Plasma Sterilization of Thermoplastic Preforms
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Solution Overview
Problem
Existing methods for sterilizing injection-molded preforms and blow-molded containers face challenges with reliable sterilization due to 'shadowing' effects caused by container contours, leading to incomplete sterilization, especially when using plasma sterilization techniques.
Innovation Solution
Implementing a plasma sterilization unit along the transport path of preforms before blow molding, utilizing a plasma generator with a high-voltage electrode positioned inside the preform and an outer electrode, and controlling the plasma treatment at ambient pressure with adjustable humidity and frequency to ensure thorough sterilization of both inner and outer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma sterilization is applied to containers after blow molding, then sterilization is achieved, but shadowing effects occur due to container contours preventing reliable sterilization
Solution Approach 1:
The patent applies plasma sterilization to the preform before blow molding instead of after container formation. This preliminary action allows the plasma to access all surfaces of the preform uniformly without the shadowing effects that occur when plasma is applied to finished containers with complex contours and recesses.
2Reliability
If a high-voltage electrode is positioned inside the preform for plasma generation, then uniform plasma distribution is achieved, but device complexity increases
Solution Approach 1:
The high-voltage electrode is inserted through the transport mandrel into the preform, utilizing the existing mandrel structure as a guide and support. This nesting approach allows the electrode to reach the preform interior without requiring a completely separate complex delivery mechanism, thereby reducing overall device complexity while achieving uniform plasma distribution.
3Productivity
If sterilization is performed before blow molding, then production time is reduced, but the preform must be handled and transported through additional processing stations
Solution Approach 1:
The plasma sterilization unit is integrated into the existing transport mandrel system that moves preforms through the blow molding machine. The electrode is inserted through the mandrel, and the sterilization occurs in-place during the normal preform transport, merging the sterilization function with the existing material handling system rather than requiring separate handling steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves reliable and efficient sterilization of preforms and containers with reduced effort, ensuring effective sterilization of both inner and outer surfaces while maintaining low energy consumption and uniform plasma distribution.
Implementation Method 1
the sterilization is carried out by using a plasma
Data Source
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AI summary
The method and the device serve for the sterilization of preforms which are made of a thermoplastic material and which are provided for the production of blow-moulded containers. The sterilization is carried out using a plasma. A sterilizing means is for this purpose provided with a plasma generator. The sterilizing means, in the area of a device for the blow moulding of containers, can in particular be arranged along a transport path of the preforms.