WO1989003598A2 - Water-activated micro-electronic circuits - Google Patents

Abstract

Electrical apparatus comprising a combination of a low-power electrical circuit (3), a source of low electrical current comprising at least one cavity (18, 19, 20) for containing liquid electrolyte; a cathode (21) of a first electrically conductive substance having a tendency to act as an oxidizing agent in the presence of a selected second electrically conductive substance and which is positioned within said at least one cavity; an anode (11, 12, 13) of a said selected second electrically conductive substance having a tendency to act as a reducing agent in the presence of said first electrically conductive substance and which is positioned within said at least one cavity; first means for permitting the introduction of a liquid electrolyte into said at least one cavity; and second means for permitting air to be discharged from said at least one cavity when said liquid electrolyte is introduced into said respective cavity; and electrical conductor means connecting said current and said electrical circuit for supplying electrical current to said electrical circuit.

Description

WATER-ACTIVATED MICRO-ELECTRONIC CIRCUITS This invention relates to water-activated microelectronic circuits for the production and use of electrical energy in which electrical energy is produced electrolytically by means of a device commonly referred to as a battery.

Batteries are a commonly used portable self-contained means of producing electrical energy and many variations in type, size and electrical capacity are known. By convention, most batteries are classified as belonging to one of four distinct groups: Primary, Secondary, Reserve, or Fuel-Cell. Most batteries classified as Primary can be recognized as small dry-cell batteries that typically have a capacity of only a few amp-hours, and are commonly employed to energize portable electrical apparatus such as electronic wrist watches, calculators, flashlights, and small radio receivers. Typical of Secondary types are large wet-cell storage batteries that have an output capacity of greater than 75-amp-hours at 12 volts, and are commonly used in vehicles for land, air and water travel, and in stationary applications involving uninterrup table power supply means. A battery is classified as Reserve, or Deferred Action, when it is to be subjected to extended periods of storage before being activated by the introduction of electrolyte, with water activated batteries being the most common of this type. Most water activated batteries can be further classified into low to intermediate output power or high output power, ranging in output from 5-watts to 4000-watts, with a useful service life ranging from 2-hours to 6-months.

In recent years there has been a substantial increase in the individual-consumer use of portable electronic devices. Electronic wrist watches and pocket calculators, for example, have become commonplace.

Miniaturization of components and drastically reduced costs, resulting from advanced technology, are primarily responsible.

A typical electronic wrist watch, for example, utilizes a battery of relatively small dimensions, of the order of 8-millimetres in diameter and 4-milIimetres in thickness, and having a capacity of about 75-milliampere-hours at 1.5-volts. Such batteries are generally of the dry-cell type, the battery having been charged with potential electrical energy during the manufacturing process by way of the stored potential energy within its constituent chemical means. Deterioration of this stored potential energy, due to spontaneous chemical corrosion within the cell, begins immediately upon introduction of caustic electrolyte. Diminished shelf-life and potential loss of goods are, therefore, of considerable concern to those responsible for distribution and sales.

Also, for a typical fully-charged dry-cell battery that is continuously subjected to relatively light use, for example providing electrical energy to an electronic wrist watch, the average maximum service-life is only about one year, and substantially less for a conventional water-activated battery. Naturally, this service-life can be further shortened under varying conditions of electrical consumption, such as a wrist watch that incorporates an alarm-beeper and an incandescent night-light. However, the limit of the useful service life for a wrist watch battery is more dependent on wasteful internal spontaneous corrosion as a result of caustic electrolyte within a dry-cell battery and contamination of the electrolyte within a water activated battery, rather than the external consumption of electrical energy.

Batteries are a traditional source of aggravation and inconvenience for the individual- consumer. As a result of the abbreviated service-life, a battery requires periodic replacement, involving time and expense. This task must be undertaken even if the electrical apparatus has not yet been called upon to provide service sufficient to have consumed the electrical capacity of the battery. During these occasional periods of battery failure, the electrical apparatus will be inoperative. For those with urgent need of the electrical apparatus and not in proximity of a supplier of a replacement battery, the loss of use of the device can be extended and inconvenient to the extent of being critical. Furthermore, it is possible that hazardous corrosive chemicals in an old dry-cell battery may escape, such as by eroding the battery case, causing damage to the electrical apparatus or to the surrounding environment.

It is the main object of the invention to remedy the foregoing and other deficiencies inherent in the prior art. In particular, it is an important object of the invention to provide electrical apparatus incorporating an electrical current source, with increased service-life of both the current source and the electrical device while eliminating hazardous caustic chemicals from the apparatus and their potential harm to the environment.

According to the invention, there is provided electrical apparatus comprising a combination of a low-power electrical circuit, a source of low electrical current comprising at least one cavity for containing liquid electrolyte; a cathode of a first electrically conductive substance having a tendency to act as an oxidizing agent in the presence of a selected second electrically conductive substance and which is positioned within said at least one cavity; an anode of a said selected second electrically conductive substance having a tendency to act as a reducing agent in the presence of said first electrically conductive substance and which is positioned within said at least one cavity; first means for permitting the introduction of a liquid electrolyte into said at least one cavity; and second means for permitting air to be discharged from said at least one cavity when said liquid electrolyte is introduced into said respective cavity; and electrical conductor means connecting said current source and said electrical circuit for supplying electrical current to said electrical circuit.

The invention provides a battery, henceforth to be referred to as a current source, especially adapted for use in combination with certain electronic devices. The current source provides steady electrical current at very-low rates of output over increased periods of time. In accordance with a preferred embodiment, the current source includes many of the component means that are typically found in a galvanic device for the production of electrical current by electrolytic means. In common with other liquid activated galvanic devices, our current source is also contained within a dielectric body or housing having at least one cavity therein. A first electrode, consisting of an electrically conductive substance (for example, graphite), having a tendency to act as. an oxidizing agent in the presence of a selected second electrically conductive substance within said at least one cavity and electrically coupled to a first terminal; a second electrode of a second electrical conductive substance (for example, zinc), positioned in spaced-apart relationship to the first electrode and having a tendency to act as a reducing agent and thus give up electrons in the presence of a said first substance and electrically coupled to a second terminal. Said first and second terminals extend exteriorallv of the body in said electrical apparatus to respective said electrodes. A means is provided for permitting the introduction of a liquid-electrolyte into said at least one cavity when activation of said battery is desired; and means is provided for permitting air to be discharged from said at least one cavity during introduction of the said liquid-electrolyte. An electrical conductor means is provided for the connection of said current source to said electrical device.

In accordance with a further embodiment of the invention, a housing for the electrical current source provides separation between a plurality of cavities, each having a said first electrode and a said second electrode residing therein. The first electrode, and the the second electrode of an adjacent cavity are electrically connected to form a series circuit. The first electrode in the first cavity is electrically connected to the first terminal while the second electrode in the last cavity is electrically connected with the second terminal. A body of liquid-pervious and absorptive cellular material resides between the first and second electrodes within each of the plurality of cavities.

Advantageously, the current source, in accordance with the preferred embodiment, may be integral with the electrical device it is to supply. It is therefore not necessary for the current source to be in the form of a periodically-replaceable battery, separable from the electrical device.

Also advantageously, electrical apparatus according to the invention has an increased servce-life due to the current source being able to produce an output current over an increased period of time as a result of both the activating liquid-electrolyte possessing a relatively-low corrosive nature (compared to caustic electrolyte typically employed in conventional dry-cell batteries), thereby substantially reducing wasteful spontaneous corrosion (self-discharge) of the electrodes, and the control of electrolyte contamination from accumulated anodic material in the absorber.

The electrical device supplied by the current source is typically an integrated circuit means, such as a Complementary Metal Oxide Semiconductor (CMOS IC). Examples of an electrical device that can be combined with the current cource according to the invention are:

An Electronic Timepiece, optionally relying upon a quartz time standard, optionally with a Liquid Crystal Display (LCD) indicator in either digital or analog display format;

An Electronic Timepiece, optionally relying upon a quartz time standard, with an electrically-actuable mechanical analog movement; An Electronic Arithmetic Calculating Apparatus

(Electronic Calculator), or other similar device for the manipulation and storage of electronic digital data, optionally with a Liquid Crystal Display (LDC) indicator in either digital or analog display format; An Electronic Termperature Sensing and Indicating Apparatus (Electronic Thermometer), optionally with a thermistor temperature sensor, or other improved temperature sensing element that may consist of an electrically conductive substance, such as conductive polymeric elastomer open-cell foam-rubber, whose relatively high ohmic-resistance changes in response to temperature changes and is capable, at the same time, of absorbing liquid-electrolyte, such as saliva from the mouth, to provide electrical current by electrolytic means to the integral measurement and display circuits within said temperature sensing apparatus, optionally with a Liquid Crystal Display (LCD) indicator in either digital or analog display format;

An Electronic Device for the temporary storage of digital data, such as a Random Access Memory (RAM) module typically employed in electronic apparatus such as microcomputers, industrial controllers, and telecommunications equipment, where the current source provides auxiliary or standby electrical power to sustain the memory-retention function of such devices, typically during periods of servicing and repair; An Electronic Apparatus for the Reception and Demodulation of Radio Frequency Electromagnetic Wave Transmissions (Radio Receiver) optionally with a low-power audio transducer, such as an earphone relying on an electret or crystal transducer element; An Electronic Apparatus, being either integral with other electrical apparatus, or separable and portable, for testing the continuity and resistance of an electrical circuit, typically employed when required servicing and repair is infrequent and remote. Further features of the invention will now be described Rejuvenation of the Electrolyte and Absorber.

According to another aspect of the invention there is provided an electrical current source comprising an electrolytic means of producing electrical current comprising a housing for the current source, including means of obtaining access to the interior. This is to allow electrolyte to be added, and/or absorber material to be cleaned or changed. There may be included an internal mechanical means of wiping clean the electrodes.

Accordingly, there is also provided according to the invention a method of cleaning an electrical current source comprising an electrolytic cell means of producing electrical current, the method comprising gaining access to the electrolytic cell means and cleaning the electrodes and absorber material and renewing and/or replenishing the liquid electrolyte. This may be done periodically to increase the life of the electrical apparatus as required. Clean water, such as that which is normally obtainable from ordinary municipal water supplies, is the safest and preferred electrolyte. One of the most serious problems affecting the service-life of the current source is the accumulation of anodic material in the absorber material (which may be sponge or fiber) as a result of the electrolytic consumption of the anode. This slow accumulation of anodic material can become so acute that the ion movement within the cell can diminish to a level below the minimum threshold necessary to provide power to the said electrical device.

To gain access to the absorber and the surfaces of the electrodes exposed to the electrolyte, the housing of the current source may be opened; the absorber may be pulled out or temporarily dislocated from its normal operating position. If the housing is opened for cleaning, it must be possible to easily separate the absorber from the surface of the anode. Typically, when an absorber is made from an ordinary material like sponge or open-cell polyester foam padding, it will have a tendency to stick or become attached to the anode surface due to an accumulation of oxide; whereas, the cathode usually shows little, it any, oxide build-up and does not attach itself to the absorber. Upon separation from the anode and subsequent removal or displacement of the absorber, both the electrodes and the absorber can be rinsed to remove any oxides. Typically, zinc oxide can be rinsed from the absorber through the employment of relatively light mechanical scrubbing of the absorber material. Once reassembled and re-filled with electrolyte, the current source should be able to continue supplying useful electrical current until the next cleaning cycle.

Typically, a current source that thas been rejuvenated in this manner should continue to operate efficiently for at least 2 to 6 months if not allowed to dry during that period. If the preferred mode is to remove the absorber, the opening created in the housing by the absence of the absorber must be sufficient to allow reasonable access to the electrode surfaces still remaining inside the housing. This is necessary to facilitate removal of any oxide coatings on those electrode surfaces. An alternative method, if access to the electrode surfaces for cleaning is not feasible, might be the attachment of a scraping or scrubbing means to a sliding absorber mechanism in such a way as to provide a self-cleaning motion when the absorber is pulled from the housing. If displacement of the absorber or anode, is preferred over their removal from the housing, anodic deposits can be flushed or otherwise removed from the interior of the cell by a sufficiently strong current of water, injected into and flowing through the housing in such a way as to gain access to the space between the electrode and its corresponding absorber. To assist in the removal of built-up deposits on the surface of the electrode, a mechanical wiping applicance can be made to slide along the surface of the electrode. Chemical Corrosion Inhibitor According to another aspect of the invention, there is provided a current source comprising an electrolytic means of producing electrical current, wherein the electrolyte contains a chemical corrosion inhibitor. This reduces the rate of wasteful self-discharge from spontaneous corrosion of the electrodes, especially the anode. The chemical corrosion inhibitor may be contained in an absorber; the inhibitor may be added to the absorber during manufacture by pre-soaking. The absorber may be a body of liquid-pervious liquid-absorptive cellular material, which may be under compression in a cavity containing electrolyte. During manufacture, even if the absorber is then allowed to dry, residual quantities of the chemical are permanently left behind, entrapped in the fibers or cells of the absorber material. The following chemical have been found to be suitable as an effective corrosion inhibitor: a) Sodium Chromate, which is typically stored dry and then mixed with ordinary tap water prior to treating the absorber material. Experimental tests showed that a 0.1% (wt.) solution was effective in helping to control excess oxidation of electrodes made from zinc. b) Sodium Phosphate (TriBasic), which is typically stored dry and then mixed with water prior to treating the absorber. Some amount of corrosion retardation was observed during tests but this substance was determined to be less effective than Sodium Chromate. Absorber Moisture Indicator Means

According to yet another aspect of the invention, there is provided an electrical current source comprising an electrolytic means of producing electrical current, including means of indicating the amount of electrolyte in the device.

During normal operation, the electrodes are effectively maintained in an immersed condition where their exposed surfaces are completely covered by the electrolyte contained within a slightly compressed abs o rb e r hel d agains t the el e ct rod e s u r f a ce . When an absorber begins to dry from evaporation, voids in the electrolyte covering over the electrode surface begin to form, exposing portions of the surface to air. At the boundary between air and water, a thin region of unusually active corrosive interaction occurs where the electrode surface is subjected to an increased rate of oxidation. As the absorber continues to dry, more voids in the electrolyte covering occur, with ever-increasing rates of excessive oxidation. The process continues until the absorber is completely dry. Interestingly, the slower the rate of electrolyte evaporation, the greater the damage that is done to the anode due to the prolonged period of drying once the voids begin to form. In other words, attempting to limit this oxidation by reducing the rate of evaporation only results in greater harm to the electrodes.

Allowing the absorber to dry is the single most significant cause of a foreshortened service-life of the current source as a result of wasteful and destructive corrosion of the anode. In fact, allowing the cells to dry can easily cancel any potential benefits to be gained from attempting to practise the other two life-extending methods: adding a chemical corrosion inhibitor and cleaning the accumulated anodic material from the absorber.

To help prevent the absorber from drying to a dangerous level, a moisture indicator may be employed. A practical indicator can be achieved through the employment of an optical means to indicate a change in moisture, which can be positioned within the cell in such a way as to provide a positive visual indication of the condition of the absorber. A lens, prism-like optical element, or textured interior surface of a transparent housing wall, can be molded directly into the housing, or attached later during any subsequent processing or assembly, to indicate wetness by application of the principle of Total Internal

Reflection or Refraction, or Optical Coupling by the liquid-electrolyte to overcome the tendency of incident light to be scattered by the transparent textured interior surface. The operation of this means relies upon a super-saturated condition of an absorber that has preferably been made from a distinctively colored material. While in a super-saturated condition, any excess liquid-electrolyte is allowed to fill the surrounding space between the absorber and the wall of the housing. Immediately upon filling with liquid-electrolyte, this space will be sufficiently filled to provide an optical coupling between the absorber and an adjacent int eriorally -textured transparent window, or lens, in the wall of the housing. Taking advantage of the optical coupling effect as a result of a change in the index of refraction between a condition of dry and wet, a visual indication can be easily discerned. Treatment of the Anode Prior To Assembly

Some amount of life extending benefit has been found experimentally through the treatment of the electrodes, especially the anode, prior to final assembly into the housing.

After thoroughly cleaning the surface of an anode (typically zinc) to remove any previous oxide or other coating, the anode might be subjected to a steam-laden environment within a sealed enclosure. Although the process employed during treatment experiments relied upon heat-generated steam with the electrodes being maintained at a relatively cool ambient temperature prior to introduction into the process chamber, or sealed enclosure, it is recognized that other methods of treatment that are more appropriate to high-volume manufacturing requirements can be employed to obtain equal or superior results. Another method might employ a controlled environment where the relative humidity has been artificially elevated by ultrasonic water atomizers where the treatment process relies upon the control of the dew-point level within that environment. However, our laboratory process relied upon the tendency of the steam to condense upon the electrode surfaces at such a rate as to limit the resultant coating of moisture, preventing the cut-off of air to the electrode surface. It was found that, if the water-droplet size and distribution across the electrode surface can be properly controlled, this process can yield a consistently even coating of oxide. If clean water, containing no additives or other chemicals, is used in the generation of the steam, and the anode (typically pure zinc) has been thoroughly cleaned before processing, the oxide layer resulting from this treatment will be of a known species (namely zinc oxide in the case of a zinc anode). Then, upon later activation of the electrical current source by the introduction of ordinary tap water bearing undesirable oxide and metallic-salt generating chemical compunds, an electrode surface would be encountered that is less susceptible to corrosive action due to the denial of fresh and unprotected metal. Regulation of the Output Voltage

Due to the normally unstable behavior of ion flow across the electrolyte means in a water-activated current source, which can cause current-density irregularities in the output, resulting in a varying level of apparent output voltage, an auxiliary means to control and regulate the effective output voltage presented to the Integrated Circuit means is advantageous.

For regulating the output of a current source suppling power to an electrical device, such as that which might be employed in an electronic wrist watch, that requires input voltage supply within the range between 1.2 and 1.8-volts, a Light Emitting Diode (LED) can be utilized. When electrically connected across the output terminals of the current source, for ex am p l e in parallel with an Integrated Circuit means, it effectively regulates the output voltage within a range normal to the operation of that circuit. The reasons behind the selection of a Light Emitting Diode (LED) as the regulating means are very specific. For comparison, a conventional signal-type diode is typically made from silicon, which has a forward voltage drop across its junction of approximately 0.7-volts when conducting with a normal current flow above several milliamperes. Under operating conditions where the average current flow is under 10-microamperes, the forward voltage drop is more typically around 0.3-volts. For example, to achieve the required voltage drop for the correct operation of a timekeeping Integrated Circuit means, several diodes would have to be connected in a series-circuit, and then that circuit connected across the output terminals of the current source. However, a Light Emitting Diode (LED), preferably made from gallium-arsenside, has a typical forward voltage drop in the range of 1.2 to 1.7-volts at current levels of a few microamperes. The supply voltage requirements for a typical timekeeping Complementary Metal Oxide Semiconductor (CMOS IC) is between 1.2 to 1.8-volts, which is advantageously compatible with a Light Emitting Diode (LED).

Specifically, a voltage regulator means incorporating a Light Emitting Diode (LED), if selected for an optimum voltage drop of 1.5-volts, has been found experimentally to draw about 1.5 to 3.0-microamperes, in parallel with a timekeeping Complementary Metal Oxide Semiconductor (CMOS IC), where the unregulated output of the current source is between 1.9 to 2.4 volts (which was obtained from a 3-cavity zinc-anode/copper-cathode current source with a cathode surface area not exceeding 60-square-millimetres per cavity). Therefore, if the Integrated Circuit means draws about 1.4 microamperes for itself, the total current demand from the current source will be about 2.9 to 4.4-microamperes. To our best understanding, this represents an acceptable operating parameter that will not appreciably diminish the overall effective service-life of the current source. Advantageously, a previously unmounted Light

Emitting Diode (LED) bare-die, obtained from a low-cost readily available wafer, allows the direct die-bonding of a Light Emitting Diode (LED) to the same circuit board employed for the die-bonding attachment of the timekeeping Integrated Circuit means and water activated current source.

Additional compensation for irregularities in current density, that can otherwise affect the visual quality of an indicating device, such as a Liquid Crystal Disply (LCD), can be achieved with the employment of a contrast enhancing colour filter lens installed over the display. Use of this filtering means has been found to be effective in obscuring momentary deficiences in contrast and viewing angle. Electrode Materials Suitable for Very-Low Rates of Pis charge There are many different electrically conductive substances that could be suitable for electrodes. Some of these materials can be classified with the family of metals, while others are considered semi-conductive, such as graphite and silicon, because of their relatively higher ohmic resistance. Furthermore, there are many suitable physical forms of these materials, for example sheetmetal or foil, electroplated or vapor-deposited coatings, or electrically conductive particles within a polymeric binder. An embodiment of our current source employs a purezinc anode in conjunction with a pure-copper cathode. We have experimentally found that employing electrodes whose own constituent material is of a mixed-species, for example alloyed metals, involves many complicated variables that are difficult and costly to control, which tends to limit their use in a low-cost consumer product. To help achieve one of the goals of this invention, which is increased service-life of the current source, we recognize the importance of eliminating as many life-shortening corrosive processes as possible. For example, pure zinc (99.99% purity) eliminates the necessity to predict and control the micro-corrosion cells that would occur at each crystal interface along an alloyed electrode surface. Whenever an electrode is formed from a mixture of two or more different electrically conductive substances (use of the term metals is intentionally avoided here since this electrolytic process also applies to some conductive materials that are not regarded as metals), a self-destruetive chemical reaction will occur along any exposed surface when immersed in an aqueous electrolyte. In a metallic electrode this is caused by the nature of crystal formation (the growth of metallic crystals making up the grain structure of the alloy) during the solidification period immediately after being poured from a crucible. It is this critical period that establishes some of the physical properties of that alloy. Even with the greatest of care during the period of solidification, achieving a perfectly homogenious mixture with perfect crystal structure is virtually impossible. Alloys of ordinary quality that are appropriately priced for the economic production of a low-cost electrical apparatus, usually have surfaces formed of crystals whose grain structure could be characterized as gross and uneven.

When two dissimilar electrically conductive substances are immersed in an electrolyte (typically water), a spontaneous chemical reaction (normally referred to as corrosion) will begin to occur. This chemical process draws no distinction as to the physical proximity of the two materials, only that they be dissimilar and electrically coupled, either directly by contact or through the electrical conductivity of the electrolyte medium in which they are immersed. Therefore, whether they are 30-centimetres apart, or merely the distance of 3-microns, this chemical process will still occur. In fact, when the two dissimilar electrodes are physically contacting each other, as adjoining metallic crystals along the surface of an alloy would, a short-circuit electrical path is provided that results in a relatively rapid rate of corrosion, severely shortening the service-life of the affected electrodes. With pure electrode material, for example 99.99 % purity, the occurance of adjacent crystals of mixed species are reduced to an acceptable level, although not totally eliminated. Many of the previous water-activated batteries produced by others employ electrodes which are made of metallic alloys combined with de-polarizing compounds to increase output current but at the sacrifice of service-life. These composite electrodes are necessary in order to effectively manage hydrogen polarization layers that form on the cathode surfaces and to increase ion flow across the electrolyte during periods of relatively high current surges. However, at very-low current outputs, such as the normal output level of our current source, significant amounts of hydrogen polarization do not occur. Because of the very-low output current levels of our current source during normal operation, we find that several alternative electrode materials are applicable that are not suitable for batteries requiring high output currents. For example, we have found that graphite-filled polymer composite compounds, while unsuitable for high current batteries, have very useful properties for our own water activated current source. When graphite is used as the electrically conductive filler for certain polymeric thick-film inks and elastomers, it provides the following improvements over metal plate cathodes:

1. Because graphite (carbon) is normally very resistant to chemical corrosion, a cathode made from a graphite-filled water-resistant polymeric compound that also possesses good resistance to the chemicals normally found in ordinary tap water, is inherently more durable than conventional metal plates.

2. Since carbon appears galvanically more electropositive than copper (which is a commonly used cathode metal), the resultant output voltage is appreciably higher when used in conjunction with an electro-negative anode, like zinc. The significance of this advantage can be appreciated when the output voltage of two cavities employing carbon cathodes can successfully provide the voltage requirements of an electrical device that previously required three cavities that employed a copper cathode. 3. When utilized in a paste or ink form, this electrically conductive polymeric compound can be printed cr sprayed onto a dielectric surface of almost any shape or texture, from a Printed Circuit Board to a complex injection-molded plastic housing. The employment of this material as an electrode can potentially lead to many design and manufacturing economies.

4. Particularly useful are electrically conductive elastomers that possess all of the valuable properties of the other polymeric compounds, with the additional advantage of being flexible and resistant to abrasion. These electrically conductive elastomers, when made from silicone-based rubbers with the additional advantage of being Room-Temperature-Curing (RTV), have shown to be very effective when employed as a bonding agent between a Printed Circuit Board and a pad made of electrically conductive elas tomeric open-cell foam-rubber.

5. Another advantageous form of electrically conductive elastomer is elastomeric open-cell foam. This material is particularly valuable as a cathode because of its property of absorption and increased surface area. As an absorber of liquid-electrolyte, it serves as both a cathode and an auxiliary reservoir of electrolyte. Also, as a result of the property of absorption, an increased surface area is made available for interaction with the electrolyte and the corresponding anode. This is an important characteristic that becomes immediately recognizable when attempting to minimize the exposed surface area of an anode. In this regard, elastomeric open-cell foam possesses many of the advantageous properties of activated (porous) carbon.

Another useful characteristic of electrically conductive polymeric materials, and especially conductive elastomers, is the behavior of its property of ohmic resistance under varying environmental temperatures. This property offers some very useful applications in temperature sensing, where the cathode not only helps to supply the operating current for the measuring Integrated Circuit means, but also provides the temperature sensing input to that same circuit. The Electrolytic Process

In order to possess the ability to design a practical very-low discharge rate water activated current source, certain corrosion processes must first be recognized. The first process, which produces a useful electrical output current, operates according to the classical Laws of Electrolytic Chemistry, and concerns itself more with the useful production of electrical current; whereas, the second process, which is responsible for the wasteful corrosive destruction of the electrodes, operates on a more complicated set of processes that are more commonly known to those practising Corrosion Engineering, and concerns itself more with the overall service-life of the current source.

Beginning with the first process, the following interrelated factors govern the production of electrical current within a galvanic cell from electrolytic means:

1) The theoretical electromotive potential between the anode material, such as zinc or magnesium, and its corresponding cathode material, such as copper or graphite. This is an immutable value controlled by the atomic nature of the electrode materials.

2) The ratio of cathode surface area to anode surface area, and the proximity or distance between the electrodes.

3) The specific electrical current demand of the external electrical circuit.

4) The activeness, or acidity of the aqueous electrolyte.

The second process is based on a set of similar electro-chemical principles, with the exception that it is more concerned with corrosive reactions that affect the overall service-life of the current source. As in the first process, certain spontaneous chemical reactions occur within the cell that result in the destructive corrosion of the electrodes. Since the rate of corrosion on the cathode is very slow in comparison to the anode, most of the problems affecting the service-life of the current source are anodic in nature. When examining the second process, two major causes of excess corrosion can be identified. The first action begins to occur when electrolyte is introduced into the cell. Dissolved in the water is oxygen and corrosive compounds, including one of the most harmful groups based on chlorine. When this oxygen and chemical bearing water comes into contact with the anode, excessive oxidation (this is oxidation that occurs as a result of spontaneous corrosion, where the electron-path is internally shunted through the cell due to the conductivity of the electrolyte rather than an external path through the electrical device) can occur, resulting in the production of a white-colored ash commonly known as white-rust or oxide. Whereas most oxide deposits can be considered relatively benign in the sense that they are easily cleaned from electrode surfaces and absorders, compounds like zinc chloride, produced when employing zinc as an anode, are very tenacious and can build up a coating on the anode that can seriously interfere with the normal electrolytic process required in the generation of electrical current. Furthermore, voltage drops can occur across the oxide and metallicsalt coatings on the electrodes which can seriously diminish the electromotive potential between electrodes that is essential to the movement of ions. The second action involves the accelerated corrosive effect typically found around the base of a drop of water. Whenever an air-water interface boundary occurs, extreme oxidation of the electrode surface can result. If enough interface boundaries occur along the surface of an electrode, serious oxidation rates could overwhelm the capacity of the absorber, typically a sponge material, to handle the excess amounts of anodic deposits, resulting in a swamping of the absorber and blockage of the ion pathway leading away from the anode. This accelerated corrosion rate is the most significant cause for the rapid formation of oxides along the surface of an absorber that has been allowed to repeatedly dry before refilling with electrolyte.

There are two significant problems encountered when attempting to operate a water-activated current source at very-low output currents over an increased service-life: Self-Discharge and Internal Impedance. Both of these problems are integrally involved with our means to extend the useful service life of the current source and both are further aggravated by our attempt to miniaturize the battery for consumer applications such as wrist watches. Self-Pis charge.

Self-discharge, which is a form of internal short-circuiting, is the most significant factor affecting the life-expectancy of a low-discharge water activated battery. If not controlled, self-discharge would end the useful output of our battery long before the anode was consumed for the useful production of electrical current. Self-discharge occurs in an electrolytic cell when internal electrical currents are allowed to flow between the electrodes through the electrolyte due to the conductivity of the electrolyte medium itself. And as conductivity increases, the rate of self-discharge, or short-circuiting, also increases. Electrical resistance of ordinary municipal tap water, recommended for use in our battery, typically ranges between 400,000-Ohms for clean water, and down to 20,000-ohms for water containing above average levels of dissolved mineral salts and other matter (For comparison, the CMOS circuit used in a typical digital wrist watch has a load-impedance roughly equivalent to 1,000,000-Ohms resistance). As the electrolyte acts on the anode to dissolve its material into solution, the concentration of spent anodic material continues to rise, increasing the conductivity of the electrolyte, which in turn increases the rate of short-circuiting. This self-destructive process continues, ever-increasing its rate, until internal short-circuiting far exceeds all other processes, and the battery eventually consumes itself after only a relatively small portion of it has been utilized for output to an external circuit. One of the most effective means for reducing the rate of self-discharge is to minimize the anode-electrode surface area exposed to electrolyte; in effect, sizing the electrodes to match the requirements of the external circuit and not uselessly over-sized. The principle is simple: the electrolyte cannot frivously dissolve something with which it is denied contact. In practice, however, this task is somewhat more complicated than simply calculating the anticipated external load, and then prescribing a formula amount of surface area to yield that output. Some of the other factors involved in establishing an optimum exposed surface area are discussed in the next section. In fact, the design-process in attempting to minimize the exposed anode surface area requires certain considerations not even relevant to the other conventional high-discharge water activated batteries. Internal Impedance.

In any battery, or any other type of power supply, an internal impedance, including ohmic- resistance, must be recognized and included as part of the total circuit design parameters, especially when employing a water activated battery. In a battery that has been intentionally sized for very-low power applications, such as our battery, internal impedance is critical to the performance and reliability of that application.

When our water battery starts out new, with fresh electrodes and electrolyte, the entire surface area of the anode is capable of interfacing with the electrolyte to produce an electrical output. However, as anodic material is consumed, oxide layers begin to build-up on the electrode's surface. If left unattended, these oxide layers could seriously interfere with the operation of the electrolytic process. To accelerate the anode's ions away from its surface, an electrical potential must exist between itself and its corresponding cathode. Two deleterious forces tend to diminish this critically needed inter-electrode potential:

Short-circuiting, caused by the conductivity of the electrolyte, will diminish the electrical tension between the two electrodes, thereby reducing the forces necessary to accelerate the ions away from the anode. Oxide-layers, built-up on the electrode surfaces, will also diminish the useful electrical potential between electrodes due to ohmic voltage drops across these layers. To help overcome the effects of internal impedance due to oxide-layer build-up, a certain amount of extra anode surface area must be added to the basic minimum as compensation to assure a sufficient amount of output current will continue to flow during the entire period allowed between predetermined rejuvination cycles. A careful balance must be maintained between that basic minimum and the extra amount in order to minimize any excess anodic material consumption caused by self-discharge. The longer the period between rejuvination cycles, the greater the amount of extra surface area required.

To help appreciate the deleterious effect of these oxide layers, a close examination is required cf the process utilized in our current source to produce very-low discharge rates. Normally, in any ohmic electrical circuit, resistance determines the rate of current flow for any given amount of voltage. However, with our current source, internal resistance within the cell takes on an importance that is normally overlooked with other electrical current sources. Even without voltage-dropping oxide layers, the internal ion flow of our current source is a very delicate process. This is primarily due to the size of our electrodes, which cause the current source to operate in a mode traditionally characterized as current-starved or current-limited. Our electrodes are intentionally designed to be undersized for two reasons. Voltage Regulation.

An important advantage to deliberately undersizing the electrodes, or more specifically under-sizing the cathode, is the ability to regulate the output voltage with great economy. The typical water activated battery has an inherent difficulty in producing a stable and constant output voltage, especially at output power levels around 100-microwatts, due to many complex internal processes. In fact, without external or auxiliary voltage regulation, our current source would probably not be commercially suitable for electronic circuits like those used for timekeeping. Operating the current source in a current-limited mode simplifies the regulation problem while at the same time allowing a simple device like a Light Emitting Diode (LED) to effectively regulate the output without seriously diminishing the useful service-life of the current- source. In one of our preferred embodiments employing voltage regulation, a Light Emitting Diode (LED) is connected across the current source output terminals, appearing as a parallel load along with the Integrated Circuit means. The operating principle is simple: The Light Emitting Diode (LED) dominates the parallel-load circuit because of its relatively lower resistance. If the current source were capable of sourcing a greater amount of current, the Light Emitting Diode (LED) would increase its consumption, up to the point where the forward conduction of the Light Emitting Diode (LED) would exceed the maximum limit and the device would burn-out. But long before the maximum current limit was exceeded, the current source would be needlessly procuding excessive current for the Light Emitting Diode (LED), leading to premature exhaustion of the anode. In one of our typical current sources, the output is effectively regulated while the load draws no more than 4-microamperes. Normally, a Light Emitting Diode (LED) (similar to the type used in one of our embodiments) draws about 10-milliamperes during forward conduction from a conventional battery, which is 2500-times greater than the same diode while connected across our current source. The Light Emitting Diode (LED) in our embodiment takes advantage of the current limiting nature of ions flowing between two under-sized electrodes. Package Miniaturization.

In order to meet the expectations of consumers and help assure market acceptance, a miniaturized current source is needed which provides for the minimum power requirements of the electrical device. Brief description of the drawings.

The foregoing and other objects, features, and advantages of the invention will be readily apparent from the following d e s c r ip t i on of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be affected wthout departing from the spirit and scope of the novel concepts of the disclosure, and in which:

Figure 1 is an exploded perspective view of a water-activated current source integral with a timekeeping Integrated Circuit means embodying the principles of the invention;

Figure 2 is an exploded perspective view of the water activated current source portion of a typical pocket electronic calculator;

Figure 3 is a fragmentary sectional view of the sliding feature of an electrode wiping appliance integral with an absorber retaining means.

Figure 4 is a fragmentary exploded perspective view of the absorber retaining means.

Figure 5 is an exploded perspective view of a disposable sensor strip for an electronic thermometer with integral temperature sensor and current source.

Figure 6 is a perspective view of the measurement and display unit for an electronic thermometer.

Figure 7 Is an exploded perspective view of a water-activated current source Integral with a timekeeping integrated circuit means embodying an alternate configuration to advantageously achieve compactness.

Best Modes for Carrying Out the Invention.

Preferred embodiments of the invention will now be described by way of non-limiting examples only, with reference to Figure 1 which illustrates an electrical apparatus for timekeeping.

Referring to Figure 1, an LCD digial quartz timepiece is provided by a single printed wiring board (1), which acts to provide both attachment sites for the various electronic components and circuit wiring means for interconnecting the various electronic components. Further, printed wiring board (1) also provides attachment sites for the various components comp ri s ing a water-activated current s ource .

Attached to printed wiring board (1) at bonding site (2), by electrically conductive epoxy die-bonding means and interconnecting wire-bonding means, is a timekeeping integrated circuit means (3); attached at (4), also by electrically conductive epoxy die-bonding means and interconnecting wire-bonding means, is a light emitting diode (LED) (5); attached at (6), by solder connection means, is a resonating quartz crystal time-standard means (7); attached at (8), (9), and (10), by solder connection means, are cylindrical posts (11), (12), and (13), formed of anodic metal (typically zinc); attached to the printed wiring board, by adhesive-bonding means, is die-electric elastomeric closed-cell foam separator pad (14); and attached to component attachment sites (15), (16), and (17), by electrically conductive (carbon-filled) room-temperature-curing silicone-rubber compound, through separator cavities (18), (19), and (20), are cyl indri cally-formed electrically conductive (carbon-filled) polymeric elastomer open-cell foam pad cathode-absorbers (21), (22), and (23). It is also preferred that each cathode-absorber element be in compression within the separator cavities. The foam separator pad (14) is adhesively attached between the printed wiring board and the compression actuator plate (shown In the Figure just behind the front case, but without an item number). This actuator plate has a pusher on its front surface that extends through the round hole of the front case and the front lens (item 36).

Within and surrounded by cathode-absorbers (21), (22), and (23), are cylindrically-f ormed polyester open-cell die-electric foam absorbers (24), (25), and (26). An outer watch-case (29) is placed over a completed printed wiring board assembly, and thereby securing in-place a liquid crystal display module (32), and its corresponding electrically conductive elastomeric connector strip (33). Integral with the outer surface of watch-case (29) is a wrist-strap attachment means (34) and (35). A front lens (36) is attached to the face of watch-case (29) at aperture (37) by adhesive-bonding or ultrasonic welding. Attached by adhesive-bonding or ultrasonic welding to the back, of watch-case (29) is a back-cover (38). Provided through the face of watch-case (29) is a plurality of water filling apertures (39), (40) and (41), communicating with water reservoir cavity (42), (43), and (44). To fill the cathode-absorber residing within and between said plurality of separator cavitities and water reservoir cavities with water, induction actuator (30), residing within watch-case, must be operated by pressing downward with sufficient force as to cause cathode-absorber to fully compress, thereby causing contaminated liquid-electrolyte to be ejected from the absorber, while simultaneously wiping the surface of anode to assist in the removal of oxides. Releasing pressure on induction actuator allows cathode- absorber to de-compress and induct fresh water into absorber through water filling apertures in face of watch-case. To monitor the effectiveness of this water-filling procedure, and to conveniently inspect the moisture content of the absorbers during normal use of the timepiece, a visual inspecting means is provided in the watch-case face by optical means, where the effect of optical coupling provides a readily discernable indication. The compressibility of the foam sandwich allows a pumping action by which the anodic materials can be flushed from the absorber during washing. With reference to Figure 2 there is seen an alternative water-activated current source in the form of a battery portion for a pocket calculator, the battery portion including a housing (42) and a sliding absorber-retaining and electrode wiping means (43). Every time the battery is opened for refilling, the slide will scrape clean the surfaces of the electrodes; this controls the build-up of anodic oxide.

As seen with additional reference to Figure 3, sliding absorber-retaining means (43) moves along an interior cavity of housing (42) while wiper is in correspondence with the recessed surface of both anode (44) and cathode (45), between indentation at (46), which provides a detent to secure the slide at an extreme position corresponding to fully closed, and indentation (47), which provides a detent to limit the travel of slide at an extreme position corresponding to fully open. Further can be seen a water reservoir cavity (48) in communication with the absorber and extending into the gripping portion of the sliding absorber-retaining means. Referring to Figure 4, the assembly sequence of the sliding absorber-retaining means can be ascertained. Secured to absorber retaining fork (49) is sprung wiping appliance (50). Inserted into fork, and extending through communicating aperture into water reservoir cavity, is absorber (51).

Referring now to Figure 5 there is seen yet another embodiment of the invention wherein a water-activated current source is retained within a flexible Printed Circuit means positioned at one end of a narrow flexible plastic strip intended for insertion into the mouth of a patient for use as a temperature sensing and measuring device. An electrically conductive (carbon-filled) polymeric elastomer open-cell foam cathode pad on the strip serves as both ambient-temperature sensing transducer and cathode in conjuction with a suitable anodic material deposited electro-chemically or by evaporated metal deposition means onto a spaced-apart electrical circuit means.

One-half of a laminated flexible Printed Wiring strip (1) provides support to an int eri orally-facing circuit path (2), that has been processed photolithographically from metallic foil or electrically conductive polymeric compound, that extends between the anode means of a current source at one end of the strip, and edge connector means (3) at the opposite end; a serpentine-like pattern (4) is formed beneath the anode of the current source to provide a flexible substrate upon which anodic material is deposited.

The other half of a laminated flexible Printed Wiring strip (5) provides support to a second and third interiorally-facing circuit path, that has also been similarily processed photo-lithogrphically. The second circuit path (6) extends between the cathode means (7) of a current source, at one end corresponding to the anode positioned at the end of the adjacent strip, and edge connector means (8), at the opposite end. The third circuit path extends between ambient temperature sensing electrically conductive elastomeric compound (9), adjacent to cathode of current source, and edge connector means (10) at the opposite end. Attached to cathode bonding site (11), facing interlorally, is a thin pad of electrically conductive elastomeric open- cell foam (12). Between cathode pad and anode is a polyester-fiber pad separator (13). A plurality of electrolyte communicating apertures are formed into strip (5) in correspondence with cathode pad. The Foam tip of the Sensor Strip is intended to absorb saliva from the mouth of the user and utilize this as electrolyte against the small deposit of anodic material on the opposite half of the strip. To encourage use by small children, the tip of the sensor is coated with a candy syrup (typically cherry flavoured) to overcome the reluctance of a child who might reject an unfamiliar object and remove it from their mouth before an accurate temperature reading has been obtained (approximately 20-sec). After one use, the sensor strip is discarded to avoid any germs that may have been absorbed by the tip. In marketing this device, an inexpensive package of spare sensor strips would be provided with a re-usable display module (shown in Figure 6 ) .

Figure 6 illustrates one means for measurement and display of electrical inputs from sensor strip. Pressing actuating lever (14) against display housing (15) opens a set of spring-loaded jaws (16) providing access to electrical connector means to edge connector at end of Sensor Strip. Releasing pressure on actuating lever closes jaw and engages electrical connector means. Behind liquid crystal display module (17) is temperature measuring integrated circuit means die-bonded to printed wiring board. While sensor strip is intended to be a one use only disposable appliance, the display unit is intended for permanent retention and re-use. Referring to Figure 7, another embodiment is seen where the current source supplies electrical power to a digital timekeeping circuit. Attached to printed wiring board (1), is timekeeping integrated circuit means (2) and crystal (3) and capacitor (4) and voltage-regulating light emitting diode (5) and electrically conductive silicone rubber switch contacts (6) and (7). Attached to back-side of board, on component mounting pad (8), by electrically conductive (carbon-filled) silicone adhesive, is an electrically conductive (carbon-filled) open-celled elastomeric foam cathode (9). Attached to component mounting pad (10) by electrically conductive epoxy adhesive, through aperture (11) of cathode, is magnesium anode (12), and then water-sealed around base by non-conductive silicone sealant. Inserted into watchcase (13) through front opening, and brought to rest against rear bezel (14) is compression actuator disk (15). Inserted into watchcase, through front opening, and brought to rest against printed wiring board mounting flange (16) and aligning with anode clearance aperture (17) of disk, is the completed board assembly. Once in place, board is sealed against flange with silicone adhesive. Inserted into watchcase and aligned with LCD connector pads on front of board is elastomer connector strip (18). Placed against connector is liquid crystal display module (19). Over front opening of watchcase is transparent lens (20), aligned to allow rubber switches to extend through switch aperture (21) and (22) and to allow LCD module to affix into detent provided in interior surface of lens; held in place by front bezel (23). Watchstrap attachment means is provided by strap attachment forks (24) and (25). To advantageously simplify assembly and help ensure the water-t ightness of the electronics compartment, solder-filled plated through hole (26) and (27) is provided between front and back of printed wiring board as battery connection means. Again, as in the first example, the absorber/cathode is simultaneously filled and cleaned by the pumping-action provided by squeezing the watchcase, or pressing on the compression actuator at the rear of the case. The anode in this embodiment is made from magnesium, allowing a single cell to provide the voltage requirements of the timekeeping circuit.

Figure 8 shows a cut-away view of a very low profile disposable paper wrist watch intended for imprinting with advertising or other design. The entire timekeeping circuitry and current source are attached to a paper strip. The paper strip can be made from resin- impregnated paper or calendared plastic paper like Tyvek (polyolefin fiber) or Nomex (nylon fiber). After attachment of the watch components, the entire strip is covered by a transparent polyester film to seal it against moisture and protection from abrasion. Holes are provided in this film covering to allow the ingress of water to the absorber/cathode of the current source. To fill with water, the watch is held under a stream of water or dipped into a standing body of water while squeezing the flexible pads of the absorber/cathode. Once filled, the watch will continue to run until the pads require replenishment of water in about 3 days.

A plurality of apertures have been formed in resin-impregnated paper wrist strap (1) to provide access clearance for the separate watch components. Extending through LCD aperture (2) is a digital liquid crystal display module (3), aligned to be flush with front surface of strap. Attached to LCD, along top edge of module, is edge connector (4) formed in end of flexible printed wiring strip (5) by heat sensitive electrically conductive adhesive. Extending through CMOS aperture (6) is timekeeping Integrated circuit means (7), attached to strip by electrically conductive (silver-filled) die attach epoxy. Extending through LED aperture (not shown) is voltage regulating light emitting diode (8). Extending through capacitor aperture (9) is chip capacitor (10). Extending through crystal aperture (11) is crystal (12). Extending through switch aperture (13) and (14) is electrically conductive silicone switch contact (15) and (16), attached to strip by silicone adhesive. Extending through anode aperture typified by (17), is up-turned appendage (18) and (19) of flexible strip, positioned to accept attachment of zinc anode (20) and (21) by solder connection means. Between anode and strip is electrically conductive (carbon-filled) open-celled elastomeric foam cathode (22) and (23), attached to lower strip by electrically conductive (carbon-filled) silicone adhesive. Applied by vacuum attachment means, and covering both sides along entire length of watch, is a transparent film of polyester or other durable material, secured by pressure-sensitive adhesive, or other suitable means, and intended to protect watch components and provide water containment means around absorber/cathodes of current source. Optionally attached to back side of watchstrap is thin polymer foam strip intended to provide increased comfort to wearer. Watchstrap is fitted with appropriate fastening means to effect secure attachment around wrist of wearer, for example pressure-sensitive adhesive strip or velcro pad.

Various modifications and changes to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair Interpretation of the following claims.

Having fully described and disclosed the present invention in such clear and concise terms as to enable those skilled in the art to understand and practise the same, that which is claimed as the invention is set forth in the following claims.

nternat ona ureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classification (11) International Publication Number : WO 89/ 035 H01M 6/32, 6/26, 4/96 A3 H01M 6/34, G04C 10/00 (43) International Publication Date: 20 April 1989 (20.04.8

'_

(21) International Application Number : PCT/GB88/00934 (74) Agent: CHETTLE, Adrian, John; Withers & Rogers, Dyer's Buildings, Holborn, London EC I N 2JT (GB

(22) International Filing Date: 14 October 1988 (14.10.88)

(81) Designated States: AT (European patent), BE (Eur

(31) Priority Application Number : 8724231 pean patent), CH (European patent), DE (Europe patent), FR (European patent), GB (European p

(32) Priority Date: 15 October 1987 (15.10.87) tent), IT (European patent), LU (European paten NL (European patent), SE (European patent), US.

(33) Priority Country : GB

Published

(71X72) Applicant and Inventor: CHAU, Patrick, Cham, With international search report Wong [GB/GB]; 15, 17 & 19th Floors, Aberdeen InBefore the expiration of the time limit for amending t dustrial Building, 236 Aberdeen Main Road, Aberdclaims and to be republished in the event of the receipt een (HK). amendments.

(72) Inventor; and (88) Date of publication of the international search report:

(75) Inventor/Applicant (for US only) : KITZMILLER, Wy- 29 June 1989 (29.06.8 ley, G. [US/GB]; 15, 17 & 19th Floors, Aberdeen Industrial Building, 236 Aberdeen Main Road, Aberdeen (HK).

(54) Title: WATER- ACTIVATED MICRO-ELECTRONIC CIRCUITS

(57) Abstract

Electrical apparatus comprising a combination of a low-power electrical circuit (3). a source of low electrical curren comprising at least one cavity (18, 19, 20) for containing liquid electrolyte; a cathode (21) of a first electrically conductiv substance having a tendency to act as an oxidizing agent in the presence of a selected second electrically conductive sub stance and which is positioned within said at least one cavity; an anode (1 1, 12, 13) of a said selected second electricall conductive substance having a tendency to act as a reducing agent in the presence of said first electrically conductive sub stance and which is positioned within said at least one cavity; first means for permitting the introduction of a liquid elec trolyte into said at least one cavity; and second means for permitting air to be discharged from said at least one cavit when said liquid electrolyte is introduced into said respective cavity; and electrical conductor means connecting said cur rent and said electrical circuit for supplying electrical current to said electrical circuit.

FOR THE PURPOSES OF INFORMAHON ONLY

Codes used to identify States party to the PCT on the front pages ofpamphlets publishing internationalappli- cations under the PCT.

AT Austria FR France ML Mali

AU Australia GA Gabon MR Mauritania

BB Barbados GB United Kingdom MW Malawi

BE Belgium HU Hungary NL Netherlands

BG Bulgaria rr Italy NO Norway

BJ Benin JP Japan RO Romania

BR Brazil KP Democratic People's Republic SD Sudan

CF Central African Republic of Korea SE Sweden

CG Congo KS Republic of Korea SN Senegal

CH Switzerland LI Liechtenstein su Soviet Union

CM Cameroon LK Sri Lanka TD Chad

DE Germany, Federal Republic of LU Luxembourg TG Togo

DK Denmark MC Monaco US United States of America

El Finland MG Madagascar

Claims

CLA IMS

1. Electrical apparatus comprising a combination of a low-power electrical circuit, a source of low electrical current comprising at least one cavity for containing liquid electrolyte; a cathode of a first electrically conductive substance having a tendency to act as an oxidizing agent in the presence of a selected second electrically conductive substance and which is positioned within said at least one cavity; an anode of a said selected second electrically conductive substance having a tendency to act as a reducing agent in the presence of said first electrically conductive substance and which is positioned within said at least one cavity; first means for permitting the introduction of a liquid electrolyte into said at least one cavity; and second means for permitting air to be discharged from said at least one cavity when said liquid electrolyte is introduced into said respective cavity; and electrical conductor means connecting said current source and said electrical circuit for supplying electrical current to said electrical circuit.

2. Electrical apparatus according to claim 1, wherein the electrical circuit includes low-power integrated circuit means.

3. Electrical apparatus according to claim 1 or 2, wherein the electrolyte contains a chemical corrosion inhibitor.

4. Electrical apparatus according to claim 3, wherein the corrosion inhibitor is selected from sodium chromate and phosphate tribasic.

5. Electrical apparatus according to claim 3 or 4, wherein said chemical corrosion inhibitor is contained in an absorber in the or each cavity.

6. Electrical apparatus according to claim 5, wherein the absorber comprises a body of liquid-pervious, liquid-absorptive cellular material.

7. Electrical apparatus according to claim 6, wherein the liquid-pervious, liquid-absorptive cellular material is in compression.

8. Electrical apparatus according to any preceding claim, including a housing for the source of electrical current Including means of obtaining access to the interior for cleaning the absorber and/or replenishing the electrolyte.

9. Electrical apparatus according to any preceding claim, inculding an internal mechanical means of wiping at least one of the electrodes.

10. Electrical apparatus according to any preceding claim, including means of indicating the amount of electrolyte In the source of electrical current.

11. Electrical apparatus according to claim 10, wherein the electrolyte amount indicator is an optical means.

12. Electrical apparatus according to any preceding claim, comprising an electrolytic means of producing electrical current wherein the electrodes are undersized by a predetermined amount.

13. Electrical apparatus according to claim 12, wherein the size of the electrodes is increased by a predetermined amount to account for oxide formation.

14. Electrical apparatus according to any preceding claim, wherein the electrodes are in a predetermined condition in the form of controlled oxide coating.

15. Electrical apparatus according to claim 14, wherein the determined condition comprises a predetermined even oxide coating.

16. Electrical apparatus according to any preceding claim, including electronic means of automatically regulating the output voltage.

17. Electrical apparatus according to claim 16, wherein the automatic-regulation electronic means comprises a light-emitting diode.

18. Electrical apparatus accordlngto claim 17, wherein the light-emit timg diode includes gallium arsenide.

19. Electrical apparatus according to any preceding claim, including at least one electrode comprising at least one of a carbon-filled polymeric compound, carbon-filled elastomeric material, carbon-filled elastomeric open-cell foam and activated carbon material.

20. Electrical apparatus according to claim 19, wherein the or each electrode comprises a film of said carbon-filled polymer on a dielectric substrate.

21. Electrical apparatus according to claim 19 or 20, wherein the polymer comprises a silicone-based elastomer rubber.

22. Electrical apparatus according to any preceding claim, wherein the electrical circuit is employed in a timepiece, apparatus for manipulation and/or storage of data, apparatus for sensing and indicating temperature, apparatus for reception and demodulation of radio-frequency electromagnetic waves, and apparatus for testing continuity and ohmic resistance of electrical circuits.

23. An electrical apparatus comprising low-powered electrical circuit means printed on a board, an electrolytic means of producing electrical current including electronic means of automatically regulating the output voltage, wherein the elctronic means is a die attached to the printed circuit board.

24. Electrical apparatus according to any preceding claim wherein the electrical circuit includes a low-power Indicator.

25. Electrical apparatus according to claim 24, wherein the indicator Is a visual indicator and includes a contrast-enhancing colour filter lens.