Patent Publication Number: US-2023155338-A1

Title: Method for Crimping an Electrical Cable and Electrical Cable

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of German Patent Application No. 102021129999.3, filed on Nov. 17, 2021. 
     FIELD OF THE INVENTION 
     The invention relates to a method for crimping an electrical cable and an electrical cable. Furthermore, the invention relates to a kit for crimping. 
     BACKGROUND 
     Electrical cables are used in numerous fields of technology to transmit energy or information between individual devices. Coaxial cables are a special type of electrical cable consisting of an inner conductor and a concentric outer conductor. The outer conductor usually consists of a shielding braid and serves to shield against interference fields. A dielectric is located between the inner conductor and the outer conductor. In addition to the shielding braid, the outer conductor can contain a shielding film to improve the shielding properties. 
     In order to connect the electrical cable to the electrical equipment, the electrical cable is usually provided with an electrical contact. The contact can be crimped to the cable. One possibility is to crimp an inner crimp sleeve (so-called support sleeve) onto a stripped area of the cable. However, the disadvantage here is that fixing the inner sleeve can lead to greater deformation of the shielding braid and thus also of the dielectric. Small variations in crimp height can therefore lead to changes in the impedance response of the cable and thus impair the quality of signal transmission. This can result in a high number of rejects. Due to the low tolerance in crimp height, it is also necessary to provide a specific crimp sleeve for each cable diameter, which increases storage and production costs. A cost-effective method for crimping an electrical cable is needed, by which the risk of faulty production is reduced and the signal transmission performance of the electrical cable is hardly or not at all impaired. 
     SUMMARY 
     A method for crimping an electrical cable with a shielding braid and an insulation enclosing the shielding braid includes removing the insulation at a predetermined area to expose an exposed portion of the shielding braid. The method includes crimping an inner crimp sleeve onto the insulation adjacent to the predetermined area and then bending back the exposed portion of the shielding braid at least sectionally over the inner crimp sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be understood by reference to the following description taken in conjunction with the accompanying figures, in which: 
         FIG.  1    is a schematic sectional view of an electrical cable according to an embodiment; 
         FIG.  2   a    is a schematic sectional view of an electrical cable before crimping; 
         FIG.  2   b    is a schematic sectional view of an electrical cable with an inner crimp sleeve crimped onto an insulation; 
         FIG.  2   c    is a schematic sectional view of the electrical cable of  FIG.  2   b    with a stripped area; 
         FIG.  2   d    is a schematic sectional view of the electrical cable of  FIG.  2   c    with a shielding braid bent back over the inner crimp sleeve; 
         FIG.  3   a    is a schematic sectional view of an electrical cable from a kit having a larger conductor diameter; and 
         FIG.  3   b    is a schematic sectional view of an electrical cable from a kit with a smaller conductor diameter. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     In the following, the invention is described in more detail by way of embodiments with reference to the attached Figures. In the Figures, elements which correspond to one another in terms of structure and/or function are provided with the same reference signs. The combinations of features shown and described in the individual embodiments are for explanatory purposes only. A feature of an embodiment can be omitted if its technical effect is not important for a particular application. Conversely, a further feature can be added to an embodiment if its technical effect should be advantageous or necessary for a particular application. 
       FIG.  1    shows a schematic sectional view of an exemplary configuration of an electrical cable  1 . In particular, the electrical cable  1  may be an intermediate product  2  which can be further processed. The electrical cable  1  may extend along a longitudinal cable axis L and has a cable diameter D. The cable  1  has a central electrical conductor  4  having a conductor diameter  5 , a shielding braid  6  enclosing the conductor  4 , and an insulation  8  enclosing the shielding braid  6 . In an embodiment, the inner conductor  4  can consist of several conductor wires. 
     A dielectric  10  can be arranged between conductor  4  and shielding braid  6 . Optionally, a shielding film can also be provided between shielding braid  6  and dielectric  10 . 
     At a free end  12  of the electrical cable  1 , the electrical cable  1  may be stripped so that the shielding braid  6  is accessible from the outside at a predetermined area  14 . At a section  16  adjoining the predetermined area  14  along the cable longitudinal axis L on the side facing away from the free end  12 , an inner crimp sleeve  18  is crimped onto the insulation  8  as a support sleeve  20 . The exposed shielding braid  6  is then bent back, at least sectionally, over the inner crimp sleeve  18  and covers the inner crimp sleeve  18 . 
     In the present invention, the inner crimp sleeve  18  is no longer crimped directly onto the shielding braid  6 , but onto the insulation  8 . Because the inner crimp sleeve  18  is fixed to the insulation  8  by crimping, further processing of the electrical cable may be facilitated. For example, it may not be necessary to pay additional attention to the positioning of the inner crimp sleeve  18  when bending back the shielding braid  6 . The insulation  8  acts as a buffer that resists deformation of the shielding braid  6  and/or the conductor  4  during crimping. Accordingly, crimping the inner crimp sleeve  18  onto the insulation  8  provides better impedance control and the electrical cable  1  has improved signal transmission performance. Fixing the inner crimp sleeve  18  to the insulation  8  makes it easier, in particular, to bend the shielding braid  6  back over the inner crimp sleeve  18 , since slipping of the inner crimp sleeve  18  is avoided. 
     Furthermore, deviations in the cable diameter or in the inner crimp sleeve  18  can be compensated by the elasticity of the insulation  8  without affecting the impedance of the electrical cable  1 . In an embodiment, the inner crimp sleeve  18  directly adjoins the predetermined area  14 . This prevents a transition area in which the shielding braid  6  rests on the insulation  8  but not on the inner crimp sleeve  18 . 
     Inner crimp sleeves  18  and also outer crimp sleeves can be used for a plurality of electrical cables  1  with different conductor  5  diameters. It is not necessary to use a crimp sleeve specific to each conductor diameter, which significantly reduces production and storage costs. For example, an inner crimp sleeve  18  intended for an electrical cable with a predetermined conductor diameter can now be used for an electrical cable  18  with a smaller conductor diameter, since the decisive cable diameter D for the inner crimp sleeve  18  is increased by the insulation  8 . 
     If a stable fit of the inner crimp sleeve  18  is to be ensured, the inner crimp sleeve  18  can be seated for the most part on the insulation  8 . A free end of the inner crimp sleeve  18  can project beyond the insulation  8  in the direction of the predetermined area  14 . Consequently, the free end of the crimp sleeve  18  may overlap at least sectionally with the predetermined area  14 . In an embodiment, the free end can protrude only minimally beyond the insulation  8 . Thus, the portion of the inner crimp sleeve  18  overlapping with the predetermined area  14  may amount to at most 1/10 of the total length of the inner crimp sleeve  18 . Alternatively, the end face of the inner crimp sleeve  18  can be flush with the insulation  8 . 
     If the inner crimp sleeve  18  is to be prevented from protruding too far beyond the insulation  8 , the section of the predetermined area  14  stripped before the inner crimp sleeve  18  is attached can be limited. For example, in particular before and after crimping the inner crimp sleeve  18 , the electrical cable  1  can be stripped sectionally at the predetermined area  14 . 
     The shielding braid  6  can substantially cover a shell surface  22  of the inner crimp sleeve  18  facing radially outward. In particular, the shielding braid  6  can completely cover the shell surface  22 . 
     Now, with reference to  FIGS.  2   a    to  2   d,  an exemplary configuration of a method for crimping the electrical cable  1  is described. 
     In  FIG.  2     a,  the electrical cable  1  is shown in an initial state  24 , i.e. the inner crimp sleeve  18  is not yet attached to the cable  1 . Furthermore, the insulation  8  of the electrical cable  1  in the initial state  24  may still cover the shielding braid  6  in the predetermined area  14 , at least sectionally. If it is intended to prevent an edge of the insulation  8  facing in the direction of the predetermined area  14  from projecting beyond an end face of the inner crimp sleeve  18  after the inner crimp sleeve  18  has been crimped, at least the section of the predetermined area  14  immediately adjacent to the insulation  8  can be stripped before the inner crimp sleeve  18  is placed on the insulation  8 . 
     The inner crimp sleeve  18  can be fed to the electrical cable  1 , in particular in a radial direction. Accordingly, the inner crimp sleeve  18  can be fitted with ease at any position of the electrical cable  1 . The inner crimp sleeve  18  does not have to be pushed over the electrical cable  1  along the longitudinal axis of the cable  1 . To allow radial feeding of the inner crimp sleeve  18 , the inner crimp sleeve  18  may be configured as an open crimp sleeve. Thus, in a non-crimped state as shown in  FIG.  2     a,  the inner crimp sleeve  18  has an open shape with two crimp flanks  26  which are connected to each other at one end via a common base  28  and whose free ends facing away from the base are spaced apart from each other. In particular, a distance between the free ends of the crimp flanks  26  may be greater than the cable diameter D. 
     The crimp flanks  26  may be provided at the free ends with complementary form-fit elements  30 , for example a locking latch and a latching receptacle, which may be engaged with each other when crimped. The locking latch can serve to better catch the opposite crimp flank  26  during the crimping process to avoid a collision between the crimp flanks  26 . 
     If the inner crimp sleeve  18  is now crimped around the insulation  8 , the crimp flanks  26  perform a form fit and nestle against the insulation  8 . In an embodiment, the overlap of the crimp flanks  26  can be individually adjusted and thus variations in the cable diameter D can be compensated for by determining the crimp height. As a result, higher tolerances are possible during production and the amount of rejects can be significantly reduced. Furthermore, identically constructed crimp sleeves  18  can be used for electrical cables  1  with a predetermined cable diameter D range. 
     A variation in the cable diameter D can be better compensated with the open crimp sleeve  18 . Consequently, the permissible tolerance increases during crimping and the inner crimp sleeve  18  can be used for electrical cables  1  with different cable diameters D. For example, the variation in cable diameter D can be compensated for by overlapping the crimp flanks  18  in the crimped state. 
     Crimping the inner crimp sleeve  18  onto the insulation  8  can cause material displacement of the insulation  8 . In order to reduce or even prevent a bulge-like accumulation of material in the longitudinal cable direction L in front of and behind the inner crimp sleeve  18 , the inner crimp sleeve  18  can be penetrated along its shell surface  22  with at least one window  32 . In an embodiment, each crimp flank  26  can have a respective window  32 . This allows a more uniform distribution of the displaced material of the insulation  8 . 
     In an embodiment, at least one of the crimp flanks  26  can have a lug as a form-fit element  30 , which avoids a collision between the crimp flanks  26  during the crimping process and thus serves as a guide element for the other crimp flank  26 . In the crimped state, the lug can engage in the window  32  of the other crimp flank  26  and thus align the crimp flanks  26  with each other if necessary. 
     After the crimp sleeve  18  is fixed to the insulation  8 , as shown in  FIG.  2     c,  the remaining insulation  8  can be removed at the section extending along the longitudinal cable axis L in the direction towards the free end  12  in the section adjoining the crimp sleeve  18 . Thus, the shielding braid  6  is completely exposed at the predetermined area  14 . Of course, the shielding braid  6  can also be completely exposed at the predetermined area  14  before the inner crimp sleeve  18  is crimped onto the insulation  8 . 
     In an embodiment, the bent-back portion of the shielding braid  6  may not extend beyond the inner crimp sleeve  18  along a longitudinal direction L at an end of the crimp sleeve  18  remote from the predetermined region  14 . The bent-back portion of the shielding braid  6  may be level with the opposite end of the crimp sleeve  18  such that the shielding braid  6  substantially completely covers the inner crimp sleeve  18 . In  FIG.  2     d,  it is shown that the exposed portion of the shielding braid  6  is bent back about 180° over the inner crimp sleeve  18  so that the shielding braid  6  covers the inner crimp sleeve  18  and the electrical cable  1  described with reference to  FIG.  1    is obtained. 
     The method can in particular be an intermediate step for crimping an electrical cable  1 . The electrical cable  1  is therefore an intermediate product that can be further processed by further method steps. 
     The conductor  4  can be exposed at the free end  12  and connected to a contact  34  (see  FIG.  3   b   ), for example a crimp contact. The contact  34  can be configured for a specific conductor diameter  5 . 
     In an embodiment, an outer crimp sleeve  36  (see  FIG.  3   b   ) can be provided, which has a crimp section  38  with which the outer crimp sleeve  36  is crimped onto the inner crimp sleeve  18  at least sectionally. As a result, the portion of the shielding braid  6  that is bent back over the inner crimp sleeve  18  can be clamped between the inner crimp sleeve  18  and the outer crimp sleeve  38 . Consequently, the outer crimp sleeve  36  can contact the shielding braid  6  and serve as a shield contact accordingly. The outer crimp sleeve  36  can have a crimping area that overlaps completely with the insulation  8  of the cable. Here, too, it is advantageous that the insulation  8  serves as a buffer and counteracts unwanted deformation of the shielding braid  6  and, in particular, of the dielectric. 
     The crimp section  38  can be divided into a wire crimp section  40  and an insulation crimp section  42 . The wire crimp section  40  can, in particular, overlap completely along the longitudinal axis L with the inner crimp sleeve  18 . The insulation crimp section  42  can be crimped directly around the insulation  8  on the side facing away from the free end  12  with respect to the inner crimp sleeve  18 . 
     The method makes it possible to use both an inner crimp sleeve  18  and an outer crimp sleeve  36 , which are provided for an electrical cable  1  with a larger conductor diameter  5 , on the electrical cable  1  with a smaller conductor diameter  5 . 
     This is reflected in a kit  44 , which will now be explained in more detail with the aid of  FIGS.  3   a  and  3   b   . The kit  44  comprises an electrical cable  1  with a larger conductor diameter  5  ( FIG.  3   a   ) and an electrical cable  1  with a smaller conductor diameter  5  ( FIG.  3   b   ). Typically, an inner crimp sleeve  18  and/or outer crimp sleeve  36  specifically configured for the cable diameter D is required for each electrical cable  1 . Each electrical cable  1  of the at least two electrical cables in the kit  44  is respectively provided with a shielding braid  6  and an insulation  8  enclosing the shielding braid  6 . 
     In the kit  44 , at least two inner crimp sleeves  18  of identical construction are provided. One inner crimp sleeve  18  of the at least two inner crimp sleeves  18  may be crimped onto an area of the electrical cable  1  exposed from the insulation  8  in the electrical cable  1  with larger conductor diameter  5 . The other inner crimp sleeve  18  of the at least two inner crimp sleeves  18  may be crimped onto the insulation  8  in the electrical cable  1  with smaller conductor diameter  5 . Further, the kit  44  may include at least two identically constructed outer crimp sleeves  36 , each crimped around the corresponding inner crimp sleeve  18 . 
     The inner crimp sleeve  18  is seated for the most part or for the largest part on the insulation  8  if at least a length section of the inner crimp sleeve  18 , the length of which corresponds to at least 50% of the total length of the inner crimp sleeve, is seated on the insulation  8 . The same applies in the case where the inner crimp sleeve  18  is crimped onto the insulation  8  for the most part. The same also applies in the case that the crimp section  38  overlaps the insulation  8  for the most part.