A nozzle tip for producing glass fibers has a pair of long-side walls and a pair of short-side walls, each of the long-side walls and the short-side walls containing platinum or a platinum alloy, and a nozzle orifice for discharging the glass melt, the nozzle orifice being formed by the long-side walls and the short-side walls. The nozzle orifice has a flat hole shape in horizontal cross-section. Each of the long-side walls has a cut-out on a discharge side of the glass melt, a width of the cut-out being 10-55% of a length of a longitudinal center axis of the flat hole shape of the nozzle orifice. The pair of long-side walls has a symmetrical shape about the center axis of the nozzle orifice. This nozzle tip makes it possible to efficiently produce glass fibers having a desired cross-sectional shape.

A bushing for producing glass fibers, including: a plurality of nozzles made of platinum or the like to discharge molten glass; and a base plate made of platinum or the like. A coating layer is preferentially formed on an outer circumferential face in a tip part on the side of glass discharge of the nozzle, and a width of the coating layer is 5% or more and 95% or less with respect to the entire length of the nozzle. The base plate includes a non-coating area. Areas of the nozzles and the base plate not provided with the coating layer act as a sacrificial metal for protecting the nozzle tip parts. In consideration of the sacrificial metal, a coverage rate P of the coating layer in the nozzle tip parts calculated e with a prescribed equation is preferably 5% or more and 350% or less.

A bushing for producing glass fibers, including: a plurality of nozzles made of platinum or the like to discharge molten glass; and a base plate made of platinum or the like. A coating layer is preferentially formed on an outer circumferential face in a tip part on the side of glass discharge of the nozzle, and a width of the coating layer is 5% or more and 95% or less with respect to the entire length of the nozzle. The base plate includes a non-coating area. Areas of the nozzles and the base plate not provided with the coating layer act as a sacrificial metal for protecting the nozzle tip parts. In consideration of the sacrificial metal, a coverage rate P of the coating layer in the nozzle tip parts calculated e with a prescribed equation is preferably 5% or more and 350% or less.

A method for producing glass fiber nozzles, comprising the steps of: A) providing or producing a base plate comprising a first material, being chemically resistant to the glass melt and dispersion strengthened, B) printing at least one tube made of a second material being chemically resistant to the glass melt onto one side of the base plate, wherein the at least one tube each comprise at least one feedthrough, C) generating at least one passage in the base plate, the passage is connected to at least one of the at least one feedthrough in such a way that each of the at least one passage through the base plate forms a common line permeable to the glass melt, with at least one of the at least one feedthrough of an associated tube leads through the base plate and through the associated tube.

A method for producing glass fiber nozzles, comprising the steps of: A) providing or producing a base plate comprising a first material, being chemically resistant to the glass melt and dispersion strengthened, B) printing at least one tube made of a second material being chemically resistant to the glass melt onto one side of the base plate, wherein the at least one tube each comprise at least one feedthrough, C) generating at least one passage in the base plate, the passage is connected to at least one of the at least one feedthrough in such a way that each of the at least one passage through the base plate forms a common line permeable to the glass melt, with at least one of the at least one feedthrough of an associated tube leads through the base plate and through the associated tube.

The present invention is directed to an inductively heated bushing box and fiber formation method for an igneous rock melting furnace. The bushing box includes side walls with a water cooling system surrounded by one or more induction coils for maintaining and even temperature distribution of melted charge before the melt is extruded through tips of a bushing plate. The bushing plate is offset from the bottom of the one or more induction coils to avoid end effects and better ensure consistent eddy current formation. By increasing the uniformity of temperature distribution over a larger surface area, the system allows for a greater number of tips per bushing plate, and therefore provides for greater efficiency.

The present invention is directed to an inductively heated bushing box and fiber formation method for an igneous rock melting furnace. The bushing box includes side walls with a water cooling system surrounded by one or more induction coils for maintaining and even temperature distribution of melted charge before the melt is extruded through tips of a bushing plate. The bushing plate is offset from the bottom of the one or more induction coils to avoid end effects and better ensure consistent eddy current formation. By increasing the uniformity of temperature distribution over a larger surface area, the system allows for a greater number of tips per bushing plate, and therefore provides for greater efficiency.

A glass fiber according to the present invention is suitable for preventing filament breakage and suitable for being stably produced for a long term, and has a ?-OH value of 0.02 mm.sup.?1 or more and less than 0.55 mm.sup.?1. The preferred content of SO.sub.3 is more than 0 ppm and 70 ppm or less on a mass basis. The glass fiber is preferably substantially free of As and Sb. SO.sub.3 can be supplied to a glass raw material as, for example, a sulfuric acid salt of an alkali metal or an alkaline-earth metal.

A bushing for producing glass fibers, including: a plurality of nozzles made of platinum or the like to discharge molten glass; and a base plate made of platinum or the like. A coating layer is preferentially formed on an outer circumferential face on a tip part on the side of glass discharge of the nozzle, and a width of the coating layer is 5% or more and 95% or less with respect to the entire length of the nozzle. The base plate includes a non-coating area. Areas of the nozzles and the base plate not provided with the coating layer act as a sacrificial metal for protecting the nozzle tip parts. In consideration of the sacrificial metal, a coverage rate P of the coating layer on the nozzle tip parts calculated with a prescribed equation is preferably 5% or more and 350% or less.

A bushing for producing glass fibers, including: a plurality of nozzles made of platinum or the like to discharge molten glass; and a base plate made of platinum or the like. A coating layer is preferentially formed on an outer circumferential face on a tip part on the side of glass discharge of the nozzle, and a width of the coating layer is 5% or more and 95% or less with respect to the entire length of the nozzle. The base plate includes a non-coating area. Areas of the nozzles and the base plate not provided with the coating layer act as a sacrificial metal for protecting the nozzle tip parts. In consideration of the sacrificial metal, a coverage rate P of the coating layer on the nozzle tip parts calculated with a prescribed equation is preferably 5% or more and 350% or less.