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 assembly with a piston reciprocated with the aid of a floating head in fluid communication with the piston. The assembly may utilize a floating head that is shifted in position to promote reciprocation of the piston through the aid of pressure supplied to the floating head from a pressure volume regulator. Alternatively, the floating head may be in fluid communication with the piston at one side of the head and isolated at the other side. In this manner changing volume and pressure at this other side of the head during reciprocation may ultimately lead to floating head movement toward the piston, thereby promoting the continued reciprocation. Additional efficiencies may also be realized through unique hydraulic layouts for both operating and working fluid circulations.

A fluid-driven linear motor comprises a cylinder (5), a piston (4) and a piston rod (3) connected to the piston (4), wherein the two sides of the piston (4) in the cylinder (5) are alternatively supplied with fluid from a slide valve arrangement, the slide valve arrangement including a slide (9) accommodated in a chamber and which is shifted between its end positions controlled by a pilot rod (22) coaxially mounted in a through bore (12) in the slide (9). The pilot rod (22) is adapted to alternately set the through bore (12) in fluid connection with the ends of the slide (9) when the piston (4) is located in its end positions. The pilot rod (22.) is provided with an extension rod (204) adapted to slide inside a bore (203) inside said piston (5) and said piston rod (3), so that the stroke length of the linear motor can be extended. Moreover, a pressure chamber (209) is provided at the distal end of the pilot rod (22), said pressure chamber (209) being adapted to hold on the pilot rod (22) with a holding force when in its end positions until mechanical forces from the piston overcome said holding force.

A differential pressure motor comprising two working pistons and a rod that move in a hollow space. Walls defining the hollow space have five openings. A valve piston moves between and against the working pistons and can be driven by the working pistons. The valve piston with the five openings forms a valve with which an alternate impact of a first pressure and a second pressure on the working pistons is controllable when the pressures are applied to three of the five openings such that the working pistons periodically move which drives a periodic movement of the valve piston. Also disclosed are a surgical drive system with, a medical lavage system for the debridement of soft tissue and/or bone tissue having, and a medical device for brushing, rasping or sawing soft tissue and/or bone tissue with such a differential pressure motor, and a method for operating a differential pressure motor.

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.

A fluid-driven linear motor comprises a cylinder, a piston, and a piston rod connected to the piston. Two sides of the piston in the cylinder are alternately supplied with fluid from a slide valve arrangement. The slide valve arrangement includes a slide and a pilot rod adapted to alternately set a through-bore of a slide in fluid connection with the ends of the slide when the piston is located in its end positions. The pilot rod is provided with an extension rod adapted to move inside a bore of the piston and the piston rod, so that the stroke length of the linear motor can be extended. A pressure chamber is provided at the distal end of the pilot rod. The pressure chamber is adapted to hold the pilot rod with a holding force when in its end positions until mechanical forces from the piston overcome said holding force.

Disclosed is a thermodynamic cycle process, performing transfer between mechanical and heat energies, by changing a state of a fluid, including: an expansion of the fluid, an energy retrieval from the fluid expansion, a step of powering a liquid pump or a gas compressor with the retrieved energy, using a cyclic free piston expander which alternatively changes direction of the free piston sliding: by alternatively: closing the fluidic communication between the both opposite sides of the free piston, to make different from each other the pressures applied respectively thereon, so the free piston slides in a first direction, opening a fluidic communication between both opposite sides of the free piston, to make equal to each other the pressures applied respectively thereon, so the free piston slides in a second direction opposite to the first direction, the free piston sliding, directly and mechanically, opening and closing, the fluidic communication.

An air motor assembly includes an exhaust block with an exhaust port that conveys exhaust air into an exhaust manifold. The exhaust port includes an expansion chamber that creates a pressure drop in the exhaust gas, thereby decreasing the temperature of the exhaust gas. The expansion chamber is defined between a first wall that is tangential to the air motor cylinder and a second wall that is transverse to an axis of the exhaust port. Poppet valves control actuation of a shuttle. The poppet valves are disposed on the exterior of the air motor assembly and are thermally insulated from the air motor assembly.