US2655594A - Railway signaling system - Google Patents

Description

3 Sheets-Sheet l OC- 13, 1953 G, D. HANCHETT, JR

RAILWAY SIGNALING SYSTEM Filed Oct. 25, 1947 Oct 13, 1953 G. D. HANcHET-r, JR 2,655,594

RAILWAY SIGNALING SYSTEM Filed Oct. 25, 1947 3 Sheets-Sheet 2 Kw.. 03% BSN EEUREE D. HANEHETLJR. BY Y rroP/viy Oct. 13, 1953 G. D. HANCHETT, JR 2,655,594

RAILWAY SIGNALING SYSTEM INVENTOR. EEDREE DHANCHETTJR Patented Oct. 13, 1953 RAILWAY SIGNALING SYSTEM George D. Hanchett, Jr., Millburn, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 25, 1947, Serial No. 782,087

4 Claims.

This invention relates to railway signaling systems and has for its principal object the provision of an improved railway signaling system and method of operation which permit the operation of trains at higher speeds and over longer blocks of track than has been practical heretofore.'

In the past, railway signals have been controlled by relays which are responsive to track voltages. That is, a track has a voltage applied to one end of a block. A relay is connected to the other end of the block. The presence of a train on the track shunts the Voltage and decreases the current owing through the relay. This decrease in current deenergizes the relay and produces operation of the switch by which the signal light or its equivalent is controlled.

With the ever increasing train speeds of tday, blocks using the relay shunt method are no longer altogether satisfactory for the reason that greater block lengths are required to accommodate the higher train speeds and the resulting shunting effect of the ties makes the sensitivity of the signaling system too low for satisfactory operation.

Important objects of the present invention are to provide a railway signaling system which is more sensitive to the presence of a train on the protected blocks of track, and to provide a railway signaling system which is of simple construction is inexpensive and operates without undue noise, thus making it suitable for use in connection with model or toy train operation.

The invention will be better understood from the following description considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

Figure 1 is a wiring diagram of an embodiment of the invention wherein the train and the signaling system are operated from the same source of alternating current.

Figure 2 is a modification whereinr the train is operated from a direct current source and the signaling system is operated from an alternating current source, and

Figure 3 is a wiring diagram of a grade crossing signal circuit which may be utilized in connection with the signaling systems of Figures l and 2.

The signaling system of Figure 1 includes three gaseous conduction tubes V1, V2 and V3 which have operating potential applied to their anodes from input leads I0 and I I through a switch I2, thence through a fuse I3 and a resistor R1. The

I I6, signal potential is applied to the control grid cause of the transformer T connections.

'I5 of the tube V1. This potential is suiliciently positive to cause conduction of the tube V1 when the rails I and 2 are not interconnected through ay train. The voltage applied between grid I5 and the cathode of V1 may be taken positive be- When the voltage is taken as more negative, no current, of course, flows in the tube. All the grids and anodes of tubes V1, V2, and V3 swing positively with respect to their respective cathodes,

at the same time on the same half cycle; as may be verified by their connections to the transformer T. Therefore, since these tubes can conduct only during this half cycle, for convenience in description, the positive-going voltages with respect to cathodes are termed simply positive, in describing Fig. l. On the other negative half cycles, none of the tubes conduct. The applied voltage is of a high enough frequency so that,

with the persistence of Vision, if the lamps I4,

I9, 2| are lighted on half cycles, they will appear to be lighted continuously.

Potential is applied to the screen grids of the tubes V1, V2 and V3 from the different taps of a resistor R2 which is connected across the lower part of the secondary winding I 6.

When a train approaches in the direction indicated by an arrow, a circuit is completed from the 33 v. lead through a connection I1, the rail 2, the train rail I and a resistor R4 back to the 6.3 v. lead of the winding I6. Since the resistor R4 is connected between the cathode and control grid I8 of the tube V3, a potential which may be taken as more positive, is applied between the grid I8 and the cathode of V3, and the tube Va begins to conduct current through the resistor R1, also resistor Rs, thus lighting a red lamp I9A by the voltage across resistor Rs, which is connected between the cathode of the tube Va and the low voltage 6.3 v. lead of the winding I6.

At the same time, the green light I 4 is extinguished due to the fact that the anode-to-cathode voltage of the tube V1 is now reduced to the the control grid of tube V2 through resistor.-

Rs. Therefore the voltage from thetransformer. v. terminal is applied to control' grid 2U. The

cathode of V2 is connectedthrough resstonRo;

to the 11.3 v. tap of transformer 'It Hennezun'f der these conditions when the train is in block B, a potential is applied to control g-ridl, more positive than that on the cathode of tube V2 by about (3o-11.3) volts or about 18.7 volts, when.

the 30 v. tap is positive with respect to the 11.3 volttap. Under these conditions, the tube V2 draws current through the resistor R1 and a yellow` lamp4 2| which is connectedv between the cathode of the tube V2 and the low voltage tap l113`v. of the winding I6 is lighted.

At. the same time, the redlamp I9 is extinguished due to the loss of voltage on the resistor l=t-,and.interruption` of the current of the tube V3. The tubevVi remains extinguished for the reason that itsoathode-to-anode voltage isnow the ionizationivoltage of the tube V2 plus voltage across Ra plusithe opposed voltage derived from the 16.34 v. and- 6.3 v. taps of the secondary I6;

TheA resistors-Rs, Rs and R7 are grid leak resistors. The resistors Raand Re are equalizing resistorswhichfunction to cause the lamps I4, la and 2I. to be lighted to the-same brightness. Since the tube V2 has more voltage than the tube V1 and thetube Va has more voltage than the tube V2 orthe tube V1, the red light would be brightest and the green light would be dimmest in theabsence of the resistors Ra and R2. Bytheuse of these resistors, equal light intensity of all three lamps is obtained.

Whenit is desired to operate the signal system from a two rail system, a special control signal must be provided. This signal-must be suseparated from the power drive voltage that the. tubes V1, V2 and V3 will be controlled only the signal voltage. In the modification of Figure 2,- this is accomplished by using unidirectlonalvoltage for motive-power and pulse voltage for signalingr purposes.

In thisvmodication, a gaseous 4conduction vtube Vrhas potential applied to its anode from the inputA leadY IB through the primary winding-2 1 of a transformer T1, and a capacitor C2 which is shunted byy a resistor R15. The cathode of the tubeVi is connected to a tap ofthe secondary winding. of transformer T at a point where the voltage is less than the lament voltage. The

.control grid 22 of the tube V1 is connected to its cathode through a phase shifting circuit including. resistors R11 and R12 and a capacitor C1. Thegridto cathode circuit may be traced as-,follows; resistorR12 andcapacitor Ciareconnected in` series across the heater of tube V1; resistor R11` is connected between their junction andthe grid 22.; the heater -terminals are connected `to the lowest (as viewed in Fig. 2) tap and the-6.3 v. tap of transformer T; the center tap (3.15 v.) between these two transformer taps is connected directly to the cathode. The secondary winding 23.of the. transformer T1 has.4 one of its ,leads coupled to the rail 2 through a capacitor C3 and has its other terminal connected to the junction between the secondary windings 24 and 25 of transformers Ta and T2. The primary windings 25 and 21 of the transformers Ta and T2 are connected respectively between the cathode and control grid 28 of the tube V2 and between the cathodeV and oontrol;grid Aron the tube V2. Power toithe-'preoeding'block- (not shown)L may be obtained through winding 23 at the junction point of the secondaries 24 and 25. It, therefore, will obtain its, unidirectional current for propulsion as well as pulse current for signal operation.

Whemnotraindss. on block A or B, the green lamp- I4; is. lighted in the current pulses from manner'previouslyfexplained, the circuit of the tube.. V4-does not induce voltages in the secondaries 25 and 2T of transformers Ta and T2. Therefore, the green lamp stays lighted, because there is no current inithe primaries 24 and 25. to actuate their secondaries to cause either of tubesVaandVa to start conduction, and tube'Vi continuesto conduct, keeping on green light I4.

The entrance of a train into block A completes acircuit whereby signal pulse current and propulsion current isdrawn through-secondary 24. Signal transient pulses are generated continuously by tube V4 andare-so phased that the anodes of; V1-V2 and V3 are positive when these pulsesI occur. The sharp pulses are produced by thecharge current of capacitor C2-through transformer T1. Capacitor Cs-isusedas a bypass to lower thev return circuit impedance for these pulses thusy the pulse current is first passed through secondaryl 24-,l the train, capacitor C: and back to winding 23,. The pulse, current passing throughl winding 24 produces a pulse voltage'across winding 2$- ionizing tube V3; thus operating lamp I9of the signal.

When the train movesonto blockA B, conduction of the tubeV2is started in thesameway by the` pulse signal voltage applied' through the transformerTzto the-grid 29. As a result, the yellow, lampv is lit and the red lamp is extinguished by the loss of voltage on the grid 28 of the -tube Vr.Y

The purpose vofthe transformers T3 and T: is to separate. theunidirectionall motive power voltagefrom'the pulsesgnal voltage. The impedance ofthe transformers T2 and T1V is made so low .that the signalfvoltage is not affected by the charging.- potentialsof the vmotive power voltage.

In either system, when the train is in two blocks, ,for elearnple blocks A and'B, at the same tim1e,only one.of tubes V1, V2, Va can be conductive. Thereason is that when one of them is conducting, the voltage drop across resistor R1 reduces the anode.- voltage available at` the anode-of' any;y other Itube to a value below that required-toallowthe'other tube to be fired. It isswelhunderstoodlthat gas tubes require a higher anode igniting voltage than that required to maintain conduction.v `Since only one oi? tubes :Va .Vs'fcanwbe conductiveatthe same time, only .oneof the yellow. vorredlights may be on at the same time.

It is to.` be noted' that when the voltages go negativefneitherf-VL V2 nor` Va willconduct, when the' voltages go positive, however, the voltage across V3 will be the first to reach firing potentialbecause of their comparative peak magnitudes, thereforel the red light will remain lighted until the train occupies block B exclusively.

The gradey crossing signal circuit of Figure 3 4may bezutilizedin connectionl with the` signaling systems of Figures 1 and 2 by connecting its lead 39 to the high voltage side of the resistor R4 of Figure 1 or the secondary winding 26 of Figure 2.

This grade crossing signal circuit includes a controlled grid rectier including the tube V7 and a low frequency inverter including the tubes V5 and V6. The tube V7 is operated as a positive grid gaseous conduction tube by returning the shield grid 3| to a tap 32 on a resistor Ris, the voltage of this tap 32 being negative when the voltage of the anode 33 is positive. As a result, the tube Vv conducts current only when a positive voltage is applied through the lead 30 to the control grid 34. When the grid 34 has a positive potential applied to it through the lead 30, the tube Vv functions to charge a capacitor C4 from the positive side of which voltage is applied through a lead 35 to the midpoint of the anode resistor R21 of the inverter. The negative terminal of the capacitor C4 is connected through a lead 36 to the common terminal of lamps 38 and 39. The individual terminals of the lamps 38 and 39 are connected respectively to the cathodes of the tubes V6 and V5.

As is usual in this type of inverter, (1) the resistor R21 is shunted by a capacitor Cv, (2) the anode of the tube Vs is coupled to the grid vof the tube V5 through a circuit including a capacitor C5 and resistor Ria and (3) the anode of the tube Vs is coupled to the grid of the tube Vs through a circuit including a capacitor C6 and resistor i9.

With these connections, the unidirectional voltage of the capacitor C4 is converted to a low frequency alternating voltage by the inverter and the lamps 38 and 39 are lighted alternately so long as a positive voltage is applied through the lead 30.

Obviously, the warning lights I9, 2|, and I4 should be placed at the entrance to block A as shown in Figs. 1 and 2, and the grade crossing lights 38 and 39 should be placed at the appropriate grade crossing which is preferably somewhere intermediate and near the center of blocks A and B, also as shown in Figs. 1 and 2.

Thus, the invention provides an improved railway signaling system Which is highly sensitive to the presence of a train, may be used in connection with either alternating or direct current motive power, and is readily combined with a grade crossing signal circuit.

What I claim is:

1. In combination, a transformer having a primary winding and a secondary winding, a plurality of signal elements, a corresponding number of gaseous conduction devices each having a cathode, an anode and a control electrode, the anodes of said devices being connected through a common impedance to one terminal of said primary winding, a point of common reference potential, the other end of said primary winding being connected to said point of common reference potential, a first tap on said secondary winding adjacent one end thereof connected to said point of common reference potential, the cathode of one of said devices being connected in series with its corresponding signal element to a second tap on said secondary winding intermediate the ends thereof, each cathode of the other of said devices being connected in series with a separate impedance to an individual tap on said secondary intermediate said second tap and said point of common reference potential, each of the other of said signal elements being connected in parallel with the separate impedance element associated With its corresponding gaseous conduction device, a connection from a tap on said secondary winding adjacent the other end thereof to the control electrode of said one device, the windings of said transformer being so poled and the voltages across said taps being so related that said one device is normally conducting and each of the other of said devices is normally non-conducting, and means for successively applying to each control electrode of the other of said devices a potential thereby causing each of said other devices to be successively made conducting and each other of said devices is rendered non-conducting, by reason of the lowered anode to cathode potential resulting from ionization of the conducting tube.

2. The combination as set forth in claim 1 in which said means for successively applying control pulses comprises impedance elements each arranged to be connected to a different block of a railway track through said secondary Winding and means for applying a voltage drop across said impedance elements each to the control grid of a different one of said other devices.

3. The combination as set forth in claim 1 in Which said means for successively applying control pulses comprises transformers each having its secondary Winding connected in the control grid circuit of a different one of said other devices and each having its primary winding connected to a different successive block of a railway track, and means responsive to the presence of a train on said successive blocks for successively energizing said other devices and de-energizing said one device.

4. The combination as set forth in claim 1 in which said means for successively applying control pulses comprises transformers each having its secondary winding connected in the control grid of a different one of said other devices and each having its primary winding connected to a different successive block of a railway track, and means including a gaseous conduction device connected to apply a pulse voltage to each of the said primary windings of said transformers in response to the entrance of a train into each successive block.

GEORGE D. HANCHE'I'T, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,674,782 Lewis June 26, 1928 2,030,675 Arkenburgh Feb. 11, 1936 2,409,044 Jerome Oct. 8, 1946

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