Abstract:
An assembly for attaching a printed circuit board to a chassis includes a mounting rail for engagement with the printed circuit board and a guide member for engagement with the chassis. In one embodiment, the mounting rail includes an elongated body member having a first side and a second side and a spacer formed in the first side. A lock member for engaging the printed circuit board is coupled to the spacer. The guide member defines a guide slot for slidably receiving the mounting rail.

Description:
BACKGROUND 
     The invention relates generally to computers and other electronic assemblies comprising printed circuit boards and, more particularly, to an apparatus for securing a motherboard within a computer. 
     A computer system includes a motherboard enclosed within a chassis. The motherboard provides a surface on which much of the computer&#39;s critical circuitry is mounted such as the control processing unit and system memory. Because of the critical circuitry contained in the motherboard, it is important to properly secure the motherboard within the chassis of the computer to ensure the dynamic and static stability of the motherboard. 
     Motherboards are typically secured within the chassis by several screws which extend through holes in the motherboard and engage threaded portions in the chassis. Sometimes, a single screw or plastic plug is used to secure the motherboard to the chassis. However, this single attachment point between the motherboard and the chassis makes the motherboard vulnerable to chassis vibrations. 
     Prior to mounting the motherboard within the chassis, the holes in the motherboard are aligned with the threaded portions in the chassis. Screws are then inserted into the holes in the motherboard and threaded into the threaded portions in the chassis. Tools, such as pneumatic, electric, or hand screw drivers are typically used to drive the screws into the threaded portions in the chassis. Installing the motherboard with a tool often means that subsequent access to the motherboard is deterred if the appropriate tool is unavailable. 
     In a manufacturing facility where an assembly line worker installs a large number of motherboards in a given day, workers may develop cumulative trauma disorder, e.g. carpel tunnel syndrome, due to repeated operation of the tool. Often, the tool may slip while installing the motherboard and cause damage to the motherboard. The pressure applied to the motherboard while operating the tool may also damage the motherboard. Thus, it would be beneficial to have a board-to-chassis connection system that does not require a tool. 
     SUMMARY 
     In general, in one aspect, a mounting rail for a printed circuit board comprises an elongated body member having a first side and a second side and a spacer formed on the first side. A lock member for engagement with the printed circuit board is coupled to the spacer. 
     In another aspect, an assembly for attaching a printed circuit board to a chassis comprises a mounting rail for engagement with the printed circuit board. The mounting rail comprises an elongated body member having a first side and a second side and a spacer formed on the first side. A lock member for engaging the printed circuit board is coupled to the spacer. A guide member for engagement with the chassis defines a guide slot for slidably receiving the mounting rail. 
     Other features of the invention will be apparent from the following description and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic of a PC board coupled to a chassis by a rail assembly. 
     FIG. 2 is a top view of a mounting rail. 
     FIG. 3 is a partial cross-section view of the mounting rail shown in FIG. 2. 
     FIG. 4 shows the mounting rail attached to a PC board. 
     FIG. 5 is a perspective view of a rail guide. 
     FIG. 6 shows the rail guide attached to a chassis. 
     FIG. 7 shows how a motherboard is secured within a chassis. 
     FIG. 8 shows a motherboard secured within a chassis. 
    
    
     DETAILED DESCRIPTION 
     The following embodiments are illustrative only and are not to be considered limiting in any respect. 
     Referring to FIG. 1, a motherboard 100 is attached to a chassis 102 by a rail assembly 104. The rail assembly 104 includes a mounting rail 200 and rail guides 500. 
     Referring now to FIG. 2, the mounting rail 200 includes an elongated body 202, lock members, e.g. fasteners 204, and grounding strips 206. The body 202 includes a pair of flat surfaces 208 which are disposed on opposite sides of a ridge 210. The ridge 210 includes a pair of slots 212 which receive the grounding strips 206. The leading edge 214 of the body 202 includes tapered portions 216 and the trailing edge 218 of the body 202 includes an arm 219. The body 202 may be injection molded from a plastic resin, e.g. nylon, or from a thermoplastic alloy, e.g. polycarbonate, acrylonytrile, butadiene, and stryrene. The grounding strips 206 may be made of Beryllium Copper. 
     Referring to FIG. 3, a pair of spacers 300 and spacer 302 are formed on the ridge 214. Apertures 304 extend through the spacers 300 and ridge 214 and open into a groove 306 beneath the ridge 214. The grounding strips 206 extend through the slots 212 and groove 306 and project from the bottom surface of the body 202. The first ends 308 of the grounding strips 206 include apertures which engage tabs 310 at a side of the walls defining the slots 212. The second ends 312 of the grounding strips 206 are mounted on the spacers 300 and include apertures which fit around a neck region of the fasteners 204. 
     The fasteners 204 are two-piece rivets which include clip members 316 and pin members 318. The clip members 316 and pin members 318 may be made of a plastic, e.g. nylon. The lower ends 321 of the clip members 316 are ultrasonically welded to the spacers 300 while the upper ends of the clip members protrude above the spacers 300. Instead of welding the lower ends 321 to the spacers, the clip members 316 may be integrally formed or molded with the body 202 or spacers 300. The clip members 316 have apertures 320 which are arranged to receive stem portions 323 of the pin members 318. Although the fasteners 204 are illustrated as two-piece rivets, it should be clear that the fasteners 204 may also be single-piece rivets. 
     Referring to FIG. 4, the mounting rail 200 is attached to the underside of a motherboard 400 by inserting the clip members 316 into pre-drilled holes in the motherboard 400. The stem portions 323 of the pin members 318 are then inserted into the apertures 320 to engage the clip members 316. When the stem portions 323 engage the clip members 316, the walls of the clip members 316 are expanded to tightly engage the motherboard 400. Thus, the mounting rail 200 is attached to the underside of the motherboard 400 without the use of a tool. 
     The second ends 312 of the grounding strips 206 make contact with the motherboard 400 when the mounting rail 200 is secured to the motherboard. The spacers 300 and 302 provide a desired spacing between the underside of the motherboard 400 and the ridge 214. 
     Referring to FIG. 5, the rail guide 500 includes a base portion 502 and a pair of opposing hook members 504 extending upwardly from the base portion 502. A guide slot 506 is defined by the hook members 504. The guide slot 506 is arranged to receive the mounting rail 200 (shown in FIG. 2). The hook members 504 include arm portions 507 and catch portions 508. The catch portions 508 are arranged to slide on the flat surfaces 210 (shown in FIG. 2) on the body 202 of the mounting rail 200. The hook members 504 include tabs 510 which snap to a chassis (not shown) to secure the rail guide 500 in place. 
     A relief groove 512 is provided on the base portion 502. The relief groove 512 provides flexing ability to the base portion 502 and functions as a loaded spring which biases the hook members 504 inward toward each other. The rail guide 500 may be made of a plastic, e.g. nylon, or a thermoplastic alloy, e.g. polycarbonate. 
     Referring to FIG. 6, the rail guide 500 is attached to a chassis 600 by inserting the hook members 504 into slots 602 in the chassis. The tabs 510 snap onto the chassis 600 and lock the rail guide 500 in place. 
     Referring now to FIG. 7, mounting rails 700 and 702 are secured to the underside of a motherboard 704. The mounting rails 700 and 702 are similar to the mounting rail 200 and are secured to the motherboard 704 in the manner previously described. A pair of rail guides 706 and a pair of rail guides 708 are secured to a chassis 710. The rail guides 706 and 708 are similar to the rail guide 500 and are attached to the chassis 710 in the manner previously described. 
     The rail guides 706 are aligned to receive the mounting rail 700 and the rail guides 708 are aligned to receive the mounting rail 702. The motherboard 704 is attached to the chassis 710 by sliding the mounting rails 700 and 702 into the guide slots of the rail guides 706 and 708, respectively. The tapered leading edges 712 and 714 of the mounting rails 700 and 702 allow ease of entry of the mounting rails into the guide slots of the rail guides. 
     The hook members 716 and the relief grooves (not shown) of the rail guides 706 bias the ground strips 718 on the mounting rail 700 against the chassis 710 to ensure good electrical contact between the chassis and the motherboard. Similarly, the hook members 720 and the relief grooves (not shown) of the rail guides 708 bias the ground strips 722 on the mounting rail 702 against the chassis 710. 
     A lever 724 is pivotally mounted on the chassis 710. The lever 724 includes a groove 726 which is arranged to receive the arm 728 of the mounting rail 700. The lever 724 includes arcuate surface 727 which co-act with the mounting rail 700 to urge the arm 728 into the groove 726. 
     Referring to FIG. 8, the motherboard is urged inwardly to mate with a motherboard connector 730 in the chassis 710 when the lever 724 is pivoted such that the arm 728 slides into the groove 726. The motherboard 704 may be released from the motherboard connector 730 when the lever 724 is swung such that the arm 728 is disengaged from the groove 726. 
     While the invention has been described with respect to a limited number of exemplary embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. For instance, the mounting rail may be mounted on a circuit board other than a motherboard. The rail guide may be an integral part of the chassis. The mounting rail and rail guides may be made of other materials besides a plastic resin and thermoplastic alloy.