Apparatus and method for mounting a backplane circuit board to an electronic chassis

An apparatus for mounting a backplane circuit board to an electronic chassis is provided. An electronic chassis includes a first card guide assembly and a second card guide assembly. The first card guide assembly includes first and second guide pins. The first guide pin of the first card guide assembly is positioned adjacent a first end of the first card guide assembly and the second guide pin of the first card guide assembly is positioned adjacent a second end of the first card guide assembly. The second card guide assembly includes first and second guide pins. The first guide pin of the second card guide assembly is positioned adjacent a first end of the second card guide assembly and the second guide pin of the second card guide assembly is positioned adjacent a second end of the second card guide assembly. A backplane circuit board includes first and second openings to receive the first and second guide pins of the first card guide assembly and third and fourth openings to receive the first and second guide pins of the second card guide assembly. The third and fourth openings have a diameter less than a diameter of the first and second openings to allow a user to first position a bottom portion of the backplane circuit board against the second card guide assembly wherein the third and fourth openings receive the first and second guide pins of the second card guide assembly and second, to position a top portion of the backplane circuit board against the first card guide assembly wherein the first and second openings receive the first and second guide pins of the first card guide assembly to allow proper alignment of the backplane circuit board to the first and second card guide assemblies.

FIELD OF THE INVENTION
 This invention relates generally to the field of electronic chassis that
 house electronic components for high speed telecommunication and
 networking applications and, in particular, to an apparatus and method for
 mounting a backplane circuit board to an electronic chassis.
 BACKGROUND OF THE INVENTION
 An electronic chassis which houses electronic components for high speed
 telecommunication and networking applications typically includes two card
 guide assemblies mounted between side walls of the chassis, one located
 adjacent the top of the chassis and the other located adjacent the bottom
 of the chassis. A backplane circuit board having various surface mounted
 connectors is typically fastened to the two card guide assemblies and
 forms the back wall of the chassis. A plurality of vertically oriented
 circuit board assemblies, each of which are typically comprised of a
 circuit board attached to a U-shaped channel member, are typically
 inserted into the chassis along the card guide assemblies. When fully
 inserted into the chassis, the circuit boards are connected to the
 backplane circuit board.
 In order to make the connections between the vertically oriented circuit
 boards within the chassis and the backplane circuit board, it is critical
 that the backplane circuit board be properly aligned with the chassis.
 Attempts have made to provide proper alignment by providing additional
 openings in the backplane circuit board and manually aligning the
 backplane circuit board prior to fastening it to the chassis. However,
 providing additional openings and manually aligning the backplane circuit
 board is labor intensive, time consuming, and results in increased
 manufacturing costs. Moreover, existing designs do not compensate for any
 deviations from specified design tolerances of the components of the
 chassis that may result during the fabrication process. As a result,
 deviations from design tolerances may make it difficult, if not
 impossible, to obtain proper alignment of the backplane circuit board.
 Accordingly, it would be desirable to have an apparatus for mounting a
 backplane circuit board to an electronic chassis that overcomes the
 disadvantages described above.
 SUMMARY OF THE INVENTION
 One aspect of the invention provides an apparatus for mounting a backplane
 circuit board to an electronic chassis. An electronic chassis includes a
 first card guide assembly and a second card guide assembly. The first card
 guide assembly includes first and second guide pins. The first guide pin
 of the first card guide assembly is positioned adjacent a first end of the
 first card guide assembly and the second guide pin of the first card guide
 assembly is positioned adjacent a second end of the first card guide
 assembly. The second card guide assembly includes first and second guide
 pins. The first guide pin of the second card guide assembly is positioned
 adjacent a first end of the second card guide assembly and the second
 guide pin of the second card guide assembly is positioned adjacent a
 second end of the second card guide assembly. A backplane circuit board
 includes first and second openings to receive the first and second guide
 pins of the first card guide assembly and third and fourth openings to
 receive the first and second guide pins of the second card guide assembly.
 The third and fourth openings have a diameter less than a diameter of the
 first and second openings to allow a user to first position a bottom
 portion of the backplane circuit board against the second card guide
 assembly wherein the third and fourth openings receive the first and
 second guide pins of the second card guide assembly and second, to
 position a top portion of the backplane circuit board against the first
 card guide assembly wherein the first and second openings receive the
 first and second guide pins of the first card guide assembly to allow
 proper alignment of the backplane circuit board to the first and second
 card guide assemblies. The first and second guide pins of the first card
 guide assembly and the first and second guide pins of the second card
 guide assembly may preferably each include a tapered end portion. The
 backplane circuit board may preferably be comprised of at least two
 circuit boards. Each of the first and second openings may preferably be
 0.215 inches in diameter. Each of the third and fourth openings may
 preferably be 0.200 inches in diameter. The first and second guide pins of
 the first card guide assembly and the first and second guide pins of the
 second card guide assembly may each be 0.187 inches in diameter. The first
 and second guide pins of the first card guide assembly and the first and
 second guide pins of the second card guide assembly may each be 0.375
 inches in length. The first and second guide pins of the first card guide
 assembly and the first and second guide pins of the second card guide
 assembly may each be comprised of metallic material.
 Another aspect of the invention provides a method of mounting a backplane
 circuit board to an electronic chassis. An electronic chassis including a
 first card guide assembly and a second card guide assembly is provided.
 The first card guide assembly includes first and second guide pins. The
 first guide pin of the first card guide assembly is positioned adjacent a
 first end of the first card guide assembly and the second guide pin of the
 first card guide assembly is positioned adjacent a second end of the first
 card guide assembly. The second card guide assembly includes first and
 second guide pins. The first guide pin of the second card guide assembly
 is positioned adjacent a first end of the second card guide assembly and
 the second guide pin of the second card guide assembly is positioned
 adjacent a second end of the second card guide assembly. A backplane
 circuit board includes first and second openings to receive the first and
 second guide pins of the first card guide assembly and third and fourth
 openings to receive the first and second guide pins of the second card
 guide assembly. The third and fourth openings have a diameter less than a
 diameter of the first and second openings. A bottom portion of the
 backplane circuit board is first positioned against the second card guide
 assembly, and the first and second guide pins of the second card guide
 assembly are received in the third and fourth bottom openings. A top
 portion of the backplane circuit board is then positioned against the
 first card guide assembly, and the first and second guide pins of the
 first card guide assembly are received in the first and second openings.
 The backplane circuit board may preferably be attached to the first and
 second card guide assemblies.
 The invention provides the foregoing and other features, and the advantages
 of the invention will become further apparent from the following detailed
 description of the presently preferred embodiments, read in conjunction
 with the accompanying drawings. The detailed description and drawings are
 merely illustrative of the invention and do not limit the scope of the
 invention, which is defined by the appended claims and equivalents
 thereof.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
 As shown in FIG. 1, a preferred embodiment of an apparatus 10 for mounting
 a backplane circuit board to an electronic chassis includes a backplane
 circuit board 12 and an electronic chassis 14. The backplane circuit board
 12 may preferably be comprised of any conventional printed circuit board
 adapted to receive a plurality of vertically oriented circuit board
 assemblies (not shown) that are positioned in the electronic chassis 14.
 In the embodiment shown, the backplane circuit board 12 is adapted to be
 positioned along a back portion of the electronic chassis, and once
 installed, forms a back wall of the electronic chassis 14. As shown in
 FIG. 1, the backplane circuit board 12 may preferably be comprised of a
 first circuit board 16 and a second circuit board 18, although any number
 of circuit boards may be used for the backplane circuit board 12, and
 various configurations are contemplated.
 The electronic chassis 14 includes a first card guide assembly 20 and a
 second card guide 22 assembly. The electronic chassis 14 may preferably be
 any suitable enclosure for housing various electronic components, and may
 preferably be comprised of steel, aluminum or any other suitable metallic
 material. In the embodiment shown, the first card guide assembly 20
 extends between side walls 24, 26 of the electronic chassis 14 adjacent
 the top end of the side walls 24, 26. Similarly, the second card guide
 assembly 22 extends between the side walls 24, 26 of the electronic
 chassis 14 adjacent the bottom end of the side walls 24, 26. The first and
 second card guides assemblies 20, 22 may be comprised of any suitable
 rigid material such as, for example, steel, aluminum or any other suitable
 metallic material. The first and second card guide assemblies 20, 22
 provide a guide for the plurality of vertically oriented circuit board
 assemblies (not shown) that are inserted into the electronic chassis 14.
 Also, as shown in FIG. 1, the first and second card guide assemblies 20,
 22 each include mounting surfaces 21, 23 for the backplane circuit board
 12.
 The first card guide assembly 20 includes a first guide pin 28 and a second
 guide pin 30. The first and second guide pins 28, 30 ensure that backplane
 circuit board 12 is properly aligned with the first card guide assembly
 20. The first guide pin 28 of the first card guide assembly 20 extends
 outward from the first card guide assembly 20 and is positioned adjacent a
 first end 32 of the first card guide assembly 20.The second guide pin 30
 of the first card guide assembly 20 extends outward from the first card
 guide assembly 20 and is positioned adjacent a second end 34 of the first
 card guide assembly 20. The first and second guide pins 28, 30 of the
 first card guide assembly 20 may preferably have tapered end portions 29,
 31, respectively. In addition, each of the first and second guide pins 28,
 30 may preferably be 0.187 inches in diameter and 0.375 inches in length.
 The first and second guide pins 28, 30 may each be comprised of steel,
 aluminum, or any other suitable metallic material.
 The second card guide assembly 22 includes a first guide pin 36 and a
 second guide pin 38.The first and second guide pins 36, 38 ensure that
 backplane circuit board 12 is properly aligned with the second card guide
 assembly 22.The first guide pin 36 of the second card guide assembly 22
 extends outward from the second card guide assembly 22 and is positioned
 adjacent a first end 40 of the second card guide assembly 22. The second
 guide pin 38 of the second card guide 22 assembly extends outward from the
 second card guide assembly 22 and is positioned adjacent a second end 42
 of the second card guide assembly 22. The first and second guide pins 36,
 38 of the second card guide assembly 22 may preferably have tapered end
 portions 37, 39, respectively. In addition, each of the first and second
 guide pins 36, 38 may preferably be 0.187 inches in diameter and 0.375
 inches in length. The first and second guide pins 36, 38 may each be
 comprised of steel, aluminum, or any other suitable metallic material.
 The backplane circuit board 12 includes a first opening 44 and a second
 opening 46 to receive the first and second guide pins 28, 30 of the first
 card guide assembly 20. The backplane circuit board 12 also includes a
 third opening 48 and a fourth opening 50 to receive the first and second
 guide pins 36, 38 of the second card guide assembly 22.The third and
 fourth openings 48, 50 have a diameter that is less than a diameter of the
 first and second openings 44, 46. For example, each of the first and
 second openings 44, 46 may preferably be 0.215 inches in diameter, and
 each of the third and fourth openings 48, 50 may preferably be 0.200
 inches in diameter. The difference between the diameter of the third and
 fourth openings 48, 50 and the diameter of the first and second openings
 44, 46 compensate for any deviations from specified design tolerances that
 may occur as a result of the fabrication process.
 In operation, a user first positions a bottom portion of the backplane
 circuit board 12 against the second card guide assembly 22 wherein the
 third and fourth openings 48, 50 of the backplane circuit board 12 receive
 the first and second guide pins 36, 38 of the second card guide assembly
 22. The third and fourth openings 48, 50 of the backplane circuit board 12
 may preferably be dimensioned to accept the first and second guide pins
 36, 38 of the second card guide assembly 22. The user then positions a top
 portion of the backplane circuit board 12 against the first card guide
 assembly 20 wherein the first and second openings 44, 46 of the backplane
 circuit board receive the first and second guide pins 28, 30 of the first
 card guide assembly 20. The backplane circuit board 12 may preferably be
 attached to the first and second card guide assemblies 20, 22 with
 conventional fasteners such as, for example, rivets, screws, or bolts. The
 arrangement of the guide pins 28, 30, 36, 38 in combination with the
 specifically dimensioned openings 44, 46, 48, 50 ensures that the
 backplane circuit board 12 can be mounted to the electronic chassis 14
 quickly and easily, and that the backplane circuit board 12 will be
 properly aligned with respect to the first and second card guide
 assemblies 20, 22 of the electronic chassis 14. This arrangement also
 compensates for any deviations from acceptable design tolerances that may
 occur during fabrication of the components of the electronic chassis 14.
 While the embodiments of the invention disclosed herein are presently
 considered to be preferred, various changes and modifications can be made
 without departing from the spirit and scope of the invention. The scope of
 the invention is indicated in the appended claims, and all changes that
 come within the meaning and range of equivalents are intended to be
 embraced therein.