Abstract:
A bracket for attaching a gearbox to an engine casing has a first portion having a first array of openings for receiving attachments therethrough, the first portion having, on a backside thereof, a first rail for engaging a slot in the engine casing, and a second portion having a second array of openings for receiving attachments therethrough. A hookup for attaching to the gearbox attaches to and in between the first portion and the second portion for diminishing effects of radial rotation between the casing and the gearbox.

Description:
BACKGROUND 
       [0001]    Gas turbine engines have a compressor for pressurizing an air stream, a combustor for burning fuel in the pressurized air to generate high energy output in the form of a hot gas stream, and a turbine, which uses a portion of the energy in the hot gas stream to drive the compressor. The remainder of the energy of the hot gas stream may be converted to a useful output by being discharged from a propulsive nozzle; by driving a turbine powering an output shaft, or by combination of both in a turbo fan engine. The powered output shaft may be used for several different purposes, for example, driving engine components such as a fuel pump and other components which are generally referred to as accessories. 
         [0002]    A gearbox is generally used to convert the rotating power from an output shaft, which may rotating at speeds as high as 100,000 revolutions per minute in smaller engines or 8,000-10,000 revolutions per minute in larger engines, to more useful speeds. 
         [0003]    A gearbox is particularly useful to convert the high rotational speed of an output shaft to usable speed for accessories. Gearboxes are typically mounted to an engine by means of a band encircling the engine and attaching to the gearbox. 
       SUMMARY 
       [0004]    According to a first embodiment disclosed herein, a bracket for attaching a gearbox to an engine casing has a first portion having a first array of openings for receiving attachments therethrough, the first portion having, on a backside thereof, a first rail for engaging a slot in the engine casing, and a second portion having a second array of openings for receiving attachments therethrough. A hookup for attaching to the gearbox attaches to and in between the first portion and the second portion for diminishing effects of radial rotation between the casing and the gearbox. 
         [0005]    According to a second embodiment disclosed herein, a bracket and casing assembly for mounting a gearbox to the casing has a first portion having a first array of openings for receiving attachments therethrough, the first portion having, on a backside thereof, a first rail, and a second portion having a second array of openings for receiving attachments therethrough. A hookup for attaching to the gearbox, attaches to and in between the first portion and the second portion for diminishing effects of radial rotation between the casing and the gearbox. A first mount is disposed on the casing for receiving the bracket. 
         [0006]    The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows a gearbox casing attaching to a diffuser section of a gas turbine engine. 
           [0008]      FIG. 1A  shows a sectional view of the gearbox and the diffuser casing and the linkages used to mount the gearbox to the diffuser casing taken along the line  1 A- 1 A as shown in  FIG. 1 . 
           [0009]      FIG. 2  shows a mount bracket  30  in accordance with a first embodiment of the invention attaching the gearbox to the diffuser casing. 
           [0010]      FIG. 3  shows a method of attaching a gearbox bracket  30  to the diffuser casing is contemplated herein. 
           [0011]      FIG. 4  shows a perspective view of a second embodiment of a gearbox bracket  30 . 
           [0012]      FIG. 5  shows a reverse view of the bracket of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring now to  FIGS. 1 and 1A , a gear box  10  is attached to a gas turbine engine casing  15 , such as a diffuser, though other engine casing portions may be used, by means of an upper mount  20  (see also  FIGS. 2 and 3 ), a lower mount  25  (see also  FIGS. 2 and 3 ), a bracket  30 , and a link  35 . 
         [0014]    Referring now to  FIGS. 2 and 3 , the bracket  30  and its upper and lower mount  25 ,  25  are shown. In this embodiment the upper mount  20  is a thickened portion of the casing  15  and has an upper first layer  40 , which is generally rectangular, conforms with a curve of the casing  15 , and a upper second layer  45 , which extends radially outwardly from the upper first layer  40  and has a bolt hole array  50  three sets  55  of three threaded bolt holes  60 . Each set  55  of bolt holes  60  is separated by a slot  65  for receiving an upper rail(s)  70  disposed on the bracket  30  as will be discussed infra. 
         [0015]    Similarly, the lower mount  25  is a thickened portion of the casing  15  and has a lower first layer  75 , which is generally rectangular, conforms with a curve of the casing  15 , and a lower second layer  80 , which extends outwardly from the lower first layer  75 , and has a bolt hole array  85 , in this case, one set of three threaded bolt holes  90 . A lower slot  95  for receiving a lower rail  100  disposed on the bracket  30 , is in register with the bolt hole array  85  as will be discussed infra. 
         [0016]    Bracket  30 , generally has an arcuate shape along its length L that conforms generally to the arcuate shape of the casing  15  so that connection between the casing  15  and the gearbox  10  is as close to the casing as is reasonably practicable to withstand tangential or circumferential loads on the bracket  30  that rotating machinery like gas turbine engines encounter. The bracket  30  has an upper flange  105  having a upper flange bolt hole array  110  that mates with the bolt hole array  50  in the upper second layer  45  of the upper mount  20 . Moreover, the upper flange has two upper rails  70  extending from a bottom side  112  thereof that approximately mate with the slots  65  in the second layer  45  of the upper mount  20 . The bracket  30  also has a lower flange  115  having a lower flange bolt hole array  120  disposed therethrough that mates with the lower bolt hole array  85  on the lower mount  25 . Moreover, the lower flange  115  has a lower flange rail  130  that approximately mates with the lower slot  95  in the lower mount  25 . 
         [0017]    The upper flange  105  has a lower level  116  at an end  117  of the upper flange, a middle level  118  attaching to and extending radially higher than the lower level  116 , and an upper level  119  attaching to and extending radially higher than the middle level  118  and attaching to a pair of lobes  135  as will be discussed herein. The upper flange  105  ramps upwardly through levels  116 ,  118  and  119  to attach to the lobes so that tangential load along the casing  15  is distributed from the lobes to the upper flange to minimize risk of breakage. The rails  70  and  100  also distribute tangential (e.g. radial) loading to the upper and lower mount  25 ,  25  to minimize loading on the bolts  133  that connect the bracket  30  to the upper and lower mount  25 ,  25 . 
         [0018]    The pair of lobes  135 , which are disposed in parallel and spaced apart from each other, are mounted transversely in plane to the upper flange  105  and the lower flange  115 . Each of the connecting lobes  135  has a larger hole  140  for receiving a larger bolt  145  and a smaller hole  150  for receiving a smaller bolt  155 . The smaller holes  150  receive a smaller bolt  155  that acts as a fail-safe mechanism. Each of the larger holes  140  and each of the smaller holes  150  are in register with each other to receive the bolts  145 ,  150 . The lobes  135  essentially form a hookup portion for attaching to the gearbox  10 . 
         [0019]    The link  35  has openings (not shown) that are in register with the larger hole  140  for receiving a larger bolt  145  and a smaller hole  150  for receiving a smaller bolt  155  and has other openings (not shown) to attach to the gearbox  10  by known means. One of ordinary skill in the art will recognize that the link may be an integral part of the gearbox  10 . 
         [0020]    Referring now to  FIGS. 4 and 5 , another embodiment of a gearbox bracket  230  is shown. Bracket  230 , generally has an arcuate shape along its length L that conforms generally to the arcuate shape of the casing  15  so that connection between the casing  15  and the gearbox  10  is as close to the casing as is reasonably practicable to withstand tangential and axial loads on the bracket  30  that rotating machinery like gas turbine engines encounter. The bracket  230  has an upper flange  305  having a upper flange bolt hole array  310  to mate with an identical bolt hole array (not shown) in the upper second layer  45  of the upper mount  20 . Moreover, the upper flange  305  has a first rail  370  extending across and from a bottom side  312  thereof for approximately mating with a slot (not shown) in the second layer  45  of the upper mount  20 . The bracket  230  also has a second rail  376  perpendicularly (at about a 90° angle) to and intersecting with the first rail  370  which engages a slot  378  (see dotted lines in  FIG. 3 ) to minimize the effect of radial loads between the casing  15  and the gearbox  10  on bolts (not shown) used therewith. 
         [0021]    The bracket  230  also has a lower flange  315  having a lower flange bolt hole array  320  on an outward portion  321  disposed therethrough that mates with the lower bolt hole array (not shown) on the lower mount  25 . Moreover, the lower flange  315  has a lower flange rail  330  that is parallel to rail  376  and approximately mates with the lower slot (see dotted line  321  in  FIG. 3 ) in the lower mount  25 . The rails  376 ,  330  minimize the effect of axial loading between the casing  15  and the gearbox  10  to minimize loading on bolts (not shown). 
         [0022]    The lower flange  315  has an inward portion  340  that angles around the casing  10  relative to the outward portion  321  to make room for a bolt head (not shown) and stay close to the casing  15  and has an opening  345  for receiving a bolt (not shown) to attaching to a link (not shown). The inward portion has an indentation  346  for receiving a bolt head (not shown) for stopping the bolt (not shown) from rotation. 
         [0023]    The upper flange  305  has a lower level  316  at an end  317  of the upper flange and an upper level  319  attaching to and extending radially higher than the lower level  316  and attaching to the lower flange  315  and an attachment plate  335  as will be discussed herein. The upper flange  305  ramps upwardly through levels  116  and  119  to attach to the inward portion  340  of the lower flange  315  so that tangential load along the casing  15  is distributed through the bracket  230  to minimize risk of breakage. The attachment plate  335  has an opening  348  disposed therethrough. 
         [0024]    The inward portion  340  and the attachment plate  335  are disposed in parallel and spaced apart from each other and holes  346  and  346  are in register with each other for receiving a link (not shown) connecting to the gearbox  10 . The attachment plate and the inward portion essentially form a fork for receiving a link (not shown) therebetween. The inward portion  340  and the attachment plate  335  essentially form a second embodiment of a hookup portion for attaching to the gearbox  10 . 
         [0025]    There is a nominal clearance between the slot(s)  65  and the rail(s)  70 , the slot  95  and the lower rail  100 , the slot  378  and the rail  376 , the slot (not shown) and the rail  370  and the slot  321  and the rail  330  to enable assembly therebetween. Regardless of the clearance, the rails  70 ,  100  and  370  within the slots  65 ,  95  take a load off of the bolts in a tangential (e.g., radial) direction. Also slots  378  and rail  376  and slot  321  and rail  330  take a load off of the bolts in an axial direction about the outside of the casing which enables the bolts and their attending holes to be made smaller for the intended weight loss thereof. 
         [0026]    Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
         [0027]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims. One of ordinary skill in the art will recognize that other combinations of rails and slots may be utilized to minimize axial and radial loading.