Servo Valve Spool Geometry for Leak-Resistant Flow Control
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Solution Overview
Problem
Existing servo valves in aerospace applications require complex calibration and have air gaps that can lead to fluid leakage and contamination, complicating precise fluid control in hydraulic systems.
Innovation Solution
A servo valve design featuring a movable member with frusto-conical sections and cylindrical sections within a valve housing, utilizing a solenoid and spring assembly for axial movement, which controls fluid flow through ports with adjustable nozzle openings, reducing the need for calibration and air gaps, and incorporating O-ring seals and cover plates for enhanced sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional servo valve design with flapper and nozzles is used, then fluid flow control is achieved, but complex calibration and air gaps leading to leakage and contamination occur
Solution Approach 1:
The patent removes the traditional flapper and nozzle components from the servo valve design. Instead, it uses a spool member with axial movement to directly control fluid flow between ports. This extraction of problematic components eliminates the air gaps and calibration complexity associated with flapper-nozzle systems while maintaining precise fluid control capability
Solution Approach 2:
The patent introduces a spool member as an intermediary component between the solenoid actuator and the fluid passages. This spool member with its axial positions provides a mechanical mediation that directly blocks or opens fluid paths without the need for complex flapper-nozzle calibration, thereby eliminating air gaps and improving reliability
2Measurement precision
If a spool member with frusto-conical sections is used to control fluid flow, then precise control is achieved, but the structure becomes more complex
Solution Approach 1:
The spool member features frusto-conical sections at specific locations (first and second ends) rather than a uniform structure. These localized conical sections provide precise fluid control at critical interfaces with the ports, while the central portion remains simple cylindrical. This local differentiation achieves precise control without requiring complex geometry throughout the entire component
Solution Approach 2:
The patent employs frusto-conical surfaces on the spool member to control fluid flow. These curved conical surfaces provide gradual transition and precise metering of fluid as the spool moves axially, enabling fine control precision. The curvature allows for progressive opening or closing of fluid passages rather than abrupt changes, enhancing control precision
3Reliability
If O-ring seals and cover plates are added to reduce air gaps, then sealing is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses O-ring seals (flexible elastomeric elements) to provide sealing between the spool member and valve body, and between cover plates and the valve housing. These flexible seals conform to slight manufacturing variations and provide reliable sealing without requiring precision-machined mating surfaces, thereby improving sealing performance while remaining manufacturable
Solution Approach 2:
The cover plates are designed to be installed first to seal the external openings of the valve housing before the internal spool and O-ring sealing arrangements are finalized. This preliminary sealing action prevents contamination during assembly and establishes a sealed environment early in the manufacturing process
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 design enables precise and simplified control of fluid flow with reduced calibration requirements and improved sealing, minimizing fluid leakage and contamination, while maintaining a simplified construction.
Implementation Method 1
the valve further comprises a solenoid having a central opening extending axially therethrough, the member comprising a first portion extending axially into the central opening, wherein the first portion comprises a ferromagnetic material such that actuation of the solenoid is configured to cause an axial movement of the member
Implementation Method 2
the first and second nozzle openings each having diameters smaller than the diameter of their respective port, wherein, in a first axial position of the member the second nozzle opening is at least substantially obstructed by the second frusto-conical surface and the first nozzle opening is at least substantially unobstructed by the first frusto-conical surface
Implementation Method 3
O-ring seals proximate the first and second sections to sealingly engage the member and the valve housing
Data Source
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AI summary
A servo valve (10) comprises a valve housing (12), a cavity (16) formed in the valve housing (12) and defining a longitudinal axis (X), and a member (26) disposed in the cavity (16) and axially-moveable therein, wherein the member (26) comprises a portion (30) with first and second cylindrical sections (32, 34) having a first diameter (R1, R2), a central section (36) located between the first and second cylindrical sections (32, 34) and having a second diameter (R3), and first and second frusto-conical sections (37, 39) connecting the first and second sections (32, 34) to the central section (36) and forming respective first and second frusto-conical surfaces (38, 40). A plurality of ports (48A, 48B, 48C), each form a fluid passage through the valve housing (12) and have first and second nozzles (50A, 50C) with first and second nozzle openings (52A, 52C).