HK1154087B

HK1154087B - Composite pendulum and method for making same

Info

Publication number: HK1154087B
Application number: HK11108315.8A
Authority: HK
Inventors: Pierre-André Bühler; Marco Verardo; Thierry Conus; Jean-Philippe Thiébaud; Jean-Bernard Peters; Pierre Cusin
Original assignee: Nivarox-Far S.A.
Priority date: 2008-03-20
Filing date: 2009-03-13
Publication date: 2012-11-23

Description

Composite balance wheel and manufacturing method thereof

Technical Field

The present invention relates to a balance and a method of manufacturing the same, and more particularly to a composite balance.

Background

The regulating element of a timepiece generally comprises an inertia wheel, called balance, and a resonator, called balance spring. These components have a determining role in the working quality of the timepiece. In fact, they regulate the movement, i.e. they control the frequency of the movement.

The balance and the balance spring differ in nature, which makes the manufacturing of the regulating element extremely complex, including the manufacturing of the balance and the balance spring and the resonant assembly of these two components.

Thus, balances have been made of various materials, but have not addressed the isochronism difficulties associated with temperature variations in the regulating element to which the balance belongs.

Disclosure of Invention

The aim of the present invention is to overcome all or part of the drawbacks cited above by proposing a composite balance whose characteristics as a function of temperature can be adjusted more easily and which can be obtained by a manufacturing method comprising fewer steps.

The invention therefore concerns a composite balance formed in a layer of silicon-based material, comprising a hub connected to a felloe by at least one arm, characterized in that said felloe comprises at least one additional portion for increasing the inertia of said balance, approximately in the shape of a notched ring, said ring having a greater density compared to said silicon-based material.

According to other advantageous features of the invention:

-said at least one additional portion is mounted on one of the main faces of the rim, which enhances the inertial adjustment;

-said at least one additional portion is mounted in a recess made in one of the main faces of the rim;

-said at least one additional portion protrudes from one of the main faces of the rim;

-the at least one additional portion comprises a series of posts spaced at regular intervals to compensate for any thermal expansion in the at least one additional portion;

-the at least one additional portion is formed from a metallic material, such as gold, which has a much higher density compared to silicon;

-the hub comprises at least one second additional portion for receiving a balance staff, into which the balance staff is pressed;

-said at least one second additional portion is mounted on one of the main faces of the hub;

-said at least one second additional portion is mounted in a recess made in one of the main faces of the hub;

-said at least one second additional portion protrudes from one of the main faces of the hub;

-said at least one second additional portion is approximately cylindrical;

-the at least one second additional portion is formed from a metallic material;

said at least one arm is elongated so as to allow it to deform axially and/or radially in the event of any shock transmitted to the balance.

The invention also relates to a timepiece characterized in that it comprises a balance according to any one of the preceding variants.

Finally, the invention relates to a method for manufacturing a balance wheel, comprising the steps of:

a) providing a substrate made of a silicon-based material;

the method is characterized by further comprising the following steps:

b) selectively depositing at least one metal layer on a substrate to define a shape/pattern of at least one metal portion of the balance;

c) selectively etching at least one cavity in the substrate to define a profile of the balance including the at least one metal layer;

d) the balance is released from the substrate.

According to other advantageous features of the invention:

-step b) comprises step e): growing a deposit at least partially on the surface of the substrate by means of a continuous metal layer so as to form a metal portion for increasing the mass of the balance made of silicon-based material and/or a metal portion for receiving the arbour pressed therein;

-step b) comprises step f): selectively etching at least one cavity in the substrate for receiving the at least one metal portion, and step g): growing a deposit at least partially in said at least one cavity by a continuous metal layer so as to form a metal portion for increasing the mass of said third portion made of silicon-based material and/or a metal portion into which the mandrel is to be pressed;

-step b) comprises a final step h): polishing the metal deposit;

multiple composite balances are made on the same substrate, which allows mass production.

Drawings

Further characteristics and advantages of the invention will be more apparent from the following description, given by way of non-limiting example with reference to the accompanying drawings, in which:

figures 1 and 2 show views of successive steps of a manufacturing method according to a first embodiment;

figures 3 to 5 show views of successive steps of a method according to a second embodiment;

fig. 6 and 7 are perspective views of a composite balance according to a first embodiment;

fig. 8 and 9 are perspective views of a composite balance according to a second embodiment;

figure 10 is a flow chart of the method of the invention.

Detailed Description

The invention relates to a method for manufacturing a balance 45, 45' for a timepiece movement, generally designated 1. As shown in fig. 1 to 5 and 10, method 1 comprises successive steps for forming at least one type of composite balance, i.e. a balance preferably formed of two different materials, such as silicon and metal.

Referring to fig. 1, 3 and 10, a first step 3 comprises providing a substrate 21 comprising a silicon layer. Preferably in this step 3, as seen in fig. 1 and 3, the substrate 21 is chosen so that its thickness substantially matches the thickness of the silicon part of the desired balance 45, 45'. Thus, the thickness of the substrate 21 may be, for example, between 100-400 μm.

Advantageously according to the invention, after the first step 3, the method 1 may comprise two embodiments 19, 20 as shown in fig. 10.

According to a first embodiment 19, in a second step 5, as shown in fig. 1, method 1 comprises performing a LIGA process (known under the german name;) "Galanoformung &Aboforming ") which comprises a series of steps of electroplating metal in a specific shape on the substrate 21 using a selective photo-structured (photo-structured) resin. Since this LIGA process is well known, it will not be described in detail here. However, the deposited metal may be, for example, gold or nickel or an alloy of these metals.

In the example shown in fig. 1, step 5 may include depositing a notched ring 23 and/or cylinder 25. In the example shown in fig. 1, ring 23 comprises a series of columns 22 substantially forming a circular arc shape and advantageously serves to increase the mass of balance 45 in the future. In fact, one of the advantages of silicon is its insensitivity to temperature variations. However, it has a disadvantage of low density.

Therefore, a first feature of the present invention is to increase the mass of the balance 45 using a metal obtained by electroplating, thereby increasing the inertia of the balance 45 in the future. However, to maintain the advantages of silicon, the metal deposited on the substrate 21 includes spaces between the pillars 22 that can be used to compensate for any thermal expansion of the ring 23, while avoiding any stresses associated with such expansion being transmitted to the silicon.

In the example shown in fig. 1, the cylinder 25 is intended to receive a balance staff, which is advantageously pressed into the cylinder. In fact, another disadvantage of silicon is that it has very small elastic and plastic regions, which means that silicon is very brittle. Therefore, another feature of the invention is that instead of fastening the balance staff against silicon, the balance staff is fastened on the inner diameter 24 of the metal cylinder 25 that is plated during step 5.

Advantageously, according to the method 1, the cylinder 25 obtained by electroplating allows complete freedom as regards its geometry. Thus, in particular, the inner diameter 24 does not have to be circular, but may for example be polygonal, which improves the transmission of forces when rotating with a spindle having a matching shape.

In a third step 7, as shown in fig. 2, cavities 26 to 34 are selectively etched in the silicon substrate 21, for example by the DRIE method.

The cavities 26 to 34 preferably form the shaping 35 of the future balance 45. As shown in the example of fig. 2, the obtained molding 35 comprises a rim 37 connected to a hub 39 by four arms 40 to 43. Advantageously, however, according to method 1, the etching on substrate 21 allows a complete freedom with respect to the geometry of shaping 35. Thus, in particular, the number and geometry of the arms may not be the same, and the edges need not be circular, but may for example be oval. In addition, the arms may be relatively elongated to allow them to deform axially and/or radially in the event of any shock being transmitted to balance 45.

It should also be noted that the cavity 34 made in the hub 39 forms, together with the inner diameter 24 of the metal cylinder 25, a hollow space that can receive a spindle. It should finally be noted that the material bridge 36 is formed to hold the shaping 35 on the substrate 21.

According to embodiment 19, method 1 ends with a final step 9, this step 9 comprising releasing the balance 45 being manufactured from substrate 21. Advantageously, step 9 can be achieved simply by applying sufficient force to balance 45 to break its material bridge 36. This force may be generated, for example, by machining or manually by an operator.

After the final step 9, as shown in the example of fig. 6 and 7, a balance 45 is obtained, mainly formed of silicon, with one or two metal portions 23, 25. It is therefore clear that balance 45 is of a composite type, having at least two types of material, and that it is made in one piece, in which element 35 and elements 23 and/or 25 cannot be separated without being damaged. Balance 45 comprises a hub 39 connected radially to rim 37 by four arms 40, 41, 42 and 43. The hub 39 is also advantageously connected axially to the metal cylinder 25, and the rim 37 comprises a notched ring 23 on a portion of its main face.

According to a second embodiment 20, the method 1 comprises a second step 11, as shown in fig. 3, in which cavities 38 and/or 44 are selectively etched in a portion of the thickness of the silicon substrate 21, for example by means of a DRIE method. These cavities 38, 44 form recesses that can be used as receptacles for at least one of the metal portions 23 ', 25'. As in the example shown in fig. 3, the resulting cavities 38 and 44 may each take the form of a ring or a disk.

Advantageously, according to method 1, the cavities 38 and/or 44 obtained by etching have a complete degree of freedom with respect to their geometry. Thus, in particular, the cavities 38 and/or 44 do not have to be circular, but may for example be polygonal.

In a third step 13, as shown in fig. 4, the method 1 comprises performing an electro-growth (galvanicgrowth) or LIGA process for filling the cavities 38 and/or 44 with a specific metal shape. Preferably, the deposited metal may be, for example, gold or nickel or an alloy of these metals.

In the example shown in fig. 4, step 13 may include depositing a notched ring 23 'in cavity 38 and/or depositing a barrel 25' in cavity 44. In addition, in the example shown in fig. 4, the ring 23 ' has a series of substantially circular-arc columns 22 ' and is advantageously used to increase the mass of the balance 45 ' in the future. In fact, as already explained above, one drawback of silicon is its low density.

Therefore, as with embodiment 19, one feature of the present invention is that the mass of the balance 45 'is increased using a metal obtained by plating, which increases the inertia of the balance 45' in the future. However, to maintain the advantages of silicon, the metal plated on the substrate 21 includes spaces between the posts 22 'that can be used to compensate for any thermal expansion in the ring 23' while preventing any stresses associated with such expansion from being transmitted to the silicon.

In the example shown in fig. 4, the cylinder 25' serves to receive a balance staff, which is advantageously pressed into it. In fact, as already explained above, one advantageous feature of the invention is that the balance staff is not fastened against the silicon, but on the inner diameter 24 'of the metal cylinder 25' that is plated during step 13. Advantageously, according to the method 1, the cylinder 25' being plated allows complete freedom as regards its geometry. Thus, in particular, the inner diameter 24' does not have to be circular, but may for example be polygonal, which improves the force transmission when rotating with a spindle having a matching shape.

Preferably, the method 1 may comprise a fourth step 15, illustrated by a dashed line in fig. 10, which fourth step 15 comprises polishing the metal deposits 23 ', 25' made during step 13 to flatten them.

In a fifth step 17, as shown in fig. 5, cavities 26 'to 34' are selectively etched in the silicon substrate 21, for example by a DRIE process.

These cavities 26 'to 34' preferably form the shaping 35 'of the future balance 45'. As shown in the example of fig. 5, the obtained molding 35 ' comprises a rim 37 ' connected to a hub 39 ' by four arms 40 ' to 43 '. Advantageously, however, according to method 1, the etching on substrate 21 allows a complete freedom with respect to the geometry of shaping 35'. Thus, in particular, the number and geometry of the arms may not be the same, and the edges need not be circular, but may for example be oval. In addition, the arms may be relatively elongated to allow them to deform axially and/or radially in the event of any shock being transmitted to the adjustment element 45'.

It should also be noted that the cavity 34 'made in the hub 39' forms, together with the inner diameter 24 'of the metal cylinder 25', a hollow space that can receive the spindle. Finally, it should be noted that the material bridge 36 'is formed to hold the build 35' on the substrate 21.

As with embodiment 19, embodiment 20 ends with a final step 9, which final step 9 comprises releasing the produced balance 45' from the substrate 21. Advantageously, step 9 is achieved simply by applying sufficient force to balance 45 'to break its material bridge 36'. This force may be generated, for example, by machining or manually by an operator.

After the final step 9, as shown in the example of fig. 8 and 9, a balance 45 ' mainly formed of silicon is obtained, with one or two metal portions 23 ', 25 '. It is therefore clear that balance 45 'is composite, comprising at least two types of material, and is made in one piece, in which element 35' and elements 23 'and/or 25' cannot be separated without being damaged. Balance 45 ' comprises a hub 39 ' connected radially to rim 37 ' by four arms 40 ', 41 ', 42 ' and 43 '. The hub 39 'also advantageously comprises a metal cylinder 25'. Finally, the rim 37 'comprises a notched ring 23'.

Advantageously, according to the method 1 of the invention described above, it is clear that a plurality of balances 45, 45' can be made on the same substrate 21, which allows mass production.

Of course, the invention is not limited to the examples shown, but is capable of numerous variations and modifications as will be clear to a person skilled in the art. In particular, the hubs 39, 39 'according to embodiments 19, 20 may not include metal press-in cylinders 25, 25'. The cylinders 25, 25 'can be replaced, for example, by elastic means etched in the hubs 39, 39' made of silicon and can take the forms disclosed in figures 10A to 10E of EP patent No.1655642 or in figures 1, 3 and 5 of EP patent No.1584994, incorporated herein by reference.

It is also possible to invert the metal portions 25, 25 ' plated in embodiments 19 and 20, i.e. the protruding portion 25 of embodiment 19 can be replaced by the integrated portion 25 ' of embodiment 20 and vice versa (this requires only minimal modification of method 1), or even to make the portion 25 ' integrated in the hub protrude from the substrate 21.

According to a similar reasoning it is also possible to reverse the metal portions 23, 23 ' plated in embodiments 19 and 20, i.e. the protruding portion 23 of embodiment 19 can be replaced by the integrated portion 23 ' of embodiment 20 and vice versa, or the portion 23 ' integrated in the rim can be made to protrude from the substrate 21.

In addition, after releasing step 9, method 1 may also advantageously provide a step of adjusting the inertia of balance 45, 45'. This step may comprise, for example, laser etching of recesses made in the circumferential wall of the rim 37, 37 'and/or on the metal portion 23, 23' being plated. Conversely, it is also conceivable to use an inertia mass adjustment structure for increasing the inertia of the balance 45, 45'.

Finally, a polishing step similar to step 15 may also be performed between step 5 and step 7.

Claims

1. A composite balance (45, 45 ') formed in a layer (21) of silicon-based material and comprising a hub (39, 39 ') connected to a rim (37, 37 ') by at least one arm (40, 41, 42, 43), characterized in that said rim (37, 37 ') comprises at least one additional portion substantially in the shape of a notched ring (23, 23 ') having a greater density compared to said silicon-based material to increase the inertia of said composite balance.

2. Composite balance wheel according to claim 1, characterized in that said at least one additional portion (23) is mounted on one of the main faces of said felloe (37).

3. Composite balance according to claim 1, characterized in that said at least one additional portion (23') is mounted in a recess (38) made in one of the main faces of said felloe (37).

4. Composite balance wheel according to claim 3, characterized in that said at least one additional portion (23') protrudes from one of the main faces of said felloe (37).

5. Composite balance wheel according to claim 1, characterized in that said notched ring (23, 23 ') comprises a series of columns (22, 22 ') spaced at regular intervals to compensate for any thermal expansion in said at least one additional portion (23, 23 ').

6. Composite balance according to claim 1, characterized in that said at least one additional portion (23, 23') is formed from a metallic material.

7. Composite balance according to claim 1, characterized in that said hub (39, 39 ') comprises at least one second additional portion (25, 25') for receiving a balance staff, which is pressed into it.

8. Composite balance according to claim 7, characterized in that said at least one second additional portion (25) is mounted on one of the main faces of said hub (39).

9. Composite balance according to claim 7, characterized in that said at least one second additional portion (25') is mounted in a recess (44) made in one of the main faces of said hub (39).

10. Composite balance according to claim 9, characterized in that said at least one second additional portion (25') protrudes from one of the main faces of said hub (39).

11. Composite balance according to claim 7, characterized in that said at least one second additional portion (25, 25') is substantially cylindrical.

12. Composite balance according to any of claims 7 to 11, characterized in that said at least one second additional portion (25, 25') is formed from a metallic material.

13. Composite balance according to claim 1, characterized in that said at least one arm (40, 41, 42, 43) is elongated so that it can deform axially and/or radially in the event of any shocks transmitted to the composite balance (45, 45').

14. Timepiece, characterized in that it comprises a composite balance (45, 45') according to any one of the preceding claims.

15. A method (1) of manufacturing a composite balance (45, 45'), comprising the steps of:

a) providing a substrate (21) made of a silicon-based material;

characterized in that the method also comprises the following steps:

b) -selectively depositing at least one metal layer (23, 23 ', 24, 24') on said substrate (21) to define the conformation of at least one metal portion of said composite balance;

c) -selectively etching at least one cavity (26, 27, 28, 29, 30, 31, 32, 33, 34, 26 ', 27 ', 28 ', 29 ', 30 ', 31 ', 32 ', 33 ', 34 ') in said substrate (21) to define a profile (35, 35 ') of said composite balance (45, 45 ') comprising said at least one metallic layer;

d) -releasing the composite balance (45, 45') from the substrate (21).

16. Method (1) for producing a composite balance (45, 45') according to claim 15, wherein step b) comprises the steps of:

e) -growing a deposit at least partially on the surface of the substrate (21) by means of a continuous metal layer so as to form a metal portion (23) for increasing the mass of the composite balance (45).

17. Method (1) for producing a composite balance (45, 45') according to claim 15, wherein step b) comprises the steps of:

e') growing a deposit at least partially on the surface of the substrate (21) by means of a continuous metal layer so as to form a metal portion (25) for receiving the mandrel pressed therein.

18. Method (1) for producing a composite balance (45, 45') according to claim 15, wherein step b) comprises the steps of:

f) -selectively etching at least one cavity (38) in the substrate (21) for receiving the at least one metal portion;

g) -growing a deposit at least partially in said at least one cavity by a continuous metal layer so as to form a metal portion (23 ') for increasing the mass of said composite balance (45').

19. Method (1) for producing a composite balance (45, 45') according to claim 15, wherein step b) comprises the following phases:

f') selectively etching at least one cavity (44) in the substrate (21) for receiving the at least one metal portion;

g ') growing a deposit at least partially in the at least one cavity by a continuous layer of metal to form a metal portion (25') for receiving the mandrel pressed therein.

20. Method (1) for producing a composite balance (45, 45') according to claim 15, characterized in that step b) is followed by the following step:

h) polishing the metal deposit (21).

21. Method (1) of manufacturing a composite balance (45, 45 ') according to any one of claims 15 to 20, wherein a plurality of composite balances (45, 45') are made on the same substrate (21).