Slotted oil scraper rings
The best-known application for slotted oil scraper rings is as the bottom ring of the three types on a piston within a combustion engine. This type of piston ring ensures the same distribution of oil over the cylinder wall and the removal of the excess oil to the crankcase through the recesses in the ring.
The piston also has channels through which this oil can flow back to the crankcase. Another part of the oil is scraped back through the cylinder wall. The classic version is a single piston ring with or without tension ring.
Nowadays, the three-piece piston rings are often used in which a central inner ring presses two narrower piston rings, in place and with tension, against the cylinder wall. The narrow working rings in this system are made of steel and provided with a hard chrome or nitride coating after treatment.