Abstract:
Apparatus for preventing incorrect installation of machinery components together includes a tab, pin and pin-receiving hole. The tab on the seal plate protrudes angularly from its periphery and laterally beyond it so as to prevent incorrect installation of two seal plates together in a faulty sealing relationship with machinery components by their tabs making interfering contact with one another producing a visible gap between the two seal plates. The pin is mounted on and protrudes axially from a surface of one machinery component facing the seal plate and prevents incorrect installation of the machinery components together in a faulty sealing relationship without the seal plate between them by the pin contacting the surface of the other machinery component and producing a gap between the machinery components. The hole extends through the seal plate to receive the pin within it when one seal plate is correctly installed between the machinery components.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to installation of components of machinery in a sealing relationship with one another and, more particularly, to apparatus for preventing incorrect installation of the machinery components together without a seal plate or with two seal plates therebetween. 
         [0002]    An auxiliary power unit for commercial and military aircraft typically includes a small gas turbine engine coupled to a generator or in some cases a starter generator (however, for purposes of brevity, hereinafter only the term “generator” will be used). The purpose of the auxiliary power unit is to provide electric and pneumatic power for aircraft systems while the aircraft is on the ground and in flight. 
         [0003]    The gas turbine engine of a typical auxiliary power unit has three main sections—the power section, the load compressor and the gearbox. The power section is the gas generator portion of the engine, producing all the rotary main shaft power for the auxiliary power unit. The load compressor is generally a main shaft-mounted compressor that provides all pneumatic power for the aircraft. The gearbox transfers power from the main shaft of the engine to the oil-cooled generator for production of electrical power. Within the gearbox, power is also transferred to engine accessories, such as the fuel control unit, the lube module, and the cooling fan. 
         [0004]    The generator is fitted to the gas turbine engine of the auxiliary power unit at the gearbox and typically is cooled by oil. The source of this oil is from the auxiliary power unit itself. These are called shared oil systems. In order to provide this supply of oil leak-free to the generator, a seal plate is installed between the gas turbine engine gearbox and the generator. If the seal plate is installed incorrectly, for example the seal plate is missing altogether or two or more seal plates are installed instead of only one, a substantial oil leak will occur, causing extreme damage to the auxiliary power unit due to loss of lubricating/cooling oil. 
         [0005]    As can be seen, there is a need for an innovation to prevent incorrect installation of the seal plate between the machinery components of an auxiliary power unit in order to ensure a leak-free condition in the installation. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect of the present invention apparatus for preventing incorrect installation of a seal plate between components of machinery comprises a plurality of elements on the seal plate and one of the machinery components which interact with one another and with the one machinery component to prevent incorrect installation of two or more seal plates together in a faulty sealing relationship between respective adjacent facing surfaces of the machinery components and incorrect installation of no seal plate between the machinery components. 
         [0007]    In another aspect of the present invention, in combination with machinery components adapted for installation together and a single seal plate adapted for installation between the machinery components such that opposite faces of the seal plate provide a sealing relationship with respective facing surfaces of the machinery components, apparatus for preventing an incorrect installation of the machinery components together with two or more of the seal plates installed therebetween comprises an angular tab rigidly attached on a peripheral edge of the seal plate having a bent configuration and predetermined length such that the tab protrudes radially outwardly from the peripheral edge of the seal plate and laterally past one of the opposite faces of the seal plate such that the tab overlies a peripheral portion of an adjacent one of the machine components and is contacted by a like angular tab on another seal plate due to an incorrect installation of two of the seal plates between the machinery components, the contact between the tabs preventing adjacent surfaces of the two seal plates from contacting one another in a faulty sealing relationship and instead producing a visible gap between the adjacent faces of the two seal plates. 
         [0008]    In a further aspect of the present invention a seal plate for sealing between two machinery components comprises a body having a thin planar annular configuration and radially spaced apart inner and outer peripheral edges, a pair of oppositely facing seal faces defined on the body between its inner and outer peripheral edges, and an angular tab fixedly attached to and protruding outwardly from the outer peripheral edge on the body and laterally beyond one of its seal faces so as to prevents incorrect installation of two seal plates together due to interfering contact between the tabs of the two seal plates, thus avoiding a faulty sealing relationship between respective adjacent facing surfaces of the two machinery components. 
         [0009]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a portion of an auxiliary power unit having a single seal plate correctly installed between a gearbox and generator of the auxiliary power unit; 
           [0011]      FIG. 2  is an enlarged fragmentary view of the auxiliary power unit in  FIG. 1  in which one of a plurality of elements in accordance with the present invention is seen in a position indicative of the seal plate being correctly installed between the gearbox and generator of the unit; 
           [0012]      FIG. 3  is a perspective view of the seal plate prior to installation in the auxiliary power unit of  FIG. 1 , showing the seal plate having two of the plurality of elements in accordance with the present invention for preventing an incorrect installation of the seal plate between the components of the auxiliary power unit; 
           [0013]      FIG. 4  is an enlarged fragmentary view of the seal plate in  FIG. 3  in which the two elements shown thereon are an angular tab protruding from and laterally beyond the outer peripheral edge of the seal plate and a pin-receiving hole extending fore and aft through the seal plate; 
           [0014]      FIG. 5  is a fragmentary perspective view of an auxiliary power unit showing an incorrect installation of two seal plates between the gearbox and generator of the unit which due to interfering contact between their respective angular tabs produces a visible gap between the seal plates which serves to alert an operator of the incorrect installation; 
           [0015]      FIG. 6  is an enlarged fragmentary view of the auxiliary power unit in  FIG. 5  showing the two seal plates and the visible gap produced between them; 
           [0016]      FIG. 7  is another fragmentary perspective view of an auxiliary power unit rotated counterclockwise approximately  900  from the position of the unit in  FIGS. 1 and 5  in which an incorrect installation of the gearbox and generator of the unit is shown which is due to the absence of a seal plate between them causing another element on one of the facing surfaces of the gearbox or generator to produce a visible gap between the gearbox and generator which serves to alert an operator of the incorrect installation; 
           [0017]      FIG. 8  is an enlarged fragmentary side view of a segment of an auxiliary power unit segment encompassed by circle A in  FIG. 7  in which the another element is a pin mount on and protruding from a facing surface of the gearbox into contact with a facing surface of the generator with the seal plate missing; 
           [0018]      FIG. 9  is an enlarged fragmentary view of the pin shown in  FIG. 8 ; and 
           [0019]      FIG. 10  is a view similar to  FIG. 8  but with the seal plate present and the pin seated in the pin-receiving hole in the seal plate. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0021]    Broadly, the present invention provides a plurality of elements which interact with one another and with machinery components to prevent an incorrect installation of a seal plate (or absence of a seal plate) with machinery components in a faulty sealing relationship. While an exemplary embodiment of these elements is illustrated and described herein in reference to a gearbox and a generator of an auxiliary power unit, it will be readily apparent to those of ordinary skill in the art that these elements may be utilized in other categories of machinery. 
         [0022]    In more specifically describing the present invention,  FIG. 1  shows a portion of a well-known auxiliary power unit (APU), generally designated  10 , to which an exemplary embodiment of the present invention is applied. As well-known, the APU  10  includes a gas turbine engine which is not shown, except for a gearbox  12  located at its one end. The APU  10  also includes a generator  14  (specifically, a starter generator in this instance) connected to the gearbox  12  and a seal plate  16  installed between the gearbox  12  and generator  14 . As best seen in  FIG. 2 , the seal plate  16  is correctly installed in a tight-fitting sealing relationship of a hermetic type between facing end surfaces  12   a ,  14   a  (as best seen in  FIGS. 7-10 ) of the gearbox  12  and generator  14 , ensuring a leak-free containment of lubricating/cooling oil within this portion of the APU  10 . 
         [0023]      FIGS. 3 and 4  show the seal plate  16  by itself prior to installation in the APU  10 . The seal plate  16  typically is comprised of a flat or planar, thin, ring-like body  18 , made of aluminum, with a suitable gasket material bonded into its opposite seal faces  18   a ,  18   b  to provide a positive hermetic oil seal around the various connections between the gearbox  12  and generator  14 . The seal plate body  18  may also have an overall annular shape or configuration and is provided with radially spaced apart inner and outer peripheral edges  20 ,  22 . The seal plate body  18  may further have a plurality of embossment portions  24  formed thereon adjacent to the outer peripheral edge  22  thereof and defining apertures  26  for receiving through the body  18  a plurality of fasteners (not shown), such as bolts, used conventionally in connecting the gearbox  12  and generator  14  together with the seal plate  16  between them in the sealing relationship. 
         [0024]    Referring now to  FIGS. 1-6 , in accordance with the present invention the seal plate  16  may have an element for preventing incorrect installation of more than one seal plate  16  between the gearbox  12  and generator  14  of the APU  10 . This element may be an axial or angular tab  28  on the outer peripheral edge  22  of the seal plate body  18 . In the illustrated embodiment, the angular tab  28  is provided on one of the embossment portions  24  of the seal plate body  1   8  forming a portion of the outer peripheral edge  22  of the seal plate  16 . However, the tab  28  can be provided elsewhere on the outer peripheral edge  22  of the body  18 . The angular tab  28  may be fabricated during the fabrication of the seal plate  16  so that the angular tab  28  is rigidly or fixedly attached on the outer peripheral edge  22 . The angular tab  28  may also be purposefully provided with an overall bent configuration and a predetermined length such that it protrudes radially outwardly from the seal plate outer peripheral edge  22  and then laterally past the one opposite face  1   8 a of seal plate body  18 . 
         [0025]    More particularly, the angular tab  28  may have an inner radial portion  30  merging from the outer peripheral edge  22  of the seal plate  16  such that it protrudes radially outwardly, relative to a central axis  32  of the seal plate  16 , to beyond the exterior of the adjacent gearbox  12 . The angular tab  28  may also have an outer axial portion  34  that merges from the inner radial portion  30  and may be turned approximately ninety degrees relative thereto so as to extend in orthogonal relation to the inner radial portion  30  along the exterior of the gearbox  12  in the direction away from the generator  14 . (Alternatively, the angular tab  28  could be fabricated such that its outer axial portion  34  extends in the opposite direction toward the generator  14 .) Sufficient clearance may be provided between the gearbox exterior and outer axial portion  34  of the tab  28  such that the tab  28  will not contact the gearbox  12  nor interfere with the correct installation of a single seal plate  16  between the gearbox  12  and generator  14 . However, if an incorrect installation of multiple seal plates  16  is attempted between the gearbox  12  and generator  14  the outer axial portion  34  of the tab  28  on one seal plate  16  may contact and interfere with the inner radial portion  30  of the tab  28  on the adjacent seal plate  16 , as shown in  FIGS. 5 and 6 , so as to prevent substantial portions of the adjacent faces  18   b ,  18   a  of the seal plates  16  from touching one another. In such manner, a visible gap  36  may be produced between the adjacent seal plates  16  which will alert an operator that appropriate corrective action is needed. 
         [0026]    Also, in accordance with the present invention, the gearbox  12  may have an element for preventing incorrect installation of the gearbox  12  and generator  14  in a faulty sealing relationship together without the seal plate  16 . Referring to  FIGS. 7-10 , this element may be a pin  38  made of any suitable material, for example steel. The pin  38  may be installed in the end surface  12   a  of the gearbox  12  facing the one opposite face  18   a  of the seal plate  16 . (Alternatively, the pin  38  could be installed in the end surface  14   a  of the generator  14 .) The pin  38  can be installed by using any suitable known technique such as drilling and tapping a threaded hole therein. An exposed portion  38   a  of the pin  38  may protrude from the end surface  12   a  of the gearbox  12  and may contact the adjacent facing end surface  14   a  of the generator  14  if an attempt is made to incorrectly install the gearbox  12  and generator  14  together without a seal plate  16 . Thus, the pin  38  may prevent an incorrect installation of these machinery components together in a faulty sealing relationship without the seal plate  16  installed between them, due to contact by the pin  38  with the facing surface  14   a  of the generator  14  that produces a visible gap  40 , as seen in  FIGS. 7 and 8 , between these machinery components. The presence of the visible gap  40  will alert the operator that appropriate corrective action is needed. 
         [0027]    Further, in accordance with the present invention, the seal plate  16  may have another element for accommodating the presence of the pin  38  when a single seal plate  16  is correctly installed between the gearbox  12  and generator  14 . As seen in  FIGS. 3 and 4 , a pin-receiving hole  42  may be formed through the seal plate body  18  at a location corresponding to the location of the pin  38  on the adjacent end surface  12   a  of the gearbox  12 . The respective axial lengths of the hole  42  and the protruding portion  38   a  of the pin  38  may be such that when the seal plate  16  is correctly installed against the adjacent facing end surface  12   a  of the gearbox  12 , the protruding portion  38   a  of the pin  38  may remain within the hole  42  in the seal plate  16 , as seen in  FIG. 10 . Thus, the pin  38  may not protrude past the opposite face  18   b  of the seal plate  16  and interfere with correct installation the gearbox  12  and generator  14  in the sealing relationship with one seal plate  16  between them. 
         [0028]    In order that the seal plate  16  can only be installed in one orientation, the plurality of apertures  26  in the seal plate  16  can be provided in an asymmetrical arrangement, as seen in  FIG. 2 , to prevent the seal plate  16  from being fitted the wrong way around or incorrectly in a reverse orientation. The embossment portions  24  may be located asymmetrically relative to the central axis  32  of the seal plate body  18  such that the seal plate  16  can be installed only in one orientation between the machinery components whose mounting holes  12   b,    14   b  also are asymmetrically arranged. 
         [0029]    While the above description describes the present invention used with respect to the APU  10 , the present invention may be used in any circumstance where two components are joined together. The two components may be, as described above, a gearbox and generator of an APU, or may be other components, such as a gearbox and generator of a main engine of an aircraft. 
         [0030]    Alternatively, in the situation where the mounting holes  44  of the machinery components are symmetrically arranged, the pin  38  and the pin-receiving hole  42 , as seen in  FIGS. 4 ,  8  and  9 , can be provided asymmetrically about the axis  32  of the seal plate  16 . Thus, the pin  38  and hole  42  can serve dual functions or purposes, the first being to ensure only one seal plate  16  is installed and the second being to ensure the correct orientation of the seal plate  16 . 
         [0031]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.