Abstract:
A perimeter weld flange comprising an inner and external perimeter wall surface and a perimeter weld lip on said flange for welding said flange onto a receiving surface. The perimeter weld flange herein is particularly suitable for weldable metal-gasketed ultra-high vacuum joints, and is also conveniently welded onto tubes, cones, ellipsoids, plates and other shapes, including even irregular shapes, in addition to spheres.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon provisional U.S. patent application Ser. No. 60/028,312 filed Oct. 11, 1996. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an improved flange design for weldable metal-gasketed ultra-high vacuum (UHV) joints. The invention has particular utility with respect to all-metal flanged manifolds and will be described in connection with such utility, although other utilities are contemplated. 
     BACKGROUND OF THE INVENTION 
     Vacuum systems are used in scientific research, the semiconductor industry, many analytical instruments, and various similar applications. Processes or experiments that require high or ultra-high vacuum (UHV) typically employ all-metal vacuum joints or seals. Referring to FIG. 1, such a joint typically comprises a flange  10  that includes an annular recess  15  and an annular knife edge  20 . The flange  10  is intended for mating with another like flange  10  separated by a soft, metallic gasket  25 . The opposing knife edges  20  are pressed into the gasket  25  by tightening bolts (not shown) forming the UHV seal, e.g. in accordance with the teachings of U.S. Pat. No. 3,208,758. Non-metal gaskets may be used in certain applications. Most embodiments utilize circular flanges; however, the flanges do not need to be circular. 
     Prior art flanges  10 , seen in FIGS. 2A-2C and  3 A and  3 B, utilize a stepped internal diameter  30 , and weld easily only to tube  35  or to tube-like projections machined onto another shape  40 . Frequently, an extension tube  35  is welded into a cylindrical main vacuum chamber  70  and a flange  10  is welded onto the extension tube  35 . The weld between the extension tube  35  and the cylindrical main chamber  70  is a difficult, non-planar weld which can cause inaccuracy in the flange&#39;s positioning. For spherical main chambers  65  and centered flange ports  10  the weld is a simple planar weld, but an extension tube  35  is still required. The extension tube  35  moves the port opening away from the surface of the sphere which interferes with the access and visibility of the interior of the main chamber. Also, the weld of the extension tube  35  to the interior of the flange  10  decreases the possible working diameter of the flange&#39;s bore  45 , and can only be accessed from the interior of the chamber for smaller sized flanges. This requires that at least one port on the chamber be large enough to accommodate a welding torch, restricting the minimum size of the chamber. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a flange which overcomes the aforesaid and other disadvantages of the prior art. Another object of the invention is to provide an improved flange design and method of attaching a flange to a receiving shape. 
     SUMMARY OF INVENTION 
     The present invention provides a perimeter weldable flange design comprising a weld lip surrounding said flange, in which a hole of diameter equal to the weld lip diameter is machined into the receiving shape, and the flange attached thereto by a weld made on the interior surface of the receiving shape, i.e. the surface exposed to vacuum. With proper tooling, this interior surface weld can be performed readily though the bore of the flange from the outside. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Still other objects and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the following drawings, in which like numerals depict like parts, and wherein: 
     FIG. 1 is an exploded view of a prior art flange and metal gasket; 
     FIG. 2A is a front elevation,  2 B a side elevation and  2 C a sectional view of a prior art flange welded to an extension tube. 
     FIGS. 3A and 3B are sectional views of all-metal seal flanges welded to tubes and a cylindrical chamber utilizing the prior art methodology; 
     FIG. 4A is a front elevation,  4 B a side elevation, and  4 C a sectional view of one form of flange made in accordance with the present invention; 
     FIG. 5A is a front elevation,  5 B a side elevation, and  5 C a sectional view of another form of flange made in accordance with the present invention; 
     FIG. 6A is a front elevation,  6 B a side elevation, and  6 C a sectional view of yet another form of flange made in accordance with the present invention; 
     FIG. 7A is a front elevation and  7 B a sectional view of a spherical chamber with welded flanges made in accordance with the present invention; 
     FIG. 8A is a front elevation, and  8 B and  8 C sectional views of an alternative form of a flange made in accordance with the present invention; 
     FIG. 9A is a front elevation and  9 B a section view of a spherical chamber with welded flanges made in accordance with yet another embodiment of the present invention; and 
     FIG. 10A is yet another sectional view of the form of flange of the present invention, and 
     FIG. 10B is an enlarged view of the perimeter weld lip. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIGS. 4A-4C and  7 A and  7 B, an all-metal seal flange  60  made in accordance with the present invention is shown welded on a spherical chamber  65 . The flange  60  preferably includes an internal conical region  75  shaped and dimensioned to mate with the inside surface of spherical chamber  65 , or a raised conical region formed thereon. Flange  60  also includes a cylindrical bore  45  between the knife edge seal region  20  and the conical region  75 . Referring to FIGS. 5A-5C, if desired, circumferential grooves  85  may be formed in the inner side wall surface of bore region  45  for accommodating mounting systems for devices or accessories as disclosed in U.S. Pat. No. 5,593,123 to Crawford. 
     Referring also to FIGS. 6A and 6B, if desired, extra gasket compression holes  90  and accessory mounting bolt holes  100  may be provided in the flange. 
     The weldable flange construction of the present invention offers several advantages over prior art weldable flange constructions. For one, the flange sealing surface of the welded-in flange  60  lies close to the original surface of the spherical chamber  65 . In addition, the need for a length of tube separately welded to the chamber and to the corresponding flange such as illustrated in prior art FIGS. 2A-2C and  3 A and  3 B is eliminated. The internal conical region  75  of the present invention also provides additional internal space, a larger useful bore, and improved access as compared with prior art weldable flange assemblies. Thus, a vacuum joint assembly made in accordance with the present invention may be made much more compact than prior art systems. 
     Additionally, the total number of welds is reduced. Also, with reference to FIGS. 7A and 7B, internal welds onto spherical chambers, plates, cone ends and cylinder ends are planar and thus easier to make than non-planar welds as in the traditional, cylindrical-wall welds with the prior art flange. Also, internal, i.e. vacuum-side welds, made in accordance with the present invention, are inherently cleaner. The flange can be welded at any arbitrary angle into the receiving shape. And, assembly and accurate positioning of the flange on the receiving shape is easier due to the shape of self-locating weld lip  55 . Welded flange assemblies made in accordance with the present invention are shorter in length than prior art welded flange assemblies, which translates into higher pumping conductance and thus ease of achieving vacuum, and also easier hand and tool access. Additionally, easier access with shallow angles makes internal surfaces easier to clean. 
     The perimeter weld flange allows advantage to be taken of the inherent superiorities associated with spherical shapes. Practical production methods are available for producing hemispherical shells which can be welded together to form a sphere. Spherical chambers combined with perimeter weld flanges provide a maximized internal apparatus capacity for same size series of flanges. The result herein is therefore a vacuum assembly with much improved access for particle and/or photon beams, feedthroughs, manipulators, gauges, valves, pumps, etc. where the completed apparatus is less awkward and much more compact. 
     The invention is susceptible to modification. For example, FIGS. 8A-8C illustrate a perimeter weld flange  60  including the conical region  75  where the weld lip  55  is extended backwards for a length, forming a larger-diameter unitary extension  105 . The unitary extension  105  serves the function of a tube extension eliminating one weld, and significantly increases the extension inner diameter  110  over the prior art flange  10  with its extension tube  35  of FIGS. 2A-2C and  3 A and  3 B. Also, the unitary extension  105  can be machined to any profile and could therefore be welded to any shape. Finally, unitary extension  105  on one flange allows a perimeter weld flange  60  of the first embodiment to be welded to the opposite end, forming a single weld cylindrical chamber of any length with maximized internal volume, and improved pumping speed. 
     In another modification, with reference to FIGS. 9A and 9B, flanges  62  may be machined directly onto a spherical shell  65 , e.g. in accordance with the teachings of U.S. Pat. No. 5,625,947 to Crawford. For a spherical shell  65  with at least one protruding boss, such as the outer diameter of the machined in flange  61 , it is easier to machine on a lathe than a solitary spherical shell. With one flange machined directly into a spherical shell  62 , other flanges  60  can still be easily added at arbitrary angles by previously stated methods. 
     Finally, as shown in FIG. 10A, the perimeter weld flange of the present invention typically has the following dimensions (inches) for the indicated features: 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                 Actual OD 
                 Weld Lip OD 
                 Weld Lip ID 
                 Overall Length 
               
               
                 DIM A 
                 DIM B 
                 DIM C 
                 DIM D 
               
               
                   
               
             
             
               
                 1.330 
                 1.200 
                 1.100 
                 0.490 
               
               
                 2.730 
                 2.599 
                 2.500 
                 0.790 
               
               
                 4.470 
                 4.430 
                 4.240 
                 1.090 
               
               
                 5.970 
                 5.840 
                 5.740 
                 1.090 
               
               
                 7.970 
                 7.840 
                 7.740 
                 1.090 
               
               
                   
               
             
          
         
       
     
     In addition, as shown in FIG. 10B, the typical chamfer on the weld lip is 0.025″×45° and the typical weld lip height is about 0.050″. Other dimensions can be used. 
     The present invention provides a method for welding a flange to a receiving surface, by first supplying a perimeter weld flange  60  containing both interior  46  and external perimeter surfaces  61  defining a bore  45 , including an external perimeter weld lip  55 , and welding the perimeter weld lip  55  of the flange to the receiving surface. In addition, as noted earlier, a preferred embodiment is to weld the perimeter weld flange  60  herein onto spherical vacuum chambers  65 , wherein the chamber contains a hole of diameter equal to the weld lip diameter, wherein the weld lip diameter is reference to the outer most diameter of the weld lip  55 . In addition, attachment by a weld is conveniently made on the interior surface of the chamber  50 , which is the surface exposed to vacuum, by welding tooling positioned within the bore of the flange  45 . 
     Still other changes may be made without departing from the spirit and scope of the invention.