| 摘要 |
PROBLEM TO BE SOLVED: To reduce the size of a driving source, and to reduce electric power consumption by maintaining a position before a change in an electric current cutoff state by using an electric motor or an electromagnet for driving a screw or a can used for a moving medium of a light shielding object, and maintaining a position after a change in a current-carrying state. SOLUTION: When carrying an electric current to an electric motor 1, a screw fixed to a rotor rotates, so that a light shielding support plate 5 for fastening a light shielding object 4 is moved in the arrow direction through a prescribed mechanism. When the light shielding support plate moves to a certain distance, the electric motor 1 stops by the prescribed mechanism. Thus, the electric motor 1 stops still in a current-carrying state, and the light shielding object 4 also stops while still going to the front of an arrow, so that a light shielding reducing state is kept. At returning time, since a previously deflected torsion coil spring is locked in the prescribed mechanism when cutting off current-carrying to the electric motor 1, this coil spring returns to the former position against an idle rotation load of the electric motor 1.
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