Abstract:
An electronic printed board assembly comprises a printed circuit board which employs printed circuit card connectors electrically connected to components mounted on the board. The printed circuit board includes board level guides with slots for receiving correspondingly shaped ridges disposed on outer, lower portions of printed circuit card-bearing cartridges. The guides are preferably provided on only one side for each cartridge to improve packaging density. The surface guides, together with the cartridge design, eliminate the need for physical contact with surrounding enclosures or cabinets.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally directed to a system, method, and apparatus for packaging electronic circuit components. More particularly, the present invention is directed to a system for electronic component packaging which permits easy insertion and removal of fully populated circuit boards without having to remove printed circuit cards which have already been inserted into the boards. Even more particularly, the present invention is directed to systems, methods, and devices which enhance the ability to package electronic components in a dense manner while still being able to provide not only air cooling but which also provides an effective system for electromagnetic interference (EMI) shielding. 
     It should be appreciated that not all of the features of the present invention need to be incorporated into a single device or system. Many of the features found in the present invention may be employed independently from one another. In general, the present invention seeks to solve a number of problems with respect to electronic circuit packaging. In particular, it is desirable to employ printed circuit cards which can be easily inserted and removed from printed circuit boards without the removal of the board and without removal of any cabinet or enclosure surrounding the electronics package. In desired embodiments of the present invention, therefore, it is found that printed circuit cards are capable of being “hot plugged” into a printed circuit board. 
     Additionally, it is noted that, in preferred embodiments of the present invention, circuit components operate at relatively high frequencies. At higher frequencies, problems associated with the propagation of electromagnetic interference become more significant. Accordingly, for those situations in which higher frequency components are desired, there is a correspondingly higher desire to employ electromagnetic shielding systems. Thus, there should be provided a mechanism for providing EMI shielding that is commensurate with the notions of hot pluggability. In other words, the EMI shielding system should be compatible with the notion that printed circuit cards are removed and inserted from printed circuit boards which are themselves not pluggable. 
     Hot pluggable systems are shown in U.S. Pat. No. 6,062,894 issued May 16, 2000, and assigned to the same assignee as the present invention. However, in the system described therein, there is a dependence on the existence of an external cabinet to effect the vertical motion of the printed circuit card into a corresponding mating socket on a printed circuit board. The presence of physical contact between the mechanism for insertion and removal and an enclosure which surrounds a printed circuit board precludes the use of such devices in mechanisms for which the entire printed circuit board itself is removable. 
     It is also noted that the present discussion refers to printed circuit boards and printed circuit cards. As contemplated herein, the printed circuit board is the larger component into which at least one printed circuit card is inserted for purposes of electrical connection. The present invention places no specific limits on either the size of a printed circuit board or the size of a printed circuit card. In the most general situation, a circuit board is populated with a plurality of printed circuit cards. That is, the printed board has a number of printed circuit cards inserted therein. Accordingly, as used herein, the terms “printed circuit board” and “printed circuit card” are considered to be relative terms. However, it is also noted that one of the motivating factors in the design of the present invention is the fact that printed circuit boards are, when fully populated, relatively heavy and possess one or more connectors at the edges thereof. These board edge connectors typically possess a large number of electrical connections to accommodate the correspondingly larger number of electrical connections that must be accommodated for a board which is populated with a number of printed circuit cards. The present inventors have also contemplated a mechanism for insertion of the entire board in a tight space without the necessity of removing any of the printed circuit cards. Accordingly, some of the specific situations contemplated by the present inventors have also resulted in the inclusion of mechanisms for insertion and removal of fully populated printed circuit boards. 
     Normally the circuit board, the mother board if you will, is considered fixed and does not usually constitute a movable structure. Moreover, even in those circumstances where one might contemplate inserting or removing a circuit board, one would normally not consider such an operation without first removing the printed circuit cards from the board. Because a typical printed circuit board is often populated with a relatively large number of printed circuit cards, the size and weight of the circuit board is typically relatively large. Thus, one is normally presented with the problem of moving (in forward and reverse directions) a large, flat, relatively thin substrate. Particularly during insertion operations, such a physical structure is likely to experience bending and flexing motions typically referred to as “oil canning.” Accordingly, solutions to problems in the present art address this issue as well. 
     Accordingly, the present inventors are presented with the following sometimes competing packaging problems: oil canning, dense and close packaging, air cooling, electromagnetic interference shielding, hot pluggability, the desire to provide an easy to load cartridge for carrying printed circuit cards, mechanisms requiring a mechanical advantage for insertion and removal of entire circuit boards, the removal of fully populated boards and the insertion thereof, and means to provide a cooperative EMI shielding arrangement in a system which provides circuit board guide mechanisms which do not require physical contact with a surrounding enclosure or cabinet. 
     SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the present invention, a number of features are provided which together solve all of the competing problems indicated above. In particular, a significant aspect of the present invention is provision of a docking cartridge which serves as a printed circuit card carrier and which is capable, in and of itself, of inserting and removing electronic printed circuit cards. While the present invention is particularly suitable for the incorporation of printed circuit cards meeting the so-called PCI (Personal Computer Interface) Standard, the principles of the present invention are generally applicable to any printed circuit card having an edge connector which is insertable into a corresponding mating connector on a printed circuit board. The docking cartridge of the present invention includes an actuating mechanism for card insertion which is completely self contained and which does not rely upon any physical contact with an enclosure or cabinet. Rather, the docking cartridge of the present invention interacts with a single-sided cartridge guide mechanism which is provided at the printed circuit board level. Moreover, the docking cartridge of the present invention is provided with an easy load mechanism for the printed circuit card. In particular, the docking cartridge is provided with a front bezel which also constitutes part of an EMI shield mechanism and which is also pivotable with respect to a top cartridge wall structure. The top cartridge member is slidably disposed with respect to a circuit card carrier which contains corner clips and slidable adjustable mechanisms as shown in the aforementioned U.S. Pat. No. 6,062,894. The top member is thus slidably attached to a moveable carrier which moves the printed circuit board up and down so as to provide insertion and removal of the circuit board with respect to mating electrical connectors on the printed circuit board. 
     A front bezel of the docking cartridge is also provided with a mechanism for ensuring EMI shielding during the entire insertion and removal process. In particular, desirable circuit boards for use in connection with the present invention include a front EMI shield plate which has electrical contact with the front docking cartridge bezel. In particular, such desirable printed circuit cards having this plate also include, on the bottom of this shield plate, a tab portion which engages a flexible EMI shield strip which is disposed on an electrically conductive stiffener which provides protection against the aforementioned oil-canning effect and which furthermore provides its own degree of EMI shielding for board level circuits and components. The EMI shield strip used in the present invention possesses a geometric structure which renders it readily capable of being fabricated in stamping and forming operations. This EMI strip is disposed so that it includes slotted opening portions which engage edges of apertures found in parallel rows in the stiffener. The strip engages these apertures in one row and includes a flexible portion which extends into the opening in a parallel row of stiffener apertures. Thus, in accordance with the present invention, as the printed circuit is inserted into the printed circuit boards so as to make electrical contact with circuits on the board, there is also provided a continuous EMI shield as the tab on the printed circuit card engages a flexible tab portion on the EMI strip which is in electrical contact with the conductive stiffener. 
     One of the other significant problems addressed by the present invention is the fact that a fully populated circuit board is relatively heavy and typically possesses a large number of electrical circuit contacts thus increasing the force needed to provide proper electrical connection. The mechanism for providing this force should not be significantly large nor should it consume significant amounts of space. That is to say, the mechanism for inserting and removing the circuit board should be compact and consistent with the compact and dense packaging notions of the present invention. Furthermore, this mechanism should be compatible with the other structures provided herein, notably, the stiffener and the EMI shielding system. 
     The present invention incorporates two principle aspects. A first structural component utilizes an independent, self-contained cartridge for containing printed circuit cards intended for insertion into and removal from tight spaces. A second aspect of the present invention includes the structure of a printed circuit board which is usable in conjunction with the aforementioned cartridges. Furthermore, the cartridge and board system of the present invention cooperatively interact to provide EMI shielding mechanisms not only compatible with the easy insertion and removal of circuit cards, but which also provide a cooperative mechanism for the insertion and removal of an entire circuit board in its fully populated state, that is, with all printed circuit cards inserted and connected. 
     With respect to the first aspect of the present invention which relates to the cartridge for protecting, transporting, inserting, and the removal of printed circuit cards, it is noted that this cartridge includes three main components: a front bezel, a top cartridge wall member, and a movable carrier which is upwardly and downwardly movable with respect to the bezel and the top cartridge wall. The cartridge also includes a lever actuated mechanism attached to the top of the bezel which provides sufficient force for card insertion. The lever actuated mechanism of the cartridge is disposed in such a way as to provide both upward and downward forces to the movable carrier at a point along the carrier which is appropriate for both short and long printed circuit cards. The cartridge of the present invention also includes a side cover. In preferred embodiments of the present invention, the bezel is metal and is in continuous electrical contact with an EMI shield plate found on certain printed circuit cards which are desirably useful in conjunction with preferred embodiments of the present invention particularly when they operate at relatively high frequencies. These shield plates preferably include a lower tab portion which extends through an opening in the bottom of the front bezel and which engages an EMI shield spring which thus allows it to be electrically connected with a conductive stiffener affixed to the printed circuit board. 
     With respect to the second aspect of the present invention which relates to the printed circuit board itself, the board is provided with an electrically conductive shield and stiffener as mentioned above with respect to the incorporation of the tab and spring structures. Furthermore, printed circuit boards of the present invention include a nonconductive base member which is disposed on a side of the printed circuit board opposite the stiffener. This base support structure provides additional resistance to “oil canning” effects that can occur particularly in larger printed circuit board structures. The printed circuit board also includes special guides disposed at the printed circuit board level. These guides engage ridges disposed on side wall covers for the printed circuit card cartridges, as described above. A particular feature of the cartridges also includes a mechanism for interlocking adjacent cartridges. Accordingly, a desirable aspect of the present invention is the fact that the special guides employed herein do not require slot and ridge structures to be present on both sides of the inserted cartridge. This is significant in the present invention since this feature permits cards to be made thinner and accordingly increases the overall packaging density which, as described above, is a highly desirable aspect of the present invention. 
     The stiffener employed in conjunction with the printed circuit board includes a front row of parallel slots which are spaced to receive an EMI spring shield structure which cooperates with the cartridge structure to provide a continuous EMI shield. Additionally, the present invention also includes a force-producing mechanism which is capable of providing a significant mechanical advantage for insertion and removal of the printed circuit board itself, even when requiring all of the board edge connectors to be mated with corresponding off-board connectors. In preferred embodiments of the present invention, the insertion and removal mechanism for the printed circuit board includes a toothed arm which engages a wrench-activated pinion gear which is affixed to the above-mentioned stiffener at the front or leading edge of the printed circuit board. The toothed arm is pivotally connected to force-producing arms which include pins which ride in slots in the base structure which supports the printed circuit board from below. As the pinion gear is rotated, the combination of the toothed arm and the force-providing levers changes to and from a “T” and “Y” shape. Thus, as the pinion gear is rotated, the lever arms move in what is best described as a “backstroke” motion. These levers push against cabinet or enclosure pins and, in doing so, cause the insertion or removal of the circuit board, in its entirety, into or out of a mating electrical connector. 
     The cartridge of the present invention is also constructed in such a manner so as to employ components which are pivotally connected so as to enable easy insertion of printed circuit cards having various dimensions. In effect, the maximum size of a card employed in the present invention is thus determined by the height of the bezel and the length of the cartridge top. 
     Accordingly, it is an object of the present invention to provide a system for packaging electronic circuit components in tight spaces. 
     It is also an object of the present invention to provide an apparatus for inserting and removing printed circuit cards in tight quarters. 
     It is a still further object of the present invention to provide a cartridge which is capable of transporting, protecting, inserting, and removing printed circuit cards in a self-contained manner. 
     It is also an object of the present invention to provide mechanisms which support hot pluggability of electronic circuit cards and boards. 
     It is a still further object of the present invention to provide a mechanism which permits insertion and removal of fully populated electronic circuit boards. 
     It is also an object of the present invention to provide a cartridge, for containing printed circuit cards, which is easily loadable. 
     It is furthermore an object of the present invention to provide a system in which continuous EMI shielding is provided between an easily removable printed circuit cartridge and a printed circuit board. 
     It is yet another object of the present invention to provide a cartridge for printed circuit cards which is readily adapted to hold cards of varying sizes. 
     It is yet another object of the present invention to provide a system of interlocked printed circuit card cartridges and a supporting printed circuit board. 
     It is yet another object of the present invention to provide a mechanism by which an entire fully populated printed circuit board is readily inserted into and removed from the system in which it is electrically connected. 
     It is also an object of the present invention to provide a printed circuit cartridge card carrying mechanism which is compatible with air cooling of the components contained on the card. 
     It is a still further object of the present invention to provide a printed circuit board which is still nonetheless compatible with the incorporation of ancillary circuit components such as capacitors, resistors, heat sinks, and the like which extend upward from the printed circuit board. 
     It is a yet another object of the present invention to provide an EMI shield spring structure which is operative as a mechanism for providing electrical connections and EMI shielding continuity between a printed circuit card and an EMI shield structure disposed on a printed circuit board to which the card is also separately electrically connected. 
     It is a further object of the present invention to provide a guide mechanism on a printed circuit board for cartridge insertion so as to consume only a small space in the side-to-side direction, between loaded cartridges. 
     Lastly, but not limited hereto, it is an object of the present invention to provide an integrated printed circuit card cartridge and printed circuit board mechanism which provide compactness, air-cooling capabilities, EMI shielding, hot pluggability, and mechanical force advantages both for the insertion and removal of printed circuit cards and the insertion and removal of fully populated printed circuit boards. 
     The recitation herein of a list of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: 
     FIG. 1A is an isometric view illustrating a cartridge in accordance with the present invention; 
     FIG. 1B is a side elevation view of the cartridge shown in FIG. 1A; 
     FIG. 2 is a side elevation view of the cartridge shown in FIG. 1B except with the cover removed so as to provide a view of some of the interior components; 
     FIG. 3A is a side elevation view illustrating a preferred lever mechanism for card insertion and removal and more particularly illustrating lever arm positions when a card is fully inserted; 
     FIG. 3B is a view similar to that shown in FIG. 3A except that the lever positions shown are indicated when a card is a in the fully removed position; 
     FIG. 4 is an isometric view illustrating the combination of a top cartridge wall member together with a movable card-carrying mechanism; 
     FIGS. 5A through 5I illustrate a sequence of operations for the loading of a printed circuit card into the cartridge of the present invention; 
     FIG. 6 is an isometric view illustrating a cartridge of the present invention inserted into a single slot on a printed circuit board which also conforms to the requirements of the present invention; 
     FIG. 7 is an isometric view similar to FIG. 6 but more particularly illustrating the entire printed circuit board with a single cartridge installed; 
     FIG. 8 is an isometric view illustrating a detailed portion of a printed circuit board in accordance with the present invention and particularly illustrating a guide system as preferably employed herein; 
     FIG. 9 is an isometric view illustrating the bottom of a printed circuit board in accordance with the present invention and more particularly illustrating a preferable mechanism for circuit board insertion and removal; 
     FIG. 10 is an isometric view illustrating (in a detailed close up) a portion of the preferable board insertion and removal mechanism as shown in FIG. 9; 
     FIG. 11 is an isometric view illustrating the actuation mechanism for the drive arm shown in FIG. 9; 
     FIG. 12A is a side elevation, cross-sectional view illustrating the EMI shield system of the present invention particularly with respect to the cooperation between printed circuit board shield plates, cartridge bezels, EMI shield springs, and conductive stiffener structures; 
     FIG. 12B is a simplified view of the system shown in FIG. 12A provided to more particularly indicate movement of the components; 
     FIG. 13A is a top view of the EMI shield spring employed in conjunction with the EMI system of the present invention; and 
     FIG. 13B is a side elevation view of the spring shown in FIG.  13 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1A illustrates an isometric view of a preferred embodiment of the present invention. In particular, FIG. 1A illustrates cartridge  100  which contains printed circuit card  200  (visible in FIG.  2 ). Cartridge  100  includes front wall or bezel  130  which preferably comprises metal. Bezel  130  is pivotally attached to top wall member  120  of cartridge  100 . Side cover  110  is attached to bezel  130  at points  137  and  138 . Notably, side wall cover  110  includes ridge portion  111  extending along a bottom portion of wall  110 . Additionally, as an additional major component, cartridge  100  includes actuating lever arm  141  which is used to insert and remove printed circuit card  200  from printed circuit boards into which cartridge  100  is inserted. Additional appreciation of the operation of cartridge  100  is discernible from the side elevation view shown in FIG. 1B which particularly illustrates pivot point  144  for actuating lever arm  141 . By operation of lever arm  141 , an internal mechanism (not visible in FIG. 1A or  1 B) urges printed circuit card  200  having edge connector  201  into corresponding mating connectors ( 311  in FIGS. 6,  7 , and  8 ) on circuit board  300  whose construction is more particularly described below and which cooperatively interacts with cartridge  100  in several ways. 
     Top wall member  120  preferably comprises a polymeric material which exhibits sufficient stiffness to support the operation of the lever arm mechanism which is included in preferred embodiments of the present invention. Top wall member  120  also preferably includes apertures  121  near the front of the cartridge and aperture  122  near the read of cartridge  100  for the passage of cooling air for those situations where air cooling is desirable. Top wall member  120  is preferably formed to exhibit a generally U-shaped cross-section as a major portion of its structure. 
     Side wall  110  also preferably comprises a polymeric material which is substantially flat and is attachable to top wall  120  along the top edge of wall  110  using any convenient attachment means such as screws  176 ,  177 , and  178  as shown in FIG. 5H which is more particularly considered below. Significantly for the present invention, side wall  110  includes a raised portion or ridge  111  which extends along a bottom portion of side wall  110 . Ridge  111  may possess any convenient cross-section, however, a smooth-rounded cross-section is shown. The main feature of ridge  111  is that it possesses a cross-section which matches the cross-section of slots  351  provided in guides  350  (see FIG. 10) affixed to printed circuit board  300 . 
     Front wall portion (or bezel)  130  is pivotally attached to top wall member  120  at pivot point  137 . Front wall  130  also preferably includes mounting bracket  149  to which is attached actuating pivot arm  141  which is used as an external drive mechanism for insertion and removal of a printed circuit card  200  into a printed circuit board connector  311 . Front wall  130  preferably comprises a conductive material whenever it is desired to provide electromagnetic interference shielding. However, in those circumstances in which EMI shielding is not essential or desired, front wall  130  may comprise a polymeric material or other nonconductive material. Front wall  130  also preferably includes an opening in the front thereof through which printed circuit board shield plate  202  is visible. In other applications of the present invention, front wall  130  is provided with an opening in the front thereof so that access may be provided to various pluggable connectors that may be found on the front edge of a printed circuit card. Such printed circuit board connectors are disposed through the opening in front wall  130  and may include telephone line RJ-11 type connectors and the like. Front wall  130  also preferably includes one or more openings for the inclusion of light guides  132  which are optionally provided so that light indicators, such as LEDs found on the leading edge of printed circuit board  300 , may be viewed from external positions. 
     It is noted that the present invention incorporates a number of features that have been provided for specific purposes. For example, in those applications in which relatively high power levels are generated by an enclosed printed circuit card, it is desirable to provide top wall  120  with apertures ( 121  and  122 ) such as those shown in FIG.  1 A. However, if power dissipation is not a concern, such apertures do not have to be present. Likewise for those situations in which connector access to printed circuit card components is not necessary, front wall  130  does not have to be provided with an opening. In a similar fashion, in those situation in which electromagnetic interference is not an issue, front wall  130  may comprise materials which are not electrically conductive. In general, the nonconductive portions of cartridges manufactured in accordance with the present invention are preferably formed in polymeric molding operations. 
     The cartridge of the present invention is particularly useful in those situations in which it is desirable to have a relatively high component packaging density. Accordingly, it is desirable that cartridge  100  be shaped in as a thin a package as possible so that as many cartridges as possible may be disposed in adjacent positions. Accordingly, in preferred embodiments of the present invention, only cover  110  on one side is provided. In such embodiments, there is only one ridge  111  which engages mating guides  350  on printed circuit board  300 . The lack of necessity for providing a ridge and cover on the opposite side of cartridge  100  is eliminated. By eliminating this structure, cartridge  100  may thus be made thinner. In yet another variation of the present invention, in those circumstances in which a plurality of cartridges are inserted in adjacent positions, as is preferred in the present invention, cartridge  100  is provided with interlocking mating members  112  and  113  (see FIG. 6) which serve to slidably interlock adjacent cartridges. This further contributes to the strength and rigidity of the entire structure. This interlocking mechanism also contributes to the lack of a need for cover such as  110  to be provided on both sides of cartridge  100 . 
     FIG. 2 is a side elevation view similar to that shown in FIG. 1B except that cover  110  is removed so as to more particularly show and illustrate the internal components and the inclusion of cartridge  100 . In particular, FIG. 2 shows printed circuit card  200  with its edge connector  201  affixed in position with respect to carrier  150 . Carrier  150  is a movable portion of the present invention, and it is the part of the mechanism shown in FIG. 4 as described below which provides a description of a preferred mechanism for carrier  150 . FIG. 2 also illustrates that in those embodiments of the present invention in which air circulation is a desired factor, front wall  130  also preferably includes a plurality of apertures  131  which also facilitate the passage of cooling air. FIG. 2 also illustrates the fact that front wall  130  also preferably includes aperture  133  on the bottom thereof (see also FIGS. 12A and 12B) which provides an exiting path for tab portion  203  of EMI shield plate  202  (see FIG. 12A) which serves as part of an interconnnected EMI shield system. The remaining portion of FIG. 2 serves to particularly indicate the preferred system of linked lever arms which are employed to effect the desired motion of carrier  150  and printed circuit card  200 . The action and operation of this lever mechanism is more particularly illustrated in FIGS. 3A and 3B. 
     A preferred system of pivoting arms for moving carrier  150  is seen in FIGS. 3A and 3B. In particular, it is noted that pivot points  144  and  147  are fixed. In particular, pivot point  144  is preferably fixed in bracket  149  which is affixed to a point on front wall  130  at the top thereof as shown. Likewise, pivot point  147  is affixed on top wall  120 . In preferred embodiments of the present invention, top wall  120  comprises a polymeric material having a substantially U-shaped cross-section. As such, this provides a mechanism for extending a pin-like pivoting mechanism across the U-shaped channel. Thus, most significantly for the present invention, it is seen that the preferred leverage mechanism includes pivot points  144  and  147  which are fixed to front wall  130  and top wall  120 , respectively. The preferred levering mechanism includes external actuating arm  141 , as shown. Second arm  143  extends from fixed pivot point  147 . Connecting arm  142  linking external arm  141  with second arm  143  is also shown. Arm  141  and arm  142  are linked at pivot point  146 . Arm  142  and arm  143  are linked at pivot point  145 . Also notably for the present invention, at pivot point  145  there is provided a pin which preferably rides in a horizontal slot provided in carrier  150 . The motion of the pin in the slot is the mechanism preferably employed for imparting upward and downward motion to carrier  150 . 
     It is noted that FIG. 3A illustrates the position of the various arms employed in preferred embodiments of the present invention when printed circuit card  200  is fully inserted into board connector  311 . Likewise, FIG. 3B illustrates the position of a desired leveraging mechanism when card  200  is fully removed from board  300 . It is also noted that since front wall  130  is pivotally connected to top wall  120  at pivot point  137 , the mechanism shown in FIGS. 3A and 3B is particularly useful in that it permits the pivoting operation to occur by providing a longer distance between pivot point  147  and pivot point  146 , thus permitting extension of the configuration of the arms used for insertion and removal during bezel pivoting. 
     FIG. 4 illustrates the fact that carrier  150  preferably comprises two principal components: tail stock component  150   a  which possesses a certain degree of flexibility (as is discussed more particularly below in reference to FIG. 5B) together with flat wall member portion  150   b . Carrier wall portion  150   b  (also referred to herein using reference numeral  152 ) includes guide portions  153 . Guide structures  153  preferably include tongue and groove-like structures which serve to guide carrier  150  in a more uniform vertical motion with respect to top wall  120 . FIG. 4 also illustrates adjusting bracket  151  which includes a top portion (not visible) which rides in a toothed slot along tail stock  150   a  and includes a ratchetting pawl together with a release mechanism such as that shown in the above-referenced patent issued in the name of one of the inventors herein. Adjusting bracket  151  therefore provides a mechanism for holding various sizes of printed circuit cards in carrier mechanism  150 . 
     Attention is now directed to the sequence shown in FIGS. 5A-5I. This sequence illustrates the easy loading aspects of the present invention with respect to the placement of printed circuit cards therein. A parts list for a cartridge in accordance with the present invention includes: (1) bezel and linkage subassembly (front wall  130 , top wall  120 , linkage mechanism  141 - 149 , and carrier  150 ); (2) cover  110 , clip  154 ; (3) short card arm  155 ′; (4) long card arm  155 ″; and (5) eight screws ( 171 - 178 ). 
     In preferred embodiments of the present invention, printed circuit card  200  to be inserted is a standard PCI (Personal Computer Interface) card. However, the present invention is not limited to the utilization of these specific printed circuit cards. 
     The process for inserting card  200  into cartridge  100  of the present invention begins with a consideration of FIG.  5 A. Printed circuit card  200  is oriented as shown by loading the upper front corner of card  200  into clip  154  and rotating card  200  so that it engages its heel portion with slot  156 . This operation is done for both short and for long printed circuit cards. To accommodate cards which are short in height, clip  154  is slid down until the card is held securely at clip  154  and at heel  156  together. For a detailed description of appropriate sliding mechanisms for carrying out this operation, attention is directed to the above-mentioned patent. The operation shown in FIG. 5A is performed with front wall or bezel portion  130  rotated out of the way, as shown. 
     Next, as illustrated in FIG. 5B, tail stock portion  150   a  of carrier  150  is bent down ( 150   a ′) to allow for either short card arm  155 ′ or long card arm  155 ″ to be attached to carrier  150 . In particular, carrier  150  with tail stock portion  150   a  is shown as  150   a ′ as being bent down in FIG.  5 B. Arms  155 ′ and  155 ″ (not both present at the same time) are provided for slideable adjustment along tail stock  150   a  of carrier  150 . In particular, in preferred embodiments of the present invention, these arms slide in a ratchetting toothed strip and are provided with releasable pawl mechanisms for snugging up against inserted printed circuit card  200 . Again, attention is directed to the above-referenced patent which is incorporated herein by reference. To position arm  155 ′ and  155 ″ onto a card edge, the arm is slid horizontally. When the arm is squared to the card edge, the arms are pressed against the edge so as to engage clip or heel portions found on the bottoms of short or long card arms  155 ′ or  155 ″. 
     FIG. 5C illustrates the fact that front wall or bezel  130  may also be temporarily removed from top wall  120  to accommodate passing tab  203  on shield plate  202  of printed circuit card  200  through aperture  133  provided for that purpose in the front of bezel  130 . FIG. 5C also illustrates the relative positions of adjusting arms  155 ′ and  155 ″ (short card and long card positions, respectively). 
     FIG. 5D illustrates several additional features of the present invention and further aspects of assembly. In particular, FIG. 5D illustrates the presence of brace  136  which extends from a bottom portion of front wall  130  in a substantially diagonal direction so as to be affixable to top wall  120  at point somewhat distal from the top portion of front wall  130 . Bracket  136  preferably comprises metal. It is attached to front wall member  130  by any convenient means particularly including spot welding. Bracket  136  provides additional rigidity which is found to be at least somewhat desirable when polymeric components are employed. 
     Additionally, FIG. 5D illustrates the presence of notch  139  in the side of front wall member  130 . Notch  139  is provided to permit easy passage of clip or heel  156  as front wall  130  is reattached to the assembly during loading operations for printed circuit cards. A more detailed view of this notch is provided in FIG.  5 E. 
     Next is considered the illustration shown in FIG.  5 F. FIG. 5F illustrates yet another aspect of the present invention. In particular, FIG. 5F illustrates the relationship between top wall member  120 , front wall or bezel  130 , and moving carrier  150  which includes tail stock portion  150   a  and flat plate portion  150   b . In particular, FIG. 5F illustrates the presence of brace  136  which extends from bezel  130  to top wall member  120  to which it is ultimately attached via two screws  171  and  172  (see FIG.  5 G). Since one of the objects of the invention is to provide as thin a profile as possible, while still preserving structural rigidity, it is seen that carrier plate portion  150   b  also preferably includes recess  157 . The presence of recess  157  permits brace  136  to be mounted in corresponding recess  129  in top wall channel support  120  using screws  171  and  172  as shown in FIG.  5 G. Additionally, it is seen that top wall  120  and movable carrier  150  both include mating slidable portions  153  which provide improved guidance to more readily ensure vertical motion as lever  141  is actuated. Tongue and groove structures are employed to provide suitably mated sliding portions. It is also seen in FIG.  5 F and in FIG. 5G that front wall or bezel  130  includes notch  139  which is provided for ease of assembly and, in particular, for ease in passage of clip  156  (see FIG.  5 A). 
     In addition to the features shown above, it is seen that FIG. 5G indicates the presence and utilization of adjustable arm  155 ′. In particular, the particular form of the adjustable arm shown in FIG. 5G is that which is used to support short printed circuit cards. Additionally, it is seen that FIG. 5G illustrates the presence of tab  204  which is preferably present on the top of EMI shield plate  202  which is attached to printed circuit card  200  (see also FIGS.  5 H and  5 I). In particular, this tab preferably includes stamped or pressed prongs which slide against the interior front wall portion of bezel  130  to provide continuous electrical contact for purposes of providing continuous EMI shielding as lever  141  is actuated to move carrier  150  and board  200  into position. It is also noted that, as this motion takes place due to the actuation of lever  141 , EMI shield plate  202  also moves downward so as to move tab  203  through opening  133  in bezel  130  (see FIG.  12 B). 
     FIG. 5H illustrates a final assembly operation for a cartridge in accordance with the present invention. In particular, it is seen that cover  110  is slid into position and is fastened to top wall member  120  using screws  176 ,  177 , and  178 , as shown. Lastly, front wall member  130  is pivoted into final position and affixed to the assembly via screws  174  and  175 , as shown. The completed assembly is shown in FIG. 5I in isometric view. 
     Having described cartridges for carrying printed circuit cards, attention is now directed to the printed circuit board intended for use in conjunction with the cartridges of the present invention. In particular, FIG. 6 illustrates cartridge  100  fully inserted into printed circuit board  300 . In particular, it is noted that ridge  111  on cover  110  slidably engages grooves or slots  351  in guides  350  which are affixed to printed circuit board  300  through openings in stiffener  330 . It is also noted that cartridge  100  preferably includes interlocking mechanisms  112  and  113 . If a cartridge in accordance with the present invention were to be inserted in the slot just to the right of the occupied slot in FIG. 6, its mating interlocking portion  113  would engage the corresponding mating interlocking portion  112  on the cartridge that is already shown. In this fashion when a plurality of cartridges are inserted into a printed circuit board in accordance with the present invention, there is formed an interlocking structure which provides enhanced strength, rigidity, and alignment characteristics. 
     FIG. 6 also illustrates the presence of a parallel row of apertures  331  and  332  present in stiffener  330 . These apertures accommodate the easy insertion of EMI spring shield member  500  which is more particularly described below (see FIGS.  13 A and  13 B). It is EMI shield spring  500  which is engaged by tab portion  203  of EMI shield plate  202 . Tab  203  is deployed downwardly through opening  133  in bezel  130  to provide continuous EMI shielding between card  200  and stiffener  330  which preferably comprises a conductive material such as metal when employed for EMI shielding purposes. 
     Attention is next directed to the apparatus shown in FIG.  7 . FIG. 7 illustrates a number of the cooperating subsystems of the present invention. As with FIG. 6, it illustrates the cooperative interaction between cartridge  100  and printed circuit board  300  particularly with respect to guides  350  present on board  300 . Guides  350  also include optional alignment tabs  353  which serve as helpful guides during cartridge insertion. In operation of the systems of the present invention, cartridge  100  is aligned with slots or grooves  351  (see FIG. 8) in guides  350  and is inserted so as to occupy the position as shown in FIG.  7 . At this point, lever arm  141  is actuated, preferably by a lifting motion, which causes internally disposed carrier  150  to move downward and to thereby insert card edge connector  201  into corresponding printed circuit board connector  311 . During actuation of lever arm  141 , plate  202  with tab  203  is moved likewise downward so that tab  203  makes contact with EMI spring shield  500  which is already in contact with stiffener  330 . 
     FIG. 7 also shows the preferable positioning for board insertion and removal mechanism  400 , or at least so much of that system as is visible in FIG.  7 . Additional aspects of board removal system  400  are more particularly described below. However, spur gear  411  and toothed arm  420  (see FIG. 11) are nonetheless visible in FIG.  7 . 
     FIG. 7 also indicates the inclusion of rear board edge connector  340  disposed on the back edge of board  300 . Also discernible in FIG. 7 is the preferred structure of the present invention in terms of the printed circuit board assembly itself. In particular, it is seen that board  300  includes insulative base  320 , printed circuit subboard  310 , and stiffener  330 . Stiffener  330  preferably comprises metal when employed for EMI shielding purposes. However, in those embodiments of the present invention in which EMI shielding is not a factor, nonconductive materials may be employed in the fabrication of stiffener  330 . However, in preferred embodiments of the present invention stiffener  330  preferably comprises a single stamped and formed sheet of metal. 
     As an additional observation with respect to FIG. 7, it is seen that, as is often the case with printed circuit board structures, certain circuit components extend upwards from its surface. Accordingly, it is seen that stiffener  330  may include selective apertures therein for the passage of components, such as capacitors  342  and/or heat sinks  341 . Those skilled in the electronic arts will readily appreciate that other components may be employed and may be positioned in different places with respect to stiffener  330 . 
     FIG. 8 provides a more detailed view of some of the structures seen in FIG.  7 . In particular, it is seen that circuit board connectors  311  are disposed between rows of board level guides  350 . In preferred embodiments of the present invention, guides  350  are formed from an integral polymeric structure as is readily fabricated in a molding operation. 
     Attention is next directed to the description of the mechanism employed in the present invention for the insertion and removal of entire circuit board  300  together with any cartridges  100  which may be inserted into and connected with the board. Preferred embodiments of this mechanism include rigid driving arm  420  with toothed portion  419  which is driven by spur gear  411  (see FIG. 11) which is affixed to plate  412  which in turn is attached to a formed portion of stiffener  330  (seen in greater detail in FIG.  11 ). Spur gear  411  preferably includes central hexagonal opening  413  for the insertion of an Allen wrench which causes rotation of gear  411  which moves drive arm  420  inwardly and outwardly in a recessed groove portion of base support member  320 . There is preferably provided at least one lever arm attached to drive arm  420 . In preferred embodiments of the present invention, two lever arms are provided. These lever arms,  421   a  and  421   b , are seen in FIGS. 9 and 10. Lever arms  421   a  and  421   b  are pivotally attached to drive arm  420  at pin or rivet  422 . Lever arms  421   a  and  421   b  also include pins  423   a  and  423   b  respectively as best seen in FIG.  10 . These pins ride in slots  360   a  and  360   b  respectively formed in base support member  320 . 
     In what is best as described as a “back stroke motion,” as drive arm  420  is driven inwardly, drive arm  420  together with lever arms  421   a  and  421   b  change configuration from a “Y” configuration as seen in FIG. 10 to a “T” configuration as illustrated in FIG.  9 . As the configuration of these arms changes, edges of arms  421   a  and  421   b  push against pins found on the enclosure or frame into which the board is inserted. These pins are located externally to the printed circuit board shown but are present at corresponding positions  430   a  and  430   b  on circuit board  300 . It is these positions which correspond to the pin positions on the external enclosure. Likewise, during removal operations, the other edges of arms  421   a  and  421   b  press against horizontally mounted external pins found in slots  435   a  and  435   b , respectively. These slots are present in base support member  320 . However, the pins which lie in these slots are in fact part of the enclosing apparatus or the frame into which the circuit board assembly is inserted. In this way, through a “reverse back stroke” operation, the entire board assembly is easily removed from the system into which it is connected. 
     FIG. 11 is also useful for illustrating part of the EMI shielding system of the present invention. In particular, FIG. 11 shows the inclusion of EMI spring shield  500  which is shaped to be readily inserted into apertures  331  and  332  in stiffener  330 . In particular, aperture  331  includes a forward edge which engages a forwardly facing slot or pocket (reference numeral  502  in FIG.  13 B). Accordingly, shield  500  includes an edge which is in firm electrical contact with stiffener  300 . The other edge of shield  500  includes a flexible portion  501  which extends through aperture  332 . The leading edge portion of shield spring  500  includes peak  504  which electrically contacts bezel  130  during cartridge insertion (see FIG.  12 A). FIG. 12A illustrates the insertion an edge of aperture  331  into slot or pocket  502  in spring shield  500 . FIG. 12A also illustrates the presence of printed circuit card shield plate  202  in its fully downward position extending through aperture  133  in bezel  130 . In doing so, tab  203  on plate  202  also electrically engages a portion of shield spring  500 . In particular, tab  203  engages edge  507  seen in FIG.  13 A. 
     FIGS. 13A and 13B provide a detailed description of the structure of EMI shield spring  500 . This spring shield preferably comprises a single sheet of stamped metal which is formed as shown. Preferable materials for this shield spring include beryllium copper ½ hard with an alternate of stainless steel ½ hard. FIG. 13A provides a top view of the desired structure, and FIG. 13B provides an end view. There are apertures in spring shield  500  between edges  505  and  507 . It is through these apertures that tab  203  is disposed so as to contact edge  507 . Region  509  is a tab region of the structure as is region  501 . Top or peak  504  engages the bottom portion of bezel  130 . Also of note is the presence of pocket or slot  502  which engages an edge of aperture  331  in stiffener  330 . In particular, it is noted that as stamped shield  500  preferably includes prongs  503  which are formed by the stamping operation employed in the manufacture of the shield spring. Prong  503  is also employed to provide improved electrical contact between shield  500  and stiffener  330 . It is further noted that FIG. 13B is particularly useful in that it identifies a plurality of surfaces or edges that are also visible in FIG.  13 A. Correspondingly numbered parts are shown in these two figures. 
     From the above, it is seen that the present application describes an interrelated system of structures and devices all of which are aimed at providing tightly packed, dense, well-shielded printed circuit board and cartridge structures which renders it possible to insert and remove entire printed circuit boards even when fully populated by printed circuit cards. In particular, it is seen that the printed circuit card cartridges of the present invention provide a cooperative housing and insertion structure for board level guides and which also incorporate an integrated EMI shield system which is fully operative before, during, and after card insertion. It is further seen that the system of the present invention includes a relatively stiff printed circuit board which is capable of sustaining insertion and removal forces even when fully populated with electronic printed circuit card components. 
     It is also seen that the present invention includes structures which provide continuous EMI shielding which mates with and matches shielding from a printed circuit card to corresponding EMI shield structures found on the printed circuit board itself. It is also seen that the cartridge preferably employed in the present invention includes pivotably mounted components which make printed circuit card insertion relatively easy. Lastly, but not limited hereto, it is seen that the system and apparatus described in the present application fulfills, either individually or collectively, in its various embodiments, all of the objectives set forth above though not necessarily all of them simultaneously. 
     While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.