US3340963A - Railway car retarder control systems - Google Patents

Description

p 1967 E. o. GARRETT, JR ETAL RALLWAY CAR RETARDER CONTROL SYSTEMS 2 Sheets-$heet 1 Filed June 24, 1966 1H1 H i I NIH 7 0 (1011/1 06 /1 0 nmwfa:5.

p 1967 E. o. GARRETT, JR ETAL 3,340,963

RAILWAY CAR RETARDER CONTROL SYSTEMS Filed June 24, 1966 2 Sheets-Sheet I l [V V I; IV @7035 2! Edward 0. (,Qufle J1. and J BY Pezjen v M/Vobla United States Patent 3,340,963 RAILWAY CAR RETARDER CONTROL SYSTEMS Edward 0. Garrett, Jr., Penn Hills Township, Allegheny County, and Peter M. Noble, Valencia, Pa., assignors to Westinghouse Air Brake Company, Swissvale, Pa., a corporation of Pennsylvania Filed June 24, 1966, Ser. No. 560,178 15 Claims. (Cl. 188-62) Our invention relates to railway car retarder control systems and more particularly to hydraulically-actuated pneumatically-powered electrically-controlled systems for weight proportional car retarders which may be rapidly and selectively conditioned to assume either a braking or a non-braking position,

It has been found that an inert car retarder when equipped with an appropriate control system is ideally suited for group and hump car retarder operations in classification yards since this type of retarder applies a braking force which is directly proportional to the respective Weight of the car under retardation and therefore removes approximately the same velocity head from all cars irrespective of their weight. While various types of weight proportional car retarders and control systems for such reta-rders have been previously proposed, it is noted that these previous proposals lack certain essential requirements and necessary characteristics which limited the use of such retarder arrangements. For example, many of the previous weight proportional car retarder arrangements were preferably employed at the end of the class tracks in a classification yard for simply stopping and holding the first car entering the respective class track in lieu of track skates. Accordingly, the control system for such a skate retarder was mainly employed for the purpose of extending the life of the brake shoes of the retarder when the classed cars were pulled from the class track by a locomotive. That is, it was common practice to utilize an open-type of hydraulic releasing system which would permit the opening of the car retarder so that the cars could be easily removed from the class track without excessive wear on the braking surfaces of the brake shoes. Such a hydraulic releasing system normally included a suitable controlled cylinder and piston properly positioned beneath the running rail or under the levers of the operating units of the car retarder for effecting the opening of the brake shoes. While the use of such a hydraulically controlled weight proportional car retarder arrangement is quite satisfactory at the exit end of class tracks, its use in a group or a hump retarder application is generally not acceptable due to the inherent slow or sluggish operation and the intrinsic leakage problems associated therewith. That is, the speed with which an open hydraulic control system moves the car retarder between its non-braking and braking positions is limited and generally too slow for high speed repetitive acting retarder operations, such as, demanded by group and hump retarder installations. Similarly, since the apparatus of hydraulic control system is quite extensive and normally includes hydraulic pumps, reservoirs, valves, stop-cocks, pressure switches, and extensive piping, it is constantly susceptible to loss of liquid and to drop in pressure due to leaks. While several attempts have been made to utilize such car retarders and open hydraulic systems in group and hump applications, the results were generally unsatisfactory in that once the retarder was released during car retardation it could not be elfectively reactivated to its normal braking position for the same car. It is obvious that in order to achieve effective braking and control of the car passing through the retarder, the retarder must be capable of reclosing at least between the trucks of the car so that 3,340,963 Patented Sept. 12, 1967 the braking effort may be reapplied in case the speed of the car increases above the preselected given speed. While it would appear obvious to simply increase the pressure of the hydraulic control system such an expedient is generally objectionable in that the leakage problem is proportionally increased with greater pressures, and therefore improved operation is only obtained with increased cost and decreased effectiveness. Accordingly, the complexity and expensiveness of these former open hydraulic control systems are not only physically prohibitive but also economically unjustifiable in terms of reliable and eflicient operation.

Accordingly, it is an object of the present invention to provide an improved control system for a car retarder which has universal application.

A further object of our invention is to provide a hydraulically-actuated pneumatically-powered electricallycontrolled systems for weight proportional car retarders.

Another object of our invention is to provide a unique system for controlling weight proportional retarders which may be employed in group and hump applications as well as used in place of track skates.

Still another object of our invention is to provide an improved low pressure control system having a short response time so that a car retarder may be quickly moved from its non-braking position to its braking position for achieving repetitive braking action on a railway car.

Yet another object of our invention is to provide new and improved Weight proportional car retarder control system which renders and retains the car retarder ineffective in retarding a car when moved to its non-braking position.

Still yet another object of our invention is to provide a unique pneumatic-hydraulic-electiic control system for a car retarder with greater security in that a hydraulic leak does not adversely alTect the general operation and elfectiveness of the entire car retarder.

Yet a further object of our invention is to provide a unique pneumatic-hydraulic-electric control system for a car retarder which assumes and/or maintains its braking position for positively stopping railway vehicles during periods of electrical power failures.

Still yet a further object of our invention is to provide an improved car retarder control system which is simple in design, economical to manufacture, endurable in use, and eflicient and reliable in operation.

Briefly, our invention relates to pneumatically-powered hydraulically-actuated electrically-controlled systems for a weight proportional car retarder which may be conditioned either to retard a vehicle in accordance with its weight or to permit the free passage of a vehicle. The car retarder is of the friction wheel engaging type and preferably includes a plurality of operating units each having a pair of supporting levers positioned on opposite sides of the running raiL'The inner lever of each operating unit is pivoted about a point having a fixed height while the other lever of each operating unit is pivoted about a point having a variable height. The height of the variable pivot point of each outer lever is controlled by individual hydraulic rams which when fully extended cause the retarder to assume its braking or closed position and which when fully contracted cause the retarder to assume its non-braking or open position. The hydraulic rams form part of a closed-type of hydraulic circuit which is under the control of an open-type of pneumatic circuit. The hydraulic and pneumatic circuits include solenoid control valves which when deenergized complete a unidirectional communication path from a source of pneumatic pressure to the hydraulic rams for placing the retarder in its braking position. On the other hand, when the solenoid control valves are energized a bidirectional com- 3 munication path is completed between the hydraulic rams and atmosphere thereby allowing the retarder to assume its non-braking position. The retarder remains in its nonbraking position until the source of pneumatic pressure is again applied to the pneumatic control circuit.

In the first embodiment, the pneumatic control system and the hydraulic controlled circuits are interconnected by a plurality of individual pneumatic-hydraulic transducers.

I In the second embodiment the pneumatic control circuit is interconnected to the hydraulically-controlled circuit by a single pneumatic-hydraulic transducer.

The above objects and other attendent features and advantages of this invention will become more fully evident from the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a diagrammatic view of one form of a control system for a weight proportional car retarder embodying the present invention.

FIG. 2 is a diagrammatic view of a modified form of a control system embodying the present invention showing a sectionalized end view of the weight proportional car retarder of the type preferably employed in our invention.

Referring to the drawings wherein like parts are indicated by like reference numerals, and in particular to FIG. 2, there is shown a sectionalized elevational view of the weight proportional car retarder in its braking position and specifically the details of an operating unit OU. While the control system is illustrated as being capable of controlling a five-unit group or hump car retarder, it is understood that the system may be designed and constructed to accommodate a greater or lesser number of retarder operating units, as desired. It has been found that only five operating units are required for a car retarder having a length of approximately sixteen feet (16) for effectively and efliciently handling even the heaviest railway car in use at the present time. As will be described hereinafter the particular retarder length is chosen as such that the retarder may be reset between the trucks of even the shortest railway vehicle in commercial existence. As shown in FIG. 2, the reference character 1 designates one track rail of a stretch of railway track over which the wheels of railway vehicles pass. The rail 1 is supported by the operating units U each of which consists of a pair of substantially identical levers 2A and 2B disposed laterally on opposite sides of the rail 1. The inside bottom portions of the levers are securely held in suitable relationship by means of a through-type tie bolt 3. As shown, the upper surface of the inside bottom portion of the levers engages the flange of the rail 1 while the bottom surface of the inside bottom portion normally rests on a thrust or hearing plate not characterized, suitably mounted on cross tie 4, when the car retarder is in its braking position and no vehicle is being retarded or when the car retarder is in its non-braking position. The inside top portion of each lever has secured thereto in any suitable manner, the braking elements of the car retarder. These braking elements may consist of braking rails or as shown brake beams 5 and brake shoes 6 which are adapted to frictionally engage the opposite sides of the car wheels when the retarder is in its braking position. The underside of the outside end of lever 2B is shown pivotally mounted on a suitable supporting member 7. The supporting member 7 has a predetermined height and is suitably secured by means of, for example, a tie plate which may be suitably mounted on the cross tie 4. The outside end of lever 2A of each operating unit 0U is suitably connected to a vertically movable piston or plunger 10 of a hydraulic ram R which when fully extended, as shown, has a height substantially equal to that of support 7. The piston is shown interconnected to the outside end of lever 2A by means of an eye-bolt type of mechanical link 11; however. it is understood that any suitable mechanical interconnection may be employed which will allow pivotal movement therebetween. As shown, the cylinder 12 of each hydraulic ram R is also suitably secured to and supported by the cross tic 4.

Referring now to FIG. 1, wherein the details of the operating units 0U have been excluded for the sake of convenience, there is shown one form of a retarder control system for a five-unit weight proportional car retarder. The control system of FIG. 1 is illustrated as consisting of a plurality of independent closed hydraulic controlled circuits cooperatively associated with the car retarder operating units, see uppermost ram R and lever 2A, and an open pneumatic control circuit.

The closed hydraulic circuits comprised within the blocks 20 may be of the type shown and described in our copending application for Letters Patent of the United States, Ser. No. 618,417, filed Feb. 24, 1967, for Railway Braking Apparatus. As shown, each hydraulic circuit comprises a packaged unit including a separate hydraulic ram R, a solenoid control valve designated generally at 21, and a pneumatic-hydraulic transducer 26. The control .valves may be of the internally piloted poppet two-way two-position spool type which allows bidirectional flow when solenoid 22 is energized and which only permits unidirectional flow when solenoid 22 is deenergized. That is, each valve 21 is provided with a check valve 23 which only permits fluid to flow from the transducer 26 to the hydraulic ram R. Each valve 21 also includes a biasing spring 24 for urging the valve to its unidirectional flow position. As shown, the input side of each valve 21 is coupled by suitable conduit to the hydraulic side of the separate pneumatic-hydraulic transducers 26 while the output side of each valve 21 is coupled by conduit to a separate hydraulic ram R.

As shown, the pneumatic control circuit comprises a suitably regulated motor-driven compressor 30 pneumatically communicating and feeding reservoir or tank 31 which form a low pressure supply, such as, p.s.i. source. The output from reservoir 31 is connected by conduit to the input port of a solenoid control valve 32. The control valve 32 is preferably a two-way two-position spool valve which includes operating solenoid 33 and return spring 34. When solenoid 33 is deenergized, a fluid communication path is established from reservoir 31 through valve 32 to conduit manifolded together, and designated generally at 35, which in turn is interconnected to the pneumatic-side of each of the pneumatic-hydraulic transducers 26. On the other hand, when the solenoid 33 is energized, the valve 32 is shifted so that the output from reservoir 31 becomes blocked and the manifold 35 and, in turn, the pneumatic side of transducers 26 are vented, for example, to atmosphere.

Each of the solenoids 22 of valve 21 are electrically connected in parallel by conductors 40 which in turn are connected to the control apparatus by suitable leads 41. Similarly, the solenoid 33 is connected to the control apparatus by means of suitable conductors 42. The control apparatus which may be operated manually under visual observance of an operator or automatically under supervision of a programmed computer is preferably remotely situated at a suitably located control oflice.

In describing the operation of the retarder control system, it will be initially assumed that a railway vehicle or car is approaching the retarder at a speed in excess of a predetermined computed speed which is normally necessary for it to safely couple with a preceding vehicle in its destined class track. Therefore, it is desirous that the retarder be moved in its braking position, in the manner illustrated in FIG. 1, so that the brake shoes 5 may frictionally engage the opposite sides of the vehicle wheels for reducing the speed of the fast approaching railway vehicle. As previously mentioned, the brake shoes will close and the retarder will move to its braking position by raising the pistons 10 of the hydraulic rams R to their fully extended positions. The hydraulic rams R are extended, as shown in the drawings, when solenoid 33 of the pneumatic control valve 32 and the solenoid 22 of the hydraulic control valve are deenergized. With the solenoid 33 deenergized, a pneumatic flow path is established from the reservoir 31 through the pneumatic valve 32 to the input of manifold 35 and in turn to the pneumatic side of each of the transducers 26. With the solenoids 22 of the hydraulic valves 21 deenergized a unidirectional fluid path is established from the hydraulic side of transducers 26 to the hydraulic rams R. The pressurization by the 100 p.s.i. source on the pneumatic side of the transducers 26 is transmitted to the hydraulic side of transducers 26 so that the fluid flows through check valve 23 to the hydraulic rams R. Accordingly, the pistons are rapidly forced toward their fully extended positions. The 100 p.s.i. source of pressure is relatively low but is of suflicient magnitude to displace pistons 10 of the hydraulic rams R and lift the levers 2A and in turn the entire retarder to its braking position. When the pistons 10 of rarns R reach their fully extended positions, the solenoid 33 is energized and valve 32 is shifted so that manifold 35 and the pneumatic-side of transducers are vented to atmosphere, the purpose of which will be described hereinafter. The shifting of valve 32 also causes the output from reservoir 31 to become closed so that the motor and compressor need not be operated unnecessarily.

It is noted that once the hydraulic rams R have been fully extended, the venting of the pneumatic circuit by the energization of the solenoid 32 of pneumatic valve 33 does not materially affect the closed hydraulic system and the retarder remains in its braking position. That is, even though the pneumatic-sides of transducers 26 are now at atmospheric pressure, the check valves 23 prevent reverse fluid flow from the hydraulic rams R so that the retarder is locked in its braking position. Accordingly, as the front Wheel of the first truck of the railway vehicle enters the retarder, the levers 2A and 2B of the operating units OU pivot about their respective support 6 and the hydraulic ram R. The pivoting action of the levers about their outer extremity causes a lifting of the rail 1 and the vehicle along with a clamping or braking action on the sides of the vehicle wheel by the brake shoes 5 in proportion to the weight of the railway vehicle. This braking action on the wheels and retardation of the vehicle continues until it is determined, assuming automatic operation, by suitable speed measuring means, such as radar, that the speed of the vehicle has reached a preselected computed value. When the speed of the vehicle reaches this preselected value, it is desirous to quickly release the retarder so that the speed of the vehicle is not reduced below the speed necessary for the vehicle to reach its destination and couple with the preceding vehicle in its respective class track. Accordingly, it is advantageous to have as short as possible release response time in order to efliciently and accurately control the velocity of railway cars. To release the retarder it is simply necessary to energize the solenoids 22 of the hydraulic valves 21 so that the spool establishes'a fluid communication path from the hydraulic rams R to the transducers 26. That is, when the solenoid control valve 21 is moved upwardly as viewed in FIG. 1 by the energization of solenoids 22, a bidirectional flow path is established between the hydraulic rams R and transducers 26. This unlocks the hydraulic fluid trapped in rams R so that the weight of the vehicle and retarder causes the hydraulic fluid in the rams R to be rapidly transferred through the valves 21 to the hydraulic side of the vented transducers 26. The downward displacement of piston 10 causes the brake shoes 5 to open wider than the width of the Wheels of the railway vehicle so that the railway vehicle now may pass freely through the retarder. In actual practice it has been found that the car retarder will move from its braking to its non-braking position in approximately one-third A) of a second. It is noted that the hydraulic rams R will remain in their compressed position and the brake shoes 5 will stay open even after the departure of the wheels of the first truck of the vehicle from the retarder since the hydraulic circuit remains in a state of equilibrium and the weight of the retarder alone is sufficient for holding the pistons 10 depressed. That is, the retarder remains in its non-braking position until such time as it is again desirous to operate and move the retarder to its braking position. It is readily apparent that after the pistons 10 are fully depressed the solenoids 22 of the hydraulic valves may be deenergized and the retarder will still remain in its non-braking position. Accordingly, it is simply necessary to momentarily energize solenoids 22 since the hydraulic rams will be fully compressed in approximately /3 of a second, and therefore the power requirement is minimized due to the pulse energization of the solenoids.

As previously mentioned, the overall length of the retarder is less than the distance between the adjacent trucks of a railway vehicle so that the retarder may effect a braking action on the wheels of the second truck of the same vehicle. That is, if the speed of the vehicle increases while passing through the retarder, it is necessary to again close the retarder and reduce the speed of the vehicle to the preselected value. Let us assume that the retarder has been released in the manner as described above and that the speed of the vehicle has risen above the preselected value so that it is desirable to reclose the retarder. With solenoids 22 deenergized, it is simply necessary to deenergize solenoid 33 of the pneumatic valve 32 to again pressurize the pneumatic-side of transducers 26. Under such a condition the control system is made ready and upon departure of the second wheel of the first truck from the retarder, the rams R are rapidly forced upwardly to their fully extended positions and the retarder again assumes its braking position. In actual practice it has been found that the control system will displace the pistons 10 to their fully extended position or, in other words, the retarder will be moved from its non-braking to its braking position in less than 0.5 second. It has been found that with a response time of 0.5 second in moving the retarder between its non-braking to its braking position, the retarder may be reclosed and elfect braking on vehicles moving at a speed in excess of 15 miles per hour. When the rams reach their fully extended position, thesolenoid 33 of the pneumatic valve may be energized so that the transducers 26 are again vented to atmosphere and the retarder is again ready for effecting a braking action on the wheels of the second truck, the same as described for the wheels of the first truck. When the speed of the vehicle is reduced to its preselected value, the retarder may be again opened or released simply by pulse energizing the solenoids 22 of the hydraulic control valves 21 so that the retarder will move to its non-braking position, in the manner as described above. Accordingly, the amount of retardation applied to any particular railway vehicles is effectively controlled in accordance with the characteristics of the vehicle under retardation and therefore the leaving speed of the vehicle may be accurately controlled.

Now if the speed of an approaching railway vehicle is at or below its preselected computed value, and the retarder and control system are in their respective non braking positions, no control action is taken and the railway vehicle is permitted to pass freely through the retarder. However, if the retarder arrangement is in its braking position and the speed of an approaching vehicle is at or below its preselected computed value, it is necessary to exercise a controlling action to open the retarder. Under this condition the solenoids 22 are simply energized so that the fluid in rams R is unlocked. This allows the pistons 10 to decend and as the vehicle enters the retarder the weight of the front wheel quickly forces the levers and brake shoes to open. Accordingly, the retarder promptly assumes its non-braking position so that only a slight dragging effect is exerted on the front wheel of the first truck and no retarding action is applied to the following wheels of the railway vehicle.

The fast release or snapopen action of the car retarder is the result of utilizing a closed-hydraulic controlled circuit in combination with an open-pneumatic control circuit. Generally speaking, this unique combination provides an instantaneous responsive type of retarder control which alleviates the long time delays and slow operation that are normally inherent in the prior art type of open-type of hydraulic control systems. In addition, by employing an open-type of pneumatic system for powering and closing the car retarder, the actuating time is minimized. That is, since an open-type of pneumatic system is much faster acting than an open-type of hydraulic system, the car retarder may be moved from its non-braking to its braking position in a shorter period of time than was heretofore possible.

It should be noted that the present retarder control system requires only a relatively low pressure source so that the major portion of the conduit and particularly the field piping is generally less susceptible to leakage problems. A further advantage in utilizing a pneumatic-powered hydraulic-actuated control system resides in the fact that a dual-line network is not necessary since the pneumatic circuit may be directly vented to the atmosphere. Further, in reviewing FIG. 1, it is readily noted that only a small portion of the hydraulic control circuit is susceptible to high pressures, namely, the rams R and the conduit that leads to the output side of valves 21, and only during the retardation of the railway vehicles. An additional advantageous feature of our system is that of utilizing a plurality of individual closed hydraulic circuits, a failure of any one hydraulic circuit will not result in total system failure. That is, the remaining hydraulic circuits will supplement each other so that the retarder will function properly for eflectively reducing the speed of the railway vehicle. Accordingly, a failure of any hydraulic unit does not materially affect the braking operation of the car retarder. Further, the system is fail-safe from an electrical standpoint in that it will assume and/ or remain in its braking position to retard and positively stop a railway vehicle. For example, let us assume that the retarder is in its braking position when an electrical power failure occurs. The loss of power simply allows the return spring 34 to shift the hydraulic valve 32. This does not materially affect the retarder and its control system since the fluid within the rams R remains trapped and the retarder is held in its braking position. Now, if power failure should occur when the retarder is in its non-braking position, the springs 24 quickly urge the hydraulic valves 21 to their undirectional fluid flow positions while spring 34 quickly returns the pneumatic valve 32 to its power position. The pressure within reservoir 31 is suflicient to quickly and fully extend the pistons 10 of the hydraulic rams R so that the retarder assumes its braking position in which position it is positively locked due to the deenergization of solenoids 22 of valves 21. Accordingly, the highest degree of safety and security is achieved by the present control system and a chance of physical injury and damage to personnel and property due to a run-away car is minimized.

Referring now to FIG. 2, there is shown a modified version of a retarder control system in accordance with the present invention. In the control system of FIG. 2 the individual hydraulic rams R are fed from a single pneumatic-hydraulic transducer 26. The hydraulic side of the transducer 26' is interconnected by manifold 35 to the individual hydraulic valves 21. However, in FIG. 2, the pneumatic side of transducer 26 is directly connected to the pneumatic valve 32 by a single conduit rather than being manifolded as in FIG. 1. It is understood that the transducer 26' may be of the same general type as transducers 26 with the exception that the volume of transducers 26' is greater than, and in the case at hand, approximately five (5) times as great as,

8 the volume of transducers 26. It is noted that the operation of the control system of FIG. 2 is the same as that of FIG. 1 so that the rapid closing feature and snapopen releasing action are also inherent characteristics of this latter version. Like in FIG. 1, the retarder control system of FIG. 2 is shown in its brake actuating position wherein the retarder is being moved to its braking position. Accordingly, solenoid 33 is deenergized so that pneumatic valve 32 is effective in establishing a fluid communication path between the reservoir 31 and the pneumatic-side of transducer 26. As in FIG. 1, the pressurization of the transducer 26' causes the hydraulic field to be displaced from the hydraulic side of transducer 26' through the check valve 23 and in turn to the cylinders 12 of the hydraulic rams R. This fluid displacement causes the pistons 10 to be moved upwardly toward their fully extended position. When the hydraulic rams R become fully extended and the retarder occupies its braking position, the solenoid 33 is energized so that the transducer 26' is vented to atmosphere. To release and unlock the retarder it is simply necessary to energize solenoids 22 so that fluid communication paths are established from the hydraulic rams R to the transducer 26. The retarder moves from its braking position to its non-braking position in a snap-open fashion under the influence of the vehicle weight to quickly allow free passage of the railway vehicle. As in FLIG. l, the control system may be repetitively operated to reapply retardation to the same vehicle in cases where the vehicle accelerates while passing through the retarder. Similarly, the retarder may be rendered ineffective in the same manner as described in FIG. 1 when retardation on a vehicle is not desired.

While the control systems and the carretarder have been described in relation to group or hump operations, it is readily apparent that the retarder apparatus may be employed at the end of a class track for stopping and holding the first vehicle entering it, and when desired the retarder may be opened to permit the free and unimpelled withdrawal of the railway vehicles from the class track. Accordingly, we have described a Weight proportional car retarder and particularly an improved control system having universal application in a classification yard.

It will also be appreciated that while our invention finds particular utility in classification yards and in particular to hump and group retarder operations, it is readily evident that the invention is not merely limited thereto but may be employed in other environments, such as car dumper applications. But regardless of the manner in which the invention is used, it is understood that various alterations may be made by persons skilled in the art without departing from the spirit and scope of this invention. It will also be apparent that other modifications and changes can be made in the present described invention and therefore it is understood that all changes, equivalents, and modifications within this spirit and scope of the present invention are here meant to be included in the appended claims.

Having thus described our invention, what we claim is:

1. A system for controlling the position of a car retarder comprising: hydraulic actuating means cooperatively associated with the car retarder, hydraulic circuit means fluidly coupled to said hydraulic actuating means, and pneumatic circuit means interconnected to said hydraulic circuit means and having a source of pressure for causing the car retarder to assume a first position when fluid is permitted to flow through said hydraulic circuit means in one direction and for enabling the car retarder to assume a second position when fluid is permitted to flow through said hydraulic circuit means in the other direction.

2. A system as defined in claim 1 wherein said hydraulic actuating means comprises a ram.

'3. A system as defined in claim 1 wherein said hydraulic circuit means includes a solenoid control valve which permits fluid to flow in only one direction when said solenoid is deenergized and which permits fluid to flow in the other direction when said solenoid is energizcd.

4. A system as defined in claim 1 wherein a pneumatichydraulic transducer interconnects said pneumatic circuit means to said hydraulic circuit means.

5. A system as defined in claim 1 wherein said pneumatic circuit means includes a solenoid valve for connecting said source of pressure to said pneumatic circuit means when said solenoid is deenergized and for disconnecting said source of pressure from said pneumatic circuit means when said solenoid is energized.

6. A system as defined in claim 1 wherein said source of pressure includes a pneumatic compressor and reser- Volt.

7. A control system for car retarders comprising a plurality of first fluid means each having at least one ram cooperatively associated with the car retarder and a directional control valve for regulating the flow of fluid to and from said ram, and at least one second fluid means interconnected to said plurality of first fluid means and including a source of pressure for causing the car retarder to assume a first position when the fluid of said first fluid means flows to said ram and for enabling the car retarder to assume a second position when the fluid of said fluid means flows from said ram.

8. A control system as defined in claim 7 wherein said first fluid means comprises a hydraulic system and said second fluid means comprises a pneumatic system.

9. A control system as defined in claim 7 wherein a transducer interconnects said second fluid means to said plurality of first fluid means.

10. A control system as defined in claim 7 wherein a plurality of transducers interconnect said second fluid means to said plurality of first fluid means.

11. A control system as defined in claim 7 wherein said directional control valve comprises an electric solenoid valve which permits the flow of fluid to said ram when said solenoid is dcenergized and which permits the flow of fluid from said ram when said solenoid is energized.

12. A control system as defined in claim 7 wherein said source of pressure includes a compressor and a for cutting-off said source of pressure when said solenoid is deenergized.

14. A pneumatically-powered hydraulically-actuated electrically-controlled system for a weight proportional car retarder comprising: a source of pneumatic pressure including a compressor and a reservoir, a first solenoid control valve pneumatically coupled to said reservoir, a plurality of pneumatic-hydraulic transducers pneumatically coupled to said first solenoid control valve, a plurality of second solenoid control valves hydraulically coupled to separate ones of said plurality of pneumatichydraulic transducers, and a plurality of hydraulic rams hydraulically coupled to separate ones of said plurality of second solenoid control valves and mechanic-ally connected to the car retarder for rendering and maintaining the car retarder in its braking position when said first and sec-0nd solenoid control valves are deenergized and for rendering and sustaining the car retarder in its non-braking position when said first and second solenoid control valves are energized.

15. A pneumatically-powered hydraulically-actuated electrically-controlled system for a weight proportional car retarder comprising: a source of pneumatic pressure including a compressor and a reservoir, a first solenoid valve pneumatically coupled to said reservoir, a pneumatic-hydraulic transducer pneumatically coupled to said first solenoid control valve, a plurality of second solenoid control valves hydraulically coupled to said pneumatichydraul-ic transducer, and a plurality of hydraulic rams hydraulically coupled to separate ones of said plurality of second solenoid control valves and mechanically connected to the car retarder for rendering and maintaining the car retarder in its braking position when said first and second solenoid control valves are deenergized and for rendering and sustaining the car retarder in its non-braking position when said first and second solenoid control valves are energized.

References Cited UNITED STATES PATENTS 3,200,245 8/1965 Brown 188-62 X 3,209,865 10/1965 Wynn 188-62 3,227,246 1/ 1966 Wilson 18862 DUANE A. REGER, Primary Examiner.

Claims (1)

1. A SYSTEM FOR CONTROLLING THE POSITION OF A CAR RETARDER COMPRISING: HYDRAULIC ACTUATING MEANS COOPERATIVELY ASSOCIATED WITH THE CAR RETARDER, HYDRAULIC CIRCUIT MEANS FLUIDLY COUPLED TO SAID HYDRAULIC ACTUATING MEANS, AND PNEUMATIC CIRCUIT MEANS INTERCONNECTED TO SAID HYDRAULIC CIRCUIT MEANS AND HAVING A SOURCE OF PRESSURE FOR CAUSING THE CAR RETARDER TO ASSUME A FIRST POSITION WHEN

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