Rolling probe unit for ultrasonic railway track inspection

Abstract

A rolling probe unit for ultrasonic inspection of railway tracks utilizes a wheel assembly comprising a fluid-filled tire that rolls along the track. During inspection, an ultrasonic transducer transmits an ultrasonic beam through the fluid and tire into the underlying track. The beam, reflected from track defects, returns to the transducer for detection and analysis for subsequent maintenance. The wheel assembly also includes an anti-rotation baffle to reduce fluid rotation with the tire and a pressure regulator to control the fluid pressure within the tire at various speeds.

Description

[0001] This patent application is a divisional application; the filing date of the original application is December 4, 2020, with application number 202080084405.1, and the title of the invention is “Rolling Probe Unit for Ultrasonic Railway Track Inspection.” The original application is an international application with international application number PCT / US2020 / 063223, an international filing date of December 4, 2020, and the date of entry into the Chinese national phase is June 6, 2022.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application is a non-provisional application that claims priority to U.S. Provisional Patent Application No. 62 / 990,805, filed on March 17, 2020, the contents of which are incorporated by reference in their entirety into this application. Technical Field

[0004] The present invention relates to improved apparatus and methods for performing nondestructive testing and inspection of railway track. More specifically, the present invention relates to a rolling sounding unit (RSU) and method for detecting and identifying defects in the underlying railway track using an ultrasonic transducer mounted within a wheel assembly having a fluid-filled tire. The fluid within the tire is an ultrasonic coupling fluid that propagates an ultrasonic beam between the transducer and the tire. The beam penetrates the tire and the underlying track and is reflected from defects in the track back to the transducer for analysis. To maximize the signal strength of the ultrasonic beam traveling back and forth between the transducer and the tire, the coupling fluid must completely fill the interior of the tire under all operating conditions. Background Art

[0005] From time to time, railroad tracks may develop one or more harmful flaws or defects due to a variety of reasons. These flaws can include transverse flaws, vertical shear or split head flaws, horizontal shear or split head flaws, and can originate from manufacturing and construction processes, environmental factors, or normal wear and tear. These flaws typically appear in the rail head, but can also appear on the rail web and base, around bolt holes, or in any other part of the rail cross-section. Due to the nature of rail transportation, where locomotives weighing tens of thousands of pounds regularly transport hundreds of tons of freight on track at varying speeds, cracks within the rail can, over time, extend or propagate throughout the track. Unattended or unresolved flaws or defects can lead to a variety of problems, the most serious of which can include catastrophic track failures or train derailments, potentially posing serious financial, health, and safety risks to freight and personnel, as well as the rail industry as a whole.

[0006] Track failures can be predicted and avoided through routine nondestructive inspections, enabling rail operators to identify and repair hidden or minimal defects within the track before they develop into larger problems. To detect such defects, track inspection carriages have been constructed that are mounted on a vehicle or railcar and include ultrasonic track inspection equipment that travels along the railroad track and continuously performs ultrasonic inspections of the underlying track in the field by transmitting an ultrasonic beam into the track and analyzing the portion of the beam that may be reflected by track defects. Kocur et al. disclose such a track inspection carriage in U.S. published patent application 2019 / 0023286.

[0007] Havira, in U.S. Patent 7,849,748 B2, discloses an example of an ultrasonic rail inspection device for in-situ rail inspection. The device includes a wheel assembly with a fluid-filled tire for maintaining rolling contact with the rail head of the underlying rail. According to Havira's teachings, the tire forms a contact surface with the rail head of the underlying rail and includes an ultrasonic transducer supported within the tire. The ultrasonic beam is projected along a beam axis through the fluid, the tire, and a liquid coupling medium sprayed between the tire and the rail, and into the rail head of the underlying rail. The coupling medium is typically a thin layer of liquid, such as water or a mixture of water and other agents, that improves contact between the tire and the rail head. The ultrasonic beam propagates through the underlying rail and is reflected by any defects or flaws therein, causing some or all of the beam signal to return to the transducer or be received by an ultrasonic detector. One or more computer processors then analyze the reflected beam signal to determine the type, size, and location of the flaw or flaw corresponding to the reflected beam.

[0008] When an ultrasonic transducer is suspended within a fluid-filled tire, as disclosed by Havira, the tire and fluid provide a propagation medium between the ultrasonic transducer and the underlying track. Due to the nature of sound propagation, the intensity and quality of the ultrasonic waves transmitted and received by the transducer depend on the continuity of the propagation medium. Air pockets and other discontinuities in the medium through which the ultrasonic beam propagates disrupt the beam and the signal information carried by the beam.

[0009] At slower speeds during inspection operations, i.e., less than 30 kph, the ultrasonic coupling fluid within the tire typically maintains the necessary continuity between the medium and the tire for wave transmission. However, pursuing higher speeds to shorten inspection times and reduce disruption to rail traffic presents various challenges.

[0010] Figure 1 A prior art rolling probe unit 10 is shown having a wheel assembly having a tire 12 and components mounted within the tire including an ultrasonic transducer and a heat exchanger 16 shown in phantom. Figure 2As shown, the tire is filled with a coupling fluid 18, such as a mixture of water and ethylene glycol, which serves as a medium for propagating the ultrasonic beam between the transducer 14 and the tire 12. The function and purpose of the heat exchanger 16 is to maintain the coupling fluid 18 at a uniform temperature, as described in more detail in U.S. Patent 8,739,631 to Havira et al.

[0011] When the unit is placed on the rail head H of the underlying track with a light load to perform an inspection operation, the tire 12 is slightly flattened and forms a contact surface P with the rail head H. The tire 12 is made of a flexible film material, such as polyurethane, and is filled with a coupling fluid. Shear forces within the fluid and between the fluid and the tire cause the fluid to rotate with the tire. When the driving speed increases, the rotating coupling fluid generates centrifugal force, which is applied to the inner surface of the tire and stretches the tire. The stretching simultaneously increases the internal volume of the tire by a limited amount, and with the volume of the coupling fluid fixed, the static pressure of the fluid that inflates the tire decreases. Figure 2 , arrow A shows the centrifugal force of the coupling fluid 18 pressing outwardly against the tire 12 as the unit rotates in the direction shown by arrow R.

[0012] It should also be noted that as the speed increases, the static pressure decreases and a "cupping phenomenon" C occurs, where the tire membrane wrinkles or lifts away from the rail head at the center of the tire-rail contact surface P. The cupping phenomenon C also occurs Figure 2 The cupping phenomenon forms a cavity filled with a thicker-than-expected layer of liquid coupling medium and acts as a discontinuity in the medium along the path of the ultrasonic beam B between the transducer 14 and the rail head H. This discontinuity causes beam distortion and reduced signal strength, leading to loss of information from the inspection operation.

[0013] Another problem with this type of rolling inspection device is that the ultrasonic beam bounces around within the tire 12 due to reflections from various surfaces within the tire. The bounced beam may be received by the same or a different transducer from which the beam originated and, if absent, may be misinterpreted as a defect.

[0014] The above problems can be solved by the improved rolling probe unit and the characteristics of the method for ultrasonic inspection of railway tracks, as described below. Summary of the Invention

[0015] The aforementioned problems are addressed by an improved rolling probe unit (hereinafter referred to as RSU) for ultrasonic inspection of railway tracks. The improved RSU includes a wheel assembly having a tire filled with an ultrasonic coupling fluid. The wheel assembly is rotatably mounted on an axle via a hub so that during inspection operations, the tire rolls in contact with the head of the underlying rail of the railway as the wheel assembly translates along the track. The tire is made of a flexible film material that forms a contact surface when placed on the head of the underlying rail during inspection operations.

[0016] The ultrasonic transducer, supported on an axle within the tire, transmits an ultrasonic beam through the coupling fluid and tire into the rail head of the underlying track. It then receives the ultrasonic beam reflected from defects encountered in the underlying track. The reflected beam, indicating the defect, can then be further analyzed to determine the severity of the defect and decide whether remedial action is necessary.

[0017] The baffle is mounted in a fixed relationship to the shaft within the coupling fluid within the tire, inhibiting the coupling fluid from rotating with the tire as the tire rotates about the shaft. By inhibiting the fluid's rotation, the centrifugal force generated by the rotating fluid and the centrifugal force exerted outward on the tire are significantly reduced. Consequently, the flexible film material forming the tire does not stretch significantly at higher speeds, and the internal volume of the tire occupied by the fluid does not expand significantly. Consequently, static pressure losses within the tire are reduced or can be eliminated.

[0018] The baffle is mounted on the shaft and dialed into the coupling fluid from the shaft. It also intercepts stray ultrasonic beam reflections within the wheel assembly. By eliminating stray reflections, the probability of the ultrasonic transducer receiving the reflection and generating a false defect signal is also minimized.

[0019] A further improved rolling probe unit (RSU) for ultrasonic railway track inspection includes a wheel assembly having a tire filled with an ultrasonic coupling fluid. The wheel assembly is mounted on an axle and rotates so that the tire rolls in contact with the head of the underlying railway track. The tire is made of a flexible film material that forms a contact surface when placed on the head of the underlying track during inspection operations.

[0020] The ultrasonic transducer is supported on an axle within the tire and generates an ultrasonic beam that propagates through the coupling fluid and tire into the rail head of the underlying track. The transducer also receives ultrasonic waves reflected from defects in the underlying track for analysis.

[0021] A further improved RSU includes a pressure regulator for regulating the pressure of the coupling fluid within the wheel assembly during inspection operations. The pressure regulator includes a pressurizing component installed in the coupling fluid within the wheel assembly to pressurize the coupling fluid within the tire. In one embodiment, the pressurizing component is a pressurized airbag.

[0022] The expanded volume of the tire caused by stretching the film material at higher speeds through the pressurized bladder is supplemented by the coupling fluid to keep the tire full, maintain or increase the pressure within the tire, and eliminate "cupping" and other dampening effects created at higher inspection speeds by pressing the tire against the rail head and squeezing out the thicker layer of liquid coupling medium between the tire and rail head.

[0023] Increasing the inspection speed increases centrifugal force and tire stretch, further amplifying the attenuation effect of the ultrasonic signal strength passing through the coupling medium at the contact surface, tire, and coupling fluid. Therefore, the pressure regulator may include a speed sensor that detects the inspection speed and increases the regulated pressure of the coupling fluid in the tire based on the inspection speed.

[0024] The present invention also provides an improved method for ultrasonic inspection of railway tracks. The method includes the steps of providing a wheel assembly having a tire filled with an ultrasonic coupling fluid and mounted on an axle for rotation so as to engage a rail head of an underlying railway track. The tire is made of a flexible film material that forms a contact surface when placed on the rail head of the underlying track during an inspection operation.

[0025] The ultrasonic transducer is supported on an axle within the tire and is used to transmit an ultrasonic beam through the coupling fluid and tire into the rail head of the underlying track and to receive ultrasonic waves reflected from defects encountered in the underlying track. The transducer is activated during the inspection operation while the wheel assembly is rolled along the railway track with the tire in contact with the rail head.

[0026] According to the present invention, the ultrasonic coupling fluid in the tire is pressurized at a regulated pressure during the inspection operation to overcome the above-mentioned problems when inspecting at higher speeds. The regulated pressure can be increased as a function of the inspection speed.

[0027] Further features and advantages of the improved rolling probe unit and the method for ultrasonic inspection of railway tracks can be gathered from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a side perspective view of a rolling probe unit at a rail head during an ultrasonic inspection operation for defects in a railway track according to the prior art.

[0029] Figure 2 is cross-cutting Figure 1 Cross-section of the rolling probe unit's axis of rotation.

[0030] Figure 3 is a perspective view of a rolling probe unit according to the present invention, with the field side portion cut away to show the anti-rotation baffle and the pressurized airbag.

[0031] Figure 4 is a cross-sectional view transverse to the axis of rotation of the rolling probe unit, the field side portion of the unit is as follows Figure 3 Shown resected.

[0032] Figure 5 It is along Figure 3 Cross-section of the rolling probe unit's axis of rotation.

[0033] Figure 6 It is from Figure 3 Perspective view of the instrument side of the rolling probe unit with the tire removed from the wheel hub. DETAILED DESCRIPTION

[0034] Figure 1 and 2 A rolling probe unit 10 in the prior art is shown to illustrate the problems solved by the above-mentioned improved rolling probe unit. Figure 3-6 An improved rolling probe unit 20 (RSU) incorporating features of the present invention is shown. RSU 20 has all the features of the prior art rolling probe unit 10. RSU 20 includes a wheel assembly 22 having a tire 12 filled with a coupling fluid 18 and a plurality of ultrasonic transducers immersed in the coupling fluid. During inspection operation, the transducers generate ultrasonic beams B directed in various downward directions to propagate through the fluid and tire 12 into the rail head H of the underlying track.

[0035] When the ultrasonic beams B encounter defects at the rail head or deeper in the track, they are reflected back to the transducer by the rail, tire 12, and coupling fluid 18. The transducer captures and analyzes the signal information carried by the reflected beams. This information can provide detailed information about the defect type, defect size, and its location relative to the RSU.

[0036] Figure 3-6 The wheel assembly 22, shown most clearly in FIG, is supported in a bracket 24 with legs 26 on the instrument side and legs 28 on the field side so that the legs straddle the wheel assembly. Figure 6 As shown, a stub shaft 30 is connected to the instrument side leg 26 of the bracket 24. Another stub shaft 34 is similarly connected to the field side leg 28 of the bracket. Figure 5 As shown, the stub axles 30, 34 are connected to each other at their inner ends by bolts 38. The stub axle 30 supports a plurality of components within the tire 12 in a fixed relationship with the bracket 24 as will be described below. Figure 5 A floating shaft 42 is shown mounted within the stub shaft 34 and connected through a cross-section of the stub shaft to a yoke 40 that mounts the transducer 14. The floating shaft protrudes from the field side of the stub shaft 34 and has a slotted flange 36 with a clamping screw 37 for securing the floating shaft 42 within the stub shaft 34 by rotating it and then tightening the clamping screw 37 to adjust the transducer mounting angle. When the floating shaft is clamped to the stub shaft 34, the stub shafts 30, 34, and floating shaft 42 are all secured to the bracket 24 in a fixed relationship. These shafts and yoke are non-rotating and serve as fixed mounts for all internal components of the wheel assembly 22, including the transducer 14 and heat exchanger 16.

[0037] An electrical plug 44 is connected to the field-side end of the stub axle 34 and provides an electrical connection to the transducer 14 within the wheel assembly 22 .

[0038] It will be appreciated that during inspection operations, the bracket 24 with the wheel assembly 22 and typically a plurality of other similar wheel assemblies are suspended from a rail inspection carriage, such as disclosed in U.S. Published Patent Application 2019 / 0023286. These carriages are in turn suspended from beneath a railcar or rail vehicle for traveling along the railroad track and performing on-site inspections of the track. The wheel assembly is lowered into contact with the rail head H with limited downward force, causing the tire of the wheel assembly to flatten slightly, as shown in FIG. Figure 5 The most clearly shown and formed Figure 1 and 2 The contact surface P in the rail head is large enough so that all ultrasonic beams B passing from the tire through the rail head can be transmitted smoothly.

[0039] like Figure 5 As shown, wheel assembly 22 includes hub 50 and wheel 52, with tire 12 mounted on the instrument side of hub 50 and tire 12 mounted on the field side of hub 52. Tire 12 is a flexible film material, such as polyurethane, molded into a toroidal configuration with beads 54, 56 at each circular edge. The hub is provided with corresponding grooves for the beads. An annular clamping plate 58 has grooves that mate with beads 54 and clamps the beads to hub 50 in a fluid-tight manner via cap screws 60. A similar clamping plate 62 has grooves that mate with beads 56 and clamps the beads to hub 52 in a fluid-tight manner via cap screws 61. Hubs 50, 52, beads 54, 56, and clamping plates 58, 62 together form a sealed connection between tire 12 and hub, preventing the pressurized coupling fluid 18 from escaping the tire.

[0040] To fill the tire with coupling fluid, a fill valve 64 is provided in the site-side hub 52. The fill valve is a self-closing valve, such as a Schrader valve. To remove air from the tire 12 while filling with coupling fluid, the site-side hub 52 is provided with an exhaust valve 66 and an exhaust port 68 leading from the valve to the interior of the tire. The exhaust valve is a manually operated valve that opens and closes the exhaust port to remove air from the tire.

[0041] like Figure 5 As shown, during inspection operations, in order to rotate the wheel assembly 22 in the bracket 24 so that the tire 12 is against the rail head H, the hub 50 is mounted on the stub axle 30 via roller bearings 70, and the hub 52 is mounted on the stub axle 34 via roller bearings 72. A shaft seal 74 is installed in the hub 50 to prevent the coupling fluid from escaping through the bearing 70. A similar shaft seal 76 is installed in the hub 52 to prevent the coupling fluid from escaping through the bearing 72. Other seals are provided at various joints between the bolts, valves, and shafts to ensure that the coupling fluid 18 does not escape from the tire 12.

[0042] As above combined Figure 2 As noted, as tire 12 rotates, shear forces between the tire and coupling fluid 18 cause the fluid to rotate with the tire. These forces exert centrifugal forces on the tire, stretching it by a finite amount. Given a fixed volume of fluid, the static pressure of the fluid within the tire, typically 5-8 psi, will decrease, potentially leading to cupping C, cavitation, and bubbling, all of which can interfere with the transmission of ultrasonic beam B.

[0043] In order to suppress the rotation of the coupling fluid and the tire and the corresponding centrifugal force, such as Figure 3-5 The anti-rotation baffle 80 is shown supported on the yoke 40 in a fixed relationship with the yoke 40 within the tire, as shown in FIG. Figure 3 and 4 As best seen in the figure, the baffles project radially outward from the axial tire and are shaped to normally prevent the coupling fluid from rotating with the tire. However, the baffles are spaced from the tire's inner surface so that they do not interfere with the tire's rotation. The baffles, and their blocking of the coupling fluid, significantly reduce the centrifugal force on the fluid and the associated static pressure losses within the tire. Consequently, cupping is suppressed, and the ultrasonic beam transmission between the transducer and the rail head remains continuous.

[0044] The anti-rotation baffle 80 is shown as being flat, but may be curved or otherwise shaped to provide the desired resistance to fluid rotation while maintaining a spaced relationship to the inner surface of the tire 12. The baffle shape may also accommodate other components within the tire. Furthermore, more than one baffle may be used at different locations within the tire to inhibit fluid rotation.

[0045] In addition to preventing the coupling fluid from rotating, the anti-rotation baffles 80 are also used to intercept and dissipate unwanted ultrasonic beam reflections within the tire. One or more baffles can be strategically shaped, positioned, and surface textured to achieve the beam interception and dissipation functions.

[0046] To further improve the continuity of the fluid medium through which the ultrasonic beam B passes between the transducer 14 and the tire 12, the RSU 20 has a pressure regulator for controlling the pressure of the coupling fluid 18 in the wheel assembly during the inspection operation. The pressure regulator includes components located within the tire 12 and a pressure regulating source 100 located outside the wheel assembly at a bracket 24 or other location. Figure 3-6 As shown, the component is a pressurized air bag mounted on a short axle 30 inside the tire. Figure 5 As best shown in FIG, a pressurized bladder 90 has a housing 92 defining a pressure chamber 94 enclosed by a flexible diaphragm 96. The pressurized bladder is preferably supplied with pressurized air from a regulated pressure source 100 external to the tire. When pressurized air is delivered to the bladder, the diaphragm expands into the interior space of the tire occupied by the coupling fluid and pressurizes the fluid.

[0047] In one embodiment, the pressure regulating source 100 is an air compressor that provides regulated air pressure. Figure 5 As best shown in FIG, a pressurized air source 100 is connected to a fitting 102 on the instrument side bracket leg 26 and supplies regulated air pressure from outside the wheel assembly 22 to the pressurized air bag 90 within the wheel assembly through a drilled passage 104 in the bracket leg 26 and a manifold 106 formed in the stub axle 30.

[0048] Fittings 112, 114 are used to supply heating / cooling fluid to the heat exchanger 16 through similar but separate passages and manifolds in the stub shaft 30. Heating or cooling is required to maintain the temperature of the coupling fluid through which the ultrasonic beam B passes at a fixed level in order to standardize the results, as rail inspections are performed in the field and can be performed in all seasons.

[0049] When the wheel assembly 22 is not moving, the static pressure of the coupling fluid in the tire 12 is nominal, for example, 5-8 psi. The regulated pressure supplied from the regulated pressure source 100 will remain the same. However, when the wheel assembly moves and the centrifugal pressure of the rotating fluid causes the tire to stretch, the regulated pressure source 100 provides increased air pressure to the pressurized bladder 90, causing the flexible diaphragm 96 to expand relative to the fluid in the tire.

[0050] For this purpose, the voltage regulating source 100 receives voltage from Figure 5 The speed sensor 110 shown in FIG. 1 is used to adjust the air pressure provided by the regulated air source as a function of speed. The speed sensor 110 may be responsive to the rotational speed of the wheel assembly 22, or the translational speed of the wheel assembly along the track being inspected. Generally, the speed signal causes an increase in the regulated air pressure provided by the regulated air source as speed increases.

[0051] In this manner, the pressure regulator formed by the pressurized bladder 90 and the pressure regulating source 100 maintains or increases the pressure in the tire to compensate for the limited increase in tire volume and the decrease in tire pressure due to stretching. Accordingly, at higher speeds, the increased pressure presses the tire 12 against the rail head H, eliminating cupping and the thicker layer of liquid coupling medium that would otherwise reduce the intensity of the ultrasonic beam B and its reflection from the contact surface P.

[0052] While the present invention has been described in various embodiments, it should be understood that various modifications may be made without departing from the spirit of the present invention. For example, while the anti-rotation baffle 80 is intended to prevent the coupling fluid from rotating with the tire 12, due to the spacing between the baffle and the tire, some fluid will pass through the baffle and potentially generate centrifugal forces that could inflate the tire. Therefore, it is advantageous to use the baffle together with the pressurized bladder 90 in the wheel assembly.

[0053] The internal components of the pressure regulator disclosed herein, such as the boost bladder 90 and the pressure regulating source 100, can take various forms. The boost component formed by the boost bladder 90 can take the form of other inflatable devices, such as a bellows or a piston within or extending from a cylinder, to displace or replace fluid within the tire. The pressure source can also provide pressurized liquid at a regulated pressure to activate the boost component of the pressure regulator.

[0054] Thus, the present invention has been described in terms of several embodiments by way of illustration and not limitation.

Claims

1. A rolling probe unit for ultrasonic railway track inspection, comprising: Wheel assembly, with a tire filled with an ultrasonic coupling fluid and rotatably mounted on an axle for rolling contact with a rail head of an underlying rail of the railway, the tire being formed of a flexible film material that forms a contact surface when placed on the rail head of the underlying rail during an inspection operation; an ultrasonic transducer supported on a shaft within the tire, for transmitting an ultrasonic beam into a rail head of the underlying rail through the coupling fluid and the tire, and for receiving the ultrasonic beam reflected from a defect detected in the underlying rail; as well as A baffle is mounted on the shaft in a fixed relationship with the shaft in the coupling fluid within the tire, and is used to inhibit the coupling fluid from rotating with the tire when the tire rotates around the shaft.

2. The rolling probe unit for railway track ultrasonic inspection according to claim 1, characterized in that: The baffle is mounted on the shaft to dial in the coupling fluid and intercept ultrasonic wave reflections within the wheel assembly.

3. The rolling probe unit for railway track ultrasonic inspection according to claim 1, characterized in that: The baffle is subtended into the coupling fluid in spaced relation to the interior of the tire.

4. The rolling probe unit for railway track ultrasonic inspection according to claim 1, characterized in that: The baffle is dialed into the coupling fluid and has a shape that maintains a spaced relationship with an interior of the tire.

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