Tamperproof closure

Claim 1

In a tamperproof closure arrangement for a generally cylindrical container with a body wall having, adjacent the open end thereof, an internal flange presenting an axially inwardly facing abutment, an insertable lid comprising: (a) a central portion, including a generally circular center panel; (b) an annular outer rim; (c) said rim being formed of molded plastic and including: (i) a base portion joined to said center panel; (ii) a skirt portion disposed radially outward of and pivotal with respect to said base portion, said skirt portion being molded at an oblique angle to said base portion; (iii) a relatively thin, annular, integral hinge interconnecting said skirt portion and said base portion for accommodating pivotal movement of said skirt portion relative to said base portion to permit insertion of the lid into the container; (d) said skirt portion including: (i) a generally frusto-conical wall prior to insertion into the container; (ii) an integral annular retaining flange extending radially outward from a lower portion of said frusto-conical wall for engagement with said container body wall, said lower portion being spaced axially downwardly from said hinge; (iii) a second flange extending radially outward from an upper portion of said frusto-conical wall and defining with said retaining flange an annular channel for receiving said container body wall flange, said upper portion being spaced radially outwardly from said base portion and being spaced axially upwardly from said hinge; whereby when the lid is inserted into the open end of the container, the contact of the container with the lid causes said skirt portion to pivot with said retaining flange moving radially outwardly and with said second flange moving radially inwardly so that said retaining flange lockingly engages with the underside of said container body wall flange to prevent removal of the lid from the container without causing visible damage thereto.