Bellows Servomechanism Scraper Force Control
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Solution Overview
Problem
Existing filtering devices for plastic melts face challenges in maintaining consistent cleaning efficiency due to wear on scraper members and pressure variations within the filter chamber, leading to inadequate removal of dirt particles.
Innovation Solution
The implementation of a servomechanism using a bellows cylinder with a deformable bellows element and a pressure chamber of variable volume, allowing for controlled and uniform pressing force on the scraper members, independent of wear and pressure fluctuations, and minimizing pressure losses through sealless adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scraper members are pressed continuously onto the filter element surface to ensure reliable contact, then cleaning effectiveness is improved, but the pressing force decreases over time due to wear and temperature effects
Solution Approach 1:
The patent implements a dynamic pressing force mechanism where the servomechanism continuously adjusts the pressing force applied to scraper members based on real-time feedback from force sensors. This allows the system to maintain optimal cleaning pressure despite wear, temperature changes, and variations in filter element surface conditions, resolving the contradiction between initial cleaning effectiveness and long-term durability
Solution Approach 2:
The patent incorporates a feedback control system using force sensors that monitor the actual pressing force applied to the filter element surface. This feedback is fed to the servomechanism which automatically adjusts the scraper member positioning to maintain the desired pressing force, ensuring consistent cleaning performance throughout the service life of the scraper members
2Productivity
If high pressing force is applied to remove dirt particles, then cleaning efficiency is improved, but pressure losses in the filter chamber increase
Solution Approach 1:
The patent applies pressing force locally and selectively at specific contact points between scraper members and the filter element surface, rather than applying uniform high pressure across the entire filter chamber. This localized approach maintains high cleaning efficiency at the scraper-filter interface while minimizing overall pressure losses in the plastic melt flow through the filter chamber
3Device complexity
If spring-based biasing is used to press scraper members onto the filter element, then simple construction is achieved, but consistent pressing force cannot be maintained due to wear and temperature effects
Solution Approach 1:
The patent replaces the passive spring-based mechanical biasing system with an active servomechanism controlled by force sensors and a control unit. This substitution eliminates the limitations of springs (wear, temperature sensitivity, non-adjustability) while maintaining relatively simple construction through the use of standard servo control technology and modular sensor integration
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
Ensures reliable and consistent removal of dirt particles from plastic melts by maintaining uniform pressing force and compensating for pressure variations, reducing wear-related issues and pressure losses.
Implementation Method 1
a deformable bellows element (52) which is sealingly connected to the foot section (54) and to the head section (56), and a pressure chamber of variable volume (20) which is adapted to move the head section (56) relative to the foot section (54) depending on the pressure prevailing in the pressure chamber (20)
Data Source
AI summary
A filtering device for removing dirt particles and contaminants from a plastic melt is disclosed. The filtering device includes a housing having a filter chamber, an inlet for feeding plastic melt, an outlet for channeling plastic melt out, and a dirt outlet for discharging dirt particles from the housing. The filtering device also includes a filter element arranged in the filter chamber to retain any dirt particles contained in the stream of melt, and a cleaning unit for cleaning the filter element of dirt particles retained by means of the filter element. The cleaning unit having a cleaning head with a scraper member for detaching dirt particles from the filter element. The scraper member is coupled to a servomechanism to press the scraper member onto the surface of the filter element. The servomechanism has at least one bellows cylinder including a foot section, a head section, a deformable bellows element, and a pressure chamber of variable volume.