Electron Beam Emitter Modulation for Uniform Web Sterilization
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Solution Overview
Problem
Electron beam sterilization of packaging materials is compromised when they are advanced in a non-continuous manner, leading to uneven ebeam dose delivery and potential overheating of the emitter's exit window, which can result in vacuum loss and system failure, especially when sterilants like peracetic acid or vaporized hydrogen peroxide come into contact with the electron beam window.
Innovation Solution
A method and apparatus that control the beam energy output from the electron beam emitter by varying current and voltage, using a modulator to maintain a consistent ebeam dose and thermal load on the window, and utilizing exhaust manifolds to prevent sterilant exposure to the irradiation zone, ensuring effective sterilization without damaging the electron beam system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If packaging material is advanced non-continuously through the irradiation zone to accommodate processing steps, then the material can be processed by upstream/downstream machines, but the ebeam dose becomes uneven and portions of material receive larger doses than required
Solution Approach 1:
The electron beam current is dynamically adjusted in real-time based on the web speed. When the web slows or stops during processing operations, the current is reduced proportionally to maintain a constant dose rate, ensuring uniform sterilization despite non-continuous advancement
Solution Approach 2:
A feedback control system continuously monitors web speed and adjusts the electron beam current accordingly. The controller receives speed signals and modifies the beam current to maintain constant dose delivery, preventing both under-dosing and over-dosing of the packaging material
2Reliability
If the ebeam current is increased to maintain dose delivery during slow or stopped web advance, then sterilization effectiveness is maintained, but the exit window overheats and may fail
Solution Approach 1:
The system changes the energy parameters of the electron beam by adjusting current and voltage in a coordinated manner. When web speed decreases, the current is increased to maintain dose rate, but the voltage is simultaneously adjusted to control the thermal load on the exit window, preventing overheating while maintaining sterilization effectiveness
3Reliability
If sterilants like peracetic acid or vaporized hydrogen peroxide are used to sterilize the irradiation zone, then sterilization coverage is improved, but the sterilants can damage the electron beam window and reduce system lifespan
Solution Approach 1:
The harmful sterilants are extracted or removed from the irradiation zone before they can contact and damage the electron beam window. Exhaust manifolds with ports positioned downstream of the web create air currents that sweep sterilants away from the window area, protecting the emitter while maintaining sterilization coverage
Solution Approach 2:
Air flow acts as an intermediary medium that carries sterilants through the irradiation zone without allowing them to reach the electron beam window. The exhaust manifold system creates controlled air currents that mediate between the sterilization need and the protection of sensitive components
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 approach maintains a consistent ebeam dose for effective sterilization of packaging materials while preventing overheating of the emitter's window and minimizing damage from sterilants, thereby extending the emitter's lifespan and ensuring continuous operation.
Implementation Method 1
electron beam (ebeam) emitting apparatus have been used over the years to treat moving webs for various purposes, such as to sterilize a web of packaging material
Implementation Method 2
electrons, after being accelerated, exit the chamber through that window and are directed to the packaging material being treated
Implementation Method 3
the exit window will absorb some amount of the electron energy which results in heating of the foil
Implementation Method 4
controlling, as a function of the advance of the material along the process line, the beam energy output from the emitter and/or the 'transmission factor' of an electron beam modulator
Implementation Method 5
exhaust manifolds to prevent sterilant exposure to the irradiation zone
Data Source
AI summary
A method and apparatus for sterilization of webs and products made therefrom using electron beams (ebeams) is provided. A controller is configured to modulate an ebeam to ensure that a non-continuously moving web is sterilized within a desired range of exposure. During sterilization in place operations, manifolds are configured to operate to ensure that sterilants do not enter an irradiation zone to prevent damage to ebeam emitters.