Abstract:
A high efficiency multi-directional airflow system for a telecommunications equipment assembly used for housing electronic apparatuses which facilitate telecommunications functionality. The equipment assembly defines an internal cavity which can be divided into a plurality of air flow channels. Each of the plurality of air flow channels captures a sub-portion of the overall volume provided by the internal cavity. The smaller volume flow channels provide a smaller cross-sectional area through which the majority of air travels. Since the cross-sectional area is smaller, the velocity of the air through the flow channels is increased. Since the air velocity is increased, the heat transfer coefficient is also increased, thus allowing for the more efficient removal of heat from the electronic apparatuses. A set of fan trays can include a plurality of fans each directionally positioned to work in series to cause air to flow through the plurality of flow channels.

Description:
BACKGROUND 
     1. Field of Invention 
     This invention relates to telecommunications equipment systems, and specifically to an apparatus for providing air flow in a card based telecommunications equipment assembly. 
     2. Relevant Art 
     Most modern telecommunications equipment contains electronic apparatuses mounted in a chassis (also referred to as “shelf”). The chassis is generally enclosed, with a front access door, side walls, and a backplane. The chassis is enclosed to prevent stray material from entering the casing and damaging the electronic apparatus and to prevent stray emission of electromagnetic energy. Typically, the electronic apparatus housed inside the chassis includes heat generating components. Most heat generating components must not be allowed to overheat or else they may lose their effectiveness. Thus, it becomes necessary to provide for the cooling of components within the chassis. 
     Typically, components are cooled using air that is forced into the chassis and made to flow over the components. Conventional fan trays are typically employed to force the air through the chassis. For example, in a conventional push-pull air flow system, a fan tray is positioned at a bottom part of the chassis with an inlet opening while a second fan tray is positioned at the top part of the chassis with an exhaust opening. Unfortunately, due to the density in today&#39;s telecommunications products, the push-pull air flow system uses valuable space, which could otherwise be used for fiber routing. 
     SUMMARY 
     The present invention provides a high efficiency multi-directional airflow system for a telecommunications equipment assembly used for housing electronic apparatuses which facilitate telecommunications functionality. In accordance with the present invention, the equipment assembly defines an internal cavity which can be divided into a plurality of air flow channels. Each of the plurality of air flow channels captures a sub-portion of the overall volume provided by the internal cavity. The smaller volume flow channels provide a smaller cross-sectional area through which the majority of air travels. Since the cross-sectional area is smaller, the velocity of the air through the flow channels is increased. Since the air velocity is increased, the heat transfer coefficient is also increased, thus allowing for the more efficient removal of heat from the electronic apparatuses. 
     In accordance with the present invention, a set of fan trays can be used to achieve push-pull air flow through the channels. The single set of fan trays can include a plurality of fans each directionally positioned to work in series to cause air to flow through the plurality of flow channels. Advantageously, the single set of fan trays can be positioned on the same side of the equipment assembly, which allows the use of the same area for inlet and exhaust of the cooling air to increase the amount of vertical space used for routing fibers. 
     In one aspect of the present invention, a telecommunications equipment assembly is provided, which includes a chassis defining an internal cavity for receiving a plurality of electronic apparatus. The assembly also includes at least one divider mechanism coupled to each of the plurality of electronic apparatus, where the divider mechanisms define at least two flow channels within the internal cavity. The assembly further includes a first fan tray configured to cause air to flow through the first flow channel; and a second fan tray configured to cause the air flowing in the first channel to flow through the second flow channel. The first fan tray and the second fan tray are positioned on an area at the first end of the chassis. 
     In another aspect of the invention, a telecommunications equipment assembly is provided. The assembly includes a chassis defining an internal cavity for receiving a plurality of electronic apparatuses. The assembly also includes a means for defining a plurality of flow channels within the internal cavity; and a first fan placed in series with a second fan to pull air into the plurality of flow channels and to push air out from the plurality of flow channels. The first fan and the second fan are positioned on an area proximate to the same portion of the chassis. 
     In another aspect of the present invention a method is provided for providing air flow through a telecommunications equipment assembly. The method includes providing a chassis including an internal cavity; dividing the internal cavity into a plurality of flow channels, where the flow channels include a first end and a second end; and pulling and pushing air through the flow channels. 
     In yet another aspect of the present invention, a telecommunications equipment assembly is provided which includes a chassis having a first surface and which defines an internal cavity. The assembly also includes a means for dividing the internal cavity into a plurality of flow channels, and a means for pulling and pushing air through the flow channels. The means being combined on a first surface of the chassis. 
     The present invention provides many advantages over conventional air flow systems. For example, the use of fans in series provides a reduction in back pressure acting on each fan, which prolongs the life of each fan. The higher air velocity generated by the present invention provides for more efficient cooling due to an increase in the heat transfer coefficient. The present invention, also provides a more consistent temperature rise when used in a rack mount multi-shelve system. Because of the more efficient heat transfer capability, a higher degree of fan failure can be tolerated in the system. Since the exhaust and intake are positioned using the same area, less openings in the equipment assembly are required, thus substantially reducing the potential for unwanted EMI emission. 
     These and other objects, features and advantages of the present invention will be more readily apparent from the detailed description of the preferred embodiments set forth below taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified perspective view of a telecommunications equipment assembly in accordance with an embodiment of the present invention; 
     FIG. 2 is a simplified top view of a fan tray section including a row of intake fans and a row of exhaust fans in accordance with an embodiment of the present invention; 
     FIG. 3 is a simplified cut away side view of an embodiment of the telecommunications equipment assembly of FIG. 1; and 
     FIG. 4A is a perspective view of an electronic apparatus including a divider mechanism coupled thereto in accordance with an embodiment of the present invention; 
     FIG. 4B is a simplified top view of a representative portion of the telecommunications assembly of FIG. 1 including side-by-side mounted electronic apparatuses of FIG. 4A in accordance with an embodiment of the present invention; 
     FIG. 5A is a simplified illustration of air flow in one embodiment in accordance with the present invention; 
     FIG. 5B is a simplified illustration of air flow in an alternative embodiment in accordance with the present invention; 
     FIG. 5C is a simplified illustration of air flow in an alternative embodiment in accordance with the present invention; 
     FIG. 5D is a simplified illustration of air flow in an alternative embodiment in accordance with the present invention; and 
     FIG. 6 is a simplified side view of the telecommunications assembly including electronic apparatuses having multiple divider mechanisms and multiple flow channels in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a telecommunications equipment assembly  10  (hereinafter “shelf assembly  10 ” or “shelf  10 ”) configured in accordance with an embodiment of the present invention. In this embodiment, shelf assembly  10  can include at least four sections: Cage section  42 , fan tray section  44 , intake/exhaust section  46  and fiber management section  48 . 
     Cage section  42  includes a housing or chassis  12 , which includes several components, such as top wall  14 , a bottom wall  16 , a side wall  18 , a side wall  20 , and a back wall  22 , which collectively define an internal cavity  30 . Generally, housing  12  may be made with sheet metal, injection molded plastic, or other similarly suited structural materials. 
     Interior cavity  30  is suitable for removably receiving one or more electronic apparatuses. In one embodiment, interior cavity  30  is large enough to be capable of removably receiving electronic apparatuses, such as optical line cards, cross-connect cards (CXC), timing and system control cards (TSC) and other types of plug-in cards (not shown), which may provide a telecommunications functionality to shelf assembly  10 . An access opening  24  provides access to interior cavity  30  for replacement, removal, assembly, servicing, and/or repair of the electronic apparatuses. Optionally, top and bottom walls  14  and  16  may have slots or grooves used to support, guide, and align the plug-in cards while housed in interior cavity  30 . 
     Back wall  22  can include a backplane, which is a printed circuit board that extends substantially the width of housing  12 . The backplane includes circuitry identical to circuitry in a conventional backplane well-known in the telecommunications industry, which provides electrical characteristics, such as shielding, conductor path characteristics, including controlled impedance, current carrying capacity, paths for instrument buses, data busses, unit under test (UUT) stimulus busses, and power busses. In one embodiment, the backplane provides the electrical interface between the electronic apparatus enclosed in housing  12  and external cables. Generally, the external cables are routed through fiber management section  48 . 
     Intake/exhaust section  46  includes an intake opening  96  and an exhaust opening  98 . Intake opening  96  can include an air filter  102  (FIG.  3 ). Optionally, air filter  102  can be positioned at an angle relative to intake opening  96  to increase the effective size of the air filter. Each opening  96  and  98  is designed to allow air to flow out from housing  12 , with a minimal amount of air pressure build-up. In one embodiment, openings  96  and  98  may extend substantially the width of housing  12  and have a height of between about 2 inches to about 3 inches. In some embodiments, due to the configuration of backplane  22 , exhaust opening  98  may have to be reduced in size relative to intake opening  96  to accommodate backplane  22 . To avoid unwanted pressure build-up within housing  12 , a perforated exhaust section  104  (FIG. 3) can be formed on, for example, side walls  18  and  20  to allow exhaust air to escape. 
     In one embodiment, fan tray section  44  can include multiple fans trays. As shown in FIGS. 1 and 2, fan tray section  44  can include three fan trays  106 ,  108 , and  110 , which can include at least six tube axial fans  72 . In this embodiment, each fan tray  106 ,  108  and  110  can include at least two fans  72 . Fans  72  are directionally positioned to force air either into or out from housing  12 . For example, fan trays  106 ,  108 , and  110  include intake fans  73   a,  which include propellers positioned to force air into housing  12 . Similarly, fan trays  106 ,  108  and  110  include exhaust fans  73   b,  which include propellers positioned to exhaust air out from housing  12 . In this embodiment, when fan trays  106 ,  108  and  110  are slidably mounted into fan tray section  44 , the fan trays form a first row  114  of side-by-side positioned intake fans and a second row  116  of side-by-side positioned exhaust fans, one row on each side of housing centerline  112 . 
     FIG. 3 is a simplified side view of housing  12  arranged in accordance with one embodiment of the present invention. In this embodiment, intake opening  96  is positioned proximate top wall  14  on the side of centerline  112  corresponding to intake fan row  114  (FIG.  2 ). Exhaust opening  98  is similarly positioned on the side of centerline  112  corresponding to exhaust fan row  116  (FIG.  2 ). In this configuration, air can be forced into housing  12  through opening  96  using intake fans  73   a  and forced out from housing  12  through exhaust opening  98  using exhaust fans  73   b.  This configuration allows intake fans  73   a  and exhaust  73   b  to work in series to move air through housing  12  in the direction indicted by arrows  75 . Fans  72  can be any type of suitable fan, for example, a Maltese® AC or DC tube axial fan available from Comair Rotron of San Diego, Calif. 
     FIG. 4A is a perspective view of an exemplary electronic apparatus  120  for use in shelf assembly  10  (FIG. 1) coupled to a divider mechanism  88  in accordance with an embodiment of the present invention. In one embodiment, divider mechanism  88  is a substantially flat rectangular member that is coupled on a first side  121  of electronic apparatus  120 . Divider mechanism  88  can extend out perpendicular to first side  121 . The amount that divider mechanism  88  extends can be made equal to approximately the distance w (FIG. 4B) between electronic apparatuses  120 . 
     The height of divider mechanism  88  can be a percentage of the entire height h of the electronic apparatus  120 . In this embodiment, divider mechanism  88  reaches substantially the entire height h. In other embodiments, the height of divider mechanism  88  can be between about 40% to about 100% of the height h. 
     Divider mechanism  88  can be positioned at any point along a depth d of apparatus  120 . For example, divider mechanism  88  can be mounted at a location on electronic apparatus  120 , which corresponds to a point in-between a row of intake fans  73   a  and exhaust fans  73   b,  such as along centerline  112  of equipment assembly  10  (FIG.  4 B), when electronic apparatuses  120  are mounted on backplane  22 . 
     Divider mechanism  88  can be coupled to apparatus  120  in a conventional manner, such as by bending extended portions of divider mechanism  88  to form flanges  123  and screwing, or otherwise mounting, the flanges onto apparatus  120 . Divider mechanism  88  can be made of any structurally rigid material, such as plastic or sheet metal. 
     In one embodiment, at least one divider mechanism  88  is coupled to each of a plurality of electronic apparatuses  120 , such as CXC, TSC and optical line cards (hereinafter “cards  120 ”). As shown in FIG. 4B, when cards  120  are positioned side-by-side in shelf assembly  10  and coupled to backplane  22 , each divider mechanisms  88  lines up with divider mechanism on each other card  120  to form a barricade. The barricade divides internal cavity  30  (FIG. 1) into separate flow channels, for example, as illustrated in FIGS. 5A-5D. It should be noted that divider mechanisms  88  are not intended to necessarily create a barricade that creates an air tight seal between the separate flow channels, but instead are intended to direct the majority of air through the channels thus created. Because of the relative velocity of the air through the flow channels, air leakage between divider mechanisms  88  can be considered negligible. 
     FIG. 5A is a simplified cut away side view of telecommunication equipment assembly  80  illustrating airflow direction created by divider mechanism  88  in accordance with the present invention. Telecommunications equipment assembly  80  (hereinafter “equipment assembly  80 ”) includes a card cage section  82 , which is divided into two channels  84  and  86  using the barricade created by the alignment of divider mechanisms  88  in card cage section  82 . In one embodiment, intake opening  96  and exhaust opening  98  are operably positioned adjacent intake fan tray  92  and exhaust fan tray  94 , respectively. In this embodiment, flow channel  84  is an intake channel coupled to intake opening  96  through intake fan tray  92 . Similarly, channel  86  is an exhaust channel coupled to exhaust opening  98  through exhaust fan tray  94 . Air can be forced via intake opening  96  into card cage section  82 . As indicated by arrow  125  air travels through flow channel  84 , around divider mechanisms  88  via plenum  90 , and through flow channel  86 . The air is removed from card cage section  82  via exhaust opening  98 . Each fan tray  92  and  94  can include any number of fans needed to adequately provide sufficient airflow into, and out from, flow channels  84  and  86 . Plenum  90  can be located on the bottom portion  50  of equipment assembly  80  to provide an open space for receiving air for distribution through card cage section  82 . 
     FIG. 5B is a simplified illustration of an alternative embodiment of equipment, assembly  80 . In this embodiment fan trays  92  and  94  are positioned on bottom portion  50  of equipment assembly  80 . In a manner similar to that shown in the illustration of FIG. 5A, air travels in a path indicated by arrow  125 . 
     FIG. 5C is a simplified illustration of an alternative embodiment of equipment assembly  80 . Fan trays  92  and  94  are positioned on top portion  52  of equipment assembly  80 . In this embodiment, equipment assembly  80  does not include a plenum  90  to provide an airflow path at the bottom portion  50  as in FIG.  5 A. Accordingly, divider mechanism  88  can be made to extend a height which is less than the height h of electronic apparatuses  120  (FIG.  4 A). The shorter divider mechanism  88  allows air to travel from flow channel  84  to flow channel  86  around divider mechanism  88  in a path indicated by arrow  125 . 
     FIG. 5D is a simplified illustration of an alternative embodiment of equipment assembly  80 . In this -embodiment, fan trays  92  and  94  are replaced by an impeller fan  91  positioned on bottom portion  50  of equipment assembly  80  between flow channels  84  and  86 . Alternatively, impeller fan  91  can be positioned on top portion  52 at the end of flow channel  86 . Impeller  91  can receive air parallel to the rotational axis of impeller fan  91  and dispatch air perpendicular to the rotational axis of impeller  91 . Accordingly, air travels in a path indicated by arrows  125 . 
     In electronic equipment assemblies, the continuous flow of cooling air helps to contain and eventually extinguish fires, since the air can keep the components in the assembly from reaching the flash temperature. Advantageously, positioning fan trays  92  and  94  on top portion  52  can help to increase fan survivability. In this embodiment, intake fan tray  92  positioned on top portion  52  pushes cool air down into card cage section  82  and therefore is not affected by a fire burning within card cage section  82 . Since exhaust fan tray  94  is also positioned on top portion  52 , any fire debris that may be blown down by the fans of intake fan tray  92  falls safely into plenum  90  or onto the bottom of card cage section  82 . Since the survivability of each fan is increased in this configuration, any fire in card cage section  82  is more likely to be extinguished before any significant damage is realized. 
     In this operational embodiment, air flow area is reduced into smaller cross sectional areas. Accordingly, for the same flow rate, the air flow velocity is multiplied, thus increasing the heat transfer coefficient. For example, in a typical equipment assembly with a total fan output of 600 cfm, the air speed may be expected to be about 300 lfm, due in part to high back pressure. In the present invention, when the same equipment system is divided into two flow channels using divider mechanisms  88  and intake and exhaust fans  73   a  and  73   b  (FIG. 2) at each end of the flow, respectively, the velocity can be expected to be increased to about 600 lfm. In this embodiment, any high pressure that may otherwise occur is compensated for by the series arrangement of the intake and exhaust fans  73   a  and  73   b.  Since intake and exhaust openings  96  and  98 , respectively, are positioned on the same side of shelf assembly  10 , much desired vertical space for routing fibers is provided. 
     FIG. 6 is a simplified cut away side view of shelf assembly  200  in accordance with an alternative embodiment of the present invention. Equipment assembly  200  includes electronic apparatuses  120  each including a plurality of divider mechanisms  88  to create a plurality of flow channels within shelf assembly  200 . In this exemplary embodiment, four flow channels  202 ,  204 ,  206  and  208  are created with fans  210  and  212 , representative of a row of fans, for providing the push-pull effect. In this embodiment, air flows into intake opening  96  and through each flow channel  202 ,  204 ,  206 , and  208  in the direction of arrows  140  until exhausted through exhaust opening  98 . 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.