GB1595969A - Electrical connector with protective hold-off means - Google Patents

Description

(54) ELECTRICAL CONNECTOR WITH PROTECTIVE HOLD-OFF MEANS (71) We, AUTOMATION INDUSTRIES INC., a corporation organised and existing under the laws of the State of California, United States of America, of 1901 Building, Century City, Los Angeles, California, 90067 United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to electrical connectors having plug and receptacle means having pin and socket contacts for electrical engagement, said pin and socket contacts being oriented axially for alignment thereof to permit engagement by relative axial movement of the plug and receptacle means.

Axial alignment of polarisation of a plug and a receptacle means is not sufficient to provide foolproof reliable proper intercon necflon of pin and socket contacts of the plug and receptacle means.

Electrical connectors are constructed in accordance with detailed specifications to provide interconnection of cables having selected numbers of wires to provide the desired number of circuits. The plug and receptacle means at which the wires of the cables are terminated for interconnection through the pin and socket contacts of the connector may vary in diameter, for example, one half inch and greater diameters.

The number of circuits in the cables to be interconnected may vary for example from one circuit to any number of circuits. The same diameter size or construction of an electrical connector may include a varying number of circuits or lines to be connected so that plug and receptacle shells of the same diameter and of the same number of circuits may not be necessarily compatible with respect to mating because the pin and socket arrangements in the shells may be different.

It is difficult to visually ascertain plug and receptacle means adapted for compatible mating when a large number of circuits are being connected. In addition, visual inspection of the plug and receptacle means may not be readily made because the location of one of the connector parts to determine whether the parts are compatible.

Prior proposed cylindrical electrical connectors have been provided with key and keyway systems for aligning the connectors prior to engagement to the pin and socket contacts therein. In some prior electrical connectors additional and different key and keyway arrangements were provided so that mismating of connectors could be prevented if mating was not intended. Such prior key and keyway systems served to prevent complete mating of incompatible connector parts, but often in such prior systems a partial engagement or a false mating condition was present. In other words, one or more keys might partially engage its mating keyway while other keys would not be engaged with their mating keyways. As a result, as the proper alignment of the connector parts was sought by the operator, axial mas- alignment sometimes referred to as "hooking" or dipping action would produce wear on the key and keyway arrangements and resulted in an improper "feel" during the movement of the connector parts into an attempted mating condition. It should be understood that often the attempted mating of connector parts occurs under conditions where the connector may not be completely visible and often the connecting of the two parts is done entirely by feel; that is, by the operator's manually sensing the position of the connector parts. In such prior proposed constructions utilizing the prior key and keyway systems, if both of the plug and receptacle contained pin contacts and had the same key and keyway arrangement, they could be brought into a coupling position.

In such coupling position, because the contacts were pin to pin, contact damage would result and there would be malfunction of circuits.

Thus, while some prior electrical connectors have been so constructed to allow partial false mating of incompatible connector parts, none of such prior proposed constructions known to us have by positive means prevented such false mating prior to engagement of the electrical contacts and in a manner which prevented axial misalignment of the connector parts at an early stage of the coupling operation.

The present invention relates to an electrical connector constructed and arranged for mating of compatible plug and receptacle means for preventing mating of noncompatible plug and receptacle means and for obviating disadvantages of such prior connector constructions. The invention particularly relates to an improved electrical connector having means for stopping, early in the coupling operation, further relative axial movement of a plug and receptacle means towards a fully mated position and to avoid a false mating condition when the plug and receptacle means are noncompatible.

According to the invention there is provided an electrical connector having a plug part carrying electrical contact elements and a compatible receptacle part carrying electrical contacts for mating engagement with the contact elements carried by the plug part, the plug part and receptacle part being relatively axially movable to mate with the electrical contact elements and contacts, the connector further including at least two angularly spaced keys on one part and corresponding angularly spaced stop faces on the other part adapted to abut when the parts are angularly misaligned, keyways on said other part positioned to correspond with the keys, and a cylindrical guide surface portion on one part extending forwardly of its keys or keyways, and co-operating with a flange surface on the other part to restrict relative tilting movement of the parts during an axial mating movement.

Preferably the connector as described above includes a retractable plug shell incorporating said contacts, a coupling nut threaded on said plug shell, and a rotatable coupling housing having driving engagement with said coupling nut for rotation of the coupling nut to axially move said retractable plug shell with its electrical contacts into mating relation at one stage of said relative axial movement of said plug and receptacle, a coupling flange on said coupling housing, defining said flange surface, spaced in an axial direction from said electrical contacts on said plug part in the retracted position of the plug shell and having spaced keys and keyways, a receptacle shell having spaced locking lands thereon defining keys and keyways, said keys defining said stop faces, said keys on said flange and on said receptacle shell having abutment at at least three circumferentially spaced points for facilitating maintaining said plug in axial alignment with said receptacle while said plug means is turned to seek alignment of said key and keyway means.

According to another aspect of the invention there is provided an electrical connector plug means and receptacle means axially movable into mated and unmated condition of pin and socket contacts carried thereby and including a plug shell and a receptacle shell, comprising in combination: means for protecting said pin and socket contacts by foolproof indentification of compatible plug and receptacle means and rejection of incompatible plug and receptacle means comprising: said receptacle shell having a first external key and having a set of external locking lands of selected arcuate length; the ends of said set of locking lands being spaced from a diameter passing through said first key; said plug shell having internal locking land receiving recesses and having a first keyway receiving said first key; a rotatable coupling ring encircling said plug shell and having a radially inwardly extending coupling flange said flange having a first flange keyway alignable in one position of said coupling ring with said first keyway; said first key on said receptace shell and said first flange keyway on said coupling flange being dimensioned to identify pin and socket contacts on said plug and receptacle means and to reject incompatible attempted pin to pin mating; and a second key on said coupling flange and a second keyway on said receptacle shell within the length of said locking lands for identification of compatible pin and socket arrangements in said plug and receptacle shells; whereby said coupling flange identifies, accepts, and rejects a plug and receptacle means at front faces of said locking lands and said first key; said first key on said receptacle shell and said first keyway on said coupling flange having preselected widths to determine compatible pin and socket means and noncompatible pin and pin means of plug and receptacle means.

In the connector of the present invention axial tilting or misalignment of connector parts will not result in damage to pins or sockets because one connector part is held off from another connector part by abutment of keys with locking lands on the other connector part, said abutment areas occurring at angularly spaced locations so that further axial misalignment of the connection parts is restricted and minimised. Further advantages of the electrical connector of this invention include the employment of locking lands on one connector shell to serve not only as interlock means for the plug and receptacle means but also to serve as stop means for preventing mating of mismatched connector shells, and wherein the means for preventing a mated mismatch of connector parts is provided on a coupling housing.

An embodiment of this invention is hereafter described with reference to the accompanying drawings, in which: FIGURE 1 is an exploded view, partly in section, of a plug means and a receptacle means of an electrical connector embodying this invention.

FIGURE 2 is a transverse sectional view taken in the planes indicated by line II--II of Fig. 1.

FIGURE 3 is a fragmentary sectional view taken in the plane indicated by line 111-Ill of Fig. 1.

FIGURE 4 is an elevational view, partly in section, of the plug means ,and receptacle means of the electrical connector shown in Fig. 1 in a partially telescoped relation with the pin and socket electrical contacts aligned but in axial spaced relation.

FIGURE 5 is a transverse sectional view of Fig. 4 taken in the plane indicated by line V-V of Fig. 4.

FIGURE 6 is an elevational view, partly in section, of the electrical connector shown in Fig. 1 with the plug means and the receptacle means further advanced axially toward each other but with the pin and socket electrical contacts still out of electrical engagement, and with the coupling housing fully advanced axially.

FIGURE 7 is a transverse sectional view taken in the plane indicated by line VII VII of Fig. 6.

FIGURE 8 is a perspective view of a detent spring means of this invention.

FIGURE 9 is a fragmentary sectional view taken in the same plane as Fig. 7 and illustrating position of the detent spring means at an intermediate rotatative position of the coupling ring housing.

FIGURE 10 is an elevational view, partly in section, of the electrical connector shown in Fig. 1 and showing the plug and recess tacle means in full electrical and mechanically locked mating relation.

FIGURE 11 is a transverse sectional view taken in the plane indicated by line XI XI of Fig. 10.

FIGURE 12 is an enlargd fragmentary sectional view showing RFI means between the plug shell and receptacle shell of the electrical connector shown in Fig. 1.

FIGURE 13 is an enlarged fragmentary view of the RFI means shown in Fig. 12 out of engagement with the receptacle shell.

FIGURE 14 is a fragmentary plan view of a metal blank from which the RFI means shown in Figs. 12 and 13 are formed.

FIGURE 15 is a fragmentary plan view of one step in forming the RFI means from the blank shown in Fig. 14.

FIGURE 16 is a fragmentary perspective view of the RFI means showing the relation of the fingers when the RFI means is formed into an annulus.

FIGURE 17 is a transverse sectional view taken in the plane indicated by line XVII- XVII of Fig. 10 illustrating a lock means for retaining the coupling nut and spring means associated therewith in assembly with the coupling ring housing.

FIGURE 18 is a fragmentary sectional view taken in the same plane as Fig. 17 and showing the lock means rotated to an unlocking position.

FIGURE 19 is an exploded fragmentary sectional view of one of the shells and an insert retainer ring for securing an insert member within said shell.

FIGURE 20 is an enlarged fragmentary exploded view of the thread configuration on the shell and on the retainer ring in juxtaposition.

FIGURE 21 is a diagrammatic view showing points of interengagement of the threads of the retainer ring with the threads of the shell.

FIGURE 22 is a fragmentary sectional view showing configuration of the locking lands on the receptacle shell and the keyways and master key provided thereon.

FIGURE 23 is a sectional view taken through the coupling housing flange on the plug means showing the floating keys and master keyway.

FIGURE 24 is a sectional view showing the keys and keyways on the receptacle and on the coupling housing flange in proper mating relation to permit further relative axial movement of the plug and receptacle means.

FIGURE 25 is a transverse sectional view through the coupling housing flange of a plug means which is non-compatible with the receptacle means shown on the drawings to illustrate the angular relationship of the keys and keyways to prevent false mating.

FIGURE 26 is a sectional view similar to Fig. 25 showing alignment of the master key and keyway of non-compatible plug means and receptacle means to illustrate the contact of the keys on the flange to prevent further mating of the non-compatible connector parts.

In Fig. 1 is shown a receptacle means 30 coaxially aligned with and separated from a plug means 31, both receptacle and plug means providing an electrical connector generally indicated at 32 (Fig. 4). The electrical connector 32 serves to couple and electrically connect a plurality of cables or wires, the ends of which are secured to the receptacle and plug means at electrical contact elements in known manner. Five cables are shown for coupling by the connector 32, it being understood that the bundle of cables may vary in number and can include as many as 20 cables or more. The plug means 31 is adapted to be advanced along the axis of receptacle means 30 to move the plug means 31 into desired full electrical and mechanical mating of the plug and receptacle means.

Receptacle Means In this embodiment of the invention, receptacle means 30 includes a receptacle shell 36 comprising a cylindrical wall having a radially outwardly directed annular flange 37 which may be placed against the front face of wall 33 and secured thereto by screw bolts 34. Receptcle shell 36 extends through an opening 38 in wall 33 and may include a back cylindrical shell wall 39 which extends beyond the back face of wall 33.

Receptacle shell 36 receives and holds a composite insert member 40 of cylindrical form. The external cylindrical surface of insert member 40 may be provided with a plurality of axially spaced radially inwardly stepped shoulders 41, 42 (Fig. 6) for cooperable seating engagement with correspondingly axially spaced and radially inwardly formed shoulders 41a and 42a on the internal cylindrical surface of shell 36.

Insert member 40 is restricted against axial movement in one direction by the abutment of said shoulders. Axial movement of insert member 40 in the opposite direction, that is backwardly of the back shell 39, is restrained by an insert sleeve retainer means as later described in connection with Figs. 19-21 inclusive.

The front portion of insert member 40 may be made of a resilient dielectric material and the back portion made of a relatively hard dielectric material. Contact pins 45 project from conical bosses 44 of the resilient material, the bosses providing circular sealing contact with hard dielectric material surrounding corresponding socket contacts in the plug means. The axial position of insert member 40 in receptacle shell 36 is such that contact pins 45 carried thereby have their pin ends spaced a predetermined distance inwardly from the edge face 46 of receptacle shell 36. Contact pins 45 are thereby exposed for mating contact with the plug means relatively deeply within the chamber formed by receptacle shell 36 and are protectively enclosed by receptable shell 36.

Receptacle shell 36 is provided with an external cylindrical surface 47 provided with two sets of circumferentially spaced external radially outwardly directed shell locking lands 48, 49 to provide respective locking faces 49a, 48a spaced uniformly from the opposed annular face 51 of flange 37. The overall circumferential dimension of "L" (Fig. 5) of each set of lands 48, 49, may remain unchanged for receptacle shells of the same diameter. The arcuate length of each land 48, 49 of each set of lands may be varied to provide a specific different set of lands for receptacles having selected pin contact arrangements or other differing characteristics to avoid mismatching of receptacle and plug means.

A master key 50 is provided on receptacle shell surface 47 between the two sets of locking lands and in the same transverse planar zone as lands 48, 49. Key 50 has a face 50a spaced from flange face 51 the same distance as land faces 48a, 49a. Key 50 may be varied in width or arcuate length to be compatible with a selected plug means and serves to angularly orient the plug and receeptacle means.

The interconnection at the insert member between the cables, insert member 40 and contact pins 45 may be made in suitable well-known manner. It is understood that insert member 40 firmly holds the contact pins 45 against relative axial movement and that electrical continuity is preserved through insert member 40 without electrical leakage loss.

Plug Means Plug means 31 comprises a plug shell 60 having a particularly configured cylindrical wall 61 having an internal diameter slightly greater than the outer diameter of receptacle shell 36 so that shell 36 may be axially and telescopically received therewithin. The plug shell 60 also includes an internal annular flange 62 defining an opening 63 and a shoulder 64 serving to index axially a plug insert member 66 with respect to the plug shell. Flange 62 includes a keyway 62a which receives a plastic key 62b on insert member 66 to angularly index member 66 also with respect to the plug shell 60. Annular shoulder 65 spaced from shoulder 64 serves as a seat for one end of an insert retainer ring member as later described. A cylindrical plug insert member 66 of suitable hard dielectric material receives ends of cables which are electrically connected within insert member 66 to electrical socket contacts 67 spaced and arranged about the axis of the plug insert member to correspond with the spacing and arrangement of the contact pins 45 on the receptacle insert member 41. The cylindrical portion 68 of plug insert member 66 has an outer diameter which is slightly less than the inner diameter of recepetacle shell 36. The outer cylindrical surface of insert member portion 68 defines with the internal cylindrical surface of cylindrical wall 61 of plug shell 60 an annular space 69 for reception of receptacle shell 36 during mating of the plug and receptacle means.

Plug means 31 also includes means for coupling or connecting the plug and receptacle means whereby the pin and socket contacts 45 and 67 respectively are properly aligned for electrical mating contact when the receptacle and plug shells 36 and 60 respectively are coaxially drawn together into full electrical mating and mechanical locking engagement. In this example, the coupling means generally indicated at 70 includes a coupling ring housing 71 and a coupling nut 72 within coupling housing 71 and provided with threaded engagement at 73 with external threads provided on cylindrical wall 61 of plug shell 60. Coupling ring housing 71, Fig. 3, is provided on an intermediate portion of its internal surface with a plurality of circumferentially spaced radially inwardly directed lands 75 and grooves 76 for cooperation with complementary lands 77 and grooves 78 on coupling nut 72.

Certain of the interengaging lands and grooves may be of different width to angularly orient and position the coupling housing and nut with respect to each other.

Coupling ring housing 71, when turned about the axis of the connector, will transmit such turning forces to coupling nut 72 through the interleaved lands and grooves of the coupling housing and nut while permitting relative longitudinal or axial movement between coupling housing and coupling nut.

Coupling housing 71 is provided with a coupling end portion 80 having a radially inwardly directed breech flange 81 provided with circumferentially spaced radially inwardly directed breech recesses 82 and 83 defining lugs or keys 85 and a keyway 84.

The inner diameter of flange 81 with spaced keys 85 is slightly greater than the outer diameter of receptacle shell 36 so that the shell 36 may be inserted, after proper orientation of receptacle shell lands and breech lugs or keys 85, through the breech flange openings for reception between the plug shell and the plug insert member.

Coupling housing 71 also includes between breech flange 81 and an interior radially inwardly directed annular rib 88 a part circular, about 270 , groove 86 to receive a spring detent means 87 of about 1800 arcuate shape to audibly and tactilely signal full locked and unlocked condition of the plug and receptacle means as later described.

Coupling housing 71 also encloses an annular spring means 91 which imparts an axially directed spring force against coupling nut 72. One end of nut 72 abuts face 89 of rib 88, the other end of nut 72 providing an annular seating face 90 for one end of spring means 91 which is seated at its opposite end against an annular retaining member 92 breech interlocked with coup ling housing 71 as more particularly described hereafter.

The threaded engagement at 73 between plug shell 60 and coupling nut 72 comprises a four lead fast thread adapted to rapidly axially advance plug shell 60 into full mated relationship with receptacle shell 36 unpon rotation of coupling ring housing 71. An example of a suitable thread is an Acme stub thread.

Electrical continuity with respect to grounding and radio frequency interference shielding means 95 may be carried within plug shell 60 for engagement with receptacle shell 36, the shielding means 95 being particularly described hereafter. In this example, the RFI shield means 95 is positioned and located on an annular rib 96 provided on the interior surface of plug shell 60 and cooperable with a particular mounting configuration of the shield means to securely position shield means 95. RFI shield means 95 comprises a plurality of resilient fingers 97 which are adapted to be compressed by the forward portion of the receptacle shell 36 to provide electrical contact therewith as hereinafter described in detail.

The construction of receptacle means 30, plug means 31, and coupling means 70 embody novel features of construction and operation which will be further described in detail in connection with a coupling and uncoupling operation of the plug and receptacle means. In this example, receptacle means 30 is fixedly mounted on a wall 33 and is nonrotatable and is non-axially movable. It will be understood that the plug and receptacle means may be moved relative to each other in order to accomplish the coupling and uncoupling functions and that the present example contemplates such an operation.

In Fig. 1, receptacle means 30 and plug means 31 are in spaced relation and positioned along aligned axes of the plug and receptacle means. Plug shell 60 is in retracted axial relation with respect to coupling means 70. Further, in this retracted position, keyway 84 on coupling ring housing 71 is in alignment witth an internal keyway 100 on the plug shell. Plug means 31 is then angular or rotatably aligned by suitable reference marks on the coupling housing and receptacle shell so that the keyway 84 is in linear alignment with master key 50 on the receptacle shell.

If keyway 84 and key 50 are compatible, which determines whether the plug and receptacle means are designed for mating, plug means 31 may then be advanced along the axis of the connector to permit entry of master key 50 into keyway 84 of the coupling housng, Fig. 4. It will be apparent that the ends of contact pins 45 are spaced from socket contact 67 of the plug insert member 66 and that the end portion of receptacle shell 36 has entered the annular space 69 between insert member 66 and cylindrical wall 61 of the plug shell. In such position (Fig. 4) the pin contacts and socket con tacts are in alignment, are not in electrical contact, and the plug and receptacle shells are interengaged over a sufficient axial distance to minimize or effectively restrict cocking or axial misalignment of one shell with respect to the other shell. The relative relationship of coupling means 70 with respect to plug shell 60 is unchanged.

Plug means 31, after having been properly aligned and oriented with receptacle means 30 as illustrated in Fig. 4, may be still further advanced axially until the front face of the coupling housing breech flange 81 moves against upstanding annular flange 37 on the receptacle means 30. During this relative axial movement of the plug and receptacle means, the coupling ring housing and associated coupling nut and plug shell are turned only to the extent of matching key 50 with keyway 84 and matching the receptacle shell lands 48 and 49 with the openings provided in the inner circumference of housing flange 81. At the position shown in Fig. 6, the pin contacts 45 are at the openings of the socket contacts on the plug insert member but have not entered the openings.

It should be noted that the breech flange 81 includes keys 85 spaced about 1200 from keyway 84, said keys 85 being alignable with and passing through keyways 85a, Figs.

22-26, formed between locking lands 48 and 49 on receptacle shell 36. The correct orientation of keys 85 anld keyways 85a permits axial advancement of plug means towards the receptacle means so that the shells can be properly mated. As later described, keys 85 and keyways 85a serve to prevent mating of plug means and receptacle means which are not designed or intended to be mated because of different numbers of pin and socket contacts carried by each of the plug and receptacle means.

Advancement of the plug means into full electrical contact of the contact pins and contact sockets is accomplished by turning the coupling ring in one direction through about 900. Turning of coupling ring housing 71 drives the coupling nut 72 which moves plug shell 60 axially without rotation towards the receptacle means. Plug shell 60 is held against rotation by interlocking of key 50 on the receptacle shell and the keyway 100 on the plug shell, master key 50 having enetered keyway 100 upon the last axial movement of the plug means and is disengaged with the keyway 84 on coupling ring housing 71. Thus, in position shown in Figs.

6 and 10, the coupling ring 71 may be turned relative to the shells; however, plug and receptacle shells are held against relative rotation by the key and keyway 50 and 100. Since the pin and socket contacts have been aligned, the ends of the pins enter the sockets for electrical engagement Upon completion of turning the coupling housing through 90" (Fig. 10) the breech locking lugs 82 and 83 on the coupling housing are located axially behind the locking lands 48 and 49 on the receptacle shell and the annular flange formed thereon. Relative axial movement of the coupling housing with respect to the plug shell is thereby prevented.

Spring Detent Means Means for aulibly and tactilely indicating that the plug and receptacle means are in full mated and locked condition both electrically and mechanically and to hold them in locked condition is provided by the spring detent means 87. Detent means 87 is carried in part-circumferential groove 86 formed in the internal surface of the coupling ring housing 71. As shown in Fig. 8, spring detent means 87 is of arcuate configuration and has an internal key 110 midway between ends of the detent spring means, the key 110 being axially slidably loosely engageable in a keyway 111 provided on the outer surface of the end portion 61 of the plug shell 60. Spring detent means 87 is operable within groove 86 in the coupling ring housing but does not rotate or turn with the coupling housing.

Spring detent means 87 includes arcuate arms 112 with radially outwardly extending projections 114 having convex surfaces 115.

The arcuate arms 112 are progressively reduced in cross-sectional area towards ends 114 arcuate arms 112 to radially inwardly compress and projections 114 to disengage recesses 116. As the coupling housing reaches the end of its 900 turn, spring arms 112 snap outwardly as projections 114 are biased into detent recesses 116a. When this occurs, a very distinct relatively loud snap or click is heard and felt.

When such an audible and tactile signal is given by rotation of the coupling housing 71, such signal clearly indicates that coupling housing 71 has completed breech locking engagement with receptacle shell 36 and that coupling nut 72 has driven axially forwardly plug shell 30 and insert member therein so that the pin contacts 45 are in full electrical engagement with the contact sockets carried by the plug means.

When the plug and receptacle means are uncoupled, the coupling housing is rotated in the opposite direction, the spring detent arms 112 are radially inwardly eompressed upon leaving recesses 116a. The coupling housing 71 drives coupling nut 72 in the opposite direction so that the plug shell 60 and its insert body member with socket contacts is axially withdrawn without rotation.

The spring detent means 87 again audibly indicates that plug means 31 has become disengaged electrically from the receptacle means 30 by the audible and tactile force of the spring detent means snapping against the coupling housing as the projections 114 enter recesses 116. The coupling housing is then positioned with the keys and keyways on the breech locking flange and shell locking lands aligned so that the plug means can be withdrawn from the receptacle means in an axial direction without rotation.

It should be noted that the coupling nut 72 is biased axially forwardly toward the receptacle means by springs 91. Springs 91 not only facilitate turning of the coupling ring housing 71, which drives coupling nut 72, into full mated and locked relationship desired between the plug and receptacle means, but also after such full mating engagement, the spring means 91 may serve to bias and hold the plug and receptacle means in assembled relation.

Detent spring means 87 may vary in curvature, such curvature is always sufficient to cause forceful snapping of the projections 114 into recesses 116, 116a to be heard and felt. Such forceful snapping of detent projections into the detent recesses is facilitated by the loose clearance key 110 has with keyway 111, such loose clearance allowing the detent member to quickly shift position to help produce the loud snapping sound.

The loose clearance of key 110 and keyway 111 is correlated to the curvature of the detent projections 114 and recesses 116 so that the detent member does not bind in its contacts with the coupling housing and plug shell and is free to quickly respond as the projections 114 move into the recesses 116.

The convex faces 115 and concave recesses 116 and 11 6a and difference in curvature thereof facilitates the snapping effect and also is one of the factors which tends to maintain assembly because coupling housing 71 cannot be turned until sufficient torque force is applied thereto to release the projections 114 from recesses 116, elba. The amount of force required is predetermined and the arrangement of curved surfaces on projections 114 and recesses 116, 1 16a may be varied to provide a desired release and snap-in. The construction and bending characteristics of arms 112 may also be varied to obtain a desired force, RFI Shielding Means Means for grounding and shielding electrical connector 32 against frequency interference in the range from 100 MHz to 10 GHz comprises shield means 95 shown in detail in Figs. 12-16 inclusive. Shielding integrity is provided by a 360" continue low resistance path from one cable shield to the other cable shield through the electrical connector. In this example, the cable shields are electrically connected to the plug and receptacle shells in well-known manner. The shielding means 95 is in shield ing contact relationship with the forward end portion of receptacle shell 36 as shown in Figs. 6 and 10. As noted in Fig. 6, shielding engagement with receptacle shell 36 occurs prior to electrical contact of contact pins 45 with contact sockets 67.

As previously briefly described, shield means 95 is mounted on an internal annular rib 96 of plug shell 60 and includes a plurality of circularly arranged resilient folded fingers 97 adapted to slidably and electrically contact the external cylindrical surface of receptacle shell 36. Shielding means 95 is so constructed and formed that when installed on the interior of plug shell 60, the spaces or windows between adjacent edges of fingers 97 are minimized and will be in the order of a few thousandths of an inch, for example 0.004 inches.

In the method of forming such an RFI shield means 95 a rectangular blank 120 of suitable metal stock material such as beryllium copper of about 0.004 inches thick of selected length and width is provided, Fig.

14. On one face of blank 120 is printed or inscribed a preselected pattern of securement tabs 121 and spring fingers 122 extending from an intermediate longitudinally extending band 123. The configuration of fingers 122 is trapezoidal and tapers from band 123 to the end distal therefrom. Securement tabs 121 and fingers 122 are connected to band 123 by narrow neck portions 124.

Material of the blank 120 between the in scribed tabs, fingers and band is then chemically etched away so that a precise dimensional configuration of tabs and fingers results.

While the etched blank 120 is in flat form, the material is subjected to a forming operation wherein the securement tabs 121 are bent into generally U-shape as shown in Fig. 16 wherein outer leg 121a of the securement tab is initially formed slightly inclined toward the opposed leg of the tab. The inclination of leg 121a facilitates tight frictional grasping of rib 96 when the shielding means is mounted on plug shell 60.

Fingers 122 are formed as by bending each finger about an intermediate portion which forms an arcuate nose 125 joining a base or first cantilever portion 126 angular disposed and connected to band 123 and to a second cantilever portion 127 which terminates in an inwardly bent or return end portion 128. As shown in iFg. 14, in flat form, adjacent edges of fingers 122 continuously diverge from their base portion adjacent band 123 to the return end portion 128.

The etched and formed blank is still in linear form as shown in Fig. 15. The formed blank may then be turned and shaped about a selected radius into an annulus in which the radially outwardly directed surface of band 123 has a diameter approximately corresponding to the inner diameter of plug shell 60 adjacent to annular rib 96. When the annulus is formed about such radius, the diverging edges of adjacent fingers 122 (Fig. 15) are drawn into close uniform spaced relation (Fig. 16) at 129. The spaces at 129 are each approximately 0.004 inches.

Such extremely close spacing of a plurality of resilient fingers throughout 360" is achieved by the precise correlation of the dimensions of the etched trapezoidal shaped fingers 122 and their relation to the radius of the resulting annulus of the shielding means 95.

The shielding means 95 may be secured as by suitable electrically conductive bonding or soldering to annular rib 96. The annulus may be formed while the securement tabs 121 are being inserted over rib 96. Tab and rib contacting surfaces are preefrably made electrically conductive and soldered. Band 123 has an end extension 130 which may overlap the opposite end of the band and be secured thereto in suitable manner as by electrically conductive brazing, soldering or bonding.

It will be understood that the resilient fingers 122 may be plated with a noble metal such as gold, and the surfaces contacted by the fingers on the recepetacle shell 36 and plug shell 60 may also be plated or coated with a noble metal such as gold or silver. In Fig. 12, band 123 may be provided with a contact surface at 131 of noble metal. In fully mated position, the plug shell 60 and receptacle shell 36 are provided with a substantially continuous 3600 electrically conductive path of low resistance between the metal shells 60 and 36 through the shielding means 95. The precise configuration of the resilient fingers 122 provides minimal window area for transmission of stray frequencies and radio frequency leakage attenuation is maximized.

It should also be noted that the forward edge of the receptacle shell 36 may be chamfered or beveled at 133 so that during relative axial movement of the plug and receptacle means for mating the bevel edge 133 will first contact the radially inwardly biased cantilever portion 127. Surfaces of the shell and fingers will be effectively pressure wiped to remove surface oxidation thereon because of spring biasing forces provided by bending of cantilever portion 127 about nose 125 and by bending of cantilever portion 126 at band 123. Entry of shell 36 into the opening defined by portion 127 of the fingers 122 causes the resilient folded fingers to uniformly move radially outwardly or expand until finger portions 126 are in pressure contact with plug shell 60.

The fulcruming of each finger portion 126 about its connection to band 123 enhances the resilient biasing forces available for pressure contact with the shells 36, 60 (Figs.

6, 10). The precise shape of the fingers in relation to the formed radius of the shielding member permits radially outward flexing of the fingers with virtually little change in the size of the window openings or spaces between fingers. Shielding effectiveness is substantially unchanged. The angular and bent configurations of finger portions 127 and 128 permit relative axial movement of the two shells 36 and 60 without interference. As noted in Fig. 6, contact of shielding means 95 occurs before the pin contacts 45 enter the socket contacts 67 in the plug means.

Coiipllng Assembly Breech Retaining Means Coupling ring housing 71 with enclosed coupling nut 72 and springs 91 bearing against one end of the coupling nut are retained in assembly by annular retainer member 92. With particular reference to Figs. 1, 17 and 18, annular retainer member 92 has an inner diameter approximately the same as the inner diameter of couling nut 72 and provides an inner annular surface 135 against which one end of springs 91 may seat in assembly. The outer circumference of member 92 is provided with arcuate circumferential breech lands or lugs 136 in spaced relation and defining therebetween openings 137. As shown in Fig. 18, breech lugs 136 may be aligned with internal through openings 138 provided in end portion 139 of coupling ring housing 71. End portion 138, internally of the edge face of the coupling housing is provided with a plurality of circularly spaced recesses 140 having end walls 141, recesses 140 being adapted to receive and to hold therewithin breech lugs 136. Annular retainer member 92 may be provided with three angular spaced detent indentations or impressions 143 in the outer annular face of member 92.

The coupling assembly breech retainer member 92 may be sleeved over plug shell 60 with breech lugs 136 aligned with the through openings 138 provided in end portion 139 of the coupling housing 71. By using a tool having three prongs corresponding to the spacing of indentations 143, annular member 92 may be pressed uniformly axially toward coupling nut 72 and against the spring forces of springs 91. After retainer member 92 has been axially advanced into contact with the inward shoulder 144 formed by the annular recess 140, the member 92 may be rotated in either direction so as to move the locking breech lugs 136 into the back space of the recesses 140. Upon release of installing pressure, retainer member 92 is urged axially outwardly by springs 91 to position the breech lugs 136 in recesses 140. In such position it will be apparent from Fig. 17 that turning or rotational movement of member 92 is restricted by the engagement of ends of breech lugs 136 with the end walls 141 of the recesses 140.

Disassembly of the retainer member 92 from the coupling ring housing 71 is accomplished by a reversal of the installation steps described above. The three-pronged tool is again employed to exert an axial pressure on the retainer member 92 to force it axially inwardly against the spring pressure and to then rotate the ring through the necessary angle to align breech lugs 136 with through openings 138 in the end portion of the coupling ring housing. Upon release of pressure from the tool, the retainer member 92 is withdrawn from the end portion of a coupling ring housing. Springs 91 and the coupling ring housing and associated coupling ring nut may then be removed for disassembly.

Insert Refaiinng Means Insert members 40 and 66 must be precisely axially positioned and angularly- accurately oriented with respect to their respective shells so that proper alignment and mating of the pin and socket contacts may be accomplished. Insert members have been axially located within a shell by seating an insert member against a reference shoulder on the shell to restrain movement in one direction and then by bonding or using a threaded ring or lock washer to restrict movement of the insert member in the opposite direction. Use of such prior devices introduced unwanted tolerances which - detracted from such precise positioning. Under some operating conditions, a slightest relative axial movement of the insert member with the shell was objectionable because of its effect upon multiple pin and socket connections and upon securement of the contacts in the insert member. The present electrical connector 32 embodies means for retaining and positively positioning an insert member against a shoulder or other fixed reference without adjustments and without bonding to the shell.

In Figs. 4 and 19-21 inclusive, an insert retainer means 158 is applied to insert member 50 of receptacle means 30. Back shell 39 of receptacle shell 36 is provided with an outer cylindrical portion 150 of relatively thin cross section. Inwardly from portion 150 the back shell is provided with a relatively thicker cylindrical portion 151 provided on its inner surface with a particularly shaped buttress type thread 152. In this example, threads 152 are formed with a single lead, right hand pitch, and include 50 threads per inch. Cross sectional configuration of threads 152 include a flat crest 153 and a relatively wider flat root 154. Inwardly directed face 155 of the thread is normal to the flat crest and root 153, 154 respectively. Outwardly directed face 156 of the thread is slightly inclined from the root 154 to the crest 153. Spacing between crests 153 of adjacent threads is indicated at B and in this example may be approximately 0.020 inches. The length of the back shell provided with threads 152 may be any suitable length depending upon the axial dimensions of the insert member to be carried by receptacle shell 36. In this example, depth of threads 152; that is, from flat crest 153 to flat root 154, may be approximately 0.005 to (6.006 inches. As noted in the above description, insert member 40 has shoulders 41 seated against reference positioning shoulder 41a provided in the receptacle shelf.

An insert retaining ring 158 may be made of a suitable compressible thermoplastic material, such as Torlon or Nylon. Ring 158 includes a cylindrical smooth inner surface 159 through which may be received, as by a clearance fit (a few thousandths inches), the back end portion of insert member 40.

The outer cylindrical surface of ring 158 is provided with a thread 160 which has two leads, a left hand pitch and includes 25 turns per inch. The thread configuration, also of buttress type, includes a generally triangular cross section having a sharp corner 161 at its crest, a relatively long inclined face 164 leading to a narrow flat root 162 having a width approximately one-third or one quarter of the space between adjacent crests 161 as identified by the letter A, and an outwardly directed face 163 normal to flat root 162. The crest spacing A in this example may be about 0.020. The outer diameter of the insert retaining ring 158 is slightly larger than the inner diameter of the shell, the sharp corners 161 reaching into the root areas 154 of threads 152.

As shown in Fig. 21, the unique configuration of the threads 152 and 160; that is, one being a single lead right hand pitch of 50 threads per inch and the other being a left hand pitch two leads at 25 turns per inch, together with the specific cross sectional configuration of the two threads provides a unique thread interengagement in which mating or meshing thereof will occur at three points spaced approximately 120Q apart as indicated in Fig. 21 at 165, 166 and 167. The manner of such interengagement is now described.

In assembly, after the insert member 40 has been angularly oriented and axially positioned against reference shoulder 41a within receptacle shell 36, insert retaining ring 158 is sleeved over the end of the insert member 40 and moved axially toward back shell 39. When the sleeve member begins to enter intermediate portion 151 with threads 152, a cylindrical drive tool is employed to forcibly press the insert ring into the receptacle back shell 39 and axially along the shell threads 152. Because the threads are pitched in an opposite direction and are of non-threading, non-mating characteristics, the forcing of the threads of the plastic ring along the threads of the metal back shell 39 places the insert ring under radial compression and causes the threads 160 to successively interengage and forcibly interfit with the threads 152 at three angularly spaced areas indicated in Fig. 21.

Such radial pressure interfitting of the threads 152 and 160 during relative axial movement is facilitated by inclined faces 156 and 164. Restraint against opposite relative axial movement is positively restricted by the interabutment of faces 155 and 163 which are normal to the axis of the ring and shell. Such interengagement of compressible thermoplastic threads 160 with metal threads 152 successively and angular progressively occurs at three angularly spaced places around back shell 39, the thermoplastic retainer ring 158 being deformed under radial compression into somewhat triangularly related locked or interfitting abutment areas 165, 166 and 167 provided by the opposed normal faces 155, 163 of the two different thread configurations.

The tapered configuration of the leading end 169 of ring 158 facilitates entry of the ring end 169 into the shell. The end face of the leading end 169 may be driven against a thrust shoulder 170 on the insert member or against a thrust ring provided on the back portion of an insert member so that the insert member is immovably locked between positioning shoulder 41a on the recepetacle shell and the insert retainer ring pressed against shoulder 170 and threadably interlocked with the back shell.

The compressible retainer ring is linearly pressure driven into engagement with and between the back shell and insert member.

The insert retaining ring locks and meshes with the threaded shell to precisely position the insert member in the shell against reference shoulder 41a regardless of coarse or loose tolerances between shoulder 41a and shoulder 170.

While the example describes the insert retaining member in relation to the receptacle shell, it will be understood that a similar insert retaining ring may be employed at the back portion of plug shell 60 to retain the plug insert member in fixed axial position relative to the plug shell in the same manner as above described.

While a present example of an insert retaining ring has been described with respect to an electrical connector having a cylindrical metal shell and a cylindrical dielectric insert member received within said shell and fixedly holding the insert member in immovable position with respect to the shell, it will be understood that such a compressible insert retaining ring may be employed to restrict to a minimum axial movement between two concentric members utilized in different environment.

It will be understood that when the terms "thread means", "thread configuration" and "thread interengagement" are used herein, that "threads" include the usual helical type thread shown as well as part-helical projections pitched at a desired angle to the axis of the shell and retainer ring. Either or both cooperable threads may be hedical or non-helical. The selected pitch of each thread should provide for crossing of the interengaging threads at at least three abutment areas with the insert ring under radial compression.

It will be noted that use of insert retainer ding 158 and such a cooperable back shell 39 provides quick foolproof assembly of the insert member within the receptacle shell and no additional adjustments are required to positively seat and hold insert member 40 against positioning shoulder 41a.

Breach Holdofi Means In some prior electrical connectors relative axial movement of plug and receptacle sections were permitted under undesirable conditions which could result in damage to the connector and failure to properly mate electrical contacts. Such undesirable condi tions include partial engagement of one or more key-keyway systems resulting in wear thereof and inaccurate sensing of the partially mated connector section, relative axial movement of the sections with a bent contact pin, attempting to mate connector sections in which sections include projecting contact pins, jamming or cross-starting of the coupling means, and permitting relative axial movement under axial misalignment conditions of connector sections not meant to be mated.

The present electrical connector construction embodies features which obviate and prevent the occurrence of the undesirable conditions mentioned above. It should be noted that master keyway 84 on the coupling flange 81 receives master key 50 on the receptacle shell for orienting the two shells with respect to polarization or axial alignment or mating pin and socket patterns.

Master key 50 and master keway 84 are preferably made in two different width "W", "W1" (Fig. 22, 23) so that a receptacle shell having a key of one width will reject attempted mating of a similarly sized shell which has pin contacts and a keyway of different width. In other words, compatible shells, when aligned by the master key and keyway 50 and 84, may be readily oriented as to pin and sockets; however, if both shells carry pin contacts, the rejection of one of the shells is made by the different widths of master key and keyway. A color coded visual reference indicia is provided on the coupling housing and on the receptacle shell in linear alignment to facilitate such orientation and identification of pin or socket shells.

The master key and keyway will permit relative axial movement of the plug and receptacle shells only if proper pin or socket combinations are present. It will be understood that if both connector sections were provided with sockets only, no electrical connection would be made and no pin or connector section damage would occur.

When the master key and keyway of the plug and receptacle means are compatible, relative rotative movement of the plug and receptacle means about the center axis determines whether the arrangement of pin and socket contacts are of mating capability.

Before the plug means can be advanced axially with respect to the receptacle means, keys 85 must be oriented with keyways 85a and master key 50 with master keyway 84.

Such orientation of keyways is shown in Fig.

24.

In the event proper visual orientation of master key 50 and keyway 84 is made and appear to be compatible, but the receptacle shell and plug shell are not compatible for mating because of a difference in number of pin contacts or in the arrangement thereof, the angular position of keys 85 on coupling ring flange 81 and keyways 85a on shell 36 of such noncompatible shells will cause keys 85 to bear against front faces 48b and 49b for locking lands 48, 49 on the noncompatible shell ,as for example as shown in Fig. 25. where the transverse section is taken through coupling flange 81.

The particular arrangement of keys 85 and keyways 85a should be noted. The keys on the coupling housing flange 81 and the keyways 85a on the receptacle shell may be angularly varied within the included angle determined by the overall arcuate length "L" of lands 48, 49 (Fig. 5). For example, five or more angular arrangements of such key-keyway systems may be made. The arrangement of the sets of locking lands on shell 36 with their inclusive keyways 85a, together with the location of the master key 50 on shell 36 and keyway arrangement on ring flange 81 is such that one end 49c of one set of lands and other end 48c of the other set of lands are not diametrically opposite. In this example, angular spacing of other land end 48c is about 45" from a diameter through key 50, and angular spacing of said one land end 49c is about 30 from such a diameter. With this arrangement of the sets of lands and their location with respect to the master key and keyway, it will be apparent that when mismatched shells are attempted to be brought together into mating relationship that contact areas of keys 85 with abutment surfaces 48b and 49b of the locking lands will form a triangle with the master key and keyway system such that the axis of the connector shells will always lie within a triangle formed by such areas of contact of keys 85 with the faces of the locking lands and by contact of master key 50 with a portion of the end face of flange 81. The geometry of the key-keyway hold off pattern is such that at least three contact areas are provided in a triangular arrangement in which one side of the triangle is always beyond the center axis of the connector shells (Fig. 25). Thus, when an operator blindly rotates, or rotates by manual dexterity, the plug means against the receptacle means, cocking, tilting, misalignment of one section with respect to the other section is prevented by the contacting areas of keys 85 and key 50 respectively with the faces 48b, 49b at the locking lands and face 81a of flange 81, until the keys 85 and keyways 85a and master key and keyway become aligned.

When the master key and keyway are compatible and aligned, the two keys 85 will act as a contact or hold off means bearing against locking land faces 48b, 49b, if the shells are incompatible. In the example shown in Fig. 26, inrompatible keys 85 and keyways 85a are moved to a different keying angular position and are spaced 900 from the compatible master key and keyway. Keys 85 abut land faces 48b, 49b in dimetrically opposite relation and restrict tilting about the vertical diameter of the shells as viewed in Fig. 26. Restriction against tilting about the horizontal diameter as viewed in Fig. 26 is provided by the flat surface area contact of keys 85 with the land faces and by the tolerances between the inner diameter of flange 81 and the diameter of the outer cylindrical surfaces on shell 36 including lands 48, 49. In such above described relationship of the key- and keyway system, it will be apparent that there are at least two diametrically spaced areas of contact to restrict tilting or axial misalignment of the two shells. It should also be noted that before the master key 50 and master keyway 84 are in compatible alignment that the keys 85 and key 50 provide three contact areas forming a triangle to provide axial stability between the plug and receptacle means and thereby avoid the disadvantages of possible cocking or misalignment and false mating as one shell is rotated relative to the other while seeking proper mating of the two shells.

The stabilized hold off means provided by the key and keyway arrangement described above facilitates seeking the mating relationship of compatible plug and receptacle means because while the plug means is being rotated relative to the receptacle shell, the coupling flange 81 will turn in a plane normal to the axis of the connector and thereby prevent false indication of key-keyway alignment which might occur if one key dipped into a keyway during such turning. The above described key-keyway arrangement also serves as a potitive deterrent to the false mating of noncompatible plug and receptacle means because even in the condition where the master key and keyway are compatible, the keys 85 provide widely spaced areas of contact with the locking land faces whereby the stable relation of the plug means with the receptacle means is substan

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. from the compatible master key and keyway. Keys 85 abut land faces 48b, 49b in dimetrically opposite relation and restrict tilting about the vertical diameter of the shells as viewed in Fig. 26. Restriction against tilting about the horizontal diameter as viewed in Fig. 26 is provided by the flat surface area contact of keys 85 with the land faces and by the tolerances between the inner diameter of flange 81 and the diameter of the outer cylindrical surfaces on shell 36 including lands 48, 49. In such above described relationship of the key- and keyway system, it will be apparent that there are at least two diametrically spaced areas of contact to restrict tilting or axial misalignment of the two shells. It should also be noted that before the master key 50 and master keyway 84 are in compatible alignment that the keys 85 and key 50 provide three contact areas forming a triangle to provide axial stability between the plug and receptacle means and thereby avoid the disadvantages of possible cocking or misalignment and false mating as one shell is rotated relative to the other while seeking proper mating of the two shells. The stabilized hold off means provided by the key and keyway arrangement described above facilitates seeking the mating relationship of compatible plug and receptacle means because while the plug means is being rotated relative to the receptacle shell, the coupling flange 81 will turn in a plane normal to the axis of the connector and thereby prevent false indication of key-keyway alignment which might occur if one key dipped into a keyway during such turning. The above described key-keyway arrangement also serves as a potitive deterrent to the false mating of noncompatible plug and receptacle means because even in the condition where the master key and keyway are compatible, the keys 85 provide widely spaced areas of contact with the locking land faces whereby the stable relation of the plug means with the receptacle means is substantially maintained. The electrical connector 32 described above provides many advantages of construction and operation of which some have been particularly emphasized. In the general concept of the electrical connector, it is important to not that the coupling housing ring serves as a single component part which is constructed to perform a number of important functions. First, the coupling ring housing has a breech flange 81 which locks the plug and receptacle means against axial movement by interlocking abutment with the locking lands 48, 49 on the receptacle shell. Such locking lands provide a substantial abutment area so that the loading per square inch is reduced. Second, the coupling ring housing provides in breech flange 81, - keys 85 which perform the holdoff function described above to prevent mating of noncompatible plug and receptacle means. Thus, the locking flange 81 provides a key means in which the keys 85 may be varied in spacing so that positive means is provided for preventing attempted coupling of non compatible plug and receptacle means; and such mating prevention occurs without damage to pin and socket contact members. Third, the coupling ring housing with its locking flange 81 provides a visual and a nonchangeable orientation of the plug means with the receptacle means by the alignment of the keyway 84 with the key 50 on a receptacle shell. Thus, positive orientation or polarization of the contact elements of compatible mating plug and receptacle means is assured. Fourth, the coupling ring housing provides an annular part-circular internal channel or groove for housing the detent spring 87, the detent spring being positively oriented with the plug shell and coupling housing through the central key 110 which is movable in an axial direction in the keyway 111 on the plug shell. Fifth, the coupling ring housing provides an annular shoulder 89 for abutment of one end of the coupling nut 72 and also provides the full lock breech recess 140 which secures the annular lock ring 92, which serves as a seat for the springs 91 which bias the coupling nut against the shoulder 89. It will thus be apparent that the specific construction of the coupling ring housing of the electrical connector 32 combines many features which provide an electrical connector which is reliable and in which there are safeguards against damage to connector parts in the event mismatching or attempted coupling of noncompatible connector parts is attempted. WHAT WE CLAIM IS:-

1. An electrical connector having a plug part carrying electrical contact elements and a compatible receptacle part carrying electrical contacts for mating engagement with the contact elements carried by the plug part, the plug part and receptacle part being relatively axially movable to mate with the electrical contact elements and contacts, the connector further including at least two angularly spaced keys on one part and corresponding angularly spaced stop faces on the other part adapted to abut when the parts are angularly misaligned, keyways on said other part positioned to correspond with the keys, and a cylindrical guide surface axial direction from said electrical contacts on said plug part in the retracted position of the plug shell and having spaced key and keyway means, a receptacle shell having -spaced locking lands thereon defining keys and keyways, said keys defining said stop faces, said keys, on said flange and on said

receptacle shell having abutment at at least portion on one part extending forwardly of its keys or keyways, and co-operating with a flange surface on the other part to restrict relative tilting movement of the parts during an axial mating movement.

2. A connector according to claim 1 including a retractable plug shell incorporating said contacts, a coupling nut threaded on said plug shell, and a rotatable coupling housing having driving engagement with said coupling nut for rotation of the coupling nut to axially move said retractable plug shell with its electrical contacts into mating relation at one stage of said relative axial movement of said plug and receptacle, a coupling flange on said coupling housing, defining said flange surface, spaced in an three circumferentially spaced points for facilitating maintaining said plug in axial alignment with said receptacle while said plug means is turned to seek alignment of said key and keyway means.

3. A connector according to claim 2 wherein said plug and receptacle parts include a master key on said recepracle shell, a cooperable master keyway on said plug shell for orienting said electrical contacts before interengagement thereof; said keys on said coupling flange including a pair of spaced keys angular spaced from the master keyway on said coupling flange, and said spaced locking lands on said receptacle shell providing angular spaced keyways for said spaced keys on said coupling flange.

4. An electrical connector having plug means and receptacle means axially movable into mated and unmated condition of pin and socket contacts carried thereby and including a plug shell and a receptacle shell, comprising in combination: means for protecting said pin and socket contacts by foolproof indentification of compatible plug and receptacle means and rejection of incompatible plug and receptacle means comprising: said receptacle shell having a first external key and having a set of external locking lands of selected arcuate length; the ends of said set of locking lands being spaced from a diameter passing through said first key; said plug shell having internal locking land receiving recesses and having a first keyway receiving said first key; a rotatable coupling ring encircling said plug shell and having a radially inwardly extending coupling flange, said flange having a first flange keyway alignable in one position of said coupling ring with said first keyway; said first key on said receptace shell and said first flange keyway on said coupling flange being dimensioned to identify pin and socket contacts on said plug and receptacle means and to reject incompatible attempted pin to pin mating; and a second key on said coupling flange and a second keyway on said receptacle shell within the length of said locking lands for identification of compatible pin and socket arrangements in said plug and receptacle shells; whereby said coupling flange identifies, accepts, and rejects plug and receptacle means at front faces of said locking lands and said first key; said first key on said receptacle shell and said first keyway on said coupling flange having preselected width to determine compatible pin and socket means and noncompatible pin and pin means of plug and receptacle means.

5. A connector according to claim 4 wherein each set of said locking lands on said receptacle shell is of selected arcuate length and the ends of each set are nondiametrically opposed; and said second key and second keyway means are selectively spaced along said locking land length to provide identification of different pin and socket arrangements.

6. An electrical connector according to claim 1 substantially as described herein with reference to the accompanying drawings.

7. A set of electrical connectors, each of the connectors being as defined in claim 1 and comprising a plug shell carrying electrical contacts, a receptacle shell carrying electrical contacts for mating engagement with the contacts of the plug shell, the contacts on one of the shells comprising pins and the contacts on the other shell comprising sockets, and a coupling member rotatably mounted on one of the shells for releasably locking the shells together, the coupling member having a locking flange extending forwardly of the front end of the shell on which it is mounted and an arrangement of keys and keyways being provided on the flange for engagement with corresponding keyways and keys provided on the other shell when the shells are axially advanced towards one another, the key/keyway arrangement on the locking flange being positioned behind the key/keyway arrangement of the receptacle shell in a position such that rotation of the coupling ring in said position provides locking engagement of the keys on the locking flange behind those on the receptacle shell; the set including a plurality of connectors with different numbers and arrangements of pins and sockets and selected different key and keyway patterns, the key and keyway patterns being selected such that if mating of a shell of one connector is incorrectly at tempted with a shell of another connector having incompatible contacts, a key or keys on the locking flange of one shell will abut against a key or keys of the other shell to prevent axial advance of the incompatible contacts towards each other.