Cross-Axis Flexural Pivot Joints for Stable Small-Scale Articulation
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Solution Overview
Problem
Current surgical instruments face challenges with joint mechanisms that are either too rigid, leading to high friction and wear, or too flexible, resulting in instability and limited range of motion, particularly when scaled to smaller sizes for minimally invasive surgery.
Innovation Solution
A cross-axis flexural pivot mechanism with a design that includes a first and second joint member and flexures, allowing for two or more degrees of freedom, with a central portion of the flexure contacting a contact surface to control deformation and reduce stress, enabling increased range of motion and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pin-in-slot joint is used to allow rotation between tool portions, then mobility is achieved, but friction and wear increase leading to performance decline
Solution Approach 1:
The patent replaces the traditional pin-in-slot mechanical joint with a compliant mechanism that uses elastic deformation of flexible members to achieve rotation. This substitution eliminates the need for physical contact between rigid components, thereby reducing friction and wear while maintaining mobility.
Solution Approach 2:
The patent employs flexible members with specific cross-sectional geometries (such as elliptical or I-shaped cross-sections) that bend elastically to provide rotational motion. These flexible thin-walled structures enable movement without the need for traditional mechanical joints, reducing friction and wear.
2Reliability
If a flexible member is used to produce mobility through elastic deformation, then friction and wear are reduced, but stability decreases and fatigue failure risk increases
Solution Approach 1:
The patent applies local quality by designing flexible members with non-uniform cross-sectional geometries along their length. The cross-section varies to optimize both flexibility where needed and stiffness where required, allowing the member to achieve sufficient angular deflection while maintaining stability and resisting fatigue failure.
Solution Approach 2:
The patent employs composite material structures in the flexible members, combining materials with different mechanical properties to achieve the desired balance between flexibility and stability. The composite construction allows the member to deform elastically for mobility while maintaining structural integrity and resistance to fatigue.
3Length of moving object
If the tool diameter is reduced to approximately 3 mm for minimally invasive surgery, then incision size is minimized, but flexibility and range of motion are reduced
Solution Approach 1:
The patent achieves large angular deflections in a compact radial space by using compliant mechanisms that deform in controlled directions. The flexible members are designed to bend along specific paths that maximize rotational range within the constrained diameter of the tool, effectively utilizing dimensional space efficiently.
Solution Approach 2:
The patent changes the geometric parameters of the flexible members, including cross-sectional shape and size variations along the length, to optimize the balance between tool size and flexibility. By carefully controlling these parameters, the mechanism achieves sufficient range of motion while maintaining a small overall tool diameter suitable for minimally invasive surgery.
4Adaptability or versatility
If wrist articulation is added to provide both wrist articulation and gripping function, then versatility is improved, but the throw distance from shaft axis to end effector tip increases
Solution Approach 1:
The patent merges the wrist articulation mechanism and gripping function into a single integrated compliant structure. The flexible members provide both the rotational articulation and the gripping motion through their elastic deformation, eliminating the need for separate mechanical subsystems and reducing the overall throw distance.
Solution Approach 2:
The patent uses flexible members with optimized cross-sectional geometries to provide wrist articulation in a compact form. These thin-walled flexible structures enable multiple degrees of freedom including wrist rotation and gripping motion without requiring the large throw distances associated with traditional rigid wrist mechanisms.
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
The solution provides a joint mechanism with low friction, reduced part count, and increased angular deflection, suitable for small-scale surgical instruments, allowing for effective tissue manipulation with minimal stress and reduced operational footprint.
Implementation Method 1
The flexure is configured to deform elastically when the first joint member and the second joint member move from a first configuration to a second configuration
Data Source
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AI summary
The embodiments described herein can be used in a variety of grasping, cutting, and manipulating operations. In some embodiments, an apparatus includes a first joint member, a second joint member, and a flexure. The first joint member includes a first connection portion and a contact surface. The second joint member including a second connection portion. A first end portion of the flexure is coupled to the first connection portion, and a second end portion of the flexure is coupled to the second connection portion. The flexure is configured to deform elastically when the first joint member and the second joint member move from a first configuration to a second configuration. When in the first configuration, the central portion of the flexure is spaced apart from the contact portion. When in the second configuration, the central portion of the flexure contacting the contact portion.