Abstract:
ABSTRACT OF THE DISCLOSURE A computer system uses a modular fan design. Multiple fan modules can be used, and identical fan modules can be used for directing air into and out of the computer system enclosure. Each fan module is hot swappable, and can be replaced quickly without the use of tools or fasteners. Optional mounting features on the fan and the computer enclosure prevent misassembly, and an optional color coding scheme aids in assembly. An optional splitting light pipe directs light from a single status-indicating source to both the front and back of the fan module.

Description:
PARENT APPLICATION  
       [0001]    This application is a continuation under 37 CFR 1.53(b) of application Ser. No. 10/135,942 filed on Apr. 29, 2002 which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to computer systems, and more specifically to cooling methods for computer systems.  
         BACKGROUND OF THE INVENTION  
         [0003]    The cooling of internal components is critical to the operation of modern computer systems. The combined goals of increasing computing performance and smaller size drive computer designers to fill computer enclosures more densely with heat-generating components. If heat is not adequately removed from the computer enclosure, the temperature inside the enclosure may rise to levels that degrade the life and reliability of the computer.  
           [0004]    Typically, a computer may use one or more fans to force air through the enclosure. The air movement increases the convective heat transfer coefficient between the electronic components and the air, and exhausts the heat efficiently to the surrounding environment.  
           [0005]    Modern computers, especially when used as file servers, are often required to operate for extended periods. If a computer system fails or is shut down for maintenance, there may be disruptions in service, or complex measures may be required to avoid disruptions. For example, an additional, or redundant, computer may be required to provide service during the idle periods of the first computer, and a method must be provided for allowing the second computer to intercede when the first computer is idled. To avoid the complex measures and the cost of additional computers, it is desirable to build computer systems that require a minimum of down time. Ideally, some components may be repaired or replaced without shutting down the computer at all. Such components are often called “hot swappable” components.  
           [0006]    The fan or fans in a computer system may be hot swappable, but in some systems, the attachment the fan to the computer system enclosure may utilize screws, wing nuts, bolts, thumb screws, or other hardware fasteners. The fasteners may add to the complexity and time required for servicing the computer system. They may also add to the complexity and cost of manufacturing the computer, both in the assembly process and in the process of maintaining parts inventories and supplier contacts. Often, the fasteners require that tools be used for replacing the fan or fans.  
           [0007]    A computer system may employ fans on more than one side of the computer system enclosure. The fans may be configured so that one fan directs air into the enclosure and another fan on another side of the enclosure directs air out of the enclosure. In this way, both fans contribute to the motion of air through the enclosure. In some computer systems, a different fan design may be used in different locations on the enclosure. Using more than one fan design adds to the cost and complexity of the computer system and to the cost and complexity of maintaining the computer system.  
           [0008]    In addition, the attachment for the fan or fans may be designed in such a way that it is possible to mount a fan incorrectly. This may result in a fan directing air in the wrong direction or even countering the effect of other fans, thus reducing the cooling effectiveness in the computer system.  
           [0009]    If a computer system fan fails, the failure may not be immediately obvious, especially when a computer system uses multiple fans or when multiple computer systems are in close proximity. In the absence of an indication of the failure of a fan, the fan failure may go undetected, compromising the reliability of the computer system.  
           [0010]    There is a need for a computer system fan arrangement that provides effective cooling with a minimum number of unique parts, that can be serviced quickly and effectively without tools and with little chance of error, and that can provide a signal when a fan fails.  
         SUMMARY OF THE INVENTION  
         [0011]    A computer system uses a modular fan design. Multiple fan modules can be used, and identical fan modules can be used for directing air into and out of the computer system enclosure. Each fan module is hot swappable, and can be replaced quickly without the use of tools or fasteners. Optional mounting features on the fan and the computer enclosure prevent misassembly, and an optional color coding scheme aids in assembly. An optional splitting light pipe directs light from a single status-indicating source to both the front and back of the fan module. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 shows a front perspective view of an example embodiment of a computer system with a modular fan assembly.  
         [0013]    [0013]FIG. 2 shows a partial front perspective view of the example computer system of FIG. 1 with a modular fan assembly removed.  
         [0014]    [0014]FIG. 2 a  shows guiding features and constraining features on the example computer system of FIG. 2 in greater detail.  
         [0015]    [0015]FIG. 3 depicts a cutaway view of a modular fan assembly of FIG. 1 installed on an outer wall of a computer system enclosure.  
         [0016]    [0016]FIG. 3 a  depicts a detail view of a constraining feature and its interaction with an outer shell of the modular fan assembly of FIG. 3.  
         [0017]    [0017]FIG. 4 depicts a rear perspective view of the example computer system of FIG. 1 with modular fan assemblies installed.  
         [0018]    [0018]FIG. 5 shows a plan view of the outer shell pieces of an example modular fan assembly, using dashed lines to depict hidden edges.  
         [0019]    [0019]FIG. 6 depicts an example embodiment of an optional failure indicator light.  
         [0020]    [0020]FIG. 7 is a detail view of an example splitting light pipe.  
         [0021]    [0021]FIG. 8 depicts a partial front perspective view of an alternative embodiment of a computer system with a modular fan assembly.  
         [0022]    [0022]FIG. 9 shows a partial rear perspective view of the example computer system of FIG. 8. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    [0023]FIG. 1 shows a front perspective view of an example embodiment of a computer system  100 . The computer system  100  is enclosed by enclosure  101 , but no decorative outer shell is shown. Two example embodiment modular fan assemblies  102 ,  103  are installed on an outer wall  104  of the computer system enclosure  101 .  
         [0024]    [0024]FIG. 2 shows a partial front perspective view of example computer system  100  with modular fan assembly  102  removed. Outer wall  104  of enclosure  101  is perforated to allow airflow into or out of the enclosure  101 . Hole pattern  201  allows airflow caused by modular fan assembly  102 . Attached to outer wall  104  are guiding features  202 . During assembly, guiding features  202  engage guide slots  208  in modular fan assembly  102  and aid in positioning modular fan assembly  102 . Also attached to outer wall  104  are constraining features  203  that engage openings  209  in modular fan assembly  102 . These features are shown in more detail in FIGS. 2 a  and  3   a.    
         [0025]    A wall attached to outer wall  104  holds a connector  204  for supplying power and control information to modular fan assembly  102 . Modular fan assembly  102  has a mating connector  205  that connects with connector  204  when the modular fan assembly  102  is installed in the computer system  100 . Affixed to outer wall  104  is a locking feature  207 . Locking feature  207  comprises a spring loaded plunger pin  211  that engages detent feature  206  on modular fan assembly  102 , thereby holding modular fan assembly  102  in place. Other embodiments may include other kinds of locking features, such as a spring-loaded lever, pushbutton, or other device.  
         [0026]    To install modular fan assembly  102  on outer wall  104 , modular fan assembly  102  is placed against outer wall  104  such that guiding features  202  protrude into guiding slots  208 , and constraining features  203  protrude through openings  209  in the outer shell  210  of modular fan assembly  102 . Modular fan assembly  102  is then slid toward connector  204 . During the sliding, guiding features  202  and constraining features  203  serve to constrain the motion of modular fan assembly  102  to a single degree of freedom. Constraining features  203  engage openings  209  in outer shell  210 , constraining modular fan assembly  102  against outer wall  104 . This engagement is shown in more detail in FIG. 3 a . Mating connector  205  is engaged with connector  204  as a result of the sliding motion. The sloped surface of detent feature  206  engages locking feature  207 , forcing spring loaded plunger pin  211  to retract until detent feature  206  has passed spring loaded plunger pin  211 , at which time spring loaded plunger pin  211  extends to lock modular fan assembly  102  in position. A profile view of detent features  206  and  212  is shown in FIG. 5.  
         [0027]    Referring again to FIG. 2, modular fan assembly  103  is installed on outer wall  104  in a similar manner. Modular fan assembly  103  is a substantially identical copy of modular fan assembly  102 , but is simply installed in a different orientation, as defined by a pattern of guiding and restraining features similar to those guiding and constraining modular fan assembly  102 . A second detent feature  212  is provided on the modular fan assemblies so that a second locking feature  213  may be engaged when modular fan assembly  103  is installed in its orientation. A second connector  214  is provided on enclosure  101  for engaging the connector on modular fan assembly  103 .  
         [0028]    [0028]FIG. 2 a  shows guiding features  202  and constraining features  203  in greater detail. Each of guiding features  202  may comprise a cylindrical pin attached to outer wall  104 , although a variety of other shapes would function as well. The outer end of each guiding feature  202  may be chamfered, rounded, or have some other shape that facilitates its engagement with one of guiding slots  208  in modular fan assembly  102 . Each of constraining features  203  may have a larger cylindrical portion  215  suspended at a distance from outer wall  104  by a smaller cylindrical portion  216 . The distance between larger cylindrical portion  215  and outer wall  104  may be slightly more than the thickness of outer shell  210  of modular fan assembly  102 . Constraining features  203  may have other shapes that constrain modular fan assembly  102  against outer wall  104  in a similar manner.  
         [0029]    [0029]FIG. 3 depicts a cutaway view of modular fan assembly  102  installed on outer wall  104 . Only the portion of the outer shell  210  of modular fan assembly  102  that is disposed against outer wall  104  is shown. FIG. 3 a  depicts one of constraining features  203  and its interaction with outer shell  210  of modular fan assembly  102 , showing how modular fan assembly  102  is constrained against outer wall  104 .  
         [0030]    The installation of the modular fan assemblies onto enclosure  101  may be accomplished without the aid of tools. Because features built into enclosure  101  constrain and lock the modular fan assemblies in place, no additional fastening hardware is required. The modular fan assemblies snap into place easily.  
         [0031]    The modular fan assemblies may also be removed without the use of tools, allowing their replacement quickly and efficiently. The removal process is generally the reverse of the installation process. Using modular fan assembly  102  as an example, spring loaded plunger pin  211  may be disengaged from detent feature  206  by lifting it up with fingers. Modular fan assembly  102  is then slid away from connector  204 , until constraining features  203  can pass through openings  209 . Modular fan assembly  102  is then lifted away from outer wall  104 .  
         [0032]    The modular fan assemblies may be removed and replaced while computer system  100  remains in operation. That is, the modular fan assemblies are hot swappable.  
         [0033]    [0033]FIG. 4 depicts a rear perspective view of computer system  100 , showing two additional example embodiment modular fan assemblies  402  and  403  installed on a second outer wall  401  of enclosure  101 . Modular fan assemblies  402  and  403  are substantially identical copies of modular fan assemblies  102  and  103 , but are simply installed in different orientations. The modular fan assemblies  402  and  403  installed on outer wall  401  direct air in the same direction as modular fan assemblies  102  and  103 , thus aiding modular fan assemblies  102  and  103  in causing air to flow through computer system  100 . For example, modular fan assemblies  102  and  103  may direct air into computer system enclosure  101  and modular fan assemblies  402  and  403  direct air out of enclosure  101 . Or modular fan assemblies  102  and  103  may direct air out of computer system enclosure  101  and modular fan assemblies  402  and  403  direct air into enclosure  101 .  
         [0034]    Guiding features and constraining features are attached to outer wall  401 , but in a different pattern from those on outer wall  104 . When a modular fan assembly is constrained against outer wall  104 , one outer surface of the modular fan assembly is disposed against outer wall  104  and the opposite outer surface of the modular fan assembly is exposed. When a substantially identical modular fan assembly is constrained against outer wall  401 , the disposition of the outer surfaces of the modular fan assembly is reversed. That is, the wall that would be disposed against outer wall  104  is exposed when the modular fan assembly is installed on outer wall  401 . The patterns of guiding slots and openings on the two outer surfaces of the modular fan assembly are different, such that a surface of the modular fan assembly that can be disposed against computer system enclosure outer wall  104  cannot be disposed against computer system enclosure outer wall  401  due to the interference of the modular fan assembly outer surface with the guiding and constraining features on outer wall  401 . This arrangement ensures that each modular fan assembly can be installed only in the correct orientation to assist the other modular fan assemblies in expediting airflow through computer system  100 .  
         [0035]    [0035]FIG. 5 shows a plan view of the outer shell pieces of modular fan assembly  102  with some hidden lines shown as dashed. This view allows comparison of the patterns of guiding slots and openings in the two outer surfaces of the modular fan assembly. The guiding slots  208  and openings  209  on the near side are shown in solid lines, and the guiding slots  501  and openings  502  on the far side are shown in dashed lines. The two patterns are offset, indicating that the modular fan assembly cannot be installed incorrectly.  
         [0036]    Additionally, the front and back sides of the modular fan assembly may optionally be of different colors. Two halves of a “clamshell” fan body may be molded of different colored materials, or the two sides of the modular fan assembly may be painted different colors, or some other method may be used to provide different colors on the two sides of the modular fan assembly. For example, one side may be black and one side may be gray, although any two distinguishable colors will suffice. The pattern of guide slots and openings in the black side of modular fan assembly  102  may match the pattern of guiding and constraining features attached to computer system enclosure outer wall  104 , and the pattern of guide slots and openings in the gray side of modular fan assembly  102  may match the different pattern of guiding and constraining features attached to computer system enclosure outer wall  401 . Thus modular fan assembly  102  could only be installed with its black side against outer wall  104 , or with its gray side against outer wall  401 . This color coding gives a computer service technician or other person replacing the modular fan assembly a visual cue as to how to install it, thus making the replacement process simple and efficient. Because fans may usually be replaced one at a time, the process of positioning the modular fan assembly is facilitated by orienting an assembly so that its exposed side is the same color as the exposed side of the modular fan assembly next to it.  
         [0037]    The computer system  100  may also comprise circuitry or other means for detecting and indicating failure of the fan in a modular fan assembly. For example, a mechanical detector could be actuated by airflow lack of airflow caused by the fan. The detector may be integrated into each modular fan assembly, or may be inside the computer system. Detecting and indicating a failure of a fan may be especially helpful in an installation with multiple computer systems, where the sound and airflow generated by other computers may make the detection of a fan failure in a particular computer difficult without some failure indication.  
         [0038]    A fan failure indicator  404  is depicted in FIG. 4. In the example embodiment, each modular fan assembly has light for indicating a fan failure.  
         [0039]    [0039]FIG. 6 depicts an example implementation of a failure indicator using a failure indicator light. Part of the modular fan assembly has been removed in the figure to reveal the example indicator light implementation. When circuitry in the modular fan assembly or elsewhere in the computer detects a fan failure, a signal is sent to light emitting diode (LED)  601 . The wiring leading to LED  601  has been omitted from the figure for clarity. LED  601  then emits a visual signal that indicates a fan failure. For example, LED  601  may turn on, emitting light to indicate a failure, or may change the color of the illumination it emits. For example, a two-color LED may be used. The two-color LED may emit green light when the fan is operating properly, and may emit red light when the fan fails. Of course, other colors may be used.  
         [0040]    Because each modular fan assembly may be installed on either the front outer wall  104  or the rear outer wall  401  of the computer system enclosure  101 , either the front or back side of the modular fan assembly may be visible to a repair technician. In the example embodiment, the light from LED  601  is channeled by a splitting light pipe  602  so that it is visible from either side of the modular fan assembly. The splitting light pipe channels light from the LED principally by internal reflection within the light pipe material.  
         [0041]    Splitting light pipe  602  is depicted in greater detail in FIG. 7. Light, represented by ray  704 , is accepted by splitting light pipe  602  at face  701 , and is channeled as shown so that light is emitted from splitting light pipe  602  faces  702  and  703 . In this way, a fan failure indication is visible regardless of whether a modular fan assembly is installed on the front or rear outer wall of computer system enclosure  101 .  
         [0042]    [0042]FIG. 8 depicts a partial front perspective view of an alternative embodiment of a computer system with a modular fan assembly. In this second example embodiment, computer system  800  has an enclosure  801  having an outer wall  802 . Modular fan assembly  803  may be installed on outer wall  802 . A second modular fan assembly  804 , substantially identical to modular fan assembly  803  may also be installed on outer wall  802 .  
         [0043]    Modular fan assembly  803  has tabs  805  formed into one of its sides, and tabs  806  formed into the other side. During installation, tabs  805  are placed into openings  807 , which are adjacent to constraining features  808 , until modular fan assembly  803  is against outer wall  802 . Constraining features  808  serve to align modular fan assembly  803  correctly. When modular fan assembly  803  is against outer wall  802 , modular fan assembly  803  is slid in the direction of its connector  809 , until connector  809  engages a mating connector attached to enclosure  801 . At approximately the same time, a locking  810  feature on enclosure  801  engages a detent feature  811  on modular fan assembly  803 , locking modular fan assembly  803  in place. As a result of the sliding motion, tabs  805  pass between constraining features  808  and outer wall  802 , thus holding modular fan assembly  803  against outer wall  802 . If an attempt is made to install modular fan assembly in an incorrect orientation, tabs  805  or  806  will interfere with constraining features  808 , making the incorrect installation impossible.  
         [0044]    Modular fan assembly  804  may be installed similarly. A similar pattern of constraining features ensures that modular fan assembly  805  may be installed only it its correct orientation.  
         [0045]    [0045]FIG. 9 shows a partial rear perspective view of the example computer system of FIG. 8. Modular fan assembly  903  may be installed on enclosure outer wall  902  in a manner similar to how modular fan assembly  803  was installed on outer wall  802 . Constraining features  908  with openings  907  accept tabs  906  on modular fan assembly  903 , and guide modular fan assembly  903  into place. Tabs  906  pass behind constraining features  908 , constraining modular fan assembly  903  against outer wall  902 . A detent feature engages a locking feature to lock modular fan assembly  903  in place.  
         [0046]    Constraining features  908  serve to guarantee that the correct surface of modular fan assembly  903  is constrained against outer wall  902 , and that modular fan assembly  903  cannot be installed incorrectly. Modular fan assembly  904  may be installed in a similar manner.  
         [0047]    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. For example, LED  601  could emit light when the fan is operational, and switch off when the fan fails, rather than the reverse. Or for example, other configurations could be envisioned that ensure that a modular fan assembly cannot be installed incorrectly. The embodiment was 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.