Cam Pulley Jaw Assembly for Robotic Surgical Force Control
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Solution Overview
Problem
Robotic surgical tools with small cross-sectional areas face limitations in applying high forces between jaws and lack customizable force options depending on jaw position, due to the use of three cables or cable pairs providing only three degrees of freedom.
Innovation Solution
A jaw assembly with cam pulleys and cam followers that allow for customizable force application by rotating cam pulleys to open or close jaws, featuring arcuate slots and angled slots to multiply closure force and vary clamping force, enabling high force application with adjustable jaw positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If three cables or cable pairs are used to provide three degrees of freedom, then the wrist assembly can achieve basic movement control, but the cross-sectional area cannot be reduced further and force application is limited
Solution Approach 1:
The jaw assembly is segmented into multiple independent cam mechanisms (first cam pulley with cam plate for jaw opening/closing, second cam pulley for jaw positioning) that can be actuated separately. This allows the system to maintain a compact cross-sectional area while achieving high force multiplication through the mechanical advantage of each cam mechanism, resolving the contradiction between small size and high force capability.
Solution Approach 2:
The cam mechanisms change the parameter of force application by transforming rotational motion into linear jaw movement with variable force characteristics. The cam plates and followers create non-uniform force distribution throughout the jaw closing cycle, enabling high peak forces while maintaining a small cross-sectional area, thus resolving the contradiction between size and force capability.
2Adaptability or versatility
If three cables or cable pairs are used for movement control, then basic jaw motion is achieved, but customizable force settings based on jaw position are not possible
Solution Approach 1:
The control system is segmented into independent cam mechanisms where the first cam pulley controls jaw opening/closing force and the second cam pulley controls jaw positioning force. Each cam can be independently actuated and configured, allowing customizable force settings for different surgical tasks without requiring a complex multi-cable system, thus resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The cam mechanisms provide dynamic force adjustment capabilities where the force characteristics can be changed by modifying cam profiles or actuation timing. This allows the system to adapt force settings based on jaw position and surgical requirements, achieving high adaptability while keeping the mechanical structure relatively simple compared to traditional multi-cable systems.
3Area of moving object
If smaller cross-sectional area tools are developed, then minimally invasive surgery is improved, but the total force that can be applied between jaws is reduced
Solution Approach 1:
The cam mechanisms transform the input force into amplified output force through mechanical advantage. By changing the parameter of force multiplication through cam geometry, the system achieves high total force between jaws while maintaining a small cross-sectional area, directly resolving the contradiction between miniaturization and force capability.
Solution Approach 2:
The cam plates and followers utilize curved surfaces to achieve smooth force transmission and multiplication. The arcuate geometry of the cam mechanisms allows for efficient force conversion that maintains high forces in a compact configuration, resolving the contradiction between small cross-sectional area and high force application.
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
The solution enables surgical tools to apply high forces between jaws while allowing customizable force settings based on jaw position, overcoming the limitations of traditional robotic surgical tools with small cross-sectional areas.
Implementation Method 1
the first cam pulley (360) multiplies a closure force acting on the first and second jaws as the first cam pulley is rotated to close the first and second jaws
Implementation Method 2
a cam follower coupling the first and the second pulleys to each of the first and second jaws
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
A surgical tool comprising: a jaw assembly comprising first and second jaws pivotable about a first axis; a first cam pulley and a second cam pulley rotatable about a second axis and coupled to the first and second jaws; and a cam follower coupling the first and the second pulleys to each of the first and second jaws; wherein: a rotation of the first cam pulley opens or closes the first and second jaws about the first axis; and a force applied to the second cam pulley rotates the first and second jaws about the second axis, and the pivot point of each of the jaws is spaced a lateral distance from the second axis, wherein the first cam pulley multiplies a closure force acting on the first and second jaws as the first cam pulley is rotated to close the first and second jaws, and wherein the first cam pulley includes at least one cam plate, and wherein a cam link is pivotally connected to the respective at least one cam plate and a respective second cam pulley.