Abstract:
A Wide-body Valve Having an Internalized Actuator is disclosed. The preferred valve provides exceptional conductance while also providing a compact valve and actuator package. The valve incorporates a geometry wherein the internal diameter of the valve is approximately 180% of the diameter of the valve&#39;s port. Furthermore, the stroke of the valve is preferably 30% or more of port diameter. Also, the valve actuator housing is designed to cooperate with the valve body housing such that the actuator housing is encapsulated within the valve body housing such that the valve part count and valve part volume is reduced over conventional valves.

Description:
[0001]    This application is filed within one year of, and claims priority to Provisional Application Ser. No. 61/063,806, filed Feb. 5, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to valves and actuators and, more specifically, to a Wide-body Valve Having an Internalized Actuator. 
         [0004]    2. Description of Related Art 
         [0005]    Pneumatic (and other remotely-controllable) valves are very prevalent in semiconductor and other high-purity manufacturing and processing equipment. One typical valve is depicted in  FIG. 1 .  FIG. 1  is a perspective view of a conventional pneumatic actuator valve assembly  10 . The assembly  10  has two major elements: the valve  14  and the valve actuator assembly  12 . The actuator assembly provides the actuation force that opens and closes the valve  14 . The valve  14  depicted here is commonly known as a “poppet” valve. The poppet valve is used extensively in all manner of gas lines used in the semiconductor industry. The poppet valve  14  has in inlet port  22  and an outlet port  20 , in this case, at right angles to one another. The housing  24  of the actuator assembly  12  conventionally attaches to the top portion of the valve body housing  16  at the body flange  18 . As depicted here, the conventional pneumatic actuator valve assembly  10  has an actuator added to the top of the valve.  FIG. 2  further clarifies this typical arrangement 
         [0006]      FIG. 2  is a cutaway side view of the valve assembly  10 . The actuator assembly has a housing  24 , within which is an air piston  36 , which is forced to travel up and down within the housing  24  by application of gas under pressure. The movement of the air piston  36  drives the valve stem  32  up and down, which in turn causes the valve to open or close. Valves are also available that have solenoid actuators, wherein the depicted pneumatic actuator assembly  12  is exchanged with an actuation mechanism that obtains its force from operation of an electrical solenoid. 
         [0007]    The essential moving components within the valve  14  are contained within the valve body housing  16 . The valve stem  32  extends between the actuator assembly  12  air piston  36 , and the poppet  26 . The depicted valve is known as a “bellows” valve because the valve stem  32  is encapsulated within a bellows  31 . The bellows  31  creates the opportunity for high level vacuum conditions within the valve body housing  16  while preventing contaminants (such as lubricants, etc.) from transferring from the valve stem  32  or housing  24  and into the interior of the valve body housing  16  (and of course into the process stream). The bellows  31  allows for the extension and contraction of the valve stem. 
         [0008]    The side port  20  allows flow into or out of the interior of the valve body  2 o housing  16 . Fluid flows in or out past the valve seat  30  and into or out through the bottom port  22 . The poppet  26  is located at the distal end of the valve stem  32 . When the poppet  26  is lifted away from the valve seat  30 , the valve  14  is in the “open” position. When the poppet  26  is pressed against the valve seat  30 , the poppet seal  28  creates a seal with the valve seat  30 , and the valve  14  is in the “closed” position. Many valves use a spring to determine the “home” position of the valve actuator. 
         [0009]    A primary performance feature for poppet valves is the “conductance” or speed through which fluid can flow through the valve. In particular, it is typically most beneficial if the valve  14  and associated system can be drawn down into a high vacuum condition very rapidly (thereby removing contained fluid from the valve and piping system). Historically, it has been understood that the theoretical conductance of a particular valve was determined simply by the cross-sectional size of its inlet and outlet ports  20 ,  22  and a to theoretical minimum amount of separation of the poppet and the poppet seat. There are several formulas that are used to calculate flow in and around objects. This is commonly called Computational Fluid Dynamics (CFD). Each set of formulas in CFD applications is empirically verified to work within a given pressure range. Therefore, the application of these equations in vacuum is at best an approximation, since no formula covers the entire pressure range typically seen by a vacuum valve. The problem is that the approximate solutions based on current readily available CFD programs have resulted in a general design of valves that are not ideally suited to the large pressure range that they operate within. Furthermore, the user base in the industry is constantly striving to make the valve functional components smaller and smaller. 
       SUMMARY OF THE INVENTION 
       [0010]    In light of the aforementioned problems associated with the prior devices, it is an object of the present invention to provide a Wide-body Valve Having an Internalized Actuator. The valve should provide exceptional conductance while also providing a compact valve and actuator package. It is a further object that the valve incorporate a geometry wherein the internal diameter of the valve is approximately 180% of the diameter of the valve&#39;s port. Furthermore, the stroke of the valve should be approximately 30% or greater of the port diameter. A still Her object is that the valve actuator housing be designed to cooperate with the valve body housing such that the actuator housing can be encapsulated within the valve body housing such that the valve part count and valve part volume is reduced over conventional valves. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, of which: 
           [0012]      FIG. 1  is a perspective view of a conventional pneumatic actuator valve assembly; 
           [0013]      FIG. 2  is a cutaway side view of the aforementioned valve assembly shown in  FIG. 1 ; 
           [0014]      FIG. 3  is a partially exploded perspective view of a preferred embodiment of the wide-body valve having an internalized actuator of the present invention; 
           [0015]      FIG. 4  is a cutaway side view of the device of  FIG. 3 ; 
           [0016]      FIG. 5  is a partial cutaway side view of the poppet geometry of the valve of  FIGS. 3 and 4 ; and 
           [0017]      FIG. 6  depicts the performance comparison between the conventional valve of  FIGS. 1 and 2  with the valve of  FIGS. 3-5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a Wide-body Valve Having an Internalized Actuator. 
         [0019]    The present invention can best be understood by initial consideration of  FIG. 3 .  FIG. 3  is a partially exploded perspective view of a preferred embodiment of the wide-body valve  40  having an internalized actuator of the present invention. The valve assembly  40  operates essentially the same as does the prior art valve discussed above, namely, that the valve is opened and closed by application and removal of control gas to a pneumatic valve actuator. Non-pneumatic actuators could also be utilized in the same arrangement discussed below. Also, springs can be used to create a “Home” position for the actuator. 
         [0020]    The valve  40  comprises a valve body housing  44 , which has an open top flange  50 , to which a top cap  52  seals to enclose the valve body housing  44 . What is unique here is that rather than the valve&#39;s actuator being located above/outside of the top cap  52 , it is rather contained within the valve body housing  44  (i.e. under/within the top cap  52 ). The actuator assembly  42 , as with the prior valve assembly, has a valve stem  32  that terminates in the poppet  48 . The portion of the valve stem  32  that is below/external to the actuator assembly  42  is encapsulated within a bellows  46 . What is unique is that the actuator assembly  42 , bellows  46  and poppet  48  are all contained within the valve body housing  44 . 
         [0021]    The discovery that lead to this valve/actuator arrangement and geometry is that valve conductance could be optimized by increasing the relative size of the valve body internal diameter  54 , as compared to the outer diameter of the poppet  48 . For a defined outlet port  22  diameter (which loosely determines the poppet  48  diameter), a valve&#39;s conductance can be increased substantially by enclosing the poppet  48  within a valve body housing  44  that has a significantly larger internal diameter  54 . Empirically, it has been determined that the minimum ratio at which beneficial conductance results are obtained is 1.8 (i.e. that the internal body diameter  54  is nearly twice the diameter of the poppet  48  and the port that it seals). 
         [0022]    The relationship between body diameter and poppet/port diameter to valve conductance has allowed designers to more efficiently utilize a common valve design for manufacturability guidelines and thereby substantially reduce part count. The useable volume in the wide body concept allows the entire actuator to be fully contained within the internal volume of the valve body. This is a marked improvement over the volume required by the valve in  FIG. 1 . 
         [0023]    All testing was conducted on a valve with 1.5 inch diameter inlet and outlet ports  20 ,  22 . It was discovered that the time required to evacuate a chamber of a given volume (110 liters) to a given pressure (5 Torr) is significantly affected by the diameter of the valve body  44  and the distance that the poppet  48  moves from the valve seat (i.e. valve stroke). The testing determined that there was a slight improvement in changing barrel diameter from 2.0 to 2.5 inches and then more significant changes when the diameter  54  was increased to 3.0 and then 3.5 inches. As mentioned above, it was resolved that the minimum effective ratio was approximately 1.8. The prior art valves, apparently in the interest of manufacturing efficiency (and most likely resulting from the built-in inaccuracies of common CFD programs), use a ratio of 1.3 or less. Additionally, the stroke of the valve played a significant role in evacuating the chamber. This effect reached diminishing returns at 30% or more of port diameter of stroke. The result is a valve that has a body to port diameter ratio greater than 1.8 and a stroke of 30% or more of port diameter. In addition to the performance improvements depicted in  FIG. 6 , this “nested” design drastically reduces the number of parts required for the assembly, and a smaller part volume. 
         [0024]      FIG. 4  is a cutaway side view of the device/assembly  40  of  FIG. 3 . When seen in its fully assembled form, the distinction from the prior art is clear. The entire valve and actuator assembly is contained within the body housing  44 . The air piston  58  and upper portion of the valve stem  32  is contained within the actuator housing  56 . The actuator housing  56  is fully covered by the top cap  52 . The actuator seal  57  is pressed between the actuator housing  56  and the valve body housing  44  by the top cap  52  in order to seal the upper end of the valve body housing  44 . Disassembly is a simple matter of removal of the top cap  52  and actuator assembly (contained within the housing  56 ). 
         [0025]    As discussed at length above, the design change that facilitated the internalization of the actuator is the ratio between the valve body housing diameter and the poppet  60 . Of course, increasing this ratio results in a larger sidewall gap  66  between the outer perimeter of the poppet  60  and the inner wall of the housing  44 . As can be seen in this depiction, the sidewall gap  66  is substantially greater than the (unlabeled) sidewall gap in valve of  FIG. 2 . 
         [0026]      FIG. 5  addresses the issue of valve stroke.  FIG. 5  is a partial cutaway side view of the poppet  60  geometry of the valve of  FIGS. 4 and 5 . The range of motion of the depicted valve is in excess of 30% or more of port diameter, which combines with the relationship of the body  44  diameter being greater than 1.8 times the diameter of the poppet  60 , results in substantial conductance benefits, as depicted below in the chart of  FIG. 6 . 
         [0027]      FIG. 6  depicts the performance comparison between the conventional valve of  FIGS. 1 and 2  with the valve of  FIGS. 3-5 . The rate of decay of pressure curve for the conventional valve is depicted in dashed line and labeled as  70 . The pressure curve for the valve depicted in  FIGS. 3-5  is shown as a solid line and depicted as  72 . While the long-range (low) pressure for the two curves is essentially identical, the valve of the present invention has a clear advantage over the prior art in terms of rate of reduction of pressure to a very low pressure state. This benefit is the direct result of observing the sidewall gap and valve stroke geometries discussed herein above. 
         [0028]    Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.