Lars wrote:

Here in the UK many of the desk lamps I can buy nowadays take a bulb
with an Ediscon Screw fitting. Also many wall lights for outdoor use
(sometimes with a PIR detector) take an ES fitting bulb.

Until recently all I ever needed for a general purpose light bulb was
a bayonet fitting. Now ES fittings seem to be appearing!
Pictures: http://www.bltdirect.co.uk/base.htm


Is there a particular advantage of the ES fitting over the bayonet
fitting in these sorts of applications?

Not my field but just a lay observation:

The only one I can think of is for making a water/vapour
tight seal between the lamp and fitting.

The screw-in fittings can facilitate a compression seal
between lamp and fitting.

A bayonet-type can obviously apply compression on the way
in, but some of that compression will be lost at the pins
move outward as they lock into place.

From the manufactuing viewpoint, I would think that both
screw fittings and lamps are cheaper to make than bayonet. I
may be wrong, but the ES fittings I see look to be cheap
alternatives to bayonet equivalents..

Presumably the heating and cooling cycles of use for a lamp
do have a greater effect on screw than bayonet - I would
have thought that they would tend to either get tigher and
tighter or the converse. I am not sure how this is designed
for, as it would seem very difficult to get it exactly
right, with no creep at all.

--
Sue