Background of the invention

The invention relates to an apparatus for the measurement of the quality of rails, and of the kind disclosed in the preamble to claim 1.

From German patent no. 2.609.260, a measuring table is known for measuring apparatus for the measuring of the quality of rails, said measuring table being suspended in a bogie under a railway coach. The measuring table is flex¬ ibly suspended in a measuring frame which, via hinge-like elements, is suspended in longitudinal beams between the free journals of the wheel axles. The measuring table is hereby positioned between two wheel axles in a bogie. The relative displacements of the measuring table in the lat¬ eral direction in relation to the coach body are measured by means of measuring equipment placed on the underside of the coach body, said measuring equipment being in engage¬ ment with the measuring table. Via lenses, mirrors etc. , beams of light are transmitted from the measuring table towards the rails, so that their quality with regard to displacement of the track element and differences in the distance between a pair of rails can be measured during railway operations. Since the measuring table is constantly moving in relation to the position of the track element, the method of measurement is difficult to use, the reason being that it is difficult to obtain measuring results which are precise enough to be used in a qualititive evalu¬ ation of the rails.

In the book "Modern Railway Track" from 1989 by Coenraad

Esveld, published by MRT-Productions, D-4100 Duisburg 66, Germany, in Chapter 12, "Recording Systems", under section

12.5, pages 288-309, in the section "Recording of track

geometry according to BMS-1", there is a detailed descrip¬ tion of a number of different measurements which can be undertaken, and of how these can be carried out, among other things using laser beams directed towards the head of each rail, while at the same time transducers are used for the measurement of the vertical displacement between an axle bearing box and the coach body, or the displacement between a wheel axle and the bogie frame.

Today, there is a great need to be able to measure not only the parameters known as the basic geometry parameters, but also the parameters called other geometry parameters for railway tracks. It is preferable to be able to carry out these measurements simultaneously and under full oper- ational speed, i.e. also at speeds in excess of 100 km/h, so that even intensive railway operations on a section are not disturbed during the measurements. At the same time, the measurements must naturally be precise and be available as digital signals which can be stored and data-processed for practical use and evaluation of the quality of the track section regarding the quality of the rails. From the above-mentioned handbook it appears that the parameters which are desired to be measured are "CANT", "LEVEL", "ALIGNMENT", "GAUGE", "TWIST" and "CURVATURE". At present, there is no existing apparatus which can undertake these measurements with the desired accuracy during full oper¬ ational speeds. Consequently, there is a great need for the improvement of the known apparatus.

Advantages of the invention

By configuring the apparatus according to the invention as disclosed and characterized in claim 1, the resulting measuring apparatus is one which can be mounted on the bogie in a normal railway coach and carry out the desired measurements under full operational speed. The core of the

apparatus is a measuring frame which is suspended in such a manner that to all intents and purposes it always lies at a certain, fixed distance above the rails during operations. Since the measuring frame is continuously adjusted in the transversal direction in relation to the rails, it is poss¬ ible to achieve a relatively short distance, e.g. 13-20 cm, which provides many technical advantages and which gives better and more accurate measurements than those obtained with the known measuring systems. This suspension of the measuring frame also means that it is mechanically isolated from the rails.

Moreover, the types of measurements it is possible to carry out are almost unlimited, in that the fundament on which the measurements are based is a measuring frame which during operations always lies in a certain position above the track element, and can hereby form the basis for the mounting of different types of measuring apparatus. The measuring frame is continuously servo-controlled in the vertical direction and the lateral direction. This posi¬ tioning of the measuring frame close to the rails results in greater measurement solubility and considerably less measurement noise than with the known systems, and thus the desired accuracy of measurement can be achieved during full operational speed.

With signals, e.g. data signals from the inertial measuring system, correction signals are obtained for use in the cor¬ rection of the measurement results if the measuring frame is displaced in the horizontal direction in relation to the rails, and for the adjustment of the horizontal position of the frame. The inertial measuring system comprises at least one gyro for each measurement direction and at least one accelerometer for each measurement direction.

The starting point for the measurements and the servo-

control of the frame is thus the wheels and the wheel axle, in that the position of the frame is regulated on the basis of the distance to the wheel axle and measurements of the distance between the frame and the rails.

With so-called high-speed trains, i.e. trains which travel at speeds considerably in excess of 100 km/h, in order to be able to allow the greater speeds it is necessary to be able to measure all of the track-element parameters a great deal more preecisely than they are today.

By configuring the apparatus according to the invention as disclosed and characterized in claim 2, a robust measuring frame is achieved, the four corners of which can be regu- lated individually with regard to the distance of the frame from the rails. Consequently, it is not merely the frame as a whole which is adjusted in height in relation to the rails, but also the individual parts of the frame. The frame must be configured of robust and rigid material, e.g. aluminium profiles. Moreover, the suspension elements must be configured in such a way that they can absorb those movements which can be permitted.

By configuring the apparatus according to the invention as disclosed and characterized in claim 3, it is achieved that the same apparatus which is used for measuring the distance of the frame from the rail is also used for the continuous scanning of the cross-sectional profile of the rail head.

By configuring the apparatus according to the invention as disclosed and characterized in claim 4 or 5, the measuring frame can be positioned relatively close to the upper edge of the rails, so that laser measuring devices with limited ranges of measurement can be used, in that these are dis- posed relatively close to the head of the rail. This solves many problems where measurement technique is concerned, and

also reduces the cost of the apparatus. Moreover, the measuring frame according to the invention makes it poss¬ ible to use commonly-known measuring equipment, e.g. a commonly-known laser-scanner.

The apparatus according to the invention is preferably con¬ figured as disclosed and characterized in claim 6, whereby the possibility is provided of being able to automate the measurements and postpone parts of or the whole of the data processing of the measurement results until a later date.

The apparatus according to the invention is preferably con¬ figured with laser-scanners as disclosed and characterized in claim 7, whereby the possibility is provided of under- taking the measurements at very high operational speeds, so that the measurements do not interfere with the normal railway operations on the track.

When the apparatus according to the invention is configured as disclosed and characterized in claim 8, a reliable con¬ struction is achieved with completely fixed synchronization between the laser beam transmitted and the light reflected from the rail. A greatly increased speed of measurement is achieved hereby without any increase of inaccuracies in the measurements. Furthermore, it is possible even at high speeds of operation to carry out many rail profile measure¬ ments per unit of length.

Finally, the apparatus according to the invention can be configured as disclosed and characterized in claim 9, whereby the possibility is provided of carrying out a total measurement of the cross-sectional profile of the rail head, which in some cases is of great practical signifi¬ cance and provides very valuable measurement results.

The drawing

The invention will now be described in more detail with reference to the drawing, which shows an embodiment of the apparatus according to the invention, in that

fig. 1 shows in perspective parts of a bogie for a rail¬ way coach on which there is mounted a measuring frame according to the invention,

fig. 2 shows the measuring frame and the wheels from fig. 1 seen in the direction at right-angles to a wheel axle,

fig. 3 shows a system diagram of the apparatus according to the invention in the form of a block diagram covering the electronic measuring and servo cir¬ cuit,

fig. 4 shows in principle and in perspective a laser scanner for measurements according to the inven¬ tion,

fig. 5 shows in more detail how a laser scanner and its rotating mirrors are arranged, and

fig. 6 shows an example of how several scanners with rotating mirrors are used for the total measure¬ ment of the cross-sectional profile of a rail.

Description of the example embodiment

In figs. 1 and 2 are seen parts of an ordinary standard bogie 2 for a railway coach, which with wheels 4 mounted fixedly on a rigid axle 5 runs on a track element consist¬ ing of a pair of rails 6. In fig. 1 is shown the use of a

commonly-known, rectangular, robost bogie frame 3, which is also the basis for suspension of the measuring frame ac¬ cording to the invention.

The measuring frame 1, consisting of four frame parts la, lb, lc and Id, is assembled to form a rectangular frame which is positioned under the wheel axles. The frame 1 con¬ sists of four longitudinal girders which are joined in the corners, possibly with special corner joints which enable the frame parts to rock slightly in relation to one another. The frame 1 is suspended in the bogie frame 3 by means of a number of suspension elements 7, in the shown example by four suspension elements 7. The suspension el¬ ements 7 are adjustable so that they can raise or lower the measuring frame 1 at the suspension points as a function of electrical signals received from a computer, which will be described later. The measuring frame 1 is also coupled positionwise to the bogie frame 3 by means of the measuring system 9,10, which in a commonly-known manner with movable arms and the like is in engagement with the measuring frame and can continuously measure the distance between the bogie frame 3 and the axle journals 5' on the wheel axles 5. There is hereby measured the relative displacement of the axle ends 5 ' in relation to the bogie frame 3.

On the measuring frame 1 there are also mounted four laser scanners 11, which partly measure the distance of the frame 1 from that rail 6 towards which the scanner is directed, and at the same time scan the cross-sectional profile of the head of the rail.

Furthermore, on the measuring frame 1 there is mounted at least one inertial measuring apparatus or system 8 which measures the acceleration of the frame in three directions and the dimension in the three directions, as shown sche¬ matically by the arrows 8' . The apparatus comprises at

least one gyro and at least one accelerometer for each direction of measurement, and electronic circuits to carry out the necessary calculations. Such an apparatus can be purchased on the present market, or can be configured using commonly-known equipment.

Fig. 2 shows in more detail how the laser scanners 11 are directed towards the rails 6, so that the cross-sectional profile of the rail head can be scanned, while at the same time the distance between the frame 1 and the rail 6 is continuously measured.

The measuring frame, which constitutes a kind of stabilized platform for measuring instruments, is arranged to be con- tinuously positioned at a fixed distance and position over the track element. In figs. 1 and 2, only the frame parts la, lb, lc and Id are shown, but there is naturally nothing to prevent a platform or the like from being mounted be¬ tween the frame parts lc and Id for the support of measur- ing instruments etc. All measurements on the rails are hereafter undertaken in relation to the platform or the frame 1. The platform is built as an additional frame around and under the normal bogie frame 3. It is suspended in such a manner that it is effectively isolated from vibrations from the railway coach and the wheels, and the position of the frame 1 is servo-controlled on the basis of measurements which, via a computer, control the setting of the suspension elements 7. The suspension elements can be commonly-known adjusting devices which can be controlled by a servo mechanism, e.g. electrically-driven actuators.

Fig. 3 of the drawing is a block diagram covering the whole of the measuring apparatus. The measuring apparatus con¬ sists of an inertial measuring system 8, four transducers 9, which measure the vertical displacement of the bogie frame 3 in relation to the wheel axles 5' , and four laser

scanners 11. Each of the laser scanners 11 is coupled via an amplifier 12 to a computer, which in the drawing is shown as two cooperating computers 13, 14. The coupling is effected through input or interface circuits 15, 16, through which the above-mentioned transducers are also coupled to the computers. On the basis of the measurements taken and the control by programs installed on the com¬ puters, control signals are generated which, via one or more interface circuits 17, are fed to the four suspension elements 7, which ensure that the measuring frame 1 is always positioned at a fixed distance from the track el¬ ement 6.

The signals from the four laser scanners 11 are also fed to the computers, preferably to the computer 14, which also receives digital data from the other computer 13, so that the computer 14 can continuously calculate the cross- sectional profile 20 of the two rails and other parameters for the rails. The parameters measured can either be shown directly on a display 18, 21, or stored in suitable data memories or sent further to a central computer store as shown in position 19, 22.

In the shown example, the data processing unit itself con- sists of two computers 13, 14 which cooperate via a data bus, but there is naturally nothing to prevent a practical and usable solution from being configured with one computer or a number of cooperating computers or PLCs.

In fig. 4 is shown a rail portion 6, the cross-sectional profile of which is continuously scanned by a laser scanner 11 according to the invention. The laser scanner 11 com¬ prises a laser unit 26 which emits a focussed, mono¬ chromatic laser beam 28 via a rotating mirror 27, so that the reflected light 29, similarly via the rotating mirror 27, is detected in the laser unit 26. The laser unit 26

can, for example, be of the SELCOM OPTOCATOR type, which can carry out direct measurements of the distance to the rail 6 at the individual points along the line 24 which is scanned. The rotating laser mirror 27 itself, which is shown as a hexagonal prism with reflecting surfaces, has been developed for use in connection with the invention.

The laser scanner 11 with the rotating mirrors is shown in more detail in fig. 5, where 26 indicates the actual laser unit, and where the rotating mirror is divided into two rotating mirrors 30, 31, both of which are mounted in a fixed manner on a rigid spindle which is driven by an electromotor 32, and where the other end of the spindle is connected in a fixed manner to a goniometer 33, so that the electronic control and servo system always knows the angle of the mirrors 30, 31. The rotating mirrors 30, 31, which in the drawing are shown as two mirrors, but which can naturally be configured as one common mirror, are made of precision-processed RS plastic, which on the external sur- faces are coated with a plane, reflecting metal layer, so that the external surfaces are made reflective.

Finally, in fig. 6 there is shown a principle setup with three laser scanners 11, each comprising a laser unit 26 and a rotating mirror unit 27, with which, as described above, when such a laser scanner configuration is mounted on the measuring frame 1 according to the invention, it is possible to achieve a total scanning of the head of the rail 6.

The apparatus according to the invention must naturally be arranged to function in the robust environment which exists at and around a railway bogie, and at a temperature range of at least -10°C to +40°C.

At high speeds of operation, i.e. in excess of 100 km/h,

oscillations in the suspension of the measuring frame will have wavelengths in the order of 10-50m and with moderate levels of acceleration, which without any problems are completely equalized by the servo system according to the invention. Shortwave inaccuracies in the rails will gener¬ ate a certain level of high-frequency acceleration, which via the optical measuring system will be able to be com¬ pensated for in a purely electronic manner.

In principle, the inertial measuring system 8 consists of three accelerometers and three ^τ . ometers. The transversal and longitudinal accelerometers must be precise inclino¬ meters with a bandwidth of approx. 20 Hz, and the vertical accelerometer must have a bandwidth of approx. 140 Hz. The characteristics of the gyrometers will depend on the desired accuracy of the measurements.

For control of the data collection, and in order to obtain precise measurements for measuring speed and distance covered, an odometer will normally be coupled to the com¬ puters 13, 14. The odometer can, for example, be an encoder mounted on one of the wheels of the bogie, or a special measuring wheel can be mounted in rolling contact with the rails between the two pairs of bogie wheels.

With the apparatus according to the invention, it is poss¬ ible, for example, to measure the following:

1 ) The cross-sectional profile of the rails for the measuring/evaluation of wear etc.

2) The track gauge.

3) The inclination of the rail plane in relation to the horizontal.

4) The longitudinal profile of the rails.