Abstract:
A pressure switch device for controlling gas without calibration of pressure in a vacuum system is disclosed. The pressure switch device comprises an isolation valve for controlling gas flow between a chamber and a pump, a pressure balance switch bypassing said isolation valve and detecting a pressure difference between the chamber and the pump, and a control line used by said pressure balance switch to control said isolation valve, wherein said pressure balance switch open said isolation valve whenever the pressure difference between the chamber and the pump is larger than a predetermined value.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to a pressure switch a vacuum system, and more particularly to pressure balance switches of a vacuum system without any calibration of the pressures.  
           [0003]    2. Description of the Prior Art  
           [0004]    In a conventional vacuum system, a plurality of manometers are utilized in order to separately detect pressures in different portions of the vacuum system and maintain vacuum condition of the vacuum system. However, since the pressure in each portion of the vacuum system usually would not be identical and the detecting range of each manometer is not necessarily the same, the pressure may exceed the detecting range of some manometer and render the vacuum system dangerous when gates or valves isolating portions are open.  
           [0005]    [0005]FIG. 1 shows a conventional vacuum system. The vacuum system has an isolation valve  11 , a pipe  12 , a chamber  13 , a pump  14 , and manometers  15  and  16 . The pipe  12  connects the pump  14  and the chamber  13 . The pump  14  and the chamber  13  are isolated and linked by the isolation valve  11 . The manometer  15  is used to detect the pressure in the chamber  13  and the manometer  16  is used to detect the pressure in the pipe  12  of the pump side. The vacuum condition of the chamber  12  is maintained by the open/close of the isolation valve  11  and the pumping of the pump  14 . In operation, the isolation valve is closed when the pressure in the chamber  13  detected by the manometer  15  is lower the pressure in the pipe  12  of the pump side detected by the manometer  16 . The isolation valve is open when the pressure in the chamber  13  detected by the manometer  15  is larger the pressure in the pipe  12  of the pump side detected by the manometer  16  and the pump  14  pumps out gas in the chamber  13 .  
           [0006]    However, the vacuum system set forth has some drawbacks. For example, since the detecting ranges of the manometers  15  and  16  may be different, the pressure either in the chamber  13  or the pipe  12  of the pump side may exceed the detecting ranges of the manometers  15  and  16  and render the vacuum system dangerous when the isolation valve  11  is open.  
           [0007]    In view of the drawbacks mentioned with the prior art system, there is a continued need to develop new and improved systems that overcome the disadvantages associated with prior art system. The advantages of this invention are that it solves the problems mentioned above.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the invention to provide a pressure switch adapted in a vacuum system to control an isolation valve of the vacuum system and provide a balanced pressure when two portions of the vacuum system are connected.  
           [0009]    It is another object of the invention to provide an automatic control of an isolation valve and automatic maintenance of vacuum condition of a chamber without any calibration of the pressures separately in the chamber and the pipe of the pump side.  
           [0010]    To achieve these objects, and in accordance with the purpose of the invention, the invention provide a pressure switch device for controlling gas without calibration of pressure in a vacuum system, said pressure switch device comprises an isolation valve for controlling gas flow between a chamber and a pump, a pressure balance switch bypassing said isolation valve and detecting a pressure difference between the chamber and the pump, and a control line used by said pressure balance switch to control said isolation valve, wherein said pressure balance switch open said isolation valve whenever the pressure difference between the chamber and the pump is larger than a predetermined value. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0012]    [0012]FIG. 1 illustrates the conventional vacuum system;  
         [0013]    [0013]FIG. 2 illustrates the conventional vacuum system of the present invention;  
         [0014]    [0014]FIGS. 3A and 3B show how the pressure balance switch of the invention operates; and  
         [0015]    [0015]FIGS. 4 and 5 show how the pressure balance switch of the invention operates when the pressure switch is adapted in a vacuum system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    It is to be understood and appreciated that the system and method described below do not cover a complete system and method. The present invention can be practiced in conjunction with various hardware that are used in the art, and only so much of the commonly practiced components and steps are included herein as are necessary to provide an understanding of the present invention.  
         [0017]    The present invention will be described in detail with reference to the accompanying drawings. It should be noted that the drawings are in greatly simplified form.  
         [0018]    The pressure switch, of present invention is applied to a broad range of vacuum system and can be assembled from a variety of the vacuum system. The following description discusses a preferred embodiment of the pressure switch of the present invention in a vacuum system. The present invention may also be employed in a common factory, and particularly a semiconductor factory. Accordingly, application of the present invention is not intended to be limited to those devices fabricated in semiconductor materials, but will include those devices fabricated in one or more of the available semiconductor materials. Moreover, while the present invention is illustrated by a preferred embodiments directed to pressure switch, it is not intended that these illustrations be a limitation on the scope or applicability of the present invention.  
         [0019]    Referring to FIG. 2, a vacuum system having an isolation valve  21 , a pipe  22 , a chamber  23 , a pump  24 , a pressure balance switch  25 , a control line  26  and a bypass pipe  27  is shown. The pump  24  provides the chamber  23  with a vacuum condition via pumping out the gas in the chamber  23 . The pipe  22  connects the pump  24  and the chamber  23  when the isolation valve  21  is open. The pipe  22  and the pump  24  and the chamber  23  are disconnected when the isolation valve  21  is closed. The pump  24  and the chamber  23  are also isolated or connected by the pressure balance switch  25  and the bypass pipe  27 . The control line  26  connects the pressure balance switch  25  and the isolation valve  21 . The pressure balance switch  25  is used to automatically compare the pressures separately in the chamber  23  and the pipe of the pump side. In another word, the pressure balance switch  25  acts as a pressure difference detector to control the isolation valve  21  by the control line  26 . When the pressure difference between the chamber  23  and the pipe of the pump side is over a predetermined value, the pressure switch  25  opens the isolation valve  21 .  
         [0020]    [0020]FIGS. 3A and 3B show how the pressure balance switch  25  operates and render the isolation valve  21  opened/closed. The pressure balance switch  25  has a membrane  31  inside. The membrane  31  divides the pressure balance switch  25  into rooms  25 - 1  and  25 - 2 . The rooms  25 - 1  and  25 - 2  separately connect to the chamber  23  and the pump  24  via the bypass pipe  27 . Hence the pressures separately in the rooms  25 - 1  and  25 - 2  are the same as the pressures in the chamber  23  and the pipe of the pump side. The pressure difference between the chamber  23  and the pipe of the pump side thus would force the membrane  31  to deform or bend. The pressure balance switch  25  therefore can utilize the deformation of the membrane  31  to recognize the pressure difference between the chamber  23  and the pipe of the pump side. As shown in FIG. 3A, when the pressure in room  25 - 1  is lower than the pressure in room  25 - 2 , the membrane  31  is bent toward the room  25 - 1 . The membrane  31  is bent toward the room  252  when the pressure in room  25 - 1  is larger than the pressure in room  25 - 2  as shown in FIG. 3B. The pressure balance switch  25  controls the isolation valve  21  to open/close via the control line  26  according to the deformation of the membrane  31  induced by the pressure difference between the chamber  23  and the pipe of the pump side. The pressure balance switch  25  comprises a membrane manometer. Nevertheless, other membrane manometers in accordance with the invention can also be used. It is known that the pressure balance switch  25  can also use other device to detect and respond the pressure difference between the chamber  23  and the pump  24  and utilizes the device to open the isolation valve  21  whenever the pressure difference between the chamber  23  and the pump  24  is larger than a predetermined value.  
         [0021]    [0021]FIGS. 4 and 5 show how the pressure balance switch  25  operates when the pressure balance switch  25  is adapted in a vacuum system. The rooms  25 - 1  and  25 - 2  are separately connected to the chamber  23  and the pump  24 . As shown in FIG. 4, when the pressure in the chamber  23  is lower than the pressure in the pipe of the pump side, the membrane  31  is forced to bend toward the room  25 - 1 , and the isolation valve  21  is closed. The membrane  31  is forced to bend toward the room  25 - 2  as the pressure in the chamber  23  is larger than the pressure in the pipe of the pump side, and the isolation valve  21  is opened as shown in FIG. 5. When the isolation valve  21  is opened, the pump  24  pumps out the gas in the chamber  23  through the pipe  22 . The invention utilizes the automatic deformation of the membrane  31  induced by the pressure difference between the chamber  23  and the pipe of the pump, side to control the open/closure of the isolation valve  21  without any calibration of the pressures separately in the chamber  23  and the pipe of the pump side. That is, no manometers are needed to be used separately on the chamber  23  and the pipe of the pump side. The isolation valve  21  can be opened when a predetermined pressure difference between the chamber  23  and the pipe of the pump side is achieved. This predetermined pressure difference or threshold pressure difference can be adjusted by the membrane  31 . The deformation of the membrane  31  is used to control the isolation valve  21  via the control line  26 . The pressure balance switch  25  can control the isolation valve  21  via the control line  26  by a mechanical manner, an electronic manner, a hydraulic manner and a pneumatic way.  
         [0022]    Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.