Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR AND METHOD OF DETECTING
DEFECTS IN A RAIL JOINT BAR
FIELD
100011 The present invention relates generally to an apparatus for and
method of
detecting defects in a rail joint bar and, more particularly, to a mobile
apparatus for and method
of performing nondestructive-type testing using ultrasonic transducers to
detect flaws and defects
in a rail joint bar.
(Docket 541.024)
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BACKGROUND
[0002] The United States Federal Railroad Administration has published
statistics
which indicate that train accidents caused by track failures including rail,
joint bars and
anchoring resulted in approximately 2700 derailments from 1992 to 2002. The
primary cause of
these track failures is a transverse defect and fissure running perpendicular
to the rail running
direction in the rail and rail bar joint.
[0003] A pair of rail joint bars holds the two ends of a rail in place
and act as a bridge
between the rail ends. The rail joint bars prevent lateral and vertical
movement of the rail ends
and permit longitudinal movement of the rails to accommodate expansion and
contraction. Bolts
extending through holes in the joint bars and the rail ends secure the rail
ends together. Rail joint
bars are typically 24 or 36 inches long with four or six bolt holes,
respectively.
[0004] Various methods of rail inspection include magnetic, contact,
ultrasonic and
video. One such video system is the Automated Optical Joint Bar Inspection
System developed
by ENSCO, Inc. in cooperation with the Federal Railroad Administration.
100051 One problem with video inspection systems is the inability to
see into the rail
joint bar and the area of the rail joint bar hidden under the head of the
rail. Further, the most
common failure of rail joint bars begins in an area centrally located within
the bar. Video
systems are also susceptible to false readings because of debris, rust and
discoloration or streaks
on the joint bar.
[0006] Ultrasonic testing of rails is performed with ultrasonic
transducers housed in a
liquid-filled wheel. The wheel rides along the top of the rail head while the
transducers transmit
ultrasonic waves into the rail head and receive reflected waves from the rail
head. The
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orientation of the transducers and the wave path are used to identify defects
in the rail head and
web. However, the wave cannot pass from the rail head into the rail joint bar.
[0007] Two such systems are disclosed in U. S. Patent No. 6,055,862
entitled -Method
of and an Apparatus for Detecting. Identifying and Recording the Location of
Defects in a
Railway Rail," and U. S. Patent No. 7,882,742 entitled --Apparatus for
Detecting, Identifying and
Recording the Location of Defects in a Railway Rail ".
An ultrasonic joint bar defect detection method and apparatus has been
proposed in
co-pending application Serial No. 12/872.460 entitled -Apparatus for and
Method of Detecting
Defects in a Rail Joint Bar-.
[0008] There is a need for a system that can detect defects in joint
bars and in
particular a system that can identify the presence of a joint bar to activate
the defect detection
system and that can identify and avoid obstructions to prevent damage to the
defect detection
system.
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SUMMARY
[0009] The present invention provides an apparatus for and method of
detecting
defects in a rail member such as a joint bar. The apparatus includes a pair of
opposed liquid-
filled transducer roller search units ("RSU") which are repositionable
laterally and vertically.
Each RSU is protected by a pair of idler rollers one on opposite sides of the
RSU to ensure that
the RSU is in contact with the head of the rail joint bar and that the
ultrasonic transducers
contained within the RSU are properly spaced from the joint bar head for
measurement.
[0010] Pneumatic or hydraulic cylinders or electromechanical devices
may be used to
reposition the RSUs laterally and vertically to align the RSUs with the joint
bar head and to
move the wheel assembly away from rail obstructions. A laser profile system
utilizes two lasers
per rail to collect profile data, which is analyzed to recognize certain
features, such as the rail
head, the joint bar shoulder and obstructions or hazards. A position sensor is
utilized to allow
precise placement of the RSUs to test the joint bars. The apparatus is mounted
to a carriage
assembly which is secured to a rail inspection vehicle.
[0011] RSU with embedded ultrasonic transducers pressed against the
joint bar head
eliminates air gaps and eliminates the negative effects of a rough surface.
Higher performance of
the RSU and ultrasonic transducers may be attained by wetting the surface of
the joint bar head
with water to remove debris to improve the surface contact between the RSU and
the joint bar
head surface.
[0012] The transducers are excited to emit an ultrasonic wave which is
coupled to the
joint bar head. The emitted ultrasonic wave enters the joint bar head. If the
wave encounters a
defect it is reflected by the defect. The reflected wave is received by the
transducer where it is
-
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detected as a pulse echo signal. The defect location, size and depth are
determined by the depth
of penetration of the ultrasonic wave. The depth of penetration is determined
by measuring the
time from the emission of the ultrasonic wave to the detection of the pulse
echo signal. When
the ultrasonic wave impinges on a defect such as a crack, the ultrasonic wave
is refracted at the
discontinuity scattering the ultrasonic wave energy in all directions. The
time delay from
emission to detection is a function of the dimensions and orientation of the
defect and the angle
of refraction. By measuring the time delay from the transducer to the defect
and back to the
transducer, the defect dimensions and orientation may be geometrically
determined.
[0013] These calculations depend on knowing the beam profiles of the
ultrasonic
waves that propagate into the joint bar head by controlling the orientation of
the transducer head
with respect to the joint bar head surface. The angle of refraction within the
joint bar head is
controlled by the ultrasonic wave's angle of incident relative to an axis
normal to the surface of
the joint bar head. The angle of incidence is determined according to Snell's
Law, which can be
mathematically expressed as sin a/sin b = VI/V2 where a is the angle of
incidence, b is the angle
of refraction, and Ili and V2 are the ultrasonic wave velocities in the first
and second media,
respectively.
[0014] A challenge in a dynamic and relatively harsh environment of a
railroad is
identifying a joint bar, determining the height of the head and identifying
possible obstructions
within an operational envelope to properly place and align the RSUs to engage
the surface of the
joint bar head for testing, while moving along a railway.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Fig. 1 is an illustration of a test vehicle with a joint bar
inspection apparatus of
the present invention mounted thereto.
[0016] Fig. 2 is a diagrammatic illustration of the laser profiler
system.
[0017] Fig. 3 is an illustration of two-dimensional profile data
output by the profiler
system.
[0018] Fig. 4 is a perspective view of a carriage for support of the
joint bar inspection
assemblies.
[0019] Fig. 5 is a perspective elevation view of one side of the
carriage and the
mounted joint bar inspection assemblies of Fig. 4.
[0020] Fig. 6 is an exploded view of one side of the carriage and the
mounted joint
bar inspection assemblies of Fig. 4.
[0021] Fig. 7 is a partial sectional view of one side of the carriage
and one of the joint
bar inspection assemblies.
[0022] Fig. 8 is a cross-sectional view of Fig. 7 along line 8-8.
[0023] Fig. 9 is a functional block diagram of the rail joint bar
apparatus.
[0024] Fig. 10 is an illustration of the analyzed and displayed data
from the profile
data.
[0025] Fig. 11 is a partial diagrammatic illustration of the
operational envelope
around the rail head and joint bars.
[0026] Fig. 12 is a software flowchart illustrating control of the
joint bar inspection
apparatus.
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DETAILED DESCRIPTION
[0027] As required, detailed embodiments of the present invention are
disclosed
herein. However, it is to be understood that the disclosed embodiments are
merely exemplary of
the invention that may be embodied in various and alternative forms. The
drawings are not
necessarily to scale; some features may be exaggerated or minimized to show
details of
particular components. Therefore, specific structural and functional details
disclosed herein are
not to be interpreted as limiting, but merely as a representative basis for
the claims and/or as a
representative basis for teaching one skilled in the art to variously employ
the present invention.
[0028] Moreover, except where otherwise expressly indicated, all
numerical quantities
in this description and in the claims are to be understood as modified by the
word "about" in
describing the broader scope of this invention. Practice within the numerical
limits stated is
generally preferred. Also, unless expressly stated to the contrary, the
description of a group or
class of materials as suitable or preferred for a given purpose in connection
with the invention
implies that mixtures or combinations of any two or more members of the group
or class may be
equally suitable or preferred.
[0029] Referring to Figs. 1-3, a joint bar inspection apparatus is
generally indicated
by reference numeral 20. The joint bar inspection apparatus includes a
carriage 22 supporting
test assemblies 23 mounted behind a test vehicle 24, a laser profile system 26
mounted under the
test vehicle 24, and an encoder 28 mounted to a front flanged rail wheel 30,
which are coupled to
a control system 25.
[0030] The test vehicle 24 includes front 32 and rear 34 rubber tires
and flanged rail
wheels 30 and 36 which serve to keep the test vehicle 24 on the rails 38 and
40 when in a hi-rail
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configuration. Carriage 22 and the flanged rail wheels 30 and 36 are lifted
when the test vehicle
24 is driven off the rails 38 and 40.
[0031] The encoder 28 outputs position information to the control
system 25. The
encoder 28 is preferably an absolute rotary encoder that outputs an analog or
digified signal as
the rail wheel 30 rotates. The signal from the absolute rotary encoder gives
an unambiguous
position within the travel range without knowledge of any previous position.
The encoder 28
outputs a running counter which corresponds to the rotation of the rail wheel
30 which in turn
corresponds to the position of the test vehicle 24.
[0032] The laser profiler system 26 includes two pairs 42 and 44 of
laser transceivers,
each of which is directed at rails 38 and 40, respectively. Laser pair 42
includes a gauge side
laser transceiver 45 and a field side laser 46 transceiver directed at rail
38. Gauge side laser
transceiver 45 scans the area from the gauge side transceiver 47 of the rail
38 across the rail head
48, which includes joint bar 50. The field side laser 46 scans the area from
the field side 49 of
the rail 38 across the rail head 48, which includes joint bar 51. Laser pair
44 includes a gauge
side laser transceiver 52 and a field side laser transceiver 53. The gauge
side laser transceiver 52
scans the area from the gauge side 54 of the rail 40 across the rail head 55,
which includes joint
bar 57. The field side laser transceiver 53 scans the area from the field side
of the rail 40 across
the rail head 55, which includes joint bar 57. It should be understood that
each laser transceiver
may include a laser transmitter and laser receiver, or a laser transmitter and
optical receiver such
as a camera, as separate components or in combination, for example.
[0033] Each laser transceiver scans at a rate of 1000 Hz. The data
output from each
pair of laser transceivers 42 and 44 is combined to construct a two-
dimensional profile or slice
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59 of each rail 38 and 40, joint bar 50, 51, 57 and 58 and the surrounding
area at a rate of 1,000
times per second. Each pair of lasers 42 and 44 is surrounded by a housing 60
and 62,
respectively, each of which encloses the respective laser pair 42 and 44 on
the four vertical sides
and top to protect the laser system 26 from the environment, to improve the
performance of the
lasers 45, 46, 52 and 53 in all ambient lighting conditions and to protect the
eyes of any
individuals located around the test vehicle 24.
[0034] Referring to Figs. 4-9, the carriage assembly 22 includes right
64 and left 66
carriages. The right 64 and left 66 carriages are connected together by a
cross member 68, which
includes a pneumatic or hydraulic cylinder 70 to adjust the width of the
carriage assembly 22 to
engage the rails 38 and 40. The right carriage 64 is a mirror image of the
left carriage 66 so only
the right carriage 64 will be described in detail, it being understood that
the same detailed
description applies to the left carriage 66.
[0035] The right carriage 66 includes a pair of flanged rail wheels
72, which support
the carriage 64 on the rail 38. The flanged rail wheels 72 are mounted to a
frame 74 to which a
field-side wheel assembly 76 and a gauge-side wheel assembly 78 are mounted.
Wheel
assemblies 76 and 78 are identical and thus like numbers will be used to
identify the components
and will be identified only for the field-side wheel assembly 76.
[0036] Field-side wheel assembly 76 includes a vertical slide assembly
80 and a
horizontal slide assembly 82. The vertical slide assembly 80 includes a
vertical servopneumatic
cylinder 84 fastened to a vertical cylinder mount 86, which is fastened to a
slide interface block
88. The slide interface block 88 is slidably coupled to a pair of vertical
slide shafts 90, which
extend through a pair of bushings 92 and are secured at an upper end to a
vertical slide cap 94
_
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and at a lower end to a base 96 of frame 74. A piston rod 98 extends from the
vertical
servopneumatic cylinder 84 and is secured to the base 96 of frame 74. As the
vertical
servopneumatic cylinder 84 is actuated, the slide interface block 88 slides up
or down in a
vertical plane on the vertical slide shafts 90.
[0037] The horizontal slide assembly 82 includes a horizontal
servopneumatic
cylinder 100 fastened to a horizontal cylinder mount 102 which is fastened to
a test assembly
body 104. The test assembly body 104 includes a pair of idler rollers 106
horizontally mounted
on opposite sides of a rolling sensor unit ("RSU") 108. RSU 108 is a liquid-
filled wheel, known
in the art, which houses one or more ultrasonic transducers mounted at an
angle of between 35
degrees and 55 degrees, and more particularly 37.5 degrees and 52.5 degrees
relative to the
vertical surface 110 of a head 112 of a joint bar 50. The inside surface or
inner circumferential
edge of the RSU 108 extends beyond the inside surface of the idler rollers 106
so that when the
idler rollers 106 are engaged with the vertical surface 110 of the head 112 of
the joint bar 50 the
RSU 108 is compressed or biased against the vertical surface 110 so that the
ultrasonic
transducers embedded within the RSU 108 are positioned at a known distance
from the vertical
surface 110. A liquid spray nozzle 109 may be secured to the test assembly
body 104 to spray a
liquid such as water on the joint bar head 112 to remove debris and to improve
contact of the
RSU 108 with the vertical surface 110 of the joint bar head 112.
[0038] The test assembly body 104 is slidably coupled to a pair of
horizontal slide
shafts 116, which are secured at one end to the slide interface block 88 and
at the other end to a
horizontal slide cap 118. A piston rod 120 extends from the horizontal
servopneumatic cylinder
100 with its free end secured to the slide interface block 88. As the
horizontal servopneumatic
õ.
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cylinder 100 is actuated, the test assembly body 104 along with the idler
rollers 106 and RSU
108 slide back and forth in a horizontal plane on the horizontal slide shafts
116 toward and away
from the vertical slide assembly 80.
100391 Referring to Figs. 1-11, before the test vehicle 24 travels
along the pair of rails
38 and 40, the control system 25 is initialized and begins receiving data from
the encoder 28,
laser profile system 26 a GPS unit 132 and the test units 23. The lasers 42
and 44 scan the rails
38 and 40, respectively, at a rate of 1000 Hz, providing a two-dimensional
"slice" 59 of each rail
and surrounding area. As the test vehicle 24 travels along the rails 38 and
40, the encoder 28
provides precise linear position data in the form of a counter. Each count
output by the encoder
28 represents a distance traveled by the test vehicle 24. For example, the
encoder 28 may have a
fixed output of 512 counts per foot, or may have a programmable number of
counts per selected
unit of distance.
100401 The encoder 28 count is stored along with the output of laser
profile system 28
and analyzed by the system controller 25 for certain contours and features
based on a slice-to-
slice 59 comparison. For example, the system controller 25 recognizes a rail
head contour 134
and a joint bar shoulder 136, as well as obstructions. For each joint bar
shoulder 136 recognized,
the system controller 25 calculates the width of the shoulder 138, defined as
X1, and the distance
the joint bar head 112 is below the upper surface 142 of the rail head 48,
defined as Y1. These
calculations are derived from range data received from the laser profile
system 24 in a manner
generally known in the art. These X1 and Y1 values are derived for each side
of the rail head 48
(but not shown in Fig. 11). Because the carriage 22 rides on the rail 38, the
zero position of the
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test apparatus 23 is know and only the horizontal and vertical offset of the
joint bar shoulder 136
from the zero position need be determined.
[0041] Also calculated is the operational envelope of the test units
23 in order to
effectively position the RSU 108 against the surface 110 of the joint bar head
112. The diameter
of the RSU 108 is known and height of the joint bar head 112 is derived from
that range data.
The operational envelope is determined by adding a clearance distance to the
RSU diameter or
multiplying the RSU diameter by a clearance factor, defined as Xl, and by
adding a clearance
distance to the height of the joint bar head 112 or multiplying the joint bar
height by a clearance
factor defined as Y2, for example. The operational parameters may be defined
by X and Y
coordinates (X, Y), where (0, 0) is the stowed position, (X 1 , Y1) is the
outside corner 139 of the
joint bar shoulder 138, and (X2, Y2) is the outer envelope of operation. The
area defined by
X1 + X2 and Y1 + Y2 determines the operational envelope of the test units 23.
This area may be
dynamically calculated by the system controller 25 for each side of the rail
38. In the presence
of a joint bar 50, obstructions or hazards within this envelope or outside of
the envelope but close
enough to the envelope to present a risk of contact with any part of the test
unit 23 are identified.
[0042] Based on the known distance between the lasers 42 and 44 of the
laser system
26 and each of the wheel assemblies 76 and 78, precise control and placement
of the wheel
assemblies 76 and 78 may be accomplished by the system controller 25.
[0043] Referring to Figs. 1-12, the system 20 is initialized before
testing begins 198.
As the test vehicle 24 travels down the rails 38 and 40, system controller 25
receives data from
the laser profile system 26, block 200, and the encoder 28, block 202. The
laser profile system
26 outputs four channels of data corresponding to each of the lasers. The
encoder data and laser
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profile data are processed by the system controller 25 and a rail profile (see
Fig. 10) is calculated
206 and stored 209. Each rail profile stored is compared to the previous
stored rail profile to
detect and classify joint bars and other objects based on position, presence
and persistence of the
features detected 208. The position is a function of identifying an object
that matches the profile
of a joint bar head and shoulder. The presence is a function of the object
being in the expected
location next to and below the rail head 48. And persistence is a function of
identifying the
object a predetermined number of times consecutively.
[0044] Next, based on the collected data, the system controller 25
determines if a
joint bar has been recognized 210. If a joint bar has not been detected 212,
then processing
returns to block 200. If a joint bar has been detected 214, then the ideal
position of the RSU for
testing is calculated 216 and a check is made to determine if there are any
other objects within
the ideal operational envelope of the RSU 218.
[0045] If no object has been detected within the operational envelope
of the RSU
220, then the test unit 23 is commanded by the computer system 130 to activate
the vertical and
horizontal servopneumatic cylinders 84 and 100 to move to the calculated
position 222 at an
encoder 28 count offset by the distance from the laser profile system 26 to
the particular wheel
assembly 76 or 78. Because the wheel assemblies 76 and 78 are arranged in
tandem, the distance
from the laser profile system 24 to the field side wheel assembly 76 is
different than the distance
to the gauge side wheel assembly 78. The position information is received by
the
servopneumatic controller 224, and the servopneumatic vertical and horizontal
cylinders 84 and
100 are positioned 226. The servopneumatic cylinders 84 and 100 provide
position feedback to a
servopneumatic controller 224 to ensure that they have reached the calculated
position. Once in
..
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position the ultrasonic transducers in the RSU assembly 108 are energized and
data from the
ultrasonic transducers 218 is collected and coupled with data output from the
GPS receiver132 at
block 230 by the ultrasonic test hardware and software 232.
[0046] The ultrasonic transducer data is analyzed for defects 233 and
presented on a
display (not shown) to a system operator 234 and checked for defects 236. If
no defect(s) are
identified 238, the ultrasonic and GPS data are stored 208 with the
corresponding profile data
and processing returns to block 200. If one or more defects are identified
240, the data is flagged
for hand inspection 242 and the ultrasonic and GPS data are stored 243 with
the corresponding
profile data and processing returns to block 200.
[0047] Returning to block 218, if an object has been detected within
the operational
envelope of the RSU 244 then the controller 25 may determine if the ideal
position of the RSU
may be adjusted to avoid the object 246, if the test range (i.e., contact
range of the RSU 108 with
the joint bar head surface 110) may be shortened or modified to avoid the
object 248 or if the test
should be aborted 250. If the position of the RSU 108 may be adjusted to avoid
the hazard 252,
then the position is recalculated 253 and processing continues at block 222. A
typical situation
may include the corner of a bolt or nut head extending into the lower edge of
the operational area
of the RSU 108 where the vertical positioning of the RSU assembly 108 may be
higher than
optimal but still within an acceptable range.
[0048] If the RSU position does not need to be adjusted 247, then a
determination
may be made to the start or end position of the RSU 108 may be adjusted to
avoid the hazard
248. If the start and/or end point is adjusted 254 and then a different
starting and/or end point is
calculated 255 and processing returns to block 222. A typical situation may
include an
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obstruction within the RSU operational envelope at the beginning of the joint
bar 50 or toward
the end of the joint bar 50 relative to the direction of travel of the test
vehicle 24. The majority
of defects in a joint bar are found near the longitudinal middle where the two
sections of rail are
joined together.
[0049] If the obstruction cannot be practically avoided 259, then a
determination is
made to whether to abort the test 250. If the test is aborted 256, then the
RSU position is set to
(0, 0) 257, GPS data is collected 258 and stored 260, and processing returns
to block 200.
[0050] It is to be understood that while certain now preferred forms
of this invention
have been illustrated and described, it is not limited thereto except insofar
as such limitations are
included in the following claims.
