Electric watch having an electromechanical movement including a correction mechanism for small errors
CROSS-RELATED APPLICATION 
     This application is a continuation of copending application Ser. No. 438,455 filed Jan. 31, 1974 now abandoned. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The invention relates to electric watches having an electromechanical movement and particularly to such watches including means for correcting relatively small errors of the order of magnitude of 30 seconds or less. 
     2. Prior Art 
     There are presently known electronic watches with quartz oscillators in which electromechanical means are employed to drive the watch movement, i.e. a step motor driving a wheel, or a rotating motor with a synchronized hairspring balance. It has also been proposed to utilize a generator driven by a spring and synchronized by an electronic circuit containing the quartz oscillation. See, for example, my earlier application Ser. No. 417,588 filed Nov. 20, 1973. In all of these types of watches, the resetting of the time is difficult and the user can not easily avoid committing errors. Accordingly, the user often ignores resetting the time when the error is less than thirty seconds. However, the quartz oscillator gives to the watch a precision of this order of magnitude. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an electronic watch with means capable of easily correcting errors of less than thirty seconds with elimination of the need to reset the time, except at the time when the watch is started. 
     The watch according to the invention is of the type comprising a precision resonator, an oscillator, a frequency divider, an electromechanical watch movement, control means for controlling or synchronizing the watch movement. 
     The watch of the invention is characterized in that it includes a counter A synchronized with the electromechanical watch movement, a reference counter B fed by a divider, comparator means connected to counters A and B and acting, on the basis of the states of the counters, on the control means to keep and maintain the counters A and B in phase while varying the speed of the watch movement, and means for putting counter B in a predetermined state independent of counter A, this latter means being acted on from the exterior of the watch and optionally being combined with the means for resetting the time or for correction of the date. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a diagrammatic illustration, partly in section, of an electronic watch with means for resetting counter B; 
     FIG. 2 is a diagrammatic illustration of an electronic circuit for a watch including a step motor driving the gear mechanism of a watch movement; and 
     FIG. 3 is a diagrammaic illustration of an electronic circuit including a motor associated with a watch movement and whose speed of rotation is dependent on the energy it receives. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, therein is diagrammatically shown a watch casing have a push button 1 which when depressed closes the contacts 2&#39;,2&#34; of a switch 2. The contacts 2&#39;,2&#34; are electrically connected to the terminals 4,5 of an electronic circuit 6 whose construction will be described later with reference to FIGS. 2 and 3. A return spring 3 acts on push button 1 to urge it to its initial position to open switch 2 when the push button is released. The watch includes a stem 7 by which the hands can be reset to any desired time. It is possible to construct stem 7 in such a way that it will behave in the manner of pushbutton 1 so as to control switch 2. 
     Referring to the embodiment of FIG. 2 of the electronic circuit, therein is seen a quartz resonator or other precise resonator connected to an oscillator 11 which is in turn connected to a frequency divider 12 which delivers impulses at a frequency of 2Hz. These impulses are fed to a counter by two&#39;s i.e. a binary counter 13 and then to a reference counter B constituted by a counter by thirty 14 or referred hereafter simply as a &#34;thirty&#34; counter which produces a signal when thirty impulses have been fed thereto, and a binary counter 15 connected to counter 14. The period of the output of the latter counter is 60 seconds. 
     The impulses at the output of divider 12 are also fed to a gate 19 which when open passes the impulses to a shaper 22 of the impulses for a step motor 23 and to a counter A. Each time that the motor 23 receives an impulse from shaper 22 and advances one step, the counter A counts one impulse. The counter A is therefore synchronized with the motor 23 and thereby with the watch movement which is driven by motor 23. Therefore, the state of counter A can be made to coincide with the 00 position of the second hand of the watch movement by means of the reset switch 25 for counter A. 
     The counter A is constituted, similarly to counter B, by a thirty counter 26 and a binary counter 27. The state between counters A and B is determined by a comparator 28, of any suitable well known type (e.g. National Semiconductor Form&#39;s DM8200), which detects the states, A&lt;B or A≧B, and two OR gates 29, 30. This arrangement acts on gate 19 such that it is blocked when A≧B i.e. when counter A is ahead of counter B. The 2Hz impulses are no longer fed to shaper 22 or counter A which are thus stopped. The counter B, in contrast, receives impulses of 1Hz from counter 13. Its state increases until A=B. In the other case when A&lt;B the impulses of 2Hz are fed to shaper 22 and to counter A. As the frequency is twice that applied to counter B, the counter A advances with respect to counter B up to the time when A=B. Then, there is synchronization between the counters A and B. Since the counter A is already synchronized with motor 23 and the watch movement, it can be said therefore, at equilibrium, that the counters A and B and the watch movement are synchronized, i.e. when the second hand passes position 00, the counters A and B are at 0. 
     Assuming the watch to be 15 seconds slow, when, the counters A and B are at 45, the second hand is at the 45 second position and if the reset switch 24 of counter B is closed this will shift counter B to 00 and the phase comparator 28 will react and open gate 19 to introduce the double frequency 2Hz to motor 23 and counter A. The motor 23 and counter A progress at a double speed up to the time when counter A catches up to counter B. This will occur 15 seconds after the reset switch 24 of counter B has been depressed and during such time the motor 23 will have driven the watch movement through the equivalent of 30 seconds of time to compensate for the initial 15 seconds which the watch was slow. 
     If the watch is fast by 15 seconds, when counters A and B are at 15 and the second hand is at the 15 second position, the reset switch 24 of counter B will be closed, this will shift counter B to 00. The comparator 28 reacts to stop motor 23 and counter A until counter B has caught up to counter A. 
     It is seen therefore that the time in the two cases can be reset by acting on the reset switch 24 of counter B (corresponding to switch 2 in FIG. 1), for example, at the instant when a time signal is given and the second hand is to be reset. This setting of the time is registered in counter B, then transmitted via the operation of comparator 28 and the logic elements to motor 23 and to counter A. 
     Therefore, by the simple action on a push button, it becomes possible to eliminate small errors of less than 30 seconds and therefore maintain the time of the watch without need for, resetting the watch mechanism which would involve relatively difficult manipulations. 
     Referring to FIG. 3, therein is seen a circuit which can act on a rotating motor or a motor having a synchronized hairspring lever or a generator driven by a spring. Such drive arrangements can be found in my earlier application, Ser. No. 417,588 filed Nov. 20, 1973. In this embodiment the induced voltage in coil 23&#39; of the motor acts on counter A. 
     In FIG. 3 similar elements to those in FIG. 2 will be given the same numerals but with primes. In this embodiment, the divider 12&#39; produces an output signal of a frequency of 8Hz. The states of the counters A and B are compared in comparator 28&#39; and exclusive OR gates 29&#39; and 30&#39;. The counters A and B include counters by two-hundred and forty 44 and 54, respectively, and respective binary counters 45,55. The period of the output is 60 seconds. The phase comparator 28&#39; acts on gate 19&#39; such that when A≧B i.e. when A is ahead of B, the gate is opened and the energy transmitted to the coils of motor 23&#39; is reduced and thereby its speed whereby the energy subtracted at the terminals of the drive of the watch movement is increased (see my aforesaid applicaton for a detailed explanation). Hence, the watch movement will be slowed until A=B at which time gate 19&#39; is closed. Conversely, when A&lt;B i.e. when A is behind B, the energy transmitted to the coils of motor 23&#39;  is increased and thereby its speed whereby the energy subtracted at the terminals of the drive of the watch movement is reduced. Hence, the watch movement will be speeded up until A=B at which time gate 19&#39; is closed. In this manner, the counter A and thereby the watch movement, are maintained in phase with counter B. 
     When one resets counter B to the actual time, this acts on the motor and on the counter A up to the time when these elements are resynchronized with counter B. They therefore set themselves to the time.