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