Note: Descriptions are shown in the official language in which they were submitted.
llQ4339
This invention relates to track alignment devices and, more particu-
larly, to track alignment devices utilising a "chord system" to obtain track
alignment error and correct track alignment.
It has previously been proposed in Russian patent 471,413 which was
granted on May 25, 1~75 to Turovskiy et al, to use a wire stretched between
forward and rearward stations of a track alignment device, the wire serving
as a chord of a curved section of the track over which the alignment device
is passing to establish a datum or reference line. A first measuring device
located relatively near the forward station cooperates with the wire to
measure the distance of the track at successive points from the reference
line. A predetermined number of measurements are obtained and averaged. A
second measuring device located relatively near the rearward station cooper-
ates with the wire to measure successively the distance from the reference
line of the track at a point immediately forwardly of the already corrected
track portion. The actual value obtained is compared with the mean value
obtained from the first measuring device and an error signal generated if
- there is a difference. The error signal causes an alignment mechanism to
shift the track in a direction left or right and by an amount to remove
or reduce the error.
This prior system suffers from the disadvantage that the length of
the chord is limited physically by the practical problems associated with
supporting the wire on rail cars. This places a practical limitation on
the precision of the measurements because the longer the chord the more
precise the measurements.
Another disadvantage of the prior system is that because the first
measuring device is located near the forward end of the wire the~ if the
forward end of the wire is on a badly misaligned point on the track, a large
deviation from a "true" displacement from the reference will ~e present in
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the reading obtain~d.
The present invention comprises an apparatus for reducing railroad
track position errors comprising a first measuring system having a leading
point and a trailing point and means for establishing a reference line be-
tween said points; a measuring means located between said points adapted to
measure track position values relative to said reference line; means to move
said first measuring system over a section of track so as to measure a series
of said track position values at a series of points extending over the section
of track; means to store the series of track position values and to average
them; a track correcting means attached to and trailing said ~irst measuring
system; an independent track location sensing system for said track correct-
ing means, which location sensing system includes a leading point and a trail-
ing point and means for establishing a second reference line between the lead-
ing and trailing points; sensor means located between said leading and ~rail-
ing of the second reference line, for sensing a track location value relative
to said second reference line; comparator means connected to said means to
store and average the track position values and to said sensor means to com-
pare said average position value with said location value and provide a posi-
tion error value; and means connected to said comparator means for applying
said position error value to control the operation of the track position
correcting means to reduce an existing track position error.
In a preferred configuration the first reference line is a chord
extending between the leading and trailing points of the first measuring
system and the second reference line is a chord extending between the lead-
ing and trailing points of the track location sensing system. The chords
may overlap each other.
The present invention further comprises a method of reducing rail-
road track position errors comprising the steps of passing a measuring system
llQ4;}39
over a section of the track, the measuring system having a first reference
line extending between a first leading point and a first trailing point on
the track, and measuring track position values relative to the measuring
system at a first series of points throughout the section; automatically
summing and averaging the measured position values to obtain an average
position value; passing track correcting means equipped with a track location
sensing system independent of the measuring system through the same section
of track, the track location sensing system having a second reference line
extending between a second leading point and a second trailing point on the
track, obtaining a track location value from the track location sensing
system at at least one location on the section, comparing the track location
value with the average position value to ob~ain a position error value and
applying the position error value to control the operation of track position
correcting means at the at least one location to reduce an existing track
position error.
In a described embodiment, the step of re-measuring a track position
value after the operation of the track position correcting means and resumming
and re-averaging the track position values to obtain a new average position
value is taken.
In the drawing which illustrates an embodiment of the invention, the
apparatus is shown in diagrammatic form.
An apparatus for calculating the track position error and realigning
railway track is shown generally at 1. A first measuring system comprises
leading and trailing points 2, 3 being conveniently located on rail engaging
buggies forming a frame 20 and means to move the frame and buggies over the
track, each point being located at the track center line. Between the points
2, 3, a chord 4 is formed which is conveniently merely a 20 meter long wire
pulled taut between the two points. A measuring device 5 of any suitable
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design is located at a predetermined point between points 2, 3 for obtaining
the distance of the chord from the track at the predetermined point. Con-
veniently, the measuring device is a fork which engages the wire and pivots
to the right or left relative to a frame mounted indicator thereby giving the
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1~4;~39
amount of deviation between the track and chor~. The frame mowlted indicator
is, suitably, a rotary differential transformer which derives an analog volt-
age dependent on the deviation. The measuring device 5 is operated in con-
junction with a distance measuring apparatus shown schematically at 15 such
that at convenient increments, for example every two meters, a contact is
closed to sample the analog voltage on the transformer.
An averaging apparatus 12 receives the analog voltages sampled.
The averaging apparatus 12 is designed to receive the analog voltages sampled
at ten consecutive points, sum them and obtain a mean track pGSitiOn value
over the twenty meter distance travelled. The apparatus 12 may conveniently
include an analog to digital converter, the digital values being subsequently
summed and divided by the number of samples. It should be understood that as
the apparatus traverses the track continuously the first of the ten samples
is dropped and a new sample is added to the remaining nine and in this way a
running average is obtained every 2 meters.
A second measuring system comprises leading and trailing points 9,10
also conveniently located at the track center line on rail engaging buggies
forming a second frame. Associated with the second frame and stretched be-
tween the points 9,10 is a second 20 meter long taut wire forming a second
chord or reference line 8 and a second measuring device 14 which operates in
a manner identical to that of measuring device 5 and obtains the track dis-
tance from chord 8 at successive points.
Comparator 6, well known in the art, is provided which utilises as
two inputs, respectively, the mean track distance calculated by averager 12
and the track distance "y" obtained by the second measuring device 14. The
magnitude of the voltage output from ~he comparator 6 depends on the differ-
ence between the mean track distance and the track distance "y".
The error output voltage from comparator 6 is forwarded to track
11(~4~
correcting means 7 which can be any suitable device for shifting track later-
ally as is known in the art~ e.g. ~ s~rvo valve 7a controlling hydraulic jack
7B. The track correcting means 7 thereby realigns the track in accordance
with the magnitude and sign of the error signal from comparator 6 is a sense
to reduce or remove the error.
In an arrangement which has proved very satisfactory, the measuring
devices 5 and 14 were located 4 meters from the rear points 3 and 9 of their
respective chords and the chords were overlappcd such that the point 3 of the
first chord was a~jacent the midpoint of the second chord and the poin~ 10 of
the second chord was adjacent the mid point of the first chord. The overlap-
ping of the chords conveniently reduces the overall length of the apparatus
but there is a limit to the overlapping as excessive overlapping would tend
to reduce the accuracy of the results. This is because the ten sample read-
ings obtained by the first measuring device are normally obtained over the
ten meters immediately preceding and the ten meters immediately following
the particular point being measured by device 14 so that half of the samples
upon which the mean value is obtained are taken on a portion of the track
which has subsequently been corrected. Thus, the distance between the measur-
ing devices 5 and 14 determines the maximum distance over which the samples
can be taken.
Because of the overlapping chords it is possible to incorporate a
feedback provision into the averager 12 by arranging that the sensing device
14 and track correcting means 7 are located at point 3, i.e. the trailing
end of the first chord. Thus, the trailing end 3 of chord 4 is continuously
moved to a corrected position on the track as the track correcting device 7
- operates. The corrected point 3 represents a more exact reference point
than uncorrected point 3 and so any value measured by measuring device 5
when chord 4 terminates at the corrected point 3 is, obviously, more accurate.
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The system can, therefore be arranged to derive measurements from measuring
device 5 while the point 3 is on the corrected portion of the track, i.e.
immediately after operation of the track correcting device, these being
the values which are stored and sampled.
As an additional feature of the invention it is possible to incor-
porate a device for measuring the superelevation of the track. According to
the A.R.A. standard, the superelevation of a railroad track "x" is given by
the formula E = .0007 V D where.
E = th0 superelevation in inches,
V = the proposed train speed in miles per hour, and
D = the curvature of the track in degrees measured
as the angle subtended by the radii from a 100
foot chord.
The device includes a comparator 11 to which is fed an output from
the averager 12 which output is obviously related to the track curvature D.
The second input to the comparator 11 originates by the provision
of a track speed adjuster 18. If the proposed train speed V, for example,
is 60 miles/hr., this value is simply selected on the track speed adjuster
whereby it is fed to the comparator 11.
The third input to the comparator 11 is derived from a pendulum
sensor 13 which is carried by the apparatus on the track center line near
the sensing device 14. The sensor 13 is well known in the art and derives
an analog voltage the magnitude and sign of which depends on by how much
the elevation of the outer rail of the curve differs from the inner rail.
The comparator 11 compares this superelevation with .0007 ~2D and
any resultant signal denotes the magnitude of the track superelevation error.
This signal commands a servo valve 16a to operate a hydraulic lift-
ing jack 16b or 16c depending on which rail has to be lifted.
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It should be understood that the voltages passed to the first two
inputs of the comparator have to be matched to the voltage produced by the
pendulum and, thus, constants based on the parameters of the pendulum must
be used to process the voltages on the first two inputs. This is preferably
done in the comparator.
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