Electrohydraulic Mixing Valve With Fail-Fixed Temperature Control
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Solution Overview
Problem
Existing thermostatic control valves for water temperature regulation lack efficient and reliable mechanisms to maintain precise temperature control, especially in systems where electrical actuation is involved, and often fail to maintain set points upon electrical communication breakdown.
Innovation Solution
A thermostatically controlled fluid system using a mixing valve actuated by an electrical actuator, which combines hot and cold fluid sources and adjusts the mixing ratio based on temperature feedback from a thermostat, ensuring temperature stability through a combination of mechanical and electrical control mechanisms, including a PID algorithm for precise temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electrical actuator is used to control the mixing valve, then temperature control precision is improved, but reliability deteriorates due to electrical communication breakdown
Solution Approach 1:
A thermostat acts as an intermediary between the electrical actuator and the mixing valve. The thermostat mechanically senses temperature and directly actuates the valve, providing a reliable backup control path that does not depend on electrical signals. This mechanical intermediary ensures the system maintains temperature control reliability even when electrical communication fails.
Solution Approach 2:
The thermostat provides self-service temperature control by automatically sensing temperature deviations and mechanically adjusting the mixing valve position without requiring external electrical commands. This self-regulating capability ensures the system maintains temperature precision and reliability autonomously, especially during electrical failures.
2Measurement precision
If a PID algorithm is implemented for temperature management, then temperature control precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex electronic PID control algorithms with a simpler mechanical thermostat-based control system. The thermostat's inherent mechanical response characteristics provide sufficient temperature management precision without requiring sophisticated electronic computation, thereby reducing overall device complexity while maintaining adequate control accuracy.
3Reliability
If the system uses both mechanical thermostat and electrical actuator, then reliability is improved through fail-safe mechanism, but device complexity increases
Solution Approach 1:
The patent merges the electrical actuator and mechanical thermostat into a unified control system where both components work together on the same mixing valve. The electrical actuator provides primary controlled adjustment while the thermostat provides automatic mechanical backup, creating a fail-safe mechanism that improves reliability. The merging of these two control approaches allows them to complement each other rather than add separate independent systems.
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 system effectively maintains a consistent water temperature within a plumbing system, even in the event of electrical failures, by using a fail-safe mechanism that retains the set point, ensuring reliable temperature control and minimizing temperature fluctuations.
Implementation Method 1
a thermostat operably connected to the valve to move the valve in response to the temperature of the mixed fluid
Implementation Method 2
an electrical actuator operably connected to the valve to move the valve in response to an electrical signal
Data Source
AI summary
Apparatus and methods for providing fluid such as water at a controlled temperature. In some embodiments, hot and cold fluid is provided to a thermostatically controlled mixing valve, which then provides fluid at a mixed temperature to a plumbing system. The thermostat provides a first loop for closed-loop control of fluid exit temperature, and preferably there is a second, electronically controlled closed loop for adjusting the temperature of fluid exiting the valve. In yet other embodiments the electronic control loop is fail-fixed, such that a loss of electrical communication to the actuator results in the actuator maintaining its last position. In yet other embodiments there is a system including a flow sensor and a recirculation pump such that the temperature of the fluid exiting the valve cannot be adjusted if there is insufficient flow, or if the pump is actuated.