CA1103030A - Method and apparatus for fiberizing attenuable materials - Google Patents
Method and apparatus for fiberizing attenuable materialsInfo
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- CA1103030A CA1103030A CA290,253A CA290253A CA1103030A CA 1103030 A CA1103030 A CA 1103030A CA 290253 A CA290253 A CA 290253A CA 1103030 A CA1103030 A CA 1103030A
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- jet
- blast
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- stream
- zone
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Abstract
METHOD AND APPARATUS FOR
FIBERIZING ATTENUABLE MATERIALS
ABSTRACT OF THE DISCLOSURE
Method and apparatus are disclosed for converting a stream of attenuable material into a fiber by employment of a gaseous jet penetrating a gaseous blast, thereby producing a zone of interaction in which the stream is attenuated to form a single long fiber. It is contemplated to employ a gaseous jet having lower velocity than the blast and at the same time lower temperature than the blast, thereby providing a jet of higher kinetic energy than the blast so that the jet will penetrate the blast.
It is also contemplated that the glass stream may be initially delivered to the jet to be carried thereby into the zone of interaction with the blast, thereby providing for preliminary attenuation in the jet before the stream reaches the blast.
FIBERIZING ATTENUABLE MATERIALS
ABSTRACT OF THE DISCLOSURE
Method and apparatus are disclosed for converting a stream of attenuable material into a fiber by employment of a gaseous jet penetrating a gaseous blast, thereby producing a zone of interaction in which the stream is attenuated to form a single long fiber. It is contemplated to employ a gaseous jet having lower velocity than the blast and at the same time lower temperature than the blast, thereby providing a jet of higher kinetic energy than the blast so that the jet will penetrate the blast.
It is also contemplated that the glass stream may be initially delivered to the jet to be carried thereby into the zone of interaction with the blast, thereby providing for preliminary attenuation in the jet before the stream reaches the blast.
Description
3(~
~, BACKGROUND:
The invention relates to the production of fine fibers from attenuable materials, particularly thermoplastic materials or materials which soften upon entering a molten state as a result of the application of heat and which harden or become relatively solid upon cooling.
The method and equipment of the invention are especially suited to the formation of fibers from mineral materials such as glass and the disclosure herein accordingly describes the invention as applied to the production of glass fibers from molten glass.
Many techniques are already known for production of fibers from molten glass, some of the techniques most widely used heretofore being identified and briefly described just below.
1. _ngitudinal Blowing: Other terms sometimes used i:nclude "blown fiber", "steam blown wool", "steam blown bonded mat", "low pressure air blow-ing", or "lengthwise jets".
~, BACKGROUND:
The invention relates to the production of fine fibers from attenuable materials, particularly thermoplastic materials or materials which soften upon entering a molten state as a result of the application of heat and which harden or become relatively solid upon cooling.
The method and equipment of the invention are especially suited to the formation of fibers from mineral materials such as glass and the disclosure herein accordingly describes the invention as applied to the production of glass fibers from molten glass.
Many techniques are already known for production of fibers from molten glass, some of the techniques most widely used heretofore being identified and briefly described just below.
1. _ngitudinal Blowing: Other terms sometimes used i:nclude "blown fiber", "steam blown wool", "steam blown bonded mat", "low pressure air blow-ing", or "lengthwise jets".
2. Strand: Other terms sometimes used are "contin-uous filament", or "textile fibers".
3. Aerocor: Another term sometimes used is "flame attenuation".
4. Centrifuging: Other terms sometimes used in-clude "rotary process", "centrifugal process", "tel process", or "supertel process".
There are numerous variants of each of the above four processes, and some efforts in the art to combine cer-- tain of the processes. Further, there are other techniques discussed in the prior art by which prior workers have at-tempted to make glass fibers. However, the variants, attempted combinations, and attempted other techniques, for the most part have not met with sufficient success to achieve a sep-arate and recognizable status in the art.
The four techniques above referred to may briefly be described as follows.
1. Longitudinal Blowing Longitudinal blowing (examples of which are referred to as items 1, 2, 3 and 4 in the bibliography herebelow) is a glass fiber manufacturing proces~ according to which melted glass flows from the forehearth of a furnace through orifices in one or two rows of tips protruding downwardly from a bushing, the glass being thereby formed into multiple glass streams which flow down into an attenuating zone where the streams pass between downwardly converging gaseous blasts.
The blast emitting means are located in close proximity to the streams so that the converging blasts travel in a downward direction substantially parallel to the direction ~ .
.
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of travel of the glass streams. Generally the glass streams bisect the angle between the converging blasts. The blasts are typically high pressure steam.
There are two longitudinal blowing techniques.
In the first technique the attenuating blasts engage already drawn fibers and the product resulting is typically a mat, commonly known as "steam blown bonded mat", suitable for reinforcement. In the second longitudinal blowing technique the attenuating blasts strike directly on larger streams of molten glass and the product resulting is typically an insulation wool commonly known as "steam blown wool".
In a variation (see item 5) of the first longitudi-nal blowing technique, the entire bushing structure and associated furnace are enclosed within a pressure chamber so that, as the streams of glass emerge from the bushing, the streams are attenuated by pressurized air emerging from the pressure chamber through a slot positioned directly beneath the glass emitting tips of the bushing, this varia-tion being commonly referred to as "low pressure air blow-ing", and products being commonly known as "low pressureair blown bonded mat and staple yarn".
2. Strand The strand glass fiber manufacturing process (see items 6 and 7) begins in the manner described above in con-nection with longitudinal blowing, that is, multiple glass streams are formed by flow through orifices in tips pro- -truding downwardly from a bushing. However, the strand process does not make use of any blast for attenuation pur-poses but, on the contrary, uses mechanical pulling which is accomplished at high speed by means of a rotating drum onto which the fiber is wound or by means of rotating rollers between which the fiber passes. The prior art in the field of the strand process is extensive but is of no real signi-ficance to the present invention. Strand techniques there-fore need not be further considered herein.
3. Aerocor In the aerocor process (see items 8 and 9) formaking glass fibers, the glass is fed into a high temperature and high velocity blast while in the form of a solid rod, rather than flowing in a liquid stream as in the longitudinal blowing and strand processes discussed abo~e. The rod, or sometimes a coarse filament, of glass is fed from a side, usually substantially perpendicularly, into a hot gaseous blast. The end of the rod is heated and softened by the blast so that fiber can be attenuated therefrom by the force of the blast, the fiber being carried away entrained in the blast.
4. Centrifuging In the centrifuging glass fiber manufacturing process (see items lO and ll) molten glass is fed into the .
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interior of a rapidly rotating centrifuge which has a plur-ality of orifices in the periphery. The glass flows through the orifices in the form of streams under the action of centrifugal force and the glass streams then come under the influence of a concentric and generally downwardly directed hot blast of flames or hot gas, and may also, at a location concentric with the first blast and farther out-board from the centrifuge, come under the action of another high speed downward blast, which latter is generally high pressure air or steam. The glass streams are thereby atten-uated into fine fibers which are cooled and discharged down-wardly in the form of glass wool.
In addition to the four categories of fiber form-ing techniques which have been very generally referred to and distinquished above, various refinements and variations of those techniques have also been known and repeated efforts have been made to optimize the manufacture of glass fibers by one or more of the processes which start with molten streams of glass. Various of these prior art techniques have been concerned with trying to optimize the attenuation process by extending or lengthening the attenuation zone, either by providing special means to accomplish the addition of heat to the streams of glass and to the embryonic fibers (see item 12), or through the use of confining jets (see items 13 and 14), or both (see item 15).
The approach taken in the just mentioned prior art technique suggests that the realization of optimum fiberi-zation lies in extending the length of a single attenuating zone.
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In contrast, in the preferred practice of the present invention, attenuation is accomplished by subjecting :
a glass stream to two sequential stages of attenuation, performed under different conditions, as will further appear.
Various other approaches have been suggested for introducing glass in the molten state into an attenuating blast (see items 16, 17, 18 and 19). In such attempts to introduce a stream of molten glass into an attenuating blast it has been noted that there often is a tendency for the glass stream to veer to a path of travel on the periphery of the blast, that is, to "ride" the blast, rather than penetrating into the core region of the blast where attenu-ating conditions are more effective. Suggestions have been made to deal with this "riding" problem, including the use of physical baffles as in Fletcher (item 16), and the trans-fer of substantial kinetic energy to the glass stream as, for example, by the modifications of the centrifuging pro-cess taught in Levecque (item 11), Paymal (item 18), and Battigelli (item 19).
An alternate approach to the problem, more closely akin to the aerocor process, has been the introduction of the glass in the form of a solid (item 9) or presoftened (item 20) glass rod or in the form of powdered glass (item 14).
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BIBLIOGRAPHY OF PRIOR USA PATENTS
(1) Slayter et al 2,133,236 (2) Slayter et al 2,206,058 (3) Slayter et al 2,257,767
There are numerous variants of each of the above four processes, and some efforts in the art to combine cer-- tain of the processes. Further, there are other techniques discussed in the prior art by which prior workers have at-tempted to make glass fibers. However, the variants, attempted combinations, and attempted other techniques, for the most part have not met with sufficient success to achieve a sep-arate and recognizable status in the art.
The four techniques above referred to may briefly be described as follows.
1. Longitudinal Blowing Longitudinal blowing (examples of which are referred to as items 1, 2, 3 and 4 in the bibliography herebelow) is a glass fiber manufacturing proces~ according to which melted glass flows from the forehearth of a furnace through orifices in one or two rows of tips protruding downwardly from a bushing, the glass being thereby formed into multiple glass streams which flow down into an attenuating zone where the streams pass between downwardly converging gaseous blasts.
The blast emitting means are located in close proximity to the streams so that the converging blasts travel in a downward direction substantially parallel to the direction ~ .
.
il~3~
of travel of the glass streams. Generally the glass streams bisect the angle between the converging blasts. The blasts are typically high pressure steam.
There are two longitudinal blowing techniques.
In the first technique the attenuating blasts engage already drawn fibers and the product resulting is typically a mat, commonly known as "steam blown bonded mat", suitable for reinforcement. In the second longitudinal blowing technique the attenuating blasts strike directly on larger streams of molten glass and the product resulting is typically an insulation wool commonly known as "steam blown wool".
In a variation (see item 5) of the first longitudi-nal blowing technique, the entire bushing structure and associated furnace are enclosed within a pressure chamber so that, as the streams of glass emerge from the bushing, the streams are attenuated by pressurized air emerging from the pressure chamber through a slot positioned directly beneath the glass emitting tips of the bushing, this varia-tion being commonly referred to as "low pressure air blow-ing", and products being commonly known as "low pressureair blown bonded mat and staple yarn".
2. Strand The strand glass fiber manufacturing process (see items 6 and 7) begins in the manner described above in con-nection with longitudinal blowing, that is, multiple glass streams are formed by flow through orifices in tips pro- -truding downwardly from a bushing. However, the strand process does not make use of any blast for attenuation pur-poses but, on the contrary, uses mechanical pulling which is accomplished at high speed by means of a rotating drum onto which the fiber is wound or by means of rotating rollers between which the fiber passes. The prior art in the field of the strand process is extensive but is of no real signi-ficance to the present invention. Strand techniques there-fore need not be further considered herein.
3. Aerocor In the aerocor process (see items 8 and 9) formaking glass fibers, the glass is fed into a high temperature and high velocity blast while in the form of a solid rod, rather than flowing in a liquid stream as in the longitudinal blowing and strand processes discussed abo~e. The rod, or sometimes a coarse filament, of glass is fed from a side, usually substantially perpendicularly, into a hot gaseous blast. The end of the rod is heated and softened by the blast so that fiber can be attenuated therefrom by the force of the blast, the fiber being carried away entrained in the blast.
4. Centrifuging In the centrifuging glass fiber manufacturing process (see items lO and ll) molten glass is fed into the .
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interior of a rapidly rotating centrifuge which has a plur-ality of orifices in the periphery. The glass flows through the orifices in the form of streams under the action of centrifugal force and the glass streams then come under the influence of a concentric and generally downwardly directed hot blast of flames or hot gas, and may also, at a location concentric with the first blast and farther out-board from the centrifuge, come under the action of another high speed downward blast, which latter is generally high pressure air or steam. The glass streams are thereby atten-uated into fine fibers which are cooled and discharged down-wardly in the form of glass wool.
In addition to the four categories of fiber form-ing techniques which have been very generally referred to and distinquished above, various refinements and variations of those techniques have also been known and repeated efforts have been made to optimize the manufacture of glass fibers by one or more of the processes which start with molten streams of glass. Various of these prior art techniques have been concerned with trying to optimize the attenuation process by extending or lengthening the attenuation zone, either by providing special means to accomplish the addition of heat to the streams of glass and to the embryonic fibers (see item 12), or through the use of confining jets (see items 13 and 14), or both (see item 15).
The approach taken in the just mentioned prior art technique suggests that the realization of optimum fiberi-zation lies in extending the length of a single attenuating zone.
3~3~
In contrast, in the preferred practice of the present invention, attenuation is accomplished by subjecting :
a glass stream to two sequential stages of attenuation, performed under different conditions, as will further appear.
Various other approaches have been suggested for introducing glass in the molten state into an attenuating blast (see items 16, 17, 18 and 19). In such attempts to introduce a stream of molten glass into an attenuating blast it has been noted that there often is a tendency for the glass stream to veer to a path of travel on the periphery of the blast, that is, to "ride" the blast, rather than penetrating into the core region of the blast where attenu-ating conditions are more effective. Suggestions have been made to deal with this "riding" problem, including the use of physical baffles as in Fletcher (item 16), and the trans-fer of substantial kinetic energy to the glass stream as, for example, by the modifications of the centrifuging pro-cess taught in Levecque (item 11), Paymal (item 18), and Battigelli (item 19).
An alternate approach to the problem, more closely akin to the aerocor process, has been the introduction of the glass in the form of a solid (item 9) or presoftened (item 20) glass rod or in the form of powdered glass (item 14).
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BIBLIOGRAPHY OF PRIOR USA PATENTS
(1) Slayter et al 2,133,236 (2) Slayter et al 2,206,058 (3) Slayter et al 2,257,767
5 (4) Slayter et al 2,810,157 (5) Dockerty 2,286,903
(6) Slayter et al 2,729,027
(7) Day et al 3,269,820
(8) Stalego 2,489,243 10(9) Stalego 2,754,541 (10) Levecque et al 2,991,507 (11) Levecque et al 3,215,514 (12) Stalego 2,687,551 (13) Stalego 2,699,631 15(14) Karlovitz et al 2,925,620 (15) Karlovitz 2,982,991 (16) Fletcher 2,717,416 (17) Eberle 3,357,808 (18) Paymal 3,634,055 20(19) Battigelli 3,649,232 (20) Stalego 2,607,075 General Statement of the Invention and Objects In contrast with all of the foregoing prior art techniques, it is a major objective of the present invention to provide certain improvements in the production of fibers from streams of molten glass or similar attenuable materials.
The technique of the present invention in part utilizes the fiber toration techniques or principles disclosed in our prior Canadian applications Serial No. 265,560, 12 Novem-ber, 1976, Serial No. 245,501, filed 11 February, 1976, and serial No. 196,097, filed 27 March, 1974 and issued July 13, 1979 as patent 1,059,321. Thus, the technique of the present invention makes use of the attenuating capability of a zone of interaction developed by the direction of a secondary jet of relatively small cross section transversely into a principle blast or jet of relatively large cross section. However, according to one aspect of the preferred practice of the present invention, instead of directly admitting or delivering a stream of molten glass to the zone of interaction, the glass stream is delivered from an appropriate orifice spaced an appreciable distance above the zone of interaction.
Moreover, in a typical technique according to the preferred practice of the present invention, the blast is discharged in a generally horizontal direction, the glass admission orifices are arranged in spaced relation above the blast, and at an intermediate elevation, secondary jets are directed downardly toward tne blast, the jet orifices being positioned adjacent to the decending glass streams, ~
and preferably inclined somewhat with respect to the verti- -cal, so that the glass streams enter the influence of the jets at a point above the upper boundary of the blast, but well below the glass orifices. Preferably also each secon-dary jet orifice and the associated glass stream are spaced from each other in a direction upstream and downstream of the direction of flow of the blast, with the jet orifice located, with respect to the direction of flow of the blast, on the upstream side of the glass stream.
The system of the invention, as just briefly des-cribed, functions in the following manner:
Each secondary jet, being spaced appreciably above the upper boundary of the blast, causes induction of the ambient air so that the jet develops a sheath or envelope of induced air which progressively increases in diameter as the upper boundary of the blast is approached. The jet thus is comprised of two portions, i.e. the core itself which is initially delivered from the jet orifice and the main body of the jet which is frequently referred to as the mixing zone, i.e. the zone represented by the mixture of the gas of the core with induced air.
In a typical embodiment, the jet core extends for a distance beyond the jet orifice equal to from 3 to 10 times the diameter of the jet orifice, depending primar-ily upon the velocity of the jet through the orifice. Since in installations of the kind here involved, the jet orifices _.9 _ 31~
are of only very small diameter, the extent to which the jet core is projected beyond the orifice is relatively short.
The iet core is conical and the mixing zone surrounds the jet core from the region of delivery from the jet orifice and is of progressively increasing diameter downstream of the jet, including a length of travel extended well beyond the tip of the jet core cone. In such a typical installa-tion, the spacing between the jet orifice and the boundary of the blast is such that the point of intersection of the blast lies beyond the tip of the core, although with certain proportions the jet core may come close to or somewhat pene-trate the blast. In any event, it is contemplated that at the point of intersection of the jet and blast, the body of the jet or jet stream retains sufficient kinetic energy to penetrate the blast and thereby develop a zone of interac-tion between the jet and the blast. This zone of interaction has the same general characteristics as the zone of interac-tion referred to and fully described in our prior applications Serial No. 245,501 and Serial No. 196,097 above identified~
With the foregoing in mind, attention is now directed to the-glass stream and its behavior in relation to the jet and blast. As already noted, the glass stream is deliv-ered from an orifice spaced above the blast and also spaced appreciably above the point of delivery or discharge of the secondary jet. Preferably the glass discharge orifice is so located as to deliver a stream of glass which by free-fall under the action of gravity will follow a path which ~ ~3~
would intersect the jet flow at a point appreciably above the upper boundary of the blast and thus also above the zone of interaction. As the glass stream approaches the jet, it is influenced by the currents of induced air and is thereby caused to deflect toward the jet above the point where the glass stream would otherwise have intersected the axis of the jet flow. The induction effect causes the stream of glass to approach the jet and, depending upon the position of the glass orifice, the induction effect will either cause the glass stream to enter the envelope of induced air surrounding the core, or will cause the glass stream to enter the main body of the jet at a point down-stream of the jet core. In either case, the glass stream will follow a path leading into the mixing zone and the glass stream will travel within the body of the jet down-wardly to the zone of interaction with the blast.
Thus, the glass stream is carried by the induced air currents into the mixing zone of the jet, but does not penetrate the jet core. The glass stream may be carried by the induced air even to the surface of the jet core, but still will not penetrate the core, which is desirable in order to avoid fragmentation of the glass stream. Since the glass stream is at this time in the influence of the mixing zone of the jet, the stream of glass will be sub-jected to a preliminary attenuating action and its velocitywill increase as the upper boundary of the blast is approach-ed, ~3~3a~
In addition to this attenuating action, which is aerodynamic in character, the attenuating stream is sub-jected to certain other dynamic forces tending to augment the attenuation. This latter attenuation action is caused by the tendency for the attenuated stream to move toward the center of the jet and then be reflected toward the boun-dary of the jet into the influence of the air being induced.
The attenuating stream is then again caused to enter into the interior of the jet. This repeated impulsion supple-ments the aerodynamic attenuating action.
In the region of interaction with the blast, thepartially attenuated stream of glass will be caused to enter the zone of interaction, in part because of the acceleration of the glass resulting from the action of gravity and from the preliminary attenuation described just above, and in part under the influence of the currents established in the zone of interaction itself, in the manner fully explained in our prior applications Serial No. 245,501 and Serial No. 196,097, above identified.
Thus it will be seen, that according to the inven-tion, the glass stream is subjected to two successive stages of attenuation. It is also to be observed that since the glass stream is caused to come under the influence of the jet by virtue of the induced currents surrounding the jet, the preliminary attenuation is accomplished without fragment-ing the glass stream. Moreover the succeeding or second stage of attenuation which is effected in the zone of inter-3~3~
action between the jet and the blast is also accomplished without fragmenting the fiber being formed. By this two-stage attenuatint technique it is thus possible to produce long fibers.
This multi-stage attenuation technique of the present invention has important advantages as compared with various prior techniques. Thus, it provides a technique for the production of long fibers while at the same time making possible greater separation between certain compon-ents of the equipment, notably the blast generator or bur-ner, with its nozzle or lips, the jet nozzle and the gas or air supply means associated therewith and the glass supply means including the bushing or similar equipment having glass orifices. This separation of components is not only of advantage from the standpoint of facilitating the struc-tural installation, but is further of advantage because the separation makes possible more convenient and accurate regulation of operating conditions, notably temperature of the blast, jets and glass supply means. Still another advantage of the arrangement according to the present inven-tion, is that the spacing of the glass supply means with its orifices for discharging streams of glass makes possible the utilization of larger glass orifices (which is sometimes desirable for special purposes or materials) because, in the distance of free fall provided for the glass streams, such streams decrease in diameter under the influence of the gravitational acceleration. The streams should of course ~;W3~
be of relatively small diameter at the time of initiation of attenuation, and the desired small diameter can readily be achieved, because of the distance of free fall, notwith-standing the employment of delivery orifices of relatively large size.
The foregoing has still another advantageous fea-ture, namely the fact that a higher temperature may be util-ized in the glass bushing or other supply means, thereby enabling use of attenuable materials at higher temperatures, because during the distance of free fall of the glass stream, the stream is somewhat cooled because of contact with the surrounding air, thereby bringing the stream down to an appropriate temperature for the initiation of attenuation.
Because of various of the foregoing factors, the system of the present invention facilitates the use of cer-tain types of molten materials in the making of fibers, for instance slag or certain special glass formulations which do not readily maintain uniformity of flow through discharge orifices of small size. However, since both larger diameter discharge orifices and higher temperatures may be used in the supply of the molten material, it becomes feasible to establish uniformity of feed and attenuation even with certain classes of attenuable materials which could not otherwise be employed in a technique based upon production of fibers by attenuation of a stream of molten material.
It is also noted that various of the four prin-ciple prior art techni~ues referred to above are subject to a number of limitations and disadvantages. For example, various of the prior techniques are limited from the stand-s point of production capacity or "orifice pull rate", i.e.
the amount of production accomplished within a given time by a single fiber producing center. In other cases, the fiber product contains undesirable quantities of unfiberized material. Strand type of operations, while effective for producing strand material, are not best suited for produc-tion of insulation type of fiber blanket and other similar types of products. Centrifuging, while effective for pro-ducing fiber insulation blanket has the disadvantage that the centrifuge must rotate at high speed, thus necessitating special working parts and maintenance, and further because the centrifuge is required to be formed of special alloys capable of withstanding the high temperatures.
Another general objective of the present invention is to provide a technique which overcomes various of the foregoing disadvantages or limitations of the prior art techniques referred to.
Moreover, the technique of the present invention provides for high production rates and utilizes only static equipment.
25In accordance with another aspect of the present invention it is contemplated that certain novel temperature and velocity relationships of the blast and the jet be em-.
' ~ . ' ,. - ' ' ., ~ . ~ .
~1~ 3~ 3119 ployed, providing additional advantages as compared with the techniques of our prior application Serial No. 196,097 hereinabove referred to, regardless of whether the stream of molten glass is delivered directly into the zone of inter-action of the jet and the blast, or is delivered initiallyinto the influence of the jet to be carried thereby into the zone of interaction with the blast. These novel relation-ships will be fully developed and explained herelnafter, following the description of the embodiment of the invention illustrated in the accompanying drawings.
In summary of the above, therefore, the present invention broadly provides a process for forming fibers from attenuable material, characterized by generating a gaseous jet, generating a gaseous blast in a path intercepting the jet, the cross sectional dimension of the jet being smaller than that of the blast in a direction transverse to the blast and the jet being of velocity in the range of from sub-stantially lower than that of the blast to not substantially higher than that of the blast but also being of temperature sufficiently below that of the blast to provide a density and thus a kinetic energy per unit of volume higher than that of the blast and thereby provide for penetration of the jet into the blast to produce a zone of interaction of the jet and blast, and delivering a stream of attenuable material 2~ into the zone of interaction.
Detailed Description of the Invention -The accompanying drawings illustrate, on an enlarged scale, a preferred embodiment of the present invention, and in these drawings -, - . . , - . . , . :
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Figure 1 is a fragmentary isometric view showing e~uipment including means for developing a blast, means or developing a series of secondary jets above the blast and directed downwardly toward the blast, together with means for establishing giass streams delivered by gravity from a r~gion above the jets downwardly into the zone of in-fluence of the -l~a~
,~
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jets and ultimately into the influellce of the zone of inter-action with the blast;
Figure 2 is a vertical sectional view through equip-ment for establishing a single fiberizing station as arranged according to the present invention; and lob a -a p/ ,~
-~ 3g:P3~) Figure 3 is a view similar to Figure 2 but more diagrammatic and further illustrating certain dimensional relationships to be taken into account in establishing oper-ating conditions in accordance with the preferred practice of the present invention.
In the drawings, the glass supply means includes a crucible or bushing 1 which may be supplied with molten glass in any of a variety of ways, for instance by means of the forehearth indicated at 2 in Figure 3. Glass supply orifices 3 deliver streams of molten glass downwardly under the action of gravity as indicated at S.
A gaseous blast is discharged in a generally hori-zontal direction from the discharge nozzle 4, the blast being indicated by the arrow 5. The blast may originate 15 in a generator, usually comprising a burner, so that the ;
blast consists of the products of combustion, with or with-out supplemental air.
As will be seen from the drawings, the blast is directed generally horizontally below the orifices 3 from which the glass streams S are discharged.
At an elevation intermediate the crucible and the blast discharge device 4, jet tubes 6 are provided, each having a discharge orifice 7, the jet tubes receiving gas from the manifold 8 which in turn may be supplied through the connection fragmentarily indicated at 9.
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As is disclosed in various of our prior appli-cations above identified, the gases for delivery to and through the jet tubes 6 may originate in a gas generator taking the form of a burner and the products of combustion may serve for the jet, either with or without supplemental air. Preferably such combustion gases are diluted with air so as to avoid excessively high temperature of the gas delivered through the jet tubes. On the other hand, in the preferred practice of the present invention and as will be explained more fully hereinafter, the gas employed for the jet may comprise air at temperatures well below those of gases derived from a burner.
Each jet tube 6 and its orifice 7 is arranged to discharge a gaseous jet downwardly at a point closely adjacent to the feed path of one of the glass streams S
and preferably at the side of the stream S which, with respect to the direction of flow of the blast 5, is upstream of the glass stream. Moreover, each jet tube 6 and its orifice 7 is arranged to discharge the jet in a path directed downwardly toward the blast and which is inclined to the vertical and so that the projection of the paths of the glass stream and the jet intersect at a point spaced above the upper boundary of the blast 5.
It is contemplated that the vertical dimension of the blast and also the width thereof be considerably greater than the cross sectional dimensions of each secon-dary jet, so that adequate volume of the blast will be avail-~3~ `
able for each jet to develop a zone of interaction with the blast. For this purpose also, it is further contem-plated that the kinetic energy of the jet in relation to that of the blast, in the operational zone of the jet and blast, should be sufficiently high so that the jet will penetrate the blast. As pointed out in our applications above referred to, this requires that the kinetic energy be substantially higher than that of the blast, per unit of volume. Still further, the jet preferably has a velocity considerably in excess of the velocity of the glass stream as fed under the action of gravity downwardly toward the point of contact with the jet and sometimes also in excess of the velocity of the blast, depending upon the tempera-tures of the jet and blast, as will be explained more fully hereinafter.
The operation of each fiberizing center is as follows:
From the drawings and especially from Figure 2, it will be seen that the core C of the jet causes the induc-tion of currents of air indicated by the lines A, the amountof air so induced progressively increased along the path of the jet. When the body of the jet, i.e. the gas of the core intermixed with the induced air, reaches the boundary of the blast, a zone of interaction is established in the region indicated by cross-lining marked I in Figure 2.
As the stream S of molten glass descends and appro~
aches the jet delivered from the orifice 7, the currents `
of air induced by the action of the jet cause the stream of glass to deflect toward the jet core as indicated at 10. Although the glass orifice 3 may be of substantially larger diameter or cross section than the jet orifice 7, the gravity feed of the glass stream S results in substantial reduction in diameter of the glass stream, so that when the stream meets the jet, the diameter of the stream is much smaller than the diameter of the glass orifice. With the higher velocity of the jet, as compared with that of glass stream, even when the glass stream meets the jet in the upstream region adjacent the jet core, the glass stream will not penetrate the jet core. However, because of the induced air currents surrounding the jet, the glass stream is caused to "ride" on the surface of the jet core within the surrounding sheath of induced air or to enter the body of the jet downstream of the jet core.
The action of the induced air in bringing the glass stream to the jet stabilizes the feed of the glass stream and will also assist in compensating for minor mis-alignment of the glass orifice with respect to the jet ori-fice. Because of the reliance upon induction effects of an isolated jet, the glass stream is brought into the mixing zone of the gas or breakage of the stream or the fiber being formed. This action is enhanced by virtue of the fact that in the arrangement as above described and illustrated, the glass stream is not subjected to any sharp angled change in its path of movement before it has been subjected to some appreciable attenuation, thereby reducing its diameter and inertia.
3~3~) In consequence of the glass stream being carried in the mixing zone of the jet, the glass stream is partially attenuated, this action representing the first stage of the two-stage attenuation above referred to. In turn, in consequence of this partial attenuation, the length of the embryonic fiber is increased, and this increase in ~ength is accommodated by an undulating or whipping action, thereby forming loops, as indicated at 12. It is to be noted, how-ever, that the glass stream remains intact, the loops of the embryonic fiber being carried downwardly in the mixing zone.
At the point where the blast 5 intercepts the jet, the jet penetrates the blast. This penetration of the blast by the jet establishes currents in the zone of interaction of the jet with the blast, which currents carry the partially attenuated glass stream into the interior of the blast and in consequence a second staye of atten-uation occurs. This results in further increase in the length of the fiber being formed. The increase in fiber length is accommodated by additional undulating or whipping action, forming further enlarged loops. Thus a single stream of molten glass is converted into a single glass fiber by a two-stage attenuation operation. It will be understood that in effecting this two-stage attenuation, the temperature of the glass and the temperature of the jet, as well as the temperature of the blast, are estab-lished at values which will retain the glass in attenuable ~., 3~
condition throughout the first stage of attenuation and throughout the second stage until the attenuation has been completed in the zone of interaction between the jet and the blast.
In connection with the arrangement of the inven-tion, it is to be understood that fiberizing centers may be arranged in multiple, as illustrated in Figure 1. This is accomplished by employing a blast 5 which is broad or of large dimension in the direction perpendicular to the plane of Figure 2, and by employing a similarly extended crucible 1 having a multiplicity of glass orifices, and further by employing a multiplicity of jet tubes 6 each having an orifice adjacent to one of the streams S of glass being delivered from the several glass orifices, all as shown in Figure 1. Such a multiplicity of jet tubes may be supplied with the jet gas from a common manifold 8.
As hereinabove indicated, the present invention contemplates employment of certain combinations of lower jet velocities and temperatures than used in the arrange-ments described in our earlier applications Serial Nos.
245,501 and 196,097, in which prior applications the stream of glass is delivered directly into the zone of interaction between the jet and blast. Such lower jet velocities and temperatures are also referred to in our prior application Serial No. 265,560, in which the stream of glass is deliv-ered first into the influence of the jet, to be carried thereby into the zone of interaction with the blast.
~3~3t3 Such use of lower jet velocities and temperatures is thus applicable not only to toration techniques in which the glass stream is initially delivered into the influence of the jet, to be carried thereby into the æone of inter-action with the blast, but is also applicable to torationtechniques in which the stream of glass is initially deliv-ered into the zone of interaction of the jet with the blast.
Certain operating characteristics and advantages are to be noted in connection with the employment of lower jet velocities and temperatures and these are explained herebelow.
It is first to be noted that in any of the tora-tion techniques referred to above it is contemplated that the jet have kinetic energy per unit of volume higher than that of the blast in the operational area of the jet and blast, this being a requirement for penetration of the jet into the blast. This is necessary in order to develop the toration zone, i.e., the zone of interaction characterized by high velocity currents under the influence of which the attenuation of the glass stream takes place as is fully explained in prior applications referred to and especially in application Serial No. 196,097. With both the jet and the blast supplied with operating fluid from burners, the jet and the blast would normally both have temperatures above at least several hundred degrees centigrade. For example Table III in the above mentioned application, refers to jet and blast temperatures of 800C and 1580C, respective-ly. In contrast to the above, and by way of example, it is contemplated according to the present invention that the jet ~3~3~
temperature may approximate ambient or room temperature.
Furthermore, certain of the prior toration techniques util-ized a jet having a velocity usually higher than the velo-city of the blast. Thus, Table III of the prior application S referred to indicates a jet velocity of 580 m/sec, and a blast velocity in the range from 224 m/sec to 283 m/sec.
According to the present invention it is contem-plated to use a jet velocity considerably lower than that referred to just above and even lower than the blast velo-city. The lower temperature and velocity contemplated bythe present invention still provides the required kinetic energy ratio between the jet and blast, i.e., a jet having kinetic energy higher than that of the blast so that the jet will penetrate the blast and create a zone of inter-action. The reason why this desired kinetic energy ratiois still present with the lower velocity of the jet is be-cause of the higher density of the jet fluid at the lower temperature. The density, of course, increases with de-crease of temperature and since the kinetic energy is deter-mined not by the velocity alone but also by the densityof the jet fluid, a jet may readily be provided having a higher kinetic energy per unit of volume than the blast, even at velocities lower than the velocity of the blast.
By employing the lower 3et temperatures (for in-stance a temperature approximating ambient or room temper-ature) a number of advantages are attained. In the first 3~3~
place when utilizing such temperature for the jet, it is feasible to employ a commonly available source of compressed air as the source of fluid for the jet. The lower tempera-ture also makes it practical to use commonly available mater-ials, such as stainless steel for the jet generating device,rather than more sophisticated and expensive materials, such as platinum alloys or ceramics, which are needed where very high temperature jets are used.
The lower temperatures for the jet also reduce oxidation problems, and further reduce or avoid certain thermal warpage problems, and in addition the maintenance of more uniform temperature from jet to jet in a multiple center fiberizing installation is more readily achieved.
Still further, the arrangement of the lower tempera-tures for the jet facilitates introducing the fiber being formed into a re].atively cool environment as soon as the fiber is attenuated, this consideration being of importance in the toration technique, for reasons which are fully brought out in our prior application above referred to.
The capability of utilizing commonly available sources of compressed air, which is made possible by virtue of employing lower jet temperatures, also has a distinct advantage in that the air is much less expensive than high temperature fluids, for example products of combustion or steam.
3'~
It is also to be kept in mind that by employing a jet fluid at a temperature approximating ambient or room temperature, consumption of energy to heat the ~et is elimi-nated.
The foregoing advantages are achieved regardless of whether the toration technique is one in which the stream of glass is initially delivered directly into the zone of interaction or whether the stream of glass is initially delivered into the influence of the jet, to be carried there-by into the zone of interaction, and in the latter case, the advantages are attained whether or not the jet is de-flected from its initial path. Where a jet deflector is used the low temperature jet is of special advantage because it assists in maintaining dimensional accuracy of the deflec-tor in relation to the jet generator including the jet ori-fice.
In addition to the foregoing, in the two-stage attenuation technique disclosed herein, as well as in the arrangements of our copending application Serial No. 265,560, in which the stream of attenuable material is initially delivered to the jet, the lower jet velocities and tempera-tures may assist in avoiding fragmentation of the stream of attenuable material.
The disclosure of the above identified applica-tions Serial No. 245,501 and Serial No. 196,097, may be referred to for further information in connection with the general arrangements providing for accommodation of multiple fiberizing centers and also for numerous other features, such, for example, as fiber collection means, glass feed systems and blast and jet generating and delivery systems, and including also information concerning the parameters involved in establishing a zone of interaction of a jet and blast.
In connection with various dimensional relation-ships involved in the equipment of the present invention, particular attention is directed to Figure 3 on which cer-tain symbols have been applied to identify some of the dimen-sions. These are identified in the following table which also gives an average or typical value in milimeters, as well as a usable range for each such value.
AVERAGE VARIA-FEATURE DIMENSION SYMBOL VALUE TION
(mm) LIMITS
tmm) 20 Bushing Diameter of dT 4 1 - 10 glass orifice Distance between 10 5 2 holes Jet Inner diameter d 1 0.3 - 3 of jet tube t Outer diameter 1.5 0.7 - 5 of jet tube Separation between 10 5 2 tubes 30 Blast Vertical distance lB 25 10 - 50 between the lips or thickness of the discharge section Width of the 300 20 - 500 discharge section :
~3~3~
In addition to the foregoing dimensions, certain spacing relationships and also angular relationships should be observed, as indicated in the following table which gives an average or typical value in millimeters or degrees, as well as a usable range for each such value.
AVERAGE VARIATION
FEATURES SYMBOL VALUE LIMITS
(mm or (mm or degree) degree) Vertical distance of jet JB 45 ~0 ~ 60 discharge orifice to the upper boundary of flow of the blast Vertical distance from Z 85 0 - 150 the discharge opening of JF
the glass stream to the jet discharge orifice Horizontal distance from X 5 1 - 15 the axis of the glassJF
stream of the jet dis-charge orifice Horizontal distance from XBF 5 0 - 30 the axis of the glass stream to the lip of the blast nozzle Angle of jet tube to the ~f 10 3 - 45 axis of glass stream Angle of jet tube to the JB 80 87 - 45 direction of Plow of the blast With further reference to parameters of operation when employing the technique of the present inventionr it is first pointed out that it is of course important that the glass be discharged from the glass orifice in a continu-ous stable stream. For this purpose, the rate of glassflow, the temperature of the bushing and the diameter of 1~3~3~
the glass discharge orifice should preferably be above cer-tain predetermined limits. Thus, the pull rate of glass should be greater than 60 kg/hole for each 24 hour period;
the bushing temperature should be greater than 1250C, and the diameter of the glass discharge orifice should be greater than 2.5 milimeters. With at least certain types of glass formulations, observing these limits may assist in avoiding pulsations which have a tendency to accentuate until dis-tinct droplets are formed. This phenomenon is incompatible with proper fiberization. In a typical or average working condition, the following values are appropriate; 100 kg/hole per day, bushing temperature 1400C, glass orifice diameter 3 milimeters.
Additional operating ranges are as follows:
15 Velocity - jet 200 m/sec - 900 m/sec blast 200 m/sec - 800 m/sec Pressure - jet .5 to 50 bars blast .05 to .5 bars Temperature - jet 20 to 1800C
blast 1300 to 1800C
Kinetic Energy Ratio - jet to blast 10/1 - 1000/1 A typical operation according to the present inven-tion may be carried out as given in the Example below.
.
~1~3~
Example Glass formulation:
SiO2 46.92 Fe23 1.62 A1203 9.20 MnO 0.16 CaO 30.75 MgO 3.95 Na20 3.90 K20 3.50 All parts by weight.
Physical Properties Viscosity 30 poises at 1310C
100 poises at 1216C
300 poises at 1155C
Glass - orifice 3 mm flow 100 kg/day per orifice Blast - temperature 1550C
pressure .25 bar velocity 530 m/s Jet - temperature 20C
pressure 6 bar velocity 330 m/s orifice diameter 1 mm 3~
Ratio of Kinetic energies ~et = 24 Blast Fiber ~iameter - 6 ~icrons In connection with the tabulations just above, particular attention is callea to the figures given for tle temperature and velocity of the jet and blast. ~iere it will be seen that the velocity of the jet is even lower than the velocity of tihe blast, which is in marked contrast to the examples given in our prior application Serial No. 196,097 above referred to, but it will further be noted that the ter,lperature of the jet is also very much lower than the tera~erature of the blast. Thus, notwithstanding the employ-ent of a jet of lower velocity than that of the blast as is noted in tile preceeding tabulation, the ratio of kinetic energies of the jet to the blast i3 of the order of 24 to 1.
This relatively high kinetic energy ratio per unit of volume of the jet and blast results in penet.ration of the jet into the blast, as :is desired, in order to de~elop ~he toration ~one or zone of interaction of the jet and bla.st.
The foregoing represents an e~a~lple of the tora-tion technique according to Figure 2 of the drawings, i.e., a technique in whicn the strea~l of attenuable ~aterial (in this case the glass) i9 subjected to a two-stage attenuation Operation, because the glass is introducéd into the influ-ence of the jet before the jet reaches the blast, thereby providing a preliminary stage of attenuation under the influ-ence of the jet, and a second stage of attenuation in conse quence of introduction of the partially attenuated stream ~' .
-1~3~3~
of glass into the zone of interaction of the jet with the ; blast.
In connection with the above it is pointed out that a jet of adequate velocity is readily obtained when using a source of compressed air as the source of the jet fluid. This is in distinct contrast to the employment of relatively high jet temperatures, with which it is techni-cally more difficult to obtain high velocity, and because of the lower density of the fluid at high temperature it is therefore much more difficult to attain sufficient velocity to achieve the kinetic energy ratio required to effect penetration of the jet into the blast.
As above noted, it is convenient to employ jet temperatures near ambient or room temperature, but it will be understood that the jet temperature need not necessarily be as low as ambient or room temperature. Preferably the jet temperature is well below the softening point of the thermoplastic material being attenuated, and in the case of attenuation of glass or similar mineral materials, the jet temperature is preferably selected at a value below 200C, and most desirably below 100C, and this is true whether the jet is employed in a toration operation in which the stream of glass is subjected to two stages of attenua-tion, or in various other toration techniques in which only a single stage of attenuation is employed by introducing the stream of glass directly into the zone of interaction of the jet with the blast, as is disclosed in prior applica-tions Serial Nos. 245,501 and 196,097 above identified.
3t~
With respect to the temperatures and velocities of the jet and blast which are contemplated according to the present invention, it is pointed out that in the tora-tion of thermoplastic materials such as glass, it is desir-able to employ a blast temperature at least as high as atemperature approximating the lower end of the softening range of the thermoplastic material to be attenuated. Main-tenance of such a temperature is desirable because substan-tial attenuation is desired within the blast. Thus, with most glass formulations and with similar types of thermo-plastic mineral materials (either naturally occurring or synthetic), the lower end of the softening range is between about 600 C and 900C. With most of such materials it is preferred to employ a blast having a temperature of at least 1000C. Although the blast temperature may be higher than just indicated, it is desirable to avoid excessive temperature because, if the temperature is too far above the softening range, the attenuation will be adversely affected, with resultant fragmentation of the fibers, or formation of slugs or shot.
Blast temperatures of the order of magnitude just referred to are advantageously achieved by employment of a gaseous fuel burner, and the utilization of the gaseous products of combustion as the blast.
In contrast with the foregoing, it is advantageous for various reasons already noted above to employ a jet of much lower temperature. The jet therefore need not be ~ 3~3~
produced by the combustion of fuel, with resultant unneces-sary fuel and energy consumption, but in contrast a common source of compressed air may be utilized for the supply of the jet gas, thereby providing a jet at a temperature near ambient or room temperature. Some variation from am-bient temperature may be employed, as may result for example from action of a compressor, or by exposure of a storage tank to other equipment or atmospheric conditions tending to either raise or lower the temperature somewhat with re-spect to ambient. For most purposes, a jet temperaturebelow about 100C is useable and would be available from various forms of compressed air systems in common use.
With the temperature relationship of the jet and blast above referred to, it is contemplated that the velo-cities of the jet and blast be such that the kinetic energyof the jet per unit of volume should be higher than that of the blast, so that the jet will penetrate the blast and thereby provide the desired toration zone or zone of inter-action. With a gaseous jet at a temperature near ambient or room temperature, the density of the air or gas of the jet is much higher than would be the case with products of customary combustion of fuel with air at temperatures of the order of those contemplated for use for the blast.
In view of this, the desired kinetic energy of the jet may be obtained while still utilizing a jet velocity even well below the velocity of the blast. Indeed, in a typical case with blast velocities of the order of 200 m/sec to 800 m/sec, 3~3~
which is a suitable range as already indicated hereinabove, the jet velocity may even be considerably lower than the blast velocity. This in turn makes possible a further econ-omy in that it is not necessary, (in order to provide the desired kinetic energy ratio and thus achieve penetration of the jet into the blast) to impart high velocity to the jet.
With a blast comprising products of combustion at a temperature above about 1000C and a velocity in the range from about 250 m/sec to 800 m/sec, and with a jet comprising air (or a gas of similar density) at a temperature below about 100C, the desired predominance of kinetic energy of the jet over the blast can be attained by employment of a jet velocity less than about that of the blast, for instance in the range of from about 200 m/sec to about 400 m/sec.
It is also mentioned that when attenuating certain materials having relatively high melting temperatures or with which it is desired to use high temperatures for pur-pose of feeding the material, the initial delivery of thematerial into the influence of a jet of relatively low temper-ature is desirable in order to bring the temperature of the stream of attenuable material down to the optimum temper-ature for the attenuation to be effected in the blast.
The technique of the present invention in part utilizes the fiber toration techniques or principles disclosed in our prior Canadian applications Serial No. 265,560, 12 Novem-ber, 1976, Serial No. 245,501, filed 11 February, 1976, and serial No. 196,097, filed 27 March, 1974 and issued July 13, 1979 as patent 1,059,321. Thus, the technique of the present invention makes use of the attenuating capability of a zone of interaction developed by the direction of a secondary jet of relatively small cross section transversely into a principle blast or jet of relatively large cross section. However, according to one aspect of the preferred practice of the present invention, instead of directly admitting or delivering a stream of molten glass to the zone of interaction, the glass stream is delivered from an appropriate orifice spaced an appreciable distance above the zone of interaction.
Moreover, in a typical technique according to the preferred practice of the present invention, the blast is discharged in a generally horizontal direction, the glass admission orifices are arranged in spaced relation above the blast, and at an intermediate elevation, secondary jets are directed downardly toward tne blast, the jet orifices being positioned adjacent to the decending glass streams, ~
and preferably inclined somewhat with respect to the verti- -cal, so that the glass streams enter the influence of the jets at a point above the upper boundary of the blast, but well below the glass orifices. Preferably also each secon-dary jet orifice and the associated glass stream are spaced from each other in a direction upstream and downstream of the direction of flow of the blast, with the jet orifice located, with respect to the direction of flow of the blast, on the upstream side of the glass stream.
The system of the invention, as just briefly des-cribed, functions in the following manner:
Each secondary jet, being spaced appreciably above the upper boundary of the blast, causes induction of the ambient air so that the jet develops a sheath or envelope of induced air which progressively increases in diameter as the upper boundary of the blast is approached. The jet thus is comprised of two portions, i.e. the core itself which is initially delivered from the jet orifice and the main body of the jet which is frequently referred to as the mixing zone, i.e. the zone represented by the mixture of the gas of the core with induced air.
In a typical embodiment, the jet core extends for a distance beyond the jet orifice equal to from 3 to 10 times the diameter of the jet orifice, depending primar-ily upon the velocity of the jet through the orifice. Since in installations of the kind here involved, the jet orifices _.9 _ 31~
are of only very small diameter, the extent to which the jet core is projected beyond the orifice is relatively short.
The iet core is conical and the mixing zone surrounds the jet core from the region of delivery from the jet orifice and is of progressively increasing diameter downstream of the jet, including a length of travel extended well beyond the tip of the jet core cone. In such a typical installa-tion, the spacing between the jet orifice and the boundary of the blast is such that the point of intersection of the blast lies beyond the tip of the core, although with certain proportions the jet core may come close to or somewhat pene-trate the blast. In any event, it is contemplated that at the point of intersection of the jet and blast, the body of the jet or jet stream retains sufficient kinetic energy to penetrate the blast and thereby develop a zone of interac-tion between the jet and the blast. This zone of interaction has the same general characteristics as the zone of interac-tion referred to and fully described in our prior applications Serial No. 245,501 and Serial No. 196,097 above identified~
With the foregoing in mind, attention is now directed to the-glass stream and its behavior in relation to the jet and blast. As already noted, the glass stream is deliv-ered from an orifice spaced above the blast and also spaced appreciably above the point of delivery or discharge of the secondary jet. Preferably the glass discharge orifice is so located as to deliver a stream of glass which by free-fall under the action of gravity will follow a path which ~ ~3~
would intersect the jet flow at a point appreciably above the upper boundary of the blast and thus also above the zone of interaction. As the glass stream approaches the jet, it is influenced by the currents of induced air and is thereby caused to deflect toward the jet above the point where the glass stream would otherwise have intersected the axis of the jet flow. The induction effect causes the stream of glass to approach the jet and, depending upon the position of the glass orifice, the induction effect will either cause the glass stream to enter the envelope of induced air surrounding the core, or will cause the glass stream to enter the main body of the jet at a point down-stream of the jet core. In either case, the glass stream will follow a path leading into the mixing zone and the glass stream will travel within the body of the jet down-wardly to the zone of interaction with the blast.
Thus, the glass stream is carried by the induced air currents into the mixing zone of the jet, but does not penetrate the jet core. The glass stream may be carried by the induced air even to the surface of the jet core, but still will not penetrate the core, which is desirable in order to avoid fragmentation of the glass stream. Since the glass stream is at this time in the influence of the mixing zone of the jet, the stream of glass will be sub-jected to a preliminary attenuating action and its velocitywill increase as the upper boundary of the blast is approach-ed, ~3~3a~
In addition to this attenuating action, which is aerodynamic in character, the attenuating stream is sub-jected to certain other dynamic forces tending to augment the attenuation. This latter attenuation action is caused by the tendency for the attenuated stream to move toward the center of the jet and then be reflected toward the boun-dary of the jet into the influence of the air being induced.
The attenuating stream is then again caused to enter into the interior of the jet. This repeated impulsion supple-ments the aerodynamic attenuating action.
In the region of interaction with the blast, thepartially attenuated stream of glass will be caused to enter the zone of interaction, in part because of the acceleration of the glass resulting from the action of gravity and from the preliminary attenuation described just above, and in part under the influence of the currents established in the zone of interaction itself, in the manner fully explained in our prior applications Serial No. 245,501 and Serial No. 196,097, above identified.
Thus it will be seen, that according to the inven-tion, the glass stream is subjected to two successive stages of attenuation. It is also to be observed that since the glass stream is caused to come under the influence of the jet by virtue of the induced currents surrounding the jet, the preliminary attenuation is accomplished without fragment-ing the glass stream. Moreover the succeeding or second stage of attenuation which is effected in the zone of inter-3~3~
action between the jet and the blast is also accomplished without fragmenting the fiber being formed. By this two-stage attenuatint technique it is thus possible to produce long fibers.
This multi-stage attenuation technique of the present invention has important advantages as compared with various prior techniques. Thus, it provides a technique for the production of long fibers while at the same time making possible greater separation between certain compon-ents of the equipment, notably the blast generator or bur-ner, with its nozzle or lips, the jet nozzle and the gas or air supply means associated therewith and the glass supply means including the bushing or similar equipment having glass orifices. This separation of components is not only of advantage from the standpoint of facilitating the struc-tural installation, but is further of advantage because the separation makes possible more convenient and accurate regulation of operating conditions, notably temperature of the blast, jets and glass supply means. Still another advantage of the arrangement according to the present inven-tion, is that the spacing of the glass supply means with its orifices for discharging streams of glass makes possible the utilization of larger glass orifices (which is sometimes desirable for special purposes or materials) because, in the distance of free fall provided for the glass streams, such streams decrease in diameter under the influence of the gravitational acceleration. The streams should of course ~;W3~
be of relatively small diameter at the time of initiation of attenuation, and the desired small diameter can readily be achieved, because of the distance of free fall, notwith-standing the employment of delivery orifices of relatively large size.
The foregoing has still another advantageous fea-ture, namely the fact that a higher temperature may be util-ized in the glass bushing or other supply means, thereby enabling use of attenuable materials at higher temperatures, because during the distance of free fall of the glass stream, the stream is somewhat cooled because of contact with the surrounding air, thereby bringing the stream down to an appropriate temperature for the initiation of attenuation.
Because of various of the foregoing factors, the system of the present invention facilitates the use of cer-tain types of molten materials in the making of fibers, for instance slag or certain special glass formulations which do not readily maintain uniformity of flow through discharge orifices of small size. However, since both larger diameter discharge orifices and higher temperatures may be used in the supply of the molten material, it becomes feasible to establish uniformity of feed and attenuation even with certain classes of attenuable materials which could not otherwise be employed in a technique based upon production of fibers by attenuation of a stream of molten material.
It is also noted that various of the four prin-ciple prior art techni~ues referred to above are subject to a number of limitations and disadvantages. For example, various of the prior techniques are limited from the stand-s point of production capacity or "orifice pull rate", i.e.
the amount of production accomplished within a given time by a single fiber producing center. In other cases, the fiber product contains undesirable quantities of unfiberized material. Strand type of operations, while effective for producing strand material, are not best suited for produc-tion of insulation type of fiber blanket and other similar types of products. Centrifuging, while effective for pro-ducing fiber insulation blanket has the disadvantage that the centrifuge must rotate at high speed, thus necessitating special working parts and maintenance, and further because the centrifuge is required to be formed of special alloys capable of withstanding the high temperatures.
Another general objective of the present invention is to provide a technique which overcomes various of the foregoing disadvantages or limitations of the prior art techniques referred to.
Moreover, the technique of the present invention provides for high production rates and utilizes only static equipment.
25In accordance with another aspect of the present invention it is contemplated that certain novel temperature and velocity relationships of the blast and the jet be em-.
' ~ . ' ,. - ' ' ., ~ . ~ .
~1~ 3~ 3119 ployed, providing additional advantages as compared with the techniques of our prior application Serial No. 196,097 hereinabove referred to, regardless of whether the stream of molten glass is delivered directly into the zone of inter-action of the jet and the blast, or is delivered initiallyinto the influence of the jet to be carried thereby into the zone of interaction with the blast. These novel relation-ships will be fully developed and explained herelnafter, following the description of the embodiment of the invention illustrated in the accompanying drawings.
In summary of the above, therefore, the present invention broadly provides a process for forming fibers from attenuable material, characterized by generating a gaseous jet, generating a gaseous blast in a path intercepting the jet, the cross sectional dimension of the jet being smaller than that of the blast in a direction transverse to the blast and the jet being of velocity in the range of from sub-stantially lower than that of the blast to not substantially higher than that of the blast but also being of temperature sufficiently below that of the blast to provide a density and thus a kinetic energy per unit of volume higher than that of the blast and thereby provide for penetration of the jet into the blast to produce a zone of interaction of the jet and blast, and delivering a stream of attenuable material 2~ into the zone of interaction.
Detailed Description of the Invention -The accompanying drawings illustrate, on an enlarged scale, a preferred embodiment of the present invention, and in these drawings -, - . . , - . . , . :
~ ~3~
Figure 1 is a fragmentary isometric view showing e~uipment including means for developing a blast, means or developing a series of secondary jets above the blast and directed downwardly toward the blast, together with means for establishing giass streams delivered by gravity from a r~gion above the jets downwardly into the zone of in-fluence of the -l~a~
,~
~i~3(~
jets and ultimately into the influellce of the zone of inter-action with the blast;
Figure 2 is a vertical sectional view through equip-ment for establishing a single fiberizing station as arranged according to the present invention; and lob a -a p/ ,~
-~ 3g:P3~) Figure 3 is a view similar to Figure 2 but more diagrammatic and further illustrating certain dimensional relationships to be taken into account in establishing oper-ating conditions in accordance with the preferred practice of the present invention.
In the drawings, the glass supply means includes a crucible or bushing 1 which may be supplied with molten glass in any of a variety of ways, for instance by means of the forehearth indicated at 2 in Figure 3. Glass supply orifices 3 deliver streams of molten glass downwardly under the action of gravity as indicated at S.
A gaseous blast is discharged in a generally hori-zontal direction from the discharge nozzle 4, the blast being indicated by the arrow 5. The blast may originate 15 in a generator, usually comprising a burner, so that the ;
blast consists of the products of combustion, with or with-out supplemental air.
As will be seen from the drawings, the blast is directed generally horizontally below the orifices 3 from which the glass streams S are discharged.
At an elevation intermediate the crucible and the blast discharge device 4, jet tubes 6 are provided, each having a discharge orifice 7, the jet tubes receiving gas from the manifold 8 which in turn may be supplied through the connection fragmentarily indicated at 9.
3~3~
As is disclosed in various of our prior appli-cations above identified, the gases for delivery to and through the jet tubes 6 may originate in a gas generator taking the form of a burner and the products of combustion may serve for the jet, either with or without supplemental air. Preferably such combustion gases are diluted with air so as to avoid excessively high temperature of the gas delivered through the jet tubes. On the other hand, in the preferred practice of the present invention and as will be explained more fully hereinafter, the gas employed for the jet may comprise air at temperatures well below those of gases derived from a burner.
Each jet tube 6 and its orifice 7 is arranged to discharge a gaseous jet downwardly at a point closely adjacent to the feed path of one of the glass streams S
and preferably at the side of the stream S which, with respect to the direction of flow of the blast 5, is upstream of the glass stream. Moreover, each jet tube 6 and its orifice 7 is arranged to discharge the jet in a path directed downwardly toward the blast and which is inclined to the vertical and so that the projection of the paths of the glass stream and the jet intersect at a point spaced above the upper boundary of the blast 5.
It is contemplated that the vertical dimension of the blast and also the width thereof be considerably greater than the cross sectional dimensions of each secon-dary jet, so that adequate volume of the blast will be avail-~3~ `
able for each jet to develop a zone of interaction with the blast. For this purpose also, it is further contem-plated that the kinetic energy of the jet in relation to that of the blast, in the operational zone of the jet and blast, should be sufficiently high so that the jet will penetrate the blast. As pointed out in our applications above referred to, this requires that the kinetic energy be substantially higher than that of the blast, per unit of volume. Still further, the jet preferably has a velocity considerably in excess of the velocity of the glass stream as fed under the action of gravity downwardly toward the point of contact with the jet and sometimes also in excess of the velocity of the blast, depending upon the tempera-tures of the jet and blast, as will be explained more fully hereinafter.
The operation of each fiberizing center is as follows:
From the drawings and especially from Figure 2, it will be seen that the core C of the jet causes the induc-tion of currents of air indicated by the lines A, the amountof air so induced progressively increased along the path of the jet. When the body of the jet, i.e. the gas of the core intermixed with the induced air, reaches the boundary of the blast, a zone of interaction is established in the region indicated by cross-lining marked I in Figure 2.
As the stream S of molten glass descends and appro~
aches the jet delivered from the orifice 7, the currents `
of air induced by the action of the jet cause the stream of glass to deflect toward the jet core as indicated at 10. Although the glass orifice 3 may be of substantially larger diameter or cross section than the jet orifice 7, the gravity feed of the glass stream S results in substantial reduction in diameter of the glass stream, so that when the stream meets the jet, the diameter of the stream is much smaller than the diameter of the glass orifice. With the higher velocity of the jet, as compared with that of glass stream, even when the glass stream meets the jet in the upstream region adjacent the jet core, the glass stream will not penetrate the jet core. However, because of the induced air currents surrounding the jet, the glass stream is caused to "ride" on the surface of the jet core within the surrounding sheath of induced air or to enter the body of the jet downstream of the jet core.
The action of the induced air in bringing the glass stream to the jet stabilizes the feed of the glass stream and will also assist in compensating for minor mis-alignment of the glass orifice with respect to the jet ori-fice. Because of the reliance upon induction effects of an isolated jet, the glass stream is brought into the mixing zone of the gas or breakage of the stream or the fiber being formed. This action is enhanced by virtue of the fact that in the arrangement as above described and illustrated, the glass stream is not subjected to any sharp angled change in its path of movement before it has been subjected to some appreciable attenuation, thereby reducing its diameter and inertia.
3~3~) In consequence of the glass stream being carried in the mixing zone of the jet, the glass stream is partially attenuated, this action representing the first stage of the two-stage attenuation above referred to. In turn, in consequence of this partial attenuation, the length of the embryonic fiber is increased, and this increase in ~ength is accommodated by an undulating or whipping action, thereby forming loops, as indicated at 12. It is to be noted, how-ever, that the glass stream remains intact, the loops of the embryonic fiber being carried downwardly in the mixing zone.
At the point where the blast 5 intercepts the jet, the jet penetrates the blast. This penetration of the blast by the jet establishes currents in the zone of interaction of the jet with the blast, which currents carry the partially attenuated glass stream into the interior of the blast and in consequence a second staye of atten-uation occurs. This results in further increase in the length of the fiber being formed. The increase in fiber length is accommodated by additional undulating or whipping action, forming further enlarged loops. Thus a single stream of molten glass is converted into a single glass fiber by a two-stage attenuation operation. It will be understood that in effecting this two-stage attenuation, the temperature of the glass and the temperature of the jet, as well as the temperature of the blast, are estab-lished at values which will retain the glass in attenuable ~., 3~
condition throughout the first stage of attenuation and throughout the second stage until the attenuation has been completed in the zone of interaction between the jet and the blast.
In connection with the arrangement of the inven-tion, it is to be understood that fiberizing centers may be arranged in multiple, as illustrated in Figure 1. This is accomplished by employing a blast 5 which is broad or of large dimension in the direction perpendicular to the plane of Figure 2, and by employing a similarly extended crucible 1 having a multiplicity of glass orifices, and further by employing a multiplicity of jet tubes 6 each having an orifice adjacent to one of the streams S of glass being delivered from the several glass orifices, all as shown in Figure 1. Such a multiplicity of jet tubes may be supplied with the jet gas from a common manifold 8.
As hereinabove indicated, the present invention contemplates employment of certain combinations of lower jet velocities and temperatures than used in the arrange-ments described in our earlier applications Serial Nos.
245,501 and 196,097, in which prior applications the stream of glass is delivered directly into the zone of interaction between the jet and blast. Such lower jet velocities and temperatures are also referred to in our prior application Serial No. 265,560, in which the stream of glass is deliv-ered first into the influence of the jet, to be carried thereby into the zone of interaction with the blast.
~3~3t3 Such use of lower jet velocities and temperatures is thus applicable not only to toration techniques in which the glass stream is initially delivered into the influence of the jet, to be carried thereby into the æone of inter-action with the blast, but is also applicable to torationtechniques in which the stream of glass is initially deliv-ered into the zone of interaction of the jet with the blast.
Certain operating characteristics and advantages are to be noted in connection with the employment of lower jet velocities and temperatures and these are explained herebelow.
It is first to be noted that in any of the tora-tion techniques referred to above it is contemplated that the jet have kinetic energy per unit of volume higher than that of the blast in the operational area of the jet and blast, this being a requirement for penetration of the jet into the blast. This is necessary in order to develop the toration zone, i.e., the zone of interaction characterized by high velocity currents under the influence of which the attenuation of the glass stream takes place as is fully explained in prior applications referred to and especially in application Serial No. 196,097. With both the jet and the blast supplied with operating fluid from burners, the jet and the blast would normally both have temperatures above at least several hundred degrees centigrade. For example Table III in the above mentioned application, refers to jet and blast temperatures of 800C and 1580C, respective-ly. In contrast to the above, and by way of example, it is contemplated according to the present invention that the jet ~3~3~
temperature may approximate ambient or room temperature.
Furthermore, certain of the prior toration techniques util-ized a jet having a velocity usually higher than the velo-city of the blast. Thus, Table III of the prior application S referred to indicates a jet velocity of 580 m/sec, and a blast velocity in the range from 224 m/sec to 283 m/sec.
According to the present invention it is contem-plated to use a jet velocity considerably lower than that referred to just above and even lower than the blast velo-city. The lower temperature and velocity contemplated bythe present invention still provides the required kinetic energy ratio between the jet and blast, i.e., a jet having kinetic energy higher than that of the blast so that the jet will penetrate the blast and create a zone of inter-action. The reason why this desired kinetic energy ratiois still present with the lower velocity of the jet is be-cause of the higher density of the jet fluid at the lower temperature. The density, of course, increases with de-crease of temperature and since the kinetic energy is deter-mined not by the velocity alone but also by the densityof the jet fluid, a jet may readily be provided having a higher kinetic energy per unit of volume than the blast, even at velocities lower than the velocity of the blast.
By employing the lower 3et temperatures (for in-stance a temperature approximating ambient or room temper-ature) a number of advantages are attained. In the first 3~3~
place when utilizing such temperature for the jet, it is feasible to employ a commonly available source of compressed air as the source of fluid for the jet. The lower tempera-ture also makes it practical to use commonly available mater-ials, such as stainless steel for the jet generating device,rather than more sophisticated and expensive materials, such as platinum alloys or ceramics, which are needed where very high temperature jets are used.
The lower temperatures for the jet also reduce oxidation problems, and further reduce or avoid certain thermal warpage problems, and in addition the maintenance of more uniform temperature from jet to jet in a multiple center fiberizing installation is more readily achieved.
Still further, the arrangement of the lower tempera-tures for the jet facilitates introducing the fiber being formed into a re].atively cool environment as soon as the fiber is attenuated, this consideration being of importance in the toration technique, for reasons which are fully brought out in our prior application above referred to.
The capability of utilizing commonly available sources of compressed air, which is made possible by virtue of employing lower jet temperatures, also has a distinct advantage in that the air is much less expensive than high temperature fluids, for example products of combustion or steam.
3'~
It is also to be kept in mind that by employing a jet fluid at a temperature approximating ambient or room temperature, consumption of energy to heat the ~et is elimi-nated.
The foregoing advantages are achieved regardless of whether the toration technique is one in which the stream of glass is initially delivered directly into the zone of interaction or whether the stream of glass is initially delivered into the influence of the jet, to be carried there-by into the zone of interaction, and in the latter case, the advantages are attained whether or not the jet is de-flected from its initial path. Where a jet deflector is used the low temperature jet is of special advantage because it assists in maintaining dimensional accuracy of the deflec-tor in relation to the jet generator including the jet ori-fice.
In addition to the foregoing, in the two-stage attenuation technique disclosed herein, as well as in the arrangements of our copending application Serial No. 265,560, in which the stream of attenuable material is initially delivered to the jet, the lower jet velocities and tempera-tures may assist in avoiding fragmentation of the stream of attenuable material.
The disclosure of the above identified applica-tions Serial No. 245,501 and Serial No. 196,097, may be referred to for further information in connection with the general arrangements providing for accommodation of multiple fiberizing centers and also for numerous other features, such, for example, as fiber collection means, glass feed systems and blast and jet generating and delivery systems, and including also information concerning the parameters involved in establishing a zone of interaction of a jet and blast.
In connection with various dimensional relation-ships involved in the equipment of the present invention, particular attention is directed to Figure 3 on which cer-tain symbols have been applied to identify some of the dimen-sions. These are identified in the following table which also gives an average or typical value in milimeters, as well as a usable range for each such value.
AVERAGE VARIA-FEATURE DIMENSION SYMBOL VALUE TION
(mm) LIMITS
tmm) 20 Bushing Diameter of dT 4 1 - 10 glass orifice Distance between 10 5 2 holes Jet Inner diameter d 1 0.3 - 3 of jet tube t Outer diameter 1.5 0.7 - 5 of jet tube Separation between 10 5 2 tubes 30 Blast Vertical distance lB 25 10 - 50 between the lips or thickness of the discharge section Width of the 300 20 - 500 discharge section :
~3~3~
In addition to the foregoing dimensions, certain spacing relationships and also angular relationships should be observed, as indicated in the following table which gives an average or typical value in millimeters or degrees, as well as a usable range for each such value.
AVERAGE VARIATION
FEATURES SYMBOL VALUE LIMITS
(mm or (mm or degree) degree) Vertical distance of jet JB 45 ~0 ~ 60 discharge orifice to the upper boundary of flow of the blast Vertical distance from Z 85 0 - 150 the discharge opening of JF
the glass stream to the jet discharge orifice Horizontal distance from X 5 1 - 15 the axis of the glassJF
stream of the jet dis-charge orifice Horizontal distance from XBF 5 0 - 30 the axis of the glass stream to the lip of the blast nozzle Angle of jet tube to the ~f 10 3 - 45 axis of glass stream Angle of jet tube to the JB 80 87 - 45 direction of Plow of the blast With further reference to parameters of operation when employing the technique of the present inventionr it is first pointed out that it is of course important that the glass be discharged from the glass orifice in a continu-ous stable stream. For this purpose, the rate of glassflow, the temperature of the bushing and the diameter of 1~3~3~
the glass discharge orifice should preferably be above cer-tain predetermined limits. Thus, the pull rate of glass should be greater than 60 kg/hole for each 24 hour period;
the bushing temperature should be greater than 1250C, and the diameter of the glass discharge orifice should be greater than 2.5 milimeters. With at least certain types of glass formulations, observing these limits may assist in avoiding pulsations which have a tendency to accentuate until dis-tinct droplets are formed. This phenomenon is incompatible with proper fiberization. In a typical or average working condition, the following values are appropriate; 100 kg/hole per day, bushing temperature 1400C, glass orifice diameter 3 milimeters.
Additional operating ranges are as follows:
15 Velocity - jet 200 m/sec - 900 m/sec blast 200 m/sec - 800 m/sec Pressure - jet .5 to 50 bars blast .05 to .5 bars Temperature - jet 20 to 1800C
blast 1300 to 1800C
Kinetic Energy Ratio - jet to blast 10/1 - 1000/1 A typical operation according to the present inven-tion may be carried out as given in the Example below.
.
~1~3~
Example Glass formulation:
SiO2 46.92 Fe23 1.62 A1203 9.20 MnO 0.16 CaO 30.75 MgO 3.95 Na20 3.90 K20 3.50 All parts by weight.
Physical Properties Viscosity 30 poises at 1310C
100 poises at 1216C
300 poises at 1155C
Glass - orifice 3 mm flow 100 kg/day per orifice Blast - temperature 1550C
pressure .25 bar velocity 530 m/s Jet - temperature 20C
pressure 6 bar velocity 330 m/s orifice diameter 1 mm 3~
Ratio of Kinetic energies ~et = 24 Blast Fiber ~iameter - 6 ~icrons In connection with the tabulations just above, particular attention is callea to the figures given for tle temperature and velocity of the jet and blast. ~iere it will be seen that the velocity of the jet is even lower than the velocity of tihe blast, which is in marked contrast to the examples given in our prior application Serial No. 196,097 above referred to, but it will further be noted that the ter,lperature of the jet is also very much lower than the tera~erature of the blast. Thus, notwithstanding the employ-ent of a jet of lower velocity than that of the blast as is noted in tile preceeding tabulation, the ratio of kinetic energies of the jet to the blast i3 of the order of 24 to 1.
This relatively high kinetic energy ratio per unit of volume of the jet and blast results in penet.ration of the jet into the blast, as :is desired, in order to de~elop ~he toration ~one or zone of interaction of the jet and bla.st.
The foregoing represents an e~a~lple of the tora-tion technique according to Figure 2 of the drawings, i.e., a technique in whicn the strea~l of attenuable ~aterial (in this case the glass) i9 subjected to a two-stage attenuation Operation, because the glass is introducéd into the influ-ence of the jet before the jet reaches the blast, thereby providing a preliminary stage of attenuation under the influ-ence of the jet, and a second stage of attenuation in conse quence of introduction of the partially attenuated stream ~' .
-1~3~3~
of glass into the zone of interaction of the jet with the ; blast.
In connection with the above it is pointed out that a jet of adequate velocity is readily obtained when using a source of compressed air as the source of the jet fluid. This is in distinct contrast to the employment of relatively high jet temperatures, with which it is techni-cally more difficult to obtain high velocity, and because of the lower density of the fluid at high temperature it is therefore much more difficult to attain sufficient velocity to achieve the kinetic energy ratio required to effect penetration of the jet into the blast.
As above noted, it is convenient to employ jet temperatures near ambient or room temperature, but it will be understood that the jet temperature need not necessarily be as low as ambient or room temperature. Preferably the jet temperature is well below the softening point of the thermoplastic material being attenuated, and in the case of attenuation of glass or similar mineral materials, the jet temperature is preferably selected at a value below 200C, and most desirably below 100C, and this is true whether the jet is employed in a toration operation in which the stream of glass is subjected to two stages of attenua-tion, or in various other toration techniques in which only a single stage of attenuation is employed by introducing the stream of glass directly into the zone of interaction of the jet with the blast, as is disclosed in prior applica-tions Serial Nos. 245,501 and 196,097 above identified.
3t~
With respect to the temperatures and velocities of the jet and blast which are contemplated according to the present invention, it is pointed out that in the tora-tion of thermoplastic materials such as glass, it is desir-able to employ a blast temperature at least as high as atemperature approximating the lower end of the softening range of the thermoplastic material to be attenuated. Main-tenance of such a temperature is desirable because substan-tial attenuation is desired within the blast. Thus, with most glass formulations and with similar types of thermo-plastic mineral materials (either naturally occurring or synthetic), the lower end of the softening range is between about 600 C and 900C. With most of such materials it is preferred to employ a blast having a temperature of at least 1000C. Although the blast temperature may be higher than just indicated, it is desirable to avoid excessive temperature because, if the temperature is too far above the softening range, the attenuation will be adversely affected, with resultant fragmentation of the fibers, or formation of slugs or shot.
Blast temperatures of the order of magnitude just referred to are advantageously achieved by employment of a gaseous fuel burner, and the utilization of the gaseous products of combustion as the blast.
In contrast with the foregoing, it is advantageous for various reasons already noted above to employ a jet of much lower temperature. The jet therefore need not be ~ 3~3~
produced by the combustion of fuel, with resultant unneces-sary fuel and energy consumption, but in contrast a common source of compressed air may be utilized for the supply of the jet gas, thereby providing a jet at a temperature near ambient or room temperature. Some variation from am-bient temperature may be employed, as may result for example from action of a compressor, or by exposure of a storage tank to other equipment or atmospheric conditions tending to either raise or lower the temperature somewhat with re-spect to ambient. For most purposes, a jet temperaturebelow about 100C is useable and would be available from various forms of compressed air systems in common use.
With the temperature relationship of the jet and blast above referred to, it is contemplated that the velo-cities of the jet and blast be such that the kinetic energyof the jet per unit of volume should be higher than that of the blast, so that the jet will penetrate the blast and thereby provide the desired toration zone or zone of inter-action. With a gaseous jet at a temperature near ambient or room temperature, the density of the air or gas of the jet is much higher than would be the case with products of customary combustion of fuel with air at temperatures of the order of those contemplated for use for the blast.
In view of this, the desired kinetic energy of the jet may be obtained while still utilizing a jet velocity even well below the velocity of the blast. Indeed, in a typical case with blast velocities of the order of 200 m/sec to 800 m/sec, 3~3~
which is a suitable range as already indicated hereinabove, the jet velocity may even be considerably lower than the blast velocity. This in turn makes possible a further econ-omy in that it is not necessary, (in order to provide the desired kinetic energy ratio and thus achieve penetration of the jet into the blast) to impart high velocity to the jet.
With a blast comprising products of combustion at a temperature above about 1000C and a velocity in the range from about 250 m/sec to 800 m/sec, and with a jet comprising air (or a gas of similar density) at a temperature below about 100C, the desired predominance of kinetic energy of the jet over the blast can be attained by employment of a jet velocity less than about that of the blast, for instance in the range of from about 200 m/sec to about 400 m/sec.
It is also mentioned that when attenuating certain materials having relatively high melting temperatures or with which it is desired to use high temperatures for pur-pose of feeding the material, the initial delivery of thematerial into the influence of a jet of relatively low temper-ature is desirable in order to bring the temperature of the stream of attenuable material down to the optimum temper-ature for the attenuation to be effected in the blast.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for forming fibers from thermoplastic attenuable material having a softening range the lower end of which is above 600°C, characterized by generating a gaseous jet, generating a gaseous blast in a path inter-cepting the jet, the cross sectional dimension of the jet being smaller than that of the blast in a direction trans-verse to the blast, the jet being of temperature lower than 200°C and the blast having a temperature above 1000°C, and the velocities of the jet and blast providing a jet of higher kinetic energy per unit of volume than the blast thereby providing for penetration of the jet into the blast to thereby provide a zone of interaction of the jet and blast, and delivering a stream of the attenuable material into said zone of interaction.
2. A process for forming fibers from attenuable material, characterized by generating a gaseous jet, generating a gaseous blast in a path intercepting the jet, the cross sectional dimension of the jet being smaller than that of the blast in a direction transverse to the blast and the jet being of velocity in the range of from substantially lower than that of the blast to not substantially higher than that of the blast but also being of temperature sufficiently below that of the blast to provide a density and thus a kinetic energy per unit of volume higher than that of the blast and thereby provide for penetration of the jet into the blast to produce a zone of interaction of the jet and blast, and delivering a stream of attenuable material into said zone of interaction.
3. A process as defined in Claim 2 in which the attenuable material delivered to the zone of interaction is a thermoplastic mineral material and in which the tempera-ture of the blast is at least 1000°C.
4. A process as defined in Claim 3 in which the temperature of the jet approximates room temperature.
5. A process for forming fibers from thermoplastic attenuable material having a softening range the lower end of which is above 600°C, characterized by generating a gaseous jet, generating a gaseous blast in a path intercepting the jet, the cross sectional dimension of the jet being smaller than that of the blast in a direction transverse to the blast, the jet being of temperature lower than 200°C and the blast having a temperature above 1000°C and the jet having a higher kinetic energy per unit of volume than the blast thereby providing for penetration of the jet into the blast to thereby provide a zone of interaction of the jet and blast, and delivering a stream of the attenuable material into said zone of interaction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/780,589 US4070173A (en) | 1973-03-30 | 1977-03-24 | Method and apparatus for fiberizing attenuable materials |
| US780,589 | 1985-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1103030A true CA1103030A (en) | 1981-06-16 |
Family
ID=25120018
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA290,253A Expired CA1103030A (en) | 1977-03-24 | 1977-11-04 | Method and apparatus for fiberizing attenuable materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1103030A (en) |
-
1977
- 1977-11-04 CA CA290,253A patent/CA1103030A/en not_active Expired
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