Thermoplastic container blow molding process involves heating tool parts with temperature control fluids at different temperatures and switching fluid flow between different tool areas

摘要

During the blow molding stage the tool shells(5,6) and base part(7) are heated by at least two temperature control fluids at different temperatures. Flow of each temperature control fluid can be switched to heat or cool different areas of the tool. Switching(40) between the different temperature control fluids is performed either electrically or electropneumatically and the operation is monitored. Inner and outer shells and the tool base may be heated to different levels relative to each other. Various combinations of heating(48,49) and cooling(46,47) include: a) cooling the outer shells and base part while passively heating the inner shells; b) heating the outer shells and base to a temperature above that of the surrounding environment while passively cooling the inner shells; c) heating the outer and inner shells to a moderately warm temperature, e.g. 21-100[deg]C, while inner shells are heated to higher temperatures, e.g. 101-180[deg]C; d) cooling the base part while outer shells are heated to a moderately warm temperature and inner shells to a high temperature or e) inner shells are indirectly heated by contact with the outer shells. An independent claim is included for the blow molding plant each of whose blow molding tools are linked to a heating system with a fluid flow changeover valve(40). The latter unit is connected to two or more temperature control fluid supply lines at different temperatures and can switch(41,42;44,45) the different fluids to each part of a blow molding tool as required.