U.S. patent number 3,794,833 [Application Number 05/256,888] was granted by the patent office on 1974-02-26 for train speed control system.
This patent grant is currently assigned to Westinghouse Air Brake Company. Invention is credited to Frank V. Blazek, William B. Dufer, Raymond C. Franke, Philip R. Schatzel.
United States Patent |
3,794,833 |
Blazek , et al. |
February 26, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
TRAIN SPEED CONTROL SYSTEM
Abstract
High frequency detector track circuits are coupled to the rails
at crossbonds which divide the track stretch into sections without
insulated joints. The HF transmitters supply track energy both
directions from alternate bonds into each track section of the
adjoining pair. Correspondingly tuned receivers at the other end of
each section control track relays which indicate the track
occupancy condition. Successive pairs of track sections have
different frequencies selected on a random basis from a
predetermined plurality. Train control energy of a different,
single frequency is supplied to the rails at the exit end of each
section and is modulated by one of a plurality of low frequency
code rates selected in accordance with the track occupancy
condition of advance sections as determined by the track circuits.
Each train is equipped with train control apparatus including at
least cab signals and overspeed protection. Receivers inductively
coupled to the rails pick up and supply the speed signals through a
demodulator and active filters to register an allowed speed
indication in accordance with the detected code rate. Train speed
sensing apparatus registers the actual train speed. Overspeed
detection apparatus then compares allowable and actual speeds,
detects an overspeed condition, and actuates an automatic braking
action if the train operator does not initiate a speed reduction
within a preset time limit.
Inventors: |
Blazek; Frank V. (Monroeville,
PA), Dufer; William B. (Penn Hills Township, Allegheny
County, PA), Franke; Raymond C. (Glenshaw, PA), Schatzel;
Philip R. (Danville, CA) |
Assignee: |
Westinghouse Air Brake Company
(Swissvale, PA)
|
Family
ID: |
22974012 |
Appl.
No.: |
05/256,888 |
Filed: |
May 25, 1972 |
Current U.S.
Class: |
246/63C;
246/187B; 246/34CT |
Current CPC
Class: |
B61L
3/221 (20130101) |
Current International
Class: |
B61L
3/22 (20060101); B61L 3/00 (20060101); B61l
003/10 () |
Field of
Search: |
;246/34CT,63C,63R,187B,36 ;303/21P,20 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Forlenza; Gerald M.
Assistant Examiner: Libman; George H.
Attorney, Agent or Firm: Williamson; H. A. Williamson, Jr.;
A. G.
Claims
Having thus described our invention, what we claim is:
1. A train control system for trains moving along a stretch of
track, comprising in combination,
a. a track circuit arrangement dividing said stretch into a
plurality of sections and including a center fed detector track
circuit for each pair of adjacent track sections supplied by a
transmitter means with energy of a distinctive frequency different
from that supplied other pairs of sections in said track
stretch,
1. the track circuit for each pair of sections individually
detecting the occupancy of each section by a train;
b. said track circuit arrangement further including another energy
source for each track section connected at the exit end thereof for
supplying to the corresponding section at times energy with a
single preselected frequency different from any of said distinctive
frequencies and modulated with one of a plurality of allowable
speed signals, selected in accordance with the detected occupancy
conditions of sections in advance,
1. each other energy source being controlled by the associated
track circuits for supplying said preselected frequency energy only
when the corresponding section is occupied and at least the next
advance section is unoccupied,
c. receiver means on each train inductively coupled to the track
rails for receiving the modulated preselected frequency energy
supplied by a second energy source to the track section then
occupied by that train and responsive thereto for producing a
distinctive output in accordance with the selected modulation
signal,
d. registry means on each train connected for receiving the output
of the associated receiver means and recording an indication of the
allowable train speed,
e. speed measuring means on each train coupled to the train
propulsion apparatus for registering an indication of the actual
train speed,
f. overspeed detection means on each train jointly controlled by
the associated registry means and the associated speed measuring
means for comparing allowable and actual train speeds and further
connected to the train braking apparatus for at times initiating an
automatic brake application to reduce the train speed in response
to a detected overspeed condition of actual speed greater than
allowable speed, and
g. time delay means on each train controlled by the associated
overspeed detection means and responsive to deceleration of said
train for measuring a predetermined time period after an overspeed
condition detection and connected for inhibiting an automatic brake
application when deceleration of said train is otherwise initiated
during said predetermined time period.
2. A train speed control system for trains moving along a stretch
of track, comprising in combination,
a. a track circuit arrangement dividing said track stretch into
preselected track sections and operable for detecting the presence
and location of trains within said stretch,
1. said track circuit arrangement further supplying to each section
a train control signal carrying a selected one of a plurality of
code frequencies each designating a different maximum allowable
speed for an approaching train in accordance with the detected
location of any preceding train,
b. a signal receiving means on each train coupled for responding to
said train control in the occupied section to register the maximum
allowable speed in accordance with the received code frequency,
c. a speed measuring means on each train coupled for registering
the actual speed of the train,
d. overspeed detection means on each train connected to receive the
registered train speed and controlled by the associated signal
receiving means for comparing the registered actual and allowable
train speeds,
e. an automatic brake application control means having a nonbraking
condition and more than one different braking conditions which
provide successively greater deceleration rates,
f. said brake application control means connected for actuating an
initial train brake application when operated to its first braking
condition and successively stronger train brake applications when
succesively operated to each other braking condition,
g. said brake application control means controlled by said
overspeed detection means for holding in its nonbraking condition
when the actual speed is less than the allowable speed,
1. said brake application control means operable to each successive
braking condition a distinct and successively longer preselected
time interval after the overspeed detection means detects that the
actual speed is greater than the allowable speed if no other
braking action has occurred, and
h. a brake assurance means coupled for responding to deceleration
of the train to operate from a first to a second position,
i. said brake assurance means connected in its second position for
retaining said brake application control means in its nonbraking
condition if train deceleration occurs prior to the expiration of
the least preselected time interval and in its existing braking
condition if deceleration occurs prior to the expiration of the
next longer time interval.
3. A speed control system as defined in claim 2 in which,
a. said automatic brake application control means has only a
nonbraking, a normal braking, and an emergency braking condition
and is connected for actuating a train service brake application
when operated to its normal braking condition and an emergency
brake application when operated to its emergency braking
condition,
b. said brake application control means operates to its normal
braking condition a first preselected time interval and to its
emergency braking condition a second and longer preselected time
interval after the overspeed detection means detects that the
actual speed is greater than the allowable speed if no other
braking action has occurred, and
c. said brake assurance means is connected in its second position
for retaining said brake application control means in its
nonbraking condition if train deceleration occurs prior to the
expiration of said first time interval and at least in its normal
braking condition if deceleration occurs prior to the expiration of
said second time interval.
4. A speed control system for railroad trains moving along a
stretch of track, comprising in combination,
a. a track circuit arrangement connected for dividing said track
stretch into a plurality of sections and for normally supplying
energy having a distinctive frequency, to each adjoining pair of
track sections at their common junction location, to feed through
the rails to the distant end of each section,
b. an occupancy detection means coupled at the distant end of each
of the pair of track sections supplied with the same distinctive
frequency energy for registering the occupancy condition of the
corresponding section,
c. a second source of energy for each track section coupled at the
exit end thereof for at times supplying energy having a selected
frequency different from said plurality of distinct frequencies and
the same for each section,
d. a modulating means coupled to each second source and controlled
by said track circuit arrangement for modulating the second source
energy by a selected one of a plurality of code frequencies in
accordance with the section occupancy conditions in advance of the
corresponding section,
1. each code frequency designating a predetermined maximum
allowable train speed,
e. the supply of said second source energy to a particular section
being further controlled by,
1. the occupancy detection means for the advance section to
interrupt the energy supply when that advance section is
occupied,
2. the occupancy detection means for that particular section to
complete the energy supply when an approaching train occupies that
section, and
f. train control apparatus on each train traversing said stretch
responsive to the modulated selected frequency energy successively
supplied to the sections and connected for monitoring the speed of
that train and maintaining the speed below the maximum allowable
speed designated by the received code frequency.
5. A speed control system as defined in claim 2 in which each
train-carried apparatus further includes,
a. a zero speed detection means coupled to said speed measuring for
registering a zero train speed condition,
b. said zero speed detection means producing another output when
zero train speed is detected and coupled for holding said overspeed
detection means in its nonactuating condition to permit that train
to restart when an allowed speed is registered,
c. said zero speed detection means also connected for holding said
brake application control means in its nonbraking condition when a
registered zero speed condition results from other than an
automatic brake application.
6. A speed control system as defined in claim 5 further including
in each train-carried apparatus,
a. a stop and proceed restricted speed relay means normally
occupying a first position and operable at times to a second
position,
b. a timing means controlled by said zero speed detection means for
measuring a predetermined delay period after zero speed is
registered,
c. a first circuit means completed by said restricted speed relay
means in its second position for controlling said overspeed
detection means to authorize train movement at a preselected
restricted speed when no code frequency is received,
d. an energizing circuit means connected for operating said
restricted speed relay to its second position and completed jointly
by said signal receiving means when no code frequency is being
received, said brake application control means in its nonbraking
condition, and said zero speed detection means when a zero speed
condition is registered, and
e. a second circuit means completed by said timing means when said
delay period is expired for alternately controlling said overspeed
detection means to authorize train movement at said preselected
restricted speed when no code frequency is received.
7. A speed control system as defined in claim 4 which further
includes,
a. traffic direction means operable to a first and second positions
for establishing normal or reverse direction traffic, respectively,
through the track stretch,
b. remotely controlled switch means connected for operating said
traffic direction means to its first or second positions as normal
or reverse traffic selection commands are registered by said switch
means, and
c. the supply of second source energy at each junction between
sections is further controlled by said traffic direction means for
supplying such energy only to that section whose exit end is at
that junction in accordance with the established traffic
direction.
8. A speed control system as defined in claim 7 in which
the track section limits are defined by cross-bond devices
connected between the rails without insulated joints, said energy
sources and detection means being coupled to the section rails by
transformer windings of said crossbonds.
9. A speed control system as defined in claim 8 in which all
apparatus except said crossbond devices for said track circuit
arrangement for said stretch of track is located at a central
housing.
Description
Our invention pertains to a train speed control system. More
particularly, the invention is an arrangement in which the actual
speed of a train moving along a stretch of track is compared to the
allowable speed established by traffic conditions in advance, and
the train is controlled to bring the speed within the existing
allowable speed limits.
In all railroad systems, including those specifically defined as
being rapid transit systems, the matter of safe control of train
speed is of prime importance. Various speed control systems, in use
and known to the art, provide selected degrees of sophistication of
control. In general, each such system is designed specifically to
provide the desired degree of speed control. All such systems
require wayside means to detect the presence of the trains moving
through the stretch and their location within predetermined
sections. All systems further require wayside means which can
transmit this information onto the train to establish the speed at
which it may move based on the position of trains in advance along
the track and/or existing track hazards. These means for
transmitting speed information onto the train may or may not be the
same apparatus as used for the detection of train position.
Further, each train is equipped with apparatus for receiving and
decoding the speed indications received from the wayside and for
providing a corresponding signal for the train operator or control
apparatus. Each train requires some means for measuring and
registering its own speed and for comparing this registered speed
with the maximum allowable speed. Having completed the comparison,
apparatus is then needed to actuate the necessary controls or to
indicate to the operator when an overspeed condition exists. Due to
the multiplicity of the present systems, depending upon the
sophistication of the control desired, a basic system which
provides the listed features and is also adaptable to any degree of
train control sophistication will be advantageous in the art. In
other words, a single basic system is desirable which is compatible
with all systems from simple overspeed protection with manually
operated control to the full automation of train operation.
Accordingly, an object of our invention is an improved speed
control system for railroad trains.
Another object of the invention is an improved speed control
arrangement for railroad trains compatible with any desired degree
of automation in the train operation.
A further object of the invention is a speed control system for a
stretch of railroad track including a simplified train detection
apparatus, a superposed signal system for transmitting a speed
signal onto trains traversing the stretch, and efficient
train-carried means for comparing the allowed and actual train
speeds to actuate the necessary controls for maintaining but not
exceeding the allowed speed.
Still another object of our invention is a train control system for
a stretch of track including high frequency track circuits for
train detection, a single selected frequency, code modulated in
accordance with advance traffic conditions, for transmitting
allowed speed signals to trains traversing the stretch, and
train-carried apparatus for receiving the allowed speed signals,
recording the actual speed of the train, and comparing the speeds
to actuate overspeed control measures when such conditions are
detected.
A still further object of the invention is a train speed control
system including high frequency track circuits for detecting trains
occupying a stretch of track, superposed code modulated, single
different frequency track circuits for transmitting the allowed
speed signals, and, on each train, signal receivers inductively
coupled to register the allowed speed signal from the track, speed
sensing apparatus to determine the train speed, and signal
comparison apparatus for comparing the allowed and actual speed
registered signals to control the overspeed protection apparatus to
actuate braking procedures to maintain the train speed equal to or
less than the allowed speed.
Other objects, features, and advantages of our invention will
become apparent from the following specification, accompanying
drawings, and appended claims.
SUMMARY OF THE INVENTION
In practicing our invention, a stretch of railroad track is divided
into sections by crossbonds connected between the rails at the
junction locations between desired track sections. No insulated
joints are inserted in the rails at these points, thus maintaining
a continuous rail for propulsion return where electrified operation
is in effect, particularly as in rapid transit systems. Train
detection throughout the stretch is provided by high frequency
track circuits. The high frequency energy transmitters are coupled
to the rails through the crossbonds at alternate bond locations and
feed in both directions into the rail. Thus, each pair of adjoining
track sections or track circuits has the same frequency. However,
the successive track circuit pairs are assigned different
frequencies which are shown as generated at centralized oscillator
units, amplified, and then coupled to the rails at the proper
section junctions. Two track circuit receivers are coupled to the
rails at the intervening bond location between the transmitters,
one receiver for each adjoining track circuit. Each such receiver
is tuned to respond only to the track circuit frequency of the
associated transmitter at the other end of the corresponding track
section.
A separate energy transmitter with a different frequency is also
coupled to the rails at each bond location to provide train control
track energy. A single oscillator unit generates a selected single
frequency for the train control track circuits. Such an oscillator
may be part of the same bank of oscillators which provide the basic
energy for the detector track circuits but having a different
selected frequency. The train control track circuit energy is
supplied also from the central location for the stretch to each
bond location and is activated to supply such energy to the rails
at the exit end of the section only when a train enters at the
opposite end. For each section, the train control, or speed
control, energy is modulated by a code frequency selected in
accordance with the advance traffic conditions throughout the
stretch as detected and determined by the high frequency detector
track circuits. The code frequency is selected at the instant the
train enters the track section although the selection may change in
accordance with changes in the advance traffic conditions while the
train is traversing that particular track section. Each code
frequency represents a preset different maximum allowed speed for
train movement. These code frequencies representing speed limits
are generated at the central location for the stretch, and the
modulation is determined by the detector track circuit apparatus in
accordance with train occupancy. The actual modulation selection is
accomplished over contacts of track relays which are actuated by
the track circuit receivers. Such relays are used in order to
provide a final degree of fail-safe operation to the track
circuits. It is emphasized that in our inventive arrangement, for a
particular stretch of railroad track, all apparatus except
crossbonds is concentrated at a central location, that is, the
frequency oscillators, amplifier transmitters, track receivers,
coupling units, and track relays. From this central location,
direct connections are made to the crossbonds for coupling the
energy to or from the rails of a specific track section, the
crossbond apparatus connected between the rails being the only
device located at the actual junction between the track
sections.
Each train traversing the stretch of track is equipped with train
control apparatus which is capable of receiving an allowed speed
signal from the rails and displaying a corresponding indication,
comparing the actual train speed and the allowed speed, and
controlling the speed of the train in accordance with the
relationship. The speed control provided may be of any one of
several degrees of sophistication, from a mere overspeed warning to
full automatic train operation. The train-carried receiving
apparatus is inductively coupled to the rails and tuned to receive
only the modulated cab signal or train control energy transmitted
through such rails. The received energy is amplified and
demodulated and then filtered in accordance with the existing code
or modulation frequency to energize a selected speed indication
relay corresponding to the received code frequency and thus to a
designated maximum allowable speed. Through a matrix of contacts of
these relays, the corresponding speed indication is selected for
display on a signal panel. The actual train speed is measured by a
magnetic pickup from the driving gears which generates an
alternating current voltage whose frequency varies in accordance
with the actual train speed. This alternating current developed as
a measure of train speed is then shaped and passed through various
low pass filters, one filter being provided for each maximum speed
range represented by the signals picked up from the rails. These
low pass filter outputs are passed through solid state switches,
one to each filter which is closed only when the corresponding
speed signal received from the rails represents an allowable speed
corresponding to the actual speed signal passed by that filter. The
output from the solid state switches is passed through a checking
circuit matrix, composed primarily of speed relay contacts, to a
voltage level detector to check that the actual speed of the train
corresponds to the received allowable speed signal. The level
detector output energizes an overspeed relay. This relay releases
if an overspeed condition occurs so that the output through the low
pass filter and corresponding switch decreases below the level at
which the level detector will provide sufficient relay
energization. Release of the overspeed relay actuates automatic
train braking apparatus if there is no action by the train
operator. Various check and timing arrangements are provided to
allow the train operator a preselected time in which to take action
and further to assure that braking is actually occurring. An added
zero velocity detector provides, through the filter and switch
circuit paths, an alternating current frequency sufficient to hold
the overspeed relay energized when the train is stopped. This
allows the train to start again when a proceed signal is received
from the track.
BRIEF DESCRIPTION OF THE DRAWINGS
Prior to defining the novel features of our invention in the
appended claims, we shall describe now the system apparatus in more
detail, referring from time to time to the accompanying drawings in
which:
FIG. 1 is a block diagram of the train-carried apparatus
illustrating, in addition to the parts provided by our invention,
options of automatic train operation which may be added to the
basic arrangement.
FIGS. 2A and 2B, when placed adjacent, provide a diagrammatic
illustration of the wayside apparatus for a stretch of track which
cooperates with apparatus similar to that of FIG. 1 to complete a
speed control system for the trains embodying the arrangement of
our invention.
FIG. 3 illustrates, in a diagrammatic manner, a specific
train-carried apparatus which cooperates with the wayside circuits
of FIG. 2 to provide a complete basic speed control system
embodying our invention.
Where possible, similar reference characters designate equivalent
or similar apparatus in each of the drawings. In FIG. 3, where
energy is required for the operation of specific apparatus,
connections to the positive and negative terminals of a suitable
source of direct current energy are designated by the references B
and N, respectively. The specific direct current energy source for
FIG. 3 apparatus is not shown since several suitable sources are
known in the art, any one of which may be used. In the parts of
FIG. 2, a source of direct current energy for operating all the
apparatus is shown as a battery, designated by a conventional
symbol in the lower left of FIG. 2A, with positive and negative
terminals again designated by the references B and N, respectively.
Where these references appear elsewhere in FIGS. 2A and 2B, they
designate a connection to these terminals of the battery. The
negative or N terminal of the battery is also connected to a common
ground for the wayside system designated by a conventional symbol.
Therefore, a connection elsewhere in these circuits to the ground
terminal is an actual connection also to terminal N of the
source.
DETAILED DESCRIPTION OF BASIC SYSTEM APPARATUS
Referring now to FIG. 1, a block diagram of train-carried apparatus
is illustrated embodying our invention and including some options
which may be added for more sophisticated control of the train
speed. The upper dot-dash rectangle includes, as noted, the
apparatus which provides cab signals and overspeed control when
manual operation of the train is in effect, either selected by
positioning the changeover switch shown at the far right or by
providing none of the additional options available. The lower
dot-dash rectangle includes the apparatus which would be added,
either partially or in whole, to provide automatic speed control,
station-stop control, and door control so that the entire package
of apparatus on the train would provide for automatic train
operation. The conventional blocks shown outside the dot-dash
rectangles represent the train propulsion apparatus and associated
controls including cab signal indicators, a speedometer, and an
overspeed warning device. As previously mentioned and as
illustrated, even if all of the apparatus is chosen for automatic
train operation, provision is still made for manual control
selection by a changeover switch which converts between manual and
automatic operation as may be necessary. These controls are
illustrated at the right of FIG. 1 by the changeover switch block
and the dotted line indicating the various changeover connections,
depending upon the control selected by the switch position.
Considering now the basic apparatus, a train control signal
supplied in the rails is received through inductive coupling by the
receiver coils shown in the upper left and fed into a receiver
unit. This receiver, shown conventionally, amplifies and
demodulates the received signal and a single code or modulation
frequency output is applied to the bank of code frequency filters,
each turn to pass an indicated signal. The resulting filter output
activates a selected gating arrangement to establish a circuit for
displaying a cab signal indication designating the maximum
allowable train speed under the existing traffic conditions.
Simultaneously, the train speed is sensed and an amplified signal
representing the speed is applied to a bank of low pass filters,
each representing a particular speed range used in the operation,
the output being applied to a filter gating network. This gating
network is also responsive to the received speed signal from the
rails to allow a comparison between the actual and allowed speed
ranges. If the actual train speed is within the allowable limits
determined from the track signal pickup, the overspeed control is
maintained in the condition to permit the train to continue its
movement along the rails. If an overspeed condition is detected,
the overspeed control apparatus actuates a braking action and
removes the propulsion power from the train. If the train is in
manual operation under control of a train-carried operator, either
because the changeover switch is so positioned or because that type
of control has been installed, such operator exercises the manual
controls in accordance with the cab signals, the speedometer
indication, and the overspeed warning to avert emergency stops. In
exercising such control, certain reaction time delays are applied
to the automatic braking applications to allow the operator time to
institute the proper braking and propulsion controls to bring the
train speed within the allowable limits.
If automatic train operation is provided and is selected by the
changeover switch, the actual and allowed speed signals are applied
to encoders shown within the lower dot-dash rectangle. The allowed
speed limit signal is then applied through a comparing amplifier to
develop a desired velocity signal. This desired signal, together
with a signal representing the actual train speed, and a brake
feedback signal are compared in the error amplifier to develop the
proper signal to control the train propulsion apparatus. In
accordance with the character of this signal, a brake applying or
brake release control and various types of power propulsion
controls are applied through corresponding devices to the train
propulsion and brake apparatus. The resulting control of the train
movement brings the speed of the train within the allowable limits
designated by the signal picked up from the rails and already
processed.
If the full automatic train operation provided includes the station
stop and door control options, an additional pickup coil mounted on
the train receives a station stop signal from the wayside at
locations in approach to the station platform, as illustrated in
FIGS. 2A and 2B and which will be discussed in some detail in
connection with the wayside apparatus. When the station stop
control signals are picked up and recognized by the trigger
receiver, they are applied to an amplifier which serves as a
distance integrator. The actual train speed signal is also applied
to this amplifier together with a zero velocity signal when the
train is actually stopped. This distance integrator amplifier
provides a signal of the train location with respect to the station
location in advance to a distance profile generator. This latter
unit outputs a profile speed to the desired speed amplifier which,
also comparing it with the allowable speed limit, controls the
desired velocity signal in order to assure a station stop under a
full automatic control of the train propulsion and braking
apparatus. A door control signal is received by this same pickup
coil within the station platform area, as illustrated in FIG. 2A.
The zero speed signal and the door signal actuate a door control
device which outputs a signal to cause the opening of the train
doors at the station platform. The door control also resets the
distance integrator since a station stop has been made and the
speed distance profile generator may be reset for a subsequent
station stop operation. The door opening and closing, that is, the
actual time open, may be on a preset time basis or may be
terminated by the operator actuating a closing control. The train
then resumes its automatic train operation mode and moves away from
the station under control of the allowable speed signals received
from the track circuits. This automatic train operation apparatus
is not a specific part of the present invention but this
conventional illustration is provided to show how it might be
interfaced with the basic apparatus provided by the arrangement
embodying our invention. Several types of such automatic operation
apparatus are available and thus the conventional block diagram
illustration is here used, it being only necessary to know that the
actual train speed signal and an allowable train speed signal need
be provided for purposes of the train movement control together
with trigger signal pickups from the track to initiate station stop
procedures and door opening controls.
We shall now described the wayside apparatus which is part of our
inventive system to provide the train detection and train control
signals necessary for the operation of the train-carried apparatus.
Reference will be made to FIGS. 2A and 2B, when placed adjacent
with FIG. 2A to the left and the corresponding connecting lines
matched, during the description of the wayside apparatus. When
these two drawings are thus positioned, across the top in
conventional double line representation is shown a stretch of
railroad track. Although our invention is not limited to specific
systems, it is herein assumed that this track is part of a rapid
transit system in which the trains operate by electric propulsion.
Such trains normally move from right to left in the drawing, which
direction will be designated as the westbound direction. However,
when so directed and established by the dispatcher in charge,
trains may on occasion move in the reverse direction over the
stretch of track shown. The track stretch is further divided into
track sections by crossbonds connected between the rails. Each
section thus established is designated by the reference T with a
numerical prefix, odd numbers in succession from left to right.
Thus, the section at the left is designated as section 1T and the
numbers increase numerically in odd-numbered progression so that
section 13T is shown at the right.
The crossbonds effectively join the two rails into a single
propulsion return path since no insulated joints are used. In other
words, each rail is a continuous electrical circuit path and the
bonds, by connecting them together at periodic intervals, equalize
the return current flowing in each rail. Each bond is illustrated
as comprising a single turn primary winding which actually connects
between the two rails and a multi-turn secondary winding coupled
thereto and to which the wayside apparatus is connected. Although
several types of such bonds exist, a specific example is that
illustrated in Letters Patent of the U.S. Pat. No. 3,268,843,
issued to Ralph Popp on Aug. 23, 1966 for Electric Induction
Apparatus. The connections from the secondary of each crossbond to
the other wayside apparatus are through coupling units which are
shown by conventional blocks since the circuit design of such
coupling units is well known in the art. Actually the circuitry
within each coupling unit varies in accordance with the type and
amount of wayside apparatus which is being coupled to a particular
crossbond. It is herein assumed that all the wayside apparatus for
the stretch of track shown, except for the crossbonds themselves,
is located in some form of central housing. The connections from
each coupling unit to the associated crossbond are then made by a
direct pair of wires or a pair in a cable extending along the
wayside. In rapid transit system operation, where relatively short
track sections are used, such central housing of the apparatus for
a particular stretch is possible and practical. It is also assumed
that the stretch shown is that between the station whose platform
is shown adjacent track section 3T and the immediately preceding
station for the normal traffic direction which is adjacent to the
next track section 15T off the right-hand of the drawing. Section
13T, a portion of which is shown, is actually a part of the
preceding stretch of track but is here shown to complete the
overall operating concept.
Each track section is provided with a high frequency track circuit
for train detection purposes. In each such circuit, the energy
source is at one end of the section and the receiver apparatus with
a final track relay, designated by the reference TR, at the other
end. For purposes of track circuit energy supply, the sections are
paired in succession along the stretch of track and a single common
track circuit energy source, of a frequency distinct from that of
adjacent pairs, provided at the adjoining ends of each pair of
sections with receivers being at the opposite ends. Said another
way, in effect each pair of track circuits is provided with a
common center fed track circuit with the energy source at the
junction of the adjacent ends of the pair and the two tracks relays
located at the distant ends of the pair. Each track section is also
provided with a track circuit for train control or speed control
signaling purposes. This is also a high frequency track circuit but
the same high frequency energy, different than used in any detector
track circuit, is used for each section to enable the train
apparatus to have a single type of tuning and thus be of a more
simple nature than if different frequencies were used. For the
train control track circuits, energy is supplied to the rails at
the exit end of each track section in accordance with the selected
direction of train operation. This energy is coded or modulated in
order to provide more than one speed signal or instruction
representing allowable train speeds. The receiver for such train
control energy is on the train, to be later discussed, and no
wayside receivers for this train control frequency track circuit
are used. It will be noted that all track circuit energy, that is,
all energy provided to the rails, is coupled to the rails through
the previously described cross-bonds. In addition, at each junction
point between track sections where track energy is supplied, the
coupling unit provides an additional interface between the wayside
apparatus and the track crossbond.
Before specifically describing in detail the track circuit and
train control energy circuits, we shall describe the central
apparatus for generating the selected frequencies for the various
track circuits and the code or modulation frequency source for such
circuits. Since it is assumed that a central housing for wayside
apparatus along each stretch is provided, a central source for the
track circuit and train control frequencies is entirely practical.
In the lower right of FIG. 2B, illustrated by conventional block,
are the oscillators for the high frequencies used for the track
circuits, different frequencies being used to obtain separation and
non-interference between the track circuits for adjacent pairs of
track sections. Any type of oscillator which will provide reliable
service may be used and the details are not part of our inventive
concept. The block is shown as providing four detector track
circuit high frequency outputs, designated as F3, F5, F9, and F11,
and a single train control or cab signal frequency output
designated as FC. The frequency of the output FC is the same not
only for all track sections within this stretch but for all
stretches of track for the overall assumed transit system in which
cab signal or speed control is provided. The intervening high
frequency outputs in the numerical succession will be used in other
stretches. Each such central oscillator unit may provide all
frequencies so that ready interchange of a single unit between
different stretches of track is possible. In one specific case, the
high frequency range for the detector track circuits was from 2.5
to 6.0 KHz. In the same installation, the cab signal or train
control frequency was selected at 990 Hz, in other words, on the
order of 1KHz.
The single, central code or modulation frequency source is shown by
a similar conventional block in the lower left of FIG. 2A. This
group of oscillators provides four outputs shown as being the code
frequencies CF1, CF2, CF3, and CF4, but additional code frequencies
may be used if additional instructions for speed control are
required. These are conventional oscillator circuits known in the
art, any of several types being useable which will provide a square
wave output at the selected code frequency. In the specific system
previously mentioned, the code frequencies were selected in the
range from 5.0 to 16.8 Hz. It is herein specifically assumed also
that code frequency CF1 designates a 50 mph allowable maximum
speed; frequency CF2, 25 mph; and frequency CF3, 15 mph. These
three speed limits are otherwise designated as high, approach, and
low speed limits. Code frequency CF4 is a special cutout signal
which, when received on board the train, locks out the speed
control equipment when a train departs from speed control territory
into a stretch of track in which cab signals and/or speed control
is not provided. Such lockout enables manual operation without
automatic emergency braking provision and the principle of such
lockout operation is known in the prior art. It is further obvious
that the specific high frequency, the train control frequency, and
the code frequency ranges given are examples only and not
limitations on the system embodying our invention.
There is one other item of central apparatus, the traffic direction
selection arrangement. Traffic direction is registered by the
traffic relay WFR for westbound traffic, and relay EFR for
eastbound traffic. These are biased relays, as indicated by the
arrow within the relay winding symbol, and are properly energized
to pick up and close front contacts only when current flows through
the relay winding in the direction of the arrow. The circuits for
these relays are basically controlled by a traffic controller
contactor FR which, as indicated by the note, is remotely
controlled by the dispatcher of the system and operated to its left
or right position for westbound or eastbound traffic direction,
respectively. Since westbound traffic is normal, the contact arms
of controller FR are normally in their left-hand position. The
block repeater relay BP, associated with this traffic direction
circuitry, releases to repeat the occupancy of any section of the
stretch of track. A circuit for controlling this relay will be
described later but basically the relay is picked up when there is
no train occupying any portion of the stretch of track
illustrated.
Under normal traffic conditions, a circuit for properly energizing
relay WFR extends from terminal B of the source over FR contact a
in its left-hand position, front contact a of relay BP, the
windings of relays WFR and EFR in series, front contact b of relay
BP, and FR contact b in its left position to terminal N. The
conventional flow of current in this circuit is obviously such to
properly energize relay WFR to close its front contacts while relay
EFR is energized by reverse current and thus its contacts remain
released. If reverse direction traffic is desired, controller FR,
by remote control, is placed in its right-hand position so that a
circuit may be traced from terminal B over FR contact b in its
righthand position, front contact b of relay BP, windings of relays
EFR and WFR in series, front contact a of relay BP, and FR contact
a in its right position to terminal N. This reverses the flow of
current in the traffic direction relay windings so that relay EFR
will pick up and relay WFR releases.
When relay BP releases to repeat the occupancy of the stretch by a
train, holding circuits are completed for maintaining the traffic
direction relays in their existing positions. For example, with
westbound traffic established, the release of relay BP completes a
circuit for holding relay WFR picked up which is traced from
terminal B over front contact a of relay WFR, back contact a of
relay EFR, back contact a of relay BP, the windings of relays WFR
and EFR, back contacts b of relays BP and EFR, and front contact b
of relay WFR to terminal N. Flow of current in this circuit
obviously holds relay WFR picked up. An equivalent circuit is
established if eastbound traffic is in existence when relay BP
releases, the easily traced circuit including back contacts a and b
of relay WFR and front contacts a and b of relay EFR to maintain
the proper flow of current to the winding of relay EFR. Other
contacts of relays WFR and EFR are shown elsewhere in the wayside
circuit drawings, each designated by the relay reference and a
lower case letter for a specific contact reference to distinguish
it from other contacts.
We are now ready to discuss the train detector track circuits and
the train control or cab signal energy circuits. At alternate bond
locations where track circuit energy is received for train
detection, two track circuit receiver units are coupled to the
rails, one receiver for the track section in each direction from
the junction location, the coupling being through the corresponding
crossbond and associated coupling unit. Each track receiver is
tuned to accept only coded track circuit energy of the frequency
being transmitted through the section with which it is associated.
Each receiver unit shown by conventional block includes a further
designation indicating the track circuit frequency to which it is
tuned. This tuning is broad enough to receive the basic track
circuit frequency modulated with any of the code frequencies in use
in the particular system. Such track receivers, in response to the
reception of track circuit energy, demodulate the energy, provide
various checks for the received energy, and energize the associated
track relay only when the coded energy is of the proper carrier
frequency. The details of these receiver units are not shown since
any conventional circuits for tuning, amplification, demodulation,
and detector arrangements may be used, preferably of course of
solid state or integrated circuit type. The associated track relays
are designated by the reference TR with a prefix in accordance with
the track section with which they are associated. Thus, at the
junction of sections 5T and 7T, at the right of FIG. 2A, are track
relays 5TR and 7TR associated respectively with track sections 5T
and 7T. It is to be noted that the track receivers at these
locations are tuned for the basic track frequencies F3 and F9,
respectively. Each track relay is energized by the associated
receiver and picked up when the corresponding track section is not
occupied by any part of a train. Conversely, the relay releases
when one or more wheel and axle units of a train occupy any part of
the corresponding track section.
Each crossbond location, that is, the location of each track
section division, is provided with a bank of apparatus to provide
track energy at the selected frequency and code rates provided by
the common oscillator devices previously discussed. Each set of
apparatus includes mixer and preamplifier sections and a final
power amplifier to provide energy of sufficient level for track
circuit operation. Each section or sub-unit incorporates
conventional solid state or integrated circuit elements to perform
the designated functions. Thus, each unit is shown by conventional
block since the circuit details are not part of our invention and
various specific circuit elements to provide the desired functions
may be used.
Each mixer unit receives an input at the train control or cab
signal frequency FC from the central oscillator. At alternate
locations, that is, where detector track circuit energy is to be
supplied, the mixer unit also receives a track circuit high
frequency input from the same central oscillator unit. Each mixer
unit also receives a code frequency input through a switching
portion of the preamplifier element which in turn receives the code
frequency from the code frequency central oscillator unit. The
coded input actuates the alternate connection of the detector track
circuit and cab signal frequencies to the mixer output at the
selected code frequency. The alternate mixer outputs occur only
when the corresponding energy connection to terminal B of the local
source is complete. For example, for the mixer element of the
apparatus associated with the junction between sections 3T and 5T,
a permanent connection from terminal B to the right side of the
mixer is provided for energizing the supply of track circuit energy
at frequency F3. However, the connection to the left side of the
mixer for the cab signal frequency energy is completed to terminal
B only when one of two circuit paths is complete. The first
includes front contact a of relay 3TR, front contact c of relay
WFR, and back contact b of relay 5TR. This circuit is obviously
complete when westbound traffic direction is established, section
3T is not occupied, and section 5T is occupied by a train. A second
path includes back contact a of relay 3TR, front contact c of relay
EFR, and front contact b of relay 5TR. This circuit path is active
when eastbound traffic direction is established, section 5T is
unoccupied, and a train first occupies section 3T.
At locations where detector track circuit energy is supplied, such
as that just described, the corresponding mixer connection to
terminal B is continuous. Where no detector track circuit energy is
supplied, there is no such connection from the mixer element to
terminal B nor to any HF terminal of the central oscillator unit.
In such cases, although the alternate connections are made during
the code frequency application, obviously no detector track circuit
energy output from the mixer occurs, only the cab signal energy
output portion being active. The output of the mixer section at
whatever frequency and modulation, is supplied directly to and
amplified in the preamplifier section to a level to properly drive
the power amplifier portion. This power amplifier section further
increases the signal energy to drive the detector track circuit and
to also provide a sufficient level of track energy for cab signal
receiver inductive pickup.
It will be noted, of course, that the same detector track circuit
frequency is used for a pair of adjoining track sections, one each
way from each track circuit supply location. However, a different
frequency is used in the next pair in each direction and the shift
is not in the successive order supplied by the track current
oscillators but is variable. Such random selection assures that
there will be no interference between adjacent center fed track
circuits. As previously mentioned, the same cab signal frequency is
used or supplied at each crossbond location in order to simplify
the tuning and operation of the train-carried receiver elements.
The code or modulation frequency is selected in accordance with the
established traffic direction and the advance track section
occupancy conditions. For a reverse traffic move, that is, in the
eastbound direction, a single speed is fixed so that code frequency
CF2 is always selected over a front contact of relay EFR when such
traffic direction is established. For example, for the previously
discussed apparatus supplying energy to the crossbond at the
junction between sections 3T and 5T, the code frequency input to
the preamplifier, and thus to the mixer element, over front contact
d of relay EFR is from terminal CF2 of the code frequency
oscillator. It will be noted, however, that this modulated cab
signal energy at this code rate will not be supplied to section 3T
for an eastbound move unless the power energy connection for the
mixer element to terminal B is completed over front contact b of
relay 5TR to assure that section 5T is not occupied by a train. Cab
signal energy is also supplied only after the approaching eastbound
train occupies section 3T, causing the release of relay 3TR to
close its back contact a.
For westbound traffic, random traffic and/or hazard oriented speed
selection is normally used in establishing the code frequency of
the cab signal energy in the rails. However, near station
locations, fixed maximum speed limits for westbound traffic are
also used similar to the fixed limit for eastbound traffic. For
example, for section 3T, the cab signal energy applied at the exit
end of the section, the far left crossbond shown, is modulated at
the fixed code frequency CF3 selected over front contact e of relay
WFR for application to the preamplifier section. This provides the
low speed limit, sufficient to start a train from the station
location shown within section 3T. Nevertheless, this train is not
permitted to leave the station, that is, section 3T, if advance
section 1T is occupied by a preceding train. This check is assured
by applying cab signal energy from terminal B to the mixer element
over a connection including back contact b of relay 3TR, which is
released with the train occupying the station area, front contact f
of relay WFR, and front contact a of relay 1TR. Obviously, if
section 1T is occupied, front contact a of relay 1TR will be open
to interrupt the supply of energy from terminal B to the mixer
element. However, if front contact a of relay 1TR is closed, then
cab signal energy at frequency FC and modulated at code frequency
CF3 is applied from the mixer unit through the preamplifier and
power amplifier elements to track section 3T, the connections to
the crossbond at the exit end of the section being as usual through
a coupling unit. The westbound speed limit for section 5T is also
fixed at the low speed, code frequency terminal CF3 being selected
for application of coded energy to the preamplifier unit over front
contact d of relay WFR. Again, the connection to terminal B for the
associated mixer element is checked over front contact a of relay
3TR so that a train in section 5T is forced to stop if section 3T
is also occupied.
Since the westbound speed limit for section 7T is fixed at the
approach speed, a single connection from the preamplifier unit to
terminal CF2 is sufficient, there being no selection necessary over
contacts of the traffic relays since eastbound traffic in section
5T is also limited to this approach speed. However, the connection
to terminal B for the mixer element of the associated units at this
location, in order to generate a modulated cab signal energy, is
checked over front contact a of relay 5TR for westbound traffic and
over front contact b of relay 7TR for eastbound traffic so that
west and eastbound traffic in sections 7T and 5T do not receive any
cab signal energy if the advance track section for that traffic
direction is already occupied. This connection to terminal B for
the mixer element at this location over the multiple paths,
depending upon the established traffic direction, is similar to
that already discussed for the energy supply units at the junction
of sections 3T and 5T. In fact, the mixer element at each location
is connected to terminal B, to supply a modulated cab signal
current, over a similar type circuit network. Obviously, such
connections serve for either direction of traffic to apply a cab
signal energy only upon the entry of a train into the section to
which cab signal energy is being supplied.
At the junction between sections 7T and 9T, code frequency CF2 is
selected over front contact g of relay EFR for modulating the cab
signal energy applied to section 7T for reverse moves. However, the
cab signal energy for section 9T for westbound traffic selects
between code frequency CF1 and CF2. As usual, the connection to
terminal B for the mixer element, which generates the cab signal
energy at frequency FC and modulated at a selected code rate, is
checked over front contact a of relay 7TR to assure that the
immediately preceding advance track section is not occupied by a
train. Obviously, no energy at frequency FC is applied into section
9T if this front contact is open indicating occupancy of section 7T
by a train. However, if section 7T is clear, further selection
between code frequencies CF2 and CF1 is made in accordance with the
occupancy condition of section 5T. This selection circuit, tracing
from the preamplifier unit, includes front contact g of relay WFR,
closed for the usual westbound traffic condition, and thence over
the interdrawing connection line 21. Terminal CF1 or CF2 is
selected, respectively, as front or back contact d of relay 5TR is
closed to indicate no occupancy or occupancy of section 5T. Thus, a
train entering section 9T will receive a high or approach speed cab
signal indication depending upon the occupancy condition of section
5T if section 7T is checked clear.
Similar code frequency selections are made for the cab signal
energy applied to sections 11T and 13T for westbound moves. The
code frequency selection for the preamplifier unit at the junction
between sections 9T and 11T, when westbound traffic is established
and thus front contact h of relay WFR is closed, is made, tracing
over interdrawing connector 25, by contact d of relay 7TR, this
being the track relay for the second section in advance of section
11T. If the section is clear, front contact d of relay 7TR selects
code frequency CF1, but if the section is occupied, back contact d
selects code frequency CF2. Of course, the application of any cab
signal energy is dependent upon front contact a of relay 9TR being
closed. For section 13T, assuming that front contact a of relay
11TR is closed to indicate no occupancy of the immediate preceding
advance section, code frequency selection for the preamplifier unit
is made over front contact i of relay WFR and thence over front
contact d of relay 9TR to apply a code frequency CF1, or if section
9T is occupied, over back contact d of relay 9TR to select a code
frequency CF2.
Although each track section T illustrated in FIGS. 2A and 2B
appears of relatively equal length, actually the track sections
closer to the station location in section 3T are of shorter length
so that the lower maximum speed limit does not adversely affect the
average speed for train operation throughout the entire system.
These shorter track section lengths are practical since the lower
maximum speed allowed permits shorter train stopping distances if
emergency braking is necessary. It is obvious too that the specific
speed selections for the various sections for westbound moves and
the single speed selection for eastbound moves illustrated herein
are by way of example only. Actual installations embodying our
invention are not limited to such specific speed selections but cab
signal application of allowable speed limits will be in accordance
with the characteristics and requirements of any particular
installation.
It is to be noted that the circuit network for connecting terminal
B of the energy supply to the cab signal energy side of the mixer
element at the junction between sections 11T and 13T includes front
and back contacts b of track relay 13TR. The winding for this relay
is not shown since it would be located at the central housing for
the next track stretch to the right of drawing FIG. 2B. Such a
track relay would be controlled by supply of track circuit
frequency F5 energy to the rails of section 13T through the
coupling unit and crossbond connections at the junction between
sections 11T and 13T. It may be noted also at this point that the
circuit for block repeater relay BP, previously mentioned,
includes, in series, front contacts c of each track relay TR for
the stretch of track shown, including front contacts of relays 1TR
and 13TR. Obviously release of this relay repeats the occupancy of
any track section within the stretch shown as well as the occupancy
of section 13T. As previously described, the release of relay BP
completes circuits for holding the FR relays in their existing
traffic condition during the time that the stretch is occupied by a
train moving in either direction.
Although not a specific part of the system of our invention, the
relation of an automatic station stop control operation to our
system is illustrated. In section 7T, a predetermined distance in
approach to the station platform located within section 3T, a
wayside coil or loop is positioned to provide a first stop control
signal to a westbound train. This signal actuates the apparatus
such as included in the bottom apparatus block of FIG. 1. As
previously explained, the reception of this station stop signal by
a special pickup coil on the train actuates the station stop
program preset into the train apparatus. It may be noted that the
maximum allowable train speed in section 7T for westbound trains is
the approach speed, as established by the use of code frequency CF2
to modulate the cab signal energy. This assists in developing a
proper station stop since the train will be slowing from a maximum
or high speed level. A second coil or loop in section 5T, at a
second predetermined distance in approach to the station, provides
a second signal to correct the station stop program to allow for
slight variances in train response. One specific form of such
wayside loops and stop program apparatus is disclosed in Letters
Patent of the U.S. Pat. No. 3,493,741, issued February 3, 1970, to
J. W. Lubich, for an Object Stopping System. Another form of such
station stop apparatus which may be used with the system of our
invention is disclosed in the copending application for Letters
Patent of the United States, Ser. No. 166,033, filed Feb. 17, 1971,
by R. H. Grundy and D. R. Little, for Station Stop Control
Arrangement for Self-Propelled Vehicles, now U.S. Pat. No.
3,731,088, issued May 1, 1973, the present application having the
same assignee. The final loop at the end of the station platform in
section 3T provides a door opening control signal, received on the
train by the same extra pickup coil when the train arrives and
stops over the loop. It is to be also noted that, to assist in the
station stopping, the maximum allowable speed in sections 5T and 3T
is the low speed provided by modulating the cab signal energy at
code frequency CF3.
We shall turn now to the basic train-carried apparatus, as
specifically shown in FIG. 3, which cooperates with the wayside
apparatus embodying our invention. The cab signal or speed control
energy from the rails is picked up by a selected set of
train-carried coils, two pairs of which are shown in the upper left
of FIG. 3. This provides for either direction opertion of the
train. However, most of the apparatus on the train is provided
single unit only, that is, is not duplicated, and serves for either
direction operation of the train. Although only one cab signal
panel appears in the upper right within the dot-dash rectangle,
actually one such indication panel will be provided at each
operator's position and the lamps and alarm apparatus connected in
parallel. Also, the single bypass controller switch, shown at the
left center, may be duplicated at each operator's location, if so
desired. In order to select a direction of operation and actuate
the proper receiver coils, a train selection detector, shown at the
left of the drawing, is placed in the desired position to select
the A or B end of the train as the leading end for operation. Such
a selector switch may take any one of several forms, but for
convenience a lever having a single arm or contactor is
illustrated. Relay AF or BF is energized by an obvious circuit in
accordance with the selection of the A or B end of the train by the
lever arm. For the remainder of the description, we shall assume
that the A end of the train has been selected in accordance with
the lever position specifically shown and the A forward relay AF is
picked up.
The receiver coils, actually the pair at each end but here the pair
at the A end specifically, are so mounted as to be in inductive
relation or coupled to the rails. Thus the coils pick up
inductively the cab signal energy flowing in the rails modulated by
a code frequency selected in accordance with the traffic in advance
or as specifically selected by the location along the track. The
signal produced in these coils is applied over front contact a of
relay AF to a tuned amplifier, demodulator unit shown by a
conventional block. The details of the circuitry within this
amplifier demodulator unit are not shown since they are not
specifically part of our invention and conventional and known
circuitry, preferably of solid state or integrated circuit type,
may be used to detect, amplify, and demodulate the cab signal
frequency energy. It may be noted that the tuned amplifier will
receive and detect only energy at the cab signal frequency CF and
demodulates the received energy to produce a code frequency output
in accordance with the modulation frequency of the received
energy.
The output from the demodulator element, which will be one of the
four code frequency signals discussed in connection with the
wayside apparatus, is applied to the bank of active filter units.
These units are so tuned, one for each code frequency signal, that
they pass only that signal. Conventional circuitry may be used for
these active filter units and thus is not shown in detail, each
conventional block being marked to designate the frequency which it
will pass, that is, CF1 to CF4. The output from each filter, when
present, energizes an associated allowed speed registry relay S,
or, for filter CF4, a No Control relay NC used for cutout purposes,
to be described later. The allowed speed registry relays may be
specifically defined as the high speed relay HS, the approach speed
relay AS, and the low speed relay LS, associated respectively with
filters CF1, CF2, and CF3. The first three filter outputs also
actuate associated vital solid state switches, shown conventionally
in a bank at the bottom with the control being conventionally
indicated by the heavy dashed line connecting the two banks of
apparatus. When an output exists from a particular filter, the
correspondingly designated solid state switch provides a completed
circuit to pass an input from its left to the output at its right.
Since only a single filter is active to provide an output at any
one time, only the single corresponding solid state switch is
activated at the same time. If there is no output from any of the
filters CF1, CF2, or CF3, the No CF switch is actuated.
Whenever one of the speed relays is energized and picked up, the
corresponding allowed speed indication lamp in the cab signal panel
is also illuminated. This, of course, occurs only one lamp at a
time since only the one speed relay is properly energized at any
one time. The lamp circuits include a common portion beginning from
terminal B at back contact a of the alarm indication relay AK and
extending over front contact a of overspeed relay OS, thence, if
relay LS is picked up, over its front contact a and through the
filament of lamp L to terminal N. If relay AS is picked up instead,
the circuit extends over back contact a of relay LS and front
contact a of relay AS through the filament of lamp A to terminal N.
Likewise, the circuit for lamp H includes, in addition to the
common portion, back contacts a of relays LS and AS and front
contact a of relay HS. If all three speed relays are released, the
series circuit extends over back contact a of each of these relays
through the filament of lamp R to terminal N. Lamp R is a
restricted speed indication which requires that the train be
brought to a stop and then proceed at a restricted speed which is
less than the allowable low speed. Since it was previously
established that speeds of 50, 25, and 15 may be specifically
assigned to the high, approach, and low ranges, the restricted
speed would be on the order of 10 to 12 mph so that the train could
be readily stopped short of an obstruction. As will become evident
shortly from a further description, the stop and proceed action
will be enforced by the automatic overspeed and emergency apparatus
also provided.
An alternate source of energy for lamp illumination which exists at
times extends from the multiple connection to terminal B over front
contacts b of relays AF and BF, one of which is closed, and thence
over back contact a of cutout relay CO and through a flasher unit
to contact a of relay LS. This circuit becomes effective any time
that relay AK picks up or overspeed relay OS releases and causes a
flashing indication at a preset rate to appear in the cab signal
panel to call the operator's attention to the changed condition or
emergency warning.
The circuit for initially energizing No Control relay NC extends
from the output of filter CF4 over back contact a and the winding
of relay NC, and thence over back contacts b, in series, of relays
LS, AS, and HS to terminal N. When filter CF4 is active, producing
an output, relay NC thus picks up and completes a stick circuit
over its own front contact a which includes back contacts b of the
speed relays and bypasses the filter output. The closing of front
contact b of relay NC completes an obvious circuit for the winding
of relay CO which then picks up and holds as long as relay NC
remains energized. Under these conditions, a circuit for
illuminating lamp W exists from terminal B at front contact b of
either relay AF or relay BF over front contact c of relay NC and
through the filament of lamp W to terminal N. As was previously
described, code frequency CF4 is used when the train is to leave
the speed control area and enter territory in which no cab signals
or speed control is provided. Lamp W thus indicates to the operator
that he is to control his train in accordance with wayside
indications only or special train orders depending upon the
circumstances. Obviously, as soon as the train reenters a
controlled territory, the energization of any one of the speed
relays to open its back contact b deenergizes relay NC which
releases. This also releases relay CO and restores the various
control circuits and operation of the apparatus.
The remaining device on the cab signal panel is an alarm bell or
buzzer which is energized under alarm conditions by a circuit
including front contact a of relay AK. As will become apparent
shortly, this alarm device is actuated or energized for a preset
time period only sufficient to allow the operator to react to a
signal change or emergency condition otherwise existing. All of the
apparatus in the cab signal panel is provided to give the operator
information under manual operating conditions as to the allowed
speed and the established condition of operation by the
illumination of one of the lamps. In addition, the speed relays
establish a condition, that is, a preset maximum speed limit which
the overspeed portion of the train-carried apparatus must meet, as
will now be described.
To monitor the actual speed and actuate the overspeed detection
apparatus, a magnetic or electromagnetic pickup device is
positioned near the main driving gear for the train propulsion
equipment, as shown in the lower left of FIG. 3. This magnetic
pickup device produces an output, the frequency of which is
proportional to train speed. A shaper-limiter unit of any
conventional circuit design receives this frequency signal and
produces an output of proper wave shape and amplitude to apply to
the low pass filter bank. The output of each low pass filter is fed
to an associated allowed speed solid state switch. Each such switch
has a low resistance only when the corresponding allowed speed
signal is being received by the cab signal apparatus. In other
words, the circuit path through a particular solid state switch,
e.g., a silicon controlled rectifier, is completed when the
designated code frequency CF is modulating the received cab signal
energy of frequency FC. As previously described, if the CF1 signal
is modulating the received cab signal energy, the CF1 filter is
active to pass the demodulator output and solid state switch CF1 is
actuated. When any specific low pass filter passes the output of
the shaper-limiter unit, other higher speed LP filters also pass
this input signal. Thus if the train is moving at the approach
speed but the allowed speed is at the high range, i.e., signal CF1
received, solid state switch CF1 is actuated to pass the output of
the high speed LP filter which also passes the approach speed
frequency signal.
When any one of the speed relays is picked up to close its front
contact c, a path is complete through the circuit network to apply
any output of the solid state switches, connected in multiple, over
front contact b of the automatic braking relay AB to the level
detector unit and thence to the winding of relay OS. The level
detector, which is designed as a vital circuit unit, will deliver a
direct current voltage to overspeed relay OS as long as the input
is of sufficient magnitude. Each low pass filter is designed to
have a sharp cutoff of output voltage at the maximum allowable
speed corresponding to its speed assignment. In other words, at the
maximum allowable speed for the high speed filter, assumed to be 50
mph, the output of the low pass filter will decrease, if this speed
limit is exceeded, to just below the detection point of the level
detector and thus would deenergize the overspeed relay. Thus, when
the input to the level detector is of sufficient magnitude, it
indicates that the vehicle or train is moving at less than the
maximum allowable speed. Of course, the output from the high speed
low pass filter will be applied to the level detector only if a
corresponding cab signal or speed signal indication is being
received so that filter CF1 is active and thus has actuated solid
state switch CF1 as well. Each of the low pass filter units
operates in a similar manner but with the output decreasing when
the corresponding speed is exceeded. Thus relay OS will be held
energized by the output of the level detector as long as the train
speed remains at or below that of the low pass filter whose output
is applied to the level detector because the corresponding solid
state switch is actuated by the reception of the corresponding
speed signal by the cab signal apparatus.
When the vehicle is stopped there is, of course, no output from the
magnetic pickup which would normally cause relay OS to be
deenergized, thus locking the brakes. In order to prevent a lockout
condition when the train is ready to start again, a zero velocity
(V=O) detector unit is provided. When the train is stopped, this
detector checks the integrity of the pickup circuit and produces a
sufficient output which may be passed through the filter bank to
the vital level detector to keep the overspeed relay OS energized.
When there is any train motion, the V=O detector stops oscillating
and the circuitry acts on the output of the magnetic pickup, as
already explained. If desired, a second output from the
shaper-limiter unit may be differentiated and averaged to provide a
direct current proportional to the speed which would then be used
to actuate a speedometer to advise the train operator of his actual
speed. This is not shown in FIG. 3 since such is conventional
practice. The V=O detector apparatus is shown by a conventional
block since such elements are known in the art and need not be
shown in detail. An output from this detector also energizes the
velocity zero relay VZ during the time that the train is
stopped.
Various other relays and apparatus are also associated with this
overspeed control arrangement. An automatic braking relay AB,
already mentioned, is normally held energized by a simple circuit
including front contact b of relay OS. Relay AB has a stick circuit
which includes its own front contact a and either front contact a
of brake assurance relay BA or front contact a of relay VZ. Relay
AB is provided with a capacitor-resistance shunt of its winding to
produce a selected period of slow release, for example, on the
order of 2.5 seconds, for purposes of allowing reaction time for
the train operator. This slow release characteristic is further
designated by the conventional downward pointing arrows drawn
through the relay contact armatures to denote the slow acting
direction.
The brake assurance relay BA is controlled by a deceleration
detector, shown at the left of the drawing, which detects
deceleration of the train to close its left or right normally open
contact, depending upon the direction of movement, and thus
complete a connection from terminal B through that contact. With
the train operating with A end forward, deceleration will cause the
left contact of the deceleration detector to close and complete a
circuit including front contact c of relay AF to energize the
winding of relay BA, which then picks up. Front contact c of relay
BF is included in the circuit for energizing relay BA if the
opposite direction of movement is in effect. Front contact a of
relay BA, when closed, completes a stick circuit already traced for
relay AB. Front contact b of relay BA, upon closing, completes a
stick circuit for the emergency relay EM which includes also front
contact a and the winding of this latter relay. Relay EM is
normally held energized by a simple circuit including front contact
c of relay OS. An alternate circuit for holding relay EM energized
under speed control cutout conditions includes front contact b of
relay CO. Relay EM is provided with a capacitor-resistor snub of
its winding to establish a slow release period slightly longer than
that of relay AB, e.g., on the order of 4.0 seconds.
A time element relay TE is energized upon the expiration of a
preselected delay period after the closing of front contact b of
relay VZ. Various types of pickup and delay elements may be used to
delay the pickup of relay TE and thus only a conventional block is
shown. In a specific example, the time delay may be on the order of
10 seconds before relay TE picks up after the energization of the
delay element. Of course, if desired, the delay period may be
incorporated within the winding and mechanism of relay TE
itself.
A restricted speed relay TS is provided to enforce the stop and
proceed action when a restricted signal is received by the cab
signal apparatus, that is, a lack of any code frequency modulation
occurs and lamp R is illuminated. Relay RS is normally deenergized
and is energized by a pickup circuit including back contacts d, in
series, of each of the speed relays S, front contact c of relay AB,
front contact c of relay VZ, and the winding of relay RS. When
relay RS picks up, it closes its own front contact a to complete a
stick circuit which bypasses fron contact c of relay VZ.
Relay AK is energized for a predetermined time interval each time
an existing allowed speed or cab signal is replaced by a lower
allowed speed limit. This relay is also energized for the same
predetermined period if relay AB or OS releases. The predetermined
interval of energization is preset to be the same as the release
time of relay AB. This allows the operator to judge his reaction
time to actuate the braking of a train upon a lower speed signal
occurrence. Various means of providing the predetermined energizing
period are available in the art so that only a conventional block
is shown with an explanatory note as to its operation. Energy is
supplied to this block over several multiple circuits. Two of these
circuits include, respectively, back contact d of relay AB and back
contact b of relay OS so that the release of either one of these
relays will apply energy to the timing unit to energize relay AK
for the preset interval. Energy is also supplied to the timing
block over a matrix of contacts of the speed relays S which
complete a circuit path under the cited conditions. In other words,
a circuit path through the matrix of contacts of the S relays will
exist to apply energy when a particular S relay releases, and a
lower speed relay S picks up, or no S relay is energized. If
energization of a particular S relay is replaced by the
energization of a higher speed S relay, no circuit path will exist
from terminal B to the timing unit for relay AK. The normal release
time of the S relays is sufficient to assure that the next relay,
corresponding to either a higher or lower speed, will pick up prior
to the release of the deenergized relay. Other means or methods of
supplying energy to the timing unit for relay AK, when the speed
limit changes, may be used and our system is not limited to the use
of a circuit matrix including contacts of the S relays which is
used here to illustrate the operation only.
We shall now describe the operation of the train-carried apparatus
in performing its speed control functions. It is assumed that the
train is moving with the A end in the lead, as previously set, and
that cab signal energy is being received modulated by code
frequency CF2. Thus a 25 mph maximum speed limit is in effect with
relay AS energized. Lamp A in the cab signal panel is illuminated
and, for this description, it is assumed that the train is under
manual operation by the operator on board on the driving control
position. Relay OS is energized as long as the train remains at or
below the 25 mph speed, energy being provided in response to the
magnetic pickup signal by the shaper-limiter through the approach
speed low pass filter and solid state switch CF2 and the circuit
network through the level detector and the relay winding. If the
train exceeds 25 mph, plus whatever tolerance is permitted, the
output cutoff characterisitic of the approach speed low pass filter
reduces the energy being applied to the level detector to the point
where relay OS releases. The opening of front contact b of relay OS
deenergizes relay AB but this relay is provided with a
preestablished slow release period so that it holds its front
contacts closed for the present. Relay AK, however, is picked up
since the closing of back contact b of relay OS applies energy to
the timing unit and the alarm device on the cab signal panel is
actuated to indicate to the operator that an overspeed condition
exists. It will be noticed also that the common portion of the lamp
circuit providing steady illumination is interrupted, both at back
contact a of relay AK and front contact a of relay OS, so that the
alternate circuit including the flasher unit is effective and lamp
A begins to flash to also call the attention of the operator to the
overspeed condition.
If the operator applies the brakes within his allowed reaction
time, the deceleration detector will close its left contact in
response to train deceleration, energizing relay BA. The closing of
front contact a of relay BA completes a stick circuit for relay AB
which thus is retained energized. When the train slows to the
allowed speed limit, plus or minus the tolerance, relay OS will
again be energized and pick up so that the operator may release the
brakes and continue the movement of the train with or without power
application as is appropriate. It will be noted that, since front
contact b of relay AB remains closed, the full output of the low
pass filter, in this case the approach speed filter, is applied to
the level detector as the train speed is reduced below the allowed
speed limit.
If the operator does not respond in time to establish a braking
condition within the release time of relay AB, this relay releases
and opens its front contact d to initiate an automatic service
brake application. The control apparatus for this automatic brake
application is illustrated by a conventional block at the left of
FIG. 3. The specific apparatus may be of any known type and will
vary in accordance with the specific requirements of the train
braking apparatus installed. All that is necessary to understand
the operation of our system is that removal of energy from either
input connection to this apparatus block actuates a brake
application of the type corresponding to that noted for each lead.
When relay AB releases, the opening of its front contact b removes
the shunt on the level detector resistor LDR which is now in series
with the level detector and attenuates the signal applied thereto.
This forces the train, under the automatic brake application, to
slow down to some preselected point below the actual speed limit,
for example, to 20 mph, before the output from the low pass filter
is of sufficient level to provide energy to the level detector for
reenergizing relay OS. Thus, a penalty of additional speed
reduction is imposed if the train operator does not initiate the
braking action in time when an overspeed condition occurs.
The automatic brake application, of course, causes a deceleration
which is detected to energize relay BA. The closing of front
contact b of relay BA will retain relay EM energized since this
relay has a longer slow release period than does relay AB. However,
relay AB will be reenergized only when relay OS, being reenergized,
picks up to close its front contact b. It is also to be noted that
relay AK releases at the end of the preset energized period, thus
deenergizing the alarm. However, the flashing indication on the cab
signal panel will continue until relay OS again picks up. A similar
action will occur when a lower speed signal is received unless the
operator reacts within the release time of relay AB to initiate a
braking application to reduce the train speed to the new lower
speed limit. For example, if the received code frequency changes
from CF2 to CF3 so that relay AS releases and relay LS picks up,
the speed of the train must be reduced below the 15 mph low speed
limit before sufficient energy is passed by the low speed low pass
filter through solid state switch CF3 to energize relay OS.
However, an immediate braking action retains relay AB energized as
previously described.
If the service brakes fail, either during a manual or an automatic
application, the brake assuring circuitry will cause an emergency
brake application. When relay OS releases, the opening of its front
contact c interrupts the circuit for normally energizing relay EM.
As previously indicated, this relay has a slow release period
established by the resistor-capacitor winding shunt which is
somewhat longer than the release time of relay AB. If a suitable
braking rate is not established within this release time of relay
EM, so that relay BA picks up to close its front contact b and
retain relay EM energized by its stick circuit, relay EM releases.
The opening of its front contact b interrupts the application of
energy to the emergency input connection of the automatic brake
apparatus which initiates an emergency braking condition. It is
evident that, once released, relay EM cannot be reenergized until
the train speed is reduced to a safe level so that relay OS
reenergizes, perhaps with the train at a stop. If a cutout
condition is effected, relay CO is energized and closes its front
contact b to hold or reenergize relay EM.
The stop and proceed at restricted speed command is initiated
whenever a train enters a section with no cab signal energy.
Regardless of the entering speed, relay OS will deenergized because
all the S relays release so that the open front contacts c of these
relays interrupt all circuit paths to the level detector. This is
true since front contact a of relay TE and front contact b of relay
RS are also open at this time so that no circuit path exists over
back contacts c of the S relays between the solid state switch
output bus and the level detector. The alarm is sounded, while
relay AK is energized, and lamp R flashes. If the operator
initiates braking action in sufficient time, relay BA will energize
and close its front contact a to retain relay AB energized over its
stick circuit. When the train stops, relay VZ will be energized to
complete the energizing circuit for relay RS which includes back
contacts d, in series, of the S relays, front contact c of relay
AB, and front contact c of relay VZ. Relay RS picks up and
completes its stick circuit which bypasses contact c of relay VZ.
With front contact b of relay RS now closed, a circuit exists,
including back contacts c of the S relays, by which energy from the
V=0 detector may be applied through the filters and solid state
switches to the input of the level detector and thus reenergize
relay OS. This permits the train to immediately proceed at
restricted speed, the operator being so informed by the steady
illumination of lamp R in his cab signal panel.
However, if the operator does not initiate the braking action under
these conditions in sufficient time, relay AB will release at the
end of its slow release period, initiating an automatic brake
application which continues until the train stops. Now, however,
with front contact c of relay AB open, there is no circuit for
energizing relay RS when relay VZ picks up and closes its front
contact c. The closing of front contact b of relay VZ at this time
initiates the pickup delay period for relay TE which, as previously
mentioned, in one particular situation is a time of 10 seconds.
This time compares with the situation previously discussed with
release times for relay AB being 2.5 seconds and for relay EM 4.0
seconds. When relay TE picks up at the end of this delay period,
the closing of its front contact a completes another circuit
including back contacts c of the three S relays to apply the energy
developed by the V=0 detector to the input of the level detector to
reenergize relay OS. Thus, if a stop and proceed action occurs with
an automatic brake application, the penalty of the pickup time
delay for relay TE, for example, the 10 seconds, is enforced before
the train can again proceed. This extra delay encourages prompt
response on the part of the train operator.
As previously described, in the last track section before leaving
cab signal or speed control territory, cab signal energy is
modulated by code frequency CF4. The reception of this energy and
its demodulation energizes relay NC which picks up and sticks up,
the circuit including in series back contacts b of all the S
relays. Relay CO is then energized over front contact b of relay NC
and in turn holds relay EM energized over front contact b of relay
CO. This in effect cuts out the overspeed protection and the alarm
and cab signal indication circuits are all open. However, the
wayside indication lamp W is illuminated over front contact c of
relay NC, and the operator controls the train in accordance with
wayside signals and/or train orders.
If the cab signal and speed control apparatus on the train fails,
resulting in an emergency application of the brakes, a restoration
of the train to manual operation without speed control is provided
by a sealed bypass switch. An example of such bypass control is
shown at the left center of FIG. 3. The illustration is that of a
stick type pushbutton with normally open contacts. If such an
emergency stops occurs and the apparatus is nonfunctional, the
breaking of the seal and the operation of the pushbutton to close
its normally open contacts, which then remain closed until the
controller is manually returned to its normal condition, will
complete a circuit, under the present conditions, over the lower
contact of the bypass controller, front contact d of relay AF, and
back contact b of relay NC to the winding of relay CO. Relay CO is
thus energized and held in this condition and the closing of its
front contact b reenergizes relay EM. Again, the alarm and cab
signal indication circuits are interrupted and the overspeed
protection is removed, but the train may be operated under
published rules for such conditions to proceed to the nearest
station.
The system of our invention thus provides an efficient and
economical speed control arrangement for trains. Apparatus is
compatible with manual operation with simple overspeed protection
and with increasingly sophisticated systems up to and including
full automatic train operation with its station stop and door
control options. The wayside apparatus is effective to detect the
presence of trains and provide cab signal and speed control signals
to the trains themselves. No insulated joints are required in the
rails to separate the various track sections used for train
detection. All the apparatus for each distinct stretch of railroad
track may be centrallized for efficient maintenance and economical
housing and protection. Thus, a fail-safe, efficient, and
economical system of train speed control is provided.
Although we have herein shown and described but one form of train
speed control apparatus embodying our invention, it is to be
understood that various changes and modifications may be made
therein within the scope of the appended claims without departing
from the spirit and scope of our invention.
* * * * *