Patent Publication Number: US-2023133454-A1

Title: Clamping device for cable connector assembly

Description:
The present disclosure relates to a clamping device for a cable connector assembly for clamping an armour layer of a cable, and relates particularly, but not exclusively, to a clamping device for clamping single wire armour or braid of a cable within a cable gland. 
     Cable glands provide a mechanical connection between a cable and an installation, such as a junction box. The connection may have to satisfy one or more physical requirements, such as the ability to resist pulling forces experienced by the cable, to prevent the ingress of water from the surrounding environment, or the force of an explosion. 
     A cable may include an integrated layer of armour for providing mechanical strength to the cable and for preventing damage to the inner layers and wires of the cable. The armour layer may for example be single wire armour, metallic tape, braid or screen. 
     Armour layers are metallic and it is therefore often necessary for electrical safety to provide a secure connection between the armour layer and earth when the cable is installed in the cable gland. Therefore, in addition to providing a secure mechanical connection between the installation and the cable, the cable gland must maintain a reliable electrical connection between the armour layer of the cable and earth. This is usually achieved by means of a clamping device arranged in the cable gland housing. The clamping device has an inner part known as a cone and an outer part known as a clamping ring, and the cable armour layer is clamped between the cone and the clamping ring and held in the clamping position by the cable gland housing. 
     Different armour types have different physical characteristics. For example, single wire armour comprises wires which are thick and stiff, while braid comprises a large number of finer wires. In order to provide a sufficiently secure mechanical and electrical connection, the clamping device of the cable gland must be chosen so that it closely matches the physical dimensions of the armour layer of the cable being clamped. 
     Clamping devices for cable glands are known in which a pair of cones of different sizes is provided, wherein the cone of one size is used for braid, and the cone of the other size is used for single wire armour. Alternatively, a double cone can be provided, wherein one end of the cone is suitably sized for braid and the other end of the cone is suitable sized for single wire armour, and the double cone is reversibly arranged in a cable gland, the orientation of the double cone depending on the type of armour to be clamped. However, because two cones are usually provided when a cable gland assembly is supplied, there is a possibility of choosing the inappropriately sized cone for a particular cable armour type, which means that when installed, the mechanical or electrical connection has an increased risk of failure. 
     Clamping devices are also known in which a tapering gap is formed between the cone and the clamping ring. The cable armour layer is held in a clamped condition in the tapering gap, but the position of the cone and clamping ring relative to each other varies, depending on whether braid or single wire armour is being clamped. This in turn means that the position of the two mutually engaging cable gland housing parts also varies with the type of cable armour being clamped, as a result of which it is difficult to determine whether a reliable clamping connection has been made. 
     Preferred embodiments of the present disclosure seek to overcome one or more of the above disadvantages of the prior art. 
     According to a first aspect of the present disclosure, there is provided a clamping device for clamping an armour layer of a cable in a cable connector, the clamping device comprising: an insert adapted to be received in a cable connector, wherein the insert defines an aperture for receiving an inner part of a cable and defines at least one clamping surface adapted to engage an armour layer of the cable; and 
     a clamping member adapted to be arranged outwardly of the insert in a direction transverse to an axial direction of the cable to clamp the armour layer between at least one said clamping surface and the clamping member, wherein at least part of at least one said clamping surface is displaceable towards the inner part of the cable when said inner part extends through said aperture as a result of engagement of the insert with the armour layer clamped between the clamping surface and the clamping member to enable a range of thicknesses of said armour layer to be clamped between the clamping surface and the clamping member when the insert and the clamping member are in a predetermined position relative to each other. 
     By providing a clamping member and an insert to clamp the armour layer between at least one said clamping surface and the clamping member, wherein at least part of at least one said clamping surface is displaceable towards the inner part of the cable when said inner part extends through said aperture as a result of engagement of the insert with the armour layer clamped between the clamping surface and the clamping member to enable a range of thicknesses of said armour layer to be clamped between the clamping surface and the clamping member when the insert and the clamping member are in a predetermined position relative to each other, this provides the advantage that cables having different types of armour layer may be securely clamped by means of a single type of cable connector assembly without requiring the correct selection of an interchangeable insert, thereby improving the reliability of the clamping connection. The advantage is also provided that the provision of a displaceable clamping surface avoids the need for the clamping action to be effected by a tapering gap of varying length between the cone and clamping ring, as a result of which the cable gland can be made more compact and the mutually engaging parts of the cable connector housing can be arranged to have the same position relative to each other in the clamping position, regardless of the type of cable armour being clamped. The advantage is also provided that the overall length of the clamping apparatus, in an axial direction of the cable, can be kept constant, which enables the relative position of two cable connector housing parts accommodating the clamping apparatus to also be kept constant. This in turn enables a necessary clamping torque to be more reliably applied to the clamping apparatus and to be more reliably identified by a user of the cable connector, thereby making reliable connection of the cable connector to the cable armour easier to determine. This further improves the reliability of operation of the cable connector assembly, since it is easier to determine that a reliable clamping connection has been made when the clamping device is located inside an assembled cable connector. 
     At least part of at least one said clamping surface may be displaceable towards the inner part of the cable by means of deformation of said part of the clamping surface. 
     This provides the advantage of reducing the complexity of the insert and reducing the manufacturing cost of the insert. 
     At least part of at least one said clamping surface may be defined by a plurality of inwardly displaceable portions separated by slots. 
     This provides the advantage of enabling the mechanical characteristics of the clamping surface to be tailored, and enables a wider variety of materials to be used for the clamping surface. 
     The slots may terminate at a location spaced from an end face of the clamping insert. 
     This provides the advantage of enabling the insert to be more easily manufactured, while increasing the mechanical strength of the insert. 
     The insert and the clamping member may be adapted to abut each other in an axial direction of the cable when said armour layer is clamped between the insert and the clamping member when the insert and the clamping member are in a predetermined position relative to each other. 
     This provides the advantage of enabling the length of the clamping apparatus, in an axial direction of the cable, to be constant for a range of cable armour thicknesses, thereby enabling reliable connection of a cable connector to the cable armour easier to determine. 
     The clamping member may be deformable. 
     This provides the advantage of further distributing the stress experienced by the clamping member to further reduce the likelihood of wear or failure of the clamping member. 
     According to a second aspect of the present disclosure, there is provided a cable connector assembly, comprising: a clamping device as defined above; a first housing part adapted to receive said insert; and a second housing part adapted to engage said first housing part to maintain said insert and said clamping member in position relative to each other to clamp an armour layer of a cable between at least one said clamping surface and said clamping member. 
     The first and second housing parts may be co-operatively threaded such that engagement of the first housing part by the second housing part causes one housing part to abut the insert and the other housing part to abut the clamping member to move the clamping member to surround the insert and to thereby engage the armour layer between the clamping member and at least one said clamping surface of the insert. 
     This provides the advantage of increasing the ease of installation of the armour within the assembly. 
     A position of the first housing part relative to the second housing part may be defined by abutment with said insert and said clamping member in an axial direction of the cable when said armour layer is clamped between the insert and the clamping member when the insert and clamping member are in a predetermined position relative to each other. 
     This provides the advantage of enabling more reliable connection of the cable connector assembly with the cable by causing abutment with the insert and clamping member of the clamping apparatus to occur when the clamping apparatus is in the correct clamping condition. 
     Said position of the first housing part relative to the second housing part may be defined by abutment of the first housing part with one of said insert and said clamping member, and abutment of the second housing part with the other of said insert and said clamping member. 
     The cable connector assembly may be a cable gland assembly. 
    
    
     
       A preferred embodiment of the present disclosure will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: 
         FIG.  1    is a cross sectional view of a cable gland embodying the present disclosure in a first condition before clamping of a cable armour layer of a first type; 
         FIG.  2    is a cross section view of the cable gland of  FIG.  1    in a second condition clamping the cable armour layer of a first type; 
         FIG.  3    is a cross sectional view of the cable gland of  FIG.  1    in the first condition before clamping of a cable armour layer of a second type; 
         FIG.  4    is a cross sectional view of the cable gland of  FIG.  3    in the second condition clamping the cable armour layer of a second type; and 
         FIG.  5    is a perspective view of an insert of a clamping device used in the cable gland of  FIGS.  1  to  4   . 
     
    
    
     REFERENCE NUMERALS 
     
         
           10  cable gland assembly 
           12  cable 
           14  clamping device 
           16  outer sheath 
           18  armour layer 
           20  inner sheath 
           22  core 
           24  first housing part 
           26  second housing part 
           28  third housing part 
           30  entry item 
           31  second thread 
           32  first thread 
           33  outer part 
           34  first abutment 
           35  insert 
           36  clip 
           37  groove 
           38  housing body 
           40  first thread 
           42  second thread 
           44  second abutment 
           46  ferrule 
           48  outer seal 
           50  outer nut 
           52  first thread 
           54  insert body 
           56  annular sleeve 
           58  annular end portion 
           60  aperture 
           62  compensator 
           63  compensator parts 
           64  third abutment 
           66  elongate slots 
           68  end face 
       
    
     Referring to  FIGS.  1  to  4   , a cable gland assembly  10  is shown for connection to a cable  12 . The assembly  10  includes a clamping device  14 . The cable  12  is shown arranged within the clamping device  14  so that the clamping device  14  makes a clamping connection to an armour layer  18  of the cable  12 . The cable  12  also has an outer sheath  16 , an inner sheath  20 , and cores  22 . 
     The cable gland assembly  10  also comprises a first housing part  24 , a second housing part  26 , and a third housing part  28 . The first housing part  24  comprises an entry item  30  having a first thread  32  on its outer surface, a first abutment  34 , a second thread  31  for engaging a thread on an enclosure (not shown) or a nut (not shown) for securing the cable gland to the enclosure, and an outer part  33  for engagement by a tool such as a wrench to enable rotation of the first body part  24 . 
     The second housing part  26  comprises a housing body  38  having a first thread  40  on its inner surface for co-operating with the first thread  32  of the first housing part  24 , a second thread  42  on its outer surface, and a second abutment  44 . The third housing part  28  comprises a ferrule  46 , an outer compression seal  48 , and an outer nut  50  having a first thread  52  on its inner surface for co-operating with the second thread  42  of the second housing part  26 . 
     The clamping device  14  comprises an insert  35 , the insert  35  having an insert body  54 , and a clamping portion in the form of an annular sleeve  56 . The annular sleeve  56  is shown having a C-shaped cross-section. The insert body  54  is releasably held in the first body part  24  by means of a compressible, discontinuous metallic clip  36  located in a groove  37  in the insert body  54 . 
     Referring also to  FIG.  5   , the insert body  54  has an annular end portion  58  defining an aperture  60  through the insert body  54  for passage therethrough of the inner sheath  20  and cores  22  of the cable  12 , and a clamping member in the form of a compensator  62 . The insert body  54  further comprises a third abutment  64  on its outer surface. 
     The compensator  62  is annular in shape and is mounted or fixed to the insert body  54 . The compensator  62  is adapted to be displaceable inwardly, that is toward the insert body  54 . In one embodiment, the compensator  62  has greater flexibility than the annular sleeve  56 . The compensator  62  is shown comprising a plurality of slots  66  which enable the parts  63  of the compensator  62  between the slots  66  to displace independently of one another and provide additional flexibility to the compensator  62 . The compensator  62  is shown having an end face  68 , and the slots  66  are shown terminating at locations spaced from the end face  68 . 
     Referring to  FIGS.  1  and  3   , the compensator  62  is seen in an uncompressed condition prior to clamping of the armour  18 . In  FIGS.  2  and  4   , the compensator  62  is shown in a clamping condition wherein the annular sleeve  56  is arranged around the insert body  54  to engage the armour layer  18  between an inner surface of the annular sleeve  56  and the flexed compensator  62 , thereby gripping the armour layer  18 . 
     Referring to  FIG.  2   , the compensator  62  is shown engaging an armour layer  18  in the form of braid. In  FIG.  4   , the compensator  62  is shown engaging an armour layer  18  in the form of single wire armour, which is comparatively thicker and stiffer. The insert body  54  shown in  FIGS.  1  to  4    is the same insert and is capable of engaging both types of armour  18  to provide a reliable mechanical and electrical connection without requiring modification of the clamping device  14  and without requiring a particular choice of a cable gland insert from a variety of such inserts. 
     The installation of the cable  12  in the clamping device  14  will now be described. 
     Referring to  FIGS.  1  and  3   , the cable  12  to be installed in the clamping device  14  is located through the clamping device  14 . The cable  12  enters the third housing part  28  and the outer sheath  16  terminates within the third housing part  28 . The protruding armour layer  18  is arranged adjacent and radially outward of the compensator  62  and is located to meet the third abutment  64  of the insert body  54 . The inner sheath  20  and cores  22  pass through the aperture  60  of the insert body  54  and onward through the first housing part  24  and out of the clamping device  14 . 
     Referring to  FIGS.  2  and  4   , once the cable  12  is located at the correct position relative to the insert  35 , the first housing part  24  and second housing part  26  are threaded together by means of first thread  32  on the first housing part  24  and the first thread  40  on the second housing part  26  to move the first and second housing parts  24 ,  26  closer to one another. The first abutment  34  of the first housing part  24  abuts the insert body  54  while the second abutment  44  of the second housing part  26  abuts the annular sleeve  56 . As the first housing part  24  and second housing part  26  are moved toward one another by action of the threading, the annular sleeve  56  and insert body  54  are moved toward one another such that the annular sleeve  56  moves over the armour layer  18  and pushes the armour layer  18  radially inwardly towards the outer surface of the compensator  62 . As the armour layer  18  meets the compensator  62 , the compensator  62  displaces or flexes radially inwardly toward the inner portion  56  to accommodate the shape of the armour layer  18  and the armour layer  18  is gripped between the inner surface of the annular sleeve  56  and the outer surface of the compensator  62 . The threading action is continued until the annular sleeve  56  abuts the insert body  54 . 
     Since the axial length of the assembled clamping device  14  is the same for a range of thicknesses of armour layer  18 , when the annular sleeve  56  abuts the second housing part  26 , and the insert body  54  abuts the first abutment  34  of the first housing part  24 , it can be determined that the assembled clamping device  14  has reached its minimum axial length, and that the armour layer  18  of the cable  12  has therefore been securely clamped between the insert  54  and the annular sleeve  56 . 
     When clamping of the cable armour layer  18  is complete, the third housing part  28  is mounted to the second housing part  26  to axially compress the seal  48 , which causes radial expansion of the seal  48  to bring the seal  48  into sealing engagement with the outer sheath  16  of the cable  12 . 
     It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the disclosure as defined by the appended claims.