Key work
The key work is an element of train protection with which the protection of mutually exclusive routes of trains can be implemented in a technically simple and inexpensive way using keys enclosed in a bolt box.
functionality
In contrast to the interlocking , the dependencies on the guideway elements are not created using wire or electrical cables, but with the help of keys that are unique in the secured track system . These are at the crossover to track locks or rarely also barriers cranks , but also applied to other roadway obstacles such as mobile bridges or gates locks whose keys can only be removed when this track element is in the desired location. With turnouts, there is a separate key for each position.
The key work here establishes the dependency between the track elements and contains a large number of locks that are interdependent by means of push rods. Key works are often structured in tabular form. The keys of the guideway elements move vertical slides, while the so-called route keys move horizontal slides. The two types of slides are made dependent on each other via locking pieces as required. In concrete terms, this means that a route key can only be moved and removed if all of the keys fixed by the locking pieces are in the key system. At the same time, these are set by removing the route key and removing these keys is prevented.
In addition, dependencies between the route keys are also possible, so that additional route exclusions (e.g. preventing simultaneous entry from both sides into the same track) can be easily implemented. Some key work types also have the option of coupling them with block fields and thus also realizing direct dependencies between the key work and other key work or signal boxes in the station .
use
Key works can be used in a wide variety of ways. The spectrum ranges from securing simple junctions to complex train stations with local switches, but key works can also be used to create dependencies within interlocking systems.
In the simplest design for securing junctions, the key system only contains a route key which, when removed, holds the switch key for the main track and the key for the side protection switch or track barrier . In train control operations , key works are often used as the only technical safeguarding of the route in the stations. In addition to the route through the continuous main track , other routes can also be secured using route keys. In the basic state, the route through the continuous main track or, if fallback switches are used, is placed on the two entry tracks and the associated route key is removed. The train driver of each train receives the so-called train driver's key when driving on the route, with which he can unlock the route lock of the key factory if necessary.
But key works can also be used in more complex train stations that are permanently manned by a dispatcher . Most of these stations are equipped with entry signals . In the case of form signals , signal levers are arranged in or in front of the interlocking, which can be unlocked and shifted with the help of the route key. In the case of light signals, the route key can be used to operate an electrical switch that switches the entry signal to travel. Exit signals are usually not set up, instead consent for a train to exit is given with the help of a command staff (Germany) or verbally / by telephone (Austria).
In such arrangements, the switches are often designed as manual switches that have to be adjusted by the dispatcher on site and locked with switch keys. However, it is rare to find arrangements in which all points and signals are electrically or mechanically remote controlled, but the dependency between the points and signals is established using keys and one or more key mechanisms.
In the case of large train stations, it is also possible to connect the key works with fields in the station block, so that dependencies can be established between the various key works and signal boxes of the station . Here the points are then set by point officers . While this arrangement can only be found at a few train stations in Germany, central locks with local switches and light signal devices or a lever bank for the signal levers can still be found on many less traveled routes in Austria.
In addition, there are other special applications such as the production of additional dependencies when switching through mechanical interlocking.
Types
German standard key work
The standard key system was a widespread technique, especially in smaller train stations with manually operated points.
The key system consists of 16 locks, of which a maximum of 10 can be used for routes. For each route there is a colored horizontal line with holes. Behind each hole there is a colored marking of the switch slide, which either takes the color of the line or is red. A route key can only be excluded when the correct keys are included or excluded. Then the line of the respective route is continuous. If the route key is blocked, the signalman can use the red points in this line to determine which points still need to be set. There are also 16 additional slides that are connected from above. In this way, additional switch locks or block fields for station or route blocks can be built above the locking register.
internal structure
The standard key system consists of a number of locks and the lock register. Route keys are marked green in Germany, signal keys (in combination with the route) are marked red and points / track lock keys are marked blue. A vertical slide is connected to the locks, which is referred to as a switch slide (yellow in the sketch), but is also available on routes. Various locking pieces (gray) can be attached to the slide. If the key is locked, the slide is at the top; if the key is locked, the slide is in the lower position. In the case of routes, the route slide (light green) is connected via an angle piece (green). There are teeth (gray) on the route slide, which together with the locking pieces realize the exclusion.
If the route key is excluded, the (turnout) slide moves down and the route slide moves to the right. However, this only works if there is no locking piece in the way, otherwise both slides and the key will be blocked.
In the example (sketch), the track barrier 1 (with consequential dependency on switch 3) is placed and locked, the locking pieces are not an obstacle for any of the routes. If route b is to be set (lowest route slider), the locking piece of the minus position of switch 1 is in the way. The switch must therefore be brought into this position and locked in this way, the key 1 must be included in the key work. Then the locking piece is at the top and therefore no longer in the way, the slides can move and the route key can be removed. At the same time, however, the tooth of the route slider slides under the locking piece and thus blocks the slider and key of the switches and track barriers secured for the route. Only when the route key is locked again in the key system can they be reset.
Custom-made products (Germany)
Key works are often put together from a combination of individual locks and metal slides that are cut to match and are mounted on a wooden plate.
Combination of several mechanical key locks (Germany)
Simple key works in train control operations can also be composed of several individual mechanical Daum key locks. When it comes to securing, a distinction is usually not made between the different directions of travel, but a key lock is used for each route.
With the Daum key locks, no interdependencies are possible, so route exclusions cannot be implemented in a simple way. However, two or more key locks can be combined to increase the number of keys to be blocked. A route key then blocks all turnout keys from several cooperating locks, as can be seen here in the picture with the two middle key locks.
It can therefore only be used in very simple circumstances. Here, a key lock is usually arranged for each route. Often the routes of the two station heads are locked together with a route key, so that if the route key is withdrawn, it is generally possible to drive through the station.
Central Castle (Austria)
The structure of the Austrian central lock is similar to the German standard key system. However, the route locks are not attached here next to the switch locks, but one above the other on the right edge of the central lock. The route sliders are thus operated directly by the route keys and not indirectly via angles.
Due to the smaller design of the Austrian locks and keys, as well as an offset arrangement, the Austrian central lock is also much more compact than the standard key system.
The central locks were built in many different sizes. One of the largest examples has 22 route locks and 44 switch locks.
A direct connection with field block fields for the station block is not possible.
Central locks are still in use in large numbers in Austria.
Drum key factory (Austria)
The drum key system was first used in Austria in 1931 and served on the one hand as a temporary replacement for signal boxes that were out of order due to construction work, and on the other hand for the permanent security of stations with locally operated key-dependent switches.
The structure differs significantly from the conventional key works. The locking pieces are housed here on two rotatable rollers. The route is selected by turning the roller; the name of the route and the switch keys required for the setting are displayed in a shop window. If all the necessary keys are locked, the roller can then be moved inwards by 12 mm. One or more signal keys are then released by the shift. In contrast to the route keys of the central lock, one signal key can be released from several different routes.
In a drum key system, up to 10 signal keys can be made dependent on up to 20 turnout keys. 6 routes are possible per roller, i.e. a total of 12 routes. In addition, the key system can be made dependent on other interlockings or key systems of the station via field block fields attached to it.
Thanks to its particularly compact design, the drum key system is also easy to transport and can be set up in the switchman's office without any problems .
Only a few examples of the drum key factories are still in operation in Austria.
literature
Arnold, H.-J .: Railway safety technology, transpress Verlag, Berlin 1987, page 36ff
Individual evidence
- ^ A b F. Zuleger: The key work of the Austrian Federal Railways . In: Journal for the entire railway safety system (Das Stellwerk) . No. 3, 1932, pp. 25ff, 44ff.