To simplify a metallic mold configuration and to improve mass- productivity by constituting a water separator so that it is bisected into upper and lower parts.

The water separator 14 is bisected into an upper side water separator 141 and a lower side water separator 142. Then the blades 141a and 142a of the upper and lower separators 141 and 142 are constituted by providing slope which is lower at its outer side, abutting the both slopes and forming one blade. Then the water separator 14 is integrally connected to the fan shaft 11 of a blade wheel by a fitting nut 11a. Then water intrusion is prevented in spite of a gap in the case of joining by obliquely forming the cross section of a joining part K between the upper and lower blades 141a and 142a. Thus, a mold being suitable for mass-productivity is produced. Besides, it is easily dissolved or cleaned.