Abstract:
A plenum assembly for a shallow chassis in a rack-mount system. The rack mount system includes a first set of posts at a first end of the rack, a second set of posts at a second end of the rack, and guide rails that extend between the first and second sets of posts. A shallow chassis mounted on the guide rails extends from the first end of the rack to an intermediate location, between the first and second ends of the rack. The plenum assembly is also mounted on the guide rails, and extends from the second end of the rack to the intermediate location, providing an airway from the second end of the rack to the shallow chassis. The plenum assembly can include telescoping sections to extend various lengths. Alternately, the plenum assembly can have a two piece construction, which is assembled after routing cables to the shallow chassis.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Patent Application 61/578,737, entitled “Plenum Kit”, which was filed on Dec. 21, 2011, and is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a rack mountable plenum kit. 
       RELATED ART 
       [0003]    ‘Pizza box’ and chassis-based systems are typically housed in racks or rack cabinets. The depths of the systems into the rack vary. One end (front or back) of all the systems in a rack are typically aligned to a set of posts in the rack. For example, the front end of all systems mounted in the rack may be aligned with a set of front posts in the rack. Airflow in the rack can be front to back or back to front. The intake side is designated the “cool aisle” while the exhaust side in designated the “warm aisle”. There can be interfaces and connections on either side of the system which need easy access. An issue occurs when systems of different depths are housed in the same rack. There is the possibility of warm exhaust air being re-circulated into the intakes of a less deep chassis. This issue is illustrated by  FIGS. 1 and 2 . 
         [0004]      FIG. 1  is a top view of a typical pizza box chassis  100 , which includes power supplies  101 - 102  having cords  103 - 104  and fans  105  at the rear of the chassis, and interface and cabling  106  at the front of the chassis. The airflow  108  in this example, as induced by the fans  105 , is from the rear of the chassis (i.e., the cool aisle) toward the front of the chassis (i.e., the warm aisle). Chassis  100  is mounted in a rack  110  with brackets on the front. That is, the front of chassis  100  is aligned with (and attached to) the front rack posts  111 - 112  of rack  110 . The rear end of chassis  100  is supported by guide rails  121 - 122 , which extend between the front rack posts  111 - 112  and the rear rack posts  113 - 114 , as illustrated. Note that chassis  100  does not extend the full depth of rack  110 . Thus, chassis  100  may be referred to as a ‘shallow’ chassis. 
         [0005]      FIG. 2  is an isometric view that illustrates the shallow chassis  100  of  FIG. 1  installed in rack  110  above a deeper (full-length) chassis  200 . The deeper chassis  200  has its air intake located immediately adjacent to the cool aisle  201 , and its air outlet located immediately adjacent to the warm aisle  202 . Shallow chassis  100  draws in air from the middle of the rack  110 , which is not immediately adjacent to the cool aisle  201 . That is, the air intake of shallow chassis  100  is closer to the warm aisle  202  than the air intake of full-length chassis  200 . As a result, the air drawn into the shallow chassis  100  is typically warmer than the air in the cool aisle  201 , due to recirculation of hot air from the warm aisle  202  (as illustrated by arrow  205 ) and heating effects of the chassis in the rack  110 . 
         [0006]    It would therefore be desirable to have an efficient method and structure for reducing the temperature of air drawn into shallow chassis  100 . 
       SUMMARY 
       [0007]    Accordingly, the present invention provides a plenum assembly for use with a shallow chassis in a rack-mount system. The rack mount system includes a first set of posts at a first end of the rack, a second set of posts at a second end of the rack, and guide rails that extend between the first and second sets of posts. A shallow chassis mounted on the guide rails extends from the first end of the rack to an intermediate location, between the first and second ends of the rack. The plenum assembly is also mounted on the guide rails, and extends from the second end of the rack to the intermediate location, providing an airway from the second end of the rack to the shallow chassis. In this configuration, air can be drawn directly from the second end of the rack (e.g., the cool aisle), through the airway of the plenum assembly, to the shallow chassis. As a result, recirculation of air from the first end of the rack (e.g., the warm aisle) is eliminated. 
         [0008]    In one embodiment, the plenum assembly includes slots for engaging protrusions on the guide rails, and mounting tabs for engaging the second set of posts. A support strut can be included within the plenum assembly to prevent crushing of the airway. 
         [0009]    In one variation, the plenum assembly can include telescoping sections, which allow the plenum assembly to be extended to various lengths. In another variation, the plenum assembly has a two piece construction, which can include a tray and a lid. In this variation, tray may be mounted on the guide rails/second set of posts, wherein cables from the shallow chassis are easily routed through the tray. After the cables are routed through the tray, the lid is attached to the tray, thereby forming the airway of the plenum assembly. In a particular embodiment, the lid is slid into slots in the tray. 
         [0010]    The present invention will be more fully understood in view of the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a top view of a conventional shallow pizza box chassis mounted in a rack. 
           [0012]      FIG. 2  is an isometric view illustrating the shallow chassis of  FIG. 1  installed in a rack above a full-length chassis. 
           [0013]      FIG. 3  is an isometric view of a rack-mountable plenum assembly in accordance with one embodiment of the present invention. 
           [0014]      FIG. 4  is an exploded view of the plenum assembly of  FIG. 3  in accordance with one embodiment of the present invention. 
           [0015]      FIG. 5  is a front isometric view of a shallow chassis installed in a rack, with the plenum assembly of  FIG. 3  positioned for insertion into the rack, in accordance with one embodiment of the present invention. 
           [0016]      FIG. 6  is a front isometric view of a shallow chassis and the plenum assembly of  FIG. 3  installed in a rack in accordance with one embodiment of the present invention. 
           [0017]      FIG. 7  is a rear isometric view of a shallow chassis and the plenum assembly of  FIG. 3  installed in a rack in accordance with one embodiment of the present invention. 
           [0018]      FIG. 8  is an isometric view illustrating the interaction between a shoulder bolt and a mounting slot when the plenum assembly of  FIG. 3  is attached to the rack of  FIGS. 6 and 7 , in accordance with one embodiment of the present invention. 
           [0019]      FIG. 9  is a cross sectional view of a plenum assembly having telescoping sections that are capable of sliding along one another, thereby allowing the length of the plenum assembly to be adjusted in accordance with another embodiment of the present invention. 
           [0020]      FIG. 10  is an isometric view of a two-part plenum assembly in accordance with an alternate embodiment of the present invention. 
           [0021]      FIG. 11  is a cross sectional view of a plenum assembly that includes end portions that extend around a shallow chassis, and also includes a compliant gasket in accordance with alternate embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 3  is an isometric view of a rack-mountable plenum assembly  300  in accordance with one embodiment of the present invention.  FIG. 4  is an exploded view of plenum assembly  300  in accordance with one embodiment of the present invention. Plenum assembly  300  includes a first section  301  and a second section  302 , that are connected (e.g., by rivets  331 - 337 ) to form a hollow air pathway  305 . In general, the first and second sections  301 - 302  form a rectangular box  310 , having rectangular openings  310 A and  310 B at opposing ends. A support strut  303 , which is coupled to the first and second sections  301 - 302  near the middle of the width of the plenum assembly  300 , provides support to maintain the shape of the hollow pathway  305  (i.e., prevent crushing of the hollow pathway  305 ). Plenum assembly  300  includes mounting tabs  311 - 312  having holes  313 - 314 , respectively. As described in more detail below, screws (or other connector elements) are inserted through holes  313 - 314  to hold plenum assembly  300  within a rack. As also described in more detail below, holes  313 - 314  are positioned between screw holes that are used to mount an associated guide rail system in the rack. (See, e.g.,  FIG. 7 .) Plenum assembly  300  also includes mounting slots  321  and  322 , which are located to engage with shoulder bolts on a guide rail system in a rack. (See, e.g.,  FIGS. 6-8   8 .) As described in more detail below, plenum assembly  300  is fitted onto the same guide rails as a shallow chassis, thereby bridging the gap that would otherwise exist between the rear of the shallow chassis and the cool air aisle. In this configuration, air from the cool aisle flows through the hollow pathway  305  to the rear of the shallow chassis, advantageously preventing the recirculation of warm air. 
         [0023]    As described in more detail below, the cables that extend from the rear of the shallow chassis (e.g., the rear (power) cords of the shallow chassis) are routed through the hollow pathway  305  of plenum assembly  300  in accordance with one embodiment of the present invention. However, it is understood that plenum assembly  300  can alternately include openings that allow top, bottom and/or side cable egress.  FIG. 4  illustrates locations  401 ,  402  and  403 , wherein openings can be formed to allow top, bottom and side cable egress, respectively, through plenum assembly  300 . In one variation, these openings may be formed by knocking out perforated tabs formed in the plenum assembly  300 . In another variation, plugs (or other means for closing the openings) may be included to close these openings if top/bottom/side cable egress is not necessary. 
         [0024]      FIG. 5  is an isometric view of a shallow chassis  500  installed in a rack  510  that includes front posts  511 - 512 , rear posts  513 - 514  and guiderails  521 - 522 , wherein plenum assembly  300  is positioned for insertion into the rack  510 . Note that the shallow chassis  500  has already been installed into the rack  510  using the guiderails  521 - 522 , in a manner known to those of ordinary skill in the art. In accordance with one embodiment of the present invention, guide rails  521 - 522  include corresponding shoulder bolts  601 - 602 , respectively, which extend centrally inward from the guide rails  521 - 522 . Shoulder bolts  601  and  602  are positioned to engage the mounting slots  321  and  322 , respectively of plenum assembly  300 , thereby supporting the rear of the plenum assembly  300  within the rack  510 . 
         [0025]      FIG. 6  is an isometric front view that shows plenum assembly  300  mounted to rack  510 .  FIG. 7  is an isometric rear view that shows plenum assembly  300  mounted to rack  510 . In the position illustrated by  FIGS. 6 and 7 , the mounting slots  321  and  322  have been slid onto the corresponding shoulder bolts  601  and  602  of guide rails  521  and  522 . Note that mounting slot  321  and shoulder bolt  601  are shown in dashed lines in  FIG. 6 , and mounting slot  322  and shoulder bolt  602  are shown in dashed lines in  FIG. 7 . 
         [0026]    The mounting tabs  311  and  312  are attached to center holes on the rear posts  513  and  514  by screws  701  and  702 , respectively, thereby holding plenum assembly  300  in place within rack  510 . Note that guide rails  521  and  522  also include mounting tabs  521 A and  522 A, respectively, which are similarly attached to rear posts  513 - 514  by screws (including screws  701  and  702 ). Plenum assembly  300  is easily removable from rack  510  by releasing screws  701 - 702  and sliding the plenum assembly  300  from the rack  510 . As illustrated by  FIG. 7 , the hollow pathway  305  of plenum assembly  300  provides an airway from the cold aisle to the rear of shallow chassis  500 , whereby recirculation of hot air from the warm aisle is minimized. As also illustrated by  FIG. 7 , the power cords  501 - 502  that are connected to the rear of shallow chassis  500  extend through the hollow pathway  305 , and out the back side of the rack  501 . 
         [0027]      FIG. 8  is a side view illustrating the interaction between the shoulder bolt  601  on guide rail  521  and the mounting slot  321  of plenum assembly  300 . The mounting slot  321  includes a large tapered lead-in area  801 , which is continuous with a narrower parallel slot  802 . The lead-in area  801  facilitates the movement of shoulder bolt  601  into the parallel slot  802  when the plenum assembly  300  is installed in the rack  510 . 
         [0028]    Although plenum assembly  300  has a fixed length (L), as illustrated in  FIG. 3 , it is understood that this plenum assembly  300  could be modified to have a telescoping capability to accommodate multiple chassis and rack depths.  FIG. 9  is a cross sectional view of a plenum assembly  900  having telescoping sections  901  and  902 , which are capable of sliding along one another (as illustrated by the dashed arrows), thereby allowing the length of the plenum assembly  900  to be easily adjusted. Catches or thumbscrews (not shown) can be provided to prevent the telescoping sections  901 - 902  from coming apart. Although not explicitly illustrated in  FIG. 9 , it is understood that plenum assembly  900  includes the same general features described above in connection with plenum assembly  300 . 
         [0029]    Although plenum assembly  300  has been illustrated as having a height to fit a  1  rack unit high chassis, it is understood that plenum assemblies of multiple heights can be designed using the same principles described above. 
         [0030]    Although plenum assembly  300  has been described in connection with a configuration wherein the hollow pathway  305  operates as a cold air intake, receiving cold air from the cold aisle, it is understood that plenum assembly  300  can alternately be used as a warm air exhaust. In this embodiment, shallow chassis  500  would be mounted immediately adjacent to the cold aisle, and warm air expelled from shallow chassis would be routed through plenum assembly  300  to the warm aisle. 
         [0031]    Plenum assembly  300  requires that power cords (and possibly signal carrying cables) coupled to the rear of shallow chassis  500  to be threaded through the hollow pathway  305  of plenum assembly  300 . With this configuration, rear access to shallow chassis  500  may be difficult. In accordance with one variation of the present invention, the plenum assembly  300  is split into two parts to facilitate access to the rear of shallow chassis  500 .  FIG. 10  is an isometric view of a two-part plenum assembly  1000  in accordance with this variation. Plenum assembly  1000  includes a lower tray  1001  and a lid  1002 . Lower tray  1001  includes mounting tabs  1011 - 1012  and mounting slots  1021 - 1022 , which are similar to the mounting tabs  311 - 312  and mounting slots  321 - 322  of plenum assembly  300 . The lower tray  1001  is installed in rack  510  in the same manner as plenum assembly  300 . Lower tray  1001  is fully open at the top, thereby allowing cables to be easily connected to the rear of shallow chassis  500  after the lower tray  1001  is installed in rack  510 . Alternately, lower tray  1001  can be easily installed in rack  510  after the cables have been connected to the rear of shallow chassis  500 . 
         [0032]    After the cables are connected and lower tray  1001  is installed in rack  510 , lid  1002  is attached to lower tray  1001 , thereby forming a hollow pathway  1005  between lid  1002  and lower tray  1001 . In the illustrated embodiment, the upper edges of lower tray  1001  includes opposing slots  1031 - 1032 , wherein lid  1002  is slid into these slots  1031 - 1032 , as illustrated by the dashed arrows in  FIG. 10 . Lower tray  1001  includes a connector element  1041  that is aligned with a connector element  1042  on lid  1002  when lid  1002  is slid into lower tray  1001 . A fastener  1043  (e.g., screw) may be used to attach connector elements  1041 - 1042 , thereby joining lower tray  1001  and lid  1002 , while providing a support that prevents the closing of hollow pathway  1005 . 
         [0033]    In another embodiment of the present invention, cable management devices, such as cable tie-downs, hooks or channels can be included within the plenum assembly of the present invention to assist with the orderly routing of cables through this plenum assembly (and ensure optimal airflow through these plenum assemblies). 
         [0034]    In yet another embodiment, an elastic/compliant gasket can be included on the end of the plenum assembly  300  that abuts shallow chassis  500 , wherein the gasket forms a substantially airtight seal between the plenum assembly  300  and the shallow chassis  500 , thereby providing efficient airflow through the plenum assembly and minimizing the recirculation of hot air. In another embodiment, the plenum assembly  300  can extend around the shallow chassis  500  on one or more sides, with or without a compliant gasket. 
         [0035]      FIG. 11  is a cross sectional view of a plenum assembly  1100  that includes end portions  1101 - 1102  that extend around the upper and lower surfaces of shallow chassis  500  in the manner suggested above. Note that similar end portions of plenum assembly  1100  can extend around the side surfaces of shallow chassis  500 .  FIG. 11  also illustrates an optional compliant gasket  1150 , which forms a substantially airtight seal between plenum assembly  1100  and shallow chassis  500 . 
         [0036]    Although the present invention has been described in connection with various embodiments, it is understood that variations of these embodiments would be obvious to one of ordinary skill in the art. For example, although the present invention has been described in connection with a rack mount system having four posts, it is understood that the present invention can be implemented in other types of rack mount systems, including, but not limited to, rack mount systems having two posts (e.g., two front mounting posts or two mid-mount posts). In these embodiments, the manner of attaching the plenum assembly to the rack mount system will be dictated by the specific nature of the rack mount system, and will be apparent to one of ordinary skill in the art in view of the teachings provided herein. For example, the plenum assembly of the present invention may be attached to a rail-based structure of a two post rack mounting system, in a manner similar to that described above. In yet another embodiment, a plenum assembly of the present invention can be engaged with a shallow chassis outside of a rack mount system. For example, the plenum assembly of the present invention can be engaged with a shallow chassis on a tabletop or other non-rack structure. Thus, the present invention is limited only by the following claims.