Apparatus for forming a lightweight plastic bottle

Claim 1

Apparatus for blow molding a plastic bottle having a base including a bottom intended to rest upon a supporting surface, an integral body portion extending upwardly from said base and including a central area, a shoulder portion above said central area and a neck extending upwardly from said shoulder portion, said shoulder portion having an integral handle extending therefrom, said apparatus comprising: (a) an extrusion die for forming a tubular parison in heated moldable condition; (b) means for positioning said parison between partible blow mold sections, said sections, when closed having a cavity with (i) a first portion defining a bottom forming surface, a body forming surface and a neck forming surface lying on an axis and (ii) a second portion defining the shape of said handle, said second portion being offset with respect to said axis and said neck forming surface and communicating with said first portion throughout a line of juncture of reduced size defined by a third portion; (c) an air supply for introducing low pressure gas into said parison to pre-blow (i) that portion of said parison intended to form said integral handle to a radial extent to be captured within said cavity second portion upon closing of said mold sections and that, upon expanding in said cavity first portion, said shoulder portion will have a target minimum thickness of 0.015 inch and a target average thickness between 0.020 inch and 0.030 inch and (ii) that portion of said parison intended to form said central area to cause such parison portion to thin to an extent such that, upon expanding in said cavity first portion, said central area will have a target maximum thickness of 0.012 inch; (d) means for closing said partible blow mold sections around said pre-blown parison to enclose a major portion thereof in said cavity first portion while compression molding a minor portion in said cavity second portion to form a solid handle; (e) means for introducing high pressure gas into that portion of the mold enclosed parison lying within said cavity first portion; and (f) a restrictor for preventing high pressure gas from entering that portion of said parison enclosed within said cavity second portion, said restrictor forming a single line of juncture between the handle and the shoulder which is thinner throughout its entire length than the portion of the handle adjacent thereto.