Signals and indicators – Indicators – Chemically activated type
Patent
1987-10-02
1989-07-11
Shoop, Jr., William M.
Signals and indicators
Indicators
Chemically activated type
116207, 116216, 116219, G01K 1106
Patent
active
048460958
ABSTRACT:
Device for indicating a critical temperature, such as, for example, the freezing point of a liquid. The device comprises a sheet which is a layer having a multiplicity of micropores therein and a mixture comprising at least two liquids, said mixture incapable of wetting said sheet at a given temperature, but capable of wetting said sheet when the temperature of said mixture reaches a critical value, such as the freezing point of one of the liquids in the mixture. The micropores, or voids, in the microporous layer cause scattering of transmitted light, causing the microporous layer to appear opaque. When the voids are filled with a liquid having substantially the same index of refraction as the material of the microporous layer, the filled voids do not scatter transmitted light, thus rendering the microporous layer transmissive to visible light.
A visible indicator is associated with the layer of microporous film such that at a temperature above the freezing point of the liquid composition, the visible indicator is masked by the layer of microporous film, but at a temperature at or below the freezing point of the liquid composition, the liquid wets out the layer of microporous film, thereby allowing the visible indicator to be seen through the layer of microporous film.
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Ip Paul
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Sell Donald M.
Shoop Jr. William M.
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