Cross Reference to Related Applications This invention disclosed herein claims priority and is related to co-pending U. S. Provisional Patent Application Serial No. 60/198,760 filed April 21,2000 entitled MONITORING DEVICE WITH AUTOMATIC VISUAL EXPIRATION INDICATOR, which is hereby incorporated in its entirety by reference.

Background of the Invention Field of the Invention The invention is related to indicators and more particularly to indicators that change state upon expiration of a period of time.

Description of Related Art Timers are known in the prior art electronic devices in which a clock drives a counter until it reaches a program value, at which time the counter issues a signal which triggers other electronic devices to perform their functions.

Thin film power sources such as lithium-ion batteries are also known.

Examples of some thin film technology used for power source might be a lithium sulfur battery such as shown in U. S. Patent No. 6,030,720 or a thin film chemical cell shown in U. S. Patent No. 5,948,464. Paper power sources have also been recently introduced.

Porous plastics are known in the art. They come in a variety of migration or diffusion rates and directionality and are available from several companies, including Porex Technologies of Fairburn, Georgia and Genpore of Reading, Pennsylvania.

Chemical timers in some forms are known. For example, U. S. Patent No.

4,292,916 issued October 6,1981 to Bradley et al. discloses a disposable timer and product storage condition indicator in which the components of a carrier mixture react physically or chemically with one or more layers of laminate. In some embodiments, various time out periods are controlled by the rate of migration or diffusion through a permeable layer.

Problems of the Prior Art Electronic timers of the prior art have the disadvantage that they are dedicated to a single function. Typically, they are hardwired into electronic devices and serve a single dedicated function. Timers of the prior art are not flexible in that they are not fabricated so they can be attached in a cost-effective way to different products or devices. In addition, they are not sufficiently versatile that they can be manufactured in a variety of configurations inexpensively. Activation techniques for chemical timers do not permit for selective activation by a user after manufacturing or dispensing.

Brief Summary of the Invention The invention described herein overcomes the problems of the prior art by providing expiration indicators which can be cheaply and efficiently

manufactured in a variety of configurations and applied to a variety of products and devices and yet provide an unmistakable indicator of expiration of the set time period.

The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Brief Description of the Drawings The object, features and advantages of the system of the present invention will be apparent from the following descriptions, in which: Figure 1 is an exemplary timer circuit suitable for use in accordance with the invention.

Figure 2 shows an exemplary clock and timer circuit of Figure 1.

Figure 3 shows one layout of indicator components in accordance with the invention.

Figure 4 shows a multi-layer display element in accordance with one embodiment of the invention.

Figure 5 shows a simplified timed indicator in accordance with the invention.

Figure 6 shows another embodiment of the invention.

Figure 7 shows a multiple message display.

Figure 8 shows a mechanism for activating a timer by removing a strip.

Figure 9 illustrates an alternative mechanism for activating the timer and display.

Figure 10 shows an alternative arrangement for activating the display.

Figures 11A and 11B illustrate an embodiment of a chemical timer indicator in accordance with the invention.

Figure 12 illustrates an alternative way of activating a display device.

Figure 13 shows a chemical multi-message display embodiment in accordance with the invention.

Figure 14 shows an alternative method of activating a chemical timed indicator.

Figure 15 illustrates how a plurality of time indicators can be formed on a flexible sheet in accordance with the invention.

Figure 16 illustrates an alternative chemical timed indicator in accordance with the invention.

Figure 17 shows an exemplary multi-message timed indicator in accordance with the invention.

Figures 18A, 18B and 18C show a plurality of timed indicators of different size factors.

Figures 19A and 19B show the front and back sides of an exemplary timer indicator sheet which can be assembled into pads as shown in Figure 19C.

Figure 19C illustrates a plurality of timed indicators formed into a pad.

Figure 19D is a block diagram showing exemplary control circuitry for the timed indicator illustrated in Figure 17.

Figures 20A and 20B illustrate a plurality of timed indicators of standard duration formed into a pad.

Figure 20C shows an alternative exemplary time indicator which provides a notice area which repeats every first Monday.

Figures 21A, 21B, 21C, 21D and 21E show top views of a timer indicator in accordance with another embodiment, showing changes in appearance at respective times, each later than in the proceeding figure.

Figures 22A, 22B, 22C, 22D and 22E show progressive fluid flow through a channel.

Figure 23 is a section view of two reservoirs coupled by a channel of porous material.

Figure 24 shows an exemplary embodiment of a design with four porous strips for showing the progression of time in accordance with one aspect of the invention.

Figure 25 shows another embodiment in accordance with one aspect of the invention.

Figures 26,27,28 and 29 show different embodiments of the invention using a microcontroller.

Detailed Description of the Invention In Figure 1 a clock 100 drives a timer circuit or a count down circuit 110.

When the countdown circuit reaches zero or a count up circuit reaches its maximum value or a programmed value, the state of the output line of the timer 120 will change triggering a switch 130 which will cause a display 140 to indicate that the end of the time interval has been reached.

Figure 2 shows the clock 100 and timer circuit of Figure 1. The timer circuit 110 is preferably comprised of a programmable divider 200 and a programmable counter 210. The programmable divider 200 divides down the clock signal from the clock 100 and can be used to coarsely set the interval desired for time out. The programmable counter 210 can be set to either count up from a given value to a trigger value or to count down from a given value to a trigger value. The trigger value for the programmable counter is programmed in over lead 215. The division ratio N for the programmable divider is programmed in over line 205.

If, for example, the time interval desired to be measured were thirty (30) days, the programmable counter could be set to trigger on the count of 30 and the programmable divider could be set to issue a pulse once a day. Thus, the clock frequency would need to be taken into consideration when determining the programmable division ratio so that only one pulse occurred every 24 hours. The pulse from programmable divider 200 which occurred every 24 hours would then

be applied to programmable counter 210 to, for example, increment the counter from zero to the trigger value programmed in over line 215. At the end of thirty (30) days, the programmable counter would issue a trigger signal causing a change of state of a display, as discussed more hereinafter.

Figure 3 shows one layout of indicator components in accordance with the invention. Preferably, the circuitry shown in Figure 1 is implemented on a thin flexible film 350.

For some embodiments, the back side of film 350 may be provided with an adhesive layer and a cover which can be peeled off, exposing the adhesive layer so that the entire film 350 can be applied to a surface in a relatively non- removable manner. In some embodiments, shown hereinafter, removal of the cover from the adhesive layer also serves to trigger activation of the timing device.

A battery or power source 300 is applied to a normally off switch 320. A display area 310, described more hereinafter, is normally transparent but becomes opaque once power is applied to it. The timer circuit 110 is designed to normally provide a voltage to the normally off switch, holding the switch in an on-state and permitting power to be applied to display area 310, rendering the area opaque.

The clock 100 drives the timer circuit 110 as discussed previously. Contacts 330A, 330B and 330C can be used to program the programmable divider 200 and the programmable counter 210, in this exemplary embodiment. The contacts, preferably normally accessible for programming, enable one to program the time that one desires to elapse from initial programming until the display area displays a message once the power is removed from the display area.

In operation, once the timer is set for the appropriate interval, the display area remains opaque until such time as the timer reaches the end of that interval.

At that time, there will be a change of state on the output line of timer circuit 110 which will cause the normally off switch, which has been held in an on condition by the timer until the trigger event, to permit power to be removed from the display area resulting in display of a message which had previously been covered

by an opaque layer. Such a message might read"expired"or contain other information about the significance of the expiration of the time period. In another embodiment, in one state a light source, such as a blinking green light emitting diode, might be turned off and replaced by another light source of a different color, such as a red blinking light emitting diode.

Figure 4 shows a multi layer display element in accordance with one embodiment of the invention. In this particular implementation, a flexible layer 400 serves a base for the display. This layer 400 can optionally be reflective to enhance the amount of light viewed through the top of the display assembly. A printed layer 410 containing the message to be displayed when the time interval expires is shown above the base layer 400. It too is printed on a flexible material such as Mylar. Optionally, the base layer may have printing on the top of it or have both printing and reflective materials applied to the top surface. Two layers of polarized film, 420 and 440 are included in the laminate with their planes of polarization aligned. An optically layer 430 is included between the polarizer 440 and the analyzer 420. In one form of the invention, liquid crystal is utilized between the polarizer 440 and the analyzer 420. Liquid crystal has the property that the plane of polarization is rotated based on an electric field applied across the liquid crystal material. Conductive layers 450 and 460 are located on either side of the liquid crystal material, in this embodiment. The conductive layers can be either thin film of a metallic material or conductive polymers or similar flexible conductive materials.

When a voltage is not applied across the liquid crystal material, light from outside coming from the top of the assembly shown, will pass through the polarizer, through the liquid crystal material (with the polarization unchanged) through the analyzer and reflect off the reflective material thus displaying the printed matters shown in layer 410. Thus, when no voltage is applied to layers 450 and 460, the message printed on layer 410 can be displayed and viewed by a user from the top. However, with the voltage applied across layers 450 and 460, the polarization of the liquid crystal material changes causing a rotation which

essentially blocks the transmission of light through the polarizer and analyzer layers. Accordingly, the information printed on layer 410 is not visible and the message printed there cannot be seen.

Figure 5 shows another very simple approach for providing a timed indicator in accordance with the invention. In this approach, a capacitor 500 replaces the clock 100, timer circuit 110, switch 130 and battery/power source area 300 discussed above. In this arrangement, a voltage is applied to capacitor 500 from external terminals 510 and 520, charging the capacitor to a voltage VI.

VI is sufficient to cause the display 400, such as that described in Figure 4 to change state from transparent to opaque. The capacitor itself and the display 400 can be viewed as an effective resistance 530 which results in a gradual discharge of capacitor 500. As the capacitor 500 discharges, eventually a point is reached where the voltage is not sufficient to cause sufficient rotation of the plane of polarization by the electroptically active material 430 which results in the printed message becoming visible through the layers of the display. This particular embodiment has the additional virtue that reasonable timing ranges can be defined by the size of the capacitor and a more refined control of the time interval can be achieved by controlling the amount of voltage applied to the capacitor 500. This embodiment also has the advantage that it is very easy to manufacture.

Figure 6 shows another embodiment of the invention which is more flexible in some respects. A power source 300 is placed on the flexible indicator film 350 as well as the display 140 and a capacitor 500. The voltage of the power source, the size of the capacitor and the effective resistance caused by the display and other leakage across capacitor 500 operate as discussed in conjunction with Figure 5. However, once the display has timed out and the message has appeared, the timer can be reused by simply activating switch 600 long enough to charge capacitor 500. Once the display has been reset by recharging capacitor 500 to be opaque, the timing process begins again and eventually the circuit will time out resulting again in a visible display message. Preferably, in a flexible film environment, the switch 600 can be activated by simply pushing two metallic

layers, normally separated from each other, across a gap together so that the metallic portions on either side of the gap engage each other for long enough to charge the capacitor 500.

Preferably, the power source for each of the embodiments is a thin film battery such as a lithium ion battery or any other of several technologies available for providing a power source on a flexible substrate. It is also possible to provide a power source, such as those used in smart cards, or other small footprint electronic devices. Examples of some thin film technology usable for a power source might be a lithium sulfur battery such as shown in U. S. Patent No.

6,030,720 or thin film chemical cells shown in U. S. Patent No. 5,948,464, Figure 7 shows a multiple message display. Essentially three display elements 140A, 140B, and 140C are combined on a single substrate, in this case, on a single flexible film. Each display has individual capacitors C1, C2 and C3, respectively. A voltage Va is applied to terminals from, in this case, an external source, and is divided down into different voltage values by, in this case, three zener diodes, Zl, Z2 and Z3, respectively. When voltage Va is applied to the input terminals, capacitor Cl charges to the voltage level set by the value of zener diode Z1. Capacitor C2 charges to the voltage level provided by zener diode Z1 + Z2 and capacitor C3 charges to the voltage value Va (= Zl + Z2 + Z3). Once the voltage is removed, capacitor C1, presumably will discharge first, assuming the displays are identical, followed by capacitor C2, followed by capacitor C3. Thus, messages will become visible in the order of display 1, display 2, and display 3 depending on the voltages to which the capacitors are charged, respectively. If, in this example, Cl were set to expire at a time roughly approximating the time to ship a product from the manufacturer to a distribution point, a green printed layer would become visible. After a second, longer interval, the charge on C2 would be reduced to the point where the voltage dropped to the point where the display changed state, displaying, in this example, a yellow substrate. Finally, at the end of the shelf life, capacitor C3 would discharge sufficiently to change state and make visible a red substrate, indicating that the life of the product was at an end.

Figure 8 shows a mechanism for activating a timer by removing a strip, such as the cover on the adhesive backing on the back of the film 350. A portion of the cover of the adhesive layer is metallic and is positioned to come in contact with the two terminals 820A and 820B permitting current to flow between terminals 820A and 820B. This applies a positive voltage to one input of AND gate 800. The inverting input of AND gate 800 is connected to ground. AND gate 800, thus activated, applied the potential to the gate of field effect device 810, preventing current flow from the positive input terminal from the power source to the timer display. Thus, in this environment, the printed matter will be visible through the display. However, once the cover for the adhesive material is removed, the contact between pads 820A and 820B are no longer connected together, changing the state of AND gate 800 which permits field effect device 810 to conduct, applying power from the power source to the timer display terminals. This causes a display to become opaque hiding the message on the printed material. The timer then counts down until it reaches its trigger event and, when the event is reached, the power to the display is removed and the message on the printed material again becomes visible, signifying the end of the timing interval.

Figure 9 illustrates another way of activating the timer and display. In this arrangement, power is applied to the clock, timer and display shown in Figure 1 (910) by applying a momentary voltage to a silicon controlled rectifier, silicon controlled switch or other semiconductor device which takes only a momentary application of a voltage to turn on. The device then stays on until such timer's power is removed. Two terminals, 920A and 920B are arranged so that when a strip 930, is pulled in either direction, metallic areas 940A and 940B come into contact with terminals 920A and 920B, thus completing its circuit to momentarily turn on the silicon control device, such as SCR 950. Thus activated, SCR applies power to the clock timer and display 910 which remains on and causes the count down to begin. The timer is preprogrammed with a divide by value and a count

value that will result in a change of state of the display, to display the message, once the time interval expires.

Figure 10 is a similar arrangement in which the metal areas on the strip 1000 permit the power source to charge the capacitor for activating the display.

The strip can be arranged to be pulled completely from the timing device or it can be arranged to only provide a momentary contact of the metal so the capacitor can charge, before being repositioned so that no contact occurs so that the capacitor can discharge normally. Preferably, the metalized areas are on either side of a blank area so that pulling the strip, in either direction, will result in charging the capacitor.

Each of the preceding implementations has been electrical in nature, however, it is also possible to utilize chemical timers to display the message.

Figures 11A and 11B illustrate a first embodiment of a chemical timer indicator. As shown in Figure 11A, two reservoirs are provided, each containing chemicals of some sort. In one embodiment, each reservoir contains a dye. In another embodiment, each reservoir contains a component of a two component chemical mix which reactively changes color. In this description, we will assume that the first reservoir 1100A contains red dye and the second reservoir 11 OOB contains blue dye. Message area 1110, sandwiched between two layers, is made, in this embodiment, of porous plastic, and the message area 1110 communicates over channels 1120A and 1120B with respective reservoirs 1100A and 1100B once the device is activated.

In this embodiment, a plunger 1130 contains a porous plastic section 1140 and has a point, 1150. The plunger 1130 is installed by piercing through the uppermost layer, stopping short of the reservoir. When the timer is to be activated, plunger 1130 is depressed, penetrating the wall of the reservoir and permitting a porous plastic section of the plunger 1140 to receive fluid from the reservoir and to transport it via migration or diffusion up into the channel connecting the reservoir with the message area 1110. By selecting porous plastics

of different migration rates, the rate at which the red dye from reservoir 1100A reaches the message area is faster than the blue dye found in reservoir 1100B.

If the arrangements shown in Figures 11A and 11B were to be utilized for measuring, for example, the aging of meat, when the device was applied to a tag on a side of beef, for example, both plungers 1130 would be activated, putting the reservoirs in fluid communication with the respective channels connecting to the message area 1110. In this example, the porous plastic 1140 from the plunger for the red reservoir is made of a quick migration porous plastic which would result in a quick passage of red dye from the reservoir into the message area 1110 through the channel 1120A. However, the porous plastic 1140 from the blue reservoir 1100B is selected to have a much slower migration rate. Whereas the indicator would first appear red as the red dye from reservoir 1100A reached the message area, after a period of time, for example 30 days, the blue dye would migrate into the message area 1110, changing the red dye to green, assuming the dyes are reflectively additive.

Figure 12 illustrates another way of activating a display device. A reservoir 1100, containing dye, is sealed with a low melting point conductive material, such as indium or a lead-tin alloy, such as solder. The channel communicating between the reservoir and the message area is positioned opposite the seal on the reservoir 1200. To activate the display device, a voltage is applied to the conductors 1210A and 1210B and current is caused to flow through the junction causing resistive heating of the seal. Because of the low melting point, the seal material quickly melts, and fluid from the reservoir can reach the channel leading to the message area 1120. Seal 1200 essentially acts as a thermal fuse which is activated by electricity and permits the contents of the reservoir, the dye, to flow to the message area changing its visual properties.

Figure 13 shows the chemical analog to the multiple message display embodiment shown in Figure 7. In this example, three different reservoirs communicate with three different display areas by selection of different diffusion rates for the various channels connecting reservoirs with their respective display

areas, different activation times for each display area can be achieved. Although the reservoirs are shown on the same level with the display areas, it is possible to place the reservoirs under the display areas in separate layers of the laminate or, if positioned as shown, a partially opaque layer can cover the reservoir and the feeding tubes permitting only the display areas 1,2 and 3 to be seen, when they are activated.

Figure 14 shows an alternative method of activating a timer. In this arrangement, each reservoir is surrounded by a plastic material which is self sealing. In this case, the timer is activated by filling each reservoir with its appropriate liquid contents using a syringe of the type used in medical care. The syringes can also be applied using automated equipment so that an appropriate amount of liquid is dispensed through the wall of the reservoir into the reservoir until the reservoir is full and the needle extracted. However, the reservoir does not leak, because it is made of a self sealing material, such as surgical rubber.

Once activated, the diffusion process begins and by carefully selecting the diffusion material, one could control a wide variety of time intervals before a display message becomes visible.

Porous plastic of a type suitable for use in this invention can be obtained from several companies, including Porex Technologies of Fairburn, Georgia and Genpore of Reading, Pennsylvania. They come in a variety of migration or diffusion rates and directionality.

Figure 15 illustrates how a plurality of timer units can be formed on a flexible sheet of substrate, such as Mylar or other insulating material. Techniques are known for fabricating semiconductor devices, batteries, capacitors, and other components needed to carry out the invention in the various embodiments. A substrate can be deposited in each of the areas 1500A through 1500F. The electronics can then be fabricated on each of those substrates in a manner well known in the art.

Figure 16 illustrates another chemical or fluid embodiment. Views 1-3 are top views. Views 4-6 are side views. Views 7-9 are functional views. Views 1,4

and 7 show states in which this embodiment is"inactive", that is, in which no timing is ongoing. Views 2,5 and 8 show states in which the timing function has been activated, but no message is visible yet. Views 3,6 and 9 show states in which the message is visible. In this embodiment, an"activation wall"separates the fluid reservoir from the channel (s) of porous plastic leading to the exposed message area. The activation wall is made of a frangible material so that by snapping or bending the activation wall, it breaks, allowing the fluid to pass through to the message area. At the top of this embodiment, a message template forms the message so that only the desired areas of the message receive the fluid from the reservoir through the porous plastic. Areas that will not be involved with forming the message are blocked from view. The message template can be made from non-porous plastic so that fluid may not permeate it, where the message itself is formed from porous plastic so the fluid can cause the message to become visible.

In a chemical implementation, the substrate or another layer can be stamped to provide reservoir cavities. The reservoirs and other areas where no message dye is desired can be selectively masked and porous plastic with appropriate migration or diffusion constants deposited to form the message material and to permit communication with the reservoirs. Then a second layer can be applied over the entire surface, protecting the message areas and the reservoirs from outside influences. Preferably, after sealing, the reservoirs can be filled with appropriate dye or other chemical components using the needle approach discussed above in conjunction with Figure 14. The sheet covering the formed devices 1500A through 1500F, can be totally transparent or partially opaque, partially transparent in order to permit only the desired message (s) to show through.

In either the chemical implementations or the electrical implementations, the devices can find use in a plurality of applications including but not limited to the following: Credit card expiration notice, Driver License expiration notice, Security badge/visitor passes expiration sticker, Private sector electrical appliance

service sticker, Manufacturing equipment service sticker, Private motor vehicle registration sticker, Private motor vehicle inspection sticker, Parking validation sticker, Commercial vehicle registration/inspection sticker, Municipal vehicle registration/inspection sticker, Motor/sail boat registration sticker, Commercial boat registration sticker, Military equipment service sticker, Private fixed/non- fixed wing aircraft registration/inspection sticker, Commercial fixed/non-fixed wing aircraft registration/inspection sticker, Residential/commercial elevator inspection sticker, Medical equipment inspection sticker, Hazardous waste material inspection sticker, Security badge expiration sticker, Visitor pass badge expiration sticker, Gas pump inspection sticker, Wholesale/retail scale inspection sticker, Retail cash register inspection sticker, Utility meter inspection sticker, Prescription drug expiration sticker, OTC pharmacy drug expiration, Certified calibration, Fire Extinguisher inspection, Price change tags, Time-driven discount coupons, Guaranteed package delivery notice, Out-of-warranty notification, Time driven"Unsafe To Use"notice, Consumer/hospital change bandage notice, End user specified Sticky Tag"Reminder"application, Ski Resort/Theme park ticket expiration notice, Overdue Rented videos/library books, Food expiration sticker, Valid parking sticker, Photographic Film"Developed By"notice, Expiration on perishable food, Large visual medical reminders for appointments several months out, Large visual medical reminders for illiterate members of third world countries, Greeting cards that display a distinct message on the appropriate day, Discount coupons that are valid until the message changes, Military equipment inspection, Private./commercial aircraft registration, Hazardous waste inspection, Security, badge expiration, Visitor pass expiration, Residential/commercial elevator inspection, Medical equipment inspection, Gas pump inspection, scale inspection, Cash register inspection, Utility meter inspection, Certified calibration, Fire extinguisher inspection, Credit card expiration, drug expiration, Equipment service date, Out-of-warranty notice, Unsafe usage notice, Price change tags, Overdue video/book rental, Guaranteed package delivery, Valid

parking sticker, Water plant reminder, Sticky tag reminder note, and Change bandage indicator.

Figure 17 shows an exemplary multi-message timed indicator in accordance with the invention. The timer indicator in accordance with the invention is shown as item 1700. The uses of the various fields shown on this timer indicator are described in conjunction with an exemplary scenario in which the timer indicator might be utilized on a personal computer to indicate expiration of a warranty. The timer indicator is described in accordance with the previous principles discussed above. In area 1710, a notice would be printed, which in this scenario, would be"warranty expired."The notification warning field 1720 would include some type of pre-expiration warning such as"warranty expires in one month."The on-area 1730, when activated, would give an indication that the timer is operating and counting is in progress. The Serial No. field 1740 and the bar code 1740A can either be preprinted or programmed to be displayed. Each would be a unique indicator of the particular unit to which the timer indicator would be attached. The notification date 1750 would give an indication of the date when time out would occur, or in this example, when the warranty would expire. The activation date 1760 would be the date on which the strip 1796, shown in dotted lines to indicate that it is on the back of the timer indicator, is pulled in order to activate the device to begin counting down. The"activate by" field 1770 can be utilized to protect a manufacturer against a retailer selling outdated products. For example, when a retailer sells a personal computer, the retailer would peel the strip 1796 on the back of the timer indicator to begin the warranty period and begin the count down. The retailer, however, may have an inventory of products, the sale of which after a certain date could disparage the manufacturer's trademark if the retailer providing a consumer with an outdated product. If the activation date 1760 is later than the activate by date 1770, the consumer and the manufacturer would both know that the retailer sold the product in question at a point in time in which the product was considered outdated.

The void field 1780 can be utilized to indicate that the warranty is void for failure to comply with certain requirements of the warranty. For example, as shown in Figure 17, an optional section 1700A of the timer indicator would have contained therein a conductive area 1795 which functions, much like a fine wire.

That section or some other section of the tag itself containing such a conductive area 1795, can be placed across a case opening 1797 so that the case cannot be opened without damaging or destroying the conductive area 1795. When the conductive path 1795 is interrupted, the void field 1780 would be activated to indicate that the user had violated the terms of the warranty. The system failure field 1790 can be activated once any type of failure condition is detected.

Exemplary failure conditions that might result in activation of the system failure field 1790 would be a loss of processor clock or a loss of power.

Figures 18A, 18B and 18C show a plurality of timed indicators of different size factors. Figures 18A-18C illustrate the flexibility of the types of notices and information provided to a user in a small size factor. Figure 18C has no printed fields whatsoever, but rather only a round dot indicating a change of state. Figure 18B has only a single field of information, whereas Figure 18A has a plurality of fields of information, all previously described, that could be available on the small size form shown there.

Figures 19A and 19B show the front and back sides of an exemplary timer indicator sheet which can be assembled into pads as shown in Figure 19C. In Figure 19A, the front of the timer indicator sheet 1900 has a conductive area 1910. The backside, of the sheet contains two conductive areas 1920A and 1920B. When timer indicator sheets as shown in Figures 19A and 19B are assembled into pads, they are arranged so that conductive strip 1910 from a lower sheet bridges the conductive layers 1920A and 1920B from the sheet above the sheet containing 1910 so that when the sheet above becomes the top sheet and is peeled off the pad, the electric circuit between conductive areas 1920A and 1920B is broken and the timer function for that sheet being peeled off is activated,

using, for example, the activation technique of Figure 8. The relationship of conductive layers in a pad environment is shown in Figure 19C.

Figure 19D is a block diagram showing exemplary control circuitry for the timed indicator illustrated in Figure 17. As described above, timer indicator 1900 contains a processor 1910 and a power source 1920 activated using, for example, the activation strip 1920A. A variety of display fields 1730,1780,1750,1710, 1720,1760 and 1790, previously described in conjunction with Figure 17, are available for selective activation by the processor under a variety of conditions.

The programming for the processor 1910 can be transmitted over a communications link 1925 between the encoded input data/command transmission device 1930 and the decoding input data command section 1920.

Exemplary programming that might be transmitted across the communications link 1925 would include the contents for display on the various fields 17XX discussed above and the conditions under which the processor might activate those fields. The processor 1910 typically includes one or more date functions utilized to facilitate easy display of dates on the display fields.

Figures 20A and 20B illustrate a plurality of timed indicator sheets formed into a pad. Figures 20A and 20B show two different time indicators of a type that might be utilized in a pad. One pad might have timers that expire seven (7) days after activation. Another might have one that expires fourteen (14) days after activation. As before, a user can utilize the space not occupied by display fields for physically writing notes. The notice used might read something link "overdue"or"due today"and relates to the content in relationship to the content of the note the user has applied to the sheet. Figure 20C shows an alternative time indicator which provides a notice area which repeats every first Monday. The notice, in this approach, would reset after the first Monday had occurred and then reoccur one month later, on the first Monday of that month. As before, the time notation at the bottom field can either be preprinted or can be programmably set so as to display the timer interval for which the pad is designed.

Figures 21A, 21B, 21C, 21D and 21E show top views of a timer indicator in accordance with another embodiment, showing changes in appearance at respective times, each later than in the proceeding figure. The fluid is visible in these figures through a transparent top film, 2100. These figures should be viewed in conjunction with the corresponding Figures 22A, 22B, 22C, 22D and 22E.

Figures 22A, 22B, 22C, 22D and 22E show progressive fluid flow through a channel, portions of the upper surface of which are visible from the top views as shown in Figures 21A-E. Fluid from the reservoir 2200 begins flowing or migrating along the channel when the timer indicator is activated as discussed previously. The length of the channel (it may follow a convoluted path not visible from the top surface in order to assist in controlling timing), the pore size of a porous medium or filament size of the medium in the channel, the viscosity of the fluid, the size of fluid molecules in relation to pore size and other factors apparent to one skilled in the art may be used to control the time needed for the full message (21E) to become visible. In some embodiments, the fluid in reservoir 2200 may be under pressure. As fluid migrates along the channel (progressing as shown in Figures 22A-22E), the message becomes progressively more complete until the entire message area is visible.

Figure 23 illustrates two reservoirs, A and B, for containing a liquid. A porous strip"a"having pore diameters of D is placed in the equation 1 liquid and has a length that is an amount"hl"above the liquid level in the first reservoir. In contact with the first porous strip is a second strip"b"having pores of D2 and is "h2"long. We know from equation (1) in the preceding discussion that the liquid from the reservoir will be able to rise in the first porous strip an amount equal to h = (4 6)/ (D p) above the liquid level. Therefore, if the length of the strip above the liquid level is equal or shorter than that value, liquid will rise to the top and contact the second porous strip. (It should be noted that as the liquid in the reservoir enters the porous strip, the level of the liquid in the reservoir would drop. As a result,

the height of the strip should be measured above the final level of the liquid, which would be the bottom surface of the reservoir.) If the second porous strip is longer than h = (4 a)/ (D p) the liquid cannot be held in it and the liquid will slowly drip out of the second strip. As a result when"hl"is less than the value calculated by equation (1) and "h2"is greater than the value calculated by equation (1), the liquid in reservoir A is transferred to reservoir B through the first strip to the second strip and then to reservoir B. The liquid can be caused to drip out of the second strip by choosing either the proper length or pore size.

It will be instructive to put actual dimensions on the two strips to obtain a feeling for the rates to be expected.

Figure 23 illustrates the system with storage reservoir"A"that contains colored water and a receiving reservoir"B". The porous strip"a"is immersed into reservoir"A"while the porous strip"b"is positioned over reservoir"B".

Strip"a"has spores of 0.012- in. diameter and is 0.20 in. above the bottom of the reservoir"A". We see from equation (1) that the liquid would rise to the top of strip"a"even when reservoir"A"is almost empty.

The strip"b"is in physical contact with strip"a". It could actually be a part of strip"a"as long as the height of it is greater than the value given by equation (1). For example if the pores are 0.012 in. in diameter, the length must be greater than 3.83 in. above the maximum level of the liquid in reservoir"B) (i. e. the level after all of the liquid is transferred to reservoir"B"). This is an unreasonably long strip. Instead, it would be desired to increase the pore size of strip"b"in order to decrease the required length. If the pores were 0.184 in. diameter, then the strip"b"would have to be only 0.25 in. above the maximum level of the liquid in reservoir"A"in order to drip into reservoir"B".

If the cross-sectional area for the flow in strip"a"is 0.03 sq. in., 1/2 oz. of liquid will be transferred from reservoir"A"into reservoir"B"in 48 hours. The quantity of liquid that is transferred varies directly with the duration. For

example, if 1/2 oz. is transferred in 48 hours, 1/4 oz. will be transferred in 24 hours, 1/8 oz. would be transferred in 12 hours, etc. Also, the amount that is transferred varies directly with the cross-sectional area for the flow. For example, if instead of an area of 0.03 sq. in., the strip"a"is 1/10 x 1/10 in., it will transfer only 1/6 oz. of liquid in 48 hours. It is seen that this passive, very inexpensive system would provide a warning signal for any duration of up to 48 hours using very small reservoirs. The system is not dependent on the ambient temperature but is controlled only by the accuracy of the cross-sectional flow area and the pore size.

Figure 24 illustrates one design to utilize this concept that shows the progression to the expiration time. In this case four porous strips are placed in reservoir"B"that has a transparent wall. Each of the strips is located at a different vertical position. As the liquid rises in the reservoir"B"each of the four strips becomes progressively in contact with the liquid and, as a result, become colored by the liquid. The result is that a colored band progresses from left to right to indicate the amount of duration that is available before the expiration date.

Alternatively, the actual level of the liquid in reservoir"B"could be viewed through a sight glass (in place of the four strips) to indicate the percentage of duration.

Another concept is illustrated in Figure 25. This concept also overcomes the problem that the liquid travels through a porous medium at close to a constant speed regardless of the pore size. A porous strip"a"has a small cross-section for transport of the liquid and is immersed in the colored liquid. The small area strip is in contact with a much larger area strip"b". The large area strip"b"would absorb the liquid from the small area strip and become colored. However, since the liquid entering the large area strip is small because of the small area of strip "a", it will take a relatively long time for it to become colored thereby extending the duration before the warning signal is complete. The color would progress from left to right as the expiration time approaches. The duration is controlled by the cross-sectional area of the strip"a"and the volume of the strip"b".

There are many systems that could be envisioned using a small watch-type 3 volt battery. The main problem in this case is to devise an economically feasible system if it is desired to have the entire system cost approximately two dollars. The commercially available small batteries cost over one dollar wholesale which leaves only one dollar for the electronic circuit. There is no need for an activating switch since the system can be activated by inserting the battery.

The heart of any active system is the microcontroller. There are several commercially available ones e. g., part number PIC 12C509A manufactured by Microchip Technology, Inc. in Arizona. This microcontroller is an 8-pin, 8-bit CMOS chip costing about 45 cents. Figure 26 illustrates one design with an external resistor of 10K and capacitor of 0.0003 microfarads each with one- percent accuracy. (The actual shape of the microcontroller is shown in the right portion of Figure 26 at approximately four times its true size, 0.193 x. 154 x. 061, to illustrate how small a unit it is.) The output goes high at any designed duration ranging from minutes to about 36 months. The maximum duration is controlled by the life of the commercial battery. It is easy to program the duration to any value at your facility. It can also be programmed for a sequence of durations. For example, the first one may be set for one week and the second for two weeks and the third still another duration. This feature can be used to indicate the times that sequential action should be taken. This is probably the least expensive active system but it would have an accuracy of only about 7.5 percent e. g. if it were desired to indicate in one-week duration, it could be either 12.5 hours early or 12.5 hours late).

In order to obtain greater accuracy, a crystal oscillator could be used in place of the resistor and capacitor as illustrated in Figure 27. This change would add about 55 cents to the cost but would provide one-percent accuracy e. g., if it were desired to indicate in a one-week duration, it could be either 1.7 hours early or 1.7 hours late. An improved accuracy can be obtained but with an increase in the cost.

need for an activating switch since the system can be activated by inserting the battery.

The heart of any active system is the microcontroller. There are several commercially available ones e. g., part number PIC 12C509A manufactured by Microchip Technology, Inc. in Arizona. This microcontroller is an 8-pin, 8-bit CMOS chip costing about 45 cents. Figure 26 illustrates one design with an external resistor of 10K and capacitor of 0.0003 microfarads each with one- percent accuracy. (The actual shape of the microcontroller is shown in the right portion of Figure 26 at approximately four times its true size, 0.193 x. 154 x. 061, to illustrate how small a unit it is.) The output goes high at any designed duration ranging from minutes to about 36 months. The maximum duration is controlled by the life of the commercial battery. It is easy to program the duration to any value at your facility. It can also be programmed for a sequence of durations. For example, the first one may be set for one week and the second for two weeks and the third still another duration. This feature can be used to indicate the times that sequential action should be taken. This is probably the least expensive active system but it would have an accuracy of only about 7.5 percent e. g. if it were desired to indicate in one-week duration, it could be either 12.5 hours early or 12.5 hours late).

In order to obtain greater accuracy, a crystal oscillator could be used in place of the resistor and capacitor as illustrated in Figure 27. This change would add about 55 cents to the cost but would provide one-percent accuracy e. g., if it were desired to indicate in a one-week duration, it could be either 1.7 hours early or 1.7 hours late. An improved accuracy can be obtained but with an increase in the cost.

Figure 28 illustrates the microprocessor with switches connected to pins 5, 6 and 7. Instead of programming the unit at your facility, these switches allow the user at home to choose the duration. The switches are merely thin copper strips that make the contact. To open the connection, the copper strip is scratched open

with any sharp object. The switch connected to pin 7 is illustrated open while the other two switches are closed. The desired duration can be chosen by scratching open one or two of the switches to get durations in the multiple of two. For example, the duration could be minutes, days, weeks, etc. and changed in multiples of two. Durations of 2,4,6,8,10,12,14 or 16 minutes, days or weeks, etc. can be obtained.

The microcontroller will supply the battery voltage to some device that will give a visual image that the unit has expired. The following are some examples of how the image could be demonstrated.

One technique, illustrated in Figure 29, is to employ electrophoresis to cause a colored liquid to migrate in a porous medium. In this case a porous strip made of a basic read material could be saturated with a colored liquid that causes the color to be yellow or any color other than red. When the microprocessor goes high and places the battery voltage across the porous strip, the colored liquid is caused to flow to one end of the porous material exposing the basic red material.

For this application, the liquid is made conductive by dissolving in it a small amount of salt. Instead of revealing the red basic material when the colored liquid is removed, a written message could be visible.

Many systems can be envisioned that do not employ liquids or porous materials. For example, a message indicating that the system is valid could be exposed through a window and when the microcontroller supplies the battery voltage, an expiration message is caused to cover the valid message by releasing a spring. Another possibility is to use an LED to indicate the expiration. Since the small battery has very limited capacity, we would cause the LED to blink rather than remain on constantly. Another possibility is to cause a protrusion to come out of the indicator. This device would be useful particularly for persons with visual problems. There are many other possibilities that we can include if you desire.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation.