Delicate Laundry Dryer Control With Variable Drum Speeds
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Solution Overview
Problem
Rotatable-drum laundry dryers struggle to accurately measure moisture levels and determine the completion of the drying cycle for delicate laundry when sensors are located outside the drum, leading to potential felting and damage due to incorrect moisture detection.
Innovation Solution
A method involving variable drum rotation speeds, where a first high speed keeps laundry pressed against the drum and a second lower speed allows it to slide and tumble, ensuring contact with external sensors for accurate moisture measurement, and adjusting these cycles based on sensor contacts to calculate the optimal end of the drying cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the drum rotates at high speed to press laundry against the inner wall, then rubbing damage is reduced, but moisture measurement accuracy deteriorates when sensors are located outside the drum
Solution Approach 1:
The patent applies periodic action by alternating between high-speed rotation (for pressing laundry against the drum wall to reduce rubbing) and low-speed rotation (for allowing laundry to contact external sensors for moisture measurement). This periodic switching resolves the contradiction by enabling both protective functions at different time intervals during the drying cycle.
2Stability of the object's composition
If the drum rotates at high speed to prevent laundry from sliding, then laundry stability is improved, but sensor contact probability deteriorates
Solution Approach 1:
The system periodically switches between high-speed rotation (maintaining laundry stability against the drum wall) and low-speed rotation (enabling laundry to slide and contact sensors). This periodic alternation ensures both stability during protection phases and reliable sensor contact during measurement phases.
Solution Approach 2:
The patent employs dynamics by varying the drum rotation speed between high and low states. This dynamic adjustment allows the system to adapt between maintaining laundry stability (high speed) and enabling sensor contact (low speed), resolving the contradiction through speed modulation.
3Measurement precision
If the drum rotates at variable speeds, then moisture measurement accuracy is improved, but energy consumption increases
Solution Approach 1:
The system uses periodic action by alternating between high-speed and low-speed rotation phases. During low-speed phases, moisture measurement is performed; during high-speed phases, drying continues with reduced measurement activity. This periodic pattern achieves accurate moisture measurement while minimizing energy consumption compared to continuous high-speed operation.
Solution Approach 2:
The system employs self-service by using the laundry's own movement during low-speed rotation to naturally bring it into contact with sensors for moisture measurement. This eliminates the need for additional active mechanisms, reducing energy consumption while maintaining measurement accuracy.
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 approach reduces felting and damage to delicate items, ensures precise moisture measurement, and accurately determines the end of the drying cycle, even with sensors outside the drum, enhancing the drying process for delicate laundry.
Implementation Method 1
rotating the drum at a first rotation speed higher than, or equal to, a rotation speed, at which centrifugal acceleration of the inner surface of the drum equals gravitational acceleration, so that the laundry is pressed by centrifugal force against the inner surface of the drum
Implementation Method 2
a rotation speed, at which centrifugal acceleration of the inner surface of the drum equals gravitational acceleration
Data Source
Figure 1
Figure 2
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AI summary
A method of controlling a rotatable-drum laundry drier (1) to dry delicate laundry in a drum (3) of the rotatable-drum laundry drier (1). The method includes the steps of feeding drying air into the drum (3); rotating the drum (3) at a variable rotation speed about an axis of rotation (6); rotating the drum (3) at a first rotation speed (V1) higher than, or equal to a rotation speed, at which centrifugal acceleration of the inner surface of the drum (3) equals gravitational acceleration; making interruptions in rotation of the drum at the first rotation speed (V1); and performing, at each interruption, one or more rotation cycles (21) at a second rotation speed (V2), so that, at each cycle (21), at least part of the laundry (5) slides/tumbles slowly inside the drum (3) while remaining in contact with the inner surface of the drum (3) and/or another part of the laundry (5) contacting the drum (3).