CH718579B1 - Natural escapement for a clock movement and clock movement comprising such an escapement. - Google Patents

Abstract

The invention relates to a natural escapement (1) for a watch movement, the natural escapement (1) comprising a balance wheel (20) which moves from a first extreme position to a second extreme position and vice versa while passing through a of median rest, this balance (20) comprising a balance wheel (22) on an axis (24) of which is fitted a balance plate (26), the natural escapement (1) also comprising a first escapement wheel set arranged to be driven by a wheel set of the gear train of the timepiece movement and in turn driving a second escapement wheel set, the first and second escapement wheels forming a kinematic chain cooperating with an anchor (34) comprising a first and a second safety lever (84, 86) arranged so that, in the absence of the balance wheel (20), the second or the first escapement mobile respectively, by acting on the second or the first safety lever (86, 84 ), causes the pivoting of the anchor (3 4) to ensure the rest of the first or the second escapement wheel set by pressing on a part (88) of the anchor (34) which performs the function of stop pallet, the first and second safety lifts (84, 86) not interfering with the normal operation of the natural escapement (1) during which it is the balance plate (26) which causes the pivoting of the anchor (34). The invention also relates to a clock movement comprising such a natural escapement (1).

Description

Technical field of the invention

The present invention relates to a natural escapement for clockwork also known by its name tangential impulse escapement. The present invention relates more particularly to a natural escapement protected against the damage that may be caused by premature triggering of the escapement pulse in the absence of the balance wheel. The present invention also relates to a timepiece movement comprising such an escapement.

Technology background

[0002] The principle of the natural escapement was imagined by Abraham Louis Breguet at the beginning of the 19th century. Breguet's natural escapement has the particular advantage of being a free escapement insofar as the balance is only disturbed by the operation of the escapement over a small fraction of its oscillation. Breguet's natural escapement also has the advantage of giving each alternation a direct and tangential impulse to the balance wheel. In other words, the energy is transferred directly from the escape wheel to the balance wheel, without passing through an anchor. Furthermore, the transmission of energy takes place only tangentially, so that the friction generated by the operation of this escapement is limited. Contrary to a detent escapement, a natural escapement does not present a lost blow in its function of maintaining the oscillations of the balance wheel; it delivers a similar pulse at each alternation, in a symmetrical and more uniform way, so that the losses of mechanical energy by lost blow are eliminated. All these qualities thus make the natural exhaust one of the potentially most efficient exhausts.

[0003] Breguet nevertheless subsequently discovered that the natural escapement he had imagined had certain drawbacks, first and foremost of which we can cite the fact that the last escape wheel is not under the tension of the gear train when the first wheel gives the impetus or when the latter is at rest. The different sets of gears and the manufacturing quality of the various components that go into the composition of a natural Breguet escapement can thus cause incorrect positioning of the last escapement wheel and, consequently, poor functioning of the escapement s 'accompanied by extraneous noises. Furthermore, since the escape wheel is free, its position is unstable, so that the safety of operation of such a natural escapement is poor.

[0004] Of course, many improvements have been made to the original Breguet natural escapement in an attempt to overcome the drawbacks mentioned above. Nevertheless, despite the efforts of successive watch manufacturers, difficulties persist. Some watchmakers have thus proposed superimposing the two escapement 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 watch manufacturers have proposed positioning the lever between the two escapement wheels, in the plane of the latter. Again, such a solution is cumbersome, this time in the plane of movement. In addition, whether the escapement wheels are superimposed or whether the anchor is placed between the two escapement wheels, it has been realized in use that watchmakers experience difficulties in accessing the various components of the escapement, in particular when it came to adjusting the depth of penetration of the teeth of the first and second escapement wheel with the exit and entry pallets of the anchor. In addition, when the watchmaker performs control or adjustment manipulations and removes the balance wheel for this purpose, it may happen that the impulse is triggered without either of the two impulse pallets carried by the balance plate is located on the perimeter of rotation of one or other of the escape wheels to ensure the escapement function. In such cases, the escape wheels are not restrained by the escapement function and may spin uncontrollably. This then causes at best a loss of the timepiece function with an undesired 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 deterioration of the components of the gear train and the escapement.

Summary of the invention

The object of the present invention is to remedy the problems mentioned above as well as still others by providing a natural escapement for a clockwork movement which is protected against the effects of a triggering of the function of escapement when the balance wheel is not present.

[0006] To this end, the present invention relates to a natural escapement for a clock movement performing a succession of operating cycles each consisting of a first and a second alternation of a balance wheel during which the balance wheel moves from a first extreme position to a second extreme position passing through a median rest position, then from its second extreme position to its first extreme position by returning a second time through its median rest position, this balance wheel comprising a balance wheel on a axis of which a balance plate is fitted, this natural escapement also comprising a first escapement wheel set provided with at least one toothing, this first escapement wheel set, arranged to be driven by a wheel set of the gear train of the clockwork movement , in turn driving a second escape wheel set provided with at least one toothing, the first and second escape wheel sets forming a cooperating kinematic chain nt with an anchor capable of pivoting around an anchor rod, the balance plate causing the pivoting of the anchor at each of the first and second alternations, this anchor being arranged to block the first and the second escapement wheel set temporarily during an operating cycle, the anchor further comprising a first and a second safety lift, these first and second safety lifts being arranged so that, in the absence of the pendulum, one or the other of the second and first escapement wheel sets, by driving the second or the first safety lift, causes the lever to pivot to ensure that the first or second escape wheel sets rest by abutment of this first or this second escapement wheel set on a part of the anchor which performs the function of a stopper for this first or this second escapement wheel set in normal operation of the natural escapement, the first and second safety lifts being ag indented so as not to be in contact with the first and second escapement mobiles in normal operation of the natural escapement during which it is the balance plate which causes the lever to pivot.

According to special embodiments of the invention: a first lever, pivoted about a pivot axis, being connected to the first arm of the anchor via at least one pivoting joint, the anchor comprising a second lever which extends its second arm, these first and second levers being arranged to temporarily block the first and second escape wheels during the alternations of an operating cycle, the travel of the first and second pivoting levers being limited; the first and second levers are pivoted around respective pivot axes and are respectively connected to the first and second arms of the anchor via at least one pivot joint; each at least one pivoting joint is formed of a lug which protrudes into an oblong opening; the movement in pivoting of the anchor is limited by first and second limit stops; the first and second limit stops are pins; the first and second stops are machined in a fixed element of the timepiece movement; the first and second limit stops are eccentrics; the first lever is made in one piece and has a geometry that performs the function of a first stopper pallet to temporarily block the first escapement wheel during an operating cycle, and the second lever is made of 'one piece and has a geometry that performs the function of a second stopper pallet to temporarily block the second escape wheel during an operating cycle; the first escapement wheel comprises a first drive toothing by which it meshes with a second drive toothing of the second escapement wheel, and the first and second escapement wheels each comprise an impulse toothing and rests by which they supply a direct and tangential drive impulse to the balance plate, the drive and impulse and rest teeth of each of the first and second escapement wheels extending in a single plane or in two parallel planes ; the pallet fork comprises a fork formed of a first and a second horn, the balance plate abutting by its balance pin against the second horn of the fork and causing the pivoting of this pallet in a first direction during the first alternation, and against the first horn during the second alternation, causing the lever to pivot in a second direction opposite to the first; the fork carries a dart which cooperates with the balance plate to prevent accidental movements of the fork during a period called additional arc; the first and second escape wheels are each one-piece; a reduction wheel set is arranged to be arranged between the wheel set of the gear train of the clockwork movement and the first escapement wheel.

The invention also relates to a clock movement comprising a natural escapement of the type described above.

[0009] Thanks to these characteristics, the present invention provides a natural escape protected against the damage that premature triggering of the pulse can create. Indeed, by teaching to provide the first and second arms of the anchor with a first and second safety lifting, the rest of the first escapement mobile is advantageously ensured when, in the absence of the balance plate, this rest is not ensured by the cooperation between this balance plate and the anchor. Indeed, it is understood that in the absence of the balance plate, the second escapement mobile is not retained by the escapement function and can therefore rotate without control, which can cause a loss of the guard function -time with an undesired advance, or even a sudden stop after acceleration of the train of the timepiece movement, which can lead to deterioration of the components of the train and of the escapement. To achieve this objective, the first and second safety lifts are arranged so that, in the absence of the balance wheel, the second escapement mobile, by action on the second safety lift, causes the pivoting of the second arm of the anchor, of the anchor and of the first arm of the anchor to ensure that the first escapement wheel is at rest on the part of this anchor which, in normal times, that is to say when the balance plate is present , performs the function of a stop pallet to temporarily block the first escapement mobile during an operating cycle of the natural escapement. Of course, the first and second safety lifts are designed so as not to be in contact with the first and second escapement wheels in normal operation of the escapement during which it is the balance plate which causes the pivoting of the anchor. Similarly, it will be understood that the symmetrical situation is also possible, namely that by pivoting of the anchor controlled by the first escapement wheel set, the rest of the second escapement wheel set is ensured by pressing against the part of this anchor which , in normal times, performs the function of a stop pallet to temporarily block the second escapement wheel set during an operating cycle of the natural escapement.

Brief description of figures

Other characteristics and advantages of the present invention will emerge more clearly from the following detailed description of an embodiment of a natural exhaust according to the invention, this embodiment being given for purely illustrative purposes and not limited by figures 8 to 10 in connection with the other figures shown in the appended drawing in which: FIG. 1 is an overall top view of a natural escapement in its rest position in which the second escapement wheel bears against the second lever; FIG. 2 is a top view of the natural escapement in its position in which the balance pin comes into contact with the second horn of the fork, which will cause the start of the release of the second escape wheel from its taken with the second lever; FIG. 3 is a top view of the natural escapement in its position in which the balance plate drives the anchor and the levers, which causes the start of the first fall by release of the second escapement wheel from its taken with the second lever; FIG. 4 is a top view of the natural escapement in its position in which the first escapement wheel comes to rest on the first impulse pallet and begins to give an impulse to the balance plate, which marks the end of the first fall; FIG. 5 is a top view of the natural escapement in its position in which the first escapement wheel imparts momentum to the balance plate while the second lever bears against the second limit stop; FIG. 6 is a top view of the natural escapement in its position in which the first escapement wheel finishes imparting an impulse to the balance plate, which marks the start of the second fall, while the second lever is resting on the second limit stop; Figure 7 is a top view of the natural escapement in its position in which the first escapement wheel rests on the first lever, which marks the end of the second fall, while the balance plate ends its alternation freely; FIG. 8 is a top view of a natural escapement according to one embodiment of the invention in the case where the balance wheel has been removed, the anchor being fitted with safety levers in accordance with the invention, the the natural escapement being in the position in which the second escapement wheel, by action on the second safety lift, will cause the lever to pivot to ensure that the first escapement wheel is at rest by pressing, via the one of the teeth of its impulse and rest toothing, on the part of this anchor which, in normal times, that is to say when the balance plate is present, performs the function of a first pallet of stopping to temporarily block the first escapement wheel during an operating cycle of the natural escapement; Figure 9 is a top view similar to that of Figure 8 in which, in the absence of the balance wheel, the first escapement wheel will, by acting on the first safety lift, cause the pivoting of the lever so as to allow the second escapement wheel to come into the rest position by pressing one of the teeth of its impulse and rest toothing on the part of this lever which, in normal times, performs the function a second stop pallet whose role is to temporarily block this second escape wheel; FIG. 10 is a view from above which illustrates the position of the natural escapement following the position in which this natural escapement is found in FIG. 8 and in which, the balance wheel being absent, the second balance wheel escapement has, by action on the second safety release, caused the lever to pivot so as to allow the first escapement wheel to assume its rest position by pressing one of the teeth of its impulse toothing and resting on the part of this lever which, in normal times, that is to say when the balance wheel is present, performs the function of a first stop pallet to temporarily block the first escapement wheel during a natural exhaust operating cycle.

Detailed description of the invention

The present invention proceeds from the general inventive idea which consists in providing the first and second arms of the lever with a natural escapement, also known by its name tangential impulse escapement, with a first and a second safety release with the aim of guaranteeing that, if the watchmaker, for whatever reason, needs to remove the balance wheel, an unexpected triggering of the rotation of the first and second escapement mobiles is immediately stopped by bringing the one of the first and second escapement wheels in its rest position. To this end, the safety lifts are arranged so that, when the balance wheel is withdrawn, the second escape wheel, by action on the second safety lift, causes the anchor and the first arm of this anchor to pivot. to allow the first escapement wheel set to immobilize in its rest position resting against the part of this anchor which, in normal times, that is to say when the balance plate is present, performs the function of a stop pallet for temporarily blocking the first escapement mobile during an operating cycle of the natural escapement.

Designated as a whole by the general reference numeral 1, the natural escapement is shown in its rest position in Figure 1. This natural escapement 1 is arranged to be driven by a mobile part of the clockwork, for example a seconds wheel 2 which, according to a preferred but non-limiting embodiment, meshes with a pinion 4 fixedly mounted on an axis 6 of a first escape wheel set comprising a first escape wheel 10. This first escape wheel 10 for its part meshes via a first drive toothing 12 with a second drive toothing 14 of a second escape wheel set comprising a second escape wheel 16 which pivots about an axis 18.

[0013] The natural escapement 1 also comprises a balance wheel 20 which comprises a balance wheel 22 on an axis 24 of which is fitted a balance plate 26. This balance plate 26 carries a balance pin 28 as well as a first and a second pulse pallet 30 and 32 whose respective roles will be described below.

[0014] The natural escapement 1 also comprises an anchor 34 pivoted around an anchor rod 36. This anchor 34 comprises an anchor body 38 which carries a fork 40 formed of a first and a second horn 42a and 42b as well as a dart 44. This dart 44 cooperates with the balance plate 26 in order to prevent accidental movements of the fork 40 during the periods commonly called additional arcs, periods during which the balance plate 26 is distant from its middle resting position called the angle of lift.

As can be seen on examination of Figure 1, the anchor body 38 comprises a first and a second arm 46a and 46b which are preferably but not limited to arranged symmetrically on either side of the fork 40. According to an embodiment illustrated in Figures 8 to 10 given purely by way of illustration only, first and second levers 48a, 48b, pivoted around respective pivot axes 50 and 52, are connected to the first and second arms 46a, 46b of the anchor body 38 via a pivot joint 53. In this embodiment, the first lever 48a is made in one piece and has a geometry which performs the function of a first stop pallet for temporarily block the first escapement wheel 10 during an operating cycle of the natural escapement 1, and the second lever 48b has a geometry which performs the function of a second stopper pallet to temporarily block the second wheel exhaust 1 6 during the same operating cycle of natural escapement 1.

According to the embodiment shown in the drawing, the first and second levers 48a, 48b each carry a lug 54, 56 respectively, which projects into an oblong opening 58, 60 respectively, formed in the first and second arms 46a , 46b of the anchor body 38. Of course, the lugs 54 and 56 could be carried by the first and second arms 46a, 46b, and the oblong openings 58, 60 could be provided in the first and second levers 48a, 48b. Thus, by engagement of the lugs 54, 56 in the oblong openings 58, 60, the first and second levers 48a, 48b are able to pivot relative to the first and second arms 46a, 46b of the anchor body 38.

[0017] In the mode of execution of the natural escapement 1 shown in the drawing, it is assumed that the second wheel 2 which supplies the natural escapement 1 with the energy necessary for its operation rotates clockwise. a watch. The second wheel 2 therefore tends to rotate the pinion 4 and the first escapement wheel 10 on the axis 6 of which the pinion 4 is fixed counterclockwise, and the second escapement wheel 16 in the direction hourly.

[0018] An operating cycle of the natural escapement 1 comprises two alternations during which the balance plate 26 goes successively from a first extreme position to a second extreme position passing through a middle rest position, then from its second extreme position to its first extreme position by going back a second time through its middle rest position. Thus, at the start of a cycle (see FIG. 1), the balance wheel 26 rotates towards its middle rest position by rotating clockwise, while the second escape wheel 16 is in support. on the second lever 48b.

[0019] At a given moment of its movement illustrated in Figure 2, the balance plate 26 arrives in a position in which it abuts by its balance pin 28 against the second horn 42b of the fork 40 and begins to cause the pivoting of the anchor 34 counterclockwise. The pivoting of the lever 34 counterclockwise has the effect of beginning to release the second escapement wheel 16 from its grip with the second lever 48b, which will allow the second wheel 2 to drive, via the first escape wheel 10, the second escape wheel 16 clockwise.

In Figure 3, the natural escapement 1 is in a position in which the balance plate 26 drives the anchor 34, which causes the start of the first fall by release of the second escapement wheel 16 from its grip with the second lever 48b. By "fall" is meant the periods of operation of the natural escapement 1 according to the invention during which the first and second escapement wheels 10 and 16 are not in contact with either of the first and second levers 48a, 48b, nor with either of the first and second impulse paddles 30, 32.

It will be understood that at the same time as the first escapement wheel 10 drives the second escapement wheel 16 in clockwise pivoting, the first escapement wheel 10 also begins to give a driving impulse to the plate of balance 26 via a tooth 66 of an impulse and rest toothing 68 which drives the first impulse pallet 30 (see FIG. 4). This driving impulse is said to be direct and tangential because it is given directly by the first escapement wheel 10 to the balance plate 26 and the path of the tooth 66 catches up with that of the first impulse pallet 30 of the balance plate 26 of tangentially, which allows an almost punctual and frictionless contact. It will also be noted that the coming of the tooth 66 of the first escapement wheel 10 into contact with the first impulse pallet 30 of the balance plate 26 marks the end of the first fall.

[0022] Figure 5 is a top view of the natural escapement 1 in its position in which the first escapement wheel 10 imparts the impulse to the balance plate 26, while the second lever 48b pivots around its axis 52 and bears against the second limit stop 64. This movement is controlled by the anchor 34 which, driven by the balance pin 28, pivots around its anchor rod 36 in the counter-clockwise direction. 'a watch.

In Figure 6, the first escapement wheel 10 finishes imparting an impulse to the balance plate 26, which marks the start of the second drop. It can in fact be seen that the tooth 66 of the first escape wheel 10 will no longer be in contact with the first impulse pallet 30 of the balance plate 26. Furthermore, the second lever 48b bears against the second stop of the restriction 64.

Finally, Figure 7 is a top view of the natural escapement 1 in its other rest position in which the first escapement wheel 10 bears on the first lever 48a, which marks the end of the second fall, while the balance plate 26 ends its alternation freely by rotating clockwise. The following alternation during which the balance plate 26 will rotate counterclockwise reproduces the same functions as those illustrated in Figures 2 to 7 symmetrically in reverse order.

Figure 8 is a top view of the natural escapement 1 of Figure 1 in the case where the balance 20 has been removed, situation schematically illustrated by representing the balance 20 in dotted lines. In accordance with the invention, the first and second levers 48a, 48b of the anchor 34 are respectively provided with a first safety lift 84 and a second safety lift 86. As can be seen in this figure 8, the natural escapement 1 is in the position in which the second escapement wheel 16 will, by pivoting clockwise, act via one of the teeth of its impulse and rest toothing 70 on the second safety release 86 carried by the second lever 48b and cause the lever 34 to pivot to ensure the rest or locking of the first escapement wheel 10 by pressing one of the teeth 66 of its impulse and rest toothing 68 on the part 88 of this anchor 34 which, in normal times, that is to say when the balance plate 26 is present, performs the function of a first stop pallet to temporarily block the first escapement wheel 10 during a natural escape operating cycle 1.

The situation described above is illustrated in Figure 10 in which, the balance 20 being still absent, the first escapement wheel 10 is at rest by pressing one of the teeth 66 of its impulse toothing and rest 68 on the part 88 of the anchor 34 which performs the function of stop pallet. In fact, under the effect of the pivoting of the lever 34 caused by the rotation of the second escapement wheel 16, the part 88 of the lever 34 which performs the function of stopper pallet is found in the perimeter of rotation of the first escapement wheel 10 and the first escapement wheel 10 comes via one of the teeth 66 of its impulse and rest toothing 68 bearing against this part 88 of the lever 34.

Finally, the situation illustrated in Figure 9 is symmetrical to that shown in Figure 8, namely that it is the first wheel 10 escapement 10 which, by pivoting counterclockwise, will act on the first safety release 84 carried by the first lever 48a and causing the pivoting of the anchor 34 to ensure rest or blocking of the second escapement wheel 16 by pressing one of the teeth of its impulse and rest toothing 70 on the part 90 of this anchor 34 which, in normal times, that is to say when the balance plate 26 is present, performs the function of a second stop pallet to temporarily block the second wheel of exhaust 16 during an operating cycle of natural exhaust 1.

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 can be envisaged without departing from the scope of the invention as defined by the claims. annexed. It will be understood in particular that, although the natural escapement 1 has been described in connection with an anchor 34 to the arms 46a, 46b of which are connected first and second levers 48a, 48b, it is entirely possible, in a form of simplified execution, to provide only one lever pivotally connected to one of the arms of the anchor, the other lever being made in one piece with the second arm of the anchor 34. It will be noted also that the presence of the first and second levers 48a, 48b is not essential, the anchor 34 being able to comprise only the arms 46a, 46b, the first arm 46a having a geometry which ensures the function of a first pallet of stopper to temporarily block the first escapement wheel 10 during an operating cycle of the natural escapement 1, and the second arm 46b has a geometry which performs the function of a second stopper pallet to temporarily block the second escapement wheel 16 during the same operating cycle of the natural escapement 1. It will also be noted that a reduction mobile can be arranged between the second wheel 2 and the first escapement wheel 10. The first escapement wheel 10 comprises a first drive toothing 12 by which it meshes with a second drive toothing 14 of the second escapement wheel 16. Similarly, the first and second escapement wheels 10, 16 each comprise an impulse and rest toothing 68, 70 by which they provide driving impulse direct and tangential to the balance plate 26. The drive teeth 12, 14 and impulse and rest teeth 68, 70 of each of the first and second escapement wheels 10, 16 extending in a single plane or in two parallel planes. Preferably, the first and second escape wheels 10, 16 are each one-piece.

Nomenclature

1. Natural exhaust 2. Second wheel 4. Pinion 6. Axis 10. First escapement wheel 12. First drive toothing 14. Second drive toothing 16. Second escapement wheel 18. Axis 20 Balance 22. Balance wheel 24. Shaft 26. Balance plate 28. Balance pin 30. First impulse pallet 32. Second impulse pallet 34. Anchor 36. Anchor rod 38. Anchor body 40 Fork 42a. First horn 42b. Second horn 44. Stinger 46a. First arm 46b. Second arm 48a. First lever 48b. Second lever 50. Pivot pin 52. Pivot pin 53. Pivot joints 54. Pin 55. Pin 56. Pin 57. Circular opening 58. Oblong opening 60. Oblong opening 62. First limit stop 64. Second limit stop 66. Tooth 68. Impulse and rest gear 70. Impulse and rest gear 76. Eccentrics 84. First safety lift 86. Second safety lift 88. Part 90. Part

Claims (19)

1. Natural escapement (1) for a clock movement carrying out a succession of operating cycles each consisting of a first and a second alternation of a balance (20) during which the balance (20) moves from one first extreme position to a second extreme position passing through a median rest position, then from its second extreme position to its first extreme position by returning a second time through its median rest position, this balance (20) comprising a balance wheel (22) on an axis (24) of which a balance plate (26) is fitted, this natural escapement (1) also comprising a first escapement wheel set provided with at least one toothing (12; 68), this first escapement wheel set, arranged to be driven by a wheel set of the gear train of the timepiece movement, in turn driving a second escape wheel set provided with at least one toothing (14; 70), the first and second wheel sets exhaust forming a coo kinematic chain working with an anchor (34) capable of pivoting around an anchor rod (36), the balance plate (26) causing the pivoting of the anchor (34) at each of the first and second alternations, this anchor ( 34) being arranged to block the first and the second escape wheel set temporarily during an operating cycle, the anchor (34) further comprising a first and a second safety lever (84, 86), these first and second safety levers (84, 86) being arranged so that, in the absence of the balance (20), one or the other of the second and first escapement wheels, by driving the second or of the first safety release (86; 84), causes the lever (34) to pivot to ensure the rest of the first or second escapement wheel set by abutment of this first or this second escapement wheel set on a part (88; 90) of the anchor (34) which performs the function of a stop pallet for this first or this second escapement wheel set in normal operation of the natural escapement (1), the first and second safety levers (84, 86) being arranged so as not to be in contact with the first and second escapement wheels in normal operation of the natural escapement (1) during which it is the balance plate (26) which causes the lever to pivot (34). 2. Exhaust according to claim 1, characterized in that the anchor (34) comprises a first and a second arm (46a, 46b) arranged to respectively block the first and the second mobile escapement temporarily during an operating cycle, the first safety lever (84) being arranged on the first arm (46a) of the anchor (34), while the second safety lifting (86) is arranged on the second arm (46b) of the anchor (34). 3. Natural exhaust according to claim 2, characterized in that a first lever (48a), pivoted about a pivot axis (50) and on which the first safety lift (84) is arranged, is connected to the first arm (46a) of the anchor (34) via at least one pivoting joint (53), the anchor (34) comprising a second lever (48b) which extends its second arm (46b) and on which the second safety release (86), these first and second levers (48a, 48b) being arranged to respectively temporarily block first and second escape wheels (10, 16) that comprise the first and second escape wheels during of an operating cycle, the movement of the first and second levers (48a, 48b) in pivoting being limited. 4. Exhaust according to one of claims 2 and 3, characterized in that the balance plate (26) carries a first impulse pallet (30) by which this balance plate (26) receives a direct and tangential driving impulse of the first escapement wheel set during the first alternation, and a second impulse pallet (32) via which this balance plate (26) receives a direct and tangential drive impulse from the second escapement wheel set during the second alternation. 5. Natural exhaust according to one of claims 2 to 4, characterized in that the balance plate (26) carries a balance pin (28) by which this balance plate (26) causes the pivoting of the anchor ( 34) at each of the first and second alternations. 6. Natural exhaust (1) according to claim 5, characterized in that the first and second levers (48a, 48b) are pivoted around respective pivot axes (50, 52) and are respectively connected to the first and second arms ( 46a, 46b) of the anchor (34) via at least one pivot joint (53). 7. Natural exhaust (1) according to claim 6, characterized in that each at least one pivoting joint (53) is formed of a lug (54, 56) which projects into an oblong opening (58, 60). 8. Natural exhaust (1) according to one of claims 5 to 7, characterized in that the pivoting movement of the anchor (34) is limited by first and second limiting stops (62, 64). 9. Natural exhaust (1) according to claim 8, characterized in that the first and second limiting stops (62, 64) are pins. 10. Natural escapement (1) according to claim 8, characterized in that the first and second limiting stops (62, 64) are machined in a fixed element of the clock movement. 11. Natural exhaust (1) according to claim 8, characterized in that the first and second limiting stops (62, 64) are eccentrics. 12. Natural exhaust (1) according to one of claims 5 to 11, characterized in that the first lever (48a) is made in one piece and has a geometry which performs the function of a first stop pallet for temporarily block the first escapement wheel (10) during an operating cycle, and the second lever (48b) is made in one piece and has a geometry which performs the function of a second stop pallet for temporarily blocking the second escapement wheel (16) during the operating cycle. 13. Natural exhaust (1) according to one of claims 5 to 12, characterized in that the first escape wheel (10) comprises a first drive toothing (12) by which it meshes with a second toothing of drive (14) of the second escapement wheel (16), and in that the first and second escapement wheels (10, 16) each comprise an impulse and rest toothing (68, 70) by which they provide a direct and tangential drive impulse to the balance plate (26), the drive (12, 14) and impulse and rest (68, 70) teeth of each of the first and second escapement wheels (10, 16) extending in a single plane or in two parallel planes. 14. Natural exhaust (1) according to claim 13, characterized in that the first and second escape wheels (10, 16) are each in one piece. 15. Natural exhaust (1) according to one of claims 5 to 14, characterized in that the anchor (34) comprises a fork (40) formed of a first and a second horn (42a, 42b), the balance plate (26) abutting by its balance pin (28) against the second horn (42b) of the fork (40) and causing the pivoting of this lever (34) in a first direction during the first alternation, and against the first horn (42a) during the second alternation, causing the anchor (34) to pivot in a second direction opposite to the first. 16. Natural exhaust (1) according to claim 15, characterized in that the fork (40) carries a pin (44) which cooperates with the rocker plate (26) to prevent accidental movements of the fork (40) during a period called additional arc. 17. Natural escapement (1) according to one of claims 5 to 16, characterized in that it comprises a reduction wheel set arranged to be arranged between the wheel set of the gear train of the clockwork movement and the first escapement wheel ( 10). 18. Clock movement comprising a natural escapement (1) according to one of claims 1 to 17. 19. Clockwork movement according to claim 18, characterized in that the wheel set of the gear train of this clockwork movement which drives the first escapement wheel set (10) of the natural escapement (1) is a second wheel ( 2).