Abstract: A method and an apparatus for measuring the light gap tightness of a piston ring, that is provided with a joint and produced so as to be non-round by clamping the open piston ring, while substantially closing the joint, by way of an accessory device in the circumferential direction, and by exerting a defined force in the region of at least one of the joint ends of the piston ring in the direction of a wall of the accessory device, wherein optical means are used to establish whether the joint region of the piston ring which is subjected to the action of the force is seated against the wall of the accessory device in a light-tight manner.

Abstract: A method and an apparatus for measuring the light gap tightness of a piston ring, that is provided with a joint and produced so as to be non-round by clamping the open piston ring, while substantially closing the joint, by way of an accessory device in the circumferential direction, and by exerting a defined force in the region of at least one of the joint ends of the piston ring in the direction of a wall of the accessory device, wherein optical means are used to establish whether the joint region of the piston ring which is subjected to the action of the force is seated against the wall of the accessory device in a light-tight manner.

Abstract: A piston ring, in particular a compression piston ring, includes a running surface, upper and lower flank areas, an inner peripheral area and a joint. The wall thickness of the piston ring is uniform over its periphery and at least the running surface is provided with a PVD coating or a CVD layer in such a manner that the running surface layer has a lesser layer thickness in the peripheral area close to the joint than in the remaining peripheral area of the running surface.

Abstract: A piston ring, in particular a compression piston ring, includes a running surface, upper and lower flank areas, an inner peripheral area and a joint. The wall thickness of the piston ring is uniform over its periphery and at least the running surface is provided with a PVD coating or a CVD layer in such a manner that the running surface layer has a lesser layer thickness in the peripheral area close to the joint than in the remaining peripheral area of the running surface.