Abstract:
A straight electrical coaxial cable connector ( 2 ) for connecting first and second coaxial cables ( 8, 10 ) each including a core ( 16, 24 ) and a shield layer ( 20, 28 ), the connector ( 2 ) including first and second interengeagable housing parts ( 68, 70 ), first and second crimp ferrules ( 34, 52 ) for respectively engaging the shield layers ( 20, 28 ) of the first and second cables ( 8, 10 ), shield connection means ( 38 ) for electrically interconnecting the first and second shield layers ( 20, 28 ), core connection means ( 36, 64 ) for electrically interconnecting the two cores ( 16, 24 ), and first and second ferrule engagement means ( 76, 88 ) operable to respectively secure the first and second ferrules ( 34, 52 ) relative to respective said housing parts ( 68, 70 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application was filed on Oct. 14, 2011, U.S. application Ser. No. 13/264,613, and is the National state entry of PCT/EP2010/054761, International Filing Date Apr. 12, 2010, which claims the foreign priority benefit of 0906474.2, filed on Apr. 17, 2009. 
     BACKGROUND 
     The present invention relates to a straight connector for interconnecting two coaxial cables and to a method of interconnecting two such cables. 
     SUMMARY 
     Existing straight connectors for connecting two coaxial cables generally include a pair of housings parts in each of which a cable sub-assembly, at the end of a cable, is mounted such that when the housing parts are interengaged core and shield portions of one cable sub-assembly are brought into engagement with those of the other cable sub-assembly. Latch and terminal position assurance devices for holding complementary core connection members of the terminal sub-assemblies firmly in engagement with each other result in the sub-assemblies being bulky. This in turn results in the overall outer dimensions of the connector being larger than is desirable. One preferred object of the invention is to reduce the overall size of the cable sub-assembly and also preferably the overall size of the connetor. 
     Thus according to a first aspect of the invention there is provided a straight electrical coaxial cable connector for connecting first and second coaxial cables each including a core and a shield layer, the connector including first and second interengeagable housing parts, first and second crimp ferrules for respectively engaging the shield layers of the first and second cables, shield connection means for electrically interconnecting the first and second shield layers, core connection means for electrically interconnecting the two cores, and first and second ferrule engagement means operable to respectively secure the first and second ferrules relative to respective said housing parts. Securing each cable to its associated housing part by means of a ferrule engagement means removes the necessity for a latch or terminal position assurance device on the core connection, permitting the cable sub-assembly to be smaller. This in turn permits the housing parts to be smaller also. The mating and unmating load on the core connection are transmitted to the housing latch via the cable crimp and ferrule. As an alternative to the first and second ferrule engagement means for securing the first and second ferrules relative to the housing parts, engagement of parts other than the core connection means is possible to secure the core connection means in engagement. For example engagement of the shield connection means is possible as an alternative. The intention is that direct latching of the core connection means is not required as the mating and unmating loads are transmitted via the cables and cable crimps. 
     Preferably each ferrule engagement means is integrally formed with one of said housing parts. Such an arrangement will reduce the number of part required for the manufacture of the connector. 
     To guard against accidental release of the ferrule engagement means and unintentional release of the cable sub-assemblies, the connector preferably further includes at least one displaceable secondary lock or position assurance member which is engageable with a respective ferrule engagement means. 
     Conveniently the shield connection means comprises a tubular shield connection means which provides efficient all round shielding and facilitates fabrication of the connector. 
     In order to still further improve the shielding the tubular shield connection means may comprises a one-piece shield tube which extends from the first crimp ferrule to the second crimp ferrule. Such an arrangement also removes the need for a connection in the shield connection means which in turn enables the cable sub-assembly to be still more compact. 
     Preferably a cable sub-assembly of the connector includes tubular insulating means interposed between the shield connection means and the core connection means. This enables the assembly to be smaller as the required distance between the shield and the core, to provide electrical isolation, can be reduced. 
     To reduce the number of parts in the connector, the tubular insulating means preferably comprises a one-piece insulation tube which extends from the first crimp ferrule to the second crimp ferrule. This arrangement is particularly advantageous when the shield connection means comprises a one-piece tube since these tubes can be nested inside and support each other thus providing a relatively rigid extension of the cable sub-assembly. 
     In situations in which distal ends of the cable sub-assemblies may be subject being knocked, plug parts should be as robust as possible and accordingly should not include long extensions. For such applications the tubular insulation means preferably includes an insulation tube mounted in each housing part and forming part of a cable sub-assembly, the two insulation tubes including overlapping interengagement portions to help provide the required electrical creepage distance. 
     When the shield connection means and the insulating means each comprise a one-piece tube as described above the core connection means preferably includes two interengeagable core connector members each configured to be connected to a respective one of the cores and situated within the one-piece shield tube. 
     When the shield connection means comprises a one-piece tube which is engaged with one of the ferrules, upon mating of housing parts, preferably the relevant crimp ferrule comprises a main ferrule body and spring means arranged to bias the main ferrule body into engagement with the shield connection means. With such an arrangement a material such as copper can be used for both ferrules. While copper can provide a low resistance contact it tends to stress relax over time which could degrade contact between the ferrule and a shield connection means with which it slidingly engages upon mating of connector parts. The main ferrule body may include plural longitudinally extending engagement portions and the spring means may surround and inwardly bias the engagement portions. 
     In order for parts of the core connection means to be held firmly in engagement with each other as a result of the crimp collars being secured relative to the housing parts, a thrust collar is preferably interposed between at least one of the crimp ferrules and the respective core connector member for biasing the core connector members into engagement with each other. More preferably each crimp collar is provided with such a thrust collar. This arrangement prevents the core connection mating loads from being transmitted via the cables and cable crimps. 
     According to a second aspect of the invention there is provided a method of interconnecting two aligned coaxial electrical cables each including a core and a shield layer, the method comprising the steps of: (i) forming a cable sub-assembly at an end of each cable including engaging a crimp ferrule with the shield layer and joining a core connection member to the core of the respective cable; (ii) providing shield connection means for electrically interconnecting the shield layers; (iii) providing two interengageable housing parts; (iv) securing each cable sub-assembly relative to a respective housing part with an engagement means which engages one said crimp ferrule or said shield connection means; and (v) interengageing the housing parts such that the core connection members interconnect the cores and the shield connection means interconnects the shield layers. With such a method no direct latching of the core connection means is required. 
     Preferably the step of providing the shield connection means comprises providing a one-piece shield tube which extends from one crimp ferrule and is engageable with the other crimp ferrule when the housings are interengaged. 
     Preferably the step of forming each cable sub-assembly includes the step of positioning a thrust collar between the crimp ferrule and the core connection member which transfers load therebetween when the housing parts are interengaged. This prevents core connection mating loads from being transmitted via the cables and cable crimps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example only with reference to the accompanying drawings in which: 
         FIG. 1  shows two interengaged cable sub-assemblies which form part of a coaxial cable connector according to a first embodiment of the invention; 
         FIG. 2   a  shows the two sub-assemblies shown in  FIG. 1  prior to interengagement; 
         FIG. 2   b  shows the two sub-assemblies shown in  FIG. 1  after interengagement; 
         FIG. 3  shows a cross-section of a coaxial connector according to the first embodiment of the invention incorporating the sub-assemblies shown in  FIGS. 1 and 2  in a connected state; 
         FIG. 4  shows a perspective view of the two parts of the coaxial connector shown in  FIG. 3  prior to connection; 
         FIG. 5  shows two interengaged cable sub-assemblies which form part of a coaxial cable connector according to a second embodiment of the invention; 
         FIG. 6   a  shows the two sub-assemblies shown in  FIG. 5  prior to interengagement; and 
         FIG. 6   b  shows the two sub-assemblies shown in  FIG. 5  after interengagement. 
     
    
    
     DETAILED DESCRIPTION 
     A straight coaxial connector according to a first embodiment of the invention, and a method of making it will be described in detail with reference to  FIGS. 1 to 4 . 
     The connector  2  shown in  FIGS. 3 and 4  comprises a first part  4  and a second part  6  which are interengageable with each other. The connector first part  4  is configured to be connected to two first coaxial cables  8  and the connector second part  6  is configured to be connected to two second coaxial cables  10 . Each connector part could however be configured to be connected to a different number of coaxial cables such a one or more than two. Since the manner in which the two first coaxial cables  8  are connected to the connector first part  4  is the same, the connection of only one first coaxial cable  8  will be described in detail. Likewise for the connection of the second coaxial cables  10  to the connector second part  6 . 
     Each first cable comprises a core  8 , surrounded by a layer of inner insulation  18 , surrounded by a shield layer in the form of braid  20 , surrounded by a layer of outer insulation  22 . Likewise each second cable  10  comprises a core  24 , a layer of inner insulation  26 , a shield layer in the form of braid  28  and a layer of outer insulation  30  arranged in a like manner. Ends of the first and second cables are formed respectively into first and second cable sub-assemblies  12  and  14  shown disengaged from each other in  FIG. 2   a , engaged with each other in  FIGS. 1 and 2   b  and engaged with each other and incorporated into the coupled connector in  FIG. 3 . 
     Prior to forming the first cable sub-assembly  12 , a strain relief member  31  followed by a first cable seal  33 , the functions of which will be described below, are threaded over an end portion of the first cable  8 . To form the first cable sub-assembly  12  the outer insulation  22  is first stripped back from the end portion of the first cable  8 . The braid  20  and inner insulation  18  are then stripped back such that portions thereof project from the outer insulation  22  and a core end  32  is exposed. A first crimp ferrule  34  is then threaded over the outer insulation  22  past the exposed braid  20  to a position to the left of where it is shown in  FIG. 1 . A first core connection means in the form of a first core connection member  36  is then slid over the core end  32  and crimped thereonto. An insulation tube  40  is then slid into a shield tube  38 . These two tubes a substantially the same length. The exposed portion of the braid  20  is then formed outwardly into an outwardly formed braid portion shape shown in  FIG. 1  and adjacent ends of the nested tubes  38  and  40  are inserted into the outwardly formed braid portion  42 . The first crimp ferrule  34  is then slid along the first cable  8  such that a proximal portion  44  thereof overlies the outer insulation  22  and a distal portion  46  thereof overlies the outwardly formed braid portion  42  and ends of the insulation tube  40  and shield tube  38 . The proximal part  44  of the first crimp ferrule  34  is then crimped inwardly such that it grips the cable  8  by pressing inwardly on the outer insulation  22 . The distal part  46  of the first crimp ferrule  34  is then crimped inwardly such that the outwardly formed braid portion  42  is firmly sandwiched between the distal part  46  and the end  48  of the shield tube  38 . These crimping steps may be performed simultaneously and are the final step in the formation of the first cable sub-assembly  12 . 
     Prior to forming the second cable sub-assembly  14  a second strain relief member  49  followed by a second cable seal  51 , the functions of which will be described below, are threaded over an end portion of the second cable  10 . To form the second cable sub-assembly  14  the outer insulation  30  is first stripped back from an end portion of the second cable  10 . The braid  28  and inner insulation  26  are then stripped back such that portions thereof still project from the outer insulation  30  and a core end  50  is exposed. A second crimp ferrule  52  is then threaded over the outer insulation  30  past the exposed braid  28  to a position to the right of where it is shown in  FIG. 1 . The second crimp ferrule  52  includes a proximal part  54  configured to overlie the outer insulation  30  and a distal part  56  configured to engage the shield tube  38  which together make up a main ferrule body. The distal part  56  includes longitudinally extending engagement portions in the form of engagement fingers  58 . The engagement fingers are separated from each other by slots  60 . End portions of the engagement fingers  58  are surrounded by spring means in the form of a ring spring which acts to bias the engagement fingers  58  inwardly. A second core connection means in the form of a second core connection member  36  is then slid over the core end  50  and crimped thereonto. An inner crimp collar  66  is then slid over an end of the outer insulation  30  and the exposed portion of the braid  28  is formed outwardly and doubled back over the inner crimp collar  66  as shown in  FIG. 1 . The second crimp ferrule  52  is then slid along the second cable  10  such that the proximal part  54  thereof overlies the outer insulation  30 . The proximal part  54  of the second crimp ferrule  52  is then crimped inwardly such that it grips the cable  10  by pressing inwardly on the outer insulation  30 . This crimping step is the final step in the formation of the second cable sub-assembly  14 . 
     The first and second cable sub-assemblies  12  and  14 , shown individually in  FIG. 2   a , are then respectively secured in first and second connector housings  68  and  70 , shown in  FIGS. 3 and 4 . 
     The first connector housing  68  includes a passage  72  containing ferrule engagement means. The ferrule engagement means is in the form of an inwardly projecting ferrule stop shoulder  74  and a resilient and outwardly displaceable ferrule retaining latch  76  spaced therefrom which constitutes a primary latch. Both the shoulder  74  and the latch  76  are integrally formed with the connector housing  68 . Other constructions are however possible. The ferrule retaining latch could for example be replaced with a latch member which is formed separately from the connector housing  68  and is engageable with the connector housing  68  and the first crimp ferrule  34  to hold it against the ferrule stop shoulder  74  to secure the first crimp ferrule  34  relative to the first connector housing  68 . With the arrangement shown in  FIG. 3 , the first cable sub-assembly  12  is inserted into the first passage  72  until the first crimp ferrule  34  comes into contact with a sloping cam surface  78  of the latch  76 . Further insertion of the first cable sub-assembly into the first connector housing  68  causes the latch  76  to be displaced outwardly until a leading end of the first crimp ferrule  34  comes into contact with the ferrule stop shoulder  74  at which point the latch resiles inwardly and engages a rearwardly facing shoulder  80  of the first crimp ferrule  34  situated between the distal part  46  and the proximal part  44  thereof. A first locking member  82  which is displaceable relative to the first connector housing  68 , and constitutes a secondary lock, is then displaced so as to engage the latch  76  to prevent it from being displaced out of engagement with the first crimp ferrule  34 . This results in the first crimp ferrule  34  and accordingly the first cable sub-assembly  12  being secured relative to the first connector housing  68  as shown in the left hand portion of  FIG. 4 . 
     The first seal  33  and strain relief  31  are then slid along the first cable  8  into an outer part of the first passage  72  and held in place by some suitable means, not shown, such as a feature on the strain relief  31  which is securable to the first connector housing. 
     The second connector housing  70  includes a passage  84  containing ferrule engagement means. The ferrule engagement means is in the form of an inwardly projecting ferrule stop shoulder  86  and a resilient and outwardly displaceable ferrule retaining latch  88  spaced therefrom which constitutes a primary latch. Both the shoulder  86  and the latch  88  are integrally formed with the second connector housing  70 . Other constructions are however possible. The ferrule retaining latch could for example be replaced with a latch member which is formed separately from the connector housing  70  and is engageable with the connector housing  70  and the second crimp ferrule  52  to hold it against the ferrule stop shoulder  86  to secure the second crimp ferrule  52  relative to the second connector housing  70 . With the arrangement shown in  FIG. 3 , the second cable sub-assembly  14  is inserted into the second passage  84  until the second crimp ferrule  52  comes into contact with a sloping cam surface  90  of the latch  88 . Further insertion of the second cable sub-assembly  14  into the second connector housing  70  causes the latch  88  to be displaced outwardly until a leading end of the second crimp ferrule  52  comes into contact with the ferrule stop shoulder  86  at which point the latch  88  resiles inwardly and engages a rearwardly facing shoulder  92  of the second crimp ferrule  52  situated between the distal part  56  and the proximal part  54  thereof. A second locking member  94 , which is displaceable relative to the second connector housing  70 , and constitutes a secondary latch, is then displaced so as to engage the latch  88  to prevent it from being displaced out of engagement with the second crimp ferrule  52 . This results in the second crimp ferrule  52 , and accordingly the second cable sub-assembly  14  being secured relative to the second connector housing  70  as shown in the right hand portion of  FIG. 4 . 
     The second seal  51  and strain relief  49  are then slid along the second cable  10  into an outer part of the second passage  84  and held in place by some suitable means, not shown, such as a feature on the strain relief  49  which is securable to the second connector housing  70 . 
     The first part  4  and the second part  6  of the connector  2 , assembled as explained above, are then confronted with each other as shown in  FIG. 4  ready for connection. 
     As the first and second parts  4  and  6  of the connector  2  are brought together the second connector housing slides into the first connector housing. The second core connection member  64 , which is in the form of a pin connector, passes into the insulation tube  40  of the connector first part  4  and further engagement of the connector parts results in the second core connection member  64  slidingly engaging a passage in the first core connection member  36 , which is in the form of a receptacle connector. Finally the shield tube  38  slides into and electrically engages the distal part  56  of the second crimp ferrule  52 . As this occurs a distal part of the shield tube  38  displaces the engagement fingers  58  of the second crimp ferrule  52  displacing them slightly outwardly against the inward biasing force of the ring spring  62  which thereafter holds the second crimp ferrule in secure electrical contact with the shield tube  38 . A nib  96  on the second connector housing  70  engages an aperture  98  in the first connector housing  68  to hold the connector housings firmly together. 
     A second embodiment of the invention will now be described with particular reference to  FIGS. 5 ,  6   a  and  6   b . Parts of the second embodiment which correspond to those of the first embodiment are designated with the same reference numerals and will not necessarily be described in detail. The following description refers mainly to features of the second embodiment which differ from those of the first embodiment. Features and method steps not referred to below can be assumed to be the same as for the first embodiment. 
       FIGS. 5 and 6   b  show a first cable sub-assembly  200  and a second cable sub-assembly  202  of the second embodiment engaged with each other and  FIG. 6   a  shows these cable sub-assemblies in an unengaged state. 
     The first cable sub-assembly  200  includes a crimp ferrule  204  with an inner annular part  212  situated around an end of the cut-back outer insulation  22 . The crimp ferrule  204  also includes a shoulder  208  which faces away from an end of the cable  8 . The braid  20  of the first cable  8  is doubled back and folded so as to overlie the annular part  212  of the first crimp ferrule  204 . A first thrust collar  216  of insulating material is slid onto an end  220  of the inner insulation  18  that extends past the cut-back outer insulation  22 . A proximal end of the thrust collar  216  abuts a portion of the braid  20  that is folded around the end of the crimp ferrule  214  and a distal end  224  of the thrust collar  216  is inwardly stepped and extends past the end of the inner insulation  18 . A first core connection member  36 , in the form of a receptacle contact, is then slid over an end of the core  16  that extends past the stripped back inner insulation  18  until a proximal end  228  of the first core connection member  36  contacts the distal end  224  of the first thrust collar  216  and is then crimped onto the core  16 . The first thrust collar  216  is accordingly positioned between the first crimp ferrule  204  and the first core connection member  36  and able to transmit load therebetween. A tubular first insulation sleeve  232  is then positioned with a proximal end overlying and latching to the first thrust collar  216  and a first shield sleeve  236  of a conductive material is positioned around the outside of the first insulation sleeve  232  with a proximal end thereof overlying a portion of the annular part  212  of the first crimp ferrule  204  with the folded back portion of the braid  20  positioned therebetween. A portion of the first shield sleeve  236  overlying the first crimp ferrule is then crimped inwardly in order to provide a secure electrical connection between the first shield sleeve  236  and the braid  20 . This crimping process will also crimp the first crimp ferrule  204  inwardly so that it grips the first cable  8 . A secondary crimp is possible in a recess behind the ferrule shoulder  208 . A distal end of the first insulation sleeve  232  comprises an insulation overlap portion  242  and a distal end of the first shield sleeve  236  comprises a shield overlap portion  240 . This completes the formation of the first cable sub-assembly  200 . 
     The second cable sub-assembly  202  includes a crimp ferrule  206  with an inner annular part  214  situated around an end of the cut-back outer insulation  30 . The crimp ferrule  206  also includes a shoulder  210  which faces away from an end of the cable  10 . The braid  28  of the second cable  10  is doubled back and folded so as to overlie the annular part  214  of the second crimp ferrule  206 . A second thrust collar  218  of insulating material is slid onto an end  222  of the inner insulation  26  that extends past the cut-back outer insulation  30 . A proximal end of the thrust collar  218  abuts a portion of the braid  28  that is folded around the end of the crimp ferrule  206  and a distal end  226  of the thrust collar  218  is inwardly stepped and extends past the end of the inner insulation  26 . A second core connection member  64 , in the form of a pin contact, is then slid over an end of the core  24  that extends past the stripped back inner insulation  26  until a proximal end  230  of the first core connection member  64  contacts the distal end  226  of the second thrust collar  218  and is then crimped onto the core  24 . The second thrust collar  218  is accordingly positioned between the second crimp ferrule  206  and the second core connection member  64  and able to transmit load therebetween. A tubular second insulation sleeve  234  is then positioned with a proximal end overlying and latching to the second thrust collar  218  and a second shield sleeve  238  of a conductive material is positioned around the outside of the second insulation sleeve  234  with a proximal end thereof overlying a portion of the annular part  214  of the second crimp ferrule  206  with the folded back portion of the braid  28  positioned therebetween. A portion of the second shield sleeve  238  overlying the second crimp ferrule is then crimped inwardly in order to provide a secure electrical connection between the second shield sleeve  238  and the braid  28 . This crimping process will also crimp the second crimp ferrule  206  inwardly so that it grips the second cable  10 . A secondary crimp is possible in a recess behind the ferrule shoulder  210 . A distal end of the second insulation sleeve  234  comprises an insulation overlap portion  242  and a distal end of the second shield sleeve  238  comprises a shield overlap portion  240 . This completes the formation of the second cable sub-assembly  202 . 
     The first and second connector housings into which the cable sub-assemblies described above are secured are not illustrated but will be broadly similar to the connector housings  68  and  70  of the first embodiment. Movement of the first cable sub-assembly  200  into the first connector housing will be limited by a forwardly facing abutment surface  242  on the first crimp ferrule  204 , which projects outwardly past the first shield sleeve  236 , abutting against a ferrule stop shoulder ( 74  in the first embodiment) in the first connector housing. A first ferrule retaining latch ( 76  in the first embodiment) will engage the shoulder  208  of the first crimp ferrule  204 , in the same manner as in the first embodiment, to secure the first cable sub-assembly  200  in the first connector housing. As in the first embodiment a locking member will be provided to hold the latch in engagement with the first crimp ferrule  204 . The second cable sub-assembly  202  will be secured in a second connector housing in a like manner. A forwardly facing abutment surface  244  is provided on the second crimp ferrule  206  and projects outwardly past the second shield sleeve  238  for abutting against a ferrule stop shoulder in the second connector housing. 
     When the first and second connector housings are brought into engagement with each other the first and second core connection members  36  and  64  will become engaged with each other as in the first embodiment. In addition the shield overlap portions  240  of the shield sleeves  236  and  238  will become engaged with each other and the insulation overlap portions  242  of the insulation sleeves  232  and  234  will become engaged with each other as shown in  FIG. 5 . When the connector housings are so engaged and latched together the cable sub-assemblies  200  and  202  will be engaged as shown in  FIG. 5 . In this state each core connection member is secured firmly in the connector housing by being held by the associated thrust collar, which is held in place by the associated crimp ferrule, which in turn is secured to the connector housing. 
     The embodiments described above provide a straight coaxial cable connector which is compact and can be made from fewer parts than corresponding prior art connectors. The embodiments have been described for the purpose of illustration only and should not be construed as limiting the invention. Furthermore it should be noted that features of one embodiment may be used in combination with features from the other embodiment.