Cassette Transport Airflow Control Against Deceleration Contamination
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Solution Overview
Problem
Cassette transport devices in clean rooms face contamination issues due to ambient airflow, which allows particles to penetrate from the travel rail into the cassette, especially when decelerating, disrupting the flow rate and contaminating substrates during display device fabrication processes.
Innovation Solution
A cassette transport device equipped with a main body, travel unit, flow-rate maintaining members (including fans), speed and air-pressure sensing units, and a control processing device to adjust airflow strength based on speed and pressure measurements, ensuring a consistent flow rate opposite to the travel direction and reducing contamination by maintaining airflow through flow-rate maintaining and reducing members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an overhead shuttle is used to transport cassettes in a clean room, then equipment and lines can be disposed under the transport path, but particles or foreign substances on the travel rail penetrate into the cassette due to ambient airflow and vortex generated during deceleration
Solution Approach 1:
A flow rate maintaining member (air blowing device) is introduced as an intermediary between the ambient environment and the cassette. This device blows air into the cassette to maintain positive pressure inside, preventing particles from the travel rail from penetrating into the cassette during transport and deceleration phases.
Solution Approach 2:
The air blowing device operates in advance to maintain a flow rate inside the cassette before contamination can occur. By continuously blowing air to maintain positive pressure, the system preemptively prevents particle ingress rather than reacting to contamination after it happens.
2Speed
If the cassette transport device decelerates or stops, then the transport process can be completed, but a vortex is generated behind the device causing severe contamination near the rear side of the cassette
Solution Approach 1:
The air blowing device positioned at the rear of the cassette acts as a mediator to counteract the vortex effect during deceleration. By blowing air into the rear portion of the cassette, it maintains positive pressure that prevents vortex-generated particles from entering the cassette during speed changes.
3Ease of operation
If ambient airflow is present during transport, then the transport device can move freely, but particles on the travel rail are carried into the cassette
Solution Approach 1:
The flow rate maintaining member serves as a protective intermediary that allows the transport device to move freely while simultaneously protecting the cassette from ambient airflow carrying particles. The air blowing creates a pressure barrier that decouples the cassette interior from the contaminated external 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
The solution effectively reduces contamination and maintains airflow within the cassette, preventing particle ingress and ensuring consistent substrate cleanliness during transport, even when decelerating, by dynamically adjusting airflow strength based on speed and pressure conditions.
Implementation Method 1
a plurality of flow-rate maintaining members to generate a flow of air in a direction opposite to a traveling direction of the main body, and flow-rate maintaining members of the plurality of flow-rate maintaining members are stacked on one another on the main body, arranged on a rearward side with respect to the traveling direction of the main body, and include a plurality of fans
Implementation Method 2
a plurality of air-pressure sensing units disposed in front of the flow-rate maintaining members, respectively, and a control processing device configured to control the plurality of flow-rate maintaining members, wherein the control processing device is configured to generate a signal for controlling a strength of the flow-rate maintaining members based on information provided from the speed sensing unit and the air-pressure sensing units
Data Source
AI summary
A cassette transport device and a cassette transport system including the same are provided. A cassette transport device includes a main body, a travel unit to move the main body, and a plurality of flow-rate maintaining members to generate a flow of air in a direction opposite to a traveling direction of the main body, and flow-rate maintaining members of the plurality of flow-rate maintaining members are stacked on one another on the main body, arranged on a rearward side with respect to the traveling direction of the main body, and include a plurality of fans.