MAINTAINING CONNECTOR ALIGNMENT ACROSS CIRCUIT CARD

CHASSIS

CROSS-REFERENCE TO RELATED APPLICATIONS: Priority is claimed to U.S. Provisional Patent Application No. 61/948,546, filed March 6, 2014 (Attorney Docket No. 1161-002), the contents and teachings of which are incorporated herein by reference in their entirety. BACKGROUND

Many diverse electronic applications require the use of printed circuit card assemblies (PCAs) housed within one or more chassis. The chassis may be freestanding or installed in racks. Data centers and other facilities commonly include many racks, each holding one or more chassis. The racks may be provided together in rooms, which employ environmental controls for maintaining stable temperature and/or humidity.

A conventional chassis includes a backplane, PCAs, card guides, and fans. The PCAs have edge connectors for mating with the backplane. The PCAs are typically inserted into a front opening of a chassis, connectors first, along card guides that direct the PCAs toward the backplane. As the edge connectors approach connectors on the backplane, alignment pins extending from the backplane engage alignment holes in the PCAs, or vice-versa, to bring the respective connectors into approximate alignment for mating. Connector shells on the PCA and/or backplane connectors may include rounded or beveled edges to further define alignment as connectors engage.

Some chassis use midplanes in place of, or in addition to, backplanes. In these arrangements, the midplanes act essentially as double-sided backplanes. Some PCAs may be inserted from the fronts of such chassis to engage the midplanes from one end, and other PCAs may be inserted from the backs of such chassis to engage the midplanes from the other end. Chassis using midplanes may achieve alignment between PCA connectors and midplane connectors in a manner similar to that described above for backplanes. SUMMARY

Unfortunately, conventional PCA alignment techniques do not always provide sufficient accuracy. For example, one chassis currently under development, referred to herein as an "axial chassis," provides backplane and/or midplane boards that are oriented orthogonally and edge-to-edge with one or more arrays of PCAs, which plug in from the front and/or back of the chassis. Such axial chassis, as well as any other chassis involving similar board-to-board connections, present particular alignment challenges when mating PCA connectors with connectors on backplanes and/or midplanes.

Whereas backplanes and midplanes in conventional chassis designs are planar circuit board assemblies with connectors placed precisely at predetermined locations relative to their surfaces, backplane and/or midplane connectors in an axial chassis may be disposed on different surfaces of different circuit boards, such that spacing between connectors can vary. Variations in connector spacing can cause

misalignments to arise between pairs of mating connectors, making it difficult to plug PCAs into a backplane or midplane. What is needed is a way to facilitate alignment between backplane and/or midplane connectors and connectors on PCAs in chassis arrangements in which circuit boards connect orthogonally and edge-to-edge.

In contrast with conventional approaches, an improved technique for aligning connectors of a backplane or midplane (i.e., a "plane") in a chassis with connectors of a PCA (Printed Circuit Assembly) includes providing a set of spacing strips, each spacing strip extending along a length within the chassis and having a set of aligners disposed along the length. For each aligner of each spacing strip, the technique further includes mechanically engaging an edge of a respective plane assembly to hold connectors attached to the respective plane assembly at predetermined vertical positions for mating with connectors of a PCA. Advantageously, the improved technique promotes precise alignment of mating connectors in a chassis in which circuit boards connect orthogonally and edge-to-edge.

In some examples, a set of stabilizing strips oriented at right angles to the set of spacing strips interlock with the set of spacing strips to horizontally stabilize the set of spacing strips within the chassis. In some examples, the set of stabilizing strips also serve to direct PCAs into horizontal alignment as the PCA are plugged into the chassis, such connectors on the PCAs align horizontally with connectors on the plane assemblies.

Some embodiments are directed to an apparatus for promoting alignment in a chassis between connectors of a set of plane assemblies and connectors of a set of PCAs, the chassis constructed and arranged to support connections between plane assemblies and PCAs orthogonally and edge-to edge. The apparatus includes a set of spacing strips, each spacing strip extending along a length within the chassis and having a set of aligners disposed along the length. Each aligner of the respective spacing strip is constructed and arranged to mechanically engage an edge of a respective plane assembly to hold connectors attached to the respective plane assembly at predetermined vertical positions for mating with connectors of a PCA.

According to some variants, the above-described embodiments further include a set of stabilizer strips oriented at right angles to the set of spacing strips and interlocking with the set of spacing strips to horizontally stabilize the set of spacing strips within the chassis.

Other embodiments are directed to a method for promoting alignment in a chassis between connectors of a set of plane assemblies and connectors of a set of PCAs (Printed Circuit Assemblies), the chassis constructed and arranged to support connections between plane assemblies and PCAs orthogonally and edge-to edge. The method includes providing a set of spacing strips, each spacing strip extending along a length within the chassis and having a set of aligners disposed along the length. For each aligner of each spacing strip, the method further includes mechanically engaging an edge of a respective plane assembly to hold connectors attached to the respective plane assembly at predetermined vertical positions for mating with connectors of a PCA. The method still further includes horizontally stabilizing the set of spacing strips within the chassis. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings, in which like reference characters refer to the same or similar parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. In the accompanying drawings,

FIG. 1 is an isometric view of an example chassis according to an embodiment of the invention, with covers removed to expose internal components;

FIG. 2 is an isometric view of the example chassis of FIG. 1 from a different perspective;

FIG. 3 is another isometric view of the example chassis of FIG. 1, but with a printed circuit assemblies (PCAs) at the rear of the chassis removed to reveal midplane connectors;

FIG. 4 is yet another isometric view of the example chassis of FIG. 1, but shown with covers in place and revealing openings at a side of the chassis for inserting and removing fan trays;

FIG. 5 is yet another isometric view of the example chassis of FIG. 1, which is similar to FIG. 4 but shows fan trays being inserted or removed through the openings at the side of the chassis;

FIG. 6 is an isometric view of an example plane assembly, which includes a first circuit board and a second circuit board;

FIG. 7 is a front elevation view of a PCA, which in this example is a half- height PCA that engages connectors on a single plane assembly;

FIG. 8 is a front elevation view of example portions of a plane assembly, and includes an enlarged view of an example spring-loaded spacer that spaces apart the first and second circuit boards of the plane assembly;

FIG. 9 is a front elevation view of the example spring-loaded spacer of FIG. 8, shown with the first and second circuit boards removed; FIG. 10 is a front elevation view of an example prefabricated backer, from which the spring-loaded spacer of FIGS. 7 and 8 may be constructed;

FIG. 11 is a combined view of different example spring-loaded spacers having different numbers of shim washers for accommodating different thicknesses of the first and/or second circuit boards of the plane assembly;

FIG. 12 is a front elevation view of an interior portion of the chassis of FIG. 1, which shows a plane assembly (FIG. 6) spaced apart by spring-loaded spacers (FIGS. 8 - 1 1) and having an edge that engages an example external aligner;

FIG. 13 is a front elevation view showing an example full-height PCA, which engages three plane assemblies;

FIG. 14 is a perspective view of an example spacing strip for precisely spacing apart example external aligners for facilitating alignment of three plane assemblies;

FIG. 15 is a front elevation view of an interior portion of the chassis of FIG. 1, which shows multiple example plane assemblies (FIG. 6) each having first and second circuit boards spaced apart by example spring-loaded spacers (FIGS. 8-11) and each having an edge that engages an example external aligner;

FIG. 16 is a perspective view of an example alignment lattice; and

FIG. 17 is a perspective view showing portions of the example chassis of FIG. 1 opened to review an example alignment lattice.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described. It is understood that such embodiments are provided by way of example to illustrate various features and principles of the invention, and that the invention hereof is broader than the specific example embodiments disclosed.

An improved technique for aligning connectors of a backplane or midplane (i.e., a "plane") in a chassis with connectors of a PCA (Printed Circuit Assembly) includes providing a set of spacing strips, each spacing strip extending along a length within the chassis and having a set of aligners disposed along the length. For each aligner of each spacing strip, the technique further includes mechanically engaging an edge of a respective plane assembly to hold connectors attached to the respective plane assembly at predetermined vertical positions for mating with connectors of a PCA.

To assist the reader, this Detailed Description is provided in sections, as follows:

• Section I is directed to an example environment in which alignment

techniques disclosed herein may be practiced;

• Section II is directed to example techniques for aligning connectors of a plane assembly with connectors of a PCA that plugs into a chassis; and · Section III is directed to example techniques for aligning connectors across multiple plane assemblies 600 and/or across multiple PCAs in the chassis.

Section I: Example axially chassis:

FIGS. 1-5 show various views of an example chassis 100 in which embodiments of the invention hereof may be practiced. Starting with FIG. 1, the chassis 100 is shown with its covers removed to reveal internal components. The chassis 100 includes a first region 110, a second region 120, and a third region 130. The regions 110, 120, and 130 are spaces within the chassis 100 for containing components. As shown, the first region 1 10 includes a first array of one of more circuit board assemblies (PCAs) 112, the second region 120 includes a second array of one or more PCAs 122 (e.g., backplane and/or midplane boards, as best seen in FIG. 6), and the third region 130 includes a third array of one or more PCAs 132.

A legend 102 indicates a relative orientation in mutually orthogonal X-Y-Z space. The PCAs 112 and 132 can be seen as oriented parallel to a Y-Z plane of the X-Y-Z space, while the PCAs 122 can be seen as oriented parallel to an X-Z plane of the X-Y-Z space. The first, second, and third regions 1 10, 120, and 130 are seen to extend successively back in a positive Z direction.

In the particular example shown, the first array of PCAs 112 are provided as half-height PCAs (i.e., they occupy half the vertical height for housing PCAs in the region 110). However, this is merely an example, as the PCAs may alternatively occupy some other fraction of the total height or the entire height. In some embodiments, the PCAs in the upper half of the first region 110 can be regarded as yet another array of PCAs, which interconnects with other components of the chassis 100 in a similar way to the first array of PCAs 112.

The second region 120 is seen to further include multiple fan trays 126, with each fan tray 126 including multiple fans 128. A total of eight fan trays 126 are shown; however, any suitable number may be provided. The fan trays 126 are positioned among the PCAs 122 within the second region 120. For example, two fan trays 126 are shown disposed between upper and lower pairs of PCAs 122.

In the example shown, six PCAs 122 are provided in second region 120. Any suitable number of PCAs 122 may be included, however, as best suited for the particular implementation. In an example, the PCAs 122 are provided in plane assemblies 600 (see FIG. 6), which each plane assembly 600 including two PCAs 122. In some examples, plane assemblies 600 are provided at the bottom of the region 120 (e.g., beneath the lower-most fan tray 126), at the top of the region 120 (e.g., above the upper-most fan tray 126). Plane assemblies may also be provided at other vertical locations, such as between different fan trays 126.

With the orientations of PCAs 112, 122, and 132 as shown, the PCAs 122 in the second region 120 can be seen to contact the PCAs 112 and 132 in the first and third regions 1 10 and 130 edge-to-edge and orthogonally, such that each of the PCAs 122 cuts across multiple PCAs 1 12 and 132 and forms connections therewith. For example, the PCAs 112 in the first region 1 10 include connectors 1 14, which engage with connectors 124a on the PCAs 122. Similarly, the PCAs 132 include connectors 134 (best seen in FIG. 2), which engage connectors 124b on the PCAs 122. The array of PCAs 122 can thus be regarded as forming a midplane, and the individual PCAs 122 can be regarded as midplane boards. PCAs 112 and 132 can be inserted along card guides into designated locations within the chassis 100, with the connectors 114 engaging the connectors 124a on the PCAs 122 (midplane boards) and the connectors 134 engaging connectors 124b on the PCAs 122.

In some examples, the chassis 100 includes first and second regions 1 10 and 120 only, with no third region 130 provided. In such examples, the array of PCAs 122 in the second region 120 can be regarded as forming a backplane, with the individual PCAs 122 forming backplane boards.

The PCAs 122 typically include conductive traces, ground planes, power planes, etc., for conveying electrical signals between different PCAs. Different implementations have different requirements, however, and the PCAs 122 can be provisioned with traces, planes, and even electrical components as needed to suit the requirements of particular use cases. Typically, the PCAs 122 include conductive traces that establish electrical connections between different PCAs 112 in the first region 110, between different PCAs 132 in the third region 130, and between the PCAs 112 and the PCAs 132. It is not required, however, that all PCAs 122 provide all of these connections. For example, the illustrated arrangement shows PCAs 122 near the vertical middle of the chassis 100 provided with connectors 124b for mating with connectors 134 on the PCAs 132 but no connectors 124a for mating with PCAs 112. Other PCAs 122 include both sets of connectors. The "middle" PCAs 122 can thus function as backplane boards with respect to the PCAs 132 in the third region 130, while in the same chassis 100 other PCAs 122 (e.g., those nearer to top and bottom) function as midplane boards.

Because the PCAs 122 have a length, signal routing is often more easily achieved than when using conventional backplanes and midplanes, since the entire length of the PCAs 122 may be available for routing traces. In some examples, the PCAs 122 may be made longer or shorter, based on routing requirements, desired numbers of PCA layers, available space, cost, and other factors. The length of PCAs 122 thus provides an additional degree of freedom, which designers may exploit when developing chassis for particular applications.

With the arrangement shown, it is also evident that airflow 150 can be established in the Z direction of the X-Y-Z space without any substantial bends or turns. For example, air enters the first region 110 of the chassis 100, passes among and between the PCAs 112 in the first region 1 10, passes through the fans 128 in the second region 120, and passes among and between the PCAs 132 in the third region 130, before exiting the third region 130 at the rear of the chassis 100. Because all PCAs 112, 122, and 132 are oriented parallel to the direction of airflow 150 (i.e., parallel to the Z-axis), air passes over and through the PCAs 1 12, 122, and 132 substantially unimpeded. It should be understood that electronic parts, connectors, heatsinks, fan frames, and other components may interfere slightly with airflow 150 and thus alter the flow of packets of air on a small scale. Such packets of air may thus take minor turns as they pass around and between components of the chassis 100. Obstructions like these are expected and desired, however, as they promote efficient cooling of components. But airflow 150 when viewed in the aggregate maintains a straight line course as it passes from the front of the chassis 100 to the back.

Although the direction of airflow 150 is shown as extending front-to-back, example embodiments work equally well with the direction of airflow 150 reversed.

The chassis 100 provides a number of distinct advantages over conventional chassis. For example, because airflow 150 follows a straight line course, there is no need for the fans 128 to force large amounts of air around corners. Thus, the fans 128 can be made significantly smaller and/or lower power, and/or fewer fans can be provided. The chassis 100 can thus consume less electricity than conventional chassis. Further, the direct path of airflow 150 avoids the need for intake and/or outlet plena, thus allowing the chassis 100 to be made smaller than conventional chassis. Further still, the PCAs 122 used as midplane/backplane boards can often be manufactured less expensively than conventional backplane and midplane cards, with fewer layers and fewer routing constraints. Together, these factors can significantly reduce the parts cost of the chassis 100. They can also reduce operating costs and failure rates of the chassis 100 as compared with conventional designs. Other figures show additional views. FIG. 2 shows the chassis 100 from the rear, providing a view of connectors 124b on the PCAs 122 and their mating with connectors 134 on the PCAs 132. FIG. 3 shows the chassis 100 with the first array of PCAs 112 removed, thus also exposing connectors 124a on the PCAs 122. FIG. 4 shows the chassis 100 with covers 400 in place. It can be seen from FIG. 4 that the chassis 100 includes openings 410 at a side of the chassis 100 for allowing fan trays 126 to be inserted and withdrawn. FIG. 5 shows several fan trays 126 partially withdrawn through the openings 410 at the side of the chassis 100. By providing the fan trays 126 in the second region 120 and allowing the fans to be accessed from the side of the chassis 100, the rear or the chassis 100 is kept free of fans, thus providing more space for cable management and promoting easier access to the PCAs 132.

FIG. 6 shows an example plane assembly 600 that includes two PCAs 122, i.e., a first PCA 122a and a second PCA 122b. Each of the PCAs 122 shown in FIG. 6 has a first array of connectors 124a at a first end 610a, which connectors 124a are arranged to engage with connectors 114 (FIG. 1) on the PCAs 112 in the first region 110. Each of the PCAs 122 also has a second array of connectors 124b at a second end 610b, which connectors 124b are arranged to engage connectors 134 on the PCAs 132 in the third region 130 (FIG. 2). The two PCAs 122 shown in FIG. 6 are fastened together, e.g., using screws 940, adhesive, or some other type of fastener or material. In some examples, an insulative layer is interposed between the PCAs 122 to prevent short circuits and/or to fill air gaps. In a further example, a metal layer (not shown) is placed between the PCAs 122. The metal layer is connected or AC-coupled to an electrical ground of the chassis 100 to provide an electrostatic shield between the two PCAs 122a and 122b. One or more insulative layers may also be provided to prevent the PCAs 122 from shorting to the shield. In still further examples, the two PCAs

122a and 122b are fastened together using spring-loaded spacers, which are described more fully in connection with Section II.

In the example shown in FIG. 6, the two PCAs 122a and 122b are constructed substantially as mechanical mirror images of each other. The connectors 124a and 124b on the top PCA face up (i.e., in the positive Y direction), whereas the connectors 124a and 124b on the bottom PCA face down (i.e., in the negative Y direction), opposite the direction of connectors on the top PCA. Providing PCAs 122 in the form of plane assemblies 600 makes efficient use of space in the second region 120 and helps to minimize resistance to airflow 150. It should be understood, however, that assemblies of PCAs 122 can be constructed in other ways than that shown in FIG. 6. For example, PCAs 122 with similar geometry (not mirror images) can be stacked one on top of the other in any suitable arrangement. In addition, PCAs 122 may be provided individually, separate from any assembly of multiple PCAs 122. Further, although the assembly 600 is seen to include two PCAs 122, other assemblies can be constructed that include a greater number of PCAs. The example shown is merely illustrative.

Section II: Example techniques for aligning a plane assembly with a PCA:

Example techniques will now be described for promoting alignment between connectors of a plane assembly and connectors of a PCA in a chassis, such as the chassis 100, in which a backplane or midplane mates with a PCA orthogonally and edge-to-edge.

FIG. 7 shows an example plane assembly 600 mating with a PCA 132a, which in this case is a half-height PCA disposed in the third region 130 of the chassis 100. The PCA 132a I has connectors 134 (upper and lower) attached to respective connectors 124b (upper and lower) of a plane assembly 600. To establish the illustrated connections, the PCA 132a is inserted into the chassis 100 along card guides 702. As the PCA 132a approaches the plane assembly 600, a pin 710 that extends from an internal portion of the chassis 100 enters a hole formed in a bracket 712 in the PCA 132a, to bring the connectors 134 into coarse alignment with the connectors 124b. To establish fine alignment, additional features are provided, such as spring-loaded spacers and external aligners, which are discussed below. Although this example applies to half-height PCAs 132a in the third region 130 of the chassis 100, it applies equally to any PCAs 1 12 or 132 of any height.

FIGS. 8-10 show different views of example spring-loaded spacers 810. As best seen in FIG. 9, a spring-loaded spacer 810 includes a lower boundary portion 910, a connecting member 912 (such as a standoff), and a threaded boss 952. In an example, the connecting member 912 and the boss 952 are integral with or attached to the lower boundary portion 910 and form a prefabricated backer 1000 (FIG. 10). For example, the parts 910, 912, and 952 may be molded as a single unit. Alternatively, they may be screwed, press-fit, or otherwise fastened together. The spring-loaded spacer 810 is further seen to include an upper boundary portion 930, such as a cap washer, which may be screwed onto the connecting member 912 using cap screw 940, or attached to the connecting member 912 using some other type of fastener. A screw 960 passes through split washer 970 and screws into boss 952, although, again, other fastening means may be used.

The spring-loaded spacer 810 further includes a spring mechanism, which exerts a force that tends to bias the first and second circuit boards 122a and 122b away from each other. The spring mechanism may be provided, for example, in the form of a set of conical washers 914 (e.g., Belleville washers), which are

compressible in the vertical dimension. Although two conical washers 914 are shown, any number of such washers may be used, as space constraints permit, and depending on the desired extent of compression. In an example, the conical washers 914 are disposed between the first and second circuit boards 122a and 122b in the completed assembly (FIG. 8). Shim washers 920 may accompany the conical washers 914 to provide additional spacing and to keep the conical washers 914 under at least slight compression when the circuit boards are in place. Although not shown, it should be understood that the first and second circuit boards 122a and 122b each have clearance holes through which the connecting member 912 passes in the completed assembly.

The connecting member 912 is seen to have a height 912a (FIG. 9), which here corresponds to a vertical distance between the top of the lower boundary portion 910 and the bottom of the upper boundary portion (cap washer) 930. In the completed assembly (e.g., FIG. 8), an outer surface 812a of the first circuit board 122a rests against the top of the lower boundary portion 910 and an outer surface 812b of the second circuit board 122b rests against the bottom of the upper boundary portion 930. Thus, assuming no external source of compression, the distance between the outer surfaces 812a and 812b closely matches the height 912a of the connecting member 912, independent of the thickness of the circuit boards 122a and 122b. In an example, installation of the spring-loaded spacers 810 proceeds as follows. With screws 940 and 960 and washers 914, 920, 930, and 970 removed, the lower boundary portions 910, e.g., provided in the form of prefabricated backers 1000 (FIG. 10), are applied from underneath the first circuit board 122a, with the connecting members (standoffs) 912 and bosses 952 projecting through respective clearance holes in the first circuit board 122a, such that the lower boundary portions 910 lie flush against the outer (bottom) surface 812a of the first circuit board 122a. Screws 960 and washers 970 may then be applied to tighten the prefabricated backers 1000 to the first circuit board 122a. It should be understood that the boss 952 and associated screw 960 and washer 970 promote convenient assembly but should not be regarded as required.

Shim washers 920 and conical washers 914 may then be applied over and concentrically around the connecting members (standoffs) 912. As shown in FIG. 1 1, a greater number of (or thicker) shim washers 920 and/or conical washers 914 may be used for thinner-than normal-circuit boards or portions thereof, whereas a lesser number of (or thinner) shim washers 920 and/or conical washers 914 may be used for thicker-than-normal circuit boards or portions thereof. The second circuit board 122b is then placed over the connecting members 912 loaded with the washers 914 and 920, such that the connecting members 912 pass through clearance holes in the second circuit board 122b. Cap washers 930 are applied to the connecting members 912 and cap screws 940 are applied and tightened. In an example, tightening the cap screws 940 slightly compresses the conical washers 914 as the cap washers 930 firmly seat on the tops of the connecting members 912. Although the conical washers 914 are slightly compressed, there is still preferably capacity for additional compression. With the cap screws 940 tightened down, the distance between the outer surfaces 812a and 812b of the first and second circuit boards 122a and 122b closely matches the height 912a of the connecting member 912.

FIG. 12 shows an example external aligner 1210. In the example shown, the external aligner 1210 has a U-shaped channel 1212 having an upper wall 1214a, a lower wall 1214b, and a height 1220. In an example, the external aligner 1210 is made from stamped or machined sheet metal or from some other dimensionally stable material. As shown in FIG. 12, the edge 610a of the plane assembly 600, or a portion thereof, is disposed within the channel 1212 of the external aligner 1210, such that the outer surfaces 812a and 812b of the first and second circuit boards 122a and 122b lie adjacent to the lower and upper walls 1214b and 1214a of the channel 1212, respectively. The lower wall 1214b limits a lower position within the chassis 100 of the outer surface 812a of the first circuit board 122a near the edge 610a of the plane assembly 600 to a lower limit. Similarly, the upper wall 1214a limits an upper position within the chassis 100 of the outer surface 812b of the second circuit board 122b near the edge 610a of the plane assembly 600 to an upper limit. With connectors 124a and 124b mounted to the outer surfaces 812a and 812b, either directly of spaced off the surfaces by a known distances, the lower wall 1214b of the channel 1212 establishes the precise vertical position or positions of the connectors 124a and 124b extending down from the outer surface 812a. Likewise, the upper wall 1214a of the channel 1212 establishes the precise vertical position or positions of the connectors 124a and 124b extending up from the outer surface 812b.

In some examples, the role of the external aligner 1210 is merely to hold the edge 610a of the plane assembly 600 at a proper vertical position within the chassis 100 for mating with PCAs. In such examples, the height 1220 of the channel 1212 is made to closely match the height 912a of the connecting member 910 (FIG. 9), such that the edge 610a of the plane assembly 600 has a close-tolerance fit within the channel 1212.

In more typical examples, however, the external aligner 1210 serves both to hold the edge 610a of the plane assembly 600 at the proper vertical position and to establish a proper spacing between connectors 124b on the circuit boards 122a and 122b. Such spacing precisely matches the spacing between mating connectors 134 on the PCA 132a (FIG. 7). To this end, the height 1220 of the channel 1212 is made smaller than the height 912a of the connecting member 912 (FIG. 9), such that the spring-loaded spacers 810, or some subset of them, are made to compress (or further compress) in order for the end 610a of the plane assembly 600 to fit within the channel 1212. Such compression ensures that a close-tolerance fit is established within the channel 1212 without requiring high precision from the spring-loaded spacers 810. It should be understood that a chassis may employ any number of external aligners 1210, e.g., at different locations along the edge 610a of the plane assembly 600. In some examples, the chassis 100 employs external aligners 1210 at both edges 610a and 610b (FIG. 6) of the plane assembly 600, to facilitate alignment with both PCAs 132 and with PCAs 112, which may plug in from both ends of the chassis 100. In other examples, external aligners 1210 are used on only one edge, e.g., where the plane assembly 600 acts as a backplane and/or where connector alignment is critical on one edge only.

Although the embodiments shown involve the spring-loaded spacers 810 biasing the circuit boards 122a and 122b apart, other embodiments may use different types of spring-loaded spacers to bias the circuit boards together. For example, referring briefly back to FIG. 6, an alternative design of the plane assembly 600 may provide similar circuit boards 122a and 122b but with each of the boards flipped over such that connectors 124a and the connectors 124b face toward each other rather than away from each other. In such an arrangement, the spring-loaded spacers may be configured to pull the circuit boards 122a and 122b toward each other, e.g., limited to some minimum distance, rather than to push them apart. Here, the external aligner 1210 may be replaced with an internal aligner, such as a tab. The tab can extend between the circuit boards 122a and 122b at the end 610a and can press against their internal surfaces to hold them apart by a precise distance. The tab has a

predetermined height established so as to align the connectors on the plane assembly with those on the PCA.

Section III: Example alignment techniques for multiple plane assemblies and/or Multiple PCAs

Example techniques will now be described for promoting connector alignment among multiple plane assemblies and multiple PCAs in a chassis, such as the chassis 100, in which plane assemblies mate with arrays of PCAs orthogonally and edge-to- edge. The illustrated techniques build upon those described in Section II for aligning connectors of a plane assembly 600 with connectors of a PCA.

FIG. 13 shows an example full-height PCA 132b, which may be inserted, for example, in the third region 130 of the chassis 100. The PCA 132b has connectors 134 that engage connectors 124b on three different plane assemblies 600, identified here as 600a, 600b, and 600c. Here, it is desired to align connectors on all three plane assemblies 600 with connectors 134 on the PCA 132b. To achieve coarse alignment, pins 710 engage holes on brackets 712 as the PCA 132b plugs into the chassis 100. To achieve fine alignment, the chassis 100 employs spring-loaded spacers 810 and external aligners 1210, as described in Section II, as well as additional features, described below. These additional features include one or more spacing strips that run vertically within the chassis 100. In some examples, the chassis 100 employs one or more stabilizer strips to horizontally stabilize the spacing strip(s). In further examples, multiple spacing strips and multiple stabilizer strips engage to form an alignment lattice. One alignment lattice may serve to align plane assemblies 600 with any number of PCAs 1 12 in the first region 1 10 of the chassis 100 (FIG. 1), and another alignment lattice may serve to align plane assemblies 600 with any number of PCAs 132 in the third region 130 of the chassis 100. Although spacing strips, stabilizer strips, and lattices are described in connection with a full-height PCA 132b, their application is not limited to full-height PCAs and may be used with PCAs of any size. Also, although the example shown depicts alignment across three plane assemblies (e.g., 600a, 600b, and 600c), the features disclosed may operate over any number of plane assemblies 600.

FIG. 14 shows an example spacing strip 1410. The spacing strip 1410 vertically positions multiple external aligners 1210 (e.g., 1210a, 1210b, and 1210c) at precise locations (e.g., 1414a, 1414b, 1414c) along its length 1410a. Each external aligner 1210 engages a respective pair of circuit boards 122a and 122b of a respective plane assembly 600 at an edge (610a or 610b) of a plane assembly 600 and holds the pair of circuit boards in a precisely spaced arrangement. The spacing strip 1410 with its external aligners 1210 therefore ensures both precise vertical positioning of plane assemblies 600 and precise spacing between them.

In an example, the spacing strip 1410 is a narrow, thin strip, which is dimensionally stable lengthwise to maintain precise spacing between external aligners 1210 and, therefore, between plane assemblies 600 and their connectors. In some examples, the external aligners 1210 are implemented as features of the spacing strip 1410 itself, rather than as separate components, such that the spacing strip 1410 includes multiple channels, like the channels 1212. The spacing strip 1410 preferably has a low profile so that it negligibly resists airflow 150 (FIG. 1). Thus, the spacing strip 1410 maintains alignment between PCAs and plane assemblies while having virtually no negative impact on cooling within the chassis 100. In an example, the spacing strip 1410 has tabs 1412a and 1412b at its ends that attach to respective internal surfaces of the chassis 100. The spacing strip 1410 may further include notches 1420. As will be described, the notches 1420 engage with similar notches on stabilizer strips to form interlocking joints.

FIG. 15 shows an example view of the inside of the chassis 100, where a spacing strip 1410 (shown at left) is seen to engage with three plane assemblies 600. Additional support structures are shown, including a side panel 1510 with openings 410, an internal support 1520 for plane assemblies 600, and an alignment bracket 1530.

FIG. 16 shows an example alignment lattice 1600. The alignment lattice 1600 is seen to include multiple spacing strips 1410 in a spaced arrangement separated by stabilizer strips 1610. Although the alignment lattice 1600 as shown includes two spacing strips 1410 and two stabilizer strips 1610, other examples may alternatively include any number of strips of each type, including a single strip, and the number of spacing strips 1410 need not be the same as the number of stabilizer strips 1610.

In an example, the spacing strips 1410 interlock with the stabilizer strips 1610 by means of the notches 1420 on the spacing strips 1410, which engage with respective notches 1620 on the stabilizer strips 1610 to form dovetail joints. In this interlocked arrangement, the stabilizer strips 1610 serve to horizontally stabilize the spacing strips 1410, e.g., to hold them firmly in place and to resist their horizontal bending or movement. Each stabilizer strip 1610 is seen to include tabs 1614. In an example, the tabs 1614 promote horizontal alignment of PCAs (e.g., 112, 132) for proper engagement with connectors (124a, 124b) on plane assemblies 600. For example, as PCAs are plugged into the chassis 100, leading edges of the PCAs make contact with tabs 1614 and are guided into spaces 1616 between adjacent tabs 1614. The tabs 1614 may have tapered ends 1614a to facilitate guidance of PCAs into spaces 1616. Like each of the spacing strips 1410, each of the stabilizer strips 1610 is preferably a thin, narrow strip, which is dimensionally stable lengthwise and has a low profile that negligibly resists airflow 150. Each of the stabilizer strips 1610 has tabs 1612a and 1612b at the ends thereof for attaching to internal surfaces of the chassis 100. Alternatively, each stabilizer strip 1610 has only a single tab on one end thereof for attaching to a single internal surface of the chassis 100.

FIG. 17 shows an example of the alignment lattice 1600 installed within the chassis 100. Here, it can be seen that the lattice 1600 employs first external aligners (top-most) for aligning plane assembly 600a. The lattice 1600 also employs second external (middle) for aligning plane assembly 600b and employs third external aligners (bottom-most) for aligning plane assembly 600b.

Once installed, the lattice 1600 forms a stiff, stable structure that facilitates alignment of connectors without impairing airflow 150. The spacing strips 1410 precisely position the external aligners 1210 vertically within the chassis 100, while the stabilizer strips 1610 stabilize the external aligners 1210 horizontally. Tabs 1614 further assist in aligning PCAs horizontally for mating with plane assemblies 600. A difficult challenge of aligning connectors is thus addressed and overcome.

Having described certain embodiments, numerous alternative embodiments or variations can be made. For example, although alignment techniques have been shown and described for a particular chassis 100 having an axial design, the improvements hereof are not limited to use with this particular chassis or with any axial chassis. Rather, these alignment techniques may be used with any chassis design in which circuit boards meet orthogonally and edge-to-edge.

Further, although features are shown and described with reference to particular embodiments hereof, such features may be included and hereby are included in any of the disclosed embodiments and their variants. Thus, it is understood that features disclosed in connection with any embodiment are included as variants of any other embodiment.

As used throughout this document, the words "comprising," "including," and "having" are intended to set forth certain items, steps, elements, or aspects of something in an open-ended fashion. Also, as used herein and unless a specific statement is made to the contrary, the word "set" means one or more of something. This is the case regardless of whether the phrase "set of is followed by a singular or plural object and regardless of whether it is conjugated with a singular or plural verb. Although certain embodiments are disclosed herein, it is understood that these are provided by way of example only and the invention is not limited to these particular embodiments.

Those skilled in the art will therefore understand that various changes in form and detail may be made to the embodiments disclosed herein without departing from the scope of the invention.

Table of Reference Numerals:

100 including three assemblies 600

600c "Bottom" plane assembly 600 in chassis

100 including three assemblies 600

610a First end (or edge) of plane assembly 600 facing first region 110

610b Second end (or edge) of plane assembly

600 facing third region 130

702 Card guides

710 Male alignment feature (e.g., pin or

blade) in chassis 100 for aligning PCAs 132 within chassis 100

712 Female alignment feature, e.g., bracket having a hole or channel on PCA 132 for receiving male alignment feature 710 in chassis 100

810 Spring-loaded spacer that holds circuit boards 122a and 122b in plane assembly 600 and biases them apart

810a Spring-loaded spacer for circuit board

122 of nominal thickness

810b Spring-loaded spacer for circuit board

122 of less than nominal thickness

810c Spring-loaded spacer for circuit board

122 of greater than nominal thickness

812a Outer surface of first circuit board 122a of plane assembly 600

812b Outer surface of second circuit board

122b of plane assembly 600

910 Lower boundary portion of spring-loaded spacer 810, disposed under "bottom" circuit board 122a in plane assembly 600; forms a base of the spring-loaded spacer 810.

912 Connecting member (e.g., standoff)

912a Height of connecting member (standoff)

912, which defines distance between outer surfaces of circuit boards 122 in plane assembly 600

914 Spring-loaded washers (e.g., conical washers, such as Belleville springs)

920 Shim washers 930 Upper boundary portion, such as cap washer, disposed over "top" circuit board 122b in plane assembly 600

940 Cap screw, which holds cap washer 930 and standoff 912 to base 910

950 Attachment fastener for holding

prefabricated backer to bottom circuit board 122a

952 Threaded boss; fixed to base 910 and may fit in hole in bottom circuit board 122a

960 Screw

962 Threads of screw 960

970 Lock washer

1000 Prefabricated backer

1210 External Aligner, which holds circuit boards 122a and 122b to establish their vertical position within the chassis 100 and, in some cases, the spacing between boards.

1210a "Top" external aligner positioned to align top plane assembly 600a

1210b "Middle" external aligner positioned to align middle plane assembly 600b

1210c "Bottom" external aligner positioned to align bottom plane assembly 600c

1212 Channel of external aligner 1210

1214a Upper wall of channel 1212

1214b Lower wall of channel 1212

1220 Height of channel 1212 of external aligner 1210

1410 Spacing strip, which holds external aligners 1210a, 1210b, and 1210c in specified positions

1410a Length of spacing strip 1410

1412a "Upper" fastening tab, which attaches to inner "roof of chassis

1412b "Lower" fastening tab, which attaches to inner "floor" of chassis 1420 Notch, which interlocks with notch 1620 on stabilizer strips 1610 to form dovetail

1510 Side panel with openings 410

1520 Internal support for PCA assemblies 600

1530 Attachment bracket

1600 Alignment lattice

1610 Stabilizer strip

1612a "Left" fastening tab, which attaches to inner wall of chassis

1612b "Right" fastening tab, which attaches to inner wall of chassis

1614 Tabs extending from stabilizer strip 1610, which assists in aligning PCAs 112, 132

1614a Tapered ends of tabs 1614

1616 Spaces between adjacent tabs 1614

1620 Notch in stabilizer strip 1610, which interlocks with notch 1420 in spacing strip 1410