Method and apparatus for adding shielding for circuit packs

Abstract: A method and apparatus for adding shielding for electronic circuit packs (105). The invention includes a circuit pack cage (101), which has a first pair of parallel longitudinal circuit pack slots (103) for receiving the circuit packs (105) and further has a first longitudinal shield slot (107) disposed between first pair of circuit pack slots (103) for receiving a conductive sheet member (109). At least one conductive resilient member (111) is disposed in the first shield slot (107) in electrical coupling with a conductive chassis (113). Upon sliding the conductive sheet member (109) between the pair of circuit packs (105) and into the shield slot (107), the resilient member (111) flexibly engages the conductive sheet member (109) and electrically couples the conductive sheet member (109) with the conductive chassis (113).

Description: Field of the Invention The invention generally relates to shielding electromagnetic radiation and more particularly relates to adding shielding for electronic circuit packs. Background of the Invention Various schemes for shielding circuit packs are known in the prior art. Shielding is especially important for circuit packs that are VXI (Versabus eXtensions for Instrumentation) instrumentation modules, since electromagnetic radiation from adjacent modules would corrupt sensitive measurement made by the VXI instrumentation modules. One such scheme relies on a complex assembly of shielding and threaded grounding screws for keeping the shielding grounded and in place. While such schemes provide some advantageous some limitations still remain. As circuit packs or added or rearranged, tedious labor is needed to carefully extract, insert, or adjust the grounding screws. It has been observed in some instances that the grounding screws were not properly arranged in contact with the shielding, which allowed the shielding to assume a floating electrical potential. This in turn resulted in poor electromagnetic isolation between circuit packs. What is needed is a simplified, efficient, flexible, and convenient method and apparatus for adding shielding for circuit packs. Summary of the Invention The present invention provides a simplified, efficient, flexible, and convenient method and apparatus for adding shielding for electronic circuit packs. Briefly and in general terms the invention includes a circuit pack cage, which has a first pair of parallel longitudinal circuit pack slots for receiving the circuit packs and further has a first longitudinal shield slot disposed between first pair of circuit pack slots for receiving a conductive sheet member. At least one conductive resilient member is disposed in the first shield slot in electrical coupling with a conductive chassis. Upon sliding the conductive sheet member between the pair of circuit packs and into the shield slot, the resilient member flexibly engages the conductive sheet member and electrically couples the conductive sheet member with the conductive chassis. Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Brief Description of the Drawings FIG. 1A is an exploded perspective view of a preferred embodiment of the invention. FIG. 1B is a cut away perspective view of the preferred embodiment of the invention. FIGS. 1C and 1D are detailed views of FIG. 1B. FIGS. 1E and 1F are further detailed views of the conductive resilient member employed in conjunction with the preferred embodiment of the invention. FIG. 1G shows another exploded perspective view of the preferred embodiment of the invention. Detailed Description of Preferred Embodiment FIG. 1A is an exploded perspective view of a preferred embodiment of the apparatus of the invention 100. As shown, a circuit pack cage 101 has a first pair of parallel longitudinal circuit pack slots 103 for receiving a pair of electronic circuit packs 105. In the preferred embodiment, the circuit packs are VXI (Versabus eXtensions for Instrumentation) instrumentation modules. The efficient shielding provided by the present invention is particularly advantageous for shielding VXI instrumentation modules, since electromagnetic radiation from adjacent modules would corrupt sensitive measurements made by the VXI instrumentation modules. The flexibility in adding the shielding of the invention is particularly advantageous to VXI instrumentation modules, since VXI modules may be frequently rearranged into different configurations, depending on various instrumentation requirements. As shown in FIG. 1A, the circuit pack cage further has a first longitudinal shield slot 107 disposed between the first pair of circuit pack slots 103 for receiving a conductive sheet member 109, preferably a sheet of aluminum. At least one conductive resilient member 111 is disposed in the first shield slot in electrical coupling with a conductive chassis 113. In the preferred the preferred embodiment two conductive resilient members 111 are disposed in the first shield slot. Preferably, an expanded pocket for retaining the resilient member extends into the shield slot 107. For the sake of simplicity, conductive cross members coupled with the conductive chassis 113 are not shown in the figures. Upon sliding the conductive sheet member 109 between the pair of circuit packs 105 and into the shield slot 107, the resilient member 111 flexibly engages the conductive sheet member 109 and electrically couples the conductive sheet member 109 with the conductive chassis 113. In the preferred embodiment the conductive resilient member features a substantially U shaped cross section. As shown, the conductive resilient member has a central region feature for flexibly engaging an edge of the conductive sheet member and also features a pair of arms extending outwardly from the central region for engaging the conductive chassis. It should be understood that these features contribute to advantageously retaining the resilient member in the shield slot and to ease of sliding the conductive sheet member into place. As shown in FIG. 1A, in the preferred embodiment, the circuit pack cage further has a second pair of parallel longitudinal circuit pack slots 123, opposing the first pair of circuit pack slots 103 and similar thereto, for receiving the pair of circuit packs 105 and spatially arranging the circuit packs in parallel. The circuit pack cage further has a second longitudinal shield slot 127, opposing the first longitudinal shield slot 107 and similar thereto. As shown, another expanded pocket 128 for retaining other resilient member 131 extends into the second shield slot 127. As shown, the second shield slot 127 is disposed between second pair of circuit pack slots 123 for receiving the conductive sheet member 109. Said another conductive resilient member 131 is disposed in the pocket 128 of the second shield slot 127 and arranged for electrically coupling the conductive sheet member 109 with the conductive chassis 113. FIG. 1B is a cut away perspective view of the apparatus of the invention. One of the circuit packs and portions of the conductive chassis and card cage are shown cut away to reveal resilient members 111, 113 disposed in pockets of the shield slots and flexibly engaging the conductive sheet member, as further shown in detailed views in FIG. 1C and FIG. 1D. FIGS. 1E and 1F are further detailed views of the conductive resilient member employed in conjunction with the preferred embodiment of the invention. As discussed previously herein and as shown in the figures, the conductive resilient member features a substantially U shaped cross section. In the preferred embodiment, the conductive resilient member is fabricated from a beryllium copper alloy plated with tin. Of course the principles of the invention are not strictly limited to application to just a pair of circuit packs. The principles of the invention are advantageously applied to electromagnetically shielding a plurality of electronic circuit packs from one another. FIG. 1G shows another exploded perspective view of the preferred embodiment of the invention. As shown, a plurality of conductive sheet members are used in conjunction with a circuit pack cage having a first set of parallel longitudinal circuit pack slots for receiving the circuit packs and for spatially arranging the circuit packs in parallel with one another, and further having a first set of parallel longitudinal shield slots interdigitated with the first set of circuit pack slots for receiving the conductive sheet members and for arranging each conductive sheet member between a respective pair of the circuit packs. A first set of conductive resilient members are each disposed in a respective one of the first shield slots and are arranged for electrically coupling the respective conductive sheet member with the conductive chassis. The circuit pack cage further has a second set of parallel longitudinal circuit pack slots, opposing the first set of circuit pack slots, for receiving the pair of circuit packs, and further has a second set of longitudinal shield slots, opposing the first set of longitudinal shield slots, and interdigitated between second set of circuit pack slots for receiving the conductive sheet members. As shown, a second set of conductive resilient members are each disposed in a respective one of the second set of shield slots and arranged for electrically coupling the respective conductive sheet member with the conductive chassis. As discussed, the present invention provides a simplified, efficient, flexible, and convenient method and apparatus for adding shielding for electronic circuit packs. Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated, and various modifications and changes can be made without departing from the scope of the invention as defined in the claims. Within the scope of the appended claims, therefor, the invention may be practiced otherwise than as specifically described and illustrated.

Claims: An apparatus for electromagnetically shielding at least a two members of a plurality of electronic circuit packs (105) from one another comprising: a conductive sheet member (109); a circuit pack cage (101): having a first pair of parallel longitudinal circuit pack slots (103) for receiving the two circuit packs (105) and for spatially arranging the circuit packs (105) in parallel with one another, and further having a first longitudinal shield slot (107) disposed between first pair of circuit pack slots for receiving the conductive sheet member (109) and for arranging the sheet member (109) between the circuit packs (105); a conductive chassis (113) mechanically coupled with the circuit pack cage (101) for supporting the cage (101) and the circuit packs (105); and at least one conductive resilient member (111) disposed in the first shield slot (107) and arranged for electrically coupling the conductive sheet member (109) with the conductive chassis (113). An apparatus as in claim 1 wherein the conductive resilient member (111) has a substantially U shaped cross section. An apparatus as in claim 2 wherein the conductive resilient member (111) has a central region for flexibly engaging an edge of the conductive sheet member (109) a pair of arms extending outwardly from the central region for engaging the conductive chassis (113). An apparatus as in claim 1 wherein: the circuit pack cage (101): further has a second pair of parallel longitudinal circuit pack slots (123), opposing the first pair of circuit pack slots, for receiving the pair of circuit packs (105), and further has a second longitudinal shield slot (127), opposing the first longitudinal shield slot (107) and disposed between second pair of circuit pack slots (123) for receiving the conductive sheet member (109); and another conductive resilient member (111), which is disposed in the second shield slot (127) and arranged for electrically coupling the conductive sheet member (109) with the conductive chassis (113). An apparatus as in claim 1 wherein the circuit packs (105) are VXI instrumentation modules. An apparatus as in claim 1wherein: the circuit pack cage: has a first set of parallel longitudinal circuit pack slots for receiving the circuit packs and for spatially arranging the circuit packs in parallel with one another, and further has a first set of parallel longitudinal shield slots interdigitated with the first set of circuit pack slots for receiving the conductive sheet members and for arranging each conductive sheet member between a respective pair of circuit packs; and the apparatus further comprises a plurality of conductive sheet members; and a first set of conductive resilient members each disposed in a respective one of the first shield slots and arranged for electrically coupling the respective conductive sheet member with the conductive chassis. An apparatus as in claim 6 wherein each of the conductive resilient members has a substantially U shaped cross section. An apparatus as in claim 7 wherein each of the conductive resilient members has a central region for flexibly engaging an edge of the conductive sheet member a pair of arms extending outwardly from the central region for engaging the conductive chassis. An apparatus as in claim 6 wherein: the circuit pack cage: further has a second set of parallel longitudinal circuit pack slots, opposing the first set of circuit pack slots, for receiving the pair of circuit packs, and further has a second set of longitudinal shield slots, opposing the first set of longitudinal shield slots, and interdigitated between second set of circuit pack slots for receiving the conductive sheet members; and a second set of conductive resilient members, which are each disposed in a respective one of the second set of shield slots and arranged for electrically coupling the respective conductive sheet member with the conductive chassis. A method for shielding a pair of electronic circuit packs (105) from one another comprising the steps of: providing a conductive sheet member (109), a conductive chassis (113) and a circuit pack cage (101), which has a first pair of parallel longitudinal circuit pack slots (103) and further has a first longitudinal shield slot (107) disposed between first pair of circuit pack slots (103); sliding the pair of circuit packs (105) into the circuit pack slots (103) so as to arrange the circuit packs (105) in parallel with one another, disposing at least one conductive resilient member (111) in the first shield slot (107) in electrical coupling with the conductive chassis (113); and sliding the conductive sheet member (109) between the pair of circuit packs (105) and into the shield slot so as to flexibly engage the resilient member (111) and electrically couple the conductive sheet member (109) with the conductive chassis (113) through the resilient member (111).

Inventors: MILLARD ROBERT A, MILLARD, ROBERT A.
Applicants: AGILENT TECHNOLOGIES INC, AGILENT TECHNOLOGIES, INC. (A DELAWARE CORPORATION)
Application year: 1998
Main classification: H05K9
IPC codes: H05K9