7; 6) The orifice diameter distribution was as shown in Table 7; and 7) The extension burner 40 was adjusted such that the average diameter of obtained glass fibers was 7.0 um.

As the result, the respective temperatures at various portions of the circumferential wall 39 and the estimated temperature and the estimated viscosity of the melted glass passing through each of the orifices were as shown in Table 8 and the standard deviation of the diameter distribution of the obtained glass fibers was 2.74 um.

The formation manner of the secondary fibrous filament in the blow flame flow 41 was as shown in Fig. 7 and glass fiber entanglement was scarcely observed.

Table 8

Distribution of Temp. of When passing through Thickness Diameter Temp. & Orifice Circum- Orifice, Glass' of of Dia. in Rotor farential Estimated Estimated Circumferen- Orifice Circumferential Wall of Temp. Visc. tial Wall Wall Rotor C C Poise mm mm Uppermast Part 1st Row 1052 1082 7200 3.4 1.3 Center Part 12th Row 1087 1117 3850 4.7 1.1 Lower Part 23rd Row 1063 1093 5640 5.5 1.2 Lowermost Part 30th Row 1045 1075 8400 4.5 1.2 Examining the temperature of the melted glass distributed to the inside ot the cIrnum1it;ii'ic wall of the cylindrical hollow body of revolution in each of the above-mentioned embodiments, there occurs a low portion as the temperature of glass approaches its devitrificating range.

To cope with this phenomenon, it is necessary to eliminate portions where the melted glass stays inside the body of revolution as small as possible, and to this end, in each embodiment, a large number of orifices bored in the circumferential wall of the body of revolution for discharging melted glass are uniformly disposed from the position where they are in contact with the boundary between the inner surface of the bottom wall and the inside of the circumferential wall to the position where they are in contact with the boundary between the inside of the circumferential wall and the inner surface of the upper annular flange so that the melted glass is discharged out of the orifice to form the glass into fibers with no time to generate glass devitrification.

In the base where melted glass is used such that the viscosity thereof abruptly varies as the temperture changes in the temperature-to-viscosity curve of the used glass, it is possible to copy with the melted glass having the above-mentioned characteristic by using a cylindrical hollow body of revolution in which the thickness of the circumferential wail thereof is arranged to the thicker in the center region than in each of the upper and lower regions, or to be the thickest of all in the center region, the thinnest of all in the upper region and intermediate in the lower region, and in which the orifices are bored in the circumferential wall in the manner such that the diameters of the orifices bored in the center region are selected to be smaller than those of the orifices bored in each of the upper and lower regions.

The invention provides such a meritorious effect that a larger quantity of high quality glass fibers or glass fibers of high quality glass with a glass material which is harder than the conventionally ordinarily used glass can be manufactured without generating fiber entanglement and without increasing the quantity of energy consumed in the conventionally performed glass fiber manufacturing.

The meritorious effect can be attained by suitable design of the structure of the cylindrical hollow body of revolution without accompanying energy consumption increase, complication of equipment, etc.

Claims (8)

1. A method of forming fibers from glass by using a cylindrical hollow body of revolution provided with numbers of orifices in its circumferential wall, in which said cylindrical hollow body of revolution is rotated at a high speed to discharge melted glass out of said orifices of said circumferential wall, a primary filament advanced straight ahead being formed by centrifugal force at the tip end of a small circular cone of glass discharged out of each of said orifices, this primary filament being formed into a thinner fibrous secondary filament by an inner flame of a blow flame flow of an extension burner, and at this time a lower portion of the outer surface of said circumferential wall of said cylindrical hollow body of revolution is contacted by an outer flame of said blow flame flow of a velocity lowered to an extent not to destroy said small circular cone of glass and an upper portion of said circumferential wall of said cylindrical hollow body of revolution is heated by a heating burner, characterised in that, while maintaining the temperature of said circumferential wall of said cylindrical hollow body of revolution in the state that it is the highest of all in the vertical center region, lower than the center region in the upper region of said circumferential wall, and lower than the upper region in the lower region of said circumferential wall, by the selection of the diameter of the orifices in said circumferential wall and/or the thickness of said circumferential wall, the primary filament formed from the melted glass discharged out of each said orifices in the upper region of said circumferential wall is extended to the farthest position in the inner flame of said blow flame flow from the outer surface of said circumferential wall to be formed into the thinner secondary filament, the primary filament formed out of the melted glass discharged out of each of said orifices in the center region of said circumferential wall is extended to a position in the inner flame of said blow flame flow midway between the farthest and the closest positions respectively from the outer surface of said circumferential wall to be formed into the secondary filament, and the primary filament formed out of the melted glass discharged out of each of said orifices in the lower region of said circumferential wall is extended to the closest position in the inner flame of said blow flame flow to the outer surface of said circumferential wall to be formed into the secondary filament.

In a centrifugal force system glass fiber producing apparatus, comprising a cylindrical hollow body of revolution having a bottom wall, a circumferential wall provided with numbers of orifices therein for discharging melted glass, and an upper annular flange disposed at the inside upper end of said circumferential wall, a fire nozzle of an extension burner for forming a primary filament formed at a tip end of each of small circular cones of glass discharged out of said cylindrical hollow body of revolution into a secondary fibrous filament, said fire nozzle of the extension burner being disposed such that only an outer flame portion of flame flow emitted from said nozzle having a velocity lowered to the extent not to destroy said glass circular cone is brought into contact with the lower portion of the outer surface of said circumferential wall of said cylindrical hollow body of revolution, a heating burner being provided at the inside of said upper annular flange of said cylindrical hollow body of revolution, said heating burner being arranged such that the flame of which is directed in the direction on an extended plane of said upper annular flange and parallel with the plane of said upper annular flange and that the heating of which is to the extent that the flame contacts and passes by the upper surface or both the upper and lower surfaces of said upper annular flange whereby the heat reaches at least a connection portion between said annular flange and said circumferential wall of said cylindrical hollow body of revolution, an apparatus for forming fibers out of glass by using said cylindrical hollow body of revolution characterised in that said orifices in a center region of said circumferential wall are reduced in diameter in comparison with those in each of upper and lower regions of said circumferential wall.

3. An apparatus for forming glass fibers as claimed in claim 2, characterised in that said circumferential wall is made thicker in the center region than in each of the upper and lower regions of said circumferential wall.

4. An apparatus for forming glass fibers as claimed in claim 2 or claim 3 characterised in that said cirnumferential wall is thinness of all in the upper region, thickest of all in the center region, and intermediate between the respective thicknesses of the upper and center regions in the lower region.

5. An apparatus for forming glass fibers as r.laimed in any one of claims 2 to 4, characterised in that the diameters oF said small apertures in the center region of said circumferential wall of said cylindrical hollow body of revolution are made smaller than the diameters of said orifices in the upper region of said circumferential wall, and are equal to or smaller than the diameters of said orifices in the upper region of said circumferential wall.

6. An apparatus for forming glass fibers as claimed in claim 2, characterised in that orifices in said circumferential wall of said cylindrical hollow body of revolution are formed intermediate between the position adjacent to the boundary between the inside of said bottom wall of said body of revolution and the inside of said circumferential wall and the position adjacent to the boundary between the inside of said upper annular flange of said body of revolution and the inside of said circumferential wall.

7. A method of forming glass fibers substantially as hereinbefore described with reference to and as shown in Fig. 3 and Figs. 4 to 7 of the accompanying drawings.

8. An apparatus for forming glass fibers substantially as hereinbefore described with reference to and as shown in Figs. 1 and 2 as modified by Figs. 3, 5, 6 and 7 of the accompanying drawings.