Abstract:
The invention relates to a strain relief apparatus ( 50 ) for cables, in particular for fiberoptic cables with Kevlar fibers, the strain relief apparatus ( 50 ) being designed to have at least two parts and having an outer part ( 30 ) and an inner part ( 10 ), the inner part ( 10 ) having a receptacle for inserting at least part of the cable, in particular the Kevlar fibers, and a winding region ( 12 ), the inner part ( 10 ) being designed to be capable of rotating with respect to the outer part ( 30 ), the strain relief apparatus ( 50 ) having a stop ( 43, 44; 45, 46 ) for the cable.

Description:
[0001]    This application claims benefit of Ser. No. 10 2008 027 380.5, filed 9 Jun. 2009 in Germany and which application is incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a strain relief apparatus for cables, in particular fiberoptic cables with Kevlar fibers. 
         [0003]    In particular in the case of fiberoptic cables with Kevlar fibers (aramid fibers) as mechanical supporting elements there is the problem of mechanically fastening the cable. Cable ties, for example, are used for this purpose or the Kevlar fibers are clamped separately. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention is based on the technical problem of providing an improved strain relief apparatus for cables, in particular fiberoptic cables with Kevlar fibers. 
         [0005]    In this regard, the strain relief apparatus for cables, in particular for Kevlar fibers of fiberoptic cables, comprises an outer part and an inner part, the inner part having a receptacle for inserting the Kevlar fibers and a winding region, the inner part being designed to be capable of rotating with respect to the outer part. Capable of rotating in this case generally means that the inner and outer parts are capable of rotating relative to one another, preferably with the outer part being fixed. As a result, the cable is held fixedly in a simple and secure manner. The cable requires a stop, with the result that strain is applied to the Kevlar fibers by means of the winding and the Kevlar fibers are tensioned, which results in the strain relief. The cores or fibers can be of any desired nature, the strain relief of braided Kevlar fibers being a preferred application field. In principle the strain relief apparatus can also be used for braided shields of electrical cables, for example. 
         [0006]    In a preferred embodiment, the receptacle is formed by a slot in the upper part of the inner part, which slot merges with a preferably cylindrical bore. The cylindrical bore in this case has the effect that the inserted fibers cannot slide so easily out of the receptacle. The outer part is preferably formed in the region of the slot or the bore likewise with a slot or cut-free portion, so that the fibers can be inserted horizontally. Retainers, which are beveled inwards, are preferably arranged at the slots or cut-free portions of the outer part. The retainers hold the Kevlar fibers down, with the result that they cannot get caught on protruding parts, in particular on the latching device which will be explained further below. 
         [0007]    In a further preferred embodiment, the outer part has at least one fixing device, which presses the cable or part of the cable, in particular the Kevlar fibers, against the winding region. As a result, the wound-on Kevlar fibers are prevented from being rotated back and it is ensured that the fibers are wound on more tightly and therefore the required self-locking effect is achieved. The fixing device can be designed to be integral with the outer part or can be designed as a separate component part. The winding region is preferably designed to be conical towards the center of the outer surface. 
         [0008]    In a further preferred embodiment, the inner part and the outer part are formed with a latching device which fit one another, it being possible for the number of latching devices of the inner part to be different than the number of latching devices of the outer part. Thus, for example, the outer part can have a latching tab and the inner part can have a large number of latching receptacles for the latching tab of the outer part, or vice versa. 
         [0009]    In a further preferred embodiment, the latching device of the inner part is arranged on the circumference of the upper part or on the lower side of the inner part. 
         [0010]    In a further preferred embodiment, the outer part comprises at least one element, which protrudes beyond the upper part of the inner part and thus prevents any sliding out. 
         [0011]    Further preferably, the upper part of the inner part is formed with cutouts for a tool. 
         [0012]    In a further preferred embodiment, the inner part is designed to be additionally translatorial with respect to the outer part. In this case, the translatorial movement of the inner part compensates for the winding length of the fiber, with the result that it is not necessary for a reserve length to be kept in supply prior to the winding operation. The movement can in this case take place, for example, via gearwheels or latching teeth, the outer part being U-shaped in cross section, for example. As a result of the rotation, the inner part then moves additionally into the outer part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The invention will be explained in more detail below with reference to a preferred exemplary embodiment. In the figures: 
           [0014]      FIG. 1  shows a perspective front view of an inner part of a strain relief apparatus, 
           [0015]      FIG. 2  shows a perspective view from below of the inner part, 
           [0016]      FIG. 3  shows a perspective plan view of an outer part of a strain relief apparatus as a constituent part of a fiberoptic connection module, 
           [0017]      FIG. 4  shows a perspective plan view of the assembled strain relief apparatus, 
           [0018]      FIG. 5  shows a perspective front view of an inner part in an alternative embodiment, 
           [0019]      FIG. 6  shows a perspective plan view of an outer part of a strain relief apparatus as a constituent part of a fiberoptic connection module for the alternative embodiment, 
           [0020]      FIG. 7  shows a perspective plan view of the assembled strain relief apparatus of the alternative embodiment, 
           [0021]      FIG. 8  shows a perspective plan view of an outer part of a strain relief apparatus as a constituent part of a fiberoptic connection module for the alternative embodiment with retainers, and 
           [0022]      FIG. 9  shows a schematic plan view of a strain relief apparatus with additional translatorial movement between the inner and outer parts. 
       
    
    
     DETAILED DESCRIPTION  
       [0023]      FIGS. 1 and 2  show the inner part  10  of a strain relief apparatus. The inner part  10  comprises an upper part  11 , a winding region  12  and a lower part  13 . A slot  14 , which passes centrally over the entire diameter of the circular upper part  11 , is introduced into the upper part  11 . The slot  14  merges with a cylindrical bore  15 , which passes through the winding region  12 , the slot  14  and the bore  15  being parallel to one another. Cutouts  16  for a tool, for example a crosshead screwdriver, are provided in the upper part  11  in the region of the slot  14 . In order to facilitate insertion of the fibers, the upper part  11  has bevels  17  on the slot  14 . Latching tabs  19  are arranged on the lower side  18  of the lower part  13 , with latching receptacles  20  being formed between said latching tabs. The winding region  12  can in this case also run conically towards the center of the outer surface, with the result that in the center the diameter is smaller than at the top and at the bottom. 
         [0024]      FIG. 3  illustrates an outer part  30  of the strain relief apparatus, the outer part  30  being an integral part of a fiberoptic connection module  40 . The fiberoptic connection module  40  in this case has various fiber guides  41  and retainers  42 . It should be noted here that the strain relief apparatus can also be in the form of a completely separate part. The outer part  30  has walls  31 , which form virtually a lateral cylinder surface, which means that this lateral cylinder surface has cut-free portions  32 . Two elements  33 , which protrude beyond the inner part  10  in the inserted state (see  FIG. 4 ), are arranged on the upper side of the walls  31 . Furthermore, the outer part  30  has a fixing device  34  in the form of a sprung web, which protrudes into the interior of the outer part  30  through one cut-free portion  32 . The height of the fixing device  34  is selected such that, in the inserted state of the inner part  10 , the fixing device  34  presses against the winding region  12  of the inner part  10 . Furthermore, the outer part  30  has a latching arm  35 , which protrudes via a cut-free portion  32  in the region of the latching tabs  19  or latching receptacles  20  into the outer part  30 , the front part forming a latching tab  36 , which corresponds to the latching receptacles  20 . Depending on the direction from which the cable is inserted, the faces  43  and  44  or  45  and  46  form the stop for the cable. Behind the faces  43 ,  44  or  45 ,  46 , the cable is then guided without a sheath, the thicker cable sheath stopping against the faces  43 - 46 . 
         [0025]      FIG. 4  shows the assembled strain relief apparatus  50 , comprising an inner part  10  and an outer part  30 . In the basic position, as illustrated in  FIG. 4 , the slot  14  is aligned with the cut-free portions  32 . The Kevlar fibers can then be inserted through the slot  14  into the cylindrical bore  15 . By rotation of the inner part  10  by means of a tool, the fibers are wound onto the winding region  12 , the latching tab  36  successively latching into the latching receptacles  20  of the inner part  10  and thus preventing any back-rotation. The fixing element  34  in the process presses the fibers against the winding region  12 . Preferably, the inner part  10  performs at least one complete revolution. It should be noted here that in this embodiment the length of the wound-on fibers must be provided in advance as a reserve length since otherwise, as a result of the rotation, the cable would also be drawn in as well. 
         [0026]      FIG. 5  illustrates an alternative exemplary embodiment of the inner part  10 , with identical reference symbols to those used for the embodiments shown in  FIGS. 1 and 2  being used for identical parts. The only difference is the fact that the latching tabs  19  and the latching receptacles  20  are not arranged on the lower side  18  of the lower part  13 , but on the circumference of the upper part  11 . The outer part  30  is matched correspondingly, which is illustrated in  FIG. 6 , again with identical parts being provided with identical reference symbols. The difference is that the latching arm  35  is dispensed with and a latching tab  37  is arranged on a wall  31 , which then engages in the latching receptacle  20  on the upper part  11 . Finally,  FIG. 7  illustrates the completely assembled strain relief apparatus  50 . 
         [0027]      FIG. 8  illustrates an alternative embodiment for the outer part  30  shown in  FIG. 6 , with identical elements being provided with identical reference symbols. In contrast to  FIG. 6 , retainers  47 , which are designed so as to be beveled inwards towards the cut-free portion  32 , are arranged next to one another to the left and right of the cut-free portions  32 . As a result of the bevels, the insertion of the Kevlar fibers is facilitated, with the narrow gap between the retainers  47  beneath the bevels preventing the Kevlar fibers from sliding up, with the result that said Kevlar fibers cannot get caught in the latching tabs of the inner part  10 . Correspondingly, the fixing device  34  can be dispensed with. 
         [0028]      FIG. 9  illustrates an embodiment of a strain relief apparatus  50  with rotary and translatorial movement of the inner part  10  with respect to the outer part  30 . The inner part  10  is designed substantially as illustrated in  FIG. 5 , with the cutouts  16  being used for receiving a slotted screwdriver. The arrow R indicates the direction of rotation of the inner part  10 . The outer part  30  is in the form of a trough, with the result that a depression is formed between the walls  31 , with the inner part  10  being located in said depression. The outer part  30  therefore has a substantially U-shaped cross section. Latching teeth  48  are arranged on the inner sides of the left-hand wall  31 . In the upper region of the left-hand wall  31 , a slot or cut-free portion  32  is illustrated, through which Kevlar fibers  49  can be inserted. The Kevlar fibers  49  are then inserted through the cut-free portion  32  and the slot  14  of the inner part  10 . If the inner part  10  is then rotated in the direction R, said inner part rolls with its latching tabs  19  or latching receptacles  20  on the latching teeth  48  of the outer part  30 . This rolling movement results in a translatorial movement with the translatorial direction T. The translatorial movement in this case compensates for the shortening of the Kevlar fibers owing to the winding movement around the inner part, with the result that it is not necessary for a reserve length to be retained. The end position of the inner part  10  is in this case illustrated by dashed lines. In  FIG. 9 , the latching teeth  48  are designed so as to be unsymmetrical in order to prevent the inner part  10  from sliding back. In this case, the upper flank of the latching teeth  48  is set at a steeper angle (virtually 90°) than the lower flank. Alternatively, further structure for securing the inner part  10  can also be provided which prevent it from automatically rotating back. Furthermore, structure can be provided which, corresponding to the elements  33  (see, for example,  FIG. 8 ), prevent a linear movement of the inner part  10 . In this case, this is a cover  51  covering at least partially the depression of the outer part  30 . 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           10  Inner part 
           11  Upper part 
           12  Winding region 
           13  Lower part 
           14  Slot 
           15  Bore 
           16  Cutouts 
           17  Bevels 
           18  Lower side 
           19  Latching tabs 
           20  Latching receptacles 
           30  Outer part 
           31  Walls 
           32  Cut-free portions 
           33  Elements 
           34  Fixing device 
           35  Latching arm 
           36  Latching tab 
           37  Latching tab 
           40  Fiberoptic connection module 
           41  Fiber guides 
           42  Retainer 
           43  Face 
           44  Face 
           45  Face 
           46  Face 
           47  Retainer 
           48  Latching teeth 
           49  Kevlar fibers 
           50  Strain relief apparatus 
           51  Cover 
         R Rotational direction 
         T Translatorial direction