Abstract:
The invention relates to a strain relief device ( 1 ) for a plug connect for communications and data technology, comprising a base part ( 10 ) for holding at least part of the plug connector, and a cable ( 51 ) which can be connected to the plug connector, with the base part ( 10 ) being designed with first latching means, and closure means ( 30 ), with the closure means ( 30 ) being designed with second latching means which form a latching connection with the first latching means on the base part ( 10 ), wherein the closure means ( 30 ) are in the form of a spring comprising two limbs ( 31 ) which can be pushed along a guide ( 20 ) onto the base part ( 10 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. Ser. No. 11/540,431, filed Sep. 29, 2006 which is a continuation of U.S. Pat. No. 7,114,987, issued on Oct. 3, 2006, which is the National Stage of International Application No. PCT/EP02/09023 filed Aug. 12, 2002, which claims priority to German Application No. 101 46 119.4 filed Sep. 19, 2001, and which application(s) is/are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a strain relief device for a plug connector for communications and data technology.  
       BACKGROUND  
       [0003]     Strain relief devices for cables for communications and data technology have been known in widely differing embodiments for a long time.  
         [0004]     DE 40 09 297 C2 discloses an apparatus for attaching at least one cable to the racks or housings of telecommunications devices, having at least two toothed rods which are arranged on the rack part, in which case at least one cable is inserted between the toothed rods and can be secured by means of a spring element which can be clamped between the toothed rods.  
         [0005]     DE 198 11 476 C1 discloses a cable clamp for making contact with the shield of cables when they are being fixed on a contact plate, comprising a web and two outer limbs which are connected to this web and are provided with cut-free lugs as holding elements for fixing the cable clamp on the contact plate, with the web being in the shape of a circular arc pointing outward in order to make contact with the cable shield, and being provided with web strips on the edges, pointing inward, for pressing into the cable shield, with the circular arc of the web being arranged symmetrically with respect to the cross section of the cable clamp, being matched to the external circumference of the cable to be connected, and, in terms of cross section, extending over only a portion of the length of the web.  
         [0006]     The known strain relief devices have the disadvantage that the cable conductors are not aligned in a precisely defined manner with respect to the contacts of a plug connector which is to be connected to the cable. Particularly for very high transmission frequencies, this results in very large tolerances for crosstalk between adjacent conductor pairs and contact pairs.  
         [0007]     DE 100 51 097, which has not yet been published, discloses a strain relief device for a plug connector for communications and data technology. The strain relief device in this case comprises an essentially U-shaped base part for holding at least part of the plug connector and of a cable which can be connected to the plug connector, with the base part being formed with the first latching means, and closure means, with the closure means being formed with second latching means, which form a latching connection with the first latching means on the base part. The base part is formed, on the lower face of the limbs, with guides which point inward, run parallel, and run at right angles to a rear wall of the base part. In the upper region, on the inside of the limbs, the base part is formed with in each case one obliquely running guide edge. The obliquely running guide edges are in this case designed to be complimentary to the guide edge of a cable manager. When the base part is put onto the cable manager and a plug connector housing, the cable manager is moved in the direction of the plug connector housing, and latches with it. During this process, the cable conductors make contact with the electrical contacts in the plug connector housing. Furthermore, the base part has two jaw parts which can be bent together and are articulated in a sprung manner on a base which is arranged on the upper face of the guide edges. The jaw parts are in the form of steps on the sides. Four openings, in the form of elongated holes, are arranged on each of the two sides on the upper face of the base. In the internal region, the two jaw parts are formed with pyramid-like structures. A spring, which acts as a locking means, can then be inserted into the openings, and a rigid closure element can be latched on. The essentially U-shaped closure element is for this purpose formed on the insides with latching troughs, which latch in on the legs of the spring. The known strain relief device has the disadvantage that its design is mechanically relatively complex owing to the moving jaw parts, which means that it must be manufactured from plastic.  
       SUMMARY  
       [0008]     The invention is thus based on the technical problem of providing a strain relief device for a plug connector for communications and data technology, which, while having a simpler mechanical design, allows a defined force fit and defined alignment of the cable and plug connector.  
         [0009]     For this purpose, the strain relief device has a base part for holding at least part of the plug connector and a cable which can be connected to the plug connector, with the base part being designed with first latching means, and closure means, with the closure means being designed with second latching means which form a latching connection with the first latching means on the base part, in which the closure means are in the form of a spring comprising two limbs which can be pushed along a guide onto the base part, with the base part being designed with at least one support point for the spring, and the spring being designed such that an opposing force, which is produced by the cable moves the second latching means, which are arranged on the limbs, toward the first latching means on the base part. There is thus no need for any sprung elements on the base part, so that the base part need not necessarily be produced from plastic but, for example, can also be produced as a die casting which, apart from increased strength, also has considerable cost advantages.  
         [0010]     In one preferred embodiment, the spring is essentially W-shaped.  
         [0011]     In one preferred embodiment, the spring is designed with a concave indentation in the middle, so that the spring can rest against the cable circumference.  
         [0012]     The latching means of the spring are preferably in the form of latching hooks, which are preferably formed by a region cut free from the limbs of the spring.  
         [0013]     In one preferred embodiment, bends are arranged at the free ends of the limbs of the spring, in order to make it easier to detach the spring from the base part when required.  
         [0014]     In one preferred embodiment, the base part is designed with a moving head part on which the first latching means are arranged. This allows cables of different diameter to be fixed such that they are centered, so that the cable conductors are always secured in a defined position with respect to the plug connector contacts.  
         [0015]     In a further preferred embodiment, the head part can be latched as a separate component, in a captive manner, on top of the base part. Designing it as a separate component simplifies manufacture, since there is no need to manufacture any moving parts while, on the other hand, the captive attachment makes it possible to handle the base part and the head part as a single component during use.  
         [0016]     The component is preferably designed with an incline which runs upward inward, with the base part having a depression behind the incline. The head part then has a latching tab which can be pushed over the incline and then slides into the depression in a captive manner.  
         [0017]     The head part is preferably designed to be completely symmetrical on the upper face and lower face.  
         [0018]     The strain relief device can at the same time also be used to make contact with a cable shield. In this case, the base part is preferably structured on the inside, in order to improve the contact quality. This structuring may, for example, be pyramid-shaped.  
         [0019]     In order to improve the contact quality further, a spring may also be formed with beads in the region of the concave indentation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The invention will be explained in more detail in the following text using a preferred exemplary embodiment. In the Figures:  
         [0021]      FIG. 1  shows a perspective exploded illustration of a strain relief device for a plug connector,  
         [0022]      FIG. 2  shows a perspective exploded illustration of the strain relief device with a female connector body and a cable to be connected, and  
         [0023]      FIG. 3  shows a perspective illustration in the assembled state. 
     
    
     DETAILED DESCRIPTION  
       [0024]     The strain relief device  1  has a base part  10 , closure means  30  and a head part (i.e., latching member)  40 . The base part  10  has two side walls  11 , a rear wall  12  and an upper part  13 . Guide edges  14  are arranged on the lower face of the side walls  111  and are at right angles to the rear wall  12 . Guide edges  15 , which run obliquely toward the rear, run on the upper face of the side walls  11  and on the lower face of the upper part  13 . In the front region, the upper part  13  has a rounded cutout for holding a cable, which is not shown. On the side facing the rear wall  12 , the upper part  13  has an incline  16  which runs inward and upward, and behind which a depression  17  is located. Two guide elements  18  are arranged in the front, side region of the upper part  13 . Each guide element  18  firstly forms a guide  19  on the inside, and a guide  20  on the outside. In the region of the guide  20 , the side wall  11  is raised somewhat above the upper part  13  in the front region, and forms a first support point  21 . Furthermore, in the front region of the guide  20 , the guide element  18  has an angle  22 , which points downward and forms a second support point. In addition, the side walls  11  have indentations  23  on the insides.  
         [0025]     The closure means  30  are essentially in the form of a W-shaped spring with two limbs  31 . Angles  32  which point outward are arranged on the free ends of the limbs  31 . The limbs  31  are each formed with a latching hook  33  which points inward. The closure means  30  include a central support element  34  configured to about cable  51 , The central support element  34  of the W-shaped spring forms a concave bulge. Four beads  35  are introduced into the spring in the region of the concave bulge  34 .  
         [0026]     The head part  40  is essentially U-shaped. The free limbs are in this case formed as a smooth guide edge  41  on the outside in the front region, and as an incline  42 , which runs outward, on the inside. In the front region, the limb is stepped and is designed to be set-back, thus forming a further guide surface  43 . In the rear region, the limbs are formed with ribs  44  on the outside. There is in each case a latching tab  45 , which runs obliquely upward toward the rear, centrally on the upper face and lower face of the head part  40 . Pyramid-like structures  46  are arranged in the inner, central region of the head part  40 . Furthermore, material-saving cutouts  47  are provided in the rear region of the head part  40 . The transition from the guide edge  41  to the outside with the ribs  44  forms a stop surface  48 . The stop surface  48  is preferably inclined, with the rear wall of the guide element  18  being inclined in a correspondingly complimentary manner. The head part  40  is preferably designed to be completely symmetrical on the upper face and lower face.  
         [0027]      FIG. 2  shows the strain relief device  1  with a female connector housing  50  and a cable  51 . The female connector housing  50  has, on its upper face, a cable manager  52  with inclines  53 , which are designed to be complimentary to the guide edges  15  on the base part  10 . The cable manager  52  has the function of guiding and positioning the conductors of the cable  51  in a defined manner. For this purpose, the conductors are routed from the upper face of the cable manager  52  through an opening, and are firmly clamped in a defined manner on the lower face, which cannot be seen, of the cable manager  52 . The cable manager  52  is then placed on the female connector housing  50  with the conductors, positioned on the lower face, then being located above associated insulation-displacement terminal contacts, but not yet being pressed into them. This situation is illustrated in  FIG. 2 . The insulation-displacement terminal contacts are arranged in the interior of the female connector housing, and thus cannot be seen in  FIG. 2 . In a first preparatory step, the head part  40  is first of all pushed onto the base part  10 . In the process, the latching tab (which is arranged on the lower face of the head part  40 , cannot be seen in the illustration but is identical to the latching tab  45  which can be seen on the upper face) runs along the incline  16  and then slides into the depression  17 . In the process, the rear wall of the depression  17  forms a stop for the head part  40 , so that they are connected to one another in a captive manner. The forward movement of the head part  40  is limited by the guide element  18 , since the head part  40  with the guide edges  41  can be moved only along the guide  19 . Once the guide edges  41  have been completely inserted, then the stop surface  48  abuts against the rear face  24  of the guide element  18 . The head part  40  is thus connected to the base part  10  such that it can move in a restricted manner. The range of movement is in this case preferably restricted to half of the cable diameter variation, as will be explained in more detail later.  
         [0028]     In a next step, the base part  10  is pushed with the connected head part  40  onto the female connector housing  50  along the guide edges  14  and  15 . Owing to the incline on the guide edge  15 , the cable manager  52  is in the process pressed downward in the direction of the rest of the female connector housing  50 . The conductors, which are positioned in the cable manager  52 , are thus pressed into the insulation-displacement terminal contents. The guide edge  15  in this case acts like a drive, converting a sliding movement into a vertical movement. This makes it possible for the necessary contact-making force to be distributed more uniformly, so that contact can be made with the conductors, without any further tool, by means of the base part  10 .  
         [0029]     Once the base part  10  has been pushed onto the female connector housing  50 , the closure means  30  can be latched on. To do this, the limbs  31  are moved along the guide  20  until the latching hooks  33  latch in a rib  44  on the head part  40 . The diameter of the cable  51  determines which of the ribs  44  the latching hooks  33  latch into. The limbs  31  of the sprung latched-on closure means  30  are, in this case supported on the support point  21  and on the angle  22 . Any opposing force from the cable  51  results in compression of the internal spring regions, thus producing a spring force which acts outward on the outer limbs  31 . Since the outer limbs  31  are fixed by the support point  21  and the angle  22 , this spring force leads to the free ends of the limbs  31  moving in the direction of the base part  10 . The latching hooks  33  are thus pressed more deeply into the ribs  44  and counteract the opposing force. This results in virtually unlimited strain relief for the cable  51 .  
         [0030]     Particularly in plug connectors with high data transmission rates, such as Category 5 or Category 6 plug connectors, the conductors and the contacts must be arranged in a precisely defined manner with respect to one another. In this case, it is also important for the cable to be aligned in a defined manner with respect to the cable manager  52 . If the base part  10  were now rigidly connected to the head part  40 , then the closure means  30  would need to be pushed on to a different extent for different cable diameters and would be the only means to compensate for the different diameters. However, this would mean that the cable  51  was bent to a different extent, which is undesirable, however, owing to the stringent requirements with regard to crosstalk. This is where the mobility of the head part  10  comes into play. In this case, a different cable diameter is compensated for equally by the head part  40  and by the closure means  30 , so that the cable is always at right angles to the cable manager  52 , irrespective of its diameter. For this purpose, the base part  10  together with the head part  40  and the closure means  30  are preferably pushed onto the female connector body  50  at the same time and uniformly. The strain relief device  1  thus allows cables  52  of different diameter to be secured such that they are centered. In this case, half of the additional cable diameter is compensated for by the movement of the head part  40 , and the other half is compensated for by the closure means  30 , whose latching hooks  33  latch into one of the front ribs  44 .  
         [0031]     Furthermore, the strain relief device  1  can also be used to make contact with the shield. For this purpose, the base part  10  and the head part  40  are preferably in the form of zinc die-cast parts, which are thus electrically connected to one another. Depending on whether the shield  55  is a foil or a wire mesh, the shield  55  is bent upward over the insulation of the cable  51  while parts are being fitted to the cable manager  52 . When the strain relief device  1  is being fitted to the female connector body  50  and to the cable  51 , the head part  40  then makes contact with the shield  55  via the pyramid-like structures  46 , and the closure means  30  make contact with the shield  55  via the concave indentation  34  and the projecting beads  35 . At the same time, the base part  10  makes contact with the ground plate  54  in the female connector body  50 , so that the shield  55  can then be connected to ground via the ground plate  54 .  
         [0032]      FIG. 3  shows the completely assembled strain relief device. As can be seen, the cable  51  is clamped in the region of the bent-up shield  55  by the concave region  34  of the W-shaped spring and by the structures of the head part  40 , with the latching hooks  33  being latched into the ribs  44  on the head part  40 . As can also be seen, the guide surface  43  of the head part  40  rests on the upper edge of the guide element  18 . The free limbs  31  of the W-shaped spring are supported by the support point  21  and by the angle  22  on the front part of the base part  10 .