Abstract:
A card guide assembly for isolating printed circuit boards from each other during insertion and removal from a mounting array. The assembly includes first and second isolation channels that are configured to permit the receipt of a variety of PC board sizes therein and a securement cap for receipt thereover. The cap may be adjustably positioned within the isolation channels for establishing a secured mounting for a variety of PC board sizes. A locking mechanism is provided between the cap and the channels for secured engagement therebetween. The channels are mounted on opposite sides of the PC board connector region permitting conventional mounting of the PC board into a mounting connector.

Description:
This application is a continuation of Ser. No. 08/659,004 filed Jun. 4, 1996, now U.S. Pat. No. 5,754,406. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to printed circuit board mounting fixtures and, more particularly, to a PC board card housing and guide for facilitating insertion and removal of the card from a mounting connector and preventing the electrical contacts on the card from shorting out against other cards during that process. 
     2. History of Related Art 
     Early designs of electrical circuits included a plurality of discrete components which were electrically connected to one another by means of wires. A major advance occurred with the advent of printed circuit boards whereby components were mounted on rigid insulative substrates and electrically interconnected with one another by a pattern of conductive leads formed on the upper and lower surfaces of the substrate by a photoresist and etch process. Each so-called printed circuit card is electrically connected with circuitry on other cards is by rows of electrically conductive plated fingers spaced from one another along both sides of one edge of the printed circuit card. The card edge containing the conductive fingers is received into a card edge connector in which each plated finger removably engages a connector contact for electrical connection to other circuitry on other printed circuit cards. 
     Rows of card edge connectors are conventionally mounted adjacent to one another in rows on a, so-called, motherboard with the printed circuit cards being received into each of the card edge connectors. The connectors mounted on the motherboard have their contacts interconnected with one another by means of similar conductive wiring placed on the surfaces of the motherboard. The use of the printed circuit card edge connector concept in the design of electronic equipment, such as digital computers, allows cards to be added and removed for repair, upgrade, and/or changes in functionality in the circuitry. 
     Originally, a rule of practice in the maintenance of electrical circuitry, such as computer hardware, was that of always turning the power to the motherboard off before cards were added or removed from the card edge connectors. Such a policy was for both reasons of safety of the technician as well as to avoid injury to the circuitry on the cards. 
     Recent innovations in this area have addressed the desirability to insert and remove printed circuit cards from electrical equipment, such as computer hardware, when the computer is electrically connected and operational, i.e. “hot.” In these cases, it is now possible to disconnect the power from only the connector of the card to be inserted and removed while allowing the adjacent cards to remain “hot.” In these situations, and because of the close spacing between adjacent card edge connectors on a motherboard, it is possible to inadvertently allow the plated fingers along the edge of the printed circuit card to touch an adjacent card which is hot and thereby produce a short circuit and create a hazard to the technician and the circuitry on both of the PC cards. Data stored within memory elements of the circuitry may be irretrievably lost when this occurs. It is thus important to minimize the exposure of adjacent PC boards during the insertion or removal process. 
     It would be an advantage therefore to provide a printed circuit (PC) board assembly that would eliminate the possibility of an electrical short while not interfering with the normal functional insertion and removal of the PC board assembly. The present invention provides such an assembly by providing a PC board card guide for securement to the PC board. The card guide is comprised of at least one pair of isolation arms in the form of a channel that is adapted to receive a wide variety of PC board sizes. The channel arms are configured to extend outwardly on opposite sides of the PC board forming a nonconductive bumper to eliminate accidental engagement between adjacent PC boards. 
     SUMMARY OF INVENTION 
     The present invention relates to a PC board card guide. More particularly, the present invention comprises a PC board card guide formed of electrically insulative material that may be assembled to the PC board to maintain its spaced relationship from adjacent boards during the insertion and/or removal process. The card guide comprises first and second isolation arms in the form of a channel adapted for receipt of the PC board therein and for placement adjacent one end of the connector region thereof. A securement cap is provided and adapted for receipt within the arms to secure a PC board therein in a generally parallel spaced relationship therewith. The cap is adjustable within the arms for affording flexibility in accommodating various PC board sizes. 
     In another embodiment, the above-described invention includes at least two channels for securement to the PC board on opposite sides of the connector region. Individual securement caps may be provided for each channel, or a single cap may connect both channels to secure the PC board therein. In another embodiment, the above described invention includes the isolation arms being formed with ridged side walls which are adapted for receiving the cap therebetween. The ridged side walls are constructed to form a ratchet assembly for facilitating securement of the cap and permitting the adjustable positioning of the cap to various sizes of printed circuit boards therein. The cap may include means for gripping the upper surface thereof for removal of the cap from the channel for access to the printed circuit board. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the method and apparatus of the present invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
     FIG. 1 is a perspective view of the several embodiments of card guide assemblies inserted within a computer chassis; 
     FIG. 2 is an enlarged, exploded view of one of the card guide assemblies of FIG. 1 illustrating the removal of a PC card therefrom; and 
     FIG. 3 is an enlarged side elevational cross-sectional view of a card guide assembly illustrating the placement of a PC board therein. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, there is shown a perspective view of one embodiment of a plurality of PC boards and card guide assemblies  10 ,  10 A and  10 B, constructed in accordance with the principles of the present invention. Each PC board and card guide assembly includes at least one channel member  12  which is adapted for receiving a printed circuit board (PC)  16  therein. A second channel member  14  is preferably used in association with first channel member  12  in one embodiment of the invention. A cap  18  is provided for securement over the printed circuit board  16  and may be mounted individually to each of the channels  12  and  14  as a single cap  17  or to both channels  12  and  14  as a double cap  18 . The double cap  18  extends between and is attached to each of the channels  12  and  14  for secured mounting of both channels to the circuit board. 
     Still referring to FIG. 1, the plurality of PC board and card guide assemblies  10 ,  10 A and  10 B of the present invention are shown either in, or being inserted in, an electric circuit housing such as a computer chassis  20 . A variety of combinations of card guide assemblies is also presented to illustrate the flexibility of the present invention as discussed below. Card edge connectors  22  within the hardware mounting chassis  20  are adapted for receiving each of a plurality of conductive contact fingers  26  which extend along opposed edges of each of the PC boards  16  and form a connector region  24 . Each of the contact fingers  26  are gold plated and adapted for removable engagement with mating contact fingers  28  mounted within the interior of the card edge connector  22 . The connector region  24  provides for both electrical and mechanical mounting of the PC board  16  when it is received within the card slot of the card edge connector  22 . However, misdirection or misalignment of the PC board  16  during insertion and/or removal of the PC board  16  from the connector  22  mounted within the computer chassis  20 , while the circuitry is “hot,” can cause inadvertent contact of the conductive fingers  26  along its connector region  24  with the conductive regions of the PC board within adjacent card edge connectors resulting in an electrical short. Electrical shorts create a safety hazard for the service technician as well as damage to both the PC boards and the computer. In some instances, a short can cause a computer to be shut down and/or the loss of valuable data. The PC board and card guides  10 A and  10 B of the present invention thus provide a means for isolating individual PC boards  16  one from the other during the insertion and removal process to prevent accidental shorting therebetween and for facilitating the insertion and removal process. 
     Referring still to FIG. 1, the variety of combinations of card guide assemblies permits accommodation of various PC board shapes and constructions. For example, PC board and card guide assembly  10  incorporates a PC board  16  of generally uniform size wherein channels  12  and  14  are received on opposite sides of connector region  24  with a double cap  18  received positioned thereacross. PC board and card guide assembly  10 A illustrates a PC board  16  of nonuniform dimensions wherein channels  12  and  14  are secured to opposite sides of connector region  24  by single caps  17 . PC board and card guide assembly  10 B illustrates a PC board of uniform width but which has mounted near one end a cable connector  9  to which is connected a ribbon cable  8  leading to external circuitry. The channels  12  and  14  are secured to opposite sides of connector region  24  by single caps  17   a  and  17   b.    
     As can be seen one of the caps  17   b  of assembly  10 A is positioned at a greater height in channel  14  than is the cap  17   a  within channel  12  to accommodate the differing widths of the different parts of the PC board with which they are in contact. Likewise, PC board and card guide assembly  10 B illustrates the accommodation of a ribbon cable  8  which is coupled to the PC board  16  by a cable connector  9 . The cable connector  9  also creates a height differential for the channels  12  and  14  on opposite sides of the connector region  24 , which height differential is accommodated by the two single caps  17   a  and  17   b  used in conjunction therewith. It may thus be seem that a wide variety of PC board shapes and sizes and/or peripheral component aspects thereof may be accommodated in accordance with the principles of the present invention. 
     Referring now to FIG. 2, there is shown a PC board  16  in the form of a hot plug PCI card which is to be inserted and removed from a card edge connector  22  on the motherboard  23  of a computer (see FIG. 1) while the power to the computer is turned on. Each of the first and second channel members  12  and  14  of the PC board assembly and card guide  10  include a pair of upstanding spaced apart arms  21  and  22  which are joined at the lower end by a transversely extending bottom (or lower) wall  23  to form a generally U-shaped channel member. The upper portion of the inside wall of each of the arms  21  and  22  has formed thereon an array of laterally spaced ridges  31  each of which extends transversely across the breadth of the inner wall from a first laterally extending shoulder portion  32  to a second laterally extending shoulder portion  33 . The ridges  31  are laterally spaced from one another and include inwardly extending teeth-like edges, each of which is angled downwardly away from the upper open end of the U-shaped channel member toward the transversely extending lower wall  23 . The teeth-like edges of the ridges  31  include a stepped surface  31   a  extending in a plane generally transverse to the longitudinal axis of the arms  21  and  22  and a ramped surface  31   b  extending in a plane at a sharp angle upwardly and outwardly from the longitudinal axis of the arms  21  and  22 . Preferably, the ridges  31  form one-half of a pair of ratchet surfaces as is further explained below. The transversely extending ridges  31  are shown in FIG. 2 as extending slightly more than half the length of each of the arms  21  and  22 , however, it can be seen that they may extend virtually the entire length of the arm if necessary to accommodate PC cards of relatively small width. The bottom wall  23  of each of the channel members  12  and  14  include a transversely extending slot  35  approximately the same width as the thickness of the printed circuit card  16  to snugly receive the edges of the card into the slot  35 . 
     The cap portion  18  of the PC board and card guide assembly  10  includes an flat, elongate body portion  36  within the lower surface of which is formed an longitudinally extending groove  37  approximately the same width as the edge of the printed circuit card  16  for snugly receiving that edge. The upper surface of the body portion  36  includes a pair of semicircular loop portions  41  which are firmly affixed to the upper surface of the body portion  36  so that upward pressure by the fingers of a technician within the loops  40  will serve to pull the entire PC board and card guide assembly  10  in the upward direction. 
     Both the U-shaped channel members  12  and  14  and the cap members  17  and  18  are preferably formed by molding from an electrically insulative material such as thermoplastic or nylon, however, other materials may be used as long as they are electrically insulative. 
     Two pairs of openings  41   a-b  and  42   a-b  are formed in the body portion  36  of the cap  18 . Each opening  41   a  and  41   b  is sufficiently wide to receive one of the arms  21  and  22  of the channel member  12  and each opening is spaced from the other approximately the same width as the distance between the arms  21  and  22  of the channel member  12 . Similarly, each of the openings  42   a  and  42   b  are wide enough to receive the arms  21  and  22  of the channel member  14  and the openings  42   a  and  42   b  are spaced from one another a sufficient distance to receive the arms  21  and  22  of the channel member  14 . Referring to both FIGS. 2 and 3, within each of the openings  41   a-b  and  42   a-b  is a tab  43   a  and  b  and  44   a  and  b , respectively, with each tab being positioned on the inside edge of each of the respective openings within which the tab is located. Each of the tabs  43   a-b  and  44   a-b  may, for example, be integrally molded with the body portion  36  of the cap  18  and include a upwardly extending tab release arm  45   a-b  and  46   a-b . Each tab is transversely displacable by pressure against its release arm tending to push the two adjacent tab pairs toward one another. Release of pressure on the tab release arms  45   a-b  and  46   a-b  allows them to resiliently spring back away from one another and partially the close their respective openings  41   a-b  and  42   a-b . The lower outside portion of each of the tabs  43   a-b  and  44   a-b  includes an engagement face upon which is formed a plurality of transversely extending ridges  51  for gripping engagement with mating ones of the ridges  31  on the insides of the arms  21  and  22  of the channel members  12  and  14 . 
     As best shown in FIG. 3, the ridges  51  on the outside edges of the engagement face of each of the tabs  42   a-b  and  43   a-b  are formed with sharp angular tooth-like edges each including a stepped surface  51   a  extending in a plane generally parallel to the upper surface of the body portion  36  and a ramped surface  51   b  extend in a plane extending at a sharp angle downwardly and inwardly from the upper surface of the body portion  36 . When the cap portion  18  is placed down over the upper open ends of the arms  21  and  22  of the channel members  12  and  14 , the upper ends are received into the opening pairs  41   a-b  and  42   a-b , respectively. Downward pressure in the direction of arrow  52  on the upper surface of the cap  18  causes resilient lateral displacement of the release arms of the tabs  45   a-b  and  46   a-b  toward one another so that the teeth-like ridges  51  and  31  on the tabs of the cap and the arms of the channel members, respectively, slide passed each other due to the engagement of the ramped surfaces of the respective ridges  31  and  51 . Once downward pressure on the cap  18  in the direction arrow  52  is released, the stepped surfaces of each of the respective ridges  31  and  51  engage each other to lock the cap from upward movement thereby gripping the printed circuit board  16  between the grooves  35  and  37  on the channel members  12  and  14  and cap  18 , respectively. In general, a ratchet-like action between the ridges  31  on the channel members  12  and  14  and the ridges  51  on the cap  18  allow relative movement in a direction to clamp a PC board  16  between the two parts but prevent movement in the opposite direction unless the tab release arms are depressed. 
     As can also be seen from FIG. 3, inward pressure on the tab release arms  45   a  and  45   b  in the direction of arrows  53  flexes the tabs toward one another to cause the stepped surfaces  51   a  of the ridges  51  on the tabs  43   a  and  43   b  to disengage from the stepped surfaces  31   a  of the ridges  31  on arms  21  and  22  of the U-shaped channel member  12 . The cap portion  18  can then be gripped by the loops  40  and lifted upwardly in the opposite direction of arrow  52  and removed from the upper open ends of the arms  21  and  22  thereby allowing the printed circuit card  16  to be released and removed from within the channel between the arms  21  and  22 . As can also be seen from FIG. 3, the length to which the ridges on the inside arms  21  and  22  of the channel members  12  extend down its length is determined by the width of the printed circuit card  16  to be gripped by the card guide assembly of the present invention. 
     Referring again to FIGS. 2 and 3 together, a printed circuit card  16  contains a plurality of electrical components  61 - 64  mounted thereon and which are connected to one another by printed wiring (not shown) on the card. One end of the card includes a bracket  65  on which a connector  66  is mounted for external connection from the card  16  to other circuitry. The connector edge  24  of the card  16  contains a plurality of gold plated edge contacts  26  to be received within the slot of a printed circuit card edge connector as illustrated in FIG.  1 . 
     The PC board and card guide assembly  10  is assembled to the printed circuit card  16  by insertion of the card down between the opposed arms  21  and  22  of the U-shaped channel members  12  and  14  so that the lower edges of the card  16  engage the slots  35  in the bottom walls  23  of the channel members  12  and  14 . Once the printed circuit card is in place within the channel members, the cap portion  18  is lowered down onto the upper open end of the channel members  12  and  14  so that the opposed arms  21  and  22  are received up into respective ones of the openings  41   a  and  b  and  42   a  and  b  formed in the corners of the body portion  36  of the cap  18 . As downward pressure is applied to the cap  18 , the resilient tabs  43   a  and  b  and  44   a  and  b  ratchet back and forth as the ridges  51  on the engagement surfaces of the tabs pass over the ridges  31  on the inside walls of the U-shaped channel members. Once the cap  18  is in place so that the upper edge of the printed circuit board  16  is received into the slot  37  in the lower surface of the body portion  36  of the cap  18 , the opposed stepped surfaces  51  a and  31  a of the respective ridges  51  and  31  lock the cap  18  in place so that the PC board and card guide assembly  10  is rigidly affixed to the printed circuit card  16 . When the completed card guide assembly and printed circuit card  16  are inserted down into the chassis to insert the connector edge  24  of the card  16  into a printed circuit card edge connector, it is impossible for the circuit board  16  to move very far in either lateral direction. The insulative side walls of the U-shaped channel members act as insulative bumpers to prevent any electrically conductive portions of the PC board such as the conductive fingers  26  along both edges of the connector region  24  from coming in contact with any adjacent printed circuit cards or other unprotected electrical circuitry which might produce a short. Similarly, when the circuit board  16  secured in the card guide assembly  10  is removed from a card edge connector, the insulative side walls of the U-shaped channel members acting as bumpers make it virtually impossible for the assembly to move very far in either lateral direction and thereby cause any shorting of the conductive fingers  26  against any other circuitry. 
     The construction of the card guide assemblies  10 A and  10 B of FIG. 1 which only include half caps  17   a - 17   b  is essentially the same as that described above in connection with the assembly  10  which includes a full cap  18 . The openings, tabs and grooves formed in the half-caps  17   a  and  17   b  are the same as those on each of the opposite ends of the full cap  18 . The caps  17   a  and  17   b  are, of course, installed one at a time over the areas of their respective U-shaped channel members to accommodate the specific width requirements of the PC board to be received within each channel. 
     Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying drawings and described in the foregoing detailed description, it is to be understood that the invention is not limited to the embodiment(s) disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.