| 摘要 |
PROBLEM TO BE SOLVED: To provide a rotational position deciding device which can decide the rotational position of a mercury flag 7 with high accuracy, in the process of manufacturing a fluorescent lamp. SOLUTION: In a fluorescent tube 2 driven rotationally by means of a motor 18, a mercury flat 7 is arranged eccentrically. In order to position the flag 7 to a target rotation position A, a pair of sensors 21 and 22 which produce analog outputs correspondingly to the position of the flag 7 is arranged at positions B and C, which are shifted from the position A by prescribed angles in the opposite directions. The analog outputs from the sensors 21 and 22 are inputted to a comparator 23, which makes a reverse output at the time the magnitude relation between the analog outputs is switched. A controller 24 discriminates the target rotational position A, based on the reverse output and instantaneously stops the rotational driving of the tube 3 by means of the motor 18. Consequently, the mercury flag 7 can be positioned to the target rotational position A with high accuracy.
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