Patent ID: 8250884

Claim:
A method of forming fibers from molten mineral material, the method comprising the steps of: rotating a spinner, the spinner having an orificed peripheral wall, the orificed peripheral wall having a top row of orifices; introducing molten mineral material to the spinner to create a fan of primary glass fibers; creating an annular combustion flow of heated gas with an annular burner and directing the annular combustion flow of heated gas substantially through the primary fibers, the annular burner having an exit and apertures, wherein the annular burner exit is positioned above the top row of orifices by a distance in a range of from about 1.40 inches (35.6 mm) to about 1.60 inches (40.6 mm) and the annular blower apertures are positioned a distance from the top row of orifices of about 0.160 inches (4.1 mm); positioning a bottom center casing between the annular burner and the spinner such that a top surface of the bottom center casing is below a bottom of the annular burner and a bottom surface of the bottom center casing is above a top of the spinner, wherein the bottom center casing has a thickness of about 1.2 inches (30.5 mm); creating an annular flow of induced air in a passage positioned between the annular burner and an annular blower; directing the annular combustion flow of heated gas and the annular flow of induced air so that they are radially spaced apart at the level of the top row of orifices; and directing the annular combustion flow of heated gas and the annular flow of induced air so that they are brought together at a position below the top row of orifices.