Electrosurgical Forceps Knife Deployment Mechanism

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Solution Overview

Problem

Existing electrosurgical forceps require surgeons to manually sever treated tissue after coagulation or sealing, which can be inefficient and prone to errors due to the need for precise cutting.

Innovation Solution

The design incorporates a pair of pivotably coupled shaft members with a knife deployment mechanism that includes a trigger and a crank, where a detent mechanism allows the knife to be selectively translated from a retracted to an extended position, enabling precise tissue cutting with a threshold actuation force, ensuring accurate severing of treated tissue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a knife is selectively deployed through the end effector assembly to sever tissue, then the efficiency and accuracy of tissue cutting is improved, but the device complexity increases due to the additional knife deployment mechanism

Engineering Contradiction:

Improveefficiency of tissue cuttingVSAvoidcomplexity of knife deployment mechanism

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The knife is nested within the first shaft member and can be selectively translated through the end effector assembly. The knife deployment mechanism is integrated within the existing shaft members, with the crank and detent mechanism housed inside the first shaft member, creating a compact nested structure that reduces overall device complexity while maintaining the severing function

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The crank acts as an intermediary mechanism between the trigger and the knife. When the trigger is actuated, it rotates the crank, which then translates the knife from its retracted position to its extended cutting position. This intermediary mechanism provides controlled knife deployment with a threshold actuation force while maintaining a relatively simple overall structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a detent mechanism is used to resist crank rotation and require threshold actuation force, then the reliability and precision of knife deployment is improved, but the ease of operation decreases due to the additional force requirement

Engineering Contradiction:

Improveprecision of knife deploymentVSAvoidease of trigger actuation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The detent mechanism is pre-positioned to engage with the crank at a specific point in its rotation path. This preliminary positioning ensures that when the trigger is actuated, the crank must overcome the detent resistance at the precise moment needed for reliable knife deployment, preventing accidental activation while ensuring accurate deployment when intended

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The detent mechanism is designed with specific geometric parameters and material properties that create a defined threshold actuation force. By carefully selecting the detent spring constant, engagement angle, and crank lever arm length, the system achieves reliable deployment with a controlled force threshold that balances precision with operational ease

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11510725B2Electrosurgical forceps

Publication Date: 2022.11.29 COVIDIEN LP

AI summary

An electrosurgical forceps includes a pair of first and second shaft members pivotably coupled to one another, an end effector assembly coupled to the pair of first and second shaft members, a knife, and a knife deployment mechanism. The knife deployment mechanism has one or more safety features that resist an inadvertent deployment of the knife.