Self-starting profile for a clock escapement

Abstract

To provide a timepiece escapement mechanism improved in the self-starting of calibers not sufficient for an escapement to start on its own.SOLUTION: A timepiece escapement mechanism includes a lever 10 and an escapement wheel. The lever 10 is arranged to cooperate with an inertial mass of a mechanical oscillator and, at pallets 1 carried by the lever 10 or included in the lever 10, cooperate with teeth of the escapement wheel. The contact between a pallet 1 and an escapement tooth includes at least three zones, namely: a rest zone where the torque is in the negative direction, where the angle between the normal to the contact and the radius vector of the lever 10 is negative; a first zone corresponding to the first half lift angle, where the torque is in the positive direction, and where the angle ω1 is positive; and a second zone corresponding to the second half lift angle, where the torque is in the positive direction, and where the angle ω2 is positive.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an escapement mechanism for a timepiece, including at least one lever and at least one escape wheel, wherein the at least one lever cooperates on the one hand with the inertial mass of a mechanical oscillator and is directly or indirectly subjected to the action of elastic return means included in the mechanical oscillator, and on the other hand, in a plurality of pallets carried by or included in the lever, is arranged to cooperate with a plurality of teeth included in the at least one escape wheel.

[0002] The present invention relates to the field of escapement mechanisms for timepieces.

Background Art

[0003] One of the important characteristics of an escapement mechanism for a timepiece is self-starting. This is the ability of the escapement mechanism to restart "by itself" after the movement has stopped. There are two important situations where this characteristic is relevant. · At the end of the power reserve, the barrel is completely lowered and the movement stops. At this time, if the barrel is wound up by the stem without moving the timepiece, it will be evaluated that the escapement restarts, that is, the movement is vibrated again without the need to move the timepiece. · When winding the barrel, due to an impact or sudden acceleration to the timepiece, the movement may temporarily stop, for example, at a position close to its stop position. In such cases of impact or sudden acceleration, it will be evaluated that the escapement restarts, that is, the movement is vibrated again without the need to move the timepiece again.

[0004] Most known escapements can be broadly classified into two classes: · Potentially self-starting escapements such as Swiss lever escapements and coaxial escapements · Essentially non-self-starting escapements such as detent escapements and Robin escapements widely used in marine chronometers into which they are classified.

[0005] The criterion for differentiating between these two classes is whether the gang wheel can be in the stop plane when the template is in its stop position (the torque of the hairspring or flexible guide blade is zero). When the gang wheel is in the stop plane when the template is in the stop position, the escapement cannot start by itself.

[0006] Most escapements used in wristwatches potentially self-start, especially due to the risks associated with acceleration. The template must not stop due to shock or sudden acceleration and must not be able to start vibrating again.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The invention described in this specification relates to optimizing the self-start of escapement mechanisms that already potentially self-start.

[0008] For a potentially self-starting escapement to start, the barrel torque must be sufficient to wind the hairspring, and more generally, sufficient to overcome the return torque of the oscillator (e.g., the stiffness of the flexible guide). This means that when the barrel is almost fully unwound, a potentially self-starting escapement will not start by itself. When the barrel is fully wound, the situation varies depending on the calibre in question. Some calibres self-start, while others require a little "shaking" to start them.

[0009] The object of the present invention is to improve the self-start of calibres where "potentially self-starting" but the torque of their fully wound barrel is not sufficient for the escapement to start by itself.

Means for Solving the Problems

[0010] The present invention consists in optimizing the shape of the pallet of the lever and / or the teeth of the escape wheel in order to promote self-starting. To achieve this, specific pallet and / or tooth geometries are created such that the return torque of the pendulum directly attached to the escape wheel is substantially constant over the full restraint angle.

[0011] For this purpose, the present invention relates to the escapement mechanism of a clock according to claim 1.

[0012] The present invention also includes a clock movement comprising such an escapement mechanism.

[0013] The present invention also includes a clock, in particular a wristwatch, comprising at least one such clock movement.

Brief Description of the Drawings

[0014] The objects, advantages and features of the present invention will become more apparent upon reading the following detailed description with reference to the accompanying drawings.

Figure 1

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Embodiments for Carrying out the Invention

[0015] The present invention relates to a decoupling mechanism 100 of a timepiece including at least one lever 10 and at least one escape wheel 20. This at least one lever 10 is, on the one hand, arranged to cooperate with the inertial mass 40 of a mechanical oscillator 400 and is directly or indirectly subjected to the action of elastic return means 50 included in this mechanical oscillator 400. And this at least one lever 10 is, on the other hand, arranged to cooperate with a plurality of teeth 2 included in this at least one escape wheel 20 in a plurality of pallets 1 carried by this lever or included in this lever 10.

[0016] According to the invention, at least one of the pallets 1 and / or at least one of the teeth 2 includes an impulse zone including two zones, one for an inclined portion for which the elastic return means serves to drive the escape wheel 20 and the other for another inclined portion for which the elastic return means 50 serves to oppose the escape wheel 20, the two zones being arranged to minimize the maximum moment of the elastic return means as seen from the escape wheel 20.

[0017] More specifically, each of the pallets 1 and / or each of the teeth 2 includes an impulse zone including two zones, one for an inclined portion for which the elastic return means serves to drive the escape wheel 20 and the other for another inclined portion for which the elastic return means 50 serves to oppose the escape wheel 20, the two zones being arranged to minimize the maximum moment of the elastic return means as seen from the escape wheel 20.

[0018] Figure 1 shows a prior art escapement, for example, but not limited to, a "standard" Swiss lever escapement as described in the Illustrated Professional Dictionary of Horology by M. G-A Berner, FH Swiss Watchmaking Industry, item 1660F, where the curve showing the return torque CR of the pendulum directly attached to the escape wheel as a function of the angle of the escape wheel on the vertical axis has a linear shape between symmetrical moment values, +Mmax and -Mmax.

[0019] The angular range of the escape wheel corresponds to the half angle θ = 360° / number of teeth / 2 between two teeth. This is the forward angle of the escape wheel during the alternation of the pendulum when the pendulum moves through the restraint angle.

[0020] In the left half of the angular range, it can be seen that the return torque of the pendulum (for example, the torque of the hairspring) helps the displacement of the lever (negative torque), so the escape wheel does not need to apply torque to displace the lever. However, in the right half of the angular range, since the return torque of the pendulum returns the lever to its intermediate position, the escape wheel needs to apply an increasing amount of torque (positive increasing torque) to displace the lever. Here, the "intermediate position" refers to the position of the lever when the inertial mass of the pendulum is in the equilibrium position. At this position, the elastic return means such as a spiral spring or a flexible guide does not apply any force or torque to the lever.

[0021] The object of the present invention is to propose a pallet and tooth profile such that the return torque CR of the pendulum directly attached to the escape wheel is close to the following shape shown in Figure 2. · A small angular range on the left where the return torque of the pendulum directly attached to the escape wheel is strongly negative. In this range, the elastic return means of the pendulum helps the forward movement of the lever, so the escape wheel has no torque to overcome. · For all the rest of the angular range where the torque is generally positive and constant.

[0022] By energy inference, it can be shown that by doing this, the torque required for the gang gear to displace the lever is in the range of up to one-fourth of the prior art. In fact, when the coefficient of friction is zero, mechanical energy is conserved. This means that the integral of torque with respect to the angle in the gang gear must be equal to the elastic energy Eel of the return spring of the pendulum when the pendulum exits the restraint angle.

[0023] In the prior art, the integral value of torque with respect to the angle of the gang gear is Mmax / 2 × θ / 2 (the area of each of the two left and right triangles in FIG. 1). Therefore, since Mmax / 2 × θ / 2 = Eel, Mmax = 4Eel / θ, and θ = 4Eel / Mmax.

[0024] In the case of the present invention, two cases for the moment values Mleft (denoted as Ml in FIG. 2) and Mright (denoted as Mr in FIG. 2) are processed separately. · In the left range, the energy calculation is Mleft × θ / 10 = -Eel, and Therefore, Mleft = -10Eel / θ = -2.5Mmax. · In the right range, Mright × θ × 9 / 10 = Eel, Therefore, Mright = 10 / 9 × Eel / θ = approximately 1 / 4Mmax.

[0025] When the coefficient of friction is other than zero, these calculations become more complicated, but the law that "if the restoring torque of the pendulum directly attached to the gang gear is managed to be constant, the torque required for self-starting becomes smaller" generally remains valid.

[0026] Therefore, it becomes a problem to define the appropriate geometric shape of a plurality of pallets (or a plurality of teeth) so that the restoring torque of the pendulum directly attached to the gang gear becomes substantially constant. FIG. 3 shows a lever pallet 1 on the left side and a tooth 2 of the gang gear 20 that presses this lever pallet 1 on the right side. The pallet 1 includes a contour that brings about a change according to the present invention suitable for addressing this problem, and the contour includes the following series of three zones. · In particular, but not limited to, a first zone Z1 including a stop plane. · A second zone Z2 where the elastic return means 50 of the pendulum 400 helps drive the gang gear. More specifically, when the pendulum is a beard escapement assembly, this second zone Z2 is a "template drive" surface, in particular, but not limited to, a "template drive" plane. · A third zone Z3 where the elastic return means of the pendulum helps counteract the gang gear. More specifically, when the pendulum is a beard escapement assembly, this third zone Z3 is, without limitation, a "constant torque" surface. The protrusion 2 of the tooth of the gang gear 20 pushes the lever 10 throughout this third zone Z3. When the protrusion of the tooth reaches the heel portion of the pallet 1, the impulse to the tooth 2 begins, and the "plane" of the tooth 2 pushes the heel portion of the pallet.

[0027] FIG. 4 shows a standard lever pallet 1 having a stop plane ZR and an impulse plane Z0 on the left side, and a tooth 2 of the gang gear 20 that presses the edge of this standard pallet separating the stop plane ZR and the impulse plane Z0 on the right side.

[0028] FIG. 6 shows the pallet 1 according to the present invention.

[0029] The first zone Z1 according to the present invention is the conventional stop plane ZR of a standard lever pallet.

[0030] The second zone Z2 is connected to the first zone Z1 at a first edge A. In a specific case, the second zone Z2 and the first zone Z1 are planes and form a dihedral angle.

[0031] The third zone Z3 is connected to the second zone Z2 at the second edge B. In a specific case not shown, the second zone Z2 and the third zone Z3 are planes and form a dihedral angle. In another specific case not shown, the third zone Z3 is formed by two planes that form a dihedral angle.

[0032] Through various simulations, the curves of FIGS. 5 and 7 below, which show the change in torque on the vertical axis as a function of the angle of the gangue vehicle on the horizontal axis, can be drawn. · The curve of FIG. 5 for the standard pallet of FIG. 4. · The curve of FIG. 7 for the pallet according to FIG. 3 specific to the present invention.

[0033] FIGS. 5 and 7 show, on the one hand, the ideal case without friction represented by a dashed line, and on the other hand, the case with a friction coefficient of 0.15 represented by a solid line.

[0034] For the standard pallet of FIG. 4, FIG. 5 shows a torque diagram from the simulation, and since the teeth of the gangue vehicle are not "in contact" with the pallet, the "negative" torque of the helical spring directly attached to the gangue vehicle is not shown. The maximum torque is approximately 0.59 without friction (0.85 with a friction coefficient of 0.15) (in arbitrary units).

[0035] FIG. 6 shows the pallet according to the present invention on the left side and, on the right side, the teeth of the gangue vehicle that compress the second edge B of this pallet, which separates the second zone Z2 from the third zone Z3. The outline of the standard pallet of FIG. 4 is drawn in dashed lines superimposed together with its impulse plane Z0 and its stop plane ZR, and the stop plane ZR is here constituted by the first zone Z1. It is clear that the lever pallet according to the present invention is longer than the standard pallet if all conditions are the same, and the impulse plane Z0 of the standard pallet is replaced by the composite plane resulting from the juxtaposition of the second zone Z2 and the third zone Z3. More specifically, the third zone Z3 includes at least one flat surface and, more specifically, is a plane.

[0036] The right side of Figure 7 shows the torque diagram of the solution according to the present invention, the optimized pallet (+ teeth). The maximum torque is about 0.29 without friction (0.45 with a friction coefficient of 0.15) (in any unit of torque). The desired torque smoothing is obtained, which is obtained in both a theoretical variant without friction and a variant close to the actual conditions with a friction coefficient of 0.15.

[0037] The relative gain of the moment of the return torque CR is close to the coefficient 2 and smaller than the expected coefficient 4. The reason is as follows. · The actual impulse is not symmetric as shown in the figure. · The transmission ratio of the "lever and gang gear" changes at the end of the impulse (when shifting from the contact of the "tooth protrusion and pallet plane" to the contact of the "tooth plane and pallet protrusion"). This is already moving in the direction of optimization with a standard pallet.

[0038] Figure 8 shows the geometric shape suitable for this simulation. For each surface, a tangent to the curve is drawn at the center of the relevant contact zone, and from this point, · The normal to the curve (and thus perpendicular to this tangent) is drawn as a dashed line, · A radial line connecting the pivot axis of the angle to this point is drawn as a solid line.

[0039] The angle from the normal to the radial is not always in the same direction. Here, the angle in the trigonometric direction in the figure is called positive, and the angle in the opposite direction is called negative.

[0040] More specifically, · In the first zone Z1, particularly but not limited to, in the first plane, the first angle ω1 formed between the first normal N1 of the first zone Z1 at the midpoint P of this first zone Z1 and the first radial OP connecting the pivot axis O of the other lever to this point P is negative, and the torque is in the negative direction. · In the second zone Z2, and more particularly, but not limited to this, in the second plane, the second angle ω2 formed between the second normal N2 of the second zone Z2 at the midpoint Q of the second zone Z2 and the second radius vector OQ connecting the pivot axis O of the lever to this point Q is positive, and the torque is in the positive direction. · In the deformation example shown in the figure, although it is a curved surface, in the third zone Z3 which can also include (but is not limited to this) at least one third plane, the third angle ω3 formed between the third normal N3 of the third zone Z3 at the midpoint R of the third zone Z3 and the third radius vector OR connecting the pivot axis O of the lever to this point R is positive, and the torque is in the positive direction.

[0041] More specifically, the second angle ω2 between the second normal N2 and the second radius vector OQ is smaller than atan(μ), where μ is the coefficient of friction between at least one pallet 1 and at least one tooth 2, and the notation "atan" means arctangent. The coefficient of friction μ is preferably included between 0.10 and 0.30. More specifically, the coefficient of friction μ is included between 0.12 and 0.24. Even more specifically, the coefficient of friction μ is equal to 0.2. As a result, the angle ω1 between the normal N1 and the radius vector OQ is smaller than atan(0.2).

[0042] More specifically, the third angle ω3 between the third normal N3 and the third radius vector OR is larger than atan(μ). The coefficient of friction μ is preferably included between 0.10 and 0.30. More specifically, the coefficient of friction μ is included between 0.16 and 0.24. Even more specifically, the coefficient of friction μ is equal to 0.2. As a result, the angle ω1 between the normal N1 and the radius vector OQ is larger than atan(0.2).

[0043] It is understood that this geometric shape can be applied to both the plurality of pallets of the lever and the plurality of teeth of the gang gear.

[0044] The plurality of pallets can be fixed to the oscillator (friction stop).

[0045] The special contour described in this specification can be adapted to the teeth of the gang gear.

[0046] More specifically, the contact portion between the lever pallet 1 and the tooth 2 of the gang wheel 20 is called a stop zone, and includes at least three zones: a first zone where the torque is in the negative direction and the angle between the normal line of the contact portion and the radius vector of the lever is negative; a second zone corresponding to the first half of the restraint angle, where the torque is in the positive direction and the angle is positive and smaller than a predetermined value; and a third zone corresponding to the second half of the restraint angle, where the torque is in the positive direction and the angle is positive and has a limiting value larger than this predetermined value.

[0047] More specifically, this predetermined value is atan(0.2) when the coefficient of friction μ is 0.20, and atan(0.15) in the case of the simulations of FIGS. 5 and 7 where the coefficient of friction μ is 0.15.

[0048] The present invention further includes, among other things and without being limited thereto, a timepiece movement 500 as described in the Illustrated Professional Dictionary of Horology by M. G-A Berner, Swiss Watchmaking Federation FH, item 3091A, the timepiece movement 500 being arranged to transmit energy to at least one such escapement mechanism 100 ru e an energy storage and distribution means 200 and a gear train 300, and at least one mechanical oscillator 400 having at least one inertial mass 40 returned by an elastic return means 50, the inertial mass 40 being arranged to cooperate with the at least one lever 10 at least and includes.

[0049] More specifically, the mechanical oscillator 400 is a hairspring oscillator.

[0050] Naturally, the present invention is also applicable when the pallet 1 is made of a material other than the lever 10 itself, and the optimal coefficient of friction μ can be adjusted. More specifically, at least one pallet 1 is directly attached to the body included in the lever 10 and is made of a material other than the material of this lever body.

[0051] More specifically, the mechanical oscillator 400 is a flexible induction oscillator having at least one inertial mass 40 suspended by a thin elastic blade constituting the elastic return means 50 of the oscillator 400.

[0052] The invention also includes a timepiece 1000, in particular a wristwatch, comprising at least one such timepiece movement 500.

Claims

**Claim 1** An escapement mechanism (100) for a timepiece, comprising at least one lever (10) and at least one escape wheel (20), wherein said at least one lever (10) cooperates on the one hand with the inertial mass (40) of a mechanical oscillator (400) and is arranged to be directly or indirectly subjected to the action of elastic return means (50) included in said mechanical oscillator (400), and on the other hand, in a plurality of pallets (1) carried by said lever (10) or included in said lever (10), is arranged to cooperate with a plurality of teeth (2) included in said at least one escape wheel (20), at least one of said pallets (1) and / or at least one of said teeth (2) comprising an impulse zone including two zones, one for an inclined portion for which said elastic return means serves to drive said escape wheel (20) and another for another inclined portion for which said elastic return means serves to oppose said escape wheel (20), the contact portion between one of said pallets (1) and one of said teeth (2) of said escape wheel (20) comprising at least three zones: a first zone (Z1) in which the torque is in the negative direction and the first angle (ω1) formed between the first normal (N1) of said contact portion and the first radius vector (OP) of said lever is negative, corresponding to the first half of the restraint angle, in which the torque is in the positive direction and the second angle (ω2) formed between the second normal (N2) of said contact portion and the second radius vector (OQ) of said lever is positive; and a third zone (Z3) corresponding to the second half of the restraint angle, in which the torque is in the positive direction and the third angle (ω3) formed between the third normal (N3) of said contact portion and the third radius vector (OR) of said lever is positive. An escapement mechanism (100) for a timepiece, characterized in that it comprises at least three zones. **Claim 2** The escapement mechanism (100) for a timepiece according to claim 1, characterized in that said second angle (ω2) is a value smaller than a predetermined value and said third angle (ω3) is a limiting value larger than said predetermined value. **Claim 3** The escapement mechanism (100) for a timepiece according to claim 2, characterized in that said predetermined value is atan(μ), where μ is the coefficient of friction between at least one of said pallets (1) and at least one of said teeth (2). **Claim 4** The escapement mechanism (100) for a timepiece according to claim 3, characterized in that said coefficient of friction μ is included between 0.10 and 0.

30. **Claim 5** The escapement mechanism (100) of the watch according to claim 4, characterized in that the coefficient of friction μ is 0.

2.

6. The escapement mechanism (100) of the watch according to claim 1, characterized in that at least one of the pallets (1) is directly attached to the body included in the lever (10) and is made of a material other than the material of the body of the lever (10).

7. The escapement mechanism (100) of the watch according to claim 1, characterized in that the escapement mechanism (100) of the watch is of a type that can potentially self-start.

8. The escapement mechanism (100) of the watch according to claim 7, characterized in that the escapement mechanism (100) of the watch is a Swiss lever escapement.

9. The escapement mechanism (100) of the watch according to claim 7, characterized in that the escapement mechanism (100) of the watch is a coaxial escapement.

10. A watch movement (500) comprising at least an energy storage and distribution means (200) and a gear train (300) arranged to distribute energy to at least one escapement mechanism (100) according to claim 1, and at least one inertial mass (40) returned by an elastic return means (50), wherein the inertial mass (40) is arranged to cooperate with at least one lever (10) and at least one mechanical oscillator (400).

11. The watch movement (500) according to claim 10, characterized in that the mechanical oscillator (400) is a hairspring oscillator.

12. The watch movement (500) according to claim 10, characterized in that the mechanical oscillator (400) is a flexible induction oscillator having the inertial mass (40) suspended by a thin elastic blade constituting the elastic return means (50) of the mechanical oscillator (400).

13. A watch (1000) comprising at least one watch movement (500) according to claim 10.

14. The watch (1000) according to claim 13, characterized in that it is a wristwatch.

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