Magnetic Rotor Cartridge Locking Against MRI Setting Drift
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Solution Overview
Problem
Existing implantable fluid flow control devices, such as those used in hydrocephalus treatment, are susceptible to inadvertent setting changes due to strong external magnetic fields, like those encountered in MRI procedures, and suffer from decreased magnetic coupling with external adjustment tools, making intentional adjustments challenging.
Innovation Solution
The design incorporates a rotor assembly with magnets having vertical or angled polarity to resist alignment with external magnetic fields and a cartridge assembly with mechanical stops, such as grooves and splines, to prevent inadvertent rotation, while maintaining strong magnetic coupling with external tools for deliberate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotor assembly with horizontally aligned magnets is used, then the device can be adjusted by external magnetic fields, but the device becomes susceptible to inadvertent setting changes in strong magnetic fields like MRI
Solution Approach 1:
The patent applies asymmetry by changing the magnet configuration from horizontal alignment to vertical alignment. This asymmetric reorientation creates a magnetic field configuration that is insensitive to external horizontal magnetic fields (such as those in MRI machines), thereby preventing inadvertent rotor rotation while preserving the ability to adjust the device using a specialized adjustment tool that applies magnetic force in the appropriate direction.
2Reliability
If magnets with vertical polarity are used, then resistance to external magnetic field interference is improved, but magnetic coupling with external adjustment tools may be weakened
Solution Approach 1:
The patent introduces a specialized adjustment tool as an intermediary device that bridges the gap between the vertically polarized magnets and the desired adjustment function. This tool is specifically designed with magnetic properties and geometric features that enable it to effectively couple with the vertical magnets, transmit rotational force, and overcome any coupling weaknesses, thereby maintaining ease of operation while preserving the benefits of vertical magnet orientation.
3Reliability
If mechanical stops are added to prevent inadvertent rotation, then device stability is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by designing the rotor assembly to be inherently stable through vertical magnet orientation, which passively resists external magnetic field interference without requiring active mechanical restraint systems. The vertical polarity configuration itself provides the stability function, eliminating the need for additional mechanical stops, locks, or restraining mechanisms that would increase device complexity.
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 solution effectively minimizes unintended adjustments of the fluid flow control device in strong magnetic fields and enhances the magnetic coupling with external tools, allowing for precise and reliable pressure setting adjustments.
Implementation Method 1
The magnetic rotor or rotor assembly may magnetically couple with an external magnetic adjustment tool or tools
Implementation Method 2
A rotor or rotor assembly having a single magnet or dual magnets with aligned horizontal polarity may cause the magnetic rotor to be susceptible to movement or inadvertent setting adjustment by a strong nearby magnetic field
Data Source
Figure 1~3
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Figure 5~6A
AI summary
A cartridge assembly for an adjustable fluid flow control device comprising a cartridge housing (41) comprising a stair-step array and a plurality of stops (632) each projecting from an inner wall of the cartridge; a rotor assembly (100) comprising a magnet mounted in a base and a protrusion projecting from a lower surface of the base; wherein the rotor assembly is configured for placement at least partially within the cartridge housing and the protrusion is configured to be located between pairs of adjacent ones of said plurality of stops when resting on each step of the stair-step array, the protrusion configured to rest on a first step of the stair step array between two stops of the plurality of stops such that the rotor assembly is in a first, locked position in the cartridge housing.