Light conductor coupling

A light conductor coupling has a first and a second coupling part which coupling parts are couplable with one another and in each of which a light conducting element is held. At least one of the light conducting elements is elastically biased so that the two light conducting elements are pressed against one another with their end surfaces when the coupling parts are coupled with one another, to allow the transmission of light from one light conducting element to the other. The end surface of the one light conducting element is spherically concave and the end surface of the other light conducting element is formed spherically convex with the same radius of curvature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in German Patent Application No. 103 10 148.9 filed on Mar. 7, 2003.

FIELD OF THE INVENTION

The present invention concerns a light conductor coupling, especially for the transmission of optical signals between vehicles a coupled with one another, with a first and a second coupling part which are couplable with one another and in each of which is contained a light conducting element, of which light conducting elements at least one is elastically biased so that the light conductor elements are pressed against one another with their end surfaces, when the coupling parts are coupled with one another, to permit a transmission of light from one light conducting element to the other.

BACKGROUND OF THE INVENTION

One such light conductor coupling is for example known from DE 28 54 962 C2, in which an intermediate buffer coupling for rail vehicles is described. A cable coupling belongs to the intermediate buffer coupling which among other things serves to transmit impulses for the control of the braking and driving currents from one vehicle to the other in a train of vehicles. The cable coupling consists of two contact carriers each of which is carried by a respective one of the vehicles and in which along with a plurality of electrical contacts a light conductor is as well arranged. Of the two light conductors at least one is elastically biased so that the two light conductors are pressed against one another with their end faces when the contact carriers upon the coupling of the vehicles are moved against one another. Through these pressed together light conductors optical signals can be transmitted from one vehicle to the other.

From DE 198 07 596 C2 a light conducting plug connector of the previously mentioned type is known in which not only one, but both light conductor elements are elastically biased.

When light conductor couplings of the above-mentioned type are used under rough conditions, such as for example for the transmission of signals between coupled vehicles, there however appear many transmission failures. A reason for this lies in that the optical signals are heavily attenuated in their transmission from one light conductor element to the other, both because of a dislocating movement as well as because of a tilting of the optical axes of the two light conductors relative to one another, which leads to a falsification of the optical signals. One such dislocating movement or such a tipping of the optical axes of the light conducting elements can however hardly be avoided in the case of vehicles which are coupled with one another, since the two coupling parts are not rigidly connected with one another and are relatively heavily mechanically stressed. Further reasons for an unreliable signal transmission lie in the sensitivity of such light conductor couplings to abrasion and contamination which in relatively rough conditions are likewise unavoidable.

To circumvent these problems an optical signal coupling is proposed in DE 29 22 937 C2 in which the light conductors are not pushed together at their end surfaces, and instead the light is transmitted with the help of lens pieces through the air from one light conductor to the other. Such a signal coupling is however relatively complicated and expensive and cannot offer the reliability which was expected of it.

In consideration of the above mentioned difficulties in DE100 52 020 A1 it has been proposed, in the case of applications under rough conditions, to do away entirely with a customary optical coupling of light conductors and instead of this to first convert the optical signals conducted in a first light conductor into electrical signals, to transmit these signals over customary electric couplings, to again convert the electrical signals into optical signals and to feed those optical signals into a second light conductor. With this solution, one loses above all the previously mentioned advantages of a light conductor coupling, namely the increased transmission bandwidth and a lower susceptibility to electromagnetic disturbing fields, especially those which always appear if in the immediate vicinity high currents are also transmitted, as for example in cable couplings for rail vehicles is often the case.

The invention has as its basic object the provision of a light conductor coupling which is of simple construction and which permits a disturbance insensitive signal transmission.

SUMMARY OF THE INVENTION

This object is solved by way of a light conductor coupling of the above-mentioned kind in that the end surface of one of the light conductor elements is spherically concave and the end surface of the other light conductor element is formed spherically convex with the same radius of curvature.

In the coupled condition the convex end surface of the one coupling part lies exactly fittingly into the convex end surface of the other coupling part, and indeed without an air gap between the end surfaces, which air gap would lead to an attenuation of the optical signals.

By the biasing of the one or both light conductor elements, the convex end surface is pressed into the hollowing of the concave end surface so that the two coupling parts are automatically centered with one another. Thereby with the light conductor coupling of the invention a mechanical displacement of the optical axes of the light conducting elements is avoided, which in the case of customary light conductor couplings likewise leads to an attenuation of the optical signals.

Moreover, the spherical end faces allow a tilting of the optical axes of the light conductor elements relative to one another without the end surfaces being lifted from one another. In the case of such a tilting the spherical convex surface slides on the spherical concave surface, like a socket joint head in a socket joint socket, without producing an air gap between the end faces. This is a great advantage in comparison to customary light conductor couplings with flat end faces between which in the case of a tilting of the coupling parts relative to one another without fail an air gap is formed, which leads to a non-permissible attenuation of the transmitted signal.

The possibility of a small attenuation as a result of a tilting of the coupling parts relative to one another is especially of great significance if the light conductor coupling is used to transmit optical signals between coupled vehicles, such as rail vehicles. Although in the case of customary light conductor couplings for rail vehicles it is attempted to guide the coupling parts of signal couplings and electric couplings linearly, that is to prevent a tilting of the coupling parts relative to one another, this is not achieved reliably in practice because of the high mechanical loads, which leads to an excessive attenuation of the transmitted optical signals. With the described improved light conductor coupling a linear guiding can be entirely forgone as a matter of principle, because even a relatively large tilting of the coupling parts relative to one another leads to a tolerable attenuation of the signals. The improved light conductor coupling is therefore to a given degree “bendable.”

Preferably, the light conducting elements each include a light opaque sleeve and a transparent core received in the sleeve. When the coupling parts are coupled, the light opaque sleeves form a light tunnel shielded from daylight.

The spherical end surfaces of the transparent cores are each smoothly continued into the ends of the respectively associated sleeves. Thereby even in the case of a tilting of the light conducting elements relative to one another no daylight can fall into the transparent core, assuming that the wall thicknesses' of the sleeves in the region of the end faces are not too small. Preferably these wall thicknesses' have values which are at least {fraction (1/10)} and preferably at least ⅕ of the radius of curvature of the end surfaces.

The previously described light conductor coupling can be used in customary ways and with the described advantages as a passive-coupling element between two light conductors. For example, an optical signal can be conducted through a first light conductor over a given stretch of distance to the first coupling part and can there be supplied to the light conductor element of the first coupling part. That optical signal is then transmitted through the end surfaces of the two light conducting elements to the light conducting element of the second coupling part, from which it is then fed into a second light conductor and by that conducted over a further stretch of distance.

Because of its simple construction and its reliable coupling properties the described light conductor coupling is however also suitable for a broader and more multifaceted use. A larger multifaceted capability is achieved if the light conductor coupling is equipped with active elements for signal processing or for the creation of new signals.

In a preferred further development the first coupling part therefore includes a sending device which creates optical signals from electric signals and feeds the optical signals into the light conductor element of the first coupling part. Additionally or alternatively the second coupling part includes a receiving device which creates electric signals from the optical signals transmitted to the light conductor element of the second coupling part.

Moreover, the first coupling part can include a microprocessor which prepares the electric signals for the sending device. Also the second coupling part can include a microprocessor which processes the electric signals created in the receiving device. With this processing in the microprocessor of the second coupling part a test for example can be made as to whether the signals have been entirely transmitted. In the event this is not the case, the microprocessor of the first coupling part can be commanded to send the signals again. The microprocessor of the first coupling part can for example prescribe to the sending device the strength of the optical signals to be created by it so as to compensate for a possible attenuation of the optical signal transmission as a result of dirtying or moistening of the end faces of the light conductor elements.

In a preferred further development the microprocessor of the first coupling part is programmed to merge several individual signals into electrically multiplexed signals and the microprocessor of the second coupling part is programmed to divide the electric multiplexed signals into individual signals. Then several individual signals can be transmitted through the light conductor coupling at the same time, so that further light conductor couplings can be spared.

Preferably, the first and/or the second coupling part has a housing on an axial end of which a sleeve-like section is formed in which the light conductor element is axially slidably supported and is elastically biased in the direction toward that one axial end, and in the other end of which a connecting pin is formed which is intended for insertion into a contact carrier. The connecting pin preferably consists of two sections insulated from one another, of which sections one is connected to ground potential and the other connected to an electric signal conductor, when the contact pin is inserted into the contact carrier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown inFIG. 1is a longitudinal sectional view of the first coupling part10of a light conductor coupling according to a development of the present invention in exploded illustration (upper) and in assembled condition (lower). InFIG. 2is shown a longitudinal sectional illustration of the second coupling part12of the same light conductor coupling in exploded illustration (upper) and in assembled condition (lower). Since the first and the second coupling parts10and12are identical in many features, they will be described in common in the following with similar parts being indicated by the same reference characters.

The coupling parts10and12each have a metal housing14with a sleeve-like section16in which a light conducting element18is axially slidably supported. The light conducting element18can be pressed into the sleeve-like section16of the associated housing14against the biasing force of a spring20. In place of the spring20, the light conducting element18can also be pneumatically biased by a gas captured in the sleeve-like section16. Each light conducting element18includes a light opaque sleeve22and a transparent core24received in the sleeve22.

The light conducting element18of the first coupling part has a spherically concave end surface26facing away from the sleeve-like housing section16(FIG.1), and the light conducting element18of the second coupling part12has a spherically convex end surface26′ (FIG.2), the radius of curvature of which corresponds to that of the spherically concave end surface26. The spherically concave end surface26and the spherically convex end surface26′ are formed not only in the transparent core24but are also continued in the axial ends of the associated sleeves22of the light conducting elements18.

Guide grooves27are formed in the sleeves22, which guide grooves receive guide pins28. The shifting movement of the light conducting element18is thereby limited by one of the ends of the guide groove27engaging a guide pin28.

The inner space of the sleeve-like housing section16is made up of two cylindrical sections, one being an inwardly lying section30and the other being a more outwardly lying section32, the diameter of which is larger than that of the inwardly lying section30. Between the cylindrical sections30and32is a shoulder34formed in the housing inner wall. In the outwardly lying section32are located the light conducting element18and the spring20, which spring at one end engages the light conducting element18and with its other end engages a metal ring36which in turn lies on the shoulder34.

In the inwardly lying section30in the case of the first coupling part10is a sending device38(FIG. 1) and in the case of the second coupling part is a receiving device40(FIG.2). Each of the sending device38and the receiving device40has a ground connection42which is soldered to the sleeve-like section16of the housing14, and each has a signal terminal44.

The housing14has at its end facing away from the light conducting element18a hollow connecting pin46with a ground connector section48, a signal connector section50, and lying between them an insulating piece52which electrically isolates the sections48and50from one another. The signal terminal44is guided through the hollow space of the connector pin46and is soldered with the signal connector section50. The inwardly lying section30and the hollow space of the connector pin46are filled with pottant material illustrated inFIGS. 1 and 2by cross hatching,

FIG. 6shows an enlarged cross sectional view of the housing14of the first coupling part10. As is to be seen inFIG. 6the ground connector section48of the connecting pin46has an external thread54formed on it, by means of which the first coupling part10is threadable into a socket at ground potential of a contact carrier. On the inner side of the ground connector section48is an internal thread56into which the insulating piece52is threadable (see FIG.1). In the sectional illustration ofFIG. 6is further shown a bore57into which the ground connector section48of the sending device38is soldered.

FIG. 8shows a cross section through the housing14of the first coupling part10taken along the line A—A of FIG.6. As is to be seen, the sleeve like section16of the housing14has a hexagonal external cross section to which a work tool is applyable to screw the coupling part10by way of its thread54into a socket. The sleeve like section16of the housing14has two recesses of58for the guide pins28, which have already been described in connection withFIGS. 1 and 2. In place of two recesses58, three recesses60can be provided which are displaced from one another by 120°, as is shown in FIG.7. In this case the light opaque sleeve22has three correspondingly arranged guide grooves27.

InFIG. 3the first coupling part10and the second coupling part12are shown in coupled condition. In this condition, the end faces26and26′ of the associated light conductor elements18are pressed onto one another so that the optical signals which are fed into the transparent core24of the light conducting element18of the first coupling part10are transmitted through the end faces26and26′ into the transparent core24of the light conducting element18of the second coupling part12. Thereby the light opaque sleeves22of the light conducting elements18form a light tunnel shielded from daylight.

Since the two light conducting elements18are each slidable in the housing of14of the associated coupling part10or12the coupling parts can be moved somewhat away from and toward one another without disturbing the functioning of the signal coupling. InFIG. 4, for example, the coupling parts10and12ofFIG. 3have been moved somewhat toward one another without that having changed the positions of the light conducting elements18to one another, so that the light transmission remains undisturbed. The illustrated light conductor coupling therefore allows a certain tolerance in the relative arrangement of the two coupling parts10and12in the coupling direction, that is along the optical axes of the light conducting elements18, which optical axes are formed by the middle axes of the light conducting elements18. Further, the spring pressure biased end faces26and26′ prevent displacement of the optical axes of the light conducting elements18against one another, that is they help to orient the coupling parts to one another and to maintain the oriented positions.

InFIG. 5, the two coupling parts10and12are likewise shown in coupled condition. Differently than inFIGS. 3 and 4, in this case the coupling parts10and12are not aligned with each other, but instead are tilted relative to one another. That means that the optical axes of the light conducting elements18, each of which coincides with the symmetry axis of the associated transparent core24, stand at an angle to one another. Because of their spherical shape, the end surfaces26and26′ nevertheless lie without gap on one another, so that the attenuation of the light upon passage through the end surfaces26and26′ is held within limit. The light conducting coupling is therefore bendable to a certain degree, without such bending influencing its function. This is a large advantage in comparison to customarily used flat end faces which upon such a bending become lifted from one another so that the light transmission from one coupling part to the other becomes heavily attenuated.

InFIG. 5, the light conductor coupling is shown in its maximally bent condition, in which the coupling parts are bent about 11° relative to one another. In the case of a further bending daylight would enter the light tunnel and falsify the optical signal. The limiting angle at which daylight penetrates into the light tunnel depends on the relationship of the wall thicknesses of the light opaque sleeves in the region of the end faces26and26′ to the radius of curvature of the end faces26and26′. In the illustrated example, the wall thickness of the light opaque sleeve22of the first coupling part10in the area of the end face26is smaller than that of the light opaque sleeve22of the second coupling12, and is therefore determinative of the value of the limiting angle. It measures about ⅕ of the radius of curvature of the spherical end surfaces26and26′.

It is to be emphasized, that although the light conductor coupling shown inFIGS. 1to5includes a sending device38and a receiving device40, the previously described features, especially the spherical formation of the end surfaces26and26′ are also assumed in the customary sense for light conductor couplings in which no such active elements are provided. In this case light from one light conductor is fed into the light conducting element18of the first coupling part10, is transmitted through its end surface26and through the end surface26′ of the light conducting element18of the second coupling part12and is further conducted by a light conductor connected with the light conducting element18of the second coupling part. The sending and receiving devices38and40represent only an advantageous further development of the invention which is described in the following.

FIG. 9shows a functional sketch of the sending device38. As is to be taken from this, an input voltage Vinis applied between the ground connection42and the signal connection44through a scaling resistor64and is applied through a high pass filter, consisting of a capacitor62and a resistor64, to a light emitting diode66, which emits light corresponding to the applied voltage. The relationship between the applied voltage Vinand the radiated power S of the light emitting diode66is schematically represented in the diagram in the right portion ofFIG. 9, whose abscissa indicates time and whose ordinate gives the input voltage Vinand the radiation power S in undefined units.

FIG. 10shows a functional sketch of the receiving device40. The receiving device40includes a photodiode68which in dependence on the intensity of the incoming light produces a voltage. This voltage is suitably amplified in a first circuit section with the help of an operational amplifier70, a resistor72, and a capacitor74, and is inverted with the help of a further operational amplifier76to an output voltage Vout. The relation between the received emission power S′ (which multiplied by an attenuation factor corresponds to the radiation power emitted from the LED66) and the output signal Voutof the receiving device40is schematically illustrated in the diagram in the right portion ofFIG. 10, the abscissa of which again shows time and the ordinate of which shows the received emission power S′ and the output voltage Voutin undefined units.

The sending device38and the receiving device40are so designed that the output signal Voutof the receiving device40despite a possible attenuation of the transmitted optical signal corresponds to the input voltage Vin. Therefore, even if the optical signal transmitted between the coupling parts10and12is subjected to a certain attenuation, the effective transmitted electric signal Voutis not attenuated in respect to the original signal Vin.

The electric input signal Vin, can for example be an electrical high frequency signal which inside of two vehicles is conducted through a co-axial cable and only to suit the signal coupling is converted into an optical signal with the help of the sending device38. The light conductor coupling with the active elements38and40, however, finds for example other uses if in the vehicle optical signals are already transmitted through light conductors. These signals are then in the first coupling part10first converted to an electric signal which is then applied to the sending device38. The output signal Voutof the receiving device40is then in the second coupling part again converted into an optical signal and supplied to a subsequent light conductor.

FIG. 11shows in sectional illustration a section of a conductor coupling for use in combination with an automatic rail vehicle coupling. An automatic coupling is used if the towed members have to be often coupled and de-coupled. Then the associated conductor coupling is so designed that its electrical and optical contacts are likewise automatically coupled along with the automatic coupling of the towed members.

The conductor coupling includes two contact carriers78and80in which, along with a row of electrical contacts (not shown), the above-described coupling parts10and12of the light conductor coupling are also used. The coupling parts at10and12are forwardly threaded into the contact carriers78and80by means of the thread54of the connector pins46, whereby the thread54is subjected to ground potential. At the same time, the signal contact section50of the first coupling part10comes into electrical contact with a schematically illustrated first signal processing unit82and the signal connector section50of the second coupling part12comes into electric contact with a schematically illustrated second signal processing unit84.

In the illustrated exemplary embodiment the first signal-processing unit82is supplied with electric signals over a co-axial cable86and optical signals over a light conductor88. The optical signals of the light conductor88are converted into electrical signals in a converter unit90and together with the electrical signals of the electrical conductor86are delivered to a control unit92. In the control unit92the two inputted electrical signals are processed into a multiplexed signal which is transmitted to the signal connector50of the first coupling part. For this the control unit92has a microprocessor, (not shown), which is constituted by an industrial PC or a so-called field programmable gate array (FPGA).

The control unit92further has a data input94through which further information for the signal processing can be delivered. For example, through the data conductor94, it can be signaled that already transmitted signals have not been completely received and should be sent again.

The conversion of the electric multiplexed signals into optical signals by the sending device38and their transmission from the first coupling part10to the second coupling part12takes place in the way described above. From the signal connector50of the second coupling part12, the electrical signals created in the receiving device40reach a control unit96of the second signal-processing unit84. In the control unit96the multiplexed signals are divided into individual signals. The original ingoing signals from the electric conductor86are further conducted by an electrical conductor98. The original ingoing signals from the light conductor88are converted again into optical signals in a converter unit100and are supplied to a light conductor102.

By means of a further data conductor104signals from the control unit96can be further conducted, for example fault reports if signal errors have been received. The control unit96contains likewise an industrial PC or an FPGA (not shown).

The signal processing units82and84can also be contained in the housings14of the coupling parts. Further, the signal processing units82and84can each be connected with a transmission capable coupling part (similar to the first coupling part10) and a receiving capable coupling part (similar to the second coupling part12). Then, signals can be transmitted from both sides of the coupling to the other side and the signal processing units of82and84can communicate with one another in both directions.

The coupling parts10and12can above all be not only arranged in special contact carriers as shown inFIG. 11, but can also be arranged in the coupling heads of a mechanical rail vehicle coupling, for example in an automatic intermediate buffer coupling (not shown). The above described insensitivity of the optical signal coupling with respect to mechanical tolerances makes this arrangement possible, which would not function in the case of a customary optical signal coupling. Thereby in many cases a separate conductor coupling can be spared.