Jaw Closure Transmission With Compliant Cable Force Feedback
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Solution Overview
Problem
Existing minimally invasive surgical tools face challenges in reliably transmitting high force loads from the proximal end to the distal end while maintaining output displacement, with rigid transmission members leading to increased wear and friction, and lacking feedback on grip strength.
Innovation Solution
The design incorporates a jaw closure transmission system with a finite stiffness transmission member that acts as an energy storage device, providing a varying mechanical advantage throughout the input stroke to enhance closure security and feel, using a combination of rigid and compliant elements, including a transmission cable and flexible conduit, to facilitate efficient force transmission and articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid transmission members are used to transmit high force loads, then force transmission reliability is improved, but wear and friction increase
Solution Approach 1:
The patent changes the stiffness parameter of the transmission member from rigid to compliant, allowing the transmission member to deform elastically under load. This compliance reduces impact forces and friction while maintaining reliable force transmission through the elastic deformation of the member
Solution Approach 2:
The transmission system uses a composite structure combining rigid components (handle mechanism, jaw mechanism) with compliant transmission members (flexible cables, springs). This composite approach allows rigid force transmission paths where needed while using compliant elements to reduce wear and friction in the transmission path
2Power
If rigid transmission members are used, then force transmission is efficient, but feedback on grip strength is lost
Solution Approach 1:
The compliant transmission member acts as a feedback element, transmitting tactile information about jaw closure and grip strength back to the operator through the handle. The elastic deformation of the compliant member provides tactile feedback proportional to the force being applied, allowing the operator to sense grip strength without visual confirmation
Solution Approach 2:
By changing the stiffness parameter of the transmission member to be compliant rather than rigid, the system enables tactile feedback transmission while maintaining sufficient force transmission efficiency for surgical operations
3Manufacturing precision
If complex ratcheting mechanisms are added to control clamping forces, then force control precision is improved, but device complexity increases
Solution Approach 1:
The compliant transmission member with varying mechanical advantage provides self-regulating clamping force control. As the jaw closes, the changing geometry of the transmission system automatically adjusts the mechanical advantage, providing progressive force increase without requiring external control mechanisms or ratchets
Solution Approach 2:
The system uses dynamic mechanical advantage variation throughout the input stroke. The mechanical advantage is lower at the beginning of closure and increases as closure progresses, providing automatic force control that adapts to the closing process without complex mechanisms
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 approach allows for reliable high force transmission with reduced wear and friction, improved grip strength feedback, and enhanced ergonomic control, enabling precise clamping forces without damaging the object being grasped, while minimizing the need for complex ratcheting mechanisms.
Implementation Method 1
a transmission cable having a finite stiffness in a transmission direction... the transmission cable is stretched in the jaw assembly closed configuration... resulting tension in the transmission cable is converted by the jaw mechanism to an increasing force between the first and second jaws
Data Source
AI summary
A jaw closure transmission system is presented that includes an input sub-system, output sub-system and a transmission sub-system. These transmission sub-systems may utilize the transmission member as an energy storing device over a certain portion of an input stroke, to achieve a specific desired performance of the surgical tool. These apparatuses and methods may be particularly useful with hand-held, minimally invasive surgical tools having jaws.