Concentric Screw Drive Actuation for Bile Duct Lithotripsy

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Solution Overview

Problem

Existing devices for mechanical lithotripsy and stone removal in the bile duct or urinary system face challenges with precise positioning and force transmission, leading to potential stone loss or severe patient wounding during extraction of large calculi.

Innovation Solution

A concentrically arranged actuation device with a screw drive mechanism, combining precise and fast movements for opening and closing the stone collecting basket, and a separate mechanism for controlled crushing, eliminating the need for additional transmission elements and allowing enhanced tractive force application.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a separate lithotripter is attached to the actuating element, then lithotripsy function is added, but device complexity increases and additional transmission elements are required

Engineering Contradiction:

Improvelithotripsy functionVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the lithotripsy function and basket actuation into a single integrated actuation device. The first screw drive mechanism serves dual purposes: it actuates the stone collecting basket for capture and simultaneously performs lithotripsy by applying crushing force to the calculus, eliminating the need for separate lithotripter attachment and reducing overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The actuation device is designed with multi-functionality, where the same mechanical structure (screw drive) performs multiple functions: basket opening/closing, stone capture, and lithotripsy. This universal design allows one component to replace what would traditionally require separate specialized components

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If conventional actuation mechanisms are used, then device simplicity is maintained, but positioning precision and movement control are insufficient

Engineering Contradiction:

Improvepositioning precisionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces conventional mechanical actuation mechanisms (such as direct cable pulling or simple lever systems) with a screw drive mechanism. This substitution provides precise positioning control through the threaded engagement, allowing incremental and controlled movement of the basket while maintaining a relatively simple overall device structure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Force

If strong tractive force is applied to extract large stones, then extraction capability is improved, but patient injury risk increases

Engineering Contradiction:

Improveextraction forceVSAvoidpatient injury

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by performing lithotripsy (crushing the stone) before extraction. The screw drive mechanism first reduces the calculus into smaller fragments that can then be safely removed, preventing the need to apply dangerous levels of tractive force during extraction and thereby reducing patient injury risk

Inventive Principle:

Principle #10Preliminary action

4Speed

If the stone collecting basket opens rapidly, then capture speed is improved, but control precision is reduced

Engineering Contradiction:

Improvebasket opening speedVSAvoidcontrol precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The screw drive mechanism provides dynamic control capability, allowing the operator to adjust the basket opening speed as needed. The threaded engagement enables both rapid opening when needed and precisely controlled gradual opening when precision is required, adapting the motion characteristics to the specific operational requirements

Inventive Principle:

Principle #15Dynamics

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

Enables precise capture, crushing, and extraction of calculi with reduced risk of stone loss and patient injury by providing precise control over the stone collecting basket's movements and force application.

Implementation Method 1

a first actuating element configured as a screw drive being provided for the lithotripsy of the calculus

Methodology Applied

Scientific EffectScrew mechanism: Screw

Data Source

PatentUS8790353B2Device for mechanical lithotripsy and removal of calculi that form in the bile duct or in the urinary system

Publication Date: 2014.07.29 MEDWORK

AI summary

The device for mechanical lithotripsy and removal of stones that form in the bile duct or urinary system has a stone collection basket at a distal end of a tube and two actuators at the proximal end of the tube. A cable runs through the tube and connects each actuator to the basket. The actuators are screw drives and form a common structural unit that is concentric to the tube and the cable. One actuator controls the opening and closing of the basket while the other actuator controls the force transmitted through the cable to the basket to allow for crushing of the stone in the basket.