||The helical compact fluorescent lamp was invented by Ed Hammer at GE in 1976. His proposal was to coil a long, thin high efficiency tube into this form, such that it would better match the size and light distribution of a frosted incandescent lamp. However GE felt that coiling glass tubes into this complex shape was not compatible with high speed manufacturing techniques, and the idea was shelved.
It was not until 1992 that GE completed a machine for bending the glass, and samples of the so-called Heliax lamp that it produced were issued to the market that year. Sadly the lamp never made it to mass production, owing to extreme difficulty in controlling the production process.
The commercial introduction of the lamp had to wait a further three years until a Chinese firm, Shanghai Xiangshan, marketed the first successful design. The low labour rates in China allowed this company to economically undertake the manufacture by employing a small army of glassblowers to create the spiral form. Since then the market has taken off and many of the major firms now out-source a spiral CFL lamp from China. This is Philips' first lamp from 2003.
In fact the spiral CFL is a very poor lamp in terms of efficacy. There are two ways to make it. The first is to coil the pre-coated glass tube. This causes damage to the phosphor layer during the deformation of the glass. The second is to first coil the glass, and then coat it. Owing to action of gravity, coating thickness cannot be uniformly controlled. It is too thick on the lower half of each coil, and too thin above. The result is a lamp of lower efficacy than when straight tubes are used, but owing to its compact size the lamp remains popular.