Abstract:
A metal gasket made of soft, malleable metals such as aluminum, copper, or shape memory metals formed with specified deformable geometric features that enable the gasket to form ultra high vacuum or ultra high purity hermetic seals with very low permeation. These features permit a simple shape that may be used in unique grooves, conventional elastomeric o-ring grooves, or independently.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Application No. 62/055,058 Entitled “Deformable All Metal Gaskets for Ultra High Vacuum and Ultra High Purity Sealing” filed Sep. 25, 2014. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to equipment and method of manufacture for metal gaskets to be used as drop-in replacements for elastomer O-rings used to seal vacuum vessels. 
       BACKGROUND INFORMATION: 
       [0003]    Elastomeric seals (polymers industrially known by many names such as Viton, Burna, Kalrez PTFE) are commonly chosen as the sealing gasket for vacuum chambers. They are often configured as O-rings installed in grooves that are captured between two faces which create a vacuum-tight seal. For low and high vacuum and low and high purity regimes, O-rings are cost-effective and reliable. However, O-rings polymers themselves are permeable and allow disruptive quantities of gasses and contaminants to enter the vacuum environment in the ultra-high vacuum (UHV) range and beyond. Furthermore, the inherent permeation in elastomeric compounds are consequential in ultra high purity (UHP) environments and may contaminate the environment. To operate in UHV or UHP, chambers must be built with special sealing flanges such as Conflat (CF) or Wire Seal flanges which have knife like edges that crush all-metal gaskets (typically copper or aluminum). These all-metal gaskets have little to no gas permeation and are required for achieve UHV and UHP. These CF and wire seal flanges are available in standard round sizes. 
         [0004]    Not all UHV and UHP vessels may be sealed with conventional CF or wire seal flanges. When an opening is required in a chamber that is square or rectangular, too large, or oddly shaped, a special flange may be machined that deforms a soft foil (e.g., indium, tin) to create the requisite all-metal seal. Alternatively,  4  aluminum wires may be strung over a flat rectangular flange face such that they intersect at the corners, where the mating rectangular flange may then compress the wires with considerable force to create a suitable UHV or UHP seal. Each of these solutions is time consuming and expensive in material and requires a large space to properly execute. 
         [0005]    There also are industrially available all-metal “C” shaped seals that may be used for UHV and UHP. They may also have a deformable metal ridge on the top and the bottom of the seal which improves their UHV functionality by yielding under the stress of compression. These C seals have an internal spring that energizes the seal and compresses it against the mating chamber surfaces. These C seals are unreliable and expensive. They are also not suitable for tight radii and do not readily fit already cut oring grooves. 
         [0006]    There also are soft metal gaskets with deforming wedge shaped sealing edges which are fixed by an outer support frame. These support frames type seals come in two varieties. First, there are circular shaped locating frames fixed to the outside of the circular wedge shaped sealing edge. The locating frame is tube-like and suspends wedge shaped edges inside of either face of the tube. The second type has flat support frames that span outside the center plane of the deforming wedge-shaped sealing face. These support frames are plates of sheets of metal with bolt holes that provide the location for the wedge type seal relative to the bolts. 
         [0007]    Both of these support frame type metal gaskets are machined from larger plates of a soft metal such as copper or aluminum and are consequently costly. All of these support frame type seals are restricted to sealing flat flange faces and do not fit into grooves like elastomeric o-ring grooves. If either the flat plate surfaces are damaged, the seal will not work. 
         [0008]    There are no all-metal seals that offer the flexibility and versatility of elastomeric or polymer seals. There are many standard and non standard shaped flanges and ports such as rectangular, circular, oval, and hexagonal, and each geometry may vary widely in size being small or very large. Many may only be sealed with elastomeric seals or the crushed wire or foil method. 
         [0009]    Accordingly, there is an as of yet unmet need in the art for deformable metal seals that may be used interchangeably with polymer elastomeric seals. There also is a need to upgrade existing chambers to UHV and UHP regimes by using all metal seals that fit standard elastomeric o-ring grooves. 
       SUMMARY OF THE DISCLOSURE 
       [0010]    An all-metal gasket system for sealing vacuum with very low permeation comprising a soft, malleable metal gasket of aluminum, copper, nickel, tin, silver, gold or other metal with a hardness of &lt;70 Rockwell B Scale (100 kg 1/16″ Ball), a yield strength of 20 to 220 MPa and a vapor pressure of &lt;1×10−8 Ton at 600 K. The gasket is extruded or machined into a specified shape and formed into a circular or otherwise continuous ring-shape with the same dimensions as the receiving O-ring groove. The gasket is designed with specific shapes for desired deformation properties. The existing O-ring is removed from the vacuum chamber and the deformable metal gasket is inserted into the groove. As the two opposing faces of the vacuum chamber are tightened down on the gasket, the gasket deforms and fills the O-ring groove in such a manner that there are no voids or pockets where gasses may transmit from the atmosphere side to the vacuum side. The gasket is crushed between the two sealing faces and now forms a UHV barrier. 
         [0011]    The invention may be coated or treated in any manner (for example, nickel-plating or anodizing) to alter hardness or deformation properties. Additionally, advanced memory retention metals may be used to return the gasket to the pre-crushed state if removed by the user. 
         [0012]    The invention creates a vastly less permeable vacuum seal in an existing O-ring groove than the original elastomer O-ring. Similar to other UHV sealing methods, the invention creates an entirely metal barrier between a vacuum environment and the outside atmosphere. The invention may be used as an upgrade of an existing vacuum chamber for UHV use without the need for re-machining or expensive physical alterations to the chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention is described in more detail with reference to the attached drawings, in which: 
           [0014]      FIG. 1  is a cross section view of a simple version of the all metal gasket before it is compressed between two plates; 
           [0015]      FIG. 2  is a cross section of the metal gasket in an unused form in a conventional dovetail shaped elastomeric o-ring groove; 
           [0016]      FIG. 3  is a cross section view of the metal gasket when installed and crushed in a typical O-ring groove; 
           [0017]      FIG. 4  is cross section view of the uncompressed gasket with one compressive force limiter cut out per side. This also serves as a volume that captures the displaced deformed metal when the gasket is compressed; 
           [0018]      FIG. 5  is a section view of the uncompressed gasket showing two cut-out reliefs per side of the gasket that are located on the 60 degree slip planes of deformation; 
           [0019]      FIG. 6  shows a narrower embodiment of the uncompressed gasket held between two flanges with grooves; 
           [0020]      FIG. 7  shows the joint of two ends of an extruded gasket forming a continuous hermetic ring; and, 
           [0021]      FIG. 8  shows an alternate version of the all metal gasket that is a hybrid between a conventional sheet meal Conflat style gasket and the all metal seal disclosed in this patent. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following detailed description illustrates the invention by way of example, not by way of limitation of the scope, equivalents or principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention. 
         [0023]    In this regard, the invention is illustrated in the several figures, and is of sufficient complexity that the many parts, interrelationships, and sub-combinations thereof simply cannot be fully illustrated in a single patent-type drawing. For clarity and conciseness, several of the drawings show in schematic, or omit, parts that are not essential in that drawing to a description of a particular feature, aspect or principle of the invention being disclosed. Thus, the best mode embodiment of one feature may be shown in one drawing, and the best mode of another feature will be called out in another drawing. 
       Deformable All Metal Gaskets for Ultra High Vacuum and Ultra High Purity Sealing  
       [0024]      FIG. 1  shows the simple state of the  100  crushable gasket before being crushed between flange plates  200  and  300 . As an opposing metal surface  201  and  301  drawn down on top of the gasket the gasket deforms and creates a vacuum barrier between flanges  200  and  300 . 
         [0025]      FIG. 2  shows the cross section of a crushable metal gasket designed for use in existing dovetail O-ring grooves. The gasket is rectangular sided to ensure that the gasket may be extracted from the O-ring groove after use. 
         [0026]      FIG. 3  shows the metal gasket  100  when installed in dovetail  210  O-ring groove similar to  FIG. 2 . The gasket is first formed to match the shape and dimensions of the receiving O-ring groove so that it may be installed by the user without any alterations to either the chamber or the gasket. The invention is specifically designed in such a manner that as stress builds upon the  110  Crushed gasket seal, they do not cause deformation in the bulk of the gasket beyond the  155  maximum allowable gasket width dimension. This is so it may be extracted from the  210  groove after being crushed between the  200  and  300  flanges due to use. 
         [0027]      FIG. 4  shows the  100  is the Metal Gasket in a  210  dove tail shaped o-ring groove. It has two large  151  cut outs (reliefs) that enable the metal displaced during compression of the  110  crushed gasket seal to fill. This helps keep the width profile  155  only slight beyond the outer width edge of the gasket  150 . This enables the gasket to be removed after use and not be trapped by the constricted throat  250  or interfere with the  255  minimum groove wall. 
         [0028]      FIG. 4  also shows the  160  compressive force limiter which deforms (yields) as the  110  crushed gasket seal face widens under an increasing level of compressive force. This  160  limiter serves to reduce the maximum stress in the gasket and stress on the mating flanges  200  and  100 . As the compressive force flattens  120  tip it grows to the size of the line shown in  110 . Beyond that point, the deformation tends to occur in the  160  compressive force limiting feature. 
         [0029]    Also shown in  FIG. 4  are vectors where the displaced metals tend to flow  510 . They are located on 60 degree angles ( 510 ) at the center of the central vector of compression  500  on each side of the  100  gasket. 
         [0030]      FIG. 5  shows the  100  is the Metal Gasket in a  210  dove tail shaped o-ring groove. It shows the  110  crushable wedge-shaped surface with a 120 degree compression angle which demonstrates the shape-agnostic attributes of the deformable metal wedge  120  that initially concentrates stress on the sealing surfaces  201  and  301  of the flanges. 
         [0031]      FIG. 5  shows a version of the  100  gasket with two  151  cut-out reliefs. This demonstrates that the reliefs may be embodied a large number of ways. Also shown in 
         [0032]      FIG. 5  are vectors where the displaced metals tend to flow  510 . They are located on 60 degree angles ( 510 ) off the central vector of compression  500 .  FIG. 5  also shows the  160  compressive force limiter in two places which deforms (yields) as the  110  crushed gasket seal face widens under an increasing level of compressive force. This  160  limiter serves to reduce the maximum stress in the gasket and stress on the mating flanges  200  and  300 . 
         [0033]      FIG. 6  shows the  100  is the Metal Gasket in its uncompressed state in straight shaped grooves  210 . It shows the  110  crushable wedge shaped surface with narrower shape profile which demonstrates that the width of the gasket may be varied.  FIG. 6  shows the narrow profile of the  160  compression limiter. It also shows the  151  cut-out relief that encompass both 60 degree slip planes of deformation in one  151  cut-out per side. 
         [0034]      FIG. 7  shows the  190  joined seam between ends  191  of the  100  metal gasket seal. The  190  joint enables the  100  gasket to be formed a continuous hermetic ring from long extruded bars or wires. 
         [0035]      FIG. 8 . shows a modified all metal gasket  100  pinched by a knife edge of a Conflat flange and pressed against a flat metal plate  200 . The  100  all metal gasket has a flat surface on the  600  Conflat flange side which is pinched by the knife edge  610  and held within the gasket retaining well  620  on the Conflat flange  600 . The  120  gasket tip is deformed by the downward compressive forces becoming flatted to the  110  ompressed gasket profile. 
         [0036]    Referring to  FIGS. 1 through 8 , in general terms, the invention comprises one or more of the following features: 
         [0037]    1. A metal gasket defining two stress concentrating features that deform upon compression against flange  200  and  300 . The stress concentrating features may comprise a sharp point or dull lump that focuses the compressive force upon itself beyond its elastic deformation strength limit. 
         [0038]    2. A metal gasket that has been joined to form a continuous hermetic perimeter around mating flanges  200  and  300 . 
         [0039]    3. A metal gasket that has no internal or external frame. 
         [0040]    4. A metal gasket that does not include a separate internal metal spring member. 
         [0041]    5. A metal gasket having a defined shape that may be compressed along its vector of compression and that may absorb the displaced metal material in its body such that it does not considerably extend beyond its uncompressed outermost width profile (perpendicular to the vector of compression). This may be done either by minimizing the size of the deformable metal wedge or by storing the displaced metal in reliefs (cut-outs) that are located inside the outer most width profile dimension ( 155 ). 
         [0042]    6. A metal gasket that is located (or positioned) by grooves on one flange face or both flange faces. After being fully compressed, the displaced metal still does not protrude considerably beyond its outermost uncompressed width profile dimension ( 155 ). 
         [0043]    7. A metal gasket having a compressive force limiter. A compressive force limiter is a necked or narrowed section of the gasket that deforms upon a critical level of compressive stress. The compressive force limiter limits the stress and deformation at the sealing surface and instead directs the deformation into the necked section of the gasket. 
         [0044]    8. A metal gasket that is located (or positioned) on a flange face by conventional elastomeric o-ring grooves. After being fully compressed, the displaced metal still does not protrude considerably beyond it outermost uncompressed width profile dimension. 
         [0045]    9. A metal gasket with cut-outs or reliefs that are located in approximate 60 degree increments from the center of the central axis of compression (vector of compression). The cutouts or reliefs may be merged such that both of the 60 degree axis on each side of the gasket are formed into one central cut-out feature. The cut-outs store the displaced metal from the deformed sealing edges or the compressive force limiter and prevent the gasket from getting wider than the uncompressed maximum width profile of the gasket. 
         [0046]    10. A metal gasket with guide edges on its width profile that keep it located it within grooves on one or both mating flanges. 
         [0047]    11. A metal gasket with a narrow profile that not only deforms along its vector of compression, but also is able to rock laterally. This permits a flange of one coefficient of thermal expansion (CTE) to be hermitically sealed with a flange of another coefficient of thermal expansion (CTE) when both flanges are heated or cooled. 
       ALTERNATE EMBODIMENTS 
       [0048]    The invention may be used in more sealing applications than vacuum, such as high pressure applications where metal seals enable better seals. For example, pressurized gas or liquid that would otherwise corrode, degrade or permeate through an elastomeric seal could be stored in the same container with the new metal seal. Additionally, new vessels that are designed for UHV may eschew more expensive metal sealing techniques with complicated frame structures and instead machine simple grooves on sealing faces. The gasket used as an adapter to seal conventional Conflat flanges directly to flat metal plates. 
       INDUSTRIAL APPLICABILITY 
       [0049]    It is clear that the inventive nature of this application has wide applicability to the scientific, semiconductor, particle physics, petrochemical industries and more, namely to provide the ability to use all metal seal gaskets to reduce permeation with simple flexible geometries. 
         [0050]    It should be understood that various modifications within the scope of this invention may be made by one of ordinary skill in the art without departing from the spirit thereof and without undue experimentation. This invention is therefore to be defined as broadly as the prior art will permit, and in view of the specification if need be, including a full range of current and future equivalents thereof. 
       Parts List 
       [0051]      100  is the compressed all metal gasket.  110  is the crushed sealing face of the gasket against the  200  Base Flange and  300  Top Flange. 
         [0052]      120  is the wedge shaped deformable feature that creates the vacuum seal. It located against the top flange and the bottom or base flange. 
         [0053]      150  is the side (both inside and outside) of the seal that. 
         [0054]      151  is the relief or reliefs that provide an empty area which can be filled with the displaced gasket material when the gasket is compressed against the flange sealing faces  201  and 
         [0055]      301 . The reliefs may be any shape or number. There can be one or more reliefs. The reliefs may be large or small. 
         [0056]      155  is the gasket width profile. This is where, when the gasket is compressed, little of the displaced gasket material is permitted extend beyond the boundary. 
         [0057]      160  is the compressive force limiter. When the compressive force builds upon the compressed sealing face  110 , the force become distributed upon a wider and wider compressed sealing face profile  110 . When the compressed sealing face profile  110  becomes as wide as the width of the  160  compressive force limiter the compressive force limiter yields rather than the  110  gasket sealing face. 
         [0058]      190  is the permanent joint between the ends  191  of the  100  gasket. 
         [0059]      191  are the ends of the gasket length. 
         [0060]      86  is the uncompressed profile of a typical elastomeric round o-ring seal. 
         [0061]      200  is the base flange. We have defined it as the flange with the gasket groove. 
         [0062]      210  is the gasket grove which is located in the base flange ( 200 ). 
         [0063]      250  is the restricted throat of the gasket groove. 
         [0064]      255  is the throat profile that which defines the strict outer limit for the displaced gasket material. 
         [0065]      300  is the top flange which is the other sealing member. 
         [0066]      500  is the vector of compression against the metal gasket. 
         [0067]      510  are the vectors of displacement. For face centered cubic (FCC) structured metallic crystal structures, the slip planes tend to be greatest along 60 degree angles off the vector of compression ( 500 ). The displaced aluminum reliefs are located so that the displaced aluminum is stored in the reliefs  151  this minimizes the increase in the gasket width  155 . 
         [0068]      600  is a conventional ConFlat flange with a knife edge sealing feature. 
         [0069]      610  is the knife edge sealing feature on the Conflat flange. 
         [0070]      620  is the gasket well that retains the gasket in the Conflat flange.