Abstract: At least two discharge units (2, 3; 14, 15, 16; 21, 22, 23, 27, 28, 29) are ocated adjacent each other, each of the discharge units preferably including a unitary U-shaped tube having two longitudinal leg portions (2a, 2b; 3a, 3b) extending parallel to each other, and a cross portion (4, 5) connecting the leg portions at the base of the U. The free ends of the U are pinch-sealed and air-tight, and the two discharge units are so positioned relative to each other that the longitudinal leg portions extend parallel to each other, selectively, in a single plane, in parallel planes, or angled with respect to each other; the cross elements are located at adjacent end portions of the respective units.

Abstract: To prevent weakened corners when forming a U-shaped discharge tube with sharp corners (28, 29) during a bending operation from a straight tube, two glass tubes (1, 3) having a wall dimension suitable for a compact fluorescent tube are fused to a central tubular glass element (2) of thicker wall dimension so that, upon bending into U-shape with sharp corners (28, 29), the thicker wall portion can stretch and form the essentially right-angle corners of requisite wall thickness. Preferably, during the heating steps for forming the glass, the initially straight glass portions (1, 2, 3) are rotated.

Abstract: A tubular discharge vessel for a compact low pressure discharge lamp, espally a compact fluorescent lamp, is formed by heating and bending a straight glass tube into a U-shape with a plurality of straight sections and a 180.degree.-bend. Adequate vessel wall thickness is assured at the tubular sections where the bends are formed, by first heating a central section, moving sections lateral to the central section axially toward one another, thereby compressing the heated central section and thickening its walls, and bending or rotating the lateral sections into a parallel orientation. This prevents the bending process from unduly thinning the vessel walls, leading to breakage or rupture under internal gas pressure.

Abstract: To reduce the operating temperature of a U-shaped or multiple U-bent fluocent lamp, the respective longitudinal and transverse sectional elements of the U-shaped lamp are so related that the outer generating line M.sub.Q of the individual transverse tube sections (4; 20, 21, 22) is substantially straight;the diameter D.sub.LQ in the tube bends (5, 6; 23, 24, 25, 26, 27, 28) at the transition between the longitudinal tube sections (2, 3; 16, 17, 18, 19) and the respective transverse tube sections (4; 20, 21, 22) is larger than the diameter D.sub.Q of the individual transverse tube sections in the middle thereof,and the diameter D.sub.Q of the transverse tube section is at least as large as the diameter D.sub.L of the longitudinal tube sections;a depression or dent can be formed at the center of the outer surface of the transverse tube section, and the corners of the transverse tube section can include additional heat dissipating material to further reduce the operating temperature.

Abstract: An improved low pressure mercury vapor discharge lamp, particularly of the fluorescent type. The inner wall of the glass envelope is coated with a layer of SiO.sub.2 particles which, in turn, is coated with a phosphor layer. The SiO.sub.2 particles have a particle size of below about 100 nm. The SiO.sub.2 particle containing layer containing between 0.5 and 0.7 mg of SiO.sub.2 particles per square centimeter of glass envelope which is coated.