Abstract:
For optical waveguide connections that can be freely laid for transmitting optical signals, there is proposed, in accordance with the dimensions specified by the MOST Co-operation of the automobile manufacturers, a releasably formed optical plug-in connector for an modular connector system that comprises two casing parts that can be inserted in one another. In this connection, there is inserted in a casing a mounting part that receives optical waveguides provided with ferrules, wherein the ferrules of the optical waveguides are provided with a reference surface. 
     A defined distance for an optimized signal transmission from the end face of the optical waveguides reaches by a stop of said reference surface when assembled with a reference surface of a counterplug.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an optical plug-in connector having optical waveguides held in ferrules for the pluggable connection to a counterplug. 
     Optical plug-in connectors are needed for the mechanical and optical connection of optical waveguides for an interference-immune transmission of analog and/or digital signals at high data transmission rates in the communications engineering sector. 
     It is known to connect together optical waveguides having a plug and counterplug, or having an expensive combination of plug-coupling-plug together. 
     2. Prior Art 
     U.S. Pat. No. 6,102,581 discloses an optical adapter having ferrules that can be plugged together, in which ferrules for coupling optical waveguides are held in specially manufactured ferrule casings that are in turn plugged together in an adapter casing, it being possible to combine ferrules of different size with one another. 
     Furthermore, U.S. Pat. No. 5,674,812 describes a mounting for optical plug-in connectors in which two separate optical plug-in connectors are latchably combined in one mounting. 
     In this connection, in the known optical plug-in connectors, the arrangement of the fiber end sleeves and their mounting in a plug casing have to be matched precisely to one another for correct plugging with minimal signal attenuation, it being necessary to take account of the error tolerances of the plug-in connector casing and also the fiber end sleeves during manufacture. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is therefore to develop an optical plug-in connector of the type mentioned at the outset so as to reduce the error tolerances necessary for a minimum signal attenuation in the arrangement of fiber end sleeves provided with optical waveguides in a plug casing and in a counterplug to a minimum extent. 
     This object is achieved by a plug-in connector wherein the plug-in connector has a mounting part for at least one optical waveguide held in a ferrule, wherein the ferrule has a reference surface formed by a collar with a defined distance between the reference surface and the end face of the optical waveguide, and wherein, when the plug-in connector is plugged together with a counterplug, the reference surface comes to a stop at a reference surface of a ferrule of the counterplug, and wherein the reference surfaces are fixed in a defined distance. 
     The advantages achieved by the invention are firstly that the external design and the plug face of the optical plug-in connector comply with the dimensions which have been laid down by the automobile manufacturers in the so-called MOST Co-operation, are compatible with it, but are also capable of being produced more inexpensively and is easier to manipulate during assembly. 
     A further advantage is in the use of optical waveguides that are provided with ferrules and that have a mechanical coding means for non-interchangeable fitting in the plug-in connector. This eliminates faulty plugging that may result in unserviceability or, under some circumstances, in a destruction of electrical components. 
     Furthermore, an additional pull relief for the optical waveguides via the casing is unnecessary since the fiber end sleeves are directly crimped onto the fiber and additionally onto the cladding and, consequently, the tensile forces are first convoyed to the ferrules and only then onto the plug-in connector casing. In this connection, the basic principle advantageously applied here of a body of revolution mounted in a casing for mounting an optical waveguide can also readily be extrapolated to similar variants, for example those involving an electrical conductor. 
     An important advantage is, however, in the direct coupling of the ferrules to one another, the reference surfaces formed by the stop of a collar relative to a defined distance from the end faces of the fiber, the ferrules held in the plug casings, being held axially against one another. In this connection, the ferrules in the counterplug are additionally provided with a compression spring that effects a constant contact pressure of the two ferrules. 
     Consequently, the dimensional tolerances of the plug casing that normally also enter in addition into the error consideration are eliminated relative to the signal transmission attenuation. 
     Because of the necessary manufacture of only two components, a mounting part for the optical waveguides provided with ferrules and a casing made by plastic injection moulding technology, an inexpensive manufacture of such optical plug-in connectors is possible. 
     Advantageously, the ferrules provided with coding means, which are in this case regions projecting from the cylindrical turned part of the sleeve body placed in matchingly designed, negatively shaped chambers of the mounting part in a non-interchangeable manner and held at the same time by the shaping of the chambers in the latter. 
     It is furthermore advantageous that the mounting part with the inserted ferrules can already be used as plug-in connector, but can also be provided with a casing depending on the field of application. 
     If an additional casing is used, in the case of assembly or preparation of the plug-in connector, the already advantageously prelatched parts of mounting part and casing are supplied as a single piece and completed solely by insertion of the ferrules provided with optical waveguides and, finally, latched together by further pushing into one another. 
     Forming two latching plugs arranged at a distance one behind the other on each side of the mounting part first achieves during the assembly a preliminary latching with the latching of the first latching lug into a recess, the two casings thereby first being held loosely together. Only after the second latching lug pair has been latched into the recesses is the mounting part audibly latched to the casing. 
     A further securing latching is formed in a fold-down manner on the casing. In this connection, this latching is advantageously kept open in its rest position by a hinge mechanism by means of a spring element so that the ferrules can be inserted into the mounting part without difficulty. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     An exemplary embodiment of the invention is shown in the drawing and is explained in greater detail below. In the drawing: 
     FIG. 1 shows a perspective view of an optical plug-in connector, 
     FIG. 2 a  shows a plan view of a mounting part of the plug-in connector, 
     FIG. 2 b  shows a side view of the mounting part on the lead-in side for the optical waveguide, 
     FIG. 3 a  shows a side view of the casing with latching means opened, 
     FIG. 3 b  shows a view of the casing on the lead-in side for the mounting part, 
     FIG. 4 shows a plan view of the mounting part with ferrules, 
     FIG. 5 a  shows a sectional view of the not connected plug-in connector with a counterplug, 
     FIG. 5 b  shows a sectional view of the connected plug-in connector with a counterplug, and 
     FIG. 6 shows an exploded, perspective view of the optical plug-in connector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective view of an assembled plug-in connector  1  having a surrounding casing  20  and a mounting part  10  inserted therein in which the plug face of the plug casing is provided with fibers all round the outside edges, which fibers ensure simple insertion into a counterplug. 
     Inside the plug face, ferrule  3 ,  3 ′ with optical waveguide  4  held therein can be discerned in two cylindrical recesses. 
     FIG. 2 a  shows a plan view of the mounting part  10  of the optical plug-in connector  1 . 
     The mounting part comprises a shell structure that is formed from two mutually adjacently situated, elongated chambers  11 ,  11 ′ that are also open upwards on both sides. 
     The internal dimensions of the differently shaped chambers match as a negative shape the ferrule  3 ,  3 ′ to be inserted therein, but are so dimensioned that, when the ferrule are inserted, a pressing action is exerted on them to effect an automatic mounting of the ferrule in the chambers. 
     Furthermore, there are provided in the chambers  11 ,  11 ′ to match the ferrule coding means that are formed in the shape of projecting ribs  13 ,  13 ′ that are formed on transversely to the plug direction and that ensure an error-free assembly of the ferrules. 
     Provided on both sides of the outer side walls of the mounting part  10  are a plurality of latching lugs  14 ,  15  that each latch into a matching recess  23  in the casing  20  and in total form a first latching means. 
     An individual latching lug  16  formed on in the edge region of a sidewall is provided for latching the finally assembled plug-in connector to a counterplug not shown here. 
     Provided in the center of the mounting part between the two chambers  11 ,  11 ′ is a slot  12  proceeding from the plug side and comprising at least half the casing length into which a partition  22  of the casing  20  is inserted during the assembly of the plug-in connector (FIG.  5 ). 
     FIG. 2 b  shows the mounting part  10  with a view onto the lead-in side  18  for the optical waveguide. 
     The external contours of said region  18  are offset from the front plug region (as can be seen from FIG.  5 ), constructed with a thicker wall and increased in height and width, since this region comes up against the wall of the casing  20  during assembly and, to that extent, has the same dimensions without a junction as the casing. Provided on both sides underneath the chambers  11 ,  11 ′ on the external wall of the mounting part are symmetrically arranged 45° chamfers  17  as a polarization means that serve for the non-interchangeable plugging to the casing  20 , but at the same time are also necessary as positioning means during the plugging to the counterplug not shown here. 
     In the region of the recesses  19 , a second latching means having a latching block  25  is inserted for final latching of mounting part  10  and casing  20 . 
     FIG. 3 a  shows in a side view the casing  20  with a second means for latching with the latching block  25  folded up through about 90°. On the side face, there can be perceived a rectangular recess  23  that is provided on both sides of the casing and into which, when the mounting part  10  and the casing  20  are pushed together, the latching lug pair  14  is first inserted so that mounting part and casing are latched in a preliminary manner. During further insertion, the second latching lug pair  15  audibly latches at the stop of the two parts  10 ,  20  (FIG.  1 ). 
     FIG. 3 b  shows the casing  20  with a view of the lead-in side for the mounting part  10 . 
     The casing is provided as a rectangular hollow body with a central longitudinal wall  22  and has two mutually adjacently situated chambers  21 ,  21 ′ open on both sides. 
     Underneath each of the chambers  21 ,  21 ′ on both sides there are perceivable external contours  38 , inclined through about 45° that, in interaction with matchingly shaped counterpieces of a counterplug not shown here, are provided as polarization to prevent incorrect plugging. Furthermore, such chamfers  37  are likewise provided inside the two chambers  21 ,  21 ′ in the lead-in side for the mounting part into which the similarly shaped chamfers  17  of the mounting part  10  can be inserted. 
     The chambers  21 ,  21 ′ are of circular design in the front plug region of the ferrules, as can already be seen from FIG.  1 . 
     Provided above the two chambers  21 ,  21 ′ the second latching means that is formed as a double latching and that is formed out of the wall of the casing  20  shown here situated at the top and is held by means of film hinges  28 . 
     In this connection, for each chamber there is provided latching means with a latching block  25  disposed above the chamber and held together because of the small dimensions by means of a transverse joint  29  so that only one device has to be actuated to latch mounting part  10  and plug casing  20 . 
     In total, four webs  26  are provided with film hinges  28 , of which two are joined in each case by a connecting web  24  to each of which a latching block  25  is attached. Both latching blocks are joined to one another by means of the transverse joint  29 . 
     Formed on between each of the webs  26  in the direction of the chambers  21 ,  21 ′ is a spring element  27  whose end is not joined to the casing  20 , but whose length extends beyond the material thickness of the casing down into the interior of the two chambers. This achieves for said latching means a hinge mechanism that holds the latching block  25  in its open rest position until the assembly of the plug-in connector has been completed or the latching means is folded down if necessary. 
     FIG. 4 shows a plan view of the mounting part  10  and ferrules  3 ,  3 ′, inserted in the latter, with optical waveguides  4  again held therein. 
     This version is provided for a modular system plug-in connectors with a higher number of poles in which a surrounding casing  20  around the mounting part  10  can be dispensed with. Both ferrules  3 ,  3 ′ are designed as metallic sleeves and are crimped directly onto the fiber by means of a crimping operation and also onto the cladding of the optical waveguide  4 . 
     By forming a simple collar  32  or a double collar  33 ,  34  out of the preform of the ferrules  3 ,  3 ′ and also by means of recesses  35 ,  36 , the ferrules are provided with mechanical codings that make it possible to insert only into a matching negative form. 
     The matching counterpieces to the codings are provided in the two chambers  11 ,  11 ′ of the mounting part  10 . 
     For this purpose, there is formed on in the chamber  11 ′ in the front plug region a transverse rib  13 ′ into which only the recess  35  of the fiber end sleeve  3 ′ can be inserted. 
     Formed on in the chamber  11  in the front plug region are two transverse ribs  13  between which only the ferrules  3  having the narrow collar  34  and the recesses  36  on both sides thereof can be inserted. 
     On the plug side of the ferrules, it is possible to perceive the terminating edges of collar  32  and  33  that are formed perpendicularly to the plug direction and that each form a reference surface  31  that is at a defined distance (A) from the end face of the ferrules. 
     When assembled with a matchingly shaped counterplug, its reference surface comes up against the reference surface  31  and a defined distance of the end faces of the two ferrules is ensured so that manufacturing tolerances of the casing surrounding the two ferrules are eliminated. 
     FIG. 5 a  shows in a sectional view the ferrule  3 , which is held within the plug-in connector  1 . The ferrule is formed with a collar  32 ,  33  and a perpendicularly reference surface  31  and a defined distance A between the reference surface and the end face  30 . 
     A ferrule  5  with an according form to the ferrule  3  is held within the counterplug  2  wherein the defined distance B is between the inner end face  52  and the reference surface  51 . 
     FIG. 5 b  shows in a sectional view the connected plug-in connectors  1 ,  3  wherein between the both reference surfaces  30 ,  52  is a defined distance C for an optimized signal transmission. 
     FIG. 6 shows a perspective and exploded view of a plug-in connector comprising the components: casing  20 , mounting part  10  and also the ferrules  3 ,  3 ′ in which the optical waveguides  4  are held. 
     When the plug-in connector is assembled, the ferrules  3 ,  3 ′ provided with the optical waveguides are first inserted into the half open chambers  11 ,  11 ′ and are clamped therein by a matching dimensional accuracy and forming of the chamber walls. 
     Then the mounting part  10  with the ferrules is pushed into the casing  20 , in which process the latching lug  14  first latches into the recess  23  and effects a preliminary latching between mounting part and plug casing. When pushed further in, the latching lug  14  slides further forward in the recess until the second latching lug  15  likewise latches in the recess  23 . 
     The mounting part  10  is consequently positively held up to the stop in the casing  20 , the region  18  adjoining the external contours of the casing  20  flushly. 
     When the second latching means with the latching block  25  is swung down, casing  20  and mounting part  10  are finally latched, but are releasable again. 
     Provided as a further type of mounting, the mounting part  10  is first preliminarily latched by means of the latching means comprising latching lug  14  and recess  23  in the plug casing  20 , then the ferrules with the optical waveguides are inserted into the chambers  11 ,  11 ′ of the mounting part, the mounting part and casing are subsequently pushed together and are latched to one another by means of the second latching means. This has the advantage that, to assemble the optical plug-in connectors, mounting part and plug casing are already delivered as one part and only the ferrules have to be inserted.