US739918A

US739918A - Inertia-governor for fluid-pressure brakes.

Info

Publication number: US739918A
Application number: US11673602A
Authority: US
Inventors: Robert A Parke
Original assignee: Individual
Current assignee: Individual
Priority date: 1902-07-23
Filing date: 1902-07-23
Publication date: 1903-09-29
Anticipated expiration: 1920-09-29

Description

A No. 799,919. PATENTBD sE-PT.29,1999.

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INBRTI GOVERNOR POR FLUID' PRESSURE BRAKES. 'APPLIOATION FILED JULY 2s, 1992. lo' MDBL. a SHEETS-sum 1.

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INERTIA GOVERNOR EUR ELU-VID PRESSURE BRAKES. APPLICATION FILED JULY 23, 1902. i NO MODEL. 3 SHHBTS-SHEET 2.

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PATENTBD SEPT. 29,1903..

. R. A. PARKE. INERTIAl GOVERNOR FOR FLUID PRESSURE BRAKES.

APPLIOATION FILED .TULY 23,- 1902.

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UNITED STATES atented September 29, 1903;.

PATENT OFFICE..

ROBERT A. PARKE, 'ou NEW YORK, N. Y.

SPECIFICATIONTorming part of Letters Patent N0. 739,918, dated September 29, 1903. Application filed July 23, 19 02v Serial No. 116,736. (No model.)

-at high speeds and in which a higher than ordinary degree of pressure is utilized in the brake-cylinder.

It has long been a well-known fact that the brake-shoes may be applied to the wheels with much greater pressure when the train is running at high speedV than at low speed without danger ofsliding thewheels, because while the static friction of the wheels upon the rails which causes the Wheels to rotate is practically constant at all speeds the retarding friction of the brake-shoes upon the moving surface of the wheels is much less at high than at low speeds'. To secure the greatest retarding eect of. the brakes and to stop the train in .the shortest distance, therefore, it isi necessary :to apply the brake-shoes to the f wheels with the maximum force at high speedl and to reduce thatr force, as by'discharging a portion of the air-pressurefrom the brake cylinders beforethe low speeds near the end of the stop occur, to compensate for the increased friction due to those low speeds and prevent the wheels from sliding. Hitherto it has been supposed that the friction gradually and continually increases as the speed declines during the stop, and it has therefore been considered desirable and necessary to gradually and continuously reduce the airpressure in the brake-cylinder after the initial maximum application vuntil thezremaining pressure is no greater than may be safely retained in the brake-cylinder without sliding. the wheels toward the end of the stop. A reducing-valve operated by lthe brake-cylinder air-pressure, such as is shown and de'-l -Scribed in my former patent, No. 506,185, of

October 3, 1893, issued jointly to myself and two others, `has been employed to effect such a gradual reduction of the air-pressure in the brake-cylinder after an emergency application and to limit the brake-cylinder pressure in service applications, and this construction is'found to operate Very advantageously in practice, stopping trains from high speeds in from twenty-five to thirty per cent. shorter distances than can be effected by the ordinary quickaction brake, in the use of which the' brake-cylinder pressure remains uniform throughout the stop and is therefore necessarily so limited that it shallnot slide the wheels at the lower speeds; but through more recent experiments upon the friction of brake-shoes it has been discovered and is now a well-known fact that although the friction causedby a given pressure of the brake-shoe upon the wheel varies inversely with the speed of the wheel it also varies from other causes, among which is some not yet clearly-defined influence accompanying continued rubbing of the brakeshoes upon the wheels, but apparently structural changes of the material through heating. For quite a material interval of time, at least after the brake-shoe is applied to the wheel, the eect of continued rubbing is to reduce the friction, so that while in an emergency application of the brakes the .ciect of the continually-declining speed is to gradually and continuously increase the friction of the brake-shoes the operative eect of that iniiuence is opposed and modified by the influence of kcontinued rubbing in such a manner that the friction does notvary greatly from that at or near the beginning of the application of the shoes to the Wheels (which depends largely upon the initial speed) until near the end of the stop, when the speed has V become comparatively low, when the friction increases rapidly to somethinglike double theinitial. The general characteristic variation of the friction of brake-shoes throughout the stop is a slight and gradually-decreasing decliue during the earlier portion of the stop after a quickly-attained initial maximum, after which it increases, at first very slowly, but with gradually-increasingrapidity until near the lend of the stop, when itincreases quite rapidly to a inal maximum. VIt

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thus occurs that instead of gradually and continuously reducing the air-pressure in the brake cylinder from the beginning of an emergency application to compensate for the formerly-supposed continuous increase of the friction it is of high importance to retain the initial high emergency air-pressure in the brake-cylinder until toward the end of stops from high speeds, when the brake-shoe friction increases, so that a further continuance of the high air-pressure Would be likely to cause the wheels to slide.

The purpose of my present invention is to realize the advantage of retaining the high initial air-pressure in the brake-cylinder as long as possible without danger of sliding the wheels and to then so reduce the pressure that the wheels shall not be caused to slide by the remaining pressure when the high. friction of low speed occurs near the end of the stop.

At the same time also it isa purpose of my invention to provide for such a prompt reduction of the high brake-cylinder pressure under any conditions in which Wheel-sliding is threatened that the high-speed brake may thereby become adapted for use upon trains of ordinary speed, and the greatly-increased protection from disaster may be thus extended to all classes of passenger-trains.

Vhere the reducing-valve alone is employed for gradually decreasing the pressure in the brake-cylinder, it is essential to the eectiveness of the apparatus in materially shortening .the length of emergency stops from high speeds that a considerable interval of time shall be occupied in reducing the high pressure down to the safe limit, and when adjusted to meet this requirement the high pressure is retained in the brake-cylinder too long in stops from the lower speeds, resulting in injurious wheel-sliding, and so restricting the employment of the high-speed brake apparatus to high-speed trains. \Vith my present invention the high pressure in thebrake-cylinder is promptly relieved Whenever the brake-shoe friction reaches a certain predetermined maximum insuiiicient to cause the Wheels to slide whether at the end or the beginning or at any other time of the stop, and an emergency application may therefore be made under any conditions without sliding the wheels.

Various speed-controlled devices for reducing the brake-cylinder pressure have been proposed, but for various reasons have not been found practicable. To secure the highest eiciency of the brake apparatus, itis obviously necessary to maintain the greatest safe brake-shoe pressure, and therefore the highest consistentbrake-cylinder pressure,as long as possible'during the stop regardless of the varying relationship between the friction and pressure of the brake-shoes at different speeds under the same conditions or at the same speed under different conditions. The wheels Will not be caused to slide upon the rails unless the retarding friction of the brake-shoes overcomes the motor friction of the rails upon the Wheels. The motor friction of the rails upon the wheels having been ascertained, the maximum safe brake-shoe friction may readily be determined, and if this so-established maximum brake-slice friction could be caused to act directly as the operating agent to open a suitable brake-cylinder reliefvalve the highest safe brakeshoe pressure could be employed without sliding wheels; but the serious diihculties and complication of apparatus attending such direct control of the brake-cylinder pressure by the brake-shoe friction have been found to make it impracticable.

The total brake-shoe friction is the measure of the retarding force acting upon the train, and the quotient obtained from dividing this retarding force by the mass of the train is the rate of retardation of the entire mass ofwhichthetrainisconstituted. Whenit has been ascerained what is the maximumfrictional resistance that the rails may be safely depended upon under all conditions to exert upon the braked wheels of the train, that redation of the brakes be so loosely or flexibly supported by or attached to a part of the train that it may have a degree Of'independent movement relative to such part ot' the train in thedirection of the motion of the train such separate mass may, through suitable connection with a brake-cylinder relief-valve and the interposition of a properly-proportioned resistance to its independent motion, be caused by virtue of its inertia to open the relief-valve, and thereby reduce the air-pressure in the brake-cylinder, when the rate of retardation of that part of the train corresponds with that resulting from the maximum safe brake-shoe friction, or, otherwise stated, instead of opening the brake-cylinder relief-valve by means of the direct operation of the force of the friction of the brake-shoes I find that the same result may be indirectly attained through employing a suitably-connected independent mass of matter operated upon by the retarding force (which bears a practically uniform ratio to the brake-shoe friction) and operatingby its inertia to cause the brake-cylinder relief-valve to be opened.

My invention, broadly stated, consists of utilizing this means, which I designate as an inertia-governor, for operating a reliefvalve, and comprises, essentially, a valve for discharging airto reduce the pressure there- IIO of, a mass of matter subjectv to the retarding effect of the brakes, which is capable of some degree of movement independent of that of the vehicle by which it is supported and in the general direction of motion of the latter and which is so directly or indirectly connected with the valve that its described independent movementinsuflicientdegree,caused by the resistance of inertia to a iixed or particular rate of retardation, regardless of the speed, shall cause the valve to operate to reduce the pressure of the brake-shoes upon the wheels.

It further consists in certain novel combinations and improved constructions, as hereinafter more fully described, andset forth in the claims. f

I am aware that it has been proposed to operate a brake-cylinder relief-valve by a centrifugal governor connected tothe wheels or axle to reduce the air-pressu re for the purpose of preventing injury to sliding wheels, also that it has been proposedto control a brake-cylinder relief-valve by the action of wind-pressure upon an exposed vane or diaphragm for the purpose of maintaining a higher air-pressure in the brake-cylinder at high than at low speeds. The operation of such devices is entirely controlled by the Speedv either of the vehicle or of the rotation of the wheels, Whereas the operation of my invention is radicallydifferent therefrom. While each of the devices just mentioned must obviously operate to produce a specific effect at and only at one specific speed, my. governor may operate to produce thesame speciiic eect at any speed, (though in practice it would ordinarily occur within the limits of a certain range of speedsg) but it is not required to operate at any particular speed whatsoever, since its operation does not depend upon either the speed or theiextent to which the speed is reduced by the retardation, but it depends simply and solely upon the rate of retardation or the rate of rapidity with which any speed is reduced. My invention therefore does not include a device which depends for its actuation or control only upon some particular speed or speeds.

The terms fixed or particular rate of retardation as employed in. the specification and claims are intended merelyto distinguish the character of operative control from that which results from the eect of continued retardation in changed rate of speed, and theyl are not employed in the limiting sense of an exact or precise rate of retardation. The purpose does not requireand the conditions do not permit great nicety or` exactness of determinationpof the rate of re- .tardation or ofx adjustment of the device, as the vehicle is subject to irregular vibrating iniuences and its motion is characterized by more or less uncertain oscillations or joltings, &c., and it is only essential that the operative rate ofrretardation shall be so ap,- proxinately defined that the relief-valve all familiar with the art. ing valve 5 is connected with the brake-cyl-..

shall operate to effectively reduce the brake'- cylinder pressure when, but not until, the brake-shoe friction'(thev eective retarding force) has so nearly approached the point of interrupting continued rotation of the Wheels that a material increase is likely under any conditions of ordinary service to result in wheel-sliding.

In the accompanying drawings, Figure 1 is a side eleva-tion showing the general arrangement ofthe air-brake equipment of a car embodying one form of my invention. Fig. 2is an enlarged detail view showing a pressurereducing valve and a longitudinal section of the form of my inertia-governor device shown in Fig. 1. Fig. 3 is a transverse sectional view of a modified form of my inertia-governordevice, and Fig. tis a longitudinal sectional -view of the same. Fig. 5 is a longitudinal sectional view of another modification of the invention.

Various forms of construction may bede- Yvised for the practice of my invention, and Vwhile in the forms chosen for its illustration in the drawings I have shown my improvements applied in connection with a highpressure reducing-valve it is to be understood that my invention is-not limited to such construction or combination, but may be employed with other forms of brake apparatus. In Fig. 1 is shown the usual car equipment of an automatic air-brake apparatus comprising train-pipe 1, auxiliary reservoir 2, triplevalve device 3, .and brake-cylinder 4, all of 'which is of the ordinary high-speed construction, the operation of which is well known to A pressure-reducinder by pipe 6, and its outlet-port is connected with the inertia-valve device 7 .by `means of pipe S. The pressure-reducing valve may be of ordinary construction, such as that used in the Westinghouse high-speed brake apparatus and shown in Fig. 2--that is, comprising slide-valve 9, connected to piston 10, which is exposed on itsupper face to the air-pressure in the brake-cylinder and on its opposite side to the pressure of the adjustable spring 11; but it will be noted that the outlet-port 12 in the slide-valve is made rectangular instead of tapering, so that'as soon as the brake-cylinder pressure exceeds that for which spring 11 is adjusted the -port 12 will be forced to so register with outletport 13 in the bushing 14 that the latter port shall bewide open and remain so until the brake-cylinder pressure is subsequently reduced sufficiently to allow the spring to force the piston and its valve upward and close it.

As illustrated in Fig. 2,"the inertia-governor device comprisesa casting 15, having flanges for securing it beneath the iioor of the car, and a chamber 16, communicatingv with pipe 8, in which is located valve 17, resting upon seat 1S. The valve is provided with suitable guiding-stems, the lower stem Y19'extending down through the outlet-*open- IOO IIO

ing 2O and through a guide 21, secured to the casting. The weight 22, which represents the independently-moving mass operating upon relief-valve 17 through its inertia, is shown adjustably mounted upon a stem 23, (although it may be made integral therewith, if preferred,) the upper end of which is provided with a cross-head 24, resting upon the two fulcrum-bolts and 26, supported by the casting 15. A lever pivoted at one end 28 to casting l5 extends at its other end 29 beneath the depending stem 19 of valve 17 and bears at an intermediate point upon the cross-head midway between the two fulcra 25 and 2G. This arrangement constitutes, in eect, a double fulcrum-lever connection, by means of which valve 17 is opened when the inertia-weight 22 moves a short distance in either direction and turns the head of the stem about either fulcrum 25 or 26. The lever 27 is not essential tothe operation of the device, as it is obvious that valve 17 might be located directly above the stem 23 of inertia-weight 22 and valve-stem 19 extended downward until nearly approaching the crosshead 24 and be acted upon directly by the cross-head instead of through the intermediation of lever 27; but the latterserves to widen the range of adjustment and is convenient in the arrangement of the device chosen for illustration.

Inertia-weight 22 is of such form that when supported by both fulcra its center of gravity lies in a'vertical plane midway between the two fulcra. The force of gravity acts downward upon weight 22 and opposes rotation about either fulcru'm with a degree of effectiveness proportional to the distance between the fulcra. The air-pressure upon valve 17 also operates to resist effective rotation of weight 22 about either fulcrum to a greater or less degree, depending upon the size of the valve, the proportions of lever 27, and the distance between the

fulcra

25 and 26. The retarding force of the brakes upon the car is transmitted in due proportion through the fulcrum-bolts to weight 22 at its upper extremity, and the force with which inertia opposes retardation operates, in eect, at its center of gravity toward inducing rotation about the rear fulcrum (with reference to the direction of motion of the car) with an eifectiveness proportional to the vertical distance from the center of gravity to the horizontal plane ofthe fulcra. It will be noted, therefore, that there is a considerable range of means for such an adjustment of proportions that the relief-valve 17 shall be opened when the retarding force applied to weight 22 corresponds with any particular degree of brakeshoe friction chosen. It is of course essential that the device shall be so secured to the car thatthe swinging motions of weight 22 shall be parallel to the longitudinal axis of the car or direction of its motion.

Encircling the upper guiding-stem of valve 17 the spiral spring 31 is shown exerting a downward pressure upon the valve. This spring may be employed, if desirable, to assist gravity in seating valve 17 or as an added resistance to the opening of the valve if it should prove a desirable expedient; but in view of the wide range of means for adjustment already enumerated the use of a spring as a means of resistance to the opening ofthe valve is not ordinarily essential, gravity alone being suiiicient. It is also to he noted that when the weight 22 has rotated about either fulcrum and opened valve 17 the operative potency of the various active forces may be altered. In such movement the lever-arm with which gravity operates to return the weight to its normal position (shown in Fig. 2) becomes greater than before the rotation occurs, while the leverage with which inertia operates to hold the valve open is somewhat less than that before the opening movement begins. On the other hand, the opening of valve 17, and the consequent discharge of air, causes a reduction of the air-pressure upon the valve and opposing the rotation of the inertia-weight. In proportioning the area of valve 17 and the lengths of lever-arm with which the forces of gravity and inertia operate the device is adapted to both open the valve under the retarding eect of a selected degree of brake-shoe friction and to thereafter hold it open a suitable time to meet the required purpose.

The operation is as follows: .When in an application of the brakes the air-pressure in the brake-cylinder exceeds that for which the reducingvalve is adjusted, the reducingvalve is thereby opened, and valve 17 of the inertia-governor prevents escape of air from the brake-cylinder. As soon as the brakeshoes have become eiectively applied to the wheels the motion of the tr'ain begins to be retarded; but the brake-shoe friction at high speeds does not produce sufficient retardation to cause the weight of the inertia-governor to rotate, and valve 17 remains seated; but after the speed of the train has been so reduced that the brake-shoe friction increases sufficiently to produce the rate of retardation for which the inertia device is adjusted (which may occur at any speed within a range of considerable extent) the increased force lwith which inertia opposes the increased retarding force overcomes the various resistances and causes the weight 22 to move forward relatively' to the car body, rotating about the rear fulcrum, and lifting valve 17 to discharge air from the brake -cylinder, the device being so proportioned and adjusted that the reduction of pressure upon valve 17 resulting from the escape of the air permits the valve to remain open. The air-pressure in the brake-cylinder is then rapidly reduced until it falls to that for which the reducing-valve is adjusted, whereupon the reducing-valve operates to cut olf further escape of air and retains thereafter and until the stop only so much pressure in the brake- I air-.pressu re is then discharged and the brakes released in the usual way by the engineer. The inertia device may, however, be so proportioned and adjusted that after valve 17 is first opened, notwithstanding the consequent reduction of pressure upon the valve, the reduced brake-shoe friction, and therefore reduced retardation, accompanying the reduced brake-cylinder pressure causes the weight to fall back toward its normal position (shown in Fig. 2.) and closes valve 17. The remaining air-pressure is then retained in the brakecylinder until the increasing brake-shoe friction again causes the inertia device to operate and discharge more air from the brake-cylinder and further reduce the pressure, the operation being repeated as often and as many times as may be necessary to prevent wheelsliding until the traincomes to a stop or until the reducing-Valve,if one is employed, cuts olf further escape of air from the brake-cylinder.

With such an adjustment of the device the use of the reducing-valve is unnecessary, as the valve 17 always remains closed to retain the air-pressure in the brake-cylinder, except when the brake-shoe friction becomes so great that a reduction of pressure is desirable to prevent wheel-sliding, and when the pressure has been sufficiently reduced to avoid that danger the retardation is correspondingly reduced and being no longer sufficient to enable the inertia of weight 22 to hold valve 17 open the valve closes and cuts off further escape of air from the brake-cylinder. It is merely essential to so proportion the valve and discharge-passages that the airpressurev may be reduced at least as rapidly as thebrake-shoe friction may possibly increase, so thatthe rate of retardation for which the device ,is adj usted may in no case be materially exceeded. It `will be understood, however, that while I prefer in` the practice of my invention toproportion the device so that it shall operate in these reductions of the air-pressure at a practically uniform rateof retardation it is notk necessarily limited tooper'ation at any one particular rate of retardation. The rate of retardation required to openfvalve 17 depends upon the resistance to the movement ofweight 22, and valve 17 may be so proportioned that theairpressure upon that valve shall constitute an .important part of that resistance. As the air-pressure becomes reduced the resistance accordingly declines, and the operative rate of retardation may thus be caused to be ma'- terially reduced at each succeeding reduction of the air-pressure. It is of course obvious that if the valve 17 be reversed in its direction of motion, beingnormally held to its seat at the lower'or outer end of passage k2O to become greater, and an increased instead of a reduced rate of retardation will be required to open the valve after each succeeding reduction of air-pressure. Thus in either case by properly proportioning the parts of the device'it may be adapted to operate at different rates of retardation under different lconditions if for any reason it should be so desired. While thus avoiding injurious wheel-sliding, I simultaneously provide for the utilization of the maximum braking effeet, and consequently secure shorter stops for any kind of train-service than have hitherto been attainable in regular practice.

A. clearance-space is shown between valvestem 19 and lever 27. This is generally desirable to insure proper seating of the valve and to allow for settling of the valve upon the seat through wear and continued service. t Figs. 3 and 4 show a modification of my inertia-governor device, in which the inertiaweight rotates in a horizontal instead of a vertical plane and in which its operation -under the influence of inertia is unopposed by gravity. The casting 15 has, as in Fig. 2, suitable [langes for securing it to the car and a chamber 16, communicating with pipe S, in which is located slide-valve 17, seated in the bushing 18. Casting 15 also provides pockets 33, in which are located the adjustable springs 3l, abutting against collars 34 of supportingstems 32. Inertia-weight 22 is mounted upon stem 23, which is attached by pin 25 to casting 15. It is forked near the end to secure greater stability and freedom from undesirable vertical vibration and is confined laterally between the ends of the spring-stems 32, so that it cannot move in either direction Without compressing one of the springs 31. A vertical pin or valve-guide 19 is secured to stem 23 and extends upward through the outletopening 2O into a corresponding cavity in the lowerface of valve 17, therebyengaging the valve in movements of stem 23 in either direction. A sufcient movement of valve 17 in either direction uncovers outlet-opening 2O and dischargesv air from the brake-cylinder. The device must of course be so secured to the car that the stem 23 of inertiaweight 22 shall normally-stand crosswise of the carror transverse to the direction of the carsmotion. The springs 31 are each 'so adjusted by means vof plugs 35that the operative effect of the inertia of weight 22 in opposing the retarding force applied through pin 25 is insuicient to compress the resisting spring and move valve 17 to discharge air from the brake-cylinder until the retarding force has increased to correspond with the maximum desirable brake-shoe friction. The inertia of Weight 22 then causes the spring to be compressed and valve 17 to be moved into a position to uncover outlet-opening 20, and the brake-cylinder pressure is thereby reduced. When the brake-cylinder pressure has become sufficiently reduced, the resulting decline of the eective retarding force actingv IOS IIO

upon inertia-weight 22 enablesthe compressed spring 3l to return the stem 23 and weight 22 to their normal positions, (shown in Figs. 3 and 4,) and valve 17 therebycuts olf further escape of air from the brake-cylinder until conditions again occur to cause the valve to be moved into a position to uncover outlet 20.

Although two springs 3l are shown in Fig. 4 for controlling the movement of stem 23 in the two directions, it is obvious that a construction similar to that of Fig. 2 may be employed, in which a single spring with a doublefulcrum lever will resist movement of stem 23 in either direction.

Fig. 5 isa diagrammatic illustration of still another form of my invention. Casting 15 is formed with a valve-chamber 16, communieating with pipe S, in which slide-valve 17 is seated in bushing 18, as in the form illustrated in Figs. 3 and 4. Casting 15 also provides a cylindrical chamber 39 below valvechamber 16, which contains two pistons 37, provided with packing-rings 38 and connected by the stem 3G. Valve-guide 19 is secured to piston stem 36 and projects upward through the outlet-opening 2O into a correspending cavity in valve 17, thereby connecting the valve with pistons 37 in such a manner that a movement of the pistons in either direction is accompanied by a corresponding movement of the valve. In the cap at each end of chamber 3i) a chamber is provided, in which a spiral spring 3l abuts at one end against collar 34 of stem 32 and at the other against the adjusting-screw35. Stem 32 projects through the cap into chamber 39, so that pistons 37 cannot move from their normal p0- sition,in which slide-valve 17 occupies its central position, without engaging one of these stems and compressing the spring 3l encircling it. At each end of chamber 39 a passage 40 leads by a pipe 4l to a chamber 42 at the end of a horizontal tube or tank 43, secured conveniently to the vehicle, so that it shall be parallel to the axis of the vehicle or the direction of its movement. This tube or tank contains a body of mercury or other suitable liquid 22, extending throughout its length and part way up into the vertical chamber 42 at either end. In operation, the brakes having been applied, the inertia of the body of liquid 22 causes it to progressively move forward, lowering its level in the rear chamber 42 and raising it in the forward chamber as the retardation of the train increases. The air confined in the space between the liquid in the forward chamber 42 and the piston 37, with which it communicates, is thereby compressed, while the pressure of the air in the rear chamber 42 and acting upon the correspondingpiston 37is rednced. WVhen the retardation becomes sufficient to produce such a change of level of the liquid that the resulting increase of air-pressure upon one piston 37 in combination with the resulting reduction of pressure upon the opposing face of the other piston overcomes the resistance of the opposing spring 3l, the pistons are moved in a direction opposite to that of the cars motion, causing valve 17 to uncover outlet-port 20, and thereby reducing the pressure of the air in the brake-cylinder.

The initial adjustment of the device is accomplished by suitably proportioning the weights of the horizontal and vertical columns of liquid, the area of liquid exposed to `Instead of interposing a column of air be-v tween the surface of the liquid in chamber 42 and the piston 37 the space so occupied may be filled with the same or another' liquid operating directly upon the piston. It is obvious also that flexible diaphragms maybe optionally employed in the place of pistons 37.

It will thus be seen that I provide a device which operates upon an entirely new principle for eliecting a reduction of the braking force to correspond with the increased brakeshoe friction of the diminished speed of the train, and it will also be evident that my invention may be practiced in many different forms dillering materially in appearance and utilizing a wide range of dilferent'means to accomplish the purpose. I have illustrated the employment of two dilferent forms of- Valve to show that the form of valve is immaterial, the capabilities of retainingand releasing the pressure of the operating fluid at the proper times being alone essential. I have shown that a variety of means may be employed for keeping the valve closed at times when it is desirable to retain the pressure, including gravity, a spring, and fluid-pressure, or a combination of such means. The mass of matter through which inertia operates to open the relief-valve may be of any suitable material or form, may be either directly or indirectly connected with the valve, or may be integral with the valve itself. It is merely essential that it shall be capable of a sulicient degree of movement relative to the valve-seat that such movement, due to its inertia, may actuate the valve to relieve the pressure, the term valve-seat broadly referring to that member of any pressure-controlling mechanism which is secured to the vehicle and partakes of its 'motion and the term valve similarly referring to the member which by a relative movement releases the pressure, and thereby reduces the force with which the brakes are applied. I do not limit myself, therefore, to the particular constructions shown, but wish to cover, broadly, any inertia device operating by its momentum during the retardation of the Speed of the train to effect a reduction in the force with which the brakes are applied.

Having now described my invention, what I claim, and desire to secure by Letters Patent, is

1. In a brake system, the combination with means for applying the brakes, of an inertia device operated by the rate of retardation of lOO IIO

the vehicle for effecting a reduction in the force with which the brakes are applied.

2. In a fluid-pressure brake, the combination with a brake-cylinder, of an inertia valve device operated by the rate of retardation of the vehicle lfor effecting a reduction in the pressure in the brake-cylinder.

3. In a fluid-pressure brake, the combination With a brake-cylinder having an outletpassage, of an inertia valve device operated by the rate of retardation of the vehicle for controlling said outlet-passage.

4. In a duid-pressure brake, the combination With a brake-cylinder having an outletpassage,of a pressure-operated valve for opening and closing said passage, and an inertia valve device operated by the rate ofretardation of the vehicle for also controlling said passage.

5. In a fluid-pressure brake, the combination With a brake-cylinder having an outletpassage, of a valve operated by the brakecylinder pressure for opening and closing said passage, another Valve also controlling said passage and an inertia device for operating the last-named valve, said inertia device being actuated by the rate of retardation.

6. In a fluid-pressure brake, the combination With a brake-cylinder having a normally closed outlet-passage, of a valve for said passage and an inertia device operated by the rate of retardation of the vehicle to open said passage.

7. In a duid-pressure brake, the combination with an auxiliary reservoir, triple valve and a brake-cylinder having an outlet-passage, of a quick-action valve device for producing an increased pressure in the brakecylinder, and an inertia valve device operated by retardation of the vehicle for control- 8. In a fluid-pressure brake, the combination with an auxiliary reservoir, triple valve and a brake-cylinder having an outlet-passage, of a quick-action valve device for producing an increased pressure inv the brakecylinder, a valve operated by brake-cylinder pressure for opening and closing said outletpassage, and an inertia valve device operated by retardation of tlie vehicle also controlling said outlet-passage.

9. In a fluid-pressure brake, the combination with a brake-cylinder having an outletpassage, of a valve in said passage and an inertia-Weight adapted to open said valve during retardation of thevehicle.

l0. In a Huid-pressure brake, the combination of a brake-cylinder having an outlet-passage, a valve controlling said passage, an inertia-weight mounted to move in either direction lengthwise of the car, and intermediate connections between the Weight and the valve for opening said Valve when the Weight moves in either direction relatively to the car.

l1. In a fluid-pressure brake, the combination of a brake-cylinder having an outlet-passage, a valve controlling said passage, an inertia-weight mounted to swing in either direotion lengthwise of the'vehicle, and a double-fulcrum-lever connection for operating said valve.

In testimony whereof I "have hereunto set my hand.

ROBERT A. PARKE.

Witnesses!- JENNIE S. LEONARD, ROBT. N. PARKE.