Articulating Surgical Knife Drive Rod Attachment With Retention Fins
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrosurgical forceps face challenges in securing a knife drive rod to a knife blade effectively, particularly in articulating mechanisms where the drive rod needs to be flexible for articulation while strong enough to advance and retract the knife through tissue, and materials with dissimilar properties often result in weak welds.
Innovation Solution
The knife assembly incorporates a retention mechanism, such as a cap or enlarged area, to secure the knife drive rod to the knife, with additional mechanical engagements like fins, tubes, and welding to enhance stability and strength, ensuring a strong connection between dissimilar materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the knife drive rod is made flexible to allow articulation of the jaw members, then the articulation capability is improved, but the strength to advance and retract the knife blade through tissue deteriorates
Solution Approach 1:
The knife drive rod is constructed as a composite structure combining a flexible Nitinol core with a stainless steel outer sheath. The Nitinol provides flexibility and articulation capability through its shape memory properties, while the stainless steel sheath provides the necessary strength and rigidity to advance and retract the knife blade through tissue. This composite construction resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
Different portions of the knife drive rod have different material properties optimized for their specific functions. The core portion is made of flexible Nitinol for articulation, while the outer sheath is made of strong stainless steel for cutting force transmission. This local differentiation of material quality allows each region to perform its optimal function without compromising the other.
2Adaptability or versatility
If dissimilar materials like Nitinol and stainless steel are used for the drive rod and knife, then the flexibility and strength requirements are met, but the weld strength deteriorates
Solution Approach 1:
A transition portion or intermediate structure is introduced between the Nitinol drive rod and the stainless steel knife to facilitate the join. This intermediary element acts as a mediator that can be mechanically or chemically bonded to both dissimilar materials, creating a strong connection without direct welding between the incompatible materials. The transition portion may be designed as a separate component or an integrated structure that bridges the two materials.
Solution Approach 2:
The welding process is replaced or supplemented with alternative joining methods such as mechanical fastening, friction fit, or diffusion bonding that are more suitable for dissimilar materials. This substitution eliminates the weak weld joints that result from direct welding of Nitinol and stainless steel, while still achieving the necessary connection strength.
3Device complexity
If a simple attachment method is used for the drive rod to knife, then the device complexity is reduced, but the reliability of the attachment deteriorates
Solution Approach 1:
The attachment structure is segmented into multiple functional elements including engagement features on the knife, corresponding receptacles on the drive rod, and retention mechanisms. This segmentation allows each element to perform a specific function: engagement features provide initial connection, retention mechanisms prevent disengagement, and the distributed structure increases overall reliability without requiring a single complex attachment system.
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 provides a robust and reliable attachment of the knife drive rod to the knife, preventing mechanical failure and ensuring smooth operation during articulation and tissue cutting, even with materials like Nitinol and stainless steel.
Implementation Method 1
a retention mechanism operably disposed at a distal end of the knife drive rod and configured to secure the knife drive rod in engagement between the fins
Implementation Method 2
a weld operably engages the tube to the knife. In aspects according to the present disclosure, the knife and the tube are made from similar metals to increase the strength of the weld
Data Source
AI summary
A knife assembly for use with a surgical instrument includes a knife having proximal and distal ends, the proximal end including an aperture defined therein having a series of spaced apart fins extending thereacross. A knife drive rod is included and is configured to operably engage the fins to secure the knife drive rod to the knife. A retention mechanism is operably disposed at a distal end of the knife drive rod and is configured to secure the knife drive rod in engagement between the fins.