Thermal measuring and testing – Temperature measurement – Nonelectrical – nonmagnetic – or nonmechanical temperature...
Patent
1997-12-17
2000-02-29
Miska, Vit
Thermal measuring and testing
Temperature measurement
Nonelectrical, nonmagnetic, or nonmechanical temperature...
116204, G01K 1106, G01D 512
Patent
active
06030118&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for irreversibly indicating that the permissible temperature of goods, rooms or the like has been temporarily exceeded, consisting of a container which has a heat-conducting connection to the goods or to the surrounding room and which contains, in its interior, a suspension consisting of a medium having a melting point or softening range which is in the range of the control temperature and magnetizable particles suspended in the medium. The present invention furthermore relates to a process for temperature monitoring with the corresponding apparatus and a process for the production of the apparatus.
Apparatuses or processes of the generic type defined at the outset are described in U.S. Pat. No. 3,675,501 and DE-A 42 10 739 of the same applicant.
In deep-freeze storage of certain foods, a storage temperature of at least -18.degree. C. must be maintained if a relatively long shelf life is to be ensured, although said storage temperature may be briefly exceeded. If a temperature of from -10 to -15.degree. C. is exceeded, the shelf life of many foods is no longer ensured; the frozen material is considered to have started to thaw although it still appears frozen on the outside. Temperature monitoring is subject to, inter alia, EC Directives 89/108 and 98/108.
A similar situation applies to the storage of prepared food, for which a temperature of a few degrees above zero degrees Celsius is generally prescribed, to blood plasmas or to other articles for which there is a prescribed maximum acceptable storage temperature.
There is also a need to monitor the ambient temperature or the temperature of closed spaces and the like and irreversibly to register impermissible deviations.
Usually, freezers are equipped with built-in thermometers which indicate the temperature in a certain part of the freezing space, or a conventional thermometer is placed on or next to the frozen material and is removed from the freezer for readings. In these cases, there is no guarantee that the temperature of the frozen material will be measured exactly. Moreover, air convection in the freezing space may be hindered by stacking and packing of the frozen material, so that the minimum temperatures required for ensuring the shelf life of the foods may be exceeded in certain parts of the freezing space, even when the equipment functions satisfactorily. The user of the frozen material cannot detect the fact that the maximum storage temperature has been exceeded, so that he cannot counteract spoilage of the food by removing it in good time and using it immediately. The danger that deep-frozen food will start to thaw without this being noticed is particularly great, for example, when a relatively large amount of material to be chilled is introduced in a warm state into the freezer. It is therefore desirable to have a temperature indicator which shows, for every food bag or group of bags, whether they have always been sufficiently chilled during their storage time.
The abovementioned U.S. Pat. No. 3,675,501 describes a kind of fever thermometer, consisting of various closed containers which contain, in the temperature-relevant range, media, such as waxes or fatty acids, in which magnetic particles, such as barium Lerrite, are suspended. A magnetic film which is present at the instant of the phase transition from liquid to solid and effects orientation of the magnetic pigments is drawn over this arrangement. The film is then removed and the container is then administered to the patient; after removal, it is possible to determine the container in which the frozen magnetic order has broken down, this being taken as a measure of the temperature. DE-A 42 10 739, which is likewise mentioned, discloses a container, preferably a flat bag, consisting of a transparent plastics film and a magnetic medium contained therein, together with an eutectic mixture having a melting point of from about 0.degree. C. to -50.degree. C. Handling is similar to that in the U.S. Patent, and optically and/or magnetically readable
REFERENCES:
patent: 3675501 (1972-07-01), De Kanter
patent: 3915006 (1975-10-01), Ayres
patent: 4576781 (1986-03-01), Duncombe et al.
patent: 4850716 (1989-07-01), Baker et al.
patent: 4993843 (1991-02-01), Toupin et al.
patent: 5490476 (1996-02-01), Veitch et al.
Bettinger Gunther
Schneider Norbert
Veitch Ronald
EMTEC Magnetics GmbH
Miska Vit
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