Abstract:
An apparatus for cooling a computer system includes a fan for flowing an air to a first assembly and a second assembly, a first filter for filtering an air to a first assembly, and a second filter for filtering an air to a second assembly. The first filter is disposed at a side of the first assembly and the second filter is disposed on an opening of a wall which separates the first assembly and the second assembly.

Description:
BACKGROUND 
     FIG. 1  shows a perspective view of a typical computer server  101  with blade servers  103  disposed therein.  FIG. 2  shows a perspective view of a computer server  101  in  FIG. 1  where blade servers  103  are removed. As can be seen in  FIGS. 1 and 2 , a chassis  105  has a plurality of slots  107  for enclosing blade servers  103  inside of the chassis  105 . Each blade server  103  is removably attached to each socket  201  disposed on a middle wall  203  of a chassis  105 . Further, three fan trays  109  are removably disposed under the slots  107  and inside the chassis  105 . Each fan tray  109  has an inlet  111  for an air at the front of the fan tray  109 . 
     FIG. 3  shows a sectional view of computer server  101  along the line A-A of  FIG. 1 . As can be seen in  FIG. 3 , a front printed circuit board (PCB) assembly  301  of the blade server  103  is disposed at a middle plane  203  of the chassis  105  via the socket  201  so that the front PCB assembly  301  is removably disposed inside the chassis  105 , while the rear PCB assembly  307  is fixedly disposed on the rear surface of the middle plane  203 . Further, the fan tray  109  is removably disposed inside the chassis  105  under the front PCB assembly  301 . The fan tray  109  has an air inlet  111  at the front plane of the fan tray  109  and also has two fans  309  in a row at the upper plate of the fan tray  109  so that the fans  309  provide an air directly to the front PCB assembly  301  as shown in a direction B in  FIG. 3 . An air filter  311  is disposed between the front PCB assembly  301  and the fans  309  when the fan trays  109  are inserted in the chassis  105 . The air filter  311  filters the air from the fans  309  to the front PCB assembly  301 . The middle plane  203  of the chassis  305  has an opening  313  beside the back of the fan tray  109  when the fan tray  109  is inserted in the chassis  105  so that the air from the fan is also directed to the rear PCB assembly  307  through the opening  313 . In addition, the front PCB assembly  301  and the rear PCB assembly  307  include some electric parts  303  and  305  respectively. 
   In operation, most of the air from the inlet  111  is directed to the front PCB assembly  301  by the fan  309  as shown in arrow B in  FIG. 3 , while some of the air from the fans  309  is directed to the rear PCB assembly  307  by the fans  309  through the opening  313  as shown in arrow D in  FIG. 3 . The air to the front PCB assembly  301  is filtered by the air filter  311 , while the air to the rear PCB assembly  307  is not filtered because the rear PCB assembly  307  is not active components and does not require that the air to the rear PCB  307  is filtered. 
   SUMMARY OF INVENTION 
   One or more embodiments of the present invention relate to an apparatus for cooling a computer system including a fan for flowing an air to a first assembly and a second assembly, a first filter for filtering an air to a first assembly, and a second filter for filtering an air to a second assembly. The first filter is disposed at a side of the first assembly and the second filter is disposed on an opening of a wall which separates the first assembly and the second assembly. 
   One or more embodiments of the present invention relate to a method for retrofitting an air filter to a chassis of a computer server having a first front PCB assembly, a rear PCB assembly, a middle wall separating the first front PCB assembly and the second PCB assembly, and a removable fan tray enclosing a fan and having an inlet of an air, wherein the fan provides the air to the first assembly that is disposed above the fan tray when the fan tray is inserted in the chassis. The method includes: removing a fan tray from a chassis of a computer server; making an opening at a rear plate of the fan tray; installing the air filter to the surface of the rear plate around the opening to cover the fan tray; and returning the fan tray to the chassis so that the air filter is attached to an opening of the middle wall to provide a air from the inlet to the second assembly through the air filter. 
   Other aspects and advantageous of the invention will be apparent from the following description and appended claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  shows a perspective view of a typical computer server with blade servers disposed therein. 
       FIG. 2  shows a perspective view of a computer server in  FIG. 1  where blade servers are removed. 
       FIG. 3  shows a sectional view of computer server along the line A-A of  FIG. 1 . 
       FIG. 4  shows a perspective view of a computer server with blade servers disposed therein in accordance with one or more embodiments of the present invention. 
       FIG. 5  shows a perspective view of a computer server in  FIG. 4  where blade servers are removed. 
       FIG. 6  shows a sectional view of the computer server along the line B-B of  FIG. 4 . 
       FIG. 7  shows a sectional view of the fan tray shown in  FIGS. 4-6  from the back. 
       FIG. 8  shows a block diagram showing a circuit used to the server system in accordance with one or more embodiments of the present invention. 
       FIG. 9  shows a flow diagram of retrofitting the second filter to the computer server for the rear PCB assembly in accordance with one or more embodiments of the present invention. 
   

   DETAILED DESCRIPTION 
   Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. 
   In the following detailed description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. 
     FIG. 4  shows a perspective view of a computer server  402  with blade servers  405  disposed therein in accordance with one or more embodiments of the present invention.  FIG. 5  shows a perspective view of a computer server  402  in  FIG. 4  where blade servers  405  are removed. As can be seen in  FIGS. 4 and 5 , a chassis  401  has a plurality of slots  403  for blade servers  405  at the upper and front portion of the chassis  401 . Each blade server  405  is removably attached to each slot  403  via each socket  407  disposed on a middle wall  409  of the chassis  401 . Further, three fan trays  411  are removably disposed inside the chassis  401  under the slots  403 . Although three fan trays  411  are shown in  FIGS. 4 and 5 , one of ordinary skill in the art will appreciate less or more numbers of fan trays are disposed in the chassis  401 . The front plane of the fan tray  411  has an inlet  413  of an air, which is covered by a wire netting. Thus, an air is able to enter into the fan tray  411  through this inlet  413 . Also, each fan tray  411  has a handle  415  at the front surface of the inlet  413  for removing the fan tray  411  from the chassis  401  by pulling the handle  415 . Although the handle  415  is attached to the fan tray  411  via a wire netting, one of ordinary skill in the art will appreciate that the handle  415  is directly attached to each fan tray  411 . The wire netting is perforated to allow an airflow therethrough, but each hole of the wire netting is not too wide to enable electromagnetic interference to radiate out from the chassis  401 . Additionally, the chassis  401 , the wire netting and the handle  415  is made of iron, aluminum or any other suitable material known in the art. Also, the end of the wire netting may be attached to the handle  415  by screws, adhesives, bonding or other attachment methods known in the art. 
     FIG. 6  shows a sectional view of the computer server  401  along the line B-B of  FIG. 4 . As can be seen in  FIG. 6 , the blade servers  405  in  FIGS. 4 and 5  are constituted of a printed circuit board (PCB) assembly  601  including printed circuit board (PCB)  605  and various kinds of electric parts  603  such as semi-conductor chips and connectors. The blade servers  405  may also be covered by a housing (not shown). A rear PCB assembly  607  is constituted of a printed circuit board (PCB) assembly  607  including printed circuit board  609  and various kinds of electric parts  611 . The rear PCB assembly  607  may also be covered by a housing (not shown). Additionally, active components are used in both the front PCB assembly  601  and the rear PCB assembly  607 . 
   As can be seen in  FIG. 6 , the front PCB assembly  601  is disposed on the front surface of the middle plane  409  of the chassis  401  via a socket  407  so that the front PCB assembly  601  is removably disposed inside the chassis  401 . On the other hand, the rear PCB assembly  607  is fixedly disposed on the rear surface of the middle plane  409 . Although the rear PCB assembly  607  is fixedly disposed in this embodiment, one of ordinary skill in the art will appreciate that the rear PCB assembly  607  is removably disposed on the rear surface of the middle plane  409  via a socket (not shown) similar to the front PCB assembly  601  as explained above. Further, one of ordinary skill in the art will appreciate the other position of the socket  615  on the surface of the middle plane  409  so long as the front PCB assembly  601  is tightly held in the chassis  401 . 
     FIG. 7  shows a sectional view of the fan tray  411  shown in  FIGS. 4-6  from the back. As shown in  FIGS. 6 and 7 , the inside of the fan tray  411  is hollow so that air can pass freely therethrough and each fan tray  411  is removably disposed inside the chassis  401  under the front PCB assembly  601  when the fan tray  411  is inserted. The fan tray  411  has two fans  617  in a row along the upper plate of the fan tray  411  at a useful distance from each other. Each fan  617  is a typical fan and has a casing  615 , a fan blade  621  and a motor (not shown) to rotate the fan blade  621 . The side plate of the casing  615  may be attached to the fan tray  411  by screws  701  or other attachment methods known in the art. Although each fan tray  411  includes two fans  617  in this embodiment, one of ordinary skill in the art will appreciate that the fan tray  411  may includes only one fan or more than two fans according to the size of the chassis and/or the energy consumption of the front PCB assembly  601  and the PCB assembly  607 . Also, the position on which the fans  617  are disposed are not limited to those in  FIGS. 6 and 7 , and other position on the surface of upper plate of the fan tray  411  may be used, if such positions of the fans  617  enable the fan trays  411  to be inserted the chassis  401  appropriately and the fans  617  to provide enough air. 
   As shown in  FIG. 6 , a first air filter  623  is disposed between the front PCB assembly  601  and the fans  617  when the fan trays  411  are inserted in the chassis  401 . The first filter  623  is removably fixed to the middle wall  409  of the chassis  401 . The first filter  623  is removed at a maintenance service, and the service interval ranges, for example, from one month for dusty environmental air to one year for clean environmental air. The first air filter  623  filters the air from the fans  617  to the front PCB assembly  601 . One of the ordinary skill in the art will appreciate that the first filter  623  is disposed at the fan tray  411  itself above the fans  617 . Also, although the first filter  623  is one filter for a plurality of the fan trays  411  in  FIG. 6 , one of the ordinary skill in the art will appreciate a plurality of filters per one fan tray  411 , one filter per one fan tray, or even one filter per each fan  617 , if such filter or filters enables to filter the air to the first PCB assembly  601  appropriately. 
   As can be seen in  FIG. 7 , the fan tray  411  has an opening  629  at the rear plate of the fan tray  411 . A second filter  703  is removably attached to the rear plate of the fan tray  411  at the end thereof tightly by screws  705 , adhesives, bonding, or other attachment methods known in the art. Similarly to the first filter  623 , the second filter  703  is removable at a maintenance service. The second filter  703  fully covers the opening  629  of the fan tray  411 . Also, the middle wall  409  of the chassis  401  has an opening  625  at the lower portion of the middle wall  409  so that, when the fan tray  411  is inserted into the chassis  401  as shown in  FIG. 6 , the second filter  703  is situated on the opening  625  of the middle wall  409  to fully cover the opening  625 . At this time, the second filter  703  is touched on the surface of the middle wall  409  around the opening  625 . In other words, when the fan tray  411  is inserted into the chassis  401 , there is no gap between the surface of the middle wall  409  and the surface of the second filter  703 . Thus, only the filtered air by the second filter  703  is directed to the second rear PCB assembly  607 . In addition, more than 80% of the dust arrestance of the second filter  703  may be preferable. 
   One of the ordinary skill in the art will appreciate any other shapes of the openings  625  and  629  and the second filter  703  so long as the second filter  703  is able to cover the whole openings  625  and  629 . Also, although the fan tray  411  has the second filter  703  outside the fan tray  411  in this embodiment, one of ordinary skill in the art will appreciate that the second filter  703  is included inside the fan tray  411  so long as only the air filtered by the second filter  703  is directed to the second rear PCB assembly  607 . Also, the position of the opening  629  is not limited to those in  FIGS. 6 and 7 , and other position on the surface of rear plate of the fan tray  417  may be used, if such positions of the fans enable the fan trays to be inserted the chassis  401  and the fans  617  to provide enough air to the rear PCB assembly  607  when inserted. 
     FIG. 8  shows a block diagram showing a circuit for controlling fans  617  in accordance with one or more embodiments of the present invention. As shown in  FIG. 8 , a first sensor  801  and a second sensor  802  are electrically connected to a controller  803 . Also, a first motor  804  and a second motor  805  are electrically connected to the controller  803 . The first motor  804  and second motor  805  rotate the blades  621  of the fans  617  respectfully. The first sensor  801  and the second sensor  802  are sensors for detecting temperatures. The first sensor  801  may be disposed at the slots  403  to detect the temperature of the blade servers  405 . The second sensor  802  may be disposed at the rear of the middle wall  409  and inside the chassis  401  to detect the temperature of the rear PCB assemblies  607 . One of the ordinary skill in the art will appreciate that other positions of the first and second sensor  801  and  802 , if such positions do not prevent the front PCB assembly  601  and the rear PCB assembly  607  from being inserted and removed from the chassis  401 . 
   Thus, the controller  803  controls the rotation speed of the first motor  804  and the second motor  805  respectively according to the temperatures detected by the first sensor  801  and the second sensor  802 . For example, when the temperature of the rear PCB assembly  607  is higher than the predetermined temperature, the rotation speed of the motor that is close to the middle wall  409  is controlled to be faster to provide more air filtered by the second filter  703  to the rear PCB assembly  607 . In addition, one of ordinary skill in the art will appreciate that the controller  803  controls the rotation speeds of the first motor  804  and the second motor  805  at the same speed according to the temperatures detected by the first sensor  801  and the second sensor  803 . 
   In operation, as can be seen in arrows F and G in  FIG. 6 , most of the air from the inlet  413  is directed to the front PCB assembly  601  by the fans  617 , while some of the air from the fans  617  is directed to the rear PCB assembly  607  by the fans  617 . 
   Also, the air to the front PCB assembly  601  is filtered by the first air filter  623 , while the air to the rear PCB assembly  607  is filtered by the second air filter  703 . The arrows F and G describes only some flow of the air, the air flow should not limited to these arrows. 
   Thus, not only the air to the front PCB assembly  601  from the inlet  413  but also the air to the rear PCB assembly  607  is filtered so that the problems caused by the impacts of the unfiltered air flow to the rear PCB assembly  607  are prevented when the energy to be put into the rear PCB assembly  307  has increased as the new standard has evolved. Further, the second air filter  703  affects a wider area than afforded by the inlet holes at the middle plane. This allows greater air flow around the rear PCB assembly  607 , while providing a larger area to collect dust which would make maintenance intervals longer. 
     FIG. 9  shows a flow diagram of retrofitting the second filter  703  to the computer server without the filter for the rear PCB assembly  607  as shown in  FIGS. 1-3 . In one or more embodiments of the invention, one or more of the steps described below may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 9  should not be construed as limiting scope of the invention. 
   First, each fan tray  411  is removed from the chassis  401  by pulling the handle  415  (Step  901 ). As explained above, the fan tray  411  has the handle  415 , so each fan tray  411  is easily removed. Next, the opening  629  of each fan tray  411  is made respectively at the rear plane of the fan tray  411  to install the second filter  703  by methods known in the art (Step  902 ). The size and width of the opening  629  are adjusted according to the size and width of the opening  625  of the middle wall  409  of the chassis  401  and the second filter  703  to be installed. Then, the second filter  703  is installed to each fan tray  411  to cover the opening  629  made (Step  903 ). The second filter  703  is attached to the fan tray  411  by screws, adhesives, bonding or other attachment methods known in the art to be held tightly by the fan tray. Finally, each fan tray  411 , on which the second filter  703  was installed in Step  903 , is returned to the chassis  411  (Step  904 ). When each fan tray  411  is returned, there are no gaps between the second air filter  703  and the surface of the middle wall  409  around the opening  625  of the middle wall so that only the air filtered by the second air filter  703  is directed to the rear PCB assembly  607  as shown in  FIGS. 4-6 . 
   Thus, when installing the second filter  703 , all the fan trays  411  are removed from only the front side of the chassis  401 , and, therefore, installing the second filter  703  to the computer server systems is easy and efficient. Also, the cost and time for installing the second filter  703  to the computer server are reduced because the whole chassis  401  of the computer server does not need to be replaced. 
   As an alternative, although  FIGS. 4-6  show that the chassis  401  encloses the blade servers  405  at the upper portion of the chassis  401  and fan trays  411  at the lower portion of the chassis  401 , one of ordinary skill in the art will appreciate that the chassis encloses blade servers  405  and the fan trays  411  at different positions. In that case, according to the positions of blade servers  405  and the fan trays  411 , the positions of first and second filters  623  and  703 , fans  617 , openings  627  and  625  and the middle wall  409  are adjusted such that the first filter  623  and the second filter  703  provide the appropriate filtered air to the front PCB assembly  605  and the rear PCB assembly  607  respectively in the light of the explanation above. 
   While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.