Method of manufacturing a photoflash lamp having an indicator-insulator

Abstract

A photoflash lamp having an hermetically sealed envelope containing a pair of lead-in wires spaced apart by a glass bead and having a glass insulator sleeve located about one of the lead-in wires between the bead and the inner end of the wire. A moisture indicating material is coated on portions of the lead-in wires and the glass sleeve for indicating by a change in coloration the presence of air contamination within the envelope and for insulating the lead-in wires to prevent pre-ignition short circuits through filamentary combustible material located within the envelope. The indicating material comprises a mixture of cobaltous cobalticyanide and colloidal magnesium silicate, which composition tends to minimize pressure build up during flashing. The indicating material may be applied after sealing the ignition assembly into the glass tubing to be formed as the envelope by dipping a portion of the lead-in wires and glass insulator sleeve into a liquid preparation of the indicating material contained in a tube fitting through the open end of the glass envelope tubing.

Dependencies are inferred from the claim text.