Rolling Stent Retaining Sheath with Cold-Drawn Plastic
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Solution Overview
Problem
Existing stent delivery devices face challenges in efficiently retracting the retaining sheath without applying excessive axial forces, which can lead to stent device damage and incomplete expansion, particularly when using rolling mechanisms that require high pulling forces or leave the sheath caught between the stent and the bodily lumen.
Innovation Solution
A delivery device with a retaining sheath made of cold-drawn plastic, allowing for a reduced profile and easier rolling retraction, combined with a pull line that extends axially along the stent device to facilitate the rolling mechanism, reducing the pulling force required for sheath retraction and enabling a single-walled retaining sheath design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rolling mechanism is used to retract the retaining sheath, then the sheath can be removed from the body, but excessive axial forces are applied to the stent device during retraction
Solution Approach 1:
The retaining sheath is divided into two functional segments: a radially inner first portion and a radially outer second portion. The first portion remains in place while the second portion is retracted, segmenting the retraction function to reduce forces on the stent while maintaining reliable sheath removal.
Solution Approach 2:
The solution transitions from pure axial retraction to a combination of radial and axial movement. The outer portion is pulled axially while the fold portion rolls, creating a dimensional change that reduces the pulling force required and minimizes axial forces on the stent device.
2Length of moving object
If the retaining sheath is made thinner to reduce profile, then the delivery device size is reduced, but the sheath becomes more difficult to retract
Solution Approach 1:
The sheath is segmented into inner and outer portions with different thickness characteristics. The outer portion can be thinner while the inner portion provides structural support, enabling both reduced profile and easy retraction of the outer portion.
Solution Approach 2:
By introducing radial dimensionality with the fold portion mechanism, the sheath structure transitions from a simple thin wall to a multi-layered configuration that is easier to retract while maintaining a reduced overall profile.
3Length of moving object
If a single-walled retaining sheath is used, then the profile is reduced, but the sheath may become caught between the stent and the bodily lumen
Solution Approach 1:
The single-walled sheath is functionally segmented into an inner first portion and an outer second portion. This segmentation allows the outer portion to be retracted separately, preventing entrapment while maintaining the reduced profile benefits of a thin-walled construction.
Solution Approach 2:
The outer portion is preliminarily configured to be retracted before complete stent expansion occurs. This preliminary retraction action prevents the sheath from becoming caught between the expanding stent and the bodily lumen.
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 solution enables reliable, predictable, and low-force retraction of the retaining sheath, minimizing stent device damage and allowing for complete expansion, while maintaining a reduced profile in the delivery device region, thus improving the deployment efficiency and reducing the risk of sheath entrapment.
Implementation Method 1
the retaining sheath is made of a cold drawn plastic at least along the path of travel of the fold portion in retracting the retaining sheath from over the stent device
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
A delivery device (1) for delivering a stent device (3) that is expandable from a radially reduced, delivery configuration to a radially expanded, deployed configuration. A retaining sheath (4) is disposed over the stent device for maintaining the stent device in the delivery configuration. A pull line (13) to be pulled upon is provided to retract the retaining sheath in a rolling manner such that the retaining sheath is folded back on itself to provide a radially inner sheath (7) of the retaining sheath, a radially outer sheath (8) of the retaining sheath and a fold portion (9) therebetween. The pull line is moveable by pulling thereon to move the outer sheath over the inner sheath and thus to move the fold portion axially relative to the stent device to retract the retaining sheath from over the stent device to release the stent device for expansion to the deployed configuration. The pull line extends axially along the stent device and joins the retaining sheath substantially at or beyond an axial end of the stent device in a pre-retracted configuration of the retaining sheath. The retaining sheath is made of a cold drawn plastic at least along the path of travel of the fold portion in retracting the retaining sheath from over the stent device.