Abstract: This invention provides a compact, efficient and well-designed circular fluorescent lamp with high output power. The circular fluorescent lamp has less non-luminant region and good characteristics of luminous intensity distribution, and keeps high level of lamp lumen output. Circular arc tubes are disposed concentrically on the same plane. Electrodes are attached to the tube-end parts of the one side of the circular arc tubes respectively, and the other tube-end parts of non-electrode side are sealed. The circular arc tubes are joined each other near the tube-end parts of the non-electrode side with a bridge-jointed portion, so that a discharge path is formed between the electrodes inside the arc tubes. The tube outer diameter of the circular arc tubes is 14 mm, the circle outer diameter of the outer circular arc tube is 150 mm, and the circle inner diameter of the inner arc tube is 90 mm.

Abstract: A fluorescent lamp device with an incandescent bulb type base cap. The fluorescent lamp device has a luminous tube unit and a case with one end supporting the luminous tube unit, and the other end has an outwardly projecting portion. A ballast is provided in the case, and a base cap is adapted to be rotatably fitted to the projecting portion of the case. The outer periphery of the projecting portion of the case has an engagement groove formed in it and a stopper portion which is formed in the axial direction of the case. An engagement portion, a guide groove and a rotation limiting groove having a rotation stopper portion are successively provided for the inner surface at one end of the base cap disposed in that order starting from the one end of the base cap.