||In 1999 Osram set a new standard in mains voltage halogen with its HaloPin capsule which launched the G9 lamp format. It presents an extremely compact alternative to ordinary GLS incandescent lamps, offering the features of halogen capsules but without the difficulty of low voltage transformers. Although compact single ended mains halogen capsules existed previously, few were available below about 75W rating. Additionally they had to be operated in enclosed fixtures owing to the potential end of life explosion risk.
The Osram Halopin lamp is filled to low gas pressure to avoid the explosion hazard, and also incorporates a unique safety fuse to quickly shut down the lamp if arcing should develop following filament failure. The high current during arcing is sufficient to cause heating of the thin foils in the seal, and may cause the quartz to shatter near the welds.
Osram circumvented this problem by eliminating the traditional quartz bridge arrangement that is used to hold a set of support wires for the filament. The wires from the bridge were previously welded to the molybdenum foils, but their large diameter meant that they could withstand heavy arcing currents for some time, with destructive results.
In its Halopin lamps, Osram supports the filaments with small dimples in the bulb, completely eliminating the need for any additional support structure. Consequently the thin single-coiled filament tails can be brought right through the pinch and welded directly to the foils. Should arcing develop, the delicate filament tails act as fuses and are promptly evaporated, thus breaking the circuit and stopping the arcing within about 0.7 milliseconds, with 100% reliability.