Abstract: The inner arc tube of some jacketed discharge lamps transmits ultraviolet radiation which is normally intercepted by the glass outer envelope. To prevent harmful release of such radiation in the event the outer envelope should be shattered, a mechanical disconnect is provided in the interenvelope space comprising separable conductors which are part of the arc tube supporting frame and which are maintained in engagement by the outer envelope. Upon fracture of the outer envelope, spring pressure forces the conductors apart whereupon the circuit is opened and the arc tube is disabled.

Abstract: The inner arc tube of some jacketed discharge lamps transmits ultraviolet radiation which is normally absorbed without harm by the glass outer envelope but may be released should the outer envelope be broken off. This is prevented by a fuse heater and shunting thermal switch connected in series with the arc tube and located within the outer envelope. Should the outer envelope be broken, air cools the switch so that it opens. Current flow through the heater now raises its temperature and causes it to oxidize, thereby opening the circuit and disabling the lamp.

Abstract: A high pressure sodium vapor lamp utilizing an alumina ceramic arc tube within an outer glass envelope is provided with a bi-metal switch which short circuits the arc tube at starting. Current flow through the switch causes it to heat up and open the short circuit, producing a voltage pulse which starts the lamp. The bi-metal is fastened to a pin conductor extending from the metal exhaust tube of the arc tube to the frame. The pin conductor, which receives heat by conduction from the exhaust tube and is also heated by lamp current flow, transmits sufficient heat to the bi-metal to maintain it deflected during normal operation.