PURPOSE: To obtain an excellent operational sense and to prevent an abnormal sound from occurring by holding an assembly of perforated sheets between a front grill and a back retainer and forming an airstream guide hole using the front surface of a housing or the intermediate surface thereof as a fixed surface.

CONSTITUTION: An airstream guide member 12 consisting of an assembly of a number of perforated sheets 13 is held between a front grill 18 and a rear grill 14 in such a manner that respective sheets 13 are mutually slidable and movable manner. Through a hole 12a to be driven formed at the central part of an airstream guide member 12 is inserted a driving bar 17b of an operating member. Connecting rods 15b and 15h are inserted through laterally long guide slit 12b and 12b formed on both side portions of the airstream guide member 12, and the driving bar 17b of the operating member is inserted through the longitudinally long guide slit 14a of the rear retainer. Accordingly, the mutually contacted state of sheets of the sheet assembly undergoes no change and the operation load constantly assumes a predetermined value and hence an excellent operational sense can be obtained.