EP2557461B1 - Metal anchor with polymer horns - Google Patents

Description

Field of the invention

The invention relates to an exhaust system of a timepiece and, more specifically, to such a system comprising an anchor whose function of the rod and that of the fork can be decoupled.

Background of the invention

The Swiss-anchor type free-escapement systems are difficult to develop because they are the compromise between the lowest possible inertia and a pallet and fork tribology, the best possible. Thus, it is difficult to avoid snags between the plateau pin and the horns of the fork while preserving minimal inertia and even insensitivity to magnetic fields.

The document EP 2 320 280 discloses an anchor for an exhaust system whose dart came form with the rod. The fork is formed apart from the rod and then mounted on it.

Summary of the invention

The object of the present invention is to overcome all or part of the disadvantages mentioned above by proposing a method of manufacturing an anchor whose rod has a low inertia and a range with favorable tribological qualities.

1. a) former à l'aide d'un premier matériau le corps de l'ancre dont une première extrémité comporte le dard et une deuxième extrémité comporte deux bras destinés à recevoir chacun une palette ;
2. b) surmouler un deuxième matériau au niveau de ladite première extrémité afin de former une fourchette, le deuxième matériau étant différent du premier ;
3. c) ajuster lesdites palettes et une tige afin de pouvoir monter l'ancre à rotation.

For this purpose, the invention relates to a method of manufacturing an anchor for an exhaust system characterized in that it comprises the following steps:

1. a) forming with a first material the body of the anchor, a first end comprises the stinger and a second end comprises two arms each for receiving a pallet;
2. b) overmolding a second material at said first end to form a fork, the second material being different from the first;
3. c) adjusting said pallets and a rod so as to mount the rotary anchor.

• a') former à l'aide d'un premier matériau le corps de l'ancre dont une première extrémité comporte le dard et une deuxième extrémité comporte deux bras formant chacun une palette venue de forme ;
• b) surmouler un deuxième matériau au niveau de ladite première extrémité afin de former une fourchette, le deuxième matériau étant différent du premier ;
• c') monter une tige afin de pouvoir monter l'ancre à rotation.

According to a first alternative, the manufacturing method according to the invention differs in that it comprises the following steps:

• a ') forming with the aid of a first material the body of the anchor whose one end comprises the stinger and a second end comprises two arms each forming a pallet come form;
• b) overmolding a second material at said first end to form a fork, the second material being different from the first;
• c ') mount a rod in order to mount the rotary anchor.

• a) former à l'aide d'un premier matériau le corps de l'ancre dont une première extrémité comporte le dard et une deuxième extrémité comporte deux bras destinés à recevoir chacun une palette ;
• b') surmouler un deuxième matériau au niveau de ladite première extrémité afin de former une fourchette et au niveau de ladite deuxième extrémité afin de former lesdites palettes, le deuxième matériau étant différent du premier ;
• c') monter une tige afin de pouvoir monter l'ancre à rotation.

According to a second alternative, the manufacturing method according to the invention differs in that it comprises the following steps:

• a) forming with a first material the body of the anchor, a first end comprises the stinger and a second end comprises two arms each for receiving a pallet;
• b ') overmolding a second material at said first end to form a fork and at said second end to form said pallets, the second material being different from the first;
• c ') mount a rod in order to mount the rotary anchor.

Thus, advantageously according to the invention, the mechanical characteristics provided by the material of the rod are no longer dependent on those of the fork. Therefore, as an example, the baguette can advantageously offer a low inertia and the range an optimized tribology.

• l'étape a) ou a') est réalisée par un processus LIGA, un estampage ou un décolletage ;
• le premier matériau est un métal ou un alliage métallique ;
• le premier matériau comporte du titane, de l'aluminium ou un alliage de cobalt austénitique ;
• l'étape b) ou b') est réalisée par une injection dans un moule formé à l'aide d'un processus LIGA ;
• le deuxième matériau est un polymère ;
• le deuxième matériau comporte du polyoxyméthylène ;
• la tige est formée en l'acier, en laiton ou en maillechort.

According to other advantageous features of the invention:

• step a) or a ') is carried out by a LIGA process, a stamping or a bar turning;
• the first material is a metal or a metal alloy;
• the first material comprises titanium, aluminum or an austenitic cobalt alloy;
• step b) or b ') is performed by injection into a mold formed using a LIGA process;
• the second material is a polymer;
• the second material comprises polyoxymethylene;
• the rod is formed of steel, brass or nickel silver.

Finally, the invention relates to an anchor as defined in claims 11 to 13.

Brief description of the drawings

• la figure 1 est une représentation d'une ancre selon l'invention ;
• la figure 2 est une représentation en coupe partielle d'une pièce d'horlogerie comportant une ancre selon l'invention ;
• la figure 3 est une représentation d'une ancre non finie selon l'invention ;
• la figure 4 est une représentation d'une étape de surmoulage selon l'invention ;
• la figure 5 est un schéma fonctionnel d'un procédé selon l'invention.

Other particularities and advantages will emerge clearly from the description which is given hereinafter, by way of indication and in no way limiting, with reference to the appended drawings, in which:

• the figure 1 is a representation of an anchor according to the invention;
• the figure 2 is a representation in partial section of a timepiece comprising an anchor according to the invention;
• the figure 3 is a representation of an unfinished anchor according to the invention;
• the figure 4 is a representation of an overmolding step according to the invention;
• the figure 5 is a block diagram of a method according to the invention.

Detailed Description of the Preferred Embodiments

In the example shown in Figures 1 and 2 , we can see an exhaust system 1 for a timepiece. As visible at figure 2 in section, the exhaust system 1 comprises in particular an anchor 3 intended to cooperate with a plate 5. The plate 5 is preferably driven on the balance shaft 2 and comprises a small plate 4 provided with a notch 6 and a large tray 8 with ankle 7.

The anchor 3 preferably comprises a rod 9 formed by a first metal material which is preferentially chosen for its low density, its low sensitivity to magnetic fields and possibly its ability to change pallets 10, 12 for example ruby.

Thus, preferentially, such a rod material 9 may be, for example, titanium, aluminum or an austenitic cobalt alloy.

The rod 9 comprises arms 11 and 13 for supporting the pallets 10 and 12 to cooperate with at least one escape wheel (not shown) of the exhaust system 1. Between these two arms 11 and 13 is mounted the anchor rod 14 to pivotably mount the anchor 3. The rod 14 may be made, for example, of a material such as steel, brass or nickel silver. Finally, at the end opposite the arms 11 and 13, the rod 9 comprises a dart 15 and a fork 17.

Advantageously according to the invention, the dart 15 has come in shape with the rod 9 and, preferably, an extension of the latter. The dart 15 is intended to cooperate with the small plate 4 to prevent accidental movements of the fork 17.

The fork 17 preferably comprises an overmoulding 19 formed by a second material, different from the first material of the rod 9 and intended to allow the improvement of the tribological qualities of the fork 17 on the ankle 7, without affecting the inertia 3. Preferentially, the material of the fork 17 is also paramagnetic in order to reduce the sensitivity of the anchor 3 to the magnetic fields.

The material of the fork 17 is ideally a material having a low wear and a low coefficient of friction in association with the pin 7 of the large plate 8. Such a material may be a polymer.

Preferably, the polymer used is polyoxymethylene (POM) for its special shock absorbing capabilities in addition to its low sensitivity to magnetic fields and its very good tribological qualities. During development, it was found that the air pressure exerted by the ruby ankle on polyoxymethylene horns was limited to 54 MPa, an 85% decrease in mechanical stress compared to standard steel horns.

The fork 17 is preferably overmolded over the rod 9 at the stinger 15 and comprises two horns 16 and 18 intended to come into contact with the pin 7 of large plate 8 in order, following the rotation of the pin 7, to drive the anchor 3 pivoting about its rod 14 in a movement back and forth.

Advantageously according to the invention, by uncoupling the materials of the fork 17 from that of the rod 9, the anchor 3 is optimized between the desired sensitivity to the magnetic fields and / or the desired inertia of the rod 9, on the one hand, and on the other hand the low wear and the low coefficient of friction in association with the ankle 7, of the fork 17.

Preferably, the overmolding of the fork 17 traps the rod 9 to ensure that it does not disengage. Thus, as visible figures 2 and 4 , the rod 9 comprises notches 25, 26 allowing overmoulding to form bridges 20 and 21 of polymer material blocking the fork 17 against the rod 9.

Of course, the rod 9, the pallets 10, 12 or the rod 14 may differ. Thus, by way of example, according to a first alternative, the pallets 10, 12 may have come in shape with the rod 9 if it is not desired to be able to change the pallets 10, 12. For the same purpose, according to a second alternative, the pallets 10, 12 may be overmolded identically or similarly with respect to the fork 17, that is to say with a polymer such as polyoxymethylene.

The method 31 for manufacturing the anchor 3 will now be explained in connection with the figure 5 . The method 31 comprises a first step 33 intended to form with a first material the body of the anchor 3 whose one end comprises the stinger 15 and a second end comprises the two arms 11, 13 for each suppoprtre a pallet 10, 12.

Step 33 can be performed by many techniques such as, for example, a LIGA process, stamping or bar turning. This step 33 allows the manufacture in one piece of the rod 9, the arms 11, 13 and the dart 15. As visible in the figure 3 the rod 9 has a hole 22 for adjusting the rod 14. In addition, each arm 11, 13 has a hole 23, 24 for adjusting a pallet 10, 12.

Of course, in the case of the first alternative mentioned above, step 33 is also intended to form a pallet 10, 12 formed on each arm 11, 13.

Finally, as explained above, step 33 also makes it possible, preferably, to form notches 25, 26 intended to be filled by the future overmolding (s).

The method 31 continues with the second step 35 for overmoulding a second material at the first end, that is to say at the level of the stinger 15, to form the fork 17 and, possibly, at the level of said second end to form the pallets 10, 12. Preferably, in order to ensure optimum structural quality, the mold 27 used for the overmolding is performed by a LIGA process, that is to say a photolithography followed by electroplating.

The mold 27 has stops 28 and 29 for respectively locking the arms 13, 11 and the rod 9. Only the cavity 30 of the mold 27 is intended to be filled. Of course, several overmouldings could be made on the same mold 27, that is to say that the mold 27 has several cavities 30 and that are placed several anchor bodies in the mold and / or other parts of the mold. the rod 9 are molded as, for example, to achieve the second alternative.

As explained above, preferably, the second material is a polymer. Therefore, the step 35 consists, in a preferred manner, in over-molding the body of the anchor by injecting the polymer into the cavity 30 of the mold 27 in order to form the body of the fork 17 with, in particular, the horns 16 and 18 and, optionally, according to the second alternative, to form the pallets 10, 12 at the arms 11, 13.

The third step 37 of the method 31 is intended to mount the pallets 10, 12 in the holes 23, 24 and the rod 14 in the hole 22 in order to mount the anchor 3 to rotate. At the end of these last two steps, the anchor 3 is finished and can be mounted in a timepiece as part of an exhaust system 1 of the Swiss type.

Of course, in the case of the first and second alternatives, it must be considered that step 37 is limited to mounting the rod 14 in the hole 22 in order to mount the anchor 3 to rotate.

Therefore, the anchor 3 is of the composite type, i.e. it is formed from two different materials. So, as visible at the figure 2 it can be seen that the anchor 3 preferably comprises, at the level of the axis A, a height entirely made by the second material thanks to the notch 25 made during the step 31 forming in particular an eyelet in the rod 9.

Of course, the present invention is not limited to the illustrated example but is susceptible of various variations and modifications that will occur to those skilled in the art.

In particular, the shapes of the anchor 3 and / or the plate 5 may be different. The anchor 3 may thus comprise, for example, at least a third arm intended to support at least a third pallet for the application of the invention to a coaxial type exhaust system.

It can also be imagined to adapt the shape of the fork 17 and, more precisely, that of the horns 16 and 18 to adapt to another type of tray or other type of material of the ankle 7 to avoid wear and gluing during successive contacts.

Finally, the first and second different materials can also be understood in a difference in outer coating while their soul is identical. By way of example, the rod 9 could thus be formed of silicon coated with a polymer without departing from the fact that the first material of the rod 9 is different from the second material of the fork 17.

Claims (15)

1. Method (31) for fabricating pallets (3) for an escapement system (1) characterized in that it includes the following steps:

   a) forming (33), using a first material, the lever of the pallets (3) a first end of which includes the dart (15) and a second end includes two arms (11, 13) each for receiving a pallet stone (10, 12);

   b) over-moulding (35) a second material on said first end in order to form a pallets fork (17), the second material being different from the first material;

   c) mounting (37) said pallet stones and a staff (14) to enable the pallets (3) to be rotatably mounted.
2. Method (31) for fabricating pallets (3) for an escapement system (1) characterized in that it includes the following steps:

   a') forming (33), using a first material, the lever of the pallets (3), a first end of which includes the dart (15) and a second end includes two arms (11, 13) each forming an integral pallet stone (10, 12);

   b) over-moulding (35) a second material on said first end in order to form a pallets fork (17), the second material being different from the first material;

   c') mounting (37) a staff (14) to enable the pallets (3) to be rotatably mounted.
3. Method (31) for fabricating pallets (3) for an escapement system (1) characterized in that it includes the following steps:

   a) forming (33), using a first material, the lever of the pallets (3) a first end of which includes the dart (15) and a second end includes two arms (11, 13) each for receiving a pallet stone (10, 12);

   b') over-moulding (35) a second material on said first end so as to form a pallets fork (17) and on said second end in order to form said pallet stones (10, 12), the second material being different from the first material;

   c') mounting (37) a staff (14) to enable the pallets (3) to be rotatably mounted.
4. Method (31) according to any of the preceding claims, characterized in that step a) or a') is achieved by a LIGA process, stamping or bar turning.
5. Method (31) according to any of the preceding claims, characterized in that the first material is a metal or metal alloy.
6. Method (31) according to the preceding claim, characterized in that the first material includes titanium, aluminium or an austenitic cobalt alloy.
7. Method (31) according to any of the preceding claims, characterized in that step b) or b') is achieved by injection into a mould formed using a LIGA method.
8. Method (31) according to any of the preceding claims, characterized in that the second material is a polymer.
9. Method (31) according to the preceding claim, characterized in that the second material includes polyoxymethylene.
10. Method (31) according to any of the preceding claims, characterized in that the staff (14) is formed of steel, brass or copper-nickel-zinc alloy.
11. Pallets (3) for an escapement system (1) comprising:

    - a body made integrally of a first material, a first end of which includes the dart (15) and a second end includes two arms (11, 13) each for receiving a pallet stone (10, 12);

    - a staff (14) mounted on said body;

    - a fork (17) made of a second material being different from the first material,
    characterized in that said fork is over-moulded onto said first end of the body.
12. Pallets (3) for an escapement system (1) comprising:

    - a body made integrally of a first material, a first end of which includes the dart (15) and a second end includes two arms (11, 13) each forming a pallet stone (10, 12) in a single piece;

    - a staff (14) mounted on said body;

    - a fork (17) made of a second material being different from the first material, said fork being over-moulded onto said first end of the body.
13. Pallets (3) for an escapement system (1) comprising:

    - a body made integrally of a first material, a first end of which includes the dart (15) and a second end includes two arms (11, 13) each for receiving a pallet stone (10, 12);

    - two pallet stones (10, 12) onto said two arms (11, 13);

    - a staff (14) mounted on said body;

    - a fork (17) made of a second material being different from the first material,
    characterized in that said fork is over-moulded onto said first end of the body and in that said pallet stones are also over-moulded onto said two arms (11, 13).
14. Escapement system (1) characterized in that it includes pallets (3) according to any of claims 11 to 13.
15. Timepiece characterized in that it includes an escapement system (1) according to the preceding claim.

Images