Other

Sunpower Corporation

Government of the United States

Data Instruments, Inc.

Robert W Redlich

William T Beale

David M Berchowitz

Christopher G Scheck

Douglas Bliss

A thermal machine that can function as either a refrigerator or an external combustion heat engine is disclosed. A working gas undergoes four thermodynamic processes that comprise a Brayton cycle. Two of these processes, adiabatic compression and adiabatic expansion, take place in the same cylinder, within which a piston, driven by a crankshaft, reciprocates. The remaining two processes, each of which is a transfer of heat at constant pressure, take place in a high pressure heat exchanger and a low pressure heat exchanger. A rotary valve, rotating at one-half crankshaft speed, creates passages between the cylinder and the heat exchangers, and is constructed so that compression and expansion ratios are equal.

Reciprocating four-stroke Brayton refrigerator or heat engine

A Triac and a phase-locked loop are used to control the amplitude of reciprocation of an AC linear motor. The phase locked loop generates a square wave that is synchronized with an AC power source but is substantially isolated from electrical noise on the power source. The phase of the square wave is varied with an amplitude control signal, and Triac firing pulses are generated at the transitions of the square wave.

Linear motor control with triac and phase locked loop

Disclosed is a method of generating magnetic centering force on the permanent magnets of a reciprocating permanent magnet motor or generator, by allowing the ferromagnetic structure of the machine to saturate magnetically when the permanent magnets are near the ends of their travel.

Auto-centering linear motor

A refrigerator that efficiently cools multiple cold spaces at different temperatures with one compressor and one condenser is disclosed. Multiple, fan equipped evaporators are in series, and an expansion valve regulates superheat from inlet to outlet of the series evaporators. Cold space temperatures are regulated with an on-off thermostat in each space. If only one fan is turned on, system performance approaches that of a single evaporator refrigerator with controlled superheat. More than one evaporator fan may be turned on for initial cooldown.

Multiple evaporator refrigerator with expansion valve

In a vapor compression refrigerator with closed loop feedback control of evaporator superheat, a superheat stabilizer consisting of a cavity connected between the evaporator outlet and the suction line inlet, the cavity combining the functions of liquid separation and vapor superheating in order to stabilize superheat by preventing liquid from reaching the outlet vapor temperature sensor and also by achieving preset superheat downstream of the evaporator.

Evaporator superheat stabilizer

Circuits for converting DC voltage into controllably variable amplitude AC voltage, for the purpose of driving an oscillating linear motor with controllable amplitude, are disclosed. Unlike pulse width modulation circuits for the same purpose, the disclosed circuits do not require suppression of electromagnetic interference and have negligible switching loss.

Circuits for controlling reciprocation amplitude of a linear motor

Disclosed is a reed valve which uses a simple electromechanical actuator to apply a force that overcomes pressure force and opens the valve. The valve is closed by pressure and the elastic restoring force of the reed. Two of the disclosed valves in a back-to-back connection accommodate bi-directional flow. The disclosed valve is especially suited for application as a pulsed expansion valve for refrigerators and heat pumps.

Electrically actuated reed valve

Disclosed is an AC electric motor with oscillating rotary output, a permanent magnet rotor having radially magnetized magnets, and feedback control of oscillation amplitude. Amplitude control is accomplished without a separate amplitude sensor by using an accurate model of the motor as a basis for calculation of amplitude from measurements of motor voltage and current. The motor has high efficiency, low inertia, and uses a relatively small volume of permanent magnet per unit power output.

Electric motor with oscillating rotary output and controlled amplitude

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.

Triac control circuit

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.

Method and apparatus for measuring piston position in a free piston

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.

Pulse width modulator

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.

Control of stirling cooler displacement by pulse width modulation of

Disclosed is an improvement to Integral Monitoring of two-frequency Instrument Landing System Localizer transmitting antenna arrays, by means of which the Clearance signal can be precisely separated from the combined Course and Clearance output of an Integral Monitor recombiner and monitored as if it existed alone. A first detector detects a composite Clearance and Course signal input, and sends an output to a separation filter which does not pass frequencies of 0, 90 or 150 hertz, but does pass frequencies of the difference between Course and Clearance frequencies (.DELTA.f), .DELTA.f.+-.90 hertz, and .DELTA.f.+-.150 hertz. The output of the filter is input to a second detector which measures the difference between the percentages of 90 and 150 hertz amplitude modulations of an amplitude modulated carrier having a frequency .DELTA.f.

Monitor for instrument landing system

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. This increased spring constant results in greater energy storage in the magnetic spring and decreased efficiency due to decreased phase angle.

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Athens, OH, United States of America

Robert W Redlich