Thermoformed snap closures

Claim 1

A thermoformed container comprising first and second sheet portions of a synthetic organic thermoformable thermoplastic polymeric material, at least one of said first and second sheet portions having a thermoformed packaging cavity therein, said first sheet portion having an at least substantially cylindrical thermoformed columnar projection therein, said seecond sheet portion having an at least substantially cylindrical thermoformed columnar depression therein, the exterior dimensions of said columnar projection having a relationship with the corresponding interior dimensions of said columnar depression permitting the insertion of said columnar projection into said columnar depression with significant frictional engagement between the exterior surface of said columnar projection and the interior surface of said columnar depression, such frictional engagement being sufficient to lock said columnar projection and said columnar depression together for normal handling of said first and second sheet portions and insufficient to prevent withdrawal of said columnar projection from said columnar depression upon the application of a desired minimum separation force; said columnar projection having a top continuous with the side wall thereof, and said columnar depression having a bottom continuous with the side wall thereof so that an at least substantially air tight chamber is formed upon the insertion of said columnar projection a desired distance into said columnar depression, whereby the buildup of the pressure of the air trapped in said chamber resists the further insertion of said columnar projection into said columnar depression and the reduction of the pressure of the air trapped in said chamber resists the withdrawal of said columnar projection from said columnar depression.