CONTAINER FOR ELECTRICAL DEVICE USING A METAL AIR CELL
This invention relates to a container for an electrical device driven by a metal air cell and designed for average low current operation, but which intermittently requires high current 7. An example would be a wristwatch case which contains an electronic clock movement driven by a zinc air cell and requiring a continuous low current in order to operate the watch for a timing operation, but which includes a mechanism for Illuminate the clock when a button is pressed, or to operate a radio receiver as a location device. These latter devices require a relatively high current for a short time when they are operating and therefore a high current cell is required to support them. Metal air cells are well known in the art, generally consisting of a consumable metallic anode, a non-consumable catalytic cathode, oxygen consumer and a suitable electrolyte. The metal air cells have been manufactured in the form of micrometer-sized cells for devices for hearing aids and watches and the like. A typical zinc / air cell of micrometer size generally includes the following components: 1. A cathode vessel which includes at least one opening for the air inlet and contains a non-consumable air cathode structure generally consisting of a polymeric film. hydrophobic permeable to the gas on which a metal intake grid and an impermeable, porous catalyst material such as activated catalyzed metalized carbon mixed with a hydrophobic binder are pressed. Although in reality it is an independent component of the cell, one or more separating layers that absorb electrolytes are placed on the catalytic layer of the cathodic structure to separate it from the anode. 2. An anodic vessel which is attached to the cathodic vessel in general by fold and which includes an anodic mass of zinc usually in the form of amalgamated zinc powder (eg, containing 3-8% by weight of Hg) or a conglomerate of porous zinc, saturated with an alkaline electrolyte as a 30-40% aqueous solution of KOH. 3. An insulator of polyethylene, polypropylene, nylon, etc. between the cathode and anodic vessel. The insulator also works in many cases as an electrolytic seal. The control of the air intake to the air consuming electrode is provided by small holes in the micrometer sized cell container as illustrated in U.S. Patent No. 3,897,265 published July 29, 1975 to Jaggard. These cells are suitable for relatively high current discharges such as 10 milliamps which are used in hearing aids. Subsequently, zinc / air cells have been developed for long-term low-current discharge, as required in electric wristwatches by adding a special membrane to control the admission of oxygen to the air-consuming catalyst. A type which is permeable to oxygen is known from U.S. Patent No. 4,105,830 published on August 8, 1978 from Kordesch. In U.S. Patent Number 4,118,544 published October 3, 1978, Przybyla et al. Using very thin pores or passages through a cathode barrier. In all the above constructions, the mechanism for controlling the oxygen admission to the cathode is adapted for a specific application or kind of current discharge which is expected to be found by the cell. The above constructions do not lend themselves to alternating operation of the cell in an average low current mode or a high current mode. The prior art explains that the entry and exit of gases such as air or water vapor, a and a zinc / air accumulator, can be delayed by restricting the opening (s) in the walls of the required cell (s) to allow air to enter the cell. The control of relative humidity is especially important to extend the life of the cell. A zinc / air cell will dry in an atmosphere of low humidity and Rood in a high humidity condition. Both conditions prevent the full power capacity of the cell from being obtained --- for a longer period of time and are especially significant at average discharge speeds bja, ie, in cases where the nominal capacity would not be exhausted in six weeks or less. The initial concentration of the accumulator electrolyte sets the internal humidity (RH) of the cell to approximately 58%. The exposure of the activated cell to levels of ambient RH, more or less than this value, causes the entry and exit of vapor, respectively. The entry and exit of water vapor can be restricted by reducing the size of the air intake holes.
But the opening that restricts the transfer of water vapor also limits the transfer of oxygen to the cell. The opening in a high current cell must be adjusted to accommodate the oxygen input necessary to support the maximum discharge velocity.
Metal air cells having a high current discharge capacity, such as those used in hearing aids, are not suitable for use in wristwatches without modification. Metal air cells have been modified for use with electrical devices that require a normal average low current discharge with intermittent high current discharge requirements. Examples of this modification are seen in U.S. Patent 4,262,062 to Zatsky published April 14, 1981 assigned to the Applicant's assignee and to Ultman and others U.S. Patent 5,451,473 issued September 19, 1995. In the latter patent, a metal air cell includes a restrictive membrane that controls the flow of air from air inlet ports at the bottom of the cell to an internal air reservoir. The air reservoir provides sufficient oxygen to the cathode assembly during short periods of discharge of high current in the cell. Another mechanism for coupling the cell to the electrical device receiving power from the cell is shown in U.S. Patent 5,191,274 published March 2, 1993 by Lloyd et al. In this patent, the number of holes of admission or supply of air to the cell is controlled by a seal which determines the number of holes or ports which are activated to admit oxygen into the cell. Throughout the prior art, the design of the metal air cell itself determines the speed of air flow to the cell. It is also known that in the prior art an electrical device and a metal air cell are placed which is designed to be coupled to the current requirements of the electrical device in a container. Since the cell requires a supply of air to work, the container can be hermetically sealed. The prior art has allowed a generous supply of air to the container to meet the current requirements of the electrical device under all conditions. This intake of air with accompanying steam allows the relative humidity within the container to fluctuate widely as determined by many factors such as variations in relative humidity outside the container, temperature variations in the container and oxygen consumption by the container. cell. However, water in liquid form can also enter the container through the air inlet passages if the device is subjected to excessive humidity or is proposed for underwater operation. It is known that it uses gas-permeable hydrophobic membranes in the walls of the container, which admit air without admitting water in a liquid state. US Patent 4,292,681 published September 29, 1981 by Kloss et al. Exemplifies this housing for an "instrument." Kloss's patent discloses a container for an electrical device having a cap and a seal, which either the seal itself, or an opening in the lid, or the housing itself can be composed of a microporous, hydrophobic, gas-permeable substance. Referring to Fig. 1 of the drawing, in the Patent of the States U.S. 4,292,681 to Kloss discloses a prior art container for an electrical device.
1 and 2 in which the housing portions are connected in a waterproof manner to each other by means of a non-gas-transmitting sealing ring 3. The ^ portion
2 which takes the form of the housing cover is provided with a gas passage 4, which is closed by a microporous component.hydrophobic The oxygen elements of the air (electrical device and metallic air cell) which are housed inside the box are supplied with air - through this component which can, for example, be made of unsintered polytetrafluoroethylene. It is also possible to provide several air transmitting openings, closed by microporous sealing bodies. By way of example, the zinc / air cell contained within the housing uses about five microliters of air per hour. In the case of immersion in the water, the water continues to run using the air contained within the housing. The zinc / air cell described in the aforementioned prior art should be adapted especially for a wristwatch, if it should have a useful useful life, by means of restrictive membranes of air flow inside the cell or by similar devices as those described in the Patents of the United States 4,292,681; 5,191,274 or 5,451,473 mentioned above. In the Kloss patent, the use of a hydrophobic, gas-permeable material (usually in the form of a membrane) is for the purpose of restricting the entry of water into the liquid state without trying to substantially restrict the rate of air entry or other gases, including water vapor. . - Accordingly, an object of the present invention is to provide an improved container for an electrical device driven by a metal air cell which will extend the life of the cell. Another object of the present invention is to provide an improved container for extending the life of a metal air cell with high current capacity by supplying power to an electrical device having average low current requirements. Another object of the invention is to provide an improved container for controlling changes in relative humidity experienced by a metal air cell inside the container. Another object of the invention is to provide an improved process for using a high capacity zinc / air standard cell of the hearing aid apparatus type to drive the movement of a wristwatch contained in a water resistant case. SUMMARY OF THE INVENTION Briefly stated, the invention comprises a container for controlling the inlet and outlet velocity of air and water vapor to a metal high-current air cell supplying power to an electrical device having average low current requirements and requirements. High-current intermittent, metal air cell and electrical device being placed in the container with the metal air cell having air inlet ports adjusted to admit an oxygen flow substantially above that necessary for the cell to meet the requirements of average low current of the electrical device. The container comprises a sealed housing defining an air reservoir containing the metal air cell, the sealed housing having a wall defining a restricted flow passage communicating between the air reservoir and the atmosphere outside the housing and adjusted to admit the oxygen flow rate only sufficient to satisfy the average low current requirements of the electrical device. In its preferred form, the housing further includes a hydrophobic, gas permeable membrane positioned between the restricted flow passage and the atmosphere outside the housing and adapted to block the liquid from entering the housing while admitting the flow of oxygen to the passage of restricted flow. In the preferred embodiment, the restricted flow passage is a thin hole in the wall of the container having a diameter of about .08 mm (.0032 inches) which is supplied with an opening covered with a GORE-TEX® membrane. any other material having suitable hydrophobic bonds.
gas transmitters or gas permeable. DRAWINGS Other objects and advantages will be better understood by reference to the following specification, together with the accompanying drawings, in which Fig. 1 is a simplified cross-sectional simplified elevation view of a prior art container for an electrical device. , Fig. 2 is a simplified cross-sectional simplified elevation view of a housing for an electrical device and energy cell in accordance with the present invention, - Fig. 3 is a similar view illustrating a modified form of the invention, Fig. 4 is a similar view illustrating another modified form of the invention, Fig. 5 is a similar view illustrating another modified form of the invention, Fig. 6 is a similar view illustrating another modified form of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT The container according to the present invention, in its simplest form, is illustrated schematically in Fig. 2. A sealed housing is provided by portions 5 and 6 connected in an impermeable manner to each other by means of a sealing ring not "gas transmitter" 7. Located inside the housing is an electrical device 8, which requires the supply of electrical energy from an energy cell 9 electrically connected to it by conductors 10. Since the figures of the drawing they are shown in simplified schematic form, no mechanical structure or supports for electrical device 8 or 9 are shown, it being understood that these are required The electrical device 8 represents a device such as an electric clock movement or electrical instrument which requires a flow continuous low current to time in the range of microamps (2 to 250 microamps) and also require periodic or intermittent high current flow in the milliamp range (2 to 12 milliamps). An example is a wristwatch with an electric locator which consumes a permanent current of about five microamps to operate the timing functions, but which intermittently requires a relatively high current in the order of 10 milliamps to operate the locator. Since the locator is used only occasionally, the average current discharge is low. The energy cell 9 is a standard high capacity zinc / air cell or high current flow cell as used in hearing aids, for example cell number 13 or number 675 which is commercially available but has not been modified to restrict the air supply to the cathodic structure by one of the previously discussed schemes. As such, the high current zinc / air cell 9 is designed to have a useful life only in the order of three to six weeks after being activated by removing the covers of its air inlet ports shown as 9a. All cells of this type are sensitive to changes in relative humidity and other atmospheric conditions which can alter the chemicals in the cells causing degradation of the accumulator and premature energy consumption. In an environment of low humidity, moisture evaporates from the electrolyte and will escape from the cell, decreasing the volume of the electrolyte and finally causing drying. With high humidity, the cell will collect water which has the effect of diluting the electrolyte and finally flooding the cell. In this case, the dividing line between "low" humidity and "high" humidity is a relative humidity equilibrium value which the cell tries to "maintain by its internal chemistry, of around 58% relative humidity. % relative humidity, the cell absorbs water and below 58% relative humidity, the cell loses water.Water increases and losses are facilitated by the diffusion of water vapor inside and outside the ports of air inlet 9a in the wall of the cell. Air also flows to cell 9 through air inlet ports 9a and oxygen is consumed by reaction with water to produce hydroxide ions. Examples of the number and size of normal air inlet ports in typical zinc / high current air cells commercially available for hearing aids are given in the following table: - --- ----- ---- - Size Diameter Total Hole Flow Area Cell Number of Holes Mm (Inches) mm2 (inches2)
A 4 .51 (.020) .82 (.0013)
B 2 .46 (.018) .33 (.0005)
C 6 .28 (.011) .37 (.0006) The oxygen flow which would be admitted through the above air inlet ports is substantially higher than necessary for the cell to meet the average low current requirements of the device electrical in the microampere region, but it is sufficient to supply instantaneous high current requirements of the electrical device of the class of a few milliamperes.
In accordance with the present invention, the entrance and exit of water vapor and the air inlet (oxygen) for the sustained average low current requirements of the electrical device are controlled by means of a restricted flow passage 11. Step 11 communicates between an air reservoir 12 inside the housing and the ambient atmosphere outside the housing. In the embodiment described in Fig. 2, the restricted flow passage comprises a thin hole perforated or formed by laser in a metal plate 13. The plate 13 is sealed or otherwise supported within an opening 14 in the wall of the housing portion 6. A suitable size of restricted flow passage 11 to support an average low current discharge of 2 milliamps is a single small hole with a diameter of .08 mm (.0032 inches), or a flow area of. 005 mm2 (.000008 inches2). A useful range of hole diameters for a restricted flow passage 11 is between 0.05 mm and 0.1 mm, depending on the expected average low current discharge. This diameter can be calculated or determined empirically. The flow of air through a hole of this size to the air reservoir 12 is sufficient to satisfy the average low current requirements of the electrical device 8 on a sustained basis. However, we have discovered that the hole substantially also obstructs and decreases the rate of diffusion of water vapor in and out of the air reservoir 12 and substantially lengthens the life of the metal air cell. In the case of blocking the hole or in the case of high current discharge requirements by the electrical device 8, the tank 12 supplies the needs of the cell 9 for a short time. Referring to Fig. 3 of the drawing, another embodiment is shown, in which the same elements are indicated by the same reference numbers as in Fig. 2. However, in this case, the plate 13 with its pitch of Restricted flow 11 is towards the inside of the opening 14 and the outside of the opening 14 is closed with a hydrophobic gas-transmitting element comprising a membrane 15. The membrane 15 is preferably a poly-tet-rafluoroethylene sheet not Sintered A suitable membrane 15 commercially available under the brand name GORE-TEX®, which allows air and water vapor to penetrate but inhibit the passage of water in a liquid state. The membrane 15 covers the opening 14 and is supported and sealed around its edges in the wall of the container. A chamber 6a in the wall of the housing 6 between the needle 11 and the membrane 15 collects air and water vapor which passes through the pores of the membrane. The membrane 15 is not designed to appreciably restrict the flow of air to the air reservoir 12, this function being performed by the restricted flow passage 11. The size of the opening is selected such that the air flow through the membrane 15 is sufficient to satisfy the average low current requirements of the electrical device. However, the membrane 15 ensures sufficient air flow to the chamber 6a without allowing the entry of water in liquid form so that the uninterrupted operation of the electrical device 8 can continue in inclement weather. In the case of complete immersion of the housing in water, the cell is supplied with air from the reservoir 12 for a substantial period of time under the requirements of low current discharge. In the case of instantaneous high current requirements, cell 9 is also supplied for short periods of time by the air reservoir 12 surrounding the cell. Since the water vapor is a gas, it will also pass through the membrane 16. Its inlet or outlet velocity by diffusion is shown to a large extent by the combined action of the membrane and the restrictive flow passage 11-.
Referring to Fig. 4 of the drawing, a modified housing portion 16 having a lid 5 and a sealing ring 7 is shown as before. Inside the housing is an accumulator compartment wall 17 which defines an accumulator compartment 18, serving as an air reservoir surrounding the cell 9. A removable accumulator plug 9 gives access to the accumulator compartment 18. The plug 19 is provided with a sealing gasket or O-ring 20 and may be joined to the housing 16 by a bayonet lock or thread or some other suitable method. The cap 19 defines an opening 21. Sealed within the opening 21 on the inner side facing the accumulator compartment is a plate or washer 22 with a restricted flow passage 23 similar to that previously described for the restricted flow passage 1. Covering the opening 21 that gives into the atmosphere is a membrane-shaped gas-transmitting hydrophobic material 24, which may be identical to the one described above in Fig. 3 by the reference numeral 15. A chamber 19a collects air and steam from water which passes through the membrane 24. Fig. 4 is representative of constructions often found in an electric clock, where the electrical device is in a separate compartment of the energy cell, the latter being removable through a opening separated by means of a removable plug such as 19. Electrical conductors 25 connect cell 9 to device 8 through seals 26 in wall 17. The arrangement of Fig. 4 can be more practical in actual use, since the plug 19 can be removed and the flow passage 23 and the membrane 24 can be easily inspected or refined, in addition to providing the normal replacement of the power cell 9. Referring to Fig. 5 of the drawing, a modification is shown which is similar in each aspect to Fig. 3, except that the lower portion of the housing identified by the reference numeral 27 is constructed of plastic material, such as polycarbonate. An opening 28 in the outer surface of the housing portion 27 is connected to a restricted flow passage 29 in the interior surface of the housing 27. A suitable diameter of the opening 28 is 1075 mm (.069 inches). As before, a satisfactory diameter for the restricted flow passage 29 which is molded into the wall at the time of manufacture, is .08 mm (.0032 inches). The drawing is not to scale, but it is exaggerated for clarity of the presentation. A membrane 15 of hydrophobic gas-transmitting material covers the opening 28 and is supported by and sealed to the outer wall of the housing-27. An intermediate chamber 30 collects gas passing through the pores of the membrane 15 as before. In Fig. 6 of the drawing another modification is illustrated, which specifically describes an electric wristwatch with a plastic case or housing 31. While this embodiment is described to show the invention as applied to a watch, it will be appreciated that this can be applied to any electrical device driven by a metal air cell as more generally shown in Figs. 2-5. The housing 31 incorporates an interior wall 32 of the storage compartment defining an accumulator compartment 33. The compartment 33 contains a pair of metal air cells 34b connected in series. An accumulator access plug 36 is provided with a sealing gasket or O-ring 20 and connected to the housing 31 by means of a bayonet lock or threads. An opening 37 in the outer surface of the wall of the housing 31 is narrowed to a restricted flow passage 38 in the inside wall of the accumulator compartment 33. The dimensions of the opening 37 and the restricted flow passage 38 may be as previously described in connection with Fig. 5. Closing the opening 37 is a membrane 15, constructed and joined as previously described in relation to Fig. 5. The membrane b admits gas into a chamber 39, but excludes the liquid thereof which, in turn, supplies the accumulator compartment 33. The zinc / air cells 34, 35 connected in series provide a clock movement 40 by means of conductors 41 passing through the wall 32 of the accumulator compartment. The clock movement b is of conventional construction and includes operating buttons and mechanisms for illuminating the watch face when "buttoned (not shown)." An appropriate movement is shown in U.S. Patent 5,265,071 published on 23 November 1993 by Thorgersen et al. and assigned to the current assignee, which is hereby incorporated by reference.The operation of the button requires high current for a short period of time of approximately 6 milliamps.The accumulator compartment 33 provides a deposit of air which can be preselected in volume to supply the intermittently required high current of the lighting device in movement 40 for a specified time.The restricted flow passage 38 is of sufficient size to supply the average low current requirements of the movement of 8. These calculations are within the reach of a person skilled in the art. transparent body 42 is sealed to housing 31 in order to see the time indicated in the movement of the watch. The air reservoir 33 shown in Fig. 6 is designed to be of sufficient size in order to operate the movement for a selected time in a selected current discharge if the air path is blocked. For example, if there are two cells connected in series and if the air in the tank is composed of the normal proportion of 21% oxygen, 1 cubic centimeter of volume in the tank (above that occupied by the cells themselves) will provide approximately% milliampere hour. Therefore, if the container is submerged in water and the movement requires a continuous current supply of 2 ma, the two cells will operate the movement for approximately 15 minutes. EXAMPLE A test was conducted under controlled conditions using a 675 hearing aid apparatus cell placed in a sealed container with an electrical device arranged to extract 500 milliamperes for a period of four months. The container was provided with a single opening of .08 mm in diameter (.0032 inches). The relative humidity outside the container remained constant for three tests over a period of four months, one with a relative humidity of 10%, one with a relative humidity of 90% and the third with a relative humidity of 58% which is maintained by the cell electrolyte. In each case, the cell performed correctly during the four-month period. In a control test without the container and cell exposed, the same conditions of relative humidity were maintained. With relative humidity of 10% and relative humidity of 90%, the cell stopped working after a week in each case, considering that with relative humidity of 58%, the cell continued to function properly throughout the test. In this way an improved housing for an electrical device has been described which can utilize and extend the useful life of a standard zinc / air high current cell. The housing itself controls the speed of entry and exit of water vapor, decreasing the speed of changes in the conditions of relative humidity which shorten the life of the cell. The housing also controls the rate of oxygen supply to an air reservoir containing the zinc / air cell to make it more closely match the requirements of the electrical device. In modified form, the housing also provides the aforementioned advantages but becomes resistant to liquids with a membrane arranged to prevent the ingress of water. The membrane ensures an air flow through the restricted flow passage controlling the use of the cell inside the housing, acting at the same time together with the restricted flow passage to reduce the entry and exit of water vapor. By delaying the diffusion of water vapor in and out of the air reservoir in which the cell is located, the life of the cell is substantially increased. While what has been described as the preferred embodiment of the invention and various modifications thereof has been described, it is desired to ensure in the appended claims all these modifications included in the true spirit and scope of the invention.