US3491258A - Oscillatory system with two turning mass bodies - Google Patents

Description

' J-L :0. 11m mm 3, 91,258

I OSCILLATOR! SYS'I'EI VIIT B TWO TURNING llASS BODIES man. 5. 196B 3 Sheets-Shoot 1 R. SIE FERT OSCILLATORY SYSTEM WITH TWO TURNING MASS BODIES Filed Feb. 5, 1968 3 Sheets-Sheet 2 J 20, 1970 R. SIEFERT 3,491,258

OSCILLATOR! SYSTEM WITH TWO TURNING MASS BODIES Filed Feb. 5, 1968 3 Sheets-Sheet 5 United States Patent O U.S. Cl. 310-36 Claims ABSTRACT OF THE DISCLOSURE The invention is a mechanical oscillator, electrically driven, for timepieces and of the type having two mass bodies connected together by a torsion or restorative spring member and turnable in counter phase, so as to reduce reaction against mounting bearings and consequent dissipation of energy. The nodal portion of the torsion member is connected by a separate spring to the works frame on which the oscillator is mounted.

CROSS REFERENCE TO RELATED APPLICATION Roland Siefert, Speed Controlled Clock Motor be ing filed of even date.

BACKGROUND OF THE INVENTION Field of the invention Directly driven mechanical oscillator for timepieces and having two relatively turnable mass bodies.

Description of the prior art Oscillatory systems having a turning mass and a spring are known to run quite accurately when the frequency of the system is high and the amplitude is held low. But this condition introduces the great drawback that such energy is dissipated to the framework. The amount of dissipation is essentially determined by the energy content of the oscillatory system.

In order to avoid these drawbacks it has been proposed to make so-ca-lled double swingers wherein the turning masses are out of phase by 180, and with such a construction the energy loss to the frame should be minimized owing to the reactions on the pivot bearings being counteracted. Such a construction heretofore has been beset with much difficulty in practice. The double swinger can have its spring connected to the frame only at the node of oscillation of the spring and the node must therefore be determined exactly. During tuning of the system to the requisite frequency both mass bodies and their respective spring halves must be tuned accurately with respect to each other in the prior art. That is to say, each of the two oscillators must have exactly like frequencies, the same spring length and the same turning mass. When these conditions are not obtained the position of the node of oscillation of the spring is not that of the point of connection on the frame. The results are then a beat or surge resulting in a dissipation of energy to the frame, with appreciable influence on accuracy of the timepiece. The reason for this is that one of the swinger halves is in forced oscillation at a frequency only near the natural frequency of the half.

3,491,258 Patented Jan. 20, 1970 2 SUMMARY OF THE INVENTION In the oscillatory system of the above named sort this is solved in that the connection between spring and frame is made elastic so that the fastening point of the connector at the torsion member enables movement which corresponds to the oscillatory movement of the spring near the node.

In a one sided mass alteration owing to balancing of the system it is possible that the node of oscillation can be adjusted by an alteration of the resulting location itself which does not coincide with the point of mounting. The natural frequency and the existing frequency of one half are then equal to those of the other half.

The two mass bodies are suitably connected with each other by a small torsion strip bar or pin. The torsion strip and frame are connected to each other in the neighborhood of the node of oscillation by means of a spring 'with the result that the mounting point of the oscillator spring may undergo turning movement. It is to be noted that the spring which effects the connection between the torsionstrip and frame in operational bearing position and at nul position of the oscillatory system should be tension-free. Hence the stress in the system is minimized.

For a system having a vertically disposed axis of oscillation a bearing support for mass bodies is not necessary. Owing to eventual shocks to which the system will be subjected it is, however, preferable to support the bodies by thrust bearings. Also the upper mass body can be held against lateral movement by ball bearings. For an axially horizontal system both mass bodies are mounted on ball bearings. As explained later herein this will minimize bending under the force of gravity.

Owing to the favorable development of the natural frequencies of the two half swinger upon frequency adjusting of only one mass body, only one of the masses is provided with permanent magnets which cooperate with the exciting and drive coils of an electronically controlled drive.

Preferably the rough balancing to the requisite frequency is obtained by alteration of mass of the bodies as by drilling out a part of the body, while fine regulation with respect to the mounting point of the torsion bar is accomplished by variation of the effective length of the bar. This variation can be obtained with two cam plates clamped on opposite faces of the torsion strip or bar by an adjustable screw.

Instead of a torsion bar a helical spring may be used to connect the two mass bodies to each other. A mounting spring connects the frame to the helical spring near the node of the latter and at its circumference.

Instead of two coaxially mounted mass bodies, two bodies side by side may be used and be connected to each other by a helical spring. The latter consists of two helical spring portions which are produced by opening up a normal helical spring.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a form of the invention having two turnable mass bodies connected to each other by a torsion strip.

FIGS. 1a and 112 show details of the connection between the system and a framework.

FIGS. 2a and 2b sho-w means for fine control of the frequency of the system.

FIGS. 3a and 3b shows a form of the invention having a helical spring instead of a torsion strip.

FIGS. 4a and 4b show a system with mass bodies axially side by side and FIG. shows radial bearings for mounting the system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 the two mass bodies 1 and 2 are connected to each other by a torsion spring strip or bar 3. The node of oscillation for this system, which operates with small amplitude and a frequency between and 100 c.p.s. is situated in the general vicinity of point 4. In balancing out the system to the nominal frequency only one of the bodies is adjusted. In the course of this one sided adjustment the location of the node is changed. That is to say, if the nodal point had been exactly at 4 before balancing, it is moved above or below the point 4. The connection between the torsion strip 3 and the framework 6 (FIGS. 1a and 1b) is made through a serpentine spring 5, which connection permits the fastening point 4 or zone to move corresponding to the turning movement of the spring.

Such turning movement of the end of spring 5 arises when the location of the node of oscillation does not coincide with the attachment point 4. The spring 5 can be fastened as by spot welding on the torsion strip 3. The mounting of spring 5 on the frame 6 is done free from strain with the oscillatory system in nullage by a clamping or cementing in situ of the spring 5 to the frame at 7 so that the position of the outer end of the spring is not altered during the process.

The upper mass body half is provided with permanent magnets 12 cooperating with inductor coils 13 and 14 as the exciting and drive coils of a conventional electronic drive system. A plate 15 provides shielding to reduce the effect of stray fields. The various parts are mounted on a bushing 10. The lower body which is suitable adjusted to nominal frequency consists essentially of two small blocks 16 mounted on a bush 17. The connections of the strip 3 with the bodies 1 and 2 are carried out by widened ends 8 and 9 of the strip 3 stuck in slits 11 and 18 in bushes 10' and 17. The connections are made secure by parts 19 screwed into the bushes.

If the system is to oscillate about a vertical axis it is only necessary that the system be secured against shocks by the thrust bearings 21 and 22. In case the torsion strip 3 is not inherently formed stable enough, the upper body 1 can be provided with a radial ball bearing as in FIG. 5. If the system operates about a horizontal axis both bodies should be supported against downward and lateral movement by bearings in order to minimize sagging of the torsion strip.

A fine adjustment of the frequency of the system can be attained by shortening or lengthening the effective length of the torsion strip. A means for doing this is shown in FIGS. 2a and 2b wherein two eccentric cam shaped plates 23 are mounted on opposite faces of the strip 3 and can be turned and drawn together by means of a screw 24 so that they engage tightly on the opposite faces of the strip 3 selective distances along the strip according to position of turning of the plates. By means of those plates can the mid portion of the torsion strip be stitfenend over variable lengths due to shape of the plates engaging thereon as a result of the clamping so as to vary the effective length of the strip 3. The mounting of the spring 5 on the torsion strip is accomplished by a circumferential groove in the screw 24 in which the forked end of the Spring 5 interengages.

Instead of the torsion strip a helical spring 27 may be used as in FIG. 3a, the remaining features being very much as in FIG. 1, with the connection of the nodal portion of spring 27 to the frame being carried out by a spring 25. Owing to the resilience of the spring 25 the attachment point need not be exactly at the node.

The two mass bodies need not be coaxial but may be side by side at 29 as in FIG. 4a. The bodies 29 are connected by interconnected helical springs 28' and 2-8" which are really two legs of an ordinary helical spring opened out in the middle to provide connecting tangential portion 228". The legs are connected at their terminal ends to the oscillatory mass bodies 29. The node of oscillation is near the point 4 which is connected to the frame 6, 'by a spring 30. Both mass bodies carry permanent magnets 32 cooperating with a common coil 31. The coil 31 is an exciter end drive coil of a conventional electronically controlled electric drive system. In order to reduce the effects of stray fields a shielding plate 33 is carried on each mass body. If the system is to oscillate about vertical axes only one thrust bearing need be provided for each body.

If such a system as shown above requires a radial bearing to prevent lateral movement such a hearing as a pivot bearing 36 about at the center of mass of one of the bodies, the body 29' being the one shown in FIG. 5 as a modification of the invention of FIGS. 4a and 4b. The bearing 36 receives a pointed rigid pivot pin 34 fixed on the frame 6, making it a thrust bearing as well, while the other thrust bearing is shown at 35.

In the embodiment as shown in FIGS. 4a and 4b both mass bodies may carry a drive pawl for driving a stepping wheel in a work train.

As will be obvious to those skilled in the art, pawls may be provided on almost any part of any of the turning bodies for taking off power to the train.

I claim:

1. A mechanical oscillator for an electrically powered timepiece comprising two turnable mass bodies and a torsion spring member connecting the two bodies, mag netic means for setting a least one of the bodies in turning oscillation, the masses of the bodies and the elasticity and length of the spring member being so related that at resonant frequency the two bodies are in counter phase and a nodal point exists on the member; a frame for carrying said bodies, and a spring secured to the frame and directly to the torsion spring member near said nodal point for steadying the member and permitting limited movement of the member whereby movement of the torsion spring member at the zone of securement between the member and spring during oscillation may be absorbed by the spring means and obviate the need for fixing the spring to the frame at the exact nodal point.

2. An oscillator as claimed in claim 1, and having a resonant frequency of between 10 and c.p.s.

3. An oscillator as claimed in claim 1, the spring enabling turning of the torsion member whereby oscillation of one body will induce oscillation of the other body.

4. An oscillator as claimed in claim 3, and adjustment means for varying the effective springy length of the member between the bodies to vary the resonant frequency.

5. An oscillator as claimed in claim 4 said member having opposite side faces between the bodies, and cam shaped stiff plates disposed against the respective faces and turnably mounted on the member to provide variable lengths of engagement along the faces to effect a variable length of clamping by the plates to render said length substantially stiff.

6. An oscillator as claimed in claim 4, said bodies being coaxial and said member being of strip material and having widened end portions, the bodies having hub-like bushings provided with diametric slots and receiving said portions respectively and plug means screwed into the bushings for holding the end portions in the slots.

7. An oscillator as claimed in claim 2, said member having helical coils.

8. An oscillator as claimed in claim 7, the member having like counter wound parallel legs and an integral tie piece substantially tangential to both legs and con- 5 6 necting the latter, the bodies being axially parallel, each 3,217,485 11/1965 Musseu et a1. 582 connected to a leg, each body being provided with said 3,214,662 10/1965 De Wolf 318138 magnetic means, and said spring being secured to said 3,192,488 6/1965 Faith et al 318-138 XR tie piece. 2,594,749 4/1952 Ehrat et a1. 31025 XR 9. An oscillator as claimed in claim 2 wherein the spring is substantially strain-free when the oscillator is 5 FOREIGN PATENTS at nu11 880,355 5/ 1950 Germany.

10. An oscillator as claimed in. claim 1 said spring 516,115 2/ 1955 yhaving loops.

Refere Ci 10 MILTON O. HIRSHFIELD, Primary Examiner UNITED STATES ATENTS B. A. REYNOLDS, Assistant Examiner 3,308,313 3/1967 Favre 310-36 U.S. Cl. X11.

amass 12/1955 l-I ettich 5s 1 q 58-131

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