Multi-terminal rotary connector
BACKGROUND OF THE INVENTION 
     This invention relates generally to a multi-terminal connector for joining two electrical cables or joining a cable to a mounted fixture such as a panel receptacle. 
     In such a connector it is desirable that connection and disconnection be made easily and quickly and that the connections, when made, be highly reliable. It is also desirable and often imperative that there be no inadvertent touching of the contacts except as desired in order to eliminate damage to connected circuits. In this regard, it is desirable that means be employed to keep the contacts separated to avoid inadvertent touching until the connector parts are properly aligned and in position to establish electrical contact. Once aligned, connection should be made easily and securely as the contacts are engaged. While the contacts are engaged, they should be free from external forces which would otherwise disturb their electrical continuity. 
     SUMMARY OF THE INVENTION 
     The invention is embodied in a multi-terminal biparte rotary connector assembly including a plug and receptacle. The plug is made of insulating material having a generally circular first end with an axial aperture in the first end for receiving an anti-separation and polarization stud in a singular orientation. A plurality of rounded electrical contacts are exposed on the first end of the plug. The receptacle also is of insulating material and has a generally circular opening to mate with the first end of the plug and has an anti-separation and polarization stud disposed axially of this opening. The stud is inserted into and, when fully inserted, is rotated with respect to the plug aperture to releaseably lock the plug and receptacle in a singularly oriented and mated position. A plurality of rounded electrical contacts are exposed inside the opening of the receptacle and positioned so that the plug contacts engage the receptacle contacts only when the polarization stud is received into the axial aperture and the plug is rotated with respect to the receptacle to its locked position. As the plug is rotated, the apexes of the plug contacts slide past the apexes of the receptacle contacts to inhibit counter-rotation. 
     Strain relief may be provided for the electrical cables where they attach to the connector assembly. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a rotary connector employing teachings of this invention. 
     FIG. 2 is a perspective view of a receptacle as in FIG. 1 adapted for mounting in a panel. 
     FIG. 3 is a longitudinal cross section of the connector of FIG. 1 showing a plug inserted into a receptacle in the locked position. 
     FIG. 4 is a side view of a contact used in the plug and receptacle of FIGS. 1, 2, 3, 4, 5A and 5B. 
     FIG. 5A is a cross-sectional view of FIG. 3 showing a plug inserted into a receptacle in the unlocked position with no contact engagement. 
     FIG. 5B is a cross-sectional view of FIG. 3 showing a plug inserted into a receptacle in the locked position with the contacts engaged. 
     FIG. 6 is an end view of a plug looking towards the cable end. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide an improved multi-terminal connector assembly for joining two multi-conductor electrical cables. 
     It is a further object of the present invention to provide an electrical connector which may be coupled only in the desired position and insure isolation of the plug contacts from the receptacle contacts unless the connector parts are correctly mated. 
     It is a further object of the present invention to provide an electrical connector whose plug and receptacle portions mate easily with a minimum of force. 
     It is a further object of this invention to provide an improved circular connector affording so-called zero insertion force, i.e. without wiping contact between the contacts during insertion or withdrawal. 
     It is still a further object of the present invention to provide an improved anti-separation and polarization device to insure that the plug and receptacle may be joined in only the desired orientation, and once joined, remain so until unlocked. 
     It is still a further object of the present invention to provide an improved set of contacts which provide reliable electrical continuity and help maintain the plug and receptacle in their mated position. 
     These and other objects will become readily apparent from this present specification, drawings, and appended claims. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in FIG. 1 of the drawings, a connector plug 1 and a connector receptacle 2 are shown in line with strain relief means 3 for both the plug 1 and receptacle 2. The strain relief may be utilized to grip the respective wires or cables to minimize strain on the contacts when the connector joins two electrical cables. 
     Referring also to FIG. 3 the plug 1 comprises a body which preferably is a unitary molding of insulating material, and a plurality of contacts 10A. A main body portion 11 is larger than a generally circular mating end 12. The main body 11 may be of any convenient shape. Extending through the main body 11 parallel to the axis thereof is a plurality of contact chambers 13 which continue to the mating end 12 to receive the contacts 10A. The chambers 13 are radially spaced from the main axis of said plug and allow sufficient insulating material between the contacts 10A, as at 13a of FIG. 5A, to insure electrical isolation of one contact from another. A contact guiding and stop shoulder 14 extends into each chamber 13 near its inner end. The number of chambers 13 may be varied in accordance with the number of contacts desired in a particular embodiment of the connector. The configuration of each chamber 13 and the respective shoulder 14 may be altered as desired to facilitate use and assembly of various contacts. Each contact 10A typically is attached to one end of a wire of a first cable (not shown) by a portion 44 prior to mounting in the connector body. Portion 44 is then disposed in the respective contact chamber 13 and extends therethrough to a portion 41 which is exposed on the mating end 12 of the plug 1. The chambers, and thus the contacts, typically are disposed at regular intervals along a common circle concentric with the plug. 
     Referring now to FIGS. 3 and 6, the plug body also includes a central web 32 defining an axial aperture 32A of irregular shape, within the mating end 12. Inwardly of the aperture 32A and on the same axis, the plug defines a recess 34 which is larger in average diameter than the irregular shape of aperture 32A. 
     Referring again to FIGS. 1 and 3, the connector receptacle 2 includes a body molded of insulating material and having an enclosing end 26 defining a generally circular opening 20. Said opening 20 has a larger diameter than the mating end 12 of plug 1 in order to mate with and enclose said mating end 12. The radial clearance between the mating end 12 and opening 20 may be varied in accordance with the particular contact design, provided the connector may be readily assembled and separated, and reliable electrical contact is maintained. 
     Disposed about the periphery of the opening 20 are receptacle contacts 10B for attachment to one end of the wires of a second cable (not shown) in the same manner as contacts 10A. Referring also to FIG. 3, and as with the plug 1, extending through the cable end 21 of the receptacle 2 are contact chambers 23 with contact guide shoulders 14. However, the chambers 23 are generally aligned with the inner surface defining opening 20, whereas the chambers 13 are generally aligned with the outer surface of end portion 12. The number of contact chambers 23 and contacts 10B in the receptacle 2 is usually equal to the number of chambers 13 and contacts 10A in the plug 1. In order to simplify maintenance and reduce costs, contacts of the same design and size may be used in the plug in the receptacle. 
     Both the plug 1 and the receptacle 2 include projections 15 for extending into corresponding openings 16 in the strain relief means 3 for detachable interconnection therewith. A cable clamping sleeve, e.g. of a tortuous path clamp design or a radially collaring gripper type (not shown), is provided in each shell 3, and a slotted tail 17 is provided for strain relief and cable retention to prevent undue strain on the contacts 10A and 10B from forces applied to an attached cable or wire. 
     An annular flange 25 at the distal end 26 of the receptacle 2 fits into a corresponding annular groove 26A in plug 1, or vice versa as desired. The groove 26A is located at the base of end portion 12, where the smaller diameter mating end 12 joins the larger diameter main body 11. This interface may be of a design, with or without a sealing gasket or ring, to exclude contaminants, such as gases, liquids, and foreign particles. 
     Referring to FIGS. 1 and 3, an anti-separation and polarizing stud 30 is axially disposed in the receptacle opening 20. The stud 30 protrudes from a central web 30A of the receptacle body with which it is integral. An enlarged irregularly shaped head 31 corresponds to the shape of the axial aperture 32A in the mating end 12 of the plug 1. The head 31 and aperture 32A are shaped so that insertion is possible only when the two shapes are aligned in one desired orientation, thereby insuring correct polarity between the plug 1 and receptacle 2. The head 31 may also be radially compressible and larger, in its rest state, than the aperture 32A, e.g. of a bifurcated design as illustrated. The head 31 includes leading cam surfaces 31A and is compressed, once aligned with the aperture 32A, as it is squeezed through the aperture 32A, and expands in recess 34 once inserted. Shoulder 35 on head 31 bears against shoulder 36 formed by web 32 between aperture 32A and recess 34 upon expansion, and further upon relative rotation of the two connectors. This engagement precludes removal of the stud 30 and head 31 and hence precludes separation of the connectors except upon realignment of the stud head 31 with aperture 32A and compression of the bifurcated head. The resilience of the material provides the spring action of the head 31. 
     Referring to FIG. 5A, the axial orientation of the head 31 and the receptacle contacts 10B is such that when the head 31 is congruently aligned with the plug aperture 32A, the receptacle contacts 10B are positioned between but not engaging the plug contacts 10A. 
     The head 31 may be removed from recess 34 by rotating the plug 1 to align the shape of the head 31 with that of the aperture 32 and deliberately applying sufficient longitudinal force to compress the head 31 and remove it from recess 34. So long as the plug 1 and receptacle 2 are separated and the head 31 is not aligned with the aperture 32, abutment of the head 31 against the web 32 or the mating end of the plug 1, without fitting into the aperture 32A, prevents inadvertent touching of the plug contacts 10A and the receptacle contacts 10B, and thereby prevents damage to the connected electrical circuits. 
     Referring now to FIG. 6, the configuration of aperture 32A in the plug 1, as defined by web 32, corresponds to the shape of the head 31 on stud 30. Once the head 31 is fully inserted, it may be rotated counterclockwise as shown until the lateral surfaces of the head 31 abut against the ridges 36 formed by web 32. 
     Referring to FIGS. 3 and 4, identical contacts 10 may be used in the plug 1 and receptacle 2. The exposed contacting portion 41 has an elongated domed or rounded shape in this example, but may take on any convenient shape such as a button or blade. The exposed surface 41 of the plug contacts 10A may interfere with the exposed surface portion 41 of the receptacle contacts 10B after the plug 1 has been inserted into the receptacle 2 and the plug is rotated. A circumferential ridge or rib 42 on each contact results in a substantial pressure increase at the point where the ridge 42 bears against the mating contact surface 41 and thereby maintains very low electrical contact resistance. A tab 43 extends from the contact body and interferes with the respective guide rib or shoulder 14 in the contact chamber 23 to lock the contact in place. The terminal portion 44 of the contact 10 is crimped around an electrical conductor, such as a wire from a cable. The crimping attachment may be accomplished prior to insertion of each contact into its chamber 23. 
     Referring to FIG. 1, the panel mount receptacle 4 is identical to the connector receptacle 2 so that it may accept the same connector plug 1. However, it may be attached to a panel or other relatively smooth surface by attaching a panel mount collar 51 over projections 15. Resilient stop wings 52 protrude from said collar 51 for resiliently bearing against a panel opening. These wings 52 may include a locking lip or groove or be tapered to prevent inadvertent removal of the collar, as is well known in the art. 
     DESCRIPTION OF THE OPERATION OF THE PREFERRED EMBODIMENT 
     A multi-conductor cable is inserted through slotted tail 17 of the strain relief means 3. One contact 10 is connected to each conductor in said cable and said contacts are inserted into contact chambers 13 of the appropriate receptacle or plug. Said contacts 10 are held in place as tabs 43 snap over and thereafter bear against guide ribs 14 in contact chambers 13 while the contact shoulder 44 bears against the opposite sides of the ribs 14. This precludes further inward movement or retraction of the contacts. 
     Referring now to FIGS. 1 and 3, and utilizing either a connector receptacle 2 or a panel mount receptacle 4, the connector plug 1 is pressed against the connector receptacle 2. The head 31 of the anti-separation and polarization stud 30 contacts the mating end 12 of plug 1 and prevents the connector contacts 10A from engaging the receptacle contacts 10B. As the connector plug 1 is rotated with respect to receptacle 2, the irregularly shaped connector aperture 32A aligns with the correspondingly shaped head 31 of the polarization stud 30. Once aligned, the mating end 12 of plug 1 is inserted into the opening 20 of receptacle 2 concurrently as the polarization stud is inserted into aperture 32A as the plug is being inserted into the receptacle. The plug contacts 10A thereby are spaced between the receptacle contacts 10B. As the plug 1 is inserted into the receptacle 2, the aperture 32A radially compresses the polarization head 31 until the plug 1 is completely seated into the opening 20. Once seated, the head 31 expands to its usual diameter in recess 34 inhibiting the separation of the plug 1 and receptacle 2. This provides an audible, positive snap action lock to insure proper insertion of the plug 1. Once the head 31 is clear of aperture 32, plug 1 may be rotated with respect to receptacle 2 to engage the contacts. As rotation occurs, the exposed portion 41 of the contacts 10A and 10B engage each other at their respective circumferential ridges 42 and rotation continues until the apexes 43A of the plug contacts 10A slide just past the apexes 43B of the receptacle contacts 10B to inhibit counter-rotation (see FIG. 5B). The plug 1 is removed from receptacle 2 by reversing the above procedure and applying sufficient unlocking torque in the direction indicated in FIG. 5B to overcome the contact pressure. 
     The invention has been described in detail with particular reference to a preferred embodiment and the operation thereof, but it is understood that variations, modifications, and the substitution of equivalent mechanisms can be effected within the spirit and scope of this invention, particularly in light of the foregoing teachings.