An apparatus 11, wherein {HEAD ~ said suction duct} is closed by {TAIL ~ pivotable flaps} 
is closed by
An apparatus 11 , wherein { HEAD ~ said suction duct } is closed by { TAIL ~ pivotable flaps }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL