Liquid and/or temperature activated elapsed time indicators suitable, in particular, as doneness indicators for foodstuffs
First Claim
1. A liquid-activated elapsed time indicator, which comprises:
- structure, having open pores to permit entry, retention, and egress of fluids, which structure comprises an optically thin porous transparent film covering an at least partially reflective metal substrate and which generates a first color by optical interference effects when pores of said structure are gas-filled and a second contrasting color when pores of said structure are liquid-filled;
a transparent or translucent cover overlying said porous transparent film and adhered adjacent to lateral edges of said structures but remaining, at least in limited areas thereof, unattached to said structure and spaced therefrom by a distance which results in capillary movement of liquid positioned between said structure and said cover in said at least limited areas; and
an entrance to permit liquid to enter between said structure and said cover;
said entrance being positioned with respect to said at least limited areas such that an area of said second contrasting color expanding from said entrance as liquid passes therethrough can serve as an indicator of elapsed time.
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Accused Products
Abstract
Liquid and/or temperature activated elaspsed time sensors suitable, in particular, for use as doneness indicators for foodstuffs and for other purposes. The liquid activated indicators include a porous structure which generates a first color by effects which include optical interference when pores of the structure are gas-filled, and a second contrasting color when the pores of the structure are liquid filled. The porous structure is covered with a transparent or translucent cover which is unattached in certain areas to allow for capillary movement of liquid between the cover and the porous structure. An entrance permits liquid to enter between the cover and the porous structure. When contacted with liqiuid, the liquid is drawn into the device and produces an expanding area of contrasting color which is used to indicate the elapse of time. In one form, the doneness indicator, when located on the outside of a food container, can be activated by water condensed from steam generated as the food is heated, preferably by microwaves. In an alternative form the activated elapsed time indicator may contain a meltable solid which provides the liquid to operate the liquid activated indicator described above at a predetermined temperature.
26 Citations
13 Claims
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1. A liquid-activated elapsed time indicator, which comprises:
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structure, having open pores to permit entry, retention, and egress of fluids, which structure comprises an optically thin porous transparent film covering an at least partially reflective metal substrate and which generates a first color by optical interference effects when pores of said structure are gas-filled and a second contrasting color when pores of said structure are liquid-filled; a transparent or translucent cover overlying said porous transparent film and adhered adjacent to lateral edges of said structures but remaining, at least in limited areas thereof, unattached to said structure and spaced therefrom by a distance which results in capillary movement of liquid positioned between said structure and said cover in said at least limited areas; and an entrance to permit liquid to enter between said structure and said cover; said entrance being positioned with respect to said at least limited areas such that an area of said second contrasting color expanding from said entrance as liquid passes therethrough can serve as an indicator of elapsed time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A package for a water-containing foodstuff, which comprises:
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a container for said foodstuff having an exterior wall; an opening, or a region capable of being penetrated to form an opening, in said exterior wall, and a liquid-activated elapsed time indicator to provide an indication of doneness of said foodstuff upon heating of said package, said indicator being positioned outside said exterior wall sufficiently close to said opening or said region to be contacted by water emerging from said opening as said foodstuff is heated; said indicator comprising; a structure, having open pores to permit entry, retention and egress of fluids, which structure comprises an optically thin porous transparent film covering an at least partially reflective metal substrate and which generates a first color by optical interference effects when pores of said structure are gas-filled and a second contrasting color when pores of said structure are liquid-filled; a transparent or translucent cover overlying said porous transparent film and adhered adjacent to lateral edges of said structure but remaining, at least in limited areas thereof, unattached to said structure and spaced therefrom by a distance which results in capillary movement of liquid positioned between said structure and said cover in said at least limited areas; and an entrance to permit liquid to enter between said structure and said cover; said entrance being positioned with respect to said at least limited areas such that an area of said second contrasting color expanding from said entrance as liquid passes therethrough can serve as an indicator of elapsed time. - View Dependent Claims (10, 11)
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12. A package for a foodstuff, which comprises:
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a container for said foodstuff having an exterior wall with at least one transparent section, and a liquid-activated elapsed time indicator to provide an indication of doneness of said foodstuff, said indicator being attached to an inner surface of said exterior wall in such a manner that said indicator is visible through said at least one transparent section, said indicator also being positioned to come into contact with water condensed from said foodstuff as said foodstuff is heated and said indicator comprising; a structure, having open pores to permit entry, retention, and egress of fluids, which structure comprises an optically thin porous transparent film covering an at least partially reflective metal substrate and which generates a first color by optical interference effects when pores of said structure are gas-filled and a second contrasting color when pores of said structure are liquid-filled; a transparent or translucent cover overlying said porous transparent film and adhered adjacent to lateral edges of said structure but remaining, at least in limited areas thereof, unattached to said structure and spaced therefrom by a distance which results in capillary movement of liquid positioned between said structure and said cover in said at least limited areas; and an entrance to permit liquid to enter between said structure and said cover in said at least limited areas;
said entrance being positioned with respect to said at least limited areas such that an area of said second contrasting color expanding from said entrance as liquid passes therethrough can serve as an indicator of elapsed time.
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13. A temperature-activated elapsed time indicator, comprising:
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a reservoir for a solid which melts to form a liquid at a predetermined elevated temperature, a structure, having open pores to permit entry, retention, and egress of fluids, which structure comprises an optically thin porous transparent film covering an at least partially reflective metal substrate and which generates a first color by optical interference effects when pores of said structure are gas-filled and a second contrasting color when pores of said structure are liquid-filled; a transparent or translucent cover overlying said porous transparent film and adhered adjacent to lateral edges of said structure but remaining, at least in limited areas thereof, unattached to said porous structure and spaced therefrom by a distance which results in capillary movement of liquid positioned between said structure and said cover in said at least limited areas; and an entrance to permit liquid to enter between said structure and said cover in said at least limited areas;
said entrance being positioned with respect to said at least limited areas such that an area of said second contrasting color expanding from said entrance as liquid passes therethrough can serve as an indicator of elapsed time;said entrance communicating with said reservoir to permit said liquid from said reservoir to enter between said structure and said cover.
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Specification