Electro-Pneumatic Converter Roughness Control Against Flapper Sticking

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Solution Overview

Problem

Existing electro-pneumatic converters based on the nozzle-flapper principle face dynamic controllability issues at outlet pressures close to admission pressure due to Bernoulli effects, which cause the flapper to stick to the nozzle, leading to hysteresis and unreliable control.

Innovation Solution

The design incorporates a controllable electro-pneumatic converter with a baffle plate and nozzle edge that promotes turbulent airflow by adjusting the surface roughness and edge width, ensuring a proportionality factor between 10 and 28, preventing laminar flow and thus reducing Bernoulli forces, allowing for dynamic control even at high outlet pressures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If the working air gap between the nozzle and the baffle plate is reduced to achieve outlet pressures close to admission pressure, then the outlet pressure control range is improved, but Bernoulli effects occur causing the flapper to stick to the nozzle

Engineering Contradiction:

Improveoutlet pressureVSAvoiddynamic controllability

Core Design Contradiction:

Stress or pressureVSReliability

Solution Approach 1:

The invention changes the physical parameters of the air flow by introducing turbulence through specific geometric configurations (nozzle edge radius, baffle plate positioning) to alter the flow regime from laminar to turbulent, thereby changing the pressure distribution characteristics and eliminating the sticking effect while maintaining high outlet pressure control

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If the baffle plate completely closes the nozzle to achieve full admission pressure, then the outlet pressure reaches maximum value, but the system loses dynamic controllability due to hysteresis

Engineering Contradiction:

Improveoutlet pressureVSAvoiddynamic control

Core Design Contradiction:

Stress or pressureVSEase of operation

Solution Approach 1:

The invention applies partial action by maintaining a controlled residual gap between the baffle plate and nozzle, preventing complete closure. This partial opening allows continuous air flow that eliminates hysteresis while the baffle plate position can still effectively regulate pressure, achieving full pressure control without sacrificing dynamic responsiveness

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If smooth surfaces are used at the nozzle and baffle plate to achieve tight closure, then the sealing performance is improved, but laminar flow occurs causing Bernoulli effects and flapper sticking

Engineering Contradiction:

Improvesystem tightnessVSAvoidBernoulli effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention applies local quality by differentiating the surface characteristics at different locations: smooth surfaces are maintained where tight closure is needed, while specific localized regions (nozzle edge, baffle plate surface near the gap) are designed with geometric features that induce turbulence. This localized turbulence generation prevents Bernoulli effects without compromising overall system tightness

Inventive Principle:

Principle #3Local quality

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 effectively prevents the flapper from sticking to the nozzle, enabling reliable and dynamic control of the system at high outlet pressures by ensuring turbulent airflow, thereby improving the system's controllability and tightness.

Implementation Method 1

an electromagnetic transducer system with a coil (120) and a yoke (130)

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

the pneumatic force repelling the baffle plate (100)

Methodology Applied

Scientific EffectPneumatic force: Pressure Gradient

Implementation Method 3

The system is supplied with a constant admission pressure Pv via a restrictor (160)

Methodology Applied

Scientific EffectFlow restriction: Pressure Drop

Implementation Method 4

the air flows turbulently between them when the nozzle opening is closed by the baffle plate

Methodology Applied

Scientific EffectTurbulent flow: Turbulence

Data Source

PatentEP3626976B1Electric pneumatic converter, use of an electric pneumatic converter, position controller and control device

Publication Date: 2021.10.27 SAMSON AG

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Figure 3A~3B

AI summary

A controllable electro-pneumatic converter based on the nozzle-impact plate principle is proposed. A defined roughness (Rz) of the impact plate surface prevents the occurrence of Bernoulli forces at outlet pressures close to the inlet pressure, i.e., when the outlet nozzle (140) is almost completely closed by the impact plate (100). This improves the system's dynamic controllability under these conditions. Such a converter can be used to control various consumer systems, such as air power amplifiers for electro-pneumatic positioners.