Laundry Dryer Drum Control for Delicate Fabric Airflow
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Solution Overview
Problem
Rotatable-drum laundry dryers risk damaging delicate laundry due to high air flow rates generated by centrifugal fans during high-speed rotation, causing the laundry to separate from the drum surface and leading to sliding, tumbling, and subsequent damage or shrinkage.
Innovation Solution
A control method that adjusts the rotation speed and direction of the drum and airflow rate based on the type of laundry, using a single electric motor to rotate both the drum and centrifugal fan, with specific algorithms for delicate and non-delicate laundry cycles to manage centrifugal acceleration and air temperature, reducing surface rubbing and airflow impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drum rotates at high speed to press delicate laundry against the inner wall using centrifugal force, then the laundry is prevented from sliding and tumbling, but the centrifugal fan generates very high air flow rate that separates the laundry from the drum surface and pushes it against the inner flange causing damage
Solution Approach 1:
The patent divides the drying cycle into distinct phases: a first phase with the drum rotating in a first direction at high speed to press laundry against the drum wall, and a second phase with the drum rotating in a reverse second direction at lower speed to reduce air flow rate and prevent laundry separation. This temporal segmentation allows each phase to optimize for its specific function without causing harm.
Solution Approach 2:
The patent reverses the drum rotation direction between phases. During the first phase, the drum rotates in one direction to generate centrifugal force for laundry stabilization. During the second phase, the drum rotates in the opposite direction at reduced speed, which reverses the air flow pattern and reduces the harmful separation effect while maintaining drying functionality.
2Device complexity
If a single electric motor is used to drive both the drum and centrifugal fan, then device complexity is reduced, but control precision for managing both centrifugal force and air flow rate simultaneously becomes more difficult
Solution Approach 1:
The patent combines the drum and centrifugal fan into a single integrated assembly where the centrifugal fan is mounted on the drum and rotates with it. This merging eliminates the need for separate motors and control systems, reducing device complexity while maintaining functional effectiveness through the unified rotational motion.
Solution Approach 2:
The patent implements variable speed control of the single motor to dynamically adjust the drum rotation speed according to the drying phase. The motor operates at high speed during the first phase to generate sufficient centrifugal force, then reduces to lower speed during the second phase to control air flow rate, providing adaptive control without requiring multiple motors.
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 effectively prevents delicate laundry from sliding or tumbling, minimizing damage and shrinkage while utilizing a single motor to rotate both the drum and fan, ensuring efficient and safe drying.
Implementation Method 1
a centrifugal fan which is located along the recirculating conduit and is designed to produce, inside the recirculating conduit, an airflow flowing through the drum
Implementation Method 2
the drum is controlled to reach a prefixed high rotation speed during the drying cycle, so that delicate laundry is pressed by centrifugal force against the inner wall of the drum
Data Source
Figure 1
Figure 2
AI summary
Laundry dryer (1) comprising: a laundry drum (3) which is designed to rotate about an longitudinal axis (6); an air recirculating conduit (10) connected to said laundry drum (3) ; heater device (10) located along air recirculating conduit (10) to heat the airflow; a rotatable fan (11) located along air recirculating conduit (10) to produce an airflow flowing through drum (3); the fan (11) being designed to be rotated in a main and secondary direction of rotation for providing different air flow rates; an electric motor (14) which is mechanically connected with the fan (11) and the drum (3) for rotating the fan (11) and drum (3), simultaneously. The home laundry dryer (1) comprising electric control means (18) configured to control said electric motor (14) so as to cause: the drum (3) to rotate at a first rotational speed (v1) in a forward direction of rotation, thereby resulting in the fan (11) being rotated in the main direction of rotation for providing a first air flow rate; or the drum (3) to rotate at a second rotational speed (v2) greater than said first rotational speed (v1) in a reverse direction of rotation, thereby resulting in the fan (11) being rotated in the secondary direction of rotation for providing a second air flow rate lower than the first air flow rate.