Cups capable of nesting

Claim 1

A cup of cellular plastic material comprising a bottom wall and conical side wall extending upwardly and outwardly relative to the bottom wall, the cup being configured so as to be assembled into a stack of identical cups with the upper of two adjacent cups supported by the cup below without jamming and creating a sealed space between bottom walls of adjacent cups, a first external support and sealing surface means formed on each cup adjoining the bottom wall thereof said first surface being in the form of a continuous annular flat peripheral surface, a second external sealing and locking surface means having its maximum diameter spaced upwardly and outwardly a slight distance from the maximum of said first surface forming a crest and extending upwardly relative to the first surface and inwardly from said crest toward the inner sidewall surface of the cup, a third, internal support and sealing surface means formed in the inner sidewall of the cup, said third surface being spaced upwardly relative to the second surface and first surface and being in the form of an annular, continuous flat ledge with a minimum diameter which is less than the maximum diameter of the first furface, wherein the first surface of an upper of two adjacent identical cups cooperate with the third surface of a lower of two adjacent identical cups to form a positive support and a space between the outer lower wall surface of the upper cup and the inner lower wall surface of the lower cup, a fourth internal sealing and locking surface means having its maximum diameter spaced upwardly a slight distance from the third surface, said slight distance being not greater than the distance between the first and second surfaces, the fourth surface extending inwardly and downwardly into the wall to its maximum diameter, the minimum diameter of the fourth surface means being less than the maximum diameter of the second surface means wherein the second surface means of an upper of two adjacent identical cups cooperate with the fourth surface of a lower of two adjacent identical cups to compressingly seal the respective first and third surfaces together as well as compressingly seal said second and fourth surfaces together while permitting selective camming disengagement of the lower cup downward relative to the upper cup.