Variable Pitch Helical Spring for Surgical Instrument Actuation
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Solution Overview
Problem
Existing surgical instruments for minimally invasive surgery face issues with unreliable guidance of internal wires and high stress on spring coils due to sharp angling and uneven bending, leading to potential damage and inefficient force transmission.
Innovation Solution
A surgical instrument with a helical spring that has varying spring constants and cross-sectional areas, allowing for adaptable bending behavior, reduced stress on coils, and secure guidance of wires, achieved through different material properties and manufacturing methods such as milling, winding, or 3D printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the spring coils are spaced apart or just touch at maximum bending, then the spring structure is simpler, but internal wires are not securely guided
Solution Approach 1:
The patent applies local quality by varying the pitch of spring coils in different regions. The pitch is smaller in the first and second regions (near the ends) and larger in the intermediate region, creating different local densities of coils. This ensures that wires are securely guided in regions where they pass through while maintaining adequate spacing in other regions to prevent excessive stress concentration.
2Ease of operation
If the spring is bent sharply at a single point, then the bending is concentrated, but the coils in that area are subjected to high stress
Solution Approach 1:
The patent segments the spring into multiple regions with different pitch characteristics. Instead of a single uniform structure, the spring is divided into a first region, an intermediate region, and a second region, each with specific pitch properties. This segmentation distributes the bending stress across multiple regions rather than concentrating it at a single point, reducing the risk of coil failure.
Solution Approach 2:
The patent changes the geometric parameter of pitch along the length of the spring. By varying the pitch from smaller values at the ends to larger values in the intermediate region, the spring's mechanical properties are optimized to distribute stress more evenly during bending operations, preventing excessive stress concentration at any single location.
3Ease of operation
If adjacent areas of the spring are not bent or bent to a significantly lesser degree, then the bending is localized, but force transmission is less smooth
Solution Approach 1:
The patent creates a dynamic bending distribution through its non-uniform pitch design. When the instrument shaft bends, the varying pitch allows different regions of the spring to deform at different rates and to different degrees. This dynamic response enables smooth force transmission through the spring structure while still achieving effective bending at the required locations.
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
Ensures reliable and continuous force transmission with reduced risk of wire damage, enabling precise and safe operation of the instrument head during minimally invasive procedures.
Implementation Method 1
a helical spring (34) that bridges the hinge (22) and connects the end effector (24) to the coupling element (26, 30) for rotating the end effector (24)
Data Source
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AI summary
A surgical instrument for minimally invasive surgery has an instrument shaft (12) with a distal end and a proximal end. The proximal end can be connected to a signal transmitter. The surgical instrument has an instrument head (20) that is pivotably connected to the distal end of the instrument shaft (12) via a joint (22), and an end effector (24) that is rotatably mounted in the instrument head (20) about its longitudinal axis. The instrument further comprises a mechanical coupling element (26, 28, 42) that is at least partially arranged in the instrument shaft (12) and is designed to transmit and/or translate mechanical actuation signals from the signal transmitter for pivoting and rotating the instrument head (20), as well as a helical spring (34) that bridges the joint (22) and connects the end effector (24) to the coupling element (26, 28, 42) to rotate the end effector (24).The coil spring (34) has areas with different spring constants (D).