Abstract: A method for limiting the amplitude of reciprocation of a piston reciprocating in a cylinder of a free-piston Stirling engine. The method is the combination of both at least partially covering the heat rejecter cylinder port by the piston sidewall during a peak part of the inward reciprocation of the piston and at least partially covering the heat rejecter cylinder port by the displacer sidewall during a peak part of the outward reciprocation of the displacer. The piston and the displacer, at times during their reciprocation, fully cover the effective heat rejecter cylinder port when the piston amplitude of reciprocation is large and approaches the physical limit of the amplitude of reciprocation in order to avoid internal collisions by a reciprocating component.

Abstract: A free-piston Stirling engine that limits piston amplitude and reduces engine power as the piston amplitude increases beyond its maximum power. The inward edge of the heat rejecter cylinder port is located outward of the most inward excursion of the inward end of the piston sidewall during a part of the piston's reciprocation cycle so that the heat rejecter cylinder port is entirely covered by the piston sidewall during an inward portion of the piston reciprocation when the engine is operating at the selected maximum engine power. A leaker port extends from a gas bearing cavity through the piston sidewall and is positioned axially outward from the gas bearing pads of the engine's gas bearing system and vents working gas to the engine's back space at a piston amplitude of reciprocation that exceeds the piston's amplitude of reciprocation at maximum engine power. A resilient damping bumper is attached to the outward end of the piston and a displacer gas cushion is disclosed.

Abstract: A free-piston Stirling engine that limits piston amplitude and reduces engine power as the piston amplitude increases beyond its maximum power. The inward edge of the heat rejecter cylinder port is located outward of the most inward excursion of the inward end of the piston sidewall during a part of the piston's reciprocation cycle so that the heat rejecter cylinder port is entirely covered by the piston sidewall during an inward portion of the piston reciprocation when the engine is operating at the selected maximum engine power. A leaker port extends from a gas bearing cavity through the piston sidewall and is positioned axially outward from the gas bearing pads of the engine's gas bearing system and vents working gas to the engine's back space at a piston amplitude of reciprocation that exceeds the piston's amplitude of reciprocation at maximum engine power. A resilient damping bumper is attached to the outward end of the piston and a displacer gas cushion is disclosed.

Abstract: An improvement to a free-piston Stirling machine having a cylinder mounted within a housing. The cylinder has a flange for mounting the cylinder within the housing to a transition plate with a central opening for receiving the cylinder. An elastic rim bounds and surrounds the opening and extends in an axial direction from the plate to a crest of the rim. The crest of the rim is in contact against a first axially facing side of the cylinder flange. The interior side of the rim is outwardly spaced from the exterior side of the cylinder. A compliant clamp is attached to the transition plate and is positioned on the opposite, axially facing side of the cylinder flange. The compliant clamp has an elastic spring extending against the cylinder flange which applies a force urging the cylinder flange in an axial direction against the crest of the elastic rim.

Abstract: A free piston Stirling engine with a heat exchanger that has an inner component part assembled within an outer component part. The outer component part has a tubular outer wall and circumferentially spaced ridges that extend radially inward from the tubular outer wall and are separated from each other by inward opening slots. The inner component part has a tubular inner wall and circumferentially spaced ridges that extend outward from the inner tubular wall and are separated from each other by outward opening slots. The ridge widths of the outer and inner component parts are less than the slot widths of the corresponding slots into which they fit. The two component parts are assembled with the ridges of each component part extending into the slots of the other component part to form gas passages between interfacing sidewall surfaces of the ridges.

Abstract: A flexure bearing “planar” spring that can spring multiple, independently reciprocating bodies, such as springing each body to a third body or springing a first body to a second body and springing the second body to a third body. A primary arm set of primary spring arms are separated from each other by openings and extend inwardly from a peripheral frame along a non-radial primary path progressing inwardly toward a central axis and angularly about the central axis. A secondary arm set of at least one secondary spring arm extends along a non-radial secondary path progressing radially and angularly about the central axis. Each secondary arm is interposed in an opening between the primary arms allowing the primary arms and the secondary arms to pass by each other through the openings without interfering with each other.

Abstract: A flexure bearing “planar” spring that can spring multiple, independently reciprocating bodies, such as springing each body to a third body or springing a first body to a second body and springing the second body to a third body. A primary arm set of primary spring arms are separated from each other by openings and extend inwardly from a peripheral frame along a non-radial primary path progressing inwardly toward a central axis and angularly about the central axis. A secondary arm set of at least one secondary spring arm extends along a non-radial secondary path progressing radially and angularly about the central axis. Each secondary arm is interposed in an opening between the primary arms allowing the primary arms and the secondary arms to pass by each other through the openings without interfering with each other.

Abstract: Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

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: Vibrations of a principal machine are reduced at the fundamental and harmonic frequencies by driving the drive motor of an active balancer with balancing signals at the fundamental and selected harmonics. Vibrations are sensed to provide a signal representing the mechanical vibrations. A balancing signal generator for the fundamental and for each selected harmonic processes the sensed vibration signal with adaptive filter algorithms of adaptive filters for each frequency to generate a balancing signal for each frequency. Reference inputs for each frequency are applied to the adaptive filter algorithms of each balancing signal generator at the frequency assigned to the generator. The harmonic balancing signals for all of the frequencies are summed and applied to drive the drive motor. The harmonic balancing signals drive the drive motor with a drive voltage component in opposition to the vibration at each frequency.

Abstract: Method for fabricating a cold finger for attachment to a base assembly of a cold head of a Stirling cycle or pulse tube cryocooler. The exterior of a titanium alloy workpiece is machined to form a cylindrical outer surface. The exterior surface of the titanium workpiece is nickel plated and then brazed to a stainless steel workpiece to form an integral body. The brazed stainless steel workpiece is machined to form it into an adapter ring for attachment to the base assembly. An intermediate segment of the titanium workpiece is machined into a cylindrical surface including removing all of the nickel plating from the intermediate segment and removing a portion of underlying titanium alloy to reduce the diameter of the titanium alloy workpiece in order to reduce the thickness of the cold finger wall. The interior of the integral body is machined to form a cylindrical interior surface.

Abstract: Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

Abstract: Vibrations of a principal machine are reduced at the fundamental and harmonic frequencies by driving the drive motor of an active balancer with balancing signals at the fundamental and selected harmonics. Vibrations are sensed to provide a signal representing the mechanical vibrations. A balancing signal generator for the fundamental and for each selected harmonic processes the sensed vibration signal with adaptive filter algorithms of adaptive filters for each frequency to generate a balancing signal for each frequency. Reference inputs for each frequency are applied to the adaptive filter algorithms of each balancing signal generator at the frequency assigned to the generator. The harmonic balancing signals for all of the frequencies are summed and applied to drive the drive motor. The harmonic balancing signals drive the drive motor with a drive voltage component in opposition to the vibration at each frequency.

Abstract: A free piston Stirling machine including a thermal buffer tube extending from the machine's expansion space and surrounded by its heat rejector and its regenerator, a displacer cylinder extending from the thermal buffer tube to the compression space and surrounded by the heat rejecting heat exchanger, and a displacer that reciprocates within an excursion limit that extends into the regenerator by no more than 20% of the length of the regenerator during normal operation and preferably within excursion limits that are substantially the length of the heat rejector.

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: 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: 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: An electromagnetic, reciprocating linear motor or alternator having at least two armatures that are adjacent along an axis of reciprocation. The armatures have gaps that are linearly aligned along a gap path parallel to the axis. Field magnets reciprocate within the gap path. The field magnets include a main field magnet associated with each armature, each main field magnet having a magnetic polarization in the same direction across the gap path. A secondary magnet provides a centering spring force and is interposed between the main magnets. The secondary magnet extends in an axial direction from within a gap of one armature core to within an adjacent gap of an adjacent armature core. The secondary magnet is magnetically polarized in a direction opposite the polarization of the main magnets.

Abstract: A sensor for sensing the position of a reciprocating free piston in a free piston Stirling machine. The sensor has a disk mounted to an end face of the power piston coaxially with its cylinder and reciprocating with the piston The disk includes a rim around its outer perimeter formed of an electrically conductive material A coil is wound coaxially with the cylinder, spaced outwardly from the outer perimeter of the disk and mounted in fixed position relative to the pressure vessel, preferably on the exterior of the pressure vessel wall.

Abstract: A free piston Stirling machine including a thermal buffer tube extending from the machine's expansion space and surrounded by its heat rejector and its regenerator, a displacer cylinder extending from the thermal buffer tube to the compression space and surrounded by the heat rejecting heat exchanger, and a displacer that reciprocates within an excursion limit that extends into the regenerator by no more than 20% of the length of the regenerator during normal operation and preferably within excursion limits that are substantially the length of the heat rejector.