Screw coupling
The screw coupling , even UIC coupling or UIC standard coupling , is the most European railway vehicles used clutch . In contrast to more modern couplings , the screw coupling can only transmit tensile forces and must be connected or disconnected by hand.
technology
Every wagon equipped with screw couplings has a spring-mounted draw hook in the base frame , on the eye of which the lugs are hung with a bolt behind the draw hook mouth . The first nut of the spindle is attached to the brackets . On the spindle, with an occasional folding clapper to be moved, which is provided with a further nut bracket attached. All connections can be rotated about axes across the track, the bracket also about the axis in the longitudinal direction of the track. With the clapper may spindle are rotated, which on the one hand, left-hand thread and on the opposite side of a right hand thread which are constructed as round threads are executed. By turning the spindle, the distance between the two nuts is shortened or lengthened. This process is called short and long in railway terminology . When not in use , the coupling chain is hooked into a hook on the buffer beam under the draw hook. In the shunting service, it is also common practice to hang the coupling chain of shunting locomotives into one's own tow hook.
To connect two vehicles, the bracket is hooked into the towing hook of the neighboring car and the connection is shortened by turning the spindle with the help of the lever until the buffers are slightly pressed in. After shortening, a maximum of two thread turns remain free on both sides of the spindle between the nut and the thread attachment of the spindle. The engine supports the operation of coupling by during which presses against the train - in the jargon impress called. Depending on the type of vehicle, electrical and pneumatic connections must also be made.
For coupling or uncoupling, a railway employee must step under the side buffers between the vehicles in the middle of the track. Due to the limited space, this process poses the risk of accidents and is particularly dangerous in snow and ice. In order to enable work , a minimum free space called the " Berner Raum " is defined between the vehicles . Climbing in and out between the vehicles is made easier by handles under the side buffers.
A correctly connected screw coupling results in a backlash-free connection between the vehicles, which is under a slight bias. If the screw coupling is not shortened sufficiently, this can lead to violent jolts when the load changes. If the play is too large, the sudden load on the coupling can cause it to break.
Normal screw couplings on newly commissioned vehicles must have a breaking load of 850 kN according to TSI WAG. Previously, a breaking load of around 700 kN was common, which is why screw couplings can only be loaded with a maximum of 4000 t tensile mass or approx. 550 kN tensile force in operation on low inclines. A further strengthening of the coupling chains is not possible due to the physical stress of the shunting personnel. For heavier trains, other couplings must be used or intermediate or push locomotives must be used. For the heavy ore trains between the North Sea ports and the steel plants Peine-Salzgitter example, special cars were very reliable automatic couplings design Unicupler procured and a number of locomotives of the class 151 converted accordingly. The 151s were later replaced by the 189 series.
For railcars, there are screw couplings in a much lighter design. They can be coupled with the usual couplings, but vehicles equipped with them may only be used in regular trains at the end of the train. These couplings allow individual passenger or freight wagons and also transfers. Both options have been used in the past. These light couplings were particularly widespread on the Czechoslovak State Railways. Numerous railcars and sidecars equipped with them are still in operation with their successors. In the case of multiple units that are only coupled to one another, automatic central buffer couplings such as Scharfenberg couplings have otherwise prevailed.
A semi-automatic screw coupling was developed in Poland. With the help of a guide and two pneumatic actuators, it now allows the coupling bracket to be caught, lifted and attached to the draw hook. Two degrees of freedom of the system enable the coupling of two rail vehicles in curves. To handle the semi-automatic screw coupling, the train driver or shunting worker uses control buttons, which are usually attached to the vehicle front sides of the locomotive.
history
With the screw coupling, the chain couplings used up until then were replaced from 1840, which could no longer withstand the increased trailer loads. After the front wagons in the train set repeatedly damaged the floor frame due to excessive tensile forces in the early days of the railway, the tow hooks were connected to almost all wagons by a continuous tie rod from 1866 onwards. This was connected to the floor frame roughly in the middle of the car via springs, mostly coil springs . This made it possible to keep the load-bearing structures of the wagons largely free from the tensile forces, but the wagon trains were no longer elastic for tensile loads. In addition, the plain bearings used as axle bearings had a noticeable breakaway resistance . In order to be able to start heavy freight trains in particular, about every fourth to fifth coupling was left long. This made it possible to break loose the wagon groups of a train one after the other, but with the acceptance of a considerable background noise. The continuous drawbar was abandoned around the middle of the twentieth century. Their installation causes difficulties in bogie wagons and newer vehicles with floor frames in welded steel construction cope with the pulling force much better. With the preparation of all wagons for the installation of central buffer couplings and the associated upgrading for the introduction of compressive forces in the vehicle center axis from around 1970, it was no longer necessary for new buildings. Since then, split drawbars have also been standard in the European standard gauge network for wagons using the standardized installation space for the central buffer coupling.
In order to simplify the work, there were various plans after the Second World War to replace the screw coupling on all vehicles with automatic couplings. Many modern vehicles, in principle all built since the mid-1960s, are structurally prepared for this changeover. Due to technical and, above all, economic difficulties and because it was believed at the time that such a changeover would have to take place across Europe at the same time, everything stayed the same, and it is not to be expected that the screw coupling will actually be replaced by another one in the medium term System is replaced. The mixed coupling, which enables simple coupling between vehicles with screw and SA3 and UIC central buffer couplings, was only permitted in shunting service at the time. In Finland, the mixed coupling was used in regular operation early on, also for coupling passenger trains. In the meantime, with the Unilink and Transpact types, central buffer couplings with an integrated coupling chain have been developed that no longer require additional mixed coupling devices.
Clutch failure
Train separations were comparatively common in the 19th century, especially due to fluctuating material quality. The individual parts of the coupling were therefore designed relatively early on in such a way that the link plates of the coupling chain are the weakest link and thus represent a predetermined breaking point. In addition, practically all wagons with screw couplings received an emergency tow hook attached to the tow hook bolt, which hung down in the basic position. The unused coupling chain of the neighboring vehicle was hooked into these. The disadvantage of this arrangement was that it was much more complicated to use. With the general introduction of continuous and automatically acting pull brakes, emergency pull hooks could be dispensed with again from around the 1920s.
Breakdown of the clutch it is still occasionally Zugtrennungen (as on December 8, 2007, a regional express the DB AG in Fuerth ). As a result of the separation of the main air line , both pulling parts are then braked automatically. A train separation is dangerous for travelers who are currently at the affected interchange. However, the two parts of the train can also collide due to different braking behavior, especially if the rear part of the train has its own drive power (pushed train or second locomotive ).
After the train has been separated at the breaking point, the train parts can be reconnected, as each car has a complete coupling (tow hook and coupling chain) at each end of the car, of which only one is required in operation. Detachable connections of the main air line and the main air tank line are available twice, at least in the case of passenger coaches, so that the train can continue its journey after recoupling, provided that no further damage has occurred.
Web links
Individual evidence
- ↑ 2006/861 / EG: Commission decision of July 28, 2006 on the technical specification for interoperability (TSI) for the rolling stock subsystem - freight wagons of the conventional trans-European rail system (announced under file number K (2006) 3345) Document 02006D861-20090701- de.pdf Section 4.2.2.1.2.2. https://eur-lex.europa.eu/legal-content/de/TXT/PDF/?uri=CELEX:32006D0861
- ^ Eisenbahn-Revue International , 2/2008, p. 54