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 – discuss]
Scharfenberg as a technical design principle and brand name
Scharfenberg and the abbreviation Schaku are registered trademarks of Voith Patent GmbH.[2][3] For this reason, only couplings from Voith can use this name. The associated coupling principle is also referred to as latch type design.[4] It is not protected by a patent and is used with fully compatible couplers from manufacturers such as Dellner or Wabtec.
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
Layout of a Scharfenberg coupler (Labels in German)
Coupling process of a Scharfenberg coupler (Labels in German)
Uncoupling process of a Scharfenberg coupler (Labels in German)
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:
CargoFlex: For freight trains, based on the type 10 Scharfenberg coupler head
Couplers for freight trains based on the Scharfenberg principles: [12][13]
Digital automatic coupler for freight trains, based on the Scharfenberg coupler head Type 10.
Hybrid digital automatic coupler for locomotives, based on the Scharfenberg coupler head type 10. The coupler can be used with both automatic and screw couplings.
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Layout of a Scharfenberg coupler (Labels in German)
Coupling process of a Scharfenberg coupler (Labels in German)
Uncoupling process of a Scharfenberg coupler (Labels in German)
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Media related to Scharfenberg coupler at Wikimedia Commons
