The present invention is in the field of temperature control. More specifically the invention is a temperature controlled valve for restricting gas flow.
Cryostats of the Joule-Thomson effect type are used to cool devices tat require low temperature for functioning. Cryostats such as disclosed in U.S. Pat. No. 5,077,979 and EP application 0747644A3 use a gas expansion for cooling and a gas flow control to control the temperature obtained. EP patent 0245164B1 discloses a Joule-Thomson type cryostat that employs a shape memory alloy component in the mechanism of gas flow control, in which a bias spring is used to deform a bias spring in the cold.
Shape memory alloy metals (SMA) are typified as exhibiting two distinct crystallographic states (or phases). Each of the states is associated with a specific set of mechanical properties. The technological aspects of this issue are discussed in “Engineering aspects of shape memory alloys”, by T. W. Duerig, K. N. Melton, D. S. Tockel and C. M. Wayman, Butterworth Heinemann, 1990.
Shape memory alloys (SMA) possess characteristic properties at two different phases, namely the austenite state or phase at higher temperatures, and the martensite state or phase, at lower temperatures. In the austenitic state the SMA is rigid, while in the martensite state, the metal is relaxed, softer and stretchable. Typically SMA alloys are made from a combination of copper-zinc-aluminum, or copper-nickel-aluminum or nickel-titanium combinations.
If deformed in the colder temperatures, at the martensite state, an SMA metal tends to return to the original form in warmer temperatures, in which the austenite state prevails. The temperature limits of the martensite and austenite state, are defined largely by the nature of the alloy used.
In the present application, the cooling gas flow is used to change the shape of a SMA component directly, to control the cooling gas flow.
The present invention is embodied in an automatic regulative component that implements a certain restrictive rule on the flow of cooling gas through a conduit. An embodiment of the invention is shown in
In
The valve and control of cooling in accordance with the present invention is better illustrated in
A variety of alloys are available that provide a wide range martensite and austenite limits for matching the proper temperature range required for obtaining a control over the cooling temperature range.
Number | Date | Country | Kind |
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178633 | Oct 2006 | IL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL07/01241 | 10/16/2007 | WO | 00 | 4/16/2009 |