Torsional Spring Cam Assembly for Slam-Shut Valve Reliability
Solution Overview
Problem
Current slam-shut safety valves in gas distribution systems rely on flexion springs for biasing forces, which may not provide reliable rearming after closure, potentially leading to inconsistent performance and reduced safety in pressure regulation.
Innovation Solution
The implementation of a torsional spring mechanism with a cam assembly that includes a pair of stationary and pivotable arms, allowing the cam to be biased into a position for reliable rearming, coupled with overpressure and underpressure springs to set pressure tolerances, ensuring consistent operation and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the cam arm is allowed to move freely for pressure sensing, then the valve can respond to pressure changes, but lateral displacement occurs reducing precision
Solution Approach 1:
The patent segments the cam arm into distinct functional zones: a lateral movement region that allows pressure-responsive rotation, and a longitudinal axis that provides geometric constraint. The torsional spring acts specifically on the rotational degree of freedom while the cam arm's geometry constrains lateral displacement, separating the adaptive pressure response function from the precision positioning requirement.
Solution Approach 2:
The cam arm is designed with asymmetric geometry where the longitudinal axis is offset from the pivot point, creating a mechanical constraint that prevents lateral displacement while allowing rotational movement for pressure sensing. This asymmetric configuration ensures the cam arm follows a precise arc path during operation.
2Device complexity
If a single wire flexion spring is used, then the device complexity is reduced, but the biasing force reliability is insufficient
Solution Approach 1:
The patent transitions from a static linear spring configuration to a dynamic torsional spring mechanism that provides rotational torque. The torsional spring's coil structure winds and unwinds during cam arm rotation, dynamically adjusting the biasing force to maintain reliable engagement throughout the cam's range of motion, while remaining a single-component solution.
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 torsional spring mechanism enhances the reliability and repeatability of the slam-shut safety valve by maintaining the cam in a desired position for rearming, improving the valve's ability to respond to pressure deviations and preventing lateral displacement, thus ensuring consistent gas pressure regulation and enhanced safety.
Implementation Method 1
a torsional spring adapted to engage the first cam arm of the cam. The pair of inner arms is adapted to act on the first cam arm to bias the cam into a position that allows the cam to be relatched in a valve rearming process
Implementation Method 2
coupled with overpressure and underpressure springs to set pressure tolerances
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A cam assembly for use in a slam- shut safety valve includes a cam having an elongated first cam arm, and the cam is pivotable about a rotational axis. The cam assembly also includes a torsional spring having a pair of stationary outer arms and a pair of pivotable inner arms, wherein the pair of stationary inner arms is coupled to a portion of the first cam arm. The pair of inner arms is adapted to act on the first cam arm to bias the cam into a position that allows the cam to be relatched in a valve rearming process. The pair of inner arms is symmetrically disposed about the first cam arm to prevent lateral displacement of the cam.