GB2058422A - Method of and Means for Detecting Hot Bearings in Railway Vehicles - Google Patents

Abstract

An alarm system for providing warning of an overheating bearing railway vehicle serves to sense the temperatures of the individual bearings of the vehicle, to extract the mean thereof, to compare each sensed temperature with the mean, and to initiate an alarm in the event of any one of said sensed temperatures exceeding the mean by more than a predetermined limit.

Description

SPECIFICATION Method of and Means for Detecting Hot Bearings in Railway Vehicles This invention relates to a method of and means for detecting hot bearings in railway vehicles.

The wheel or axle bearings are amongst those components of railway vehicles which are most highly stressed, in that they provide the rolling connection of axle and wheel which makes possible the motion of a train. They have to withstand considerable loads and have to contend with particularly heavy operating conditions, being subjected to vertical and transverse stresses which increase with increase in speed of the train.

Bearing overheating may arise from various causes, such as mechanical damage or lack of lubrication and can have harmful consequences both for persons and for property, because it can develop and cause axle breakage and consequent deraiiment, which also results in interruption of traffic.

Traditionally, inspection of the bearings is generally carried out on trains halted in stations.

In recent years the considerable advances made in the field of electronics have made it possible to provide arrangements which detect the temperature of the bearings in movement, these being based on the picking up of infra-red rays.

The normal temperature range of a bearing in movement is from 400C to 1 00C with a consequent emission peak at 7 to 8 ,um.

Superimposed on the emission from the bearing is an undesirable radiation, due to ambient conditions, of a wave-length in the range from 3 to4m.

By using infra-red detectors of high sensitivity in the wave-length range in question, and by providing them with suitable filters which eliminate disturbances of solar origin, one can obtain a signal/noise ratio which is satisfactory for the applications in question.

The detectors which can be used are of several kinds. However, the best, by far, are those of a photoelectric kind, in which any incident radiation creates a corresponding electromotive force which is proportionate thereto. Moreover such detectors have very short response times of the order of a millisecond.

Another characteristic which the detectors must have is good resistance to mechanical stresses in that they have to be fixed along the lines, at locations not staffed by personnel.

Difficulties in the operation and in the designing of the apparatus arise from the fact that the bearings, when running, are not all the same and the detector has to have an angle of visibility which is sufficiently large to cover all the types, but not so large as to allow the detector to be influenced by other hot moving parts. These and other circumstances have suggested a particular solution, which is that of unblocking (or activating) the detecting device only when a bearing passes in front of the detector. To do this, use is made of electromagnetic mechanisms which control the opening of a window placed on the detector proper and only simultaneously with the passage of a bearing in front thereof.

The equipment currently in use picks up the electrical signal from the detector, amplifies it and sends it to analogue recording equipment. After passage of the train the recording equipment makes available a paper strip on which there are visible vertical segments, one for each bearing, and the amplitudes (or widths) of which are proportional to the temperatures which have been detected. Those bearings for which the amplitude of the recording segment is greater than a specific predetermined danger threshold are considered to be dangerous.

There also exists an automatic dangerous bearing detector which fixes the position thereof and which signals the presence thereof by optical and acoustic alarms.

The known forms of equipment for detecting hot bearings lend themselves to various criticisms. The first and most important of these is that these systems are affected by ambient conditions too much to be considered reliable. For example, let it be supposed that, in a train, there are some bearings which are hot beyond that which is allowed, and that before arriving at a control point of the equipment, the train passes through a storm. As a consequence of the storm, the temperature of each bearing may drop considerably, and it may transpire that, when the train passes in front of the equipment, dangerous temperature levels are not detected.

Nevertheless, these bushes continue to be dangerous in that they continue to overheat. It is thus necessary for the equipment to be completely freed from uncertainties arising from environment circumstances.

Another considerable disadvantage of the existing system is the fact that they are unable to provide early indications of the start of bearing overheating. To achieve this, it would be necessary to compare the recordings obtained from one and the same bearing at two successive detection points.

An object of the present invention is to provide a method of and means for detecting hot bearings as aforesaid, in which the above-discussed difficulties and disadvantages are eliminated or obviated, the arrangement enabling early detection of bearing overheating to be achieved.

With this object in view, the present invention provides a method of detecting hot bearings in railway vehicles using a detector, such as an infrared ray detector, which detects the temperature of the individual bearings of a railway train and provides respective signals corresponding thereto, characterised in that the temperature signals relating to the individual bearings of each side separately are processed to extract the mean thereof, in that each signal is compared with the said mean, and in that an alarm signal is established as a function of deviation of any of said temperature signals from the mean by a value greater than a predetermined proportion of the said mean.

Advantageously several thresholds are established; the one or other threshold is preselected as a function of the extracted mean value of the detected temperatures, and an alarm signal is initiated when one of the temperature signals exceeds this threshold. The said alarm signal is preferably also capable of localising or identifying the bush from which the temperaturethreshold-exceeding signal emanates.

In the event that the number of temperature signals is below a pre-established limit, for instance in the case of a short train or of an individual locomotive, the extracted mean may be distorted by the presence of an anomalous signal which corresponds to an overheated bearing. To avoid this, provision may be made for the temperature signals to be processed together with stored signals derived from a preceding train.

For the same purpose, alternatively provision may be made for the temperature signals to be processed to extract the mean of the detected temperatures after exclusion, from the calculations, of the signal corresponding to the maximum detected temperature.

In a system wherein the temperatures are sensed at a plurality of detection stations, the method of the invention may be characterised in that the signals sensed at an upstream one of said stations are stored and are compared with the corresponding signals arising from temperatures sensed at a downstream station, in order to monitor the progress of a heating phenomenon.

For carrying out the method described above, the invention further provides means comprising a detector disposed to detect the temperatures of the individual bearings of a railway train and adapted to provide respective signals corresponding to each said detected temperature; means for storing the temperature signals; processing means for extracting the mean of said signals; means for establishing an alarm threshold limit above said mean; and means for comparing the temperature signals with said threshold and for initiating an alarm signal when the threshold is exceeded by one of the temperature signals.

Advantageously the system comprises means for selecting the alarm threshold as a function of the extracted mean.

In practice the processing means preferably comprises a microprocessor, and the arrangement may include a transmission system, for transmitting the data (i.e. the temperature signals or information derived from said signals), including for example a telephone loop, one or more optical fibres, or the like, to a central processor, or of the processed data, e.g. at a monitoring station.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram illustrating a practical embodiment of the means of the invention; Figure 2 is a flow diagram illustrating the manner of processing the sensed temperature signals in the arrangement of Figure 1; and Figures 3, 4 and 5 are diagrammatic illustrations of representative records or displays which may be produced by the apparatus of Figures 1 and 2.

The apparatus of the invention may employ, as means for receiving and processing the data, a microprocessor of the type known under the designation Signetics 2650. This microprocessor receives analog signals (see Figure 1) from a trackside unit, represented as a detector at block 1, for detection, transduction and amplification (block 3) of temperature signals T emanating from the bearings of vehicles of a passing train, and after having converted these temperature signals into digital signals (block 5) passes them to a service store or memory 7 comprising erasable processing registers RAM. Indicated by the numeral 9 is the whole of a central calculation unit; this is connected to a memory EPROH for a permanent programme as well as a viewer or display 12 and a register or recorder 14.The data travels, from the converter 5, to the stores 7 and 10, the display 12, the recorder 14 and the C.P.U.

unit (data bus); from these latter three units data also arrives at the stores as input data (address bus).

The programme followed by the C.P.U. is such as to free the processing from the ambient situations discussed in detail in the foregoing and follows the flow diagram of Figure 2, in which: Tm=the mean temperature of the bearings of the entire train; A, B a C=the ranges in which the mean temperature can fall; S, S2 a S3=comparison thresholds associated with the aforesaid ranges A, B a C; ATi=Tbi-Tm=deviation from the mean of the temperatures of the individual bearings; K=ATi-S=deviation of a temperature above a safety threshold.

The first operation carried out immediately after acquisition of the data is extraction of the mean Tm; depending on Tm being within one of the three ranges A, B, C envisaged, there is correspondingly selected one of the thresholds S2, S3, which has to be understood as the safety threshold which must not be exceeded by the deviations which the temperatures of the bearings may exhibit, beyond the mean, in the ambient conditions.

The different thresholds are adapted to provide for different ambient conditions; it is clear that the higher the external temperature, then the lower the safety threshold has to be, and vice versa. The extracted mean is practically unaffected by the influence of the various temperatures of overheated bearings; this is all the more true the fewer are the bearings measured, whilst overheated bearings are very limited in number, even if there are any of them, as has statistically been proved.

If, for example, only a single locomotive passes in front of the detector, and this has one or two overheated bearings, the mean could turn out to be distorted, so that the whole process could be incorrect. In this difficult situation, that is to say if the number of axles passing the detector is fewer than eight, a lower threshold is introduced and reference can be made directly to the mean of the preceding train in order to create a less-restrictive comparative parameter, or else a comparison can be carried out between the right-hand bearings and the left-hand ones, that is to say with a differential alarm criterion.

In terms of signals, the algorithm which is referred to herein under, works in the manner indicated in Figures 3, 4 and 5, in which: Tm is the mean of the temperatures Tbi of the bearings; ATi=Tbi-Tm is the deviation between the extracted mean temperature and an individual bearing temperature and S is the threshold value.

In Figure 3 there is shown the choise of Tm; in Figure 4 there is indicated the threshold chosen automatically on the basis of Tm; if ATi > S, the alarm is initiated because there is overheating beyond that which is allowed. In Figure 5 there is indicated a dangerous condition of one bearing (Tp) when this has a temperature superelevation ATi in comparison with the extracted mean Tm greater than the threshold S, that is when ATi-S=K > 0.

When a situation occurs such as the one described with reference to Figures 3, 4 and 5, the bearing in question is considered to be dangerous and its condition is passed for exhibition on the display 12.

When a train has passed, there will therefore be available at the display 12 which may comprise a cathode ray tube, or at the register, the following information:- mean temperature of the bearings of the train (right and left, with detectors correspondingly positioned); position, represented as a number counting from the front of the train, of the bearing or bearings which exceed a specific safety threshold; indication of the temperature superelevation with respect to the safety threshold of each of the bearings indicated as per the preceding point; number of axles which have passed.

There may also be available an analogue registration of the heat signals, for example in the form of segments marked in succession on a tape, of amplitude (or height) proportional to the temperature of each bearing. There is, then, also the possibility of carrying out comparisons between traditional measurements and relative measurements in accordance with the method which is the subject of the present invention.

To these indications-if desired-there can be added others, such as a chronological registration of the event (that is the time at which the train has passed) and, so that the information may be absolutely complete, also the number of the train to which all the data refers, the whole obviously in an automatic manner. There can also be provided an interface with a printer so that the the discussed information can be printed in order to provide a permanent documentation of the different situations which have occurred. It is also possible to register all of the data on magnetic tapes, which is particularly useful subsequent statistical processing or analysis, again in an automatic manner.

The apparatus in question also makes it possible, in a simple manner, to forsee the start of overheating in a bearing, in that the digital data, relating to a specific observation post can be sent by cable to a subsequent processing station and be retained in store there for comparison with data coming from the detector of this subsequent processing station. Although this may entail a heavy burden in the expense of the detecting apparatus, it has the advantage that it allows early rectification of a potentially dangerous condition, to the entire advantage of safety.

Alternatively, provision may be made for centralisation of the data, for example by the despatch of the data collected along a stretch of line which is relatively long to a single processing post; from this same point provision can also be made for signalling any operational bearing abnormalities to engine personnel by way of a ground/train connection.

Amongst the more important features of the processing system of the invention is the possibility of making an auto-test, that is to say of verifying automatically, when the occasion so requires, the proper operation of the entire means for processing and displaying the data.

In conculusion, th.e system described is completely indpendent of ambient conditions, and it is possible to arrange the detection point at any site, such as on a viaduct, at the exit from a tunnel, on bends even having a small radius, close to embankments and in other locations which would produce spurious alarms if recourse were not had to the method in question.

Since the method of the invention is realisable with modern techniques of programmed logic by means of microprocessors, it has very high flexibility and operational speed and is readily capable of expansion such as to make possible innumerable variations and additions, without having to modify excessively the pre-existing structure, even during a short interval between the passage of one train and the next one. One can thus, also, hypothesize the personalising programmes, in accordance with particular requirements which may occur, if problems should arise dictated by the experience in any specific system.

It is understood that the drawing illustrates only an example given only as a practical realisation of the invention; modifications and variations can, accordingly, be made without departing from the scope of the invention as defined by the following claims.

Claims (11)

Claims

1. A method of detecting hot bearing in railway vehicles using a detector, such as an infra-red ray detector, which detects the temperatures of the individual bearings of a railway train and provides respective signals corresponding thereto, characterised in that the temperature signals relating to the individual bearings of each side separately are processed to extract the mean thereof, in that each signal is compared with the said mean, and in that an alarm signal is established as a function of deviation of any of said temperature signals from the mean by a value greater than a predetermined proportion of the said mean.

2. A method as claimed in claim 1 characterised In that several thresholds are established, in that one of said thresholds is preselected as a function of the value of the mean, and in that an alarm signal is established when a temperature signal exceeds the said threshold, the said alarm signal being identifiable to localise the bearing from which the said temperaturethreshold-exceeding signal emanates.

3. A method as claimed in claim 1 or 2 characterised in that, in the event that the number of temperature signals is below a pre-established limit, for instance in the case of short trains and individual locomotives, said temperature signals are processed together with stored signals derived from a preceding train.

4. A method as claimed in claim 1 or 2 characterised in that, in the event that the number of temperature signals is below a pre-established limit, for instance in the case of short trains and individual locomotives, said temperature signals are processed to extract the mean of the detected temperatures after exclusion, from the calculations, of the signal corresponding to the maximum detected temperature.

5. A method as claimed in any preceding claim wherein the temperatures are sensed at a plurality of stations and characterised in that the signals pertaining to the temperature sensed at an upstream one of said stations are stored and are compared with the corresponding signals arising from temperatures sensed at a downstream station, in order to monitor the progress of a heating phenomenon.

6. A method of detecting hot bearings in railway vehicles as claimed in claim 1 and substantially as herein described.

7. Means for detecting hot bearings in railway vehicles comprising a detector disposed to detect the temperatures of the individual bearings of a railway train and adapted to provide respective signals corresponding to each said detected temperature; means for storing the temperature signals; processing means for extracting the mean of said signals; means for establishing an alarm threshold limit above said mean; and means for comparing the temperature signals with said threshold and for initiating an alarm signal when the threshold is exceeded by one of the temperature signals.

8. Means as claimed in claim 7 characterised in that it comprises means for selecting the alarm threshold as a function of the mean.

9. Means as claimed in claim 7 or 8 characterised in that the processing means comprises a microprocessor.

10. Means as claimed in claim 7, 8 or 9 characterised in that it comprises a transmission system selected from a telephone loop and optical fibres, for transmitting selected data to a central monitoring station.

11. Means for detecting hot bearings in railway vehicles substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.