Patent ID: 7612503

Claim:
An electric lamp comprising an outer bulb having an elongate inner bulb defining a longitudinal axis (A) and which is sealed in a vacuum-tight manner at mutually opposing ends by sealing pans, the outer bulb being placed, with an attached tube piece, over the inner bulb and being fixed to a sealing pad by means of an annular beading formed on the inner bulb, wherein the beading protrudes from a wall defining the inner bulb on a side facing the outer bulb, and wherein the tube piece is attached radially to the beading, and wherein the tube piece extends axially to intersect at least the maximum diameter of the beading, the beading having three axially sequential parts, which on a corresponding side of the wall facing away from the outer bulb define a hollow cavity having an axial width greater than the wall thickness: a convex central part MT, and two concave outer parts AT, wherein there is a point of inflection between the convex central part and each concave outer part, and wherein the axial length Lm of the convex central part MT, measured from one point of inflection to the other, is at least 50% of the total length L of the beading and in which the axial length La of each concave outer part AT makes up in each case at most 25% of the total length of the beading.