Pneumatic Detector Assembly Bellows Switch Design
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Solution Overview
Problem
Pneumatic fire detectors for aircraft have complex designs and numerous parts, making them difficult to manufacture and ensuring hermeticity, which is a challenge for reliable fire detection systems.
Innovation Solution
A simplified pneumatic detector assembly using a housing, sensor tube, and switches with bellows and contact pins, where the bellows are configured to change contact with the pins based on pressure changes, allowing for a reduced number of parts and easier assembly, with alarm and integrity switches designed to respond to specific pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pneumatic detector design with pre-formed diaphragms is used, then detection function is achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines the alarm switch and integrity switch into a single housing, sharing common components such as the sensor tube, bellows mechanism, and sealing structures. This merging reduces the overall number of parts and simplifies manufacturing while maintaining both detection functions.
Solution Approach 2:
The bellows structure serves multiple functions: it acts as both the sensing element for pressure detection and the actuating mechanism for both the alarm and integrity switches. The single sensor tube serves both switches, eliminating the need for separate sensing mechanisms.
2Reliability
If traditional pneumatic detector with multiple parts is used, then detection capability is maintained, but manufacturing ease and assembly simplicity decrease
Solution Approach 1:
The detector is segmented into modular components: a housing containing the switches, a separate sensor tube, and bellows assemblies. This segmentation allows for simplified manufacturing of individual parts that can be assembled together, reducing overall manufacturing complexity.
Solution Approach 2:
The bellows are pre-assembled with their respective contact pins and sealing structures before final integration into the housing. The sensor tube is prepared with appropriate fittings and connections in advance, enabling easier final assembly and reducing manufacturing steps.
3Reliability
If traditional design with numerous parts is used, then hermeticity can be achieved, but the number of brazing or welding operations increases
Solution Approach 1:
By combining multiple sealing functions into integrated components such as the housing that seals both switches and the sensor tube connections, the patent reduces the total number of separate sealing joints requiring brazing or welding operations.
4Measurement precision
If traditional pneumatic detector is used, then detection accuracy is maintained, but the number of hermeticity tests required increases
Solution Approach 1:
The integrated housing and sealed chamber design combines multiple detection pathways into a single hermetic enclosure, reducing the number of separate hermeticity tests required while maintaining detection accuracy through the shared pressure-sensing mechanism.
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 solution simplifies the manufacturing process and reduces the complexity of pneumatic detectors, ensuring reliable operation by using fewer parts and easier assembly, while maintaining effective detection of overheat and fault conditions through pressure-induced switch activations.
Implementation Method 1
the first contact face of the first bellows configured to be out of contact with the first contact pin in a normal operating condition and to be in contact with the first contact pin in an alarm condition based on a pressure in the sensor tube
Implementation Method 2
When the sensor tube portion of the pneumatic detector is exposed to high temperature, the pressure is increased inside the tube as the inert gas expands in accordance to physical gas laws
Data Source
Figure 1~2B
Figure 3~5
Figure 6~8
AI summary
A pneumatic detector assembly (10) includes a housing, a sensor tube (40), a contact pin (24, 34), and at least one switch (20, 30) having a bellows (22, 32) operatively associated with the sensor tube (40) and the contact pin (24, 34). The bellows (22, 32) is configured to move into and out of contact with the contact pin (24, 34) based on a pressure in the sensor tube (40).