BACKGROUND OF INVENTION

The invention described herein relates to improvements made to a quartz analog time measuring device like a wristwatch that works on the principle of photovoltaic technology. A device like the wristwatch described in this invention has a dial that is semi transparent and allows a portion of the light incident on it to pass through to the photovoltaic layer placed beneath it. Light incident on the face of the watch is collected at this layer and converted into electrical energy that is stored in a rechargeable lithium ion battery. The energy thus stored is used for working of the device.

Such a device as explained above also consists of an integrated circuit with automatic detection of pulse width. The Application Specific Integrated Circuit (ASIC) also includes 3 other features - sleep mode, quick start and end of battery life indicator.

FULL PRIOR ART DETAILS

A light powered quartz analog time measuring device consists of a photovoltaic cell capable of converting light energy into electrical energy. This energy is then stored in a rechargeable battery. The entire process of converting light energy into electrical energy, the charging of rechargeable battery and the management of power consumed from the battery is controlled by the ASIC.

This IC, using solar cell as its power supply, has extremely low power consumption. A 32,768Hz quartz crystal oscillator provides a precise time base for the IC in application. The device also employs a rechargeable titanium lithium ion battery as the backup power; the rechargeable battery will be charged when surrounding light is sufficient and will provide power to maintain the working of the device in darkness.

Most of the earlier patents identified in the search has been centered on designing a watch wherein the purple color of the solar cell is reduced or eliminated. The patents ref US5761158 and EP0890887 describe the invention of a solar battery powered watch consisting of a ceramic dial with a possibility of designing dials with any color and at the same time transmitting light to generate power. Similarly, JP 62-237385 describes the invention of a solar battery type wrist watch with a glass dial fitted with a solar cell using double side adhesive tape. A rubber packing absorbs the impact force and prevents the glass dial from cracking. In both of the above cases, since ceramic & glass is brittle in nature and the cross section being thin, chances of dial cracking / breaking is high when the watch is subjected to shock.

The patent ref JP 2001-272477 & JP 2001-264460 describe the construction of a solar cell/battery type watch with a translucent display panel or a flat ring type solar cell. These methods are specifically invented to eliminate the dark purple color of the solar cell and thus improve aesthetics. Similarly the invention described in patent ref JP 2001-264459 explains the construction of a display device structure for solar watch by matching the color of the solar display plate with the color of the solar cell thus obscuring the dark purple color of the solar cell.

The patent JP10-039055 describes the invention of a clock with a solar cell and a translucent film that is sandwiched between the dial and the solar panel. This translucent film also could be provided in the clock through a process of screen printing or pad printing on the rear surface of the dial. In the above invention, efficiency of the solar panel largely depends on the amount of light passing through the transparent / translucent film placed above the panel.

The patent ref JP 10 002971 describes the invention of a watch provided with solar cell where a ceramic dial with a coating film is used to cover the deep purple color of the solar cell without affecting transparency of dial.

The following inventions identified explain the use of capacitors that supply power for working of a watch with solar cell. The compact electric apparatus powered by solar cells in the patent ref US4714352 explains the use of a capacitive storage element along with a threshold value circuit to control power supply during start up. The structure of watch with solar cell described in the invention ref JP 08-201540 explains the use of contact springs instead of soldering lead wires and uses a double layer capacitor with 2 or more solar cells. It has been noticed that use of capacitive storage elements can supply required power for working of a device only for a limited period of time.

The watch with solar cell described in the invention ref JP 2002-022856 claims a low cost construction of a watch movement driven by energy from the solar cell. The construction involves a transparent solar cell support frame to which is fixed the solar cell which makes the process of molding the component more complex.

OBJECTIVES OF INVENTION
The main objective of the invention is to provide a time measuring device like a wristwatch which has an integrated circuit working on photo voltaic principle and automatically synchronizes the pulse width with the working of the stepper motor. This provision makes it compatible for the integrated circuit to work with an existing stepper motor of any pulse width less than 5.8 milli seconds and with a coil resistance of more than 2.7 KΩ.

Another objective of the invention is to provide a time measuring device like a wristwatch which has an integrated circuit working on photo voltaic principle with a sleep mode function that cuts off power to other systems when voltage supplied from the battery is < 0.7V, a quick start function that makes the device start working the moment it is exposed to light and an end of battery life indicator that indicates through some means that the battery is nearing a predetermined low voltage level, in this case 1.3 V.

STATEMENT OF THE INVENTION
In this invention, a timekeeping device like the wristwatch that works on the principle of photo voltaic technology which has an integrated circuit working on photo voltaic principle capable of automatically adjusting its pulse width according to the functioning of stepper motor. This device also includes a sleep mode function, a quick start function and end of life indicator for indicting the level of charge in the rechargeable battery incorporated into the Application Specific Integrated Circuit.

BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows an exploded view of the mechanism used in the device, in
this case a wrist watch.
FIG. 2 illustrates the working of the device in terms of conversion of light
energy incident on the face of the device, its conversion and subsequent
usage of power from the battery for its intended purpose.
FIG. 3 shows the movement holder with dial held in place.

DESCRIPTION OF THE DRAWING

The photovoltaic device described herein works by converting light energy into electrical energy. A translucent dial (1) is placed above a photovoltaic layer (2) that is fixed on the supporting plate (3). The supporting plate (3) is fitted on a plastic housing (4). The plastic housing (4) forms the chassis where the base movement (5), electronic circuit board (6), rechargeable battery (7) and metal mount (8) are assembled to form the complete movement. The movement holder (9) is fitted over the plastic housing (4) and holds the dial (1) in place (see FIG. 3).

Light energy incident on the translucent dial face (1) is absorbed by the photovoltaic layer (2) placed beneath the dial where it is converted to electrical energy. This energy is supplied to the battery through the IC placed on the electronic circuit board (6). The IC regulates output from the photovoltaic layer (2) and provides a constant current & constant voltage which is used for charging the rechargeable battery (7). The IC prevents overcharging of the rechargeable battery by controUing the amount of energy received from the photovoltaic layer.

Electrical energy from the rechargeable battery (7) is used for working of the step motor which is part of the base movement (5). In addition to managing the conversion of light energy into electrical energy, the IC also controls frequency of the quartz crystal that is placed on the electronic circuit board. The frequency of 32,768Hz generated by the quartz crystal is converted to an amplified 1Hz / second signal which is used to drive the step motor. The step motor in turn drives hands to indicate time to the wearer of the watch.
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The integrated circuit (IC) chip has been built around a mechanism called "battery voltage sensing" and the IC will continuously monitor battery voltage and automatically trigger a corresponding feature viz., sleep mode or quick start function or time setting warming. This flexibility can be used to effectively adapt the light powered technology on a wide range of step motors whose pulse width is less than 5.8 milli seconds.

In normal working viz., when the voltage from the rechargeable battery (7) is more than 1.30 volts, the integrated circuit pro vides a pulse every second to the step motor. When the device is not exposed to a light source for long periods of time, the voltage in the rechargeable battery (7) becomes low. If the voltage falls below a predetermined value, the integrated circuit (IC) makes the second hand jump twice in a second to indicate the wearer that the device needs charging. In case voltage in the battery falls further, the IC cuts flow of energy to step motor apart from reducing its own consumption to conserve energy in the rechargeable battery. This feature is termed as "sleep mode" when the device does not perform its intended function of time keeping.

At this point, if the device is exposed to a light source, the watch starts working within 10-15 seconds by using the energy stored in a capacitor. This feature is termed as "Quick start function".

When the watch starts working, the second hand makes 4 jumps / sec which is subsequently changed to either 2 jumps / sec or one jump / sec, based on the battery voltage. The 4 jumps / sec of second hand is to warm the wearer that there is a need for resetting time (see FIG. 2). This feature is called "time setting warning".

WE CLAIM

1) A quartz analog device like a wristwatch consists of a photovoltaic layer included in the movement for conversion of light energy into electrical energy. The light energy can be tapped and converted from a very low intensity of 200 lux to as high an intensity as 1,00,000 lux.

2) A quartz analog device like a wristwatch as claimed in claim 1 that consists of a movement with a photovoltaic layer which starts working under office lighting of 350 lux intensity and above.

3) A quartz analog device like a wristwatch as claimed in claim 1 to 2 consists of an electrical circuitry that helps in storing of the converted electrical energy from the photovoltaic layer in a rechargeable battery.

4) A quartz analog device like a wristwatch as claimed in claim 1 to 3 has an integrated circuit capable of preventing overcharging of battery and controlling normal function of the wristwatch.

5) A quartz analog device like a wristwatch as claimed in claim 1 to 4 of detecting the voltage level in the battery and charging the rechargeable battery at a constant current and constant voltage such that battery is not charged beyond a predetermined limit thus avoiding danger due to explosion.

6) A quartz analog device like a wristwatch as claimed in claim 1 to 5 has an integrated circuit capable of adapting to the pulse width of an existing design of stepper motor.

7) A quartz analog device like a wristwatch as claimed in claim 1 to 6 has an integrated circuit capable of showing "end of battery life" by a double jump of second hand which is an indication that the wristwatch needs to be exposed to a light source for charging of battery.

8) A quartz analog device like a wristwatch as claimed in claim 1 to 7 has an integrated circuit capable of indicating to the consumer through a four jump of second hand that the wristwatch needs resetting after it has stopped working due to the battery voltage falling below the predetermined voltage.

9) A quartz analog device like a wristwatch as claimed in claim 1 to 8 has an integrated circuit that enables "quick start" when a stopped wristwatch is exposed to a light source.

10) A quartz analog device like a wristwatch as claimed in claim 1 to 9 has an integrated circuit that enables ‘switching off’ power to the step motor apart from reducing its own consumption thus reducing consumption from the battery when the voltage falls below a predetermined value. Such a mechanism allows the battery shelf life to be enhanced when customers opt for keeping the watch unused for a long period of time.