Temperature responsive device
AssigneeInternational Standard Electric Corporation
InventorWilliam A. Crossland
Life of this patent
Estimating the term…
Abstract
A liquid crystal temperature indicator that gives a visual indication of whether the device is at a temperature above or below one or more threshold values has a homeotropically aligned nematic or smectic layer incorporating a pleochroic dye. The color of the cell changes as the dye will only absorb normally incident light when the temperature causes the liquid to go isotropic. Electrodes may be provided to provide electronic detection of the passage of the liquid through the threshold temperature.
Claims8
A temperature indicator that provides a visual indication as to whether its temperature is above or below each of at least two predetermined threshold values, comprising at least two temperature responsive cells each of said cells comprises a liquid layer the major constituent of which is a liquid that exhibits a nematic-isotropic or smectic-isotropic phase transition, in which layer a pleochroic dye has been dispersed, which layer is bounded by cell walls formed by two plates at least one of which is transparent and wherein the interior of said walls are such that homeotropic alignment is induced in said liquid without the application of an electric field when its temperature is below that of said phase transition and wherein the liquid in one cell has a different phase transition temperature from that of the liquid in another cell.
A temperature indicator that provides a visual indication of its temperature by identifying one of a plurality of temperature ranges comprising:
- a plurality of temperature responsive cells each of which exhibits a distinct phase transition temperature;
- said cells comprising a liquid crystal layer which exhibits a reversible phase transition without the application of any electrical field, and which assumes homeotropic alignment when below said phase transition temperature absent any electric field;
- a plurality of pleochroic dyes respectively dispersed into said cells to impart a distinct color to each cell when above its distinct transition temperature;
- means for retaining said plurality of cells in close proximity to provide an integral array of cells,
- whereby, visual inspection of said array will provide an indication of which cells are above their phase transition temperatures and which are not.
Dependencies are inferred from the claim text.