Self-righting cups

Claim 1

A two-piece self-righting drinking cup comprising a generally rigid cylindrical hollow cup container having a downwardly inwardly curved side wall of uniform thickness and a bottom wall which is for the reception and retention of a liquid, a separate base member which is circular in cross section and on which the hollow cup container is mounted, means for mounting said cup container on said base member, said base member being rigid and having a convex outer surface progressively decreasing in diameter from the junction of said base member and said hollow cup member to the lowermost portion of said base member, said lowermost portion defining a flat bottom the diameter of which is at least 39% of the greatest external diameter of the hollow cup container, said base member having a structure including an enclosed compartment containing ballast, said ballast having a center of gravity which lies on a vertical axis extending through the center of said cup container, wherein said self-righting drinking cup is characterized by the following critical parameters: (a) the ratio of the diameter of the lowermost portion of the base to the greatest diameter of the drinking cup itself is about 0.39 to 0.75, (b) the ratio of cup height to maximum cup diameter is about 0.80 - 1.1, (c) the ratio of the cup height to the diameter of the lowermost portion of the base is about 1.3 to 2.5, and (d) the ratio of cup height to the height of the convex portion of the base member is about 1.8 to 3.2. wherein said self-righting drink cup resists being knocked over but quickly self right itself without any substantial subsequent wobble after being knocked over.