A friction braking system for a railway train is powered from an air supply. The level of brake demand has been traditionally controlled by an on car control valve (the distributor valve) which senses the air pressure in a brake control pressure pipe, the pressure in this pipe dictating the current brake demand.

Such a system has generally (but not always) been used for freight applications where no electrical supply has been available.

However the rail industry may move in the future to a system where an electrical supply is made available throughout the train. In this circumstance the brake control pressure pipe control system will be replaced with an electrical equivalent, i. e. a serial communications link or a radio link.

Nevertheless, a period of time will exist where trains will be made up of mixed cars, some being purely air controlled and some electrically controlled. In the transition period the electrically controlled units will need to be dual systems being able to use either the brake control pressure pipe or the electrical control signal system.

According to the present invention, there is provided apparatus for controlling a brake system operable using an air supply, the apparatus including electronic control means for controlling air distribution and air to electrical conversion means for generating an electrical

supply for energising the electronic control means using air under pressure from said air supply.

Said air supply could be derived from sources including a train brake control pressure pipe or a train brake supply pipe, for example.

Said air to electrical conversion means may be supplied with said air under pressure directly from said air supply.

The apparatus may include a distributor valve coupled with said air supply and which is controlled by said electronic control means and distributes air to at least one brake actuator of the apparatus via a supply connection.

In this case said air to electrical conversion means may be supplied with said air under pressure from an exhaust outlet of said distributor valve and/or from said supply connection.

Said electronic control means may control air distribution either as a result of sensed pressure in a brake control pressure pipe or as a result of an electronic brake control signal. Such an electronic brake control signal may be providable via a signal line and/or a radio link control (which control may have an electrical supply provided by said air to electrical conversion means).

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of apparatus according to an example of the invention; and

Figures 2 and 3 are schematic representations of apparatus according to alternative examples of the invention.

Referring to Figures 1,2 and 3, in which the same reference numerals are used for the same items, reference numeral 1 designates a train brake air supply line, reference numeral 2 designates a distributor valve which distributes air to one or more brake actuators 3 via a supply connection 4 and reference numeral 5 designates an air exhaust outlet of valve 2.

Reference numeral 6 designates a train brake control pressure pipe from which a signal representing sensed pressure on a line 7 is applied to an electronic controller 8, which also receives on a line 9 a train electronic brake control signal and on a line 10 a signal representing sensed pressure from distributor valve 2. On a line 11, controller 8 provides a valve control signal to distributor valve 2.

In the Figure 1 example, an air to electrical converter 12 is fed with air directly from supply line 1 and provides an electrical supply to controller 8 on a line 13. However, the air supply may be instead supplied from the air exhaust outlet 5 as shown in Figure 2 or from the air supply connection 4 as shown in Figure 3 (or by a combination of two or more of the techniques of Figures 1,2 and 3).

In each example, the apparatus may operate as a dual system in that the electronic controller 8 is able to respond either to the brake control pressure pipe signal or the electrical signal, so will be able to function in either environment.

In each example, the apparatus draws its power by converting air under pressure into electrical energy via

converter 12, from the air supply line 1 in the case of Figure 1, the air exhaust outlet 5 in the case of Figure 2 or the air supply connection 4 in the case of Figure 3.

The electrical energy produced is used to power electronic controller 8. This in turn monitors the input control signal and produces output control signals to the distributor valve 2. This ensures the air pressure sent to the brake actuator (s) results in the required level of brake effort.

No extra energy down the train, local generation or storage is therefore required.

In each example, in addition to or as an alternative to the provision of signals on line 9, there may be an optional radio link control 14, whose electrical supply is provided on a line 15 from converter 12, control 14 providing brake electronic control signals to controller 8 on a line 16.