EP3982203B1 - Timepiece escapement with semi-direct pulse - Google Patents

Description

The present invention relates to a timepiece escapement with semi-direct impulse, that is to say an escapement whose escapement wheel communicates to the balance wheel a direct impulse and an indirect impulse (via a rocker) at each period of oscillation, the direct impulse being communicated during one of the two cycles of the balance and the indirect impulse during the other of the two cycles.

The present invention relates more particularly to an escapement of the type described in the patent EP 2941673 B1 . This escapement comprises an escape wheel, a rocker and a balance plate secured to the balance shaft. The balance plate comprises a pin arranged to cooperate with a fork of the rocker and a pallet intended to receive the direct impulse of the escape wheel when the balance plate rotates in a first direction (first alternation). In addition to the fork, the rocker includes a first resting surface, a second resting surface and an impulse surface.

When the platter rotates in the first direction (first alternation), the first resting surface locks the escapement wheel in an entry rest position then releases it under the action of the pin cooperating with the fork so that the wheel escapement communicates its direct impulse to the pallet of the balance plate. When the plate rotates in the opposite direction to the first direction (second alternation), the second resting surface locks the escape wheel in an output rest position then releases it under the action of the pin cooperating with the fork so that the escape wheel comes into contact with the impulse surface of the rocker to communicate the indirect impulse to the balance wheel.

A special feature of this exhaust according to the patent EP 2941673 B1 is that the angle between the entry and exit rest positions is smaller than the angle between the entry rest position and the axis of the rocker, these angles being seen from the axis of the escape wheel. This feature makes the escapement compact.

The exhaust according to the patent EP 2941673 B1 nevertheless has a drawback: the unbalance of the rocker is significant, which increases the sensitivity of the escapement to shocks and to variations in the orientation of the watch with respect to the gravitational force. It is of course possible to balance the rocker by adding protrusions to it at selected locations, but this increases its inertia and therefore the energy consumption.

The present invention aims to provide a timepiece escapement of the type described in the aforementioned patent but whose lever can be more balanced without having to increase its inertia.

To this end, a timepiece escapement according to claim 1 is proposed, particular embodiments being defined in the dependent claims.

The present invention further proposes a timepiece comprising such an escapement.

• les figures 1 à 10 montrent différents états de l'échappement selon l'invention pendant son cycle de fonctionnement ;
• la figure 11 montre deux positions de repos successives de l'échappement selon l'invention ;
• la figure 12 montre schématiquement une amélioration apportée par la présente invention à l'échappement décrit dans le brevet EP 2941673 B1 ;
• la figure 13 montre en perspective un plateau de balancier de l'échappement selon l'invention.

Other characteristics and advantages of the present invention will appear on reading the following detailed description given with reference to the appended drawings in which:

• them figures 1 to 10 show different states of the escapement according to the invention during its operating cycle;
• the figure 11 shows two successive rest positions of the escapement according to the invention;
• the figure 12 schematically shows an improvement made by the present invention to the escapement described in the patent EP 2941673 B1 ;
• the figure 13 shows in perspective a balance plate of the escapement according to the invention.

With reference to the figure 1 , a timepiece escapement 10 according to a particular embodiment of the invention, for a timepiece such as a watch or a clock, comprises an escapement wheel 12, a rocker 14 and a balance plate 16 The escapement wheel 12 is pivoted around a first axis A and is coaxially integral with a pinion 18 which meshes with the second wheel of a going train (not shown). The latter tends to rotate the escape wheel 12 in a single direction, which is counterclockwise in the figures. Rocker 14 is pivoted around a second axis B and comprises a fork 20, a first arm 22 and a second arm 24. Balance plate 16 is pivoted around a third axis C to rotate coaxially and integrally with a balance (not shown). The balance plate 16 carries a plate pin 26 and an impulse tooth 28.

The escape wheel 12, the rocker 14 and the balance plate 16 can be held on their respective physical axes elastically, as shown, or in another way, for example by gluing or brazing.

At its distal end, the first arm 22 of rocker 14 defines a first resting surface 30 of concave shape. Similarly, at its distal end the second arm 24 of rocker 14 defines a second resting surface 32 of concave shape. These concave surfaces 30, 32 can be curved surfaces or consist of two inclined planes. A side impulse surface 34 adjoins the second resting surface 32 on the second arm 24.

The escape wheel 12 comprises on its periphery, on the same level and alternately, short teeth 36 and long teeth 38. By the terms "short" and "long" is meant that the distance between the top of the tooth and the first axis A is smaller for the short teeth 36 than for the long teeth 38. The short teeth 36 are identical and regularly distributed. The long teeth 38 are also identical and regularly distributed. However, each short tooth 36 may be closer to one of the two teeth long 38 adjacent between which it is located than the other, as seen in the drawings.

The escapement 10 is of the type with one pulse per alternation, more precisely of the semi-direct pulse type. Each alternation (half-period of oscillation) of the balance comprises a rest phase, a release phase and an impulse phase. The figures 1 to 10 show successive states of the escapement during the period of oscillation.

In a first state ( figure 1 ), a short tooth 36a bears against the first resting surface 30 of the rocker 14. The concave shape of the first resting surface 30 allows the escapement wheel 12 and the rocker 14 to mutually lock. The escape wheel 12 and the rocker 14 are in an entry rest position. The balance plate 16 rotates freely in a first direction S1, namely clockwise on the figure 1 , under the action of the return spring (typically a hairspring) of the balance wheel.

At a given moment, pin 26 of balance plate 16, still rotating in direction S1, engages in fork 20 and comes into contact with inner surface 40a of one 40 of the latter's horns to pivot rocker 14 and disengage escapement wheel 12 from first resting surface 30 ( figure 2 ). The escape wheel 12 is partially released, its rotation being braked by a transition surface 44 of the first arm 22 on which the short tooth 36a must slide.

As soon as rocker 14, still under the action of pin 26, has completely freed escape wheel 12 ( picture 3 ), a long tooth 38a catches the impulse tooth 28 to drive it and thus communicate a direct impulse to the balance plate 16 in the direction S1 ( figure 4 and 5 ).

After this impulse, another long tooth 38b abuts against the second resting surface 32 of rocker 14 ( figure 6 ). The concave shape of the second resting surface 32 allows the escapement wheel 12 and the rocker 14 to interlock with each other. The escape wheel 12 and the Rocker 14 are in an output rest position. The balance plate 16 continues its travel in the direction S1 then reverses its direction of rotation, which becomes S2, under the action of the return spring of the balance.

Then, as shown in figure 7 , the pin 26 of the balance plate 16, rotating in the direction S2, comes into contact with the inner surface 42a of the other horn 42 of the fork 20 to cause the rocker 14 to pivot and disengage the escapement wheel 12 from the second rest surface 32 ( figure 8 ). Long tooth 38b reaches pulse surface 34 and cooperates with it to impart a pulse to flip-flop 14 ( figures 9 and 10 ). This impulse is transmitted from rocker 14 to balance plate 16 by the interaction between fork 20 and pin 26.

After this impulse, another short tooth 36b of the escapement wheel 12 abuts against the first resting surface 30 of the rocker 14 and the balance plate 16 continues its course in the direction S2 until it reverses its direction again. of rotation under the action of the balance return spring. The escapement is then in the state illustrated in figure 1 and the cycle repeats.

The figure 11 shows the two rest positions of the escape wheel 12 superimposed. The solid line shows the entry rest position and the dotted line the exit rest position. It can be seen that, as in the patent EP 2941673 B1 , the angle α between these entry and exit rest positions is smaller than the angle β between the entry rest position and the axis of rotation B of the rocker 14, these angles being seen from the axis of rotation A of the escape wheel 12.

An important difference between the escapement according to the invention and that described in the patent EP 2941673 B1 consists of the teeth of different lengths of the escapement wheel 12. As results from the above description of the operating cycle of the escapement, the short teeth 36 cooperate exclusively with the first resting surface 30 whereas the teeth long 38 interact with the second resting surface 32, the impulse surface 34 and the impulse tooth 28.

To illustrate the advantage of this difference, we have represented figure 12 the exhaust according to the patent EP 2941673 B1 with the escape wheel in its entry rest position and an additional tooth has been added to the escape wheel, in dotted line, shorter than each of the five teeth it carries. For locking the escape wheel in the entry rest position, this additional tooth can work with a shorter rocker arm than the arm illustrated in said patent. In this way, the lever will be better balanced and the escapement will be less sensitive to shocks and to variations in the orientation of the watch with respect to the gravitational force.

The invention thus amounts to doubling each tooth of the escapement wheel of the escapement according to the patent EP 2941673 B1 into two teeth of different lengths and to separate the functions performed by these two teeth. The number of long/short teeth can however be different from the number of teeth (five) carried by the escape wheel in said patent. This is the case in the example illustrated in the attached figures where three short teeth 36 and three long teeth 38 are provided, which corresponds to an escape wheel according to said patent which would include three teeth.

According to another advantageous characteristic of the invention, the balance plate 16 further comprises a self-starting tooth 46. This tooth 46 facilitates the restarting of the escapement when the disarming of the driving member (typically a spring barrel) means that the torque on the escape wheel 12 is no longer sufficient to overcome the resistance of the return spring of the balance wheel during the impulse, causing the escapement to stop. It is possible to adjust the neutral angular position of the balance wheel, i.e. the angular position at which the torque of the return spring of the balance wheel is zero, so that the escapement always stops in a position where a tooth long 38 of the escapement wheel 12 is located between the impulse tooth 28 and the self-starting tooth 46 of the balance plate 16. When the drive member is reset, the escapement wheel 12 starts moving again and the long tooth 38 which is located between the impulse and self-starting teeth 28, 46 cooperates with the self-starting tooth 46 to drive the balance plate 16 in the direction S1 and restart the oscillation of the balance, without the user needing to shake the watch.

The balance plate 16 is preferably in two levels, as shown in the figure 13 . On a first level, it comprises a circular body 48 and, on the periphery thereof, the impulse and self-starting teeth 28, 46 and a radial protrusion 50. A second level comprises the pin 26 projecting from the end of the radial protrusion 50 in the axial direction of the balance plate 16, a truncated circular body 52 aligned with the circular body 48 and, between the pin 26 and the truncated circular body 52, a clearance 54.

The balance plate 16 can be obtained, for example, by multi-level deep reactive ion etching (DRIE) of a silicon substrate, by etching on both sides of a silicon-on-insulator (known as SOI) substrate or by mono -level of two separate silicon substrates then assembly of the two substrates etched by fusion (“fusion bonding”) or another appropriate technique. Materials other than silicon can of course be used. In a variant of the invention, the impulse and self-starting teeth 28, 46 could be in the form of pallets embedded in the circular body 48.

The clearance 54 allows the horns 40, 42 of the fork 20 to pass behind the peg 26 during the clearance phases and the indirect impulse phase (cf. figure 2 , 8 and 10 ). This gives more freedom in the design of the exhaust. Alternatively, however, pin 26 could be the end of a single radial protrusion on a single level as is known per se.

The circular part of the periphery of the truncated circular body 52 serves as a stop on the reverse side of the lugs 40, 42 in the event of an impact to prevent the flip-flop 14 from being overturned from one of its rest positions to the other when the pin 26 is in outside the fork 20. The truncated circular body 52 and the reverse of the lugs 40, 42 advantageously replace the small notched plate and the stinger of traditional escapements and reduces the number of levels (from three to two) of the balance plate and therefore the height of the exhaust.

The rocker 14 is also preferably in two levels, the fork 20 being raised relative to the rest of the rocker 14 to cooperate with the second level 26, 52 of the balance plate 16 and not collide with the wheel. exhaust 12 ni with the impulse and self-starting teeth 28, 46.

Preferably, the impulse surface 34 and the active surface of the long teeth 38 and of the impulse and self-starting teeth 28, 46 have curved profiles allowing cooperation by rolling, in the manner of gears, rather exclusively by sliding, in order to reduce friction and increase the efficiency of the escapement. These profiles can in particular be in the form of an involute of a circle.

The respective inner surfaces 40a, 42a of the horns 40, 42 of the fork 20 can be asymmetrical with respect to each other, in other words, they can have different shapes, as illustrated in the drawings. Thus, the inner surface 40a, which works during the disengagement and the indirect impulse, can have a shape optimized for these two phases and adapted to cooperate by rolling with the pin 26 during the indirect impulse. The lower surface 42a, which works only during the release, can have a shape optimized exclusively for the release.

The present invention has been described above by way of example only. It goes without saying that modifications could be made without departing from the scope of the claimed invention.

Claims (8)

1. Timepiece escapement comprising an escapement wheel (12), a lever (14) and a balance plate (16), the balance plate (16) comprising a peg (26) and an impulse tooth (28), the lever (14) comprising a fork (20), a first rest surface (30), a second rest surface (32) and an impulse surface (34), the escapement being arranged so that, when the balance plate (16) turns in a first direction (S1), the first rest surface (30) blocks the escapement wheel (12) in an entry rest position then releases it under the action of the peg (26) cooperating with the fork (20) so that the escapement wheel (12) comes into contact with the impulse tooth (28) in order to transmit an impulse to the balance plate (16), and when the balance plate (16) turns in the direction (S2) opposite to the first direction (S1), the second rest surface (32) blocks the escapement wheel (12) in an exit rest position then releases it under the action of the peg (26) cooperating with the fork (20) in order that the escapement wheel (12) comes into contact with the impulse surface (34) in order to transmit an impulse to the balance plate (16) via the lever (14), the angle (α) between the entry and exit rest positions being smaller than the angle (β) between the entry rest position and the spindle (B) of the lever (14), these angles (α, β) being seen from the spindle (A) of the escapement wheel (12), characterised in that the escapement wheel (12) comprises short teeth (36) and long teeth (38), the short teeth (36) being intended to cooperate exclusively with the first rest surface (30), the long teeth (38) being intended to cooperate with the second rest surface (32), the impulse surface (34) and the impulse tooth (28).
2. Timepiece escapement as claimed in claim 1, characterised in that the balance plate (16) further comprises an auto-start tooth (46), with which a long tooth (38) of the escapement wheel (12) can cooperate in order to restart the escapement after a stop owing to a lack of torque on the escapement wheel (12).
3. Timepiece escapement as claimed in claim 1 or 2, characterised in that the balance plate (16) comprises, level with the peg (26), a truncated circular body (52), the periphery of which serves as an abutment for the fork (20) in the event of a shock when the peg (26) is outside the fork (20) in order to prevent reversal of the lever (14).
4. Timepiece escapement as claimed in claim 3, characterised in that the balance plate (16) comprises, between the truncated circular body (52) and the peg (26), a clear space (54) able to receive a part of the fork (20).
5. Timepiece escapement as claimed in any one of claims 1 to 4, characterised in that the impulse surface (34) and/or the active surface of the impulse tooth (28) have a curved profile.
6. Timepiece escapement as claimed in claim 2 or any one of claims 3 to 5 when dependent on claim 2, characterised in that the active surface of the auto-start tooth (46) has a curved profile.
7. Timepiece escapement as claimed in any one of claims 1 to 6, characterised in that the fork (20) comprises two horns (40, 42), the respective inner surfaces (40a, 42a) of which are asymmetrical with respect to each other.
8. Timepiece comprising an escapement as claimed in any one of claims 1 to 7.

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