GB2555485A

GB2555485A - Electrical connector

Info

Publication number: GB2555485A
Application number: GB1618412.9A
Authority: GB
Inventors: Ross Norman Philip
Original assignee: Ross Robotics Ltd
Current assignee: Ross Robotics Ltd
Priority date: 2016-10-31
Filing date: 2016-10-31
Publication date: 2018-05-02
Anticipated expiration: 2036-10-31
Also published as: GB201618412D0; EP3533111A1; GB2555485B; WO2018078312A1

Abstract

An electrical connector 10 comprises a socket 11 having an annular recess 13 which has a conductive outer annular wall surface 13a and a conductive inner annular wall surface 13b electrically isolated from each other. The electrical connector also comprises a plug 18 having an annular projection 21 which has a conductive outer annular wall surface 21a and a conductive inner annular wall surface 21b electrically isolated from each other. The projection of the plug is receivable in the recess of the socket with space in between. The connector further comprises two resilient conductive annular contact elements (25, 27), such as canted coil springs, which are retained in respective grooves (26, 28) that are provided on the outer and inner wall surfaces of the recess or the projection. The annular contact elements are resiliently compressible to produce electrical connections of the opposing outer wall surfaces (13a, 21a) and the opposing inner wall surfaces (13b, 21b) of the recess and projection, and provide two concentric electrical paths respectively.

Description

(54) Title of the Invention: Electrical connector

Abstract Title: Coaxial electrical connector with resilient ring shaped coil springs (57) An electrical connector 10 comprises a socket 11 having an annular recess 13 which has a conductive outer annular wall surface 13a and a conductive inner annular wall surface 13b electrically isolated from each other. The electrical connector also comprises a plug 18 having an annular projection 21 which has a conductive outer annular wall surface 21a and a conductive inner annular wall surface 21b electrically isolated from each other. The projection of the plug is receivable in the recess of the socket with space in between. The connector further comprises two resilient conductive annular contact elements (25, 27), such as canted coil springs, which are retained in respective grooves (26, 28) that are provided on the outer and inner wall surfaces of the recess or the projection. The annular contact elements are resiliently compressible to produce electrical connections of the opposing outer wall surfaces (13a, 21a) and the opposing inner wall surfaces (13b, 21b) of the recess and projection, and provide two concentric electrical paths respectively.

Fl&.l

FIG.2

ELECTRICAL CONNECTOR

The present invention relates to an electrical connector such as is usable for, inter alia, power supply between electrically connectible components.

Electrical connectors exist in a wide variety of forms, including coaxial plug-and-socket connectors for making and breaking electrical connection by insertion of a plug into and removal of the plug from a socket. In general, the electrical connection within the plug and socket is produced by interengaging electrically conductive pins and sleeves or by frictionally interengaging surface areas. Problems commonly associated with conventional forms of such electrical connection are insecure interengagement, for example as a consequence of wear, and build-up of insulating oxide coatings at points of interengagement, leading to intermittent or permanent disruption of the electrical path produced by the interengagement. In addition, many such coaxial connectors are limited to specific relative rotational relationships of the plug and socket.

A further issue with conventional connectors is complexity of manufacture, such as precision production and positional fixing of pins and sleeves or other mating components which require specific alignments in the plug and socket.

It is therefore an object of the present invention to provide an electrical connector which while utilising the proven plug-and-socket concept enables creation of a secure electrical connection resistant to unintended interruption of electrical paths, especially a connector which may remain capable of reliably functioning in the face of temperature change, vibration and ingress of foreign matter and which may be readily configured for use in the presence of potentially disturbing magnetic forces.

A further object of the invention is to provide a connector of the kind mentioned which is of relatively simple and compact construction and which, in particular, allows discrete makeand-break connection of individual conductor tracks with a minimum of complexity and by an easy action.

Yet another object of the invention is creation of an electrical connector which is scaleable to provide multiple positive/negative paths.

A subsidiary object of the invention is provision of such a connector based on a plug-andsocket principle in which it may be possible to produce electrical connection in any desired relative angular relationship of plug-and-socket components.

A further subsidiary object is provision of a connector which may allow combination in one unit of higher voltage paths for power supply and lower voltage paths for data signal transmission.

Other objects and advantages of the invention will be apparent from the following description.

According to the present invention there is provided an electrical connector comprising a socket defining an annular recess having an electrically conductive outer annular wall surface and an electrically conductive inner annular wall surface electrically isolated from the outer annular wall surface, a plug defining an annular projection which is receivable in the annular recess of the socket to be spaced from both the outer annular wall surface and the inner annular wall surface of the recess and which has an electrically conductive outer annular wall surface and an electrically conductive inner annular wall surface electrically isolated from that outer annular wall surface, a first resilient electrically conductive annular contact element retained in a groove in one of the outer annular wall surface of the recess and the outer annular wall surface of the projection and resiliently compressible to produce an electrical connection of those surfaces when the projection is fully received in the recess, and a second resilient electrically conductive annular contact element retained in a groove in one of the inner annular wall surface of the recess and the inner annular wall surface of the projection and resiliently compressible to produce an electrical connection of those surfaces when the projection is fully received in the recess, a first electrical path being established by way of the outer annular wall surface of the recess, the compressed first annular contact element and the outer annular wall surface of the projection when the projection is fully received in the recess and a second electrical path electrically isolated from the first electrical path being established by way of the inner annular wall surface of the recess, the compressed second annular contact element and the inner annular wall surface of the projection when the projection is fully received in the recess.

In such a connector the contact-making between socket and plug is achieved with a high level of maintained security by the resilient annular contact elements, which in the state of reception of the projection of the plug in the recess of the socket are subject to compression between the outer annular wall surfaces in the case of the first contact element and between the inner annular wall surfaces in the case of the second contact element. Each of the annular contact elements is thus squeezed between the surfaces of the respectively co-operating pair of surfaces so as to achieve a particularly secure electrical connection. The annular form of each contact element in conjunction with the co-operating annular surfaces allows constructions with relatively large areas of electrical contact, which enables highly secure electrical contact in conjunction with low or negligible resistance at the contact zones. Creation of two electrical paths by way of two pairs of cooperating annular wall surfaces, i.e. the outer annular wall surfaces and the inner annular wall surfaces, has the result that the paths, which may be at opposite polarities, are physically separated in a simple manner without any risk of inappropriate cross-connection transiently occurring if making and breaking are carried out when current is being conducted.

For preference the contact elements are annular coil springs, in which case contactmaking in each of the established electrical paths is produced by multiple contact points, in particular each individual coil of such a spring makes contact with the co-operating annular wall surfaces of the recess and projection at the outer and inner circumferences of the spring. Depending on the number of coils in the spring, there can be up to a 100 or more points or zones of electrical contact at each of the outer and inner circumferences of the spring. Even if contact-making is or becomes lost or diminished at individual ones of those points or zones for any reason, overall contact is not at risk of being lost.

The annular coil springs, in effect endless garter springs, are preferably canted coil springs in which the coils are canted or slanted by comparison with the coils of a conventional coil spring. The canting of the coils assists radial compression and relaxation of each spring, since compression and relaxation are accommodated not only by change in stress in the spring, but also by change in the angle or lay of the individual coils. Canted coil springs are readily available as proprietary products, in which case choice of diameters of the annular wall surfaces and/or the grooves can, if desired, be linked with the commercially available sizes of spring.

The resilient annular contact elements are preferably seated under constant resilient bias in the grooves so that even when the socket and plug are not interengaged the contact elements are securely retained in the grooves, thus under compression or expansion depending on the groove location. For preference, both grooves are in the wall surfaces of the same component of the connector so that the annular contact elements, for example coil springs, are fitted just to the socket or just to the plug, which simplifies manufacture and assembly. If the component is the socket, the contact elements are permanently located within the recess and thus largely protected from being dislodged or damaged during handling of the connector components.

Maintenance of the interconnected state of the socket and plug is provided in the first instance by the friction created by the resilient contact elements under compression. Enhanced maintenance of that state can, however, be achieved if the outer annular wall surface without the groove and/or the inner annular wall surface without the groove has or each have a depression in which the annular contact element or respective annular contact element retained in that groove is so engaged when the projection is fully received in the recess as to supply mechanical resistance to separation of the socket and plug. Thus, either or each of the resilient contact elements is effectively detented in a groove at one of its inner and outer circumferences and in a depression at the other one of its inner and outer circumferences. The shape of the depression, and for that matter the groove, can be selected to provide secure mechanical detenting without obstructing intentional separation of the socket and plug by pulling apart, in which case it should preferably be ensured that when pulling apart takes place the contact element or elements involved in mechanical detenting preferentially release from the depression or depressions rather than the groove or grooves.

Additionally or alternatively, the connector can comprise releasable locking means to releasably lock the socket and plug together to resist or prevent unintentional removal of the projection from the recess. Such locking means may render other forms of securing the socket and plug together, such as the mentioned mechanical detenting, redundant depending on the circumstances of use of the socket and plug. The locking means can be of any desired kind, for example, a bayonet coupling, spring-loaded radial catches, threaded fasteners, etc.

In a preferred embodiment, the annular contact elements are arranged to be offset relative to one another in a given direction of insertion of the projection into the recess, which has the advantage that compression of the annular contact elements takes place successively rather than simultaneously, so that there is reduced resistance to insertion of the projection into and removal of the projection from the recess. Coupling and uncoupling of the socket and plug thus requires less force on the part of the user and a lighter action is possible. Moreover, the relative offset of the springs in the given direction of insertion has the further benefit of making the connector, in assembled state, more stable than if the annular contact elements were aligned in a radial plane, in particular there is better resistance to exertion on the connector of a lateral force which might otherwise tend to pivot the socket and plug relative to one another.

A connector embodying the present invention is readily capable scaling to provide one or more additional electrical paths. Accordingly, with respect to co-operating outer annular wall surfaces, in one embodiment the recess has at least one further electrically conductive outer annular wall surface electrically isolated from each other annular wall surface of the recess and the projection has a respective further electrically conductive outer annular wall surface associated with the or each further outer annular wall surface of the recess and electrically isolated from each other annular wall surface of the projection, the connector comprising a respective further resilient electrically conductive annular contact element retained in a groove in the or each further outer annular wall surface of the recess or in the associated further outer annular wall surface of the projection and resiliently compressible to produce an electrical connection of those associated surfaces when the projection is fully received in the recess thereby to establish a respective further electrical path by way of that contact element and the associated surfaces. In analogous manner, with respect to co-operating inner annular surfaces the recess can additionally or alternatively have at least one further electrically conductive inner annular wall surface electrically isolated from each other annular wall surface of the recess and the projection in that case has a respective further electrically conductive inner annular wall surface associated with the or each further inner annular wall surface of the recess and electrically isolated from each other annular wall surface of the projection, the connector then comprising a respective further resilient electrically conductive annular contact element retained in a groove in the or each further inner annular wall surface of the recess or in the associated further inner annular wall surface of the projection and resiliently compressible to produce an electrical connection of those associated surfaces when the projection is fully received in the recess thereby to establish a respective further electrical path by way of that contact element and the associated surfaces.

The provision of at least one additional pair of co-operable electrically conductive annular wall surfaces, which are electrically isolated from all other such surfaces, and an associated additional annular contact element so as to establish at least one further electrical path, means multiple conductor tracks can be combined in a single connector, for example, a total of two or three tracks each with a positive and a negative path, or several positive polarity tracks and a single negative polarity track. Coaxial electrical connectors of the prior art able to provide multiple tracks of that kind commonly employ a multiplicity of interengageable pins and sleeves which have to be mated in a specific rotational relationship; by contrast in the case of a connector of the present invention with multiple in particular more than two - tracks, contact-making by way of annular wall surfaces and annular contact elements allows the socket and plug to be coupled in any rotational relationship.

In such a case of multiple conductor tracks, it is advantageous if the at least one further outer annular wall surface of each of the recess and projection has a smaller diameter than the first-mentioned outer annular wall surface of, respectively, the recess and projection so as to prevent the first annular contact member from contacting such a further outer annular wall surface during insertion of the projection into and removal of the projection from the recess, or if the at least one further inner annular wall surface of each of the recess and projection has a smaller diameter than the first-mentioned inner annular wall surface of, respectively, the recess and projection so as to prevent the second annular contact member from contacting such a further outer annular wall surface during insertion of the projection into and removal of the projection from the recess. The smaller diameter can be produced by, for example, inwardly stepping or tapering the recess and projection in a given direction of insertion of the latter into one former. Thus, by the simple expedient of a reduction in diameter between outer annular wall surfaces or between inner annular wall surfaces which are successive in the direction of insertion of the projection into the recess and at which electrical paths are to be established in succession it is ensured that during the process of insertion and removal it is not possible for transient contact-making to occur between annular wall surfaces which are not associated as a pair. The socket and plug can therefore be coupled and decoupled, while current is being conducted, without the risk of temporary creation of cross-connections.

In a particularly preferred construction, at least one of the socket and the plug comprises electrically insulating material partly coated with electrically conductive coating material to provide the respective electrically conductive wall surfaces. This represents a particularly simple and economic means of achieving wall surface conductivity, for example by metallisation or metal-plating of a substrate of electrically insulating material. The electrically conductive wall surfaces provided by the coating material can in that case be electrically isolated from one another by intermediate areas without the coating material. Partial coating with electrically conductive coating material can be achieved by selective application of the coating material in just those areas which are to be conductive or, for preference, by a more general application of the coating material and subsequent selective removal to provide the electrical isolation. This also allows the possibility of using the coating of conductive material to additionally form conductors connected with the annular wall surfaces. Thus, for example, if the socket or plug comprises a suitably shaped body of electrically insulating material, that body can be coated with metal or other electrically conductive material and the metal or other material removed - or omitted from application at the outset - in areas intended to provide not only the electrically conductive annular wall surfaces, but also electrical conductors extending to or from those surfaces.

Additionally or alternatively, the electrically conductive annular wall surfaces of at least one of the socket and the plug may be present on parts separated by an air gap to provide the electrical isolation of those surfaces. Insulation by air gap can be used conjunctively with or as an alternative to electrical isolation by a method such as omitted areas of electrically conductive coating material, for example the outer annular wall surface on the one hand and the inner annular wall surface on the other hand of the socket may be provided in separately constructed parts of the socket.

For preference, the socket is provided in a region thereof remote from an entrance of the recess with a plurality of terminals each electrically connected with a respective one of the electrically conductive annular wall surfaces of the recess. Similarly, the plug is preferably provided in a region thereof remote from a free end of the projection with a plurality of terminals each electrically connected with a respective one of the electrically conductive annular wall surfaces of the projection. Provision of terminals in such locations simplifies connection of external conductors to the socket and plug, for example in a linear arrangement of leads. Electrical connection of the terminals with the annular wall surfaces can follow any suitable route, but in the case of the plug it is preferred if at least one of the terminals thereof is electrically connected with the respective electrically conductive annular wall surface of the projection by way of an electrical connection provided in a via in the plug. The electrical connection can be formed by, for example, a wire, strip, rod or other connecting element, but in the case of coating an electrically conductive material on a constituent electrically insulating material of the plug as described further above an advantageous and economically producible connection can be achieved by application of such a coating within the via. Such an application may be simplified if the plug is of multipart construction and the via is formed by recesses respectively provided in mating parts of the plug. The recess in at least one of the parts can then be coated with the coating material before the parts are mated and, in particular, permanently joined together.

With respect to the terminals themselves, advantageously at least one of the terminals is electrically connectible with a respective external electrical conductor, the at least one terminal in that case being releasably connectible with the external conductor by, for example, a fastening such as a receiving sleeve and fixing screw or permanently connectible by, for example, soldering. Equally at least one of the terminals can be electrically connected with a respective electrically conductive point or track on a circuitboard, the circuitboard preferably being fitted to the socket or plug. The circuitboard can then include electronic components so that the connector functions as the output point of controlled/controllable or otherwise influenced electric current as operating power, a signal carrier or other desired use. However, it is also possible to mount electronic components directly on the socket or plug to reduce cost and the parts count. In either case, such components can include, for example, microprocessors, sensors and lightemitting diodes; components of this kind may impart further functionalities to the connector, for example a capability to identify what is connected with the connector and the characteristics of a larger system linked with the connector and other such connectors.

The configuration of the socket with an annular recess offers the particular advantage of a usable area radially inwardly of the recess, which can be appropriately exploited if, for example, the socket has a passage centrally of the recess and the connector includes an auxiliary electrical coupling received or receivable in the passage. The connector can in that case be employed to conduct operating power by way of the annular wall surfaces and co-operating resilient contact elements and the auxiliary electrical coupling specifically to conduct low voltage for data transmission or similar. The coupling can be of any desired kind, preferably a pin insertable in a sleeve and configured to provide multichannel transmission and a make/break connection. A single connector so equipped thus has a dual capability of conducting different levels of voltage for different purposes, such a capability in the prior art more usually requiring multiple connectors rather than a single connector. The centrally located passage in the socket can also be used, in the absence of an auxiliary electrical coupling, for other purposes such as a conduit for gas or a housing for a photonic coupling.

In a preferred construction of the connector the socket and plug have centring surfaces of mutually complementary form interengageable to centre the socket and plug relative to one another when the projection is fully received in the recess. The centring surfaces, which preferably interengage in the region of an entrance to the recess, ensure concentricity of the annular wall surfaces of the recess on the one hand and the annular wall surfaces of the projection on the other hand when the projection is fully received in the recess and also firm seating of the former in the latter so as to preclude relative movement of the socket or plug such as might otherwise possibly be permitted by the resiliently compressible contact members under lateral loading of one, rather than both, of the assembled parts of the connector.

Preferably, the recess and projection in the state of reception of the projection in the plug are rotationally symmetrical with respect to a common axis, which guarantees the desirable feature of the socket and plug being able to be connected in any rotational setting of either component. However, if so desired the recess and projection can be shaped, such as by a polygonal or otherwise non-circular cross-section or by a key-andgroove rotational lock or similar, to define specific interconnection orientations should this be desired for any reason.

Preferred embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-section of a first electrical connector embodying the invention; and

Fig. 2 is a schematic cross-section of a second electrical connector embodying the invention.

Referring now to the drawings there is shown in Fig. 1 an electrical coaxial plug-and10 socket connector 10 suitable for, but not limited to, typical power supply applications ranging from direct voltages such as 6, 12, 24 or 33 volts to alternating voltages such as 110 or 240 volts. Higher and lower voltages can be accommodated by scaling up or scaling down the connector components with respect to, inter alia, breakdown voltage, prevention of arcing and electric path resistance and the connector is also usable in very low voltage applications for data transmission. Both Fig. 1 and Fig. 2 show connectors in highly diagrammatic form to illustrate the principles of the two embodiments; the actual realisation, i.e. constructional form, of the connector components can widely vary depending on the purpose or context of use of the connector.

The connector 10 of Fig. 1 comprises a socket 11 which has as its basic element a socket body 12 of generally cylindrical form. The body 12 has an annular recess 13 which defines, centrally of the recess 13, a spigot 14 with a stepped axial bore 15. The recess and bore are rotationally symmetrical with respect to a cylinder axis 16 of the socket body. The socket body 12 is injection-moulded from an electrically insulating material, preferably a plastics material, which carries a coating 17 of electrically conductive material, preferably a coating produced by a non-magnetic nickel plating, especially a nickel with a high phosphor component, over a copper base layer. The coating 17 provides, inter alia, an electrically conductive outer annular wall surface 13a and an electrically conductive inner annular wall surface 13b of the recess 13.

The electrically conductive wall surfaces 13a and 13b are electrically isolated from one another by areas of omitted electrical conductive coating, preferably through selectively removing the applied coating 17 by, for example, abrading, etching or laser erosion, or alternatively, but less easily, through applying the coating at the outset only in discrete zones, especially zones separated by masking off intermediate areas. In Fig. 1 the electrical isolation is provided by annular areas of omitted coating at the base of the recess 33 and at the lower (in Fig. 1) end face of the socket body 12 remote from the open end, which represents an entrance of the recess 13. The sections of the coating 16 on the body apart from the outer and inner wall surfaces 13a and 13b of the recess provide conductors electrically connecting those surfaces with respective terminals in a terminal zone, in this instance at the lower end face of the socket body. The terminals are marked, by way of purely arbitrary designation, with positive and negative symbols.

Although conductors formed by the coating 17 are for convenience shown in enveloping form on the socket body 12 in Fig. 1 this is not necessary and the conductive material forming the conductors can be confined to, for example, recessed, shrouded or buried channels, grooves, passages or vias linking the electrically conductive wall surfaces 13a and 13b with the terminals in the terminal zone. This will eliminate possible problems arising from the presence of electrically conductive surfaces in touch-sensitive areas, such as the outer circumference of the socket body, although conductive surfaces in such areas can, in use, be covered by separate housings, caps, shrouds, etc. As already indicated, omission of the electrically conductive coating 17 from areas where conductivity is not desired, in this instance the route between the wall surfaces 13a, 13b and the terminal zone, can be achieved by selective removal or by omission at the time of application.

The connector 10 further comprises, for coupling with the socket 11, a plug 18 which similarly to the socket has as its basic element a plug body 19 in the form of a substantially circular disc 20 with an annular projection 21 and, centrally of the projection 21, a stepped axial bore 22. The disc 29, projection 21 and bore 22 are rotationally symmetrical with respect to an axis 23 which in Fig. 1 is coincident with the axis 16. The plug body 19 similarly to the socket body 12 is injection-moulded from an electrically insulating material, preferably a plastics material the same as that of the socket body 12, which carries a coating 24 of electrically conductive material, again preferably nickel plated over a copper base layer. The coating 24 provides, inter alia, an electrically conductive outer annular wall surface 21a and an electrically conductive inner annular wall surface 21b of the projection 21.

The electrically conductive wall surfaces 21a and 21b are, similarly to the surfaces 13a and 13b, electrically isolated from one another by areas of omitted electrical conductive coating, preferably through selectively removing the applied coating 24 by, for example, abrading or etching, or through applying the coating at the outset only in discrete zones, especially zones separated by masking off intermediate areas. In Fig. 1 the electrical isolation is provided by annular areas of omitted coating at the free end or tip of the projection 21 and at the upper (in Fig. 1) end face of the disc 20 of the plug body 19 remote from the tip of the projection. The sections of the coating 24 on the body apart from the outer and inner wall surfaces 21a and 21b of the recess provide conductors electrically connecting those surfaces with respective terminals in a terminal zone, in this instance at the upper end face of the disc 20. The terminals are marked, again by way of arbitrary designation, with positive and negative symbols.

The conductors formed by the coating 24 are also shown in enveloping form on the plug body 19 in Fig. 1. Again, this is not necessary and the conductive material forming the conductors can be confined to, for example, recessed, shrouded or buried channels, grooves, passages or vias running between the electrically conductive wall surfaces 21a and 21b and the terminal zone, so as to eliminate electrically conductive surfaces in touchsensitive areas, such as the outer circumference of the disc 20 of the plug body 19. The omission of the electrically conductive coating 24 from areas where conductivity is not desired, in this instance the route between the wall surfaces 21a, 21b and the terminal zone, on the plug body can be achieved by selective removal or by omission at the time of application.

The projection 21 - in particular the wall thickness and length of the annulus forming the projection - is dimensioned so that when the plug 18 is coupled to the socket 11 by reception of the projection 21 in the recess 13 an air gap surrounds the projection, specifically the outer annular wall surface 13a of the recess 13 is disposed opposite to, but spaced from, the outer annular wall surface 21a of the projection 21 and the inner annular wall surface 13b of the recess 13 is similarly disposed opposite to, but spaced from, the inner annular wall surface 21 b of the projection 21. The tip of the projection is also spaced from the base of the recess. In the state of reception of the projection 21 in the recess 13 there is thus no direct contact, in particular no direct electrical connection, of the wall surfaces 13a, 13b of the recess with the wall surfaces 21a, 21b of the projection.

In order to establish electrical paths between the terminal zones of the socket 11 and plug 18 when coupled together the connector 10 includes a first resilient electrically conductive annular contact element 25 retained in a groove 26 in the outer annular wall surface 13a of the recess 13, the groove 26 including part of the coating 17 of electrical conductive material on that wall surface 13a, and a second resilient electrically conductive annular contact element 27 retained in a groove 28 in the inner annular wall surface 13b of the recess 13, the groove 28 similarly including part of the coating 17 of that wall surface 13b. The diameters of the annular contact elements 25 and 27 are such that each is retained in its respective groove 26 or 28 under a constant resilient bias and each, when the socket 12 and plug 18 are coupled together with the projection 21 fully received in the recess 13, bridges the gap to the respective juxtaposed wall surface 21a or 21b of the projection and pressurably bears against that surface. Each of the elements 25 and 27 is thus resiliently compressed between and produces an electrical connection with on the one hand the outer annular wall surfaces 13a and 21a of the recess and projection and on the other hand the inner annular wall surfaces 13b and 21b of the recess and projection. Consequently a first electrical path is established between the terminal zones of the socket and plug by way of the outer annular wall surface 13a of the recess 13, the first contact element 25 and the outer annular wall surface 21a of the projection 21 and a second electrical path is established between those terminal zones by way of the inner annular wall surface 13b of the recess, the second contact element T1 and the inner annular wall surface 21b of the projection. The two electrical paths are, in the embodiment of Fig. 1, of opposite polarity, but they could be of the same polarity depending on the specific use of the connector.

Each of the contact elements 25 and 27 is formed by a circularly annular coil spring, preferably a canted coil spring in which the individual coils have a slanted lay, such springs being known for applications such as seal expanders and electrical conductors. By comparison with non-canted coils of a conventional annular coil spring the cant of the coils imparts to the spring a greater capability of deflection for a given coil-wire thickness, particularly in the sense of radial compression and radial expansion. The coil spring of the first contact element 25 has an outer diameter slightly greater than the maximum diameter of the groove 26 in which it is seated so as to produce the mentioned constant resilient bias by spring compression. Conversely, the coil spring of the second contact element 27 has an inner diameter slightly smaller than the minimum diameter of the groove 28 in which it is seated to as to produce the constant resilient bias in the case of that seat by spring expansion. The contact of the spring forming each contact element with the associated wall surfaces of the recess 13 and projection 21 is produced at multiple locations by the individual coils, which ensures that electrical contact is maintained in all circumstances and neither of the first and second electrical paths produced in the coupled state of the socket and plug can, in the normal course, be interrupted. Moreover, the multiple contact locations make it possible to conduct relatively high current levels, for example 20 amps continuously or 60 amps transiently, in the context of a small connector size. The electrical contact may be increased if each groove is concavely curved preferably to generally match, specifically to be slightly larger than, the curvature of the individual coils of the spring forming the respective contact element 25 or 27. An oversize of the curvature of the groove in relation to the curvature of the coils accommodates deformation of the spring concerned. Since the contact points are, depending on the groove shape, essentially points or lines there is no extended area contact such as might give rise to a significance level of capacitance.

The springs are preferably made of an austenitic stainless steel or of copper, in either case a non-magnetic material so as to allow use of the connector in the presence of strong magnetic fields. The material can be coated with gold or silver to reduce galvanic corrosion.

The locations of the grooves 26 and 28 in the wall surfaces of the annular recess 13 of the socket as described above and shown in Fig. 1 are merely by way of example; it would be equally possible for the first contact element 25 to be located in a groove in the outer wall surface 21a of the projection 21, for the second contact element 27 to be located in a groove in the inner wall surface 21b of the projection 21 or for the two contact elements 25 and 27 to be located in grooves in, respectively, the outer wall surface 21a and inner wall surface 21b of the projection. The contact elements 25 and 27 are, however, preferably located in grooves in the wall surfaces of the recess so that they are in a protected position when the socket and plug are apart and thus are not readily able to be dislodged. It is also possible for a depression 29 to be provided in either or each wall surface without the groove 25 or 26, in particular opposite the groove concerned, so as to receive the associated spring when the projection 21 is fully engaged in the recess 13. Two such depressions 29 are shown, by way of example and in simplified form, in the righthand half of Fig. 1; the depressions also include the electrically conductive coating 17 or 24 of the respective wall surface. Such a depression can be concavely curved in similar manner to the grooves 26 and 28 as described further above to provide increased electrical contact area, but the depression primarily serves to provide mechanical resistance to separation of the intercoupled socket 12 and plug 18, i.e. to function as a mechanical detent. In that case, the or each depression 29 can be shaped so that the contact element 25 or 27 receivable therein preferentially departs from the depression rather than the groove 26 or 28 during separation of the plug and socket, i.e. withdrawal of the projection 21 from the recess 13. Thus, for example, the junction of the depression 29 with the cylindrical section of the respective annular wall surface could be defined by a radiussing and the junction of the groove 26 or 28 by an edge, in each instance at the side of the depression or groove at the top in Fig. 1.

If one or more depressions 29 are provided, the coil diameter of the spring forming the associated contact element 25 and 26 will need to be appropriately dimensioned, for example - for a given spacing of wall surfaces to be bridged by the spring - with a larger coil diameter than in the case of an embodiment without a depression.

As can be seen in Fig. 1, the first and second contact elements 25 and 27 are offset relative to one another in the direction of the axis 16 (and/or axis 23 as the case may be), thus direction of insertion of the projection 21 into the recess 13. Provision of such an offset has the advantage that compression/relaxation of the resilient contact elements is sequential during insertion of the projection into and removal of the projection from the recess, which reduces initial resistance to insertion on the one hand and assists final removal on the other hand. However, it is equally possible for the contact elements to lie in a single plane.

Centralisation of the plug 18 relate to the socket 11, in particular of the projection 21 of the plug in the recess 13 of the socket, can be achieved by various means; most simply by provision of tapered centring surfaces of mutually complementary form on the socket and plug bodies such as shown in Fig. 1, the centring surfaces being interengageable to centre the socket and plug relative to one another when the projection is fully received in the recess. Centralisation is in any case promoted by the resilient contact elements 25 and 27, but centring surfaces of the kind described ensure stability of the socket and plug in the interengaged state, i.e. create a rigid unit from the socket and plug bodies. The socket 11 and plug 18 can be releasably locked together in this state by suitable locking means such as a bayonet coupling, screw cap or ferrule, spring-loaded detent dogs or other suitable locking system. In order to prevent direct electrical contact of the centring surfaces, which would bypass the contact to be produced by the contact element 25, one of the centring surfaces - in the case of Fig. 1, that of the socket body - is formed with a groove with the electrical conductive coating only at the base of the groove. The coating is omitted from that centring surface as such. Undesired electrical contact at the centring surface can, however, be achieved by any other suitable method.

Each of the socket 11 and plug 18 is, as mentioned, provided in the respective terminal zone with terminals electrically connected by conductors with the associated electrically conductive annular wall surfaces 13a, 13b or 21a, 21b. One or more of these terminals can be constructed for electrical connection with a respective external electrical conductor, for example a wire, as indicated in Fig. 1 by dashed lines adjacent to the polarity symbols.

In one embodiment of the connector, the connection additionally includes a circuitboard (not shown) mounted on the socket or plug in the respective terminal zone and connected at a respective electrically conductive point or track to at least one terminal in that zone. The circuitboard can carry electrical and/or electronic components for influencing electrical current conducted along at least one of the first and second electrical paths when established, for example by switching, timing, modulation, etc. If a circuitboard is present, the connector can in that case optionally function as a power output point, preferably with the socket 11 in a fixed location and the plug 18 selectably connectible with and disconnectible from the power source by way of the socket.

With particular advantage the bores 12 and 22 of, respectively, the socket body 12 and plug body 19 are adapted to receive an auxiliary electrical coupling 30, here in the form of a sleeve 31 and a pin 32 engageable in the sleeve. The coupling 30 can be in the form of entirely separate components or can be integrated in the socket and plug, for example the sleeve 31 can be fixed in the socket 11 and the pin 32 fixed in the plug 18. For that purpose, the sleeve and pin can each be provided with a flange which is seated in a wider diameter step of the respective bore 12 or 22 and at which the sleeve or pin is mechanically positively fixed, for example by a bayonet fixing or screw connection, to the socket or plug. The sleeve 31 and pin 32 can also have tapered centring surfaces to assist precise interengagement and stability of the coupled state. The coupling 30 can be of any desired kind - the illustration in Fig. 1 is merely symbolic - and preferably is a multipath coupling optimised for low-voltage data signal transmission. In that case, the connector 10 can combine both power transmission and data transmission in a single unit with secure separation of the power transmission paths from the data transmission paths. The configuration of the connector 10, i.e. with annular recess and annular plug receivable in the recess, has the significant advantage of leaving free a central region of the socket and plug to accommodate the auxiliary electrical coupling.

Fig. 2 shows an electrical coaxial connector 40 according to a further embodiment of the invention. The connector 40 differs from the connector 10 by the inclusion of additional structuring and components to enable at least one further electrical path - in this instance two further electrical paths - to be established. The connector 40 comprises a socket 41 with an annular recess 42 and a plug 43 with an annular projection 44 receivable in the recess. The basic construction and features of the socket 41 and plug 43 correspond with those of the socket 11 and plug 18 of the connector 10 of Fig. 1, for which reason the detail description of the connector 40 will be confined to the differences from the connector 10. As indicated above, these differences are centred on additional shaping and components to allow to additional electrical paths to be created.

Accordingly, in the Fig. 2 embodiment the recess 42, in which again part of a coating of electrically conductive material on the socket body is present, has two axially successive electrically conductive outer annular wall surfaces 42a and 42b which are electrically isolated from one another and two axially successive electrically conductive inner annular wall surfaces 42c and 42d which also are electrically isolated from one another. The coating material is omitted, for example removed after application of an overall coating, in a region between the surfaces 42a and 42b and in a region between the surfaces 42c and 42d so as to provide the required electrical isolation. The recess 42 has a stepped configuration so that the outer annular wall surfaces 42a has a larger diameter than the outer annular wall surface 42b and the inner annular wall surface 42c has a smaller diameter than the inner annular wall surface 42d.

The projection 44 of the plug 43 is formed in corresponding manner. Thus, the projection 44, in which part of a coating of electrically conductive material on the plug body is present, has two axially successive electrically conductive outer annular wall surfaces 44a and 44b which are electrically isolated from one another and two axially successive inner annular wall surfaces 44c and 44d again electrically isolated from one another. The coating material is omitted, preferably removed after application of an overall coating, in a region between the surfaces 44a and 44b and in a region between the surfaces 44c and 44d in order to provide the electrical isolation. In similar manner to the recess 42 the projection 44 has a stepped configuration so that the outer annular wall surface 44a has a larger diameter than the outer annular wall surface 44b and the inner annular wall surface 44c has a smaller diameter than the inner annular wall surface 44d.

Terminal zones with individual terminals and conductors respectively connecting those terminals with the annular wall surfaces 42a to 42d and 44a to 44d are provided in similar manner to the embodiment of Fig. 1, but with additional arrangements to accommodate the greater number of electrically conductive annular wall surfaces and associated terminals. Specifically, in the case of the outer wall surface 42c and inner wall surface 42d of the recess 42 electrical isolation is achieved by provision of a via 45 extending through the base of the recess to communicate with the lower (in Fig. 2) end face of the socket 41.

The via 45 is shown diagrammaticaiiy and has the form of a bore or other passage carrying two separate strip-like parts of the coating of electrically conductive material on the socket body. The conductors, which are formed by these parts and which are respectively connected with the wall surfaces 42c and 42d of the recess 42, link with lower end face terminals which are electrically isolated - such as by omission of the electrically conductive material - from lower end face terminals connected with the other wall surfaces 42a and 42b of the recess.

Analogously, in the case of the outer wall surface 44c and inner wall surface 44d of the projection 44 electrical isolation as provided by a via 46 extending through the projection from its tip to the upper (in Fig. 2) end face of the plug 43. The via 46 is also shown diagrammaticaiiy and has the form of a bore or other passage carrying two separate striplike parts of the coating of electrically conductive material on the plug body. The conductors, which are formed by these two parts and which are respectively connected with the wall surfaces 44c and 44d of the projection 44, link with upper end face terminals which are electrically isolated - such as by omission of the electrically conductive material from upper end face terminals with the other wall surfaces 44a and 44b of the projection.

In the case of the via 46, if coating material as distinct from, for example, insulated wires is indeed used to connect the wall surfaces 44c and 44d of the projection with the respective upper end face terminals the application of the coating material to the surface of the via may be facilitated if the plug 43 is produced in two segments with a mating zone running longitudinally through the via. The portion of the via in each segment can then be coated with the electrically conductive material before the two segments are mated in the zone and permanently joined, such as by bonding with the use of heat or adhesive. The separation of the coating of electrically conductive material in the via 46 into separate striplike parts can be achieved by confining the coating in each portion of the via to a track in such a way that when the two segments are mated the tracks are at a spacing from one another, for example as shown in Fig. 2.

Electrical connection of the electrically conductive annular wall surfaces 42c to 42d and 44a and 44c of the recess 42 and projection 44 when the latter is fully received in the former is produced in analogous manner to the embodiment of Fig. 1 with the principal difference that two additional annular contact elements are present in order to produce the connection with the additional wall surfaces. The annular contact elements are again annular coil springs, especially canted coil springs such as described beforehand, and are again seated in annular grooves, which carry electrically conductive coating material, present in the annular wall surfaces. The grooves are preferably provided entirely in the annular wall surfaces 42a to 42d of the recess 42, but could be provided entirely in the annular wall surfaces 44a to 44d of the projection 44, or in certain circumstances partly in the former and partly in the latter. As can be seen in Fig. 2, the annular contact elements here comprise a first element 47 for electrical connection of the outer annular wall surfaces 42a and 44a respectively of the recess and the projection, a second element 48 for electrical connection of the further outer annular wall surfaces 42b and 44b, a third element 49 for electrical connection of the inner annular wall surfaces 42c and 44c and a fourth contact element 50 for electrical connection of the further inner annular wall surfaces 42d and 44d. The first and third contact elements 47 and 49 optionally lie in the same plane, whereas the second and fourth contact elements 48 and 50 are offset in the axial direction of the plug and socket not only from the elements 47 and 49, but optionally also from each other.

When the projection 44 of the plug 43 is fully engaged in the recess 42 of the socket 41 then, as apparent from Fig. 2, respective electrical paths are established by each of the annular contact elements 47 to 50 via the respectively associated annular wall surfaces 42a to 42d and 44a to 44d and the conductors leading to the total of eight electrically separate terminals at the mutually remote end faces of the socket and plug. These four electrical paths can be used for voltage conduction for any desired purpose. It will be apparent that although four paths can be produced by the connector construction shown in Fig. 2, by reducing or increasing the number of annular contact elements and annular wall surfaces with which they co-operate merely three paths can be established or more than four paths can be established. A significant feature of the embodiment of Fig. 2 is the stepped form of the recess 42 and projection 44 so that, due to the diametral differences of the associated pairs of annular wall surfaces, an inappropriate cross-connection cannot be produced during insertion of the projection into and removal of the projection from the recess, for example (in the case of the annular contact elements being seated in annular grooves entirely in the annular wall surfaces of the recess) a transient cross-connection produced by the annular contact elements 48 and 50 with the further annular wall surfaces 44c and 44d of the projection.

It will be evident that the exact construction of the connector can take various forms and the embodiments serve merely to illustrate the principles of interaction of the socket and plug and the production of discrete electrical paths. A connector embodying the invention is simple to use and provides secure electrical connections within two or more electrical paths. The annular form of the recess and projection leaves a central zone available for accommodating an auxiliary electrical coupling and a particular merit of the connector is its capability of construction from metallised bodies of insulating material, particularly injection-mouldable plastics material, in which case electrical isolation of conductive zones can be achieved by the expedient of simply removing conductive material where appropriate.

Claims

1. An electrical connector comprising:

a socket defining an annular recess having an electrically conductive outer annular wall surface and an electrically conductive inner annular wall surface electrically isolated from the outer annular wall surface, a plug defining an annular projection which is receivable in the annular recess of the socket to be spaced from both the outer annular wall surface and the inner annular wall surface of the recess and which has an electrically conductive outer annular wall surface and an electrically conductive inner annular wall surface electrically isolated from that outer annular wall surface, a first resilient electrically conductive annular contact element retained in a groove in one of the outer annular wall surface of the recess and the outer annular wall surface of the projection and resiliently compressible to produce an electrical connection of those surfaces when the projection is fully received in the recess, and a second resilient electrically conductive annular contact element retained in a groove in one of the inner annular wall surface of the recess and the inner annular wall surface of the projection and resiliently compressible to produce an electrical connection of those surfaces when the projection is fully received in the recess, a first electrical path being established by way of the outer annular wall surface of the recess, the compressed first annular contact element and the outer annular wall surface of the projection when the projection is fully received in the recess and a second electrical path electrically isolated from the first electrical path being established by way of the inner annular wall surface of the recess, the compressed second annular contact element and the inner annular wall surface of the projection when the projection is fully received in the recess.

2. A connector according to claim 1, wherein the annular contact elements are coil springs.

3. A connector according to claim 2, wherein the coil springs are canted coil springs.

4. A connector according to any one of the preceding claims, wherein the annular contact elements are seated under constant resilient bias in the grooves.

5. A connector according to any one of the preceding claims, wherein both grooves are in the wall surfaces of the same component of the connector.

6. A connector according to claim 5, wherein that component is the socket.

7. A connector according to any one of the preceding claims, wherein the outer annular wall surface without the groove has a depression in which the annular contact element retained in that groove is so engaged when the projection is fully received in the recess as to supply mechanical resistance to separation of the socket and plug.

8. A connector according to any one of the preceding claims, wherein the inner annular wall surface without the groove has a depression in which the annular contact element retained in that groove is so engaged when the projection is fully received in the recess as to supply mechanical resistance to separation of the socket and plug.

9. A connector according to any one of the preceding claims, comprising releasable locking means to releasably lock the socket and plug together to resist or prevent unintentional removal of the projection from the recess.

10. A connector according to any one of the preceding claims, wherein the annular contact elements are arranged to be offset relative to one another in a given direction of insertion of the projection into the recess.

11. A connector according to any one of the preceding claims, wherein the recess has at least one further electrically conductive outer annular wall surface electrically isolated from each other annular wall surface of the recess and the projection has a respective further electrically conductive outer annular wall surface associated with the or each further outer annular wall surface of the recess and electrically isolated from each other annular wall surface of the projection, the connector comprising a respective further resilient electrically conductive annular contact element retained in a groove in the or each further outer annular wall surface of the recess or in the associated further outer annular wall surface of the projection and resiliently compressible to produce an electrical connection of those associated surfaces when the projection is fully received in the recess thereby to establish a respective further electrical path by way of that contact element and the associated surfaces.

12. A connector according to any one of the preceding claims, wherein the recess has at least one further electrically conductive inner annular wall surface electrically isolated from each other annular wall surface of the recess and the projection has a respective further electrically conductive inner annular wall surface associated with the or each further inner annular wall surface of the recess and electrically isolated from each other annular wall surface of the projection, the connector comprising a respective further resilient electrically conductive annular contact element retained in a groove in the or each further inner annular wall surface of the recess or in the associated further inner annular wall surface of the projection and resiliently compressible to produce an electrical connection of those associated surfaces when the projection is fully received in the recess thereby to establish a respective further electrical path by way of that contact element and the associated surfaces.

13. A connector according to claim 11, wherein the at least one further outer annular wall surface of each of the recess and projection has a smaller diameter than the firstmentioned outer annular wall surface of, respectively, the recess and projection so as to prevent the first annular contact member from contacting such a further outer annular wail surface during insertion of the projection into and removal of the projection from the recess.

14. A connector according to claim 12, wherein the at least one further inner annular wall surface of each of the recess and projection has a smaller diameter than the firstmentioned inner annular wall surface of, respectively, the recess and projection so as to prevent the second annular contact member from contacting such a further outer annular wall surface during insertion of the projection into and removal of the projection from the recess.

15. A connector according to any one of the preceding claims, wherein at least one of the socket and the plug comprises electrically insulating material partly coated with electrically conductive coating material to provide the respective electrically conductive wall surfaces.

16. A connector according to claim 15, wherein the electrically conductive wall surfaces provided by the coating material are electrically isolated from one another by intermediate areas without the coating material.

17. A connector according to claim 15 or claim 16, wherein the coating material additionally forms conductors connected with the electrically conductive annular wall surfaces.

18. A connector according to any one of the preceding claims, wherein the electrically conductive annular wall surfaces of at least one of the socket and the plug are present on parts separated by an air gap to provide the electrical isolation of those surfaces.

19. A connector according to any one of the preceding claims, wherein the socket is provided in a region thereof remote from an entrance of the recess with a plurality of terminals each electrically connected with a respective one of the electrically conductive annular wall surfaces of the recess.

20. A connector according to any one of the preceding claims, wherein the plug is provided in a region thereof remote from a free end of the projection with a plurality of terminals each electrically connected with a respective one of the electrically conductive annular wall surfaces of the projection.

21. A connector according to claim 20, wherein at least one of the terminals of the plug is electrically connected with the respective electrically conductive annular wall surface of the projection by way of an electrical connection provided in a via in the plug.

22. A connector according to claim 21, wherein the plug is of multi-part construction and the via is formed by recesses respectively provided in mating parts of the plug.

23. A connector according to any one of claims 19 to 22, wherein at least one of the terminals is electrically connectible with a respective external electrical conductor.

24. A connector according to any one of claims 19 to 23, wherein at least one of the terminals is electrically connected with respective electrically conductive point or track on a circuitboard.

25. A connector according to any one of the preceding claims, wherein the socket has passage centrally of the recess and the connector includes an auxiliary electrical coupling received or receivable in the passage.

26. A connector according to any one of the preceding claims, wherein the socket and plug have centring surfaces of mutually complementary form interengageable to centre the socket and plug relative to one another when the projection is fully received in the recess.

27. A connector according to any one of the preceding claims, wherein the recess and projection in the state of reception of the projection in the plug are rotationally symmetrical with respect to a common axis.

Intellectual

Property

Office

Application No: GB 1618412.9