Abstract:
A system for securing first and second tubular coaxial components carrying a roller bearing is provided. The system includes a forcing nut mounted inside the coaxial components and axially abutting against the first component after screwing-in of the second component; and a locking pin for preventing unscrewing of the nut and being arranged between the nut and the first component. The system also includes a cylindrical sleeve being arranged between the pin and the first component, being secured axially relative to the first component, and including an axial stop against which the pin is applied; and first and second devices for linking the pin and the first component in rotation, respectively, with the sleeve.

Description:
SUMMARY OF THE INVENTION 
     The present invention relates to a system for securing, by means of a forcing nut and a pin for locking the nut, the end of a first tubular component to the inside of a second tubular component carrying a roller bearing to be flanged relative to said components after mounting and tightening of the system. 
     More particularly, although not exclusively, the invention relates to aeronautics and, notably, to gas-turbine engines (turbofans, turboprops, etc.). 
     In this specific application, the system is designed to secure the shaft (first component) of the high-pressure compressor of the engine to a reentrant-angle conical wheel on which is mounted the interior ring of the roller bearing of which the position is to be flanged axially, the shaft and the wheel being integral in rotation. 
     The invention will be described with regard to this application, in the knowledge that the securing system is not restricted thereto and may be used, generally speaking, on any device, mechanism, etc. that is designed to retain a roller bearing in a position and requires a locking pin to prevent unscrewing of the forcing nut through vibrations or the like generated, in the case of the above application, during operation of the turbine engine. 
     To recall, as shown schematically in  FIG. 1  and the associated magnification L, a motor  1  of this type comprises, from upstream to downstream relative to the longitudinal axis A thereof, and in the direction of the gas flow F, a fan  2 , a low-pressure compressor  3 , a high-pressure compressor  4 , a combustion chamber  5 , a high-pressure turbine  6  receiving the gases from the combustion chamber, and a low-pressure turbine  7 . The fan  2 , the low-pressure compressor  3  and the low-pressure turbine  7  form a part of the rotor  8  of the engine  1  and are connected together by a line of rotating shafts  9  arranged in the axis A of the engine. In addition, the compressor  4  and the high-pressure turbine  6  form another part of the rotor  8 , independent of the preceding part, and are connected together likewise by a line of rotating shafts  10  concentric with the line of shafts  9  arranged on the axis A, the lines of shafts  9  and  10  together providing an annular axial passage  11 . 
     The stator  13  of the engine is provided around the rotor  8  and comprises a plurality of fixed casings, and all the cited components of the rotor and of the stator, except for the combustion chamber, carry alternating either movable  12 A or fixed  12 B blades located in the stream of the gas flow F defined between the rotor  8  and the stator  13 . 
     The way in which a motor of this type operates is well-known and will not be described here. 
     One of the casings of the stator  13 , designated generally as the intermediate casing  13 A, and located downstream of the fan casing, is mounted, notably, on the relevant roller bearing  14  by the securing system  15  of the invention, namely the bearing commonly referenced bearing three since it is the third in the engine from upstream to downstream. 
     Bearings one and two (not shown) support the line of shafts  9  of the fan  2  and of the low-pressure compressor  3  and other bearings four and five (likewise not shown) are provided downstream at turbine level. 
     Bearing three  14  has its exterior ring  16  linked to the fixed intermediate casing  13 A, while its interior ring  17  supports the end journal  19  of the rotating shaft  20  of the high-pressure compressor  4  by means of a cylindrical jacket  21  or wall of the rotating conical wheel  22 . The latter meshes with another conical wheel  23  to form a perpendicular reentrant angle and thereby to drive in rotation the radial shaft  24  of the engine, symbolized by an axis line B, and designed to drive, by means of a gearbox, engine equipment and/or accessories such as pumps, current generators, etc. 
     In order to secure the shaft  20  (corresponding to the first component) to the inside of the conical wheel  22  (corresponding to the second component) carrying the bearing  14  and to thereby immobilize the interior ring thereof, the securing system  15  is engaged in the axial passage  11 , between the lines of shafts, and includes, as suggested by document FR 2 783 579:
         a forcing nut  25  mounted inside the coaxial components and axially abutting against the first component after screwing-in of the second component; and   a locking pin  26 , for preventing unscrewing of the nut, arranged between the latter and the first component.       

     Thus, upon screwing-on of the nut  25 , the conical wheel  22  and the shaft  20 , which are integral in rotation, approach one another until they abut, which has the effect of axially immobilizing the interior ring of the bearing  14  relative to the conical wheel and to the shaft, with the aid of abutment rings (not illustrated). 
     In addition, the forcing nut  25 , screwed on to the required torque, is immobilized in position by elastically deformable lateral fingers (or tabs)  27  of the pin, which are shown in larger form in the magnification L of  FIG. 1  and engage in an internal receiving groove  28  of the end journal  19  of the shaft  20  of the compressor, which prevents the axial withdrawal of the pin  26  and hence that of the nut  25 , and thus the unscrewing thereof. 
     Although this arrangement is satisfactory, the fingers  27 , or at least some of those fingers, may appear to undergo significant bending during mounting/removal operations owing, notably, to the fact that the space of the axial passage  11  between the lines of shafts  9  and  10  is restricted. There is then a risk that they will permanently deform plastically and will no longer take an active part in axial locking of the pin and consequently of the nut. Given the operating conditions of the engine (vibrations, etc.), it is likely that the pin  26  will no longer perform its role perfectly, with the consequences this entails for the surrounding components in the event of rupture of the fingers or the emergence thereof from the shaft groove. 
     Furthermore, a pin  26  of this type with elastically deformable fingers  27  is complicated to produce and difficult to set in position and to remove. 
     Other securing systems  15  are also known, in which the forcing nut is self-extracting and to that end includes a supplementary nut and a locking stud for said supplementary nut. The supplementary nut is arranged around the forcing nut and interacts with the shaft journal by means of screwing-in on relatively small diameters owing to the restricted space of the passage between the forcing nut and the end of the journal. 
     In this solution of the system, the thread of the supplementary nut is, however, of small pitch to allow for high-pressure compressor pumping and, furthermore, as the same thread is likewise produced on the journal, in a small internal diameter, there is a significant risk of a component such as this being damaged. 
     The object of the present invention is to remedy the above drawbacks and it proposes a solution in which the design of the securing system is simplified and guarantees immobilization of the forcing nut once mounted without the risk of unscrewing, immobilization of the interior ring of the bearing and safe, reliable mounting/removal of the two associated tubular components (the compressor shaft and the conical wheel). 
     To that end, the system for securing the end of a first tubular component to the inside of a second tubular component carrying a roller bearing for holding the latter in position is of the type with a forcing nut and a pin for locking the nut, as defined previously. 
     According to the invention, the system is noteworthy in that it furthermore comprises a cylindrical sleeve arranged between the pin and the first component, being secured axially relative to the latter, and including an axial stop against which the pin is applied, and first and second means for linking the pin and the first component in rotation, respectively, with the sleeve. 
     Thus, by virtue of the invention, a simple intermediate sleeve between the pin and the first component, axially secured in position, makes it possible to fulfill the functions of linking in rotation between the pin and the first rotary component and axial abutment for the pin. In this way, as the pin is immobilized axially and linked in rotation to the first component via the cylindrical sleeve, axial withdrawal of the forcing nut and thus the unscrewing thereof are prevented, even under conditions of significant vibrations. 
     Production of the pin is thus simplified owing to the absence of elastically deformable fingers, and the ensuing operations of mounting and removal are likewise easier, quicker and safer. 
     In the preferred application, the sleeve corresponds to the rotary shaft of the high-pressure turbine, the corresponding end of which is extended to come between the end journal of the rotating shaft of the compressor and the locking pin and to axially immobilize the pin and hence the forcing nut. This sleeve originating from the turbine shaft thus plays a part in the securing system of the invention instead and in place of the elastically deformable fingers that are complex to produce and tedious to mount and to remove, and of the drawbacks of the other solution with supplementary nut and thread. The system of the invention consequently overcomes the aforesaid drawbacks. 
     For example, axial stop is defined simply by an internal shoulder provided in the lateral wall of the sleeve and against which the corresponding transverse face of the pin is applied. 
     In preferred embodiments, the first means for linking in rotation includes parallel flutes, regularly distributed over the exterior periphery of the pin and interior periphery of the cylindrical sleeve, and interacting with one another upon axially abutting relative engagement of the pin in the sleeve. In addition, the second means for linking in rotation includes at least one stud housed radially in the wall of the first tubular component and being engaged in an opening provided in the wall of the sleeve. 
     Furthermore, said locking pin is linked in rotation with the forcing nut when in axial abutment against the sleeve. Preferably, the link in rotation of the pin to the nut is defined by lateral claws provided in the opposing transverse faces of the nut and of the pin and being assembled one in the other. 
     Advantageously, the pin is in the form of a cylindrical ring. The simplicity of production of the pin will be noted, which, combined with that of the cylindrical sleeve, define a securing system offering a high level of reliability during use. 
     In particular, the forcing nut includes, in addition to its thread for the link to the second component, an external annular edge suitable for abutting against an internal shoulder of the first component, and an external collar between the thread and the edge suitable for interacting with a corresponding bore provided in the first component for centering purposes. 
     In the preferred application of the securing system, the first tubular component is the journal of the shaft of the high-pressure compressor of a gas-turbine engine; the second tubular component is the conical wheel, supported by the bearing, for driving the transmission shaft of the accessory gearbox; and the sleeve is the shaft of the high-pressure turbine of the engine. 
     The present invention also relates to the gas turbine engine that comprises a system for securing the shaft of the high-pressure compressor to the conical wheel driving the transmission shaft of the accessory gearbox for flanging the roller bearing supporting the wheel. The securing system is as defined above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures of the appended drawing will make it possible satisfactorily to understand how the invention may be implemented. In these figures, identical reference numbers denote similar elements. 
         FIG. 1  shows schematically, in axial section, an aircraft gas turbine engine with a securing system of the prior art for flanging the roller bearing located at the high-pressure compressor of the engine. 
         FIG. 2  is an enlarged view in partial axial section of the securing system according to the invention, for flanging said bearing. 
         FIG. 3  is a transverse section along axis III-III of  FIG. 2 , passing through the first and second means for linking in rotation the sleeve to the pin and to the high-pressure compressor shaft. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in greater detail in  FIG. 2 , the bearing  14  of ball-bearing type is mounted between the hub of the fixed intermediate casing  13 A of the engine stator and the line of rotating shafts  10  composed, at this point of the rotor  8  of said engine, by the tubular wall  21  originating from the rotating conical wheel  22  and the end journal  19  of the rotating tubular shaft  20  of the high-pressure compressor  4 . The journal  19  of the shaft and the wall  21  of the toothed wheel of the line of rotating shafts  10  delimit the axial passage  11  with the line of rotating shafts  9  of compressor and low-pressure turbine  3  and  7  and are associated with one another along the axis A by the securing system  15  of the invention mounted in the passage  11 , the aim of which is likewise to axially lock the interior ring  17  of the bearing. 
     It may be seen in said  FIG. 2  that the bearing  14  is contained in an enclosure delimited by an upstream sealing flange  30  and a downstream sealing flange  31 . The upstream flange  30  securely connects the intermediate casing  13 A to a casing  13 B of the radial shaft  24 , and the downstream flange  31  securely connects the intermediate casing  13 A to the shaft  20  of the high-pressure compressor  4 . In particular, the interior ring  17  of the bearing  14  is mounted about the cylindrical wall  21  of the toothed wheel  22  and is immobilized axially between an external radial shoulder  33  provided on the cylindrical wall and a retention ring  34  that is in axial contact with an external radial shoulder  38  of the shaft  20  of the compressor and which lies about the end of the cylindrical wall  21  of the wheel in order, in turn, to be in contact with the interior ring  17 . 
     The securing system  15  of the invention locks the rotating interior ring  17  of the bearing  14  in position. Before giving a description thereof, the exterior ring  16  of the bearing is itself immobilized axially between an annular edge  35  ending a component of the fixed intermediate casing  13 A and a component  36  attached securely thereto. 
     The securing system  15  to be mounted in the axial passage  11  of the line of shafts comprises the forcing nut  25  and the locking pin  26  of the latter, which is made indispensible by reason of the vibrations generated by operation of the engine  1 . 
     For example, the forcing nut  25  in the form of a cylindrical ring comprises, first, a part with an external thread  40  and, second, an external annular edge  41 . In addition, between the thread and the edge there is a projecting collar or crown  43 . The thread is screwed onto a corresponding internal screwthread  44  provided in the bore  45  of the toothed wheel, while the external annular edge  41  is designed to come into contact with an internal shoulder  46  provided in the end journal  19  of the shaft during screwing-on of the nut. The journal engages coaxially in the cylindrical wall  21  of the toothed wheel. 
     Prior to mounting of the nut  25 , the shaft  20  and the toothed wheel  22  are linked in rotation one to the other, preferably by flutes  47  provided at the external periphery of the end journal  19  and at the internal periphery of the cylindrical wall  21  of the wheel. 
     It will thus be understood that screwing-on of the forcing nut  25  via its thread  40  in the internal screwthread  44  of the toothed wheel causes the wheel and the compressor shaft to move closer together axially until the external edge  41  of the nut abuts against the internal shoulder  46  of the journal. The stop ring  34 , pushed by the shoulder  38  of the shaft  20 , is thus applied on the interior ring  17  of the bearing  14 , and the ring  17 , on the other side, abuts against the external shoulder  33  of the wheel  22 . The ring  17  is held in position axially. 
     The collar  43  of the nut guarantees guiding and centering of the nut  25  in the bore  39  of the journal  19 , defining a bearing surface relative thereto. 
     The transverse face  48  of the forcing nut, on the external edge  41  side, is crenellated and ends in lateral claws  49  with which a tool can interact in order to screw/unscrew the nut and also the pin, as will be seen below. 
     As regards the locking pin  26  of the forcing nut  25 , this is in the form of a cylindrical ring and is arranged in the axial passage  11  of the line of shafts, substantially in the extension of the ring-form nut. This locking pin  26  must thus be immobilized axially in position and in rotation with the shaft  20  of the compressor and interact with the forcing nut  25  in order to prevent any likelihood of unscrewing (helical displacement) of the nut and to guarantee a failure-proof link between the toothed wheel  22  and the shaft  20  of the compressor, and optimum flanging of the interior ring  17  of the ball bearing of the bearing  14 . 
     To that end, the securing system  15  furthermore comprises an intermediate sleeve  51  that corresponds, in the aforesaid application, to the cylindrical sleeve of annular transverse section of the shaft  50  of the high-pressure turbine  6  of the engine, which shaft is located in the axial passage  11 . 
     This cylindrical sleeve  51  therefore forms an integral part of the turbine shaft  50  of the line  10  in question of the rotor  8  and, in this case, it is suitable for engaging between the cylindrical pin  26  and the shaft  20  of the compressor by acting as linking interface between them. 
     In order axially to lock the pin  26  in position and thus prevent withdrawal along the axis A of the forcing nut  25 , the sleeve  51  has an axial stop formed, in this example, by an internal shoulder  52  provided in the lateral wall  56  of the sleeve and against which the corresponding transverse face  53  of the pin is applied. Quite obviously, once the turbine shaft is in position, the turbine is immobilized axially in position and is thus fixed along the axis A of the engine. The sleeve  51  of the rotating shaft is consequently fixed axially, with the face  53  of the pin  26  in axial abutment against the shoulder  52 . 
     The opposite transverse face  54  of the locking pin has lateral claws  55  interacting with those  49  of the forcing nut  25  in such a manner as to link pin and nut in rotation. 
     In addition, to ensure a global link in rotation between, on the one hand, the intermediate sleeve  51  of the turbine rotating shaft and the locking pin  26  and, on the other, between the rotating shaft  20  of the compressor and the sleeve  51 , the securing system  15  includes specific means shown in  FIG. 2  and  FIG. 3 . 
     A first means for linking in rotation is in the form of parallel flutes  57  and  58  that secure in rotation the cylindrical pin to the sleeve. The flutes  57  are regularly distributed at the exterior periphery of the cylindrical pin  26  and are suitable for engaging with corresponding flutes  58  provided regularly at the internal periphery of the wall  56  of the cylindrical sleeve  51 . 
     It should be pointed out that, if, during mounting of the pin, the flutes  57 ,  58  and the claws  49 ,  55  are slightly offset angularly with respect to one another, preventing axial assembly of the components, a tightening excess torque is exerted on the nut to align the claws with the flutes. 
     A second means for linking in rotation is in the form of a radial stud  60  associating the shaft  20  of the compressor with the sleeve  51  of the turbine shaft. In particular, the stud  60  is housed radially in a hole  61  provided in the wall of the end journal  19  of the shaft  20  and engages in an opening  62  made so as to correspond in the cylindrical lateral wall  56  of the sleeve. This opening is, for example, in the form of a circular hole such that the stud accommodated in this hole provides, in addition to linking the shaft  20  and the sleeve  51  in rotation, axial immobilization of these latter in position, being in abutment against the pin as a result of the mounting of the sleeve  51  of the turbine shaft between the pin  26  and the shaft  20  of the compressor. 
     It will therefore be understood that, via the sleeve and the means for linking in rotation and for axial abutment, a robust, compact system between the pin  26 , the sleeve  51  and the shaft  20  is obtained, which prevents any unscrewing of the nut  25 . Furthermore, no part of the aforementioned components is deformed when mounting and removing said components, thus guaranteeing significant reliability during use. 
     The forcing nut  25  of the system  15  clamps the toothed wheel  22  with the journal  19  of the compressor in order to hold the interior ring  17  of the bearing  14 , and the locking pin  26  immobilizes the nut  25  and prevents any inopportune unscrewing, even at high levels of vibration, and does so without elastically deformable fingers. The flutes, the design of which is simple and reliable, and the stud guarantee there is no rotation between the sleeve, the pin and the shaft of the compressor, ensuring links in rotation, and the sleeve of the system thus designed also ensuring axial abutment of said pin. The securing system thus achieves its objectives by means of the simplification of its component parts by virtue of the advantageous use of the sleeve of the turbine shaft, which consequently reduces manufacturing and maintenance costs and allows pooling of functions. 
     Furthermore, to recap, the conical wheel  22  comprises teeth that interact with those of a conical pinion  23  arranged perpendicularly to the axis A of the engine  1  and integral with the radial shaft  24  partially shown in  FIG. 2 . The original cones of the wheel  22  and of the pinion  24  converge toward the intersection of the geometric axes A of the engine and B of the radial shaft. The latter extends as far as the fan casing, where it is connected to a gearbox for driving the auxiliary engine equipment.