Abstract: A gas bearing structure including a cylindrical core and a cylindrical sleeve. The core has a radially outwardly facing surface with longitudinal and circumferential grooves formed thereon. The sleeve has a radially inwardly facing surface that sealingly abuts the outer core surface. The inwardly facing sleeve surface bridges over the grooves, defining fluid, preferably gas, flow paths within each groove. The gas flow paths permit gas to flow from the workspace to radial passages formed through the sleeve sidewall, thereby forming a gas bearing.

Abstract: In a free piston machine, a coil is mounted to its housing and magnetically linked to a permanent magnet or electromagnet on its piston member to form a linear motor. The coil and magnet are either added to embody the invention or are part of an AC linear alternator or AC linear motor which are a part of the free piston machine. A source of DC electrical current and a switch for connecting the DC source to the coil supply DC current to the coil when the switch is closed so that the coil and magnet temporarily operate as a DC linear motor until the piston is adequately centered for start-up without collision. The DC source voltage is temporarily applied to the coil to move the piston away from an end wall of the cylinder. This is accomplished by applying the DC current to the coil for a predetermined time interval, or by sensing when the piston has reached an adequately centered position.

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 refrigeration system having a modulatable compressor and a Rankine cycle refrigeration circuit having at least two evaporators. The flow rate of the compressor is modulated in response to the sensed temperature of the masses being cooled, and the control circuit switches valves to control the refrigerant flow path and modulates the flow rate of the compressor to optimize the efficiency of the refrigeration system.

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 refrigeration system having a modulatable compressor and a Rankine cycle refrigeration circuit having at least two evaporators. The flow rate of the compressor is modulated in response to the sensed temperature of the masses being cooled, and the control circuit switches valves to control the refrigerant flow path and modulates the flow rate of the compressor to optimize the efficiency of the refrigeration system.

Abstract: A refrigerator having a heat pump mounted within the insulated portion of the refrigerator cabinet which is cooled by the heat pump. The heat pump is a Stirling cycle or Rankine cycle heat pump, is used to cool the interior of the refrigerator cabinet, and is mounted in an insulated housing to limit the transfer of heat from the heat pump into the refrigerator cabinet. A heat transporting conduit connects the heat pump to an exterior heat exchanger mounted outside the refrigerator cabinet.

Abstract: A reciprocating magnetic body support structure for a linear motor or a linear alternator is claimed. The body comprises a cylindrical, metallic support sleeve having a plurality of longitudinal slots evenly spaced around the circumference of the sleeve. An equal number of magnet segments is mounted to the sleeve extending over at least a portion of the associated slot and attaching to the wall of the sleeve on both sides of the associated slot. The longitudinal slots preferably extend completely through the sleeve from near one longitudinal end of the sleeve to near an opposite longitudinal end of the sleeve. The sleeve is preferably stainless steel or titanium, but should, regardless of metal, have a high resistivity, i.e., above 50 micro ohms per centimeter.

Abstract: A common and inexpensive integrated 555 timing circuit is used to vary the timing of triac firing pulses in response to a control voltage. A trigger pulse generator generates a pulse at each zero cross-over of an AC line. This pulse initiates a variable, one shot pulse generator which generates a rectangular pulse. The rectangular pulse terminates following a time interval which is controlled by the magnitude of a control input signal. A pulse forming circuit generates a triac firing pulse at the termination of the rectangular pulse from the one shot pulse generator.

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 method of measuring the distance at closest approach between the piston of a free piston compressor and the cylinder head. The method derives measurements of both the alternating and average components of piston position from direct measurements of the voltage and current applied to the linear permanent magnet motor that drives the piston, and thus eliminates any requirement for an additional position sensor located within the compressor.

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: An electrical circuit and method for generating a continuous train of width modulated pulses. A square wave is generated and a delay circuit provides a delayed analog of the square wave. A controllable duration one-shot multivibrator generates a modulating pulse having a duration proportional to the sum of the absolute value of the modulating signal and a constant offset. The constant offset is chosen so that, in the absence of a modulating signal, the offset provides the largest control signal to the one-shot multivibrator which causes an output modulating pulse from the multivibrator equal in duration to the minimum duration which the multivibrator intrinsically is capable of obtaining. The polarity of the modulating signal is detected, a logical OR operation is performed upon the delayed square wave and the modulating pulse and an EXCLUSIVE OR operation is performed upon the combination of the result of the OR operation and the polarity detector output logic level.

Abstract: Free piston Stirling coolers and engines are improved by a spring coupling the displacer to the piston and having a variable spring constant. Controllable variation of its spring constant permits controllable variation of displacer stroke, engine power output and cooler thermal pumping rate and thus the invention is useful for stroke limiting and load matching.

Abstract: A method of measuring the distance at closest approach between the piston of a free piston compressor and the cylinder head. The method derives measurements of both the alternating and average components of piston position from direct measurements of the voltage and current applied to the linear permanent magnet motor that drives the piston, and thus eliminates any requirement for an additional position sensor located within the compressor.

Abstract: The displacement of a Stirling cycle cryocooler is controlled as a function of temperature by controlling the amplitude of the fundamental component of an AC signal which is applied to the motor at its operating frequency. A pulse train is generated, having a frequency which is a harmonic of the operating frequency. The duty cycle of the pulse train is modulated between 50% and 100% as a function of the temperature. The modulated pulse train is applied to the motor during one-half of the load's operating period and the complement of the pulse train is applied to the load during the other half of its operating period. Modulating the duty cycle of the pulse train (and consequently simultaneously of its complement) as a function of temperature variably controls the amplitude of the fundamental component of the drive voltage and therefore variably controls the displacement of the motor and, as a consequence, of the cryocooler piston.