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Патент USA US2108483

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Feb. 15, 1938. Y
Fihed May‘ 17, 1955
Law" 0. Groncz'alzl
Patented Feb. 15, 1938
Lars 0. Grondahl, Pittsburgh, Pa., assignor to
The Union Switch & Signal Company, Swiss
vale, Pa., a corporation of Pennsylvania
Application May 17, 1935, Serial No. 22,052
4 Claims.
My invention relates to railway signaling apparatus, and more particularly to apparatus of the
type involving track circuits.
One of the objects of my invention is to provide
5 novel and improved means to insure the release
of a track relay when a vehicle'or train enters
the associated section.
The apparatus for insuring the release of a
track relay set forth in the present application
10 is somewhat similar to that set forth in my 00pending application Serial No. 705,558, ?led on
January 6, 1934, for Railway track circuit apparatus, and the said copending application con-
tains claims which cover broadly certain features
15 of the invention described in my present application.
(01. 246-41)
mally closed contacts of an auxiliary relay Al;
and the latter relay is normally energized over a
local circuit in series with the microphone and an
auxiliary battery D. The use of the auxiliary relay
makes it possible to design the relay to match UT
the microphone and also removes the micro?
phone resistance from the track relay circuit.
When a train enters the section and passes the
microphone, its resistance increases to a point
where the relay Al can no longer hold its contact 10
closed. It will be apparent, therefore, that
whether the train efficiently shunts the track re
lay or not it will be caused to release.
In the form of the invention covered by Fig.
3, the track circuit at the relay end includes the 15
microphone M, the track relay TR, and a bal
vTn the accompanying drawing, Figs. 1 to 8, inelusive, show various forms of track circuits each
ancing resistance l6.
The potential of the battery 3 is greater than
embodying my invention.
ordinarily employed, but with that portion of the
Similar reference characters refer to similar
parts in each of the several views.
Referring ?rst to Fig. 1, the reference characters la and lb designate the rails of a stretch of
railway track, which rails are divided by insu25 lated joints ID to form. track sections, only one of
which is shown in the drawing and is designated
A-—-\B. The track sectionA-B is provided with a
track circuit including a track relay TR con-
electromotive force in excess of that normally 26
employed balanced out by an auxiliary electromo
tive force so that a smaller fractional change in
the voltage at the entering end of the track cir
cuit is required to effect release of the track
relay than ordinarily required. The auxiliary 2'5
circuit extends from the positive terminal of bat
tery D through resistance l8 to the lower ter
minal of resistance l6, where it joins the track
circuit path to the one terminal of the track
nected across the rails la and lb at one end of
'30 the section in series with a microphone M, and a
relay; and from the negative terminal of battery 30
track battery. 3 connected across the rails la and , D through the balancing resistance IE3 at the up
lb at the other end of the‘ section. The micro- per terminal of which it joins the track circuit
phone M is of the type which increases its resist_ ance when a train passes over the track rail to
path to the other terminal of the track relay.
The values of resistances l5 and I6 are such that >
35‘ which it is attached. A microphone of this type
is fully disclosed in Patent No. 1,834,077, issued
December 1, 1931, to A. J. Sorensen.
When a train moving in the direction indicated
with proper setting of the adjustable resistance 35
ill the electromotive force of the track circuit
across the terminals of resistance l5 will exceed
that of the auxiliary circuit by the potential re
, ,. by the arrow enters the section A—B, the vibra-
quired to pick up the relay.
40 tion of track rail la, caused by the train as it
passes the microphone M, causes the microphone
to vibrate and its resistance to increase at the
same time that the track rails are being shunted,
,. thereby insuring the release of the track relay
45 TR. Once the track relay TR. has released its
For example, if the track relay requires two 40
volts across its terminals to pick it up, the dif
ference in potential required across resistance l5,
between the track and auxiliary circuit, Will be
two volts while the actual potential of each of
the respective current sources 3 and D may be 45
armature, a less effective shunt than that required to release the relay without the assistance
much higher. If now we assume that the relay
will release when the potential across its termi
of the microphone will be sufficient to prevent the
nals is reduced to one volt, then in the conven
‘, _ trackrelay again picking up after the resistance
tional track circuit this will represent a require
50 of the microphone is again. reduced to its normal
value. When the train clears the section, the relay TR again picks up in the usual manner.
ment of a 50% drop» in voltage to effect release of 50
the track relay. With the circuits herein provid
ed the energization of the relay is effected ‘by
In Fig. 2, the track relay TR, instead of being
two volts, and the drop in voltage required to- ef
__ connected to rails la and. lb in series with the feet the release of the relay is one volt as be
55 microphone M, is connected in series with nor-> , fore. However, the track circuit potential avail- 55
able at the relay may, for example, be ten volts
and. that of the auxiliary circuit, eight volts in
the opposing direction. .Under these conditions,
the relay is energized by a potential of two volts,
as before, but a less efficient track shunt, ef
fective to obtain a 10% drop in potential will
in the resistance of the microphone M to obtain
the release of the track relay.
As in the direct current circuit application, pro
cause the required one volt decrease in potential
?ow through winding P2 by connecting one terminal
required to e?ect release of the track relay.
of winding Pl to a ground electrode 2| direct and
the other terminal thereof to a ground electrode
In order to retain a constant relationship be
10 tween the current ?owing through the track relay
from source D with respect to that supplied over
visions are made for as nearly as possible com
pensating for the effect variations in weather
and moisture ballast conditions have on current
22 through inductance 23 and resistance 24, re 10
spectively. These ground electrode connections
the track circuit, ground electrodes II and I2 are
connected in shunt of the battery D. These elec
are position-ed as explained in connection with the
description of Fig. 3, and in a similar manner
trodes are so positioned with respect to the sec
maintain the relationship between the two primary
15 tion A—B that their shunting action on the cur
rent supplied to relay TR will be similar in its
behavior with respect to changes in weather
conditions to that of the ballast leakageresist
ance across the rails of the section on the cur
20 rent supplied to relay TR over the track circuit
under the same weather conditions.
If the shunt placed across the rails by the train
at any time becomes of su?iciently low resistance,
windings Pi and P2 the same irrespective of 15
variations in ballast conditions.
It may further be explained that variable in
ductance and resistance elements 23 and 24 enable
the characteristic of the leakage path for current
?owing through winding Pl to be adjusted to 20
closely simulate that of the ballast leakage path of
the current ?owing through winding P2, While
the value of choke coil 20 is such that with no cur
the current flow from source D may be augmented
rent flowing through winding P2, that ?owing
25 su?iciently, bythe additional current which will
then ?ow to the relay through microphone M and
the wheels and axles of the train in multiple with
resistance E5 to effect operation of the relay.
Under such a circumstance however, the polar
contact included in the controlling circuit of the
relay opens and prevents premature closure of the
controlling circuit resulting from the closure of
its neutral contact. If desired, a neutral relay
through Pl will be insu?icient to operate the relay.
In the form of the invention illustrated in Fig.
5, the track relay TR is again of the alternating
current type and is connected across the railsv la
and lbv in series with a contact of the auxiliary
may be employed instead of a polarized relay. In
such case, the resistance values and operating
characteristics of the relay must be adjusted in
such manner that with an efficient shunt across
the track rails the current supplied to the relay
from source D will still be insufficient for picking
40 up the relay. In either of the foregoing forms of
the invention, when a train clears the section
current flow in the normal direction is reestab
lished and accordingly the relay picks up its
neutral armature. Also, in the case where a
45 polarized relay is employed, should its polar con
tact have been reversed, such contact is also re
stored to its normal position.
In Fig. 4, the principles employed in the pre
ceding ?gure are shown in the form they take
50 when alternating current is employed. In this
?gure the secondary S of a transformer T sup“
plies operating current to the rails la and lb
at the exit end of the section. At the entrance
end of the section, the alternating current track
relay is energized from the secondary S2 of a
transformer Tl. The transformer Tl has two
primary windings. The winding Pl receives cur
rent from the secondary S3 of a transformer T2 in
series with a choke coil 29. The transformer T2
60 has its primary winding connected to an alter
nating current source in reverse relation to the
connection of the primary winding of the trans
former T so that the current supplied to the pri
mary winding P2 is at any instant substantially
180° out of phase with respect to that supplied
to the primary winding Pl. The current flow
through winding PI is, however, restricted suf
?ciently by choke coil 20 to enable the winding
P2 to induce sufficient current in the secondary
70 winding S2 to pick up the track relay when the
section is unoccupied.
When a train enters the
section, the current ?ow through the winding P2
is readily reduced su?iciently by the shunting
action of the wheels and axles of the train and
75 decrease of current required to effect the increase
relay Al. The auxiliary relay in this instance is
held energized by battery D connected to rail lb
and to the corresponding rail of the adjacent sec
tion, separated by the insulator [0.
As a vehicle enters the section a front wheel
thereof momentarilybridges the upper rail joint In 3.5
at location B and thereby shunts current from the
relay Al which accordingly drops and opens the
circuit of the track relay. The vehicle, While in
the section, also maintains a shunt across the
rails la and lb until the train clears the section.
Once the track relay has released its armature,
the shunting action of the train will ordinarily
be sufficiently eifective to prevent the track relay
again picking up until the train clears the sec
The arrangement of Fig. 6 differs from that of
Fig. 5 only in that the section junctions are stag
gered and theauxiliary battery D is connected
across the opposite rails of adjacent sections.
The auxiliary relay Al will accordingly deenergize
as the train enters the section and remain de
energized so long as a portion of the train oc
cupies the space between the junctions of ad
jacent sections. After the train clears the junc
tion the usual shunting action of the train will 55
come into play to prevent the picking up of the
track relay until the train clears the section.
In the form of the invention illustrated by Fig.
7, the usual battery feed arrangement, as illus
trated in Figs. 1, 2 and 3, is employed. The track 60
relay is also of the conventional type and is con
nected across the rails la and lb at the entrance
end of the section in series with a photo-electric
element or cell P with an appropriate shield and
normally receiving light from a suitable lamp L 85
focused toward the cell P. The light shining on
the cell P enables su?icient current to ?ow over
the track circuit to hold the track relay energized.
When a train enters the section it passes between
the cell P and light L. The cell P immediately in 70
creases the resistance of the track relay circuit,
thereby insuring the release of the relay in re
sponse to the shunting of the track circuit.
It will be obvious that the photo-electric cell
P may, if desired, be employed to control an aux- 75,
iliary relay in the same manner that such a re
lay is controlled by the microphone M in the
disclosure of Fig. 2.
If it is desired to positively insure the dropping
of-the track relay irrespective of the end of the
section entered, this may be accomplished by ap—
plying the apparatus at both ends of the track
In Fig. 8, such an arrangement is illus
In this ?gure an arrangement such as
shown in Fig. 6 is modi?ed by including a front
contact of the A! relay in the track feed. circuit
of the adjoining section B-‘—C. It will be evident
then that when a train in’ section A-B enters
section B--C, the auxiliary relay AI will open
the feed circuit to the track relay of section
B-A-C so that the track shunt need be only suf
?ciently effective to prevent the picking up of
the track relay after Al has ceased to function.
The movement of a train from section B--C into
track relay when the shunting action of the
wheels and axles of a train occupying said sec
tion is restricting the current flow to said track
relay from said track circuit source, and means
including a ground path for varying said reverse
current flow in accordance with changes in
ground resistance.
2. In combination with a section of railway
track and a source of current connected across
the rails of the section, a relay having a winding 10
receiving energy from the track rails of the
section, a circuit controlling armature adapted
to be moved by the force developed by said wind
ing, means for establishing a potential which
opposes the normal track potential effective 15
across said winding by an amount such that the
resultant potential is sufficient to move said ar
mature when the section is unoccupied, said op- I
posed potential predominating over the normal
potential when the section is occupied, and an
corresponding movement as described in connec-‘
auxiliary circuit including a ground connection
tion with Fig. v6, except that as the train. leaves for varying said opposed potential in response
the section the Al relay at the leaving end of to variations in the ground resistance to main
the section will hold the track circuit open until , tain the unbalanced condition of said potentials
the train clears the junction of the adjoining sec
constant during changes in weather conditions. 25
3. In combination, a section of railway track,
Although the microphone M is only shown con
a track circuit for said section including a main
source of current and a track relay, means in
nected in serieswith the track circuits illus
' trated by Figs. 1, 3 and 4, and the photo-electric. ~ cluding an auxiliary source in the wayside‘ for
cell P is only shown as employed in the track passing a current in the reversepdirection to'that 30
circuit of Fig. 7, it will be apparent that either supplied from said main source through said
20 A-B will be effective in a manner similar to a
or both of these may be included in any of the
track circuits shown to increase the release sensi¢
tivity of the track relay. ,Also, although the
35 microphone is only shown in circuit with the Al
relay in Fig. 1, it maylikewise as well, be in
cluded in series with the Al‘ relay as employed
in Figs. 5, 6 and 8.
track relay, the magnitude of said reverse cur
rent being such that normally the track relay
energization from said main source predominates
su?‘iciently to maintain said relay picked up, and 35
means including a ground path for by-passing
a portion of the current from said auxiliary
source in accordance with variations in the
Although I have herein shown and described ' ground resistance whereby when a train enters
40 only a few forms of apparatus embodying my said section a small reduction in the energizer. 40
invention, it is understood that various changes tion from said main source renders the reverse
and modi?cations may be made therein within energization from said auxiliary source e?ective ..
the scope of the appended claims without de
parting from the. spirit and scope of my inven
Having thus described my invention, what I
claim is:
1. In combination, a railway track section; a‘
track circuit for said section including a source
50 of current, a trackrelay and a current limiting
element; a'second circuit for said relay includ
ing a second source of current and a second
current limiting element with the current flow
in the reverse direction to that supplied over
55 the track circuit, means included in said sec
ond circuit for reducing the current flow therein
to release said track relay.
4. In combination, a section of railway track,
7 a track circuit for said section including a source 45
of current and a track relay, an impedance con
nected across the terminals of said track relay,
means for establishing a potential drop across
said impedance in the opposite direction to that
established by the potential drop due to the track
circuit source, the magnitude of the opposed po
tential drop being such that said track relay is
normally maintained energized from said track
circuit source, and means including a ground
path for varying said opposed potential drop in 55
accordance with changes in ground resistance
to the extent required to prevent its interference
whereby when a train enters said section and a
with the actuation of said relay by current sup
plied over said track circuit when the section
60 is unoccupied, the current flow over said second
circuit becoming‘ effective to aid release of said
slight reduction occurs in the normal energiza
tion said opposed potential drop will be effective
to cause a release of said track relay.
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