A piston unit of a working cylinder has first and second coupling partners. The first coupling partner is a piston. The second coupling partner a piston rod. The piston rod is inserted axially into the piston. Each of the coupling partners has an annular groove. The groove of the piston rod is an external groove. The groove of the piston is an internal groove. The grooves of the coupling partners lie opposite one another. The unit has a coupling strand which engages in the grooves of the coupling partners and is placed into engagement by insertion into an annular groove gap defined by the grooves. The engagement of the coupling strand in the grooves produces a form-locking connection between the partners. The piston rod is oversized in relation to the piston and provides an additional frictional connection.

A piston main body in a piston assembly of a fluid pressure cylinder includes a first piston member and a second piston member including a plate-shaped member. The first piston member and the second piston member are joined in a state overlapping in the axial direction of a piston rod. The second piston member is not provided with a hole that passes through in the plate thickness direction.

A piston main body in a piston assembly of a fluid pressure cylinder includes a first piston member and a second piston member including a plate-shaped member. The first piston member and the second piston member are joined in a state overlapping in the axial direction of a piston rod. The second piston member is not provided with a hole that passes through in the plate thickness direction.

An internal combustion engine may include an engine block, a cylinder defining at least one combustion chamber, and a piston in the cylinder. The piston may travel in a first stroke from one end to an opposite end of the cylinder, and may be sized relative to the cylinder to enable an expansion stroke portion of the first stroke while the piston travels under gas expansion pressure, and a momentum stroke portion of the first stroke for the remainder of the first stroke following the expansion stroke portion. A passageway may be formed in the piston rod to communicate gas flow between a first combustion chamber and an area external to the cylinder when the piston is in a first position, and to communicate gas flow between a second combustion chamber and an area external to the cylinder when the piston is in a second position.

An internal combustion engine may include an engine block, a cylinder defining at least one combustion chamber, and a piston in the cylinder. The piston may travel in a first stroke from one end to an opposite end of the cylinder, and may be sized relative to the cylinder to enable an expansion stroke portion of the first stroke while the piston travels under gas expansion pressure, and a momentum stroke portion of the first stroke for the remainder of the first stroke following the expansion stroke portion. A passageway may be formed in the piston rod to communicate gas flow between a first combustion chamber and an area external to the cylinder when the piston is in a first position, and to communicate gas flow between a second combustion chamber and an area external to the cylinder when the piston is in a second position.

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-rod unit for a hydraulic cylinder including a first end piece that is a piston-side end piece and a second end piece that is a rod-eye-side end piece. The piston-rod unit also includes a hollow piston rod with a cavity and that is arranged between the first end piece and the second end piece. The cavity extends at least partially into one or both of the first end piece and the second end piece. A plug is inserted into the cavity such that the plug supports the piston rod and/or the first end piece or second end piece.

A piston-rod unit for a hydraulic cylinder including a first end piece that is a piston-side end piece and a second end piece that is a rod-eye-side end piece. The piston-rod unit also includes a hollow piston rod with a cavity and that is arranged between the first end piece and the second end piece. The cavity extends at least partially into one or both of the first end piece and the second end piece. A plug is inserted into the cavity such that the plug supports the piston rod and/or the first end piece or second end piece.

Provided is an actuator apparatus including a positioning actuator device configured to position a first carrier member of the actuator apparatus. The positioning actuator device includes a first hydraulic fluid actuator having a first clamping means and a second hydraulic fluid actuator having a second clamping means, wherein the first and second hydraulic fluid actuator are configured to alternately clamp around a guide arrangement for moving the positioning actuator device along the guide arrangement. The first carrier member is provided with a first coupling member configured to be releasable coupled to the positioning actuator device. A method of positioning a first carrier member by means of the positioning actuator device is provided.