Process for injection molding of thin-walled preform

Abstract

An injecting/blowing device includes a mold for injecting a thin-walled hollow preform capable of being transformed into a more voluminous hollow body. The mold includes a counter mold defining a cavity, a cure located in the cavity, and a preform impression located between the counter mold inner surface and the core which will receive the melt, at least two main preferential flow channels or at least two secondary preferential flow channels having a recessed zone at the surface of the core and the inner surface of the cavity. The main flow channels are located only at the impression zone corresponding to the zone for transforming the preform, and in the optional secondary flow channels are flow channels discontinuous from the main flow channel.

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         7 . A thin-walled preform, comprising main variable-thickness zones located only in its transition zone and optionally discontinuous secondary variable-thickness zones, separate from the main variable-thickness zones and located on at least one of the bottom, the body, or the neck. 
     
     
         8 . The thin-walled preform as claimed in  claim 7 , wherein the variable-thickness zones are symmetrical. 
     
     
         9 . The thin-walled preform as claimed in  claim 8 , wherein the variable-thickness zones are distributed equiangularly over the circumference of the preform. 
     
     
         10 . The preform as claimed in  claim 7 , wherein an average thickness (w av ) is defined by w av ≦a+L/b, with 1.20<a<1.36 and 88<b<98, L being the total length in question of the preform. 
     
     
         11 . The preform as claimed in  claim 7 , wherein the variable-thickness zones are located longitudinally or helically with respect to the axis of the preform.