GB2107453A

GB2107453A - Hot box detector system

Info

Publication number: GB2107453A
Application number: GB08221938A
Authority: GB
Inventors: Cornelius A Gallagher
Original assignee: Servo Corp of America
Current assignee: Servo Corp of America
Priority date: 1981-10-05
Filing date: 1982-07-29
Publication date: 1983-04-27
Also published as: CA1211529A; SE8204618L; IN156288B; DE3236275A1; BR8203508A; AU8880082A; AU563788B2; GB2107453B; JPS5876362A; SE8204618D0

Abstract

A hot box detector system is provided in which an infra-red scanner (16) is arranged to scan the wheel bearings of railway rolling stock passing over a section of track (10) and to generate signals which are processed to determine the temperature of the bearing, the nature of the bearing, and, for signals derived from bearings within a closed housing (24, 26), to determine if the scanned surface of the housing is an inner sidewall (32, 34) or an outer sidewall (36, 38) of the housing (24, 26) relative to the bogie (22) to which the bearing belongs. Train speed is also determined from wheel detectors 12, 14. The signals are then normalised to account for differences in the heat dissipating characteristics of the inner outer sidewalls, and the air stream cooling resulting from the movement of the train before being analyzed to determined whether or not the bearing is overheated. <IMAGE>

Description

SPECIFICATION Hot box detector system The present invention relates to hot box detector systems for detecting overheated wheel bearings in railway rolling stock as it moves along a track.

In order to protect against wheel bearing failure in the rolling stock, most railways have hot box detectors in selected positions along the tracks which use an infra-red scanner to scan the bearings of the rolling stock as a train passes over a section of track defining a sensing zone. If an overheated bearing is detected, an alarm is triggered to alert the driver to stop the train and correct the potentially dangerous situation which, if allowed to continue, could result in a derailment. While it is extremely important that no overheated bearings (i.e. hot boxes) be missed by the detectors, it is almost equally important that no false alarms be generated since the unscheduled stopping of a train is a costly and time consuming operation that could result in substantial disruption of schedules.

The infra-red scanner and the associated circuits for detecting overheated bearings are highly developed and examples of such equipment are disclosed in U.S. Patent specifications Nos. 3,545,005; 3,454,758; 3,812,343; 3,872,456 and 4,113,211.

Hot box detector systems of the type described in the above patent specifications and which are available commercially are designed to safely detect hot boxes on trains passing through the scanning zone under a wide variety of different conditions, but without regard to the speed and other specific conditions of the train. Such systems operate to process the scanner signals the same way irrespective of whether the signal is generated from a train moving at five miles an hour (8 kms/hour) or from a high speed train moving at 100 miles per hour (161 kmslhour) or more.

As pointed out in the above patent specifications, railway goods wagons in the United States of America usually have one of two types of bearings, i.e. plain bearings (sometimes called friction bearings) or roller bearings. Although plain bearings are present on only approximately 16% of the total effective rolling stock in the U.S.A., the problems associated with the accurate analysis of signals from plain bearings are of particular importance to the railway industry since in 1980 rolling stock having plain bearings accounted for 74% of derailments.

Because the different types of bearing have different operating characteristics, the waveform of the infrared scanner signal resulting from any bearing must be analysed to permit proper bearing identification, and proper alarm criteria must be set depending on the type of bearing identified. For the purpose of the present discussion, the principal difference between roller and plain bearings which leads to problems in scanner signal analysis is that the portion of a plain bearing on which the infra-red scanner is focussed is contained within a housing, whereas a roller bearing is viewed directly by the scanner. The plain bearing housing, which protrudes from the wheelset or bogie frame of the railway wagon and is fixed to the frame, serves to siphon off some of the heat generated by an operating bearing and to dissipate it through the frame.Since a pair of bearing housings are usually provided on each side of each bogie frame, located towards the ends of the frame, the surfaces of the housings facing each other on each side (i.e., the housing inner sidewall surfaces) dissipate more heat than the surfaces of the housings facing away from each other (i.e., the housing outer sidewall surfaces). Since it is these inner and outer sidewall surfaces of the housings which are viewed by the hot box detector scanner, each output signal from the scanner depends on which surface of a housing is viewed.

In addition to the above, since the housings protrude from the bogie frame, the leading surface of each housing is exposed to the cooling effect of the air stream generated by virtue of the train movement, while the lagging surface is minimally affected by the air stream. The leading surface of each housing may be the inner or outer housing sidewall surface depending on the direction of movement of the train and on whether it belongs to the leading or lagging wheel of the bogie. Roller bearings are not subjected to these problems since roller bearings are directly viewed and are rotating while being scanned.

As a result of the above, the accurate early detection of overheated plain bearings has been extremely difficult.

According to the present invention, a hot box detector system for detecting overheated wheel bearings on railway rolling stock moving along a track comprises radiant energy scanner means which is positioned adjacent a section of the track so as to scan in succession the bearings of passing railway wagons and which generates a signal in response to each bearing scanned, means for determining if the surfaces of the bearings scanned dissipate heat generated by the bearings differently from one bearing to the next, means for processing the scanner signal relating to each bearing scanned to determine the condition of the bearing, and means for adjusting the scanner signal processing means as a function of the heat dissipating qualities of the surface of the bearing being scanned.

In a preferred embodiment of the invention the system determines if a scanned bearing is enclosed within a housing (in which case the bearing is a plain bearing) and, if so, if the scanned surface of the housing is an inner sidewall or an outer sidewall of the housing relative to the bogie to which the bearing belongs. The system preferably also determines if the scanned sidewall surface is a leading surface or a lagging surface with respect to the air stream caused by movement of the train in order to take into account cooling by the air stream as well as the different heat dissipation from inner and outer sidewalls of bearing housings when determining whether or not a bearing is overheated.

Such a hot box detector system in accordance with the invention can more accurately sense an abnormally high temperature in a plain bearing than has hitherto been possible. Furthermore, the system can be made using, to a great extent, conventional components, and can readily be adapted from existing hot box detector systems.

An example of a system in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a block diagram representation of the system; Figure 2A is a simplified waveform diagram of the heat signal generated by the scanner of the system as a result of scanning the wheel bearings of a two bogie wagon having plain bearings and moving in the direction indicated in Figure 1 in relation to the scanner orientation shown in Figure 1; Figure 2B is a simplified waveform diagram similar to that of Figure 2a but obtained when the train is moving in the opposite direction; and, Figure 3 is a diagram plotting against time the temperature rise of a plain bearing and inner and outer sidewalls of its housing as the bearing is overheated.

Figure 1 depicts a section of railway track 10 along which wheel sensors 12 and 14 are mounted. A radiant energy scanner 16, such as an infra-red hot box detector as described in U.S. Patent Specification No. 3,545,005, is positioned alongside the track so as to scan the wheels of each passing railway wagon as the wheels pass through a sensing zone defined by the wheel sensors 12 and 14, the scanner16 being focussed to view the bearing of each passing wheel. In practice, a pair of scanners are usually provided mounted on opposite sides of the track with each scanner focussed to view the bearings on its side of the track. The wheel sensors 12 and 14 and the infra-red scanner 16 are all of conventional design and are commercially available from the Servo Corporation of America of Hicksville, New York.In operation, the wheel sensors 12 and 14 generate a signal each time a wheel passes, and together define a time interval during which the scanner 16 is operative to generate a signal having an analog waveform indicative of the temperature of the bearing scanned.

Thus, as each of the wheels 18,20 of each bogie 22 of each wagon of a train passes through the sensing zone, a heat pulse in the scanner output is generated. Between bogies the scanner 16 views the under-carriage or bottom of the passing wagon, and between wagons the scanner may get a glimpse of the sky.

The problem with which the present invention is concerned is peculiar to those wheel bearings which are not exposed directly to the imaging spot of the scanner 16 but which are shielded from the scanner by a bearing housing. The bogie 22 shown in Figure 1 is provided with plain wheel bearings which are located in housings 24 and 26 mounted near the ends of the frame of the bogie 22. The housings 24 and 26 protrude laterally from the bogie frame and serve to contain a quantity of oil for lubricating the bearing. The oil is fed through covers 28,30 in the housings.As each housing 24, 26 passes through the sensing zone, the scanner 16 images on either the inner sidewall 32,34 or the outer sidewall 36,38 depending upon the direction of movement of the train and the orientation of the scanner, although it should be appreciated that in any pass each bogie 22 will have one of its bearing housings scanned on an inner sidewall and the other of its bearing housings scanned on an outer sidewall.

The inner sidewalls 32, 34 are those sidewalls which face each other and the spring nest of the bogie, and the outer sidewalls 36,38 are those sidewalls directed away from each other. As can be seen in Figure 1, the inner sidewalls 32,34 are contiguous to the large heat conducting mass comprising the main portion of the bogie frame, while the outer sidewalls 36, 38 are not. As a result, more of the heat from a bearing within a housing 24,26 will manifest itself on the outer sidewall 36, 38 than on the inner sidewall 32,34, and since a bogie will always have one housing scanned on its inner sidewall and the other housing scanned on its outer sidewall, regardless oftrain movement direction or scanner orientation, the scanner output signals derived from the two bearing housings will have different magnitudes.This is illustrated in Figures 2A and 2B wherein the pulse 40 corresponds to the bearing of the wheel 18, the pulse 42 corresponds to the bearing of the wheel 20, and the pulses 44 and 46 correspond to the bearings of the next bogie when it passes through the sensing zone. Figure 2A shows the form of the pulses generated when the train is moving in the direction indicated in Figure 1 and the initial surface imaged by the scanner is the inner sidewall 32 of the bearing housing 24, and Figure 28 shows the form of the pulses when the train is moving in the opposite direction and the initial surface viewed is the outer sidewall 36 or 38.

In Figure 3 a graph of temperature rise against time is presented for a deliberately generated hot box in a plain bearing. As may be seen, the temperature of the inner sidewall of the bearing housing is approximately 30% lower than that of the outer sidewall.

In the illustrated embodiment of the present invention, the output of the scanner 16 is fed to an alarm monitor 56 and also to a disciminator 48 which determines if the bearing under investigation belongs to a goods wagon (since plain bearings are only used on goods wagons). Such a discriminator is described, for example, in U.S. Patent No. 4,256,278.

If it is determined that a goods wagon is under observation, it is next determined whether the wagon has plain bearings or roller bearings. This is done in a discriminator 50 which relies on well known differences in the characteristic waveforms generated by the different bearings. The leading and lagging axle of each bogie is then determined by a circuit block 52 according to the sequence of wheel sensor signals for each bogie, and in this regard additional wheel sensors 53 and 53' are utilized in the manner described in the aforementioned U.S.

Patent No. 4,256,278. This information is then used by a circuit block 54 to determine which sidewall of the plain bearing housing is being scanned, and an adjustment of the alarm monitor 56 may then be made through a circuit block 58 to compensate for the differences in the heat dissipating characteristics of the inner and outer sidewalls of the housing.

Since the bearing housings 24 and 26 of the bogie 22 protrude from the bogie frame they are subject to exposure to an air stream caused by motion of the train. The cooling effect of this air stream is particularly noticeable when the train is moving in a direction which is oncoming to the scanner aperture (i.e. if the scanner 16 were directed in the opposite direction, or the train motion were in the opposite direction, to that shown in Figure 1). The speed of the train and hence the magnitude of the air stream effect may readily be determined by use of a train speed detector 60 which obtains inputs from a pair of wheel sensors spaced a fixed distance apart along the track in accordance with well known procedures.

Compensation for air stream cooling may then also be made in the circuit block 58, according to the train speed and its direction of travel relative to the scanner orientation.

While the above description of one embodiment of the present invention is concerned with the detection and analysis of plain bearings in particular, it should be appreciated that the invention is applicable to any system wherein different surfaces of a bearing may be scanned and the heat signal generated depends on the surface imaged.

Claims

1. A hot box detector system for detecting overheated wheel bearings on railway rolling stock moving along a track, the system comprising radiant energy scanner means which is positioned adjacent a section of the track so as to scan in succession the bearings of passing railway wagons and which generates a signal in response to each bearing scanned, means for determining if the surfaces of the bearings scanned dissipate heat generated by the bearings differently from one bearing to the next, means for processing the scanner signal relating to each bearing, and means for adjusting the scanner signal processing means as a function of the heat dissipating qualities of the surface of the bearing being scanned.

2. A system according to claim 1, in which the heat dissipation determining means comprises means for distinguishing between housed bearings and exposed bearings.

3. A system according to claim 2, in which the heat dissipation determining means further comprises means for determining whether the scanned surface of a housed bearing is an inner sidewall or an outer sidewall of the bearing housing in relation to the bogie to which the bearing belongs.

4. A system according to any one of claims 1 to 3, in which the heat dissipation determining means includes means for distinguishing goods wagon bogies from those of other rolling stock.

5. A system according to claim 2 or claim 3, in which the heat dissipation determining means further comprises means for determining whether the scanned surface of a housed bearing is affected by the air stream resulting from movement of the train.

6. A system according to claim 2 or claim 3, in which the heat dissipation determining means further comprises means for determining whether the scanned surface of a housed bearing is affected by the air stream resulting from movement of the train, and means for determining the speed of the train connected to the adjusting means whereby the scanner signal processing means may be further adjusted as a function of the speed of the train.

7. A hot box detector system for detecting over heated wheel bearings on railway rolling stock moving along a track, the system comprising radiant energy responsive scanner means which is positioned adjacent a section of the track so as to scan the bearings of passing railway wagons and which generates signals in response thereto, the signals having an amplitude and waveform indicative of the passing of a wheel bearing, the type of bearing, the temperature of the bearing, and whether or not the bearing is enclosed within a bearing housing, an alarm monitor connected to the scannerfor generating an alarm in the event of the amplitude of the scanner signal exceeding a threshold for the type of bearing scanned, means for processing the scanner signals to determine which of the scanned bearings are contained within a bearing housing and to distinguish signals derived from scanning an inner sidewall of a bearing housing from signals derived from scanning an outer sidewall of a bearing housing, and means interconnecting the processing means and the alarm monitorfor adjusting the alarm threshold as a function of whether the inner sidewall or the outer sidewall of a housed bearing is scanned.

8. A hot box detector system for detecting overheated wheel bearings on railway rolling stock moving along a track, the system comprising radiant energy responsive scanner means which is positioned adjacent a section of the track so as to scan the bearings of passing railway wagons and which generates signals in response thereto, the signals having an amplitude and waveform indicative of the passing of a wheel bearing, the type of bearing, the temperature of the bearing, and whether or not the bearing is enclosed within a bearing housing, an alarm monitor connected to the scanner for generating an alarm in the event of the amplitude of the scanner signal exceeding a threshold for the type of bearing scanned, means for processing the scanner signals to determine which of the scanned bearings are contained within a bearing housing, means for determining the direction of travel of the train, and means for adjusting the alarm monitor threshold as a function of whether the scanned side wall of a bearing housing is the leading or the lagging sidewall of the housing in the direction of travel of the train.

9. A system according to claim 8, further comprising means for distinguishing signals derived from scanning an inner sidewall of a bearing housing from signals derived from scanning an outer sidewall of a bearing housing.

10. A system according to claim 4, including means for determining the speed of the train connected to the adjusting means in controlling relationship whereby the amount of adjustment of an alarm threshold set by the scanner signal processing means is a function of the train speed.

11. A system according to claim 1, substantially as described with reference to the accompanying drawings.