US1757410A - Train control - Google Patents

Description

' May 6,1930. c. s. BUSHNELL TRA I N CONTROL Original Filed May 10 1924 2 Sheets-Sheet l BY WTTORNEY May 6, 1930. c. s. BUSHNELL TRAIN CONTROL Original Filed May 10 1924 2 Sheets-Sheet 2 IN ENTOR L %ATTORNEY Patented May 6, 1930 CHARLES S. BUSHNELL, ROCHESTER, NEW YORK, ASSIGNOR I0 GENERAL RAILWAY b SIGNAL COMPANY, or noonnsrna, NEW YORK TRAIN CON T3013 Original application filed May 10, 1924, Serial No. 712,289. Divided and. this application This invention relates to automatic train control systems for railroads and deals more particularly with the problem of maintain inglor enforcing vigilance on the part ofthe engineer in obeying the unfavorable indicationsot the trackway block signals, or cab signals if used.

This application is a division of my prior application Ser. No. 712,269, filed May 10, 1924. i

According to the theory on which the pres ent inventionmaybe said to be predicated, it is desirablefln designing an automatic train control system, to maintain to the highest degree the vigilance and care of the engineer in the handling of his train which exists at present and aiiords a ivery high degree of safety. In other words, it is considered expedient to avoid substitution of the safety atforded by automatic devices for that now I givenby the engineer, making the automatic train control system of such a character as to supplement the present vigilance andcare of the engineer. It is thought that a train control system of this type would surely add to the safety of train movement, retaining all of the safety at present obtained and providing the automaticprotection in addition.

Roughly speaking, the object of an automatic train control system is to stop the train or reduce its speed, it safety requires, in the event that the engineer fails to do so. This means that it becomes necessary to determine automaticallywhat the safespeed for a train is at different points inits travel under different conditions of traffic and impose automatic control of the brakes if these sate speed limits are exceeded. As a' practical proposition, on account of the variation in grades, braking power of trains, block lengths, and other practical limitations, it

becomes very-diflicult to accurately determine automatically the safe speed limits at all points, with the result that the speed limits which are enforced by the system of train control are more or less-inaccurate in. practics and frequently represent a compromise between conflicting factors.

One simple way of enforcing vigilance of the engineer is to inflict some sort of penalty 1927. Serial No. acacia.

whenever the engineer fails to control his train properly and the automatic traincontrol system has to apply the brakes. In short, every automatic brake application is accompanied by a penalty. 1n earrying' out this scheme or maintaining vigilance, it becomes necessary for the engineer to have the speed of his train at all times below the arbitrary speed limits automatically set up,that is, the engineermust keep below the dead-line ,of automatic control in order to avoid the penalty. On account of the inaccuracies in' this deadline of automatic control, not only does it become difficult under some circumstances "for the engineer, without special inanipiila tion, to keep below this line, butalsothere is likely to be an unnecessary delay and impairment of train movement; F or these reasons, it is proposed, according to the presentinvention, to enforce vigilance of the engineer-in another way whichybriefly stated, consists ininflictinga penalty whenever an' automatic brake application occurs, unless the engineer has maniiested liis'vigh lance by taking the appropriateaction prior to such automatic brake application In other words, the engineer may suppress the penalty associated with the automatic brake application by taking suitable action prior thereto. According to this invention, the engineer may suppress the penalty by manually controlling the brakes in such a fashion as to bring about a stop or reduction in speed of the train just as ettectively as would be brought about by the automatic control. The idea is that, it the engineer goes about slowing down or stopping the train himself be fore the automatic control takes effect. he has manifested his vigilance in the fashion and is entitled to avoid the pen-anaemia though an automatic brake application should occur on account of the inaccuracies of the arbitrary speed limits.

This invention is specially concerned with the problem of providing automatic devices operating only if the engineer has brought about the proper brake control in time to justify suppression of the penalty. In this Con]1QCti01),lt is reasoned that,inasmuch as the manual brake application required is asfiled. June 30,

sumed to be the equivalent or a substitute for the automatic brake application, such manual application should be of the same character and intensity as the automatic brake application on which the arbitrary speed limits automatically set up are based. Similarly, the critical speed limits automatically enforced are selected on the assumption that the initiation of a brake application at that particular speed and point along the track will sufice to stop the train or reduce its speed safely, and, consequently, it is sufficient to justify suppression of the penalty if the engineer ust prior to exceedingthe critical speed. limits himself initiates a manual brake application.

' Explainingmore specifically, the theorytis that the engineer mayproperly suppress the penalty if he places the engineers brake valve in the service position before exceeding the critical speed limits, since such movement initiates a manual brake application as promptly as necessary for safety.

With the ordinary type of air-brake equipment,ifthe engineer were required to keep this engineers brake valve in the service position for a considerable time in order to suppress the penalty, there would be an unnecessary over-reduction in the brake pipe pressure and waste of air. Hence, it is desirable to provide additional means permitting the V engineerto lap his brake valve, provided he has kept this valve in the service position long enough to assure an adequate brake application. One type of such means,,herein disclosed, operates upon the drop in pressure in the equalizing reservoir and permits lapping of the engineers brake valve after-the equalizing reservoir pressure has been reduced the desired amount. V

Since the penalty under consideration is associated with the automatic brake application, this penalty'may be suppressed byIpreventing operation of the devices causing such brake application, inasmuch as the penalty exists only if there is an automatic brake application, and a suppression of operation of such automatic brake applying mechanism carrieswith it the suppression of the penalty.

The particular disclosure, however, is more illustrative of the character of means constituting the present invention than a comprehensive showing of all Ways in which the invention may be practiced; and it should be understood that the invention is not limited to any particular structure or organiza- 7 tion herein disclosed, but is susceptible of adaption and modification to meet the needs of any particular situation.

Various specific objects, purposes, advantages, and characteristic features of the invention will appear as the description progresses.

Indescribing the invention in detail reference will be had to the accompanying drawings in which:

Fig. 1 illustrates the main control relay and amplifying apparatus of the car-carried equipment and also the trackway apparatus of a train control system of the continuous inductive type having my inventionapplied thereto; and

Fig. 2 shows the remaining portion of the car-carried apparatus and its relation to the main control relay.

Traclcwag apparatus Referring particularly to Fig. 1, there has been shown trackway apparatus for a train control system applied to a portion of automatic signal territory. The track rails 1 are divided by insulated joints 2 into blocks. Since the various blocks are the same, like parts of each block are designated by like reference characters with distinctive exponents. Although the train control system in question may be usedin connection with trackway signals of any type, either color light, position light or semaphore signals, semaphore signals Z have been shown conventionally without illustrating their wellknown control devices and circuits.

In this drawing there is not only illustrated a section of trackway/ equipped for three position distinctive wayside trafic indicationbut the apparatus also includes a means for continuously transmittting to suitable car-carried apparatus a control influence corresponding to the particular traffic condition existing. For convenience the block N and the adjacent ends of two other blocks M and 0 only have been shown. These blocks are provided with the usual track circuit including an alternating current source of energy as indicated by the-track transformer lOand the usual limiting impedance 1.39 at the exit end thereof, and with a suitable track relay 141 adapted to respond to alternating current. As well known by those skilled in the art of railway signaling, this track transformer 140 results in the flow of alternating current in one direction in one of the rails and back again in the opposite direction in the other rail; and for convenience this current may be called the track circuit or loop circuit current.

In addition to this track circuit current, it is desirable to transmit another current which is distinctive and which for convenience may be called the simplex current. This simplex current flows through both rails along the trackway in multiple in the same direction. In order to transmit this simplex current, balancing resistances 14:2, 1&3, and 144 are bridged across'the'trackway at the entrance, at an intermediate point, and at the exit end of each block. The middle points of these balancing resistances areconnected v tion to the loop circuit current; and under caution traific conditions, with the contacts 146 and 147 111 their lower posltion, a 011'- cuit is completed for the flow of simplex current between the entrance of the block and the balancing resistance 1 13 which has a negative phase relation to the loop circuit current of the block. In other words, if these currents are detected on the railway vehicle they may be applied to a relay to produce torque in anormal direction when passing 1 through a clear block, in a reverse direction when passing through a caution block between the entrance end of such block and the balancing resistance 143, and cause deenergization of this relay when the vehicle moves in a caution block beyond the balancing re sistance 143, because no simplexcircuit current is present beyond this point under caution traiiic conditions, and said relay will also assume the deenergized position when moving in an occupied block because even though simplex circuit current is present, loop circuit current is shunted awayby the train ahead. i

There are also shown in Fig. 1 above the block N horizontal dotted lines 14%9, 150 and 151 indicating suitable permissive speed limits automatically imposed on the train respectively, under clear traffic conditions, as it enters the block N under caution conditions, and as it approaches the exit end of this block under caution conditions. Fig. 1 also shows a speed-distance curve 152 which may be said to be representative or typical o1": con-:cnr plated train performance. This illustration is for explanatory purposes primarily, and it should be understood that the speed limits selected and the shapes and the curves are merely representative of typical braking characteristics.

Oar-carried apparatus Speed responsive .cZcoicc.-The car carried apparatus shown in Fig. 2 includes a speed responsive device of the centrifugal type oi the usual construction and provided with an external groove in the collar 71% A contact arm 153 is pivctally supported adjacent this speechresponsive device G and has a bifurcated extension engaging the groove of the collar 71 so that the arm 153 assumes a po sition depending on the speed of the train.

Arranged to be engaged by this arm 153 are curved contact strips of different length, so that circuit connections are made for different ranges of speed of the train.

Influence commtmicatiag meana.Supported by the locomotive and in front of the first axle thereof is a pair of influence re ceiving car elements LE, each of which comprises a core 154 of magnetic material having thereon coil 155. These coils 155 are connected in series so that voltages induced therein due to currents flowing in the opposite direction in the two rails are cumulative. The circuit including these coils is connected to the input side of a loop circuit amplifying device LA, having its output leads connected to a winding 156 of a main car relay MR. This amplifying device LA includes suitable thermionic or Vacuum tube amplifiers and associated devices of a suitable type familiar to those skilled in the art, and serves to magnify the feeble current detected by the elements LE. Atanother point on the locomo tive, and preferably in the rear of the tender, is a simpler; receiving element SE, which comprises a core 157 extending across both of the track rails, and which has a coil 158 connected to the input side of a simplex amplifying device SA, this device SA being similar to the device LA and having its output circuit connected to the other winding 159 of the main car relay MR.

Since the track or loop circuit is a reaclive circuit and the simplex circuit is a resistive circuit the currents flowing in these two circuits will. be considerably displaced in phase and if these currents are detected, amplified and applied to the relay MR, they cause this relay to produce a torque in a direction to close the contacts as shown, when the train is moving in a clear block, and produce a torque in the reverse direction when the sin'iplezzclu'rent is reversed.

The main car relay MB is a suitably constructcd two-element alternating current relay which has its rotor or vane, constituting the movable or operating element, biased to a neutral or deenergized position by counterweights or equivalent means. The contacts of this relay MR are shown conventionally as swinginglingers arranged to cooperate with stationar contacts (shown as arrows) in the three di "erent positions of the operating element of this relay. When the track ra are supplied with simplex and loop ci rcuit clurrents having one phase relation, corresponding to clear trailic conditions, the contact lingers of the relay MR assume the left hand inclined position shown in l'ull lines; when this phase relation is reversed to correspond with caution traffic conditions, these figures swing to the other inclined position shown by dotted lines; and when either the simplex or the loop circuit current is cut off, corresponding to danger trailic conditions, one or the other of brakes.

the field windings of the relay MB is deenergized and its contact fingers drop to the biased position shown by vertical dotted lines.

Other detail features of the circuit arrange- .ments and operation of the system of contin uous inductive control between the track and a train are familiar to those skilled in the art and need not be described in detail.

Gab imZ-icators.ln order to inform the engineer as to trafiic conditions ahead, at a convenient place in the cab suitable signals are preferably used to show the position of the main carrelay MB. In the particular arrangement shown, these signals comprise a green, a yellow and a red lamp designated G,Y and R respectively which are illuminated to indicate. clear, caution or danger conditions respectively by circuits which may readily be traced in the drawings.

Brake control apparatu=s.Suitable means are employed to act upon the regular airbrake equipment of the locomotive or train and produce, an automatic application of the The circuit organization shown in Fig. 2 provides for the automatic control of an electro-pneumatic valve EPV; and it should be understood that this valve acts in a suitable manner, whenever deenergized, to set into operation a device, such as a brake valve actuator, which causes an automatic application of the brakes. The particular form of means controlledby the valve EPV for producing a brake application is not material; and this valve EPV may control an automatic brake application valve, or in fact any sui able type of means acting upon the regular air arake system to produce an automatic brake application.

The arrangement of Fig. 2 is assumed to include contact 44 of the engineers brake valve, as shown, which is closed in the service or emergency position of said'valve or its handle, together with means for closing contacts 54 after a predetermined reduction has been made in the equalizing reservoir pressure.

Operation Under clear traiiic conditions both simplex and loop circuit currents of the normal or positive polarity or phase relation are picked up and amplified on the train, and the con tact fingers of the relay MR assume the fullline positions shown in Fig. 2, lighting the proceed or green lamp G (the circuit for which is obvious), and energizing the electropneumatic valve EPV by a circuit which may be traced as follows :beginning at B, wire 160, push button 161 and its normally closed contact, wire 162,, contact 163 of relay MR normal, wire 164, contact strip 165, arm 153, wires 166, 167 and 168, valve EPV, wires 169 and 170, normally closed contacts 171 of valve EPV, and wire 172 to C.

The length of the contact strip 165 is such that the arm 153 will not leave engagement therewith until the actual running speed of the train is above the selected maximum speed limit, indicated by the line 149 (Fig. 1), and assumed to be 65 miles per hour. At all speeds below this maximum of 65 miles per hour, and

.so long ascleartrafic conditions prevail,

the electro-pneumatic valve EPV is maintained energized by the circuit just traced.

7 Assuming the block N (Fig. 1) to be a cantion block due to the presence of another train in the block 0, thetrack relay 141 of the block 0 is deenergized and the phase relation of the simplex and loop circuit currents is reversed for the first part of the block N between the resistances 142 and 143, while the simplex circuit current is cut ofi for the last portion of the blockN between the resistances 143 and 144. As the following train enters the caution bloclr N, the car relay MR moves its contact fingers to the reverse. position, on account of the rover ed phase relation of the loop and simplex circuit currents picked up, amplified and supplied to its field windings 156 and 159. This reversal of the relay MR extinguishes the clear lamp G and lights the caution lamp Y, and also shifts the energizing circuit for the valve EPV (Fig. 2) just traced through contact strip 165 over to the contact strip 178. The contact strip 178 is shorter, and the arm 153 remains in engagement therewith only so long as the speed of the train is below the sub-maximum or medium speed represented by the line 150 (Fig. 1) and assumed to be 40 miles per hour. Consequently, in order to maintain the electropneumatic valve EPV energized by this circuit, the speed of the train must be below 40 miles per hour. As the train advances beyond the resistance 143 and fails to pick up simplex circuit current, the contact fingers of the relay MR assume the middle deenergized position, shifting the circuit for the valve EPV (Fig. 2) over to Wire 174 and through the shortest contact strip 179, corresponding to a minimum speed,indicated by the line 151 (F i 1) and assumed to be 20 miles per hour. At the same time the caution or yellow lamp Y is extinguished andthe danger or red lamp R is lighted. v

As the train advances into the block'O, assumed to be still occupied, the contact fingers of the relay MR remain in their deenergized positions, since the loop circuit current is cut off from the following train due to the presence of the other train ahead.

The foregoing is a brief description of a three-speed continuous inductive control system, employing the usual cabsignals, and providing for a quick or abrupt change in speed limits from a maximum to a medium or sub-maximum, and to a minimum or low speed- It should be understood that this showing and description of, this particular type of continuous inductive system is mere- 1y. illustrative and that other well-known adaptations or modifications may be eniployed, using cams or equivalent means, such as shown in the patent to Simmen #1,150,309, August 17, 1915, or other delayed action means, for making a gradual change from the maximum the medium and from the medium to the low speed limits. instead of an abrupt change. It is recognized that other substitutions or adaptations of means may be made in the form of speed control system to be used in connection with the subject matter of this invention; butin order to simplify the disclosure, no attempt is made to show the various adaptations and modifications that would have the characteristic features of the invention and come within its scope.

in the continuous inductive control system, the vehicle-carried apparatus is in continuous communication, so to speak, with the trackway equipment, and may respond instantaneously to any change in the track circuits or to the presence or absence of trains in the same block. In other words, any change in traffic conditions, either favorable or unfavorable, is immediately manifested upon the train by a changein the position of the contact fingers of the relay MR. Consequently, if a train is traveling in a caution block and the next block in advance becomes unoccupied, the relay MR assumes its normal position, and the maximum speed limit is at once automatically reinstated. Similarly, if a train is traveling in a danger block and is in the rear of the balancing resistance 143, the removal of danger conditions by theclosure ofa switch, in advance of the train ahead, or the like, results in the relay MR assuming its reversed or caution condition, changing the speed limit from the minimum to the submaXimum or medium; but if the train in the danger block is ahead of the resistance 143, the advance of the train ahead into the next block in advance ooes not cause change of the MR, which remains in its deenergized co dition and continues to enforce the minimum speed limit. Likewise, any unfavorable change in traflic conditions, from clear to caution, or from either to danger, results in the relay MR assuming a corresponding condition and immediately imposing the corresponding speed limit. These features are charac eristic of the type of continuous inductire control system shown and need not be elaborated upon.

PenaZtg and suppressing means.-The train may travel at all times without penalty so long as its speed is below the particular speed then in force. For instance, if the train enters the caution block N at a speed below the medium speed of a0 miles per hour, no action upon the part of the engineer is necessary, nor is there any penalty. Likewise, if the train reduces its speed below the minimum speed of 20 miles per hour before reaching the resistance 143, then no action by the engineer is necessary and there is no penalty.

It will be readily appreciated, however, that strict adherence to these maximum, medium and minimum speed li1nits, which are arbi trarily selected and automatically established, at all points along the railroad, in all blocks, on all grades, and on all trains of the same class (freight or passenger), will not permit the train to travel as rapidly at all times as safety would permit. To take a specific example, referring to the block N of Fig. 1, at the entrance to the block the speed of the train may safely be somewhat less than miles per hour, providing a brake application is immediately initiated; and it is not necessary for the train to be at such a low speed as a0 miles per hour. For these reasons, one purpose of the invention is to make it possible for the train to berunning at speeds in excess of the arbitrary speed limits, and at the same time provide for enforcement of vigilance.

Engineer not oz'giZmrt-peaalty.-Let us assume that the train, with the parts of the car equipment as shown in Fig. 2, enters the block N while in the caution condition, and further assume that the engineer is asleep or negligent, and for some reason fails to observe the caution indication of the block signal Z or take the appropriate action in recognition of the caution indication of thissignal. Also, assume that the speed of the train is somewhat less than its maximum speed limit of 65 miles per hour and above 40 miles per hour. When the train enters the block N and the car relay MR changes to the caution condition, the speed limit of 40 miles per hour is immediately put into effect; and since the speed of the train is assumed to be above this limit, and also remembering that the engineer is supposed to take no action, the electropneumatic valve EPV is deenergized, producing an automatic application of the brakes. The speed controlled energizing circuits for the valveEPV all include its own contacts 171 closed only so long as this valve is energized. Consequently, upon deenergization of the valve EPV, contacts 171 open, and the only way this valve can again be energized is by operation of the resetswitch RS.

Upon deenergization of the valve and the resultant automatic brake application, the contact disk 54 will shift to its circuit closing position, provided the automatic brake applying means is of such character as to act upon the regular equalizing reservoir. With other types of brake applying means, the engineer must move his brake valve to the service position to close the contacts 44- 417 in order to be able to reset the valveEPV. Assuming either the contacts 54 or the contacts d4le7 to be closed, then upon operation of the reset switch RS, a circuit is established for energizing the valve EPV as follows from B, wire 128, disk 54 wires 127 and 167 to wire 168, or from B, wire 180, contacts 44-47 and wire 121 to wire 168, thence through valve EPV, wires 169 and 175, push button 176 closed, and wire 177 to C.

The reset switch RS cannot be fastened down, because upon operation thereof the opening of the normally closed contacts of push button 161 cutsoff energy from the relay contact finger 163, so that the valve EPV cannot be energized by any one of its regular speed controlled circuits. With the reset switch RS operated, the valve EPV can be maintained energized only so long as either the engineers brake valve is in the service position so as to close contacts 4:47-47, or else the equalizing reservoir pressure is reduced so as to shift the contact disk 54 to its circuit closing position. Obviously, the train cannot proceed under these conditions, and any attempt to release the brakes merelybrings the automatic brake control into efiect. Consequently, the reset switch RS after each operation thereof must be restored to the normal position before the train can proceed.

The same operation is true on a change in the speed limit from the medium to the minimum, if the speed is excessive and the engineer is not vigilant.

Engineer m'gilcmtpenalty suppresserl. To avoid the penalty just described, if the engineer does not keep the running speed of his train below the speed limits set up, he must have his brake valve in the service position before the speed controlled circuits for the electro-pneumatic valve (through the contact strips 165, 178, and 179) are broken, that is, before the valve EPV becomes deenergized and opens its contacts 171. Assume that the englneer, recognizing the existence of danger and his excessive speed, places his brake valve 7 in the service position before the valve EPV is .deenergized on account of i the excessive speed. Under these conditions an auxiliary circuit for maintaining the valve EPV energized is established as follows :-commencing at B, wire 180, contacts 4447, wires 121 and 168, valve EPV, wires 169 and 170, contacts 171 of valve EPV and wire 172 to C.

After the engineer has held his valve in the service position long enough to produce the required reduction for an effective brake application, in this instance determined by the miniature triple valve, auxiliary reservoir and brake cylinder, the contact disk 54 assumes the circuit closing position, and establishes an alternative multiple circuit, includmg wires 127 and 128, to maintain the valve EPV energized, so that the engineers brake valve may be returned to the lap position. This, expedient avoids useless waste of air that otherwise might be occasioned by requiring the engineer to keep his brake valve in the service position for an extended period.

So long as the speed of'the'train is above the existing speed limit, so that there is no circuit through the particular one of the speed contact strips 165, 178 and 179 which is capable of energizing the valve EPV, then the engineer must either have his brake valve in the service position, or must be maintaining a certain reduction in equalizing reservoir pressure. In short, the brakes must either be applying or must be held applied, meaning that the train is being slowed down by an efmovement of the engineers valve to release position. If the valve EPV controls an automatic brake application valve, such as to be later described, this application valve will automatically maintain the brake application, and may bring about a still further reduction in brake pipe pressure, depending on its construction. In any event, the engineefs attempt to release the brakes is futile, and the deenergization of the valve EPV occurs so quickly that there is not sufficient time to bring about any actual release of the brakes. One important and valuable characteristic feature of this arran ement will be reco t3 nized by reference to the performance curve 152 in Fig. 1 which shows the speed-distance curve along which the train may run without penalty, if the engineer is vigilant, and by comparing the facility of train movement established by such curve with that existing if the train were obliged to enter the block at a speed below the medium speed limit of 40 miles per hour, indicated by the line 150. Assuming that the entrance speed of a train into a caution block is just a little below the normal clear running or maximum speed limit, it will be evident that this invention permits the train to advance with just as much facility as safety will permit, in spite of the fact that there is an abrupt change in speed limits. If the train should be entering :7

the caution block or passing the correspondmg control point at an intermediate speed between the maximum and the medium speed limit, the enforced manual brake application will, of course, bring about a reduction in speed somewhat earlier than is actually necessary for safety; but on account of the capability of the system of giving instantaneous release upon clearing up of traffic conditions, i

such premature reduction in speed will not ordinarily reduce the facility of train movement. If the train should enter the caution block at a low speed, as for example, when passing a signal that has changed from stop W, to caution, thls train may accelerate up to the medium speed and advance with as much facility as safety permits up to the point where the further reduction from the medium to the minimum speed should be made; Other advantageous features of organization of the invention will be readily apparent in view of the foregoing disclosures.

The particular form of means selected to exemplify any suitable means for suppressing an automatic brake application and the accompanying penalty consists of a minias ture brake cylinder which indicates the extent of bralre application that will result, in which pressui'e exists corresponding to that existing in the brake cylinders on the train, which is controlled by a control valve similar to a triple valve. In the arrangement shown, however, this control valve CV, which corresponds to the usual triple valve, is connect- 4 ed directly to the equalizing reservoir instead of the brake pipe as is the regular triple valve. This is done so that the pressure in the miniature bra-lie cylinder 272 reflects equalizing reservoir pressure rather than brake pipe pressure. It takes a period of time for the brake pipe pressure to be reduced to correspond to equalizing reservoir pres- :sure, .depencing on the length of the train; andisince the engineerhas done all that is necessarv by reducing equalizing reservoir pressureto the required amount, it is not necessary to wait for the brake pipe pressure to drop before allowing the engineer to lap lus valve. In other words this reduction indicat- J= ing means predicts the reduction which will for operatinga slidevalve 268 is adapted to move. The slide valve 268 end otthis piston extendsint-o the chamber 269 which is connected to a miniature auxiliary reservoir 270. in the .normalposition of this control valve CV, as shown, the chambers 266 and 269 are connected together through a feed groove 271 extending around the piston 267; and the various chambers are normallyat equalizing reservoir pressure. The miniature brake cylint r 272 is connected to atmosphere through the exhaust port 273 under normal conditions, as shown. y

Let us assume that the pressure in the equalizing reservoir, chambers 276 and. 269, and in the miniatureauxiliary reservoir is about 96 pounds per sduare inch, and that the engineer moves his brake valve to the service position. for 6 or, 7 seconds, thereby venting the equalizing reservoir to about pounds. As soon as the equalizing reservoir pressure drops, the restricted feed groove 271 allows insutticient flow of air .therethrough and causes the pressure onthe right hand side otpiston 267 to drop and allovv the piston to move toward the right, blanking the feed groove 271, so that chambers 276 and269 are no longer in communication. Movement 01'' the piston 267 further toward the right causes the small slide valve 275 to move oil' oi port 276; and when this piston 267 assumes its extreme right hand position, the miniature brake cylinder 272 is connected to the miniature auxiliary reservoir through the port 276. This causes air to flow from the miniature auxiliary reservoir to the brake cylinder, thereby further reducing the pressure on the left side of piston 267. As soon as the pressure on the left side of piston 267 is reduced to a little less than that of the equalizing reservoir, the piston 267 moves toward the left far enough to cause the small slide valve 275 to block the port 276, so that no further flow of air into cylinder 272 is permitted. This position or. the control valve CV is called the lap position, since in this position all of the ports are blocked. By reason of the pressure existing in the miniature brake cylinder 273, as a result of a service brake application, the contact 5-1 assumes a position to just engage the contacts 127 and 128 upon a full service reduction, the spring 278 being of the proper strength to accomplish this end. i

it the engineer releases the brakes by moving his brake valve to the running or release position, the pressure in the equalizing reservoir is increased and causes the piston 267: to move to the led, agaln connecting the miniature brake cylinder 272 to atmosphere through the exhaust port 273, and again rccharging the miniature auxiliary reservoir 270 to that of the equalizing reservoir through the feed groove 271.

It is thus noted that the control valve CV functions very much like the triple valve of the usual air brake system, and that the miniature brake cy inder pressure corresponds to that of the usual car brake cylin dcr, but that this pressure exists before that in the usual braue cylinder because it is controlled directly by the equalizing reservoir instead oi' being controlled by the brake pipe. 'lhepressure in the miniature brake cylinder- 272 corresponds very closely to vmat actually exists eventually in the brake cylindersou the train due to the reduction in equalizing res rvoir pressure that has been mace; and this is true irrespective of the initial brake pipe pressure. 7

l Vith respect to the accuracy this construction, it is of course, evident that the spring 278 is compressed under the varying pressures, so that there is a change in the volume of the cylinder 272 at the left hand side of the piston 27% in this cylinder 272; whereas in the regular car brake cylinder, the volume behind the piston. is theoretically the same, with a fixed adjustment of piston travel, regardless of the pressure in the cylinder. The movement of the piston 274, re quired to move the contact 54 throughout its operating range, may, however, be made small and so that the position assumed by the contact 54 corresponds very closely to tlamount of braking eflort actually ent. Arrangements may be made in pra ce, desired, to give the piston 2H free travel before engaging the spring 21 8 to correspond with the free piston travel in the regular car brake cylinder.

The spring 278, together with the change in volume on the left hand side of the piston, is so selected that the piston will not move out far enough to put the contact di k .5-l in its circuit closing position until some p redetermined reduction in equalizing reservoir pressure has been made. It will be evident that there is a decided advantage in this con struction, in that the penalty is suppressed as soon as the engineer has made the required reduction in equalizing reservoir pressure, and the engineer may lap .his valve at that time instead of being obliged to keep his brake valve in the service position until the brake pipe pressure itself has fallen to a certain value.

The various arrangements embodying this invention have been illustrated and described with the view of disclosing the nature of the invention and the idea of means underlying it; and a complete system of train control for practical use may require additional features, such as provisions for freight and passenger service, operation pilot or tender first, with or against tralfic, single rack operation, nonequipped territory, and the like.

I desire to have it understood, therefore, that the invention is not limited to the par ticular means, construction, organizations and arrangements of parts and circuits shown and described.

What I claim is 1. In an automatic brake control apparatus in combination with the usual air brake system, a brake control device automatically actuated if the speed of the train is excessive and elfective to cause an application ofthe brakes by said system, a penalty inflicting device'for inflicting a penalty of the engineer allows the speed of the train to exceed a predetermined value, and means for suppressing actuating of said penalty inflicting device effective if an adequate brake application has been initiated comprising, a miniature auxiliary reservoir, a miniature brake cylinder and a control valve connected between the brake pipe of the usual air brake system and said reservoir and cylinder whereby air is conducted from said reservoir to said cylinder until the pressure in said reservoir is equal to that in the brake pipe when a reductionin the brake pipe pressure is being made, whereby the condition of said miniature brake cylinder may be used to determine when an adequate brake application has been initiated.

2. In an automatic train control system the combination with a brake control device acting on the usual air brake system and automatically actuated to cause a brake application by said system if the speed of the train is excessive, a penalty inflicting device for inflicting a penalty if the engineer allows the sped of the train to exceed a predetermined value, and means for suppressing actuating of said penalty inflicting device efiective if an adequate brake application has been initiated comprising, a miniature brake cylinder having a contact associated therewith which is closed if a predetermined pressure exists in said cylinder, a miniature auxiliary reservoir of a capacity having a certain ratio to that of said cylinder, and a control valve connected to said reservoir and cylinder for conducting air from said reservoir through said valve to said cylinder until the pressure in said reservoir is equal to that in the brake pipe, whereby said contact is closed when a predetermined reduction from normal has been made in the brake pipe pressure.

3. An automatic train control system com prising, a normally energized brake control device acting on the usual air brake system which applies the brakes when deenergized, means for deenergizing said device if the speed of the train as indicated by a device driven from the wheels of the train is excessive, means for inflicting a penalty if said device is deenergized, and means for preventing deenergization of said device if an adequate brake application has been initiated or is effective, said last mentioned means including a contact closed if a. predetermined ratio of pressure between the equalizating reservoir and the initial brake pipe pressure exists;

4. In an automatic train control system of the continuous inductive type, the combination with vehicle carried speed control apparatus for imposing abrupt changes in speed limits in accordance with changes in traflic conditions ahead as manifest by currents flowing in the track rails ahead of the train which are inductively detected and amplified by this apparatus, means for automatically applying the brakes of the vehicle if the imposed speed limit has been exceeded, and means for preventing such automatic brake application if either the engineer has placed his engineers brake valve in the service position or has initiated a full service brake application by venting the usual equalizing reservoir to a predetermined ex tent as evidenced by the pressure existing in a miniature brake cylinder associated with a miniature triple valve and a miniature auxiliary reservoir.

5. In a train control system, the combination with a railway vehicle having brakes associated therewith, normally energized brake control means for maintaining said brakes inactlye and controlled from the tra-ckway and 1n accordance with traffic conditions ahead, and other means for maintaining said brakes inactive eifective if either the engineer has placed his engineers brake valve in the service position or has initiated a full service brake application by venting the usual equalizing reservoir to a predetermined extent as evidenced by the pressure existing in a miniature brake cylinder associated With a miniature triple valve and a miniature auxiliary reservoir.

6. In an automatic train control system of the continuous inductive type, the combination With vehicle carried speed control apparatus for imposing changes in speed limits in accordance With traflic conditions, means for automatically applying the brakes of the vehicle if the imposed speed limit has been exceeded, and means for preventing such automatic brake application if either the engineer has placed his engineers brake valve in the service position or has initiated a full service brake application by venting the usual equalizing reservoir to a predetermined extent as evidenced by the pressure existing in a miniature brake cylinder associated with a miniature triple valve and a minature auxiliary reservoir.

In testimony whereof I aflix my signature.

CHARLES S. BUSHNELL.

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