Abstract:
A clamping system for high or ultra-high vacuum system components including a clamping member surrounding a flange of the vacuum system component. A bead along the inside diameter of the clamping member engages a groove in the peripheral surface of the flange. When a clamping force is applied to the clamping member, as by a bolt, the force is transmitted to the flange providing sufficient clamping force to form a vacuum seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 60/243,527 filed on Oct. 26, 2000, the teachings of which are incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     This invention relates to clamping systems for high and ultra-high vacuum systems. 
     BACKGROUND OF THE INVENTION 
     Vacuum systems find wide applications in research, education, product development, and production. Typical systems are comprised of independent and interchangeable components. Components include testing chambers, pumps, gauges, valves, specimen holders, electron sources, ion sources, photon sources, molecular beam sources, detectors of various types, etc. 
     Processes or experiments that require high or ultra-high vacuum (UHV) currently employ all metal vacuum joints. A typical all-metal joint, such as that described in U.S. Pat. No. 3,208,758, is illustrated in FIG.  1 . Such a joint comprises a flange  20  (FIG. 2) that includes an annular recess  26  and an annular knife edge  30 . The flange  20  is intended for mating with another like flange  24  separated by a soft, metallic gasket  34 . The opposing knife edges  30 ,  32  are pressed into the gasket  34  by tightening bolts  38  forming the UHV seal. 
     In UHV systems, the level of vacuum is dependant upon the speed of the vacuum pumps, the leak rates of the vacuum joints and vacuum walls, the surface area of the chamber and pumping lines, and the surface roughness of the interior components. Cleanliness or purity of the vacuum environment depends upon the interior component&#39;s material, forming method, and surface finish. The practicality of a vacuum system depends on the ease of access for changing specimens, the required down-time to trouble shoot and to do repairs, and the ease with which components may be added and removed from the system. The expense of a vacuum system lies in the cost of components, the required pump types and speeds, and the number and type of extra adapters needed to attach components to a system. Methods of accurately placing testing apparatus, processing equipment, or samples within a system are often required for an experiment or process. The prior art flanges do not adequately optimize some of these requirements, in some cases. 
     Standard thickness flanges depend on the thickness of the flange to transfer force from the bolts to the sealing gasket in order to crush the gasket and form the seal. This requires that mating flange configurations be one flange with clear bolt holes and one flange with either clear or tapped bolt holes. If both flanges have clear holes, then there must be room for bolt heads on one side of the flange pair and for nuts on the other. If at least one of the flange pairs is not rotatable, then the possible mounting configurations are limited to the number of bolt holes. 
     Methods for directly attaching two vacuum components that both have tapped holes currently involve one of several options, all of which significantly increase size or complexity of the vacuum system. One method includes inserting an adapter comprised of two flanges on each end of a thin wall tube. Unfortunately, the tube has to be long enough to provide bolt clearance. Another method uses double-sided couplers that bolt to the two components. Such a coupler is described in Crawford U.S. Pat. No. 5,671,956. However, even couplers of this type add length. Adding length and surface area significantly decreases molecular conductance, as well as increasing the overall system size. 
     SUMMARY OF THE INVENTION 
     A clamping system for a vacuum system comprising a pair of facing flanges to be joined as part of a vacuum system, each having an external mounting groove in the outer perimeter of the flange. Clamp members are attached to the external mounting groove of each of the flanges. Bolts are disposed extending between the clamp members and are configured to draw the clamp members toward each other. The interaction between the clamp member bead and the groove on the flange transmits the closing force from the bolts to a sealing surface on the flange, whereby sufficient compressive force may be generated to create a vacuum tight seal. 
     Consistent with the present invention, it is possible to insert an additional component or components between two flanges, using only minimal space. The decrease in required space has the advantage of increasing the conductance of the vacuum system. Also, since the present invention does not require modifications to the inserted component or components, industry standard parts may be used in conjunction with the present invention. This last feature is particularly useful in mounting industry standard valves, as opposed to specially modified or specially manufactured valves. Furthermore, because all of the surfaces of the clamp members are machined, and there are no welds, all parts may be fully disassembled. Additionally, it is possible that two vacuum components, both with tapped holes, may be directly attached to each other. Arbitrary angular orientations are possible between non-rotatable flanges. Alternatively, the external mounting grooves of the present invention may be utilized for attachment of support structures or apparatus external to the vacuum system. Because the grooves are symmetric around the perimeter of the flange, support structures may have arbitrary angular orientation with respect to the flange. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are set forth in the following description and shown in the drawings, wherein: 
     FIG. 1 is a perspective view of a prior art flange; 
     FIG. 2 shows an all metal seal of the prior art in cross-sectional view; 
     FIG. 3 is a plan view illustration of an exemplary clamping system consistent with the present invention; 
     FIG. 4 is a sectional view of the exemplary system illustrated in FIG. 3, as taken along section line A—A; 
     FIG. 4A is a detailed view of the indicated region of FIG. 4; 
     FIG. 5 is a perspective view of an exemplary clamp member disposed on flange; 
     FIGS. 6 through 9 illustrate various exemplary details and features of an exemplary clamp member consistent with the present invention; 
     FIGS. 10 through 12 illustrate an alternate exemplary employment of the clamping system consistent with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to first to FIGS. 3 and 4, an exemplary embodiment of the clamping system consistent with the present invention. FIG. 3 shows a first and a second vacuum system component  41  and  43  each having a corresponding clamp member  44  and  46  respectively attached thereto. The two clamp members  44  and  46  are further joined or secured to one another using auxiliary bolts, one of which is indicated at  47 . 
     Turning to FIG. 4, a sectional view of the assembly shown in FIG. 3 is illustrated. The individual clamp members  44  and  46  are each attached to respective flanges  52  and  54  of vacuum system components  41  and  43 . Each of the flanges  52  and  54  comprise a groove  42  and  45  formed in the outer edge of each flange  52  and  54 . The attachment of the clamp members  44  and  46  may advantageously be achieved by means of beads  53  and  55  projecting from the clamp members  44  and  46 . It should be appreciated that the beads  53  and  55  may be either continuous or discontinuous, and may also be either integral with the clamp members  44  and  46 , or may be a separate component secured thereto. The interaction of the beads  53  and  55  with the grooves  42  and  45  about a substantial portion of the circumference of each flange  52  and  54  serves to securely affix each clamp member  44  and  46  to the flanges  52  and  54 . These features of this exemplary embodiment are illustrated in better detail in FIG. 4A, which is an enlarged view of the pertinent regions of FIG.  4 . 
     With both of the individual clamp members  44  and  46  secured to the corresponding flanges  52  and  54 , the vacuum system components  41  and  43  may be joined to one another by means of auxiliary bolts disposed around, but spaced outside of, the perimeter of the flanges  52  and  54 . One such auxiliary bolt is indicated at  47 . The auxiliary bolts  47  apply a compressive force on the flanges  52  and  54  through the clamp members  44  and  46 . This compressive force presses the knife edges  48  and  49  of the flanges  52  and  54  into the metallic gasket  50 , thereby forming a vacuum tight seal between the first and the second vacuum system components  41  and  43 . 
     Turning to FIG. 5, one half of the above-described clamping system is illustrated in perspective view. As shown, the clamping member  44  is disposed around a flange  52 . The illustrated flange  52  comprises a plurality of bolt holes  61  disposed about the circumference of the flange  52 . Conventional clamping utilizes two such flanges clamped together by way of bolts passing between these bolt holes  61  and similarly arranged holes in a mating flange. It will be appreciated that successful sealing of two such flanges can only be achieved if the bolt holes of each flange are of the same size and disposed about the same diameter. Furthermore, the individual vacuum components may only be oriented in the limited rotational increments provided for by the bolt holes. Consistent with the present invention, the clamping system is not indexed to the vacuum system components, and therefore alignment of flange bolt holes, or other features, is irrelevant to achieving a vacuum tight seal. 
     Referring to FIGS. 6 through 9, the individual components of an exemplary clamp consistent with the present invention are illustrated. For illustrative purposes, a single clamp member  44  is shown generally in FIG.  7 . Each clamp member  44  may advantageously be divided into at least two sections  44 A and  44 B. This division is made in order for clamp member  44  to be applied to the flange  52  while permitting the beads  53  to engage the groove  42  of the flange  52 . While in the exemplary embodiment the clamp member  44  is bisected into two pieces  44 A and  44 B, it will be appreciated that the clamp member may be further divided, advantageously so depending upon the geometry of the flange, which may be other than circular. 
     In the interest of maintaining the clamp member  44  securely disposed on the flange  52 , it is desirable that the individual portions of the bisected clamp member  44 A and  44 B are capable of being rejoined in a strong manner. Accordingly, while not necessary, the clamp member section  44 A and  44 B may mate using a lap joint, or similar. As shown in FIG. 6, each clamp member section  44 A may be a generally semicircular member terminating in alternating laps  80  and  82 . With reference to FIG. 7, the clamp member sections  44 A and  44 B may be joined by circumferentially oriented bolts  84  and  86  at each lap joint, and/or by bolts  88  and  90  passing through the thickness of the clamp member  44 . 
     As discussed above, after the clamp members  44  and  46  have been appropriately secured to respective flanges  52  and  54 , a seal is achieved by applying a compressive force between the clamp members  44  and  46 . The compressive force is most easily generated by auxiliary bolts  47  passing between the clamp members  44  and  46 . The auxiliary bolts  47  may extend between the respective clamp members  44  and  46  through bolt holes  92  disposed about the circumference of clamp members  44  and  46 , as indicated in FIG.  7 . Alternately, the auxiliary bolts  47  may extend between the clamp members  44  and  46  via slots or cutouts  94  in each clamp member, as indicated in FIG.  8 . According to this last embodiment, the slot  94  may comprise a stepped slot, wherein the larger region of the slot  96  may be configured to receive a bolt head and/or a nut. 
     With further reference to FIGS. 8 and 9, the clamp members may be configured with special mounting features, such as bolting facilities  82 , providing mounting locations for externally mountable apparatus. In this manner, external systems such as heating systems, cooling systems, etc. may be located adjacent to the vacuum system by mounting to the clamping system. Additionally, these features may be used for attaching support structures to the relevant portions of the vacuum system. Alternately, external systems may advantageously be attached to the grooves disposed in the flange members. The symmetrical configuration of the grooves around the perimeter of the flanges permit supports structures or external systems to be mounted to the vacuum system with an arbitrary angular orientation. Accordingly, such support structures and external systems may be mounted to a vacuum system in such a manner that no undue stresses or strains are experienced by the vacuum system. 
     In a final illustrative exemplary embodiment, the clamping system consistent with the present invention may be employed to incorporate components into a vacuum system, wherein the component may be disposed between two flanges. Such an embodiment is illustrated in FIGS. 10 through 12. With particular reference to FIGS. 11 and 12, a valve  60  is shown disposed between two flanges  62  and  64 . Each of the flanges is fitted with a clamp member  71  and  75 . Consistent with the previous disclosure, each clamp member  71  and  75  comprises two individual clamp member portions  70 ,  72  and  74 ,  76  respectively. Each of the two flanges  62  and  64  is sealed against the valve  60  using a conventional metal gasket  66  and  68  and knife edge sealing surfaces (not shown). The two clamp members  71  and  75  are drawn toward one another, therein applying the compressive force necessary to seal metal gaskets  66  and  68 , by auxiliary bolts, one of which is indicated at  79  in FIG.  10 . It should be appreciated that the width of valve  60 , or similar component which may be accommodated, is only limited by the available length of auxiliary bolts  79 . 
     Further embodiments of the exterior flange mounting grooves and exterior clamp members may obviously be configured to accommodate different industry standard flange sizes, and different exterior mounting arrangements. Longer length versions may also be used for mounting larger apparatus. Along the same lines, tees and crosses of various sizes are also contemplated herein. 
     Accordingly, while the present invention has been disclosed with reference to particular exemplary embodiments, the invention herein is susceptible to many variations and alteration that will be obvious to one having skill in the art, without materially deviating from the spirit of the invention. Therefore, the invention should not be limited to the exemplary embodiments disclosed above, but rather only by the claims appended hereto.