Driver's brake valve

The driver's brake valve (abbreviated FBV ) is a complicated valve block to control the air brake system of railway vehicles. It regulates in dependence of its position, whether the brake pipe a compressed-air brake is vented and will thus be initiated or maintained, braking, or if the brake line is connected to a compressed air producer and compressed air storage tank, and thus the brake is released again and remains dissolved. This apparatus is located in the cab of locomotives, power or control car, which explains its name.

Positions

A driver's brake valve has mostly about following detented positions of the control lever, the arrangement may differ depending on the design though.:

Filling position - In this position the main air line (HLL ) of the train bypassing the pressure regulator to the main air reservoir ( for locomotives ) or the main air reservoir pipe is placed (when control car ). This causes rapid filling of the main air line, and thus a release of the brakes.
Driving position - the main air reservoir is connected to the HLL via the pressure regulator in the FBV, which regulates constant 5.0 bar in the HLL. Air losses through leaks or the desserts of the auxiliary reservoir to the vehicles are offset by.
Center position - In this position the FBV will close its connection to the main air line completely. Pressure losses in the HLL are not balanced. On locomotives with multiple driver's brake valves can be shut down so that the FBV unused. Furthermore, the center position is used in the HLL - tightness test under the brake test.
Final position - for FBV with continuous air venting in the braking position, this position serves to maintain a certain HLL pressure permanently. For this purpose, air losses are compensated on the train from the pressure regulator. This was since the beginning of 20th century art. Older FBV had to instead be placed in the center position, thus increasing the braking effect caused by leaks in the train inadvertently reinforced over time.
Braking position - This is either a position in which the brake pipe can be vented continuously and infinitely ( " time-dependent activity" ), or by several detented level with which a specific HLL - pressure can be selected directly ( " position-dependent activity" ). There are typically combinations of infinitely variable pressure in the range of weak braking effect and stepped Vorwählung in higher braking speeds. Flat slide and rotary vane FBV work always time-dependent, self- regulator depending on position, electronic FBV are available in both time-and position-dependent types.
Quick braking position - over a broad cross-section of the HLL is quickly vented to ambient air pressure, so that the maximum braking force is quickly available.

Technical Development

Flat slide valves

In the simplest case, controls the position of the operating lever, only the size of the valve openings, as quickly escapes the compressed air from the brake pipe or to flow into the brake pipe from the reservoir. Namesake of FBV was the built-in flat slide with different sized holes. Such driver's brake valve had the following disadvantages: Lack of make-up in the final position, thus it came through leaks in the train to a slow self-energizing braking effect. The individually -propelled locomotive had to be braked with the indirectly acting and einlösigen brake, which was extremely unsatisfactory shunting. For the flat slide, the installation of an additional direct-acting mehrlösigen brake acted on the existing brake linkage indirect locomotive brake was not possible. Due to long remain in the filling, the brakes could be overloaded in the train and were made permanent until they were completely exhausted. Furthermore, certain the length of the train, how long had to remain the driver's brake valve in the braking position.

The latter problem was solved in the early 20th century by a surge tank was added by a defined size to FBV. The FBV lowered then first the pressure in the expansion tank, which was on time, regardless of the length of the train. It was only via a relay valve then the HLL pressure to the pressure in the expansion tank was adjusted.

Rotary valves

Next step was the development of the use of a rotary valve instead of the flat slide. This allowed the installation of a supplemental brake valve for direct-acting brake. As early as 1910, therefore, were flat slide valves overhauled than technical.

A further improvement of the rotary valve involved adding the final position. This was made possible by integration of a make-up in the balancing mechanism so that any desired HLL pressure could be held.

Driver's brake valve, the rotary valve design are partly still in use today. In German-speaking countries these are in particular the types Knorr 8 ( for locomotives with a cab ) and Knorr 10 ( for traction unit with two driver's brake valves).

Self- regulator

Last stage of development purely pneumatically acting driver's brake valve was the so -called self- control. For FBV this type of pressure regulator is integrated into the FBV rather than fixed at 5.0 bar, but designed to be adjustable. It thus replaces the dessert Mechanism of old rotary valves. Overloading of the brakes is prevented by a filling surge is only a function of pressure and time- limited. For parties brakes, the control valve bar HLL pressure does not dissolve completely in 5.0, called component of HLL pressure can be temporarily increased to up to 5.3 bar with a " equalizers ". By a slow reduction of the increased pressure of 5.0 bar, a response of the control valves can be prevented. This then set themselves to the control pressure of the FBV, so that the Angleichvorgang must be executed only once. Although the self - regulator valve had been developed before the Second World War by the company Knorr, it sat only in the postwar period through and was used in virtually all new build locomotives. In Germany, widespread are the types Knorr D2, D5 its variant ( with the possibility of a controller coupled to carry a dynamic brake or independently of this braking ) and for railcars Knorr EE4.

Electronic driver's brake valve

The latest generation of driver's brake valves no longer works purely pneumatically, but uses the lever positions by means of potentiometers electrically from. The desired brake pipe pressure is formed in regular operation outside the FBV control unit by means of outlet and filling solenoid valves by a braking computer. There are typically automatic Angleicherfunktionen by the braking computer. It will first be given a slightly higher pressure in the event of transfer of HLL generally FBV in the ride position before it is slowly lowered to the usual 5.0 bar. Only as a fallback is still a step in the pneumatic driver brake valve is present, especially for the quick braking position. A common representative of this type is the FS42 Knorr, which comes on many three-phase locomotives used.

Knorr-Bremse Control car (rail)

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