Surgical Instrument Wrist Assembly With Rocking Hinge Articulation
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Solution Overview
Problem
Conventional surgical instruments face challenges in being both compact and maneuverable, often leading to tissue pinching and reduced efficiency due to limitations in hinge design, which compromises the internal bend radius and increases steering input forces.
Innovation Solution
A wrist assembly with a rocking hinge mechanism that reduces the rolling radius without shortening the link length, preserving the internal bend radius, thereby enhancing maneuverability and reducing tissue pinching while maintaining drive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rolling radius of the wrist assembly is reduced to make the instrument more compact, then the instrument size is reduced, but the internal bend radius is also reduced which increases tissue pinching and shear wear
Solution Approach 1:
The wrist assembly is divided into multiple links (first link, second link, third link) connected by rocking hinges. This segmentation allows each link to have a reduced rolling radius while the cumulative effect of multiple links maintains the overall internal bend radius, resolving the contradiction between compact size and reduced tissue damage.
Solution Approach 2:
The rocking hinge mechanism introduces an additional degree of freedom by allowing the pivot point to rock within a curved guide path rather than rotating around a fixed center. This dimensional change enables the mechanism to achieve the same articulation range with smaller rolling radii, reducing tissue pinching while maintaining instrument flexibility.
2Length of moving object
If the link length is reduced to make the wrist assembly more compact, then the instrument is easier to maneuver, but the internal bend radius is reduced which increases steering input forces
Solution Approach 1:
The rocking hinge creates a dynamic pivot point that moves along a curved guide path during articulation, rather than rotating around a fixed center. This dynamic behavior allows shorter links to generate the same moment arm effect as longer links, reducing steering input forces while maintaining compact dimensions.
Solution Approach 2:
The mechanism changes the geometric parameters of the hinge joint by introducing a curved guide path for the pivot point. This parameter change allows the system to achieve equivalent mechanical advantage with shorter link lengths, reducing both instrument size and required steering forces.
3Device complexity
If a fixed hinge design is used, then the structure is simpler, but tissue can be pinched between the pivotable links during articulation
Solution Approach 1:
A curved guide path acts as an intermediary element between the two links, constraining the pivot point to move along a predetermined arc. This intermediary structure prevents the links from converging and pinching tissue, while adding minimal complexity to the overall hinge design.
Solution Approach 2:
The curved guide path pre-defines the motion trajectory of the pivot point, preventing tissue pinching before it can occur. By establishing the correct geometric constraints in advance, the design eliminates the harmful effect without requiring complex active control mechanisms.
Data Source
AI summary
The present disclosure provides a surgical instrument, such as a tissue sealing instrument, with an elongate shaft and an end effector movably coupled to the shaft with a joint or wrist assembly. The wrist assembly includes a first outer link, a second outer link, and an inner link. The first outer link is connected to the elongated shaft and movably coupled to the second outer link by the inner link. The inner link includes a pair of posts, and the first and second outer links each include a recess configured to receive a respective one of the pair of posts. The posts and recesses defining a rocking hinge, which permits the wrist assembly to accommodate a reduction in the size of the rolling radius to reduce the likelihood of grabbing and pinching tissue during articulation of the end effector without sacrificing the internal bend radius of the hinge joint.