Abstract: A two piston, free piston, alpha Stirling cycle machine has a compression piston with a cylindrical bore that is coaxial with the cylinders in which the pistons reciprocate. An expansion piston sealingly extends into both an expansion cylinder and into the cylindrical bore in the compression piston. The expansion piston has the same diameter within both the expansion cylinder and the cylindrical bore. A spring, preferably a gas spring, drivingly connects the pistons. The reciprocation of the expansion piston varies only the volume of the expansion space and the reciprocation of the compression piston varies only the volume of the compression space. The spring that drivingly connects the pistons allows the two pistons to be properly phased without a mechanical linkage so that they can operate in a thermodynamically effective phase over a range of strokes.

Abstract: Multiple free-piston Stirling (FPS) machines are arranged in a group and connected for preventing or minimizing vibration. A first set of identical beta FPS machines are arranged in a mechanically co-directional orientation and configured to reciprocate in thermodynamically synchronous reciprocation with each other. The first set has axes of reciprocation intersecting a first point. A second set of beta FPS machines are arranged in a mechanically co-directional orientation that is the same as the mechanical orientation of the first set of beta FPS machines and are configured to reciprocate in thermodynamically synchronous reciprocation with each other but in thermodynamically opposed reciprocation to the first set. The FPS machines of the second set are identical to the FPS machines of the first set and have axes of reciprocation intersecting a point, which may be a point at infinity.

Abstract: The power output of a free piston Stirling engine mounted in a free casing configuration is controlled by having a spring drivingly linking the displacer to the casing and controllably varying the amplitude of reciprocation of the casing. A variable casing reciprocation restraint is linked to the casing for applying a variable restraining force to the casing. The restraining force is increased for decreasing the displacer amplitude of reciprocation and thereby decreasing the power output from the Stirling engine and the restraining force is decreased for increasing the displacer amplitude of reciprocation and thereby increasing the power output from the Stirling engine.

Abstract: A two piston, free piston, alpha Stirling cycle machine has a compression piston with a cylindrical bore that is coaxial with the cylinders in which the pistons reciprocate. An expansion piston sealingly extends into both an expansion cylinder and into the cylindrical bore in the compression piston. The expansion piston has the same diameter within both the expansion cylinder and the cylindrical bore. A spring, preferably a gas spring, drivingly connects the pistons. The reciprocation of the expansion piston varies only the volume of the expansion space and the reciprocation of the compression piston varies only the volume of the compression space. The spring that drivingly connects the pistons allows the two pistons to be properly phased without a mechanical linkage so that they can operate in a thermodynamically effective phase over a range of strokes.

Abstract: Multiple free-piston Stirling (FPS) machines are arranged in a group and connected for preventing or minimizing vibration. A first set of identical beta FPS machines are rigidly connected together, arranged in a mechanically co-directional orientation and configured to reciprocate in thermodynamically synchronous reciprocation with each other. The first set has axes of reciprocation intersecting a first point, which may be a point at infinity. The axes of the first FPS machines make the same angle with a central axis of motion and are equi-angularly spaced around the central axis. A second set of beta FPS machines are rigidly connected together and rigidly connected to the first set of machines. The second set of machines are arranged in a mechanically co-directional orientation that is the same as the mechanical orientation of the first set of beta FPS machines.

Abstract: The reciprocatable power piston of a free-piston Stirling machine is drivingly linked to a reciprocatable component body of an associated apparatus by at least one spring with no rigid connection linking the piston to the component body. The spring drive linkage allows the power piston and the reciprocatable component body of the associated apparatus to reciprocate at different amplitudes of oscillation. Therefore, the Stirling machine and the associated apparatus can be optimized at different amplitudes of piston and the component body oscillation thereby improving the optimization of two very different dynamic systems that are drivingly connected together.

Abstract: The reciprocatable power piston of a free-piston Stirling machine is drivingly linked to a reciprocatable component body of an associated apparatus by at least one spring with no rigid connection linking the piston to the component body. The spring drive linkage allows the power piston and the reciprocatable component body of the associated apparatus to reciprocate at different amplitudes of oscillation. Therefore, the Stirling machine and the associated apparatus can be optimized at different amplitudes of piston and the component body oscillation thereby improving the optimization of two very different dynamic systems that are drivingly connected together.

Abstract: An automatically and smoothly continuously variable transmission, particularly for a bicycle, for transmitting input mechanical energy from a crank to the drive wheel. A ratchet, having an oscillatory, alternating motion member and a continuous rotary motion member, connected to the driven wheel, has a drive spring drivingly linked between the ratchet alternating member and the crank for driving the ratchet alternating member in one direction of motion. A return spring is linked to the ratchet alternating member for applying a return force upon the ratchet alternating member to return the alternating member in the opposite direction.

Abstract: A heat exchanger in which a fluid and a surface transfer thermal energy effectively with a smaller pressure drop than is conventionally realized. In a preferred embodiment, gas at one end of a piston flows into a piston chamber and passes radially through a plurality of axial slots formed through the piston sidewall and into a gap between the piston sidewall and the surface of the housing in which the piston slidably mounts. Between each pair of through-slots, longer axial slots are formed that extend only partially through the sidewall radially, and almost the entire length of the piston. Thus, around the circumference of the piston the slots alternate in structure between through-slots and longer slots. Gas that enters the gap through the through-slots flows circumferentially through the gap and into the longer slots. The gas exits the longer slots at the opposite end of the piston from the first gas space.

Abstract: An automatically and smoothly continuously variable transmission, particularly for a bicycle, for transmitting input mechanical energy from a crank to the drive wheel. A ratchet, having an oscillatory, alternating motion member and a continuous rotary motion member, connected to the driven wheel, has a drive spring drivingly linked between the ratchet alternating member and the crank for driving the ratchet alternating member in one direction of motion. A return spring is linked to the ratchet alternating member for applying a return force upon the ratchet alternating member to return the alternating member in the opposite direction.

Abstract: A heat exchanger in which a fluid and a surface transfer thermal energy effectively with a smaller pressure drop than is conventionally realized. In a preferred embodiment, gas at one end of a piston flows into a piston chamber and passes radially through a plurality of axial slots formed through the piston sidewall and into a gap between the piston sidewall and the surface of the housing in which the piston slidably mounts. Between each pair of through-slots, longer axial slots are formed that extend only partially through the sidewall radially, and almost the entire length of the piston. Thus, around the circumference of the piston the slots alternate in structure between through-slots and longer slots. Gas that enters the gap through the through-slots flows circumferentially through the gap and into the longer slots. The gas exits the longer slots at the opposite end of the piston from the first gas space.

Abstract: A free piston internal combustion engine having improved valve timing. A pair of oppositely disposed combustion chamber passageways extending between the combustion chamber and the earth's atmosphere, each have a combustion chamber valve for controlling the passage of gas through the passageways. The combustion chamber valves are essentially simultaneously opened and closed to permit independent variation and control of the compression ratio, expansion ratio, and stroke of the engine. When the valves are opened, the combustion chamber is purged or supercharged with combustion supporting air, and closed to initiate compression. Variable control of the piston positions at which the valves are opened and closed permits the engine to operate at a high efficiency over a broad range of power output loading conditions.

Abstract: This invention is an efficient free-piston internal-combustion engine having an expansion ratio greater than the compression ratio and preferably with gas bearings supporting the piston. The use of gas bearings in combination with high-temperature ceramic materials allows the engine to be nearly adiabatic and with exhaust temperatures in excess of 600.degree. C. These high exhaust temperatures in turn allow the engine to operate as a topping cycle for gas turbines, Stirling engines, steam engines, etc. An improved valving system for flexible control of the engine may include the use of a valve actuator in a piston. In one embodiment, a pair of oppositely disposed combustion chamber passageways extending between the combustion chamber and the earth's atmosphere, each have a combustion-chamber valve for controlling the passage of gas through the passageways.

Abstract: A centering apparatus for a free piston Stirling engine including a pressure regulator valve which connects a passageway between the work space and the back space when both (a) the average pressure in the back space exceeds the average pressure in the work space as a result of the piston deflecting a spring, and simultaneously (b) the instantaneous pressure in the back space exceeds the instantaneous pressure in the work space. A diaphragm spans across an actuator housing cavity, dividing the cavity into an upper chamber and a lower chamber. A connector valve is linked to the diaphragm for opening and closing the valve upon displacement of the diaphragm. When the average back space pressure exceeds the average work space pressure, the diaphragm is displaced to open the valve, connecting the work space and the back space in fluid communication. A check valve permits the flow of gas in only one direction: from the back space to the work space.

Abstract: A free piston internal combustion engine having improved valve timing. A pair of oppositely disposed combustion chamber passageways extending between the combustion chamber and the earth's atmosphere, each have a combustion chamber valve for controlling the passage of gas through the passageways. The combustion chamber valves are essentially simultaneously opened and closed to permit independent variation and control of the compression ratio, expansion ratio, and stroke of the engine. When the valves are opened, the combustion chamber is purged or supercharged with combustion supporting air, and closed to initiate compression. Variable control of the piston positions at which the valves are opened and closed permits the engine to operate at a high efficiency over a broad range of power output loading conditions.

Abstract: A piston end position limiter for a free piston machine of the type having a piston sealingly reciprocating in a cylinder and separating a work space bounded at one end of the piston from a second space bounded at the opposite end of the piston. The work space and the second space contain a working fluid having an average pressure. A first valve is connected in communication between a fluid reservoir and the work space and is adapted to open only when the working fluid pressure varies sufficiently in one direction from its average pressure. A second position responsive valve is connected between the reservoir and the second space and is operatively linked to the piston for opening in response to the piston reaching a selected end limit of its reciprocation.

Abstract: An improved mechanical transducer of the type having a body reciprocating in a chamber, the body being linked to a housing by a linkage including an axially compliant spring. An anti-friction fluid bearing applies a lateral centering force upon the body and a linkage component of the linkage has a lateral compliance sufficient for the centering forces exerted by the fluid bearing to at least equal the sum of lateral force exerted by the linkage and other lateral forces exerted upon the body. That lateral compliance allows the centering forces of the fluid bearing to be effective in moving the body away from the chamber wall and thereby minimize contact and consequent wear of the interfacing surfaces between the body and the chamber wall.

Abstract: Free piston Stirling coolers and engines are improved by a variable power transmitting linkage connecting the displacer to the piston and coupling more power from the displacer to the piston while piston displacement exceeds a selected limit than coupled while piston displacement is less than the selected limit. Adjustment of the position of the limit is used to control stroke amplitude, power output or thermal pumping rate.

Abstract: A piston centering system for a free piston machine. The invention uses a centering passageway which is in communication between a work space and a second space which spaces are formed in a housing and are separated by a piston which reciprocates in a cylinder in the housing. The centering passageway has a valve, such as a spool valve formed in the piston and cylinder or a center post, the valve opening in response to the piston being near the center of the opposite limits of its reciprocation. The improvement is the inclusion of a pressure responsive, one way valve interposed in the passageway. The one way valve is oriented to permit the passage of the working gas through the passageway from one space to the other in a direction opposite to a net leakage flow from one space to the other through the annular gap between the piston and cylinder and to prevent substantial flow through the passageway in the reverse direction.

Abstract: A centering apparatus for a free piston Stirling engine including a pressure regulator valve which connects a passageway between the work space and the back space when both (a) the average pressure in the back space exceeds the average pressure in the work space as a result of the piston deflecting a spring, and simultaneously (b) the instantaneous pressure in the back space exceeds the instantaneous pressure in the work space. A diaphragm spans across an actuator housing cavity, dividing the cavity into an upper chamber and a lower chamber. A connector valve is linked to the diaphragm for opening and closing the valve upon displacement of the diaphragm. When the average back space pressure exceeds the average work space pressure, the diaphragm is displaced to open the valve, connecting the work space and the back space in fluid communication. A check valve permits the flow of gas in only one direction: from the back space to the work space.