Patent Abstract:
A latch for a Compact PCI board, which incorporates inject and eject and engage and disengage functions, has a low profile shape, whereof a fold-down handle operates through a total arc of 90 degrees. Enhanced electromagnetic compatibility (EMC) is provided, by more efficient EMC shielding and by reduced electromagnetic force (EMF) radiation pass-through. The latch, in its inject/eject operation, undergoes a two-phase motion, which utilizes a rotary motion to insert/extract the board from electrical connection, and utilizes a linear motion to engage/disengage the latch pawl from the chassis (keeper). A separate alignment pin block, normally carrying a lead guide pin and a seating guide pin, is independent of the structure for the base of the latch. This permits the alignment pin block to be mounted to the inside of the faceplate and the latch to be mounted to the outside of the faceplate. By so doing, the cumulative (aggregate) area of the opening(s) through the faceplate is reduced, which thereby increases the EMC (electromagnetic compatibility) of the design by reducing EMF radiation pass-through.

Full Description:
RELATED APPLICATIONS  
       [0001]    Applicant claims the benefit under 35 U.S. Code 119( e ) of U.S. Provisional Application SER. NO. 60/477,274, filed Jun. 9, 2004 on the present invention, and incorporates the disclosure thereof herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to latches and levers, specifically ejector latches and ejector levers which may be adapted for use to secure and release computer-type boards in racks and cabinets, such as large boards known as peripheral component interconnect (PCI) boards. These boards are used to hold such electronic components as processor circuits, banks of switches, banks of transducers, transformers and other components and modules. Such PCI boards are generally larger than PC boards (personal computer boards) and can be generally square or rectangular in shape; and are generally sized from six (6) inch to ten (10) inches on a side. Compared to the much larger boards, previously used in the computer, the switching circuit, and the telecommunications industries, these boards have become known as compact PCI boards. It important to be able to easily insert such a module carrying PCI board with a positive snap-in connection and positive snap-out release. Moreover, it is important to have an insertion aid and/or a pull-out aid, such as a handle or a hold. This snap-in and snap-out operation has been implemented with ejector latches.  
           [0003]    However, these latches must also comply with the general industry standards for this type of latch, including the standards for mounting on a faceplate on the front of a board, and the engagement with the chassis mounted flange, which acts as combination guide block and keeper. These standards are defined as a subset of IEEE1101.1 and IEEE 1101.10 specifications known as Compact PCI (PICMG  2.0) standards. Many inject/eject latches are in the marketplace and meet these standards. Examples are those sold by manufacturers such as Rittal, Schroff, Elma and Bivar. As manufactures are using higher frequency circuits on compact PCI boards, electromagnetic compatibility (EMC) is becoming an increasing concern. The existing prior art ejector latch configuration requires a large cutout in the aluminum faceplate normally mounted to the outside edge of a compact PCI board. This large cutout often is a source of electromagnetic radiation. Furthermore, such prior art compact PCI board latches often do not have a low profile and generally have a limited degree of movement and mechanical leverage.  
           [0004]    [0004]FIG. 1 shows a typical example of a prior art compact PCI board  21  with a pair of prior art inject/eject latches  23  mounted on its outboard edge faceplate  25 . Chassis connectors  27  have wire leads  29  into the board  21 . Each latch  23  includes a base/alignment pin block  31  that carries a larger leading guide pin  33  and a smaller seating guide pin  35 .  
           [0005]    [0005]FIG. 2 shows a perspective side view of the prior art pin  23  of FIG. 1 showing the single structure combination housing  37  having a claw-shaped end pawl  37   a  and a thumb handle  37   b.  The base/alignment pin block  31  is a casting with a number of openings and shoulders. A spring biased release button  39  is shown in Fig.3, which is a longitudinal cross-sectional view of FIG. 2 taken as shown in FIG. 2. The spring  41  biases the thumb release button away from the pawl  37   a  to have a projection shoulder  39   a  extend through the opening in the back of the housing  37  to prohibit the rotation thereof and to keep the pawl  37   a  locked in position.  
           [0006]    This prior art device has a high profile and its faceplate mounting with relatively large cutout results in a relatively large amount of EMF signal leakage (electromagnetic frequency radiation).  
           [0007]    The IEEE Compact PCI specification defines the location, with respect to a chassis, of the faceplate in its fully inserted and fully extracted positions, where fully extracted is defined as being loose for removal. It also defines the area of the chassis to which a latch is to interact when inserting and extracting (ejecting) a board.  
           [0008]    An object of this invention is to meet these IEEE requirements for a latch for Compact PCI board installations, which allows for more efficient EMC shielding.  
           [0009]    A second object of this invention is to provide a latch that needs a smaller cutout in the PCI board faceplate.  
           [0010]    An third object of this invention is to provide such a latch that has a low profile when folded closed.  
           [0011]    A further object of this invention is to provide such a latch with a greater degree of rotation and a two-phase operation.  
           [0012]    An even further object of this invention is to implement such a two-phase operation by having the ejector successively operating first in a rotary motion and then secondly in a linear motion.  
         SUMMARY OF THE INVENTION  
         [0013]    The objects of the present invention are realized in a low profile Compact PCI board latch, having a fold-down handle that operates with a greater degree of rotation, and has a separate alignment guide block, which facilitates its mounting to the board&#39;s faceplate and thereby requires a smaller faceplate aggregate cutout area thereby reducing EMF leakage and enhancing EMC compatibility.  
           [0014]    The invention is an inject/eject latch, for mounting on the outside of a PCI board faceplate. This latch engages and disengages a chassis keeper, whereof the chassis environment, including the shape, position and size of the chassis keeper, is specified by IEEE standards for Compact PCI boards. The latch includes a claw-shaped pawl that engages and disengages from a flange-type keeper under a two-phase motion, whereof each motion is a movement, such as a rotation, about a separate and distinct point.  
           [0015]    This pawl includes an elongate arm extension and an abutment shoulder with which fold-down latch handle operates. The fold-down handle rotates through 90 degrees from its flat, folded-down position to the upright standing position facing outwardly from the faceplate.  
           [0016]    The latch has a base that is mounted to the outside face of the compact PCI board&#39;s faceplate with its entire structure being outboard of the PCI board faceplate. A separate alignment guide block mounts to inside face of the faceplate to extend inwardly towards the chassis connectors. The latch, including its base and the separate alignment guide block are mounted to the faceplate with but two screws. The two-phase operation of the pawl permits the faceplate to extend further beyond the outside edge of the board than with solely rotational movement pawls. This increases the EMF shielding and enhances EMC levels for the latch and faceplate combination.  
           [0017]    The latch housing has two juxtaposed plates each carrying facing guide openings and facing pivot openings. A one-piece handle is assembled to ride on and pivot between the juxtaposed housing faces. A claw-shaped pawl is acted upon by the handle to first rotate into a small rectangular cutout opening and then to translate longitudinally into a flange-shaped keeper on injecting. A reverse path of motion of longitudinally withdrawing from the flange-shaped keeper and then rotating is carried out on ejecting.  
           [0018]    A spring-biased, plate-shaped catch with a small projecting hook acts as a locking device in the folded-down position. Releasing the catch permits the latch&#39;s handle to be rotated upwardly.  
           [0019]    From the fully inserted configuration/position, the user first rotates the spring loaded catch which in turn releases the handle from the base and permits it to be rotated outwardly from the board&#39;s faceplate. As the handle is rotated though the first 75 degrees, it pivots around the end of a central slot in the base halves (juxtaposed base plates). Slots in the end of the handle contact pins on the pawl. The pawl rotates around a pin and ejects the faceplate/board structure from the chassis connector by moving the board outwardly above the chassis keeper flange. A further 15 degree rotation of the handle causes the handle to pivot around the end of semi-circular slots in the base halves (juxtaposed base plates). The first slots now drive the pawl pins down vertical portions of “L”-shaped slots in the base plates, causing the pawl to disengage from the chassis keeper flange with a longitudinal movement. The board is now free to be removed (pulled) from the chassis. The ends of the pins on the pawl have a tear-drop shape which prevents them from beginning the vertical travel before the extraction rotation is completed (the full 75 degrees of rotation).  
           [0020]    Insertion reverses the motion and sequence of operation of extraction. The insertion and the extraction is a two-step process. With extraction, the process uses first one pivot location for the handle acting on the pawl extension to provide the extract motion, and then uses a second pivot location for the handle to provide the linear disengagement movement. With injection the order sequence is reversed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The features, advantage and operation of the present invention will become readily apparent and further understood from a reading of the following detailed description with the accompanying drawings, in which like numerals refer to like elements, and in which:  
         [0022]    [0022]FIG. 1 is a side view of a prior art Compact PCI board with prior art inject/eject latches positioned on the faceplate;  
         [0023]    [0023]FIG. 2 is a perspective view of the prior art inject/eject latch of FIG. 1;  
         [0024]    [0024]FIG. 3 is a longitudinal cross-sectional view of the prior art latch of FIG. 2 taken as shown in FIG. 2;  
         [0025]    [0025]FIG. 4 is a perspective view of the latch of the present invention assembled on the faceplate of a Compact PCI board and engaging a chassis keeper;  
         [0026]    [0026]FIG. 5 is a perspective view of the latch of the present invention assembled on the faceplate of a Compact PCI board with the board removed, the view is from the bottom of the latch, i.e., the inboard face of the faceplate;  
         [0027]    [0027]FIG. 6 is a bottom/inboard view of the PCI board faceplate showing a detail of the two mounting screw holes and the faceplate extension permitted by the unique operation of the latch of the present invention;  
         [0028]    [0028]FIG. 7 is a perspective view of the left sidewall of the base for the latch of FIGS. 5-6 showing the inside face thereof;  
         [0029]    [0029]FIGS. 7 a - 7   e  are outside, inside, top, claw-end, and thumb handle end views, respectively, of the left sidewall shown in FIG. 7;  
         [0030]    [0030]FIG. 8 is a perspective view of the right sidewall of the base for the latch of FIGS. 5-6, showing the outside face thereof, with the left sidewall and right sidewall of the base having, respectively, inside face cavities, projections, ramps and journals being mirror images;  
         [0031]    [0031]FIGS. 8 a - 8   e  are outside, inside, top, claw-end, and thumb handle end views, respectively, of the left sidewall shown in FIG. 8;  
         [0032]    [0032]FIG. 9 is a perspective view of the thumb handle member for the latch of FIGS. 5-6;  
         [0033]    [0033]FIGS. 9 a - 93  are left side, right side, top, claw-end and thumb grasping-end views, respectively, of the handle of FIG. 9;  
         [0034]    [0034]FIG. 10 is a perspective view of the claw-shaped pawl with elongate arm for the latch of FIGS. 5-6;  
         [0035]    [0035]FIGS. 10 a - 10   e  are left side, right side, top, claw-end and thumb/catch-end views, respectively, of the pawl of FIG. 10;  
         [0036]    [0036]FIG. 11 is a perspective view of the catch for the latch of FIGS. 5-6;  
         [0037]    [0037]FIGS. 11 a - 11   e  are left side, right side, top, catch tang-end, and free-end views, respectively, of the catch of FIG. 11;  
         [0038]    [0038]FIG. 12 is a perspective view of the alignment pin block for the latch of FIGS. 5-6;  
         [0039]    [0039]FIGS. 12 a - 12   e  are left side, right side, faceplate side, inboard side, and outboard views, respectively, of the alignment pin block of FIG. 12;  
         [0040]    [0040]FIG. 13 shows the latch of the present invention in the fully closed and locked position;  
         [0041]    [0041]FIG. 14 shows the latch in the unlocked position with the catch depressed;  
         [0042]    [0042]FIG. 15 shows the latch with the handle rotated to about the 75 degree position whereby the ejection step is about completed; and  
         [0043]    [0043]FIG. 16 shows the latch with the handle fully rotated to about 90 degrees and the latch fully open and free of the chassis keeper. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0044]    The present invention is fold-down low profile inject/eject latch which meets IEEE standards for compact peripheral interconnection (PCI) boards. Such compact PCI boards have been standardized to have aluminum faceplates at their outermost edges. These faceplates primarily provide EMF shielding. The operation of this latch permits a construction/structure which yields enhanced EMC (electromagnetic compatibility) by permitting increased shielding and reduced EMF emissions past an IEEE standards PCI board faceplate. The design and operation of the present latch invention permits a reduction in the cumulative openings and the aggregate area of the openings through the board&#39;s faceplate, including the addition of lateral extensions to the faceplate outboard its side edges, which lateral extensions are a part of and within the scope of the present invention.  
         [0045]    The invention creates a motion control of the pawl and handle that is created by separately and sequentially pivoting about two different pivot points. The fold-down handle of the latch swings through an arc of 90 degrees from a position parallel to the faceplate to one upstanding perpendicular to the faceplate. The sequential dual pivot point motion, coupled with an elongate slot, enable the pawl to transcribe two separate motions as it disengages from the chassis, the first being a pivoting eject motion against the keeper, and the second being a longitudinal withdrawal motion to release from the keeper. During the first 75 degrees of eject motion, the handle&#39;s rotation pivot point is located close to the pawl pin which the handle bears against. This short-coupled lever action is important to have during the first 75 degrees of eject motion of the handle&#39;s swing so as to maximize the mechanical advantage for ejecting from the printed circuit board/housing connectors with the least amount of effort on the handle during extraction sequence.  
         [0046]    During the next 15 degrees of handle rotation (75-90 degrees), the handle pivot shifts to a second pivot point so as to pull on the pawl structure, and then to cause it to undergo a sliding translation away from the chassis keeper flange, thus freeing the board by completely disengaging the latch. Very light loads are present during this portion of the latches movement.  
         [0047]    Ejection therefore, becomes a two-step process. The first step is rotating the handle to rotate the pawl to eject the board from its connectors. The second step is further rotating the handle to horizontally (laterally) translate (pull) the pawl out of engagement with the chassis keeper flange. This operation, and the resulting process is reversed for the injection process.  
         [0048]    [0048]FIG. 4 is a perspective top-wise view of the two-phase operation latch  43  of the present invention, mounted according to the IEEE standards to the outside of a PC board faceplate. The claw-shaped pawl  47  engages a flange-type keeper  49 . In the closed position, as seen in FIG. 4, the latch  43  presents a low-profile, with its thumb-end handle  51  folded down parallel with the faceplate  45 . A flat plate shaped catch  53  is mounted to pivot underneath the free end of the handle  51 . The latch has a base (or housing)  55  comprised of two juxtaposed plates  55  mounted to either edge of the faceplate  45 , FIGS. 4 and 5. These base plates  55  support the pawl, which operates there between, and the handle  51 . These base plates  55  engage the faceplate end projecting tabs  57  which each carry a square (or rectangular) slot  59  into which a respective foot  61  on each base plate  55  seats.  
         [0049]    The outboard extension of the faceplate  45  comprising the projecting tabs  57 , the interlocked base plate feet  61 , and the rectangular pawl opening  63 , FIG. 5, are new with the present invention and a part hereof. This added structure extends the faceplate shielding further than previously available and enhances EMC by providing greater EMF shielding. The claw portion of the pawl  47  has a solid bar upper lip  65  and a bifurcated lower lip  67 . This bifurcated lower lip  67  creates a pair of parallel projecting feet, which engage the adjacent openings  69  in the chassis keeper plate shown in FIG. 4.  
         [0050]    The faceplate  45 , FIG. 6, previously terminated in a square shoulder  71  which was spaced from the edge of the chassis keeper flange  49 , and slightly inboard of the spacing  73  provided for the operation of a pawl.  
         [0051]    This invention has added an extension  57   a  and associated structure onto the end of the faceplate, this being the solid portion  57   a  and a pair of outboard side tabs  57  extending there from. The rectangular (or square) slots  59 , which receive the feet  61  of the latch&#39;s left side and right side base plates  55 , each open onto the outboard edge of each tab  57 .  
         [0052]    The left base plate  55  is shown in perspective view in FIG. 7 and carries on the inside wall facing the opposite or right side base plate  55 , that side being its mirror image. There is an L-shaped cam slot  75  near the pawl end thereof and above the foot  61 , FIGS. 7 a - 7   e.  Adjacent this L-shaped slot is an oval-shaped pivot opening  77  with the rearward portion slightly cocked upward. Above the oval-shaped pivot opening  77 , and also being rearward towards the handle end of the plate  55 , is a arc shaped slot  79  traversing and arc distance of about 90 degrees about the oval-shaped pivot opening  77 .  
         [0053]    A French curve-like ramp surface  81  projects from the inward face of each base plate, to extend rearward of the arc shaped slot  79 , beginning just about below the edge of the oval-shaped pivot opening  77  and extending to a rearward positioned top planer surface  83  with a tapered leading edge  85 . This planer surface  83  which is formed on a shoulder structure has a ramped surface and a flat surface and carries a pair of holes  87  for assembly pins. A partial-cylindrical spacer  89  projects outwardly from the inner face of the curve-like surface ramp  81 . A further, longitudinally extending slot  91  extends adjacent the planer surface  83  and below the projecting cylindrical spacer  89 .  
         [0054]    The right base plate  55 , shown in FIG. 8 and in the respective various views FIGS. 8 a - 8   e,  are each respective mirror images of the left base plate, shown in FIG. 7, and the respective side, top, and end views FIGS. 7 a - 7   e.  The only departure from this mirror imaging is the pair of assembly pins  93  which extend inwardly from the inner face of the right respective planer surface  83  structure.  
         [0055]    The thumb handle  51  is shown in detail in the perspective view, FIG. 9, and in the. respective side, top, and end views FIGS. 9 a - 9   e.  Thumb handle  51  has a thumb engaging flat gripping portion  94  and a pawl engaging portion. The pawl engaging portion comprises the two parallel extending C-shaped (round) pawl engaging pickup plates  95 . Each pickup plate  95  has a curved outer edge and an outwardly projecting center pivot pin  97 , which engages the oval-shaped pivot opening  77 , in an adjacent, respective right and left side base plate  55 . A second, rearward positioned cam pin  99  engages the arc shaped slot  79 , in a respective side base plate  55 , and controls the degree of pivoting of the handle  51  and its gripping portion, from the horizontal to the vertical, for traversing 90 degrees of rotation.  
         [0056]    The pickup plates  95  each have a pickup slot  101 . Each slot  101  has a curved bottom and parallel faces. The pickup slots  101  are paired to engage a respective projecting pin on the pawl  47  which will be discussed below. A pivot boss  103  is positioned on the bottom face of the thumb gripping portion  93  slightly inboard of the free end thereof, thereby providing a structure for the catch plate  53  to pivot on.  
         [0057]    The claw-shaped pawl  47  is shown in FIG. 10 in a perspective view, and in a side, top and end views, respectively, in FIGS. 10 a - 10   e.  This pawl has the upper lip  65  and lower bifurcated lip  67  at one end and an elongate bar-shaped body extending rearward there from. Approximate the claw end  105  of the pawl is a pair of tear-drop shaped pivot pins  107 , each with a cam lobe  107   a  at the end thereof, to form a tear-drop end shape. These pivot pins  107  extend outwardly from each side of the pawl  47  and are the pivot stub shafts thereof.  
         [0058]    The elongate body  105  of the pawl  47  has paired opposite sidewall bump-ins  109 , each of which ride-against a respective partial cylindrical spacer  89 . Cam pins  111 , one on each side of the rearward end of the pawl body  105  mate with a respective one of the rearward facing longitudinal cam slots  91  in a respective side base plate  55 .  
         [0059]    The stub shafts  107  ride in the L-shaped cam slots  75  of a respective side base plate  55 . This L-shaped slot  75  allows the pawl  47  to first rotate and lift the latch  43  and attached faceplate  45  upward, and then forces the pawl to retract horizontally rearward (traverse the horizontal leg of the “L) once the full length of the upward leg of the “L” has been traversed.  
         [0060]    The tear-drop shaped stub shafts  107  are also simultaneously engaged with the pickup slot  101  of the handle  51  pickup plates  95 . The creates the movement of the pawl  47  when the handle  51  is moved. The L-shaped slot  75  and the rear horizontal slot  91  provide the primary direction of motion. The elongation of the oval-shaped pivot opening  77  and the cam lobe  107  forming the tear-drop shaped stub shafts  107  refine the motion.  
         [0061]    The catch plate  53  is shown in FIG. 11 in a perspective view, with the top, side and end views, respectively shown in FIGS. 11 a - 11   e.  This catch plate  53  has paired outside journals  113  though which a shaft (not shown) extends to mount the catch plate  53  on the paired catch pivot bosses  103  on the handle  51 . A projection  115  on the circumference of each outside journal  113  limits the movement thereof. The inside face of the catch plate  53  carries a circular cavity  117  for holding a compression spring  119  shown in FIG. 13. This spring acts to bias the catch plate  53  away from the bottom of the flat thumb gripping portion  94  of the handle  51 .  
         [0062]    A transversely projecting hook  121  extends from the inboard edge of the catch plate  53  towards the bottom face of the handle  51 . This hook  121  engages the very rearward edge  92 , seen in FIGS. 7 b,    8   b,  of each of the right and left side base plates  55  shown in FIGS. 7 b  and  8   b,  to hold the handle  51  in a fixed position with regards to the base plates  55  and fixed parallel to the faceplate  45 . Pushing against the catch  53  to depress the spring  119  moves the hook  121  and permits the handle  51  to rotate.  
         [0063]    The separate alignment pin block structure  58 , FIG. 5, is shown in detail in the perspective view of FIG. 12. The back, side and end views, respectively, of this alignment pin block  58  are shown in FIGS. 12 a - 12   e.  This block  58  has a bracketed back plane  123  with a plurality of rectangular through-holes  125  and two mounting tabs  127  each with a screw hole  129 . A larger tapered lead guide pin  131 , with successive diameters each leading into with a tapered shoulder, extends from the larger of the two tabs  121 . A cylindrical stub pin  133 , which acts as the smaller seating pin, extends from the smaller of the two tabs  121 .  
         [0064]    [0064]FIG. 13 shows the latch  43  in the closed and locked position. FIG. 14 shows the latch  43  after it has been unlocked by moving the catch  53  to have its hook  121  release the base  55 . FIG. 15 shows the latch after the handle  51  has been rotated to about 75 degrees of rotation. This is the transition for the pawl  47  to change over from rotational motion to rearward, horizontal, longitudinal motion. This occurs at the point where the lower bifurcated lip  67  has fully lifted the board  21  out of its connector socket. FIG. 16 shows the handle  51  fully rotated to the 90 degree position and the pawl  47  with its chassis  49  engaging upper and lower lips  65 ,  67  free of the chassis flange  49 .  
         [0065]    Referring to FIGS. 13-16, from the fully inserted configuration (closed) FIG. 13, latch is moved to the unlocked position, FIG. 14, then to the board ejected position, FIG. 15, and finally to the fully open position, FIG. 16. Reinsertion of a board reverses the process.  
         [0066]    In operation, the pawl  47  undergoes two distinct motions, those being first rotating against a portion of the chassis to eject the PCI board (by ejecting the face plate  45 ), then sliding out of the way to disengage itself from the chassis frame  49 . The handle  94  accomplishes this two-motion pawl operation in one 90 degree rotational stroke of the handle  94 , utilizing a “short-coupled” mechanical advantage during the pawl&#39;s rotation and ejection during the first 75 degrees of handle rotation, and then with a longer-coupled lever action during the remaining 15 degrees of handle rotation, whereby the pawl is more rapidly disengaged by its longitudinal sliding away from the chassis engagement position.  
         [0067]    The secondary catch hook  121  keeps the handle positively locked in the closed position until it is released. The catch  53  must be operated to release the hook  121  to in turn release the handle  94  for its operation.  
         [0068]    The compound operation of the latch is accomplished because the handle and pawl pivot about two separate pivot points, one being a real pivot point and the second being a “virtual” pivot point.  
         [0069]    For unlocking, ejecting and withdrawing a compact PCI board, the user first rotates the spring-loaded catch  53 , which releases the hook  121  from the base side plate  55  and allows the handle  51  to be rotated. As the handle  51  is rotated through 75 degrees, it pivots around the position “A” of the central elongate slot  77  in the base plates  55 . Slots “B” in the end of the handle  51  contact (ride on) the pins at position “C” on the pawl. The structure of the device thereafter allows a longitudinal movement of the handle away from the pivot position “C” by the sliding along the slots “B” of the handle  94 . The elongation of slots  77  and  91  permits this withdrawal of the pawl  47  from the chassis. The total amount of rotation of the pawl  47  from the closed position to the fully open position is about 15 to 20 degrees. This permits a small pawl opening  63  in the faceplate extension  57   a  thereby minimizing EMF leakage and enhancing EMC compatibility.  
         [0070]    The pawl rotates around the pin at position “D”, i.e., the cam pins  111  engaging the respective longitudinal slots  91 , and ejects the faceplate  45  and its attached PCI board from the chassis  49 . This ejection operation is under the leverage of the entire length of the pawl arm from pivot pin  107  to cam pin  111 . A further 15 degree rotation of the handle causes it to pivot around the end of the arc slots at position “E”, these being the arc slots  79  in the base halves, i.e., base plates  55 .  
         [0071]    The pawl pins  107  first move along the horizontal leg of the L-shaped slots  75 , then down the vertical leg of these slots  75 . In this regard, slots “B” drive the pawl pins “C” down the vertical portion of the L-shaped slots  75  in the base halves  55 , causing the pawl  47  to retract in order to disengage from the chassis  49  and allowing the PCI board to then be removed from the chassis. The ends of the pins “C” have a tear-drop shape, lobe  107   a,  which prevents them from beginning the vertical travel before the extraction rotation is completed.  
         [0072]    Insertion of the PCI board take an opposite sequence of operation and a reversal in travel paths. In the fully closed and the unlocked positions, FIGS. 13, 14, the handle  94  is close to the chassis  49  and the round pickup plates  95  of the handle are off of the curved ramp surface  81  of the base plates  55 . When the latch is in the fully open position, FIG. 16, the handle not only rotated, but has also laterally translated to have moved away from the chassis  94  and the round pickup plates  95  abut the curved ramp surfaces  81 .  
         [0073]    Many changes can be made in the above-described invention without departing from the intent and scope thereof. It is therefore intended that the above description be read in the illustrative sense and not in the limiting sense. Substitutions and changes can be made while still being with the scope of the appended claims.

Technology Classification (CPC): 7