Optical Water Level Sensor for Removable Household Appliance Tanks
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Solution Overview
Problem
Existing household appliances with water tanks face challenges in determining the fill level accurately and efficiently, as existing methods require complex optical alignments and special design features on the tank.
Innovation Solution
An optical sensor system is used externally on the tank's side wall, utilizing an IR light source and receiver with a wide radiation cone, positioned between the upper and lower edges of the tank, allowing for easy installation and alignment-free operation, with multiple sensors for redundancy and an air gap to prevent water droplet interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an optical sensor is positioned outside the tank opposite a side wall, then the tank can be removed without the level sensor and manufacturing is simplified, but direct irradiation of the receiver by the emitter must be prevented requiring an optical barrier
Solution Approach 1:
The patent introduces an optical barrier as an intermediary element positioned between the emitter and receiver to prevent direct light transmission. This barrier serves as a mediator that blocks the harmful direct irradiation while allowing the sensor to function externally on the tank wall, thus resolving the contradiction between simplified tank manufacturing and the need for optical isolation.
2Ease of operation
If the emitter radiates into a larger solid angle, then alignment is simplified, but the air gap between the emitter and tank wall increases requiring larger housing dimensions
Solution Approach 1:
The patent applies partial action by having the emitter radiate into a larger solid angle than the minimum required, which simplifies alignment tolerance. The excessive radiation angle is acceptable because it ensures reliable detection despite variations in tank positioning, and the resulting increased air gap is managed within the housing design constraints.
3Reliability
If multiple sensors are mounted at the same height, then reliability against droplet formation is improved, but device complexity increases
Solution Approach 1:
The patent employs beforehand cushioning by mounting multiple sensors at the same height to create redundancy against droplet formation. This prior protective measure ensures that if one sensor is blocked by water droplets, other sensors at the same location can still provide reliable measurements, thus cushioning against potential measurement failures.
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
This solution simplifies the production of the tank, ensures accurate fill level measurement, and allows for easy removal and maintenance of the tank without affecting the level sensor functionality, reducing the likelihood of measurement errors from water droplets.
Implementation Method 1
an optical sensor is used to determine the fill level. This sensor is located outside the tank, opposite one of its side walls... An 'optical sensor' is defined as a sensor comprising at least one emitter and one receiver of light waves, the intensity of which depends on the water level in the tank
Implementation Method 2
The emitter is preferably a radiation source emitting in the infrared (IR) range, e.g., an IR light-emitting diode (LED)
Implementation Method 3
Direct irradiation of the receiver by the emitter is preferably prevented by an optical barrier between the two parts
Implementation Method 4
there is an air gap of at least 1 mm, and in particular at least 3 mm, between the most prominent component and the side wall of the tank. Within such a gap, water droplets can run off without becoming trapped between the sensor and the wall
Data Source
Figure 1A~1C
Figure 1D~2C
Figure 3A~3C
AI summary
A household appliance with a tank (11) for holding water and an optical level sensor (14) is described, wherein the level sensor (14) comprises at least one emitter (143-1,343-1) and one photoreceiver (143-2,343-2), which are mounted in the household appliance opposite a transparent side wall (112) of the tank (11) in the installed and ready-to-use state at a level (114) below an upper edge of the tank (11) and above a bottom of the tank (11).