An oil scraper piston ring which includes a running face region formed by at least two running face lands, an inner circumferential surface, and upper and lower flank surfaces extending between the running face region and the inner circumferential surface, also includes a joint and oil passage openings extending radially between the running face lands from the outside to the inside, optionally operatively connected to a spring element, wherein the joint is formed by at least two spaced slotted regions having a predefinable shape and dimensions, which are not directly connected to one another, so that each slotted region formed by a slot extends, proceeding from the associated flank surface, at least into one oil passage opening provided between at least two running face lands.

A seal ring (100) makes contact with a low-pressure-side (L) side wall surface of an annular groove (510) and slides against an inner circumferential surface of a shaft hole of a housing (600) through which a shaft (500) is inserted. The seal ring includes a pair of recessed portions (130) extending in a circumferential direction on an outer surface, wherein a distance between a side surface on one side of a protruding portion (120) that is disposed between the pair of recessed portions (130) and a side surface on another side of the seal ring (100), and a distance between a side surface on another side of the protruding portion (120) and a side surface on one side of the seal ring (100) are set to be shorter than a distance between an inner circumferential surface of the seal ring and an outer circumferential surface of the protruding portion (120).

A seal ring (100) makes contact with a low-pressure-side (L) side wall surface of an annular groove (510) and slides against an inner circumferential surface of a shaft hole of a housing (600) through which a shaft (500) is inserted. The seal ring includes a pair of recessed portions (130) extending in a circumferential direction on an outer surface, wherein a distance between a side surface on one side of a protruding portion (120) that is disposed between the pair of recessed portions (130) and a side surface on another side of the seal ring (100), and a distance between a side surface on another side of the protruding portion (120) and a side surface on one side of the seal ring (100) are set to be shorter than a distance between an inner circumferential surface of the seal ring and an outer circumferential surface of the protruding portion (120).

A piston ring which is resinous includes an annular main body portion having an inner peripheral surface and an outer peripheral surface facing each other and a pair of side surfaces interconnecting the inner peripheral surface and the outer peripheral surface and a joint portion 3 formed in the main body portion. The joint portion has a step shape when viewed from at least one of the pair of side surfaces and the outer peripheral surface. The outer peripheral surface has a tapered surface having an outer diameter increasing from a side of one side surface of the pair of side surfaces of the main body portion toward a side of the other side surface.

A piston ring which is resinous includes an annular main body portion having an inner peripheral surface and an outer peripheral surface facing each other and a pair of side surfaces interconnecting the inner peripheral surface and the outer peripheral surface and a joint portion 3 formed in the main body portion. The joint portion has a step shape when viewed from at least one of the pair of side surfaces and the outer peripheral surface. The outer peripheral surface has a tapered surface having an outer diameter increasing from a side of one side surface of the pair of side surfaces of the main body portion toward a side of the other side surface.

An anti-extrusion ring for supporting a sealing unit of a piston or rod system is disclosed. The anti-extrusion ring is split across two surfaces for ease of installation and the split is configured to effectively prevent extrusion at either split surface and eliminate nibbling of the sealing components.

An anti-extrusion ring for supporting a sealing unit of a piston or rod system is disclosed. The anti-extrusion ring is split across two surfaces for ease of installation and the split is configured to effectively prevent extrusion at either split surface and eliminate nibbling of the sealing components.

To provide a long-life compression ring without an increase in the outer peripheral abrasion near the gap regardless of the ring material or the presence or absence of the outer peripheral hard coating, in an annular compression ring having a pair of gap faces opposed to each other to form a free gap and a nominal diameter d1 equal to an inner diameter of a cylinder to which the compression ring is attached to along with a piston, a self tangential force is 5N to 50N, and a radius of curvature R1 and the nominal diameter d1 satisfy a relationship:
?0.01?(2R1?d1)/d1<0.002
where the radius of curvature R1 is that of outer peripheral arcs of gap end portions in a free shape state before the compression ring is attached to the cylinder, and the gap end portions are defined in ranges between the gap faces and positions where a center angle from a midpoint of the free gap is 35?.

Embodiments of a combination piston and piston ring to reduce the volume of a crevice defined between the circumferential wall of a cylinder and a portion of the outer wall of a piston within the cylinder, the portion extending down from the top of the piston. The combination piston and piston ring is configured such that pressurized fluid within the cylinder reliably urges a radial face of the piston ring to sealingly engage the circumferential wall of the cylinder, even as the piston reciprocates within the cylinder.

Embodiments of a combination piston and piston ring to reduce the volume of a crevice defined between the circumferential wall of a cylinder and a portion of the outer wall of a piston within the cylinder, the portion extending down from the top of the piston. The combination piston and piston ring is configured such that pressurized fluid within the cylinder reliably urges a radial face of the piston ring to sealingly engage the circumferential wall of the cylinder, even as the piston reciprocates within the cylinder.