Patent ID: 8389085

Claim:
A preform for a plastic bottle produced by injection stretch blow molding, the preform comprising: a barrel section; a neck section continuous with an upper portion of the barrel section; and a bottom section continuous with a lower portion of the barrel section, said bottom section includes: a flat bottom surface central portion having a diameter d less than an inner diameter D of the barrel section and a thickness t 2 less than a thickness t 1 of the barrel section, a bottle bottom surface-forming portion formed by bending, at a height position h, a portion that forms a bottom edge of the bottle, the bottle bottom surface-forming portion extending to a circumference of the bottom surface central portion and including a bottle bottom edge-forming portion, and a curved portion interposed between a lower portion of the bottle bottom surface-forming portion and the bottom surface central portion, wherein the bottom section has an inverted truncated conical shape, wherein the bottle bottom surface-forming portion is continuous with the lower portion of the barrel section and inclined toward the bottom surface central portion, the bottle bottom edge-forming portion is an upper portion of the bottle bottom surface-forming portion and is continuous with the lower portion of the barrel section, an inner surface of the bottle bottom surface-forming portion is formed as a gently curved convex surface extending from a lower portion of the bottle bottom edge-forming portion to an upper portion of the curved portion such that a thickness t 3 of the bottle bottom surface-forming portion is increased to be greater than the thickness t 1 of the barrel section, and wherein the bottle bottom edge-forming portion is formed to have a thickness t 4 less than the thickness t 3 of the bottle bottom surface-forming portion.