Note: Descriptions are shown in the official language in which they were submitted.
~0368Z0
This invention relates to apparatus for melting heat-
softenable materials and more particularly to stream feeders or
bushings made of platinum, rhodium or other prec.ous metal alloys
for producing continuous glass fibers and to a method of
fabricating stream feeders from such metals.
Several methods have heretofore been employed in
processing glass for forming continuous glass filaments or fibers.
One method involves the steps of melting glass in a comparatively
large furnace, refining the glass in a refining chamber, and
forming the glass into spherical bodies or marbles. The glass
marbles are subsequently delivered into a stream feeder which is
electrically heated to remelt the glass to a viscosity at which
the streams of glass may be flowed through orifices in the feeder
and attenuated into fibers.
The more common method used today is the direct melt
process wherein glass batch is reduced to a molten state and
reined in a furnace. The molten glass flows from the furnace
along a forehearth channel to stream feeders disposed along the
forehearth. The feeders are heated by electrical resistance
heating to control glass viscosity. And the streams of the glass
are delivered through orifices in the feeders or bushings for
attenuation into fibers.
Both of the above fiber forming processes employ stream
feeders or bushings made of high temperature resistant metal
alloys such as platinum or rhodium. The stream feeder is a long
metal box having orificed tips or projections attached to its
bottom wall through which streams of glass flow for attenuation
into fibers. Terminals to which electrical bus bars are attached
for supply of current through the feeder are welded to either end
of the box~shaped feeder. The feeder is then heated by its own
A`~ 1
1036820
electrical resistance. To achieve the desired heating character-
istics in the feeder, it has conventionally been the practice to
vary the thickness of the feeder walls to control the amount of
current passing therethrough.
Feeders have typically been manufactured from precut
parts which are welded together by conventional fusion welding
techniques. The plate for the bottom wall or tip section is
u~ually of uniform thickness and the plates for the sides and
flanges are of various lesser thicknesses to produce the desired
heat pattern and/or to reduce the amount of precious metal
required. Using thinner pieces for the side walls and flanges
causes several difficulties in conventional feeder fabrication
as well as feeder performance. For example, additional rolling
of the thinner sections is required. The welding together of the
pieces is time consuming and the uniformity of the welds may
vary. Also, because of the cast nature of the fusion bead as-
compared to the wrought sheet, resistivity is changed through the
weld zone and the same heat pattern may be difficult to stabilize
or reproduce from feeder to feeder. Severe warpage of the
thinner sheet material may occur when fusion welded to the
thicker material. In addition, if the welds are not made
extremely carefully, they may leak glass. Also, if failures or
fractures occur in the feeders, they usually occur in or adiacent
to the welds.
If a technique could be developed for reducing the
adverse effects of fusion welding during construction of the
feeders or for improving current distribution through the feeder
when it is in operation, a substantial contribution would be
made to advance the art of forming high-temperature continuous
fibers.
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Accordingly, it is an object of the present invention
to provide feeders for heat softenable fiber-forming materials
that have predetermined and controlled current carrying and res-
istance heating characteristics.
Another object is to provide glass stream feeders that
are formed with a minimum of welding.
A still further object is to provide a method for fab-
ricating feeders for high temperature heat softenable fiber form-
ing materials that involves minimizing welds and yet retains the
necessary varied wall thickness for controlling the resistance-
heating of the feeders.
The present invention seeks to accomplish the above
objectives by fabricating the feeder tip section, sidewalls and
flanges from one piece of precious metal plate. A plate of the
same thickness as the desired tip section, but somewhat wider, is
centrally positioned over a rectangular opening or die formed by
two spaced apart, ironing inserts held in a solid retainer block.
A tapered punch or ram presses the plate downwardly between the
surface of the inserts and the ram surface under controlled con-
ditions to compress and draw the thick plate to form thinner side-
walls. Successive passes of various sizes of punches or inserts
may be used to compressively iron the sidewalls to the desired
taper and thickness. After the part is formed to the desired
cross-sectional shape, the flanges and perhaps end plates can be
formed and trimmed by hand or by conventional die-set methods.
Accordingly, one aspect of the invention involves a
resistance heated feeder for supply of molten mineral material in
the form of streams to be attenuated into fibers, said feeder
comprising end walls, sidewalls and a stream flow region at a
normally lower wall; said sidewalls and lower wall being formed
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from a single piece of ductile, high temperature resistant,
electric current-conducting material, and wherein the thicknesses
of said sidewalls are structured to provide non-uniformity in
thickness along at least a portion thereof, said wall structuring
facilitating a pattern of heat generation to provide uniformity
of temperature in the molten material at the stream flow region.
Preferably, each of the sidewalls comprises an upper
region and a lower region wherein the wall thickness of at least
a portion of the lower region is greater than the wall thickness
of at least a portion of the upper region. It is recommended
that the wall thickness of a portion of the lower region is at
least fifty percent greater than the wall thickness of a portion
of the upper region.
Preferably the sidewalls are rectangular in shape having
end regions and a center region wherein the wall thicknesses of
the end regions are a different thickness than the wall thickness
of the center region. It is recommended that the difference in
wall thicknes5 between the end regions and the center region is
at least twenty-five percent.
A further aspect of the invention includes a method for
forming a channel-shaped member from a planar member of ductile,
electric current-conducting material for use in fabricating a
feeder which supplies molten mineral material in the form of
streams to be attenuated into filaments, comprising the steps of:
disposing the planar member between a tapered projecting member
and a block having an aperture formed therein and a raised land
defining a linear pressing surface along the interior of the
ap~rture; moving the projecting member and the block relative to
each other such that the projecting member contacts a major surface of the
iO36~20
planar member; forcing the tapered projecting member and planar
member through the aperture in the block thereby urging the
planar member to move in a direction transverse to the lands
defining the pressing surface of the aperture; compressing the
planar member between the tapered surface of the projecting member
and the lands defining the pressing surface to form a channel-
shaped member having sidewalls of predetermined varied thickness
corresponding to the clearance between the surface of the tapered
projecting member and the pressing s~urface~ and removing the
channel-shaped member from the block.
It is possible to employ the following apparatus for
forming a component of a resistance heated feeder for supply of
molten streams of fiber forming mineral material, in which appara-
tus the sidewalls and a normally lower wall are made from a plate
of ductile, electric current-conducting and high temperature re-
sistant material, comprising: a ram shaped to conform to the in-
terior shape of the portion of the feeder component bounded by
the side and lower walls, a structure defining an opening, oppos-
ing linear pressing surfaces extending lengthwise of both sides
of the opening, the opposing pressing surfaces each being a re-
latively narrow land, the surface defining the shortest distance
between a pair of spaced apart members in the structure; means for
disposing a plate of said ductile, high temperature resistant
current conducting material between the ram and the opening; means
for moving the ram against the plate to force the ram and plate
between the pressing surfaces thus urging the plate to move in a
direction transverse to the linear pressing surfaces of the opening,
the space between the ram and the pressing surfaces being such as
to effect progressive compression of the sidewall portions of the
plate between the surface of the ra~ and the pressing surface as
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10368Z0
the ram moves past the pressing surfaces to form the plate into the
feeder component; and means for moving the feeder component from
the apparatus for further fabrication into a stream feeder.
The operational advantages of using this method to for~
feeders includes better or more stable control of feeder wall thick-
ness, fewer weld lines, greater flexibility in feeder design, in-
creased feeder strength and increased average feeder life. The
fabrication advantages include reduced fabrication time, reduced
inventory of precious metals, consistent dimensional characteristics,
reduced rolling, stock cutting and layout and reduced skill needed
to fabricate the feeders.
Other advantages and features of this invention will
appear in the following description and appended claims reference
being had to the accompanying drawings wherein like reference
characters designate corresponding parts in the several views.
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10368Z0
FIGURE 1 is a generalized isometric view of apparatus
for producing continuous glass fibers utilizing a resistance
heated molten glass feeder made of metal.
FIGURE 2 is a front elevational view with parts in
section of the punch and drawing apparatus of the present
invention.
FIGURE 3 is a front elevational view similar to FIGURE
2 showing another embodiment of the invention.
FIGURE 4 is a front elevational view with parts in
section of one step in the use of the apparatus shown in FIGURE
2.
FIGURE 5 is a front elevational view similar to FIGURES
2 and 4 illustrating another step in the use of the invention.
FIGURE 6 is a cross sectional view taken substantially
along line 6-6 of FIGURE 4.
FIGURE 7 is an enlarged sectional view of the pressing
member shown in FIGURE 2.
FIGURE 8 is an enlarged sectional view similar to
FIGURE 7 showing another embodiment of the pressing member.
20FIGURE 9 is a cross sectional view similar to FIGURE
2 illustrating release means for the invention.
FIGURE 10 is a sectional view of apparatus made by the
invention.
FIGURE 11 is a sectional view similar to FIGURE 10
illustrating another form of the apparatus made by the invention.
Before explaining the present invention in detail it is
1036820
to be understood that the invention is not limited in its
application to the details of construction and arrangement of
parts illustrated in the accompanying drawings, since the
invention is capable of other embodiments and of being practiced
or carried out in various ways to produce elements for other
end uses. Also it is to be understood that the phraseology or
te~minology employed herein is for the purpose of description and
not of limitation.
As shown in FIGURE 1, continuous glass fibers are
formed utilizing a stream feeder or bushing 40 provided with
electrical terminals 42 to which electric lines ~not shown) are
connected. Electric current is supplied from a source and is
passed through the feeder to heat the same by its own electrical
resistance. An insulating refractory (not shown~ is typically
provided around the bushing to retain heat and improve
eficiency.
Glass fiber forming material in the form of molten
glass i9 fed by gravity int~ the feeder 40 from a forehearth
connected to a glass melting furnace (not shown). In the feeder
the molten material is further conditioned or heated and
discharged downwardly as small molten streams 48 from orifices
46 formed in aligned array along the bottom of the feeder. This
bottom orificed plate is generally referred to as the tip section
44 since the orifices are usually formed in projecting tips 45.
The streams are attenuated into fibers 50 by a tension device
such as a winder, pull wheel or blower (not shown). Then the
fibers may be lubricated by a liquid sizing or binder and pulled
or conveyed to a conventional collection device.
The stream feeder or bushing 40 is basically a
specially shaped box made of high temperature resistant alloys
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such as platinum, rhodium or the like. It has been a practice
to fabricate the feeders using precut metal strips manually
welded together. As previously stated, the welding process
requires skilled labor and the welds even if accurately executed
may cause feeder operating problems. The present invention
minimizes the number of welds required in feeder fabrication and
maintains the variable wall thickness needed for optimum
operation of the feeder.
The apparatus used for fabricating glass stream
feeders in accordance with the present invention is illustrated
in FIGURES 2 - 6. It comprises modified forms of apparatus
sometimes used by the drawing industry when deep drawing cans or
pressure vessels. The apparatus includes a ram or male portion
20 and a die or female portion 10. The ram 20 is a tapered
rectangular member designed to be passed through the larger
rectangular opening formed by the die 10. The die 10 includes a
heavy duty retainer block 12 with removable ironing or pressin~
inserts 14 set therein to form the femal portion o the system.
A tip nest or support plate 16 is connected by means of a rod 18
to a hydraulic or air cushion means (not shown). The tip plate
nest or support 16 is designed to move freely up and down within
the rectangular opening formed by the inserts 14 and the retainer
block 12. The support 16 applies resistive pressure to the
bottom of the plate 30 to be formed. Thus, the support 16 helps
to hold the plate 30 and stabilize the process.
FIGURES 2, 4 and 5 illustrate the progressive steps of
forming a glass stream feeder of the present invention. The
metal plate 30 from which the feeder 40 is to be formed is
properly rolled, cut to size and annealed. The prepared plate
30 is formed to the thickness of the desired tip section 44.
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~036820
Projections or tips 45 are fused to the plate and holes 46 are
drilled through the plate and projections by a techni~ue similar
to that disclosed in U.S. Patent No. 3,598,952. Other methods for
forming or attaching the projections which can also be used are
described in U.S. Patent Nos. 3,514,841 and 2,933,950. The main
advantage of forming the tips 45 at this point in the fabrication
process is the ease of attachment because the flat rectangular
plate 30 is more easily indexed in an auto~ated process than an
already formed box-shaped feeder. However if desired, it is also
possible with this invention to form the feeder to its final
shape before adding the tips 45 and providing the orifices 46.
FIGURE 3 shows such a plain flat plate being readied for forming.
Once the plate 30 is ready with the attached orificed
rips 45, it is placed over the rectangular opening of the die 10.
Fixtures (not shown) may be used to help assure proper positioning
of the plate. The tip nest and ~upport 16 is brought into
contact with the bottom of the plate 30. As shown in FIG~RE 6,
slot5 17 are provided in the support 16 to form a tip nest which
accommodates the rows of tips 45 and yet provides support for the
plate.
The ram 20 is lowered into contact with the top of the
plate 30 and pressure is applied to both sides of the plate by the
ram 20 on one side and the support 16 on the other side. The
hydraulic or air cushion means of the support or tip nest 16
provides a pneumatic force which resists the force of the ram by
a predetermined amount. The opposing forces of the ram and
support act to hold the plate firmly between the ram and support
plate and isolate the stress in one sidewall 47 from the other.
It has been found that a constant resistance or back-up pressure
of four to five tons against the support 16 is sufficient to
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:1036820
securely hold the plate 30 and keep it in a stable position for
the pressing of the metal which follows in later process steps.
Once the plate is securely held, the pressure on the
ram or punch 20 is increased to overcome the resistance force of
the support 16 and move and compress the thick plate 30 by
passing it through the confined opening 22 that is formed between
the tapered surface of the ram and the pressing surface 13 of the
inserts 14. The space or clearance 22 varies because the ram is
tapered. As the ram moves relative to the die opening the thick
plate is forced or urged between the tapered ram and the die
inserts and is compressively ironed to a reduced thickness filling
the clearance space 22.
Because the plate 30 is being compressively irone~
between the ram and the ironing or pressing inserts 14,
substantial frictional resistance is built up between the inserts
and the metal plate. However, most of this force is directed
against the inserts. It has been found that a pressure of only
fity tons on the ram is enough to compressively form and reduce
the plate in thickness from forty to fifty percent.
Great compressive and frictional forces are exerted on
the inserts. Therefore, the retainer block 12 and the inserts 14
must be sufficiently strong to resist deformation. Also, the
insert material must be sufficiently hard and smooth so that the
plate metal is not galled or otherwise damaged. An insert having
a hardness of about forty-five to fifty on the Rockwell C scale
has been used successfully in the operation of this invention.
The resistance between plate metal and insert is also
reduced by using an extreme pressure type lubricant to avoid
metal to metal contact.
-- 10 --
~4
~036820
Another feature of the apparatus is the shape and size
of the inserts. The corners or shoulders 11 of the inserts 14 are
rounded to allow the plate to be fed or urged more easily into
the clearance 22 between the ram and inserts. The opening formed
by the shoulder must necessarily be wider than the initial
thickness of metal being driven therethrough. FIGURE 7 shows the
beveled form of the shoulder portion 11 of the pressing surface.
In this embodiment the corner 11 has been cut off at a forty-five
degree angle A. An angle in the range of thirty to sixty degrees
9hould be satisfactory depending upon the metal to b~ formed. If
the angle A is less than thirty degrees the opening leading to
the pressing surface 24 is longer and narrower and may cause
detrimental frictional forces between the surfaces. If the angle
A is greater than 60 degrees the shoulder surface may act to cut
or peel back the metal rather than feed it between the surfaces
to be pressed. Also, all exposed corners that may come in contact
with the metal plate are rounded to likewise avoid damage to the
plate. F}GURE 8 shOws a form using a rounded corner greater than
the original thickness of the metal plate 30 to assure smoother
feed of the metal between the surface of the pressing inserts 14a
and the ram 20.
Each shoulder 11 of the insert 14 provides a gradually
diminishing dimension in the region of the entrance to assist the
compression of the metal plate 30 between the pressure applying
surface of the ram 20 and the ironing surface 13 of the die
inserts 14. By providing a converging region for application of
pressure the rounded shoulder or inlet 11 helps to urge the thick
metal plate 30 between the thinner space between the ram 20 and
the lands 13 of the inserts 14.
The lands or pressing surfaces 13 are the raised
1036820
portions on the inserts 14 which do the actual pressing of the
plate metal to its desired thickness. Shims (not shown) may be
positioned between the inserts and the retainer block to obtain
the desired clearance. The lands 13 are maintained as small as
possible to reduce the frictional forces. Lands as small as one-
quarter inch wide have been used successfully. However, it may
be possible to reduce the area of the lands even more.
As pressure exceeding the resistance force of the
support 16 is applied to the ram, the plate is forced between the
ram 20 and the lands 13 of the insert 14 and the plate is
compressively ironed to the desired thickness. The change in
shape of the plate 30 is not like conventional drawing In
conventional drawing processes a constant wall thickness is
desired. Ideally, the plate change5 shape but not thickness.
Therefore, there is always a reduction in diameter or length and
width of the part in one direction as well as an increase in
height or width in another direction. When a change in thickness
does occur, it is uncontrolled and may result in fracture of the
part. The increase in height is almost totally dependent on the
2Q amount of reduction in another direction. Conversely for the
compressive ironing in this invention, a change in thickness or
tapering of the wall is desired. The diameter or the width of
the plate is not effectively changed. The increase in height of
the feeder walls is totally dependent upon the amount of cross-
sectional reduction in thickness.
The amount of taper of the plate is controlled mainly by
the shape or taper of the ram. The ram shown in FIGURES 2, 3 and
5 is uniformly tapered. And, therefore, the feeder wall made
therefrom is thicker at the bottom taperins uniformly to a
thinner cross-sectional area near the top. This taper
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1036~ZO
approximates the feeder wall shape conventionally used.
To remove the formed plate 30 from the die 10 it has
been found that the formed plate should be pushed completely past
the lands 13 as shown in FIGURE 5. Because the inside walls of
the pressing inserts diverge from the narrower lands, the
pressure on the sidewalls 47 of the formed plate 30 is released
and the ram can be more easily removed. FIGURE 9 illustrates an
embodiment of the invention which provides means for aiding in the
release of the part. As shown, wiper blades 25 may be inserted
from their retracted position in the retainer blocks 12 to
restrain the formed plate 30 and aid withdrawal of the ram 20
therefrom.
Once the ram is withdrawn, the hydraulic system of the
support or tip nest 16 may be activated and the formed part
pushed upwardly and out of the die 10. Alternatively, if the
formed plate is not easily ejected upwardly from the die, the
support plate 16 may be retracted further than that shown in
FIGURE 5 and the part removed from an open end of the die 10 or
from beneath the die.
Prior to forming the plate 30 into a feeder 40 it may
be necessary to anneal the plate. The type or degree of annealing
depends upon the reduction in the cross-section of thickness per
pass and the type of alloy composition used. It has been found
that for an alloy comprised mainly of platinum and rhodium that an
annealing of ten minutes at 1850F followed by a ten minute
cooling period yields a plate having sufficient tensile strength
to avoid tearing yet ductile enough to go through the forming
operation without fracture. The forming process of the invention
also promotes grain growth in a different direction than that
normally encountered with prior rolling and feeder fabrication
methods 1036~20
FIGURES 10 and 11 illustrate completed forms of the
unitary bottom wall 44 and sidewalls 47 of the present invention.
The change in thickness illustrated was attained by passing the
metal through the compressing and forming apparatus at least two
times. However, for some feeder designs or alloy compositions
one pass may be sufficient. Once the plate is compressed to its
predetermined thicknesses, the sidewalls 47 and flanges 49 are
bent and formed by conventional metal working techniques to the
final 8hape such as shown in FIGURE 11. Thereafter the thicker
end plates 43, electric terminals 42 and other necessary parts
are attached by conventional fusion bonding techniques.
The present invention does not eliminate all the welds
in a feeder but does eliminate a major portion of them. Of
special significance is the elimination of the long-welds that
heretofore were necessary for attachment of the tip plate or
bottom wall 44 to the feeder sidewalls 47 and for connection of
the upper and thinner sidewall portions to the lower and thicker
8idewall portions.
One of the most important features of the invention is
that for a particular feeder design, the bottom wall 44 and
sidewalls 47 can be made more nearly identical. There is less
variation of the type previously caused by differences in welding
machines or in the ability of the personnel fabricating the
feeders.
Although the invention has been described with regard
to platinum-rhodium alloys, it will be evident that feeders in
accordance with the present invention can be made from other
ductile high temperature resistant metals.
It is apparent that, within the scope of the invention,
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10368Z0
modifications and different arrangements may be made other than
as herein disclosed, and the present disclosure is illustrative
merely, the invention comprehending all variations thereof. For
example, many variations in the thickness of the feeder sidewalls
are possible by using different shapes and sizes of punches and
die inserts. Also, the plate 30 initially used may be rolled or
formed to shapes other than the uniform thickness shown in FIGURES
2 and 3.
In addition, the contour of the ram 20 or pressing
inserts 14 can be varied in the longitudinal direction from end
to end. Heretofore, the feeder wall thickness has been varied
mainly in the vertical direction; thickness variations along the
length were too difficult to fabricate. Using the present `
invention variations in feeder sidewall thickness along the length
are practical and reproducible. Thus for a particular feeder
that operates characteristically hotter near its center portion,
the ram and die can be modified to change the wall thickness in
that typically hotter area, thereby making a feeder that operates
with more uniform temperatures from end to end.
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