WO2020043720A1

WO2020043720A1 - Clockmaking escapement

Info

Publication number: WO2020043720A1
Application number: PCT/EP2019/072833
Authority: WO
Inventors: Fabiano Colpo; Xuan Mai Tu
Original assignee: Rolex Sa
Priority date: 2018-08-28
Filing date: 2019-08-27
Publication date: 2020-03-05
Also published as: EP3844572A1; CH716705B1

Abstract

The invention relates to an escapement wheel (1; 1') comprising at least one escapement tooth (10; 10'), at least one of the escapement teeth having a transmission surface (11; 11') comprising a first proximal contact surface (11a; 11a') and a second distal contact surface (11b; 11b') which are intended to come into contact with the escapement lock (2), the first proximal contact surface (11a; 11a') being exclusively dedicated to the mechanical transmission of torque from the escapement wheel towards the lock and being arranged so as to act by means of linear contact with the lock during the mechanical transmission of torque from the escapement wheel towards the lock.

Description

Watch escapement.

The invention relates to a watch escapement wheel. It also relates to a watch escapement system comprising such a wheel. It also relates to a watch movement comprising such a wheel or such an escapement system. It also relates to a timepiece, in particular a wristwatch, comprising such a wheel or such a system or such a movement. Finally, it relates to a method of operating such a system or such a movement or such a part.

Patent application WO2013182243 discloses an exhaust comprising an escape wheel designed to cooperate with a blocker made of two separate mobiles. During the pulse phases of the exhaust system, the escape wheel and the blocker mobile then in contact with the escape wheel rotate in opposite directions. It is then said that the drive of the blocker by the escape wheel is tangential. Such a method of operating an exhaust system is advantageous because it requires little energy, the friction being low between the escape wheel and the two mobiles of the blocker. The teeth of the escape wheel each comprise a transmission surface which comprises a distal contact surface intended to come into contact with a blocker mobile, as well as a proximal surface intended to come into contact with a contact surface. impulse of said blocker mobile, these proximal and impulse surfaces being flat. Thus, during a pulse phase of the exhaust system, a transmission surface of a tooth of the escape wheel and a surface of the blocker mobile are at least partially in planar support. Such a conformation is not optimal. The object of the invention is to provide an escape wheel and an exhaust system making it possible to further improve the exhaust systems known from the prior art. In particular, the invention provides a simple escape wheel and making it possible to limit the energy losses by means of a transmission surface of an optimized escape wheel tooth.

An escape wheel according to the invention is defined by claim 1.

Different embodiments of the escape wheel are defined by dependent claims 2 to 9.

A timepiece escapement system according to the invention is defined by claim 10.

Different embodiments of the watch escapement system are defined by the dependent claims 1 1 and 12.

A watch movement according to the invention is defined by the claim

13.

A timepiece according to the invention is defined by the claim

14.

An operating method according to the invention is defined by claim 15.

The attached figures show by way of example two embodiments of a timepiece. Figure 1 is a view of an embodiment of a timepiece comprising a first embodiment of an escapement wheel, an escapement of the timepiece being in a first rest position.

Figure 2 is a detail view of Figure 1 at the contact between a blocker and an escape wheel.

FIG. 3 is a view of the embodiment of the timepiece, the escapement of the timepiece being in a first impulse step.

Figure 4 is a detail view of Figure 3 at the contact between a blocker and an escape wheel.

FIG. 5 is a detailed view of the blocker-escapement wheel contact at a transition time between the first impulse step and a second impulse step.

FIG. 6 is a view of the embodiment of the timepiece, the escapement of the timepiece being in the second impulse step.

Figures 7 and 8 are detail views of Figure 6 at the blocker-escapement wheel contact level.

FIG. 9 is a view of the embodiment of the timepiece, the escapement of the timepiece being in a second rest position. Figure 10 is a detail view of an embodiment of a tooth of an escape wheel.

Figure 1 1 is a view of a second embodiment of the escape wheel.

Figure 12 is a view of a variant of the second embodiment of the escapement wheel.

An embodiment of a timepiece 300 is described below with reference to Figures 1 to 10. The timepiece is for example a watch or a wristwatch. The timepiece may include a mechanical watch movement 200, in particular an automatic watch movement. The timepiece may also include a timepiece assembly, in particular a watch case intended to contain the movement.

The watch movement includes an exhaust system 100 interposed between an oscillator 3 and a gear train connecting an energy accumulator, such as a barrel, to the exhaust system.

The oscillator 3 or resonator is for example of the balance-spring type. The oscillator, in particular the pendulum, for example comprises a plate 32 and a pin 31 or a finger 31. The pin is for example intended to cooperate with a fork 21 c produced on the blocker in order to transmit pulses to the oscillator. The oscillator, in particular the pendulum, is for example pivoted about an axis A on a frame of the movement.

The exhaust system is preferably of the tangential type. The exhaust system includes a blocker 2 and an escape wheel 1.

Preferably, the blocker 2 comprises a first mobile 21 and a second mobile 22. For example, the first mobile is pivoted about an axis B on the frame of the movement. For example, the second mobile is pivoted around an axis C on the movement frame. The axes B and C are preferably distinct and parallel or substantially parallel to each other. In addition, the axes B and C are preferably parallel or substantially parallel to the axis A.

Advantageously, the first mobile 21 comprises a first toothing 21 d and the second mobile 22 includes a second toothing 22d, the first and second toothing being arranged to mesh with one another. Preferably, the first and second teeth are arranged so that the teeth have conjugate profiles theoretically rolling against one another without sliding. The blocker 2 therefore comprises two mobiles 21, 22 configured to mesh with one another.

Each of the first and second mobiles comprises an impulse surface 21 a, 22a and a rest surface 21 b, 22b.

Preferably, the impulse surface 21a of the first mobile 21 includes a portion of cylinder whose director is an involute of a circle or a circle and / or whose generatrices are parallel or substantially parallel to the axis B.

Preferably, the impulse surface 22a of the second mobile 22 includes a portion of cylinder whose directrix is an involute of a circle or a circle and / or whose generatrices are parallel or substantially parallel to the axis C. By "cylinder", we mean, throughout this document, a geometric surface formed by a set of generating lines parallel to each other and resting on or intersecting a directing curve.

The impulse surfaces preferably extend substantially radially relative to the axes of rotation of the mobiles. The impulse surfaces are intended to receive drive forces from the oscillator applied by the teeth of the escapement wheel driven by the energy accumulator via the gear train. Preferably, the rest surface 21 b of the first mobile 21 includes a concave portion, as shown in FIG. 2.

Preferably, the rest surface 22b of the second mobile 22 includes a concave portion.

The rest surfaces preferably extend substantially orthoradially relative to the axes of rotation of the mobiles.

The rest surfaces are intended to block the escapement wheel by action on one of its teeth.

Preferably, such a rest or blocking blocking surface is concave in order to provide security in the event of an impact or a rebound of the escape wheel. Also preferably, such a blocking surface 21b, 22b of the blocker 2 is formed by two sides 210b, 220b, 21 1 b, 221 b configured in hollow and making an angle between 120 ° and 170 °.

The fork 21 c for driving the oscillator is for example made on the first mobile 21.

The escape wheel is mounted so that it can rotate on the frame around an axis D. The axis D is for example parallel to the axes A, B and C. The escape wheel can comprise one or more teeth 10, in particular two, four, five or six teeth or, for example three teeth as in the embodiment shown.

At least one of the escape teeth 10 comprises a transmission surface 1 1 which comprises a first proximal contact surface 1 1 a and a second distal contact surface 1 1 b intended to come into contact with the blocker, the first proximal surface of contact 1 1 a being dedicated exclusively to the mechanical transmission of torque from the escape wheel to the blocker and being arranged to act by punctual contact with the blocker during the mechanical transmission of torque from the escape wheel to the blocker.

By “point contact between surfaces”, it is meant that there is a point contact between these surfaces in one or more planes perpendicular to the axis D. Consequently, considering the thickness of the escape wheel and the blocker , there is in fact a linear or linear contact between the wheel and the blocker, that is to say that there is a contact along a line or substantially along a line between the wheel and the blocker. This linear contact is preferably rectilinear. It can nevertheless be curvilinear. Thus, the term "punctual" does not have a temporal meaning in this document. Advantageously, the first proximal contact surface 1 1a extends over at least 20%, or even at least 30%, even at least 40%, of the extent of the transmission surface 1 1. This extent is advantageously measured in a plane perpendicular to the axis D.

The contact surfaces 1 1 a and 1 1 b are intended to come into contact with the blocker, namely that all of the points of these surfaces are capable of coming into contact with the blocker. The proximal and distal surfaces constitute all or part of the transmission surface 1 1.

The transmission surface 1 1 extends from a first contact point P1 between the first proximal contact surface 1 1 a and an impulse surface of the blocker initiating a pulse phase of the exhaust device at a second point contact P2 between the second distal contact surface 11 b and said pulse blocker surface closing said pulse phase of the exhaust device.

“Pulse phase” means a phase in which the escapement wheel transmits a motor torque to the oscillator 3 or resonator by means of a contact drive of the blocker 2. During a phase of impulse, a transmission surface 11 of the wheel is thus in contact with a pulse surface 21 a, 21 b of the blocker 2. The transmission surface 1 1 constitutes all or part of a tooth surface of the wheel escapement extending radially or substantially radially relative to the axis D. By "distal surface" and "proximal surface" is meant surfaces arranged so that the distal surface is farther from the D axis than is the proximal surface. Preferably, the distance to the D axis from any point on the surface distal is greater than the distance to the D axis from any point on the proximal surface.

The proximal surface is optimized and is exclusively dedicated, during the exhaust system's impulse phases, to the mechanical transmission of torque from the exhaust wheel to the blocker. More particularly, the proximal surface is designed to cooperate exclusively, by punctual or linear contact, with impulse surfaces 21a, 22a of the blocker. Advantageously, the distal surface is also intended to cooperate with impulse surfaces 21a, 22a of the blocker. The distal surface is furthermore also intended to cooperate with blocking or resting surfaces 21b, 22b of the blocker during rest positions of the exhaust system. In such positions, a tooth 10 of the escapement wheel bears against a predefined locking surface 21b, 22b of the blocker 2.

Thus, the transmission profile or surface 1 1 of tooth 10 of the escape wheel 1 is provided to make coexist a first function of torque transmission from the escape wheel to the blocker and a second function of blocking the wheel d exhaust, while optimizing the first torque transmission function by minimizing, in particular as much as possible, the sliding contact between the escapement wheel and the blocker. This improves energy transmission from the escapement wheel to the blocker.

According to a first embodiment, the transmission surface 11 comprises a first proximal contact surface 1 1 a convex, as well as a second distal contact surface 1 1 b convex, the proximal and distal surfaces being connected by at least one edge or at least one intermediate surface 1 1 c. According to a particular variant of the first embodiment as illustrated by Figures 1 to 10, the proximal and distal surfaces are connected by an intermediate surface 1 1 c concave. Alternatively, the intermediate surface 1 1 c could be flat. Preferably, the intermediate surface 1 1 c is not intended to come into contact with the impulse surfaces 21 a, 22a of the blocker.

By "convex surface" is meant that the surface of the tooth forms a boss oriented in a first direction, in particular a protruding boss. By "concave surface" is meant that the surface of the tooth forms a boss oriented in a second direction, in particular a hollow boss.

In other words, according to the first embodiment, at least one of the escape teeth 10 comprises a proximal contact surface 1 1 a and a distal contact surface 1 1 b having a radius of curvature of the same sign, the distal surfaces and proximal being connected by at least one edge or at least one intermediate surface 1 1 c:

- of radius of curvature zero; or

- whose sign is opposite to that of the radius of curvature of the proximal contact surfaces 1 1 a and distal contact 1 1 b; or

- plane ; or

- whose radius of curvature is greater than 0.02 mm.

By "edge" is meant a line of intersection between two continuous surfaces.

The proximal contact surface is advantageously configured to come exclusively into contact with the impulse surface 21 a, 22a of the blocker 2. Advantageously, this proximal contact surface may comprise a portion of a first cylinder of revolution R1 a parallel to the axis D as shown in FIG. 10 or may substantially comprise a portion of a first cylinder of revolution R1 a parallel to the axis D or may include a portion of cylinder whose directrix is an involute of a circle and whose generatrices are parallel to the axis D.

The distal surface 1 1b of the profile 1 1 or of the surface 1 1 of transmission of the tooth 10 of the escape wheel 1 may, for its part, have, due to its convexity, a geometry complementary to that of said surface of blocking 21 b, block 22b of blocker 2. This complementarity is not necessarily strict. Indeed, the complementarity can simply result from the fact that the distal surface is convex and that the rest surface (s) are concave. The distal surface 11 b of the profile 1, during the rest positions of the exhaust system, is preferably shaped so as to be positioned tangent to said blocking surface 21b, 22b of the blocker, in particular tangent to the two sides 210b, 220b and 21 1b, 221b forming a concave blocking surface 21b, 22b of the blocker 2.

The distal contact surface is advantageously configured to come into contact with the impulse surfaces 21a, 22a of the blocker 2 and to come into contact with the rest surfaces 21b, 22b of the blocker 2.

Advantageously, the distal contact surface comprises a portion of a second cylinder of revolution R1 b parallel to the axis D as shown in FIG. 10 or substantially comprises a portion of a second cylinder of revolution R1 b parallel to the axis D. The ratio of the radius of the first cylinder to the radius of the second cylinder can be between 7 and 1 1, 7 and 9 inclusive, in particular between 8 and 10, 8 and 10 inclusive, preferably equal to 9 or substantially equal to 9 .

The intermediate surface can, for its part, comprise a portion of a third cylinder of revolution R1 c parallel to the axis D as shown in FIG. 10 or substantially comprise a portion of a third cylinder of revolution R1 c parallel to the 'axis D.

According to a second embodiment, the escape wheel 1 'partially shown in Figures 1 1 and 12 comprises a first proximal contact surface 1 1 a' formed in the continuity of a second distal contact surface 1 1 b ' , or vice versa, so as to form a transmission surface 1 1 ′ without an intermediate surface. In this embodiment, the proximal and distal surfaces constitute the transmission surface 1 1. Advantageously, such an embodiment allows torque transmission without contact discontinuity between the transmission surface of the escape wheel and the surface d pulse from the blocker. The direction of the planes tangent to the transmission surface therefore evolves continuously and without rupture along the transmission surface.

In Figures 1 1 and 12, the elements having the same functions as those already shown in the previous figures have the same references to which a "‘ "has been added.

According to a particular variant of the second embodiment as illustrated in Figure 1 1, the proximal contact surface 1 1 a 'may include at least a first flat or substantially flat portion 1 1 1 a ', 1 12a' and at least one second concave portion 1 13a '. As for the distal contact surface 11 b ', it is convex.

Whatever the embodiment considered, the different teeth of the escapement wheel can be identical. Alternatively, only one or certain teeth of the escapement wheel can be shaped as described above.

As shown exaggeratedly in FIG. 12, microscopic or nanoscopic discontinuities can be formed on the proximal and distal surfaces of the transmission surface, in particular for the purpose, for example, of accommodating a lubricant therein. This does not change the planar, convex, or concave character of these surfaces on the macroscopic scale.

An embodiment of an operating method of an exhaust system as mentioned previously or of a timepiece movement as mentioned previously or of a timepiece as mentioned previously is described below in reference to Figures 1 to 10.

The oscillator and the exhaust system are initially assumed to be in the position of FIGS. 1 and 2, the pin of the oscillator being in a position of limit of contact with the first blocker mobile. The oscillator rotates counterclockwise relative to the axis A in Figure 1. The first blocker mobile is in the locking position of the escape wheel, the distal surface 1 1b being in abutment against the resting surface 21 b. The distal surface 11 b of the profile 11 of the tooth 10 is here tangent to the sides 210b, 21b of the blocking surface 21b of said mobile 21. The oscillator rotating counterclockwise relative to the axis A in Figure 1, it drives, via the pin 31 and the fork 21 c, the first movable clockwise until reaching the position shown in Figures 3 and 4 .

We then reach the positions of the oscillator and the exhaust system illustrated by Figures 3 and 4. These Figures 3 and 4 illustrate the start of a first stage of an impulse phase, the proximal surface 1 1 a of the profile 11 of the tooth 10 of the wheel 1 starting its cooperation by contact with the impulse surface 21 a of the first mobile 21 of the blocker 2 at a contact point P1. During this first step, the proximal surface 11 a of the profile 11 of the tooth 10 of the wheel 1 leads the first mobile 21 by cooperating by contact with the impulse surface 21 a of the first mobile 21. In the case where the surface proximal 1 1 a and the impulse surface 21 a each have a tooth profile in involute form of a circle, the escape wheel and the first mobile theoretically roll against each other without slipping. During this cooperation by contact of the proximal surface 1 1 a and the impulse surface 21 a, the point of contact between the tooth 10 and the impulse surface 21 a is located on a line of engagement or line of pressure L1 represented in FIG. 5. Preferably, the pressure angle formed by the perpendicular PC to the line of centers LC of the escapement wheel 1 and of the first mobile 21 (or passing through the axes B and D) and the line of engagement L1 is of the order of 20 °. Of course, this angle can be between 10 ° and 40 °. FIG. 5 illustrates such a meshing line L1 at the moment when the first step of said pulse phase ends, namely at the moment when the distal surface 1 1b of the profile 1 1 comes into contact with the surface of pulse 21 a of the first mobile 21. Thus, the method comprises a first step of applying a first mechanical action of the proximal contact surface 1 1 a convex of a tooth 10 of the escape wheel on the impulse surface of the blocker 21 a. This first step is a first step of the impulse phase. The first mobile of the blocker consequently applies a force, in particular a torque, or a pulse on the oscillator.

The first mobile 21 continuing to rotate under the action of the tooth on the impulse surface 21 a, the positions of the oscillator and of the exhaust system illustrated by FIGS. 6 to 8 are then reached. 8 illustrate a second step of an impulse phase, the escape wheel 1 cooperating by contact with the first mobile 21 of the blocker 2. During this second step, the distal surface 1 1 b of the profile 1 1 of tooth 10 of the wheel 1 leads the first mobile 21 by cooperating with the impulse surface 21 a of the first mobile 21. During the cooperation of the surfaces 11b and 21a, the point of contact between the tooth 10 and the impulse surface 21a is located on a meshing line or pressure line L2. Preferably, the pressure angle b formed by the perpendicular PC to the line of centers LC of the escapement wheel 1 and of the first mobile 21 (or passing through the axes B and D) is zero or substantially zero.

Thus, preferably, the angle y (represented in FIG. 8, by means of a virtual extension of the line L1 drawn in light gray and dotted) formed by the lines L1 and L2 is of the order of the value from angle a. This angle can be between 10 ° and 40 °. FIG. 8 illustrates such a meshing line L2 at the moment when the second step of said pulse phase is about to end while the distal surface 1 1b is in contact with the pulse surface 21 a at a point P2, namely when the distal surface 1 1 b of profile 1 1 is about to no longer cooperate with the impulse surface 21a of the mobile 21.

Thus, the method comprises a second step of applying a second mechanical action of the distal contact surface 11 b of the tooth on the impulse surface 21 a of the blocker. This second step is a second step of the impulse phase. The first mobile of the blocker consequently applies a force, in particular a torque, or a pulse on the oscillator.

Preferably, the first stage is maintained during a stroke of the blocker whose amplitude is equal to or greater than 30%, or even is equal or greater than 40%, or even is equal or greater than 50%, of the amplitude of the stroke total of the blocker during the pulse phase.

More preferably, the second step is maintained during a stroke of the blocker whose amplitude is equal to or greater than 30%, or even is equal or greater than 40%, or even is equal or greater than 50%, of the amplitude of the total stroke of the blocker during the pulse phase.

During the pulse phase of the exhaust system, the escape wheel 1 transmits a torque to the blocker 2 so as to cause and maintain the oscillations of the oscillator 3 by means of the fork 21c of the mobile 21 of blocker cooperating with the pin 31 of the plate 32 of the resonator 3. During the pulse phase of the exhaust system, the escape wheel 1 transmits a driving torque to the oscillator 3 or resonator by means of a drive by blocker contact 2.

At the end of the impulse phase, the tooth of the escape wheel leaves the impulse surface 21 a (under the effect of the torque produced by the member engine) and abuts against the rest surface 22b of the second mobile 22 of the blocker as shown in FIG. 9.

Thus, interaction steps similar to those described above can occur between a tooth of the escapement wheel and the second blocker mobile.

Thus, the escape wheel 1 can cooperate in the same way with the second mobile 22 of the blocker 2, and in particular with the pulse surface 22a of the second mobile 22 during another pulse phase of the exhaust system. .

The operation of the exhaust system or the movement or the timepiece can therefore include iterations of the following cycle:

- Rest of the escapement wheel on the rest surface 21 b of the first mobile 21; then

- Impulse of the escape wheel on the impulse surface 21a of the first mobile 21 comprising:

o First impulse step of the proximal surface 11 a of the escapement wheel on the impulse surface 21 a of the first mobile 21; then

o Second step of impulsing the distal surface 11 b of the escapement wheel on the impulse surface 21 a of the first mobile 21; then

- Rest of the escapement wheel on the rest surface 22b of the second mobile 22; then

- Release of the pin 31 of the plate 32 of the oscillator 3 of the fork 21 c of the first mobile 21; then

- Impulse of the escape wheel on the impulse surface 22a of the second mobile 22 comprising: o First impulse step of the proximal surface 11 a of the escape wheel on the impulse surface 22a of the second mobile 22; then

o Second impulse step of the distal surface 11 b of the escapement wheel on the impulse surface 22a of the second mobile 22; then

- Release of the pin 31 of the plate 32 of the oscillator 3 of the fork 21 c of the first mobile 21.

Preferably, the first proximal surface of the transmission surface of an escape wheel tooth is shaped so as to generate a point or line contact between said escape wheel and a blocker wheel during a phase of pulse from the exhaust system. Preferably, this point or line contact is maintained throughout the first impulse step or for a portion greater than 50%, even 70%, or even 90% of the first step (this portion representing the stroke of the blocker in point contact or linear with the wheel on the travel of the blocker during all the first impulse step).

Preferably, the point of point or line contact moves on the first proximal surface and / or on the impulse surface of the blocker during the first impulse step.

Preferably, the impulse surfaces of the blocker are also arranged so as to ensure punctual or linear contact between the escapement wheel and the blocker, as described above.

This operation can also be implemented using an escape wheel as described with reference to FIGS. 11 and 12. The second mobile 22 can therefore cause and maintain the oscillations of the oscillator 3 by means of the first mobile 21, and in particular by means of the toothing 22d cooperating with the toothing 21 d of the mobile 21, as taught within patent application WO2013182243.

Overall, the escape wheel and the exhaust system operate in a similar manner to those disclosed in application WO2013182243.

However, as seen previously, the escapement wheel described above has the particularity here of comprising teeth provided with optimized mechanical transmission surfaces between the escapement wheel and a blocker taking part in the timepiece escapement. This optimizes the transmission ratio between the mobiles and minimizes friction during the operation of the exhaust. In addition, the geometries chosen make it possible to make the torque transmitted from the escapement wheel to the oscillator as constant as possible throughout the pulse phase.

Claims

Claims:

1. Escape wheel (1; 1 ') comprising at least one escape tooth (10; 10'), at least one of the escape teeth comprising a transmission surface (1 1; 11 ') which comprises a first proximal contact surface (1 1 a; 11 a ') and a second distal contact surface (1 1 b; 1 1 b') intended to come into contact with an exhaust blocker (2), the first surface contact proximal (1 1 a; 1 1 a ') being dedicated exclusively to the mechanical transmission of torque from the escape wheel to the blocker and being arranged to act by linear contact with the blocker during the mechanical transmission of torque the escape wheel towards the blocker.

2. Escape wheel according to the preceding claim, characterized in that the second distal contact surface is configured to come into contact with a pulse surface (21a, 22a) of a blocker (2) and to come into contact with a rest surface (21b, 22b) of said blocker (2).

3. Escape wheel according to one of the preceding claims, characterized in that the second distal contact surface (1 1 b) is convex and the first proximal contact surface (1 1 a) is convex, the second distal surface and the first proximal surface being connected by at least one edge or at least one intermediate surface (1 1 c) planar or concave.

4. Escape wheel according to the preceding claim, characterized in that the intermediate surface comprises a portion of a third cylinder of revolution (R1 c) or comprises substantially a portion of a third cylinder of revolution (R1 c).

5. Escape wheel according to claim 3 or 4, characterized in that the first proximal contact surface comprises a portion of a first cylinder of revolution (R1 a) or substantially comprises a portion of a first cylinder of revolution ( R1 a) or includes a portion of cylinder whose directrix is an involute of a circle.

6. Escape wheel according to one of the preceding claims, characterized in that the second distal contact surface comprises a portion of a second cylinder of revolution (R1 b) or substantially comprises a portion of a second cylinder of revolution (R1 b).

7. Escape wheel according to claims 5 and 6, characterized in that the ratio of the radius of the first cylinder to the radius of the second cylinder is between 7 and 1 1, in particular between 8 and 10, preferably equal to 9 or substantially equal to 9.

8. Escape wheel according to one of claims 1 and 2, characterized in that the first proximal contact surface (11 a ’) is formed in continuity with the second distal contact surface (1 1 b’).

9. Escape wheel according to one of claims 1, 2 and 8, characterized in that the first proximal contact surface (1 1 a ') comprises at least one concave portion (1 13a'), in particular in that the first proximal contact surface (1 1 a ') comprises at least a first flat or substantially flat portion (1 1 1 a ', 1 12a').

10. Watch exhaust system (100), the system comprising an escape wheel according to one of the preceding claims.

1 1. Watchmaking exhaust system according to the preceding claim, characterized in that the system is of the tangential type and / or in that the system comprises a blocker (2) including two mobiles (21, 22) configured to mesh the one with the other.

12. Watchmaking exhaust system according to one of claims 10 and 1 1, characterized in that the system comprises two mobiles (21, 22) each having a pulse surface (21a, 22a) including a cylinder portion the director of which is an involute of a circle and / or each having a concave rest surface (21b, 22b) and / or in that the blocker and the escape wheel are arranged so that a pressure angle (a ) trained by :

a perpendicular (PC) to a line of centers (LC) of the escapement wheel and the blocker, and

a line of meshing (L1) at the level of a contact between the proximal contact surface (1 1 a) convex and an impulse surface (21 a, 22a) of the blocker,

is between 10 ° and 40 °, 10 ° and 40 ° inclusive, or even is between 15 ° and 30 °, 15 ° and 30 ° inclusive, for example is equal or substantially equal to 20 °.

13. Watch movement (200) comprising a system according to one of claims 10 to 12 and / or an escapement wheel according to one of claims 1 to 9.

14. Timepiece (300), in particular wristwatch, comprising a timepiece movement (200) according to the preceding claim and / or a system according to one of claims 10 to 12 and / or an escape wheel according to the one of claims 1 to 9.

15. Method of operating an exhaust system (100) comprising an escape wheel (1) and an escape wheel blocker (2), in particular a system according to one of claims 10 to 12, the process comprising:

a first step of applying a first mechanical action of a first proximal contact surface (1 1 a;

1 1 a ') of an escapement wheel tooth (10; 10') on a blocking impulse surface (21a, 22a), in particular a first step of applying a first mechanical action of a first proximal contact surface (1 1 a) convex of an escape wheel tooth (10) on a pulse surface of the blocker (21 a, 22a); and

a second step of applying a second mechanical action of a distal contact surface (1 1 b; 1 1 b ’) convex of the tooth on the impulse surface of the blocker.