US3381628A - Wagon speed-control system - Google Patents

Description

May 7, 1968 D. E. LAMBETH ET AL 3,381,628

WAGON SPEED'CONTROL SYSTEM Filed Sept. 8, 1966 2 Sheets-Sheet 1 IUU lNvENToR W161 ATTORNEY May 7, 1968 D. E. LAMBETH ET AL 3,381,628

WAGON SPEED-CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Sept. 8, 1966 id m w Tm. A N L E ME vz M -5%, M e m United States Patent 3,381,628 WAGON SPEED-CONTROL SYSTEM Dennis E. Lambeth, Cheltenham, and Anthony G. L. Shore, Winchcombe, England, assignors to Dowty Technical Developments Limited, Brockhampton, England, a British company Filed Sept. 8, 1966, Ser. No. 577,987 Claims priority, application Great Britain, Sept. 16, 1965, 39,546/65 6 Claims. (Cl. 104-162) This invention relates to a system for controlling the speed of wagons moving along a railway track.

It is known to control the speeds of wagons moving along a railway track by a piston and cylinder device which is actuated by a wheel flange and which displaces liquid through control valve mechanism in such manner that, if a wagon is moving at less than a critical speed, a force caused by high fluid pressure is exerted on the wheel to accelerate the wagon, and if the wagon is moving at greater than the critical speed, a force caused by high fluid pressure is exerted on the wheel to retard the wagon. Some of the devices only perform one of these functions and not both.

According to the present invention a system for controlling the speeds of wagons moving along a railway track, comprises at least one pair of hydraulic displacement devices fixed to the track so that both devices execute contraction and then extension movements, for the most part at least, together under rolling engagement by one at least of a pair of co-axial wagon wheels, and control valve mechanism providing controllable connections between each device and either a low pressure liquid source or a high pressure liquid source, said mechanism including a speed-sensing valve responsive to the flow rate of liquid discharged by contraction of a first one of said devices, the speed-sensing valve acting when the flow rate is less than a pre-determined value to cause liquid discharged by both devices to flow to the low pressure source, and acting when the flow rate exceeds the pre-determined value to cause liquid discharged by both devices to flow to the high pressure source, and a position-sensing valve including operating means responsive to the quantity of liquid flowing from and to the second of said devices, the operating means acting on the position-sensing valve substantially upon completion of liquid discharge from the second device to the low pressure source, to connect both devices to the high pressure source, and acting substantially upon completion of the ensuing high pressure liquid flow into the second device to isolate the high pressure source from both devices.

The first and second hydraulic displacement devices, which may take the form of pistons mounted in cylinders, may be mounted against the respective rails at the same position in the normal direction of travel of a wagon so that both execute con-traction and extension movements substantially together. However, the second of the devices may be spaced a small distance from the first in the direction of travel so that the contraction and extension sequence of the first device starts before that of the second device, but that for the most part the sequences overlap in time. The purpose of this spacing is to reduce the risk of lifting a lightly loaded wagon since the initial application of forces generated by high fluid pressure do not occur simultaneously.

It the devices are spaced apart, it is possible to mount both against a single rail for rolling engagement by only one wheel.

In the accompanying drawings:

FIGURE 1 is a plan view of a length of railway track fitted with a wagon speed control system in accordance with the invention,

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FIGURE 2 is an enlarged sectional View on the line II-II of FIGURE 1 showing an installed piston and cylinder device,

FIGURES 3 and 4 are diagrams of control valve mechanism showing different stages of operation at low wagon speeds, and

FIGURE 5 is a diagram of the control valve mechanism showing different stages of operation at higher wagon speeds.

FIGURE 1 shows two hydraulic displacement devices formed as piston and cylinder devices 11 and 13 secured to the inner side of the left hand rail 6 at spaced-apart positions, and two similarly spaced devices 12 and 14 secured to the inner side of the right hand rail 7. The spacing of the second device 12 from the first device 11, and of the device 14 from the device 13, in the direction of travel of a wagon may be a short distance of four inches or thereabouts, for the purpose referred to but the spacing of the pair of devices 13, 14 from the pair of devices 11, 12 is greater so that a pair of wagon wheels having a common rotational axis leave the devices 11, 12 before engaging the devices 13, 14.

Each piston and cylinder device has a variable volume chamber filled with liquid, the chambers of the devices 11 and 13 being connected in parallel by a pipe 15 to control valve mechanism 17, and the chambers of the devices 12 and 14 being connected in parallel by a pipe 16 to the control valve mechanism 17. The latter is also connected by a branch pipe 18 to a high pressure main 8, and by a branch pipe 19 to a low pressure main 9'.

FIGURE 2 shows the mounting of the cylinder of the first device 11 in a generally upright position against the rail, and a piston head 10 which is engaged by the flange of a wagon wheel 20 so that the head is depressed to the position 10', and then rises to its uppermost position 10 as the wheel 20 rolls over the device.

In FIGURE 3, the pipe 15 is connected through the body of the valve mechanism 17 to a speed-sensing valve 22 and a high pressure relief valve 31, both of which can discharge to the low pressure branch pipe 19. The pipe 15 is also connected through a non-return valve 29 to the high pressure branch pipe 18. The speed-sensing valve 22 is formed as a hollow plunger which is loaded against a stop 38 by a spring 28 to open a connection through orifices 21 in the plunger, between the pipe 15 and a bore 39 to which the low pressure branch pipe 19 is connected. The relief valve 31 is formed as a piston which is loaded by a spring 41 to close orifices 42 in a cylinder-like valve housing 43. The effective area over which fluid pressure acts is that of the piston rod 44 because there is a hole 45 across the piston itself.

The pipe 16 is connected to a bore 46 containing a dummy piston 23, and to a high pressure relief valve 33. The pipe 16 is also connected through a non-return valve 32 to the high pressure branch pipe 18. The fluid displacement of the dummy piston 23 over its total travel is substantially equal to that of each of the piston and cylinder devices 12, 14. In its upper position in the drawing, the dummy piston 23 just closes a passage 27 leading from the bore 46 to the speed sensing valve. In its lower position, the dummy piston 23 closes another passage 47 which leads from the bore 46 to a second orifice 48 in the speed sensing valve 22. A friction ring 40 is mounted in the piston 23 to engage the bore 46. A port 30 is formed in the wall of the dummy piston 23 to connect the underside of the piston to the passage 27 when the piston descends. The dummy piston 23, moreover, constitutes operating means for a high pressure valve which consists of a ported sleeve 25 slidable on a ported spigot 49. The final downward movement of the dummy piston 23 opens the high pressure valve to supply of fluid from the pipe 18, and the final upward movement closes the high pressure valve. A tappet 5t) formed in the dummy piston 23 for shifting the sleeve valve 25 on its downward stroke is preferably formed as a spring device, while a spring detent may act between the ported spigot 49 and the ported sleeve 25, whereby the ported sleeve will move rapidly when the spring force overcomes the detent force.

The high pressure relief valve 33 is of generally similar construction to the high pressure relief valve 31. It comprises a piston which is loaded by the spring 28 to close orifices 51 in a cylinder-like valve housing 52. The effective area over which fluid pressure acts is that of the piston rod 53 because there is a hole 54 across the piston itself. In this valve 35, however, there is a stop 55 against opposite sides of which thc piston 33 and the housing 53 are urged by a spring 56 which acts between the piston and the housing. This valve is operable under an excess of pressure in the pipe 19 over that in the pipe 16 as a non-return valve, since low fluid pressure can act over the annular area of the housing 52 between the bore 39 and the stem 53 to move the housing 52 against the load of the spring 56 until the orifices 51 are uncovered by movement past the piston 33.

The operating sequence of the control valve mechanism under the influence of a pair of concentric wagon wheels which roll slowly over the piston and cylinder devices 11 and 12 will now be described with reference to FIG- URES 3 and 4.

When the flange of a wagon wheel engages the first piston and cylinder device 11, hydraulic liquid is expelled from the pipe 15 through the orifices 21 of the speedsensing valve 22 to the low pressure pipe 19, FIGURE 3. The pressure difference across the orifices 21, which acts on the valve 22 is not sufiicient to overcome the load of the spring 28, and the valve remains unaffected throughout the contraction stroke of the piston and cylinder device 11 because the maximum flow occurs at the beginning of the stroke. At only a short interval after the first evice 11 starts to contract, the flange of a concentric wheel on the other rail engages, and starts to contract, the second device 12. Hydraulic liquid then expelled from the pipe 16 displaces the dummy piston 23 downwardly, so that liquid on the underside of this piston passes through the second orifice 48 in the valve 22 to the low pressure pipe 19.

Near the end of the contraction stroke of the second device 12, that is, at about the time the first device 11 is fully contracted and starting to extend, the dummy piston 23 shifts the ported sleeve valve 25 on the ported spigot 49 to connect the high pressure in pipe 18 to the underside of the dummy piston 23, FIGURE 4. High pressure liquid now flows through the wall port 36 of the dummy piston 23 and the passage 27 to the pipe 15, causing the speed-sensing valve 22 to close, so that the first device 11 extends in contact with the wheel flange under high fluid pressure. High fluid pressure is also transmitted by the dummy piston 23 to the pipe 16, so that the device 12 extends in contact with the other wheel flange. Near the end of the extension stroke of the second device 12, that is, at about the time the first device 11 is fully extented, the dummy piston 23 lifts the sleeve valve 25 to cut off the supply of high pressure from both devices 11 and 12. Thus it is seen that the devices 11 and 12 are contracted by the respective wheels against low liquid pressure which exerts little, if any, appreciable resistance to movement of the wheels, but that the devices extend under high liquid pressure to exert an acceleration force against the wheels. During the sequence described, the devices 13 and 14 remain fully extended.

At a critical wheel speed along the rail, a pro-determined rate of initial flow from the first device 11 causes a pressure drop across the orifices 21 which balances the load of the spring 28. If therefore the speed of a wagon is above the critical value, liquid expelled from the first device 11 through the pipe 15 at the beginning of the contraction stroke, closes the speed-sensing valve 22, as

shown in the full line position in FIGURE 5. The liquid is then expelled through the non-return valve 29 to the high pressure pipe 18 and, at high flow rates, also through the orifices 42 of the high pressure relief valve 31. When, after a short interval, the second device 12 starts to contract, the expelled liquid cannot displace the dummy piston 23 because the passage 47 to the speed-sensing valve 22 is closed. Expelled liquid flows instead through the non-return valve 32 to the high pressure pipe 18 and, at high flow rates, also through the orifices 51 of the high pressure relief valve 33 to the low pressure pipe. The sleeve valve 25 remains raised and closing the high pres sure connection of the pipe 18 throughout the contraction stroke of the second device 12. When the first device 11 starts to extend, pressure falls in the pipe 15 so that the Speed-sensing valve 22 can open as shown by the chain dot position in FIGURE 5. Low pressure liquid now flows from the pipe 19, through the bore 39 and the orifices 21 into the pipe 15. The valve 33 then operates as a non-return valve under low pressure in the pipe 19, whereby the housing 52 lifts against the load of the spring 56 to allow low pressure liquid to flow through the orifices 51 and towards the pipe 16. If the dummy piston is not in its uppermost position, it will be raised by liquid from the passage 47 under the pressure difference across the valve 33.

Thus, it is seen that the devices 11 and 12 are contracted by the respective wheels against high liquid pressure resistance so that a retarding force is exerted against the flanges of the wheels, but that extension of the devices takes place under low liquid pressure so that there is no appreciable acceleration force exerted.

Upon completion of the extension sequence of the devices 11 and 12, the control valve mechanism is restored to the state of readiness shown in FIGURE 1, for responding to movement of the devices 13 and 14.

In practice, there will be some variation in flange depth of the wagon wheels causing a corresponding variation in the hydraulic displacement of the second device 12. It is therefore arranged that under low speed operation, when the dummy piston 23 moves downwardly, it will always move far enough to open the high pressure valve 25, 49. Any excess of liquid displaced will be discharged through the high pressure relief valve 33. If subsequently the piston 23 reaches its uppermost position slightly before extension of the second device 12 is complete, there will be a fall of pressure in the pipe 16 which allows this extension to be completed under low pressure liquid flowing through the valve 33. Thus it is seen that the dummy piston 23 is maintained in correct phase.

A small hole 60 is formed in the dummy piston 23 to pass any long term leakage from the non-return valve 32, when the system is not operating, so that such leakage can flow to the passage 47 and thence to low pressure without depressing the piston 23.

We claim as our invention:

1. A system for controlling the speeds of wagons moving along a railway track, comprising at least one pair of hydraulic displacement devices fixed to the track so that both devices execute contraction and then extension movements, for the most part at least, together under rolling engagement by a pair of co-axial wagon wheels, and control valve mechanism providing controllable connections between each device and either a low pressure liquid source or a high pressure liquid source, said mechanism including a speed-sensing valve responsive to the flow rate of liquid discharge by contraction of a first one of said devices, the speed-sensing valve acting when the flow rate is less than a pre-determined value to cause liquid discharged by both devices to flow to the low pressure source, and acting when the flow rate exceeds the predetermined value to cause liquid discharged by both devices to flow to the high pressure source, and a positionsensing valve including operating means responsive to the quantity of liquid flowing from and to the second of said devices, the operating means acting on the position-sensing valve substantially upon completion of liquid discharge from the second device to the low pressure source, to connect both devices to the high pressure source, and acting substantially upon completion of the ensuing high pressure liquid flow into the second device to isolate the high pressure source from both devices.

2. A system according to claim '1, wherein the first device is fixed with respect to one rail and the second device is fixed with respect to another rail for engagement by the respective Wheels of the pair, the second device being spaced from the first device in the normal direction of travel of the Wagon.

3. A system according to claim 1, wherein the operating means for the position-sensing valve comprises a piston which is movable in a cylinder bore and which transmits pressure between liquid on one side flowing from or to the second device, and liquid on the other side flowing respectively to the low pressure source or from the high pressure source.

4. A system according to claim 3, wherein the closing of the speed-sensing valve provides a hydraulic lock which prevents movement of the piston by liquid discharge during contraction of the second device, and wherein the connection through which discharge liquid then flows to the high pressure source is provided by a non-return valve.

5. A system according to claim 1, wherein a high pressure relief valve is interposed between each device and the low pressure source.

6. A system according to claim 5, wherein extension of both devices by liquid from the low pressure source takes place by reverse liquid flow through the speed-sensing valve to the first device, and by reverse liquid flow through one of the relief valves to the second device, this relief valve being arranged to operate under reverse flow as a low pressure non-return valve.

References Cited UNITED STATES PATENTS 3,107,633 10/1963 Bick l04162 3,128,721 4/1964 McGowan 104-162 3,148,633 9/1964 Bick l04162 ARTHUR L. LA POINT, Primary Examiner.

D. F. WORTH, Assistant Examiner.

Claims (1)

1. A SYSTEM FOR CONTROLLING THE SPEEDS OF WAGONS MOVING ALONG A RAILWAY TRACK, COMPRISING AT LEAST ONE PAIR OF HYDRAULIC DISPLACEMENT DEVICES FIXED TO THE TRACK SO THAT BOTH DEVICES EXECUTE CONTRACTION AND THEN EXTENSION MOVEMENTS, FOR THE MOST PART AT LEAST, TOGETHER UNDER ROLLING ENGAGEMENT BY A PAIR OF CO-AXIAL WAGON WHEELS, AND CONTROL VALVE MECHANISM PROVIDING CONTROLLABLE CONNECTIONS BETWEEN EACH DEVICE AND EITHER A LOW PRESSURE LIQUID SOURCE OR A HIGH PRESSURE LIQUID SOURCE, SAID MECHANISM INCLUDING A SPEED-SENSING VALVE RESPONSIVE TO THE FLOW RATE OF LIQUID DISCHARGE BY CONTRACTION OF A FIRST ONE OF SAID DEVICES, THE SPEED-SENSING VALVE ACTING WHEN THE FLOW RATE IS LESS THAN A PRE-DETERMINED VALUE TO CAUSE LIQUID DISCHARGED BY BOTH DEVICES TO FLOW TO THE LOW PRESSURE SOURCE, AND ACTING WHEN THE FLOW RATE EXCEEDS THE PREDETERMINED VALUE TO CAUSE LIQUID DISCHARGED BY BOTH DEVICES TO FLOW TO THE HIGH PRESSURE SOURCE, AND A POSITIONSENSING VALVE INCLUDING OPERATING MEANS RESPONSIVE TO THE QUANTITY OF LIQUID FLOWING FROM AND TO THE SECOND OF SAID DEVICES, THE OPERATING MEANS ACTING ON THE POSITION-SENSING VALVE SUBSTANTIALLY UPON COMPLETION OF LIQUID DISCHARGE FROM THE SECOND DEVICE TO THE LOW PRESSURE SOURCE, TO CONNECT BOTH DEVICES TO THE HIGH PRESSURE SOURCE, AND ACTING SUBSTANTIALLY UPON COMPLETION OF THE ENSUING HIGH PRESSURE LIQUID FLOW INTO THE SECOND DEVICE TO ISOLATE THE HIGH PRESSURE SOURCE FROM BOTH DEVICES.

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