Pneumatic Servovalve Assembly High Temperature Sealing
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Solution Overview
Problem
Single stage pneumatic servovalves used in aircraft air management systems face difficulties in high ambient and supply air temperatures, particularly at engine high pressure bleed locations, due to limitations in existing O-ring seals and materials.
Innovation Solution
A servovalve assembly with a central control portion of higher stiffness than the resiliently deformable end portions, utilizing a planar central control portion and curved end portions, along with a bellows seal and adjustable soft magnetic core, to maintain effective operation at high temperatures, and a solenoid assembly with PTFE/graphite bearings for low friction and high temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional O-ring seal is used to seal the pneumatic nozzle subsystem from the torque motor cavity, then the servovalve can operate at various pressures and temperatures, but the seal reliability deteriorates at high ambient and supply air temperatures especially at engine high pressure bleed locations
Solution Approach 1:
The patent changes the sealing mechanism from elastic deformation (O-ring) to mechanical interlocking (tapered groove and wedge-shaped seal). The wedge-shaped seal with included angle of 10-30 degrees mechanically locks into the tapered groove, preventing seal failure at high temperatures where elastic materials would deform excessively or degrade.
Solution Approach 2:
The patent uses a composite sealing approach combining the wedge-shaped seal element with the tapered groove structure in the nozzle housing. This composite mechanical sealing system replaces the single-material O-ring approach, providing temperature-resistant sealing through geometric interlocking rather than relying on material elasticity alone.
2Ease of manufacture
If the control element is made uniformly thick throughout, then manufacturing is simpler, but the resiliently deformable end portions cannot elastically deform before the central control portion when tension is applied
Solution Approach 1:
The patent applies local quality by making the end portions thinner than the central control portion. The end portions have reduced thickness to increase their flexibility and allow them to deform elastically first when tension is applied, while the thicker central portion maintains structural integrity and dimensional stability for precise control.
Solution Approach 2:
The control element is segmented into regions of different thickness: a thicker central control portion and thinner resiliently deformable end portions. This segmentation allows each region to perform its specific function - the central portion provides structural stability while the end portions provide elastic deformation capability for actuation.
3Temperature
If high-temperature resistant materials are used throughout the servovalve assembly, then temperature resistance improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies high-temperature resistant features locally where needed rather than throughout the entire assembly. The wedge-shaped seal and tapered groove are implemented only in the pneumatic nozzle subsystem where high-temperature sealing is critical, while other parts can use conventional materials, reducing overall complexity.
Solution Approach 2:
Instead of using soft elastic seals that fail at high temperatures, the patent inverts the approach by using a rigid mechanical interlocking system (wedge-shaped seal in tapered groove) that actually improves with temperature. This inverted sealing mechanism provides temperature-resistant operation without requiring exotic materials throughout the assembly.
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 servovalve assembly maintains accurate fluid control and reduces maintenance costs by ensuring reliable operation in high temperature environments through differential stiffness and high-temperature resistant materials, while the modular design simplifies assembly and reduces maintenance time.
Implementation Method 1
the resiliently deformable end portions are configured to elastically deform before the central control portion does, when the control element is placed under tension by a force applied parallel to the central control portion
Implementation Method 2
The bellows seal comprises a high temperature metal alloy, such as a nickel-cobalt alloy. In this manner, the bellows seal provides a high temperature seal for the pneumatic subassembly.
Implementation Method 3
a solenoid assembly with PTFE/graphite bearings for low friction and high temperature resistance
Implementation Method 4
a solenoid assembly with PTFE/graphite bearings for low friction and high temperature resistance
Data Source
AI summary
The present disclosure relates to a servovalve assembly comprising a pair of opposed nozzles spaced apart by a first gap. A control element positioned in the first gap (G) between the pair of opposed nozzles. Each nozzle has an outlet opening. The control element has a central control portion and two resiliently deformable end portions at opposite ends of the central control portion. The central control portion is perpendicular to a central axis (C) of each nozzle outlet opening. The control element is configured such that the two resiliently deformable end portions elastically deform when the control element is placed under tension by a force applied parallel to the central control portion, so as to move the control element in a direction parallel to the central axis (C) of each nozzle outlet opening.