Abstract: A vertical glass melting furnace of the type having an inlet for raw materials at the top thereof, an outlet for molten glass at the bottom thereof, and a tabular electric resistance heating element for melting which is immersed at some level in molten glass, has at least one opening, and covers almost entirely the cross-section of the furnace at that level, the vertical glass melting furnace comprising a stirrer which extends from above the furnace and passes through the batch layer and the tabular heating element so that the stirrer brings about forced circulation for homogenization of the molten glass which has passed through the tabular heating element and stays in the region below the tabular heating element.

Abstract: A plasma ashing apparatus has a vacuum treatment chamber for receiving therein a substrate coated with a resist film, a reactive gas introduction pipe equipped with a plasma applicator, a vacuum exhaust pipe, a heating means for heating the substrate, and two pieces of electrodes disposed in parallel to each other. One of the electrodes is a substrate electrode and the other thereof is a circular counter electrode. These two electrodes are commonly connected to an RF power source to thereby constitute a cathode electrode. Multiple concentric perforations are formed in the counter electrode except for a rib portion. A central perforation is formed in the center of the counter electrode. The concentric perforations are formed at every distance, from the center, equivalent to a diameter of the central perforation, while leaving circular electrode surfaces corresponding in width to a radius of of the perforation.

Abstract: In a melting furnace (1), toxic, volatile chemical compounds from introduced filter dust from industrial incineration units are vaporized at about 1300.degree. C. and forced to leave the reaction space. The non-vaporizing residue forms a glassy melt which is discharged continuously or intermittently from the reaction space. Heating of the melt and of the filter dust is affected by resistance heaters in protective ceramic sheaths (4) above the melt (2). In order to prevent corrosion of the resistance heater protection sheaths (4) by exit gases (7) especially in the flow lee thereof, the exit gases are forced, by partitions (10) and an exit gas extraction pipe (9) with an inlet orifice (16) at a low level, to flow below the resistance heater protection sheaths (4) to an exit gas outlet (5).

Abstract: Electrode blocks and multiple-piece assemblies are provided for electric, glass-melting furnaces to reduce the occurrence and extent of cracking which occurs in monolithic electrode blocks from thermal stresses induced by a high temperature gradient between such blocks or the block assembly and a fluid-cooled electrode and from thermal shock encountered in repositioning the electrode. An insert block of a high thermal stress and glass corrosion/erosion resistant refractory material is configured to receive an electrode assembly. A holder block, which may be of the same material or another material, including a material having less thermal stress strength or less glass corrosion/erosion resistance than the insert block material, has a passageway therethrough to receive at least part of the insert block with electrode assembly therethrough.

Abstract: A batch charger for feeding raw batch material to a glass making furnace of the type having a reciprocating charger plate positioned under a hopper chute. A pusher bar is supported substantially parallel to the front edge of the charger plate, and rams are connected to the pusher bar to move it from a position under the charger plate such that raw batch that has been delivered over the edge of the charger plate can be pushed further into the furnace.

Abstract: A melting apparatus in which a material to be melted is accommodated in a crucible made of platinum or its alloy, and electric current passes through the crucible to generate heat ot melt the material. At least a part of the crucible is formed into a double-wall structure having inner and outer peripheral walls. The electric current is caused to pass through the double-wall structure to generate the heat.

Abstract: The invention relates to a novel palladium-based alloy.This palladium-based alloy comprises tin in an amount, preferably of 5 to 20% by weight, which is sufficient to impart an acceptable resistance to corrosion by molten glass, preferably being essentially equivalent to that of platinum-rhodium 10% alloys.An alloy of this type can be used in the glass industry for making components which come into contact with molten glass, which preferably essentially contains no oxides less stable than tin oxide, such as lead oxide, because it has an excellent resistance to corrosion by molten glass and is much less expensive than the platinum-rhodium 10% alloy normally used. Moreover, by the addition of at least one element selected from platinum (0-50% by weight), rhodium (0-20% by weight), iridium (0-20% by weight) and ruthenium 0-20% by weight), the mechanical strength at high temperature, especially the creep strength, is significantly improved.

Abstract: An electric melting furnace for vitrifying waste, having a melting tank having walls of refractory bricks, the melting tank being provided at the upper portion thereof with a supply port for a glass additive and waste and at the bottom portion thereof with a discharge port for molten glass containing the waste; at least a pair of side electrodes horizontally provided on opposite side walls of the melting tank; and at least one central electrode having a polarity opposite to that of the side electrodes, the central electrode being horizontally positioned in the interior of the melting tank at substantially the middle portion between the side electrodes. By such melting furnace construction, as described above, the heating current selectively flows through between the side electrodes and the central electrode, and does not flow electrically conductive substances deposited on the furnace bottom.

Abstract: The invention relates to a novel palladium-based alloy.This palladium-based alloy comprises at least one additional element selected from indium, bismuth, silver and copper, in an amount sufficient to impart an acceptable resistance to corrosion by molten glass, preferably being essentially equivalent to that of platinum-rhodium 10% alloys.An alloy of this type can be used in the glass industry for making components which come into contact with molten glass, which preferably essentially contains no oxides less stable than the oxide of the additional element, such as lead oxide, because is has an excellent resistance to corrosion by molten glass and is less expensive than the platinum-rhodium 10% alloy normally used. Moreover, by the addition of at least one element selected from platinum (0-50% by weight), rhodium (0-20% by weight), iridium (0-20% by weight), ruthenium (0-20% by weight) and tin (0-20%), the mechanical strength at high temperature, especially the creep strength, is significantly improved.

Abstract: A method of melting materials at power densities in excess of 25 KW/ft.sup.2 of area within the metal shell of a melting vessel which method consists essentially of continuously feeding the material to be melted to a plasma arc furnace which is equipped with at least two transferred arc plasma electrodes and with means to rotate at least the portion of the furnace containing the material to be melted, melting the said feedstock material using the at least two transferred arc plasma electrodes whilst rotating at least the rotatable portion of the furnace containing the material to be melted and continuously discharging the material which has been melted from the furnace.Apparatus for melting materials under power densities of greater than 25 KW/ft.sup.2 is also disclosed.

Abstract: An apparatus and method which provides for controlled melting of both components of coal-ash, as well as the melting of selected additives, the melted coal-ash with additive being immediately available to a conventional fiberizing spinner stage. An arc furnace provides a shallow vat for molten pig iron. A first chute allows for introduction of coal-ash into the vat, and a second chute allows for the introduction of selected additives into the vat. The molten pig iron quickly melts any coal-ash and additive entering the vat, and the molten coal-ash/additive thereupon spreads out across the surface of the molten pig iron (the molten pig iron having a much higher specific gravity). In order to ensure that the molten coal-ash/additive has a predetermined fluidity at an adjacent spinner stage, the furnace is provided with a specially structured spout located above the spinner stage.

Abstract: A vertical glass melting furnace provided with a material entrance at the uppermost portion and a molten glass exit provided at the lowermost portion. A resistance heating element 6 is provided over the substantially entire part of the horizontal section of the furnace at at least one level which is immersed in the molten glass.

Abstract: A refractory product is shown in the form of a dense sintered alumina-chromia, zirconia-alumina-silica, zirconia-alumina body, or zirconia-chromia-alumina having less than about 8% of homogeneously distributed closed porosity formed by sintering an intimate interdispersion of fine particles of alumina-chromia, zirconia-alumina-silica, zirconia-alumina, or zirconia-chromia-alumina.

Abstract: An electrically heated forehearth for use in glass production is heated by means of a plurality of radiant heating elements, each element traversing the forehearth substantially at right angles to the direction of glass flow and each element comprising heating zones at each edge portion and a central, non-heating zone. With the forehearth according to the present invention the molten glass is heated electrically at its edge, cooler, portions only. The central and therefore hotter part of the molten glass under the non-heating zone of the element is unheated.

Abstract: A vessel for inductively heating molten material such as glass is provided with a ceramic refractory lining bound by the electrical coil. The coil may comprise a single turn sheath. In preferred embodiments the lining comprises an inner layer of melt-compatible refractory and an outer layer of thermal insulation.

Abstract: A method of manufacturing practically stria-free, bubble-free, and homogeneous quartz-glass plates of any desired configuration and with a surface area that exceeds the cross-section of the full circular quartz-glass cylinder that is employed as a starting material. The cylinder is continuously lowered into a furnace shell flooded with an inert gas, in which it is heated to a flowing temperature in the range of 1700.degree. to 1900.degree. C. until some of the quartz-glass flows off into a graphite crucible. The crucible is preferably clad with zirconium-oxide.

Abstract: Glass or the like is melted by liquefying batch materials in a first stage by means of radiant heating, and further advancing the melting process in a second stage where the melt is heated by induction heating. Another aspect of the invention provides a residence zone at the exit of the induction heating stage to aid elimination of gaseous inclusions.

Abstract: An induction furnace (60) for reflowing a portion of an optical preform (12) in order to draw a lightguide fiber (11) therefrom includes a tubular susceptor (80) which is disposed centrally within a beaker (75) and a sleeve (82) which is disposed concentrically about the susceptor. The sleeve is spaced from the susceptor and is surrounded by insulating grain (83). A high frequency coil (84) is energized to couple its electromagnetic field to the susceptor to heat and reflow a portion of the preform. The movement of contaminating particles of the insulating grain into the interior of the susceptor is prevented substantially by annular, felt-like discs (91, 105) at the bottom and top of the beaker. The discs collect particulates which move downwardly and upwardly and because of their compliant engagement with the beaker and with the sleeve, they provide seals at those interfaces.

Abstract: A device for continuously making elongated bodies, particularly rods of glass or optical fibers, includes a melting tube for containing molten material and surrounded by a cooling jacket. Within the cooling jacket exists a high frequency electromagnetic coil for heating and melting the starting material in the melting tube. A plurality of metal wires extending parallel to the axis of the melting tube and being grounded as well as a tube of insulating material are located between the wall of the melting tube and the coil. The melt traverses a heating zone and a refining zone so that a solid elongated body is withdrawn from the bottom of the melting tube.

Abstract: An arc glass-melting furnace comprising: a chamber adapted for holding a body of molten glass, such chamber including means for supplying batch material thereto and means for withdrawing molten glass therefrom; an arc electrode positioned in the chamber above the upper surface of the body of molten glass; a plurality of electrodes positioned in the bottom of the chamber; and power supply means having a first terminal connected to the arc electrode and a second terminal connected to the plurality of bottom electrodes.

Abstract: A method of and apparatus for controlling the position of an electrode in relation to the upper surface of a body of molten glass in an arc glass-melting furnace comprising providing an alternating current of constant effective magnitude to the electrode, sensing the effective voltage supplied to the electrode, determining if the sensed voltage is within a predetermined range of voltages, and modifying the position of the electrode if the sensed voltage is not within the predetermined range of voltages.

Abstract: Flat, transparent slabs of vitreous silica of optical quality are produced by melting granular starting material in a vacuum by means of an electrical heating system. The starting material is melted while sustaining a heat flow from the top to the bottom of the crucible. The bottom of the crucible is made permeable to gases. The heat isolation power of the crucible wall increases from the bottom to the top of the crucible.

Abstract: A device is provided for melting by direct induction substances which are dielectric when cold and whose temperatures of inductibility and melting are close to each other, such as glasses or vitreous enamels. This melting is carried out inside a receptacle whose sidewall comprises a multi-turn inductor made from metal tubing whose inward-looking faces are exposed and which combines the functions of heating the charge by induction and cooling the periphery thereof. Such a receptacle which is at the same time a heating inductor and a cooling surface is applicable more especially to industrial electric furnaces for the production of molten glass or enamel by direct induction.

Abstract: An optical fiber drawing furnace includes a graphite element of generally cylindrical shape with a reduced central cross-sectional configuration having a flange at opposite ends thereof and having an axial hole therethrough including a central internal element chamber for receiving a glass preform, means for water cooling the flanges, and means for applying electric power across the flanges to resistively heat the reduced cross-sectional configuration and, hence, the central internal element chamber so that an optical fiber can be drawn from the preform. The invention relates to prolonging the useful life of the graphite element by suitable methods and apparatus. The water used for cooling the flanges can be regulated to a temperature such as to avoid condensation of atmospheric moisture within the room (in which the furnace is located) upon the furnace. The application of electric power across the flanges can be increased and decreased at a gradual rate so as to avoid thermal shock to the graphite element.

Abstract: A substantially spherically-shaped electric melting furnace includes a carbon-lined crucible. The interior of said crucible is sealed from the atmosphere outside the crucible and a vacuum pump and venturi device control the atmosphere within the crucible by removing oxygen therefrom. A feeder lock allows material to be fed into the crucible without interfering with the atmospheric control of the crucible and a tap hole adjacent the lower portion of the crucible allows molten material to be removed. When used in the manufacture of mineral wool insulation, slag is fed into the crucible to be melted and the molten slag from the tap hole is delivered to a fiberizing device.

Abstract: A method of and apparatus for detecting the level of molten glass in a glass melting furnace comprising transmitting an electromagnetic wave towards the surface of the molten glass, detecting the electromagnetic wave reflected from the surface of the molten glass, determining the amount of time elapsed from the transmission of the electromagnetic wave to the detection of the reflected electromagnetic wave, and generating a signal responsive to the amount of elapsed time as an indication of the level of molten glass in the furnace.

Abstract: A heating system comprising one or more heaters capable of heating by radiation as well as convection incorporating nozzle means extending from an electrically heated gas glow pipe to direct the flow of hot gas providing said convection heating to a region where pressure flow and heat are desired.

Abstract: The invention provides a method and apparatus for the manufacture of glass film having a thickness not in excess of 0.003 inches and accomplished by drawing the film through a narrow slot-like orifice. The walls of the orifice are defined by an electrically conductive, hot glass resistant metal and electrical currents are introduced into the metal walls of the orifice to effectively maintain the central portions of the orifice walls at a higher temperature than each of the two lateral end walls of the orifice, thereby producing a temperature differential in the drawn film on the order of 40.degree. F. between the edges of the film and the central portions of the film.