Valves and valve actuation – Mechanical movement actuator – Cam
Reexamination Certificate
1999-07-09
2001-06-12
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Mechanical movement actuator
Cam
C251S257000, C251S325000, C251S340000
Reexamination Certificate
active
06244566
ABSTRACT:
The present invention relates to a valve assembly which can be used for controlling the flow of either gases or liquids. When used for controlling the flow of gases, it can function as a dry break valve for sealing inlet and outlet ports of a mass flow controller or similar device. When used for liquids, it can be part of a hydraulic fluid flow system.
BACKGROUND OF THE INVENTION
With respect to its use as a dry break valve, semi-conductor manufacturing involves building up layers of conducting and insulating films on silicon wafers to produce miniature transistors. These films are deposited or etched using reactive gases, liquified gases or liquids. It is imperative to get precise properties of the films and to get repeatability from wafer to wafer. One of the requirements for achieving precision is to deliver exactly the flow rate of gas called for by the process and at exactly the required pressure and temperature. This is achieved by using several reactant delivery components. These are arranged into a “gas box” (sometimes called a “gas panel” or a “gas jungle” or a “gas tray”). A gas box contains an assembly of “gas sticks,” each of which monitors and controls the flow of one gas to the process chamber. A gas stick is built around a component called a mass flow controller. The mass flow controller controls the flow rate of gas (or in some instances liquid). It is a thermal based device that reads the flow rate based on the temperature rise of the gas as it passes through the device. The temperature rise is calibrated to flow for the particular gas.
At the completion of the construction of the mass flow controller, the manufacturer may purge the mass flow controller with a gas such as dry argon. At the completion of the purged cycle, it is desired that the purge gas (i.e., dry argon for example) be maintained in the mass flow controller under a pressure on the order of 2 psig during shipment of the mass flow controller to the customer.
SUMMARY OF THE PRESENT INVENTION
The valve assembly of the present invention is self-sealing. It has one end designed to mate with a standard VCR assembly such as that manufactured and sold by Cajon Company, Macedonia, Ohio to achieve a metal-to-metal seal which is desirable for high purity assemblies requiring vacuum or a positive pressure. See for example, U.S. Pat. No. 5,605,358.
The dry break assembly valve of the present invention has its own internal valving which permits the introduction of the purging gas such as dry argon into the mass flow controller. Following introduction of such purging gas in a quantity sufficient to provide a build-up of pressure, for example on the order of 2 psig, the internal valving of the dry break assembly may be closed thereby retaining such purging gas within the mass flow controller. The dry break assembly of the present invention may then be shipped with the mass flow controller and remain with it during shipping and storage until its installation in a gas stack. By maintaining a positive pressure on the purge gas within the mass flow controller assembly, it is assured that contaminants cannot enter the mass flow controller.
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patent: 5727773 (1998-03-01), Dunnigan
patent: 6047949 (2000-04-01), Beauchemin, Jr.
France Richard M.
Rogers Russell L.
Aeroquip Corporation
Emch, Schaffer, Schaub & Porcello & Co., L.P.A.
Keasel Eric
Shaver Kevin
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