{HEAD ~ The vent hole} is closed by the base plate of {TAIL ~ the fixed scroll member} for the majority of its operational cycle 
{ HEAD ~ The vent hole } is closed by the base plate of { TAIL ~ the fixed scroll member } for the majority of its operational cycle
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH