Thermal measuring and testing – Temperature measurement – Nonelectrical – nonmagnetic – or nonmechanical temperature...
Patent
1988-03-21
1991-02-19
Yasich, Daniel M.
Thermal measuring and testing
Temperature measurement
Nonelectrical, nonmagnetic, or nonmechanical temperature...
116204, 116217, 335215, G01K 1106
Patent
active
049938436
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Means exist for detecting the thermal level to which materials have been subjected. Detectors are known whose functioning is based for example on the variation in fluidity of a coloured matter, of which the progression by capillarity in a support gives a visual indication of exceeding a given temperature. Detectors using a different principle are also known, where an enzymatic reaction is translated by the variation in coloration of a surface of which the extent also indicates exceeding a thermal threshold. Such detectors are generally placed in the immediate proximity of the material to be monitored or thereon.
Such detectors present drawbacks: they are expensive, which does not allow use thereof for verifying the freshness of a food product, for example presented in the form of individual portions. Furthermore, these detectors, applied on a product, always indicate the exceeding of a superficial temperature or one in the proximity. In addition, they are of a certain fragility and cannot without drawbacks be immersed in a liquid or be subjected to compressions or inevitable shocks in the handling and transport operations. Furthermore, their structure does not allow them to be driven into the material or product to be monitored.
The evolution of eating habits of populations living in so-called developed countries is more and more oriented towards prepared dishes, cooked in vacuo for example. The life duration of such foodstuffs is a function of several parameters of which the most important appears to be the temperature which, when it lies below a determined maximum value, limits proliferation of bacteria. The same applies to the preservation, with maintenance of innocuosness, of certain drugs, including vaccines and sera. The examples of application set forth hereinabove are not limiting.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and apparatus for detecting a rise in temperature to which a material (solid, liquid or gaseous) has been subjected, wherein there is applied to a piece mobile in an at least partially transparent tube a force of displacement towards a final position which tends to cause the mobile piece to leave an initial position where it is immobilized by a meltable substance placed inside the tube, which, on melting when the temperature rises sufficiently, releases the mobile piece.
In order to overcome these problems, the invention has a further object to improve the process of the type described above, so that it makes it possible to produce devices for detecting a rise in temperature which, although simple and inexpensive, are efficient and offer considerable reliability.
According to the process and above-described object of the invention, the force of displacement applied to the mobile piece is of purely magnetic origin and is produced by the interaction of magnetic elements comprising at least one permanent magnet and mounted respectively on the tube and on the mobile piece.
According to another feature of this process, the mobile piece is previously brought into initial position by application to this piece of an arming force likewise of purely magnetic origin, the meltable material having been temporarily liquefied to allow this prior operation.
In general, each of the forces of displacement and of arming employed is either a force of magnetic attraction or a force of magnetic repulsion.
The method according to the invention is based on the combination of two simple physical phenomena:
The first phemomenon is, the existence of materials meltable at diverse temperatures which, in the solid state, may prohibit the displacement of a mobile piece located therewithin and subjected to a force, this displacement becoming possible when the material takes the liquid state, the change of phase being effected at the melting temperature which is a characteristic constant of the material used;
The second phenomenon relates to the properties of the magnetic elements, thanks to which it is possible to apply forces without phys
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patent: 3965741 (1976-06-01), Wachtell et al.
patent: 3965848 (1976-06-01), Shotkin
patent: 4143617 (1979-03-01), Youngren
patent: 4187799 (1980-02-01), Zwarun
patent: 4644310 (1987-02-01), Anderson, III et al.
"PCT International Publication" document No. WO 87/07373 filed May 19, 1987, J. F. Toupin, published 12/3/87, Method and Device for Detecting the Temperature to which a Solid, a Liquid or a Gas May Have Been Subjected.
Douesnel Xavier
Toupin Joseph
Douesnel Xavier
Yasich Daniel M.
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