Stem with molded back-fill gas directional diffuser

摘要

A lamp stem having integral glass structure for controlling gas flow into the lamp outer envelope of an electric lamp during back-fill. The lamp stem having a protrusion adjacent the stem press through which a conduit connected to the exhaust tube extends with a curved profile. The end portion of the conduit extends in the direction of the stem skirt and defines an acute angle with the exhaust tube. The end portion is angled for directing the gas flow during back-fill away from coated portions of the lamp envelope in which the stem is sealed. The conduit may have a cross-sectional area which increases in the direction of the gas flow so that the conduit functions as a gas diffuser for reducing the velocity of the gas in addition to directing the gas flow in a desired direction. In an alternative embodiment, the conduit terminates adjacent the stem press. A glass portion integral with the stem extends over the conduit opening and has a concave surface facing the opening for deflecting the gas flow during back-fill away from portions of a lamp envelope having a coating.