U.S. patent number 3,781,543 [Application Number 05/251,369] was granted by the patent office on 1973-12-25 for highway crossing protection apparatus.
This patent grant is currently assigned to Westinghouse Air Brake Company. Invention is credited to Crawford E. Staples, Donald E. Stark.
United States Patent |
3,781,543 |
Staples , et al. |
December 25, 1973 |
HIGHWAY CROSSING PROTECTION APPARATUS
Abstract
Each approach detection track circuit in a multiple track
stretch crossed by one or more highways is sequentially connected
to a track energy source, including a distance monitor means, by a
multiplexing means, shown as a bank of relays operated in repeated
cycles by a central process controller. The distance monitor, as it
is sequentially connected to each track circuit, provides a
distance proportional signal to the central process controller for
a train approaching along any track. The process controller
registers the detection of the approaching train and determines its
continued approach by successive distance measurements received
from the same track circuit. When the train is determined to be a
predetermined warning time or distance from the crossing, the
process controller actuates the highway warning signals.
Multiplexing the connections of the track circuits to the distance
monitor allows the use of a single set of centralized highway
crossing apparatus including the distance monitor and the process
controller.
Inventors: |
Staples; Crawford E. (Edgewood,
PA), Stark; Donald E. (Penn Hills Township, Allegheny
County, PA) |
Assignee: |
Westinghouse Air Brake Company
(Swissvale, PA)
|
Family
ID: |
22951662 |
Appl.
No.: |
05/251,369 |
Filed: |
May 8, 1972 |
Current U.S.
Class: |
246/130;
361/169.1; 246/125 |
Current CPC
Class: |
B61L
29/286 (20130101) |
Current International
Class: |
B61L
29/00 (20060101); B61L 29/28 (20060101); B61l
001/06 () |
Field of
Search: |
;246/125,128,130,122R
;317/137,139,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sheridan; Robert G.
Assistant Examiner: Libman; George H.
Claims
Having thus described our invention, what we claim is:
1. A highway crossing protection arrangement for a highway
intersecting multiple parallel railroad tracks, comprising in
combination,
a. a normally deenergized separate track circuit for each direction
of approach to said highway along each parallel track, capable when
energized of detecting the presence of a train within approach
warning limits,
b. a warning signal means along said highway operable when actuated
for displaying a signal warning highway users of the approach of a
train,
c. distance monitor means for at times individually supplying
energy to a particular track circuit and responsive to the
detection of a train therein for determining the distance of the
approaching train from said highway,
d. a mutliplexing means operable for sequentially coupling said
distance monitor means individually to each separate track circuit,
and
e. a process controller means coupled for receiving the approaching
train distance information from said distance monitor means and
responsive thereto for actuating said warning signal means to
display the warning signal when the train is a preselected minimum
time period from said crossing.
2. A protection arrangement as defined in claim 1 in which,
a. energy supplied by said distance monitor means is an alternating
current of preselected frequency, and
b. each track circuit includes,
1. a transformer for coupling said distance monitor means to the
rails of the corresponding approach track section, and
2. a shunt connected across the rails at the end of the
corresponding section distant from the crossing.
3. A protection arrangement as defined in claim 2 in which,
a. the separate track circuits for each direction of approach along
each parallel track are paired as a center fed track circuit,
coupled to the rails by a single transformer to form also a
positive detector section including the actual crossing,
b. each shunt at the distant end of each approach section is tuned
to said preselected frequency, and
c. the rail connections of each coupling transformer include a
series capacitor selected to inhibit the shunting of any other
superposed track circuit of different frequency.
4. A protection arrangement as defined in claim 2 in which said
multiplexing means includes,
a. a bank of multiplexer relays controlled by said process
controller means for operating through a predetermined sequence of
conditions in repeated cycles, and
b. a contact matrix controlled by said relay bank for completing a
different circuit path through said matrix for each sequential
condition of said relays,
c. each said circuit path connected for supplying energy from said
distance monitor means to a different track circuit to detect an
approaching train in the corresponding section.
5. A protection arrangement as defined in claim 4 which further
includes,
a. interface apparatus coupling said process controller means to
said relay bank and to said warning signal means, and
b. analog to digital converter means connected for receiving train
distance signals from said distance monitor means and operable in
response thereto for converting each signal from analog to digital
form,
1. said converter means being coupled through said interface
apparatus for supplying each digital distance signal to said
process controller means.
6. A highway crossing protection arrangement for a plurality of
highways intersecting in relatively close proximity a railroad
track, comprising in combination,
a. a warning signal means along each highway operable when actuated
for displaying a signal warning highway users of the approach of a
train,
b. a normally deenergized detector track circuit for each crossing
capable when energized of detecting a train approaching that
crossing in either direction within limits of that track
circuit,
c. a shunt connected across the rails at a location along said
track a selected distance in each direction away from all said
plurality of crossings for defining the distant limits of each
track circuit,
d. distance monitor means for at times supplying energy to each
track circuit and responsive to the detection of a train therein
for determining the distance of that train from the associated
highway crossing,
e. a process controller means coupled for receiving train distance
information from said distance monitor means and responsive thereto
for actuating a selected warning signal means to display the
warning signal when an approaching train is a predetermined time
interval from the corresponding crossing, and
f. a multiplexing means operable for sequentially coupling said
distance monitor means to each detector track circuit.
7. A protection arrangement as defined in claim 6 in which,
a. energy supplied by said distance monitor means is an alternating
current of preselected frequency,
b. each shunt at the distant ends of said track circuits is tuned
to said preselected frequency, and
c. each track circuit further includes,
1. a transformer for coupling said distance monitor means to the
rails in a manner to form also a positive detector section spanning
the corresponding highway crossing, and
2. a capacitor connected in series in the rail connections of said
coupling transformer to inhibit the shunting of any other
superposed track circuit of different frequency.
8. A protection arrangement as defined in claim 7 in which said
multiplexing means comprises,
a. a bank of multiplexer relays controlled by said process
controller means for operating through a predetermined sequence of
conditions in repeated cycles, and
b. a contact matrix controlled by said relay bank for completing a
different circuit path through said matrix for each sequential
condition of said relays,
c. each said circuit path connected for supplying energy from said
distance monitor means to a different track circuit to detect a
train.
9. A protection arrangement as defined in claim 8 in which,
a. said process controller means is a digital data process
controller, and which further includes,
b. interface apparatus coupling the process controller output to
said multiplex relay bank and to said warning device, and
c. analog to digital converter means coupling said distance monitor
means through said interface apparatus to said process controller
and operable for changing the distance signal output of said
distance monitor means from analog to digital form.
Description
BACKGROUND
This invention pertains to highway crossing protection apparatus.
More particularly, our invention relates to protection and/or
warning arrangements for complex rail and highway crossing layouts,
for example, multiple tracks with different speeds of approach or
plural highway crossings within overlapped warning distances, using
a minimum amount of apparatus by multiplexing the detection and
control processes to the various approach track stretches.
There is an increasing demand for protecting highway users at grade
crossings with railway tracks. This is partly because of public
opinion regarding the reduction of highway accidents. However,
there does exist a positive need for increased safety, both for
highway users and train operation, which requires active crossing
warning systems rather than a mere passive or inert wayside sign
along the highway. Ideally, of course, a complete grade separation
of the highway and railroad tracks is the ultimate safety solution
but the physical conditions at many crossings do not permit such
improvements. The resulting need, therefore, is to improve the
operation and reduce the cost of highway crossing protection
apparatus arrangements. The reduction of cost is particularly
necessary at complex crossing situations where there may be
multiple railroad tracks, that is, two or more parallel tracks;
where there is a plurality of highways crossing with overlapped
warning areas along the single stretch of track; and finally within
urban areas where the two situations are frequently combined. A
related requirement, of course, is for uniform warning times at any
crossing, without regard to varying train speeds and multiple
crossings, so that the effectiveness of the warning indication upon
the public remains constant and undue periods of waiting will not
cause drivers to ignore such signals. One solution for reducing the
cost of complex installations is the use of a centralized set of
detection and control apparatus that may be time shared over
several approach stretches or at the various highways in a plural
and complex physical layout. Such centralized apparatus, of course,
provides an economic advantage in reducing the total apparatus
requirement and has an operational advantage in that a centralized
signal control process may be used having preset warning
conditions.
Accordingly, an object of our invention is an improved highway
crossing protection arrangement.
Another object of the invention is a crossing protection
arrangement providing improved operation at complex grade crossing
layouts.
Still another object of our invention is highway crossing
protection apparatus using centralized train detection and warning
signal control devices time shared between several approach tracks
and/or grade crossings in a single area.
It is also an object of our invention to provide highway crossing
protection using centralized detection and signal control apparatus
to provide substantially uniform warning at each of several
adjacent highways intersecting a single stretch of railroad
track.
Yet another object of the invention is an arrangement at highway
crossings for detecting approaching trains on any one of a
plurality of tracks intersecting the highway, using a single set of
distance detection apparatus coupled in sequence to each of the
several approach track sections.
A further object of our invention is a highway crossing warning
arrangement including single train distance detection means
connected in sequence by multiplexing means to each of a plurality
of approach sections in several parallel tracks intersecting the
highway.
It is a still further object of our invention to provide, using
centralized train detection and signal control means time shared
over various approach track stretches, a relatively uniform warning
signal operation at each of several highways intersecting a
plurality of parallel tracks over which trains move in each
direction across all of the highways.
Other objects, features, and advantages of our invention will
become apparent from the following specification when taken in
connection with the accompanying drawings and appended claims.
SUMMARY
In practicing our invention, a central process controller means
including suitable input and output interface apparatus is provided
for controlling the warning system for the highway crossing
complex. A single distance monitoring device is used to detect the
approach of trains toward the crossing or crossings and to provide
an output signal proportional to the distance of the train from the
crossing. A minimum warning time and/or distance for each possible
approach is predetermined and set into the system, that is, into
the process controller. In the principal showing, the distance
monitoring device is connected in a repeated sequence to detector
track circuits installed in each approach to the crossing along a
plurality of parallel railroad tracks. One track circuit at a time
is connected to the distance monitor by a multiplexing means, shown
as a bank of relays controlled by the process controller. Each
track circuit is operable for detecting a train when energized
through the distance monitor, and also to provide the distance
monitor with a signal for determining the distance to the
approaching train. The train distance signal is fed in digital form
into the process controller which compares successive distance
measurements to determine the speed of the approaching train and
thus the time prior to its arrival at the crossing. When the
determined arrival time of a train is equal to the predetermined
minimum warning time for the corresponding approach, the process
controller actuates the warning signal means to indicate to highway
users that a train is approaching within the preset distance or
time. If a plurality of closely adjacent crossings are positioned
along the stretch of track so as to have overlapped approach
sections or distances, a minimum time for each crossing is set into
the controller so that, with the single approach detection track
circuit, the various warning signals at each crossing may be
individually actuated at the proper time during the passage of the
train. The signal control process may also include a detection of
trains entering the stretch from a spur track within the approaches
to determine which and when various crossing signals are
actuated.
DETAILED DESCRIPTION
We shall now describe the arrangement of our invention in more
specific detail, prior to pointing out the novel features thereof
in the appended claims, referring from time to time to the
accompanying drawings in which:
FIG. 1 is a diagrammatic circuit representation of a crossing
warning system for a multiple track crossing by a single highway
embodying the arrangement of our invention.
FIG. 2 is a schematic illustration of a multi-crossing installation
along a stretch of track, to which the invention is applied using a
different type of detector track circuit.
In each of the figures, similar items are designated by similar
reference characters.
Referring to FIG. 1, three parallel railroad tracks, each shown by
a double line representation, are illustrated as intersected by a
highway H, which is also shown by a double line symbol. A warning
signal device is located along the highway on each side of the
railroad tracks to warn highway traffic moving in each direction of
the approach of a train. These signal devices, designated as G1 and
G2, are shown by conventional symbols as well-known flashing light
apparatus. It is understood, of course, that other types of warning
signals are available, for example, automatic gates in addition to
the flashing lights may be provided, and the use of any such
alternate or additional warning apparatus is included in the
arrangement of our invention. The necessary and proper operating
controls for the warning signals are supplied through an
input-output interface apparatus from a central process controller,
which will be discussed later.
Since trains may move in either direction on each of the three
tracks, the detection of trains approaching from either side of the
highway must be accomplished. For this purpose, a detector track
section in each direction along each track is provided, separated
by the insulated joints J shown in each rail immediately to the
right of highway H. Each approach track section is terminated by a
shunt S connected between the rails at the distant end of the
section, the points of connection of the shunts being predetermined
in accordance with allowable train speeds and the desired detection
times. Each track section is designated by the reference T with a
prefix in accordance with the track number, in sequence, from the
top, and an indication as to whether the section extends to the
west (left) or to the east (right) of the highway. For example, in
the upper or track No. 1, the two approach detector sections are
1WT, extending to the left, and 1ET, extending to the right.
Each track section is provided with a track circuit for the
detection of approaching trains. Since energy, as will be
described, is supplied from the highway end and with a permanent
shunt across the distant end, each track circuit is of the type
which permits the measurement of the distance to the permanent
shunt or to an intervening shunt provided by train wheels and
axles. Each track circuit is normally deenergized and energy is
supplied periodically through a distance monitor device, shown as a
conventional block so labeled. This energy is preferably an
alternating current of a preselected frequency which will permit an
indication of the distance to the rail shunt. The distance monitor
device is shown by a conventional block since the detailed
circuitry thereof is not a particular part of our invention and may
be of any known type. For example, one such device is shown in
Letters Patent of the U.S. Pat. No. 3,342,989, issued Sept. 19,
1967, to E. C. Dwyer and B. Mishelevich, for a Track Fullness
System. Another type of such distance monitor devices which may be
adapted to use in the presently disclosed arrangement is shown in
Letters Patent of the U.S. Pat. No. 3,155,350, issued Nov. 3, 1964,
to R. D. Campbell, also for a Track Fullness System. Either of
these disclosed distance measuring means or any equivalent
apparatus may be adapted for use in an arrangement embodying our
invention.
Although direct rail connections may be used, energy is normally
coupled to the rails of each section through a track transformer.
Herein each is designated by the reference T with a combined suffix
including the track number and a letter W or E, designating the
associated west or east track section, respectively. For example,
for track sections 1WT and 1ET, the track transformers are
designated by the references T1W and T1E, respectively. The
secondary of each transformer is connected across the rails, the
two secondaries in each track being insulated from each other by
the joints J. The primary of each transformer is periodically
connected to the source of alternating current energy through the
distance monitor device.
The track circuits may be considered to be normally deenergized
since they are only periodically supplied with energy from the
distance monitor apparatus which serves as a constant current
source. The sequence of application of energy to the various track
circuits, that is, their connection to the distance monitor
apparatus, is controlled by a multiplexer means, shown specifically
as a bank of relays A, B, and C. These relays, in their sequencing
operation, are illustrated as being controlled through the
interface circuitry by the process controller, which is to be
discussed later. The time sharing or multiplexing connection
sequence for supplying energy from the distance monitor to the
track circuits is actually performed by the matrix of contacts of
relays A, B, and C. The contact matrix connections, as shown, are
for binary operation of the relays with relay A representing the
least significant binary digit, and relays B and C being of
increasing significance in that order. Since only six track
sections or track circuits are specifically illustrated, two of the
possible eight code combinations of the three relays in binary
operation are unused.
The first multiplex circuit connection used is that with relay A
alone energized, designating the binary code 1. Under these
conditions, energy is supplied to the track circuit of section 2ET
from terminal BX of a suitable alternating current source, which
may be a commercial frequency source, through the distance monitor
and over front contact a of relay A, back contact a of relay B,
back contact b of relay C, and the primary of transformer T2E to
terminal NX of the alternating current source. During the
immediately following relay code combination, relay B alone is
picked up, signifying a binary 2. The completed circuit now
includes back contact a of relay A, front contact b of relay B,
back contact c of relay C, and the primary of transformer T1E, so
that the track circuit of section 1ET is supplied with energy.
During the next relay combination representing binary 3, relays A
and B are both picked up and the circuit over front contacts a of
these two relays and back contact a of relay C supplies energy to
the primary of transformer T3E for the track circuit of section
3ET. The binary 4 combination, relay C alone picked up, is not used
in this specific showing. During the following relay combinations,
the track circuits for sections 2WT, 1WT, and 3WT, in that
sequence, are energized, as may be traced by reference to the
drawing. The binary 0 combination of all relays released is also
not used. However, the possible circuit connections shown from back
contact b of relay B by dotted lines, including front and back
contacts d of relay C, could provide energy to two additional track
circuits during the herein non-used relay combinations. The cycle
of relay operation in the multiplexing arrangement normally
immediately repeats and such continuous repeating of the cycle
occurs under control of the process controller to periodically
provide energy to detect train approach through each of the track
sections. Obviously, other relay operational sequences can be used
and the contact matrix connections revised to accommodate such
operations. As each track circuit is energized during the
sequential operations, the distance monitor device checks for train
approach detection and develops a distance measurement signal to
the permanent shunt S or to the shunt resulting from the entrance
of a train into the section.
Although shown as a bank of relays, obviously other switching
apparatus may also be used as the multiplexing means. For example,
transistors or controlled rectifiers can replace the relay contacts
and the gating of such devices in selected sequence controlled by
signals from the process controller. Further, the multiplexing
means, relay or solid state, can be designed, if desired, to be
free running or self operating through at least the normal
predetermined sequence without control signals from the process
controller. This latter device could then exercise specific control
to vary the normal sequence if extra scanning of specific track
circuits is desirable, e.g., one occupied by a train. If free
running, the multiplexer would of necessity indicate to the process
controller the step or condition in the normal sequence to which it
had advanced.
The process controller means, shown in the lower left of FIG. 1, is
the heart of the control for the crossing system, determining when
the warning signals are actuated to provide sufficient but not
excessive warning time to highway users. The degree of
sophistication of uniform operating time desired in any particular
installation fixes the requirements for the process controller
operation. This device is herein shown by a conventional block
since it may be any one of different types comprising known circuit
elements. The operation desired can be provided by any of the types
known and it is the operation only, and not the specific circuit
details which are included as part of our invention. This process
controller may be either a hard wired or a stored program
apparatus. In either case, the operating functions provided are the
same. This device sorts the incoming data, particularly the train
detection and distance information, and registers it on a per track
circuit basis. It calculates the distance to the approaching train
and provides for scaling of the individual approaches where their
characteristics differ. By comparison of the successive distance
calculations for a track, the velocity of an approaching train and
its direction of travel may be determined. Once the distance,
velocity, and/or direction have been calculated, the time of
arrival at the crossing may then be determined, thereby making
possible a constant approach warning time for the highway traffic.
The process controller, of course, provides the actuating controls
for the warning signal devices, the control being of a nature to
match the type of signal provided. The process controller also
controls the sequential track circuit scanning cycle by controlling
the operation of the multiplexer, here relays A, B, and C. In
installations where several highway crossings exist in relatively
close relationship along the same stretch of tracks, the functions
of the controller can provide implementation of the different
highway warnings, without having separate track circuits, by being
programmed with the required sequencing and timing for actuating
and clearing the successive signals during the passage of a
particular train.
The distance proportional signal or indication provided by the
distance monitor for any particular track circuit is digitized by
the analog to digital converter and then applied through the
interface to the process controller. The digital output may be of
binary form but is not limited to this type of digitizing. The
resolution of the converter is such as to provide measurements of
the precision necessary to establish the location of the
approaching rail traffic to the accuracy required by the overall
system requirements. The analog to digital converter is shown by a
conventional block since the specifics of the circuitry depend upon
the type of distance monitor used and the required accuracy of the
conversion for input to the process controller. Since such
converters are well known in the art, the selection of the specific
type required may be made during the design engineering for a
particular highway crossing installation.
The input and output interface apparatus, also shown by a
conventional block, provides the interconnection between the
distance monitor and associated analog to digital converter outputs
and the process controller and also couples the outputs from the
process controller to control the multiplexing relays and the
various highway signals. The specifics will depend upon the
requirements of the individual installation, the type of process
controller used, and the characteristics of the input and the
output signals developed. The input portion of the interface
accepts the digital data from the A/D converter and passes it to
the process controller. The output portion of the interface
provides for control of the multiplexer relays and for the control
of the other external equipment, such as the warning signals which
may include crossing gates, flashing lights, and bells. The energy
levels and power handling capabilities of the various circuits are
proportioned to accommodate the need of the devices they control.
In addition, the interface may also contain supplementary
apparatus, such as times and flashers, for control of the warning
signals. As indicated, the size and sophistication of the interface
circuitry and apparatus will depend upon the type of process
controller selected and the signals required for operation of the
various external apparatus.
FIG. 2 shows a single track stretch intersected by a plurality of
highways H1, H2, and H3, which are in relatively close proximity to
each other. Although only a single track is shown, obviously the
several highways could intersect parallel tracks, such as are shown
in FIG. 1. It has already been mentioned that the process
controller embodied in the arrangement of our invention can be
wired or programmed, depending upon its type, to handle a situation
such as shown in FIG. 2. Under these conditions, the proper
actuation of the warning signal at each highway, in order to
provide sufficient warning of proper duration to the highway users
as the train passes along the stretch, can be accomplished.
Also shown in FIG. 2 is an alternate type of track circuit which
may be used when it is desired to avoid any interference between
train detection for the highway crossing warnings and the regular
track circuit detection of the railroad signal system controlling
the movement of trains. Although shown in the specific
circumstances illustrated in FIG. 2, such a track circuit may
actually be substituted for the pair of track circuits in each one
of the parallel tracks shown in FIG. 1. Specifically, each track
circuit shown in FIG. 2 is of a center fed type and the connections
from the secondary winding of the track transformer TT span the
width of the associated highway to provide positive detection over
the crossing without requiring multiple track feeds or other
special handling. A tuned shunt TS is shown at each distant end of
the approach track sections since it is intended that the energy
source will supply audio or higher frequency current for overlay
track circuit operation, which is well known in the art. Such
overlay track circuits include no insulated joints and thus do not
interfere with the regular train detection track circuits of the
railroad signal system. The capacitor shown in series with the
secondary of each track transformer TT, in conjunction with the
inductance of the transformer winding, provides a high impedance to
signals of other frequencies which may be used for train detection
in the train signal system, and thus preserves the integrity of the
train detection track circuits otherwise in use. Depending upon the
existing circumstances, the energy source for each track circuit
may be coupled or connected to the rails by other known
arrangements.
Three distinct track circuits are shown, one for each highway
crossing. Each track circuit uses the same pair of distant shunts
TS but applies track current at the associated crossing. The
secondary of each transformer TT is connected to the rails to span
the associated highway for the purpose previously mentioned.
Specifically, the secondary connections of transformer TT1 span
highway H1; of transformer TT2, highway H2; and of transformer TT3,
highway H3. The primary windings of transformers TT1, TT2, and TT3
are supplied with energy in sequence from the distance monitor,
with the sequence controlled by a multiplexing means such as the
relays A, B, and C of FIG. 1. Thus each track circuit is energized
at a different time and no interference results. Obviously, each
overlay track circuit shown in FIG. 2 will detect the presence of
the train within the limits defined by the distant tuned shunts TS
and, in conjunction with the distance monitor means which supplies
track energy in sequence, provides a distance proportional signal
to the process controller for the installation. This latter
apparatus, as previously described, then functions to calculate the
distance to the approaching train from any one of the highway
crossings shown and actuates the corresponding warning signals at
the proper time during the movement of the train through the
stretch of track shown.
It will be understood by those skilled in the art that a failure in
either type of track circuit, under which the track circuit becomes
open due to a break in a rail or interruption of the connection of
the shunt across the rails, will result in a much higher distance
measurement from the distance monitor means. The process controller
may be programmed or wired to respond to such a fault condition to
actuate the signals since the much higher distance indication will
indicate a fault which may preclude the detection of an approaching
train.
The system of our invention thus provides an economical arrangement
for providing highway crossing warning signals for any highway
crossing installation and particularly one which is of a complex
nature due to the presence of a plurality of parallel tracks and/or
several closely spaced highway crossings. The central process
control means and the multiplex use of the train detection and
distance monitoring apparatus reduces the total apparatus
requirement for the whole installation. At the same time, the
efficiency of the centralized process controller to determine the
distance and arrival time of approaching trains, and to compare
these with the preset warning distances and times, allows the
proper operation of the warning signals at each of several
crossings and for trains approaching over any one of the tracks.
The final result then is an efficient, effective, and economical
highway crossing protection apparatus.
Although we have herein shown and described but two forms of
highway crossing protection apparatus embodying our inventive
concept, various changes and modifications therein within the scope
of the appended claims may be made without departing from the
spirit and scope of our invention.
* * * * *