Power plants – Motor operated by expansion and/or contraction of a unit of... – Mass is a solid
Patent
1985-01-22
1988-07-12
Husar, Stephen F.
Power plants
Motor operated by expansion and/or contraction of a unit of...
Mass is a solid
60529, F03G 706
Patent
active
047561580
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a method for converting thermal energy to mechanical energy by means of a thermal power machine, wherein a member of metal alloy contained in it is heated to a certain temperature, whereat its physical properties, in particular its elastic constant, are changed and this physical change is used as the drive power of the thermal power machine. The invention is also concerned with equipment for converting thermal energy to mechanical energy, the said equipment comprising a thermal power machine which includes one or several metal alloy members, which change their physical properties, in particular their elastic constant, at a certain temperature, whereat this physical change provides the thermal power machine with drive power.
Several metal alloys are known in which the so-called memory phenomenon occurs. The patent claims refer to all of these so-called "memory alloys". One of such "memory alloys" is an alloy of titanium and nickel, known by the name Nitinol. After an object of such a material has been brought to a certain shape by means of an appropriate heat treatment, it always tends to return to this shape when it is heated to its transition temperature. On the contrary, below its transition temperature, the material is readily deformable. Thereat, the material can be deformed by means of a substantially lower force as compared with the force that is generated by it at a higher temperature when it returns to its heat-treated shape. The transition temperature can be adjusted by varying the composition of the alloy, and it may vary within the range of about -90.degree. C. to 150.degree. C., most commonly about 40.degree. to 90.degree. C.
Different applications of thermal power machines are known that are based on the ability of Nitinol to convert thermal energy to mechanical energy. One thermal power machine of this sort is described in the U.S. Pat. No. 4,275,561 (Finnish Patent Application No. 79-2398). The apparatus described therein is based on the tendency of a Nitinol loop to become straight at a temperature of, e.g., about 50.degree. C. When such a loop has been fitted around two wheels placed side by side and when one of the wheels is heated, e.g., by keeping it in warm water, the Nitinol loop tends to be straightened and to move at this wheel, making the wheel revolve by means of friction. The power can be taken out of the apparatus from the shaft of the unheated wheel. Such an apparatus has proved highly reliable and durable in operation.
Thermal power machines have also been developed that are based on easy extensibility of a Nitinol wire below the transition temperature and on the force generated by its shrinkage at the said temperature. Such a reversible elongation in the case of Nitinol is about 6 per cent. The power required for extending is considerably lower than the force generated by the shrinkage. Applications in which the shrinkage force is used for rotating a crankshaft, which again extends Nit elements, have been described in the U.S. Pat. Nos. 3,937,019 and 4,086,769.
The object of the present invention is to provide further applications for the conversion of thermal energy to mechanical energy by means of a memory alloy. The method in accordance with the invention is characterized in that the metal alloy member of a thermal power machine is heated by means of heat which is transferred by means of one or several heat pumps from an external medium that contains heat and that the heat pump is operated by means of part of the mechanical energy generated by the thermal power machine and the rest of this mechanical energy is used for other purposes. The equipment in accordance with the invention is characterized in that a heat pump is connected for heating the metal alloy member or members of the thermal power machine and that the output power of the thermal power machine has been connected so as to operate the heat pump.
According to the invention, the internal energy of the metal alloy can be converted to mechanical energy with maximum efficiency
REFERENCES:
patent: 4086769 (1978-05-01), Smith
patent: 4150544 (1979-04-01), Pachter
patent: 4175390 (1979-11-01), Koslow
patent: 4246754 (1981-01-01), Wayman
patent: 4275561 (1981-06-01), Wang
Arvola Ilkka
Kajamaa Jaakko
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