Patent Publication Number: US-8992180-B2

Title: Replaceable staking insert assembly and method

Description:
TECHNICAL FIELD 
     The present application relates generally to a replaceable staking insert assembly for the retention of a wheel attachment, and more particularly relates to a replaceable staking insert assembly for a blade mounted on a compressor rotor. 
     BACKGROUND OF THE INVENTION 
     Gas turbine systems generally include a compressor rotor having a number of stages. Air flowing into the compressor is compressed at each stage. Each stage includes a number of rotor buckets or blades mounted to a rim of a rotor wheel or a disk in a spaced relationship. A typical compressor rotor may have dozens of rotor blades mounted thereon. 
     Generally described, each blade may have a dovetailed portion that interlocks with a dovetail region of the rim to secure the blade to the rotor. The blade dovetails may be secured to the rotor via a process called “staking” Specifically, the rotor blade is placed within the rim slot and then “staked” into place at both ends by deforming the metal material around the blade dovetail with a tool similar to a nail punch. This process is then repeated for each rotor blade for each rotor assembly stage. Staking provides an economical and mechanically secured means of securing a blade or other attachment to the rotor or other type of wheel slot. 
     In an inspection or an overhaul process, the rotor blades may be removed from the rotor wheel and the original “stakes” may be ground out. There are a finite number of attachments due to a limited number of viable staking locations about the rotor wheel. As such, the rotor wheel generally must be replaced once these staking locations have been consumed even if the rotor wheel is otherwise still in operation. 
     There is a desire, therefore, for improved methods and devices for securing a blade or other type of wheel attachment to a rotor or other type of wheel without destroying the rotor or wheel or limiting its part life. These improved methods and devices should provide for simple but secure attachment of the blade or other component to the wheel in a fast and efficient manner. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present application describes a rotor assembly. Embodiments of the rotor assembly may include a rotor, at least one axial slot positioned about a rim of the rotor having a first staking recess positioned therein, a blade positioned within each axial slot having a second staking recess positioned therein, a staking insert having a base portion and a projection extending therefrom with the base portion being disposed within the first staking recess and the projection being disposed within the second staking recess, and a shim positioned within the first staking recess and adjacent to the base portion, opposite the projection, of the staking insert. 
     The application further describes a gas turbine having a rotor assembly disposed therein. Embodiments of the rotor assembly may include a rotor, at least one axial slot positioned about a rim of the rotor having a first staking recess positioned therein, a blade positioned within each axial slot having a second staking recess positioned therein, a staking insert having a base portion and a projection extending therefrom with the base portion being disposed within the first staking recess and the projection being disposed within the second staking recess, and a shim positioned within the first staking recess and adjacent to the base portion, opposite the projection, of the staking insert. 
     The application still further describes a method for staking a blade in a rotor assembly. Embodiments of the method may include providing a rotor having at least one axial slot positioned about a rim of the rotor having a first staking recess positioned therein, providing a blade having a second staking recess positioned therein, inserting a staking insert having a base portion and a projection therefrom into the first staking recess, thereafter positioning the blade within the axial slot of the rotor, inserting a shim into the first staking recess such that the projection of the staking insert is positioned within the second staking recess of the blade and the shim is adjacent to the base portion, opposite the projection, of the staking insert, and deforming the staking insert such that the shim is retained within the first staking recess. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a rotor blade according to an embodiment of the invention. 
         FIG. 1B  is a perspective view of an embodiment of a rotor for receiving the rotor blade of  FIG. 1A . 
         FIG. 1C  is a perspective view of an embodiment of a staking insert. 
         FIG. 2  is a perspective view of a staking insert being positioned within the rotor illustrated in  FIG. 1B . 
         FIG. 3  is a perspective view of an embodiment of a rotor blade assembly including the rotor blade of  FIG. 1A  and staking insert of  FIG. 2  positioned within the rotor of  FIG. 1B . 
         FIG. 4  is a perspective view of a shim being positioned within the rotor assembly of  FIG. 3 . 
         FIG. 5  is a perspective view of the completed rotor assembly of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which several embodiments of the application are shown. Like numbers refer to like elements throughout the drawings. 
     In one aspect, a rotor assembly is provided.  FIGS. 1A and 1B  show a rotor blade  102  and a rotor  104 , respectively, which are components of a rotor assembly. The rotor  104  may include at least one axial slot  106  positioned about the rim of the rotor  104 . The axial slot  106  may be any shape known in the art. In certain embodiments, the axial slot  106  has a dovetail-like shape. The axial slot  106  may include a first staking recess  114  positioned therein. In some embodiments, the first staking recess includes a base and at least one sidewall. In one embodiment, the first staking recess  114  is positioned at one end of the axial slot  106  and has a base  116  and a concave sidewall  118  that defines an axial opening  120 . However, other shapes of the first staking recess also are envisioned. For example, the first staking recess may have a trapezoidal, circular, triangular, T-shaped, or rectangular cross-section, or a combination thereof. The first staking recess may be conical or tapered. Those skilled in the art should appreciate that the shape and dimensions of the first staking recess may vary with the geometry of the axial slot and the rotor assembly as a whole. 
     In some embodiments, the blade  102  includes a root  108  with an airfoil  110  extending therefrom. The root  108  may have a substantial dovetail-like shape that conforms to the dovetail-like shape of the axial slot  106 . Additionally, the rotor blade  102  may include a second staking recess  122  positioned therein. In certain embodiments, the second staking recess  122  is positioned on the base  112  of the root  108  of the blade  102 . In some embodiments, the second staking recess includes a base and at least one sidewall. In one embodiment, the second staking recess  122  is positioned near one end of the root  108  and has a base  124  and a cylindrical sidewall  126 . However, other shapes of the second staking recess also are envisioned. For example, the second staking recess may have a trapezoidal, circular, truncated triangular, T-shaped, or rectangular cross-section, or a combination thereof. The second staking recess may be conical or tapered. Those skilled in the art will appreciate, however, that the shape and dimensions of the second staking recess may vary with the geometry of the blade and the rotor assembly as a whole. 
       FIG. 1C  shows a staking insert  130 . The staking insert  130  may include a base portion  132  and a projection  134  extending therefrom. In certain embodiments, the base portion  132  of the staking insert  130  has a convex sidewall  136  extending from a flat sidewall  138 . Other shapes of the base portion are also envisioned. For example, the base portion may be cylindrical, cubic, conical, T-shaped, or a combination thereof. The base portion may also be tapered. In certain embodiments, the projection  134  is cylindrical in shape. Other shapes of the projection are also envisioned. For example, the projection may be conical, cubic, T-shaped, rectangular, tapered, or a combination thereof. 
     In certain embodiments, one or more surfaces of the staking insert may be textured. For example, the projection  134  may be ribbed, as shown in  FIGS. 1C ,  2 , and  3 . In some embodiments, one or more sidewalls of the second staking recess are textured in a complementary pattern to the projection of the staking insert. In some embodiments, one or more sidewalls of the first staking recess are textured in a complementary pattern to the base portion of the staking insert. 
     As illustrated in  FIG. 1C , The base portion  132  of the staking insert  130  may have a thickness  133  (the “base thickness”) between 5 mm and 200 mm or, more specifically, between 5 mm and 75 mm or, even more specifically, between 5 mm and 35 mm. The projection  134  of the staking insert  130  may have a thickness  135  (the “projection thickness”) between 5 mm and 200 mm or, more specifically, between 5 mm and 75 mm or, even more specifically, between 5 mm and 35 mm. In certain embodiments, the base thickness  133  and the projection thickness  135  are substantially equal. For example, the base thickness and the projection thickness may both be about 15 mm, giving the staking insert an overall thickness of about 30 mm. 
       FIG. 2  shows a staking insert  130  being positioned within the axial slot  106  of the rotor  104  illustrated in  FIG. 1B . In certain embodiments, the first staking recess  114  is sized and shaped to receive the base portion  132  of the staking insert  130 . For example, the first staking recess  114  may have a complementary shape to the base portion  132  of the staking insert  130 . Where the base portion  132  of the staking insert  130  has a flat sidewall  138  with a convex sidewall  136  extending therefrom, the flat sidewall  138  may be positioned in the axial opening  120  of the first staking recess  114 . In some embodiments, the first staking recess has a depth (the “first depth”) that is at least about the sum of the base thickness and the projection thickness of the staking insert. For example, where both the base and projection thickness are about 15 mm each, the first depth may be at least about 30 mm. In certain embodiments, the first depth of the first staking recess is between 10 mm and 400 mm or, more specifically, between 10 mm and 250 mm or, even more specifically, between 10 mm and 100 mm. 
     The first staking recess  114  may function to retain the base portion  132  of the staking insert  130  within the rotor  104 . In certain embodiments, the first staking recess  114  axially secures the staking insert  130  therein during operation. As used herein, the term “axially” refers to a direction of movement parallel to the length of the axial slot. 
     In certain embodiments, the second staking recess is sized and shaped to receive the projection of the staking insert. The second staking recess may have a complementary shape to the projection of the staking insert. For example, where the projection of the staking insert has a substantially cylindrical shape, the second staking recess may comprise a substantially cylindrical shape with a larger diameter than that of the projection. In some embodiments, the second staking recess has a depth (the “second depth”) that is substantially equal to the projection thickness of the staking insert. For example, where the projection thickness is about 15 mm, the second depth may be about 15 mm. 
     The projection of the staking insert  130  functions to secure the blade  102  within the axial slot  106  in both the forward and aft directions during operation. As used herein, the terms “forward direction” and “aft direction” refer to directions of movement parallel to the length of the axial slot. 
       FIG. 3  shows a staking insert  130  positioned within the first staking recess  114  of the axial slot  106  of the rotor  104  illustrated in  FIGS. 1 and 2 . The root  108  of the blade  102  is positioned within the axial slot  106  of the rotor  104  such that the base of the root  108  of the blade  102  faces the first staking recess  114 . In certain embodiments, the second staking recess disposed on the base of the root  108  of the rotor blade  102  faces the first staking recess  114 . The blade  102  may function to retain the staking insert  130  within the rotor  104 . In certain embodiments, the blade  102  radially secures the staking insert  130  within the first staking recess  114  during operation. As used herein, the term “radially” refers to a direction of movement in a plane transverse to a plane containing the axial slot. 
       FIG. 4  shows a shim  140  positioned to be inserted into the first staking recess  114  in which the base portion  132  of the staking insert  130  is already disposed. The root  108  of the rotor blade  102  is disposed in the axial slot  106  such that the projection of the staking insert  130  is disposed within the second staking recess of the blade  102 . 
     In one embodiment, the shim has a thickness (the “shim thickness”) that is at least substantially equal to the second depth of the second staking recess of the blade. For example, where the second depth is about 15 mm, the shim thickness may also be about 15 mm. In certain embodiments, the shim thickness is between 5 mm and 200 mm or, more specifically, between 5 mm and 75 mm or, even more specifically, between 5 mm and 35 mm. The shim  240  may function to secure the staking insert within the first and second staking recesses during operation. 
       FIG. 5  shows the completed rotor assembly  200  of  FIG. 4  in which the shim  240  is positioned within the first staking recess  214 , adjacent to the base portion  232 , and opposite the projection, of the staking insert  230 . 
     In certain embodiments, the staking insert  230  is deformed to retain the shim  240  within the first staking recess  214 , as shown in  FIG. 5 . For example, the staking insert may be deformed mechanically with a nail punch or similar tool. 
     The staking insert and shim may be constructed from such materials as are known in the art and are suitable for use in turbines and turbine-like conditions. For example, the staking insert and shim may be constructed from a metal alloy such as steel alloy, nickel alloy, or another heat and corrosion resistant material. 
     In another aspect, a gas turbine is provided having the rotor assembly disposed therein. The rotor assembly may include at least one axial slot positioned about the rim of a rotor and a blade positioned within each axial slot. Each axial slot may have a first staking recess and each blade may have a second staking recess. A staking insert having a base portion and a projection may be positioned within each axial slot, the base portion being disposed in the first staking recess and the projection being disposed within the second staking recess. A shim may be positioned within each first staking recess, adjacent to the base portion, and opposite the projection, of the staking insert. Each staking insert may be deformed to retain the shim within the first staking recess. For example, a gas turbine may include a plurality of axial slots positioned about a rotor with a plurality of blades secured by a plurality of staking inserts and shims therein. 
     In a third aspect, a method for staking a blade in a rotor assembly is provided. The method includes (i) providing a rotor having at least one axial slot positioned about a rim of the rotor with each axial slot including a first staking recess positioned therein, (ii) providing a blade having a second recess positioned therein, (iii) inserting a staking insert having a base portion and a projection therefrom into the first staking recess, (iv) positioning the blade within the axial slot, (v) inserting a shim into the first staking recess such that the projection of the staking insert is positioned within the second staking recess of the blade and the shim is adjacent to the base portion, and opposite the projection, of the staking insert, and (vi) deforming the staking insert such that the shim is retained within the first staking recess. 
     In certain embodiments, the method for staking a blade in a rotor assembly also includes a step of removing an existing staking insert prior to the step of inserting the staking insert into the first staking recess. The step of removing the existing staking insert may include (a) removing an existing shim from the first staking recess, (b) removing the blade from the axial slot of the rotor, and (c) removing the existing staking insert from the first and second staking recesses. For example, removing the existing staking insert may include grinding down the deformed portion of the staking insert and pulling out the shim with a suitable tool, such as needle-nose pliers. 
     Although the use of embodiments of the rotor assembly has been described herein with the use of a rotor, the present invention also may be applicable to any other type of rotating assembly or turbomachine. For example, other potential applications include rotating buckets of gas turbines, rotating buckets/blades of steam turbines, or the retention of any device that is mechanically attached to a rotating wheel or disk with an axial slot or dovetail arrangement. 
     It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and equivalents thereof.