Patent Publication Number: US-7905742-B2

Title: Coaxial plug for connecting to a BNC coaxial socket

Description:
CROSS REFERENCED TO RELATED APPLICATION 
     This application is a National Phase filing under 35 U.S.C. §371 of PCT/EP/2007/010623 which was filed Dec. 6, 2007, and claims priority to German Application No. DE 20 2006 019 203.4 filed Dec. 20, 2006. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a coaxial plug having a housing, a plug-side end for connection to a BNC coaxial socket which has two BNC pins of a bayonet fitting, and having a cable-side end for connection to an RF transmission line. 
     2. Description of Related Art 
     By way of example, in order to connect a probe head to an instrument such as an oscilloscope, it is known for BNC coaxial sockets (BNC=Bayonet Naval Connector) to be arranged on the instrument, onto each of which coaxial sockets a corresponding BNC coaxial plug on the probe head can be plugged. However, additional electrical connecting lines are frequently required between the probe head and the instrument in order, for example, to transmit further signals and a supply voltage for the probe head. Since it is an intrinsic form of the BNC plug connection with a bayonet fitting that the BNC coaxial plug can rotate freely relative to the BNC coaxial socket, these additional connecting lines cannot initially be produced by means of the BNC plug connection. In order to circumvent this problem and to produce additional connecting lines between a probe head and instrument for example via contact pins which are arranged on a BNC coaxial socket and BNC coaxial plug, it is already known for an interlock to be provided between a housing of the instrument and a housing of the BNC coaxial plug of the probe head. The BNC coaxial plug can now be plugged onto the BNC coaxial socket only when it is specifically oriented relative to the latter, such that the correct contact pins on the BNC coaxial plug and BNC coaxial socket make contact with one another in a functionally reliable manner. However, this is complex and is dependent on the housing forms of the instrument and probe head having to be individually matched to one another. In other words, probe heads from different manufacturers are not compatible with all instruments from different manufacturers. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of refining a coaxial plug of the above-mentioned type such that a plug connection which cannot be twisted can be produced to a BNC coaxial socket and with a predetermined orientation relative to this BNC coaxial socket, irrespective of the form of the housing of the coaxial plug. 
     According to the invention, this object is achieved by a coaxial plug of the above-mentioned type having the characterizing features in claim  1 . Advantageous refinements of the invention are described in the further claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a perspective view of one preferred embodiment of a coaxial plug according to the invention; 
         FIG. 2  shows a section view of the coaxial plug shown in 
         FIG. 1 ; 
         FIG. 3  shows a perspective view of the coaxial plug shown in  FIG. 1 , in a state in which it is plugged onto a BNC coaxial socket; and 
         FIG. 4  shows a side view. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     In describing the preferred embodiment of the present invention, reference will be made herein to  FIGS. 1-4  of the drawings in which like numerals refer to like features of the invention. 
     In the case of a coaxial plug of the above-mentioned type, the invention provides that the housing of the coaxial plug has two slots which are arranged opposite, run in the axial direction starting from the plug-side end of the coaxial plug and are each arranged with and designed to hold a BNC pin such that they each form an axial stop for a BNC pin, with a latching fork being arranged on the housing of the coaxial plug and having two latching tines, with each latching tine engaging tangentially over an axial slot in the housing of the coaxial plug, between the stop and the plug-side end of the coaxial plug, such that, when a coaxial plug is plugged onto the BNC coaxial socket, one BNC pin is in each case held firmly between a latching tine and a stop of the axial slot, and a locked connection is produced between the coaxial plug and the BNC coaxial socket, with the latching fork being arranged such that it can pivot on the housing of the coaxial plug and having the capability to pivot between a locking position, in which the latching tines tangentially cover the axial slots, and a release position in which the latching tines release the axial slots over their entire length, such that the BNC pins can be inserted into the axial slots in the axial direction and can be pulled out of them in the axial direction. 
     This has the advantage that a coaxial plug which does not comply with the BNC Standard per se with regard to a rotating sleeve for a bayonet fitting can be connected in a functionally reliable manner to a BNC socket, with the axial slots at the same time ensuring a predetermined orientation between the coaxial plug and the BNC coaxial socket, as well as security against twisting of the coaxial plug relative to the BNC coaxial socket. Interacting with the BNC pins, the axial slots form a guide for the coaxial plug when it is pushed axially onto the BNC socket and, with the stop, limit the axial insertion depth. In addition, the latching fork is provided for locking, such that, instead of a rotary movement in order to lock a bayonet fitting, the latching fork just has to be pivoted into the locking position in order to produce a firmly locked connection between the coaxial plug and the BNC socket. 
     Automatic latching of the coaxial plug on the BNC coaxial socket is achieved by means of the latching fork by the latching fork having an elastic spring force applied to it in the direction of the locking position. This results in the coaxial plug being connected with a latched connection to the BNC coaxial socket simply by manually pushing the coaxial plug onto the BNC coaxial socket, with the locking on the latching fork latching on the BNC pins without any additional manual operations. 
     In one preferred embodiment, the axial slots are designed such that the BNC pins overhang the housing radially on the outside. 
     Since each latching tine has a first inclined surface on a side facing the plug-side end of the coaxial plug such that, when the latching fork is in the locking position, the tangential coverage of the axial slot by the latching tine increases, when seen in the direction from the plug-side end of the coaxial plug to the cable-side end of the coaxial plug, the latching fork is automatically pivoted to the release position by the BNC pins while the coaxial plug is being plugged onto the BNC socket. 
     An additional contact force for a coaxial plug which is locked to the BNC coaxial socket and draws the BNC coaxial socket axially into the coaxial plug, or vice versa, is achieved in that each latching tine has a second inclined surface on a side facing the cable-side end of the coaxial plug such that, when the latching fork is in the locking position, the tangential coverage of the axial slot by the latching tine decreases, when seen in the direction from the plug-side end of the coaxial plug to the cable-side end of the coaxial plug. 
     The preferred embodiment of a coaxial plug  10  according to the invention as illustrated in  FIGS. 1 and 2  with a plug-side end  12  and a cable-side end  14  comprises a housing  16  in which two opposite, axial slots  18  are formed, which extend in the axial direction starting from the plug-side end  12 . Each axial slot  18  ends with a stop  20 . The cable-side end is used to connect the coaxial plug  10  to an RF transmission line, for example a coaxial cable. A latching fork  22  is arranged on the housing  16  such that it can pivot about a pivoting axis  24 . The latching fork  22  comprises two latching tines  26 , each of which covers an axial slot  18  tangentially between the plug-side end  12  and the stop  20  when the latching fork  22  is located in the locking position as illustrated in  FIGS. 1 and 2 . A leaf spring  28  applies an elastic spring force to the latching fork  22  such that the latching fork  22  is pressed into the locking position. 
     When pressure is exerted on the latching fork  22  at the point indicated by the arrow  30 , the latching fork  22  is pivoted about the pivoting axis  24  to a release position (not illustrated), in which the latching tines  26  no longer cover the axial slots  18 , as a result of which the axial slots  18  can be passed through freely in the axial direction. 
     Each latching tine  26  has a first inclined surface  32  on a side facing the plug-side end  12  of the coaxial plug  10  such that, when the latching fork  22  is in the locking position, the tangential coverage of the axial slot  18  by the latching tine  26  increases, when seen in the direction from the plug-side end  12  of the coaxial plug  10  to the cable-side end  14  of the coaxial plug  10 , as can be seen in particular in  FIG. 2 . Each latching tine  26  has a second inclined surface  34  on a side facing the cable-side end  14  of the coaxial plug  10  such that, when the latching fork  22  is in the locking position, the tangential coverage of the axial slot  18  by the latching tine  26  decreases, when seen in the direction from the plug-side end  12  of the coaxial plug  10  to the cable-side end  14  of the coaxial plug  10 , as can be seen in particular in  FIG. 2 . 
       FIGS. 3 and 4  illustrate the coaxial plug  10  according to the invention in the state in which it is plugged onto a BNC coaxial socket  36 . This BNC coaxial socket  36  comprises two BNC pins  38 , which were originally used for a known bayonet fitting of a correspondingly designed BNC plug with a bayonet rotating sleeve, as is normal practice with BNC plug connectors. When the coaxial plug  10  according to the invention is pushed onto the BNC coaxial socket  36  in the axial direction or the insertion direction  40 , the axial slots  18  engage over the BNC pins  38 , such that the coaxial plug  10  according to the invention can be plugged onto the BNC coaxial socket  36  in only one specific position relative to the BNC coaxial socket  36 . Interacting with the axial slots  18 , the BNC pins  38  additionally form a guide and twisting protection. When the coaxial plug  10  according to the invention is plugged axially onto the BNC coaxial socket  36 , the BNC pins  38 , which overhang the housing  16  in the radial direction, first of all slide along the first inclined surfaces  32  of the latching tines  26  and in this way press or pivoting the latching fork  22  against the elastic spring force of the leaf spring  28  out of the locking position into the release position. The axial slots  18  are therefore released, and the BNC pins  38  can be pushed further in the axial direction into and along the axial slots  18 , as far as the respective stops  20 . During the process, the BNC pins  38  leave the area of the first inclined surfaces  32 , and the latching fork  22  pivots back to the locking position, under the influence of the elastic spring force of the leaf spring  28 . The BNC pins  38  are therefore locked between the stops  20  and the latching tines  26 , and cannot once again be pulled out of the axial slots  18  in the direction of the arrow  40 . The coaxial plug  10  and the BNC coaxial socket  36  are therefore firmly connected to one another. The second inclined surfaces  34  of the latching tines  26  press against the BNC pins  38  under the influence of the elastic spring force of the leaf spring  28 , as a result of which these pins  38  are pressed against the stops  20  in the direction of the arrow  40 , or in the opposite direction to the arrow  40 . This produces a corresponding contact pressure in order to make an electrical contact between the coaxial plug  10  and the BNC coaxial socket  36 . 
     Overall, the mechanical and electrical connection of the coaxial plug  10  to the BNC coaxial socket  36  is achieved by simply plugging the coaxial plug  10  onto the BNC coaxial socket  36  in the insertion direction  40  until the BNC pins  38  strike the stops  20 . The locking connection between the coaxial plug  10  and the BNC coaxial socket  36  is in this case produced automatically by the latching fork  22 . In order to release the coaxial plug  10  from the BNC coaxial socket  36 , a pressure is exerted manually on the latching fork  22  as indicated by the arrow  30 , as a result of which the latching fork  22  pivots about the pivoting axis  24  to the release position, against the elastic spring force of the leaf spring  28 . The movement of the BNC pins  38  out of the axial slots  18  in the direction of the arrow  40  is therefore no longer blocked by the latching tines  26 , as a result of which the coaxial plug  10  can be pulled off the BNC coaxial socket  36 , in the opposite direction to the insertion direction  40 . 
     While the present invention has been particularly described, in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.