Abstract:
A device useful in the field of digital telecommunications, particularly for on-site mounting of a connector on a coaxial cable which has a portable clip ( 10 ) adaptable to the diameter of the coaxial cable in order to immobilize the cable. The clip includes a base with a first edge, an opposed second edge and a reference plane formed therebetween. The reference plane supports the coaxial cable and includes a groove formed therein adapted to receive a ferrule of a connector.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device used for the on-site fitting of a connector on a coaxial cable. The application of the invention lies, more particularly, in the field of digital telecommunications. 
     Links within a telecommunications network are made using cables and directional radio. Directional radio involves point-to-point links using microwaves in the range 1 GHz-50 GHz as the transmission medium. A radio link makes it possible to establish two-way communication between two terminal stations, it being possible for the communication to be routed via intermediate stations separated from one another by about 50 kilometres. Each station is then connected to a telecommunications landline network. 
     The equipment of these stations essentially consists of an antenna and a transmitter/receiver. The antenna is usually composed of a horn-shaped aperture which radiates a wave carried by a wave guide, and one or more deflectors of parabolic general shape. The radiating aperture is always located at the focus of the parabola. The waveguide is connected by its other end to a transmitter/receiver located in a room close to the antenna. 
     However, the waveguide is a very expensive transmission medium. Therefore, in order to limit the length of the waveguide, the transmitter/receiver has for some years been installed directly on the antenna. The transmitter/receiver is then connected to the antenna via a short waveguide and to the telecommunications landline network via a coaxial cable which is less expensive than the waveguide. 
     The coaxial cable is a high-frequency medium consisting of an inner copper conductor surrounded by a concentric screen, made of copper or aluminium and in principle at the potential of the earth. They are separated by a polyethylene dielectric. The cable is furthermore covered with an insulating sheath. 
     In order to make it easier to install the coaxial cable on the pylon which supports the antenna, and in order to adjust its length optimally, the connector joining the cable to the transmitter/receiver is fitted once the cable is in place. The connector essentially comprises a core and a ferrule. The core is a hollow metal rod into which the central conductor of the coaxial cable is inserted and soldered. The ferrule is a metal ring which will be placed around the screen of the cable. 
     The operations which need to be carried out on the coaxial cable when fitting a connector to the cable are essentially operations of cutting and stripping the insulating sheath of the cable. This preparation of the cable is followed by a step of positioning and welding the elements of the conductor on the coaxial cable. 
     FIGS. 1A and 1B illustrate the positioning of two types of connectors on coaxial cables having different diameters. In both figures, a connector consisting of a core  1  and a ferrule  2  is fitted on a coaxial cable  3 . Orifices  5  and  6  are provided respectively in the core  1  and in the ferrule  2  in order to solder the core  1  on the central conductor  4  of the coaxial cable  3 , and the ferrule  1  on the screen of this coaxial cable  3 . The connectors which are represented are of the N type in FIG.  1 A and of the TNC type in FIG.  1 B. The dimensions of the elements of the connectors differ according to the type of connector. The positioning of the core  1  on the coaxial cable  3  is represented by a value d in FIG.  1 A and by a value d′ in FIG.  1 B. These values represent the distance between a shoulder situated close to the tip of the core and the end of the polyethylene dielectric. The values d and d′ are respectively 15 millimeters and 6 millimeters. 
     The quality of the fitting of the connector on the coaxial cable is of essential importance in the field of digital telecommunications. This is because the transmission of digital data will not tolerate possible bad contacts in the connector. Bad contacts of this type often give rise to synchronization losses or breaks in connection. 
     However, it may sometimes be very difficult to fit the connectors. This is because the operation is generally carried out on site, at windy places and in all weathers. In the case of maintenance, these unfavourable working conditions are further aggravated by the fact that it is common practice to work at night, when the network activity is less. 
     It will then be understood that all these conditions can lead to connection faults. 
     OBJECT AND SUMMARY OF THE INVENTION 
     One object of the invention is to provide ergonomic tools for the on-site fitting of a connector on a coaxial cable. 
     To this end, the invention consists of a device used for on-site fitting of a connector on a coaxial cable, characterized in that it includes a portable clip which can be adapted to the diameter of the coaxial cable in order to immobilize the coaxial cable. 
     In order to make it possible to grip the coaxial cable by hand for the operations of cutting and stripping the cable, the clip may have a cylindrical external shape of appropriate diameter. In a preferred embodiment, this diameter is about 4 centimeters. This clip will then constitute a device which makes it easier to hold the end of a coaxial cable in one hand. 
     For the operations of soldering the core and the ferrule of the connector, another device may be provided which is characterized in that it includes a clip having at least one channel for receiving a coaxial cable, as well as positioning means for putting the connector elements in position for assembly on the coaxial cable. 
     The clip preferably comprises two channels, each for receiving a coaxial cable with a different diameter. 
     Furthermore, fastening means are provided for fastening the device to a point of the site, for example on a pylon element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages of the invention will become apparent on reading the following detailed description, which is given with reference to the appended drawings, in which: 
     FIGS. 1A and 1B are diagrams of the positioning of two types of connectors on two coaxial cables of different diameters; 
     FIGS. 2A and 2B are respectively an exploded view and a sectional view of a device according to the invention for gripping a coaxial cable by hand; 
     FIGS. 3A to  3 C respectively represent a front view, a profile view and a side view of a device for holding and positioning the end of a coaxial cable with respect to a connector according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A and 1B have already been described in the preamble of the description. 
     FIG.  2 A and FIG. 2B are respectively an exploded view and a sectional view of a device  10  according to the invention for gripping a coaxial cable by hand. Because they complement one another, these two figures will be described together. This device  10  is a portable clip which adapts to the diameter of a cable by means of a cable clamp. It is composed of three elements: a female part  11 , a male part  12  and a cable clamp  13 . 
     The female part  11  essentially comprises a cylindrical body whose diameter and external surface condition are designed so that they can be gripped readily by hand. The diameter of the cylindrical body is about 4 to 5 centimeters. A bore  14  for receiving an end-piece  15  of the male part  12  passes axially through this body. This bore  14  continues in the channel  16  for passing a coaxial cable through. The bore  14  is screw-threaded near its entry orifice, while at its inner end it terminates in a conical bearing surface  17  forming the junction with the channel  16 . The conical bearing surface  17  is intended to interact with the cable clamp  13 . 
     The cable clamp  13  is inserted like a piston into the bore  14  of the female part  11 . This cable clamp  13  consists of a cylindrical ring  18  continuing in a set of jaws  19  with conical ends, interacting with the conical bearing surface  17  of the female part  11 . The male part  12  abuts against the cable clamp  13 . 
     The male part  12  consists of a cylindrical part with the same diameter and the same external condition as the female part  11 . This cylindrical part continues in a screw-threaded end-piece  15  intended to be screwed into the screw-threaded part of the bore  14  of the female part  11 . 
     Furthermore, a channel  20 , through which a cable is intended to be passed, extends axially through the male part  12 . When this male part  12  has been engaged in the female part  11 , the channel  20  lies in continuation of the channel  16  of the female part  11 . 
     It is very simple to use this tool for holding a coaxial cable. First, the male part  12  is unscrewed from the female part  11 , so that the set of jaws  19  is in an open position. Secondly, the coaxial cable is passed through the channel  20 , the ring  18  and the channel  16 , and the male part  12  is screwed on. 
     As the end-piece  15  moves through the bore  14 , the set of jaws  19  closes on the cable and locks it in place. 
     This tool allows the coaxial cable to be gripped substantially better by hand. In particular, it allows gloves to be kept on when carrying out the stripping operations on the coaxial cable. 
     FIGS. 3A to  3 C are respectively a plan view, a profile view and a side view of a positioning device  21  according to the invention, used for holding and positioning a coaxial cable and a connector with a view to assembling them. As with FIGS. 2A and 2B, FIGS. 3A to  3 C will be described together. For the sake of clarity, an element which is labelled  39  is not represented in FIG.  3 B. Furthermore, a coaxial cable provided with a connector is placed in the positioning device  21  in order to illustrate the use of the device. 
     The positioning device  21  comprises a base  22  continuing vertically on one side in a first edge  23 , and on the opposite side in a second edge  24 . On top of the first edge  23 , there is a clamping block  25  intended to form a clip for locking a coaxial cable  26  in place. The clip has two channels  27  and  28  for receiving the coaxial cables. Each channel consists of two grooves made transversely in the opposing surfaces of the edge  23  and the clamping block  25 . The cross-sections of the different channels are preferably adapted to different diameters of coaxial cable. A clamping screw  29  passes vertically through the block  25  and engages in the edge  23  in order to make it possible to lock the coaxial cables  26  in place in their respective channels. 
     The base  22  also comprises a reference plane  30  on which the coaxial cables  26  bear. This reference plane  30  lies in continuation of the channels  27  and  28  of the clip and is delimited, on one side, by the edge  23  and, on the other side, by a groove  31 . The groove  31  makes it possible to position the ferrule of the connector on the screen of the coaxial cable once the latter has already been cut and stripped. The width and depth of the groove  31  are designed so as to obtain optimum purchase of the ferrule in the groove  31 . A lip  32  of the groove  31  is slightly raised so that the dielectric of the coaxial cable abuts against this lip. 
     Furthermore, the device  21  also includes means for positioning and holding the core of the connector on the central conductor of the coaxial cable. This is why the second edge  24  has two knurled screws  33  and  34  passing through it, the screws being positioned respectively in alignment with the axes of the channels  27  and  28  of the clip. The stems of the knurled screws are axially pierced close to their free end in order to receive the core of the connector, the inner conductor of the coaxial cable having already been inserted into the core of the connector. The length of the stems of the knurled screws depends on the type of connector which will be fitted on the coaxial cable. 
     In order to make it possible to fit two types of connector on the same model of coaxial cable, a hammerhead-shaped stop  35  is provided. The stop  35  then makes it possible to adjust the length of the stem of the screw  34  emerging from the edge  24 . The stop  35  is produced in such a way that it can move along the edge  24  and is kept fixed to this edge by a knurled screw  36 . Notches  37  on the edge  24 , and a notch  38  on the stop  35 , make it possible to position the stop  35  accurately relative to the knurled screw  34 . 
     Finally, a support  39  is provided in order to attach the positioning device  21  to a separate structure  40  (e.g., a pylon element) using, for example, a vise or clamping collars.