Abstract:
An insulating guard is mounted over a backplane or motherboard in an electronic system that accepts hot pluggable circuit cards. The insulating guard has openings that expose only the connectors and allow a hot pluggable circuit card to be inserted without the possibility of shorting the backplane. In order to prevent contact between a card being inserted and adjacent cards that have already been connected to the system, the invention provides for insulating card dividers which are connected to the insulating guard and fit between adjacent cards. The card dividers can be attached to the insulating guard by parts which snap together, fasteners or adhesives.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to computer systems which utilize devices on printed circuit cards which may be added to or removed from the system the system is initialized and while the system is powered up. 
     BACKGROUND OF THE INVENTION 
     Complex electronic equipment is typically constructed as a set of printed circuit cards which connect to a backplane or motherboard (hereinafter together referred to as a backplane), wherein each printed circuit card contains a section or module of the equipment and the backplane contains the interconnections between the circuit cards. This construction allows cards to be physically removed and inserted into connectors or expansion “slots” which are, in turn, connected to the backplane or motherboard. The connectors allow a card and the associated peripheral to be easily added or removed from the computer system, thereby allowing for maintenance and system configuration, changes. 
     In many electronic systems, the printed circuit cards must be inserted or removed from their connectors in order to configure the system before the system is powered up or initialized. However, more recently, electronic systems have been designed so that some or all of the printed circuit boards can be inserted or removed from their connectors while the associated electronic system is powered up and continues to operate, a capability called “hot swapping” or “hot pluggable.” 
     Some standards that include hot swapping capability have been developed. For example, computers and peripheral devices which adhere to the Personal Computer Memory Card International Association (PCMCIA) standard permit the hot insertion and hot removal of peripherals and this standard is presently in common use with notebook and laptop computers. Consequently, many peripheral devices that adhere to the PCMCIA standard are already in existence. 
     Aside from obvious power surge problems that occur when a card is inserted into the system, one impediment to inserting or removing peripheral devices from some electronic systems while they continue to operate arises from operator error. For example, when the card is being inserted, the operator may inadvertently touch the card against another adjacent card or against exposed connections in the backplane or motherboard. The result is that an electrical short circuit is created which can apply power to inappropriate places in the inserted card or the existing cards and damage them. Since there is no way to predict how the shorts will occur, they cannot be eliminated by design. 
     Consequently, although hot pluggable cards are designed to be inserted and removed from. an operational system, in some cases their use is curtailed to prevent the possibility of a catastrophic failure. Accordingly, there is a need to prevent such a possibility. 
     SUMMARY OF THE INVENTION 
     In accordance with the principles of the invention, an insulating guard is mounted over the backplane or motherboard. The insulating guard has openings that expose a only the connectors and allow a hot pluggable circuit card to be inserted without the possibility of shorting the backplane. In order to prevent contact between a card being inserted and adjacent cards that have already been connected to the system, the invention provides for insulating card dividers that are connected to the insulating guard and fit between adjacent cards. In accordance with one embodiment, the card dividers are attached to the insulating guard by parts that snap together. In accordance with another embodiment, the card dividers are attached to the insulating guard by fasteners. In accordance with still another embodiment, the card dividers are attached to the insulating guard by adhesives. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
     FIGS. 1A,  1 B,  1 C and  1 D are plan, side elevation, cross-sectional and top elevation views of the insulating guard. 
     FIG. 2 is a perspective view of the insulating guard. 
     FIGS. 3A,  3 B and  3 C are plan, elevation and cross-sectional views of an insulating card divider. 
     FIG. 4 is a perspective view of an insulating card divider. 
     FIG. 5 is a perspective view of an electronic system chassis with the inventive insulating guard and card dividers in place. 
     FIG. 6 is a perspective view of an electronic system chassis with the inventive insulating guard and card dividers in place illustrating several printed circuit cards in place. 
     FIG. 7 is a perspective view of an illustrative backplane showing the electrical connectors into which circuit boards are inserted. 
    
    
     DETAILED DESCRIPTION 
     The inventive hot pluggable card insulating system comprises an insulating guard and one or more insulating card dividers. The insulating guard is shown in detail in FIGS. 1A-1D and FIG.  2 . FIGS. 1A,  1 B,  1 C and  1 D illustrate plan, side elevation, cross-sectional and top elevation views, respectively. The insulating guard  1  comprises a flat base panel  10  of generally rectangular shape which has a size and shape sufficient to cover a portion of the backplane used for hot. pluggable card connections. The insulating guard  1  is intended to cover the exposed electrical conductors on the backplane in the hot pluggable card area and one or more. hot pluggable circuit cards can be inserted through. the insulating guard and plugged into connectors on the underlying backplane. A number of rectangular openings, such as opening  13 , are provided to accommodate the edge connector of the circuit cards. The insulating guard  1  illustrated in FIGS. 1A-1D accommodates eight circuit cards; however, more or less printed circuit cards can be accommodated by changing the shape and size of the guard  1  without departing from the spirit and scope of the invention. 
     Each of the printed circuit card openings is surrounded by a raised flange, of which flanges  11 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24  and  26  are illustrated. The flanges guide the edge connector of a circuit card into position over the connector of the underlying backplane. The guard  1  preferably has stiffening ribs near the flanges, such as ribs  15  and  17 . Other rib configurations will be apparent to those skilled in the art. The flanges may also have stiffening bolsters, such as bolsters  19  and  21  molded along their edges. 
     The insulating guard  1  is preferably constructed out of a suitable insulating material such as a resin polymer material that is easily moldable. Suitable materials include General Electric Cycoloy C2950HF or Bayer FR110PC/ABS resin polymer materials. 
     In use, the insulating guard  1  is fastened over the backplane as illustrated in FIGS. 5 and 6. The fastening means can be any suitable mechanism. For example FIG. 1A illustrates four holes  42 ,  44 ,  46  and  48  located along the periphery of the guard  1 . These holes can accommodate hold down screws that fasten the backplane board to the equipment chassis and these hold down screws can be used to hold the guard in position. Screws other than the hold down screws can also be used. Preferably, each of holes  42 - 48  has a small raised land on the underside of the guard. Two of these lands are shown as lands  23  and  25  in FIG.  1 D. The lands provide a small clearance between the guard and the backplane board to prevent the guard from damaging the conductors on the surface of the backplane board. Other mounting mechanisms could be used such as clips or other fasteners which would allow the insulating guard  1  to be removed for maintenance purposes. For example, FIG. 1B shows insulating guard  1  and a back-plane board  89  with two clips  40  that fasten the guard  1  to the backplane board  89 . Although only two clips  40  are shown, additional clips may also be used. 
     The insulating guard  1  is preferably used with an insulating card guide mounted between each pair of circuit cards. In order to provide more integrity to the insulating system, the insulating guard and the card dividers are connected together. In a preferred embodiment, the card dividers snap onto the insulating guard. In particular, the insulating guard  1  has resilient fingers associated with each pair of connector slot flanges, which. resilient fingers are used to hold an insulating card divider in position between the flanges. For example, resilient fingers  30 ,  32 ,  34  and  36  illustrated in FIGS. 1A and 1D are located between flanges  24  and  26 . In a similar manner, identical fingers are located between each of the other flanges to hold the card dividers in position. Each of the pair of resilient fingers bend inward and have hooked ends (as shown in FIG. 1D) which grip the card divider as will be hereinafter described. The raised flanges,  11 - 26  and the resilient fingers  32 - 36  are shown in more detail in the perspective view of FIG.  2 . 
     The insulating card dividers are shown in FIGS. 3A,  3 B and  3 C that represent plan, elevation and cross-sectional views, respectively. Each insulating divider consists of an approximately rectangular planar panel  50  which may have raised stiffening rails  52  and  54  molded therein. Along one side of the card divider, mounted perpendicular to the flat surface of the panel  50 , is an extension shelf  56  that extends at right angles to the panel  50 . The extension shelf  56  has two holes illustrated as holes  58  and  60  through which the aforementioned resilient fingers in the insulating guard  1  can pass through, and expand outward and lock. The extension shelf may also have various stiffening ribs known to those in the art. The extension shelf  56  is shown in more detail in the perspective view illustrated in FIG.  4 . 
     The insulating card divider can illustratively be manufactured from the same plastic material as the insulating guard or from another suitable material. The card divider may also be provided with fingers  62  and  64  that slide into slots provided in the electronic module chassis as illustrated in FIGS. 5 and 6. 
     Although the insulating card dividers are connected to the insulating guard by the resilient fingers in a preferred embodiment, other means of fastening the two pieces together can also be used. For example, a card divider can also be fastened to the insulating guard by means of separate fasteners, such as screws or bolts. Alternatively, the two pieces can be fastened together by means of a suitable adhesive. This adhesive can be placed on surfaces  55 ,  57  and  59  shown in FIG. 3A in order to fasten the pieces together. 
     FIG. illustrates an electronic module chassis  80  comprised of two side panels  84  and  88  and two ends panels of which only end panel  86  is illustrated in FIGS. 5 and 6. The side panels  84 ,  88 , and the end panels  86  form an open box with the backplane card  89  mounted in the bottom. 
     FIG. 7 illustrates the backplane card  89  and shows a hot pluggable area  90  containing connectors  91 ,  92 ,  93 ,  94 ,  95 ,  96 ,  97 ,  98  and  99  into which circuit boards can be hot plugged. Also mounted on backplane board  89 , are a number of electrically conductive elements and conductors, of which elements  100 ,  102  and  104  and conductors  106  and  108  are shown. Without protection, a circuit board being inserted into one of connectors  91 - 99  could electrically short against one of these conductive elements and cause a failure. 
     In FIG. 5, the insulating guard  1  is shown mounted over the hot pluggable area of the backplane board  89 . FIG. 5 illustrates the insulating system with eight insulating card dividers mounted in position. In each card divider the resilient fingers of the underlying guard (for example, fingers  30 ,  32 ,  34  and  36 ) extend through holes  58  and  60 , respectively, in the extension shelf of the card divider and lock in position to hold the insulating card divider in position relative to the insulating guard  1 . The module chassis.  80  may have recesses, for example recess  82 , molded in its side with slots to receive one or both fingers  62  and  64  of each insulating card divider to hold the divider in position after the module is assembled. 
     FIG. 6 illustrates the module chassis  80  with a plurality of circuit boards  92 - 106  inserted in position between the insulating card dividers. As shown, any of printed circuit cards  92 - 106  can be inserted and removed with no danger of shorting between boards or shorting inadvertently against some exposed electrical elements on the underlying backplane  89 . 
     Although an exemplary embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. For example, it will be obvious to those reasonably skilled in the art that, in some implementations, the insulating card dividers may not be necessary. Other aspects, such as the specific materials utilized to manufacture a particular element, as well as other modifications to the inventive concept are intended to be covered by the appended claims.