The apparatus 4 wherein said opening is the open bottom end of said cylindrical casing and said element is circular and substantially concentric with said cylinder and wherein said diaphragm when subjected to pressure head balloons upwardly in an annulus in {HEAD ~ the space} between the inner wall of said cylinder and {TAIL ~ the edge} of said element 
between
The apparatus 4 wherein said opening is the open bottom end of said cylindrical casing and said element is circular and substantially concentric with said cylinder and wherein said diaphragm when subjected to pressure head balloons upwardly in an annulus in { HEAD ~ the space } between the inner wall of said cylinder and { TAIL ~ the edge } of said element
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 REL OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH