Buoyancy-Actuated Cell Plug Irrigation Without Sensors

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Solution Overview

Problem

Existing irrigation systems for seedlings require complex configurations, such as soil moisture sensors and valves, to supply an appropriate amount of liquid to cell plugs without excess or deficiency, which is inefficient and costly.

Innovation Solution

An irrigation device with a simple configuration using a liquid supply unit and a cell plug lifting unit that adjusts liquid supply based on the state of the culture medium, utilizing capillary action and buoyancy or elastic members to intermittently supply liquid without excess or deficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a soil moisture sensor and valve are used to detect moisture amount and control liquid supply, then the liquid supply precision is improved, but the device complexity increases

Engineering Contradiction:
Improveliquid supply precisionVSAvoiddevice complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The cell plug itself serves as the detection mechanism through its buoyancy response to moisture content changes. The system uses the natural physical property of the cell plug (buoyancy change with moisture) to trigger liquid supply, eliminating the need for external sensors and control valves. The cell plug automatically rises when dry to receive liquid and lowers when wet, creating a self-regulating irrigation system.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces the electronic sensing and control system (sensors, valves, electronics) with a simple mechanical buoyancy-based system. The cell plug's ability to rise and fall based on moisture content substitutes for complex electronic detection and control mechanisms, achieving the same function with vastly simplified hardware.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If a complicated irrigation device with sensors and valves is used, then the liquid supply precision is improved, but the ease of operation deteriorates

Engineering Contradiction:
Improveliquid supply precisionVSAvoidease of operation
Core Design Contradiction:
Manufacturing precisionVSEase of operation

Solution Approach 1:

The irrigation system operates autonomously through the passive buoyancy mechanism. The cell plug automatically rises when its moisture content decreases and falls when moisture content increases, triggering liquid supply only when needed. This self-regulating mechanism eliminates the need for user intervention, system monitoring, or complex operation procedures.

Inventive Principle:
Principle #25Self-service

3Device complexity

If a simple irrigation device without sensors is used, then the device complexity is reduced, but the liquid supply precision deteriorates

Engineering Contradiction:
Improvedevice complexityVSAvoidliquid supply precision
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The system utilizes changes in the physical parameter of buoyancy force in response to moisture content variations. As the culture medium absorbs or releases moisture, the cell plug's buoyancy changes, causing it to rise or fall. This physical parameter change serves as a natural indicator of irrigation needs, providing precise control without electronic sensors.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The cell plug acts as an intermediary between the moisture condition of the culture medium and the liquid supply mechanism. Its buoyancy-mediated rising and falling motion translates the invisible moisture content changes into visible mechanical motion that triggers the irrigation process, bridging the gap between moisture status and liquid delivery.

Inventive Principle:
Principle #24Intermediary (Mediator)

4Measurement precision

If power-consuming sensors and valves are used, then the measurement precision is improved, but the use of energy increases

Engineering Contradiction:
Improvemoisture detection precisionVSAvoidenergy consumption
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces active electronic sensing systems that consume power with a passive mechanical buoyancy system. The cell plug's rise and fall in response to moisture content changes provides continuous moisture detection without requiring any energy input, eliminating the power consumption associated with sensors, processors, and control electronics.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses the inherent physical properties of the cell plug and culture medium interaction to provide moisture detection and control. No external power source is needed as the system leverages natural buoyancy forces and capillary action to achieve both measurement and actuation functions.

Inventive Principle:
Principle #25Self-service

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

The device supplies an appropriate amount of liquid to the culture medium of cell plugs without excess or deficiency, preventing issues like bacterial propagation and seedling decay, while avoiding the need for power-consuming sensors or valves.

Implementation Method 1

utilizing capillary action and buoyancy or elastic members to intermittently supply liquid

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Implementation Method 2

utilizing capillary action and buoyancy or elastic members to intermittently supply liquid

Methodology Applied
Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Data Source

PatentEP4023056B1Irrigation device and cell plug used for same
Publication Date: 2025.09.17 KUSAKABE KIKAI
  • EP4023056B1 patent drawingFigure 1
  • EP4023056B1 patent drawingFigure 2
  • EP4023056B1 patent drawingFigure 3A~3B

AI summary

An irrigation device includes: a cell plug that includes an opening facing upward and an accommodation part that accommodates a predetermined amount of culture medium in communication with the opening; a liquid supply unit that supplies a liquid to a culture medium of the cell plug; and a cell plug lifting unit that lowers the cell plug when a weight of the cell plug is increased by a liquid supplied by the liquid supply unit and lifts the cell plug when a weight of the cell plug is decreased by drying of a culture medium. The liquid supply unit includes a contact end that is intermittently brought into contact with a culture medium by lifting and lowering of the cell plug by the cell plug lifting unit, performs liquid supply while the contact end is in contact with a culture medium, and stops liquid supply when the contact end is separated from a culture medium.