Centrifugal Pump Shaft Surface Roughness for Blood Compatibility
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Solution Overview
Problem
Centrifugal pumps used in heart-lung machines during cardiac surgery often cause hemolysis and thrombus formation due to sliding between the shaft and pivot bearing, leading to impeller rotation issues.
Innovation Solution
The centrifugal pump design features shaft ends with surface roughness Ra equal to or less than 0.21 µm and Ry equal to or less than 1.49 µm, supported by pivot bearings, with the option of the shaft being formed from alumina ceramic to prevent hemolysis and thrombus formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pivot bearing is used to support the shaft, then the pump can prevent thrombus formation in the circulation circuit, but hemolysis occurs due to sliding between the shaft and the pivot bearing
Solution Approach 1:
The invention changes the surface roughness parameter of the shaft end to Ra≤0.21μm and Ry≤1.49μm, transforming the sliding interface from a high-roughness state that causes hemolysis to a low-roughness state that protects blood cells while maintaining the pivot bearing configuration
Solution Approach 2:
The invention replaces the conventional metal shaft material with ceramic material (such as alumina), substituting the mechanical properties of the shaft to reduce friction and sliding damage to blood cells while maintaining the pivot bearing support system
2Device complexity
If a pivot bearing is used to support the shaft, then the pump structure is simple and reliable, but a thrombus is likely to be formed on the sliding surface between the shaft and the pivot bearing
Solution Approach 1:
The invention changes the surface roughness parameter of the shaft end to Ra≤0.21μm and Ry≤1.49μm, preventing thrombus formation on the sliding surface while maintaining the simple pivot bearing structure without requiring complex modifications to the bearing configuration
3Object-affected harmful factors
If the shaft surface is smooth, then hemolysis is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The invention replaces conventional metal shaft material with ceramic material (such as alumina), which inherently provides a smooth surface that meets the Ra≤0.21μm and Ry≤1.49μm requirements while the material substitution simplifies the manufacturing process compared to achieving such fine surface finish on traditional metals
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 configuration effectively prevents hemolysis and thrombus formation, enhancing the prevention of blood damage and pump efficiency by controlling surface roughness and material selection.
Implementation Method 1
bearings that respectively and pivotally support shaft ends provided on both sides of the shaft in an axial direction
Implementation Method 2
a centrifugal pump which delivers liquid such as blood and the like... a centrifugal pump which delivers blood by utilizing centrifugal force occurring due to rotations of an impeller
Data Source
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AI summary
A centrifugal pump (10) includes a housing (26), an impeller (28) that is rotatably disposed inside the housing (26), a shaft (62) that is provided at a center in a radial direction of the impeller (28), and bearings (70) that respectively and pivotally support shaft ends (66) provided on both sides of the shaft (62) in an axial direction. At least one of the shaft ends (66) has surface roughness Ra equal to or less than 0.21 µm or surface roughness Ry equal to or less than 1.49 µm.