Snap ring
A snap ring is a special form of the locking ring and is used in mechanical engineering for the positive, axial fixing of components such as wheels or bearings on axles , shafts or bearings, axles, etc. in bores. The snap ring itself consists of spring steel wire with a constant cross-section , which is bent into a ring . Snap rings are produced with diameters from a few millimeters to a few meters.
species
Many rings can be mounted in a groove on a shaft as well as in a bore. However, the industry offers precisely coordinated variants for each of the two applications.
Snap rings for screw connections
The locking ring for screw connections consists of a circularly bent spring steel, which is also used for washers . The ends are not aligned with one another and therefore generate an axial force during the radial tightening movement, which is intended to prevent screw connections from loosening by themselves, for example due to vibrations.
Shaft circlips
This type is characterized by a relatively small gap (approx. 4 mm for a ring of a shaft ø40). This type of "snap ring" is also known as a "shaft circlip".
Bore retaining rings
Compared to the shaft ring, the gap is significantly larger (approx. 12 mm for a ring with a hole diameter of 40). However, the designation of the "snap ring" is misleading here. This is correctly referred to as a bore retaining ring.
Special forms
There are also numerous variants of the ends, as well as geometries deviating from the circular shape, e.g. B. radially or axially corrugated rings.
Manufacturing
history
Before large-scale industrial production, rings with a square cross-section were cut from a pipe on a lathe and then broken open at one point. Rings with a round, and later also with a square cross-section were made by “ blowing open ” (separating) a spiral made of spring steel wire ; this fact gave the ring its name.
process
Today, most of the snap rings are produced on special ring winding machines that create a finished ring from profile wire per operation. Depending on the type of material used, a subsequent hardening process and / or stress-relieving annealing is necessary to achieve the desired spring properties.
Finishing
For some applications (e.g. tolerance compensation in a gear) the side surfaces are ground even more precisely. Further possible after-treatments are slide grinding (to remove the burr) and all conceivable industrial surface coatings such as B. burnishing , phosphating , galvanizing , copper plating . For automatic assembly , snap rings are sometimes still stacked and packed so that they are aligned in the gap.
Assembly
Because of the strong spring tension , particular care must be taken when installing a snap ring, otherwise there is a considerable risk of injury . The removal must be carried out carefully to avoid the ring jumping off in an uncontrolled manner.
requirements
To absorb axial forces, each snap ring needs a groove that is 0.1–0.2 mm wider than the ring.
Shaft circlips
To avoid deformation of the ring during assembly, a conical assembly mandrel is usually placed on the shaft end, over which the ring is pushed. For sensitive shafts (bearings, aluminum components, etc.), a thin-walled sleeve is also used, which is pushed over the shaft. Alternatively, the ring can be spread with the help of snap ring pliers and pushed over the shaft.
Bore retaining rings
Similar to the wave rings, a conical sleeve is used here, through which the ring is pushed into the bore.
Selection and interpretation
For most applications, the manufacturers provide the necessary data such as the nominal diameter of the shaft or bore, maximum axial force, groove geometry, etc. in their catalogs .
Norms
The snap rings with a square profile offered in the catalogs are usually not subject to any standard . For the installation of rolling bearings from a diameter of 30 mm, however, there are special rings that are standardized according to DIN 5417.
Round wire snap rings are mostly standardized according to DIN 7993.
literature
- Dieter Muhs: Machine elements . Vieweg + Teubner Verlag, Wiesbaden 2005, ISBN 3-528-17028-X , p. 263 f .
