GB2324611A - Product life timer - Google Patents

Abstract

An electrochemical cell 12 is used as a lining mechanism. The cell 12 is sized to supply electrical power to a display 14 for a period of line related to the intended life of a product by the value of load resistor 16. The display remains in an active state giving a fast message in response to a level of power output by the cell above a threshold and reverts to a default state, blank or a second message, in response to a level of power output below the threshold. The cell and the display can be arranged in layers on a common substrate for incorporation into a label or product packaging.

Description

1 PRODUCT LIFE TIMER 2324611

The invention relates to the field of electrochemical timing devices, particularly those used for measuring product life.

Many manufacturers eager to ensure tile best performance of their products advise consumers of their products' expected shelf or service fives. For example, the packaging of products that degrade predictably with the passage of time are often imprinted with a date indicating the time of their manufacture or the time within which the products should be sold or used. "Sell by:", "use by:", and "expiration date:" notices are now commonplace on perishable goods.

Sometimes, the expiration date of a product depends upon when the product is put into service. Some such products degrade predictably with use, and others begin to similarly degrade upon exposure to the environment. Examples include air fresheners, pet treatment collars, air and water filters, and cosmetics. Since tile expiration date of such products is not known at tile time of their manufacture, manufacturers generally advise only on their intended length of service and rely oil their customers to calculate the actual expiration date from the date the product is entered into service and the suggested length of service.

In place of written notices, timers are known that automatically advise customers of product life. Mechanical and electronic timing mechanisms are generally too expensive for this purpose. Accordingly, much of the attention of this art has been directed to the development of less expensive chemical or electrochemical timers. These la Her timers generally rely on slow chemical reactions or the migration of materials to produce a cumulative change in appearance with the passage of time. None of these timers have enjoyed much commercial success.

2 Bradley et al. in U.S. Patent 4,292,916 disclose a disposable timer and product storage condition indicator with two alternative types of timing mechanisms. An insoluble ink of one of the timing mechanisms migrates through a barrier layer at a controlled rate to produce a color change visible through a stenciled pattern. A soluble ink of the other timing mechanism dissolves in the presence of a migrating mixture to reveal a similar stenciled pattern. Both ti ' mers are activated by releasing their migrating mixtures from impervious confinements. Also, both timing mechanisms are sensitive to 0 ambient conditions, especially temperature. Accordingly, the timers are intended for use on products whose service lives are similarly affected by the same conditions.

Kang et al. in U.S. Patent 4,804,275 use an advancing color change boundary in an electrochromic strip to rnark the passage of time. An electrode dissolves in an acidic electrolyte, injecting electrons into the electrochrornic strip and causing a reaction that chemically alters the electrochromic strip along the color change boundary. Like the above-described chemical timing mechanisms of Bradley et al., (lie electrochemical timing mechanism of Kang et al.

is also temperature sensitive. Activation is also similar by releasing the acidic electrolyte from confinement. However, the acidic electrolyte is dangerous and limits the usefulness of this t i ni e r.

A much earlier U.S. Patent 3,045,179 to Maier discloses a solid state elapsed time indicator in which an electrochromic display is powered by an external electrical source. The electrochromic display, which is relatively insensitive to temperature variations, gradually changes in color with the flow of current. A resistor connected in series with the display regulates the flow of current through (lie display. A series switch activates (lie timer. The gradual chemical change in the display provides the timing mechanism. The electrical source is required to maintain the flow of current at a steady rate until the color change is complete.

KUo et al. in U.S. Patent 5,250,905 disclose a battery tester 35 that is connected in parallel with a-battery to common external 3 loads. The tester is itself an electrochemical cell having only a tiny fraction of tile battery's capacity. The electrochernical cell's voltage is also less than the voltag e of tile battery, so the cell does not begin to discharge until tile battery's voltage drops; and when it does discharge, a much higher impedance of the electrochemical cell slows its discharge rate to match tile discharge rate of the battery.

During its discharge, ail anode of the electrocilemical cell gradually oxidizes, revealing a message.

Accordingly, tile timing function of Kuo et al.'s battery tester -10 is also performed by a gradual chemical change in tile display. Like all of (tie other electrochernical timing mechanisms described above, energy is supplied to support an irreversible chemical reaction that permanently changes the display's appearance. Tile amount of change is a function of the cumulative amount of current that passes through the display.

Our invention includes a timing mechanism that operates independently of visible chemical or physical changes in a display of a product life tinier. Instead of supporting cumulative changes in [lie display, ail efectrochernical cell preferably shifts tile display between active and default states in accordance with its power output. Above a threshold power output, the display remains in an active state; and below the same threshold, tile display reverts to its default state. Tile discharge rate of the cell is equated with product life so that tile display remains in its active state throughout (lie intended life of (lie product and reverts to its default state at the expected end of product life.

In contrast with tile usual requirements for electrochemical cells, which involve maximizing power capacities, the electrochemical cells of our invention have only limited power capacities. This enables a wider selection of materials for making the cells, including safer, environmentally compatible materials, as well as less expensive materials thgt contribute to ease of manufacture.

4 The electrochernical cell rather than the display undergoes a chernical change to provide a timing mechanism. The display merely reflects different levels of power output by the electrochemical cell. For example, different states of the display can be triggered by different levels of (lie electrochemical cell's power output. One of the states is preferably an active state triggered by power output above a given threshold. The other state is preferably a default state triggered by power output below the given threshold.

The active state can display a message affirming the product's efficacy, and tile default state can display a message indicating tile need for refurbishing or replacing tile product (or even no message at all). The electrochernical cell is designed to output a level of power above the threshold throughout the expected life of the product, thereby maintaining the display in the active state throughout the sanle period. A drop in tile electrochemical cell's power output at [lie end of this period allows the display to revert to its default state indicating tile end of product life.

A circuit controlled by a switch preferably interconnects tile elect roch e mical cell and the display. Resistance of tile circuit includes internal resistance of the electrochemical cell and tile display as well as any additional resistors used to regulate the rate of discharge from tile electrochernical cell. Tile switch, which opens and closes tile circuit, can be used to start tile tinling mechanism.

Our new product life tinier can be used as a stand-alone tinier, incorporated within product packaging, or made as a label that can be removably mounted on product packaging. The label version can be removed from the product packaging when the product is first put into service and remounted in a new location where it can be more conveniently observed. A switch for activating the timer can be closed automatically upon removal or remounting of the label or can be closed manually at the convenience of the customer.

FIG. 1 is a circuit diagram showing an arrangement of our product life tinier with discreet components.

FIGS. 2A and 213 illustrate two different states of a display 5 component of [lie product life timer of FIG. 1.

FIGS. 3A, 313, and 3C illustrate three different states of the display component.

FIG. 4 is a cross-sectional view of an integrated version of our product life timer incorporated within a label.

FIGS. 5A and 513 illustrate another integrated version of our product life timer incorporated within product packaging. A crosssectional side view is provided in FIG. 5A, and a cross-sectional top view is provided by FIG. 5B.

In a basic form, our product life timer 10 includes four well- known electrical components: an electrochemical cell 12, a display 14, a resistor 16, and a switch 18 all joined together within a common circuit 20. Each of the components can be made in a variety of ways from a variety of materials; but each is preferably arranged in a layered form for assembly into a label, a product package, or oilier laminated structure. Examples of such layered structures are described in more detail later.

U.S. Patent 5,350,645 to Lake et al., which is hereby incorporated by reference, discloses a laminated array structure that includes a number of individual battery cells that can be used as the electrochemical cell 12 of our product life timer 10. The cells of Lake et al. include the usual anode, electrolyte, and cathode layers spaced by suitable masking. Substrates supporting the anode and cathode layers form conductive end caps for connecting the cells to external circuits.

1.1 6 Another example of an electrochemical cell that can be used as the electrochemical cell 12 of our product life timer 10 is disclosed in U.S. Patent 5,055,968 to Nishi et al., which is also incorporated by reference. Nishi et al.'s cells are formed by an in-line processing technique as a part of an information card. Electroconductive and battery activator materials are applied in patterns to adjacent surfaces of two webs, and an electrolyte impregnated sheet is mounted on one of the web surfaces prior to laminating the two webs together.

0 The display 14 preferably has at least two distinct states for displaying one or more contrasting messages 22 as shown in FIGS.

2A and 213. One of the states, illustrated by FIG. 2A, is an active state triggered by application of a voltage (i.e., electromotive force) above a given threshold. The other of the states, illustrated by FIG.

213, is a default state (no message) triggered by a drop in the voltage below the threshold. The messages can be conveyed in words, colors, symbols, or other graphics.

FIGS. 3A-3C illustrate ail alternative combination of three distinct states for tile display 14. The first state, shown in FIG. 3A, is an initial state, prior to power being applied for a first time. Tile second and third states, shown in FIGS. 313 and 3C, are active and default states triggered similar to tile corresponding states of FIGS. 2A and 2B. All three states reveal word messages 26, 28, and 30.

rhe display 14 can include an electrochromic material that produces a reversible change in color in response to the application of voltage between opposing electrodes. For example, the message 22 of the active state of FIG. 2A can be produced by a color change in the electrochromic material from a color matching a background 24 of the display to a color that contrasts with the background 24. The default state of FIG. 2B restores the color of the electrochrornic material to its initial color matching the background 24.

The initial state of FIG. 3A can be produced by a removable film overlay 32 that covers the message 30 conveyed by the default state. The active and default messages 28 and 30 of FIGS. 3B and 3C 35 can be produced by writing them against a background 34 in colors

7 that contrast with background colors assumed by the electrochromic material. The active message 28 is written in a color that matches the initial color of the electrochrornic material but contrasts with (lie color of the electrochrornic material after voltage is applied.

The default niessage 30 nialches the color of the electrochrornic material after voltage is applied but contrasts with the initial color of the electrochromic material.

U.S. Patent 5,413,739 to Coleman, which is hereby incorporated by reference, discloses an electrochromic display that can be used as the display 14 of our product life timer 10. Coleman's display is also a laminate made up of various' composite layers between electrodes. Color change occurs in response to a voltage applied across the electrodes at an interface between an ionically conductive layer and a layer of electrochromic material.

The circuit 20 connects the display 14 in series with tile electrochernical cell 12 and the resistor 16. A total resistance of the circuit 20, which limits a discharge rate of tile electroellemicat cell 12, is a sum of the resistance contributed by tile electrochemical cell 12, tile display 14, and the resistor 16.

Alternatively, tile resister 16 can be connected in parallel with tile display 14 to increase tile discharge rate. More cells can be connected in series to increase the available electromotive force. A further modified circuit can be used to compensate for resistance fluctuations of the display 14 and to maintain tile threshold voltage across tile display 14 throughout the expected life of tile electroche mica[ cell 12.

Any portion of [lie circuit 20 can be interrupted by the switch 18, including internal layers of the electrochemical cell 12 or (lie display 14. Closing the switch 18 starts the timing mechanism of our product life timer 10 by completing the circuit 20 and shifting the display 16 from its default state to its active state. The electrochemical cell 12 is sized to supply electrical power to the display 16 at (at least) the thresholdvoltage for a period of time corresponding to an intended life of a product. The switch 18 can be constructed in a variety of known ways, such as by arranging a pair 1 1 1 1 1 8 of conductive layers that can be actively moved into contact or biased into contact upon removal of an intermediate insulating layer.

A much wider choice of materials is available for practicing our invention because the functional requirements for each component are less stringent than the requirements associated with their regular use. For example, maximizing the power capacity of the electrochemical cell 12 is generally not necessary, because its capacity for a given discharge rate is equated with a limited product life. Reaction time of the display 14 to shift between different states is also less critical. Accordingly, other objectives can be optimized by material selections including cost, safety, and ease of manufacture.

Product life timer 40 depicted in FIG. 4 is incorporated within a label 42 having the usual layers of a substrate 44, a pressure sensitive adhesive 46, and a release liner 48. An electrochemical cell 52, an electrochemical display 54, a resistor 56, and a switch 58 are assembled in layers on the substrate 44. The electrochernical cell 52 has an electrolyte layer 60 between two electrodes 62 and 64 (anode and cathode). The electrochemical display 54 has electrolyte and electrochromic layers 66 and 68 between two electrodes 70 and 72.

Examples of electrolytes for the layers 60 and 66 include polyethylene oxide, electrolytic adhesive such as hydrogels, or ammonium chloride in a gel. The electrodes 62, 64, and 72 can be, among other things, copper, silver, aluminum, manganese dioxide, zinc, carbon, lithium, or sulfur. The electrode 70 can be made of similar materials including aluminum, zinc, carbon, lithium, and sulfur or of indiurn tin oxide. Electrochromic materials, such those listed in the Coleman patent, including polyaniline, poly-pyrrole, polythiophene, nickel oxide, polyvinylferrocene, polyviologen, tungsten oxide, iridiurn oxide, molybdenum oxide, and Prussian blue can be used in layer 68.

Pairs of conductors 76, 78 and 80, 82, which can be made from a carbon-based ink of high conductivity, straddle the electrodes 62, 64 and 70, 72 of the cell 52 and the display 54. The conductors 78 9 and 82 are connected by the resistor 56, which can be made of a high resistance carbon-based ink. The switch 58 interrupts a connection between the conductors 76 and 80. A non-conducting adhesive mask 84 otherwise separates the electrochemical cell 52 from the electrochemical display 54, and another substrate 86 covers both the cell 52 and the display 54. The substrate 86 is preferably a transparent polyester film, but paper or card stock with an opening for viewing the display 54 could also be used. A graphics layer 88 can be applied to the substrate 86 for communicating information 10 and improving appearance.

One terminal 90 of the switch 58 at an end of the conductor 76 is laid on the non-conductive adhesive mask 84, and another terminal 92 at an end of the conductor 80 is laid in a collapsible dirnple 94 of tile substrate 86. Depressing the dimple 94 moves tile terminal 92 15 into contact with tile terminal 90 for competing a circuit between [fie electrochemical cell 52 and the electrochernical display 54, triggering a change from ail initial state to ail active state of [lie display 54. Preferably, tile display 54 remains in this active state until power capacity of the cell 52 is nearly exhausted. A removable overlay similar to that shown in FIG. 3A can be used to cover (lie display until it is activated, such as by removing the overlay.

Another example of an integrated product life timer 100 is depicted by FIGS. 5A and 5B. The product life timer 100 is incorporated into a product package 98. Similar to the preceding embodiment, an electrochernical cell 102, an electrochemical display 104, a resistor 106, and a switch 108 are mounted on a substrate 110. Materials similar to those listed in the preceding embodiment can be used to form these components.

A non-conducting adhesive mask 112 separates the cell 102 and the display 104 and bonds to a'printable layer 114, which is transparent at least in the vicinity of the display 104. A graphics layer 116 on the printable layer 114 and the substrate 110 also form integral portions of the product package 98.

In contrast to the preceding embodiment, electrodes 116 and 35118 (anode and cathode) are laid out laterally on the substrate 110.

1 An electrolyte layer 120, which is initially isolated by a breakable seal 121, covers both electrodes 116 and 118. The breakable seal 121 functions as the switch 108. The display 104 includes overlying electrolyte and electrochromic layers 122 and 124. A pair of conductors 126 and 128, which are also laid out laterally on the substrate 110, connect the electrodes 116 and 118 to the display 104. The resister 106 connected in parallel with the display 104 regulates a rate of discharge from the cell 102. The conductors 126 and 128 are shaped in cornplementary patterns under the 10 electrochrornic layer 124 to display a message.

When the cell 102 is activated by breaking the seal 121, a portion of the electrochromic layer 124 adjacent to one of tile conductors 126 lightens in color and another portion of the electrochromic layer 124 adjacent to the other conductor 128 darkens in color. Contrast between the different color portions of the electrochromic layer 124 can be used to reveal a message similar to FIG. 2A.

Although only two examples have been depicted, those of skill in the ail will appreciate that the layers of cells and displays in our integrated product life timers can be arranged in a variety of ways, including being stacked one upon another. The default state of the display can be the sarne or different from an initial state. For example, the default state can undergo a chemical change associated with the drop in voltage within the cell. The display could also be divided into different portions for displaying different messages in the different states. In addition to products per se, our tinier can also be used to tirne events.

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Claims (36)

CLAIMS:

1. A product life timer having a timing mechanism that operates independently of visible changes in a display comprising: an electrochemical cell that discharges at a controlled rate to provide the timing mechanism; said display having active and default states and at least one of said states displays information concerning the product life; electrochemical cell being electrically related to said display to shift the display between said active and default states in accordance with different levels of power output by said electrochemical cell; and said display remaining in said active state in response to a level of the power output of the electrochemical cell above a threshold and said display reverting to said default state in response to a level of power output of the electrochemical cell below the threshold.

said

2. The timer of clairn 1 in which said electrochemical cell is rnade in a succession of layers including two electrode layers and an electrolyte layer, and said display is also made in a succession of layers including an electrochromic layer and an electrolyte layer.

3. Tile timer of claim 2 in which both said electrochemical cell and said display are mounted on a common substrate and interconnected by a pair of conductors.

4. The timer of claim 3 further comprising a switch interrupting one of said pair of conductors for opening and closing a circuit between said e lectroche mica[ cell and said display.

5. The timer of claim 3 further comprising a layer of adhesive on said substrate for mounting the timer on another object.

6. The timer of claim 1 in which said electrochemical cell is sized to output electrical power above the threshold for a period of time related to the product life.

12

7. The timer of claim 6 further comprising a resistor located with a circuit between said electrochemical cell and said display for further controlling the discharge rate of the electrochemical cell.

8. A timer for a product having a limited life comprising:

a cell sized to supply electrical power for a period of time related to the intended life of the product; a resistance circuit that exhausts the supply of electrical power at a controlled rate without supplying any power to the product; a display having two sensorially distinguishable states triggered by different amounts of the remaining electrical power of the battery; and a first of said states triggered by a larger of the different amounts of remaining electrical power provides an indication that the product is within its intended life and a second of said states triggered by a smaller of the different amounts of remaining amount of electrical power provides an indication that tile product is at least approaching an end of its intended life.

9. The timer of claim 8 in which said second state is a default state, and said display reverts to said default state when the display does not receive enough power to remain in said first state.

10. The timer of claim 8 in which said display is connected within said resistance circuit and exhibits a resistance to a flow of current within said resistance circuit.

11. The timer of claim 10 further comprising a switch for opening and closing said resistance circuit.

12. The timer of claim 11 further comprising a removable overlay for covering at least a portion of the display.

13. The timer of claim 12 in which removal of said overlay contributes to closing the resistance circuit.

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14. The tirner of claim 8 in which the timer is formed as a laminate, and said resistance circuit is formed entirely within said laminate.

15. The tinier of claim 14 in which the timer is rernovably 5 mounted on packaging for the product.

16. The timer of claim 14 further comprising an adhesive layer for attaching the timer to an object other than the product.

17. The timer of claim 14 in which the timer is incorporated within packaging for the product.

18. A tirner for a product that undergoes change with tirne comprising: a cell sized to supply an electromotive force above a threshold 2.0 against an external resistance for an amount of lime related to an anticipated change in tile product; a display connected within a circuit to said cell and exhibiting at least a portion of said external resistance to a flow of current within tile circuit; a switch for opening and closing the circuit between said cell and said display; and said display providing a notice concerning the change in the product when the electromotive force drops below the threshold electromotive force.

19. The timer of claim 18 in which said display includes a first state triggered by an electromotive force above the threshold electromotive force and a second state triggered by an electromotive force below tile threshold electromotive force.

20. The tirner of claim 19 in which said display includes an initial state prior to application of an electromotive force above the threshold electromotive force.

21. The tinier of claim 20 in which said initial state is produced by a removable overlay covering said-display.

j 14

22. The tinier of clairn 21 in which removal of said overlay contributes to closing the resistance circuit.

23. The timer of claim 18 in which both said electrochemical cell and said display are mounted on a common substrate independent of the product being timed.

24. The timer of claim 23 further comprising a layer of adhesive on said substrate for mounting the timer on another object.

25. The timer of claim 23 in which said substrate forms a portion of a package for the product being timed.

26. An integrated tirner comprising:

a substrate; a succession of layers mounted on said substrate including an anode layer, a cathode layer, and an electrolyte layer forming an electrochemical cell; a switch interrupting a closed circuit mounted on said substrate within the label having a predetermined resistance to a flow of current between said anode and cathode layers; a rnediurn mounted on said substrate containing a message relating to the passage of time; and said message being displayed in response to a voltage drop between the anode and cathode layers.

27. The timer of claim 26 in which said medium is an electrochemical display.

28. The timer of claim 27 in which said display is also made in a succession of layers including an electrochromic layer and an electrolyte layer.

29. The timer of claim 28 futther comprising a non-conductive adhesive mask separating said electrochemical cell and said electrochemical cell.

30. The timer of claim 28 in which said switch interrupts one of a pair of conductors extending between said electrochemical cell and said electrochernical display.

31. The tinier of claim 30 further comprising another 5 substrate covering said electrochemical cell.

32. The timer of claim 31 in which one of said pair of conductors is mounted on said another substrate.

33. The tinner of claim 32 in which a dimple is formed in said another substrate within which a portion of said one conductor is mounted for forming a switch with the other of said pair of conductors.

34. The timer of claim 28 further comprising a layer of adhesive mounted on a surface of said substrate opposite to another surface of said substrate on which said electrochemical cell is mounted for mounting the timer on another object.

35. The tinier of claim 28 in which said substrate is a portion of a product package.

36. A product life timer as herein described with reference to the accompanying drawings.