Vertically Stacked Constant-Force Spring Pressure Relief Valve
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Solution Overview
Problem
Existing external pressure relief valves for railroad tank cars struggle with high flow rates due to the prohibitively large size of helical compression springs, which exceed the allowed height for protective housings, and constant-force spring valves are hindered by size, complexity, and cost constraints, limiting their acceptance in the industry.
Innovation Solution
The design employs vertically aligned constant-force spring assemblies made of numerous leaf springs, attached to a spring block with spring bolts, and incorporates a bearing assembly to reduce friction and torque requirements, along with a roller bearing assembly to minimize wear and friction, allowing for increased spring force within a smaller footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If helical compression springs are used in external pressure relief valves, then the valve can provide the required spring force, but the valve height becomes prohibitively large (at least seventeen inches) exceeding the maximum allowed height of approximately thirteen inches
Solution Approach 1:
The patent transitions from a horizontal arrangement of helical springs to a vertical stacking configuration of constant-force spring assemblies. This dimensional reorganization allows multiple spring units to be arranged in series vertically, compressing the horizontal footprint while managing the height constraint through optimized vertical stacking and a compact valve body design.
Solution Approach 2:
The patent divides the spring system into multiple discrete constant-force spring assemblies, each comprising stacked leaf springs. These segmented assemblies can be independently configured and stacked vertically, allowing flexible arrangement to achieve the required total spring force while maintaining a compact overall valve height within the thirteen-inch regulatory limit.
2Speed
If constant-force spring valves are used to achieve instant maximum venting capacity, then the valve opens instantly at pre-set pressure, but the size, complexity and cost prevent general acceptance in the industry
Solution Approach 1:
The constant-force spring assemblies are designed to automatically generate the required force without external intervention. The leaf spring configuration inherently provides constant force throughout its deflection range, enabling the valve to open instantly at the preset pressure without requiring complex control systems, actuators, or external power sources, thereby reducing overall system complexity.
Solution Approach 2:
The patent modifies the spring force characteristics by using constant-force spring assemblies with leaf springs stacked in series. This parameter change allows the spring to maintain relatively constant force over a range of deflections, enabling instant valve opening at the preset pressure while keeping the mechanical structure simpler compared to traditional helical spring systems that require larger sizes to achieve the same effect.
3Force
If more constant force springs are added to increase spring force, then the valve force capacity increases, but the valve size and complexity increase beyond space restrictions
Solution Approach 1:
The patent arranges multiple constant-force spring assemblies in a vertical stacking configuration rather than spreading them horizontally. This vertical arrangement in the height dimension allows multiple spring units to be compacted into a smaller horizontal footprint, increasing the total spring force capacity while maintaining a compact valve area that fits within the specified space restrictions.
Solution Approach 2:
The leaf springs within each constant-force spring assembly are nested or stacked in series, with multiple thin leaf springs arranged one over another. This nested configuration allows multiple spring elements to occupy the same spatial envelope, multiplying the spring force capacity without proportionally increasing the valve's external dimensions or horizontal area.
4Force
If vertically aligned constant force spring assemblies are used, then the valve dimensions are smaller and spring force is substantially increased, but friction and torque requirements increase
Solution Approach 1:
The patent introduces a bearing assembly as an intermediary element between the vertically stacked constant-force spring assemblies and the valve closure mechanism. This bearing assembly acts as a mediator that supports the vertical load from the springs while minimizing friction during valve operation, allowing the high spring force to be effectively transmitted without excessive energy loss to friction.
Solution Approach 2:
The patent replaces traditional direct-contact mechanical interfaces with a bearing assembly that uses rolling or sliding contact surfaces. This substitution reduces the coefficient of friction between moving parts, allowing the vertically aligned spring assemblies to generate high force while minimizing the torque required to operate the valve and reducing energy loss to friction.
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 configuration achieves higher flow rates and reduces the size and complexity of the valve, making it more compact, reliable, and cost-effective while maintaining precise pressure relief and preventing fluid venting below the preset pressure, thus addressing the limitations of traditional valves.
Implementation Method 1
The constant force springs are of a type that maintain a substantially constant force as they are deflected from their rest position.
Implementation Method 2
The bearing assembly also reduces the friction between the adjustment screw and disc, and thereby eliminates the requirement for constant lubrication of the contact area between these two components.
Data Source
AI summary
Described herein is an improved externally mounted pressure relief valve that is especially adapted for rail tank cars or other large closed containers that contain or transport fluids, including liquids and gases. The pressure relief valve comprises a plurality of spring assemblies, and each spring assembly contains a pre-determined number of spring leaves. Each spring assembly is coiled upon a corresponding spring drum, and each spring drum is penetrated by a corresponding spring drum bolt. The spring assemblies are preferably aligned in at least two horizontal planes that are parallel to each other and normal to the vertical length of a spring block. The spring block and sealing disk are mounted vertically over the valve seat and within the confines of vertically extending spring brackets.