Note: Descriptions are shown in the official language in which they were submitted.
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".
2. Strand: Other terms sometimes used are "contin-
uous filament", or "textile fibers".
3. Aerocor: Another term sometimes used is "flame
attenuation".
--1--
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
~ .
.
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
--4--
.
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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
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
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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,
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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-
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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
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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-
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.
' ~ . ' ,. - ' '
., ~ . ~ .
~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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,
- . . , - . . , . :
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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
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,~
~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.
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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-
-18-
~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.
-20-
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
-21-
~.,
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
-23-
~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
-24-
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.
-25-
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
-27-
:
~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
-28-
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.
-29-
.
~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
-30-
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
-31-
~'
.
-
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.
-32-
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
-33-
~ 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,
-34-
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.
-35-
