Abstract:
Reversely identical transmissions for a tiltrotor aircraft may include reconfigurable gearbox lubrication systems to accommodate operation in either direction of propeller rotation, using common parts. In a typical installation, at least two separate winged tiltrotor transmissions may operate with opposing propeller rotations. Common parts of the two transmissions may include cast housings, rotor shafts, pinion gears, lubrication sump tanks, lubrication pumps, and lubrication filter manifolds including filters having reversible orientations. Either transmission configuration may be utilized on either the left or right side of a tiltrotor aircraft by swapping the lubrication sump tank and lubrication filter manifold locations on the gearbox. In addition, a plug may be used to manually reconfigure an opposite lubrication oil path to accommodate first and second rotational directions of the lubrication pump.

Description:
FIELD 
       [0001]    The present disclosure relates generally to tiltrotor transmission oil lubrication systems, and more specifically to use of common parts employed in their manufacture to reduce part count and complexity. 
       BACKGROUND 
       [0002]    Modern aircraft construction typically involves assembly of a voluminous number of parts and subassemblies. Efforts to minimize sheer numbers of parts are continuously being sought, as any reductions in physical numbers of parts translate directly into cost savings, as well as reduced complexity of structures involved. 
         [0003]    In today&#39;s manufacturing environment, many of the subassemblies may be contracted to third parties for manufacture and subsequent installation into the overall aircraft structure. The simpler the subassembly, the simpler and less expensive will be overall costs of an aircraft. 
         [0004]    Toward this end, efforts have been directed to maximizing interchangeability of parts in, for example, left and right side airframe devices, such as left-hand and right hand transmissions or gearboxes utilized in tilt rotor aircraft. Such interchangeability, for example, may permit one gearbox to be rotatable in a clockwise direction, while the other, using interchangeable or common parts, may be rotatable in a counterclockwise direction. 
       SUMMARY 
       [0005]    In accordance with one aspect of the present disclosure, a gearbox for a tiltrotor aircraft includes housing, and a gear rotatably fixed within the housing. The gear is configured to rotate in opposite first and second directions. The housing contains a lubrication system having a reversely rotatable lubrication pump. Rotation of the gear is configured to control rotation of the pump in either the first or second direction of rotation. 
         [0006]    In accordance with another aspect of the present disclosure, the lubrication system includes a filter manifold, and the housing has a first attachment interface and a second attachment interface. The filter manifold is configured to be coupled to the first attachment interface when the gear is rotating in the first direction, and the filter manifold is configured to be coupled to the second attachment interface when the gear is rotating in the second direction. 
         [0007]    In accordance with another aspect of the present disclosure, the lubrication system includes a sump tank; and the housing includes a first attachment interface and a second attachment interface; and the sump tank is configured to be coupled to the second attachment interface when the gear is rotating in the first direction; and the sump tank is configured to be coupled to the first attachment interface when the gear is rotating in the second direction. 
         [0008]    In accordance with another aspect of the present disclosure, the first and second attachment interfaces of the housing have identical footprints, and the gearbox is configured to have a vertical orientation, a horizontal orientation, and orientations between the vertical and horizontal orientations during operation on one wing of a tiltrotor aircraft. The gear is configured to rotate in a direction corresponding to that of a propeller on each wing of a tiltrotor aircraft having two wings, with each wing supporting a different direction of rotation of each propeller. 
         [0009]    In accordance with another aspect of the present disclosure, the gearbox incorporates common parts irrespective of direction of rotation of the gear, the common parts including a cast housing, a rotor shaft, a pinion gear, an oil sump tank, and the filter manifold. The filter manifold contains a filter, and the filter can be used in either the first or second attachment interface upon rotation of the filter manifold 180° to accommodate a reversed oil flow direction, and the lubrication pump is a positive displacement pump rotatable in either the first or second directions of rotation. 
         [0010]    In accordance with yet another aspect of the present disclosure, a method of making a gearbox for a tiltrotor aircraft includes the steps of: forming a housing having a gear rotatably fixed within housing, the gear being configured to rotate in opposite first and second directions of rotation; configuring a lubrication system within the housing, the lubrication system including a reversely rotatable pump such that the gear controls rotation of the pump in either the first or the second direction of rotation. The method may further include the step of configuring a first attachment interface and a second attachment interface on the housing, and forming the interfaces to have identical footprints. 
         [0011]    The features, functions, and advantages disclosed herein can be achieved independently in various embodiments or may be combined in yet other embodiments, the details of which may be better appreciated with reference to the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a tiltrotor aircraft having left and right side transmission or gearboxes constructed in accordance with the present disclosure. 
           [0013]      FIG. 2  is a view of the left side transmission or gearbox of  FIG. 1 . 
           [0014]      FIG. 3  is a view of the right side transmission or gearbox of  FIG. 1 . 
           [0015]      FIG. 4  is a cross-sectional schematic depiction of the left side transmission or gearbox of  FIG. 2 , as viewed along lines  4 - 4 , thereof. 
           [0016]      FIG. 5  is a cross-sectional schematic depiction of the right side transmission or gearbox of  FIG. 3 , as viewed along lines  5 - 5 , thereof. 
           [0017]      FIG. 6A  is a view along lines  6 A- 6 A of  FIG. 2 . 
           [0018]      FIG. 6B  is a view along lines  6 B- 6 B of  FIG. 3 . 
       
    
    
       [0019]    It should be understood that the drawings are not necessarily to scale, and that the disclosed embodiments are illustrated only schematically. It should be further understood that the following detailed description is merely exemplary and not intended to be limiting in its application or uses. As such, although the present disclosure is for purposes of explanatory convenience only depicted and described in illustrative embodiments, the disclosure may be implemented in numerous other embodiments, and within various systems and environments not shown or described herein. 
       DETAILED DESCRIPTION 
       [0020]    The following detailed description is intended to provide both apparatus and methods for carrying out the disclosure. Actual scope of the disclosure is as defined by the appended claims. 
         [0021]    In  FIG. 1 , a tiltrotor aircraft  10  is displayed; the aircraft  10  is constructed as an unmanned aerial vehicle, although the principles of this disclosure may apply generally to unmanned as well as manned aircraft. The tiltrotor aircraft  10  includes a fuselage  12  oriented along a fore and aft axis “x-x”, as shown. The tiltrotor aircraft  10  includes a left wing  14  having a wingtip  14 ′, and a right wing  16  having a wingtip  16 ′. The left and right wings  14 ,  16  are oriented along a lateral axis “y-y”, which extends orthogonally to the “x-x” axis. 
         [0022]    As depicted in  FIG. 1 , the tiltrotor aircraft  10  is in a forward flight mode. However, it will be appreciated that the tiltrotor aircraft  10  is a flying machine that includes a hovering capability, as would be typical of a helicopter, in addition to conducting straight forward flight as a basic airplane. For transitioning between its hovering and flight modes, the aircraft  10  includes a left wing engine assembly  20 , having a propeller  20 ′, and a right-wing engine assembly  22 , having a propeller  22 ′, each of which engine assemblies  20 ,  22  are capable of being rotated between horizontal (as shown) and vertical orientations, including any orientation in between, depending on desired performance and mode. In the hovering mode, the engine assemblies  20 ,  22  are oriented vertically (as shown only in  FIGS. 2 and 3 ) such that their propellers  20 ′,  22 ′ are oriented upwardly along an axis “z-z” ( FIG. 1 ), orthogonal to each of the described axes, “x-x” and “y-y”. 
         [0023]    For purposes of hovering, engine assemblies  28  and  30  housed within the fuselage  12  can become operational. The engine assembly  28  is situated in a forward portion of the fuselage  12  along the axis x-x, as shown, and includes a propeller  28 ′permanently oriented along the z-z axis. The engine assembly  30 , on the other hand, is situated in a rear portion of the fuselage  12 , also along the axis x-x, and includes a propeller  30 ′ that is also permanently oriented along the z-z axis. As situated, the forward engine assembly  28  is near the nose  18  of the aircraft  10 , as shown, while the rear engine assembly  30  is just forward of the tail portion, or empennage  34 , of the aircraft  10 . 
         [0024]    Referring now also to  FIG. 2 , a transmission  40 R is depicted; the transmission is associated with the right-wing engine assembly  22 . The transmission  40 R, which may be also referred to as a gearbox is one of four transmissions depicted in  FIG. 1 , the others being transmission  40 L, associated with the left wing engine assembly  20 ; transmission  40 F, associated with the front fuselage engine assembly  28 ; and transmission  40 A, associated with the aft fuselage engine assembly  30 , as described above. 
         [0025]    Transmission  40 R includes a housing  42 R, which may be cast as shown, and which may incorporate a main gear  44 R driven by a pinion input gear  48 R. In the view of  FIG. 2 , the transmission  40 R is shown in its vertical or hovering orientation, and the pinion input gear  48 R is oriented along the axis y-y of  FIG. 1  (although the pinion gear  48 R is only visible in  FIG. 2 ). The transmission  40 R includes a lubrication system  46 R, as do the other transmissions  40 , as will be appreciated by those skilled in the art. 
         [0026]    Referring now also to  FIG. 3 , the transmission  40 L is depicted as being reversely similar to the transmission  40 R of  FIG. 2 , as described. In the transmission  40 L, a similar housing  42 L also incorporates a main gear  44 L, driven by a pinion input gear  48 L. Again, in the view of  FIG. 3 , the transmission  40 L is shown in its vertical or hovering orientation, and the pinion input gear  48 L is also oriented along the axis y-y of  FIG. 1  (although the pinion gear  48 L is only visible in  FIG. 3 ). Similarly, the transmission  40 L includes a lubrication system  46 L. 
         [0027]    The configurations of the two transmissions  40 R and  40 L are such that common parts may be used between them, in a manner to be described. It should be noted that interior lubrication oil paths ( 66 R and  66 L of  FIGS. 4 and 5 ) of the lubrication systems  46 R and  46 L are configured to move in opposite directions, to the extent that the pinion gear  48 R of the transmission  40 R is configured to rotate counterclockwise, in the view of  FIG. 2  as shown, while the pinion gear  48 L is configured to rotate clockwise in the corresponding view of  FIG. 3 . In both  FIGS. 2 and 3 , vertically oriented rotor shafts  70 R and  70 L are shown, each of which is configured to have a propeller  22 ′ and  20 ′, respectively, secured thereto. 
         [0028]    Referring now to  FIGS. 4 and 5 , it will be apparent that the pinion gear  48 R of  FIG. 4  drives a reversely rotatable oil pump  50 R, while the pinion gear  48 L of  FIG. 5  drives a reversely rotatable oil pump  50 L. As noted, the flow path of the lubrication oil in  FIG. 4  is clockwise, indicated by the arrows  66 R. Thus, in the configuration of the transmission  40 R of  FIG. 4 , the pump  50 R pulls the oil from a sump tank  58 R (on the right side in the view of  FIG. 4 ), and moves it through an oil filter  68 R (visible only in view of  FIG. 6A ) in a filter manifold  54 R, before distributing it in a clockwise direction to lubrication jets (indicated by the vertical arrow). Conversely, in the configuration of the transmission  40 L of  FIG. 5 , the pump  50 L pulls the oil from a sump tank  58 L (on the left side in the view of  FIG. 5 ), and moves it through a filter  68 L ( FIG. 6B ) and a filter manifold  54 L, before distributing it in a counterclockwise direction (arrows  66 L), and ultimately to lubrication jets (vertical arrow). 
         [0029]    The filter manifolds  54 R and  54 L, as well as the sump tanks  58 R and  58 L can be readily interchanged to permit the configuring of a transmission  40 R and  40 L for use on either the right or left wings  16 ,  14  of the tiltrotor aircraft  10 . For this purpose, the respective transmissions  40 R and  40 L each have a first attachment interface  60 R and  60 L, and a second attachment interface  62 R and  62 L. The attachment interfaces  60  and  62  are essentially mounting pads for the respective filter manifolds  54 R and  54 L, and sump tanks  58 R and  58 L, that have virtually identical footprints, even including similar patterns of bolt-holes  74 R and  74 L ( FIGS. 6A and 6B ), and thus may be entirely interchangeable. As such, to configure a left-wing transmission  40 L, in lieu of a right-wing transmission  40 R, the filter manifold  54  and respective sump tank  58  can be positionally swapped. Continuing reference to  FIGS. 4  and  5 , plugs  64 R and  64 L are also installed within the lubrication systems  46 R and  46 L, respectively, to prevent oil flow through either undesired portion of the oil flow path  66 R or  66 L, since each lubrication system  46 R,  46 L has an opposite direction of rotation, as will be appreciated by those skilled in the art. 
         [0030]    Referring now to  FIGS. 6A and 6B , respective oil filters  68 R and  68 L may be secured in place within respective oil filter manifolds  54 R and  54 L via securement means  80 R and  80 L to respective housings  42 R and  42 L. Since the transmissions  40 R and  40 L have opposite lubrication flow paths, the filters  68 R,  68 L may be slightly offset as shown on the manifolds, so as to be seamlessly interchangeable by simply reversing orientation of the filter manifold, i.e. by turning same 180°, to accommodate oil flow direction, e.g. “oil in” or “oil out” as reflected by filter indicators  72 R and  72 L. 
         [0031]    In the described structures of the transmissions  40 R and  40 L, common parts would at least include the cast housing  42 R,  42 L, the rotor shafts  70 R,  70 L, the pinion gears  48 R,  48 L, the oil sump tanks  58 R,  58 L, oil pumps  50 R,  50 L, filters  68 R,  68 L, and the filter manifold  54 R,  54 L, along with numerous other parts, including bearings and seals, not shown. For example, assuming straight bevel gears are used in pumping oil, the main gears  44 R,  44 L, and the pinion input gears  48 R,  48 L may be common to both transmissions  40 R,  40 L. If, on the other hand, the gears are spiral bevel gears, then above-described common parts could be utilized except for unique left-hand and right-hand gear sets to accommodate the latter. 
         [0032]    Based on the foregoing, those skilled in the art will appreciate that the term “common” as used throughout refers to interchangeability of above-described parts of the transmissions  40 R and  40 L. As such, among the various aspects described herein, the filter manifolds  54 R and  54 L, and the sump tanks  58 R and  58 L may, respectively, be mounted on either of the pads  60  and  62 , depending on desired direction of pump rotation and resulting flow path  66 R or  66 L. 
         [0033]    A method of making a gearbox for a tiltrotor aircraft may include the steps of: forming a housing having a gear rotatably fixed within the housing, the gear being configured to rotate in opposite first and second directions of rotation; configuring a lubrication system within the housing, the lubrication system including a reversely rotatable pump such that rotation of the gear controls rotation of the pump in either the first or the second direction of rotation. The method may further include the step of configuring a first attachment interface and a second attachment interface on the housing, and forming the interfaces to have identical footprints. 
         [0034]    The disclosed transmissions/gearboxes  40 R and  40 L may have other variations and alternative constructions neither described nor suggested herein. For example, although described only in terms of use with or in a tiltrotor aircraft, other configurations and components of transmissions/gearboxes may be utilized in other types of aircraft, and potentially in other environments. Moreover, although the components described may have been formed only in shapes and sizes depicted, numerous variations of the disclosed structures may be envisioned for use in constructing alternative embodiments of aircraft  10  and transmissions  40 , as may be appreciated by those skilled in the art.