Note: Descriptions are shown in the official language in which they were submitted.
~5~0~
PROCESS AND APPARATUS FOR MAKING FIBERS
FROM T~-lERMOPLASTIC MATF.RIALS
In our Canadian application No. 196,097, filed
March 27, 1974, there is disclosed a new technique for produc-
ing fibers from attenuable materials, such as molten glass.
Thus, in said prior application a gaseous jet is arranged to
penetrate transversely into a larger gaseous blast in order
to establish a zone of interaction, and the attenuable material
such as the molten glass is admitted into the zone of inter-
action and this results in attenuation of the attenuablematerial thereby forming fibers or filaments. For introduction
of the glass or other attenuable material into the zone of inter-
action, a stream of the molten glass is delivered fro~ a glass
supply orifice usually located in a position which, with
reference to the blast, is downstream of the jet. This
fiberization technique is referred to as "toration" in the
prior application above referred to.
The present invention is concerned with improvements
and variations both in the apparatus and in the methocl for
forming fibers by toration, i.e. by techniques of the kind
disclosed in the prior application above identified and also by
the modified toration techniques herein disclosed, which are
applicable to attenuable materials generally, particularly heat-
ed softenable materials such as glass.
Before referring to the accompanying drawings,
certain aspects and features of the present invention are
preliminarily and generally described,as follows.
One aspect of the present invention relates to the
employment of novel arrangements and construction of plate
. ' . ' : , ~ ~
`` 1~75908
or wall elements positioned at the boundary of the blast down-
stream from the location of the point of entry of the molten
glass or other attenuable material. Downstream plates of cer-
tain types are disclosed in a number of figures of the drawings
of the prior application above identified, for instance in Figures
10 and 11. Such a downstream plate may be positioned at an
angle to the blast which is indicated at 12A in the prior ap-
plication and also in the present application, in which event
the downstream plate acts to deflect the blast, as clearly ap-
pears in Figures 10 and 11 of said prior application, and alsoin certain figures of the present application as will further
appear.
In fiberization where such a downstream plate is em-
ployed, the fibers some times tend to adhere to the plate, and
this is particularly true where the plate is positioned at an
angle in order to deflect the blast.
; One of the purposes of the technique according to
the present application is to reduce tendency for fibers to
adhere to and accumulate upon a downstream plate or wall element.
For this purpose, the arrangement provides for the introduc-
tion of a tertiary gas supply, for instance the introduction
of air into the blast in the region of the upstream edge of
the downstream plate and in a position, with respect to the
flow of the blast, which is just downstream of the orifice through
which the molten glass is admitted. Such introduction of air
at the upstream edge of the plate results in development of
; a boundary layer of air at the surface of the plate presented
to the blast, and this tends to avoid adherence and build up
of glass upon the surface of the plate.
In equipment having a plurality of fiberizing stations
2-
~ .,
`10759(~8
spaced from each other transversely of the blast and each includ-
ing both a secondary jet penetrating the blast and an orifice
for introduction of the molten glass, the arrangement for intro-
ducing the tertiary gas may comprise either a series of individual
jets, each one aligned with one of the fiberizing stations,
or a gas admission slot extended transversely of the blast.
In either event, the admission of the tertiary gas tends to
establish a curtain or boundary layer of gas at the surface
of the downstream plate presented to the blast, and also has
a tendency to cause the stream of molten glass introduced through
the glass orifice to penetrate farther into the blast before
the fiber is drawn from the glass stream.
According to another aspect of the arrangements dis-
closed in certain figures of the present application, a unitary
structure is provided in the region in which both the secondary
jet and the glass are delivered to the blast. Certain purposes
of this unitary structure are related to the problem of estab-
lishing and maintaining accurate alignment of the secondary
jet and the glass admission orifice in the direction upstream
and downstream of the blast, and this problem is of a special
- importance in equipment embodying a multiplicity of fiberizing
centers, each including a secondary jet and a glass orifice,
and arranged in a series spaced from each other transversely
of the blast.
In toration, i.e. the fiberizing technique utilizing
the interaction of a jet and a blast to effect attenuation and
fiberizing, it is important, for uniformity of the fibers pro-
duced, that in each fiberization center the secondary jet and
the glass admission orifice be accurately aligned with each
other upstream and downstream of the blast. One technique for
achieving accuracy of alignment in the upstream and downstream
3.
.
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75908
sense as disclosed in the prior application referred to is to
employ a series of separate secondary jets, but only a single
glass orifice, the orifice being in the form of an elongated
slot extended transversely of the blast in a position which,
with respect to the blast, is downstream of the jets, as shown
for example in Figures 12, 12A, 13A and 13B of said prior ap-
plication. In the arrangement using the slot, under the influence
of the individual secondary jets, the molten glass is delivered
to the blast from the slot only at spaced points transversely
of the blast, one such point being accurately located downstream
of each of the secondary jets.
According to the arrangements shown in the drawings and
described hereinafter, instead of utilizing a glass admission
slot, a crucible or bushing for the glass is provided with a
15 series of transversely spaced glass admission orifices. This
crucible or bushing further is provided with a plate or wall
structure adjacent to the glass admission orifices at the side
thereof which, with relation to the flow of the blast, is up-
stream of the glass admission orifices. This upstream plate
20 is formed unitarily, preferably integrally with the crucible
or bushing, and is provided with a series of bores or apertures
formed therein, one aligned with each one of the glass admission
orifices. By providing a common or unitary structure in which
both the glass admission orifices and the secondary jet admission
orifices are formed or drilled, accurate alignment of each pair
of orifices is more readily achieved. Because of the proximity
of these orifices the temperature of the carrier jet influences
the temperature of the glass stream, which makes possible control
of glass stream temperature by regulating the temperature of
the carrier jet.
4.
- iO75~08
In combination with the upstream plate formed unitarily
with the crucible or bushing, this arrangement also provides
a new and improved form of device for delivering the secondary
jets through the orifices provided in said unitary plate. This
improved arrangement includes the use of individual tubes from
which the secondary jets are discharged, such tubes being of
slightly smaller outside diameter than the diameter o-E the
secondary jet orifices in the unitary upstream plate, and these
jet tubes project into but not through the jet oriEices. Prefer-
ably the jet tubes are mounted in groups, For instance, inan arrangement in which the bushing is provided with approximate-
ly 80 glass admission orifices, the tubes are arranged and mounted
in groups of approximately 20 and each such group is also prefer-
ably separately supplied with the jet gas. Although, for most
glass formulations it would be contemplated to employ platinum
alloys for the unitary crucible and upstream plate, the arrange-
; ment described just above with the provision of separate jet
tubes, permîts the fabrication of the unitary plate and crucible
of platinum alloys, while the tubes and the associated mounting
and gas supply means are fabricated from less expensive metals,such as stainless steel. It is also of advantage, especially
where the crucible and upstream plate are formed of platinum
and the jet tubes are formed of stainless steel to provide for
the mounting and supply of the jet tubes in groups representing
a subdivision of the total associated with a multiple orifice
bushing, because subdivision into groups more readily accommodates
differential thermal expansion and contraction as between the
structure of the crucible on the one hand and the structure
of the jet tubes and the jet mounting and supply structures
on the other hand.
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~75908
For purposes of protection of the jet tubes in the
region where they project into the jet apertures in the upstream
plate which is unitarily formed with the crucible or bushing,
the individual jet tubes are desirably coated with an insulating
material, for instance alumina.
The various figures of the accompanying drawings are
briefly described as foliows:
Figures 1 to 8 inclusive illustrate various parts
of an embodiment according to the invention, incorporating pro-
vision for introducing a tertiary jet or gas, and in this groupof figures -
:~ Figure 1 is an elevational view partly in vertical
section showing glass supply means, means for developing a blast ~:
and secondary jet, and further for introducing tertiary gas
in the manner to be described;
.
Figure 2 is a plan view of certain parts taken asindicated by the line 2-2 on Figure 1;
Figure 3 is an enlarged vertical sectional view of
the crucible or bushing, with an integral plate, this view
also showing the association of the secondary jet and tertiary
gas admission devices, this view being taken as indicated by
the line 3-3 on Figure 4;
Figure 4 is a plan view looking upwardly at certain
parts shown in Figure 3, Figure 4 being taken as indicated by
the line 4-4 on Figure 3;
1075908
Figure 5 is a somewhat diagrammatic view of some
parts shown in Figure 3 and particularly showing the fiberizing
action achieved by the employment of not only the blas~ and
secondary jet but also of the tertiary gas admission means;
Figure ~ is an isometric view of certain gas supply
and distributing means employed for supplying gas to the second-
ary jets;
Figure 7 is a horizontal sectional view through cer-
tain of the parts at the fiberizing centers, the central portion
of this view being broken out and the view showing the arrangement
of certain parts making up a multiple center fiberizing installa-
tion; and
Figure 8 is an isometric view of equipment employed ; .
to mount a plurality of secondary jet tubes and supply such
tubes with jet gas.
Figures 9 and 10 are views illustrating a modified :~ :
form of equipment for introducing the tertiary gas, Figure 9
being taken as indicated by the section line 9-9 on Figure 10
and Figure 10 being taken as indicated by the section line 10- :
10 on Figure 9. -
Figures 11 and 12 are fragmentary views taken in a
manner similar to Figure 3, but illustrating additional embodiments
of the equipment for introducing the tertiary gas.
Figures 13 and 14 are views illustrating still an-
other arrangement of parts for establishing fiberizing centersarranged according to the present invention, Figure 13 being
,
:
~C~7S908
taken in the same general manner as portions of Figure 1, and
Figure 14 being a fragmentary plan view looking up at certain
of the parts shown at Figure 13.
The embodiment illustrated in Figures 1 to 8 is des-
cribed just below.
In the following description a few of the reference
symbols used in the prior application referred to above are
also employed in this description for corresponding items,
but most of the reference characters are new ones, beginning
with number 200.
;
The general arrangement (see particularly Figures
1 to 4) includes a fiberizing crucible or bushing 200 associat-
ed with a glass supply forehearth 201, although it is to be
understood that instead of supplying the molten glass from
a forehearth of a glass forming furnace, a resistively heated
melting crucible may be employed to melt and supply the forming
glass,
The crucible of Figures 1 to 4 is provided with a
series of glass discharge orifices 37, adapted to deliver the
glass into the zone of interaction between a primary jet or
blast and a series of secondary or carrier jets, one such carrier
jet being associated with each glass supply orifice in order
to establish a plurality of fiberizing centers. The blast
is indicated by the arrow 12A (see Figure 5) and the jets are
delivered from jet supply tubes (to be described hereinafter)
through jet orifices 36 (also referred to more fully hereinafter).
8.
1~7S908
The blast is delivered from the duct 202, the blast
being generated by combus~ion of fuel in the combustion chamber
203 ~see Figure 1) which may be supplied with a mixture of gas
and air at 204.
A burner 205 supplied with a mixture of gas and air
at 206 provides the gas to be delivered through the orifices
36 through the jet tubes above referred to. The arrangement
of these parts which establishes each of the fiberizing centers
is shown to best advantage in Figures 3 and 5. As there illu-
strated, it will be seen that jet tubes 207 which are supplied
from the burner 205 in the manner to be explained below, pro-
ject into the apertures 36 and deliver jets or gas streams trans-
versely into the blast 12A discharged from the duct 202. As
shown in the embodiment of Figures 1 to 8, the jet orifices
36 are formed in a wall or lip 208 lying adjacent to the boundary
of the blast 12A and formed unitarily, preferably integrally
with the crucible 200.
Each fiberizing center provided as just described
functions in the general manner fully disclosed in our earlier
application above identified, and the parameters including the
kinetic energy of the blast and the secondary jet in the operation-
al area thereof and the temperatures and velocities of the blast
and jet, as well as the temperature of the glass, relationship
between the size of the glass and the jet orifices, the spacing
thereof and the like, may all conform with various parameters
set out herein and also in the above identified application.
It is here mentioned that the blast should be of larger section
than the jet and that the kinetic energy of the jet per unit of
volume should be greater than that of the blast in the operational
area thereof. With gaseous jets and blast this energy relationship
9.
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.: ~
. . . - . ...
1~759~)B
is desirably provided by employment of a jet of hi~her velocity
than the blast.
One of the improvements involved in the modification
here under consideration relates to the employment of a "down-
stream" wall or plate element of the general kind shown in Figures10 and 11 of said earlier application. Such a plate is referred
to as a "downstream" plate because it is situated, with respect
to the direction of flow of the blast 12A, in a position down-
stream of the fiberizing center, i.e. downstream of the glass
orifice 37, which in turn is located downstream of the secondary
jet orifice 36. The downstream plate is especially illustrated
in Figures 1, 3 and 5, being identified in general by the ref-
erence numeral 209. As seen in Figure 1, the downstream plate
is mounted by means of joint linkage 210 which provides for
adjustment of the position and inclination of the plate. In
these figures, the plate 209 is adjusted to a position which
is inclined so as to deflect the blast after it passes the glass
discharge orifice.
The downstream plate is provided with a passage 211,
with connections 212, providing for the circulation of a cooling
medium, for instance water, through the channel 211 thereby
effecting cooling of the downstream plate.
As mentioned above, the employment of a wall or plate
downstream of the fiberizing centers some times results in tendency
for the fibers to contact the plate and thereby tends to build
up deposits of glass upon the surface of the plate presented
to the blast. According to the present improvements, this tendency
is substantially eliminated by dynamically exerting a localized
action affecting the flow of the blast by introducing air, pre-
ferably in the form of a boundary layer along the lower surfaceof the downstream plate or along the leading or upstream edge
of the plate. The air or gas for this purpose may for convenience
; be referred to as the "tertiary jet". The means for dynamically
10 .
1075908
exerting the localized action af-fecting the flow of the blast
may for example comprise structure at the boundary of the current
formed by the interaction of the blast and jet, said structure
including means for bringing an additional gaseous jet into con-
tact with the interaction current.
In the embodiment of Figures 1 to 8, the leading edge213 is positioned in slightly spaced relation to the lower portion
of the crucible 200, so that a slot is provided between the
crucible and the leading edge of the plate, through which slot
tertiary gas may be supplied in a region which, with relation
to the direction of flow of the blast, is downstream of the
glass orifices 37. The plate 209 has a channel 214 formed therein,
with connections 215 for supply of the tertiary gas, for instance
air. A series of ports 216 communicates with the supply channel
214 and delivers air in an upstream direction toward the leading
edge of the downstream plate, thereby supplying the air for
entry through the slot adjacent to the crucible. In order to
close the space between the crucible and downstream plate and
thus assure that the tertiary gas will not escape and will be
delivered through the slot at the leading edge of the plate,
a sheet metal plate 217 is connected with the mounting structure
218, with the lower edge of the plate turned upwardly to engage
the lower wall of the crucible, and thereby provide a space
to accommodate a fibrous insulating material 219 of high thermal
resistance, such as aluminum oxide fiber. The enclosure plate
217 may advantageously be formed of stainless steel having some
appreciable resilience and is configured to establish contact
with the plate 209, thereby closing the space between the crucible
and the`plate. With this arrangement, and with the enclosure
217 made of resilient material, the downstream plate may be
adjusted in position in the manner described above while retaining
- engagement of the enclosure 217.
11 ~
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10'75908
The action of the tertiary jet is indicated in Figure
5 of the drawings, in which flow lines indicate not only the
blast 12A and the secondary je~ from the jet tube 207, but also
the tertiary jet delivered from the passage 216 to the leading
edge of the plate, at which point the tertiary air passes through
the slot and enters the system at the boundary of the blast,
producing a current or boundary layer at the lower surface of
the plate 209. The equipment includes a plurality of fiberizing
centers of the kind shown in Figure 5 spaced from each other
transversely of the blast. It is contemplated that a tertiary
gas passage 216 be provided in alignment with each secondary
jet orifice 36 and its associated glass admission orifice 37.
With a plurality of tertiary gas delivery passages, the tertiary
gas from the several passages tends to merge and thus form a
more or less complete curtain of gas as the flow passes through
the slot and follows the lower surface of the downstream plate
at the boundary of the blast. Because of this, the fibers being
formed are effectively prevented from contacting the surface
of the downstream plate.
It is also pointed out that the provision of the tertiary
gas supply channel 214 and the flow of the tertiary gas over
the surfaces of the downstream plate assists in cooling *he
plate, so that the action of the tertiary gas, together with
the action of the cooling medium circulating through the channel
211 will maintain the plate at a relatively low temperature,
which is also of benefit in avoiding sticking of glass to the
surface of the plate.
In an installation in which a large number of fiber-
izing centers are provided in spaced relation transversely
12.
1q~75908
of the blast, for instance in the neighborhood of 80 fiberizing
centers, it is preferred to sectionalize the downstream plate.
As seen in Figures 2 and 7, the downstream plate associatedd
with the multiplicity of fiberizing stations there shown, is
s sectionalized and formed in three sections, each one of which
is provided with a water cooling channel 211 and a tertiary
gas supply channel 214, respectively having water circulating
and a;r supply connections as already described. Forming the
plate in such sections facilitates effective and accurate circu-
1~ lation of the cooling water and assures accurate distributingof the tertiary gas supply, thereby assisting in maintaining
the desired operating conditions within close tolerances.
Turning now to the arrangement of the secondary jets
as embodied in Figures 1 to 8, it is again pointed out that
an upstream plate 208 is preferably formed integrally with the
crucible 200, this structure desirably being made of a pla-
tinum alloy when employing typical glass formulations used
for fiber manufacture. For the purposes of ensuring accurate
fiber formation, and particularly for the purpose of assuring
uniformity of fiber formation at each of the multiplicity of
stations, it is of importance to provide accurate upstream-
downstream alignment of the secondary jet orifices 36 and the
glass admission orifices 37. In Figures 12, 12A, 13A and 13B
of the earlier application above identified, this accuracy
of upstream-downstream alignment of the secondary jet and the
stream of glass to be fiberized is automatically achieved by
the employment of an elongated slot for the admission of glass,
rather than a series of separately formed glass admission orifices,
as has already been noted above. The arrangement shown in
Figures 1 to 8 also provides for accuracy of alignment of the
secondary jets with the streams of glass, but in this case,
13.
1075908
the accuracy of alignment is provided for notwithstanding the
use of separate glass admission orifices. This accuracy is
assured by virtue of the unitary formation of the wall or upstream
plate 208 with the crucible 200. Since both the secondary
jet orifices and the glass orifices are drilled in the same
unitary structure, accuracy of alignment is provided for and
will be maintained even under varying conditions of thermal
expansion and contraction of various parts of the structure.
This accuracy of alignment is further facilitated 10 by virtue of certain other arrangements included in the embodi-
ment shown in Figures 1 to 8. Thus, from examination of Figures
2, 3, 4, 7 and 8, it will be seen that each secondary jet is
delivered from a jet tube 207 which extends into the orifice
36, the jet tube 207 being of slightly smaller diameter than
lS the diameter of the orifice 36. The jet tubes 207 are subdivided
into groups, four such groups being shown in the embodiment
illustrated and each group is mounted upon a jet fluid manifold
220 which is connected with the supply pipe 221. By this subdi-
vision of the total number of jet tubes and the separate mounting
of each group, thermal expansion and contraction of the manifold
which mounts and supplies each group, is more readily accommodated
; than would be the case if all of the jet tubes were mounted
on a single structure extended throughout the entire series
of fiberizing stations. Moreover, by utilizing jet tubes 207
projecting into individual drilled jet orifices 36, and by
employing jet tubes of slightly smaller outside diameter than
the diameter of the orifices, additional clearance is provided
for accommodation of expansion and contraction. The grouping
`~ of the jet tubes and the arrangement and mounting thereof as
just described in order to provide for accommodation of expansion
and contraction is particularly importannt where, as here con-
templated, the crucible 200 and the upstream plate 208 are
14.
` iO7S908
formed of platinum alloys and the jet tubes and associatedparts are formed of some other less expensive metal such as
stainless steel, because these different metals have different
coefficient of thermal expansion and contraction.
As best seen in Figure 8 each group of jet tubes
207, together with its mounting manifold 2Z0 and the associated
supply connection 221 form a structure generally resembling
a rake, and this structure is adapted to be mounted at the
base end of the supply connection 221. As seen in Figures
1 and 2, the supply connections 221 are adapted to communicate
with the burner 205 for developing the secondary jet gas, and
preferably provision is made for introducing air into the gas
stream entering each supply connection 221. This is accom-
plished by supply means in the form of a fitting 223 (see also
Figure 6) interposed between the burner chamber 205 and the
mounting plates 222 for the supply connections 221 for the
groups of jet tubes. This "air diluter" is provided with air
supply pipes 224 connected therewith through the tubes 225,
there being several of the supply pipes 224 distributed along the
length of the air diluter, the tubes 225 delivering the air
to the passages 226 in the air diluter. One such passage 226 is
provided for each of the groups of secondary jet tubes, and in
this manner the jet tubes are supplied with diluted products
from the combustion chamber 205. The dilution of the gases coming
from the combustion chamber 205 is important because of the
use of those gases in the jet tubes 207 and the contemplated
employment of less expensive metal than the platinum alloys
used for the crucible. As already indicated, stainless
15.
.
.
1.f)7S~3~8
steel is appropriate for the jet tubes 207, but will not with~
stand the temperatures generated in the combustion chamber
205 without dilution,
As will be seen from Figures 2, 4 and 7, there is
included an "outboard" secondary jet orifice 36 and a secondary
jet tube 207 laterally offset beyond each end of the glass admiss-
ion orifices 37~ This is in conformity with the disclosure of
other multiple orifice arrangenents described in the prior ap~
plication above identified and assures uniform fiberi~ing activity
at the glass admission orifices at the opposite ends of the
series~ In addition to this provision, it is contemplated
according to arrangements disclosed herein that a similar provi-
sion be made with respect to the tertiary gas admission passages,
: In other words, as will be seen from Fi~ures 2, 4 and 7, there
is a tertiary gas admission passage located in offset relation
beyond each end of the series of glass admission orifices,
this arrangement being provided for reasons similar to those
referred to in connection with the offset or r'outboard" secondary- iet orifices,
A modified form of downstream plate and tertiary
jet supply is illustrated in F.igures 9 and 10.; Here the down-
: stream plate is shown at 227, being provided with a cooling
mediunl circulation channel 228 with connections 229, and also
with an air supply channel 230, ~rith supply connections 231.
Here the individual passages or ports 232 which deliver the
tertiary air from the supply channel 230 connect with the base
of a groove or slot 233 having an open edge presented toward
and just above the leading edge 234 of the downstream plate.
It will be understood that this structure is adapted to be
-16-
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1~75908
mounted in relation to the fiberizing stations in the same
general manner as described above with respect to Figure 1.
The downstream plate of Figures 9 and 10 is also adapted to
cooperate with a structure for closing the space between the
5 downstream plate and the crucible in the same manner as indi-
cated at 217 and 219 in Figures 1, 3 and 5. A slot such as
shown at 233 may be employed to assist in the spreading of
the tertiary gas along the upstream edge of the plate, and
thereby assist in providing a blanket of the tertiary gas between
10 the surface of the plate and the blast.
Still another modified form of construction of the
downstream plate and the tertiary gas supply is illustrated
in Figure 11. As here shown, the lower portion of the crucible
200 is of somewhat modified configuration and the downstream
15 plate 234 is also of modified shape adapted to cooperate with
the lower portion of the crucible in the manner mentioned just
below. The plate 234 is provided with a cooling medium circulat-
ing channel 235 with connections 236 and the tertiary gas supply
channel 237 has supply connections 238, with passages 239 which
20 communicate with a slot like chamber or passage formed between
the leading edge portion of the plate 234 and the bottom portion
of the crucible. Sealing means is also provided between the
plate and the crucible to insure flow of the tertiary gas in
the desired direction and out of the slot at the leading edge
25 of the plate, as will now be understood.
Still another modified arrangement of the downstream
plate is shown in Figure 12. In this embodiment, the crucible
is again indicated at 200, having an upstream plate 208 with
17.
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1~75908
orifices 36 cooperating with jet tubes 207. ~lere the construction
of the downstream plate 209 is essentially the same as that
described above with reference to Figures 1 to 8, but the system
for sealing the space between the plate and crucible is different.
Thus, the downstream plate is provided with an upper metallic
closure strip 240 which is extended along the length of the
plate 209 and cooperates with the lower portion of the plate
in defining an elongated slot for admission of the tertiary
gas into the blast. This structure is here thermally isolated
from the crucible by means of a layer of insulating material
such as indicated at 241 overlying the wall 240. The insulation
241 may for example comprise a layer of material of high thermal
resistance, such as alumina. Insulation of this kind and also
the insulation 219 described above is of advantage in the equip-
ment in order to minimize heat loss from the crucible.
In all of the embodiments described above, whereverthe jet tubes 207 are employed projecting into orifices formed
in a structure integral with the crucible, it is desirable
to provide thermal insulation between the jet tubes and the
jet orifices. This is advantageously provided by applying
a thermal insulating coating to the tubes, for instance a coating
of alumina. This also diminishes heat loss from the crucible
and in addition will serve to protect the metal of the jet
tubes.
All of the arrangements described just above are
also adaptable to an installation of the general kind shown
in Figure 1 in which the crucible is mounted below a glass
18.
1~'75908
supply forehearth indicated at 201, the crucible being isolated
or insulated from the glass supply structure by a ceramic insula-
tion element 242, in which a tube 243 for a cooling medium
is embedded (see Figures 1 and 2). I~igh temperature fibrous
insulating material 244 is also desirably used as indicated
at the lower side of adjoining surfaces of the forehearth in
order to retard thermal loss in this region.
.
For at least some purposes, it is also preferred
to provide electrical connections such as indicated at 245,
connected to and extended from the ends of the crucible 200
and provided for resistive heating of the crucible.
Still another embodiment of equipment incorporating
tertiary gas supply means is disclosed in Figures 13 and 14.
In this embodiment the glass supply forehearth or the like
is indicated at 246 and the crucible or bushing at the bottom
: is indicated at 247. The glass supply orifices are again indicat-
ed by the number 37 and in this case the secondary jets are
; supplied through orifices 36 provided in the projections 248
which extend from the secondary jet gas supply manifold 249.
: 20 A supply conduit 250 is connection with the manifold 249.
The blast 12A is delivered from the structure 251,
with the upper boundary of the blast close to the secondary
jet and glass orifices 36 and 37.
At the downstream side of the orifices 37, a down-
stream plate structure indicated at 252 is provided, this struc-
ture being hollow to provide a manifold 253 supplied by supply
, 19.
.
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~7S~8
duct 254. The manifold is provided with projecting nozzle
structures 255 having orifices 256 for discharge of the tertiary
air in a position which, with respect to the direction of flow
of the blast is downstream of the fiberizing center established
by the glass and secondary jet orifices.
As is shown in Figure l4, the secondary jet orifices,
the glass supply orifices and the tertiary gas orifices are
arranged in groups aligned with respect to each other in the
upstream and downstream sense, and each group providin~ a fiberiz-
ing center.
It will be noted that in the arrangement of Figures13 and 14, a downstream plate is provided without employing
any circulation passage for a cooling liquid, the arrangement
being such as to provide for cooling of the downstream plate
by virtue of the hollow construc.ion of the plate and the flow
of theairthrough the interior hollow of the plate.
; With regard to the operation of the fiberizing system
when employing tertiary gas as herein disclosed, it is pointed
out that the air employed may have a pressure of the order
of 0.5 to 2 bars, preferably between about 0.8 and 1.2 bars.
In an installation having about 80 fiberizing stations
as in the embodiment of Figures 1 to 8, the air flow used for
the tertiary gas supply may be of the order of 15 to 30 m3
per hour, preferably about 17 to 25 m3.
The kinetic energy of the tertiary jet should be
considerably lower than the kinetic energy of the secondary
jet.
20.
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