Abstract:
An apparatus for guiding a card enclosure into a daughter card enclosure includes a daughter card removeably positioned within a cage for connecting the daughter card with a mother card. A cassette assembly removably positioned with the daughter card enclosure for connection with said daughter card includes a card configured for pluggable signal interconnection with the daughter card. A guide means for guiding the cassette assembly into proper alignment with the daughter card is mountable therewith and an associated stiffener using two mounting locations. The guide means is configured to insure full insertion of said cassette assembly before plugging in the card and insure an unplugged status of the card before extraction of the cassette assembly from the daughter card enclosure.

Description:
BACKGROUND OF THE INVENTION 
     Computers are customarily provided with sheet metal cage structures that contain a back plane. A back plane is a circuit board (e.g., mother card) or framework that supports other circuit boards, devices, and the interconnections among devices, and provides power and data signals to supported devices. The mother card is the main circuit card in the computer which connects to the back plane of the logic board. The computer cage structure is adapted to receive and removably support at least one and preferably a plurality of options or daughter cards (blades or nodes) which when operatively installed in their associated cage structure, upgrade the operating capabilities of the computer. For example, it is known to place an assembly, including a backplane and various circuit boards, such as a processor card, an input-output card and a so-called memory riser card, within an open cage. This forms a so-called central electronics complex (CEC) of a computer system. The cage is subsequently fixed within a computer housing. 
     A standard containing enclosure or cage protects the individual daughter cards and facilitates the easy insertion and removal of the daughter cards from a mother card (mother board) or back plane slot. These daughter cards may be installed in the computer during the original manufacture of the computer and or subsequently installed by the computer purchaser. The cage serves to position the circuit boards within the computer housing, and acts as an EMC (electromagnetic compatible) shield. An EMC shield allows operation in an electromagnetic environment at an optimal level of efficiency, and allows static charges to be drained to a frame ground. Moreover, the cage helps to protect the components contained therein from environmental damage, for example, vibrations, which could cause the components to fail. 
     Additionally, the cage is typically fixed within a so-called system chassis, which is a frame that provides further support for the cage, and which is removably stacked upon other system chassises within a system rack. The chassis may contain other components and sub-systems, such as power supplies and cooling fans, for example, which are connected to the components within the cage using cables, for instance. 
     A daughter card may include a relatively small rectangular printed circuit having a connecter along one side edge, a 24″×24″ node weighing over a hundred pounds, or a server, for example. The mother card or system back plane slot has a socket connector. The daughter card connector plugs into a corresponding socket connector of the mother card to operatively couple the daughter card to the mother card or system back plane slot. 
     The daughter card is in turn engaged with a number of input-output cassettes housing a respective I/O card for connection within a daughter card enclosure. In such daughter card enclosures, the I/O card is mounted within a removable card enclosure or cassette. Each of these input-output cassettes must be blind swapped into the daughter card enclosure. This removable card enclosure allows for I/O card installation or removal from the daughter card enclosure when the card enclosure is installed or removed from the computer cage structure. 
     Given the extremely dense pitch and packaging of present I/O blind swap cassettes and the population of the daughter card into which the I/O card plugs, it has become necessary to develop a guidance system into the daughter card enclosure which minimizes both the mounting points to the mother card enclosure and the physical space such a solution may consume. 
     Thus, there is a need for an arrangement that will allow for blind swapping of an I/O card from a daughter card for servicing, for example, which does not require manually connecting and disconnecting various electrical connectors to provide signal interconnection therebetween while providing an easy and reliable means to align the I/O card to make such signal interconnections within the daughter card enclosure. 
     SUMMARY OF THE INVENTION 
     An apparatus for guiding a card enclosure into a daughter card enclosure includes a daughter card removably positioned within a cage for connecting the daughter card with a mother card. A cassette assembly removably positioned with the daughter card enclosure for connection with said daughter card includes a card configured for pluggable signal interconnection with the daughter card. A guide means for guiding the cassette assembly into proper alignment with the daughter card is mountable therewith and an associated stiffener using two mounting locations. The guide means is configured to insure full insertion of said cassette assembly before plugging in the card and insure an unplugged status of the card before extraction of the cassette assembly from the daughter card enclosure. 
     In another embodiment, a multiple card enclosure includes a mother card cage having a mother card enclosed therein; a daughter card removably positioned within the cage for connecting the daughter card with the mother card, the daughter card having a signal connector configured to connect to the mother card for signal interconnection therebetween; a cassette assembly removably positioned with a daughter card enclosure for connection with the daughter card, the cassette assembly having a card configured for pluggable signal interconnection with the daughter card; and a guide assembly configured to guide the cassette assembly into proper alignment with the daughter card for pluggable signal interconnection therewith, the guide assembly mountable to the daughter card and an associated stiffener using two mounting bosses extending from the guide assembly. The guide assembly is configured to insure full insertion of the cassette assembly before plugging in the card and insure unplugging of the card before extraction of the cassette assembly from the daughter card enclosure. 
     In yet another embodiment, a central electronics complex of a computer system includes a cage configured to be received in a rack; a backplane disposed in the cage, the backplane including a mother card having at least one card slot on a surface thereof; a plurality of daughter cards removably positioned within the cage, each daughter card having a signal connector configured to connect with a corresponding card slot in the mother card for signal interconnection therebetween; a cassette assembly removably positioned with a daughter card enclosure for connection with each daughter card, the cassette assembly having a card configured for pluggable signal interconnection with each daughter card; and a guide assembly configured to guide the cassette assembly into proper alignment with each daughter card for pluggable signal interconnection therewith, the guide assembly mountable to each daughter card and an associated stiffener using two mounting bosses extending from the guide assembly. The guide assembly is configured to insure full insertion of the cassette assembly before plugging in the card and insure unplugging of the card before extraction of the cassette assembly from the daughter card enclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the exemplary drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is a perspective view of an multiple card enclosure illustrating one daughter card enclosure interfacing with a midplane for signal interconnection and two I/O cassettes interfacing the daughter card; 
     FIG. 2 is a perspective view of the exemplary daughter card enclosure of FIG. 1 with a stiffener removed therefrom; 
     FIG. 3 is a reverse perspective view of FIGS. 1 and 2 illustrating an I/O cassette removed from an exemplary embodiment of a blind swap cassette guide mounted to a printed circuit board and stiffener of the daughter card configured to properly guide a corresponding I/O card in and out of the daughter card; 
     FIG. 4 is an enlarged perspective view of the exemplary embodiment of a blind swap cassette guide removed from the daughter card illustrating a tactile feedback snap system and twin catch feature incorporated therewith for receiving corresponding features configured in the I/O cassette housing; 
     FIG. 5 is a partial bottom perspective view of FIG. 4 illustrating a locating feature of the guide; 
     FIG. 6 is an enlarged cross section view of a tactile feedback snap system shown in FIG. 4; 
     FIG. 7 is an enlarged sectional perspective view of FIG. 6 illustrating only the cassette housing engaged with the blind swap cassette guide; 
     FIG. 8 is an enlarged view of circle portion  8 — 8  of FIG. 7 illustrating engagement of cassette housing with one of twin catch features disposed in a back wall of the guide; 
     FIG. 9 is a reverse perspective view of FIGS. 1 and 2 with the tall stock removed illustrating an I/O cassette docked with the blind swap cassette guide via the twin catch features and cutout section configured in the stiffener; and 
     FIG. 10 is a bottom view of FIG. 6 illustrating a slot and pin feature of the cassette assembly as it cooperates with an edge defining a wall extending from the blind swap cassette guide. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will now be described in more detail by way of example with reference to the embodiments shown in the accompanying figures. It should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as limiting the inventive concept to any particular physical configuration. 
     Further, if used and unless otherwise stated, the terms “upper”, “lower”, “front”, “back”, “over”, “under”, and similar such terms are not to be construed as limiting the invention to a particular orientation. Instead, these terms are used only on a relative basis. 
     FIGS. 1 and 2 illustrate a so-called central electronics complex  10  (CEC) of a computer system. The CEC  10  is comprised of an enclosure (such as a cage  12 ), a backplane or midplane  14  as illustrated, and a circuit board or daughter card, such as a blade or node  16  having two processor multi-chip modules  17 , 256 GB memory on 16 cards (not shown), two input/output (I/O) cards  18 , and a control multiplexer card (not shown), for example, attachable to the backplane  14 . 
     As shown, the cage  12  has a box shape with a generally rectangular cross-sectional profile, and is formed of two cavities on one side of midplane  14 , generally shown at  20  and  21 , while three cavities are defined on an opposite side of midplane  14  with generally horizontal, spaced apart walls  22 ,  23 , and  24  joined together by generally upright, midwall  26  extending from wall  24 . Wall  22  defines a bottom floor defining cage  12 . Wall  23  extends to midwall  26  defining a bus bar access area discussed more fully herein. Wall  24  defines a floor defining a cavity in which a plurality of daughter cards  16  may be disposed and interconnected with midplane  14 . The walls  22 ,  23 , and  24  define spaces within the cage  12 , which contain air, power, and docking systems for a plurality of daughter cards  16  installed in the cage. 
     The cage  12  is dimensioned to accommodate the midplane  14  and a plurality of daughter cards  16 , (up to four as shown). Moreover, the cage  12  is preferably comprised of sheet metal, which can be easily manipulated to form the walls  22 ,  23 ,  24 ,  26 , although other materials, such as plastic, may also be used. However, it is preferable that the material used to form the cage  12  be conductive, so that the cage can serve as an EMC shield. 
     As best shown with reference to both FIG.  1  and FIG. 2, the backplane or midplane  14  is a generally planar, rectangular structure, and is accommodated within the cage  12  so that its major surfaces are substantially vertical and essentially perpendicular to the walls  22 ,  23 , and  24  of the cage. Moreover, the daughter card  16  is comprised, for example, of a printed circuit board  28  (PCB) (FIG.  2 ), and a stiffener panel  30  (FIG. 1) disposed beneath (i.e., on one side of) the printed circuit board  28 . An insulator panel, not shown, may also be provided between the stiffener panel  30  and the printed circuit board  28 . 
     The stiffener panel  30  is connectable to the cage  12 , for example, by fastening the stiffener panel to a flange  32  disposed on a lower bottom edge of walls  24 . For example, the stiffener panel  30  can be screwed, bolted or welded to the flange  32 . Other means for connecting the stiffener panel  30  to the cage  12  are within the scope of the present invention. When connected, the backplane  14  partially divides the cage  12  in two, and serves as a partial divider of the cage, with the printed circuit board  28  perpendicular thereto. 
     Preferably, an end distal from a backplane stiffener panel  33  has a tailstock  34  disposed thereon. As is known, a tailstock is a fixture or bezel that provides physical support for the associated electrical device (for example, I/O card  18 ), and which provides for a limited amount of electromagnetic radiation shielding and is configured to be reworkable. 
     The tailstock  34  is provided with a plurality of apertures  36 , which form ports that allow various external peripherals to be connected to the backplane  14 . For example, in the exemplary illustrated embodiment, the tailstock  34  is provided with eight such ports (FIG.  2 ). However, the number and size of the apertures  36  can be modified without departing from the spirit and scope of the present invention. 
     The tailstock  34  is preferably tailored to allow it to be fastened to stiffener  30  (shown in FIG.  1 ). For example, in the illustrated exemplary embodiment, the tailstock  34  is operably fastened to stiffener  30  via four apertures  38  in tailstock  34  aligned with corresponding threaded apertures configured in stiffener  30 . When the daughter card  16  is received within cage  12 , the portions of the tailstock  34  that extend to wall  24  can be fastened thereto. This secures the card  16  within the cage  12 , and prevents fretting of any electrical connections between the backplane  14 , and other system components disposed within the cage  12 , for example. As is known, fretting is a phenomenon in which surface damage occurs when metal contacts are subjected to microvibrations. 
     Each daughter card  16  is generally planar, rectangular structures, with lengths that are substantially the same as their heights, as illustrated, but not limited thereto. As previously mentioned, the cage  12  can then be advantageously tailored in the same manner (with a length that is about the same as its height), so as to receive the respective cards  16  therein with a minimum amount of wasted space. 
     When installed in the cage  12 , the cards  16  are essentially parallel to each other, and essentially perpendicular to the major surfaces of the backplane  14 . However, other orientations may be possible, within the scope of the present invention. 
     The daughter card  16  is preferably removably coupled to the backplane  14  by inserting a known corresponding plug connector, such as a dual row of full edge length very high density metricinterconnector (VHDM)  39  (not shown in detail FIG. 2) on the respective card into an associated backplane card slot  40  (FIG.  2 ). However, other suitably configured plug connectors are contemplated and is not limited to VHDM  39 . As will be appreciated, since the cage  12  is open at its front, each card  16  is inserted through the open front and moved in a horizontal vertical direction until the cards engage with the associated card slots  40  and power interconnects to be discussed more fully below. 
     As illustrated in FIGS. 1 and 2, the backplane  14  is adapted to receive and electrically interconnect a plurality of daughter cards  16 . For example, the illustrated backplane  14  is adapted to receive four cards  16 . 
     Further, and as illustrated best in FIG. 2, each daughter card  16  can accommodate a plurality of electrical components, for example, two MCMs  17 , 256 GB memory on  16  cards (not shown), eight concurrently maintainable I/O hub cards (two shown installed) and a control multiplexer card (not shown). 
     Although the present embodiment has been described in connection with a daughter card  16  having a pair of MCMs  17 , it is contemplated that the same inventive scheme can be utilized with other types of circuit boards. Moreover, it is also contemplated that the respective cards will be specifically tailored for use with the cage  12 . For example, in the above-described exemplary embodiment, the plug connector of the daughter card is disposed symmetrically, that is, along a full length of the edge of the card. 
     As best shown in FIG. 3, in order to facilitate the removal of I/O card  18  from daughter card  16 , the I/O card  18  is disposed in a cassette assembly  50  that is advantageously slidably disposed on one blind swap cassette guide  52  which is operably connected to daughter card  16  and stiffener  30  via two diametrically disposed bosses  54  extending from guide  52 . Each boss  54  is configured to receive a mechanical fastener  56 , such a screw, for example, to be threadably engaged with stiffener  30  through card  16 . Thus, when it is desired to install I/O card  18  with card  16 , I/O card  18  is simply slid in a horizontal direction  58  into daughter card enclosure  60  defined by a corresponding aperture  36  and surrounding card  16  and tail stock  34  and is supported via a wall  62  extending from guide  52 . 
     Guide  52  is preferably configured to guide cassette assembly  50  having card  18  into enclosure  60  and insure full insertion thereof before engaging a connector of card  18  with a corresponding connector  66  electrically connected to daughter card  16  and surrounded by guide  52 . Two guide pins  68  extend on opposing sides of connector  66  to guide card  18  when cassette assembly  50  is fully inserted in enclosure  60 . 
     Referring now to FIG. 4, guide  52  is shown removed from enclosure  60 . Guide  52  is defined by a top rail  68  and a bottom rail  70  substantially parallel with each other and connected via a front side rail  72  and an opposite back side rail  74 , each substantially parallel to each other, and substantially normal to top and bottom rails  68 ,  70 . Front side rail  72  interfaces with bottom rail  70  at one boss  54 , while the other diametrically opposed boss  54  interfaces with back side rail  72  and a back wall  76  normal to back side rail  74 . Back wall  76  extends between top and bottom rails  68 ,  70  and provides a stop for further insertion of cassette assembly  50 . Each boss  54  is preferably counter sunk as indicated generally at  78  so that a flat headed mechanical fastener  56  (e.g., flat head screw) is flush with surfaces defining back side rail  74  and bottom rail  70 . 
     Referring to FIG. 5, a partial bottom perspective view of back side rail  74  and corresponding boss  54  is illustrated. Each boss  54  includes a locating feature  80  extending from boss  54  configured to locate guide  52  in a complimentary configured aperture (not shown) in card  16  for proper alignment of guide  52  with respect to connector  66  extending therefrom. In an exemplary embodiment as shown, locating feature  80  is a pilot cylinder smaller in diameter than a cylinder defining boss  54 , however, other configurations are contemplated suitable for the desired end purpose of properly locating guide  52  with daughter card  16  using only two locating bosses  54 . It will be noted that more than two bosses  54  may be employed, but additional bosses take up more space in mounting the same and is not desired. 
     Referring again to FIG. 4, wall  62  extends from bottom rail  70  forming a support ledge for a bottom of cassette assembly  50 . Wall  62  is a substantially planar and extends a majority of a length defining bottom rail  70 . A leading or front edge  80  of wall  62  is preferably ramped to aide insertion of cassette assembly  50  into enclosure  60 . 
     Referring to FIGS. 4 and 7, bottom rail  70  also includes a plurality (three shown) catch features  82  depending therefrom to slidably engage a flange  74  extending from cassette housing  77  defining cassette assembly  50 . Flange  74  extends from a bottom portion of cassette housing  77  and substantially extends a length defining a length of cassette assembly  50 . Catch features  82  are preferably configured as an offset flange to slidably retain flange  74  in a bight portion  84  defined by the offset flange. In this manner, cassette assembly  50  may be slidably translated in and out of enclosure  60  along a plane defined by daughter card  16 . Furthermore, catch features  82  aide is stabilizing cassette assembly  50  with respect to card  16  as well as distribute forces when plugging and unplugging connectors associated with cards  16  and  18 . 
     Still referring to FIG. 4, top rail  68  is defined by a planar member  84  substantially parallel with wall  62 . Planar member  84  includes a top rail catch feature  86  extending therefrom disposed generally at a middle portion defining a length of top rail  68 . Top rail catch feature  86  is an offset flange extending from a bottom surface defining top rail  68  similar to the offset flange forming bight portion  84  in catch feature  82  extending from a side surface defining bottom rail  70 . Top rail catch feature  86  is configured to engage an edge  88  defining a top housing  90  of cassette housing  77 . Top rail catch feature  86  defines a groove  92  in which edge  88  is slidably retained to prevent pivotal movement of cassette assembly  50  relative to a plane defining daughter card  16 . 
     Top rail  68  further includes a tactile feedback snap feature  94  extending therefrom configured to form a groove  96  similar to groove  92  in which edge  88  is slidably retained to prevent pivotal movement of cassette assembly  50  relative to a plane defining daughter card  16 . Moreover, tactile feedback snap feature  94  is preferably configured as a snap feature  94  to indicate full insertion of cassette assembly  50  when snap feature  94  is aligned with a notched portion or a cutout  97  (FIG. 3) in edge  88  extending from a top portion of housing  77 . 
     More specifically referring to FIG. 6, when cutout  97  is slidably aligned with snap feature  94  upon insertion of cassette assembly  50  in a direction  58  (see FIG.  3 ), at least one of an audible alert and/or a snap feel is experienced when two opposing edges  98  of cutout  97  defined by edge  88  becomes engaged with a resilient snap feature head  100  extending within cutout  97 , otherwise snap feature head  100  rides along a bottom surface defining member  84  defining top housing  90  until cutout  97  is aligned therewith. 
     Referring now to FIGS. 4,  7  and  8 , guide  52  includes twin catch features  102  configured in back wall  76 , each feature  102  is aligned with a corresponding top and bottom rail  68 ,  70  interface with back wall  76 . Each catch feature  102  is configured to receive and removably retain a tab  104  extending from cassette housing  77 . In this manner, each tab  104  stabilizes a back portion or insertion end of cassette housing  77  when plugging and unplugging card  18  with daughter card  16 . In particular, an edge  106  defining tab  104  abuts end wall  108  defining each catch feature  102  when plugging complimentary connectors of cards  16  and  18  together. 
     Referring now to FIG. 9, cassette assembly  50  is shown fully inserted with respect to guide  52  where tabs  104  are engaged with a respective catch feature  102  to stabilize and distribute forces at an insertion end or back end of the assembly  50 . A front end is stabilized via a first slot  110  configured in cassette housing  77  having a first edge defining slot  110  engage an outside surface defining stiffener  30  while an opposite second edge defining slot  110  engages an opposite edge defining stiffener  30 . In this manner, when cassette assembly  50  is fully inserted via direction  58  in FIG. 3, cassette assembly  50  is stabilized from movement in a direction indicated with arrow  112 . Furthermore, when a corresponding second slot  110  is configured on a bottom surface defining cassette housing  77  aligned with first slot  110  in a top portion of cassette housing  77 , cassette assembly  50  is further stabilized and pivotal movement thereof is restricted about a plane defining daughter card  16 . 
     Referring now to FIG. 10, a bottom view of guide  52  having cassette assembly  50  fully inserted is illustrated. Bottom portion  120  of cassette housing  77  includes a slot  122  having a pin  124  extending therethrough. Pin  124  is operably connected to I/O card  18  and translates therewith in a direction indicated at  126  and opposite thereto. Direction  126  corresponds to plugging card  18  with card  16  while an opposite direction corresponds with unplugging the same. A side edge  130  defining one edge of wall  62  opposite leading edge  80  and corresponding to a width of wall  62  extending from bottom rail  70  is aligned with one edge  132  defining slot  122  when cassette assembly  50  is fully inserted in direction  58 . In this manner, pin  124 , and hence card  18 , is allowed to translate in direction  126  and thus allow plugging of connectors generally shown at  150  from corresponding cards  16  and  18 . Guide  52  further includes a recessed region  134  in bottom rail  70  (shown in phantom) proximate side edge  130  and aligned with slot  122  in cassette housing  77  when cassette assembly  50  is fully inserted. 
     When cassette assembly  50  is not fully inserted in direction  58 , pin  124  is aligned with an extended edge  136  defining a length of wall  62  and is prevented from being translated in direction  126 , as it will be recognized by one skilled in the pertinent art, thus preventing plugging of card  18  with card  16 . In this manner, misplugging between connectors  150  is eliminated when cassette assembly  50  is not fully inserted with respect to direction  58 . Like wise, after cards  16  and  18  are plugged together via corresponding connectors  150 , cassette assembly  50  may not be withdrawn from enclosure  60  in a direction opposite to direction  58  until card  18  is fully unplugged from card  16  via full translation of pin  124  in a direction opposite to direction  126 . When card  18  is not fully unplugged with card  16 , pin  124  is aligned along a length of side edge  130  and translation of cassette assembly in a direction opposite to direction  58  is restricted until pin  124  is free from side edge  130  as illustrated in FIG.  10 . With this arrangement, damage to the very high density metricinterconnector (VHDM&#39;s) associated with connectors  150  for cards  16 ,  18 , for example, is eliminated by assuring full insertion of cassette assembly  50  before plugging and full unplugging before extraction of cassette assembly  50 . 
     Most blind swap cassette guides of this nature require more than two fasteners to implement, only work in a vertical application, and have no additional card protection features. In summary, the above described invention allows a more accurate insertion of the I/O blind swap cassette using several new and innovative techniques. First only two bosses are used as mounting points having locating features to a planar board or daughter card, thereby eliminating the need for additional holes to be drilled in the planar board or daughter card. Second, by choosing plastic as the material from which the guide is fabricated, the highest degree of accuracy and structure is achieved while minimizing cost and space consumption. Finally, the plastic guide described above works equally well in horizontal or vertical applications. 
     In an exemplary embodiment, the plastic guide includes a wall configured for cooperation with a slot and pin feature of the cassette assembly which prevents the I/O card from being prematurely plugged without having the cassette fully inserted (potentially damaging both the I/O card connector and planer board). In addition, the guide involves a tactile feedback snap indicating that the cassette has been fully inserted. Finally, two catch features disposed at an insertion end or back end the guide stabilize the cassette during the plugging process and distribute the connector force. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.