Abstract:
An aircraft engine starter assembly provides for liquid cooling of the clutch assembly and overrunning engine by integrating a pitot pump in the system. The system includes a starter motor, a torque transfer connection, a clutch assembly and the pitot pump. The torque transfer connection is adapted to be coupled to the aircraft engine. The clutch assembly is coupled to one of the starter motor or the torque transfer connection. The pitot pump is coupled to one or both of the torque transfer or the clutch assembly via a first oil line and a second oil line. The pitot pump comprises a pitot tube in fluidic communication with an oil reservoir for the delivery of oil under pressure to lubricate one or both of the torque transfer or the clutch assembly.

Description:
TECHNICAL FIELD 
   The present invention generally relates to engine starters and, more particularly, to an air turbine driven starter assembly for aircraft engines that incorporates a pitot pump for lubricating rotating components of the air turbine. 
   BACKGROUND 
   It is known in the art to provide engine starters that employ over-run clutches or one-way torque transfer gear assemblies between the starter motor and the engine. The over-run clutch or other one-way drive assembly allows the starter motor to turn the engine when the engine is substantially stationary, and then automatically disengage when the engine starts to run on its own, turning faster than the starter motor. During operation, lubrication of the over-run clutch and other moving parts is typically accomplished by a pump that operates in conjunction with the starter. Currently, either a small centrifugal, gear, or g-rotor (gerotor) pump is used to supply lubricating oil to the overrunning section of the air turbine starter. While such pump systems are useful, they suffer from a number of disadvantages, especially when applied to air turbine starters for aircraft engines. Among these disadvantages are complexity, reliability, cost, and sensitivity to altitude. Accordingly there continues to be a need for an improved lubricating method and pump for use in an engine starter, especially for aircraft engines. 
   Accordingly, it is desirable to provide an improved aircraft engine starter assembly that incorporates a pump for providing a lubricating fluid to rotating components housed within the starter assembly, including a clutch system, bearings, seals and gears. In addition, it is desirable that the improved aircraft starter assembly incorporate a means for lubricating the rotating components of the system in which the lubricating means is not sensitive to altitude. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
   BRIEF SUMMARY 
   An aircraft engine starter assembly has a torque transfer connection adapted to be coupled to the aircraft engine, a starter motor, a clutch assembly coupled to one of the starter motor or the torque transfer connection, and a pitot pump coupled to the overrunning section of the clutch assembly and delivering oil under pressure to lubricate one or both of the torque transfer or the clutch assembly. The pitot pump comprises a pitot tube in fluidic communication with a rotating oil reservoir. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
       FIG. 1  is a simplified schematic block diagram of an air turbine starter assembly according to the present invention; 
       FIG. 2  is a simplified partial cross-sectional view through a portion of the assembly of  FIG. 1 , showing further details; 
       FIG. 3  is an enlarged cross-sectional view of a portion of the assembly of  FIG. 2  showing still further details; and 
       FIG. 4  is an enlarged cross-sectional view of yet another portion of the assembly of  FIG. 2  showing still further details. 
   

   DETAILED DESCRIPTION 
   The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     FIG. 1  is a simplified schematic block diagram of air turbine starter assembly  20  according to the present invention. Assembly  20  comprises air turbine starter motor  22 , generally including reduction gear  21 , a clutch assembly  24 , an aircraft engine  26  and an internal pitot pump  28 . When it is desired to start aircraft engine  26 , air turbine starter motor  22  provides torque over a connection  23  to clutch assembly  24 . Provided that a torque transfer connection  25  between clutch assembly  24  and aircraft engine  26  is stopped or turning slower than connection  23 , clutch assembly  24  engages and transfers torque over torque transfer connection  25  to aircraft engine  26 , causing it to turn. At the same time, the rotation of torque transfer connection  25  causes pitot pump  28  to pump oil  29  to clutch assembly  24 , thereby preventing frictional damage. 
   As aircraft engine  26  begins to operate, the rotational speed of torque transfer connection  25  increases and gradually exceeds the rotational speed of connection  23 . When this occurs, clutch assembly  24  automatically releases and acts as an over-running clutch allowing torque transfer connection  25  to rotate freely. Air turbine starter motor  22  and connection  23  can then stop, while an overrunning section remains operational. When aircraft engine  26  is running it supplies power over torque transfer connection  25  to turn a portion of clutch assembly  24  and drive pitot pump  28 . As long as engine  26  and torque transfer connection  25  are turning, pitot pump  28  provides pressurized lube oil  29  so that clutch assembly  24  can operate with low friction in the over-run mode. 
     FIG. 2  is a simplified partial cross-section view through a particular physical implementation of a portion  40  of assembly  20  of  FIG. 1 , showing more detailed, physical implementations of clutch assembly  24  and pitot pump  28 . In  FIG. 2 , only half the structure is shown, it being substantially rotationally symmetric about centerline and axis of rotation  41 . For convenience of description, the exterior housing around clutch assembly  24  and pitot pump  28  is not shown so that attention can be focused on the interior operating elements of portion  40 . 
   With the above background in mind, it is seen that portion  40  includes a substantially stationary frame member (stator)  42  that conveniently supports an inner race  43 - 1  and a bearing  43 . Portion  40  further includes a substantially stationary frame member (stator)  44  that conveniently supports a plurality of outer races  45 - 1 ,  47 - 1  of a plurality of bearings  45 ,  47 . While three bearings  43 ,  45 ,  47  are preferred, they are not essential. Bearing  43  coupling stator portion  42  and driving member  50  may be omitted. Driving member  50  is conveniently coupled via connection  23 , to the air turbine starter motor  22  via a spline or other attachment means  48 . Thus, connection  23  can also be used to support driving member  50 , but this is not essential. Similarly, while two bearings  45 ,  47  are desirably used to couple the stator  44  and a driven member  52 , this is not essential since the driven member  52  can be supported by the torque transfer connection  25 . However, at least one of the bearings  43 ,  45 ,  47  is convenient, two of the bearings  43 ,  45 ,  47  are desirable, and the three bearings  43 ,  45 ,  47  are preferred. For example, having at least two bearings  45 ,  47  coupling stator  44  and driven member  52  is desirable, since a double suspension reduces or eliminates radial whip in driven member  52  independent of connection  25 . This is especially desirable after engine start when driven member  52  is driven at high rotational speed by the torque transfer connection  25 . 
   Bearing  43  has outer race  43 - 2  supporting the driving member  50  and the bearings  45 ,  47  have inner races  45 - 2  and  47 - 2  supporting the driven member  52 . Driven member  52  is coupled to torque transfer connection  25  between the aircraft engine  26  and the clutch assembly  24 . Any convenient coupling means may be used and a spline, a rotating flex joint, a rigid mount, a vibration damper, or a combination thereof are non-limiting examples of suitable connections, depending upon the needs of the user and the type of aircraft engine  26  coupled to the torque transfer connection  25 . Persons of skill in the art will understand that a speed changing gearbox and other equipment (not shown) may be associated with the aircraft engine  26 , and for the purposes of this invention are assumed to be a part of the engine  26 . While member  52  is referred to for convenience of explanation as a “driven” member, persons of skill in the art will understand based on the explanation given herein that this status preferably occurs only during engine start when torque is being transmitted from the starter motor  22  through the clutch assembly  24  to the aircraft engine  26 . Once start has occurred, and the clutch assembly  24  has disconnected the input connection  23  and the output torque transfer connection  25 , then member  52  is being driven by the aircraft engine  26  through the torque transfer connection  25 . However, for consistency and to more easily distinguish the various rotating parts, member  52  will continue to be referred to as a “driven” member unless specifically noted otherwise, even though it is a driving member in post-start operation. 
     FIG. 3  is an enlarged cross-sectional view of a portion  80  of the portion  40  of  FIG. 2 , taken horizontally perpendicular to the plane of  FIG. 2  looking in the direction of arrow  79  on  FIG. 2 , and showing still further details. Referring now to  FIGS. 2 and 3  together, the driving member  50  has a face  54  that is conveniently, but not essentially, substantially perpendicular to the axis of rotation  41  of portion  40 . Set into the face  54  are one or more notches  62 . The driven member  52  has a face  70  that is conveniently, but not essentially, substantially perpendicular to the axis of rotation  41  of portion  40 . Set into the face  70  are one or more pockets  72 . Located in each of the pockets  72  is a moveable pawl or strut  74  having a first end  74 - 1  that mates with a first end  72 - 1  of the pocket  70  and a second distal end  74 - 2  that is urged outward from the face  70  by a spring  76  so as to engage the first end  62 - 1  of the notch  62  in the face  54  when member  50  is driving member  52 , and retract into the pocket  72  when the clutch assembly  24  is in the over-run operation mode, that is, not driving member  52 . Separating the faces  54  and  70  of the members  50  and  52  is an inter-plate space  78  filled with an oil  29  supplied by the pitot pump  28  via a channel  82 . The oil  29  conveniently returns to the pitot pump  28  via a channel  84  and others (not shown) that separate and/or penetrate the members  42 ,  50 ,  52  but this is not essential. Any convenient means of returning the oil  29  to the pitot pump  28  may be used. The combination of the pocket  72 , the strut or the pawl  74 , the notch  62 , the spring  76 , the pitot pump  28  and the other elements described herein, provide one type of clutch for use in the starter assembly  20 , commonly referred to as a planar ratcheting one way (PROW) clutch. Typically, a PROW clutch is utilized in that it is a quick engaging and releasing, low friction, one-way torque transfer mechanism. It should be understood that other more common types of clutches can be used in the starter assembly  20 , and that a PROW clutch is merely shown for exemplary purposes. 
   When the driving member  50  begins to turn, as soon as one or more of the pawls or struts  74  in the pockets  72  engages one or more of the notches  62  in the face  54  of driving member  50 , the pitot pump  28  supplies oil  29  to the inter-plate space  78  between the faces  54 ,  70  and the channels  85 ,  87 ,  89  to cushion the strut or pawl  74  as it rotates against the face  54  of the now stationary member  50 . In the preferred embodiment, the faces  54 ,  70  are substantially perpendicular to the axis of rotation  41 . However, this is convenient but not essential. Alternatively, the faces  54 ,  70  can be, for example and not intended to be limiting, cone shaped or cylindrically shaped, that is not substantially perpendicular to the axis of rotation  41  but forming a predetermined angle with the axis  41  or parallel to the axis  41 . Either arrangement is useful. What is more important is that the faces  54 ,  70  be substantially parallel and comparatively closely spaced so that one or more of the struts  74  may bridge between the pockets  72  and the notches  62  and so that the struts  74  are retained in the pockets  72  in the over-run state. Thus, in the preferred embodiment, the inter-plate space  78  between the faces  54  and  70  is small and readily filled by the oil  29  which provides a lubricating film on which the struts  74  ride against the face  54  when the clutch assembly  24  is in the over-run state. 
   The foregoing description has been in terms of the driving member  50  having the notch plate face  54  and the driven member  52  having the pocket and strut plate face  70 , but this is merely for convenience of explanation and not intended to be limiting. Persons of skill in the art will understand that the present invention works equally well when these roles are reversed, that is, when the face  70  with its associated pockets  72  and struts  74  is coupled to the driving member  50  in place of the face  54  and the face  54  with its associated pockets is coupled to the driven member  52  in place of the face  70 , that is the notch and pocket plates faces are swapped. Stated another way, the notch plate  54  can be coupled to either the starter motor  22  or the aircraft engine  26  and the strut pocket plate  70  is then correspondingly coupled to the other of the starter motor  22  or the aircraft engine  26 . Either arrangement is useful. 
   The inventive oil cooling system of the illustrated embodiment comprises the pitot pump  28  positioned in a trough as seen best in  FIGS. 2 and 4 . More specifically, pitot pump  28  is comprised of a trough, or annulus,  60  that is added to the overrunning section of the air turbine starter  20 . The overrunning section maintains rotation when the main aircraft engine  26  is running. The trough  60  is positioned at least partially below an oil level  64  (see  FIG. 4 ) of an oil reservoir  76 , so that rotation of the trough  60  causes oil to travel toward pitot pump  28 . The trough  60  is designed so that it dips into an oil reservoir  76  so that it is always full of oil. In this particular embodiment, the oil in oil reservoir  76  is contained by a structural member  78 . Alternatively, the oil reservoir  76  may be contained within the trough  60 . 
   The pitot pump  28  further comprises an elongated tube or conduit  66  which terminates in a tapered open end  68 . The elongated tube or conduit  66  is positioned into the trough  60  so that the spinning oil impacts the tube  66 . The tube  66  thus picks up the oil inside the rotating trough  60 . More specifically, oil in the trough  60  enters the open end  68  and expands through the taper thereby forming a pressure differential which forces the oil to flow through the tube or conduit  66 . The speed of the oil produces pressure going into the tube  66  and thus allows oil to flow through the tube  66  to the air turbine starter components that require lubricating oil while the engine is running. In  FIG. 4 , the trough is shown partially cut away to reveal the pitot tube  66 . 
   The cooling system transfers the lubricating fluid, or oil, from conduit  66  of pitot pump  28  via the oil channel  82  ( FIG. 2 ) to the overrunning section and any rotating components of starter  20 , and more particularly to the clutch assembly  24 . The oil channel  84  ( FIG. 3 ) returns the oil from the overrunning section, and more particularly the clutch assembly  24 , to the oil reservoir  76 . 
   It will be apparent that the circulating oil, propelled by the action of pitot pump  28 , removes heat from clutch assembly  24  as well as other rotating components within air turbine starter  20 . It will be seen that the cooling system of the present invention may be configured as a closed loop system where oil in the oil reservoir  76  is recirculated to remove heat from the clutch assembly  34  while also providing lubrication to the gears in air turbine system  20 . Thus, the present invention provides for the integration of a pitot pump as a lubricating means in an air turbine system which provides for an effective heat removal apparatus for sealed, high power engine components. 
   While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.