Abstract:
An aircraft comprising a mechanical connection device including a body that extends along a longitudinal axis. The body comprises two opposite end portions disposed along the longitudinal axis and adapted to receive external axial loads in compression and in tension, a spring member that is adapted to be compressed axially, and a mechanism which, in the event of external axial loads in compression or in tension on the end portions, is able to transmit to the spring member compression forces oriented in opposite directions according to whether the external axial loads are in compression or in tension. This device forms a flexible connection that accommodates equally well external loads in compression and in tension.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the French patent application No. 1360683 filed on Oct. 31, 2013, the entire disclosures of which are incorporated herein by way of reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a mechanical connection device in an aircraft. 
     Mechanical connection devices between two parts of a structure such as an aircraft are known. 
     These devices are subjected to external compression and/or tension loads by the parts that they connect to each other. 
     These devices must therefore be configured and/or sized accordingly in order to be able to accommodate such external loads without being damaged. 
     It would be useful to design a new mechanical connection device that can be subjected to external compression and tension loads without being damaged. 
     SUMMARY OF THE INVENTION 
     In this regard, in accordance with a first aspect, the invention provides an aircraft that includes at least one mechanical connection device including a body that extends along a longitudinal axis, the body comprising:
         two opposite end portions disposed along the longitudinal axis and adapted to receive external axial loads in compression and in tension,   at least one spring member that is adapted to be compressed axially,   a mechanism which, in the event of external axial loads in compression or in tension on the two end portions, is able to transmit to said at least one spring member compression forces oriented in opposite directions according to whether the external axial loads are in compression or in tension.       

     This device thus forms a flexible connection that can accept equally well external loads in compression or in tension. 
     This device is designed so that at least one spring member (housed in the body) is compressed by the action of external compression and/or tension stresses that are transmitted by an internal mechanism. 
     Such a flexible connection makes it possible to modify the modal response and the dynamic behavior of the assembly of the two parts (external to the device) connected to each other by the device when acted on by vibratory loads. 
     In accordance with other features considered separately or in combination with one another:
         said at least one spring member also has a shock absorber function;   said at least one spring member comprises at least one axial compression spring;   said at least one spring member comprises two axial compression springs mounted concentrically inside the body;   each axial spring is formed of a stack of friction spring elements each having the shape of a ring;   said at least one spring member comprises at least one flexible and shock absorbing material (of elastomer, natural rubber, silicone, etc. type) element;   the body comprises two mobile parts aligned axially with each other and between which is axially arranged said at least one spring member, a first end portion of the body being mobile axially when acted on by external axial loads in compression and in tension and including a piston mobile axially inside the body and a peripheral contact area around the piston, the first end portion being adapted to transmit:
           an axial compression force to a first of the two mobile parts via the peripheral contact area when said first end portion is subjected to an external axial load in compression,   an axial tension force to the second mobile part via the piston when said first end portion is subjected to an external axial load in tension;   
           the so-called central piston passes through the central portion of the two mobile parts, said at least one spring member being arranged around this central portion and the central piston, the central piston including at its free end a head that is shaped to cooperate with the second mobile part and to exert an axial tension force thereon in the direction of the first mobile part when the first end portion is subjected to an external axial load in tension;   the body defines an axial internal housing and includes two opposite end walls spaced from each other along the longitudinal axis and disposed transversely, the internal housing receiving between the two end walls the two mobile parts, said at least one spring member and the piston, at least one shock absorber element being disposed between each end wall and the facing mobile part;   at least one of the two opposite end portions includes at least one yoke;   the device includes, inside the body, elements that are adapted to limit or to eliminate impacts between the parts of the mechanism on changing from a tension load to a compression load and vice-versa;   the device is equipped with a system of internal abutment(s) that is adapted to create a transfer of (high) force greater than the vibratory forces (with a high stiffness) when the internal abutment or abutments is or are loaded by parts of the mechanism;   the system of internal abutment(s) includes said at least one shock absorber element.       

     Such a device incorporated into an aircraft notably makes it possible to replace rigid connection devices such as rigid links. 
     In accordance with one possible feature, the aircraft includes an engine pylon structure, said at least one mechanical connection device forming a mechanical attachment between the engine pylon primary structure and at least one of the following elements of the aircraft: engine, fuselage, wings, tail unit. 
     In accordance with other possible features:
         in the case of external axial loads in compression, the head of the central piston is adapted to come into contact with a first shock absorber element disposed between a first end wall and the facing second mobile part and in contact with each of them.   in the case of external axial loads in tension, the central portion of the second mobile part is adapted to come into contact with the central portion of the first mobile part, therefore moving the first mobile part axially so that a second shock absorber element disposed between a second end wall and the facing first mobile part is in contact with each of them.       

     In accordance with another possible feature, said at least one mechanical connection device is adapted to modify the dynamic response of the engine pylon primary structure in the event of vibrations generated by the engine following accidental blade loss. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages will become apparent in the course of the following description, given by way of nonlimiting example only and with reference to the appended drawings, in which: 
         FIG. 1  is a diagrammatic general view in perspective of a connection device in accordance with a first embodiment of the invention; 
         FIG. 2   a  is a diagrammatic cutaway view in perspective of the device from  FIG. 1  (the plane of the cutaway being an axial plane); 
         FIG. 2   b  is a perspective view of a stack of friction spring elements in the form of rings; 
         FIGS. 3   a  to  3   d  illustrate the transmission of forces inside the device from  FIG. 2   a  in different situations; 
         FIG. 4  is a diagrammatic view in axial section of a connection device in accordance with a second embodiment of the invention; 
         FIG. 5  is a diagrammatic general view in perspective of a connection device in accordance with a third embodiment of the invention used as a strut; 
         FIG. 6  is a diagrammatic perspective view showing the installation in an aircraft of connection devices in accordance with the three embodiments of the invention referred to above; 
         FIG. 7  is a diagrammatic perspective view of the installation in an aircraft of the devices from  FIG. 5  as seen from a different angle and with the engine removed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As represented in  FIG. 1 , a connection device  10  includes a body  12  of elongate general shape and circular cross section that extends along a longitudinal axis L. 
     The body  12  includes two opposite end portions  14 ,  16  that are disposed along the longitudinal axis L at a distance from each other. 
     The first end portion  14  includes a main yoke  18  provided with a ball joint connection  20  that is perpendicular to the longitudinal dimension of the yoke. 
     The second end portion  16  includes twin yokes  24 ,  26  disposed facing each other and offset transversely relative to the longitudinal axis. The orifices  24   a ,  26   a  through the two yokes are face to face. 
     As represented in  FIG. 2   a , the body  12  includes an external casing  28  that defines an internal housing  30  extending axially along the longitudinal axis L. 
     The external casing  28  of the body  12  comprises a plurality of elements fixed to one another: 
     a central wall  28   a  of cylindrical shape that extends axially along the longitudinal axis L, 
     two hoods or caps disposed at the two opposite ends of the central wall  28   a  and that respectively cap its two opposite ends, thus leaving uncovered a central portion in the form of a strip. 
     One of the caps corresponds to the second end portion  16 . 
     The two caps are screwed onto the central wall  28   a.    
     Each cap includes a transverse wall that is an end wall  28   c ,  28   d  of the internal housing  30 . 
     Thus the housing  30  is defined by the axially extending wall  28   a  and the two transverse end walls  28   c ,  28   d.    
     The end wall  28   c  is pierced axially to enable a portion of the first end portion  14  that is described later to pass through it. 
     The internal housing  30  encloses: 
     two axially mobile parts  32 ,  34  that are aligned with respect to each other along the longitudinal axis L, 
     at least one spring member  36  that is arranged between the two parts  32 ,  34  and in contact with them. 
     Said at least one spring member  36  bears on each of these two parts. 
     Each part  32 ,  34  bears in turn against a shock absorber element  38 ,  40 , for example in the form of a metal disk, disposed against the respective end wall  28   c ,  28   d.    
     The two parts  32 ,  34  are both perforated in their central portion aligned along the longitudinal axis L in order to receive the aforementioned portion of the first end portion  14 . 
     As represented in  FIG. 2   a , the first part  32  includes a peripheral base  32   a  disposed transversely inside the central wall  28   a  and a central portion  32   b . The central portion  32   b  has transverse dimensions smaller than those of the base  32   a  and extends axially away from said base in the direction of the second part  34 . 
     A central hole through the whole of the part  32  has its diameter increased inside the central portion  32   b  in order to form an internal shoulder. 
     The second part  34  has the general shape of a hat and includes a peripheral base  34   a  disposed transversely inside the central wall  28   a  and a central portion  34   b . The central portion  34   b  has transverse dimensions smaller than those of the base  34   a  and extends axially away from said base and in the direction of the part  32 . 
     A central hole through the whole of the part  34  has a diameter that is constant inside the central portion  34   b  and smaller at the open end of said central portion  34   b  in order to form an internal shoulder. 
     The respective bases and central portions of the two parts  32 ,  34  are aligned with one other along the axis L and have the same transverse dimensions. 
     The first end portion  14  includes a hollow first portion  42  that is arranged in a central hole in the end wall  28   c  of the cap  28   b  and a peripheral area  42   a  which bears against the shock absorber element  38 . The first portion  42  is disposed between the shock absorber element  38  and the yoke  18 . The first portion  42  forms an element for adjusting the position of the first end portion  14  on the body  12 . This adjustment is effected by screwing this first end portion  14 , a portion of the external surface of which is threaded, inside the first portion  42 , which is threaded in a complementary manner. 
     The first end portion  14  also includes a second portion  44  connected to the yoke  18 , passing through the hollow first portion  42  and extending axially inside the housing  30 . 
     The second portion  44  includes a central piston that includes a rod  44   a  and, at its free end, a head  44   b.    
     The rod  44   a  is mounted at its base inside a sheath  44   c  that is fastened to the yoke  18  and forms an axial extension thereof. 
     The sheath  44   c  has an outside diameter that matches that of the hole in the base  32   a.    
     The rod  44   a  is held in a fixed position inside the sheath  44   c  by means of an immobilizing element  46  such as a screw that is screwed into the body of the second portion  44  and presses on the rod  44   a.    
     The rod  44   a  passes axially through the respective central holes of the two parts  32  and  34 . 
     The head  44   b  of the piston is inside the central portion  34   b  and is retained therein by the internal shoulder of said central portion. 
     The central piston  44  is therefore shaped to cooperate with the second part  34 . 
     In the position shown in  FIG. 2   a , the shoulder of the head  44   b  bears on a third shock absorber element  39  in the form of a ring that is disposed against the shoulder inside the central portion  34   b.    
     As will emerge later, the first end portion  14  is mobile axially inside the internal housing  30 . 
     In this embodiment said at least one spring member  36  comprises two axial compression springs  36   a  (external),  36   b  (internal) that are mounted coaxially with respect to each other. 
     The external spring  36   a  and the internal spring  36   b  each comprise a stack of friction spring elements, each of which is in the form of a ring. As represented in  FIG. 2   b , the spring  36   a  (like the spring  36   b ) is formed by a set of rings  36   a   1 -a 7  juxtaposed in an offset manner. 
     These two stacks of spring elements are mounted in the annular housing delimited by the bases  32   a  and  34   a  of the two parts  32  and  34 , their central portions  32   b  and  34   b  and the central wall  28   a . To be more specific, the exterior surface of the spring  36   a  is adjacent the central wall  28   a  and the interior surface of the spring  36   b  is adjacent the central portions  32   b  and  34   b.    
     A peripheral rib  32   c ,  34   c  is provided on each base to locate each stack and to separate it from the other stack. 
     These spring members  36   a ,  36   b  provide a connection that is both flexible (with a low stiffness) and absorbs shock (due to the rubbing or friction created between the various rings). 
     These spring members are adapted to be compressed axially along the longitudinal axis L by whatever type of axial force (compression or tension) is applied to the device  10 . 
       FIGS. 3   a - d  described hereinafter illustrate the operation of the device  10  from  FIGS. 1 and 2  when it is subjected to axial compression and tension stresses by the parts that the device connects. 
     For clarity, only a few reference numbers are repeated in  FIGS. 3   a - d.    
     In  FIG. 3   a , axial external stresses in compression symbolized by the arrows directed toward each other are transmitted to the connection device  10  and follow the path indicated by the arrows inside the device. 
     The axial compression stress exerted on the main yoke  18  of the first end portion  14  causes movement thereof. The stress is transmitted successively, via the peripheral area  42   a  of the first portion  42 , to the shock absorber element  38 , the first part  32  and the spring members  36   a ,  36   b , which are compressed axially. 
     The spring members apply this stress to the second part  34  which in turn transmits it to the shock absorber element  40  and to the cap bearing the yokes  24  and  26  of the second end portion  16 . 
     In return, the second end portion exerts a force on the longitudinal axis of the part. 
     In  FIG. 3   b , axial external stresses in tension symbolized by the arrows directed away from each other are exerted on the connection device  10  and follow the path indicated by the arrows inside the device. 
     The effect of the tension force exerted on the main yoke  18  is to exert tension on the central piston, the head  44   b  of which transmits the tension forces to the second part  34 . 
     The second part  34  is therefore drawn toward the right in the figure (in the direction of the first part  32 ) and axially compresses the spring members  36   a ,  36   b , which transmit the stress to the first part  32 . 
     In turn, the first part  32  transmits the stress to the end cap  28   b  of the main yoke, which retransmits it via the external casing of the body to the cap bearing the yokes  24  and  26  of the second end portion  16 . 
       FIGS. 3   a  and  3   b  each illustrate a so-called flexible mode of operation that enables the attachment to have a low stiffness. This mode of operation is therefore defined for a range of forces in tension and in compression that is specific and similar to the level of vibrational force. If the forces applied are greater than the vibrational forces, the mechanism comes into a situation of abutment, as represented in  FIGS. 3   c  and  3   d , and goes to a so-called rigid mode. The internal abutments are the shock absorber elements  38  and  40  referred to above, which form an internal abutment system. 
     High axial compression stresses ( FIG. 3   c ) push the central piston of the first portion  14  into the internal housing  30 . The head  44   b  of the piston comes into contact with the shock absorber element  40  (for example a disk-shaped shock absorber pad) and the force is therefore transmitted to the cap bearing the yokes  24  and  26 . 
     The axial compression stresses exerted on the main yoke  18  are also transmitted to the cap bearing the yokes  24  and  26  successively via the shock absorber element  38 , the first part  32 , the spring members  36   a ,  36   b , which are compressed, the second part  34  and the shock absorber element  40 . 
     It will be noted that in this position ( FIG. 3   c ) there is an axial clearance between the facing open ends of the two central portions  32   b  and  34   b  in order to prevent peening of these two parts. 
     High axial stresses in tension ( FIG. 3   d ) pull the central piston of the first end part out of the internal housing  30  (toward the right in the figure). 
     The head  44   b  of the piston is moved axially in the direction of the first part  32  and entrains the second part  34  with it via its shoulder inside the central portion  34   b.    
     The central portion  34   b  comes to bear against the central portion  32   b  and the spring members  36   a ,  36   b  are compressed axially, therefore transmitting the forces to the first part  32  and to the cap bearing the yokes  24  and  26  via the same path as that shown in  FIG. 3   b . The first end portion  14  moves away from the body  12 . 
     As explained above, the connection device  10  is therefore particularly suitable for providing a reliable, flexible and shock-absorbing connection when it is subjected even to very high axial stresses in compression and in tension ( FIGS. 3   c  and  3   d ). 
     This is made possible by its construction and its internal mechanism that enables one or more spring members to be compressed axially whether the external stresses are in compression or in tension. 
     Such a device makes it possible to modify the modal response of the system on which it is mounted in order to attenuate the levels of vibration and acceleration to which the structures may be subjected. 
     It will be noted that the spring members may be sized differently. 
     Accordingly, the number of rings to be stacked may vary as a function of the levels of force and stiffness to be achieved. 
     The number and shape of the spring members may also vary as a function of the stresses to which the device is liable to be subjected and the dynamic behavior that is expected of this device. 
     In accordance with a variant embodiment that is not represented, the spring member or members is or are elements made from a flexible and shock-absorbing material, for example of elastomer, natural rubber, silicone, etc. type. 
     The body  12  of the device may have a different shape and the shape of the internal housing  30  may notably vary and have a cross section that is not circular but, for example, square or rectangular. 
     Moreover, the external casing of the body may alternatively be made in one piece instead of three parts ( 28   a ,  28   b  and  16 ). 
     Alternatively, a single yoke aligned with the main yoke  18  may be provided on the cap of the second end portion  16  instead of the two yokes  24 ,  26 . 
       FIG. 4  shows a connection device  50  in accordance with a second embodiment of the invention. 
     This device provides only a flexible connection (stiffness) with no shock absorber effect. 
     The device  50  comprises a structure virtually identical to that of the device  10  with the exception of the spring members. 
     In fact, the spring members  36   a ,  36   b  of the device  10  are replaced here by two coil springs  52   a  (external spring),  52   b  (internal spring) mounted coaxially around the longitudinal axis L of the device. 
     This device behaves as described with reference to  FIGS. 3   a - d.    
       FIG. 5  shows a connection device  60  in accordance with a third embodiment of the invention. 
     This device differs from the preceding ones in its external structure. Its internal structure may be that of the devices  10  or  50  or a variant thereof 
     The device  60  again includes the main yoke  18  of the first end portion  14 . 
     However, the second end portion is modified: the cap bearing the two yokes  24  and  26  in  FIGS. 1 to 3  is replaced by a link  62  fixed, for example welded, to the end cap  64  of the body. This link  62  carries at its free end twin yokes  66 ,  68  analogous to the yokes  24 ,  26  but offset relative to the latter. 
     The device  60  therefore forms a strut. 
     The connection devices of the preceding embodiments are particularly suitable, notably because of their internal mechanism, for the stresses encountered on board an aircraft and that do not exist on board other mobile machines such as motor vehicles, trains, etc. In particular, such devices are particularly suitable for resisting the levels of acceleration to which aircraft are subjected (notably on take-off) and the variations of temperatures and pressure cause by changes of altitude. 
     These connection devices also have the advantage of being neither too heavy nor too bulky. 
       FIGS. 6 and 7  illustrate the use of the connection devices of the foregoing embodiments on an aircraft  80  of which only a portion is represented. 
     The aircraft  80  includes an engine pylon primary structure  82  connected to a fuselage (not represented). 
     The aircraft  80  also includes an engine  86  ( FIG. 6 ) the frame of which is connected to the engine pylon primary structure  82  by means of a set of mechanical connection elements. 
     Thus the set of mechanical connection elements comprises a plurality of mechanical connection devices  10  of the first embodiment and mechanical connection devices  60  of the third embodiment. 
       FIG. 7 , which is a view from the other side, at the wing end (without the engine  86 ), shows the integration of the devices to a part  88  known as the engine spar. 
     The devices are integrated onto parts such as fittings  90 ,  92  fixed to the engine spar  88  or to a part such as an interface part  94  between the primary structure and the engine mounts. This is a plate of “flexible” metal such as titanium, for example. 
     The use of the devices in accordance with the invention as attachments between an aircraft engine and the engine pylon primary structure enables static loads to be transmitted to the primary structure and the levels of dynamic load and acceleration on the latter to be reduced. 
     These devices therefore notably make it possible to modify the dynamic response of the engine pylon primary structure and therefore of the aircraft in the event of vibrations generated by the engine following accidental blade loss. 
     These devices are particularly suitable for aircraft with contra-rotating propellers. 
     These devices can advantageously replace rigid connection devices in an aircraft such as rigid links. 
     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.