Electric incandescent lamp with two envelopes - has plastics external envelope fixed to cap by removable ring

摘要

An incandescent electric lamp has two outer envelopes of different materials. It has a cap which is fixed to both envelopes. The lamp has two envelopes (11, 12) and a cap (10). The first envelope (11) is made of glass and encloses a filament. The second envelope (12) surrounds the first envelope (11) and is made of either polyvinyl chloride, polycarbonate or other semi-transparent or transparent plastic material. The second envelope (12) is fitted to a ring (13) around the cap (10). The ring (13) may be of plastic material and has a groove to take the rim (20) of the second envelope (12). The ring (13) has an inner collar which fits into a collar (15) of the cap (10). The ring (14) has two recesses which mate with two shoulders (18) on the cap (10). The ring (13) is removable and the second envelope (12) may be replaced by an envelope with other shape or colour.