Narva Infrared Linear Double Ended

During the later 1950s there was a drive towards increased power densities from infrared lamps, primarily from the automotive industry which demanded shorter paint drying times. There was also a desire for better uniformity of irradiation. This lamp was one of the more novel departures from established practices to meet those requirements. Narva took the innovative step of shifting from single ended GLS and blown reflector lamps to this linear design, presumably allowing closer packing of lamps for higher radiation levels along with greater uniformity.

The filament is a single coil supported by molybdenum wires, themselves mounted in a hard glass rod that runs axially along the lamp. The supports are staggered to give the filament a zig-zag shape. Not only would this design take up the considerable thermal expansion of the filament when heated to prevent sagging of the coil, it possibly also allows the lamp to be operated in any burning position. The filament does not run centrally along the tube axis but is offset - this feature which brings the filament closer to the glass bulb was perhaps intended to reduce the distance from the filament to a reflector and allow greater efficiency and precision in the beam of infrared radiation.

The end caps are simple deep-drawn brass pressings, having a parallel-sided end of approx 8mm diameter, enlarged via a conical section and then cemented to the glass bulb in the usual fashion. These lamps appear not to have been a commercial success, and were probably supserseded very quickly by linear quartz types once the technology for the manufacture of those types had arrived in the former Eastern German markets dominated by Narva.
Manufacturer: Narva
Lamp Power: 500 Watts
Lamp Voltage: 220 Volts
Lamp Current: 2.27 Amperes
Cap Type: S8 Brass
Bulb Type: TD-51 TD-16 in eighths/inch
Bulb Finish: Clear Borosilicate glass
Filament Type: C-8Z Coiled Axial zig-zag
Atmosphere: Nitrogen Red P getter
Luminous Flux: 1950 lumens
Luminous Efficacy: 3.9 lm/W
Luminous Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2250K Ra 100
Chromaticity Co-ordinates: CCx: 0.498 CCy: 0.413
Lifetime: >5000 hours
Burning Position: Universal
Overall Length: 360mm 143/16 Inches
Light Centre Length: N/A
Factory: Berlin? Germany
Date of Manufacture: 1957 November? Date Code: L7
Original Value:
References: 1) Photoelectric measurement.