Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

A homogeneous charge compression ignition free-piston linear generator is disclosed. The linear generator includes a housing having cylinders at opposite ends. A double-ended piston assembly is to move linearly in the housing to convert kinetic energy of the piston assembly into electrical energy, and to enable conversion of electrical energy into kinetic energy of the piston assembly. Sensors measure one or more states of the cylinders and/or piston assembly, and a controller controls the linear generator based on the sensor data.

A combustion driven fastener hand tool is disclosed having a fuel system subassembly including a fuel nozzle and a metering valve, disposed in a common bore of the combustion driven fastener apparatus. The metering valve comprises a hollow cylindrical housing having a cap at each end and a central dual valve stem therebetween. Movement of the dual central valve stem closes an inlet valve at one end and opens an outlet valve at an opposite end in a coordinated manner to release a metered amount of fuel through the outlet valve while preventing additional fuel through the inlet valve. The combustion driven fastener hand tool includes numerous other features affording improvements over the prior art.

Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

An internal combustion engine for providing a linear reciprocating movement of an output shaft along a longitudinal axis. The engine has a double sided cylinder that is bounded by an engine head at each side of the cylinder. An exhaust unit is positioned at each side of the cylinder. A piston is positioned within a cylinder inner space and freely slides with respect to the cylinder along the longitudinal axis. Two piston rods are aligned with the longitudinal axis. Each piston rod is connected at a different side of the piston. Each of the piston rods has exhaust openings.

An internal combustion engine for providing a linear reciprocating movement of an output shaft along a longitudinal axis. The engine has a double sided cylinder that is bounded by an engine head at each side of the cylinder. An exhaust unit is positioned at each side of the cylinder. A piston is positioned within a cylinder inner space and freely slides with respect to the cylinder along the longitudinal axis. Two piston rods are aligned with the longitudinal axis. Each piston rod is connected at a different side of the piston. Each of the piston rods has exhaust openings.

A linear reciprocating engine may include an engine block, a cylinder having combustion chambers at opposing ends, cylinder heads located at an end of the respective combustion chambers, respectively, and a double-faced piston. The engine may further include piston rod portions extending from both faces of the piston through the combustion chambers. The engine may further include an exhaust outlet in a peripheral cylinder wall and elongated channels in the piston rod portions being configured to serve as an intake inlet for gas from a location external to the cylinder. When the piston is in a combustion stage in a first combustion chamber, the piston blocks the exhaust outlet from communicating with the first chamber with the first channel access opening outside the first chamber, while simultaneously the exhaust outlet is in communication with a second combustion chamber with the second channel access opening within the second chamber.

A linear reciprocating engine may include an engine block, a cylinder having combustion chambers at opposing ends, cylinder heads located at an end of the respective combustion chambers, respectively, and a double-faced piston. The engine may further include piston rod portions extending from both faces of the piston through the combustion chambers. The engine may further include an exhaust outlet in a peripheral cylinder wall and elongated channels in the piston rod portions being configured to serve as an intake inlet for gas from a location external to the cylinder. When the piston is in a combustion stage in a first combustion chamber, the piston blocks the exhaust outlet from communicating with the first chamber with the first channel access opening outside the first chamber, while simultaneously the exhaust outlet is in communication with a second combustion chamber with the second channel access opening within the second chamber.

An internal combustion engine may include an engine block, a cylinder within the engine block, and a piston within the cylinder. The piston may have an outer peripheral wall, and a groove in the outer peripheral wall of the piston may have a first edge and a second edge spaced from the first edge. The piston may have a piston ring in the groove, and the piston ring may have a shape that meanders within the groove, such that the shape of the piston ring differs from a shape of the groove and such that the piston ring does not substantially fill the groove. The piston ring may be constructed of a material that when subjected to heat causes a shape of the meanderings to change, thereby enabling the piston ring to expand in an axial direction of the piston, between the edges of the groove.