Thermally-actuated flow-restrictor device for aircraft beverage maker
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Solution Overview
Problem
Conventional backflow prevention mechanisms in aircraft galley inserts are inadequate, as they either fail to provide sufficient relief for highly pressurized hot water or are large, heavy, and costly to install and maintain, posing a safety risk to crew members from unexpected hot water expulsion.
Innovation Solution
A thermally-actuated flow-restrictor device that is compact, lightweight, and fits within a standard aircraft galley insert, using a bimetal closure element with different thermal expansion coefficients to restrict backflow of hot water while allowing pressure relief, eliminating the need for external installation and electrical operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional backflow prevention mechanisms (check valves, thermal valves, or electrically operated valves) are installed in the aircraft galley's plumbing system, then backflow of hot water is prevented, but the device becomes large, heavy, costly to install and maintain, and requires external installation directly in the plumbing system
Solution Approach 1:
The invention extracts the backflow prevention function from the central plumbing system and relocates it to a compact device installed locally at the beverage maker. This allows the main plumbing system to remain simple while providing backflow prevention at the specific point where it is needed, eliminating the need for large, heavy valves in the main system.
Solution Approach 2:
The flow restrictor device is designed to fit within the existing beverage maker housing, nesting the backflow prevention mechanism inside the available space of the beverage maker. This eliminates the need for external installation in the plumbing system and reduces overall system complexity.
2Reliability
If check valves are used to prevent complete backflow, then backflow is restricted, but sufficient outlet for pressure relief is not provided, causing hot pressurized water to be expelled at high speed from the beverage maker
Solution Approach 1:
The device provides different flow characteristics at different locations: the first portion (check valve) prevents backflow toward the plumbing system, while the second portion (flow restrictor) controls the rate of water expulsion from the beverage maker. This local differentiation of flow control properties solves both the backflow prevention and pressure relief needs simultaneously.
Solution Approach 2:
Instead of completely blocking backflow with a check valve alone, the invention uses a flow restrictor that allows partial backflow at a controlled rate. This partial action provides sufficient pressure relief to prevent hazardous expulsion while still preventing dangerous backflow into the plumbing system.
3Device complexity
If a compact, lightweight flow-restrictor device is installed within the aircraft galley insert, then external installation and maintenance costs are reduced, but the device must still effectively prevent backflow and provide pressure relief
Solution Approach 1:
The device is segmented into two functional portions: a check valve portion for preventing backflow and a flow restrictor portion for controlling pressure relief. This segmentation allows each component to be optimized for its specific function while maintaining a compact overall size that can be installed within the beverage maker without external plumbing modifications.
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 device effectively prevents unanticipated hot water expulsion from galley sink faucets and inserts, ensuring crew safety by restricting backflow and providing pressure relief without requiring external installation or electrical power, thus reducing costs and complexity.
Implementation Method 1
A thermally-actuated flow-restrictor device... using a bimetal closure element with different thermal expansion coefficients to restrict backflow of hot water
Data Source
AI summary
A thermally-actuated flow-restrictor device in an aircraft galley insert is provided that includes a housing formed of first and second flanged fittings. The first fitting includes an outlet port for connection to an aircraft galley insert, and the second fitting includes an inlet port for connection to an aircraft potable water supply. The second fitting also includes a boss surrounding the inlet port. A closure element contained within the housing includes a plurality of metals having different coefficients of thermal expansion. This allows the element to actuate depending upon the temperature of water contacting the closure element. When water having a predetermined temperature contacts the closure element, its surface facing the inlet port becomes convexly positioned proximal to the boss, thereby restricting the backflow of water through the flow-restrictor device. Once the closure element cools, its surface facing the inlet port becomes concave, resulting in normal device operation.