Cam-Based Jaw Actuation for Electrosurgical Forceps

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Solution Overview

Problem

Electrosurgical forceps face issues with frictional losses and reduced operational life due to shaft bending or deformation during procedures, which impede the effective transfer of closure force to jaw members and diminish the instrument's performance.

Innovation Solution

The design incorporates a resilient member with cam slots and a cam member that provides a camming force to bias the jaw members into a clamping position, reducing frictional losses and maintaining consistent closure force, even with shaft bending, by using a flexible drive element and lubricious materials to facilitate smooth movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a drive rod is used to translate through the shaft to move jaw members, then mechanical force can be transmitted to the end effector, but frictional losses increase and operational life decreases when the shaft bends or deforms

Engineering Contradiction:

Improveclosure forceVSAvoidfrictional losses

Core Design Contradiction:

ForceVSLoss of energy

Solution Approach 1:

The patent replaces the traditional drive rod translation mechanism with a cam-based rotational mechanism. The cam member rotates within cam slots defined in the jaw member, converting rotational motion into the desired jaw movement. This substitution eliminates the need for linear translation through the shaft, thereby eliminating frictional losses associated with drive rod movement through bent shafts.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The resilient member operates in conjunction with the cam mechanism to provide controlled mechanical motion. The resilient member biases the jaw member and works with the cam profile to ensure smooth, consistent movement through the cam slots, maintaining reliable force transmission regardless of shaft position or bending.

Inventive Principle:

Principle #18Mechanical vibration

2Ease of operation

If the shaft is bent intentionally or unintentionally during procedure, then mechanical advantage can be gained at the surgical site, but frictional losses increase and transfer of closure force is impeded

Engineering Contradiction:

Improvemechanical advantageVSAvoidtransfer of closure force

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The cam-based rotational mechanism replaces the drive rod translation system, making the force transmission mechanism independent of shaft bending. Since the cam rotates locally at the end effector rather than translating through the shaft, shaft bending no longer creates frictional losses that impede force transfer, ensuring reliable closure force delivery regardless of shaft configuration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Force

If a spring is used to facilitate actuation of the handle assembly, then closure force can be maintained within working ranges, but operative life of the spring and instrument decreases due to frictional losses

Engineering Contradiction:

Improveclosure forceVSAvoidoperative life

Core Design Contradiction:

ForceVSDuration of action of moving object

Solution Approach 1:

The patent replaces the spring-based force maintenance system with a cam-based rotational mechanism. The cam profile itself provides the mechanical advantage and force multiplication needed to maintain closure force within working ranges, eliminating the need for a spring that would otherwise accumulate frictional losses and wear over time. This extends the operative life of the instrument.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This solution ensures consistent and uniform tissue sealing with reduced frictional losses and extended operational life of the electrosurgical instrument, maintaining effective closure force and mechanical advantage during procedures.

Implementation Method 1

A resilient member is operably coupled to the jaw member that includes the one or more cam slots. The resilient member is configured to provide a camming force to the cam slot and to bias the first and second jaw members in the clamping position.

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

using a flexible drive element and lubricious materials to facilitate smooth movement

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS11583304B2Apparatus for performing an electrosurgical procedure

Publication Date: 2023.02.21 COVIDIEN LP

AI summary

An endoscopic forceps is provided and includes a housing having a shaft. An end effector assembly operatively connects to a distal end of the shaft and has a pair of first and second jaw members. One of the first and second jaw members is movable relative to the other jaw member from an open position, to a clamping position. One of the first and second jaw members includes one or more cam slots defined therein and configured to receive a cam member that upon movement thereof rotates the movable jaw member from the open position to the clamping position. A resilient member is operably coupled to the jaw member that includes the one or more cam slots. The resilient member is configured to provide a camming force to the cam slot and to bias the first and second jaw members in the clamping position.