Manufacturing method for polyethylene-terephtalate containers with out-of-centre mouth

Abstract

Method for manufacturing plastic bottles, including the step in which respective preforms are removed from the respective moulds, and the step in which said preforms are transferred into temperature conditioning stations for a predetermined period of time, during which said preforms are caused to undergo an asymmetrical heat treatment that is effective in heating in a different manner a preform sector having an angular spread of a definite value that is anyway not less than 180°. The method includes the step in which said surface sector of the preform is heated up with the help of heating means that are partially arranged in a crown-like manner around the respective preform. The blow-moulding process comprises the sub-steps in which: the stretching rod is inserted into the preform up to the point in which it almost comes into contact with the bottom thereof; a stretching counter-rod is approached from the outside of the preform up to the point in which it almost comes into contact with the bottom of the preform; the preform undergoes blow-moulding while, at the same time, said stretching rod moves further forward into the preform and, by in this way pressing against the bottom of the preform, pushes the stretching counter-rod in a direction of ejection from the blow-moulding cavity.

Description

technical field [0001] The invention relates to a particular method for the manufacture of containers of thermoplastic resins, especially PET, provided with a cylindrical neck on which a conventional cap can be screwed, but which has a body whose shape forms To be asymmetric with respect to all planes passing through the axis of said neck of the container, except a single plane, which therefore forms a single plane of symmetry for the container. Background technique [0002] Such containers are usually manufactured by first obtaining a preform by extruding a melt of granular plastic material in a suitable manner, and then subjecting this preform to blow molding in order to form it into the appropriate shape of the final container. These containers will be referred to herein as "asymmetrical" simply because it is common practice to call them that; The total usable volume is greatly reduced by the sum of the volumes of a predetermined number of containers. It is well known t...

AI Technical Summary

Problems solved by technology

[0007] The second major disadvantage is related to the downward stretching of the preform

[0013] French Patent No. 2508004 to AOKI discloses a method of using a contrast and reference rod 12 for abutting against the outside of the container bottom during the blow molding process; however, in this method, The purpose of said rod is quite different from the rod used to position the bottom of the container, since it can be clearly inferred that this bottom is fully stretched, so it is guided by the stretch rod before the step of letting compressed air in begins, so there is actually no Consider maintaining the correct position of the bottom at the beginning of the blowing process, but before the penetrating movement of the stretching rod starts, since then blowing can only start after said stretching rod has moved completely into the preform

Images