Fluorescent lamp having meandering discharge path and manufacturing method of the same

A fluorescent lamp comprising:

• a base;
• a first constituent tube that has a U-shaped discharge path and is disposed on the base so that a first end and a second end thereof are positioned on the base side of the fluorescent lamp, and a turning portion thereof where the discharge path turns is positioned away from the base;
• a second constituent tube that has a U-shaped discharge path and is disposed on the base so that a third end and a fourth end thereof are positioned on the base side of the fluorescent lamp, and a turning portion thereof where the discharge path turns is positioned away from the base;
• and
• a bridge that connects a first area in a vicinity of the first end of the first constituent tube with a second area in a vicinity of the third end of the second constituent tube so as to join the discharge paths, wherein
• distances between the first constituent tube and the second constituent tube gradually become smaller from the base side toward the turning portion side of the fluorescent lamp, and
• external surfaces of the first constituent tube and the second constituent tube are in contact with each other on the turning portion side of the fluorescent lamp.

A fluorescent lamp comprising:

• a base;
• a first constituent tube that (i) is made up of at least a first straight tube, a second straight tube, and a first bridge, both ends of the first straight tube and both ends of the second straight tube being closed, and the first bridge connecting an area in a vicinity of one of the ends of the first straight tube with an area in a vicinity of one of the ends of the second straight tube so as to form a U-shaped discharge path, and (ii) is disposed on the base so that unconnected ends of the first and second straight tubes are positioned on the base side of the fluorescent lamp, and the areas connected by the first bridge are positioned away from the base;
• a second constituent tube that (i) is made up of at least a third straight tube, a fourth straight tube, and a second bridge, both ends of the third straight tube and both ends of the fourth straight tube being closed, and the second bridge connecting an area in a vicinity of one of the ends of the third straight tube with an area in a vicinity of one of the ends of the fourth straight tube so as to form a U-shaped discharge path, and (ii) is disposed on the base so that unconnected ends of the third and fourth straight tubes are positioned on the base side of the fluorescent lamp, and the areas connected by the second bridge are positioned away from the base;
• and
• an inter-constituent bridge that connects a first area in the first constituent tube on the base side of the fluorescent lamp with a second area in the second constituent tube on the base side of the fluorescent lamp so as to join the two U-shaped discharge paths, wherein
• distances between the first constituent tube and the second constituent tube gradually become smaller from the base side toward the first and second bridge side of the fluorescent lamp, and
• D2/D1 is within a range of 0.05 to 0.70 inclusive, where D1 is a distance between (a) a point closest to the base within the first area and (b) a point closest to the base within the second area, and D2 is a shortest distance, on the first and second bridge side of the fluorescent lamp, between the first constituent tube and the second constituent tube.

A fluorescent lamp comprising:

• a base;
• a first constituent tube that (i) is made up of at least a first straight tube, a second straight tube, and a first bridge, both ends of the first straight tube and both ends of the second straight tube being closed, and the first bridge connecting an area in a vicinity of one of the ends of the first straight tube with an area in a vicinity of one of the ends of the second straight tube so as to form a U-shaped discharge path, and (ii) is disposed on the base so that unconnected ends of the first and the second straight tubes are positioned on the base side of the fluorescent lamp, and the areas connected by the first bridge are positioned away from the base;
• a second constituent tube that (i) is made up of at least a third straight tube, a fourth straight tube, and a second bridge, both ends of the third straight tube and both ends of the fourth straight tube being closed, and the second bridge connecting an area in a vicinity of one of the ends of the third straight tube with an area in a vicinity of one of the ends of the fourth straight tube so as to form a U-shaped discharge path, and (ii) is disposed on the base so that unconnected ends of the third and the fourth straight tubes are positioned on the base side of the fluorescent lamp, and the areas connected by the second bridge are positioned away from the base;
• and
• an inter-constituent bridge that connects a first area in the first constituent tube on the base side of the fluorescent lamp with a second area in the second constituent tube on the base side of the fluorescent lamp so as to join the two U-shaped discharge paths, wherein
• distances between the first constituent tube and the second constituent tube gradually become smaller from the base side toward the first and second bridge side of the fluorescent lamp, and
• external surfaces of the first constituent tube and the second constituent tube are in contact with each other on the first and second bridge side of the fluorescent lamp.