FILTERING ELECTRICAL CONNECTOR

Abstract: A filter connector comprising a conductive housing 88 containing a pin array traversing corresponding holes in a grommet 30, a dielectric body 36, a planar capacitor array 42, ferrite inductor beads 50 mounted on at least some of the pins 20, a non-conductive body 58 to insulate said beads from one another and from said capacitor 42, a non-conductive seal 62, a second capacitor array 72, a second grommet 78, a second interface seal 82; a grounding can 10 bound to said Pi-section filter portion and in electrical contact with a ring of contact fingers 98 mounted in the interior of said housing 88. Optionally, a conductive O-ring 102 encircles said shell, to improve shielding at the mounting interface.

Description: This invention relates to a multi-pin electrical connector with built-in electromagnetic interference (EMI) filtering capability. Filtering multi-pin electrical connectors to combat EMI problems are known. It is usual to make these connectors with ceramic capacitors and inductors, the elements of which are brittle and so fragile that they do not provide desired reliability. Also, prior filtering connectors, such as described in US Patent document US 4 494 092 are deficient in electrical continuity of the filter circuits and in provision of good attenuation. Arcing between inductors is also a problem in some of these. Objects of this invention at least in its preferred form are:- to provide a multi-pin filtering connector that possesses internal electrical integrity; to provide a connector that resists EMI coupling through connector part interfaces and accessory interfaces; to provide such a connector that is ruggedly constructed; to eliminate arcing between inductors or inductors and capacitors in a filtering electrical connector; to provide a connector as in the previous objects that provides good attenuation. According to the present invention there is provided a multi-pin filtering electrical connector providing EMI filtering, for as many pins in the connector as desired, the filtering connecter comprising: a multiplicity of electrical pins; a first non-conductive grommet seal provided with openings for the pins, the first grommet seal being positioned at the outer face of a dielectric body; the dielectric body having openings corresponding to the pins; a first planar ceramic capacitor array having openings corresponding to the pins and being positioned against the dielectric body; ferrite inductor beads mounted on and around each of the pins which is desired to be filtered; a non-conductive elastomer body provided with openings to accept each of the beads and each of the non-filtered pins, and to insulate the ferrite beads fro each other and from the first capacitor array, the elastomer body being positioned against the first capacitor array; a first non-conductive interface seal, provided with openings for the pins, positioned against the outer face of the elastomer body; a second planar ceramic capacitor array having openings corresponding to the pins positioned against the first interface seal; a second non-conductive grommet seal, provided with openings for the pins, positioned at the outer face of the second capacitor array; a second non-conductive interface seal, provided with openings for the pins, positioned at the outer face of the second grommet seal; a conductive grounding cylinder encircling the second grommet seal and the first capacitor array and also a portion of the dielectric body, and capable of being placed in electrical contact with the grounding cylinder; a conductive shell adapted for housing the pins, seals, dielectric body, elastomer body, capacitor arrays and grounding cylinder; and supported within the shell, a conductive ring element providing a multiplicity of resilient contact fingers for making electrical contact with the grounding cylinder and providing an electrical grounding path from the pin array to the shell. Desirably, each of the capacitor arrays is soldered to each of the pins. To further ensure shielding effectiveness at a connector mounting hold a conductive ring, such as an O-ring, is positioned on and around the shell. An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, of which: Figure 1 is a plan view of the blank from which an electrical ground cylinder is formed for use in the filtering connector of the invention, Figure 2 is a side elevational view of the cylinder blank of figure 1, Figure 3 is a top plan view of the ground cylinder formed from the blank of figures 1 and 2. Figure 4 is a side elevational, partial sectional, view of the filtering connector of the invention. Figures 1-3 show the details of the grounding cylinder 10 of the filtering connector of the invention. The cylinder 10 is formed from a conductive strip 12 provided with a number of tabs 14 along its top and bottom edges and a number of fastener holes 16. The tabs 14 in this embodiment conform to the configuration of the outer surface of the electrical connector contact pins with filtering elements as will be described and referred to as the "pin array". Figure 2 shows that the cylinder 10 is formed from a blank consisting of a foil thickness, which thickness is only that necessary to provide support strength to the connector contact pin array as will be described. Figure 3 shows the cylinder 10 in its formed configuration for encircling a pin array not only to strengthen the pin array, but also to permit the conductive strip 12 to be placed into electrical contact therewith. In this embodiment, the cylinder 10 is made from a beryllium copper alloy having a foil thickness such that the formed can is strong enough to support the more fragile elements of the pin array, as well as pass to ground stray electrical currents induced into the shell of the connector. Figure 4 shows in partial section one embodiment of the multi-pin electrical filtering connector of the invention. This embodiment is a circular, jam nut style configuration although the invention is not limited to this configuration. The filtering connector typically will include a multiplicity of electrical pins although only one pin 20 is shown in figure 4, each having a pin contact end 22 and an opposite end 24. It is to be understood that it is not necessary that all of the pins 20 be filtered. A mix of filtered pins and non-filtered pins may fit predetermined certain needs although on occasions all pins may be filtered. Positioned near the contact end 22 of the pin 20 is a first non-conductive grommet seal 30 provided with openings for pins 20 to pass through. The grommet 30 may be made from an electrically non-conductive elastomeric material, such as for example, fluorosilicone rubber. As used herein, 'non-conductive' and 'dielectric' are synonyms. A dielectric body 36 having openings corresponding to pins 20 is located after the grommet 30. The dielectric body 36, also referred to as a first insert, is preferably made from an epoxy molding compound, such as is sold under the Trade Mark Epiall or Fiberite, to enclose a portion of the pins 20 and to cushion against physical shocks. Positioned in contact with the interior face 42 of the insert 36, is a first planar ceramic capacitor array 40 having openings corresponding to the pins 20. These monolithic ceramic planar capacitor arrays, either circular or rectangular, are available commercially, such as MIL-C-38999 Circular Planar Capacitor Array series of AVX. Ferrite Inductor beads 50 are mounted on and around each of said pins 20 which are desired to be filtered. These ferrite beads are available commercially from several sources. A non-conductive elastomer body or second insert 58 is provided with openings to accept each of said ferrite beads 50 mounted on a pin 20 and any non-filtered pins. The second insert 58 separates physically and insulates the ferrite beads 50 one from another and also from the first capacitor 40. This insulation elates electrical arcing between beads or beads and capacitor. The elastomer body 58 has positioned against its outer face 62 a non-conductive interface seal 66 provided with openings receiving the pins 20. Positioned against the face of seal 66 is a second planar ceramic capacitor array 72 having openings corresponding to said pins 20. Positioned against the outer face of the second capacitor array 72 is a second non-conductive grommet seal 78 having openings for receiving the pins 20. After the second grommet 78 there is positioned a second non-conductive interface seal 82 having openings for receiving the pins 20. A conductive grounding cylinder 10 encircles the elements depicted in figure 3 extending from the second groat 78 to the first capacitor array 40 and beyond to include a portion of the dielectric body 36. The grounding cylinder 10 unitarily supports the various elements, as well as providing an electrical path from the pin array to a shell to be described below. The filtering connector includes outer conductive shell 88 for housing the pin array. A retaining ring 90 inside the shell 88 and interior of the grommet 30 holds the insert 36 within the shell. There is supported within shell 88 a conductive ring element 96 providing a multiplicity of resilient contact fingers 98 for making electrical contact with the grounding cylinder 10 and also providing an electrical grounding path from the pin array to said shell 88. These rings with spring contact fingers are available commercially such as beryllium copper design Q, 97-252:255, of Instrument Specialities Co., Inc., Delaware Water Gap, PA 18327. Superior results are obtained when the pin array and the two capacitor arrays are further bound together. Preferably, each of the capacitor arrays are soldered to each of the pins. Desirably this is done using a Phase Four Model 1214 Vapor Phase Soldering System of Dynapert HTE-- Emhart, Concord, MA 01742. In jam nut 99 installations, apertures may permit entry of stray EMI at the mounting interface. To further ensure shielding effectiveness at the connector mounting opening, the shell 88 has positioned on and around it a conductive ring 102. Typically the ring 102 is a conductive elastomer O-ring. Exemplary Six specimens of the filtering connector of the invention fabricated by vapor phase soldering where subjected to sine-wave vibrations in accord with a standard military test. Visual inspection at the conclusion of each test revealed no damage to any specimen. Specimens were tested and found to be acceptable for military usage of filtering connectors of the invention, including vapor phase soldering, having receptacle shell sized: 11, 13, 15, 17, 19, 21, 23 and 25; Mount Type: box mount, wall mount, jam nut, Pin size: 22D and 20; the Filter Circuit was low-pass Pi-section. These specimens displayed: CAPACITANCE 5000 pf to 15000 pf @ 1KHz and +25C WORKING VOLTAGE 50V, 100V, 200V CURRENT RATING 5 Amps., 7.5 Amps. R.F. CURRENT CAPACITY 3.0 Amps. INSULATION RESISTANCE 10,000 Megohms @ +25C DIELECTRIC WITHSTANDING VOLTAGE 300VDC, 500VDC @ +25C OPERATING TEMPERATURE -55C to +125C ATTENUATION 18 dB minimum at 10MHz 65db minimum at 100MHz

Claims: A multi-pin filtering electrical connector providing EMI filtering, for as many pins in the connector as desired, the filtering connecter comprising: a multiplicity of electrical pins (24); a first non-conductive grommet seal (30) provide with openings for the pins, the first grommet seal being positioned at the outer face of a dielectric body (36); the dielectric body (36) having openings corresponding to the pins (24); a first planar ceramic capacitor array (40) having openings corresponding to the pins (24) and being positioned against the dielectric body (36); ferrite indictor beads (50) mounted on and around each of the pins (24) which is desired to be filtered; a non-conductive elastomer body (58) provided with openings to accept each of the beads (50) and each of the non-filtered pins, and to insulate the ferrite beads (50) from each other and from the first capacitor array (40), the elastomer body (58) being positioned against the first capacitor array; a first non-conductive interface seal (66), provided with openings for the pins, positioned against the outer face (62) of the elastomer body; a second planar ceramic capacitor array (72) having openings corresponding to the pins positioned against the first interface seal (66); a second non-conductive grommet seal (78), provided with openings for the pins (24), positioned at the outer face of the second capacitor array; a second non-conductive interface seal (82), provided with openings for the pins (24), positioned at the outer face of the second grommet seal (78); a conductive grounding cylinder (10) encircling the second grommet seal (78) and the first capacitor array (40) and also a portion of the dielectric body (36), and in electrical contact with the first capacitor array (40); a conductive shell (88) adapted for housing the pins (24), seals, dielectric body (36), elastomer body (58), capacitor arrays (40, 72) and grounding cylinder (10); and supported within the shell (88), a conductive ring element (96) providing a multiplicity of resilient contact fingers (98) for making electrical contact with the grounding cylinder (10) and providing an electrical grounding path from the pin array to the shell (88). A filtering connector according to claim 1 wherein each of the two capacitor arrays (40, 72) is soldered to each of the pins (24). A filtering connector according to claim 1 or 2 wherein a conductive ring (102) is positioned on and around the shell (88) to further ensure EMI sheilding effectiveness at a connector mounting hole.

Inventors: TANG, TIAN-PENG
Applicants: G & H TECHNOLOGY, INC.
Application year: 1988
Main classification: H01R13
IPC codes: H01R13