Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
2002-06-24
2004-06-01
Martin, David (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
C368S203000, C368S206000
Reexamination Certificate
active
06744699
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronic regulation module for the movement of a mechanically wound watch, and a process for regulating the speed of a mechanically wound watch movement by means of an electronic module.
DESCRIPTION OF THE RELATED ART
All watches need a source of energy to drive the movement and move the hands.
In the case of mechanical watches, this energy is supplied by the user by winding the stem or, in the case of automatic watches, by movements of an oscillating mass arising from movement of the wrist and permitting loading a spring.
Mechanical watch movements most often use an anchor escapement as a regulation member to guarantee precise operation of the watch. This purely mechanical element however does not permit ensuring satisfactory precision of operation.
Electronic watches, particularly quartz watches, have greater precision. The energy is most often supplied by a battery. These batteries have particularly the following drawbacks:
Requiring returning periodically to a watchmaker to replace the battery.
The risk of losing watertightness of the watch during that replacement.
Requiring distributing to a network of dealers a very large assortment of different batteries for as long a period as possible.
Ecological problems associated with disposal of the batteries.
Substantial cost of replacement and changing.
Different attempts have thus been carried out to omit batteries from quartz watches. The use of photovoltaic cells is attractive, but imposes substantial aesthetic drawbacks. Sources of energy based on temperature gradient or on the acidity of the skin of the wearer are also in an experimental stage. Other sources of energy envisageable for other portable apparatus cannot be sufficiently miniaturized to be integrated into the reduced volume of a wristwatch.
To prolong the lifetime of batteries, quartz watches are known in which the battery is recharged by a mechanical energy source. In this case, the mechanical energy produced by movements of the user is accumulated in a spring, as in automatic watches, then transmitted through a gear train to a generator which converts it into electrical energy used to recharge the battery. This battery supplies a conventional quartz movement with a stepwise clock motor. This system thus permits prolonging the lifetime of the battery, but not completely eliminating it. It is nevertheless quite necessary to replace it periodically. Moreover, these watches require a generator in addition to the motor, which gives rise to increased cost and occupies a substantial volume in the watch. Finally, the movement of the hands is characteristically jerky, which is not attractive, in watches with a stepwise motor.
The patent CH597636 provides a construction permitting completely eliminating the battery from a quartz watch. In this movement, the energy produced by movements of the user is accumulated in a spring, then transmitted through a gear train to the hands of the watch as well as to a generator which converts it into electricity (source of AC voltage). This voltage source is rectified so as continuously to supply an electronic circuit including a quartz oscillator. The electronic circuit adjusts the operation of the watch by acting on the electrical torque applied to the generator. When the generator turns too rapidly, the electronic circuit brakes it by short-circuiting it (all-or-nothing braking). The ideal reference speed is supplied by the quartz oscillator.
The document EP0 239 820 discloses a process for adjusting the speed of a generator in which the speed of the generator is also adjusted all-or-nothing, with the help of a brake control signal. The brake control signal is synchronized with a reference signal obtained from a quartz oscillator. At each cycle of the reference signal, the brake control signal passes first of all from the zero logic condition to the logic condition one, and then returns from the logic condition one to the zero logic condition.
The brake control signal thus depends solely on the reference signal and is not synchronized with the measuring signal produced by the generator. When the phase or frequency of the reference signal and of the measuring signal from the generator are quite different, which can take place for example at the startup of the system or following a violent shock, the control impulses of the brake can arise at the most unfavorable time for the generator, for example when the voltage at the output terminals just passes through a maximum. As will be seen later, this situation can give rise to abrupt stopping of the watch.
EP0 679 968 discloses another control module permitting applying “all-or-nothing” braking to the generator. When the generator rotor advances, the control module sends very short control pulses which have the effect of short-circuiting the generator. Braking by short-circuiting being very abrupt, the duration of the braking pulses is necessarily very short.
The all-or-nothing braking process described in the above documents has the drawback of imposing very brief and very intense decelerations on the rotor of the generator. After each braking pulse, the rotor and the gear train need considerable energy to accelerate and then to return to a speed near the reference speed fixed by the quartz oscillator. This mode of operation by shock is thus less energetically efficient, such that sufficient autonomy of the watch can be obtained only by using energy storage means, in the mechanical form of a spring or in the electrical form of capacitors, which are very voluminous. The watch movements obtained with this technology thus cannot be miniaturized without decreasing the autonomy of the watch below an acceptable minimum.
The application EP0 816 955, to which the reader can profitably refer, as well as the patent EP0 848 842 disclose another control module permitting applying to the rotor of the generator a braking couple which depends on the advance of the rotor. The braking circuit comprises several impedances of different values, which can be independently selected to apply different separate braking couples that are not zero, to the generator. The resulting impedance of the braking circuit depends on the advance of said generator. This device thus permits applying a braking couple proportional to the advance of the generator. The generator is so dimensioned as to turn slightly more rapidly than the reference speed, so as to permit adjustment of the speed. In a stable state, the braking circuit thus brakes continuously with a braking couple much weaker than in the all-or-nothing braking systems. Braking is interrupted solely when the generator turns too slowly, for example at startup or following a shock. This module thus permits avoiding abrupt decelerations of the rotor and thus is more energy efficient.
The control module described in this document has however the drawback of braking even when the AC voltage at the terminals of the generator passes through a maximum. When the generator is advancing, which is to say in the most usual situation, the peak-to-peak voltage at the output terminals of the generator is thus reduced by this braking. The storage capacities hence can use only a decreased recharge voltage. So as to maintain sufficient supply voltage for the electronic circuit, it is thus necessary slightly to overdimension the generator or in any case to provide storage capacities of a sufficient value, for the energy.
This problem is even more crucial in the circuit disclosed by EP0 239 820 mentioned above, because in this case the braking pulses, which are synchronized with the quartz reference signal, can according to the relative dephasing of the measuring signal and of the reference signal sometimes be produced just at the time at which the voltage of the terminals of the generator is at a maximum. The short-circuiting of the generator produces an instantaneous abrupt voltage drop, such that the storage capacitances are not at all recharged. If the voltage in the storage capacitances falls below the minimum requir
Klein Eric
Schafroth Konrad
Lindinger Michael L.
Martin David
Richemont International SA
Young & Thompson
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