Abstract:
Some embodiments of the present invention provide an apparatus that isolates a computer system from vibrations generated by one or more fans inside the computer system. The apparatus includes a fan deck upon which the one or more fans are mounted inside the computer system, and three spring assemblies. Each spring assembly includes: a pin that extends through a clearance hole in the fan deck, wherein a first end of the pin is rigidly coupled to the computer system; a lower spring that extends between a first side of the fan deck and a lower spring mount coupled to the pin; and an upper spring that extends between a second side of the fan deck and a upper spring mount coupled to the pin.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention generally relates to techniques for isolating vibrations in computer systems. More specifically, the present invention relates to a method and an apparatus that isolates a computer system from vibrations generated by one or more fans inside the computer system. 
         [0003]    2. Related Art 
         [0004]    Many new computer systems include powerful processors that require powerful fans to cool them. These powerful fans can increase the vibrations generated in the computer system, which can lead to performance problems for components in the computer system. For example, many new higher density disk drives have smaller track sizes and tighter tolerances to increase their storage capacity. However, smaller track sizes and tighter tolerances make these disk drives potentially more sensitive to vibrations during operation of the computer system. 
         [0005]    Often, computer system manufacturers try to isolate vibrations generated by fans from the rest of the computer system using elastomeric mounts for the fan. Typically, each fan in the computer system is separately mounted and isolated. However, the elastomeric mounts can undergo stress relaxation over their life cycle due to temperature cycling and flexing which may reduce the ability of the elastomeric mounts to damp vibrations. The loss of damping ability may occur before the computer system has reached the end of its estimated useful life cycle, and may allow vibrations from the fan to be transmitted to the rest of the computer system, including the disk drives. Moreover, since each fan is typically separately isolated, the deterioration of one of the elastomeric mounts on any one of the fans can lead to a failure of isolation and result in vibrations being transmitted to the computer system. This can lead to performance degradation or even failure of the computer system, or can require a reduction in fan speed to reduce the vibrations generated by a fan, thereby limiting the maximum amount of heat that can be safely generated by a processor cooled by the fan, and hence limiting the maximum speed of the processor. 
         [0006]    Hence, what is needed is a method and system that isolates a computer system from vibrations generated by one or more fans inside the computer system without the above-described problems. 
       SUMMARY 
       [0007]    Some embodiments of the present invention provide an apparatus that isolates a computer system from vibrations generated by one or more fans inside the computer system. The apparatus includes a fan deck upon which the one or more fans are mounted inside the computer system, and three spring assemblies. Each spring assembly includes: a pin that extends through a clearance hole in the fan deck, wherein a first end of the pin is rigidly coupled to the computer system; a lower spring that extends between a first side of the fan deck and a lower spring mount coupled to the pin; and an upper spring that extends between a second side of the fan deck and a upper spring mount coupled to the pin. 
         [0008]    In some embodiments, the lower spring mount in each spring assembly is located between the computer system and the first side of the fan deck, and the upper spring mount in each spring assembly is located between the second end of the pin and the second side of the fan deck. 
         [0009]    In some embodiments, the lower spring in each spring assembly is preloaded between the first side of the fan deck and the lower spring mount, and the upper spring is preloaded between the second side of the fan deck and the upper spring mount. 
         [0010]    In some embodiments, at least one of the lower spring in each spring assembly and the upper spring in each spring assembly includes a cylindrical helical coil spring. 
         [0011]    In some embodiments, at least one of the lower spring in each spring assembly and the upper spring in each spring assembly includes a metal spring. 
         [0012]    In some embodiments, a spring constant of the lower spring in each spring assembly, a spring constant of the upper spring in each spring assembly, and a mass of the fan deck and the one or more fans are selected so that a ratio of a fundamental vibration frequency generated by the one or more of the fans during operation of the computer system to a resonant vibration frequency of the fan deck is greater than the square root of 2. 
         [0013]    In some embodiments, a spring constant of the lower spring in each spring assembly is equal to a spring constant of the upper spring in each spring assembly. 
         [0014]    In some embodiments, the computer system includes a molded plastic mount wherein the molded plastic mount includes the lower spring mount in each spring assembly. 
         [0015]    In some embodiments, the one or more fans mounted on the fan deck are attached to a stress-relieved power cable. 
         [0016]    Some embodiments include as fourth spring assembly. 
         [0017]    In some embodiments, all fans in the computer system are mounted on the fan deck. 
         [0018]    In some embodiments, the transmission of the vibrations generated by the one or more fans to the computer system is modified by adjusting a mass of the fan deck. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0019]      FIG. 1A  depicts a side-view of a system that isolates a computer system from vibrations generated by one or more fans inside the computer system in accordance with some embodiments of the present invention. 
           [0020]      FIG. 1B  depicts a top-view of the system depicted in  FIG. 1A  that isolates a computer system from vibrations generated by one or more fans inside the computer system in accordance with some embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
         [0022]      FIG. 1A  depicts a side-view of a system that isolates a computer system from vibrations generated by one or more fans inside the computer system in accordance with some embodiments of the present invention. Computer system  100  includes fan deck  102  with four fans  104  mounted on top. Furthermore, the system includes four spring assemblies, two of which, spring assembly  106 A and spring assembly  106 B, are visible. The other two spring assemblies are hidden in this view, one behind spring assembly  106 A and one behind spring assembly  106 B. 
         [0023]    Spring assembly  106 A includes spring  108 A preloaded between fan deck  102  and upper spring mount  110 A, and spring  108 B preloaded between fan deck  102  and lower spring mount  10 B in mount  112 . Furthermore, pin  114 A is coupled to mount  112  and extends through clearance hole  116 A in fan deck  102  and is coupled to upper spring mount  108 A. Additionally, spring assembly  106 B includes spring  108 C preloaded between fan deck  102  and upper spring mount  110 C, and spring  108 D preloaded between fan deck  102  and lower spring mount  110 D. Furthermore, pin  114 B is coupled to mount  112  and extends through clearance hole  116 B in fan deck  102  and is coupled to upper spring mount  110 C. Note that each of the four spring assemblies includes two springs. 
         [0024]    In the embodiment of  FIGS. 1A and 1B , CPU  118  and power supply  120  are shown for exemplary purposes and represent computer system devices that may be cooled by one or more fans mounted on fan deck  102 . In other embodiments, fans  104  and/or other fans mounted on fan deck  102  can be used for any purpose in computer system  100 , including but not limited to providing air flow in computer system  100  or cooling any system or device. 
         [0025]      FIG. 1B  depicts a top-view of the system depicted in  FIG. 1A . In  FIG. 1B , upper spring mount  110 A of spring assembly  106 A and upper spring mount  110 C of spring assembly  106 B are visible. Additionally, upper spring mount  110 E is visible and is part of the spring assembly hidden behind spring assembly  106 A in  FIG. 1A . Also, upper spring mount  110 F is visible and is part of the spring assembly hidden behind spring assembly  106 B in  FIG. 1A . Note that fans  104  are controlled and powered through stress-relieved cables that are not shown in  FIGS. 1A and 1B . The stress-relieved cables prevent vibrations generated by fans  104  from being transmitted to computer system  100 . 
         [0026]    In some embodiments, the preload on the springs in a spring assembly can be adjusted by adjusting the top spring mount. For example, the preload on spring  108 A and spring  108 B can be adjusted by moving upper spring mount  110 A with respect to pin  114 A. In some embodiments, one or more of upper spring mount  110 A, upper spring mount  110 C upper spring mount  110 E, and upper spring mount  110 F include a plate and a nut. 
         [0027]    For example, if upper spring mount  110 A includes a plate and a nut and pin  114 A is threaded, then the preload on spring  108 A and spring  108 B can be adjusted by threading the nut in spring mount  110 A up or down on pin  114 A. In other embodiments, spring mount  110 A is adjusted on pin  114 A and fixed in position using other methods, including but not limited to epoxy, solder, press-fit, interference-fit, or a ratchet and pawl mechanism. 
         [0028]    Note that the four clearance holes in fan deck  102 , clearance hole  116 A, clearance hole  116 B and the clearance holes for the 2 spring assemblies not shown in  FIG. 1A , have large enough diameters so that as fan deck  102  vibrates laterally, pin  114 A, pin  114 B, and the pins for the two spring assemblies not shown will not collide with fan deck  102 . Additionally, each of the four clearance holes is small enough to provide support for the springs of the spring assembly. For example, clearance hole  116 A and clearance hole  116 B are small enough to provide support, respectively for spring  108 B and spring  108 D. Furthermore, fan deck  102  may also include a seat for each spring so that the spring does not shift laterally. 
         [0029]    In some embodiments, mount  112  is the case for computer system  100  or is separately manufactured and attached to the case or some other portion of computer system  100 . Additionally, in some embodiments, the four pins, pin  114 A, pin  114 B and the two pins for the two hidden spring assemblies, are molded or manufactured as part of mount  112 . For example, in some embodiments, mount  112  is a plastic molded part that is molded as one piece which includes four pins (pin  114 A, pin  114 B, and the two hidden pins). Furthermore, lower spring mount  110 B and lower spring mount  110 D may be molded into mount  112 . In some embodiments, a lower spring mount includes a seat for a spring so that the spring is constrained from moving laterally on mount  112  or interfering with the pin inside the spring. For example, referring to  FIG. 1A , lower spring mount  110 B may be formed, molded, or built into mount  112  with a lip or a ring that prevents spring  108 B from moving laterally along mount  112 . 
         [0030]    Note that as depicted in the embodiment of  FIG. 1A , the springs are helical coil springs with a cylindrical shape. In some embodiments, other types of springs can be used including but not limited to conically shaped helical coil springs, or coil springs with any desired shape, and can be composed of wire of any cross-section desired. For example, the wire in the spring can be round, oval, rectangular, square or any other desired shape. Furthermore, the springs can be made of metal or plastic. 
         [0031]    Additionally, spring constants of the eight springs in the four spring assemblies and the mass of fan deck  102  and fans  104  can be selected so that the resonant frequency of fan deck  102  is a predetermined value. In some embodiments, the resonant frequency of fan deck  102  is selected based on the vibration frequencies generated by one or more of fans  104  during operation of computer system  100 . For example, a fundamental vibration frequency generated by one or more of fans  104  may be measured during the operation of computer system  100 . Then, spring constants of the eight springs and the mass of fan deck  102  may be selected so that the ratio of the measured fundamental vibration frequency to the resonant frequency of fan deck  102  is a predetermined ratio. In some embodiments, the ratio can include but is not limited to 1, the square root of 2, 2 or a value based on the measured transmission of vibrations from fans  104  to computer system  100  during the operation of computer system  100 . For example, if it is desired to reduce the vibrations that are transmitted to computer system  100  from fans  104  in one or more predetermined frequency ranges and/or above a predetermined frequency, then the vibrations of computer system  100  can be monitored as the resonant vibration frequency of fan deck  102  is altered by, for example, adjusting the mass of fan deck  102 . 
         [0032]    Note that although fan deck  102  has a rectangular shape in the embodiment depicted in  FIG. 1B , in other embodiments, fan deck  102  can have any shape desired, and may be a non-planar and/or a non regular shape. For example, the shape of fan deck  102  may be determined based on the desired locations for fans  104  in computer system  100 . Additionally, note that although in the embodiments depicted in  FIGS. 1A and 1B  fan deck  102  includes four fans  104 , more or fewer fans may be mounted on fan deck  102 . Additionally, in some embodiments, all fans in computer system  100  are mounted on fan deck  102 . 
         [0033]    Furthermore, although in the embodiments depicted in  FIGS. 1A and 1B  there are four spring assemblies, more spring assemblies may be used or three spring assemblies may be used. Additionally, in some embodiments, the spring assemblies are arranged so that they are not all collinear. For example, in embodiments in which three spring assemblies are used, the three spring assemblies may be arranged so that when the fan deck is viewed from above, as in  FIG. 1B , the spring assemblies form a triangle and are not collinear. Furthermore, in some embodiments, spring assembles are placed to limit out of plane torsion or flexing modes of fan deck  102 . 
         [0034]    The foregoing descriptions of embodiments have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present description to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present description. The scope of the present description is defined by the appended claims.