Abstract:
A Personal Computer Memory Card International Association (PCMCIA) or other access opening of an electronic device is provided with a conductive cover which may be hinged or otherwise coupled to allow the cover to be moved from a covering position to an uncovering position. A highly conductive pathway is provided from the covering to the chassis or faceplate of the electronic device such as using a conductive washer in a hinge coupling. The conductive pathway is useful in reducing or preventing electromagnetic interface (EMI) from the access opening and in dissipating electrostatic discharge (ESD) before, during and after moving the cover to the open position and/or manipulation of the components behind the access opening.

Description:
The present invention relates to a cover apparatus and method for covering some or all of one or more openings provided for accessing components of electronic equipment and in particular to a grounded cover such as for avoiding or reducing electromagnetic interference (EMI) and/or electrostatic discharge (ESD). 
     BACKGROUND INFORMATION 
     A number of electronic devices are configured with openings to permit ready access to some of the components of the device (e.g. without requiring opening the entire chassis of the electronic device). In many situations, ready access involves providing access through a wall or panel which is typically exposed, such as a front panel. For example, many computers, network devices (such as routers, switches, bridges and the like) and other equipment provide one or more PCMCIA openings or slots (i.e. openings configured to receive cards in accordance with the PC Card Standard promulgated by Personal Computer Memory Card International Association e.g. at http://www.pc-card.com/pccardstandard.htm) for receiving and removing components such as disk drives or other storage devices or media, modems, network connection cards and the like. While providing such openings is convenient when it is desired to insert or remove components or media, non-covered (or easily uncovered) openings can present a security risk (e.g. a risk of theft or other unauthorized removal, tampering and the like) particularly when the accessible components are relatively expensive. Furthermore, in some devices a function of the accessible component may be critical to operation of a larger system, such as a computer network, Internet, telephone or other communication system and the like. Thus, the ease of accessibility afforded by openings for components also presents the risk that unauthorized or unintentional removal or manipulation of a component may cause catastrophic losses of a larger system such as disabling an entire telephone or computer network. Accordingly, it would be useful to provide a system which preserves the convenience of access to components, especially front panel access (without opening an entire chassis), while avoiding unauthorized or inadvertent removal or manipulation of components. 
     Many electronic devices such as computers, network or telephone equipment and the like are designed in a fashion to avoid undesirably high levels of electromagnetic radiation, extending beyond the chassis of the device which can result in undesirable effects on adjacent electronic equipment including so-called electromagnetic interference (EMI). Indeed, several standards for maximum allowable levels of EMI have been established such as the Network Equipment Building Standards (available from Bellcore). Some designs for avoiding EMI involve using a substantially conductive, preferably grounded, chassis substantially surrounding the electronic equipment forming, substantially, a Faraday shell. Provision of openings in the chassis, such as openings as described above, create a risk of breaching the Faraday shell allowing an undesirable increase in potential EMI. One approach which has been used in this regard involves constructing a pocket (With suitable covers or connectors) for receiving the removable component or medium, made of a conductive material in electrical continuity with the chassis. This approach can be somewhat expensive and often requires utilization of substantial space within the chassis, which may be at a premium, particularly when the chassis itself must conform to certain standard sizes or form factors such a so-called rU form factors. Accordingly, it would be useful to provide a system for avoiding or reducing EMI from component-access openings with relatively low cost and space requirements. 
     Many electronic components, including those designed to be accessible without fully opening a chassis, and/or which are front-panel accessible, can be susceptible to voltage surges such as those that may be caused by electrostatic discharge (ESD) including components such as high density disk drives. In such susceptible components, ESD or other voltage surges can lead to malfunction and/or permanent damage to the component. Moreover, when the component is critical to functioning of a larger system such as a computer network or telephone system, ESD or other voltage surges can lead to catastrophic loss of function of an entire system. A number of standards setting acceptable levels of tolerable ESD have been promulgated, including, e.g., NIBS standards. Accordingly, it would be useful to provide a system which tends to ground or dissipate, in a relatively benign fashion, ESD or other voltage surges such as may otherwise occur when personnel touch or manipulate an accessible component in an electronic device. 
     SUMMARY OF THE INVENTION 
     The present invention, in at least one aspect, provides a substantially conductive cover for a PCMCIA slot or other opening which is grounded to the front panel or chassis. Preferably the cover can be moved from a covering position to an uncovering position while substantially maintaining a conductive path between the cover and the chassis or front panel. In one embodiment, the cover is hinged so that the cover remains physically (pivotally) coupled to the front panel even in the open position. In one case, conductive washers, bushings or similar components are provided in a system maintaining a conductive path to the faceplate during and after pivoting of a hinged cover. Preferably the cover is normally maintained in a closed position by a fastener configured such that opening the cover requires the use of a tool, e.g. to avoid inadvertent or casual opening. In one embodiment the cover is configured for automatic, preferably gravity-forced, closing of the cover. Preferably the fully closed cover is substantially sealed to the faceplate to form a substantially continuous conductive region, reducing or preventing EMI. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a faceplate and coupled card of an electronic device including a cover according to an embodiment of the present invention; 
     FIG. 2 is an exploded view of the device of FIG. 1; 
     FIG. 3 is a perspective view of a cover according to an embodiment of the present invention; 
     FIG. 4 is a front elevational view of the cover of FIG. 3; 
     FIG. 5 is a perspective view of a hinge bracket usable for mounting the cover of FIGS. 3 and 4; 
     FIG. 6 is a plan view of a spring contact washer of a type which may be used in mounting the cover according to an embodiment of the present invention; and 
     FIG. 7 is a cross-sectional view taken along lines  7 — 7  of FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a front panel  112  and/or card carrier coupled to a circuit board  114  and having a cover  116  positioned over an opening  218  (FIG. 2) formed in the front panel  112 . The opening  218  is sized and shaped to provide access to a component positioned at least partially in a space  222  aligned with the opening  218 , behind the panel  112 . The size and shape of the opening  218  and the space  222  (or the component located in the space) will depend on what type of component or components, and what type of access, are being provided. In one embodiment, the opening  218  is substantially the size of a PCMCIA slot and the space  222  is sufficiently large to accommodate a PCMCIA device. However, the present invention can be used in connection with a wide variety of sizes and shapes of openings  218  and spaces  222  and/or components, as will be clear to those of skill in the art after understanding the present invention. 
     The electronic device of which the circuit board  114  and cover plate  112  form a part, may be an electronic device which is intended for mounting in a rack. In the case of rack mounting, where a numerous electronic devices may be positioned in tight side-by-side locations, providing practical access to a component involves positioning an access opening  218  in the faceplate  112  which is exposed and accessible when the electronic device is mounted in a rack. In these cases, reduction of EMI may involve reducing or preventing radiation outwardly beyond the faceplate  112  and adequate grounding may involve providing a grounding path to the faceplate  112  which is typically, before, during and after cover rotation  141 , substantially grounded to the rack or is independently coupled to a grounding pathway such as by a ground wire. In other situations, the electronic device may be housed in a box or chassis  119 . In the case of a chassis-mounted electronic device, providing adequate access to a component may involve positioning one or more openings in any of the various chassis surfaces (including a faceplate or a rear surface). Providing adequate grounding may involve grounding either directly to the chassis  119 , grounding directly to a grounding wire, or grounding to the faceplate  112  which is attached to, or forms a surface of, the chassis  119 . 
     The cover  116  is preferably formed of a substantially conductive material such as zinc-plated beryllium copper alloy (BeCu). The depicted cover  116  is in the form of a hollow five-sided ( 323   a,b,c,d,e ) parallelepiped having first and second upstanding ears  324   a,b  with holes  328   a,b  alignable with holes  532   a,b  of a hinge bracket  534 . The hinge bracket  534  may be coupled, e.g. via hole  535 , to the (preferably conductive) faceplate  112 , e.g. using a rivet  236 , bolt, pin or similar device. Preferably the hinge bracket  534  is formed of a conductive material such as zinc-plated BeCu. Alignment of the cover ear holes  328   a,b  with the hinge bracket holes  532   a,b  allows the cover  116  to be pivotally coupled to the faceplate  112  e.g. using pins  238   a,b,  bolts, rivets, or similar devices. The pivotal coupling permits the cover  116  to be pivoted from the closed position shown in solid lines in FIG. 1 to a substantially open position  142  (fully or partially uncovering the opening  218 ) shown in phantom lines in FIG.  1 . 
     Preferably, one or more washers  744   a,b  are positioned between, and substantially in contact with, the cover ears  324   a,b  and the hinge bracket arms  546   a,b.  Preferably the washers  744   a,b  are formed of a substantially conductive material such as (optionally zinc-coated) BeCu. As described below, the conductive washers, in contact with the cover ears  324   a,b  and bracket arms  546   a,b  are useful in providing a good conductive pathway between the cover  116  and the faceplate  112  and/or chassis. Preferably, the washers  744   a,b  are shaped to provide good physical and electrical contact to both the cover  116  and bracket  434 , even during the process of rotating  141  the cover. In one embodiment, the washer  744  is configured with a plurality of legs  748   a,b,c,d  angled upwardly  752  with respect to the plane  754  of the main body  756  of the washer. Typically, the washer  744   a,b  will be somewhat compressed (against the urging of the resilient legs  748   a,b,c,d ) between the cover ears  324   a,b  and the bracket arms  546   a,b.  The configuration and position of the washer legs  748   a,b c,d,  whose resilient compression provides substantially constant contact of the washers with both the cover ears  324   a,b  and the bracket arms  546   a,b  during cover rotation  141 , are believed to provide a good conductive pathway between the cover  116  and the faceplate  112  (or chassis  119 ) even during cover rotation  141 . Other shapes of washers may be used and devices other than washers such as bushings, pins, bolts and the like may be used, in place of or in addition to washers, to provide a conductive pathway, as will be understood by those of skill in the art after understanding the present invention. The depicted invention is believed to be advantageous at least in terms of the aspects of requiring no welds, requiring relatively few parts, and in providing a configuration which is highly reliable and maintainable. 
     In the depicted embodiment, the cover  116  may be secured in the closed position e.g. by a captive screw  262  received through cover tab hole  464  and screwed into a threaded hole  266  on the cover plate  112  (or chassis  119 ). In one embodiment, the captive screw  262  is configured to discourage or substantially avoid loosening without the use of a separate tool. In this regard, the captive screw  262  may be provided with a substantially smooth, unknurled head. The head may be provided with, for example, a screwdriver slot, a hexagonal or security socket head and the like. 
     In one embodiment, the edge or perimeter (or portions thereof) of the opening  218  are engaged or covered with an EMI gasket or shield  268 , preferably formed of a conductive material such as BeCu. Suitable gasket material available from TECH-ETCH, INC., Plymouth, Mass. 
     In use, the cover  116  is in the closed position during normal operation of the electronic device. Preferably, the captive screw  262  is sufficiently tightly coupled to the faceplate that the edges  372 ,  374  of the cover  116  are compressed against the EMI shield  268  positioned at the edges of the opening  218  so that an effectively continuous conductive region or area is provided over the opening  218 , substantially preventing EMI in region beyond the faceplate  112  and cover  116 . 
     A user wishing to access the component aligned with the opening  218  will typically employ a screwdriver, wrench or similar tool to loosen the captive screw  262 . A configuration which requires the use of a tool for loosening the captive screw  262  effectively discourages or prevents a casual tamperer from opening the cover  116  and substantially avoids accidental opening of the cover  116 . In one embodiment, the captive screw  262  is formed of a substantially conductive material or has a substantially conductive plating. Before, during or after loosening of the captive screw, the user will typically grasp or otherwise contact the cover  116 . As described above, there is a substantive conductive pathway from the cover  116  to the faceplate  112  (and, typically, to a standard ground). In this way, even though the user may have accumulated a substantial static charge, such electrostatic charge will be dissipated to ground before the cover is opened. Any electrostatic or other voltage carried by the user will continue to be dissipated to ground as the user manually rotates  141 , the cover to the open position  142 . Because of the upper position of the rotation axis  134 , gravity urges the opened cover  142  towards the closed position and accordingly, the user will typically continue to grasp the (still grounded) open cover  142 . In this manner, the user continues to be grounded for any electrostatic charge while the user is removing, manipulating or otherwise contacting the (potentially ESD-sensitive) component through the opening  218 . Following insertion, removal or manipulation of the electronic component, the cover will be released by the user (so that gravity will cause the cover to rotate back to a closed position) or the user will manually move the cover to the closed position. Preferably, the user will retighten the screw  262  to reconfigure the cover sealingly adjacent the EMI shield  268  as described above. 
     In light of the above description a number of advantages of the present invention can be seen. The present invention provides a degree of security by discouraging, avoiding or preventing accidental, casual or unauthorized opening of the cover and/or access to components located behind the cover. The present invention substantially reduces or prevents EMI with respect to an access opening. The present invention provides a grounding or discharge path for ESD which is preferably provided continuously during unfastening the cover, opening the cover and manipulation of the component through the opening. The present invention provides for substantially automatic (i.e. without the need for separate human intervention or action) closing of the cover. The present invention can achieve the described (and other) features while requiring relatively few parts, few (or, preferably no) welds, in a fashion which is reliable and maintainable. The system provides high quality grounding, shielding and immunization functions. The security, EMI, ESD and other issues raised by the presence of an access opening, preferably are addressed by embodiments of the present invention regardless of whether the electronic device is configured as a rack-mounted device (which may not be entirely enclosed on all sides by a conductive chassis), or a chassis-based device. The moveable coupling of the cover  116  to the faceplate  112  avoids misplacing or setting aside a cover member (as might occur, e.g. if the cover  116  was completely disconnected form the faceplate during uncovering of the opening  218 ). Furthermore, top-most position of the rotation axis  139  means that the action of gravity will tend to automatically close the cover  116  after the user has completed his insertion, removal or manipulation of the electronic component. Thus, even if the user neglects or forgets to take any actions after the insertion, removal or manipulation of the electronic component, the cover  116  will substantially automatically (under the urging of gravity) return to an (at least partially) closed configuration, providing at least partial EMI/ESD and/or security functions. 
     A number of variations and modifications of the invention and be used. It is possible to use some features of the invention without using others. For example, it is possible to provide a cover that achieves EMI and/or ESD protection or functions without providing automatic closing of the cover. Although it is believed preferable to provide a good conductive pathway via a hinge connection, there is no theoretical reason why similar conductive pathways cannot be provided using conductive wires or straps welded, riveted or bolted to the respective components. Although it is believed advantageous to provide a cover which substantially remains coupled (e.g. via hinge) to the faceplate even when the cover is open, at least some advantages of the present invention, such as EMI protection, can be achieved using covers which are coupled to the faceplate via a snap or similar coupling (e.g. permitting the cover to be entirely disconnected from the faceplate). Although a hollow parallelepiped-shaped cover has been depicted, other shapes can be provided including a solid parallelepiped, a plate and the like. Although a number of components described herein have been indicated as advantageously formed of a conductive material such as BeCu alloy, other (possibly less conductive) materials and/or platings may be used in various situations such as copper, aluminum, silver, gold, steel and the like. Although it is believed advantageous to use the force of gravity for providing automatic closing, other automatic closing devices can be used such as spring-loaded hinges, resilient living hinges and the like. Although a tab and screw arrangement has been described for maintaining the cover in a closed position, other arrangements can be used such as a latch or clasp. 
     The present invention, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g. for improving performance, achieving ease and/or reducing cost of implementation. 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g. as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.