Abstract:
A modular fan unit having a frame receivable within a baffle of a chassis for containing electronic components is provided. Each of a pair of brackets is connected to an end of the frame to form a slot for receiving a wall of the baffle. Moreover, each of the pair of brackets is respectively attachable to a pair of walls of a rack containing the chassis. A fan is attached to the frame so as to align with an aperture located between the pair of brackets and passing through the frame. A controller is attached to the frame and is electrically connected to the fan.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of fans and, in particular, to modular fan units for chassis. 
     BACKGROUND 
     Chassis are often used to contain circuit cards, such as circuit cards of telecommunications systems. In telecommunications applications, several chassis for containing circuit cards are, for example, stacked one above the other and are secured in a rack located in a central office or other location. Many of these circuit cards dissipate heat that if not removed from the cards and subsequently from the chassis, can cause the circuit cards to fail. 
     Many chassis are passively cooled chassis, e.g., heat is removed from the cards and chassis by a natural convection airflow induced by a temperature difference between heated air within the chassis and cooler air outside of the chassis. In one application, outside air is drawn into the chassis through openings at the bottom of the chassis. The air flows generally vertically through the chassis and over the cards so that heat is transferred from the cards to the air, thereby heating the air. The air exits the chassis through openings in the top of the chassis. However, in some stacked arrangements, the heated air flows from the top of one chassis into a chassis above, resulting in reduced heat transfer from the cards of the chassis above. Consequently, baffles are sometimes located atop passively cooled chassis for directing the air flow generally horizontally through the back of one chassis so that the heated air does not flow into a chassis above. 
     However, the natural convection airflow through some of these passively cooled chassis with baffles does not transfer enough heat from the circuit cards and chassis. Therefore, the circuit cards can overheat and fail. As a result, passively cooled chassis are sometimes replaced by actively cooled chassis, e.g., having fans or other active cooling devices for forcing air through the chassis. However, because many actively cooled chassis include integral active cooling devices, replacement of passively cooled chassis with actively cooled chassis often requires the purchase or fabrication of actively cooled chassis, which is not always cost effective. Moreover, there is not always sufficient space in a rack for a chassis having a fan, so the number of chassis within the rack has to be reduced, which is not always cost effective when renting space within a central office. Replacing passively cooled chassis with actively cooled chassis usually requires the removal of the passively cooled chassis and installation of the actively cooled chassis, which is not always cost effective from a labor standpoint and can result in a disruption of services. 
     For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for equipping existing passively cooled chassis with active cooling devices. 
     SUMMARY 
     The above-mentioned problems with replacing passively cooled chassis with actively cooled chassis and other problems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. 
     One embodiment provides a modular fan unit having a frame receivable within a baffle of a chassis for containing electronic components. Each of a pair of brackets is connected to an end of the frame to form a slot for receiving a wall of the baffle. Moreover, each of the pair of brackets is respectively attachable to a pair of walls of a rack containing the chassis. A fan is attached to the frame so as to align with an aperture located between the pair of brackets and passing through the frame. A controller is attached to the frame and is electrically connected to the fan. 
     Another embodiment provides a method for retrofitting a passively cooled chassis for active cooling. The method includes inserting a modular fan unit into a baffle for exhausting fluid from a rear of the chassis so that an aperture of the modular fan unit forms an outlet of the baffle. A fan of the modular fan unit aligns with the aperture and is located within the baffle. Respectively receiving a pair of opposing walls of the baffle within a pair of slots of the modular fan unit is also included in the method. The method includes securing a pair of brackets disposed at opposite ends of the modular fan unit to a pair of walls of a rack containing the chassis. The chassis is diposed between the pair of walls. 
     Other embodiments are described and claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an exterior of a modular fan unit according to an embodiment of the present invention. 
     FIG. 2 is an exploded isometric view of an interior of the modular fan unit of FIG.  1 . 
     FIG. 3 is an exploded isometric back view of a chassis retrofitted with a modular fan unit according to another embodiment of the present invention. 
     FIG. 4 is an assembled isometric back view chassis of FIG.  3 . 
     FIG. 5 is an assembled isometric front view of chassis of FIG.  3 . 
     FIG. 6 is a view taken along line  6 — 6  of FIG.  5 . 
     FIG. 7 is a cross-sectional view taken along line  7 — 7  of FIG.  5 . 
     FIG. 8 is an assembled isometric view of an interior of the modular fan unit of FIG. 1 according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
     Embodiments of the present invention provide for retrofitting passively cooled chassis for containing electronic components with a modular fan unit for active cooling. The modular fan unit is received within a baffle of the passively cooled chassis for actively drawing air through the chassis and is attached to a rack containing the chassis. This avoids replacing passively cooled chassis with actively cooled chassis and the above-mentioned problems associated therewith. 
     FIG. 1 is an isometric view of an exterior of a modular fan unit  100  according to an embodiment of the present invention. FIG. 2 is an exploded isometric view of an interior of modular fan unit  100 . Modular fan unit  100  has a frame  102  that includes plates  104  and  106 . In one embodiment, plate  104  is connected substantially perpendicularly to plate  106 . In another embodiment, plates  104  and  106  are integral, as shown in FIGS. 1 and 2, and are of plastic, metal, (e.g., aluminum), or the like. 
     Brackets  108  are respectively connected to ends  110  of plate  106  to form slots  112 . In one embodiment, brackets  108  are integral with plate  106 , as shown in FIGS. 1 and 2. In some embodiments, brackets  108  include plates  180  and  182  interconnected by a plate  184  that is substantially perpendicular to plates  180  and  182 . In one embodiment, plates  180 ,  182 , and  184  define a socket  186  at an end of slots  112  that, in one embodiment, protrudes from plate  106 , as shown in FIG.  1 . In another embodiment, slotted apertures  109  pass through brackets  108  to facilitate adjustable mounting of modular fan unit  100 , e.g., to a rack for containing chassis for electronic equipment, as described below. 
     Fans  114  are attached to plate  106 , e.g., using studs  116  and nuts  118 , as shown in FIG. 2, bolts, cap screws, or the like. Each of fans  114  aligns with an aperture  120  passing through plate  106 . A control circuit card  122  is attached to plate  104  using screws  124  or the like, as shown in FIG.  2 . An electrical connector  126  of control circuit card  122  passes through plate  106  and, in one embodiment, protrudes from an exterior surface  128  of plate  106 , as shown in FIG.  1 . Control circuit card  122  also includes an electrical connector  130 . Wires  132  electrically interconnect each of fans  114  and electrical connector  130  and thus electrically connect control circuit card  122  to each of fans  114 . 
     In one embodiment, a cover  800  covers control circuit card  122  as shown in FIG. 8, an assembled isometric view of an interior of the modular fan unit of FIG.  1 . In another embodiment, fasteners  802 , such as cap screws or the like secure cover  800  to control circuit card  122 . In some embodiments, cover  800  includes vents  804  for air to flow into and out of the space contained within cover  800  for cooling control circuit card  122 . In other embodiments, cover  800  forms a fire enclosure and is of a fire resistant material, such as metal or the like. 
     Control circuit card  122  receives power, e.g., from a battery or other power source, via electrical connector  126 . Control circuit card  122  transmits the power to each of fans  114  via electrical connector  130  and wires  132 . In some embodiments, control circuit card  122  monitors operation of fans  114  and transmits an alarm signal via electrical connector  126  when an alarm condition is detected, e.g., a fan failure. A number of visual indicators  134 , such as light emitting diodes, are connected to control circuit card  122  by a connector  136 , as shown in FIG.  2 . In one embodiment, each of visual indicators  134  respectively aligns with each apertures  138  passing through plate  106 . Visual indicators  134  indicate the status of fans  114 . For example, in some embodiments, one of visual indicators  134  lights when control circuit card  122  is receiving power, another lights when one or more of fans  114  fails, etc. 
     In one embodiment, modular fan unit  100  is for retrofitting passively cooled chassis for containing electronic components, such as electronic circuit cards, for active cooling. FIG. 3 is an exploded isometric back view of a chassis  300  retrofitted with modular fan unit  100  according to another embodiment of the present invention. In one embodiment, chassis  300  contains telecommunications electronic circuit cards, such as HDSL, HDSL 2 , T 1  repeater, etc. Chassis  300  is mounted in a rack  302 . In particular, chassis  300  is disposed between walls  304  of rack  302 , and opposing sides  305  of chassis  300  are attached to walls  304  by fasteners  306 , such as cap screws or the like. A baffle  308  is mounted atop chassis  300 . Prior to retrofitting chassis  300  with modular fan unit  100 , chassis  100  is passively cooled. During passive cooling, a natural convection flow passes through chassis  300  and is exhausted at the rear of chassis  300  by baffle  308 . 
     Retrofitting chassis  300  for active cooling includes receiving plate  104  of modular fan unit  100  within baffle  308  through an outlet  310  of baffle  308 . As plate  104  is received in baffle  308 , opposing walls  312  of baffle are received in slots  112  of modular fan unit  100 . Brackets  108  are respectively secured to walls  304  of frame  302  using fasteners  314 , e.g., cap screws or the like. In one embodiment, fasteners  314  pass through the slotted apertures  109  in brackets  108  and thread into apertures  315  of rack  302 . In some embodiments, slotted apertures  109  facilitate adjustable mounting of modular fan unit  100  to rack  302  for positioning modular fan unit  100  within baffle  308 . In other embodiments, slotted apertures  109  accommodate a range of distances between the apertures  315  of one of walls  304 . 
     FIG. 4 is an assembled isometric back view of chassis  300  retrofitted with modular fan unit  100 . FIG. 5 is an assembled isometric front view of chassis  300  with a cover  318  (shown in FIG. 4) removed, and FIG. 6 is a view taken along line  6 — 6  of FIG.  5 . Apertures  120  form an outlet of baffle  308 , as shown in FIG. 4, and fans  114  are located within baffle  308 , as shown in FIG.  6 . Although not shown, controller circuit card  122  is also located within baffle  308 . In one embodiment, walls  312  of baffle  308  are received within sockets  186  located at the end of slots  112 . In another embodiment, this causes plate  106  to be recessed within baffle  308 , as shown in FIG.  4 . In some embodiments, a filter  320  is located adjacent a bottom  352  of chassis  300  opposite baffle  308  so that an interior  322  of chassis  300  is between filter  320  and baffle  308 , as shown in FIG.  5 . In one embodiment, filter  320  is disposed between a filter frame  324  and a lower shelf  326  of chassis  300 , as shown in FIG.  5 . In another embodiment, filter slides into and out of chassis  300  through the front of chassis  300 , as respectively indicated by arrowheads  328  and  330  in FIG.  6 . 
     Brackets  334   a  and  334   b  secure filter frame  324  within chassis  300 . Fasteners  336 , such as nuts and bolts, cap screws, or the like, attach brackets  334  to filter frame  324 . In one embodiment, at least one of brackets  334 , e.g., bracket  334   a  as shown in FIG.  5  and FIG. 7, a cross-sectional view taken along line  7 — 7  of FIG. 5, includes a slot  338  for receiving fasteners  336 . Slot  338  enables bracket  334   a  to be adjustably positioned relative to filter frame  324  and adjacent side  305  of chassis  300 , as indicated by arrowheads  710  and  720  in FIG.  7 . In one embodiment, bracket  334   a  is adjustably positioned to extend across a gap  705  between filter frame  324  and side  305  so as to connect side  305  to filter frame  324 . In yet another embodiment, a flange  337  is attached to an edge  339  of each brackets  334  and, in one embodiment, extends into gap  705 , as illustrated for bracket  334   a  in FIG.  7 . 
     In one embodiment, brackets  334  are substantially “L” shaped so as to wrap around a corner  342  of filter frame  324 , as shown in FIG.  7 . In another embodiment, extrusions  344  of side  305  extend through brackets  334 , as shown for bracket  334   a  in FIGS. 6 and 7. In one embodiment, at least one of extrusions  344  passes through a slotted aperture  346  in brackets  334 , as shown for bracket  334   a  in FIG.  6 . In some embodiments, apertures  348  pass through extrusions  344 . In another embodiment, apertures  348  are threaded, as shown in FIG.  7 . 
     During operation, fans  114  draw air into chassis  300  through bottom  352  of chassis  300 , as indicated by arrow  354  in FIGS. 4 and 6. In one embodiment, the air flows through filter  320 , as indicated by arrow  355  in FIG.  6 . The air flows through chassis  300 , as indicated by arrows  356  in FIG. 6, and heat is transferred to the air from the circuit cards (not shown) within chassis  300 . The air flows into baffle  308 , and baffle  308  directs the flow substantially perpendicularly so as to direct the flow into fans  114 , as indicated by arrow  358  in FIG.  6 . The air passes through fans  114  and exits baffle  308  at the rear of chassis  300  through apertures  120 , as indicated by arrow  360  in FIGS. 4 and 6. 
     Conclusion 
     Embodiments of the present invention have been described. The embodiments provide for retrofitting passively cooled chassis for containing electronic components with a modular fan unit for active cooling. The modular fan unit is received within a baffle of the passively cooled chassis for actively drawing air through the chassis and is attached to a rack containing the chassis. This avoids replacing passively cooled chassis with actively cooled chassis. 
     Although specific embodiments have been illustrated and described in this specification, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. It is manifestly intended that this invention be limited only by the following claims and equivalents thereof.