| CPC F04D 29/424 (2013.01) [F04D 25/0606 (2013.01); F04D 25/10 (2013.01); F04D 29/441 (2013.01)] | 20 Claims |

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1. A head mechanism, comprising:
a casing, a primary air inlet and an air outlet are provided on a circumferential side wall of the casing, and an auxiliary air inlet is provided on an axial wall surface of the casing; and
a centrifugal volute arranged in the casing, a centrifugal fan is arranged in the centrifugal volute, and an air duct outlet corresponding to the air outlet and an air duct inlet corresponding to the auxiliary air inlet are provided on the centrifugal volute; wherein
the primary air inlet is provided opposite the centrifugal volute, the primary air inlet is in communication with the centrifugal volute, the auxiliary air inlet is in communication with the centrifugal volute, and the centrifugal fan draws air from the primary air inlet;
a filter screen structure arranged corresponding to the primary air inlet; and
air flowing from the primary air inlet and the auxiliary air inlet flows into the centrifugal volute through the air duct inlet.
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