Abstract:
A suspension assembly for an aircraft turbojet engine includes a pylon and connecting rods for taking up the thrust of the turbojet engine which is connected to the pylon. In particular, the suspension assembly includes an insulator which is separate from the pylon and thermally insulates the connecting rods from the turbojet engine.

Description:
TECHNICAL FIELD 
     The present invention relates to a suspension assembly for an aircraft turbojet engine, and a propulsion assembly comprising such a suspension assembly, a turbojet engine, and a nacelle. 
     BACKGROUND 
     As is known from the prior art, an aircraft turbojet engine assembly is housed inside a nacelle connected to a pylon allowing the propulsion assembly thus formed to be suspended under a wing of the aircraft or adjacent to the fuselage. 
     Connecting rods for taking up thrust are inserted between the pylon and the gas generator of the turbojet engine, so as to take up the forces created by the thrust of the engine. 
     In the propulsion assemblies according to the prior art, these connecting rods are subjected to very high temperatures, in particular created by the combustion chamber of the engine, which requires the use of particular steel alloys, the weight of which is substantial. 
     The present invention in particular aims to provide means making it possible to use lighter materials for the connecting rods taking up thrust. 
     This aim of the invention is achieved with a suspension assembly for an aircraft turbojet engine, including a pylon and connecting rods for taking up the thrust of said turbojet engine connected to said pylon, remarkable in that it includes means separate from said pylon for thermally insulating the connecting rods from the turbojet engine. 
     The presence of thermal insulating means for the connecting rods makes it possible to insulate the latter parts from the radiation and convention of the heat given off by the engine: these rods can therefore be made from lighter and less heat-resistant materials, such as titanium, aluminum, or composite materials. 
     According to other optional features of the suspension assembly according to the invention:
         said insulating means comprises independent insulating sheaths for each connecting rod taking up thrust: these sheaths make it possible to achieve the insulation of the connecting rods very simply;   said insulating means comprises an insulating sheath shared by the connecting rods: this solution makes it possible to reduce the number of pieces;   said sheath(s) are removable: this makes it possible to facilitate the inspection of the connecting rods;   said thermal insulating means comprises an insulating partition positioned between said connecting rods taking up thrust and the zone intended to be occupied by the turbojet engine: this solution also makes it possible to protect the pylon from heat, and thereby to make at least part of the pylon from composite materials, and therefore further reduce the weight of the assembly;   said partition is fastened on the pylon and/or on the connecting rods and/or can be fastened on the turbojet engine;   said partition can act as a firewall in case of fire in the engine compartment, so as to prevent its spread to the connecting rods taking up thrust and the pylon;   sealing devices are inserted between said insulating partition and the internal structure of said nacelle: the presence of these joints makes it possible to prevent the transfer of heat from the engine by thermal convection, as well as the spread of a flame or hot gases in case of fire in the engine compartment.       

     BRIEF SUMMARY 
     The present invention also relates to a propulsion assembly, including a suspension assembly according to the preceding, a turbojet engine suspended from said suspension assembly, and a nacelle surrounding said suspension assembly and said turbojet engine. 
     Optionally, said propulsion assembly can include channels for taking air in the secondary flow zone of said nacelle, to cool said thermal insulating means: these channels contribute to keeping the connecting rods at a low temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will appear in light of the following description and upon examining the appended figures, in which: 
         FIG. 1  shows a perspective view of a first embodiment of an assembly according to the invention, 
         FIG. 2  shows (on a larger scale) a transverse cross-sectional view of a connecting rod taking up thrust of an assembly according to the invention according to another embodiment, 
         FIGS. 3 and 4  are front and back views, slightly in perspective, of an assembly according to the invention done according to still another embodiment, 
         FIGS. 5 and 6  are views respectively corresponding to  FIGS. 3 and 4 , when the assembly according to the invention is shown in the maintenance position; 
         FIGS. 7 and 8  are diagrammatic cross-sectional views of the assembly of  FIGS. 3 to 6 , respectively shown in the normal operating position and the maintenance position; and 
         FIG. 9  shows a transverse cross-sectional view of two connecting rods enveloped by a thermal insulating sheath according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows that the assembly according to the invention comprises a pylon  1  intended to be fastened under an airplane wing, adapted to support a turbojet engine  3  including an upstream part forming a fan  5  and a downstream part forming a gas generator  7 . 
     The pylon  1  is respectively connected to these upstream and downstream parts of the turbojet engine  3  by upstream  9  and downstream  11  fittings. 
     Connecting rods  13   a  and  13   b  taking up thrust extend traditionally between the upstream part  15  of the gas generator  7  and the rear part  17  of the pylon  1 . 
     These two connecting rods  13   a ,  13   b  are spaced apart from each other in the upstream part  15 , and converging towards the rear part  17  of the pylon  1 . 
     A thermal insulating sheath  19 , which can be formed for example from a sheet of titanium or steel, or a cover made up of a film of stainless steel encapsulating an insulating material such as silica fiber, simultaneously envelopes the two connecting rods taking up thrust  13   a  and  13   b , thereby forming on the one hand a thermal insulation of these two connecting rods relative to the heat given off by the gas generator  7 , and on the other hand a heat protection screen for the pylon  1 . 
     This sheath  19 , which envelopes the two connecting rods taking up thrust, is preferably made up of two half-sheaths removably fastened on each other, which makes it possible to quickly access the connecting rods  13   a ,  13   b  for a visual examination and/or maintenance operations. 
     The assembly according to the invention also comprises a nacelle able to surround the turbojet engine  3 , not shown in  FIG. 1 , but shown in  FIGS. 3 to 8 , which will be discussed later. 
     As an alternative solution to a single sheath  19  surrounding the two connecting rods  13   a  and  13   b  taking up thrust, it is possible to consider a sheath  19  for each connecting rod  13 , as shown in  FIG. 2 . 
     As shown in that figure, each sheath  19  can be made up of two half-sheaths  21   a ,  21   b , connected to the connecting rod  13  via sheath supports  23   a ,  23   b.    
     It should be noted that in the embodiment of  FIG. 1  as in that of  FIG. 2 , the sheath  19  can extend over all or part of the length of the connecting rods  13   a  and  13   b  taking up thrust. 
     It should also be noted that the upstream  9  and downstream  11  fittings can also be covered with thermal insulation sheaths. 
     In the embodiment of  FIGS. 3 to 8 , a partition  25  is inserted between the gas generator  7  and the connecting rods  13   a  and  13   b  taking up thrust. 
     These  FIGS. 3 to 8  show the nacelle that is part of the assembly according to the invention. 
     This nacelle includes two half-shells  27   a ,  27   b , each pivotably mounted around the pylon  1  between a normal operating position shown in  FIGS. 3 ,  4  and  7 , and a maintenance position, shown in  FIGS. 5 ,  6 , and  8 . 
     Each half-shell  27   a ,  27   b  includes an outer structure  29   a ,  29   b , and an inner structure  31   a ,  31   b , these outer and inner structures defining an annular channel  33  in which the cool air sent by the fan  5  circulates. 
     The partition  25 , which extends substantially over the entire length of the gas generator  7 , includes, on its lateral edges, joints  35   a ,  35   b  cooperating with the internal structures  31   a ,  31   b  in the normal operating position (see  FIG. 7 ). 
     These joints make it possible to produce sealing between the partition  25  and the internal structures  31   a ,  31   b , which makes it possible to perfect the thermal insulation of the connecting rods  13   a  and  13   b  taking up thrust and the pylon  1  relative to the gas generator  7 . 
     As shown in particular in  FIGS. 7 and 8 , the partition  25  can be kept on the gas generator  7  via a support  37   a ,  37   b , but this partition can also be maintained, alternatively or additionally, by supports (not shown) fastened on the connecting rods  13   a  and  13   b  taking up thrust. 
     This partition  25  could also be supported by support means connected to the pylon  1 . 
     Preferably, air intakes  39   a ,  39   b  are provided in the cool air flow circulating in the annular channel  33 , so as to contribute to keeping the connecting rods  13   a  and  13   b  taking up thrust at a low temperature. 
     It should be noted that the partition  25  can be formed in a material resistant to high temperatures (sheet of titanium or steel for example) or can be coated with a thermal covering  41  withstanding high temperatures, as shown in  FIGS. 6 and 8 . 
     The advantages of the present invention result directly from the preceding description: the thermal insulation of the connecting rods  13   a  and  13   b  taking up thrust makes it possible to keep these at relatively low temperatures, a fortiori if they are cooled by the air coming from the cold flow created by the fan. 
     This maintenance at low temperatures makes it possible to produce connecting rods taking up thrust that are made from materials that are less resistant to high temperatures, but are lighter, such as titanium, aluminum, or composite materials. 
     In the specific case of the embodiment of  FIGS. 3 to 8 , the partition  25  also makes it possible to insulate the pylon  1  from the heat radiated by the gas generator  7 , which makes it possible to consider also making this pylon from lighter materials. 
     It will be noted that in all of the embodiments described above, visual and physical access to the connecting rods taking up thrust is very easy: in the embodiments of  FIGS. 1 and 2 , one need only remove the sheaths  19  surrounding the connecting rods taking up thrust; in the embodiment of  FIGS. 3 to 8 , one need only open the two half-shells  17   a  and  27   b  so an operator can immediately check the status of the connecting rods taking up thrust (see  FIGS. 5 and 6 ). 
     Of course, the present invention is in no way limited to the embodiments described and shown, which have been provided solely as examples. 
     It will be noted that the present invention can be applied both to a grid or door thrust reverser, or a so-called smooth nacelle (without thrust reverser).