Blow molded bottle with improved self supporting base

Claim 1

A plastic bottle for beverages having a hollow body with a generally cylindrical side wall and a base structure merging with said side wall, said base structure comprising: an upwardly concave inner wall having upper and lower ends and an apex at the upper end, said apex being substantially centrally of said base structure; a convex outer wall of annular shape surrounding said inner wall and having upper and lower ends, said outer wall merging with the lower end of said inner wall at the lower end of the outer wall and merging with the lower end of said side wall at the upper end of said outer wall; a plurality of upwardly projecting ribs in said base structure extending radially outwardly from said apex to said outer wall, each of said ribs being smoothly continuous over substantially the entire length thereof, said ribs interrupting said base structure inner and outer walls so as to divide said inner wall and said outer wall into a plurality of circumferentially spaced apart hollow feet located below said ribs, said ribs merging with said outer wall at the radially outer ends of the ribs; and said feet forming bearing surfaces at the lowermost points thereof for contact with a supporting surface, said bearing surfaces and said concave inner wall being relatively inclined when viewed in vertical section through said hollow feet so as to form corners directed interiorly of said bottle to stiffen said feet and resist deformation of said base structure. an annular circular arc portion merging said conical inner wall with said convex outer wall defining a bearing surface, said conical inner wall and said circular arc portion being relatively inclined when viewed in vertical section through said bottle so as to form corners directed interiorly of said bottle adjacent the juncture of said inner wall and said circular arc portions to stiffen said feet and said arc portions; three ribs upwardly projecting in said base structure extending radially outward from said apex, said ribs interrupting said base structure inner and outer walls so as to divide said conical inner wall and said convex outer wall into a plurality of spaced apart hollow feet located below said ribs, said ribs merging with said outer wall at the radially outer ends of the ribs; and hollow projections extending upward from said ribs, said upward projections increasing in width in a direction radially outwardly of said ribs from said apex.