US3318087A

US3318087A - Torsion oscillator

Info

Publication number: US3318087A
Application number: US470511A
Authority: US
Inventors: Favre Robert
Original assignee: Fabriques Movado
Current assignee: Movado Watch Co SA
Priority date: 1964-07-10
Filing date: 1965-07-08
Publication date: 1967-05-09
Anticipated expiration: 1984-05-09
Also published as: CH563765A4; CH462044A; CH904764A4; GB1106098A; DE1258803B; CH452443A

Description

May 1967 R. FAVRE TORSION OSCILLATOR 3 Sheets-Sheet 1 Filed July 8, 1965 y 1967 R. FAVRE 3,318,087

TORS ION OSC ILLATOR Filed July 8, 1965 3 Sheets-Sheet 2 y 1 1967 R. FAVRE 3,318,087

TORSION OSCILLATOR Filed July 8, 1965 3 Sheets-Sheet 3 United States Patent 3,318,087 TORSION OSCILLATOR Robert Favre, Lausanne, Switzerland, assignor t0 Fabriques Movado and Manufacture des Montres Universal, Perret Freres S.A., Geneva, Switzerland Filed July 8, 1965, Ser. No. 470,511 Claims priority, application Switzerland, July 10, 1964, 9,047/64; Apr. 22, 1965, 5,637/65 Claims. (Cl. 58-131) Torsion oscillators are already known in the watchmaking industry, which oscillators are constituted by torsion springs of which one end is secured to the clockwork frame, whereas the other end carries a mass cooperating with the means for the upkeep of its oscillations.

In certain structures, springs with a cross-shaped crosssection have been used, said crosssection being obtained by machining a cylinder or by associating four flat strips.

It has also been proposed to fit the medial section of the spring inside a support rigid with the frame, so as to allow the fitting at both ends of said spring of a mass oscillating with a difference in phase between such masses with a view to ensuring the dynamic balance of the whole arrangement.

Although this leads to very satisfactory results, the torsion oscillators equipped with'such springs have a frequency of oscillation which varies according to the slope given to the oscillatory axis.

The present invention has now for its object the provision of an oscillator wherein the position assumed by the oscillator has an effect which is considerably reduced when compared with all known oscillators. Said improved torsion oscillator includes at least one torsion spring secured on the one hand to the frame and on the other hand to at least one oscillatory mass.

According to a main feature of the invention, said spring includes chiefly two sections extending to either side of the oscillatory axis and forming with each other an angle dilferent from 180, the two sections being interconnected at least in their medial area in the vicinity of the oscillatory axis while at least one of said sections is elastically secured to the frame.

All the springs used hitherto have furthermore the drawback of a non-linear distorsion, which leads to a binding between the values of the frequency of oscillation and their amplitude. By suitably selecting the shape of the spring, it is however possible to reduce to a large extent such as non-linearity of distorsion.

Now, according to a further feature of the invention, the torsion spring is cut so as to form sections which are perpendicular to its torsional axis, which sections are located and sized so as to operate chiefly under flexional condition.

However, in the case of a simple spring such as that defined hereinabove, the mechanical stressing of the spring is concentrated within limited areas, particularly at the points where the spring is fitted in the clockwork frame and in the oscillatory mass. Such local stresses result in a lowering of the overtorsioning' coeflicient of the oscillator, the actually operative length of the spring being very small.

Under such conditions, it has been attempted to produce a structure wherein the springs operate in a more rational manner so as to improve the overtensioning factor of the oscillator and to reduce the value of the non-linear component produced by the torsion with reference to the linear components produced by flexion or bending.

According to a still further feature of the invention, the spring is constituted by a strip folded into meanders or is tortuous-shaped so as to increase its operative length; said spring operating chiefly under flexional conditions is 3,318,087 Patented May 9, 1967 thus constituted by sections the shape of which satisfies at least approximately the condition of equal or uniform resistance.

The smooth distribution of the deformations along the length of the spring leads to a more rational use of the developed length of the springs and it has for its result an improved resonant factor while the stresses due to the fitting of the spring are reduced.

Further features and advantages of the invention will appear in the reading of the following description of various embodiments of the invention given by way of examples in a non-limiting sense and illustrated in the accompanying drawings wherein:

FIG. 1 is an elevational view of an oscillator incorporating a spring of a simple Winding shape.

FIGS. 2 and 3 are plan views at two different stages of operation of the oscillator illustrated in FIG. 1.

FIG. 4 illustrates a spring assuming an improved winding shape.

FIG. 5 illustrates a double spring constituted by two elementary springs of the type disclosed by FIG. 4 when arranged in a common plane.

FIG. 5a shows the springs according to FIG. 5 after they have been bent.

FIG. 6 illustrates a spring of the type disclosed in FIG. 4 associated with means for securing it to its frame.

FIG. 7 illustrates a further spring including two twin elementary springs when arranged in a common plane.

FIG. 7a illustrates the spring according to FIG. 7 after it has been folded.

FIG. 8 illustrates an oscillatory mass fitted on two springs.

The oscillator illustrated in FIG. 1 includes four elementary springs 1 arranged in cross-formation and each. constituted by a blade of a general approximately rectangular shape, said blades being provided with slots cut perpendicularly to the torsional axis of the oscillator so that the successive sections form a Wavy shaped structure.

Each elementary spring of which two are shown in FIG. 1 has two

ends

2 and 3 which are each fitted in a

ring

4 or 5, respectively, carrying an arm which is not illustrated and the outer end of which cooperates with the electronic means provided for the upkeep of the movements of the clockwork.

The central section of each elementary spring carries a medial elastic radially directed tongue 6 adapted to be secured to a stationary support 7 rigid with the frame of the clockwork, said tongue extending between two radially directed U-shaped sections.

The torsion of the spring as a whole is obtained by a mere bending of the arms 8 and 9 of the U-shaped sections arranged perpendicularly to the torsional axis of the spring with reference to which axis the elementary springs extend radially. FIG. 2 illustrates the spring when inoperative whereas FIG. 3 shows it after a torsional stress, that is after a relative bending of the arms 8 and 9 of the different U-shaped sections of the elementary springs.

In the embodiment illustrated, intended for incorporation with a wrist watch, the spring is given for instance a length of 4 mm. and a thickness of 0.08 mm. The oscillator extends over about one degree. The alloy forming the spring should be of a self-compensating type and have a low thermal conductivity.

The frequency of oscillation is thus comparatively independent of amplitude. Furthermore, the wavy outline of the elementary springs allows obtaining, for a same height between the support and the oscillating mass, an operative length which is much larger, which leads to a structure of a reduced height together with a reduction in the frequency of oscillation.

The accuracy of the fitting plays also a lesser part in the definition of the accurate operative length of the springs, while the absence of any auxiliary distorsion allows a reduction in the clamping of the springs and this is important by reason of the difficulties generally encountered in the execution of a rigid and accurate fitting.

Lastly, the medial tongues 6 allow executing readily the elastic coupling required for the synchronized operation of the two masses oscillating with a difference in phase between them.

Instead of resorting to four independent springs, it is possible and even advantageous to associate the springs two by two by means of a connection between their medial areas. Such twin springs are obtained by folding at 90 a blade the outline of which is obtained by cuts such as those illustrated in FIG. 1, the left-hand and right-hand elementary springs of said FIG. 1 being considered in such a case as rigid with each other along the medial areas 10.

FIG. 4 illustrates a spring of an improved shape. It includes a succession of juxtaposed sections constituted by the alternation of

flat sections

1, 3, 5, 3, 1' parallel with the oscillatory axis 10 and of

flat sections

2, 4, 4, 2 perpendicular to said axis.

The sections parallel with the torsional axis operate substantially under torsional conditions while those which are perpendicular thereto operate substantially under fiexional conditions. The length of the

elements

2 and 4 being several times larger than that of the

elements

1, 3 and 5, the flexional stresses will predominate, which is an advantage since the latter follow a linear law, whereas the torsional stresses do not.

With a view to distributing as well as possible the stresses throughout the length of the spring, the latter is of a shape approximately matching the condition of equal or uniform resistance. To this end, the breadth of the elements perpendicular to the axis of oscillation 10 is reduced when the points considered thereon are further remote from said axis. This is the case for the

sections

2 and 4 whereas the

sections

3 and 5 which are parallel with the oscillatory axis are too short for them to be given a more elaborate shape. The fitting of the spring is performed along the terminal edges or

sections

1 and 1. The medial section 5 of the spring is secured to the clockwork plate in a manner to be described hereinafter with reference to FIG. 6.

FIG. 5 illustrates .an embodiment wherein the springs such as those illustrated in FIG. 4 are associated two by two and form a single member obtained through stamping and folded thereafter along a vertical axis of symmetry which allows obtaining two elementary springs forming together .an angle approximating 90 as illustrated in FIG. 5a. The connection ensured between the two

ends

1 and 1 of the two elementary springs increases considerably the rigidity of the fitting even in the case of a comparatively light clamping, the torsional stress exerted on one of the elementary springs being absorbed by the fitted end of the other spring. The radius of curvature of the fold is such that it allows associating two such pairs of elementary springs although the operation of the oscillator is in principle possible with a single pair of elementary springs in spite of the drawbacks arising through the asymmetry in the distribution of the stresses.

The means connecting the springs with the clockwork plate may advantageously form part of a fraction at least of the associated springs.

FIG. 6 illustrates a spring fitted through its

ends

1 and 1 and including an extension forming a securing lug 6 which is in one with the medial portion of the spring. Said lug is provided at its outer end with securing holes 8 and with a notch 7 registering with the torsional axis so as to allow the association of two identical springs in crossed relationship. As .a rule, a spring arrangement should include only two securing lugs forming preferably with each other an angle approximating A third spring may be fitted along the plane bisecting the plane formed by the two first elementary springs and lugs; an exaggerated number of securing lugs is however detrimental since such an arrangement leads to securing stresses which are highly objectionable as far as the isochronism of the oscillator is concerned.

FIG. 7 illustrates a further embodiment of two springs obtained through bending. The two elementary springs are interconnected by three

bridges

15, 16 and 17 located respectively between the ends of the springs and in their medial areas. It is sufiicient, in principle, to provide only one bridge, to wit; the medial bridge 17. Said bridge 17 is connected through tongues 7 and 7' with the securing lugs 6 and 6. Said tongues are given a shape corresponding to that of a solid member of equal or uniform resistance, so that they are narrow at their ends facing the oscillatory axis in order to disturb the oscillations to a minimum extent; said tongues flare outwardly so as to have a sufficient resistance against stresses parallel with the oscillatory axis, which may arise under the action of the oscillatory masses. The forces perpendicular to the oscillatory axis are absorbed by the connecting bridge 17 after folding of the spring in the manner illustrated in FIG. 7a.

The torsion to which the securing lugs are subjected during the oscillation of the spring may be still further reduced by the insertion of a corner piece 9 which is suitably located across the elementary springs, so as to give the system a greater rigidity.

The corner piece may also be located centrally as illustrated by the dotted lines 10. In the case where two oscillatory masses are used, which are respectively secured to the

ends

1 and 1 and oscillate in opposed phase-relationship, it is however essential for the securing lugs to retain a sufiicient elasticity when subjected to the oscillatory movement so as to ensure the mechanical coupling between the two oscillatory masses.

FIG. 8 shows in plan View an embodiment of a torsion oscillator incorporating springs of the type described hereinabove. The two folded elementary springs are secured to two areas 11 of the clockwork plate through their securing lugs 6, while their terminal edges 1 .are fitted in an oscillating mass constituted by four steel sector-shaped members 12 between which said edegs 1 are clamped.

The elastic ring 13 which is slotted at 18 surrounds the sector-shaped members and holds them in position during their assembly before the outer ring 14 is urged gith a tight fit round the elastic ring 13 to hold same ast.

It should be remarked that since the springs include sections parallel with the oscillatory axis which operate under torsional conditions, while the oscillating masses may move freely in an axial direction, no tensioning or compressing force can appear in the springs or in the oscillatory masses in contradistinction with the structures incorporating springs perpendicular to the axis and operating under torsional conditions. while the oscillating mass is secured to the ends of said springs.

The oscillator illustrated in FIG. 8 may be executed with numerous modifications as concerns the number of elementary springs, the number of securing points or the number of fitting areas. Said oscillator includes generally oscillatory masses secured to the opposite ends 1 and 1 of the spring and oscillating in opposed phase relationship so as to ensure the dynamic balance of the spring arrangement.

In particular, the angle between the two halves of the folded spring may be different from 90 and as already mentioned hereinabove, the

bridges

15 and 16 connecting said halves are not essential and may be omitted.

The maintenance of the oscillations may be performed for instance electromagnetically as disclosed for instance 7 in the French Patent 1,240,964. Numerous modifications and in particular more intricate shapes obtained with the aid of calculation or experimentation may obviously be imagined, within the scope of the invention as defined in the accompanying claims.

What I claim is:

1. A torsion oscillator for a clockwork movement carried inside a frame comprising at least one flexible, metallic, blade of general rectangular shape having a vertical axis of symmetry and consisting of two inter-connected elementary spring parts forming with each other an angle other than 180 along said vetrical axis, said axis forming the oscillatory axis for said elementary spring parts, said blade having radial slots cut therein perpendicularly to said axis thereby forming in each of said elementary springs a succession of sections extending outwardly and radially from said axis so as to increase the operative length of said elementary springs, said blade having medial and terminal sections, said terminal sections being secured to an oscillatory mass, said oscillator operating mainly under flexional conditions.

2. A torsion oscillator for a clockwork movement comprising two normally flat blades each having a vertical axis of symmetry and juxtaposed on either side of said axis of symmetry forming the torsional axis, each of said blades being folded along said vertical axis of symmetry thereof thereby forming two elementary springs angularly displaced by about 90 and having medial and terminal sections, each of said blades being cut axially to form several radially directed slots thus forming in said elementary springs sections alternately parallel and perpendicular to said axis, said sections parallel to said axis operating under substantially torsional conditions; said sections perpendicular to said axis operating under substantially flexional conditions, owing to said sections perpendicular to said axis being substantially longer than said parallel sections, said terminal sections of said blades being secured to oscillatory masses; and means securing said medial sections of said blades to the plate of said movement.

3. A torsion oscillator for watch or clockwork movement comprising at least one normally flat spring blade composed of low thermal conductivity, self compensating alloy material, said blade being folded along a vertical axis of symmetry thereby forming two elementary springs angularly displaced by about 90 and having medial and terminal sections, said blade having radial slots cut therein perpendicular to said axis thereby forming in each of said elementary springs a succession of sections extending outwardly and radially so as to increase the operative length of said springs, said sections being alternately parallel and perpendicular to said axis, said sections parallel to said axis operating under substantially torsional conditions; said sections perpendicular to said axis operating under substantially flexional conditions, the length of said sections perpendicular to said axis being substantially longer than said parallel sections; said terminal sections being secured to oscillatory masses and means securing said medial section of said blade to the plate of said movement.

4. A torsion oscillator for a clockwork movement carried inside a frame and comprising at least one flexible, metallic blade having a vertical axis of symmetry and consisting of two inter-connected spring parts forming with each other two inter-connected elementary springs along said vertical axis, said axis thus forming the oscillatory axis for said elementary springs, said blade having radial slots cut therein perpendicularly to said axis extending forming in each of said elementary springs a sucession of sections extending outwardly and radially from said axis to increase the operative length of said springs, said blade having medial and terminal sections, each elementary spring having a securing lug integral with said medial section, said securing lugs forming therebetween an angle of about and a third spring fitted along a plane bisecting the angle formed by said elementary springs and said lugs, said terminal sections of said springs being secured to an oscillatory mass, said oscillator operating mainly under flexional conditions.

5. A torsion oscillator for clockwork movements carried inside a frame comprising a pair of flexible blades each having a vertical axis of symmetry and bent to either side of said axis, each blade having cut therein slots extending radially of said axis thus forming a succession of sections extending outwardly of said axis; an oscillating mass secured to at least one end of the axial length of said blades, a tongue rigid with each blade extending in its plane at a point substantially at mid-distance between the ends of its axial length and secured to the clockwork frame, said tongues having a fraction at least of their radial length in outwardly flaring outline to form members of a substantially uniform tensional resistance against stresses parallel to the oscillatory axis.

References Cited by the Examiner UNITED STATES PATENTS 2,939,971 6/1960 Holt 310-15 3,201,932 8/1965 Sparing et a1. 5823 FOREIGN PATENTS 929,566 6/ 1963 Great Britain.

RICHARD B. WH.KINSON, Primary Examiner, C}. F, BAKER, Assistant Examiner,

Claims

1. A TORSION OSCILLATOR FOR A CLOCKWORK MOVEMENT CARRIED INSIDE A FRAME COMPRISING AT LEAST ONE FLEXIBLE, METALLIC, BLADE OF GENERAL RECTANGULAR SHAPE HAVING A VERTICAL AXIS OF SYMMETRY AND CONSISTING OF TWO INTER-CONNECTED ELEMENTARY SPRING PARTS FORMING WITH EACH OTHER AN ANGLE OTHER THAN 180* ALONG SAID VERTICAL AXIS, SAID AXIS FORMING THE OSCILLATORY AXIS FOR SAID ELEMENTARY SPRING PARTS, SAID BLADE HAVING RADIAL SLOTS CUT THEREIN PERPENDICULARLY TO SAID AXIS THEREBY FORMING IN EACH OF SAID ELEMENTARY SPRINGS A SUCCESSION OF SECTIONS EXTENDING OUTWARDLY AND RADIALLY FROM SAID AXIS SO AS TO INCREASE THE OPERATIVE LENGTH OF SAID ELEMENTARY SPRINGS, SAID BLADE HAVING MEDIAL AND TERMINAL SECTIONS, SAID TERMINAL SECTIONS BEING SECURED TO AN OSCILLATORY MASS, SAID OSCILLATOR OPERATING MAINLY UNDER FLEXIONAL CONDITIONS.