U.S. patent application number 09/953844 was filed with the patent office on 2003-03-20 for track receiver.
This patent application is currently assigned to PHW Inc.. Invention is credited to Frick, John S..
Application Number | 20030052233 09/953844 |
Document ID | / |
Family ID | 25494604 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030052233 |
Kind Code |
A1 |
Frick, John S. |
March 20, 2003 |
TRACK RECEIVER
Abstract
A track receiver is located on-board a locomotive for receiving
a first magnetic field produced in response to a cab signal carrier
transmitted through a rail on which the locomotive is carried. The
track receiver is oriented so that a second magnetic field produced
during operation of a traction motor of the locomotive propagates
substantially perpendicular to an axis of sensitivity of the track
receiver, and is oriented so that the first magnetic field
propagates parallel to the axis of sensitivity of the track
receiver.
Inventors: |
Frick, John S.; (Springdale,
PA) |
Correspondence
Address: |
Webb Ziesenheim Logsdon
Orkin & Hanson, P.C.
Suite 700
436 Seventh Avenue
Pittsburgh
PA
15219
US
|
Assignee: |
PHW Inc.
|
Family ID: |
25494604 |
Appl. No.: |
09/953844 |
Filed: |
September 17, 2001 |
Current U.S.
Class: |
246/194 |
Current CPC
Class: |
B61L 3/24 20130101; B61L
3/221 20130101 |
Class at
Publication: |
246/194 |
International
Class: |
B61L 003/00 |
Claims
I claim:
1. A system for use on a locomotive having a traction motor which
generates a first magnetic field during operation on, the system
comprising: at least one track receiver located on-board a
locomotive and disposed in a second magnetic field produced around
at least one of a pair of rails on which the locomotive is carried
in response to a cab signal carrier propagating through the at
least one rail, for converting the second magnetic field into a cab
signal, the at least one track receiver also disposed in a first
magnetic field generated during operation of a traction motor of
the locomotive for converting the first magnetic field into a noise
signal; and a cab signal system located on-board the locomotive and
connected to receive the cab signal and the noise signal from the
track receiver, the cab signal system configured to extract data
from the cab signal which has a frequency range at least partially
in common with a frequency range of the noise signal, wherein: the
first magnetic field propagates in a three dimensional space around
the traction motor; the first magnetic field has at each point in
the three dimensional space a magnetic vector which, with reference
to a Cartesian coordinate system, is comprised of a horizontal
component which extends parallel to the longitudinal axes of the
rails adjacent the locomotive, a lateral component which extends
laterally to the longitudinal axes of the rails adjacent the
locomotive and a vertical component with extends perpendicular to
the horizontal and lateral vectors; and the track receiver is
positioned on the locomotive in the three dimensional space and is
oriented so that at the points in the three dimensional space where
the track receiver is positioned the vector sum of at least two of
the horizontal, lateral and vertical components has a direction
vector substantially perpendicular to an axis of sensitivity of the
track receiver where the track receiver is most sensitive to a
magnetic field propagating therealong;
2. The system as set forth in claim 1, wherein the track receiver
is positioned on the locomotive so that a magnetic vector of the
second magnetic field produced around the at least one rail
propagates through the track receiver substantially parallel to the
axis of sensitivity of the track receiver.
3. The system as set forth in claim 1, wherein the axis of
sensitivity of the track receiver is received in an imaginary plane
which extends substantially parallel to top surfaces of the
rails.
4. The system as set forth in claim 3, wherein: the traction motor
has a longitudinal axis which extends transverse to the
longitudinal axes of the rails; the track receiver is positioned
adjacent one of the rails; and when viewed normal to a surface of
the imaginary plane, an extension of the axis of sensitivity of the
track receiver crosses an extension of the longitudinal axis of the
traction motor on a side of the one rail opposite the other
rail.
5. The system as set forth in claim 4, wherein the longitudinal
axis of the traction motor extends laterally to the longitudinal
axes of the rails.
6. The system as set forth in claim 1, wherein, when the track
receiver is positioned on the locomotive and oriented so that the
vector sum of two of the vertical, horizontal and lateral
components, at the points in the three dimensional space where the
track receiver is positioned, has a direction vector substantially
perpendicular to the axis of sensitivity of the track receiver, the
remaining one of the vertical, horizontal and lateral components
has a direction vector substantially perpendicular to the axis of
sensitivity of the track receiver.
7. The system as set forth in claim 1, wherein at least one of the
vertical, horizontal and lateral components has a magnitude of zero
(0).
8. The system as set forth in claim 1, wherein the track receiver
is comprised of (i) a coil of wire or (ii) a Hall effect
sensor.
9. The system as set forth in claim 1, wherein the axis of
sensitivity of the track receiver is received in a imaginary plane
which extends laterally and substantially perpendicular to the
longitudinal axes of the rails.
10. The system as set forth in claim 9, wherein the traction motor
has a longitudinal axis which extends transverse to the
longitudinal axes of the rails; the track receiver is positioned
adjacent one of the rails; and when viewed normal to a surface of
the imaginary plane, an extension of the axis of sensitivity of the
track receiver crosses an extension of the longitudinal axis of the
traction motor on a side of the one rail opposite the other
rail.
11. The system as set forth in claim 10, wherein the longitudinal
axis of the traction motor extends laterally to the longitudinal
axes of the rails.
12. A system for use on a rail vehicle received on a pair of rails
and having a traction motor which generates a magnetic field which
propagates in a three dimensional space around the traction motor,
the magnetic field having at each point in the three dimensional
space a magnetic vector which, with reference to a Cartesian
coordinate system in the three dimensional space, is comprised of
the vector sum of three components which extend perpendicular to
each other, with one of the three perpendicular components parallel
to the longitudinal axes of the rails, the system comprising a
track receiver positioned on-board the rail vehicle in the three
dimensional space adjacent one of the rails and oriented in the
three dimensional space so that at the points in the three
dimensional space where the track receiver is positioned the vector
sum of at least two of the three perpendicular components has a
direction vector substantially perpendicular to an axis of
sensitivity of the track receiver.
13. The system as set forth in claim 12, wherein the axis of
sensitivity of the track receiver is positioned at a compound angle
comprising a first angle relative to a first plane which extends
parallel to top surfaces of the rails and a second angle relative
to a second plane with extends laterally and perpendicular to the
longitudinal axes of the rails.
14. The system as set forth in claim 12, further including another
track receiver positioned on-board the rail vehicle in the three
dimensional space adjacent the other rail and oriented in the three
dimensional space so that at the points in the three dimensional
space where the other track receiver is positioned the vector sum
of at least two of the three perpendicular components has a
direction vector substantially perpendicular an axis of sensitivity
of the other track receiver.
15. The system as set forth in claim 14, wherein the track
receivers are connected so that cab signals output by the track
receivers in response to a cab signal carrier flowing through the
rail adjacent each track receiver are additive.
16. The system as set forth in claim 14, wherein: the cab signal
carrier produces another magnetic field around each rail; and each
track receiver is oriented relative to its adjacent rail so that a
magnetic vector of the other magnetic field produced around the
rail propagates through the track receiver substantially parallel
to the axis of sensitivity of the track receiver.
17. A cab signaling system for use on a locomotive having a
traction motor positioned between a front end and a back end of the
locomotive, the system comprising: a first track receiver disposed
on-board a locomotive adjacent one of a plurality of rails which
support the locomotive and in a magnetic field generated during
operation of a traction motor of the locomotive, the first track
receiver outputting a first cab signal in response to a cab signal
carrier transmitted through the rail adjacent the first track
receiver, the first track receiver outputting in response to the
magnetic field a first noise signal having a frequency in a
frequency range of the first cab signal, the first track receiver
having an axis of sensitivity which is oriented at a first position
in the magnetic field substantially perpendicular to a direction
vector of the magnetic field at the first position; and a signal
processor located on-board the locomotive, the signal processor
connected to receive from the first track receiver the first cab
signal and the first noise signal and to process signals in the
frequency range of the first cab signal, wherein the orientation of
the axis of sensitivity of the first track receiver in the magnetic
field results in a ratio of the first cab signal to the first noise
signal being of a sufficient extent so that the signal processor
can process the first cab signal without interference by the first
noise signal.
18. The system as set forth in claim 17, further including: a
second track receiver disposed on-board the locomotive adjacent
another one of the plurality of rails and in the magnetic field,
the second track receiver outputting a second cab signal in
response to transmission of the cab signal carrier through the rail
adjacent the second track receiver, the second track receiver
outputting in response to the magnetic field a second noise signal
having a frequency in a frequency range of the second cab signal,
the second track receiver having an axis of sensitivity which is
oriented at a second position in the magnetic field substantially
perpendicular to a direction vector of the magnetic field at the
second position, wherein: the signal processor is connected to
receive from the second track receiver the second cab signal and
the second noise signal and to process signals in the frequency
range of the second cab signal; and the orientation of the axis of
sensitivity of the second track receiver in the magnetic field
results in a ratio of the second cab signal to the second or noise
signal being of a sufficient extent so that the signal processor
can process the second cab signal without interference by the
second noise signal.
19. The system as set forth in claim 18, wherein: the first and
second track receivers are connected so that the first and second
cab signals sum and the first and second noise signals sum; and the
orientation of the axis of sensitivity of the first and second
track receivers in the magnetic field results in a ratio of the sum
of the cab signals to the sum of the noise signals being of a
sufficient extent so that the signal processor can process the sum
of the cab signals without interference by the sum of the noise
signals.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to on-board cab signaling
systems and, more particularly, to the rejection of magnetic field
interference imposed on inductive track receivers employed by these
systems.
[0003] 2. Description of the Prior Art
[0004] Cab signals are utilized extensively to communicate
information to a cab signal system located on-board a locomotive.
This information is utilized by the cab signal system to provide
information to an operator of a locomotive or to automatically
control the operation of the locomotive.
[0005] Cab signal systems typically employ inductive track
receivers mounted on the locomotive ahead of the lead wheels and
just above the rails for sensing and converting magnetic fields
produced by cab signal carriers transmitted through the rails into
cab signals. An advantage of cab signals is that information can be
made available to the locomotive operator on a continuous basis.
This is especially useful for communicating instantaneous changes
in the status of a track circuit to operators of locomotives on the
track circuit. By communicating this information on a continuous
basis, locomotives can be controlled to safely proceed through the
track circuit.
[0006] A prior art track receiver typically includes an iron core
inductor mounted above and orthogonal to a longitudinal axis of a
rail. The frequency of the cab signal carrier transmitted through
the rails is typically in the range from 40 Hz to 250 Hz, but may
be as high as 5 kHz. Prior art track receivers are utilized quite
successfully in older model locomotives which utilize DC traction
motors. Modern locomotives, however, utilize AC traction motors
which receive alternating current power from an inverter. The
combination of an AC traction motor and inverter provides a greater
degree of speed, power and control over a DC traction motor while
eliminating the high maintenance requirements associated with the
use of DC traction motors.
[0007] An AC traction motor receives alternating current from the
inverter at a variable frequency between 0 Hz and 300 Hz according
to the speed requirement of the train. This results in the
generation of an alternating current magnetic field by the AC
traction motor that did not exist with DC traction motors. Since
the frequency of the alternating current magnetic field generated
by the AC traction motor is in the same frequency range as cab
signal carriers, the AC traction motor is a primary source of noise
signals which can be imposed on the track receivers along with the
cab signals. Thus, the use of AC traction motors can severely
compromise cab signals as a safe and reliable information
source.
[0008] Various approaches for reducing the effect of the
alternating current magnetic fields and, hence, noise signals
produced by an AC traction motor have been proposed. One approach
is disclosed in U.S. Pat. No. 5,586,736 to Mollet. The Mollet
patent discloses pickup units 44 each having a housing 48 with a
rectangular configuration but for a missing lower side thus forming
an inverted, hollow U-shaped enclosure. An inverted U-shaped
magnetic structure is received in housing 48 and is essentially
centered within top and end segments 50 and 52 of housing 48. The
magnetic structure includes a pair of vertical legs 54 and a
horizontal cross member 56. Legs 54 and cross member 56 are formed
from cylindrical ferrite rods. Each pickup unit 44 is positioned
and oriented so that legs 54 extend toward the rail thereby
enhancing the capacity of each pickup unit 44 to receive magnetic
fields produced by the cab signal carriers. A pickup coil 58 or 60
is wound on each leg 54. Pickup coils 58 and 60 are connected so
that cab signals produced by coils 58 and 60 are additive and noise
signals produced by coils 58 and 60 are subtractive.
[0009] Another approach proposed in U.S. Pat. No. 5,622,339 to
Capan is a pair of plate antennas for sensing the magnetic fields
produced by the cab signal carrier. Each plate antenna includes a
signal coil and a noise coil wound on a rectangular core at right
angles to each other. The signal coils and the noise coils of the
plate antennas are connected so that the outputs of the noise coils
cancel any noise components in the signals output by the signal
coils, such as noise components caused by the operation of the AC
traction motor.
[0010] As can be seen from the Mollet and Capan patents, those
skilled in the art of cab signaling systems believed it necessary
for each track receiver to maintain an orthogonal relationship with
the rail, to modify the shape of the track receiver, to utilize
high permeability materials and/or to utilize additional windings
to subtract out motor noise from the cab signal. These solutions,
however, are specialized and/or costly and require application
specific tuning and calibration by empirical testing. In addition,
these solutions have limited capacity to completely subtract out
motor noise due to mutual coupling of the signal and noise
coils.
[0011] It is, therefore, an object of the present invention to
overcome the above problem and others by providing a cab signaling
system having an track receiver oriented to minimize the effects of
magnetic field motor noise produced by a traction motor during
operation while, at the same time, detecting magnetic fields
produced by a cab signal carriers transmitted through the rails
with an acceptable signal to noise ratio. Still other objects of
the present invention will become apparent to those of ordinary
skill in the art upon reading and understanding the following
detailed description.
SUMMARY OF THE INVENTION
[0012] Accordingly, I have invented a system for use on a
locomotive having a traction motor which generates a first magnetic
field during operation. The system includes at least one track
receiver located on-board the locomotive and disposed in a second
magnetic field produced around at least one of a pair of rails on
which the locomotive is carried in response to a cab signal carrier
propagating through the at least one rail. The track receiver
converts the second magnetic field into a cab signal. The track
receiver is also disposed in the first magnetic field generated
during operation of the traction motor of the locomotive for
converting the first magnetic field into a noise signal. A cab
signal system located onboard the locomotive is connected to
receive the cab signal and the noise signal from the track
receiver. The cab signal system is configured to extract data from
the cab signal which has a frequency range at least partially in
common with a frequency range of the noise signal. The first
magnetic field propagates in a three dimensional space around the
traction motor. The first magnetic field has at each point in the
three dimensional space a magnetic vector which, with reference to
a Cartesian coordinate system, is comprised of a horizontal
component which extends parallel to the longitudinal axes of the
rails adjacent the locomotive, a lateral component which extends
laterally to the longitudinal axes of the rails adjacent the
locomotive and a vertical component which extends perpendicular to
the horizontal and lateral components. The track receiver is
positioned on the locomotive in the three dimensional space and is
oriented so that at the points in the three dimensional space where
the track receiver is positioned the vector sum of at least two of
the horizontal, lateral and vertical components has a direction
vector substantially perpendicular to an axis of sensitivity of the
track receiver where the track receiver is most sensitive to a
magnetic field propagating therealong.
[0013] The track receiver is positioned on the locomotive so that a
magnetic vector of the second magnetic field produced around the at
least one rail propagates through the track receiver substantially
parallel to the axis of sensitivity of the track receiver.
[0014] The axis of the sensitivity of the track receiver can be
received in an imaginary plane which extends substantially parallel
to top surfaces of the rails. The traction motor has a longitudinal
axis which extends transverse to the longitudinal axes of the
rails. The track receiver is positioned adjacent one of the rails
and, when viewed normal to a surface of the imaginary plane, an
extension of the axis of sensitivity of the track receiver crosses
an extension of the longitudinal axis of the traction motor on a
side of the one rail opposite the other rail. Preferably, the
longitudinal axis of the traction motor extends laterally to the
longitudinal axes of the rails.
[0015] When the track receiver is positioned on the locomotive and
oriented so that the vector sum of two of the vertical, horizontal
and lateral components, at the points in the three dimensional
space where the track receiver is positioned, has a direction
vector substantially perpendicular to the axis of sensitivity of
the track receiver, the remaining one of the vertical, horizontal
and lateral components has a direction vector substantially
perpendicular to the axis of sensitivity of the track receiver.
[0016] At least one of the vertical, horizontal and lateral
components can have a magnitude of zero. Preferably, the track
receiver is comprised of (i) a coil of wire or (ii) a Hall-effect
sensor.
[0017] Alternatively, the axis of sensitivity of the track receiver
can be received in an imaginary plane which extends laterally and
substantially perpendicular to the longitudinal axes of the rails.
Where the traction motor has a longitudinal axis which extends
transverse to the longitudinal axes of the rails and the track
receiver is positioned adjacent one of the rails, when viewed
normal to a surface of the imaginary plane, an extension of the
axis of sensitivity of the track receiver crosses an extension of
the longitudinal axis of the traction motor on a side of the one
rail opposite the other rail.
[0018] I have also invented a system for use on a rail vehicle
received on a pair of rails and having a traction motor which
generates a magnetic field which propagates in a three dimensional
space around the traction motor. The magnetic field has at each
point in the three dimensional space a magnetic vector which, with
reference to a Cartesian coordinate system in the three dimensional
space, is comprised of the vector sum of three components which
extend perpendicular to each other with one of the three
perpendicular components parallel to the longitudinal axes of the
rails. The system includes a track receiver positioned on-board the
rail vehicle in the three dimensional space adjacent one of the
rails and oriented in the three dimensional space so that at the
points in the three dimensional space where the track receiver is
positioned the vector sum of at least two of the three
perpendicular components has a direction vector substantially
perpendicular to an axis of sensitivity of the track receiver.
[0019] The system can also include another track receiver
positioned on-board the rail vehicle in the three dimensional space
adjacent the other rail and oriented in the three dimensional space
so that at the points in the three dimensional space where the
other track receiver is positioned the vector sum of at least two
of the three perpendicular components has a direction vector
substantially perpendicular to an axis of sensitivity of the other
track receiver.
[0020] Preferably, the axis of sensitivity of each track receiver
is positioned at a compound angle comprising a first angle relative
to a first plane which extends parallel to top surfaces of the
rails and a second angle relative to a second plane which extends
laterally and perpendicular to the longitudinal axes of the
rails.
[0021] The track receivers are preferably connected so that cab
signals output by the track receivers in response to a cab signal
carrier flowing through the rail adjacent each track receiver are
additive.
[0022] Each track receiver is also oriented relative to its
adjacent rail so that a magnetic vector of another magnetic field
produced around the rail in response to the cab signal carrier
flowing therethrough propagates through the track receiver
substantially parallel to the axis of sensitivity of the track
receiver.
[0023] Lastly, I have invented a cab signaling system for use on a
locomotive having a traction motor positioned between a front end
and a back end of the locomotive. The system includes a first track
receiver disposed on-board the locomotive adjacent one of a
plurality of rails which support the locomotive and in a magnetic
field generated by the traction motor during operation. The first
track receiver outputs a first cab signal in response to a cab
signal carrier transmitted through the rail adjacent the first
track receiver. The first track receiver also outputs in response
to the magnetic field a first signal noise having a frequency in a
frequency range of the first cab signal. The first track receiver
has an axis of sensitivity which is oriented at a first position in
the magnetic field substantially perpendicular to a direction
vector of the magnetic field at the first position. A signal
processor located on-board the locomotive is connected to receive
from the first track receiver the first cab signal and the first
noise signal. The signal processor is configured to process signals
in the frequency range of the first cab signal. The orientation of
the axis of sensitivity of the first track receiver in the magnetic
field results in a ratio of the first cab signal to the first noise
signal being of a sufficient extent so that the signal processor
can process the first cab signal without interference by the first
noise signal.
[0024] The system can also include a second track receiver disposed
on-board the locomotive adjacent another one of the plurality of
rails and in the magnetic field. The second track receiver outputs
a second cab signal in response to transmission of the cab signal
carrier through the rail adjacent the second track receiver. The
second track receiver also outputs in response to the magnetic
field a second noise signal having a frequency in a frequency range
of the second cab signal. The second track receiver has an axis of
sensitivity which is oriented at a second position in the magnetic
field substantially perpendicular to a direction vector of the
magnetic field at the second position. The signal processor is
connected to receive from the second track receiver the second cab
signal and the second noise signal and to process signals in the
frequency range of the second cab signal. The orientation of the
axis of sensitivity of the second track receiver in the magnetic
field results in a ratio of the second cab signal to the second
noise signal being of a sufficient extent so that the signal
processor can process the second cab signal without interference by
the second noise signal.
[0025] Preferably, the first and second track receivers are
connected so that the first and second cab signals sum and the
first and second noise signals sum. The orientation of the axes of
sensitivity of the first and second track receivers in the magnetic
field results in a ratio of the sum of the cab signals to the sum
of the noise signals being of a sufficient extent so that the
signal processor can process the sum of the cab signals without
interference from the sum of the noise signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIGS. 1a-1c are fragmentary top, side and front views of a
locomotive showing the lead wheels, traction motor and inductive
track receivers positioned in accordance with the prior art;
[0027] FIG. 2 is a block diagram of a cab signaling system and an
operator display for receiving and processing signals output by the
inductive track receivers shown in FIGS. 1a-1c, and a power
generating means for supplying electrical power to the traction
motor shown in FIGS. 1a-1c;
[0028] FIGS. 3a-3c are fragmentary top, side and front views of the
locomotive, lead wheels and traction motor shown in FIGS. 1a-1c
with the inductive track receivers positioned in accordance with
one embodiment of the present invention;
[0029] FIGS. 4a-4c are fragmentary top, side and front views of the
locomotive, lead wheels and traction motor shown in FIGS. 1a-1c
with the inductive track receivers positioned in accordance with
another embodiment of the invention; and
[0030] FIGS. 5a-5c are fragmentary top, side and front views of the
locomotive, lead wheels and traction motor of FIGS. 1a-1c with the
inductive track receivers positioned in accordance with yet another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention will be described with reference to
the accompanying drawings where like reference numbers correspond
to like elements.
[0032] With reference to FIGS. 1a-1c, a rail vehicle or locomotive
2 includes a vehicle body 4 having a plurality of wheels 6 and a
plurality of axles 8 coupled to vehicle body 4 in a manner known in
the art. Each axle 8 includes a wheel 6 on each end thereof. Each
axle 8 fixes the position of the wheels 6 in spaced parallel
relation for rolling along a pair of spaced parallel rails 10 in a
manner known in the art.
[0033] Rail vehicle 2 also includes a traction motor 12 coupled
between vehicle body 4 and one or more wheels 6 for propelling rail
vehicle 2 along rails 10 in response to traction motor 12 receiving
electrical power from a power generating means 14. When traction
motor 12 is an AC traction motor, power generating means 14 is an
inverter which supplies switched AC power to the AC traction motor.
When traction motor 12 is a DC traction motor, power generating
means 14 is a DC power supply which supplies DC power to the DC
traction motor.
[0034] Connected to vehicle body 4 a distance D above a top surface
16 of each rail 10 is an inductive track receiver 18. While one
track receiver 18 above one rail 10 can be utilized, a track
receiver 18 above each rail 10 is preferred.
[0035] A longitudinal axis 38 of each track receiver 18 defines a
single axis of sensitivity along which track receiver 18 is most
sensitive to the propagation of a magnetic field vector therealong.
Each track receiver 18 is positioned and oriented with its
longitudinal axis 38 parallel to a magnetic field vector 28
generated around the closest adjacent rail 10 in response to a cab
signal carrier transmitted therethrough. Each track receiver 18
includes an inductive coil of wire 24 wrapped around an iron core
26. However, track receiver 18 can be any device, e.g., a Hall
effect sensor, having a single axis of sensitivity oriented
parallel to magnetic field vector 28.
[0036] With reference to FIG. 2 and with continuing reference to
FIGS. 1a-1c, each inductive track receiver 18 converts magnetic
field vector 28 received thereby along longitudinal axis 38 into a
cab signal which is supplied to a cab signal system 20 for
processing. Preferably, track receivers 18 are connected so that
the output of their respective coils of wire 24 are additive. Cab
signal system 20 extracts data from the cab signal and supplies the
extracted data to an operator display 22.
[0037] In practice, a cab signal carrier transmitted in one rail 10
in a first direction, shown by the cross (+) in the left-side rail
10 of FIG. 1c, travels through wheels 6 and axle 8 of locomotive 2
and returns to its source in an opposite direction in the other
rail 10, shown by the dot (.cndot.) in the right-side rail of FIG.
1c. While the cab signal carrier transmitted in rails 10 shown in
FIG. 1c is illustrated using the cross and dot conventions, it is
to be appreciated that the cab signal carrier is an AC signal, not
a DC signal.
[0038] With reference to FIGS. 3a-3c and with continuing reference
to all previous Figs., before describing the present invention it
should be appreciated that traction motor 12 generates a magnetic
field vector 30 in a three dimensional space around traction motor
12. At each point in this three dimensional space, magnetic field
vector 30 includes, with reference to a Cartesian coordinate
system, a horizontal component which extends parallel to the
longitudinal axes of rails 10, a lateral component which extends
laterally to the longitudinal axes of rails 10 and a vertical
component which extends perpendicular to the horizontal and lateral
components. Depending on the point in the three dimensional space,
however, one or two of these vectors can have a magnitude of zero
(0).
[0039] Locomotive 2 includes vehicle body 4, wheels 6, axles 8,
traction motor 12, power generating means 14 and inductive track
receivers 18. In the embodiment shown in FIGS. 3a-3c, the
longitudinal axes 38 of track receivers 18 are received in a first
imaginary plane 42 which extends laterally and perpendicular to the
longitudinal axes of rails 10 and each track receiver 18 is
positioned in first imaginary plane 42 at an angle 32, shown best
in FIG. 3c, relative to a second imaginary plane 44 which extends
parallel to top surfaces 16 of rails 10 adjacent locomotive 2.
[0040] With specific reference to FIG. 3c, track receivers 18 are
oriented so that extensions of longitudinal axes 38 of track
receivers 18 from the ends thereof which are closest together cross
between rails 10. Moreover, when viewed normal to a surface of
first imaginary plane 42, an extension of longitudinal axis 38 of
each track receiver 18 crosses an extension of the longitudinal
axis 40 of traction motor 12 on a side of rail 10 adjacent track
receiver 18 opposite the other rail 10. Stated differently, when
viewed normal to a surface of first imaginary plane 42, extensions
of longitudinal axes 38 of track receivers 18 from the ends thereof
which are farthest apart cross the extension of the longitudinal
axis 40 of traction motor 12 outside rails 10. In addition to
orienting track receivers 18 with longitudinal axes 38 at angle 32,
track receivers 18 are positioned somewhat toward the insides 34 of
their respected rails 10.
[0041] The orientation of each track receiver 18 shown in FIGS.
3a-3c is selected so that at the points in the three dimensional
space where each track receiver 18 is positioned, longitudinal axis
38 of each track receiver 18 is substantially perpendicular to the
horizontal component of magnetic field vector 30, substantially
perpendicular to the sum of the vertical and lateral components of
magnetic field vector 30 and substantially parallel to magnetic
field vector 28 produced around rail 10. In this position and
orientation, it has been observed that a noise signal generated by
each track receiver 18 in response to receiving magnetic field
vector 30 has an amplitude that does not interfere with cab signal
system 20 extracting data from the cab signal. More specifically,
the sum of the noise signals generated by track receivers 18 does
not interfere with cab signal system 20 extracting data from the
sum of the cab signals produced by track receivers 18.
[0042] With reference now to FIGS. 4a-4c, another embodiment of the
present invention includes locomotive 2 having vehicle body 4,
wheels 6, axles 8, traction motor 12, power generation means 14 and
track receivers 18. In this embodiment, however, track receivers 18
are positioned above rails 10 with longitudinal axes 38 received in
second imaginary plane 44 and with longitudinal axis 38 of each
track receiver 18 oriented at an angle 36 relative to the
longitudinal axis of its respective, adjacent rail 10, shown best
in FIG. 4a.
[0043] As shown in FIG. 4a, track receivers 18 are oriented so that
extensions of longitudinal axes 38 of track receivers 18 from the
ends thereof which are closest together cross between rails 10.
Moreover, when viewed normal to a surface of second imaginary plane
44, an extension of the axis 38 of each track receiver 18 crosses
an extension of the longitudinal axis 40 of traction motor 12 on a
side of rail 10 adjacent track receiver 18 opposite the other rail
10. Stated differently, when viewed normal to a surface of second
imaginary plane 44, extensions of the longitudinal axes 38 of track
receivers 18 from the ends thereof which are farthest apart cross
the extension of the longitudinal axis 40 of traction motor 12
outside rails 10.
[0044] The orientation of each track receiver 18 in FIGS. 4a-4c is
selected so at the points in the three dimensional space where each
track receiver 18 is positioned, longitudinal axis 38 of each track
receiver 18 is substantially perpendicular to the vertical
component of magnetic field vector 30 and is substantially
perpendicular to the vector sum of the horizontal and lateral
components of magnetic field vector 30.
[0045] Since longitudinal axis 38 of each track receiver 18 is
positioned at angle 36 relative to the longitudinal axis of rail 10
adjacent track receiver 18, longitudinal axis 38 of each track
receiver 18 is not substantially parallel to magnetic field vector
28 surrounding its respective, adjacent rail 10. However, orienting
each track receiver 18 at angle 36 has little or no effect on its
ability to produce cab signals.
[0046] In the embodiments shown in FIGS. 3a-3c and 4a-4c, track
receivers 18 are positioned with longitudinal axes 38 at angles 32
and 36 in first and second imaginary planes 42 and 44,
respectively. Each of these orientations reduces the amount of
magnetic field vector 30 detected by track receivers 18 and, hence,
reduces the amplitude of the noise signals output by track
receivers 18 sufficiently to enable cab signal system 20 to extract
data from the cab signals without interference. Recall, however,
that magnetic field vector 30 extends three dimensionally from
traction motor 12. Thus, orienting longitudinal axis 38 of each
track receiver 18 at angle 32 in first imaginary plane 40 does not
minimize to the extent possible the vertical and lateral components
of magnetic field vector 30 that propagate transverse to
longitudinal axis 38 of track receiver 18. Similarly, orienting
each track receiver 18 at angle 36 in second imaginary plane 44
does not reduce to the extent possible the horizontal and lateral
components of magnetic field vector 30 that propagate transverse to
longitudinal axis 38 of track receiver 18.
[0047] With reference now to FIGS. 5a-5c and with continuing
reference to all previous Figs., another embodiment of the present
invention includes locomotive 2 having vehicle body 4, wheels 6,
axles 8, traction motor 12, power generating means 14 and inductive
track receivers 18. In this embodiment, however, each track
receiver 18 is oriented at the combination of angles 32 and 36,
i.e., a compound angle. Orienting each track receiver 18 at this
compound angle minimizes the magnetic field vector 30 that
propagates along with the longitudinal axes 38 of track receivers
18. Stated differently, by simply orienting each track receiver 18
at this compound angle, the vector sum of the vertical, horizontal
and lateral components of magnetic field vector 30 propagates
through track receivers 18 substantially perpendicular to the
longitudinal axes 38 of track receivers 18. Orienting track
receivers 18 at this compound angle thus maximizes the ratio of the
cab signals to the noise signals.
[0048] It was theoretically determined that for track receivers 18
spaced 50 inches apart between rails 10, with the center of each
track receiver 18 positioned approximately 79 inches from the
center of traction motor 12, and with the centers of track
receivers 18 spaced 21.5 inches below the center of traction motor
12, orienting each track receiver 18 with angle 32 equal to
49.3.degree. and/or with angle 36 equal to 32.3.degree. would
reduce the noise signals received by cab signal system 20
sufficiently to permit cab signal system 20 to process the cab
signals without interference from the noise signals. For this
position of track receivers 18 relative to rails 10 and traction
motor 12, it was empirically determined that angle 32 between
40.degree.-60.degree., preferably between 45.degree.-55.degree.,
and/or angle 36 between 25.degree.-40.degree., preferably between
30.degree.-35.degree., reduced the noise signals received by cab
signaling receiver 20 sufficiently.
[0049] As can be seen, simply orienting each track receiver 18 so
that the vector sum of at least two of the vertical, horizontal and
lateral components of magnetic field vector 30 is substantially
perpendicular to longitudinal axis 38 of track receiver 18 reduces
the effect of magnetic field vector 30 on track receiver 18
sufficiently so that cab signal system 20 can readily extract data
from the cab signals without interference from the noise signals.
Moreover, orienting each track receiver 18 in this manner has
little or no effect on track receiver 18 receiving magnetic field
vector 28.
[0050] The present invention has been described with reference to
the preferred embodiments. Obvious modifications and alterations
will occur to others upon reading and understanding the preceding
detailed description. For example, it is to be appreciated that the
above described theoretical and experimental results are not to be
construed as limiting the invention. Specifically, changing the
distance between the center of each track receiver 18 and the
center of traction motor 12, changing the spacing between track
receivers 18, and the like, may affect one or both of angles 32 and
36 that each track receiver 18 must be oriented in order to
minimize the noise signal produced in response to magnetic field
vector 30 generated by traction motor 12 during operation.
Moreover, while the present invention is most useful when used in
combination with locomotive 2 having an AC traction motor, the
present invention can also be utilized with a locomotive 2 having a
DC traction motor to reduce noise signals produced by track
receivers 18 during operation thereof. Furthermore, one track
receiver 18 positioned between a pair of rails 10 on which
locomotive 2 is carried can be utilized. Lastly, each track
receiver 18 can be the inductive coil of wire 24 formed around an
air core. It is intended that the invention be construed as
including all such modifications and alterations insofar as they
come within the scope of the appended claims or the equivalents
thereof.
* * * * *