Radial Compression Machine Using String-Mediated Die Actuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing radial compression mechanisms for medical devices like stents and prosthetic heart valves are limited by low mechanical advantage and radial force capability due to the use of small pins, ball bearings, and cam-following mechanisms, which restrict the application of adequate radial force and pressure, especially for large-diameter devices.
Innovation Solution
A radial compression mechanism utilizing a string wrapped around a circular array of compression dies, where the string is coupled to a tension mechanism, allowing for increased mechanical advantage by distributing force evenly across the dies' outer surfaces, and incorporating springs for back-tension and guided motion to achieve higher radial forces without damaging the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a camming plate with pin/slot engagement is used to drive radially-movable dies, then the mechanical advantage is improved over hinged dies, but the radial force capability is still limited by the small contact area between slots and pins
Solution Approach 1:
A string wrapped around the outer perimeter of the compression dies serves as an intermediary force transmission element. The string distributes radial compressive forces evenly across the outer surfaces of multiple dies simultaneously, avoiding the localized stress concentration at pin/slot contact points. This allows high radial forces to be applied without being limited by small contact areas.
2Ease of manufacture
If hinged dies with small pins are used to transmit forces, then the device construction is simple and low-cost, but the concentrated mechanical stress reduces the radial force capability
Solution Approach 1:
The string acts as a mediator that distributes force across the entire outer perimeter of the compression dies rather than through concentrated pin connections. This maintains the simplicity of the die structure while dramatically increasing the radial force capability by eliminating stress concentration at small pin contact points.
3Device complexity
If the handle moves through a small distance of about 45mm during crimping, then the device structure is compact, but the mechanical advantage is very low resulting in inadequate radial force
Solution Approach 1:
The force application is moved from linear handle motion to circumferential string wrapping around the dies. By wrapping the string multiple times around the outer perimeter of the compression dies, the mechanical advantage is dramatically increased as each wrap multiplies the force transmission efficiency, allowing compact structure with high mechanical advantage.
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 mechanism provides higher radial forces and pressure, enabling more efficient compression of large medical devices, such as stents and prosthetic heart valves, with improved mechanical advantage and reduced risk of damage to the device or mechanism.
Implementation Method 1
a string wrapped around a plurality of compression dies to move the dies inward... the string is coupled to a string tension mechanism that enables a user to applied a desired tension to the string
Implementation Method 2
incorporating springs for back-tension and guided motion
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A radial compression mechanism utilizes a string wrapped around a plurality of compression dies to move the dies inward and close a centra! cylindrical cavity defined by the working surfaces of the dies. The string may be coupled to a string tension mechanism that enables a user to applied a desired tension to the string and thereby compress an article within the centra! cylindrical cavity. The compression dies may be coupled to a base and move along die-guiding slots from an open position fo a closed position. A spring may be configured to force the compression dies open and provide some back-tension to the string. The string may extend around a pul!y on an opposing side of the compression mechanism and both ends of the string may be coupled to the string tension mechanism.