Machine for the production of receptacles of plastic material and process for actuating such a machine

摘要

The machine for production of receptacles comprises a heating device (10) traversed in an indexed manner by at least two rows of preforms (24) disposed on double conveyors (5). The heating device (10) has four successive zones (35) each having a given number of stop positions (41), in which the preforms face ventilation-cooling openings (38). A first zone (TH1) with a heating body (50) is adopted for initial heating; a second zone (TE1) permits thermal balancing; in a third zone (TH2) with a second heating body (51), there is carried out a second heating and the fourth zone (TE2) serves to obtain final thermal equilibrium. The first and third zones (TH1, TH2) have stop positions in which the preforms are subjected simultaneously to heating and a flow of cooling air in a vertical plane. This permits obtaining a precise thermal profile through the wall of the preforms and a particularly effective and rapid heating, whilst avoiding crystallization of the surface of the preforms. The quality and the precision of the receptacles obtained are thus improved.