type 1
type 2
BLENDED-LAMP-TECHNOLOGY
In a blended lamp, a high-pressure
mercury vapour arc discharge tube was
mounted inside the glass- or quartz bulb
of an incandescent lamp and it was
connected in series with the filament of
that incandescent lamp. The filament in
fact played a double role as both infrared
source and serial ballast for the
discharge lamp, thus avoiding the use of
a heavy and expensive coil or
transformer. The first blended lamps (type
1) consisted of a glass bulb that
contained both a drop of mercury and a
specially designed filament with a twofold function. The heat of the filament made the
mercury to vaporise and at a sufficient high gas pressure a voltaic arc developed that
short-circuited the back bended middle
part of the filament. This short-circuited
part than played no further role in the
generation of the desired radiation. The
part of the filament that stayed in series
with the voltaic arc however, now lit up
fiercely and served both as a current
limiter and an infrared source. With later
designs (type 2) a complete and
separately sealed arc discharge tube
was mounted within the outer bulb, still in
series with the filament that again served
both as a current limiter and as an
infrared source.
