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