Piston Assembly Sheath Tube for Pipetting Magnet Stability
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Solution Overview
Problem
Permanent-magnet piston subassemblies in pipetting apparatuses face challenges due to deformations caused by hollow-cylindrical magnets with alternating polarizations, leading to reduced magnetic field strength and accuracy in position detection.
Innovation Solution
A permanent-magnet piston subassembly using a sheath tube to house the magnets, which increases geometrical accuracy and stability by distributing mass radially, allowing for solid magnets without central holes, and incorporating soft-magnetic separating bodies to enhance magnetic field gradients for precise position sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If hollow-cylindrical permanent magnets with alternating polarizations are used, then the radial gap between magnets and external magnetic field can be minimized, but the magnetic field strength is reduced and deformations occur
Solution Approach 1:
A non-magnetic sheath tube is introduced as an intermediary component to house the permanent-magnet arrangements. The sheath tube provides structural support and maintains the cylindrical outer contour, preventing deformations while allowing the magnets to be arranged with alternating polarizations. This mediator enables the system to maintain both the minimal radial gap configuration and the required magnetic field strength.
Solution Approach 2:
The piston subassembly combines different materials with complementary properties: permanent magnets (for magnetic field generation), non-magnetic sheath tube material (for structural support and shape maintenance), and potentially soft-magnetic separating bodies (for field gradient enhancement). This composite structure resolves the contradiction by assigning different functions to different materials.
2Shape
If hollow-cylindrical permanent magnets are used, then radial outer side formation is enabled, but deformations of the piston subassembly occur due to forces on the carrier rod
Solution Approach 1:
The non-magnetic sheath tube acts as a mediator that absorbs and distributes the forces generated by the alternating magnet polarizations. Instead of these forces acting on the carrier rod and causing deformations, the sheath tube provides a rigid framework that maintains the cylindrical contour while the magnets generate the required magnetic field.
Solution Approach 2:
The piston subassembly is segmented into functionally distinct components: the permanent-magnet arrangements (for magnetic field generation), the non-magnetic sheath tube (for structural support), and soft-magnetic separating bodies (for field gradient enhancement). This segmentation allows each component to optimize its specific function without compromising the overall system stability.
3Measurement precision
If alternating polarizations are used for position detection, then detection accuracy is enhanced, but considerable forces are exerted on the carrier rod causing deformations
Solution Approach 1:
The non-magnetic sheath tube serves as a mediator that decouples the magnetic field generation function from the structural support function. The alternating magnet polarizations can be maintained for high-position detection accuracy while the sheath tube absorbs the resulting forces, preventing carrier rod deformations.
Solution Approach 2:
The invention changes the structural parameter of the piston subassembly by introducing a sheath tube, which fundamentally alters how forces are distributed. This parameter change enables the system to maintain the alternating magnet configuration for accurate position detection while eliminating the harmful forces on the carrier rod through the sheath tube's structural support.
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
The solution improves the accuracy and stability of the magnetic field-driven piston subassembly, maintaining effective magnetic coupling while minimizing deformations and enhancing positional detection precision.
Implementation Method 1
arranged one behind another along the piston axis with alternatingly opposite polarization directions in such a way that for each two permanent-magnet arrangements directly successive along the piston axis, it is the case that magnetic poles located closest to one another along the piston axis, of different successive permanent-magnetic arrangements, are like poles
Implementation Method 2
incorporating soft-magnetic separating bodies to enhance magnetic field gradients for precise position sensing
Implementation Method 3
an external magnetic field driving the piston arrangement to move
Data Source
AI summary
A permanent-magnet piston subassembly (10) for a pipetting apparatus, the piston subassembly (10) extending along a piston axis (K) and comprising a plurality of permanent-magnet arrangements (14a to 14m) that are arranged one behind another along the piston axis (K) with alternatingly opposite polarization directions in such a way that for each two permanent-magnet arrangements (14i, 14j) directly successive along the piston axis, it is the case that magnetic poles located closest to one another along the piston axis (K), of different successive permanent-magnetic arrangements (14a to 14m), are like poles, is characterized in that the piston subassembly (10) encompasses a sheath tube (12), extending along the piston axis (K) constituting a tube axis (H), in which the plurality of permanent-magnet arrangements (14a to 14m) are received.