U.S. patent application number 11/743317 was filed with the patent office on 2008-11-06 for methods and systems for multi-tuned cab signal pickup coils.
Invention is credited to Michael Scott Mitchell, Samuel Robert Mollet.
Application Number | 20080272245 11/743317 |
Document ID | / |
Family ID | 39631578 |
Filed Date | 2008-11-06 |
United States Patent
Application |
20080272245 |
Kind Code |
A1 |
Mollet; Samuel Robert ; et
al. |
November 6, 2008 |
METHODS AND SYSTEMS FOR MULTI-TUNED CAB SIGNAL PICKUP COILS
Abstract
Methods and systems for a cab signal pickup coil assembly are
provided. The system includes an assembly including at least one
elongate magnetic core and a plurality of pickup coils
concentrically spaced about the magnetic core wherein the pickup
coils are configured to be responsive to a magnetic field in the
magnetic core. The pickup coils are grouped in sets of pickup coils
along an axial length of the magnetic core. At least two sets of
pickup coils are at least partially tuned using respective tuning
capacitors to be responsive to different respective cab signal
carrier frequencies.
Inventors: |
Mollet; Samuel Robert;
(Grain Valley, MO) ; Mitchell; Michael Scott;
(Lee's Summit, MO) |
Correspondence
Address: |
JOHN S. BEULICK (12729);C/O ARMSTRONG TEASDALE LLP
ONE METROPOLITAN SQUARE, SUITE 2600
ST. LOUIS
MO
63102-2740
US
|
Family ID: |
39631578 |
Appl. No.: |
11/743317 |
Filed: |
May 2, 2007 |
Current U.S.
Class: |
246/193 |
Current CPC
Class: |
B61L 3/243 20130101 |
Class at
Publication: |
246/193 |
International
Class: |
B61L 3/00 20060101
B61L003/00 |
Claims
1. A cab signal pickup coil assembly comprising: at least one
elongate magnetic core; and a plurality of pickup coils
concentrically spaced about said magnetic core, said pickup coils
configured to be responsive to an alternating magnetic field in
said magnetic core, said pickup coils grouped in sets of pickup
coils along an axial length of said magnetic core, at least two
sets of pickup coils at least partially tuned by respective tuning
capacitors to be responsive to different respective cab signal
carrier frequencies.
2. A system in accordance with claim 1 wherein said magnetic core
comprises a longitudinal axis, said magnetic core is configured to
be positioned proximate a rail such that a longitudinal axis of the
rail is substantially orthogonal with respect to the longitudinal
axis of the magnetic core.
3. A system in accordance with claim 1 wherein ones of said sets of
pickup coils are separated from an adjacent set of pickup coils by
an air gap.
4. A system in accordance with claim 1 wherein said tuning
capacitors comprise an electrically controlled variable
capacitor.
5. A system in accordance with claim 1 wherein the capacitance of
the tuning capacitors is at least one of switchable, variable, and
digitally variable such that a frequency response of the sets of
pick up coils is variable.
6. A system in accordance with claim 1 wherein sets of pickup coils
are separated from adjacent sets of pickup coils by a material
having a predetermined reluctance.
7. A system in accordance with claim 1 wherein pick up coils in a
set are electrically coupled in series.
8. A system in accordance with claim 1 wherein at least one set of
pickup coils reduces noise above and below a first cab signal
carrier frequency and has a center frequency between about 40 Hz
and about 250 Hz.
9. A system in accordance with claim 1 wherein at least one set of
pickup coils reduces noise above and below a first cab signal
carrier frequency and has a center frequency of about 100 Hz.
10. A system in accordance with claim 1 wherein at least one set of
pickup coils reduces noise above and below a second cab signal
carrier frequency and has a center frequency between about 1500 Hz
and about 4550 Hz.
11. A system in accordance with claim 1 wherein at least one set of
pickup coils reduces noise above and below a first cab signal
carrier frequency and has a center frequency of about 2050 Hz.
12. A cab signal system comprising: a receiver configured to be
mounted on board a locomotive; at least one pickup coil assembly
communicatively coupled to said receiver, said at least one pickup
coil assembly configured to sense an alternating magnetic field
around a rail of a railroad track produced by control information
transmitted through the rail wherein the control information is
transmitted using a plurality of carrier frequencies, said at least
one pickup coil assembly comprising sets of pick up coils each
tuned to one of the plurality of carrier frequencies.
13. A system in accordance with claim 12 further comprising a
pickup coil assembly mount configured to couple said pickup coil
assembly to a locomotive such that a longitudinal axis of said
pickup coil assembly is substantially orthogonal with respect to
the track.
14. A system in accordance with claim 12 wherein said at least one
pickup coil assembly comprises: an elongate core; and at least one
pickup coil concentrically mounted around said elongate core.
15. A system in accordance with claim 12 wherein said tuning
capacitor is external to said pickup coil assembly
16. A system in accordance with claim 12 wherein said at least one
pickup coil assembly comprises a coil wound with a plurality of
adjacent turns concentrated axially along an elongate core and a
tuning capacitor coupled electrically in parallel.
17. A method of receiving a railway cab signal on board a railway
vehicle comprises: receiving control information transmitted
through railroad rails to a signal coil assembly mounted on board
the railway vehicle using a carrier having a frequency in a first
predetermined range; and receiving control information transmitted
through railroad rails to the signal coil assembly using a carrier
having a frequency in a second predetermined range, wherein the
first and second predetermined ranges are different, the first and
second predetermined frequency ranges selected based on a tuning of
coils within the signal coil assembly.
18. A method in accordance with claim 17 further comprising
traversing from a first locale where cab signals are transmitted
using a carrier having a frequency in a first predetermined range
predominate to a second locale where cab signals are transmitted
using a carrier having a frequency in a second predetermined range
predominate.
19. A method in accordance with claim 17 further comprising
mounting a signal coil assembly to the railway vehicle such that a
longitudinal axis of the signal coil assembly is maintained
substantially orthogonal with respect to the rail.
20. A method in accordance with claim 17 further comprising
positioning a plurality of pickup coils concentrically spaced about
a signal coil assembly magnetic core wherein the pickup coils are
configured to be responsive to an alternating magnetic field in the
magnetic core, the pickup coils being grouped in sets of pickup
coils along the magnetic core wherein at least two sets of pickup
coils are at least partially tuned using a respective tuning
capacitor to be responsive to different respective cab signal
carrier frequencies.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to methods and systems for
detecting coded or modulated electrical currents that are
transmitted through the rails of a railroad track for control
purposes and, more particularly, to cab signal systems and methods
that are interoperable across two or more cab signal territories
having different carrier frequencies.
[0002] At least some known cab signal coil assemblies are formed
from a magnetic material, such as laminated steel or ferrite, with
associated windings to generate a voltage proportional to a local
alternating magnetic field surrounding a railroad rail. The
magnetic field includes a carrier frequency portion and a signal
position. In some cases, capacitors are added to the magnetic
circuit to provide tuning or selective carrier frequency
sensitivity. Tuning cab signal pickup coils increases the gain of
the circuit as well as rejects out-of-band frequency, simplifying
system design. However, current pickup coil assemblies are limited
to a single carrier frequency, which limits their use to a single
carrier frequency territory. To permit interoperable use across
additional carrier frequency territories requires adding additional
equipment and switching components.
BRIEF DESCRIPTION OF THE INVENTION
[0003] In one embodiment, a cab signal pickup coil assembly
includes an assembly including at least one elongate magnetic core
and a plurality of pickup coils concentrically spaced about the
magnetic core wherein the pickup coils are configured to be
responsive to an alternating magnetic field in the magnetic core.
The pickup coils are grouped in sets of pickup coils along an axial
length of the magnetic core. At least two sets of pickup coils are
at least partially tuned using respective tuning capacitors to be
responsive to different respective cab signal carrier
frequencies.
[0004] In another embodiment, a cab signal system includes a
receiver configured to be mounted on board a locomotive, and at
least one pickup coil assembly communicatively coupled to the
receiver. The at least one pickup coil assembly is configured to
sense an alternating magnetic field around a rail of a railroad
track produced by control information transmitted through the rail
wherein the control information is transmitted using a plurality of
carrier frequencies. The at least one pickup coil assembly includes
sets of pick up coils wherein each set is tuned to one of the
plurality of carrier frequencies.
[0005] In still another embodiment, a method of receiving a railway
cab signal on board a railway vehicle includes receiving control
information transmitted through railroad rails to a signal coil
assembly mounted on board the railway vehicle using a carrier
having a frequency in a first predetermined range, and receiving
control information transmitted through railroad rails to the
signal coil assembly using a carrier having a frequency in a second
predetermined range wherein the first and second predetermined
ranges are different and wherein the first and second predetermined
ranges are selected based on a magnetic interaction of coils within
the signal coil assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic block diagram of a cab signal system
in accordance with an exemplary embodiment of the present
invention;
[0007] FIG. 2 is a cross-sectional view of the pickup coil assembly
shown in FIG. 1 in relation to a railroad rail; and
[0008] FIG. 3 is a graph of a response of pickup coil assembly in
accordance with an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The following detailed description illustrates the invention
by way of example and not by way of limitation. The description
clearly enables one skilled in the art to make and use the
invention, describes several embodiments, adaptations, variations,
alternatives, and uses of the invention, including what is
presently believed to be the best mode of carrying out the
invention.
[0010] FIG. 1 is a schematic block diagram of a cab signal system
100 in accordance with an exemplary embodiment of the present
invention. In the exemplary embodiment, cab signal system 100
includes an inductive track receiver such as a pickup coil assembly
102 converts a magnetic field vector (not shown in FIG. 1) received
along a longitudinal axis 104 into a cab signal 106 which is
supplied to a cab signal receiver 108 for processing. Cab signal
receiver 108 extracts data from cab signal 106 and supplies the
extracted data to an operator display 110. In an alternative
embodiment, data extracted from cab signal 106 may be transmitted
to other onboard systems 112 or off board systems through a
wireless communication link 114.
[0011] FIG. 2 is a cross-sectional view of pickup coil assembly
(shown in FIG. 1) in relation to a railroad rail 202. In the
exemplary embodiment, pickup coil assembly includes a housing 204
enclosing an elongate magnetic core 206 formed of a highly
permeable material such as, for example, but not limited to,
ferrite or laminations of iron or steel. One or more pick-up coils
208 are concentrically arranged about core 206 and are magnetically
coupled to core 206 such that an alternating flux flowing in core
206 tends to generate a signal in pick-up coils 208. Sets 210 of
pick-up coils 208 are spaced along core 206 to facilitate a
magnetic independence between adjacent sets 210 of pick-up coils
208. Such spacing comprises a gap 218 between adjacent sets 210. In
an alternative embodiment, there is no intentional gap between
adjacent sets 210. In the exemplary embodiment, a first set of
pick-up coils 208 includes approximately nine individual pick-up
coils 208 tuned to a specific cab signal frequency via capacitor
220 and a second set of pick-up coils 208 includes a single pick-up
coil 208 tuned to a different cab signal frequency via capacitor
221. In an alternative embodiment, any number of pick-up coils 208
may be grouped together to determine a tuning of pickup coil
assembly to predetermined carrier frequencies.
[0012] During operation, a cab signal carrier transmitted in one
rail 202 in a first direction, shown by the cross (+) in rail 202
travels through the wheels and axle of a railway vehicle (not
shown) and returns to its source in an opposite direction in the
other rail (not shown). Because the carrier signal is an AC signal,
on a next half-cycle the cab signal is transmitted in an opposite
direction in rail 202. The current flowing in rail 202 generates a
magnetic field vector 212 around rail 202 in a direction 214.
Magnetic field vector 212 extends circumferentially outward from
rail 202 and intersects core 206, which is positioned orthogonally
with respect to rail 202 a height 216 from rail 202. Each pick-up
coil 208 surrounding core 206 interacts with the alternating
magnetic field flowing through core 206 and with a magnetic field
generated in each other adjacent pick-up coil 208. Varying the
capacitance of tuning capacitor 220 and/or 221 varies the response
of respective sets 210 of pick-up coils 208. In one embodiment, the
capacitance of tuning capacitor 220 and/or 221 is switchable,
variable, or digitally variable. An arrow superimposed on a
conventional diagram of a capacitor component represents a variable
capacitance. In the exemplary embodiment, capacitor 220 and/or 221
may comprise a varactor or an electrically controlled variable
capacitor. In the exemplary embodiment, a set of nine pick-up coils
208 is tuned to be responsive to a carrier frequency of
approximately 100 Hertz. A second set 210 of pick-up coils 208
includes a single pick-up coil 208 and is tuned to be responsive to
a carrier frequency of approximately 2050 Hertz. In the exemplary
embodiment, to enhance magnetic independence in coil sets, a gap
218 is placed between coil sets. A gap 218 between sets 210 of
pick-up coils 208 facilitates increasing the output of the pickup
coil assembly when tuning pickup coil assembly to more than a
single carrier frequency. In an alternative embodiment, gap 218 is
not required and no intention gap is formed between sets of
coils.
[0013] FIG. 3 is a graph 300 of a response of pickup coil assembly
102 in accordance with an exemplary embodiment of the present
invention. Graph 300 includes an x-axis 302 graduated in units of
frequency and a y-axis 304 graduated in units of volts/amps at a
predetermined coil height 216 above rail 202. A trace 306 indicates
a response of pickup coil assembly 102 to a cab signal transmitted
through a rail at various frequencies. In the exemplary embodiment,
pickup coil assembly 102 is tuned to a frequency of approximately
100 Hz and a frequency of approximately 2050 Hz using sets of
pickup coils 208. Trace 306 includes a first local peak 308 at
approximately 100 Hz and a second local peak 310 at approximately
2050 Hz. Rapid fall off of the cab signal above and below the tuned
frequencies permits cab signal system 100 to readily distinguish
the cab signal from noise which may be present in the rail. The
individual peaks 308 and 310 at separate carrier frequencies
permits a single pickup coil assembly 102 to be interoperable
across different carrier frequency territories without additional
components or a need to switch between separate coil
assemblies.
[0014] Although system 100 has been illustrated with a pickup coil
assembly 102 tuned to receive only two separate carrier frequency
ranges, it should be understood that any number of different
carrier frequency ranges can be accommodated using the methods and
systems described herein.
[0015] The above-described methods and systems for providing cab
signal pickup assemblies that are interoperable across two or more
cab signal territories having different carrier frequencies. The
system provides a single cab signal pickup coil that is capable of
being tuned to two or more frequencies that is cost-effective and
highly reliable.
[0016] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
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