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Патент USA US2135527

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NOV. 8, 1938. I
w‘ T, PQWELL
I
2,135,527
RAILWAY TRACK CIRCUIT
Original Filed July 28, 1934
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ATTORNEY
BY
_
Patented Nov. 8, 1938 _
2,135,527
UNITED STATES PATENT OFFICE
2,135,527
RAILWAY TRACK CIRCUIT
Winfred T. Powell, Brighton, N. Y., assignor to
General Railway Signal Company, Rochester,
N. Y.
Original application July 28, 1934, Serial No.
737,433, now Patent No. 2,083,920, dated June
15, 1937. Divided and this application Decem
ber 3, 1936, Serial No. 114,089
12 Claims.
This invention relates in general to track cir
cuits such as used in railway signalling prac
tice and it has more particular reference to
means for maintaining current through a track
5 relay associated with a stretch of railway track
substantially constant, regardless of changes in
' ballast leakage between the rails of the track
due to Weather conditions.
.
The invention also relates to means for au
10 tomatically
discriminating
between
current
changes in the track circuit due to the occupied
between the rails increases and the terminal
voltage at the usual track relay decreases. The
relay current will vary over a considerable range
and cover a range at times which may prevent
proper response of the relay under occupied or
unoccupied conditions of the track section.
It is therefore proposed in accordance with
this invention to provide means automatically
operable to permit a change in current in the
track relay eifected by the entrance of a train 10
into the associated track section, but to auto
condition of the track and due to leakage cur
matically maintain a substantially constant cur
rents resulting from poor ballast conditions.
rent in the track relay regardless of changes in
Values of leakage current through the ballast
This application is a division of my prior ap
15 plication Ser. No. 737,433 ?led July 28, 1934, now
,U. S. Letters Patent 2,083,920 dated June 15,
1937.
'
In railway operation it is quite essential that
the usual track relay connected across the track
20 section at one end of a signalling block be suf
?ciently energized when the block is unoccupied
to pick up and hold up with certainty. It is
likewise essential that the occupancy of the track
section will so effectively shunt or condition the
25 relay that it will be positively released. For ex
ample, in the usual track circuits if the normal
holding current is too high shunting may not
be effective to drop the relay and if the normal
holding current is so low that shunting is made
30 more positive then it is possible that at times
the holding current will be insu?‘icient.
Taking the above into consideration it will be
apparent that the usual variation in ballast re
sistance encountered in practice, due primarily
35 to vchanges in weather conditions, may interfere
with the proper operation of the track relay un
from one rail to the other.
It is further proposed to improve the shunt
ing ei?ciency of the track circuit and for this
sume.
,
The single ?gure illustrates one form of the
present invention in a diagrammatic and con 30
ventional manner.
'
Apparatus.---Referring to the single ?gure, a
section of railway track including rails I is
shown separated from‘ the adjacent track sec
tions by insulated joints 2. A track battery BT 35
the shunting of the relay due to track occu
pancy.
form of a Wheatstone bridge.
the current ordinarily shunted away from the
track relay by extreme ballast leakage, or for
40 discriminating between changes due to ballast
resistance and track occupancy. The present
arrangement is proposed as a means for regu?
lating the potential applied to the holding wind
ing or‘ windings of a track relay under various
45 ballast conditions and also for discriminating
between slow changes in the shunting of the re
lay due to ballast changes and rapid changes in
15
purpose a discriminating arrangement is in
cluded in the circuit of the track relay which
discriminates between a slow change in track 20
shunt due to track ballast and a rapid change in
track shunt due to train occupancy.
Further objects, purposes and characteristic
features of the invention will appear as the de
scription progresses, reference being made to the
accompanying drawing which shows by way of
example one form which the invention may as
and a track relay T are shown connected to the
track rails at opposite ends of the illustrated
section.
As typical of the control exercised by the track
relay, a semaphore signal SG is illustrated at the
left end of the track section and in the present
description it will be assumed that tra?ic moves
from left to right over this section as indicated
by the arrow appearing above the track rails.
The track relay and the track rails are con
nected to the track battery through the medium
of an electrical network comprising various re
sistors, relays and impedance coils laid out in the
less some means are provided to compensate for
50
(01. 246-41)
Normal conditions.-Referring to the drawing
resistance results .in a decrease in the leakage it will be assumed that the ballast is in a dry
current between the rails so that the voltage condition so that there is approximately no leak
across the terminals of a track relay connected
age current flowing between the rails l of the
‘across these rails increases. Conversely, as the track section. Under this condition relay T is
It will be obvious that an increase in ballast
55 vballast resistance-decreases the leakage current
energized overva circuit extending from the (+) 55
2
12,135,527
terminal of battery BT, compensating line con
ductor l5, through the bridge network in the di
rection of the arrows, lower winding of relay T
and resistor H in multiple, compensating line
Cl wire i6, upper track rail, upper winding of relay
T and lower track rail to the (—)- terminal of
battery ET.
The Wheatstone bridge is made up of two re-V
the above described conditions the dropping of
sistors comprising arms a and b and two im
10 pedances comprising arms 0 and d, all having
back contact 24 short circuits the lower winding
of relay P which allows this relay to restore its
direct current resistance values such that the
product of arms ab equals‘ the product‘of arms’
cd. Under this condition,'points A and B'of. the
contacts to neutral after a check has been made
that‘ relay T has dropped. Relay P is not ener
bridge circuit, are at equal potential so that no
den rush- of current because the bridge reaches
a stable condition, due to the direct current re
sistances of the arms of the bridge being so pro
portioned that no current ?ows between points
current ?ows through the upper winding of de
tector relay P.
'
Therefore track relay T' is energized by way
of its potential winding which is connected‘
across the track rails and also by way of its cur
rent winding which is connected in series‘ with“
the- bridge across the track- rails. It will be un
derstood that contact 33- of relay T is. used to
control the signals in any manner required by
practical conditions.
Under these conditions relays P, G and AX are
normally de-energized.
Track occupancy.-It will be assumed that a
train enters the track section at the left end
under the conditions above outlined, that is; nor
mal dry ballast conditionsr The shunt provided
across the track rails by the train, short circuits
the upper winding ofv relay T. The lower wind
ing of relay T is of such a value in ampere turns
that the relay will not hold up with current
through the lower winding alone. Therefore the
shunting of the upper winding ordinarily drops
the relay'for signalling purposes.
‘
In addition to this operation of relay T, a check
is provided. by the’ sudden» shunting of the track
40 by the train causing a sudden rush- of current
from the (+) terminal of battery BT, line I5,
arm a of the bridge,» upper winding of relay P,
arm- b of. the bridge,-resistor H, line l6, upper
track rail, through the shunt provided by the
45 train and thelower track rail to the (—) ter->
minal of battery ET. This sudden increase of
current flows in the above‘ described circuit in‘
the direction of the arrows.
The reason that
the current ?ows through-1 the winding of relay
'50 P is because the bridge is‘ out of balance under
this condition due to arms 0 and d being induc
tive so that the sudden rush of current is choked
out of these arms of the‘bridge; Therefore relay
P will operate its'polar contacts‘ to the left. It
will be understood that resistorv H is provided in
shunt-of the lower winding of relay T to provide
a non-inductive path for thesudden rush of cur
rent which would ordinarily be choked back if
it- had to go through the‘v inductive winding of
60
relay T.
'
‘
The operation of relay P to- the left closes.v a'
stick circuit for this relay and a’ pick-up‘ circuit
for the‘relay AX extending from (+), contact
28 of relay P in its left hand dotted position,
65 lower winding of relay P, contact 2| of relay P
pulse of current set up by the entrance of a
train into the track section. In the event that
relay T is dropped by the shunting of its upper
winding alone then a circuit is closed for picking
up relay AX extending from‘ (+), back contact
24 of relay T, back contact 22 of vrelay G, and
winding of relay AX, to (—~).
Under either of
giz'ed through its; upper winding after the sud
A and B'.
7
Track 1I.noccupancy.-—When the train leaves
the illustrated track section, a sudden decrease 20
of current ?ow across the track rails is effected.
The removal ofthe‘v shunt across the upper wind
ing of relay T is-eiiective to permit sufficient cur
rent to- flow through this winding to pick up re—'
lay T. Also this sudden decrease of current flow
through the‘ bridge‘ causes a momentary rush of
current in the opposite direction to that indi
cated by the arrows which is e?ective to operate
relay P'to the right. This rush of current is due
to- the self-inductance of inductances c and d
which tends‘ to maintain the original current ?ow
afterthe current flow from battery BT has been
decreased;_ The‘ decreased current ?ow from the
battery establishes an. immediate value‘ through
2.5
30
arms a and b but there are‘ momentary added
currents in; arms d and‘ c in the original direction
(due to the self-inductance of these arms), which
currents; are in aiding‘ relation for causing a re
sultant current to ?ow through the upper wind
ing. of- relay? in'a' direction opposite to the ar
row. This closes a circuit for sticking relay P
andvv for picking up'r‘elay‘G extending from (+),
contact 21' of relay P in its right hand dotted‘
position, lower winding of relay P, contact‘ 20' of
relay Pinits right hand dotted position, front
contact 25" of ‘relay AX, and‘ winding of relay G,_
to (.—).
The picking up of-relay G’ opens the circuit of‘
relay AX at back contact 22, allowing relay AX‘
to drop itsv front‘ contact 23 for removing the’ 602
shunt from. across the lower winding of relay T.
Relay AX opens its front contact 25' which'd'e
energizes the‘ stick circuit 'of relay P and the
pick-up circuit of relay G; allowing these relays
to restore to their normal positions.
Abnormal ballast ‘conditions-It will now‘ be
assumed that a high leakage current, due to an,
abnormally wet ballast condition, flows from the
(+) terminal: of battery BT, line conductor i5,
through the ‘bridge, lower winding of relay
T, line conductor l6; upper track rail, upper
winding of relay T and the lower track rail to
the <—) terminal of battery BT. Due to the low’
resistance ballast shunt, a substantial portion of v
the current is" shunted from'the' upper winding‘
in‘ its left hand dotted position, back contact 22 . of relay T. A'lso- due‘ to this leakage current an‘
of relay G- and" winding of relay AX, to (—). increase in» current ?ow is effective through the'
RelayAX short circuits resistor H and the lower lower winding of relay T so- that the increased
winding of relay T at its front contact 23-. Since shunting eiTect of the upper winding of the relay‘
70 both. windings of relay T are now effectively
(duejto' the leakage) will be compensated for by
short ci'rcuited it will be positively released.
the increased current flow through the lower
It will’ thus be seen that in’ the event of the winding of the relay due to this leakage. It will
failure of relay T to release when shunted by a
be noted» that any leakage current which flows
train_ an additional shunt is provided for posi— must go through the lower winding ‘of relay T.
75 tively releasing this relay in response to an im
Assuming that a train enters the track section
3
2,135,527
under this condition, the upper winding of relay
T is short circuited and the sudden shunting of
the track by the train causes relay P to actuate
its contacts to the left as before.
This closes a
circuit for picking up relay AX and for sticking
relay P'in its left hand position. This is assum
ing that relay T did not drop when the train
shunted its upper winding.
The picking up of relay AX short circuits the
10 lower winding of ‘relay T and since its upper
winding is shunted by the train, it will be posi
tively released. The dropping of relay T closes
the above described circuit for relay AX which
also short circuits the lower winding of relay P
15 for restoring this relay to neutral.
When the train leaves the track section it will
be assumed that, due to the extremely high leak
age current, relay T does not pick up because its
upper winding is eifectively shunted. Relay P,
however, will ‘actuate its contacts to the right
as previously described and a circuit closed for
pickingup relay G extending from (+), contact
2! of relay P in its right hand dotted position,
lower winding of relay P, contact 20 of relay P
in its right hand dotted position, front contact 25
of relay AX and winding of relay G, to (—) . It
will be understood that relay AX is picked up
because it ‘is assumed that relay T is not picked
up. It will be noticed that this operation of relay.
30 Plsticks the relay in its right hand position by
means of current ?owing through its lower wind
ing in opposition to the full line arrow, which cor
responds to the current which operated relay P
to the right which was opposite to the full line
35 arrow in the upper winding of relay P.
The picking up of relay G drops relay AX which
inserts the lower winding of relay T in the track
circuit and since the leakage current is high,
su?icient current flows through this lower wind
40 ing to positively pick up relay T. To prevent
relay AX being again picked up before relay T
picks up its back contact 24, relay G is made
slightly slow acting.
The above rather speci?c description of one
45 form of the present invention has been given
solely by way of illustration and is not intended
network responsive to said train shunt for shunt
ing said current winding, and means including
said network responsive to the removal of said
train shunt for removing the shunt from said
current winding.
_
3. In a track circuit, an insulated section of
track, a source of current connected to said track,
a track relay including windings connected to
said track and maintained picked up during the
slowly changing current values in its windings 10
due to variations in ballast resistances, a Wheat
stone bridge connected in series with said relay,
means responsive to the entrance of a train into
said section for producing a rapid change in cur
rent in the circuit of said relay and said Wheat 15
stone bridge whereby said bridge is unbalanced,
and means controlled in response to the unbal
anced condition of said bridge and said train
shunt for shunting one of said windings.
4. In a track circuit, an insulated section of 20
track, a source of current connected to said track,
a double wound track relay connected to said
track and maintained picked up by an increase of
current in one winding when the current in the
other winding decreases due to an increase in 25
ballast leakage current, the current in one of said
windings being decreased by the presence of a
train on said track circuit, and means responsive
to the entrance of a train into said section for
decreasing the current in the other winding 30
whereby said relay is released.
5. In a track circuit; in combination with an
insulated stretch of track; a source of current
connected to one end and a track relay connected
to the other end of said track; and regulating 35
means controlled over said track by current from
said source for automatically shunting at least
a portion of said relay whereby the shunting e?ect
of a train in said stretch of track is augmented,
said regulating means including a balanced de 40
tector which selectively detects current changes
in said track due to its occupancy by a train and
changes due to ballast leakage.
6. In a track circuit; in combination with an
insulated stretch of track; a source of current 45
connected to one end and a track relay connected
in any manner whatsoever in a limiting sense.
to the other end of said track; and regulating
It will be obvious that the general principles
therein disclosed may be embodied in many other
organizations widely different from those illus
trated without departing from the spirit of the
invention de?ned in the following claims.
means controlled over said track by current from
What I claim is:—
1. Ina track ‘circuit, a track relay, a source
55 of current connected to the railroad track, a po
tential winding and a current winding of said
relay connected to said track, said potential wind
ing being shunted by a train on said track cir-'
cuit, an electrical network connected to said
60 source of current, means including said poten
tial and said current windings for maintaining
said relay e?ectively energized under various
track leakage conditions, and means including
said network responsive to said train shunt for
65 shunting said current winding.
2. In a track circuit, a track relay, a source of
current connected to the railroad track, a poten
tial winding and a current winding of said relay
connected to said track, said potential winding
being shunted by a train on said track circuit,
an electrical network connected to said source
of current, ‘means, including said potential
and said current windings for maintaining
said relay 'e?ectively energized under various
track leakage conditions, means including said
said source for automatically shunting part of
the winding of said relay whereby the shunting 50
effect of a train in said stretch of track is aug
mented, said regulating means including a bal
anced detector which selectively detects current
changes of distinctive character in said track
due to its occupancy and unoccupancy by a train
and changes due to ballast leakage.
7. In a track circuit for railroads, the combi
nation with a section of track insulated from the
adjacent track by insulating joints, a source of
track circuit current connected across the track 60
rails at one end of said section through the me
dium of a Wheatstone bridge consisting of two
multiple conductors each having an intermediate
tap, said Wheatstone bridge having the four ele
ments so formed constituting impedances hav 65
ing electrical constants so that said bridge is bal
anced and has no voltage between its taps for
direct current ?owing to said bridge but has volt
age of one polarity impressed between said taps
when the direct current through the bridge is 70
increased and has voltage of opposite polarity
impressed between said taps when said direct
current is decreased, a polar relay connected be
tween said taps, a second relay, a circuit for pick
ing up said second relay when said polar relay is 75
4-
'
2,135,527
energized to one polarity position, and a holding
circuit for said second relay which is broken
when said polar relay is operated to the other
polarity position.
to assume its energized position when voltage
of the opposite polarity exists between said points.
10. In a track circuit of the normally closed
type, a section of track insulated from the rest
of the track by insulating joints, a track relay
8. In combination, a railway track divided into
blocks by insulating joints, a signal at the en
normally assuming an attracted condition and
trance to each block, a track circuit for each
block including a track battery and a Wheatstone
having two windings arranged on the same core
and having one winding connected across the
bridge connected in series, said Wheatstone bridge
HI having four elements connected end to end to
form a closed link of which two oppositely located
elements are more highly inductive than are the
other two elements which bridge is so included
in the track circuit that the track circuit current
15 divides a portion ?owing through two elements
in series and the rest ?owing through the other
two elements in series said elements having ohmic
resistances so that the bridge is balanced and
no voltage exists between the two points each
20. joining two elements in series when direct current
flows therethrough but whereby voltage of one
polarity exists between said two points when the
direct current is increased and Voltage of the
opposite polarity exists between two points when
25 the direct current is decreased, a signal control
relay for controlling the signal at the entrance
to said block, and means including said Wheat
stone bridge for picking up said relay when volt
age of one polarity exists between said points
30' and for dropping said relay when voltage of the
track rails at one end of said section, a source
of direct current connected across the track rails l0.
at the other end of said section, and means con
trolling the ?ow of current in the other winding
of said track relay to cause said track relay to
assume its retracted condition upon sudden in
crease in the flow of current from said source to
said track circuit and to assume its attracted
condition in response to a sudden decrease in the
flow of current from said source to said track
circuit.
11. In a track circuit of the normally closed‘ 20i
type, a section of track insulated from the rest
of the track by insulating joints, a track relay
normally assuming an attracted condition and
having two windings arranged on the same core
and having one winding connected across the 25
track rails at one end of said section, a source of
direct current connected across the track rails
at the other end of said section, a two-position
relay controlling the flow of current in theother
winding of said track relay to cause said track 30
opposite polarity exists between said points.
relay to assume its retracted'condition when said ,
9. In combination, a railway track divided into
blocks by insulating joints, a signal at the en
trance to each block, a track circuit for each block
including a track battery and a Wheatstone
two-position relay assumes one position and to
bridge connected in series, said Wheatstone bridge
having four elements connected end to end to
to cause it to be actuated to one position in re
sponse to a sudden increase in the flow of current
from said source to said track circuit and to cause .
form a closed link of which two oppositely lo
cated elements are more highly inductive than
\ are the other two elements and which bridge is
so included in the track circuit that the track
circuit current divides in ?owing through said
bridge a portion of the current ?owing through’
two elements in series and the rest of the current
flowing through the other two elements in series
' said elements have ohmic resistances so that the
bridge is balanced and no voltage exists between
the two points each joining two elements in series
when direct current flows therethrough but
whereby voltage of one polarity exists between
said points when the direct currentrsupplied by
said battery is increased and voltage of the oppo
site polarity between said points exists when the
direct current supplied by. said battery is de
creasecl, a normally energized signal control relay
for controlling said signal which signal control
relay is caused to assume its deenergized position
when said track circuit is interrupted, means for
causing said signal relay to assume its deener
gized position when voltage of one polarity be
tween said points exists and for causing said relay
cause it to assume its attracted condition when
said two-position relay assumes its'other position,
and means for controlling said two-position relay 35,
it to be actuated to its other positionin response
to a sudden decrease in the flow of current from
said source to said track circuit.
12. In a track circuit of the normally closed
type, a section of track insulatedfrom the rest
of the track by insulating joints, a track relay
normally assuming an attracted condition and 45,
having two windings arranged on the same core
and having one winding connected across the
track rails at one end of said section, a source
of direct current connected across the track rails
at the other end of said section, and means con: 50"
trolling the ?ow of current in the other winding
of said track relay including a neutral relay which
is picked up in response to a sudden increase in
the current supplied by said source to said track
circuit and may be held up'through a holding 55
circuit including a' back contact of said track
relay and including means for breaking said hold
ing circuit in response to a sudden decrease in
the current supplied to said track circuit by said
source,
WINFRED T. POWELL,
60
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