Shape-Memory Impeller Coupling for Weld-Free Shaft Locking
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Solution Overview
Problem
Current ventricular assist devices face challenges in efficiently pumping blood with minimal hemolysis and maintaining stability during cardiac cycles, particularly in the design of the impeller and coupling elements, which can be weakened by welding and result in inefficiencies.
Innovation Solution
A blood pump design featuring an axial shaft with a coupling element made of shape-memory material, including slits for radial expansion and contraction, and an impeller with a bushing and blades that rotate to pump blood, utilizing a snap-fit mechanism and a radial gap to enhance efficiency and reduce hemolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding is used to join the coupling element to the axial shaft, then the connection strength is improved, but the coupling element and axial shaft are weakened due to heat exposure
Solution Approach 1:
The patent replaces the thermal welding process with a mechanical interference fit system. The coupling element features an inner diameter slightly larger than the axial shaft's outer diameter, creating a press-fit connection that achieves strong mechanical bonding without thermal exposure. This substitution eliminates heat-induced weakening while maintaining connection strength through optimized dimensional tolerances and material properties.
2Stability of the object's composition
If the coupling element is made rigid to maintain stability, then structural stability is improved, but the device complexity increases due to additional coupling mechanisms
Solution Approach 1:
The patent utilizes parameter changes in the shape-memory material's physical state to achieve coupling and stabilization. By controlling temperature-induced phase transitions, the material transforms between austenite (rigid, stable) and martensite (flexible, adaptable) states. This allows the coupling element to provide structural stability when needed while simplifying the overall mechanism by eliminating complex fastening systems—the material's inherent phase-changing properties provide both coupling and stabilization functions.
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 design improves blood pumping efficiency and reduces hemolysis, providing a stable and efficient ventricular assist device that effectively supports cardiac function with minimized risk of tissue damage.
Implementation Method 1
the coupling element includes a first portion, which is disposed around the axial shaft, is made of a shape-memory material, is shaped to define one or more slits that facilitate a radial expansion of the first portion such that the first portion is placeable around the axial shaft, and is shape-set to have an inner diameter that is smaller than an outer diameter of the axial shaft such that, following a placement of the first portion around the axial shaft, the first portion becomes radially contracted around, and thus locked in place with respect to, the axial shaft
Data Source
AI summary
Apparatus and methods are described including an axial shaft and an impeller configured for rotation within a subject's body. A coupling element includes a first portion, which is disposed around the axial shaft, is shaped to define one or more slits that facilitate a radial expansion of the first portion such that the first portion is placeable around the axial shaft, and is shape-set to have an inner diameter that is smaller than a diameter of the axial shaft such that, following placement of the first portion around the axial shaft, the first portion becomes radially contracted around, and thus locked in place with respect to, the axial shaft. A second portion of the coupling element is coupled to a bushing of the impeller. Other applications are also described.