Process and device for obtaining products of predetermined thickness, such as transmission bellows (boots), by extrusion blow-moulding

摘要

Process for obtaining, by extrusion blow-moulding, products from a parison such as transmission bellows (boots). After closing the mould, the parison 1 undergoes an internal radial stretching under the influence of a bag 10 which is elastic, colder than it and progressively inflated and which comes in the first place into contact with that part 11 of the parison 1 which is to preserve the thickness maximum, and the bag 10 then continues its expansion under the influence of an internal overpressure until pressing the entire useful surface of the parison against the internal face of the mould cavities 2-3. Application to the manufacture of transmission bellows. <IMAGE>