Seal device for piston rod

A piston seal device has a combined oil scraping ring (1) that includes a steel annular oil scraping ring body having an M-, I- or H-shaped cross section, and an annular coil spring (7). The ring body has a cross-sectional cut at one location and includes an upper rail member (2), a lower rail member (3) and a strut (4) holding the upper and lower rail members and having an annular groove (6) in its outer circumferential side, the annular groove (6) having a number of circumferentially spaced oil holes (5). The annular coil spring (7) is fitted into the annular groove (6) in a stretched state for urging the strut diametrically inward toward the piston rod (8), whereby the inner circumferential surfaces of the upper (2) and lower (3) rail members are brought into pressured contact with the outer peripheral surface of the piston rod (8) owing to the constraining force of the spring. The oil scraping ring (1) contacts the outer peripheral surface of the piston rod (8) while flexing to follow up the shape of the surface, thereby improving the oil sealing effect. The upper and lower elements may be separate from the strut Fig 6. The sliding portion of the ring has a wear-resistant layer formed with nitride treatments.