US1730324A - A coeposation of stew tosk - Google Patents

Description

Oct. 1, 1929. w. K. HOWE AUTOMATIC TRAIN CONTROL SYSTEM Original Fileo. Nov. 2, 1919 2 Sheets-Sheet w 76, J QNVENTOR.

I A Y 'TORNEY I 1929- W. K. HOWE 30,324

AUTOMATIC TRAIN CONTROL SYSTEM Original Filed Nov. 12. I 1 2 Sheets-Sheet 2 Fuel.

K JALZEZITOR.

YVINTLRGP HOWE, ROCHESTER, NEW' 5503K, ASSIGNOR TO GENERAL RAILWAY SIGNAL GOltKI-ANY, O15 BGCHEEETEB, NEW YUKK, A CORTEORATION OF NEW YORK AUTGHATIC SYSTEM Griginal application filed November 12, 1919, Serial No. 337,022 new Patent No. 1,551,515, dated August This invention relates automatic train con rol systems for railroads.

This api 'Jlication is division of my prior application Ser. No. 337.527, filed llovember 12, 1919, for an automatic train control system, which application has matured into Patent No. 1,551,515, dated August 2.3,

in accordance with this invention, a controlling impulse or in.mence is transmitted from the track to the train at each caution signal, or corresponding control point, and unless the c 'ineer at the time takes some appropriate action in recognition or acknowledgement of the exit -enee I ahead, suitable apparatus ai'itoinaticall set into operation to give an application of the brakes. It the engineer permits this brake applying" appa atus to act, he will be subjected to a penalty, in the form o1 considerable annoyance, publicity, or the like, This pe .ty. imposed upon the engineer for his tailure to perform his dutiei properly, intended to im; the engineer with his carelessness and negligence at the time rather than by subsequent punisl'unent or discipline; and is assumed that the or 'neer will in this way be induced to be more careful.

The means which ll preferably employ to enable the or I 'neer to a caution signal, or corresponding control point, without receiving: automatic brake application, is some form of sirjiple acknowledging or hold-oft device, waich on account of the ease with which it can be manipulated, tends to encourage the engineer to watcn out for the signals. The engineer, however, might maliciously or carelessly hold or fasten this acknowledging device in the brake preventinn position, and to obviate this possibility, my inve it includes a checking; or protecevents the engineer device in the ac- .r the acknoi a l C3 operated position permanently, because in so doing penalty that the achnowled to prevent,

Geller objects and features oimy improved tive he will be subjected to the same mgr device able Divided and this application filed July 80,

Serial No. 47,110. Renewed January 5,

ing the description oi the specific embodiment of the invention illustrated.

In the accompanying drawing, Fig. 1 shows in a simplified and diagrammatic manner the car equipment of my invention, together with the trackway impulse device, the parts and circuits being shown more with the view of making;- the functions and mode of o 'ieration easy to understand than with the view of showing the precise construction and arrangement of parts preferably employed in practice; and i 2 shows in a simplified and diagrammatic manner a portion of a railway track, equipped with trackway impulse devices and control circuits, in accordance with my invention.

Referring first to Fig. 2, which illustrates the traekway equipment, the track rails 1 of the railroad track are divided by insulated joints 2 into blocks in the usual way, one complete block B with the adjacent ends of two other blocks A and C having been shown. Sine the trackway equipment associated with the various blocks may be assumed to be the same, for convenience the various parts and circuits will be given like reference characters with distinctive exponents. Each block is provided with a track battery 3 and a track relay 4, constituting the well known normally closed track circuit. My system of automatic train control is preferably used in connection with the usual fixed signals of the well known automatic block signal sys' tem; anu such signals S are illustrated conventionally in Fig. 2, the controlling circuits, which may take any one of the well known forms, being omitted for the sake of simplici Various types of means for transmitting impulses from the track to the train may be employed in my system; but I prefer to employ impulse transmitting; means of the inductive type, and have illustrated one form of such The detailed features of construction of the car-carried and trackway elements form no part of my present invention, and are merely illustrative of a suitable type of inductive transmitting means which may be employed in my system.

-8 and 9 respectively.

Associated with each block is a trackway element T, which is preferably located at or adjacent to the entrance end or" the block.

The particular type of trackway element illustrated (see Figs. 1 and 2) comprises a U-shaped core or yoke of magnetic material having enlarged ends constituting pole pieces, and provided with. a coil 5. This trackway element may be located. crosswise or lengthwise of the track, between or outside of the track rails, and in practice would be encased and protected against the weather, dragging brake beams and the like.

In the arrangement of trackway circuits illustrated, which is only typical and is susceptible t change and modification, a circuit for the coil. of each trackway element is controlled by the front contact of: a line relay 6, the controlling circuit for this line relay being governed by the track relay o'l. the corresponding block and the next block in advance. The essential requisite for my system of train control is that the trackway element at the entrance to each block shall be in stopping condition when the corresponding block or the next block in advance is occupied; and in the type of impulse transmitting means illustrated, this is accon'iplishcd by opening the circuit for the coil 5 of the trackway element in question by means of the line relay 6.

Referring now to Fig. 1, the car equipment, generally stated, comprises a car-carried element L and associated relays adapted to be influenced by the trackway elements T, when those have their coils 5 open-circuited; .a hold-oil or acknowledging device H, arranged for convenient operation by the engineer and protected so as to prevent the engineer from keeping it in its operation position; brake applying means including a pneumatic device l1, tending to move th engincefis bralre valve E of the usual air brake system to the service l'JOfiltlOX], and an -clectro-pncumatic valve E. P. V., said brake applying means being operated automatically whenever the train passes a trackway clement T in the active stopping condition he engineer fails to operate his acknowlde ice H; and finally a reset device U for restoring the brake applying means to normal after it is operated.

The car-carried element L comprises an inverted ll-shaped core or yoke 7 of magnetic material, preferably laminated, which is provided with. the usual. polo pieces, and is carried by the locomotive or other railway ve- Each leg of the yoke carries a coil designated The coil 8, conveniently termed the field coil, is constantly supplied with current lirom a battery 10, and produces a magusto-motiveforce tending to send flux through the yoke 7. Also included in circuitwith battery 10 and coil 8 is a check ing piece l l. This striking piece 14 is positioncd between two resilient contact springs 1515 which normally press against two electrically connected and fined contac s 16 designated conventionally by arrows. The spring 13 is adJuSted so that, with the normal current flowing in the winding 01 the relay, its armature 12 is balanced. If this normal current is increased, the attraction oi" the armature 12 overcomes the spring 13, and the striking piece 14 moves contact spring 15 out of contact with its cooperating contact 16. On the other hand, if the normal current is decreased, the spring 13 overbalances the armature 12 and causes SQPELHL- tion of contact spring 15 from its cooperating contact 16. The circuit controlled by the relays R and X is carried through the contact springs 15 and 15 and the fixed contacts 16, so that this circuit is opened whenever the current normally flowing through these relays is either increased or decreased,

The engineers hold-off or acknowledging device H comprises a casing 17 in which the several parts are enclosed for protection and also to prevent unauthorized interference, this being in practice provided in the usual manner with a suitable sealed or locked door or cover (not shown) which permits access to the interior by authorized persons for inspection. and maintenance. A lever 18 is pivoted in a suitable way to the casing, projecting out of the casing through a slot 19. This lever 18 is preferably provided with a suitable handle for lacilitating its manual operation, and also a latch 18 of suitable construction, illustrated in a simplified and conventional manner, which is adapted to co operate with a notch in a curved ridge or sector 20 integral with the casing. This sector 20 is also provided with a shoulder 21 near one end to constitute a stop for the lever 18 in its operated or hold-oil position. The other end of the lever 18 carries an insulated contact block 22 which is adapted to bridge a pair of stationary contacts 23 (shown conventionally as arrows) when the lever is shifted to its operated or holdoli position as partially shown in dotted lines.

Within the casing 17 are normally closed contacts 3637 of suitable construction (shown conventionally) which. are automatically opened. after a short time, following the movement of the hold-off lever 18 to its OJGIZLtGCl Josition b apneumatic timin de-' 7 y &

vice O, which is normally held inactive by the lever 18 and is released by the movementof said lever to its operated position. This timing device 0 in the form shown comprises a cylinder 95 containinga piston 96 which is urged in one direction by a spring 97. This movement of the piston 96 by the spring 97 is retarded by the air which is compressed in the right hand end of the cylinder 95, and which can escape only gradually through a restricted orifice 98. The piston rod 99 connected to said piston 90, carries at one end an insulated striking piece 100, which is arranged to strike the contact spring 36 and separate it from its cooperating contact 37, when the piston attains its right hand posi ion. The other end of the piston rod 99 extends through a suitable air-tight packing or stalling box in the end of the cylinder 95 into position to be engaged by the upper end of the lever 18. A suitable ball check valve 101 is provided to allow quick return of the piston 90 to its normal position shown in Fig. 1.

The operation of this construction of the engineers hold-oil device will be readily apparent. When the lever 18 is moved to its operated or hold-off position, the piston 96 free to be moved gradually to the right by the spring 9'? at a rate determined by the adjustment of the restricted orifice 9S; and after the lapse of a predetermined time, the striking piece 100 opens the contacts 36-3'7. Thus the lever 18 may be swung to its operated position, held there a short time and then r turned to the normal position, without openin contacts 3637; but if said lever is held in its operated position longer than a certain line for which the device is adjusted, the contacts 3637 will be opened.

he brake applying; apparatus for giving an automatic application of the brakes when the engineer fails to operate his hold-off device 18 may take various forms. I have provided a pneumatic device F which is coupled to the engineefls brake valve and which acts, when set into operation, to shift the brake valve to the service position, and thereby apply the lJIilKGS in the usual way. The engineers brake valve E and its operating handle 40 are illustrated conventionally. A seetor 41 is fastened to the stem or shaft of the brake valve E in a suitable manner, so that as this sector 41 is swung, the brake valve will be shifted to apply the brakes. The sector 41 meshes with the rack 42, which is integral with or connected to a rod 43. The rod 43 passes through one end of an operating cylinder 44, and loosely through a piston 45 in said cylinder, the end portion of said rod 43 being screw threaded and provided with two adj ustable clamping nuts 46 against which the piston strikes when moved to the right. Stops 47 fastened to the cylinder 44 limit the righthand movement of the piston 45; and by adjusting the nuts 46, this limited movement of the piston 45 may be employed to shift the engineers brake valve accurately to the ice position, or if desired, to an emergency position. The rod 43, since it slides loosely through the piston 45, does not prevent the engineer moving his brake valve 40 to any position he desires while running the train in the ordinary way.

Fluid pressure from the main reservoir or the like, is automatically supplied to the cylinder 44 on the lefthand side of the piston through a. pipe 48, when an electropneumatic valve E. P. V. is tie-energized. Various types of electro-pneumatic valves may be employed to supply pressure in this way to the cylinder 44. In the particular construction illustrated, the armature 52 of the usual magnet or solenoid 53 is fastened to a stem 54, which is provided with an insulated contact disc 102, said disc bridging the fixed contacts 103103 when said stem is in its uppermost position as shown. This stem 54 carries two opposed valves 104 and 105. The upper valve 104 controls the supply of compressed air from a chamber 106, which is connected by pipe 107 to the main reservoir, to the lower chamber 108 which communicates by pipe 48 with the cylinder 44. The lower valve 105 controls the connection between the chamber 108 and a passage 109 leading to atmosphere. A spring 110 on the stem 54 acts in conjunction with the main reservoir pressure on the control. valve 104 to move the stem downward when. the magnet 5-3 is (ls-energized. The magnet 53 when energized is strong enough to reclose the valve 104 against main reservoir pressure as well as hold it closed.

The reset device U comprises a casing}; 112 in which the several parts of the device are enclosed in the same way as the engineers hold off devce H. A threaded shaft 142, with a crank 143 on the outside of the casing for turning said shaft, carries a nut 144, which is arranged to move a contact spring 115 into contact with its back contact 116 when said nut is in its lowermost position. As the shaft 142 is rotated the nut 144 travels along said shaft, being held against rotation in a suitable manner, as by a rod 145. A lever 119, suitably pivoted between its ends to the casing 112 is biased in one direction (counter-clockwise as viewed in 1) by spring 120 and is swung in the opposite direction by the HOVQ- ment of tiie nut 144 to its uppermost position. This lever 119 carries an insulated striking piece 121 arranged to hit a contact spring 122 and separate it from its cooperating contact 123, when said lever is swung by the spring 120 to its extreme position. The movement of the lever 119 under the influence of the spring 120 is retarded by a dash-pot compris r in the normal position.

in g a cylinder 124, having a restricted exhaust port 125 in its bottom, and a piston 126, pro-- vided with a flexible packing and connected by a rod 127 to the lever 119. The reset device U is pre erably in practice located at such a place that it cannot be reached by the engineer while he retains hold of his brake valve handle.

The parts of my system described serve to check up the vigilance of the engineer at each caution signal or corresponding control point and th ir operation may now be described with this feature of my system in view.

Normally, while the train is traveling between trackway elements, the current in the coil 8 produces a magneto-motive-force which sends a predetermined flux through the yoke 7 and the coil 9. "When the circuit of the coil 5 of the trackway element T is opened,

U corresponding to a caution or stop signal, said trackway element is then in efl'ect a dead magnetic loop for the yoke 7 of the car-carried element L on the passing train and thus changes the reluctance of the magnetic circuit including said yoke and coils, thereby causing a corresponding change in the flux through the coil 9. This change in flux induces a voltage in said coil 9 which varies the current supplied to the control relay R from the battery 11, thereby causing it to open its contacts and momentarily interrupt the energizing circuit of the relay Q.

Under clear trafic conditions, the coil 5 of the trackway element T is in a closed circuit with low resistance and opposes or chokes back the passage of flux through the trackway element T, thereby preventing a change of flux in the yoke 7 of a passing car sufficient to cause operation of the control relay R.

Thus, the relay Q is de-en-ergized at each caution signal or corresponding control point but is not operated under clear trafiic conditions.

The parts of the car equipment are shown The circuit for normally maintaining the magnet 53 of the electro-pneumatic valve E. P. V. energized may be traced as follows :c0mmencing at ground, conductor 128, contacts 103 and coni tact disc 102, conductors 129 and 130, battery 131, conductor 132, magnet 53, conductor 133, contacts 36-37, conductor 134, contacts 122123, conductors 135 and 136, front contact 71 of the relay Q, and conductor 137 back to ground.

It will be noted that this circuit i eludes in series the conductors 3637 and the contacts 122123, so that if either the engineers holdoff lever 18 or the nut 144 of the reset device U is kept in its operated position too long, the magnet 53 is de-energized.

The engineer, upon approaching a caution or stop signal, is expected to operate the holdoif lever to its operated position. This closes contacts 2223 andestablishes a shunt nvsasza 2223, thereby maintaining the magnet 53 energized independently of the dropping of the relay Q.

In this way, if the engineer is alert and observes the unfavorable signal indication, he is able, by a simple operation of the hold-off lever 18, to avoid a brake application. The operation of the acknowledging device H, being an active movement, is thought to be such as to impress upon the engineer the fact he has passed a caution signal and entered a danger Zone, thei eby imposing upon him the responsibility of controlling his train safely.

If the engineer is careless or indif erent about watching the wayside signals and fails to note that he is about to pass a caution or a stop signal, the de-energization of the relay Q, the hold-ofi' lever 18 being in the normal position, causes deenergization of the magnet 53 of the electro-pneumatic valve E. P. V., thus closing valve 105 and opening valve 104 to supply pressure to the cylinder 44. This pressure acts to operate the engineers brake valve E to the service position and automatically applies the brakes. When the magnet 53 is de-energized, the contacts 102103 open, so that said magnet will not be re-energized when the front contact 71 of the relay Q recloses. Also, the engineer is not able to reenergize the magnet 53 by operating his holdoff lever 18 to close the contacts 23. Magnet 53 can only be re-energized by operation of the crank 143 of the reset device U to close the contacts 115116. Nhen the contacts 115- 110 are closed, the magnet 53 is re-energized its contacts 102103 being shunted by wires 140, 141 and said contacts 115116; and the valve 104 is closed to cut off further supply of pressure from the main reservoir, the valve 105 being opened to exhaust the pressure already in the cylinder 44.

To close the contacts 115116 of the reset device U, the crank 143 is turned in one direction to cause the nut 144 to travel along the shaft 142, until it engages the contact spring 115, the lever 119 being released at the same time. By turning the crank 143 in the opposite direction, the nut 144 may be moved back to its normal position so as to restore lever 119, which has been slowly moving in a direction to open cont-acts 122-123, and prevent opening of these contacts 122 123. This arrangement makes it more difficult to close the contacts 115116, and restore the parts to the normal position, there by adding to the trouble and annoyance of operating the reset device U, and increasing the incentive for operating the acknowledging device H in preference. Obviously, the exhaust port 125 must be small, enough to give enough time to move the nut 144 down and has 1.

Obviously if the engineer were able to keep n I u his hold-off device in the operated position, he would not be obliged to note each caution or stop signal and make a positive movement. To obviate this possibility, the contacts 36 3? are provided, together with their associated timing device O. As already eX- plained, the lever 18 may be swung to its operated position (shown by dotted lines), held there for a short time, and then returned to the normal position, Without opening the contacts 3637, but if said lever is held in its operated position longer than a certain time for which the device is adjusted, the contacts 36-37 will, be opened, thereby deenergizing the magnet 53. Consequently, if the hold-off lever is kept in its operated posiion longer than a certain time, the magnet 53 will be deenergized and the pneumatic device F operated. In other words, if the engineer attempts to keep his hold-off lever permanently in the operated position, he will get into as much trouble as if he failed to make timely operation of the hold-oil lever at each caution or stop signal.

The time interval of the operation of tl e timing device 0 may be varied to suit the particular working conditions, so as to give the engineer reasonable latitude in operating the hold-oil lever while approaching and passing a signal and yet prevent him from keeping the hold-off lever in its operated position while passing from one signal to another.

In my prior application, Ser. No. 337,527, I have shown and described, notably in Fig. 5, a specific embodiment of the car equipment performing the same broad functions as the specific embodiments herein shown and described; and the following claims are intended to be limited to the specific features of the embodiment herein shown and described and not found, for example, in Fig. 5 of my prior application.

Although I have particularly described the construction of one physical embodiment of the invention, explained the operation and principles thereof, nevertheless it should be understood that the structures and circuit connections shown are merely illustrative, and are susceptible of considerable variation in practice without departing from the invention.

\Vhat I claim is 1. In an automatic train controlsystem, the combination with an automatic brake setting appliance on a vehicle cooperating with the air brake system thereof to cause an automatic brake application, trafiic controlled means tending to initiate operation of said appliance for a limited time under unfavorable traffic conditions ahead, manually operable acknowledging means conveniently accessible to the engineer and capable of pre venting operation of said appliance independently of its control by said trail-tic controlled means, said appliance when once operated continuing operation in spite of said acknowledging means, and means for restoring said appliance to normal after operation thereof, said aclmowledgingmeans compri ing a movable member adapted to be manually operated, and biased time controlled means normally maintained inactive inopposition to its bias and released upon movement of said member from its normal to its operation position, said time controlled means rendering said acknowledging means inactive after a limited time for each operation.

2. In an automatic train control system, the combination with an automatic brake setting appliance upon a vehicle co-operating with the air brake system thereof to cause an automatic brak application, impulse communicating means partly on the vehicle and partly on the track tending to cause operation of said appliance for a limited time at predetermined control points along the track under unfavorable traffic conditions ahead, and manually operable acknowledging means conveniently accessible to the engineer for preventing operation of said appliance in spite of its control by said impulse communieating means, said acknowledging means com rising a sprin operated time controlled device for automatically actuating said brake settin appliance after a limited time following each manual operation of said acknowldging means, said time controlled device being automatically moved to tension its spring each time said acknowledging means is restored to its normal inactive condition.

3. In an automatic train control system, the combination with an automatic brake set ting appliance upon a vehicle cooperating with the air brake system thereof to cause an automatic brake application, impulse com inunicating means partly on the vehicle and partly on the track tending to cause opera tion of said appliance for a limited time at predetermined control points along the track under unfavorable trafiic conditions ahead, and manually operable acknowledging means conveniently accessible to the engineer for preventing operation of said appliance in spite of its control by said impulse communicating means, said acknowledging means comprising a movable member adapted to be shifted manually, a spring operated dash-pot device tending to move to an extreme position and render said acknowledging means inedective, said dash-pot device being automatically released when said movable member is shifted to the position rendering said acknowledging means effective and being restored to normal upon return of said member to its normal inactive position.

4. An acknowledging device for train control systems of the character described comprising, normally open contacts, normally closed contacts, a manually movable member open contacts, a cylinder, a piston in said cyl-i inder, a spring for moving said piston in one direction, means restricting the rate of escape of air from one side out the piston and retarding its movement to one extreme position, said piston when moved to said extreme position opening the normally closed contacts, and means operatively connecting said member and said piston to permit free movement of the latter in a direction to open the normally closed contacts upon movement of said member to the position to close the open contacts.

5. An acknowledging device for train con trol systems of the character described comprising, normally closed contacts, normally open contacts, a manually movable member.

shiftable to close the normally open contacts, time controlled means tendingto change to an ultimate condition and open said normally closed contacts, means mechanically operatively connecting said member and said time controlled means to release the time controlled means when said member is shifted to close the open contacts and restore said time controlled means to normal when said member is shifted to its normal inactive position, and means associated with said member tor restraining the tendency of said time controlled means to assume its ultimate condition while said member is in its normal inactive condition.

6. An acknowledging device for train control systems of the character described comprising, normally open contacts, normally closed contacts, a manually movable member for closing said open contacts, a dash-pot device biased to change from a normal position to an ultimate position after a limited time and open said normally closed contacts, and means mechanically connecting said clashpot device and said movable member for one direction of movement only, whereby said dash-pot device is released when said movable member is shitted to close the open con-- tacts.

7 In a train control system, a normally energized electro-responsive device on a vehicle cooperating with the air brakesystem thereof to produce a brake application when de-energized, said electro-responsive device having contacts opened upon deenergization thereof, an energizing circuit for said electroresponsive device including its contacts, an acknowledging device including a manually operable member and having closed contacts and normally open contacts included in series in said energizing circuit, said member when shifted from its normal position to its operated position closing said open contacts, and time controlled means tending to change from an initial condition to an ultimate con dition and open said closed contacts after a limited time. said time controlled means he ing released to respond to its tendency upon movement of said member to its operated position and being restored to its initial con" dition upon return or" said member to its normal position.

8. A protected acknowledging device of the character described comprising, a time element device having an inherent tendency to change from an initial. condition to an ultimate condition, and means including a manually movable member for directly mechanically engaging and restraining said time element device in its initial condition, said time element device being released to respond to its tendency when said movable member is shifted from normal to a position rendering the acknowledging device effective.

9. In a traincontrol system; a normally energized electro-responsive device on a vehicle cooperating with the air brake system thereof to produce a brake application when tie-energizer; said electro-responsive device having stick contacts opened upon de-energization thereof; restoring means having nru-mally clcsed contacts and normally open contacts associated therewith; an energizing circuit for said clectro-responsive device including its Winding, its stick contacts and the normally closed contacts of said restoring means; means for shunting said stick contact i ludii r said normally open contacts; said wtoriiu; means being manually operable and being so constructed that the normally open contacts cannot be closed until after an interval of time, and the normally closed contacts will be opened it the normally open contacts are held closed for more than a certaininterval of time.

10. Means for restoring the mechanism of an automatic train control system compr1s-.

ing; a manually operable device; normally open contacts and normally closed contacts; means for operating said normally open and said normally closed contacts by said device constructed and arranged so that the normally open contacts cannot be closed by operation of said device until after the expiration of a period of time, and so that said normally closed contacts will open if said normally open contacts are closed for more than a certain interval of time.

11. Means for restoring the mechanism of- 12. Means for restorin the mechanismot an automatic train control system comprising; a manually operable device; normally open contacts and normally closed contacts; means for operating said normally open and said normally closed contacts by said device constructed and arranged so that the normally open contacts cannot be closed by operation of said device until a period of time after operation of said device has been started, and said normally closed contacts will open it said device is left in its operated condition for more than a certain period of time.

13. Means for restoring the mechanism of an automatic train control system comprising; a manually operable device; normally open contacts and normally closed contacts; means for operating said normally open and said normally closed contacts by said device constructed and arranged so that the normally open contacts cannot be closed by operation or said device until a period of time after operation of said device, and said normally closed contacts will open it said device is operated.

14. In an automatic train control system the combination with normally energized brake control apparatus on a vehicle; a normally open auxiliary energizing circuit for said apparatus; and manually controlled means for preventing operation of said apparatus by closing said auxiliary circuit; said means comprising a chamber having a continuously active restricted orifice for venting said chamber, a. contact closed when said chamber is expanded to a predetermined extent, and means for expanding said chamber.

15. in an automatic train control system the combination with normally energized brake control apparatus on a vehicle; a normally open auxiliary energizing circuit for said apparatus; and manually controlled means for preventing operation of said apparatus by closing said auxiliary circuit; said means comprising two sets of contacts connected in series in said auxiliary circuit, a chamber continuously ventable through a restricted orifice, means for expanding said chamber requiring the opening of one of said sets of contacts, and means for opening the other set of contacts when said chamber has contains more than a predetermined amount of fluid.

17. An acknowledging device for maintaining a circuit closed for period of time comprising, an electric circuit, a chamber having an inlet for admitting air and having a continuously active orifice for venting air from said chamber to atmosphere, manually operable means for etlecting the flow of air into said chamber through said inlet, and means for opening said partial circuit when said chamber is being charged and when said chamber is vented to a predetermined extent.

18. An acknowledging device for maintaining circuit closed substantially continuously comprising, an electric circuit, a chamber having an inlet for admitting air and having a continuously active orifice for venting air from. said chamber to atmosphere, manually operable means for admitting air into said chamber through said inlet, intermittently, and means for opening said circuit when said chamber is vented to a predetermined extent.

19. Bnilway traiiic controlling apparatus comprising normally inactive means carried on a vehicle for applying the brakes; track- Way apparatus cooperating with said means to cause an application of the brakes; and manually operable means on said vehicle for removing said brake applying means from control by said trackway apparatus; said manually operable means including a chamher having a continuously active orifice for venting the same, a contact closed when said chamber contains a predetermined amount of air, and means including a handle for causing air to flow into said chamber.

In testimony whereof I aflix my signature.

lVINTHROP K. HOWE.

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