GB2314110A

GB2314110A - Railway track inspection apparatus

Info

Publication number: GB2314110A
Application number: GB9712152A
Authority: GB
Inventors: David Spencer Bowdler
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1996-06-11
Filing date: 1997-06-11
Publication date: 1997-12-17
Anticipated expiration: 2017-06-11
Also published as: GB2314110B; GB9712152D0; GB9612198D0

Abstract

An ultrasonic railway rail fault detecting device comprises an ultrasonic probe assembly 24 having an under surface adapted to slide along the rail head and a pair of double crystal piezoelectric acoustic probes (44, 46 Fig. 5), each of the probes being oriented toward an opposite end of the assembly so that as the assembly slides along the rail 2, one probe emits ultrasonic energy in the direction of travel and the other probe emits ultrasonic energy in the opposite direction. The probes are preferably oriented at angles of 10-30{ to the horizontal, and a further probe (48) may be provided to direct ultrasonic energy vertically into the rail. The assembly is mounted on a car and is guided on the rail head by a spring and wheel arrangement. Water supplied through hose 50 acoustically couples rail and probes.

Description

RAILWAY TRACK INSPECTION CAR This invention relates to testing of railway track, and in particular, to ultrasonic testing of railway track rails in order to detect defects therein.

Typical imperfections that are found in rails include so called 'squats' which are generally horizontal defects occurring under the top surface of the rail and piping defects which are vertical defects extending in the line of the rail. A further form of common defect are taches ovales which are generally oval defects that extend across the rail at an angle of about 700 to the vertical. The particular direction in which a tache ovale will depend on the general direction of traffic along the track. Any of these defects may grow, if not attended to, leading ultirnately in failure of the rail.

One method for testing rails of railway track that has been employed for many years is ultrasonic testing in which an ultrasonic probe is moved along the rail and emits high frequency ultrasonic energy into the head of the rail. The ultrasonic energy is reflected from any surfaces in the rail, for example from the foot of the rail, and from any imperfections in the rail, and is received by the test device, so that the presence of any imperfections can be monitored. - The reflected signals will typically be displayed by means of a cathode ray tube or other visual display screen, so that any such imperfection will be immediately noticed by the operator of the device.

The most common form of device in use for ultrasonic rail testing comprises an ultrasonic probe assembly that rests upon the rail head and is pushed along the rail by the operator who, at the same time, observes the trace of the reflected signal on a screen also located on the device. This method of operation, however, is relatively slow, because the operator must travel along each rail of the track in both directions, necessarily at walking speed.

According to the present invention, there is provided a device for ultrasonically detecting faults in a railway track rail, which comprises an ultrasonic probe assembly having an under surface that is adapted to be located on, and slide along, the rail head of the rail, and a pair of acoustic probes that are located in the assembly and oriented generally downwardly to direct ultrasonic energy into the rail, each of the probes being oriented toward an opposite end of the assembly so that, in operation, as the assembly slides along the rail, one of the probes is directed to emit ultrasonic energy into the rail in the direction of travel of the assembly along the rail, and the other probe is directed to emit ultrasonic energy in a direction opposite to the direction of travel of the assembly.

A device according to the invention has the advantage that the time taken to examine any length of rail is significantly reduced by virtue of the fact that, as the assembly is moved along the rail, ultrasonic signals are sent both in the forward direction and in the reverse direction, so that any defect such as a tache ovale, whose plane is not generally perpendicular to the direction of propagation of the signal emitted by one of the probes, will be detected by the other of the probes.

Preferably, each probe is oriented to direct ultrasonic energy into the rail at an angle in the range of from 10 to 300 to the horizontal, and especially about 200 to the horizontal, so that the direction of propagation of the signal from one of the probes will be substantially perpendicular to the plane of a tache ovale lying in one of two possible orientations. Preferably, in addition to the pair of probes, at least one further acoustic probe is provided which is directed substantially vertically so that signals are also directed vertically into the rail in order to detect defects in the horizontal plane such as squats.

The device according to the invention may, if desired, be manually propelled along the rail. However, according to a preferred aspect of the invention, it is located in a car that is self-propelled along the track, thereby increasing the speed at which the track can be tested. The car will typically comprise a body that is supported on the track by means of four flanged wheels, and will include an arrangement for locating the probe assembly above, and in contact with, one of the rails, for example by means of a guide, wheels or the like. In addition, the car will normally include a supply of water that is injected between the probe assembly and the surface of the rail in order to provide acoustic coupling between the probe assembly and the rail.

One form of device and car according to the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic side elevation of a test car according to the invention; Figure 2 is a schematic top plan view of the car shown in figure 1; Figure 3 is a schematic side elevation of an assembly supported on the car for testing the rail; Figure 4 is an elevation taken along the line Ill-Ill of figure 3; and Figure 5 is a side elevation of the probe assembly of figures 3 and 4 in yet greater detail.

Referring to the accompanying drawings, a self-propelled car 1 for testing a rail 2 for defects comprises an aluminium frame 4 and four flanged wheels 6, opposite pairs of wheels 6 being connected by solid axles 8 and 10. The car has a conventional electric motor 12 powered by a battery 14 and controlled by a control panel 16. Two seats 18 and 20 are provided, one seat 18 for the car driver and the other seat 20 for the operator of the rail testing equipment. The reason for employing two personnel to test the track is to enable the test equipment operator to devote his entire concentration on testing the rail without the necessity to have regard to driving the vehicle, and also because any such car is most easily mounted on, and dismounted from, the track by two people.

An assembly 22 is attached to one side-arm of the car frame so that it is located above the rail. The assembly 22 may be formed integrally with the car frame 4, but is preferably formed separately so that it can easily be attached and detached. The assembly its support mounting are shown in greater detail in figures 3 and 4. The assembly comprises an ultrasonic testing shoe 24 that is located directly above the rail 2 and is supported on the frame 4 by means of a mount 28. The mount 28 is clamped onto the frame by means of a pair of quick-release clamps 26 so that the whole assembly can easily be removed from the car. At its lower end, the mount 28 supports a carriage 30 by means of a shaft 32 that is horizontally oriented above and in line with the centre line of the rail 2. The carriage 30 includes a pair of arms 34 which support a pair of wheels 36 that run along the inner surface of the rail head. The shaft 32 is associated with springs (not shown) that bias the carriage 30 to rotate in the direction shown by the arrow, such rotation being limited by the wheels 36 abutting the inner surface of the head of the rail, thereby ensuring that the shoe 24 is at all times correctly positioned above the centre line of the rail 2. The testing shoe 24 is supported on the carriage 30 by a pair of sliding supports 38 and is biased downwardly by means of helical springs positioned on the supports 38 so that the under surface of the shoe is always in contact with the top surface of the rail head.

The test shoe 24 has a rectangular recess in which is located an ultrasonic test assembly 40 shown schematically in figure 5. The test assembly is generally rectangular in shape and extends over the major part of the test shoe 28, the remaining length of the test shoe comprising a skid profile 42 at each end of the test assembly 40.

The test assembly 40 contains three 2.25 MHz (double crystal) piezoelectric ultrasonic probes 44,46 and 48, which are directed to generate ultrasonic signals in the directions of the arrows. Probes 44 and 46 are each oriented to that they generate signals in a downward direction of about 200 to the horizontal and along the rail in opposite directions to one another, while probe 48 is oriented so that is will direct signals vertically into the rail. A hose 50 is provided to supply water to the front end (in the direction of travel) of the test assembly 40 between the end of the assembly and the skid profile 42 in order to provide acoustic coupling between the assembly 40 and the rail 2.

In operation, the car 1 is lifted onto the track and the assembly 22 attached to the flame. The car is designed to travel along the track at a speed of from 5 to 20, and especially about 10 miles per hour, at which speed adjacent acoustic reflections from the rail 2 will just overlap each other to give a continuous scan of the rail. The reflected signals are picked up and are displayed by display equipment 54 which is observed by one of the operators of the car. The orientation of the probes 44 and 46 (200 below the horizontal) is chosen so that the direction of propagation of the signal in the rail of one of the probes 44 and 46 will be perpendicular to the plane of any taches ovales in the rail whichever orientation the tache ovale presents. Probe 48 picks up other defects such as squats.

Although only one assembly 22 is shown located on the car 1, it is quite possible for a pair of such assemblies to be provided, each assembly being located over a different rail, thereby increasing the speed at which track can be tested yet further.

Claims

Claims:

1. A device for ultrasonically detecting faults in a railway track rail, which comprises an ultrasonic probe assembly having an under surface that is adapted to be located on, and slide along, the rail head of the rail, and a pair of acoustic probes that are located in the assembly and oriented generally downwardly to direct ultrasonic energy into the rail, each of the probes being oriented toward an opposite end of the assembly so that, in operation, as the assembly slides along the rail, one of the probes is directed to emit ultrasonic energy into the rail in the direction of travel of the assembly along the rail, and the other probe is directed to emit ultrasonic energy in a direction opposite to the direction of travel of the assembly.

2. A device as claimed in claim 1, wherein each probe is oriented to direct ultrasonic energy at an angle of from 10 to 30 to the horizontal.

3. A device as claimed in claim 2, wherein each probe is oriented to direct ultrasonic energy at an angle of about 200 to the horizontal.

4. A device as claimed in any one of claims 1 to 3, wherein the probe assembly includes at least one further probe that is oriented to direct ultrasonic energy substantially vertically into the rail.

5. A car adapted to travel along a railway track, which includes a device as claimed in any one of claims 1 to 4.