US3192702A - Mechanical vibrator for time base - Google Patents

Description

y 1965 YOSHIAKI KATO ETAL 3,192,702

MECHANICAL VIBRATOR FOR TIME BASE Filed April 11, 1965 5 Sheets-Sheet l r 3 1'' g; 1 2E 5 54a 6 3 2 33 5 N 32 A 24 if 7 s 42? II lllll I INVENTORb (Cal-NU KATO KA'LID TANAKA BY 5 "km fwm y 5, 1965 YOSHIAKI KATO ETAL 3,192,702

MECHANICAL VIBRATOR FOR TIME BASE Filed April 11, 1963 5 Sheets-Sheet 2 J5EE- INVENTORS Yosmm KATO*- BY KAZUO TANAKA gm, www ew y 1955 YOSHlAKl KATO ETAL 3,192,702

MECHANICAL VIBRATOR FOR TIME BASE Filed April 11, 1963 3 Sheets-Sheet 3 United States Patent 3,192,702 MECHANECAL VlllltA'lCfiR FQ'R TlME BASE Yoshialri Karo, 518, l-chorne, Hiratsulra, Shinagawznhn, and Kazuo Tanaira, HE'S-'7, 3=chome, Seld'rnachi, Nerima-liu, both of Tokyo, Japan Filed Apr. 11, 1963, Ser. No. 272,394 7 tliairns. (-Cl. 53-23) This invention relates to a mechanical vibrator for the time base of a timepiece or the like equipment.

Various mechanical vibrators, especially those employing tuning forks and the like, mostly electromagnetically driven, have been developed, especially for use as time bases of timepieces and the like.

It is one of the main objects of the present invention to provide an improved mechanical vibrator which is highly suitable for use as the ti-mebase of a small portable timepiece, like a wrist watch, on account of its superior and improved frequency performance.

Another object is to provide a mechanical vibrator capable of substantially obviating position errors inherent in conventional mechanical vibrators heretofore employed in prior small timepieces.

Yet another object is to provide a mechanical vibrator which requires very little space and thus is highly adaptable for use as a vibrator in a small time piece.

Still another object is to provide a mechanical vibrator which requires very little operating power, thus being highly suitable for the above mentioned purpose.

Still a further object is to provide a mechanical vibrator of the kind-above referred to, which is very thin so that it may be conveniently fitted in a small timepiece.

These and other objects of the invention will be more apparent to those skilled in the art from a consideration of the following detailed description when taken together with the accompanying drawings in which:

FIG. 1 represents a top plan view of one embodiment of this invention, wherein several parts are shown in section and several electrical parts and connecting means are illustrated schematically;

FIG. 2 is a side view of the vibrator shown in FIG. 1, wherein several parts are broken away;

FIGS. 3 and 4 are similar views to FIGS. 1 and 2, respectively, illustrating a somewhat modified embodiment of the invention;

FIGS. 5a, Sb and 5c are explanatory and schematic representations for the illustration of the driving and detecting principles embodied in the present invention; and

FIG. 6 represents an explanatory diagram, illustrating the operating principle of a preferred embodiment of the invention. 7

Referring now to FIGS. 1-2 of the drawings, numerals 1 and 2 represent a couple of elongated bar elements which are made of a suitable material such as Elinvar having substantially a constant temperature coeificient with respect to elasticity. These bar elements are arranged parallel to each other in a plane and have considerable masses equal to each other so as to act, in combination with other several parts to be explained, as a pair of elements vibrating with opposite but equal amplitudes as will be explained more in detail hereinafter. Spring arms 3 and t project inwardly from the both bar elements at equal included angles alpha and meet together at a definite point as at 5 which lies on a longitudinal axis A-B of the vibrator assembly. A fixing arm 6 extends a suitable distance from the meeting point 5 along the axis A-B and is fixedly attached onto a mount 7 by suitable conventional fixing means, preferably in the form of set screws 8-9. As shown, the members 16 are preferably made in one piece of the same material. Although the fixing means are not shown, the mount 6 is fixed on a base 10 of a timepiece. Bars 11 and 12 made of a soft 3,1923% Patented July 6, 1965 magnetic material such as magnetic iron are fixedly attached to one side ends of vibrator bars 1 and 2 by means of conventional fixing means such as fixing screws 13 and 14, respectively, .and in turn mounted fixedly thereon is a permanent magnet 15 and a magnetic pole piece 16, respectively. In a similar way on the other ends of vibrator vibrator bars 1 and 2, bars of soft magnetic material 17 and. 18 are fixedly attached by means of fixing screws 19 and 29, respectively, and carry fixedly thereon a magnetic pole piece 21 and a permanent magnet 22, again respectively. Each magnetic pole and permanent magnet pair 1546 or 21-21; is arranged in a precisely opposite manner as shown in FIG. 1, leaving small air gaps 23 and 24 therebetween respectively, these gaps being provided along the longitudinal axis A-B of the vibrator assembly. It will thus be clear from the foregoing that soft magnetic bars 11-12 and 17-13 constitute parts of magnetic circuits of the vibrator assembly. The upper pair of magnetic bars 11 and 17 are rigidly connected to each other at their inside ends by an inwardly convex bar 25 which is preferably made integral with the bars 11 and '17 as shown. in the similar way, the lower pair of magnetic bars 12 and 18 are connected rigidly by a curved bar 26. The curved bars 25-26 are so shaped and dimensioned that a small air gap is formed as at 27 between both bars, and there is provided a small vertical gap between the curved bars 2-5 and 26 and the spring arms 3 and 4 at the crossing point. between these members.

Each of the curved bars 25 or 26 has a considerable mass and thus vibrator bar 1, magnetic bars 11 and 17, screws 13 and 19, curved bar 25, magnetic pole piece 15 and permanent magnet 21 in combination with the spring arm 3 constitute a vibrating system. The above mentioned constituent parts 1, 11, 13, 15, 17, 19, 21 and 25 are so arranged and dimensioned that the center of gravity of the vibrating system will occupy substantially the center point of the longitudinal axis of inclined spring arm 3. In a similar way, the parts 2, 12, 14, 16, 18, 20, 22 and 26 in combination with spring arm 4 constitute a second or lower vibratory system, the center of gravity of which occupies substantially the center point of the axis of lower spring arm 4 in FIG. 1. Related constituents are so dimensioned and arranged that the both centers of gravity have a same distance from the axis A-B of the vibrator assembly measured in the opposite directions. By employing such construction and mass distribution as above described, errors due to changes in position of a timepiece employing the present vibrator assembly are reduced considerably.

The oscillating mode of the present mechanical vibrator is shown in a rather simplified and largely exaggerated form in FIG. 6. In this figure, the neutral position of each vibrating system is shown by -full lines, while the extreme biased positions of each system are shown by dotted lines and by chain lines, respectively. It will be seen that the both oscillating systems perform swing motions about the centers C and C of the spring bars, 3 and 4, respectively, in opposite senses in the plane of the drawing with the supporting springs flexed as shown so that there is parallel oscillation of the two masses. As already mentioned, all the inertial masses are so shaped and arranged that it can be deemed that two concentrated masses perform a swinging movement about the respective center points C and C in opposite senses. In the embodiment shown in FIGS. 1-2, springs 34 are straight and have acute angles relative to bars 12, respectively. However, in practice, such included angles may be right angles as shown in FIG. 6 without producing any hindrance in the proper operation of the vibrator. in addition, the springs may have curved shapes, provided that the configurations be of accurately opposite phases to each other. By placing the centers of gravity above mentioned on the vertical axes passing through the centers C and C, respectively, it can be assumed that each center of gravity is kept unchanged in its position during the oscillatory movement. Because of this if a timepiece which is fitted with the present mechanical vibrator is subjected to alteration in its attitude in a gravity field, as frequently happens with a wristwatch, the natural frequency of the vibrator as a whole is not affected noticeably so that conventional position errors inherent in known mechanical vibrators is substantially obviated. To position the center of gravity of each of the oscillatory systems, when considered theoretically, at the center of the related carrying spring, trial and error methods can be employed, or alternatively, theoretical calculations may be followed in accordance with the best knowledge in the conventional art.

Numerals 2S and 29 represent coil carriers made from a suitable insulator material into spools and mounted fixedly on the base of the timepiece and are provided with bores 3t) and 31, respectively. Bore 3i) encircles with a small anular space therebetween substantial parts of magnet and pole piece 16. In the similar way, substantial parts of the pole piece 21 and magnet 22 extend with a small annular space therebetween into the bore 31. With such construction, these four pieces may be capable of freely oscillating without hindrance.

Carrier 28 carries thereon fixedly a drive coil 32 and carrier 29 is wound with a drive coil 33 and a sensing coil 34 in an overlapped manner as shown. The sensing coil serves as conventionally to sense changes in magnetic fluxes passing therethrough as caused by the oscillatory movement of the magnetic pieces. Current thus induced in the sensing coil is supplied to an amplifier circuit including a DC. current source E, a transistor Tr, a condenser K, resistor R and amplified therein. The amplified output current is fed to drive coils 332%? which serve to keep the vibrator in oscillation at a predetermined frequency equal to the mean natural frequency of the both vibrating systems. The mechanical vibrations thus induced are transmitted through a proper transmission to the timepiece mechanism, although the transmission and the like are omitted from the drawings in consideration of the fact that these mechanisms do not constitute any part of the invention and in addition they are rather familiar to those skilled in the art.

FIGS. 3 and 4 represent a modification from the foregoing embodiment which differs therefrom substantially in that between each couple of magnet and magnetic pole 15-16 or 21-22, there is arranged with small air gaps a soft magnetic piece 46 or 41, which is fixedly mounted in the bore of a coil carrier 42 or 43, respectively, similar to that denoted by 27 or 28 in the former embodiment. These magnetic pieces 42-43 serve as magnetic conducting means included in the magnetic circuit of the whole vibrator assembly. The provision of such means will contribute to increase the length of the magnetic passage without increasing the masses of the vibrating elements employed. A further magnetic piece 37 is provided in the gap defined by the couple of curved bars a and 26a and fixedly mounted on the base panel 10 of the timepiece. Such procedure, when employed, will considerably increase the efliciency of the magnetic passage between the said both bars, especially when the air gap therebetween is made considerably wider as shown than in the case of the foregoing embodiment for the purpose of arranging the whole assembly spread on a wider area so as to decrease the height thereof. This construction will contribute considerably to improve the magnetic efficiency of the whole assembly, and further to decrease the height thereof, as frequently desired under circumstances. Similar constituents in the present modification to those employed in the preceding embodiment are shown in the drawing by denoting with same reference numerals affixed with a," that the construction and operation of the present mechanism can be easily understood from the foregoing and would require no further detailed description. Additionally, constituents of the amplifier or oscillator circuit in this case are shown with same reference characters as before.

Referring next to FIGS. 5a, 5b and 5c the operating principle of the invention will be described more in detail:

PEG. 5a represents in a simplified form the magnetic and drive coil arrangement of the first embodiment shown in FIGS. l2. If the poles N and S are taken as shown, a large magnetic circuit denoted by P and two smaller magnetic circuits Q and S will be established. The magnetic flux of the circuit P is represented by o. It is now further assumed that drive coils 32-33 are wound so as to induce magnetic fluxes in the aforementioned small circuit Q flowing in the same direction of those of the large circuit P, while magnetic fluxes induced in the other small circuit S flow in the opposite direction to those of the large circuit. Now when an instantaneous current i is fed to both drive coils 3233, magnetic fluxes a and 952 are induced in small circuits Q and S, respectively. Generally, these values ir and are relatively small values when compared with It will thus be seen that magnetic fluxes o- "(/)2 will flow in this case through air gap 23, while fluxes flows through gap 24. It is commonly known that the attractive force as the case may be, acting, between two oppositely arranged magnetic bodies varies with the square of overall magnetic flux passing through the opposing surfaces thereof. When there be a slight change in the overall magnetic flux, the corresponding change thereby caused to take place in the attracting force varies with the overall flux multiplied by the occasional increment flux. If the increment of the attractive force at air gap 23 or 24 is denoted by F or F respectively, we obtain approximately the following formulas:

Thus, the attractive force at gap 23 is increasing, while the force at gap 24 is reducing, when the direction of current i reverses, and the reverse will govern. It is from this reason why the mechanical vibrator according to this invention operates in its principle as hereinbfeore described with reference to FIG. 6.

in a modified arrangement shown in FIG. 5b, the pole arrangement is somewhat modified that the polarity of one permanent magnet employed is in opposition to that of the other body, when seen in the direction of the large magnetic circuit in the meaning above referred to. Magnetic fluxes and 0 delivered from a pair of permanent magnets 15b and 22b, respectively, in this case, flow through small magnetic circuits as shown. Drive coils 32b and 3321 are so wound that the induced magnetic fluxes o will flow through the large magnetic circuit in the same direction as those of the small magnetic circuits as shown. When an instantaneous current i is fed to these drive coils, magntic fluxes and 5 -412 will pass through air gaps 23b and 24b, respectively, as easily supposed from the foregoing. Thus, also in this case, the both inertia masses constituting the mechanical vibrator will oscillate in the similar manner as before.

FIG. illustrates the sensing operation of the vibrator. Variable fluxes delivered from permanent magnet 22 and flowing through the right-hand small circuit shown in this figure will vary with variable gap length at 24 which varies in turn with the course of the oscillatory movement of the vibrator. The thus induced current in the sensing coil 34 is fed to the amplifier circuit already described in connection with FIG. 1 and amplified therein as in the conventional manner.

Thanks to the aforementioned, well-balanced arrangements of the oscillating masses and minimum magnetic losses in the magnetic circuits employed, the mechanical vibrator constructed according to the principles of the invention will provide a superior frequency performance without noticeable position error, yet with little power consumption, as will be demonstrated by way of the following example:

Example In the embodiment shown in FIG. 1, the overall longitudinal length of the vibrator was 28 mm. The outside diameter of the coil assembly 5 mm. natural frequency of vibrator 400 c./s.; drive coils, each 9,000 turns; sensing coil 3,000 turns; 0.1). of coil wire .015 mm.; battery voltage 1.3 volts; transistor; model GE. 2N323, produced by General Electric Company, Schenectady 5, New York; condenser 1 ,uf.; resistor 2 Mn. Position ernor per day was less than 0.3 second in comparison with the order of several seconds with use of a comparative tuning fork vibrator. Currrent consumption was 5 pa, which is amazingly lower than that normally encountered.

It is recognized that, to those skilled in the art, there will be apparent various modifications and arrangements which may be made without departing from the spirit and scope of the principles entailed. For instance, the number of permanent magnets and/or of drive coils may be reduced or increased as the case may be, and the arrangements of permanent magnets may be considerably modified so as to obtain the aforementioned magnetic principles. The invention is only to be limited by the appended claims.

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

1. In a mechanical vibrator of the kind specified herein, two oscillatory masses which are arranged in substantially a common plane and which have two sets of opposing spaced magnetic pole faces with flux flowing therebetween, one set at each of two opposite ends of the oscillator; a stationary member; two spring members each having one end rigidly connected to one of said two masses and its other end mounted on the stationary member so as to permit oscillation of said masses with respect to one another substantially in said common plane and thereby change the spacing between the pole faces in each set, each said spring member being positioned so that the mass to which it is attached has its center of gravity falling substantially along the longitudinal axis of said spring member; means for detecting movement of said oscillatory masses with respect to one another and providing electric signals as a function thereof; and electromagnetic means for varying the flux flowing between said opposing spaced pole faces differentially as a function of said signals so as to cause one set of the pole faces to approach each other and the other set of pole faces to move away from each other.

2. The mechanical vibrator of claim 1 wherein one of said oscillatory masses forms a magnetic path between one pole face in each set of pole faces and the other of said oscillatory masses forms a magnetic path between the other pole face in each set of pole faces, said masses being shaped to set up three magnetic paths through said oscillatory masses, one magnetic path that passes through both. sets of pole faces and two other magnetic paths that each pass through one of said two sets of pole faces and across a gap intermediate the ends of said mechanical vibrator.

3. The mechanical vibrator of claim 2 wherein said masses are closely spaced intermediate the ends of the vibrator to form said gap.

4. The mechanical vibrator of claim 2 wherein said detection means includes a coil which detects variations in spacing of the pole pieces in one of the sets of pole pieces.

5. The mechanical vibrator of claim 2 wherein said electromagnetic means includes two coils one at each set of pole pieces and a transistor amplifier which amplifies the output of the coil of the detection means and feeds the amplified output to said two coils.

6. In a mechanical vibrator system for providing oscillatory motion, a vibratory element comprising first and second oscillatory masses which are substantially equal,

means for mounting each said mass for oscillation around an axis passing through a point coincident with or in close proximity to its center of gravity, the axis of oscillation of the first mass and the axis of oscillation of the second mass being perpendicular to substantially the same plane with said perpendiculars extending through different points in said plane, and electromagnetic oscillation means for oscillating said two masses at substantially equal amplitudes substantially out of phase with each other.

'7. In a mechanical vibrator system for providing oscillatory motion, a vibratory element comprising first and second oscillating masses which are substantially equal, means for mounting each said mass for separate oscillation around a separate axis passing through a point coincident with or in close proximity to its respective center of gravity, the axis of oscillation of the first mass and the axis of oscillation of the second mass being perpendicular to substantially the same plane with said perpendiculars extending through different points in said plane, detection means for detecting the oscillation of said masses with respect to one another and providing electrical signals as a function thereof, and electromagnetic means for exerting force on said masses for oscillating them at substantially equal amplitudes substantially 180 out of phase with each other in response to the electrical signals from said detection means.

References Cited by the Examiner UNITED STATES PATENTS 2,852,725 9/58 Clifford 318-128 2,939,971 6/60 Holt 310-15 FOREIGN PATENTS 832,781 4/60 Great Britain.

LEO SMILOW, Primary Examiner.

JOSEPH P. STRIZAK, Examiner.

Claims (1)

1. IN A MECHANICAL VIBRATOR OF THE KIND SPECIFIED HEREIN, TWO OSCILLATORY MASSES WHICH ARE ARRANGED IN SUBSTANTIALLY A COMMON PLANE AND WHICH HAVE TWO SETS OF OPPOSING SPACED MAGNETIC POLE FACES WITH FLUX FLOWING THEREBETWEEN, ONE SET AT EACH OF TWO OPPOSITE ENDS OF THE OSCILLATOR; A STATIONARY MEMBER; TWO SPRING MEMBERS EACH HAVING ONE END RIGIDLY CONNECTED TO ONE OF SAID TWO MASSES AND ITS OTHER END MOUNTED ON A STATIONARY MEMBER SO AS TO PERMIT OSCILLATION OF SAID MASSES WITH RESPECT TO ONE ANOTHER SUBSTANTIALLY IN SAID COMMON PLANE AND THEREBY CHANGE THE SPACING BETWEEN THE POLE FACES IN EACH SET, EACH SAID SPRING MEMBER BEING POSITIONED SO THAT THE MASS TO WHICH IT IS ATTACHED HAS IT CENTER OF GRAVITY FALLING SUBSTANTIALLY ALONG THE LONGITUDINAL AXIS OF SAID SPRING MEMBER; MEANS FOR DETECTING MOVEMENT OF SAID OSCILLATORY MASSES WITH RESPECT TO ONE ANOTHER AND PROVIDING ELECTRIC SIGNALS AS A FUNCTION THEREOF; AND ELECTROMAGNETIC MEANS FOR VARYING THE FLUX FLOWING BETWEEN SAID OPPOSING SPACED POLE FACES DIFFERENTIALLY AS A FUNCTION OF SAID SIGNALS SO AS TO CAUSE ONE SET OF THE POLE FACES TO APPROACH EACH OTHER AND THE OTHER SET OF POLE FACES TO MOVE AWAY FROM EACH OTHER.

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