the spindle base 53 is a u shaped base and two limiting screws 533 are screwed onto the upper surface 532 of the base plate 530 the stop block 54 provided on the head end 51 of the spindle link 5 reciprocates between the two limiting screws 533 along with the rotation of the spindle link 5 in this way when the spindle link 5 rotates to move the stop block 54 to urge against one of the two limiting screws 533 the driving shaft 21 of the motor 2 revolves to cause the fan to rotate which indirectly oscillates the fan in cycle in other words the two limiting screws 533 are used to limit the rotation range of the spindle link 5 i e the oscillation angle of the fan which is set to be 110 degrees in this embodiment further the spindle link 5 is connected in series with a clutch member 7 and a tail end 52 of the spindle link 5 is connected to a fan suspension tube 6 in this embodiment the clutch member 7 includes two wave washers 71 and two flat washers 72 the two wave washers 71 are disposed between the two flat washers 72 the clutch member 7 is fitted on the spindle link 5 in this manner the clutch member 7 of this embodiment which is formed of two wave washers 71 and two flat washers 72 is simple in construction and low in cost.