Abstract This disclosure provides a novel method of producing a channel shaped piston ring in that a plurality of relatively wide lateral slits are formed by punching together with the oil windows to save time and cost and also to avoid an ''''end effect'''' during the electrolytic Cr or Co-W plating treatment of the edge of the ring. The method is carried out by punching a sheet tape to produce the plurality of slits and windows, bending the punched tape into a channel having a C-shaped cross section, curling the C-shaped channel into a ring of larger diameter than the final piston ring, and heat treating the ring after inserting it into a hollow cylinder having an inner diameter slightly smaller than the initial diameter of the curled article. The method is further characterized in that the Cr or Co-W plating of the edges of the ring is carried out either before or after the heat treatment.
A method of producing a one-piece channel shaped piston ring comprising: punching a thin steel sheet tape with a plurality of oil windows of the same size arranged at regular intervals along a longitudinal centerline of the tape and simultaneously with a plurality of relatively wide lateral slits provided alternately for every other window on both sides of the tape for connecting each of the oil windows to respective tape edges, bending the punched tape along two lines in parallel to the longitudinal centerline of the tape to form a channel having the symmetrical C shaped cross section, curling the channel article into a ring having a diameter slightly larger than that of the final oil ring product, subjecting the outer edge surfaces of the curled article to a Co-W plating treatment, inserting the Co-W plated article into a hollow cylinder having the inner diameter slightly smaller than the initial diameter of the Co-W plated article, and heat-treating the plated article therein.