Guide Wire Coil Pitch Variation for Stress Relief
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Solution Overview
Problem
Conventional guide wires with reshaping members experience stress concentration due to differences in bending rigidity between the superelastic core material and the shaping ribbon, leading to impaired functionality, especially in bent blood vessels.
Innovation Solution
A guide wire design with a coil having varying bending rigidity along its length, where the distal end side portion has a higher bending rigidity than the proximal end side portion, achieved through differences in raw-wire pitch or overlapping number, and potentially hardness variations, to alleviate stress concentration at the joint between the wire material and the wire main body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shaping ribbon is secured to the distal end of the core material, then reshaping performance is improved, but stress concentration occurs at the joint portion due to bending rigidity difference
Solution Approach 1:
The coil's pitch is made non-uniform, with the distal end portion having a smaller pitch than the proximal end portion. This creates local variation in bending rigidity along the coil, allowing the distal end to better match the bending characteristics of the shaping ribbon while the proximal end maintains overall structural support, thereby reducing stress concentration at the joint portion
Solution Approach 2:
The guide wire employs a composite structure consisting of a core material (superelastic alloy), a shaping ribbon (plastically deformable material), and a coil (helically wound wire). This multi-material composite design allows each component to contribute its specific properties: the core provides superelasticity, the shaping ribbon enables reshaping, and the coil with varying pitch balances flexibility and stress distribution
2Ease of manufacture
If the coil has uniform pitch, then manufacturing is simplified, but stress concentration increases at the joint portion
Solution Approach 1:
The coil is designed with non-uniform pitch characteristics, where the distal end portion has a smaller pitch than the proximal end portion. This local variation in pitch creates corresponding variation in bending rigidity, allowing the coil to better accommodate the shaping ribbon at the distal end while maintaining manufacturing feasibility through controlled pitch variation
3Adaptability or versatility
If the distal end of the guide wire is shaped to conform to the branch portion, then selectability of blood vessel branches is improved, but the shaping ribbon may bend due to stress concentration
Solution Approach 1:
The coil's non-uniform pitch creates a gradient in bending rigidity along the length of the guide wire, with the distal end having smaller pitch and thus higher local bending rigidity. This local reinforcement prevents the shaping ribbon from bending or deforming during the reshaping process, ensuring structural integrity while maintaining the ability to conform to branch portions
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 design enhances the reliability and operability of the guide wire by preventing bending issues, ensuring safe insertion into blood vessels and maintaining functionality by uniformly distributing stress, thus improving reshaping performance and selectability of blood vessel branches.
Implementation Method 1
alleviate stress concentration at the joint between the wire material and the wire main body
Implementation Method 2
a superelastic core material
Implementation Method 3
bending rigidity of the coil per se of a distal end side portion located at a position corresponding to the extending portion is higher than that of a proximal end side portion
Data Source
AI summary
A guide wire for a catheter is inserted for use into the catheter and has a wire body, a reshapeable shaping ribbon (wire material) mounted such that a part of the base end side of the shaping ribbon is fixed to the front end side (small diameter section) of the wire body and a part of the front end side of the shaping ribbon extends in the direction to the front end of the guide wire from the front end of the wire body, and a helical coil installed so as to cover both the front end side of the wire body and the shaping ribbon. The coil is divided into a first coil and a second coil, and the first coil is divided into a fine pitch section and a rough pitch section. The bending rigidity of the fine pitch section is greater than that of the rough pitch section.