Abstract:
A connector is specified having a housing ( 1 ) with at least one holding shaft ( 2 ) for a complementary plug ( 3 ), the connector respectively having a spring arm ( 4 ) which bounds the holding shaft ( 2 ) on one side, presses on the corresponding side of the complementary plug ( 3 ) and locks the plug ( 3 ) there in its inserted position, and by a bow ( 5 ) as secondary locking mechanism, which holds the free end ( 6 ) of the spring arm ( 4 ) detachably in the position latched with the plug.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a connector having a housing with at least one holding shaft, the housing adapted to received a complementary plug and to the connector being in the form of an optical waveguide compling. 
     2. Description of Prior Developments 
     For some applications of such connectors, it is of decisive importance that the demountable connection cannot be undone in an uncontrolled fashion, and that it is completely certain that the plug parts are also plugged into one another correctly and completely. 
     For this purpose, in addition to a first locking mechanism, use is made of secondary locking mechanisms whose actuation is possible only if the plug parts are correctly interconnected, on the one hand, and which, furthermore, prevent the demountable connection from being inadvertently undone. Such demountable connections with secondary locking mechanisms are often complicated and generally comprise a plurality of parts. 
     The present invention relates further to an optical waveguide coupling. It is important in the case of such optical waveguide couplings for the losses in light intensity at the transition from one optical waveguide cable to the other or from an optical waveguide cable to an electro-optical element, having an optical input or output, to be kept as low as possible. For this purpose, it is necessary to keep the surface of the end face of the optical waveguide absolutely free from dust or other contaminants and to ensure this freedom from dust permanently. Moreover, such a coupling must be robust and compact. 
     Known optical waveguide couplings do not presently fulfil these requirements optimally. Thus, U.S. Pat. No. 5,134,676 discloses a fibre optic coupler in which the coaxially opposite fibre ends of optical fibres to be connected crimp between them a diaphragm which is transparent and has the same refractive index as the optical fibres themselves. The result is to produce a good optical transition between the fibres to be connected. However, owing to the mechanical contact between the end faces of the optical fibres and the diaphragm there is the risk of dust particles located thereon scratching the end faces of the optical fibres, in particular if the coupling is quite frequently undone and reconnected. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve a connector of the type mentioned at the beginning in such a way that it has a secondary locking mechanism which can be designed in one piece with the connector housing, is compact and is easy to operate. 
     It is therefore another object of the present invention to present an optical waveguide coupling which is tight against dust, liquid and gaseous media, is compact, is very secure against being pulled out inadvertently, and is easy to operate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These objects are achieved in accordance with the claims  1  and  6 , respectively. Preferred embodiments of the invention are explained in more detail in the subclaims with reference to the drawing, in which: 
     FIG. 1 shows a perspective view of a connector according to the invention, 
     FIGS. 2A to  2 C show longitudinal and cross-sections through the connector shown in FIG. 1, 
     FIG. 3 shows a second embodiment of the connector according to the invention, 
     FIG. 4 shows a longitudinal section through the optical waveguide coupling according to the invention, 
     FIG. 5 shows a perspective side view of the optical waveguide coupling according to FIG. 1, and 
     FIG. 6 shows an optical waveguide coupling with integrated electro-optical elements. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The connector shown in FIG. 1 has a housing  1 , which is essentially cuboidal and has, on the left-hand side, the opening of a holding shaft  2  for a complementary plug  3 . The upper housing surface has a spring arm  4  whose free end  6  is located in the vicinity of the inlet of the holding shaft  2  and which is surrounded by a bow  5  which, on the one hand, is separated from the rest of the housing by cutouts in the side walls and in the inlet region of the holding shaft and, on the other hand, is fastened to the housing by thin struts  10   a ,  10   b  in the end region of the bow with the result that compressing the limbs  7   a ,  7   b  of the bow  5  has the effect of moving the end face  8  of the bow forwards, that is to say against the plug-in direction of the complementary plug. In its rest position, that is to say when the two bent limbs  7   a ,  7   b  are not compressed, the end region of the bow  5  is situated such that the free end of the spring arm  4  presses elastically against said bow. This ensures that the spring arm  4  is secured in the position shown in FIG.  2 C and cannot release the complementary plug  3 . Moreover, it is evident from FIG. 2C that there is constructed on the head end of the spring arm a latching hook  13  which grips a latching nose  12  behind on the top side of the complementary plug  3 . When the complementary plug  3  is inserted into the housing  1 , it firstly pushes away the spring arm  4  via its latching hook  13  over the latching nose  12 , the spring arm  4  latching with the end face  8  of the bow  5 . By compressing the limbs  7   a ,  7   b  this fixture is undone again and the spring arm  4  is pressed under stress against the top side of the complementary plug  3  behind the latching nose  12 . The end region  8  of the bow  5  prevents the spring arm  4  from being able to be detached from this position. This ensures locking in two respects. On the one hand, inadvertent undoing, for example by holding on the cable of the complementary plug  3 , is impossible and, on the other hand, latching cannot be performed until the plug  3  is completely inserted into the housing  1 . 
     Clearly in evidence in FIGS. 2A and 2B are the guide grooves  11   a ,  11   b  in the side walls of the housing  1 , in which the complementary plug  3  is guided by means of correspondingly designed ribs in its side walls. 
     FIG. 3 shows a further embodiment of the connector according to the invention, in which two holding shafts are arranged coaxially in the housing, it being possible for two complementary plugs to be arranged in opposite senses on an axis. This type of multiple connection is used, in particular, in connecting optical waveguide cables, the plugs having end regions with carefully prepared fibre ends which are placed accurately opposite one another at a small spacing from one another, in order to transport light signals from one optical waveguide cable to the other. As is easy to see in FIG. 3, the arrangement is mirror symmetrical, with the result that the secondary locking members are merely doubled by comparison with the embodiment shown in FIG.  1 . 
     The connector described here can be produced in one piece as an injection-moulded part and is very compact. It is very simple to operate, and therefore raises no difficulty even under cramped conditions of space at the installation site. The demountable connection can be in two parts but it is also possible for a plurality of connections to be combined in one housing. 
     The housing, which is sectioned in FIG. 4 in a section coaxial with the axis of the optical waveguide  22 , preferable consists of plastic and is single-storied. The optical waveguide cables  23  to be connected are “stripped” at their ends and are located in optical waveguide connectors of the type described in Patent DE 44 10 444 of the applicants. These are connectors whose cable-side sleeve is crimped with the sheath of the optical waveguide cable  23 , the front end of the connector closely enclosing the optical waveguide. The end face of the optical waveguide connector is treated by a hot-plate method, with the result that it has an absolutely flat and optically acceptable surface. 
     Two such connectors  24  are arranged coaxially and opposite one another in the housing  21  and latched in chambers  22  provided for the purpose. The latching is performed firstly via hooks which are provided at the cable-side end of the connectors  24  and grip the connector behind in the plugged-in position, this hook  20  secondly being additionally secured in its latched position by secondary locking mechanisms  23 . 
     On the cable side, the interspace between the connector  24  and the cable  23  is sealed by an O-ring  27 . Mounted in the chamber  28  of the housing  21  is an O-ring  26 , which is lightly crimped by the head ends of the two optical waveguide connectors  24  and tightly seals a space between the head faces. As a result, the interspace  25  between the end faces of the optical waveguide cables is sealed against dust, liquid and gaseous media, and this reduces optical losses at these interfaces. 
     An optically even more effective transition is produced by eliminating the necessarily occurring refractive index discontinuity at the respective ends of the optical waveguide cables. This is achieved by filling the cavity between the optical waveguide ends and the O-ring  26  with a liquid which has the same refractive index as the optical waveguide fibres themselves. 
     The O-ring is secured in the cutout  28  against inadvertently falling out, this being done by the rear wall  15 , on the one hand, and by retaining noses  14  at the other end of the cutout  28  on the other hand. The O-ring can be removed by using a pin to press it out of the cutout  28  against the crimping force of the retaining noses  14 . 
     The O-ring  26  is centred on the ends of the optical waveguide connectors  24  by virtue of the fact that the head ends of the connector sleeves, which surround the head faces of the optical waveguide fibres, are bevelled outwards. This ensures that the O-ring  26  runs concentrically with the longitudinal axis of the optical waveguide cables  23  and does not disturb the optical transition from one cable end to the other. At the same time, the cable ends or the connector end faces are centred relative to one another, with the result that transition losses are minimized. The reference  20  denotes a latching hook which grips behind the rear edge of the connector  24  in order to lock the latter. 
     As is best to be seen in FIG.  5  and FIG. 6, laterally compressible limbs  16  are further provided, and in the compressed state they release a tongue  13  which grips elastically behind the latch  20  and locks the latter in a secondary fashion. 
     FIG. 5 further shows the opening  28  with the O-ring  26 , which is secured against inadvertently falling out by the retaining noses  14 . On the opposite side, the opening  28  has smaller dimensions than the O-ring  26  with the result that it is possible from there to press the O-ring out of the opening shown only by means of a pin. The windows left free underneath the arms  16  merely serve the purpose of making the arms  16  freely movable, and can simultaneously be used to monitor the proper insertion of the connectors  24  as far as their latching position. 
     FIG. 6 shows an embodiment of the present invention in which a double connector, that is to say two insertion shafts, arranged parallel to one another, for optical waveguide connectors, are provided, opposite which there are two electro-optical elements  18 , with the result that the end faces of the optical waveguide fibres are placed opposite the optical inputs and outputs of the electro-optical elements  18  and the interspace between these surfaces is enclosed by an O-ring in a fashion entirely analogous to the exemplary embodiment shown in FIGS. 4 and 5. The O-rings are again inserted through shafts  28 . The secondary locking of the optical waveguide connectors is performed, in turn, via the tongue  13  which grips behind the latch  10  through being released after actuation of the arms  16 .