NATURAL ESCAPEMENT FOR CLOCK MOVEMENT AND CLOCK MOVEMENT INCLUDING SUCH AN ESCAPEMENT

Description

Technical field of the invention

[0001] The present invention relates to a natural escapement for a clockwork movement, also known as a tangential impulse escapement. The present invention relates more particularly to a natural escapement protected against damage that can be caused by premature triggering of the escapement impulse. Technological background

[0002] The principle of the natural escapement was invented by Abraham Louis Breguet at the beginning of the 19th century. One of the advantages of Breguet's natural escapement is that it is a free escapement, as the balance wheel is only disturbed by the operation of the escapement for a small fraction of its oscillation. Another advantage of Breguet's natural escapement is that it provides a direct and tangential impulse to the balance wheel at each vibration. In other words, the energy is transferred directly from the escape wheel to the balance wheel, without passing through an anchor. Furthermore, the energy is transmitted only tangentially, so that the friction generated by the operation of this escapement is limited.Unlike a detent escapement, a natural escapement does not have a lost stroke in its function of maintaining the oscillations of the balance; it delivers a similar impulse at each alternation, in a symmetrical and more uniform manner, so that mechanical energy losses due to lost strokes are eliminated. All these qualities make the natural escapement potentially one of the most efficient escapements.

[0003] Breguet later discovered, however, that the natural escapement he had devised had certain drawbacks, the most important of which was that the last escape wheel was not under tension from the gear train when the first wheel was giving the impulse or when the latter was at rest. The different gear clearances and the manufacturing quality of the various components used in a Breguet natural escapement could thus cause the last escape wheel to be incorrectly positioned and, consequently, the escapement to malfunction, accompanied by unwanted noise. Furthermore, since the escape wheel was free, its position was unstable, so that the operational safety of such a natural escapement was poor.

[0004] Of course, many improvements have been made to the original Breguet natural escapement in an attempt to overcome the drawbacks mentioned above. However, despite the efforts of successive watchmakers, difficulties remain. Some watchmakers have proposed superimposing the two escape wheels, a solution which, of course, increases the thickness of the movement and makes it difficult to integrate such a movement into a watch case. Other watchmakers have proposed positioning the anchor between the two escape wheels, in the plane of the latter. Here too, such a solution is cumbersome, this time in the plane of the movement.Furthermore, whether the escape wheels are superimposed or the anchor is arranged between the two escape wheels, it has been realized in practice that watchmakers have difficulty accessing the various components of the escapement, in particular when it comes to adjusting the penetration depth of the teeth of the second escape wheel with the entry and exit pallets of the anchor. Furthermore, when a natural escapement operates at low amplitude, at the end of the barrel spring's autonomy for example, or when the watchmaker is carrying out control manipulations and holding the balance wheel for this purpose, it may happen that the impulse is triggered when neither of the two impulse pallets carried by the balance wheel is engaged within the rotation perimeter of the teeth of one or other of the escape wheels.Typically, such a malfunction occurs when neither of the two impulse pallets has yet reached the rotational range of the teeth of either escape wheel and the impulse tooth of the escape wheel passes in front of the impulse pallet without giving any impulse to the latter. This situation is observed when the balance wheel rotates too slowly with a small amplitude, or when the watchmaker manipulates the balance wheel. In such cases, the escape wheels are not held back by the escapement function and can rotate uncontrolled. This then causes at best a loss of the timekeeping function with an unwanted advance, and at worst a sudden stop after acceleration of the gear train in one or other of its rest positions which can lead to damage to the components of the gear train and the escapement.

[0005] Document EP 2 487 546 A1 describes a natural anchor escapement with a plate fitted with impulse teeth. Summary of the invention

[0006] The present invention aims to overcome the above-mentioned and other problems by providing a natural escapement for a clockwork movement that is protected against premature triggering.

[0007] To this end, the present invention relates to a natural escapement for a watch movement performing a succession of operating cycles each composed of a first and a second alternation of a balance wheel which comprises a balance wheel on an axis of which a balance plate is adjusted, this natural escapement comprising a first escape wheel provided with at least a first toothing, this first escape wheel, arranged to be driven by a wheel of the clockwork movement, in turn driving a second escape wheel provided with at least a second toothing, the first and second escape wheel forming a kinematic chain arranged to cooperate with an anchor capable of pivoting around an anchor stem, the balance plate carrying a second impulse pallet stone by which this balance plate receives a direct and tangential driving impulse from the first escape wheel during the first alternation,and a first impulse pallet by which this balance wheel receives a direct and tangential driving impulse from the second escape wheel during the second alternation, the balance wheel also carrying at least one first safety tooth arranged to cooperate with the teeth of one of the first and second escape wheel sets so as to block this first or second escape wheel set when it escapes from the second impulse pallet, respectively from the first impulse pallet before the second impulse pallet respectively the first impulse pallet is within its respective rotation perimeter.,

[0008] According to special embodiments of the invention: the balance wheel plate carries a first safety tooth arranged to cooperate with the teeth of the first escape wheel, and a second safety tooth arranged to cooperate with the teeth of the second escape wheel; the first and second safety teeth are made in one piece with the balance wheel plate; the first and second safety teeth are attached to the balance wheel plate.

[0009] The invention also relates to a timepiece movement comprising an escapement of the type described above.

[0010] Thanks to these characteristics, the present invention provides a natural escapement protected against damage that can be caused by premature triggering of the impulse. Indeed, by teaching to provide the balance wheel with at least one safety tooth arranged so that this safety tooth is engaged in the perimeter of rotation of the teeth of the escape wheel set before the corresponding impulse pallet is engaged in this same perimeter of rotation of the escape wheel sets, the present invention makes it possible to retain the escape wheel sets when they are not retained by the escapement function and to prevent these escape wheel sets from rotating without control. Brief description of the figures

[0011] Other characteristics and advantages of the present invention will emerge more clearly from the following detailed description of an embodiment of a natural escapement according to the invention, this example being given purely for illustrative and non-limiting purposes only in conjunction with the appended drawing in which: there figure 1 is an overview of a natural escapement; the Figure 2A is a view of the natural escape of the figure 1 in its first extreme position at the beginning of a cycle; Figure 2B is a view of the natural escapement in its rest position during the first vibration at the moment when the balance wheel is about to pivot the anchor; the Figure 2Cis a view of the natural escapement at the moment when the second escape wheel is released from its engagement with the output pallet, which allows the second wheel to drive, via the first escape wheel, this second escape wheel, the first escape wheel also giving, by its impulse tooth, a driving impulse called direct and tangential to the impulse pallet of the balance wheel; 2D figure is a view of the natural escapement at the moment when the pivoting of the second escapement wheel is again interrupted when, under the effect of the pivoting of the anchor, this second escapement wheel finds itself resting on the entry pallet; Figure 2E is a view of the natural escapement at the moment when the balance wheel plate is in its second extreme position in which it is completely moved away from its rest position, which marks the end of the first alternation of operation of the natural escapement; Figure 2Fis a view of the natural escapement at the moment when, during the second vibration, the balance wheel has returned to its rest position and is about to pivot the anchor again; Figure 2G is a view of the natural escapement at the moment when the second escape wheel is released from its engagement with the entry pallet, which allows the second escape wheel to drive, via the first escape wheel, this second escape wheel; Figure 2H is a view of the natural escapement at the moment when the second escapement wheel gives a so-called direct and tangential driving impulse to the balance wheel via one of its teeth which drives the second impulse pallet; the Figure 2I is a view of the natural escapement at the moment when the pivoting of the second escapement wheel is again interrupted when, under the effect of the pivoting of the anchor, this second escapement wheel finds itself resting on the exit pallet; Figure 2Jis a view of the natural escapement returning to its first extreme position, which marks the end of the operating cycle of the natural escapement according to the invention; figure 3 is a view of the natural escape of the figure 1 with the balance wheel provided with a first and a second safety tooth in accordance with the invention, and the figure 4 is a view analogous to that of the figure 3 on which one of the safety teeth of the balance wheel prevents the rotation of the second escape wheel while the balance wheel did not have sufficient speed to bring the second impulse pallet into the rotation perimeter of the second impulse tooth of the second escape wheel. Detailed description of the invention

[0012] The present invention proceeds from the general inventive idea which consists of providing the balance wheel of a natural escapement for a watch movement with at least one safety tooth which is arranged so that this safety tooth is engaged with the toothing of one of the escapement wheels when the corresponding impulse pallet carried by the balance wheel is not yet engaged in the rotation perimeter of the toothing of this escapement wheel. The present invention thus makes it possible to retain the escapement wheels when they are not retained by the escapement function and to prevent these escapement wheels from rotating without control, which can cause a loss of the timekeeping function with an undesired advance, or even, in the most unfavorable cases, a sudden stop after acceleration in the rest position which can lead to damage to certain components of the mechanism.

[0013] Designated as a whole by the general numerical reference 1, the natural escapement is arranged to be driven by a wheel of the clockwork movement, for example the seconds wheel 2, which meshes with a pinion 4 fixedly mounted on an axis 6 of a first escapement wheel which, in the example shown in figure 1 , consists of a first escape wheel 8. This first escape wheel 8 in turn meshes via a toothing 10 with a second escape wheel which, in the example shown in the drawing, consists of a second escape wheel 12 which pivots around an axis 14.

[0014] The natural escapement 1 also comprises a balance 16 which comprises a balance wheel 18 on an axis 20 from which a balance plate 22 is adjusted. This balance plate 22 carries a balance pin 24 as well as a first and a second impulse pallet 26 and 28 whose respective roles will be described below.

[0015] The natural escapement 1 finally comprises an anchor 30 pivoted around an anchor stem 32 and which carries an output pallet 34 and an input pallet 36. Thanks to these output pallets 34 and input pallets 36 which penetrate into a toothing 38 of the second escape wheel 12, the anchor 30 is able to alternately block and release this second escape wheel 12. The anchor 30 also comprises a fork 40 formed of a first and a second horn 42a and 42b and which carries a pin 44. This pin 44cooperates with the balance wheel 22 and has the function of preventing accidental movements of the fork 40 outside the periods called the lift angle during which the balance wheel 22 is close to its rest position. The anchor 30 is arranged after the second escape wheel 12, at the output of the kinematic chain formed by the first and second escape wheels 8 and 12. More precisely, according to the non-limiting embodiment shown in the drawing, the pivot point of the anchor 30, materialized by the anchor stem 32, is located outside the angle α less than 180° and delimited by two straight lines which pass through the axis 20 of the balance wheel 18 and through the axis 6 of the first escape wheel 8 for one, and through the axis 20 of the balance wheel 18 and through the axis 14 of the second escape wheel 12 for the other.The natural escapement 1 is therefore less bulky than the natural escapements of the prior art in which the anchor is usually placed between and above the first and second escape wheels. The natural escapement 1 is therefore simpler to house in the clockwork movement whose operation it regulates. Similarly, the arrangement of the anchor 30 at the end of the kinematic chain formed by the first and second escape wheels 8 and 12 makes the watchmaker's interventions less difficult, in particular with regard to measuring and adjusting the depth of penetration of the output 34 and input 36 pallets into the teeth 38 of the second escape wheel 12. The natural escapement 1 is completed by a first and a second stop 46a and 46b which limit the movement of the anchor 30 in pivoting.

[0016] In the embodiment of the natural escapement 1 illustrated in the drawing, it is assumed that the second wheel 2 which provides the natural escapement 1 with the energy necessary for its operation rotates counterclockwise. The second wheel 2 therefore tends to rotate the pinion 4 and the first escape wheel 8 on the axis 6 of which the pinion 4 is fixed in the clockwise direction, and the second escape wheel 12 in the counterclockwise direction.

[0017] An operating cycle of the natural escapement 1 comprises two alternations during which the balance wheel 22 will successively go from a first extreme position to a second extreme position via a middle rest position, then from its second extreme position to its first extreme position via its middle rest position a second time. Thus, at the start of a cycle (see Figure 2A), the second escape wheel 12 is supported on the output pallet 34 and the natural escapement 1 is blocked by the anchor 30 pressing against the second stop 46b. Indeed, the pulling angle formed by the tip of the tooth of the second escape wheel 12 pressing on the output pallet 34 provides resistance to the release of the anchor 30 by tending to pivot this anchor 30 counterclockwise against the second stop 46b. This function of pulling the anchor 30 onto the second stop 46b by the second escape wheel 12 during the free part of the alternation of the balance wheel 22 is similar to that of Swiss anchor escapements. The balance wheel 22 then leaves this first extreme position by rotating counterclockwise.

[0018] At some point during its movement during the first alternation (see Figure 2B), the balance wheel 22 reaches its middle rest position. Just before reaching this position, the balance wheel 22 comes into contact with its balance pin 24 against the second horn 42b of the fork 40 and causes the anchor 30 to pivot clockwise.

[0019] The clockwise pivoting of the anchor 30 has the effect of releasing the second escape wheel 12 from its engagement with the output pallet 34, which allows the second wheel set 2 to drive, via the first escape wheel 8, the second escape wheel 12 in the counterclockwise direction (see Figure 2C ).

[0020] The pivoting of the second escape wheel 12 is again interrupted when, under the effect of the pivoting of the anchor 30, this second escape wheel 12 comes to rest on the entry pallet 36, this position being maintained thanks to the support of the anchor 30 against the first stop 46a (see 2D figure). Indeed, the pulling angle formed by pressing the tip of the tooth of the second escape wheel 12 on the entry pallet 36 opposes a resistance to the release of the anchor 30 by tending to pivot this anchor 30 clockwise against the first stop 46a. This function of pulling the anchor 30 on the first stop 46a by the second escape wheel 12 during the free part of the alternation of the balance wheel plate 22 is similar to that of Swiss anchor escapements.

[0021] It will be noted that at the same time as the first escape wheel 8 drives the second escape wheel 12 to pivot counterclockwise, the first escape wheel 8 also gives a driving impulse to the balance wheel plate 22 via one of its teeth 48 called the impulse tooth which drives the second impulse pallet 28 (see Figure 2C). This driving impulse is called direct and tangential impulse because it is given directly by the first escape wheel 8 to the balance wheel 22 and the path of the impulse tooth 48 catches up with that of the second impulse pallet 28 of the balance wheel 22 tangentially, which allows almost punctual and frictionless contact.

[0022] The balance wheel 22 thus moves to its second extreme position in which it is completely moved away from its rest position, which marks the end of the first alternation of operation of the natural escapement 1 (see Figure 2E ).

[0023] At the start of the second alternation of operation of the natural escapement 1, the balance wheel plate 22, returned by the balance spring (not visible in the drawing), begins to rotate clockwise until it comes to abut by its balance pin 24 against the first horn 42a of the fork 40 and causes the anchor 30 to pivot counterclockwise (see Figure 2F ).

[0024] The counterclockwise pivoting of the anchor 30 has the effect of releasing the second escape wheel 12 from its engagement with the input pallet 36, which allows the second wheel set 2 to drive, via the first escape wheel 8, the second escape wheel 12 in the counterclockwise direction (see Figure 2G ).

[0025] The pivoting of the second escape wheel 12 is again interrupted when, under the effect of the pivoting of the anchor 30, this second escape wheel 12 comes to rest on the output pallet 34, this position being maintained thanks to the support of the anchor 30 against the second stop 46b (see Figure 2I ).

[0026] It will be noted that at the same time as the first escape wheel 8 drives the second escape wheel 12 to pivot counterclockwise, the second escape wheel 12 also gives a so-called direct and tangential driving impulse to the balance wheel plate 22 via one of its teeth 50 called the impulse tooth which drives the first impulse pallet 26 (see Figure 2H). The impulse is so named because it is given directly by the second escape wheel 12 to the balance wheel 22 and the path of the impulse tooth 50 catches up with that of the second impulse pallet 28 of the balance wheel 22 tangentially, which allows for almost point-like contact without friction. The balance wheel 22 thus returns to its first extreme position, which marks the end of an operating cycle of the natural escapement 1 (see Figure 2J ).

[0027] There figure 3 is a view of the natural escape of the figure 1with the balance wheel 22 provided with a first and a second safety tooth 52, 54 in accordance with the invention. As already detailed above, the natural escapement 1 performs a succession of operating cycles each composed of a first and a second alternation of the balance wheel 16 which comprises a balance wheel 18 on the axis 20 of which the balance wheel 22 is adjusted. This natural escapement 1 comprises a first escape wheel 8 provided with a first toothing 10 and which is arranged to be driven by the second wheel set 2. In turn, this first escape wheel 8 drives a second escape wheel 12 provided with a second toothing 38, these first and second escape wheels 8, 12 forming a kinematic chain after which the anchor 30 is arranged capable of pivoting around its anchor stem 32.The balance wheel 22 carries a second impulse pallet 28 by which this balance wheel 22 receives a direct and tangential driving impulse from the first escape wheel 8 during the first alternation, and a first impulse pallet 26 by which this balance wheel 22 receives a direct and tangential driving impulse from the second escape wheel 12 during the second alternation. In accordance with the invention, and as illustrated in the . figure 4, the balance wheel plate 22 also carries at least one first safety tooth 52 arranged to cooperate with the toothing 10 of the first escape wheel 8, so as to block this first escape wheel 8 when it rotates before the second impulse pallet 28 is within its rotation perimeter. Thus, by teaching to provide the balance wheel plate 22 with at least one safety tooth 52 arranged so that this safety tooth 52 is engaged in the rotation perimeter of the toothing 10 of the corresponding escape wheel 8 before this impulse pallet 28 is engaged in this same rotation perimeter of the escape wheel 8, the present invention makes it possible to retain the escape wheel 8 when it is not retained by the escapement function and to prevent the escape wheels 8, 12 from rotating without control. According to a special embodiment of the invention, the balance wheel 22 illustrated in the figure 4carries, in addition to the first safety tooth 52 which is arranged to cooperate with the toothing 10 of the first escape wheel 8, a second safety tooth 54 arranged to engage in the toothing 38 of the second escape wheel 12 before the first impulse pallet 26 is engaged in the rotation perimeter of the first escape wheel 12. This is the case on the figure 4 where we see that only the safety tooth 54 is engaged in the toothing 38 of the second escape wheel 12 and thus ensures the retention of the escape wheels 8, 12.

[0028] It goes without saying that the present invention is not limited to the embodiment which has just been described and that various simple modifications and variants may be envisaged by those skilled in the art without departing from the scope of the invention as defined by the claims annexed to the present patent application. It will be noted in particular that the first and / or second safety teeth 52, 54 may be made in one piece with the balance wheel plate 22, or may be attached to this balance wheel plate 22. The present invention also relates to a timepiece movement provided with a natural escapement of the above-described type. It also goes without saying that the present invention is not limited to the particular type of natural escapement which has just been described and that it may be applied to other versions of natural escapements. Nomenclature

[0029] 1. Natural escapement 2. Second wheel 4. Pinion 6. Axle 8. First escape wheel 10. Teeth 12. Second escape wheel 14. Axle 16. Balance 18. Balance wheel 20. Axle 22. Balance plate 24. Balance pin 26. First impulse pallet 28. Second impulse pallet 30. Anchor 32. Anchor stem 34. Output pallet 36. Input pallet 38. Teeth 40. Fork 42a, 42b. Lugs 44. Pin 46a. First stop 46b. Second stop 48. Impulse tooth 50. Impulse tooth 52. First safety tooth 54. Second safety tooth

Claims

1. Natural escapement (1) for horological movement carrying out a succession of operating cycles each consisting of a first and of a second alternation of a balance (16) that comprises a balance wheel (18) on an arbor (20) of which is adjusted a balance plate (22), this natural escapement (1) comprising a first escape wheel set having at least one first toothing (10), this first escape wheel set, arranged to be driven by a wheel set of the train of the horological movement, driving in turn a second escape wheel set having at least one second toothing (38), the first and second escape wheel sets forming a kinematic chain arranged to cooperate with an anchor (30) capable of pivoting about an anchor-staff (32), the balance plate (22) carrying a second impulse pallet-stone (28) through which this balance plate (22) receives a direct and tangential driving impulse from the first escape wheel set during the first alternation, and a first impulse pallet-stone (26) through which this balance plate (22) receives a direct and tangential driving impulse from the second escape wheel set during the second alternation, characterised in that the balance plate (22) also carries at least one safety tooth (52; 54) arranged to cooperate with the toothing (10, 38) of one of the first or second escape wheel sets so as to lock this first or this second escape wheel set when it escapes to the second impulse pallet-stone (28), respectively to the first impulse pallet-stone (26), before the second impulse pallet-stone respectively the first impulse pallet stone has reached its respective perimeter of rotation.

2. Natural escapement (1) according to claim 1, characterised in that the balance plate (22) carries a first safety said tooth (52) arranged to cooperate with the toothing (10) of the first escape wheel set, and a second safety said tooth (54) arranged to cooperate with the toothing (38) of the second escape wheel set.

3. Natural escapement (1) according to one of claims 1 and 2, characterised in that the first and second safety teeth (52, 54) are made in one piece with the balance plate (22).

4. Natural escapement (1) according to one of claims 1 and 2, characterised in that the first and second safety teeth (52, 54) are attached on the balance plate (22).

5. Horological movement comprising a natural escapement (1) according to one of claims 1 to 4.