Piezoelectric Drive Unit Series Connection for Fill Level Measurement

Solution Overview

Problem

Existing level measuring devices face issues with mechanical coupling and electrical amplitude reduction under positive and negative process pressures, leading to potential drive unit failure, especially with thin membranes and varying temperatures.

Innovation Solution

The solution involves mechanically connecting two drive units, one with a tension bolt and one with a pressure bolt, in series, ensuring that at least one drive unit remains loaded and functional across positive and negative pressures, with the option to operate them jointly or separately for enhanced signal amplitude.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stack of piezoelectric elements with a tension bolt is used as the drive unit, then the fill level measuring device is excellently suited to detecting fill levels, but the preloaded drive stack is relieved when the process pressure is positive due to the deflecting membrane, leading to decreasing electrical amplitudes and potential failure

Engineering Contradiction:

Improvedrive unit functionalityVSAvoidelectrical amplitude

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The drive unit is divided into two separate stacks of piezoelectric elements: a first stack with a tension bolt and a second stack with a pressure bolt. This segmentation allows each stack to respond independently to different pressure conditions, ensuring that at least one stack remains functional under both positive and negative process pressures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the mechanical loading parameters of the piezoelectric elements by introducing two different bolt configurations (tension bolt and pressure bolt) that apply different types of mechanical stress. This allows the system to maintain adequate mechanical coupling under varying pressure conditions by switching between the two stacks.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If a higher preload is applied to the piezoelectric elements to compensate for pressure relief, then the electrical amplitude is maintained, but the individual piezoelectric elements have a mechanical load limit that increases the risk of breakage

Engineering Contradiction:

Improveelectrical amplitudeVSAvoidmechanical load limit

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The drive unit is divided into two separate stacks of piezoelectric elements: a first stack with a tension bolt and a second stack with a pressure bolt. This segmentation allows each stack to respond independently to different pressure conditions, ensuring that at least one stack remains functional under both positive and negative process pressures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system prepares for pressure variations by having two pre-configured stacks that can compensate for each other. When one stack is relieved by positive pressure, the other stack is already positioned to provide the necessary mechanical coupling, cushioning against the effects of pressure relief without requiring excessive preload on individual elements.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Volume of moving object

If the membrane is made thin to reduce the size of the level measuring device, then the device is more compact, but the membrane experiences structural mechanical stiffening with greater pre-tensioning of the drive unit

Engineering Contradiction:

Improvedevice sizeVSAvoidmembrane flexibility

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The drive unit is divided into two separate stacks of piezoelectric elements: a first stack with a tension bolt and a second stack with a pressure bolt. This segmentation allows each stack to respond independently to different pressure conditions, ensuring that at least one stack remains functional under both positive and negative process pressures.

Inventive Principle:

Principle #1Segmentation

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 maintains a sufficient electrical signal amplitude and ensures the level measuring device remains functional across a wide pressure range, preventing failure due to pressure variations.

Implementation Method 1

A stack of piezo-electric elements with a tension bolt serves as the drive unit

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

vibrating rods regularly being formed on the diaphragm

Methodology Applied

Scientific EffectVibration: Vibration

Data Source

PatentEP2803954B1Fill level measurement device

Publication Date: 2019.01.02 VEGA GRIESHABER GMBH & CO

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AI summary

Level measuring device with the following features: - a diaphragm (3), - a first drive unit (10) with a pull bolt (12) coupled to the diaphragm (3), - a second drive unit (30) with a pressure bolt (32) coupled to the diaphragm (3), and the first drive unit (10) and the second drive unit (30) are mechanically connected in series with each other.