Key lock
A key lock is a lockable control element in railway security technology . In contrast to a normal lock, it is not possible to simply remove the key again as it is mechanically blocked. The key can only be removed if it is released from the interlocking . Then the control element (usually a switch ) can be unlocked and changed with the key, the key is now locked in the element. The key can only be removed from its lock and locked again in the key lock when the control element is back in its basic position. While the key is removed from the key lock, the interlocking prevents the actuator from being used by a second vehicle.
The key thus becomes a token, with which either the control element is locked and can be used for the interlocking or in which the interlocking gives control to e.g. B. to enable a connecting trip from the track over the converted points.
General
Manual switches and other manually operated objects to be secured are equipped with locks, sometimes one for each position. The key can only be removed from the switch in a fixed position and inserted into the key lock. The interlocking can use the key lock to determine whether the key is locked and thus the position of the points is known. If this is the case, the desired route can be set. However, as soon as the route has been determined, changing the secured switch would pose a risk of train movement. The key lock prevents this by blocking the key from being removed.
A key switch can also be used to ensure mutual dependency, as described in the section Key lock for contact line switches.
Secured in one location
Switches from the main track to shunting systems are provided with a lock in the signal boxes. The key is either in the switch and thus enables a switch to the direction of the siding or siding or in the key lock, which secures the switch for routes. In addition, z. B. water cranes that could obstruct routes, or barriers are secured by keys and the appropriate key lock. Hand-operated form signals or individual signal levers can also be locked in the holding position with a key.
A similar example is a so-called grid switch that was used on some branch lines. The switch can only be moved when the switch operator has locked himself in a cage. He can only leave it when the switch is back in its basic position.
Secured in both positions
Switches, the branches of which can be both parts of routes, can be provided with locks in both positions, whereby only one key can be removed depending on the position. This means that only one key can be present in the interlocking and by evaluating the key locks, only routes via the branch set at this point in time are possible.
Track barriers are also secured by two locks: the signalman comes with a key, locks it in, opens the track barrier and thus gets a second key. This is either locked in a key lock in the signal box or it is dependent on a turnout, i.e. In other words, you can use it to unlock a switch (locked on one side).
If it is operationally necessary, a signal can also be provided with a second key lock for the drive position.
Key works
If many parts of the system in a train station are secured by keys, then these can be combined in a key system, which mechanically regulates the exclusion between the individual keys included; this represents a simplified form of a mechanical interlocking with its locking register . If all points are correct, i.e. the respective switch keys are present in the key mechanism and no other route is disturbed, the desired route key can be excluded and the signal can be set.
Key lock for contact line switches
Fixed earthing rods are used, especially on depot and sidings, where the contact line has to be switched off frequently . The earthing rod in and of itself is movable in this case, but firmly connected to the electrical earth . These ground rods are secured in such a way that there is only one common key. This key is used, on the one hand, to operate the horn switch (standard design of a contact line switch), i.e. to switch the contact line on and off, and can only be removed when the contact line is switched off. Without a key, the horn switch can no longer be operated. The same key can be used to remove the earthing rod from its holder, whereby the key is blocked here if there is no earthing rod in the holder (for this there is usually a coded perforated plate on the earthing rod, which prevents the wrong earthing rod from being trapped). This creates a simple but effective interdependence between the switched off horn switch and the suspended earthing rod. In addition, a second key (security key) can be secured on the earthing rod. This is mainly used for occupational safety, as it can only be removed when the earthing rod is outside the bracket. The two keys are also mutually dependent, so the catenary switch key can only be removed when the security key is in place. As long as the person responsible keeps the security key with him, the contact line cannot be switched on. He may only return the safety key once he has made sure that the contact line can be switched on. In workshops, ladders and lifting platforms can also be secured with which a life-threatening approach to an activated contact line would be possible. In this case there may be several keys in the mounting of the earthing rod, all of which must be present to switch on the contact line.
application
- In signal boxes where points are set by hand but are secured by means of key locks or a key system
- Junction points (Anst / Awanst): The connecting track is secured with a track barrier. Before the service trip, the shunter in the interlocking requests the release of the key from the key lock, opens the track lock and sets the sequence-dependent switch.
- As an adapter from the key mechanism to the relay interlocking: the points are secured by a key mechanism. The route key is not used to be able to set the signal, but enclosed in a key lock in order to determine the route in the electrical interlocking. The (light) signals are then operated by the relay interlocking.
literature
- Hans-Jürgen Arnold, Peter Naumann: interlocking Service A-Z . 3. Edition. transpress, Berlin 1986, ISBN 3-344-00057-8 , pp. 132 f .