External Relief Bias Member for Compact Thermal Flow Control
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Solution Overview
Problem
Existing thermally actuated flow-control valves face challenges in configuring adequate valve movement and pressure relief in compact configurations, especially when accommodating over-extension of the actuator at temperatures above the normal operating range.
Innovation Solution
A control valve design that positions a pressure relief bias member outside the housing, reducing axial penetration of the actuator and valve, and incorporates a return bias member and thermally responsive material to manage valve movement and pressure relief, allowing for large displacement of the valve member relative to the internal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the actuator and valve are positioned inside the housing, then the valve can control fluid flow, but the axial penetration required reduces the space available for valve member movement
Solution Approach 1:
The relief bias member is repositioned from an internal axial location to an external radial location on the housing. This dimensional change allows the bias member to exert its force through the housing wall rather than occupying axial space inside the housing, thereby resolving the contradiction between minimizing axial penetration and maximizing valve member movement range.
2Volume of moving object
If the control valve is configured in a compact arrangement, then the overall size is reduced, but it becomes difficult to provide adequate valve movement and pressure relief
Solution Approach 1:
The relief bias member is extracted from the internal volume of the housing and positioned externally on the housing. This extraction allows the pressure relief function to be maintained while preserving the internal compact arrangement of the actuator and valve components, thereby resolving the contradiction between compact overall size and adequate pressure relief capability.
3Reliability
If the actuator is allowed to over-extend at temperatures above normal operating range, then damage to the actuator is prevented, but the valve member movement becomes uncontrolled
Solution Approach 1:
The relief bias member is pre-positioned and pre-loaded to automatically counteract excessive actuator extension before damage can occur. When the actuator extends beyond its normal operating range due to overheating, the relief bias member engages to provide a restraining force, preventing further uncontrolled movement. This preliminary protective action maintains reliability without requiring complex control mechanisms.
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 a compact, accurate, and reliable thermally actuated flow-control valve that effectively manages valve movement and pressure relief, minimizing hysteresis and preventing damage from excessive temperature and pressure.
Implementation Method 1
a piston arranged to reciprocate in a guide that defines a bore in communication with the reservoir. A flexible diaphragm, plug, or other seal arrangement may be disposed between the wax and the piston to contain the wax in the reservoir. The wax expands in volume as the wax becomes a liquid
Implementation Method 2
The wax expands in volume as the wax becomes a liquid, generating a force that is directed into the bore of the guide, and pushes the piston away from the reservoir. Thus, the axial length of the actuator changes according to the temperature of the wax
Implementation Method 3
The relief bias member is trapped between the closed end of the cap and the first end of the container. The relief bias member exerts a relief bias force that urges the container away from the closed end of the cap
Implementation Method 4
A return spring is positioned to return the piston and valve to the retracted/cold position when the temperature of the fluid falls and the wax returns to its smaller volume
Data Source
AI summary
A thermally actuated flow control valve mounted to a housing to control fluid flow based on temperature is provided. The control valve has a relief bias member in a cap projecting outside of the housing. Within the housing, the control valve has an actuator extending into a return bias container and a valve member. The actuator includes a thermally responsive material that expands and contracts in response to fluid flow over a predetermined range of temperatures. The actuator extends to close the valve member against a valve seat within the housing when the thermally responsive material expands. A return member moves the valve member away from the valve seat when the thermally responsive material contracts. The return bias container allows the relief bias member to accommodate pressures and temperatures beyond the predetermined range.