Since we're in the height of summer and we've had some fan threads here already, I'm adding another one

The subject fan belonged to my parents and I appropriated it when it came time to break down the household.  Try as I might have, I can't figure out how to remove the rotating grille for cleaning.  The center knob is used to control rotation speed by loosening or tightening to decrease or increase friction, but it doesn't unscrew to the point of being removable. 

There's very little information about this make of fan on line other than some auction or youtube hits.  I don't know if there are clones under different brand names that might produce useful search results.  It seems I have an oddball item here.

I really like the rotating louver system and would like to give my fan the tune-up it deserves, but I'm stuck.  If anyone has one like it and knows how to remove the grille, please post here.

Thanks,

Ralph

Martin, yes, I have a DeLonghi that operates the same as the fan you described.  The center knob is reverse threaded and allows the grille to be removed for cleaning.  That fan finally developed a problem, probably a broken or stripped plastic gear, and the grille now free-wheels and makes a clicking sound, so I've had to put a wedge between the grille and the housing to keep it from moving, and as a result the grille has to be aimed.

Justin, thanks for the Tatung lead.  I'll see what I can find.

I'm not one to collect modern plastic fans, but I think the rotating louver feature provides an alternative to oscillation in a far less bulky format, and these fans are slim enough to fit in most windows.