The diaphragm floats freely above the generally flat top of the dome, not in any significant way clamped, pinched or held against {HEAD ~ the truncated dome} shaped {TAIL ~ valve seat} 
The diaphragm floats freely above the generally flat top of the dome , not in any significant way clamped , pinched or held against { HEAD ~ the truncated dome } shaped { TAIL ~ valve seat }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL