Ultrasonic Vent Obstacle Detection in Smoke Alarm Housings
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Solution Overview
Problem
Existing alarm devices face issues with inadequate air flow due to obstacles obstructing vents, leading to unreliable obstacle detection, particularly in static positions, such as smoke, heat, and carbon monoxide sensors.
Innovation Solution
An alarm device with an ultrasonic obstacle detector using a dish-shaped guide element and ultrasonic transducer mounted flush with the housing, combined with a processor to detect ambient air stability, ensuring reliable obstacle detection by minimizing echo interference and air turbulence effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ultrasonic transducer is mounted on the alarm device to detect obstacles, then obstacle detection capability is improved, but echo interference from the housing and air turbulence noise increase, reducing measurement precision
Solution Approach 1:
A guide element is introduced as an intermediary component between the ultrasonic transducer and the housing. This guide element directs the ultrasonic waves away from the housing surfaces that would create interfering echoes, while still allowing the waves to propagate into the environment for obstacle detection. The guide element effectively mediates between the need for detection capability and the need to avoid echo interference.
Solution Approach 2:
The guide element is positioned at a specific location and orientation to create localized wave direction control. By strategically placing the guide element, the ultrasonic waves are directed into specific zones where obstacles are most likely to be detected, while avoiding zones that would create harmful echoes. This local control of wave quality improves measurement precision without sacrificing overall detection capability.
2Measurement precision
If the ultrasonic transducer is mounted flush with the housing to minimize interference, then echo interference is reduced, but the field of view for obstacle detection is limited
Solution Approach 1:
The guide element extends the ultrasonic wave propagation in additional spatial dimensions. By using a guide structure with specific geometry, the waves are directed along paths that would not be available if the transducer were simply mounted flush with the housing. This dimensional extension of the wave path increases the effective field of view while maintaining the flush mounting configuration that reduces echo interference.
3Device complexity
If ambient air instability is not monitored, then device complexity is reduced, but false alarms increase due to air turbulence affecting ultrasonic wave propagation
Solution Approach 1:
The processor monitors ultrasonic return signals to detect variations caused by air turbulence. By analyzing the characteristics of the returned waves, the system provides feedback about ambient air stability. When turbulence is detected, the system can adjust its operation or alert the user, preventing false alarms. This feedback mechanism adds complexity only when needed to maintain 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
Enhances obstacle detection accuracy by reducing echo interference and air turbulence noise, providing reliable air flow detection and preventing false alarms due to vent blockages.
Implementation Method 1
an ultrasonic transducer to emit ultrasonic waves
Implementation Method 2
the waves reflecting off surfaces
Implementation Method 3
minimize echo interference
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An alarm device (1) detects smoke and has a housing having a longitudinal axis and containing a sensor and having vents (3) for access by ambient air to the sensor, a signal processing circuit (15) with a processor linked with the sensor, a power supply for the circuit and the sensor. An obstacle detector detects presence of an unwanted obstacle to flow of ambient air to the sensor. The obstacle detector has an ultrasonic transducer (16) mounted to reflect emitted ultrasonic waves in radial directions relative to the longitudinal axis. The guide comprises a dish-shaped guide element (6) mounted to the housing (2) so that a single ultrasonic transducer can emit radially to cover a very large field of view, but also that the guide element (60) can act as a secondary source directing ultrasonic waves axially, and also to direct waves through the vents (3) so that there is immediate and effective detection of inadvertent blocking of the vents by tape. Also, there is in-built determination as to whether the air is stable enough for accurate obstacle detection.