Vacuum Relief Valve Constant Force Spring Biasing
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Solution Overview
Problem
Current vacuum relief valves for rail tank cars and trucks do not maintain a constant flow rate of air into tanks when the internal pressure decreases due to contracting fluids or gases, leading to potential tank implosion, and they are prone to leakage and debris accumulation, which can result in accidental release of commodities.
Innovation Solution
A vacuum relief valve with a biasing assembly using constant force springs and a cut flat gasket, which maintains a maximum flow rate of atmospheric air into the tank regardless of decreasing pressure and reduces leakage by compressing the gasket between the valve stem sealing disc and the seal retainer, eliminating the need for additional retaining rings and minimizing exposure to contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a helical spring is used as the biasing element in a vacuum relief valve, then the valve can be manufactured with simple components and lower cost, but the valve requires progressively greater tank vacuum to fully deflect the spring beyond the initial discharge pressure, resulting in non-constant flow rate
Solution Approach 1:
The patent changes the spring characteristic from linear (helical) to non-linear (constant force) by selecting a different spring design. Constant force springs maintain substantially constant force over a significant portion of their deflection range, enabling the valve to achieve full opening and maintain constant flow rate at a fixed discharge pressure without requiring progressively greater vacuum.
2Device complexity
If a helical spring is used to bias the valve closed, then the valve structure can be simpler, but the valve does not achieve full open position until vacuum achieves higher magnitude (six inches Hg versus four inches Hg), delaying maximum venting capacity
Solution Approach 1:
The patent changes the spring characteristic from linear to constant force, which fundamentally alters the force-deflection relationship. This enables the valve to open at a lower vacuum magnitude (four inches Hg versus six inches Hg) and achieve full open position at that same pressure, improving response time and reliability without adding structural complexity.
3Reliability
If O-rings are used to prevent leakage in the valve, then the sealing can be effective, but the O-rings are prone to dislodgement when tank contains highly viscous fluid, causing accidental release of commodity
Solution Approach 1:
The patent replaces the O-ring with a flat cut gasket that is compressed between the valve stem sealing disc and seal retainer. This gasket design is less prone to dislodgement by viscous fluids and can be easily replaced if needed, providing a more reliable sealing solution for harsh service conditions.
4Reliability
If multiple retaining rings are used to secure the baffle, then the baffle can be securely mounted, but the valve requires additional parts and assembly steps, increasing complexity
Solution Approach 1:
The patent merges the baffle mounting function with the seal retainer by integrating a single retaining ring that serves both to secure the baffle and retain the seal assembly. This reduces the number of parts and simplifies assembly while maintaining secure mounting of the baffle to prevent fluid entry into the valve body cavity.
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 ensures a constant flow rate of air into the tank without increasing the vacuum magnitude, preventing tank implosion and reducing leakage and exposure to contaminants, thus ensuring safe operation during temperature changes and unloading processes.
Implementation Method 1
a first and second constant force spring respectively attached to a spring block to form a biasing assembly
Implementation Method 2
The single flat cut gasket prevents dislodgement by compression between the valve stem sealing disc and the seal retainer
Data Source
AI summary
The invention described herein is a vacuum relief valve for rail way tanks, truck tanks, or any other analogous closed containers in which a valve prevents implosions from an interior vacuum pressure. The valve contains a novel biasing assembly and spring housing with constant force springs and this assembly is operatively attached to the tank. The pressure from these springs is such that only when the interior tank vacuum becomes greater than the springs' preset value will air enter the valve and the operatively attached tank. No increasing pressure from the biasing assembly is necessary to maintain the air flow into the valve at the air flow's initial rate.