Note: Descriptions are shown in the official language in which they were submitted.
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RAILROAD TRAFRC WARNING SYS JEM
APPARATUS AND METHOD THEREFOR
TECHNICAL FIELD
The present invention relates generally to traffic warning systems and
more particularly to a railroad crosslng traffic warning system for alerting
motorists approaching a railroad grade crossing to the presence of an
oncoming railroad train.
Additionally, t he present invention relates generally to railroad warning
systems and specifically to a warning system for railroad maintenance-of-way
personnel working on or in the vicinity of active railroad tracks.
BACKGROUND OF THE INVENTION
There are over 223,0()0 railroad grade clossi,lgs in the United States
alone. Most of these crossi-lgs, es~eci-~lly those in rural areas, have only
warning signs to alert motorists to the danger posed by an approaching train.
Typical of railtuad grade crossi~y warning signs is the familiar X-shaped
'tRAlLROAD CROSSING" sign or"crossbuck." Warning si~ns, however, only
alert motorists to the presence of a railroad crossing and do not alert them to
the presence of an oncoming train. Often, a motorist may fail to see an
approaching train because he was distracted or t)ec~-'se his view of the train
was obstructed by environmental conditions or darkness. Consequently,
collisions between trains and automobiles at railroad crossings account for
thousands of acci~ents each year, many of which result in extensive property
~ damage and serious injury or death to motorists.
Known to the art are active railroad crossing warning systems utilizing
the railroad tracks themselves to detect an approaching train and activate
warning signal apparatus such as flashing lights and bells. These systems
warn ",otorisls when a train is detected at a predetermined distance from the
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crossing. However, present active warning systems do no take into account
the speed of the train and thus make no allowance for the time it will take the
train to reach the crossing. For example, a fast moving train may reach the
crossing in only a few seconds after it is detected, while a slow moving train
may fail to reach the c~ssing until sever~l minutes have pa~sed. Motorists
may become impatient waiting for slow moving trains to reach the crossing.
Consequently, some motorists may begin to ignore the warnings and attempt
to cross the tracks possibly causing an accident should a fast moving train be
encountered. Further, installation of current active warning systems may
require the insulation and resetting of great lengths of track. Additionally, these
systems may require the inst~l~ation of expensive high voltage transformers,
relays, and b~llerias for backup systems. Unfortunately, many rural crossings
are not conducive to the installation of active warning systems that requires ACelectrical power and extensive grade preparation. Consequently, these
crossings usually remain inadequately protected. High speed rail corridors
being proposed across the United States will only exacerbate this problem.
These corridors will require improved crossing warning systems to properly
secure the safety of both passengers and motorists.
Additionally, railroad crews working on or in the vicinity of active railroad
tracks are suscel,liLlle to ~ccidents as a result of not being suf~iciently warned
of an oncol,.i"g train entering the work area. The rail work is typically
pel rul 1 l ,ecl in isolated regions away from crossi~ 1~ areas, and therefore the work
crews do not have the benefit of standard crossing signals to warn them of
approaching trains. Thus, there lies a need for a reliable warning system for
warning maintel)ance-of-way crews which allows the crew to concenl~ate on the
work at hand while providing adequate warning of oncor"i.,g train hazards in
order to clear the tracks of tools, equipment and workers to avoid an accident.
The r~:!,oad crew warning system is further required to be portable and easily
set up by the crew in a relatively short period of time. Additionally, the warning
system should be of sufficient operational e~ficiei,cy to activate the warning
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system only upon the detection of a train to thereby mitigate the natural human
tendency to ignore the warning system after false activations.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to provide an improved
railroad crossing waming system for warning a motorist, pedestrian, bystander,
or the like to the presence o~ an approaching railroad train.
It is another object of the present invention to provide an improved
railroad crossing warning system suitable for operation at remote or rural
railroad grade crossings where a source of AC electrical power may not be
1 0 available.
It is a further ob~ect of the invention to provide an improved railroad
crossing warning system that may be easily installed at existing railroad
crossings without removing, replacing or interfering with the existing railroad
track.
It is yet another object of the invention to provide an railroad crossing
warning system having improved warning signal devices, signs and the like.
It is still another object of the present invention to provide an improved
railroad crossing system wherein the warning signal device is activated at a
predetermined interval of time before the train reaches the railroad crossing.
Another object of the present invention is to provide an improved railroad
crossing warning system having means to detect a stopped train at a crossing
so that activation of the warnin~ signal device or sign may be continued.
It is an object of the present invention to provide a means of collecting
and recording data regarding the operation of the warning system and
information ~bout the trains passing the crossing.
A further object of the present invention is to provide an improved
r~il,oad crossing system comprising a primary system and redundant backup
and fail-sa~e systems for added reliability and safety.
It is yet a further object of the present invention to provide an improved
railroad crossing warning system wherein the components are reliable, easily
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maintained, and protected against vandalism.
SUMMARY OF THE INVENTION
In accordance with these objects, the present invention provides a
railroad crossing traffic warning system for alerting a motorist approaching a
railroad crossing to the presence of an oncoming train. As used herein,
"motorist" Is intended to refer not only to operators and passengers of motor
vehicles, but also to pedestrians, cyclists, bystander, and the like. Sensors
buried adjacent to the train rails at predetermined distances from the railroad
crossing detect the presence of an approaching train. A control unit,
processing signals received from these sensors, determines the speed at which
the train is traveiing and the time required for the train to reach the crossing.
At a predeter,l,i,led time before the train reaches the crossing, the control unit
activates warning apparatus to alert motorists to the presence of the oncoming
train. The motorists may then take cautionary or evasive action.
The system also includes improved warning apparatus. The warning
apparatus comprises an X-shaped railroad crossing warning sign or
"crossbuck" having reflectors, reflecting paint, or the like for reflecting the
headlights of an automobile, a plurality of strobe lights to enhance the
motorist's awareness of the approaching train and a train direction indicator.
The crossbuck may include a pluralit,v of light emitting diodes ("LED") or the like
mounted on the across the center of the crossbuck in an X-shape. The train
direction indicator comprises a plurality of lamps placed ~rlj~cent to each other
in a line. These lamps are lighted sequentially to i~ldicate the direction in which
the oncoming train is traveling. Further, the warning apparatus may further
2~ include an audible warning means such as a siren horn or bell to provide an
audible output signal. Crossing guard apparatus may also be provided to
detect the presence of a stopped train in the railroad crossing so that activation
of the warning apparatus may be continued until the train moves from the
crossing. The crossing guard includes an infrared trans",iL~er and a receiver
mounted diagonally across the crossing. The transmitter transmits an infrared
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beam of light across the crossing to tne receiver. If a train is present in the
crossing the beam is interrupted and a signal is sent to the control unit.
The system may be powered by a rechargeable battery. This battery
may be recharged by a solar panel array allowing the system to be deployed
at clossings located in rural areas where a source of AC electricat power is notreadily available.
Additionally, the present invention provides a system for warning railroad
crews working on or in the vicinity of railroad tracks of oncGr"i"s~ trains. A train
detector probe is piaced near the train rails at a predetermined distance from
the works crew in either direction along the tracks. Electronic detection,
processing and control circuitry receive and process the detector probe signal
which is transmitted via a radio frequency communications link to a receiver in
the located vicinity of the crew. The receiver processPs the received train
detection signal and thereupon activates a warning system which provides
visual and audio warning to the crew o~ the presence of an incoming train.
BRIEF DES~KIr ~ J OF THE DRAWINGS
The numerous objects and adv~nl~lges of the present invention may be
better understood by those skilled in the art by refer~"ce to the accompanying
figures in which:
FIG. 1 is a pictorial view of a typical single track grade crossi"g
employing a railroad c~ossi~g warning system according to an exemplary
embodiment of the present invention;
FIG. 2 is a top plan view of an area surrounding a typical grade crossing,
as illustrated in flG. 1, depicting the placement of the warning system's
components along the track;
FIG. 3A is an elevational view of the embodiment of the invention shown
in FIGS. 1 and 2 illu~lldli~y the operation tnereof before an oncoming railroad
train reaches the crossing;
FIG. 3B is an elevational view of the embodiment of the invention shown
in FIGS. 1 and 2 illustrating the operation thereof after passage of the train;
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FIG. 4 is a perspective view of the basic components of the warning
system accordir~g to an exemplary embodiment of the present invention;
FIG. 5 is a front elevational view depicting a warning signal device
according to an exemplary embodiment of the invention;
FIG. 6 is a schematic diagram of the warning system illustrating the
operational features thereof;
FIG. 7 is a front elevational view depicting a warning signal device
according to an exemplary embodiment of the present invention employing a
crossing gate;
FIG. 8 is a front elevational view of a warning signal device mounted on
a cantilever assembly according to alternative embodiment of the present
invention;
FIG. 9 illustrates the use of the present invention in a railroad crossing
having multiple railroad tracks, such as in an industrial area ~r near a freight yard;
FIG. 10 is a top plan view of a typical application of the present
invention;
FIG. 11 is a perspective view of the basic components of a preferred
embodiment of the present invention;
F~G. 12 is an elevation view of the present invention showing typical
operation thereof;
FIG. 13 is an elevation view of the present invention further showing
typical activation thereof;
FIG. 14 is an elevation view of the present invention further showing
25typical deactivation thereof; and
FIG. 1~ is a schematic diagram of the present invention showing the
operational features thereof.
DET~ILED DES~ ., ION OF AN EXEMPLARY EMBODIMENT
A. Dtsc,~ loN oF FlGS~ 1 To ~
FIG. 1 depicts a t,vpical single track grade crossing employing a railroad
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crossing warning systern 10 according to an exemplary embodiment of the
present invention. The warning system 10 preferably comprises several
components which operate separately of the railroad's track, equipment, or
~ systems to provide means of actively warning a motorist, pedestrian, or the like
("motorist") approaching the crossing of the presence of an oncoming train.
Warning signal devices 12 may be erected adjacent to a road or highway 14
on either side of the crossing 16. These devices 12 are preferably positioned
facing oncoming traffic so as to be clearly visible to a motorist approaching the
crossing on the road or highway 14. Preferably, each device 12 comprises a
standard X-shaped railroad crossing warning sign or "crossbuck~l 18 having
reflectors, reflective paint, or the like for reflecting the lights of an approaching
automobile. The crossbuck 18 may be mounted on a post, pole, mast or like
supporting means 20 which is anchored in the ground next to the crossing.
Visi~ility of the crossbuck 18 may be further enhanced by a plurality of light
emitting diodes ("L~D"s) 22 mounted across the center of the crossbuck 18
such that they form an X-shape. These LEDs Z2 may be animated, i e. made
to flash so as to attract the motorists attention. A strobe iiyl,Ut,din direction
advisory sign 24 may be mounted above the crossbuck 18 on the mast 20.
This sign 24 may include a plurality of strobe lights 26 which function to alertinattentive rl~olo~ to the presence of the approaching train. A train direction
indicator 28 may also be provided comprising a plurality of lamps 30 placed
adjacent to each other in a sL,~i~l,l line. Upon detection of the presence of anapproaching train by the system, these lamps 30 may be lighted sequentially
in a repetitious manner to indicate the direction in which the oncoming train istraveling. Embodi~nenl~ of the warning signal device 12 may further include an
audible warning means such as a siren horn or bell (not shown) to provide an
audible warning to the motorist.
A control unit 32 may activate the warning signal devices 12 when an
approaching train is detected. The control unit 32 may be housed in a
w~ter,uroof underground vault 34 located near the railroad grade crossing. The
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vault 34 may include a steel access door 36 secured by a locking device 38
such as a hasp to receive a padlock or the like. The buried vault 3~ may
provide physical security for the control unit 32 protect the control unit's
electronics from the extreme temperature changes that could be experienced
were the control ùnit 32 to be loc~ted in an above ground enclosure which had
no heating and air conditioning. Preferably, the vault 34 may be grounded to
provide ele~ u~l~lic shielding to the electronic components contained therein.
The system 10 is preferably powered by rechargeab~e batteries (not
shown). The batteries may be housed within the vault 34 with the control unit
32. Recharging of the batteries may be accomplished by means of a solar
panel array 40 mounted on a pole, or post 42 near the crossing. Use of solar
panels 40 to recharge the system batteries is desirable when the system 10 is
to be deployed at crossings located in rural areas where a source of electrical
power is not readily available. The crossbuck 12, strobe li~hl/llain direction
advisory sign 24, and solar panels 40 may have transparent coverings
comprising 1/2 inch thick LEXAN~ or the like to prevent darnage due to the
environment or vandalism.
As illustrated in FIG. 2, the system 10 pl~r~rably includes a series of
remote sensors probes 50 which are capable of detecting the presence of a
train 52. The sensor probes 50 may be positioned ~ cent to the train rails 54
at predetermined distances from the railroad crossing 56. Preferably, each
sensor 50 comprises a may,l~tol"el~r enclosed in a sealed housing assembly
which may be buried in the right-of-way to the railroad tracks to prevent
vandalism. The magnetometers produce a signal in response to local
disturbances of an electromagnetic field, such as the disturbance of the
magnetic field of the earth c~ Ised by the passing of a large melallic object such
as a train. The sensor probes 50 may be interconnected with electronic
circuitry in the control unit 32 which produces a binary (on or of~ signal when
the presence of a train is detected. Shielded, rodent proof, multi-conductor
s~ t cables 58, which may also be buried in the right-of way, may
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interconnect the remote sensor probes 50 to the control unit 32. These cables
58 may be further protected by electronic circuitry within the control unit 32
which monitor the integrity olF a closed loop circuit in the buried cable. In the
~ event that a cable 58 is cut or damaged, the control unit 32 will sense a break
in the closed loop circuit and place the system in a fail safe mode of operationwhich automa~ically activates the warning signal devices 12.
FIGS. 3A and 3B illustrate operation of the system 10 to ~letect an
approaching train 52 and activate warning signal devices 12 located at the
crossing 56. The railroad crossing warning system 10 pr~fer~bly comprises a
primary train detection subsystem and a secondary or backup train detection
sul~system. The primary train detection subsystem may include two speed
traps ¢O each comprising two sensor probes 50a & 50b positioned on either
side of the grade crossing 56 along the track 62 at a predetermined distance
from each other. The sensor probes 50a & 50b are preferably located at a
sufficient distance from the grade crossing 56 to permit the system ~0 to
activate the warning signal devices 12 at a predetermined interval of time
before the arrival of the train 52 regardiess of the train's speed. The sensor
probes 50a & 50b may be buried in the earth in the right-of-way ~ cent to the
track 62 to prevent damage or vandalism. As a train 52 approaches the
crossing 56, it passes a first primary sensor probe 50a positioned at a first
predetermined distance from the crossing 56 and is detected. The first primary
sensor probe 50a provides a train dele.iliol1 signal to the control unit 32 which
is preferably located in the underground vault near the crossing 56. As the
train 52 continues toward the crossing 56, it reaches a second primary sensor
probe 50b positioned at a second predetermined distance from the CluSSi"g 56
such that its distance from the first primary sensor probe 50a is known. The
second primary sensor probe 50b also detects the presence of the train 52 and
sends a second train detection signal to the control unit 32. Electronic circuit~,
preferably including a microprocessor, in the control unit 32 measures the time
interval between receipt of the first train detection signal and receipt of the
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second train detection signal and using the known distance between the first
and second primary sensor probes 50a & 50b c~lcl ~'at~s the speed of the train
52 and the time it will take the train 52 to reach the crossing 56.
A secondary or backup subsystem may also be provided should the
S primary system fail to properly detect the approaching train. Like the primary
subsystem, the backup subsystem may include magnetometer sensor probes
50c buried in the earth in the right-of-way on either side of the grade crossing56. Each backup sensor probe 5~c is preferably positioned at a predetel"lined
distance from the crossing 56 along the track 62. The backup sensor probes
50c, however, are placed between the second primary subsystem sensor probe
50b and the grade crossing 56 at a sufficient distance from the crossing to
permit activation of the warning signal devices 12 before the train 52 reaches
the crossing. During normal operation, the primary subsystem, upon proper
detection of a train 52 by both the first and second primary sensor probes 50a
& 50b, disables operation of the backup system. If, however, the primary
subsystem malfunctions or the train 52 is not detected by both of the primary
sensor probes 50a & 50b, the backup subsystem provides means of activating
the warning signal devices 12 before the train 52 reaches the c~ussi, ,9 56. Forexample, the approaching train 52 is detected by the first primary sensor probe
50a. However, due to malfunction, the second primary sensor probe 50b fails
to detect the train 52. The primary subsystem cannot determine the speed of
the approaching train 52 in order to determine the appropriate time in which to
activate the warning signal devices 12. Electronic circuitry, preferably including
a microprocessor, within the control unit 32 does not disable the backup
subsystem. As the train 52 continues toward the crossing ~6, it reaches the
first of the backup sensor probes 50c and is detected. The backup sensor
probe 50c provides a signal to the control unit 3~ which may immediateiy
activate the warning signal devices 12.
A crossing guard subsystem may be provided comprising apparatus
capable of detecting the presence of a train 52 either moving or stopped across
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the grade crossing 56. The crossing ~uard subsystem preferably allows the
warning system to continue activation of the warning signal devices 12 until thetrain ~2 clears the crossing. The crossing guard subsystem is preferably
enabled when either the primary or backup subsystems detect the presence of
s a train 62 approaching the crossing 56. An infrared ll~nsll,iKer 64 and receiver
66 may be mounted on posts 68 located near the .;, ossi"y 56 on either side of
the track 62 P~rar~bly, these posts 68 are positioned so that the transmitter
64 may transmit an infrared beam of light diagonally across the crossing 56 to
the receiver 66. If a train 52 is present in the crossing 66 the infrared beam is
interrupted and does not reach the receiver 66. The receiver 66 then may
provide a signal to the control unit 32 indicating the presence of a train 52 in the
orossing ~6. After the train S2 has passed the cr~ss;"g, the receiver 66 may
provide a signal to the control unit 32 indicating that the end of the train 52 has
cleared the crossing 56. The control unit 32 may then deactivate the warning
signal devices 12 immediately or after a predetermined interval of time, for
example 10 seconds. When no train has been detected by the warning
system's primary or backup subsystems, the crossing guard subsystem is
preferably disabled by the control unit 32 to avoid false activation of the
warning signal devices ~2 by an automobile or truck passing through the
crossing.
As illustrated in FIG. 4, the warning system 10 may include several
standard components which may be easily assembled together when deployed
at a r~m~L~ site such as a grade crossing located in a rural area. The control
unit 32 may be mounted in an above-ground enclosure 70. This enclosure 70
may be made of steel and have a locking mechanism 78 to prevent vandalism.
The enclosure 70 may be mounted to a mast or like support 42 which may also
provide means for supporting the solar panel array 40. Cables ~8 may be
provided to interconnect the warning signal device 12, sensor probes 50, and
control unit 32. These cables 58 may be buried in the earth adjacent to the
tracks during i"slallalion of the warning system 10. Conduits 72, preferably
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made of steel or the like, may be provided to protect cable not buried.
FIG. 5 depicts a railroad crossing warning signal device 12 according to
an exemplary embodiment of the present invention. The warning signal device
12 preferably comprises a standard X-shaped railroad crossing warning sign
or "crossbuck" 18 mounted on a post or mast 20. The surface of the cross-
buck 18 preferably includes a plurality of reflectors, reflecting paint or the like
for reflecting the lights of an automobile. A plurality of high intensity light
emitting diodes ("LED") 22 or the like may be mounted across the center of the
crossbuck 18 in an X-shape. These LEDs 22 may be animated, i.e. made to
repeatedly flash on and off to attract the attention of motorists and enhance
visibility of the sign at night or in poor weather conditions. Further, a shroud74 may be mounted on the mast 20 behind the crossbuck 18 to improve the
contrast ~etween the crossbuck 18 and its background. Preferably, this shroud
74 is black. A strobe light/train cli,~;lion advisory sign 24 may be mounted
above the crossbuck 18 on the mast 20. Like the crossbuck 18 this sign 24
may also have a black shroud 76 to improve the co~ sl between it and its
background. The upper half of the sign 24 may comprise an array of strobe
lights 26 which when activated function to alert the motorist of an approaching
train. Preferably the array comprises four strobe lights which may have an
intensity of approximately 4.5 million candlepower each. The strobe lights 26
are preferably red in color and may strobe or flash at a rate of approxirnately
440 flashes per min~te to indicate to the motorist that he must stop. The lower
half of the strobe lighVtrain direction advisory sign 24 may comprise a train
direction i,)dicdlor 28 which provides a means of indicating to the motorist thedirection the approaching train is traveling. The train dire.;liol) indicator 28 may
comprise a plurality of amber colored lamps 30 placed adjacent to each other
so that they form a straight line. Upon detection of the presence of an
approaching train by the system, these lamps 30 may be lighted sequentially
to i"dicala the direction in which the train is traveling. For example, if a train is
approaching the crossing from the left, the left-most lamp 30a is lighted flrst,
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then extinguished. Immediately thereafter, the next lamp in line 30b is lighted
and extinguished. then the next 30c, and so on in quick successiol1 until the
right-most lamp 30d is lighted then extin~uished so that to a motorist viewing
the sign 24, a single light appears to move from left to right. This sequence isS then repeated until the train clears the crossing and the warning signal device
12 is deactivated. If a train approaches the crossing from the right, the
sequence is reversed so that it would appear to a motorist viewing the sign 24
that a single light moves from right to left. Embodiments of the warning signal
device 12 may further include an ~ hle warning means such as a siren horn
or bell to provide an audibie output si~nal (not shown).
FIG. 6 is a block diagram illustrating the interconnection of the various
subsystems and components of the warning system. A sensor subsystem 80
may comprise a primary sensor probe array 82 and a backup sensor probe
array 84 each including several magnetometer sensor probes and
corresponding electronic circuitry to determine when a probe has detected the
presence of a train. The sensor probes of the primary sensor probe array 82
are preferably arranged to form speed traps on either side of the grade
crossing. Each speed trap may comprise two sensor probes placed at a
predetermined distance from each other. The backup sensor probe array 84
may compri~e two backup sensor probes placed on either side of the crossi"g
between the crossing intersection and the innermost primary sensor probe.
The sensor probes are preferably sealed assemblies which may be buried in
earth for their useful life. Each sensor probe may be interconnected with
electronic monitoring circuitry which produces a binary (on or of~ signal when
the presence of a train is detected by that probe. The primary sensor probe
array 82 is monitored by electronic circuitry of the primary control subsystem
86 while the backup sensor probe array 84 is monitored by electronic circuitry
of the backup control subsysltem 88~ Both the primary and backup sensor
probe array monitoring circuitry is preferably located in the control unit whichmay be housed an envir~nnlenl~lly sealed equipment enclosure 70 (FIG. 4) or
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vault 34 (FIG. 1). The sensor subsystem 80 may comprise eight Cartel CT-6
magnet~l,eter probe assemblies 50 (FIG 4) which terminate into five each CT-
2N circuit board subassemblies ~not shown). The CT-2B control board may be
modified to include the addition of a voltage spike protection zener diode
s across its probe input connectors (not shown). This modification may
substantially reduce the vulnerability of the assembly to damage should
lightning strike the immediate vicinity of a sensor probe. The CT-6 probe
construction features a sheath containing an epoxy enc~rsulated coil of wire
terminated to a shielded cable.
l O Interconnecting cable 58 (FIG. 4) may be provided between the sensor
probes and the control unit. This cable may be a foam/skin insulated filled
cable meeting REA Specification PE-89, such as CASPI~ FSF manufactured
by Essex Groups, Inc. of Decatur, Illinois. The interconnecting cable may be
buried in the earth and preferably features sheathing to provide protection
1~ against water penetration, and mechanical or rodent damage. The cable may also be shielded to reduce susceptibility to natural or manmade
electromagnetic interference. Preferably, the cable is capable of supporting
sensor probes located at distances of 2 or more miles from the associated
control unit. I lowever, the present invention would seldom require cable
lengths longer than a half mile. (A speed trap located 1/2 mile from a grade
crossing would allow 25 seconds of warning time for a train traveling at 72
miles per hcur.) A cable monitoring or cable guard subsystem 100 (FIG. 6~
may monitor the integrity of a closed loop circuit in the buried cable. In the
event that the cable is cut or damaged, the cable guard subsystem 100
preferably forces the warning system 10 into a fail safe condition 90 mode of
operation resulting in illumination of the warning signal device's displays 92,
which include the crossbuck LEDs 22 (FIG. 5), strobe lights 26 (FIG. 5), and
train cli(~-;lion indicator 28 (FIG. 5) and audible warning means.
The control unit preferably com,urises four addi~iol)al suhsystems: (1 ) the
primary control subsystem 86, (2) the backup control subsystem 88, (3) the
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data recording or data logger subsystem 94, and (4) the warning signal device
control subsystem 96. The primary control subsystem 86 may include the
speed trap sensor probe monitoring ~ir~uits and a dedicated microprocessor
- assembly. This subsystem monitors the speed trap sensor probes and uponS detection of an approaching train, determines parameters such as the train's
speed, length, and the like in order to initiate activation of the warning signal
device displays 92 located at the grade crossing. ~ r~bly, the warning
signal device displays 92 are activated at a predetermined time interval before
the train reaches the crossing, regardless of the train speed. The primary
control subsystem 86 may also initiate deactivation of the warning signal devicedisplays 92 when the sensor probe arrays 82 & 84 andlor crossil,~ guard
subsystem 98 sense that the end of the train has passed the grade crossing.
The primary control subsystem 86 may then reset the system in preparation for
another train.
The backup control subsystem 88 pre~er~bly comprises a micro
controller assembly which m~nitors the backup sensor probe array 84. If not
disabled by the primary control subsystem 86, the backup control subsystem
88 may initiate activation of the waming signal device displays 92 whenever
one or more of the backup sensor probes detects a train. Preferably, this
subsystem is automatically operational in the event of a failure of the primary
control subsystem 86.
The data recording or data logger subsystem 94 may comprise a micro
controller S uh~ssembly including a micropr~cessor, date/time ciock, and batteryprotected random access memory This subsystem may monitor the primary
control subsystem 86 and record various parameters includlng the speed and
length of each passing train as well as the function of the system during each
train passing. In addition, the data logger subsystem 94 may periodically
perform diagnostic tests of the backup control subsystem 88 and backup
sensor probe array 84. If the backup subsystem 88 is found faulty, the data
logger subsystem g4 may place the warning system 10 into the fail-sa~e
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16
condition 90 mode of operation. The microprocessor assembly (not shown)
may include a lithium battery or the like to maintain the date/time clock and tomaintain information stored in volatile memory.
The primary control subsystem and data logger micro controller
assemblies may employ 8-bit microprocessors or the like. For example, the
primary control subsystem 86 may utilize an RTC 31/52 computer board
assembly, manufactured by Micromint Inc. of Vernon, Connecticut. Similarly,
the data logger subsystem 94 may utilize a NanoLink micro controller board
assembly, manufactured by Dison Technologies of Santa Barbara, California.
Software may be employed to control the microprocessor's operation and to set
operation variables. Thus, the warning system may be configured to meet the
operational requirements of an individual site operational without modification
to the system's hardware or physical installation.
The crossing guard subsystem 98 including the crossing guard
transmitter 64 (FIGS. 3A, 3B) and receiver 66 ~FIGS. 3A, 3B) may provide a
signal to the control unit indicating the presence of a train in the crossing. The
control unit may use this signal to continue activation of the warning signal
displays 92 when a train has stopped in the crossing and thus would not
otherwise be detected by the backup sensor probe array 84. The control unit
may utilize this signal to verify when a train has cleared the crossing.
The warning signal device control subsystem 96 may comprise relay
logic circuits switched on and off by the control unit's subsystems to provide fail
safe operation of the warning signal device displays 92. All relays in the
subsystem are preferably maintained in the actuated (contacts open) state at
2~ all times. All relays are p~t:rer~bly industrial quality electro mechanical or solid
state relays.
A power supply subsystem 102 may be provided comprising one or
more lecharyeable ball~ries and ~ecl,aryi"g circuitry. This rechal-yii,g circuitry
may operate using conventional 120/240 VAC electrical power from a public
utility or other external source. In more remote areas, a solar panel array may
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provide electrical power to recharge the batteries so that the system may be
operated independently from outside power sources. The power supply's
batteries and recharging circuitry may be mounted in the same waterproof
- underground equipment vault which houses the control unit.
The railroad crossing warning system 10 may provide redundan~ means
to activate the warning device dispiays 92 loc~tecl at the railroad grade
crossing. The system pl~reral)ly comprises two basic layers of protection: (1)
the control subsystems and (2) the fail safe condition. The control subsystems
may include two separate subsystems having electronic circuitry used to control
the warning signal device displays g2: the primary control subsystem 86 and
its associated primary sensor probe array 82, and the backup control
subsystem 88 and its associated backup sensor probe array 84. The primary
control subsystem 86 monitors the primary sensor pro~e array's speed traps
and activates the waming signal device displays 92 whenever a sensed event
(i.e. the detection of a train) is deemed a normal train passing event (i.e. thetrain p~sses through a speed trap within a defined time window). If the sensed
event does not fall within "normal" train passing event criteria, control of system
preferably reverts to the backup control subsystem 88. If the sensed event fallswithin "normal" train passing event criterla, the primary control subsystem 86
may disable the backup control subsystem 8~ and take control of the system.
During the time that the backup control subsystem 88 is disabled, the primary
control subsystem 86 may analyze the backup control subsystem 88 for proper
operation. If the backup control subsystem 88 is found faulty, the primary
control subsystem 86 may place the entire warning system into the fail sa~e
mode of o~ lion. Conversely, the purpose of the backup control subsystem
88 is to activate the warning signal device displays 92 in the event that the
primary control subsystem 86 is unable to do so. Thus, redundancy is
achieved by virtue of the backup subsystem's capability to protect a grade
crossing should the pri~,)a~y control subsystem fail. Additionally, the backup
control subsystem 88 may offer protection whenever unusual events (i.e.
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events which do not fall within "normal" train passing evenl: criteria) are in
process. Examples of unusual events include:
1. A short train passes slowly through a primary sensor probe array 82
speed trap and stops. When the train again moves, it may be detected
S by the backup sensor array 84 allowing the backup control subsystem
88 to activate the warning signal device displays 92.
2. A train comes to a stop while spanning the crossing. The crossing
guard subsystem 98 may continue activation of the warning signal
device displays 92. When the train again moves, the backup control
subsystem 88 may continue activation of the warning signal device
displays 92 since the primary sensor probe array 82 would not have
detected the train.
3. A high railer passes through a primary sensor array speed trap in the
reverse direction (i.e. it is detected by the innermost sensor probe
before being detected by the outermost sensor pro5~e). When the
outermost sensor probe detects the high railer, the primary control
subsystem's micro controller is alerted that an event may be in p~ oy, ~ss.
The micro controller finds that the innermost sensor probe has already
detected the train. Since the micro controller may require about .32
seconds to become fully active after being alerted that the outermost
sensor probe is tripped, it determines that something has passed
through the speed trap in about 0.32 seconds (in excçss of 200 mph),
rejects the event as being outside normal train passing event criteria,
and does not disarm the backup control subsystem 8~.
The second level of redundancy is provided by the fail safe condition 90.
The fail safe condition 90 is the condition where a vital relay is no longer
el,eryi~ed. Upon loss of power to the vital relay the relay contacts may close
thus providing power to the warning signal device displays 92. The warning
signal device displays 92 may remain illun~il laled until maintenance is
peRormed on the system and the control unit circuitry is manually reset. The
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19
~ail sa~e condition mode of operation is the final level of redundancy regardingprotection of the grade crossing. The fail-safe condition may be achieved by
maintaining a display relay in a contacts-open position whenever the warning
- signal device displays 92 are not to be illuminated. In the event of a failure of
S the control unit circuitry the vital relay would be de-energized and would revert
to it's normally ciosed state. Closure of the relay connects the warning signal
device displays 92 directly to battery power and the dispiays remain illuminateduntil the fault is repaired and the system is reset by maintenance personnel.
FIGS. 7 and 8 depict alternative embodiments of the present invention
l 0 wherein the warning signal device may be modified for use at grade crossings
experiencing a high volume of automobile traffic. As shown in FIG. 7, the
warning signal device 12 may comprise a standard crossing gate 110 to
prevent motorists from entering the grade ~ ossi. ~ when an appro~ching train
is detected. Upon detection of an approaching train and activation of the
IS warnlng signa1 device by the system, a cantilevered arm 112 may be lowered
across the roadway at the entrance to the crossing to block automobiles from
entering the crossing. After the train has cleared the crossing, the arm 112
may be raised to allow traffic to pass through the crossing. The ~ate 110 be
mounted directly to the mast 20 of the warning signal device 12 or may itself befree standing. A plurality of lights such as LEDs 114 may be mounted along
the center of the arm 11 2. These LEDs 114 improve the motorists ability to see
the closed gate at night or in poor weather. Although a standard railroad
crossing gate 11~ is shown, the present invention anticipates the use of four
quadrant gates and the like. FIG. 8 illu~l(dtes an alternative arrangement of the
warning signs. A cantilever support structure 120 may have a cantilevered
arm, truss assembly, or the like 122 which may extend over a multilane
roadway. One or more animated crossbucks 18 may be mounted on this
structure as required to adequately warn molorisL~ in all lanes of traffic.
Likewise, multiple strobe lighVtrain directional indicator signs 24 may be
mounted on the cantilevered arm 122 of the support structure 120 to warn the
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motorists in all lanes of traffic.
FIG. 9 illustrates the use of the present invention in a crossing 128
having multiple railroad tracks such as in an industrial area or near a freight
yard. Sensor probes 50 may be placed at various positions on along of the
tracks 130 to detect the presence of oncoming trains 132. Preferably the
sensor probes 50 are buried in the right of way along the outermost train rails
134 and are capable of detecting a train moving along any of the tracks 130.
In view of the above detailed description of a pr~r~r,~d embodiment and
modifications thereof various other modificalio~s will now become apparent to
those skilied in the art. The claims below encompass the disclosed
embodiments and all reasonable modi~icdlions and variations without departing
from the spirit and scope of the invention.
B~ Description of FIGS. 10 to 15
FIG. 10 illustrates a typical application of a second embodiment of the
present invention. A maintenance-of-way crew 100 is required to work on a
length of active railroad track 120 in an area defining a construction zone 1~0.The maintenance-way-crew 100 provides necess~ry upkeep and maintenance
of the Idill uad tracks 120 which may be active meaning that the tracks 120 are
in use by trains while construction is being performed. The posslbility of an
oncoming train 160 poses a serious safety hazard to the crew 100 working on
the track 120 who must concentrate on the construction work to be performed
while constantly being alert to the possible oncoming train ~60. Often the
topography of the land and nearby flora and fauna prevent the workers 100
from becoming aware of the oncoming train hazard 160 to sufficiently move
the~oselves and their equipment to a position of safety before the arrival of the
train 160. Thus the combination of the terrain flora and fauna such as a
clustering of trees 180 and the layout of the track 120 such as bend 200 may
co,l,L i"e to block the view and sounds of an oncoming thereby increasing the
safety hazard to the mai,ll~nallce-of-way crew 100. The present invention
provides a system to detect an oncoming train 160 to provide adequate warning
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of the railroad construction crew 100 to maneuver to a position of safety in time
~ to avoid an accident.
As can be seen from FIG. 10, a remote sensor unit 220 is placed at a
predetermined distance, preferably approximately one mile, in either or both
directions along tracks 120. Each sensor unit 220 preferably includes two
sensor probes 240 which are ca,~able of ~etecting the presence of a train 160.
The sensor probes 240 are preferably responsive to local disturbances of an
electromaynetic field, such as the disturbance of the magnetic field of the earth
caused by the passing of the train 160, a large metallTc object.
~n response to the passing train 160, the sensors 240 send a detection
signal to the sensor unit 220 which contains the necessary processing
electronics to process the detection signal of the sensors probes 240. The
sensor unit 220 includss signal transmission means which is prer~r~l,ly a radio
frequency Ll dl Isr~ er with an antenna 260 to l~l,slr,it the train detection signal
to a receiver unit 280. The Feceiver unit 280 is loc~ted in the vicinity of the
construction zone 140 and l:he workers 100, and includes signal receiving
means which preferably includes an antenna 380 and a radio frequency
receiver. The receiver unit 280 includes processing electronics necessary to
receive and process train detection signals received from the sensor unit 220.
A crew warning means 400 is coupled to the receiver unit 280 to visually and
audibly alert and warn the crew 100 that an oncoming train 160 has been
detected. Upon being alerted by the crew warning means 400, the construction
crew 100 may move to a safe position until the train 160 has passed,
whereupon the crew 100 may resume working. The sensitivity of the sensor
2s probes 240 may be optimally adjusted such that only the mass of a train 160
will trigger the warning systern and that other vehicles such as a truck 420 will
not cause false alarms which degrade the confidence of the workers 1100 in the
integrity of the warning system.
FIG. 11 illustrates the main components of lthe present invention.
Sensor unit 220 preferably comprises a light weight and durable plastic,
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fiberglass or steel weatherproof housing which contains sensing, processing
and control electronics. The sensor unit 220 preferably includes a solar panel
array 440 which provides power to the electronic sensing cir~uitry contained
within the sensor unit 220 and is used primarily to maintain a charge on a
power supply battery conta;ned within the sensor unit 220. The sensor unit 220
includes receiving jacks 460 for receiving a plug 480 at the end of sensor probe240. The sensor probe plug 480 connects to a receiving jack 460 of the sensor
unit 220 via a length of probe cabling 500. The length of the pr~be cabling 500
is sufficiently long to allow the positioning of the sensor probe 240 near the
railroad track 120 while allowing for the positioning the sensor unit 220 in an
optimal position to receive ~axi~ ~um solar energy incident upon the solar panelarray 440.
The crew warning means 400 includes a portable light standard 520
which may be erected near the construction zone 140. The light standard 520
15 - preferably includes telescopic legs 560 which extend from and are hinged at a
spring resistance hinge 580 making the light standard 520 readily collapsible
and capable of being placed upon uneven terrain while remaining sturdily in
place. The light standard 520 preferably includes four legs but may
alternatively use three legs as well. Erected vertically from spring hinge 580 is
a mounting shaft 600 upon which are mounted visual warning means 620 and
audio warning means 640. The visual waming means is preferably two L.O.S.
beacons mounted on the mounting shaft such that the light emitted therefrom
sweeps horizontally in order to cover a maximum area which includes the
construction zone 140. The beacons may be Commander Strobe Beacons,
Model 5200 manufactured by Whelen Engineering Co. of Chester, Connecticut,
the beacons using a xenon flash bulb. The audio warning means 640
preferably incl~ ~des two warning siren horns capable of emiffing a high decibelwarning sound that can be heard over the noise of construction activity. The
beacons 620 and horns 640 are mounted to a mounting unit 1;60 which is in
turn mounted to the mounting shaft 600. Two safety flags 680 of bright safety
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orange color are mounted at the top end of the mounting shaft 6û0 to generally
alert others that construction activity is occurring in the vicinity. An
omindirectional antenna 380 is mounted on the shaft 520 and connected to the
receiver unit 280.
The antenna 380, beacons 620 and horns 640 are connected to the
rec~iver unit 280 via a receiver cable 700 which connects to a jack 460 with a
plug 480 at the end of the cable 700. The receiver unit 280 is generally of the
same or similar construction as the sensor unit 220 in that it is constructed o~a light weight plastic, fiberglass or steel material and is weatherproof. The
receiver unit 280 is constructed having a hinged lid 720 which is opened during
operation. A solar panel array 440 is mounted in the lid 720 of the receiver unit
280 which may receive energy when the lid 720 is in an open position. The
receiver unit 280 also includes a control panel (not shown) having basic
operational controls (e.g. on-off switch, reset switch, etc.). The receiver unitmay also include a handle 740 for ease of portability.
FIG. 12 depicts the operation of the present invention in detecting the
presence of an oncoming train. The receiver unit 220 is placed up the tracks
~20 from the construction zone 140 at a predetermined distance therefrom. In
a preferred embodiment of the present invention the receiver unit 220 is placed
approximately one mile from the construction zone 140 which provides
approximately one minute warning time to the crew 100 for average train
speeds of sixty miles per hour.
The sensor probes 240 are placed alongside the train tracks 120 parallel
thereto. Only one probe 240 is required to sense a train 160, but preferably
two probes 240 are utilized for redundancy in case of failure of one of the
probes. Further, the utilization of two probes provides both information as to
the direction and speed of the oncoming train. In an alternative embodiment
~ of the present invention, two sensor probes 240 may be utilized to detect the
direction and speed of an oncoming train 160. Further, it has been found that
the sensor probes 240 are directionally sensitive in that the probes 240 exhibit
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24
greater sensitivity at the end of the probe 240 connected to the probe cable
5~0. Preferably, the probes 240 are laid alongside the tracks 120 with the end
of the probe 240 connected to the cabling 240 pointing toward the direction
from which the oncoming train 160 will approach and the free end of the probe
240 pointing toward the construction zone 140.
A moving incoming train 160 induces current in the sensor probe 240 upon
the train passing by the probe 240. The induced signal from the train 240 is
detected by the electronic circuitry of the receiver unit 220 and transmitted to the
receiver unit 280 which is located at the construction zone 140. The sensor unit220 and the receiver unit 280 are couple via a radio frequency communications link
760. The receiver unit 280 receives the transmitted detection signal from the
sensor unit 220 and thereupon activates the crew warning means 400 which is
placed in the vicinity of the construction zone 120. The beacon and the horns are
thereby activated, visually and audibly alerting the crew 100 to the presence of the
oncoming train 160.
FIGS. 13 and 14 illustrate the operation of an embodiment of the present
invention in which two sensor units are utilized. A first sensor unit 220A and asecond sensor unit 220B each placed in either di,e~;lion down l:he tracks 120 form
the construction zone 140. As shown in FIG. 13, an incoming train 160 passing bysensor unit 220A activates the crew warning means 400 whereupon the crew 1G0
may take precautionary action.
As shown in FIG. 14, sensor unit 22B will be activated as the train 160 exits
the construction zone 140 and passes sensor unit 220B further long down the
tracks 120. When the train 16 has completely passed by sensor unit 220A, sensor
unit 220A stops transmitting the train detection signal to the receiver unit. The
sensor unit 220B will send a detection signal to the receiver unit 280 upon the
passing of the train 160. The receiving of a detection signal from down track
receiver unit 220B indicates and verifies the passing of the train whereupon thereceiver unit may initiate automatic deactivation of the crew warning means 400.
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The warning system is thereby automatically reset and ready to detect the
next incoming train. Logic processors included with the electronic circuitry of the
receiver unit are capable olF processing the presence, absence, sequence and
timing of the detection signals from sensor unites 220A and 220B, activating theS crew waming means 400 when a train 160 is incoming and deactivating the crew
warning means 400 when the train 160 has passed and then reseffing the system.
A manual reset means is also provided.
FIG. 15 illustrates schematically the electronic components of the present
invention. The sensor probes ("SENSOR") 240 connect to sensor unit 220 and are
coupled to sensor processor cards ("SP CAR~) 780. The sensor processor cards
780 interface with electronic processing means ("PROCESSOR") 800 and include
circuitry electronic circuitry to act as a buffer between the sensors probes 240 and
the processing means 800.
In a preferred embodirnent of the present invention, the sensors probes 240
comprise an inductor coil winding having a powdered iron core or other similar
paramagnetic material. The sensors probes detect varialions in the magnetic field
of the earth when a train l~sses nearby by detecting the resulting change of
permeability of the space surrounding the inductor coil. A moving train passing by
the sensor probe 240 alters the magnetic flux iines of the earth's magnetic field
through the inductor coil of the probes 240 thereby inducing a current in the
inductor coil of the sensors 240 which is detected, received and amplified by the
sensor processor cards 780. Thus, sensor probes 240 provide an ele~l, ic~l output
signal in response to local variance in the magnetic field of the earth caused by a
passing train. The sensors function similarly to musicai instrument pickups with the
~5 magnetic field of the earth acting as the perrnanent magnet and the train acting a
the vibrating strings.
The sensors probes 240 are preferably Cartel CT-6 magnetometer probes
available from Preferred Technology Group of Lancaster, Pennsylvania or similar
thereto. The sensor processor cards 780 include magnetometer control circuits
atso manufactured by Preferred Technology Group available as CT-2B circuit
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26
board subassemblies. The sensor processor cards 780 preferably include a
voltage spike protector clamp across the probe input terminals 460 to protect the
circuitry from environmental voltage spikes caused by lightnin~, for example. The
sensitivity of sensor probes 240 may be adjusted with the sensor processor cards780. The sensitivity of the sensor probes 240 is preferably optimally adjusted to
detect trains without being triggered by other types of vehicles ~e.g., cars, trucks,
etc.).
The processor means 800 connects with a detector processor and
transmitter ("DETECTOR(S) PROCESSOR & TRANSMI I I t~") 820 which includes
commullicaliGns means for communicating with the receiving unit 280 including aninternal antenna ("ANTENNA") 260. The sensor unit 220 preferably receives
operational power from a battery ("BATTERY") 840 and solar panel array
("SOLAR") 440. The battery 840 is preferably a rechargeable lead acid type
battery designed to operate in extreme environmenlal conditions. All~ lively, the
rechargeable battery 840 may comprise other various types of rechargeable
electrochemical cells such as alkaline, nickel-cadmium, nickel-metal hydride,
sealed lead-acid, zinc-air or lithium ion cells or the like, for example.
The solar panel array 440 may be utilized to provide electrical energy
converted from solar energy to charge the battery 840 and to provide a trickle
charge thereto to keep the battery 840 topped off. Additionally, the solar panelarray 440 may be utilized to provide supplemental operational power to the detector
unit 120 in case of depletion of the battery charge or battery failure, for example.
A similar battery ("BArrERY") 880 and solar panel array ("SOL~R") 44G are also
included with the receiver unit 28 for providing operational power thereto. The
battery 880 is preferably a sealed, rechargeable lead-acid type battery
manufactured by GNB Industrial Battery Company of Saint Louis, Missouri as the
"ABSOLYTF" product which is designed for solar service and railroad equipment
appli~alions. The battery 840 preferably includes a battery char~ing regulator
model ASC 12/2 available from Siemens Solar Inc. of Camarillo, California. The
solar panel 440 is a model M75 available also available form Siemens.
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W097125235 PCT~S97~001~3
Upon the detection of an oncon)ing train 160, the transmitter 820 transmits
a signal via a radio frequency comml~r~ic~lions link ("RADIO LINK"~ 760 to a
receiver ("RECEIVER PROCESSOR") 86Q col,tai"ed within the receiver unit 280.
Antennas ("ANTENNA") 260 and 820 are provided for the transmitter processor
820 and the receiver processor 860 respectively to increase the signal gain of the
radio communications link 760. The radio communications link 760 pre~erably
utilizes a band of 8 spread spectrum channels at a ~requency licensed by the
Federal Communications Commission for such type of radio fre~uency
commul~icaliolls. The radio frequency communications between the sensor unit
220 and the receiver unit 280 is preferably dual-tone multiple frequency (DTMF)
encoded, spread spectrum modulated tra-~s~ission to avoid unintended jammin~
or interference from other radio frequency sources operating in the vicinity thereby
preventing loss ~ co~ n~atisn or ~a!s~ ala~ms. The pF~~ess~fst88û, 82~, ~6G)
of the present invention are preferably implemented in RTC31/52 cornputer board
assemblies as manufactured by Micromint Inc. of Vernon, Conne~ticllt
In the event that a train encroaches the vicinity of the sensor unit 220, the
sensor probes 240 detect the presence of the train and send a detection signal
received by the sensor probe cards 780 of the receiver unit 220. The sensor probe
cards 780 send a signal to the ,urocessor 800 in response to the deltection signal
received from the sensor probes 240. The processor 800 activates the detector
transmitter 820 to commence tra"st1)isslon of a coded warning signal to the
receiver 860 of the receiver unit 280. The receiver 860 receives and decodes thetransmitted warning signal whereupon a latch relay ("LATCH RELAY~) 900 is
triggered to activate visual warning means ("WARNING LIGHT") 620. Further, a
switch and relay ("SWITCH & RELAY") 920iS triggered thereby activating audible
warning means ("HORN") 640. The visual and audible warning means (620, 640)
alert the workers of the approaching train so that they may take the necessary
evasive actions to stop work and to move themselves and any equipment to safety.After the train 160 has p~sse~l, a manual reset switch ("RESET") 94Q may
be engaged by the workers to reset the latch relay 900 and the switch and relay
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28
920, thereby turning off the visual and audible warning means (620,640) warning
and resetting tne warning system for the next train detection event. Alternatively,
the warning system may be pluy~nlmed to aulom~licall~/ rest upon passing of the
train as it is sensed passing a second sensor unit 220.
s An important feature of the present invention is a handshaking
communications protocol bet~Neen the sensor unit 220 and the receiver unit 280.
The sensor unit 220 preferably transmits an "all clear" call signal at periûdic
intervals (e.g., every five seconds) to the receiver unit. The successrul
transmission and reception of the call signal verifies the proper functioning of the
crew warning system. If the all clear call signal is not received, the receiver unit
280 immediately enters into an alarm mode. In the alarm mode, a system fail
warning light iocated on the control panel of the receiver unit or other alarm may
be activated to aler~ the workers that protection is no longer provided by the
warning system The failure to receive the call signal may be ca~sed by battery
failure, component failure, unforeseen damage to the sensor unit 220, or loss ofintegrity of the radio frequency communication link 760, for e~ample.
In an altemative embodill~e,ll of the present invention, multiple sensor units
220 may be llti~i7e~ in areas having multiple railroad tracks. Each sensor unit 220
is preferably capable of operating in conJunction with up to four sensor probes 220
simultaneously. Further, the receiver unit 280 is preferably designed to receive and
process up to eight different transl"ission codes from eight individual sensor units
220 simultaneously. Ulili~aliGn of multiple probes 240 and sensor units 220 is of
particular utility in areas having several railroad track such as wyes, spurs, or
switchyards, for example.
Additional embodiments of the present invention contemplate
implementation of an event recorder for monitoring and recording train activity. The
recorded event data may be utilized in analysis of accidents or close calls to
determine event causation and to leam how the system nnay be improved if
necessary. The event recorder may be implemented by additional programming
of the microprocessors (800, 820, 860) of the present invention in conjunction with
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29
non-volatile electronic memory (e.g., NVRAM, EEPROM, FLASH RAM) or battery
refreshed electronic memory (e.g., SRAM, DRAM) or other means for savin~ the
event data (e.g., magnetic tape). The electronic memory is preferably a 64 kilobyte
static random ~ccess memory chip (SRAM) backed by a lithium type battery. Other
types of data may also be monitored and recorded such as battery charge
condition, train speed, train length, direction of approach, etc.
In view of the above detailed descri~ lion of a preferred embodiment and
modifications thereof, various other modifications will now become apparent to
those skilled in the art. The claims below encompass the disclosed embodiments
and all reasonable modifications and variations without departing from the spirit
and scope of the invention.
