Patent Abstract:
A shaft assembly includes a shaft with a first radial shoulder and a second radial shoulder along a shaft axis. A seal retaining sleeve is defined around the shaft axis to position a shaft seal. A retainer plate at least partially between the first radial shoulder and the second radial shoulder is adjacent to the seal retaining sleeve to position and provide access to the seal retaining sleeve and shaft seal.

Full Description:
BACKGROUND 
       [0001]    The present disclosure relates to a pump, and more particularly to a fuel gear pump for gas turbine engines. 
         [0002]    Fuel gear pumps are commonly used to provide fuel flow and pressure for gas turbine engines and other systems on aircrafts. The gear pump must perform over a wide system operating range and provide critical flows and pressures for various functions. Typically, these pumps receive rotational power from an accessory gearbox through a drive shaft. 
         [0003]    In a fuel gear pump, a shaft seal is frequently used to seal internal fuel from entry into a shaft cavity. Typically, the shaft seal performance, most notably leakage, may be monitored throughout operation, where too much leakage may cause detrimental effects. In addition, the shaft seal may need to be periodically removed, examined, possibly repaired or replaced, then re-installed. Dependant on the arrangement of the unit, the shaft seal may be difficult to access, which is usually the case in a dual gear stage pump. 
       SUMMARY 
       [0004]    A shaft assembly according to an exemplary aspect of the present disclosure includes a shaft with a first radial shoulder and a second radial shoulder along a shaft axis. A seal retaining sleeve is defined around the shaft axis and a retainer plate at least partially between the first radial shoulder and the second radial shoulder is adjacent to the seal retaining sleeve. 
         [0005]    A gear pump according to an exemplary aspect of the present disclosure includes an input shaft which at least partially extends from a housing along an input shaft axis, the input shaft defines a first radial shoulder and a second radial shoulder. A seal retaining sleeve is located within a bore in the housing. A retainer plate is mounted to the housing at least partially between the first radial shoulder and the second radial shoulder to restrain an axial position of the input shaft, and the retainer plate is adjacent to the seal retaining sleeve. 
         [0006]    A method of installing a shaft assembly within a housing according to an exemplary aspect of the present disclosure includes positioning a shaft seal within a bore in the housing, a seal retaining sleeve within the bore in the housing, and a shaft at least partially within the bore through the seal retaining sleeve and the shaft seal along a shaft axis. Attaching a retainer plate to the housing, the retainer plate is located at least partially between a first radial shoulder and a second radial shoulder to restrain an axial position of the shaft, and the retainer plate is adjacent to the seal retaining sleeve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0008]      FIG. 1  is a block diagram of a gear pump driven by an accessory gearbox to communicate a fluid such as fuel to a gas turbine; 
           [0009]      FIG. 2  is an end view of a gear pump; 
           [0010]      FIG. 3  is a sectional view of the gear pump taken along line  3 - 3  in  FIG. 2 ; 
           [0011]      FIG. 4  is a sectional view of the gear pump taken along line  4 - 4  in  FIG. 2 ; 
           [0012]      FIG. 5  is a perspective view of the gear pump with the housing removed; 
           [0013]      FIG. 6  is another perspective view of the gear pump with the housing removed; 
           [0014]      FIG. 7  is another perspective view of the gear pump with the housing removed; 
           [0015]      FIG. 8  is a perspective view of the gear pump from the same perspective as in  FIG. 5 ; 
           [0016]      FIG. 9  is a perspective view of the gear pump from the same perspective as in  FIG. 7 ; 
           [0017]      FIG. 10  is a perspective view of the gear pump from the same perspective as in  FIG. 6 ; 
           [0018]      FIG. 11  is an expanded sectional view of an input shaft assembly of the gear pump; 
           [0019]      FIG. 12  is an end view of a retainer plate of the input shaft assembly; 
           [0020]      FIG. 13  is an expanded sectional view of an input shaft assembly of the gear pump while being installed into an accessory gearbox; 
           [0021]      FIG. 14  is an end view of the input shaft assembly of the gear pump; 
           [0022]      FIG. 15  is a perspective isometric view of the seal retaining sleeve; 
           [0023]      FIG. 16  is an expanded sectional view of the seal retaining sleeve with a sensor system integrated therewith; 
           [0024]      FIG. 17  is a side view of one dimensional embodiment of a seal retaining sleeve; and 
           [0025]      FIG. 18  is a side view of another dimensional embodiment of a seal retaining sleeve. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  schematically illustrates a gear pump  20  driven by an accessory gearbox  22  to communicate a fluid such as fuel to a gas turbine  24 . It should be appreciated that the present application is not limited to use in conjunction with a specific system. Thus, although the present application is, for convenience of explanation, depicted and described as being implemented in an aircraft fuel pump, it should be appreciated that it can be implemented in numerous other systems. In addition, although a dual stage gear pump is disclosed, other machines with a shaft will also benefit herefrom. 
         [0027]    With reference to  FIG. 2 , the gear pump  20  generally includes a housing  30  that includes an input shaft assembly  32  and a coupling shaft assembly  34  to power a main stage  36  and a motive stage  38  ( FIGS. 3 and 4 ). Rotational power is transferred from the gas turbine  24  to the accessory gearbox  22  then to the gear pump  20  through the input shaft assembly  32 . In the disclosed, non-limiting embodiment, the input shaft assembly  32  interfaces with the accessory gearbox  22  and receives a lubricant therefrom while the coupling shaft assembly  34  is lubricated with fuel. 
         [0028]    With reference to  FIG. 3 , the input shaft assembly  32  is defined along an input axis A and the coupling shaft assembly  34  is defined along a coupling axis B parallel to the input axis A. The main stage  36  generally includes a main drive gear  40 , a main driven gear  42 , a main drive bearing  44  and a main driven bearing  46 . The motive stage  38  generally includes a motive drive gear  50 , a motive driven gear  52 , a motive drive bearing  54  and a motive driven bearing  56  ( FIG. 4 ). 
         [0029]    The main drive gear  40  is in meshed engagement with the main driven gear  42  and the motive drive gear  50  is in meshed engagement with the motive driven gear  52  ( FIGS. 5-7 ). The input shaft assembly  32  drives the coupling shaft assembly  34  through the main stage  36  to drive the motive stage  38 . A boost stage  58  is also driven by the input shaft assembly  32  to define a centrifugal pump with an impeller and integrated inducer. 
         [0030]    The stages  36 ,  38 ,  58  work mostly independently. Each stage  36 ,  38 ,  58  includes a separate inlet and discharge ( FIGS. 8-10 ). As the meshed gears  40 ,  42  and  50 ,  52  rotate, respective volumes of fluid are communicated from the main stage inlet MI to the main stage discharge MD and from a motive stage inlet ml to a motive stage discharge mD such that the main stage  36  communicates a main fuel flow while the motive stage  38  supplies a motive fuel flow. The main stage inlet MI and main stage discharge MD as well as the motive stage inlet ml and motive stage discharge mD are respectively directed along generally linear paths through the respective gear stage  36 ,  38 . 
         [0031]    In the disclosed non-limiting embodiment, an aircraft fuel system provides flow and pressure to the boost stage inlet BI. A portion of the boost stage discharge is routed internally to the motive stage inlet ml. The remainder of the boost stage discharge is discharged from the gear pump  20  to the aircraft fuel system, then returns to the main stage inlet MI. The motive stage discharge mD is communicated to the aircraft fuel system. The main stage discharge MD is also communicated to the aircraft fuel system to provide at least two main functions: actuation and engine burn flow. There may be alternative or additional relatively minor flow directions and functions, but detailed description thereof need not be further disclosed herein. 
         [0032]    With reference to  FIG. 11 , the input shaft assembly  32  includes an input shaft  60 , a spring  62  and a retainer plate  64 . The input shaft  60  is a hollow shaft with splined end sections  66 A,  66 B and radial shoulders  68 A,  68 B therebetween. The splined end section  66 A plugs into a gear G of the accessory gearbox  22 . The splined end section  66 B interfaces with the main drive gear  40 . 
         [0033]    The radial shoulders  68 A,  68 B are generally aligned with the housing  30  to receive the retainer plate  64  therebetween. The retainer plate  64  is attached to the housing  30  through fasteners  70  such as bolts (also illustrated in  FIG. 2 ) to position an interrupted opening  65  between the radial shoulders  68 A,  68 B. The interrupted opening  65  in one disclosed non-limiting embodiment is an arcuate surface with an interruption less than 180 degrees ( FIG. 12 ). The axial position of the input shaft  60  is thereby axially constrained by the interaction of the radial shoulders  68 A,  68 B and to the retainer plate  64 . 
         [0034]    With reference to  FIG. 13 , the spring  62  biases the input shaft assembly  32  to position the input shaft assembly  32  during gear pump operation. That is, the spring  62  allows the input shaft assembly  32  to move in the housing  30  in response to impact loads, until the input shaft assembly  32  bottoms out on the retainer plate  64 , but during operation, the spring  62  positions the input shaft assembly  32  such that the radial shoulders  68 A,  68 B are spaced from the retainer plate  64 . This assures there are no rotational to stationary part contact during operation. 
         [0035]    The input shaft assembly  32  rotationally mounts the input shaft  60  within a shaft bore  80  which contains a shaft seal  82  such as that manufactured by Qualiseal Technology of Illinois USA and a seal retaining sleeve  84 . The shaft seal  82  is located within the shaft bore  80  then the seal retaining sleeve  84  is located within the shaft bore  80  to position the shaft seal  82  between the seal retaining sleeve  84  and the main drive gear  40 . The retainer plate  64 , through removable attachment to the housing  30  through the fasteners  70 , retains the seal retaining sleeve  84  and thereby the position of the shaft seal  82  ( FIG. 14 ). 
         [0036]    The shaft seal  82  seals fuel from the main stage  36  and the motive stage  38  into the shaft bore  80  then potentially into the accessory gearbox  22 . Performance of the shaft seal  82 , most notably leakage, may be monitored throughout operation, where too much leakage may cause detrimental effects. The shaft seal  82  may periodically require maintenance or replacement. Removal of the shaft seal  82  is facilitated by removal of the retainer plate  64  and the seal retaining sleeve  84  as compared to conventional systems which locate the shaft seal deep within the housing. That is, unlike many conventional designs, the gear pump  20  does not have to be mostly or completely disassembled in order to access and remove the shaft seal  82 . 
         [0037]    The seal retaining sleeve  84  includes radial end flanges  86 ,  88  which may be of different diameters ( FIG. 15 ). The different diameters facilitate the assembly-proof location of the seal retaining sleeve  84  into the shaft bore  80  which reduces in diameter toward the shaft seal  82 . The reduced diameter shaft bore  80  over the axial length thereof further facilitates and eases location of the shaft seal  82  through the shaft bore  80 . 
         [0038]    The seal retaining sleeve  84  includes apertures  90  which facilitate removal through receipt of a tool (not shown) which engages the apertures  90 . The apertures  90  may further permit receipt of a sensor system S (illustrated schematically;  FIG. 16 ) or other monitor which, for example only, senses and tracks the position of the seal retaining sleeve  84  relative the shaft bore  80  which monitors wear of the shaft seal  82 . Alternatively, or additionally, the sensor system S may be utilized to detect any fuel leakage past the shaft seal  82  and into the seal retaining sleeve  84  and the shaft bore  80 . It should be understood by those skilled in the art with the benefit of this disclosure that these functions may be enacted in either dedicated hardware circuitry or programmed software routines capable of execution in a microprocessor based electronics control embodiment. In one non-limiting embodiment, the module may be a portion of a flight control computer, a portion of a central vehicle control, an interactive vehicle dynamics module, a stand-alone line replaceable unit or other system. 
         [0039]    The seal retaining sleeve  84  may alternatively or additionally include anti-rotation features  92  such as flats (illustrated;  FIG. 15 ), grooves, keys, or other features to further rotationally assembly-proof and align the seal retaining sleeve  84  for specific leakage, performance and assembly monitoring. 
         [0040]    With reference to  FIG. 17 , the seal retaining sleeve  84  defines an overall axial length SA along the axis of rotation A and an outer diameter dimension SD of the radial end flange  86 . It should be understood that the radial end flange  86  in the disclosed non-limiting embodiment defines the maximum outer diameter dimension to closely fit into the shaft bore  80  opposite the shaft seal  82 , however, other maximum outer diameter surfaces may alternatively or additionally be utilized herewith. 
         [0041]    The axial dimension SA in one disclosed non-limiting dimensional embodiment is 1.600-2.000 inches (40.6-50.8 mm) with a nominal dimension of 1.800 inches (45.7 mm). The maximum outer diameter dimension SD in this disclosed non-limiting dimensional embodiment is 1.368-1.768 inches (34.7-44.9 mm) with a nominal maximum outer diameter dimension of 1.568 inches (39.8 mm). In this disclosed non-limiting dimensional embodiment, a ratio of SD/SA is defined between 0.68-1.11. 
         [0042]    With reference to  FIG. 18 , another non-limiting embodiment of the seal retaining sleeve  84 ′ defines an overall axial length SA along the axis of rotation A and an outer diameter dimension SD of the radial end flange  86 ′. 
         [0043]    The axial dimension SA in another disclosed non-limiting dimensional embodiment is 1.695-2.095 inches (43.1-53.2 mm) with a nominal dimension of 1.895 inches (48.1 mm). The maximum outer diameter dimension SD in this disclosed non-limiting dimensional embodiment is 1.174-1.574 inches (29.8-40.0 mm) with a nominal maximum outer diameter dimension of 1.374 inches (34.9 mm). In this disclosed non-limiting dimensional embodiment, a ratio of SD/SA is defined between 0.69-0.93. The disclosed ratios permit the seal retaining sleeve  84  to closely fit into the shaft bore  80  and properly locate the shaft seal  82  as retained by the retainer plate  64 . 
         [0044]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
         [0045]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0046]    The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.

Technology Classification (CPC): 5