a lid closing {TAIL ~ the outlet} of the outer chamber when {HEAD ~ the inner chamber} is in the first position 
a lid closing { TAIL ~ the outlet } of the outer chamber when { HEAD ~ the inner chamber } is in the first position
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH