Piston ring arrangement (40) with a piston ring (50) encircling a main axis (X), the piston ring (50) having a sealing surface (58) directed radially outward and a contact surface (55) directed radially outward, the sealing surface (58) being radially outside of the contact surface (55). To improve the service life of piston rings for reciprocating compressors, the piston ring arrangement (40) has a retaining ring (70) encircling the main axis (X) with a retaining surface (72) directed radially inward, the piston ring (50) and the retaining ring (70) being situated such that the retaining surface (72) and the contact surface (55) are adjacent in the radial direction.

Piston ring having an endless base ring and sealing ring have a radially outwardly directed base ring face side. The sealing ring has a radially inwardly directed, circularly running sealing ring inner side with three tangential cuts separating three sealing ring segments are arranged in a circumferential direction (U). The base and sealing rings are arranged in succession in a longitudinal direction (L). A top ring is arranged to adjoin the sealing ring having a top ring has a radially outwardly directed top ring outer side and a radially inwardly directed top ring inner side. The top ring has, on the side opposite the sealing ring, a radially running return flow channel extending radially, the sealing face side protrudes in a radial direction beyond the top ring outer side and the base ring face side. The base and the top rings have a greater tensile strength than the sealing ring.

A hydraulic device comprises a base member, a piston, a seal ring, and an intermediate member. The base member includes a cylinder bore and an annular groove. The annular groove includes a first inner surface and a second inner surface. The piston is movable relative to the base member from a rest position toward an actuated position in a second direction opposite to a first direction. The piston is movable relative to the base member from the actuated position toward the rest position in the first direction. The seal ring includes a first axial surface facing in the first direction and a second axial surface facing in the second direction. The seal ring is provided in the annular groove so as to define a clearance between the first axial surface and the first inner surface. The intermediate member is provided in the clearance.

A hydraulic device comprises a base member, a piston, a seal ring, and an intermediate member. The base member includes a cylinder bore and an annular groove. The annular groove includes a first inner surface and a second inner surface. The piston is movable relative to the base member from a rest position toward an actuated position in a second direction opposite to a first direction. The piston is movable relative to the base member from the actuated position toward the rest position in the first direction. The seal ring includes a first axial surface facing in the first direction and a second axial surface facing in the second direction. The seal ring is provided in the annular groove so as to define a clearance between the first axial surface and the first inner surface. The intermediate member is provided in the clearance.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a work stroke from one end to another. The work stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion, and a compression stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a work stroke from one end to another. The work stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion, and a compression stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

A piston arrangement for a clean combustion engine, such as a hydrogen engine. The piston arrangement comprises a piston configured for reciprocal movement inside a cylinder having a cylinder wall, the piston having a piston head configured to face a first compartment with pressurized gas, a sealing arrangement comprising at least one sealing ring configured to be arranged to seal the piston to the cylinder wall and separating the first compartment from a second compartment, and a water channel extending from an interior of the piston to the sealing ring to provide water for lubricating the sealing ring. The piston head comprises a pumping element configured to be arranged to pressurize the water in the water channel by pressurised gas in the first compartment.

A piston arrangement for a clean combustion engine, such as a hydrogen engine. The piston arrangement comprises a piston configured for reciprocal movement inside a cylinder having a cylinder wall, the piston having a piston head configured to face a first compartment with pressurized gas, a sealing arrangement comprising at least one sealing ring configured to be arranged to seal the piston to the cylinder wall and separating the first compartment from a second compartment, and a water channel extending from an interior of the piston to the sealing ring to provide water for lubricating the sealing ring. The piston head comprises a pumping element configured to be arranged to pressurize the water in the water channel by pressurised gas in the first compartment.

An oil control ring according the present disclosure includes a pair of side rails, and a spacer expander disposed between the pair of side rails. The spacer expander includes a plurality of sets and each set includes a lug part and a rail facing part. For each set, the lug part is in contact with an inner circumferential surface of either of the pair of the side rails, and the rail facing part is provided adjacent to the lug part and faces a side surface of either of the pair of the side rails. The lug part satisfies a following condition (1):
W/H≥1.5  (1)
In condition (1), W indicates a width of the lug part at a position 0.05 mm away from a highest position of the lug part in a direction towards the rail facing part, and H indicates a height difference between a highest position of a region on the rail facing part adjacent to the lug part and the highest position of the lug part.

An oil control ring according the present disclosure includes a pair of side rails, and a spacer expander disposed between the pair of side rails. The spacer expander includes a plurality of sets and each set includes a lug part and a rail facing part. For each set, the lug part is in contact with an inner circumferential surface of either of the pair of the side rails, and the rail facing part is provided adjacent to the lug part and faces a side surface of either of the pair of the side rails. The lug part satisfies a following condition (1):
W/H≥1.5  (1)
In condition (1), W indicates a width of the lug part at a position 0.05 mm away from a highest position of the lug part in a direction towards the rail facing part, and H indicates a height difference between a highest position of a region on the rail facing part adjacent to the lug part and the highest position of the lug part.