GB2047228A

GB2047228A - Electrode for heating glass

Info

Publication number: GB2047228A
Application number: GB8009836A
Authority: GB
Original assignee: Bulten Kanthal AB
Current assignee: Bulten Kanthal AB
Priority date: 1979-03-23
Filing date: 1980-03-24
Publication date: 1980-11-26
Also published as: SE431443B; GB2047228B; SE7902653L; JPS6212177B2; DE3011045A1; JPS55162432A; FR2452226B1; FR2452226A1

Abstract

An electrode 10 for heating a glass mass by passing electric current through it comprises a rod shaped body which is adapted to be passed through the wall 20 of a feeder or the like. The inner end 11 of the electrode, which protrudes into the glass mass, consists of molybdenum whereas at least a part 12 of the outer electrode portion, which is subjected to very elevated temperatures in air when the inner end 11 is in the glass mass, consists of molybdenum disilicide, MoSi2. <IMAGE>

Description

SPECIFICATION Electrode This invention relates to electrodes, particularly for heating glass by passing electric current directly through the glass mass.

In the glass industry the heating of the glass in many cases is performed by passing electric current directly through the glass melt. The admission of the electric current takes place through electrodes that protrude into the glass melt through the walls of a so called feeder. Advantageously, molybdenum is used as electrode material.

A molybdenum electrode posesses the advantage that it does not lead to any visible pollution of the glass, although in operation it is slightly consumed.

However, one disadvantage with a molybdenum electrode is that it requires considerable and thus elaborate cooling at the passage through the walls of the feeder since the free surfaces of the electrode would otherwise be quickly destroyed by oxidation in air at the very elevated temperature employed.

An object of the present invention is to provide an electrode therein the above-mentioned disadvantage is avoided.

The invention provides an electrode for heating a glass mass, for example by passing electric current directly through the glass, comprising a rod shaped body adapted to be passed through the wall of a glass feeder or the like and to be connected to a current lead-in element at its outer end while its inner end protrudes into the glass mass, wherein the portion of the electrode which constitutes its inner end is composed of molybdenum, whereas at least part of the outer electrode portion, which is subjected to very elevated temperatures in air when the inner end is in the glass mass, is composed essentially of molybdenum disilicide, MoSi2.

In order that the invention may be clearly understood, preferred embodiments thereof will now be described by way of example only with reference to the accompanying drawing, in which: Figure 1 is an axial section of a first embodiment of electrode according to the invention; Figure 2 is a corresponding axial section of a second embodiment of electrode according to the invention.

In Figure 1 there is shown an electrode, generally denoted 10, whose inner end protrudes into a feeder, for instance, and consists of a rod 11 of molybdenum. The molybdenum rod 11 is rigidly secured to a tube 12 which consists essentially of molybdenum disilicide, MoSi2. Preferably, the tube 12 consists of the material which is commercially available under the registered Trade Mark "Kanthal"-Super. The Molybdenum rod 11 and the molybdenum disilicide tube 12 are firmly and intimately held together by means of a tightening screw, generally denoted 13, which is screwed into a threaded bore in the end of the molybdenum rod 11 and protrudes slightly outwardly of the outer end of the tube 12 where it is provided with a nut 14. Between the nut 14 and the end surface of the tube 12 there is disposed an assembly of belleville springs 15.The tightening screw, generally denoted 13, is shown as comprising an innermost portion 16 of molybdenum and an outermost portion 17 of steel. The space 18 between the outer surface of the screw 13 and the inner surface of the molybdenum disilicide tube 12 is sealed at the outer end by means of a suitable mass 19.

As shown in Figure 1, the outer end surface of the molybdenum rod 11 and the inner end surface of the molybdenum disilicide tube 12 are preferably machined into a conical configuration in order that the contact surfaces should present a contact resistance which is as low as possible.

The embodiment shown in Figure 2 corresponds in principle with the embodiment shown in Figure 1 but differs in that the outermost portion of the molybdenum disilicide tube 12 in Figure 1 has been replaced by a length of steel tube 1 2A. This is permissible at this outermost end because the temperature here does not normally rise to such high values that there is any appreciable risk of destruction of the electrode end by oxidation.

In operation, the electrode is passed through an opening in the feeder wall, generally denoted 20 and shown broken away, in such a manner that a small portion of the glass melt may flow partially into the wall, as is shown at 21 in Figure 1, whereby the glass only contacts molybdenum surfaces of the electrode.

Modifications and alterations as to details may be carried out within the scope of the invention as defined in the appended claims. Thus, to compensate for different heat expansion coefficients of molybdenum and molybdenum disilicide, it would be possible to manufacture screw 17 and tube portion 12A, respectively, of a material otherthan steel and having a still higher heat expansion coefficient.

1. An electrode for heating a glass mass, for example by passing electric current directly through the glass, comprising a rod shaped body adapted to be passed through the wall of a glass feeder or the like and to be connected to a current lead-in element at its outer end while its inner end protrudes into the glass mass, wherein the portion of the electrode which constitutes its inner end is composed of molybdenum, whereas at least part of the outer electrode portion, which is subjected to very elevated temperatures in air when the inner end is in the glass mass, is composed essentiaily of molybdenum disilicide, MoSi2.

2. An electrode as claimed in claim 1, wherein the said part of the outer electrode portion consists of a tube which is held in intimate end to end contact with the inner end of the electrode, which inner end is in the shape of a molybdenum rod, by means of a tightening screw which passes through the tube and is screwed into the molybdenum rod, a spring assembly and a tightening nut being provided at the outer end of the electrode.

3. An electrode as claimed in claim 2, wherein the tightening screw comprises an innermost portion of molybdenum and an outermost portion of steel.

4. An electrode as claimed in any one of claims 1 to 3, wherein the said part of the outer electrode

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrode This invention relates to electrodes, particularly for heating glass by passing electric current directly through the glass mass. In the glass industry the heating of the glass in many cases is performed by passing electric current directly through the glass melt. The admission of the electric current takes place through electrodes that protrude into the glass melt through the walls of a so called feeder. Advantageously, molybdenum is used as electrode material. A molybdenum electrode posesses the advantage that it does not lead to any visible pollution of the glass, although in operation it is slightly consumed. However, one disadvantage with a molybdenum electrode is that it requires considerable and thus elaborate cooling at the passage through the walls of the feeder since the free surfaces of the electrode would otherwise be quickly destroyed by oxidation in air at the very elevated temperature employed. An object of the present invention is to provide an electrode therein the above-mentioned disadvantage is avoided. The invention provides an electrode for heating a glass mass, for example by passing electric current directly through the glass, comprising a rod shaped body adapted to be passed through the wall of a glass feeder or the like and to be connected to a current lead-in element at its outer end while its inner end protrudes into the glass mass, wherein the portion of the electrode which constitutes its inner end is composed of molybdenum, whereas at least part of the outer electrode portion, which is subjected to very elevated temperatures in air when the inner end is in the glass mass, is composed essentially of molybdenum disilicide, MoSi2. In order that the invention may be clearly understood, preferred embodiments thereof will now be described by way of example only with reference to the accompanying drawing, in which: Figure 1 is an axial section of a first embodiment of electrode according to the invention; Figure 2 is a corresponding axial section of a second embodiment of electrode according to the invention. In Figure 1 there is shown an electrode, generally denoted 10, whose inner end protrudes into a feeder, for instance, and consists of a rod 11 of molybdenum. The molybdenum rod 11 is rigidly secured to a tube 12 which consists essentially of molybdenum disilicide, MoSi2. Preferably, the tube 12 consists of the material which is commercially available under the registered Trade Mark "Kanthal"-Super. The Molybdenum rod 11 and the molybdenum disilicide tube 12 are firmly and intimately held together by means of a tightening screw, generally denoted 13, which is screwed into a threaded bore in the end of the molybdenum rod 11 and protrudes slightly outwardly of the outer end of the tube 12 where it is provided with a nut 14. Between the nut 14 and the end surface of the tube 12 there is disposed an assembly of belleville springs 15.The tightening screw, generally denoted 13, is shown as comprising an innermost portion 16 of molybdenum and an outermost portion 17 of steel. The space 18 between the outer surface of the screw 13 and the inner surface of the molybdenum disilicide tube 12 is sealed at the outer end by means of a suitable mass 19. As shown in Figure 1, the outer end surface of the molybdenum rod 11 and the inner end surface of the molybdenum disilicide tube 12 are preferably machined into a conical configuration in order that the contact surfaces should present a contact resistance which is as low as possible. The embodiment shown in Figure 2 corresponds in principle with the embodiment shown in Figure 1 but differs in that the outermost portion of the molybdenum disilicide tube 12 in Figure 1 has been replaced by a length of steel tube 1 2A. This is permissible at this outermost end because the temperature here does not normally rise to such high values that there is any appreciable risk of destruction of the electrode end by oxidation. In operation, the electrode is passed through an opening in the feeder wall, generally denoted 20 and shown broken away, in such a manner that a small portion of the glass melt may flow partially into the wall, as is shown at 21 in Figure 1, whereby the glass only contacts molybdenum surfaces of the electrode. Modifications and alterations as to details may be carried out within the scope of the invention as defined in the appended claims. Thus, to compensate for different heat expansion coefficients of molybdenum and molybdenum disilicide, it would be possible to manufacture screw 17 and tube portion 12A, respectively, of a material otherthan steel and having a still higher heat expansion coefficient. CLAIMS

4. An electrode as claimed in any one of claims 1 to 3, wherein the said part of the outer electrode portion composed of molybdenum disilicide lies adjacent the molybdenum rod, while another part of the outer electrode portion is made of steel.

5. An electrode as claimed in claim 1, substantially as hereinbefore described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawing.