Abstract:
In an aircraft duct formed with pipes connected in pairs via connectors in which the pipes are mounted with the possibility of axial displacement, there exists a risk that a pipe of the duct, with a dimension greater that the dimension of the nominal pipe, is mounted instead and in place of the latter. In this case, the wrongly mounted pipe would risk not having sufficient clearance in axial translation. In order to solve this problem, it is disclosed to equip one of the relevant connectors with an obstacle limiting the travel of the nominal pipe and preventing the mounting of a pipe with a greater dimension belonging to the duct. A method for assembling an aircraft portion is also proposed, in order to benefit from the particularities of the duct.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the French patent application No. 1463146 filed on Dec. 22, 2014, the entire disclosures of which are incorporated herein by way of reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of aircraft and more particularly concerns an aircraft portion including a structure and a duct intended for the circulation of a fluid, such as oil or fuel, and comprising a plurality of pipes and a plurality of connectors fixed to the structure and connecting the pipes two-by-two. 
     In aircraft, some ducts are formed of pipes connected two-by-two by connectors fixed to the structure of the aircraft so that the pipes can move in translation over a limited travel to make it possible to absorb defects in the positioning of the connectors resulting from the manufacturing tolerances of the pipes and the tolerances for the positioning of the connectors relative to the structure, and also to make it possible to withstand differential deformations of the duct and of the structure in service. 
     These pipes, which are preferably of the double-wall type, have opposite ends inserted in annular cavities of the connectors so as to seal the connection between the pipes and the connectors, at the same time as allowing play in translation of the pipes. 
     Moreover, the complex geometry of the ducts generally requires the use of pipes of different lengths. 
     The result of this is a risk of a pipe that is too large being mounted instead of the nominal pipe, notably if the intended play of the nominal pipe is relatively large. 
     Now, such a mounting error can lead to damage to the pipe that has been mounted incorrectly given that the effective play of the latter may be less than the nominal play necessary to take into account defects of positioning and differential deformations as referred to above. 
     SUMMARY OF THE INVENTION 
     An object of the invention is notably to provide a simple, economic and effective solution making it possible to solve this problem at least in part. 
     To this end the invention proposes an aircraft portion, comprising a structure, and a duct intended for the circulation of a fluid and comprising a plurality of pipes, and a plurality of connectors fixed to the structure and connecting the pipes two-by-two. 
     The plurality of pipes includes pipes of different lengths, each having a first end situated on a first side of the duct and a second end and a first abutment situated on a second side of the duct. 
     Moreover, each connector includes a connector internal passage that fluidically connects two pipe internal passages respectively belonging to the two pipes that the connector connects to each other. 
     Also, each connector includes two cavities surrounding the connector internal passage and in which are respectively inserted respective ends of two consecutive pipes, namely a first cavity, preferably of annular shape, situated on the second side of the duct and a second cavity, preferably of annular shape, situated on the first side of the duct. The first and second cavities of each connector having respective axes. 
     The first and second cavities of each connector are delimited internally by respective radially internal walls of annular shape respectively centered on the respective axes of the first and second cavities and are delimited externally by respective radially external walls also of annular shape and respectively centered on the respective axes of the first and second cavities. 
     Each connector includes an internal support delimiting the first and second cavities of the connector and connecting the respective radially internal walls to the respective radially external walls of the first and second cavities. 
     Also, each pipe is movable in axial translation relative to the two connectors that the pipe connects to each other. 
     Moreover, each connector includes a second abutment that limits the travel in translation of the pipe received in the first cavity of the connector in the direction of the first side of the duct by cooperating with the first end of the pipe and a third abutment that limits the travel in translation of the pipe received in the second cavity of the connector in the direction of the second side of the duct by cooperating with the first abutment of the pipe. 
     Also, the plurality of connectors comprises at least a first connector and a second connector having the following features: 
     the respective internal supports of the first and second connectors have the same conformation; 
     the first cavity of the first connector and the second cavity of the second connector respectively receive the first and second ends of a first pipe of the plurality of pipes; 
     the first end and the first abutment of the first pipe are separated from each other by a first distance; 
     the internal support of the first connector and the third abutment that is part of the second connector are separated from each other by a second distance measured parallel to the respective axes of the first cavity of the first connector and the second cavity of the second connector; and 
     the first connector and the second connector are positioned so that the plurality of pipes comprises a second pipe the first end and the first abutment of which are separated from each other by a third distance strictly greater than the first distance and strictly less than the second distance. 
     In other words, the second pipe could be mounted between the first and second connectors instead of the first pipe if these two connectors were of a conventional type. Now, the second pipe would not offer sufficient play in translation to absorb the positioning defects and the differential deformations in service referred to above, because the distance separating the first end and the first abutment of the second pipe is greater than the distance separating the first end and the first abutment of the first pipe. 
     In accordance with the invention the first connector includes a first obstacle arranged in the first cavity of this first connector, the first obstacle forming the second abutment and being separated from the third abutment of the second connector by a fourth distance less than or equal to the third distance and measured parallel to the respective axes of the first cavity of the first connector and the second cavity of the second connector. 
     Moreover, the second abutment of the second connector is formed by the internal support of the second connector or by a second obstacle arranged so that the relative position of the second obstacle and the internal support of the second connector is different from the relative position of the first obstacle and the internal support of the first connector. 
     Thus the obstacle makes it possible to prevent mounting the second pipe between the first connector and the second connector. 
     The obstacle may nevertheless be sufficiently far away from the third abutment of the second connector to allow movement in translation of the first pipe with sufficient play to absorb positioning defects and differential deformations in service. 
     The invention therefore makes it possible to prevent the use of a pipe larger than the nominal pipe between two consecutive connectors where there is a risk of confusion. 
     Moreover, the invention enables the use of connectors having an external configuration similar to the connectors of known type and therefore not necessitating modification of the structure of the aircraft portion. 
     The obstacle may moreover be added to a pre-existing conventional connector, for example by means of welding techniques or additive fabrication techniques. 
     The invention is particularly advantageous when the risk of a mounting error is aggravated by the presence of seals in the connectors, imposing frequent cycles of demounting and remounting the duct in order to verify the state of the seals. 
     Any pipe of the duct the first end and the first abutment of which are separated from each other by a fifth distance strictly greater than the first distance is preferably such that the fifth distance is greater than or equal to the fourth distance. 
     The foolproofing relating to the pipe to be mounted between the first connector and the second connector is therefore valid in respect of any pipe of the duct. 
     Moreover, the first obstacle is advantageously perforated. 
     Also, the internal support of each connector is preferably perforated. 
     Additionally, the first obstacle may be distanced from the internal support of the first connector. 
     The distance between the first obstacle and the internal support notably makes it possible to reduce the mass of the first obstacle and therefore of the connector. 
     The aircraft portion may notably be a fuselage section or a set of fuselage sections. 
     Alternatively, the aircraft portion may be a wing or a rear tail assembly. 
     The invention also concerns an aircraft including an aircraft portion of the type described above. 
     The invention also concerns a method for assembling an aircraft portion of the type described above, comprising: 
     a step comprising procuring the plurality of pipes and the plurality of connectors; 
     an assembly step comprising fixing the connectors to the structure of the aircraft portion and connecting the connectors two-by-two by means of the pipes; and 
     a verification step comprising attempting to move each pipe in axial translation after the connection of the pipe to the corresponding two connectors and, if such movement in axial translation proves impossible, replacing the initial pipe with another pipe the first end and the first abutment of which are closer to each other than the first end and the first abutment of the initial pipe. 
     The method therefore makes it possible, at least where the first and second connectors referred to above are concerned, to guarantee that a pipe of larger size than the nominal pipe is not mounted between these two connectors. 
     The verification step preferably further comprises replacing the initial pipe by another pipe the first end and the first abutment of which are farther apart from each other than the first end and the first abutment of the initial pipe if the movement in axial translation of the initial pipe enables this initial pipe to separate from one of the corresponding two connectors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be understood better and other details, advantages and features thereof will become apparent on reading the following description given by way of nonlimiting example and with reference to the appended drawings, in which: 
         FIG. 1  is a diagrammatic side view of an aircraft in accordance with a preferred embodiment of the invention; 
         FIG. 2  is a view similar to  FIG. 1  showing the division into sections of the fuselage of the aircraft from  FIG. 1 ; 
         FIG. 3  is a diagrammatic view in axial section of a portion of the aircraft from  FIG. 1  showing a duct and a structure of this aircraft portion; 
         FIG. 4  is a diagrammatic view in axial section showing the aircraft portion from  FIG. 3 . 
     
    
    
     In all these figures, identical references may designate identical or similar elements. 
     Moreover, the various elements shown in these figures are intentionally not to scale in order to improve the clarity of the figures. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a general view of an aircraft  10  comprising a fuselage  12 , wings  14 , and a rear tail assembly  16 . The fuselage  12  is for example formed of an assembly of fuselage sections  18  as  FIG. 2  shows. 
     A portion of the aircraft  10 , for example one of the sections  18  or a set comprising a plurality of these sections  18 , includes a structure  20  and a duct  22 , a portion of which is shown in  FIG. 3 . Alternatively, the aircraft portion may be a wing  14  or a portion of the rear tail assembly  16 . 
     The duct  22  is intended for the circulation of a fluid such as fuel, oil or any other type of fluid, in particular an inflammable fluid. 
     The duct  22  comprises a plurality of pipes  24  and a plurality of connectors  26  fixed to the structure  20  and connecting the pipes  24  two-by-two.  FIG. 3  shows in particular two consecutive connectors and three consecutive pipes. Where the two end pipes are concerned, only one end of each of these pipes can be seen in  FIG. 3 . Where the middle pipe is concerned, a middle portion of the latter pipe is masked to reduce the size of  FIG. 3 . 
     The structure  20  comprises, for example, circumferential frames  28  connected to one another by fuselage panels  30 . In the example shown, the connectors  26  are fixed to the circumferential frames  28 . 
     The plurality of pipes  24  includes pipes of different lengths. 
     Each of the pipes  24  has a first end  32  situated on a first side of the duct (symbolized by the arrow  34  in  FIG. 3 ) and a second end  36  and a first abutment  38  situated on a second side of the duct (symbolized by the arrow  40 ). 
     The first side  34  corresponds for example to an upstream side and the second side  40  to a downstream side of the duct, relative to the flow of the fluid in this duct in service, or vice versa. 
     The pipes  24  have a shape such that the two ends of each pipe have a common axis or respective parallel axes so as to allow movement of the pipe in translation, as will become more clearly apparent hereinafter. In this regard, the pipes  24  are preferably straight pipes, each therefore having a longitudinal axis  41 . 
     Each connector  26  includes two cavities into which are respectively inserted respective ends  32 ,  36  of two consecutive pipes  24 , namely a first cavity  42  of annular shape situated on the second side  40  of the duct and a second cavity  44  of annular shape situated on the first side  34  of the duct. 
     The first and second cavities  42 ,  44  of each connector  26  have respective axes  46 ,  48  that may coincide or not, depending on whether the connector  26  is straight or angled. The plurality of connectors may include angled connectors so as to confer a complex conformation on the duct  22 . 
     The cavities  42 ,  44  of each connector  26  are delimited internally by respective radially internal walls  50  of the connector  26 . These radially internal walls  50  are of annular shape and are respectively centered on the respective axes  46 ,  48  of the two cavities. 
     Moreover, the cavities  42 ,  44  of each connector  26  are delimited externally by respective radially external walls  52 , also of annular shape and respectively centered on the respective axes  46 ,  48  of the two cavities. 
     The radially internal walls  50  of each connector  26  delimit externally a connector internal passage  51  that communicates with a pipe internal passage  53  of each of the two pipes  24  connected to the connector so as to allow the circulation of the fluid between these pipes. 
     Each connector  26  further includes an internal support  54  delimiting the first and second cavities  42 ,  44  of the connector and connecting the respective radially internal walls  50  to the respective radially external walls  52  of the cavities  42 ,  44 . 
     It must therefore be understood that, by definition, each cavity  42 ,  44  extends axially as far as the internal support  54 . In other words, the internal support  54  extends between the two cavities  42  and  44  of the connector. 
     In the example shown, each connector  26  is formed of a plurality of parts assembled to one another, notably: 
     a first part  56  comprising the radially internal walls  50  and the radially external walls  52  of the first cavity  42  and a first portion  58  of the internal support  54 ; 
     a second part  60  comprising the radially internal wall  50  of the second cavity  44  and a second portion  62  of the internal support  54  forming a flange fixed to the first portion  58  of this internal support, for example by means of fixing screws  64 ; 
     a third part  66  comprising the radially external wall  52  of the second cavity  44 , fixed to the first part  56 , for example by means of bolts (not visible in  FIG. 3 ). 
     This configuration of the connectors  26  notably makes it possible to facilitate the assembly and the disassembly of the duct  22 . 
     Of course, the connectors  26  may instead be produced in one piece or be formed of an assembly of parts different from that shown by way of example. 
     In the example shown, the internal support  54  of each connector  26  includes perforations (not visible in the figures) that establish fluidic communication between the two cavities  42 ,  44  of the connector. Alternatively, without departing from the scope of the invention, this internal support  54  may form a solid wall separating the two cavities  42 ,  44  from each other in a sealed manner. 
     Moreover, each pipe  24  is mobile in axial translation relative to the two connectors  26  that the pipe connects to each other. By “axial translation” must be understood a movement parallel to the respective axes  46 ,  48  of the two cavities in which the ends  32 ,  36  of the pipe are respectively inserted. 
     Each connector  26  includes a second abutment  70  that limits the travel in translation of the pipe  24  received in the first cavity  42  of the connector in the direction of the first side  34  of the duct by cooperating with the first end  32  of the pipe. Moreover, each connector  26  includes a third abutment  72  that limits the travel in translation of the pipe  24  received in the second cavity  44  of the connector in the direction of the second side  40  of the duct by cooperating with the first abutment  38  of the pipe. 
     Moreover, the plurality of connectors  26  comprises at least a first connector  26 A and a second connector  26 B having the following particular features and shown in  FIG. 4 : 
     the respective internal supports  54 A,  54 B of the first and second connectors have the same conformation; 
     the first cavity  42 A of the first connector  26 A and the second cavity  44 B of the second connector  26 B respectively receive the first and second ends  32 ,  36  of a first pipe  24 A; 
     the first end  32 A and the first abutment  38 A of the first pipe are separated from each other by a first distance D 1 ; 
     the first pipe  24 A is able to move in translation parallel to the axis  46 A of the first cavity  42 A of the first connector  26 A and the axis  48 B of the second cavity  44 B of the second connector  26 B so that the travel of the first pipe  24 A is limited in the direction of the first side  34  of the duct by the first end  32 A of the first pipe  24 A coming into abutment against the second abutment  70 A that is part of the first connector  26 A and in the direction of the second side  40  by the first abutment  38 A of the first pipe  24 A coming into abutment against the third abutment  72 B that is part of the second connector  26 B; 
     the internal support  54 A of the first connector  26 A and the third abutment  72 B are separated from each other by a second distance D 2  measured parallel to the axes  46 A,  48 B; 
     the first connector  26 A and the second connector  26 B are positioned so that the plurality of pipes comprises a second pipe  24 B (shown diagrammatically in  FIG. 4  facing the first pipe  24 A for illustrative purposes) conformed so that the first end  32 B and the first abutment  38 B of the second pipe  24 B are separated from each other by a third distance D 3  strictly greater than the first distance D 1  and strictly less than the second distance D 2 . 
     In other words, the second pipe  24 B of the duct  22  could be mounted between the two connectors  26 A and  26 B instead of the first pipe  24 A (which constitutes the nominal pipe) if these two connectors  26 A and  26 B were of a conventional type. Now, the pipe  24 B would not offer sufficient play in translation to absorb the positioning defects and the differential deformations in service referred to above. 
     To solve this problem the first connector  26 A includes a first obstacle  80 A inside the first cavity  42 A of this first connector. This first obstacle  80 A defines the second abutment  70 A at a distance from the third abutment  72 B, referred to as the fourth distance D 4 , that is less than or equal to the third distance D 3 . The fourth distance D 4  is of course also measured parallel to the axes  46 A,  48 B. For example, the second abutment  70 A comprises the face of the first obstacle  80 A situated on the same side as the opening of the first cavity  42 A. 
     The obstacle  80 A therefore makes it possible to prevent mounting the second pipe  24 B between the first connector  26 A and the second connector  26 B. 
     The obstacle  80 A is nevertheless sufficiently far away from the third abutment  72 B to allow sufficient play in translation d of the first pipe  24 A. This play d corresponds to the difference between the fourth distance D 4  and the first distance D 1 . 
     As a general rule, only connectors  26  for which there would exist a risk of confusion between the nominal pipe and another pipe of the duct if these connectors were of a conventional type are equipped with an obstacle like the obstacle  80 A. 
     In particular, the first cavity  42 B of the second connector  26 B does not include any such obstacle. In other words, the second abutment  70 B of the second connector  26 B is formed by the internal support  54 B of that connector. It is therefore this internal support  54 B that limits the travel in translation of a pipe mounted in the first cavity  42 B of the second connector  26 B. 
     Alternatively, the second abutment  70 B of the second connector  26 B may be formed by a second obstacle such that the relative position of this second obstacle and the internal support  54 B of the second connector  26 B differs from the relative position of the first obstacle  80 A and the internal support  54 A of the first connector  26 A. The second obstacle is therefore suited to a foolproofing situation other than the foolproofing situation concerning the choice of the pipe to connect the first connector  26 A to the second connector  26 B. 
     In accordance with a preferred feature, any pipe of the duct  22 , the first end  32  and the first abutment  38  of which are separated from each other by a fifth distance strictly greater than the first distance D 1 , is such that the fifth distance is greater than or equal to the fourth distance D 4 . 
     The obstacle  80 A therefore makes it possible to guarantee that only the first pipe  24 A (constituting the nominal pipe) can be mounted between the connectors  26 A and  26 B. 
     Of course, it is preferable for any pair of consecutive connectors  26  of the duct  22  for which such a risk of confusion exists to conform to the principle explained above with reference to the two connectors  26 A and  26 B. 
     To summarize, in the preferred embodiment of the invention, in each connector equipped with an obstacle, that obstacle is positioned as a function of the dimensions of the pipes concerned, i.e., as a function on the one hand of the distance between the first end and the first abutment of the nominal pipe and as a function on the other hand of the distance between the first end and the first abutment of the pipe or pipes liable to be used by mistake, so that the nominal pipe may retain sufficient play but it is impossible to mount with play any pipe of the duct  22  having a size greater than that of the nominal pipe. 
     Moreover, the first obstacle  80 A is preferably perforated. The perforations make it possible to reduce the mass of the first obstacle  80 A. These perforations additionally make it possible, if the internal support  54 A is itself perforated, to provide fluidic communication between the second cavity  44 A and the portion of the first cavity  42 A situated on the same side as the opening of that first cavity  42 A, i.e. situated on the second side  40  of the duct  22 . 
     The obstacle  80 A is for example formed of three arms regularly distributed around the axis  46 A and extending radially so as to connect the radially internal wall  50  of the first cavity  42 A to the radially external wall  52  of that cavity. Only two of these arms can be seen in the  FIG. 3  sectional view while only one of the arms can be seen in the  FIG. 4  sectional view. 
     If the difference between the second distance D 2  and the third distance D 3  is sufficiently large, it may be advantageous for the first obstacle  80 A to be distanced from the internal support  54 A of the first connector, as in the example shown in  FIGS. 3 and 4 . This notably makes it possible to reduce the mass of the connector  26 A. 
     Alternatively, and notably if the difference between the second distance D 2  and the third distance D 3  is relatively small, the first obstacle  80 A may be contiguous with the internal support  54 A. In this case the first obstacle  80 A appears as an extension of the internal support  54 A. 
     The principle proposed by the invention is particularly advantageous in the case of a duct including double-wall pipes. Pipes of this type are generally used to minimize the risk of leaks, in particular when the fluid circulating in the duct is inflammable. 
     Accordingly, in the example shown in  FIGS. 3 and 4 , the pipes  24  are of the double-wall type. These pipes therefore each include an annular passage  90  around the internal passage  53  of the pipe. These two passages are separated from each other by an annular internal wall  92  of the pipe while the annular passage  90  is delimited externally by an annular external wall  94  of the pipe. Accordingly, in the event of damage to the annular internal wall  92  of the pipe, the annular external wall  94  continues to confine the fluid circulating in the duct  22 . 
     Each of the cavities  42 ,  44  of each connector  26  is in fluidic communication with the annular passage  90  of the corresponding pipe. 
     The radially internal wall  50  and the radially external wall  52  delimiting each cavity  42 ,  44  include at their respective ends, which delimit the opening of the cavity, seals  96  that provide a sealed contact with the annular internal wall  92  and the annular external wall  94  of the corresponding pipe  24 , respectively. 
     It is to be noted that in the example shown in the figures the first abutment  38  of each pipe  24  is offset relative to the second end  36  of the pipe and the third abutment  72  of each connector  26  is arranged in the plane of the opening of the second cavity  44  of the connector. 
     Of course, other configurations of the first and third abutments  38 ,  72  are possible without departing from the scope of the invention. 
     In particular, the third abutment  72  of each connector  26  may be formed by the internal support  54  of the connector, in which case the first abutment  38  of each pipe  24  is formed by the second end  36  of the pipe. 
     Moreover, the pipe  24 A being a straight pipe, the respective axes  46 A and  48 B of the first cavity  42 A of the first connector  26 A and second cavity  44 B of the second connector  26 B coincide. 
     Alternatively, the pipe  24 A may have a transverse offset between its ends  32  and  36 , in which case the respective axes  46 A and  48 B of the first cavity  42 A of the first connector  26 A and the second cavity  44 B of the second connector  26 B are offset relative to each other but are nevertheless parallel to each other. 
     Moreover, the connectors  26 A and  26 B described by way of example are straight connectors, i.e. connectors the two cavities  42  and  44  of which have respective axes  46 ,  48  that coincide. 
     Alternatively, at least one of the connectors  26 A and  26 B may be an angled connector, i.e. a connector the two cavities  42  and  44  of which have respective axes  46 ,  48  that are inclined relative to each other. 
     The duct  22  and the structure  20  may be assembled by means of a method comprising: 
     a step comprising procuring the plurality of pipes  24  and the plurality of connectors  26 ; 
     an assembly step comprising fixing the connectors  26  to the structure  20  and connecting the connectors  26  two-by-two by means of the pipes  24 ; and 
     a verification step comprising attempting to move each pipe  24  in axial translation after the connection of the pipe to the corresponding two connectors  26  and, if such movement in axial translation proves impossible, replacing the initial pipe with another pipe the first end  32  and the first abutment  38  of which are closer to each other than the first end and the first abutment of the initial pipe. 
     The method therefore makes it possible to prevent a pipe of larger size than the nominal pipe being used between each pair of consecutive connectors. 
     The verification step may be carried out after the assembly step, i.e. after the duct has been completely assembled. 
     Alternatively, the assembly and verification steps may be carried out conjointly. In this case, as soon as a pipe is connected to two consecutive connectors that have just been fixed to the structure, an operative attempts to move the pipe and if necessary proceeds to replace that pipe. 
     In accordance with a preferred embodiment of the assembly method, if the attempt to move the pipe in axial translation reveals that the pipe is liable to separate from one of the corresponding two connectors  26 , the verification step further comprising replacing the initial pipe by another pipe the first end  32  and the first abutment  38  of which are farther apart than the first end and the first abutment of the initial pipe. 
     The method therefore makes it possible to prevent a pipe of too small a size being used between each pair of consecutive connectors of the duct. 
     While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.