Abstract:
An air flow restrictor panel adapted for use in an electronics equipment enclosure to block a gap existing between a midplane and an electronics module positioned adjacent the midplane. The air flow restrictor panel may incorporate a main panel portion and a plurality of flanges extending from the main panel portion. The main panel portion may have a footprint sufficiently large in area to block the gap.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from U.S. Provisional patent application Ser. No. 61/106,302, filed Oct. 17, 2008, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to systems and methods for managing air flow through an electronics equipment enclosure, and more particularly to systems and methods that block air from flowing through a selected internal area of an electronics equipment enclosure. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Open enclosure specifications targeting the communications equipment market, such as the PICMG AdvancedTCA specification, describe mechanical building practices utilizing Rear Transition Modules (RTMs). The RTMs are printed circuit board (PCB) modules, also referred to in the art as “blades”, that are contained with a rear (i.e. RTM) card cage area of a chassis. The RTMs are physically located behind a rear surface of a midplane that is positioned within the chassis RTM. On the opposite surface of the midplane is a front board card cage area. The front board card cage area has a plurality of card slots where one or more front boards, also sometimes referred to as “blades”, are electrically coupled to the midplane. The RTMs are electrically coupled to the front boards through a connector zone known in the art as the “Zone-3” area, which is located above the midplane when the RTMs and front boards are arranged in a vertical orientation. 
         [0004]    The main purpose of the RTMs is to support the rear input/output (I/O) interfaces, thus decoupling such interfaces from the processing activities of front boards and increasing the available PCB area for performing various functions. Cooling of the RTM card cage area of an AdvancedTCA specification chassis has been traditionally accomplished through natural convection cooling, that is, without the need for electrically powered cooling fans. However, as the power dissipation of the RTMs has increased, this has necessitated a move to forced convection cooling systems for the RTM card cage area. The associated mechanical specifications of an AdvancedTCA chassis have not been optimized with the goal of implementing optimal efficiency for the forced convection cooling of the RTM cardcage. Since some degree of variability is required to allow for variations in the thickness of the midplane due to differing midplane connectivity requirements, this has resulted in the creation of a relatively large gap. Thus, with present building practices for an AdvancedTCA chassis, the gap will typically exist between the midplane and the rear edges of the RTMs installed in the RTM card cage area of an enclosure.  FIG. 1  illustrates this gap  2  within an AdvancedTCA specification enclosure  8 . The gap  2  can be seen to exist between a rear surface  4   a  of the midplane  4  and a rear edge  6   a  of an RTM  6  within the enclosure  8 . 
         [0005]    The gap  2  leaves unwanted low impedance, lateral air flow paths between the RTMs  6  and the midplane rear surface  4   a . The gap  2  essentially acts like a low air flow impedance bypass path that allows a cooling air flow directed through the RTM card slots of the RTM card cage area to be diverted away from the RTMs  6 . The existence of the gap  2  thus forms unwanted lateral flow paths that make the air flow distribution between the RTMs highly unpredictable. The air flow distribution through the RTM card cage area also becomes configuration specific, meaning that the configuration of the RTMs and their surface mounted components will play a significant role in determining the air flow distribution through the RTM card cage area. This is highly undesirable in an AdvancedTCA chassis where RTMs may be provided from multiple vendors, and therefore are not generally designed to take these effects into account. This can give rise to the need to independently verify each configuration of RTMs within the RTM card cage area, which is both time-consuming and costly, and which will need to be repeated for each subsequent configuration change. Existence of a low impedance air flow bypass path within the RTM card cage area also leads to wasted air flow and potentially to an insufficient volume of cooling air flow for the RTMs. 
       SUMMARY 
       [0006]    In one aspect the present disclosure includes an air flow restrictor panel adapted for use in an electronics equipment enclosure to block a gap existing between a midplane and an electronics module positioned adjacent the midplane. The air flow restrictor panel may incorporate a main panel portion and a plurality of flanges extending from the main panel portion. The main panel portion may have a footprint sufficiently large in area to block the gap. 
         [0007]    In another aspect the present disclosure includes an air flow restrictor panel adapted for use in an electronics equipment enclosure to block a gap existing between a midplane and an electronics module positioned adjacent the midplane. The air flow restrictor panel may include a main panel portion having a generally rectangular shape. A plurality of flanges may extend from the main panel portion. At least a subplurality of the flanges may each have a depth that is sufficient to substantially or entirely block a depth of the gap. The main panel portion may also have a footprint sufficiently large in length and height so as to block an area associated with the gap. 
         [0008]    In another aspect the present disclosure includes a method for restricting a flow of air between a gap existing between a midplane and an electronics module within an electronics equipment enclosure. The method may involve providing an air flow restrictor panel having a planar main panel portion. A plurality of flanges may be formed on the main panel portion such that the plurality of flanges extend from the main panel portion. At least a subplurality of the flanges each have a depth that is sufficient to substantially or entirely block a depth of the gap. The main panel portion may be formed with a footprint that is sufficiently large in length and height so as to block an area associated with the gap when the air flow restrictor panel is installed in the gap. 
         [0009]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0011]      FIG. 1A  is a simplified side view of a prior art electronics equipment enclosure, in this example an AdvancedTCA specification chassis, illustrating the gap that exists between a rear surface of the midplane and a rear edge of the RTM; 
           [0012]      FIG. 1B  is a more detailed perspective view of the equipment chassis shown in  FIG. 1  further illustrating the gap, and also showing in greater detail the midplane of the chassis with a plurality of alignment pins projecting therefrom that engage with portions of each RTM when the RTMs are secured with the RTM card cage area; 
           [0013]      FIG. 2  is a rear perspective view of an air flow blocking panel constructed to occupy the gap, and thus eliminate the lateral air flow paths that the gap would otherwise provide between the adjacently positioned RTMs and the midplane; 
           [0014]      FIG. 3  is a front perspective view of the air flow blocking panel shown in  FIG. 2 , and also a perspective view of an electrically non-conductive insulating sheet that may be positioned on a front surface of the air flow blocking panel; 
           [0015]      FIG. 4  is a simplified side view of the enclosure of  FIG. 1A  but with the air flow blocking panel installed to block the gap; and 
           [0016]      FIG. 5  is a perspective view showing the RTM card cage area with just the air flow blocking panel (i.e., no RTMs installed) installed over the midplane to occupy the gap. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0018]    Referring to  FIG. 2 , there is shown an air flow restrictor panel  10  in accordance with one embodiment of the present disclosure. For convenience, the air flow restrictor panel  10  will be referred to hereinafter simply as the “panel  10 ”. The panel  10  has a length “L” and height “H” that are sufficient to at least substantially, but more preferably completely, cover an area (i.e., length and height) associated with the gap, for example the gap  2  shown in  FIGS. 1A and 1B . 
         [0019]    The panel  10  may include a generally planar and generally rectangular shaped main panel portion  12  having a plurality of cutouts  14  along an upper area  16 . The cutouts  14  in this example are each semi-circular in shape, but they could be of other shapes such as rectangular, square, elliptical, triangular, etc. The upper area  16  also includes flanges  18  that extend at approximately a ninety degree angle from the main panel portion  12  between the cutouts  14 . Side areas  20  and  22  similarly include flanges  24  and  26  respectively that also extend at an angle of about ninety degrees from the main panel portion  12 . Bottom area  28  likewise includes a flange  30  that extends at about a ninety degree angle from the main panel portion  12 . 
         [0020]    The side areas  20  and  22  each include pairs of tabs  32  and  34  having holes  32   a  and  34   a , respectively, for enabling the panel  10  to be secured the sidewalls of an electronic equipment enclosure, such as for example an AdvancedTCA specification chassis (e.g., enclosure  8  in  FIGS. 1A and 1B ). The tabs  32  and  34  may be formed by punching out small sections of the main panel portion  12 . The upper area  16  similarly may include holes  36  through which push-in type fasteners, rivets or threaded fasteners may extend to secure the panel  10  within the enclosure  8 . 
         [0021]    The flanges  18 ,  24 ,  26  and  30  may all have the same depth, denoted by reference numeral  38  in  FIG. 2 . The depth is further preferably equal to, or just slightly smaller (e.g., by 1-2 mm) than the depth of the gap  2 , as indicated by dimensional arrows  40  in  FIG. 1A . The panel  10  may be formed from steel, aluminum, plastic, rubber or any other material that is impervious to air flow. However, the use of metal provides specific benefits in terms of adding rigidity to the enclosure  8 , enhancing overall structural integrity, enhancing fire resistance and limiting fire propagation. 
         [0022]    Referring to  FIG. 3 , an electrically non-conductive, insulating sheet  42  may be positioned over a front surface  44  of the panel  10 . The insulating sheet  42  has dimensions and cutouts  46  that match (or substantially match) the configuration of the panel  10 . The insulating sheet  42  provides a non-conductive barrier between the rear edge  6   a  of each RTM  6  and the front surface  44  of the panel  10  that ensures that no unwanted electrical contact will be made between the rear edges  6   a  of the RTMs  6  and the panel  10 . The insulating sheet  42  may be formed from plastic or any other suitable, non-conductive material such as rubber. The insulating sheet  42  may be secured to the panel  10  by adhesives or by independent fasteners, for example push-in type fasteners  48 , that extend through the holes  50  in the insulating sheet and aligned holes  36  in the panel  10 . The insulating sheet  42  has an area (i.e., footprint) preferably sufficient to cover the entire front surface  44  of the panel  10 . Instead of the insulating sheet  42 , the panel  10  front surface  44  may be coated with non-conductive paint or any other form of electrically non-conductive coating. However, if the panel  10  is constructed from an electrically non-conductive material, then the insulating sheet  42  would not be needed. 
         [0023]    Referring to  FIG. 4  the panel  10  can be seen installed against the midplane  4 . The panel  10 , with the help particularly of the flange  30 , effectively fills the entire cross-sectional volume of the gap  2  so that the gap is eliminated. The installed panel  10  positioned in the enclosure  8 , without any 
         [0024]    RTMs installed in the enclosure, is also shown in  FIG. 5 . From  FIG. 5  it can be seen that the cutouts  14  provide clearance for alignment pins  52  projecting from the rear surface  4   a  of the midplane  4 . The alignment pins  52  aid in providing precise alignment of the RTMs  6  when the RTMs are being installed in the card slots in an RTM card cage area  54 . 
         [0025]    The panel  10  thus provides a structure and method for eliminating the gap  2 , and thus ensuring that the cooling air flow directed into the RTM card cage area will flow through the RTM card slots in a predictable manner. A particular advantage of the panel  10  is that it eliminates the need to perform RTM configuration specific testing to ensure that the desired air flow through the RTM card slots is being achieved. Furthermore, if the RTM configuration should be changed at a later date, no re-testing of the air flow through the RTM card cage area is required. The panel  10  further does not add appreciable cost, weight or complexity to the construction of an AdvancedTCA specification chassis, and can even enhance the structural properties of the chassis such as its rigidity and fire worthiness. 
         [0026]    While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.