Drive Cable–Hollow Shaft Coupling with Pore-Fed Polymer Bonding
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Solution Overview
Problem
Current ventricular assist devices face challenges in securely coupling drive cables to hollow shafts, which is crucial for efficient mechanical circulatory support, especially in dynamic environments like the heart, where stability and durability are essential.
Innovation Solution
A method involving a drive cable with coiled wires and a hollow shaft, where a molten polymer, such as PEEK, is flowed through coupling tube pores to bond the drive cable to the shaft, with additional reinforcement from tabs and a heat-shrinking process to ensure a strong and continuous lumen connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a molten polymer is flowed through coupling tube pores to bond the drive cable to the shaft, then the strength of the coupling is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
A coupling tube is introduced as an intermediary component between the drive cable and shaft. The coupling tube contains pores that allow molten polymer to flow through and bond the drive cable to the shaft, while the tube itself provides structural support and alignment during the bonding process
Solution Approach 2:
The bonding process utilizes phase transition of the polymer material. The polymer is heated to a molten state to flow through the coupling tube pores and fill gaps between components, then cools and solidifies to form a strong permanent bond between the drive cable and shaft
2Reliability
If tabs are pushed into shaft pores to strengthen the coupling, then the reliability of the connection is improved, but the manufacturing precision requirements increase
Solution Approach 1:
Tabs are pre-formed on the coupling tube before assembly. These tabs are designed with specific geometries that guide their insertion into the shaft pores, ensuring proper alignment and reducing the precision requirements during the final assembly process
Solution Approach 2:
The shaft is designed with pores that receive the tabs. These pores provide mechanical interlocking features that enhance the connection reliability between the coupling tube and shaft, while the porous structure allows for controlled insertion of the tabs
3Strength
If a heat-shrinking process is used to force molten material between coiled wires, then the bonding strength is improved, but the energy consumption increases
Solution Approach 1:
An outer sleeve made of heat-shrinking material is used to force the molten polymer between the coiled wires of the drive cable. The sleeve is heated to expand, allowing it to be positioned, then cooled to shrink and exert radial pressure, forcing the molten material into the required positions without requiring excessive heating energy
Solution Approach 2:
The bonding process utilizes controlled temperature changes. The polymer is heated to a molten state for flow and bonding, then cooled to solidify. The outer sleeve is also heated and cooled to control its expansion and contraction, thereby controlling the pressure applied to force the molten material between the coiled wires
4Manufacturing precision
If the drive cable and shaft are placed over a mandrel to maintain continuous lumen, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
A mandrel is used as a temporary intermediary tool during assembly. The mandrel maintains the correct positioning and alignment of the drive cable and shaft components, ensuring continuous lumen formation, and is removed after the bonding process is complete
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 provides a robust and reliable coupling that maintains a continuous lumen, enhancing the stability and durability of the drive cable-shaft interface, critical for effective mechanical support in ventricular assist devices.
Implementation Method 1
a molten material is flowed between the coiled wires at the drive-cable end via the coupling-tube pores, and into the hollow-shaft end via the coupling-tube pores and shaft pores, such that, upon solidifying, the material bonds the drive cable to the shaft
Implementation Method 2
the material bonds the drive cable to the shaft
Implementation Method 3
heat is applied to the sleeve of the material and to the outer sleeve. The applied heat melts the sleeve of the material, thereby forming the molten material
Implementation Method 4
shrinks the outer sleeve such that the outer sleeve forces the molten material between the coiled wires of the drive cable and into the proximal end of the axial shaft
Data Source
AI summary
Apparatus and methods are described including inserting a drive-cable end of a drive cable, which includes a plurality of coiled wires, and a hollow-shaft end of a hollow shaft, which hollow-shaft end is shaped to define multiple shaft pores, into opposing ends of a coupling tube, which is shaped to define multiple coupling-tube pores. While the drive-cable end and hollow-shaft end are inside the coupling tube, a molten material is flowed between the coiled wires at the drive-cable end via the coupling-tube pores, and into the hollow-shaft end via the coupling-tube pores and shaft pores, such that, upon solidifying, the material bonds the drive cable to the shaft. Other applications are also described.