Method and apparatus for forming glass fibers

The invention disclosed herein relates to method and apparatus for forming glass fibers wherein a fiber forming feeder has a bottom wall comprised of a substrate and a control layer arranged to form reticulated indentations around the orifices therein to promote the movement of molten glass from a disrupted orifice to an adjoining orifice wherein attenuation is continuing.

TECHNICAL FIELD 
The invention disclosed herein relates to method and apparatus for forming 
glass fibers wherein a fiber forming feeder has a bottom wall comprised of 
a substrate and a control layer arranged to form reticulated indentations 
around the orifices therein to promote the movement of molten glass from a 
disrupted orifice to an adjoining orifice wherein attenuation of the 
molten material into a filament is continuing. 
BACKGROUND ART 
The most widely employed technique for the production of continuous glass 
filaments consists essentially of drawing the filaments from a feeder or 
bushing having a base plate provided with a plurality of nozzles or 
projections, each of the projections having an orifice adapted to permit 
the molten glass to flow therethrough to provide a stream of molten 
material in a fiberizable condition. Such projections are otherwise known 
as "tips". 
Such "tip" type bushings substantially reduce the phenomenon of "flooding" 
of the bushing bottom wall upon a disruption of a filament forming 
operation, known as a "breakout". 
Flooding, the process wherein molten glass emerging from the bushing bottom 
wall generally spreads over the lower face of the bottom wall, is an acute 
problem with "tipless" bushings. That is, flooding is a particularly 
significant problem for bushings having a bottom wall comprised of a 
generally smooth or flat perforated plate with the streams of molten glass 
flowing from the orifices through the plate. 
The flooding problems associated with such tipless bushings account for the 
fact that such bushings are not widely employed. The present invention 
provides a system wherein the phenomen of flooding and the problems 
associated therewith can be substantially reduced. 
DISCLOSURE OF THE INVENTION 
The present invention pertains to method and apparatus for producing 
continuous filaments or inorganic material wherein the feeder for 
supplying the streams of molten material to the attenuated into filaments 
is comprised of an orifice wall comprising a substrate having a plurality 
of orifices therethrough adapted to issue streams, and a control layer 
joined to said substrate, said substrate and control layer being arranged 
to form reticulated indentations around the orifices wherein at least a 
portion of recesses are comprised of a material characterized in that said 
molten material exhibits a greater tendency to move through the 
reticulated indentations than over an exterior surface of the wall 
surrounding the orifices.

BEST MODE OF CARRYING OUT THE INVENTION 
As shown in FIG. 1, feeder or bushing 10 is adapted to supply a plurality 
of streams 14 of inorganic material, such as glass, to be attenuated into 
continuous filaments 15 through the action of winder 27. Filaments 15 
receive a liquid size or coating at applicator 19 and are gathered into 
strand 23 at gathering shoe 21, as is known in the art. Strand 23 is then 
wound into a package 25 at winder 27, as is known in the art. 
Environmental control means or blower 16 is adapted to supply a stream or 
streams of cooling fluid, such as air, toward streams 14 and bottom wall 
40 to remove heat from the fiber-forming zone to facilitate attenuation of 
the streams into filaments. 
Feeder 10 is comprised of housing or upper walls 11 suitably joined to 
bottom wall 40 having terminals 12 associated therewith to electrically 
energize bottom wall and/or housing 11 to heat the molten material 
therein. As such, terminals 12 are adapted to be connected to a suitable 
source of electrical power (not shown). 
As shown in FIGS. 2 and 3, bottom wall 40 is comprised of a substrate 42 
and a control layer 44, with substrate 42 having a plurality of orifices 
46 extending therethrough adapted to issue streams of molten material 14 
therefrom to be attenuated into filaments 15. 
Portions of substrate 42 form the base of recess or seat 48 around each 
orifice 46 and a channel or groove 50 extending between and in 
communication with the adjoining recesses 48. Such recesses 48 and 
channels 50 form reticulated indentions around the orifices wherein at 
least a portion of the recesses are comprised of or lined with a material 
characterized in that the molten material exhibits a greater tendency to 
move through the reticulated indentations than over the exterior surfaces 
53 of landings or bosses 52 of bottom wall 40. 
As can be seen in the drawings, the bottom edge of orifices 46 meet the 
bottom surface of recess 48. The outwardly extending sidewalls of the 
recesses 48 and channels 50 are defined by control layer 44, and the 
bottom section of recesses 48 and channels 50 are defined by the exterior 
surface or surface of substrate 42. As such, the material of substrate 42 
should exhibit a greater tendency for the molten material to "wet" the 
surface thereof than the material of control layer 44. That is, the 
material substrate 42 should exhibit a smaller wetting contact angle when 
associated with a bead of molten material than the wetting contact angle 
of the material of control layer 44 when associated with a bead of such 
molten material. 
As is known in the art, such "wetting contact angles" are determined by the 
angle formed between the surface of a given composition and a bead of 
molten material of a given composition when in contact with each other. 
Any suitable materials exhibiting such characteristics with respect to the 
response of the molten material may be suitable. For example, substrate 42 
can be comprised of substantially pure platinum and control layer 44 can 
be comprised of rhodium. Also, substrate 42 and/or control layer 44 can be 
platinum-rhodium alloys if the rhodium content of the control layer 44 is 
greater than the rhodium content of such a substrate 42. As such, the 
molten material will exhibit a greater tendency to move through recesses 
48 and channels 50 rather than across exterior surface 53 of control layer 
44, since the molten glass will have a greater tendency to wet the 
recesses 48 and channels 50. 
Landings or bosses 52 having exterior surfaces 53 thereon are positioned 
among recesses 48 and channels 50. 
Bottom wall 40 may be fabricated by bonding control layer 44 to substrate 
42 by any suitable means, such as electrodeposition or hot isostatic 
pressing. Orifices 46 may be formed therein by any suitable means and 
recesses 48 and channels 50 may be formed in control layer 44 such that 
the surface of substrate 42 is exposed at the bottom section thereof by 
any suitable means such as selective etching and/or machining. 
In operation, if a filament 15 breaks out, the molten material flowing 
through the disrupted orifice 46 should exhibit a tendency to flow through 
recess 48 and channels 50 associated therewith to one or more of the 
surrounding orifices and streams in the absence of spreading over the 
exterior surface of bottom wall 40 in a random manner disrupting the 
entire fiber forming operation. With the controlled distribution of the 
glass from a disrupted orifice to orifices and streams still being 
attenuated, the fiber forming operation should proceed unabated. 
For the majority of fiber forming operations, the diameter of the orifices 
46 may be within the range from about 0.030 inch to about 0.090 inch or as 
is known in the art. The diameter of the counterbores forming recesses 48 
may be within the range from about 110% to about 200% of the orifice 
diameter. Further, the cross-sectional area of a channel 50 may be within 
the range from about 4% to about 25% of the cross-sectional area of an 
individual orifice 46. Further, it may be advantageous to use an 
arrangement wherein the chanenls 50 are formed deeper into the substrate 
42 than the recesses 48. 
As such, bottom wall 40 has an exterior surface that is generally planar or 
without "tips" or projections extending downwardly from bottom wall 40, as 
is generally known in the art. 
As shown in FIGS. 4 and 5, bottom wall 40 is comprised of a substrate 60 
and a control layer 64, wherein the substrate 60 is comprised of a 
laminate of first layer 61 and second layer 62. As such, first layer 61 
can be a platinum alloy containing rhodium, for example J Alloy, which 
contains approximately 25% rhodium and the remainder platinum. Second 
layer 62, which is intimately bonded to first layer 61, may be comprised 
of substantially pure platinum or a platinum-rhodium alloy having a lower 
rhodium content than the rhodium or platinum-rhodium alloy material of 
control layer 64. 
Similarly, orifices 66 extend through substrate 60 and recesses or seats 68 
individually surround each orifice 66, and channels or grooves 70 extend 
between and in communication with recesses 68. 
The orifices 46 in FIG. 2 are arranged in a rectangular array, whereas the 
orifices 66 of FIG. 4 are arranged in a staggered array. As such, each 
orifice 66 within the field of orifices is in communication with six 
adjacent orifices by means of the reticulated indentations therein. 
The three layered system as shown in FIGS. 4 and 5 may be laminated by any 
suitable means, such as by hot isostatically pressing three sheets of 
suitable material together to intimately bond them together. Seats 68 and 
groove 70 may be formed in control layer 64 and second layer 62 by any 
suitable means such as chemical etching or milling. 
As shown in FIG. 5, the bottom sections of recesses or seats 68 are defined 
by a surface of second layer 62 and the vertical walls of seat 68 and 
channels 70 are defined by surfaces of control layer 64. As such, landings 
or heads 72 having exterior surfaces 73 are located among orifices 66. 
Thus, first layer 61 of substrate 60 may contain any desired amount of 
rhodium notwithstanding the amount of rhodium employed in control layer 
64, since second layer 62 is chosen to have suitable wetting 
characteristics with respect to control layer 64. That is, the wetting 
contact angle of the material of second layer 62 should be less than the 
wetting contact angle of the material of control layer 64 to reduce the 
tendency of the bushing bottom wall to flood in the event of filament 
breakouts during attenuation. As such, exterior surfaces 73 exhibit a 
tendency to be more non-wetting or less wetting than at least a portion of 
recesses 68 and channels 70. 
As shown in FIGS. 6 and 7, bottom wall 40 is comprised of substrate 82 and 
control layer 84 having a plurality of orifices 86 extending therethough 
adapted to issue streams molten material for attenuation into filaments. 
Recesses or seats 88 and channels or grooves 90 are formed in substrate 82 
by any suitable means to form a network of indentations associated with 
orifices 86. Landings or bosses 92 having exterior surfaces 93 are formed 
among orifices 86. 
However, only recesses 88 and channels 90 are lined with control layer 84. 
Opposite from the technique employed in FIGS. 2-5, the material of control 
layer 84 should exhibit a greater tendency to be wet by the molten 
material than the substrate 82, which is exposed as exterior surfaces 93 
among recesses 88 and channels 90. Similarly, however, the molten material 
from a disrupted orifice should exhibit a greater tendency to move through 
recesses 88 and channels 90 to adjoining undisrupted streams surrounding 
the disrupted orifice to permit continuous operation of the fiber forming 
system. In essence, the molten glass should exhibit a greater affinity for 
the material of the recesses and grooves than for the exterior surfaces of 
the landings. 
Even though the recesses and seats disclosed herein are shown as being 
circular in nature and the channels or grooves disclosed herein are shown 
to be substantially rectangular in shape, it is to be understood that any 
suitable shapes of such recesses and/or channels may be employed. 
Control layer 84 may be formed along recesses 88 and channels 90 by any 
suitable means, preferably with control layer 84 being securely joined or 
intimately bonded to substrate 82 to prevent unwanted delamination of the 
system. 
It is apparent that within the scope of the present invention, 
modifications and different arrangements can be made other than as herein 
disclosed. The present disclosure is merely illustrative, with the 
invention comprehending all variations thereof. 
INDUSTRIAL APPLICABILITY 
The invention disclosed herein is readily applicable to the formation of 
continuous and/or discontinuous glass filaments.