US3500103A - Electric timepiece drive with cut-off - Google Patents

Description

United States Patent 3,500,103 ELECTRIC TlMEPlECE DRIVE WITH CUT-OFF Roger S. Swain, Wolcott, and Gerald R. Wootton,

Thomaston, Conn., assignors to Benrus Corporation, a corporation of Delaware Filed Dec. 7, 1966, Ser. No. 599,860 Int. Cl. H02p 7/00 US. Cl. 313-138 19 Claims ABSTRACT OF THE DISCLOSURE still present.

The present invention relates to an electric drive for a timepiece or the like in which the timepiece indication is advanced sequentially by a series of sequential signals and in which the powered energization of the drive is cut off when the desired indication advance has been made whether the initiating sequential signal is still in existence or not.

A major problem involved in battery-energized timepieces, and particularly watches, is the length of time that such timepieces will continue to operate satisfactorily before the battery has to be replaced or recharged. The smaller the timepiece, and hence the smaller the battery which can be used therewith, the more critical doe this problem become. It is therefore of vital importance to improve the efficiency of operation of the timepiece driving mechanism to as great a degree as possible, thereby to reduce the power consumption thereof and thus corr'espondingly increase the battery lifetime under operating conditions.

In the usual type of battery-powered timepiece the time indication means (conventionally a set of hands movable over a dial) is driven in step-by-step manner by a series of accurately timed sequentially recurrent signals, each signal being effective to advance the indicating mechanism by one step. The signals are effective to cause the energization of a driving means operatively connected to the hands or other indicating mechanism, and the movement of the hands by the driving means constitutes the major mechanical work performed by the timepiece. In order that this work should be performed it is necessary that the driving means be appropriately electrically powered, and the electric power thus provided to the driving means constitutes one of the major factors constituting the drain of electrical energy from the energizing battery. It therefore is desirable to limit the energization of the driving means only to that period of time which is required for it to perform its assigned task; any energization of the driving means after that assigned task has been performed represents a waste of energy.

Attempts to control the duration of energization of the driving means by controlling the duration of the recurrent control signals are not effective. With such an approach the control signals must, for safetys sake, have a duration somewhat longer than the maximum time required to move the indicating mechanism through a given step. If that were not done the indicating mechanism might under some operating circumstances fail to be moved properly, with consequent loss in accuracy. The safety factor which must be provided represents a con- 3,500,103 Patented Mar. 10, 1970 stant unnecessary drain on the battery. Moreover, the length of time required for the indicating mechanism to move through a given step may vary widely with different ambient conditionsthe indicated movement may be more rapid at higher temperatures than the lower temperatures, or with the Watch incertain orientations rather than in other orientations. When the signal duration is designed to take care of the slowest movement rate for the indication means, as it must if the timepiece accuracy is to be maintained, operation of the watch on those occasions when the indication means moves more freely and rapidly will result in unnecessary power consumption.

It is the prime object of the present invention to devise an electric drive for a timepiece or the like which avoids the above disadvantages, and which in particular achieves a very high degree of electrical efficiency by energizing the driving means for the indicator only for that period of time necessary at any given instant to cause the indicator to move in a predetermined fashion, the energization of the driving means thereafter being cut off whether or not the control signal is still in existence. Such a system not only ensures that driving power is applied only for those periods of time when it is really required, thereby reducing current drain and lengthening the effective life of the energizing batteries, but it also permits the use of control signals of simplified character, thereby minimizing the complexity of the circuitry required to produce such control signals and correspondingly reducing the size and cost, and increasing the reliability of the overall electronic circuitry involved.

These results are accomplished by causing the control signal to energize the driving means for the indicator, producing the desired movement of the indicator, and teranimating the energization of the driving means as soon as the desired step operation of the driving means has been sensed by appropriate sensing means. The cutting off of the energization of the driving means in that fashion is accomplished independently of the initial signal, whether it is still in existence or not. Once the energization of the driving means has been thus cut off, the circuitry is immediately readied to repeat the cycle of energization and cut-off as soon as the next control signal is received. The sensing means can sense any desired parameter of the action of the indicator or the moving means therefor.'For example, it can sense when the output member has moved a predetermined distance or when the output member has achieved a predetermined velocity of movement.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to an electric drive system for a time piece or the like, as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which:

FIG. 1 is a schematic block diagram representation of the system of the present invention;

FIG. 2 is a schematic representation of one type of mechanical drive and sensing means which can be employed;

FIG. 3 discloses another type of driving and sensing means which can be employed;

FIG. 4 is a circuit diagram of the control means, mechanical drive and cut-off means designed for terminating energization of the mechanical drive after the output member of the latter has achieved a predetermined velocity of movement;

FIG. 5 is a circuit diagram of a system similar to FIG. 4 but designed to terminate energization of the mechanical drive after the output member thereof has moved a predetermined distance; and

FIGS. 6A-E are graphical representations, on the same time scale, of different parameters of the system of FIG. 4, FIG. 6A representing input signals the time duration of which is in excess of that required to achieve the predetermined movement of the output member, FIG. 6B representing the input signal of FIG. 6A after having been differentiated, FIG. 6C representing the sensing signal output from the sensing coil, FIG. 6D representing the driving or power current, and FIG. 6E representing the movement of the indicator.

As is schematically disclosed in FIG. 1, the timepiece comprises an indicator means generally designated A which, conventionally, comprises a dial 2 over which minute and hour hands 4 and 6 move, the latter being driven in accurately timed fashion by a mechanical drive means generally designated B. The present invention relates to a mechanical drive means B which is electrically energized, but the precise nature of the mechanical drive means B, and the precise nature of the indicator means A, form no direct part of the present invention, and may be widely varied. A control means generally designated C is operatively connected to the mechanical drive means B so as to energize the latter and cause corresponding movement of the indicator means A each time that a signal is received from the timed signal source generally designated D. The precise nature of the time signal source D forms no part of the present invention, and it, too, may be widely varied, provided only that produces an output of timed signals each of which is designed to initiate or cause the initiation of a predetermined movement of the indicator means A. Operatively connected between the mechanical drive means B and the control means C is a cut-off means generally designated E. The cut-ofi" means senses the output of the mechanical drive means B, and when that output has achieved a predetermined status, such as a given amount of mechanical translation or a given speed of translation, it acts on the control means C so as to terminate the energization of the mechanical drive means B even though the signal from the source D may still be active. Indeed, in order to make the energization of the mechanical drive means B entirely independent of the time duration of each signal from the source D, so that the output of the mechanical drive means B will attain ints predetermined character whether the initiating signal has prematurely disappeared or remains in existence longer than desired, the control means C is designed to be affected by the signal from the source D only when that signal is first received, the control means C then causing energization of the mechanical drive means D continuously until the cut-off means E becomes operatively active thereupon.

FIGS. 2 and 3 illustrate, in semi-schematic form, two exemplary types of drives for the indicator A, and illustrate the manner in which the mechanical drive is actuated and the sensing for the cut-off means is accomplished.

In FIG. 2 the hour and minute hands 6 of the indicator A are designed to be driven by a rotor 8 having magnetizable teeth 10 formed on the periphery thereof. A magnetic pole piece 12 is fixedly mounted adjacent the periphery of the rotor 8 and is provided with a winding or coil 14. Each time that the coil 14 is energized a rotor tooth 10, then rotationally displaced therefrom by the angle x, is drawn into registration therewith. Subsequent de-energization of the coil 14 permits the rotor 8 to rotate further until the next suceeding rotor tooth 10 moves into position displaced from the pole piece 12 by the angle x (or else a pair of appropriately positioned and rotationally staggered pole pieces 12 and coils 14 are alternately energized). Upon the next energization of the coil 14 the said succeeding rotor tooth 10 is moved into registration with the pole piece 12, and so on, thus producing an essentially conventional step-by-step rotational movement of the rotor 8. A second pole piece 16 on which coil 18 is wound is also fixedly positioned in electromagnetic relationship with the rotor teeth 10, and when a given tooth 10 is moved into registration with the pole piece 12 another tooth 10, initially displaced from the pole piece 16 by an angle y, moves into registration with or past the pole piece 16, thereby electromagetically inducing a voltage in the winding 18, said voltage being representative of the position and velocity of the rotor 8.

In FIG. 3 a ratchet wheel 20 is rotated in step-by-step fashion by means of a pawl 22 mounted on arm 24, the latter being operatively connected to armature 26 of an electromagnet generally designated 28 and comprising a support 29.having central passage 31 through which the armature 26 is slidable. The support 29 carries on its exterior the windings or coils 14 and 18, arranged in axially spaced relationship. The armature 26 normally assumes a position to the left as shown in FIG. 3 (as through the action of a biasing spring, not shown, thereon), in which position its right hand end is outside the coil 18. When the coil 14 is energized the armature 26 is pulled to the right, thus advancing the ratchet wheel 20 one step. During this movement the right hand end of the armature 26 enters the coil 18, inducing a voltage therein which, similar to the embodiment of FIG. 2, is representative of the position and velocity of the pawl 22. When energization of the winding 14 is terminated any appropriate means, such as the biasing spring (not shown) previously mentioned, returns the armature 26, and with it the arm 24 and pawl 22, to original position as illustrated in FIG. 3. Thus here again an essentially conventional stepwise rotation of the ratchet wheel 20, and hence of the hour and minute hands 4 and 6, is achieved.

Referring now to FIGS. 4 and 6, the signals from the timed signal source D may, as illustrated in FIG. 6A, comprise voltage pulses 30 each commencing at a time t and terminating at a time with an appropriate interval between the ending of one pulse or signal 30 and the beginning of the next pulse or signal 30. As illustrated in FIG. 6A the time interval between t and t is considerably greater than that required to produce a step movement of the output member of the mechanical drive means B which is operatively connected to the indicator means A (the armature 8 of FIG. 2 or the pawl 22 of FIG. 3).

The input signal 30 is fed by lead 32 to the control means C, the lead 32 connecting with a series capacitor 34 and a shunt resistor 36 which define a ditferentiating network producing, as may be seen in FIG. 6B, a spike signal 38 in one sense at time t when the pulse 30 commences, and a spike signal 40 in the other sense at time t when the pulse 30 disappears. The output of the differentiating circuit 34, 36 is fed by lead 42 to rectifier 44, the latter being poled so as to pass spike signal 38 but block spike signal 40. The rectifier 44 is connected by lead 46 to the base of transistor 48. The emitter of transistor 48 is connected to ground via resistor 50. The collector of transistor 48 is connected to an energizing source or battery at terminal 52 via driving coil 14. The base of transistor 54 is connected by lead 56 to a point 58 between the coil 14 and the collector of transistor 48. The emitter of transistor 54 is connected by resistor 60 to the energizing source terminal 52. The collector of transistor 54 is connected by lead 62 to lead 46 and hence to the base of transistor 48.

The operation of the circuitry as thus far described is as follows: When an input pulse or signal 30 is first received, at time t the spike signal 38 is formed by the differentiating circuit 34, 36, and this spike signal passes through the rectifier 44 to the base of transistor 48, turning the latter on, that is to say, making its collector-emitter path conductive. As a result current flows through the driving coil 14 in the output circuit of the transistor 48, energizing that driving coil 14 and causing appropriate movement of the mechanical output member of the drive means B (here illustrated as the armature 8 in FIG. 2 or the pawl 22 in FIG. 3). As current flows through the driving coil 14 an appropriate bias is applied to the base of the transistor 54, causing that transistor to become conductive. The collector-emitter current passing through transistor 54 serves to provide base current for the transistor 48, keeping the latter in conductive condition. When the spike signal 38 disappears the transistor 48 thus is latched in conductive condition through the action of the transistor 54, and the driving coil 14 remains energized, thus continuing to operatively act upon the output member (8 or 22) of the drive means B.

The cut-off means E is designed to terminate the energization of the driving coil 14 as soon as the mechanical output member 8 or 22 has moved in a predetermined fashion. In the system shown in FIG. 4 that predetermined fashion constitutes movement until a predetermined velocity is attained. When the output member 8 or 22 moves in response to energization of the driving coil 14, a part operatively connected thereto moves with respect to the sensing coil 18, electromagnetically generating a signal therein, a typical such signal being shown in FIG. 6C and represented by the line 64. This signal 64. is fed by lead 66 to the base of transistor 68. The emitter of transistor 68 is connected to ground by lead 70, and its collector is connected to lead 46 by lead 72. When the signal 64 reaches a predetermined magnitude, the system of FIG. 4 being designed so that said predetermined magnitude is reached once the output member 8 or 22 has reached a predetermined velocity, the transistor 68 will be turned on. Its emitter-collector output circuit will then represent virtually a short circuit connection between lead 46 and ground, thus operatively removing base current from the transistor 48 and turning the latter olf, thereby de-energizing driving coil 14. With the de-energization of coil 14 transistor 54 is turned off and'hence transistor 48 is unlatched. When the signal 64 falls below the aforementioned predetermined value transistor 68 will turn off, but by this time transistor 48 will have been unlatched and therefore it will remain off. The circuit will therefore be in stand-by condition, awaiting the receipt of the next signal pulse 30.

As may be seen from FIGS. 6A-E, the signal 64 reaches operative cut-off value at a time t which is located between t and 1 The energizing current in coil 14, indicated at 74 in FIG. 6D, will therefore flow only from t to t and powered movement of the output member 8 or 22, and hence of the indicator means A, will likewise occur only between t and 1 as indicated at 76 in FIG. 6E.

The circuit of FIG. 5 is essentially the same as that of FIG. 4, but modified so as to produce'cut-off of the energization of the driving coil 14 when the movement of the output member 8 or 22 has attained a predetermined position corresponding to that where the flux density reaches a maximum value and reverses polarity i.e. the point of maximum coincidence of the rotor tooth and pole piece 16. Hence the sensing coil 18 in FIG. 5 is connected to the base of transistor 68 via a differentiating network comprising series capacitor 78 and shunt resistor 80. As a result the biasing of the base of transistor 68 will be determined by full coincidence between tooth 10 and pole piece 16, and hence by the position of the rotor 8. The circuit of FIG. 5 could also be used to control transistor 68 in accordance with acceleration of the rotor 8 if that should be appropriate.

From the above it will be seen that through the use of the present invention the driving coil 14 is powered only for so long as is required for it to perform its assigned task, and no longer, and that this result is achieved entirely independently of the duration of the initiating signal pulse 30. That pulse may, as specifically illustrated in FIG. 6, have a duration longer than that required to move the output member 8 or 22 in predetermined fashion. Alternatively, the timing signal 30 may have a time duration less than that required to achieve predetermined movement of the output member 8 or 22; indeed, only a momentary signal, such as the spike signal 38, is needed to initiate each step of output movement. Hence the power source 52 must provide power only when that power is required to perform useful work. The effect in radically increasing the effective life of the battery source for the power provided at terminal 52 will be obvious. In addition, the system will automatically compensate for the effects of different ambient conditions on the readiness with which the output members 8 or 22 move. Moreover, by making the operation of the driving means B entirely independent of the duration of the signal from the souce D, greater latitude is provide for design for the signal source D.

The system of the present invention is of relatively wide applicability, and the specific electrically powered timing systems here disclosed are but exemplary of many others in connection with which the system of the present invention has very advantageous results. Moreover, the specific means here disclosed to achieve the mechanical drive, the control and energization thereof, and the cutoff of that energization, may also be widely varied, the specific circuitry here disclosed being a simple and effective embodiment which is, however, capable of extensive modification. These and other variations may be made in the embodiments here specifically disclosed, all without departing from the spirit of the invention as defined in the following claims.

We claim:

1. In an electric drive for a timepiece or the like which comprises a source of signals, a movable output member, moving means for moving said output member in a predetermined fashion each time that a signal is received, and power means for energizing said moving means; the improvement which comprises control means operatively connected between said source and said power means and normally effective to cause said power means to energize said moving means upon the reception of a signal from said source and thereafter for a period of time in excess of that required to cause said output member to move in said predetermined fashion, sensing means operatively connected to said output member for sensing its motion and producing a cut-off signal when motion in said predetermined fashion has been achieved, and cut-off means operatively connected between said sensing means and said control means and effective in response to said cut-off signal to cut off said control means and terminate the energization of said moving means by said power means.

2. The electric drive of claim 1, in which said control means is effective to cause said power means to energize said moving means continuously once said signal from said source has been received until said control means is operatively acted upon by said cut-off means.

3. The electric drive of claim 2, in which said predetermined fashion of movement of said output member comprises movement for a predetermined distance.

4. The electric drive of claim 2, in which said predetermined fashion of movement of said output member comprises movement at a predetermined velocity.

5. The electric drive of claim 1, in which said signal source produces signals having a duration longer than that required to cause said output member to move in said predetermined fashion, said cut-off means being effective to override said signal and cut off said control means even in the presence of said signal.

6. The electric drive of claim 5, in which said predetermined fashion of movement of said output member comprises movement for a predetermined distance.

7. The electric drive of claim 5, in which said predetermined fashion of movement of said output member comprises movement at a predetermined velocity.

8. The electric drive of claim 1, in which said signal source produces signals having a duration longer than that required to cause said output member to move in said predetermined fashion, said cut-off means being effective to override said signal and cut off said control means even in the presence of said signal, and means for thereafter preventing re-actuation of said control means until a new signal is received from said source.

9. The electric drive of claim 8, in which said predetermined fashion of movement of said output member comprises movement for a predetermined distance.

10. The electric drive of claim 8, in which said predetermined fashion of movement of said output member comprises movement at a predetermined velocity.

11. The electric drive of claim 1, in which said control means is effective to cause said power means to energize said moving means continuously once said signal from said source has been received until said control means is operatively acted upon by said cut-off means, and in which said signal source produces signals having a duration longer than that required to cause said output member to move in said predetermined fashion, said cut-off means being effective to override said signal and cut off said control means even in the presence of said signal.

12. The electric drive of claim 11, in which said predetermined fashion of movement of said output member comprises movement for a predetermined distance.

13. The electric drive of claim 11, in which said predetermined fashion of movement of said output member comprises movement at a predetermined velocity.

14. The electric drive of claim 1, in which said control means is effective to cause said power means to energize said moving means continuously once said signal from said source has been received until said control means is operatively acted upon by said cut-off means, and in which said signal source produces signals having a duration longer than that required to cause said output member to move in said predetermined fashion, said cutoff means being effective to override said signal and cut off said control means even in the presence of said signal, and means for thereafter preventing re-actuation of said control means until a new signal is received from said source.

15. The electric drive of claim 14, in which said predetermined fashion of movement of said output member comprises movement for a predetermined distance.

16. The electric drive of claim 14, in which said predetermined fashion of movement of said output member comprises movement at a predetermined velocity.

17. The electric drive of claim 1, in which said control means comprises first means for producing a control pulse from said signal from said source, a first control transistor normally in an off-condition and operatively connected to said first means so as to be turned on by said control pulse, an output circuit for said first control transistor operatively connected to said moving means, and latching means operatively connected between said output circuit and said first control transistor and effective to maintain said first control transistor in an on-condition while operative current flows in said output circuit of said first control transistor; said cutoif means comprising a second control transistor normally in an off-condition and operatively connected to said sensing means so as to be turned on when a predetermined signal is received from said sensing means, said second control transistor having an output circuit operatively connected to said first control transistor so as to turn the latter off when said second control transistor is on, thereby stopping current flow in said output circuit of said first control transistor and de-actuating said latching means.

18. The electric drive of claim 17, in which said sensing means produces said predetermined signal when said output member has moved a predetermined distance.

19. The electric drive of claim 17, in which said sensing means produces said predetermined signal when said output member is moving at a predetermined speed.

References Cited UNITED STATES PATENTS 3,042,847 7/ 196.2 Welch 318-254 3,304, 48 1 2/ 1967 Saussele 318-138 3,329,852 7/1967 Saussele et al 318-138 3,333,171 7/1967 Platnick 318-138 3,353,076 11/1967 Haines -1 318-138 3,359,474 12/1967 Welch et al. 318-138 3,386,019 5/ 1968 Hill 318-138 G. R. SIMMONS, Primary Examiner U.S. Cl. X.R.

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