Compact Pulley-Jaw End Effector for High Grip Force
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing minimally invasive surgery (MIS) instruments face challenges in reducing size while maintaining high grip force and functionality, as scaling down components leads to reduced torque, cable life, and non-intuitive operation due to complex torque-amplifying mechanisms.
Innovation Solution
A compact end effector drive mechanism with pulley-jaw pairs that amplify torque within a defined envelope, allowing independent grip force from push-pull forces and preventing undesirable rotations, while maintaining a compact form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of wrist mechanism and end effector is reduced by scaling down components, then the instrument achieves a compact form suitable for minimally invasive procedures, but the grip force produced by the end effector is reduced
Solution Approach 1:
The end effector is divided into two separate jaw assemblies (first jaw assembly and second jaw assembly), each with its own pulley and tension member connection. This segmentation allows each jaw to be independently actuated with optimized torque amplification, enabling compact sizing while maintaining high grip force through distributed mechanical advantage across multiple segments.
Solution Approach 2:
The patent introduces a new spatial dimension by offsetting the jaw pivot axis from the central axis of the instrument shaft. This dimensional offset creates a torque amplification mechanism where the perpendicular distance between the cable tension application point and the jaw pivot axis generates rotational moment, amplifying the grip force without increasing the linear size of the end effector components.
2Force
If torque-amplifying mechanisms are added to increase grip force, then the end effector produces higher grip force, but the operation becomes non-intuitive and the mechanism complexity increases
Solution Approach 1:
The jaw assemblies are designed to automatically amplify torque through their geometric configuration without requiring complex control systems or feedback mechanisms. The offset pivot axis and pulley arrangement create inherent mechanical advantage that self-regulates during operation, maintaining intuitive control while delivering high grip force. The system serves itself by converting cable tension directly into amplified jaw closure force through pure geometric relationships.
3Force
If cable tension is increased to maintain grip force in smaller instruments, then the grip force is maintained, but the cable life is reduced and cable stretch increases
Solution Approach 1:
By offsetting the jaw pivot axis from the central axis and positioning pulleys at strategic locations in three-dimensional space, the system creates a torque amplification mechanism that multiplies cable tension effectiveness. This spatial arrangement allows lower cable tensions to generate the same jaw closure force that would otherwise require higher tensions in conventional aligned configurations, thereby extending cable life and reducing stretch.
Solution Approach 2:
The patent changes the geometric parameters of the jaw assembly configuration, specifically the offset distance between the jaw pivot axis and central axis, and the radial position of pulleys. These parameter changes optimize the mechanical advantage ratio, allowing the system to achieve high grip force with reduced cable tension, thereby improving cable reliability and extending service life.
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 high grip force with reduced cable tension, improved cable life, and intuitive operation, while maintaining a similar size to conventional instruments, suitable for minimally invasive procedures.
Implementation Method 1
Each pulley-jaw pair is configured as a kinematic assembly having a compact footprint that can amplify outputs to increase the grip force applied by the jaws
Implementation Method 2
Known instruments include tension members (e.g., cables or push /pull members) that extend through the shaft of the instrument and that connect the wrist mechanism to a mechanical structure configured to move the tension members
Implementation Method 3
pulleys and/or contoured surfaces are generally needed to reduce cable friction, which extends instrument life and permits operation without excessive forces being applied to the cables or other structures in the wrist mechanism
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An end effector drive mechanism has first and second pulleys and first and second jaws configured as a torque-amplifying tool assemblies. Each pulley-jaw pair is configured as kinematic assembly having a compact footprint that can amplify outputs to increase the grip force applied by the jaws. The end effector drive mechanism is within a pulley envelope defined by the first and second pulleys. In certain configurations, the tool assemblies are configured to produce a grip force independent from a push-pull force that is exerted on (or by) the jaws. In certain configurations, the tool assemblies are configured to prevent undesirable reverse rotations and limit the range of travel of the jaws (or pulleys).