US3635013A

US3635013A - Biassed oscillator arrangement

Info

Publication number: US3635013A
Application number: US889849A
Authority: US
Inventors: Hanns F Bertsch; Ottmar Schlachtberger; Horst Graf
Original assignee: HANNS F BERTSCH
Current assignee: HANNS F BERTSCH
Priority date: 1968-12-17
Filing date: 1969-12-17
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18
Also published as: DE1815099A1

Abstract

The balance wheel of a watch or clock is continuously biassed during oscillations of the balance wheel, by a single resilient rod concentric with the axis of the balance wheel, or by a pair of diametrically arranged resilient rods parallel to the axis, to move toward a central position so that the balance wheel oscillates at an inaudible frequency between 10 and 50 Hz.

Description

United States Patent Bertsch et al. 51 Jan. 18, 1972 [s41 BIASSED OSCILLATOR [s 1 M re-m cited ARRANGEMENT UNITED STATES PATENTS [72] Inventors: Hanns F. Bertsch, Kronenstrasse 30; Ott- 2 033 318 3/1936 Abramson 267/160 x schlachberge" Auf 2; F 2,061,047 11/1936 Schweitzer, Jr. .....58/1 16 x Gm, Kmemrasse of Schwenmn- 2,478,329 8/1949 Shaper ..324/1 13 Sen, Germany 3,168,833 2/1965 Popovitch ..74/l.5 22 Filed: 17 19 9 3,177,385 4/1965 Montagu.. .310/36 3,217,191 11/1965 Favre.... ..58/28 1 pp NM 889,849 3,343,012 9/1967 Scott ..3l/36 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley A. Wal Anorney-Michael S. Striker 30 Forei n A lication Priori Data 1 8 pp 57 ABSTRACT Dec. 17, 1968 Germany ..P 18 15 099.7 July 7 1969 Germany t p 9 34 4195 The balance wheel of a watch 01' clock 1s contmuously blas sed 1 .W.. ..-..11.V.MW3- M during osclllatlons of the balance wheel, by a smgle res1l1ent rod concentric with the axis of the balance wheel, or by a pair -58/107, R, 58/140 of diametrically arranged resilient rods parallel to the axis, to G040 3/04 move toward a central position so that the balance wheel Field of Search 1 l 16 23 A, 28 B, oscillates at an inaudible frequency between 10 and Hz.

58/23 0, 23 U, 23 TF, 107, 74/15; 267/154, 160, 310/36; 318/119 18 Claims, 7 Drawing Figures PATENTEU JAN i 8 B72- SHEET 3 OF 3 Fig.7

INVENTOR yum: -Bnlsni c'rr run scuutnranml Hour @mr I A. 0! r f ATTORNEY BACKGROUND OF THE INVENTION The present invention is concerned with oscillators controlling the timing of electric watches and clocks.

Timing oscillators are known which consist of a balance wheel or balance beam oscillating about an axis, and being driven by alternating opposite drive impulses, or by drive impulses acting only in one direction of rotation. A spiral spring biases the oscillator with a torque which tends to return the oscillator from the outermost end position to a neutral central position in which it receives a new drive impulse. Known timing oscillators operate generally at a frequency of 2.5 Hz. at amplitudes of about 240. In some cases, oscillators having a frequency of Hz. have been used for wrist watches in order to obtain greater accuracy.

More accurate timing is obtained by the use of tuning forks or like oscillators. Oscillators of this type have a substantially greater accuracy than watches provided with balance wheels, and operate at frequencies of between 100 and 1,000 Hz. Since this range of oscillations is audible, frequently disturbing oscillations are produced. A reduction of the frequency in tuning fork timing oscillators to an inaudible frequency between and 50 Hz. would cause substantial constructive difficulties, and the mechanical stability would be very low.

In order to obtain a frequency in a range lower than the audible range of oscillations, particularly for alarm clocks which are preferably noiseless, prestressed torsion bands have been used to which permanently magnetic discs are secured. Since the material of which torsion bands are made tends to fatigue after prolonged use, accuracy cannot be maintained for a considerable time.

It is therefore desirable to construct the time tested balance wheel oscillators in such a manner that they operate at a frequency higher than the usual frequency of 5 Hz. However, such constructions are more expensive and require greater precision.

It has been proposed to operate timing oscillators at a lower amplitude and higher oscillation frequency. For this purpose a rotary oscillator has been biassed by a short stiff spiral spring. However, the oscillation under the influence of such springs is not linear, and regulating and adjustment to a predetermined frequency of oscillation is very difficult.

SUMMARY OF THE INVENTION It is one object of the invention to provide a timing oscillator in the form' of a balance means which is of simple construction, inexpensively manufactured, and operates at a substantially higher frequency than conventional balance oscillators, without producing oscillations at an audible frequency.

A balance oscillator is known in which a return torque is produced by a spring which engages the balance means only shortly before and after the reversal ofthe oscillation, and is stressed and then again unstressed. In this manner, no harmonic oscillations can be obtained, since the return torque of the spring does not follow I-Iookes law due to the fact that the return torque of the spring does not vary in accordance with a linear function of the angle of oscillation of the oscillator. The arrangement of the prior art is not suitable for timing operations during a long time, when great accuracy is required.

The present invention overcomes this disadvantage by providing an oscillator arrangement with a rod-shaped resilient means extending either parallel to the axis of oscillation closely spaced from the same, or extending in axial direction of the oscillator. The resilient means is connected with the oscillator, such as the balance wheel, during the entire oscillation. Due to this arrangement, all above-explained disadvantages according to the prior art are overcome since the continuous torque action of the resilient means on the balance means produces, at least at a small amplitude, a return torque which is proportionate to the increasing and decreasing angle of oscillation.

One embodiment of the invention comprises balance means having an axisi mounting means supporting the balance means for movement about the axis between end positions when receiving driving impulses; and elongated resilient means,

either a single spring rod, or a pair of parallel diametrically disposed spring rods, extending in direction of the axis and having first end part means connected with the balance means for movement about the axis, and second end part means mounted on the mounting means nonmovably about the axis.

The resilient means tend to assume a position in which the balance means is in a central position between its end positions, and being continuously stressed during movement of the balance means to either end position so that the balance means is continuously biassed toward the central position during movement of the balance means from either end position to the central position.

This construction has not only the advantage of being very simple and consisting of few parts, but also the advantage that the low mechanical stress of the resilient means which produce the return torque, results in an accurate timing of the oscillation frequency for a long period of time. Of particular importance regarding the low noise level of the oscillator is that the rod-shaped resilient means can be dimensioned in relation to the mass and drive torque of the balance means in such a manner that an oscillation frequency in the inaudible range between 10 and 60 Hz. can be obtained at an oscillation amplitude of between 10 and 20.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial sectional view of a first embodiment in which a pair of resilient rods is slidingly connected with a balance wheel;

FIG. 2 is an axial sectional view illustrating a second embodiment of the invention in which the balance wheel is mounted for axial movement on a shaft, and fixedly secured to a pair of resilient rods;

FIG. 3 is an axial sectional view illustrating a third embodiment in which a pair of resilient rods is secured to the balance wheel at one pair of ends, and has another pair of ends secured to springs;

FIG. 4 is a schematic axial sectional view illustrating a fourth embodiment in which a single resilient rod is coaxially secured to the balance means;

FIG. 5 is a fragmentary axial section illustrating a modification providing a magnetic bearing for the balance shaft of FIG.

FIG. 6 is a fragmentary cross section taken along line A-B in FIG. 5; and

FIG. 7 is a fragmentary sectional view illustrating a modified magnetic bearing for the embodiment of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In all embodiments of the invention, the balance wheel 1 receives in a conventional manner drive impulses by a mechanical or electrodynamic drive means which is actuated in the neutral central position of the balance wheel and turns the same against the return torque exerted by the resilient means, alternatively in one or the other direction of rotation. After arriving at the end positions, in which the balance wheel is braked to a stop, the return torque of the resilient means biases the balance wheel toward the central position where it receives either a new drive impulse in the opposite direction, or continues to move due to inertia to the other end position.

Referring now to FIG. 1, the balance wheel 1 is fixedly secured to the balance shaft 2 which is mounted in center bearings 5 and 6 in walls 3 and 4 of mounting means of a clock or watch, not shown. Wall 4 carries a pair of adjusting bolts 9 which are biassed by coil springs 7, and have threaded portions 8 engaged by nuts 11. The adjusting plate 10 is carried by the bolts 9 and has a threaded bore into which an adjusting screw 12 is threaded whose free end abuts wall 4, and more particularly the bearing 6. By turning adjusting screw 12, the plate 10 is moved away from wall 4 and coil springs 7 are resiliently compressed or relieved.

A pair of resilient rods 13, which may be wires, are fixedly secured in bores of plate 10, and can be adjusted with the same. The free ends of rods 13 project through polished jewel bearings 15 and can slide in the same.

During alternating oscillations of balance wheel 1 in opposite directions with shaft 2, the resilient rods 13 are altematively bent in opposite directions, and brake the balance wheel 1 to a stop in two end positions, whereupon the resilient rods act on the balance wheel to return the same to a center position shown in FIG. 1. During the oscillations, the resilient rods 13 slide in the bores of

bearings

15 and 16, but the friction is negligible due to the provision of the jewels 16. The effective length of the resilient rods 13, and thereby the oscillation frequency of the balance wheel 1 can be adjusted by means of adjusting screw 12. The parts of the oscillator arrangement, and the watch parts driven by the same, are designed in such a manner that the oscillations take place at a frequency which is between 5 and 10 times as great as the frequency of conventional balance arrangements, and take place at an amplitude of between 10 and At such amplitudes, the damping of the oscillation produced by the friction of the resilient rods 13 in the

bearings

15, 16 is greatly reduced.

The openings 14 in wall 4 permit free movement of the resilient rods 13. The ends of rods 13 which are connected with the balance wheel 1 are displaced in circumferential direction which requires longitudinal sliding of resilient rods 13 in the

bearings

5 and 16. Plate 10 secures the other ends of the resilient rods against circumferential and axial movements.

In the embodiment of FIG. 2, the balance wheel 17 has a hub 18 provided with polished jewel bearings 19 through which a tensioned wire 20 passes so that the balance wheel 17 cannot only oscillate about the axis of wire 20, but also move along the same in axial direction. The wire 20 passes through openings in two supporting walls 21 and 22 and is secured to tensioning

members

23 and 24. Resilient rods 25 are secured to a wall 22 at one pair of ends, and also fixedly secured to the balance wheel at the other pair of ends thereof. A permanent ring-shaped magnet or a magnetizable ring 29 is secured to one end face of hub 18, and cooperates with an annular permanent magnet 28 mounted in an adjusting screw 26 which is mounted in a bore of wall 21 and permits an adjustment of the distance of permanent magnet 28 from the magnetic ring 29. An opening is provided for the tensioned wire shaft 20.

When balance wheel 17 receives driving impulses in a central position for moving toward one or the other end position about wire 20, the circumferential displacement of the ends of resilient rods 25 by the oscillating balance wheel 17 causes an axial sliding of the balance wheel along the tensioned wire 20. Due to the provision of jewel bearings 19, the friction between the balance wheel and wire 20 is negligible. The magnet 28 acts on the magnetic ring 29 to produce a return torque counteracting the oscillations toward the end positions. This torque is small as compared with the return torque produced by the resilient rods 25, but in order to adjust the oscillation frequency, it is only necessary to move magnet 28 by means of screw 26 toward or away from the hub 18 of the balance wheel. The permanent magnet 28, attracting magnetic ring 29 with balance wheel 17 and resilient rods 25, slightly pretensions resilient rods 25 so that the influence of the weight of the balance wheel 17 on resilient rods 25 is reduced.

The embodiment of FIG. 2 has the advantage that the friction of the balance wheel 17 on the tensioned wire 20 is substantially lower than the friction between the resilient rods 13 and the balance wheel 1 in the embodiment of FIG. 1, so that the quality of the oscillator system is substantially improved. The required adaptation of the drive means of the balance wheel 17 to the axial displacement of the same is constructively simple, and need not be considered in view of the improvement of the operation.

In the embodiment of FIG. 3, the balance wheel 30 is fixedly connected with a balance shaft 31 which is mounted at the ends in

jewel bearings

34 and 37 provided in walls 32 and 36. A cover jewel 35 covers jewel 34 and rearwardly thereof, a pennanent magnet 42 is inserted into the bushing 33. The jewel 37 is covered by a jewel 38 which is secured to a plate 39 attached by a screw to wall 36. A pair of leaf springs 41 is secured by screws to wall 36 and is secured to the pair of resilient rods 40. Springs 41 can yield in axial direction, but cannot be twisted in circumferential direction about the axis of shaft 3 1.

In the embodiment of FIG. 3, oscillation of balance wheel 30 causes circumferential displacement of the fixedly secured ends of resilient rods 40 so that the other ends of the same are displaced in axial direction which requires yield of springs 41. Since there are no sliding parts as in the embodiments of FIGS. 1 and 2, the friction of the oscillator system is eliminated. The axial force exerted by springs 41 through resilient rods 40 on the balance wheel 30 and shaft 31, is compensated by the magnetic force exerted by permanent magnet 42 on shaft 31.

The embodiments of FIGS. 1 to 3 have in common that a pair of resilient rods is diametrically disposed in relation to the axis of oscillation and twisted in circumferential direction during oscillations of the balance wheel.

In the embodiment of FIG. 4, only a single resilient rod 50 is provided, one end of which is fixedly secured to a wall 51 forming part of mounting means of the watch or clock, which also include a wall 46. The free end of the resilient rod 50 is secured to the end face of a shaft 45 coaxial with the same. The other end of shaft 45 is mounted in an end bearing in wall 46 which is preferably constructed as shown in FIG. 7 or FIG. 5.

Two balance discs 43 and 44 are secured to shaft 45 and oscillate with the same when receiving driving impulses. On the confronting surfaces of balance discs 43 and 44, permanent magnets 47 are fixed which cooperate with the force field produced by energized windings 48 and 49. When the same are energized at timed intervals in a conventional manner, balance means 43, 44, 45 is oscillated from a central position to two end positions, and since resilient rod 50 is secured to the balance means, the end of the same which is secured to the balance means, also oscillates about the axis of the system in the direction of the arrow C, while the torsion rod 50 is twisted and shortened, and then obtains its normal length again. Since the end of resilient rod 50, secured to wall 51, cannot turn, resilient rod 50 produces a return torque tending to move balance means 43, 44 from either end position to a central position in which it may receive a driving impulse to move to the other end position. The bearing 46a in plate 46 guides the shaft 45 in radial direction for free rotation and for free axial movement so that it is not necessary to prestress the resilient torsion rod 50, eliminating difficulties in this respect. Since the torsion rod 50 is not stressed, the

frequency of oscillation can be maintained for a long period of time, and the oscillator system has good isochronal characteristics at temperature changes.

As compared with embodiments of FIGS. 1 to 3 in which at least two resilient rods are required for producing the return torque, the embodiment of FIG. 4 has the advantage that the oscillations of the balance wheel are not transmitted, or transmitted to a very low degree, to the clockwork mechanism which is of particular importance for oscillator systems operating at high frequencies. Particularly due to the central arrangement of the resilient rod 50, improved isochronism is obtained.

The end bearing of shaft 45 may be constructed in different ways, and two preferred constructions are illustrated in FIGS. 5 and 6, and FIG. 7 in which magnetic bearings are shown.

The end 52 of shaft 50 is constructed as a permanent magnet whose end face is located opposite the end face of another permanent magnet of opposite polarity secured by an adjusting screw 55 in the wall 46. The permanent magnet 53 can be adjusted in axial direction to reduce or increase a gap formed with the permanent magnet portion 52 of the balance shaft whereby the self-frequency of the system is adjusted. Since no friction occurs between shaft portion 52 and bearing portion 53, the accuracy of the system is improved. ln order to prevent lateral or radial displacement of the magnetic end portion 52 of balance shaft 50, the same is surrounded by an annular permanent magnet 54 whose polarity is the same as the polarity of the respective portion of magnetic end portion 52 so that end portion 52 is magnetically urged to a central position in which its end face is located directly opposite the end face of the permanent bearing magnet 53.

In the embodiment of FIG. 7, an adjusting screw 57 is threaded into wall 46 and carries a permanent bearing magnet 56 formed with a conical recess whose shape corresponds to the conical end of a permanently magnetic portion 58 of shaft 59. The polarity of

permanent magnets

58 and 56 is selected so that permanent magnet 56 attracts the end of shaft 59. The gap between the cooperating conical surfaces of

magnets

58 and 56, prevents any friction during rotation of the balance means. By adjustment of screw 57, the self-frequency of the oscillator system can be adjusted.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of oscillator arrangements for clocks and watches differing from the types described above.

While the invention has been illustrated and described as embodied in a balance means continuously biassed toward a center position by an elongated resilient means extending in the direction of the axis of the system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others 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 and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. Biassed oscillator arrangement comprising balance means having an axis; mounting means supporting said balance means for movement about said axis in a plane perpendicular to said axis so that said balance means is oscillated between two end positions when receiving driving impulses; and elongated resilient means extending in the direction of said axis and having a first end part means connected with said balance means for movement about said axis, said first end part means of said resilient means being mounted in said balance means for longitudinal movement relative to the same in accordance with the displacement of said first end part means during angular oscillation with said balance means and a second end part means fixedly mounted on said mounting means nonmovably about said axis and in said longitudinal direction, said elongated resilient means tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said balance means is continuously biassed toward said central position during movement of said balance means from either end position to said central position.

2. Biassed oscillator arrangement comprising balance means having an axis; mounting means supporting said balance means for movement about and along said axis so that said balance means is oscillated between two end positions when receiving driving impulses; and elongated resilient means extending in the direction of said axis and having a first end part means connected with said balance means for movement about said axis and nonmovable in the longitudinal direction, and a second end part means mounted on said mounting means nonmovably about said axis and in said longitudinal direction, said elongated resilient means tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said balance means is continuously biased toward said central position during movement of said balance means from either end position to said central position, and is axially displaced in accordance with displacement of said first end part means during angular oscillation with said balance means.

3. Biassed oscillator arrangement comprising balance means having an axis; mounting means supporting said balance means for movement about said axis in a plane perpendicular to said axis so that said balance means is oscillated between two end positions when receiving driving impulses; elongated resilient means extending in the direction of said axis and having a first end part means connected with said balance means for movement about said axis, said first end part means being mounted on said balance means nonmovably in longitudinal direction; and a second end part means mounted on said mounting means nonmovably about said axis, said mounting means including spring means supporting said second end part means of said resilient means for longitudinal movement while blocking movement of said second end part means of said resilient means about said axis; said elongated resilient means tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said balance means is continuously biassed toward said central position during movement of said balance means from either end position to said central position; and a permanent magnet located on the side of said balance means remote from said spring means and resilient means and attracting said balance means to counteract the force exerted by said spring means on said balance means during oscillation of the same.

4. Biassed oscillator arrangement comprising balance means having an axis, said balance means including a balance wheel and a shaft fixedly carrying said balance wheel and mounted on said mounting means for rotation with said balance wheel about said axis; mounting means supporting said balance means for movement about said axis so that said balance means is oscillated between two end positions when receiving driving impulses; an elongated resilient rod concentric with said axis and having a first end part means connected with said balance means for movement about said axis and secured to one end of said shaft for angular movement therewith about said axis, and a second end part means fixedly secured to said mounting means, said elongated resilient means tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said balance means is continuously biassed toward said central position during movement of said balance means from either end position to said central position.

5. Oscillator arrangement as claimed in claim 4 wherein said mounting means include a bearing for the shaft end portion at the other end of said shaft.

6. Oscillator arrangement as claimed in claim 5 wherein said bearing includes a magnetic part, and wherein said shaft end portion at the other end of said shaft is spaced by a gap from said magnetic part and magnetically attracted by the same.

7. Oscillator arrangement as claimed in claim 6 wherein said magnetic part has a conical recess, and wherein said end portion at the other end of said shaft is conical and forms in said recess a gap of substantially unifonn thickness.

8. Oscillator arrangement as claimed in claim 6 wherein said end portion at the other end of said shaft is magnetic; and comprising an annular magnet surrounding said end portion and urging said other end to a position registering with said magnetic part.

9. Oscillator arrangement as claimed in claim 6 wherein said mounting means include adjusting means supporting said magnetic part for adjusting the position of the same in axial direction toward and away from said other end of said shaft.

10. Oscillator arrangement as claimed in claim 4 wherein said resilient means exerts on said balance means during movement to said central position such a torque, and resists the movement to said end positions with such a torque that said balance means oscillate at an inaudible frequency between 10 and 50 Hertz, and at an amplitude between 10 and ll. Biassed oscillator arrangement comprising balance means having an axis; mounting means supporting said balance means for movement about said axis so that said balance means is oscillated between two end positions when receiving driving impulses; and elongated resilient means including two resilient rods disposed diametrically to said axis and being parallel to the same and to each other, and having a first pair of end parts connected with said balance means for movement about said axis, and a second pair of end parts mounted on said mounting means nonmovably about said axis, said resilient rods tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said balance means is continuously biassed toward said central position during movement of said balance means from either end position to said central position.

12. Oscillator arrangement as claimed in claim 11 wherein said mounting means include adjusting means for adjusting said rods in axial direction for adjusting the effective length of said rods whereby the oscillation frequency of said balance means is adjusted.

l3. Oscillator arrangement as claimed in claim 11 wherein said mounting means include a tensioned wire, wherein said balance means is mounted on said tensioned wire for rotary and axial movement; wherein said one pair of ends is fixedly connected with said balance means and said other pair of ends is fixedly connected with said mounting means so that said balance means is axially displaced along said tensioned wire.

14. Oscillator arrangement as claimed in claim 13 wherein said balance means includes a hub having a magnetizable end portion; and comprising adjusting means mounted on said mounting means and including a permanent magnet axially spaced from said magnetizable end portion and being movable toward and away from the same so that the oscillation frequency of said balance means can be adjusted.

l5. Oscillator arrangement as claimed in claim 14 wherein said magnetizable end portion is a permanent magnet.

16. Oscillator arrangement comprising mounting means; balance mass means having an axis of rotation and on one side a shaft portion coaxial with said axis; a resilient unpretensioned torsion rod extending along said axis and having one end part fixedly secured to said mounting means and the other end part fixedly secured to the other side of said balance mass means, said torsion rod tending to assume an untensioned position in which said balance mass means is in a neutral position so that when said balance mass means is oscillated about said axis between two end positions by driving impulses, said torsion rod is stressed, twisted, and shortened whereby said balance mass means also moves in axial direction, said torsion rod exerting on said balance mass means during movement to said neutral position such a torque, and resisting the movement to said end positions with such a torque that said balance mass means oscillates at an inaudible frequency between 10 Hz. and 50 BL, and at an amplitude between 10 and 2Q"; and bearing means on said mounting means located on said one side of said balance mass means for axially and rotationally guiding said shaft portion during axial and rotary movement of said balance mass means.

17. Oscillator arrangement as claimed in claim 16 wherein said bearing includes magnetic means for preventing transverse movements of said shaft portion.

18. Oscillator arrangement as claimed in claim 16 wherein said axis is vertical; wherein the upper end part of said torsion rod is secured to said mounting means and the lower end part of said torsion rod is secured to the upper side of said balance mass means; and wherein said bearing means is located under said balance mass means.

Claims

7. Oscillator arrangement as claimed in claim 6 wherein said magnetic part has a conical recess, and wherein said end portion at the other end of said shaft is conical and forms in said recess a gap of substantially uniform thickness.

10. Oscillator arrangement as claimed in claim 4 wherein said resilient means exerts on said balance means during movement to said central position such a torque, and resists the movement to said end positions with such a torque that said balance means oscillate at an inaudible frequency between 10 and 50 Hertz, and at an amplitude between 10* and 20* .

11. Biassed oscillator arrangement comprising balance means having an axis; mounting means supporting said balance means for movement about said axis so that said balance means is oscillated between two end positions when receiving driving impulses; and elongated resilient means including two resilient rods disposed diametrically to said axis and being parallel to the same and to each other, and having a first pair of end parts connected with said balance means for movement about said axis, and a second pair of end parts mounted on said mounting means nonmovably about said axis, said resilient rods tending to assume a position in which said balance means is in a central position between said end positions, and being continuously stressed during movement of said balance means to either end position so that said Balance means is continuously biassed toward said central position during movement of said balance means from either end position to said central position.

13. Oscillator arrangement as claimed in claim 11 wherein said mounting means include a tensioned wire, wherein said balance means is mounted on said tensioned wire for rotary and axial movement; wherein said one pair of ends is fixedly connected with said balance means and said other pair of ends is fixedly connected with said mounting means so that said balance means is axially displaced along said tensioned wire.

15. Oscillator arrangement as claimed in claim 14 wherein said magnetizable end portion is a permanent magnet.

16. Oscillator arrangement comprising mounting means; balance mass means having an axis of rotation and on one side a shaft portion coaxial with said axis; a resilient unpretensioned torsion rod extending along said axis and having one end part fixedly secured to said mounting means and the other end part fixedly secured to the other side of said balance mass means, said torsion rod tending to assume an untensioned position in which said balance mass means is in a neutral position so that when said balance mass means is oscillated about said axis between two end positions by driving impulses, said torsion rod is stressed, twisted, and shortened whereby said balance mass means also moves in axial direction, said torsion rod exerting on said balance mass means during movement to said neutral position such a torque, and resisting the movement to said end positions with such a torque that said balance mass means oscillates at an inaudible frequency between 10 Hz. and 50 Hz., and at an amplitude between 10* and 20*; and bearing means on said mounting means located on said one side of said balance mass means for axially and rotationally guiding said shaft portion during axial and rotary movement of said balance mass means.