Abstract:
A fan tray assembly for an electronics enclosure includes two opposing, spaced apart shells made of a sheet material. The opposing shells are attached to each other by attachment features formed in the sheet material of each shell. Advantageously, the attachment features reduce or eliminate the need for separate fasteners, spring steels, or adhesives to attach the shells. Each shell has openings and grills. Each shell also has retention features formed in the sheet material around a periphery of their respective grills. A ventilation fan unit (e.g., two fans) is retained between the two shells by the retention features. An electrical connector is connected to the ventilation fan and retained by at least one of the shells. The shells may also include features for retaining the electrical connector without using fasteners or adhesives. Such features may allow the connector to float in a plane perpendicular to its principal axis of alignment. The assembly may additionally include a handle for detaching the assembly to the electronic enclosure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to snap-together modular ventilation fan assemblies for electronics enclosures. 
     2. Description of Related Art 
     Modular ventilation fan assemblies, sometimes called fan tray assemblies (or more briefly, “fan trays”) are used for mounting ventilation fans to electronics enclosures, such as computer enclosures. Conductive enclosures are used to contain electromagnetic interference (EMI) generated by electronic equipment, and ventilation fans are often used for thermal control of their enclosed interior spaces. The fan tray provides for convenient mounting of one or more ventilation fans to the electronics enclosure while maintaining the EMI-shielding integrity of the enclosure. The fan tray may also provide a convenient location for mounting a control circuit for the ventilation fan or fans in the fan tray. 
     The ventilation fan itself is usually a modular unit that includes a rotor and a motor encased in a plastic housing. As such, it does not provide EMI shielding and may itself be a source of EMI. Fan trays therefore typically provide metal grills on opposite sides of the fan to electromagnetically isolate the ventilation fan from the environment outside of the fan tray, while allowing for the passage of air through the fan tray. At the same time, the metal grills and sheet metal walls of the fan tray maintain electromagnetic isolation for the interior of the electronics enclosure and serve as part of the wall thereof. 
     Fan trays are often mounted to the electronics enclosures using a pair of opposing side rails that engage corresponding rails in the electronics enclosure. The fan tray may be mounted to, and removed from, the enclosure by sliding the tray along these rails. The fan tray may be secured to the enclosure using a screw or like fastener after being slid into place along the rails. As modular assemblies, prior art fan trays facilitate assembly and repair of electronics enclosures, particularly when a fan control circuit is included in the fan tray. 
     However, prior art fan trays are subject to various shortcomings. They are typically assembled from sheet metal components and fastened together using screws or like fasteners. Screws are also used to fasten assembled fan trays to electronics enclosures. The use of screws or like fasteners increases assembly and removal time, and increases the number of tray components. The use of these prior art fasteners can also damage the fans and/or take the fan trays out of industry standards. For example, if too much pressure is applied at the fan edges, the fans can be damaged. By contrast, if too little pressure is applied at the fan edges, the fans in the fan trays produce a high amount of acoustical noise that can take the fan trays out of industry standards (e.g., standards on restricting the amount of noise produced). All of these factors can add substantially to the cost of fan trays, as well as create inconveniences for users. 
     It is therefore desirable to provide a fan tray assembly that overcomes these and other shortcomings of prior art fan tray assemblies, while retaining their advantages. More specifically, it is desirable to provide a fan tray assembly that has features in which airflow is not impeded, acoustical noise is reduced, assembly and disassembly is simplified, and cost of manufacturing is reduced. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fan tray assembly that requires no removable fasteners, spring steels (e.g., not standard sheet steels), or other loose hardware in its assembly. The fan tray assembly can be used with prior art electronics enclosures while requiring minimal or no modifications to the enclosure. It can be assembled from inexpensive sheet metal pieces (shells) without the need of removable fasteners or spring steels, for decreased assembly cost. For this purpose, the shells can include attachment features for attaching the shells to one another, and retention features for retaining one or more ventilation fans between the shells. The attachment and retention features (or coupling elements) can be formed integrally with the shells from the same sheet of material (and/or having no spring steel). Taken together, the attachment and retention features reduce or eliminate the need to use loose hardware, spring steels, or adhesive for fastening during assembly. 
     Advantageously, the fan tray assembly may also comprise a pivoting grab handle to assist with removal of the fan tray assembly from the enclosure. The pivoting grab handle may be advantageously attached to the fan tray assembly without any fasteners. The fan tray may also provides for attachment of a fan control circuit on a printed circuit board (PCB) without the use of any fasteners. 
     Other beneficial features of the fan tray assembly include improved air grills and/or air holes that substantially improve air flow through the fan tray. A more complete understanding of the fan tray assembly will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary fan tray assembly. 
         FIG. 2  is an exploded assembly view of the exemplary fan tray assembly shown in FIG.  1 . 
         FIG. 3  is an exploded assembly view of an exemplary coupling feature for an exemplary fan tray assembly. 
         FIG. 4  is an exploded assembly view of another exemplary coupling feature for an exemplary fan tray assembly. 
         FIG. 5  is another exploded assembly view of the exemplary coupling feature shown in FIG.  4 . 
         FIG. 6  is a perspective view of a snap element shown in FIG.  3 . 
         FIG. 7  is a perspective view of another snap element shown in FIG.  3 . 
         FIG. 8  is a perspective view of a snap element shown in  FIGS. 4 and 5 . 
         FIG. 9  is an exploded assembly view of another exemplary fan tray assembly. 
         FIG. 10  is a side view of an exemplary fan tray assembly, showing operation of an exemplary handle for the exemplary fan tray assembly. 
         FIG. 11  is another side view showing operation of the exemplary handle for the exemplary fan tray assembly of  FIG. 10  in a pull mode. 
         FIG. 12  a detail view of a retention dimple on the shells of the exemplary fan tray assembly shown in FIGS.  1  and  2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a fan tray assembly that overcomes the limitations of prior art fan trays. In the detailed description that follows, like element numerals are used to indicate like elements that appear in one or more of the drawings. 
     Referring to  FIGS. 1 and 2 , exemplary fan tray  100  comprises two opposing shells  116 ,  118 , sometimes called brackets. The shells  116 ,  118  are attached to one another using a plurality of interlocking attachment features, such as top center snap element  170  and tab slot  174  and corresponding bottom center snap element  140  and snap tab  182 , shown in  FIG. 3  or bottom corner snap element  145  and hook  185  and corresponding top hook eyelet  175  shown in  FIGS. 4 and 5 . Each shell is made of a suitable sheet material, such as sheet steel or other conductive and structural material, which may be suitably surface treated or coated as known in the art. All of the features of the shells may be formed in the same sheet of material, such as by a suitable stamping and bending operation, thereby eliminating unnecessary assembly operations. In one embodiment, the shells are formed using only standard sheet material (e.g., using only standard sheet steels without spring steels). 
     Each of shells  116 ,  118  has a plurality of grills and/or openings  117 ,  138  forming an inlet and an outlet for passage of air through the shells, of which two grills  117  in the top shell  118  are shown in  FIGS. 1 and 2  and a plurality of octagonal openings  138  in the bottom shell  116  are shown in FIG.  2 . In one embodiment of the present invention, the plurality of octagonal openings  138  do not have to be substantially aligned with the grills  117  in the opposing shell, for efficient air flow through the fan tray. 
     Ventilation fans  112  are retained between the two shells by retention features, such as dimples  188  shown in  FIGS. 2 ,  5 , and  12 . The retention features are described in more detail below. Each of the ventilation fans  112 , as known in the art, can comprise a rotor (not shown) encased in a frame  124 . Frame  124  may include one or more features for engagement with retention features (such as dimples  188 ) of the shells. For example, the fan frame  124  may include a plurality of through holes  126 . Such holes are commonly used in prior art assemblies for holding threaded fasteners used for attaching the fan to an assembly. Utilization of these holes in a new and different way in the present assembly advantageously allows the fan tray assembly to make use of commonly available prior art ventilation fans. Each of the ventilation fans  112  also include a cable connector (not shown) for connecting the fan to a power source. 
     Assembly  100  additionally includes an electrical connector  122  for transmitting power to the ventilation fan. Connector  122  may also be used to transmit signals and power to a control circuit in the fan tray assembly. It may be connected to the ventilation fan using cable connector (not shown) and circuits in a printed circuit board (PCB)  120 , or in some other fashion. Connector  122  is retained by the shells  118 ,  116  and oriented towards an exterior of the fan tray assembly, as shown in FIG.  2 . Connector  122  can be retained by mounting to the PCB  120  that is, in turn, retained by the shells  118 ,  116 , via bottom corner snap element  145 , slot  156 , and partial slots  153  on the shell  116 , as shown. In the alternative, PCB  120  may be replaced by a passive structural plate (for example, if no control circuit is needed in the fan tray assembly), or mounted to the fan tray assembly separate from a PCB or plate. The embodiment shown in  FIG. 2  has the advantage of retaining the connector and a control circuit using the same mounting system, which is described in more detail below. 
     Interlocking attachment and retention features (or couplings or coupling elements) are preferably provided in areas near opposite sides  40   a  and  40   b  of the shell  116 , as shown in  FIGS. 1  to  8 . The interlocking attachment and retention features of the shell  116  are configured to engage complementary interlocking attachment and retention features of the shell  118 . The interlocking attachment and retention features of the shell  118  include a top center snap element  170  incorporated with a snap slot  174 , a hook eyelet  175  near a first end  150  of shell  118 , and an attaching tab  68  on a second end  148  of shell  118 . The interlocking attachment and retention features of  116  include bottom center snap element  140  incorporated with a snap tab  182  and bottom corner snap element  145  incorporated with a hook  185 . 
       FIGS. 3 and 6  illustrate an embodiment of the top center snap element  170  in more detail. The top center snap element  170  is coupled to the shell  118  on a bottom face  146  of the shell  118 . The top center snap element  170  extends outward from the bottom side of  146 . The top center snap element  170  can be contiguous with shell  118  and made from the same material as the shell  118 . The top center snap element  170  includes a snap tab slot  174  formed in the top center snap element  170 . The snap tab slot  174  is attachable with the corresponding bottom center snap tab  182  of the bottom shell  116 . The top center snap element  170  also includes a transition section  176  at an end distal from the shell  118 . The transition section  176  can be an angled region of the top center snap element  170  that allows for the top center snap element  170  and corresponding bottom center snap element  140  to be coupled such that binding or interference of the two elements  170 ,  140  is minimized. Opposite the transition section  176  is a base section  178  of the shell  118 . The base section  178  is located on the bottom face  146  of the shell  118 . The base section  178  allows for flexure or biasing of the top center snap element  170 , such that the top center snap element  170  can deflect aside and then return to a non-biased position when attaching with the corresponding bottom center snap element  140  when assembling the fan tray assembly  100 . In one embodiment of the present invention, the deflection and then return to the non-biased position of the top center snap element  170  is accomplished using only standard sheet steel having no spring steel. In another embodiment, the top center snap element  170  is designed using statistical tolerance analysis to ensure a good quality fit with the bottom center snap element  140 . 
     Referring now to  FIGS. 3 and 7 , an exemplary bottom center snap element  140  is shown. The bottom center snap element  140  is coupled to a top face  180  of the shell  116  such that the bottom center snap element  140  extends outward from the top face  180 . The bottom center snap element  140  can also be contiguous with the shell  116  and made from the same material as the shell  116 . The bottom center snap element  140  includes a snap (or lock) tab  182  formed in the bottom center snap element  140 . The snap tab  182  is attachable (or lockable) with a corresponding top center snap element  170  (e.g., the tab slot  174  of the top center snap element shown in FIG.  6 ). The bottom center snap element  140  also includes a transition section  184  at an end distal from the shell  116 . The transition section  184  can be an angled region of the bottom center snap element  140  that allows for the bottom center snap element  140  and corresponding top center snap element  170  to be coupled such that binding or interference of the two elements  170 ,  140  is minimized. Opposite the transition section  184  is a base section  186  of the shell  116 . The base section  186  has a flexure region  198  and a wire mount region  190 . The base section  186  is located on the top face  180  of the shell  116 . The flexure region  198  of the base section  186  allows for flexure or biasing of the bottom center snap element  140 , such that the bottom center snap element  140  can deflect aside and then return to a non-biased position when attaching with the corresponding top center snap element  170  when assembling the fan tray assembly  100 . In one embodiment of the present invention, the deflection and then return to the non-biased position of the flexure region  198  of the bottom center snap element  140  is accomplished using only standard sheet steel having no spring steel. In another embodiment, the bottom center snap element  140  is designed using statistical tolerance analysis to ensure a good quality fit with the bottom center snap element  170 . 
     Referring still to  FIG. 7 , mounting dimples (or numbs)  188  are also shown to be disposed on the base section  186  or on a face of the wire mount region  190 . The mounting dimples  188  are designed for securing the ventilation fans  112  without the use of separate fasteners. That is the mounting dimples  188  can fit into the through holes  126  of the ventilation fans  112  for coupling the fans  112  to the shell  116 . A separate wire mount  195  is also shown to be located on the shell  116  and is used to secure the wiring(s) for the ventilation fans  112  and/or other devices of the fan tray assembly  100 . Similarly, the wire mount region  190  of the base section  186  can also be used to secure the wiring(s) for the ventilation fans  112 . Other wire mounts, such as wire mount  195  shown in  FIG. 8 , can also be located on the shell  116  to secure the wiring(s) of the ventilation fans  112  and/or other devices associated with the fan tray assembly  100 . 
     Referring to  FIGS. 4-5  and  8 , an exemplary embodiment of the bottom corner snap element  145  and the top corner snap element  165  are shown. The bottom corner snap element  145  is coupled to the shell  116  on a top face  180  of the shell  116  such that the bottom corner snap element  145  extends outward from the top face  180 . The top corner snap element  165  is defined at around a corner of a first end  148  of shell  118 . The bottom corner snap element  145  includes a hook  185 , a stop block  186 , and a bottom corner block  189 . The top corner snap element  165  includes a hook eyelet  175  located on shell  118  and a top block  176  (or blocks  176  and  179 ) located on a bottom face  147  of shell  118 : The bottom face  147  is slightly lower than a second and larger bottom face  146  of shell  118  (e.g., the bottom face  146  shown in FIGS.  2  and  6 ). The top block  176 ,  179  is partially defined by a vertical plane  148  that joins the first bottom face  147  with the second bottom face  146 . The hook  185  of the bottom corner snap element  145  and bottom corner and stop blocks  186  and  189  of the bottom corner snap element  145  are all formed in the corner snap element  145 . The hook  185  is attachable (or lockable) to the corresponding top hook eyelet  175 . The bottom corner block  189  and the stop block  186  can be use to block corresponding top block  176  (or top corner block  179  and face block  176 , respectively). Thus, the corner snap elements  145  and  165  uses the hook  185  and the hook eyelet  175 , the face and stop blocks  176  and  186 , and the top and bottom corner blocks  179 ,  189  to securely snap, attach, or lock the bottom corner snap element  145  with the top corner snap element  165 . 
     Referring still to  FIG. 8 , the bottom corner snap element  145  also includes a base section  86 . The base section  86  is proximate to the shell  116  on the top face  180 . The base section  86  allows for flexure or biasing of the bottom corner snap element  145  so that the bottom corner snap element  145  can deflect aside and then return to a non-biased position when attaching with the top corner snap element  165 . In one embodiment of the present invention, the deflection and then return to the non-biased position of the bottom corner snap element  145  is accomplished using only standard sheet steel having no spring steel. In another embodiment, the corner snap elements  175  and  165  are designed using statistical tolerance analysis to ensure a good quality fit with each other. A wire mount  195  is also shown to be located on the top face  180 . The wire mount  195  secures wiring(s) for the fans  112  and/or other devices associated with the fan tray assembly  100 . For example, a bottom face of the wire mount  195  can be used with the top face  180  to sandwich (or secure) the wiring(s) in place. 
     The fan tray assembly of the present invention can further include a handle  300 . Referring now to  FIG. 9 , fan tray  200  comprises outlet grill shell  202 , inlet shell  204 , handle  300 , and, interposed between shells  202  and  204 , ventilation fans  208   a ,  208   b  and circuit board  206 . Ventilation fans  208   a ,  208   b  are connected by cables (not shown) to circuit board  206 . Circuit board  206  is mounted at an end of fan tray  200  opposite to handle  300 . The circuit board  206  includes an interface connector  212  that extends away from the end of the fan tray. The interface connector  212  is for engaging with a corresponding connector in an electronics enclosure (not shown). 
     Snap tabs  304   a ,  304   b  fit between flanges  216   a ,  216   b  of fan  208   a , and each tabs  304   a ,  304   b  is inserted into one of the mounting holes  210 . To assemble handle  300  between flanges  216   a ,  216   b , the snap tabs  304   a ,  304   b  are compressed towards one another until the tabs  304   a ,  304   b  snap into place inside of holes  210 . Thus, assembly of handle  300  to the fan tray may be accomplished without using any separate fastener such as a screw or rivet. In the alternative, handle  300  may be attached to components of fan tray  200  other than fan  208   a . Yet another alternative is to provide holes as retention features in tabs  304   a ,  304   b , which snap over dimples on a fan or other component of a fan tray. 
     The handle of the fan tray assembly of the present invention can be used to assist a user to disengage the connector of the fan tray assembly from an electronic enclosure. Referring to  FIGS. 10 and 11 , a handle  400  of an exemplary fan tray assembly of the present invention is shown. Referring to  FIG. 10 , application of force  410  causes the bump edge  408  to exert an amplified force  412  on the electronic enclosure, generally in the direction of the force arrow  412 . The pivot point is in turn determined by the location of the bushings in the tabs of the handle (e.g., as previously described referencing FIG.  9 ). In reaction to force  412 , a disengagement force  414  is exerted on fan tray  402  at the pivot point of the handle, generally in the direction of arrow  414 . With reference still to  FIG. 10 , a horizontal force acting on the fan tray towards the right will tend to disengage the connector  404 . After connector  404  has disengaged from the electronic enclosure as shown in  FIG. 11 , handle  400  may be used as a pull handle. The user then applies a pulling force on the lever arm of the handle. An exemplary pulling force is indicated by the arrow  414  of FIG.  11 . Removal of fan tray  400  will proceed in the direction of the arrow  414 . 
     It should be apparent that fan tray assembly of the present invention reduces or eliminates any need to use separate fasteners, spring steels, or adhesives in its assembly. As used herein, a “separate fastener” is any piece of loose fastening hardware, such as a screw, bolt, rivet, clip, tie, and so forth. “Spring steels” include a spring steel sheet (e.g., not a standard structural steel sheet or not a standard sheet steel) and/or a steel sheet laminated with a spring steel sheet. “Adhesive” is used broadly to include solder, braze, and welded material, as well as resin-based adhesive material. For example, shells  116 ,  118  may be attached by the above described attachment features without the use of separate fasteners, spring steels, or adhesives. Likewise, the ventilation fans  112  may be retained between the shells without the use of separate fasteners or adhesives. 
     As used herein, the terms “top” and “bottom” when applied to the shells are used merely for convenience to indicate the relative positions of the shells as shown in  FIGS. 1-5  and  7 - 8 . It should be apparent that these terms do not in any way limit the orientation of the fan tray; for example, the fan tray may be oriented so that the “top” shell is underneath the “bottom” shell, and vice-versa. It should further be apparent that the features described herein as being on one of the shells may instead be provided on the other shell, so long as the complementary nature of the shells is preserved. For example, the snap tabs  182  on the bottom shell  116  may be provided on the bottom shell  118 , so long as complementary slots  174  are provided for them on the bottom shell. Many such variations are possible within the general parameters of complementary interlocking shells in a fan tray assembly according to the invention. 
     A suitable shape for grills  117  and/or openings  138  are shown in plan view in  FIGS. 1 and 2 . Retention features (dimples)  188  are shown in  FIG. 2  arranged around a periphery of shell  116 . The dimples  188  can protrudes out of shells  116  and/or  118 , and are positioned to correspond with mounting holes in a ventilation fan frame. A detail side view of an exemplary dimple  188  is shown in FIG.  12 . In an embodiment of the invention, dimple  188  is a substantially hemispherical protrusion having a radius sufficiently small to engage the holes of the fan frame. A hemispherical shape has the advantage of being readily formed without overstressing the sheet material. 
     Other shapes may be used for the fan retention features. For example, a pyramidal protrusion may be pressed into the sheet material for engaging a round or square hole in a fan frame. Or, the sheet material may be cut and shaped to provide a tab configured to fit in a hole or slot in a fan frame, or around exterior parts of a fan frame. In the alternative, a hole or recess could be formed in a surface of shells  116 ,  118  for receiving a protruding feature of a fan frame. Whatever the configuration of the fan retention features, shells  116 ,  118  should be configured to compress the ventilation fan between their interior surfaces to prevent shifting or rattling of the fan during handling or operation. In an embodiment of the invention, this compression may be supplied mainly by snap elements  140 ,  170 ,  145 ,  165 , as shown. 
     When attached by the attachment features (e.g., snap tabs  182  and slots  174 ) the interior distance between the opposing shells should be such that the snap elements  140 ,  170 ,  145 ,  165  and/or shells  116 ,  118  compress the ventilation fan enough to hold it firmly in position. At the same time, the outward pressure exerted by the ventilation fan on the interlocked shells may help keep the shells locked firmly in position. 
     This balancing of inward compression on the fan and outward pressure on the shells stabilizes the assembly. Too much compression will impede assembly of the fan tray and may damage components. Too little compression will result in an unstable, rattling fan tray. One of skilled in the art may select a suitable sheet material and geometry to achieve a proper amount of compression for a given application. Snap elements  140 ,  170 ,  145 ,  165  advantageously provide additional resiliency to the assembled shells with respect to the fan, thereby easing the degree of precision to which the shells need be made. 
     Referring now back to  FIG. 2 , an exemplary controller PCB  120  for use with fan tray  100  is shown. PCB  120  defines an x-y plane on which connector  122  is located. The x-y plane is also shown in plan view in FIG.  9 . Connector  122  is for connecting the PCB to a parent assembly, and extends perpendicularly from the board  120  along a z-axis. Board  120  may be of a uniform thickness that is sufficiently less than the width of the mounting slots  156 ,  153  to permit sliding of the board relative to the slots. 
     PCB  120  may contain a control circuit and/or electrical traces connecting connector  122 . In an alternative embodiment, PCB  120  may be replaced by a purely mechanical board or plate, for example, for connecting a ventilation fan directly to an external control circuit. It should be apparent that, in either case, a connector mounted on the board or plate may be retained in the fan tray by the shells  116 ,  118  without using a separate fastener or adhesive. 
     Having thus described a preferred embodiment of a fan tray for an electronic enclosure, it should be apparent to those skilled in the art that certain advantages of the within system have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. For example, a fan tray for two individual ventilation fans has been illustrated, but it should be apparent that the inventive concepts described above would be equally applicable to fan trays for a single fan or more than two fans. For further example, particular shapes of shells, tabs, dimples, slots, latches, grills, holes, and so forth, have been illustrated, but one of ordinary skill may devise other suitable shapes for such elements in conformance with the inventive concepts herein. The invention is further defined by the following claims.