Abstract: A high intensity discharge lamp having an inner tube in which a discharge takes place to produce visible light and ultraviolet radiation and an outer envelope which blocks harmful ultraviolet radiation. A mechanical switching element is provided to extinguish the discharge when the outer envelope is broken.

Abstract: A high intensity discharge lamp having an inner tube in which a discharge takes place to produce visible light and ultraviolet radiation and an outer envelope which blocks harmful ultraviolet radiation. An oxidizable element of a refractory metal is provided in the voltage supply to the arc tube internally of the outer envelope which element oxidizes when the outer envelope is broken and burns through to remove the voltage from the arc tube and to extinguish the arc.

Abstract: A high intensity discharge lamp having an inner tube in which a discharge takes place to produce visible light and ultraviolet radiation and an outer envelope which blocks harmful ultraviolet radiation. An element is provided to extinguish the discharge when the outer envelope is broken.

Abstract: Safety devices for high intensity discharge lamps, having an outer envelope and an inner arc tube in which the arc discharge is produced, for extinguishing the arc in a relatively short period of time. A switching element is placed in series with the current supply to the arc tube and the element opens when the outer envelope is broken. In one embodiment, the switching element is a normally closed thermostatic switch in series with a second filament which is connected in parallel with a first filament. During starting the switching element is closed and both of the filaments are in series with the arc tube and both receive a part of the high starting lamp current. The thermostatic switch opens when the lamp reaches operating temperature so that all of the current passes through the first filament if the envelope breaks causing the first filament to burn out. The switch then closes so that all of the current passes through the second filament causing it to burn out.