Abstract:
A disk drive packaging apparatus has a chassis with open ends that encloses all of the disk drives. The open ends of the chassis are covered with conductive screens. A disk-drive carrier is provided for each drive that holds, but does not enclose, the disk drive. The screens provide both emission containment and guarantees adequate air distribution for cooling. Because the screens are able to contain the radiation emission, conductive enclosures are not needed for each separate drive, with the result that the drives can be packed more densely.

Description:
FIELD OF THE INVENTION 
     This invention concerns mechanical packaging techniques for arrays of computer disk drives in which the drives must be adequately cooled and at the same time provided with sufficient electromagnetic radiation shielding to meet prevailing emission standards. 
     BACKGROUND OF THE INVENTION 
     Large computer storage systems use multiple magnetic, optical, or magneto-optic disks to provide needed storage capacity. Frequently, these disk drives are used in combination to provide increased reliability though inter-disk coding techniques and through disk sparing. The disk drives are often packaged into arrays in order to decrease the amount of physical space needed to house them and in order to physically associate disks that are used combinations and as spares. 
     Regardless of the drive packaging arrangement, three problems have to be addressed: how to cool the drives, how to shield the drives to prevent the emission of excessive electromagnetic radiation and how to secure the drives in such a way as to minimize rotational vibration. Prior-art solutions to these problems typically entail housing each disk drive in its own metal, or combination metal and plastic, structure that allows air to flow around the drives and provides a conductive enclosure for emission control purposes. This conductive enclosure is then electrically connected to a common chassis ground using spring fingers or metal gaskets. However, the housing structure effectively increases the width of each disk drive and limits the density with which the drives can be packaged. For example, it is very difficult to fit more than thirteen conventional drives having a 3.5-inch, low-profile form factor into an Electronic Industry Alliance (EIA) standard 19-inch rack-mountable chassis using this technique. 
     Consequently, there is a need for packaging method and apparatus that enables a larger number of disk drives to be housed in the width available in a standard 19-inch rack than is possible with prior art methods and apparatus while still providing adequate cooling, radiation shielding and a mechanically secure method of mounting. 
     SUMMARY OF THE INVENTION 
     In accordance with the principles of the invention, disk drive packaging apparatus has a chassis with open ends that encloses all of the disk drives. The open ends of the chassis are covered with conductive screens. A disk-drive carrier is provided for each drive that holds, but does not enclose, the disk drive. The screens provide both emission containment and guarantees adequate air distribution for cooling. Because the screens are able to contain the radiation emission, conductive enclosures are not needed for each separate drive, with the result that the drives can be packed more densely. 
     In one embodiment, at least one conductive screen is mounted in a bezel assembly that is removably attached to one of the open chassis ends. 
     In another embodiment at least one, and preferably two fans are located in the chassis to draw air across the disk drives. The conductive screens insure uniform air distribution across all disk drives. 
     In still another embodiment, the disk drive carrier is fabricated entirely of a non-metallic material, such as a polymeric material, including carbon-reinforced nylon and glass-reinforced polycarbonate materials. 
     In yet another embodiment, the conductive screens have an open area that is approximately 52% of the total screen area that contains excess emissions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective diagram of a high density disk-array package constructed in accordance with the principles of the invention. 
     FIG. 2 is an exploded perspective diagram of selected internal components of the package shown in FIG.  1 . 
     FIG. 3 is a perspective diagram of a front bezel assembly for the package shown in FIGS. 1 and 2 illustrating the emission screen. 
     FIG. 4 is a perspective view of a disk carrier with a disk drive mounted therein. 
     FIG. 5 is an elevation view of the disk carrier shown in FIG.  4 . 
     FIG. 6 is a top view of the disk carrier shown in FIG.  4 . 
     FIG. 7 is a perspective view illustrating how a disk carrier and disk are inserted and held in the card cage of the inventive disk array package. 
    
    
     DETAILED DESCRIPTION 
     A high density disk-array package  100  that is constructed in accordance with the principles of the invention are shown in FIG.  1 . It would be obvious to those skilled in the art that the precise shape and dimension of the assembly as shown in the following figures can be varied without departing from the spirit and scope of the invention. Disk-array packages, such as package  100 , can be stacked and can be mounted in an EIA-standard 19-inch rack. 
     Each package comprises a conductive chassis and two bezels. For example, package  100  comprises shroud  108  and bezels  102  and  104 . Conductive chassis  108  comprises a conductive sheet metal box which has conductive top, bottom, and side panels and is open at the front to accommodate bezels  102  and  104  and at the back to accommodate power supplies (not shown in FIG. 1.) However, unlike prior art apparatus, the conductive chassis  108  surrounds all of the disks rather than individual disks. 
     Each bezel, such as bezel  102 , comprises a grille area  112  which provides a vent for air intake and may include additional air passages such as slots  114  and  116 . Bezels  102  and  104  may also include other ornamental or decorative molding that is not part of the functional design, but serves to enhance the aesthetics of the assembly. Not shown in FIG. 1 are internal screens in the bezels which provide radiation shielding. 
     Selected internal components of a package, such as package  100 , are shown in more detail in FIG. 2 where the chassis  108  has been removed to expose the interior of the package. FIG. 2 shows the upper bezel  102  and a single row of disks  202 . Not shown are the lower bezel  104  and a second row of disks that would be located directly beneath those shown. In a preferred embodiment, the bezel  102  is comprised of faceplate  200  fabricated from a molded polymeric material attached to a metal screen  203 . Because the faceplate  200  does not participate in the shielding aspects of the design, it can be molded in a variety of decorative shapes. Bezel  102  fits into upper portion of the front opening of the conductive chassis  108 . 
     In a preferred embodiment, each package can house up to thirty 3.5-inch, low-profile disk drives  202  that are housed in two rows (of which one is shown) inside the chassis  108 . Each disk  202  is held in a carrier  240  that is discussed below and the carrier  240  is, in turn, inserted into a card cage. Each card cage, in turn, comprises top and bottom card guides  208 ,  209  that are illustratively made of sheet metal that has been perforated at a plurality of points to form individual guides  201  for each disk carrier  240 . The sheet metal card guides  208 ,  209  are illustratively attached, for example by rivets to the enclosing chassis  108 . For example, card guide  208  can be attached to the side walls of chassis  108  by means of a flange  214  located at one end of the guide  208  and a similar flange located at the other end. Similarly, card guide  209  can be attached to the top panel of chassis  108  by means of flanges  216  and  218 . Another pair of card guides (not shown in FIG. 2) can also be attached to the side wall and bottom of the chassis  108  to support the lower row of disk drives. At the rear of the card cage is a backplane  250 . The backplane  250  is a printed circuit board that spans the two card guides  208  and  209  and provides power and ground connections, via connectors  251 , for each disk drive. 
     Two power supplies  211  and  213 , each with two fans  210 ,  220  and  222 , and  224 , slide into the rear of chassis  108  and plug into the backplane  250  in order to receive power. The fans  210 ,  220 ,  222  and  224  provide airflow over the disks. 
     In one illustrative embodiment, the dimensions of each disk-drive carrier  240  are 5.75 in. long ( 204 ) by 3.95 in. high ( 205 ) by 1.00 in. wide. The carriers  240  are spaced in the card cage at a 1.15-inch center-to-center separation ( 206 ). The card cages formed by guides  208  and  209  themselve are 17.30 inches wide ( 207 ) and can accommodate up to 15 disk drives each for a total of 30 disks per chassis. The opening of chassis  108  is 10.5 in. high and the internal backplane  250  is 7.2 inches high, allowing 1.65-inch gaps above and below it in the 10.5-inch-high chassis and thereby enabling adequate airflow around it. 
     The bezel assembly  102  is shown in greater detail in FIG. 3. A metal air vent assembly  301  is attached to the polymeric faceplate  200  by means of fasteners such as screws  310 . The air vent assembly  301  consists of the conductive screen  203  surrounded by a conductive frame  305  with four conductive side panels  302  that slide into the front opening of chassis  108 . A metal gasket  303  mounted on the side panels  302  ensures a tight fit between the side panels  302  and the chassis  108 , thereby further containing radiation emissions. 
     The screen  203  is made of a thin conductive material, such as metal, having a plurality of holes  306  arranged in a circular pattern. The diameter of the holes is chosen to produce a screen  203  that has an open area that is about one half of the total area. In one illustrative embodiment, the open area of the holes is 52% of the total screen area and the holes  306  in the screen  203  have a 0.160in. diameter. With these dimensions, holes  306  in the screen are small enough to contain electromagnetic radiation emissions at frequencies as high as 12.5 GHz. 
     In addition, because the combined area of the holes  306  is only about one half of the total area of screen  203 , screen  203  creates a pressure drop sufficient to control the distribution of air across the full span of the chassis  108 . Fans  210 ,  220 ,  222  and  224  pull air in through the screen  203 , across the drives  202  and exhaust the air out the back of the chassis  108 . A screen (not shown), identical to screen  203  in the bezel assembly  102 , is mounted to the rear surfaces  230 ,  232  of the power supplies  211  and  213  to contain emissions from the rear of the chassis  108 . In one illustrative embodiment, each of fans  210 ,  220 ,  222  and  224  has a 150 cubic feet per minute (cfm) capacity. The pressure drop provided by screen  203  in the bezel assembly  102 , combined with the 150-cfm capacity of each of the four fans  210 ,  220 ,  222  and  224  guarantees an adequate airflow across each of the disk drives  202  (and the drives in the row which is not shown in FIG. 2 even when one of fans  210 ,  220 ,  222  and  224  has failed. 
     A single disk-drive carrier  240  enclosing a disk drive  202  is illustrated in FIGS. 4,  5  and  6 . The carrier  240  consists of four non-conductive components: a U-shaped carrier comprised of a top rail  402 , a bottom rail  406  and a front component  404  that holds the rails  402  and  406  together and a handle  408 . Illustratively, the top rail  402 , the front component  404  and the bottom rail  406  can be formed from a single piece of material. In a preferred embodiment, the top rail  402 , front component  404  and bottom rail  406  are molded from a polymeric material, such as carbon-reinforced nylon 6/6 as a single piece. 
     The disk drive  202  is mounted in the carrier  240  by means of screws  424  and  426  (FIG. 6) that pass through the top rail  402  and bottom rail  406  and seat against cutouts  414  and  410  in the top rail and  450  and  452  in the bottom rail  406 . When the carrier  240  and disk  202  are inserted into the card cage, standard signal and power connectors  420  (FIG. 5) on the rear of the disk-drive  202  mate with their corresponding connectors  251  on the backplane  250  (FIG.  2 ). 
     The carrier rails  402  and  406  are slightly narrower than the disk drive  202 . For example, in one embodiment, the carrier rails  402  and  406  may have a width  440  of 0.875 in. as compared to a 1.00 in. width  446  of the disk  202  itself. The carrier  240  is housed in the card cage with a 1.15 in. center-to-center spacing ( 206 , FIG.  2 ), leaving sufficient room between them for air to flow for cooling purposes. 
     A handle  408  shown in greater detail in FIGS. 5 and 6 aids in inserting and removing the disk-drive carrier  240  from the card cage. Handle  408  is fabricated from a single piece of material. For example, it may be molded from a polymeric material, such as glass reinforced polycarbonate. The handle  408  is attached to the disk carrier  240  with a hinge pin  434  that passes through ears  454  and  456  on front component  404 . The hinge pin  434  passes through a slot  442  in a finger  436  extending from the bottom of the handle  408 . The slot allows the handle  408  to be slid up and down over the hinge pin  434 . 
     The top rail  402  has a leaf spring  412  contact which makes electrical contact with the outer cover of disk drive  202  and protrudes slightly above the surface of the rail  402 . In a similar manner, the bottom rail  406  has a similar contact  418 . Contacts  416  and  418 , in turn make electrical contact with the card guides  208  and  209  and ground the disk drive as it is being inserted into the assembly in order to avoid damage to the disk drive caused by electrostatic discharge. 
     FIG. 7 illustrates how the carrier  240  is inserted into the card cage and held there. FIG. 7 illustrates two card guides  702  and  704  which form the card cage for the bottom row of disk drives in the illustrative assembly. The top card guide  702  has two rows of stampings  720  and  724 . Similarly, the bottom card guide  704  has two rows of stampings  714  and  716 . Each stamping produces short vertical walls  710  that are bent at 90 degrees to the card guide body. The walls, in turn, form sets of carrier guide channels. For example, walls  710 ,  712 ,  714  and  716  form a guide channel  730 . Similar channels are formed between the stampings on the top guide  702  and the bottom guide  704 . 
     The disk carrier and its disk are inserted as follows. With the disk carrier  240  and drive  202  assembled and screwed together, the handle  408  is slid upwards over the hinge pin  434 . The assembly is then slid into a guide channel such as channel  730  and the corresponding channel in top card guide  702  until resistance is felt as the contacts  420  at the back of the drive  202  engage the contacts on the backplane. The back ends  419  and  420  of top rail  402  and bottom rail  406  are tapered to aid in insertion. 
     Next, the handle  408  is rotated forward and slid down causing finger  436  at the bottom of the handle  408  to engage slot  740  in the card guide  704 . With the finger  436  in the slot  740 , the handle  408  is rotated backwards towards the carrier  240  and acts as a lever to provide the mechanical advantage required to overcome the resistance generated by contacts  420 . When the handle  408  is moved towards the carrier  240 , a small tab  432  at the top of the handle  408  slides under a flexible extension  430  at the top of the front component  404 . As the tab  432  slides under the extension  430 , it enters a hole  438  in the extension  430 . The extension  430  thereupon snaps down over the tab  432  locking the carrier in position. 
     The top carrier rail  402  has two small protrusions  470  and  472 , one on each side at the front of the rail  402 . Likewise the bottom rail  406  has two protrusions  474  and  476 . These protrusions are slightly wider than the width of the guide channel  730  formed by the stampings. In one embodiment, the protrusions are 0.034 in. wider than the width of the guide channel  730 . The protrusions result in interference between the disk carrier and the card guides during the final 0.100″ of drive insertion. This interference insures that the carrier fits tightly into the guide. 
     In addition, the guide channel  730  into which the disk carrier  240  is inserted has a small dimple  742  at the rear end. A similar dimple (not shown) is formed in the upper guide  702  at the rear of the corresponding guide channel. These dimples protrude a small distance, for example 0.025 inches, above the channel floor. As the carrier is inserted, these dimples that compress the top and bottom rails  402  and  406  against the disk drive  202  enough to capture the carrier and drive in the guide. The combination of protrusions  470 ,  472 ,  474  and  476  and dimples  742  secures the carrier  240  at all four corners, contributing to the eliminating of vibration that would otherwise be possible between the drive  202  and the chassis  108 . The flexural modulus of elacticity of the material being greater than 2.5E6 PSI increases the natural frequency of the carrier sufficiently to eliminate resonance caused by the rotational forces of the drive. 
     The disk carrier and its disk are removed as follows. A user grips the handle  408  and slides the extension  430  upward with his thumb. When the extension is pushed sufficiently upwards, the tab  432  is released from the hole  438  allowing the handle to be rotated forward. The handle  408  again acts as a lever, this time to provide the mechanical advantage required to separate the contacts  420  from the backplane contacts. When the contacts  420  have been disengaged, the handle  408  can be slid upwards removing the finger  436  from the hole  740  thereby allowing the carrier  240  and drive  202  to be slid out of the card cage. 
     The inventive apparatus allows a very dense packaging of disk drives with only 0.150 inch of space between adjacent drives. Radiation emissions are contained by the metal screen  203  in the bezel assembly  200 . Acceptable thermal performance is achieved through the combination of this same metal screen  203  with its highly resistive hole pattern and high-velocity fans  210 ,  220 ,  222  and  224 . Vibration is minimized due to the interference between the plastic disk-drive carrier  240  and the metal card guides  720  and the very high strength of the material. 
     Although an exemplary embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. For example, it will be obvious to those reasonably skilled in the art that, although the description was directed to a particular construction that houses thirty disk drives, that other designs could be used in the same manner as that described. Other aspects, such as the specific parts utilized to achieve a particular function, as well as other modifications to the inventive concept are intended to be covered by the appended claims.