Patent Publication Number: US-2022240407-A1

Title: Aircraft avionics rack with interconnection platform

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a national stage entry of PCT/EP2020/025268 filed Jun. 9, 2020, under the International Convention and claiming priority over French Patent Application No. FR1906195 filed Jun. 11, 2019. 
    
    
     TECHNICAL FIELD 
     The invention concerns the field of aeronautics and relates to avionics bays of aircraft. 
     Avionics bays are electrical cabinets carried in an aircraft which make it possible to house electrical or electronic equipment items, such as computers or other instruments, and also the electrical cabling connecting these equipment items. These avionics bays are generally of a considerable size and contain numerous electronic or electrical equipment items close to one another, and also a large quantity of cables. An avionics bay generally comprises a multirack device allowing the equipment items to be inserted and removed while ensuring their mechanical support and their electrical connection. These multirack devices ensure a high level of safety in the management of the electrical equipment items, both during normal operation and during maintenance phases. 
     PRIOR ART 
     Aircraft avionics bays generally comprise shelves for supporting electrical or electronic equipment items. 
     Document U.S. Pat. No. 4,458,296 describes a shelf structure for an avionics bay. The shelf described comprises a support platform on which there are mounted retaining seats for a rackable electrical module, each retaining seat comprising a connector. The connectors of all the retaining seats are connected to an external connection interface intended to be connected to the electrical circuit of the aircraft. The connection between the connectors of the retaining seats and the external connection interface is achieved by electrical cabling arranged in various bundles held by ramps or by trunking. 
     Given the complexity of the electrical modules to be connected, this cabling constitutes a considerable mass, bulk and cost which would be appropriate to reduce. Moreover, during the manufacture of the avionics bays, this type of cabling demands numerous manual operations to be performed by qualified personnel. 
     Documents FR2977447 and FR2927222 describe avionics bays partially addressing the disadvantages described above. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to improve the avionics bays of the prior art. 
     To this end, the invention is aimed at an aircraft avionics bay comprising an arrangement of racks intended for the integration of electrical equipment items and connections, this avionics bay being provided with at least one shelf which comprises: 
     a support platform; 
     retaining seats for a rackable electrical module, these retaining seats being mounted on the support platform, each retaining seat comprising an end wall substantially perpendicular to the support platform, and a module connector mounted on this end wall; 
     an external connection interface intended to be connected to the electrical circuit of the aircraft and mounted on the support platform and connected to the module connectors. 
     Said shelf comprises: 
     an interconnection plate extending substantially parallel to the support platform, on the side opposite to the retaining seats, this interconnection plate bearing conductive connection tracks; 
     a plurality of rear printed circuits, each rear printed circuit extending opposite a module connector; 
     the conductive connection tracks of the interconnection plate extending into each rear printed circuit and into the external connection interface via flexible conductors. 
     In such an avionics bay, a considerable volume, accessibility and cost gain is achieved by means of the arrangement of the interconnection plate and of the rear printed circuits. No cable is necessary for connecting the module connectors to the external connection interface. 
     The movable parts of the interconnection are reduced to a minimum, and the interconnection function as a whole requires little or no maintenance. 
     The manufacture of such an avionics bay is greatly simplified by doing away with all the manual cabling operations involving the passage of cables and the fixing thereof to ramps or trunking. 
     The invention thus allows rapid and reduced-cost manufacturing of an avionics bay for an aircraft that proves to be more reliable and require less maintenance than the avionics bays carrying traditional cabling. 
     Moreover, aeronautical regulations currently tend to require, for safety reasons, the multiplication of the cable paths in the interconnection of the avionics bays. This multiplication of the cable paths is easily achieved within the avionics bay according to the invention, since the interconnection plate offers a surface suitable for the multiplication of the paths of conductive connection tracks without increasing the bulk or the mass of the avionics bay. 
     The invention thus allows the implementation of the new regulations for aircraft carrying more and more electronic and electrical hardware, the complexity of which hardware is increasing. 
     The avionics bay according to the invention can comprise the following additional features, alone or in combination: 
     each rear printed circuit is fixed to the module connector opposite which kit extends; 
     each rear printed circuit and its corresponding module connector are fixed on either side of a spacer; 
     the spacer comprises a flange wall extending perpendicularly to the rear printed circuit and arranged on the periphery of the rear printed circuit; 
     each module connector comprises pins connected to the rear printed circuit to which it is fixed; 
     the pins of each module connector are connected to the corresponding rear printed circuit by rigid conductive rods; 
     the rigid conductive rods are crimped or welded in the corresponding rear printed circuit; 
     each retaining seat comprises a connection window made in its end wall, each module connector comprising a connection wall which is fixed to the end wall of the corresponding retaining seat by fixings screwed into the spacer, with the result that the module connector projects from the connection window; 
     each rear printed circuit is connected to the conductive connection tracks of the interconnection plate by a flexible printed circuit; 
     the external connection interface comprises an external connection printed circuit to which the interface connectors are connected, the external connection printed circuit being connected to the conductive connection tracks of the interconnection plate by a flexible printed circuit; 
     the external connection interface comprises an external connection wall fixed substantially perpendicularly to the support platform, the interface connectors and also the external connection printed circuit being fixed to this connection wall; 
     each interface connector comprises pins connected to the external connection printed circuit; 
     the pins of the interface connectors are connected to the external connection printed circuit by rigid conductive rods; 
     said rigid conductive rods are crimped or welded in the external connection printed circuit; 
     the flexible printed circuits connected to the rear printed circuits are connected to the conductive connection tracks of the interconnection plate via a detachable connector; 
     the flexible printed circuit connected to the external connection printed circuit is connected to the conductive connection tracks of the interconnection plate via a detachable connector; 
     the interconnection plate, the rear printed circuits, the external connection printed circuit, and the flexible printed circuits are formed by a single printed circuit comprising rigid portions and flexible portions; 
     the support platform is made up of two parallel planar crossmembers formed by two lateral profiles of the shelf; 
     the interconnection plate is fixed to the shelf by a flexible reference potential setting fastener; 
     the interconnection plate comprises a protective cover fixed to the shelf and extending substantially over the whole surface of the interconnection plate; 
     the interconnection plate is made up of a rigid printed circuit in which the conductive connection tracks are etched; 
     the avionics bay comprises a device for cooling by circulation of a gas passing through the rackable electrical modules, and said shelf comprises a ventilation wall which extends parallel to the support platform, the shelf forming a ventilation casing of the cooling device, between the support platform and the ventilation wall, the interconnection plate being arranged opposite the ventilation wall; 
     the ventilation wall and the interconnection plate each comprise ventilation through-orifices; 
     the interconnection plate comprises as many ventilation orifices as the ventilation wall, each ventilation orifice of the interconnection plate being opposite a ventilation orifice of the ventilation wall; 
     the interconnection plate comprises a protective cover fixed to the shelf and extending substantially over the whole surface of the interconnection plate, this protective cover comprising ventilation through-orifices; 
     the ventilation wall comprises a ventilation window, the interconnection plate closing off this ventilation window, the interconnection plate comprising ventilation through-orifices; 
     a tightness seal is clamped between the interconnection plate and the ventilation wall, on the periphery of the ventilation window; 
     the interconnection plate comprises a protective cover fixed to the shelf and extending substantially over the whole surface of the interconnection plate, this protective cover comprising ventilation through-orifices; 
     the protective cover comprises as many ventilation orifices as the interconnection plate, each ventilation orifice of the protective cover being arranged opposite a ventilation orifice of the interconnection plate; 
     the avionics bay comprises a device for cooling by circulation of a gas passing through the rackable electrical modules, and the shelf warms a ventilation casing of the cooling device, this casing being delimited by the interconnection plate and the support platform, the interconnection plate comprising ventilation through-orifices; 
     the interconnection plate comprises a protective cover fixed to the shelf and extending substantially over the whole surface of the interconnection plate, this protective cover comprising ventilation through-orifices; 
     the protective cover comprises as many ventilation orifices as the interconnection plate, each ventilation orifice of the protective cover being arranged opposite a ventilation orifice of the interconnection plate; 
     the avionics bay comprises a protective shell for each rear printed circuit, this protective shell comprising tabs for retaining the interconnection plate; 
     the avionics bay comprises an equipment item in the facade of a shelf, this equipment item being connected by an additional flexible printed circuit to the interconnection plate. 
    
    
     
       PRESENTATION OF THE FIGURES 
       Other features and advantages of the invention will become apparent from the following nonlimiting description with reference to the appended drawings, in which: 
         FIG. 1  illustrates an avionics bay according to the invention; 
         FIG. 2  shows a shelf of the avionics bay of  FIG. 1 ; 
         FIG. 3  shows the shelf of  FIG. 2 , the module connectors and the external connection interface being demounted; 
         FIG. 4  shows the interconnection assembly of the shelf of  FIG. 2 ; 
         FIG. 5  shows the shelf of  FIG. 3  viewed from below; 
         FIG. 6  shows the shelf of  FIG. 2  viewed in section; 
         FIG. 7  shows a reference potential setting fastener of the shelf of  FIG. 2 ; 
         FIG. 8  shows a tongue of the shelf of  FIG. 2 ; 
         FIG. 9  shows the fastener of  FIG. 7  viewed in section; 
         FIG. 10  illustrates a variant of the fastener of  FIG. 7 ; 
         FIG. 11  shows the fastener of  FIG. 10  mounted on a shelf; 
         FIG. 12  is a view similar to  FIG. 6  for a second embodiment of the invention; 
         FIG. 13  is a view similar to  FIG. 6  for a third embodiment of the invention; 
         FIG. 14  is an enlarged view of the box XIV of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic representation of an avionics bay  1  according to the invention. 
     This avionics bay  1  comprises two lateral uprights  2 ,  3  between which shelves  4  extend. Each of the shelves  4  is formed by a casing whose hollow part extends between a ventilation wall  10  and a support platform  5  for rackable electrical modules  6  mounted on the shelf  4 . 
     The electrical modules  6  are, for example, electrical or power electronics devices for calculation relating to the navigation, safety, air-conditioning functions, etc. These modules  6  are referred to as rackable, since they are mounted on the shelves  4  in a removable manner by virtue of retaining seats (not shown in this schematic view of  FIG. 1 ) to facilitate the maintenance and the replacement of these modules. These rackable electrical modules  6  are also termed line-replaceable units (LRUs). They are, for example, modules in accordance with aeronautical standard ARINC. 
     Each shelf  4  comprises, in addition to modules  6 , an external connection interface  7  provided with interface connectors  8 . The electrical circuit of the aircraft is connected to the avionics bay  1  via these interface connectors  8 . 
     The external connection interface  7  of each shelf  4  is connected to each of the modules  6  mounted on this shelf  4  via an interconnection plate  9  extending parallel to the support platform  5 , on the side opposite to the modules  6 . In other words, the support platform  5  is situated between the modules  6  and the interconnection plate  9 , for each shelf  4 . 
     In the present example, the avionics bay  1  also comprises a device for cooling by circulation of air. This cooling device makes it possible to maintain the electrical and electronic equipment items of the modules  6  at an acceptable temperature given their large number, their density and the heat that they give off. 
     This cooling device organizes an air circulation shown schematically in  FIG. 1  by means of arrows. In the present example, fresh air is injected into the avionics bay  1  via one of its uprights  2  and then is distributed into the shelves  4  forming casings channeling this fresh air to pass through the modules  6 . Various portions of each shelf  4  are pierced with ventilation through-orifices (not shown in this schematic view of  FIG. 1 ) allowing the cooling air to pass through the module  6  in order to cool it. 
     The heated air passing through the modules  6  is then recovered in the shelves  4 , which discharge the hot air toward the other upright  3  of the avionics bay  1  in order then to be discharged from the avionics bay  1 . 
     Flow separation walls  11  within the casings formed by the shelves  4  make it possible to separate the fresh air and hot air flows in each shelf  4  if necessary. 
       FIG. 2  shows one of the shelves  4  of the avionics bay  1 . In this  FIG. 2 , the module  6  have not been shown. Only the retaining seats  12  intended to receive these modules  6  have been shown in  FIG. 2 . In the present example, the retaining seats  12  are in accordance with standard ARINC and allow the mechanical fixing and the electrical connection of compatible modules  6 . The mechanical locking is provided in particular by thumbwheels  13 , while the electrical connection of the modules  6  is provided by module connectors  14 . 
     In the example illustrated in  FIG. 2 , five retaining seats  12  are mounted on the support platform  5  of the shelf  4 , thus making it possible to receive five rackable electrical modules, to fix them by means of the thumbwheels  13  and to electrically connect them to the electrical circuit of the aircraft by virtue of the module connectors  14 . The thumbwheels  13  are arranged on the front part of the retaining seats  12 , that is to say the part which is accessible to the user when the latter is facing the avionics bay. 
     As described above, the shelf  4  also comprises an external connection interface  7  provided with interface connectors  8  making it possible to connect all the modules of the shelf  4  to the electrical circuit of the aircraft, in order to electrically supply, and communicate with, all the modules  6  which are intended to be mounted in the retaining seats  12 . The external connection interface  7  is also fixed to the support platform  5 . 
     The shelf  4  comprises, furthermore, a plurality of rigid rear printed circuits  15 . A rear printed circuit  15  is provided for each module connector  14 . Each of the rear printed circuits  15  is thus arranged opposite the module connector  14  of a retaining seat  12 . Each rear printed circuit  15  and its corresponding module connector  14  are rigidly fixed to one another. 
     The rear printed circuits  15  are each protected by a protective shell  16 . In  FIG. 2 , three of the rear printed circuits  15  have been shown with their protective shell  16 , while two of the rear printed circuits  15  are shown without their protective shell  16  in order to reveal the rear printed circuits  15 . 
     The retaining seats  12  are each pierced with ventilation through-orifices  17  allowing the fresh air flow emanating from the shelf  4  to pass through the module  6  which will be mounted on this retaining seat  12 . 
     Each of the rear printed circuits  15 , on the one hand, and the external connection interface  7 , on the other hand, are connected to the interconnection plate  9  (not visible in  FIG. 2 ) by a flexible printed circuit  18 ,  19 . 
     Each protective shell  16  advantageously protects a rear printed circuit  15  and also its flexible printed circuit  18 . 
     The protective shells  16  are, furthermore, provided at their bottom with protruding retaining tabs  61  or lugs in order to retain the interconnection plate  9  once they have been installed at the rear on each rear printed circuit  15 . The protective shells  16  thus provide an additional function of retaining the interconnection plate  9 . 
       FIG. 3  shows the shelf of  FIG. 2  with its module connectors  14  demounted and with its external connection interface  7  open. 
     Each of the retaining seats  12  comprises an end wall  22  extending perpendicularly to the support platform  5 , and in which a connection window  20  is made. Each module connector  14  is mounted on a connection wall  21  which is fixed (when the shelf is in its mounted position of  FIG. 1 ) to the edges of the connection window  20  such that the module connector  14  projects from the connection window  20  in order to be able to connect the module received in the retaining seat  12 . The connection walls  21  and the module connectors  14  thus each extend perpendicularly to the support platform  5 . 
     The module connectors  14  can be of any suitable type for providing the connection of a module  6  when this is inserted into the corresponding retaining seat  12  until butting against its end wall  22 . The module connector  14  can be in one piece or, by contrast, made up of a plurality of subconnectors. These module connectors  14  are provided with pins extending parallel to the support platform  5 , in the direction of the module installed on the retaining seat  12 . These pins are interconnection pins which are advantageously demounted and replaceable. These pins  60  are shown in more detail in  FIG. 14 . 
     For each retaining seat  12 , the connection wall  21  is secured to the rear printed circuit  15  by virtue of a spacer  23 . The spacer  23  is here made up of a flange wall extending perpendicularly to the rear printed circuit and arranged on the periphery of the rear printed circuit. The connection wall  21  is fixed on one side of the spacer  23 , and the rear printed circuit  15  is fixed on the other side of the spacer  23 , the printed circuit thus being parallel to the connection wall  21 . The connection wall  21  can advantageously be fixed to the end wall  22  by fixings screwed into the spacer  23 . 
     The pins of the module connector  14  are connected to the corresponding rear printed circuit  15  by any cabling means such as by connection of welded conductors, or more advantageously by force-fitting technologies of the press-fit type. The pins of each module connector  14  are thus demountable and extended by rigid conductive rods which are crimped in the corresponding rear printed circuit  15 . These rigid conductive rods are commonly termed “tulips”. The module connectors  14  are thus mounted and connected in a quick and reliable manner. The conductive rods  56  are shown in  FIGS. 6, 12 and 13 , and also in  FIG. 14 , which is an enlarged view of the box XIV of  FIG. 6 . The pins  60  of the connector  14  and the conductive rods  56  are connected by force-fitting. 
     The rigid fixing provided by the spacer  23  here allows the use of rigid connections between the module connector  14  and the rear printed circuit  15  and ensures the durability of these connections over time by virtue of a mounting in which the relative movements of the module connector  14  and of the corresponding rear printed circuit  15  are not allowed. 
       FIG. 3  reveals the possibility of movement of the module connectors  14  when they have been demounted from their connection window  20 . This movement is allowed by the flexibility of the flexible printed circuits  18 . The fixing, for each module, of the connection wall  21  to the connection window  20  preferably occurs by way of screws accessible from the inside of the retaining seat  12 , that is to say from the front face (on the thumbwheels  13  type) of the shelf. An operator can thus easily gain access to a module connector  14  by extracting the module from a retaining seat  12 , by unscrewing these screws, and by positioning the connector  14  in its position of  FIG. 3  by virtue of the flexibility of the flexible printed circuit  18 . 
     As far as the external connection interface is concerned, the latter is made up of a connection housing  24  comprising an external connection wall  25  (which is shown demounted in  FIG. 3 ). An external connection printed circuit  26  is fixed parallel to the external connection wall  25  by virtue of spacers  27  and is connected to the flexible printed circuit  19 . 
     The interface connectors  8  (visible in  FIG. 2 ) are connected to the external connection printed circuit  26  in a similar manner to the module connector  14 . The interface connectors  8  thus comprise pins (not shown in order to simplify the figures) connected by any suitable technique to the tracks of the external connection printed circuit  26 , and in particular by force-fitting technology permitted by the external connection printed circuit  26  being rigidly retained with respect to the external connection wall  25 . The pins of each interface connector  8  are thus extended by rigid conductive rods which are crimped in the external connection printed circuit  26 . The pins of the interface connectors  8  and these rigid conductive rods can be mounted in the same way as the pins  60  and the rods  56  of the module connectors  14  (that is to say in the way illustrated in  FIG. 14 ). 
     The external connection interface  7  thus provides, at the interface connectors  8 , the connection technology allowing all the pins of the module connectors  14  to be connected to the electrical circuit of the aircraft. The connection housing  24  makes it possible, moreover, to house additional equipment items such as fuses, connectors or displays intended for maintenance, these additional equipment items being able to be directly mounted on the external connection printed circuit  26 . 
       FIG. 4  illustrates the production of the electrical connection between the module connectors  14  and the interface connectors  8 . This  FIG. 4  shows an interconnection assembly, the flexible printed circuits  18 ,  19  and rigid printed circuits  15 ,  26  of which have been shown, in a flat position illustrating a preferred position for the manufacture of this interconnection assembly. 
     The rear printed circuits  15  and the external connection printed circuit  26  are each connected to the interconnection plate  9  by virtue of their respective flexible printed circuit  18 ,  19 . In the present example, the interconnection plate  9  is a printed circuit bearing conductive connection tracks  28  connecting the flexible printed circuits  18  to the flexible printed circuits  19  and possibly certain flexible printed circuits  18  to one another. The conductive connection tracks  28  extend, continuously or with possible interconnections, from the rear printed circuits  15  to the external connection printed circuit  26 . 
     In  FIG. 4 , only some conductive connection tracks  28  have been schematically shown, it being understood that a large number of modules  6  can be mounted on a shelf  4 , this generating a large quantity of electrical connections of weak and high power to be provided between the module connectors  14  and the interface connectors  8  or between two connectors  14 . Since the area of the interconnection plate  9  is limited only by the area of the shelf  4  itself, this area of the interconnection plate  9  can be adapted to these numerous conductive tracks  28  to be supported. The interconnection plate  9  can, moreover, be formed by a printed circuit with a plurality of layers if the number of conductive tracks  28  so requires. 
     Each pin of a module connector  14  can thus be connected to a pin of an interface connector  8  by a circuit passing through the rear printed circuit  15 , the flexible printed circuit  18 , the interconnection plate  9 , to the flexible printed circuit  19 , and to the external connection printed circuit  26 . 
     The interconnection plate  9  comprises, moreover, a plurality of ventilation through-orifices  29  intended to participate in the function of cooling the avionics bay. 
     The interconnection plate  9  comprises, furthermore, reference potential setting fasteners  30  making it possible both to mechanically retain the interconnection plate  9  with respect to the corresponding shelf  4  and to electrically ground the interconnection plate  9  with the metallic structure of the shelf  4 . The modules  6  and the external connection interface  7  can thus be grounded to the avionics bay  1  in a reliable manner by conductive tracks of the interconnection plate  9 . 
     According to a preferred feature, the interconnection plate  9 , the rear printed circuits  15 , the external connection printed circuit  26  and also the flexible printed circuits  18 ,  19  are made in one piece. The interconnection assembly shown in  FIG. 4  (with the exception of the fasteners  30 ) is thus formed by a single printed circuit which comprises rigid portions  15 ,  9 ,  26  and flexible portions  18 ,  19 . However, the interconnection plate  9  can also be formed by a flexible printed circuit. 
     An extremely rapid and reliable manufacture is thus permitted for the complete interconnection system of  FIG. 4 . 
     In a variant, if modularity properties are preferred for the interconnection assembly, the flexible printed circuits  18  connected to the rear printed circuits  15  can be connected to the interconnection plate  9  via detachable connectors, thereby making it possible to remove or add rear printed circuits  15 , and therefore module connectors  14 , from or to the same interconnection plate  9 . 
     Likewise, the flexible printed circuit  19  of the external connection printed circuit  26  can be either produced in one piece with the interconnection plate  9  or, in a variant, connected by detachable connectors making it possible to change the external connection printed circuit  26  in order to replace it if it is defective, or to have the choice of connecting various external connection interfaces  7  to the same interconnection plate  9 . 
     The flexible printed circuits  18 ,  19  here make it possible to connect elements perpendicular to one another. A weak bending stress is thus imposed on these flexible printed circuits  18 ,  19  which is a gauge of reliability. 
       FIG. 5  shows the shelf  4  of  FIG. 3 , viewed from below.  FIG. 5  illustrates a first embodiment of the assembly of the interconnection plate  9  with the shelf  4 . 
     In this example, the shelf  4  forms a casing inside of which there circulates the cooling air which enters and leaves the casing via aeration openings  31 . The support platform  5  delimits the upper part of this casing, whereas the ventilation wall  10  delimits the lower part of this casing, lateral profiles  32  moreover delimiting the lateral edges of the casing. 
     The interconnection plate  9  is fixed opposite the ventilation wall  10  by virtue of the reference potential setting fastenings  30  which are fixed to one of the lateral profiles  32  and also by additional fasteners  33  whose function is only to clamp the interconnection plate  9  and to fix it to the ventilation wall  10 . Moreover, as described above, the protective shells  16  comprise tabs  61  for retaining the interconnection plate  9  and thus also participate in optimally retaining the interconnection plate  9 . 
     In  FIG. 5 , the interconnection plate  9  is provided with a protective cover  34  covering virtually the whole of its surface area to physically protect it and electrically isolate it. The protective cover  34  is, furthermore, itself provided with ventilation through-orifices  35  arranged opposite the ventilation orifices  29  of the interconnection plate  9 . 
       FIG. 6  is a schematic view in cross section showing the arrangement relating to this first embodiment. In this  FIG. 6 , a module  6 , shown in section, is mounted on a retaining seat. The casing delimited by the shelf  4  comprises an inlet duct  36  and an outlet duct  37  which are separated by the flow separation wall  11 . 
     In the present example, the support platform  5  is made up of two horizontal flanges of the lateral profiles  32  forming two parallel planar crossmembers on which the retaining seats bear. The upper part of the inlet duct  36  is closed by the retaining seats and the calibration of the passage cross section for the cooling air distributed to the module  6  is realized by the diameter and the number of the ventilation orifices  17  of the retaining seats. 
     As stated above in relation to  FIG. 1 , the inlet duct  36  distributes fresh air to the module  6  via the ventilation orifices  17  of the retaining seat, and the outlet duct  37  makes it possible to draw in the hot air which has passed through the module  6  which is situated on the bottom shelf (not shown). According to this first embodiment, this hot air is drawn into the outlet duct  37  successively through the ventilation orifices  35  of the protective cover  34 , then the ventilation orifices  29  of the interconnection plate  9 , then ventilation through-orifices  38  of the ventilation wall  10 , these orifices preferably being opposite one another as shown in  FIG. 6 . 
     In a variant of  FIG. 6 , the ventilation orifices  29  of the interconnection plate  9  are smaller than the ventilation orifices  35 ,  38  of the protective cover  34  and of the ventilation wall  10 . The ventilation orifices  35 ,  38  of the protective cover  34  and of the ventilation wall  10  are therefore oversized, whereas the ventilation orifices  29  of the interconnection plate  9  ensure the calibration of the air permeability of the inlet of the outlet duct  37 . The calibration of this air permeability is an important element of the cooling system which is determined during the design of the avionics bay, according to the arrangement of the various elements allowing the generation and the channeling of the cooling air. Since the calibration of this permeability is realized by the interconnection plate, the shelves (and in particular the ventilation walls) and the protective covers  34  can be standardized. 
     The interconnection plate  9  is directly fixed to the shelf  4  (or even to the ventilation wall  10 ), with or without a tightness seal  53  or spacer maintaining a spacing between this wall  10  and the interconnection plate  9 . In the present example, the fixing of the interconnection plate  9  is ensured by the reference potential setting fasteners  30 . 
       FIGS. 7 to 9  illustrate one of the reference potential setting fasteners  30  which make it possible to connect the interconnection plate  9  to the reference electrical potential and which allows the mechanical retention of this interconnection plate  9 . 
     The fastener  30  is a flexible fastener made up of a clamp formed by two jaws  39 ,  40  clamping the interconnection plate  9  between them. At least one of the two faces of the interconnection plate  9  which is in contact with the fastener  30  comprises a conductive ground pad  41 . The conductive tracks of the interconnection plate  9  which have to be connected to the reference electrical potential of the avionics bay should be electrically connected to this conductive pad  41 . 
     The fastener  30  is made of an electrically conductive material such that, when the fastener  30  is clamped on the interconnection plate  9 , electrical continuity is established between the conductive pad  41  and a heel  42  which is secured to one of the two jaws  39 ,  40 . The heel  42  comprises in its center an orifice allowing the passage of a fixing screw  43 . 
     Optionally, for better durability and connection security, the fastener  30  is clamped by means of rivets  44  to the interconnection plate  9 , and the two jaws  39 ,  40  are clamped against one another by rivets  45  on either side of the potential setting heel  42   
     An O-ring seal  46  may, moreover, be arranged around the potential setting heel  42  in order to seal the potential setting. 
       FIG. 8  shows in perspective a portion of one of the lateral profiles  32  of the shelf  4 , this portion being intended to receive the fixing of the fastener  30 . To this end, the lateral profile  32  comprises a tongue  47  electrically and mechanically connected to the lateral profile  32  for example by welding or, as illustrated in  FIG. 8 , by riveting. The tongue  47  comprises a crimped nut  48  so that it can cooperate with the fixing screw  43 . 
       FIG. 9  shows in section, at the fastener  30 , the assembly of an interconnection plate  9  and of a shelf  4 . The fixing screw  43  is screwed and clamped on the crimped nut  48  such that the O-ring seal  46  is compressed and the potential setting heel  42  is pressed against the tongue  47 . 
     The fastener  30  thus affords mechanical retention of the interconnection plate  9  without blocking it in place by virtue of the flexibility of the fastener  30  and of the tongue  47 . This makes it possible to avoid mechanical stresses within the printed circuit constituting the interconnection plate  9 , and to achieve this while firmly retaining this interconnection plate  9 . The mounting of the interconnection plate  9  and its reference potential setting are achieved by the mere operation of clamping the fixing screw  43 . In order to promote the placement of the fastener  30  with respect to the tongue  47 , the fastener  30  comprises a flange  49 , and the tongue  47  comprises a flange  50 , these two flanges  49 ,  50  being in flat-on-flat contact when the fixing screw  43  is opposite the crimped nut  48 . 
       FIGS. 10 and 11  illustrate a variant embodiment of the reference potential setting fastener  30 . In this variant, the ventilation wall  10  comprises a perpendicular flange  51 , and the mounting of the interconnection plate  9  opposite the ventilation wall  10  is realized by fixing the fastener  30  to this flange  51 . The two jaws  39 ,  40  of the fastener  30  are here made up of parts in the form of an angle bracket which are adapted to clamp the interconnection plate  9  and to retain it perpendicularly to the flange  51  while ensuring the reference potential setting thereof. 
     The fasteners  30  deal with the need to resort to grades, cables and ground terminals generally used in addition to the conventional printed circuit fixing means. 
     The mounting and the connection of such an interconnection assembly to a shelf  4  is achieved by a very restricted number of operations reduced to the fixing of the fasteners  30 ,  33  to the shelf  4 , the fixing of the connection walls  21  to the retaining seats  12 , and the mounting of the external connection interface  7 . These mounting operations are very limited in number compared with the multiple cabling operations necessary in the avionics bays of the prior art, and this being achieved with much greater connection security while limiting the risks of error. 
       FIG. 12  illustrates a second embodiment of the assembly of the interconnection plate  9  with the rest of the shelf  4 . According to this second embodiment, the ventilation wall  10  does not comprise ventilation orifices but instead comprises a ventilation window  52  creating a wide opening in the outlet duct  37 . The interconnection plate  9  is here produced by a rigid and optionally reinforced printed circuit which is directly fixed to the shelf  4  while compressing a tightness seal  53 . In this second embodiment, the calibration of the permeability defined for the inlet of the outlet duct  37  is then realized by the number and the dimension of the ventilation orifices  29  of the interconnection plate  9 . 
     This second embodiment makes it possible to lighten the shelf  4  by doing away with virtually all of one of its walls (the ventilation wall  10 ) and by transferring this permeability calibration function to the interconnection plate  9 . 
     In the first and second embodiment, the fitting of the interconnection plate  9  to the shelf  4  with the aid of the seal  53  makes it possible to simplify the manufacture of the shelf  4  while allowing less precise geometric tolerances and surface states insofar as the calibration of the cooling air permeability is directly realized by the interconnection plate  9 . The tightness seal  53  allows a relative movement between the interconnection plate  9  and the shelf  4 , thus preserving the integrity of the electronic card constituting the interconnection plate  9  under the deformations and movements of the shelf  4  associated, for example, with the vibrations and stresses of the avionics bay. 
       FIG. 13  illustrates a third embodiment of the assembly of the interconnection plate  9  with the rest of the shelf  4 . 
     In this third embodiment, the ventilation wall  10  and the interconnection plate  9  form one and the same piece which is produced of an electrically nonconducting material, such as a polymer or a composite material. The interconnection plate  9  is formed by a wall closing off the lower part of the shelf  4 , on which wall the conductive connection tracks  28  are etched, deposited or adhesively bonded. 
     According to this third embodiment, the mass and the cost of a shelf  4  are reduced further still. 
     In a variant, the conductive connection tracks  28  can be integrated into the thickness of the interconnection plate  9  by methods of the “plastronic” type. 
     Variant embodiments of the avionics bay which has been described may be envisioned without departing from the scope of the invention. For example, the choice of a rigid interconnection plate  9  can lead to undersizing the shelf  4 . It is possible, for example, to reduce the thicknesses provided for the walls of the shelf  4 , and in particular the thickness of the ventilation wall  10 , by taking into account the additional rigidity afforded by the fixing of the interconnection plate  9  to the shelf  4 . 
     Likewise, if it is chosen for an interconnection plate  9  to be in the form of a flexible printed circuit, it is possible to provide a flexible or even deformable shelf  4 , the flexibility of the interconnection plate  9  accompanying this deformation without inducing any stress which can harm the conductive connection tracks  28 . 
     The protective shells  16  of the rear printed circuits  15  and the protective covers  34  of the interconnection plate may, furthermore, provide electromagnetic compatibility functions, for example by electromagnetically insulating the content thereof. 
     The integration of components in the front face of the shelf  4  is made possible by the interconnection system.  FIG. 6  thus illustrates an example of the integration of an equipment item  54  in the facade of a shelf  4 . This equipment item may, for example, comprise displays, relays and command buttons. This facade equipment item  54  does not require any other particular cabling than the addition of an additional flexible printed circuit  55  connected, on the one hand, to this facade equipment item  54  and, on the other hand, to the interconnection plate  9 . 
     Moreover, ribbon cables may replace the flexible printed circuits  18 ,  19  connecting the rear printed circuits  15  and the external connection printed circuit  26  to the interconnection plate  9 .