Pressure Sensor with Rotating Flexure Bearing
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Solution Overview
Problem
Existing pressure sensor arrangements for process instrumentation are complex, require exacting accuracy in welding and material properties, and are sensitive to static pressure, making them costly and prone to overload.
Innovation Solution
A pressure sensor arrangement with a diaphragm applied in the cross-section of a tube, utilizing a flexure bearing with a thinner peripheral region and a recess for reduced flexural strength, allowing external measurement of rotation without oil fill or pressure-resistant glass feedthroughs, and featuring a strain sensor for surface strain measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pressure sensor arrangement with oil fill and multiple diaphragms is used, then overload protection is achieved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The invention extracts and eliminates the oil fill and multiple diaphragm structure from the conventional design. By using a single diaphragm with a flexure bearing that rotates against the tube wall, the complex oil-filled measuring cell is replaced with a simpler direct-contact design that achieves overload protection through the flexure bearing's rotational mechanism rather than through oil pressure distribution across multiple diaphragms.
Solution Approach 2:
The invention uses a thin diaphragm that can deform and rotate against the tube wall through a flexure bearing. This flexible thin film approach allows the diaphragm to accommodate pressure variations and overload conditions through rotation rather than requiring multiple rigid diaphragms and oil fill, simplifying the overall structure while maintaining reliability.
2Measurement precision
If exacting accuracy in welding and material properties is required, then measurement precision is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
The invention segments the measurement function from the structural components. The diaphragm is separated into a distinct element that can be independently manufactured and calibrated, while the tube and flexure bearing provide the mechanical structure. This segmentation allows the diaphragm to be optimized for measurement precision without requiring the entire assembly to meet exacting welding and material property requirements across all components.
Solution Approach 2:
The invention changes the mechanical parameters of the system by introducing the flexure bearing that allows rotation. This parameter change from a rigid welded structure to a rotational joint enables the diaphragm to move independently, improving measurement precision through better stress distribution while reducing the need for exacting welding accuracy in the overall assembly.
3Measurement precision
If strain gauges are applied to the tube's outer wall for differential pressure measurement, then measurement capability is achieved, but positioning accuracy becomes difficult to achieve in practice
Solution Approach 1:
The invention introduces the flexure bearing as an intermediary between the diaphragm and the tube wall. This intermediary component provides a defined rotational axis and contact point, which serves as a natural reference for positioning strain gauges. Instead of requiring precise positioning on the curved outer wall, the strain gauges can be positioned relative to the flexure bearing's rotation point, significantly improving positioning accuracy.
Solution Approach 2:
The flexure bearing is pre-installed in a fixed position on the tube, establishing a predetermined rotation axis before the strain gauges are applied. This preliminary action creates a stable reference framework that guides the subsequent positioning of strain gauges, making the positioning process more accurate and repeatable rather than requiring direct measurement and calculation on the outer wall.
4Adaptability or versatility
If a separating diaphragm is used in the cross section of the tube, then the sensor can measure both absolute and differential pressure, but the design becomes more complex requiring multiple diaphragm sections
Solution Approach 1:
The invention makes the single diaphragm universal by enabling it to function in both absolute and differential pressure measurement modes through the flexure bearing mechanism. The same diaphragm structure can measure absolute pressure when the tube is sealed or differential pressure when connected to two pressure sources, eliminating the need for multiple specialized diaphragm sections while maintaining measurement mode flexibility.
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 results in a mechanically simple, cost-effective, and robust pressure sensor with high long-term stability and insensitivity to static pressure, suitable for process instrumentation with reduced material fatigue and improved sensitivity.
Implementation Method 1
High sensitivity for measuring the diaphragm deformation, without having to bring the transducer required for this purpose into contact with a process fluid, can be advantageously achieved if a strain sensor is disposed in the recess on the outside of the tube to measure a surface strain as a function of the rotation of the flexure bearing.
Implementation Method 2
A pressure difference present on the separating diaphragm causes deformation thereof which is transmitted to the sidewall diaphragm due to a fixed angle between the two diaphragm sections
Data Source
AI summary
A pressure sensor arrangement includes a tube with a diaphragm to pressure to be measured is applied arranged in the cross-section of the tube, wherein the diaphragm is fastened to the tube inner wall via an articulation extending along the circumferential region of the diaphragm, where deformation of the diaphragm results in rotation of the articulation directly on the wall of the tube which can therefore be detected from the outside by suitable structure such that that strain sensors, for example, which can be used to detect deformation are advantageously not in contact with the process medium and there is advantageously no need for a pressure-tight bushing for electrical signals, and where the pressure sensor arrangement has a particularly simple structure and can be advantageously used in measuring transducers for process instrumentation.