Abstract:
A device for manually rotating a core of a gas turbine engine, said device comprising a drive mechanism, an operator control, and a flexible cable rotatably coupling said drive mechanism and said operator control.

Description:
BACKGROUND OF THE INVENTION 
     The technology described herein relates generally to gas turbine engine components and more specifically to devices for manually rotating the core of a gas turbine engine. 
     Gas turbine engines typically include a compressor, a combustor, and at least one turbine. The compressor may compress air, which may be mixed with fuel and channeled to the combustor. The mixture may then be ignited for generating hot combustion gases, and the combustion gases may be channeled to the turbine. The turbine may extract energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight, such as by driving a fan or propeller, or to power a load, such as an electrical generator. 
     The compressor and turbine are linked together via a shaft to form a rotating piece of turbomachinery located inside of a casing. This assembly may be referred to as a “core” of the gas turbine engine. During maintenance or repair operations it is often necessary to inspect blades and other elements of this rotating turbomachinery within the core. However, access to and visibility of this turbomachinery is frequently limited by the casing as well as other elements of the gas turbine engine. 
     Many gas turbine engines have one or more inspection ports, openings in the casing, which may be opened via removable plugs or covers to inspect and/or service (repair, replace, adjust, etc.) internal components. Inspection can be visual with the naked eye, or with mirrors or other optical tools such as borescopes. Frequently, however, these inspection ports are positioned such that only certain elements of the rotating turbomachinery are visible with the engine stopped and the turbomachinery in a fixed position. It is therefore often necessary to rotate the turbomachinery to view and/or service other components. 
     Rotation is typically accomplished by applying torque through a drive pad which is connected to an accessory gearbox. A socket is normally provided in the drive pad to receive a ratchet wrench or other hand tool, or an output shaft of a motorized drive unit. Manual operation of the drive pad, however, may prove difficult for an operator who needs to be proximate to an inspection port which may not be adjacent to the drive pad. Therefore, two or more persons may be required to rotate and inspect or service the turbomachinery. Motorized drive units may be operated remotely by an operator who is proximate the inspection port. However, motorized drive units are expensive, often cumbersome, and do not provide the operator with a “feel” for the rotation and momentum of the turbomachinery, making precise positioning and/or reversing of the rotation somewhat difficult and time consuming. 
     Accordingly, there remains a need for a device for manually rotating or turning a core of a gas turbine engine which is inexpensive yet portable and easy to use, and enables a single operator to rotate and inspect or service the turbomachinery. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A device for manually rotating a core of a gas turbine engine, said device comprising a drive mechanism, an operator control, and a flexible cable rotatably coupling said drive mechanism and said operator control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional schematic view of an exemplary gas turbine engine. 
         FIG. 2  is a perspective view of an exemplary gas turbine engine having a manual core rotation device installed thereon. 
         FIG. 3  is a partial cut-away view of an exemplary drive mechanism of a manual core rotation device. 
         FIG. 4  is a perspective view of an exemplary operator control of a manual core rotation device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic illustration of an exemplary gas turbine engine  10  including a fan assembly  12 , a booster  14 , a high pressure compressor  16 , and a combustor  18 . The engine  10  also includes a high pressure turbine  20 , and a low pressure turbine  22 . The fan assembly  12  includes an array of fan blades  24  extending radially outward from a rotor disk  26 . The engine  10  has an intake side  28  and an exhaust side  30 . The engine  10  may be any gas turbine engine. For example, the engine  10  may be, but is not limited to being, a GE90 gas turbine engine available from General Electric Company, Cincinnati, Ohio. The fan assembly  12 , booster  14 , and turbine  22  may be coupled by a first rotor shaft  32 , and the compressor  16  and turbine  20  may be coupled by a second rotor shaft  34 . 
     In operation, air flows through the fan assembly  12  and compressed air is supplied to the high pressure compressor  16  through the booster  14 . The highly compressed air is delivered to the combustor  18 , where it is mixed with a fuel and ignited to generate combustion gases. The combustion gases are channeled from the combustor  18  to drive the turbines  20  and  22 . The turbine  22  drives the fan assembly  12  and booster  14  by way of shaft  32 . The turbine  20  drives the compressor  16  by way of shaft  34 . High pressure compressor  16 , turbine  20 , and shaft  34  form a rotating piece of turbomachinery sometimes called a core which may require inspection and/or service from time to time. This turbomachinery is enclosed within an outer casing  70  (identified in  FIG. 2 ). 
     As shown in  FIG. 2 , engine  10  includes a drive pad  20  which provides a mechanical drive connection to the rotating turbomachinery through a gearbox (not labeled). Gearbox and drive pad locations may vary in location and orientation depending upon the particular engine application. Also shown in  FIG. 2  is an exemplary manual device  30  for turning the core. Manual core turning device  30  includes a drive mechanism  40 , a flexible drive cable  50 , and an operator control  60 . 
       FIG. 3  illustrates in greater detail the elements of the drive mechanism  40 . Drive mechanism  40  includes a coupling feature  41 , an output shaft  42 , a mounting block  49 , a planetary gearbox  53 , and an input shaft  44 . 
     In operation, input shaft  44  receives torque from flexible cable  50 , transmits torque through planetary gearbox  53  through mounting block  49  to output shaft  42  and to the drive pad  20  via coupling feature  41  to rotate the turbomachinery within the core of the engine  10 . 
     As show in  FIG. 3 , additional elements may be included to enhance the operation of the manual core rotation device such as an enunciator to signal rotational position of the engine. Output shaft  42  may be coupled to a secondary shaft  43  through gearset  44  having a suitable gear ratio to rotate secondary shaft  43  one rotation per rotation of the core of the engine  10 . A pin  45  affixed to gearset  44  can be utilized to engage a microswitch  46  to send electric current from battery  47  to an sound emitter  48  and thereby provide an audible indication that the core had undergone a complete rotation (and thus inspection from a fixed reference point would have inspected all rotating elements circumferentially disposed around the core). 
     Battery  47 , microswitch  46 , and sound emitter  48  may be of any suitable design and construction, and may be commercially available items. Battery  47  may be a dry cell battery and sound emitter  48  may be a bell, buzzer, or horn of suitable sound production characteristics so as to be readily heard by the operator in the desired location. Other locations for the enunciator are possible, such as proximate to the operator control, so long as the enunciator provides a desired indication of the engine rotation. 
     Planetary gearbox  53  may provide any desired gear ratio between the output shaft  42  and the input shaft  44 . Having a gear ratio such that one turn of the input shaft  44  produces less than a full rotation of output shaft  42  may reduce the level of manual effort required to rotate the core and also enable finer control over the rotational position of the core for inspection and/or service operations. Ratios of 10 to 1 may be useful for certain engine applications, and may be specified so as to achieve a desired level of operator effort to rotate the core, such as approximate values on the order of 80 inch pounds. Higher (numerically) gear ratios may be needed for larger engines to reduce the rotational effort required. 
     Mounting block  49  may be of any suitable size, shape, material, and construction for mating the output shaft  42  and coupling  41  to the drive pad  20  of the engine  10 . It may be desirable to fabricate the mounting block  49  from, or coat mounting block  49  with, a non-stick and non-marring material such as tetrafluoroethylene or polytetrafluoroethylene, which is commercially available under the trade name TEFLON® from DuPont. Mounting block  49  may have any suitable mounting configuration, such as holes or slots to engage complementary features on the engine  10  to hold the drive mechanism in place and may utilize bolts or screws for securement. 
     As shown in  FIG. 4 , the operator control  60  includes a mounting device  61  and a wheel type device  62  for controlling the rotation of the core. The wheel  62  also includes a knob  63  to provide for increased operator control over the rotation of the wheel  62 . The wheel  62  is affixed to the flexible cable  50  through any suitable conventional coupling. Although a wheel  62  is shown, any type of device may be provided for operator use or, if desired, a tool engagement feature may be provided such that the operator can use a conventional tool such as a ratchet wrench. 
     Mounting device  61  can be of any conventional construction suitable for securing operator control  60  in a fixed position, such as affixed to the gas turbine engine, an engine holding fixture, an engine accessory or element such as a pipe or tube, or an engine nacelle or pylon (if the engine is serviced on the aircraft). Clamps or brackets may be used as required to hold the operator control, and may provide for adjustment or movement to another location as required. The operator control may be positioned as desired by the operator to provide for ease of rotation and control of rotation, as well as visibility to the inspection ports or other items the operator needs to view or operate such as service or repair tooling. 
     Elements of the manual core rotation device may be fabricated from any suitable materials, and may incorporate standard commercially-available items or materials as desired. In particular, the cable may be any type of flexible cable which is suitable in length and flexibility for the intended application. Spring cables as well as solid cables may be suitable for this low speed, comparatively low torque application. 
     The manual core rotation device may also be provided as an assembly in kit form, with one or more different mounting blocks adapted to be used with various engines and engine configurations. A carrying case may be provided for ease of storage and transportation of the device. The device may be self-contained, without requiring any external power supply or support equipment, and therefore provides a high degree of portability. It may also be suitable for use in a wide range of internal and external operating environments, and may be fabricated so as to be weather resistant as well. 
     Manual core rotation devices of the type described herein may be useful in other installations besides gas turbine engines. For example, such devices may be utilized in the automotive field or any other field where it is desired to rotate machinery from a remote location. With regard to gas turbine engines, applications may include aircraft type applications as well as land based or marine applications. 
     While this application has described various specific exemplary embodiments, those skilled in the art will recognize that those exemplary embodiments can be practiced with modification within the spirit and scope of the claims.