Patent ID: 7225945

Claim:
A leak-resistant closure for a plastic container having an inwardly curving container flange extending from a sidewall and around an inner periphery at an open end and terminating in a free edge, said closure comprising: a generally planar central portion; a peripheral portion for receiving the open end of the container, said peripheral portion defining an annular recess opening in a direction generally perpendicular to the generally planar central portion and comprising an inner wall having a secondary sealing formation on an outer surface thereof and facing said annular recess, and an outer wall having a primary sealing formation on an inner surface thereof and facing said annular recess thereby defining the primary sealing formation for engaging a complementary sealing formation on the container to form the primary seal therewith within said annular recess; and a spring structure biasing the peripheral portion radially outward from the central portion, the spring structure being positioned between the central portion and the peripheral portion, wherein the secondary sealing formation is spaced from the free edge when the primary sealing formation is engaged with the complementary sealing formation, and the secondary sealing formation engages the free end after disengagement of the primary sealing formation from the complementary sealing formation.