Surgical Needle Swage Tool Two-Hit Process
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Solution Overview
Problem
Existing methods for attaching surgical needles to sutures using swaging processes face challenges with harder alloys like 4310 SS, nickel-titanium SS, and 420 SS, as they tend to crack or break due to material malleability and elasticity issues, leading to loss of attachment over time.
Innovation Solution
A two-hit swaging process using a first and second die set, where the first compression stroke compresses the top of the needle barrel while restraining the bottom and sides, and the second stroke compresses the bottom while restraining the sides, to securely attach the suture without deforming the needle barrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple hit swaging is used to achieve good suture attachment, then attachment strength is improved, but stress accumulation in the needle barrel leads to cracking and loss of attachment
Solution Approach 1:
The swaging process is divided into multiple sequential compression strokes (first stroke, second stroke, and optional third stroke) rather than applying all compression in a single hit. Each stroke compresses the needle barrel a controlled amount, with intermediate relief periods that allow stress to dissipate before the next compression, preventing cumulative stress accumulation that leads to cracking while still achieving the required attachment strength.
Solution Approach 2:
The swaging process employs periodic compression strokes separated by intervals where no compression is applied. This periodic action allows the needle barrel material to relax between compressions, preventing continuous stress accumulation. The process alternates between compression phases (applying force) and relief phases (allowing stress dissipation), maintaining attachment strength while preventing material failure.
2Strength
If harder alloys are used for the needle barrel, then needle strength is improved, but the material becomes more prone to cracking under swaging stress
Solution Approach 1:
The process parameters for swaging are specifically adjusted when using harder alloys. The compression force, compression distance, and number of strokes are optimized based on the material properties of the alloy being used. Harder alloys receive more gradual, distributed compression over multiple smaller strokes rather than single large compressions, allowing the material to deform plastically without exceeding its fracture toughness and causing cracks.
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 method enhances the attachment strength and reduces stress on the needle barrel, minimizing the risk of cracking and breakage, while maintaining the required pull-out force, even with advanced alloys.
Implementation Method 1
moving one or both of the first and second dies toward the other during a first compression stroke causes the second die to compress the top of the needle barrel so as to compress the suture against the inner surfaces of the bore
Implementation Method 2
The groove of the first die is at least partially defined by a curved surface sized and shaped so as to protect the bottom and sides of the needle barrel from becoming substantially deformed during the compression of the top of the needle barrel
Data Source
Figure 1~2
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Figure 7~10
AI summary
in a method of attaching a suture (84) to a needle barrel (82), a first compression stroke compresses the radially-defined top (86) of the barrel (82) against a suture (84) in the bore (96) of the barrel (82) while restraining the bottom (88) and sides (90, 92) of the barrel (82) against deformation A second compression stroke compresses the bottom (88) of the barrel (82) against the suture (84) while restraining the sides (90 92) against deformation In another method, the top (86) and bottom (88) are compressed concurrently while the sides (90, 92) are restrained against deformation An apparatus for attaching a suture (84) to a needle barrel (82) includes two die sets (22, 48) each including a die (24, 52) with a groove (40, 70) therein In one die set (22), the groove (40) protects the bottom (88) and sides (90, 92) of the barrel (82) from deformation while the top (86) is compressed In the other die set (48), the groove (70) protects the sides (90, 92) of the barrel (82) from deformation while the bottom (88) is compressed.