Note: Descriptions are shown in the official language in which they were submitted.
Bac_ground of the Invention
In conventional fiber glass producing arrangements, molten
glass is delivered to an electrically heaeed busiling which includes
a plurality of tips having orifices theretllrougll for the passage of
glass streams. The glass streams are attenuated into fibers which are
grouped together as a strand and collected as a package. Cenerally,
the busllings are constructed of an alloy, sucll as 90 percent platinum
and 10 percent rhodium. The tips are painstakingly built up by dropping
molten alloy onto a bushing plate, and then drilling the built-up alloy
to form the orifices. This arrangement, although commonly used, has a
serious limitation in that only a relatively small number of orifices
can be provided in a given space.
Another and later approacll is to drill small, closely spaced
holes in the wall of a metal pipe and deliver molten glass under pressure
to the pipe so as to extrude glass through the holes. It has been found
that the number of the holes per unit of area of pipe far exceeds the
number of tips for a like area of a conventional bushing. Further, the
cost of an orifice tube of the type just described is considerably less
than the cost of conventional bushing. In such devices, it is customary
to provide at least a partial shroud for the orifice tube and to deliver
a controlled atmosphere to the shroud to envelop the tube and be discharged
near the holes to provide cooling to the filaments and, for certain embodi-
ments protect the tube against oxidation.
By utili~ing high pressures up to perhaps several hundred pounds
per square inch in the orifice tube, as opposed to convcntional one pound
pcr square inch pressure, the fibers may be attenuated from smaller
.
orifices wllile producing less tension in the filament than was the case
witll prior, larger, orifice bushings producing an equivale]-t filament at
comparable speeds. Such a higll pressure orifice tube fiberizing unit is
disclosed and claimed in U. S. Patent ~o. 3,625,025 assigned to the
assignee oE the present application
In conventional fiberizing systems, the bushillg generally requires
from 1500 to 3000 amperes at operating conditions. To provide this power,
a step-down transformer is generally used to provide a high-current, low
voltage circuit from which the current is supplied to tlle bushings, with
the high-voltage side of the transformer providing the control. Thus in
conventional systems the primary side of the transformer may include a
saturahle core reactor or a solid state semiconductor system for regulating
the flow of power to the buslling to control the temperature thereof. How-
ever, because oE the physical size of the components of such a control
system, this means of control becomes extremely impractical when con- -
sidered for load elements such as the orifice tubes described above,
particularly when they are placed in close proximity, for the small size
of the orifice tube only requires about one-tenth the space required for
a comparable conventional bushing. Further, the orifice tube requires
only about one-fifth the power to operate than is required for conventional
devices and thus the size of the conventional power supply and controller
is not necessary for orifice tube fiberizers.
It has been conventional practice in operating orifice tubes
of this type to surround the tubes with a fluid cooling system typically
an air supply system to assist in providing close temperature control over
the oriEices. 'rhis is typically accomplishe(l with a plenum chamber con-
structed nnd arranged to deliver the air across the orifice tube from
3 --
.., ' : :
.
~96~6
both sides from one end to the other. Since some orifices along the length
may require more or less cooling fluid to operate eEEectively, this system
has been found to be unsatisfactory in some instances.
SUMMARY OF THE INVENTION
Accordingly, the present disclosure relates to an improved means
for regulating the temperature of an orifice tube fiberizing unit.
Also disclosed is a compact, convenien-t, more efficient heating
control system for glass fiber orifice tubes while providing more individual
control of the cooling of the orifice tips along the length of the tube.
Still further there is disclosed an improved heating control
apparatus which is adapted to the reduced power requirements produced by the
small size of an orifice tube fiberizing unit, and which is designed to
provide means for conveniently mounting and holding the fiberiziny units in
proper relationship.
Also disclosed is a heating element control system for a plurality
of glass fiber orifice tubes~ wherein the heating elements of all of the
tubes are connected in parallel with the secondary winding of a single supply
transformer, with each element being individually controlled at the trans-
former secondary.
Briefly, a presently disclosed arrangement comprises an orifice
tube fiberizing unit mounted in compression between a combination clamp and
spring-loaded electrical connector and a high pressure glass source which
provides molten glass for the unit. The fiberizing unit
,
.. . , ~ . .
'
inclutles a tube having a multitude of small orifices formed in a portion
Or its surrace through which a heat softened material such as glass is
extruded. ~t one end of the tube is a flanged connector designed to
seat in a mating recess on the glass source, while the other end of the
oriEice tube is engaged by a clamp which includes an electrical connector
for the tube. The clamp and the connector are adjustably attached to a
fixed bus bar which serves both to provide a rigid mount for the entire
assembly and to supply power to the unit.
The bus bar is connected at one encl to a transformer oE sufficient
power capacity to handle all of the fiber units that can be secured to the
bus bar. Embedded within the bus bar and contacting the electrical
connector Eor each Ullit is a pair oE half-wave thyristors througll which
Elows the current from the bus bar to the connector, and which serve to
regulate the current to provide the power required to maintain the desired
temperature in the orifice tube. The bus bar and connector assembly are
water cooled to protect the semiconductive thyristors, and the connector
includes a finned cooling block to prevent overheating.
~ thermocouple on each orifice tube provides a signal proportional
to its temperature, this signal being fed to a suitable control system to
produce an output wllicll regulates the operation of the corresponding
thyristors. The control system, which may be a conventional three mode
system, provides the necessary control action to maintain each individual
orifice tube at a predetermined level, or set point. Each of the many
orifice tubes tllat may be connected to a single bus bar are connected in
electrical pa~allel to the secondary of the transformer, an(l each tube is
provided witll an individual controller to regulate the power expended in
accordance with the requirements of the respective tube. The power and
control system is compact and efficient, allowing close spacing of
,
10~ ii21~
adjacent orifice tube units, ancl is operable from the secondary of a power
supply transformer, thus substantially reducing the bulk and expense of the
power and control system.
According to the present invention the orifice tube is surrounded on
either side by a cooling fluid delivery system which delivers Eluid across
the long axis of the orifice tube. The fluid delivery system is provided
with means to adjust the quantity of fluid deli~-ered across a given segment
of the tube to thereby provide for variable cooling along the length of the
orifice tube at given points to allow for more individual control of cooling
at the multiplicity of orifices.
Brief Description of the Drawings
The foregoing and additional objects, features and advantages of the
present invention will be apparent to those of skill in the art from a con-
sideration of the following detailed description, taken with the accompanying
drawings, in which:
FIG. 1 is a front elevation in partial section of an orifice tube,
clamp, and electrical connector in accordance with the present invention as
viewed along line 1-1 of FIG. 2;
FIG. 2 is a side elevation of the device of FIG. 1 along line 2-2
of FIG. 1 in partial section and showing in addition a second orifice tube
clamp and connector assembly similar to the assembly of FIG. l;
FIG. 3 is a partial schematic and partial block diagram of the control
system of the present invention;
~'
'
. ~ - .
l~tG. 4 is a front elevation in partial section o~ another
cmbodim~nt o~ the invention having an orifice tube and ~:lectrical con~
ncction tllereto as well as the glass delivery system; and
I~IG. 5 is a cross section of FIG. 4 taken along lin~ 5-5
of FIG. 4 to show tlle internal fluid control passages in the air
chamber 413 of ~IG. 4.
Description of a Preferred Embodiment
Turning now to a consideration of ~IGS. 1 and 2, there are
illustrated at 10 and 12 two orifice tube Eiberiæing units each having
a plurality of orifices therein for extruding streams of molten glass
delivered under pressure to the tubes from a pressure source 14. ~s
described more fully in the aforesaid V. S. Patent No. 3,625,025, the
orifice tube 16 of fiberi~ing unit 10 is made of platinum or platinum
alloy with a plurality of orifices being formed in the lower portion of
its ~all, generally at 18, in a closely spaced arFay. One end 20 of
tube 16 is closed, while the other end 22 is open and provided with a
flanged coupler 24 to mate with a complementary coupler 26 on a supply
conduit 28 which serves to supply molten glass to the tube. The tube 16
is heated by passing an electric current therethrougll, as will be
described.
The orifice tube 16 is shrouded by a manifold 30 to which
cooling air is delivered by way of an inlet conduit 32 (FIC. 1). The
manifol(l partlally covers the orifice tube and terminaLes at an
opening 3~, the eclges of which are slightly spaced from the orifice tube
, . .~
26
~or the passage oE cooling air as may be seen in the sectional view
of the Eil)eri~.ing unit in ~IG. 2. This air flows down througll the
manifold 30 and is blown Erom opposite sides across the ori~ices
formed at 18, eventually following the streams of glass and the resultant
fi~ers down and vut opening 34. The air cools the fibers as they are
being [ormed, and insures stable attenuation of the fibers.
To protect tlle orifice tube from (listorting or rupturing under
tlle rela~ively high pressure exerted on it by the glass feed, a shield
tube 36 partially surrounds tube 16, but is separated tllerefrom by a layer
of insulating material 38 which serves to isolate tube 16 fro~ the cooling
air in maniEold 30. The shield tube 36 and the insulating material may
extend beyond the ends of the maniEold 30, as shown in FIG. 1, to cover
the tube 16 outside the manifold. t~n air shield 40 over the shield tube 36
~urther assists the shield tube in diffusing the coolin~ air, so that
cooling of the orifice tube is avoided. With this structural arrangement,
variations in the flow rate or temperature of the cooling air have sub-
stantially no effect on the temperature of the orifice tube. In order
to diffuse tlle alr flowing out of manifold 30 and distribute it along
the length of the orifice tube, a plurality oE diffusing screens and
baffles 42 are located within the manifold between the supply tube 32 and
the manifold outlet 34 as is more fully described in said ~.S. Patent
No. 3,625,025.
P.ecause of the small si~e of the orifice tube construction9 it
is possible to obtain substantial savings in the space required for producing
a given numl)er of fibers; in some cases up to ten orifice tubes can be used
in the ~space normally required for a single conventional bllslling producing
a comparable amount of fiber. In order to ta~e advantage of this considerable
space savings, the present invention contemplates the provision of a unique
-- 8 --
... . ,, . .. . , .. .. , . ~
means ~or mounting the orifice tube, whicll means include a novel electrical
connector arrangement and incorporates an electrical control circuit that
takes advalltage of the substantially reduced power requ;rements of the orifice
tuhe construction. ~s illustrated in FIGS. 1 and 2, the fiberi~ing unit 10
is secured at one end to the source 14 of high-pressure molten glass, by means
of the flanged connector 24. ~le opposite encl of the unit is secured in an
elongate clamping bar ll4, with the end 20 oE orifice tube 16 passing there-
through for contact with a spring-loaded electrical connector 46. The
connector is pressed against the end of the tube to malce a good electrical
contact, whereby an electrical current of selected amp:Litu(le is introduced
into tlle orifice tube, flowing thro-lgh the tube to a ground point at
colmector 26 to heat the orifice tube to the selected temperature.
Clamping bar 44 is adjustably attached to, but is electrically
insulated from, a fixed bus bar 43 which serves to provide a rigid mount
for a plurality of fiherizing units as well as a common power source for
the units so connected. A bolt 50 secures the clamping arm in place, the
bolt passing through a spring arm 52 (FIG. 1), a first leg portion 54 of
a curved contact arm 56, an upper elongated slot 53 in the bus bar, a
second leg-portion 60 of the contact arm 56, an opening in a spacer plate
62, and the clamping arm. The bolt 50 is surrounded by an electrically
insulative sleeve 53. ~n electrically insulative bushing 64 spaces the
bolt 50 from arm 44, and a nut 66 and washer 68 secure the bolt.
second bolt 70 provides a pivot point for the clamping arm, bolt 70 being
spaced from bolt 50 and passing through spring arm 52, leg portion 54 of
the contact arm, through a lower elongated slot 72 in the bus bar, through
Llle secolld leg portion 6C of arm 56, and througll spacer plate 62. The
ell(l oE l-olt 70 is tllreaded into an electrically insulating pivot block 74
which may be secured to spacer plate 62. ~olt 70 serves to clamp the
.. .. .. ~
.
spring arm an(l contact arm assembly together and to bllS bar 48, as well as
to provicle a pivot point for clamp arm 44. I~en nu~ 66 is threadecl onto
holt 50, it tends to pull the top o:E clamp arm 44 (as seen in FIG. 1)
toward the curved contact arm 56 and the bus bar 48. The middle portion of
the clamping arm abuts the insulating spacer 74, whicll prevents it from
coming into contact with the contact arm; accordingly, tighteninp, of nut 66
tends to move the lower portion of arm 44 away from contact arm 56, and
into contact with the fiberi~ing unit 10. I~lus, the Eiberizing unit may be
firmly clamped between the bus bar 48 and the glass supply source 14 by
the clamping arm,- thereby securing the fiberizing unit in a selected
position. The slots 58 and 72 in the bus bar allow adjustment of the exact
location oE the Eiberizing unit an(l allow close spacing oF adjacent units,
as may be seen in FIG. 2. Further, an individual fiberizing unit ~lay
easily be removed or installed without disturbin~ adjacent ~mits~ merely
by loosening nut 66 and by releasing the electrical contact 46.
Contact arm 56 is generally "J"-shaped, the J-shaped arm being
inverted and positioned over the bus bar 48 so that the shorter depending
leg portion 54 is adjacent one side of the bus bar and the longer depending
leg portlon is adjacent the other side of bus bar 48. ~lounted in corre-
sponding depressions 76 and 78 formed on opposite sides of bus bar 48 are
a pair of thyristor elements 80 and 82, respectively. These elements are
thicker than the depth of the depressions in which they are located so that
one surface of each thyristor extends above the surface of the corresponding
side oE the bus bar. Thus, the outer surface of thyristor 80 extends
ahove the bus bar at depression 76 and is adapted to contact the inner
surEace oE leg portion 54 oE connector 56. Simiarly, the outer surface of
thyristor 82 extencls above the surface of tlle bus bar 48 at depression 78,
ancl is adapted to contact the inner surface oE leg portion 60 of the
connector arm.
-- 10 --
I'rotrusion~s X4 and 86 are formed on opl~os:ite s:kles of the bus
bar in the center of depressions 76 an(l 78, respectively, and ~it into
corresponding hollows in the center of the thyristors 80 and 82 to center
the thyristors in the bus bar depressions. The contact arm 56 similarly
is provkle~ with protrusions 88 and 90 which engage corresponding hollows
in the outer surfaces of thyristors 80 and 82 whereby the contact arm
assembly is positioned with respect to the thyristors and bus bar. The
bolts 50 and 70 hold the various elements tightly togetller in firm electrical
contact, clamping tlle inner surfaces of the contact arm against the outer
surfaces of the thyristors, and holding the thyristors tiglltly against
the bus bar, whereby current may flow from the bus bar through one or
the other of thyristors 80 and 82, depending on which is conductive,
into the corresponding leg of contact arm 56.
The longer leg 60 of contact arm 56 extends downwardly and
supports at its lower end 92 the electrical connector 46 wllich is adapted
to provide electrical contact with orifice tube 16. Connector l~6 includes
a contact block 9~ secured to tlle end 92 of leg 60, the block having on
one side a cavity 96 adapted to receive the closed end 20 of the orifice
tuhe. S~cured to the otller side of block 9~ hy means of screws 98 and
100 is a finned cooling block 102 which insures that the contactor will
remain within acceptable temperatures, while yet avoiding excessive
cooling of the orifice tube.
~djustment of the pressure of connector 46 against orifice tube
16 is by means of spring arm 52, the upper end 10~ of which is secured
tightly to the bus bar by bolts 50 and 70. The spring arm tapers down at
shoulder 106 to Eorm a thin, relatively flexible central portion 108.
The sprillg arm extencls downwardly as far as the orifice tube, with the
bottom portion 110 being thickened and provided with a threaded llole
through whicll extencls a pressure adjusting screw 112. This screw is
al:igned approximately with the axis of the ori~ice tube,' and extends
througll the lower portion 110 of the spring arm into contact with the
connector hlock 46. I'referably, the end oE the screw extends into an
-- 11 -- - -
, .. . , . , . , ............ .. _ _. .. . . _
~' ' ' ~ ' ' .
6;~
opellin~ ll4 formecl in t~e coolin~, rins 102 Qn~l contacts a pacl 116 in the
bo ttom thereor.
~ len the screw 112 is threaciecl into the spring arm its end
presses against the contact block, tending to separate tile block 46 from
the end llO of the sl~ring arm. The spring action of arm 52 tends to
force contact block 46 against the end of the oriEice tube, with a
Eorce depending upon the strength of the arm 52 and the amount that the
acljusting screw is threaded into the lower end portion 110.
As indicatecl in FIC. 2, a temperature measuring device such as,
Eor example, a Pt-PtRh thermocouple, 118 is placed on the orifice tube 16
to provide an output signal on lines 120 and 122 proportional to the
temperature of the glass being extruded. A control system including a
temperature controller 124 provides the necessary control action to maintain
the oriEice tuhe 16 at a predeterniined level, or set point. The controller
regulates a thyristor firing circuit 126 in known manner by way of lines 128
nncl 130, with the output of the firin~ circuit being applied by way of
lines 132 nnd 134 to thyristors 80 and 82, as shown in FIG. 3.
The control system is of conventional type, and preferably is
oE the three mode type well known in the prior art. As shown in FIGS. 2
ancl 3, each of the fiberiæing units 10, 12, etc., are substantially
identical, and are individually controlled by corresponding control systems.
Thus, the unit 12 is shown in FIG. 2 as being mounted closely adjacent
unit 10, with all of the units being ad~justably secured to the bus bar 48
by means of slots 58 and 720 In practice, it has been found that numerous
UllitS may be placed in electrical parallel on a single bus bar, with the
center-to-center spacing being on the order of 1-1/2 inches or less. In
FIC. 2 and FIG. 3, the elements of fiberizing unit 12 that are duplicates
of similar elements on fiberizing unit 10 are similarly numbered, but
primcd.
~ s shown in FIG. 3, the bus bar 48 is connected to the secondary
wincling 13G of a power supply transformer 138 selected to have a rating
. _
- 12 -
sufficiellt to handle the maximum ret~uirements all oE the Eiberizing
units that can be connected to tlle bus bar. The transformer primary
winding 140 is energized from a voltage source (not showll) which may be
variable to provide the desired voltage level on bus bar 48. ~ach
of the fiberi2ing units 10, 12, etc., are connected across the trans- -
fonner second~ry winding 136, being connected at one end to bus bar 48
and at the other end to a ground reference point 142 or by means of
grounded coupler 26. The two thyristors 80 and 82 are half wave devices
connected in parallel with each other with one end oE the thyristor
combination being connected to bus bar 48 and the other end of the com-
bination being connected through connector 56 to the orifice tube 16,
represented here as a lleating resistance elemellt 144.
Thermocouple 118 senses tlle te~perature of orifice tube 16,
and provides a signal to three-mode temperature controller 124, whicll
may be energized by power lines 146, 148, and which compares the measured
temperature signal with a precision reference voltage representing the
set point, or desired temperature. Any difference between these signals
is ampliÇiecl and applied to a conventional three mode control device,
which feeds a signal to the firing circuit 126 to regulate the length of
time during each half cycle of the AC input voltage from transformer 138
each thyristor will conduct. This regulation is carried out by applying
appropriate control signals to the gate circuit of the thyristors 80 and
82 by way of lines 132 and 134, respectively, in known manner. In similar
manner, each fiberi~inR unit that may be connected to transformer 138 is
corlllectetl to tlle secondary, ancl is individually controlled, whereby
fully indepen(lent control is obtained Çor each orifice tubt?.
13 -
6~ 6
It will be seen from the ~oregoing that a~ter securing tlle
desired nnlnl~er of fiberizing units to tlle bu~s bar, the volta~,e at the
sccondary o~ tile transFonner is adjusted to a level that will provide
surricicnt excess volta~e to allow aclequate control for all of the units,
and the voltage is thereaEter held constant. I~en the temperature of
the orifice tuhe 16 deviates from the set point, the cnntroller 124 acts
through the ~irin~ circuit 126 to cause the thyristors ~3n and 82 to
alternately conduct, during a lar~er or smaller portion of eacl~ half
cyc]e of the supply current, as the case may be, thereby passing a con-
10 trolled amollnt oE current througll the orifice tube. This current --
regulatioll adjusts the temperature oE the ori~ice tube until the set
point is reached, and the overall effect i~s to maintain the orifice tube
at the des;red set point. ~s long as the primary power system maintains
a constant volta~,e across secondary windillg 136, each individual fiberizing
unit may be regulated from zero to mQximum power, independently of adjacent
units.
Tlle hus bar 4~ is shown in FI~. 2 as bein~ secured by means of
suitahle holts 150 and 152 to a stud 154 on transfonner 13~, which stud
provides a connection to the secondary windin~, and thus serves as an
output terminal for the transformer.
In FIG. 4, an apparatus similar to F:[~. 1 is shown but having
certain inllovative modifications tllerein in the electrical system utilized
to ~eed current to closely spaced orifice tubes. Thus in FI~.. 4 there is
sllown a glass delivery tube 414 suitably insulated with reEractory 415
wllich delivers molten glass from a furnace, not shown, to a horizontally
oriellte(l mal~ l(l tul)e 419 ~s!lown in ~section. ~long one ~side o~ tlle hori-
zont~l tul)e 419 therc is provided a plurality o~ cone sl~aped nipples, one
of which i9 sllo~n as 420 in section. These nipples 420 are shaped to
- 14 -
.
~66~
I)rovklc a mating, locatlng and ~sealillg sur~ace l~etween the or:ifice tube
416 and the molten glass source 414, and thereby insure t11e constant
supply of molten ~las9 to the tube 4:L6. ~urrounding the nipple 420 is
a ring Inem~er 424 constructed to firmly hold nipple 420 in a surrounding
relatioll~sllil) and provicled with a lower pivotecl arm member 426. The ring
424 has secured to its upper end througll holt 428 antl 425 provided at its
~ree end with a stationary pin member 427 whicll protrudes inwardly.
clarlp 431 is provided whicil engages orifice tube 416 and is provided on
its upper extremity with a curved slot 432 constructed to engage the pin
427. At its lower end arm 431 is provided with a slot For insertion of
arm 42G therein. The arm 426 is threaded to receive nut 469 wllich wllen
tirhtened urge~s clalllp 431 in a direction to~ard the molten glass source
wllicll in turn ~irmly seals orifice tube 416 against ti~e nipple 420. The
oriEice tube 416 is ritted with a circular conductor 422 whicll has a
correspon-lillg cone shape at its point o~ connection to orifice tube 416
and extenlls bac~ along the tube. ~n electrical watercooled clamp 433
surrounds the circular conductor 422 with a corresponding support ring
~23 to provide necessary clamping support. An annular space is provided
hetween the ring 423 and orifice tube 416 to allow sufficient insulation
470 and insure unrestricted movement of the orifice tuhe ~or a sealed
connection with the glass source. ~n insulator 421 is provided between
tlle conductor ring 422 and the nipple 420. This insulator 421 isolates
the electrical system used to individually control the ori~ice tube 416
in accordance with this invention from the electrical supply, not shown,
whicll is used to maintain the glass in the glass deliver-ing system in a
~oL~ c~ll(litioll. -
'
.
Oriflce tube hollsing 410 is physically positioned at its extren~ityopposite the glass source by a hallger 436 secured to bo]ts and 443 by a
connector plate which supports the entire assembly. The end oE tube 416 is
firmly connected by a clamp 454 to a connector 453 having leads 435 connected
thereto. Leads 435 are held at their other e~tremity in a concluctive block
437 bolted to plate 439 which plate is in electrical contact w4th connector
448. The connector 448 is horseshoe shaped and is in electrical communication
with thyristors 449 and 450. Plate 451 and 452 on the right side of the unit
and plates of similar design on the left side of the unit, through bolts 442
and 443 and their associated nuts 444, 446, 445 and 447 clamp tightly against
the bus bar 459 to insure good electrical contact between the thyristors 449
and 450 and the connector 448. Bolt 442 is provided with an insulated sleeve
440 and bolt 443 with a similar insulated sleeve 441. This clamping also
insures good electrical contact between the connector 448 and the electrically
conductive plate 439 which feeds current from the transformer, not shown, to
the orifice tube 416.
Current at the other end of tube 416 is passed through the ring 422
to the clamp 433 secured to connector 434 through bolt 468. This unit is
similar to the electrical system utilized in the embodiment of the invention as
is shown in FIG. 3. Thus, the bus bar 459 is connected to the secondary
winding 136 of a power supply transformer 140. The winding 140 is of course
energized by a voltage source not shown and which may be adjustable to provide
the desired voltage level on bus bar 459. The fiberizing unit 416 is connected
across the transformer secondary winding 136, being connected to bus bar 459
at one end and terminal 142 at the other end.
- 16 -
~ .
' ' ' ' " ' ' '" " "~ ' ~ ' ~ ' ' ' ' ' ' '
- ~
:
2~
In this embodiment, of course, thyristors 449 and 450 are half
~ave devices connected in parallel Witil each other with one end of the
thyristor combination connected to bus bar 459 and the other end oE the
combination being connected through connector 448 to the orifice tube 416.
The operation of the control circuitry is as described hereinbefore
in discussing FIG. 3.
~hile only one fiberizing tube 416 is shown in FIG. 4 it is, of
course, understood that the plurality of these tubes may be used with each
tube 416 being controlled Erom a common power transformer by providing each
tube with a thyristor system such as shown above.
It will be understood that, if desired, various additional cooling
means may be provided for the apparatus to prevent overheating of the thy-
ristors. Thus, for example, cooling ducts may be provided in the bus bar
459 through which cooling water may be circulated. ~s may be seen in FIG. 1,
the source 14 of molten glass may feed not only the parallel orifice tubes
of orifice tube fiberizing units 10 and 12, but an additional row of tubes
156 extending in the opposite direction from the feeder. ~ similar arrange-
ment can be made in FIG. 4 by providing suitable nipples 420 on the opposite
side of the glass delivery tube 419.
As can be seen from the drawings, particularly FIGS. 4 and 5,
the orifice tube 416 is insulated by refractory 417 in an air manifold housing
410. The manifold housing 410 is provided with an air supply inlet 411 and
air chamber 413. The air in chamber 413 is distributed along the oriEice
tube 416 by passing the air through the chamber 413 down through the restricted
air passages 472 through filtering means, for example, screens 471 and
out across the orifice tube 416. The screw type elements 473 are used
to control the opening of the passages 472 by inserting the tapered
- 17 -
~ - ~
`. ' .
,
,
6~
end 474 of each of the elements 473 to any desired length into the passages
472 thus increasing or decreaslng the amount of air that can be fed through
each Or these passages 472. The air distribution elements 477 are placed in
the plenum or air chamber 413 in surrounding relationship to the orifice tube
and along the length of the chamber 413 in side by side relationship to each
other. Each of the elements 473 controls the air flow across the orifice tube
416 for a length of about 1.5 inches (3.81 centimeters). Sufficient of the
elements 473 are provided for a given length oE orifice tube 416. Thus, for
example, with an orifice tube 416 having a length o~ 18 inches (45.72 centi-
meters~ eleven opposite pairs of elements 473 are used so that incremental
lengths of 1.5 inches (3.81 centimeters) are individually controlled. When any
discrepancy or erratic performance of a group of orifices along the length of
the tube 416 is observed, the cooling at that location can be readily adjusted
by moving the pin 474 into or out of its mating passage 472 until the condition
is corrected. Tllus, a method is provlded to achieve more accurate temperature
control over the multiplicity of orifices contained along the elongated orifice
tube 416 to insure more uniform operation thereof.
In lieu of the air distribution system described above, the system
described hereinbefore with respect to FIG. 2 can be employed.
Thus there has been disclosed an apparatus for providing fully inde-
pendent temperature control of a multitude of closely spaced heating elements by
a technique which eliminates the need for space-consuming step-down transformers
and saturable reactors for each unit, as now used on conventional bushing systems.
A single power source is used to power a plurality of such elements, through a
connector arrangement which provides means for conveniently and quickly removing
and installing
- 18 -
, .. ~. .
-
- :
. ' ' ' ~ , ' ~. '
. ~ :
- : . -: .
2~
individual fiberi~ing units. ~lthough the invention has been described
and illustrated in terms of a preferred embodiment thereof, it will be
apparent to those skilled in the art that numerous varlations and modifi-
cations can be made without depart:ing from the true spirit and scope
thereof, as defined in the following claims.
' ' .
- 19 -
.
'
