US3192701A - Vibratory motion converter for an electric timepiece - Google Patents

Description

y 6, 1955 KAZUO TANAKA ETAL 3,

VIBRATORY MOTION CONVERTER FOR AN ELECTRIC TIMEPIECE Filed Nov. 30, 1962 5 Sheets-Sheet l NVEN TA KAzu P3; SH/AK! KATo 22m" xaa.

6, 1965 KAZUO TANAK A ETAL 3,192,701

VIBRATORY MOTION CONVERTER FOR AN ELECTRIC TIMEPIECE Filed Nov. 30, 1962 3 Sheets-Sheet 2 INVENTORS KAZUQ TANA KA OSH/AKI K o y 6, 1955 KAZUO TANAKA ETAL 3,192,701

VIBRATORY MOTION CONVERTER FOR AN ELECTRIC TIMEPIECE Filed Nov. 30, 1962 3 Sheets-Sheet 3 JNVENTORS j lfl KAZUO T N KA BY YOSH IA KI KATO United States Patent 3,192,701 VIBRATORY MOTION CONVERTER FOR AN ELECTRIQ TEMEPIECE Kazuo Tanaka, 105 3-ch0me, Sehi-machi, Nerinla-lru,

and Yoshiaki Kata, 518 l-chome, Hiratsuka, Shinagawa-hn, both of Tokyo, Japan Filed Nov. 30, 1962, Ser. No. 241,351 9 Claims. (Cl. 5323) The present invention relates generally to a motion converter. More specifically, it relates to a motion converter which is capable of converting the oscillatory movement of a mechanical vibrator into rotary movement and which is highly adapted for use as the time base in a watch, although the invent-ion is not limited thereto.

Recently, battery-powered watches have been developed and refined. This kind of Watch has electrical means for oscillating a mechanical vibrator, the latter being preferably in the form of a tuning fork type vibrator. A reciprocatable drive element, such as a pawl, is attached to one of the tines of the fork through the intermediary of a leafspring and cooperates with a ratchet wheel so as .to cause rotation thereof during continuous oscillation of the tuning fork. The ratchet wheel is operatively connected to the conventional wheel train of the watch so as to actuate the watch hands.

Troubles and disadvantages have been encountered with use of such a kind of watch as above referred to. More specifically, when such a watch is subjected to a change in its position in the gravity field, so-called position error will generally be encountered, which gives rise to a considerable time lag or lead as will be more fully described hereinafter.

It is therefore a main object of the invention to provide a novel motion converter, which substantially obviates such a position error.

In a conventional motion converter employing a tuning fork as its mechanical vibrator, there is provided only one reciprocatable element, such as a pawl, as was referred to above. In such a construction, however, a well-balanced feed motion will be disturbed from the view point of driving efforts as well as reaction forces.

It is another object of the present invention to provide a unique vibrator assembly which is capable of driving a pair of feeding pawls alternately so as to drive the cooperating ratchet wheel more frequently and evenly. By employing such a measure, rotation of the ratchet wheel will be brought correspondingly nearer to a desirously continuous revolution and assure a smooth and wear-minimizing operation of the timepiece mechanism.

'It is yet another object of the invention to provide an improved motion converter which incorporates two feeding p awls operating with equal turning efforts so that a well-balanced operation of the timepiece mechanism may be assured.

It is a still further object of the invention to provide an improved motion converter, wherein changes in feeding strokes of the pawls may be minimized even when the amplitudes of the vibrating elements should be subjected to occasional and temporary changes invited by a certain cause.

Another object of the present invention is .to provide a highly accurate timepiece which may readily be massproduced at a low production cost.

The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in connection with accompanying drawings illustrating a preferred embodiment of the invention. It is tobe expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits for the invention.

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In the drawings, wherein like reference characters and numerals refer to like parts throughout the several views: FIG. 1 is an explanatory sketch illustrative of a conventional tuning fork;

FIG. 2 is a similar view to FIG. 1, showing a novel vibrator embodying the principles of the invention;

FIG. 3 is an enlarged perspective viev. essential parts of one embodiment of the motion converter according to the present invention;

FIG. 4 is an enlarged top plan view of the motion converter shown in *FIG. 3, as applied to the time base of an electromagnetically drivin watch, wherein however part is shown in section and pant in a simplified diagrammatic representation;

FIG. 5 is a sectional view taken along line XX' of FIG. 4;

FIG. 6 is a sectional view taken along line Y-Y' of FIG. 4;

FIG. 7 is a connecting diagram showing one embodiment of :a preferred transistor circuit for feeding drive coils of electromagnetic units and for electric cooperation with sensing coils embodied therein;

FIG. 8 is a similar view to FIG. 7 showing a somewhat modified circuit;

FIG. 9 is an explanatory diagram illustrative of a conventional ratchet feed; and FIG. 10 is a similar view to, FIG. 9, wherein however the novel ratchet feed according to the principles of the present invention.

in advance to detail description Olf the invention, the position error will be explained briefly in connection with FIG. 1 of the drawings:

A tuning fork is shown in FIG. 1, which fixedly carries masses m1 and m2 on the top ends of its tines t1 and t2, respectively. As shown, the centers of gravity of these both tines including the said masses are positioned at relatively distant positions G1 and G2 from the oscillating origins, denoted by O l and 02, respectively, of the tines. As is commonly known to those skilled in the art, the natural frequency of such a tuning fork is dependent, in addition to elastic restoring forces inherent in the oscillating system, upon the moment about either origin 01 or 02 provided by the weight W1 or W2 acting at gravity center G1 or G2, respectively. It will be clear that this moment is dependent naturally upon the occasional position of the timepiece and thus the abovement-ioned position error will inevitably occur. More specifically, the timepiece will experience a maximum lag when it is positioned with the masses m1 and m2 at the highest level relative to the oscillation origins O1 and 02. Conversely, when these masses are positioned at the lowest level, the timepiece will then have a maximum lead.

According to the present invention, the above-described drawback can be substantially obviated by forming the mechanical vibrator in the shape of a Z. More specifically, one oscillating element, comprising a spring time and an oscillator mass, of the vibrator is arranged at a completely l-inverted symmetry to the other oscillating element comprising a similar spring tine and oscillating mass. In FIG. 2, such a novel vibrator is illustrated and the corresponding parts are identified with the same reference characters as those used in FIG. 1, for easy comparison. In this case, however, both resilient tines t1 and t2 are connected at their roots to each other by means of a rigid and stationary connecting bar dcnoted by CB. When it be assumed that mass m1 is situated at the highest level relative to the other mass 1122, the timepiece comprising the' present vibrator would be subjected to a time lag. In this case, however, the opposite mass m2 occupies naturally the lowest position relative to the first mass, so that the above lag may be completely compensated for the lead provided by the second oscillating element. In practice, however, energy exarea's o1 change will occur between the two vibrating elements through the intermediary of the rigid connecting bar CB, so that the both spring tines will make oscillations having substantially the same frequency. In this way, the disadvantageous position error inherent "in the tuning fork vibrator can be automatically compensated for without provision of special means. It will be further clear that a highly well-balanced feed for the wheel train in the timepiece can be obtained when a pair of feed elements are employed and driven from the two spring tines of the novel vibrator, although such a feeding mechanism is not limited only thereto.

Referring now to FIGS. 3-6, references and 11a denote bar springs which serve as the spring tines abovedescribed and are preferably made of an alloy commonly used for conventional hair springs, such as Elinvar containing Ni 36.5%, Cr 12% and rest Fe; or Ni-Span-C containing Ni 42%, Cr 5.5%, Ti 2.5% and rest Fe, the latter being produced by H. A. Wilson 00., U.S.A. These bar springs are provided on their one ends integrally with arms having a high bending rigidity and being denoted by 11 and 11a, respectively. On the tip ends of these arms, cup-shaped, outwardly opening, magnetic yokes 13 and 13a are permanently and rigid-1y attached as by welding or similar way. Permanent magnets 12 and 12a, each comprising a rigid cylinder made integral with a cone, are supported rigidly and concentrically to the cups as by press fit which construct-ion is clearly seen in the upper part of FIG. 4. The opposite end of bar spring 10 is rigidly and integrally connected to the opposite end of another bar spring 10a, as can most clearly be seen in FIG. 3, by means of a connecting bar 14 having a high value of rigidity. This bar was denoted by CB in the foregoing general description in connection with FIG. 2. Therefore one of the mechanical vibrator units, each comprising bar spring, arm, 'cup and magnetic cone, is arranged substantially in a rotary symmetry to a opposite similar unit about a center point denoted by P in FIG. 4. A little deviation of the above arrangement from the theoretical symmetry is employed mainly from the space requirements.

It will be clear from the [foregoing that the said both mechanical vibrator units will oscillate in the opposite directions when electromagnetically energized in the manner as more fully described hereinafter. These vibrator units have substantially a same natural frequency by properly selecting the materials, dimensions and configurations of the constituents. In practice, bar springs, arms and the connecting bar may be preferably united into one piece as shown.

Mounting and adjusting pieces 15 and 15a are fixedly attached on the upper surfaces of said arms 11 and 11a, respectively, by means of set screws 17 and 17a, as well as adjusting screws 20 and 20a, the latter being formed in eccentric screws as shown in FIG. 6 by way of example and the heads thereof being snugly received in recesses 16 and 16a, formed in said pieces, respectively, so that the physical phase relation can be, when necessary, modified by turning one or both of the adjusting screws in one or another direction so as to bring one of said mounting pieces nearer to the other by pivoting about their respective pivot pin 2-1 or 21a. Feed springs 18 and 18a are rigidly fixed at their one ends to the free ends of said adjustable pieces by means of fixing pins 18' and 18'a, respectively. :Feed pawls 19 and 19a, made of a hard and wear-resistant material, such as artificial ruby, are mounted on the free ends of feed springs 18 and 18a, respectively and kept in pressure engagement with teeth on a sprocket wheel 22, which is operatively connected with the conventional gear train for driving watch hands, not shown. By the above-described adjustment of the distance between said both mounting pieces '15 and 15a, the relative operative distance between the both feed pawls can be accordingly modified. Connecting bar 14 is formed with an opening 23 or 23a in the neighborhood of each of the opposite ends, for removably connecting the bar to a stationary frame plate 25 of the timepiece by means of fixing screws 24. Bar springs, arms, magnetic yokes and adjusting plates are properly mounted clear from the frame plate or any other stationary or movable timepiece elements and arranged to make free oscillation in an imaginary plane extending in parallel to and separated from the upper surface of frame plate 25, which is made preferably from rigid plastics.

As is illustrated with respect to the upper unit of FIG. 4., a coil assembly comprising a sensing coil 27 and a drive coil 28 are positioned in the annular spaces defined by magnetic yokes 13a and permanent magnets 12 and 12a and are preferably wound in an overlapped manner on a bobbin frame 26. This bobbin frame is made of a proper insulating material, such as a plastics and, if necessary, integral with the frame panel 25. These coils are arranged decidedly clear from the related permanent magnets and magnetic yokes.

Electrically cooperating with the aforementioned sensing and drive coils, there is provided a transistored selfexciting circuit. A basic form thereof is illustrated in FIG. 7. This circuit comprises a transistor T1, a DC. current source or battery E1, a condenser C1 and a resistor R1. Sensing coils 27 and drive coils 28 are also shown diagrammatically in this figure so that any person skilled in the art will readily understand the operation of this circuit.

In FIG. 8, a somewhat modified circuit is shown. In this circuit, resistors R2 and R3 determine the initial conditions of transistor T2, thus serving as bias resistors. Condenser C2 serves for auto-biassing; and condenser C3 for suppressing possible higher frequencies.

In FIG. 4, various parts explained above in connection with FiG. 8 are shown diagrammatically with necessary connecting leads, partly by dotted lines and partly with practical representations L1 and L2 represent earth connections.

Various types of self-exciting circuit for use in electric timepiece are well known in their design and operation to those skilled in the art. Since the circuit per so does not constitute part of this invention and the operation is also quite clear to those skilled in the art so that it is believed that further detail description may be omitted herefrom for simplification.

Referring next to FIG. 10, the novel feed mechanism employing two alternately acting pawls according to the invention will be described more in detail hereinbelow:

As already described, feed pawls 19 and 19a are kept in meshing with the ratchet teeth of Wheel 22, which is also operatively connected with the conventional wheel train for time indicating hands of the timepiece, although not shown. In FIG. 10, a number of these teeth are shown in their developed representation. As shown, when the oscillating elements are in their middle positions in the oscillating amplitudes, the linear or developed distance between the tip ends of these pawls measured along the periphery of the ratchet is not an integral multiple of the pitch P, but there is a difference P/2 from such multiple. When a load is imposed upon the ratchet wheel tending to turn it in the reverse direction, and the both feed pawls are governed by the above space condition, the maximum allowable change in the amplitude of each feed pawl will occur. Therefore, if the relative amplitude of one of the pawls to the other is within the range of P+P/2, the wheel can make only a partial turning corresponding to P, as is apparent to those skilled in the art.

conventionally, only one pawl is attached to the mechanical vibrator and moves in response thereto. A checking pawl is also provided to check possible return movement of the ratchet during the rear-ward or idle movement of the working pawl. Thus, the amplitude of the working pawl must be PiP/ 2 in order to feed one tooth for each vibration of the vibrator. Therefore. the

wheel cannot make any working rotation during substantially a half idle period of each oscillation.

According to the invention, two feed pawls oscillate in the reverse phase relative to the other and thus one of them is making a feeding movement at every moment of time, thereby allowing the checking pawl to be dispensed with and increases the combined amplitude of the two feed pawls to twice the amplitude of each pawl so that the amplitude of each pawl to feed the wheel one tooth during every oscillation will be P/ ZiP/ 4. The ratchet wheel in this case has practically no pause.

With the conventional mono-pawl feed mechanism, load will act upon the ratchet wheel, causing the latter to turn backwards until a corresponding tooth abuts against a check pawl during every idle or return stroke of the working pawl. If, for instance, the frictional resistance provided by the feeding pawl be so high that there is no backward movement of the ratchet 'wheel and thus the latter is caused to stop, after it has been fed, at the end of the feed stroke, and if the pawl amplitude be larger than the pitch P of ratchet teeth, the wheel may be advanced two teeth instead of one at every effective stroke of the pawl. Thus, the range of allowable period of the feed pawl must be between P/2 and P. Such a drawback may not be encountered with the feed mechanism according to the present invention.

The above-mentioned conditions governing the conventional feed mechanism will now be explained more in detail in connection with FIG. 9. In this figure, I represents the feed pawl and II the check pawl. a-d represent the relative positions of the pawl I relative to the ratchet teeth at several stages during a complete period of oscillation. Line KY shows the center of oscillation of the tip end of pawl I and lines H and B B.represent the opposite ends of a stroke of pawl I. Line W represents the position of the tip end of check pawl 11. Small arrows attached to the pawl represent the direction of movement thereof during the above-mentioned several stages.

Starting from the first stage a, pawl I pushes tooth 2 and arrives at stage b after a quarter period and then starts to make the rearward idle movement. In this case, if the wheel is allowed to turn rearwards in unison with the movement with pawl I, the condition will be as at c after elapse of a further quarter period. Thus, pawl I will only pass over the top of tooth 3. After a still further quarter period, that is, after a complete period counted from the beginning, the relationship will become as at d. When comparing stage a with stage d, during which a time interval corresponding to a complete oscillating period was elapsed, it will be found that just one tooth has been stepped forward. If no back movement of the wheel is allowed, and pawl is moved rearwards while the wheel kept at stage b, it would pass over the tips of both successive teeth 3 and 4. Thus, in this case, two teeth will be forwarded after a complete oscillating period.

With the novel feed mechanism shown in FIG. 10, pawls 19 and 19a are those oscillating in the reverse phase as referred to hereinbefore. Lines fi and w signify the middle point of oscillation of the tip end of the pawls 19 and 19a respectively, while lines H, E, m and on represent end points of the strokes thereof, as before. The amplitude of each pawl is selected to be 5P/ 8. From the position as at a, the both pawls start to move so as to separate from each other and occupy after a quarter oscillating period the position denoted by b, thence commencing their movement so as to come nearer to each other. During the latter way, pawl 19a will bring itself into collision against tooth 6. This time point will be advanced correspondingly, when the wheel is allowed to make reverse movement as at 0, while it is retarded if no reverse turn should be carried into effect so that the wheel is kept in pause as at b. In these both cases, however, the relative position of the pawls to the wheel will be of the stage d after the elapse of a half oscillating period front the stage b. Thus, in these both cases, regardless of reversemovernent of the wheel, there will be no change in effect and pawl 19 will pass over only one tooth as at 3. From this time point, the pawls commence to make an approaching process. In this case, if the wheel should make reverse movement, the relative position will be that of 1 through e after elapse of a further quarter oscillating period from the preceding stage, or a complete period counted from the initial stage a. Or alternatively, if there should be no reverse movement of the wheel, the final condition will be as at g. Either stage 1 or g shows equally a lead of one tooth only. At the stage g, the related tooth somewhat offset. In this case, however, the condition will be as at h after a still further quarter period. This last condition, when compared with that of stage b, that is, the position in advance of a complete oscillating period, shows a lead amounting to just a tooth.

It will be clear from the foregoing that no change either in the stroke at each stepping stage or in the range of allowable amplitude will be encountered with the ratchet feed mechanism constructed according to the present invention, regardless of reverse turning of the ratchet wheel.

It will be understood that each of the elements described hereinbefore, two or more together, may also find a useful application in other types of motion converters differing from the type described above.

While the invention has been shown and described as embodied in an electric timepiece, it is not intended to limit the present invention to the details shown, since various modifications and structural changes may be made without departing from the spirit of the invention.

Without further detail description, the foregoing will so fully reveal the gist of the present invention that those skilled in the art can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore, such adaptations should be intended to be comprehended within the range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. Mechanical vibrator for the time base of a time piece and the like, comprising a rigid elongated base element rigidly and detachably mounted upon a stationary panel of said time piece, a cantilevered oscillating element connected to each end of said base element, said oscillating elements being shaped and dimensioned to have substantially equal natural frequencies and said oscillating elements also extending in opposite directions in the plane of said base element and at equal distances from the central axis of said base element, said base and oscillating elements being arranged substantially in a Z-con figuration for substantially avoiding otherwise possible position errors, a permanent magnet attached to the tip end of each of said oscillating elements, and a drive and sensing coil assembly mounted upon said stationary panel for cooperating with each of said magnets.

2. Mechanical vibrator as set forth in claim 1 wherein each of said oscillating elements comprises a bar spring connected physically at its one end with said base element, a rigid bar physically connected with said spring and one of said permanent magnets.

3. Mechanical vibrator as set forth in claim 1 wherein said drive and sensing coil assemblies are electrically connected with a transistor amplifier circuit.

4. Mechanical vibrator as set forth in claim 1 wherein each of said coil assemblies is formed into a double solenoid which is mounted fixedly on said panel and arranged around one of said permanent magnets with a small air 5. In a motion converter for converting oscillatory movement into rotary motion, in combination, a vibrator comprising a rigid stationary elongated base element and a cantilevered oscillating element connected to each end of said base element, said oscillating elements having substantially equal natural frequencies and extending in opposite directions in the plane of said base element and at equal distances from the central axis of said base element, said base and oscillating elements being arranged substantially in a Z-configuration for substantially avoiding otherwise possible position errors, a first pawl connected through resilient means with one of said oscillating elements, a second pawl connected through second elongated resilient means with the other of said oscillating elements, a ratchet wheel maintained in pressure engagement with both said pawls, means for adjusting the distance between said oscillating elements and means for inducing said oscillating elements to oscillate substantially 180 out of phase with each other, thereby imparting to both said pawls alternate and periodical oscillatory movements having substantially equal amplitudes.

6. In a motion converter for timepiece for converting oscillatory movement into rotary motion, a vibrator com prising a rigid stationary elongated base element and a cantilevered oscillating element connected to each end of said base element, said oscillating elements having substantially equal natural frequencies and extending in opposite directions in the plane of said base element and at equal distances from the central axis of said base element, said base and oscillating elements being arranged substantially in a Z-configuration for substantially avoiding otherwise possible position errors, a first pawl connected through elongated resilient means with one of said oscillating elements, a second pawl connected through second elongated resilient means with the other of said oscillating elements, a ratchet wheel maintained in pressure engagement with both said pawls, means for adjusting the distance between said oscillating elements, and electromagnetic drive means including a magnetic yoke rigidly connected wtih each of said oscillating elements for oscillating said oscillating elements substantially out of phase with each other, thereby imparting to both said pawls alternate and periodical oscillatory movements having substantially equal amplitudes.

7. The combination defined in claim 6 wherein said both oscillatable elements are connected rigidly by a rigid connecting bar, which is fixed to a base plate by means of screws, said base being made of a plastic material and constituting part of a frame work containing all of said parts.

8. The combination defined in claim 6 wherein said magnetic yoke has a coneshaped core which is surrounded by a sensing and a drive coil, said both coils being wound in an overlapped manner and kept in separation at a dis-.

tance from said yoke and said core.

9. The combination defined in claim 8 wherein acouple of said coils is mounted in a bobbin frame which is made from a rigid plastic material and fixedly mounted on a base made again of a plastic material.

References Cited by the Examiner UNITED STATES PATENTS 2,908,174 10/59 Hetzel 74l28 3,020,425 2/62 Steiner 3 l020 3,113,415 12/63 Musser 58- -2 OTHER REFERENCES Electronic Tuning Fork Beats Time for Accuracy, Machine design, Oct. 27, 1960, pp. 30, 31.

Guillet: (France), 579,298 on the single sheet of dwg., 576,298 on pp. 1, 3 and 4 of the spec. and 570,298 on p. 2 of the spec., July 29, 1924.

LEO SMILOW, Primary Examiner.

JOSEPH P. STRIZAK, Examiner.

Claims (1)

1. MECHANICAL VIBRATOR FOR THE TIME BASE OF A TIME PIECE AND THE LIKE, COMPRISING A RIGID ELONGATED BASE ELEMENT RIGIDLY AND DETACHABLY MOUNTED UPON A STATIONARY PANEL OF SAID TIME PIECE, A CANTILEVERED OSCILLATING ELEMENT CONNECTED TO EACH OF SAID BASE ELEMENT, SAID OSCILLATING ELEMENTS BEING SHAPED AND DIMENSIONED TO HAVE SUBSTANTIALLY EQUAP NATURAL FREQUENCIES AND SAID OSCILLATING ELEMENTS ALSO EXTENDING IN OPPOSITE DIRECTIONS IN THE PLANE OF SAID BASE ELEMENT AND AT EQUAL DISTANCES FROM THE CENTRAL AXIS OF SAID BASE ELEMENT, SAID BASE AND OSCIL-

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