GB2124421A - Railway vehicle with on-board hot-box detection system - Google Patents

Abstract

On board detection of hot boxes in railway vehicles is achieved by providing branches (8) to each axle box (6) from a train pipe (4) associated with the vehicle's air or vacuum brake system, the branches normally being obturated by closures (14) in thermal contact with the axle boxes, and the closures being fusible or otherwise released on exposure to excessive temperatures caused by a hot box. <IMAGE>

Description

SPECIFICATION Railway vehicle with on-board hot-box detection system This invention relates to provision on railway vehicles of means for detecting "hot boxes", that is to say overheating of the axle boxes supporting the axle journals of the vehicle. The invention is applicable to all such vehicles which are equipped with a train pipe for air or vacuum brake systems.

A hot box if left undetected can result in plastic necking of the associated journal and its subsequent breakage. This almost invariably leads to a serious derailment. Efforts to improve the axle box design have continued over the years. One significant outcome of this has been the gradual replacement of plain journal bearings with more expensive roller bearings in railway axle boxes.

Although the performance of roller bearings, in terms of kilometres per hot box, has been better than that-of conventional journal bearings, the rate at which a journal heats up once a bearing malfunction has occurred is usually much higher for a roller bearing axle box. Thus the need for an efficient "on-board" hot box detection and early warning system has never been felt more acutely than at the present, when increases in speeds and loads, and in the incidence of hazardous cargoes, have caused increasing public concern about the actual and potential results of freight train derailments.

Trackside hot box detectors are known and widely used, but have serious limitations. They can detect hot boxes only at the points where they are installed, and they cannot be located at points where trains will frequently be required to make brake applications, since heated brake shoes will cause false alarms. It is difficult to set the sensitivity of such detectors so that they reliably respond to actual hot boxes without excessive false alarms. An on-board detection system built into the vehicles themselves would be much preferred if it could be provided at reasonable cost and did not unduly complicate normal maintenance and operation.

Such a system should require minimum modification to existing vehicles, should be rugged enough to withstand the rigors of railway operation, should be cheap and use readily available materials, should as far as possible use technology already familiar in the railway environment, should be capable of transmitting a warning from any axle box to any desired point in the train, should identify the location of a hot box, should not require power sources and connections between vehicles other than those already generally available, and should not require every vehicle in a train to be equipped in order to be functional on those vehicles which are equipped.

This last characteristic greatly facilitates testing and introduction of any such system.

According to the invention, there is provided a railway vehicle having wheeled axles supporting axle boxes, and a through air or vacuum brake pipe adapted for connection to brake pipes of adjacent cars, wherein the brake pipe has branch pipes extending towards each of the journal boxes, each branch pipe being normally obturated by a closure consisting of or secured in place by temperature sensitive material in thermal contact with the associated axle box, the material being selected so that it will cease to maintain or secure the closure in the event of the axle box reaching a predetermined abnormally high temperature.

It will be seen that the above vehicle differs from the great majority of rail vehicles in use the world over only in the provision of the branch pipes to the axle boxes and their closures. In practice it will usually be desirable to place a manually operated valve in each branch pipe between the train pipe and the closure so as to restore normal brake operation after rupture of a closure.

It will be seen that the invention can meet the requirements set out above since it is simple and can be ruggedly constructed from readily available materials. Air and vacuum brake technology is well understood in the railway art. The train pipe of a train equipped with continuous air or vacuum brakes provides communication along the length of the train, and the loss of pressure or vacuum resulting from rupture of a closure will cause an indication to be available on any pressure air flow or vacuum gauge attached to the pipe. The rate of loss of pressure or vacuum should be sufficient to cause a readily detectable but not excessive application of the train brakes, which will alert the train crew to look for the source of the leak. The escape of air from or into a branch pipe with a ruptured closure will provide an audible indication of the location of a hot box causing the rupture.

The invention enables any axle box equipped with a branch pipe to be monitored, regardless of the proportion of vehicles in a train which are equipped in accordance with the invention. Some additional advantages can also be obtained. The flow of air occasioned by a ruptured closure can be directed so that it assists in cooling the hot box and thus can actually reduce the chance of serious damage or catastrophic failure before the train is brought to a halt. The system can be made much less prone to false alarms than lineside systems since each closure or its securement can be shielded from sources of heat that are other than its associated axle box.

The invention is described with further reference to the accompanying diagrammatic drawing which shows in plan relevant parts of a railway vehicle.

In the drawing, two wheeled axles 2 are shown, which may for example be the axles of a four wheeled truck or bogie. The vehicle is also equipped with a longitudinal train pipe 4, equipped at its ends with flexible couplings (not shown) to connect it with the train pipes of adjacent vehicles in a train, which will include at least one vehicle, usually a locomotive, equipped with an air compressor or vacuum exhauster or ejector adapted to maintain a predetermined normal degree of pressure or vacuum in the train pipe sufficient to maintain brakes fitted to vehicles in the train in an off condition.A vehicle equipped in accordance with the invention need not even be equipped with air or vacuum brakes provided that it has a train pipe, and therefore the brakes are not illustrated or described, although the operation of conventional forms of air and vacuum brakes will be well understood by those skilled in the art.

Journals 5 at the outer ends of the axles 2 support axle boxes 6 which in turn support the vehicle or a truck or bogie of the vehicle by a suspension system (not shown). The axle boxes comprise either piain or roller bearings. Thus far, every feature described is common to all railway vehicles equipped for use in air or vacuum braked trains.

In a vehicle equipped in accordance with the invention branch pipes 8 extend from the train pipe 4 towards the axle boxes 6. In most cases, these branch pipes will include portions formed by flexible hoses so as to allow for suspension and other movements of the axle boxes of the vehicle relative to its frame. In a typical arrangement, these hoses will drop from valves 10 mounted on the vehicle frame above the axle boxes, each hose being coupled at its lower end to a stub pipe 1 2 having a fusible end closure 14 in thermal contact with the surface of the axle box 4. The stub pipe should be long enough to prevent excessive heat transfer from the axle box to the hose.Each valve 10 has a normal position in which the stub pipe 12 is in communication with the associated branch pipe 8, and a closed position in which the stub pipe is isolated from the branch pipe 8 to enable normal brake operation to be restored after rupture of the end closure 1 4. A test position may also be provided in which the branch pipe is vented to the atmosphere to ensure the presence of air pressure or vacuum as the case may be.

The closure is any material which is of sufficient strength to maintain closure of the branch pipe when exposed to temperatures consistent with normal operation of the axle box, but which will rupture should the axle box tempedature reach abnormally high levels. Low fusing point metals such as lead based alloys or white metal and synthetic thermoplastic materials may both be suitable, depending upon the conditions of use, the local climate, the axle box design, and the circumstances under which warning of the axle box malfunction is desired. Thus avoidance of catastrophic failure of axle journals should be achieved by selecting a material which will fuse before the journal temperature reaches 4500 C.

Selection of a material which will be fused by lower journal temperatures will still further reduce the likelihood of serious damage to the vehicle but may in extreme climatic conditions increase likelihood of false alarms. The actual fusion temperature of the material selected will of course be dependent upon the degree of thermal transfer between the closure and the axle boxes, and the axle boxes and the journals. Whilst maximum thermal transfer could be achieved by incorporating the stub pipe 12 into the axle box itself, this would require redesign of the axle box, would complicate maintenance, probably rendering the arrangement less acceptable.

Assuming operation of the vehicle in an air brake train, the occurrence of a hot box condition in one of the axle boxes of the vehicle will heat the associated closure 14 until its material begins to fuse and it is ruptured by the air pressure within the train pipe. The branch pipe 8, valve 10 and stub pipe 12 are dimensioned so that the rate of escape of air will cause a sufficient pressure drop in the train pipe to propagate a partial brake application through the train. This combined with indications on any pressure or air flow gauges attached to the train pipe, will signal to the train crew that something is amiss. At least after stopping of the train, any attempt to restore or maintain train pipe pressure will cause the noise of escaping air at the location of the hot box to draw attention to the latter.The escaping and expanding air will furthermore play over the defective axle box and will help to keep the latter cooler than might otherwise be the case. In the event of a false alarm, or that the axle box malfunction is corrected, normal brake application can be restored by closing the valve 10 untii such a time as the closure 14 can be replaced.

Operation in a vacuum brake system is similar, except that it may be desirable to include a suitable trap, for example in the stub pipe 12, to prevent material from the closure being sucked into the brake system in the event of rupture.

In an alternative embodiment, the closure may be formed by a plug or flap or other valve member which is not intended to fuse itself but which is soldered or latched in a pipe closing position by fusible material or a fusible fastening so that fusion of the material or fastening allows the plug or valve member to move to a position in which it opens the pipe to the atmosphere, or the closure may be formed by some other form of thermostatically controlled valve which opens at a predetermined temperature in response to changes in a thermally sensitive material.

Claims (4)

1. A railway vehicle having wheeled axles supporting axle boxes, and a through air or vacuum brake pipe adapted for connection to brake pipes of adjacent cars, wherein the brake pipe has branch pipes extending towards each of the journal boxes, each branch pipe being normally obturated by a closure consisting of or secured in place by temperature sensitive material in thermally conductive relationship with the associated journal box, the material being selected so that it will cease to maintain or secure the closure in the event of the axle box reaching an abnormally high temperature.

2. A railway vehicle according to Claim 1, wherein the closure consists of or is secured by fusible material.

3. A railway vehicle according to Claim 1, wherein each branch pipe incorporates a valve between the train pipe and the closure.

4. A railway vehicle incorporating a hot box detection system substantially as hereinbefore described with reference to the accompanying drawing.