Double-wall bottle and method and apparatus for molding the same

A method of molding a double-wall bottle, comprising the steps of:

• biaxial stretch blow molding a first preform to form an outer bottle having body and bottom portions;
• forming air vent holes in the bottom portion of said outer bottle:
• setting a second preform and said outer bottle into a first blow cavity mold, said second preform being placed inside of said outer bottle, said second preform having a body portion of an outer diameter smaller than the diameter of an opening of said first preform and having a bottom portion, the body portion of the outer bottle having a longitudinal direction and a circumferential direction;
• and
• biaxial stretch blow molding said second preform to form an inner bottle within said outer bottle;
• wherein said step of forming said air vent holes includes a step of forming said air vent holes at different positions in the longitudinal and circumferential directions of said body portion of said outer bottle;
• wherein said first blow cavity mold is configured of a plurality of split molds that can freely open and close with respect to each other;
• wherein at least one of said split molds has an air expulsion groove communicating from a cavity surface of said split mold to an outer surface thereof, formed in a parting surface of said split mold;
• wherein said air expulsion groove of said split mold is formed such that the shape thereof on the side facing said cavity surface is of a longitudinally extended groove extending over the length of the region in which said air vent holes are formed along the longitudinal direction of said outer bottle;
• and
• wherein during said step of biaxial stretch blow molding said inner bottle, the air within said outer bottle is expelled via said air vent holes formed at said body and bottom portions of said outer bottle and is exhausted to the outside of said mold via said longitudinally extended groove shared by said air vent holes.

A method of molding a double-wall bottle, comprising the steps of:

• biaxial stretch blow molding a first preform to form an outer bottle having body and bottom portions;
• forming air vent holes in the bottom portion of said outer bottle;
• setting a second preform and said outer bottle into a first blow cavity mold, said second preform being placed inside of said outer bottle, said second preform having a body portion of an outer diameter smaller than the diameter of an opening of said first preform and having a bottom portion, the body portion of the outer bottle having a longitudinal direction and a circumferential direction;
• biaxial stretch blow molding said second preform to form an inner bottle within said outer bottle;
• wherein said step of forming said air vent holes includes a step of forming said air vent holes at different positions in the longitudinal and circumferential directions of said body portion of said outer bottle, the number and/or total opening area of said air vent holes formed in said bottom portion and body portion is set to be such that an opening ratio per unit area of said bottom portion is larger than an opening ratio of said body portion;
• and
• wherein, during said step of biaxial stretch blow molding said inner bottle, the air within said outer bottle is expelled via said air vent holes formed at said body and bottom portions of said outer bottle.

An apparatus for molding a double-wall bottle, comprising:

• a means of forming an outer bottle having body and bottom portions by biaxial stretch blow molding a first preform;
• a means of forming air vent holes in said body and bottom portions of said outer bottle in a predetermined pattern for enabling venting through said holes;
• a means of setting a second perform and said outer bottle into a first blow cavity mold, said second preform being placed inside of said outer bottle, said second perform having a body portion of an outer diameter smaller than the diameter of an opening of said first preform and having a bottom;
• and
• a means of forming an inner bottle within said outer bottle by biaxial stretch blow molding said second preform while expelling the air within said outer bottle through said air vent holes,
• wherein said first blow cavity mold includes means for venting the expelled air from the air vent holes including the air vent holes formed in the predetermined pattern.

An apparatus for molding a double-wall bottle, comprising:

• means for forming an outer bottle having body and bottom portions by biaxial stretch blow molding a first preform;
• means for forming air vent holes in said body and bottom portions of said outer bottle;
• means for setting a second preform and said outer bottle into a first blow cavity mold, said second preform being placed inside of said outer bottle, said second preform having a body portion of an outer diameter smaller than the diameter of an opening of said first preform and having a bottom;
• means for forming an inner bottle within said outer bottle by biaxial stretch blow molding said second preform while expelling the air within said outer bottle through said air vent holes;
• wherein said apparatus further comprising:
• a first blow molding machine for injection-molding said first preform and forming said outer bottle by biaxial stretch blow molding from said first preform while retaining the heat with which said first preform is injection-molded;
• a second blow molding machine for injection-molding said second preform and forming said inner bottle by biaxial stretch blow molding from said second preform while retaining the heat with which said second preform is injection-molded and which is placed within said outer bottle;
• a conveyor means for supplying and conveying said outer bottle, ejected from said first blow molding machine, to said second blow molding machine at a timing that matches a timing of the biaxial stretch blow molding of said inner bottle;
• and
• wherein a number N (where N.ltoreq.1) of said second blow molding machines and a number M (where M>N) of said first blow molding machines are connected by said conveyor means.