Patent ID: 8052916

Claim:
A method of manufacturing a thermoplastic material container having a petaloid bottom, the method comprising: providing a blowing mold that has a petaloid mold bottom including a plurality of radiating ridges alternating with cavities that form, during molding, valleys and feet, respectively, of the petaloid bottom of the container; placing a heated preform in the blowing mold and drawing and blowing the preform such that the preform takes the shape of the mold and forms the container; reducing heat losses in longitudinal zones of the preform during the drawing, wherein the longitudinal zones extend from a bottom of the preform to an axial portion of the preform adjacent to the bottom of the preform, wherein the longitudinal zones are distributed around a periphery of the preform such that the longitudinal zones face a respective cavity of the mold bottom; whereby the longitudinal zones remain at a higher temperature and are thereby adapted to be drawn in a homogeneous fashion, and the feet of the bottom of the containers feature an increased thickness of material and are mechanically stronger as compared to a container having a petaloid bottom that is formed without reducing heat losses in longitudinal zones; using a drawing rod for the drawing, wherein the drawing rod is provided with an external surface having a plurality of recessed zones, wherein a number of the recessed zones is equal to the number of cavities of the mold bottom and are angularly distributed substantially similar to the angular distribution of said cavities, and wherein the drawing rod is locked against rotation in a predetermined angular position such that the recessed zones are situated substantially facing the cavities of the mold bottom; whereby a portion of the preform facing the recessed zones does not contact the drawing rod and therefore suffers lower heat loss.