Railway air brake
The air brake is mainly used in railway operation for braking of the trains. George Westinghouse she developed in the U.S. in 1869 specifically for railway operation. In his invention, he received a U.S. patent on March 5, 1872.
The pneumatic brake pressure air used both as source of energy as well as for controlling the braking operation. The actual braking effect is exerted by the pressing of the brake pads on either the bearing surfaces of the wheels or brake discs. The brake discs of railway vehicles are located on the axis of the wheel and are made - for better heat dissipation - mostly from double panes.
History
The air brakes of most European railways are of international standard and are compatible with each other. The main reasons for the introduction of air brakes were the direct controllability by the driver and the ability to slow down all the cars of a train evenly. In addition, passenger trains were able to get an emergency brake that can be operated by the passengers at risk.
Before the air brake was available, the trains were manually braked. The individual cars were occupied by a brakeman, who operated a hand brake. In a corresponding signals of the engine-driver, the brakes had to be tightened or loosened. For passenger trains a pull rope was sometimes on the outside of the cars attached, which was connected to the locomotive whistle, it served as a kind of emergency by the train crew or the passengers could trigger a beep for the brakeman at risk. The activity of the brakeman was extremely distressing, since the seat was unprotected on an open platform a long time. Only later the so-called brakeman offered some protection against the weather.
When introducing an operable on the locomotive continuous brake through the entire train other systems have been considered, together with the air brake system. So it came the transfer by vacuum ( vacuum brake ) or the brake with cable (eg Heberleinbremse ) apply. Especially the cable brakes but had limited their distinct disadvantages and therefore remained on niche opposite the brakes with compressed air or vacuum. The vacuum brake gain wider appeal, in part, also full tracks (eg from 1891 with the previous tracks of today's Austrian Federal Railways or in Spain). You could meet only one of the alternatives all requirements imposed on such a brake in the same extent as the air brake system. In the vacuum brake, the disadvantages over the air brake especially on long trains noticeable. Therefore, they could hold in areas with short trains, especially on narrow gauge networks, to this day.
The trains on main lines were fitted in the 19th century to a large extent with air brakes. The First World War delayed the development of a freight train brake. Founded in 1922, The International Union of Railways took over the development of a freight train brake for international transport in the hand.
Indirectly acting pneumatic brake
1 brake clutch 2 Coupling cock 3 Notbremszug 4 Notbremshahn 5 parking brake lever 6 Brake lockers 7 brake spindle nut 8 brake shaft 9 Handbremszugstange 10 slack adjuster 11 control rod 12 Horizontal lever
13 load bar 14 Mechanical load change with empty bar 15 retraction spring 16 brake cylinder 17 Fixed point lever 18 operating linkage to mech. load change 19 brake bar 20 vertical lever 21 fixed-point 22 main air line
23 pad 24 brake triangle 25 auxiliary reservoir 26 handle to trigger valve 27 control valve 28 control container 29 Bremsausschalthahn 30 operating handle for Bremsausschalthahn 31 GP- exchange 32 Switch-over load transfer
The indirect -acting, automatic or automatic air brake is the standard brakes for trains. It is a continuous brake, with all vehicles connected to it a train or a cab Shunting from a powered unit or a driving coach from be served. In this brake, the compressed air to the brake cylinder is supplied indirectly by the control valve of the auxiliary air reservoir, which is controlled by the main air line pressure. The brake is also called automatic or automatic air brake, because it automatically causes the braking of each draft at a train separation.
Basic structure and function of
In principle, the air brakes of a system of compressed air tanks, brake cylinders, and air pipes on each vehicle, which are connected in the compilation of a train at the coupling points with each other.
All vehicles of a train have a continuous, interconnected main air line (HL). An air compressor on the traction unit provides this via the driver's brake valve with air of typically 5 bar pressure ( the normal working pressure ).
The main air line is used in addition to the main air reservoir pipe (HBL ) at the same time as an energy supplier and signal transduction. Each car also has an auxiliary air reservoir is constantly replenished via a control valve from the main air pipe, as well as compressed air-operated brake cylinder and brake pads on the wheels and disc brakes in the wheel or on the axle shaft. The principal control for the brake system is the driver's brake valve on the motor vehicle ( such as a locomotive ) or the control car.
The brake is released ( inactive ) when all auxiliary reservoir are filled and there in the main air line the normal working pressure. The pressure in the main brake pipe is lowered, the control valves direct the compressed air from the auxiliary air cylinders in the brake cylinders, press the thereon via a brake linkage, the brake pads at the wheels or discs or actuating the brake calipers of the disc brakes. The brake system is dimensioned so that when lowering the pressure of the brake pipe to about 3.5 bar (full braking) and at a completely empty main air line (0 bar at a quick, emergency or emergency brake ) in the brake cylinders, a pressure of max. 3.8 bar is pending. After a braking operation, the brake is released by the replenishment of the main air line to the normal operating pressure of 5 bar. The control valves go by in their initial position, the auxiliary air tank to be filled, the air from the brake cylinders escapes into the open air and the brake pads loosen.
Overlinked air pump design Nielebock -Knorr for steam locomotives
Air compressor of an ICE 1
To reducing the pressure in the main air line and thus trigger the braking process, the driver's brake valve is actuated on the train or locomotive usually by the driver. There is also a trigger means on the pressing Notbremsventilen that are usually present in addition to passenger cars. And the rupture of the main air pipe in the case of a train separation during driving leads to the braking operation. In contrast to the metered braking by the driver's brake valve ( service braking of the first braking step up to full braking - VB ) takes place in the last two cases, a rapid deceleration.
Einlösige brake
A " einlösig " designated as a brake does not allow a gradual Take Back the braking effect. For a minor increase in pressure in the main air line after a preceding phase, the control valves go (each of which cars each one has ) to the release position, so release the brake the car in question completely.
If the driver's brake valve is placed in the solvent or driving position not long enough for a (even minor ) increase in pressure in the brake pipe, auxiliary air tanks are not refilled each under a car with compressed air.
If you want slowed again in this situation (because the train driver has miscalculated ), the pressure in the main air line must be further lowered than in the previous braking. If there are several regulations of the braking force - without the driver's brake valve to bring sufficient time in the driving position, and thus to fill the brake system - the pressure air supply to be fully depleted from the main air pipe, but also from the auxiliary air tanks connected to it. There is then no more air for a braking effect available. In technical jargon this is known as " exhausting the brake".
For this reason, the repeated triggering and brake on is to refrain ( " follow-up "), especially when entering stump tracks. Must on long slopes brake are released, the drive is previously to slow so much that enough time is left to fill in the main air line and all auxiliary reservoir in the train on the solvent or driving position of the driver's brake valve again. The operation of the brake einlösigen required on long slopes a lot of experience.
In control mode in central Europe, the einlösige brake is no longer to be found; it was almost completely through the mehrlösigen brakes of types Knorr brake unit effect (KE ), Oerlikon ( O) and Dako ( Dk) replaced. An exception is the einlösige Matrossowbremse ( M) of the sometimes encountered on German railways freight cars of the Russian Railways. This is - adapted to there usual larger train lengths, where mehrlösige brakes can not be used without problems - as well as in the United States.
See also section control valves of the previous einlösigen air brake control valve in the article (railway)
Mehrlösige brake
To avoid exhausting the brake and train drivers to facilitate regulating the braking effect developed is mehrlösige brakes. This resulted in Germany in 1918 for the introduction of the Kunze -Knorr brake developed by Bruno Kunze and Georg Knorr. The in the variants than Kunze -Knorr brake freight train ( Kkg ) and later as a passenger train brake ( Kkp ) has been introduced. This was further developed by Wilhelm Hildebrand and Georg Knorr. The Hildebrand -Knorr -Bremse ( Hik ) you can gradually slow down and solve; when loosening the control valve fills the auxiliary reservoir under a car every once again.
While the Kunze -Knorr brake nor a brake cylinder with two working chambers had ( two-chamber brake), the Hildebrand -Knorr -Bremse ( Hik ) is a Einkammerbremse. An important innovation of the Hildebrand -Knorr -Bremse against the Kunze- Knorr -Bremse is the introduction of the three- pressure principle. While in the Kunze -Knorr brake only the pressure ratio between the main air line ( HL ) and brake cylinder was used for control - what with leaking brake cylinder led to impaired braking effect due to the constant emptying of the reservoir air tank - is at the Hildebrand -Knorr -Bremse also the reservoir pressure included. Is leaky brake cylinder and below the main air line pressure through the reservoir pressure compressed air is fed directly from the main air pipe to the brake cylinder, thus preventing depletion of braking force. To utilize this function, at the same time the self-regulating driver's brake valve was developed that only about 20 years later, however, came in large numbers to use and is now part of the standard equipment of locomotives.
See also section control valves of the mehrlösigen air brake control valve in the article (railway)
Brake positions and changeover devices
One distinguishes the braking positions after the braking effect, they can muster, and the response time. The braking positions G and P function without power, which is why they come to freight in question. The R- brake requires an anti-slip, which is mechanically, electronically controlled in modern vehicles in older vehicles to avoid locking of the wheels; only this can apply mechanically considerably more than 100% braking weight because it increases the braking force above 55 km / h.
- Braking position G = freight train slowly responding brake with a brake cylinder filling time 18 to 30 s and a release time of 45 to 60 s
- Braking mode P = passenger, also called RIC brake, fast-acting brake with a brake cylinder filling time 3-5 s and a release time of 15 to 20 s
- R braking mode = fast (Rapid), high-performance brakes with brake booster ( trains ), but the same filling and release times, as in the P- brake
- R braking mode Mg = express (Rapid) with magnetic brake ( fast moving passenger trains )
A conversion between the brake positions is done by hand. Here, the required braking position must be set in each vehicle of the train separately. The associated shift lever are mounted on cars on the outside and readily distinguishable with a yellow ball handle (brake types freight train and passenger ) or loop handle (only passenger train brake types ) provided. For tractive rolling the shift lever are largely located within the vehicle.
There are also load-dependent control of the braking force to counteract over-braking at low load and low braking force when loaded vehicles. The variable load (with A for short) is used both for wagons, as well as passenger car use. They are available in different designs of mechanical transmission: through brake linkage change or pneumatic transmission (eg via a load sensing ) with secondary steel springs. In secondary suspension air springs through the air spring pressure is used as load-dependent signal because the air suspension valve always the same spring height compensates the pressure provides a load signal. There are linear or stepwise amplification. Only applicable to wagons, one finds the manually adjusted load changes. This has the positions " empty", "loaded" and to some extent " partially loaded". The manual load changes is set over a red crank handle on the longitudinal beam of the car.
The brake equipment of the vehicles is written in abbreviated From on the long sides.
Hochabbremsung
The Hochabbremsung is an extension of the air brake for higher speeds. The characteristic curve of a friction brake decreases at higher sliding speeds of the friction elements. To compensate for the speed-dependent braking has been introduced. It regulates a Achslagerbremsdruckregler with a pressure intensifier the current brake pressure. For a higher brake pressure a pressure supply with more pressure is required; but this is only possible for locomotives. To remain backwards compatible and fail-safe, the brake like a mehrlösige brake works the same way. Only between the brake cylinder and the control valve, the pressure booster is interposed. It is important to distinguish between the Hochabbremsung of locomotives and passenger coaches. For all vehicles with electronic antiskid the Hochabbremssignal is made of Gleitschutzrechner attributable Achslagerbremsdruckregler.
Locomotives
At speeds above 70 km / h, the pressure booster increases the pressure to a maximum of 5.5 bar ( brake position P2 ) or 8 bar ( R braking mode ). When the measured speed from Achslagerbremsdruckregler below about 55 km / h ( hysteresis ), the pressure in the brake cylinder is automatically adjusted to the value of the normal Niedrigabbremsung. The compressed air for the Hochabbremsung is taken from the main air containers.
Coaches
While in passenger trains usually the main air reservoir pipe (HBL ) is mitgekuppelt that supplies the wagon train with 10 bar compressed air; in the case of train separation, but this line is opened so that no increased pressure more states available. Even when adjusting older cars without main air reservoir pipe in a wagon train with no power HBL - air at 10 bar would be guaranteed. The Hochabbremsung is therefore fed at the coaches with the normal 5 bar from the main air line. The higher deceleration is achieved by larger reservoir (up to 200 liters per car ) and usually two large-capacity brake cylinder. During normal braking the highest brake cylinder pressure is about 1.7 bar, at Hochabbremsung about 3.8 bar.
Gleitschutzregler
Due to the low Haftwiderstandsbeiwert of steel on steel rail wheels can easily block. This gives the stationary bike - due to the sliding friction on the rail - a flat point, what the smoothness impaired. To minimize this damage, centrifugal governor has been used as an anti-slip first. Two spring-loaded flyweights rotate with the shaft and hold the dump valve closed. If there is an abrupt change in rotational speed, the weights and be deflected off the brake of the axle. The axis is accelerated again, so close the flyweights the valve again for the continued braking.
Newer electronic Gleitschutzrechner determine the axle speed by magnetic sensors and compare them with a virtual vehicle speed. It is to slide the axle, the brake pressure is held, and then only gradually reduced until the shaft is rotated again. Then, the required braking pressure is built up again.
Brake pipe emptying accelerator
At high speeds, the timing is very important. The speed at which a pressure wave travels in a pipe is, with a maximum of 290 m / s ( on the order of the speed of sound) relatively slow; the real pressure drop due to the expansion of the air is even slower. Thus, the trains slow down evenly, the reaction rate of the brake valves for long freight trains was artificially slowed. For fast trains, more uniform rolling stock and shorter train lengths, this is neither necessary nor desirable. To accelerate the pressure drop and thus to shorten the response time of the brakes on the train, valves are installed, register the rapid pressure drop in the main air line and accelerate by opening additional outflows this pressure drop further. Thus, although not the breakdown rate is increased, but the rate of pressure drop, which is necessary for the response of rapid deceleration in the brake valve.
Electro-pneumatic brake ( ep brake)
Indirect electropneumatic brake ( better electro-pneumatic brake control with indirect effect ) is a superposition of the braking control of the compressed air line by the additional, but switched off control of the brake valves, by means of electronic signals. With the electro -pneumatic brake control, the disadvantage of the low penetration rate of air pressure brake is off. In addition, it allows the engineer if in doubt, to bridge a solid emergency brake (called Emergency brake, NBÜ ) to bring the train to a cheap place to rest.
In some non- UIC compliant types electropneumatic brake even without the action of the main air line operated ( so-called direct electro-pneumatic brake). The main air pipe is at all switched on only in case of tow. All brake controls run on braking computer and electro-pneumatic converter. In this construction, electrical active power brakes to work simultaneously with pneumatic brakes and act even when sliding along the axes.
Direct acting brakes
In einlösigen brakes when driving on long and steep downhill stretch was a danger of Erschöpfens the brake and the burnout of the train. Affected lanes equipped their trains with a second air line and an additional, direct-acting pneumatic brake. In this brake, referred to in Switzerland as Regulierbremse, the total amount of air only through the additional driver's brake valve ( Regulierbremsventil ) is pressed onto the train into the brake cylinder. The compressed air is taken from the main air reservoir via a pressure regulator. When releasing the air escapes through the driver's brake valve. By making small changes in pressure at the driver's brake valve can be continuously regulated during braking as well as when releasing the pressure in the brake cylinder. However, the direct-acting brakes react extremely sluggish in all trains and requires the engine driver a lot of practice, exact knowledge of the track and a farsighted driving.
With the prevalence mehrlösiger brakes, the direct-acting brakes have been expanded into the car from the mid- 1950s. The direct brake is now only on the locomotive or control car and optionally to other locomotives in a multiple unit control. Because the brake is only used for shunting, it is called in Switzerland Rangierbremse. In certain cases, the direct-acting brake is controlled by the control cars from electro- and in this case may also act on the traction unit.
Time work on brakes
As a safety-relevant components brakes on rail cars must be checked regularly and maintain. This work must be carried out by specially qualified personnel ( " brake locksmith "). The provisions of the VDV apply to the field of non- federally owned railways in Germany 885 (Maintenance Guide brakes and air tank at the NE railways - IBD -NE) as recognized rules of technology. Exist for the division of Deutsche Bahn AG rules with similar content.
The IBD -NE currently provide for four types of brake revisions before ( condensed version):