Abstract:
A brush seal assembly includes a plurality of bristles, a joint securing the bristles, and a retaining assembly. Each of the bristles has a first end and a second end. The joint has a first side and a second side and connects the first ends of the bristles. The retaining assembly sandwiches the joint and includes a side plate, a back plate, and a threaded connection. The side plate engages the first side of the joint and the back plate engages the second side of the joint. The threaded connection holds the side plate and the back plate in engagement with the joint.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to brush seals. In particular, the present invention relates to a brush seal assembly utilizing threaded members. 
         [0002]    Brush seals are commonly used in gas turbine engines and other assemblies to restrict the escape of fluid (i.e. air) through a gap between a stationary part and a rotating part. For example, the stationary part may be a diffuser case and the rotating part may be a turbine shaft. Brush seals may also be used to seal gaps between two stationary parts or two rotating parts of a gas turbine engine. In either case, minimization of leakage is important in maintaining the efficiency of the system and to reduce fuel consumption. 
         [0003]    A brush seal generally includes packs of wire bristles that are sandwiched between two plates. It is common practice to weld the bristles and plates together. The brush seal must then undergo heat treatment after welding to relieve any residual stresses. Heat treatment typically involves securing the brush seal within a fixture and placing the fixture in an oven. The heat treatment is a time consuming and expensive process. 
         [0004]    While effective, the bristles of the brush seal eventually wear and need to be replaced over time. For example, replacement may be scheduled after a given number of hours or cycles of operation. However, because conventional brush seals are welded assemblies, removal of the brush seal can be difficult. In addition, because the individual components of the brush seal are welded together, individual components such as wire bristles cannot easily be replaced. Thus, replacement of the entire brush seal must occur at significant costs in regards to material labor and down time, even though only one of the subassemblies needs replacement. 
         [0005]    A current method used that allows replacement of individual components of the brush seal is to manufacture the brush seals in subassemblies without plate welding. These brush seals combine the bristles together and sandwich the bristle packs between the plates using clips or fasteners. While these methods are effective, they also require additional machining under relatively close tolerances, thus increasing the overall cost of production. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    A brush seal assembly includes a plurality of bristles, a joint, and a retaining assembly. Each of the bristles has a first end and a second end. The joint has a first side and a second side and connects the first ends of the bristles. The retaining assembly sandwiches the joint and includes a side plate, a back plate, and a threaded connection. The side plate engages the first side of the joint and the back plate engages the second side of the joint. The threaded connection holds the side plate and the back plate in engagement with the joint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective, partial cross-sectional view of a representative brush seal assembly. 
           [0008]      FIG. 2  is a cross-sectional view of a first embodiment of a brush seal assembly. 
           [0009]      FIG. 3  is an exploded side view of the first embodiment of the brush seal assembly. 
           [0010]      FIG. 4A  is a partially exploded side view of the first embodiment of the brush seal assembly having a first bristle assembly. 
           [0011]      FIG. 4B  is a partially exploded side view of the first embodiment of the brush seal assembly having axial slots. 
           [0012]      FIG. 4C  is a partially exploded side view of the first embodiment of the brush seal assembly having a second bristle assembly. 
           [0013]      FIG. 5  is a diagram of a method of assembling the first embodiment of the brush seal assembly. 
           [0014]      FIG. 6  is a cross-sectional view of a second embodiment of a brush seal assembly. 
           [0015]      FIG. 7  is a diagram of a method of assembling the second embodiment of the brush seal assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows a perspective, cross-sectional view of a representative brush seal assembly  10 . Brush seal assembly  10  generally includes bristle assembly  12 , side plate  14 , and back plate  16 . Adjustable pin spanners  18   a  and  18   b  (shown in  FIG. 3 ) tighten side plate  14  to back plate  16 , sandwiching bristle assembly  12  therebetween. Bristle assembly  12  has a first side  19  and a second side  20  and is formed of a plurality of densely arranged wire bristles  21 . Although bristle assembly  12  is depicted in  FIG. 1  as having a full ring shape, bristle assembly  12  may have other shapes without departing from the intended scope of the present invention. For example, bristle assembly  12  may have an arcuate, segmented arcuate or linear shape. 
         [0017]    Each of wire bristles  21  has a first end  22  and a second end  24 . First ends  22  of wire bristles  21  reside at an outer diameter of bristle assembly  12  and are secured together by joint  25 , such as a weld, and are generally connected to joint  25  such that wire bristles  21  are angled to a radial line. Joint  25  has a first side  26  in line with first side  19  of bristle assembly  12  and a second side  27  in line with second side  20  of bristle assembly  12 . Second ends  24  of wire bristles  21  extend away from joint  25  and reside at an inner diameter of bristle assembly  12 . Wire bristles  21  are made of a strong, flexible material. For example, wire bristles  21  may be made of an approximately 0.002 inch diameter to an approximately 0.006 inch diameter cobalt alloy wire. In an exemplary embodiment, first ends of wire bristles  20  are connected to joint  25  such that they are angled at approximately 45 degrees from a radial line. 
         [0018]      FIGS. 2 and 3  show a cross-sectional view and an exploded view, respectively, of a first embodiment of brush seal assembly  10   a , and will be discussed in conjunction with one another. Bristle assembly  12  is positioned between side plate  14  and back plate  16 , all of which are removably connected to one another. Pin spanners  18   a  and  18   b  are used to assemble side plate  14  and back plate  16  together. Side plate  14  provides a front cover to protect bristle assembly  12  and includes first surface  28 , second surface  30 , inner diameter  32 , outer diameter  34 , recess  36 , first spanner hole  38   a , and second spanner hole  38   b  ( FIG. 3 ). Outer diameter  34  of side plate  14  includes outer threads  40 . Recess  36  is located within second surface  30  of side plate  14  and is sized to accept first side  26  of joint  25  of bristle assembly  12 . When brush seal assembly  10  is assembled, first side  20  of bristle assembly  12  is positioned immediately adjacent second surface  30  of side plate  14 . A windage cover  42  (shown in  FIG. 2 ) may also be integral to side plate  14  at inner diameter  32  of side plate  14 . Although side plate  14  is discussed as having two spanner holes  38   a  and  38   b , side plate  14  may have any number of spanner holes around the circumference of side plate  14 . In addition, although outer diameter  34  is discussed as including threads  40 , any locking feature known in the art may be used. 
         [0019]    Back plate  16  is the primary structural element of brush seal assembly  10   a  and provides downstream support to brush seal assembly  10   a  by supporting bristle assembly  12  and preventing bristle blowover due to fluid pressure differential. Back plate  16  includes first surface  44 , second surface  46 , inner diameter  48 , outer diameter  50 , back cover  52 , first spanner hole  54   a , second spanner hole  54   b , first axial slot  56   a , and second axial slot  56   b . Inner diameter  48  of back plate  16  includes inner threads  58  that are engagable with outer threads  40  of side plate  14 . Stress calculations may be performed on threads  40  and  58  of side plate  14  and back plate  16 , respectively, to determine the optimum thread size and pitch relative to the size of brush seal assembly  10   a  and the resistive and compressive axial spring rate of bristle assembly  12 . Spanner holes  54   a  and  54   b  are formed in back cover  52 , which extends across second surface  46  of back plate  16 . Back cover  52  also has a hole  59  in the center of back cover  52  to position a component, such as a shaft or rotor, with clearance. Although back plate  16  is discussed as having two spanner holes  54   a  and  54   b  and two axial slots  56   a  and  56   b , back plate  16  may have any number of spanner holes and axial slots around the circumference of back plate  16 . Also, as with side plate  14 , although inner diameter  48  is discussed as including threads  58 , any locking feature known in the art may be used. 
         [0020]    Bristle assembly  12 , side plate  14 , and back plate  16  are assembled together with the use of adjustable pin spanner tools  18   a  and  18   b . Adjustable pin spanners  18   a  and  18   b  allow the same tool to be used on brush seal assemblies having a range of diameters. First adjustable pin spanner  18   a  generally includes spanner arm  60   a , adjustment slot  62   a , fixed pin  64   a , movable pin  66   a , and threaded fastener  68   a . Second adjustable pin spanner  18   b  functions and interacts similarly to first adjustable pin spanner  18   a  and generally includes spanner arm  60   b , adjustment slot  62   b , fixed pin  64   b , movable pin  66   b , and threaded fastener  68   b . Adjustable pin spanners  18   a  and  18   b  may optionally include a torque measuring device to assure uniform assembly torques. 
         [0021]    To assemble brush seal assembly  10   a , joint  25  and bristle assembly  12  are positioned against second surface  30  of side plate  14  with first side  26  of joint  25  engaging recess  36  (shown in  FIG. 2 ) of side plate  14 . As can be seen in  FIG. 3 , outer threads  40  of side plate  14  are engageable with inner threads  58  of back plate  16 , allowing side plate  14  and bristle assembly  12  to fit within inner diameter  48  of back plate  16 . Once in place, threads  40  of side plate  14  are threaded into threads  58  of back plate  16  (shown in  FIGS. 2 and 3 ). Side plate  14  and bristle assembly  12  are threaded within inner diameter  48  of back plate  16  until second side  27  of joint  25  and second side  21  of bristle assembly  12  abuts back cover  52  of back plate  16 . Second ends  24  of wire bristles  21  extend past inner diameters  32  and  48  of both side plate  14  and back plate  16 , respectively, allowing bristle assembly  12  to reach a component, such as a rotor, to form a seal. 
         [0022]    Although not shown in  FIGS. 2 and 3 , brush seal assembly  10   a  may optionally include a washer positioned between second surface  30  of side plate  14  and first side  19  of bristle assembly  12 , as well as positioned between second side  20  of bristle assembly  12  and first surface  44  of back plate  16 . The washers would function to protect wire bristles  21  as side plate  14  and back plate  16  spin against bristle assembly  12  during assembly. 
         [0023]      FIGS. 4A-4C  show how first and second adjustable pin spanners  18   a  and  18   b  are adjustable to work with different size brush seal assemblies and different spanner slot configurations.  FIG. 4A  shows adjustable pin spanners  18   a  and  18   b  in use with spanner slots  38   a ,  38   b ,  54   a , and  54   b  of brush seal assembly  10   a .  FIG. 4B  shows adjustable pin spanners  18   a  and  18   b  in use with spanner slots  38   a  and  38  and axial slots  56   a  and  56   b  of brush seal assembly  10   b .  FIG. 4C  shows adjustable pin spanners  18   a  and  18   b  in use with brush seal assembly  10   c  having a smaller diameter than brush seal assemblies  10   a  and  10   b.    
         [0024]      FIG. 4A  shows a side view of brush seal assembly  10   a . After side plate  14  and bristle assembly  12  are positioned within back plate  16 , first adjustable pin spanner  18   a  is positioned immediately adjacent first surface  28  of side plate  14 . Fixed pin  64   a  of first adjustable pin spanner  18   a  is aligned with, and engages, first spanner hole  38   a  of side plate  14 . Movable pin  66   a  is then adjusted within adjustment slot  62   a  until aligned with second spanner hole  38   b  of side plate  14 . Movable pin  66   a  is then positioned within second spanner hole  38   b  and is maintained in place within adjustment slot  62   a  by threaded fastener  68   a . Similarly, spanner arm  60   b  of adjustable pin spanner  18   b  is positioned immediately adjacent second surface  46  of back plate  16  and engages back plate  16  in the same manner that first adjustable pin spanner  18   a  engages side plate  14 . 
         [0025]    In this position, adjustable pin spanners  18   a  and  18   b  sandwich bristle assembly  12  between side plate  14  and back plate  16 , which form brush seal assembly  10   a . After first and second adjustable pin spanners  18   a  and  18   b  are connected to side plate  14  and back plate  16 , respectively, adjustable pin spanners  18   a  and  18   b  are turned in opposing directions (as shown by arrows in  FIG. 4A ) to tighten side plate  14 , bristle assembly  12 , and back plate  16  together. As adjustable pin spanners  18   a  and  18   b  turn in opposing directions, side plate  14  is turned in the same direction as first adjustable pin spanner  18   a  and back plate  16  is turned in the same direction as second adjustable pin spanner  18   b . Because side plate  14  and back plate  16  are turning in opposing directions, side plate  14  and back plate  16  are further threaded together by outer threads  40  of side plate  14  engaging inner threads  58  of back plate  16 . After brush seal assembly  10   a  is threaded together, adjustable pin spanners  18   a  and  18   b  may be removed from side plate  14  and back plate  16 . 
         [0026]    As previously mentioned, side plate  14  and back plate  16  may each have more than two spanner holes. The additional spanner holes provide leverage for a user turning adjustable pin spanners  18   a  and  18   b  and may help facilitate threading of side plate  14  and back plate  16  if clearance is limited. Depending on the position of the spanner holes relative to the assembler, it may be advantageous for the assembler to remove pins  64   a ,  64   b ,  66   a , and  66   b  of adjustable pin spanners  18   a  and  18   b  from the original spanner holes and place them in different spanner holes to find the best leverage for threading side plate  14  and back plate  16  together. Thus, the assembler is able to place adjustable pin spanners  18   a  and  18   b  at different locations around the circumferences of side plate  14  and back plate  16  as necessary to obtain optimal handling of brush seal assembly  10   a.    
         [0027]      FIG. 4B  shows a side view of brush seal assembly  10   b  which generally includes a back plate  70 , bristle assembly  12 , and side plate  14 . While first adjustable pin spanner  18   a  interacts with side plate  14  in the manner described for brush seal assembly  10   a , fixed pin  64   b  and movable pin  66   b  of second adjustable pin spanner  18   b  engage axial slots  56   a  and  56   b  of back plate  70 . Once fixed pin  64   b  is positioned within first axial slot  56   a , movable pin  66   b  is adjusted within adjustment slot  62   b  and aligned with second axial slot  56   b . Once fixed pin  64   b  and movable pin  66   b  are properly positioned within axial slots  56   a  and  56   b , respectively, brush seal assembly  10   b  is tightened in a similar manner as brush seal assembly  10   a . Axial slots  56   a  and  56   b  may be used to tighten brush seal assembly  10   b  if back cover  52  of back plate  70  does not include spanner holes  54   a  and  54   b , if back plate  70  optionally does not include a back cover, or if it is more convenient to use axial slots  56   a  and  56   b.    
         [0028]    Similar to brush seal assembly  10   a , side plate  14  may have more than two spanner holes and back plate  16  may have more than two axial slots. The additional spanner holes and axial slots function in the same manner as the additional spanner holes in brush seal assembly  10   a , providing leverage for a user turning adjustable pin spanners  18   a  and  18   b.    
         [0029]      FIG. 4C  shows a side view of brush seal assembly  10   c  having side plate  72 , bristle assembly  74 , and back plate  76 . The components of brush seal assembly  10   c  interact and function similarly to the components of brush seal assembly  10   a  described in the discussion of  FIG. 4A , except that the outer diameters of side plate  72 , bristle assembly  74 , and back plate  76  are smaller than the outer diameters of side plate  14 , bristle assembly  12 , and back plate  16  (shown in  FIG. 4A ). Because the diameters of brush seal assembly  10   c  are smaller than the diameters brush seal assembly  10   a , movable pins  66   a  and  66   b  of first and second adjustable pin spanners  18   a  and  18   b  must be accordingly adjusted. Movable pins  66   a  and  66   b  are adjusted within adjustment slots  62   a  and  62   b , respectively, until first movable pin  66   a  is engagable with second spanner hole  38   b  of side plate  72  and second movable pin  66   b  is engagable with second spanner hole  54   b  of back plate  76 . After fixed pins  64   a  and  64   b  and movable pins  66   a  and  66   b  are positioned within side plate  72  and back plate  76 , brush seal assembly  10   c  is tightened by first and second adjustable pin spanners  18   a  and  18   b  in the same manner as side brush seal assembly  10   a . Although  FIG. 4C  depicts a brush seal assembly having a smaller diameter than brush seal assembly  10   a , brush seal assemblies of any diameter may be joined together using adjustable pin spanners  18   a  and  18   b , including a brush seal assembly having a larger diameter than brush seal assembly  10   c.    
         [0030]      FIG. 5  shows a diagram of a method of assembling brush seal assembly  10 . Bristle assembly  12  is first positioned in recess  36  of side plate  14 , Box  78 . Threads  40  of side plate  14  are then engaged with mating threads  58  of back plate  16 , Box  80 . As depicted in Box  82 , as side plate  14  and back plate  16  are threaded together, first surface  44  of back plate  16  is positioned immediately adjacent bristle assembly  12  such that bristle assembly  12  is sandwiched between side plate  14  and back plate  16 . Fixed pins  64   a  and  64   b  are positioned within first spanner hole  38   a  of side plate  14  and first spanner hole  54   a  of back plate  16 , respectively, Box  84 . As optionally shown in Box  86  (optional), movable pins  66   a  and  66   b  are then adjusted within adjustment slots  62   a  and  62   b  until they are positioned to engage second spanner holes  38   b  and  54   b  of side plate  14  and back plate  16 , respectively. Note that movable pins  66   a  and  66   b  need only be adjusted for different sized seals. Adjustable pin spanners  18   a  and  18   b  are then turned in opposing directions to tighten side plate  14 , bristle assembly  12 , and back plate  16  together, Box  88 . After brush seal assembly  10  is threaded together, adjustable pin spanners  18   a  and  18   b  may be disengaged from side plate  14  and back plate  16 , Box  90 . 
         [0031]      FIG. 6  shows a cross-sectional view of brush seal assembly  100  which generally includes bristle assembly  12 , side plate  14 , back plate  102 , and retaining ring  104 . Brush seal assembly  100  functions similarly to brush seal assembly  10   a  except that brush seal assembly  100  includes retaining ring  104  and outer diameter  106  of back plate  102  includes outer threads  108 . Retaining ring  104  is also threaded and connects side plate  14  and back plate  102  together. Retaining ring  104  has first surface  110 , second surface  112 , inner diameter  114 , outer diameter  116 , first axial slot  118   a , and second axial slot  118   b  (not shown in  FIG. 6 , second axial slot  118   b  is positioned similarly to second axial slot  56   b  of brush seal assembly  10   a  shown in  FIG. 3 ). Inner diameter  114  of retaining ring  104  includes inner threads  120  for engaging outer threads  40  of side plate  14  and outer threads  108  of back plate  102 . After joint  25  is positioned within recess  36  of side plate  14 , first surface  44  of back plate  102  is positioned immediately adjacent bristle assembly  12 . Outer threads  40  of side plate  14  and outer threads  58  of back plate  102  are then threaded to inner threads  120  of retaining ring  104 , creating brush seal assembly  100 . 
         [0032]    First adjustable pin spanner  18   a  is then positioned against first surface  28  of side plate  14  and second adjustable pin spanner  18   b  is positioned against second surface  46  of back plate  102 . Fixed pins  64   a  and  64   b  are positioned within first spanner holes  38   a  and  54   a  of side plate  14  and back plate  102 , respectively. Movable pins  66   a  and  66   b  are then optionally adjusted within adjustment slots  62   a  and  62   b  until they are positioned to engage second spanner holes  38   b  and  54   b  of side plate  14  and back plate  102 , respectively. Once fixed pins  64   a  and  64   b  and movable pins  66   a  and  66   b  are engaging spanner holes  38   a ,  38   b ,  54   a ,  54   b  of side plate  14  and back plate  102 , adjustable pin spanners  18   a  and  18   b  are turned in the same direction to tighten side plate  14  and back plate  102  to retaining ring  104 . As adjustable pin spanners  18   a  and  18   b  turn side plate  14  and back plate  102 , retaining ring  104  is held stationary by axial slots  118   a  and  118   b . As side plate  14  and back plate  102  are turned within retaining ring  104 , outer threads  40  of side plate  14  and outer threads  108  of back plate  102  are threaded to threads  120  of retaining ring  104 . Although retaining ring  104  is discussed as being held stationary by axial slots  118   a  and  118   b , retaining ring  104  may be held stationary by any means known in the art, including, but not limited to: some other feature on outer diameter  116  of retaining ring  104 , by a fixture, or by a vise. 
         [0033]      FIG. 7  shows a diagram of a method of assembling brush seal assembly  100 . Bristle assembly  12  is first positioned in recess  36  of side plate  14 , Box  122 . As depicted in Box  124 , first surface  44  of back plate  102  is then positioned adjacent bristle assembly  12  such that bristle assembly  12  is sandwiched between side plate  14  and back plate  102 . Outer threads  40  of side plate  14  and outer threads  108  of back plate  102  are then engaged with mating threads  120  of retaining ring  104  to thread side plate  14 , bristle assembly  12 , and back plate  102  within retaining ring  104 , Box  126 . Fixed pins  66   a  and  66   b  are positioned within first spanner holes  38   a  and  54   a  of side plate  14  and back plate  102 , respectively, Box  128 . As shown in optional Box  130 , movable pins  68   a  and  68   b  are then optionally adjusted within adjustment slots  62   a  and  62   b  until they are aligned to engage second spanner holes  38   b  and  54   b  of side plate  14  and back plate  102 , respectively. Adjustable pin spanners  18   a  and  18   b  are then turned while retaining ring  104  is maintained in position, tightening side plate  14  and back plate  102  within retaining ring, Box  132 . Once brush seal assembly  100  is threaded together, adjustable pin spanners  18   a  and  18   b  may be removed from side plate  14  and back plate  102 , Box  134 . 
         [0034]    The brush seal assembly of the present invention provides a convenient, inexpensive, no-weld method of sandwiching a bristle assembly between a side plate and a back plate to form the brush seal assembly. By eliminating the welding step and subsequent stress-relieving heat treatment of the full brush seal assembly, the manufacturing time and cost of the brush seal assembly is significantly reduced. The brush seal assembly uses threading and adjustable pin spanners to easily assemble and disassemble the brush seal assembly. In addition, the simple disassembly and reassembly of the brush seal assembly also allows for easy replacement of individual components. For example, the bristle assembly may be easily replaced with various wire materials and wire diameters. Similarly, the side plate and back plate may also be replaced with various materials and machined critical inner diameters. Lastly, various brush seal assembly combinations may be used that cannot be joined through conventional welding processes. The materials may include, but are not limited to: non-compatible metals, plastic-metal combinations, or high temperature carbon-based materials. The brush seal assembly may be used in any application where a seal is desired, including, but not limited to, a gas turbine engine. 
         [0035]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.