Snap-on lid and mold for making the lid

A mold for forming a disposable plastic container lid for a container having an opening surrounded by a headed rim wherein the lid is stackable with other lids, said mold comprising;

• an inner mold element and a coaxial outer mold element,
• said inner mold element including a central planar portion and an upstanding peripheral portion having an essentially flat top surface and a plurality of extensions circumferentially spaced about said top surface, said extensions being radially spaced from inner and outer circumferential edges of said top surface,
• said outer mold element including a central opening for accommodating said inner mold element, an annular planar portion, and an upstanding peripheral portion having an inner circumferential surface including a plurality of radially inwardly extending arcuate portions forming a ridge and a plurality of recesses provided between said inwardly extending arcuate portions,
• wherein said recesses vary in their circumferential length between each extending arcuate portion.

A disposable plastic circular lid for a container having an opening surrounded by a beaded rim wherein the lid can be stacked with other lids having aligned central axes and wherein said lid comprises:

• a. a generally circular closure wall including an annular central portion lying in a first plane, an annular outer portion lying in a second plane below said first plane and an annular U-shaped recess extending between said central portion and said annular outer portion and having an inner wall, an outer wall, and a bottom wall lying in a third plane below said second plane formed by said annular outer portion;
• b. a peripheral skirt depending from a rim portion of said closure wall for engaging the beaded rim of a container;
• and
• c. stabilizing means for disturbing and counteracting both lateral and axial loads during stacking to maintain stack integrity while preventing jamming of adjacent lids, said stabilizing means including:
• (i) anti-jamming means for preventing sticking of adjacent lids during stacking including a plurality of lug members extending downwardly from said bottom wall for a sufficient distance to engage the bottom wall of a lower adjacent lid, the inner radial surface of each lug member being spaced radially outwardly along its entire axial length from the inner wall of said U-shaped recess;
• and
• (ii) anti-shifting means for preventing relative lateral movement of adjacent lids during stacking, said anti-shifting means including the portion of said inner wall which lies above the bottom wall of an upper adjacent lid.