Patent ID: 6113840
Filing Date: 2000-09-05
Classification: B29C,B29K,B29L,B65D

Abstract:
A process for the thermal treatment of the body of a preform made of a thermoplastic material during manufacture of a container by blowing or stretching-blowing, said process comprising the steps of:a) disposing the preform in an oven and heating the entirety of the preform body to a temperature greater than the softening temperature of the material while at the same time providing heating zones and non- or reduced-heating zones in the oven such that the heating zones and non- or reduced-heating zones are positioned at an exterior of the preform body as the preform body rotates at a non-uniform rotational speed and travels through the oven;b) exposing at least one part of the length of the preform body in alternating fashion to the heating zones and non- or reduced-heating zones disposed in the oven, so that at least one longitudinal portion of the preform body, or a plurality of longitudinal portions circumferentially separated from each other, extending over at least said one part of the length of the body is preferentially heated to a temperature greater than that of remaining portions of the body, andc) spacing the heating zones based on the number of longitudinal portions of the preform body to be preferentially heated and on a perimeter of the preform body, so that the longitudinal portions of the preform body to be preferentially heated are exposed to successive heating zones, while interposed longitudinal portions to be heated to a lesser degree are exposed to successive non- or reduced-heating zones, whereby one or a plurality of relatively hotter longitudinal portions are produced in the body of the preform, these portions alternating with relatively cooler interposed longitudinal portions and being capable of being reshaped more easily than said cooler longitudinal portions during subsequent reshaping of the preform body, thereby resulting in the manufacture of containers having a body of complex shape and having at all points an approximately uniform wall thickness.