GE Infrared Drying Bi-Post Lamp 500T40/3

Incandescent lamps have long been used as a convenient source of heat. Even in the 1890s manufacturers offered high power carbon lamps for domestic radiators. However it it was not until the late 1930s that filament lamps suddenly gained popularity for industrial heating, following the pioneering work of Ford with standard incandescent lamps to accelerate paint drying in its automobile production.

GE was quick to recognise this new application, and during WW2 introduced the first industrial infrared lamp. It was rated 250W in a G-30 bulb, with an under-run tungsten filament to maximise the proportion of infrared energy and shift its radiation to more useful longer wavelengths. More powerful 375W and 500W versions soon followed, as well as a smaller 125W rating to provide a slower ramp-up in temperature for conveyor-belt applications.

The growth of the automotive industry fuelled a desire for more powerful lamps, but a common problem even up to 375W was degradation of the capping cement at the high ambient tempeatures of the ovens. During the early 1940s GE therefore introduced 500W and 1000W designs with glass Bi-Post bases. The filament has a unique triangular shape - this proving more efficient when used in conjunction with an external reflector to deliver beams of both high irradiance and high uniformity. The original lamps had a G-40 bulb and 3.5" LCL. The bulbs were later adjusted to the T-40 shape featured here, allowing the reflector to be brought closer to the filament for higher performance, and the LCL was later shortened to 3.0625" to provide still higher performance. This 500W rating was discontinued in 1953-54, but the 1000W remained listed until 1973-74.

Manufacturer:	General Electric U.S.A.
Lamp Power:	500 Watts
Lamp Voltage:	115 Volts
Lamp Current:	4.35 Amperes
Cap Type:	G22 Medium Bipost	Glass
Bulb Type:	T-125	T-40 in eighths/inch
Bulb Finish:	Clear	Borosilicate glass
Filament Type:	Triangular	Single Coil
Atmosphere:	Nitrogen	Red P getter
Luminous Flux:	3,375 lumens
Luminous Efficacy:	6.75 lm/W
Colour Temperature:	CCT: 2450K
Colour Rendering:	Ra 100
Chromaticity Co-ordinates:	CCx: 0.480	CCy: 0.411
Lifetime:	5000 hours min.
Burning Position:	Universal
Overall Length:	184 mm	7¹/₄ inches
Light Centre Length:	77.8 mm	3¹/₁₆ inches
Factory:	Mattoon, IL	U.S.A.
Date of Manufacture:	1950 December	Date Code: H36
Original Value:	US $5.50 (1948)


References:	1) GE Large Lamp Catalogue, 1948, USA, p.28.
	2) GE Large Lamp Catalogue, 1953, USA, p.58.
	3) Industrial Electric Lamps and Lighting, E.S.Lincoln, publ. Essential Books, 1945, p.21, pp.49-51 - including illustration of G40 Bipost lamps.
	4) US Patent 2,288,499 - Electric Lamp having Triangular Filament - Irving van Horn - General Electric USA - Filed 2nd November 1940.