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 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: 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: 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 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 radioisotope generator system may comprise a common platform convertor having two ends, and multiple heat source modules thermally coupled to each other and to the common platform convertor. A portion of the multiple heat source modules may be thermally coupled to each end of the common platform convertor. The common platform convertor may be optimized for a nominal power level.

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: 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 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: 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.

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 regenerator having a plurality of involute foils disposed in an annular gap between an inner cylindrical tube and an outer cylindrical tube. The involute shape of the foils provides uniform spacing throughout the entire regenerator and substantial surface area for fluid contact.

Abstract: A regenerator having a plurality of involute foils disposed in an annular gap between an inner cylindrical tube and an outer cylindrical tube. The involute shape of the foils provides uniform spacing throughout the entire regenerator and substantial surface area for fluid contact.

Abstract: A clamping apparatus for allowing pre-close-out access to the head of a Stirling machine and facilitating subsequent close-out welding of the head. The head is axially separable into removable and fixed portions that engage each other. Each portion has an annular flange extending radially outwardly at its engaging end, and each flange has an annular groove. O-rings are seated in the grooves. A temporary sealing ring surrounds and engages the O-rings. Clamping rings seat against axially opposite sides of the abutting annular flanges. Fasteners draw the rings together, thereby drawing the fixed and removable portions of the head together and securing them against relative axial movement. For close-out of the machine, the clamping rings, temporary sealing ring, and O-rings are removed and the grooved annular flanges serve as weld reliefs for final hermetic close-out welding.

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.