Scharfenberg coupler

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Scharfenberg coupler on ICE 3 EMU

The Scharfenberg coupler[1] (German: Scharfenbergkupplung, abbreviated Schaku) is a commonly used type of fully automatic railway coupling.

Designed in 1903 by Karl Scharfenberg in Königsberg, Germany (today Kaliningrad, Russia), the coupler has gradually spread from transit trains to regular passenger service trains, although outside Europe its use is generally restricted to mass transit systems. The Schaku is superior in many ways to the AAR (Janney/knuckle) coupler because it also automates electrical and pneumatic connections and disconnections. However, there is no standard for the placement of these electro-pneumatic connections. Some rail operators have placed them on the sides while others have placed them either below or above the mechanical portion of the coupler.[dubious ].

Working principles[edit]

The face of the Scharfenberg coupler has a protruding cone and a matching cup. Inside the cone there is a rigid metal hoop connected to a revolving, spring-loaded metal disk with a notch on the opposite side. When ready to couple, the spring turns the disk so the hoop is extended from the cone. As the cars meet, the hoop enters the cup on the other coupler, stopping against the disk. The hoops are then pressed back into their own coupler, causing the disks to rotate until the notches align with the hoops. After the hoops have entered, the notches on the disks spring back into the hoop extended position, locking the coupling. In the coupled position, forces on the hoops and disk will balance out, which means that the Scharfenberg, unlike many other couplers, is not dependent on heavy latches to stay locked.

Small air cylinders, acting on the rotating heads of the coupler, ensure the engagement of the components, making it unnecessary to use force to get a good coupling. Joining portions of a passenger train can be done at very low speed (less than 3 km/h or 2 mph in the final approach), so that the passengers are not jolted. One problem with the coupler is that it is often hard to connect it in a curve. Planned coupling is normally done on a straight flat track, while there has been trouble coupling a broken down train at an unplanned place.


Scharfenberg couplers on Swedish SL X60 EMU

Rail equipment manufacturers such as Alstom offer the Schaku as an option on their mass transit passenger cars and locomotives. Presently, Scharfenberg couplers are in use on the following passenger transit systems:


United States[edit]



United Kingdom[edit]







New Zealand[edit]


Type 10 as used on TGV
The Shanghai Metro is among several metro systems that use the Type 35 Scharfenberg coupler

Voith is known to offer the following types of Scharfenberg couplers:[6]

  • Type 10: Used for mainline railways and high speed rail applications
  • Type 35: Designed for rolling stock without a compressed air system and used for urban transit applications
  • Type 330: Used for trams and light rail transit
  • Type 430/530: A folding coupler designed for low-floor trams and monorails
  • Type 55: Designed for shunting purposes
  • Type 140: Designed for industrial railways
  • CargoFlex: For freight trains, based on the type 10 Scharfenberg coupler head
  • CargoFlex Hybrid: For locomotives, based on the type 10 Scharfenberg coupler head, can be used with both automatic and screw couplers

See also[edit]


  1. ^ Scharfenberg coupler
  2. ^ "Class 175 - Arriva Trains Wales". Archived from the original on 4 March 2016. Retrieved 8 November 2022.
  3. ^ "Class 180". The Railway Centre. Archived from the original on 27 September 2007. Retrieved 8 November 2022.
  4. ^ "System Data for Mechanical and Electrical Coupling of Rail Vehicles". Rail Safety and Standards Board. Archived from the original on 5 July 2008.
  5. ^ "Class 333 - Northern Rail (by Arriva)". Archived from the original on 27 March 2019. Retrieved 3 August 2018.
  6. ^ "Scharfenberg couplers". Voith. Archived from the original on 7 July 2019.

External links[edit]