Dishwasher Spray Arm Rotation Sensing via Total Internal Reflection
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Solution Overview
Problem
Existing solutions for monitoring the rotation of liquid spray arms in domestic appliances, such as dishwashers, are costly and prone to malfunctions, particularly when using optical means like light barriers.
Innovation Solution
A process utilizing electromagnetic radiation, specifically light, is coupled into a light-conducting element using total reflection, allowing for reliable detection of rotation without requiring changes to the spray arm, using a light-emitting diode as a transmitter and a phototransistor as a receiver, integrated within the dishwasher's internal illuminating unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical means like light barriers are used to detect spray arm rotation, then rotation detection is achieved, but the device becomes costly and susceptible to malfunctioning
Solution Approach 1:
The patent replaces complex optical detection systems with a simple optical guide element that utilizes total internal reflection. The spray arm itself acts as the detection mechanism by interrupting the light path when rotated, eliminating the need for complex light barriers or additional mechanical sensors. This substitution dramatically reduces device complexity while maintaining reliable rotation detection.
Solution Approach 2:
The spray arm serves dual functions: it performs its primary spraying function while simultaneously acting as the detection element for rotation monitoring. When the spray arm rotates, it naturally interrupts the light path within the optical guide, providing self-detection without requiring separate sensing components. This self-service approach reduces overall system complexity and cost.
2Ease of operation
If additional openings are made in the dishwasher for the rotation sensor, then rotation detection is possible, but the device structure becomes more complex and costly
Solution Approach 1:
The optical guide element serves multiple functions: it guides light from the illuminating unit, acts as the detection path for rotation monitoring, and can be integrated into existing dishwasher structures without requiring dedicated sensor openings. This multi-functionality allows rotation detection to be implemented using existing structural elements, avoiding additional openings and reducing structural complexity.
Solution Approach 2:
The patent merges the rotation detection function with existing dishwasher components, particularly the illuminating unit and its optical guide. By combining the detection path with the existing light guide structure, the system eliminates the need for separate sensor housings or additional openings in the dishwasher body, thereby maintaining structural simplicity.
3Measurement precision
If the rotation sensor is arranged on the spray arm, then direct rotation measurement is achieved, but the outlay becomes high and the sensor is susceptible to malfunctioning
Solution Approach 1:
The patent introduces an optical guide element as an intermediary between the light source and the detection point. This optical guide transmits light through total internal reflection and allows the spray arm to interrupt the light path indirectly. The intermediary protects the detection mechanism from direct exposure to water and mechanical stress, improving reliability while maintaining measurement precision.
Solution Approach 2:
The patent replaces mechanical contact-based rotation sensors with an optical detection system. Instead of using mechanical encoders or potentiometers that would require direct mounting on the spray arm, the system uses light interruption detection through the optical guide. This substitution eliminates mechanical wear and corrosion issues, significantly improving sensor reliability in the wet dishwasher environment.
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 provides a cost-effective, reliable, and compact rotation sensor that operates independently of contamination and spray arm height adjustments, reducing component count and eliminating the need for additional openings in the dishwasher.
Implementation Method 1
The emitted electromagnetic radiation, at a first location, is coupled into a path, in which the electromagnetic radiation is guided by means of total reflection
Data Source
AI summary
A process and a device are provided for ascertaining the rotation of a liquid spray arm for a domestic appliance. Lighting means serves as a light transmitter and a photoreceiver serves as a light receiver. The lighting means and the photoreceiver are assigned a light-conducting element. At a first location of the light-conducting element, at least some light emitted from the lighting means is coupled to a path so that the light is guided in the light-conducting element by total reflection. At a second location of the light-conducting element that spaced apart from the first location in the direction of propagation of the light, the light guided in the light-conducting element is coupled out of the path so that the light is received by the photoreceiver. The intensity of the light received by the photoreceiver is evaluated by an evaluation circuit with respect to the rotation of the spray arm.