Deflectable contact for providing positive surface contact for shielding electromagnetic interference

Abstract: There is disclosed an electromagnetic compatibility grounding connector having a contact portion deflectable between a first and a second position. In the first position only a line contact is established in contact with a complementary connector. In a second position a surface contact is established of greater surface contact area than the line contact. Electrical resistance is thus reduced and conductivity increased. Also disclosed is a support for an electronic device having such a connector and a personal computer housing having such supports and interconnecting with such connectors.

Description: The present invention relates to an electromagnetic compatibility grounding connector for providing effective electromagnetic interference shielding. Electromagnetic compatibility (EMC) relates to the ability of electronic equipment to perform without suffering or causing performance degradation due to electromagnetic absorption or electromagnetic emissions to its operational environment. Accordingly EMC is critical to the operation of a computer and an essential component of shielding design for its housing. More specifically, as industry develops faster and higher frequency systems, design criteria and techniques to meet required EMC standards must also increase. As is well known in the art of designing computers to meet FCC requirements, it is desirable to shield and ground all electronic components and to do so with the shortest, lowest resistance, ground path possible. Typically, in designs of the prior art, the ground path from a critical component to a grounded base of the system comprises a number of conductive contacts from part to part until the component is finally grounded to the base. Design constraints cause the length of the path to be maintained by means of a number of intermediate contact points. Each contact point exhibits an electrical resistance reduces grounding. Specifically, a typical contact is a line or point contact exhibiting a high electrical resistance. From GB-A-2061624 there is known an electromagnetic interference (EMI) shielding device used in supporting members that receive enclosure covers of electrical or electronic instruments. The EMI device comprises an L-shaped strip of metal having first contact means which maintain the device in position in a groove in the supporting member and provide electrical contact therewith and springs contacts against which an edge of an enclosure member disposed in the groove engages. An aim of the present invention is therefore to overcome the the problem imposed by increased resistance from line or point contacts in grounding paths. In accordance with the present invention as defined in claim 1, there is now provided, an electromagnetic compatibility grounding connector for an equipment housing having an electromagnetic interference shield panel mountable on one surface of the housing adjacent to a front surface of at least one electronic device, and a moveable support comprising a base having an upper surface and a lower surface, the upper surface having the electronic device mounted thereon; the connector comprising:- conductive means on the upper surface of the base interspersed between the electronic device and the upper surface, and electrically connected to a ground connection of the electronic device; and deflectable contact means extending outwardly from the horizontal plane of the base, connected to the conductive means, and the contact means deflectable between a first position and a second position, for providing a line contact when in the first position, and for providing a surface contact of greater contact surface area than the line contact when deflected into the second position by pressure exerted thereon by the electromagnetic interference shield panel, in physical and electrical contact therewith, when the housing is fully assembled to provide enhanced shielding against electromagnetic interference; the conductive means being a straight strip of stamped metal and the contact means being an arcuate strip of stamped metal integral with and extending from the conductive means and the arcuate strip of stamped metal being rotated 90 degrees relative to the horizontal surface of the straight strip to extend vertically. In an example, there is provided a support for an electronic device, specifically a direct access storage device, i.e., DASD, such as a hard disk drive, for mounting in a personal computer housing comprising the electromagnetic compatibility grounding connector. In another example of the present invention there is provided an improvement in a personal computer housing having an electromagnetic interference shield panel with the improvement being a support for supporting an electronic device such as a DASD within the personal computer housing and with the support having the grounding connector for connection to the electromagnetic shield panel of the personal computer to provide effective shielding and grounding for the electronic device. In a preferred example of, the present invention to be described later, there is provided an improvement in a personal computer housing having a top, bottom, sides, front and back, and having an electromagnetic interference shield panel mountable on the front adjacent the front surface thereof, and at least one electronic device, e.g., DASD, mounted on a movable support. Specifically, the Improvement comprises the support which is a base having an upper surface and a lower surface, with the upper surface having the DASD mounted thereon. As will be described in greater detail later with reference to Figure 2, a connector includes a conductor which extends on the upper surface of the base dispersed between the DASD and the top surface, and is electrically connected to a ground connection of the DASD. A deflectable contact portion extends outwardly from the horizontal plane of the base from the conductor with the contact portion being deflectable between a first position and a second position. In the first position, the deflectable contact portion provides a line contact against a complimentary contact and in the second position, due to pressure exerted thereon by the electromagnetic interference shield housing in physical and electrical contact therewith, it provides a surface contact with the complimentary contact of greater contact surface area than the point contact. As a result, when the personal computer housing is fully assembled there is provided enhanced shielding against electromagnetic interference as a result of the lower resistivity contact with the shield resulting from the increased surface contact area of the deflected contact. An embodiment of the present invention will now be described with reference to the accompanying drawings in which:- Figure 1A is a partially disassembled perspective view of a personal computer housing showing the grounding connector having a contact portion in accordance with the present invention. Figure 1B is an enlarged view of the circled portion of Figure 1A showing in greater detail the contact portion in undeflected form prior to abutment with an electromagnetic shield of the personal computer housing. Figure 2 is a disassembled perspective view of a removable support for an electronic device such as a DASD showing the contact portion of the invention and its relationship to the DASD and its support. Figure 3 is a side partial cross-sectional view showing an electronic device mounted on a support connected to the connector in accordance with the invention. Figures 4A, 4B, and 4C show in progression the relationship between the deflectable contact member in accordance with the invention as it engages with the electromagnetic shield within personal computer assembly, and deflects from a line contact into a surface contact with consequent reduction in resistance between the contacts to provide enhanced conductivity and shielding. In Figure 1 there is shown a personal computer housing 1 in partially disassembled form where an electromagnetic interference (EMI) shield 3a is shown separated from its supporting panel 3b of the personal computer 1. Also shown disassembled is the cover 5 of the personal computer. The electromagnetic shield 3a, preferably of, e.g., sheet metal, includes complimentary contacts 7 for contacting against the contact in accordance with the invention. The personal computer includes an electronic component bay structure 11 for having electronic components such as DASDs mounted on a support 15 having the connector 23 (shown in Figure 2) with the contact portion 27 in accordance with the invention shown in the circled portion and described in greater detail with reference to Figure 1B. More specifically, in Figure 1B there is shown a DASD such as a hard disk drive 13 on a slideable support 15 which is typically made of an electronically insulating material. Shown projecting from the DASD 13 and outwardly from the support is a deflectable contact 27 which engages with contact 7 of the EMI shield 3a. The engagement between the contacts will be explained in greater detail with reference to the other figures. In Figure 2 there is shown a disassembled view of the DASD 13, connector 23 and its support 15. As readily apparent from Figure 2, the DASD 13 includes a metal base support 19 which serves as a ground connector for the DASD 13. In this instance it is noted that the invention is being described with reference to a DASD. It should be noted that such reference is for example purposes only and that the invention can be employed with other electronic components of the type requiring a ground contact and/or shielding. Continuing, it is also shown that the metal support 19 is connected to the DASD 13 for grounding purposes with the connection to the grounded electronic circuits of the device not shown. The metal ground plate 19 serves to connect to the connector 23, and is secured to the support 15 and the connector 23 by means of connector securing portions 25 through which screws 21 are inserted through the support 15 and into the ground plate 19. The support 15 includes slide portions 17 for ease of sliding into and out of the bays 11 of the personal computer housing 1. Figure 2 also shows the flexible contact portion 27 which at the distal end includes a notch portion 26 which engages with a corresponding notch 16 of the support 15. The purpose of this notch is to limit the inward movement of the contact portion 27 so that it forces the contact upon pressure being exerted thereon to deform. On the other hand, since it does allow some movement, the notch permits the flexible contact portion 27 some flexibility of movement relative to the position of contact 7 to result in some adjustability of position prior to deflecting to achieve the result of the largest area of surface contact possible. It is also noted that the contact portion 27 is rotated 90 degrees relative to the conductor of the connector 23 which extends on the upper surface of the support 15. This facilitates establishing of the surface contact against contact 7 of shield 3a. Figure 3 schematically shows in partial cross-sectional side view the DASD 13 mounted by means of screws 21 onto the support 15. Shown interposed between the support 15 and the DASD 13 is the connector 23 having the flexible contact portion 27 projecting horizontally theref rom. In Figures 4A-4B there is shown the progressive deflection of the contact 27 as the EMI shield 3a is brought into contact with the corresponding face 3b of the personal computer assembly. Figure 4A shows the contact portion 27 spaced from its corresponding engaging contact 7 of EMI shield 3a as the shield 3a is bought progressively closer to face 3b and there is first established a line contact between deflectable contact portion 27 and its engaging contact 7 of the shield 3a. Upon full assembly the flexible contact portion 27 deforms as shown in Figure 4C, engaging contact 7 over a greater surface area thereby providing for a reduced resistance electrical connection. As to the materials for the support 15, it is preferably of polycarbonate, an insulator. This allows ease of sliding and engaging with other plastic-like parts in the computer housing bays 11. Alternatively, the support 15 can be of metal such as sheet metal or any other like material which is easily formed. With respect to the connector 23, it is preferably of stamped stainless steel. Alternative materials include stamped beryllium copper or spring steel as well as other conventional well known exotic alloys presently available in the marketplace. A problem with spring steel is that it oxidizes, reducing conductivity and increasing resistance thereby adversely affecting the control of EMI. The more exotic alloys are problematic because although performance is improved, cost far outweighs any improvement in performance.

Claims: An electromagnetic compatibility grounding connector for an equipment housing (1), the housing having an electromagnetic interference shield panel (3a) mountable on one surface of the housing adjacent to a front surface of at least one electronic device, and a moveable support (15) comprising a base having an upper surface and a lower surface, the upper surface having the electronic device mounted thereon; the connector (23) comprising:- conductive means (25) on the upper surface of the base interspersed between the electronic device and the upper surface, and electrically connected to a ground connection of the electronic device; and deflectable contact means (27) extending outwardly from the horizontal plane of the base, connected to the conductive means (25), and the contact means (27) deflectable between a first position and a second position, for providing a line contact when in the first position, and for providing a surface contact of greater contact surface area than the line contact when deflected into the second position by pressure exerted thereon by the electromagnetic interference shield panel (3a), in physical and electrical contact therewith, when the housing (1) is fully assembled to provide enhanced shielding against electromagnetic interference; the conductive means (25) being a straight strip of stamped metal and the contact means (27) being an arcuate strip of stamped metal integral with and extending from the conductive means (25) and the arcuate strip of stamped metal being rotated 90 degrees relative to the horizontal surface of the straight strip to extend vertically. A connector as claimed in claim 1 wherein the arcuate strip of stamped metal is fixed at both ends of the arc to the support and extends horizontally therefrom. A connector as claimed in claim 2 wherein one end of the arcuate strip is loosely connected in a manner permitting a sufficient amount of play before the arcuate strip deflects sufficiently to ensure a maximum area of surface contact when deflected into the second position by a complementary connecting contact of the shield panel (3a). A connector as claimed in any preceding claim wherein the base of the support (15) is made of polycarbonate material. A connector as claimed in any preceding wherein the connector is made of one of stainless steel and beryllium copper. A connector as claimed in any preceding claim wherein the connector is made of stainless steel. A computer system comprising a connector as claimed in any preceding claim. A computer system as claimed in Claim 7 wherein the electronic device is a magnetic disk drive. A computer system as in claimed 8 further comprising a plurality of magnetic disk drives on a corresponding plurality of supports having a corresponding plurality of conductive means (23) and deflectable contact means (27) all mounted in the housing (1).

Inventors: COOKE KEVIN KIEFER, DEWITT JOHN ROBINSON, GALINIS PAUL JEFFREY, COOKE, KEVIN KIEFER, DEWITT, JOHN ROBINSON, GALINIS, PAUL JEFFREY
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1990
Main classification: H05K9
IPC codes: G06F1, H05K9