Abstract: Fluorescent tube type discharge lamp has end sealed in base with terminal pins connected to lead wires passing through stem press and supporting an electrode in the form of a coil having an emitter. Bimetal strip has a first end welded to one of the leads and a second end proximate to a thin walled portion of the stem. When electrode fails and an arc discharge operates directly off the leads, the bimetal strip heats up so that second end contacts thin walled portion and arcs through to admit air for passive failure of lamp.

Abstract: The present invention is directed to new electrode structures for use in fluorescent lamps in which a tungsten base structure is provided with electron emissive materials including one or more of barium titanate, barium zirconate, barium strontium zirconate, barium cerium oxide, barium tantalate, and barium strontium yittrium oxide. Amounts of MgO may be added to improve or change emitter properties. A composite electrode structure can be formed by way of coating a tungsten coil with a slurry of this material, or providing powdered mixtures of both the electron emissive material and tungsten material and sintering this powdered material into a high density composite electrode structure.

Abstract: A rapid start fluorescent lamp having an improved hot restarting time. The lamp includes the standard envelope and end cap through which electrical connection is made by conductive feedthroughs which extend through the lamp stem to the interior of the lamp. One of the feedthroughs is connected to the cathode, and the other is connected to the leads of a fuse element which is contained within an envelope to isolate the fusible element from the lamp environment. A thermally activated bimetallic element is disposed across the leads of the fuse. The other lead of the fusible element is connected to the other end of the cathode. When the bimetal element is cold, it will bridge the connection between the other feedthrough to the other end of the cathode to permit rapid starting. When the bimetal heats up, the connection of both ends of the cathode to the heating current is broken. The location of the bimetallic element within the lamp envelope but not in the fuse container permits it to open and close more rapidly.

Abstract: A conductive link maintains the electrode of a fluorescent lamp and a conductive electrode guard at the same electrical potential to reduce lamp power dissipation. The conductive link is a bimetal strip arranged for electrically connecting an electrode lead-in with the electrode guard or electrode guard support upon heating by the discharge arc during lamp operation.