Escapement, return member for an escapement, timepiece movement, and timepiece

Abstract

The invention particularly relates to a return member for a balance wheel (10) of a timepiece, in replacement of a spiral spring. The return member comprises a rack (21) provided with sector teeth (22) arranged to engage with a balance pinion (20). The rack (21) comprises a rotation axis (24) allowing it to move between two extreme positions called working positions separated by a rest position. The return member further comprises two springs (26) arranged to push the rack (21) towards its rest position. Each spring (26) is formed by an elastic strip (27) arranged to store energy and then restore it against the rack. Each elastic strip works alternately so that they never work at the same time. The invention also relates to an escapement comprising such a return member, to a timepiece movement comprising such a return member and to a timepiece comprising such a movement.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of timepieces and in particular to the field of portable mechanical timepieces. Its subject is the replacement of the spiral spring, which is the return member of the balance, with a component that is easy to manufacture, which does not have the drawbacks of the balance spring and which can be adapted to the existing escapement systems of portable timepiece devices.

[0002] More particularly, the present invention relates to a timepiece movement escapement comprising a balance, an escapement wheel, a lever and a balance return member. It also relates to a return member for a timepiece movement comprising an escapement provided with a balance, an escapement wheel and a lever.

[0003] The present invention also relates to a timepiece movement comprising an escapement provided with a balance, an escapement wheel, a lever and a balance return member.

[0004] Finally, the present invention relates to a timepiece comprising a movement, an escapement or a return member as defined above. BACKGROUND

[0005] Fixed timepiece devices, whether floor, wall or table clocks, have provided sufficient precision for a century thanks to the invention of the pendulum. This precision of the pendulum is due to the action of gravity on the return member for returning the pendulum to its dead point. Fixed timepieces take advantage of the constancy of gravity.

[0006] The first tests of portable timepiece devices were carried out with crown wheel escapements that added a foliot balance as a return device. This system could not provide satisfactory precision and substantial improvements were only obtained after the invention of the spiral spring.

[0007] However, the spiral spring is currently less satisfactory than gravity and its performance is currently not constant. In addition to its very precise manufacture, the most important drawbacks are its variations in the vertical direction and its coupling variations between the number of windings and unwinding, which are called the angles of ascent and descent in the trade terminology. Despite all the research, a satisfactory solution has not yet been found for its drawbacks in terms of its shape and material.

[0008] Thus, despite all the research on escapements, even on the balance or other components, their arrangement and function cannot overcome the limitations of the balance spring.

[0009] Various improvements have been thought of to replace the spiral spring in a watch movement. Among them, reference can be made to Swiss patent No. 34983. In this patent, the watch movement comprises a rack acting on the pinion of the balance. This rack has a split bar and is pivoted on a shaft provided at the end of the split bar opposite the teeth of the rack. The movement comprises a flexible leaf fixed at one end to the plate and provided with a lug near the other end. The lug is arranged to slide in a slot of the split bar of the rack. The rack, the split bar and the flexible leaf work together to form a balance return member.

[0010] In this implementation, the flexible leaf must be able to store energy when it is deformed by the movement of the rack. It must then recover this energy to move the rack in the opposite direction, beyond the dead point or rest position of the rack. The maintenance of the movement and the compensation of the friction are achieved by the cooperation between the impact plane of the escapement and the pallets of the lever.

[0011] The implementation described in the aforementioned patent has various problems. The flexible leaf and the split bar are not in the same plane. The lug protrudes from the flexible leaf so that it can be in the slot of the split bar. The movement of the lug in the slot creates a torsion of the flexible leaf and a friction which results in a great loss of energy.

[0012] Furthermore, the flexible leaf must submit to two contradictory constraints. On the one hand, its stiffness must be large enough for a sufficient amount of energy to be stored during its deformation under the action of the movement of the balance and to be released when the flexible leaf returns towards its rest position. These energies must also compensate for the losses related to the friction of the lug in the slot and the torsion of the flexible leaf.

[0013] On the other hand, the stiffness must be small enough for the rack to be able to move sufficiently to achieve an angular movement of the balance of at least 300°.

[0014] A flexible leaf with too great a stiffness would prevent the rack from making a sufficient angular movement, since such a flexible leaf would tend to make the rack return to its dead point immediately after it has made a relatively weak angular movement. A flexible leaf with insufficient stiffness cannot store enough energy to allow the balance to continue its movement.

[0015] Furthermore, if the flexible leaf has too great a stiffness, the movement cannot be started. Indeed, the movement can only be started when the pallets of the lever reach the impact plane of the escapement. This is not possible when the flexible leaf has too great a stiffness.

[0016] With the system described in the aforementioned patent, the flexible leaf, existing or made from existing materials and techniques, does not allow the use of the principle of the invention, its stiffness being too great to allow the balance to make a sufficiently large movement.

[0017] The stiffness of the spring, in particular depending on its available length, allows to reduce the stiffness of the elastic blade. A typical spiral spring has 12 to 15 turns. In particular, a watch case such as a typical watch cannot accommodate an elastic blade long enough to obtain a return member that works.

[0018] The invention described in the Swiss patent 34983 tries to solve the specific problem of the spiral spring by making a symmetrical return member that avoids the problems related to the asymmetry of the spiral spring. However, the result obtained cannot be used in a watch type of watch.

[0019] The Swiss patent application No. 19698 describes, in one embodiment, a rack acting on the balance pinion. As in the patent 34983 described above, the rack is connected to an elastic rod whose deformation should allow the rotation of the balance pinion.

[0020] The invention described in this patent has the same problems as the previously described patents, making it impossible to put the invention into practice.

[0021] To replace the spiral spring and its drawbacks, it would be advantageous to find a solution that provides a balance actuation member that is more easily manufactured than a hairspring, has symmetry, allows to start the movement of a watch, has a size compatible with the use in a watch of traditional size and does not have the drawbacks of the implementation solutions of the inventions described in the prior art. SUMMARY

[0022] The drawbacks of the return members of the prior art are eliminated by the return member of the present invention.

[0023] The object of the present invention is to provide a return member that works in the same way in both directions of movement of the balance, is not disturbed in the vertical position and is not as fragile and complex in operation as the spiral spring.

[0024] These objects are achieved by the escapement of a watch movement defined in the preamble, characterized in that the balance is formed in one piece with the balance pinion and in that the balance return member comprises a rack provided with sector teeth arranged to work with the balance pinion, the rack comprising an axis allowing it to be rotated between two extreme positions called working positions separated by a rest position; the return member further comprises a return mechanism having two springs arranged to press the rack towards its rest position.

[0025] The objects of the present invention are also achieved by the return member defined in the preamble, characterized in that it comprises: a rack provided with sector teeth arranged to work with the balance pinion, the rack comprising an axis allowing it to be rotated between two extreme positions called working positions separated by a rest position; and two springs arranged to press the rack towards its rest position.

[0026] The object of the application is also achieved by a timepiece movement as defined in the preamble, characterized in that the balance is formed in one piece with the balance wheel pinion, and in that the balance return means comprise a rack provided with sector teeth arranged to work with the balance wheel pinion, the rack comprising a shaft allowing it to be rotated between two extreme positions called working positions separated by a rest position, the return means also comprising a return mechanism having two springs arranged to press the rack towards its rest position.

[0027] Finally, the object of the application is achieved by a timepiece comprising a movement, an escapement or return means as defined above.

[0028] According to the application, unlike a spiral spring, the return means are not fixed to the balance and its connection with the balance is achieved by a mechanical gearing.

[0029] The return means comprise a toothed part, hereinafter called the rack, and a return mechanism comprising two springs formed in the form of two elastic leaves. According to the application, the drawbacks due to the spiral spring, its clamping on the outer stud, its index assembly and the defects described at the beginning of this document are compensated by reducing the friction increased by the gearing between the rack and the balance wheel pinion.

[0030] The escapement of the application comprises a rack provided with sector teeth arranged to work with the balance wheel pinion. It also comprises a return mechanism provided with two elastic leaves. The rack is pivoted on its shaft between two extreme positions called working positions and corresponding to the maximum amount of rotation of the balance. These two extreme points are separated by a rest position.

[0031] When the rack moves out of its rest position, one of the elastic leaves is deformed by the rack. This deformation allows the elastic leaf to store energy. This energy is subsequently used by the elastic leaf to press the rack towards its rest position. Due to the construction of the escapement, in particular of the lever, the energy supplied to the rack allows it to go beyond its rest position. When this rest position is exceeded, the elastic leaf provided with energy no longer interacts with the rack. The other elastic leaf replaces it to store and subsequently return the energy.

[0032] According to the application, the return means have a symmetry with respect to the plane passing through the axis of rotation of the balance. Due to this symmetry, the force acting when the balance moves in one direction of rotation is the same as the force acting when the balance moves in the other direction of rotation. One of the drawbacks due to the asymmetry of the hairspring is thus eliminated.

[0033] The return member of the invention is formed by a return mechanism comprising two springs formed in the form of two elastic or spring leaves acting on the rack. These elastic leaves can be constructed and placed so that the rack can be moved slightly angularly before one of the elastic leaves acts on it to bring it back to its rest position. This allows the movement of the movement of the watch to be initiated and avoids the problem of stopping on the rest plane. The use of two elastic leaves independent of each other and never working at the same time makes it possible to halve the stiffness of the return mechanism, thus making it possible to obtain leaves of a length short enough to be able to be placed in a watch case of conventional size. This makes it possible in particular to avoid the problems of the return members described in patents CH 34983 and CH 19698.

[0034] In the return member of the invention, the two elastic strips are independent of each other. Thus, when one of the leaves is deformed to store or return energy, the other leaf is deactivated and does not interact with the rack. This avoids the problems associated with an elastic leaf that is too stiff, which can occur if the two elastic leaves act simultaneously on the rack.

[0035] The rack is formed by a sector gear that can generally have 80 to 160 teeth. Assuming that the balance performs a movement of amplitude 330° and that the balance has 10 teeth, the angular movement will be 37.125° for a rack corresponding to a wheel of 80 teeth and 18.5625° for a rack corresponding to a wheel of 160 teeth. The weaker angular movement of the rack can be controlled by the return mechanism while allowing a greater angular movement of the balance. BRIEF DESCRIPTION OF DRAWINGS

[0036] The application and its advantages will be better understood in reference to the detailed description of a particular embodiment, with reference to the attached drawings in which:

[0037] Figure 1 is a top view of a conventional Swiss lever escapement without hairspring;

[0038] Figure 2 is Figure 1 a side view of the escapement of

[0039] Figure 3 is Figure 1 and 2 a side view of the escapement of

[0040] Figure 4 is Figures 1-3 a top view of a part of the escapement of

[0041] Figure 5 shows the return member of Figure 4 in the rest position;

[0042] Figure 6 a return member of the application in the rest position; Figure 4 a return member of the application in the rest position;

[0043] Figure 7 a top view of a variant of the return member of the application in the rest position;

[0044] Figure 7a a detail of a part of Figure 7 ;

[0045] Figure 8 a top view of a return member of Figure 7 in the rest position;

[0046] Figure 9 a return member similar to Figure 6 , in which adjustment of the position of the elastic leaf can be performed;

[0047] Figure 10 a variant of the return member according to the application in the rest position;

[0048] Figure 11 a view of a return member of Figure 10 in the rest position;

[0049] Figures 12-14 a further variant of the return member according to the application in the rest position;

[0050] Figure 15 a return member of Figure 14 in the rest position; and

[0051] Figure 16 a return member having an internally toothed rack and the same return mechanism as Figure 14 and 15 . DETAILED DESCRIPTION

[0052] The application relates in particular to a clockwork escapement mechanism. In the embodiment shown, the escapement mechanism comprises traditional components and new components. The traditional components are those which are described in Figures 1-3The Swiss lever escapement is represented in its entirety by the part of the figure. It comprises a balance 10 pivoted on a balance shaft 11, a lever 12 pivoted on a lever shaft 13 and an escape wheel 14 pivoted on an escape wheel shaft 15. The lever 12 comprises in particular, in a traditional manner, a bridge 16 driven by the balance 10 and a pallet 17 acting on the teeth 18 of the escape wheel 14. Unlike a traditional escapement, this escapement does not comprise any spiral spring. It should be noted that a Swiss lever escapement is represented here, which is the most commonly used in practice. However, the return member according to the application can also be used on any other escapement in which the balance acts as a regulating member.

[0053] The new component comprises a return member 19 which functionally replaces the spiral spring.

[0054] The return device according to the application can be integrated into an existing escapement or form part of an escapement developed specifically for this movement.

[0055] Reference is made in particular to Figure 3 The balance 10 used in the application comprises a balance pinion 20 integral with the balance shaft 11.

[0056] The return member 19 according to the application comprises a rack 21 comprising a sector tooth 22 and one or two arms 23. The rack 21 is pivoted around a rack shaft 24 integral with the bridge (not shown) of the timepiece movement. It can be moved clockwise or anticlockwise between two extreme working positions of maximum movement of the balance 10 on either side of its rest position.

[0057] The return member 19 also comprises a return mechanism 25 with two springs 26, the operation of which will be described below. These springs 26 comprise two elastic blades 27 in the embodiment shown.

[0058] In Figures 4-6 In the embodiment shown, the rack 21 comprises two arms 23, one end of which is provided at each end of the sector tooth 22 and the other end of which is connected near the rotation axis 24 of the rack.

[0059] The rack 21 also comprises a rod 28, one end of which is near the axis 24 of the rack and the other end of which is integral with the elastic blades 27.

[0060] The return member 19 can be placed on the bridge of the timepiece with two pins 30 arranged so that the elastic blades 27 can bear against them according to the position of the rack 21.

[0061] In this embodiment, the rack 21, the arms 23, the rod 28 and the elastic blades 27 are integral and formed as a single piece.

[0062] Figure 4 and 5 The rack 21 is shown in a rest position. Figure 6 The rack 21 is shown in a working position.

[0063] When the balance 10 is pivoted in one direction, the balance pinion 20 acts on the sector teeth 22 of the rack 21 to make the latter pivot on its axis of rotation 24 in the opposite direction. This deforms one of the elastic leaves 27 which abuts against a corresponding pin 30 of the movement. This elastic leaf 27 stores energy. The other elastic leaf is free and does not interact with the rest of the movement or the other pin 30, so that it does not oppose the rotation of the rack 21 or the balance 10. Figure 6 In the working position shown, the balance pinion 20 acts on the sector teeth 22 of the rack 21 to make the latter pivot on its axis of rotation 24 in the opposite direction. This deforms one of the elastic leaves 27 which abuts against a corresponding pin 30 of the movement. This elastic leaf 27 stores energy. The other elastic leaf is free and does not interact with the rest of the movement or the other pin 30, so that it does not oppose the rotation of the rack 21 or the balance 10.

[0064] When the elastic leaves 27 exert sufficient stress, after a certain angular movement of the rack 21 and therefore of the balance 10, the leaves return the energy and cause the rack to pivot in the other direction of rotation. This causes the balance to rotate by the balance pinion 20. Traditionally, the balance 10 acts on the lever 12 to release the teeth 18 of the escapement wheel 14. The impact plane of the teeth of the escapement wheel 14 acts on one of the prongs 17 of the lever 12, thereby providing energy to the lever which transmits this energy to the balance 10 by the stem 16. This energy is used by the balance to pivot on its axis 11, which causes the rack 21 to rotate on its axis 24 and enables the other elastic leaf 27 of the return mechanism 25 to be loaded.

[0065] This alternating movement is similar to that produced by the hairspring. However, unlike the hairspring, the elastic leaves 27 are symmetrical to each other when the rack is in the rest position, which means that there is no operational difference when the balance 10 is pivoted clockwise or anticlockwise.

[0066] The pins 30 can be mounted on an eccentric and thus form an adjustment element 29. This eccentric can change the stiffness of the elastic leaves 27 and thus the amplitude of rotation of the rack 21 and the balance 10. More precisely, the two pins 30 of the adjustment element 29 can be moved, which enables the distance between the elastic leaves 27 and the axis of rotation 24 of the rack to be adjusted within a certain range. This allows the rate of the watch to be finely adjusted. This fine adjustment of the rate of the watch can also be achieved by a screw balance shown in the various figures or by an inertial block balance.

[0067] In the embodiment shown, Figure 7 and 8 In the embodiment shown, the return mechanism 25 is separate from the rack 21 and is not integral with it. In this implementation, the rack 21 pivots on its axis of rotation 24 and comprises a single arm 23 which connects the sector teeth 22 of the rack to its axis of rotation 24.

[0068] The return means 25 also comprises two elastic blades 27, which are manufactured separately from the rack 21. These elastic blades are integral with a support 32 fixed to the bridge of the timepiece movement. Each elastic blade 27 works with one side of the arm 23 of the rack. When the rack is moved in one direction, one of the elastic blades 27 comes to bear against the corresponding side of the rack arm and deforms. This allows the elastic blade to store energy. The other elastic blade is not in interaction with the rack 21, so that only the stiffness of one blade, and not of two, is involved.

[0069] At the end of the movement of the rack 21, the elastic blades 27 return the energy and push the rack in the opposite direction, as described above. The contact area between the elastic blades 27 and the arms 23 of the rack can be polished to minimize the friction. The rack 21 and the elastic blades 27 are disposed in the same plane, the elastic blades not experiencing torsion, but only flexion, which enables them to store and return energy.

[0070] In the embodiment of Figure 9 , the elastic blades 27 are disposed on a mobile support 33, the position of which can be adjusted on the bridge of the movement. This adjustment is achieved by the mobile support 33 comprising a toothed rod 34 and the bridge comprising an adjustment pinion 35. Rotation of the adjustment pinion 35 moves the toothed rod 34 and thus the position of the elastic blades 27. This makes it possible to vary the distance between the axis of rotation 24 of the rack and the point of contact between the elastic blades 27 and the arms 23 of the rack. This thus varies the force required to move the rack 21, which corresponds to an adjustment of the stiffness or apparent stiffness of the elastic blades 27.

[0071] Figure 10 and 11 A variant of the return means 19 according to the application is shown, in which the rack 21, the arms 23 of the rack and the elastic blades 27 of the return means are formed in a single piece. In this embodiment, as described with reference to Figures 4-6 , the timepiece comprises two pins 30, which are disposed such that the elastic blades 27 can bear against them and deform, in order to store and return energy.

[0072] In this embodiment, the elastic blades 27 slide along the pins 30 and are not integral with them. There is thus a single deformation of the flexion of one blade. The two elastic blades do not deform simultaneously nor flex, which would make the stiffness of the blades too great for the practical operation of the movement.

[0073] Figure 10 The rack 21 is shown in the rest position and Figure 11 The latter is shown in the working position. In particular as Figure 11As shown, only one leaf works at a time to store and return energy. In fact, only the elastic leaf that interacts with the pin 30 is active. Figure 11 The other elastic leaf 27 shown on the left does not interact with the corresponding pin 30 and therefore does not participate in the accumulation and return of energy during this movement phase of the rack.

[0074] In Figures 12-15 the embodiment shown, the rack 21 is similar to Figures 7-9 the rack of the movement described with reference to Figures 7-9 . The end region of each elastic leaf 27 abuts one side of the arm 23 of the rack 21 and operates according to the same principle as described with reference to

[0075] The advantage of this implementation is that it is possible to increase the length of the elastic leaves 27 and therefore to decrease their stiffness accordingly, without having to increase the size of the watch in which this return member is housed. Figure 12 and 13 The width of the leaves and the position of contact between the elastic leaves and the arms of the rack are different in the embodiment shown. The choice of the specific shape of the leaves depends in particular on the available space in the movement.

[0076] In Figure 14 and 15 the embodiment shown, the elastic leaves 27 are formed with a fold in the form of a bellows. This embodiment is advantageous in that it makes it possible to produce leaves of very great length, but without requiring a very great available space in the watch casing. In this respect, it approaches the length of a spiral spring, but without the corresponding drawbacks.

[0077] Figures 12-15 The embodiment of the movement is also advantageous in that the point of contact between the effective spring leaves 27 and the arms 23 of the rack moves as the rack 21 moves. In particular, it can be seen by comparing the diagrams Figure 14 and 15 that, when the rack 21 is in the rest position or close to this position, the point of contact between one of the elastic leaves 27 and the arm 23 of the rack is very close to the axis of rotation 24 of the rack. The elastic leaf 27 therefore gives the rack 21 very little resistance, which allows the movement to be started simply, without risk of obstruction. When the rack 21 is pivoted, as Figure 15The shape of the elastic leaf is shown to represent that the point of contact between the elastic leaf 27 and the rack 21 moves in the direction of the sector tooth 22 opposite the axis of rotation 24 of the rack, as the rack moves. The force with which the elastic leaf opposes the rack increases, which increases the energy that the elastic leaf is able to store. In this way, the energy of the return mechanism 25 is not linear with respect to the movement of the rack 21 and is very weak when the rack 21 is close to its rest position. This not only allows the movement to be started simply, but also allows the energy to be accumulated and returned optimally.

[0078] In Figure 16 an embodiment, the rack 21 comprises internal teeth. The return mechanism 25 is identical to that of Figure 14 and 15 . It is advantageous in that a part of the rack is located on the other side of the balance shaft 11 with respect to the axis of rotation 24 of the rack. This allows space to be saved, which can be advantageous in small cases and / or in the case of a space-limited escapement.

[0079] In order to allow the movement to be started when it is lifted and to avoid the problem of stopping in the rest plane, it is advantageous not to exert a stress or a weak stress on the arm 23 of the rack 21 when it is in its rest position, at the dead point. This can be achieved in various ways. According to one way, the shape of the elastic leaf 27 itself is provided for this purpose, as described with reference to Figure 14 and 15 . According to another variant, a small gap can be provided between the elastic leaf 27 and the arm 23 of the rack when the rack is at the dead point, for example as shown in Figure 7 and 8 . This gap is visible in particular in Figure 7a which represents the contact area between the elastic leaf 27 and the arm 23 of the rack shown in Figure 7 in a very exaggerated way. In this way, no force is exerted by the return mechanism 25 on the rack when it is at the dead point. The force begins to be exerted on the rack when it begins to move.

[0080] According to another way, the timepiece movement comprises an adjustment element 29, for example an eccentric pin 30 as shown in Figure 5 and 6 , which makes it possible to position the elastic leaf 27 in a suitable position, which can be adjusted and modified if necessary.

[0081] According to a preferred embodiment, the stress can begin to be exerted on the arm 23 of the rack 21 when the balance 10 is pivoted by about 10°. This rotation allows one of the prongs of the lever to be placed on the impact plane of one of the pallets, which avoids blocking the movement and allows it to be started.

[0082] The rack 21 is shown to be in Figures 4-6The embodiments shown in the figures include two arms 23 and in other figures a single arm. The specific shape of the elastic blade is indicated for each embodiment. Combinations of different embodiments are also possible. For example, it is possible to use the elastic blade shown in Figure 4 and 6 together with the double arm rack shown in Figures 12-16 .

[0083] Likewise, adjusting elements such as eccentric or movable brackets can be added to the individual embodiments shown.

Claims

1. A timepiece movement escapement comprising a balance (10) pivoted on a rotation axis (11) of the balance, an escape wheel (14), a lever (12) and a return member (19) for the balance, characterized in that: - the balance (10) is integral with a balance pinion (20); - the return member (19) for the balance comprises: - a rack (21) provided with sector teeth (22) arranged to work with the balance pinion (20), the rack (21) comprising a rotation axis (24) allowing it to rotate between two extreme positions called working positions separated by a rest position; and - a return mechanism (25) comprising two springs (26) arranged to press the rack (21) towards its rest position, the springs (26) comprising elastic leaves (27) arranged to store energy and return it to the rack (21); and - only one of the elastic leaves (27) stores and returns energy at the same time.

2. Timepiece movement escapement according to claim 1, characterized in that, The springs (26) are arranged symmetrically with respect to a plane passing through the rotation axis (11) of the balance and the rotation axis (24) of the rack when the rack is in its rest position.

3. Return member for a timepiece movement comprising an escapement provided with a balance (10), an escape wheel (14) and a lever (12), characterized in that, The return member (19) comprises: - a rack (21) provided with sector teeth (22) arranged to work with a balance pinion (20), the rack (21) comprising a rotation axis (24) allowing it to rotate between two extreme positions called working positions separated by a rest position; and - two springs (26) arranged to press the rack (21) towards its rest position, the springs (26) comprising elastic leaves (27) arranged to store energy and return it to the rack (21); and - only one of the elastic leaves (27) stores and returns energy at the same time.

4. The return member of claim 3, wherein, The springs (26) are arranged symmetrically with respect to a plane passing through the rotation axis (11) of the balance and the rotation axis (24) of the rack when the rack is in its rest position.

5. The return member of claim 3, wherein, The rack (21) comprises internal teeth.

6. The return member of claim 3, wherein, The elastic leaves (27) are integral with the sector teeth.

7. The return member of claim 3, wherein, The elastic leaves (27) are arranged against the arms (23) of the rack (21).

8. A timepiece movement comprising an escapement provided with a balance (10), an escape wheel (14), a lever (12) and a return member (19) for the balance, characterized in that: - the balance (10) is integral with a balance pinion (20); - the return member (19) for the balance comprises: - a rack (21) provided with sector teeth (22) arranged to work with the balance pinion (20), the rack (21) comprising a rotation axis (24) allowing it to rotate between two extreme positions called working positions separated by a rest position; and - a return mechanism (25) comprising two springs (26) arranged to press the rack (21) towards its rest position, the springs (26) comprising elastic leaves (27) arranged to store energy and return it to the rack (21); and - only one of the elastic leaves (27) stores and returns energy at the same time. - a return mechanism (25) comprising two springs (26) arranged to press the rack (21) towards its rest position, the springs (26) comprising elastic blades (27) arranged to store energy and return it to the rack (21); and - only one of the elastic blades (27) stores and returns energy at the same time.

9. A timepiece movement according to claim 8, characterised in that, - the movement comprises at least two pins with which the elastic blades alternately interact during the movement of the rack around its axis of rotation (24).

10. A timepiece movement according to claim 9, characterized in that, - it comprises a regulating element (29) of the escapement.

11. A timepiece movement according to claim 10, characterized in that, - the at least two pins (30) are mobile on a bridge of the movement and interact with the springs (26) and are integral parts of the regulating element (29) of the escapement.

12. A timepiece comprising a movement according to any one of claims 8 to 11.

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