Abstract:
A circuit card includes a key receptacle and at least one movable braking member, holding the circuit card in place within a card receptacle of an electronic device when a key is not fully inserted within the key receptacle. When the key is so inserted, the circuit card can be easily removed. Preferably, the key includes a releasable latch holding the key within the key receptacle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates computer hardware security and, more particularly, to an apparatus for selectively securing an externally accessible circuit card within a computing system or other electronic device. 
     2. Summary of the Background Art 
     As data becomes increasingly available in encoded formats that require an electronic device, such as a computing system, to make the data visible and usable, there is an increasing need for various organizations to make such devices publicly available under certain conditions. For example, libraries frequently provide computing systems for use by the public within the library to aid in finding and displaying information as required. A library may wish to make laptop systems available in this way in order to provide convenience of use and further to avoid the dedicated space requirements associated with the use of desktop computers. 
     One problem with making laptop computers publicly available in this way arises from the fact that, while the computers themselves are large enough to make their theft difficult, externally accessible cards, known as PC Cards, are small enough to be easily concealed and stolen. Such cards are often needed to provide a laptop computer with functions needed within such an environment, such as an ability to connect to a wired or wireless network. 
     PC Cards are built according to the standards of the PCMCIA (Personal Computer Memory Card International Association) to fit into slots that are now widely available on laptop computers, and to provide various functions that are not generally provided within the computers themselves, such as connection to networks. The slots are externally accessible, with the cards being readily installed and removed. Since the cards are the length and width of a credit card, with variations in overall thickness as provided by the PCMCIA standards, these cards are easily concealed and stolen. On the other hand, much of the usefulness of PC Cards arises from the fact that they can be easily removed and used in another standard computer, with the card mounting structures and connectors associated with the sockets being built to widely used standards. 
     Nonvolatile memory can also be added to a number of laptop computers and other electronic devices by installing removable cards having either the PC Card configuration or a somewhat different Compact Flash Card shape. 
     Therefore, what is needed is a way to make small, externally accessible circuit cards selectively difficult to remove, so that they cannot be easily stolen, while allowing the easy removal and replacement of the cards by personnel of the organization owning the cards and the computing systems. 
     In early personal computing systems, circuit cards and other optional small devices were held within the covers of the computer, with conventional locking mechanisms, having cylinders turned by keys, holding the covers shut to protect the devices inside. U.S. Pat. No. 5,169,332 describes apparatus protecting external devices, such as a cable connector, a terminator, or a shield covering a port connector from unauthorized removal by making the devices removable only through access within the locked covers of a computing system. 
     A number of other patents describe the use of additional conventional locks to prevent the removal of devices from computers and other electronic systems, or to prevent access to various parts of the systems. For example, U.S. Pat. No. 5,190,465 describes cover assemblies, fastened in place by conventional locks, for preventing the removal of an external cable from a computer. U.S. Pat. Nos. 4,655,057 and 4,964,286 describe the use of locking covers to prevent access to the slot in which a videocassette is inserted within a videocassette recorder. U.S. Pat. No. 4,685,312 describes the use of a locking device to prevent access to the slot through which removable media is inserted into a computer disk drive unit. 
     As some computing systems, such as laptop computers, became smaller and more portable, some of the functions provided by relatively large cards housed within the computing systems were assigned to the small, removable and interchangeable PC Cards. Again, what is needed is a way to prevent the unauthorized removal of such cards, preferably without requiring the use of bulky covers having locking cylinders and further without requiring modification to a conventional computer having provisions for using such cards. 
     Other patents describe methods for mounting printed circuit boards within electronic devices without addressing a means to provide for selective removal, requiring possession of a key, to prevent theft. For example, U.S. Pat. No. 6,424,542 describes a PC Card holder mounted on a circuit board, with a card retainer being mounted adjacent to the holder to prevent unintentional movement of the card out of an engaged position when the holder is subjected to vibrations. The retainer preferably includes a finger having a hook formed on a free end thereof that is yieldably biased into a position in which it blocks the unintended movement. When the card is being intentionally removed from the holder, movement of the card deflects the finger to allow passage of the card. U.S. Pat. No. 4,096,548 describes a circuit board that is retained in a fixed position within a rack frame by a leaf spring, flexibly mounted on the circuit board, which has a detent portion engageable in a recess in the rack frame. A rod mounted on the circuit board by a bracket is operable to engage the leaf spring and to move the detent portion into and out of engagement with the recess. U.S. Pat. No. 6,373,713 describes a mechanism for inserting, extracting, sensing, and locking a printed circuit board assembly in an electronic system with a single handle. 
     U.S. Pat. No. 6,269,005 describes the use of a pair of flexible arms having projections extending outward into slots within a PC Card retainer to hold a dummy card in a space within such a retainer, which has been configured for a relatively thick Type III card, above a relatively thin Type I or II card. The dummy card blocks an air passage that might otherwise allow dirt and dust to enter the computer. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a first objective of the invention to provide a means for preventing the removal of a circuit card from an electronic device without the use of a key. 
     It is a second objective of the invention to provide a means for allowing the easy removal and insertion of the circuit with the use of a key. 
     It is a third objective of the invention to provide a means for selective removal of a card from a standard PC Card slot without a need to modify the slot. 
     In accordance with a first aspect of the invention, circuit card apparatus selectively removable from a card receptacle is provided. The circuit card apparatus includes a circuit board, guiding surfaces, a key receptacle, a key, and a first braking member. The guiding surfaces are attached to the circuit board for guiding the circuit board into the card receptacle. The key is removably insertable within the key receptacle. The first braking member is movably mounted within the circuit card apparatus. The first braking member is held in an extended position, extending outward to contact the card receptacle, with the key removed from the key receptacle. The first braking member is held in a retracted position, displaced inward from the extended position, when the key is fully inserted in the key receptacle. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     FIG. 1 is a perspective view of a circuit card made in accordance with a first version of the invention, in an exploded relationship with an electronic device having a receptacle into which the circuit card is inserted; 
     FIG. 2 is a perspective view of the circuit card of FIG. 1, shown with a cover removed to reveal internal details; 
     FIG. 3 is a fragmentary perspective view of the electronic device of FIG. 1 with the circuit card of FIG. 1 installed therein; 
     FIG. 4 is a fragmentary perspective view of a circuit card built in accordance with a first alternative version of the invention, shown with a cover removed to reveal internal details; 
     FIG. 5 is a fragmentary perspective view of an electronic device and a circuit card built in accordance with a second version of the invention; and 
     FIG. 6 is a fragmentary perspective view of a circuit card made in accordance with the first version of the invention to accept a key different from the key of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a perspective view of a circuit card  10 , built in accordance with a first version of the present invention for insertion, shown in an exploded relationship with an electronic device  12 , having a card receptacle  14 , with the circuit card  10  being configured for insertion into the card receptacle  14  and for selective removal therefrom. The circuit card  10  includes a cover  16  forming a first guiding surface  18  extending along a first edge  20  of the circuit card  10  and a second guiding surface  22  extending along a second edge  24  of the circuit card  10 . A key  26  held within the circuit card  10  holds a first braking member  28  retracted within the circuit card  10 , allowing the circuit card  10  to be inserted into the card receptacle  14  and to be removed therefrom. When the key  26  is removed from the circuit card  10 , the first braking member  28  extends outward through a slot  30  in the cover  16 . 
     FIG. 2 is a perspective view of the circuit card  10  with the cover  16  removed to reveal internal structure. Preferably, the circuit card  10  additionally includes a second braking member  32  moving through a second slot (not shown) in the cover  16 , with each of the braking members  28 ,  32  being pivotally mounted within the circuit card  10  by means of a pin  34 . The circuit card  10  also includes a circuit board  36 , having a number of surface-mounted electronic modules  38  and a connector  40  including a number of sockets  42  through which external electrical connections are made to circuits extending along and within the circuit board  36 . 
     The circuit card  10  further includes a key receptacle  44  for guiding the key  26  as it is inserted into the circuit card  10  in an insertion direction of arrow  46  and as it is removed from the circuit card  10  in a withdrawal direction opposite the direction of arrow  46 . In the example of FIG. 2, the key receptacle  44  is formed by a key receptacle structure  48  extending under the key  26  as it is inserted into the circuit card  10 , together with an upper portion  50  of the cover  16  extending over the key  26  within the circuit card  10 . As the key  26  is fully inserted in the direction of arrow  46 , a distal end  52  of the key  26  extends through a pathway provided by a slot  54  within an interposing structure  56 . Preferably, the key  26  also includes key identification surfaces  58 , such as additional tabs forming an insertion limiting structure, that are unique to a type of key of which the key  26  is an example, while the interposing structure  24  includes an additional pathway, formed, for example, by slots  60 , that is unique to a corresponding type of card of which the circuit card  10  is an example. 
     The circuit card  10  additionally includes a spring member  62  extending between the braking members  28 ,  32  to hold the braking members  28 ,  32  in their extended positions, in which they extend outward through their adjacent slots  30 ,  34 , when the key  26  is not inserted into the key receptacle  44 . In the example of FIG. 2, the spring member is a “U”-shaped member, having a central portion  64  and a leg  66  at each end attached to the adjacent braking member  28 ,  32 . The legs  66  may be pressed into holes  68  within the braking members  28 ,  32 . When the key  26  is fully inserted into the key receptacle  44 , the distal end  52  of the key  26  deflects the spring member  62  into the bowed condition shown by dashed lines  70 . This deflection causes the braking members  28 ,  32  to pivot inward, as shown by dashed lines  72 ,  74 . 
     The key  26  also includes a pair of releasable latches  76  that contact latching surfaces  78  within the circuit card  10  as the key  26  is withdrawn, opposite the direction of arrow  46 , from its fully installed position. This latching function resists a tendency of the key  26  to be pushed outward by the deflected spring member  62  and facilitates handling the circuit card  10  with the key  26  installed. In the example of FIG. 2, the latching surfaces  78  form parts of the key receptacle structure  48 . Each of the releasable latches  76  includes an accessible portion  80  that extends outward from the circuit card  10  when the key  26  is fully inserted into the key receptacle  44 . When these two accessible portions  80  are pushed toward one another, the latches  76  are released by being moved to clear the latching surfaces  78  as the key  26  is withdrawn. 
     With the key  26  fully inserted in the key receptacle  44 , the circuit card  10  may be withdrawn by pulling on a central portion  81  of the key extending outward from the key receptacle  44 , by pulling on the circuit card  10  itself if it extends outward from the card receptacle  14 , or by pushing a button (not shown), commonly provided with receptacles for PC Cards, that causes a mechanism to push the card  10  outward. 
     FIG. 3 is a fragmentary perspective view of the electronic device  12  with the circuit card  10  installed therein. Various elements, including the card receptacle  14 , the key receptacle structure  48 , a cable  82 , and a cable connector  84 , are shown as partly cut away to reveal internal structures. The circuit card  10  is shown in its fully inserted position, with the connector  40  of the circuit card  10  engaging the cable connector  84  so that individual pins (not shown) extending from the cable connector make electrical contact with the individual sockets  42  within the circuit card connector  40 . In this way, individual circuits within the circuit board  36  are connected to individual conductors within the cable  82 . 
     Referring to FIGS. 2 and 3, along each edge  86 ,  88  the card receptacle  14  includes a card guide surface  90  engaging the guiding surfaces  18 ,  22  of the circuit card  10  to guide the circuit card as it is inserted in the direction of arrow  46  and as it is removed opposite this direction. The first braking member  28  and the second braking member  32  in their fully extended positions drag against these guide surfaces  90  of the card receptacle  14  whenever the circuit card  10  is moved within the card receptacle  14 . When the key  26  is not inserted within the key receptacle  44 , the undeflected spring member  62  produces a torque on the braking members  28 ,  32  to establish a normal force acting between the card guide surfaces  90  of the card receptacle  14  and the braking members  28 ,  32 . In FIG. 2, this normal force is represented by an arrow  92 . 
     In particular, when an attempt is made to remove the circuit card  10  by pulling opposite the direction of arrow  46 , a friction force, represented by arrow  94 , brought about by sliding along the adjacent card guide surface  90  of the card receptacle  14 , produces a torque about the pivot pin  34 . This torque, which arises from the friction force acting through an offset distance  96 , increases the torque producing the normal force represented by arrow  92 , so that the braking member acts as a self-actuating, or locking, brake. Similar forces act on the second braking member  32 . This self-actuating property of the braking members  28 ,  32  helps to frustrate an attempt to remove the circuit card  10  without the key  26  inserted within the key receptacle  44 . 
     FIG. 4 is a fragmentary perspective view of a circuit card  100 , built in accordance with a second version of the present invention, which is shown with a cover removed to reveal internal structure. The circuit card  100  is identical to the circuit card  10 , described above in reference to FIGS. 1-3, except that geometrical parameters associated with the braking members  102 ,  104  and of the spring member  106  of the circuit card  100  have been changed to increase the effectiveness of the self-actuating property of these braking members  102 ,  104 . Specifically, the pivot pins  108  about which the braking members  102 ,  104  are pivoted are moved inward, away from the points  110  at which forces are applied to each of the braking members  102 ,  104  by contact with adjacent surfaces of the card receptacle  14  (shown in FIG.  3 ). These forces include a normal force represented by the arrow  112  and a frictional force represented by an arrow  114 , which arises whenever an attempt is made to remove the circuit card  100  without a key  26  inserted into the key receptacle  44  of the circuit card  100 . This change in the location of the pivot pins  106  increases the offset distance  114  through which the frictional force represented by arrow  116  acts to produce a torque increasing the normal force represented by arrow  112 , so that the self-actuating braking effect is accentuated. 
     Preferably, the central portion  118  of the spring member  106  is somewhat curved in its undeflected condition so that the braking members  102 ,  104  can rotate in the directions established by the friction forces represented by arrows  116  before the central portion  118  of the spring member  106  is pulled into a straight condition. The pivoting motion of the braking members  102 ,  104  in response to these friction forces may be limited by the straightening of the central portion  118  or by a pair of optional stops  120  providing rigid stopping surfaces. 
     FIG. 5 is a fragmentary perspective view of an alternate electronic device  122  with a circuit card  124  installed therein in accordance with a third version of the invention. A cover of the circuit card  124  and a portion of the card receptacle  126  of the electronic device  122  are cut away to reveal internal structure. The alternate electronic device  122  and the circuit card  124  are similar to the electronic device  12  and circuit card  10  described above in reference to FIGS. 1-3, except that the card receptacle  128  of the alternate electronic device  122  includes a slot  130  into which a braking member  132  extends when the circuit card  124  is fully inserted within the card receptacle  128  without the key  26  inserted in the key receptacle  44  (shown in FIG.  2 ). The slot  130  includes a stopping surface  134  that prevents removal of the circuit card  124  if an attempt is made to remove the card  124  without the key  26  inserted therein. 
     The first and second versions of the invention, as described above in reference to FIGS. 1-4, have the significant advantage of being operable with cards built as described above in standard, unmodified versions of computer systems and other electronic devices. In particular, the card can be configured to fit in a conventional slot for a PC Card or for a Compact Flash Card. There are three versions of a slot for a PC card, but they all have the same configuration of card receptacle guiding surfaces, such as the guiding surfaces  90  of FIG.  3 . Thus, the braking members, acting on these common guiding surfaces  90 , can be used in any of the three kinds of slots. The braking members can also be formed according to a slot pattern used to prevent the inverted insertion of a PC Card. 
     On the other hand, the third version of the invention, as described above in reference to FIG. 5, requires the electronic device to be modified to include the slots  130 . However, this version has the advantage of providing a positive stop to prevent removal of the circuit card without the key. 
     FIG. 6 is a fragmentary perspective view of a circuit card  136 , built in accordance with the first version of the invention to be identical to the circuit card  10 , described above in reference to FIGS. 1-3, except for changes in the key identification surfaces  136  of the key  138 , and in the pathway  140  for such surfaces through the interposing structure  142 . For example, keys for circuit cards of a certain type may be made to fit only in circuit cards of a corresponding type. If a skeleton key is needed to fit in cards of all types, it may have only a portion common to the types, such as the distal portion  142 . 
     While the invention has been described in its preferred versions or embodiments with some degree of particularity, it is understood that this explanation has been given only by way of example and that numerous changes in the arrangement and configuration of parts can be made without departing from the spirit and scope of the invention, as described in the appended claims.