Filtering device for fan

A filtering device for a fan, the fan including a motor cover, a rotary shaft, an impeller combined at the rotary shaft, and a rear protective grill mounting on a mounting base provided on a front end of the motor cover, with a rear protective grill lock ring locked on the mounting base to fix the rear protective grill, with the filtering device comprising:

• an inner ring plate having a first outer ring portion, a first inner ring portion, and a plurality of first connection portions connected between an inner periphery of the first outer ring portion and an outer periphery of the first inner ring portion, with the plurality of first connection portions spaced along a peripheral direction of the inner ring plate, with the first inner ring portion provided with a support portion therein, with the support portion having a first shaft hole therein through which the mounting base extends;
• an outer ring plate having a second outer ring portion, a second inner ring portion, and a plurality of second connection portions connected between an inner periphery of the second outer ring portion and an outer periphery of the second inner ring portion, with the plurality of second connection portions spaced along a peripheral direction of the outer ring plate, with the second inner ring portion provided with a second shaft hole therein, with the inner periphery of the second inner ring portion provided with a plurality of fixing pieces extending toward the second shaft hole and spaced along a peripheral direction of the second inner ring portion;
• and
• a filter element coupled between the inner ring plate and the outer ring plate and including a through-hole therein, wherein the first shaft hole, the through-hole and the second shaft hole are aligned in an axial direction of the rotary shaft, wherein the rotating shaft is adapted to extend through the first shaft hole, the through-hole and the second shaft hole, wherein the fixing piece of the outer ring plate extends in the through-hole of the filter element and is attached to the support portion of the inner ring plate, so that the support portion of the inner ring plate and the plurality of fixing pieces of the outer ring plate is fixed between the rear protective grill and the rear protective grill lock ring.