Patent ID: 8091732

Claim:
A food container made of plastic sheet material and comprising: (a) a base having a peripheral sealing region with a downwardly facing channel which, when viewed in cross-section, is generally shaped like an inverted “U” with a horizontal, transverse portion joining the legs of the “U”, a substantial portion of the inner wall of the channel being frustoconical, inwardly inclined, and defined by an imaginary cone whose apex is located above the base; and (b) a lid having a corresponding peripheral sealing region with a downwardly facing channel generally shaped like an inverted “U” with a horizontal, transverse portion joining the legs of the “U”, a substantial portion of the inner wall of the channel of the lid being frustoconical, inwardly inclined, and defined by an imaginary cone whose apex is located above the lid, the outer wall of the channel having an inwardly extending hook portion, and the lid being sized so that it will mate and interlock with the base; (c) wherein, at least one of the transverse channel portions has a vertically projecting annular rib; and (d) wherein, when the base and lid are assembled with their U-shaped channels interlocking, (i) the frustoconical inner walls of the channels engage so that their conical surfaces are in substantial contact with each other and create a first, area seal between the base and lid, (ii) the annular rib contacts the mating transverse channel portion, creates a second seal between the base and lid, and provides substantial clearance between the transverse channel portions inwardly and outwardly adjacent the rib; (iii) the hook portion of the channel of the lid engages the outer wall of the channel of the base so as to prevent relative upward movement of the lid; and (iv) the channel of the lid is a first class lever whose fulcrum is the rib, with the lever urging the inner wall of the channel of the lid upward with respect to the inner wall of the channel of the base and thereby tightening the first, area seal.