Blow molded PET container with ribbed base structure

Claim 1

In a plastic container for a pressurized product, wherein said container has a hollow body with a generally cylindrical side wall and the base structure merging with said side wall, said base structure comprising: an upwardly concave inner wall having upper and lower ends and a generally circular area at the upper end disposed substantially centrally of said base structure; a convex outer wall of annular shape surrounding said inner wall, said outer wall having an upper end merging with said side wall and a lower end merging with the lower end of said inner wall; and a plurality of hollow reinforcing ribs projecting downwardly from said inner and outer walls, said ribs extending radially outwardly from an inner end merged with said inner wall to an outer end merged with said outer wall whereby said downwardly projecting ribs form bearing surfaces for contact with a supporting surface at the lower most points of said ribs, the exterior surface of the radially inner end of said ribs and the exterior surface of said inner wall being relatively inclined to one another when viewed in vertical cross section through said hollow ribs to form corners directed interiorly of said container to stiffen said base structure and to resist deformation thereof, the inner ends of said ribs being disposed sufficiently close to one another that said relatively inclined surfaces form a substantially continuous corner extending circumferentially about the lower end of said inner wall, said ribs being shallow in depth to provide sufficient stiffness to prevent base deformation by internal container pressures of approximately 30 psi.