Thorn Compact Fluorescent 2D 16W

The famous '2D' compact fluorescent lamp was invented by John Chapman and Basil Antonis of Thorn Lighting in 1981, and set a global standard due to its highly innovative shape.

For many years the company had experimented with various concepts of tube bending, but serious commercial interest did not arise until the invention of the Philips 'SL' lamp. That permitted the first use of narrow-diameter tubes thanks to Philips' invention of the more thermally stable rare-earth aluminate phosphors. Whereas the SL lamp involved folding a tube in three 180° bends to form a 3-dimensional shape, which was fragile and required protection within an outer bulb that limited its efficacy, Thorn landed upon the idea of a tube having two 180° bends and two 90° bends to yield this novel flat format. The 2-pin plastic base adds rigidity while also housing a glowbottle starter and RF suppression capacitor, and a long glass exhaust tube whose cool spot limits mercury pressure to achieve high luminous efficacy.

The first version was this 16W product, whose high output enabled it to replace 75W GLS lamps while also offering five times longer life. As such it was offered with an optional adapter unit comprising a magnetic ballast and ordinary bayonet or screw lamp cap. However, the greatest success for the 2D lamp arose from the freedom that its low profile and all-around light distribution offered to lighting designers. This fuelled a broad range of unusually compact commercial and industrial luminaires, making it one of Britain's most successful lighting exports of all time. This particular example was specially made up for demonstration purposes, and comprises a half-coated glass tube to reveal the electrode assembly and mercury discharge.
Manufacturer: Thorn EMI
Lamp Power: 15.5 Watts  
Lamp Voltage: 97 Volts  
Lamp Current: 0.20 Ampere  
Cap Type: GR8
Bulb Type: T-13 T-4 in eighths/inch
Bulb Finish: Triphosphor 827 Soda-lime glass
Electrodes: Triple Coil Tungsten Triple Carbonate Emitter
Discharge Length: 450-470 mm 18 inches
Atmosphere: Hg | Ar 5 torr pressure
Luminous Flux: 800 lm @ 100 hours 925 lm @ 2000 hours
Luminous Efficacy: 52 lm/W @ 100 hours
Colour Temperature & CRI: CCT: 5500K CRI: Ra 60
Chromaticity Co-ordinates: CCx: 0.330 CCy: 0.320
Rated Lifetime: 5,000 hours to 50% survival
Warm-up & Re-strike Time: 2 minutes Instant re-strike
Burning Position: Any except with U-bends below cap centre
Dimensions: 135 x 135 mm 5¼ x 5¼ inches
Thickness: 27 mm 1 1/16 inches
Factory: Enfield, London United Kingdom
Date of Manufacture: August 1984 Date Code: 08
Original Value: £5.63 (1988)
References: 1) Thorn Lighting Comprehensive Catalogue, 1983 UK, p.108
2) Thorn Lighting Price List, 1988 UK
3) Thorn Lighting Brochure, 2D & 2L Compact Fluorescent Lamps, 1988 UK
4) Thorn Lighting Company History - The First Sixty Years, 1988 UK, p.17
5) European Patent 57,974 - Discharge Lamp - Chapman J.M. & Antonis B, Thorn Lighting, priority January 1981
6) Photoelectric Measurement