Apparatus for mechanically and electrically connecting printed circuits boards

Abstract: The apparatus includes a spacer member (40) and a connecting member (30) for use in mechanically and electrically connecting two or more printed circuit boards (11-13) in a parallel spaced type arrangement. The metallic spacer member is constructed in the form of a sleeve (41) partially closed at one end (43). The plastic connecting member is also formed in the shape of a sleeve (31) but includes a male connector (33) at one end. The spacer member is attached to a printed circuit board by advancing the connector end of the connecting member into the open end of the spacer member until the connector snaps into engagement with the hole (45) in the partially closed end wall of the spacer member and a mounting hole (14) in the printed circuit board. A bolt passes through the respective mounting holes in the printed circuit boards and the connecting member for securing the spacer member between the printed circuit boards.

Description: The present invention relates to apparatus for electrically and mechanically interconnecting printed circuit boards and, more particularly, to a snap-on spacer for stacking printed circuit boards. Printed circuit boards in electronic devices such as computer workstations and personal computers are often stacked together in a parallel arrangement to reduce cabinet and board size, to accommodate cabinet design, or as a result of modular design practices. In addition, printed circuit boards are often added to existing logic circuits to provide additional features or improved functionality to the circuit. Examples of such additional printed circuit boards include drivers for colour monitors, additional memory, communication boards and disc drive controllers. Existing methods of connecting stacked printed circuit boards include the use of metallic standoffs which are pressed into or soldered into the printed circuit boards. The standoffs and boards are often aligned on straight metallic posts. The use of metal standoffs is advantageous in that it provides an electrical connection between the boards in addition to the mechanical connection. Unfortunately, stacked boards assembled with metal standoffs as described above are difficult to disassemble should the need arise to add, replace, remove or repair a printed circuit board. Alternatively, nylon standoffs that snap onto the printed circuit boards have been utilized to stack boards. Although nylon standoffs greatly simplify assembly and disassembly of connected circuit boards, they cannot provide an electrical connection between stacked boards. Neither the metal nor nylon standoffs currently in use allow additional printed circuit boards to be simply and inexpensively attached to existing boards or stacks not designed to permit attachment of additional boards. Metallic and nylon standoffs are disclosed in documents DE-A-3 427 680, US-A-4 760 495 and DE-U-8 911 654. It is therefore an object of the present invention to provide a new and improved means for mechanically and electrically connecting printed circuit boards not subject to the foregoing disadvantages. According to the present invention there is provided apparatus for mechanically and electrically connecting a plurality of printed circuit boards in a parallel arrangement, characterized by a spacer member extending between corresponding mounting holes of adjacent printed circuit boards, said spacer member serving to electrically connect together said adjacent printed circuit boards and having formed through it, a hole which is coaxial with said corresponding mounting holes, a connecting member for detachably connecting said spacer member to one of said adjacent printed circuit boards, and a fastening member placed through said corresponding mounting holes and said hole in said spacer member for the purpose of mechanically connecting together said adjacent printed circuit boards. Embodiments of the present invention are set out in the dependent claims. An embodiment of the present invention will now be described with reference to the accompanying drawings, wherein:- Figure 1 is a vertical sectional view through a stack of printed circuit boards electrically and mechanically connected together in accordance with the present invention; Figure 2 is an exploded view of the support shown in Figure 1 for connecting together multiple printed circuit boards; Figure 3 is a side view, shown partially cut away, of the retainer shown in Figures 1 and 2; and Figure 4 is a side view, shown partially cut away, of the standoff shown in Figures 1 and 2. Referring now to Figure 1, there is seen a vertical sectional view through a stack of three parallel spaced printed circuit boards 11, 12 and 13 electrically and mechanically connected together in accordance with the present invention. Each board contains a plated-through hole 14 which is coaxially aligned with the holes in the other two boards. Spacing between the boards is maintained by metallic spacers or standoffs 40, which also provide electrical connection between adjacent printed circuit boards. Each spacer 40 is secured to a printed circuit board through the use of a nylon or plastic retainer 30. The construction of retainers 30 and spacers 40 are shown in Figures 3 and 4, respectively. Circuit boards 11, 12 and 13, metallic spacers 40 and retainers 30 are secured together and mounted to cabinet base 15 by a screw 19 which traverses the column formed by the stacked spacers. The cabinet base includes supports 17, each support having a threaded insert 18 for receiving screw 19. A screw cap 20 is disposed between the head of screw 19 and printed circuit board 11 to protect the portion of the topmost retainer which protrudes through hole 14 in board 11 and to firmly clamp board 11 to the stack. The assembly of Figure 1 is shown disassembled in Figure 2 to provide a better understanding of the alignment of the holes in the circuit boards, spacers, retainers and cabinet base. The standoffs 40 and retainers 30 are not shown separated, however. Retainer 30 is shown in side view, partially cut away, in Figure 3. The body 31 of the retainer is formed from polycarbonate material in the shape of a sleeve having an inner diameter large enough to accommodate screw 19 and having, throughout most of its length, an outer diameter greater than the diameter of holes 14. One end of the retainer has a reduced outer diameter to form a male connector 33 for engagement with holes 14. A shoulder 34 is formed where the male connector is joined to the main body of the retainer. The male connector terminates in an enlarged portion 35 having a chamfered edge 37. Two cuts (apertures) 39 extend from the male end of the retainer into the main body of the retainer, dividing the male connector into two identical halves. The cuts 39 permit inward deflection of the two halves during insertion or removal of the retainer from holes 14. Figure 4 is a side view, shown partially cut away, of standoff 40. The body 41 of the standoff is formed from aluminum or another electrically conductive material in the shape of a sleeve partially closed at one end 43. The internal diameter of the sleeve is slightly larger than the outer diameter of retainer 30. End 43 contains a hole 45 having a diameter equal to the diameter of holes 14. A chamfered surface 47 provides a transition from the internal surface of the sleeve to hole 45. Retainer 30 is secured inside standoff 40 by inserting the male end of the retainer into end 49 of the standoff until the male connector engages with hole 45. The male connector has a length sufficient to engage with both hole 45 and one of holes 14. Chamfered surfaces 37 and 47 facilitate engagement of retainer 30 in standoff 40. Referring again to Figures 1 and 2, printed circuit boards 11, 12 and 13 are stacked and secured together by engaging the male connectors protruding from the retainer/standoff assemblies into holes 14 so that the standoffs are held against the bottom surfaces of boards 11 and 12. The boards are then stacked so that the corresponding holes in boards 11, 12 and 13, the retainer/standoff assemblies and threaded support 17 are aligned coaxially. Screw 19 is inserted from the top of the stack through the boards and retainer/standoff assemblies into support 17. It should be noted that the length of the retainer between shoulder 34 and end 38 is less than the length of the standoff between the chamfered surface 47 and end 49. This difference in length permits the placement of the upper retainer/standoff assembly over the end portion of the male connector which extends above board 12. Screw cap 20 protects the end portion of the male connector which extends above board 11. It can thus be seen that there has been provided by the present invention an assembly for securing two or more printed circuit boards together in a parallel spaced the relationship, and securing the stack of boards to a cabinet base. In addition, the standoffs disposed between the boards provide an electrical connection between the boards. The connecting and spacing means are simply and inexpensively constructed and permit easy separation of the boards. From the foregoing specification it will be clear to those skilled in the art that the present invention is not limited to the specific embodiment described and illustrated and that numerous modifications and changes are possible without departing from the scope of the present invention. For example, three circuit boards are shown in Figures 1 and 2. However, any number of boards which can be accommodated by the surrounding cabinetry can be stacked together utilizing the standoffs and retainers shown and described. The length of screw 19 will need to be varied in proportion with the height of the stack. In addition the dimensions, number and shapes of the retainers and standoffs utilized to connect boards together may be varied to accommodate different size boards and board components.

Claims: Apparatus for mechanically and electrically connecting a plurality of printed circuit boards (11-13) in a parallel arrangement, characterized by a spacer member (40) extending between corresponding mounting holes of adjacent printed circuit boards, said spacer member serving to electrically connect together said adjacent printed circuit boards and having formed through it, a hole which is coaxial with said corresponding mounting holes, a connecting member (30) for detachably connecting said spacer member to one of said adjacent printed circuit boards, and a fastening member (19) placed through said corresponding mounting holes and said hole in said spacer member for the purpose of mechanically connecting together said adjacent printed circuit boards. Apparatus according to claim 1, characterized in that said spacer member (40) is comprised of an electrically conductive material to provide a conductive path between said adjacent printed circuit boards (11-13). Apparatus according to claim 2, characterized in that said spacer member (40) comprises a first cylindrical sleeve (41) having an internal diameter greater than the diameter of said mounting holes (14) and an end wall (43) having a hole (45) with a diameter equal to the diameter of said mounting holes, and said connecting member (30) comprises a second cylindrical sleeve (41) for insertion within said first sleeve, said second sleeve having a length less than the length of said first sleeve and having an external diameter less than the internal diameter of said first sleeve and greater than the diameter of said mounting holes, said connecting member including a male connector (33) formed at one end of said second sleeve for engagement with the hole (45) in said end wall (43) and one of said mounting holes (14), said connecting member having formed through it, a hole which is coaxial with said corresponding mounting holes. Apparatus according to claim 3, characterized in that said connecting member (30) includes a shoulder (34) where said male connector (33) is joined with said second sleeve (31), and said male connector includes an enlarged end portion (35) and two apertures (39) extending along the length of the male connector and dividing the male connector into two halves, whereby said apertures permit inward deflection of said male connector halves during insertion or removal of said connector from said mounting holes (14) or said spacer member (40), and whereby said shoulder (34) and said enlarged portion (35) connect said spacer member with a printed circuit board. Apparatus according to claim 4, characterized in that said connecting member (30) is constructed from a polycarbonate material. Apparatus according to claim 3, 4 or 5, characterized in that said fastening member (19) is a bolt which passes through the hole in said connecting member (30), and has a threaded portion for engagement with threaded means (18). Apparatus according to claim 6, characterized in that said threaded means (18) forms part of a support member (17) mounted on a surface of a base member (15). Apparatus according to claim 7, characterized in that said base member (15) forms part of a cabinet for housing said printed circuit boards (11-13).

Inventors: MEYER JAY A, SPERAW FLOYD G, MEYER, JAY A., SPERAW, FLOYD G.
Applicants: NCR INT INC, NCR INTERNATIONAL INC.
Application year: 1991
Main classification: H05K3
IPC codes: H05K1, H01R12, H05K7