Abstract:
A rack ( 70 ) for a plurality of internal electronics modules that includes a mechanism for mounting external electronics modules ( 69 ). The rack ( 70 ) includes a heat exchanger ( 63 ) disposed between the rack ( 70 ) and the external electronics module ( 69 ). The external electronics module ( 69 ) includes a heat coupling surface for efficiently using the heat exchanger ( 63 ) for dissipating heat of the external electronics module ( 69 ).

Description:
GOVERNMENT RIGHTS 
     This invention was made with Government support under Contract No. DAAJ09-91-C-A004 awarded by the U.S. Army. The Government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a rack for mounting and connecting a plurality of electronics modules and, more particularly, to a rack for mounting and connecting a protected external module, which is coupled to a heat exchange unit. 
     2. Discussion of the Related Art 
     Many electronics systems employ independent electronic modules that are slideably positioned within an electronics rack, and electrically connected to each other therein. One particular known electronics rack is used for mounting and connecting avionics and electronics modules. As is well understood in the art, the operation of electronics systems generates heat. The closer the electronics modules are mounted together, the more heat is generated per unit volume, and the harder it is for the heat to dissipate. If too much heat is generated, the electronic modules may not operate amount of heat may create a fire hazard. Therefore, one of the primary focuses of the rack is to provide cooling of the modules. 
     In one rack design, cooling air is forced through a heat exchanger configured within the rack to provide cooling of the electronics modules. FIG. 1 is a perspective view of an electronics rack  10  of this type that is known in the art. The rack  10  includes an outer housing  12  having a front opening  14 . A lower card guide  16  is mounted at a lower location within the housing  12  by flanges  18  secured to opposing side panels  20  and  22  of the housing  12 . The card guide  16  is a single unit made of a heat conductive metal, such as aluminum. The card guide  16  includes a plurality of parallel tabs  28  extending from front to back that define a groove  30  there between each tab  28  includes an alignment nub  32  positioned proximate to the opening  14 . An upper card guide (not shown) is also mounted within the housing  12  at an upper location in the same manner, and also includes parallel tabs defining grooves there between. 
     The parallel grooves  30  in the lower card guide  16  and the parallel grooves in the upper card guide are aligned and suitably spaced apart to receive internal electronics modules  36  in a certain configuration. Each internal electronics module  36  includes a lower rail  38  that is inserted in one of the grooves  30  in the lower guide  16  and the upper rail  40  that is inserted in the corresponding groove in the upper guide. When the internal electronics module  36  is slid into the housing  12 , an electrical connector  42  is electrically connected with a meeting electrical connector (not shown) at the back of the housing  12  to provide the desired electrical connection. Multiple internal electronics modules  36  are slid into the housing  12  in a parallel format to provide the overall electrical system. It is generally desirable to set the spacing of the grooves  30  and thickness of the internal electronics modules  36  to allow as many modules as possible to be stored in the rack  10  to conserve space. 
     The internal electronics modules  36  generate heat during operation. The rack  10  therefore provides assisted cooling for the internal electronics module  36  to draw away the heat. FIG. 2 is a cross-sectional view of the rack  10 - 2  in FIG.  1 . Rails  38  and  40  make contact with the lower card guide  16  and upper card guide in a heat transfer engagement. To provide the cooling, forced air is caused to circulate across the lower card guide  16  and upper card guide to draw heat away from the internal electronics modules  36 . An inlet plenum  46  is attached to the side surface  20  at one side of the housing  12  and an outlet plenum  48  is attached to the surface  22  at an opposite side of the housing  12 . Of course, the inlet and outlet plenums  46  and  48  can be reversed. The inlet plenum  46  includes a rectangular opening  50  through a back wall  52  of the housing  12  that allows cooling air to enter the plenum  46 . The outlet plenum  48  includes a rectangular opening  54  through the wall  52  that allows the heated air to exit the outlet plenum  48  and the housing  12 . 
     A heat exchanger  60  is positioned within a specially configured cavity and a base plate  62  between the bottom wall of the housing  12  and the card guide  16 . A similar heat exchanger  63  is also provided between the top wall and the upper card guide. The heat exchangers  60 ,  63  include a plurality of spaced apart fins  64  that extend transversely to the opening  14 . The cooling air from the inlet plenum  46  is forced into the heat exchangers  60 ,  63  and flows between the fins  64  across the card guide  16  to collect the heat therein. The fins  64  increase the surface area exposed to the cooling air and increase the heat removal capacity. As the operation of the internal electronics modules  36  heat the upper and lower card guides, air flowing between the fins  64  acts to draw heat away from the internal electronics modules  36  providing the cooling. The inlet plenum  46  provides cooling air to both the upper, lower and medial heat exchangers. 
     The spacing between the cooling fin  64  and the height and width of the cooling fin  64 , is defined by the desired amount of air flow to provide the desired amount of cooling, as is understood in the art. In alternative variations, the rack  10  can include a plurality of stacked layers where internal electronics modules  36  are positioned between card guides and each separate layer, as disclosed, and cooling is provided at each layer in the manner as discussed herein. 
     The above described process of providing cooling of electronics modules in an electronics rack has been effective in removing heat from electronics modules. However, the overall electronics packaging density of the system and efficiency of the heat exchanger is reduced because only one side of the upper and lower heat exchangers  60 ,  63  is being utilized. Because the size and weight of the electronic system may be an important perimeter in different types of systems, it may be desirable to provide an electronics rack that allows for the mounting of a protected external electronic module which utilizes the exposed surfaces of two heat exchangers. It is therefore an object of the present invention to provide an electronics rack which is capable of accepting externally mounted electronics modules and efficiently takes advantage of the top heat exchanger arrangement. 
     SUMMARY OF THE INVENTION 
     In accordance with the teaching of the present invention, a rack for a plurality of electronics modules is disclosed where the rack allows for the mounting of external electronic modules. 
     The present invention proposes an external electronics module which is configured to mount to the exterior of the chassis while utilizing the existing interconnect media and cooling pass provided for the modular electronics packaged inside the enclosure. The external electronics module enclosure provides the required environmental protection and many combinations of interface hardware provide mechanisms for the external electronics module insertion/removal and external electronics module to chassis cold wall clamping for efficient heat transfer. Blind mate electrical connectors (both currently in the art and those yet conceived) provide an electrical interface to the rest of the electronics packaged within the enclosure. 
     Additional objects, features and advantages of the invention will become apparent from a consideration of the following description and appended claims when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a rack, known in the art, for mounting a plurality of electronics modules; 
     FIG. 2 is a cross-sectional view through line  2 — 2  of rack shown in FIG. 1; 
     FIG. 3 is a perspective view of a rack for mounting a plurality of electronic modules, where the rack includes mounting for an external electronic module, according to an embodiment of the present invention; 
     FIG. 4 is a top view of the external electronics module shown in FIG. 3; 
     FIG. 5 is a rear view of the external electronic module used in the rack shown in FIG. 3; 
     FIG. 6 is a front view of the external electronics module used in the rack shown in FIG. 3; and 
     FIG. 7 is a side view of the rack shown in FIG.  3  through line  7 — 7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following discussion of the preferred embodiments is directed to a rack having a plurality of heat exchangers for electronic modules is merely exemplary in nature, and is no way intended to limit the invention or its applications or uses. 
     FIG. 3 is a perspective view of an electronics rack  70 , according to an  16  embodiment of the present invention. FIGS. 4-7 are views of the external electronics module  68 . The rack  70  can be used to hold and connect the same types of internal electronics modules  36  as the rack  10 , and therefore like components are defined by the same reference numerals and are described above. The rack  70  can also be used to hold and connect a plurality of external electronic modules  68  onto the top surface  71  of the top heat exchanger  63 . Unlike the internal electronics modules  36 , which are mounted with the rack  70 , the external electronics module  68  is mounted to the rack  70  top surface  71 . Volume efficiency is improved since no additional volume needs to be allocated for heat exchangers  60 ,  63 . The external electronics module uses the existing racks  70  features for cooling. The external electronics module cover  74  provides its internal components environmental protection. In this embodiment, a single external electronics module is shown, but in alternate designs, variations in the numbers of modules coupled to the top heat exchanger  63  may be desired. 
     Each external electronics module  68  has a pair of parallel wedge clamps  78 ,  79  which are mounted to a coupling surface  76  of the external electronics module cover  74 . The coupling surface  76  is preferably aluminum and allows for a proper thermal coupling of the external electronics module  68  with the top surface  71  of the top heat exchanger  63 . 
     The top surface  71  of the top heat exchanger  63  has a pair of rails  82 ,  83  which function to engage the wedge clamps  78 ,  79 . Each rail  82 ,  83  further has locking portions  84 ,  85  for engaging the lever injector/ejectors  80 ,  81  which are mounted to the external electronics module cover  74 . 
     When the external electronics module  68  is slid into the top surface  71  of the top heat exchanger  63 , each wedge clamp  78 ,  79  is slid into its corresponding rail  82 ,  83  on the top surface  71  and an lever injector/ejector  80 ,  81  is snapped into its corresponding locking portion  84 ,  85 . When the external electronics module  68  is slid into the rack  70  an electrical connector  86  is electrically connected to a mating electrical connector  87  at the back of the rack  70  to provide the desired electrical connection. Multiple external electronics modules  68  can be slid onto the top surface  71  in a parallel format to provide the overall electrical system. It is generally desirable to set the spacing of the rails  82  and the size of the external electronics module  68  to allow as many external electronics module  68  as possible to be stored on the top surface  71  of the top heat exchanger  63  to conserve space and improve the efficiency of the top heat exchanger  63 . 
     FIGS. 4-7 depict the external electronics module  68  of the current invention. FIGS. 4 and 6 depict the injector/ejector  80 ,  81  engaged with the locking portions  84 ,  85  of the rails  82 ,  83 . By lifting the injectors/ejectors  80 ,  81 , the external electronics module  68  will be extracted from electrical connector  87 . Although a standard pin type connector arrangement  86 ,  87  is shown, a multitude of connector options are envisioned. 
     The external electronics module  68  generate heat during operation. The rack  70  therefore provides assisted cooling of the external electronics module  68  to draw away the heat. FIG. 7 is a cross-sectional view of the rack  70  through lines  7 — 7  of FIG.  3 . The rails  82 ,  83  in conjunction with the wedge clamps  78 ,  79  force the coupling surface  76  of the external electronics module cover  74  into engagement with the top surface  71  of the heat exchanger  63 . To provide the cooling, forced air is caused to circulate within the top heat exchanger  63  to draw heat away from the internal electronics modules  36  and the external electronics module  68 . As the external electronics module  68  are not positioned within the rack  10 , cooling is also possible by convection about the external electronics module cover  74 . 
     The foregoing discussion discloses and describes merely exemplary embodiments of that the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.