Particle counting system
Inventors
SEKIMOTO, Kazuma • ICHIJYO, Kazuo
Assignees
Publication Number
US-9250174-B2
Publication Date
2016-02-02
Expiration Date
2033-06-25
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Abstract
A particle counting system includes a collector, a liquid input/output operation executing means, and a particle counter. The collector performs a collecting operation to introduce the surrounding air into a container storing a liquid to collect airborne particles in the liquid. The liquid input/output operation executing means executes a series of liquid input/output operations to supply an additional liquid for the collecting operation to the collector and discharge the liquid after the collecting operation from the collector. The particle counter measures the number of particles contained in the liquid discharged from the collector with the series of liquid input/output operations.
Core Innovation
The invention relates to a particle counting system that collects airborne particles in a liquid and measures the number of the particles, facilitating efficient and continuous monitoring of particle contamination, especially in clean rooms for electronic device or pharmaceutical manufacturing. The system includes an airborne particle collector that introduces surrounding air into a liquid-containing container to collect particles, a liquid input/output operation executing means that supplies additional liquid to the collector and discharges the liquid after collecting particles, and a liquid-borne particle counter that measures particles in the discharged liquid during these liquid input/output operations.
The problem solved by this invention arises from limitations of prior arts in airborne particle counting. Conventional methods either require longer measurement times as air flow rates increase, need costly high-power lasers or sensitive detectors, or require manual intervention to transfer samples, making them unsuitable for automatic and continuous monitoring. There is also a demand for collecting large air samples quickly and measuring particles in real time to efficiently monitor clean conditions over extended periods, which prior arts cannot satisfy due to sensitivity, measurement speed, or operational constraints.
The invention automates the supply and discharge of liquid to the airborne particle collector and subsequent particle counting, enabling real-time measurement of particle number changes without manual handling. The airborne particle collector uses centrifugation to efficiently collect even submicron particles into a small fixed volume of liquid. The separated particle counter can measure viable particles using autofluorescence and operates at a constant liquid flow rate independent of air flow rate, improving sensitivity and shortening measurement time. This automated system supports both continuous and intermittent measurement modes suitable for long-term clean room monitoring.
Claims Coverage
The patent includes one independent claim defining a particle counting system composed of an airborne particle collector, a liquid supply and discharge system, and a liquid-borne particle counter, with specific configurations of flow paths, pump, and flow rate control device. The claim coverage focuses on controlling liquid supply and discharge and measurement of particles in liquid.
Particle counting system with automated liquid supply and discharge
A system comprising an airborne particle collector that collects airborne particles into a liquid in a container; a liquid supply and discharge system that supplies additional liquid to the collector and discharges liquid after collection; and a liquid-borne particle counter that measures the number of particles contained in the discharged liquid during the series of liquid supply and discharge operations.
Flow paths and pump configuration for liquid management
Inclusion of a liquid container reserving additional liquid, a first flow path from liquid container to collector, a second flow path from collector to particle counter, a third flow path for liquid after measurement, a pump disposed in the third flow path that flows liquid via the particle counter, and a flow rate control device controlling liquid amounts and flow rates.
Pump flow rate lower than air flow rate
The pump causes a liquid flow at a lower flow rate than the flow rate of the air introduced into the collector's container.
Coordinated supply and discharge operation during collection and measurement
The flow rate control device causes supply of additional liquid while the collector performs the collecting operation and activates the pump to discharge liquid from the collector to the second flow path after collection.
Liquid flow sensor and controlled liquid amount supply
The liquid supply and discharge system further includes a liquid flow sensor in the first flow path detecting the amount of liquid supplied to the collector, and the flow rate control device controls the supplied amount based on this detected amount.
The claims cover a particle counting system integrating an airborne particle collector with automated liquid supply and discharge mechanisms and a liquid-borne particle counter, coordinated by a flow rate control device and using dedicated flow paths and a pump to enable efficient, continuous, or intermittent particle measurement in liquid at controlled flow rates independent of air flow, and optionally include flow sensing for precise liquid supply control.
Stated Advantages
Enables efficient collection and automatic measurement of particles in air.
Allows real-time particle number measurement immediately after collection.
Supports continuous and intermittent operation for long-term monitoring.
Maintains measurement sensitivity without dependence on air flow rate.
Shortens measurement time by using a small fixed liquid volume for particle counting.
Eliminates need for manual sample handling between collection and measurement, supporting automation.
Documented Applications
Monitoring the clean condition of clean rooms where electronic devices or pharmaceutical products are manufactured.
Constant monitoring of changes in the number of airborne particles to maintain cleanliness quality.
Measurement of viable particle counts using autofluorescence detection in clean rooms.
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