HK40029297B - Method and production support tooling for measuring the torque of a timepiece balance spring - Google Patents

Description

Method for measuring the moment of a timepiece balance spring and production support tool system

Technical Field

The invention relates to a method for measuring the moment of a balance spring for a timepiece oscillator, wound around a balance spring axis and comprising a collet at its inner end and an outer ring at its outer end, said collet comprising a hole whose inner surface comprises a centering surface arranged to cooperate with and center said balance spring on a spindle having a shape of revolution about said balance spring axis and defining a passage diameter in a free state of said balance spring.

The invention also relates to a production support tool system for implementing such a method for measuring the torque of a balance spring, in particular made of micromachinable material or silicon.

The present invention relates to the manufacture and development of a timepiece oscillator including a balance spring and more particularly a balance spring made of micromachinable material or silicon.

Background

Currently, during balance spring torque measurement, the angular and vertical position of the silicon or similar balance spring is maintained by a cylindrical spindle. The diameter of the cylindrical mandrel is defined as a function of the internal diameter of the collet inscribed therein. During balance spring moment measurement, the angular and vertical position of the balance spring collet is maintained by clamping the collet onto the cylindrical mandrel. This clamping is achieved by elastic deformation of the collet. The value of the clamping force is defined as a function of the diameter of the mandrel.

However, this standard working method has the following disadvantages:

the risk of chipping, i.e. micro-cracks on the edges. Since silicon is known to be a very brittle material under mechanical stress, inserting the collet of a silicon balance spring onto a dummy mandrel with a conventional cylindrical profile defined to ensure that the balance spring is held in place during its torque measurement in an automatic press-fit process creates stress in the balance spring material. These harmful stresses may lead to risks of hairspring breakages and product defects. This collapse can be critical as it can lead to early cracking of the collet and the risk of collet fracture, which will then be detected as it moves;

wear and contamination of the cylindrical spindle of the tool. The principle of a cylindrical dummy mandrel creates friction between the collet and dummy mandrel during insertion and removal of the dummy mandrel into and from the balance spring collet. In an automated process, this repeated rubbing on the plurality of balance springs can cause wear that can be a source of contamination of the dummy spindle and therefore of the balance springs. This contamination is critical in terms of the quality of the final product. This repeated rubbing will also change the profile of the dummy spindle and directly affect the maintenance of the angular and vertical position of the balance spring during the moment measurement, resulting in a loss of measurement accuracy of the balance spring moment;

it is difficult to ensure the accuracy of the alignment between the collet and the torque measuring system. The principle of a cylindrical dummy mandrel requires a high precision alignment between the clamp holding the balance spring during insertion and the dummy mandrel. As a result of the misalignment, when the collet is inserted onto the dummy mandrel, an impact or shock is created and created on the collet, presenting a significant risk of collapse;

it is difficult to hold the collet correctly with good angular and vertical reference. On a cylindrical dummy mandrel, the angular and vertical retention and referencing of the balance spring is achieved by a special design of the dummy mandrel to ensure that the collet has a low clamping force on the dummy mandrel. This clamping force, which creates stress in the collet, depends on variations in the manufacturing tolerances of the dummy mandrel and the balance spring collet. Furthermore, the danger of the collet being inserted multiple times into the cylindrical dummy mandrel is that the dummy mandrel wears due to spalling, thereby creating a forced angular orientation and play between the collet and the dummy mandrel and reducing the measurement accuracy.

European patent document No. ep2423764b1 proposes a solution that overcomes these different drawbacks by using an open mandrel instead of the usual cylindrical mandrel: the open mandrel is clamped to allow insertion of the collet and released in position of the collet so as to measure the moment of the balance spring retained by the elastic return force of the open mandrel. However, the collet is therefore subjected to further stresses during the torque measurement cycle, which can distort the measurement and/or possibly lead to breakouts. This principle also requires precise alignment of the jig to prevent deformation in the measurement axis and thus measurement interference.

Disclosure of Invention

The invention proposes to develop a method for maintaining the angular orientation and vertical position of the collet of a horological balance spring, and more particularly a balance spring made of micromachinable material or silicon, in the gravitational field during the moment of the balance spring on a production support tool system designed for an automated measuring process, the deformation of the balance spring being minimal, except for the deformation caused by the oscillation.

The solution proposed by the present invention uses the static principle of holding the balance spring at the inner end.

The invention therefore relates to a method for measuring the moment of a balance spring for a timepiece oscillator according to claim 1.

The invention also relates to a production support tool system (production support tool) for implementing the method for measuring the torque of a balance spring according to claim 21.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

fig. 1 shows a schematic perspective view of a simulated arbour in the form of an obelisk according to the invention, included in a main tool of a production support tool system arranged for measuring the torque of a balance spring of a timepiece oscillator.

Figure 2 shows, in a manner similar to figure 1, the same simulated mandrel on which the collet of the balance spring is carried, the outer ring of the balance spring being held by a holding tool arranged to grip the outer ring.

Figure 3 shows a schematic cross-section through the axis of the simulated mandrel of figure 1 of the simulated mandrel and of the holding tool carrying the balance spring and of further upper and lower tools, each of which is arranged to exert an axial thrust on the balance spring.

Figure 4 shows a schematic front view of a simulated mandrel in the form of a square pyramid, comprising inclined flat portions for guiding and/or driving functions, both on the lower shank for holding the balance spring and on the upper shank for inserting the balance spring.

Figure 5 represents a schematic front view of a simulated mandrel in the form of a square pyramid comprising an inclined flat on the lower shank for holding the balance spring and a spiral groove on the upper shank for inserting the balance spring.

Figure 6 shows a schematic partial top view of the simulated spindle of figure 5 carrying a balance spring.

Figure 7 shows a schematic partial top view of the simulated spindle of figure 4 carrying a balance spring.

Figure 8 shows a schematic partial top view of a simulated mandrel similar to figure 5 but with a rectilinear groove instead of a flat and carrying a balance spring.

Figure 9 represents a schematic front view of a production support tool system comprising the simulation mandrel of figure 4, the holding tool of figure 2, the additional tool of figure 3 and the clamp arranged to handle the balance spring.

Detailed Description

The invention relates to a method for maintaining the angular and vertical position in the gravitational field of the collet of a balance spring during the measurement of the moment of a horological balance spring 1 on a production support tool system designed for automating the measurement process, said balance spring being made in particular, but not exclusively, of micro-machinable material, silicon and silica, DLC, metallic glass, other at least partially amorphous material or similar, the deformation of which is minimal, except for the deformation produced by the oscillation.

The solution proposed by the present invention uses the static principle of holding the balance spring at the inner end. The problem is to eliminate any stress applied to the collet of the balance spring by the retaining means and thus to avoid the creation of undesirable stresses in the working coil of the balance spring and to avoid the alteration of the actual working length of the balance spring.

The invention relies on the use of a specific production support tool system 1000 comprising a main tool having, instead of a traditional cylindrical or open or elastic mandrel, a dummy mandrel (mock arbor)10, which dummy mandrel 10 is specifically designed for the gentle placement by a gripper 500 or by an operator of the collet 2 of such balance spring 1, in order to correctly centre the collet on the axis DO of the dummy mandrel 10 and to drive the dummy mandrel 10 in rotation with minimum stress with respect to a holding tool arranged to grip and hold the outer ring 6 of the balance spring 1.

The profile of the simulated mandrel 10 is preferably of the pyramid type and comprises at least two zones, each of which has a clear role in ensuring the correct execution of the torque measurement process, with minimum undesired stresses.

The simulated mandrel 10 includes a first or "upper" region. More particularly, but not exclusively, the first zone has a conical portion around the axis DO; in other variants, it may have at least a portion of a shape of revolution about this axis DO, have a parabolic, elliptical or other profile, or combine a plurality of surfaces of revolution about the same axis DO.

This first area forms an interface/engagement site between, on the one hand, clamp 500, also called pick and place device, which may be a robot or the like, and arranged to carry balance spring 1, and, on the other hand, a second area, which is the area for holding balance spring 1 during torque measurement.

Obviously, the invention, which aims to achieve maximum automation, is also designed for laboratory use, in which the operator operates balance spring 1. This variant of use is not described in detail here, in which case the gripper 500 generally comprises a pair of tweezers. The following description uses the clamp 500 in its broadest sense.

The first region has two main functions:

replacing and transferring balance spring 1 from clamp 500 onto the dummy mandrel 10 without stressing collet 2 of balance spring 1;

re-centering balance spring 1 on dummy mandrel 10; this profile allows a range of positioning, for example a maximum possible angular error of +/-20 ° for the balance spring on the fixture 500 relative to the simulated mandrel 10.

This first region extends below the production support tool system 1000 by a second or "lower" region having a particular shape with a profile defined to ensure three primary functions:

precise and repeatable positioning of balance spring 1 on the balance spring torque measuring station;

maintaining the angular and vertical position of collet 2 of balance spring 1 in the gravitational field during the balance spring moment measurement on simulation mandrel 10;

the torque measurement accuracy of balance spring 1.

More specifically, therefore, the invention relates to a method for measuring the moment of a balance spring 1 of a timepiece oscillator, in particular made of micro-machinable material or silicon or similar, this balance spring 1 comprising a collet 2 at its inner end and an outer ring 6 at its outer end. Collet 2 has, in a conventional manner, a hole 3, which hole 3 has an inner surface 4 in the free state of balance spring 1. More specifically, this inner surface 4 comprises at least one flat portion, or has a substantially polygonal shape around the balance spring axis DS of balance spring 1, balance spring 1 being wound around its axis DS with a polygonal profile 5, wherein this polygonal profile 5 has N sides in projection on balance spring axis DS. More generally, inner surface 4 of hole 3 comprises a centering surface 41, centering surface 41 being arranged to cooperate with and center balance spring 1 on a spindle having a shape of revolution about balance spring axis DS; these centering surfaces define a passage diameter DP in the free state of balance spring 1. More specifically, they are tangent to a geometric cylinder defining the passage diameter DP, having a shape of revolution about the balance spring axis DS.

According to the invention:

-determining the size of the inner surface 4 or the passage diameter DP;

selecting a main tool according to these dimensions, the main tool comprising a dummy mandrel 10 in the form of a square pyramid, the cross section of the dummy mandrel 10 tapering in the tool axis DO from its base 18 in the lower part towards its apex 19 in the upper part.

The dummy mandrel 10 comprises, at the top, a first upper region with an insertion guide 12, the projection of each section of which on a plane perpendicular to the tool axis DO lies in the bore 3 of the collet 2, in particular in the inner surface 4 or the polygonal contour 5. The insertion guide 12 is arranged for the first centering of the collet 2 of the balance spring 1, which collet 2 is placed at the top on the apex 19 and is allowed to slide freely along the insertion guide 12 under the effect of its own weight. The dummy mandrel 10 has a cross-section that continuously enlarges along the linear tool axis DO from an upper apex 19 towards its base 18, where the envelope diameter of the dummy mandrel 10 is smaller than the pass-through diameter DP at the apex 19.

The insertion guide 12 is located above a second lower region comprising at least a lower shank 11 of substantially truncated cone shape, which lower shank 11 is arranged to complete the self-centering of the collet 2 on the tool axis DO and to hold the balance spring 1 unstressed on the lower shank 11. By "substantially truncated-cone-shaped" it is meant that the lower shank 11 preferably has a surface of revolution about the tool axis DO, not necessarily of full revolution, i.e. they are regularly angularly arranged segments of cone or similar shape, or even regularly arranged sides; as mentioned above, the conical shape shown in the figures is a particular shape, but the profile may be parabolic, elliptical or other, or even several different types of curves may be combined, the emphasis being that these curves are well tangent with respect to each other to allow the collet 2 to freely slide over the lower shank 11 and to allow self-centering of the collet on the tool axis DO.

In a particular embodiment, the insertion guide 12 is substantially inscribed in a cone, the upper cone angle being between 5 ° and 45 °, more particularly between 10 ° and 20 °, still more particularly between 14 ° and 16 °.

In a particular embodiment, the lower shank 11 is substantially inscribed in a cone, the lower cone angle being greater than 0 ° and less than 10 °, more particularly between 0.5 ° and 3 °, still more particularly between 0.5 ° and 1.5 °.

The lower shank 11 comprises a driving device 100, the driving device 100 being arranged to cooperate with the inner surface 4 of the collet 2 so as to drive the dummy mandrel 10 in rotation via the collet 2 without slipping, or vice versa; in the embodiment shown, these driving means 100 are either flat portions arranged to cooperate with the inner surface 4 of the collet 2, or first flat portions 110 arranged to cooperate with flat portions of the polygonal profile 5 of the inner surface 4 of the collet 2, or recesses arranged to cooperate with flat portions of the inner surface 4 of the collet 2, or first recesses 210 (for example longitudinal slots or grooves) arranged to cooperate with the profile of the inner surface or, where appropriate, with flat portions of the polygonal profile 5, to drive the balance spring 1 relative thereto when a torque is applied thereto. These first flat portions 110 or first recesses 210 or other surfaces are preferably all symmetrical about a plane passing through the tool axis DO, and the intersection of each of these surfaces forming the drive device 100 is oriented at the same angle relative to the tool axis DO in the plane passing through the tool axis DO.

The tool axis DO is then aligned in a vertical position in the gravitational field.

Next, balance spring 1 is gripped with clamp 500, balance spring 1 to be measured is placed by gravity alone on insertion guide 12 by means of clamp 500, and balance spring 1 drops onto lower shank 11 purely by its action of gravity until it is stopped in a self-centering axial position called the "measuring position".

The coaxiality of the balance spring axis DS and the tool axis DO of balance spring 1 is then checked in the measuring position. More specifically, when in the measuring position the balance spring axis DS of balance spring 1 is not aligned with tool axis DO, a thrust is applied to balance spring 1 along tool axis DO from base 18 to apex 19, or vice versa, by flat lower tool 180 to reposition the balance spring in its measuring position, and the positioning of the balance spring is repeated purely by its weight, until balance spring axis DS is aligned with tool axis DO.

When, in the measuring position, balance spring axis DS of balance spring 1 is aligned with tool axis DO, retaining tool 20, arranged to grip outer ring 6 of balance spring 1, is placed flush with the measuring position on tool axis DO, and outer ring 6 is fixed on retaining tool 20.

Using measuring device 170, the moment of balance spring 1 is then measured by rotating main tool and/or holding tool 20 about tool axis DO without stressing balance spring 1.

The measurement position may include a deviation between the collet 2 and the outer ring 6 in the vertical direction of the gravitational field: balance spring 1 may be deliberately placed in an "umbrella" position, in which it has a substantially conical envelope (envelope), and retaining means 20 may be adjusted vertically for this purpose, allowing outer ring 6 to be placed above or below collet 2, depending on the working range chosen. Depending on the measuring range to be applied, the vertical position of holding tool 20 is adjusted to hold balance spring 1 in one plane or to have a rising or falling umbrella shape according to a predetermined offset value that is less than four times the coil height of balance spring 1. More specifically, the vertical position of holding means 20 is adjusted according to a predetermined offset value less than or equal to the height of the coils of balance spring 1, so as to give said spring an umbrella shape.

Depending on the measuring range applied, retaining tool 20 is oriented to apply a slight twist of predetermined value to outer coil 6 of the balance spring, if necessary.

More specifically, after the measurement, balance spring 1 is driven over apex 19 for its removal by translation of holding tool 20 parallel to tool axis DO, and/or by translation of the main tool relative to holding tool 20, and/or by pushing balance spring 1 with flat lower tool 180 from base 18 parallel to tool axis DO to apex 19, and then removing balance spring 1 with clamp 500 or any other suitable means and identifying balance spring 1 with respect to the torque measurement performed.

More specifically, when the inner surface 4 of the collet has a polygonal profile, the drive means 100 comprise at least one section of the lower shank 11 arranged tangentially to the polygonal profile 5 at least N points of the measuring position.

More specifically, driving device 100 comprises at least one friction surface arranged to cooperate with inner surface 4 of collet 2 to drive collet 2 relatively by friction when a torque is applied to balance spring 1.

More specifically, the insertion guide 12 is an upper shank of a substantially truncated cone shape, so that, in projection on a plane perpendicular to the tool axis DO, any section of the upper shank 12 is located in the hole 3 of the collet 2, in particular within the inner surface 4, or, where appropriate, in the polygonal contour 5.

In another variant, once balance spring 1 is placed in the measuring position, it is also possible to use a third tool resting on balance spring 1 close to apex 19, or a free weight placed purely on balance spring 1, the third tool being arranged to exert an axial force on collet 2 to axially retain collet 2 during the torque measuring operation. It is clear, however, that the main advantage of the invention is that the balance spring moment measurement can be carried out with minimum stress on the balance spring, and therefore this variant is suitable for very specific situations, for example a multiple spiral balance spring comprising a plurality of distinct coils extending in a plurality of parallel planes, or a balance spring comprising a spiral portion, or a further configuration in which the lower coil of the balance spring, correctly retained on the dummy spindle 10, does not have to be parallel to another coil lying in another theoretical plane, and its outer coil 6 cooperates with the retaining means 20.

More specifically, the main tool is selected to have N first flat portions 110 or first recesses 210 provided on its lower shank 11, each being symmetrical about a plane passing through the tool axis DO and more specifically about the taper angle of the lower shank 11 when the lower shank 11 is conical, and to have N second flat portions 120 or second recesses 220 provided on its upper shank over the extension of the first flat portion 110, each being symmetrical about a plane passing through the tool axis DO and more specifically about the taper angle of the upper shank when the upper shank is conical.

And, when balance spring 1 is placed on upper shank 12 and/or balance spring 1 rests on lower shank 11, inner surface 4 or, where appropriate, inner flat portion 50 of polygonal profile 5 is then brought into angular alignment, by rotating balance spring 1 and/or the main tool, with first flat portion 110 or first recess 210 on the one hand and second flat portion 120 or second recess 220 on the other hand.

More specifically, the main tool is selected to have an entry guide profile 130 or spiral profile between its apex 19 and the second flat portion 120 provided on its upper shank 12 or between its apex 19 and the first flat portion 110 provided on its lower shank 11, so as to guide the inner flat portion 50 to rest on the second flat portion 120 or towards the first flat portion 110.

More specifically, the clamp 500 arranged to effect the placement of balance spring 1 on insertion guide 12 via gravity is chosen as a vacuum clamp, with the advantage that clamp 500 can be used to pick up balance spring 1 again once the torque measurement operation has been carried out.

More specifically, the clamp 500 may thus form a third tool for axially retaining the collet 2 during a torque measuring operation, as described above for very specific cases.

More specifically, during the measurement of the torque of balance spring 1, holding tool 20 is held fixedly and dummy spindle 10 is fixed to a cradle (calibration-holder) comprising pneumatic means 190 for rotating balance spring 1 by blowing air.

More specifically, retaining means 20 is oriented so as to twist outer ring 6 of balance spring 1 at least slightly to produce an umbrella-shaped effect in balance spring 1.

More specifically, when balance spring 1 is clamped by clamp 500, optical and/or mechanical means are used to orient the flat portion of inner surface 4, or, where appropriate, of polygonal profile 5, facing other flat portions 110 or recesses 210 included in simulated mandrel 10.

More specifically, the method is applied to balance spring 1 having a triangular polygonal profile 5 and simulates contact between mandrel 10 and inner surface 4 of collet 2 at least at six concentric points.

More specifically, the method is applied to balance spring 1 having a triangular polygonal profile 5, and the contact between simulated mandrel 10 and inner surface 4 of collet 2 is limited to six concentric points.

The invention also relates to a production support tool system 1000 for implementing a method for measuring the torque of such a balance spring 1, in particular a balance spring made of micromachinable material or silicon, and in particular, but not exclusively, for implementing the above-described invention.

The production support tool system 1000 includes at least one master tool comprising a right-angle pyramid shaped mock mandrel 10, the mock mandrel 10 having a cross-section that tapers from its base 18 at a lower portion along the tool axis DO toward its apex 19 at an upper portion.

Dummy mandrel 10 has a continuously expanding cross-section along this linear tool axis DO from its upper apex 19, where the envelope diameter of dummy mandrel 10 is smaller than the passage diameter DP of inner surface 4 of the collet of balance spring 1, towards its lower base 18, where the envelope diameter of dummy mandrel 10 is larger than the passage diameter DP of balance spring 1.

The dummy mandrel 10 comprises, at the upper part, at least one insertion guide 12, the projection of each segment of which, on a plane perpendicular to the tool axis DO, is located in the hole 3 of the collet 2, in particular within the contour of the inner surface 4 of the collet 2 of the balance spring 1, or within the polygonal contour 5, as the case may be.

This insertion guide 12 is arranged for the first centering of the collet 2 of the balance spring 1 placed on the upper part, the collet 2 of the balance spring 1 being allowed to slide freely along the insertion guide 12 under its own weight, and the insertion guide 12 being located at least above the lower shank 11, which is substantially frustoconical as described above, the lower shank 11 being arranged to complete the self-centering of the collet 2 on the tool axis DO and to hold the balance spring 1 on the lower shank 11 without stresses.

The lower shank 11 comprises a drive means 100 arranged to cooperate with the inner surface 4 of the collet 2 to drive the dummy mandrel 10 in rotation via the collet 2 without slipping, or vice versa (i.e. to drive the collet 2 in rotation via the dummy mandrel 10 without slipping).

The production support tool system 1000 further includes: a retaining means 20 arranged to grip outer ring 6 of balance spring 1; and measuring device 170 arranged to measure the torque of balance spring 1.

More specifically, the dummy mandrel 10 is rigid.

In a particular embodiment, the dummy mandrel 10 comprises at least a lower shank 11 and a lip, which is elastic at least in a radial direction with respect to the tool axis DO, which is arranged in contact with the inner surface 4 of the collet 2.

Advantageously, production support tool system 1000 comprises means for translating holding tool 20 parallel to tool axis DO, and/or means for translating the main tool with respect to holding tool 20, and/or means for pushing balance spring 1, which means for pushing balance spring 1 comprise a flat lower tool 180 movable parallel to tool axis DO. In a variant, production support tool system 1000 comprises a flat lower tool 180 arranged to be movable in the direction of tool axis DO in the vertical direction of the gravitational field from base 18 to apex 19 or vice versa, in order to position balance spring 1 in its measuring position.

More specifically, driving means 100 of lower shank 11 comprise a first flat portion 110 or first recess 210 arranged to cooperate in a complementary manner with inner surface 4 or inner polygonal profile 5 of collet 2 to drive balance spring 1 relatively when applying a torque thereto.

More specifically, production support tool system 1000 also comprises a third tool arranged to exert an axial force on collet 2 to axially retain it during the torque measuring operation, and/or a free weight arranged to be simply placed on balance spring 1 after balance spring 1 has been correctly positioned in the measuring position.

Production support tool system 1000 advantageously comprises at least one clamp 500 arranged to clamp balance spring 1 and place it on insertion guide 12 and/or on the first lower shank. In a particular variant, this clamp 500 is a vacuum clamp arranged to place balance spring 1 on said dummy mandrel 10 and/or to remove balance spring 1 after measurement.

More specifically, production support tool system 1000 comprises vision means (vision means) able to control the angular orientation of clamps 500 to place balance spring 1 on the main tool in a unique indexed angular position (unique indexed angular position) with respect to holding tool 20.

In a variant, the vertical position of the holding tool 20 can be adjusted in the gravitational field and/or by torsion.

The invention therefore provides a satisfactory response to the risk of bursting apart by retaining the balance spring and avoiding any strong local forces, and since there are no stresses on the collet other than the actual weight of the balance spring when it is retained during the torque measuring operation.

Because the conventional cylindrical dummy mandrel is eliminated, the wear and contamination problems of the tool mandrel are eliminated.

The square pointed pyramid shaped simulation mandrel of the present invention avoids the forced insertion of the collet onto the simulation mandrel. The balance spring is free to release on top of the dummy mandrel without any pressure. The angular and vertical positioning of the balance spring, due to its own weight, in the gravitational field on the profile of the trapezoidal simulation arbour ensures the accuracy of the alignment between the collet and the torque measuring system.

Finally, the particular pyramidal profile, adapted to the design of the collet profile, allows the angular and vertical retention and reference of the balance spring, in particular at the six contact points, which allows the moment of the balance spring to be measured reproducibly and reproducibly, with greater flexibility in the automation of the insertion of the balance spring onto the dummy mandrel.

Although the invention is more particularly designed to overcome the problems specific to the moment measurement of silicon or similar hairsprings, its advantages make it perfectly suitable in the case of traditional hairsprings made of steel or other alloys specific to timepiece hairsprings.

In short, the present invention provides a number of advantages over prior art methods and tools:

no mechanical stress during the measurement of the balance spring moment. There is no collet clamping action. The balance spring is held in place by its own weight.

There are no mechanical stresses during the insertion of the balance spring on the dummy mandrel and the balance spring is inserted and positioned by its own weight.

A particular profile shape of a simulated mandrel of the turret type to ensure repeatability and reproducibility of the measurements. The angular and vertical referencing of the balance spring on the dummy spindle is ensured.

Improved efficiency. The moment measurement of the balance spring does not show any bursting.

No dust or particles on the dummy mandrel and the collet, since there is no friction during the measurement.

The design of the squaring turret simulating a mandrel overcomes the manufacturing tolerances of the collet, especially in terms of its internal dimensions.

Easy to produce automatic devices for the automatic control and measurement of the moment of a balance spring made of micro-machinable material.

Claims (29)

1. A method for measuring the moment of a balance spring (1) of a timepiece oscillator, wound around a balance spring axis (DS) and comprising an outer ring (6) at the outer end of the spring and a collet (2) at the inner end of the spring, the collet having a hole (3), the inner surface (4) of the hole (3) comprising a centering surface (41), the centering surface (41) being arranged to cooperate with a spindle having a shape of revolution about the spring axis (DS) and to center the balance spring (1) on the spindle, and the centering surface (41) defining a passage Diameter (DP) in a free state of the balance spring (1), the method being characterized in that:

-determining the size or the passage Diameter (DP) of the inner surface (4);

-selecting a main tool according to said size or said passing diameter, said main tool having a dummy mandrel (10), said dummy mandrel (10) having a continuously expanding cross section on a rectilinear tool axis (DO) from an upper vertex (19) of said dummy mandrel (10) where the envelope diameter of said dummy mandrel (10) is smaller than said passing Diameter (DP) to a lower base (18) of said dummy mandrel (10), where the envelope diameter of said dummy mandrel (10) is larger than said passing Diameter (DP), said dummy mandrel (10) comprising an insertion guide (12) on an upper portion, the projection of each segment of said insertion guide (12) on a plane perpendicular to said tool axis (DO) being located in said hole (3) of said collet (2), and the envelope diameter of the dummy mandrel (10) is always smaller than the passage Diameter (DP), the insertion guide (12) is arranged for a first centering of the collet (2) of the balance spring (1) placed on the upper portion, the collet (2) is allowed to slide freely along the insertion guide (12) under the effect of its own weight, and the insertion guide (12) is located at least above a lower shank (11) of substantially truncated cone or square-pointed shape, the lower shank (11) is arranged to complete the self-centering of the collet (2) on the tool axis (DO) and to hold the balance spring (2) without stress on the lower shank (11), and the lower shank (11) comprises a drive means (100), the drive means (100) being arranged to cooperate with the inner surface (4) of the collet (2), to drive the dummy spindle (10) in rotation via the collet (2) without slipping or vice versa;

-aligning the tool axis (DO) vertically of the position in the gravitational field;

-clamping the balance spring (1) to be measured with a clamp (500), placing the balance spring (1) to be measured on the insertion guide (12) purely by the action of gravity with the clamp (500), the balance spring (1) to be measured being allowed to descend onto the lower shank (11) purely by the action of its own weight until stopped in a self-centering axial position called "measuring position";

-then checking the coaxiality of the balance spring axis (DS) of the balance spring (1) with the tool axis (DO) at the measuring position;

-placing a retaining tool (20) arranged to grip an outer ring (6) of the balance spring (1) flush with the measuring position in the direction of the tool axis (DO) and fixing the outer ring (6) on the retaining tool (20) when the balance spring axis (DS) of the balance spring (1) is aligned with the tool axis (DO) in the measuring position;

-adjusting the vertical position in the vertical direction of the position of the holding tool (20) in the gravitational field and measuring the moment of the balance spring (1) using a measuring device (170) by rotating the main tool and/or the holding tool (20) about the tool axis (DO) without stressing the balance spring (1).

2. Method according to claim 1, characterized in that, after said measurement, said balance spring (1) is driven over said vertex (9) for removal by translation of said holding tool (20) parallel to said tool axis (20), and/or by translation of said main tool with respect to said holding tool (20), and/or by pushing said balance spring (1) with a flat lower tool (180) from said base (18) parallel to said tool axis (DO) to said vertex (19), and/or by using the vacuum pressure of a vacuum clamp, then removing said balance spring (1) and identifying said balance spring (1) with respect to the moment measurements made.

3. Method according to claim 1, characterized in that, when in said measuring position said balance spring axis (DS) of said balance spring (1) is not aligned with said tool axis (DO), a thrust is applied to said balance spring (1) with a flat lower tool (18) from said base (18) to said vertex (19), and the positioning of said balance spring (1) by its own weight is repeated until said balance spring axis (DS) is aligned with said tool axis (DO).

4. Method according to claim 1, characterized in that the clamp (500) arranged to place the balance spring (1) on the insertion guide (12) by gravity is chosen as a vacuum clamp.

5. A method according to claim 4, wherein said vacuum clamp is used to perform removal of said balance spring (1) after said measurement.

6. A method according to claim 1, wherein, before placing the balance spring (1) on the main tool, the angular position of the balance spring (1) is determined with a visual means via which the angular orientation of the clamp (500) is controlled to place the balance spring (1) on the main tool in a unique angular position in which the outer ring (6) of the balance spring is positioned in a unique angular position with respect to the main tool and the holding tool (20).

7. A method according to claim 1, characterised in that the vertical position of the holding means (20) is adjusted according to the measuring range to be applied, so as to hold the balance spring (1) in one plane, or so as to give the balance spring (1) a rising or falling umbrella shape according to a predetermined offset value, which is less than four times the coil height of the balance spring (1).

8. A method according to claim 7, wherein the vertical position of the holding means (20) is adjusted according to a predetermined offset value less than or equal to the coil height of the balance spring (1) so as to give the spring an umbrella shape.

9. Method according to claim 1, characterized in that said retaining means (20) are oriented so as to impart a slight twist of predetermined value to said outer ring (6) of said balance spring (1), according to the measuring range to be applied.

10. A method according to claim 1, characterized in that the main tool is selected with the driving device (100), the driving device (100) comprising a first flat portion (110) or a first recess (210), the first flat portion (110) or first recess (210) being arranged to cooperate in a complementary manner with the inner surface (4) of the collet (2) for relative driving of the collet (2) when applying a torque to the balance spring (1) or the dummy mandrel (10).

11. The method according to claim 10, wherein the main tool is selected to have a plurality of first flat portions (110) or first recesses (210) arranged on a lower shank (11) of the main tool, each first flat portion (110) or first recess (210) being symmetrical with respect to a plane through the tool axis (DO) and following the contour of the lower shank (11) in the plane through the tool axis (DO), and the main tool has, within the extension of the first flat portions (110), the same number of second flat portions (120) or second recesses (220) arranged on an upper shank (12) of the main tool, each second flat portion (120) or second recess (220) being symmetrical with respect to the plane through the tool axis (DO) and following the contour of the upper shank (12) in the plane through the tool axis (DO), -aligning the driving surface comprised in the inner surface (4) of the collet (2) with the first flat portion (110) or first recess (210) on the one hand and the second flat portion (120) or second recess (220) on the other hand by rotating the balance spring (1) and/or the dummy mandrel (10) when the balance spring (1) is placed on the upper shank (12) and/or when the balance spring (1) rests on the lower shank (11).

12. Method according to claim 11, characterized in that the main tool is selected to have an entry guide profile (130) or a spiral profile between the apex (19) of the main tool and the second flat portion (120) provided on the upper shank (12) of the main tool or between the apex (19) of the main tool and the first flat portion (110) provided on the lower shank (11) of the main tool, in order to guide a drive surface comprised in the inner surface (4) of the collet (2) to rest on the second flat portion (120) or towards the first flat portion (110).

13. Method according to claim 10, characterized in that, when clamping and inserting said balance spring (1) onto said dummy spindle (10), said first flat portion (110) or first recess (210) comprised in said dummy spindle (10) is pre-oriented in its angular position according to the shape of said inner surface of said balance spring (1) for external retention by said retaining means (20).

14. A method according to claim 1, wherein the main tool is selected to have the driving device (100), the driving device (100) comprising a friction surface arranged to cooperate with the inner surface (4) of the collet (2) to perform a relative friction drive of the collet (2) when applying a torque to the balance spring (1) or the dummy mandrel (10).

15. A method according to claim 1, characterised in that during measuring the torque of the balance spring (1), the holding tool (20) is held fixedly and the dummy spindle (10) is fixed to a carriage comprising pneumatic means (190) for rotating the balance spring (1) by blowing.

16. Method according to claim 1, characterized in that the main tool is selected with the insertion guide (12) being an upper shank in the shape of a substantially truncated cone or pyramid.

17. A method according to claim 1, characterized in that it is applied to the measurement of the moment of the balance spring (1), wherein the inner surface (4) of the collet (2) has at least one flat portion or polygonal profile (5) with N regular sides about the balance spring axis (DS) of the balance spring (1), and the main tool is selected with the drive means (10), the drive means (100) comprising at least one section of the lower shank (11) arranged tangent to the polygonal profile (5) at least N points in the measurement position.

18. A method according to claim 17, applied to said balance spring (1), wherein the polygonal profile (5) of said balance spring (1) is triangular and the contact between said dummy mandrel (10) and said inner surface (4) of said collet (2) is made at least six concentric points.

19. A method according to claim 17, applied to said balance spring (1), wherein said polygonal profile (5) of said balance spring (1) is triangular and the contact (19) between said dummy mandrel (10) and said inner surface (4) of said collet (2) is limited to six concentric points.

20. Method according to claim 1, applied to measure the moment of the balance spring (1), made of micro-machinable material, silicon and silica, DLC, metallic glass or at least partially amorphous material.

21. A production support tool system (1000) for implementing a method for measuring the moment of a balance spring (1) of a horological oscillator, comprising at least one main tool including a dummy spindle (10), said dummy spindle (10) having, on a rectilinear tool axis (DO), a continuously expanding cross section from an upper vertex (19) of said dummy spindle (10) to a lower base (18) of said dummy spindle (10), at said vertex (19), an envelope diameter of said dummy spindle (10) being smaller than said passage Diameter (DP), at said base (18), an envelope diameter of said dummy spindle (10) being larger than said passage Diameter (DP), said dummy spindle (10) comprising, on an upper portion, an insertion guide (12), the projection of each segment of said insertion guide (12) on a plane perpendicular to said tool axis (DO) being located inside said balance spring In the hole (3) of the peg (2) and the envelope diameter of the dummy mandrel (10) is always smaller than the passage Diameter (DP), the insertion guide (12) being arranged for a first centering of the peg (2) of the balance spring (1) placed on the upper portion, the peg (2) being allowed to slide along the insertion guide (12) under the effect of its own weight, and the insertion guide (12) being located at least above a lower shank (11) of substantially truncated cone or pyramid shape, the lower shank (11) being arranged to complete the self-centering of the peg (2) on the tool axis (DO) and to hold the balance spring (2) unstressed on the lower shank (11), and the lower shank (11) comprising a drive means (100), the drive means (100) being arranged to cooperate with the inner surface (4) of the peg (2), to drive the dummy mandrel (10) in rotation via the collet (2) without slipping or vice versa, the production support tool system (1000) further comprising a holding tool (20) and a measuring device (170), the holding tool (20) being arranged to grip the outer ring (6) of the balance spring (1), the measuring device (170) being arranged to measure the moment of the balance spring (1).

22. The production support tool system (1000) of claim 21, wherein the dummy mandrel (10) is rigid.

23. Production support tool system (1000) according to claim 21, wherein the dummy mandrel (10) comprises a lip on at least the lower shank (11) which is at least radially elastic with respect to the tool axis (DO) and arranged to be in contact with the inner surface (4) of the collet (2).

24. Production support tool system (1000) according to claim 21, wherein the driving means (100) of the lower shank (11) comprise a first flat portion (110) or a first recess (210), the first flat portion (110) or first recess (210) being arranged to cooperate in a complementary manner with the inner surface (4) of the collet (2) for relative driving of the collet (2) when applying a torque to the balance spring (1).

25. Production support tool system (1000) according to claim 21, characterized in that said production support tool system (1000) comprises means for translating said holding tool (20) parallel to said tool axis (DO), and/or means for translating said main tool with respect to said holding tool (20), and/or means for pushing said balance spring (1) comprising a flat lower tool (180) movable parallel to said tool axis (DO).

26. Production support tool system (1000) according to claim 21, wherein the production support tool system (1000) comprises a flat lower tool (180), which flat lower tool (180) is arranged movable parallel to the tool axis (DO) for positioning the balance spring (1) in the measuring position.

27. Production support tool system (1000) according to claim 21, characterized in that production support tool system (1000) comprises at least one vacuum clamp (500) for placing said balance spring (1) on said dummy spindle (10) and/or for removing said balance spring (1) after said measurement.

28. The production support tool system (1000) according to claim 27, wherein the production support tool system (1000) comprises a visual device capable of controlling the angular orientation of the clamp (500) to place the balance spring (10) on the main tool in a unique indexed angular position relative to the holding tool (20).

29. The production support tool system (1000) according to claim 21, wherein the vertical position of the holding tool (20) is adjustable in the gravitational field and/or by torsion.