Abstract:
A brush seal, comprising: a bristle arrangement with a plurality of bristles; and a joint securing the bristles together; plates flanking the bristle arrangement; and a feature on the plates to receive the joint. A brush seal, comprising: a plurality of bristles, each having a first end and an opposed second end; and plates receiving the bristles therebetween, each having a first end and a second end. The first ends of the bristles extend past the first end of the plates and the second ends of the bristles reside between the first and second ends of the plates. A method of repairing a brush seal, comprising the steps of: providing a brush seal having a bristle arrangement secured between plates; removing the bristle arrangement from the plates; providing a replacement bristle arrangement; and placing said replacement bristle arrangement between the plates.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to pending United States patent application Ser. No. 10/074,191 filed on Feb. 12, 2002, herein incorporated by reference. 
     BACKGROUND OF INVENTION 
     This invention relates to brush seals. Specifically, this invention relates to the various components that form the brush seal. 
     Brush seals are commonly used on gas turbine engines. The brush seals typically prevent secondary flow in the engine from escaping through a gap between a stationary part (e.g. a diffuser case) and a rotating part (e.g. a turbine shaft). Brush seals can have other uses, such as sealing a gap between stationary parts of the engine. 
     A brush seal typically includes packs of wire bristles sandwiched between plates. The bristle packs and plates are typically welded together to form the brush seal. The brush seal must undergo heat treatment after the welding step to relieve any residual stresses. Heat treatment typically involves securing the brush seal within a fixture, then placing the fixture in an oven. The heat treatment process is time consuming and can be expensive. 
     The welding step transforms the discrete sub-assemblies of the brush seal into one piece. The one-piece arrangement prevents the removal of a sub-assembly without affecting or damaging the remainder of the brush seal. This means a mechanic must replace the entire brush seal during maintenance. Replacement of the entire brush seal must occur despite the fact that only one of the sub-assemblies (typically the bristle packs) needs replacement. 
     The bristle packs of the brush seal are expensive. The main factor influencing cost is the amount of raw material used. Each individual bristle in the bristle pack is a taken from a length of wire. A commonly used wire is a 0.002″, 0.003″, 0.004 or 0.006″ diameter cobalt alloy wire. One type of bristle pack can have approximately 5000 bristles per linear inch. This type of bristle pack clearly contains a large amount of wire. When used in a 12″ outer diameter single stage brush seal, this type of bristle pack can contain approximately 2.6 miles of wire. 
     SUMMARY OF INVENTION 
     It is an object of the present invention to provide a new and improved brush seal. 
     It is a further object of the present invention to produce a brush seal at a reduced cost. 
     It is a further object of the present invention to produce a brush seal that uses less raw material. 
     It is a further object of the present invention to provide a brush seal that may not require heat treatment. 
     It is a further object of the present invention to provide a brush seal with an extended life. 
     It is a further object of the present invention to provide a brush seal with replaceable sub-assemblies. 
     These and other objects of the present invention are achieved in one aspect by a brush seal. The brush seal comprises: a bristle arrangement, including a plurality of bristles and a joint securing the bristles together; plates flanking the bristle arrangement; and a feature on the plates to receive the joint. 
     These and other objects of the present invention are achieved in another aspect by brush seal. The brush seals comprises: a plurality of bristles, each having a first end and an opposed second end; and plates receiving the bristles therebetween, each having a first end and a second end. The first ends of the bristles extend past said first ends of said plates and the second ends of the bristles reside between the first and second ends of the plates. 
     These and other objects of the present invention are achieved in another aspect by method of repairing a brush seal. The method comprises the steps of: providing a brush seal having a bristle arrangement secured between plates; removing the bristle arrangement from the plates; providing a replacement bristle arrangement; and placing said replacement bristle arrangement between the plates. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which: 
         FIG. 1  is a perspective view of a section of a conventional brush seal; 
         FIG. 2   a  is a cross-sectional view a brush seal of the present invention; 
         FIG. 2   b  is a perspective view of a section of the brush seal in  FIG. 2   a;    
         FIG. 3   a  is a perspective view of a section of another brush seal of the present invention; 
         FIG. 3   b  is a perspective view of an alternate arrangement of the brush seal in  FIG. 3   a;    
         FIG. 4  is a perspective view of a section of another brush seal of the present invention; 
         FIG. 5  is a perspective view of a section of another brush seal of the present invention; 
         FIG. 6  is a perspective view of a section of another brush seal of the present invention; and 
         FIG. 7  is a perspective view of a section of another brush seal of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  displays a conventional annular brush seal  100 . Although shown as a single stage, the brush seal  100  could have multiple stages. The brush seal  100  includes several sub-assemblies, namely a back plate  101  , side plate  103  and a bristle pack  105 . The metal plates  101 ,  103  flank the bristle pack  105 . 
     The bristle pack  105  comprises a plurality of densely arranged wire bristles. Each of the bristles has a first end  107  and an opposed second end  109 . While extending at an angle to a radial line, the first ends  107  of the bristles reside at the inner diameter of the brush seal  100 . The second ends  109  of the bristles reside at the outer diameter of the brush seal  100 . 
     The plates  101 , 103  and the bristle pack  105  are welded together to form the brush seal  100 . Specifically, the outer diameter of the plates  101 ,  103  and the bristle pack  105  are welded together to sandwich the bristles between the plates  101 ,  103 . 
       FIGS. 2   a  and  2   b  display one alternative embodiment of a brush seal  200  of the present invention. Similar to the conventional brush seal  100 , the brush seal  200  includes a back plate  201  and a side plate  203 . 
     Differently than the conventional brush seal  100 , the brush seal  200  uses a pre-assembled bristle assembly. In addition, the brush seal  200  has plates  201 ,  203  removably secured to each other. Each of these features will now be described in further detail. 
     The brush seal  200  includes a bristle arrangement  205 . The bristle arrangement  205  includes a plurality of bristles  207  secured together by a joint  209 . The bristles  207  could be made from the same cobalt alloy wire as the bristles in the conventional brush seal  100 . 
     Since the bristle arrangement  205  described herein is annular, one could refer to the bristle arrangement  205  as a bristle ring. The bristle arrangement  205  could, however, have other shapes. For example, the bristle arrangement  205  could have an arcuate (not shown) or a linear shape (not shown). 
     The joint  209  extends continuously along the outer diameter of the bristle arrangement  205 . Preferably, the joint  209  is a weld joint. U.S. patent application Ser. No. 10/074,191 describes in more detail the method of making the bristle arrangement  205 . 
     The present invention could use other methods to produce the joint  209 . 
     The joint  209  retains the bristles  207  in the bristle arrangement  205 . 
     Differently than the conventional brush seal  100 , the joint  209  obviates the need to weld the bristles  207  to the plates  201 ,  203 . 
     The brush seal  200  retains the bristle arrangement  205  using grooves  211 ,  213  in the inner faces  215 ,  217  of the plates  201 ,  203 . When the inner faces  215 ,  217  of the plates  201 ,  203  abut ( FIG. 2   b ), the grooves  211 ,  213  define a cavity  219  which receives the joint  209  of the bristle arrangement  205 . Although the joint  209  preferably does not interference fit within the cavity  219 , the cavity  219  should prevent radial movement of the bristle arrangement  205  during engine operation. 
     The inner faces  215 ,  217  also form a gap  221  in communication with the cavity  219 . The gap  221  is sufficiently large to allow the bristles  207  to extend past the plates  201 ,  203 . Preferably, however, the gap  221  is sufficiently small to compress the bristles  207  and to prevent movement of the bristle arrangement  205  during engine operation. 
     As an alternative, the inner faces  215 ,  217  of the plates  201 ,  203  at the gap  221  could have features thereon to improve retention of the bristle arrangement  205 . Knurls (not shown) are an example of such features. 
     The use of the bristle arrangement  205  highlights one benefit of the present invention. The brush seal  200  can use shorter bristles  207  than the conventional brush seal  100 . The conventional brush seal  100  must weld the bristles  107  to the plates  101 , 103 . Since the weld is located at the outer diameter of the brush seal  100 , the bristles  100  must extend to the outer diameter. 
     The brush seal  200  does not weld of the bristles  207  to the plates  201 ,  203 . Therefore, the bristles  207  need not extend to the outer diameter of the brush seal  200 . As seen in  FIG. 2   b , the outermost extent of the bristle arrangement  205  is at a position medial to the inner diameter and the outer diameter of the brush seal  200 . 
     The present invention can reduce the length of the bristles  207  up to approximately 20%. Using the example above, reducing the length of the bristles in a 12″ outer diameter single stage brush seal by 20% can save approximately 0.5 miles of wire. 
     Rather than welding, the brush seal  200  uses a retainer to secure the plates  201 ,  203  together. Specifically, the brush seal  200  uses a clip  223  to secure the plates  201 ,  203  together. The clip  223  can have a C-shape with extensions  225 ,  227  that engage corresponding grooves  229 ,  231  in the plates  201 ,  203 . 
     To assemble the brush seal, an operator could place the back plate  201  in a fixture (not shown). The operator would then place the joint  209  of the bristle arrangement  205  in the groove  213 . The operator would then place the side plate  203  over the bristle arrangement  205  (ensuring the joint  209  enters the groove  211 ). The operator would then tighten the fixture to sandwich bristle arrangement  205  between the plates  201 ,  203 . 
     Finally, the operator secures the retaining clip  223  to the plates  201 ,  203  with conventional techniques. For example, the operator could set one extension  225  in the corresponding groove  229 . The operator would then deflect the other extension  227  over the back plate  201 . The operator continues to move the extension  227  towards the groove  231 . Upon reaching the groove  231 , the extension  227  resiles into the groove  231 . 
     The clip  223  should have sufficient strength to keep the bristle arrangement  205  between the plates  201 ,  203 . The clip  223  could be made from any suitable material. With the clip  223  secured to the plates  201 ,  203 , the operator can now remove the brush seal  200  from the fixture. 
     The use of the clip  223  highlights another benefit of the present invention. The assembly process of the brush seal  200  can eliminate the heat treating step. Since the assembly process does not weld the plates  201 ,  203  together, the process does not build up residual stresses in the materials. As discussed above, conventional processes used the heat treating step to reduce these residual stresses. 
     The present invention can use other methods to retain the bristle ring between the plates.  FIG. 3  shows one such alternative embodiment. Similar to the brush seal  200 , the figure shows a brush seal  300  with a back plate  301 , side plate  303  and bristle arrangement  305 . The plates  301 ,  303  include grooves  311 ,  313  that combine to form a cavity  319  for receiving a joint  309  of the bristle arrangement  305 . The abutting plates  301 ,  303  also form a gap  321  for the bristles to extend past the plates  301 ,  303 . 
     Rather than using the clip  223 , the brush seal  300  uses a rivet  333  to secure the plates  301 ,  303  together. The operator can install the rivet  333  using conventional techniques. Although described as a rivet, the brush seal  300  could use any other suitable fastener such as a drive pin (not shown), or a dowel (not shown) or spring pin (not shown) inserted into the plates at an angle. 
       FIG. 3   b  shows an alternative method of assembling the brush seal  300 ′ with the rivet  333 ′. Rather than just securing the plates  301 ′,  303 ′, the rivet  333 ′ also retains an annular support flange  335 ′. The flange  335 ′ provides an alternate method of installing the brush seal  300 ′ in the engine. Even though the flange  335 ′ has been described as a separate sub-assembly from the back plate  301 ′, the back plate  301 ′ and the flange  335 ′ could also be one-piece. 
       FIG. 4  displays another alternative embodiment of the present invention. Similar to the other brush seals of the present invention, the figure displays a brush seal  400  with a back plate  401 , side plate  403  and bristle arrangement  405 . The plates  401 ,  403  include grooves  411 ,  413  that combine to form a cavity  419  for receiving a joint  409  of the bristle arrangement  405 . The abutting plates  401 ,  403  also form a gap  421  for the bristles to extend past the plates  401 ,  403 . 
     Rather than using a separate retainer, the brush seal  400  uses features on the plates  401 ,  403  to retain the plates  401 ,  403  together. Specifically, the back plate  401  includes an upper extension  437  with an angled surface  439  facing the side plate  403 . Likewise, the side plate  403  has an angled surface  441  facing the back plate  401 . 
     The annular side plate  403  has a larger diameter than the extension  437 . 
     Therefore, the operator must interference fit the side plate  403  into the back plate  401  using conventional techniques. Once assembled together (as seen in  FIG. 4 ), the angled surfaces  439 ,  441  of the plates  401 ,  403  abut each other. The orientation of the angled surfaces  439 ,  441  urges the plates  401 ,  403  together. This orientation helps the plates  401 ,  403  retain the bristle arrangement  405  therebetween. 
       FIG. 5  displays another alternative embodiment of the present invention. Similar to the other brush seals of the present invention, the figure displays a brush seal  500  with a back plate  501 , side plate  503  and bristle arrangement  505 . The plates  501 ,  503  include grooves  511 ,  513  that combine to form a cavity  519  for receiving a joint  509  of the bristle arrangement  505 . The abutting plates  501 ,  503  also form a gap  521  for the bristles to extend past the plates  501 ,  503 . 
     Differently than the other brush seals of the present invention, the brush seal  500  bonds the plates  501 ,  503  together to retain the bristle arrangement  505  therebetween. Suitable bonding techniques include, for example, radial or axial welding, brazing and using an adhesive such as epoxy. 
       FIG. 6  displays another alternative embodiment of the present invention. Similar to the other brush seals of the present invention, the figure displays a brush seal  600  with a back plate  601 , side plate  603  and bristle arrangement  605 . 
     Differently than the other brush seals of the present invention, the brush seal  600  includes a snap ring assembly  643  to retain the bristle arrangement  605  between the plates  601 ,  603 . The snap ring assembly  643  includes an annular flange  645 . The flange  645  can have an L-shape in cross-section. One section of the flange has a groove  647 . 
     The operator assembles the brush seal  600  as follows. The operator places the flange  645  in a fixture (not shown). Then operator then inserts the back plate  601  against the flange  645 . The operator then places the joint  609  of the bristle arrangement  605  in the groove  613  of the back plate  601 . The operator then places the side plate  603  over the bristle arrangement  605  (ensuring the joint  609  enters the groove  611 ). 
     Finally, the operator finally places one or more snap rings  649  in the groove  647  using conventional techniques. The snap rings  649  keep the side plate  603  against the back plate  601  to sandwich bristle arrangement  605  therebetween. 
     Although described as a snap ring, the brush seal  600  could use any other suitable retainer. Examples of suitable retainers include wave washers (not shown), retaining rings (not shown) and radially oriented dowels (not shown) or spring pins (not shown) driven through the flange  645 . 
     Even though the flange  645  has been described as a separate subassembly from the back plate  601 , the back plate  601  and the flange  645  could also be one-piece. 
       FIG. 7  displays another alternative embodiment of the present invention. Similar to the other brush seals of the present invention, the figure displays a brush seal  700  with a back plate  701 , side plate  703  and bristle arrangement  705 . 
     The brush seal  700  also includes an annular support flange  735  for installing the brush seal  700  in the engine. The flange  735  mounts to the engine using suitable fasteners (not shown). In this embodiment, threaded fasteners  751  secure the plates  701 ,  703  to the flange  735 . 
     The operator assembles the brush seal  700  as follows. The operator places the flange  735  in a fixture (not shown). Then operator then places the back plate  701  against the flange  735 . The operator then places the joint  709  of the bristle arrangement  705  in the groove  713  of the back plate  701 . The operator then places the side plate  703  over the bristle arrangement  705  (ensuring the joint  709  enters the groove  711 ). 
     Finally, the operator inserts the fasteners  751  through the aligned openings in the plates  701 ,  703  and into a threaded hole  753  in the flange  735 . The operator applies a sufficient torque to the fasteners  751  to keep the side plate  703  against the back plate  701  for sandwiching the bristle arrangement  705  therebetween. Although shown as a screw, the brush seal  700  could utilize any other suitable type of fastener. 
     Even though the flange  735  has been described as a separate subassembly from the back plate  701 , the back plate  701  and the flange  735  could also be one-piece. A similar stand-alone design (not shown), incorporating only the plates  701 ,  703  and not the flange  735 , could also be produced. This design would require the back plate  701  to have sufficient thickness for placing a threaded hole therein to receive the fastener. 
     The brush seal  700  highlights another benefit of the present invention. The present invention allows a mechanic to replace the bristle arrangement  705  without replacing the other sub-assemblies of the brush seal  700 . Such replacement can occur after use of the brush seal  700  in the engine, or even before actual use. 
     The mechanic replaces the bristle arrangement  705  as follows. The mechanic removes the fasteners  751  to detach the plates  701 ,  703  from the flange  735 . The flange  735  preferably remains in the engine, while the plates  701 ,  703  and the bristle arrangement  705  are removed. Separated from the flange  735 , the plates  701 ,  703  no longer sandwich the bristle arrangement  705 . The mechanic can now remove the bristle arrangement  705  from the grooves  711 ,  713  of the plates  701 ,  703 . If necessary, the mechanic could have first removed the entire brush seal  700  from the engine by detaching the flange  735  from the engine, then performed the above steps. 
     As an alternative to removing the fasteners  751  entirely from the flange  735 , the mechanic could merely loosen the fasteners  751  (i.e. keeping the fasteners  751  in the threaded hole  753 ) sufficiently to remove the bristle arrangement  705  from the grooves  711 ,  713  of the plates  701 ,  703 . 
     After removing the bristle arrangement  705 , the mechanic then obtains a replacement bristle arrangement  705 . As a final step, the mechanic reassembles the brush seal  700  using the aforementioned assembly process. 
     The present invention has been described in connection with the preferred embodiments of the various figures. It is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.