Natural escapement for a watch movement and watch movement comprising such an escapement

Abstract

The present invention relates to a natural escapement for a watch movement, which includes a balance wheel mechanism that moves from a first extreme position through an intermediate rest position to a second extreme position and vice versa, with the balance wheel plate being adjusted on the axis of the balance wheel. The escapement further includes a first escapement wheel pair driven by a wheel pair of the watch movement train, which in turn drives a second escapement wheel pair. The first and second escapement wheel pairs form a kinematic chain that cooperates with an anchor escapement fork. The anchor escapement fork also includes first and second safety levers, which are arranged such that in the absence of the balance wheel mechanism, the second escapement wheel pair causes the anchor escapement fork to pivot by acting on the second safety lever, so as to ensure the locking of the first escapement wheel pair by pressing against a part of the anchor escapement fork that ensures the function of the locking pallet. The first and second safety levers do not impede the normal operation of the escapement, during which the anchor escapement fork is pivoted by the balance wheel plate. The present invention also relates to a watch movement including such a natural escapement.

Description

Field of the Invention

[0001] The present invention relates to a natural escapement for a watch movement, also known as a tangential impact escapement. More specifically, the present invention relates to such a natural escapement that is protected against damage caused by premature release of the escapement impact in the absence of a balance wheel mechanism. The present invention also relates to a watch movement comprising such an escapement. Background Art

[0002] The principle of the natural escapement was invented by Abraham Louis Breguet at the beginning of the 19th century. The advantages of the Breguet natural escapement lie in particular in the fact that it is a free escapement, since the balance wheel is only disturbed by the operation of the escapement during a small part of its oscillation. The advantages of the Breguet natural escapement also lie in the fact that it provides a direct tangential impact to the balance wheel mechanism during each half-cycle. In other words, energy is directly transferred from the escape wheel to the balance wheel without passing through an anchor escapement fork. Furthermore, the energy is transferred only tangentially, thus limiting the friction generated by the operation of the escapement. Unlike astronomical clock escapements, the natural escapement does not include a half-cycle without impact (coup perdu) in its function of maintaining the oscillation of the balance wheel; it transfers similar impacts in a symmetric and more uniform manner during each half-cycle, thus eliminating the loss of mechanical energy due to the half-cycle without impact. Therefore, all these qualities make the natural escapement one of the most efficient escapements.

[0003] However, Breguet subsequently found that the natural escapement he had invented had certain drawbacks, the most important of which was the fact that the last escape wheel was not under the tension of the gear train when the first wheel provided an impact or when the first wheel was at rest. Therefore, the various clearances in the gear train and the manufacturing quality of the various components integrated in the Breguet natural escapement may lead to incorrect positioning of the last escape wheel, resulting in escapement failure and accompanied by parasitic noise. In addition, since the escape wheel is free, its position is unstable, making the operation safety of this natural escapement relatively poor.

[0004] Of course, in order to overcome the above-mentioned drawbacks, many improvements have been made to the original Breguet natural escapement. However, despite the efforts of successive watch manufacturers, difficulties still remain. Some watchmakers have therefore proposed superimposing two escape wheels, which of course increases the thickness of the movement and makes it difficult to integrate such a movement into the watch case. Other watchmakers have proposed positioning the anchor escapement fork between two escape wheels and within the plane of the latter. This solution is also bulky, i.e., this time it is bulky in the plane of the movement. In addition, whether the escape wheels are superimposed or the anchor escapement fork is arranged between two escape wheels, it has been recognized that it is difficult for watchmakers to access the various components of the escapement during use, especially when it comes to adjusting the penetration depth of the entry and exit pallets of the anchor escapement fork into the teeth of the first and second escape wheels. Moreover, when the watchmaker performs control and adjustment operations and removes the balance wheel for this purpose, the release of the impulse may occur while neither of the two impulse pallets carried by the balance wheel plate is on the rotation perimeter of one or the other escape wheel to ensure the escapement function. In such cases, the escape wheel is not restricted by the escapement function and may rotate uncontrollably. Thus, in the best case, this may result in a loss of the timekeeping function of the clock due to an unwanted forward movement, and in the worst case, it may cause the gear train to suddenly stop after accelerating at one or the other of its rest positions, which may lead to damage to the components of the gear train and the escapement. Summary of the Invention

[0005] An object of the present invention is to overcome the above problems and other problems by providing a natural escapement for a watch movement, which is protected against the effects caused by the release of the escapement function in the absence of a balance wheel mechanism.

[0006] To this end, the present invention relates to a natural escapement mechanism for a watch movement. The natural escapement mechanism performs a series of operating cycles, each operating cycle including a first half-cycle and a second half-cycle of a balance wheel mechanism. During this period, the balance wheel mechanism moves from a first extreme position through an intermediate rest position to a second extreme position, and then moves from the second extreme position through the intermediate rest position again to the first extreme position. The balance wheel mechanism includes a balance wheel, and a balance wheel plate is adjusted on the axis of the balance wheel. The natural escapement mechanism includes a first escapement wheel pair having at least one first tooth portion. The first escapement wheel pair is arranged to be driven by a wheel pair of the train of the watch movement and in turn drives a second escapement wheel pair having at least one second tooth portion. The first escapement wheel pair and the second escapement wheel pair form a kinematic chain. The kinematic chain is arranged to cooperate with an anchor escapement fork that can pivot about an escapement fork axis. The balance wheel plate causes the anchor escapement fork to pivot during both the first half-cycle and the second half-cycle. The anchor escapement fork is arranged to temporarily lock the first escapement wheel pair and the second escapement wheel pair respectively during the second half-cycle and the first half-cycle of an operating cycle. The anchor escapement fork further includes a first safety lever and a second safety lever. The first safety lever and the second safety lever are arranged such that in the absence of the balance wheel mechanism, the second escapement wheel pair causes the anchor escapement fork to pivot by driving the second safety lever, so as to ensure the locking of the first escapement wheel pair by the first escapement wheel pair abutting against a part of the anchor escapement fork, wherein the part ensures the function of the stop pallet of the first escapement wheel pair during the normal operation of the natural escapement mechanism. Alternatively, the first escapement wheel pair causes the anchor escapement fork to pivot by driving the first safety lever, so as to ensure the locking of the second escapement wheel pair by the second escapement wheel pair abutting against a part of the anchor escapement fork, wherein the part ensures the function of the stop pallet of the second escapement wheel pair during the normal operation of the natural escapement mechanism. The first safety lever and the second safety lever are arranged not to contact the first escapement wheel pair and the second escapement wheel pair during the normal operation of the natural escapement mechanism. During the normal operation, the balance wheel plate causes the anchor escapement fork to pivot.

[0007] According to a specific embodiment of the present invention:

[0008] - At least one first rod is connected to the first arm of the anchor escapement fork via at least one pivot hinge. The first rod pivots about a pivot pin. The anchor escapement fork includes a second rod extending from its second arm. The first rod and the second rod are arranged to temporarily lock the first escapement wheel and the second escapement wheel respectively during the second half-cycle and the first half-cycle of an operating cycle. The pivot displacements of the first rod and the second rod are restricted.

[0009] - The first rod and the second rod pivot about their respective pivot pins and are connected to the first arm and the second arm of the anchor escapement via at least one pivot hinge portion respectively;

[0010] - Each of the pivot hinge portions is formed by a catch that extends into an oblong opening;

[0011] - The pivotal displacement of the anchor escapement is restricted by a first limit pin and a second limit pin;

[0012] - The first limit pin and the second limit pin are peg nails;

[0013] - The first limit pin and the second limit pin are machined in a fixed element of the timepiece movement;

[0014] - The first limit pin and the second limit pin are eccentric members;

[0015] - The first rod is integrally formed and has a geometry that ensures the function of the first stop pallet during the second half cycle to temporarily lock the first escape wheel. The second rod is integrally formed and has a geometry that ensures the function of the second stop pallet during the first half cycle to temporarily lock the second escape wheel;

[0016] - The first escape wheel includes a first driving tooth portion. The first escape wheel meshes with a second driving tooth portion of the second escape wheel through the first driving tooth portion. And each of the first escape wheel and the second escape wheel includes impact and locking tooth portions. The first escape wheel and the second escape wheel provide a direct tangential driving impact to the balance wheel plate through the impact and locking tooth portions. The driving tooth portions and the impact and locking tooth portions of each of the first escape wheel and the second escape wheel extend in a single plane or two parallel planes;

[0017] - The anchor escapement includes a fork head formed by a first corner portion and a second corner portion. During the first half cycle, the balance wheel plate abuts against the second corner portion of the fork head through its balance wheel pin and causes the anchor escapement to pivot in a first direction. During the second half cycle, the balance wheel plate abuts against the first corner portion through its balance wheel pin and causes the anchor escapement to pivot in a second direction opposite to the first direction;

[0018] - The fork head carries a fork head nail. During a period called the supplementary circular arc, the fork head nail cooperates with the balance wheel plate to prevent accidental movement of the fork head;

[0019] - Both the first escape wheel and the second escape wheel are integral parts;

[0020] - A reduction gear pair is provided between the gear pair of the gear train of the timepiece movement and the first escape wheel.

[0021] The invention also relates to a timepiece movement comprising a natural escapement of the above type.

[0022] Thanks to these features, the invention provides a natural escapement that is protected against damage that may result from premature release due to shock. In fact, by teaching the provision of a first safety lever and a second safety lever for the first arm and the second arm of the anchor escapement fork, it is possible to advantageously ensure the locking of the first escapement wheel pair in the absence of a balance plate, and this locking is not ensured by the cooperation between the balance plate and the anchor escapement fork. In fact, it should be understood that in the absence of a balance plate, the second escapement wheel pair is not constrained by the escapement function and may therefore rotate uncontrollably, which may result in a loss of the timekeeping function through an unwanted forward movement, or even a sudden stop after the train of wheels of the timepiece movement has accelerated, which may cause damage to the components of the train of wheels and the escapement. To achieve the above object, the first safety lever and the second safety lever are arranged such that: in the absence of the balance mechanism, the second escapement wheel pair pivots the second arm of the anchor escapement fork, the anchor escapement fork, and the first arm of the anchor escapement fork by acting on the second safety lever to ensure the locking of the first escapement wheel pair on a part of the anchor escapement fork, and in the normal case, that is, when there is a balance plate, the said part of the anchor escapement fork ensures the function of temporarily locking the first stop pallet of the first escapement wheel pair during an operating cycle of the natural escapement. Of course, the first safety lever and the second safety lever are designed not to contact the first escapement wheel pair and the second escapement wheel pair during the normal operation of the said natural escapement, during which the anchor escapement fork is pivoted by the balance plate. It should also be understood that a symmetrical situation is also possible, that is, by controlling the pivoting of the anchor escapement fork by the first escapement wheel pair, the locking of the second escapement wheel pair is ensured by abutting against a part of the anchor escapement fork, and in the normal case, the said part of the anchor escapement fork ensures the function of temporarily locking the stop pallet of the second escapement wheel pair during an operating cycle of the natural escapement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other features and advantages of the invention will become more apparent from the following detailed description of an embodiment of a natural escapement according to the invention, which example is given for purely illustrative and non-limiting purposes in conjunction with the drawings, in which:

[0024] - Figure 1 is a top view of the natural escapement in its rest position (i.e., the locked position), in which the second escapement wheel abuts against the second rod;

[0025] - Figure 2Is a top view of the natural escapement in the following position: wherein, the balance pin contacts the second corner of the fork, which will cause the second escape wheel to start unlocking from its engagement with the second lever;

[0026] - Figure 3 Is a top view of the natural escapement in the following position: wherein, the balance plate drives the anchor escapement fork and these levers, which causes the start of the first drop by unlocking the second escape wheel from its engagement with the second lever;

[0027] - Figure 4 Is a top view of the natural escapement in the following position: wherein, the first escape wheel abuts against the first impulse pallet and starts to provide an impulse to the balance plate, which marks the end of the first drop;

[0028] - Figure 5 Is a top view of the natural escapement in the following position: wherein, the first escape wheel transfers the impulse to the balance plate while the second lever abuts against the second limit pin;

[0029] - Figure 6 Is a top view of the natural escapement in the following position: wherein, the first escape wheel completes applying the impulse to the balance plate, which marks the start of the second drop while the second lever presses against the second limit pin;

[0030] - Figure 7 Is a top view of the natural escapement in the following position: wherein, the first escape wheel presses against the first lever, which marks the end of the second drop while the balance plate freely ends its half-cycle;

[0031] - Figure 8 Is a top view of the natural escapement according to an embodiment of the present invention in the following situation: wherein, the balance wheel has been removed, the anchor escapement fork is provided with a safety lever according to the present invention, and the natural escapement is in the following position: in this position, the second escape wheel will cause the anchor escapement fork to pivot by acting on the second safety lever so as to ensure locking of the first escape wheel by pressing one of the teeth of the locking tooth portion against a part of the anchor escapement fork. Under normal circumstances (that is, when there is a balance plate), the said part of the anchor escapement fork ensures the function of the first stop pallet that temporarily locks the first escape wheel during an operating cycle of the natural escapement;

[0032] - Figure 9 Is similar to Figure 8Top view, in which, in the absence of the balance wheel, the first escape wheel will cause the anchor escapement fork to pivot by acting on the first safety lever, so that the second escape wheel can enter the locked position by pressing against a part of the anchor escapement fork with one of its impact and locking teeth. Under normal circumstances, the said part of the anchor escapement fork ensures the function of temporarily locking the second locking pallet of the second escape wheel;

[0033] - Figure 10 is a top view showing the position of the natural escapement mechanism after the position of the natural escapement mechanism in Figure 8 wherein, without the balance wheel, the second escape wheel has caused the anchor escapement fork to pivot by acting on the second safety lever, so that the first escape wheel can enter the locked position by pressing against a part of the anchor escapement fork with one of its impact and locking teeth. Under normal circumstances (that is, when there is a balance wheel plate), the said part of the anchor escapement fork ensures the function of temporarily locking the first locking pallet of the first escape wheel during one operating cycle of the natural escapement mechanism. Detailed implementation

[0034] The present invention stems from the following general inventive concept: namely, to provide first and second safety levers for the first and second arms of the anchor escapement fork of a natural escapement mechanism - also known as a tangential impulse escapement mechanism - for the purpose of ensuring an accidental release of the rotation of the first and second escape wheel pairs is immediately stopped by setting one of the first and second escape wheel pairs to its locked position in the case where the watchmaker needs to remove the balance wheel for any reason. For this purpose, these safety levers are arranged such that when the balance wheel is removed, the second escape wheel pair causes the anchor escapement fork and the first arm of the anchor escapement fork to pivot by acting on the second safety lever, so that the first escape wheel pair can rest in its locked position by pressing against a part of the anchor escapement fork. Under normal circumstances (that is, when there is a balance wheel plate), the said part of the anchor escapement fork ensures the function of temporarily locking the first locking pallet of the first escape wheel pair during one operating cycle of the natural escapement mechanism.

[0035] The natural escapement mechanism generally denoted by the general reference numeral 1 is shown in Figure 1 in its rest / locked position. The natural escapement mechanism 1 is arranged to be driven by a wheel pair of the train of the watch movement, for example by the seconds wheel 2. According to a preferred but non-limiting embodiment, the seconds wheel 2 meshes with a pinion 4 fixedly mounted on the shaft 6 of the first escape wheel pair, and the first escape wheel pair includes a first escape wheel 10. The first escape wheel 10 itself meshes via a first driving tooth portion 12 with a second driving tooth portion 14 of the second escape wheel pair, and the second escape wheel pair includes a second escape wheel 16 pivoting about the shaft 18.

[0036] The natural escapement mechanism 1 further includes a balance wheel mechanism 20, which includes a balance wheel 22, and a balance wheel plate 26 is adjusted on the shaft 24 of the balance wheel 22. The balance wheel plate 26 carries balance wheel pins 28 and first and second impulse pallets 30 and 32, whose respective functions will be described below.

[0037] The natural escapement mechanism 1 further includes an anchor escapement fork 34 pivotally mounted about an escapement fork shaft 36. The anchor escapement fork 34 includes an escapement fork body 38, which carries a fork head 40 formed by a first corner 42a and a second corner 42b and a fork head pin 44. The fork head pin 44 cooperates with the balance wheel plate 26 to prevent accidental displacement of the fork head 40 during a period commonly referred to as the supplementary arc - during which the balance wheel plate 26 moves away from its intermediate rest position called the lift angle.

[0038] As can be observed Figure 1 it can be seen that the escapement fork body 38 includes a first arm 46a and a second arm 46b, which are preferably but not restrictively symmetrically arranged on both sides of the fork head 40. According to Figures 8 - 10 an embodiment given by way of example only, a first rod 48a and a second rod 48b pivotally mounted about respective pivot pins 50 and 52 are connected to the first arm 46a and the second arm 46b of the escapement fork body 38 via pivot joints 53. In this embodiment, the first rod 48a is made as a single piece, and its geometry ensures the function of temporarily locking the first stop pallet of the first escape wheel 10 during one operating cycle of the natural escapement mechanism 1, and the geometry of the second rod 48b ensures the function of temporarily locking the second stop pallet of the second escape wheel 16 during the same operating cycle of the natural escapement mechanism 1.

[0039] According to this embodiment shown in the drawings, the first rod 48a and the second rod 48b respectively carry blocks 54, 56, which respectively extend into oblong openings 58, 60 formed in the first arm 46a and the second arm 46b of the escapement fork body 38. Of course, the blocks 54 and 56 can be carried by the first arm 46a and the second arm 46b, and the oblong openings 58, 60 can be formed in the first rod 48a and the second rod 48b. Thus, by engaging the blocks 54, 56 in the oblong openings 58, 60, the first rod 48a and the second rod 48b can pivot relative to the first arm 46a and the second arm 46b of the escapement fork body 38.

[0040] In this embodiment of the natural escapement mechanism 1 shown in the drawings, it is assumed that the second wheel 2, which provides the energy required for the operation of the natural escapement mechanism 1, rotates in a clockwise direction. The second wheel 2 thus tends to rotate the pinion 4 and the first escape wheel 10 fixed to its shaft 6 in an anti - clockwise direction, and rotates the second escape wheel 16 in a clockwise direction.

[0041] One operating cycle of the natural escapement mechanism 1 includes two alternations, during which the balance plate 26 will successively move from the first extreme position through the intermediate rest position to the second extreme position, and then from its second extreme position through the intermediate rest position again to its first extreme position. Thus, at the start of a cycle (see Figure 1 ), the balance plate 26 rotates towards its intermediate rest position by rotating in the clockwise direction, while the second escape wheel 16 presses against the second lever 48b.

[0042] At Figure 2 a given moment of the movement of the balance plate 26 shown in, the balance plate 26 reaches a position where it abuts against the second corner 42b of the fork 40 via its balance pin 28 and starts to pivot the anchor escapement fork 34 in the counterclockwise direction. The counterclockwise pivoting of the anchor escapement fork 34 has the effect of starting to release the second escape wheel 16 from its engagement with the second lever 48b, which will allow the seconds wheel 2 to drive the second escape wheel 16 in the clockwise direction via the first escape wheel 10.

[0043] At Figure 3 the natural escapement mechanism 1 is in a position where the balance plate 26 drives the anchor escapement fork 34, which causes the start of the first drop by unlocking the second escape wheel 16 from its engagement with the second lever 48b. "Drop" refers to such an operating period of the natural escapement mechanism 1 according to the present invention: that is, during which the first escape wheel 10 and the second escape wheel 16 are not in contact with either the first lever 48a or the second lever 48b, nor in contact with either the first pallet 30 or the second pallet 32.

[0044] It should be understood that while the first escape wheel 10 drives the second escape wheel 16 to pivot in the clockwise direction, the first escape wheel 10 also starts to provide a driving impulse to the balance plate 26 via the impulse and locking tooth portion 68 driving one tooth 66 of the first pallet 30 (see Figure 4 ). This driving impulse is called direct and tangential because it is provided directly by the first escape wheel 10 to the balance plate 26, and the path of the tooth 66 is tangent to the path of the first pallet 30 of the balance plate 26, which achieves an almost point-like contact and no friction. It should also be noted that the contact between the tooth 66 of the first escape wheel 10 and the first pallet 30 of the balance plate 26 marks the end of the first drop.

[0045] Figure 5Is a top view of the natural escapement mechanism 1 in the following position: In this position, the first escape wheel 10 exerts an impact on the balance wheel plate 26, and the second lever 48b pivots about its pivot pin 52 and presses against the second limit pin 64. This movement is controlled by the anchor escapement fork 34, and the anchor escapement fork 34 driven by the balance wheel pin 28 pivots counterclockwise about its escapement fork axis 36.

[0046] In Figure 6 the first escape wheel 10 completes exerting an impact on the balance wheel plate 26, which marks the start of the second drop. It can actually be seen that the tooth 66 of the first escape wheel 10 will no longer be in contact with the first impact pallet 30 of the balance wheel plate 26. In addition, the second lever 48b presses against the second limit pin 64.

[0047] Finally, Figure 7 Is a top view of the natural escapement mechanism 1 in its other rest position, in which the first escape wheel 10 presses against the first lever 48a, which marks the end of the second drop, and the balance wheel plate 26 freely ends its half cycle by rotating clockwise. The next half cycle in which the balance wheel plate 26 rotates counterclockwise symmetrically reproduces the same functions as those shown in Figures 2 - 7 in the reverse order.

[0048] Figure 8 Is Figure 1 a top view of the natural escapement mechanism 1 with the balance wheel mechanism 20 removed, and this situation is schematically shown by representing the balance wheel mechanism 20 in dashed lines. According to the present invention, the first and second levers 48a, 48b of the anchor escapement fork 34 are respectively provided with a first safety lever 84 and a second safety lever 86. As Figure 8 can be seen in, the natural escapement mechanism 1 is in the following position: In this position, the second escape wheel 16 will act on the second safety lever 86 carried by the second lever 48b via one of its impact and locking teeth 70 by pivoting clockwise and cause the anchor escapement fork 34 to pivot, so as to ensure locking the first escape wheel 10 by pressing one of the teeth 66 in the impact and locking teeth 68 of the first escape wheel 10 against a part 88 of the anchor escapement fork 34. Under normal circumstances, that is, when there is a balance wheel plate 26, the said part 88 of the anchor escapement fork ensures the function of the first stop pallet that temporarily locks the first escape wheel 10 during one operating cycle of the natural escapement mechanism 1.

[0049] The above situation is in Figure 10As shown, where the balance wheel mechanism 20 is still absent, the first escape wheel 10 is locked by pressing one tooth 66 of the impulse and locking teeth 68 of the first escape wheel 10 against a part 88 of the anchor escapement fork 34, and the part 88 ensures the function of the detent escapement. In fact, under the action of the pivot of the anchor escapement fork 34 caused by the rotation of the second escape wheel 16, the part 88 of the anchor escapement fork 34 that ensures the function of the detent escapement is located on the rotation perimeter of the first escape wheel 10, and the first escape wheel 10 is pressed against the part 88 of the anchor escapement fork 34 by one tooth 66 of its impulse and locking teeth 68.

[0050] Finally, Figure 9 the situation shown is symmetric to Figure 8 the situation shown, that is, the first escape wheel 10 will act on the first safety lever 84 carried by the first link 48a by pivoting in the counterclockwise direction and cause the anchor escapement 34 to pivot, so as to ensure the locking of the second escape wheel 16 by pressing one tooth of the impulse and locking teeth 70 of the second escape wheel 16 against a part 90 of the anchor escapement fork 34. Under normal circumstances, that is, when the balance wheel plate 26 is present, the part 90 of the anchor escapement fork ensures the function of the second detent escapement that temporarily locks the second escape wheel 16 during one operating cycle of the natural escapement mechanism 1.

[0051] It goes without saying that the present invention is not limited to the embodiments just described, and various modifications and simple variations can be envisaged without departing from the scope of the present invention as defined by the appended claims. In particular, it should be understood that although the natural escapement mechanism 1 has been described in connection with the anchor escapement fork 34 to which the first rod 48a and the second rod 48b are connected to its arms 46a, 46b, in a simplified embodiment, it is entirely possible to provide only a single rod pivotally connected to one of the arms of the anchor escapement fork, and the other rod is integrally formed with the second arm of the anchor escapement fork 34. It should also be noted that the presence of the first and second rods 48a, 48b is not essential, and the anchor escapement fork 34 may include only the arms 46a, 46b. The geometry of the first arm 46a ensures the function of temporarily locking the first detent pallet of the first escape wheel 10 during one operating cycle of the natural escapement mechanism 1, and the geometry of the second arm 46b ensures the function of temporarily locking the second detent pallet of the second escape wheel 16 during the same operating cycle of the natural escapement mechanism 1. It should also be noted that a reduction gear pair can be provided between the second wheel 2 and the first escape wheel 10. The first escape wheel 10 includes a first drive tooth portion 12, and the first escape wheel 10 meshes with the second drive tooth portion 14 of the second escape wheel 16 through the first drive tooth portion 12. Moreover, each of the first escape wheel 10 and the second escape wheel 16 includes impact and locking tooth portions 68, 70 for providing a direct tangential driving impact to the balance wheel plate 26. The drive devices 12, 14 and the impact and locking tooth portions 68, 70 of each of the first escape wheel 10 and the second escape wheel 16 extend in a single plane or in two parallel planes. Preferably, both the first escape wheel 10 and the second escape wheel 16 are integrally formed.

[0052] Reference Signs

[0053] 1. Natural escapement mechanism

[0054] 2. Second wheel

[0055] 4. Pinion

[0056] 6. Shaft

[0057] 10. First escape wheel

[0058] 12. First drive tooth portion

[0059] 14. Second drive tooth portion

[0060] 16. Second escape wheel

[0061] 18. Shaft

[0062] 20. Balance mechanism

[0063] 22. Balance wheel

[0064] 24. Shaft

[0065] 26. Balance wheel plate

[0066] 28. Balance wheel pin

[0067] 30. First impulse pallet

[0068] 32. Second impulse pallet

[0069] 34. Anchor escapement fork

[0070] 36. Escapement fork shaft

[0071] 38. Escapement fork body

[0072] 40. Fork head

[0073] 42a. First corner

[0074] 42b. Second corner

[0075] 44. Fork head pin

[0076] 46a. First arm

[0077] 46b. Second arm

[0078] 48a. First rod

[0079] 48b. Second rod

[0080] 50. Pivot pin

[0081] 52. Pivot pin

[0082] 53. Pivot hinge

[0083] 54. Catch block

[0084] 55. Catch block

[0085] 56. Catch block

[0086] 57. Circular opening

[0087] 58. Oblong opening

[0088] 60. Oblong opening

[0089] 62. First limit pin

[0090] 64. Second limit pin

[0091] 66. Tooth

[0092] 68. Impulse and locking tooth part

[0093] 70. Impulse and locking tooth part

[0094] 76. Eccentric

[0095] 84. First safety bar

[0096] 86. Second safety bar

[0097] 88. Part

[0098] 90. Part

Claims

1. A natural escapement mechanism (1) for a watch movement, the natural escapement mechanism (1) performing a series of operating cycles, each operating cycle including a first half-cycle and a second half-cycle of a balance wheel mechanism (20), during which the balance wheel mechanism (20) moves from a first extreme position through an intermediate rest position to a second extreme position, and then from the second extreme position again through the intermediate rest position to the first extreme position. The balance wheel mechanism (20) includes a balance wheel (22), and a balance wheel plate (26) is adjusted on the axis (24) of the balance wheel (22). The natural escapement mechanism (1) includes a first escapement wheel pair having at least one first tooth portion, the first escapement wheel pair being arranged to be driven by a wheel pair of the train of wheels of the watch movement and in turn driving a second escapement wheel pair having at least one second tooth portion. The first escapement wheel pair and the second escapement wheel pair form a kinematic chain, and the kinematic chain is arranged to cooperate with an anchor escapement fork (34) capable of pivoting about an escapement fork axis (36). The balance wheel plate (26) causes the anchor escapement fork (34) to pivot during both the first half-cycle and the second half-cycle. The anchor escapement fork (34) is arranged to temporarily lock the first escapement wheel pair and the second escapement wheel pair respectively during the second half-cycle and the first half-cycle of an operating cycle. The anchor escapement fork (34) further includes a first safety lever (84) and a second safety lever (86), and the first safety lever (84) and the second safety lever (86) are arranged such that in the absence of the balance wheel mechanism (20), the second escapement wheel pair causes the anchor escapement fork (34) to pivot by driving the second safety lever (86) so as to ensure the locking of the first escapement wheel pair by the first escapement wheel pair against a first portion (88) of the anchor escapement fork (34), wherein the first portion (88) ensures the function of the stop pallet of the first escapement wheel pair during the normal operation of the natural escapement mechanism (1), or the first escapement wheel pair causes the anchor escapement fork (34) to pivot by driving the first safety lever (84) so as to ensure the locking of the second escapement wheel pair by the second escapement wheel pair against a second portion (90) of the anchor escapement fork (34), wherein the second portion (90) ensures the function of the stop pallet of the second escapement wheel pair during the normal operation of the natural escapement mechanism (1). The first safety lever (84) and the second safety lever (86) are arranged not to contact the first escapement wheel pair and the second escapement wheel pair during the normal operation of the natural escapement mechanism (1), and during the normal operation, the balance wheel plate (26) causes the anchor escapement fork (34) to pivot.

2. The natural escapement mechanism (1) according to claim 1, characterized in that, The anchor escapement fork (34) includes a first arm (46a) and a second arm (46b), the first arm (46a) and the second arm (46b) are arranged to temporarily lock the first escapement wheel pair and the second escapement wheel pair respectively during the second half cycle and the first half cycle of an operating cycle, the first safety lever (84) is provided on the first arm (46a) of the anchor escapement fork (34), and the second safety lever (86) is provided on the second arm (46b) of the anchor escapement fork (34).

3. The natural escapement mechanism (1) according to claim 2, characterized in that, At least one first rod member (48a) is connected to the first arm (46a) of the anchor escapement fork (34) via at least one pivot hinge portion (53), the first rod member (48a) pivots around a pivot pin and the first safety lever (84) is provided thereon, the anchor escapement fork (34) includes a second rod member (48b) extending from the second arm (46b), the second safety lever (86) is provided on the second rod member (48b), the first rod member (48a) and the second rod member (48b) are arranged to temporarily lock the first escapement wheel (10) included in the first escapement wheel pair and the second escapement wheel (16) included in the second escapement wheel pair respectively during the second half cycle and the first half cycle of an operating cycle, and the pivotal displacements of the first rod member (48a) and the second rod member (48b) are restricted.

4. The natural escapement mechanism (1) according to claim 2 or 3, characterized in that, The balance wheel plate (26) carries a first impulse pallet (30) and a second impulse pallet (32), during the first half cycle, the balance wheel plate (26) receives a direct tangential driving impulse from the first escapement wheel pair through the first impulse pallet (30), and during the second half cycle, the balance wheel plate (26) receives a direct tangential driving impulse from the second escapement wheel pair through the second impulse pallet (32).

5. The natural escapement mechanism (1) according to claim 3, characterized in that, The balance wheel plate (26) carries a balance wheel pin (28), during the first half cycle and the second half cycle, the balance wheel plate (26) pivots the anchor escapement fork (34) through the balance wheel pin (28).

6. The natural escapement mechanism (1) according to claim 5, characterized in that, The first rod member (48a) and the second rod member (48b) pivot around their respective pivot pins and are respectively connected to the first arm (46a) and the second arm (46b) of the anchor escapement fork (34) via at least one pivot hinge portion (53).

7. The natural escapement mechanism (1) according to claim 6, characterized in that, Each of the at least one pivot hinge portion (53) is formed by a clamping block (54, 56) extending into an oblong opening (58, 60).

8. The natural escapement mechanism (1) according to any one of claims 5-7, characterized in that, The pivotal displacement of the anchor escapement fork (34) is restricted by a first limit pin (62) and a second limit pin (64).

9. The natural escapement mechanism (1) according to claim 8, characterized in that, The first limit pin (62) and the second limit pin (64) are peg nails.

10. The natural escapement mechanism (1) according to claim 8, characterized in that, The first limit pin (62) and the second limit pin (64) are machined in a fixed element of the timepiece movement.

11. The natural escapement mechanism (1) according to claim 8, characterized in that, The first limit pin (62) and the second limit pin (64) are eccentric members.

12. The natural escapement mechanism (1) according to any one of claims 5-7, characterized in that, The first rod member (48a) is integrally formed and has a geometry that ensures the function of the first stop pallet fork during the second half-cycle to temporarily lock the first escape wheel (10). The second rod member (48b) is integrally formed and has a geometry that ensures the function of the second stop pallet fork during the first half-cycle to temporarily lock the second escape wheel (16).

13. The natural escapement mechanism (1) according to any one of claims 5-7, characterized in that, The first escape wheel (10) includes a first driving tooth portion (12). The first escape wheel (10) meshes with a second driving tooth portion (14) of the second escape wheel (16) through the first driving tooth portion (12). Both the first escape wheel (10) and the second escape wheel (16) include impact and locking tooth portions (68, 70). The first escape wheel (10) and the second escape wheel (16) provide a direct tangential driving impact to the balance wheel plate (26) through the impact and locking tooth portions. The driving tooth portions of each of the first escape wheel (10) and the second escape wheel (16) and the impact and locking tooth portions (68, 70) extend in a single plane or two parallel planes.

14. The natural escapement mechanism (1) according to claim 13, characterized in that, Both the first escape wheel (10) and the second escape wheel (16) are integral parts.

15. The natural escapement mechanism (1) according to any one of claims 5-7, characterized in that, The anchor escapement fork (34) includes a fork head (40) formed by a first corner portion (42a) and a second corner portion (42b). During the first half-cycle, the balance wheel plate (26) abuts against the second corner portion (42b) of the fork head (40) through its balance wheel pin (28) and causes the anchor escapement fork (34) to pivot in a first direction. During the second half-cycle, the balance wheel plate (26) abuts against the first corner portion (42a) through its balance wheel pin (28) and causes the anchor escapement fork (34) to pivot in a second direction opposite to the first direction.

16. The natural escapement mechanism (1) according to claim 15, characterized in that, The fork head (40) carries a fork head pin (44). During a period called the supplementary circular arc, the fork head pin (44) cooperates with the balance wheel plate (26) to prevent accidental movement of the fork head (40).

17. The natural escapement mechanism (1) according to any one of claims 5-7, characterized in that, The natural escapement mechanism (1) includes a reduction gear pair provided between the gear train of the watch movement and the first escape wheel (10).

18. A watch movement, which includes the natural escapement mechanism (1) according to any one of claims 1-17.

19. The timepiece movement according to claim 18, characterized in that, The gear train of the watch movement that drives the first escape wheel (10) is the seconds wheel (2).

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