US2095680A - Apparatus for the control of highway crossing signals - Google Patents

Description

Oct. 12, 1937.

A. J. SORENSEN APPARATUS FOR THE CONTROL OF HIGHWAY CROSSING SIGNALS Filed Jan. 9, 1956 2 Sheets-Sheet 2 Fey. 2

Fly. 6

INVENTOR Andrew J. 501 9123912 aw/am HIS ATTORNEY Patented Oct. 12, 1937 UNITED STATES PATENT. OFFICE APPARATUS FOR THE CONTROL OF HIGH- WAY CROSSING SIGNALS Application January 9, 1936, Serial No. 58,333

21 Claims. (01. 246-130) My invention relates to apparatus for the control of highway crossing signals, and particularly to apparatus controlled by a train approaching the crossing for governing the operation of highway crossing signals in accordance with the speed of the train. V

I will describe several forms of apparatus embodying my invention, and will then point out the novel features thereof in claims. I I A feature of my invention is the provision of novel and improved apparatus operative to measure the speed of a railway train as it passes a fixed point in approaching a highway crossing and to govern the starting'of the operation of 15 the highway crossing signal in accordance with invention. Figure 21s a diagrammatic view of a second form of apparatus which also embodies my invention. Figure 3 is a vertical sectional View showing one form of a rail microphone which may be used as an actuator for the apparatus shown in Figs 1 and 2. Figs. 4, 5' and 6 are diagrammatic views showing preferred arrangements of spacing the rail microphones. Figs. 7 and 8 are diagrammatic views of two other forms of actuators which may be'employed with the apparatus of Figs. 1 and 2 and which apparatus also embodies my invention. In each ofthe several views like reference characters designate similar parts.

Referring to Fig.1, the reference characters I and l designatethe track rails of a stretch of railway track over which traffic normally moves in the direction indicated by an arrow and which rails are intersected at grade by a highwayI-I. A highway crossing signal S is located adjacent the intersection. This signal S may take any of several different forms for highway crossing signals and, as here shown, is an audible signal in the form of an electric bell. The immediate con trol of signal S is effected through a relay L which when energized completes at its front contact 2 a simple circuit for supplying current to signal Sand causing it to sound a warning. In Fig. 1;

the rails I and l are formed by the usual insulated rail joints into a track section X--Y, the arrangement being such that the exit end Y of the track section is adjacent the highway. L1

practicing my invention the location X, that is the entrance of the section X-Y, would ordinarily be an automatic wayside signal location. The significant thing about the track section X-Y as far as this application is concerned is that the location X is remote from the highway a distance greater than that required to provide a desired warning period of the highway crossing signal, prior to arrival of a train at the intersection, when a train .approaching the intersection is traveling at the maximum permissible speed for all trains. The section XY is provided with a track circuit which includes a battery 3 and a track relay TR. V

An actuator responsive to the passing of a train is attached to at least one of the rails at a fixed location U. On the assumption that a 20 seconds warning of the highway crossing signal prior to arrival of a train at the intersection is desired and the maximum permissible speed for all trains is 90 miles per hour, the location U would be something over 2640 feet from the highway, say, 2800 feet, since the warning operation of the signal S under such maximum speed conditions is, as will appear later, preferably initiated as the forward end of the train passes the location of the actuator, and since a train operating at 90 miles per hour will advance 2640 feet in 20 seconds; I V

In Fig. 1, the actuator is a rail microphone which is shown conventionally at M, its connection with the rail l being indicated by a dotted line. This microphone M is; so designed that it has the characteristics of increasing its resistance in response to vibration of the rail to which it' is attached. This microphone may be of the type disclosed and claimed inthe United States Letters Patent No. 1,834,077, granted to myself on December 1, 1931. Referring particularly to Fig. 3, the microphone M is attachedto the rail l by means of a clamp l which is secured to the flange of the rail by a lug 9i] and a bolt 15. The microphone comprises an insulating housing I4 attached to the clamp thy a screw l5, and which housing contains two spaced vertically disposed metal electrodes E and El. The spacing between these two electrodes is partly, but not wholly, filled with loose carbon granules l3. The microphone M is provided with a circuit which passes from a battery 5 through the electrode E, the carbon granules l3, electrode El, a primary the terminals of the primary winding 6.

winding 6 of a transformer Ti and back to battery 5. A condenser i may be connected across It follows that under normal conditions when the microphone is not vibrated the resistance of the carbon granules remains constant and a direct current of a steady value flows in the primary winding 6 of transformer Tl with the result that no electromotive force is induced in the secondary windings 8, 9 and I!) of that transformer. Every time a wheel of a passing train rolls over the point where the microphone M is attached to the rail practically no current flows for an instant due to the vibration of the rail, the current then increasing to its normal value as the wheel moves away from the point of attachment. Such decrease and the following increase in the current fiowing through the primary winding 5 of transformer Ti will induce a complete cycle of alternating electromotive force in each of the secondary windings 8, 9 and it. It is clear that the passage of a train will cause a succession of such cycles of electromotive force the period of each cycle depending upon the speed of the train.

The secondary windings 8, 9 and it are connected to circuit networks selectively responsive to the periods of the cycles ofthe alternating electromotive forces induced in these secondary windings in response to a passing train. The secondary winding is connected across the input terminals of a full wave rectifier i i, the output terminals of which are connected with a top winding i2 of a relay Ri. Consequently, unidirectional current flows in winding l2 of relay Ri to energize that relay whenever an electromotive force is induced in the secondary winding 8, relay R! receiving energy irrespective of the period of the cycle of electromotive force. The secondary winding 9 of transformer Ti is connected across the input terminals of a full wave rectifier I! through a circuit network is which network consists of reactors iii and 2B and a condenser 2!,

arranged to form a hi h pass filter, The output terminals of rectifier H are connected across a top winding 22 of a relay R2. The parts of the filter network E8 are so proportioned and adjusted as to effectively pass electromotive forces, the cycle of which has a period less than a predetermined period. That is, the cycles of alternating electromotive force having a period less than a predetermined period are passed by the filter i8, rectified by the rectifier l! and an impulse of unidirectional current is supplied to the winding 22 of relayIRZ. To better understand my invention I shall assume the filter network i8 is effective to pass the cycles of electromotive force induced in the secondary winding 9 in, response to trains having speeds above 35 miles per hour'passing. the location U. That is to say, rectified current is supplied to winding 22 of relay R2 for all trains passing location U at a speed above the speed of 35 miles per hour, but that for all trains beiow such speed the cycles of electroinotive force induced in the secondary winding 9 are suppressed by the network H3. The secondary winding it of transformer Ti is connected with the top winding 23 of a relay R3 through a filter network 24 and full wave rectifier 25. The network 25 consists of reactors 26 and 2i and a condenser 28 arranged to form a high pass filter. The network 24 is so proportioned and adjusted as to pass the cycles of electromotive force induced in the secondary winding. it when the period of the cycles produced in response to a train passing location U is that corresponding to a speed above a given high speed which I shall assume to be 60 miles per hour. Hence, rectified current is supplied to winding 23 of relay R3 to energize the relay in response to trains operating past location U at speeds above 60 miles per hour, but that for all trains having speeds below such speed the cycles of electromotive force induced in secondary winding Ill are substantially suppressed by the network 24. It will be seen, therefore, that relay Ri will be effectively energized for all trains passing location U, relay R2 will be effectively energized only for trains operating above a medium speed of 35 miles per hour, and relay R3 will be energized only when the train is moving at a speed above 60 miles per hour.

As set forth above, the passing of each wheel of a train will induce one full cycle of electromotive force in each of the secondary windings of the transformer T5. The spacing of the wheels of a train will vary with the makeup of the train. In any event, the spacing of the wheels of the last truck of one car of the train and the wheels of the forward truck of the following car will give rise to four cycles in fairly rapid succession. In Fig. 4, such a condition is illustrated. VI represents a car of a train, the wheels 29 and 30 of which are the wheels of the rear truck. V2 is the car following and 3! and 32 represent the wheels of its forward truck. In standard equipment the spacing between the two pairs of wheels of a truck is about six feet and the spacing between the rear wheels of a car and the forward wheels of the following car is not greatly different therefrom. A group of four successive cycles produced by the wheel arrangement illustrated in Fig. 4 will be sufiicient to effectively operate the relays RI, R2 and R3. It is to be pointed out that it is the periodic character quantity of the cycles of the electromotive force which determine whether or not the cycles are passed by the filter networks I8 and 26, the spacing between two successive cycles being immaterial except for the fact a sufficient number of resulting rectified impulses must be sufficiently close together to pick up the respective relays. The condenser I connected across the secondary winding 6 of transformer TI will be effective to by-pass pulses of current of high frequencies caused by the minor vibrations in the microphone due to a passing train.

By using more than one actuator at a location more cycles of induced electromotive force may be obtained. In Fig. 5 a second microphone Ml is attached to the rail l spaced from the microphone M, one-halfthe distance between the two wheels of a truck, and the two microphones are serially interposed in the circuit including battery 5 and primary winding 6 of transformer Tl. With such arrangement of actuators, the forward and. rear wheels of each truck of a train will each induce two full cycles of electromotive force in the secondary windings 8, 9 and I ll of transformer Tl. Hence, each truck of a train would be identified by four successive cycles of electromotive force. In Fig. 6 the microphones M and MI are spaced apart approximately the same as the distance between the last wheel of one car and the first wheel of the'neXt car and the two microphones are serially interposed in the circuit. With this arrangement of actuators six full cycles with fairly even spacing can be obtained from the four wheels of two adjacent trucks not on the same car.

The relays RI, R2 and R3 are each provided with a stick circuit. Looking at relay RI, a stick circuit may be traced from theB terminal of any convenient source of current, such as a battery (not shown), over back contact 33 of the track relay TR providedfor thetrack circuitof section -XY, wire '34, front contact 35 of relayRL-lower winding 36 of thatrelay and thence to the opposite terminal C of the same source of current. The stick circuit for relay R2 branches from wire 34 over front contact 31 of relay R2, lower winding 38 of the relay and thence to the C battery terminal; and the stick circuit for the relay R3 branches from wire 34 over front contact 39 of the-relay,

lower winding 40 and to the C battery terminal.

It follows that when anyone of these three conare both normally deenergized, the relay Fl being energized over a simple circuit including front contact 4! of .relay RI, and the relay F2 being energized overa circuit including front contact 42 of relay R2, as will be readily understood by an inspection of Fig. l. The pickup periods for relays FI and F2 will be selected to agree with the location at which the apparatus is installed. To

agreewith the track conditions and the train speeds I have assumed for the apparatus of Fig. 1

the pickup period of Flwill be approximately 30 be 10 seconds.

The relayL is controlled over. a circuit network including three branch paths, a first one of which maybe traced from the B battery terminal over front contact 43 of relay R3, line wire 44, winding of relay L and to the C battery terminal. A second path extends from the B battery terminal over'front contact 45 of relay F2, wire 45, line wire "44 and thence as before traced for the first path. The third path passes from the B battery terminal they successively pass the location U will cause cycles of alternating electromotive forceto be induced in the secondary windings 8, 9 and ID of transformer Tl in the manner previously described. The period of each such-cycle of electromotive force will be such as to be substantially suppressed by the high pass filter networks 18 and 24, and hence only relay R! will be picked up. Relay RI once picked up will be retained energized over its stick circuitsince the track relay' TR is now down and its back contact 33 is closed. With relay RI picked up thetime element relay Fl will be energized and its front contact 41 will be closed at the end of its slow pickup period which in this case is 30 seconds. With time element relay Fl picked up current will be supplied to relay L and that relay on picking up -wi-11- startthe warning-operationof signal S.

Thus, the warning operation of signal S will be delayed substantially 30 seconds subsequent to the forward end of the train passing location pU. Since this low speed train (something less than 35 miles per hour) will require something over '53 seconds in advancing from location U to the highway intersection, a minimum warning period of 20 seconds will be assured. When this train advances over the highway crossing and the rear of the train vacates the section XY, the track relay TR will be picked up releasing the relays El and Fl, and in turn relay L will be released stopping the operation of signal S.

I shall next assume that a train approaches the highway from the left traveling at a speed something over 35 miles per hour but less than 60 miles per hour. This train will shunt the track relay TR and cause its release the same as the first train. This latter train upon passing location U will cause cycles of electromotive force to be induced in the secondary windings of transformer Tl the period of which will be such that the cycle will be passed by the high pass filter l8 but not by the filter 24, and consequently the relays RI and R2 will be picked up and stuck energized but relay R3 will remain deenergized. The picking up of relay R2 and the closing of its front contact 42 will supply current to the time element relay F2 and that relay will pick up and close its front contact 45 at the end of its 10 second pickup period. With contact 45 closed current will be supplied to the relay L and the warning operation of the signal S will be initiated. Hence, this time a delay of 10 seconds subsequent to the forward end of the train passing location U before the signal S is set into operation will be effected. Since this train will require something over 31 seconds to advance from location U to the highway intersection, a 20 seconds operation of the signal will be obtained. It is noted that relay Fl may also operate to close its front contact before the train vacates the track section XY and restores the apparatus to its normal position but operation of the relay Fl will perform no useful function at this time and need not be further considered. Assuming next that a train approaches the highway at a speed something over 60 miles per hour, this train .will

shunt the track relay TR upon entering the section XY as in previous cases. The period of the cycles of electromotive force induced in the secondary windingsll, 9 and In, due to the successive wheels of this train passing the microphone M, will be such as to be passed by both networks l8 and 24, and hence all threerelaysRl, R2 and R3will be picked up and retained energized over their respective stick circuits. The pickup of relay R3 and the closing of its front contact 43 will supply' current to relayL .and

.start the warning operation of the signal S at Since a train moving at the maximum once. permissible speed of .90 miles 'per hour requires .a little over 20 seconds to advance from location U to the highway crossingsignal, a minimum warning period of 20 seconds will be assured for alltrains operating at speeds above 60 miles per hour.

In Figure 2 the track layoutis the same as in Fig. 1, except for the fact that location V of the actuator M is to the rear of the highway, a dis-v tance greater than that required to provide a 20 seconds warning period prior to the arrival of a train at the intersection when a-train is traveling at the maximum permissible speed of 90miles per-hour. 'Toclarify the-descr-iptionl smiles-(1.7

from the highway H. The microphone M 1 of Fig. 2 is provided with a circuit including battery "5' and primary winding 6 of the transformer TI, and furthermore the secondary winding 8 of transformer TI is connected with the top winding I2 of relay RI through the rectifier H the same as in Fig. 1. In this form of the invention the secondary winding 9 is connected with the winding 22 of relay R2 through the rectifier H and a filter network 38, which network consists of a reactor 89 and two condensers 39 and 5!]. Reactor 89 and condensers 9 and 50 are arranged to form a low pass filter which is proportioned and adjusted to pass cycles of electromotive force of a period greater than a predetermined critical period. I shall assume filter 88 passes cycles of electromotive force produced in response to trains moving at a speed less than 60 miles perhour butthat for all trains traveling at speeds above 60 miles per hour the cycles of electromotive force induced in the winding 9 are substantially suppressed. The secondary winding H! is connected with the winding 23 of relay R3 through the rectifier and a filter network '51, which network consists of a reactor 52 and two condensers 53 and 54, and which reactor and condensers are arranged to form a low pass filter. The parts of the low pass filter 5! are proportioned and adjusted to pass the cycles of electro- 'motive force having a period greater than a certain critical period and I shall assume the filter 5| passes cycles of electromotive force created by trains having speeds of less than 35 miles per hour but that for all trains moving at speeds above 35 miles per hour the cycles of electromotive force induced in the secondary winding it are suppressed. It is clear, therefore, that all three control relays RI, R2 and R3 of Fig. 2 are picked up by trains moving at speeds of less than 35 miles per hour, relays R5 and R2 are picked up and relay R3 is down for train speeds between .35 and 60 miles per hour, and relay RI only is picked up for train speeds above 60 miles per hour.

In Fig. ,2 a third time element relay F3 associated with the relay R3 is provided as well as the two time element relays F! and F2 associated with relays R! and R2, respectively. In this instance the relays Fl, F2 and F3 will be adjusted to agree with the track layout of Fig. 2, and will be provided with pickup periods of 5, l8 and 46 seconds, respectively. The relay Fl is controlled over the front contact 55 of relay RI and the back contacts 56 and 5'! of relays R2 and R3, respectively. Relay F2 is controlled over the front contacts 55 and 58 of relays RE and R2, respectively, and a back contact 59 of relay R3;

and the relay F3 is controlled over the front contacts 55, 58 and E9 of the three control relays in series. The relay L is controlled over front contacts of the time element relays Fl, F2 and F3 in parallel as will be readily understood by an 'inspection of Fig. 2.

In the event a train traveling at a speed of over 60 miles per hour passes location V in approaching the highway H, relay RI only will be picked up and retained energized and the signal S will be set into operation after a delay of substantially 5 seconds since the time element relay Fl will close its front contact 6? and supply current to the relay L substantially 5 seconds after the forward'end of the train passes the location V, Since a train traveling at, the maximum speed of 90 miles per hour will require something sume: the location V is approximately 3500 feet over 25 seconds to advance from location V to the highway H, a minimum warning periodof 20 seconds prior to the arrival of the train at the highway will be assured. Again, when a train traveling at a speed between 35 and 60 miles per hour passes location V, both relays RI and R2 will be picked up and the relay R3 will remain deenerglzed. Under this condition, the time element relay F2 will be selected and signal S will be set into operation substantially 18 seconds after the forward end of the train passes location V. Trains passing location V at speeds of less than 35 miles per hour will cause all three of the control relays to be picked up and the time element relay F3 will be selected and a delay of approximately 46 seconds subsequent to the forward end of the train passing the location V will be provided. 1

Although specific values of track conditions and train speeds have been used in describing the apparatus of Figs. 1 and 2, it will be understood, of course, that such values are for illustration only and do not constitute a limitation of the invention since the actuators can readily be located with respect to the highway as desired, without interfering with existing track circuits, and since the time element relays may be adjusted to suit Various locations of the actuator.

In Fig. 7, a second form of actuator that may be provided for the apparatus of Figs. 1 and 2 is disclosed. The angle'bars 6i and 62 of a rail joint and an end post 63 are of non-magnetic material. A magnetizable core member 64 is secured to the rails 65 and 56 by bolts 61 and 68 at the opposite ends of the rail joint for magnetic relationship with the rails. A winding 69 is mounted on the core member '64 and is interposed in a circuit which includes a battery it and the primary winding ll of a transformer T2. The control relays RI, R2 and R3 are governed by secondary windings 12, i3 and M, respectively, of transformer T2 in the same manner as by the secondary windings 8, 9 and IU of transformer TI of Fig. 1, and it is thought to be unnecessary to repeat the description in detail. When a wheel of a train moves over the rail joint and spans the non-magnetic end post 63, the reluctance of the magnetic path including the two ends of rails 65 and 63 and the core member 64 will be materially varied, and the magnetic flux will be first increased and then decreased as the wheel moves over the end post 63. Such sudden increase and decrease of magnetic flux is effective to induce a full cycle of electromotive force in the secondary windings 72, 13 and M. The cyclic period of such electromotive force will depend upon the speed at which the train wheel rolls over the joint and hence will depend upon the speed of the train. The filter networks interposed between the secondary windings of transformer T2 and the control relays may be designed to selectively energize the relays in accordance with the diiferent periods of the cycles of electromotive force and hence in accordance with the different train speeds. It is apparent, therefore, that an actuator constructed in the manner described for Fig.

-7 when used with the apparatus of Figs. 1 and 2 disposed along the inside of a track rail. These core structures will be mounted in non-magnetic housings (not shown) to be securely held in place a distance from the rail suflicient to clear flanges of car wheels. The side of each core structure adjacent the rail is provided with an air gap, and each has mounted thereon a winding, the windings 18, I9 and 80 being mounted on the cores l5, l6 and H, respectively. These three windings l8, l9 and 8B are serially connected in a circuit including a battery 82 and the primary winding 8| of a transformer T3. When a wheel such as wheel 83 of a train rolls past these core structures the flange 84 of the wheel will, when it is adjacent the air gap of each core structure, materially reduce the reluctance of that core structure with the result that a full cycle of electromotive force will be induced in each of the secondary windings 85, 86 and 81 of the transformer T3 as the wheel rolls by each of the separate core structures. It follows that three full cycles of electromotive force in rapid succession will be created by the wheel 83 in moving past the actuator of Fig. 8. The parts of this actuator are so designed that only one wheel of a train will be effective at a time. The windings 85, 86 and 81 when connected through filter networks, similar to those described for Figs. 1 and 2, will be operative to selectively govern the control relays RI, R2 and R3 in the same manner as described for the other forms of apparatus. It is also clear that the actuator of Fig. 8 may be applied to a track rail without in any way interfering with the existing track circuits provided for an automatic signal system.

Although I have herein shownand described only certain forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit andscope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, operating means for operating the signal but normally in- 7 active, an actuator located adjacent a track rail at a fixed point to one side of the intersection and characterized by a change in its electrical oharacteris'tics when a wheel of a, train passes the fixed point, means including said actuator operative to create a cycle of electromotive force in response to a wheel passing the actuator, said cycle having a period which is inversely proportional to the speed of the wheel, speed measuring means controlled by said electromotive force and selectively responsive to the period of the cycle, and means controlled by the speed measuring means for rendering the operating means active in accordance with the measured speed. a

2. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, operating means for operating the signal but normally inactive, an actuator located adjacent a track rail at a fixed point to one side of the intersection and characterized by a change in its" electrical electromotive force in a secondary winding of at a fixed point to one side of the intersection,

and characterized by a change in its electrical characteristics when a wheel of a train passes the fixed point, a transformer, a circuit including said actuator and a primary winding of the transformer as well as a source of direct current, said circuit operative to induce a cycle of electromotive force in a secondary winding of the transformer in response to a wheel of a train passing the actuator, said cycle having a period which is inversely proportional to the speed of the train wheel, control means connected to said secondary Winding and selectively responsive to the period of the cycle of electromotive force, and means governed by the control means for rendering the operating means active to operate the signal in accordance with the speed of the train.

4. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, operating means for operating the signal but normally inactive, a microphone attached to a track rail at a fixed point to one side of the intersection and characterized by increasing its resistance when vibrated by a wheel of a train passing said fixed point, a transformer, a circuit including the microphone and a primary winding of the transformer as well as a source of direct current, said circuit operative to induce a cycle of electromotive force in a secondary winding of the transformer in response to a train wheel passing the fixed point the period of which cycle is in accordance with the speed of the train, control means connected with said secondary Winding and including a filter network effective to pass cycles of electromotive force of a predetermied period, and means governed by the control means for rendering said operating means active.

5. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, a microphone attached to a track rail at a fixed point to one side of the intersection and characterized by increasing its resistance when vibrated by a wheel of a train passing said fixed point, a transformer having a primary winding and a plurality of secondary windings, a circuit including the microphone and said primary winding as Well as a source of direct current, said circuit operative to induce a cycle of electromotive force in each of said secondary windings in response to a train wheel passing said fixed point the period of which cycle is in accordance with the speed of the train, a plurality of control circuits one connected with each of said secondary windings and each including a filter network, said filter networks each being effective to pass cycles of electromotive force of predetermined periods and which periods are different for the different networks, and

operating means selectively governed by said intersected by a highway, a highway crossing signal located at the intersection, a magnetizable core member disposed along a track rail at a fixed point to one side of the intersection and provided with an air gap which is bridged by a train wheel in passing said fixed. point, means including a source of direct current for providing a magnetic flux in said core member, means including a winding for inductively receiving a cycle of electromotive force in response to the changes in the flux caused by a Wheel moving by the air gap, the period of which cycle is in accordance with the speed of the train, speed measuring means connected with said winding and selectively responsive to the period of such cycle of electromotive force, and operating means governed by said speed measuring means for operating said signal.

'7. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, a magnetizable core member disposed along a track rail at a fixed point to one side of the intersection and provided with an air gap which is bridged by a train wheel in passing said fixed point, means including a source of direct current for providing a magnetic flux in said core member, means including a plurality of windings for inductively receiving a cycle of electromotive force in each of said windings in response to the changes in the fiux caused by a wheel moving by the air gap, the period of which cycle is in accordance with the speed of the wheel, a plurality of control circuits one connected to each of said windings and each including a filter, said filters each being efiective to pass cycles of electromotive force of predetermined periods and which periods are different for the different filters, and operating means selectively governed by said control circuits for operating said signal.

8. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, a rail joint at a fixed point to one side of the intersection and provided with non-magnetic angle bars, a nonmagnetic spacer between the abutting ends of the rails at said joint, a magnetizable core member attached to the rails at opposite ends of said joint for magnetic relationship with the two rails, a winding on said core member, a transformer having a primary winding and a plurality of secondary windings, a circuit including the first mentioned winding and said primary winding as well as a source of direct current for inducing a cycle of electromotive force in each of said secondary V windings in response to a wheel of a train moving over said spacer, the period of which cycle is in accordance with the speed of the train, a plurality of control circuits one connected with each of the secondary windings and each including a filter, said filters each being effective to pass cycles of electromotive force of predetermined periods and which periods are diiferent for the different filters, and operating means selectively controlled by said control circuit for operating said signal.

9. In combination, a stretch of railway track intersected by a highway, a highway crossing signal at the intersection, a plurality of magnetizable core members disposed successively along a track rail at a given location to one side of the intersection, each core member provided with an air gap which is bridged by a wheel of a train, a winding mounted on each core member, a transformer having a primary winding and a plura ty of secondary windings, a circuit including said primary winding and the windings of said core members as well as a source of direct current, said circuit operative to induce a series of cycles of electromotive force in each of said secondary windings when a wheel of a train successively bridges said air gaps, the period of such cycles being in accordance with the speed of the train, a plurality of control circuits one connected to each secondary winding and each including a filter, said filters each being eifective to pass cycles of electromotive force of predetermined periods and which periods are different for the different filters, and operating means selectively controlled by said control circuits for operating said signal.

10. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, time measuring means having a plurality of different operating times but normally inactive, means controlled by said time measuring means for starting operation of said signal at the expiration of a selected one of its operating times, a transformer having a primary winding and a plurality of secondary windings, a circuit controlling actuator attached to a, track rail at a fixed point to one side of the highway, a circuit including the actuator and said primary winding and operative to induce an alternating electromotive force in said secondary windings in response to a wheel of a train passing said fixed point, the period of the cycle of such electromotive force being in accordance with the speed at which a train wheel passes said fixed point, a plurality of control circuits one connected with each secondary winding and each control circuit including a filter network, said filter networks each being effective to pass-cycles of electromotive force of predetermined periods and which periods are diiferent for the different networks, and means controlled by said control circuits for rendering said time measuring means active and for selecting which one of its operating times is efiective.

11. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, time measuring means having a plurality of different operating times but normally inactive, means controlled by said time measuring meansfor starting operation of said signal at the expiration of a selected one of its operating times, a circuit controlling actuator attached to a track rail at a fixed point to one side of the highway and characterized by a change in its electrical characteristic in response to a wheel of a train passing said fixed point, a circuit including said actuator and operative to create'an alternating electromotive force in response to such change in the characteristic of the actuator, the period of the cycle of such electromotive force being in accordance with the speed at which a train wheel moves past said fixed point, a plurality of control circuits governed by the first mentioned circuit and each control circuit effectively influenced by cycles of electromotive force of predetermined periods and which periods are diiferent for the different control circuits, and means controlled by said control circuits for selectively governing said time measuring means.

12. In combination, a stretch of railway track, a microphone attached to a track rail at a fixed point, and characterized by increasing its resistance when vibrated by a wheel of a train passing said fixed Point, a transformer, a circuit including the microphone and a primary winding of the transformer as well'as a source of direct current, said circuit operative to induce a cycle of electromotive force in a secondary winding of the transformer in response to a wheel of a train passing said fixed point the period of such cycle being in accordance with the speed of the train, control means connected with said secondary winding and including a filter network effective to pass cycles of electromotive force of predetermined periods only, and'a signaling device governed by said control means.

13. In combination, a stretch of railway track, a microphone attached to a track rail at a fixed point and characterized by increasing its resistance when vibrated by a wheel of a train passing said fixed point, a transformer having a primary winding and a plurality of secondary windings, a circuit including the microphone and the primary winding as well as a source of direct current, said circuit operative to induce a cycle of electromotive force in each of said secondary windings in response to a Wheel of a train passing said fixed point, the period of such cycle being in accordance with the speed of the train, a plurality of control circuits one connected with each of said secondary windings and each including a filter network, said filter networks each being effective to pass cycles of electromotive force of predetermined periods and which periods are different for the difierent networks, and signaling means selectively governed by said control circuits.

14. In combination, a stretch of railway track,

a microphone attached to a track rail at a fixed point, said microphone characterized by having a normal resistance when not vibrated and by changing its resistance from said normal resistance when vibrated by a wheel of a train passing the fixed point, a transformer, a circuit including the microphone and a primary winding of the transformer as well as a source of direct current, said circuit operative to induce a cycle of electromotive force in a secondary winding of the transformer in response to a wheel of a train passing said fixed point the period of such cycle being in accordance with the speed of the train, and control means connected with said secondary winding selectively responsive to the period of said cycle of electromotive force.

15. In combination, a stretch of railway track, a rail joint including non-magnetic angle bars, a non-magnetic spacer between the abutting ends of the rails at said joint, a magnetic core member attached to the rails at opposite ends of said joint for magnetic relationship with the two rails, a winding on said core member, a transformer, a circuit including the primary winding of the transformer and the first mentioned Winding as well as a source of direct current for inducing a cycle of electromotive force in the secondary Winding of the transformer in response to a wheel of a train moving over said spacer, said cycle having a period which is in accordance with the speed at which a train wheel passes the joint, and control means connected with said secondary winding selectively responsive to the period of said cycle of electromotive force.

16. In combination, a stretch of railway track, a plurality of magnetizable core members disposed successively along a track rail and each provided with an air gap which is bridged by a wheel of a train, a winding mounted on each core memher, a transformer, a circuit including the primary winding of the transformer and the Windings of said core members as well as asource of direct current, said circuit operative to induce a series of cycles of electromotive force in the secondary winding of the transformerwhen a train wheel successively bridges the air gaps, said cycles having a periodwhich is in accordance with the speed at which'a Wheel moves past said air gaps, and control means connected with said secondary winding selectively responsive to the period of said cycles of electromotive force.

17. In combination, a railway track, a magnetizable core member disposed along a track rail and provided with an air gap which is bridged by a train wheel in moving along said rail, means including a source of direct current for providing magnetic fiuxin said coremember, means including a winding for inductively receiving a cycle of electromotive force in response to the changes in the flux caused by a Wheel moving by the air gap and the period of which cycle is in accordance with the speed of the wheel, and control means connected with said winding selectively responsive to the period of such cycle of electromotive force. 7

18. In combination, a stretch of railway track, a circuit controlling actuator attached to a track rail at a fixed point and characterized by changing its electrical characteristics in response to a wheel of a train passing said fixed point, a transformer, a circuit including said actuator and a primary winding of the transformer, said circuit operative to induce a cycle of electromotive force in a secondary Winding of the transformer in response to the change in the actuator caused by a wheel of a train passing said fixed point, said cycle having a period in accordance with the speed at which a wheel passes said point, and control means connected with said secondary winding selectively responsive to the period of said cycle of electromotive force. I

19. In combination, a stretch of railway track, a circuit controlling actuator attached to a track rail at a fixed point and characterized by a change in its electrical characteristics in response to a wheel of a train passing said fixed point, a transformer having a primary winding and a plurality of secondary windings, a circuit including the actuator and said primary winding, said circuit operative to induce a cycle of electromotive force in each of the secondary windings in response to a wheel of a train passing said fixed point the period of such cycle being in accordance with the speed at which a wheel passes said fixed point, a plurality of control circuits one connected with each of said secondary windings and each including a filter network effective to pass cycles of electromotive force of predetermined periods only, and signaling means selectively governed by said control circuits.

20. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, operating means for operating the signal but normally inactive, an actuator located adjacent a track rail at a fixed point to one side of the intersection and capable of a change in its electrical characteristics in response to a train passing the fixed point, means including said actuator operative to create an electromotive force in response to said change in the characteristics of the actuator and which electromotive force is varied in accordance to the rate at which the characteristics of the actuator are changed, and means controlled by said electromotive force selectively. responsive to the Variations thereof for initially rendering the operating means active subsequent to the train passing said fixed point in accordance with the speed at which the train passes said fixed point. 7

21. In combination, a stretch of railway track intersected by a highway, a highway crossing signal located at the intersection, operating means for operating-the signal but normally inactive, means including a current source and an 10 actuator located adjacent a track rail at a fixed point to one side of the intersection to create an

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