Abstract:
An edge guide arrangement for circuit boards is disclosed including a guide rail having a circuit board edge-receiving channel with a grounding strip therein. The grounding strip has clips at each end for resiliently grasping the guide rail thereby holding the grounding strip in its position within the channel. The grounding strip with its end clips can be standardized and inventoried in large quantities to be assembled to a variety of guide rails.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to printed circuit boards, and more particularly, it is directed to an edge guide and retainer for printed circuit boards. 
     2. Description of the Prior Art 
     Printed circuit boards provide the foundation on which electronic components such as resistors, capacitors, transistors, inductors, semiconductor chips and other discrete electronics are mounted. These circuit boards have the metal traces that provide electrical pathways to connect the electronic components to satisfy an electrical function or system requirement. While each circuit board can accommodate a large number of electronic components, in some applications several circuit boards may be needed to provide the necessary circuitry for the particular electronic product. In such cases, multiple circuit boards may either be mounted in a stacked arrangement, one board on top of the other or in a side by side arrangement. In any case, the board is typically mounted in an electronic chassis, being plugged into a card receiving connector at one end and guided by card guides along two side edges. 
     Such card guides conventionally take the form of a rail with a squared channel therein. The card guides are typically made of nonconductive materials such as plastic. While these conventional card guides are suitable for various applications, growing concerns about electromagnetic interference, radio frequency interference and electromagnetic contamination within electronic environments are necessitating reliable circuit board grounding solutions. Additionally, build up of electrical charges in the circuit card can result in damage to or ultimate failure of internal integrated semiconductor circuits or other circuit elements on the card as well as the electronic apparatus itself. Grounding may be particular important in application involving computer peripherals, accessories and removable media including hard drives, modems and external storage units. In order to mitigate the above problems, various grounding schemes have evolved. Circuit cards have been provided with conductive grounding contacts along the peripheral edge of the card in fixed locations. Cooperative grounding contacts such as clips or terminals are provided on the card-receiving connector or card guides. When the circuit card is slid into the card guide the circuit card grounding contacts line up and mate with the clips on the card guide providing a grounding pathway therebetween 
     While such conventional grounding schemes have been used in industry for many years, it would be advantageous to provide a grounding arrangement for the card receiving connector or card guides that could accommodate grounding contacts on various locations along the edge of a circuit card. Such a universal grounding clip arrangement that is also simple to manufacturer in large quantities and that provides a reliable grounding solution would provide an advancement in the art. 
     SUMMARY OF THE INVENTION 
     The foregoing mentioned disadvantages are avoided by a circuit board edge guide which has a grounding strip along its entire length. The edge guide has a squared channel adapted to guide a circuit card to its desired mounting position which typically is a connection with a card-receiving edge connector. A conductive grounding strip is mounted on the edge guide in the squared channel for engaging the edge of the circuit board and making electrical contact with any grounding contacts on the board&#39;edge. Accordingly, advantageously with the above described grounding arrangement provided along the extent of the edge guide, this circuit board edge guide can work with a variety of circuit cards with grounding contacts in various locations along the edge thereof. 
     The invention contemplates that the grounding strip be constructed as a universal structure for mounting on a variety of circuit board edge guides by simply clipping on. In the preferred embodiment, the grounding strip is formed from stainless steel having an elongated section, each end thereof having short integrally formed clips. As such, the grounding strip can simply be placed in the guide channel with the clips at ends clipped over the ends of the edge guide. Surprisingly, this simple grounding arrangement reliably affixes securely to the edge guide. Furthermore, the relative simplicity of this arrangement allows the edge guide and grounding strip to be made in large quantities and easily assembled. 
     The construction and operation of a preferred embodiment of the circuit board edge guide of the present invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an exploded perspective view of a circuit card edge guide in accordance with the principles of the invention illustrating the two parts, the edge guide beam and grounding contact conductive strip, prior to assembly; 
     FIG. 2 is a perspective view of the circuit card edge guide of FIG. 1 illustrating the conductive strip assembled onto the guide beam; 
     FIG. 3 is a perspective rear view of the circuit card guide shown in FIG. 2; 
     FIG. 4 is a cross-sectional top view of the circuit card edge guide showing the conductive strip arched to provide spring biasing action; 
     FIG. 5 is a perspective view illustrating a circuit board inserted between two circuit card edge guides; 
     FIG. 6 is a cross-sectional top view of the circuit card edge guide showing the conductive strip mounted flush to the edge guide beam; and 
     FIG. 7 is a perspective view illustrating a circuit card mounting framework. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and more particularity to FIG. 1, there is shown a printed circuit board edge guide  10  for providing grounding connection to the edge of a circuit board including an elongated beam  12  and a conductive grounding strip  14 . The elongated beam  10  has a channel  16  sized and shaped for slideably receiving the edge portion of a printed circuit board. More specifically, the elongated beam channel may take the form of a rectangularly shaped groove with a bottom wall  20  and two upright lateral walls  22  and  24 . The guide beam is preferably made of a plastic type material such as natural nylon or glass-filled nylon material, for example. A flared section of the groove at one end of the beam facilitates insertion of a printed circuit board into the edge guide. 
     The conductive grounding strip  14  is an elongated strip of metal which may be stainless steel, for example, which material resists corrosion, oxidation, has long shelf life and also resists reacting with most chemical and solvents used in electronic assembly processes. The width of the conductive grounding strip  14  is selected to fit in the channel  16  of the edge guide and overlie the bottom wall  20  thereof to form the grounding section  18  of the grounding strip. Conductive strip  14  has two integral end clips at each end of the grounding section  18 , which in this description of a preferred embodiment comprise short resilient hook or ear sections  30  and  32 . The conductive strip  14  can be easily mounted onto the elongated beam  12  by pulling on the resilient clips portions  30  and  32  to work the grounding section  18  of the conductive strip  18  into the channel  16  and clips  30 ,  32  behind the back wall  36  of the beam  12 , to provide the assembled combination shown in FIG.  2 . 
     The resilient clip portions are shown with more particularity in FIG. 3, wherein one clip portion  30 , is simply a bent over extension of the grounding section  18 , which resiliently seats directly on the back wall  36  of the beam  12 . The other clip  32  has a flared out end portion  38  with slot  40  therein. This clip by means of slot  40  is inserted over plug  42  of the beam to resiliently engage the beam. The beam in this particular embodiment has two plugs  42  shown on its back wall  36  which plugs insert into cooperative holes in the framework of the electronic unit such as a PC card housing (not shown). 
     The grounding section  18  of the conductive grounding strip  14  may be seated flush to the bottom wall  20  of the channel  16 , as shown in FIG.  6 . Alternatively, the grounding section may also be seated in the channel arching away from the bottom wall  20  of the channel, as shown with more particularity in FIG.  4 . In this alternative embodiment, the grounding strip provides a spring action against the side edge of a circuit board slid into engagement with the conductive grounding strip. When the edge guide  10  is mounted in an electronic chassis the two plugs  42  are inserted into cooperative holes in the framework, and one or both of the clips may be pressed between the back of the edge guide and metal frame work providing a grounding path from a circuit board through the grounding strip to the chassis framework. 
     Typically, two edge guides  10  are attached to a framework structure  60  in opposed relationship to guide a printed circuit card  50  into its desired position in an electronic assembly, as shown in FIGS. 5 and 7. The printed circuit card (PC card)  50  is inserted into the open flared ends of the recessed guide paths or channels  16 , slid along the opposed card guides  10  and plugged into an end connector  58 , such as a mother board connector, input output I/O connector, daughter card connector, for example. As such, the card guides  10  provide alignment of the PC card to such end connectors. 
     The framework structure  60  may include a metal base member  62  which has a plurality of vertically disposed metallic posts  64  each post having holes for receiving the plugs  42  on the back wall of the edge guide. The clip portion  32  of the conductive strip  14  is sandwiched between the vertical post and the back of the edge guide, in conductive engagement with the vertical post. A conductive path is thereby provided form the edge of the PC card  50  through the conductive strip to the metallic post and the metal base. Other vertical posts  70  support and position each of the end connectors  58  in alignment with a pair of edge connector. Any number above described edge guide arrangements could be mounted in a housing with the above-described framework providing for a number of PC cards needed to form the electronic apparatus desired such as a personal computer, medical apparatus or avionics equipment. 
     There has thus been described an improved edge guide which can be reliably preassembled and used during handling and assembly of single or multiple circuit board structures. Large quantities of edge guide or grounding spring can be readily manufactured at relatively low costs. Thus, large customer demands for product can be met quickly and reliably. Advantageously, one grounding contact arrangement can be used with a variety of edge guides. Accordingly, various modifications of the edge guide will occur to persons skilled in the art without involving any departure from the spirit and scope of the invention as set forth in the appended claims.