Abstract:
The present invention relates to a casing ( 5 ) for a rotor of a turbomachine, more particularly for a fan ( 1 ) of a turbojet engine ( 2 ), comprising a peripheral shroud ( 6 ) designed to form a clamping collar around the casing, characterized in that the shroud has at least one fitting ( 12, 13 ) or flange for the attachment of equipment.

Description:
TECHNICAL FIELD 
       [0001]    The present invention concerns a casing for a turbomachine rotor, and more particularly a casing for a turbojet engine fan. 
       BACKGROUND 
       [0002]    An airplane is moved by several turbojet engines each housed in a nacelle also housing a set of connected actuating devices related to its operation and performing various functions when the turbojet engine is in operation or stopped, such as, for example, a thrust reverser system. 
         [0003]    More precisely, a nacelle generally has a tubular structure comprising an air inlet upstream of the engine, a middle section designed to surround a fan of the turbojet engine, and a downstream section housing thrust reverser means and designed to surround the combustion chamber of the turbojet engine and housing thrust reverser means. 
         [0004]    The fan of the turbojet engine is essentially made up of a rotary shaft carrying a plurality of vanes. At their radial ends, the blades are circumferentially surrounded by a casing. 
         [0005]    The fan casings are generally machined metal elements. 
         [0006]    Such an embodiment makes it possible to easily add circumferential structural reinforcing flanges on a shroud between the two ends of the casing, said flanges then being able to serve also to support engine or nacelle equipment. 
         [0007]    For reasons related to trying to save mass, and these casings being situated in an area considered to be cold, they can be made of a composite material, in particular of carbon fibers. 
         [0008]    Such an embodiment then no longer allows, or allows at prohibitive costs, integrating flanges having the same geometric configuration as for a metal casing. Generally, these components therefore cannot be used to suspend engine or nacelle equipment. 
       BRIEF SUMMARY 
       [0009]    The present invention aims to offset the aforementioned drawbacks, and to that end comprises a casing for a turbomachine rotor, more particularly for a turbojet engine fan, comprising a peripheral shroud designed to form a clamping collar around the casing, characterized in that the shroud has at least one fitting or flange for the attachment of equipment. 
         [0010]    Thus, by providing a peripheral shroud surrounding the fan casing, the latter can be used to support the fastening elements and flanges of accessories of a nacelle or of turbojet engines intended to be fastened to said casing. 
         [0011]    The casing can thus be designed from the beginning to receive determined and adapted fastening means of the shroud and will not need to be modified to directly integrate the fittings and flanges of the accessories. 
         [0012]    Moreover, in case of addition of fittings or flanges, the latter parts can easily be added on the shroud without risk of damaging the integrity of the casing by adding new fixtures. 
         [0013]    It will also be noted that in case of damage or wear of the shroud, fittings or flanges, the replacement of these elements is greatly facilitated. 
         [0014]    Preferably, the shroud is made from a strip that can be closed on itself. 
         [0015]    Alternatively, the shroud is made from at least two strips that are partially peripheral and able to be joined to each other. 
         [0016]    Advantageously, the shroud is made from two substantially half-peripheral strips. 
         [0017]    Preferably, the shroud is primarily metal. The installation of fittings or flanges can then be done as in the prior art. 
         [0018]    Alternatively, the shroud is made primarily of a composite material, in particular from woven composite fibers. 
         [0019]    Advantageously, the casing comprises stops, situated on either side of the shroud so as to ensure the positioning and centering thereof, and/or stops able to prevent any rotational movement by the latter. 
         [0020]    Preferably, the shroud is glued on the casing. 
         [0021]    Also preferably, the casing has, at least at the shroud, a surface having a coefficient of friction with at least part of a surface of the shroud sufficient to limit or even prevent the rotation of the shroud around the casing. 
         [0022]    According to one particular embodiment of the invention, the casing comprises at least two shrouds each able to retain at least one base of at least one fitting, said base being introduced between the shroud and the casing. 
         [0023]    Advantageously, the shroud is retained on the casing by at least one discrete fastening means. 
         [0024]    The present invention also concerns a propulsion assembly comprising a turbojet engine housed in a nacelle, characterized in that it comprises a fan casing according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The present invention will be better understood using the detailed description that follows in reference to the appended drawing, in which: 
           [0026]      FIG. 1  is a diagrammatic longitudinal cross-sectional illustration of a casing surrounding a fan of the turbojet engine. 
           [0027]      FIG. 2  is an enlarged partial view in transverse cross-section of a fastening of a shroud according to the invention around the casing of  FIG. 1 . 
           [0028]      FIG. 3  is a diagrammatic illustration of a fitting mounted on the shroud of  FIG. 2 , said fitting being oriented perpendicular to the shroud. 
           [0029]      FIG. 4  is a diagrammatic illustration of a fitting mounted on the shroud of  FIG. 2 , said fitting being oriented in the plane of the shroud. 
           [0030]      FIG. 5  is a partial enlarged view in partial cross-section of the shroud of  FIG. 2  associated with a retaining stop of the casing. 
           [0031]      FIG. 6  is a partial diagrammatic view in longitudinal cross-section of a shroud arranged in a groove present in the casing. 
           [0032]      FIG. 7  is a diagrammatic illustration in longitudinal cross-section of a fitting maintained on the casing using two shrouds according to the invention. 
           [0033]      FIG. 8  is a partial diagrammatic illustration in longitudinal cross-section of two shrouds retained on the casing using discrete fastening means. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIG. 1  shows a fan  1  of a turbojet engine  2 , said fan  1  comprising a rotary shaft  4  supporting a set of peripheral vanes  3 . At their radial ends, the vanes are circumferentially surrounded by a casing  5  ensuring the internal aerodynamic continuity of an air intake structure (not visible) and an inner wall of a downstream section (not visible) of a nacelle. 
         [0035]    As shown in  FIG. 2 , the casing  5  is surrounded by a peripheral shroud  6  like a clamping collar. 
         [0036]    The shroud  6  illustrated in  FIG. 2  is made from a strip that can be closed on itself around said casing  5  having, to that end, two ends  7 ,  8  brought, in the closing position, opposite each other preferably at a longitudinal median plane of the casing  5 . 
         [0037]    The shroud  6  is kept closed around the casing  5  by a screw  9 /nut  10  system. Such a fastening system makes it possible to easily adapt the gripping of the shroud  6  on the casing  5 . 
         [0038]      FIGS. 3 and 4  each show a fitting  12 ,  13  supported by the shroud  6 . 
         [0039]    The fitting  12  has a foot  12   a  fastened in the shroud  6  using fastening means  12   b  of the nut type. The fitting  12  is mounted perpendicular to the shroud  6 . 
         [0040]    The fitting  13  has a foot  13   a  fastened in the shroud  6  using fastening means  13   b  of the nut type. The fitting  13  is mounted in the axis at the shroud  6 . 
         [0041]      FIGS. 3 and 4  illustrate the fact that the number, size, position, orientation and shape of the fittings can vary on a same shroud  6 , and their fastening therefore does not result from the production of particular fastening means on the casing. 
         [0042]    Indeed, a metal fan casing being a part taken up in revolution, this means that the fittings and fixtures are all in a same circumferential direction and require fittings with a complex configuration to adapt to the equipment to be supported. In the case of mounting on a shroud, the attached fittings can assume different orientations allowing a simple design, since it does not depend on the connecting area. 
         [0043]    As shown in  FIG. 5 , the shroud  6  is kept in position using stops formed on the casing  5 . In the case in point,  FIG. 5  shows a stop  15  situated between the ends  7 ,  8  of the shroud  6 , at the closing means  9 ,  10  thereof, and aims to prevent any rotation of the shroud  6  around the casing. 
         [0044]    Any longitudinal movements of the shroud  6  along the casing  5  are also prevented by the placement of lateral stops  16 ,  17 . 
         [0045]    Of course, it is also possible to use closing flanges, or connecting flanges with an air intake section or a downstream section, as stop aiming to prevent the longitudinal movement of the shroud  6 . 
         [0046]    As shown in  FIG. 6 , these lateral stops  16 ,  17  are formed by making a peripheral groove  18  in the casing  5 , the shroud  6  being positioned inside said groove  18 . The peripheral groove  18  is preferably made by machining in a local overthickness of the casing  5 . 
         [0047]      FIG. 7  illustrates another method of fastening a fitting  21  using two shrouds  6 . 
         [0048]    In the case in point, the fitting  21  has a mounting foot  21   a  extending on either side of said fitting  21  along a longitudinal axis of the casing  5 . The foot  21   a  thus has an upstream extension and a downstream extension that are each maintained by a shroud  6  on the casing  5 . 
         [0049]      FIG. 8  is an example of distribution of shrouds  6  along a fan casing  5 , the shrouds  6  being fastened in the casing using discrete fastening means distributed around the casing  5 . 
         [0050]    Although the invention has been described with specific embodiments, it is obviously in no way limited thereto and encompasses all technical equivalents of the means described as well as combinations thereof if they are within the scope of the invention.