Abstract:
One embodiment of the present invention is a gas turbine engine. Another embodiment is a face coupling. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for face couplings. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application 61/290,811, filed Dec. 29, 2009, and is incorporated herein by reference. 
     
    
     GOVERNMENT RIGHTS 
       [0002]    The present application was made with the United States government support under Contract No. N00019-02-C-3003 awarded by the United States Navy. The United States government may have certain rights in the present application. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates to couplings, and in particular, face couplings, such as may be used in gas turbine engine systems. 
       BACKGROUND 
       [0004]    Couplings, such as face couplings used in gas turbine engines, remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
       SUMMARY  
       [0005]    One embodiment of the present invention is a gas turbine engine. Another embodiment is a face coupling. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for face couplings. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0007]      FIG. 1  schematically depicts a lift engine system in accordance with an embodiment of the present invention. 
           [0008]      FIG. 2  schematically depicts a face coupling in accordance with an embodiment of the present invention. 
           [0009]      FIG. 3  depicts a driving side and a driven side of a face coupling having root transitions in accordance with an embodiment of the present invention. 
           [0010]      FIG. 4  depicts the driving side and driven side of the face coupling of  FIG. 3  in engagement. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain embodiments of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention. 
         [0012]    Referring now to  FIG. 1 , there is illustrated a generic representation of a lift engine system  10  for powering an aircraft  12 , such as a short takeoff and vertical landing (STOVL) aircraft. The non-limiting depiction of lift engine system  10  includes a gas turbine engine  14  and a lift fan system  16 . Gas turbine engine  14  includes a compressor section  18 , a combustor section  20  and a turbine section  22 . Lift fan system  16  includes a lift fan  24 , a shaft system  26 , and a lift thrust output system in the form of a vanebox  28 . Lift fan  24  is coupled to gas turbine engine  14  via shaft system  26 . 
         [0013]    Compressor section  18  compresses air received at the inlet of gas turbine engine  14 , and may include one or more fan stages. Turbine section  22  is drivingly coupled to compressor section  18  via one or more shafts, and provides power to operate compressor section  18  and lift fan  24 . Turbine section  22  may also be configured to provide power for other components (not shown). Power is supplied from gas turbine engine  14  to lift fan  24  via shaft system  26 . Lift fan  24  is adapted for mounting to aircraft  12 , and discharges air through vanebox  28  to provide thrust e.g., for STOVL aircraft  12 . 
         [0014]    Referring now to  FIGS. 2-4 , lift engine system  10  includes a plurality of components that are coupled together and transmit torque from one of the components to the other. Schematically illustrated are a component  30  and a component  32 . Components  30  and  32  are coupled together via a coupling  34 . Coupling  34  transmits torque between component  30  and component  32 . Components  30  and  32  may be, for example, turbine wheels, compressor disks, shafting system components, and other drive system components. In other embodiments, coupling  34  may be configured for use in any gas turbine engine or in any other type of machine. 
         [0015]    Various schemes may be employed to couple machinery components such as components  30  and  32 , including, for example, bolted joints, circumferential splines, and face couplings such as face splines. Coupling  34  is a face coupling. In one embodiment, coupling  34  is a face coupling in form of a face spline. In particular, coupling  34  of the present embodiment is a CURVIC® (The Gleason Works Corporation) coupling. Face splines, such as CURVIC® couplings, employ, on both the driving side of the coupling and the driven side of the coupling component, a plurality of teeth that are circumferentially spaced apart. The teeth of each component are positioned within the spaces between the teeth of the mating component. The teeth of each component engage adjacent teeth of the other component to transmit torque. In one form, the mating teeth function as pilots, centering the drive side and the driven side of the coupling relative to each other. In other embodiments, the mating teeth may not be configured to perform a centering function. 
         [0016]    Coupling  34  includes a driving side  36  and a driven side  38 . Coupling  34  is structured to transmit a torque load from component  30  to component  32 . In one form, driving side  36  integral with component  30 , and driven side  38  is integral with component  32 . In other forms, driving side  36  and driven side  38  may be made separately from respective components  30  and  32  and subsequently attached or joined thereto. 
         [0017]    Components  30  and  32  may be clamped together at assembly in order to ensure that driving side  36  and driven side  38  remain in full engagement during all loading conditions. For example, in one form, a tie shaft system  40  is employed as a clamping mechanism that transmits an axial clamping load through component  30 , coupling  34  and component  32 . The clamp load retains driving side  36  in engagement with driven side  38 , which may ensure adequate torque transmission through coupling  34 , as well as centering driving side  36  and driven side  38  relative to each other. In other embodiments, different clamping arrangements may be employed. 
         [0018]    Driving side  36  of coupling  34  includes a plurality of teeth  42  extending axially away from component  30 , and a corresponding plurality of spaces  44  between adjacent teeth  42 . Teeth  42  are face spline teeth, in particular, curvic teeth. Teeth  42  are equally spaced in the circumferential direction, i.e., the direction indicated by bidirectional arrow  46 . Each tooth  42  is characterized in part by a tip  48 , a root  50  and two flanks  52 A and  52 B. Tip  48  represents the axially outermost extent of each tooth  42  in the direction towards driven side  38 . Root  50  is the base portion of each tooth  42 . Each flank  52 A,  52 B extends between the tip  48  and root  50  of each tooth  42 . 
         [0019]    Each tooth  42  has a pressure surface located on one or both of the flanks that transmits the torque and is subject to Hertzian contact stresses resulting from therefrom. Depending on the clamp load, each flank may have such a pressure surface, for example, in response to the clamping forces imposed by tie shaft system  40 , in addition to the torque load. Assuming a given tooth geometry, the location of the pressure surface on each tooth  42  depends on the direction of torque transfer, the magnitude of the torque, and the magnitude of the clamp load. 
         [0020]    Neglecting the effects due to the clamp load, and assuming that driving side  36  transmits a torque in a direction  54  to driven side  38 , each tooth  42  includes a pressure surface  56  disposed on flank  52 A. If the torque were transmitted in the opposite direction, the pressure surface would be on flank  52 B. The pressure surface is the portion of flank  52 A that is in mating contact with a corresponding tooth on driven side  38 . Flank  52 A has a tip edge  58  adjacent to driving tooth pressure surface  56 . 
         [0021]    Driven side  38  includes a plurality of teeth  60  extending axially away from component  32 , and a corresponding plurality of spaces  62  between adjacent teeth  60 . Teeth  60  are face spline teeth, in particular, curvic teeth. Teeth  60  are equally spaced around driven side  38  in the circumferential direction, i.e., the direction indicated by bidirectional arrow  46 . Each tooth  60  is characterized in part by a tip  64 , a root  66  and two flanks  68 A and  68 B. Tip  64  represents the axially outermost extent of each tooth  60  in the direction towards driving side  36 . Root  66  is the base portion of each tooth  60 . Each flank  68 A,  68 B extends between the tip  64  and root  66  of each tooth  60 . 
         [0022]    Each tooth  60  has a pressure surface located on one or both of the flanks that transmits the torque and is subject to Hertzian contact stresses resulting from therefrom. Depending on the clamp load, each flank may have a pressure surface, for example, in response to the clamping forces imposed by tie shaft system  40 , in addition to the torque load. Assuming a given tooth geometry, the location of the pressure surface on each tooth  60  depends on the clamp load and the direction of torque transfer, the magnitude of the torque, and the magnitude of the clamp load. 
         [0023]    Neglecting the effects due to the clamp load, and assuming that driving side  36  transmits a torque in direction  54  to driven side  38 , each tooth  60  includes a driving tooth pressure surface  70  disposed on flank  68 B. If the torque were transmitted in the opposite direction, the pressure surface would be on flank  68 A. The pressure surface is the portion of flank  68 B that is in mating contact with a corresponding tooth on driving side  36 . Each tooth  60  has a tip edge  72  adjacent to driven tooth pressure surface  70  that may experience high stresses during service. Driving teeth  42  and driven teeth  60  are structured to cooperate to transmit the torque load from component  30  to component  32  via each driving tooth pressure surface  56  acting against an adjacent driven tooth pressure surface  70 . 
         [0024]    In order to reduce peak stresses resulting from edge effects due to contact between tip edge  58  of each tooth  42  and flank  68 B of each adjacent tooth  60 , each driven tooth  60  includes on flank  68 B a root transition  74  that is structured to prevent each driving tooth tip edge  58  from contacting flank  68 B of the adjacent driven tooth  60 . 
         [0025]    In one form, root transition  74  is a root recess  76  that is positioned on and undercuts flank  68 B of tooth  60  at a location opposite to tip edge  58  of adjacent tooth  42 . In other embodiments, other types of root transitions may be employed to prevent contact between tip edge  58  and flank  68 B. In one form, root recess  76  is in the form of a fillet radius  78 , although different recess geometries may be employed in other embodiments. 
         [0026]    An additional root transition may be employed on each tooth  60  at flank  68 A, e.g., depending on the stress field and/or in applications where coupling  34  is intended to transmit torque in both directions. For example, a root transition  80  in the form of a root recess  82  may be positioned on flank  68 A and may undercut flank  68 A of tooth  60  at a location opposite to a tip edge  84  of adjacent tooth  42 . In other embodiments, other types of root transitions may be employed to prevent contact between tip edge  84  and flank  68 A. In one form, root recess  82  is in the form of a fillet radius  86 , although different recess geometries may be employed in other embodiments. 
         [0027]    Similarly, teeth  42  may employ root transitions on one or both of flanks  52 A and  52 B in order to reduce peak stresses resulting from edge effects due to contact between tip edges of teeth  60  contacting adjacent flanks  52 A and  52 B. For example, each driven tooth  42  may include on flanks  52 A and  52 B root transition  88  and  90  that are structured to prevent each respective driving tooth tip edge  72  and  92  from contacting the respective flank  52 A and  52 B of the adjacent driven tooth  42 . 
         [0028]    In one form, root transitions  88  and  90  are in the form of root recesses  94  and  96  that are positioned on and undercut respective flanks  52 A and  52 B of tooth  42  at a location opposite to respective tip edges  72  and  92  of adjacent teeth  60 . In other embodiments, other types of root transitions may be employed to prevent contact between tip edges  72  and  92  and respective flanks  52 A and  52 B. In one form, root recesses  94  and  96  are in the form of fillet radii  98  and  100 , although different recess geometries may be employed in other embodiments. 
         [0029]      FIG. 4  illustrates driving side  36  in engagement with driven side  38 . It is noted that, by virtue of root transitions in the form of root recesses  76 ,  82 ,  94  and  96 , tooth tip edges  58 ,  72 ,  84  and  92  do not contact the flank portions of the adjacent teeth. Although the present embodiment includes root transitions in the form of recesses at the base of each side of each tooth on driving side  36  and driven side of coupling  34 , it will be it will be understood that the root transitions described herein may be used at a lesser number of locations in other embodiments, e.g., on only one side of the teeth of one or both of driving side  36  and driven side  38 . 
         [0030]    One embodiment of the present invention is a gas turbine engine which may include a first component, a second component, and a face coupling structured to transmit a torque load from the first component to the second component. The face coupling may include a plurality of driving teeth extending axially from the first component. Each driving tooth may have a driving tooth pressure surface and a driving tooth tip edge adjacent to the driving tooth pressure surface. The face coupling may also include a plurality of driven teeth extending axially from the second component. Each driven tooth may have a driven tooth pressure surface. The plurality of driving teeth and the plurality of driven teeth may be structured to cooperate to transmit the torque load from the first component to the second component via the driving tooth pressure surfaces acting against the driven tooth pressure surfaces. The plurality of driven teeth may include a first root transition structured to prevent the driving tooth tip edge from contacting an adjacent driven tooth. 
         [0031]    In one refinement of the embodiment the root transition may include a root recess positioned opposite the driving tooth tip edge. 
         [0032]    In another refinement of the embodiment the root recess may include a fillet radius. 
         [0033]    In another refinement of the embodiment each driven tooth may have a driven tooth tip edge adjacent to the driven tooth pressure surface. The plurality of driving teeth may include a second root transition structured to prevent the driven tooth tip edge from contacting an adjacent driving tooth. 
         [0034]    In another refinement of the embodiment the root transition may include a root recess positioned opposite the driven tooth pressure surface tip edge. 
         [0035]    In another refinement of the embodiment the root recess may include a fillet radius. 
         [0036]    In another refinement of the embodiment the face coupling may be a face spline. The plurality of driving teeth and the plurality of driven teeth may be face spline teeth. 
         [0037]    In another refinement of the embodiment the face coupling may be a curvic coupling. 
         [0038]    Another embodiment of the present invention is a face coupling a face structured to transmit a torque load from a first component to a second component. The face coupling may include a plurality of driving teeth extending axially from the first component. Each driving tooth may have a driving tooth pressure surface and a driving tooth tip edge adjacent to the driving tooth pressure surface. The face coupling may also include a plurality of driven teeth extending axially from the second component. Each driven tooth may have a driven tooth pressure surface. The plurality of driving teeth and the plurality of driven teeth may be structured to cooperate to transmit the torque load from the first component to the second component via the driving tooth pressure surfaces acting against the driven tooth pressure surfaces. The plurality of driven teeth may include a first root transition structured to prevent the driving tooth tip edge from contacting an adjacent driven tooth. 
         [0039]    In one refinement of the embodiment the root transition may include a root recess positioned opposite the driving tooth pressure surface tip edge. 
         [0040]    In another refinement of the embodiment the root recess may include a fillet radius. 
         [0041]    In another refinement of the embodiment each driven tooth may have a driven tooth tip edge adjacent to the driven tooth pressure surface. The plurality of driving teeth may include a second root transition structured to prevent the driven tooth tip edge from contacting an adjacent driving tooth. 
         [0042]    In another refinement of the embodiment the root transition may include a root recess positioned opposite the driven tooth tip edge. 
         [0043]    In another refinement of the embodiment the root recess may include a fillet radius. 
         [0044]    In another refinement of the embodiment the face coupling may be a face spline. The plurality of driving teeth and the plurality of driven teeth may be face spline teeth. 
         [0045]    In another refinement of the embodiment the face coupling may be a curvic coupling. 
         [0046]    Another embodiment of the present invention is a face coupling structured to transmit a torque load from a first component to a second component. The face coupling may include a means for transmitting torque from the first component. The means for transmitting may be coupled to the first component. The coupling may also include a means for receiving torque from the means for transmitting. The means for receiving may be coupled to the second component. The face coupling may also include a first means for preventing a tip edge of the means for transmitting from contacting the means for receiving. 
         [0047]    In one refinement of the embodiment the first means for preventing may include a root recess. 
         [0048]    In another refinement of the embodiment the face coupling may include a second means for preventing a tip edge of the means for receiving from contacting the means for transmitting. 
         [0049]    In another refinement of the embodiment the second means for preventing may include a root recess. 
         [0050]    In another refinement of the embodiment the means for transmitting may be integral with the first component. The means for receiving may be integral with the second component. 
         [0051]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.