Abstract:
A shim is provided for repairing damage in a surface of a mechanical piece at or near an outer edge of a bore in the surface. The damage may penetrate a given distance within the surface and the bore is in close proximity to an attachment hole. The shim has a body having a first side and a second side and a thickness therebetween that is equal to or greater than the depth of the damage penetrating the given distance and contiguous to the attachment opening, wherein the body fits within an area machined into an outer surface surrounding the bore.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    This invention was made with Government support under F33657-99-D-2051 awarded by The United States Air Force. The Government has certain rights in this invention. 
     
    
     BACKGROUND 
       [0002]    It is common that machinery is made of functional modules that attach to each other usually by means of bolts, clamps, screws and the like. Common openings between modules may allow for the transfer of fluids such as gasses or liquids, and mechanical, electrical or other types of energy to enable adjacent modules to cooperate. 
         [0003]    If the modules are separated, it is important that the areas that link the modules together are not damaged to avoid leaks, contamination, inefficiencies or the like. 
         [0004]    If an edge of a circular opening, for instance, gets nicked, it is typical to machine the bore of the opening to remove enough material to eliminate the damage. A bead or an insert is then welded to the bore to rebuild the bore of the opening to its initial tolerance. 
       SUMMARY 
       [0005]    According to an embodiment disclosed herein, a shim is provided for repairing damage in a surface of a mechanical piece at or near an outer edge of a bore in the surface. The damage may penetrate a given distance within the surface and the bore is in close proximity to an attachment hole. The shim has a body having a first side and a second side and a thickness therebetween that is equal to or greater than the depth of the damage penetrating the given distance and contiguous to the attachment opening, wherein the body fits within an area machined into an outer surface surrounding the bore. 
         [0006]    According to a further embodiment disclosed herein, an assembly for repairing damage in a gas turbine engine includes a gas turbine engine component that has a bore and a machined area disposed on an outside surface of the component contiguous to the bore. The machined area has a first depth equal to or greater than a depth of damage to the component. A shim has a body having a first side and a second side and a thickness therebetween that is equal to the first depth, wherein the body fits within the machined area and is flush thereto. 
         [0007]    According to a further embodiment disclosed herein, a method of repairing damage in a gas turbine engine component includes: locating damage in a surface of the component in proximity to or within an edge of a bore; machining an area into an outer surface of the component in proximity to and touching the bore to a first depth that is equal to or greater than a depth of the damage in the outer surface; and inserting a shim into the area, the shim having a body having a first side and a second side and a thickness therebetween that is equal to the first depth wherein the shim is flush with the surface. 
         [0008]    The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a side, sectional view of a gear box for a jet engine incorporating a plurality of shims as described herein. 
           [0010]      FIG. 2  shows an orthogonal view of a representative opening in a gear box as shown in  FIG. 1 . 
           [0011]      FIG. 3  is a plan view of a shim that is installed in the gear box of  FIG. 1 . 
           [0012]      FIG. 4  is a side view of the shim of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIG. 1 , the side, sectional view of a mechanical piece, such as a gas turbine engine gear box,  10  is shown. The gear box  10  has a multitude of representative openings  21 ,  22 ,  23 ,  24 ,  25 ,  26 ,  27 ,  28 ,  29 , and  30  that bolt, or otherwise attach, to another half (not shown) of a casing or to other individual pieces of machinery (not shown). This particular type of gear box is constructed of cast magnesium or aluminum and is therefore more susceptible to damage than harder, but heavier, materials. 
         [0014]    Referring now to  FIG. 2 , if the gear box  10 , or other machinery, is assembled or disassembled damage, such as nick  35 , to an edge  40  (or in proximity to) of opening  23  may occur particularly because of the softer, but lighter materials required for aircraft applications. Opening  23  has a central bore  45  having a diameter D disposed about axis  47  and is surrounded by three bolt holes  50  so that an accessory (not shown) may be bolted to the gear box  10 . The nick extends into the bore a distance N 1  and into the surrounding gear box  10  a distance N 2 . 
         [0015]    In the past, the bore diameter D was machined out the distance N 2  to eliminate the nick, but the Applicants have discovered that there are two distinct problems with such actions: it can be seen in  FIG. 1  that there are so many openings  21 - 30  that are close to each other that increasing the bore diameter D may not be possible without damaging other openings  21 - 30  or other holes  50 ; and, repairing the bore to its initial tolerances usually required higher temperatures, like for welding a bead or an insert, that tends to warp the gear box  10  and cause holes  50  to migrate and misalign with holes on other machinery modules (not shown) which required other costly repairs. 
         [0016]    In the disclosed embodiment, instead of machining out the bore  45 , an area  55  corresponding to the shape of a shim  60  (see also  FIGS. 3 and 4 ) is machined into the outer surface  65  of the gear box  10  a distance N 1  to eliminate the nick  35 . By using the shim  60 , no high temperatures are needed for repair and there is no interference with other holes  21 - 30 . 
         [0017]    Referring now to  FIGS. 3 and 4 , an exemplar shim  60  is shown in place in area  55  on a gear box  10 . The shim  60  has a flat, annular (though other shapes are contemplated herein), body  70  with a plurality of lobes  75  extending radially outwardly from the body  70 . Each lobe  75 , which may be differently or even oddly shaped depending on the shape of the gear box  10  or other machinery, has an opening  80  extending therethrough that are placed to be in register with holes  50  so that bolts (not shown) may join the gear box halves without modification. The shim  60  has a diameter D which is the same as the bore  45  thereby effecting repair. 
         [0018]    The body  70  may have a plurality flanges  85  disposed around the outer edges  90  of the body. The area  55  may have a deeper opening  95  machined therein for receiving the flanges  85  therein. The flanges  85  and openings  95  act to locate the ship properly within the area  55 . 
         [0019]    Referring to the  FIG. 5 , a method for applying a shim  60  is shown. A damaged bore  45  in a machine is located (step  200 ). An area  55  is machined into the surface  65  around the bore  45  to the depth N 2  of the damage (e.g., nick  35 ) around the bore and is shaped to receive the shim (step  205 ). The area  55  may also include openings for receiving connectors (not shown) corresponding to the bore  45  (step  210 ). The area  55  may have openings  95  machined deeper therein to receive shim flanges  85  (step  215 ). A crafted shim  60  having flanges  85  extending therefrom to mate approximately with openings  95  and having a body  70  with a depth N 2  is inserted into the area  55  (step  220 ) and the bore and its surrounding surface is now back to original spec without warpage or damage to adjacent openings. Because the shapes of the openings  21 - 30  and the shapes of damage (e.g., nick  35 ) to them are so varied, the shim may need to be constructed for each application. In areas  55  where the machine casing  10  is not thick enough, the flanges  85  may be eliminated from the design. Existing bolt holes  50  are always used to place the shims to avoid extra work in the machining or interfering with required tolerances. As stated hereinbelow, the shim may be made of or coated with different materials. 
         [0020]    The shim  60  and its lobes  75  may take many shapes and may repair more than one nick  35  on more than one bore  45 . For instance, shim  105  about opening  21  has an ovate shape with two holes  80 . Shim  110  is circular and has a plurality of crafted lobes  75  extending outwardly from the body  70  of the shim  60 . Shim  115 , which is seen in  FIGS. 2-4 , has three lobes  75  about its circumference. Shim  120  has one lobe  75  extending therefrom, which may be an opening  80  or another bore  45  and a plurality of openings  80  distributed around the body  70 . Shim  125  has four regularly spaced lobes  75  extending thereabouts. Shim  130  has four lobes  75  (two of which are larger) which may also correspond to other bores  45 . Shim  135  shows one large lobe  76  which is square shaped, and several openings  80  around the circumference of the shim  135 . Shim  140  has four lobes with three lobes  75  regularly shaped and a fourth lobe  77  with a rectangular shape. Shim  145  has four regular lobes  75  and a break  150  in its circumference. Shim  150  has no lobes but does have a plurality of tabs  155  extending therefrom. 
         [0021]    The shim  60  material may also be crafted by constructing or coating it with different materials or coatings to enhance the functionality of the gear box  10 . For instance, if the second half (not shown) of the gearbox  10  or other connectors (not shown) are made of a hard material, relative motion therebetween tends to damage the gearbox that is constructed of generally softer magnesium or aluminum. The shim  60  may be coated or constructed of a harder material such as an oxide, or coated with a lubricious material such as PTFE. The shim  60  may also be coated with a thermal spray or a PVD coating. If electrical resistance between the parts is desired, the shim may be made of an oxide or painted. Similarly if electrical resistance between the parts is not desired, the shim may be made of or coated with an inorganic material or anodized. Also, the part may have an inert coating for chemical resistance. Other coatings and materials for the shim  60  are contemplated herein depending on the shim environment and the types of parts used therewith. 
         [0022]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0023]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.