Since annular container flange 18 has a downwardly sloped upper annular surface to act as {HEAD ~ a cam surface} and annular lower portion 38 is resiliently hinged, passage of annular lower portion 38 thereover is facilitated without the realization of great stress in {TAIL ~ annular frangible area} 28 
Since annular container flange 18 has a downwardly sloped upper annular surface to act as { HEAD ~ a cam surface } and annular lower portion 38 is resiliently hinged , passage of annular lower portion 38 thereover is facilitated without the realization of great stress in { TAIL ~ annular frangible area } 28
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH