Abstract:
A seal is retrofit to an existing seal groove and made whole after being positioned in the groove. It can be an initial coil shape to allow it to slip over a shaft to get to the groove or it can be in a plurality of sections that are joined in place. The sections can be abutting or overlapping and are preferably coated with a brazing material that will ultimately join such ends. The ends can then have a nano-engineered coating that comprises alternating layers of aluminum and nickel that when initiated with applied heat becomes reactive exothermically to join the ends using the brazing material.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is retrofit applications for seals that are located in grooves so as to upgrade the seal performance without having to redesign the underlying part containing the groove. 
       BACKGROUND OF THE INVENTION 
       [0002]    Seals are used in a variety of downhole tools. Typically they are disposed around shafts or other components in a circular groove. As frequently they are made of a resilient material such as an elastomer. For a variety of reasons, the service life of such seals, commonly referred to as o-rings may need to be improved. Service life can deteriorate for o-rings for a variety of reasons. The service temperature can rise, the cycling frequency of the parts where the o-ring is mounted can increase or the fluid composition can change. Sometimes the quality of the fluid that is sealed can deteriorate such as when solid contaminant levels rise. 
         [0003]    In the past the equipment would be taken out of service and disassembled and another o-ring installed in the pre-existing groove. If it were possible the material for the o-ring might be upgraded to try to get a little longer service life when the equipment was again reassembled and put into service. However, there were limits to the material options available while still retaining a resilient quality in the o-ring so that it could be worked down a shaft to the groove where it was intended to be mounted. 
         [0004]    Trying to retrofit with a metal seal in an existing groove in the past was not a workable option because the part with the o-ring groove would have to be redesigned to accept a non-resilient seal. In essence the groove would have to be turned into a shoulder that would allow a metallic ring for example to go over the shaft and then a sleeve would have to be advanced over the shaft against the metallic seal to hold it in position. Doing this would require a full redesign of the part, such as a shaft, and for that reason was not a viable solution in the past. 
         [0005]    The present invention focuses on how to retrofit a metallic or other material for a resilient o-ring seal in an existing groove without having to re-engineer the underlying part that has the groove. A single or multi-component design is revealed that is joined either to itself or to other components while in the groove. In that manner the existing groove can be used and the seal material can be upgraded. The cross-sectional shape of the replacement seal can be varied and the section can be solid or tubular. In the preferred embodiment the portions to be joined can be coated with a brazing material for example and then a coating of nano-engineered material such as NanoFoil® made by Reactive NanoTechnologies of Hunt Valley, Md.; www.rntfoil.com. With the replacement seal in position, a heat source starts a reaction that is exothermic in the nano-engineered material and the heat generated in conjunction with the brazing material, for example, then results in making the seal within the groove. If the seal is a one piece helical shape then abutting or overlapping ends can be joined. Alternatively, the seal can start as two or more parts which are joined in the groove to make a unitary seal from the desired materials without re-engineering the underlying part. 
         [0006]    The following methods could be considered for alternative methods of joining a seal. Non-densified, i.e. ceramic and powder metal parts could be sintered or densified around the seal groove. A seal could be deposited in the seal groove. This could include a spray on operation of polymer or metal and could include deposition techniques such as laser deposition or cladding, electron beam deposition and so forth such that sealing material was deposited from unformed material into the seal area. Finally a mold in place technique could be used which uses more traditional pressure molding operations to form the seal directly in the seal area. 
         [0007]    The following patents are relevant to the discovery and development of the nano-engineered foil that is preferred for use in the present invention. 
         [0008]    PAT.NO. Title
   1 U.S. Pat. No. 7,361,412 Nanostructured soldered or brazed joints made with reactive multilayer foils   2 U.S. Pat. No. 7,297,626 Process for nickel silicide Ohmic contacts to n-SiC   3 U.S. Pat. No. 7,143,568 Hermetically sealing a container with crushable material and reactive multilayer material   4 U.S. Pat. No. 7,121,402 Container hermetically sealed with crushable material and reactive multilayer material   5 U.S. Pat. No. 6,991,856 Methods of making and using freestanding reactive multilayer foils   6 U.S. Pat. No. 6,991,855 Reactive multilayer foil with conductive and nonconductive final products   7 U.S. Pat. No. 6,863,992 Composite reactive multilayer foil   8 U.S. Pat. No. 6,736,942 Freestanding reactive multilayer foils   9 U.S. Pat. No. 6,596,101 High performance nanostructured materials and methods of making the same   10 U.S. Pat. No. 6,534,194 Method of making reactive multilayer foil and resulting product   11 U.S. Pat. No. 5,547,715 Method for fabricating an ignitable heterogeneous stratified metal structure   12 U.S. Pat. No. 5,538,795 Ignitable heterogeneous stratified structure for the propagation of an internal exothermic chemical reaction along an expanding wavefront and method of making same   
 
         [0021]    These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings that appear below while recognizing that the full scope of the invention is to be determined by the appended claims. 
       SUMMARY OF THE INVENTION 
       [0022]    A seal is retrofit to an existing seal groove and made whole after being positioned in the groove. It can be an initial coil shape to allow it to slip over a shaft to get to the groove or it can be in a plurality of sections that are joined in place. The sections can be abutting or overlapping and are preferably coated with a brazing material that will ultimately join such ends. The ends can then have a nano-engineered coating that comprises alternating layers of aluminum and nickel that when initiated with applied heat becomes reactive exothermically to join the ends using the brazing material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a two segment version shown with the segments apart before assembly; 
           [0024]      FIG. 2  is the view of  FIG. 1  with the segments joined in an abutting manner in a groove; 
           [0025]      FIG. 3  shows a one piece helically shaped embodiment before mounting in a groove; 
           [0026]      FIG. 4  is the embodiment of  FIG. 3  shown outside the groove for clarity and with its ends joined as they would be in the grove; 
           [0027]      FIG. 5  is a detail with some wall material removed to create flush surfaces after joining ends. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]      FIG. 1  illustrates an object such as a mandrel  10  that is part of a tool that has a groove  12 . Normally the groove  12  houses a resilient o-ring (not shown) and the objective is to replace that o-ring with a seal that will provide better service life without forcing a re-engineering of the part  10 . It is preferred to replace the original o-ring with a metallic seal however other joinable and durable materials such as ceramics and composites for example are also contemplated. The problem has been with the use of more rigid materials that it will not be possible to get them over the end  14  to get into groove  12  because they are not resilient. In the past splitting a seal ring has been rejected as a solution because of the difficulties in getting it to seal again once inserted into the groove  12 . However, the present invention accepts that challenge and addresses it by providing a joining method for a single or multi-component ring while the ring is in the groove  12 . 
         [0029]      FIG. 1  shows two segments  16  and  18  that are preferably u-shaped in cross section such that opposed edges  20  and  22  for example will span a gap to be sealed that goes from the curved surface that defines the depth of the groove  12  to a surrounding body (not shown) that encircles the part  10 . The u-shape is but one of many optional cross-sectional shapes which can be open such as a u-shape or closed such as a tubular diamond shape. The cross-section can be open throughout or tubular and closed throughout or a combination of part open and part closed. It can also be solid in cross-section or fully tubular while closed or partially or totally open in cross-section as the parts  16  and  18 . Metallic is a preferred material but any materials that can function as a seal and be joinable by the described method can be used depending on the parameters of the application. Alternative materials could be ceramics or composites. 
         [0030]    Referring back to  FIG. 1  the ends  24  and  26  are illustrated schematically. They can be slant cut as shown so as to butt up to slant cut ends  28  and  30  on part  16 . The angle of the cut can be varied and it includes the cut at  90  degrees which is a square cut. Apart from butting ends  24  and  28  together for joining in the manner that will be described below, the ends for example  24  and  28  can be overlapped and joined where they contact each other in the overlap areas. For example, end  24  can be placed over end  28  and the overlapping contact areas can be joined in trough  32 . Alternatively some portion of the wall in trough  32  to dashed line  34  can be removed and a like amount of wall can be removed from the underside of the trough  36  such that when parts  16  and  18  are brought together troughs  32  and  36  will butt up flush to each other rather than having a step at dashed line  34  if there was no wall removed and the end  24  merely was laid over past end  28 .  FIG. 5  illustrates one way described above to get a flush mating of troughs  32  and  36 . It can be done in other ways such as a groove in the end wall of one part extending over a mating projection in the other part. 
         [0031]    The joining method involves putting a soldering or brazing compound on the surfaces to be joined and then adding at least one thick foil layer. The foil consists of hundreds of nano-scale aluminum and nickel layers that are vapor deposited into a thick foil. Alternative material combinations can include TiB2, ZrB2, HfB2, TiC, ZrC, HfC, Ti5Si3, Zr5Si3, Nb5Si3, NiAl, ZrAl, or PdAl. Preferably the soldering or brazing compound or other joining material responsive to heat is placed on the parts to be joined on both sides of the foil. The foil consists of hundreds of nanoscale aluminum and nickel layers that are vapor deposited into a thick foil. Pressure is applied to prevent the components from moving and the chemical reaction between the Al and Ni layers in the foil is activated. Heat from the foil&#39;s reaction melts the solder or brazing material layers and enables metallic bonding at room temperature in less than one second. The reaction in the foil may be activated with a small pulse of local energy that can be applied using optical, electrical, or thermal sources. Common examples include an electrical pulse, spark, hot filament, a laser beam, etc. 
         [0032]    The average time that it takes for a reaction to start or components to join after activation of the foils is 10 milliseconds, or just 1/100th of a second. The bonding time is essentially instantaneous, and the entire device cools and can be handled within seconds. 
         [0033]      FIG. 2  shows the ends  24  and  28  abutting and joined together in the manner described above in groove  12 . 
         [0034]      FIGS. 3 and 4  illustrate how a seal can be made in groove  12  using a one piece component  40 . It can be fabricated as a helix and have a running length so that when placed in groove  12  the ends  42  and  44  abut or overlap. While the cut is shown as square the ends  42  and  44  can be cut on a slant if they are to be abutted or overlapped. As before with the multi-component design some wall material can be remove at overlapping surfaces so that a continuous trough  46  can be formed even with ends  42  and  44  that overlap.  FIG. 4  happens to show the ends abutting. Depending on the resiliency of the selected material, the split ring design of  FIG. 3  can encompass  360  degrees and can be made to form a single plane. In that case it is elastically spread to get it into groove  12  for closing with the technique described above. Alternatively the one piece can be a helix that wraps for more than 360 degrees and designed to flex over the object  10  to get into a groove  12 . Here again the cross-sectional shape can vary from an open shape such as shown in  FIG. 3  being a u-shape or a closed tubular structure in section or a solid section of a desired geometric shape that can present sharp edges for sealing to the groove  12  and the surrounding object as well as blunt ends to accomplish the same purpose. Tubular cross sections can also accommodate a filler material for structural strength or to enhance sealing performance. The material selections can vary as previously described and the filler material should be compatible with well or operating environment conditions. 
         [0035]    While the preferred application is for downhole tools allowing for a retrofit of seals without reengineering the part, the split seals whether in one piece or multiple pieces can be used in a variety of application as o-ring replacements. Some downhole applications are subsurface safety valves, seal bores, jars or fishing tools to name a few. The retrofit advantage with the ability to upgrade sealing material and still get a reliable seal without having to reconfigure the part having the seal groove is the advantage of the present invention. The split can be bonded or joined with resistance welding or micro welding techniques, or adhesives and activators such as UV, heat, or chemical bonding agents. 
         [0036]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.