Surgical Knife Bar Articulation Stress Reduction
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Solution Overview
Problem
Surgical instruments used in endoscopic procedures face challenges in articulating the end effector without damaging the knife blade, which experiences bending moments and shear forces during articulation, leading to degradation.
Innovation Solution
A surgical loading unit with a flexible knife bar and an elongate guide member, where the knife bar bends and shifts in a direction opposite to the articulation, maintaining a larger radius of curvature to reduce stress and extend the knife blade's life, combined with an articulation assembly that includes a drive nut, drive screw, and articulation link to facilitate varied orientations of the end effector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the end effector is articulated to improve access to tissue, then the articulation angle and versatility are improved, but the knife blade experiences bending moments and shear forces that degrade it over time
Solution Approach 1:
The knife assembly is segmented into a rigid proximal portion (within the elongate body) and a flexible distal portion (knife bar within the end effector). This segmentation allows the proximal rigid guide member to maintain structural integrity while the distal flexible knife bar accommodates articulation movements, resolving the contradiction between articulation capability and blade durability.
Solution Approach 2:
The knife bar's flexibility parameter is specifically optimized to allow bending during articulation while maintaining cutting functionality. By changing the material or structural parameters of the knife bar to be flexible rather than rigid, the system enables articulation without subjecting the entire knife assembly to damaging bending moments and shear forces.
2Manufacturing precision
If a rigid knife assembly is used to maintain cutting precision, then the cutting accuracy is improved, but the knife blade cannot accommodate articulation movements without damage
Solution Approach 1:
Different portions of the knife assembly have different mechanical properties: the proximal guide member is rigid to maintain cutting precision and structural stability, while the distal knife bar is flexible to accommodate articulation. This local differentiation of quality allows the system to simultaneously achieve cutting accuracy and articulation capability.
Solution Approach 2:
The knife assembly transitions from a static rigid structure to a dynamic system where the distal knife bar can flex and adapt during articulation. This dynamic flexibility allows the knife to maintain cutting precision when needed while accommodating articulation movements that would otherwise damage a purely rigid assembly.
3Adaptability or versatility
If the knife bar is made flexible to accommodate articulation, then the articulation capability is improved, but the structural stability and cutting precision may be compromised
Solution Approach 1:
The knife assembly is divided into rigid and flexible segments, with the rigid proximal guide member providing structural stability and the flexible distal knife bar providing articulation capability. This segmentation resolves the contradiction by assigning different functional requirements to different portions of the assembly.
Solution Approach 2:
The flexible knife bar acts as an intermediary between the rigid proximal guide member and the articulating end effector. It mediates the transmission of motion while isolating the rigid structural components from the stresses of articulation, thereby maintaining both flexibility and stability.
Data Source
AI summary
A surgical loading unit includes an elongate body, an end effector pivotably coupled to the elongate body, and a flexible knife bar extending through a distal portion of the elongate body and a proximal portion of the end effector. Articulation of the end effector relative to the elongate body in a first direction moves a first segment of the knife bar in the first direction and moves a second segment of the knife bar in a second direction, opposite the first direction.