Liquid purification or separation – Flow – fluid pressure or material level – responsive – Check valve
Reexamination Certificate
1998-07-31
2001-02-13
Walker, W. L. (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Check valve
C210S429000, C210S430000, C210S431000, C210S450000, C137S541000, C137S543170
Reexamination Certificate
active
06187182
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to filter cartridge assemblies, and more particularly relates to a filter cartridge assembly for a gas purging system.
2. Description of Related Art
A modular isolation chamber such as a standard mechanical interface (SMIF) box, or pod, can be of various sizes and configurations, but typically provides a microenvironment to isolate and control the environment surrounding a wafer, cassette of wafers or substrates used in manufacturing integrated circuits, during storage, transport and processing of the materials. Processing of such materials traditionally has been carried out in a particulate free environment generally known as a “clean room”. However, maintenance of such “clean rooms” in a contaminant free state can require a great deal of care and effort, particularly during processing of the materials.
In one conventional system in which a SMIF system is used to replace a traditional clean room, filtered air is circulated in the SMIF box, and still air is used to achieve cleanliness in the SMIF box. Purge systems are also known in which manufacturing materials are subjected to cold nitrogen purge cycles. Another conventional method and apparatus for cleaning integrated circuit wafers utilizes dry gases. There remains a need for a filter cartridge assembly for SMIF pods that can be readily removed and replaced from the SMIF pods on a regular basis or as needed, to consistently protect the SMIF pods from gas leakage into the SMIF pods, such as through check valves during handling of the SMIF pods such as in a fabrication facility, to maintain desired levels of particulates within the SMIF pods. The present invention meets these needs.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention provides for a filter cartridge assembly for use in a SMIF pod to help to insure that only a clean, gaseous working fluid enters the SMIF pod, to provide a controlled environment around the contents of the SMIF pod with a very low particulate content.
The invention accordingly provides for a filter cartridge assembly comprising a valve body having an interior flow passage with an inlet end and an outlet end, a filter element disposed in the valve body across the interior flow passage, and a valve seat defined in the interior flow passage. The filter element comprises a filter media that preferably removes particulates as small as 0.003 microns at an efficiency of about 99.9999%.
A valve element such as a check valve element is disposed in the interior flow passage adjacent to the valve seat. The check valve element has a check valve poppet and a stem, with the poppet being oriented toward the outlet end and the stem being oriented toward the inlet end. The valve seat has an annular seating surface that is tapered inwardly toward the inlet end at an oblique angle relative to the longitudinal axis of the valve body. The check valve poppet has an outer diameter that is less than the inner diameter of the valve seat, and a relatively narrow neck with an inner diameter that is less than the outer diameter of the check valve poppet. The surface of the check valve poppet is also preferably tapered inwardly from the outlet end of the check valve poppet toward the neck at an oblique angle relative to the longitudinal axis of the valve body that is substantially equal to the oblique angle of the annular seating surface. A spring is disposed between a flange on the stem upstream of the seating surface and an interior shoulder facing the filter cartridge inlet end and upstream of the seating surface to bias the check valve element toward the inlet end of the valve body to close the flow passage. A deformable resilient O-ring is also disposed on the narrow neck of the check valve poppet, and the outer diameter of the O-ring is preferably greater than the inner diameter of the annular seating surface of the valve seat. Alternatively, other types of valve elements, such as a butterfly-type valve, may also be suitable.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.
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Burns John
Gallagher Gary M.
Reynolds Gerald D.
Smith Mark V.
Fleming Michael A.
Fulwider Patton Lee & Utecht LLP
Semifab Incorporated
Walker W. L.
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