Method of mounting a replaceable emi spring strip

Abstract: A plug-like conductive shell (10) of an electrical connector includes a peripheral recess (20) therearound in which is disposed a metal strip (50) having a plurality of spring fingers (66,68) for EMI protection upon mating with a receptacle-like conductive shell of a mating connector. The EMI strip (50) is held in place by one or two elastomeric rings (52). A first system includes a ridge (24) in the shell recess bottom (22) and a corresponding formed ridge (60) in the metal strip (50) disposed thereover, with a pair of rings (52) one on each side of the formed ridge (60) securing the strip (50) against axial movement. A second system includes a groove (102) in the shell recess bottom (104) and a corresponding formed ridge (106) in the metal strip (108) disposed therein, defining a corresponding groove (114) within which is disposed a single ring (112), securing the strip (108) against axial movement. The EMI strip (50) is easily assembled to the shell (10) and is easily removable and replaceable, and retrofitting preexisting in-service connectors is possible to replace damaged EMI spring strips even if originally conventionally secured to the shell.

Description: The present invention relates to electrical connectors and more particularly to connectors shielded against electromagnetic interference. The present invention is specifically related to a method for securing a repairable means for conductively connecting a mating pair of conductive plug and receptacle shells according to the preamble of claim 1 and to an assembly according to the preamble of claim 3. Electrical connectors are known which include metal or conductive shells around dielectric inserts housing the plurality of electrical terminals, so that the metal shells shield the terminals and their signal transmissions from the influence of electromagnetic interference (EMI) commonly present in the environment. The metal shells have forward ends which extend beyond the forward ends of the respective terminals within the inserts so to provide a complete conductive periphery, are associated one within the other in a plug and receptacle relationship. In order for the terminals of the mating connectors to mate in a precisely aligned manner, the shell forward ends perform initial centering prior to terminals engaging each other, and a controlled radial spacing is defined between the plug shell forward end and the receptacle shell forward end therearound when mated. The shells are electrically interconnected by a grounding means which commonly comprises a plurality of spring portions attached in strip form to one of the shells near its forward end, so that the spring portions extend radially to be engaged by the other shell upon connector mating, whereafter the spring portions remain under slight spring bias commoning the shells with each other at a plurality of locations completely surrounding the terminals mated at the mating interface of the connectors. Most commonly such spring strips are secured to the plug-type shell, around and facing radially outwardly from the forward end for the outwardly extending spring portions to engage the inside surface of the receptacle-type shell upon connector mating. Conventional securing techniques include welding, bonding, swaging, magneforming and soldering, such as in US-A-4 673 236 wherein a pair of strips with mutually offset spring arms are secured within a shell recess by spot welding. Mechanical securing of EMI spring strips commonly involves special shell structure beyond a simple annular recess, or special assembly steps, or both: examples are found in US-A-4 512 623 and US-A-4 655 533 in which leading and trailing edges of the annular strip disposed in an annular shell recess are secured beneath undercuts of the recess walls to hold the strip to the shell; US-A-4 428 639 in which an inwardly directed flange of the strip's trailing edge is mechanically held against a radial shell flange by being wedged by a compression ring having been deformed; and US-A-3 678 445 and US-A-4 248 492 in which outwardly extending spring tabs at the strip's trailing edge abut against a radial shell flange urging a leading strip edge against a ledge or beneath an undercut. In US-A-4 239 318, US-A-4 326 768 and US-A-4 470 657 the ends of the EMI spring strips are fastened, soldered, or welded together to define bracelet-like annular strips which are continuous and elastically flexible to be stretched while being mounted over the forward shell end and seated within an annular recess having an outer diameter slightly larger than the inner diameter of the strip when unstretched. An electrical connector assembly according to the preambles of claims 1 and 3. is sold by AMP Incorporated, Harrisburg, Pennsylvania under the trade designation ARINC 600 Connector, Part No. 213011-1 and is disclosed in the data sheet "Military ARINC 600 Connector System", by AMP, 4676-8, September 15, 1988. in which a plug-like metal shell of the connector has secured around its periphery an EMI strip of spring fingers, which strip is located within an annular recess near the shell forward end and bonded in place by adhesive material. Within the recess is a small annular ridge which comprises a strip locating means, and the EMI strip has a continuous annular body section which includes an outwardly extending ridge defining a groove along the inside surface within which the shell ridge is received, locating and aligning the strip prior to bonding. The EMI strip includes both forwardly and rearwardly extending spring fingers where the forwardly extending fingers first engage a mating receptacle-type shell leading end before the electrical contacts within the connectors engage, and the rearward fingers continuously engage the mating shell's inside surface after mating. In US-A-4 529 257 an annular EMI grounding member is seated within an annular recess of a plug-type shell in one embodiment and comprises a continuous coil spring partially embedded within an intermediate portion of a sleeve-like ring of elastomeric material in which leading and trailing portions of the ring sealingly engage surfaces of the mated connector shells, while exposed surfaces of the coil spring engage surfaces of the mated shells, whereby the member simultaneously provides grounding and environmental sealing between the connector shells. It is desirable to provide an EMI spring strip for a connector shell which is easy and economical to assemble. It is desirable to provide such an EMI spring strip which is securable to a shell requiring only simple structural features on the shell. It is desirable to provide an EMI spring strip not required to be joined to be continuous prior to assembly nor to require bonding, welding, soldering or the like to the shell. It is further desirable to provide an EMI spring strip which is easily removable from and replaceable on the shell. The present invention provides a method as defined in claim 1 and an assembly as defined in claim 3. Embodiments of the invention are defined in the dependent claims. The present invention and/or embodiments thereof comprise a member for providing grounding connections between metal shells of electrical connectors for EMI protection, wherein a strip of spring fingers is wrapped around a plug-type shell within a recess thereof and is held in place by an elastomeric ring member or pair of members, such as O-rings. One O-ring acts in cooperation with a ring-receiving groove of the strip in turn disposed within a corresponding annular shell groove; alternatively a pair of O-rings are seated within spaced grooves of a strip on both sides of an annular ridge of the strip disposed over a ridge of the shell. A pair of spaced shell ridges also may define a groove therebetween, and two O-rings may be used side-by-side. Given a wider shell groove and corresponding EMI strip groove, an elastomeric band may be used having a rectangular cross-section. For ease of assembly and removal from the shell it is preferred that the strip not be joined at its ends but merely be of a length to just meet when secured to the shell within the recess by the O-ring or O-rings. Spring arms preferably extend from a central strip body section both forwardly toward a leading edge of the strip and rearwardly toward a trailing edge, to engage the mating receptacle-type shell. The EMI strip and O-rings are usable on either rectangular or cylindrical connector shells, and retrofitting pre-existing in-service connectors is possible. The present invention and/or embodiments thereof provide an EMI spring finger strip easily and economically manufactured and assembled to a plug-type connector shell without separate processes such as welding or soldering. The present invention and/or embodiments thereof also provide an EMI strip which is easily removable from a shell and replaceable without fixturing or tooling. The present invention and/or embodiments thereof additionally provide a means for retrofitting connectors already in service having damaged EMI strips conventionally secured, in order to continue use of the existing connectors. The present invention and/or embodiments thereof further provide EMI strips which can be manufactured in continuous strip form on reels and cut to length at the assembly station for any of several sizes and shapes of connector shells, and immediately assembled. Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: FIGURE 1 is an isometric view showing a plug-type metal shell of an electrical connector, having an EMI strip according to the present invention secured therearound by two O-rings; FIGURE 2 shows the EMI strip and O-rings of Figure 1 exploded from the shell; FIGURE 3 is an enlarged part section view taken along lines 3-3 of Figure 1; FIGURES 4A and 4B generally are enlarged part cross-sectional views of the assembly of Figure 3, and also showing a mating shell, shown in mated engagement in Figure 4B; and FIGURES 5 to 7 are similar to Figure 4A showing alternate embodiments of the present invention. An electrical connector shell 10 is shown in Figure 1 with an EMI strip 50 secured thereto by a pair of elastomeric O-ring members 52. Within the shell although not shown would be disposed a conventional dielectric insert containing a plurality of electrical terminals matable with terminals of a mating connector, also not shown. Shell 10 is shown as an integral portion of a plate 12 which may have a plurality of such shell portions. In Figure 2 shell 10 is shown as square and includes a plug section 14 having a forward end 16 and an outwardly tapered lead-in surface 18. The shell with which the present invention is useful could also be rectangular or circular, and could be die cast aluminum, machined metal, or metal-plated plastic or be otherwise conductive for connector shielding. A wide recess 20 within which EMI strip 50 will be seated is provided peripherally around the outer surface of shell 10 just rearwardly of lead-in surface 18. A small rounded ridge 24 extends around shell 10 in the center of recess bottom 22 and defines generally a forwardly facing stop surface 26 and a rearwardly facing stop surface 28 which will provide a means for securing the EMI strip 50 against axial movement during connector shell mating and unmating. Shell 10 and EMI strip 50 as shown are conventionally known, and ridge 24 was previously utilized for locating and aligning the EMI strip of corresponding shape but soldered thereto. EMI strip 50 is preferably photoetched and formed in loose pieces of selected length such as of beryllium copper alloy, and includes an outwardly facing major surface 54 and an inwardly facing major surface 56. Body section 58 includes a central arcuate ridge 60 formed therein extending outwardly from major surface 54, and ring-receiving seats 62,64 on both sides of ridge 60. Extending rearwardly from ring-receiving seat 62 are a plurality of closely spaced first spring fingers 66, which also extend at a selected angle outwardly to free ends 68 which are curved inwardly. Extending forwardly from ring-receiving seat 64 are a plurality of closely spaced second spring fingers 70, which also extend at a selected angle outwardly to free ends 72 which are curved inwardly. Where EMI strip 50 is to be used with a rectangular shell, each strip is preferably formed into the shape of the shell prior to heat treatment. Where EMI strip 50 is to be used with cylindrical shells, the strips may be stamped and formed on a continuous strip, and stored and shipped on reels. O-rings 52 may be made of conventional fluorosilicone rubber with a durometer of 60 or other elastomeric material, and having a circumference selected to be slightly smaller than the circumference of shell 10 along the bottom of recess 20 so that when located in place around strip 50 are slightly stretched. Referring to Figures 3 and 4A, central arcuate ridge 60 defines a corresponding groove 74 along inward major surface 56 which is formed to fit over ridge 24 in shell recess 20. A pair of O-rings 52 are placed one on each side of ridge 60 in respective ring-receiving seats 62,64 and hold strip 50 in place against shell 10. Corresponding groove 74 defines a rearwardly facing surface 76 to stop rearward axial movement of strip 50 along shell 10 when held against forwardly facing shell stop surface 26; corresponding groove 74 also defines a forwardly facing surface 78 to stop forward axial movement of strip 50 along shell 10 when held against rearwardly facing shell stop surface 28. With ends 80 remaining unattached to each other assembly of EMI strip 50 to the shell is facilitated. It is preferable for ends 80 to be slightly spaced rather than overlap, with perfect abutment not being realistically attainable. Eventual replacement is also facilitated, if replacement of the EMI strip becomes necessary after in-service use of the connector has begun. Referring to Figures 4A and 4B, first spring arms 66 extend rearwardly and outwardly at an angle so that free ends 70 are engageable by an inside surface 42 of a mating shell 40 and deflected radially inwardly toward recess bottom 22. Second spring arms 68 extend forwardly and outwardly at an angle so that free ends 72 are engageable by inside surface 42 of mating shell 40 and also deflected radially inwardly. Second spring arms 68 are the first physical engagement between the connectors, and arms 68 serve to discharge the existing electrostatic potential between the connectors when free ends 72 first engage mating shell 40. First spring arms 66 continue to engage mating shell 40 after mating, and depending on the profile of the mating shell inner surface 42, second spring arms 68 also may continue to engage mating shell 40 after full mating. A second embodiment of the present invention is shown in Figure 5, which is a view similar to Figure 4A. Shell 100 includes a small groove 102 centrally along recess 104. EMI strip 106 includes a formed projection 108 extending inwardly from inward major surface 110 and shaped and dimensioned to fit within shell groove 102. A single elastomeric member 112 is disposed within corresponding groove or seat 114 defined by formed projection 108 along outward major surface 116. The arrangement provides a system for preventing axial movement of EMI strip 106 with respect to shell 100. Third and fourth embodiments are shown in Figures 6 and 7. In Figure 6 shell 200 includes a wide groove 202, EMI strip 204 includes a corresponding wide groove or seat 206, and a pair of O-rings 208 are disposed therein side-by-side. In Figure 7, shell 300 includes a pair of ridges 302 spaced apart thus defining a wide groove 304; EMI strip 306 includes a pair of corresponding radially outward ridges 308 which define a groove or seat 310; and an elastomeric band 312 having a rectangular cross-section is seated within seat 310 which is located within shell groove 304. Forward and rearward stops are defined in each of the embodiments. In either embodiment it is easily seen that the EMI strip is easily assembled to a shell using one or two O-rings, and is just as easily removed for replacement in the field by a like EMI strip and O-ring arrangement without special tools or involved process. The present invention enables not only continued use of the shells but also continued use of the shells in place without removal to another site for repair of the EMI protection mechanism, simply by removal of the O-rings and replacement of the damaged EMI strip and O-rings with like ones. It is easily seen that the present invention may be used to retrofit certain connectors already in service having damaged EMI spring strips, which have utilized conventional EMI strip securing methods such as bonding, so long as the shell has a physical feature such as a ridge or groove to define forward and rearward stop surfaces, and an EMI strip is fabricated to correspond to the existing shell feature. The damaged EMI strip is removed, the material previously used is removed such as by solvents applied to remove adhesive or the shell locally heated along the outside surface to melt and remove solder which otherwise may tend to prevent accurate seating of the EMI strip of the present invention, and the EMI strip and elastomeric members are placed on the shell allowing continued use of the shell. Further, for cylindrical shells the EMI strips may be retained on continuous strip on reels during original manufacture thereof and kept in reel form during assembly of the connector, needing only to be cut to an appropriate length at the assembly station, and is immediately usable with circular shells of any size without being formed into a continuous annular member, thereby greatly simplifying connector manufacture.

Claims: A method for securing a repairable means for conductively connecting a mating pair of conductive plug (10) and receptacle (40) shells of a pair of electrical connectors to protect against electromagnetic interference, wherein a plug shell (10) is used which has an EMI strip (50) therearound including a plurality of spring fingers (66,70) extending outwardly from a body section (58) and either forwardly or rearwardly or both to free ends (68,72) adapted to engage the inside surface (42) of the receptacle shell (40) for grounding when the connectors are mated, and wherein the EMI strip (50) is disposed in a peripheral recess (20,104) around the outer surface of the plug shell (10) near the forward end (16) thereof, and the plug shell (10) including a means (24) along the recess bottom (22) for locating the EMI strip (50) during assembly in cooperation with a correspondingly shaped cooperating locating means (74) along the body section (58) of the EMI strip (50), said securing characterised by the steps of: selecting an elastomeric fastening means (52,112,208,312) comprising at least one elastically deformable annulus having a circumference slightly less than the circumference of the plug shell (10,100,200,300) along the recess bottom (22); disposing the EMI strip (50,106,204,306) in and along the shell recess (20,104) with said cooperating locating means (74,108,206,308) adjacent said shell locating means (24,102,202,302); and securing said at least one elastomeric annulus tightly around the EMI strip (50,106,204,306) within an annular seat (62,64,114,206,310) along the outwardly facing surface (54) thereof and proximate said cooperating locating means (74), thereby securing the EMI strip to the plug shell and also securing the EMI strip against axial movement during connector mating by maintaining the shell locating means and cooperating strip locating means tightly together, whereby removal and replacement of the EMI strip is facilitated. A method as set forth in claim 1 further characterised in that the steps are preceded by the step of removing a damaged EMI strip from an in-service plug shell (10,100,200,300), defining a retrofit method. An assembly of an electrical connector comprising a shielding conductive plug or receptable shell (10) and an EMI Strip (50) therearound, the EMI Strip (50) including a first locating means (74, 108, 206,308) extending along a body section (58) thereof for locating the EMI Strip (50) at the shell (10), the shell (10) including a correspondingly shaped second locating means (24, 102, 202, 302) cooperating with the first locating means (74, 108, 206,308), characterized in that the EMI Strip (50) has at least one annular seat (62, 64, 114, 206, 310) extending on the outwardly facing surface (54) thereof and on or along the first locating means (74, 108, 206, 308), and in that at least one elastically deformable annulus (52, 112, 208, 312) is secured tightly around the EMI Strip (50) within the at least one annular seat (62, 64, 114, 206, 310). An assembly as set forth in claim 3 further characterised in that said plug shell (10) includes a ridge (24) along said recess bottom surface (22) and said EMI strip (50) includes a groove (74) formed along the inside surface (56) thereof to receive said shell ridge (24) thereinto during assembly, and said elastomeric fastening means comprises a first ring (52) disposed in a respective seat (64) forwardly of said shell ridge (24) and a second ring (52) disposed in a respective seat (62) rearwardly of said shell ridge (24). An assembly as set forth in claim 3 further characterised in that said plug shell (300) includes two ridges (302) spaced apart to define a groove (304) therebetween and said EMI strip (306) includes two corresponding outwardly extending ridges (308) adapted to fit over said shell ridges (302) and defining an inwardly extending ridge (310) adapted to fit in said shell groove (304) and receive thereinto said elastomeric fastening means (312). An assembly as set forth in claim 3 further characterised in that said plug shell (100,200) includes a groove (102,202) along said recess bottom surface defining forwardly and rearwardly facing stop surfaces, said EMI strip (106,204) includes an inwardly directed ridge (108,206) adapted to just fit within said shell groove (102,202) and define a seat to receive thereinto a said elastomeric fastening means (112,208). An assembly as set forth in any of claims 3 to 6 further characterised in that each said elastomeric annulus is a band (312) having a rectangular cross-section. An assembly as set forth in any of claims 3 to 6 further characterised in that each said elastomeric annulus is an O-ring (52,112,208) having a circular cross-section.

Inventors: PAUKOVITS EDWARD J, WRIGHT SUSAN ELAINE, PAUKOVITS, EDWARD J., WRIGHT, SUSAN ELAINE
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1989
Main classification: H01R13
IPC codes: H01R13, H01R4