U.S. patent application number 15/799275 was filed with the patent office on 2018-02-22 for method and apparatus for making a profiled tubing and a sleeve.
The applicant listed for this patent is Corning Incorporated. Invention is credited to Antoine Gaston Denis Bisson, Patrick Joseph Cimo, Thierry Luc Alain Dannoux, Ronan Tanguy.
Application Number | 20180050949 15/799275 |
Document ID | / |
Family ID | 49213088 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180050949 |
Kind Code |
A1 |
Bisson; Antoine Gaston Denis ;
et al. |
February 22, 2018 |
METHOD AND APPARATUS FOR MAKING A PROFILED TUBING AND A SLEEVE
Abstract
An apparatus for making a profiled tubing includes a mandrel
adapted for positioning proximate a tubing. The mandrel has a
nozzle section with a select cross-sectional profile that will
define a final cross-sectional profile of the tubing. The nozzle
section has a feed chamber for receiving a gas and a porous
circumferential surface through which the gas can be discharged to
an exterior of the mandrel. The gas when discharged to the exterior
of the mandrel forms a film of pressurized gas between the porous
circumferential surface and the tubing. A method of forming a
profiled tubing using the apparatus is disclosed. A sleeve formed
from the profiled tubing is also disclosed.
Inventors: |
Bisson; Antoine Gaston Denis;
(Corning, NY) ; Cimo; Patrick Joseph; (Corning,
NY) ; Dannoux; Thierry Luc Alain; (Avon, FR) ;
Tanguy; Ronan; (Grez Sur Loing, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Corning Incorporated |
Corning |
NY |
US |
|
|
Family ID: |
49213088 |
Appl. No.: |
15/799275 |
Filed: |
October 31, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14422462 |
Feb 19, 2015 |
9834467 |
|
|
PCT/US13/57248 |
Aug 29, 2013 |
|
|
|
15799275 |
|
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|
|
61694913 |
Aug 30, 2012 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03B 23/045 20130101;
C03B 17/04 20130101; C03B 23/0476 20130101; C03B 33/06 20130101;
Y10T 428/131 20150115; C03B 40/04 20130101; C03B 23/07
20130101 |
International
Class: |
C03B 23/07 20060101
C03B023/07; C03B 40/04 20060101 C03B040/04; C03B 33/06 20060101
C03B033/06; C03B 23/047 20060101 C03B023/047; C03B 23/045 20060101
C03B023/045; C03B 17/04 20060101 C03B017/04 |
Claims
1. An apparatus for making a profiled tubing, comprising: a mandrel
adapted for positioning proximate a surface of a tubing, the
mandrel having a nozzle section with a select cross-sectional
profile that will define a final cross-sectional profile of the
tubing, the nozzle section having a feed chamber for receiving a
gas and a porous circumferential surface through which the gas can
be discharged to an exterior of the mandrel, wherein the gas when
discharged to the exterior of the mandrel forms a film of
pressurized gas between the porous circumferential surface and the
tubing.
2. The apparatus of claim 1, further comprising a tubing forming
apparatus for forming the tubing, wherein the mandrel is arranged
inline with the tubing forming apparatus.
3. The apparatus of claim 1, wherein the porous circumferential
surface comprises a pair of edge surfaces that are in opposing
relation and ramped relative to a tool axis along which the mandrel
is aligned.
4. The apparatus of claim 1, wherein the porous circumferential
surface further comprises a pair of side surfaces that are in
opposing relation and form webs between the pair of edges
surfaces.
5. The apparatus of claim 4, wherein each of the pair of side
surfaces has a depressed area.
6. The apparatus of claim 3, further comprising at least a pair of
edge chambers formed in the nozzle section and in communication
with the feed chamber, each of the pair of edge chambers being
adjacent to and substantially parallel to one of the pair of edge
surfaces.
7. The apparatus of claim 3, further comprising a pair of chamber
clusters formed in the nozzle section, each chamber cluster
comprising at least two edge chambers in communication with the
feed chamber, each chamber cluster being adjacent to and
substantially parallel to one of the pair of edge surfaces.
8. The apparatus of claim 7, wherein the at least two edge chambers
of each chamber cluster are equidistant from the adjacent edge
surface.
9. The apparatus of claim 8, wherein the at least two edge chambers
of each chamber cluster have different lengths.
10. A method of forming a profiled tubing, comprising: disposing a
mandrel adjacent to a surface of a tubing made of a glass material,
the mandrel having a nozzle section with a select cross-sectional
profile that will define a final cross-sectional profile of the
tubing; discharging a gas from a porous circumferential surface of
the nozzle section to create a film of pressurized gas between the
nozzle section and the surface of the tubing, the film of
pressurized gas exerting pressure on the surface of the tubing that
is sufficient to locally deform the tubing into conformity with the
nozzle section; advancing the film of pressurized gas along a
length of the tubing; and heating the tubing such that in any local
section of the tubing where the film of pressurized gas is exerting
pressure, the local section of the tubing is at a viscosity at
which the local section of the tubing can be deformed by the
pressure.
11. The method of claim 10, wherein deformation of the tubing into
conformity with the nozzle section comprises stretching a wall of
the tubing by 5 to 30%.
12. The method of claim 10, further comprising delivering the gas
to a feed chamber in the nozzle section at a pressure of 1 to 10
atm.
13. The method of claim 10, wherein the film of pressurized gas has
a thickness in a range from 60 .mu.m to 70 .mu.m.
14. The method of claim 10, further comprising arranging the
mandrel inline with a tubing forming apparatus that forms the
tubing.
15. The method of claim 10, further comprising cutting at least one
sleeve from a section of the tubing that has been deformed into
conformity with the nozzle section.
16. The method of claim 10 wherein discharging the gas comprises a
combination of discharging the gas from the porous circumferential
surface and venting the gas from depressed areas of the porous
circumferential surface such that the film of pressurized gas is
locally created between the tubing and the nozzle section.
17. A sleeve made of a glass material, the sleeve having a seamless
wall, the wall having an inner surface with a surface roughness
less than 1 .mu.m and an outer surface with a surface roughness
less than 1 .mu.m, the wall having opposed flat sections, each of
the flat sections having a flatness better than 50 .mu.m on an area
of 70.times.120 mm.sup.2.
18. The sleeve of claim 17, having an oblong cross-sectional shape.
Description
[0001] This application is a Divisional of U.S. patent application
Ser. No. 14/422,462, filed on Feb. 19, 2015, which claims the
benefit of priority to International Application Serial No.
PCT/US13/57248, filed on Aug. 29, 2013, which, in turn, claims the
benefit of priority of U.S. Provisional Application Ser. No.
61/694,913, filed on Aug. 30, 2012, the content of each are relied
upon and incorporated herein by reference in their entireties as if
fully set forth below.
FIELD
[0002] The invention relates to manufacture of three-dimensional
(3D) glass articles.
BACKGROUND
[0003] Glass has been used as front covers for electronic devices.
Electronic device manufacturers are now desiring that the back
covers of electronic devices are also made of glass and that the
back covers meet the same high dimensional accuracy and surface
quality as the front covers. It is possible to make the front and
back covers separately with the requisite dimensional accuracy and
surface quality and then assemble them together. However, this adds
extra steps to the manufacturing process and may result in loss of
dimensional control. The alternative is to manufacture a monolithic
glass sleeve, where the front side of the glass sleeve will serve
as the front cover and the back side of the glass sleeve will serve
as the back cover. Many electronic devices incorporate flat
displays. Thus the monolithic glass sleeve would need to have a
cross-sectional profile that can accommodate a flat display. In
general, this cross-sectional profile will have flat sides that can
be arranged in parallel to the flat display. The flatness of the
flat sides would also have to meet stringent requirements specified
by the electronic device manufacturers.
[0004] It is known to make glass tubing and then convert the glass
tubing into containers. Thus one practical approach to making a
monolithic glass sleeve would be to make a glass tubing having the
desired cross-sectional profile and then cut the glass tubing into
glass sleeves. Methods for forming glass tubing from molten glass
are known. The most common ones are the Danner process, the Vello
process, and the downdraw process. These processes are described
in, for example, Heinz G. Pfaender, "Schott Guide to Glass," 2nd
ed., Chapman & Hall, 1996. These processes are typically used
to form glass tubing with a round cross-sectional shape. Extrusion
can be used to form glass tubing with a non-round cross-sectional
shape, e.g., a cross-sectional shape that could have flat sides.
However, extrusion involves tool contact with the glass surface,
which could diminish the surface quality of the glass.
SUMMARY
[0005] In one aspect, the present invention relates to an apparatus
for making a profiled tubing. The apparatus includes a mandrel
adapted for positioning proximate a surface of a tubing. The
mandrel has a nozzle section with a select cross-sectional profile
that will define a final cross-sectional profile of the tubing. The
nozzle section has a feed chamber for receiving a gas and a porous
circumferential surface through which the gas can be discharged to
an exterior of the mandrel. The gas when discharged to the exterior
of the mandrel forms a film of pressurized gas between the porous
circumferential surface and the tubing.
[0006] In one embodiment, the apparatus further comprises a tubing
forming apparatus for forming the tubing, wherein the mandrel is
arranged inline with the tubing forming apparatus.
[0007] In one embodiment, the nozzle section is made of a porous
material having a porosity of 10 to 20% and a mean pore size of 10
.mu.m or less.
[0008] In one embodiment, the nozzle section is perforated.
[0009] In one embodiment, the porous circumferential surface
comprises a pair of edge surfaces that are in opposing relation and
ramped relative to a tool axis along which the mandrel is
aligned.
[0010] In one embodiment, the porous circumferential surface
further comprises a pair of side surfaces that are in opposing
relation and form webs between the pair of edges surfaces.
[0011] In one embodiment, each of the pair of side surfaces has a
depressed area.
[0012] In one embodiment, the apparatus further includes at least a
pair of edge chambers formed in the nozzle section and in
communication with the feed chamber. Each of the pair of edge
chambers is adjacent to and substantially parallel to one of the
pair of edge surfaces.
[0013] In one embodiment, the apparatus further includes a pair of
chamber clusters formed in the nozzle section. Each chamber cluster
includes at least two edge chambers in communication with the feed
chamber. Each chamber cluster is adjacent to and substantially
parallel to one of the pair of edge surfaces
[0014] In one embodiment, the at least two edge chambers of each
chamber cluster are equidistant from the adjacent edge surface.
[0015] In one embodiment, the at least two edge chambers of each
chamber cluster have different lengths.
[0016] In another aspect, the present invention relates to a method
of forming a profiled tubing made of a glass material. The method
includes disposing a mandrel proximate to a surface of a tubing.
The mandrel has a nozzle section with a select cross-sectional
profile that will define a final cross-sectional profile of the
tubing. The method includes discharging a gas from a porous
circumferential surface of the nozzle section to create a film of
pressurized gas between the nozzle section and the surface of the
tubing. The film of pressurized gas exerts pressure on the surface
of the tubing that is sufficient to locally deform the tubing into
conformity with the nozzle section. The method includes advancing
the film of pressurized gas along a length of the tubing. The
method includes heating the tubing such that in any local section
of the tubing where the film of pressurized gas is exerting
pressure, the local section of the tubing is at a viscosity at
which the local section of the tubing can be deformed by the
pressure.
[0017] In one embodiment, the tubing has an initial circumference
before being conformed to the nozzle section and a final
circumference after being conformed to the nozzle section. The
method includes selecting the tubing such that a ratio of the
initial circumference to the final circumference is between 0.7 and
0.95.
[0018] In one embodiment, deformation of the tubing into conformity
with the nozzle section includes stretching a wall of the tubing by
5 to 30%.
[0019] In one embodiment, the method includes delivering the gas to
a feed chamber in the nozzle section at a pressure of 1 to 10
atm.
[0020] In one embodiment, the film of pressurized gas has a
thickness in a range from 60 .mu.m to 70 .mu.m.
[0021] In one embodiment, the method further includes arranging the
mandrel inline with a tubing forming apparatus that forms the
tubing.
[0022] In one embodiment, the select cross-sectional shape is
oblong.
[0023] In one embodiment, the method further includes cutting at
least one sleeve from a section of the tubing that has been
deformed into conformity with the nozzle section.
[0024] In one embodiment, discharging the gas includes a
combination of discharging the gas from the porous circumferential
surface and venting the gas from depressed areas of the porous
circumferential surface such that the film of pressurized gas is
locally created between the tubing and the nozzle section.
[0025] In another aspect, the present invention relates to a sleeve
made of a glass material. The sleeve has a seamless wall. The wall
has an inner surface with a surface roughness less than 1 .mu.m and
an outer surface with a surface roughness less than 1 .mu.m. The
wall also has opposed flat sections. Each of the flat sections has
a flatness better than 50 .mu.m on an area of 70.times.120
mm.sup.2.
[0026] In one embodiment, the sleeve has an oblong cross-sectional
shape.
[0027] It is to be understood that both the foregoing summary and
the following detailed description are exemplary of the present
invention and are intended to provide an overview or framework for
understanding the nature and character of the present invention as
claimed. The accompanying drawings are included to provide a
further understanding of the present invention and are incorporated
in and constitute a part of this specification. The drawings
illustrate various embodiments of the present invention and
together with the summary and detailed description serve to explain
the principles and operation of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The following is a description of the figures in the
accompanying drawings. The figures are not necessarily to scale,
and certain features and certain views of the figures may be shown
exaggerated in scale or in schematic in the interest of clarity or
conciseness.
[0029] FIG. 1 is a perspective view of a conforming tool.
[0030] FIG. 2A is a surface roughness profile of a glass sleeve
formed by the conforming tool.
[0031] FIG. 2B is a surface roughness profile of a glass surface
formed by a prior art method.
[0032] FIGS. 3A-3G are oblong cross-sectional shapes.
[0033] FIG. 4A shows the conforming tool used as an internal
shaping tool.
[0034] FIG. 4B shows the conforming tool used as an external
shaping tool.
[0035] FIG. 5 is a cross-section of FIG. 1 along the tool axis.
[0036] FIG. 6 is a bottom end view of the conforming tool of FIG.
1.
[0037] FIG. 7 is a side view of the conforming tool of FIG. 1.
[0038] FIG. 8 is a cross-section of FIG. 7 along line 8-8.
[0039] FIG. 9A is a perspective view of another conforming
tool.
[0040] FIG. 9B shows the nozzle of the conforming tool of FIG.
9A.
[0041] FIG. 10 is a setup for forming a profiled tubing using the
conforming tool of FIG. 1.
[0042] FIGS. 11A-11E illustrate a process of shaping a tubing using
the conforming tool of FIG. 1.
[0043] FIG. 12 illustrates gas discharge during use of the
conforming tool of FIG. 1.
[0044] FIG. 13 is a perspective view of a glass sleeve formed by
the conforming tool of FIG. 1.
[0045] FIG. 14 shows a continuous glass tubing process
incorporating use of the conforming tool of FIG. 1.
DETAILED DESCRIPTION
[0046] In the following detailed description, numerous specific
details may be set forth in order to provide a thorough
understanding of embodiments of the present invention. However, it
will be clear to one skilled in the art when embodiments of the
present invention may be practiced without some or all of these
specific details. In other instances, well-known features or
processes may not be described in detail so as not to unnecessarily
obscure the invention. In addition, like or identical reference
numerals may be used to identify common or similar elements.
[0047] FIG. 1 shows a conforming tool 100 for non-contact shaping
of an initial tubing made of a glass material into a profiled
tubing. The glass material will typically be glass. The glass
material may also be glass-ceramics, but only glass-ceramics that
can avoid nucleation or crystallization under the shaping
conditions will generally be suitable. A possible example of
glass-ceramics is transparent beta spodumene, available as KERALITE
from Eurokera. The choice of glass is much wider and would be based
on the desired properties of the profiled tubing or sleeves to be
made from the profiled tubing. The conforming tool 100 can be used
with ion-exchangeable glasses, which are generally desired in
applications where toughness and damage resistance are important.
Examples of ion-exchangeable glasses are alkali-aluminosilicate
glasses or alkali-aluminoborosilicate glasses. The conforming tool
100 can also be used with glasses having high coefficient of
thermal expansion.
[0048] In one embodiment, the conforming tool 100 is configured as
a mandrel 101 that can be inserted inside a tubing. For shaping of
the tubing, the conforming tool 100 generates a gas bearing that
exerts forming pressure on the tubing and acts as a barrier between
the conforming tool 100 and the tubing. The gas barrier will allow
the surface quality of the tubing to be preserved through the
shaping process with the conforming tool 100. The gas barrier can
prevent imperfections such as streaking from developing on the
inner surface of the tubing during the shaping process. FIG. 2A
shows an inner surface roughness profile of a glass sleeve cut from
a glass tubing shaped by the conforming tool 100. The profile shows
that the glass sleeve has a maximum inner surface roughness of 0.18
nm. The surface roughness measurement shown in FIG. 2A was made on
a Zygo Interferometer. For comparative purposes, FIG. 2B shows an
inner surface roughness profile of a rectangular glass sleeve cut
from a glass tubing shaped by a prior art method that involved
contact of a tool with the wall of the glass tubing. For the prior
art sleeve, streaks on the glass surface were measured. The streaks
appeared as waves with 1 .mu.m amplitude (peak to valley distance)
and a 0.6 mm period. If the amplitude is taken as a measure of
surface roughness, then the maximum surface roughness observed in
the prior art sleeve will be approximately 1 .mu.m, which is much
greater than the surface roughness of the glass sleeve made using
the conforming tool 100. Further, the streaks are apparent on the
surface when viewed with the naked eye because they introduce a
significant and very local slope change to the surface, ultimately
producing a glass cover that looks distorted and unattractive.
[0049] In one embodiment, a profiled tubing or sleeve shaped by the
conforming tool 100 has an inner surface roughness less than 1
.mu.m on 40 mm length and an outer surface roughness less than 1
.mu.m on 40 mm length. In another embodiment, a profiled tubing or
sleeve shaped by the conforming tool 100 has an inner surface
roughness in a range from 0.2 nm to 10 nm on a 40 .mu.m.times.40
.mu.m area and an outer surface roughness in a range from 0.2 nm to
10 nm on a 40 .mu.m.times.40 .mu.m area. It should be noted that
since the surface quality of the tubing is preserved through the
shaping process, the surface roughness of the tubing after shaping
by the conforming tool 100 will depend on the surface roughness of
the tubing before shaping by the conforming tool 100. Therefore,
the specification of the surface roughness for the tubing shaped by
the conforming tool 100 is also a specification of the surface
roughness for the tubing prior to being shaped by the conforming
tool 100.
[0050] The conforming tool 100 is configured to shape a tubing from
an initial cross-sectional profile to a final cross-sectional
profile, where the final cross-sectional profile is different from
the initial cross-sectional profile. The cross-sectional profile of
the tubing is characterized by a shape and a size. Therefore,
shaping of the tubing may involve shape transformation and/or
dimensional transformation. In one embodiment, the conforming tool
100 is used to shape a tubing from an initial round cross-sectional
shape to a final non-round cross-sectional shape. In a more
specific embodiment, the final non-round cross-sectional shape is
an oblong shape. "Oblong" means elongated. In one embodiment, the
oblong shape has an aspect ratio greater than 5:1. In another
embodiment, the oblong shape has an aspect ratio greater than
10:1.
[0051] Several examples of oblong cross-sectional shapes are shown
schematically in FIGS. 3A-3G. These oblong shapes are made of
different combinations of splines, radiuses, tapers, and flats.
FIG. 3A shows an oblong shape 400 with flat sides 402, 404 and
round ends 406, 408. FIG. 3B shows an oblong shape 410 with flat
sides 412, 414 and round ends 416, 418. FIG. 3B is similar to FIG.
3A, with the exception that the ends 416, 418 are rounded with a
smaller radius than the ends 406, 408. In FIG. 3C, oblong shape 420
has flat sides 422, 424 and flat ends 426, 428, i.e., a rectangle.
In FIG. 3D, oblong shape 430 has flat sides 432, 434 and tapered
ends 436, 438. FIG. 3E shows an oblong shape 440 with splined sides
442, 444 and splined ends 446, 448. FIG. 3F shows an oblong shape
450 with splined ends 452, 454 and flat ends 456, 458. FIG. 3G
shows an oblong shape 460 with a splined side 462, a flat side 464,
and flat edges 466, 468. The oblong shape 460 is asymmetric.
[0052] When the conforming tool 100 is used as an internal tool,
convex cross-sectional profiles, such as shown in FIGS. 3A-3G, can
be formed in the tubing. FIG. 4A shows an example of using the
conforming tool 100 as an internal tool for shaping a tubing 470.
To form concave or convex-concave cross-sectional profiles, the
conforming tool 100 may be used as an external tool that is located
outside of the tubing. FIG. 4B shows an example of using the
conforming tool 100 as an external tool for shaping a tubing 472.
When the conforming tool 100 is used as an external tool, the gas
bearing generated by the conforming tool 100 will be between the
outer surface of the tubing and the conforming tool 100. Without
making any modifications to the conforming tool 100, the conforming
tool 100 will not circumscribe the circumference of the tubing and
will apply the shaping force only in a section of the circumference
of the tubing. The conforming tool 100 may be rotated about the
tubing if full coverage of the shaping force along the
circumference is desired. Alternatively, the conforming tool 100
can be reconfigured to a ring shape that will circumscribe the
circumference of the tubing. It is also conceivable that any
combination of internal and external, gas bearing and
non-gas-bearing, conforming tools may be used to shape the
tubing.
[0053] Returning to FIG. 1, the mandrel 101 is aligned with a tool
axis 104 and may be symmetric or asymmetric about the tool axis
104. Typically, the mandrel 101 will be symmetric about the tool
axis 104. The mandrel 101 is made of a nose 102 and a nozzle 120.
The nose 102 and nozzle 120 can be formed as separate parts that
are joined together or as an integral body. The nose 102 forms the
leading part of the conforming tool 100 and aids insertion of the
mandrel 101 into a tubing, whereas the nozzle 120 forms the
trailing part of the conforming tool 100 and determines the shape
to which the tubing will be conformed. The nose 102 is shaped and
sized for entry into the tubing under initial conditions of the
tubing. That is, if D.sub.TI is the initial cross-sectional
dimension of the tubing and D.sub.M is the maximum cross-sectional
dimension of the nose 102, then D.sub.M is less than D.sub.TI. The
nose 102 may be generally tubular in shape and may have a
cross-sectional profile that is generally round in shape. In this
embodiment, the glass tubing may also have an initial
cross-sectional profile that is round in shape. In this case,
D.sub.M can be the maximum cross-sectional diameter of the nose 102
and D.sub.TI can be the initial cross-sectional diameter of the
tubing. However, the cross-sectional shape of the nose 102 is not
limited to a round shape, and neither is the initial
cross-sectional shape of the tubing.
[0054] Referring to FIG. 5, the top end of the nose 102 includes a
connection port 106, and the bottom end of the nose 102 includes a
connection pin 108. The connection port 106 receives a connection
114 of a plug 112 located above the nose 102. The plug 112 is
coupled to the nose 102 by securing the connection pin 114 to the
connection port 106 by a suitable method, such as a threaded or
welded connection between the connection pin 114 and the wall 116
of the connection port 106. The connection pin 108 extends into a
connection port 122 in the nozzle 120. The nose 102 is coupled to
the nozzle 120 by securing the connection pin 108 to the connection
port 122 by a suitable method, such as a threaded, welded, or
bonded connection between the connection pin 108 and the wall 124
of the connection port 122. A conduit runs 110 runs through the
nose 102, from the connection port 106 to the connection pin 108.
The conduit 110 may be straight and axially aligned with the tool
axis 104. Alternatively, the conduit 110 may not be straight and/or
axially aligned with the tool axis 104.
[0055] The plug 112 has a conduit 118 that is in communication with
the conduit 110 in the nose 102 via the connection port 106. The
conduit 118 may be straight and axially aligned with the tool axis
104. Alternatively, the conduit 118 may not be straight and/or not
axially aligned with the tool axis 104. Regardless of the
configurations of the conduits 110, 118, communication between the
conduits 110, 118 should be possible. The plug 112 can be coupled
to a pipe (not shown), which can be coupled to a source of gas, for
delivery of gas to the conduits 110, 118. The gas delivered to the
conduit 110 will ultimately be delivered to the nozzle 120. The gas
may be air or an inert gas such as nitrogen. As in the case of the
nose 102, the plug 112 is shaped and sized for entry into the
tubing under initial conditions of the tubing. That is, if D.sub.P
is the maximum cross-sectional dimension of the plug 112 and
D.sub.TI is the initial cross-sectional dimension of the tubing,
then D.sub.P is less than D.sub.TI.
[0056] Returning to FIG. 1, the nozzle 120 has an upper section
120a, which like the preceding nose 120 is shaped and sized for
entry into the tubing under initial conditions of the tubing. If
the maximum cross-sectional dimension of the upper nozzle section
120a is D.sub.NU and the initial cross-sectional dimension of the
tubing is D.sub.TI, then D.sub.NU is less than D.sub.TI, and
preferably D.sub.NU is approximately equal to D.sub.TI minus
2.delta., where .delta. is the width of a gas bearing gap that will
be formed between the upper nozzle section 120a and the tubing when
the mandrel 101 is inserted in the tubing. The upper nozzle section
120a can be tubular in shape and have a cross-sectional shape in a
plane transverse to the tool axis 104 that is round. In general,
the upper nozzle section 120a will have a cross-sectional shape
that matches or is similar to the initial cross-sectional shape of
the tubing. This is so that an even gas bearing gap can be formed
between the upper nozzle section 120a and the tubing when the upper
nozzle section 120a is inserted in the tubing. Even pressurized gas
in the even gas bearing gap may have the effect of centering the
upper nozzle section 120a within the tubing.
[0057] The nozzle 120 has a lower nozzle section 120b, which
defines the shape to which the tubing will be conformed during use
of the conforming tool 100. For this reason, the cross-sectional
shape of the lower nozzle section 120b is dictated primarily by the
final cross-sectional shape of the tubing, although the
cross-sectional shape of the lower nozzle section 120b may not be
an exact copy of the final cross-sectional shape. In one
embodiment, the lower nozzle section 120b has a non-round
cross-sectional profile. In a more specific embodiment, the lower
nozzle section 120b has an oblong cross-sectional profile, where
"oblong" means elongated. The aspect ratio of the oblong shape may
be as previously mentioned for the final cross-sectional shape of
the tubing. FIG. 6 shows an example of a cross-sectional shape of
the lower nozzle section 120b that is suitable for forming the
tubing or sleeve final cross-sectional shape shown in FIG. 3A. In
the case of the lower nozzle section 120b, there are depressions
138a, 138b in the "flat" sides 402a, 402b of the oblong shape.
These depressions are for flux venting and will enable forming of
the flat sides 402, 404 shown in FIG. 3A.
[0058] In one embodiment, the lower nozzle section 120b has a
bi-tapered shape made of a major tapered shape and a minor tapered
shape. Referring to FIG. 5, the major width of the lower nozzle
section 120b, as measured along axis 125 that is transverse to the
tool axis 104, is gradually narrowing in a direction towards the
nose 102. The major width of the lower nozzle section 120b defines
the major tapered shape. The minor width of the lower nozzle
section 120b, as measured along axis 127 that is transverse to the
tool axis 104 and orthogonal to axis 125, is gradually narrowing in
a direction away from the nose 102. The tapering of the minor width
is best seen in FIG. 7. The minor width of the lower nozzle section
120b defines the minor tapered shape.
[0059] In FIG. 5, the smallest major dimension of the lower nozzle
section 120b occurs at the intersection 119 of the lower nozzle
section 120b with the upper nozzle section 120b and will generally
be the same as the largest dimension of the upper nozzle section
120b. The largest major dimension of the lower nozzle section 120b
occurs at the bottom end 117 of the nozzle 120 (or the distal end
of the nozzle 120 remote from the nose 102). If D.sub.TF is the
final dimension of the tubing, i.e., the dimension of the tubing
after shaping by the conforming tool 100, and D.sub.NL is the
maximum major dimension of the lower nozzle section 120b, then
D.sub.NL is approximately equal to D.sub.TF minus 2.delta., where
.delta. is the width of a gas bearing gap that will be formed
between the lower nozzle section 120b and the tubing during use of
the conforming tool 100. Typically, .delta. will be determined by
the thickness of the pressurized gas film to be created between the
lower nozzle section 120b and the tubing.
[0060] Returning to FIG. 1, the lower nozzle section 120b has
opposed edges 128a, 128b with edge surfaces 132a, 132b,
respectively, that are ramped relative to the tool axis 104. The
lower nozzle section 120b has a web 130 extending between and
connecting the opposed edges 128a, 128b. The web 130 has opposed
side surfaces 134a, 134b (in FIG. 7), which are contiguous with the
edge surfaces 132a, 132b. The distance between the edge ramped
surfaces 132a, 132b in a direction transverse to the tool axis 104
defines the major width of the lower nozzle section 120b. The
distance between the side web surfaces 134a, 134b in a direction
transverse to the tool axis 104 defines the minor width of the
lower nozzle section 120b. The edge ramped surfaces 132a, 132b and
web side surfaces 134a, 134b together define a lower nozzle
circumferential surface 136b. The upper nozzle section 120a has an
upper nozzle circumferential surface 136a. Together, the
circumferential surfaces 136a, 136b make up the circumferential
surface 136 of the nozzle 120.
[0061] The web surfaces 134a, 134b have depressed areas 138a, 138b,
respectively, which will serve as venting flux sites during use of
the conforming tool 100. Referring to FIG. 5, in one embodiment,
the ramped surfaces 132a, 132b are symmetrically disposed about the
tool axis 104, and the inclination angles of the ramped surfaces
132a 132b relative to the tool axis 104 are the same. In alternate
embodiments, the ramped surfaces 132a, 132b may be asymmetrically
disposed about the tool axis 104 and/or have different inclination
angles relative to the tool axis 104. The inclination angles of the
ramped surfaces 132a, 132b will generally be a function of the
width of the lower nozzle section 120b at the intersection 119, the
width of the lower nozzle section 120b at the bottom end 117, and
the height of the lower nozzle section 120b. Typically, the
inclination angles will be selected such that gradual shaping of
the glass tubing is achieved.
[0062] A feed chamber 140 is formed in the nozzle 120. The feed
chamber 140 extends from the connection port 122 to a non-distal
point in the lower nozzle section 120b. The feed chamber 140 is in
communication with the conduit 110 of the nose 102. Two edge
chambers 142a 142b are formed in the nozzle 120. The edge chambers
142a, 142b extend from the top end 123 of the nozzle 120 to
non-distal points in the lower nozzle section 120b. The edge
chambers 142a, 142b are offset from the feed chamber 140. In one
embodiment, the feed chamber 140 is axially aligned with the tool
axis 104, and the edge chambers 142a, 142b are disposed
symmetrically about the tool axis 104. However, it is possible in
other embodiments that the feed chamber 140 may not be axially
aligned with the tool axis 104 and/or the edge chambers 142a, 142b
may be disposed asymmetrically about the tool axis 104.
[0063] The edge chambers 142a, 142b are arranged on opposite sides
of the nozzle 120, with the edge chamber 142a being adjacent to the
ramped surface 132a and the edge chamber 142b being adjacent to the
ramped surface 132b. In FIGS. 1 and 8, the edge chamber 142a may be
one of a plurality of chambers in a chamber cluster 144a adjacent
to the ramped surface 132a. For example, the chamber cluster 144a
may include edge chambers 146a, 148a in addition to the edge
chamber 142a. Similarly, the edge chamber 142a may be one of a
plurality of chambers in a chamber cluster 144b adjacent to the
ramped surface 132b. For example, the chamber cluster 144b may
include edge chambers 146b, 148b in addition to the edge chamber
142b.
[0064] The chamber clusters 144a, 144b are disposed symmetrically
about the tool axis 104. However, it is possible in other
embodiments that the chamber clusters 144a, 144b may be disposed
asymmetrically about the tool axis 104. The edge chambers 142a,
142b, 146a, 146b, 148a, 148b are generally tubular in shape. The
cross-sectional shape of each of the edge chambers 142a, 142b,
146a, 146b, 148a, 148b may be circular or oblong. In one
embodiment, each of the edge chambers in each of the chamber
clusters 144a, 144b, have different lengths. However, it is
possible that in other embodiments the lengths of the edge chambers
in each of the chamber clusters 144a, 144b may be the same. The
lengths of the edge chambers 142a, 142b, 146a, 146b, 148a, 148b
will affect distribution of the gas discharged from the adjacent
ramped surfaces 132a, 132b during use of the conforming tool
100.
[0065] In one or more embodiments, the edge chambers 142a, 146a,
148a are oriented in the same direction as the adjacent ramped
surface 132a, i.e., the edge chambers 142a, 146a, 148a are
substantially parallel to the adjacent ramped surface 132a. In one
embodiment, the edge chambers 142a, 146a, 148a are distributed
along the adjacent ramped surface 132a in such a way that they are
substantially parallel to and substantially equidistant from the
adjacent ramped surface 132a. Similarly, in one or more
embodiments, the edge chambers 142b, 146b, 148b are oriented in the
same direction as the adjacent ramped surface 132b. That is, the
edge chambers 142b, 146b, 148b, i.e., the edge chambers 142b, 146b,
148b are substantially parallel to the adjacent ramped surface
132b. Also, in one embodiment, the edge chambers 142b, 146b, 148b
are distributed along the adjacent ramped surface 132a in such a
way that they are substantially parallel to and substantially
equidistant from the adjacent ramped surface 132b. It is possible
to arrange the edge chambers so that they are not equidistant from
their respective adjacent ramped surface. The edge chambers
essentially serve as plenums for distribution of gas to the ramped
surfaces 132a, 132b.
[0066] Referring to FIG. 1, the edge chambers 142a, 142b, 146a,
146b, 148a, 148b are in communication with the feed chamber 140 via
interconnecting holes 150 in the nozzle 120. The nozzle 120 is
porous, which means that the edge chambers 142a, 142b, 146a, 146b,
148a, 148b are also in communication with the feed chamber 140 via
the porous structure of the nozzle 120. The feed chamber 140 and
edge chambers 142a, 142b, 146a, 146b, 148a, 148b are in
communication with the ramped surfaces 132a, 132b and web surfaces
134a, 134b via the porous structure of the nozzle 120. The ramped
surfaces 132a, 132b and web surfaces 134a, 134b, being part of the
nozzle 120 that is porous, are porous and allow fluid supplied to
the feed chamber 140 and edge chambers 142a, 142b, 146a, 146b,
148a, 148b to be discharged to the exterior of the nozzle 120 or
mandrel 101.
[0067] The porous structure of the nozzle 120 may be due to the
material used in making the nozzle 120 or due to perforations in
the nozzle 120. In one embodiment, the nozzle 120 is made of a
porous material, examples of which include porous graphite, porous
silicon carbide, and porous zirconia. It should be noted that
porous silicon carbide and porous zirconia are prone to stick with
glass. Therefore, when these materials are used, it may be
desirable to coat them with high-temperature non-stick material,
i.e., in case the nozzle 120 accidentally contacts the tubing while
the glass material of the tubing is soft. The porosity of the
porous material may be in a range from 10% to 20%. Preferably, the
porous material will have a mean pore size less than 50 .mu.m to
allow for precise machining of the nozzle 120. More preferably, the
porous material will have a mean pore size of 10 .mu.m or less. In
another embodiment, the nozzle 120 is made of a non-porous or
semi-porous material that is perforated to provide the nozzle 120
with the desired pore structure. The perforations may be made by
machining or other suitable method for forming holes in a body.
[0068] Gas flow through a porous layer depends on gas pressure,
layer thickness, and material permeability. The pore structure of
the nozzle 120 is selected to achieve the desired permeability of
the nozzle 120 to gas. Preferably, the pore structure of the nozzle
120 is such that permeability of the nozzle 120 to gas is
homogeneous and sufficiently low to allow the development of a gas
cushion in the gas bearing gap that can counteract the attraction
forces created by the surface of the tubing. The gas pressure to
create the gas cushion will generally be in a range of 1 to 10 atm.
This low gas pressure range is allowed by the arrangement of the
gas distribution chambers 142a, 142b, 146a, 146b, 148a, 148b in the
nozzle 120 and a sufficient distance between the gas distribution
chambers and the surface of the nozzle 120. Too large a gas
pressure should be avoided to limit failure risks. Gas can be
distributed by a porous material, allowing uniform flow, both at a
small scale and on a large scale area. Other means of distributing
gas such as perforations formed in a non-porous or semi-porous
material are also possibilities.
[0069] FIG. 9A shows another mandrel 160 having a nose 162 and a
nozzle 164. The main difference between the mandrel 160 and the
mandrel 101 described above appears in the nozzle 164, which is
shown separately in FIG. 9B. The nozzle 164 has an upper nozzle
section 164a, an intermediate nozzle section 164b, and a lower
nozzle section 164c. The edge chambers 170, 172 start from the
upper nozzle section 164a, pass through the intermediate nozzle
section 164b, and end at non-distal points in the lower nozzle
section 164c. The feed chamber 168 extends from the upper nozzle
section 164a into the intermediate nozzle section 164b and ends at
the interface between the intermediate nozzle section 164b and the
lower nozzle section 164b. The upper nozzle section 164a has a
generally oval cross-sectional shape. The intermediate nozzle
section 164b changes from a generally oval cross-sectional shape at
the top interface with the upper nozzle section 164a to a generally
splined rectangular shape at the bottom interface with the lower
nozzle section 164c. The lower nozzle section 164b is generally
bi-tapered as described for the lower nozzle section 120b above.
The mandrel 160 may be used to shape a tubing whose initial
cross-sectional shape is generally oval or round. FIGS. 9A and 9B
show that the mandrel of the conforming tool 100 is not restricted
to one shape and also that the nozzle section of the mandrel may
have any desired cross-sectional profile to form a desired
cross-sectional profile in a tubing.
[0070] FIG. 10 shows a setup for shaping a glass tubing 200 using
the conforming tool 100. The glass tubing 200 is arranged in a
vertical orientation, i.e., with the axial axis of the glass tubing
200 being vertically oriented. In other setups, the glass tubing
200 may be arranged in a horizontal or inclined orientation. The
conforming tool 100 is suspended on the end of a pipe 204, which
runs through the glass tubing 200. The pipe 204 is preferably a
rigid pipe made of a material that can withstand the temperatures
at which the glass tubing will be reformed and that also won't
generate spurious material that can contaminate the glass tubing.
The pipe 204 may be made of stainless steel, for example. The pipe
204 is attached to a support 206 above the glass tubing 200. The
pipe 204 is in communication with a fluid source 207. In one
embodiment, the fluid source 207 is a source of pressurized gas or
air. In operation, the glass tubing 200 is pulled downwardly so
that the conforming tool 100 advances along the length of the glass
tubing 200 in the upward direction. The pulling force 203 can be
provided by any suitable pulling system, such as, for example, a
belt tractor that imposes a constant pulling force or a constant
speed on the glass tubing 200. Alternatively, the pulling force 203
can be provided by gravity. Alternatively, the glass tubing 200 can
be supported in a fixed position and the conforming tool 100 can be
pulled upwardly.
[0071] The glass tubing 200 extends through a metal cylinder 208,
which is disposed within a helical inductor 210. The metal cylinder
208, acting as a susceptor, absorbs electromagnetic energy from the
helical inductor 210. The absorbed electromagnetic energy is
re-emitted as infrared radiation towards the glass tubing 200. Any
portion of the glass tubing 200 within the metal cylinder 208 will
be heated by infrared radiation from the metal cylinder 208. The
metal cylinder 208 and helical inductor 210 thus constitute one
type of heating arrangement of the glass tubing 200. In general,
any suitable method and arrangement for heating the glass tubing
200 may be used. Heating may be radiant heating, induction heating,
resistive heating, or any combination of the preceding. Other
heating methods not specifically mentioned may also be used
provided the heating methods can elevate the temperature of the
glass tubing 200 to a level at which the glass tubing 200 can be
deformed when fluid pressure is applied by the conforming tool 100.
The heating arrangement may also provide different temperature
zones, e.g., a preheating zone, a reforming zone, and a cooling
zone. For a glass material such as Corning code 7740 borosilicate
glass, for example, the preheating zone and cooling zone may be at
650.degree. C. while the forming zone is at 780.degree. C.
[0072] The entire glass tubing may be heated to a forming
temperature T.sub.1.+-..delta..sub.1, where .delta..sub.1 is some
acceptable margin of error, e.g., less than 11% of T.sub.1.
T.sub.1.+-..delta..sub.1 is a temperature at which the glass has a
relatively low viscosity, e.g., <10.sup.9 Poise or in a range
from 10.sup.8 Poise to 10.sup.9 Poise. Forming temperature
T.sub.1.+-..delta..sub.1 may be between the annealing point and
softening point of the glass. In one embodiment, forming
temperature T.sub.1.+-..delta..sub.1 is at least 20.degree. C.
below the softening point. At forming temperature
T.sub.1.+-..delta..sub.1, the viscosity of the glass is low enough
that the glass can be permanently deformed. While the glass tubing
200 is at the forming temperature T.sub.1.+-..delta..sub.1, the
conforming tool 100 can be translated along the glass tubing 200 to
shape the glass tubing 200 to the desired final cross-sectional
profile. The temperature requirements may be different from what is
stated above if the tubing is made of glass-ceramics, particularly
if nucleation or crystallization is to be avoided. However, in
general, the conforming tool 100 will be applied to the tubing
while the tubing is at a temperature at which it can be
deformed.
[0073] Instead of heating the entire glass tubing 200 to
T.sub.1.+-..delta..sub.1, the entire glass tubing 200 may be heated
to an initial temperature T.sub.0.+-..delta..sub.0, where
.delta..sub.0 is some acceptable margin of error, e.g., less than
11% of T.sub.0. At initial temperature T.sub.0.+-..delta..sub.0,
the glass has a relatively high viscosity, e.g., between
6.times.10.sup.9 Poise and 10.sup.12 Poise. At initial temperature
T.sub.0.+-..delta..sub.0, deformation of the glass tubing or
optical defects in the glass tubing can be avoided. Initial
temperature T.sub.0.+-..delta..sub.0 may be near the annealing
point of the glass. In one embodiment, initial temperature
T.sub.0.+-..delta..sub.0 is within 10.degree. C. of the annealing
point. The glass tubing 200 can then be locally heated to the
forming temperature T.sub.1.+-..delta..sub.1 mentioned above, where
T.sub.1.+-..delta..sub.1 is greater than T.sub.0.+-..delta..sub.0.
At any instance, the portion of the glass tubing 200 at the forming
temperature T.sub.1.+-..delta..sub.1 can be deformed using the
conforming tool 100. This means that to shape the entire glass
tubing 200 using the conforming tool 100, the local heat and
conforming tool 100 will have to be applied along the length of the
glass tubing 200.
[0074] FIGS. 11A-11E illustrates use of the conforming tool 100 to
shape the glass tubing 200. The heating arrangement is not
specifically shown in these figures. However, as discussed above,
for the shaping process to work, the glass tubing has to be at a
temperature at which it can be deformed. Relative to the
orientation of the glass tubing 200 in FIG. 11A, the process starts
from the bottom end of the glass tubing 200. As the glass tubing
200 is pulled downwardly, the plug 112 and nose 102 of the
conforming tool 100 first enter the glass tubing 200 through the
bottom end of the glass tubing 200. Then, the upper nozzle section
120a follows the nose 102 into the glass tubing 200. At this point,
gas is supplied into the chambers of the nozzle 120 and discharged
outside of the nozzle 120 via the porous circumference 136 of the
nozzle 120. Because of the sizing of the upper nozzle section 120a
as discussed above, a circumferential gap 314 is defined between
the upper nozzle section 120a and the glass tubing segment 316 in
opposing relation to the upper nozzle section 120a. The discharged
fluid from the upper nozzle section 120a forms a film of
pressurized gas in the circumferential gap 314. The film of
pressurized gas in the circumferential gap 134 functions as a gas
bearing between the surfaces of the upper nozzle section 120a and
the glass tubing 200. The gas bearing exerts pressure on the wall
of the glass tubing segment 316. This pressure radially expands the
glass tubing segment 316, allowing a small portion of the lower
nozzle section 120b to then enter into the glass tubing 200, as
shown in FIG. 11B.
[0075] Two gaps 318a, 318b are created between the opposed ramped
surfaces 132a, 132b of the lower nozzle section 120b and the glass
tubing 102. The discharged gas from the lower nozzle section 120b
forms a film of pressurized gas in each of the gaps 318a, 318b. The
films of pressurized gas in the gaps 318a, 318b function as gas
bearings between the ramped surfaces 132a, 132b and the glass
tubing 200. The gas bearings exert pressure on the wall of the
glass tubing segment 316. This pressure laterally expands the glass
tubing segment 316, allowing more of the lower nozzle section 120b
to enter into the glass tubing 200. This process continues until
the entire nozzle 120 has entered into the glass tubing 200 and
passed through the glass tubing segment 316. As the nozzle 120
passes through the glass tubing segment 316, the glass tubing
segment 316 will assume the shape of the nozzle 120, as shown in
FIGS. 11C-11E. The last cross-section of the nozzle 120 to pass
through any particular point along the length of the glass tubing
will determine the cross-sectional profile at that particular point
in the tubing.
[0076] The conforming tool 100 can be advanced inside and along the
glass tubing 200 until the nozzle 120 has completely passed through
the entire glass tubing 200 or a desired length of the glass tubing
200. Advancing of the conforming tool 100 can involve pulling the
glass tubing 200 downwardly and over the conforming tool 100 as
discussed above, pulling the conforming tool 100 upwardly and
inside the glass tubing 200, or a combination of the preceding. The
conforming tool 100 has to be advanced in a single direction for
the conforming or shaping operation. Advancing of the conforming
tool 100 can be at a constant or variable speed. However, the speed
will need to be tailored such that conforming or shaping of the
glass tubing can be completed accurately and efficiently.
[0077] Shaping of the glass tubing 200 is achieved by applying gas
pressure to the glass tubing 200 while the glass tubing 200 is at
the temperature at which it can be deformed. The gas pressure is
provided by thin film(s) of pressurized gas created between the
glass tubing 200 and the nozzle 120 via discharge of gas from the
nozzle 120 as described above. The film(s) of pressurized gas
serves not only to exert pressure on the glass tubing 200 but to
also separate the conforming tool 100 from the glass tubing 200 so
that there is no physical contact between the glass tubing 200 and
the conforming tool 100 while the glass tubing 200 is at the
forming temperature, where the glass tubing 200 will generally be
soft. The thickness of each thin film of pressurized gas is
typically in a range from 60 .mu.m to 70 .mu.m, but may be up to
120 .mu.m in some embodiments. The thin film(s) of pressurized gas
is translated along the length of the glass tubing 200 as the
conforming tool 100 advances along the length of the glass tubing
200. The thin film(s) of pressurized gas constitutes a gas bearing.
The width of the gas bearing gap, which will determine the
thickness of the film, will depend on glass viscosity, conforming
speed (i.e., the speed at which the conforming tool 100 is
advancing along the glass tubing), and venting flux in the
depressed areas of the nozzle 120.
[0078] FIG. 12 shows an end view of the shaping process. Gas is
discharged through the ramped surfaces 132a, 132b of the lower
nozzle section 120b, wherein the discharged gas forms two gas
bearings between the ramped surfaces 132a, 132b and the glass
tubing 200. These gas bearings exert opposing forces on the glass
tubing 200 to laterally expand the glass tubing 200 in opposite
directions. The opposing forces are applied at the portions of the
glass tubing 200 in opposing relation to the ramped surfaces 132a,
132b. While the portions of the glass tubing 200 facing the ramped
surfaces 132a, 132b are being laterally expanded, the portions of
the glass tubing 200 facing the web surfaces 134a, 134b will be
flattened. Also, due to venting flux at the depressed areas 138a,
138b in the web surfaces 134a, 134b, films of pressurized gas that
can exert pressure on the glass tubing 200 will not be
substantially formed between the web surfaces 134a, 134b and the
glass tubing 200. The force available for lateral expansion of the
glass tubing 202 will depend on the pressure of the opposed gas
bearings, which in turn will depend on the pressure of the gas
supplied to the feed chamber of the nozzle 120, the configuration
of the edge chambers of the nozzle 120 that distribute gas to the
ramped surfaces 132a, 132b, and the pore structure of the nozzle
120. The flattening of the portion of the glass tubing 200 opposite
to the web surfaces 134a, 134b will also depend on the venting flux
at the web surfaces 134a, 134b.
[0079] In general, the diameter and lengths of the edge chambers
142a, 142b, 146a, 146b, 148a, 148b (see FIG. 1), the depression of
the web surfaces 134a, 134b, the positioning of the edge chambers
relative to the ramped surfaces 132a, 132b, and the pressure of the
gas supplied to the edge chambers can be appropriately selected to
provide the desired gas bearing pressure distribution around the
nozzle 120 to form the desired oblong cross-sectional shape in the
glass tubing 200. For example, to form an oblong internal
cross-sectional shape of 6 mm by 65 mm, the edge chambers can be 3
mm in diameter and be positioned 1.5 mm from the adjacent ramped
surfaces. The depressed areas of the web surfaces may be between
0.5 mm and 1.5 mm deep. Gas such as nitrogen or air may be used as
the supplied gas. The venting flux in the depressed areas may be
0.5 to 1.5 m.sup.3 per hour, measured at 780.degree. C. With this
configuration, flat faces can be obtained in the portion of the
glass tubing opposite to the web surfaces. The localized gas
bearing at the ramped surfaces will also ensure lateral tensioning
to help in flatness control of the flat faces. However, it should
be clear that the properties of the conforming tool 100 and
supplied gas will need to be set based on the shape to be formed
and the pressure distribution needed to form the shape and should
not be limited to the specific example given above.
[0080] It is possible to have web surfaces 134a, 134b without
venting flux sites such that gas bearings may be formed between the
web surfaces 134a, 134b and the glass tubing 200, e.g., if it is
desired to have an oblong cross-sectional shape with splined sides
rather than flat sides. In this case, the geometry of the nozzle
120 may be such that the gas bearings formed between the web
surfaces 134a, 134b and the glass tubing 200 are different compared
to the gas bearings formed between the ramped surfaces 132a, 132b
and the glass tubing 200 so that lateral expansion force can be
applied to the glass tubing 200 biaxially in different amounts. In
general, the portion(s) of the glass tubing 200 where greater
lateral expansion is desired will have higher gas bearing pressure
than the portion(s) of the glass tubing 200 where lower to no
lateral expansion is desired.
[0081] In one or more embodiments, the initial circumference of the
glass tubing 200, i.e., the circumference before conforming the
glass tubing 200 to the final cross-sectional profile, is selected
to be smaller than the final circumference of the glass tubing 200,
i.e., the circumference after conforming the glass tubing 200 to
the final cross-sectional profile. In other words, there will be
some geometrical lateral tensioning of the wall of the glass tubing
200 during the reforming. The ratio between the initial
circumference and the final circumference is less than 1.
Preferably, the ratio between the initial circumference and the
final circumference is below 0.96. More preferably, the ration is
between 0.7 and 0.95, which will result in stretching of the glass
tubing wall by 5 to 30%. The ratio of 0.7 and 0.95 can be used
where intentional thinning of the wall of the glass tubing 200 is
desired along with the conforming.
[0082] A glass sleeve can be cut from a glass tubing shaped using
the conforming tool 100 and process described above. In one
embodiment, the glass sleeve has a seamless wall and an oblong
cross-sectional shape, with an aspect ratio greater than 5:1.
Preferably, the aspect ratio is greater than 10:1. In one
embodiment, the glass sleeve has an absolute thickness (see 182 in
FIG. 13) less than 12 mm. The absolute thickness includes the glass
thickness. In one embodiment, the glass sleeve has an absolute
width (see 184 in FIG. 13) up to 70 mm. The absolute width includes
the glass thickness. In one embodiment, the glass sleeve has an
inner surface roughness that is less than 1 .mu.m, preferably in a
range from 0.2 nm to 10 nm. In one embodiment, the glass sleeve has
an outer surface roughness that is less than 1 .mu.m, preferably in
a range from 0.2 nm to 10 nm. In one embodiment, the wall of the
glass sleeve has opposing flat sections. The flatness in each of
the flat sections is better than 50 .mu.m on 50.times.90 mm.sup.2,
as measured by a confocal microscope or mechanical gage system.
Preferably, the flatness in each of the flat sections is better
than 30 .mu.m on 70.times.120 mm.sup.2, as measured by a confocal
microscope or mechanical gage system. Flatness is measured in terms
of deviation from a perfectly flat surface. Therefore, the smaller
the deviation, the better the flatness. The glass tubing from which
the glass sleeve is cut may be made of an ion-exchangeable material
so that the glass sleeve can be subjected to an ion-exchange
process for chemical strengthening.
[0083] FIG. 13 shows a glass sleeve 180 cut from a glass tubing
shaped using the conforming tool 100 and process described above
and meeting the requirements described above. Other glass sleeves
with different cross-sectional profiles can be similarly formed.
The glass sleeve 180 has a mean surface roughness of 0.18 nm, as
measured on a Zygo Interferometer, which is comparable to the mean
surface of a pristine glass tubing that has not been shaped by the
conforming tool 100. This means that, as mentioned earlier, the
surface quality of the glass tubing is preserved through the
reforming process. In addition, the flat sides of the glass sleeve
180 meet the requirements stated above. The glass sleeve 180 can
function as a case for an electronic device. The components of the
electronic device can be arranged in the compartment of the glass
sleeve 180, with any flat display of the electronic device adjacent
to a flat side (or surface) of the glass sleeve 180. The open ends
of the glass sleeve 180 can then be sealed with a suitable plug,
which may be made of a material other than glass. It is also
possible to flame seal one end of the glass sleeve 180 before
arranging the components of the electronic device in the glass
sleeve. After arranging the components of the electronic device in
the glass sleeve 180, the remaining open end of the sleeve 180 can
be sealed with a plug. The assembled product will have seamless,
same-quality, top and bottom surfaces.
[0084] The conforming tool 100 can be used advantageously in a
glass tubing process to enable continuous production of a profiled
glass tubing. FIG. 14 shows an example of a glass tubing process
incorporating the conforming tool 100. The glass tubing apparatus
in FIG. 14 is configured to form the glass tubing by a Vello
process. However, the conforming tool 100 is not limited to a Vello
process. Other glass tubing processes such as the Danner process or
downdraw process may also take advantage of the conforming tool 100
to continuously generate a profiled glass tubing having the
required cross-sectional shape and wall thickness. In the process
shown in FIG. 14, molten glass 500 flows from a tank 502 through an
orifice 504 surrounding a bell 506. Air is blown through a hollow
tip 508 of the bell 506 to form the glass tubing 510. Below the
hollow tip 518 is the conforming tool 100. The glass tubing 510
passes over the conforming tool 100 (160) while the conforming tool
100 (160) shapes the glass tubing 510 to the final cross-sectional
profile 512. After the conforming tool 100, the glass tubing 510
progressively passes from a high viscosity state to a frozen state
below the softening point (.about.10.sup.8 poise), and
advantageously below 10.sup.11 poise for accurate dimensional
control.
[0085] In one embodiment, the glass tubing 510 turns from the
vertical to the horizontal while at a very high viscosity. This
would allow the horizontal portion of the glass tubing 510 to be
cut periodically, as shown at 514, 516, without disturbing the
upper part of the process near the tank and conforming tool. The
turning is possible at the very high viscosity state partly because
of the relative thinness of the glass tubing, e.g., less than 12
mm, and the large turn radius, e.g., 2 to 4 m. In an alternate
embodiment, the glass tubing is not turned from the vertical to the
horizontal and the periodic cutting of the glass tubing is operated
vertically. Pulling means such as roller or belt tractors can be
arranged after the conforming tool to support the glass tubing, and
the vertical cutting can take place after the pulling means.
[0086] Fine diamond saw cutting may be used in both the horizontal
and vertical cutting of the glass tubing. Fine diamond saw cutting
would allow straight and close-to-chip free cutting that will only
require a final beveling and polishing operation to assure expected
aesthetic and mechanical performances. Other methods of cutting,
such as laser cutting, may also be used. Large profiled tubes may
be initially cut from the continuous profiled glass tubing. Then,
smaller sleeves, e.g., of the size suitable for containing a small
electronic device, can be cut from the large profiled tubes. The
sleeves can be subjected to an ion-exchange process for improved
strength.
[0087] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
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