CS196203B2 - Device for indirect heating channels,feeders and dosing heads for conducting glass - Google Patents

Abstract

INVENTOR HELMUT PIEPER TITLE RESISTANT HEATING OF CERAMIC REFRACTORY CHANNELS In order to maintain glass in its molten state as it passes, during a process, from one region to another as through channels, passages, feeders and feeder heads, heat must be advantageously supplied to the molten glass to maintain its liquid state. If the glass carrying channels, passages, feeders, and feeder heads themselves are designed to carry electric currents and thus are imparted with sufficient heat to insure that the molten glass does not lose its molten state. Thus, in order to effect uniform heating a plurality of heating currents may be conducted through a plurality of electric circuits within the refractory material of the glass carrying channels, passages, feeder or feeder heads.

Description

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for indirect heating of ducts, dispensers and dispensing heads for conducting glass formed of a refractory ceramic material conductive at operating temperature.

It is already known and widely used to heat dispensers, glass guide ducts and dispensing heads, where they are heated either by electrodes. which are introduced into a glass bath, or by taking on. the indirect side of the refractory is placed by indirect resistance heating means which are surrounded by insulation on the outside.

However, direct heating by means of electrodes immersed in a glass bath is characterized by the disadvantage that the energy delivered concentrates on the electrode tips, where the glass is heated more intensively and thermal irregularities can occur. In addition, the electrodes are either of a reducing (molybdenum) or oxidizing (tin oxide) material, so that undesirable impurities can occur. . In addition, during intensive heating with individual electrodes, bubbles may form in the area of contact between the glass and the electrode.

Indirect heating by resistive wires outside the refractory material trough has also not proven useful, since the cross-sections of these resistive wires must be relatively small in order to allow the wires to absorb sufficient energy, while at the required continuous temperatures from. approximately 1300 ° C ', in part, leads to premature destruction of the wires as a result. their small diameters.

Heating with radiant heaters has also not been proven, since much of the energy is reflected on the surface and the surface heats up most intensively, which can also cause temperature irregularities.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for heating flowing glass in channels, dispensers and dispensing heads, and a device for carrying out such a process, wherein high temperature variations in flowing glass are avoided. in the case of resistance heating, and where the formation of dirt and gases in the glass and sunburn is prevented.

SUMMARY OF THE INVENTION The present invention relates to an apparatus for indirect heating of ducts. dispensers and dispensing heads for glass conduction formed of a refractory ceramic material conductive at operating temperature, comprising transformers and current feeds to channels, dispensers, and dispensing heads for conduction glass, which according to the invention further comprises at least two flat, electrically connected electrodes that externally adhere to the refractory ceramic - electroconductive material - at the operating temperature.

For ease of control of the individual heating current circuits, the secondary side of the isolation and / or reduction transformer for supplying each of the independent power supply circuits can be divided into at least two electrically isolated coils into the flat electrodes. An overcurrent relay or fuse for tripping the current circuit when a certain power is reached can be placed in each heating current circuit.

When using the device according to the invention, it is advantageous to form a dispenser or dispensing channel for guiding the glass as a tube, which is up to its peak discharged, with the flat electrodes being designed as band-shaped electrodes surrounding the tube material. current. it always passes, from one to the next, the next electrode. The electrode strips may be formed such that at least one of their ends is bent so that it can protrude out of the insulation and is connectable to the power supply.

The flat electrodes are preferably supported by pressure resilient means for pressing them against the refractory material.

By using the invention, the known and mentioned drawbacks of the dispenser heating methods are eliminated and the invention, by using a completely new technical principle of dispenser heating device, is not susceptible to malfunctions, which allows the glass to be guided with hitherto uneven temperature variations, which, moreover, makes it possible, without difficulty, to adapt to different types of glass and to adapt the temperature to different processing conditions.

The invention is explained in more detail below with reference to the accompanying drawings. In these drawings it indicates:

FIG. 1 is a schematic cross-sectional view of the dispenser provided in accordance with the invention; FIG. 2 is a schematic cross-section similar to FIG. 1 but with three electrodes; as in Figs. 1 and 2, but with - five. electrodes and transformer with, two secondary. Fig. 4a is a schematic top view of a dispensing channel with a dispensing head in accordance with the method of the invention; Fig. 4b a vertical section through the assembly of Fig. 4a; Fig. 5a a schematic top view; and FIG. 6 is a temperature-dependence of electrical resistance for typical refractory materials.

The principle of the device according to the invention is based on the fact that the refractory material, especially if it is a glass-phase material cast in a molten liquid state, is conductive at high temperatures. The device is therefore suitable for glass channels, dispensers and dispensing heads in which this condition is met. Such a material is known, for example, by the trade names Zac (curves (Ta B), Jargal (curve A in Fig. 4), etc. In the latter the structure consists of very small crystals of aluminum compounds with alpha modification (corundum) , and with beta modification (11 Al2O3, NaO) The spaces between the individual crystals are filled with a glassy phase, but the proportion of the glassy phase is very small.

Therefore, the resistance of the refractory material to be taken into account is the consideration of the temperatures in the ducts - the conductivity of the glass is approximately five times as high as that of normal soda-lime glass. In conventional feed channels (about 15 centimeters), it is possible to allow the current to flow through the refractory material in conventional feed channels. to heat this material. Voltage lies between 200 and 300 volts which assume electrical insulation of the parts of the conducting voltages to protect the operating personnel.

The temperature to be considered for the refractory is at least 900 ° C - and the trough leading - the glass must therefore be insulated - in order to - create a temperature difference between the outer and inner surface of the wall, which is as small as possible the temperature is maintained above 900 ° C.

Electrodes are placed between the insulation 14 and the refractory material 1 to the outer surface of the refractory material 1 of the metering trough, adapted to the purpose, or the corresponding channel or dosing head, between the insulation 14 and the refractory material 1.

2. These electrodes 2 consist of a material resistant to high temperatures, for example of the known resistance heating material "Aluchrom". or. other high-alloy steels, such as high-alloy steels containing nickel, chromium or molybdenum. It is expedient to make the insulation of known materials movable at the location of the electrodes -2 and can be pressed against the electrodes 2 by the pressure resilient means 4, in this case coil springs, so that these electrodes are themselves pressed against the refractory material 1 and electrodes 2 - good electrical contact is ensured.

If the electrodes 2 are located below the refractory material 1, the contact pressure of the weight of the refractory material or the glass guide channel is sufficient to ensure a sufficiently good contact.

The electrodes 2 are expediently designed in the form of a longitudinal strip, one end of which 3 passes through the insulation 14 and serves as a contact strip to which the power supply 5 can be connected.

For uniform heating of, for example, the dispenser, it is necessary that the electrodes 2 are arranged according to the shape of the dispenser so that as much as possible more uniform heating can occur.

The temperature of the trough is the lowest. It is therefore expedient to locate - especially - a large number of electrodes in these places, or 2. - set-up - the corresponding - required - amount of current .. -With this in mind - one hundred,. . that ... the current - chooses - the path - - the smallest - the - resistance - according to the - known - physical - laws ice blankets over the - particularly .heated - spots - - or - along the - shortest - paths · -r it is necessary to take into account that in this material the resistance decreases with increasing temperature. • According to □ Ьг. 1 to 3, electrodes 2 with their bent ends 3, which are, are enclosed in the above-mentioned dosing channel near the bottom of the channel. The compression 14 prevents the heat loss and ensures that the temperature of the refractory material 1 is set to the correct level.

The predicted main -pro.ud_ov.ou - path is indicated by lines 1S. Since the resistance of the glass is, as mentioned, substantially less than the resistance of the refractory material, some of the current will pass through the glass melt itself.

The electrodes 2 are arranged mainly in the lower part of the trough to heat up the lower part, or because the temperature is self-aligning from below, but not from above, but not from above. -down.

The essential advantage of the foaming according to the invention is that the heating plates can be purposefully applied so that each part of the duct can be heated as it is. - results from drawings. The energy density or the energy flow in the refractory material in relation to the volume unit are kept at a very low level, since the surfaces covered by the electrodes 2 can be chosen at will. With -sufficient insulation, the tray temperature can be set at any height, or any -distribution-temperature can be set, so that in-. dispenser, dispenser - head or other channel - for - guiding the glass - can be forced to a large extent - ensuring - uniform distribution - of temperature.

According to FIG. 4, a plurality of electrodes 2 can be arranged side by side along the entire length of the metering channel, the current always passing across the metering channel. In the dispensing head itself, a circular electrode 11 is disposed below the outlet 10 and is connected to the electrodes 2 arranged around the dispensing head. Thus, it is very easy to adequately heat the otherwise coldest point of the dispenser, namely the underside of the dispensing head, thus avoiding temperature variations in the effluent glass resulting from its cooling in the outlet.

According to the invention, it is expedient to separate the heating of the metering head or metering head in a number of different bands which are independently supplied with electricity in separate current circuits from galvanically separated secondary coils. It is also expedient to maintain the resistance of the two parallel connections at approximately the same level, or to match the resistance of the corresponding, parallel-heating heating currents of the auxiliary circuits. -30. For this purpose, the secondary side of the isolation or control transformer 20 may consist of a series of coils which are excited by a common It has a coil of 8, and is marked as indicated. - arrows 7 - possible - individual regulation of individual secondary - circuits.

The resolution of such separating and regulating transformers 20 is known to those skilled in the art and therefore need not be described in detail.

Each heating current circuit 30 includes a fuse 9, or a corresponding overcurrent relay, which, when a higher heating power is reached, than the one at which the switch is determined, switches the circuit off. - Avoid - so - - overloading of individual circuits - and reaching-too-high temperatures.

However, the heating device is in a series of mutually independent heating circuits 30 and the use of fuses 9 is also necessary because, due to the never-incurable possibility of cracking, the refractory material can be a single path of the current influenced by the ingress of glass into the formed clay.

When glass penetrates into such a crack, the resistance in this place is substantially reduced. This causes a concentration of energy in the crack, resulting in crack expansion, and the heating circuit must therefore be protected from the risk of such a failure. This allows - the - described - distribution to several heating circuits as described above. which - are individually secured.

Z .obr. 1 through 3, the connection of the individual heating circuits can be seen, and according to FIG. 1 are - two opposing - electrodes 2 - provided by - leads 5 through - - fuse - -9 - from the secondary coil, according to - FIG. 2 is - from the secondary coil 6-current leads -5 and through-fuse Fig. 9 supplies - also - the middle electrode - which is - connected - together with two mutually opposed - and interconnected - electrodes -2 -a according to Fig. -3 supplies the transformer with two secondary coils by means of the above lines - total five electrodes. In this case, the middle electrode is also connected with the two outer opposing electrodes and the two electrodes located to the left and right of the middle electrode are supplied from the second secondary coil.

According to FIG. 4, a plurality of flow circuits can be arranged one after the other in the flow direction of the outgoing glass, each flowing across the refractory material as well as the glass strip, with four secondary coils being actuated each time . However, each circuit contains of course - also in this case, where. This is not shown in the drawing, conventional fuses 9. The first four-circuit heating section is followed by another corresponding section and the dosing head heating device is connected to the annular electrode 11 described above. In this case, the circuit is arranged such that from the electrode 2a to the electrode 2b, from which current can again flow not only to the electrode 2a but also to the other side adjacent to the electrode 2c and to the circular electrode 11.

Again, current from the electrode 2c can pass to the central electrode 2d. Further details are apparent to those skilled in the art from FIGS. 4a and 4b.

According to a further embodiment of the invention, according to FIG. 5, the dispensing channel can also be designed in the form of a tube, the glass level reaching to the top of the tube and the formation of a glass cushion is avoided; In this case, the electrodes 12 are band-shaped and the current flows from one electrode 12 to two adjacent electrodes in each case if the band electrode 12 does not lie at the end of the heated section so that only one-sided current flow can occur.

Here, too, each heating circuit 30 is separately protected to prevent disadvantageous local overheating. The band electrodes 12 are formed of the same high temperature resistant material as described above; and it is also advantageous to divide them where there is a gap 13 in the refractory material. Instead of splitting it is bridged by a conductive connector, thereby preventing the glass possibly present in the gap from undesirably creating a separate flow path and thus disadvantages. resulting from cracking, as described above.

From the foregoing, it is clear that the solution according to the invention provides a completely new and advantageous way of heating all kinds of ducts, tubes and similar glass guiding devices.

Claims (6)

1. Apparatus for indirectly heating glass channels, dispensers and dispensing heads, made of a refractory ceramic material, conductive at operating temperature, comprising transformers and current leads to glass channels, dispensers and dispensing heads, characterized in that it comprises at least two flat electrically connected electrodes (2) externally adjacent to a refractory ceramic material [1], conductive at operating temperature. Device according to claim 1, characterized in that the secondary side of the isolation and / or control transformer (20) for supplying each independent current circuit for supplying electrical energy to the flat electrodes (2) is divided into at least two galvanically separated coils (6). Device according to Claims 1 and 2, characterized in that in each heating current circuit (30) there is an overcurrent relay or fuse (9) for switching off the current circuit when a certain power is reached. Device according to one of Claims 1 to 3, characterized in that the gob dispenser or dispensing channel is designed as a tube (16) which can be filled with glass to its top, the flat electrodes (2) being designed as ribbon electrodes (12) encircling the material (1) of the tube (16), the current always passing from one to the next nearest electrode (12). , Device according to Claims 1 to 4, characterized in that the flat electrodes (2) are designed as ribbon electrodes (12) and at least one end (3) is bent so that it can protrude out of the insulation (14) and is connectable to the power supply (5). Device according to one of Claims 1 to 5, characterized in that pressure resilient means (4) for pressing the electrodes against the refractory material (1) are supported on the flat electrodes (2).