Abstract: A glass composition comprising 54-60% by weight of SiO.sub.2, 13-16% by weight of ZrO.sub.2, 12-15% by weight of Na.sub.2 O, 5.5-14% by weight of MnO and 0-7% by weight of CaO, in which MnO+CaO is 11% by weight or more and MnO.gtoreq.CaO, can produce alkali resistant glass fibers which can be used for reinforcing cement products.

Abstract: Disclosed is a bushing for spinning glass fibers having at its bottom an orifice plate provided with a great number of extremely densely disposed plain holes constituting orifices. In order to stiffen the orifice plate, beam members are provided in the bushing to extend substantially in parallel with and spaced from the orifice plate. Each beam member is fixed at its both ends to confronting walls of the bushing, and is connected to the orifice plate by means of rod members having a small diameter.

Abstract: The orifice plate 2 in the bottom of a bushing 1 is uniformly inwardly curved in a concave manner, whereby its resistance to outward deformation or sagging under the weight of molten glass in the bushing and the tension of glass filaments 5 withdrawn therethrough is greatly increased. The plate may be rectangular or circular, i.e. arch-shaped or domed, and may be further strengthened by reinforcing bars 7 secured to the interior side walls of the bushing and to the crown portion of the plate.

Abstract: In an apparatus for producing glass fibers wherein an orifice plate formed with a greater number of orifice holes in high density is provided to draw glass fibers therethrough and air nozzle means is provided for impinging air flow against the undersurface of the orifice plate so that the adjacent cones of molten glass formed on the undersurface of the orifice plate may be prevented from coalescing to each other, an air nozzle assembly is provided which includes a plurality of tubular nozzles arranged in such a way that their discharge ports may be arranged in line and in parallel with the longitudinal direction of the array of orifice holes in the orifice plate and spaced apart from each other by a predetermined distance.

Abstract: An alloy for a nozzle plate for spinning glass fibers which contains between 82 and 92 percent by weight platinum, between 3 and 10 percent by weight gold, and between 3 and 12 percent by weight palladium. This alloy displays an excellent resistance to wetting by molten glass, a superior machinability, and a superior durability.

Abstract: A method of detecting breakages of glass fiber filaments being drawn through orifies of an orifice plate by converting the variation in intensity of radiant light or heat emitted from a bead of molten glass which grows on the undersurface of the orifices plate at an orifice at which a breakage occurs into an electrical signal by a radiation thermometer which is so arranged as to reciprocate horizontally in parallel with both one side and said undersurface of said orifice plate, whereby the breakage may be detected.

Abstract: Disclosed is an orifice plate for use in glass-fiber spinning having a number of densely arranged orifices. Each orifice has a larger diameter at the inlet side thereof facing the molten glass and a smaller diameter at the outlet side thereof facing the ambient air. The ratio of the larger diameter to the smaller diameter is so selected to fall within a range between 1 : 0.4 and 1 : 0.9. The reduced diameter of the orifices at their outlet side provides sufficiently large space between adjacent orifices at their outlet sides, in spite of the high density at which the orifices are arranged, so that the joining of glass cones suspended from respective orifices is conveniently avoided even after the brims of the orifices are ground by the viscous cooled molten glass.

Abstract: Disclosed is an orifice plate for use in a bushing for spinning glass fibers having a number of orifices each of which consists of two cascaded coaxial cylindrical bores of different diameters, one of which opens in the upper surface of the orifice plate to constitute a molten-glass inlet-side bore, while the other opens in the lower surface of the orifice plate to constitute a molten-glass outlet-side bore.The orifices are so densely arranged as would allow joining of molten glass cones formed at adjacent orifices if a suitable countermeasure such as a cooling by air flow were not taken.

Abstract: In a process for spinning glass fibers continuously from a nozzle plate having 25- 200 orifices per cm.sup.2, a start-up operation is improved by using the nozzle plate made of a material having a contact angle of 60.degree. or more, drawing flooded molten glass which has spread over the whole undersurface of the nozzle plate at a greater speed than the flowing speed of the molten glass by its own weight from each orifice, while maintaining the normal spinning temperature, and finding the ends of the individual filaments.