CZ36242U1 - Composite fibre optic sensor for detecting the pressure force generated by the passage of a rolling stock wheel and its arrangement - Google Patents

Description

(54) Name of utility model:

Composite fiber optic sensor for detecting the pressure force generated by the passage of a rolling stock wheel and its arrangement

In the registration procedure, the Industrial Property Office does not determine whether the subject of the utility model meets the conditions of eligibility for protection according to § 1 of Act. E. 478/1992 Coll.

CZ 36242 UI

Composite fiber optic sensor for detecting the pressure force generated by the passage of a rolling stock wheel and its arrangement

Field of technology

This technical solution relates to a multi-purpose composite sensor of rolling stock with optical fibers, in particular a composite fiber optic sensor suitable for detecting the pressure force generated by the passage of a wheel of a rolling stock, while also relating to its arrangement.

Current state of the art

In the current state of the art (see the article "Optical and fiber optic sensors in railway applications" in the magazine Nová železniki technika, 3/2021, p. 25-29) microbending optical sensors belonging to the group of amplitude sensors are known. These sensors work on the principle of violation of the boundary conditions of light propagation in an optical fiber. Due to the influence of the measured quantity, the geometry of the optical fiber changes and thus the condition of complete reflection at the core-cladding interface is violated. These sensors evaluate the decrease in the intensity of the light emerging from the end of the optical fiber or the increase in the intensity of the light that escapes through the sheath into the surrounding environment. Using micro-bending sensors, for example, the following quantities can be sensed: weight, mechanical pressure, acceleration, deformation and vibration. The main advantages of these sensors are the simple construction, the use of multimode optical fibers and the associated low price. In a specific design, micro-bending sensors were placed in two places under the heel of the rail, and when the axle passed through, the sensors were deformed in proportion to the weight by the pressure exerted. With the help of two sensors, it was possible to reliably measure the speed and direction of the railway and tram sets.

The document DE 10057740 AI describes a device for detecting roundness defects of rolling stock wheels by means of an optical fiber sensor, which is placed either between the rail heel and the base or sleeper, or in the transverse opening of the rail web, and also the method of detecting roundness defects of rolling stock wheels with the said device. Said sensor contains a housing and an optical fiber embedded in it, which is elastically deformable in response to the load caused by the passage of the wheel. This deformation affects the input light signal in the optical fiber in proportion to the load and can consist of a temporary change in the length or diameter of the fiber, thereby lengthening the path or increasing the attenuation of the light signal. The signal changed in this way is detected by a measuring device which, on the basis of high- or low-frequency deviations of the signal, detects the presence or absence of the passing wheel itself and, in particular, defects in its roundness.

The disadvantage of the mentioned sensor is that at high loads (e.g. a fully loaded freight train), changing the length or diameter of the optical fiber itself can lead to irreversible deformations and damage to the sensor.

DE 19518123 AI describes a device for detecting the passage of wheels of rolling stock and for building elements affected by electrical or electromagnetic interference, which includes an optical fiber sensor and an evaluation unit. Said sensor contains a body and an optical fiber embedded in it, both of which are elastically deformable in response to the load caused by the passage of the wheel. In addition, the body in one embodiment includes almost non-deformable metal pins that are placed above and below the optical fiber, spaced from each other (i.e. not on top of each other, and not too close to each other) and without direct contact with the optical fiber (see Fig. 2 of the document DE 19518123 AI). Under the action of a compressive force, these metal pins push through an elastically deformable body on the optical fiber, thereby deforming it from both sides. Said deformation proportionally to the load affects the input light signal in the optical fiber and can consist of reversible microbending, misalignment or angle change, thereby increasing the attenuation of the light signal. The signal changed in this way is detected by the evaluation unit, which, based on the deviations of the signal, detects the presence or absence of the passing wheel itself.

- 1 CZ 36242 UI

The main disadvantage of said sensor is that said pins are made of metal, which can cause problems in sensors that are subject to intense electrical or electromagnetic interference and require exclusively non-metallic components. Another disadvantage of the mentioned sensor is that the pressure force acts from the metal pins on the optical fiber only indirectly through an elastically deformable body, so that it can be spread over a larger area, and in addition, in combination with the sensitivity of the metal pin to temperature fluctuations due to its high thermal expansion, the detected signal can inaccuracies arise.

Document EP 0608645 AI describes a device for detecting pressure force, e.g. for detecting the passage of a wheel, which contains an optical fiber sensor and an evaluation unit. Said sensor contains a body (made of e.g. rubber) and an optical fiber embedded in it, both of which are elastically deformable in response to the load caused by the compressive force. In the first embodiment, the body additionally contains a metal strip with projecting ribs which are located only under the optical fiber, at a distance from each other (i.e. not too close to each other) and in direct contact with the optical fiber (see Fig. 3 of EP 0608645 A1). In a second embodiment, the body additionally includes a metal strip that is placed below the optical fiber and a deformation fiber of hard material spirally wound around the optical fiber at a point between the elastically deformable body and the metal strip so as to create deformation intersection points that are located above and under the optical fiber, at a distance from each other (i.e. not above each other, and not too close to each other) and in direct contact with the optical fiber (see Fig. 4 of document EP 0608645 AI). Under the action of compressive force, these projecting metal ribs or these deformation intersection points of the deformation spiral fiber push the optical fiber through the elastically deformable body, thereby deforming it from one side (first embodiment) or from both sides (second embodiment). Said deformation affects the input light signal in the optical fiber in proportion to the load and can consist of reversible microbending, thereby increasing the attenuation of the light signal. The signal changed in this way is detected by the evaluation unit, which detects the presence or absence of pressure force on the basis of signal deviations.

The main drawback of said sensor is that said fins and said deformation spiral fiber are made of metal or other hard material, which can cause problems in sensors that are subject to intense electrical or electromagnetic interference and require exclusively non-metallic components. Another disadvantage of the mentioned sensor is that due to its hardness (metal or hard material), the ribs or the deformation spiral fiber can lead to damage to the sensor and to irreversible plastic deformations of the optical fiber, especially to changes in its diameter.

The disadvantage of the above-mentioned sensors is their low resistance to intense electrical or electromagnetic interference due to the presence of metal components and the risk of damage to the optical fiber by too hard deformation elements under high loads.

In the state of the art, there is therefore a need for a new optical fiber sensor for detecting the pressure force generated by the passage of a rail vehicle wheel, which is resistant to intense electrical or electromagnetic interference and which does not damage the optical fiber under high loads.

The essence of the technical solution

The aim of this technical solution is to provide an optical fiber sensor that overcomes the aforementioned disadvantages of the state of the art.

According to the first embodiment, the goal of this technical solution is achieved by a composite fiber optic sensor for detecting the pressure force generated by the passage of a rail vehicle wheel. Said sensor includes a housing for protecting internal parts, a first elastically deformable member stored in the housing, and an optical fiber stored in the first elastically deformable member and connectable

-2CZ 36242 UI with evaluation unit containing light source, detector and processor. The evaluation unit is located outside the sensor itself. The first elastically deformable member contains, on one (bottom) side, a first deformation surface in which at least one continuously extending notch for accommodating the optical fiber is arranged. At least one first deformation protrusion is arranged in the notch, which is lower than the depth of the notch and which is configured so that by transferring a compressive force from a load (eg, a rail vehicle wheel) through the rail, the housing and the first elastically deformable member to the first deformation protrusion and pushing of the first deformation protrusion on the optical fiber is caused by the reversible microbending of the optical fiber.

This reversible microbending leads to partial decoupling of the guided light energy from the optical fiber. The size of the bound light energy is dependent on the degree of deformation of the optical fiber by the compressive force, and therefore proportional to the weight of the load. Microbends are disturbances in the straightness of the fiber axis and small errors in the geometry of the fiber. In the aforementioned sensor, they arise during the deformation of the optical fiber in the places of deformation protrusions, where the optical fiber is compressed and the geometry of the optical fiber in the section changes. At the microbends, some rays (modes) are reflected at a large angle, they escape outside the core of the optical fiber and thus its attenuation increases. The reversibility of the microbending is ensured at loads smaller than the maximum load in the elastic degree of deformation of the optical fiber material. Changes in the pressure force acting on the sensor are transmitted using a change in the power (intensity) of the light beam guided in the optical fiber to the evaluation unit.

In the vicinity of the deformation member, there is another change in the curvature of the optical fiber - the macrobend, which also takes part in changes in the transmission properties of the fiber. Macrobends occur when the optical fiber is bent below a certain limit of the radius of curvature and cause the condition of total reflection at the interface of the core and the cladding to be not met and the light to escape from the optical fiber. In the aforementioned sensor, macrobends occur around deformation protrusions around which the optical fiber bends. As the radius of curvature of the optical fiber decreases, the amount of bound energy of the light beam increases from the core of the optical fiber towards its sheath and further out into the surroundings, thereby increasing the transmission attenuation of the fiber. In other words, macrobending of light occurs wherever the minimum radius of curvature of the fiber, critical for a given type of fiber, is exceeded. Changes in this curvature due to compressive force cause additional energy release, which is added to the reversible changes in the microbends. The result of the forces acting on the sensor is the amplitude modulation of the intensity of the output light signal, while the input light signal with a constant intensity enters the sensor. The evaluation unit then converts the optical signal into an electrical signal and then evaluates the passage and the presence of a railway wheel near the sensor.

The essence of this technical solution is that the first deformation protrusion is made of plastic, which ensures resistance to intense electrical or electromagnetic interference, since plastic is a non-metallic material, and which further eliminates the risk of damage to the optical fiber in direct contact with the first deformation protrusion, since plastic is compared to metal, a soft and pliable material that copies the irregularities of the optical fiber and does not cause its irreversible deformations, especially changes in the diameter of the fiber. The sensor thus creates a robust electrical isolation between the rail and the evaluation unit.

3D printing technology was used for the production of deformation members due to the large number of filament types, within which it is possible to choose a filament with the required properties: strength, hardness, operating temperature, resistance to external influences, etc. Suitable plastics (filaments for 3D printing) for production of deformation protrusions include poly(acrylonitrile-co-styrene-co-acrylate) (ASA), poly(acrylonitrile-co-butadiene-co-styrene) (ABS), poly(acrylonitrile-co-butadiene-co-styrene-co- methyl methacrylate) (transparent ABS;

ABS-T; MABS), a blend of polycarbonate and poly(acrylonitrile-co-butadiene-co-styrene) (PC/ABS), glycol-modified poly(ethylene-co-terephthalate) (PETG), a blend of poly(ethylene-co-terephthalate) modified glycol and carbon fibers (PETG/CF; CFJet), and poly(etherimide) adapted for 3D printing (PEI; PeiJet). A suitable plastic for making deformation protrusions can be, for example, poly(acrylonitrile-co-styrene-co-acrylate) (ASA) or poly(ethylene-co-terephthalate) with glycol modification (PETG), with a hardness measurable within the Shore A scale ( generally stated values approximately

-3 CZ 36242 UI to approximately 100, e.g. 25, 30, 40, 50, 60, 70, 80, 90 or 100) or within the Rockwell scale B (generally given values from 0 to approximately 100, e.g. 0, 10, 20, 30, 40, 50, 60, 70, 75, 80, 85, 90, 95 or 100). In addition, polyurethane (PU) can also be used, especially cast polyurethane, from which plates can be cast and hardened to the required hardness, e.g. in the ranges mentioned above. For the production of deformation members, it is also possible to use other procedures and materials that meet the above-mentioned, required parameters.

According to the second embodiment, the goal of this technical solution is achieved by a composite fiber optic sensor for detecting the pressure force generated by the passage of a rail vehicle wheel. Compared to the sensor according to the first embodiment, this sensor additionally contains a second elastically deformable member stored in the housing and containing on one (top) side a second deformation surface adjacent to the first deformation surface of the first elastically deformable member. At least one second deformation protrusion is arranged on the second deformation surface so that, after the first and second deformation surfaces are brought together, it protrudes into the notch for accommodating the optical fiber and beyond the first deformation protrusion. The first and second deformation protrusions are therefore at a distance from each other and at the same time in direct contact with the optical fiber. The second deformation protrusion is configured such that by transmitting a compressive force through the housing, the first elastically deformable member, and the first deformation protrusion to the optical fiber and pushing the optical fiber against the second deformation protrusion, reversible microbending of the optical fiber is caused. The second deformation protrusion is also made of plastic for the same reasons as the first deformation protrusion.

In the sensor according to the first embodiment, the reversible microbending of the optical fiber occurs only by the action of the first deformation element from one side (from above), which makes this sensor less sensitive and therefore suitable for higher loads (e.g. fully loaded freight trains, or railway vehicles in general). To a small extent, the effect of the first deformation element in its vicinity also manifests itself in the macrobending of the optical fiber. Conversely, in the sensor according to the second embodiment, reversible microbending of the optical fiber occurs due to the action of the first and second deformation elements from both sides (from above and from below), which makes this sensor more sensitive and therefore suitable for lower loads (e.g. tram vehicles). Due to the action of the first and second deformation elements, the macrobending of the optical fiber is also manifested in their surroundings to a significantly greater extent than in the case of the sensor according to the first embodiment.

In an advantageous embodiment, the first and/or second deformation protrusions can be arranged in a matrix of deformation points, e.g. in a matrix 1x2, 1x3, 1x4, 1x5, 1x6, 2x2, 2x3, 2x4, 2x5, 2x6, 3x3, 3x4, 3x5, 3x6 etc. .The serial model of the increase in fiber attenuation at microbends is applied to the optical fiber, i.e. the number of deformation points multiplies the change in the optical signal, thereby increasing the sensitivity of the sensor. The dependence is not completely linear, with a large number of deformation points on the surface, this will cause forces to dissipate and reduce the effect of increasing the sensitivity of the sensor.

For single row/column arrays, the slot to accommodate the optical fiber may be linear and/or curved. For matrices with at least two rows and two columns, it is necessary that the slot to accommodate the optical fiber is curved. Various loops, hairpins, spirals, etc. can be created by the curvature of the notch. A minimum radius of curvature is defined for each type of optical fiber. By bending the optical fiber in the notch, only a negligible intrinsic attenuation of the light signal occurs, because this curvature has a sufficiently large radius of curvature where macrobend does not occur. Theoretically, there can be more notches, but this also requires more optical fibers, which complicates the sensor itself.

In a preferred embodiment, the optical fiber is multi-mode. Multi-mode fibers have a diameter approximately an order of magnitude larger than single-mode fibers, they are characterized by better mechanical resistance, greater resistance to vibrations on the connecting connectors with the same manufacturing accuracy and significantly higher sensitivity to bends compared to single-mode fibers.

In a preferred embodiment, the housing, the first elastically deformable member and the second elastically deformable member are made of rubber or a similar elastically deformable material to ensure elastic deformability and effective transfer of pressure force to the deformation projections

-4CZ 36242 UI and optical fiber. The choice of rubber materials for sensor components is determined by resistance to external influences, resistance to petroleum products and other chemicals that can be expected to occur in the place where the sensor is deployed.

In an advantageous embodiment, the case contains an upper part and a lower part. The top part may include two protruding opposite edges extending over the bottom part to prevent unwanted displacement or slippage of the sensor when the rail moves due to its springing and thermal expansion. The upper part can also contain protective elements to protect the connection of the optical fiber and the optical cable led from the sensor to the evaluation unit, see below. The output of both ends of the optical fiber can be next to each other or on opposite sides of the housing. The dimensions of the sensor are determined by the type of rail, base plate, rail attachment method, etc.

In an advantageous embodiment, a plastic intermediate layer is arranged between the first deformation surface of the first elastically deformable member and the lower part (first embodiment), or between the first deformation surface of the first elastically deformable member and the second deformation surface of the second elastically deformable member (second embodiment), which is preferably made from poly(ethylene terephthalate) with glycol modification (PETG). This intermediate layer enables the tuning of the properties of the sensor, through its thickness and material stiffness. E.g. an interlayer with greater stiffness achieves lower sensitivities and shifts the sensing working area to greater pressures acting on the sensor, while an interlayer with less stiffness achieves an analogously opposite effect.

According to the third embodiment, the goal of this technical solution is achieved by arranging the mentioned composite fiber optic sensor for detecting the pressure force generated by the passage of a wheel of a rolling stock, where the composite fiber optic sensor is placed under the heel of the rail and on the base. The sensor thus replaces the standard rubber damping under-rail pad inserted into the rail attachment mechanism. Rail mounting can be done in all standard ways, i.e. by means of screws, spring mounts or their combinations. The placement of the sensor between the heel of the rail and the base plate ensures that the pressure acting on the rail is sensed over a more distributed area compared to sensing in the web of the rail. In addition, the placement of the sensor in the web of the rail (as stated in the document DE 19518123 AI) disrupts its mechanical integrity and is therefore less suitable, while this placement requires a structurally completely different arrangement of the sensor and the course of pressure depending on the driving of the vehicle is partially different.

Both ends of the optical fiber coming from the sensor are connected to a multi-mode fiber optic cable, which is used to supply the light energy and remove the residual energy from the sensor. The optical cable is further connected to an evaluation unit containing a light source for supplying the input light signal to the sensor, a detector for converting the output light signal into a voltage, optionally an amplifier and an A/D converter, and electronic circuits containing a processor with memory and a stored computer program for processing the output signal, and further with a power source, outputs and a data line (e.g. RS485) for indicating the evaluation results and for transmission to a possible superior system. Electronic circuits also ensure temperature and current stability and signal processing. The optical cable connectors are both at the interface of the evaluation unit and the optical cable, and also at the interface of the optical cable and the optical fiber in the sensor (which is usually enclosed in an underground waterproof optical cabinet).

The mentioned arrangement, when the measuring point (sensor under the heel of the rail) is separated from the evaluation point, allows the sensor to be installed in places with electromagnetic interference, by which current sensors based on monitoring changes in electrical parameters and sensor values can be negatively affected. At the same time, the measuring point under the heel of the rail behaves as an electrically passive sensor, which does not need any electrical energy at the measuring point, both for its own power supply and for its own measurement. At the point of measurement, there is only light, e.g. with a power of up to 1 mW.

The light source in the case of multimode fibers can be a emitting laser diode or an LED. These sources are particularly subject to requirements for stability of the output power and easy connection to the input optical fiber in the optical cable. The wavelength of the light used can be limited

-5CZ 36242 UI for wavelengths up to 1000 nm (visible region of the spectrum and near infrared radiation), but the working wavelength is not critical. For economic reasons, it is advantageous to use wavelengths of light sources that are the same as those used in telecommunications and transmission technology. The minimum optical power required for the operation of the mentioned sensor is 10 pW. This value depends on the distance between the measurement point and the location of the evaluation unit. As the distance increases, the requirement for the amount of power coupled from the light source to the multimode optical fiber increases, up to a value of 100 pW for distances of around 1 km.

The detector of light proceeding from the sensor and carrying information about the position of the rolling stock can be a receiving photodiode. Several suitable types of photodetectors can be used, such as a PN junction photodiode, a PIN photodiode, a receiving laser diode, or a phototransistor. It is essential that the photodetector is capable of detecting light with a wavelength of up to 1000 nm. All silicon photodetectors meet this condition. To increase the resolving power, it is convenient for the photodetectors to have a small noise expressed in the dark current parameter, the value of which should not exceed 20 nW.

The optical cable between the location of the sensor and the evaluation unit does not require special protective elements. In order to maintain full electrical insulation (dielectricity), the optical cable should not contain any metallic elements. Common optical cables used in telecommunications and data transmission meet this requirement. The second requirement for optical cables is that the optical fibers in it are multimode, so that there is no additional loss at the interface between the optical fiber in the sensor and the fiber of the optical cable. The third requirement is the number of fibers in the optical cable, which sets the number of fibers to, for example, two. One fiber is intended for power supply, the other fiber for its output from the sensor and signal transmission to the evaluation unit. Since there are two dimensional standards for optical multimode fibers, namely 50 pm and 62.5 pm, it is more suitable for the sensor to use a fiber with a core diameter of 50 pm and a cladding diameter of, for example, 125 pm. With these fibers, there is less difference in the refractive indices of the core and the cladding, which leads to easier balancing of the conducted energy in the sensor and thus higher sensitivity.

The above-mentioned composite fiber optic sensor or the above-mentioned arrangement can be used to detect the pressure force generated by the passage of a wheel of a rail vehicle, which can be, for example, a railway vehicle, a tram, a ground cableway, etc. The detected passage of a wheel can be used to detect the position of the wheel, the number of axles, weight per axle, speed of passage, defects of roundness of the wheel or against false influence by another type of vehicle or no vehicle at all. There is also a theoretical possibility of miniaturization for railway modeling.

The above-mentioned arrangement can be influenced by a computer-implemented method of detecting the pressure force generated by the passage of a rolling stock wheel, which includes the following steps:

a) bringing the input light signal from the light source to the optical fiber;

b) detecting and processing the first output light signal from the optical fiber by the evaluation unit into a first output signal, wherein the first output signal corresponds to a reference state where the sensor does not detect any pressure force;

c) the application of a pressure force on the sensor, which causes a reversible microbending of the optical fiber and a decrease in the intensity of the input light signal resulting in a second output light signal;

d) detecting and processing the second output light signal from the optical fiber by the evaluation unit into a second output signal, wherein the second output signal corresponds to a state where the sensor detects a pressure force; and

e) comparison of the first and second output signals and evaluation by the evaluation unit, the detected pressure force appears to be caused by the passage of the wheel of the rolling stock.

The evaluation of the detection of the passing of a wheel from the data obtained with the mentioned sensor is based on the search for the characteristic shape of the output signal. This signal in the form of a voltage is obtained using a detector, and optionally an amplifier and an A/D converter. A shape is searched for in the obtained data

-6CZ 36242 Signal UI specific for two wheels of a rolling stock. For the shape of the signal, several time and level parameters are compared, and if the examined signal meets them within certain tolerances, this signal is evaluated as having passed through two wheels of a rolling stock. If the signal does not meet these parameters, it is evaluated as a non-track vehicle, or as no vehicle at all. These parameters can be fixed or float in the processor. The combination of monitored parameters of time, level and the size of the change in level in a short time makes it possible to detect both slow and fast passage of rail vehicles with different weights (axle loads). The rolling stock can also accelerate or decelerate and the detection quality will not be affected. The evaluation algorithm also works with a floating reference value, thanks to which there are no false detections of rolling stock caused, for example, by the natural movement of the rail, such as thermal stress caused by a change in ambient temperature.

Another aspect of the above-mentioned method may be a computer program containing instructions that cause the above-mentioned arrangement to perform the steps of the above-mentioned method, and further a computer-readable data carrier on which the said computer program is stored, or a data carrier signal carrying the said computer program.

Clarification of drawings

The essence of this technical solution is further clarified by examples of its implementation, which are described using the attached drawings, where Fig. 1 shows a side view in section of the sensor according to the first embodiment;

Fig. 2 shows a side sectional view of a sensor according to a second embodiment;

Fig. 3 shows a bottom view of the upper part of the housing;

Fig. 4 shows a bottom view of the first elastically deformable member;

Fig. 5 shows a side view in section A-A of the first elastically deformable member;

Fig. 6 shows a side view in section B-B of the first elastically deformable member;

Fig. 7 shows a top view of the second elastically deformable member;

Fig. 8 shows a side view in section C-C of the second elastically deformable member;

Fig. 9 shows the dependence of the change in the intensity of the light signal on time when the wheel passes over the sensor (full graph A, details B and C);

Fig. 10 shows a perspective view of the arrangement of the sensor, rail and base plate; and Fig. 11 shows a block diagram of the evaluation unit.

Examples of implementing a technical solution

The technical solution will be further explained on examples of implementation with reference to the relevant drawings.

The first embodiment is a composite fiber optic sensor 14 in Fig. 1, comprising a lower part 2 of the housing and an upper part 1 of the housing with two protruding edges 8 extending over the lower part of the housing 2 (see Fig. 3), and further a first elastically deformable member stored in the housing 3, in which the optical fiber 9 is stored (Fig. 4). The first elastically deformable member 3 contains na

-7 CZ 36242 UI side adjacent and oriented towards the lower part 2, the first deformation surface, in which at least one continuously extending notch 6 for accommodating the optical fiber 9 is arranged. At least one first deformation projection 5a is arranged in the notch 6, while in fig. 1 and 4, more are shown and arranged in an exemplary 6x3 matrix. The first deformation protrusion 5a is lower than the depth of the notch 6 (comparing the section A-A in Fig. 5 and the section B-B in Fig. 6) and is configured so that by transmitting the compressive force through the upper part 1 of the housing and the first elastically deformable member 3 to the first deformation protrusion 5a and by pushing the first deformation projection 5a on the optical fiber 9, a reversible microbending of the optical fiber 9 is caused, which is also generally shown in Fig. 12 at the place 28 of microbending together with the places 27 of macrobending. This phenomenon is recorded, transmitted from the optical fiber 9 through the interface 7 and the optical cable 22 and processed into an output signal in the evaluation unit 23. The first deformation projection 5a is made of plastic (non-metallic and soft material) which ensures resistance to intense electrical or electromagnetic interference and reduces the risk of damage to the optical fiber at high loads. In a preferred embodiment, an unillustrated plastic intermediate layer is arranged between the first deformation surface of the first elastically deformable member 3 and the lower part 2 of the housing. The plastic can be any of the materials named above, e.g. ASA, ABS, ABS-T, PC/ABS, PETG, PETG/CF, PEI or PU.

The second embodiment example is the composite optical fiber sensor 14 in Fig. 2, containing all the features of the first embodiment from Fig. 1, except for the arrangement of the plastic intermediate layer. Said composite optical fiber sensor 14 further contains a second elastically deformable member 4 (Fig. 7) stored in the housing, containing on the side oriented towards the upper part 1 a second deformation surface adjacent to the first deformation surface of the first elastically deformable member 3. On the second deformation surface is arranged at least one second deformation protrusion 5b so that after the first and second deformation surfaces are brought together, it protrudes into the notch 6 for accommodating the optical fiber 9 (section C-C in Fig. 8) and outside the first deformation protrusion 5a. A plurality of second deformation protrusions 5b are shown in Figures 2 and 7 and are arranged in an exemplary 6x4 matrix. The second deformation protrusion 5b is configured such that by transmitting a compressive force through the upper part 1, the first elastically deformable member 3, and the first deformation protrusion 5a to the optical fiber 9 and pushing the optical fiber 9 against the second deformation protrusion 5b, reversible microbending of the optical fiber 9 is caused. the phenomenon is recorded, transmitted from the optical fiber 9 through the interface 7 and the optical cable 22 and processed into the form of an output signal in the evaluation unit 23. The second deformation protrusion 5b is also made of plastic (non-metallic and soft material), which ensures resistance to intense electrical or electromagnetic interference and reduces the risk of damage to the optical fiber at high loads. In a preferred embodiment, an unillustrated plastic intermediate layer is arranged between the first deformation surface of the first elastically deformable member 3 and the second deformation surface of the second elastically deformable member 4. The plastic can be any of the materials named above, e.g. ASA, ABS, ABS-T, PC/ABS, PETG, PETG/CF, PEI or PU.

Giant. 9 further shows the dependence of the change in the intensity of the light signal on time when the bike passes over the sensor 14. Fig. 9A shows the passage of three trams. Fig. 9B shows a detail of the passage of one tram with three double axles with a total of six railway wheels. Fig. 9C shows a detail of the passage of one double axle containing two railway wheels.

Giant. 10 further shows the arrangement of the composite optical fiber sensor 14 according to the first or second embodiment, the not shown evaluation unit 23, the rail 10, the base plate 12 and the sleeper 13. The sensor 14 is placed under the heel 11 of the rail 10 and on the base plate 12. Both ends of the optical fiber 9 are connected to optical cable 22. which is further connected to the evaluation unit 23 (see Fig. 11).

Fig. 11 shows the general arrangement of the evaluation unit 23. The evaluation unit 23 is used to process the light signal from the sensor 14 guided by the optical cable 22. The evaluation unit 23 contains a detector 20 in the form of a receiving laser diode, which is optically connected to the optical cable 22 and further with sensor 14. and on the one hand electrically

-8CZ 36242 UI with amplifier 18. Amplifier 18 is further connected to A/D converter 16, which is further connected to processor 15 for signal processing and evaluation, containing memory 17 with recorded software application. The memory 17 can be a separate component, or it can use a combination of a number of memory units, and it is connected to the processor 15. The processor 15 is connected to the source 19 of electrical voltage and to the outputs 24 and the data line 25 for indicating the evaluation results. The evaluation unit 23 also contains a source 21 of light in the form of a emitting laser diode, which is powered by an electrical source 19 and at the same time is optically connected to an optical cable 22 and further to a sensor 14. This emitting laser diode serves as a source 21 of the input light signal, which is changed in the case of a load on the sensor 14 and the thus changed signal is fed to the detector 20.

Both the A/D converter 16 and the amplifier 18 can be omitted if the corresponding converter 16 is directly integrated into the processor 15, or if the signal from the receiving laser diode of the detector 20 can be processed directly by the A/D converter 16 or the processor 15.

The result of the evaluation can be transmitted to the superior system 26 either state-wise via the digital indication outputs 24 or via the data line 25, where the electrical signal or data is further processed or the result is displayed. The data line 25 can be implemented in the form of a digital communication interface such as RS485, or another suitable interface.

Industrial applicability

The multi-purpose composite optical fiber sensor of rail vehicles is intended for spot detection of railway or tram vehicles in front of the signal, for traffic management in depots and depots and where there are substances with a risk of explosion or fire or where there is strong interference with interfering fields that have their own origin in strong electromagnetic fields. These cause outages and errors in the activities of current sensors, which are based on the principle of measuring the electrical parameters of these sensors.

Furthermore, the sensor can be used as a replacement for induction loops located in switches or in tram depots, through applications with automatic activation of light warning elements in tram crossings or crossings, to applications intended for the preference of tram traffic. Using the same sensing principle, but with a modified mechanical solution of the sensor and with added software for signal processing, it is also possible to diagnose the operation of a railway switch, or shifter.

Claims (11)

1. A composite fiber optic sensor (14) for detecting the pressure force generated by the passage of a wheel of a rolling stock, comprising a housing (1, 2), a first elastically deformable member (3) housed in the housing (1, 2), and an optical fiber (9) housed in to the first elastically deformable member (3) and connectable to the evaluation unit (23) comprising a light source (21), a detector (20) and a processor (15), wherein the first elastically deformable member (3) contains on one side a first deformation surface in which at least one continuous notch (6) is arranged for accommodating the optical fiber (9), wherein at least one first deformation projection (5a) is arranged in the notch (6) which is lower than the depth of the notch (6) and which is configured so that that by transferring the compressive force through the housing (1, 2) and the first elastically deformable member (3) to the first deformation protrusion (5a) and pushing the first deformation protrusion (5a) on the optical fiber (9), reversible microbending of the optical fiber (9) is caused, characterized by in that the first deformation protrusion (5a) is made of plastic. 2. Composite fiber optic sensor (14) according to claim 1, characterized in that it contains a second elastically deformable member (4) housed in a housing (1, 2) and containing on one side a second deformation surface adjacent to the first deformation surface of the first elastically deformable member (3), while at least one second deformation protrusion (5b) is arranged on the second deformation surface so that, after the first and second deformation surfaces are brought together, it protrudes into the notch (6) for accommodating the optical fiber (9) and beyond the first deformation protrusion ( 5a), wherein the second deformation projection (5b) is configured such that by transmitting a compressive force through the housing (1, 2), the first elastically deformable member (3) and the first deformation projection (5a) to the optical fiber (9) and pushing the optical fiber (9) reversible microbending of the optical fiber (9) is caused to the second deformation protrusion (5b), while the second deformation protrusion (5a) is made of plastic. 3. Composite fiber optic sensor (14) according to any one of the preceding claims, characterized in that the first and/or second deformation protrusions (5a, 5b) are arranged in a matrix. 4. Composite fiber optic sensor (14) according to any one of the preceding claims, characterized in that the first and/or second deformation protrusions (5a, 5b) are made of plastic selected from the group containing poly(acrylonitrile-co-styrene-co-acrylate) ), poly(acrylonitrile-co-butadiene-co-styrene), poly(acrylonitrile-co-butadiene-co-styrene-co-methyl-methacrylate), a mixture of polycarbonate and poly(acrylonitrile-co-butadiene-co-styrene), poly( ethylene-co-terephthalate) with glycol modification, a blend of glycol-modified poly(ethylene-co-terephthalate) and carbon fibers, poly(etherimide) and polyurethane. 5. Composite optical fiber sensor (14) according to any of the preceding claims, characterized in that the notch (6) for accommodating the optical fiber (9) is linear and/or curved. 6. A composite optical fiber sensor (14) according to any one of the preceding claims, characterized in that the optical fiber (9) is multi-mode. 7. Composite fiber optic sensor (14) according to any one of the preceding claims, characterized in that the housing (1, 2), the first elastically deformable member (3) and the second elastically deformable member (4) are made of an elastically deformable material, in particular of rubber. Composite fiber optic sensor (14) according to any one of the preceding claims, characterized in that the housing (1, 2) comprises an upper part and a lower part, the upper part comprising two protruding opposite edges (8) extending over the lower part. 9. Composite optical fiber sensor (14) according to any one of the preceding claims, characterized in that the upper part of the housing (1, 2) contains protective elements for protecting the connection of the optical fiber (9). - 10CZ 36242 UI 10. Composite fiber optic sensor (14) according to any one of the preceding claims, characterized in that between the first deformation surface of the first elastically deformable member (3) and the lower part of the housing (1, 2), or between the first deformation surface of the first elastically deformable member ( 3) and the second deformation surface of the second elastically deformable 5 member (4) is arranged with a plastic intermediate layer, preferably made of glycol-modified poly(ethylene terephthalate). 11. Arrangement of a composite fiber optic sensor (14) for detecting the pressure force generated by the passage of a rail vehicle wheel according to any of the preceding claims, characterized in that the composite fiber optic sensor (14) is placed under the heel (11) of the rail (10) and on the base rail (12), while both ends of its optical fiber (9) are connected to an optical cable (22), which is further connected to an evaluation unit (23) containing a light source (21), a detector (20) and a processor (15).