US3375483A - Electrical connector - Google Patents

Description

March 26, 1968 J. J. PHILLIPS ELECTRICAL CONNECTOR Filed Aug. 5, 1966 v United States Patent 3,375,483 ELECTRICAL CONNECTOR John J. Phillips, Rolling Hills, Calif., assignor to Gray & Huieguard, Santa Monica, Calif a corporation of California Filed Aug. 3, 1966, Ser. No. 569,938 3 Claims. (Cl. 339-143) ABSTRACT OF THE DISCLOSURE The present invention relates to electrical connectors for use with a cable having electrically conductive shielding that must be grounded. In the embodimnet of the invention disclosed the space where the cable or bundle of wires enters the connector is filled with a sealing mixture containing a large number of magnetically conductve particles. A magnetic field is maintained across the sealing mixture while it hardens whereby the magnetic particles are attracted together to form a large number of electrically conductive paths which extend between the shield ing and the connector. After the sealing mixture has hardened all of the particles are maintained bonded into the conducting relationship.

Electrical circuits and particularly those contained in separate pieces of equipment, are frequently interconnected by a large number of electrical conductors grouped into a bundle or cable. Each conductor includes a central Wire covered with electrical insulation so as to be maintained electrically isolated from all of the other conductors. In addition each conductor may be surrounded by an electrically conductive shield. Although the shields, are electrically isolated from the central wires they are electrically connected to ground whereby any stray fields or currents are bypassed to ground before they reach the wire.

In order to facilitate interconnecting the conductors in the bundle or cable with a second group of conductors a pair of mating connectors may be employed. The connectors employ housings that may be fastened together whereby a plurality of contacts in the two housings electrically mate. The wire in each of the conductors iselectrically connected to one of these contacts whereby the desired paths are formed between the various conductors.

In order to insure an effective shielding action it is highly desirable, if not essential, that the shielding on the individual conductors be electrically coupled together and to the electrical ground and/or .to the connectors. If this condition is satisfied any stray currents present in the shielding-r the connector housing will be effectively shorted to ground and prevented from being coupled into the conductors.

Heretofore, in order to overcome this difiiculty the shielding around the various conductors and/ or the cable have been electrically connected to ground and/or the connector by means of mechanical clamps, soldering etc. Although such arrangements have been satisfactory for many applications it has been found that it is time consuming and/or expensive to provide such connectors. Also it has been found that frequently a discontinuity occurs in the portion of the shielding in the region of the interconnection between the conductors and the connector whereby a complete shielding action is not maintained. This problem becomes particularly acute when it is necessary to also provide a moisture proof seal at the same time.

The present invention provides means for overcoming the foregoing difliculty. More particularly the present invention provides electrical connector means which are not only simple and inexpensive to assemble but also are very effective and reliable in preventing any stray or spurious signals entering into the electrical conductors and/or the coupling connectors. In addition. a hermetic, moisture proof seal is also provided that precludes moisture entering into the connector or the cable. In the single embodiment of the present invention disclosed herein this is accomplished by providing a sealing or potting compound at the junction of the cable with the connector. At least a portion of this compound is electrically conductive whereby one ,or more low resistance paths are formed between the shielding and the connector housing.

These and other features and advantages of the present invention will become readily apparent from the following detailed description of a single embodiment thereof, particularly when taken in connection with the accompanying drawings wherein like reference numerals refer to like parts and wherein;

FIGURE 1 is a cross sectional view of a connector embodying one form of the present invention, and

FIGURE 2 is a fragmentary cross sectional view of a portion of the connector of FIGURE 1 during one step of the assembly thereof.

Referring to the drawings in more detail the present invention is particularly adapted to be embodied in means for sealing a plurality of electrical conductors and electrically connecting the shielding around the conductors to ground. By way of example it may be employed in a connector 10 on the end of a cable 12 or a bundle of conductors 16. The connector 14] is effective to mate with another connector 14 on the end of a second cable, a bulkhead etc.

Although the electrical conductor 16 may all be enclosed in a single cable 12, in the present instance they are illustrated as being in a loosely associated bundle. Normally this bundle will include a large number of conductors. However for purposes of illustration, only two conductors are actually illustrated. Each of the conductors 16 includes a center wire 1'8 or similar device for carrying an electrical current. Each wire 18 is in turn surrounded by an electrically non-conductive insulation 20. This insulation 20 may include one or more layers of a material, such as rubber, plastic etc.

A suitable shielding 22 in turn surrounds the layers of electrical insulation 24 Although the shielding 22 may be of any desired variety it is preferably as flexible as the conductors 16. Also, it is preferably sutficiently electrically conductive to provide a low resistance path. One form of shielding 22 that has been found particularly well adapted for this purpose is braided from a plurality of small conductors. This is so flexible it will not materially interfere with the bending of the conductor 16.

Since the shielding 22 is electrically conductive if the conductors 16 are present in any stray fields currents will be produced in the shielding 22. These currents circulate through the shield 22 and along the conductor 16 and prevented from ever reaching the central wire 18. However, it should be noted that the effectiveness of the shielding 22 is dependent to a large degree on the shielding 22 being electrically connected to ground by a low resistance path.

Each of the connectors 10 and 14 includes a housing 24 and 26. The housings 24 and 26 are substantially cylindrical with enlarged passages 28 and 30 extending axially therethrough. One of the housings 26 has a threaded exterior 32 while the other has a mating collar 34. This collar 34 is rotatably mounted and internally threaded so as to engage the external threads 32. By tightening the collar 34 the mating ends of the housings 24 and 26 are drawn together so as to compress a gasket 36 therebetween. As a consequence the two housings 24 and 26 will be rigidly locked and sealed together.

The housings 24 and 26 are preferably an electrically conductive material. As a consequence they will also act as an electrical shield and prevent stray fields entering into the center thereof. Normally the housings 24 and 26 are fabricated of a light weight material such as by die casting.

The first connector 24 includes a plurality of pin contacts 38. These are normally mounted in an electrical non-conductive block or insert 40 so as to be electrically isolated from each other. A small radial flange 42 on the end of the housing 24 engages the end of the block 40 and prevents it moving out of the connector 24.

Each pin contact 38 includes an enlarged head 44 which is seated on the back side of the insert 40. Each contact 38 also includes a shank 46 which projects outwardly beyond the exposed face of the insulating insert 40. The exposed portions of the shanks 46 are surrounded by the collar 34 so as to be protected thereby.

The mating connector 14 also includes an electrically non-conductive block or insert 50. The insert 50 is mounted so that its exposed face is closed to the exposed face of the insert 40 when the connector and 12 are mated. A plurality of socket contacts 52 are positioned in the insert 50. Each socket 52 includes an enlarged head 54 that is anchored in the back surface of the insert 50. They also includes a recess 56 in substantial alignment with the pin contacts 38. When the two connectors 10 and 12 are coupled together the exposed faces of the two inserts 40 and 52 will mate and theshanks 46 of the pin contacts 38 will be in electrical contact with the recesses 56 in the socket contacts 52. The gasket 36 may also be compressed between these faces to hermetically seal the junction.

The wire 18 in each conductor'16 is coupled to one of the pin or socket contacts 38 or 52. In order to accomplish this the insulating layer and the braided shielding 22 are first stripped back from the end of the conductor 16. This provides a short section of exposed wire 18. The exposed end of the wire 18 is then inserted into the head 44 or 54 of the appropriate contact 38 or 52. It is then secured in position by soldering, crimping, etc.

After all of the wires 18 have been attached to the contacts 38 and 52 the contacts are mounted on the inserts and 50, the inserts are placed within the housings 24 or 26. Following this a layer 58 of encapsulating or potting material may be poured into the recessed end of the connector. This layer 58 is normally electrically non-conductive and is just sufficiently deep to cover the exposed portions of the wire 18 and part of the insulation 20 remaining on the wires. This will be effective to cover all of the exposed electrical conductive materials, i.e. the Wire 18 and heads 44 and 46 of the contacts 38 and 52. As a consequence the various contacts 38 and 52, conductors 16 etc. will be retained in position and electrically isolated from each other and from the housing 24 or 26.

After the foregoing layer 58 of insulating encapsulating material has been provided a second layer 60 of encapsulating material may be formed thereover. The second layer 60 is formed of an electrically conductive potting material. Normally this layer 60' is sufficiently thick to completely fill or substantially fill any space remaining in the passage 28 or 30. The material in this layer 60 completely surrounds the braided shielding 22 on the con- -ductors=16 and is in intimate contact with the braiding and the housing 24 and 26. Since this layer 60 of potting material is electrically conductive it forms a conductive path between the various shields and the interior of the housing.

Although a wide variety of electrically conductive potting compounds may be employed it has been found desirable to include electrically conductive particles 62 within the compound whereby its conductivity is increased. If .such particles 62 are included the potting compound may be electrically non-conductive and, in fact, may be the same material used in the first layer 58.

It has been found the contacting of the conductive particles 62 is of a random nature. As a consequence the resistance is also random and on some occasions may be relatively large. In order to eliminate this effect the particles 62 may be of a magnetic nature. By way of examples the particles may be iron filings, copper slivers coated with a magnetic material such as nickel, etc.

After a layer 60 of the potting compound with the magnetic particles 62 'has been flowed around the conductors 16 and before it has an opportunity to set up, a magnetic field may be applied to the potting compound. This may be provided by magnetic poles 64 and 66 on the opposite sides of the housing. This field will act upon the particles 62 and cause them to become aligned with the field and each other. Moreover if the magnetic field is sufficiently strong the various particles 62 will not only align themselves but will also become attached to each other and thereby form a large number of parallel low resistance paths. After the layer 60 of potting compound has cured, the field may be removed. However, since the layer 60 is now stiff the magnetic particles 62 are no longer free to move relative to each other and they will remain coupled to each other. Accordingly a large number of electrically conductive paths will be maintained across this portion of the encapsulating material whereby the metal shielding 22 on the conductors 16 will be grounded to the housing 24 or 26. In order to insure a positive contact with the shielding 22, the shielding 22 may be made of a magnetic material or else the end portions thereof may be coated with a magnetic material, for example by nickel plating. 1

In the event there are any stray magnetic or electromagnetic fields in the vicinity of the conductors 16, they may still produce electrical currents in the braided shielding 22. However, any such currents will be coupled through the layer 60 of electrical conductive encapsulating material and into the housing 24 or 26 of the connector It) or 14. As a consequence all of the electrical currents will be shunted to ground and prevented from entering into any of the electrical Wires 16 or contact pins 38 or sockets 52, etc. It will thus be seen that a highly effective moisture seal is formed and a highly effective grounding is provided.

While only a single embodiment of the present invention is disclosed herein it will be readily apparent to persons skilled in the art that numerous changes may be made thereto without departing from the spirit of the invention. More particularly the structures of the connectors, i.e. the housings, contacts, inserts, etc. may be modified to suit any particular application. Moreover the various encapsulating materials and particularly the electrically conductive layer and the manner of their formation may be modified to suit any particular application. If the conductive particles are employed the manner in which they are aligned may also be varied as required. It should also be noted that this technique is not necessarily limited to connectors of the type shown but may be utilized in connection with any type of electrical insulation where any form of shielded connection is used. Accordingly the foregoing disclosure and description thereof are for illustraitve purposes only and do not in any way limit the invention which is defined only by the claims which follow.

I claim:

1. The method of assembling an electrical connector including the steps of providing an electrically conductive connector housing having a plurality of separate electrical contacts therein,

interconnecting a plurality of shielded electrical conductors with the contacts and forming an open space around the shield on the conductors and inside of the housing, preparing a mixture which includes electrically conductive magnetic particles and a fluid that permanently hardens into a substantially rigid mass, said magnetic particles being mobile within said mixture before said fluid hardens.

at least partially filling said space with said mixture and allowing said fluid to harden into a substantially rigid mass at least partilly filling the space whereby the particles become immobile within said mass,

maintaining a magnetic field in said space and in said mixture whereby the magnetic particles are attracted to each other, to the shielding and to the housing so as to form electrically conductive paths grounding said shielding to said housing, and

maintaining said field in said mixture until after the fluid has hardened into said rigid mass whereby the particles are rigidly maintained in said conductive paths.

2. An electrical connector of the class described including the combination of an electrically conductive outer housing having a passage extending inwardly from one end thereof,

an electrically non-conductive insert disposed in said passage,

a plurality of electrical contacts mounted in said insert and maintained electrically insulated from each other by said insert,

a plurality of conductors extending through said passage and electrically joined to the contacts in the insert,

electrically conductive shielding surrounding the conductors and terminating inside of said passage adjacent said insert, and

a conductive layer in said housing and surrounding the shielding on the conductors, said layer including a substantially rigid material containing a large number of magnetic particles, said particles being magnetically attracted to each other and permanently retained in fixed immobile positions to form a large number of electrically conductive paths, said paths being effective to electrically interconnect said shielding and said housing whereby the shielding is electrically grounded to the housing.

3. The connector of claim 2 including an electrdically non-conductive layer in said housing between the insert and the condutive layer, said non conductive layer being eifective to insulate the joined conductors and contacts from the others.

References Cited UNITED STATES PATENTS 2,570,856 10/1951 Pratt et al. 2,660,640 11/1953 Wolf 335280 X 2,917,599 12/1959 Ovshinsky 3351 3,140,342 7/1964 EhITeich et al. 174-35 3,322,885 5/1967 May et al. 174-78 RICHARD E. MOORE, Primary Examiner.

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