US2761962A - Intermittent inductive speed control system for railroads - Google Patents

Description

Sept 4, 1956 J D. HUGHsoN ErAL 2,761,962

INTERMITTENT INDUCTIVE SPEED CONTROL SYSTEM FOR RAILROADS 5 Sheets-Sheet l Filed Aug. 2, 17952 @Haw so..

soma wzmn S528 SePt- 4, 1955 .l D. HUGHSON x-:T AL 2,761,962

INTERMITTENT INOUOTIVE SPEED CONTROL SYSTEM FOR RAILROAOS Filed Aug. 2, 1952 5 shee'tS-Sheet 2 SePt- 4, 1955 .I D. I-IUGI-IsoN ET AL 2,761,962

INTERMITTENT INDUCTIVE SPEED CONTROL SYSTEM FOR RAILROADS Filed Aug. 2, 1952 5 shee'Ls-sheet s F-lGLS, INDUCTOR wINDING OPEN CIRCUITED (STOP CONTROL) DIR. ECEIVER NORMAL SECONDARY PICKUP CURRENT R CURRENT LEVEEFOR PR RELPNRWNDING SEC.

LEVEL POR NR. RELAY \zERO SECONDARY CURRENT M+) INDUCTOR WINDING ENERGIZED FOR AIDING FIELD CAUTION CONTROL NORMAL SECOND- PICKUP CURRENT DIR ARY CURRENT LEVEL FOR PR RELAY RECEIVER SEC. wINDING E 5 PNR wINDING YTDRYDAW nCURRENT N 'NDUCTOR LEVEL FOR NR. RELAY HD \ZERO SECONDARY CURRENT SEE HG2 L ,ym xx5 D (CLEAR FIOLE. l

INDUCTOR WINDING ENERGIZED FOR OPPOSING FIEL CONTROL) PICKUP CURRENT NORMAL SECOND ARY CURRENT LEVEL FOR PR RELAY DIR SEC. RECEIVER Y WINDING PNR WINDING YD RcTAWA-Y CURRENT s INDUCTOR LEVEL FOR NR. RELAY HD zE-RO SECONDARY CURRENT @g55 FICg 6 NRP I-xw'l-em IGI. I

PR e 1R T/ I--T 351 37 L# T24 +P ,P- NR INVENTORS R3 I JDHUOI-ISON AND C. F. STAFFORD Il THE\R ATTORNEY Sept. 4, 1956 .I D. HUGI-ISON ET AL 2,761,962

INTERNITTENT INDUOTIVE SPEED CONTROL SYSTEM FOR RAILROADS Filed Aug. 2, 1952 5 Sheets-Sheet 4 STOP OONTROI. SEQUENCE RR NRR- R5 M R5 {.//I-AOKNOWLEDGEMENT REQUIRED MS l SOME TIME PRIOR TO DROPPING OF RELAY R5 H S l l I l l 4|;\AOKNOWLEDGEIIAIENT NOT REQUIRED AFTER RELAY R5 PICKS UP FIC-N8.

I I``ACKNOWLEDGEMENT NOT REQUIRED AFTER RELAY R5 PICKS UP INVENTORS. JDHUGHSON AND .C.F. STAFFORD MMM,

THEIR ATTORNEY 'Sept 4, 1956 .I D. I-IUGHsoN ETAI. 2,761,962

INTERIIIITTENT INOUCTIVE SPEED CONTROL SYSTEM POR RAILROADS Filed Aug. 2, 1952 5 sheets-sheeI'S FIS. 9.

CLEAR CONTROL SEQUENCE (FIRST) NR A- PR A\ l MS I -ACKNOWLEDGENIENT REQUIRED MSP lffZ/f SOMETIME PIQQRE To I OROPPINC O LAY NRP H S A\}\ HSP I ACK llr I I ACKNOWLEDGEMENT NOT REQUIRED l AFTER RELAY HSP PICKS UP FIQJO.

CLEAR CONTROL SEQUENCE (SUCCESSIVE) MSP I-IS A\ HSP ACK NO ACKNOWLEDGEMENT REQUIRED INVENTORS. J. D. HUGHSON -AND BY C F STAFFORD M C m,

THEIR ATTORNEY Application August 2, 1952, Serial N'oli'l 9 Claims. (CL 24663) This invention relates to an Yintermittent inductive train control system, and more particularly pertains to a system wherein any one of a number of different speed iimitsfrnay be imposed upon moving trains by the inductive transfer to appropriate" train-carried equipment' of' respectively Idifferent controlling inuences from ixedwayside-locations.

In some prior intermittent inductive: train controlsystems, a controlling influence is made eiective on a train as it passes each wayside signal locationfonlywhen traic conditions ahead require that the signal display a restrictive indication. To avert an automatic penalty'brake application in response to this controlling inuence, it is required in these prior systems that the engineer aeknowiedge his observance of the restrictive signal by performing a'.- prescribed manual actas he passes suchsignal. iniths way, alertness of the engineer to the' wayside signals is required. But in these systems, the' engineer is'not forced to heed the restrictive signal indication afterfacknowledging'. it, since he may operate the train at any speedv he chooses.

In thesel prior systems, it hasnotbeen feasible tcr irnposeA a control with a corresponding speed limit upon-a train as it passes a signal location and have this control remain' steadily eiective until the train reaches the next wayside signal location. The reason is that sucl-l asystem requires more than one kind ofcontrol from a wayside United States Patent signal location so that a previously imposed yrestrictive control can be removed when traffic condi-'tions warrant; and such a plurality of controls from a xed wayside'vlocation" to passing trains: has'not been available in; a1 safe and reliable organization'.

It is proposed according to this invention to provdelan intermittent inductiveY train' control system in'whi'ch a phi# ralityof dilierentl controls are inductively transfer-'redv or transmitted to appropriate apparatus on passing trains from each wayside location so thatrestrictive' controls: are selectively appliedand removed asY required. .'In thisfway, a.v particular speed limit is imposed with eachdiierent controlyand,A through the cooperationof speed governor equipment on the train, the system is soy organized asto cause the brakes to be automatically applied wheneventhe ,then effective-speed limit is violated. Thus, thersystem may actually be termed an intermittent inductive speed .control system.

Described briey, the train control system of this linventio'n' comprises both wayside apparatus and v.traincarried apparatus with the various controls' transferred inductively from each Wayside location tov passing vehicles. The Wayside apparatus includes an inductor havinga control Winding: which may 'be f selectively open-circuited or energized with direct current'of one polarity or' 'the' other dependent upon- Whether a stop,.: caution: or" clear' control to be; etective upon the train.

The train-carried apparatus comprisesa receiver-which moves through an inductive couplingj relationship-With theV wayside inductor during train movement.- -receiver. has Va corey structureuponwhich is mounted aprimary Winding and a secondary winding. The primary current.

winding isfnorrl-ially energized with direct current so` as to magnetizethe core structure. rl`hus, the secondary winding -ismaglnetically coupled tothe primary'winding through the receiver` core structure. Distinctive changes occur in vtheiiux'of'the receivers magnetic circuitas` the receiver and inductor pass through an inductive coupling relationship in accordance with Whether the control windingl on :the inductor isopen-circuited or energized with'one polarityorr'theother.. These distinctive fluxchanges result in `correspondingly distinctive changes of current in' a sec- .,trol andrequires'that the train move' atthe slowest of several established speed limits. When the control winding of the inductor isenergized'with direct current of one particular polarity a less restrictivel or caution control is transmitted toy the vehicles; whereas, Awhen the control winding of the: inductor is energized'withthe'opposite .polarity a, still less restrictiveor: clearing' control is transmitted to passingvehiclcs In this way, the system is organized on thegfail` safe. principle. It',^for example, a train is vtravelling atthe-permitted high speed, andV triic .conditions ahead become such that it' shouldf receive' a medium. speed control inuence upon passing thernext Wayside inductor, such Wayside inductor has its control winding energized with; said particular polarity of direct However, if such energization of lthe control .winding -is not established because; of somecircuitfaiiurc, the control winding becomesopen-circuited. and the inductor then transmits the most restrictive; control influence to thel passing train.

With such an organizationwhere the controlwinding of the wayside inductor is selectively open-circui-ted or energized with one polarity or the other, it may happen .thata circuit is completed to energize the controi Winding but due to a power failure the winding is in ele'ct` short- 'circuited Since.- anv inductor WithV atshort-circuitcd winding is ineffective to transmit a controlling inuence to. the train-carried apparatus, an unsafeV condition would thus arise if trac conditions were such as torequirethe1trans- Vmission of a caution control. However, the wayside` apparatus according to this invention is so` organized as to eliminate this unsafe conditionv by causingfthecontrol winding of an inductor to become open-circuited if the energization of the wayside inductorv for' either polarity drops below a certain prescribed level. vIfsuch a condiytion occurs, then .the Waysidey inductor becomes eiective to transmit the most restrictive control to the traincarried apparatus of a passing train.

The system of the present invention mayK alsobe` organized to require that the engineer operate, anacknowledging contactor eachv time his trainzpasses a Wayside inductor immediately in advance of a signal" displaying 'a stop or caution control. In addition, the apparatus 's organized so that the engineer is required to operate his .acknowledging contactor when his train passes tliewaysidef inductor immediately in advance of the'- rstrclear signal following the operation of the train under previously received .restrictive controls. However, means isrprovided so that after a train has receivecithe. irsticlearr control, it may receive successive clear controls without; requiring the engineer to actuate his acknowledging contactor. This arrangement is provided to give vthe utmost protection to the system by avoiding the possibility ofa train-carried receiver being affected falsely from some extraneous source to give a clearing control while the train is being operated under a restrictive control previously received.

In view of the above considerations, one object of the present invention is to provide an intermittentinductive train control system in which any one of a plurality of controls can be safely and reliably transmitted from a wayside inductor to a receiver or a passing train.

Another object of the present invention is to provide the plurality of controls for such an intermittent inductive train control system by selectively opening the control winding of an inductor or energizing it with positive or negative direct current in sucha way that the tailure of the source of energy cannot result inthe transmission of a less restrictive control.

Another object of this invention is to provide an intermittent inductive train control system in which the plurality of controls may be transmitted to a passing train from each of a plurality of successive wayside locations, with the train-carried receiving apparatus so acting-in cooperation with a speed governor on the train as to impose predetermined speed limits on the train as it passes successive wayside locations which speed limits are maintained until the train passes a successive wayside location transmitting a different control.

`A further object of the invention is to so organize the train-carried apparatus that the engineer is required to acknowledge the signal at each wayside location for the reception of all controls except the reception of successive clear or high speed controls. This will require that the engineer acknowledge whenever the train passes a signal location with a wayside inductor controlled to a restrictive condition and also will require that the engineer acknowledge when the train passes the rst wayside location where the inductor is caused to give a clear or high speed control.

Other objects, purposes, and characteristic features of this invention will in part be obvious from the accompanying ldrawings and in part pointed out as the description of the invention progresses.

In describing this invention in detail, reference is made to the accompanying drawings in which like reference characters designate corresponding parts throughout the various views, and in which: i

Fig. 1 is a circuit diagram illustrating in detail one embodiment of the vehicle-carried equipment of this invention;

Fig. 2 diagrammatically shows one way in which the wayside inductors may be selectively controlled in a line wire block signalling system;

Figs.'3, 4, and 5 illustrate respectively the different eiects produced in the receiver secondary winding as the Wayside inductor is respectively open-circuited or energized with one polarity or the other;

Fig. 6 shows a portion of the circuit of Fig. 1, particularly that portion involving the receiver secondary windings and the relays directly controlled by it; and

Figs. 7, 8, 9, and l() are timing charts which indicate the sequence of relay operations in response to the different received controls.

To simplify the illustration and facilitate in the explanation of this invention, the various parts and circuits are shown diagrammatically and certain conventional illustrations are used. The variousrelays and their contacts are illustrated in a conventional manner. The symbols (-l) and are used to indicate connections to the opposite terminals of a battery or other source of electric inductor, is provided with a winding CW as shown in Fig.A 1, ,and this Winding may be controlled by the wayside signalling system in the manner shown in Fig. 2.

Briefly, the wayside circuit organization of Fig. 2 includes a stretch of track divided into a plurality of track sections such as the track section 2T each having a track relay TR connected across the rails at the entrance end with a track battery TB connected across the rails at the exit end through a limiting resistor LR. An inductor IND is shown located just ahead of the entrance to each track section, and an auxiliary inductor 87 is located at approximately braking distance for medium speeds ahead of each regular inductor IND.

The inductors governing the movement oi trains into any track section are controlled by a home-distant relay HD such as the relay SHD. This relay is of the polarretained neutral type having both polar and neutral con tacts. When the winding of this relay is energized with either polarity of direct current, the neutral front contacts are closed, whereas the polar contacts are operable to either right or left-hand positions depending upon the polarity of energization applied to the winding.

The circuit organization for controlling the control winding CW of each inductor includes contacts of the as,- sociated HD relay, and also a check relay CK. An approach relay such as relay 3A indicates by its dropping away the entrance of trains into the track section 2T. A slow release repeater relay of this approach relay, such as the repeater relay SAP, together with the check relay CK provides means for causing the control winding CW to becomeV open-circuited if the required level of energization is not maintained as will later be explained. The wayside signals such as the signal S3 are shown diagrammatically with their control being dependent upon the approach relay A and upon the actuated condition of thc associated HD relay.

Although the wayside circuit organization and in particular the manner of control of the control winding CW of the inductors will later be described in greater detail, it may be briey stated that the circuits associated with the control of the winding CW cause this winding to be open circuited when trai'lc conditions warrant transferring the most restrictive control to passing vehicles; energization of one particular polarity is used when a clearing control is to be inductively transferred, and of the opposite polarity when a medium speed or caution control is to be transferred.

The train-carried receiver REC is shown diagrammatically in Fig. l. The receiver is mounted upon the locomotive or tender in such a manner that it passes through a relatively close inductive coupling relationship with the current instead of showing all of the connections to these terminals.

The detailed circuit of Fig. l also includes, in addition to the train-carried equipment, a diagrammatic View of a wayside inductor IND. The detailed structure of a typical wayside inductor of the kind contemplated to be used in this invention may be as shown in the patent to C. S. Bushnell, No. 1,706,839, dated March 26, 1929. This wayside inductor IND. As indicated by the direction of the arrow shown above the receiver, the assumed direction of motion of the receiver relative to the stationary wayside inductor is from left to right. In this Fig. l, the relative positions of receiver and inductor are shown as those occurring at the instant when they are directl opposite each other.

The train-carried receiver REC is provided with both a primary winding and a secondary winding which are magnetically coupled to each other through the ycore structure of the receiver. In one specific embodiment of this invention, the receiver used was of the kind shown in the Patent 1,733,982 t0 C. S. Bushnell, dated October 29, 1929. Merely by way of illustration, the secondary and primary windings are so situated on the receiver with respect to-the normal direction of travel of the receiver in the embodiment of the invention shown in Fig.V l that the primary winding is towards the front of the vehicle and becomes inductively coupled with the wayside inductor before the secondary winding. The Vprinciples of the invention apply equally well when the sec'- ondary rather than the primary winding is located towards the front of the receiver. The eiect produced with primary "of the' 'receiver is 'energized' with "directcurrent Theampereturns of the magnetization applied tothe receiver'by th'e eld offthe primary windingfare suicieu't to 'establish a relatively 'strong magnetic lfield. 'In the embodiment of the 'invention showntinFig. 1, rthe'polarity of energi'zation of the receiver primary was selected to cause the pole 'of the receiver bearing"the primary winding 'to' be a south pole, "so that the other -legbf kthe receiver bearing the` 'secondary winding then became anorth'pole. "Thisparticular selection of polarivtiesis'meritionedrnerely for purposes ofillnstr'ation; "the opposite polarities may as well be used. l

The train-carried'v apparatus also includes anrelec'tro- I:pneumatic valve vlPVfwhich lisv `diagramrnatically illus-v 1trated in Fig. l. Whenelectr'ical energy is applied 'to "this valve, the control of the air brakes 'on the train is entirely under the direction lof the engineer. If this'electfrical energy Vsupplied to the EPV valvev removed, the 'valve causes the air pressure for the' brakesfto beim- Yinediately reduced with the effect of' causingas'ervice brake' application. One valve EPV of this'kind is'sho'wn iinfthe-Patent No. 1,649,444 to- C. 'S. Bushnell, 'dated Nov'emher'li 1927.

A speed governor SG is also shown diagrammatically Fig. 1. Although illustrated in the drawing as being Va speed'governor of the centrifugal type, other types vof rspeedgovernor may also be used without departing from -the -scope ofthe invention. One' type of speed governor -thatmay be used' is illus'trate'dimdetail inthe Patent `lo-21,457,748 `to H. B. Taylor,'datedDecember'28, 1949. As' indicated in Fig. 1 the various governor'con- 'tacts'fopen at different train speeds vforei'ecting different .control-of the train-carried equipnlent attirevv di'er'en't frain; speeds.

:The acknowledge contactor ACK is i-llusit-rated'diag'ramlrrlatically in Fig. l as controlling a plurality -of contacts. contacter also has 'associatedfwith it a timing device Which controls' 'the' contact 30. If the'acknowledge contactoris continuously actuated for a relatively long time interval a`s,for example, in excess of fifteen seconds,l then the timing device which is initiated into operation when the acknowledge contactor-ACK is first operated, ycauses this V'contact' to open. then opened and an automatic brake Vapplication occurs. '.Thisaction discourages any attempt to hold the acknowlfedge contactor actuated in order to eliminate the-need 'for-acknowledging each-restrictivesignal indication. In

one .particular embodiment of the invention, the acknowledge'contactor ACKv which was used was' of the y-type 'shown in the Patent No. 1,725,729 'to C S. Bushnell, dated August 20, 1929.

The suppression contactor SC shown in Fig. 1 prer`vents deenergizationvof the Valve EPVunder certain conditions even though ythe timing relay TD has dropped away. If, for example,a restrictive'control become'sl'effective `on the train-carried equipment and the train is vatithat time moving at a speed in excess 'of the speed vlimit corresponding to that control, the timing relay TD becomes deenergized as will later be more fully described. The opening of front contact -31 of relay TD ordinarily results lin the deenergization of the valve EPV so that an automatic brake application follows. But this -action can be circumvented by the engineers making aeservice .brake application prior tothe dropping away of relay TD. A service brake application causes an increase -in pressure at the inlet pipe 32 of the brake suppression valveV BSV so that the contacts 33 become closed-through the contact 34 on the cylinder of the brake suppression valve. In one specific embodiment of this invention, the brakesuppression valve BSV was ofthe type illustrated inthe patentto C. VS. Bushnell,-No. 1,757,410, ldted May 6, .1930.

The train-carried equipmentalsocornprisesa number The circuit -to thevalve'EPV is i "troingitic'relaysl no'gtlesearetle'igatief A nsive and'psitive-rsprls'ive relays NR 'and VPR which are distinctively"controlledinaccordance ii'v'tlv the variations' of currer'it"'tak'1ig 151`ce"in` the receiver second'- ary windingfthrou'ghthe iridlctive effects ffthefw' yslde inducto'rs. 'THerela/YLRS is a'p'enl'tyrelay;'tle'df'p i away of this relay may Occur, for example, through:` 'ilure 'toproperly "acknowledge "restrictive signal indications. When this :relay drops away th'e valve 'EPV lcomes de'energized and Van automatic b'rake'ppliciatin follows. The trainca'rrie'd equipment can tlen be reset to its 'normal condition nly'y'bring'ing ihetinto a very slewspeed. Y A Y 'The4 slow release elayRSl is ordinarily drppedaway whenever the trains passes "an"l iductor' at arestrictive ignal location. During the time tli'at'tli'is relay' R5 dropped away, the acknowledge contador ACK 're'- quired to'beV operated orider'to'l prevent; dropping' away of the penalty relay R3. The relay NRPs arepeater of the relay NR and o'n'e of its functions isto cauthe receiver secondary circuitto he closed'after thefcifrg'guit has been openedV b'y" Vtlie dropping'awayrof relaX'lR'. The medium-speed and high speledielaysfMs and Hs respectively a're selectivelyactuated in accordancefwith whether a mediurn'sp'eedor `high"speed control is received *at a wayside inductor location. Theserelaylsl`store such "a control only momentarily; such momentarily storedl'comjtrolls transferred to a corresponding repeater relay MSP 'ori HSP d'e'pendin", up'ontheI control received. 'Ihefseiatl ter relays 'a'revprovided with stick circuits which hold contolrecived'at one'wyslde iriductr loatin`l1`nti1 va different control is received 'at a'followig ilidit'i' location. y,

relay TDis a slow release 'relay as indicated -by the heavy lj le f'lftlie symbol representing this-relay. This relay TD-is ordinarily requiredltobein a-'picked -up`cndition in V'order'forthe valve EPV'to'be energized. `'vl'lie energiz'tin tof this relay TD 'is, in turn, dependent'up'o'n-'the Atr-ain Vspeed being"lepl: below the then eective speed limit as established-by the control received froln'the wayside 'inductor last passed By the train.

The conditionof 'the various Arelays included in 'the vehicle-carried apparatus are those vthey assume Vwhen the train-carrie`d apparatus has beenproperly re'seff no controlling inuence has -yet heen'received from a'wayside inductor,l and the'trainis'mov-ing below itsmost 'rsi'c tive speed. Thernanne'r'in-whi'ch the'var'io'u's relays'and contacts are closedto assume these conditions'up'ohresetting willl nowbe described.

Prior i@ nie resetting voperation--almiit,tolse describen; the Various relaysnd `devices"rei'riairi in deenergized coriditions. The reason that allfof the relays `and devices (see Fig. l) -reniaindeenergized is'that they receii/"eelectricalener'g'y 'over wire -1-0, -and this wire is normally "ein ergized from andlthrough front cnt'pact Iii-of relay Rs and from Contact -12 ef relay R3. Bilt with 'relay R3 along with all the other relays initiallyV deenergized, the front contact 1'2 of this relay R3 is open so that electrical energy is not applied 4i0 the wire 10. 'iidei this condition, the'electfropner'riaticvalve PV is'also deenergized and,-as will tfer be described, the brakes'ou the train cannot bef released iiiitil this valve'be'comes eri; ergized.

with the ltrain at asfaiid'stili, 'contadas of' -tliespeeli governorSG is'closed'as indicated in Fig. l. v'y actu ating the acknowledge contacter-ACK atAv this time,` energy is applied from through the whistle valve WV, back contacts14 of the acknowledge contactor ACK, closed Contact 13 -of the speed 'governor SG, back contact is of the acknowledge co'iiia'for ACK to tliewiie 10. with wire 1e new energized, acircuifis esrallishe'd through the winding of 'relay R3, the bllasillnip BL and Athe 4p'rilha'r'y 'winding VPRI on the reiverRrG, to i-i. niisfcirciiii causes-lie relay Rato piek up and 'ballast lamp BL is included in series with the primary lwinding to keep the energization of this winding at a fairly constant level despite variations in the value of supply voltage that may occur. In this way, the degree of magnetization of the receiver is held substantially constant.

The electrical energy appearing on wire 10 as a result of actuation of the acknowledge contactor ACK during the resetting operation also causes current to ow'from 'wire 10 through back contact 16 of relay NRP, the winding of relay PR, the secondary winding SEC of the receiver REC, the winding of relay NR, the ballast lamp BL, and the primary Winding PR1 of the receiver to Since the resistance of relays NR and PR is fairly high, the amplitude of current through relays NR and PR and Vthe secondary winding is maintained at a fairly low value .as compared to that existing in the receiver primary winding.Y Therefore, the number of ampere turns contributed by the energization of Vthe secondary winding to the magnetic circuit of the receiver is very small as compared to that furnished by the energized primary winding. The normal current level through the receiver secondary winding and the operating characteristics of the relays PR and NR are so selected in relation to each other that the normal receiver secondary current is greater than the 'pick-up current level for relay NR but is below the drop away current level for the relay PR. Normally, therefore, the relay NR is picked up by the circuit just described while the relay PR remains dropped away.

With relay NR now picked up, a circuit is completed to energize the front repeater relay NRP of relay NR. This circuit extends from the now energized wire 10, through front contact 17 of relay NR, wire 18, back contact 19 of the acknowledge contactor ACK, back contact 20 of relay R5, back contact 21 of relay HSP, back contact 22 of relay MSP, and the winding of relay NRP to As soon as this relay NRP is picked up, it is held up through a stick circuit which includes the front contact 23 of this relay.

When relay NRP is picked up, the opening of its back Contact 16 opens the pick up circuit for relay NR but this relay NR and the receiver secondary winding remain energized through the stick circuit for relay NR which includes front contact 24 of this relay NR. The picking up of relay NRP also completes a circuit for the energization of relay R5. This circuit extends from Wire 10 and includes the front contact 2S of relay NRP and the winding of relay R5 to Now with relays R3 and R5 both energized, the acknowledge contactor ACK can be released as electrical energy is now applied to wire l0 from (-f-), through front contact 11 of relay R5 and front contact 12 of relay R3.

When energy rst appears on the wire 10 during the resetting operation, a circuit is completed to energize the slow release timing relay TD. This circuit is established from the wire 10, through contact 26 of the speed govcrnor SG, back contacts 27 and 28 of relays HSP and MSP, and the winding of the relay TD to As soon as relay TD picks up, a circuit is completed from wire 10 and including the normally closed contact 30 of the acknowledge contactor ACK and front contact 31 of relay TD to energize the valve BPV. With the valve EPV energized, the engineer is able to release the brakes and put thetrain into motion. now completed, the various Vrelays and devices are in the condition illustrated in Fig. 1.

lNDUCTlV E RELATIONSHIPS 'v Prior to giving a detailed description of the manner of operation of this invention, it is believed that the description of the invention will best be facilitated by describing the dilerent effects produced in the receiver secondary circuit as the receiver passes wayside inductors controlled to different conditions. These diierent eects on the With the resetting operation receiver secondary'current are .illustrated graphically-,n the Figs. 3, 4, and 5.

The winding of a typical wayside inductor isiillustrated in these Figs. 3 5 as being controlled through rthe. contacts of a HD relay as already briey explained. This manner of control is shown in greater detail in Fig. 2. The graphical illustrations of Figs. 3 5 are not intended to show exactly the way in which the receiver secondary current is varied; they represent the current variations in 4only an approximate matter. Fig. 6 shows ay portionof the circuit of Fig. l,r particularly illustrating the circuit relationships involved in the control of the relays NR and PR by the inductive action affecting the secondary winding SEC.

When the vehicle-carried receiver passes through an inductive coupling relationship with an inductor having its control winding open-circuited as in Fig. 3, the current in the secondary winding of the receiver experiences a substantial decrease. The normal level of receiver secondary current is at some value which is above the drop away current level for the relay NR but is below the pick-up current level for the relay PR as shown in Fig. 3. This normal current value is also above the pick-up current level for relay NR which is somewhat above the drop away current level shown for this relay. As the receiver passes the open-circuited inductor, the secondary current in the receiver is momentarily decreased to a level below the drop away currentlevel for they NR relay. As described, the NR relay (see Fig. 6) is maintained normally energized through a stick circuit which includes the front contact 24 of this relay. Therefore, even a momentary reduction of the energizing current for this relay suicient to cause the front contact 24 to open for an instant results in the complete deenergization and dropping away of thisfrelay. Upon the dropping away of relay R1 the circuit for the secondary Winding of the receiver is opened for a brief interval. The dropping away of relay NR results in the deenergization of relay NRP so that this relay NRP quickly drops away, and, by the closing of its back contact, causes the receiver secondary circuit to become closed. The effect on the receiver secondary current caused by the momentary opening of the secondary circuit is not shown in Figs. 3-5.

In Fig, 4, the relay HD is shown energized so as to cause the front contact 35 to be closed, and the polarity of the energization vcauses the polar contacts 36 and 37 of this relay to be in their left-hand positions. The resulting polarity of energization of the control winding CW for the wayside inductor iND is assumed to so magnetize the wayside inductor that its polarityfaids the magnetic field of the receiver in that, with unlikel poles opposite each other, the normal magnitude of receiver flux is increased. Under these circumstances, the secondary current level is first reduced to a level that is below the drop away current level for the NR relay so that this relay drops aWay.- Immediatelyafterwards, the secondary current level rises momentarily above its normal value to a level that causes the picking up of relay PR. These current variations are illustrated roughly in Fig. 4.

The effect on the receiver secondary Winding when the control winding of the inductor is energized with the opposite polarity from that of Fig. 4 is shown in Fig. 5. Here the relay HD is shown energized so that front contact 3S is closed, and the polarity of this energization causes the polar contacts 36 and 37 to be in their righthand positions. This polarity of energization results in a magnetic eld for the receiver opposite that shown in Fig. 4. This magnetic eld is designated as an opposing eld since, with like poles opposite each other when receiver and inductor are directly opposite, the normal receiver flux is decreased. In response to these conditions the receiver secondary current varies approximately as shown in this Fig. l5 as the receiver passes Y9 'the inductor incthat the -current-1 -rst' rises:v above =itsfnor mal value to a value sufficient to cause the relayePR topick'up and'lthendecreasesto a valuev below its normal value soy zthat Vthe NR relay is dropped away.

*The "distinctively different veffects produced on "the receiversecon'dary currentin -response to the vdiiierently controlled conditions -of the control winding for the wayside inductor are demonstrated Ain anV approximate manner 'by^these-Figs. 2,'3, and 4. To-summarize, aninductor -with its control winding 'CW open-circuited produces substantially only a currentdecrease in the receiver secondarywinding-so' that the only-effect on-the associated'relaysis to cause relay -NR to drop away. Under-thesecircumstances thel inductor is notY elective to cause operation Aof the PR relay.

When the` inductorsA control :winding CW is energized with"ajpolafrityl to' cause 'its magnetic field to aid that of thereceiver'fwhen 'the receiver and inductor are oppositeeachother,l the-receiver current is first reduced andthen increased. The sequence ofV relay operations produce'dby this changeinv receiver secondary current is rst a dropping away of' the NR relay followed ,by the picking `up vof the PRY relay.

Upon'reversal of the polarity of magnetization of "the"iriductor` byreversing the polarity of the current applied tothe'control winding CW, the eiect produced onthe 4receiversecondary current is substantially also reversed. 'Instead ofradecrease of current followed by ank increase as'iillustrated in' Fig.13, the current now rst increases and then decreases. This reversal also reverses'ithesequence'of operation of the relays NR and PR'inthafthe'iirst occurring current increase causes relay PR to pick up and then the following currentdecrease causes relay NR to drop away. K

Aspreviously'mentioned, the receiver REC maybe constructed so that the secondary rather than the primary'winding is towards the front of the vehicle. "Then during normal forward-movement of the vehicle, the waveformof receiver secondary current caused. by wayside inductors having their control winding energized is substantially opposite that shown in Figs.. 4 and 5. In other words, a receiver havingitssecondary winding toward the front but with relative polarities of .magnetization unchanged and becoming inductively .coupled with a wayside inductor controlled to supply an aiding magnetic field as in Fig. 4 experiences ya current, change in its secondary-winding thatcomprises .first a.y current increase .followed by a. current decrease as .shown in Fig. 5l rather than the` opposite. condition illustrated `iny Fig. 4. Similarly, a receiver in thiscondition and becoming inductively coupled with an inductor energized. to have an"opposi ng Vmagnetic. eld ,as in. Fig. 5l experiences a secondary current change approximately likethat shown in Fig. 4. The reasonfor this'elect is believed tobe caused by the, fact that the circuit associated with Vthe secondary winding. of the .receiver is of high impedance; whereas, the circuit associated .withthe primary winding is of considerably lower impedance. The coupling of the leg. of the receiver bearing the secondary winding with theinductor thus isbelieved to produceia` substantially greater ,effect onsecondary current than-When the legbearing they primaryV winding is so linductively coupled. .Thisdissyrnmetry'with respect tothe two legs of the. receiver structure causes the effect produced vin the receiver secondary circuit to 4-be idependent upon whether the leg bearing .the primary or the secondary windingrst becomes inductively .coupled with the wayside inductor.

Thesequence of relay operations of the relays NR and PR..that occurs as the train-carried receiver passes a wayside inductor'determines the nature of the received control. .The manner in. whichv this sequence-of relay operations is effective. to imposey different controls x'w'ith .correspondingly different ,speedf limits will be fullydescribed. .Brieflyyhowevcnin the embodimentv oftli'e invennen-snowman Pig.1,'--if the relay Nkhalonefs actuated, the most restrictive-control and 'lowest-speedllmit Vis put intofeiect; ifltherelay NR -is rst dropped-away followed bythe-picking :up of the relay PR, an'in'trmediate speedvlimitds established; and if lthe PR 'relay rst picks up followed by the dropping away-of relay NR, {themaximu'm speed-limit becomes permissible.

In .other wordsfthe differently controlled conditions of the wayside inductor Ishown in Figs. 4 and 5 -are Vutilized for transferring lcautionand clear vcontrols respectively to the train-carricdequipment ats-indicated in Athese drawings. It should beunderstood, however'7 vthat the opposite selection of -pola'rities'for the-control winding 'CWr may also be used. Thatis,-a'n inductor energizedfor -an aiding field may aswell-be-used to give a clear control -a'sfto give a caution control. 7ln lthat event, an vinductor having its .control winding energized toran opposing'fieldvthen becomes effective to give a caution control.

* QPERATlN Normal condition The normal condition of most of the train-carried equipment has already been-described. The vrelays MS, HS, MSP, and HSP initially remain deenergized Iwhen the vehicle-carried equipment is Vfirst-put into its norma-Loper.- ating condition by the resettingv operation previouslyV described. With both relays HSP and MSP'deenergized, the trainV speed yshould not be allowed to exceedvthe -predetermined low speed limit because the dropped away condition of the relays HSP and MSP causes relay TD to be energized through the lowspeed -lcontact 26 of .the speed governor. Increasing the speed above this lou speed limit causes this contact .'26 to open and relayAT-D to be de energizred with a resulting deenergization ofgthe valve EPV. This action causesl the brakes to be tautomatically applied unless a lservice brake application .is immediately made so as to .close the suppression contactor SC.

Receiving most restrictive or stop and proceed" control When the vehicle-carried receiver REC .passeslhllQugh an inductive coupling relationship with a wayside yinductor that is-open-circuited, a momentary decrease of thek normal current level through the secondary winding of the receiver results. This variationv in receiver secondarycurrent is illustrated graphically in an approximate manner in Fig. 3. Asalready described, this current, decrease causes the relay NR to drop away but-does not affect relay PR since the level of current through the relay PR doesnot rise above the pick up level of current required for this relay.

With relay NR'deenergized, its front contact .24 vopens to thereby open the receiver secondary circuit. Relay NRP then ldrops away as indicated in Fig. 7 because of the.

opening ofl front contact 17 of relay NR. Relay NRP drops away quickly thereby again closing thefsecondary circuit at back contact 16 Vof relayNRP, and relay-NR picks up as the secondary current.increases toward its normal value. Relay .NRP cannot. again become .picked up at this time because of its open front Contactv 23.

The dropping away of relay NRP also` opens front contact25 sothat relayRS is. deenergized (see Fig'.1 7). The resulting release of the relay R5 after a short interval due to itsslow dropaway characteristics would ordinarily result in'the removal of energy from -wire 10. But this can be circumvented by timely operation of the acknowledge contacter ACK so as to clos'eits back contact 14-andthereby maintain the wire 10 energized.

TheVV dropping away of relay RS also causes front contacts 4t) and 41 ofithls relay to open'the stick' circuits for both :relays AHSP and MSP. With either relay HSP or-MSP in avpickedup condition, the caution or clear control is then in foreeaswill be more fully explained. The dropping'away of relayRS ensures that both of'tl'ies'tV relays-HSP and MSP are released so that the mostrestrictive control comes into effect.

When back contact 20ct relay R5 closes and assuming that the acknowledge contactor ACK has been actuated to close its back contactor 19, the pick-up circuit for relay NRP previously described is again established so that this relay picks up. The pick-up circuit for relay NR is thereby opened again by the opening of back contact 16 of relay NRP so that the receiver secondary circuit is once more closed only through the front stick contact 24 of relay NR. Also, with relay NRP now again picked up, its front contact is closed to energize relay R5. When relay R5 picks up and closes its front contact 11, energy is once'more applied through this contact to wire 10 so that the acknowledge contactor ACK can be released.

vThe circuit conditions established when the receiver' passes a wayside inductor that has its control winding op'en-circuited in this way result in the relays HSP and MSP being dropped away. With both back contacts 27 and 28 of the relays HSP and MSP closed, the energizing circuit for relay TD is required to be completed through contact 26 of the speed governor SG. The train speed should not exceed the selected speed at which this governor contact opens as otherwise the relay TD becomes deenergized, requiring that the brakes be applied to restore the speed to the proper level under penalty o an automatic brake application. Y

Throughout the time that the train-carried apparatusis effected by the wayside inductor, the acknowledge contactor ACK is required to be actuated so that wire lf3 will remain energized through back contact 14 of this contactor during the interval that the relay R5 is dropped away. Otherwise, the penalty relay R3 is dropped away, and, it this happens, subsequent actuation of the contactor ACK will not suice to reenergize wire lli because of the open front contact 12 of relay R3. The valve BPV then becomes deenergized and an automatic brake application follows. The train-carried equipment can then be restored to its normal operating condition only through the resetting operation already described. This can take place only when the train speed has been suiciently reduced to allow contact 13 of the speed governor to close. This requirement of a very low train speed before resetting can occur is the penalty inicted for failure to acknowledge the restrictive signal.

The pneumatic train brake system may be organized so that the brakes cannot immediately be released following an automatic brake application until a certain time has elapsed-even after the train-carried equipment such as shown in Fig. l has been restored to its normal condition and the valve EPV again energized. The means for such control may take the form illustratedin Pat. No. 1,855,595 to C. S. Bushnell, dated April 26, i932. When the brakes are applied by the engineer, they can quickly be released by him. It is to his interest, therefore, to prevent an automatic brake application. Otherwise the brakes remain effective tor a time even after the train speed lhas been reduced to the level Where closure of speed governor contact 13 allows resetting to occur so that the train is, in practice, usually brought to a full stop.

Reception of caution or medium .speed control When the vehicle-carried receiver passes through an inductive coupling relationship with the wayside inductor under the conditions shown in Fig. 4, the current in the secondary winding `of the receiver is first momentarily decreased below its normal level and then increased above its normal level. The first-occurring current decrease causes relay NR to drop away. When front contact 17 of this relay opens, relay NRP drops away (see Fig. 8). The closure of back contact 16 of relay NRP shunts the now open front contact 24 of relay NR to thereby close the receiver secondary current so that the following current increase will Ybe effective upon the relay PR.

The dropping away of relay NRP opens the energizingY circuit for relay R5 at front contact 25 of relay NRP. rl`he slow release characteristics of relay R5 are selected so that this relay does not drop away upon its deenergization until after the current increase in the receiver secondary circuit has been etective to cause the momentary picking up of relay PR even for the lowest train speeds when there may be a substantial interval after relay NR drop-)s away before relay PR picks up.

When relay PR does pick up momentarily in response to the current increase, a circuit is completed from the energized wire l0, through front contact 42 of relay PR and hack contact 43 of relay NRP to energize the relay MS. Relay PR remains picked up only for a short time, but during this interval the circuit described causes energy to be applied to both the winding of relay MS and to the capacitor 44 which is in series with the current limiting resistor 45' across the winding of relay MS. This capacitor 44 receives a substantial charge during the short time that the relay PR is picked up. v

When the train is operating at high speeds, the duration of the positive current pulse is shorter than at slower train speeds; but it has been found that even under conditions where relay PR is picked up only for a very brief interval, the capacitor 44 receives a substantial charge while front contact 42 of relay PR is closed. Even though front contact 42 may open before relay MS picks up, the subsequent discharge of capacitor 44 through the winding of relay MS causes this relay to pick up. After relay MS has once closed its front contact 46, the capacitor 47, which was charged through back contact 46 when relay MS was in its dropped away condition, discharges through the upper winding of relay MS and holds this relay picked up for a time.

When front contact 48 of relay MS closes, wire 10 which is connected to the right-hand terminal of the winding of relay PR is connected to wire 49 which is connected to the left-hand terminal of the same winding. In this way, one result of the picking up of relay MS is that it results in the short-circuiting of the winding of relay PR and ensures that this relay is restored to its original dropped away condition.

After relay NRP has been dropped away for some time and the momentary picking up of relay PR has resulted in the energization of relay MS, relay R5 drops away (see Fig. 8). In doing so, the front contacts 40 and 4l of this relay open the stick circuits for the relays HSP and MSP. In the event that either of these relays was picked up as the vehicle passed the preceding inductor, such relay is now once more dropped away to clear out the previously received control and to allow the new control to become effective.

The dropping away of relay R5 again opens the normal energizing circuit for wire l0. For this reason, the engineer is required to operate the acknowledge contacter ACK when passing a signal displaying a caution indicatlon.

When relay R5 drops away, its back contact 20 closes. Since the acknowledge contactor ACK is now actuated and its back contact 19 closed, and since the relays HSP and MSP are now both dropped away, the pick-up circuit for relay NRP already described is once more established and this relay picks up. With the opening of back Contact E5 of relay NRP, the shunt on the front contact 24 of relay NR is removed so that relay NR is again maintained energized through its stick circuit. Also, energy is now applied from wire 10, through the now closed front contact l5 of relay NRP and through the stili closed front Contact 5@ of relay MS to energize `the windingv of relay MSP as indicated in Fig. 8.

At the same time, the closure of front contact `25 of relay NRP causes relay VR5 to be picked up. Wire 10 is then once more energized through front contact 11 of this relay RS so that the .aclmowledge contacter ACKneed geniee brake application -as already described. The Whole cycle v of relay operations involved inl imposinga caution control with an intermediate speed limit on thetrain is thus completed. Sunimarized, the action of the-NR-andvPR relays results in the dropping awaygof relay NRP followed by the-deenergization of -relay R5 whichremains picked up for a time. Relay MS is picked up when relay PR is momentarily actuated. Actuation of ythe acknowledge contactor ACK is required to prevent dropping away of thepenalty relay R3 vbecause relay vR5 soon dropsl away. The dropping away of relay R5 opens the stick circuits to relay HSP and MSP so that any previously received control less restrictive than -a stop control is removed, and this is followed by the picking up of relay NRP. With relay NRP picked up, relay R5 is picked-up as is also-relay MSP which latter relay is maintained picked up by a stick circuit which can now again be established because relay R5 is picked' up. yThe control of relay TD is now governed through the medium speed contact of the speed governor SG so that the medium speedl limit must be adhered to.

Reception of clear `control (first) Whenrthe vehicle passesa wayside signal location and that signal is displaying a clear orproceed indication, the wayside inductor according to the present embodiment of the-invention has its control winding Yenergized togproduce the conditions outlined in Fig. 5. As describedin connection with this Fig. 5, the effect produced on the current in the receiver secondary windingas the receiver passes the wayside inductor is an increase of the'current above-its normal level for a brief time followed byf-a negative current pulse whichcauses the current to drop below its normal value. The result is a momentary picking-up of the relay PR followed by avvdropping away of the relay NR.

When the vehicle is operating through regions where the trac conditions require train movement at restricted speeds, it is desirable that all rpossible precautions be taken to ensure that a false clearing signal will-not be eiective on the vehicle. Magnetized objects lying along the track rails might conceivably atleet therreceiver so as to produce a variation of current-in the secondary winding which roughly approximates that obtained under the conditions of Fig. 5. lf thetrain has been controlled to operate at some restricted speed limit, such spurious response would cause the restriction to be removed. For this reason, the vehicle-carried apparatus has'been organized so that acknowledgement by the engineer is required when a clearing input is received only if the vehicle at and prior to the time of such clearing impulse has been required by a previously received control to operate at a restricted speed. Since the engineer performs the act of acknowledgement only at wayside signal locations, the possibility of receiving a spurious input which would produce a clearing effect on the vehicle is greatly reduced. But when the vehicle has been operating through clear territory and has already received a clearing control, acknowledgement by the engineer is not required as the vehicle passes successive wayside signals which display a clear or proceed indication. When considered desirable, the train-carried apparatus may be s0 organized that acknowledgement is not required at any clearV signal.

The eect of a wayside inductor having its-'controlzwind ingerrergized to give Va clearing'control will rst beldescribed from the standpoint of tseectfon train-carried equipment that has .been operating in responsetoJa re strietive'inp'utfrom a previously passed ywayside inductor. if the winding ofthe wayside inductor 'previouslyrpassed were controlled to give the mostrestrictivelcontrol, both relays HSP and MSP would 'bedeenergized -If the -wayside inductor previously passed had its control winding energized to give an intermediate or cautionl control, the relay MSP would be picked up but the relay HSP V-would still be dropped away. Theser' are the principal effects of thel two restrictive controlsA on the train-carried apparatus. Under'either of these fconditions,:the receipt of aV clearing input from the wayside inductor requires that the acknowledge contactor ACK'be actuated in order'that'the restrictive control then inleiect Acan .be-removed and the vehicle allowed to operate iat its 4maximum speed and also-'to avert an automaticy application of the brakes.

The rst efrect produced on the train-carried equipment as thereceiver'passes the wayside inductor IND is-theA momentary picking up of relay PR in'resp'onse to the positive 'current pulse. As the frontgcontact 42 of relay PR momentarilycloses, energy is applied'to the Winding of relayv HS from wire 1li-and `also to its shunting capacitor-'Sefthroughl thefresistor 455. Relay HS picks up in response to this momentary euergization and remains picked up for a time afterront contact 42 of relay PR open as the charged capacitor 65 discharges through front contactfS into the upper winding'of'this relay HS. The closure of front'contactSTl of relay HSshunts the Winding of relayPR in a Vmanner similar" to that occurring' when relay MS picks upI when an 'intermediatespeed control is received so that' relay'PRquickly drops away.

Shortly afterward, thereceiver secondary current'is abruptly 'decreased in' value'below its normal current level so that relay NR drops away. With front contact'24`of relay "NR open, thereceiversecondary circuitis `also opened. `But the openingoffront'contact 17'of`relay NR also causes relay NRP to :drop away so thatA the receiverv secondary circuit is'again quickly closed-at back Contact 16 of relay NRP and relay NR is 'quickly picked up as the receiver secondary current Vrisesl to its normal value.

'With' relay NRP now dropped away and relay'v HS still picked up, assuming the vacknowledge contactor ACK has'been actuatedas requiredforr the clearing'control to be properly received, a circuit sfcompleted from Wire 1i) to energize the relay HSP. 'I'hiscircuit extends from wire 10 and includes back contact .58 of the contactor ACK, front contact 59'of the 'high speed relay HS, and back contact 60 of the relay NRP. When relayHSP picks up, a stick circuit is completed to hold this' relay energized, and this stick circuit extends from wire v10, through front contact 40 of relay'RS, front contact 61 of relay HSP, and. through the winding of relayHSP to At the same time, thepicking up of the relay HSP causes a pick-up circuit to be closed' for the relay NRP. This circuit extends from the wire 10 arid .includes front Contacty 62 of relay HSP, front contact 63 of relay HS and the winding .of relay NRP to.'(-). With relay NRP picked up, the piek-up. circuit for relay HSP is opened so that this relay isheld energizedonly through its stick circuit.

The energization circuit. for relay R5 is again closedby the-closing of front contact 25 of relay NRP. Since the dropping away of relay NRP resulted in the picking up of relay HSP and the picking up of relay HSP, in turn, causes relay NRP to be picked up, relayv R5 is deenergized for only a very short time and -does/nothave time to be dropped away under these conditions.r

lf Athe engineer failed to acknowledge, not only would the clearing control fail to become elective bynoty pickingup relay HSP, but theA failure of relayy HSP topick up would also prevent the'- pickingupofrelayNRP through front contact 62 of relay HSP. Relay R5 would then drop away followed by the dropping away of relay R3 and an automatic Vbrake application would occur. From this description it becomes clear that if the relay HSP is not in its picked up condition, the acknowledge contactor ACK must be operated as the receiver passes the wayside inductor controlled to give a clearing control in order for the pick-up circuit for relay HSP to be completed and the maximum speed limit for the vehicle to be established. In summary, the initial picking up of relay PR with relay NRP still picked up causes relay HS to be energized. When relay NR. drops away and then relay NRP also, relay HSP is picked up provided that the acknowledge contactor ACK has been actuated. Relay NRP then picks up and relay HSP is maintained energized through a stick circuit.

When relay HSP picks up, the opening of its back contact 5l .opens the stick circuit for relay MSP to ensure that any previously received intermediate speed control is cancelled. With relay HSP picked up and relay MSP dropped way, relay TD is energized from wire 1Q through the high speed contact 64 of the speed governor SG, front contact 27 of relay HSP, and back contact 28 of relay MSP. The train speed need only be kept below the speed at which this contact 64 opens for relay TD to remain energized and an automatic brake application forestalled.

Reception of clear control (successive) The apparatus on the vehicle is organized so that acknowledgement by the engineer is not required to receive a clearing control if the vehicle has previously been controlled to operate up to its maximum speed limit. Under these circumstances, relay HSP is in a picked up condition when the train approaches the inductor, and this condition is utilized to eliminate the need for acknowledging.

The effect on the receiver secondary circuit in response to the effect produced by an inductor controlled to give a clearing infiuence is a momentary current increase followed by a decrease of current. As the current increases, relay PR is momentarily picked up. A circuit is then completed from the energized wire 10, through front contact 42 of relay PR, and front contact 43 of relay NRP to energize the lower winding of relay HS. As soon as relay HS picks up, a circuit is completed from wire 10, through front contact 62 of relay HSP, frontcontact 63 of relay HS, and the winding of relay NRP to which maintains the relay NRP energized. Even though the picking up of relay PR is but a momentary condition, the relay HS remain picked up for some time after the front contact 42 opens because of the discharge of capacitor 65 through its upper winding. With front contact 62 of the relay HS held closed for a time, relay NRP continues to receive energy over this pick up circuit.

When the subsequent negative current pulse in the receiver secondary winding causes relay NR to momentarily drop away, the stick circuit for relay NRP is opened at the open front contact 17 of relay NR. But relay NRP cannot drop away because it is maintained energized through the circuit just described. With relay NRP prevented from dropping away, the relay R5 is not deenergized so that the stick circuit for the relay HSP is not interrupted nor is energy removed from the wire l() by the opening of front contact 11 of relay R5. For this reason, operation of the acknowledge contacter ACK is not required and the train can then continue to operate,

at speeds up to its maximum speed limit. When relay HS is picked up in response to the picking up of relay PR, front contact 57 of relay HS closes to shunt the winding of relay PR and front contact 24 of relay NR. One effect of this shunting action is to ensure that relay PR drops away. Another effect is to provide a circuit wherebyl relay NR may be picked up because under these circumstances relay NRP does not drop away so as to close the secondary circuit at back contact 16.

15 WAYSIDE APPARATUS Fig. 2 illustrates the wayside signalling apparatus which controlsI the wayside inductors. A typical portion of track signalled by a line wire block signalling system is shown.

Each track section such as the track section 2T has connected to its rails at the exit end thereof a track battery ZTB connected in series with a current limiting variable resistor ZLR. At the entrance end of each track section a track relay TR is connected across the track rails. A home-distant relay HD is also located at the entrance end of each track section. This relay is controlled over line wires extending from the next signal location ahead. The relay HD is of the kind known commonly as a polarretained neutral relay as previously mentioned. The polarity of the cnergization applied to each HD relay is determined by whether the HD relay for the track section ahead is picked up or dropped away. Assuming that the track relay ZTR is picked up because of non-occupancy of the track section 2T so that front contacts 66 and 67 of relay ZTR are closed, the relay ZHD has its polar contacts 36 and 37 actuated to their right-hand positions when the relay SHD is picked up. But the polar contacts 36 and 37 are operated to their left-hand positions when the relay SHD is dropped away.

At each signal location there is an approach relay such as the relay 3Aat the signal S3 location. This relay is included in the line wire circuit including line wires 68 and 69 extending from this signal location to the relay ZHD at the entranceV of track section 2T. The function of this relay 3A is to prevent energy from being applied to the wayside inductor lND and to the lamps of the wayside signal S3 except when there is a train actually occupying the track'section 2T.

The wayside signalling apparatus shown in Fig. 2 is i1- lustrated as being in the normal condition, i. e. the condition that it assumes when traic conditions warrant unrestricted train movement and when there is no train in any of the track sections shown. Consequently, the track relay TR at the entrance to each track section is picked up. Also, each HD relay such as the relay 2HD is energized because of the closed front contact of the associated track relay ZTR. With each relay HD picked up, the polarity of the energy applied over the line wires to the HD relay at the next preceding signal location is such as to cause the polar contacts of such HD relay to be operated to their right-hand positions. At the same time, each approach relay such as relay 3A is picked up, and its associated repeater relay AP is also energized. The relay SAP 'is energized, for example, through the front contact 70 of the relay 3A.

If a train occupies the track section 3T, the track relay STR is dropped away. The relay 3HD is also dropped away because of the open front contacts 71 and 72 of relay STR. If another following train enters the track section 2T, the track relay ZTR also drops away and because of the opening of front contacts 66 and 67 of relay ZTR, relay ZHD is deenergized. With no current following in the line wires 68 and 69, the approach relay 3A aiso becomes deenergized and drops away. A circuit is then completed through back contact 73 of relay 3A, back contact 74 of relay SHD and lamp R of the wayside signal S3 to A red aspect is thus displayed by the signal S3 to warn the approaching train in the track section 2T of the occupancy of track section 3T by another train.

Because relay 3HD is dropped away and its front contact 75 is open, a circuit cannot be completed to energize the control winding CW of the wayside inductor IND at the signal S3 location. When the train-carried receiver passes this wayside inductor, the open-circuited control winding CW will cause the most restrictive control to be inductively transmitted to the train-carried equipment.

It will now be assumed that a train is still occupying the track section 3T, that track section 2T is not occupied by any train, and that a train enters the track sectionV 1T.

Relays STR and SHD are still `in their dropped away condition but relays ZTR and '2l-ID are now picked up. With back contacts 76 and 77 of relay BHD closed, the polarity of the energization applied over line - wires 68 and 69 to relay ZHD causes the polar contacts lof this relay to be in their left-hand positions. Since track section 1T is occupied, the approach relay 2A becomes deenergized when the train iirst enters this track section 1T. A circuit is then completed from (Jr), through back contact 7S of relay 2A, front contact 79 of relay ZHD, and left-hand contact Si) of relay ZHD, and through the lamp Y of the wayside signal S2 to in this way, a caution indication is displayed by the wayside signal 2.

The closure of back contact S1 of relay 2A completes a circuit for energizing thecontrol winding CW of the wayside inductor IND at this location. This circuit extends from (-1-), and includes left-hand contact 37 of relay ZHD, the winding of relay ZCK, front contact S2 of relay 2AP, back contact 81 of relay 2A,` the control winding CW of wayside inductor IND,A and the left-hand contact 36 of relay ZHD to The polarity of the energization that is applied to the control winding CW under these conditions causes the magnetic field of the wayside inductor to be aiding with respect to that of the traincarried receiver. Under these circumstances, acaution or intermediate speed control becomes effective on the train-carried equipment as it passes the wayside inductor.

The circuit for energizing the control winding is not completed until the approach relay 2A drops away and closes its back contact 81. At the same time, the dropping away of relay 2A opens its frontcontact 83 and causes the relay 2AP to become deenergized. Since a front contact 82 of the relay 2AP is included in the energizing circuit for the control winding CW, the dropping-away of relay 2AP must be prevented if the control winding is to remain energized. Because of the relatively large inductance of the control winding CW, the current through it builds up fairly slowly after back contact 81 Iof relay 2A closes; The slow release characteristics -for the relay 2AP, as designated by the heavy base line for the symbol of this relay, are chosen so that this relay will ordinarily not drop away during the time required for the current in the control winding to assume its normal value beginning with the time of closure of back contact 81. The normal current level in the energizing circuit for the control winding CW causes the relay ZCK to be picked up. If relay 2CK picks up before the relay 2AP can drop away, a stick circuit is completed for the relay 2AP which includes the front contact 84 of relay ZCK and fronthoutact 85 of relay 2AP. The relay 2AP is then prevented from dropping away so that its front contact 82 remains closed and the control winding remains energized.

As a result of this circuit organization, the current level through the control winding of the inductor is required to remain above the drop away current level for the relay ZCK. Otherwise, the relay ZCK drops away and opens the stick circuit for the relay 2AP. lf relay 2AP should drop away, it could not again be picked up because the presence of a train in the track section T causes the pick-up circuit for relay 2AP to remain open at front contact 83 of relay 2A. This circuit arrangement makes it impossible for the circuit to the control winding CW to remain closed in the event that the energization level to this winding drops below the required value. The reason for this precaution is that there otherwise would be substantially a short-circuit across the control winding in the event of failure of the power supply while the energizing circuit remained intact. It has been found that shortcircuiting of the control winding of an inductor has the eiect of making the wayside inductor substantially ineiective with respect to the train-carried receiver. A wayside inductor with a short-circuited control winding would, therefore, be incapable ot inductively transmitting a re- `sti'ictive influence to passing vehicles. 'The possibility or" occurrence of such a dangerous situation is eliminated by this circuit arrangement whrh open circuits the Vcontrol winding if the -proper energization level for the `winding cannot be maintained. v When so open-circuited, the wayside inductor is elective to provide the most restrictive control on train-carried apparatus as has' already been described.

if neither track-section 3T. nor 2T is occupied, then both track relays STR and ZTR are energized, and the respective relays BHD and 2HD are also energized. With front contacts 76 and 77 of'relay SHD closed, the line wires 63 and 69 are energized with apolarity that causes the polar contacts 36 and 37 of relay 2HE to be in their right-hand positions. If a train then enters the track section iT so that approach relayJZA is dropped away, a circuit is cornpleted from-(-|), through back contact 78 of relay 2A, front contact 79 of relay ZHD, and right-hand contact Si) of relay ZHD, and the larnp G of wayside signal SZ to Under these'circumstances,` a clear or proceed indication is displayed by the wayside signal 2.

Upon closure of back contact Zil of relay 2A, a circuit is again completed to energize the' control winding CW of the wayside inductor IND at this location. This circuit is, similar to the one previously described except that it now includes the right-.hand polar contacts 36 and 37 of relay 2HD so that'the polarityof the energization is reversed. 'This polarity of energization causesl the way side inductor to have a magnetic eld opposing that of the train-carried receiver. As already described, an opposing eld causes a clearing influence to be inductively transmitted to the train-carried equipment of passing vehicles.

It vis frequently desirable that an auxiliary wayside inductor be located along the trackway some distance to therear of each signal, location. 'When a train occupies the track section 3T, for example, the wayside inductor IND at this signal location has its control winding CW open-circuited so that a vehicle passing this location receives the most 'restrictive control. lf an auxiliary infductor such-as the inductor 37 is not used, it is ordinarily necessary with a train occupying track section 3T also to Vopen-circuit-the control winding of the wayside inductor IND. at the signal 2 location. The reason is that a train occupying the track section 3T may actually be close to the signal S3 location. VIf the waysideindnctor iND at the signal 2 location were controlled so as to inductively trans-v fer only anI intermediate speed control to vehicles entering the track section 2T, such vehicles would travel through the track section 2T at what is still a fairly high speed. Although the engineer would receive a stop indication fromfthe Wayside signal S3, the train speed probably .could not be reduced suiciently to avoid a serious collision-with the-preceding train just within the track section 3T-with itsrearcars still near the signal S3 location.

To avoid this situation without using an auxiliary in'- ductor, it would be necessary to control the wayside in i ductors IND at both the signal S3 and S2 locations to inductively transfer the most restrictive control to passing vehicles whenever the tracksection 3T is occupied. The diiliculty yarising from this solution is that a train occupying thesection 3T butabout to leave that section and move into the next section ahead would still cause the wayside inductor INDat theV signal S2 location to be controlled so as to give the-most restrictive control to passing vehicles. A vehicle entering the track 'section 2T would then be required to travel theentire length of this track section as well as track section 3T at a very slow speed even though the wayside signal S3 might change to a less restrictive aspect shortly after the vehicle enters the track sectionZT.

By using the auxiliary inductor`87 some distance to the rear of each `wayside signal location, these diiiculties are alleviated. The wayside inductor 87 is sho-wn as having its control winding CW selectively short-circuited or Iopennal S2 location to be energized i9 circuitedrthrough the front contact 88 lof the relay lSHD which is'at the signal S3 location. .This Wayside inductor S7 is shown as being located at-brakingdistance inadvance of the signal S3 location; braking distance vhere meaning the distance required for the heaviest train to come to a stop from the intermediate speed.

When a train occupies the' track section 3T, the relay SED is dropped away so that the control winding for the Wayside inductor IND `at the signal S3 location is open-circuiteuV as yalready described. .With relay SHD dropped away, the polarity of the energization transmitted over line wires 68 and 69 to relay'- ZHD causes the control winding of the wayside inductor IND' at the sigto give a caution or medium speed control.

A train approaching the signal S2flocation at speeds above the medium speed limit is required to reduce its speed after it passes the inductor at this location or pay the penalty of an automatic'application of the brakes. Assuming that the train speedis properly reduced, the train continues to move through the track sectionlT at speeds below the medium speed limit until the vehiclecarried receiver passes over thewayside inductor 87. If the vehicle .ahead has in the meanwhile moved out of the track section 3T, the track relay STR is picked up so that-the relay BHD is again energized. With front contact 88 of relay SHD closed, the control winding CW for the wayside inductor 87 is Vshort-circuited. The short-circuiting of this control winding causes the wayside inductor 87 to have substantiallyno etect upon the vehicle-carried apparatus. The vehicle can then proceed through the rest of the track section 2T at the medium speed limit. When the train passes the wayside inductor at the signal S3 location, either a clear or an intermediate control is transferred to the .Y vehicle depending upon whether the train rahead is inthe second or thirdblock inadvance.

Assume now that the vehicle enters the track section 2T'while there is a vehicle occupying the track section 3T. The medium speed limit is .again imposed upon the vehicle as the receiver passes over the wayside inductor at this signal S2 location. Upon reducingv the-train speed below this medium speed limit, thevehicleis allowed to travel through the track section 2T at-speeds not exceeding the medium speed limit until the wayside inductor 87 is reached. If the vehicle ahead has in the meanwhile not moved out of the track section 3T, the track relay 3TR for that track section will still `be dropped away. The relay SHD will be dropped away also because of the open front contacts 71 and 72 of relay- STR so that open front contact 88 of relay BHD willcause the control winding for inductor 87 to be open-circuited. As the receiver passes over this wayside inductor 87, the most -restrictive -control will be inductively transferred to the vehicle-carried equipment. To avoidan automatic application of the brakes, the engineer is required to acknowledge the presence -of this auxiliary inductor and to immediately reduce the train speed below the newly imposed lowest speed limit. yBecause this Waysideinductor is located at braking distance ahead of thesignal S3 location, the train speed can be reduced -to` the lowest' speed limit by the time is arrives at the entrance to the track section 3T so that if the train ahead is occupying the track section 3T near the entrance end of this track section,l the train to the rear can be stopped i-n time to avoid a collision. y

The use of the auxiliary wayside inductor to the rear of the entrance t-o each track section provides for safe train operation in that it gives a forewarning if the track section ahead is occupied. At the same time, it makes .it unnecessary for a train to operate at the lowest speed throughout an entireV track section when the-'trackfsection ahead may during a great portion of thispinterval be unoccupied. The marker signal M is located at the wayside near this auxiliary inductor as a warning .to the engiv20 neer of an approaching train travelling at' restricted speeds that he is about to pass-an inductorthat may be open-circuited so that acknowledgement"may be required. K

:Having describedran intermittent inductive speed control system for railroads as a specific embodiment vof this invention, we desire it to be understood thatv this form is selected to facilitate inthe disclosure` of this in# vention rather than to limit the number of forms it may assume. alterations may be applied tothe specific form shown-to meet the requirements of practice without in Iany manner departing from the spirit -or-scope of this invention.

What we claim is:

1. An intermittent inductive speed control system for railroads comprising, wayside apparatus including an inductor having a control winding, circuit means for selectively open-circuiting said winding or energizing said winding with one polarity or the other of direct current, train-carried'apparatus including a receiverhavingV both a primary and a single secondary winding inductively coupled together through a comin-on magnetizable core structure, circuit means forenergizing saidprimary Winding-to thereby magnetizeV said core structure, a circuit for said secondary winding comprising two series connected electro-magneticV relays and a source of direct current, said relays being constructed to operate in response toditerent-levels of direct current, said source supplying a Apredetermined value of direct current to said seriesconnected relays to cause one of said relays to be norma'lly picked up and the other of said relays to be normally dropped away,'said receiver when passing through al1-inductive coupling relationship with said inductorhaving the current in its secondary winding selectively varied above and below saidpredetermined value depending upon whether said control winding is open-circuited or energized with said one or-theV other of said polarities of direct current to selectively drop awayV and pick up said one and said other of said relays respectively, and circuit means responsive to the conditions said relays are actuated to as said receiver and inductor pass through said coupling relationship vto establish a speed limit for said train.

2; An intermittent inductive speed control system for railroads'in which controlling'influences are transferred from -the wayside at xed locations to passing trains through theV inductive cooperation of wayside inductors and receivers associated with train-carried equipment cornprising, ysaid wayside inductor at each wayside location provided with a control winding and circuit means controlled VVin accordance with the controlling inuencedesired to become eective on passinig vehicles for selectively open-circuiting said control winding or energizing said control'winding with direct currentvofone polarity or the other, train-carried apparatus including said receiver being adapted to pass through an inductive coupling relationship with said Ainductor during train movement, said receiver having a magnetized core structure and a winding about said core structure, a receiver circuit including in series connection said winding and two electro-magnetic relays and a source of` current for energizing said circuit, said energization of said receiver circuit being elective to cause one of said relays to be normally picked up and the other of said relays to be normally dropped `away, the current in said receiver when said receiver and said inductor pass through said inductor coupling relationship being distinctively varied, said current vbeing substantially only reduced toI cause said rst relay to drop away lwhen said control winding is open-circuited, said current varying tirst above and then below its normal value to cause said second relay first to pick up and then said rst relay to drop away when said control winding is energized with said one polarity of direct current, and said current varying rst below and then above its normal value causing said first relay to drop away and then said second relay to pick up when said control winding is Also, various modifications, adaptations, and

energized with the opposite polarity of current, and circuit means responsiveto the distinctive actuations of said two relays for effecting correspondingly'diferent controls with respect to the speed of said train.

3. Train-carried apparatus for an intermittent inductive train control system wherein wayside inductors at fixed locations are provided with control Winding selectively open-circuited or energized for distinctively diterent control induences comprising, a receiver having a magnetized core structure and a winding about said core and adapted to pass through an inductive coupling relationship with said inductor during train movement, relay4 circuit means including said receiver winding being diterently responsive to distinctive current changes occurring in said receiver winding by inductive action according to whether said control winding is .open-circuited or energized, a speed control relay and speed control means associated therewith for permitting maximum train speeds when said speed control relay is energized, a manually operable acknowledge contactor, circuit means responsive to asuecessively occurring current increase and decrease produced in said receiver winding in response to a clearing control iniuence for energizing said speed control relay provided said acknowledge contactor has been operated, stick circuit means for said speed control relay to maintain said relay energized between successive wayside inductor locations when once energized, circuit means including a penalty relay becoming deenergized in response to said current decrease unless said acknowledge contactor is actuated, circuit means responsive to an occurrence of said successively occurring current increase and decrease when said speed control relay is energized for preventing deenergization of said penalty relay'even though said acknowledge contactor has not been operated, whereby said acknowledge contactor must be voperated when the iirst clearing control inuence is received but is not required to be operated when clearing controls after the rst are being received.

4. Train-carried apparatus for an intermittent inductive train control system wherein wayside inductors at fixed locations are provided with control windings selectively open-circuited or energized for distinctively different control influences comprising, a receiver having a magnetized core structure and a winding about said core structure and adapted to pass through an inductive coupling relationship with said inductor during train movement, relay circuit means comprising said receiver winding being differently responsive to distinctive current changes occurring in said receiver winding by inductive action according to whether said control winding is open-circuited or energized, said distinctive current changes comprising substantially only a current decrease for a restrictive speed control and a current increase followed by a current decrease for a clearing speed control, a manually operable acknowledge contactor, said circuit means being effective in response to said current decrease to cause an automatic brake application unless said contactor is operated to acknowledge said restrictive control, circuit means including a speed control relay being actuated by said relay circuit means in response to a clearing speed control only provided said acknowledge contactor has been operated, stick circuit means to hold said speed control relay actuated between successive Wayside inductor locations after receiving a clearing control and until a restrictive control is received, means governed by the actuated condition of the speed control relay and by the response of said relay circuit means to a current increase in said receiver winding for preventing a response of said relay circuit means to the immediately following current decrease, whereby said acknowledge contactor is required to be operated when the iirst clearing control inuence is received but is not required to be operated when clearing controls after the rst are being received.

5, in an intermittent inductive train control system, wayside apparatus including an inductor having a magnetizable core structure with a control winding about said core, inductor control circuit means governed by wayside signalling apparatus for selectively energizing said core winding in accordance with distinctive control inuences desired to become effective on passing vehicles, and relay circuit means responsive to the amplitude of current energizing said control winding and acting on said inductor control circuit means to open-circuit said control Winding when said amplitude falls below a prescribed level.

6. In train-carried apparatus for an intermittent inductive train control system in which control windings of wayside inductors at fixed locations are selectively conrolled to distinctively influence said train-carried apparatus through inductive action for correspondingly different train controls, a receiver having a magnetized core structure with a winding about said core structure, relay circuit means including said receiver winding being distinctively actuated momentarily by the respectively diierent current changes produced by inductive action in said secondary winding according to the control of said control winding, a plurality of electro-magnetic relays each having pick up windings adapted to be energized in response to a correspondingly distinctive actuation of said relay circuit means7 a capacitor shunting said pick up Winding of each of said relays to permit said relays to become picked up in response to the momentary actuation of said relay circuit means and auxiliary windings of each of said relays, circuit means associated with each relay and including a normally charged capacitor becoming effective in response to said actuation of said relay to energize said auxiliary winding to thereby maintain said associated relay picked up for a limited time.

7. An intermittent inductive speed control system for railroads comprising, wayside apparatus including an inductor having a control winding, circuit means for selectively open-circuiting said winding or energizing said winding with one polarity or the other of direct current, traincarried apparatus including a receiver having secondary and primary windings inductively coupled together through a common magnetized core structure, a circuit for said secondary winding comprising two electromagnetic relays connected in series with said winding, said receiver when passing through an inductive coupling relationship with said inductor having the current in its winding varied distinctively in both directions with respect to the normal current level in said winding depending upon whether said inductor control winding is energized with one or the other of said polarities of direct current to selectively actuate thereby both of said electromagnetic relays, said electromagnetic relays being both operated and in a distinctive sequence in accordance with the polarity of energization of said control winding, said current in said secondary Winding varying substantially in only a single direction to cause only one of said electromagnetic relays to be operated when said receiver passes through an inductive coupling relationship with an inductor having its control winding open-circuited, and circuit means responsive to the selective sequential operations of said relays for establishing corresponding speed limits for said train.

S. In an intermittent inductive speed control system for railroads comprising, wayside apparatus including an inductor having a control winding, circuit means for selectively open-circuiting said winding or energizing said winding with one polarity or the other of direct current, train-carried apparatus including a receiver having secondary and primary windings inductively coupled together through a common magnetizable core structure, circuit means for energizing said primary winding to thereby magnetize said core structure, a positive responsive control relay and a negative responsive control relay connected in series with said secondary winding, circuit means for energizing said secondary winding and said relays with a normal current level to cause said positive responsive relay to be dropped away and said negative responsive relay to be picked up, said secondary winding experiencing successive positive and negative current variations with respect to its said normal current level when said receiver passes said inductor having its control Winding energized with direct current to thereby cause said relays to be sequentially operated, the sequence of operation of said positive and negative responsive relays independent of the polarity of energization of said control winding, said receiver secondary winding experiencing substantially only a negative current variation when said receiver passes an indicator having its control winding open-circuited to thereby cause only said negative responsive relay tokbe actuated, and circuit means responsive to the selective actuation of said electromagnetic relays for imposing different speed limits upon said vehicles. 'v

9. Train-carried apparatus for an intermittent inductive train control system of the type wherein wayside inductors at xed locations are each provided with a control winding selectively open-circuited or energized for distinctively dilerent control influences comprising, a receiver on said train having a magnetized core structure and a winding about said core structure and adapted tov pass through an inductive coupling relationship with said inductor during train movement, a positive responsive relay and a negative responsive relay being both connected in series with said winding, means for energizing said Winding with direct current of a level to cause said positive responsive relay to be normally dropped away and said negative responsive relay to be normally picked up, said receiver winding experiencing distinctive current changes as said receiver passes an inductor having its control winding energized with direct current, said current in said winding increasing above its normal levelV to momentarily pick up said positive responsive relay and then decreasing below its normal level to drop away said negative responsive relay when said control winding is energized with one polarity of direct current, said current in said secondary winding rst decreasing below its normal level to drop away said negative responsive relay and 24 thenincreasing above its normal level to pick up said positive responsive relay for the other polarity of direct current applied to saidlcontrol winding, circuit means for restoring saidv negative responsive relay to its normal picked-up condition a predetermined interval after it has dropped away, a rstspeed control relay being picked up when said positive responsive relay is picked up provided that said negative responsive relay has not yet dropped away, a second speed control relay being picked up when said positive responsive relay is picked up provided that said negative responsive relay has previously dropped away, a repeater relay for each of said speed control relaysvfor storing a received control received at one inductor location until said train reaches the next inductor location, stick circuit means for said repeater relays of said speedcontrol relays for maintaining a repeater relay energized between successive inductor locations, means responsive to the dropping away of only said negative responsive relay when said receiver passes an inductor having its control winding open-circuited for interrupting said stick circuits to thereby cause said repeater relay for said speed control relays to be dropped away, and circuit means comprising a speed governor and said repeater relays of said speed control relays for imposing rpreselected speed limits upon said train in accordance with the control then effective upon the control winding of each inductor.

References Cited in the file of this patent UNITED STATES PATENTS Hughson Mar. 24, 1953

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