Abstract:
A coupling device for coupling a turbine upstream guide vane which is coupled to a supporting part which itself attached to a stabilizing part is disclosed. The coupling device includes a interlocking device for interlocking a supporting end of the supporting part with a stabilizing end of the stabilizing part, and a retaining part to keep the supporting end and the stabilizing end interlocked. The coupling device may be used to couple an upstream guide vane of a turbojet turbine.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to turbojet turbines. More precisely, it involves the coupling of an upstream guide vane of a turbojet turbine. 
     The subject of the invention is a device for coupling an upstream guide vane of a turbine to fixed structures of this same turbine. A further subject is a turbine comprising such a coupling device. A final subject is a turbojet fitted with at least one such coupling device and/or such a turbine. 
     The turbine may be a high-pressure turbine. 
     A turbojet turbine comprises fixed elements (stator) and movable elements (rotor). The movable elements are wheels carrying airfoils, inserted between grilles of fixed airfoils, also called an upstream guide vane. The upstream guide vane/wheel assembly forms a turbine stage. To make it easier to install the turbine, the upstream guide vanes are sometimes obtained by assembling at least two upstream guide vane sectors. Each upstream guide vane sector comprises a certain number of fixed airfoils distributed between an outer ring called an outer platform and an inner ring called an inner platform. Usually, the inner platform is extended radially inward via a coupling flange used to attach the upstream guide vane or the upstream guide vane sector to a supporting part. To simplify the rest of the description, the term “upstream guide vane” will be employed to designate a complete upstream guide vane or an upstream guide vane sector. 
     DESCRIPTION OF THE PRIOR ART 
     An existing design of a coupling device is illustrated in  FIG. 7 , which represents a portion of a turbojet and shows a shaft  102 , the combustion chamber  104 , a high pressure turbine stage whose wheel consists of a disk  106  and movable airfoils  108  and whose upstream guide vane comprises fixed airfoils  110 , a lower platform  112  and a coupling flange  114 . 
     In existing designs, such as that illustrated in  FIG. 7 , the coupling of the upstream guide vane uses as a supporting part a casing  122  of the injectors  116 . This supporting part is stabilized by attachment to a fixed structural part, that is an extension  124  of a support  118  made of abradable material. The coupling is achieved by the combined action of a locking of the coupling flange  114  relative to said casing and/or relative to said extension, and a bolted connection  126  between said extension  124  and said casing  122 . 
     According to an existing design, the locking of the coupling flange  114  is achieved by locking means that comprise a first pin placed in a radial direction and pressing on a circumferential shoulder of said extension, this first pin being designed to lock the coupling flange against said casing in the axial direction. According to this same design, the locking means also comprise a second pin traversing both said casing and said coupling flange, this second pin being designed to lock the coupling flange in the radial and circumferential directions. 
     According to another existing design, each coupling device comprises a locking recess of said casing, said recess opening radially outward and being dimensioned to receive said coupling flange and lock the latter radially inward. According to this same other existing design, the coupling device also comprises a pin placed in an axial direction and designed to lock the coupling flange in the radial and circumferential directions, this pin traversing both said coupling flange and said casing, and butting axially against said extension. 
     According to one and the other of the two existing designs of a coupling device, the injector casing and the extension support made of abradable material are attached together by at least one bolted connection. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to propose a simplified coupling, and in particular a coupling that does not use the bolted connection. The subject of the invention is a coupling device for an upstream guide vane of a turbine, said upstream guide vane being coupled to a supporting part itself attached to a stabilizing part. 
     According to a first aspect, the invention relates to a coupling device that comprises:
         interlocking means for interlocking a supporting end of the supporting part with a stabilizing end of the stabilizing part, and   a retaining part to keep said supporting end and said stabilizing end interlocked.       

     The interlocking means comprise a crank of the supporting end, and matching shape and dimensioning of the stabilizing end. 
     The coupling device also comprises retaining means for preventing a relative rotation of the supporting end and the stabilizing end. 
     Said retaining means comprise at least one groove having a semicircular section hollowed out in a facet of the supporting end and at least one groove having a semicircular section hollowed out in a face of the stabilizing end, the two grooves being placed, in service, opposite one another, so as to define together an orifice when the two ends are interlocked. 
     Said retaining means also comprise at least one retaining pin designed to be inserted into said orifice when the two ends are interlocked. 
     The retaining part is an annular part that has a substantially J-shaped section. It comprises a central framework that extends to one end via a radiating portion itself extending via a terminal portion which extends parallel to the central framework, said central framework, radiating portion and terminal portion defining between them a retaining recess, and said central framework extends to another end via a collar which for its part is substantially perpendicular and which overhangs the radiating portion and the terminal portion. 
     The retaining part also comprises a gripping flange which extends in a substantially perpendicular direction from the central framework, on the side opposite to the retaining recess relative to said central framework. 
     The coupling device also comprises means for snap-fitting the supporting end and the retaining part. 
     Said snap-fitting means comprise teeth of the supporting end and matching teeth of the retaining part. The teeth of the supporting end are on a rim of said supporting end. The matching teeth of the retaining part are on the terminal portion of said retaining part. 
     The coupling device also comprises immobilizing means for preventing the retaining part from rotating relative to the supporting end. The immobilizing means comprise a domed profile of the retaining part. They also comprise a hole for immobilizing the supporting end and a hole for immobilizing the retaining part, the two immobilizing holes having substantially the same diameter, and an immobilizing pin designed to traverse these two immobilizing holes. The hole for immobilizing the retaining part is on one of the matching teeth of the retaining part and said hole for immobilizing the supporting end is on one of the teeth of the supporting end. 
     The coupling device also comprises means for locking the upstream guide vane relative to the supporting end, said upstream guide vane comprising fixed airfoils angularly distributed between two substantially annular and concentric platforms. Said locking means comprise:
         a flange for coupling the upstream guide vane, that extends beyond the platform with the smaller curvature radius, relative to the airfoils,   holes traversing said coupling flange that are distributed in the circumferential direction of the latter,   a recess for locking the supporting end, said locking recess opening radially outward,   holes traversing the walls of said locking recess, and   a locking pin designed to traverse both said holes of the coupling flange and said holes of the walls of the locking recess.       

     Preferably, said locking pin is a shouldered pin. Said locking pin is retained, in service, between the supporting end and the retaining part. 
     According to one embodiment of the invention, the supporting part consists of an injector casing, and the stabilizing part consists of an extension of a support made of abradable material. 
     According to a second aspect, the invention relates to a turbine comprising at least one upstream guide vane coupling device according to the first aspect. 
     According to a third aspect, the invention relates to an aircraft engine comprising a turbine according to the second aspect and/or at least one coupling device according to the first aspect. 
     One advantage of the invention lies in the fact that the total weight of the aircraft engine is reduced, since the coupling of the upstream guide vane no longer uses bolted connections. The result of this is a reduction in the operating costs of the aircraft engine, achieved by fuel savings during the flight phases of the aircraft. 
     Another advantage of the invention lies in the fact that the installation times are reduced since there is no bolted connection. The result of this is a reduction in maintenance costs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood on reading the following detailed description of a particular embodiment of the invention, supplied as an indication and in no way limiting, and illustrated by means of the appended drawings, in which: 
         FIG. 1  represents, in axial section and in a schematic manner, a turbojet fitted with a turbine provided with a coupling device according to the invention; 
         FIG. 2  represents, in axial section, a coupling device according to the invention; 
         FIG. 3  represents, in a perspective view, the supporting end and interlocking means and snap-fitting means; 
         FIG. 4  illustrates, in a perspective view, the interlocking of the supporting end with the stabilizing end, and the retaining means; 
         FIG. 5  represents, in a perspective view, the retaining part, and snap-fitting means and immobilizing means; and 
         FIG. 6  illustrates, in radial section, the interlocking of the supporting end with the stabilizing end, and their retention by means of the retaining part; and 
         FIG. 7  already described, represents, in axial section, a portion of a turbojet illustrating a coupling device of the prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference first of all to  FIG. 1 , it represents schematically a turbojet  1 , comprising a high-pressure turbine  2 , a low-pressure turbine  3 , a combustion chamber  4 , a high-pressure compressor  5 , a fan  6 . The high-pressure turbine  2  is provided with upstream guide vanes  8 . 
     Now with reference to  FIG. 2 , it represents a coupling device  20  of a turbine upstream guide vane  8 , the upstream guide vane  8  comprising fixed airfoils  10  distributed between an outer platform (not shown) and an inner platform  12 . A coupling flange  14  extends from this inner platform  12 , being opposite to the fixed airfoils  10  relative to said inner platform  12 . 
     In a manner similar to the previously described existing designs of a coupling device, the upstream guide vane  8  is coupled to a supporting part, and this supporting part is itself attached to a stabilizing part. In the example illustrated in the figures, the supporting part is a casing  22  of the injectors (not shown), and the stabilizing part is an extension  30  of a support  18  made of abradable material. 
     The coupling device  20  according to the invention uses a retaining part  60  that contributes to the attachment of the stabilizing part  30  and of the supporting part  22 , and that contributes to the coupling of the upstream guide vane  8  to the supporting part  22 . 
     In a manner similar to one of the previously described existing designs of the coupling device, the locking of the upstream guide vane  8  relative to the supporting parts  22  is achieved by means of the coupling flange  14 , that is locked in a locking recess  16  of the end  26  of the injector casing  22 , by means of a locking pin  28 . Accordingly, the dimensions of the locking recess  16  are adapted to the dimensions of the coupling flange  14 , the coupling flange  14  is pierced with a coupling flange hole (not visible in the figures), and the walls of the locking recess  16  are respectively pierced with wall holes  160  (see  FIG. 4 ). The locking pin  28  traverses said coupling flange hole and said wall holes. The locking pin  28  is a shouldered pin, so that it butts against one of the walls of the locking recess  16 , that is the wall furthest downstream in  FIG. 2 . 
     The coupling flange  14 , the locking recess  16 , the locking pin  28  and the respective holes form the means for locking the coupling device  20  according to the invention. 
     In addition to the locking means  14 ,  16 ,  28 , the coupling device according to the invention comprises means  44  for interlocking one end  26  of the injector casing  22  with one end  30  of the extension  24  of the support  18  made of abradable material, retaining means  46 ,  48 ,  50 ,  52  for preventing a relative rotation of the casing  22  relative to the extension  24 , a retaining part  60  for keeping the casing  22  and the extension  24  together, means  34 ,  72  for snap-fitting the retaining part  60  to the casing  22 , and immobilizing means  76 ,  78 ,  80 ,  82  for preventing a rotation of the retaining part  60  relative to the casing  22 . All these means will be described below. 
     To clarify the rest of the description, the end  26  of the casing  22  will be called the “supporting end  26 ”, and the end  30  of the extension  24  will be called the “stabilizing end  30 ”. 
     As illustrated in  FIG. 3 , the supporting end  26  is a part of revolution about an axial direction that comprises an end body  36  from which the two walls delimiting the locking recess  16  described above extend radially outward. The end body  36  has a substantially rectangular axial section. The end body  36  has an inner face  38  situated opposite to the locking recess  16 , an outer face  39  and a rear face  40  extending radially. 
     The furthest rearward wall of the recess  16  comprises a rim  32  which extends it rearward relative to the rear face  40  of the body  36 . This rim  32  extends radially parallel to the direction opposite to the direction of opening of the recess  16 . A rear recess  42  is formed between the rim  32  and the rear face  40 . On the free end of this rim  32 , teeth  34  are cut out that follow one another over the whole periphery of the rim  32 . These teeth  34  are directed radially inward. 
     At the junction of the inner face  38  and the rear face  40 , the end body  36  has a crank  44  having a first facet  442  substantially parallel to the rear face  40  and a second facet  444  substantially perpendicular to said first facet  442 . Grooves  46  are arranged in said second facet  444 , said grooves being oriented in the axial direction and having a substantially semicircular profile. 
       FIG. 4  illustrates the interlocking between the supporting end  26  and the stabilizing end  30 . Accordingly, the tip of the stabilizing end  30  has a shape and dimensions that match those of the crank  44  of the supporting end  26 . In particular, the stabilizing end  30  comprises a first face and a second face designed to come into contact respectively with said first facet  442  and second facet  444  of the supporting end  26 . Grooves  48  are arranged in said second face, said grooves  48  being oriented in the axial direction and having a substantially semicircular profile. 
     In service, the supporting end  26  and the stabilizing end  30  are interlocked with one another by an interlocking of the mortise and tenon type. This interlocking is achieved by butting the respective first facet  442  and second facet  444  of the supporting end  26  with the respective first face and second face of the stabilizing end  30 . The interlocking is achieved so that the grooves  46  of the second facet  444  of the supporting end  26  come opposite the grooves  48  of the second face of the stabilizing end  30 , in order to form together retaining orifices  50 . Retaining pins  52  are inserted into said retaining orifices in order to prevent said supporting end  26  and said stabilizing end  30  from rotating axially relative to one another. 
     The interlocking means of the coupling device  20  comprise said crank  44  of the supporting end  26 , and the matching shapes and dimensions of the stabilizing end  30 . 
     The means for retaining the coupling device  20  comprise said grooves  46  of the supporting end  26 , said grooves  48  of the stabilizing end  30  and said retaining orifices  50 , and said retaining pins  52 . 
     The interlocking between the supporting end  26  and the stabilizing end  30  is retained by means of a retaining part  60  that is illustrated in  FIG. 5 . 
     The retaining part  60  is a part that is annular of revolution about an axial direction. It comprises a rectilinear central framework  62 . The latter extends to one end via a radiating portion  64  itself extending via a terminal portion  66  which returns to the central framework  62  and extends parallel to the latter. The central framework  62 , the radiating portion  64  and the terminal portion  66  define between them a retaining recess  68 , and said central framework  62  extends to another end via a rectilinear collar  70  which for its part is substantially perpendicular and which overhangs said radiating portion  64  and said terminal portion  66 . In axial section, the retaining part  60  has a substantially J-shaped section whose vertical bar corresponds to the central framework  62  and whose horizontal bar corresponds to the collar  70 . 
     The central framework  62  forms an elastically deformable zone of the retaining part  60 , which allows the latter to be installed by an operator, as will be described below. 
     On the free end of the terminal portion  66 , teeth  72  are cut which succeed one another over the whole periphery of this terminal portion  66 . The shape and dimensions of the teeth  72  match the shape and dimensions of the teeth  34  of the rim  32  of the supporting end  26 . 
     The retaining part  60  also comprises a gripping flange  74  which extends from the central framework  62 , on the side opposite to the retaining recess  68  relative to said central framework  62 , and being slightly offset relative to the collar  70 . This gripping flange  74  comprises two successive zones that are angularly offset relative to one another and that make it easier for an operator to grasp this gripping flange  74  and deform the central framework  62 . 
       FIG. 6  illustrates, in radial section, the retention of the interlocking of the two ends  26 ,  30  by means of the retaining part  60 . The retaining part  60  has been snap-fitted onto the supporting end  26 , that is shown only partially. 
     The snap-fitting operation is carried out in the following manner. The operator holds the retaining part  60  by its gripping flange  74 . He inserts the free end of the terminal portion  66  of the retaining part  60  into the rear recess  42  of the body  36  of the end  26 , by placing the matching teeth  72  of the retaining part  60  between the teeth  34  of the rim  32 . Simultaneously, the rim  32  of the supporting end  26  is inserted into the retaining recess  68  of the retaining part  60 . This insertion is made easier by the presence of the elastic zone of the retaining part  60 . The operator then releases the gripping flange  74 . The central framework  62  of the retaining part  60  is then pressed against the rim  32  of the supporting end  26 , and the collar  70  of the retaining part  60  is pressed against the outer face  39  of the supporting end  26 . The operator then rotates the retaining part  60  relative to the supporting end  26  with an axial rotation. The teeth  34  of the rim  32  and the matching teeth  72  of the retaining part  60  overlap and prevent the supporting end  26  and the retaining part  60  from separating from one another. The snap-fitting thus obtained is of the bayonet locking type. 
     The result of the snap-fitting that has just been described is that the stabilizing end  30  is pressed axially against the first facet  442  of the supporting end  26  by the terminal portion  66  of the retaining part  60 . 
     The snap-fitting means of the coupling device  20  comprise the teeth  34  of the rim  32  of the supporting end  26  and the matching teeth  72  of the retaining part  60 . 
     The coupling device  20  comprises further immobilizing means designed to prevent an inverse rotation of the retaining part  60  relative to the supporting end  26  that would lead to an undesired disengagement of the latter. 
     These immobilizing means comprise a slightly domed profile  76  of the central framework  62 , the convexity of this slightly domed profile  76  being situated on the side of the retaining recess  68  (see  FIG. 5 ). This slightly domed profile  76  causes an axial tension in the retaining part  60 , which creates a friction between said retaining part  60  and the rear face  40  of the supporting end  26 , and prevents a relative rotation of these two parts (see  FIG. 6 ). 
     Supplementary immobilizing means are illustrated in  FIGS. 3 and 5 . They comprise a hole  78  for immobilizing the supporting end  26 , pierced in one of the teeth  34  of the rim  32 . They also comprise a hole  80  for immobilizing the retaining part  60 , pierced in one of the matching teeth  72 . Finally they comprise an immobilizing pin  82  designed to be inserted into these two immobilizing holes  78 ,  80  that accordingly have substantially the same diameter. Preferably, the immobilizing pin  82  is a shouldered pin (see  FIG. 3 ). During the snap-fitting operation, the operator is sure to place the two teeth pierced with these two immobilizing holes  78 ,  80  in line with one another and immobilizes the two snap-fitted parts by inserting the immobilizing pin  82  into the two immobilizing holes  78 ,  80  thus placed in line. 
     The invention is not limited to the particular embodiment that has just been described. It also applies to equivalent embodiments within the scope of those skilled in the art.