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Патент USA US2128590

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Aug. 30, 1938.
R. A. M'cCANN '
2,128,590
RAILWAY S IGNALING
Filed March e, 1956
2 Shee?s-Sheei 1 '
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Ronald A .MQGanzz
BY
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ATTORNEY
Aug. 30, 1938.
R, A, MCCANN
2,128,590
RAILWAY’ SIGNALING
Filed March 6, 1936
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Patented Aug. 30, 1938
'UNE'E'ED STTE S PATET OFFICE‘
2,128,590
'
Ronald A.
RAILWAY SIGNALING
McCann, Swissvale, Pa., assignor to
-The Union Switch & Signal Company, Swiss
vale, Pa., a corporation of Pennsylvania
Application March 6, 1936, Serial No. 67,467‘
19 Claims.
(01. 246-50)
My invention relates to railway signaling and
particularly to signaling involving wayside signals
tion. Each semaphore arm assumes its horizontal
position when deenergized.
located along a trackway for governing the pas
polarized signal control relay designated by the
The apparatus of this invention is an improve
ment over that disclosed in application Serial No.
26,784, of James J. Vanhorn, ?led June 15, 1935,
for Railway signaling.
A feature of my invention is the provision of
reference characters HD with a pre?x the same
as the pre?x in the reference character of the as
sociated signal.
Each section is also provided with an alternat
ing current neutral signal control relay desig
novel and improved apparatus for establishing
nated by the reference character H with a pre?x
a distinctive control for each of three sections in
the rear of an occupied section. Each distinctive
control is effective to cause a corresponding aspect
the same as the pre?x in the reference character
of the associated signal.
produced a three-block,
-
two-wire line circuit over a back contact of the as
sociated alternating current relay H, and the as- .
four-indication system
sociated neutral alternating current relay H is
of signaling.
I will ‘describe one form of apparatus embody
ing my invention, and vwill then point out the
novel features thereof in claims.
In the accompanying drawings, Figs. 1A and 1B
20
are diagrammatic views which, when placed end
.
Each direct current relay HD is connected to a
of the associated wayside signal, whereby there is
is_
-
Each section is provided with a direct current
sage of trains.
10
‘
“stop” position and a vertical or “proceed” posi
connected to the sameline circuit through a con
denser designated by the reference character Q
-
‘to end in the order named, illustrate one form of
apparatus embodying my invention.
Referring to the drawings, the reference char
designate the rails of a stretch of
25 acters 8.and 9along
which traffic normally moves
railway track
in the direction indicated by the arrows. These
rails are divided by insulated joints [4 into a
plurality of track sections or blocks W—-X, X-Y,
30 and Y-Z.
with a pre?x the same as the pre?x in the ref 20
erence character for the associated signal. It
will be apparent, therefore, that the condenser Q
will prevent the energization of the alternating
current relay H by direct current and the contact
of the alternating current relay H will prevent the
energization of the direct current relay HD when
the alternating current relay H is energized.
Each section is provided with an alternating
current transfer relay designated by the reference
character GP with a pre?x the same as the pre?x 30
in the reference character of the associated signal,
Each track section is divided by insulated joints Each relay GP when energized is effective to sup
it into at least two sub-sections IT, 2T, 3T, 4T, ;ply alternating current to the line circuit for the
etc. Each sub-section is provided with a track section next in rear and when deenergized is ef
circuit which includes a'track battery l5 con . fective to supply direct current to that line cir 35
at one end of the sub-sec
35 nected across the rails designated
by the reference
tion and a track relay,
Operably connected to each top semaphore arm
character TR with a pre?x the same as the Tis a pole changer designated by the reference
numerical pre?x in the‘ reference character of the character P with a pre?x the same as the pre?x
associated sub-section, connected across the rails in the reference character for the associated
the other end of the sub-section.
signal. Each pole changer Poccupies its normal
4.0 at To
govern the passage of trains through the condition when the associated semaphore armis
wayside signal, designated
cuit.
stretch of railway, a
45
by the reference character S with a suitable dis
tinguishing pre?x, is provided for each track sec
, tion. Each of these signals comprises a top unit T
and a lower unit L.
These units may take any
one of several forms of signal mechanisms such
as semaphore, color light, Searchlight, or position
As here shown, each top unit is, a sema
light.
phore arm capable of assuming three positions
.750 and‘ each lower unit is a semaphorearm capable
of assuming two positions. That is, the top arm
has a ‘horizontal or “stop” position, a 45° or
“caution” position, and a vertical or “proceed”
55 position, and the lower arm has a horizontal or
.
‘
‘
in its caution position or in its vertical position
or at any point between these‘two positions, and
occupies its reverse condition when such arm is
at any point below the caution position. Also‘
operably connected to each top semaphore arm T
is a contact l8—-l8A closed only when the arm is
in its- caution position and a contact 1 l9—l9A
which is closed when the arm is in its caution 50
position or its vertical position or at any point‘
between these two positions. Operably connected
to each‘ lower semaphore arm L is a contact
20-20A which is closed only when that arm is in
its vertical position.‘
55
2,128,590
Each top semaphore arm T and each lower
semaphore arm L is provided with a lamp TE and
passes from terminal B of the source of direct
current at signal HES, through contact 24 of
pole changer MP, back point of contact 25 of
relay MGP, front contact‘ 26 of track relay 6TB,
front contact 21 of track relay 5TB, relay Isl-ID,
back contact'28 of alternating current relay I3H,
LE, respectively, for displaying supplementary
color light indications corresponding to the posi
UK tion of the associated semaphore arm. The lamps
TE and LE at each signal are controlled by an ap
proach lighting relay designated by the reference
character ER with a pre?x the same as the pre?x
in the reference character of the associated signal;
1.0 The approach lighting relay for each signal is in; I,
cluded in series with the line circuit for the sec
tion next in rear and is so controlled as 'to become
energized whenever the associated line circuit is
energized either by direct current or alternating
current and to become deenergized only when that
line circuit is opened; that is, when a train is ap
proaching the signal. Each approach lighting
relay is provided with a shunt-path including .a
recti?er R which is so poled and controlled that
20 when the associated line circuit is energized with
alternating current the recti?er is effective to by-.
pass one-half of the alternating current wave so
that the approach lighting relay is energized in
as
30
one direction only and when the line circuit is
energized with direct current the recti?er is dis
connected from the shunt path around the ap
proach lighting relay so that all of the direct cur
rent must pass through the relay. Referring to
signal l 28, for example, it will be noted'that since
relay IZGP is energized so that its front contact
62 becomes closed, the recti?er IZR 'will be ef
fective for by-passing one-half of the alternat
ing current wave. The approach lighting relay
I ZER, therefore, will be energized in one direc
tion and willinaintain its back contact 63 opened
so that the lamps TE and LE for signal 125 will
not become lighted. When relay [2GP is deener
gized so that its front contact 62 becomes opened,
the recti?er I>2R is no longer connected across the
relay I2ER. Regardless of the polarity of the line
circuit, therefore, relay IZER willbe energized by
direct current so that its back contact 63 remains
opened. When a train enters section W—_X so
that the line circuit for that section becomes
opened, thenrelay lZER will become released.
When relay I~ZER is released so that its back con
tact ‘63 becomes closed, ‘the lamps TE and LE of
signal |2S will become lighted to provide a light
indication corresponding to the indication dis
50 played by the position of the semaphore arms.
7
For supplying the direct current and alternat~
ing current energy, each section is provided with
a suitable source of direct current energy, the
terminals of which are designated by the refer
ence characters B and C; and each section is
provided with a suitable source of alternating
current energy, the terminals of which are desig
nated by the reference vcharacters BX and OK.
The manner in which the signals are con
60 trolled to cause the display of the different as—
pects will best be understood by tracing the cir
cuits and explaining the operation of the appaé
ratus simultaneously.
A train K is here shown occupying the section
' immediately to the right of location Z so that the
line circuit for the control of relays 141-1 and
MI-ID is opened.
.
c
,
Signal MS, therefore, is displaying both its
semaphore arms T and 'L in the horizontal posi
tion to indicate “stop”.
’
With signal MS in this condition, pole changer
:MP is occupying its reverse position and relay
“3GP is deenergized.
The polarized direct current relay I'3HD is'en
75 ergized in the reverse direction by a circuit which
front contact 29 of track relay 5TH, front con
tact 36 of track relay 6TB, approach lighting
relay MER, back point of contact 3| of relay
lllGP and contact 32 of pole changer MP to
terminal 0 of the same source of direct current.
Since relay I3HD is energized in the reverse
direction, a caution circuit for the top sema
phore arm T of the signal MS is energized by
current which passes from terminal 13 through
front contact 33 of relay l3I-ID and semaphore
arm T tov terminal C. The signal I38, therefore,
is displaying its top semaphore arm in the cau
tion position and its lower semaphore arm in
the horizontal position to indicate “approach 20
next signal prepared to stop”.
7
The 'polarizeddirect current relay I2HD is
energized in the normal direction by a circuit
which passes from terminal 13, at signal I3S,
through contact 38 of pole changer l3P, back
point of contact 39 of relay I3GP, approach
lighting relay I3ER, front contact 40 of relay
4TB, front contact 4! of relay 3TR, back contact
42 of relay 12H, relay IZHD, front contact 43 of
relay 3TH, front contact 44 of relay 4TB, back
point of contact Q5 of relay I3GP, and contact
46 of pole changer HP to terminal C‘.
Since relay i2HD is energized in the normal
direction, the caution circuit for the top sema
phore arm T of signal lZS isv energized over front
contact 41 of relay IZHD; and a clear circuit
a
for the lower semaphore arm is energized by cur
rent which passes from terminal B through front
contact 4? of relay EZHD, normal polar‘contact ,
Eli-35 of relay lZHD, contact |8—l8A of top “'
semaphore arm T, and lower semaphore arm L
to terminal C. The signal :28, therefore, is dis
playing its top semaphore arm in the caution
position and its lower semaphore arm in the Ver- .
tical position to indicate “approach next signal
at medium speed”.
The transfer relay I 2GP is energized over a
‘circuit which passes from terminal BX of the
source of alternating current, at signal IZS, H
through contact 28-20A of lower semaphore arm
50
L of signal I 2S, contact Iii-49A of top sema
phore arm T and relay lZGP to terminal CX of
the same source of alternating current.
Since relay 'IEGP is energized, neutral alter- ,,
nating current relay H H is energized by alter
nating current over a circuit which passes from
terminal BX, at signal 523 through front point
of contact 50 of relay IZGP, approach lighting
relay IZER, front contact 5! of relay ZTR, front
contact;52 of relay lTR, relay Ill-I, condenser "*1"60
HQ, front contact 53 of relay ITR, front con
tact 54 of relay ZTR, and front point of contact
55 of relay I2GP to terminal CX.
Since relay HH is energized, both the caution
circuit and the clear circuits for the top sema- "
vphorerarm T of signal HS are energized over
frontcontacts 5'? and 58, respectively,v and since
relay HHD is deenergized the lower
armvL is deenergized because front
of relay HHD is opened. The signal
fore, is displaying its top semaphore
semaphore
contact 59
HS, there? 70
arm in the
vertical position and its lower semaphore arm
in the horizontal position to indicate “proceed at
normal’ speed”.
The transfer relay H'GP is energized over a‘
3
2,128,590
2. In combination, vtwo successive sections of
circuit which vpasses from‘ terminal BX through
front contacts 60 of relay IIH, contact l9--l9A
railway track, a signal for the forward section
having a semaphore arm operable to diiferent _
of'top semaphore arm T of signal HS and relay
HGP to terminal OK. The line circuit for the
section next in rear of signal HS, therefore, is
supplied with alternating current so that the
signal (not shown) for the section next in rear
is displaying the “proceed at normal speed” indi
cation.
positions, said semaphore arm normally occupy
ing a‘ vertical position, a normally energized relay
for'controlling said signal in accordance with
traf?c conditions in advance of the signal, an
other relay, a circuit for said other relayinclud
ing a front‘ contact of said normally energized
relay and a contact closed when the said sema
‘
When the train K vacates the section imme
diately to ‘the right of location Z, the line circuit
for the control of signal MS will be then sup
plied with direct current energy-in the reverse
direction so that that signal will display its top
semaphore arm in the caution position and its
lower semaphore arm in the horizontal position
10
to indicate “approach next esignal prepared to
circuit, and a signal for the rear section con
trolled by said two relays.
stop”.
When signal MS is in' this condition, the line
circuit for the control of signal |3S will be then
- 3. In combination, two successive sections of 2,0
railway track, a signal for the forward section
energized by direct current of normal polarity so
that signal will display'its top semaphore arm
in the caution position and its‘lower semaphore
arm in the vertical position to indicate “approach
next signal at medium speed”.
25
~
having a ?rst semaphore arm and a second sema
phore arm, said ?rst arm capable of assuming a
caution position as well as a vertical and a hori
zontal position and said second arm capable of 25
assuming a vertical and a horizontal position,
means for controlling said signal in accordance
with tra?ic conditions in advance of said section,
a contact closed when the ?rst arm occupies its
I
When signal ass is displaying this indication,
relay l3GP'will become energized so that the
line circuit for the control of vsignal IZS will be
then supplied with alternating current energy
caution position, a circuit for the second arm 30
over front points 39 and d5 of ‘relay I3GP to
including said contact, another contact closed
when the second arm occupies its vertical posi
cause signal Us to display the normal proceed
indication.
>
It will be noted that in the event of the absence
of the alternating current source of power the
line circuits will be supplied with direct current
so that signal indications will be provided to keep
traf?c moving. For example, if the alternating
current source of power at signal IZS should fail,
the transfer relay lZGP would become released
so that direct current of normal polarity would
be supplied to the line circuit for signal HS and
that signal would change its indication vfrom
“proceed at normal speed” to “approach next
signal at medium speed”.
14.5
-
tion, a relay, a circuit for said relay including
said other contact, a circuit controlled by traf?c
conditions in said rear section, said circuit being 85
controlled by said other relay, and a signal for
the rear section controlled by said circuit.
4. In combination, two successive sections of
railway track, a signal for the forward section,
a source of alternating current, an alternating 40
_ current relay which is deenergized when said
'
It will also be noted that but'two line wires
are required between signals.
'
'
I
It will be apparent, therefore, that the appa
ratus embodying my invention provides a simple,
reliable and economical means for controlling a
three-block, four-indication, system of signaling.
Although I have herein shown and described
only one form of apparatus embodying my inven
tion, it ‘is understoodthat various changesiand
modi?cations may be made therein within the
scope of‘ the'appended claims without departing
from the spirit and scope of my invention.
Having thus described my invention, what I
claim is:
-
-
1. In combination, two successive sections‘ of
railway track, a signal for the forward section
"60 having a ?rst semaphore arm capable of assum
‘ing a caution position as well as'a vertical‘ and
a horizontal position, said signal also having a
second semaphore arm capable of assuming a
vertical and a horizontal position, means for
causing said signal to assume its different posi
tions in accordance with traf?c conditions in ad
vance of the signal, a contact closed when the
?rst arm occupies either its caution or its verti
cal position, a contact closed when the second
arm occupies its vertical position, a relay, a cir
cuit for said relay including said two. contacts,
a pair of conductors including contacts. of said
relay, and a signal for the rear ise tion‘controlled
75
by said conductors.
~
'
10
phore arm occupies its vertical position, a cir
cuit controlled by traffic conditions in said rear
section, said circuit being supplied with alternat
ing current when said other relay is energized
and with direct current when said other relay 1.5
is deenergized, an alternating current relay and
a direct current relay both connected to said
signal displays certain indications and which is
energized when said signal displays certain less
restrictive indications provided said alternating
current is present, a pole changer operably gov
45
erned by said signal and connected to a source
of direct current, a circuit which is connected
to said pole changer when said relay is deener
gized and which is connected to said ‘source of
alternating current when said relay is energized, 50
said circuit being controlled by traffic conditions
in said rear section, a direct current polarized
relay and a neutral alternating current relay
both controlled by said circuit, and a signal for
55
the rear section controlled by said two relays.
5. In combination, two successive sections of
railway track, a signal-for the forward section
having a lamp and controlled by tra?ic condi
tions in that. section, a pole changer controlled
by said signal and connected to a source of direct 60
current, a source of alternating current, a circuit
for the rear section controlled by tra?ic condi- ,
tions in said section, a relay controlled by said
signal for connecting said circuit with either said '
pole changer or said source of alternating cur
rent, an approach lighting relay responsive to
either direct current or alternating current and
connected in said circuit for controlling said
lamp, and signaling means for the rear section
controlled by said circuit.’
6. In combination, a railway signal including a
lamp, a circuit controlled by traffic conditions in
rear of said signal, a direct current relay con
nected in said circuit for controlling said lamp,
va sourceof direct current, a source of alternat
4
ing current, a normally energized alternatingcur
rent relay which becomes deenergized when-said
alternating current source is absent, means in
cluding contacts of said alternating current re
lay for'su-pplying said circuit with either alter
nating current or direct current according as said
alternating current relay is energized or de
energized respectively, and means including a
recti?er for causing said direct current relay to
become responsive to alternating current.
7. In combination, a section of railway track
having a pair of conductors governed by traffic
conditions in said section, a signal for said sec
tion capable of assuming several distinctive as
pects, a direct current polarized relay and an
alternating current neutral relay for jointly con
trolling the di?erent aspects of said signal, said
relays being supplied with current from said
pair of conductors, and means selectively gov
20 erned by traffic conditions in advance of said
section for supplying direct current of one polar
ity or direct current of the other polarity or
alternating current to said conductors but not
both direct and alternating current simultane
ously.
,
8. In combination, a section of railway track
having a pair of conductors governed by tra?ic
conditions in said section, a polarized direct cur
rent relay and a neutral alternating current re
lay both receiving energy from said conductors,
means selectively governed by tra?‘ic conditions
in advance of said section for supplying to said
conductors direct current of normal polarity or
direct current of reverse polarity or alternating
35 current'but not both direct current and alter
nating current simultaneously, and traffic gov
erning means for said'section controlled by said
two relays.
-
9. In combination, a section of railway track,
a pair of conductors governed by traffic condi
tions in said section, a direct current polarized
relay and an alternating current neutral relay
both receiving energy from said conductors,
means governed by trai‘?c conditions in advance
of said section for supplying either alternating
current or direct current of one polarity or the
other polarity but not both direct current‘ and
alternating current simultaneously to said con
ductors, means for preventing the energization
of said direct current relay when said alternat
ing current relay is energized, means- for pre
venting the energization of said alternating cur
rent relay when said conductors are supplied with
direct current, and a tra?ic governing device con
trolled'by said two relays.
'
> '
10. In combination, a section of railway ‘track,
a pair of conductors governed by traf?c condi
tions in said section, a direct current relay and
an alternating current relay both receiving ener
60 gy from said conductors, means governed by
tra?ic conditions in advance of said section for
supplying either alternating current or direct
current but 'not both simultaneously to said con
ductors, means including a back contact of said
alternating current relay for preventing the
energization of said direct current relay when the‘
alternating current relay is energized, means in
cluding a condenser for preventing the energiza
tion of said alternating current relay when said
conductors are supplied ‘with direct current, and
traffic governing means controlled by said two
relays.
"
'
'
'
‘
direct current relay and an alternating current
relay both for governing said signal, means in
cluding a condenser for connecting said alternat
ing current relay to said conductors, means in
cluding a contact of said alternating current re
lay for connecting said direct current relay to
said conductors, and means governed by tra?ic
conditions in advance of said section for supply
ing either alternating current or direct current
to said conductors.
10
12. In combination, a section of railway track,
a pair of conductors governed by traf?c condi
tions in said section, a signal in advance of said
section, a pole changer supplied with a source
of direct current and operably connected to said 15
signal, a relay which when energized supplies
alternating current to said conductors and when
deenergized connects said pole changer to ‘said
conductors, means for, energizing or deenergizing
said relay depending upon the condition of said 20
signal, and signaling means for said section con
trolled by said conductors and selectively re
sponsive to alternating current and direct cur
rent.
13. In combination, two successive sections of
railway track each such section having a pair of 2,5
conductors governed by traffic conditions in said
section, a signal for the forward section controlled
by the conductors for that section and capable
of displaying four distinctive aspects including 30
a proceed aspect and an approach medium aspect
as well as an approach aspect and a stop aspect,
a relay which is energized when said signal is
displaying either the proceed or the approach
medium aspect and which is deenergized when 35
said signal is displaying either the approach or
the stop aspect, means controlled by said relay
according as said relay'is energized or deenergized
for supplying alternating current or direct cur
rent to the pair of conductors for the rear sec
tion, an alternating current ‘relay and a direct 49
current relay both connected to said conductors
for, the rear section, and a signal for the rear
section co-ntrolled'by said two relays.
14. A railwayrsignaling system comprising a
stretch of track divided into sections each hav 45
ing a pair of conductors governed by tra?ic con-v
ditions in said section, two relays for each section
one polarized direct current relay and one neutral
alternating current relay and both connected to
the’ associated conductors, means controlled by 50
said two relays for each section for selectively
supplying to the conductors for the section next
in rear direct current'only of normal polarity or
direct current ‘only of reverse polarity or for sup
plying alternating current only; and a signal for 55
each section controlled by said two relays of that
section and arranged to‘ have a ?rst aspect when
both relays are deenergized, a second aspect when
‘the direct current relay is energized reverse and
the alternating curent relay is deenergized, a 60
third aspect when ‘the direct curent relay is en
ergized normal and the alternating curernt relay
is deenergized, and’ a fourth aspect when the
direct curent relay is deenergized and the alter
nating current relay is energized.
65
15. In combination, a section of railway track
having a pair of conductors governed by traf?c
conditions in said section, a signal for each sec
tion, said signal having a ?rst unit capable of dis
playing three diiferent conditions and a second
unit capable of displaying two different condi
tions, a polarized direct current relay and a
70'
11. In combination, a section of railway track,
a pair of conductors governed by ‘tra?i'c condi ‘neutral alternating current relay energized from
tions in said section, a signal for said section, a said pair of conductors and controlling said sig
75
2,128,590
nal, means responsive to tra?ic conditions in ad
vance of said section for supplying said pair of
conductors with direct current of normal or with
direct current of reverse polarity or with alter
nating current, a circuit including a front contact
of said direct current relay for causing said ?rst
unit to assume one condition, another circuit in
cluding a front contact of said alternating cur
rent relay also for causing said ?rst unit to as
10 sume said one condition, a circuit including an
other front contact of said alternating current
relay for causing said ?rst unit to assume a dif
ferent condition and a circuit including a normal
polar contact and a front contact of said polar:
15
ized relay for causing said second unit to assume
one condition provided said ?rst unit then occu
pies a particular condition.
16. In combination, a railway signal including
a lamp, a circuit controlled by tra?ic conditions
20 in rear of said signal, a relay for controlling said
lamp andv connected in said circuit, a source of
direct current, a source of alternating current,
another relay controlled in accordance with tra?ic
conditions in advance of said signal for connect
ing said circuit to the direct current source or the
alternating current source, a recti?er, and a
shunt path across the winding of said one relay
and including said recti?er as well as a contact of
said other relay.
‘
17. A railway signal system comprising a
stretch of railway track divided into a plurality
of track sections, a pair of conductors for each
section governed by tra?ic conditions in said sec
tion, a polarized direct current relay for each sec—
tion receiving energy from the associated conduc
tors, an alternating current relay also receiving
energy from the associated conductors, means
controlled by the two relays for selectively sup
plying alternating current only or direct current
only of one polarity or of the other polarity to
the conductors for the section next in rear of the
associated section whereby a distinctive control is
e?ected for each of three consecutive track sec
tions next in rear of an occupied section.
18. In combination, a stretch of railway track
5
divided into a plurality of successive block sec
tions a pair of conductors for each section gov
erned by tra?ic conditions in said section, a signal
for each section capable of assuming several dif
ferent aspects, each signal having associated
therewith a direct current polarized relay and an
alternating current neutral relay jointly control
ling the different aspects of said signal, said re
lays being supplied with energy from the pair of
conductors for the section with which said signal 10
is associated, and means controlled jointly by said
relays for supplying direct current of one polarity
or direct current of the other polarity or alter
nating current but not both direct and alter
nating current simultaneously to the pair of con 15
ductors for the adjacent block section in the rear
of the section with which said relays are asso
ciated.
19. In combination, a stretch of railway track
divided into a plurality of successive block sec 20
tions each having associated therewith a pair of
conductors governed ‘by tra?ic conditions in said
section, a signal for each section capable of dis
playing a ‘stop indication and a plurality of dif
ferent proceed indications having varying degrees 25
of speed restriction, each signal having associated
therewith a direct current polarized relay and an
alternating current neutral relay supplied with
current from the pair of conductors for the sec
tion with which the signal is associated, said re
30
lays jointly controlling the signal with which they
are associated and the supply of direct current of
normal or reverse polarity and also jointly con
trolling the supply of alternating current to the
pair of conductors for the adjacent block section .
in the rear, the control of the signal by the relays
associated therewith being arranged in such a
manner that the direct current relay alone is
effective to condition the signal to display at least
one of its restrictive proceed indications, whereby 40
said signal will not be caused to display a stop
indication as a result of the absence of alter
nating current.
RONALD A. MCCANN.
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