Abstract:
An oil transfer assembly supplies oil into a moving, rotating tube extending along an axis. The assembly is provided with a support plate transversal to the axis and a sleeve, which is angularly fixed with respect to the support plate, it is configured to be coupled in a sliding and watertight way to a terminal section of the inlet of said tube and has at least one chamber for transferring oil into said terminal section of the inlet. The assembly is also equipped with at least two tubular bodies, which project axially from the support plate, define between them an annular channel communicating with the chamber and join the sleeve to the support plate in a watertight manner and with clearances so as to leave freedom of orientation of the sleeve around any direction orthogonal to the axis.

Description:
BACKGROUND 
       [0001]    Embodiments of the present invention relate to an oil transfer assembly for supplying oil into a moving, rotating tube. In particular, the present description refers explicitly to a tube that transfers oil to the nose cone of a propeller driven by a planetary gearbox, without loss of generality as a result. 
         [0002]    In aeronautical turbo-propeller engines, it is known how to provide a planetary gearbox to operate a drive shaft that supports the propeller and makes it rotate. In general, the nose cone of the propeller has inside it a hydraulic actuator which is controlled in such a way as to vary the pitch of the propeller blades and is supplied with oil through a tube, normally called a beta tube. This tube extends along the axis of the propeller and the drive shaft and has an intermediate section supported inside the nose cone of the propeller and an axial end housed in the drive shaft. When in use, this tube rotates together with the propeller and translates axially upon activation of the hydraulic actuator. 
         [0003]    The need has been felt for supplying oil in this tube to the hydraulic actuator, without providing radial holes through the drive shaft. It is also appropriate to provide for such arrangements so as to compensate for the imperfect alignment between the axial ends of the tube, due to inevitable assembly tolerances and processing and to the distortions due to the operating loads. 
       BRIEF DESCRIPTION 
       [0004]    The purpose of the embodiments of the present invention is to provide an oil transfer assembly for supplying oil into a moving, rotating tube that allows for meeting the abovementioned requirements in a relatively simple manner and allows for performing the necessary maintenance operations in a relatively simple manner. 
         [0005]    According to an embodiment of the present invention, an oil transfer unit for supplying oil into a moving, rotating tube is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Embodiments of the present invention will now be described with reference to the attached drawings which illustrate an example of the embodiment without limitations, wherein: 
           [0007]      FIG. 1  is a diagram which shows, in a sectional view and with parts removed for clarity, an embodiment of the oil transfer assembly for supplying oil into a moving, rotating tube, according to an embodiment of the present invention; 
           [0008]      FIG. 2  shows the assembly from  FIG. 1  on an enlarged scale; 
           [0009]      FIGS. 3 and 4  show in perspective and in a sectional view, some of the components shown in  FIG. 2 ; and 
           [0010]      FIG. 5  is a different perspective view showing in detail the assembly of the previous figures. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    With reference to the simplified diagram of  FIG. 1 , the reference number  1  indicates an oil transfer assembly for supplying oil into a moving, rotating tube  2  (partially illustrated), which makes up part of a propeller  3  (partially illustrated) supported by a drive shaft  4 , normally also called a propeller shaft. The drive shaft  4  extends along a rotational axis  5 , is axially hollow and is driven by a planetary gearbox  6  (partially illustrated) housed in a drive housing  7 . 
         [0012]    As can be seen in  FIG. 2 , the planetary gearbox  6  comprises a satellite gear holder  8  (partially illustrated), in turn comprising a support plate  11  which extends transversely to the axis  4 , and is fixed with respect to the drive housing  7  in the particular example taken into consideration. At the same time, the drive shaft  4  is driven by a crown gear (not illustrated) of the planetary gearbox  6  by means of a bell-shaped element  12  (partially illustrated), so as to rotate around the axis  5 . In general, it cannot be ruled out that other configurations of the planetary gearbox  6  may be provided for transmitting the rotation motion to the drive shaft  4 . 
         [0013]    Again with reference to  FIG. 1 , the propeller  3  comprises an nose cone  14  and a number of blades  15 , for which the pitch can be adjusted by operating a hydraulic actuator (not illustrated), which is housed in the nose cone  14  and is supplied with oil through the tube  2 . The tube  2  also extends along the axis  5  and is supported in a manner not illustrated so as to rotate together with the propeller  3  around the axis  5  and in such a way as to translate axially in response to the activation of the hydraulic actuator. One of the axial ends of the tube  2  is coupled to the hydraulic actuator in a known way (not illustrated), while the opposite axial end is designated by the reference number  20 , extends inside the drive shaft  4  and defines an inlet for the oil. 
         [0014]    As can be seen in  FIG. 2 , the tube  2  has an axial channel  21  for the transfer of oil from the end  20  to the hydraulic actuator. More generally, however, a greater number of channels could be provided in the tube  2  for the axial transfer of oil, for example, in the case in which the hydraulic actuator of the propeller  3  is of the double-acting type. 
         [0015]    At the end  20 , the channel  21  is axially blind and, in particular, is watertight by an element  23  making up part of a sensor that provides a feedback signal on the axial position of the tube  2  and indicates, indirectly, the value of the pitch of the blades  15 . 
         [0016]    The end  20  is defined radially by a cylindrical outer surface  24  provided with one or more radial holes  26  in order to convey oil from the assembly  1  into the channel  21 . The assembly  1  comprises the plate  11 , a sleeve  28  fitted on the surface  24  and three tubular bodies  29 ,  30  and  31  that join the sleeve  28  to the plate  11 , so as to maintain the sleeve  28  in an axial position that is substantially fixed and angularly stopped around the axis  5  with respect to the plate  11 . 
         [0017]    The surface  24  and the sleeve  28  define two chambers  32 ,  33 , from which the oil flows directly into the holes  26 . In particular, the sleeve  28  comprises a tubular wall  34 , which is coaxial and spaced radially from the surface  24 , and three internal flanges  35  that protrude from the wall  34 , axially delimit the chambers  32 ,  33  and terminate with the respective cylindrical surfaces  36  joined to the surface  24  in a sliding and watertight manner with metal-to-metal coupling without any additional seal ring. Therefore, the sleeve  28  is perfectly concentric with the end  20 , while it ensures the sealing of the fluid when the oil goes from the chambers  32 ,  33  to the channel  21  through the holes  26 . 
         [0018]    The tubular bodies  29 ,  30 ,  31  radially delimit between their two annular channels  37 ,  38 , each of which communicates permanently with a related chamber  32 ,  33  through radial holes  39  made in the wall  34  in order to convey oil from the plate  11  to the chamber  32 ,  33 . According to variations not illustrated, the number of the chambers  32 ,  33  and of the corresponding channels  37 ,  38  may be other than two, for which there may be a different number of tubular bodies  29 ,  30 ,  31  to convey the oil to the sleeve  28  and support the sleeve  28  itself. 
         [0019]    The tubular bodies  29 ,  30 ,  31  project axially from the plate  11  in the axial cavity of the drive shaft  4  and, according to an embodiment of the present invention, they support the sleeve  28  “softly”, i.e. in such a way as to let the sleeve  28  float with respect to plate  11  with freedom to move around in any one direction orthogonal to the axis  5  and with the freedom to move radially. This freedom of movement of the sleeve  28  compensates for the inevitable concentricity tolerances of the end  20  with respect to the axis  5  and is conferred by the appropriate coupling clearances between the sleeve  28  and the tubular bodies  29 ,  30 ,  31  and/or between the tubular bodies  29 ,  30 ,  31  and the plate  11 ; these clearances are set during the phases of the project on the basis of the specific application, in particular, due to appropriate simulations on the computer. 
         [0020]    In particular, the tubular body  29  is the outermost one and comprises two end sections  40 ,  41  opposite each other: the section  40  is coupled to the plate  11  in a fixed position, for example, by means of screws  42 ; the section  41 , instead, is joined to an axial end  44  of the wall  34  in a fixed angular position and with coupling clearance in a radial and axial direction. As can be seen in  FIG. 5 , the angular locking is determined by the coupling between a tooth or projection  46  and a corresponding retention base  47 . In particular, the tooth  46  forms part of an outer flange  48  of the end  44 , while the base  47  is obtained in the section  41 . 
         [0021]    With reference to  FIG. 2 , the assembly  1  also comprises a plate with an axial stop  49  axially facing the section  41  and fixed to the latter, for example, by means of the screws  50 . The flange  48  is axially constrained, albeit with the aforesaid axial clearance between the section  41  and the plate  49 , to which the sleeve  28  remains in an axial position substantially fixed, as mentioned above. 
         [0022]    The tubular body  30  is between the tubular bodies  29  and  31  and comprises two end sections  51 ,  52  opposite one another: the section  51  engages a base  53  defined by a protruding collar  54  of the plate  11 ; the section  52 , instead, is fitted on an intermediate section  56  of the wall  34 . 
         [0023]    Similarly, the tubular body  31  includes two end sections  58  and  59 , of which the section  58  engages a base  60  defined by a protruding collar  61  of the plate  11 , while the section  59  is fitted on an axial end  64  of wall  34 , opposite the end  44 . 
         [0024]    The sections  40 ,  51  and  58  are joined to the plate  11  by means of respective sealing rings  65 ,  66 ,  67  for ensuring the seal of the inlet of the channels  37  and  38 . Similarly, the sections  41 ,  52  and  59  are joined to the outer surface of the wall  34  by the respective sealing rings  68 ,  69 ,  70  for ensuring the seal of the outlet of the channels  37  and  38 . 
         [0025]    To ensure the freedom of direction of the sleeve  28 , the sections  51  and  58  are not secured to the plate  11 , but are joined to the corresponding collars  54  and  61  in an axially sliding manner and with radial clearance so as to allow a slight rotation of the tubular bodies  30  and  31  around any direction orthogonal to the axis  5  and passing through the coupling zone (in practice, this rotation axis intersects the sealing rings  66  and  67 , which then define a virtual hinge). 
         [0026]    As an alternative or in combination with the freedom of movement provided for the sections  51  and  58  on the bases  53  and  60 , a similar relative freedom of movement may be provided between the sections  52  and  56  and between the section  59  and the end  64 . 
         [0027]    As can be seen in  FIGS. 3 and 4 , the tubular body  29  comprises an intermediate section  71  that is shaped internally so as to define a radial shoulder  72  and an axial shoulder  73  arranged around and, respectively, facing the section  52 , with pre-set clearances, which leave freedom of movement for the section  52  itself. In the meantime, the axial shoulder  73  is intermittent in a circumferential direction so as to allow the oil to flow out freely into the channel  37 . 
         [0028]    Similarly, the tubular body  30  comprises an intermediate section  76  that is shaped internally so as to define a radial shoulder  77  and an axial shoulder  78  arranged around and, respectively, facing the section  59 , with pre-set clearances that leave freedom of movement for the section  59  itself. In the meantime, the axial shoulder  78  is intermittent in a circumferential direction to allow the oil to flow out freely into the channel  38 . 
         [0029]    The shoulders  72 ,  73 ,  77  and  78  define respective bases that, when in use, place a limit on the freedom of movement of the tubular bodies  30  and  31 . In particular, the shoulders  73  and  78  prevent the tubular bodies  30  and  31  from axially disengaging the corresponding bases  53  and  60 . In addition, the shoulders  72  and  77  define a centering system that supports the tubular bodies  30  and  31  when the sleeve  28  is withdrawn axially from the tubular body  29 , for example, during maintenance operations, in order to be able to axially insert the sleeve  28  back into its original position relatively easily. 
         [0030]    With reference to  FIG. 2 , when in use, the oil passes through the plate  11  in the manner illustrated, so as to arrive at the inlet of the channels  37 ,  38 . Through the latter and through the holes  39 , the oil flows into the chambers  32 ,  33 . During normal operating conditions, the chamber  32  is closed, while the holes  29  are located at the chamber  33  and make the oil flow from the channel  38  into the tube  2 , which then conveys the oil to the hydraulic actuator of the propeller  3 . The chamber  32  communicates with the holes  29  and then transfers oil from the channel  37  to the tube  2  only in the case of the reverse thrust of the blades  15 . 
         [0031]    The rotation of the propeller  3  causes the rotation of the tube  2  around the axis  5 , but the actual axis of the end  20  may not perfectly coincide with the axis  5 , because of the tolerances of assembly and implementation and distortions due to the operating loads. These concentricity errors are, however, compensated for by the capacity that the sleeve  28  has to move with respect to the plate  11 , as a result of the clearances described above. In fact, the actual axis of the sleeve  28  and the end  20  can be arranged parallel to the axis  5  or can be slanted with respect to the axis  5 , as a result of the radial clearance that the sleeve  28  has with respect to the tubular body  29  and plate  11 . The axial clearance of the sleeve  28  with respect to the tubular body  29  is calibrated simply to allow the pitch of the sleeve  28  with respect to axis  5 , and not to allow a substantial axial translation. 
         [0032]    As mentioned above, it is possible to perform maintenance operations in a relatively simple manner after uncoupling the propeller  3  from the drive shaft  4  and removing the tube  2  from the sleeve  28 . In fact, continuing to operate from the side where the propeller  3  was mounted, the screws  50  are unscrewed so as to remove the plate  49 , in order to then axially withdraw the sleeve  28  from the tubular bodies  29 ,  30 ,  31 . 
         [0033]    As mentioned above, after removing the sleeve  28 , the section  52  of the tubular body  30  is supported radially on the shoulder  72  of the tubular body  29 , and the section  59  of the tubular body  31  is supported radially on the shoulder  77  of the tubular body  31 . In other words, the shoulders  72  and  77  stop the pitch of the tubular bodies  30  and  31  due to their weight and, therefore, they keep sections  41 ,  52  and  59  substantially aligned. It is thus possible to insert the sleeve  28  again in these sections  41 ,  52  and  59  at the end of the maintenance operations without any difficulty. 
         [0034]    From the above description, it is obvious that the assembly  1  makes it possible to supply oil into the channel  21  without providing radial holes through the drive shaft  4 , ensures the necessary watertight seal around the end  20  of the tube  2  during the operation and, at the same time, compensates the misalignment of the end  20  with respect to the axis of rotation  5  as a result of the clearances provided between the sleeve  28  and the plate  11 . 
         [0035]    The assembly  1  also has a relatively low number of components, which are manufactured and then assembled in a relatively simple manner. The same simplicity of assembly is also found in the maintenance operations which, in particular, can be performed from an axial side of the drive housing  7 , and not radially through the drive shaft  4 . 
         [0036]    From the foregoing it is evident that the assembly  1  can be subject to modifications and variations without thereby departing from the protective scope as defined by the attached claims. 
         [0037]    In particular, the sleeve  27  and/or the tubular bodies  29 ,  30 ,  31  may have dimensions and/or shapes different from those illustrated by way of example. 
         [0038]    Finally, the assembly  1  may be used in applications other from that of a propeller  3  of a turbo-propeller engine, for example, in facilities for wind energy and marine propulsion facilities. 
         [0039]    This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.