Tubular fluorescent lamp with intermediate electrode

Claim 1

A fluorescent lamp having a curved discharge path, comprising: at least first and second linear tubular bulbs forming a portion of said curved discharge path, said first and second bulbs being arranged in a predetermined positional relationship and each bulb having a phosphor coating; at least one cap interconnecting end portions of said first and second bulbs and constituting in combination with said first and second bulbs said curved discharge path; terminal electrodes provides at end portions of said first and second bulbs constituting ends of said curved discharge path for enabling said curved discharge path to emit light; an intermediate electrode provided within said cap, said intermediate electrode and said terminal electrodes, selectively enabling one of said at least first and second bulbs to emit light; and a seal plate having communication ports provided in a connection part between said first and second bulbs and said cap, the inside of each bulb being allowed to communicate with the inside of said cap through said communication ports, and the position of each communication port being displaced from a center of a cross section of each bulb towards the outside of a curved area of said curved discharge path.