Abstract:
An equipment rack including front and back doors is configured with fans for air cooling enclosed electronic devices in both doors. The fans in each door are sufficient, by themselves, to provide sufficient airflow to cool the electronic devices. The two doors include switches and magnetic interlocks configured such that when one door is opened, the magnetic interlock on the other door is activated preventing both doors from being opened at the same time. This ensures that at least one door is always closed while the system is powered up, and since the fans in each door provide sufficient cooling for the equipment rack, the rack is always sufficiently cooled to prevent electronic device failure from overheating.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to the field of enclosures, and more particularly to the field of enclosures including cooling fans and front and back doors. 
   BACKGROUND OF THE INVENTION 
   As electronic devices increase in speed and power consumption, cooling these devices becomes critical to their proper operation. Particularly when placed inside enclosures, which may modify the natural airflow around the device, proper cooling device operation is critical. Many enclosures include fans on either a front door or a back door to force air through the enclosure (since the sides are often solid) cooling the enclosed electronic devices. However, it is sometimes necessary to open either the front door or the back door of the enclosure while the electronic devices within the rack are operating. In this case, if the fans are mounted on the door that is opened, the airflow over the electronic devices may be disrupted while the door is open, and the devices may overheat to the point of failure. In some enclosures, fans are included in both the front and back doors to allow one door to be open while the fans in the other door are sufficient to provide proper airflow over the electronic devices in the enclosure. However, if both doors are opened at the same time, the fans in the front and back doors are no longer providing airflow, and the electronic devices may overheat to the point of failure. 
   SUMMARY OF THE INVENTION 
   An enclosure including front and back doors is configured with fans for air cooling enclosed electronic devices in both doors. The fans in each door are sufficient, by themselves, to provide sufficient airflow to cool the electronic devices. The two doors include switches and magnetic interlocks configured such that when one door is opened, the magnetic interlock on the other door is activated preventing both doors from being opened at the same time. This ensures that at least one door is always closed while the system is powered up, and since the fans in each door provide sufficient cooling for the enclosure, the enclosure is always sufficiently cooled to prevent electronic device failure from overheating. 
   Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view of an enclosure including a front door according to the present invention. 
       FIG. 2  is a view of an enclosure including a back door according to the present invention. 
       FIG. 3  is a flow chart of a method for constructing an enclosure with redundant fans in doors with interlocks according to the present invention. 
       FIG. 4  is a simplified schematic diagram of a system of switches and interlocks for use in an enclosure according to the present invention. 
       FIG. 5  is a simplified schematic diagram of a system of switches and interlocks for use in an enclosure according to the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a view of an enclosure including a front door according to the present invention. The example embodiment of the present invention shown in  FIG. 1  is an enclosure  100  including a front  102  and a back  104 . The front  102  of the enclosure  100  includes a front door  106 . The front door  106  includes a lock  108 , at least one fan  110 , a switch  114  configured to close when the front door  106  is opened, and a latch  112 . This latch  112  is configured to activate and prevent opening of the front door  106  when the power to the enclosure  100  is on, and the back door  200  is open. Those of skill in the art will recognize that there are many different ways of implementing the latch  112  within the scope of the present invention. For example, any of the variety of magnetic latches may be used, mechanical latches activated by a solenoid, or simple solenoid latches may be used within the scope of the present invention. 
     FIG. 2  is a view of an enclosure including a back door according to the present invention.  FIG. 2  is a view of the back of the enclosure from  FIG. 1 . The example embodiment of the present invention shown in  FIG. 2  is an enclosure  100  including a front  102  and a back  104 . The back  104  of the enclosure  100  includes a back door  200 . The back door  200  includes a lock  202 , at least one fan  204 , a switch  208  configured to close when the back door  200  is opened, and a latch  206 . This latch  206  is configured to activate and prevent opening of the back door  200  when the power to the enclosure  100  is on, and the front door  106  is open. Those of skill in the art will recognize that there are many different ways of implementing the latch  206  within the scope of the present invention. For example, any of the variety of magnetic latches may be used, mechanical latches activated by a solenoid, or simple solenoid latches may be used within the scope of the present invention. 
     FIG. 3  is a flow chart of a method for constructing an enclosure with redundant fans in doors with interlocks according to the present invention. In a step  300 , an enclosure having a front and a back is provided. In a step  302 , a front door and a back door for the enclosure is provided. In a step  304 , at least one fan is mechanically coupled to the front door. In a step  306 , at least one fan is mechanically coupled to the back door. In a step  308 , latches are mechanically coupled to the front and back doors and the enclosure. In a step  310 , a switch configured to switch when the front door is opened or closed is mechanically coupled to the front door or the enclosure or both. In a step  312 , a switch configured to switch when the back door is opened or closed is mechanically coupled to the back door or the enclosure or both. Those of skill in the art will recognize that these switches may be normally open when the door is closed, or in an alternative embodiment may be normally closed when the door is closed. Which type of switch is used will depend on the type of latch used. Some latches operate to lock the door when power is applied to them, and default to unlock the door when the power is interrupted. Other latches operate to allow the door to open when power is applied to them, and default to locking the door when power is interrupted. Thus, either type of latch and either type of switch may be used within the scope of the present invention, and it is simply a design decision about which to use. In a step  314 , the back door switch is electrically coupled to the front door latch in a configuration that activates the front door latch when the back door switch is closed. In a step  316 , the front door switch is electrically coupled to the back door latch in a configuration that activates the back door latch when the front door switch is closed. 
     FIG. 4  is a simplified schematic diagram of a system of switches and interlocks for use in an enclosure according to the present invention. In the example embodiment of the present invention shown in  FIG. 4  the components present in the front door  400  and the back door  402  are shown. The front door  400  of the enclosure includes a front door switch  408 . In some embodiments of the present invention this front door switch  408  is configured to open when the front door  400  is closed, and to close when the front door  400  is open, while in other embodiments of the present invention this front door switch  408  is configured to close when the front door  400  is closed, and to open when the front door  400  is open. The back door  402  of the enclosure includes a back door switch  410 . In some embodiments of the present invention this back door switch  410  is configured to open when the back door  402  is closed, and to close when the back door  402  is open, while in other embodiments of the present invention this back door switch  410  is configured to close when the back door  402  is closed, and to open when the back door  402  is open. Which switch configuration is used is dependent on the type of latches used on the doors. The front door  400  also includes a magnetic latch  412  connected in series with the back door switch  410 , and configured to activate and prevent the front door  400  from being opened when the back door switch  410  is closed. The back door  402  also includes a magnetic latch  414  connected in series with the front door switch  408 , and configured to activate and prevent the back door  402  from being opened when the front door switch  408  is closed. In some embodiments of the present invention, these latches may be configured to lock the doors when power is applied to them, while in other embodiments of the present invention, these latches may be configured to unlock the doors when power is applied to them. These series circuits are powered by a power supply between nodes  404  and  406 . This power supply may be the enclosure power supply and configured to always be activated whenever any electronic device within the enclosure is powered up. Other example embodiments of the present invention may use a different power supply for this circuit within the scope of the present invention. 
     FIG. 5  is a simplified schematic diagram of a system of switches and interlocks for use in an enclosure according to the present invention. In the example embodiment of the present invention shown in  FIG. 5  the components present in the front door  500  and the back door  502  are shown. The front door  500  of the enclosure includes a front door switch  508 . In some embodiments of the present invention, this front door switch  508  is configured to open when the front door  500  is closed, and to close when the front door  500  is open, while in other embodiments of the present invention, the front door switch  508  is configured to close when the front door  500  is closed, and to open when the front door  500  is opened. The back door  502  of the enclosure includes a back door switch  510 . In some embodiments of the present invention, this back door switch  510  is configured to open when the back door  502  is closed, and to close when the back door  502  is open, while in other embodiments of the present invention, the back door switch  510  is configured to close when the back door  502  is closed, and to open when the back door  502  is open. Which switch configuration is used is dependent on the type of latches used on the doors. The front door  500  also includes a latch  512  connected in series with the back door switch  510 , and configured to activate and prevent the front door  500  from being opened when the back door switch  510  is closed. The back door  502  also includes a latch  514  connected in series with the front door switch  508 , and configured to activate and prevent the back door  502  from being opened when the front door switch  508  is closed. In some embodiments of the present invention, these latches may be configured to lock the doors when power is applied to them, while in other embodiments of the present invention, these latches may be configured to unlock the doors when power is applied to them. These series circuits are powered by a power supply between nodes  504  and  506 . This power supply may be the enclosure power supply and configured to always be activated whenever any electronic device within the enclosure is powered up. Other example embodiments of the present invention may use a different power supply for this circuit within the scope of the present invention. Those of skill in the art will recognize that there are many different ways of implementing the latches  512 , and  514  within the scope of the present invention. For example, any of the variety of magnetic latches may be used, mechanical latches activated by a solenoid, or simple solenoid latches may be used within the scope of the present invention. 
   The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.