Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engine inspections and, more particularly, to a method and apparatus utilized to perform gas turbine maintenance.  
         [0002]     Aircraft engines typically include a compressor, a combustor, and a turbine that is coupled to the compressor. Moreover, at least one known turbine engine includes an accessory gearbox having an inlet that is coupled to either the compressor or the turbine, such that rotation of gearbox inlet provides the rotational force to drive various accessory devices that may be coupled to the gearbox output.  
         [0003]     During operation, turbine engines may suffer performance degradation and fabrication limitations due to an increase, over time, in accumulation of deposits on turbine components. Turbine components suffer an increase in their surface roughness, particularly those located in an engine operating environment, partially because they are exposed to engine combustion gases. A maintenance procedure, for example, a borescope inspection, of these components typically reveals a significant accumulation of dirt and other deposits on surfaces of the engine components.  
         [0004]     To borescope a turbine engine, at least one known turbine engine includes a removable plug to faciliate rotating at least a portion of the turbine engine during the maintenance procedure. More specifically, at least one known turbine engine includes a plug that is removed from the accessory gearbox such that an operator can insert a tool through the an opening created by removing the plug and thus gain access to the internal gears within the gearbox. The tool is then utilized to manually rotate the gearbox and thus rotate the compressor and/or the turbine to perform the maintenance procedure.  
         [0005]     After the maintenance procedure is completed, the tool is removed and the plug is reinstalled. However, if the plug is not properly replaced following the maintenance procedure the plug may loosen during flight resulting in low oil pressure and an engine In Flight Shut Down (IFSD).  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     In one aspect, method for assembling a gas turbine engine is provided. The method includes coupling a maintenance tool to the gas turbine engine such that the maintenance tool enables the gas turbine engine to be selectively rotated during non-operational periods and such that the maintenance tool is coupled to the gas turbine engine during normal operation, and selectively operating the maintenance tool to rotate the gas turbine engine.  
         [0007]     In another aspect, a maintenance tool for a gas turbine engine is provided. The tool includes a housing coupled to the gas turbine engine, and a drive portion inserted at least partially through the housing. The drive portion is configured to enable the gas turbine engine to be selectively rotated during non-operational periods. Moreover, the maintenance tool is coupled to the gas turbine engine during normal operation.  
         [0008]     In a further aspect, a gas turbine engine is provided. The gas turbine engine includes a compressor, a combustor, a turbine coupled to the compressor, a gearbox coupled to at least one of the compressor and the turbine, and a maintenance tool coupled to the gearbox. The maintenance tool includes a housing coupled to the gearbox, and a drive portion inserted at least partially through the housing, the drive portion configured to enable the gas turbine engine to be selectively rotated during non-operational periods, the maintenance tool is coupled to the gas turbine engine during normal operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exemplary aircraft including at least one gas turbine engine;  
         [0010]      FIG. 2  is a schematic illustration of the gas turbine engine shown in  FIG. 1  including an exemplary maintenance tool;  
         [0011]      FIG. 3  is a cross-sectional view of the maintenance tool shown in  FIG. 2  in a first operational configuration; and  
         [0012]      FIG. 4  is a cross-sectional view of the maintenance tool shown in  FIG. 2  in a second operational configuration. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  is a schematic illustration of an exemplary aircraft  8  that includes at least one gas turbine engine  10  and an access panel  11  that is removable to perform maintenance on gas turbine engine  10 .  
         [0014]      FIG. 2  is an illustration of an exemplary gas turbine engine  10  that may be utilized with the aircraft shown in  FIG. 1 . Gas turbine engine  10  includes a low pressure compressor  12 , a high pressure compressor  14 , and a combustor  16 . In one embodiment, engine  10  is a CF34 gas turbine engine commercially available from General Electric Company, Cincinnati, Ohio.  
         [0015]     In the exemplary embodiment, gas turbine engine  10  also includes a number of accessory devices, such as fuel pumps, lubrication pumps, generators and control units, which are driven by the core engine utilizing an accessory gearbox  20 . Moreover, to perform maintenance on the gas turbine engine, the accessory gearbox  20  includes at least one drive pad  22  that is utilized to couple a maintenance tool  100  to the gas turbine engine, such that when the maintenance tool  100  is manually operated, the gas turbine engine rotates to facilitate borescoping the engine, for example.  
         [0016]      FIG. 3  is a cross-sectional view of maintenance tool  100  that may be utilized with the exemplary gas turbine engine shown in  FIG. 2  in an engaged position.  FIG. 4  is a cross-sectional view of maintenance tool  100  in a disengaged position. Maintenance tool  100  is a cranking plug that is utilized by an operator to manually rotate gas turbine engine  10  during a variety of maintenance procedures.  
         [0017]     In the exemplary embodiment, cranking plug assembly  100  includes a substantially cylindrical drive portion  102  and a housing  104  that circumscribes drive portion  102 . Drive portion  102  includes has a substantially T-shaped cross-sectional profile and includes a head portion  120  that is utilized to operate drive portion  102 , a body portion  122  having a first end  124  that is coupled to head portion  120  and a second end  126  that is sized to be inserted at least partially within gearbox  20 . In the exemplary embodiment, head portion  120  is formed unitarily with body portion  122 .  
         [0018]     More specifically, head portion  120  includes a shoulder  128  that has a first diameter  130  that is greater than a diameter  132  of head portion  120  to facilitate retaining a biasing mechanism that is discussed later herein. Body portion  122  includes a radial projection  134 , or travel stop, that extends radially outward and substantially perpendicularly from body portion  122 , and has an outer diameter  136  that is greater than a diameter  138  of body portion  122 . Radial projection outer diameter  136  defines a substantially circular cross-sectional profile for radial projection  134 . Body portion  122  also includes a first channel or groove  140  that is positioned between radial projection  134  and second end  126 . Channel  140  has a diameter  142  that is less than body portion diameter  138  and is sized to receive a seal  144  therein. Body portion  122  also includes a second channel or groove  150  that is positioned between first groove  140  and second end  126 . In the exemplary embodiment, second groove  150  is positioned proximate to second end  126  and has a diameter  152  that is less than body portion diameter  138  and is sized to receive a retaining device therein.  
         [0019]     Body portion  122  also includes second end  126  that is sized to engage a female bushing  160  that is coupled to gearbox  20 . More specifically, and in the exemplary embodiment, second end  126  has a square cross-sectional profile and bushing  160  has an opening  162  that is sized to received second end  126 .  
         [0020]     Housing  104  includes a first end  170  and a second end  172  and has an inner diameter  174  that is sized to circumscribe at least a portion of drive portion  102 . Second end  172  also includes a groove  176  or channel that is formed proximate to second end  172  and is sized to receive a seal  178  therein.  
         [0021]     Cranking plug assembly  100  also includes a substantially cylindrical wiper  180  that is coupled proximate to housing first end  170  and substantially circumscribes body portion  122 . In the exemplary embodiment, wiper  180  is fabricated from a material such as Viton to facilitate inhibiting dirt or similar debris from entering between body portion  122  and housing  104 . To facilitate securing wiper  180  to housing portion  104 , cranking plug assembly  100  also including a retaining device  190 , or wiper housing that is coupled to housing  104  proximate to housing first end  170 . More specifically, the wiper housing  190  includes a channel  192  therein that is sized to receive wiper  180  and thus maintain wiper  180  in a substantially fixed position with respect to housing  104 . Wiper housing  190  also includes a recess  194  that is formed at a forward end  196  of the wiper housing  190 . In the exemplary embodiment, recess  194  and shoulder  128  cooperate to secure a biasing mechanism  198  within cranking plug assembly  100 .  
         [0022]     To assembly cranking plug assembly  100 , seal  144  is inserted into groove  140  in drive portion  102 . Moreover, wiper  180  is secured to housing  104  utilizing wiper housing  190 . Spring  198  is then positioned around drive portion  102  such that a spring first end  200  is positioned proximate shoulder  128 . Drive portion  102  is then at least partially inserted through housing  104  such that seal  144  is in sliding contact between drive portion  102  and an interior surface of housing  104 , such that seal  180  is sliding contact between drive portion  102 , and such that a biasing mechanism second end  202  is seated within recess  194  formed within wiper housing  190 . To secure drive portion  102  within housing  104 , retaining device  150  is coupled to drive portion  102 . To secure cranking plug assembly  100  to gearbox  20 , seal  178  is inserted into groove  176  and the cranking plug assembly is positioned at least partially into an opening in the gearbox  20 . To secure cranking plug assembly  100  to gearbox  20 , a retaining device  210  is utilized. In one embodiment, the retaining device  200  is a spring clip such as a C-clip for example. Optionally, cranking plug assembly  100  is secured to the gearbox  20  utilizing a plurality of mechanical fasteners.  
         [0023]     During operation, a tool is coupled to cranking plug assembly  100  to facilitate operating the cranking plug assembly. More specifically, and in the exemplary embodiment, drive portion head  120  has a substantially hexagonal shape that is sized to receive either as standard socket or wrench. To operate cranking plug assembly  100 , a socket or wrench is coupled to drive head portion  120 , and force is exerted by an operator on head portion  120  such that drive portion  102  is moved in a first or engaged direction  220 . Moving drive portion  102  thus moves drive portion second end into gearbox bushing  162  and thus in engagement with gearbox  20 . The operator then rotates drive head portion  120  in either a clockwise or counterclockwise direction to facilitate rotating at least a portion of the gas turbine engine  10 . In the exemplary embodiment, radial projection  134 , i.e. the stopper, facilitates limiting the distance which drive portion  102  may moved in first direction  220  since stopper  134  will contact seal  180  at a predetermined distance. Moreover, as shown in  FIG. 3 , because the housing inner diameter  174  is slightly tapered, as drive portion  102  is moved or pushed into gearbox bushing  162  in first direction  220 , the pressure on seal  144  is reduced to facilitate reducing the wear on seal  144 . However, when the force exerted by the operator on head portion  120  is removed such that drive portion  102  is moved in a second or disengaged direction  222 , because the housing inner diameter  174  is slightly tapered, as drive portion  102  is moved or pushed into gearbox bushing  162  in second direction  222 , the pressure on seal  144  is increased to facilitate forming a seal between drive portion  102  and housing  104 .  
         [0024]     To stop rotation of gas turbine engine  10 , the force exerted by the operator on head portion  120  is removed such that drive portion  102  is moved in a second or disengaged direction  222 . More specifically, biasing mechanism  198 , i.e. spring  198  acts against both drive portion should  128  and wiper housing  190  to facilitate moving drive portion  102  in second direction  222  when the force has been removed from the head portion  120 . Accordingly, when cranking plug assembly  100  is not being utilized, biasing mechanism  198  facilitates maintaining the drive portion  102  is a disengaged or standby position.  
         [0025]     The above described cranking plug assembly includes a housing and a sealed square drive crank shaft. The crank shaft telescopes in its housing to engage the square drive in the gearshaft. When engine cranking is complete, the spring pushes the crank shaft out of engagement. The assembly stays on the engine and faciliates sealing the gearbox during all operational conditions.  
         [0026]     Moreover, although the exemplary embodiment, illustrates a cranking plug that is coupled to a gas turbine engine installed on an aircraft, it should be realize that the cranking plug may be utilized with a gas turbine engine that is utilized in any environment, such as a power plant, for example.  
         [0027]     The above-described cranking plug assembly is cost-effective and highly reliable. The cranking plug assembly is configured to be installed on a gas turbine engine during all engine operating conditions. Moreover, as explained previously, a known tool is installed through a plug opening in the gas turbine engine. After the inspection is completed the plug is reinstalled. However, if the plug is not properly replaced following the maintenance procedure the plug may loosen during flight resulting in low oil pressure and an engine In Flight Shut Down (IFSD).  
         [0028]     Accordingly, the cranking plug assembly described herein is coupled to the gas engine and is configured to remain with the gas turbine engine during all operational conditions. Specifically, the cranking plug assembly described herein remains with the engine while the engine is running and during flight operations. As a result, the cranking plug assembly described herein faciliates reducing the time to perform maintenance, the cranking plug described herein also faciliates eliminating low oil pressure and as a result eliminate In Flight Shut Downs associated with low oil pressure.  
         [0029]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Technology Category: y