Endoscopic Forceps Mechanical Advantage for Tissue Sealing
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Solution Overview
Problem
Existing electrosurgical forceps face challenges in consistently applying the required mechanical forces to seal large tissue structures within a specific pressure range, leading to variability in seal effectiveness and potential mechanical failure due to high closure forces.
Innovation Solution
The design incorporates a mechanical arrangement with a pivot located above the longitudinal axis and a drive flange along the axis, providing a lever-like mechanical advantage to facilitate closing jaw members with reduced user force, while ensuring consistent closure pressure between 3 kg/cm2 to 16 kg/cm2, and includes a knife assembly for tissue cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large closure force is applied between jaw members to seal large vessels, then sealing effectiveness is improved, but the risk of mechanical failure increases due to high forces requiring large moments about the pivot
Solution Approach 1:
The forceps is divided into multiple segments including a shaft, jaw members, and a mechanical advantage mechanism. The jaw members are segmented from the shaft and connected through a drive assembly that provides mechanical advantage, allowing the system to generate high closure forces without requiring the entire structure to withstand these forces directly.
Solution Approach 2:
A mechanical advantage mechanism acts as an intermediary between the user's applied force and the jaw members. This intermediary system (including levers, cams, or springs) amplifies the user's input force to generate the necessary closure forces while protecting the pivot and other components from direct exposure to these high forces.
2Device complexity
If the jaw members are positioned close to the pivot with small moment arms, then device complexity is reduced, but the ability to generate sufficient closure force is compromised
Solution Approach 1:
A mechanical advantage mechanism serves as an intermediary that bridges the gap between the simple pivot configuration and the requirement for high closure forces. This intermediary system amplifies the force generated by the small moment arm configuration, allowing sufficient closure force to be achieved without increasing the moment arm length.
Solution Approach 2:
The system changes the parameters of force transmission by introducing mechanical advantage elements that transform the small force applied over a large distance (or small moment arm) into a large closure force at the jaw members. This parameter transformation allows the simple pivot configuration to generate adequate closure forces.
3Strength
If metal pivot pins are used to provide structural support, then strength is improved, but electrical insulation is compromised as the pins may act as alternate current paths
Solution Approach 1:
An insulating coating or layer acts as an intermediary between the metal pivot pin and the surrounding electrical environment. This intermediary layer provides the necessary electrical insulation to prevent the pivot pin from serving as an alternate current path, while the metal pin maintains its structural support function.
Solution Approach 2:
The pivot pin is constructed as a composite structure combining metal (for strength) and insulating material (for electrical isolation). This composite approach allows the pivot pin to simultaneously provide structural support and electrical insulation, resolving the contradiction between these two requirements.
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 enables consistent and effective tissue sealing and cutting with reduced user effort, ensuring a uniform seal quality and minimizing mechanical failure risks by maintaining the necessary closure pressure and facilitating precise tissue division.
Implementation Method 1
Each of the jaw members is adapted to connect to an electrosurgical energy source, thus enabling the jaw members to conduct energy through tissue held between the jaw members to create a tissue seal
Implementation Method 2
electrosurgical forceps for sealing and/or cutting large tissue structures... heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue
Implementation Method 3
The design incorporates a mechanical arrangement with a pivot located above the longitudinal axis and a drive flange along the axis, providing a lever-like mechanical advantage to facilitate closing jaw members with reduced user force
Implementation Method 4
includes a knife assembly for tissue cutting
Data Source
AI summary
An endoscopic bipolar forceps includes a housing having a shaft affixed thereto, the shaft including jaw members at a distal end thereof. The shaft includes a longitudinal axis defined therethrough and the jaw members are adapted to connect to a source of electrosurgical energy such that the jaw members are capable of conducting energy through tissue held therebetween to effect a tissue seal. The forceps also includes a drive assembly which moves the jaw member relative to one another from a first position wherein the jaw members are disposed in spaced relation relative to one another to a second position wherein the jaw members are closer to one another for manipulating tissue. A movable handle is included which is rotatable about a pivot to force the drive assembly to move the jaw members between the first and second positions. The pivot is located a fixed distance above the longitudinal axis. A knife assembly is also included which has a movable knife bar having a generally t-shaped proximal end dimensioned to operatively engage a corresponding slot defined within the housing, the slot being dimensioned to guide the movement of the knife bar during translation thereof.