JPS5749093A - Electric fan - Google Patents

Abstract

PURPOSE: To provide an electric fan, capable of producing healthy draft of air at a short period of draft repetition, by providing a brake means the braking force of which is changed with rotation of a wind-direction changing grille, and causing high-speed and low-speed rotation of the grille alternately during each one turn of the grille.

CONSTITUTION: Rotation of an air flow-direction changing grille 7 is increased by an overdrive mechanism consisting of a gear train of a gear wheel 16A, pinion 17A, gear wheel 16B and pinion 17B, and causes high-speed rotation of an electrically conductive disk 19. Along with the rotation of the disk 19, magnetic flux of a permanent magnet 20 is cut by the disk 19 and dynamic brake is acted to the disk 19, so that the grille 7 is turned at a low speed. On the other hand, along with rotation of a main shaft 9, a short-circuit pole piece 15 approaches pole pieces N21, S22 and most of the magnetic flux is passed through the short-circuit pole piece 15. Therefore, magnetic flux passing across the disk 19 is reduced and the dynamic brake acted is also reduced, so that the grille 7 is turned at a high speed. Thus, it is enabled to cause high-speed and low-speed rotation of the grille alternately during one rotation of the same and to shorten the period of draft repetition.

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