Glass manufacturing – Processes – Fining or homogenizing molten glass
Reexamination Certificate
1999-02-12
2001-03-20
Vincent, Sean (Department: 1731)
Glass manufacturing
Processes
Fining or homogenizing molten glass
C431S004000
Reexamination Certificate
active
06202445
ABSTRACT:
The present invention belongs to the technical field of a vacuum degassing apparatus for molten glass which removes bubbles from molten glass continuously supplied, and a method to rise a vacuum degassing apparatus temperature.
In order to improve the quality of glass products, there has been used a vacuum degassing apparatus which removes bubbles generated in molten glass before the molten glass which has been molten in a melting tank is formed by a forming apparatus. Such a conventional vacuum degassing apparatus is shown in FIG.
5
. The vacuum degassing apparatus
110
shown in
FIG. 5
is used in a process wherein molten glass G in a melting tank
120
is vacuum-degassed and is continuously supplied to a forming treatment vessel (not shown). A vacuum housing
112
where a vacuum is created has a vacuum degassing vessel
114
substantially horizontally housed therein, and an uprising pipe
116
and a downfalling pipe
118
housed in both ends thereof so as to extend vertically and downwardly.
The uprising pipe
116
has a lower end immersed in the molten glass G in an upstream pit
122
which communicates with the melting tank
120
. The uprising pipe has an upper end communicated with the vacuum degassing vessel
114
. The molten glass G before degassing is drawn up from the upstream pit
122
into the vacuum degassing vessel
114
. The downfalling pipe
118
has a lower end immersed in the molten glass G in a downstream pit
124
which communicates with the successive forming treatment vessel (not shown). The downfalling pipe has an upper end communicated with the vacuum degassing vessel
114
. The molten glass G after degassing is drawn down from the vacuum degassing vessel
114
and is led out to the downstream pit. In the vacuum housing
112
, thermal insulation material
130
such as bricks for thermal insulation is provided around the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
to cover these parts for thermal insulation.
The vacuum housing
112
may be a casing made of metal such as stainless steel. The vacuum housing is evacuated by a vacuum pump (not shown), for instance, to maintain the inside of the vacuum degassing vessel
114
provided therein in a depressurized state such as a pressure of {fraction (1/20)}-⅓ atmosphere.
The inlet temperature of the forming treatment vessel is limited to a certain temperature, such as a temperature in a range from 1,000° C. to 1,300° C. As a result, the temperatures of the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
, which are located upstream of the forming treatment vessel, are limited to a temperature from 1,200° C. to 1,400° C. for instance. JP-A-2221129 in the name of the applicants discloses that the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
have portions in direct contact with the molten glass G made of noble metal such as platinum and platinum alloy. Specifically, the paths for the molten glass in the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
are constituted by circular shells which are made of noble metal such as platinum and platinum alloy in JP-A-2221129.
The use of noble metal in the vacuum degassing vessel
114
and so on not only is quite costly but also is accompanied by various problems.
It is proposed to constitute the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
by refractory material less expensive than noble metal, such as electro-cast bricks, and to continuously vacuum-degas the molten glass as in the use of noble metal, coping with such various problems caused by the use of noble metal.
However, when the vacuum degassing vessel
114
is constituted by refractory material such as electro-cast bricks, the following problem is created.
When starting operating the vacuum degassing apparatus
110
, it is required that the molten glass G be drawn up from the upstream pit
122
into the vacuum degassing vessel
114
and be drawn down through the downfalling pipe
118
to be led out to the downstream pit
124
. The temperature at portions which work as the paths for the molten glass G is required to have been preliminarily risen by that time. Otherwise, it is difficult to obtain a required flow of the molten glass G since the viscosity of the molten glass G is risen or the molten glass G is solidified on the way to the downstream pit.
The conventional vacuum degassing vessel
114
made of noble metal can preliminarily rise the temperature at the portions to be served as the paths for the molten glass G by flowing a current in the noble metal circular shell per se to self-heat the circular shell at the time of starting the operation of the vacuum degassing apparatus
110
. On the other hand, when the vacuum degassing vessel
114
, the uprising pipe
116
and the downfalling pipe
118
are constituted by refractory material such as electro-cast bricks, it is difficult to carry out heating by energization.
Although it is proposed to provide heating devices such as electric heaters around the uprising pipe
116
and the downfalling pipe
118
to heat the molten glass G, it is insufficient to use only such heating devices as a heat source for rising the temperature of the vacuum degassing vessel
114
per se. In particular, it is difficult to uniformly heat the vacuum degassing vessel
114
, the uprising pipe and the downfalling pipe
118
to a temperature near to the temperature of the molten glass G. It is necessary to form spaces in the thermal insulation material
130
for providing heating devices such as electric heaters therein or to modify the structure of the thermal insulation material
130
, creating a problem the vacuum degassing apparatus
110
can not have a simple structure.
It is an object of the present invention to provide a vacuum degassing apparatus for molten glass and a method to rise a vacuum degassing apparatus temperature capable of preliminary rising temperatures of a vacuum degassing vessel, an uprising pipe and a downfalling pipe to sufficient temperatures before introduction of molten glass so as to uniformly rise temperatures of portions of the vacuum degassing vessel, the uprising pipe and downfalling pipe in contact with the molten glass to a certain temperature near to a molten glass temperature under temperature control when starting operating the vacuum degassing apparatus for molten glass, which has paths for the molten glass made of refractory material.
The present invention provides a vacuum degassing apparatus for molten glass which comprises a vacuum housing which is evacuated to be depressurized therein; a vacuum degassing vessel provided in the vacuum housing to vacuum-degas molten glass; an uprising pipe communicated to the vacuum degassing vessel to draw up the molten glass before degassing and to introduce the molten glass into the vacuum degassing vessel; a downfalling pipe communicated to the vacuum degassing vessel to draw down the degassed molten glass from the vacuum degassing vessel; and the vacuum degassing vessel, the uprising pipe and the downfalling pipe having paths for the molten glass therein made of refractory material; wherein a temperature rising device are provided at a time before operating the vacuum degassing apparatus, the temperature rising device including temperature rising burners provided at lower ends of the uprising pipe and the downfalling pipe, and an exhaust pipe communicated to an upper end of the vacuum degassing vessel; and wherein, before operating the vacuum degassing apparatus, the temperature rising burners are used to burn fuel, and burned gas from the temperature rising burners is exhausted through the exhaust pipe; thereby rising temperatures of the vacuum degassing vessel, the uprising pipe and the downfalling pipe.
The present invention also provides a method to rise temperatures of a vacuum degassing vessel, an uprising pipe and a downfalling pipe in a vacuum degassing apparatus for molten glass before operating
Hirabara Yasuharu
Iketani Takashi
Inoue Shigekuni
Kurata Hiroshi
Sugimoto Mitsuo
Asahi Glass Company Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vincent Sean
LandOfFree
Vacuum degassing apparatus for molten glass and method to... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum degassing apparatus for molten glass and method to..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum degassing apparatus for molten glass and method to... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2497079