Epsilon tension clamp
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The epsilon tension clamp is a steel spring bent in the shape of an epsilon , with which railroad tracks are elastically attached to the sleepers . This special type of tension clamp (railway techn. Abbreviation: Skl) made of thick round wire and inserted between the sleeper screw and the rail foot was developed at the beginning of the 1960s at the Technical University of Munich and has been manufactured and used since 1967. Compared to the older type of fastening Oberbau K , it combines the functions of two components - a type of spring washer and the so-called clamping plate as a support piece on the rail foot. The variant of Oberbau K in which this tension spring is used is called Oberbau KS . The partial word clamp in the tension clamp comes from the clamping plate .
In principle, a tension clamp is not a new component for elastic rail fastening. There were and are various other designs. There are also various versions of the epsilon tension clamp today, which are distinguished from one another with skl and an additional number.
Mode of action
A safety measure to ensure that the axial fastening force held by a screw does not change during operation or only changes to a tolerable degree is to place a spring under the that is as "soft" as possible, ie. H. one with a flat spring characteristic . In the construction of Oberbau K , a kind of spring washer is placed under the head of the sleeper screw , which is a helical spring with just two turns. This is sufficient for wooden sleepers (the sleeper is sufficiently elastic to make a contribution to the elasticity of the screw connection), but not for concrete sleepers (which are much less elastic than wooden ones). For the latter, u. a. the existing and softer tension clamp in epsilon form is required.
The two outer arms are primarily responsible for their elastic resilience. The middle part of the clamp ( middle loop in the form of an open oval ) is the contact part to the sleeper screw . The two outer arms are elastically bent and twisted . They transmit the contact pressure to the rail foot without the need for an additional component. At the transition from the middle loop, they lie on the plate on the sleeper to guide the rail foot. When the sleeper screw is turned, the two arms bend, for example, by 12 mm and then press the rail foot with 9 kN.
The sleeper screw is screwed in until the front part of the middle loop comes to a stop with a protruding bar on the plate lying on the sleeper. In the direction of the rail, the middle loop protrudes slightly, which serves as a stop to prevent the rail from lifting or tilting if the elastic hold-down forces should be exceeded. The gap between the central loop and the rail foot is less than 2 mm.
The high elasticity of the rail fastening system reduces the vibrations caused by the complete system of gravel, concrete sleepers, rails and the vehicle wheels - taking place in particular on the inner rail in curves corrugation .
Footnotes
- ^ Meier, Hermann: On the rail fastening on the concrete sleeper , in: Verkehr und Technik, special print 1963
- ^ History of the Vossloh Group , accessed on October 17, 2016.
- ↑ gleisbauwelt.de: Oberbauarten (various rail fastenings) : (historical designs, see Figures 4, 6, 12, 13 and 16 to 20)
- ↑ Metalcom: Padrol tension clamp (a modern design)
- ↑ Schubart + Co AG, rail fastening systems for wooden sleepers: supplier for z. B. skl 3, skl 12 and skl 24
- ↑ The principle at work is applied directly to the expansion screw without an additional spring. The screw shank is made relatively long and, in this way, "soft to stretch", which is time-consuming and takes up space.
- ↑ Siegfried Wetzel: An elastic rail connection , section: Suspension calculation (deformation calculation)
- ↑ Vossloh fastening systems: System W 14
- ↑ Florian Auer: To reduce the formation of corrugations - Constructive options for delaying the formation of corrugations on the inside rails in narrow curves.