Railroad Hot Box Detector

In the accompanying drawings:

FIG. 1 is a block diagram representation of the overall system of the present invention;

FIG. 2a is a simplified waveform diagram of the heat signal generated by the passing of a freight car provided with plain bearings through a sensing zone moving in the direction indicated in FIG. 1;

FIG. 2b is a simplified waveform similar to FIG. 2a for a freight train moving in the direction opposite to that indicated in FIG. 1; and,

FIG. 3 is a plot of time vs. temperature rise as determined from the inner and outer housing sidewall surfaces.

Reference is now made to the drawings and to FIG. 1 in particular wherein a section of track 10 is depicted along which wheel sensors 12 and 14 are mounted. A radiant energy scanner 16, such as an infra-red hot box detector disclosed in U.S. Pat. No. 3,545,005 is positioned along the track to scan each passing railroad car as the wheels of the car pass through the sensing zone defined by wheel sensors 12 and 14. The scanner 16 is focused to image on the bearings of each passing wheel. In practice, a pair of scanners is usually provided mounted on opposite sides of the track with each scanner imaging on the bearings on its side of the track. The wheel sensors 12 and 14 and infra-red scanner 16 are all of conventional design and are commercially available from sources such as the Servo Corporation of America of Hicksville, N.Y. In operation, the wheel sensors 12 and 14 serve to generate a signal each time a wheel passes which together define a time interval during which the scanner 16 serves to generate an analog waveform indicative of the heat of the bearing scanned.

Thus, as each of the wheels 18, 20 of each truck 22 of each car of the train pass through the sensing zone, a heat pulse (such as those shown in FIG. 2) is generated. Between trucks the scanner 16 views the under-carriage or bottom of the passing car and between cars the scanner may get a glimpse of the sky.

The problem with which the present application is concerned is peculiar to those bearing which are not exposed directly to the imaging spot of scanner 16 but which must be imaged indirectly through a bearing housing. In FIG. 1, truck 22 is provided with plain bearings which are located in housings 24 and 26 mounted at the ends of truck 22. The housings 24 and 26 protrude from the truck frame and serve to contain a quantity of oil to lubricate the bearing. The oil is fed through covers 28, 30 in the housings. As the housings pass the scanner 16, scanner 16 images on either the inner sidewalls 32, 34 of housings 24, 26 or the outer sidewalls 36, 38 depending upon the direction of movement of the train and orientation of the scanner.

The inner sidewalls 32, 34 are those sidewalls which face each other and the spring nest of truck. The outer sidewalls 36, 38 are directed away from each other. As can be seen in FIG. 1, the inner sidewalls 32, 34 are contiguous to the large heat conducting mass comprising the main portion of the truck frame while the outer surfaces 36, 38 are not. As a result, more of the temperature rise of an overheated bearing within a housing 24, 26 would manifest itself on the outer sidewalls 36, 38 than on the inner sidewalls 32, 34. It should also be noted from FIG. 1 that regardless of train movement direction or scanner orientation each truck must have one housing imaged on an inner sidewall and the other housing imaged on an outer sidewall. This is shown in FIG. 2 wherein the pulse 40 is generated as a result of the bearing for wheel 18, pulse 42 is generated as a result of the bearing for wheel 20 and pulses 44 and 46 are generated by the bearings of the nex truck when it passes through the sensing zone. Had the train been moving in the opposite direction, the initial surface imaged by the scanner would have been an outer sidewall surface resulting in the waveform distribution of FIG. 2b.

In FIG. 3 a graph of temperature rise vs. time is presented for a deliberately generated hot box in a plain bearing. As may be seen, the inner sidewall temperature rises are approximately 30% lower than on the outer sidewall.

In accordance with the present system, the output of scanner 16 is first fed to a discriminator 48 which determines if the truck under investigation is a freight truck (since plain bearings are only used on freight trucks). Such discriminators are disclosed, for example, in U.S. Pat. No. 4,256,278. If it is determined that a freight truck is under observation, it must next be determined whether the freight truck has plain bearings or roller bearings. This is done in discriminator 50 which relies on well known differences in the characteristic waveforms generated. The leading and lagging axle of each truck is then determined in block 52 by the sequence of wheel sensor signals for each truck. In this regard additional wheel sensors 53 and 53' are utilized in the manner disclosed in the aforementioned U.S. Pat. No. 4,256,278. Once the direction of the train is determined (which may readily be done by observing the sequence of activation of the wheel sensors or based on the determination of which axle of a truck is the leading axle and which is the lagging axle) the side of the bearing housing being scanned is determined in block 54. This determination may readily be made based on (1) whether scanner 16 is looking forward or backwards at a particular train and (2) the direction of the train. Thus, for a forward looking scanner (as shown in FIG. 1) the inside surface 32 of housing 24 would be viewed first followed by the outside surface 38 of housing 26. If the orientation of the scanner had been reversed, the outside surface 36 of housing 24 would be viewed first followed by the inside surface 34 of housing 26. An adjustment of alarm monitor 56 may then be made through block 58 to compensate for the differences in the heat dissipating characteristics of the sidewalls of the housing.

Since the housings 24 and 26 protrude from the truck frame 22 they are subject to exposure to an air stream caused by motion of the train. The air stream cooling effect is particularly noticeable when the train motion is oncoming to the scanner aperture (i.e., if scanner 16 were directed in the opposite direction or train motion were opposite to that shown in FIG. 1). The speed of the train and hence the magnitude of the air stream effect may readily be determined by use of a speed detector 60 which obtains inputs from a pair of sensors spaced a fixed distance apart in accordance with well known procedures. Since the lead and lag axle as well as the housing side information are available from the analysis discussed above, normalization for air stream cooling may also be made in block 58.

While the above description of a preferred embodiment of this invention has been disclosed in connection with plain bearings, it should be appreciated that the invention would have application to any system wherein different surfaces of a bearing may be scanned and the heat signal generated depends on the surface imaged.

Thus, in accordance with the above, the aforementioned objects ar attained.