Ultrasonic Transducer Pre-Compression Rod Assembly

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Solution Overview

Problem

Ultrasonic surgical instruments face challenges in maintaining efficient pre-compression of piezoelectric stacks within the transducer assembly, which affects the transmission of ultrasonic energy to the tissue, leading to inconsistent treatment outcomes.

Innovation Solution

The ultrasonic transducer assembly employs a rod secured between proximal and distal end masses, with pre-compression mechanisms such as transverse lumens and expandable wedges to maintain consistent compression of the piezoelectric stack between the horn and end masses, ensuring efficient energy transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional transducer assembly design is used, then assembly is simpler, but pre-compression of piezoelectric stack is inconsistent leading to unreliable ultrasonic energy transmission

Engineering Contradiction:

Improvepre-compression consistencyVSAvoidtransducer assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The rod is pre-compressed against the piezoelectric stack during assembly using compression mechanisms (such as expandable balloons or spring-loaded systems) before final sealing. This preliminary compression action ensures consistent pre-load on the piezoelectric elements, addressing the reliability issue while containing the complexity within the assembly process rather than the operating structure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A compression medium (such as fluid-filled balloons or elastic elements) is introduced as an intermediary between the rod and the piezoelectric stack. This intermediary transmits and distributes compressive force uniformly across the piezoelectric elements, ensuring consistent pre-compression without requiring direct complex mechanical contact structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stress or pressure

If rigid compression structures are used, then pre-compression is maintained, but thermal management of piezoelectric stack deteriorates

Engineering Contradiction:

Improvepre-compression forceVSAvoidpiezoelectric stack temperature

Core Design Contradiction:

Stress or pressureVSTemperature

Solution Approach 1:

Fluid-filled balloons or hydraulic compression elements are used to apply pre-compression force to the piezoelectric stack. These fluid-based mechanisms provide uniform radial compression while allowing thermal energy to conduct through the piezoelectric elements to the surrounding housing and cooling structures, preventing heat buildup that would occur with rigid solid compressors.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

Flexible compression elements (such as elastic membranes or thin-walled balloons) are employed to maintain pre-compression force. These flexible structures conform to the piezoelectric element geometry, providing uniform contact pressure while allowing thermal energy to dissipate through the element surfaces, thus managing temperature without compromising compression.

Inventive Principle:

Principle #30Flexible shells and thin films

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 configuration ensures consistent pre-compression of the piezoelectric stack, enhancing the transmission of ultrasonic energy and improving the reliability and effectiveness of tissue treatment.

Implementation Method 1

Ultrasonic surgical instruments utilize ultrasonic energy, i.e., ultrasonic vibrations, to treat tissue. More specifically, ultrasonic surgical instruments utilize mechanical vibration energy transmitted at ultrasonic frequencies

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a rod secured to the horn and extending proximally from the horn through the longitudinal opening of the piezoelectric stack... to maintain a pre-compression of the piezoelectric stack between the horn and the proximal end mass

Methodology Applied

Scientific EffectMechanical compression: Compression

Implementation Method 3

ultrasonic surgical instruments utilize mechanical vibration energy transmitted at ultrasonic frequencies to coagulate, cauterize, fuse, seal, cut, desiccate, and/or otherwise treat tissue

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Data Source

PatentUS12004769B2Ultrasonic transducer assembly for an ultrasonic surgical instrument

Publication Date: 2024.06.11 COVIDIEN LP

AI summary

A ultrasonic transducer assembly of an ultrasonic surgical instrument includes a horn, a piezoelectric stack positioned proximally of the horn and defining a longitudinal opening extending therethrough, a proximal end mass positioned proximally of the piezoelectric stack and defining a longitudinal opening, and a rod secured to the horn and extending proximally from the horn through the longitudinal opening of the piezoelectric stack and the longitudinal opening of the proximal end mass. The rod is secured to the proximal end mass to pre-compress the piezoelectric stack between the horn and the proximal end mass.