Pressure Relief Valve Assembly With Fluid-Retained Spring
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Solution Overview
Problem
Conventional pressure relief valves used in aircraft engine cowl maintenance are unreliable due to ice formation at cold temperatures, which alters the set point and can cause damage by applying excessive pressure, especially during short stopovers when heating devices are not feasible.
Innovation Solution
A pressure relief valve assembly with a secondary valve that retains hydraulic fluid around the primary valve spring, preventing ice formation and maintaining the set point by keeping the spring immersed in fluid, thus avoiding exposure to atmosphere and debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pressure relief valve with a simple ball and spring assembly is used, then the device complexity is low and the valve is small and light, but ice formation on the spring at cold temperatures alters the set point and causes unreliable operation
Solution Approach 1:
The pressure relief valve assembly is segmented into two distinct valve systems: a primary pressure relief valve with ball and spring assembly, and a secondary valve with plug and spring assembly. Each valve handles different aspects of pressure control, with the secondary valve specifically protecting the primary valve's spring from ice formation by maintaining a fluid environment around it.
Solution Approach 2:
Hydraulic fluid acts as an intermediary substance that surrounds the primary valve spring and is retained by the secondary valve. This fluid barrier prevents atmospheric moisture from contacting the spring and forming ice, thereby maintaining the spring's mechanical properties and the valve's set point accuracy in cold temperatures.
2Reliability
If heating devices are incorporated to prevent ice formation, then ice formation on the spring is prevented, but the device becomes too large and heavy for feasible implementation
Solution Approach 1:
Instead of using thermal heating devices, the invention uses hydraulic principles by retaining hydraulic fluid around the spring with the secondary valve. The fluid's physical presence prevents ice formation through displacement of atmospheric moisture, leveraging the existing hydraulic system's fluid rather than introducing separate thermal control systems.
3Device complexity
If the pressure relief valve is exposed to atmosphere, then the structure is simple, but condensation and ice formation occur on the spring altering the set point
Solution Approach 1:
The secondary valve creates a protected environment around the primary valve spring by retaining hydraulic fluid, effectively replacing the atmospheric environment with a fluid environment that is inert to ice formation. This fluid barrier prevents atmospheric moisture and condensation from contacting the spring.
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
Ensures reliable operation within the desired pressure tolerance range, preventing damage to the cowl opening system by maintaining the set point and preventing ice formation, even in cold conditions.
Implementation Method 1
a secondary valve is positioned relative to the primary valve to retain fluid around the valve spring of the primary valve
Implementation Method 2
a primary pressure relief valve having a valve ball and a valve spring, the valve spring biasing the valve ball in a first direction into a valve seat
Implementation Method 3
the spring force is selected such that a fluid force above a predetermined set point acting against the ball in a second direction opposite the first direction causes the ball to move out of the valve seat
Data Source
AI summary
A pressure relief valve assembly comprising a valve housing within which is provided a primary pressure relief valve having a valve ball and a valve spring, the valve spring biasing the valve ball in a first direction into a valve seat to prevent the passage of fluid from a fluid line through the valve, and wherein the spring force is selected such that a fluid force above a predetermined set point acting against the ball in a second direction opposite the first direction causes the ball to move out of the valve seat against the spring force to allow fluid to flow from the fluid line through the valve seat and through the valve, and wherein a secondary valve is positioned relative to the primary valve to retain fluid around the valve spring of the primary valve at a fluid force below the predetermined set point.