Method of manufacturing a low-pressure mercury vapor discharge lamp and low-pressure mercury vapor discharge lamp manufactured by means of this method

A method of manufacturing a low-pressure mercury vapor discharge lamp comprising two parallel tube parts and a transverse section joining said tube parts near adjacent ends, said method comprising:

• (a) providing a single elongate circular cross-section glass tube having a given diameter and a given tube wall thickness;
• (b) coating the interior of said tube with a luminescent material;
• and
• (c) dividing said coated tube into two tube parts having respective facing end walls each having a thickness at least at an area of transition between the tube wall and the end wall between 0.4 and 0.8 times said given tube wall thickness, comprising
• heating an axial section of said coated tube over a length less than said diameter causing said axial section to rise to a temperature such that the heated glass softens,
• drawing cooler portions of said coated tube away from each other until a construction is formed in said heated axial section having a diameter approximately half said given diameter, and
• heating said axial section with said cooler portions fixed relative to each other until said constriction is at a temperature such that the heat-softened glass moves in the direction of the cooler portions, said single tube separating into said two tube parts and said heat-softened glass forms respective end walls on said tube parts,
• said wall thickness being selected and said dividing step being carried out such that the movement of the soft glass towards the cooler portions forms the end walls and avoids penetration of the luminescent material into the glass.