Electrocautery End Effector Cable Routing for Small-Diameter Articulation
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Solution Overview
Problem
Existing mechanisms for powering electrocautery end effectors in robotic surgical instruments with small diameters, such as less than 6 mm, fail to effectively manage power cables without causing strain or interference during articulation, as described in US 2004/0267254, which is designed for larger diameters.
Innovation Solution
A robotic surgical instrument with an articulation system featuring a first and second joint driven by pairs of driving elements, allowing the electrocautery element to rotate around symmetric paths using pulley arrangements, ensuring the power cable remains taut and flexible without restricting movement, even with small diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power cable is fed through the interior of the shaft and articulation to the electrocautery end effector, then the power supply is stable and reliable, but the cable may become taught or slack during articulation, restricting movement or causing interference with internal components
Solution Approach 1:
A cable management mechanism acts as an intermediary between the power cable and the articulation joints. This mechanism includes a cable routing system with guides and tensioning elements that mediate the cable's path through the articulation, preventing direct interference between the cable and joint movements while maintaining continuous power supply to the end effector
Solution Approach 2:
The cable management system is designed to be dynamic rather than fixed, allowing the cable routing to adapt automatically during articulation movements. The system includes movable cable guides and tensioning elements that adjust their position and tension based on the articulation state, ensuring the cable remains properly positioned whether the articulation is stationary or moving through its range of motion
2Object-affected harmful factors
If the external diameter of the surgical instrument is reduced to minimize tissue damage, then the body's healing ability is improved and recovery time is reduced, but the mechanism for managing the power cable becomes ineffective as it puts too much strain on the cable
Solution Approach 1:
The cable management mechanism employs a nested structure where the power cable is routed through concentric pathways within the shaft and articulation. The cable passes through nested guides and protective channels that are integrated into the existing instrument structure, allowing efficient cable management within the constrained small diameter without adding significant external size
Solution Approach 2:
The design changes critical parameters including the cable routing geometry, tension distribution, and structural support configuration to optimize performance for small diameters. The cable path is engineered with specific curvature radii and tensioning points that prevent excessive strain, while the supporting structures are dimensioned appropriately for the reduced scale of the instrument
3Duration of action of stationary object
If the power cable is insulated to prevent degradation from rubbing, then the cable longevity is improved, but the cable may still rub on internal components during articulation, leading to insulation degradation
Solution Approach 1:
The power cable is extracted from direct contact with internal articulation components through dedicated cable routing channels and protective sleeves. The cable path is separated from moving parts by introducing intermediate protective structures, eliminating the rubbing contact that would cause insulation degradation while maintaining the necessary flexibility for articulation movement
Data Source
AI summary
A robotic surgical instrument comprising a shaft, an electrocautery end effector powered by an electrocautery element, and an articulation connecting the electrocautery end effector to the shaft. The articulation comprises: a first joint driveable by a first pair of driving elements which permits the electrocautery end effector to rotate about a first axis transverse to a longitudinal axis of the shaft; and a second joint driveable by a second pair of driving elements which permits the electrocautery end effector to rotate about a second axis transverse to the first axis. The electrocautery element is constrained to move around the first axis and constrained to wrap at least one full revolution around the second axis. The path of the electrocautery element between the shaft and the second joint symmetrically opposes the path of a first one of the second pair of driving elements between the shaft and the second joint.