US 3573677 A
Description (OCR text may contain errors)
United States Patent lnventor Donald R. Detar Stratford, Conn.
Appl. No. 625,893
Filed Feb. 23, I967 Patented Apr. 6, 1971 Assignee Litton Systems, Inc. Beverly Hills, Calif.
CONNECTOR WITH PROVISION FOR MINIMIZING ELECTROMAGNETIC INTERFERENCE 2 Claims, 9 Drawing Figs.
US. Cl 333/79 Int. Cl H0lh 7/14 Field ofSearch 333/70, 79; 339/9, 255
References Cited UNITED STATES PATENTS 3,275,954 9/1966 Coda et al 333/70X 3,435,387 3/1969 Reinkeetal Primary Examiner-Herman Karl Saalbach Assistant ExaminerTim Vezeau Attorneys-Earl R. Evans, Alan C. Rose and Alfred B. Levine ABSTRACT: An electrical connector provided with shielding and filtering of the contacts to suppress electromagnetic interference, i.e., leakage into or radiation of energy from the connector and conduction of undesired high-frequency current through the connector contacts. In the illustrative embodiment, the connector contacts are provided with filter units which are held in place on the contacts by resilient noninductive contact washers which protect the fragile filter units against damage and connect the elements of the filter in circuit. The outer electrodes of the filter units are connected through conductive gaskets to a metal plate forming a common ground plane for the respective filters.
Patented Aprilfi, 1971 3,573,677
2 Sheeta-Shaet 1 1 1 j 2 EH44 Patented April 6, 1971 3,573,677
2 Sheets-Sheet 2 LP p/rw CONNECTOR WITH PROVISION FOR MINIMIZING ELECTROMAGNETIC INTERFERENCE The present invention relates to shielded and filtered electrical connectors for the suppression of electromagnetic interference.
The object of the invention is to provide an improved connector having subminiature filter units connected to the contacts to prevent the undesired coupling of energy between the input and output of the connector, the connector also having electrostatic shielding.
A problem which has always plagued the users of electronic gear is that of radio frequency interference. High-frequency signals generated in one piece of electronic equipment are fed, by radiation or conduction, into another piece of equipment and cause interference or other difficulties. Radiation of highfrequency energy is usually prevented by enclosing the equipment in a tight metal cover which effectively stops the radiation component. However, the conductors passing through the shielding enclosure may also serve to conduct spurious signal currents which can be prevented or suppressed by the use of suitable networks.
The ideal location for such filter units is inside the connector mounted on the wall of the enclosure. An integrated network in the form of a subr'niniature tubular filter unit having a low-pass frequency characteristic is of a size which can be mounted within the connector. These filter units are quite fragile and must be mounted so that they are protected against undue stress. For efficient operation, low-resistance connections must be provided between the contact areas of the filter units and ground, and also between separated points on the connector contact.
In accordance with a feature of the invention, the tubular filter units are mounted on the connector contacts, for example, the pin contacts, and are held in position by spring washers designed to have a low inductance at the frequencies of the interference signal currents and to provide a low-resistance connection between the contact tips of the filter elements and the contact member of the connector. In this manner the filter unit is properly connected in the network circuit for effective operation and is protected against breakage when the connector contact is subjected to strain due to bending or thermal expansion.
Another feature of the invention relates to improved means for providing a ground plane and resilient conductive means for effectively connecting the ground electrode of each filter unit to the ground plane. The ground plane may comprise a metallic mounting plate passing through the central portion of the half of the connector which is mounted on a panel, for example.
Another feature of the invention is the provision of a panel connector which is separable at the ground plane interface to permit easy replacement or removal of any pin-filter assembly.
Another feature of the invention is the adaptation of a shielded connector design to the use of filtered contacts.
The miniature filter networks may be of a type well known in the art and require no detailed description. Essentially the filter consists of a tubular unit which can be assembled over a connector contact, for example, the pin contact. The tubular unit comprises a sleeve of ferrite or similar high permeability material and a surrounding tube of insulating material, such as barium titanate. The insulating tube is coated internally and externally with metal, as by plating, to form two capacitors with a common ground electrode on the outside. The highpermeability sleeve increases the inductance of the contact pin so that it serves as the inductive element of a pin filter. The capacitors serve to shunt the high-frequency currents in the connector ground through the connection from the ground electrode to the ground plane. The internal diameter of the hollow filter unit is preferably somewhat larger than the diameter of the pin so that fiexure of the pin will not damage the filter unit.
Other advantages and features of the invention will become apparent from the following description in connection with the accompanying drawings, wherein:
FIG. 1 is a side elevation view, partially in section, of a panel mounted multiple-contact connector embodying the invention;
FIG. 2 is an end view of the connector shown in FIG. 1;
FIG. 3 is a view of a modification illustrating the use of a filter unit with pin contacts inside the enclosure where it is desired to use crimp terminations;
FIG. 4 is a detail view, to an enlarged scale, showing a section of a portion of the connector shown in FIG. 1, illustrating a suitable mounting arrangement for the filter connector contacts according to the invention;
FIG. 5 is a view illustrating one method of assembly of a filtered pin contact drawn to an enlarged scale; and
FIGS. 6-9 are detail views of alternative forms of spring contacts that may be employed for holding the filter in place.
Referring to FIGS. 1 and 2 of the drawings, a shielded, panel-mounted multiple-contact electrical connector embodying the invention is shown by way of example. The connector consists of a conventional socket connector 10 adapted to cooperate with a pin connector II shown as abutting against a plate 12 which may, for example, be attached to a wall or panel 13 of an enclosure for equipment to be attached to terminals 14 of the connector II. The socket connector 10 is provided with a series of socket contacts 16 arranged side by side, of which one is shown in FIG. 1. A corresponding series of pin contacts 17 is provided in the connector 11. The connector contacts 16 and 17 are mounted in molded insulating bodies 18 and 19, respectively, and enclosed in shielding metallic covers 20 and 21 to prevent leakage or radiation of highfrequency interference or inductive interference from the circuits including the connector contacts 16 and 17.
While the male or pin connector 11 is shown as provided with solder terminals 14, obviously it may be provided with any suitable type of terminals. Thus, as shown in FIG. 3, where crimped terminal contacts are desired, the connector may be provided with pin contacts 14a to extend the circuit connections from a first connector 10a to a second connector 10b to which crimped connections of the usual type may be made. The connector 110 is shown as mounted on a panel 13 similar to connector 11.
The pin connector 11 of FIG. 1 further includes a second insulating body 15 on the opposite side of the ground plate 12 from the body 19. The bores in the bodies 15 and 19 for the pin contacts are shaped so as to retain the contacts in position when the connector is assembled as shown in FIG. 4, with sufficient play to insure alignment with the mating contacts 16. The body 15 is removably secured to the ground plate 12 by threaded nuts 22 and 23 which engage the threaded ends of holding members such as bolt 24, so that the insulating body 15 may be removed for replacement or repair of the pin contact assemblies. The other end of the bolt 24 is adapted to receive the threaded end 25 of a jackscrew 26, 27 which is used to mate and unmate the pin and socket elements of the connector and to compress a sealing ring or gasket 29 between the inner end of the shield member 20 and the inside wall of the shield member 21. The sealing ring or gasket 29 is preferably made of resilient conductive material and thereby insures adequate shielding by eliminating any opening or crack in the shield surface at the end of cover 20.
The jackscrews 26 and 27 are mounted for rotation in the casing 20 in any suitable manner, as by means of a bracket 30 which is attached to the wall of the cover 20 by a screw 31. The bracket 30 is notched where it engages the screw so that, upon loosening the screw 31, the bracket 30 may be pivoted to permit the jackscrew to be withdrawn from the cover. The screw 31 also secures an auxiliary bracket 32 in position, said bracket serving to hold the insulating body 18 in place in the connector casing or cover 20. The jackscrew 26 is further provided with a cupped spring 37 underneath the knurled head or thumbpiece of the jackscrew. The spring 37 bears on a sealing ring 36 and a conductive gasket 35, which seals the opening through which the jackscrew passes when the screw is tightened.
The wires or cable conductors connected to the connector contacts 16 are shielded where they enter the cover 20. As shown, the cover is provided with an integral nozzlelike extension 38 to which the shield of cable 39 is tightly clamped. Any equivalent shielding arrangement may be used at this point.
In accordance with a feature of the invention, each pin contact consists of a tip portion 17 and a shank portion 40 of reduced diameter which passes through the bore of a tubular filter unit 41, as shown more clearly in FIGS. 4 and 5. The diameter of the shank 40 of the pin contact may be of the order of 0.040 inches, depending upon the dimensions of the filter unit. The filter 41 is an integrated filter network such, for example, as the type F filter of Allen Bradley Company of Milwaukee, Wis. 53204. The type F0 filter is a low-pass filter having tip contacts at either end and a central external elec trode surface to be grounded. The filter is fragile and must be protected against stresses that would be caused, for example, by bending of the contact pin. In addition, low-resistance electrical connections must be made to the electrode contacts of the filter unit.
FIG. 5 shows, by way of example, a method of assembly of the filter unit 41 and the pin contact, said filter unit being slipped over the reduced cross section 40 of the pin contact and held in place by the contact tip 17 with resilient contacts 43 at the ends of the filter unit. The contact tip portion 17 is held against the springs 43 with predetermined pressure while the end of the pin 17 is filled with solder to secure the tip contact in place and maintain the resilient contact springs 43 if firm engagement with the filter unit. The contact springs 43 thus secure the fragile filter unit in place and effect a low-resistance connection at spaced points to the pin 17. A hole 44 is provided in the contact tip 17 so that a flow of solder between the parts of the pin contact may be observed through the hole as an aid in securing a good solder joint. The holding contact springs 43 may be formed from cupped discs of spring metal, one of which is shown, to an enlarged scale, in elevation and cross section in FIGS. 6 and 7. Two of these cupped discs are placed face to face to form a conductive assembly of low resistance between the filter unit tip contacts and the connector contact 17. Other suitable compressible resilient contacts may be used, such as in the shape of a bellows 45 formed of thin resilient metal, as shown in end and side elevation views in H08. 8 and 9. The corrugated holding spring 45 would be inserted in place of the cupped spring 43 and serves the same purpose. Both springs constitute current-conducting elements of low inductance even at high frequencies, as compared with a coiled wire spring. Obviously other forms of low-inductance washers or gaskets may be employed.
The connection from the central external electrode surface of the filter unit 41 to the ground plane formed by the plate 12 may be effected in any suitable manner, as by a leaf spring contact. Preferably, however, a resilient conductive gasket 42 having a snug fit on the external surface of the filter unit is employed, said gasket being compressed against the face of the plate 12 in assembling the connector to provide a low-resistance ground connection for the ground electrode of the filter unit.
While a typical embodiment of the invention has been shown and described to provide a clear understanding of the underlying principles thereof, it is obvious that changes and modifications in the detailed construction may be made without departing from the scope of the invention. Thus, by way of example and not of limitation, the filter units may be mounted on the socket or female contacts of the connector instead of the pin contacts as shown, and the form and mounting of the connector contacts l6, 17 may be substantially changed. Furthermore all of the contacts need not be filtered, the filter units being omitted where not required.
1. An electrical connector in which electromagnetic interference is suppressed, comprising:
a body of insulating material;
a plurality of contact members mounted in said bod a plate forming an electrically conductive ground p ane provided with apertures through which said contact members extend;
one or more tubular low-pass filter units mounted respectively on one or more of said contact members in conductive relation to said plate, said filter unit including contact tips at both ends and a central contact portion intermediate the ends of the filter unit and connected to said ground plane; and
resilient contact washers consisting of metallic discs forming an electrical connection of low inductance located at both ends of the filter unit to secure the unit in place and provide low-resistance connection from the filter unit to spaced points on the connector contact member.
2. An electrical connector according to claim 1, in which said resilient contact washers consist of corrugated tubular elements forming an electrical connection of low inductance.