Patent Publication Number: US-2005124180-A1

Title: Removable card guidance block

Description:
BACKGROUND  
      A backplane or midplane (hereafter called backplane) is an electronic circuit board that may include circuits and sockets into which other circuit boards or cards are plugged. For instance, in a computer the backplane (sometimes referred to as a motherboard) is a circuit board that includes sockets (also referred to as expansion slots) for cards. The cards (also referred to as expansion cards, boards, adapters and so forth) include circuits that provide a functional capability to the computer. The card is typically made of a rigid material and is plugged into one of the computer&#39;s expansion slots in the backplane. Cards have a variety of sizes to match corresponding socket dimensions. A card can be of full height, half height, or some other height. For example, two half-height cards would fit into one full height card slot.  
     SUMMARY  
      In one aspect, the invention features a guidance block that includes a base. The guidance block also includes a first set of opposing sides attached to a top side of the base, the first set of opposing sides provide a first separation configured to accept a first circuit board. The guidance block also includes a second set of opposing sides attached to a bottom side of the base, the second set of opposing sides provide a second separation configured to accept a second circuit board.  
      Embodiments may include one or more of the following. The first set of opposing sides can accept the bottom edge of a first circuit pack and the second set of opposing sides can accept the top edge of a second circuit pack. The sides can accept multiple thicknesses of circuit packs.  
      The guidance block can also include a spring member. The spring member can provide alignment of a primary side of the circuit pack. The spring member and the guidance block can be comprised of an electrically conductive material.  
      The base can include apertures to allow the guidance block to be removably attached to a backplane or midplane. The guidance block can include a aperture in the base and a fastener. The fastener can be positioned in the aperture to attach the base to a backplane or midplane. The guidance block can also include a retaining pin, the retaining pin can prevent the complete removal of the fastener from the guidance block.  
      In another aspect, the invention features a guide pin retainer block and a guidance block. The guide pin retainer block includes an aperture configured to accept a fastener. The guidance block includes a base and a first set of opposing sides attached to a top side of the base, with the first set of opposing sides providing a first separation configured to accept a first circuit board. The guidance block also includes a second set of opposing sides attached to a bottom side of the base with the second set of opposing sides providing a second separation configured to accept a second circuit board.  
      Embodiments can include one or more of the following. The guide pin retainer block can include apertures to allow the guide pin retainer block to be removably attached to a backplane or midplane. The guide pin retainer block can include a guide pin and the guidance block can include a aperture configured to accept the guide pin and align the guidance block to the guide pin retainer block. The aperture can be conical shaped. Alternately, the guidance block includes a guide pin and the guide pin retainer block includes an aperture configured to accept the guide pin and align the guidance block to the guide pin retainer block. The aperture can be a conical shaped aperture. The guidance block can include a fastener such that the guidance block can be attached to the retainer block by inserting the fastener in the aperture configured to accept the fastener.  
      In another aspect, the invention features a guidance system comprising a backplane including a guidance block. The guidance block includes a base and a first set of opposing sides attached to a top side of the base, with the first set of opposing sides providing a first separation configured to accept a first circuit board. The guidance block also includes a second set of opposing sides attached to a bottom side of the base, with the second set of opposing sides providing a second separation configured to accept a second circuit board.  
      Embodiments may include one or more of the following. The first set of opposing-sides can accept the bottom edge of a first circuit pack and the second set of opposing sides can accept the top edge of a second circuit pack. The guidance block can include a spring member that provides alignment of a primary side of the circuit pack. The spring member and the guidance block can be comprised of an electrically conductive material. The guidance block can be grounded and the electrically conductive material can provide an electrostatic discharge (ESD) path.  
      In one aspect, the removable card guidance block provides the advantage of allowing a single full height card slot to be configured to accept cards of alternate heights. For example, placing one removable card guidance block in the middle of a full height slot allows two half-height cards to occupy a full height slot.  
      In another aspect, the removable card guidance block includes a spring to bias a card to the primary side of the removable card guidance block. This allows a user to insert a board into the device without regard for thickness of the board. The spring member aligns the connectors on the card with the connectors in the slot.  
      In another aspect, the removable card guidance block extends to the same extent as the card. This allows a user to insert and/or remove the removable card guidance block while cards remain active in adjacent slots.  
      The removable card guidance block also provides full guidance of the card from the card entry to the shelf to card termination. The removable card guidance block also permits for keying and faceplate side movement control.  
      The removable card guidance block provides the alignment for the top edge of a lower card, and the bottom edge of a higher card as the cards are cascaded within a single slot of a shelf. When removed, a full height card can be plugged into the same space as the cascade of smaller cards.  
      An integrated guide pin receptacle and a captivated extension fastener aligns and fastens the removable card guidance block to a guide pin retainer block that is permanently or semi permanently attached to the backplane.  
      An EMI gasket and integrated threaded female fasteners attached to face of the removable card guidance block allows for the continuous EMI shield and lockdown of cascaded faceplates. 
    
    
     DESCRIPTION OF DRAWINGS  
       FIG. 1  depicts a backplane and a removable card guidance block that divides a full height slot to accept two half-height cards.  
       FIG. 2  is a diagram of the spring side of the removable card guidance block.  
       FIG. 3  is a diagram of the primary side of the removable card guidance block.  
       FIG. 4  is a diagram of the spring connection region of the removable card guidance block.  
       FIG. 5  is a composite view of removable card guidance block. 
    
    
     DESCRIPTION  
      Referring to  FIG. 1 , a backplane  10  includes multiple slots  20 . A user aligns and plugs a card  30  into one of the slots  20 . Each slot fits a particular card thickness (typical card thicknesses range from 0.05 inches to 0.2 inches). In some situations, it can be advantageous to insert two half-height cards into one full height slot. For example, some applications do not require the board space of a full height card, two half-height cards can be used. By limiting the space necessary for such cards, a user can attach a greater number of cards (and greater amount of functionality) to the slots present in the backplane. The option for smaller cards also permits lower granularity per application. In order to accommodate two half-height cards  30   a  and  30   b  in a full height card slot  20 , a removable card guidance block  16  attaches to the backplane  10  in the middle of the full height card slot and divides the slot into two half-height slots. The removable card guidance block  16  provides alignment of two half-height cards  30   a  and  30   b  to the slot  20 . The removable card guidance block  16  includes a top slot  12   a  and a bottom slot  12   b , each slot  12  accepts the edge of a card  30 . For example, a bottom slot  12   b  guides the topside  26  of a first card  30   a  while a top slot  12   a  guides the bottom edge  28  of a second card  30   b . Fasteners  36  screw into apertures  32  and  34  to secure cards  30   a  and  30   b  to the removable card guidance block  16 .  
      Removable card guidance block  16  removably attaches to the backplane using a guide pin retainer block  14 . Retainer block  14  attaches to the backplane using fasteners or permanently attaches to the backplane for example by bonding or soldering. The guide pin retainer block  14  does not interfere with the use of the slot for a full height card. The placement of the guide pin retainer block  14  determines the number of slots the full height slot is divided into when a removable card guidance block  16  is attached to the guide pin retainer block  14 . For example, placing a single guide pin retainer block  14  in the middle of a slot  20  provides the option to divide the slot into two half-height slots. The guide pin retainer block  14  includes a threaded hole into which a fastener  11  fits to attach the guide pin retainer block to the backplane  10 . Fastener  22  secures removable card guidance block  16  to guide pin retainer block  14  and allows a user to insert and remove the removable card guidance block  16  based on the current system needs.  
      In this example, the removable card guidance block  16  is approximately the same length as card  30 . The length of the removable card guidance block  16  allows a user to attach and remove the removable card guidance block  16  while cards occupy adjacent slots. Since the fastener  22  extends past the other boards and the removable card guidance block is non-conductive (e.g., plastic), it is not necessary to insert a tool (e.g., a screwdriver) between the cards to tighten the fastener  22 . This allows other cards to remain in use while a single slot  20  configured to accept a full height card is re-configured to accept two half height cards or vice versa. While, in this example the removable card guidance block  16  is approximately the same length as card  30  the removable card guidance block  16  can be any length. If the removable card guidance block is much shorter than the card  30 , special tools or the removal of adjacent cards may be necessary to attach the removable card guidance block  16  to the backplane.  
      Referring to  FIGS. 2-5 , the removable card guidance block  16  has a spring side  60  ( FIG. 2 ), a primary side  80  ( FIG. 3 ), and a spring region  62  ( FIG. 4 ).  FIG. 5  shows a composite view of the removable card guidance block  16 . The spring side  60  ( FIG. 2 ) and primary side  80  ( FIG. 3 ) attach to a body  78 . The sides  60  and  80  extend vertically from both the top-side and the bottom side of the body  78  to provide slots  12   a  and  12   b . Slots  12   a  and  12   b  each provide a separation between the opposing sides  60  and  80  into which a card can be inserted. When a user inserts a card into slot  12   a  or  12   b , a spring  18   a  or  18   b  biases the primary side of the card to the primary side  80  of the removable card guidance block  16 .  
      The body  78  extends the length of the device and forms the bottom of slot  12   a  and the top of slot  12   b . Body  78  includes a card attachment piece  79  on an end not attached to the backplane. The card attachment piece  79  has three apertures  24 ,  32 , and  34  for fasteners such as screws. A user inserts an extension fastener, e.g., fastener  22  through aperture  24  to fasten the removable card guidance block  16  to the backplane  10  (described in detail below). While aperture  24  is used to secure the removable card guidance block  16  to the backplane  10 , apertures  32  and  34  are used to secure card  30  to the removable card guidance block  16 . When a user inserts a card  30  into slot  12 , the card is secured to body  78  by fasteners  36  (as seen in  FIG. 1 ). Fasteners  36  placed through apertures  32  and  34  fasten a card  30  to the card attachment piece  79 . While in this example, card is attached to the body  78  using screws as the fasteners, other attachment devices can be used.  
      In order to fasten the removable card guidance block  16  to the backplane  10 , a user aligns the removable card guidance block  16  to the guide pin retainer block  14  and tightens fastener  22 . For alignment, the guide pin retainer block  14  includes a guide pin  52 . Guide pin  52  extends from the guide pin retainer block  14  and has a conical shaped end  54 . The conical end  54  provides easier insertion of the guide pin  52  into guide pin receptacle  84  ( FIG. 3 ). Guide pin receptacle  84  is attached to the primary side  80  of removable card guidance block  16  and has a guide pin aperture  82 . The insertion of guide pin  52  into the guide pin aperture  82  aligns fastener  22  with the aperture  50 . The fastener  22  extends the entire length of the removable card guidance block  16  so that a user may attach the removable card guidance block  16  to the backplane  10  without removing cards from adjacent slots. This allows a user to change a single slot from a full height card configuration to: dual half-height card configuration while other cards in adjacent slots are in use.  
      In the example above, the guide pin  52  includes a conical shaped end  54 . In another example, the aperture  82  could include a conical shaped region to guide the guide pin  52 . In another example, the guide pin attaches to the removable card guidance block  16  and the guide pin retainer block  14  includes guide aperture configured to accept the pin.  
      A roll pin  56  ensures that the fastener  22  does not fall out of the removable card guidance block  16 . The roll pin  56  passes through a aperture  58  in the body  78  of removable card guidance block  16 . The fastener  22  includes a region of lesser diameter  66  between two regions  64  and  68  of full diameter. By positioning the roll pin  56  through the roll pin aperture  58  in a location where the fastener is of lesser diameter (i.e. region  66 ), the pin  56  forms an aperture of a smaller diameter than the full diameter regions of the fastener  22  (i.e. regions  64  and  68 ). As a user inserts the fastener  22  into removable card guidance block  16 , the region of the fastener  22  with a limited diameter  66  allows the fastener to be pushed into removable card guidance block  16 . However, if the roll pin  56  reaches the end of the region of lesser diameter  66  and hits the region  68  of average diameter the roll pin prevents the fastener  22  from being further inserted. In a similar manner, the roll pin  56  prevents the fastener  22  from pulling out of the removable card guidance block  16  when the roll pin  56  hits region  64 .  
      Alternately, the force to lock or seat the removable card guidance block comes from the shoulder  71  of fastener  22  seating on surface  63  of removable card guidance block. This method provides a circumferential shoulder between the screw and removable card guidance block reducing the risk of tipping or bending the plastic.  
      Once the removable card guidance block  16  is secured to the backplane  10  using the fastener  22 , a user inserts a card  30  into a slot  12 . A primary side  80 , the base  78 , and the spring side  60  form slot  12  to provide a separation into which the card  30  fits. The base forms the bottom/top horizontal surface of the slot  12 , while spring side  60  and primary side  80  oppose each other forming parallel vertical extensions perpendicular to base  78  defining the separation into which the card fits (i.e. defining a card guide slot  12 ).  
      Spring side  60  includes an extension card guide region  72  and a spring region  62 . The extension card guide region  72  of spring side  60  includes two side extension pieces  74   a  and  74   b  forming the spring side of slots  12   a  and  12   b  respectively. The extension region  72  includes an angled outer region  76  used to guide the card into the card guide slot  12 . Since the angled region  76  makes the slot wider on the outer end, (where the user inserts the card  30 ) it provides a lead-in feature for the user to more easily insert the card  30  into the slot  12 .  
      A spring region  62  provides macro alignment of the card  30  to the connectors in the backplane. A spring  18  attaches to spring region  62  using a lip  92  on spring  18 . Lip  92  extends around a side of spring region  62  ( FIG. 4 ). The lip  92  includes an attachment aperture  90  that snaps into a raised tab  94  on the spring region  62 . The locking of the raised tab  94  into the attachment aperture  90  secures the spring  18  to the removable card guidance block  16 . Spring  18  biases the card  30  toward the primary side  80  of the removable card guidance block  16 . This biasing aligns a connector on the primary side of a card  30  with a connector in the backplane  10 . Since the spring  18  can be depressed in varying amounts and slot  12  is wider than the card, removable card guidance block  16  can accept cards of varying thickness. Thus, if the cards are not thicker than the card guide slot  12  in the removable card guidance block  16 , the removable card guidance block  16  can be used with a backplane without concern for the card thickness the backplane was configured to accept.  
      The spring  18  can be made of an electrically conductive material, or plastic provided it acts as a spring, moves the card, and returns to its original position after deflection. For example, the spring  18  can be made of beryllium copper stainless steel or spring steel. When the spring  18  is composed of an electrically conductive material, the guidance block  16  is composed of an electrically conductive material, and the block is grounded, the electrically conductive material provides an electrostatic discharge path from the card  30  to backplane  10 . The exact shape and attachment of spring  18  can vary. For example, the spring  18  can be adhesively bonded or affixed via fasteners to spring region  62 .  
      An electro-magnetic interference (EMI) gasket  82  attaches to the face  79  of removable card guidance block  16  and provides a continuous EMI shield of cascaded faceplates ( FIG. 2 ). EMI gasket  82  has apertures to allow screw down of the cards at the faceplate to threaded female fasteners that are press fitted in the removable card guidance block  16 . The EMI gasket can be attached to the surface using adhesive.  
      In one example, the spring side  60 , primary side  80  and body  78  are molded from plastic producing a unitary piece having the features discussed above. Base  78  and sides  60  and  80  could instead be composed of multiple parts bonded together to form the desired structure. In another example, the base  78  and sides could be composed of metal or another firm material.  
      While in the example described above, each removable card guidance block  16  individually attaches to a backplane  10 , multiple removable card guidance blocks  16  can be grouped to form a larger unit. For example, a backplane might include eight card slots. Thus, a grouping of eight removable card guidance blocks  16  provides splitting of each full height slot into two half-height slots.  
      While in the example above a single removable card guidance block  16  is used to divide a full height card slot into two half-height card slots, the removable card guidance blocks  16  could be used to divide the full height slot into a variety of heights allowed by the backplane. For example, two removable card guidance blocks  16  could be used to divide a full height slot into three ⅓-height slots or three removable card guidance blocks  16  could be used to divide a full height slot into four quarter-height slots.  
      A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.