Blood Pump Impeller Support Using Dual Bearings for Axial Load Relief
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Solution Overview
Problem
Blood pumps experience increased mechanical wear in contact-type bearings due to magnetic coupling between the impeller and the electric motor, leading to high loads on small bearing surfaces, which can cause excessive wear and potential failure.
Innovation Solution
The blood pump design incorporates a first bearing with an enlarged projection and a corresponding cavity to share axial loads, reducing the mechanical stress on a second bearing by supporting the impeller in the same axial direction, combined with magnetic or spring support to further alleviate load on the second bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact-type bearings are used to support the impeller, then the impeller can be reliably supported, but mechanical wear increases due to high contact pressure from magnetic coupling
Solution Approach 1:
The patent divides the bearing support function into multiple segments: a first contact-type bearing and a second magnetic bearing are used in sequence along the axial direction. This segmentation allows the contact-type bearing to handle radial loads while the magnetic bearing supports axial loads, reducing contact pressure and mechanical wear on any single bearing surface.
Solution Approach 2:
The patent replaces part of the mechanical bearing system with a magnetic bearing. The magnetic bearing uses magnetic fields instead of mechanical contact to support the impeller, eliminating friction and mechanical wear while maintaining reliable support. This substitution directly addresses the mechanical wear problem caused by high contact pressure in purely mechanical bearing systems.
2Power
If magnetic coupling is used to drive the impeller, then efficient power transmission is achieved, but contact pressure on bearing surfaces increases leading to excessive wear
Solution Approach 1:
The bearing support function is segmented into radial support (first contact-type bearing) and axial support (second magnetic bearing). This segmentation isolates the magnetic coupling's axial attraction force to be handled by the magnetic bearing, preventing it from increasing contact pressure on the contact-type bearing's radial surface, thus maintaining power transmission efficiency while reducing wear.
Solution Approach 2:
The magnetic bearing acts as an intermediary between the magnetic coupling and the contact-type bearing. It absorbs the axial forces generated by magnetic coupling, serving as a buffer that prevents these forces from being transmitted to the contact-type bearing, thereby reducing mechanical wear while allowing efficient power transmission to continue.
3Device complexity
If a single bearing is used to support the impeller, then the structure is simple, but the bearing surface area is small leading to high contact pressure and wear
Solution Approach 1:
The bearing support system is segmented into two bearings arranged in sequence along the axial direction. This segmentation increases the total bearing surface area available to support the impeller, distributing the loads and reducing contact pressure on each bearing surface, thereby reducing mechanical wear without significantly complicating the overall structure.
Solution Approach 2:
The patent transitions from a single-point or single-surface bearing support to a distributed support system along the axial dimension. By arranging bearings at different axial positions, the load is distributed over a longer axial length, effectively increasing the bearing surface area and reducing contact pressure, while maintaining relatively simple structural implementation.
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 design reduces mechanical wear and load on the bearings, allowing for stable operation and reduced vibration, particularly during critical speeds, thereby enhancing the durability and efficiency of the blood pump.
Implementation Method 1
In non-contact bearings the bearing surfaces do not contact each other, e.g. in magnetic bearings, in which the bearing surface 'levitate' due to repelling magnetic forces.
Implementation Method 2
Mechanical wear may be increased by a magnetic coupling between the electric motor of the pump and the impeller for driving the impeller.
Data Source
AI summary
A blood pump comprises a pump casing having a blood flow inlet and a blood flow outlet connected by a passage, and an impeller arranged in said pump casing so as to be rotatable about an axis of rotation. The impeller is provided with blades sized and shaped for conveying blood along the passage from the blood flow inlet to the blood flow outlet, and is rotatably supported in the pump casing by a first bearing at a first axial end of the impeller and a second bearing axially spaced apart from the first bearing. The first bearing comprises a projection extending along the axis of rotation and connected to one of the impeller and the pump casing and a cavity in the other one of the impeller and the pump casing, the projection comprising an enlarged portion that engages the cavity such that the first bearing and the second bearing are arranged to bear axial forces in the same axial direction.