Abstract:
A cranking pad assembly for a gearbox of a turbomachine including a cranking pad shaft rotatably secured in a gearbox housing and engageable with a gearbox drivetrain when urged inwardly into the gearbox housing. The cranking pad shaft includes an interface for a cranking tool. An interlock pin retains the cranking tool at the cranking pad shaft and a disconnect spring is operably connected to the gearbox housing to bias the cranking pad shaft outwardly from the gearbox housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to turbomachines. More specifically, means for manually rotating an interior shaft of a turbomachine when the turbomachine is not operating. 
         [0002]    When performing maintenance and/or inspection (such as boroscope inspection) of a turbomachine, for example, a gas turbine engine for an aircraft, it is often desired to rotate the shaft of the gas turbine to provide access to interior components of the core of the gas turbine. This is typically accomplished by turning the accessory gearbox which is connected to the core. To turn the accessory gearbox, a simple cover is removed from the gearbox and a cranking tool is inserted into a cranking pad of the gearbox and the cranking tool is used to rotate the gearbox which in turn rotates the shaft of the gas turbine. Once the cranking operation is completed, the tool is removed and the cover must be replaced to seal the gearbox and gas turbine from oil leakage. If the cover is not replaced, the oil leakage can result in damage to and/or failure of the gas turbine. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    A cranking pad assembly for a gearbox of a turbomachine including a cranking pad shaft rotatably secured in a gearbox housing and engageable with a gearbox drivetrain when urged inwardly into the gearbox housing. The cranking pad shaft includes an interface for a cranking tool. An interlock pin retains the cranking tool at the cranking pad shaft and a disconnect spring is operably connected to the gearbox housing to bias the cranking pad shaft outwardly from the gearbox housing. 
         [0004]    A turbomachine system includes a turbomachine having a turbine shaft and a gearbox operably connected to the turbine shaft. The system includes a cranking pad assembly having a cranking pad shaft rotatably secured in a gearbox housing and engageable with a gearbox drivetrain when urged inwardly into the gearbox housing. The cranking pad shaft includes an interface for a cranking tool, an interlock pin to retain the cranking tool at the cranking pad shaft, and a disconnect spring operably connected to the gearbox housing to bias the cranking pad shaft outwardly from the gearbox housing. 
         [0005]    A method of rotating a turbine shaft includes connecting a gearbox to a turbine shaft and inserting a cranking tool into a cranking pad shaft of the gearbox. An interlock pin is urged radially outwardly by the insertion of the cranking tool into the cranking pad shaft and the cranking pad shaft is pushed into engagement with a drivetrain of the gearbox. The cranking tool is retained at the cranking pad shaft via the interlock pin. The cranking tool is rotated about a gearbox axis to rotate the turbine shaft. Removal of the cranking tool ensures that the cranking pad shaft is disconnected from the drivetrain. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  is a schematic of an exemplary turbomachine; 
           [0009]      FIG. 2  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock; 
           [0010]      FIG. 3  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock with a cranking tool installed; 
           [0011]      FIG. 4  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock engaging a drivetrain; 
           [0012]      FIG. 5  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock disengaging a drivetrain; 
           [0013]      FIG. 6  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock with a cranking tool withdrawing therefrom; and 
           [0014]      FIG. 7  is a cross-sectional view of an exemplary embodiment of a cranking pad interlock with a cranking tool withdrawn. 
       
    
    
       [0015]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Shown in  FIG. 1  is an embodiment of a turbomachine, for example, gas turbine  10 , having a turbine shaft  12 . The turbine shaft  12  is connected to a gearbox  14  via a transmission shaft  16  such that the turbine shaft  12  can be rotated via rotation of the transmission shaft  16 . 
         [0017]    Referring now to  FIG. 2 , the gearbox  14  includes a gearbox housing  18  in which the components of the gearbox  14  are located. The gearbox housing  18  includes a crank pad opening  20  through which a crank pad shaft  22  extends. The crank pad shaft  22  is rotatably secured in the gearbox  14  at a gearbox axis  24  and is sealed to the gearbox housing  18  via one or more seals  26  to prevent leakage of oil or other substances from the gearbox  14  and to prevent contamination of the gearbox  14 . 
         [0018]    The crank pad shaft  22  is biased outwardly from the gearbox housing  18  by a disconnect spring  28 . The disconnect spring  28  may be interactive with a disconnect clip  30  located in a clip groove  32  in an outer surface  34  of the crank pad shaft  22  to bias the crank pad shaft  22  outwardly from the gearbox housing  18 . A shaft stop  36  at the crank pad shaft  22  limits an outward travel of the crank pad shaft  22  by an interference with the gearbox housing  18 . The crank pad shaft  22  includes a tool cavity  38 , with an interlock pin  40  extending from a shaft detent  42  in the outer surface  34  through the crank pad shaft  22  into the tool cavity  38 . The tool cavity  38  may be a ⅜″ square drive or other suitable configuration. A spring clip  44  is located in the shaft detent  42  radially outboard of the interlock pin  40 . When the spring clip  44  is in the shaft detent  42 , the spring clip  44  blocks axial travel of the crank pad shaft  22  by an interference between the crank pad shaft  22 , the spring clip  44  and the gearbox housing  18 . The travel is blocked even if a force great enough to overcome the spring force of the disconnect spring  28  is applied by, for example, pushing axially on the crank pad shaft  22 . 
         [0019]    Referring to  FIG. 3 , the tool cavity  38  is configured so that a cranking tool  46  is insertable into the tool cavity  38 . When the cranking tool  46  is inserted into the tool cavity  38 , the cranking tool  46  pushes the interlock pin  40  radially outwardly which pushes the spring clip  44  out of the shaft detent  42  and into a housing cavity  48 . As the cranking tool extends into the tool cavity, the interlock pin  40  follows the profile of the cranking tool and settles into a tool detent  54  which aligns the outside surface of the interlock pin  44  with the housing  18  bore and the spring clip  44  is aligned with the outer diameter of the cranking shaft  22 . The cranking pad shaft  22  and the cranking tool  46  may now be pushed axially inwardly into the gearbox housing  18  by overcoming the spring force of the disconnect spring  28 . As shown in  FIG. 4 , as the cranking pad shaft  22  moves axially inward, the cranking pad shaft  22  engages a gearbox drivetrain  50 . The engagement between the cranking pad shaft  22  and the gearbox drivetrain  50  may be, for example, a spline connection. The spring clip  44  falls radially inwardly into a locking detent  52  in the cranking pad shaft  22  to again limit the axial travel of the cranking pad shaft  22  by an interference between the cranking pad shaft  22 , the spring clip  44  and the gearbox housing  18 . The interlock pin  40  which has extended into the tool detent  54  in the cranking tool  46  locks the cranking tool  46  in engagement with the cranking pad shaft  22 . Once the cranking pad shaft  22  is engaged with the drivetrain  50 , the cranking tool  46  is rotated thus rotating the cranking pad shaft  22  and the drivetrain  50 . The drivetrain  50  is connected to the turbine shaft  12  via the transmission shaft  16 , so rotational energy is transferred to the turbine shaft  12 , rotating it. 
         [0020]    Referring to  FIG. 5 , to disengage the cranking pad shaft  22  from the drivetrain  50  and remove the cranking tool  46 , the cranking tool  46  is pulled axially outwardly from the crankshaft housing  18 . This axially outwardly movement pulls the cranking pad shaft  22  from engagement with the drivetrain  50  because the interlock pin  40  is positioned in the tool detent  54 . The axial motion forces the spring clip  44  out of the locking detent  52  and into the housing cavity  48 . 
         [0021]    Now referring to  FIG. 6 , the cranking tool  46  cannot be disengaged from the cranking pad shaft  22  until the cranking pad shaft  22  has traveled sufficiently far that the interlock pin  40  can be pushed radially outward into the housing cavity  48  behind the spring clip  44 . When the cranking tool  46  is withdrawn from the tool cavity as shown in  FIG. 7 , the spring clip  44  forces the interlock pin  40  radially inward into the shaft detent  42 . Now, the axial position of the cranking pad shaft  22  is locked by the bias of the disconnect spring  28  and by the interference between the spring clip  44  and the gearbox housing  18  and cranking pad shaft  22 . 
         [0022]    Use of this cranking configuration with the interlock pin  40  and spring clip  44  ensures disengagement of the cranking pad shaft  22  from the drivetrain  50  when the cranking tool  46  is removed. Further, the gearbox housing  18  remains sealed to prevent leakage from the gearbox  14  and/or contamination of the gearbox  14  without the need for a cover of the prior art. Further, this configuration removes the human element of having to reinstall a cover after removal thereby preventing leakage and contamination leading to failure of the gearbox and/or the gas turbine. 
         [0023]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.