Abstract:
A rotatable electrical coupling comprising a male connector having at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal, and a further electrical contact member for conducting or transmitting a high-frequency and/or a high-speed data signal. The coupling further comprises a female connector for receiving the male connector such that the male connector is adapted for rotation relative to the female connector. The female connector includes complementary electrical contact members configured to maintain uninterrupted electrical contact with each of the respective contact members of the male connector throughout a relative rotational movement between the male and female connectors preferably at least about 180°. An electrical connector for such a rotatable electrical coupling, as well as a swivel or pivot joint of a mounting arm for supporting or suspending technical equipment, wherein the joint incorporates such an electrical coupling.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a rotatable electrical coupling and to an electrical connector for such a coupling. 
         [0002]    The rotatable electrical coupling of the invention is desirably designed for use in a swivel or pivot joint of a mounting arm, such as the type of mounting arm used for supporting or suspending technical equipment, e.g. in medical and in commercial or industrial environments. In this way, the rotatable coupling of the invention is able to provide reliable electrical communication through the joint of the mounting arm to the technical equipment, regardless of rotary movement of that joint. As such, it will be convenient to hereinafter describe the invention in this particular context. It will be noted, however, that the rotatable electrical coupling and the electrical connector of the invention are not limited to use in a swivel or pivot joint of a mounting arm. 
       BACKGROUND OF THE INVENTION 
       [0003]    An electrical coupling of the type to which the present invention relates typically comprises two connector components which are configured to be coupled together to interconnect two or more transmission paths to provide electrical communication there-between. Typically, one connector component will be configured as a male or plug-type connector and the other connector component will be configured as a female or socket-type connector for receiving the male or plug-type connector. 
         [0004]    An example of a rotatable electrical coupling of the type for use in a swivel or pivot joint of a mounting arm is described in International Patent Application Publication No. WO03/092127 A1. It has been found, however, that such coupling designs are not always suitable to meet the requirements demanded of equipment mounting systems in modern healthcare, commercial and industrial applications. In particular, the technical equipment which is to be supported or suspended on such carrier arm systems often demand connection performance not provided by prior art coupling arrangements. 
       SUMMARY OF THE INVENTION 
       [0005]    Thus, the present invention has been developed to meet this need. In particular, the present invention provides a new and improved rotatable electrical coupling for use in a swivel or pivot joint of an equipment mounting system. 
         [0006]    According to one broad aspect, the present invention provides a rotatable electrical coupling comprising: a first connector having at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal, and a further electrical contact member adapted to conduct or transmit a high-frequency and/or high-speed data signal; and a second connector to be coupled with the first connector such that the first and second connectors are adapted for relative rotation. The second connector includes complementary electrical contact members configured to maintain uninterrupted electrical contact with each of the respective contact members of the first connector throughout a relative rotational movement between the first and second connectors. The relative rotational movement may be through an angle of at least about 60°, more preferably at least about 90°, further preferably at least about 180°, and most preferably at least about 360°. 
         [0007]    In the context of the present invention, the reference to “high-frequency” data signals in this description will be generally understood to refer to frequencies in the UHF range and higher, namely electromagnetic signals having a frequency of about 300 MHz and higher (the UHF band range generally deemed to extend to about 3 GHz), and preferably including SHF signals up to about 30 GHz, and more preferably including EHF signals up to about 300 GHz. Further, the reference to “high-speed” data signals in this description will be generally understood to refer to digital data transmission rates of about 100 kbit/s or more, and preferably includes transmission rates up to about 100 Mbit/s, and more preferably includes transmission rates up to about 100 Gbit/s, and even higher. In this way, the further electrical contact member adapted conduct or transmit a high-frequency and/or high-speed data signal may, for example, be adapted for high quality image transmission via UHF, digital video, and/or digital HDTV signals. 
         [0008]    In a preferred form of the invention, the first connector is a male or plug-type connector, and the second connector is a female or socket-type connector for receiving the male connector. Thus, in a preferred form, the invention provides a rotatable electrical coupling comprising: a male connector having at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal, and a further electrical contact member adapted to conduct or transmit a high-frequency and/or high-speed data signal; and a female connector for receiving the male connector such that the male connector is adapted for rotation relative to the female connector, or vice versa. The female connector includes complementary electrical contact members configured to maintain uninterrupted electrical contact with each of the respective contact members of the male connector throughout the relative rotational movement between the male and female connectors. The male connector is desirably adapted to be readily inserted and/or withdrawn from the female connector by a user. That is, the connectors of the electrical coupling of the invention are typically adapted for repeated releasable interconnection with one another. 
         [0009]    In a preferred form of the invention, the male connector comprises a protruding portion for receipt within a cavity or socket of the female connector, and the at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal is arranged on an exterior of the protruding portion. In this regard, the at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal may be arranged on an end of the connector for axial or facing engagement with the complementary contact member of the other connector. More usually, however, this at least one electrical contact member will be arranged on a lateral exterior of the protruding portion for radial engagement with the complementary contact member of the other connector. 
         [0010]    In a preferred form of the invention, the male connector comprises a plurality of electrical contact members adapted to conduct or transmit a supply current or a low-frequency control signal. This plurality of electrical contact members are preferably arranged spaced apart from one another on the male connector. For example, they may be radially spaced apart from one another. More preferably, however, they are spaced apart along a length of the male connector, i.e. along a length of the protruding portion. Each of these electrical contact members is preferably arranged around and/or extends circumferentially of the protruding portion and is preferably adapted to engage or connect with a complementary contact member in a radial direction to establish an electrical connection there-between. Thus, each contact member may be ring-shaped. Accordingly, the female connector member preferably comprises at least one complementary electrical contact member located inside the cavity or socket for electrical contact with the at least one electrical contact member of the male connector for conducting or transmitting a supply current or a low-frequency control signal. This at least one complementary electrical contact member of the female connector is preferably arranged around or extending circumferentially within the cavity, and is preferably also substantially ring-shaped. 
         [0011]    In a preferred form of the invention, the further electrical contact member adapted to conduct or transmit a high-frequency data signal and/or high-speed data signal is arranged substantially centrally of the male connector and/or along the rotational axis thereof. This further electrical contact member is preferably elongate and may be substantially encompassed or surrounded by the electrical contact member(s) that conduct(s) or transmit(s) a supply current or a low-frequency control signal. Where, for example, the male connector comprises a plurality of contact members for conducting a supply current or a low-frequency control signal spaced apart along a length of the male connector, the further electrical contact member for the high-frequency data signal may extend axially through those contact members and/or be substantially encompassed or surrounded by them. Thus, the female or socket-type connector typically also includes a complementary further contact member adapted to conduct or transmit a high-frequency and/or high-speed data signal arranged substantially centrally thereof and/or along the rotational axis. 
         [0012]    In a preferred form of the invention, the further electrical contact member adapted to conduct or transmit a high-frequency and/or a high-speed data signal is substantially fully insulated from the one or more electrical contact members for conducting or transmitting a supply current or low-frequency control signal. That is, the further electrical contact member for conducting or transmitting a high-frequency and/or high-speed data signal is preferably substantially encased within or surrounded by a sheath or mantle of dielectric (i.e. electrically insulating) material, such as a polymer plastic material like polyethylene (PE) or polytetrafluoroethylene (PTFE). 
         [0013]    In a preferred form of the invention, the further electrical contact member for conducting or transmitting a high-frequency data and/or high-speed data signal is configured to be at least partially rotationally symmetrical about the rotational axis of the coupling—i.e. at least in the region where the further electrical contact member comes into engagement or contact with a complementary contact member. That is, the further electrical contact member is at least partially, and preferably substantially fully, rotationally symmetrical about a central or longitudinal axis of the electrical coupling. 
         [0014]    In a highly preferred form of the invention, the further electrical contact member is configured to engage and/or connect with its complementary contact member in the axial direction to establish an electrical connection there-between. The engagement or connection is preferably effected via the axial mating of opposed ends of the respective contact members; for example, in a relatively light frictional fit or via a releasable axially locking attachment. 
         [0015]    In a preferred form of the invention, the further electrical contact member is formed as a coaxial contact member, e.g. designed for use with coaxial cable, and includes a screen or shield conductor spaced or arranged radially outwards from a core or central conductor. Thus, the core or central conductor is preferably fully screened or shielded along its length, and the two conductors (i.e. core and shield) are preferably separated by a layer or mantle of dielectric material, such as polyethylene (PE) or polytetrafluoroethylene (PTFE). By carefully selecting the geometry, material and dimensions of the conductors and the layer or mantle of dielectric material, the coaxial contact member can be designed to have a specific characteristic impedance for high signal transmission performance with minimised reflection. For example, the characteristic impedance may be designed to be 30 Ohm, 50 Ohm or 75 Ohm, and is preferably designed to be within the range of 30 to 200 Ohm. Furthermore, by forming the coaxial contact member fully shielded, little or no interference and little or no sensitivity to interference arises in transmission of the high-frequency and/or high-speed data signal via this contact member. 
         [0016]    In another preferred form of the invention, the further electrical contact member comprises a waveguide, such as an optical waveguide for conducting or transmitting electromagnetic waves in the optical spectrum (i.e. light). In other words, the high-frequency and/or a high-speed data signals may be transmitted as light via an optical waveguide. In this context, one of the most common examples for such a waveguide is one or more optical fibre, particularly optical glass fibres. 
         [0017]    The further (e.g. coaxial) contact member may be configured as a plug-type contact member or a socket-type contact member, for engagement with the complementary one of those two. Importantly, it will be noted that the choice of whether the further contact member is configured as a plug-type or a socket-type contact member is independent of whether the connector of the electrical coupling is a male connector or a female connector. That is, the further contact member in the male connector may be of either the plug-type or the socket-type for respective connection with the complementary further contact member in the female connector. 
         [0018]    Thus, the present invention provides an electrical coupling which is configured for conduction or transmission not only of supply currents and/or low-frequency control signals as is known in conventional rotatable electrical couplings via wiper or sliding contact arrangements, but which is also specifically designed to incorporate transfer of high-frequency data signals and/or high-speed data signals, such as UHF, digital video, and digital HDTV signals, while still permitting rotation of the coupling through at least about 180°, more preferably through at least about 360°, and most preferably with unlimited or full rotational flexibility permitting repeated rotation. Thus, the electrical coupling of the invention is able to provide multiple transmission paths for simultaneous communication of power supply, control signals and high-frequency and/or high-speed data signals to or from one or more items of technical equipment mounted on an end of an articulated support arm, with the coupling and cabling incorporated within the support arm. 
         [0019]    According to another broad aspect, the present invention provides an electrical connector for electrical connection with a complementary component e.g. socket or plug, the connector comprising: at least one electrical contact member adapted to conduct or transmit a supply current or a low-frequency control signal, and a further electrical contact member adapted to conduct or transmit a high-frequency data signal and/or a high-speed data signal. The connector is configured to provide an uninterrupted electrical connection to each of the electrical contact members throughout a rotational movement of the connector relative to the complementary socket or plug, wherein the relative rotational movement is preferably through an angle of at least about 60°, more preferably at least about 90°, further preferably at least about 180°, and most preferably at least about 360°, to provide an unlimited or full rotational flexibility permitting repeated or continual rotation. 
         [0020]    In a preferred form of the invention, the further electrical contact member is arranged substantially centrally of the connector and/or on the rotational axis, and is preferably substantially encompassed or surrounded by the at least one contact member adapted to conduct or transmit a supply current or low-frequency signal. The further electrical contact member is preferably formed as a coaxial member. 
         [0021]    In a preferred form of the invention, the connector comprises a plurality of electrical contact members adapted to conduct or transmit a supply current or low-frequency control signal. The plurality of electrical contact members are preferably arranged spaced apart from one another on the connector. They may be radially spaced apart from one another, for example. More preferably, however, they may be spaced apart along a length of the male connector. In this case, the plurality of electrical contact members may comprise: at least one first electrical contact member adapted to conduct or transmit a supply current, and at least one second electrical contact member adapted to conduct or transmit a low-frequency control signal. 
         [0022]    As noted above, in a preferred form of the invention the further electrical contact member for conducting or transmitting a high-frequency and/or high-speed data signal is substantially fully shielded from the at least one first or second electrical contact members. For example, the further electrical contact member may be substantially fully sheathed and electrically insulated from the at least one first or second electrical contact members. That is, the further electrical contact member is preferably substantially surrounded by a sheath or mantle of dielectric material, such as a polymer plastic material. 
         [0023]    In one particular form of the invention, the electrical connector is a male or plug-type connector for electrical connection with a complementary socket. The male connector thus comprises a protruding portion for receipt within the socket, and the at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal is arranged on an exterior of the connector, preferably arranged around or extending circumferentially of the connector, and in a particular embodiment being substantially ring-shaped. 
         [0024]    In another particular form of the invention, the electrical connector is a female or socket-type connector for electrical connection with a complementary plug, such that the connector has a cavity for receipt of the complementary plug. The at least one electrical contact member for conducting or transmitting a supply current or a low-frequency control signal is then preferably arranged within the cavity, preferably arranged around or extending circumferentially of the cavity, and in a particular embodiment is again substantially ring-shaped. 
         [0025]    In a preferred form of the invention, the further electrical contact member for conducting or transmitting a high-frequency data and/or high-speed data signal is configured to be at least partially rotationally symmetrical about the rotational axis of the coupling—i.e. at least in the region where the further electrical contact member comes into engagement or contact with a complementary contact member. That is, the further electrical contact member is at least partially, and preferably substantially fully, rotationally symmetrical about a central or longitudinal axis of the electrical coupling. 
         [0026]    In a highly preferred form of the invention, the further electrical contact member is configured to engage and/or connect with its complementary contact member in the axial direction. The engagement or connection is preferably effected via axial mating of opposed ends of the respective contact members; for example, in a relatively light frictional fit or a releasable axially locking attachment. Thus, the opposed ends of the respective contact members approach one another and engage in the axial direction. 
         [0027]    In a preferred form of the invention, the electrical contact members are formed from a material selected from the group consisting of: copper, silver, gold, alloys of any one of copper, silver, and gold, and any combination of same, including plating. The materials may thus also include alloys such as bronze and brass. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The above and further features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the invention with reference to the accompanying drawings, in which like reference characters identify like features, and in which: 
           [0029]      FIG. 1  is a perspective view of a rotatable electrical coupling according to a preferred embodiment of the invention in an assembled state; 
           [0030]      FIG. 2  is a plan view of the rotatable electrical coupling of  FIG. 1 ; 
           [0031]      FIG. 3  is a vertical cross-section of the rotatable electrical coupling of  FIG. 1  along the central axis X of the coupling and viewed in the direction of arrows A-A in  FIG. 2 ; 
           [0032]      FIG. 4  is an exploded perspective view of the components of the rotatable electrical coupling of  FIG. 1 ; 
           [0033]      FIG. 5  is a perspective view of a male or plug-type electrical connector according to a preferred embodiment of the invention for a rotatable electrical coupling. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    With reference to  FIGS. 1 to 4  of the drawings, a rotatable electrical coupling  10  according to a preferred embodiment of the invention will now be described. The electrical coupling  10  comprises a male or plug-type connector  20  and a female or socket-type connector  40 , which are shown combined in  FIGS. 1 to 3  of the drawings in rotatable coupled engagement. As  FIG. 1  and  FIG. 2  of the drawings only show external views of the coupling  10  with the male connector or plug  20  and the female or socket-type connector  40  in a combined or coupled state, the precise nature or structure of the male and female connectors  20 ,  40  is not fully clear from those two drawings. Details of the male connector  20  and the female connector  40  can be more clearly seen in  FIG. 3  and  FIG. 4  of the drawings. 
         [0035]    With particular reference now to  FIGS. 3 and 4  of the drawings, therefore, the male or plug-type connector  20  can be seen to comprise an elongate protruding portion  21  which extends from a proximal end  22  of the male connector  20  and terminates at a free distal end  23 . The protruding portion  21  of the male connector  20  is designed to be received within a corresponding cavity  41  formed within a generally cylindrical casing  42  of the female or socket-type connector  40 . The cavity or socket  41  in the female connector  40  extends approximately centrally of the cylindrical casing  42  from a proximal end of the connector  40  to an opening at a distal end  43 , into which opening the free end  23  of the protruding portion  21  is designed to be inserted. In this connection, the cavity  41  of the female connector  40  desirably has a geometry which essentially complements the size and shape of the protruding portion  21  of the male connector or plug  20 . In particular, as the male and female connectors  20 ,  40  of the electrical coupling  10  are designed for relative rotation, the respective geometries of the protruding portion  21  and the cavity  41  are selected or configured to accommodate such relative rotation. 
         [0036]    In this embodiment, the male connector  20  has a plurality of ring-shaped electrical contact members  24  which extend completely around an outer periphery of the protruding portion  21  and are arranged spaced apart and generally axially aligned along a longitudinal extent of the protruding portion  21 . These ring-shaped contact members  24  are preferably fabricated from copper, silver, gold, or alloys thereof and are designed as wiper or sliding ring contacts for electrical communication via their radial outer surfaces when those outer surfaces come into physical engagement (e.g. wiping or sliding contact) with complementary electrical contact members of the female connector  40 . Furthermore, each of the ring-shaped contact members  24  has a lead  25  which extends longitudinally to the proximal end  22  of the male connector  20  for connecting the respective contact members  24  either to an electrical supply or signal source (not shown) on the one hand, or to an electrical load or a signal receiver (not shown) on the other hand. The leads  25  of the male connector  20  preferably extend radially inwardly of the contact members  24 . 
         [0037]    In this particular embodiment, the ring-shaped contact members  24  are divided into two groups, and include three first wiper rings  26  of somewhat broader width arranged adjacent one another at the distal end  23  of the protruding portion  21  for conducting or transmitting a supply current, with each of the first wiper rings  26  having a respective connecting lead  27 . Furthermore, the ring-shaped contact members  24  also include three second wiper rings  28  of narrower width arranged adjacent one another for conducting or transmitting a low-frequency control signal, with each of the second wiper rings  28  having a respective connecting lead  29 . In this way, the male connector  20  is configured to conduct or transmit three separate power supply currents and three separate control signals in parallel, and these may optionally be communicated to three items of equipment. 
         [0038]    As can be clearly seen in the drawings, arranged centrally of the male connector  20  is a further, third electrical contact member  30  provided in form of a coaxial contact adapted to conduct or transmit a high-frequency and/or high-speed data signal, such as a HDTV signal. The coaxial contact member  30  is an elongate component which is arranged substantially aligned on a central longitudinal axis X of the protruding portion  21  such that it extends through each of the ring-like contact members  24  (i.e. ring contacts  26 ,  28 ). In this regard, the third contact member  30  comprises a central or core conductor  31  and an outer screen or shield  32  typically having a generally cylindrical shape and formed as a conductor sleeve or tube which surrounds the core  31  to provide a full and continuous shield along the length thereof. The central or core conductor  31  and the outer screen/shield  32  are separated by a generally cylindrical (i.e. annular) layer or mantle  33  of dielectric material. Furthermore, it will seen that an annular jacket or mantle  34  of insulating dielectric material is provided between the coaxial contact member  30  and the first and second ring-shaped contact members  26 ,  28  extending around the periphery or circumference of the protruding portion  21 . The first and second ring contacts  26 ,  28  are thereby insulated from one other and from the third coaxial contact by the annular jacket or mantle  34  of dielectric material. The leads  27 ,  29  of the first and second ring contacts  26 ,  28  extend embedded within slots within the jacket or mantle  34  spaced radially inwards of the ring contacts  26 ,  28 . 
         [0039]    With further reference to drawing  FIGS. 3 and 4 , it will be appreciated that the assembly of the male connector  20  involves securing an end of the elongate coaxial contact member  30  within a recess  35  formed centrally in a mounting collar  36  provided at the proximal end  22  of the male connector  20 . For this purpose, a small threaded screw or pin  37  is screwed into a threaded hole  38  such that an end of the screw or pin  37  engages and securely fastens the end of the coaxial contact member  30  within the recess  35  in the mounting collar  36 . It will be appreciated that more than one such pin or screw  37  may be provided, e.g. radially offset from one another in the collar  36 . The proximal end of the elongate coaxial contact member  30  may be inserted through the annular jacket or mantle  34  of dielectric material (which is typically somewhat resilient) in an interference fit to combine it with the ring-shaped contact members  24  of the protruding portion  21 . This thereby unifies all of the first, second, and third contact members  26 ,  28 ,  30  within the construct of the male connector  20 . 
         [0040]    Radial slots  39  extend from the central recess  35  of the mounting collar  36  for receiving ends of the connecting leads  25  extending from the ring-shaped contact members  24 . In this particular embodiment, the respective connecting leads  27 ,  29  from the first and second ring contacts  26 ,  28  are offset at substantially equal angular spacings (i.e. about 60°) around the central axis X of the protruding portion. Thus, the slot-like recesses  39  extend radially outwards from the central recess  35  spaced apart at about 60°. It will be appreciated that these radial slots  39  may also be formed as circular holes for receiving the ends of each of the leads  27 ,  29 . This construction helps ensure that torque applied to the mounting collar  36  is transferred to the first and second ring contacts  26 ,  28 . Similarly, the threaded screw or pin  37  helps ensure that torque applied to the mounting collar  36  is transferred to the third contact member  30 . A further pin  18  may be provided to interconnect the collar  36  with the insulating jacket  34  for reliable torque transfer there-between, the pin  18  being received within an eccentric hole (not shown) in the mounting collar  36  and a corresponding hole in the jacket  34 . 
         [0041]    As is apparent from the drawings, the end of the coaxial contact member  30  at the proximal end  22  of the male connector  20  may include a screw thread  19  for connection e.g. with a coaxial cable for conducting or transmitting a high frequency and/or high-speed data signal. Similarly, the ends of the leads  27 ,  29  which project at the proximal end  22  of the male connector  20  are available for connection to a power supply/power load and to a signal source/signal receiver, respectively. 
         [0042]    Focussing now on the female connector  40  in this embodiment of the invention, it will be appreciated that the female connector has a complementary structure to the male connector  20 . Thus, in a corresponding manner, the female connector  40  in this embodiment comprises a plurality of ring-shaped electrical contact members  44  which extend completely around an inner periphery of the socket or cavity  41  and are arranged spaced apart and generally axially aligned along a longitudinal extent of that cavity. Again, these ring-shaped contact members  44  are designed as wiper ring-contacts for electrical communication via their exposed, radially inner surfaces when those surfaces come into physical engagement (e.g. wiping or sliding contact) with the complementary contact members  24  of the male connector  20 . Further, each of these ring-shaped contact members  44  has a lead  45  which extends longitudinally to the proximal end of the female connector  40  for connecting the respective contact member  44  either to an electrical supply or signal source (not shown) on the one hand, or to an electrical load or a signal receiver (not shown) on the other hand. The leads  45  of the female connector  40  extend within the casing  42  at positions radially outwards of the contact members  44 . 
         [0043]    As with the male connector  20 , the ring-shaped contact members  44  of the female connector  40  are divided into two groups, and include three first wiper rings  46  of somewhat broader width arranged adjacent one another and adapted to conduct or transmit a supply current, with each of the first wiper rings  46  having a respective connecting lead  47 . In addition, the ring-shaped contact members  44  include three second wiper rings  48  of narrower width arranged adjacent one another and adapted to conduct or transmit a low-frequency control signal, with each of the second wiper rings  48  having a respective connecting lead  49 . Thus, the first and second ring contacts  46 ,  48  of the female connector or socket  40  are positioned at an inner periphery of the cavity  41  in the cylindrical casing  42  for registration or alignment with the corresponding first and second ring-shaped contact members  26 ,  28  of the male connector  20  when the protruding portion  21  of the male connector is inserted into the cavity. The casing  42  is typically formed of a relatively robust dielectric material, such as polyvinyl chloride (PVC) or another suitable non-conducting material. 
         [0044]    Also corresponding with the male connector, the female connector  40  can be clearly seen in the drawings to include a further, third electrical contact member  50  in the form of a coaxial contact arranged centrally thereof and adapted to conduct or transmit a high-frequency and/or high-speed data signal, such as a HDTV signal. This coaxial contact member  50  is again an elongate component which is arranged in alignment on the central longitudinal axis X of the casing  42 . The coaxial contact member  50  in the female connector  40  is much shorter than the complementary coaxial contact  30  in the male connector  20  because it does not extend through any of the ring-like contact members  44  (i.e.  46 ,  48 ). On the contrary, its most distal end is still within the proximal end of the cavity  41  in the casing  42  in order to leave sufficient space for insertion of the male connector  20 . As before, the coaxial contact member  50  comprises a central or core conductor  51  and an outer screen or shield conductor  52  typically having a generally cylindrical shape and formed as a sleeve or tube which surrounds the core  51  and forms a full shield along the length thereof. The central or core conductor  51  and the outer screen/shield  52  are separated by a generally cylindrical or annular mantle  53  of a dielectric material. It will be noted, however, that the coaxial contact member  50  is not surrounded by any jacket or mantle of insulating material. In this regard, the jacket or mantle  34  of dielectric material in the protruding portion  21  already provides an insulating barrier between the ring-shaped contact members  24 ,  44  and the coaxial contact members  30 ,  50  when the male component  20  is received within the female component  40 . Nevertheless, a small jacket or mantle of insulating material around the proximal end of the coaxial contact member  50  could optionally be provided. 
         [0045]    The female connector  40  is also assembled in a manner similar to that for the male connector  20 . In particular, the assembly of the female connector  40  again involves securing the coaxial contact member  50  within a recess  55  formed centrally in a mounting collar  56  provided at the proximal end of the connector  40 . To this end, a small threaded pin or screw  57  is screwed into a threaded hole  58  formed through the casing  42  and collar  56 . In this case, the pin or screw  57  firstly secures the collar  56  to the casing  42  and an end of the screw also engages and securely fastens the coaxial contact member  50  within the recess  55  in the mounting collar  56 . As before, it will be noted that more than one such pin or screw  57  may be provided, e.g. radially offset from one another in the collar  56 . As the ring-shaped first and second contact members  46 ,  48  of the female connector  40  are arranged at an inner periphery of the cavity  41  of the connector, the leads  47 ,  49  are arranged and received within longitudinally extending slots or grooves  59  formed in the casing  42 . As a result, the mounting collar  56  which receives and holds the coaxial contact member  50  of the female connector  40  need not receive the leads  45  of the ring-shaped contact members  44 , as is the case with the male connector  20 . Rather, in this example, the leads  45  of the ring-shaped contact members  44  extend radially outwardly of the mounting collar  56  and are arranged angularly spaced from one another, again at about 60° angular spacings. Again the proximal end of the coaxial contact member  50  may include a screw-thread  61  for attaching a cable. 
         [0046]    When the male connector  20  is coupled with the female connector  40  by inserting the protruding portion  21  into the cavity  41  of the cylindrical casing  42  fully (as shown in  FIG. 3  of the drawings), the rotatable electrical coupling  10  of the present invention is brought into an electrically coupled state. In this state, the respective first contact rings  26 ,  46  and the respective second contact rings  28 ,  48  of the male and female connectors  20 ,  40  come into alignment and wiping or sliding contact with one another (i.e. at their respective opposing surfaces). Furthermore, the respective third electrical contact members  30 ,  50  also come into axial alignment and axial mating engagement with one another on a common central axis X of the male and female connectors  20 ,  40 . That is, the facing or opposite free ends of the respective third electrical contact members  30 ,  50  are adapted to engage with one another (e.g. matingly) in the axial direction such that a continuous, and preferably fully shielded coaxial connection is obtained there-between. The coaxial contact members  30 ,  50  are preferably configured as a coaxial plug-type member and a coaxial socket-type member, respectively. Thus, it will be appreciated that the coaxial contact member  30  of the male connector  20  may be configured as a socket-type member and the coaxial contact member  50  of the female connector  40  may be configured as a plug-type member, or vice versa. 
         [0047]    In this connection, the distal end of the shield or screen  32  of the third contact member  30  in the male connector  20  may have an inner diameter which is slightly larger than an outer diameter of the distal end of the shield of screen  52  of the coaxial contact member  50  in the female connector  40 . The distal end of the shield or screen  32  may thus receive the distal end of the shield of screen  52  with a slight overlap in a very light friction fit, which ensures continuity of the shielding through the join. Similarly, the distal end of the core conductor  31  may terminate in a cup-shaped receptacle which is adapted to receive and engage the distal end of the core conductor  51 . In this way, the facing or opposite ends of the third electrical contact members  30 ,  50  may be adapted to engage with one another in the axial direction. 
         [0048]    Significantly, the engagement or connection between the ends of the coaxial contact members  30 ,  50  is adapted to permit relative rotation of those members. In particular, these contact members  30 ,  50  are in alignment on a common central or longitudinal axis X which is also the axis of relative rotation for the male and female connectors  20 ,  40 . The facing and engaging ends of the coaxial contact members  30 ,  50  are designed to be rotationally symmetrical to thus provide uninterrupted (and fully shielded) signal transmission irrespective of relative rotation between the connectors  20 ,  40  about the central or longitudinal axis X. The engaging ring-shaped contact members  24 ,  44  similarly provide uninterrupted current and/or signal transmission irrespective of relative rotation between the connectors  20 ,  40  about the longitudinal axis X. 
         [0049]    The protruding portion  21  of the male connector  20  is desirably dimensioned such that it is able to be relatively easily inserted into and withdrawn from the cavity  41  of the female connector  40 . Furthermore, the male and female connectors  20 ,  40  of the invention are quite precisely dimensioned such that all of the electrical contact members, i.e. the first ring-shaped contact members  26 ,  46  for conducting supply current, the second ring-shaped contact members  28 ,  48  for transmitting low frequency control signals, and the third coaxial contact members  30 ,  50  for transmitting high-frequency and/or high-speed data signals come into full contact or engagement with one another substantially simultaneously—i.e. upon the protruding portion  21  of the male connector  20  being fully inserted into the cavity or socket  41  of the female connector  40 . In this way, the coupling provides for the simultaneous transmission of three supply currents, three control signals, and a high-frequency and/or high-speed data signal for multiple items of equipment. At the same time, the electrical coupling  10  of the invention is configured such that the male connector  20  may rotate about the central axis X relative to the female connector  40  e.g. through a full 360° while providing uninterrupted electrical contact between the respective electrical contact members of the coupling. 
         [0050]    In a preferred configuration, the respective electrical contact members of the male and female connectors  20 ,  40  may have a degree of springiness or resilience to enhance their contact with one another. For example, the ring-shaped electrical contact members  24  of the male connector  20  may be resiliently biased in a radially outward direction, the ring-shaped electrical contact members  44  of the female connector  40  may be resiliently biased in a radially inward direction, and/or the coaxial contact members  30 ,  50  may be resiliently biased in an axial direction (i.e. along the X-axis towards the distal end of the respective connector). On the one hand, this resilient bias may help to ensure that the desired uninterrupted electrical contact is maintained despite small manufacturing tolerances and/or a small degree of wear during the service life of the coupling. On the other hand, such resilient bias may also help to prevent damage to the contact members in the event that the male and female connectors  20 ,  40  of the coupling  10  are too forcefully combined. The male and female connectors  20 ,  40  may also be configured to prevent an axial over-loading of the third contact members  30 ,  50  by providing a stop or abutment (e.g. the collar  36 ) against further or excessive insertion of the male connector  20  into the cavity  41  of the female connector  40 . 
         [0051]    Furthermore, the electrical coupling  10  of the invention may optionally include a latch mechanism (not shown) for preventing the male and female (i.e. plug and socket) connectors  20 ,  40  from inadvertently separating or disconnecting from each other during use. Thus, the latch mechanism may need to be released, for example by applying a threshold axial force (e.g. against a spring biased pawl mechanism) or by activating a switch, button or lever device, in order then to separate or disconnect the coupled male and female connectors  20 ,  40 . 
         [0052]    With reference now to  FIG. 5  of the drawings, a schematic perspective view of a protruding portion  21  of a male or plug-type connector  20  according to the present invention is illustrated. In this particular embodiment, four ring-shaped contact members  24  are shown provided around an outer radial periphery of the protruding portion  21  and a centrally located coaxial contact member  30  is also illustrated. The coaxial contact member  30  extends along a central longitudinal axis X of the protruding portion  21  and, as before, is radially separated from the surrounding ring-shaped contact members  24  by a jacket or mantle  34  of dielectric material. This jacket or mantle  34  electrically isolates the ring-shaped contact members  24  both from each other and from the coaxial contact member  30 . The ring contacts  24  are again designed for wiping or sliding contact over their radially outer surfaces with complementary contact members in a female or socket-type connector designed to receive the protruding portion  21  of the plug  20 . 
         [0053]    It will be appreciated that the above description of the preferred embodiments of the invention with reference to the drawings has been made by way of example only. Thus, a person skilled in the art will appreciate that various changes, modifications and/or additions may be made to the parts particularly described and illustrated without departing from the scope of the invention as defined in the claims. In this regard, while the preferred embodiments of the invention have been described as comprising male and female connectors or plug- and socket-type connectors, it will be understood that connectors may be designed which embody the features of this invention despite the fact that, by their appearance, they may seem to be neither strictly “male” nor “female”. As the skilled person will appreciate, however, such connectors may nevertheless fall within the scope of the invention as defined in the appended claims.