Smoke Detector External Sampling Volume Lag Time
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Solution Overview
Problem
Conventional smoke detectors, such as ionization and photoelectric types, have significant lag times due to internal sensing chambers that restrict smoke flow, delaying detection and potentially reducing Available Safe Egress Time in fire situations, and lack effective testing mechanisms for the smoke-detecting element.
Innovation Solution
A smoke detector using a proximity sensor to detect smoke outside the device, combined with a gas sensor for byproducts like CO or CO2, which reduces lag time by directly measuring smoke density and enables continuous automatic testing of the smoke-detecting element through an evaluation circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an internal sensing chamber with baffle is used to isolate the smoke-detecting element from ambient environment, then the detector structure is protected and sealed, but smoke flow is restricted causing substantial lag time in detection
Solution Approach 1:
The patent removes the internal sensing chamber and baffle structure that were isolating the smoke-detecting element. The smoke detector now directly exposes the detecting element to ambient smoke without physical barriers, extracting the protective enclosure that was causing lag time. This allows smoke to reach the detecting element immediately without being restricted by chamber walls or baffles.
Solution Approach 2:
The patent segments the detection function from the protective housing structure. Instead of having the smoke-detecting element enclosed within a sealed chamber, the detector design allows the detecting element to be accessible to ambient smoke while the housing provides external protection. This segmentation enables direct smoke exposure for immediate detection while maintaining structural integrity.
2Ease of manufacture
If conventional test mechanisms are used to test electrical circuitry, then the electrical components can be verified, but the smoke-detecting element operation cannot be tested
Solution Approach 1:
The patent implements a self-testing mechanism where the smoke detector uses its own smoke-detecting element to test itself. During normal operation, the detecting element continuously monitors ambient smoke levels. The system can verify the element's functionality by analyzing its response to known smoke conditions or by using internal reference comparisons, allowing the detector to self-verify without external testing equipment.
Solution Approach 2:
The smoke-detecting element serves dual functions: it detects ambient smoke for fire detection and simultaneously serves as the testing mechanism for verifying its own operational status. This multi-functionality eliminates the need for separate test mechanisms while ensuring the detecting element's reliability.
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 significantly reduces lag time in smoke detection and allows for continuous testing of the smoke-detecting element, enhancing the reliability and speed of smoke and gas detection, thereby improving safety in fire scenarios.
Implementation Method 1
The proximity sensor generally operates by emitting a beam of light and detecting any reflected signal from an object located within a specified range
Implementation Method 2
a gas sensor to detect the presence of gaseous fire byproducts such as carbon monoxide (CO) or carbon dioxide (CO 2)
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
In accordance with certain embodiments, a smoke detector comprises a housing, a light source, one or more light detectors, and an evaluation circuit for determining the presence of smoke particles outside the housing.