Evaluating Railway Ties

Abstract

A method of evaluating railway ties for deterioration is mounted on a moving vehicle along the rails where the presence of the tie is detected and an impact energy source is used to create at least one wave in a surface of the tie which travels longitudinally along the tie. At positions spaced longitudinally from the source, the time of arrival of the wave is detected typically by a series of sensors responsive to air pressure changes to determine a speed of propagation of the wave in the tie and, in the event that the speed in said tie is below a predetermined speed, an output indication is provided regarding the deterioration of the tie, which can include a real time marking of the tie detected.

Claims

1. A method of testing railroad ties comprising: providing an impact energy source that impacts the tie so as to create waves that propagate through the tie; providing one or more sensing devices arranged to sit above the surface of the tie so as to avoid contact therewith, where the sensing devices detect movement of the surface caused by the waves propagating therein; and analyzing and/or recording the detected pressure waves to determine properties of the tie.

2. The method according to claim 1 wherein including moving a vehicle continually along rails mounted on the ties, detecting presence of one of the ties under the vehicle, at positions spaced longitudinally from the impact energy source providing a plurality of sensing devices to detect said at least one wave and detecting a time of arrival of said waves and analyzing the time of arrival from said sensing devices to determine a speed of said waves in the tie.

3. The method according to claim 2 including, in the event that the speed in said tie is below a predetermined speed, providing an output indication of a deterioration of the tie.

4. The method according to claim 1 wherein the impact energy source comprises a body carried on a support which provides an impact on the surface of the tie and is immediately retracted so as to prevent sliding movement across the surface.

5. The method according to claim 1 wherein the impact energy source is shaped, arranged and actuated to provide a frequency of waves in the tie which includes frequencies below 25 kHz and preferably below 10 kHz and more preferably below 5 kHz.

6. The method according to claim 1 wherein the impact energy source is shaped, arranged and actuated to provide an energy at impact of greater than 3 Joules.

7. The method according to claim 1 wherein the analysis includes detecting the speed of the waves at different locations across the tie and comparing the different speeds to determine a uniformity of the speed.

8. The method according to claim 1 wherein the analysis includes detecting the waves at different locations across the tie and generating for each impact a waveform over a period of time of the impact at the location and comparing the waveforms from different locations and/or from different ties.

9. The method according to claim 1 wherein the period of time includes times in advance of the impact obtained by recording a continual waveform and obtaining from the continual waveform recorded a window of time in advance of and after the impact.

10. The method according to claim 1 wherein the sensors detect waves at the surface which are changed by wave components that are reflected and diffracted between surfaces of the structure and are indicative of delamination of or cracks in the structure below the surface.

11. The method according to claim 1 wherein the impact energy source is provided by a ball carried on a tether and operated by a rotational drive device so as to engage a surface of the tie.

12. The method according to claim 1 wherein the presence of one of the ties is detected by a proximity sensor, a magnetic sensor, a contact sensor, or a video sensor for actuating the impact energy source.

13. The method according to claim 1 wherein the sensing devices are spaced away from a surface and detect air movement generated by the surface wave in the tie.

14. The method according to claim 13 wherein sensors comprise a microphone positioned inside a tube, an open end of which is directed toward the surface of the tie.

15. The method according to claim 1 wherein the non-contact sensor is a laser sensor for detecting movement of the surface.

16. The method according to claim 1 wherein an output indication of a deterioration of the tie is used to place the ties in categories of a degree of deterioration.

17. The method according to claim 16 wherein velocity ranges for deteriorated ties are determined and then used to classify the tie tested in the categories of deterioration.

18. The method according to claim 1 wherein including a marking system for marking the tie under test in the event that it is determined to be deteriorated.

19. The method according to claim 1 wherein there is provided a position recording function to record a position of each defective tie along the rails and the data is analyzed in a post-survey analysis of the data to produce a summary report of the number and location of defective ties.

20. The method according to claim 19 wherein data from a subsequent survey is compared to previously recorded data for each tie to determine deterioration vs time and rate of deterioration of ties.

21. The method according to claim 1 wherein the rail clips are used to position the sensors on each tie.

22. The method according to claim 1 wherein the analysis establishes a zero time when the wave from the impact first passes a first senor closest to the impact energy source, and the time for the signal to propagate to a second and third sensor is used to calculate wave velocity.

23. The method according to claim 1 wherein there is provided a vehicle with wheels for rolling on the rails where the wheels are formed of a resilient polymer, plastics or rubber material.

24. The method according to claim 1 wherein the analysis is repeated after a period of time and results from the separate analyses compared to determine a rate of deterioration.

25. The method according to claim 1 wherein there is provided a camera for generating a visual image of the tie under test which is recorded with data from the analyses.

26. The method according to claim 1 wherein there is provided a first impact energy source at a first end of the tie and a first array of sensors along the tie for a first analysis and a second impact energy source at a second end of the tie and a second array of sensors along the tie for carrying out a second analysis.

27. The method according to claim 26 wherein the first array comprises a first sensor between the first impact source at the first end of the tie and a first rail, a second sensor on the other side of the first rail and a third sensor adjacent the second rail and the second array comprises a first sensor between the second impact source at the second end of the tie and the second rail, a second sensor on the other side of the second rail and a third sensor adjacent the first rail.

28. The method according to claim 1 wherein each array includes a respective sensor for detecting the tie.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:

[0091] FIG. 1 is a top plan view of the components of the system according to the present invention operating on a rail track including a plurality of ties.

[0092] FIG. 2 is an end elevational view of the system of FIG. 1.

[0093] FIG. 3 is an end elevational view similar to that of FIG. 2 showing the components mounted on a schematically illustrated vehicle.

[0094] FIG. 4 is a top plan view similar to that of FIG. 1 showing the vehicle of FIG. 3.

[0095] FIG. 5 is an isometric view of the vehicle of FIG. 4.

[0096] FIG. 6 is a side elevational view of the components of the system of FIG. 1.

[0097] FIG. 7 is a schematic illustration of a modified microphone system for use with the system of FIG. 1.

[0098] FIG. 8 is a chart showing the selection of ratings of the concrete ties after testing depending upon the velocity of the waves that detected.

[0099] FIG. 9 is a graph showing the waveforms from two separate sensors where the waveform is stored in windows containing data from before and after the arrival of the leading edge from the impact.

[0100] In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION

[0101] One example of a concrete testing system can be seen in the conceptual illustrations of FIGS. 1 (top view) and 2 (front view). In both figures a concrete testing system 10 may be moved upon railroad tracks 12 to evaluate the concrete railroad ties 14 to which they are secured. Waves which are typically Rayleigh but include compressional pressure waves 16 are propagated along and through the railroad tie 14. Sensing devices 18, such as microphones, detect the air pressure waves that emanate from the tie 14 due to movement of the surface of the ties due to the waves 16 within the structure.

[0102] The pressure waves 16 are generated at contact point 20 at one end of a concrete railroad tie 14 and propagate through the tie 14 from one end to the other. The sensing devices 18 are located along the length of the tie 14 to detect the pressure waves 16, allowing an assessment of the degree of cracking/concrete deterioration of the concrete tie 14.

[0103] FIG. 2 shows the location of the sensing devices 18 above a railroad tie 14 with the emitted pressure waves 16 being detected by the sensing devices 18.

[0104] FIG. 2 shows a front view of concrete testing system 10 with an energy impact source 22 at the point 20 and three sensing devices 18 above a railroad tie 14, with two rails 12 attached upon the railroad tie 14.

[0105] FIG. 3 shows a top view of a concrete testing system 10 as it is positioned upon railroad tracks 12 and the respective supporting railroad ties 14. This embodiment has two sets of impact energy sources 22 and sensing devices 18, each arranged above opposing ends of the railroad ties 14. These are located at 1 foot spacing along the rail so that one is between one tie and the next as the other is carrying out the testing procedure, with the ties 2 feet on center. This allows testing to be done on both ends of the ties 14 as the testing system 10 progresses along the rails 12 from one railroad tie 14 to the next. Proper positioning over the relevant railroad tie 14 to be tested is maintained by a proximity switch 27 activated by the metal tie clips 19 which fasten the railroad tracks 12 to the ties 14. The concrete testing system 10 moves along rails 12 and continues to move as the impact source 22 generates the Rayleigh waves detected by the sensing devices 18. A sweeper can be provided to clear debris from the top of the tie so the impact source 22 may provide an impact on a clean surface. In this embodiment impact energy source 22 is a metal ball manipulated by an electrical rotational solenoid 22B. The surface of the tie 14 is impacted by the metal ball 22 when proper positioning has been established by the proximity switch above an individual concrete railroad tie 14. A data processing system 26 may be used to analyze the data from the sensing devices 18 to determine the degree of deterioration of the subject tie 14. The sensing devices 18 are located with the first at or near the impact energy source 22 and others farther away along the tie 14. Three or more sensors may be used and they may be positioned approximately 1.5 inches above the tie being tested. The sensors may be positioned at different distances above a tie being tested as long as the distance is consistent from one tested tie to another. Testing is optimized by reducing the distance as much as possible. Sensors are located approximately 6 to 8 inches from the end of the tie, therefore allowing data to be collected along the body of the tie 14.

[0106] The machine 10 is carried on a frame 10A with parallel axles 10C and 10D carrying plastic wheels 10B for rolling on the rails such that it can be rolled along a railway and test the ties as the machine passed over them. The frame includes longitudinal connecting beams 10E and upstanding front and rear supports carrying manually engageable handle 10F and a front hitch 10K. A platform 10G carries a container for the processing system. The machine components can also be assembled on a powered rail vehicle or train such that ties could be tested as the train moves along the track.

[0107] The machine includes the magnetic proximity switch 27 which is suspended from the frame such that it is in close proximity to the steel rail clips 27A when the machine passes by a tie. The processor is programed to activate the rotating solenoid 22B when the magnetic proximity switch 27 detects one of the rail clips located on each rail tie as the vehicle rolls forward along the rails. The magnetic proximity switch 27, controller 26 and rotational solenoid impactors 22 are mounted on the frame. The frame further includes the toolbars 10X and 10Y extending parallel to the axle 10C and 10D. The toolbars carry the various components described herein at the required positions along the length of the tie 14 and at the required positions relative to the centreline 14A of the tie 14.

[0108] In this way the cart or vehicle moves continuously along the track carried on the plastic wheels so as to avoid excessive noise which could interfere with the microphones. As soon as the position sensor 27 detects the presence of the rail clip 27A, without halting the movement of the system, the processor 26 actuates the rotating solenoid 22B which moves the impact ball 22A from a raised storage position 22P to a position impacting the upper surface of the tie. The relative positions of the components are shown in FIG. 6 so that the detection of the clip occurs at a position where the ball 22A impacts the tie 14 approximately at the centre line 14A. The microphone sensors are mounted on the toolbar 10X of the frame and detect the arrival of Rayleigh waves. The sensors detect Rayleigh waves. The timing of the impact from the impact ball 22A on the tie does not need to be calculated relative to the sensors 18 since the sensors 18 themselves detect the wave generated by the impact. The sensor 18 which is closest to the impact therefore receives the wave first and acts as a method for detecting time zero which is fed to the processor 26. The time difference between the receipt of the wave at the first sensor and the receipt of the wave at the further sensors set at a predetermined distance from the first sensor provides an ability for the processor 26 to calculate the velocity of the wave as it travels along the tie. Depending upon the deterioration in the body of the tie, the velocity will change so that a number of different velocities maybe calculated by the processor using the detection of the waves by the sensors. The processor acts to detect from the complex waveform generated by the sensors the leading edge of the waveform which can be consistently detected as the leading edge passes each of the sensors. In this way there is no need to carefully coordinate the timing of the impact relative to the sensors.

[0109] The microphones are mounted in a shotgun configuration where the microphone M is mounted in a tube 18A so that the source of the sound detected by the microphone is from one direction longitudinal of the tube. A ½ inch PVC tube 18A with the microphone M positioned approximately 3 inches inside the shotgun tube from the mouth 18B and approximately 2 inches above the surface S of the concrete crosstie under test gives good results.

[0110] A directional microphone housing mounted within the tube to increase the directional effect can reduce noise and allow detection of Rayleigh wave signals when the microphone is not positioned directly over the crosstie. The results did not indicate an improvement in signal quality but did allow for the microphones to be off the edge of the crosstie but the signal was nosier.

[0111] In addition to using the microphone as a sensor, the microphone can be used as a trigger to initiate measurements to be made. A concern with using a microphone as a trigger is background noise; spurious background noises could trigger the data collection process. Background noise experiments conducted using a radio at high volume with static to simulate high frequency noise and drums to simulate low frequency noise. The background noise did not appear to have any significant effect on the data recorded and a microphone thus can be used as a trigger.

[0112] Alternative energy sources including a pneumatic projectile energy source, spring activated point source similar to a machine shop center punch; metal ball on a stiff wire arm; electric solenoid; pneumatic solenoid; and a bar drop impact were considered. All energy sources use microphones in the optimal tube configuration described above. The machine shop center punch produces a reasonably good Rayleigh wave signal.

[0113] Electric and pneumatic vertical solenoids can produce a lower frequency signal but were not practical to take measurements while moving as it is necessary to immediately retract the impact body so as to rebound or retract to prevent drag along the rail tie surface creating a noisy signal which will provide difficulty reading Rayleigh wave arrivals.

[0114] The processor 26 includes software arranged to acquire, archived on the display the microphone data from two separate sensor arrays with sensors spaced 1 foot apart to be able to acquire data at opposite ends of each rail ties. Each array is triggered by its own proximity switch activated when the machine moves past the rail clips. The program includes that if data is not able to be acquired or is missed on the ends of two consecutive ties an audible alarm is sounded with a visual recording on the display.

[0115] The impact energy source shown in FIG. 6 includes at the solenoid 22B a spring schematically shown at 22C which acts so that the body 22A is immediately retracted after impact so as to prevent sliding movement across the surface. The spring is typically a part of the solenoid itself so that it is not a separate component there is provided either as an integral or separate component an arrangement for immediate retraction of the ball of body after it impacts the surface.

[0116] The processor 26 includes a program component causing analysis which includes detecting the speed of the waves at different locations across the tie and comparing the different speeds to determine a uniformity of the speed.

[0117] As shown in FIG. 9, the analysis includes detecting the waves at different locations as indicated at SENSOR 1, SENSOR 2, 3 across the tie. Each sensor generates and stores in the program SENSOR 26 for each impact a waveform W for each sensor over a period of time or window W1, W2 and W3 of the impact at the location. The program in the processor acts to compare the time of arrival for each waveforms W in the windows W1, W2 and W3 from different locations. The waveforms in the windows W1, W2 can also be compared from different ties. As shown the impact generates a waveform W with a leading edge L1, L2 or L3 recorded at each sensor location caused by the impact with a waveform of decreasing amplitude behind the leading edge. When L1 is detected, the recording time for sensors 1, 2, and 3 is advanced by W4 of the continual waveform W and extracted from the continual waveform. W1, W2 and W3 are recorded for a designated time period. Thus the continual waveform W1, W2 and W3 are stored in a buffer and the window extracted from that buffer when triggered by the detection of the leading edge L.

[0118] The analysis is repeated by travelling the vehicle along the same track over the same ties after a period of time which can be several months or even years and results from the separate analyses compared to determine a rate of deterioration.

[0119] As shown in FIG. 3 there is provided a camera C carried on the vehicle for generating a visual image of the tie under test which is recorded with data from the analyses so that the review of the condition state of a series of tests along the rail track can be carried out using both the velocity data stored and the visual image stored.

[0120] FIG. 7 shows a more complex microphone system provided for the sensors 18. In this arrangement a complex waveguide tube 18X is provided which includes three separate legs connecting to a central collector portion 18Y for communication to an amplifier 18Z. In this way the specific location of the sensor 18 to the surface of the tie is less sensitive since one or other of the legs can be located beyond the edge of the tie.

[0121] In FIG. 8 is shown a flow chart providing the analysis of the velocities of the waves in the tie which are detected by the senses relative to the conventional rating system providing an indication of rating of 1 to 5.

[0122] Benefits of the system include:

[0123] Automation of rail tie evaluation to use steel tie clips to locate and trigger sensors and energy source near the middle of each tie.

[0124] Use of non-contacting microphone sensors as well as contact sensors if desired.

[0125] Use a range of energy sources (mechanical, impact and non-contacting).

[0126] Data acquisition software that can sense when a reading should be made and instantaneously evaluate and rate/rank and log data for each tie tested.

[0127] Automatically mark ties according to the rating/ranking measured.

[0128] Equipment can be mounted on a portable rail mounted cart or can be attached to a high rail vehicle or train.

[0129] Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.