HK1194492B - Timepiece balance spring - Google Patents

Description

Watch hairspring

Technical Field

The invention relates to an anti-trip balance spring for a timepiece, comprising at least one band wound between a first end and a second end and comprising at least two pairs of coils (pair of coils), each formed by a first coil and a second coil immediately adjacent to each other, said first and second coils respectively comprising stop means and complementary stop means staggered from each other in a quincuncial pattern, the local coupling of the first and second coils being produced as a result of the stop means and the complementary stop means cooperating against each other in the event of an acceleration greater than a desired value upon contraction or extension of the balance spring, during which the stop means and the complementary stop means together define a respective maximum angular travel for each of the pairs of coils, so as to limit the number of active coils of the balance spring.

The invention also relates to a timepiece sprung balance comprising at least one balance spring of the above type and comprising a balance pivoting about an axis, the first end or the second end of the balance spring being fixed to the balance.

The invention also concerns a timepiece movement including at least one sprung balance of the type described above and a plate carrying a balance spring stud for pinning one of the ends of the balance spring.

The invention also concerns a timepiece including at least one movement of the above type and/or at least one sprung balance of the above type.

The present invention relates to the field of horological mechanisms, and more particularly to a regulating member for a watch.

Background

In mechanical watches, the regulating member, in particular the escapement, must satisfy a number of "safety" criteria. One such safety device is an anti-trip system designed to prevent the corners of the balance from extending beyond the normal angle of rotation.

The technical problem is to devise a safety mechanism, in particular an anti-trip system, which limits the pivoting angle of the balance during over-acceleration, in particular in the event of an impact, in particular for detent escapements. The anti-trip mechanism must be able to act in both directions of pivoting of the balance, i.e. both during extension and retraction of the balance spring.

One solution consists in modifying the geometry of the balance spring by making the lugs of successive coils cooperate against each other, in order to render some of the coils inoperative and thus to modify the stiffness of the balance spring and its reaction to the impact. A mechanism of this type, able to limit the angular travel of the balance in both pivoting directions, is known from EP patent No2434353a1 in the name of monttresbreguettsa, which discloses an anti-trip balance spring in which notches belonging to successive coils cooperate during the retraction and extension of the spring. This solution is effective, but the torque recovery is sudden.

The aim of the invention is to improve the safety by limiting the angular travel of the balance in both directions of rotation and gradually restoring the moment, while having only a very slight disturbance to the inertia of the balance.

Disclosure of Invention

The invention therefore concerns an anti-trip balance spring for a timepiece comprising at least one band wound between a first end and a second end and comprising at least two pairs of coils, each pair of coils being formed by a first coil and a second coil immediately adjacent to each other, said first and second coils respectively comprising stop means and complementary stop means staggered from each other in a quincunx shape, said stop means and said complementary stop means together defining, during partial coupling, a respective maximum angular travel for each said pair of coils in order to limit the number of active coils of said balance spring, in the case of a contraction or an extension of said balance spring at an acceleration greater than a desired value, the respective stop means and complementary stop means are arranged to define different maximum angular travel values so as to progressively limit the pivoting amplitude between said first end and said second end of the balance spring during angular or radial accelerations of the balance spring greater than said desired value, so as to cause said stop means and said complementary stop means of one of said pairs of coils to cooperate against each other before the stop means and complementary stop position of the other pair of coils, and thus to progressively change the resulting/obtained stiffness (restingness) of the balance spring by sequentially deactivating or reactivating certain of the coils.

The invention also relates to a sprung balance for a timepiece, the balance comprising at least one balance spring of the type described above and including a balance that pivots about an axis, the first end or the second end of the balance spring being fixed to the balance, characterized in that the amplitude of pivoting of the balance is less than 360 °.

The invention also concerns a timepiece movement including at least one sprung balance of the type described above and a plate carrying a balance spring stud for pinning one of the ends of the balance spring.

The invention also concerns a timepiece including at least one movement of the above type and/or at least one sprung balance of the above type.

Drawings

Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings, in which:

fig. 1 shows a schematic top view of an anti-trip balance spring according to the invention, designed to oscillate about a pivot axis and pinned via its outer end to a balance spring stud and via its inner end to a collet fixed to the balance; the balance spring comprises stop elements staggered in a quincunx on adjacent coils, which interfere with each other in the event of an impact or an excessive amplitude, the two groups of adjacent coils being arranged in such a way as to have different limiting angles between a first, more internal group, which has the largest limiting angle, and a second, more external group, which has the smaller limiting angle.

Figure 2 shows a diagram of the moment of the balance spring as a function of the angle of rotation.

Fig. 3 shows a block diagram of a timepiece, in particular a watch, including a movement including a sprung balance including a balance spring according to the invention.

Detailed Description

The present invention relates to the field of horological mechanisms, and more particularly to a timepiece regulating member.

The object of the invention is to improve the safety of any oscillating mechanism or energy storage mechanism, including a balance spring, in particular a sprung balance.

The basic principle consists in changing the resulting stiffness of the balance spring when an accident different from normal operation occurs in the use condition, in particular when a severe acceleration or shock occurs.

Varying the stiffness of the balance spring can have other applications, and the detailed description relating to a preferred application of the invention to an anti-trip system for escapements is in no way limiting.

The aim of the invention applied to a sprung balance is to limit the angle of rotation of the balance in a mechanical watch to a given angle, in particular for amplitudes greater than 360 °. The limitation of the angular travel is achieved in both directions of rotation without changing the inertia of the balance. Since the system does not cause any impact during the normal movement of the balance, the balance is said to be "free" during its normal angular travel (with respect to the anti-trip system).

The working principle of the proposed system depends on a temporary change of the balance spring geometry. During the extension or retraction of the balance spring due to the rotation of the balance, relative angular and radial movements occur between the coils. The limit stop element formed by the two stop elements and the stroke locking arm are placed on two consecutive coils of the balance spring. For a maximum given angle of rotation, the stop element is placed on the ring so as to limit the relative angular travel between the two rings. When the stop element locks the travel of the locking arm according to the direction of rotation, the balance spring loses its active coil, thus changing its stiffness. The stop system is therefore dependent on the relative angular movement between the two rings.

The distance between the stop element and the latching arm may be asymmetrical.

The system according to the invention therefore limits the number of active coils according to the rotation angle and to the movement of the coils of the balance spring. Thus, since the stop element system is attached to at least one pair of coils and at most to all the coils, the stiffness of the balance spring can be temporarily changed according to the angle of rotation. The stiffness according to the rotation amplitude can therefore be determined by the distribution and number of the system of stop elements distributed on the balance spring. The invention limits the angle of rotation gradually as much as possible by gradually changing the resulting stiffness of the balance spring.

According to the invention, pairs of turns are provided in the manner described above. The balance spring comprises stop elements distributed on adjacent coils in a quincunx staggered arrangement, which interfere with each other in the event of an impact or an excessive amplitude, the stop elements interfering with each other, the two pairs of adjacent coils being arranged in such a way as to have different limiting angles between a first, more internal group, which is larger, and a second, more external group, which is smaller.

In an advantageous but non-limiting embodiment, it is ensured that the center of gravity of the balance spring is balanced. The geometry, distribution, position and number of the stop elements require a specific design and the invention is only briefly described in principle.

The manufacture of this type of balance spring relies on micro-fabrication methods that allow a large degree of freedom in the design of the flat surface. This type of balance spring can be manufactured using silicon technology. The invention is not limited to this technique and can use the "LIGA" method and other microfabrication methods currently used for timepiece components and particularly escapement mechanisms.

The invention therefore concerns, in particular, a timepiece anti-trip balance spring 1, this balance spring 1 comprising at least one band 2 wound between a first end 3 and a second end 4. The balance spring 1 comprises at least two coil pairs 50. Each turn 50 is formed by a first turn 51 and a second turn 52, the first turn 51 and the second turn 52 being immediately adjacent to each other and respectively comprising a stop means 11 and a complementary stop means 12 offset from each other in a quincunx.

It is clear that, for each pair of rings 50, the stop means 11 and the complementary stop means 12 together define a respective specific maximum angular travel CA.

The stop means 11 and the complementary stop means 12 together define the maximum angular travel CA of the pair of turns 50 to which they belong during the partial coupling of the first and second turns 51, 52. During accelerations greater than desired values when balance spring 1 is contracted or extended or during excessive amplitudes when balance spring 1 is rotated, said partial coupling is produced due to stop means 11 and complementary stop means 12 cooperating against each other so as to limit the number of active coils of balance spring 1.

According to the invention, in at least two of these pairs of coils 50, the respective stop means 11 and complementary stop means 12 are arranged to define different maximum angular travel values CA so as to progressively limit the pivoting amplitude between the first end 3 and the second end 4 of balance spring 1 during angular or radial accelerations of balance spring 1 greater than said desired value, so that said stop means 11 and complementary stop means 12 of one pair of coils 50 cooperate against each other before the stop means and complementary stop means of the other pair cooperate against each other, and thus progressively vary the resulting stiffness of balance spring 1 by sequentially deactivating or reactivating certain coils of coils 5.

The graph of fig. 2 shows the variation of the moment with the rotation angle. At each point corresponding to the detent and coupling configuration, a slope discontinuity can be seen, as described below.

In the preferred but non-limiting variant shown in fig. 1 and 3, in each pair of turns 50, the stop means 11 located on one of the two turns of the pair 50 comprise two limit stop elements 13, 14, the trajectory of these two stop elements 13, 14 interfering with at least one complementary limit stop element 15, this complementary limit stop element 15 being located on the other of the two turns of the same pair 50 and being contained in the complementary stop means 12. The interference at the end stop position defines a spacing that limits the angular travel CA of the first ring 51 relative to the second ring 52. This limitation allows temporarily limiting the number of active coils of balance spring 1 when said at least one complementary limit stop element 15 abuts against one of said two limit stop elements 13, 14.

In the particular variant shown in fig. 1, in addition to the limit stop elements provided on the two opposite turns of the same pair 50 of turns, one turn, for example the first turn 51 or the second turn 52, comprises at least one radial stop element 6, which radial stop element 6 limits the radial movement of the first turn 51 with respect to the second turn 52. This particular coupling is based on relative radial movement between the rings. However, this is limited to the retraction of the balance spring and therefore to a single direction of rotation of the balance.

In this same particular variant, advantageously, at least one radial stop element 6 comprises a friction surface 61, this friction surface 61 being arranged to cooperate with a complementary friction surface 62 contained in the second ring 52 or in the first ring 51.

In another variant of the extreme stop element and radial stop element 6 combined with the collar pair 50, the stop means 11 or the complementary stop means 12 comprise the at least one radial stop element 6.

The invention also concerns a timepiece sprung balance 10, this mechanism 10 comprising at least one balance spring 1 of this type and comprising a balance 7 pivoting about an axis D, the first end 3 or the second end 4 of the balance spring 1 being fixed to this balance 7. Preferably, the amplitude of pivoting of balance 7 is less than 360 °.

The invention also concerns a timepiece movement 20, this movement 20 including a sprung balance 10 of the type described above and a plate 8 carrying a balance spring stud 9, this balance spring stud 9 being intended to pin-connect one of the ends 3, 4 of the balance spring 1.

The invention also concerns a timepiece 30, this timepiece 30 including at least one movement 20 of the type described above and/or at least one sprung balance 10 described above.

This system has the advantage of limiting the travel of the balance in both directions of rotation. This limitation is achieved by varying the stiffness of the balance spring. The stiffness change can be adjusted by selecting the number and distribution of stop surfaces included in the balance spring.

The inertia of the sprung balance system is changed only by changing the inertia of the balance spring. The trip prevention system does not interfere with the normal oscillation of the sprung balance system; it affects its operation only when the amplitude of rotation is exceeded.

Claims (8)

1. Anti-trip balance spring (1) for a timepiece, the balance spring (1) comprising at least one band (2) wound between a first end (3) and a second end (4) and comprising at least two turns (50), each turn being formed by a first turn (51) and a second turn (52) immediately adjacent to each other, the first turn (51) and the second turn (52) comprising, respectively, stop means (11) and complementary stop means (12) staggered from each other in a quincunx shape, a partial coupling of the first turn (51) and the second turn (52) being produced due to the stop means (11) and the complementary stop means (12) cooperating against each other in the event of an acceleration greater than a desired value upon contraction or expansion of the balance spring (1), during which partial coupling the stop means (11) and the complementary stop means (12) together define a respective maximum angular travel (CA) for each of the turns (50), in order to limit the number of active turns of said balance spring (1), characterized in that, in said at least two pairs of turns (50), the respective stop means (11) and complementary stop means (12) are arranged to define different maximum angular travel values (CA), so as to progressively limit the amplitude of pivoting between said first end (3) and said second end (4) of said balance spring (1) during angular or radial accelerations of said balance spring (1) greater than said desired value, such that the stop means (11) and the complementary stop means (12) of one of the turns (50) cooperate against each other before the stop means and the complementary stop positions of the other turn cooperate against each other, and therefore gradually varying the resulting stiffness of the balance spring (1) by sequentially deactivating or reactivating certain of its coils (5).

2. Balance spring (1) according to claim 1, characterized in that in each of said pairs of coils (50), said stop means (11) comprise two limit stop elements (13, 14), the trajectory of which (13, 14) interferes with at least one complementary limit stop element (15) contained in said complementary stop means (12) to define a pitch limiting the maximum angular travel (CA) of said first coil (51) with respect to said second coil (52) so as to limit the number of active coils of said balance spring (1) when said at least one complementary limit stop element (15) abuts against one of said two limit stop elements (13, 14).

3. Balance spring (1) according to claim 2, characterized in that said first coil (51) or said second coil (52) comprises at least one radial stop element (6), this radial stop element (6) limiting the radial movement of said first coil (51) with respect to said second coil (52).

4. Balance spring (1) according to claim 3, characterized in that said at least one radial stop element (6) comprises a friction surface (61), this friction surface (61) being arranged to cooperate with a complementary friction surface (62) comprised in said second ring (52) or said first ring (51).

5. Balance spring (1) according to claim 3, characterized in that said stop means (11) or said complementary stop means (12) comprise said at least one radial stop element (6).

6. A timepiece sprung balance (10) comprising at least one balance (1) according to claim 1 and comprising a balance (7) pivoting about an axis (D), said first end (3) or said second end (4) of said balance (1) being pinned to said balance (7), characterized in that the amplitude of pivoting of said balance (7) is less than 360 °.

7. A timepiece movement (20), the movement (20) comprising a timepiece sprung balance (10) according to claim 6 and a plate (8) carrying a balance spring stud (9), the balance spring stud (9) being intended to pin-joint one of the ends (3, 4) of the balance spring (1).

8. Timepiece (30), the timepiece (30) comprising at least one timepiece movement (20) according to claim 7 and/or at least one sprung balance (10) according to claim 6.