Abstract:
A high vacuum valve assembly comprising a valve body with an air chamber formed therein. A gate unit is disposed within the air chamber and includes a valve gate portion disposed to mate to a valve seat, the valve gate portion and the valve seat portion each being disposed at the same angle to provide increased sealing force. The gate unit is urged into closure against the valve seat by a first tension source, which may be a spring, and away from the valve seat by a second tension source, which may be compressed gas, such that the gate unit comprises the only moving part of the valve.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    High vacuum valves are widely used in the high technology industry. Most of the models that are available comprise several moving components, such as wheels, fulcrums, bearings and linkages. These mechanical components experience substantial friction caused by the rapid cycling of the valve encountered during normal operation. The wear of these components is a major source of particulate contaminants, such as metal debris, which affects adversely the production of materials such as integrated circuits and semiconductors, whose effectiveness and usefulness are closely related to the purity of their components. The presence of multiple mechanical parts also increases the complexity of the structure, hinders the accessibility to the individual parts, and hinders the overall maintenance of the valve.  
           [0002]    The function of known valves is generally accomplished by a linkage-locking device, which relies on the alignment/unalignment of the valve shaft and the link, on and off center, along a common axis. The force required for the functioning of such a piston valve is considerable and causes the entire valve unit to shake and vibrate vigorously. 
       
    
    
     FIGURES  
       [0003]    [0003]FIG. 1 is a cross-sectional view of an exemplary embodiment of a valve assembly in accordance with the present invention  
         [0004]    [0004]FIG. 2 is a partial cross-sectional view of the embodiment of FIG. 1 but rotated relative thereto.  
         [0005]    [0005]FIG. 3 is a bottom view of the valve assembly of FIG. 1. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0006]    The valve of the present invention is designed for use in high vacuum applications, such as thin film coating and the manufacture of integrated circuits on silicon wafers. The present invention is a high-vacuum sealing gate valve, which operates by the vertical movement of a single moving part, a gate unit. The importance of a single moving part is underscored by the minimal wear of a single mechanical part, which reduces particle contamination.  
         [0007]    In an exemplary embodiment, the valve is closed by spring pressure that forces a piston of the gate unit downward to drive the gate unit to seal the flow channels. In an exemplary embodiment, the valve is opened by air pressure, which pushes the underside of the piston to drive the gate unit upward to open the seal of the flow channel. In an exemplary embodiment, there is no lateral movement of the stem. This mode of operation eliminates the noise normally created by the linkage and vibrations that are typical of the most widely used linkage carriage and gate type valves that use over center locking mechanisms.  
         [0008]    In an exemplary embodiment, the invention is configured to provide a high vacuum sealing gate valve, which includes a single moving component.  
         [0009]    In an exemplary embodiment, the invention is configured to minimize the amount of particulate contamination during manufacturing processes, which occur under high vacuum.  
         [0010]    In an exemplary embodiment, the invention is configured to provide a gate valve, whose few parts are readily accessible and more easily maintained, thus rendering the valve unit more durable and more easily manufactured.  
         [0011]    In an exemplary embodiment, the invention is configured to provide a gate valve constructed of materials which allow for the use of metal bushings and which obviate the use of bellows, thus keeping the movement of the valve silent and vibration free.  
         [0012]    [0012]FIGS. 1, 2, and  3  show different aspects of the high-vacuum valve in an exemplary embodiment of the present invention. In an exemplary embodiment, the valve includes a valve assembly and a gate unit  150 .  
       General  
       [0013]    [0013]FIG. 1 shows a longitudinal section through a high vacuum gate valve in an exemplary embodiment of the present invention. The valve is depicted in the open state. In an exemplary embodiment, the valve assembly includes a housing comprised of an air cylinder  102 , a bonnet  103 , a valve body  104 , and a valve seat  105 . In an exemplary embodiment, air cylinder  102 , bonnet  103 , valve body  104  and valve seat  105 , are rigidly connected to each other to define an interior space which encloses the gate unit  150 . In an exemplary embodiment, valve seat  105  and valve body  104  define a right flow channel  106  and a left flow channel  106 A, respectively, for the passage of process flow.  
         [0014]    In an exemplary embodiment, gate unit  150  is, in vacuum, the only movable component of the valve. In an exemplary embodiment, gate unit  150  includes a piston  155 , which is unitary with a valve stem  160 , which, in turn, is unitary with the valve gate  165 . Valve gate  165  may be fixedly attached to valve stem  160 . Alternatively, valve gate  165  and valve stem  160  may be machined as an integral unit. In an exemplary embodiment, as shown in FIG. 1, valve seat  105  provides a first sealing surface  170 , which is machined at an angle with respect to center line A-A that is equal to the angle with respect to center line A-A at which a second sealing surface  107  of the valve gate  165  is machined. In an exemplary embodiment, first sealing surface  170  and second sealing surface  107  are machined at 45° angles with respect to center line A-A. In an exemplary embodiment first sealing surface  170  and second sealing surface  107  are machined at equal angles with respect to center line A-A, where the angles range from 0 degrees to 75 degrees.  
         [0015]    In an exemplary embodiment, as shown in FIG. 1, air cylinder  102  and piston  155 , define an upper air chamber  108  and a lower air chamber  109 , which are sealed from each other by a first O-ring  110  and a second O-ring  111 . Air cylinder  102  also defines a cylindrical passage  112 . Air chambers  108  and  109  enclose actuation components of the valve. In an exemplary embodiment, the actuation components of the valve include an air cylinder cap  114 , a spring member  116 , and piston  155 .  
         [0016]    In an exemplary embodiment, as shown in FIG. 1, air cylinder cap  114  is mushroom-shaped and serves to cap air cylinder  102 . In an exemplary embodiment, air cylinder  102  is spring activated by spring member  116 . A retaining ring  122  and air cylinder cap  114  are easily removed to allow for effortless access to the other components of the valve. In an exemplary embodiment, a second retaining ring  125  holds piston  155  at a fixed position relative to stem  160 .  
         [0017]    In an exemplary embodiment, as shown in FIG. 1, the upper portion of spring member  116  surrounds the narrow portion of air cylinder cap  114  and faces the interior side of cylinder cap  114 , while the lower part of spring member  116  surrounds the uppermost portion of valve stem  160  and faces the upper side of piston  155 . In an exemplary embodiment, spring member  116  is biased toward closing the valve and functions to maintain valve gate  165  in a closed position by preventing the upward movement of valve stem  160  in the event of a sudden loss of air pressure.  
         [0018]    [0018]FIG. 2 is a partly sectional view along center line A-A of the gate valve shown in FIG. 1, where the valve is turned counterclockwise by 90° relative to the exemplary embodiment shown in FIG. 1. In an exemplary embodiment, an air fitting  224  is present on the exterior of air cylinder  102 , to provide air to lower air chamber  109  via an air duct  226 . The position of air fitting  224  relative to the other components of the valve is also shown in FIG. 3. FIG. 3 is a view of the invention seen from the underside of the gate valve in an exemplary embodiment of the present invention.  
         [0019]    In an exemplary embodiment, as shown in FIG. 1, air chamber  109  extends into narrow cylindrical passage  112  through which stem  160  of gate unit  150  moves during the operation of the valve. In an exemplary embodiment, as shown in FIGS. 1 and 2, a low friction guide bushing  126  extends longitudinally to line cylindrical passage  112 . In an exemplary embodiment, as shown in FIG. 2, bushing  126  is secured in position by first fasteners  228  which extend from the outer surface of air cylinder  102  through the wall of air cylinder  102  and partially into guide bushing  126 . In an exemplary embodiment, first fasteners  228  are screws.  
         [0020]    In an exemplary embodiment, as shown in FIG. 1, a (1) third O-ring  128  and (2) a fourth O-ring  130  and a lower bushing  131 , surround stem  160  at positions above and below bushing  126 , respectively, to maintain the pressure or vacuum as stem  160  moves upward or downward. Cylindrical passage  112  extends through bonnet  103  and into a valve body chamber  132 .  
         [0021]    In an exemplary embodiment, as shown in FIG. 1, a guide pin  134  aligns stem  160  to be perpendicular to valve seat  105 .  
         [0022]    In an exemplary embodiment, as shown in FIG. 2, air cylinder  102  is rigidly attached to bonnet  103  by second fasteners  236 . In an exemplary embodiment, second fasteners  236  are screws. In an exemplary embodiment, as shown in FIG. 2, a first pin  234  spans the thickness of bonnet  103  and anchors bonnet  103  to air cylinder  102  and valve body  104 , thus preventing axial rotation of these components about each other. In an exemplary embodiment, a fifth O-ring  136  completes the seal between bonnet  103  and valve body  104 .  
         [0023]    In an exemplary embodiment, as shown in FIG. 1, the lowermost portion of the valve assembly includes valve body  104  and valve seat  105 . In an exemplary embodiment, as shown in FIG. 3, a second pin  334  aligns valve seat  105  with valve body  104 .  
         [0024]    In an exemplary embodiment, as shown in FIG. 1, valve body chamber  132  houses valve gate  165 . In an exemplary embodiment, as shown in FIG. 1, valve body  104  defines left flow channel  106 A. In an exemplary embodiment, as shown in FIG. 1, valve seat  105  defines right flow channel  106 . In an exemplary embodiment, as shown in FIG. 1, valve seat  105  provides sealing surface  170  which interfaces with sealing surface  107  to close the valve.  
         [0025]    In an exemplary embodiment, as shown in FIGS. 1 and 3, valve body  104  is secured to valve seat  105  by third fastener  336 , fourth fastener  338 , fifth fastener  340 , and sixth fastener  342 . In an exemplary embodiment, third fastener  336  is a screw. In an exemplary embodiment, fourth fastener  338  is a screw. In an exemplary embodiment, fifth fastener  340  is a screw. In an exemplary embodiment, sixth fastener  342  is a screw.  
         [0026]    In an exemplary embodiment, fasteners  336 ,  338 ,  340 , and  342  and a sixth O-ring  138  seal the interior environment of the valve chamber. In an exemplary embodiment, a seventh O-ring  140  may seal connections to right flow channel  106 , which may be attached to the valve assembly. In an exemplary embodiment, an eighth O-ring  141  may seal connections to left flow channel  106 A, which may be attached to the valve assembly.  
         [0027]    In an exemplary embodiment, the components of the valve, except for the O-rings, bushings, the spring member, and fasteners, are constructed of aluminum. In an exemplary embodiment, the components of the valve, except for the O-rings, bushings, the spring member, and fasteners, are constructed of refined aluminum. In an exemplary embodiment, the components of the valve, except for the O-rings, bushings, the spring member, and fasteners, are constructed of AL6061-T6. In an exemplary embodiment, the components of the valve, except for the O-rings, bushings, the spring member, and fasteners, are constructed of 2011 aluminum.  
         [0028]    In an exemplary embodiment, the components of the valve, except for the O-rings, bushings, the spring member, and fasteners, are electropolished. The electropolishing helps to keep these components clean.  
         [0029]    In an exemplary embodiment, the O-rings are constructed of materials which is suitable for ultra-high vacuum (UHV). In an exemplary embodiment, the O-rings are constructed of elastomer seals which are suitable for ultra-high vacuum (UHV). In an exemplary embodiment, one or more of the O-rings are constructed of VITON. In an exemplary embodiment, one or more of the O-rings are constructed of KALREZ. In an exemplary embodiment, O-rings  110 ,  111 , and  128  are constructed of VITON. In an exemplary embodiment, O-rings  130 ,  136 ,  138 ,  140 , and  142  are constructed of KALREZ.  
         [0030]    In an exemplary embodiment, bushings  126  and  131  are constructed of bronze. In an exemplary embodiment, bushings  126  and  131  are constructed of phosphor bronze. In an exemplary embodiment, bushings  126  and  131  are constructed of other bearing surface material. In an exemplary embodiment, bushings  126  and  131  are constructed of composite PTFE.  
         [0031]    In an exemplary embodiment, spring member  116  is constructed of music wire.  
         [0032]    In an exemplary embodiment, the fasteners are constructed of stainless steel. In an exemplary embodiment, the fasteners are constructed of  304  SS.  
       Valve Actuation  
       [0033]    Actuation of the valve occurs via the movement of gate unit  150  within the valve assembly.  
       Opening the Valve  
       [0034]    The state of the gate valve shown in FIG. 1 is the state in which the valve is open. In an exemplary embodiment, as shown in FIGS. 1, 2, and  3 , the valve is opened by supplying compressed air through air fitting  224 , along air duct  226 , and into lower air chamber  109 . In an exemplary embodiment, the compressed air pushes the underside of piston  155  in an upward direction along with stem  160  and valve gate  165 . In an exemplary embodiment, this movement (1) resiliently deforms spring member  116  against its restoration force pushing against air cylinder top  114  and (2) separates valve gate  165  from valve seat  105  to allow flow through flow channels  106  and  106 A.  
       Closing the Valve  
       [0035]    In an exemplary embodiment, the straight movement of gate unit  150  in a direction closing flow channel  106  and  106 A is achieved by decompressing spring member  116  to its normal state. In an exemplary embodiment, the decompressing of spring member  116  to its normal state forces the movement of piston  155 , stem  160 , and valve gate  165  in a downward direction. In an exemplary embodiment, flow channels  106  and  106 A are sealed by the pressure exerted by first sealing surface  107  on a ninth O-ring  142  present on second sealing surface  170 .  
         [0036]    In an exemplary embodiment, O-ring  142  is not vulcanized onto the valve seat  105 . In an exemplary embodiment, O-ring  142  is held in place by a dovetail groove  143  provided on the angled surface of valve seat  105 , although any suitable method of maintaining this and the remaining O-rings in position will be acceptable in at least some embodiments.  
         [0037]    In an exemplary embodiment, the force of the downward movement of gate unit  150  is amplified by the wedge effect at the interface of sealing surfaces  107  and  170 , thereby providing a well-secured seal. In an exemplary embodiment, in the event of a sudden loss of air pressure, the closed position of the valve is maintained by the force of spring member  116  against the upper side of piston  155 .  
         [0038]    In an exemplary embodiment, air is the actuating medium and is used to drive gate unit  150 . In an alternative embodiment, a gas, other than air, is the actuating medium and is used to drive gate unit  150 . In an alternative embodiment, dry nitrogen is the actuating medium and is used to drive gate unit  150 .  
         [0039]    The gate valve of the present invention makes high-speed movement of valve gate  165  possible. The simple up/down movement of gate unit  150  makes the operation of this valve reliable, silent and smooth.  
       Conclusion  
       [0040]    The present invention relates to a valve apparatus for high-pressure differential/vacuum environments. More particularly, the invention relates to a high-vacuum gate valve with a single moving component.  
         [0041]    Having filly described a preferred embodiment of the invention and various alternatives, those skilled in the art will recognize, given the teachings herein, that numerous alternatives and equivalents exist which do not depart from the invention. As a result, the invention is not to be limited by the foregoing description, but only by the appended claims.