Shaft seal
Shaft sealing rings (WDR) are seals that are used to seal off machine housings on emerging elements (usually shafts or push rods ) from the environment.
Radial shaft seal
General
|
DIN 3760 |
|---|---|
| Area | Sealing technology |
| title | Radial shaft seals |
| Latest edition | 9.1996 |
| ISO | - |
Radial shaft seals (RWDR) are installed with a tight fit in the housing or housing cover. Its sealing lip runs on the surface of the rotating shaft and is usually pressed radially onto the shaft surface by a hose spring (worm spring). In order to reduce wear on the rubber lip and ensure the sealing effect, high demands are made on the condition of the shaft surface; The shaft is therefore often ground free of twist in the area of the seal running surface . Newer designs of the RWDR sometimes no longer have a worm spring (membrane shaft sealing rings) or have a PTFE sealing lip.
The designation / dimensions are as follows:
Code letter inside diameter × outside diameter × depth / width
Code letters include A for rubberized (elastomer outer jacket), B for WDR with an open metal housing and C with a closed metal housing. Depending on the manufacturer and version, the code letters are extended, such as AS / BS with dust lip and WAS / WBS additional dust lip.
Contrary to its original purpose, RWDR is also used as a fork sealing ring on motorcycles to prevent oil and air from escaping between the standpipes and immersion pipes and thus ensure the function of the damper integrated in the fork. During compression and rebound, the seals move axially over the (mostly chrome-plated and polished) immersion tubes.
If there are pressure differences between the areas separated by the seal, the open side of the sealing ring should face the area with the higher pressure. The sealing lip is then pressed against the shaft by the pressure difference. In the opposite case, the sealing lip can be pressed away from the shaft against the spring force. The sealing effect is then lost.
The most common radial shaft seals in Germany are standardized in the DIN standard DIN 3760 .
Simmerring
A radial shaft seal is often colloquially referred to as a Simmerring . These product names and Simmer-Ring are registered trademarks of Freudenberg Sealing Technologies .
Simmerring is derived from the name of its developer, the Austrian engineer (later professor) Walther Simmer who was then working at Freudenberg . He developed this component, initially made of leather and metal, in Kufstein in 1929 .
Axial shaft seal
Axial shaft sealing rings are used to fulfill secondary sealing tasks, for example dust protection or splash protection. In contrast to the RWDR, the sealing lip does not seal on the shaft, but usually on a housing part in the axial direction.
The most common designs are the V-ring and the gamma ring, which also has a labyrinth function.
Axial shaft sealing rings are often used as secondary seals by RWDR when an exceptional level of contamination is to be expected. Examples are applications in construction machinery or the railroad.
The behavior of the V-ring at high speeds is interesting. The sealing lip lifts off and the seal then functions as a slinger. Thus there is no more power loss.
literature
- H. Wittel, D. Jannasch, J. Voßiek, C. Spura: Roloff / Matek machine elements. Springer Vieweg, Wiesbaden 2019, ISBN 978-3-658-26280-8 .