Valve Over-Travel Spring Mechanism for Reliable Closure
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Solution Overview
Problem
Existing safety shut-off valves face challenges in reliably closing to a prescribed leakage rate due to manufacturing tolerances, leading to mechanical complications and increased closing force requirements, which are undesirable for compact and efficient design.
Innovation Solution
Incorporating an over-travel spring between the main valve closure member and the solenoid or plunger, which provides a biasing force during the over-travel stroke without diminishing the sealing force, allowing for reduced actuator size and cost while assisting the opening force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stem over-travel is used to overcome manufacturing tolerances, then valve closure reliability is improved, but mechanical complications increase
Solution Approach 1:
The valve closure process is segmented into two distinct phases: primary sealing phase where the valve seal contacts the seat to achieve prescribed leakage rate, and over-travel phase where the stem continues moving to engage a hard stop. This segmentation allows the POC switch to be closed at the primary sealing point without requiring the entire stem travel to complete closure, thereby reducing mechanical complexity while maintaining reliability.
Solution Approach 2:
The valve seal is designed to make preliminary contact with the valve seat before the stem completes its full travel. This preliminary action achieves the sealing function and closes the POC switch early in the closure sequence, eliminating the need for complex mechanical linkages that would otherwise be required to coordinate switch closure with full stem travel.
2Reliability
If seal over-travel with auxiliary seal is used, then leakage reduction is improved, but additional closing force is required
Solution Approach 1:
Instead of requiring full seal over-travel with an auxiliary seal system, the invention uses partial over-travel of the stem beyond the primary seal contact point. The stem continues to travel a limited distance to engage a hard stop, providing sufficient additional sealing pressure without the complexity and force requirements of a multi-seal system. This partial action achieves the necessary leakage reduction while minimizing additional closing force requirements.
3Reliability
If larger actuator is used to overcome larger closing force, then valve closure reliability is improved, but device size and cost increase
Solution Approach 1:
The POC switch is designed to close preliminarily when the valve seal first contacts the seat, before the stem completes its full travel. This preliminary switch closure provides immediate feedback that the valve has reached the prescribed leakage rate, allowing the actuator to be sized for the primary sealing force rather than the maximum force required for full stem travel. This reduces actuator size and cost while maintaining closure reliability.
Solution Approach 2:
The invention extracts the reliability verification function from the mechanical closure process by using a separate POC switch that operates independently of full stem travel. The switch closes based on seal-to-seat contact rather than stem position, allowing the actuator to be sized for sealing requirements alone without needing to overcome the full mechanical over-travel force.
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 efficient valve operation without additional closing force, maintaining sealing integrity and reducing mechanical complexity, thus enhancing design efficiency and compactness.
Implementation Method 1
an over-travel spring having a first end attached to the main plate and a second end connected to the valve seal structure
Implementation Method 2
provides a biasing force during the over-travel stroke
Data Source
AI summary
A valve having an over-travel spring that does not necessarily need an excessively additional force to further close the valve once its valve seal comes into contact with a valve seat. The feature may be achieved by inserting an over-travel spring between a plate or stop attached to a valve stem, and a valve seal. The valve seal may come in contact with a valve seat when the valve is closed with movement of the valve stem. The valve stem may continue to travel after contact between the valve seal and the valve seat without additional force, other than that added by compressing the over-travel spring, and with a proof-of-closure sensor indicating valve closure. The valve stem may be moved in either direction for closing and opening the valve with an assist, such as a solenoid or other mechanism.