Segmented Screw Thread Eccentric Pump for Viscous Media Dosing
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Solution Overview
Problem
Conventional eccentric screw pumps face challenges in efficiently conveying and dosing highly viscous media due to high pressure requirements and complex pressure control, especially during start-up, which can lead to pressure drops and cavitation issues.
Innovation Solution
The design incorporates a conveying element with a first and second screw thread, where the first thread acts as a booster for the second, ensuring stable dosing by providing sufficient pre-pressure and minimizing parameter deviations, featuring different materials and configurations to optimize displacement volumes and reduce pressure levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-screw-thread design is used, then the pump structure is simple, but the dosing stability is poor and cavitation occurs during start-up
Solution Approach 1:
The single screw thread is segmented into two distinct screw threads with different pitch values (first pitch and second pitch). The first screw thread provides a first displacement volume while the second screw thread provides a second displacement volume. This segmentation allows the pump to create different pressure levels in different zones, with the first screw thread acting as a booster to prevent cavitation and the second screw thread providing stable dosing, thereby improving reliability without excessive complexity.
2Productivity
If high pressure levels are applied to convey highly viscous media, then the conveying capability is improved, but the pressure drops during start-up and complex pressure control is required
Solution Approach 1:
The first screw thread is designed to act as a booster that creates high pressure in advance during the start-up phase and in the suction zone. By establishing this preliminary high pressure before the fluid enters the second screw thread, the system prevents pressure drops and cavitation without requiring external pressure control systems. This preliminary action eliminates the need for complex pressure control while maintaining conveying capability for highly viscous media.
3Stress or pressure
If a booster pump or pressure tank system is used to achieve high pressure, then the pressure level is sufficient, but the supply system becomes complex
Solution Approach 1:
The pressure-generating function previously requiring separate booster pumps or pressure tank systems is merged directly into the pump's screw thread structure. The first screw thread is integrated as an internal booster mechanism that generates the necessary high pressure within the pump itself. This merging eliminates external pressure control equipment and simplifies the supply system while maintaining sufficient pressure levels for conveying highly viscous media.
4Measurement precision
If the first screw thread acts as a booster for the second screw thread, then the dosing accuracy is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention achieves improved dosing accuracy by changing the pitch parameter of the screw threads. The first screw thread has a first pitch value optimized for pressure generation, while the second screw thread has a second pitch value optimized for precise dosing. By varying this single critical parameter (pitch) while maintaining the basic screw thread geometry, the invention achieves both booster and dosing functions with a manufacturing process that remains relatively simple and compatible with conventional machining methods.
Data Source
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AI summary
The pump has a stator with internal screw threads for providing flow volumes (v1, v2), and a rotor (1) arranged in the stator. The rotor has thread pitches with an external screw thread (2) for providing one flow volume. Another external screw thread (3) for providing another flow volume is connected with the external screw thread along longitudinal direction, where the former flow volume is preferably 1.5 to 3 times higher than the latter flow volume. The internal and external screw threads are formed as integral parts.