Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In the past, a wide variety of proposals have been made relating to multiple plug connections in which a plurality of coaxial cables are connected to a circuit board for radio-frequency purposes in one plugging operation at the same time. In the case of multiple coaxial cable plug connections of this type, it is not only necessary to align the contact arrangements of the individual connection points with one another, but it is also necessary to ensure that the RF connection is made up to the highest frequencies with the lowest possible attenuation. Furthermore, care should be taken that, when there are a large number of connection points or coaxial cables to be connected, the plugging forces which have to be expended during the plugging operation can be managed. 
     2. Discussion of Related Art 
     WO-A1-92/22943 discloses, for example, a coaxial connector system of high density for use in printed circuits, in which, on the cable side, the cables which are provided with a coaxial contact arrangement are inserted into holes in a grouping plate and latched there. A plurality of grouping plates are held in parallel in one housing, with the coaxial contact arrangements projecting forward out of the housing and being inserted into corresponding holes in a mating piece which is arranged on the circuit board. Electrical contact is established in the mating contact via a central pin for the internal conductor and via a contact tongue, which is arranged laterally in the hole, for the external conductor. In the case of this solution, the design is very simple and the plugging force is comparatively low. On the other hand, this solution is unsuitable for higher and extremely high frequencies in the GHz range owing to the unfavorable contact geometry and lack of precision. 
     EP-A1-0 582 960 discloses an RF coaxial plug connection in which the coaxial mating plug connector for the coaxial plugs are integrated in a metal monoblock which forms the common external conductor for all the mating plug connectors. The coaxial plugs themselves are combined to form one unit by means of a common mounting plate, arranged on a board and attached by means of press-in contacts with a specific spacing. Flexible alignment of the individual plug connections with one another is not possible here. 
     WO-A2-98/33243 discloses a comparable RF coaxial plug connector in which, instead of the metal block in the mating plug connector, a plastic housing with a metallized inner wall as the external conductor is inserted. Flexible alignment in the case of individual plug connections is not possible in this case either. 
     SUMMARY OF THE INVENTION 
     The object of the invention is therefore to provide a multiple coaxial cable plug connection, which is suitable for use in circuit boards in particular, in which a very high degree of precision in the plugged connections and therefore an achievable operating frequency in the two-digit GHz range, in particular up to 40 GHz, with easily manageable plugging forces and a sufficient number of plugging cycles, is achieved on account of the flexible alignment of the individual plug connections with one another, and also to specify a method for installing said multiple coaxial cable plug connection. 
     The object is achieved by all the features of claims  1  and  17 . The essential features of the invention are two plug connectors, with the first plug connector having a plurality of first coaxial contact arrangements which are arranged next to one another transverse to the plug axis, and the second plug connector being equipped with the second coaxial contact arrangements which match the first coaxial contact arrangements, and with the first coaxial contact arrangements in each case being attached to the end of an associated coaxial cable. The advantageous properties of the plug connection according to the invention are achieved in that the first coaxial contact arrangements are mounted in a floating manner in a first housing, while the second coaxial contact arrangements are fixedly installed in a second housing. In this way, it is possible to align the (highly precise) first and second contact arrangements in pairs, so that plugging contact which is optimum for RF purposes and a low plugging force are achieved at the same time when the plug connection is inserted. 
     According to one embodiment of the invention, the two plug connectors are in the form of multiple connector strips in which the individual connections are arranged, in particular, in a plurality of parallel rows. 
     Another embodiment of the invention is distinguished in that the second plug connector is designed for direct connection to a circuit board. In particular, the second plug connector can be mounted on the circuit board using SMD mounting technology. 
     A further embodiment of the invention is distinguished in that the first coaxial contact arrangements to be mounted in a floating manner in the first plug connector are inserted transverse to the plug axis so as to latch into a bearing plate, and in that the bearing plate is held with radial play in the first housing. In particular, the bearing plate is in the form of a comb with outwardly projecting teeth, with accommodation spaces for accommodating the inserted first coaxial contact arrangements being arranged between said teeth. Depending on requirements, the comb can be fitted with the maximum number of contact arrangements, but also with a lower number of contact arrangements, and therefore a system which can be used in a flexible manner is provided. 
     A preferred development of this embodiment is characterized in that the first coaxial contact arrangements have a cylindrical shape, and in that the accommodation spaces in each case comprise a round accommodation section, of which the diameter is matched to the first coaxial contact arrangement, and a straight insertion section which connects the accommodation section to the exterior and has a width which is slightly smaller than the diameter of the accommodation section, in such a way that the first coaxial contact arrangement can be inserted through the insertion section so as to latch into the accommodation section. Mounting of the plug connector is considerably simplified as a result. 
     In this case, positioning of the first coaxial contact arrangement can be simplified by the first coaxial contact arrangement having a peripheral latching groove, of which the outside diameter is matched to the diameter of the accommodation section. 
     The first housing preferably has an interior which proceeds in the direction of the plug axis and is open at the ends, with the bearing plate or the comb being held with play in recesses in the first housing which are intended for this purpose. 
     According to another embodiment of the invention, the first contact arrangements are permanently connected, in particular soldered, to the associated coaxial cable. 
     It is also advantageous if the bearing plate or the comb is composed of a plastic. 
     A further embodiment of the invention is characterized in that the first coaxial contact arrangement is in the form of a socket and has a contact sleeve, which acts as an external conductor, with an insertion opening for inserting the second coaxial contact arrangement, in which insertion opening a first internal conductor is arranged in a concentric manner and is held in the contact sleeve by means of a first insulating piece, said internal conductor merging with a contact socket in the direction of the insertion opening. 
     A preferred development of this embodiment is distinguished in that the second coaxial contact arrangement is in the form of a plug and has an annular base in which a second internal conductor is arranged in a concentric manner and is held in the base by means of a second insulating piece, said second conductor merging with a contact pin at the front, and in that a crown of sprung contact arms which extend in the axial direction is integrally formed on the base, said crown moving into the contact sleeve of the associated first coaxial contact arrangement and making contact with the inside of said contact sleeve when the plug connection is inserted. It is also advantageous if the second housing is composed of a metal or a metallized plastic and has a number of holes of graduated diameter which corresponds to the number of second coaxial contact arrangements, and if the second coaxial contact arrangements are pressed, by way of their base, into the holes so as to be fixedly seated. 
     In order to assist the alignment of the first contact arrangements with the second contact arrangements, particularly in the case of rigid coaxial cables, a cable guide can be provided according to another embodiment of the invention to guide the coaxial cables departing from the first contact arrangements. 
     In particular, the cable guide can be in the form of a separate, integral body which has a number of passage holes for conducting the coaxial cables which corresponds to the maximum number of coaxial cables, with the cable guide being composed of a plastic, and being attached to the first housing in an interlocking or cohesive manner. Latching means which are matched to one another are preferably provided on the cable guide and on the first housing for attaching the cable guide to the first housing. 
     The method according to the invention is distinguished in that, in a first step, the coaxial cables which are provided for the multiple coaxial cable plug connection are cut to length and the first coaxial contact arrangements are in each case attached, in particular soldered or crimp-connected, to the ends of the coaxial cables so as to make contact, in that, in a second step, the coaxial cables manufactured in this way are inserted into the bearing plate or the comb in a latching manner by way of the first coaxial contact arrangements, and in that, in a third step, the bearing plate or the comb, with the manufactured coaxial cables held therein, is inserted into the first housing and fixed there. 
     If, in particular, a first housing comprising metal is used, after being inserted into the first housing, the bearing plate or the comb are calked there. 
     If a first housing comprising plastic is used, the bearing plate or the comb can be inserted so as to latch into the first housing in the third step. 
     One embodiment of the method according to the invention is characterized in that, in a fourth step, the coaxial cables are guided through a cable guide which is attached to the first housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in greater detail below with reference to exemplary embodiments in conjunction with the drawing, in which 
         FIG. 1  shows a perspective view of the basic elements of a plug connection with 16 individual connections according to one exemplary embodiment of the invention; 
         FIG. 2  shows, in an illustration which is comparable to  FIG. 1  and in which the housing of the plug connectors are at least partially transparent, the internal design of the plug connection according to the exemplary embodiment; 
         FIG. 3  shows a longitudinal section through the upper plug connector from  FIGS. 1 and 2 ; 
         FIG. 4  shows a plan view, from above, of the upper plug connector from  FIGS. 1 and 2 ; 
         FIG. 5  shows the enlarged detail (B) from  FIG. 3 ; 
         FIG. 6  shows a first perspective view of the housing of the upper plug connector from  FIGS. 1 and 2 ; 
         FIG. 7  shows a second perspective view of the housing of the upper plug connector from  FIGS. 1 and 2 ; 
         FIGS. 8-10  show various views of the comb which is inserted into the upper plug connector from  FIGS. 1 and 2 ; 
         FIG. 11  shows a perspective illustration of the first coaxial contact arrangement from the upper plug connector from  FIGS. 1 and 2 ; 
         FIG. 12  shows a longitudinal section through the lower plug connector from  FIGS. 1 and 2 ; 
         FIG. 13  shows a plan view, from above, of the lower plug connector from  FIGS. 1 and 2 ; 
         FIG. 14  shows an enlarged detail of the second contact arrangement from the contact connector of  FIG. 12 ; 
         FIG. 15  shows the plan view from below of the lower plug connector from  FIGS. 1 and 2 ; 
         FIG. 16  shows a perspective illustration of the second coaxial contact arrangement from the lower plug connector from  FIGS. 1 and 2 ; 
         FIG. 17  shows, in an illustration which is comparable to  FIG. 3 , the upper plug connector from  FIG. 3  with a cable guide, which is additionally latched into the first housing, as an alignment and kink-prevention element; 
         FIG. 18  shows a perspective illustration of the cable guide from  FIG. 17 ; 
         FIG. 19  shows two enlarged details (B and C) from  FIG. 17 ; and 
         FIG. 20  shows a perspective illustration of the plug connector, with the cable guide, from  FIG. 17 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  show the basic elements of a multiple coaxial cable plug connection  50  according to one exemplary embodiment of the invention for the connection of a plurality of coaxial cables to a circuit board  52  (PCB, multilayer board etc., not illustrated further). The multiple coaxial cable plug connection  50  comprises a multiple connector strip  20  which is mounted on and connected to the circuit board  52  by means of SMD mounting technology, and a multiple connector strip  10  which is inserted into the multiple connector strip  20  along a plug axis  51  (arrows in  FIG. 1 ) in the manner of a plug. 
     The multiple connector strip  20 , of which the configuration and the internal design are also illustrated in  FIGS. 12 to 16 , comprises a housing  21  which is in the form of a metal block and in which, in the present exemplary embodiment, 2 parallel rows of in each case eight axial holes  22  of graduated diameter are made. The holes  22  in the two rows are at a standardized distance from one another (in the present example 4 mm), which corresponds to the distance between the corresponding plug inserts ( 26 ) in the multiple connector strip  10 . Each of the 16 holes  22  can produce a coaxial cable connection, and therefore the multiple coaxial cable plug connection  50  of the exemplary embodiment permits the simultaneous plug-connection of a total of a maximum of 16 coaxial cables. 
     As can be seen in  FIGS. 2 ,  12  and  14 , in each case one contact arrangement  27  is inserted (pressed) into the holes  2 , said contact arrangements being illustrated individually in  FIG. 16  and the design of said contact arrangements being shown in  FIG. 14 . The contact arrangement  27  has an annular base  37  with a stop  38 . Said contact arrangement is pressed into the hole  22  by way of the base  37  so as to form an annular gap  45 . 
     An internal conductor  42  is arranged in an axial hole in the base in a concentric manner, said internal conductor being centered and held in the base  37  by means of an insulating piece  41 . The internal conductor  42  terminates flush with the mounting face  23  of the housing  21  in the direction of the circuit board  52  ( FIGS. 2 ,  14 ) and is accessible from below through the opening  46  ( FIG. 15 ), while the insulating piece  41  is recessed. On the insertion side, the internal conductor  42  has, for the purpose of impedance matching, a central piece  43  of enlarged diameter, and then merges with a tapered contact pin  44 . The central piece  43  and the contact pin  44  are concentrically surrounded by a crown of axially oriented contact arms  39  which are separated from one another by slots  49 , start from the base  38  and can be radially deflected by way of their free ends. Contact beads  40  are arranged on the outside at the free ends of the contact arms  39 , said contact beads being used to establish, upon insertion, electrical contact between the contact arms  39  and the inner wall of the contact sleeve  29  ( FIG. 5 ) of the associated contact arrangement  26  in the mating piece (multiple connector strip  10 ). 
     The metal housing  21  of the multiple connector strip  20  forms a common external conductor for all the individual plug connections. In addition, said metal housing has an asymmetrical cross-sectional contour with a coding  17 ′ in the form of a corner which projects obliquely outward and corresponds to a coding  17  on the housing  11  ( FIG. 7 ) of the multiple connector strip  10  and ensures that the two plug connectors can be plug-connected to one another only in a predetermined manner. Milled-out portions  24  which lead outward from the holes  22  are provided in the mounting face  23  of the housing  21  ( FIG. 15 ), said milled-out portions enabling the internal conductor  42  to be guided to the outside in a manner insulated from the housing  21  on the upper face of the circuit board  52 . In order to position the housing  21  on the circuit board  52 , asymmetrically arranged guide holes  47  and  48  are arranged in the housing  21  between the two rows of holes  22  ( FIG. 15 ). 
     As already mentioned, each contact arrangement  27  in the multiple connector strip  20  has an associated corresponding contact arrangement  26  in the multiple connector strip  10 . The contact arrangement  26 , of which the design is shown in  FIG. 5 , comprises a contact sleeve  29  which acts as an external conductor and in which an internal conductor  31  is centered and held by means of an insulating piece  33  in a concentric manner. The internal conductor  31  merges with a contact socket  32  in the direction of the plugging side, said contact socket accommodating the contact pin  44  of the contact arrangement  27  upon insertion. At the other end, the internal conductor  31  accommodates the internal conductor of a coaxial cable  28 , the contact arrangement  26  being soldered to the end of said coaxial cable. The external conductor of the coaxial cable  28  is connected to the rear end of the contact sleeve  29  in this case. The contact sleeve  29  is conically widened on the inside in the direction of the plugging side, in order to facilitate insertion of the contact arms  39  of the contact arrangement  27 . The electrically conductive contact parts of the two contact arrangements  26 ,  27  are preferably composed of CuBe and are surface-treated, in particular gold-plated. 
     In order to facilitate alignment of the contact arrangements  26 ,  27  in pairs when the multiple connector strip  10  is inserted into the multiple connector strip  20 , and therefore to achieve a high degree of precision in the plugged connection together with a reduced plugging force, this allowing operating frequencies of up to 40 GHz, the coaxial cables  28  are mounted in a floating manner in the housing  11  of the multiple connector strip  10  by way of the contact arrangements  26  which are soldered to the ends. To this end, a mounting plate, which is in the form of a comb  18 , is used, said mounting plate being separately illustrated in  FIGS. 8-10 . The external design of the comb  18 , which is preferably composed of a suitable plastic, is matched to the cross-sectional contour of the housing  11 . On the outer periphery, said comb has a plurality of outwardly projecting teeth  19 ,  19   a, b , accommodation spaces  25  for the contact arrangements  26  being left free between said teeth. Each of the accommodation spaces  25  in each case comprises a round accommodation section  25   a , of which the diameter is matched to the first coaxial contact arrangement  26 , and a straight insertion section  25   b  which connects the accommodation section  25   a  to the exterior. The round accommodation sections  25   a  correspond, in terms of their lateral arrangement, to the holes  22  in the housing  21  of the other multiple connector strip  20 . The insertion section  25   b  has a width b ( FIG. 8 ) which is smaller than the diameter D of the accommodation section  25   a , specifically in such a way that the first coaxial contact arrangement  26  can be inserted laterally through the insertion section  25   b  so as to latch into the accommodation section  25   a . The contact arrangement  26  which is held in the comb  18  is fixed in the axial direction by a peripheral latching groove  30  being formed on the contact sleeve  29  ( FIG. 11 ), the width of said latching groove corresponding to the thickness of the comb  18 . 
     If all 16 coaxial cables  28  are snapped into the respective accommodation sections  25   a  by way of their soldered contact arrangements  26  in the comb  18 , the comb  18  which is equipped in this way is inserted into the interior  12  of the housing  10  from the rear and is held there in a floating manner. This process differs depending on whether the housing  11  is produced from metal or from a yielding plastic. In the illustrated exemplary embodiment, it is assumed that the housing  11  is composed of metal. In each case two parallel slots  13 ,  13 ′ and  14 ,  14 ′ and  15 ,  15 ′ are provided in the wall of the housing  11  on all four sides. The lower, wider slots  13 ,  14  and  15  (slot width=comb thickness) accommodate the comb  18  and hold said comb with radial play. The upper, narrower slots  13 ′,  14  and  15 ′ each define a web which is situated between the pairs of slots and can be used to calk the comb  18  in the housing  11 : the central teeth  19   a  of the comb  18  are longer than the other teeth  19   b . In accordance with the longer teeth  19   a , a recess  16  which is matched to the longer teeth  19   a  is made in the housing  11  on each of the opposite walls, said recess running forward from the rear and ending in the region of the slots  13 . When the comb  18  is inserted into the housing  11 , the longer teeth  19   a  can move forward into the recesses  16  without obstruction ( FIG. 4 ) until they butt against the end of the recess  16  level with the slots  13 . The webs between the slots  13 ,  13 ′ and  14 ,  14 ′ and  15 ,  15 ′ can then be calked on the inside in order to hold the comb in this position. 
     If the housing  11  is composed of a plastic, the webs can be used as latching means which are deflected elastically outward when the comb  18  is inserted and snap back behind the comb  18  in a latching manner. However, other latching systems are also feasible. 
     If, upon insertion, the housing  11  of the first multiple connector strip  10  is pushed over the housing  21  of the second multiple connector strip  20 , the contact arrangements  26  which are held in the comb  18  with the connected coaxial cables  28  can be matched to the opposite contact arrangements  27  on account of the play, and therefore very precise coaxial connections are produced. 
     Given comparatively rigid coaxial cables  28 , considerable laterally acting forces can act on the first contact arrangements  26  which are fitted to the ends and are snapped into the comb  18 , said forces causing the first contact arrangements to tilt and making the plugging operation more difficult. In order to reliably avoid such difficulties, a cable guide  53  can be inserted according to  FIGS. 17 to 20 , said cable guide aligning the coaxial cables  28  emerging from the first housing  11  in parallel and at the same time preventing kinks. 
     The cable guide  53  is designed as an integral plastic body ( FIG. 18 ) and has a number of parallel passage holes  54  for conducting the coaxial cables  28  which correspond, in terms of number and arrangement, to the holes  22  in the multiple connector strip  20 . The diameter of the passage holes  54  can be selected such that the finished coaxial cables  28  with the first contact arrangement  26  can be pushed through, before they are then snapped into the comb  18 . 
     The edge contour of the cable guide  53  corresponds to the edge contour of the interior  12  of the first housing  11 . In particular, a thickened portion  55  is provided on the long sides of the cable guide  53 , said thickened portion being matched to the recess  19  in the inner wall of the first housing  11  and serving to guide the cable guide  53  in the housing  11 . At the lower edge of the cable guide  53 , laterally projecting latching lugs  56 ,  57  are arranged on each of the four sides, said latching lugs latching into the upper slots  13 ′,  14 ′,  15 ′ when the cable guide  53  is inserted into the first housing  11 . In the exemplary embodiment shown, the inserted cable guide  53  terminates virtually flush with the upper edge of the first housing. However, it is also feasible for the cable guide to project to a greater or lesser extent out of the housing  11  toward the rear in order to further increase the support and alignment of the coaxial cables. It is also feasible for the cable guide to be formed by injection-molding using a plastic compound and/or to be attached to the first housing in a cohesive manner. 
     Overall, the invention provides a multiple coaxial cable plug connection which is distinguished by the following properties and advantages:
         multiple cable connection for making contact on a printed circuit, in an extremely narrow space for a high data transmission rate (40 GHz, 40 Gb/s) and a large number of plugging cycles (&gt;3000);   good shielding properties, low plugging force;   cable assemblies, which are mounted in a floating manner, in multiple connector strips and a multiple connector strip with SMD mounting technology on the printed board as the mating piece;   the cable plugs are guided in a comb. The comb is mounted in the multiple connector strip with radial play and allows tolerance compensation in relation to the socket arrangement on the printed board;   the comb, together with the inserted cable assemblies, is snapped (plastic housing) into or calked (metal housing) in the housing of the connector strip;   can be used primarily in measurement technology: for precise and efficient testing of printed circuit arrangements; or   for several cables for printed connections of all types.

Technology Category: 5