Abstract: The invention relates to thermomechanical transducers drivingly linked to a linear motor or alternator, preferably a free piston Stirling engine in which the piston is drivingly linked to the field magnet of an alternator. There are symmetric and coaxial secondary magnets attached at opposite ends of the field magnet. The field magnet is polarized radially in one direction and the secondary magnets are polarized radially in the opposite direction. When the field magnet is displaced from a centered position, the secondary magnets have an oppositely directed axial net force exerted upon them. This causes a centering bias on the field magnet and therefore a centering of the piston in the Stirling engine or cooler.A secondary effect produced by the magnetic spring of the secondary magnets is amplitude limiting during load reduction on the Stirling engine. Amplitude limiting is a result of increased spring constant of the magnetic spring past a certain amplitude.

Abstract: In a free piston Stirling machine, a gas spring apparatus for applying two distinctly different spring rates to the displacer during the displacer's excursion past a center point in opposite ends of the work space. The apparatus comprises a cylinder formed in a gas spring housing, in which a gas spring piston is slidably mounted. On opposite sides of the gas spring piston there are two unequal volume gas spring chambers. Between the gas spring chambers there is a bleed hole which divides the cylinder into the two chambers and allows communication between the gas spring chambers and a gas reservoir. While the piston is compressing one gas spring chamber, the opposite is in communication with the gas reservoir and vise versa. This creates two distinctly different spring rates applied to the displacer.

Abstract: The invention is for the prevention of power piston overstroke in a Stirling cycle machine, wherein there is a gas valve which vents the gas spring acting upon the displacer. The valve and its accompanying control system switch on a leak in the gas spring to vent the gas spring upon piston stroke beyond a selected magnitude. This reduces the spring constant which reduces the displacer amplitude and phase lead over the power piston and thereby reduces power output.

Abstract: A compensation winding for improving the linearity of a displacement transducer. The displacement transducer is the type having an electrically conducting non-ferromagnetic wall which moves in telescoping relation with the coil and is excited by a signal at a sufficiently high frequency that skin effect on the wall permits displacement of the wall to vary the reluctance of the coil flux path and thereby vary its inductance proportionally to displacement of the wall. The compensation winding is wound in telescoped, coaxial relationship to the coil in a fixed position. The compensation winding has a pitch which is a decreasing function of the distance from the end of the coil which is nearest the wall when the wall and the coil are in their least overlapping relationship.

Abstract: The power output of a free piston Stirling engine is matched to a gas compressor which it drives and its stroke amplitude is made relatively constant as a function of power by connecting a gas spring to the drive linkage from the engine to the compressor. The gas spring is connected to the compressor through a passageway in which a valve is interposed. The valve is linked to the drive linkage so it is opened when the stroke amplitude exceeds a selected limit. This allows compressed gas to enter the spring, increase its spring constant, thus opposing stroke increase and reducing the phase lead of the displacer ahead of the piston to reduce power output and match it to a reduced load power demand.

Abstract: A linear displacement transducer has an elongated current conducting, tubular coil which is mounted to an end cap in a hydraulic or pneumatic cylinder and extends into a hole bored in the piston/piston rod unit within the cylinder. An electrically conducting, nonferromagnetic tube lines the wall of the bore and reciprocates axially with the piston/piston rod unit varying its overlap of the coil and thereby varying the inductance of the coil at an applied frequency. An AC electrical energy source is connected to apply an AC signal to the coil, the frequency of this signal being at least high enough that the skin depth in the tubular wall is less than the physical depth of the tubular wall. A detector circuit means is connected to the coil for detecting a signal which is proportional to the coil inductance and therefore is proportional to the displacement of the piston/piston rod unit within the cylinder.

Abstract: The apparatus of the invention relates to a free piston Stirling engine that contains a power piston and a displacer piston which each reciprocate in a coaxial cylinder. At least one piston is hydrodynamically lubricated to avoid friction based wear by spinning the piston about its axis through the utilization of at least one magnetic article mounted onto one of the interfacing wall surfaces. The article magnetically interacts with a track made of magnetic material mounted on the opposing, interfacing surface so that during operation the interaction creates a torque which spins the piston about its axis and causes the desired lubrication to take place.

Abstract: An apparatus and method for synchronizing the phase of a pair of free piston Stirling machines without changing the design parameters or operating characteristics from the operating mode of each machine alone. Energy is coupled from corresponding gas spaces of each machine into an interconnected sonic transmission line to generate a standing wave in the transmission line. Preferably the transmission line is a tube which is, for example, one wavelength long to cause the two machines to run with their pressure waves in phase.

Abstract: The relative displacement of two bodies is measured by moving an electrically conducting, non-ferromagnetic wall means in proportion to the relative movement of the bodies in order to increase its overlapping, telescoping relationship to a first current conducting coil while simultaneously decreasing its overlapping, telescoping relationship to a second current conducting coil. Each of the coils are excited with an AC signal at a frequency which is at least high enough that the skin depth of the wall means is less than the physical depth of the wall means. A signal is detected which is proportional to the difference in the amplitude of the voltages across the two coils which results in improved sensitivity while improving linearity and substantially reducing temperature dependence.

Abstract: A temperature compensation structure for a displacement transducer of the type having a coil and an electrically conducting, non-ferromagnetic wall moving in telescoping relationship with the coil and excited by a signal at a sufficiently high frequency so that skin effect in the wall permits wall displacement to vary the reluctance of the coil flux path and thereby vary its inductance proportionally to displacement. The improvement provides temperature compensation for and essentially eliminates variation in the electrical scale factor which is caused by change in the temperature of the transducer. The improvement is to interpose between the coil and the core of the transducer a wall which has a thickness which is small compared to the skin depth of the wall material at the operating frequency of the device.

Abstract: The power output of a free piston Stirling engine is regulated by a valve in the gas flow path from the cold space through the regenerator to the hot space. The valve causes restriction of the gas flow path as in response to piston excursion beyond a selected excursion amplitude. Increased excursion causes increased restriction. The result is that, for piston excursions beyond the selected amplitude, the power out diminishes for increased stroke making the engine stable with any load from zero to maximum and avoiding runaway.

Abstract: A Stirling cycle engine is provided with gas cavities at an interface between an engine piston and a mating surface that guides the piston in its reciprocative motion to thereby achieve improved lubrication with the resulting gas film.

Abstract: A linear alternator capable of delivering multi-phase power and yet being driven by a free piston Stirling engine. The alternator has a permanent magnet mounted to the power piston of the free piston Stirling engine and an armature coil member mounted radially outwardly from the piston cylinder for generating one phase. A body, such as a second piston mounted in the same cylinder, is drivingly linked through a spring to be driven by the power piston. A second permanent magnet is mounted to the body and a second armature coil member is formed outwardly of the cylinder disposed outwardly from the body to provide the second phase. Proper design selection of the mass of the body and the spring constant of the spring, together with all other springs connected to the body, causes the body to be driven in phase quadrature with the power piston so that the voltage outputs of the two phases are in quadrature.

Abstract: A load regulator for a linear alternator driven by a free piston Stirling engine. A substantially constant output voltage is maintained across the useful load by shunting a portion of the armature output current of the alternator through a variable energy absorbing conductance and varying that conductance in proportion to changes in the output voltage of the alternator in order to maintain a constant total armature power output. The regulator may be made more efficient by forming the armature coil as a plurality of series connected coils by one or more taps and then switching the number of series coil turns in connection to the load approximately in inverse proportion to the square root of the steady state power demand of the load so that the total armature output power is switched between discrete levels while the output voltage is maintained constant for all those levels by the variable impedance.

Abstract: An electromechanical transducer particularly useful as a linear alternator driven by a free-piston Stirling engine is disclosed. A relatively high permeability material is formed into a flux loop having at least two pairs of spaced gaps formed transversely through the loop. Each pair of gaps is aligned along a reciprocation path for a magnet which is mechanically mounted for reciprocation between alternate positions within the gaps of each pair. The magnets have a magnetization vector transverse to the reciprocation path and are drivingly linked to a mechanical energy input or output for operation respectively as an alternator or motor. The armature coil is wound around a portion of the flux loop.

Abstract: An electromechanical transducer particularly useful as a linear alternator driven by a free-piston Stirling engine is disclosed. A relatively high permeability material is formed into a flux loop having at least a pair of spaced gaps formed transversely through the loop. The gaps are aligned along a reciprocation path for a magnet which is mechanically mounted for reciprocation between alternate positions within the gaps. The magnet has a magnetization vector transverse to the reciprocation path and is drivingly linked to a mechanical energy input or output for operation respectively as an alternator or motor. The armature coil is wound around a portion of the flux loop.

Abstract: In a free piston Stirling engine, an improved method and apparatus for preventing the creep of the mean position of the piston as a result of leakage of the working gas between the working space and the bounce space. A passageway is formed between the bounce space and the working space and extends through ports which interface with the piston and the displacer. Unlike the prior art, the port in the piston which registers with another port is offset from the mean position of the piston. Instead, the ports register when the bounce space and working space pressures are supposed to be equal. Additionally, the displacer blocks another port to prevent communication between the bounce space and the work space when the piston is moving outwardly from the work space, but opens to permit communication, and an equalizing flow of gas to counterbalance leakage, when the piston is moving into the working space.

Abstract: An improved linkage which is advantageously used in linking the crank of a Stirling machine to its coaxially reciprocating pistons. A swing lever having at least three spaced pivot axes is connected at one of its pivot axes to the machine housing and at a second pivot axes to one of the pistons. A bell crank, also having at least three pivot axes which are triangularly arranged, is rotatably connected at one of its pivot axes to the crank throw pin and pivotally connected at a second one of its pivot axes to the other piston. The bell crank is pivotally connected at its third pivot axis to the third pivot axis of the swing lever.

Abstract: A Stirling heat pump driven by a Stirling engine has its stroke limited under conditions of decreasing pump load. This stroke limitation is accomplished by effecting the flow of gas from the engine to the heat pump in response to a maximum piston stroke. Preferably, a valved passageway is formed in communication between the gas in the engine and the gas of the pump. The passageway is valved by a means which normally blocks the flow of gas but opens when the piston of either the pump or the engines strokes to an extreme selected position. The passageway opens into the engine and into the pump at zones so that when the valve is open the zones are at a pressure differential which will cause a flow of gas from the engine to the pump. By this means the power delivered by the heat engine portion of the machine can be made to be equal to the power absorbed by the heat pump at all conditions of heat pump temperature differential.

Abstract: A torsionally flexible seal formed with alternating layers of elastic and reinforcing material provides a gas-tight barrier between a drive shaft and a portion of the Stirling engine housing surrounding a passageway through which the drive shaft extends. The shaft is connected to a series of mechanical linkage devices located within the housing which transmits power between the linearly reciprocative power piston and rotationally reciprocative drive shaft and which eliminates substantially the side forces exerted on the piston.