Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
The invention relates to a novel
communication link for permitting communications
between cars of multi-car vehicles such as railway
or subway trains. More specifically, the invention
relates to such a communication link which includes
free space radio communications between adjacent
cars of the multi-car vehicle.
BACKGROUND OF INVENTION
Description of the Prior Art
In order to adapt to changing system
requirements, such as passenger or freight volume,
routing, maintenance, crew or rolling stock
availability, etc., rail cars are coupled and
uncoupled frequently. Train configuration and
reconfiguration in this sense represents a
significant proportion of all train operation,
whether considered in terms of rolling-stock-hours,
man-hours, out-of-service hours, or whatever.
Therefore, these processes must be made as simple
and as automated as possible.
While it is true that trains are made up
of a variety of different types of cars, and in
some cases, certain groups of cars are rarely
uncoupled, it is nonetheless a fact that a great
number of individual couplings and uncouplings are
performed every day. An example of a present
system is illustrated in U.S. Patent 5,121,410,
Demarais, June 9, 1992. As can be seen in Figure 4
and 5 of the '410 patent, communication lines
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between cars (car n-l, car n and car n+1) is
effected by twisted pairs of wires.
This invention addresses the problem of
how to provide adequate information transfer
between cars without inhibiting train car coupling
or uncoupling.
This invention proposes a solution which
provides high-volume, high-reliability information
transfer between cars.
Information transfer between devices
installed on different cars, in the form of
electrical signals, has been a common feature of
trains for a number of years. The electrical
pathway that carries these signals is called a
"tramline" . It is made up of a bundle of wires,
each of which is connected in an electrically
continuous path over the length of the train.
On board devices that use the tramline
can interact with each other in a wide variety of
20. ways. For example, a device on one car, such as a
switch, may be used to control a number of similar
devices, such as lights, on every car of the train.
For another example, a specific type of sensor may
be installed on every car. If certain conditions
arise on one car, the sensor may need to activate a
warning buzzer installed in the cab of the head
car. Many other configurations are possible.
The changing tramline information
transfer requirements brought on by advances in
electronic technology over the past two decades
have given rise to new problems for tramline
designers. Two interrelated factors are at issue
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here: information volume and information
reliability.
In general, the volume of information
transferred between rail cars has increased over
the period mentioned. It promises to continue to
increase for some time to come; as train systems on
board each car utilize more and more electronic and
electrical equipment. This increased information
flow may be addressed in two ways. The increased
flow may be handled by an increasing number of
wires, or else each wire must handle a larger
volume of information.
Reliability of information transfer
between cars is and always has been essential to
safe, efficient train operation. Within each car,
reliability is accomplished by providing
mechanically secure conventional electrical
connectors that are rarely opened. However, for
communications between adjoining cars, the
connecting elements on the adjoining cars must be
automatically and frequently connected and
disconnected, rendering conventional electrical
connectors inefficient.
The use of such connecting elements cause
many problems leading to a large percentage of
service interruptions. Some of the problems are as
fol lows
1. Faulty electrical contact caused
by pin oxidation.
2. Faulty electrical contact caused
by dirt, grease and foreign matter on pins that
accumulates when the pins are disconnected and
therefore exposed.
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3. Electrical contact is prevented
when a pin fails to spring back out to its proper
position due to accumulated dirt, grease and
foreign matter inside the pin tube.
4. Electrical contact is prevented
when returned springs fail due to los s of spring
elasticity, which in turn is caused by de-tempering
of the spring steel when abnormally high electrical
current passes through the spring rather than the
electrical shunt.
All of the above problems produce service
interruptions and require expensive maintenance.
Periodically, the pins must be checked and cleaned
to ensure correct operation.
It is also known in the art to use
optical arrangements to provide communication links
between cars within a subset, and between the
subsets of a train, as illustrated in U.S. Patent
4,682,144, Ochiai et al, July 21, 1987. Such a
system is illustrated in Figure 4 of the '144
patent.
The problem with optical systems in the
environment of either subway or railroad trains is
that the systems are operating in very dirty
environments so that the optical couplers will very
shortly become dirty themselves. Due to the dirt
which will accumulate on the optical couplers,
optical transmission is degraded and possibly
completely eliminated. Accordingly, the system as
illustrated in the '144 patent is not a practical
solution to the provision to communication links
between the end cars of subsets of a train.
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In U.S. Patent 3,994,459, Miller et al,
November 30, 1976, a radio system is used to
provide communications between a car which is
derailed from a train and the remainder of the
train. However, the '459 patent does not teach any
other communications between the cars of the train
using radio signals.
Another factor affecting reliability is
the increase in information volume mentioned above.
All else being equal, as information volume
increases, overall reliability tends to decrease.
In summary, current train communications
systems attempt to provide reliability by two
methods: coupler pins and cable connectors. While
the method of cable connectors between cars
provides excellent reliability, it makes coupling
and uncoupling the cars a laborious process. On
the other hand, although coupler pins provide
excellent ease of operation, they require high
maintenance to maintain adequate reliability:
Coupler pins are sensitive to environmental
factors, and other problems. By far the highest
incidence of communication failure, especially
intermittent failure, occurs due to coupler pin
problems.
Increasing the number of wires may work
up to a point, but limitations are imposed on this
method by a number of factors. Among the most
serious of these factors is the problem of large
numbers of electrical connections between cars that
must be coupled and uncoupled frequently. These
connections are at best a trade-off between
reliability and automation; as their numbers
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increase, reliability and/or automation are
reduced.
Increasing the volume of information
handled by each wire eliminates the necessity of
large numbers of electrical connections between
cars. However, the high volume of information
carried by each wire makes these connections
vulnerable to both data loss and increased
maintenance, due reliability problems associated
with the current state of the art of high-volume
information flow through coupler pins.
U.S. Patent 3,696,758, Godinez, Jr.,
October 10, 1972, teaches a control system for
permitting control between cars of a multi-car
vehicle. Godinez, Jr. uses inductive couplers 18
for effecting a communications link between the
various cars. Thus, coupling between cars in
Godinez, Jr. is effected by magnetic coupling.
As is well known, such magnetic coupling
can support only very narrow band operations.
Accordingly, it is not possible to transmit a great
deal of data from one car to another using the
Godinez, Jr. system.
U.S. Patent 4,582,280, Nichols et al,
April 15, 1986 and 5,039,038, Nichols et al, August
13, 1991, teach a system having what appears to be
RF antennas connected to radios 28. However, it is
noted that such antennas are not shielded. With
such unshielded antennas, it is possible that a
radio in a car of one multi-car vehicle will pick
up signals from the radio of a car of a second
multi-car vehicle. Such signals would, of course,
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be incorrect. Thus, the solutions provided by
Nichols et al are not complete and satisfactory.
U.S. Patent 4,723,737, Mimoun, February
9, 1988, teaches a system for effecting
communications between cars of a multi-car vehicle
wherein the coupling is effected by microwave
signals. However, as is well known, the beam of a
microwave antenna is highly directional. For this
reason, when the train is going around the bend, it
is possible that the transmitted signal will miss
the receiving antenna. Accordingly, in accordance
with Mimoun, it is required that one of the cars
include two parallel antennas 28 as shown in Figure
3 of the Patent.
SUMMARY OF INVENTION
It is therefore an object of the
invention to provide a communication link for
communications between cars of a train which
overcomes the disadvantages of the prior art.
It is a more specific object of the
invention to provide such a novel communications
link which comprises a radio link through free
space.
It is an even more specific object of the
invention to provide such a novel communications
link by disposing, at the ends of each car,
antennas. The antennas of adjacent cars are
aligned with each other.
It is a still more specific object of the
invention to provide such a communications link
wherein means are provided for maintaining antennas
of adjacent cars in alignment with each other.
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In accordance with the invention, the
antennas are mounted on the coupling hooks of
adjacent cars which couple the cars together to
thereby maintain them in alignment.
In accordance with the invention, the
antennas are mounted on the coupling hooks in
shielded containers.
It is a still more specific object of the
invention to provide such a novel communications
link which comprises a multiplexer and a
demultiplexer on selected ones of the cars of the
train.
In accordance with a particular
embodiment of the invention, there is provided a
communication link for permitting communications
between adjacent cars of a railway or subway
trains, said link comprising:
on at least a first one of said cars, a
multiplexing means for multiplexing digital signals
representative of the status of various systems on
said first one of said cars, and for processing
said digital signals into a first digital tramline
signal to a radio frequency signal;
means for transmitting said radio
frequency signal by free space radio communication
from said first one of said cars to a second one of
said cars;
said second one of said cars including
means for receiving said radio frequency signal;
said second one of said cars also
including means for converting said radio frequency
signal to a second digital trainline signal;
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said second one of said cars including a
demultiplexer for demultiplexing the second digital
tramline signal into appropriate formats readable
by the train systems on board the second car.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be better understood
by an examination of the following description,
together with the accompanying drawings, in which:
FIGURE 1 is a. schematic drawing
illustrating two back-to-back
cars of a train, the radio
link between the cars, and
the circuits linked by the
radio links;
FIGURE 2 illustrates in greater detail
a Train Line Multiplexer
(TMX);
FIGURES 3A and 3B illustrate two
modulation approaches for the
transmitters of the radio
link transceiver (RLT);
FIGURE 4 illustrates a particular
embodiment of the RLT
receiver;
FIGURE 5 illustrates a duplexer
arrangement constituting a
part of the RLT; and
FIGURE 6 illustrates in greater detail
the radio link between the
end cars;
FIGURE 7 illustrates a top view of
coupling means for coupling
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adjacent ends of two cars to
each other in the uncoupled
position;
FIGURE $ is the same .as Figure 7 which
shows the coupling means in
the coupled position;
FIGURE 9 shows the coupling means in side
view with antennas mounted
thereon in the uncoupled
position;
FIGURE 10 illustrates the coupling means
with the antennas mounted
thereon in the coupled
position;
FIGURE 11 is an exploded view of the
antenna enclosure;
FIGURE 12 shows schematically the RF
waves when the couplers are
in the uncoupled position;
and
FIGURE 13 shows schematically the radio
frequency waves when the
couplers are in the coupled
position.
DESCRIPTION OF PREFERRED EMBODIMENTS
As ~ seen in Figure 1, a free space
communication link 15 permits communications
between cars 3 and 5. Each car includes a train
line multiplexer/demultiplexer (TMX) 17' and 17 "
and a radio link transceiver (RLT) 19' and 19 " .
As seen in Figure 2, the
multiplexer/demultiplexer 17 will receive digital
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signals of samples from different train systems,
for example, monitoring system 21, brake system 23,
propulsion system 25, ventilation system 27 and
intercom system 29. These signals are arranged in
a predetermined order to form a frame which can be,
for example, 125 microseconds long. As can be
seen, each frame includes a frame synchronization
signal at the beginning of the frame.
These signals are then passed to the
transmitter which transmits them, via the
communications link, to a different adjacent train
car.
At the receiving end; the
multiplexer/demultiplexer 17 will provide the
digital signals to the various trains systems, that
is, the monitoring system 21, the brake system 23,
the propulsion system 25, the ventilation system 27
and the intercom system 29. Multiplexing/demulti
plexing systems are, of course, well known in the
art so that no further description is required.
The output of the TMX is, as seen in
Figures 3A and 3B, fed to the modulation unit of
the RLT. Figure 3A illustrates a direct modulation
unit while Figure 3B illustrates an indirect
modulation unit. Each unit includes a line
interface (31 or 41) and a signal processor (33 or
43). These units process the signals to put them
into condition for use in the modulator. Thus, if
there is long strings of zeros in the signals, then
the signals must be modified to include ones and
zeros, and such modification will take place in the
units 31, 41 and 33, 43.
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Referring now to Figure 3A, the output of
the signal processor 33 is fed to a modulator 37
which has a second input terminal fed by an RF
generator 35. The output of the modulator is fed
to a bandpass filter 39, and the output of the
filter is fed to a duplexer circuit illustrated in
Figure 5.
Turning to Figure 3B, the output of the
signal processor 43 is once again fed to a
modulator 47. However, in this case, the second
terminal of modulator 47 is fed from IF source 45,
The output of the modulator 47 is once again passed
through a bandpass filter 49, the output of the
filter 49 is fed to a mixer 53. The second input
terminal of mixer 53 is fed from an RF generator
51, and the output of mixer 53 is fed to bandpass
filter 55. The output of bandpass filter 55 is
once again fed to the duplexer circuit.
Figure 4 illustrates one embodiment of
the receiver portion of the RLT. The output of the
duplexers circuit is fed to a bandpass filter 57
whose output is fed to a mixer 59. The received
signal is then mixed with an RF signal from RF
generator 61 applied to the second terminal of the
mixer 59. The output of the mixer is fed to a
bandpass filter 63 whose output is fed to a
demodulator 65. The synchronization signal is fed
from the demodulator 65 to symbol and bit clock
recovery circuit 67, and the output of both 65 and
67 are fed to signal processor 69. The output of
69 is fed to line interface 71 whose output is then
fed to the TMX.
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Figure 5, which illustrates the duplexer
77, and the transmitter 73 and the receiver 75 is
self-explanatory.
Turning now to Figure 6, the free space
s electromagnetic link 15 between car 7' and car 7"
is effected by RF antennas 83' and 83 "
respectively. In a particular embodiment, the
antennas are mounted in housings 79' and 79"
respectively, which housings are made of a
~o dielectric material, for example, polycarbonate
material. Each housing comprises a sealed enclosure
which protects the antenna from humidity and water
damage.
Disposed around the housings 79' and 79"
~s are metallic shields 81' and 81' ' . As can be seen,
the shields do not extend across the front of the
housings 79' and 79" (that is, the parts of the
housings facing each other) but do extend around the
antennas to prevent a spurious dispersion of the RF
2o signals from the antennas 83' and 83 " in any
direction from one car to another car, and do not
allow the antennas to pick up any spurious
electromagnetic signals except those originating
from the other end car.
z5 The shields also include conductor
elements 85' and 85" to prevent backward
transmission or reception from the rear. Connector
cables 87' and 87' ' connect the antennas to the RLT
units of their respective cars.
30 The couplers are mounted on the exterior
of the car and, when the cars are coupled to each
other, are physically close to each other. They are
sealed against water and humidity and protected
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from flying stones both by the housing 79' and 79 "
and the shields 81' and 81 " .
Although the housings illustrated in Fig.
6 would be necessary for a particular type of
antenna, if the antennas are small enough, then
they would not have to be protected by such a
housing. In fact, in some situations, it might be
possible to mount the housings inside of the cars.
Accordingly, the housing is for a particular
situation.
The present inventive arrangement is not
subject to the physical disadvantages of the pin
and spring arrangements, and they are not effected
by the fact that they have to operate in a dirty
environment.
Although the inventive system as above
described has advantages and features making it
preferable to prior art arrangements, problems can
arise if the antennae are not maintained in fixed
relationship to each other. In order to prevent
such problems, the following improvement is
provided.
As is well known in the art, cars of
multi-car vehicles are coupled to each other so
that they will maintain a fixed relationship to
each other. Thus, referring to Figures 7 and 8,
two adjacent cars will be coupled to each other by
a coupling arrangement which includes, on one end
of one of the cars, a coupling arm, 101' which
extends towards a second car, and on an adjacent
end of a second car, a coupling arm 101" extending
toward the first car. Figure 7 shows the coupling
arms in an uncoupled condition. Figure 8 shows the
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coupling arms in a coupled condition. It is
understood that Figures 7 and 8 are just an
illustration and that the invention is not limited
thereto.
s The coupling arms as illustrated above
are, of course, schematic and can actually be quite
different in physical shape.
With such coupling means, the trains are
maintained in fixed arrangement with each other,
~o including, in fixed alignment with each other.
Thus, as a train turns a bend, the cars will not be
misaligned with each other but will instead continue
in a straight line.
In accordance with the improvement to the
15 invention, the antenna housings are mounted on the
coupling arms as illustrated in Figures 9 and 10.
As seen in Figures 9 and 10, the housings 107',
107" are connected to the hook members 103' , 103"
respectively. The antennas are connected by coaxial
zo cables 87', 87 " respectively, and when the coupling
means are in a coupled condition, as shown in Figure
10, there is free air space 111 between the antenna
housings.
As seen in Figure 7, the coupling arms
z5 101' and 101" will include switch means,
illustrated schematically at 105' and 105 "
respectively, which will indicate when a positive
coupling has been effected. The switches would be
used to turn on the communication systems of the
3o adjacent cars when a positive coupling has been
effected, and to turn them off when the cars are
decoupled.
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As the antenna housings are mounted on the
coupling means, the antenna housings will remain in
fixed relationship to each other when the cars are
coupled to each other as shown in Figure 10. The
s free space 111 between the antenna housings can be
adjusted for any convenient distance.
The alignment of the antenna houses will
remain in line at all times because the coupling
arms will remain in fixed position with each other.
~o Accordingly, the problem of misalignment has been
overcome with the inventive improvement. In
addition, because the communication system will be
turned off when the cars are uncoupled, any minor
spurious signals which could be emitted at that time
15 W1.11 be prevented.
Turning now to Figure 11, as can be seen,
the housing 79 for the antenna comprises a fourt-
sided box having a front window 111. The shielding
107 comprises a metallic member which is also in the
zo shape of a four-sided box. A protective means 111
is disposed at the front end of the shielding and
fits into the window 109 of the housing 107. This
provides mechanical protection against flying stones
or the like. Preferably, a water seal, such as a
z5 rubber gasket, would be disposed around the
peripheral end of the protective member 111 which
can comprise a fiberglass window.
The shields also include the metallic back
plate cover 85 which may be screwed onto the flange
30 113 of the housing 107.
The antenna 83 is mounted in the housing.
Although not illustrated, it will of course be
obvious that each antenna will be mounted in fixed
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position in its respective housing, so that when the
shielding of two adjacent cars are maintained in
fixed relationship to each other, the antennae will
also be maintained in fixed relationship to each
s other.
The electronic signals will be brought to
the antenna by coaxial cable 87.
As seen in Figure 12, when the cars are
uncoupled, the emission of the antennas 83' and 83 "
~o will have a certain range, which range is
substantially eliminated when the cars are in
coupled position as shown in Figure 13. As seen in
Figure 13, with the cars in the coupled position, it
is virtually impossible for the antennas 83' and
15 83 " to communicate with anything except each other.
Accordingly, the trains of the multi-car vehicle
will not be receiving spurious signals from other
sources, nor will the signals from the cars of the
present multi-car vehicle be emitting spurious
20 signals to other trains. Therefore it becomes
possible to use the same frequency on several
different trains. In addition, it becomes possible
to have a wide band signal without having to be
concerned about interfering with any other systems.
2s Because of the possibility of using a wide band
signal, a great deal of data can be transmitted from
one car to another and back.
Although a particular embodiment has been
described, this was for the purpose of illustrating,
3o but not limiting, the invention. Various
modifications, which will come readily to the mind
of one skilled in the art, are within the
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scope of the invention as defined in the appended
claims.
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