WO1991003921A1

WO1991003921A1 - Watchband battery powered system

Info

Publication number: WO1991003921A1
Application number: PCT/US1990/004263
Authority: WO
Inventors: Lawrence H. Ragan
Original assignee: At&E Corporation
Priority date: 1989-08-29
Filing date: 1990-07-30
Publication date: 1991-03-21
Also published as: AU6188690A

Abstract

Portable, electrically powered electronic devices (52) to be worn on a user's wrist, for example clocks, calculators, and paging receivers, are powered by a flat, solid-state polymer battery (32, 34) disposed within the watchband (22, 24) that secures the device to the user's wrist. A separate polymer battery may be provided in each of the two sections of such a watchband. The conductive current collector layer of the polymer battery may be used as a antenna for a wrist-borne receiver. Preferably, a loop antenna extending about the user's wrist is formed by interconnecting the conductive collector layers of polymer batteries in each of the two sections of the watchband through a conductive clasp or buckle assembly.

Description

WATCHBAND BATTERY POWERED SYSTEM

BACKGROUND OF THE INVENTION This invention relates to the field of portable electronic devices and, in particular, to powering such devices as are arranged to be worn on a user's wrist. Recent advances in microelectronics and related technologies have lead to the miniaturization of various electronic devices such as watches, calculators, radio receivers, and even television receivers. Portable electronic devices of the types mentioned are now available in packages small enough to be worn on a user's wrist in the same manner as a conventional wristwatch. An example of such a device is a watch-pager described in U.S. Patent 4,713,808. All such devices require a portable power source such as a battery. For powering miniature electronic circuits, known batteries include alkaline, lithium, nickel cadmium or silver oxide varieties. However, these types of batteries are fairly bulky relative to the overall size of a wrist-worn electronic device. For example, the battery in a typical electric wristwatch adds substantially to the overall thickness of the watch.

What is needed is a way to power portable miniature electronic devices, such as those worn on a user's wrist, without the bulkiness associated with conventional battery technologies. SUMMARY OP THE INVENTION Accordingly, it is an object of the present invention to provide electrical power to wrist-worn electronic devices while reducing or eliminating the volume occupied by a conventional battery power source.

The present invention is applicable to powering virtually any electronic device arranged to be worn on a user's wrist. An apparatus according to the invention includes an electrically powered device, a watchband connected to the device for removably mounting the device onto the user's wrist, and a solid-state polymer electrolyte battery, disposed within the watchband and electrically coupled to the device, for powering the device. The watchband includes first and second elongate sections each having a free end and a clasp assembly affixed to the free ends of the elongate sections for removably connecting the free ends together. The polymer battery may be disposed within either one of the two elongate sections. Optionally, a second battery may be disposed within the other one of the elongate sections. Additional polymer batteries may be disposed in parallel with one another within the watchband as they are quite thin. Another aspect of the invention pertains to portable receivers in particular. All receivers require, in addition to a suitable power source, an antenna for receiving electromagnetic signals. Wrist-worn or watch receivers, however, impose severe limitations on the size and nature of the antenna. One method of providing an antenna for such a receiver includes forming a loop antenna out of a strip conductor mounted within a watchband. Such an antenna is described in detail in U.S. 4,713,808. According to another aspect of the present invention, one in which the electrically powered device includes a receiver, the cdnductive current collector layer of the solid-state polymer battery is coupled to the receiver so as to form an antenna. To form a loop antenna, the watchband clasp assembly is arranged for electrically interconnecting the conductive current collector layers of polymer batteries in each of the two elongate sections of the watchband. The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment which proceeds with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a watch pager according to the present invention, in which the watchband is broken away to reveal a power source disposed within the watchband. FIG. 2 is an enlarged cross-sectional view taken through the watchband of FIG. 1. FIG. 3 is a fragmentary view of the watchband of FIG. 1 showing portions of polymer electrolyte batteries adjacent the clasp assembly and showing the outline of the watchband in phantom. FIG. 4 is a side view of the watch pager of FIG. 1 with the watchband covering removed to show a pair of batteries and their connections to the pager. FIG. 5 is a schematic diagram of a watch receiver according to the present invention showing alternative loop antenna and battery interconnections to polymer batteries disposed within the watchband.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates in perspective view an electrically powered watch pager in accordance with the present invention. The watch or other electronic device is housed within a casing (10) . A watchband (20) is connected to- the casing for removably mounting the device to a user's wrist. The watchband (20) includes two elongate sections (22) and (24) . The elongate watchband sections are formed of a nonconductive material such as leather or a plastic. A clasp assembly (42) is connected to the free end of section (24) for closing the watchband. To do so, the free end (40) of the other section (22) is threaded through the clasp (42) , and then the clasp assembly closed to hold section 22 in place. The watchband is broken away to expose a battery (32) . The battery (32) is a solid-state polymer electrolyte battery. Solid-state polymer batteries are described in M. Zafar, et al., "Flat Polymer Electrolytes Promise Thin-Film Power" IEEE Spectrum, August 1989, pages 32-35, incorporated herein by reference. M. Zafar, et al. describe batteries using modified polymer electrolytes that can operate throughout a temperature of -20 degrees C to +140 degrees C at voltages as high as 3.5 volts. This operating temperature range and voltage make solid-state polymer batteries practical for many applications such as those described herein. For example, experimental studies on small laboratories cells, from 1 to 6 square centimeters in area, show that such batteries now provide an energy capacity of up to 200 watt-hours per kilogram. Sustained power density has reached 1,000 watts per kilogram, with a peak power of 800 watts per kilogram at half-charge. Ultimately, researchers expect the energy capacity of a typical packaged battery, based on a lithium anode and a vanadium oxide (V6013) cathode, to rise as high as 150 Wh/kg. Typical designs for polymer-electrolyte batteries include the following components, formed in thin, parallel sheet-like layers, each abutting the next in the following sequence. First, a first current collector layer, formed, for example, of aluminum foil. Next is a cathode- layer made of a composite that includes an electroactive solid insertion compound like vanadium oxide or titanium disulfide (TiS2) , carbon and a small amount of electrolyte to enhance the insertion compound's ionic conductivity. The anode is generally lithium, and the electrolyte can be one of a number of polymers, among them polyethylene oxide, that have sufficient ionic conductivity and are flexible enough to be configured in thin, flat cells. Finally is a second current collector layer, also formed of aluminum foil. During discharge, lithium is oxidized at the interface between the lithium anode and the polymer electrolyte, and the positive lithium ion is transported across the electrolyte. Simultaneously, lithium ions from electrolyte pass into the positive electrode at the interface between it and the polymer. Such batteries are able to sustain several hundred charge-discharge cycles without a loss in energy capacity. A battery cell such as those described above have thicknesses on the order of 200 to 300 micrometers. While such cells are quite thin, it is desirable to provide for substantial surface area, as the energy capacity of the device is proportional to its area. A watchband of the kind illustrated in FIG. 1 provides sufficient area to encapsulate a battery of sufficient size to power a wristwatch, watch pager, or the like. FIG. 2 shows an enlarged cross-sectional view of one elongate section (22) of the watchband (20) . The watchband section includes a covering (30) , formed of a nonconductive material, and the solid-state polymer battery (32) disposed within the covering (30) to protect it. One of the current collector layers of the battery (32) is shown as layer (36) . The polymer battery may be of any convenient shape, formed to fit within the confines of the watchband. It is generally rectangular, sized to correspond and fit within either one of the sections 22 or 24 of the watchband (20) . One or more batteries may be disposed within either section of the watchband and, optionally, one or more additional batteries may be' disposed in the other section of the watchband. Multiple polymer batteries could be stacked in parallel to each other within either or both sections of the watchband to increase energy capacity. For example, four batteries of the type described would have a total thickness of only about 1 millimeter. The battery (or each battery) may be electrically connected to the pager or other electrically powered device in various ways. For example, electrical connection may be provided through metal pins (34) which also serve to mechanically connect the watchband to the watch pager. The electrical connection may be insulated. from the casing (10) . Details of providing for such electrical connections between a watchband and a watch pager in this manner are disclosed in U.S. Patent 4,713,808. Other methods may be used for connecting the batteries to the electrically powered device, such as one or more plugs or mating metal fingers or contacts. The watchband may be formed of a flexible material, as the polymer batteries are quite thin and flexible. The watchband may not be of the expanding type, however, because the polymer batteries cannot withstand stretching. In general, it is most convenient to interconnect the batteries to the electrically powered device adjacent the interconnection of the watchband and the device. Where one or more batteries are employed within only one section of the watchband, two electrical connections of that section to the electronic device are required, corresponding to the two terminals of the battery(ies) . Where one or more additional batteries are employed in the other section of the watchband, two additional connections may be provided for connecting the other section of the watchband to the device, as described below with regard to FIG. 4. In such an embodiment, there is no requirement for any electrical connection between the two sections of the watchband for powering the device. Alternatively, provision may be made in or about the clasp assembly for electrically interconnecting the two sections of the watchband. Referring now to FIG. 3, the free ends of the watchband elongate sections (22,24) are shown in phantom. Each of the two sections of the watchband has an internal battery (32, 34). A clasp assembly (44) is provided for mechanical and electrical interconnection of the two sections. The clasp assembly (44) may be conductive or, if not, it may include conductive contact points for electrical interconnection of the two sections. By using such a clasp assembly (44) , the batteries may be interconnected so that only two electrical connections to the electronic device, one from each section of the watchband, are required. FIG. 4 illustrates the preferred interconnection of a watch pager to a pair of flat batteries such as polymer electrolyte batteries. In the figure, a watch pager contained in a casing (10) is shown with the watchband covering removed to reveal' the batteries (32,34) . The first battery (34) has positive and negative electrodes (conductive current collector layers) connected to the watch pager by a pair of conductors (76) . Similarly, the second battery is connected to the pager by a pair of conductors (78) . Inside the casing, the batteries may be connected in series or parallel configurations, as required by the application. This arrangement is preferred because it is more economical to provide multiple connections at the casing than to provide them at the clasp assembly. A loop antenna is provided to the watch pager as follows. Either the positive or the negative electrodes of the two batteries (32,34) are interconnected by a conductive path (80) . Conductive path (80) extends through a clasp assembly (not shown) , such as clasp assembly (44) described above, such that the path is electrically complete when the clasp is engaged. Accordingly, when the watch pager is worn on a user's wrist, the corresponding current collector layers of the batteries in the two sections of the watchband are electrically coupled together along conductive path (80) to form a conductive loop. The conductive loop may be utilized by the watch pager as a loop antenna. Breaking the loop antenna at the clasp, i.e. intermediate the two batteries, has the advantage of providing a balanced antenna. Referring now to FIG. 5, an alternative arrangement is illustrated. The watch'pager or other portable electronic device includes a receiver (52) . The receiver has RF signal input terminals (54,56) for connecting a loop antenna to the receiver's RF input circuitry. The receiver also has positive (+) and negative (-) power input terminals. Solid-state polymer batteries (32,34) are disposed within a first section (22) and within a second section (24) of the watchband, respectively, as described above. The polymer batteries are connected to the battery input terminals via conductors (58,60). Polymer battery (32) is connected in parallel to polymer battery (34) via conductors (66,70). The two portions of conductors (66,70) are removably interconnected to each other through connections (68,72), respectively. These connections are provided within or adjacent a clasp assembly as described above. A loop antenna is provided to the receiver as follows. One of the conductive current collector layers of the polymer battery (32) is connected to a first antenna input terminal (54) via a conductor (62) . The corresponding current collector layer of the other battery (34) is connected to the other antenna input terminal (56) via a conductor (64) . The corresponding current collector layers of the batteries in the two sections of the watchband are electrically coupled together via conductor 70 to complete the antenna loop.

In another embodiment, in which a polymer battery is disposed only within one of the watchband sections, a strip conductor may be disposed within the other section and electrically coupled to the polymer battery and to the appropriate receiver antenna input terminal to complete the antenna loop. In that case, only a single conductor interconnecting the two sections of the watchband is required. Having illustrated and described the principles of my invention in a preferred embodiment thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. I claim all modifications coming within the spirit and scope of the accompanying claims.

Claims

I claim:

1. An apparatus comprising: an electrically powered device sized to be worn on a user's wrist; a watchband connected to the device for removably mounting the device onto the user's wrist; and a battery, disposed within the watchband and electrically coupled to the device, for powering the device.

2. An apparatus according to claim 1 in which: the watchband includes: first and second elongate sections each having a free end; and a clasp assembly fixed to the free ends of the elongate sections for removably connecting the free ends together; and the battery is disposed within a selected one of the first and second elongate sections.

3. An apparatus according to claim 2 in which the battery includes a solid-state polymer electrolyte.

4. An apparatus according to claim 3 including a second polymer electrolyte battery disposed within the other one of the elongate sections and electrically coupled to the device.

5. An apparatus according to claim 2 including: a second battery disposed within the other one of the elongate sections; and means in the clasp assembly for electrically interconnecting the first battery and the second battery so that the first battery is electrically connected to the second battery when the clasp assembly is engaged.

6. An apparatus according to claim 5 in which the first and second batteries are connected in series.

7. An apparatus according to claim 1 in which: the electrically powered device includes a receiver having a power input terminal and an RF signal input terminal; and the battery includes an elongated, flat conductive current collector layer disposed lengthwise within the watchband; further including means for coupling the current collector layer to the receiver RF signal input terminal so as to form an antenna; and means for coupling the conductive current collector layer to the receiver power input terminal to power the device.

8. An apparatus comprising: an electronic device, sized to be worn on a user's wrist; a watchband connected to the device for removably mounting the device onto the user's wrist; and a solid-state polymer electrolyte battery disposed within the watchband and electrically connected to the device for powering the device.

9. An apparatus according to claim 8 in which: the electronic device includes a receiver; the receiver includes an antenna input terminal; the battery includes a conductive current collector layer; and the conductive current collector layer is coupled to the antenna input terminal whereby the said layer forms an antenna.

10. An apparatus according to claim 9 in which: the watchband includes a pair of elongate sections and a clasp assembly for removably connecting the elongate sections; a first polymer battery is disposed within a first one of the elongate sections and electrically coupled to the receiver; a second polymer battery is disposed within the other one of the elongate sections and electrically coupled to the receiver. the first and second batteries include corresponding conductive current collector layers; the receiver has first and second loop antenna input terminals; the corresponding current collector layers of the first and second batteries are coupled to the clasp assembly for electrically interconnecting said collector layers by engaging the clasp assembly; the current collector layer of the first battery is coupled to the first loop antenna input terminal; and the current collector layer of the second battery is coupled to the second loop antenna input terminal so as to form a loop antenna that includes the said collector layers.

11. A method of providing electrical power to an electronic device contained in a casing sized to be worn on a user's wrist, the method comprising the steps of: providing a watchband for mounting the casing onto the user's wrist; forming a flat, solid-state polymer electrolyte battery to fit within the watchband; encapsulating the battery within the watchband; connecting the watchband to opposite sides of the casing; and electrically coupling the battery to the device.

12. A method according to claim 11 in which: the electronic device includes a receiver having an RF signal input terminal; and the step of forming the battery includes providing a flat, elongated conductive layer; further including the step of electrically coupling the conductive layer to the RF signal input terminal whereby the conductive layer forms an antenna.