A combination of piston rings assembled to a piston of an internal combustion engine includes four compression rings. An outer peripheral surface of a first compression ring includes a barrel surface, an outer peripheral surface of a second compression ring includes an outer peripheral end portion and a taper surface, an outer peripheral surface of a third compression ring includes an outer peripheral end portion and a taper surface, and an outer peripheral surface of a fourth compression ring includes an outer peripheral end portion and a taper surface.

A piston ring for a piston, the piston ring having a circumferential surface configured to engage an inner surface of a cylinder, the inner surface having at least one recess indented into the inner surface, the engagement of the circumferential surface of the piston ring with the inner surface of the cylinder defining a contact zone therebetween, wherein the circumferential surface of the piston ring is configured such that the ratio of the dimension of the contact zone the direction of travel of the piston to the dimension of the recess in the direction of travel of the piston is in the range of approximately 5:1 to 5:3.

A process of forming a turbine engine seal includes the steps of: providing a flat strip of material; roll forming the flat strip of material forming an asymmetric profile in the flat strip of material; coiling the formed asymmetric profile into an overlapping ring shape; cutting the circular shape to a predetermined length; and joining ends of the predetermined length forming the seal. The seal includes at least two peaks that are formed on opposing sides of a gap. The at least two peaks contact opposing sides of a U shaped profile at a zero radius. The asymmetric profile includes a circular shape and the ends are joined.

A combination of a cylinder 62 of an internal combustion engine and a piston ring 40 for sliding an inner periphery of the cylinder, wherein at least a sliding face of the cylinder is composed of an aluminum alloy including 8 mass % to 22 mass % of Si and at least one or more particles selected from the group consisting of Si, Al.sub.2O.sub.3 and SiO.sub.2 particles each having a diameter of 3 m or more, and at least an outer periphery of the piston ring is coated with a hard carbon coating 14 composed only of hydrogen and carbon.

A combination of a cylinder 62 of an internal combustion engine and a piston ring 40 for sliding an inner periphery of the cylinder, wherein at least a sliding face of the cylinder is composed of an aluminum alloy including 8 mass % to 22 mass % of Si and at least one or more particles selected from the group consisting of Si, Al.sub.2O.sub.3 and SiO.sub.2 particles each having a diameter of 3 m or more, and at least an outer periphery of the piston ring is coated with a hard carbon coating 14 composed only of hydrogen and carbon.

A piston ring for an internal combustion engine or for a compressor, in particular a piston ring includes an exterior running surface (3), two flanks (5, 6), and an interior circumferential surface (7); the running surface (3) has a profiled section with a groove (2), the groove (2) being located between an upper portion (3) of the running surface and a lower portion (3) of the running surface in relation to the cross-section of the piston ring (1).

A linear actuator includes a housing and a piston slidably mounted within the housing. The piston has a first portion forming a sliding fit between the piston and the housing, a second portion spaced apart from both the housing and the first portion, and a groove formed between the first and second portions.

A linear actuator includes a housing and a piston slidably mounted within the housing. The piston has a first portion forming a sliding fit between the piston and the housing, a second portion spaced apart from both the housing and the first portion, and a groove formed between the first and second portions.

This invention relates to a technique for hermetically sealing an artificial leg including a cylinder device. A rod member of the cylinder device extends from the inside to the outside of a shell structure of the cylinder device. The rod member is hermetically sealed at the periphery thereof by a bellows packing member. The bellows packing member comprises an inner bead, an outer bead which concentrically surrounds the outside of the inner bead, and a bellows packing body part which connects the inner and outer beads. The bellows packing body part includes corrugations, and each corrugation is less curved than an imaginary circle which is concentric with the inner bead and the outer bead. Both ends of each of the plurality of corrugations extend to the outer bead or are located at positions closer to the outer bead than the inner bead.

This invention relates to a technique for hermetically sealing an artificial leg including a cylinder device. A rod member of the cylinder device extends from the inside to the outside of a shell structure of the cylinder device. The rod member is hermetically sealed at the periphery thereof by a bellows packing member. The bellows packing member comprises an inner bead, an outer bead which concentrically surrounds the outside of the inner bead, and a bellows packing body part which connects the inner and outer beads. The bellows packing body part includes corrugations, and each corrugation is less curved than an imaginary circle which is concentric with the inner bead and the outer bead. Both ends of each of the plurality of corrugations extend to the outer bead or are located at positions closer to the outer bead than the inner bead.