Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
1999-06-09
2002-06-25
Vincent, Sean (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S481000, C065S498000, C065S512000
Reexamination Certificate
active
06408654
ABSTRACT:
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
This invention relates generally to an apparatus for and method of producing continuous glass filaments, and in particular, to an apparatus having a bushing and a cooling apparatus positioned beneath the bushing to induce a uniform air flow between a filament forming area beneath the bushing and the cooling apparatus to cool the area. The invention is useful in the production of continuous glass filaments that may be used as reinforcement in molded resinous articles.
BACKGROUND OF THE INVENTION
In the manufacture of continuous glass filaments, glass is melted in a filament forming apparatus and flows to one or more bushings. Each bushing has a number of nozzles or tips through which streams of molten glass flow. The glass streams are mechanically pulled from the nozzles by a winding apparatus to form continuous glass filaments.
The temperature of the molten glass within the bushing must be high enough to maintain the glass in a liquid state. However, if the temperature is too high, the molten glass will not cool sufficiently so as to become viscous enough to form filaments after passing through the bushing tips. Thus, the glass must be quickly cooled or quenched after it flows from the bushing tips and forms glass filaments. If the glass cools too slowly, the glass filaments will break and the filament forming process will stop.
There are numerous apparatuses for cooling the glass filament forming area beneath a filament forming machine. Conventional cooling apparatuses use air, water, or both to transfer heat from the filament forming area beneath a bushing and cool the glass filaments.
A conventional glass filament forming apparatus
5
with a heat transfer apparatus
50
is shown in FIG.
1
and is disclosed in U.S. Pat. No. 4,662,922 to Hill et al. (Hill), the disclosure of which is expressly incorporated herein by reference. Filaments
20
are drawn from a plurality of nozzles
12
of a bushing
10
and gathered into a strand
22
by a roller
42
. Size is applied to coat the filaments by a size applicator
40
. A reciprocating device
34
guides strand
22
, which is wound around a rotating collet
32
in a winding apparatus
30
to build a cylindrical package
24
. The heat transfer apparatus
50
is located beneath a bottom plate
14
of the bushing
10
to cool filament forming area
16
beneath the bushing
10
.
Another conventional filament forming apparatus is shown in FIG.
2
and is disclosed in U.S. Pat. No. 4,197,103 to Ishikawa et al. (Ishikawa). The forming apparatus in Ishikawa includes a cooling system that uses both air and a cooling fluid to cool the filament forming area
16
.
The cooling system includes a heat transfer apparatus
50
with a manifold
52
and cooling fins
54
that extend from the manifold
52
between rows of nozzles
12
. A cooling fluid flows through a channel formed in manifold
52
. Heat from the glass is transferred to the fins both radiantly and, via the ambient air surrounding the fins and glass, convectively. Heat travels to the manifold
52
from cooling fins
54
conductively and is transferred to the cooling fluid convectively.
The cooling system also includes a cooling apparatus
60
with an air manifold
66
. An air source, such as a pump, supplies air to the manifold
66
from which it is introduced on one side of the bushing
10
. The air travels along the nozzles
12
and fins
54
. The air is introduced during the initial start-up period of a filament forming operation. After the operation stabilizes (approximately 5 to 10 seconds after start-up), the air flow is reduced or terminated.
Cooling apparatus
60
introduces air from only one side of the bushing
10
. The air quickly heats up as it flows along the fins
54
and through the filament forming area
16
. As a result, an insufficient amount of heat is removed from the filament forming area and the risk of bushing breaks and shut downs of the filament forming process increases. Further, the short periods of air flow are insufficient to continuously cool the filament forming area and the filaments.
Additional conventional cooling systems disclosed in Hill are shown in
FIGS. 3A and 3B
. The cooling system shown in
FIG. 3A
includes a heat transfer apparatus
50
and a cooling apparatus
60
. The heat transfer apparatus
50
includes a manifold and cooling fins
54
similar to Ishikawa.
The cooling apparatus
60
includes a tube
62
with several apertures
64
along its bottom surface. Air is supplied to a channel in tube
62
and flows through the apertures
64
to the area between banks
13
of bushing nozzles
12
. The air from tube
62
is cooler than the air in the filament forming area
16
. The air flow entrains and induces air from the sides of the bushing
10
along the cooling fins
54
and in a generally downward direction. The induced air flow also cools filament forming area
16
.
In the cooling apparatus
60
shown in
FIG. 3B
, a cooling fluid tube
68
supports tube
62
. Tube
68
has a passage
70
through which a cooling fluid, such as water, flows. The fluid is used in conjunction with air from tube
62
to remove heat and maintain the temperature of the filament forming area
16
. In Hill, the amount of heat removed from the filament forming area is limited by the volume of air flow.
Another conventional cooling apparatus is disclosed in U.S. Pat. No. 4,612,027 to Marra (Marra). Marra discloses a glass filament forming apparatus with a cooling apparatus. Cooling apparatus
80
includes a manifold
82
having a plurality of nozzles
81
as shown in
FIG. 1
of Marra. Nozzles
81
are adapted to direct streams of cooling air toward the streams of molten glass and bottom plate of the bushing
10
.
Another conventional cooling apparatus is disclosed in U.S. Pat. No. 4,003,731 to Thompson (Thompson). Thompson discloses a filament forming apparatus having a nozzle
10
through which air is introduced toward the bottom plate of a bushing and the glass filaments attenuated therefrom. Nozzle
10
includes a chamber
12
with apertures
18
through which air flows into skirt
14
as shown in
FIG. 3
of Thompson. The air from the nozzle prevents overheating and rapidly quenches the glass streams. However, Thompson teaches that the upward movement of the air from the nozzle serves to substantially eliminate the induction of air by the downwardly moving glass streams.
A conventional apparatus for cooling a filament forming area that uses a vacuum to draw warm air out of the area is disclosed in U.S. Pat. No. 5,693,118 to Snedden et al. (Snedden). In Snedden, hollow fins similar in shape to the conventional cooling fins are mounted to a manifold through which a vacuum is applied. Each fin includes a hollow chamber and apertures along its top wall through which warm air in the filament forming area is drawn by the vacuum.
Each filament forming apparatus has an “operating” condition and a “hanging” condition. In an “operating” condition, continuous filaments are attenuated from a bushing at high speeds. The attenuation of the filaments induces the air surrounding the filaments in the direction that the filaments are drawn. The flow of surrounding air induces air from the perimeter of the bushing into the interior of the filament forming area to help cool the molten glass.
A “hanging” condition occurs when some or all of the filaments are not drawn at production speed and molten glass slowly flows from a bushing. During this condition, minimal air flow is induced into the filament forming area, thereby decreasing the cooling of the filament forming area and the filaments.
The filament forming apparatus must be adequately cooled during the hanging condition to permit filament attenuation to quickly restart after a disruption. The failure to quickly restart reduces the operating efficiency of the apparatus and lowers the overall throughput.
If heat is more rapidly removed from a filament forming area, the operating temperatures of the bushing and the glass in the bushing can be raised to increase thr
Boessneck Douglas Scott
Coon Jeffrey
Gao Guang
Prescott Patrick John
Snedden Andrew Lawrence
Eckert Inger H.
Owens Corning Fiberglas Technology Inc.
Vincent Sean
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