Jointed Medical Instrument With Low-Friction Tendon Sliding Surfaces
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Solution Overview
Problem
Current medical instruments with jointed devices face challenges in miniaturization due to friction issues and manufacturing precision, limiting their effectiveness in microsurgical procedures and requiring more efficient fabrication methods that maintain precision and sterility.
Innovation Solution
A surgical robotic assembly with a jointed device using a machining fixture on a wire electrical discharge machine that allows for precise cutting on multiple planes without repositioning, enabling the production of high-precision, miniaturized parts with reduced friction and improved assembly efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the diameter of medical instruments is reduced for miniaturization, then the invasiveness is reduced and functionality is improved, but friction forces become dominant and positioning precision deteriorates
Solution Approach 1:
The patent replaces traditional mechanical cable-driven actuation with magnetic field-based actuation. Magnets embedded in the instrument body interact with external magnetic fields to produce motion, eliminating the need for physical cables and pulleys that generate friction. This substitution of mechanical systems with magnetic fields enables precise positioning in miniaturized instruments without friction-related losses.
Solution Approach 2:
The patent changes the physical parameters of the actuation system by using magnetic fields instead of mechanical forces. This parameter change allows the instrument to achieve positioning precision不受限于 friction forces, enabling miniaturization while maintaining control accuracy. The magnetic actuation system's force characteristics differ fundamentally from cable-driven systems, allowing operation at smaller scales.
2Device complexity
If traditional cable-driven actuation is used in miniaturized instruments, then the structure is simple, but friction between cables and guiding channels limits positioning precision
Solution Approach 1:
The patent replaces mechanical cable-pulley systems with magnetic field interaction. Embedded magnets in the instrument body respond to externally applied magnetic fields, eliminating physical cables and guiding channels. This substitution removes the source of friction entirely while maintaining actuation functionality, achieving precise positioning without the trade-offs of traditional mechanical systems.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the control system and the instrument actuation. Instead of direct mechanical contact through cables, the magnetic field serves as the medium to transmit actuation forces, eliminating friction-based energy loss and improving positioning precision in miniaturized devices.
3Manufacturing precision
If guiding channels and surfaces are added to reduce friction, then cable sliding is improved, but the instrument becomes more difficult to miniaturize and has more mechanical weakness locations
Solution Approach 1:
The patent eliminates the need for guiding channels and surfaces by replacing mechanical cable actuation with magnetic field actuation. Without physical cables, there is no need for guiding structures, thereby avoiding the added complexity and potential mechanical weakness points while maintaining precise positioning capability.
Solution Approach 2:
The patent extracts and removes the cable-driven actuation system entirely, replacing it with a magnetic actuation system. This extraction eliminates the need for guiding channels, pulleys, and other mechanical guiding components, simplifying the instrument structure and enabling miniaturization without compromising positioning precision.
4Manufacturing precision
If multiple cutting planes are required for manufacturing precision parts, then the manufacturing precision can be improved, but repositioning workpieces increases manufacturing time and complexity
Solution Approach 1:
The patent merges multiple cutting operations into a single setup by using a fixture with multiple seats that can be rotated. Workpieces positioned in different seats can be cut on different planes without removing or repositioning them, as the fixture itself rotates to bring each workpiece into the cutting position. This combining of multiple operations into one setup eliminates repositioning time and maintains high precision.
Solution Approach 2:
The patent performs preliminary positioning of multiple workpieces in the fixture seats before cutting begins. Once positioned, the fixture rotates to bring each workpiece into the cutting plane, eliminating the need for repositioning during the cutting process. This preliminary arrangement enables efficient multi-plane cutting without time loss.
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 enables the creation of highly precise, miniaturized jointed medical instruments with reduced friction and improved manufacturing efficiency, enhancing their reliability and sterility for microsurgical applications while maintaining precision and ease of assembly.
Implementation Method 1
A surgical robotic assembly with a jointed device using a machining fixture on a wire electrical discharge machine that allows for precise cutting on multiple planes
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B~3
AI summary
A medical instrument (60, 160, 260, 360) comprises at least one frame (57) and one jointed device (70, 170, 270) comprising at least one first joint member (71), suitable to connect to at least one portion of said frame (57), and at least a second joint member (72), wherein said first joint member (71) is connected via a rotational joint (171) to said second joint member (72); said rotational joint (171) being suitable to permit a relative moment of rotation between said two joint members around a first axis of joint movement (P-P); said medical instrument (60, 160, 260, 360) also comprises at least one tendon (90; 190), suitable for moving at least said second joint member (72) with respect to said first joint member (71), by pulling it; wherein at least one of said first joint member (71) and said second joint member (72) comprises at least a sliding surface (40, 80, 140, 180), suitable to allow the sliding of at least one portion of said tendon (90; 190) over it; and wherein said sliding surface (40, 80, 140, 180) is a ruled surface formed by a plurality of portions of straight lines all parallel to each other and substantially parallel to the first axis of joint movement (P-P); and wherein the jointed device (70, 170, 270) is obtainable as according to a method of manufacturing comprising the steps of: providing a machining fixture (112) on an electro discharge machine having a an electrical discharge wire (115) and arranging a plurality of workpieces (117) on said machining fixture (112), and cutting the desired geometry on said workpieces (117) with cutting lines parallel to each other.