Devices and methods for processing performs for production of plastic containers have been known for some time from the prior art. Plastic preforms made for example from PET, usually with circular cross section, are first heated and then expanded within a blow mould into plastic containers. During this expansion process the plastic containers are pressurised with compressed air in order to be thus expanded against the inner wall of the blow mould.
However sometimes plastic containers are required on the market which do not have a circular cross section but have a different cross section, such as for example an oval base shape. Several methods for production of such plastic containers are also known from the prior art. Thus it is known for example that certain regions of the outer wall of the plastic preform are heated more greatly so that they expand further in the subsequent stretch blowing process, so that overall a bottle form deviating from the circular cross section is produced. This process is also known in the prior art as “preferential heating”.
Japanese patent publication JP 08174552 A discloses a blow mould device. Heat-insulating reinforcing materials are used so that the mould as a whole has a double structure. Furthermore heating devices and water bores for cooling water are provided. Japanese publication JP 63207630 A also describes a possibility of controlling a thickness in a peripheral direction of a bottle. Here too an elliptical blow mould is provided.
U.S. Pat. No. 4,380,526 discloses a device and a method for producing non-cylindrical articles from PET preforms. Blow moulds are used which themselves have an elliptical cross section. The surface of the blow mould against which the thermoplastic material is pressed can have effects on the shaping. For this it is proposed to apply a heat-insulating material in the region which forms the container. This teflon material is intended to improve the coefficient of friction with the plastic material of the plastic preform and reduce a heat transfer from the preform material to the blow mould.
German patent application DE 10 2009 021 792.4 (not yet published) by the applicant describes a method in which the plastic preforms are partially touched by means of a contact element and thus tempered. The disclosure content of this application is hereby fully incorporated by reference in the present disclosure.
Here too the objects of the patent application submitted by the applicant on the same day which concern “preferential heating” are fully incorporated by reference in the present application.
It may be desirable to provide a device which allows or facilitates the production of oval containers.