FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a system and method for information gathering and alert generation from railways.

BACKGROUND OF THE INVENTION

Piezoelectric materials having the ability to transform mechanical strain energy into dielectric electrical output are commonly used for the purpose of power harvesting.

Some details regarding energy harvesting and piezoelectric generators may be found in the following patents and patent application publications which are incorporated herein by reference:

US 2010/0045111 "Multi-Layer Modular Energy Harvesting Aparatus, System and Method";

US7, 830,071 "Power Harvesting Apparatus, System and Method";

US7, 812,508 "Power Harvesting From Railway; Apparatus, System and Method";

US 2011/0291526 "Piezoelectric Stack Compression Generator"

Rail is an important means of transporting goods over long distances in specialized container cars. As cars in trains are often heavily loaded, both wheels and tracks suffer wear and fatigue which may cause failure. Such failures may be highly expensive and may cause massive injuries, loss of service and may even cost life.

Systems for real time monitoring of railroads are known in the art. For example, US application publication 2001/0022332, titled "Automated railway monitoring system" discloses a method and apparatus for determining the real time location of wheeled cars linked together in a train traveling on a fixed track". The method creates a wheel count and a location point for the train by counting the number of wheels on the train in a sequential order as the train passes a first wheel counting station, wherein the wheel counting station is stationary at a fixed location. The wheel count and location point for the train is then recorded on a computer. As the train passes subsequent wheel counting stations positioned along the track, the train is identified by recounting the wheels on the train and matching the number of recounted train wheels to the wheel count. The location point of the train is updated in the computer to correspond to the location of the last wheel counting station and to count the number of wheels on the train. Subsequently, a rail car location in the computer is created, wherein the rail car location corresponds to the last updated location point for the train. Accordingly, the method apparatus use a plurality of wheel counting stations, sensors, and a computer to determine the location of linked cars on a fixed track. However, failure due to wear of the wheels is not found.

SUMMARY OF THE INVENTION

It is therefore provided in accordance with a preferred embodiment of the present invention, a sensor pad comprising a plurality of piezoelectric elements, wherein the sensor pad is sized to replace a vibration damping pad,

Furthermore, in accordance with another preferred embodiment of the present invent, the sensor pad is inserted between a railroad rail and a railroad sleeper.

It is provided with yet another preferred embodiment of the present invention, a sensor for railroad monitoring comprising a plurality of elements, wherein the signal produced by the sensor in response to a passing train requires no amplification.

Furthermore, in accordance with another preferred embodiment of the present invent, said piezoelectric elements are made of material selected from a group consisting of: ceramic materials, piezoelectric polymers, and single crystal.

Furthermore, in accordance with another preferred embodiment of the present invent, the sensor comprising:

a base plate;

a cover plate; at least a first matrix plate positioned between said base plate and said cover plate, said first matrix plate comprising:

a first insulation layer;

a conductive layer electrically connected to a first lead of an electric cable; and

a second insulation layer, wherein said second insulation layer comprises a plurality of cavities (761); wherein said plurality of piezoelectric elements (760) are sized to fit in said cavities such that one side of said plurality of piezoelectric elements forms mechanical and electrical contact with said conductive layer;

and wherein forces applied by a passing train on the railroad rail causes said plurality of piezoelectric elements to produce an electrical signal at said electrical cable.

Furthermore, in accordance with another preferred embodiment of the present invent, the pad further comprising at least a second matrix plate positioned between said base plate and said cover plate, said second matrix plate comprising:

at least a first insulation layer;

a conductive layer electrically connected to a second lead of said electric cable, such that the other side of said plurality of piezoelectric elements forms mechanical;

electrical contact with said conductive layer of said second matrix plate.

Furthermore, in accordance with another preferred embodiment of the present invent, said second matrix plate comprises a second insulation layer, wherein said second insulation layer comprises a plurality of cavities such that each of the piezoelectric elements fits in a cavity formed in said second insulation layer and a corresponding cavity in said second insulation layer.

Furthermore, in accordance with another preferred embodiment of the present invent, said plurality of piezoelectric elements are sized to snugly fit within said cavities. Furthermore, in accordance with another preferred embodiment of the present invent, said base plate and said cover are made of a rigid material.

Furthermore, in accordance with another preferred embodiment of the present invent, said at least one of said matrix plates is made of printed board.

Furthermore, in accordance with another preferred embodiment of the present invent, the sensor pad is encased in elastomer.

It is therefore provided and in accordance with yet another preferred embodiment of the present invention, a system for railroad monitoring comprising:

at least one sensor pad inserted between a railroad rail and a railroad sleeper, wherein the sensor pad is sized to replace a vibration damping pad inserted between the railroad rail and the railroad sleeper, and wherein forces applied by a passing train on the railroad rail causes said at least one sensor pad to produce an electrical signal;

at least one signal extracting unit receiving said electrical signal from said at least one sensor pad and converting said signal to digital information;

at least one processor capable of receiving said digital information from said signal extraction unit, and processing said information to produce processed information;

a communication unit capable of receiving said processed information from said processor; and

a remote server capable of receiving information from said

communication unit, and capable of monitoring at least one parameter of said passing train based on information derived from signals produced by the sensor pad.

Furthermore, in accordance with another preferred embodiment of the present invent, further comprising at least two sensor pads installed on two different rails.

Furthermore, in accordance with another preferred embodiment of the present invent, further comprising at least two sensor pads installed at a known distance along the length of the railroad. Furthermore, in accordance with another preferred embodiment of the present invent, said least one parameter of said passing train is selected from a group consisting of: train location; number of axels in a train; number of cars in a train; uneven loading of a car; weight of a car; speed of traveling of a train; direction of a traveling train; and distance between two trains.

Furthermore, in accordance with another preferred embodiment of the present invent, said least one parameter of said passing train is a defect in a wheel of the passing train.

Furthermore, in accordance with another preferred embodiment of the present invent, said defect in a wheel of said passing train is selected from a group consisting of: a crack in said wheel; a flat in said wheel; a loose bearings in said wheel; a stuck bearings in said wheel; and excessive wear of said wheel.

Furthermore, in accordance with another preferred embodiment of the present invent, the system further comprising:

at least one piezoelectric generator, installed in a cavity in a sleeper of a railroad and capable of producing electrical energy in response to forces applied by a passing train;

a power source capable of receiving said electrical energy from said at least one generator, and powering the system for railroad monitoring; and; an energy storage capable of receiving electrical energy from said power source when a train passes over said at least one generator, storing said electrical energy received from said power source, and supplying energy to said power source when a train is not passing over said at least one piezoelectric generator.

Furthermore, in accordance with another preferred embodiment of the present invent, said least one parameter of said passing train is a defect in a wheel of said passing train.

Furthermore, in accordance with another preferred embodiment of the present invent, the system further comprising at least one sensor patch glued to said railroad rail, wherein said at least one sensor patch is capable of producing electrical signal in response to a train passing upon said rail over said sensor patch. Furthermore, in accordance with another preferred embodiment of the present invent, said at least one sensor patch glued to said railroad rail in a location selected from the group consisting of: the base of the crown; the sides of the neck; the shoulders; and the bottom of said rail.

Furthermore, in accordance with another preferred embodiment of the present invent, the system further comprising at least one display, connected to said processor, wherein said processor is capable of analyzing said digital information receiver from said signal extraction unit and display results derived from analyses of said digital data on said display.

Furthermore, in accordance with another preferred embodiment of the present invent, said least one display is a track side traffic light, and said results derived from analyses of said digital data is a warning of detected hazard.

Furthermore, in accordance with another preferred embodiment of the present invent, the system is capable of monitoring at least one parameter selected from a group consisting of: condition of a rail, condition of a sleeper; change in the conditions of said rail.

Furthermore, in accordance with another preferred embodiment of the present invent, wherein said sensor pad comprises:

a base plate;

a cover plate;

at least a first matrix plate positioned between said base plate and said cover plate, said first matrix plate comprising:

a first insulation layer;

a conductive layer electrically connected to a first lead of an electric cable; and

a second insulation layer, wherein said second insulation layer comprises a plurality of cavities; and

a plurality of piezoelectric elements, sized to fit in said cavities such that one side of said plurality of piezoelectric elements forms mechanical and electrical contact with said conductive layer. Furthermore, in accordance with another preferred embodiment of the present invent, said a plurality of piezoelectric elements are arranged in an array comprising at least a first row and a second row, wherein said first row and said second row are in a direction substantially along the railroad rail, wherein elements in said first row and elements in second row are electrically connected such that sideways force applied to said railroad rail is detectable by comparing the electrical signal produced by elements in said first row and electrical signal produced by elements in said second row.

Furthermore, in accordance with another preferred embodiment of the present invent, the system further comprising:

at least one piezoelectric generator, installed in a cavity in a sleeper of a railroad and capable of producing electrical energy in response to forces applied by a passing train;

a power source capable of receiving said electrical energy from said at least one generator, and powering the system for railroad monitoring; and; an energy storage capable of receiving electrical energy from said power source when a train passes over said at least one generator, storing said electrical energy received from said power source, and supplying energy to said power source when a train is not passing over said at least one piezoelectric generator.

Furthermore, in accordance with another preferred embodiment of the present invent, when said piezoelectric elements are made of a single crystal, the sensor pad is capable of harvesting power.

In addition, there is provided in accordance with another preferred embodiment of the present invention, a system for railroad monitoring comprising:

at least one piezoelectric generator inserted in a railroad sleeper;

at least one signal extracting unit receiving said electrical signal from said at least one generator and converting said signal to digital information; at least one processor capable of receiving said digital information from said signal extraction unit, and processing said information to produce processed information; a communication unit capable of receiving said processed information from said processor; and

a remote server capable of receiving information from said communication unit, and capable of monitoring at least one parameter of said passing train based on information derived from signals produced by the generator.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

Figure 1 schematically illustrates a block diagram of an exemplary embodiment of a piezoelectric train monitoring system according to an exemplary embodiment of the current invention. Figure 2 schematically illustrates an exploded view of a sensor pad placed between rail sleeper and rail according to an exemplary embodiment of the current invention.

Figure 3A schematically illustrates an exploded view of sensor pad according to an exemplary embodiment of the current invention.

Figure 3B schematically illustrates a top view of the sensor pad shown in Figure 3A according to an exemplary embodiment of the current invention.

Figure 3C schematically illustrates a side view of the sensor pad shown in Figure 3A according to an exemplary embodiment of the current invention.

Figure 3D schematically illustrates another side view of the sensor pad shown in Figure 3A according to an exemplary embodiment of the current invention.

Figure 4 schematically illustrates a cross section view of a piezoelectric load sensing pad using a plurality of separately operated piezoelectric elements placed between rail and sleeper according to an exemplary embodiment of the current invention.

Figure 5 schematically depicts a cross section view of a rail with piezoelectric sensor patches attached to a rail according to an exemplary embodiment of the current invention.

Figure 6 schematically illustrates an exploded view of a sensor patch according to an exemplary embodiment of the current invention.

Figure 7 schematically depicts a cross section view of an implementation of a generator for energy harvesting in a sleeper according an embodiment of the current invention.

Figure 8 schematically illustrates profiles of voltages received from sensors coupled to a rail, when a wheel of a train passes on the rail section to which the sensors are coupled according to an exemplary embodiment of the current invention. DETAILED DESCRIPTION OF THE SELECTED EMBODIMENTS

Various embodiments of a railway information gathering system and method are disclosed hereinbelow.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

In discussion of the various figures described herein below, like numbers refer to like parts. The drawings are generally not to scale. Some optional parts were drawn using dashed lines. For clarity, non-essential elements were omitted from some of the drawings.

To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. Thus, for example, one or more of the functional blocks (e.g., processors or memories) may be implemented in a single piece of hardware (e.g., a general purpose signal processor or random access memory, hard disk, or the like) or multiple pieces of hardware. Similarly, the programs may be stand alone programs, may be incorporated as subroutines in an operating system, may be functions in an installed software package, and the like. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. Figure 1 schematically illustrates a block diagram of an exemplary embodiment of a piezoelectric train monitoring system 200 according to an exemplary embodiment of the current invention.

Although presented in the block diagram as a collection of separate blocks, the system may optionally be integrated differently.

The exemplary embodiment of train monitoring system 200 comprises at least one, and optionally a plurality of sensor pads 700. Sensor pads 700, which will be detailed in the following figures, are preferably thin, reliable, long-lasting data gathering pads, placed between the rail and the sleeper. These data gathering sensor pads are preferably waterproof and resistant to mechanical strain, and preferably may replace standard pads commonly used for damping vibration caused by passing trains. Sensor pads 700 comprises at least one, and optionally a plurality of piezoelectric elements which produce electrical signal in reaction to, and in relation to the mechanical force caused by stresses, forces and motion produced by the passing train. The piezoelectric elements used within this invention may be piezoelectric ceramic materials, piezoelectric polymers or similar material such as single crystals. Because of the high voltage output of these materials no signal amplifications is needed. In fact, when single crystal materials are being used, sensor pad 700 may produce enough energy to be used for other purposes. As an example, it is used to power the monitoring system. In these cases, sensor pad 700 may be used as a similar manner to generator 210 as explained herein below.

In some embodiments, sensor pads 700 are spread over a long section of tracks, or in contrast, located in a small section. Preferably, sensor pads are installed under both tracks.

Sensor pads 700 are connected to at least one signal extraction unit 220. The signal extraction unit 220 is an electronic "front-end" unit providing digital information indicative of the detected signal to at least one processor 230. When a plurality of sensor pads or other sensors are used, a plurality of signal extracting units may be used, wherein each signal extractor unit serves one or a plurality of sensors. In some embodiments, signal extraction unit 220 may optionally be integrated with, or placed closed to the sensors. Data from extraction unit 220 is transferred to processor 230 for further analysis or in preparation for transferring the data to a remote server 255 via communication unit 250 and communication channel 255. Communication channel 252 may be wired; optical fiber; or wireless communication channel. Optionally, processor 230 may store information in optional data storage 240 and use the stored information for local processing.

Optionally, the processes information may be locally displayed on one or more optional local displays 260. For example, optional local display 260 may be used to alert train operators (on the train or at train station) if abnormal or hazardous conditions were detected. For example, display 260 may be a track side traffic light, or a conventional display at a train control facility. Communication unit 250 or remote server 255 may optionally send alerts to track side traffic lights and semaphores, prepare reports for repair crew, or train maintenance crew, or issue testing and inspection requests.

Optionally, train monitoring system 200 comprises at least one, and optionally a plurality of optional sensor patches 702. Sensor patches 702, which will be detailed in the following figures, are sensors attached or glued to the railroad track. These data gathering sensor patches are not subjected to the weight of the passing train and thus may be cheaper to manufacture and install. Optional sensor patches 702 are connected to at least one signal extraction unit 220. When a plurality of sensor patches are used, a plurality of signal extracting units may be used as well, wherein each signal extractor unit serves one or a plurality of sensors. In some embodiments signal extraction unit 220 may optionally be integrated with, or placed closed to the sensor patches 702.

It should be noted that typically, sensor pads 700 and sensor patches 702 are not used for energy harvesting, as the amount of energy generated by a sensor pad or patch is small. As mentioned herein above, in the case single crystal is used, energy may be sufficient. Power source 270 provides power 720 to system 200. Power source 270 may be connected 714 to main electric grid. Alternatively, electric power used for powering electric trains may be used. Optionally, additionally or alternatively, renewable power sources such as wind power or sun power (nor seen in this figure) may be used. In these cases, energy storage 280 may be used for storing excess energy for use when the alternative power source is not operational. Optionally, additionally or alternatively replaceable or rechargeable batteries may be used.

In some optional embodiments, at least one, and optionally a plurality of piezoelectric generators 210, which will be detailed in the following figures, are used to harvest energy from the passing train as disclosed for example in the references cited in the background. Optional generator 210 is a piezoelectric generator embedded in the sleeper below the railroad track such that passing train generates compressive forces that causes piezoelectric elements within generator 210 to generate electric energy. This energy may be used in power source 270 to charge energy storage 280 and to provide power 720 to system 200. Energy harvested from piezoelectric generators 210 and stored in energy storage unit 280 may serve as an independent power source for system 200, and optionally for other uses such as, but not limited to powering surrounding traffic signs and lights. Energy storage unit 280 or power source 270 may further be connected 714 to an external power source or external power users such as external load or a main power grid. Main power grid may provide energy to the systems when needed, and optionally receive excess energy when available.

In some exemplary embodiments, generator or a plurality of generators 210 may be used for both energy harvesting and sensing at the same time. In these optional embodiments, generator 210 is connected to signal extraction unit 220. Optionally, extraction unit 220 is used for generating signal indicative of the forces applied to the generator 210, while transferring 716 the majority of the energy to be harvested to power source 270.

Processor 230 and/or remote server 255 are capable of analyzing data received from signal extraction unit 220 to determine parameters of the passing train.

Optionally, the processor uses some parameters to analyze and translate the data to useful information. Such parameters may be calibration factors of the sensors, sensor locations, stored signal wave functions and the like. Parameters may be stored in an optional data storage unit 240. Data is optionally recorded and stored in data storage unit 240 for further reference. Processor 230 is optionally further capable of sending analyzed data to remote server 255 by using a communication unit 250 via a wired or a wireless communication channel such as, but not limited to phone, radio or cellular communication. Processor 230 may use optional display units 260 for displaying analyzed data to users. Display units 260 may be for example and without limitation computer screens, laptops, PDAs, cellular phone screens, printed sheets, integrated LCD screens (e.g. Thin Film Transistors, touch screens) or the like. In some applications, railway authorities may be alerted when safety violation or hazardous condition is detected. This may include one or combination of: excessive load, uneven or unbalanced loading, above limit travel speed, wheel defects or such like violations and hazardous conditions. Alert may be issued locally, for example using display 260, or remotely for example and without limitation using the communication unit 250.

Data storage unit 240 may be a database, or any other data storage means which suit requirements. Optionally, data storage unit 240 is located at a remote location not residing in physical proximity to sensors 700, processor 230 or other components of system 200.

Optionally, each system 200 may have its own dedicated data processor 230, storage unit 240 and display system 260, for processing, storing and displaying data locally. Alternatively, a number of systems 200 may share one or few of: processors 230; storage units 240; display unit 260; power source 270; and remote server 255.

In an exemplary embodiment of the invention, signals from sensors and/or energy generating patches may be used for monitoring train traffic along the railway. Dielectric electrical outputs produced by the patches may be used to monitor location, speed and direction of travel of a train along the railroad. The profile of the dielectric electrical outputs produced by the patches may be studied and compared to predefined patterns for recognizing optional defects in the rail, the train's wheels, or the like.

The exemplary embodiment of the invention may transform a conventional railroad to a smart railroad maintenance system with minimal modification, and assist in providing critical information about the train and the railway's condition.

Figure 2 schematically illustrates an exploded view of a sensor pad 700 placed between rail sleeper 10 and rail 20 according to an exemplary embodiment of the current invention. Data sensor pad 700, which will be detailed in the following figures, preferably comprises piezoelectric elements capable of measuring forces produced by passing trains. Preferably, the sensor pads are configured to be used instead of a vibration damping pads that are commonly used in railroad tracks. For example, sensor pad 700 is sized to fit in the location where standard vibration damping pads are used. It should be noted that the use of piezoelectric elements in sensor pad 700 should not be perceived as limiting in any way. Other data gathering components may be used in combination with or instead of piezoelectric elements, such as strain gauges. Piezoelectric elements embedded within patches can be used to transform mechanical energy produced by passing trains into dielectric electrical outputs. Electrical outputs may be produced by forces such as but not limited to shearing, stretching, bending, or pressing.

Several types of standard sleepers and rail attachments are currently used. In the exemplary, non-limiting embodiment depicted in figure 2, rail 20 is attached to concrete sleeper 10 by screwing screws 21a and 21b into tapped inserts 22a and 22b respectively, creating pressure on springs 23a and 23b that pushes against retainers 24a and 24b that hold rail 20 down. This pressure, combined with the weight of the rail creates a bias compressive pressure on sensor pad 700 which is placed between the rail 20 and sleeper 10. This bias compressing may be helpful for detecting vibrations by a piezoelectric sensing element.

Data sensor pads 700 may be installed when a new railway track is placed or during maintenance of the railway tracks. Alternatively, a conventional pad may be replaced with a sensor pad 700 by unscrewing screws 21a and 21b from several adjacent sleepers, lifting at least slightly rail 20, removing the conventional pad, replacing it with sensor pad 700, and fastening the unscrewed screws.

Figure 3A schematically illustrates an exploded view of sensor pad 700 according to an exemplary embodiment of the current invention.

Figure 3B schematically illustrates a top view of sensor pad 700 according to an exemplary embodiment of the current invention. Figure 3C schematically illustrates a side view of sensor pad 700 according to an exemplary embodiment of the current invention.

Figure 3D schematically illustrates another side view of sensor pad 700 according to an exemplary embodiment of the current invention.

In this exemplary embodiment, sensor pad 700 comprises a base 751 and cover 752. Side walls 753 are attached to the cover using screws 754 (for clarity, screws are marked only on one side). Screws 755 (only two are shown in figure 3 A) inserted through holes 756 (for clarity only few are marked), and fasten to tapped holes 757, holding cover 752 to base 751. Holes 756 may be made large enough to allow the head of screws 755 to stay below the surface of cover 752, and to allow forces applied to cover 752 not to be transferred to screws 755.

Piezoelectric elements 760 (for clarity, only two are seen) are maintained in place in cavities 761 in a lower matrix plate 762. Preferably, lower matrix plate 762 is a printed board (PCB) having an insulated layer at the bottom, a conductive layer, exposed at the bottom of cavities 761 and at connection tab 763, and an upper insulation layer having holes forming cavities 761. Optionally, the piezoelectric elements 760 fit snugly in cavities 761. Optionally, elements 761 are cylindrical. Optionally, elements 760 are arranged in a two-dimensional array of rows and columns. Optionally, elements 760 are pulled along the cylinder axis. Optionally, elements 760 have a cylinder axis substantially shorter than their diameter.

Upper matrix plate 772 may be identical or similar to lower matrix plate 762, turned upside down. When screws 755 are fasten, elements 760 are in physical and electrical contact with the conductive layers in lower matrix plate 762 and upper matrix plate 772 while each is held in its respective cavity. The thickness of the upper insulation layer is large enough to hold elements 760 in place, but small enough as not to make physical contact between the lower matrix plate 762 and the upper matrix plate 772. The conductive layers in the upper or lower matrix plates electrically connects the opposing sides of elements 760. Force applied between the cover and the base creates an electrical signal to appear between the conductive layers exposed at tabs 763 and 773. An electric cable (not seen in this figure) inserted trough orifice 766 is connected to tabs 763 and 773 and transfers the electric signal to signal extraction unit 220 shown in Figure 1. Alternatively, cavities 761 are formed only in one of the upper or lower matrix plates and the upper insulation layer is missing. Alternatively, one of the upper or lower matrix plates is missing and the cover or base are used as one of the conductive layers. Optionally, cover 752 and walls 753 are made as one unit. Preferably, cover 752, base 751 and walls 753 are made of metal, however, other materials such as plastic, rubber or composite material may be used. Optionally, sensor pad 700 is encased in rubber to make it similar in physical dimensions and mechanical properties such as elasticity and vibration damping to a standard pad. It should be noted that in some countries metallic pads are commonly used, specifically when heavy loaded trains are traveling. It should be noted that the number of elements 760, their shape and arrangements is for illustration purpose only and may vary.

Figure 4 schematically illustrates a cross section view of a piezoelectric load sensing pad using a plurality of separately operated piezoelectric elements placed between rail and sleeper according to an exemplary embodiment of the current invention.

For figure clarity securing screws and/or other means were omitted.

Load-sensing pad 300 using a plurality of separately operated piezoelectric elements 301a to 301e is placed between sleeper 10 and rail 20. For figure clarity, securing screws and/or other means were omitted.

The weight applied by the rail and mainly by the wheel of the train is schematically depicted by an arrow 311. In some cases such as when the train is unevenly loaded or travelling on a curve, or when the tracks are on a slope, or due to other forces or defects in the tracks or the train's car, side force schematically depicted by arrow 312 is applied to rail 20. The combination of forces 311 and 312 creates unequal distribution of compression forces on load-sensing pad 300 and on piezoelectric elements 301 a-e within it. In the depicted example, force 315 applied to element 301 a is larger than force 314 applied to piezoelectric fibers 301e.

It should be noted that sensor pad 700 shown in Figure 3 A may be converted to load-sensing pad 300 by connecting rows of elements 760 separately, referring to jointly connected elements 760 as elements 301x, ("x" stands for "a", "b", etc.) and using a separate cable for each jointly connected row. It also should be noted that number of elements 30 lx may be two or more and is not limited to the five elements seen in figure 4 or the five rows of elements seen in figure 3A. For example, a sensor pad having an array of six rows of elements may be configured as a two-element load sensing pad by electrically connecting together elements in rows 1-3, and separately connecting elements in rows 4-6.

Additionally, shear forces (not marked in the figure) may also develop within pad 300, and may be detected by piezoelectric elements or other sensors within the pad.

Figure 5 schematically depicts a cross section view of a rail with sensor patches attached to a rail according to an exemplary embodiment of the current invention.

Figure 5 schematically depicts some optional locations for placing sensor patches on rail 20. Generally, sensor patches 702 are attached or glued to the rail itself, at the base 501 of the crown 502, at the sides 505 of the neck 506 at the shoulders 507 or at the bottom 508 of rail 20.

It should be noted that locations of sensor patches is unrestricted except for the shoulders 507 and bottom 508 of rail 20, where their location is restricted as to not interfere with the sleeper 10 and retainers 24a and 24b that hold rail 20 down.

In contrast to sensor patches 700 and 300 that are mainly responsive to compressive forces, patches 702 generate electrical signal in response to stretching, contraction and bending forces that are caused by deformation of rail 20.

Sensor patches may be based on piezoelectric element or elements, for example in the shape of a thin sheet of piezoelectric material or a piezoelectric bar, or strip or a fiber. Preferably, the piezoelectric element or elements are encased in a thin protective layer or coating.

Alternatively, sensor patch 702 may use other methods of responding to mechanical strains. For example, using Vishay Precision Group of 3 Great Valley Parkway; Suite 150; Malvern, PA 19355; USA that offers a compression strain gauge (Manganin Pressure Sensor). Manganin is a copper-manganese-nickel alloy with low strain sensitivity, but a relatively high sensitivity to hydrostatic pressure. Resistance change as a function of applied pressure is linear in extremely high pressure. Other types of strain gauges are available. Strain gauges sensitive to specific strain directions are available from the same and other manufactures. Some strain gauges are resistive sensors, changing resistance in response to applied stain, and thus require electrical bias for their operation.

Sensor patches 702 may provide information on side forces applied to rail 20. These forces may be generated by the "undulation" of the car on the track. Typically, a train car moves in side-to-side oscillations having approximately 15 meter period under normal conditions. Changes in the periodicity may be an indication of abnormal conditions such as reduction of the radius of one or several wheels due to excessive wear. In some embodiments a plurality of sensors such as sensor pads 700 and/or sensor patches 702 are installed on a track, on one rail or both, over length of 15 meter or more at intervals such that the oscillation period may be estimated from analyzing the signals from the sensors.

Sensor patches may be constructed to provide information on a specific type of strain such as the component of stretching, contracting, shearing or bending in a specific direction. A directional sensor patch may be installed aligned in a desire red direction to provide specific readings.

Figure 6 schematically illustrates an exploded view of a sensor patch 702 according to an exemplary embodiment of the current invention.

Sensor patch 702 comprises a piezoelectric element 110 (or a plurality of elements) coated with thin layers 120a and 120b of flexible waterproof material, for example and without limitation elastic polymer. In preferred embodiments, sensor patch 702 is thin, and its thickness may range from tens to hundreds of microns. However, dimensions of sensor patch 702 and the piezoelectric element or elements within it may vary. An electric cable 1 15 is shown for transferring electrical signals produced by the piezoelectric elements embedded within the thin, waterproof coating layers of sensor patch 702. Figure 7 schematically depicts a cross section view of an implementation of generator 210 for energy harvesting in a sleeper according an embodiment of the current invention.

The cross sectional view depicted in figure 7, shows the sleepers 10 resting on gravel 570. A thin elastic layer, such as conventional pad 540 is preferably placed between sleeper 10 and mount 550. Washers 527a and 527b, pressed down by screws 523a and 527b, and nuts 525a and 525b respectively, hold rail 20 to mount 550 and sleeper 10.

In this cross section view, generator 210 is seen placed in a recess in sleeper 10. When a train traverses along rail 20, stress caused by the train's weight is transferred via rail 20, mount 550 and elastomeric layer 540 and presses generator 210 causing charge to be generated by generator 210.

Figure 8 schematically illustrates profiles of voltages received from sensors coupled to a rail, when a wheel of a train passes on the rail section to which the sensors are coupled according to an exemplary embodiment of the current invention.

Graphs 801 (solid line) and 901 (dotted line) represent signals produced by a first and a second sensors separated by a distance L along the same rail.

Referring to graph 801, the signal displays two peaks, 803 and 804, corresponding to traversing of first and second wheels respectively over the first of the two sensors. With proper calibration, the magnitude of the peaks may be used for determine the dynamic force applied by each wheel. Further calculations taking into account parameters such as but not limited to the train' s speed and a friction coefficient can be made to determine the static weight of the train.

Train's speed may be estimated for example from the width W of the peaks.

Additionally or alternatively, by knowing the distance D between the axels, and the time dt between peaks 803 and 804, the speed of the train V may be determined from a single sensor using the equation V= D/dt.

Additionally or alternatively, the train velocity V may be found from calculating V= LI At wherein L is the distance between the first and second sensors, and At is the time difference between signals from the first and second sensors as indicated by the time difference between peaks 804 and 904 associated with the passage of the same (second) wheel over the first and second sensor respectively.

In the Figure, areas marked in rectangles (809a and 809b) represent waveforms typical to a wheel having defects that passes upon the rail. A defect such as a fiat section on the circumference of the wheel may cause high frequency vibrations or other abnormalities in the signal. Such data can be used to detect and identify train wheel defects such as flats, and other types of defects while the train is in motion. This method is superior to tedious, costly and error prone visual inspection, and may reveal hidden defects such as loose bearings and the likes.

Some information may be obtained from a single sensor:

1. Weight supported by the sensed wheel.

2. Speed of the train. In this case, more accurate estimation of the speed and the direction may be obtained from two sensors installed at some distance from each other.

3. Location of the train that may be used for collision avoidance.

4. Length of the train, number of axels, and number of cars.

5. Cracks, flats, Wheel balance, loose or stuck bearings, deviations from

roundness, and other defects in the wheels.

6. Condition of the track and sleeper at the vicinity of the sensor.

Additional information may be obtained from at least two, or from a plurality of sensors:

1. Total weight of each car.

2. Accurate measurement of the train's speed and direction.

3. Uneven loading of the car.

4. Reduction in the radius of wheel. For example, due to wear that causes a reduction of the cycle of the side to side undulation of the car (less than 15m).

Additional information may be obtained from a network of sensors over large distances:

1. The distance between consecutive trains. This information may be used to generate alerts if the recorded distance is smaller than a pre-configured distance agreed upon .

2. The distance between trains travelling in opposite directions towards each other.

The use of only two sensors, one on each rail, installed at a known distance from each other along the track, may enable obtaining most of the above mentioned information.

Additionally, data received from multiple sensors over time may be used for a more accurate calibration of the system. For example and without limitation, the data can be used to calculate the preloading effect of consecutive wheels on piezoelectric sensors.

Some possible interpretations of data obtained from the sensors are described in some detail herein:

The number of axles of the train may be determined by counting and analyzing the number of peaks in signals produced by a single patch.

Defects in the perimeter of a train's wheel may be detected when a wheel inflicts a strong pounding effect to the rail. The pounding effect typically increases the vibration caused when the wheel passes upon the rail. This causes high frequency, large amplitude signals.

Train wheels wear out - The wear out in trains' wheels is typically stronger in the wheel' s internal perimeter. Typical wear out of a train' s wheel in its internal perimeter may reach 8 millimeters per year. A worn out wheel typically applies lateral pressure directed towards the internal or the external perimeter of the rail. This effect will be reflected in the signals produced by the sensor pads of the kind seen in figure 4 and sensor patches installed, for example, on the neck of the rail and adapted to measure side bending of the rail. This effect can also be reflected from sensor patches installed on the rail's internal and external sides.

Condition of the rail - when the rail section's infrastructure is kept up, the system will continuously generate similar signals from the sensors. When the rail infrastructure is damaged, optionally as a result of poor weather conditions or continuous friction, the sensors may generate electrical output which will be different than the expected values, thus indicating possible damages to the rail section. This application may be useful for maintenance monitoring of critical rail sections.

The sensor patches and pads can be easily applied according to exemplary embodiments of the current invention, without the need to replace or modify the existing sleeper or rail. Preferably, the rail original retaining structure may be used. Optionally, patch and pad coupling or replacement may be performed while the railway is being maintained.

Lateral pressure exerted by the wheels on the tracks may be an accurate indicator of the balance between the wheels on mutual axles. The energy produced by the generators allows the system to be self-powered, and nullifies the need to supply energy to the system.

It should be noted that piezoelectric sensors produce strong electrical signals, need no bias or amplification and are not susceptible to electronic interference.

It should also be noted that piezoelectric elements may be configured to exhibit tensor reaction to applied strain, and thus different orientation of the piezoelectric elements may provide different information such as compression, bending or shear strain. Imbalance of reading from sensors on opposing rails may be used for detection of improper centering of the load on a train car. Such imbalance may be caused for example by one or more of: uneven loading of the train car, a slope in the rail foundation, misaligned wheels, and centrifugal forces caused by traveling over a curve in the railway, and the likes.

Additionally, the sensors may be used for monitoring and quality control of maintenance and construction works. For example, sensors' reading from "before" and "after" repair or welding of a track may be compared, and the results used for evaluating the quality or integrity of the weld.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.