P/N junction device having porous emitter
Granted: November 1, 1994
Patent Number:
5360990
In a semiconductor P/N junction device, a porous emitter is provided which has high saturation current to limit injected charge when the device is conducting. The porous emitter includes a lightly doped region abutting a contact on the surface of the device to regulate minority carrier injection under forward bias and shield the contact from stand-off field when the device is not conducting. One or more heavily doped regions are provided in the first region to provide low contact…
Method and apparatus for measuring piston position in a free piston compressor
Granted: August 30, 1994
Patent Number:
5342176
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.
Vertically pivotal security gate
Granted: November 23, 1993
Patent Number:
5263281
A security gate system including a supporting structure and a gate mounted on the supporting structure for pivotal movement about a generally horizontal pivot axis between a closed position and an open position. A drive wheel is rotatably mounted on the supporting structure and is drivingly coupled to the gate so that rotation of the drive wheel in a gate opening direction drives the gate from the closed position to the open position. A first motor drives the drive wheel and a releasable…
Monolithic series-connected solar cells having improved cell isolation and method of making same
Granted: November 17, 1992
Patent Number:
5164019
Series connected cells of a solar array formed in a monolithic semiconductor substrate are electrically isolated by forming grooves in a first major surface partially through the substrate between cells and then fracturing the substrate from the bottom of the grooves to an opposing major surface. Metallization interconnecting the cells provides physical integrity of the cell array after the fracturing of the substrate. The grooves can be formed prior to completion of fabrication of the…
Control of stirling cooler displacement by pulse width modulation of drive motor voltage
Granted: October 20, 1992
Patent Number:
5156005
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…
Linear generator or motor with integral magnetic spring
Granted: September 15, 1992
Patent Number:
5148066
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…
Asymmetric gas spring
Granted: April 2, 1991
Patent Number:
5003777
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…
Leaky gas spring valve for preventing piston overstroke in a free piston stirling engine
Granted: August 7, 1990
Patent Number:
4945726
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.
Precision variable pitch compensation winding for displacement transducer
Granted: May 15, 1990
Patent Number:
4926123
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…
Variable gas spring for matching power output from FPSE to load of refrigerant compressor
Granted: April 3, 1990
Patent Number:
4912929
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…
Actuator displacement transducer having external flux excluding tube
Granted: March 27, 1990
Patent Number:
4912409
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…
Magnetic driven hydrodynamic lubrication system for free piston stirling engine
Granted: December 26, 1989
Patent Number:
4888950
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…
Phase synchronization and vibration cancellation for free piston Stirling machines
Granted: December 26, 1989
Patent Number:
4888951
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…
Displacement transducer with opposed coils for improved linearity and temperature compensation
Granted: September 12, 1989
Patent Number:
4866378
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…
Temperature compensation for displacement transducer
Granted: September 5, 1989
Patent Number:
4864232
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…
Stirling engine power regulation system
Granted: February 21, 1989
Patent Number:
4805408
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…
Sliding surface lubrication particularly advantageous for a free piston stirling engine
Granted: February 7, 1989
Patent Number:
4802332
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.
Multi-phase linear alternator driven by free-piston Stirling engine
Granted: March 10, 1987
Patent Number:
4649283
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…
Adaptive regulation system for a linear alternator driven by a free-piston stirling engine
Granted: February 10, 1987
Patent Number:
4642547
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…
Electromechanical transducer particularly suitable for a linear alternator driven by a free-piston Stirling engine
Granted: November 18, 1986
Patent Number:
4623808
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…
