Glass manufacturing – Melting pot or furnace with structurally defined delivery or...
Reexamination Certificate
2001-07-12
2004-06-22
Griffin, Steven P. (Department: 1731)
Glass manufacturing
Melting pot or furnace with structurally defined delivery or...
C065S346000, C065S355000, C065S356000, C065S135600, C373S030000, C373S039000, C373S144000, C373S161000
Reexamination Certificate
active
06751989
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a device for the melting or refining of glasses or glass ceramics.
BACKGROUND OF THE INVENTION
Such devices have become known in the configuration of the so-called “skull pot”. They comprise a pot walling. This is generally cylindrical. It is constructed of a crown of vertical metal pipes. Slots remain between adjacent pipes. The bottom of the pot can also be constructed of metal pipes. However, it can also consist of refractory material. The ends are connected to vertical pipes for the introduction of cooling agent or for the discharge of cooling agent.
Heating is conducted by means of an induction coil, which surrounds the pot walling and by means of which high-frequency energy can be input into the contents of the pot.
Such a skull pot has been made known, for example, from EP 0 528,025 B1.
A skull pot operates as follows: The pot is filled with a [fresh] glass batch or refuse glass or a mixture thereof. The glass or the melt must first be preheated in order to obtain a certain minimum conductivity. Preheating is primarily conducted by means of burner heating. If the temperature for [HF energy] input has been reached, then further energy input can be supplied by means of irradiation by high-frequency energy. During the operation, in addition to the high-frequency energy heating, the melt is also heated by means of burners, which operate from the top onto the melt, or by means of hot off-gases. This additional heating is particularly necessary in the case of the use of a skull pot for refining. That is, if the surface layer is cold and correspondingly highly viscous, then bubbles will be prevented from exiting the melt or a foaming will occur.
Usually, the skull pot is arranged in a standing position. It is generally operated discontinuously.
JP 57 [1982]-95,834 describes a device with a quartz channel, which is arranged horizontally.
A high-frequency oscillating circuit, which contains a cylindrical coil, is assigned a to the quartz channel. The cylindrical coil wraps around the quartz channel. The quartz channel is actually cooled, However, when aggressive glasses are melted, it does not have a high long-term stability and a high breaking strength. In addition, a special heating of the melt surface is not possible. In fact, a certain cooling occurs, which can lead to the formation of a tough skin in the surface region. If such a channel is to be used as a refining device, then bubbles can no longer rise up unhindered and be discharged from the melt. The channel therefore cannot be used for refining. If the channel is used for melting, and the melt contains readily volatile components, then there is a risk of condensation at the cooled superstructure of the channel. The condensate can thus drip into the melt in an uncontrolled manner. This can lead to glass defects in the form of nodes, blisters or streaks. If corrosion of the coil material occurs, then this leads to discoloration of the glass, depending on the material of the coil. This is not acceptable, particularly in the case of optical glasses.
Further, there are very many optical glasses, which have a high proportion of fluorine, phosphate or other highly aggressive components. These can also attack the material of the coil. The corrosion can be strong enough that discharge of cooling water occurs, so that the operational safety of the plant is no longer assured.
SUMMARY OF THE INVENTION
The object of the invention is to create a device, in which the advantages of the technique of inductive heating are utilized, which is reliable in operation, which is also suitable for the refining of melts, and which leads to glasses of a perfect quality. This object is resolved by the features of claim
1
.
According to the invention, not only is use made of the high-frequency technique, but also the skull technique is used. A channel is used, which has a structure similar to that of a skull pot. The upper space is not covered by water-cooled pipes in this way. Rather, it is freely accessible and can be used for thermal insulation or for an additional heating by means of a burner or by means of radiant heat.
The invention, however, introduces the following additional advantage, which the inventors have recognized:
If the water-cooled metal pipes of a skull device run in the direction of the glass flux, then flashovers between the glass melt and the metal pipes of the skull channel can occur at high melt temperatures, if the solidified cold glass insulation layer is very thin. This can lead to arcing between the skull channel and the melt, which can have as a consequence a disruption of the skull frame. It is presumed that the arc formation is produced by high-frequency voltages induced in the skull pipe.
In one embodiment according to the invention, the water-cooled metal skull pipes run perpendicular to the direction of glass flow, thus not in the direction of glass flow. In this way, the formation of arcs between the skull pipes and the melt is extensively avoided.
In another embodiment of the invention, the tendency toward flashover, i.e.: the tendency to form arcs, is fully prevented in that the ends of the U-shaped piece of the skull pipe are joined with each other in a conductive manner for purposes of forming a short-circuit bridge [shunt].
The invention introduces the following additional advantages:
It is excellently suitable for continuous operation. It can thus operate very economically.
Another advantage consists of the following:
Due to the configuration and arrangement of the induction coils in the lying-down position, the channel is open at the top. The level of the melt is exposed. The surface of the melt is thus freely accessible for the installation of an additional heating device, for example, a gas burner or an electrical heating device. This top heating is of particular advantage for the case when the channel is utilized as a refining aggregate. High surface temperatures can be obtained accordingly, so that the bursting of bubbles is assured in the region of the surface.
The heating from above is also helpful if high-frequency energy failure occurs. In this way, at least the glass transport can be assured. Also, the melt temperature can be maintained at such a value that a recoupling is possible when high-frequency heating is again started up.
Further, there is no danger of condensation of products of evaporation on the water-cooled coil pipes, since these are not found above the level of the melt.
Additionally, a complex superstructure is provided in the case of the skull channel according to the invention, which includes ceramic plates that cover thechannel. The ceramic plates can be heated on the top side by means of burners. The plates then radiate heat onto the glass surface by their lower side, so that the glass is indirectly heated. This has the advantage that strong and turbulent atmospheric interferences do not occur directly below
*
the level of the glass melt in the case of glasses containing components that have a high tendency toward evaporation (B
2
O
3
, P
2
O
5
, F, S, Se, Te or the like). Such interference would entrain the easily volatile components, which would lead to a modification of the glass composition. A premature blockage of filter devices is also avoided in this way.
*
sic; above?—Trans. note.
Another advantage of the skull channel according to the invention lies in the fact that when additional heating is produced by means of burners, with or without ceramic cover, a reducing atmosphere can be established. This is necessary for the production of thermal insulation glasses or glasses with high UV transmissivity, in which it happens that the Fe
3+
/Fe
2+
ratio is shifted as extensively as possible to the reduced form. Fe
2+
, which absorbs in the IR, and thus is used for heat radiation (thermal insulation glass), whereas Fe
3+
, which absorbs in the UV, must be avoided as extensively as possible in the case of glasses with high UV transmissivity. Since these glasses ar
Räke Guido
Schmidbauer Wolfgang
Griffin Steven P.
Hug Eric
Ohlandt Greeley Ruggiero & Perle L.L.P.
LandOfFree
Device and method for melting or refining glass or glass... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for melting or refining glass or glass..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for melting or refining glass or glass... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3364142