Abstract:
A device for damping vibration in mounting vibration-prone devices, such as fans or other devices with moving parts. A fan may be mounted at the center of a spiral spring to prevent transmission of vibrations including sounds from the fan to a surrounding structure, such as a cell phone powered by a metal-air battery.

Description:
FIELD OF THE INVENTION 
     The present invention relates to damping vibrations in mounting vibration-prone devices, such as fans or other devices with moving parts, and more particularly relates to a mount relying on a spring to prevent transmission of vibrations including sounds from a vibration-prone device to a surrounding structure. 
     BACKGROUND OF THE INVENTION 
     Many types of equipment include both components that cause vibrations and components that are sensitive to vibrations. One example is scientific equipment containing sensitive transducers as well as heavier components such as vacuum pumps. Other sensitive measuring devices may be associated with computer processors that require cooling fans. Attempts have been made to isolate fan vibrations by suspending the fan from a network of coil springs, as shown in U.S. Pat. No. 5,308,224, or by hanging the fan on a cantilever beam. 
     The need to isolate computer cooling fans to prevent vibration and attendant housing structure vibration noise, is recognized in U.S. Pat. No. 5,208,730. However, a complex resilient mounting apparatus is described to address the problem. 
     A cordless or cellular telephone powered by a fan-ventilated metal-air battery presents a difficult challenge because the components must be very small and also must not produce noise that would interfere with a conversation over the telephone. Space within the apparatus cannot be spared for spring suspension systems. 
     Thus, there has been a need in the art for a simple, inexpensive vibration damping mount, useable with miniaturized electronic components, and capable of effectively preventing vibration and noise without occupying any significant space. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide a vibration damping mount capable of minimizing vibration and noise while minimizing the space it occupies. The invention also seeks to provide a vibration damping mount suitable for use with hand held electronic devices. 
     These objects are accomplished by providing a mount that includes a spring shaped to support the vibration-prone device and damp its vibrations. The mount can be shaped to adapt to the device it is holding and to the surrounding hardware for the purpose of minimizing the space it occupies. 
     Generally described, the present invention provides a damping device for mounting a vibration-prone device to a structure, comprising a retainer shaped to receive the vibration-prone device; a spring extending from the retainer in an arc, the spring being held to the structure at a location spaced along the arc from the retainer. In selecting a particular structure for the spring, many variations are possible. The arc may be smooth or may be a plurality of connected discrete segments. Preferably, the arc is shaped to turn through at least 180 degrees. In some applications a full turn or multiple turns will provide optimal support and damping. 
     In a preferred embodiment, the spring is a spiral, the turns of which may lie generally in one plane. In the alternative, the turns may lie on a three dimensional shape such as a cone, hemisphere, or pyramid. The planar spring mount is space efficient. The spiral may comprise wire shaped at the center of the spiral to receive a part of the mounted device. Also, an outer turn can be shaped to be received in a peripheral groove provided by the structure. For example, when the vibration-prone device is a fan, a mandrel from the central stator member of the fan may be held in a winding at the center of the spiral, and the spiral may be positioned in an opening in a wall of a housing with the outer turn fitted in a groove in the opening. With the spiral mount thus generally coplanar with wall of the housing, and positioned in the opening required for air supply to the fan, little or no additional space is needed for the mount. 
     The present invention further contemplates a ventilation system including a fan mounted on a damping device as described above, and a metal-air cell housing including a fan mounted on a similar damping device. The present invention is particular useful in cellular telephones where noise due to vibration is undesirable. 
     According to another aspect of the invention a vibration-damping fan mount is provided, comprising a support member having a thickness and defining therethrough an opening having a peripheral wall; and a spiral spring defining a central fitting shaped to engage a portion of a fan and an outer turn shaped to engage the peripheral wall of the opening. The peripheral wall of the opening may optionally define a groove, and the outer turn of the spiral spring may fit into the groove. Preferably, the groove encircles the peripheral wall, and the outer turn forms a loop that resiliently snaps into the groove. 
     According to another aspect of the invention, a damping device for mounting a vibration-prone device to a structure is provided, comprising a retainer shaped to receive a vibration-prone device; and a spring extending from the retainer in a figure, the spring being held to the structure at a location spaced along the figure from the retainer, and the shape of the figure between the retainer and the structure allowing resilient motion in at least two orthogonal directions. In a preferred embodiment, the resilient motion allowed by the spring is omni-directional. 
     Other objects, features, and advantages of the present invention will become apparent upon review of the following description of embodiments of the invention, when taken in conjunction with the drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some of the advantages of the present invention having been stated, others will appear as the description proceeds, when considered in conjunction with the accompanying drawings, which are not necessarily drawn to scale, in which: 
     FIG. 1 is a plan view of a vibration damping mount embodying the present invention. 
     FIG. 2 is a side view of the mount of FIG.  1 . 
     FIG. 3 is a plan view of a structure in which a fan is mounted according to the invention. 
     FIG. 4 is a cross sectional view of the structure of FIG. 3, taken along line  4 — 4  of FIG.  3 . 
     FIG. 5 is a pictorial view of the structure of FIG. 3 with portion s of the wall broken away to shoo detail. 
     FIG. 6 is an exploded pictorial view of an additional embodiment of the present invention showing a fan mounted in a blower housing. 
     FIG. 7 is a plan view of an alternate spiral spring mount. 
     FIG. 8 is a plan view of another alternate spiral spring mount. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limit ed to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     FIG. 1 shows a plan view of a preferred embodiment of a vibration damping mount  10  according to the present invention. The preferred mount  10  is made from a single piece of piano wire formed into a spiral spring. The mount  10  includes a central retainer  20  formed as a winding from the inner end of the wire into a cylinder three coils high and having an inside diameter of about 0.13 inch . The shape and size of the retainer  20  can be varied depending on the shape of a member to be engaged by the retainer in mounting a vibration-prone device, as described below. From the retainer  20 , the wire spirals outwardly for three and one-half turns  22 . The outer turn gradually approaches the next inner turn at a wire end  25  to form a circular periphery  24  of the mount spring  10 . 
     As best shown in FIGS. 3-5, the mount  10  may be used to mount a fan  12  adjacent to or wholly or partly ventilation opening  41  in a housing wall  16 . The opening  41  is circular, and ripheral wall  42  through the thickness of the housing wall  16 . A peripheral groove  44  is formed around the peripheral wall  42 . The periphery  24  of the spring mount  10  is sized slightly larger than the ventilation opening  41 , so that the periphery  24  can be snap fit into the groove  44 . The outer end  25  of the wire forming the spring  10  is formed to approach the previous turn of the spiral. When snap fit into the groove  44 , the spring mount  10  is positioned within the plane of the housing wall  16 , with the retainer  20  at the center of the opening. No space inside or outside the housing wall  16  is needed for the mount itself. 
     The fan  12  may be attached to the mount  10  as shown in FIG.  4 . In the example shown, the fan has a rotor  30  from which protrude a plurality of vanes  32 . The rotor and vanes rotate about the fan stator  33 . A mandrel  36  extends behind the stator  33 . A printed circuit board  38  is fitted onto the mandrel  36  part way along the length of the mandrel, and is connected to the fan  10  and to a power source, such as a battery, by conductors (not shown). In one embodiment, the fan is mounted to provide reactant air to a metal-air battery, and the fan and circuit board draw operating power from the metal-air battery. The end of the mandrel is press fit into the spring mount&#39;s retainer  20 , which is sized slightly smaller than the mandrel. 
     Another embodiment of the present invention is shown in FIG. 6, in which an air manager  70  for a metal-air battery is shown. The air manager  70  is designed to provide air to air cathodes of metal-air cells (not shown) in a removable battery pack for a cellular telephone or the like. The air manager  70  includes a base  72  on which is mounted a generally circular blower housing  74 . The blower housing  74  defines a tangential blower outlet  76  that leads to the air cathodes (not shown). In the alternative, the fan may draw air from the air cathodes and the outlet  76  may lead to the outside environment. A suitable plastic material may be used to mold the base  72  and blower housing  74 , integrally if desired, although the choice of material and construction is not critical. A spacer ring  78  of plastic or gasket material is press fit into the blower housing to form a platform for a spring mount  10  as described herein. The ring  78  may be glued in place if desired, and may be spaced above the floor of the blower housing  74 . The isolation spring mount  10  preferably has its peripheral turn  24  glued to a surface of the spacer ring  78 , leaving the other turns free. 
     In this embodiment, the mandrel of the fan  12  is formed by an oil cap  80  that contains oil for lubricating a bearing (not shown) of the fan  12 . The oil cap  80  is glued to the center of the fan stator in a manner allowing communication of the oil to the bearing, in a manner well known in the art. Fixed to the fan stator, the oil cap can be press fit into the spring retainer  20 , or glued if desired. As described above, the fan  12  and its control circuit  38  are connected to the metal-air battery, which provides power for their operation. When power is supplied, the fan rotor  30  turns, the vanes  32  draw air axially into the blower housing  74 , and force air tangentially out through the outlet  76 . The outlet  76  may be aligned to force air through a diffusion passageway of the type described in U.S. Pat. No. 5,919,582 (incorporated herein by reference) for isolating the metal-air cells when the fan is not operational. 
     It should be understood that the damping characteristics of the mount  10  can be selected to fit the device to be mounted on it. One characteristic is the strength of the spring, which should be able to support the weight of the fan or other device, and maintain it in position despite the forces exerted by the vibrating device. Another characteristic is the damping capability of the spring, which depends on its spring constant K. The spring constant K is determined by the material and dimensions of the wire forming the spring, and preferably is selected in relation to the vibration frequency of the supported device. For example, a fan operating at a known rpm will produce a related vibration frequency. 
     An advantageous material is a wire between 0.012 and 0.020 inch in diameter, and the preferred diameter is about 0.016 inch. The preferred material is piano wire. An advantageous length of wire forming the spring is at least 4 inches, preferably between 4 and 8 inches, and most preferably about 6.25 inch. An advantageous diameter of the spiral at its periphery  24  is at least 0.375 inch, preferably between 0.375 and 0.630 inch, and most preferably about 0.580 inch. An advantageous spring constant is between 0.188 and 0.5, preferably about 0.312. 
     Although the preferred mount  10  is a flat spiral spring, the invention can be practiced using springs having many different shapes. For example, a spring  100  may be a spiral consisting of connected discrete segments  55 , as shown in FIG. 7, extending from a retainer  120 . Also, as shown in FIG. 8, a spiral spring  200  may climb out of a plane to a retainer  220  and form a cone. These are only examples of many ways in which the spring may be shaped to extend through an arc from the retainer to a location where the spring is held to a structure. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.