Wheels of railway vehicles, whether locomotives, trucks or carriages, gradually become worn during use.

Any excessive wear may increase the risk of derailment of the vehicle, and railway companies hence have a need to monitor wheel shapes. In particular, the thickness of the flange may decrease as a result of wear, and if the thickness is less than a specified value then the wheel must be replaced. It would therefore be desirable to be able to monitor flange thickness on a frequent basis.

In this specification the inside' (of a rail, wheel or flange etc) refers to the side nearest the centreline of the track.

According to a first aspect of the present invention, there is provided an apparatus for monitoring the thickness of the flange of a wheel of a railway vehicle rolling along a rail, the apparatus comprising a block supported adjacent to the inside of the rail by a resilient support structure fixed to a base clamped to the rail, inner and outer probe members projecting above the block such that the inside of the flange pushes the inner probe member and hence the block away from the rail, the outer member consequently being pulled into contact with the outside of the flange, at least one of the probe members being resiliently displaceable relative to the block, and means to provide signals indicating the separation of the probe members, wherein at least one probe member comprises a flexible strip combined with a strain gauge.

At least the inner probe member preferably defines a datum surface parallel to the side of the rail, and defines an inclined surface on each side of the datum surface, so that the block is pushed gradually away from the rail as the flange moves along the inclined surface to reach the datum surface. If vehicles can only approach the apparatus from one direction, then only one such inclined surface need be provided, but provision of two such inclined surfaces is still desirable to reduce the shocks to which the apparatus is subjected. Damping means may also be provided to prevent oscillation of the block.

The inner probe member may be substantially inflexible, and fixed rigidly to the block, and may be integral with it.

Preferably both the probe members define datum surfaces, comprising opposed strips of hard wear- resistant material, such as silicon carbide.

The outer probe member may locate in a recess in the side of the rail, being pulled out by the block into contact with the outside of the flange. Such a recess may be machined into the side of the rail head at the location where the apparatus is installed. Alternatively the apparatus may include two wedge members fixed to the side of the rail head so as to increase the effective width of the rail head, a recess being defined between the wider parts of the two wedge members.

In a second aspect, the present invention provides an apparatus for monitoring the separation between the insides of the flanges of a wheelset of a railway vehicle rolling along a track comprising two rails, the apparatus comprising a first block supported adjacent to the inside of the first rail. by a resilient support structure fixed to a base clamped to the first rail, with an inner probe

member projecting above the block such that the inside of a flange pushes the inner probe member and hence the first block away from the first rail, and a second block supported adjacent to the inside of the second rail by a resilient support structure fixed to a base clamped to the second rail, with an inner probe member projecting above the block such that the inside of a flange pushes the inner probe member and hence the second block away from the second rail, the first block and the second block being at positions directly opposite each other along the track, and each resilient support structure incorporating sensor means to indicate the displacement of the respective block.

Preferably, in each aspect of the invention, the or each resilient support structure comprises a pair of parallel leaf springs; and in the second aspect the sensor means comprise strain gauges arranged to monitor the strain in one of the leaf springs. By using a pair of parallel leaf springs to provide the resilient support structure, the block is held in a fixed orientation to the rail as it is pushed away from the rail by the flange. The block is allowed to move sideways against the resilience of the leaf springs, but vertical movement is prevented. The use of a flexible strip for a probe, and leaf springs for the resilient support, avoids the inaccuracies that friction may cause where surfaces must slide relative to each other.

The apparatus of the second aspect may also incorporate outer probe members for measuring flange thickness, as in the first aspect of the invention, such outer probe members locating in recesses machined into the sides of the rail.

To ensure accurate measurements, in each aspect, the

apparatus may incorporate scrapers or brushes to remove contamination in particular from the inside of the flange.

The apparatus of the first or second aspect of the invention is preferably installed on a portion of track along which trains pass slowly, for example at a depot, and there may be a speed limit such as 10 or 20 km/hr imposed on that portion of track to reduce the shocks to which the apparatus is inevitably subjected. Such apparatus enables the flange thickness, and the inter- flange separation, on every wheelset of every train to be monitored for example twice a week, so that any excessive wear can be detected and appropriate action taken in good time.

The invention also provides methods of monitoring flange thickness, and inter-flange separation, using such apparatus as described above.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a flange thickness monitoring apparatus of the invention; Figure 2 shows a sectional view of of the apparatus of figure 1; Figure 3 shows a sectional view corresponding to that of figure 2 when a wheel is present; Figure 4 shows a perspective view, partly broken away, of a modification of the apparatus of Figure 1; and

Figure 5 shows a detailed view, in elevation, of the outer probe in the apparatus of Figure 4.

Referring to figure 1, an apparatus 10 for measuring the thickness of flanges of railway vehicles is shown attached to a rail 12, on the inside of the rail 12 (that is to say on the side nearest to the centre line of the track). When a vehicle passes along the track, the wheel tread rolls on the rail head 13, while the wheel flange is adjacent to the inside face 14 of the rail head 13.

The apparatus 10 includes a support pillar 16 in the form of a square cross-section steel tube, welded to a clamp 18 by which the apparatus 10 is fixed to the rail 12.

The apparatus also includes an anvil block 20 connected to the support pillar 16 by two parallel steel leaf springs 22; each spring 22 (when flat) lies in a vertical plane, and the springs 22 extend horizontally from the support pillar 16 to the block 20. The anvil block 20 consists of a spacer 24 between the springs 22, and an anvil plate 25 integral with the spacer 24 and projecting upwardly. The face of the anvil plate 25 facing the rail 12 defines a vertical datum surface 26 parallel to the longitudinal axis of the rail, and sloping surfaces 27 on each side of the datum surface 26. The pillar 16, the springs 22, and the spacer 24 of the anvil block 20 are sufficiently far below the rail head 13 to be clear of any wheel flange, whereas the upper edge of the anvil plate 25 is above the level of the rail head 13.

Adjacent to the anvil block 20 a recess 30 is machined into the side 14 of the rail head 13. A spring steel probe 32 extends upwardly from the edge of the spacer 24 next to the rail 12, the top of the probe 32 being a short distance (for example 3 mm) below the level of the rail head 13, and the probe 32 locating in the recess 30. The probe 32 carries an electronic strain

gauge 34, and near its top is attached a wear-resistant strip of ceramic 36 that extends horizontally.

Referring now to figure 2, which shows a sectional view in the plane immediately adjacent to the anvil block 20, rubber stops 37 are attached on the face of the spacer 24 adjacent to the rail 12, and hydraulic dampers 38 (shown diagrammatically, and not shown in figure 1) may act on the opposite face of the spacer 24. The orientations of the sloping faces 27 and the datum face 26 are shown more clearly in this view. A typical wheel profile is shown in a broken line. When such a wheel rolls along the rail 12 the flange 39 comes into contact with the anvil plate 25, initially with the sloping face 27, so pushing the anvil block 20 away from the rail 12, until the inside of the flange 39 comes into contact with the datum surface 26.

Referring now to figure 3, at this point the inside of the flange 39 pushes against the datum surface 26, while the probe 32 has been pulled into contact with the outer surface of the flange 39. Consequently the signals from the strain gauge 34, indicating the amount that the probe 32 has bent, are an indication of the thickness of the flange 39 at the distance below the rail head 13 of the strip 36. The strip 36 would typically be arranged to be 13 mm below the rail head 13.

As the wheel continues to roll along the rail 12, the flange 39 reaches the second sloping surface 27, gradually releasing the anvil block 20, which springs back under the influence of the leaf springs 22 to the position shown in figure 2. The apparatus 10 is then ready to monitor the thickness of the flange of the next wheel. It will be appreciated that the parallel leaf springs 22 ensure that the datum surface 26 of the anvil

plate 25 always remains parallel to the longitudinal axis of the rail 12.

Although the apparatus 10 only provides an indication of the thickness of the flange 39 at one position around its circumference, this is sufficient to indicate if the flange 39 is suffering excessive wear.

It will be appreciated that the apparatus 10 may be modified in various ways. In particular the datum surface 26 may also incorporate a wear-resistant strip similar to the strip 36 on the probe 32. Rather than cutting the recess 30 into the rail head 13, a recess to locate the probe 32 might instead be formed by a wedge fixed to the side 14 of the rail head 13, for example such a wedge might be of length 0.5 m, and of thickness from zero increasing to 5 mm. If vehicles can only approach from one direction, then a single such wedge would be sufficient, with the probe 32 just after the thick end of the wedge; if vehicles may approach from either direction then the probe 32 would be located in a gap between the thicker ends of two such wedges. Such wedges may be attached using adhesive to the sides of the rail head 13. In yet another alternative, a check rail is provided along the other side of the track in the vicinity of the apparatus 10 to ensure there is sufficient clearance between the side 14 of the rail 12 and the flanges 39; in that case no recess is needed for the probe 32, as it lies next to the side of the rail 12 in its resting position.

The probe spring 32 would typically be of width 30 mm (parallel to the longitudinal axis of the rail) and of length between 50 mm and 100 mm, and of thickness between 1.0 mm and 2.0 mm. The leaf springs 22 would typically be of width about 50 mm and of length about 300 mm, and of thickness about 1.0 mm. The use of spring structures

in each case has benefits in avoiding any bearings, which may introduce measurement errors.

Where two such apparatuses 10 are arranged on each rail of a track, at the same position along the track, then it is desirable to also incorporate strain gauges in the leaf springs 22. The signals from these strain gauges may be interpreted to indicate the inter-flange spacing for each wheelset.

Referring now to figure 4, there is shown an apparatus 40 for measuring the thickness of flanges, which has several features in common with the apparatus 10 of the previous figures. In this case the parallel steel leaf springs 22 (which are connected at one end to the rail 12 via a support pillar 16, as in figure 1) support a spacer block 42 between the springs 22. Two 2 mm thick spring steel probes 43 and 44 project above the block 42, each probe 43 and 44 defining a respective vertical face 46 parallel to the longitudinal axis of the rail, and sloping surfaces 47 on each side. The inner probe 43 extends to above the level of the rail head 13, whereas the top of the outer probe 44 is a short distance below the level of the rail head 13. Like the probe 32 of figure 1, each probe 43 and 44 carries an electronic strain gauge (not shown), and near its top is attached a wear-resistant strip of ceramic (not shown) that defines its datum position.

Operation of the apparatus. 40 is substantially as described above in relation to the apparatus 10, differing only in that the inner probe 43 (which is equivalent to the anvil plate 25) is flexible.

Consequently in calculating the flange thickness, the deflections of both probes 43 and 44 must be taken into account. It is again necessary to ensure that the datum

position (i. e. the ceramic strip) on the outer probe 44 is at the desired distance below the rail head 13, typically this being 13 mm, as this determines the position on the flange at which its thickness is measured. The outer probe 44 may therefore be attached to the spacer block 42 in such a way that its height can be adjusted during installation of the apparatus 40. For example, referring to figure 5, the lower end part of the outer probe 44 may be clamped between, two plates 48, the plates 48 and the probe 44 each defining an oval aperture 49 in which is an eccentric cam 50. These components are secured by a bolt 52. With the bolt 52 slack, rotation of the cam 50 allows the height of the probe 44 to be adjusted; the bolt 52 is then tightened. It will be appreciated that such adjustment is not required on the inner probe 43, as it contacts a part of the wheel profile that is substantially vertical.