Note: Descriptions are shown in the official language in which they were submitted.
1049078
The present invention relates to electrical melting
apparatus. More specifically, the invention relates to such
apparatus for processing high temperature batch material in the
production of, for example, glass filaments.
Production demands have pressed to the limit existing
furnace or melter technology using heat generated from a heating
element extending across a melting chamber to melt high tempera-
ture fusing mineral material into a heat softened body. Prior
concepts were especially stale in furnace apparatus using a heat-
ing element across a melting chamber to heat batch mineral materi-
al into a molten body of glass supplying a feeder from which mol-
ten glass streams flow for producing glass filaments.
Prior furnaces using a heating element employ a sheet-
like, usually curved, metal electrical current conducting heater
element across a melting chamber. When high amperage electrical
current passes through the sheet-like heating element, ensuing
intense heat from the energized element continuously converts in-
put material into a molten mass in the melting chamber. When an
arrangement uses the furnace or melter to supply molten material
to other apparatus, prior arrangements orient the heater element
across the direction of flow of the molten material towards the
outlet to the other apparatus. The heating element has perfora-
tions or slots through which molten material travels towards the
outlet.
In producing continuous glass filaments, it was found
that increased output or "throughput" requires faster molten glass
movement through the openings in the sheet-like heating element.
As the speed of the molten glass increases, the heating element
can not satisfactorily convert batch to molten glass. According-
ly, heating capacity became the limiting factor in "throughput"of the apparatus. The only answer appeared to be larger melting
units; however, the expense and difficult operating characteris-
- 2 -
~J r~.
''
1049078
tics of larger melting units based on prior concept~ pre~ented a
dismal outlook for effectively increasing "throughputn.
An object of the invention i8 to provide improved appar-
atus for heating a body of flowable material.
According to the present invention there is provided
electrical melting apparatus comprising a melting receptacle of
high temperature resistant material for holding molten material,
~aid melting receptacle having a bottom opening for discharging ,
the molten material from said melting receptacle, and a plurality
of heating elements extending in parallel directions acrosq the
interior of said receptacle, each of said heating elements having
a depth, from the top to the bottom of the respective heating
element, which is greater than the thickness of said heating ele-
ment, and each of said heating elements comprising two vertically
spaced central portions extending longitudinally of the respective
heating element and end portions connecting the ends of said cen-
tral portions.
Such apparatus is particularly suited to heating batch
mineral material into molten glass for processing into glass fila-
ments at substantially increased rate~.
Preferred embodiments of the invention will be described
by way of example with reference to the accompanying drawings in
which;
Figure 1 is a front elevation view of apparatus for
producing continuou~ filament glas~ strand according to the prin-
.~ ciples of the invention.
Figure 2 is a side levation view of the apparatusillustrated in Figure 1.
A~
1049078
Figure 3 is a longitudinal sectional view of a melter
and feeder arrangement according to the principles of the invention
used in the apparatus shown in Figures 1 and 2.
Figure 4 is a transverse section view taken substan-
tially on the line 4-4 of Figure 3.
Figure 5 is an enlarged side elevation view of one of
the heating elements shown in Figures 3 and 4.
Figure 6 is a plan view of the heating element shown
in Figure S.
Figure 7 is an end elevation view of the heating ele-
ment shown in Figures S and 6 taken substantially on the line
7-7 of Figure S.
Figure 8 is a diagram of an electrical supply arrange-
ment and control circuit for the heating elements.
Figure 9 is another heating element orientation with-
in a melting receptacle.
Figure 10 is a side elevation view of another heating
element according to the principles of the invention.
Figure 11 is a plan view of the heating element shown
in Figure 10.
Figure 12 is a plan view of another heating element
according to the principles of the invention.
Figure 13 is a side elevation view of the heating
element shown in Figure 12.
While the invention finds particular use in manufac-
turing glass filaments, one may use the invention in processing
flowable and heat softenable materials generally. The use of glass
filament forming apparatus is an example only to explain the
operation of the invention.
Figures 1 and 2 show apparatus on three levels oper-
..
1049078
ating to produce continuous filament glass strand that collects
as a wound package. As illustrated an upper level floor 10
between the upper and intermediate levels supports a processing
assembly 12 that supplies molten glass streams 14 from a feeder
or bushing 16. A winder 18 on the lower level attenuates the
molten glass streams 14 into continuous glass filaments 20. A
gathering shoe 22 at the intermediate level combines the advancing
continuous glass filaments 20 into a glass strand 24. The winder
`18 advances the strand 24 downwardly through an opening 26 in the
10 intermediate floor 28 to wind the strand 24 as a package 30 on
a suitable collector such as a tubular collector 32 telescoped
onto a collet 34. The winder 18 drives the collet 34 in rotation.
A reciprocatable and rotatable strand traversing means 36 recip-
rocates the advancing strand 24 lengthwise of the collecting tube
32 to distribute the strand 24 on the strand package 30.
At the intermediate level an applicator 40 supported
within a housing 42 applies sizing liquid or other coating mater-
ial to the advancing filament~ 20. The applicator 40 may be any
suitable means known to the art such as an endless belt that moves
- 20 to pass through a sizing liquid or other coating material held
in the housing 42. As the filaments 20 travel across the surface
of the moving applicator 40, some of the sizing liquid or other
coating material on the applicator transfers to the filaments.
The processing assembly 12 includes a frame 48 sup-
porting a batch feeding section 50, a furnace receptacle or melter
52 heating batch mineral material supplied from the feeding sec-
tion 50 into molten glass and the feeder of bushing 16 receiving
molten glass from the melter 52. The frame 48 includes vertical
portions 54 and horizontal bottom portions 56.
In the embodiment illustrated the feeding section 50
- 5 -
,,
~0490'78
includes a batch supply portion 60 and a batch distributing
portion 62 that cooperate to continuously provide a layer of
batch material in comminuted form over the upper surface of a
body of molten glass held in the melter 52. The batch supply
portion 60 positions a relatively stationary hopper 64 with a
supply of batch mineral material in comminuted form above a sup-
plemental hopper 66 that is part of the batch distributing por-
tion 62. Cross members 68 forming part of the frame 48 hold the
relatively stationary hopper 64 above the supplemental hopper
66.
As shown the batch distributing portion 62 both meters
and regulates the delivery of batch mineral material into the
melter 52 and distributes the batch mineral material over the
entire open area of the open top of the melter 52. Accordingly,
apparatus regulates batch material leaving the supplemental
hopper 66 and moves the hopper 66 for batch distribution. In the
arrangement the supplemental hopper 66 mounts on a shaft 70 held
in ~ournal bearings 72 carried by cross members 74 on the frame
48. An electric motor 76 drives a rotational batch regulating
means through a speed reducing mechanism 78 and a drive system.
The output shaft 80 of the speed reducing mechanism 78 drives the
shaft 70 through a chain 84 connecting a sprocket 82 on the shaft
70 with a sprocket 86 on the output shaft 80. The rotational
energy of the shaft 70 transfers to the batch regulation means.
As the shaft 70 rotates, a sprocket 88 fixed on the shaft 70
drives a sprocket 90 on a shaft 92 through a second chain 94. The
shaft 92 is at the outlet region of the supplemental hopper 66 and
mounts for rotation in bearings carried by the supplemental hop-
per 66. The shaft 92 extends across the outlet of the hopper 66
and has radially extending blades or veins 96. As the electrical
-- 6 --
-
~ 049078
motor 76 rotates the shaft 92 through the drive system of chains
and sprockets, the veins 96 move to regulate batch material from
the supplemental hopper 66 to the melter 52. One may control the
rate of delivery of the batch material from the supplemental hop-
per 66 into the melter 52 by varying the speed of rotation of the
shaft 92 and consequently the movement of the veins 96.
The supplemental hopper 66 is swingable or oscilla-
table about the axis of the shaft 70 for distributing batch ma-
terial from the hopper 66 over the open area of the melter 52,
such motion providing a substantially uniform layer of batch
material on the surface of the body of molten glass in the melter
52. The arrangement secures a bracket 102 to one wall of the hop-
per 66 near the bottom or outlet region of the hopper 66. A plat-
form 104 on the upper floor 10 supports an electric motor 106
that drives a speed reducing mechanism 108. The output shaft 110
of the speed reducing mechanism has fixed on it an arm 112 that
pivotally connects with a rod or link 114. The other end of the
l~nk 114 pivotally connects to the bracket 102. As the electric
motor 106 rotates the output shaft 110 of the speed reducing
mechanism 108, the arm 112 moves the link 114 to oscillate the
outlet of the supplemental hopper 66 back and forth across the
open entrance to the melter 52.
Figures 3 and 4 show the construction of the melter
52 and feeder or bushing 16 arrangement forming part of the pro-
cessing assembly 12 shown in Figures 1 and 2. The melter 52 con-
verts batch mineral material to molten glass through heat supplied
by spaced apart generally parallel electrical current conducting
heating elements 120 extending across the interior or melting
chamber 122 of the melter 52. Molten glass in the melter 52 flows
into the bushing 16 through the melter' 8 outlet or exit passage-
1049078way 124.
The melter 52 comprises a refractory cover 128, a
liner 130 and a heating arrangement including the heating ele-
ments 120.
The refractory cover 128 is built of high temperature
resistant refractory. The refractory cover 128 includes length-
wise extending portions 134 and transversely extending portions
136. These portions define an entrance region for receiving
batch material from the supplemental hopper 66.
The liner 130 conforms to the interior arrangement of
the refractory construction of the melter 52 to define the melt-
ing chamber 122. Because the liner 130 must not deteriorate ap-
preciably under high melting temperatures generally present dur-
ing the operation of the melter 52, the liner 130 is normally
made of platinum or a platinum alloy such as an alloy containing
a substantial percentage of rhodium. It is possible to use other
high temperature resisting materials for the liner 130.
The liner 130 is not electrically energized; it is
separated electrically from electrical circuits and supplies.
A~ more easily seen in Figures 3 and 4 the lower portion of the
liner 130 defines the outlet passageway 124 and terminate~ at its
lower portion with flanges 140.
An electrical arrangement supplies low voltage and
high amperage electrical energy to the heating elements 120. The
electrical arrangement supplying current to the heating elements
120 is electrically separate from the liner 130. Intense heat
generated from electrically energizing the heating elements 120
melts the batch material into molten glas~.
The position of the heating element~ 120 is beneath
the surface of a body of molten glass in the melting chamber 122.
- 8 -
.. ~ i
1049078
As shown in Figures 3 and 4 the heating elements 120 are under
the surface of a body of molten glass 141, the upper surface of
the molten glass being covered by a layer 142 of unmelted batch
mineral material in comminuted form continuously supplied from
the supplemental hopper 66. Both the electrical arrangement sup-
plying current to the heating elements 120 and the heating ele-
ments 120 themselves are electrically separate from the liner 130.
The current conducting heating elements 120 have a
width or depth at least as large as their thickness; the depth
of the heating elements 120 is oriented generally normal to the
surface of the body of molten glass. In a specific form, which is
more plainly seen in Figures 5 through 7, the current conducting
heating elements have an appreciable depth compared with their
thickness. As shown the heating elements 120 are made of electri-
cal current conducting tubular material formed into longitudinal
units having a somewhat flattened elliptical or race-track ~haped
central portion 144 and connectors 146 extending from the end~ of
the central portion 144. The elongated central portion 144 includes
two spaced apart parallel straight middle elements 148 and shorter
end elements lS0 connecting the adjacent ends of the straight
element 148. In the form illustrated the end elements 150 are
semi-circular. In figure 5 "w" indicates the width or depth of
the heating elements 120; in Figure 6 "t~ indicates the thickness
; of the elements 120. In the specific form shown the thickness of
the heating elements 120 is the diameter of the tubular material
comprising the elements 120.
Because of the elongated shape of the central portions
144, electrical current divides as it leaves the connectors 146
to flow into the elongated central portions 144. As shown in
Figure 5 the central portions 144 provide two distinct current
Al~
1049078
paths, viz. Path I and Path II.
As with the liner 130, the material tubular units
comprising the heating elements 120 is platinum or an alloy of pla-
t~num.
The connectors 146 are curved tubular members. A
pGrtion 146a extends axially away from the central portion 144
for a short distance; then the connectors 146 turn with a portion
146b extending obliquely of the element's lengthwise axis before
again turning with a portion 146c extending in a direction axial-
ly away from the central portion 144. Moreover, the connectors
146 include metal strip portions 152 and 154 extending outwardly
and generally lengthwise of the portions 146a and 146b. These
metal strips provide additional metal for electrical current; the
strips assist uniform division of electrical current into the dis-
tinct current paths of the elongated central portion 144.
To assist heat distribution that promotes more uniform
heat emmission throughout the current conducting heating element~
120, heat resistant material in the form of refractory is within
the hollow tubular units comprising the current conducting ele-
ments 120. In Figure 7 one can see that refractory 156 fills the
interior of the connectors 146. Refractory also fills the interior
of the curved end elements lS0. It has been useful to use an alu-
minum oxide refractory. A refractory tubing 158 snugly fits against ~'!
the inner surface of the straight middle elements 148. The tubing
158 strengthens the middle elements 148. An aluminum oxide tubing ~ -
commercially available from McDaniel Company under the deQignation
"AP-35~ gives good results.
As shown in Figures 3 and 4, the electrical current
conducting heating elements 120 extend transversely across the
melting chamber 122 in spaced apart adjacent generally parallel
-- 10 --
, . . .
.
.
1049078
relationship. The distance between adjacent elements 120 is
normally from 1 to 3 inches, 2 inches being most common. More-
over, the depth or width "w" of the heating elements are orien-
ted generally in the direction of flow of molten glass moving to
the exit passageway or opening 124 to the feeder 16. In the ver-
tical process shown in Figures 1-4 the heating elements are verti-
cal and normal to the surface of the body of molten glass 141.
Electrical current carrying bus bars support and
electrically interconnect the current conducting heating elements
120 at their ends. As shown two sets of bus bars, viz. bus bars
160 and 162, each extend lengthwise along the upper surface of the
refractory cover 128. Cooling tubes 164 extend through each of the
upper and heavier bus bars 160 to carry cooling water that con-
trols the temperature of the bus bars. Each of the bus bars 160
and 162 contains generally semi-circular recesses. The recesses
in each bar 160 align with the recesses in bar 162 to form grip-
ping regions into which fit the end portions of the connectors
146. When pressed together such as by bolts 166, the gripping
regions of the bus bars rigidly hold the current conducting heat-
ing olements 120.
An electrical arrangement supplies electrical current
to each set of bus bars 160 and 162 and consequently to the ele-
ments 120 from transformers 168 and 170 through conductors 172
and 174 respectively.
In operation, electrical current flows from the bus
bar arrangement to the central portion 144 of the current conduct-
ing heating elements 120 through the connectors 146. As the cur-
rent reaches connector portions 146b and 146a, the current more
easily flows through the metal strips 152 and 154. In a sense, at
start-Up of the melter 52 these strips tend to orient the current
-- 11 --
. ,, ,~ .
~049078
for substantially uniform current split between the two distinct
current paths, i.e. Paths I and II, of the heating elements
120.
As the supplemental hopper 66 supplies the layer 142
of batch material to the surface of the molten glass 141 in the
melting chamber 122, the energized elements 120 provide intense
heat under controlled conditions that regulate the melter's melt-
ing rate with the rate of molten glass delivery from the feeder
16. Because the heating elements 120 are submerged in the body of
molten glass 141, batch normally does not directly engage the
heating elements 120. Usually the heating elements are from 1-3
inches beneath the surface of the molten glass 141 in the melting
chamber 122.
If in the melting chamber 122 the temperature of mol-
ten glass at the upper leg(Path I) of the heater elements 120 be-
comes cooler than molten glass near the lower leg ~Path II), re-
sistance of the metal in the tubular material along Path r becomes
,. ~ . ,.
less than resistance of metal along Path II. Accordingly addition-
al current flows along Path I to increase the temperature of that
portion of the heating elements. In similar fashion, if conditions
reduce the temperature of the metal in the lower leg (Path II) of
the elements 120, additional current flows along Path II to in-
crease temperatures in that leg. Consequently, temperature con-
ditions along the length and width of the elements 120 effect cur-
rent flow to somewhat compensate and make more even thermal treat-
ment of molten glass by the heating elements 120.
The refractory within the heating elements 120 pro-
motes more uniform heat emission throughout the heating elements
120. Accordingly, the molten glass receives a more uniform ther-
mal treatm~nt. The refractory tends to store thermal energy.
- 12 -
A
.~ . ~ . . .
.
~049078
If for any reason a cool zone develops on a heating element 120,
heat from the refractory flows to that cooler zone to assist
in raising the temperature of the zone to a temperature substan-
tially equal to the surrounding temperature.
Figure 8 shows a circuit for controlling electrical
energy supplied to the heating elements 120 from the transfor-
mers 168 and 170 and consequently generally controlling the ther-
mal energy emitted by the heating elements 120.
As shown, the secondary 178 of the power transformer
168 and the secondary 180 of the power transformer 170 connect
to adjacent ends of the bus bars at terminals 182 and 184 respec-
tively. Suitable electrical means supplies the primaries 186 and
188 of the power transformers 168 and 170 respectively with elec-
trical power through leads Ll and L2. The electrical power to the
leads Ll and L2, for example, may be 60 cycles alternating cur-
rent of 440 volts. The secondaries 178 and 180 reduce the voltaqe
from the primaries 186 and 188 to provide around 5 to 6 volts to
the bus bars with ~ufficently high current flow, for example,
5,000 amperes, to heat the elements 120 by conventional resistance
heating to the high temperatures needed in the melter 52 to con-
vert the batch mineral material into molten glass for delivery
to the feeder 16.
A control circuit using a silicon control rectifier
190 senses voltage variations caused by resistance changes in the
heating elements 120; changes in resistance may occur, for exam-
ple, upon interruption of normal glass flow from the feeder 16
occurring as the winder 18 completes a package 30 and an operator
puts a new collector on the collet 34. The sensing circuit modi-
fies the power supply current to restore a predetermined temper-
ature to the heater strips 120 for better control of molten glass
- 13 -
~'
. . ::.
' :
1049078
flow through the melter 52 to the feeder 16. Because the time-
constant characteristics of the silicon control rectifier 190
are small, any deviation from a preselected flow rate is at a
minimum.
As shown the control circuit uses a control transfor-
mer 192 with its primary 194 connected across the terminals 182
and 184. The transformer 192 preferably provides a 4 to 1 reduc-
tion in voltage; accordingly, the circuit uses a center tap secon-
dary 196. Diodes 198 rectify the current in the secondary 196.
A pi filter circuit 200 receives the rectified current. The pi
filter circuit 200 comprises a pair of parallel connected conden-
sers 202 and 204 having interposed between them a resistance 206
and an inductance 208 connected in series.
The resulting direct output from the pi filter circuit
200 is applied across a voltage divider 210 that gives an exceed-
ingly small output signal, for example an approximately 10 milli-
volt DC output, to a control unit 212 of conventional construction.
The silicon control rectifier 190 receives the output of the con-
trol unit 212. The silicon control rectifier 190 holds the time-
constant factor of the power circuit below one-quarter cycle.
The voltage sensing circuit is a more rapid sensing
system than a thermocouple system. Through the electrical supply
and control arrangement shown in Figure 8, the melter 52 provides
a more stable temperature for melting batch material to molten
glass as the winder 18 attenuates glass fibers from the molten
streams supplied at the outlets of the feeder 16. The result is
glass fibers of more uniform dimension throughout package build
and between package~ produced using the apparatus of the invention.
Figure 9 shows another arrangement for the heating
elements 120 in the melter 52. In Figure 9 there are an even num-
.~.`!
1049078
ber of elements 120; the distance "D" between the upper legs(Path I) of the middle two ~lements 120 i8 approximately twice
the distance between the other elements 120. Because the distance
between the adjacent elements 120 is normally from 1 to 3 inches,
the distance "D" is usually from 2 to 6 inches, 4 inches being
more common. To give more uniform heat paths for molten glass in
the melter 52, the arrangement orients most of the elements 120
to slant towards the central region of the melting chamber 122. As
shown all the elements 120, except for the outermost or end ele-
ments, make an angle ~ with the vertical. While the end elementsare vertical, the other elements slant towards the central region
of the melter 52 with a progressively increasing angle ~; normally
angle ~ varies from 5 to 25 degrees, angle ~ is largest for the
center most heating elements 120. The arrangement shown in Figure 9
orient~ the lower legs (Path II) at substantially equal distances
apart.
As the heating element arrangement of Figure 9 operates
to convert batch mineral material to molten glass, the molten glass
encounters substantially the same thermal treatment as it flows
along its path to the outlet of the melting receptacle.
Figures 10 and 11 show another electrical current con-
ducting heating element,i.e. heating element 220, according to the
principles of the invention. The heating element 220 has an elonga-
ted generally rectangular central portion 244 with connectors 246
extending from the ends of the central portion 244. The central por-
tion 244 includes two spaced apart side walls 248 and two spaced
apart thickness wall portions 250 that unite to provide a hollow
unit. Refractory 252 fills the interior of the central unit 244.
The central portion has a depth or width~wN and a thickness "t~.
The central portion 244 includes oblique end wall por-
- 15 -
.,~,. . .
1049078
tions 254 and a middle portion 256 from which extend the connec-
tors 246.
The connectors 246 are curved tubular members and have
generally the same configuration as the connectors 146. A portion
246a extends axially away from the middle end portion 256 of the
portion 244 for a short distance; then the connectors 246 turn
with a portion 246b extending obliquely of the element's length-
wise axis before again turning with a portion 246c extending axi-
ally away from the central portion 244.
As in the case of the heating elements 120, the con-
nectors 246 include metal strip portions 258 and 260 running gen-
nerally lengthwise of the portions 246a and 246b. These metal
strips, as in the case of portions 152 and 154, provide addition-
al metal that tends to assist uniform division of electrical cur-
rent into two generally distinct current paths lengthwise of the
central portion 244.
As indicated by the dashed lines in Figure 10, the
current flow from the connectors 246 to the central portion 244
tends to follow two generally distinct electrical paths, viz. an
upper Path I and a lower Path II.
The current conducting heating elements 220 fit across
the melter 52 like the heating elements 120.
If in a receptacle, e.g. the melting chamber 122, the
temperature of molten glass at the upper Path I of the heater
elements 220 becomes cooler than molten glass near the lower Path
II, resistance of the metal in the elements 220 along Path I be-
comes less than the resistance of the metal along Path II. Accor-
dingly, additional current flows along Path I to increase the
temperature of the upper portion of the heating elements. In si-
milar fashion, if conditions reduce the temperature of the metal
- 16 -
A
,.~ .... .
.. .. .
1049078
in the lower Path II of the elements 120, additional current
flows along that path to increase temperatures of the lower por-
tion of the heating elements. Consequently, temperature conditions
along the length and width "w" effect current flow to somewhat
compensate and make more even thermal treatment of molten glass
treated by the heating elements 220. Thus, the operation of the
heating elements 220 i8 simil.ar to the operation of the heating
elements 120.
Referring to Figures 3 and 4, the feeder or bushing
16, which is beneath and is registered with the melter outlet
passageway 124, includes a bottom wall 270, side walls 272 and
end walls 274. The side and end walls terminate with laterally
extending flanges 276. Refractory members 278 thermally and elec-
trically insulate the flanges 276 of the feeder 16 from the bottom
flanges 140 of the liner 130. Moreover, refractory 280 surrounds
the exterior of the feeder 16. Frame members 282 supportthe high
temperature resistant refractory 280 in a conventional manner.
As in the case of the liner 130 and the current con-
ducting heating element~ 120, the walls 272,274 and 270 are made-
Of platinum or an alloy of platinum.
A group of orificed tips or tubular projections 284extend from the exterior of the bottom wall 270. It is through
these tubular projectings 284 that molten glass discharges from
the feeder 16 in the form of the molten glass streams 14.
As more clearly seen in Figure 1-3, the end walls 274
have terminals 286 that receive electrical energy from a power
transformer 288 through conductors 290. Electrical current sup-
plied to the feeder 16 through the terminals 286 heats the feeder
16 by resi~tance heating to maintain the molten gla~s ln the
feeder 16 at desired temperatures and viscosities.
- 17 -
j~
.,~
..
10490!78
Disposed adjacent to and somewhat below the bottom
wall 270 of the feeder 16 is manifold 292. Extending transversely
from the manifold 292 are fins or veins 294 that conduct heat away
from the molten glass streams 14 to render the glass of the streams
more viscous for efficient attenuation of the continous glass fil-
aments 20. The manifold 292 has an inlet tube 296 and an outlet
tube 298 that circulate heat absorbing fluid such as water through
the manifold 292. A mounting structure 300 ~ecured to a frame mem-
ber 3~1 supports the manifold 292.
As shown in Figures 1 and 2, the processing assembly
12 includes a cover or hood 302 disposed above the batch supply
portion 60 and batch distributing portion 62. From the top of the
hood 302 extends a stack or pipe 304 preventing the batch distri-
buting portion 62 from contaminating with fine particles of batch
the filament forming region at the bottom wall 270. The stack or
pipe 304 may connect to a suction blower to initiate forced air
circulation around the batch distributing portion 62.
Figures 12 and 13 shOw yet another embodiment of an
electrical current conducting heating element, denoted by the re-
ference numeral 320, according to the principles of the invention.
Like the other heating elements, the element 320 has appreciable
depth or width compared with its thickness. And it is made of the
same electrical current conducting tubular material as is the ele-
ment 120; heat resistant material, like the element 120, in the
form of refractory (aluminum oxide) is within the tubular material.
The elongated element 320 includes a central portion
324 that i~ formed by two spaced apart parallel elements 326 and
328 and by shorter straight elements 330 connecting the elements
326 and 328 together. Straight connector portions 334 extend from
each end of the element 320. As shown in the portions 334 are ex-
- 18 -
~1
. ."~,. ~ ~ .
w~
~049078
tensions of the straight element 326.
So, like elements 120, elements 320 each includes;
an elongated central portion including two spaced apart parallel
straight cylindrical portions, shorter end portions connecting
the straight portions, and connectors extending from each end and
extending along the longitudinal axis of the element. The connec-
tors (334) are straight.
Elements 320 are connected for melting like the ele-
ments 120 as shown in Figures 3 and 4.
-- 19 --
~1
'
. ~:
