Method and apparatus for producing fibers

Method and apparatus are provided for fluidically attenuating streams of material into filaments wherein the blower is designed according to a number of parameters to provide a stream of working fluid at sonic velocity.

TECHNICAL FIELD 
The invention disclosed herein relates to improved process and apparatus 
for fluidically attenuating streams of molten material into filaments, 
such as glass filaments. 
BACKGROUND ART 
In the production of fluidically attenuated glass filaments, the need to 
improve process efficiency and controllability has been ever present. 
Particularly important is the need to produce a uniform mass flow having a 
high attenuative force while minimizing the operating expense of doing so. 
There have been a number of attempts to produce such systems. For example, 
Russian Pat. No. 371,178 discloses the use of a Laval nozzle to attenuate 
the streams of molten glass into filaments. German Pat. No. 848,990 
discloses a system for adjusting the blowers relative to each other to 
produce maximized operating conditions. U.S. Pat. No. 2,224,466 discloses 
the use of a skirted blower for the production of staple filaments. 
DISCLOSURE OF THE INVENTION 
This invention provides method and apparatus for fluidically attenuating 
streams of material into filaments through the action of fluidic or 
gaseous blasts. The design of the blower or attenuation means has been set 
forth in a range of parameters to maximize the efficiency and 
controllability of the process.

BEST MODE OF CARRYING OUT THE INVENTION 
As shown in FIG. 1, feeder 10 which has a bottom wall 11 having projections 
12 extending therefrom is adapted to supply a stream of molten filament 
forming material, such as glass, from the distal end 14 of each projection 
12. Through the action of a pair of opposed blowers 40, the streams of 
molten material are attenuated into filaments 17, which then advance along 
a path 18. 
Joined to the bottom of blowers 40 are skirts 20. Each skirt 20 is 
comprised of a wall 22 and a flange 23 which abuts bottom wall or lower 
exterior wall 73 of the blower 40. Flange 23 can be joined to wall 73 by 
conventional means such as screw 25. Preferably, skirt 20 is laterally 
adjustable along lower exterior wall 73 from flush with the beveled wall 
75 to a point recessed a distance d.sub.3 therefrom. Preferably, the 
distance d.sub.3 is .ltoreq.0.125 inches. 
As can be seen in FIG. 1, the blowers 40 are laterally adjustable to 
optimize the distance d.sub.2 as needed. At start-up, however, the 
distance d.sub.2 should be great enough to permit the beads of glass to 
freely fall between the blowers without striking the surface of the 
blowers. 
For maximized operating efficiency, the upper exterior surface 44 of each 
of the blowers should be located a distance d.sub.1 below the distal ends 
14 of projections 12. Preferably, d.sub.1 is .gtoreq.0.125 inches. 
Since blowers 40 emit a stream of high velocity fluid, the fluid at the 
region between the feeder 10 and blowers 40 is induced to flow inwardly 
and downwardly therewith. 
In some instances, ambient air induced to flow between feeder 10 and 
blowers 40 is acceptable to produce some forms of fibers. However, it has 
been found that with the addition of an induced or second fluid supply 
means 28 associated with each blower 40 adapted to supply a quantity of 
conditioned fluid between the blower 40 and feeder 10, the characteristics 
of the resulting product can be modified. 
Since such induced fluid is controlled and directed to cool the streams of 
molten material issuing from the projections 12, supplying a second fluid 
from supply means 28 at an elevated temperature, that is above ambient, 
generally alters the heat transfer characteristics of the forming region. 
For example, heated air or steam characteristics and/or the process 
efficiency and/or throughput. 
For example, by supplying heated air at a temperature of approximately 
650.degree. F. at volumes and velocities sufficient to generally supply 
substantially all of the induced air requirements of the system, finer 
diameter filaments can be formed than by using ambient air. Similarly, the 
throughput of the system can also increased. 
Similarly, the length l.sub.1 of wall 22 can affect the product 
characteristics. Altering the length l.sub.1 can, among other things, 
change the relative lengths of the staple filaments formed by the system. 
Even though the system may be operated without skirts 20, it is preferred 
that the length l.sub.1 of wall 22 be within the range from about 6 inches 
to about 18 inches for the production of staple glass filaments. 
Each of the blowers 40 is comprised of a first or upper portion 42 having 
an upper exterior surface 44 and a front or forward surface 46. 
Intermediate upper surface 44 and forward surface 46, beveled surface 45 
is angled upwardly and inwardly from front surface 46 at an angle "E". To 
provide the proper flow characteristics of the induced air at the 
fiber-forming region, angle "E" should fall within the range from about 
0.degree. to about 20.degree.. Preferably, angle "E" is within the range 
from about 5.degree. to about 7.degree.. More specifically, angle "E" 
should be .gtoreq.0.degree. and .ltoreq.20.degree., and preferably angle 
"E" should be .gtoreq.5.degree. and .ltoreq.7.degree.. 
Front surface 46 forms a portion of lip 48 which also includes a base 49 
and a nozzle edge 50. 
Opposite front surface 46, landing 52 and arcuate surface 53 which is 
contiguous with landing 52 are adapted to form the upper portion of the 
nozzle according to the principles of this invention. Chamber surface 54 
of first portion 42 is contiguous with arcuate surface 53 and serves to 
define plenum 95 when first member 42 is joined with lower or second 
member or portion 71. 
Since the fiber-forming systems generally require a long continuous slot 
for the nozzle thereof, it is important that the thickness 1.sub.2 of base 
49 be sufficient to prevent appreciable bowing or deformation when the 
high pressure working fluid is supplied to the blower 40. If the lip 48 
deforms, the nozzle gap or distance d.sub.6 will not be uniform; thereby 
creating a non-uniform velocity profile over the width of the blower. A 
non-uniform velocity profile generally tends to produce filaments of 
different diameters over the width of the blower system. 
For the purposes of this invention, the lip length d.sub.4 is the distance 
lip 48 projects from chamber surface 54 of first member 42. That is, it is 
the vertical distance between the plane containing base 49 and the plane 
containing chamber surface 54. 
For the purposes of this invention, the lip width d.sub.5 is the distance 
between the transition point between arcuate surface 53 and chamber 
surface 54 and the front surface 46. 
For proper design, it is believed that the ratio R.sub.4 which is the ratio 
of the lip length d.sub.4 to the lip width d.sub.5 should be less than 3. 
That is, R.sub.4 =d.sub.4 /d.sub.5, and R.sub.4 .ltoreq.3. Preferably, 
ratio R.sub.4 is approximately 1. 
Similarly, the ratio R.sub.5 which is the ratio of the lip length to the 
base length l.sub.2 of base 49 should be .ltoreq.30 and preferably ratio 
R.sub.5 is .ltoreq.10. That is, R.sub.5 =d.sub.4 /1.sub.2, and R.sub.5 
.ltoreq.30 and preferably R.sub.5 .ltoreq.10. 
The lower or second member or portion 71 of blower 40 is comprised of a 
lower exterior or bottom wall 73 and a forward wall 75 having beveled wall 
74 therebetween. Beveled wall 74 is contiguous with forward wall 75 and is 
angled downwardly and inwardly at an angle "F" therefrom. 
For proper system performance, it is believed that angle "F" should be 
.gtoreq.0.degree. and .ltoreq.3.degree., preferably, angle "F" is within 
the range from about 0.degree. to 1.degree.. That is, angle "F" should be 
.gtoreq.0.degree. and is .ltoreq.1.degree. in the preferred system. 
First arcuate section 77 extends from forward wall 75 and joins head 
section 78 at the side opposite forward wall 75. Second arcuate section 79 
is contiguous with head section 78, and head section 78 is located 
intermediate first arcuate section 77 and second arcuate section 79. 
Extending obliquely into the blower, chamber section 80 is contiguous with 
second arcuate section 79 to further define plenum 95. 
A number of relationships are believed to be important to produce an 
efficient high velocity blower according to the principles of this 
invention. From FIGS. 2, 3 and 4, it can be seen that head section 78 and 
chamber section 80 form an angle "G" therebetween. It is believed that 
angle "G" should fall within the range from about 65.degree. to about 
145.degree. with the value of "G" falling between 75.degree. and 
105.degree. preferably. That is, angle "G" should be .gtoreq.65.degree. 
and .ltoreq.145.degree. in the broad sense, and preferably angle "G" 
should be .gtoreq.75.degree., but .gtoreq.105.degree.. 
As shown in FIG. 4, the first member 42 and second member 71 are fastened 
together by means of screws 100. Of course, members 42 and 71 can be 
fastened together by any suitable means. The width of the nozzle gap 
d.sub.6 is adjusted by adding or removing shims 98 from between members 42 
and 71. 
When joined together, first member 42 and second member 71 are designed to 
provide a smoothly or monotonically converging passageway having a point 
or edge convergence at the end thereof. That is, nozzle edge 50 should be 
located immediately adjacent head section 78. The gap between edge 50 and 
head section 78 being equal to the nozzle gap or distance d.sub.6. 
At the nozzle, landing 52 and head section 78 form an angle "A" 
therebetween. For proper performance, it is believed that angle "A" should 
be .gtoreq.5.degree. and .ltoreq.60.degree., with "A".gtoreq.10.degree. 
and .ltoreq.30.degree. being preferred. For the purposes of this 
invention, angle "A" is as the convergence angle. 
As shown in FIG. 2, landing 52 is angled slightly with respect to front 
surface 46. The angle "D" is formed between a line extending generally 
parallel to front surface 46 and the plane containing landing 52. As shown 
in FIG. 2, angle "D" is approximately 5.degree., and as it can be seen in 
FIG. 2, an angle "C" is formed between same line generally parallel to 
front surface 46 and the plane containing head section 78. 
As such, angle "A" is the difference between angle "C" and angle "D". As 
shown in FIG. 2, angle "C" is approximately 25.degree., thus convergent 
angle "A" is approximately 20.degree.. 
The angle formed between the central line "X" that bisects angle "A" and 
the path 18 of the filaments is designated as "B". Impingement angle "B", 
it is believed, should be .gtoreq.0.degree., but .ltoreq.40.degree., with 
"B".gtoreq.10.degree. and .ltoreq.25.degree. being preferred. The 
impingement angle "B" directly affects the amount of attenuative force 
supplied to the filaments, and thus the efficiency of the operation. 
As can be seen from FIG. 3, arcuate surface 53 has a radius of r.sub.2, 
while arcuate section 79 has a radius of r.sub.1. 
For proper performance, it is believed that the ratio R.sub.1 of radius 
r.sub.1 to gap d.sub.6 should be .gtoreq.3, with a ratio R.sub.1 .gtoreq.6 
being preferred. That is, R.sub.1 =r.sub.1 /d.sub.6, and R.sub.1 
.gtoreq.3. Preferably R.sub.1 .gtoreq.6. 
Also, the ratio R.sub.2, which is equal to the ratio of radius r.sub.2 to 
the gap d.sub.6 should be greater than the ratio R.sub.1. That is, R.sub.2 
=r.sub.2 /d.sub.6 and R.sub.2 .gtoreq.R.sub.1. 
The converging section length l.sub.3 is equal to the sum of the lengths of 
the landing 52 and arcuate surfaces 53. It is believed that the ratio 
R.sub.3 which is equal to the ratio of the converging section l.sub.3 to 
the gap d.sub.6 should be .gtoreq.10 and .ltoreq.2,000, with R.sub.3 
.gtoreq.10 and .ltoreq.300 being preferred. That is, R.sub.3 =l.sub.3 
/d.sub.6 and 10 .ltoreq.R.sub.3 .ltoreq.2,000. Preferably 
10.ltoreq.R.sub.3 .ltoreq.300. 
Also, it is believed that wherein A.sub.1 is equal to the cross-sectional 
area of the orifice formed between the edge and the head section and 
A.sub.2 is the area of the transverse cross section of the plenum 95 as 
shown in FIG. 4, the ratio R.sub.6 of the area of the plenum to the 
cross-sectional area of the nozzle orifice shold be .gtoreq.5. That is, 
R.sub.6 =A.sub.2 /A.sub.1 and R.sub.6 .gtoreq.5, and preferably R.sub.6 
.gtoreq.10. 
A blower, according to the principles of this invention, having the 
following parameters: 
Angle A=20.degree. 
Angle B=15.degree. 
Angle C=25.degree. 
Angle D=5.degree. 
Angle E=5.degree. 
Angle F=1.degree. 
Angle G=96.degree. 
falling within the aforementioned ratios has provided a highly efficient 
and highly controllable blower system for producing staple glass fibers. 
It is apparent that within the scope of the 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 described herein is readily applicable to the formation of 
continuous and/or staple organic and/or inorganic filaments.