US3515914A

US3515914A - Mechanical oscillator including a torsion bar

Info

Publication number: US3515914A
Application number: US649892A
Authority: US
Inventors: Samuel Steinemann
Original assignee: Institut Straumann AG
Current assignee: Institut Straumann AG
Priority date: 1966-09-26
Filing date: 1967-06-29
Publication date: 1970-06-02
Anticipated expiration: 1987-06-02
Also published as: CH1385466A4; DE1673758B2; GB1175550A; FR1605076A; CH481412A; DE1972490U; DE1673758A1; NL6709050A

Description

June 2, 1970 s; STEINE MANN MECHANICAL OSCILLATOR INCLUDING A TORSION BAR Filed June 29, 1967 2 Sheets-Sheet 1 Y 515.2 M 14 H 16' I3 4 /7 7.9 D '1 l5 78 ,0 20

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MECHANICAL OSCILLATOR INCLUDING A TORSION BAR Filed June 29, 1967 2 Sheets-Shet z /nven/vr 5A M051. \STE/NEM N F|g.17

United States Patent 3,515,914 MECHANICAL OSCILLATOR INCLUDING A TORSION BAR Samuel Steinemann, Waldenburg, Switzerland, assignor to Institut Dr. Ing. Reinhard Straumann A.G., Waldenburg, Switzerland Filed June 29, 1967, Ser. No. 649,892 Claims priority, application Switzerland, Sept. 26, 1966, 13,854/ 66 Int. Cl. H021: 33/02 US. Cl. BIO-37 9 Claims ABSTRACT OF THE DISCLOSURE A mechanical oscillator includes a torsion bar provided at both ends with inertia masses, the torsion bar being mounted at the location of the node of oscillatory movement. The oscillator has a generally H-shaped configuration, With the web or cross bar portion of the H- shaped configuration comprising the torsion bar and the legs of the H-shaped configuration constituting the inertia masses. Additional masses may be disposed at the four ends of the arms or legs of the H-shaped configuration, and at least one of these masses, or more than one of the masses, form part of an electro-mechanical transducer.

BACKGROUND OF THE INVENTION Various forms of mechanical oscillators are known, including particularly tuning forks and so-called flexion vibrators. Known types of mechanical oscillators are characterized by losses and frequency shifts, and by disturbances due to mechanical stresses and the like. They are also characterized by a limited number of modes of oscillation, as well as by radiation or loss of energy through mounting means.

Additionally, prior known mechanical oscillators are operationally affected by thermally induced expansion and contraction, and physical damping mechanisms limit the range of usable frequencies. Generally, the natural frequency of known mechanical oscillators is dependent upon the position or orientation thereof, due to the effects of gravity.

SUMMARY OF THE INVENTION In accordance with the present invention, a mechanical oscillator is provided including a torsion bar provided at both ends with inertia masses. The moments of inertia of the two masses, when taken about the longitudinal axis of the torsion bar, are substantially equal to each other, and the center of each mass lies on the axis of the torsion bar. The torsion bar is mounted at the position of the node of its oscillatory movement so that, in use, oscillations on one side of the node are transmitted to the other side and both sides oscillate oppositely and substantially equally. The masses of the oscillator may be so distributed that the center of'gravity of the oscillator coincides with the node of its oscillatory movement.

The oscillator preferably has a substantially H-shaped configuration, with the web portion of the configuration comprising the torsion bar. A fastening member may be provided at the center of the web, and extend perpendicularly to the Web. Masses may be disposable at the four ends of the arms or legs of the H-shaped configuration, and preferably at least one mass forms part of an electro-mechanical transducer.

Alternatively, the oscillator may include at least three transducers, at least two of which serve for detecting movement and for compensating disturbing oscillations. Alternatively, a plurality of transducers may be provided, with the transducers being coupled together through an Patented June 2, 1970 electric switch circuit. Also a plurality of transducers may be provided with the transducers being directly connected to each other. A coil of one transducer may be also served as a coil for a second transducer.

One or several of the mentioned legs or masses may comprise the pawls of a stepping mechanism, and the mechanical oscillator in accordance with the invention may form part of a time piece or of an electric filter.

An object of the present invention is to provide an improved mechanical oscillator.

Another object of the invention is to provide a mechanical oscillator comprising a torsion bar provided at both ends with inertia masses.

A further object of the invention is to provide such a mechanical oscillator in which the moments of inertia of the two masses, taken about the longitudinal axis of the torsion bar, are substantially equal to one another, with the center of each mass lying on the axis of the torsion bar.

Still another object of the invention is to provide such a mechanical oscillator in which the torsion bar is mounted at the position of the node of its oscillatory movement.

A further object of the invention is to provide an oscillator of the type just mentioned in which the center of gravity of the oscillator coincides with the node of oscillatory movement.

Yet another object of the invention is to provide such an oscillator in a substantially H-shaped configuration in which the web portion comprises the torsion bar.

A further object of the invention is to provide such an H-shaped configuration for a mechanical oscillator in which a fastening member is provided at the center of the web and extends perpendicularly to the latter.

Still another object of the invention is to provide such an H-shaped configuration mechanical oscillator having masses disposable at the four ends of the arms of the H-shaped configuration and at least one mass forming part of an electro-mechanical transducer.

DESCRIPTION OF THE DRAWINGS An understanding of the principles of the invention, reference is made to the following description of the typical embodiments thereof as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a perspective view of one form of oscillator embodying the invention;

FIG. 2 illustrates the various natural vibrations of the oscillator shown in FIG. 1;

FIGS. 3 and 4 are sectional views illustrating electrodynamic transducers embodying the oscillator shown in FIG. 1;

FIG. 5 is a view similar to FIGS. 3 and 4 illustrating an electro magnetic transducer embodying the oscillator shown in FIG. 1;

FIG. 6 is a partial perspective view illustrating an electro-static transducer embodying the oscillator shown in FIG. 1;

FIG. 7 is a perspective view illustrating another form of oscillator embodying the invention; and

FIGS. 8 through 14 somewhat diagrammatically illustrate various couplings of the transducers through electric circuits and through the polarization of electro-mechanical transducers and FIGS. 15-17 illustrate the use of the inventive oscillator in conjunction with a filter, a stepping mechanism and a time-piece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, the mechanical oscillator therein illustrated has substantially the form of the letter H. Web 1 of the H-shaped configuration forms the torsion bar, while the two arms or legs 2 and 3, at opposite ends of this bar or web, form the inertia masses. Mass 2 carries, at each of its opposite ends, magnets 4, and mass 3 carries, at each of its opposite ends, magnets 5. The magnets may have any shape and, in the arrangement shown in FIG. 1, also serve as weighting masses. Other shapes or configurations of the magnets as shown in FIGS. 3 and 4.

Two mutually symmetrical fastening lugs 6 and 7 are provided to extend perpendicularly from the center of web 1 in opposite directions therefrom, lugs 6 and 7 having

respective apertures

6a and 7a at their free ends. Lugs 6 and 7 serve for mounting of the oscillator.

In the selection of dimensions care must be taken that the moments of inertia of the two masses, referred to the axis of web 1, are equal to one another and that the center ofeach of the two inertia masses (which is designated as the integral {r dm.) lies on the axis of web 1. If the entire H-shaped configuration is of symmetrical construction, the masses are so distributed that the center of gravity of the entire oscillator coincides with the node of movement, which is at the center of torsion bar 1. Since the oscillator illustrated in FIG. 1 does not contain only an elastic member and inertia masses distributed discretely, by which the frequency of resonance would be accurately predetermined, it can perform the most diverse oscillations.

These various oscillations are illustrated in FIG. 2, and were ascertained by energizing the oscillator at one arm and observing the phase and amplitude at the other arms. In addition to the important natural frequency of 998 c./s., there are three subsidiary resonances caused by torsion and bending of the fastening lugs 6 and 7 and also be deflection of the beams or legs 3 and 4. However, the amplitudes of these subsidiary resonances are small, and they do not disturb the perfect excitation of the oscillator at the natural frequency thereof of 998 c./s.

From experiments, it has been found that, largely irrespective of whether the torsion bar 1 has a rectangular cross-section or a circular cross-section, the oscillator has a high quality factor and good stability, which is due to the fact that the mechanical stressing is distributed and the macroscopic thermoelastic damping is absent, because no dilatations occur in a torsion bar. In addition, the invention oscillator has a natural frequency which is independent of position due to the fact that its mounting point coincides with its geometrical center and, at the same ime, forms the center of gravity and the center of inertia. Thus the contribution of the gravity field to the potential energy is cancelled out.

The mechanical stressing occurring in the event of blows being applied to the oscillator is superimposed on the torsional tensions, but is not of the same type or distribution so that the oscillations are not directly disturbed. With good mass adjustment, there is no radiation of energy of the oscillator through its mounting, so that losses and frequency shifts are avoided. In addition, and unlike the bending oscillator, a torsion oscillator is not anisochronous through the geometry of the movement. That is, to say, its frequency is independent of amplitude.

To excite the oscillator and maintain the oscillation, it is possible to use known transducers. For example, excitation may be effected magnetically, electrodynamically, or electrostatically, and either at one end only of one of the two beams 2 or 3 are else at a plurality of these ends. If more than one transducer is used, it is possible not only to suppress all undesired oscillations through the arrangement of electrical switching circuits, but also to make the entire oscillator insensitive to blows, the arrangement being such that the tensions induced by the blows are ineffective.

FIG. 3 illustrates an electrodynamic transducer in which a pot magnet 11 is mounted on the free end of an arm 10 of the oscillator, this pot magnet 11 oscillating in the field of a stationary coil 12. FIG. 4 illustrates a somewhat different form of construction of an electrodynamic transducer, in which the pot magnet 13 is uniformly cylindrical, as contrasted to the frusto-conical shape of the pot magnet 11, with the coil 14 cooperating with the pot magnet 13.

In the electro-magnetic transducer shown in FIG. 5, a yoke 16 of an electro magnet is situated opposite the free end of an arm 15 of the oscillator, the core of the yoke being shown at 17 and the associated coil or winding at 18. FIG. 6 illustrates an electrostatic transducer in which the two stationary electrodes are shown at 19 and 20.

The embodiment of the mechanical oscillator shown in FIG. 7 differs somewhat from the embodiment thereof shown in FIG. 1, although the oscillator of FIG. 7 has an H-shaped configuration including a web or cross bar forming the torsion bar 21 and a pair of arms or

legs

22 and 23 disposed at the ends of torsion bar 21.

Arms

22 and 23 act as inertia masses inthe same manner as described for the embodiment of the oscillator shown in FIG. 1. However, as distinguished from the embodiment of the oscillator shown in FIG. 1, the oscillator shown in FIG. 7 has only a single fastening lug or mounting member 24 extending from the center of torsion bar 21 and perpendicular to the torsion bar. This mounting arrangement provides an elasticity of the suspension adapted to correspond to any external disturbances which may occur.

Like the fastening lugs or mounting arms 6 and 7, fastening lug 24 must be sufiiciently elastic that, although it can be used to mount the oscillator, the oscillations of one half of torsion bar 21 are transmitted to the other half and the two ends of the torsion bar oscillate equally and oppositely. Stated in another way, the torsion bar is a single oscillator with a node of oscillation situated at its center. Completely rigid securing of the oscillator torsion bar would transform the single torsion bar into two torsion bars which are independent with respect to their oscillations being, in effect, clamped at one end. With the elastic mounting means shown in FIG. 7, the subsidary oscillations caused by the torsion and bending of the mounting means still occur. The natural frequency of these ocillations caused by such torsion and bending amount to about 0.3 to 1.2 times the main frequency. Thus, as already mentioned for the oscillator shown in FIG. 1, the subsidiary oscillations had a frequency of 850 c./s. for a natural main oscillation of 998 c./s., or about 9.84 times the frequency of the main oscillation.

In the oscillator shown in FIG. 7, the ends 22a and 23a of the

respective arms

22 and 23 have secured thereto

respective magnets

25 and 26. A single winding 27 is passed through the magnetic field of both

magnets

25 and 26 so that the voltages induced in the transducers for the movements of the basic harmonic are thus directly coupled.

In the arrangements of electrical circuits or direct coupling through transducers shown in FIGS. 8 through 14, the directions of polarization of the transducers, which may be magnetic, dynamic, or electrostatic transducers, are indicated by arrows. FIG. 8 illustrates a simple resonator or filter in which excitation of an oscillator 29, as well as decrease of the oscillation thereof, is effected by means of a single transducer 28.

FIG. 9 illustrates a simple feed back resonator utilizing the invention oscillator and including two

transducers

29 and 30 in circuit connection with an amplifier 31.

FIGS. 10 and 11 illustrate phase-sentive systems each including three

transducers

32, 33 and 34 and an amplifier 31', in FIG. 10 and 31" of differential type, in FIG. 11. In the arrangements of FIGS. 10 and 11, the transducers, by means of the circuitry or of the polarization thereof, utilize the phase of the induced voltage. Two

transducers

32 and 33 are used for the detection of oscillation and the third transducer 34 is exciting the oscillation. Since the sum of signals of the two

oscillation detection transducers

32 and 33 are not disturbed by blows which provoke other movements than the normal oscillation, high insensitivity to external disturbance can be obtained and the oscillation is rigidly held. In FIG. 10,

transducers

32 and 33 are connected in parallel to a single input to amplifier 31' where as in FIG. 11,

transducers

32 and 33 are connected to separate inputs to diflerential amplifier 31".

FIGS. 12 and 13 illustrate further developed phasesensitive systems. In FIG. 12, four transducers 35 are associated with the mechanical oscillator and connected with an amplifier 37. Each transducer is connected to a separate input or output of the dilferential amplifier 37, the phase of the input and output being such that only the fundamental oscillation is excited and the external disturbances do not induce excitation. In FIG. 13 four transducers 36 are associated with an amplifier 38, with two of the transducers being connected in parallel to a single input of amplifier 38 and two others of the transducers being connected in parallel to a single output of amplifier 38, the phase relationships for the transducers being correct only for normal oscillation.

FIG. 14 illustrates an electro-mechanical filter including four transducers 39 associated with the mechanical oscillator, the transducers at corresponding ends of the two arms of the H-shaped configuration being connected in parallel with each other. Other combinations are also possible, such as the connection of a plurality of transducers in series or transportation of the positions of the transducers.

In FIG. 15 the use of the inventive oscillator in conjunction with a filter is diagrammatically shown. Z is a [filter section with the particular impedance behavior of a resonating element, with its transducers. The configuration of the resonating element and the transducers corresponds to that of FIGS. 9-14.

Referring now to FIG. 16, a stepping mechanism incorporating the inventive oscillator construction is shown. Reference numeral 40 indicates the resonator with transducers and mounting. Pawl 41 is coupled with the oscillator. Reference numeral 42 indicates a fixed pawl, the ratchet wheel being shown at 43.

Turning now to FIG. 17 which refers to the use of an oscillator in connection with a time-piece, it will be noted that oscillator 44 is coupled with the mechanical time indicator 45 and the electronic time indicator 46.

Oscillators embodying the invention are thus suitable not only for controlling an electrical oscillation, for example for keeping it constant, but also are suitable for direct mechanical supply of power, for example for driving a ratchet wheel in a manner similar to that already known and using tuning fork oscillations.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A mechanical oscillator comprising a one-piece H- shape substantially flat metal member including a pair of substantially parallel legs integrally interconnected, at substantialy their mid points, by a cross web; said legs acting as polar inertia moments for said web, and said web serving as a torsion rod; means supporting said torsion bar web at the position therealong of the node of this oscillatory movement whereby, during oscillation of said oscillator, oscillations on one side of the node are transmitted to the other side of the node so that both sides oscillate oppositely and substantially equally; additional masses at the four ends of the legs of said H-shape flat metal member; the distribution of the masses of said mechanical oscillator being such that the center of gravity of the oscillator coincides with said node of oscillatory movement; at least three of said additional masses each comprising a part of a respective electrical-mechanical transducer; at least two of said electrical-mechanical transducers operating together as oscillation detectors and being connected with each other in a manner such that their signals add for the torsion oscillation.

2. A mechanical oscillator, as claimed in claim 1, including oscillator electronic circuitry coupling said transducers and eifective to cancel disturbing oscillations.

3. A mechanical oscillator, as claimed in claim 1, including electrical circuitry directly interconnecting said transducers and effective to cancel disturbing oscillations.

4.. A mechanical oscillator, as claimed in claim 1, including an oscillation detector winding common to two of said transducers.

5. A mechanical oscillator, as claimed in claim 1, in which said common winding serves further for excitation of said oscillator.

6. A mechanical oscillator, as claimed in claim 1, in which at least one of said legs includes a pawl forming part of a stepping mechanism.

7. A mechanical oscillator, as claimed in claim 1, including a time piece, said mechanical oscillator constituting a component of said time piece.

8. A mechanical oscillator, as claimed in claim 1, including an electric filter, said mechanical oscillator constituting a component of said electric filter.

9. A mechanical oscillator, as claimed in claim 1, in which at least one of said additional masses includes a magnet.

References Cited UNITED STATES PATENTS 3,308,313 3/1967 Favre 31036 3,242,445 3/1966 Kameya 3108.2 XR 3,080,538 3/1963 Johnson 33371 3,192,488 6/1965 Faith et al. 310-36 XR 3,277,394 10/1966 Holt et a1. 331l54 XR 3,281,725 10/ 1966 Albsmeier 3108.2 XR 3,351,788 11/1967 Favre 310--37 XR 2,594,749 4/ 1952 Ehrat et a1. 84--409 3,201,932 8/1965 Sparing et al. 5823 3,149,274 9/1964 Hetzel 318128 3,150,337 9/1964 Allison 331-116 XR 2,959,746 11/ 1960 Sears. 2,730,665 1/1956 Hart 318-128 2,861,256 11/1958 Hart. 3,316,708 5/ 1967 Waldburger 5 823 FOREIGN PATENTS 1,130,012 10/ 1968 Great Britain.

726,856 2/1966 Canada.

111,660 1964 Czechoslovakia.

283,314 1962 Netherlands.

I D MILLER, Primary Examiner B. A. REYNOLDS, Assistant Examiner US. Cl. X.R.