GB2133099A - Train brake control system - Google Patents

Abstract

A multiple unit train comprising a mixture of motor cars and trailer cars has a pneumatic brake control system in which the total variation in brake pipe pressure is divided so that the first part of the variation controls the motor car brakes only and the second part of the pressure variation controls the trailer car brakes only. To the standard system shown in the drawing is added valve 5 which, on the motor car, multiplies the output of the standard distributor 2 by a value equal to the ratio of the total braking effort or weight, of the train to the total braking effort or weight of the motor cars, and on the trailer cars by a value equal to the ratio of the total braking effort, or weight of the train to the braking effort or weight of the trailer cars. The motor car includes valve 6 which is a limiting valve. Included in the trailer car is valve 7 which ensures that no air will pass from distributor 2 to the control side of valve 5 until the output pressure of the distributor 2 is at such a level that the motor car brake cylinder pressure should have reached its maximum level. <IMAGE>

Description

SPECIFICATION Brake control system In a multiple unit train comprising a mixture of motor cars and trailer cars, where the motor cars are fitted with dynamic brakes, a brake system in which the motor car brakes are applied first and the trailer car brakes are only used if the train retardation rate is still below that required, will have advantages over a brake system without these features.

The advantages gained depend on the type of dynamic braking system employed. If the dynamic braking system is of the non-regenerative type then the advantage is in the saving in wear of the friction elements of the friction brake. If the dynamic braking system is of the regenerative type there is an added advantage of increased energy saving.

Known braking systems which provide this feature require a division of the control means for the motor cars and the trailer cars. Such control systems cannot easily be applied to the normal automatic air brake system where the brake control signal is transmitted down the train by an air brake pipe and where changes of pressure in this pipe cause distributor valves on each car to charge and discharge associated brake cylinders to a value appropriate to the change in brake pipe pressure.

The car brake cylinder pressure can be further modified by an intermediate valve such that the brake cylinder pressure is appropriate to the car weight. Also on the motor cars the brake effort produced by the brake cylinder pressure may be substituted by an equivalent level of dynamic brake effort by suitable blending means.

One object of the present invention is to provide a brake control system which may easily be applied to the normal automatic air brake system by a relatively simple modification.

According to the present invention there is a brake control system for a multiple unit train comprising a mixture of motor cars and trailer cars, in which the total variation in brake pipe pressure is divided so that the first part of the variation (which may be the first part of a pressure drop) controls the motor car brakes only and the second part of the pressure variation controls the trailer car brakes only, this division preferably being in a ratio to provide an approximately linear relationship between the variation in brake pipe pressure and the total train braking effort.

For example, the division may be obtained by providing: 1) on the motor cars, a device which multiplies the output of a standard distributor by a value equal to the ratio of the total braking effort of the train to the braking effort of the motor cars, and a means of limiting the motor car braking pressure to the maximum full service pressure; and 2) on the trailer cars a device which multiplies the output of a standard distributor by a value equal to the ratio of the total braking effort of the train to the braking effort of the trailer cars, and a means of limiting the trailer car brake cylinder pressure to zero until the motor car brake pressure has reached its maximum value.

Braking effort need not necessarily be directly related to the vehicle weight. It may, for example, be biased so as to provide a greater braking effort on the motor car, or cars, than on the trailer car or cars.

If variable load braking is fitted to the cars the variable load value can be set to provide the multiplying function on both motor cars and trailer cars. The limiting values includes in the distributor can be set to limit the output to the required values on the motor car and a set load, such as that provided by a spring, may be included in the variable load valve of the trailer cars such that its output will be zero until the set load is overcome.

In the accompanying drawings:- Fig. 1 illustrates in diagrammatic form one example of a brake system embodying the invention; Fig. 2 shows a multiplying relay valve included in the system shown in Fig. 1; and Fig. 3 shows a modification of a variable load valve in accordance with the invention.

In the brake system shown in Fig. 1, the brakes on the motor cars are applied first and the brakes on the trailer cars are only used if the retardation rate is still below that required. The system of the present invention is applied to a standard automatic air brake system in which the brake control signal is transmitted down the train by the air brake pipe 1 and changes in pressure in this pipe between set levels causes the distributor valves 2 on each car to pass air to, or vent air from, the brake cylinder 4.

When the brake pipe 1 is at the highest pre-set pressure, the release pressure, the distributor valve 2 is in the release condition and the brake cylinder 4 is vented to atmosphere. As the pressure in the brake pipe is reduced, the distributor 2 operates to pass air from the auxiliary reservoir 3 to the brake cylinder 4. The pressure which is attained in the brake cylinder 4 is proportional to the pressure drop in the brake pipe 1.

When the pressure in the brake pipe 1 is reduced to the lower pre-set level, the full service brake pressure, the brake cylinder pressure is at its maximum level i.e. full service brake pressure. Any further reduction in the pressure in brake pipe 1 will not result in any decrease in brake cylinder pressure as distributor 2 includes a limiting valve (not shown) set to the value of the full service brake pressure.

Included in the motor car system is the equipment to provide the dynamic braking. This equipment 9 takes a pneumatic signal via path 11 which indicates the total level of braking required and, via path 12, it provides a signal, which may be pneumatic or electric, which is a measure of the dynamic braking actually being obtained.

Blending valve 8 then sums the brake demand signal and the dynamic brake signal such that the pressure in the brake cylinder 4 on the motor car is at a level to make up for any deficiency in the dynamic braking.

To the standard system there has been added valve 5 which is set so that on the motor car it multiplies the output of the standard distributor 2 by a value equal to the ratio of the total braking effort, or weight as desired, of the train to the total braking effort, or weight of the motor cars, and on the trailer cars by a value equal to the ratio of the total braking effort, or weight of the train to the braking effort or weight of the trailer cars.

As shown, it has been assumed that valve 5 will be some form of multiplying relay valve and the output of distributor 2 is fed to it via a dummy cylinder 10.

The motor car equipment includes valve 6 which is a limiting value to limit the maximum pressure applied to the control side of valve 5 to a valve which ensures that the pressure in brake cylinder 4 does not exceed the maximum full service pressure.

Included in the trailer car equipment is valve 7 which ensures that no air will pass from the distributor 2 to the control side of valve 5 until the output pressure of the distributor 2 is at such a level that the motor car brake cylinder pressure should have reached its maximum level.

As valve 6 duplicates the function of the limiting valve included as part of a standard distributor fitted to the motor car, by arranging that the limiting valve in the distributor has the necessary range, valve 6 can be omitted and the distributor limiting valve set to the required value.

One suitable form of multiplying relay valve is shown in Fig. 2, where control pressure entering port C acts on diaphragm F and the resultant force acts on end of lever D which moves about pivot E to operate inlet/exhaust valve G. The inlet/ exhaust valve G then operates to pass air from the supply point A to the supplied point B, or to vent air from the supplied port B. The pressure at the supplied port B acts on diaphragm H, the resultant force acting on the other end of lever D. The ratio between the pressure at supplied port B and the control port C is dependent on the leverage ratio and therefore on the position of pivot E. A valve of this type may be used as the multiplying valve 5, on both motor and trailer cars.

As this type of valve is used to provide load control of braking by varying the position of pivot E in proportion to the vehicle weight, where variable load braking is required the same valve can be used to provide a variable load control and to provide the multiplying function.

To meet these requirements a variable load valve similar to that shown in Fig. 2 would be included in the system in the position of valve 5.

.The output of distributor 2 would be connected to port C via the dummy cylinder 10, port A would be connected to auxiliary reservoir 3 and port B connected to a blending valve 8 on the motor car and brake cylinder 4 on the trailer car. The position of pivot E would be chosen at some load condition, say full load, to provide the multiplying factor required and the pivot E would then vary about this chosen position as the load varies.

The arrangement as described above would enable a standard automatic air brake system which includes variable load control to be modified to provide the feature required with the addition of only valve 7 to the trailer cars equipment. Valve 7 can also be omitted if the variable load valve fitted to the trailer cars is designed to include a spring J, as shown in Fig. 3, which provides a force to oppose the force resulting from control pressure at pot C acting on diaphragm F. The force from the spring J is such that there will be no output from the variable load brake to the brake cylinder 4 until the output pressure of distributor 2 is at such a level that the motor car brake pressure should have reached its maximum level.

Claims (10)

1. A brake control system for a multiple unit train comprising a mixture of motor cars and trailer cars, in which the total variation in brake pipe pressure is divided so that the first part of the variation controls the motor car brakes only and the second part of the pressure variation controls the trailer car brakes only.

2. A brake control system according to Claim 1 and in which the division of brake pipe pressure is in a ratio to provide an approximately linear relationship between the variation in brake pipe pressure and the total train braking effort.

3. A brake control system according to Claim 1 or Claim 2 in which the division of brake pipe pressure is obtained by providing: 1) on the motor cars, a device which multiplies the output of a standard distributor by a value equal to the ratio of the total braking effort of the train to the braking effort of the motor cars, and a means of limiting the motor car braking pressure to the maximum full service pressure; and 2) on the trailer cars a device which multiplies the output of a standard distributor by a value equal to the ratio of the total braking effort of the train to the braking effort of the trailer cars, and a means of limiting the trailer car brake cylinder pressure to zero until the motor car brake pressure has reached its maximum value.

4. A brake control system according to any preceding Claim and in which braking effort is directly related to the vehicle weight.

5. A brake control system according to any of Claims 1 to 3 in which the division of braking effort is biased so as to provide a greater braking effort on the motor car, or cars, than on the trailer car or cars.

6. A brake control system according to any of Claims 1 to 3 in which variable load braking is fitted to the cars and the variable load value is set to provide the multiplying function on both motor cars and trailer cars.

7. A brake control system according to Claim 6 and in which limiting values are included in the distributor which is set to limit the output to the required values on the motor car; and a set load is included in the variable load valves of the trailer cars such that their output will be zero until the set load is overcome.

8. A brake control system according to Claim 7 and in which said set load is provided by a spring.

9. A brake control system, according to Claim 3, when used to modify a standard air brake system on a train comprising one or more motor cars and one or more trailer cars, the modification including the addition of said devices.

10. A brake control system substantially as hereinbefore particulariy described and as illustrated in the accompanying drawings.