US2046179A - Railway traffic controlling apparatus - Google Patents

Description

June 3Q E936. F. H. NICHOLSON RAILWAY TRAFFIC CONTROLLING APPARATU-S Filed May 27, 1933 2 Sheets-Sheet l 5m@ my 3935-' FA H. NICI-101.59m

l RAILWAY TRAFFIC CONTROL-LING APPARATUS Filed May 27, 1933 2' SheeCS-Sheei 2 .N @MNE www MN NS@ mm, Q@

@QQ www HAY A TTORNEY Patented June 30, 1936 iJNlTED STATES PATENT @FFME RAILWAY TRAFFIC CONTROLLING APPARATUS Application May 27, 1933, Serial No. 673,209

13 Claims.

My invention relates to railway traflic controlling apparatus, and particularly to apparatus of the type comprising train carried train controlling means governed by energy received from the track rails.

A feature of my present invention is the provision of apparatus for superposing on the usual direct current signal controlling track circuit an uninterrupted or non-coded alternating current under certain trail'lc conditions, and for superposing an interrupted or coded alternating current under other traflic conditions. The train carried apparatus is selectively responsive to the coded and noncoded alternating current. In systems of 'this type heretofore proposed coded alternating current has been employed under clear trac conditions and non-coded current employed under caution or the more restrictive traffic conditions. In such former systems code operation of the trackway equipment or at least is required for the major portion of the time. Furthermore, in such systems code operation of the train carried apparatus is also required for the major portion of the time a train is travelling over the equipped trackway. A further feature of my present invention is the provision of apparatus both on the trackway and on the train wherewith code operation is required only for the traffic condition least encountered in railway service, the arrangement of the apparatus being such that a false clear indication will not result from a failure of the coding apparatus. Code operation being thus reduced to a minimum time interval, longer life and reliability for such apparatus is assured, and the usual common type of relays may be employed to thereby greatly reduce the first cost and maintenance of such systems. A still further feature of my invention is the provision of apparatus for adding a third cab signal indication to the single element two-position cab signal now in use on many of the railroads in connection with train brakevcontrolling equipment. The addition of this third cab indication serves to reconcile the present two-indication cab signal With the standard three-indication wayside signal system. Other features and advantages of my invention will appear as the specification progresses.

I will describe one form of trackway apparatus and one form of train carried apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view illustrating one form of trackway apparatus embodying my invention. Fig. 2 is a is continuously required,

diagrammatic View showing one form of train carried apparatus suitable for cooperating with the trackway apparatus of Fig. 1 and also embodying my invention.

In both of the drawings similar reference characters refer to similar parts.

Referring rst to Fig. 1, the reference characters l and Ia designate the traiiic rails of a stretch of railway over which traflic normally moves in the direction indicated by the arrow. These trafiic rails are divided by means of the usual insulated rail joints 2 into a plurality of successive track sections A-B, B-C, etc., the track section B-C being subdivided at Bl to form the subsections B-B| and B I-C. Each track section 15 and subsection is provided with a standard direct current track circuit which comprises the traflic rails with a battery 3 connected across the rails at the exit end of the section, and a relay R, with an exponent corresponding to its location, connected across the traflic rails at the entrance end of the section. Between the track battery 3 and one of the traffic rails is inserted the secondary winding 4 of a track transformer T with an appropriate exponent,` a customary impedance 5 being also inserted in the connection to limit the current flow. The primary winding I3 of each track transformer T is supplied at times with uninterrupted or non-coded alternating current, and at other times the alternating current is periodically interrupted or coded. The manner of governing the supply of alternating current to the track transformers will appear later in the description.

In accordance with the usual practice each track section is preferably provided With a wayside signal designated by the reference character S with an exponent corresponding to the location. These signals may be of any standard form and are here shown as semaphore signals each capable of displaying a clear, an approach and a stop indication. It will be understood that my invention is not limited to any specic form of Wayside signals and position light, color light, or search light signals may be employed equally as Well as the semaphore signals should it seem desirable to do so. As a matter of fact, my invention does not require wayside signals, and, as will appear when the operation of my system is described, the wayside signals may be omitted. The circuits for icontrolling the signals S form no part of my present invention and are not shown in Fig. 1 for the sake of simplicity. For present purposes, it is deemed sufcient to say that any of the Wellknown standard arrangements of control circuits responding to the location. Each circuit controller W and X occupies one position when'the associated signal indicates stop, a second position when the signal indicates approach, anda thirdposition when the signal indicates clear'.

To put it another way, each of the controllers W and X occupies one position when the immediate section in advance is'occupied, a second-posi- Vtionvwhen the immediate section in advance is unoccupied and the second section Vin advance isV occupied, and a third position when the immediate section and the secondI section in advance are both unoccupied. It is evident, therefore, that thelpositions of these controllers W and X are made to Vcorrespond with different traic conditions in advance. When semaphore Vwayside signals are provided as shown in Fig. 1, the usual mechanism for the signal forms a convenient means for operating the controllers.` In the event some form of -light signal is provided, then these controllers W and X would be operated by theusnal signal controlling relays, and in the event no wayside signals are provided, the controllers Wand X would beroperated by re= lays governed by traffic conditions in advance in the manner pointed out above. Y

YEach track section is further provided with a normally inactive code transmitter designated by the'reference character CT with an exponent corresponding to the location. These code trarns- Y mitters may take diierent forms and are here Shown as a mechanically oscillating type preferably of a structure similar to that disclosed .and described in the United States Letters Pat- Vciated therewith, which members normally engage the contacts I4 and il, respectively.' A Vfield, winding B of the `code transmitter CTA is provided with a circuit extending from the positive terminalV of a lconvenient source of'dii rect current sr-.ch as a battery l5, over controller WA when moved to its position corresponding to the stop indication of signal SA, wire Ill, contact It, contact member S, winding I5 and tothe opposite terminal of battery 715. It follows that the winding 6 is energized whenever the signal SA indicates stop.

With eld winding 6 energized, the armature AH will be rotated in a clockwise direction as indicated by the arrow. After a small movement Vof armature AH, thecontact member 8 will disengage the contact I4 to open the circuit just traced andthe eld winding l will be deenergized. Armature VAI-I will rotate a little farther and then its movement will be reversed'due to the bias and will swing backward to bring contact member 8 again into engagement with contact l to reenergize the field winding 6. armature AH will swing slightly past its normal position due to the inertia of its parts and it will then again rotate in a clockwise direction due Yto the inuence of the eld winding 5. It is clear that as long as the signal SA indicates stop the armature AH will oscillate at its natural period, the period of oscillation being determined by its biasing and the weight of its parts. lAlthough the period of oscillation may be any convenient frequency,1 shall consider it to be 60 cycles per minute. As stated above, the contact member 9 is operatively connectedV with the armature AH, Vand hence contact member V9 will oscillate between the right-hand contact II and a left-hand contact I2 at the code frequency of 60 cycles per minute as long as the code transmitter CTA is active.

The contact member 9 governs the' supply ofY train governing alternating current to the track transformer TA. Non-coded alternating current is normally supplied to the primary winding I3 of the track transformer TAV by a circuit ex- The Y tending from the BX terminal of any convenient source of alternating current such Vas theV second` ary winding of a line'transformer not shown,

contact member 9, right-hand contact II, controller XA occupying the position corresponding to Veither the clear or approach indication ofV sign-al SA, primary winding i3 and to the opposite terminal CX of the source of alternating current. At such time as signal SA'in-dicates stop and thecode transmitter CTA is rendered active as described.V hereinbefore, 'the primary winding i3 of transformer TA receives current from the BX lterminal kof the sourceof alternating current, over contact member B, left-hand contact I 2, controller XA and winding I3 to the opposite terminal CX ofthe source of alternating current. It follows thatY as long as traflic'condin tions in advance of location A are such that signal SA indicates either clearl or approach, the

code transmitter CTA is inactive and non-coded alternating current is superposed on the direct current track circuit for the section to the left of location VA. When traffic conditions in advanceof location A are such as to cause signal SA to indicate stop, the rcode transmitter CTAV is rendered active and the alternating current superposed on the direct current track circeV cuit for the section to the left of location A is codedat the frequency of 60 cycles per minute. The alternating current may be of any convenient frequency, such, for example, as 100 cycles per second. The supply of Valternating current to each of the'remaining track transformers is controlled by the associated circuit controller X andcode transmitterV in the saine manner as explained for transformer TA. VIn connection with' the'track transformer TBIQlocated at the cut section location BI, it is supplied'with alternating current in parallel with the track transformer TC at theA exit end of the section B-C as will be readily understood by an inspection of Fig; l.V The connection to the primary winding I3 of transformer TBI is also controlled by a Y frontk contact I5 of the tracl; relay RBI.

As shown in Fig. '1, thesection to the right of location C is occupied by -a train indicated diagrammatically at V. The track rails for'that portion rof the section to the rear of train V are deprived of both track circuit current and train controlling current. by the shunting effect of the Wheels and axles of train V. Relay RC is therefore deenergized and signal SC indicates stop, causing the controllers WC and XC to occupy their corresponding positions. Under these conditions the circuit to the field winding 'c of the code transmitter CTC is closed at the. controller WC and that transmitter is active. Controller XC being now closed to. complete the connection from the left-hand contact t2 of code transmitter CTC, bothv track transformers TC and TBI are supplied with coded alternating current. The signal SB indicates approach and the controller WB is open and the code transmitter CTB is inactive. Controller )Q3 is closed to complete the circuit for supplying uninterrupted alternating current to the track transformer TB. Signal SA indicates clear so that controller WA is open and code transmitter CTA is inactive. Controller XA is closed to complete the circuit for supplying uninterrupted alternating current to the track transformer TA.

TheV section to the left of location A is occupied by a second train indicated diagrammatically at Ve. For the purpose of controlling the train carrie-d apparatus of train Va by the alternating current superposed on the direct current track circuit the train Va" is provided with a receiver designated in general by the reference character M. Receiver M comprises two magnetizable cores i6 and ii carried on the train in advance of the forward axle and located in inductive relation with the two trafc rails i and la, respectively. Core I6 is provided with a winding i8 and core I is provided with a winding I9,

the windings I8 and I9 being connected in series in such manner that the voltage induced therein by alternating ciurent owing in opposite directions in the traine rails at an instant are additive.

Referring to Fig. 2, the windings i8 and I9 are connected through a condenser 29, with the primary winding 2l of an autotransformer T2. The windings I8 and i3V and the condenser 2i) are tuned to series resonance at the frequency o the alternating current supplied to the trafc rails which I have assumed to be i90 cycles per second. The secondary winding 22 of the autotransformer T2 is tuned to parallel resonance at the frequency of the alternating current by means of a condenser 23. The resonant voltage. at the terminals of condenser 23 isv amplified by two electron tube ampliers PJ2 and PM. The laments of these tubes are connected in. series witha ballast lamp two control resistances 25 and 25 and a reactor 2l, and are supplied with current from a suitable source such as the usual headlight generator HG. The reactor 21 constitutes. a. choke to suppress the commutator ripples in the current. supplied by the generator HG.. The secondary winding 22 oi autotransforrner T2 is connected. across the grid and lainent of the tube PJZ through the resista-nce 25 anda comparatively high resistance The plates of the electron tubes PJ 2 and PJ 4 are provided with a comparatively high unidirectional electromotive force from a suitable source such as the high potential. winding 34 of a dynamctcr DM, having a low potential winding 35 and a eld winding fifi constantly supplied with energy from the generator HG. The high potential winding 34 has its positive terminal connected with the plate of the tube PJ2 through a reactor 3l, plate Si of a condenser it, and

a second reactor 33; and with the plate of the tube PJG through reactor 3l, condenser plate 8'I and a reactor 39. The negative terminal of winding 34 is connected directly to the negative lead4 of the filament circuit. The second plate i8 oi condenser l@ is made an integral part of the lament circuit. The reactor 3i' and the condenser 16 thus form a iilter for bypassing the ccininutator ripples of the high potential electromotive force away from the electron tubes. The various elements of this lter being made an integral part of the associated circuits, this unit operates on the closed circuit principle. The functionv of this filter will also appear later. 'l1 is the usual grounding condenser associated with the lament circuit, one plate 'I9 being made an integral part of the filament circuit and the second plate 8d being connected with ground as shownin Fig. 2. The plate of tube P52 is also connected through a condenser di and a resistancedi with the negative lead of the filament circuit, the grid of tube PJQ being connected betweenthe resistance SI and condenser 4G. It is clear, therefore, that tubes PJ2 and PJ@ and the associated apparatus comprise an amplifier of the well-known choke coil type.

The energy ldelivered by tube PJIIS is supplied to il'v the primary winding i2 of a transformer T3 which is connected across the plate and filament of that tube, a blocking condenser L23 being connected in series and a tuning condenser i4 being connected in parallel with the primary winding MA, It follows that alternating currents ilowing the traflic rails i and i@ create in the windings l and i9 an alternating current which is amplied by the tubes PJ 2 and PJ I and create in the secondary winding 5.5 of transformer T3 an alternating current which is rectied to unidirectional current by the rectier 46 and which serves to energize relay MA. The relay MA is preferably a direct current quick-acting neutral relay and hence as long as alternating current is continuously picked up from the traflic rails, the relay MA is energized continuously. With the alternating rail current coded, the relay MA releases at the termination of each code impulse and picks up at the beginning or the next code impulse. That is to say. relay MA is picked up continuously as long as the train controlling current is a non-coded alternating current, and is operated at the code frequency when the train controlling current is coded.

The autotransformer T2 and condenser 20 operate as a iilter to prevent energization of the relay MA by stray currents oi a frequency diierent from that of the train controlling current. The reactor 3l and condenser iS operate as a bypass filter to bypass the high frequency commutator ripples in the high electromotive force supplied to the plate circuit of the electron tubes to prevent such pulsations being amplified and then rectified at the rectier 3E to energize the relay MA. The reactor 2 operates as a choke coil to prevent the commutator ripples of the current supplied tothe filament circuit from being amplied and then rectified to energize the relay MA. As pointed out above, the condensers T6 and i? are each preferably of a construction such that their respective plates become an integral part of the associated circuit whereby these units operate on the closed circuit principle.

A second train carried relay designated by the reference character L is provided, and is governed Il U by the train controlling current of the trackway equipment in the following manner. The top Yterminal of the primary winding 4'! of a transformer Tl is connected with the positive terminal of the generator HG over the front contact i8 of relay MA, and the bottom terminal of the primary'winding 47 isconnected with the positive terminal of generator HG over the back contact 59 or" relay MA, a center tap ofthe primary vwinding 4l' being connected with the negative terminal of generator HG. It follows that at such Y time as relay MAis'rpicked up continuously or is deenergized continuously, the top half or the bottom half of the primary winding 4l, as the case may be, is steadily excitedwith direct current and no voltage is induced in the secondary winding 99 of the transformer T5. Thealternate excitation of the top and bottom halves of the primary winding 41 in response to code operation ofthe relay MA will, however, induce anY alternating voltage in the secondary winding 95, Ythe frequency of which will correspond to the code frequency Vat which the relay MA is operated. A portion ofthe secondary winding S9 is connected to the input terminals of a full-wave rectifier 55, the output terminalsof which are connected with the winding of the relay L. -A

rspark arresting condenser 5l is connected across the winding 99 to reduce the sparking at the contacts 38 and 49 on relay MA. It is clear that as long as non-coded alternating current is picked up from the traic rails or no current Yis received by the trainV carried equipment, the relay L is 1 deenergized,V and when theralternating current picked up from the trac rails is coded, the relay L is picked up continuously. Relay L is preferably slow releasing in character` to prevent its being released from one code impulse until the next. Y

The train is provided with a visual cab signal ACS having three lamps G, Y, and R, each capable of displaying a distinctive indication. For

Y' example, the lamp G Vdisplays a green light, the

Vlamp Y a yellow light and the lamp R a red light.

Referring now to the relays MA and L, it is to be noted that when relay MA is energized and relay L is deenergized, current will ow from the positive terminal of the generatorI HGY over wire front Contact 48 of relay MA, back contact 52 of relay L, wire B'Llarnp G, wire 83, front contact 54 of relay MA, and'thence to the negative terminal of generator HG. YThe lamp G will now be illuminated. When relay L is energized, current will flow from the positive terminal of the generator HG over wire B32, front contact 6l of relay Ljwire 62, lamp Y, wire 89, front contact 53 of relay L, and thence to the negative terminal of the generatorV HG to illuminate lamp Y. Again,

Y when both relays-MA and L are deenergized, current will flow from the positive terminal of generator HG over wire B32, back contact i9 of relay MA, back contact 64 of relay L, wire 55, lamp R,

wire 95, back contact 66 of relayMA, and thenceVV ditions at-which time no current is supplied to Ythe train will cause both relays MA and Lto be Y deenergized and the cab signal to display a red light.

It is desirable to audibly call the vattention of the engineman toa change of the visual indication of the cab signal resulting from archange 5 in traiiicconditions,especially when such change represents amore restrictive condition. This is referably accomplished by an air Whistle desig-j nated bythe reference character WS and controlled by a magnet valve designated as a whole l by the reference character H'. As shown'diagrammatically, iluid pressure is supplied to a chamber 53 through a pipe 28 connected with a suitable source of fluid pressure not shown. At

such time as the winding 61 of the magnet valve 15 H is energized, a valve 68 is seated andthe pres-` sure is shut off from the pipe 69 leading to the whistle WS and the whistle is silent. When the winding l is deenergirzed, the valve 68 is lifted and the fluid kpressure Yin chamber 53 escapes to 20 Athe atmosphererthrough thepipe 68 and the whistle WS causing the whistlel to blow. For reasons to appear hereinafter a whistle delayer Y WD is connected in the pipe 69 withv the result that there will be a slightV delay between the time the winding 51 is Vdeenergized and the sounding cf the Whistle WS. YThis Awhistle delayer WD shown as a'rectangle in series with the pipe 69 Vis a pneumatic device for preventing the whistle from blowing untila given pressureV is built up. 30. This whistle'delayerV may take different kforms and it need not be considered further inasmuch as its speciiic structure forms no part of my present invention.Y Y Y In order that the engineman may silence the whistle by acknowledging the change in the indication ofthe cab signal the train carried equipment is further provided with two stick relays SP and RP andan acknowledging switch ACK..Y The relay SP is a direct current neutral relay and is provided with slow-releasing characteristics. The relay RP is a double winding direct current neutral relay capable of closing its front contacts when either of its two windings is energized. Y

n Again, referring to the relays MA and L, it will be noted that with relay MA picked upcontinuously and the relay L down, current will flow from the positive terminal of generator HG over wire B32, front contact 48 of relay MA, back contact 52 of relay L, Ywires 81 and 55, back contact 56 of the relay RP as that relay is normally deenergized, wire 51, winding 61 of magnet valve H, controller 58 of the switch ACK and normally closed, wire 9|, back contact 59 of the relay SP 55 which is also normally deenergized, a second back contact 60 of relay RP, wires 92 and 88, front contact 54 of relay MA, and thence to the negative terminal of the generator HG, andV magnet valve H will be energized. That is to say, clear 60 traffic conditions that cause relayV MA to be picked up continuously, result in the magnet valve H being energized and the whistle WS being silent. vAssuming that the traine conditions change from clear to approach Vwith the result that the relay MA Yis code operatedand relay L is picked up, the above-traced circuit for winding 5l will be open at the back contact 52 of relay L and consequently magnet valve H will be deenergized and after a slight delay caused by the 7.0 whistle delayer WD, the audible signal WS will be sounded to call the enginemans attention to the change in the indication of the cab signal.

lThe winding 61 of the magnet valve H may be reenergized and the whistle WS silenced in the following manner. The engineman will actuate the acknowledging switch ACK to the position for closing a controller it, and will then restore the switch to its normal position Where the controller 58 is closed. During the interval that the controller 's is closed, current will flow from the positive terminal of the generator HG over wire B32, back contact 49 of relay MA when that relay releases at the end or" the first code impulse, wire il, controller '56, wire '52, top winding of relay RP, and thence to the negative terminal of the generator HG, and relay RP will be picked up. At the same time current will flow over this same circuit just traced up to wire l2, and thence through the winding oi relay SP, and to the negative terminal of the generator HG, Vand relay SP will also be picked up. That is to say, the same manually controlled circuit will be effective to energize both the stick relays SP and RP in parallel. Under this condition, namely, a change of indication rom clear to approach, the picking up of the stick relay SP serves no useful purpose and that relay will release at the end of its slow release period as soon as the acknowledging switch ACK is restored to its normal position. The stick relay RP, however, once picked up will be retained energized after the switch ACK has been restored to its normal position over a stick circuit. This stick circuit for relay RP can be traced from the positive terminal of the generator HG, along wire B32, front contact 6l of relay L, its own iront contact i3, lower winding of relay RP, and thence to the negative terminal of the generator HG. Relay L and the stick relay RP being now both energized, current will flow from the positive terminal of the generator HG over wire B32, front contacts 5l and 'i4 of relays L and RP, respectively, wire 5l', winding 6l of magnet valve H, controller 58, wire 9| back contact 59 of relay SP, iront contact 82 of relay RP, wires 93 and 89, front contact 63 of relay L, and thence to the negative terminal of generator HG and the magnet valve H will be reenergized and the whistle silenced. As long as the approach indication continues, the stick relay RP remains picked up and the magnet valve H is energized over the circuit just traced.

VIn the eve-nt that clear traffic conditions are reestablished and relay MA is again energized continuously and the relay L is deenergized, the stick circuit for the relay RP is opened at the front contact 5i of relay L and relay RP is released. The winding 6l of the magnet valve H is now energized over the circuit rst traced for that winding which circuit includes the front contacts @8 and 5d or relay MA. Consequently, the whistle WS is not sounded at the change from approach indication tothe less restrictive clear indication.

Returning to the assumption that the train is travelling under approach indication and that the stick relay RP is energized to complete the circuit to the winding 6l of the magnet valve H, I will further assume that trafic conditions change from approach to stop and that both relays MA and L are deenergized. The stick circuit ior the relay RP will be open at the front contact 6l of relay L and that relay will be released to open in turn the circuit to the winding El' resulting in the whistle WS being sounded after a brief delay to call the enginemans attention to the change in the indication from approach to the more restrictive stop indication. To silence the whistle WS, the engineman will operate the acknowledging switch ACK to close the controller 'lil for a brief interval and will then restore the switch to its normal position to close the controller 53. Controller I when closed completes the pick-up circuit for the two stick relays SP and RP the same as described hereinbefore. This time the stick relay SP will be retained energized by current supplied from the positive terminal of the generator HG over wire B32, back contact of relay MA, back contact 64 of relay L, wires and 83, its own front contact 84, winding of relay SP and to the negative terminal of the generator HG. Relay RP will be retained energized over the circuit extending irom the positive terminal of generator HG over wire B32, front contact 85 oi relay SP, bottom winding of relay RP, and to the negative terminal of generator With both stick relays SP and RP picked up and both relays MA and L down, current will iiow from the positive terminal of generator HG over wire B32, front contact Se of relay SP, front contacts 'i3 and 14 of relay RP, wire l', winding iii, controller 58, Wire 9i, a second front contact 36 of relay SP, and to the negative terminal of generator HG. Hence, the magnet valve H will be reenergized and the whistle WS will be silenced. It is clear, therefore, that if the engineman acknowledges the operation of the audible signal WS upon a change from clear to approach indication, or upon a change from approach to stop indication by operating the switch ACK, he may prevent the continuous operation o the whistle.

I will now assume that with the train proceeding under a stop condition, the traflic conditions change from stop to approach so that relay MA is operating at code frequency and relay L is picked up. When this condition of relays MA and L is established, the stick circuit for the relay SP is open at the back contact 64 of relay L, and relay SP is released. The stick relay RP continues to receive current over the front contact 6l or" relay L and its own front contact 13,

and hence remains energized. With relay RP picked up along with the relay L, the circuit to the winding 6l of the magnet valve H traced heretofore under approach conditions is completed, and hence magnet valve H remains energized and the whistle WS is not sounded in response to the change from stop to approach indication. Upon a change from stop to clear indication the stick circuits for both relays SP and RP are opened and both relays are released, but the winding El of the magnet valve H now receives current over the normal circuit for that winding, and which circuit includes the front contacts 48 and 512 of relay MA. Hence, the whistle WS is not sounded in response to a change from stop to clear indication. It follows that any change from a less restrictive to a more restrictive indication causes the whistle WS to be operated, and it continues to operate until the engineman acknowledges the change by actuating the switch ACK. Upon a change from a less restrictive to a more restrictive indication, the whistle WS does not operate and no acknowl edgement by the engineman is necessary.

In actual installations of systems of the type here involved it is not always convenient to locate the insulated rail joints 2 of Fig. 1 directly opposite each other, and, consequently, as the train passes from one track section into the next successive track section momentary loss of train control current with the result that the relay MA may release for a brief interval. Such operation of the relay MA may there may occur a vnance is obtained.

lresult'in the momentary deenergization of the `magnet valve The whistle'delayer WD is ef-V fective at such periods to prevent any sounding .of the whistle WS before the relay MA is reenergized.

Y To Yexplain the operationV of the apparatus as a whole I will assume that the train Va' proceeds through the stretch of' track shown in Fig. 1, the

Y train V remaining standing in the section to the right of location C. Alternating currentis con- Y tinuously superposed en the direct current track circuit for the section to the lerft'ofv location A l and is also superposed on the direct current track circuit for the sectionA-B. Consequently, the

relay MA of train Va is picked up continuously as the train proceeds through the section to the Vleft oi location A and also as it proceeds through the section Air-B. Under these conditions,` the cab signal light G is illuminated to display a clear indication and the magnet valve H is'energized to retain the whistle WS silent..V When the train VVa enters section B-C, the alternating current superposed on the direct current track circuitY forV the subsection B-Bi and also for the subsection Bl-C is coded and, consequently, the

- relay L of the train carried equipment is picked up continuously.

Under these conditions, the indication displayed by thev cab signal changes from Y green to yellow and the winding 61 ofVY the magnet valve H becomes deenergized and the audible signal WS is sounded. VThe engineman will acknowledgeV this change of the? indication in the cab signal by operating the switch ACK which causes the stick relay RP to ne picked up with the result that the winding G7 ofthe magnet valve H is reenergizedand the whistle silenced. As the train passes from the subsection B--BIV into the subsection Bl-C, no change in the train carried equipment takesV place. When the Y`train V2L enters the section to the right of location C, the Vsupply of train controlling current to the train ,Vab shunted away by the wheels and axles of the train V and, consequently, both relays L and MA of the train Va are deenergized.

Under these conditions the cab signal displays Vred and the winding Si oi the magnet valve His deenergized to cause the whistle WS to sound. The engineman will acknowledge this change in the indication of the cab signal by operating the switch ACK and both relays SP and RP are picked up, the magnet valve H reenergized and 1 the whistle WS silenced.

Y VIt will be noted that operation of a code transmitter is required for the track section immediately to theirear of an occupied section only, and Vthatcode operation of the train carried relay MA is required only during the interval when a train occupies theV section immediately to the rear'oi'an occupied section. I have found that in actual railroad service these periods are only a small proportion of the time a trainis on the road. Code operation of the equipment being required only for short periods, long life and re-Y liability for such equipment are obtained. Furthermore, a less expensive construction for Ysuch devices is permitted than where such devices are normally operated under clear conditions and hence a materialv saving in rst cost and maintevAlthough Ifliave herein shownY and described only oneform of trackway'apparatus and onlyV one' form of Vtrain carried apparatus embodying my invention,j it Vis understood that various Vclrianges and nodications may be made therein within the scope of the appended claims wither-it "6 Y Y vacteurs' departing from their, spirit and scope of my invention. if f Having thus described my invention, what I claim is: Y Y fr 1. Railway trame' controlling apparatus comprising a section of railway track, a source of a1- ternating current for said section, a code transmitter normally inactive, means governed by clear tranic conditions to supply current contin- V uously from said source to the traflic railsof said l0V section in series, means governed by approach traiiic conditions to render said code transmitter active andY tor supply current from the source through the code transmitter to the rails o the section in series, a rst and a second trainrcarl;

rie. relay, means for energizing saidrst relay continuously when .alternating current ows continuously through the rails of the Vsection, oc-

cupied by the Atrainand to operate fsaid nrst relay Yat code frequency when the alternating Vcur- '20 Y rent is coded, means forY energizing said second relay continuously when the rst relay is operated at code frequency; and a three-position cab'signal controlled by said relays and arranged todisplay a'clear indication when the irst relay is energized'continuously, tc display an approach,Y indication when said second relay is energized continuously andY to display a stop indication whenV both relays are continuously deenergized.

2T Railway traic controlling apparatus comr prising a stretch of railway track V*divided into track sections, a direct current track circuit for each section responsive'to VYtrailc conditions of the section, a codetransmitter for. each section normally inactive, a? first and a second controller governed by the track circuit and each operated i to a rst pcifsition when the section is unoccupied andY to a second position when the section is V occupied, neans' including the first lposition of said rst controller for superposing alternating current on the track circuit for the sectie-ri to therear, means including the second position of the second controller for rendering the icodeY transmitter active, means including the second position of the first controller for superpcsing Y alternating current coded by said transmitter on the track circuit for the'track section to the rear, a rst and a second train carried relay,

tact of each of 'said'relays 60 3. Railway trailic controlling: apparatus com- Y prisinga stretch ci railway track divided into track sections, Ya direct current trackl circuit for each section; a wayside signal for each section VYadapted todisplay a clear, an approach and a'65 stop indication inaccordance with the conditions Y of the track circuits of the sections in advance of the signal, a code transmitter for each section but normally inactivarmeans including arrst controller governed by the clear and approach 70 positions of a signal for superposing alternating current continuously onthe track circuit foia the section to the rear of said signal, means includinga second'controller governed by the stop position of the signal for rendering the coder trans- 75 Cil iii]

mitter active, means including a contact member' or" the code transmitter and the stop position of said first controller for superposing coded alternating current on the track circuit to the rear of said signal, a first and a second train carried relay, means for energizing said rst relay continuously when alternating current flows continuously through the rails of the section occupied by a train and to operate said relay at code frequency when the alternating current is coded, means for energizing said second relay continuously when the first relay is operated at code frequency; and a three-position cab signal controlled by said relays and arranged to display a clear indication when the rst relay is energized continuously, an approach indication when said second relay is energized continuously and a stop indication when both relays are deenergized.

4. Railway traffic controlling apparatus comprising a section of railway track, a code transmitter normally inactive, means for at times supplying alternating current continuously to the traffic rails of the section in series, means for at times rendering said code transmitter active for supplying coded alternating current to said traffic rails in series, a first and a second train carried relay, means for energizing said first relay continuously when alternating current ows continuously through the traffic rails and to operate said rst relay at code frequency when the alternating current is coded, a transformer having one-half of its primary winding excited with direct current over a front contact of said first relay and the other half excited over a back contact of said first relay, a rectifier interposed between the secondary winding of said transformer andsaid second relay, a less restrictive cab signal circuit including a front contact of the first relay, a more restrictive cab signal circuit including a front contact of the second relay and a still more restrictive cab signal circuit including a back contact of each of said relays.

5. Railway traic controlling apparatus comprising a section of railway track, a source of alternating current for said section, a code transmitter normally inactive, means governed by clear traflic conditions to supply current continuously from said source to the traflic rails of the section in series, means governed by approach trafiic conditions to render the code transmitter active and to supply .current from the source through the code transmitter to the rails of the section in series, a iirst and a second train carried relay, amplifying apparatus on the train receiving energy from the traffic rails, a rectifier interposed between said amplifying apparatus and said first relay, a transformer having onehalf of its primary winding excited with direct current over a front Contact of the rst relay and the other half excited over a back contact of said relay, a second rectifier interposed between the secondary winding of said transformer and the second relay, a clear cab signal controlled by a front contact of the rst relay and a back contact of the second relay, an approach cab signal controlled by a front contact of the second relay only, and a stop cab signal controlled by a back Contact of each of said relays.

6. Railway traic controlling apparatus comprising a section of railway track, a source of alternating current of a given frequency, a code transmitter normally inactive, means for at times supplying current from said source continuously to the traffic rails, means for at times rendering said code transmitter active for supplying current from said source to traino rails coded at a given frequency, receiving means including a filter tuned to resonance at said given frequency of the alternating current to receive energy from the traiic rails, amplifying apparatus including an electron tube governed by the energy picked up by said receiving means, a source of high potential unidirectional current for the plate circuit of said tube, a source of low potential unidirectional current for the lament circuit of said tube, a rst and a second train carried relay, a rectifier interposed between the amplifying apparatus and the first relay, means controlled by 'said first relay when operated for supplying current at a frequency corresponding to the frequency of operation, a second rectier interposed between said last mentioned means and said second relay, a filter interposed between said source of high potential and the plate of said tube, and a choke coil interposed between said source of iow potential and the filament of said tube whereby pulsations of the high or low potential sources are ineffective to energize said relays.

7. Railway traffic controlling apparatus comprising a section of railway track, a source of alternating current, means for at times supplying current from said source to the trahie rails of the section, train carried receiving means to receive energy from the traflic rails, amplifying apparatus including an electron tube governed by the energy picked up by the receiving means, a source of high potential unidirectional current for the plate circuit of said tube, a train carried traffic governing relay, a rectifier interposed between the amplifying apparatus and said relay for energizing said relay in response to alternating current owing through the traiiic rails. a lter including a reactor and a condenser interposed between the source of high potential and the plate of said tube, the connections of the reactor and condenser being arranged in such a manner that the failure of a connection will destroy the plate voltage of said tube, whereby pulsations of the high potential source are ineffective to energize said relay and said lter operates on the closed circuit principle.

8. Railway traffic controlling apparatus cornprising a first and a second train carried relay; means located partly on the trackway for energizing the first relay continuously in response to energy received on the train from the trackway under clear tra-nic conditions to operate said first relay and to continuously energize the second relay under approach traflic conditions and to deenergize both relays under stop trafic conditions, a first and a second stick relay, manually controlled means for energizing said stick relays, means for subsequently holding the rst stick relay closed as long as said second train carried relay is energized and for subsequently holding both stick relays energized as long as both train carried relays are deenergized, a magnet valve, a first circuit for said magnet valve including a front contact of the iirst train carried relay and a back contact of each of the stick relays; a second circuit for the magnet valve including a front contact of the second train carried relay, a front contact of the first stick relay and a back contact of the second stick relay; a third circuit for said magnet valve including a front contact of each of the stick relays, and an audible signal operated by said magnet valve.

9. Railway traffic controlling apparatus comprising a first and a second train carried relay; means located partly on the trackway for energizing the rst relay continuously in responsel to energy received on the train from the track- Way under clear traiilc conditions, Vto operate said iirst relay and to continuously energize the second relay under approach trafc conditions and to deenergize both relays under stop traffic a. first circuit for said Ymagnet valve including a iront contact of the iirst train carried relay and a back contact of each of the stick relays; a second circuit for the magnet valve including a front Y contact of the second train carrieolrelay, a front contact oi. the rst stick relay and a back contact of the second stick relay; a third circuit for said magnet valve including a front contact of each of the stick'relays, and an audible signal operated Vby said magnet Vvalve When deenergized.

10. Railway traflic controlling apparatus comprising, a track section, aV source of alternating current, acode transmitter normally inactive, a first and a second Contact member governed by said transmitter, a normal contact for s aid first member and a normal and a reverse contact for said second member, a first and a second controller, means governed by safe trailic conditionsV in advance of said section for operating said controllers to a first position, means governed by unsafe trac conditions-in advance of said section for operating said controllers to a second position; means including said source, the normal contact of said second member and the first position of said iirst controller for supplying alternating current continuously to the rails of the section Yin series; means including the normalV contact of said iirst member andthe -second position of said second controller for rendering said code transmitter active; and means including said source, the reverse contact of said sec- Vondrmember and the second position of the rst controller' for supplying coded alternating current to the rails of the section in series.

l1. Railway traffic controlling apparatus comprising, a track section, a source of alternating current, a code transmitter normally inactive, means governed by clear traffic conditions in advance of the rsection and rendered eiective Y by the inactive condition of said code transmitter to continuously supply alternating current from said source to the traic rails of the section in series, means governed by approach traic conditions in advance of said section Lto c render said code transmitter active, and other means governed by approach traflic conditions in advance of said section Vand rendered. effective by the active condition of said code transmitter to supply coded alternating current from the source to the traic rails of the section in series.

l2. Railway trafcV controlling apparatus comprising, a track section, a source of alternating current, a code transmitter normally inactive, aY

contact member operated by said code transmitter,ia first and a second circuit controller,

means governed by safe trafiic conditions inV advance of the section for operating said controllers to a first position, means governed by unsafe traiilc conditions in advance of said section for operating said controllers to a second position, means including saidrsource and eiective by the normal position of the contact member and the first position of said iirst controller for supplying alternating'current continuously to the rails of the section in series, means including the second controller in its second position for rendering the code transmitter active, and other means including said source andl effective by the active condition of said contact member and the second position of said first controller for supplying coded alternating current to the rails of the section in series.'

i3. Railway traiiic controlling apparatus comprising, a first and a second track section, a direct current track circuit'for each section including the traiiic rails in series, a code transmitter for each section normally inactive, a contact member operated by said code transmitter,

a rst and a second'circuit controller, means governed by the track circuit of the iirst section when unoccupied to move said controllers to a rst position, means governed by the track circuit of said rst section when occupied to move said controllers to a second position, a source of alternating current, means including said source and effective by thenormal position of the contact member and the rst position of said first controller for superposing alternating current continuously on the trackcircuit of the second section, means including the second position of said second controller for rendering the code transmitter active, Vand other means including said source and effective by the active condition of the contact member and the second position of said rst controller for superposing coded alternating current on the track circuit of said second track section.

- FRANK H. NICHOLSON.

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