Patent Publication Number: US-9845705-B2

Title: Systems and methods for centering bearing compartments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a nonprovisional of, and claims priority to, and the benefit of U.S. Provisional Application No. 61/924,566, entitled “SYSTEMS AND METHODS FOR CENTERING BEARING COMPARTMENTS,” filed on Jan. 7, 2014, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally gas turbine engines. More particularly, the present disclosure relates to systems and methods for centering bearing compartments in gas turbine engines. 
     BACKGROUND 
     Gas turbine engines typically comprise a plurality of bearing compartments which support the spools of the engine with minimal friction. The tolerances for centering the bearing compartments may be very low. Centering the bearing compartments may allow for precise alignment and decreased friction of the spools. Struts which are coupled to the outer engine case may support and center the bearing compartments. 
     SUMMARY 
     A tool may comprise a cylindrical body and a swaging ramp. The cylindrical body may comprise a first end and a second end. The swaging ramp may be located adjacent to the first end. The swaging ramp may extend radially inward from an inner circumference of the first end. 
     In various embodiments, the second end may define a draw-in hole. In various embodiments, the draw-in hole may be configured to receive a draw-in bolt. In various embodiments, the draw-in bolt may be configured to threadedly receive a threaded washer. In various embodiments, the tool may comprise a guide sleeve. In various embodiments, the swaging ramp may be aligned with a face of the guide sleeve. In various embodiments, the guide sleeve may be hexagonal. In various embodiments, the swaging ramp may be configured to swage a collar of a retaining plate. In various embodiments, the tool may comprise three swaging ramps. 
     A system for locking a nut may comprise a retaining plate and a swaging tool. The retaining plate may comprise a planar body and a cylindrical collar. The cylindrical collar may be substantially perpendicular to the planar body. The system may further comprise a swaging tool. The swaging tool may comprise a swaging ramp. The swaging tool may be configured to swage the collar. 
     In various embodiments, the collar may define a nut opening. In various embodiments, the planar body may comprise an aperture. In various embodiments, the swaging tool may comprise a cylindrical body having a first end and a second end. In various embodiments, the swaging ramp may be configured to form indentations in the collar. 
     A method of centering a bearing compartment may comprise inserting a nut through an outer case of a gas turbine engine. A retaining plate may be positioned over the nut. The retaining plate and the nut may be coupled to the outer case. A swaging tool may be positioned over the nut. The retaining plate may be swaged with the swaging tool. 
     In various embodiments, the method may further comprise applying tension to a strut by rotating the nut. In various embodiments, the method may further comprise inserting a draw-in bolt through the swaging tool and into the nut. In various embodiments, the method may further comprise tightening the draw-in bolt such that the swaging tool contacts the retaining plate. In various embodiments, the swaging the retaining plate may comprise creating an indentation in a collar of the retaining plate. In various embodiments, the indention may extend into a dimple in the nut. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures. 
         FIG. 1  illustrates a schematic cross-section view of a gas turbine engine in accordance with various embodiments; 
         FIG. 2  illustrates a system for centering a bearing compartment in accordance with various embodiments; 
         FIG. 3  illustrates a perspective view of a nut in accordance with various embodiments; 
         FIG. 4  illustrates a perspective view of a retaining plate in accordance with various embodiments; 
         FIG. 5  illustrates a perspective view of a swaging tool, a retaining plate, and a nut in accordance with various embodiments; 
         FIG. 6  illustrates a perspective view of a swaging tool in accordance with various embodiments; 
         FIG. 7  illustrates a cross-section of a retaining plate being swaged in accordance with various embodiments; and 
         FIG. 8  illustrates a flow diagram of a process for centering a bearing compartment in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
     Conventional systems for centering a bearing compartment may be limited to discrete positions of a nut which applies tension to a rod in order to center the bearing compartment. However, such discrete positions may limit the ability to precisely center the bearing compartment. 
     Systems and methods are disclosed herein for centering a bearing compartment in a gas turbine engine. A nut may be rotated in order to tension a strut which centers and supports the bearing compartment. There may be very low tolerances for tensioning the strut. The disclosed systems and methods may allow the nut to be rotated to a continuum of positions in order to tension the strut within the desired tolerance. The nut may be coupled to the outer case of the engine with locking bolts. The nut may comprise locking slots which allow the nut to be rotated to many positions while still aligning with bolt holes in the outer case. A retaining plate may be placed over the nut, and the locking bolts may be inserted through apertures in the retaining plate, the locking slots in the nut, and into the bolt holes in the outer case. A swaging tool may be tightened over the nut, and may swage indentations into a collar of the retaining plate. The indentations may be formed into dimples in the nut which may prevent the nut from rotating, allowing for precise tensioning of the strut. 
     Referring to  FIG. 1 , a gas turbine engine  100  (such as a turbofan gas turbine engine) is illustrated according to various embodiments. Gas turbine engine  100  is disposed about axial centerline axis  120 , which may also be referred to as axis of rotation  120 . Gas turbine engine  100  may comprise a fan  140 , compressor sections  150  and  160 , a combustion section  180 , and a turbine section  190 . Air compressed in the compressor sections  150 ,  160  may be mixed with fuel and burned in combustion section  180  and expanded across turbine section  190 . Turbine section  190  may include high pressure rotors  192  and low pressure rotors  194 , which rotate in response to the expansion. Turbine section  190  may comprise alternating rows of rotary airfoils or blades  196  and static airfoils or vanes  198 . A plurality of bearings  115  may support spools in the gas turbine engine  100 .  FIG. 1  provides a general understanding of the sections in a gas turbine engine, and is not intended to limit the disclosure. The present disclosure may extend to all types of turbine engines, including turbofan gas turbine engines and turbojet engines, for all types of applications. 
     The forward-aft positions of gas turbine engine  100  lie along axis of rotation  120 . For example, fan  140  may be referred to as forward of turbine section  190  and turbine section  190  may be referred to as aft of fan  140 . Typically, during operation of gas turbine engine  100 , air flows from forward to aft, for example, from fan  140  to turbine section  190 . As air flows from fan  140  to the more aft components of gas turbine engine  100 , axis of rotation  120  may also generally define the direction of the air stream flow. 
     Referring to  FIG. 2 , a bearing alignment system (“BAS”)  200  is illustrated according to various embodiments. BAS  200  may comprise nut  210  and irod  220 . Nut  210  may be coupled to irod  220  through outer case  230 . Trod  220  may be coupled to inner case  240 . Inner case  240  may hold bearing compartment  250 . In various embodiments, bearing compartment  250  may be the #4 bearing for a gas turbine engine. In various embodiments, the #4 bearing may be located at a mid turbine frame of gas turbine engine  100 . 
     BAS  200  may be configured to center inner case  240  and bearing compartment  250 . In various embodiments, engine  100  may comprise a plurality of BASs  200  circumferentially disposed about inner case  240 . In various embodiments, engine  100  may comprise eight BASs  200  symmetrically disposed about inner case  240 . In various embodiments, nut  210  may threadingly engage irod  220 . Nut  210  may screw onto threads on irod  220 , drawing irod  220  and inner case  240  toward outer case  230 . Locking ring  330  may prevent nut  210  from being drawn through outer case  230 . The plurality of BASs  200  may be adjusted by rotating nuts  210  until inner case  240  and bearing compartment  250  are centered to within a desired tolerance. 
     Referring to  FIG. 3 , a perspective view of nut  210  is illustrated according to various embodiments. Nut  210  may comprise head  310 , neck  320 , locking ring  330 , and pivot guide  350 . In various embodiments, head  310  may comprise a hex-head, such that head  310  comprises six lateral sides  312 . Head  310  may define a threaded draw-in hole  314  located on a top side  316  of head  310 . 
     Neck  320  may be located adjacent to head  310 . Neck  320  may comprise a plurality of dimples  322  in lateral surface  324  of neck  320 . In various embodiments, neck  320  may comprise a dimple  322  corresponding to each lateral side  312  of head  310 . In various embodiments, dimples  322  may comprise a concave depression in lateral surface  324 . In various embodiments, dimples  322  may extend into top surface  326  of neck  320 . 
     Nut  210  may further comprise locking ring  330  located adjacent to neck  320 . In various embodiments, locking ring  330  may generally comprise a disk-shaped component adjacent to and co-axial with head  310  and neck  320 . Locking ring  330  may define locking slots  332 . Locking ring  330  may comprise any number of locking slots  332 . In various embodiments, locking ring  330  may comprise three locking slots  332 . In various embodiments, locking slots  332  may be curved and form an annular series of locking slots  332  about neck  320 . 
     Nut  210  may further comprise pivot guide  350 . Pivot guide  350  may comprise a substantially cylindrical component configured to mate with irod  220  shown in  FIG. 2 . In various embodiments, pivot guide  350  may threadingly engage irod  220 . 
     Referring to  FIG. 4 , a perspective view of retaining plate  400  is illustrated according to various embodiments. Retaining plate  400  may comprise collar  410  and retaining body  420 . In various embodiments, retaining body  420  may be substantially planar. In various embodiments, retaining body  420  may comprise an aperture  422 . In various embodiments, aperture  422  may be configured to receive a locking bolt. In various embodiments, retaining body  420  may define three apertures  422 . In various embodiments, each aperture  422  may correspond to a locking slot  332  shown in  FIG. 3 . Collar  410  may be substantially cylindrical. In various embodiments, collar  410  may extend substantially perpendicularly from a top side  424  of retaining body  420 . Collar  410  may define a nut hole  430 . 
     Referring to  FIG. 5 , a perspective view of a swaging tool  500 , nut  210 , and retaining plate  400  is illustrated according to various embodiments. Nut  210  may be rotated to a desired position to center a bearing compartment, and retaining plate  400  may be coupled to nut  210  with locking bolts  518 . Locking bolts  518  may be inserted through apertures  422  and locking slots  332 . Swaging tool  500  may be placed over head  310  and collar  410 . Swaging tool may define a draw-in guide  502  in a top side  504  of swaging tool  500 . Draw-in bolt  520  may be inserted through draw-in guide  502  and into draw-in hole  314 . Draw-in bolt  520  may be tightened by rotating draw-in bolt  520  such that threads on draw-in bolt  520  mate with threads in draw-in hole  314 , forcing swaging tool  500  in the direction of retaining body  420 . Swaging tool  500  may contact a portion of collar  410  and force indentations  530  radially inward on collar  410 . Indentations  530  may intersect with dimples  322 . Indentations  530  may prevent retaining plate  400  from rotating relative to nut  210  by contacting dimples  322 . 
     Referring to  FIG. 6 , a perspective view of swaging tool  500  is illustrated according to various embodiments. Swaging tool  500  may generally comprise a cylindrical body  501  with a first end  510  and a second end  512 . Swaging tool  500  may comprise a stop face  514  located at an outer circumference of first end  510 . Swaging tool  500  may comprise a plurality of swaging ramps  528  adjacent to and extending radially inward from an inner circumference of first end  510 . In various embodiments, swaging tool  500  may comprise three swaging ramps  528 . However, in various embodiments, swaging tool  500  may comprise any number of swaging ramps  528 . Swaging tool  500  may further comprise a guide sleeve  540 . In various embodiments, guide sleeve  540  may comprise a hexagonal shape. 
     Referring to  FIG. 7 , a cross-section view of swaging tool  500 , retaining plate  400 , and nut  210  is illustrated according to various embodiments. First end  510  of swaging tool  500  may be placed over head  310  of nut  210 . Guide sleeve  540  may be positioned around head  310 . In various embodiments, the size and shape of guide sleeve  540  may correspond to the size and shape of head  310 . Guide sleeve  540  may thus align swaging tool  500  in order to swage retaining plate  400 . Draw-in bolt  520  may be inserted though draw-in guide  502  and into draw-in hole  314 . In various embodiments a pivot washer  710  may be positioned between draw-in bolt  520  and swaging tool  500 . Pivot washer  710  may distribute pressure from draw-in bolt  520  onto swaging tool  500 . Draw-in bolt  520  may be threaded into draw-in hole  314 , forcing swaging tool  500  in the direction of retaining plate  400 . As swaging tool  500  is forced toward retaining plate  400 , swaging ramps  528  (shown in  FIG. 6 ) may contact collar  410 , creating indentations  530  (shown in  FIG. 5 ) in collar  410 . The alignment of swaging tool  500  caused by the shape of guide sleeve  540  and head  310  may align swaging ramps  528  with dimples  322 , such that indentations  530  are formed within dimples  322 . Draw-in bolt  520  may be further tightened until stop face  514  contacts retaining plate  400 . A torque wrench may be used to tighten draw-in bolt  520  a specified amount in order to assure uniform indentations  530  in collar  410 . 
     Swaging tool  500  may further comprise a threaded washer  720 . Threaded washer  720  may be threaded onto draw-in bolt  520 . In various embodiments, friction between swaging tool  500  and retaining plate  400  and/or nut  210  may increase an amount of force required to remove swaging tool  500  from nut  210  after swaging. As draw-in bolt  520  is rotated counter-clockwise to remove draw-in bolt  520  from draw-in hole  314 , threaded washer  720  may be forced against removal surface  730  of swaging tool  500 , which may in turn force swaging tool  500  away from nut  210  and assist with removal of swaging tool  500 . 
     Referring to  FIG. 8 , a flowchart of a process for centering a bearing compartment in a gas turbine engine is illustrated according to various embodiments. A nut may be inserted through an outer case of a gas turbine engine (step  810 ). The nut may be coupled to a strut. In various embodiments the strut may comprise an irod. The strut may be coupled to an inner case of the gas turbine engine, and the inner case may hold a bearing compartment. The nut may be rotated to apply tension to the strut (step  820 ). Applying tension to the strut may center the inner case and the bearing compartment. The nut may be rotated until a desired tension is obtained. A retaining plate may be positioned over the nut (step  830 ). Locking bolts may be inserted through apertures in the retaining plate and through locking slots in the nut. The locking bolts may be threaded into locking holes in the outer case, clamping the retaining plate and the nut to the outer case (step  840 ). A swaging tool may be placed over a head of the nut (step  850 ). A draw in bolt may be inserted through a draw-in guide in a top side of the swaging tool. The draw-in bolt may be threaded into the head of the nut (step  860 ). The draw-in bolt may be tightened by rotating the draw-in bolt clockwise, drawing the swaging tool toward the retaining plate until a stop face of the swaging tool contacts the retaining plate. 
     Swaging ramps located at an inner circumference of the swaging tool may contact a collar of the retaining plate. The swaging ramps may form indentations in the collar (step  870 ). The indentations may extend into dimples in a neck of the nut. The indentations may prevent the nut from rotating by contacting the dimples. The draw-in bolt may be rotated counter-clockwise to remove the swaging tool from the nut. A threaded washer on the draw-in bolt may contact a removal surface of the swaging tool to assist in removal of the swaging tool from the nut (step  880 ). 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.