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US 4,382,700 AGranted
Shelf life indicator
OwnerFred R. Youngreninventor
Life of this patent
Estimating the term…
Abstract
An indicator attached to perishable goods to show the remaining useful life are described. The preferred embodiment described includes a material, as for example a mineral jelly, which is in contact with a wick, such as a paper strip, such that the mineral jelly diffuses into the paper in accordance with changes in ambient temperature over a period of time. The amount of diffusion is indicated by an apparent change in color of the paper and is analogous to a change in the useful characteristic of the perishable goods.
Claims2
An indicator comprising:
- (a) a mass of ablative material whose ablation rate is a direct function of temperature;
- (b) a colored strip disposed on one side of the ablative material such that as the ablative material evaporates, the strip is progressively exposed;
- and
- (c) means for holding the ablative material in position over the colored strip while allowing the evaporative products of the material to escape to the atmosphere.
1 more element
An indicator for measuring the useful life of a perishable item within a container comprising:
- (a) a material in the non-gaseous state whose rate of evaporation is a function of temperature;
- (b) a porous strip tapered in thickness which is made translucent by being impregnated with said material;
- (c) a colored strip disposed on the back side of the porous strip such that as the material evaporates from the porous strip the translucence of the porous strip decreases, thereby progressively obscuring the colored strip;
- and,
- (d) means for holding the porous strip in position over the colored strip and allowing the evaporative products of the material to escape to the atmosphere.
2 more elements
Dependencies are inferred from the claim text.