Hollow body of thermoplastic material

Claim 1

In a molded, molecularly oriented hollow body of thermoplastic material including a side wall of generally cylindrical shape, a reentrant base, and a peripheral annular support radially connecting the lower end of the side wall to the outer edge of the base, the improvement wherein said base comprises more than two substantially planar, axially staggered, concentric annular zones of respectively different widths, which widths increase progressively in the direction from the center of said base, each said concentric annular zone being inclined relative to the longitudinal axis of said hollow body such that when said body is standing upright on its base, the interior edge of each said annular zone is located at a higher level than the exterior edge thereof, connecting portions of rounded cross section connecting adjacent annular zones together, a central part in the form of a spherical dome pointing towards the exterior of said hollow body, and a further connecting portion of rounded cross section which connects said central part to the adjacent annular zone, whereby the base region of said body has an enhanced impact strength.