Horological hairspring

Abstract

The present invention relates to a spiral spring (1) intended to be associated with a balance wheel in a regulating organ of a watch movement and comprising a series of turns formed by a blade wound upon itself between a first inner turn (2) and a last outer turn (6), said blade having a constant or variable cross-section. Said blade comprises, on at least one of the first inner turn (2) and the last outer turn (6), at least one zone (e1, e2) of local softening centered approximately ¾ of a turn of said turn (2, 6) from its free end (2a, 6a), said zone (e1, e2) of local softening having a cross-section smaller than the cross-section of the blade in the vicinity of said zone (e1, e2) of local softening. The present invention also relates to a regulating organ comprising a balance wheel and such a spiral spring (1), as well as a timepiece comprising such a spiral spring (1) or such a regulating organ.

Description

Domaine technique

[0001] The present invention relates to a spiral spring intended to be associated with a balance wheel in a regulating organ of a watch movement and comprising a series of turns formed by a blade wound on itself between a first inner turn, intended to be attached to a ferrule attached to the axis of the balance wheel, and a last outer turn, intended to be attached to a stud attached to the balance cock, said blade having a constant or variable section.

[0002] The present invention also relates to a regulating organ comprising a balance wheel and such a spiral spring, as well as a timepiece comprising such a spiral spring or such a regulating organ. Etat de la technique

[0003] The balance spring used in watchmaking, in conjunction with a balance wheel to form the regulating organ of a watch, is an essential component, as the balance spring is primarily responsible for the accuracy of a mechanical watch movement. Consequently, balance springs have been the subject of extensive research and development. It has long been established that the flat balance spring, whether in the form of an Archimedean spiral or an involute of a circle, with a constant pitch, has the disadvantage of developing eccentrically during its expansion and contraction. This eccentricity is caused by its attachment to the ferrule and stud. This defect results in a deviation from the standard timekeeping.

[0004] Several known solutions have been proposed to minimize rate disturbances caused by the non-concentric development of the balance spring during the oscillation of the regulating organ. These include the Breguet or Philipps terminal curve balance spring, the Grossmann internal curve balance spring, the angle-curved balance spring, and other inventions offering various coil arrangements. However, the proposed solutions may require complex implementation or fail to sufficiently reduce the eccentricity of the resulting balance spring development.

[0005] It is therefore necessary to propose a new spiral spring allowing for a development with reduced eccentricity in order to minimize rate disturbances. Disclosure of the invention

[0006] For this purpose, the invention relates to a spiral spring intended to be associated with a balance wheel in a regulating organ of a watch movement and comprising a series of turns formed by a blade wound on itself between a first inner turn and a last outer turn, said blade having a constant or variable section.

[0007] According to the invention, said blade comprises, on at least one of the first inner turn and the last outer turn, at least one local softening zone centered at approximately ¾ of a turn of said turn from its free end, said local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said local softening zone.

[0008] According to a preferred embodiment, said at least one local softening zone is a first local softening zone centered approximately ¾ of a turn from the last outermost turn from its free end, said first local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said first local softening zone.

[0009] The specific positioning of the first softening zone proposed by the invention advantageously reduces the trajectory of the end of the spiral spring attached to the pin when the spiral spring is contracting or expanding during the oscillations of the regulating organ. Thus, the spiral spring of the invention closely follows its pinning point. Consequently, the pinning of the end of the spiral spring will result in a very small eccentricity.

[0010] Advantageously, the blade of the spiral spring of the invention further comprises at least a second local softening zone centered at approximately 3 / 4 of a turn from the first inner coil from its free end, said second local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said second local softening zone.

[0011] The specific positioning of the second softening zone proposed by the invention advantageously reduces the trajectory of the end of the spiral spring attached to the ferrule when the spiral spring is contracting or expanding during the oscillations of the regulating organ. Thus, the spiral spring of the invention closely follows its ferrule attachment point. Consequently, the ferrule attachment of the end of the spiral spring will result in a very small eccentricity.

[0012] Advantageously, the blade of the spiral spring of the invention further comprises at least a third local softening zone centered at approximately 5 / 4 of a turn from the last outer coil from its free end, said third local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said third local softening zone.

[0013] Advantageously, the blade of the spiral spring of the invention further comprises at least a fourth local softening zone centered at approximately 5 / 4 of a turn from the first inner coil from its free end, said fourth local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said fourth local softening zone.

[0014] The specific positioning of these third and fourth flexing zones proposed by the invention advantageously allows for a further reduction in the trajectories of the ends of the spiral spring attached to the ferrule and the stud when the spiral spring is contracting or expanding during the oscillations of the regulating organ. Thus, the concentricity of the spiral spring's development is further improved.

[0015] Advantageously, the x-th local easing zone, where x is an integer preferably between 1 and 4, can extend over a spiral segment with an angle Δαx between about 8° and 100°, and preferably less than about 90°, and more preferably between about 30° and 50°.

[0016] Preferably, said x-th local softening zone has a thickness hx between 0.5Hx and 0.9Hx, where Hx is the thickness of the blade in the vicinity of said x-th local softening zone.

[0017] Advantageously, said x-th local softening zone can vary between a zone extending over a spiral segment with an angle Δαx of about 8°, and a thickness hx of about Hx / 2, and a zone extending over a spiral segment with an angle Δαx of about 90°, and a thickness hx of about 0.9Hx.

[0018] The present invention also relates to a regulating organ comprising a balance wheel and a spiral spring as defined above.

[0019] The present invention also relates to a timepiece comprising a regulating organ or a spiral spring as defined above. Brève description des dessins

[0020] Other features and advantages of the present invention will become apparent from the following detailed description of various embodiments of the invention, given by way of non-limiting examples, and made with reference to the accompanying drawings in which: there figure 1 is a schematic plan view of a spiral spring according to a preferred embodiment of the invention, in its rest position; the figure 2 is a detailed view of the last coils of an embodiment of a spiral spring according to the invention in its rest position, said spiral spring exhibiting the first zone of local softening; the figure 3 is a graph that represents the thickness h of the blade as a function of the winding angle α of the blade for different embodiments of the first local softening zone of the spiral spring of the figure 2 ; there figure 4 is a detailed view of the last coils of another variant of the spiral spring of the figure 2 , in a resting position; the figure 5 is a detailed view of the first coils of an embodiment of a spiral spring according to the invention in its rest position, said spiral spring having the second zone of local softening; the figure 6 is a graph that represents the thickness h of the blade as a function of the winding angle α of the blade for different embodiments of the second local softening zone of the spiral spring of the figure 5 ; there figure 7 is a detailed view of the first coils of another variant of the spiral spring of the figure 5 , in a resting position; the figure 8 is a detailed view of the last coils of another embodiment of a spiral spring according to the invention in its rest position, said spiral spring having the first and third zones of local softening; the figure 9 is a graph that represents the thickness h of the blade as a function of the winding angle α of the blade for different embodiments of the first and third local softening zones of the spiral spring of the figure 8 ; there figure 10 is a detailed view of the first coils of another embodiment of a spiral spring according to the invention in its rest position, said spiral spring having the second and fourth zones of local softening; the figure 11 is a graph that represents the thickness h of the blade as a function of the winding angle α of the blade for different embodiments of the second and fourth local softening zones of the spiral spring of the figure 10 ; there figure 12 is a plan view of a spiral spring according to a preferred embodiment of the invention, in its rest position; the figure 13 represents the trajectory followed by the pinning end of a spiral spring according to the invention and of a spiral spring without a local softening zone; the figure 14 represents an enlargement of the figure 13 at the ends of the pitons; the figure 15 represents the trajectory followed by the ferrule end of a spiral spring according to the invention and of a spiral spring without a local softening zone; and the figure 16 represents an enlargement of the figure 15 at the ferrule ends. Modes de réalisation de l'invention

[0021] With reference to the figure 1 The present invention relates to a spiral spring 1 intended to be associated with a balance wheel in a regulating organ of a watch movement. The spiral spring 1 comprises a series of coils formed by a single blade wound on itself between a first inner coil 2, the free end 2a of which is intended to be fixed to a ferrule 4, which is itself fixed to the balance staff (not shown), and a final outer coil 6, the free end 6a of which is intended to be fixed to a stud 8, itself fixed to the balance cock or bridge (not shown).

[0022] With the exception of the first and last coils, the spiral spring 1 is preferably in the shape of an involute of a circle, undeformed when at rest, so that its pitch is represented on the figure 1 is preferably constant or substantially constant.

[0023] The spiral spring 1 is preferably flat, as shown in the figure 1 It might not be flat, as the outer coil could have a raised terminal curve of the Breguet or Phillips type. The balance spring 1 can be made of various known materials, such as silicon.

[0024] The blade has a cross-section, preferably rectangular, whose thickness corresponds to the dimension represented by the reference h on the figure 1 Except for the local softening zones described below, the cross-section of the blade can be constant or variable. More specifically, a constant cross-section is obtained by maintaining a constant thickness h along the entire length of the blade. A variable cross-section is obtained by varying the thickness h according to the winding angle α of the spiral spring blade 1.

[0025] According to the present invention, the blade of the spiral spring 1 comprises, on at least one of the first inner coil 2 and the last outer coil 6, at least one local softening zone centered at approximately ¾ of a turn of said coil 2, 6 from its free end 6a, 2a, said local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said local softening zone.

[0026] In a preferred embodiment, said at least one local easing zone is first a first local easing zone e1 centered about ¾ of a turn from the last outer turn 6 from its free end 6a which is intended to be integral with the pin 8, said first local easing zone e1 having a cross-section smaller than the cross-section of the blade in the vicinity of said first local easing zone e1.

[0027] It is specified that, throughout this description, the position indicated for the local softening zones is the position indicated when the spiral spring is at rest, the blade being undeformed, unless otherwise indicated (particularly in cases where bends are provided as will be described below).

[0028] Preferably, the variation in the section of the blade is achieved by varying the thickness h of said blade.

[0029] More specifically, and with reference to figures 2 et 3 , the first local softening zone e1 has a thickness h1 less than the thickness H1 of the blade in the vicinity of said first local softening zone e1.

[0030] Whatever its proportions, the first local softening zone e1 is provided on the last outer coil 6 centered at approximately ¾ of a turn, i.e. at an angle α1 = 270°, from the free end 6a of the spiral spring 1.

[0031] This first local softening zone e1 advantageously allows for a minimum displacement of the spiral spring 1 at the point of attachment to the pin 8 during the expansion and contraction of said spiral spring 1.

[0032] Advantageously, the first local softening zone e1 extends over a spiral segment with an angle Δα1 between approximately 8° and 100°, and preferably less than approximately 90°, and more preferably between approximately 30° and 50°.

[0033] Advantageously, said first local softening zone e1 has a thickness h1 between 0.5H1 and 0.9H1, where H1 is the thickness of the blade in the vicinity of said first local softening zone e1.

[0034] Preferably, said first local softening zone e1 can vary between a zone extending over a spiral segment with an angle Δα1 of about 8°, and a thickness h1 of about 0.5H1, and a zone extending over a spiral segment with an angle Δα1 of about 90°, and a thickness h1 of about 0.9H1.

[0035] When the blade does not include a third local softening zone, the first local softening zone e1 may preferably extend over a spiral segment with an angle Δα1 of approximately 44°, said first zone e1 having a thickness h1 of approximately ¾ H1, as illustrated in bold on the figure 3 and as depicted on the figure 2 .

[0036] On the figure 3 other possible proportions of the first local softening zone e1 appear in fine lines, which also allow minimizing the displacement of the fixing point (end 6a) of the spiral spring 1 to the pin 8. Thus, the first local softening zone e1 can be either narrower (Δα1 = 9°, h1 = 0.5H1) or more flared (Δα1 = 90°, h1 = 0.85H1).

[0037] According to a first embodiment, the spiral spring 1 has a single local softening zone which corresponds to the first local softening zone e1 on its last coil 6 as described above.

[0038] According to a second embodiment, the blade of the spiral spring 1 may include, in addition to the first local softening zone e1 on the last coil 6 as described above, at least one other local softening zone, namely at least a second local softening zone e2 centered about ¾ of a turn from the first inner coil 2 from its free end 2a which is intended to be integral with the ferrule 4, said second local softening zone e2 having a cross-section smaller than the cross-section of the blade in the vicinity of said second local softening zone e2.

[0039] More specifically, and with reference to figures 5 et 6 , the second local softening zone e2 has a thickness h2 less than the thickness H2 of the blade in the vicinity of said second local softening zone e2.

[0040] Whatever its proportions, the second local softening zone e2 is provided on the first inner coil 2 centered at approximately ¾ of a turn, i.e. at an angle α2 = 270°, from the free end 2a of the spiral spring 1.

[0041] This second zone e2 of local softening advantageously allows obtaining a minimum displacement of the spiral spring 1 at the point of attachment to the ferrule 4 during the expansion and contraction of said spiral spring 1.

[0042] Advantageously, the second local easing zone e2 extends over a spiral segment with an angle Δα2 between approximately 8° and 100°, and preferably less than approximately 90°, and more preferably between approximately 30° and 50°.

[0043] Advantageously, said second local softening zone e2 has a thickness h2 between 0.5H2 and 0.9H2, where H2 is the thickness of the blade in the vicinity of said second local softening zone e2.

[0044] Preferably, said second local softening zone e2 can vary between a zone extending over a spiral segment with an angle Δα2 of about 8°, and a thickness h2 of about 0.5H2, and a zone extending over a spiral segment with an angle Δα2 of about 90°, and a thickness h2 of about 0.9H2.

[0045] When the blade does not include a fourth local softening zone, the second local softening zone e2 may preferably extend over a spiral segment with an angle Δα2 of approximately 40°, said second zone e2 having a thickness h2 of approximately ¾ H2, as illustrated in bold on the figure 6 and as depicted on the figure 5 .

[0046] On the figure 6 other possible forms of the second local softening zone e2 appear in fine lines, which also allow minimizing the displacement of the end 2a of the spiral spring 1 fixed to the ferrule 4. Thus, the second local softening zone e2 can be either narrower (Δα2 = 8°, h2 = 0.5H2) or more flared (Δα2 = 90°, h2 = 0.9H2).

[0047] According to other embodiments, the blade of the spiral spring 1 may include, in addition to the first local softening zone e1 or in addition to the first and second local softening zones e1, e2, at least one other local softening zone, namely at least a third local softening zone e3 centered about 5 / 4 of a turn from the last outer coil 6 from its free end 6a which is intended to be fixed to the pin 8, said third local softening zone e3 having a cross-section smaller than the cross-section of the blade in the vicinity of said third local softening zone e3.

[0048] More specifically, it is represented in reference to figures 8 et 9 an embodiment in which the spiral spring 1 includes on its last coils at least the first zone e1 of local softening and the third zone e3 of local softening.

[0049] The first local softening zone e1 is broadly similar to that of the first embodiment described above and has a thickness h1 less than the thickness H1 of the blade in the vicinity of said first local softening zone e1. The third local softening zone e3 has a thickness h3 less than the thickness H3 of the blade in the vicinity of said third local softening zone e3. H3 may be equal to or different from H1 depending on whether the cross-section of the spiral spring blade 1 is constant or not.

[0050] Preferably, when the blade includes the first and third local softening zones e1, e3, said first local softening zone e1 has a thickness h1 less than the thickness h3 of the third local softening zone e3, as shown in the figure 9 .

[0051] Whatever their proportions, the first local softening zone e1 is provided on the last outer coil 6 centered at approximately ¾ of a turn, i.e. at an angle α1 = 270°, from the free end 6a of the spiral spring 1, and the third local softening zone e3 is provided on the last outer coil 6 centered half a turn further, i.e. at approximately 5 / 4 of a turn, i.e. at an angle α3 = 450°, from the free end 6a of the spiral spring 1.

[0052] The presence of the third local softening zone e3 in addition to the first local softening zone e1 advantageously allows for an even smaller displacement of the spiral spring 1 at the point of attachment to the pin 8 during the expansion and contraction of said spiral spring 1.

[0053] Advantageously, the first zone e1, respectively the third zone e3, of local easing extends over a spiral segment of angle Δα1, respectively Δα3, between about 8° and 100°, and preferably less than about 90°, and more preferably between about 30° and 50°.

[0054] Advantageously, said first local softening zone e1 has a thickness h1 between 0.5H1 and 0.9H1, where H1 is the thickness of the blade in the vicinity of said first local softening zone e1 and said third local softening zone e3 has a thickness h3 between 0.5H3 and 0.9H3, where H3 is the thickness of the blade in the vicinity of said third local softening zone e3.

[0055] In this embodiment comprising at least two local softening zones e1, e3 on the last coils, the first local softening zone e1 preferably has a thickness h1 that is less than the thickness h1 of the local softening zone e1 used alone on the last coils according to the first embodiment. Consequently, the first local softening zone e1 is more flexible (the spiral spring 1 is thinner at zone e1) when the blade includes both the first and third local softening zones e1, e3 than when the blade includes only the first local softening zone e1 on the last coils.

[0056] Preferably, said first local softening zone e1 may vary between a zone extending over a spiral segment with an angle Δα1 of approximately 8°, and a thickness h1 of approximately 0.5H1, and a zone extending over a spiral segment with an angle Δα1 of approximately 90°, and a thickness h1 of approximately 0.9H1 and said third local softening zone e3 may vary between a zone extending over a spiral segment with an angle Δα3 of approximately 8°, and a thickness h3 of approximately 0.5H3, and a zone extending over a spiral segment with an angle Δα3 of approximately 90°, and a thickness h3 of approximately 0.9H3.

[0057] Preferably, the first local easing zone e1 extends over a spiral segment with an angle Δα1 of approximately 47°, said first zone e1 having a thickness h1 of approximately 2 / 3 H1, and the third local easing zone e3 extends over a spiral segment with an angle Δα3 of approximately 48°, said third zone e3 having a thickness h3 of approximately 3 / 4 H3, as illustrated in bold on the figure 9 and as depicted on the figure 8 .

[0058] On the figure 9 other possible shapes of first zone e1 and third zone e3 of local softening appear in fine lines which also allow to further minimize the displacement of the end 6a of the spiral spring 1 fixed to the pin 8. Thus, the first zone e1 and third zone e3 of local softening can indifferently be narrower (Δα1 = 17°, h1 = 0.5H1 ; Δα3 = 10°, h3 = 0.5H3 ;) or more flared (Δα1 = 90°, h1 = ¾ H1 ; Δα3 = 91°, h3 = 0.8H3).

[0059] According to other embodiments, the blade of the spiral spring 1 may include, in addition to the first and second local softening zones e1, e2 or in addition to the first, second and third local softening zones e1, e2, e3, at least one other local softening zone, namely at least a fourth local softening zone e4 centered about 5 / 4 of a turn from the first inner coil 2 from its free end 2a which is intended to be integral with the ferrule 4, said fourth local softening zone e4 having a cross-section smaller than the cross-section of the blade in the vicinity of said fourth local softening zone e4.

[0060] More specifically, it is represented in reference to figures 10 et 11 an embodiment in which the spiral spring 1 includes on its first coils at least the second zone e2 of local softening and the fourth zone e4 of local softening.

[0061] The second local softening zone e2 is broadly similar to that of the second embodiment described above and has a thickness h2 less than the thickness H2 of the blade in the vicinity of said second local softening zone e2. The fourth local softening zone e4 has a thickness h4 less than the thickness H4 of the blade in the vicinity of said fourth local softening zone e4. H4 may be equal to or different from H2 depending on whether the cross-section of the spiral spring blade 1 is constant or not.

[0062] Preferably, when the blade includes the second and fourth local softening zones e2, e4, said second local softening zone e2 has a thickness h2 less than the thickness h4 of the fourth local softening zone e4, as shown in the figure 11 .

[0063] Whatever their proportions, the second local softening zone e2 is provided on the first inner coil 2 centered at approximately ¾ of a turn, i.e. at an angle α2 = 270°, from the free end 2a of the spiral spring 1, and the fourth local softening zone e4 is provided on the first inner coil 2 centered half a turn further, i.e. at approximately 5 / 4 of a turn, i.e. at an angle α4 = 450°, from the free end 2a of the spiral spring 1.

[0064] The presence of the fourth local softening zone e4 in addition to the second local softening zone e2 advantageously allows for an even smaller displacement of the spiral spring 1 at the point of attachment to the ferrule 4 during the expansion and contraction of said spiral spring 1.

[0065] Advantageously, the second zone e2, respectively the fourth zone e4, of local easing extends over a spiral segment of angle Δα2, respectively Δα4, between about 8° and 100°, and preferably less than about 90°, and more preferably between about 30° and 50°.

[0066] Advantageously, said second local softening zone e2 has a thickness h2 between 0.5H2 and 0.9H2, where H2 is the thickness of the blade in the vicinity of said second local softening zone e2 and said fourth local softening zone e4 has a thickness h4 between 0.5H4 and 0.9H4, where H4 is the thickness of the blade in the vicinity of said fourth local softening zone e4.

[0067] In this embodiment comprising at least two local softening zones e2, e4 on the first coils, the second local softening zone e2 preferably has a thickness h2 that is less than the thickness h2 of the local softening zone e2 used alone on the first coils according to the second embodiment. Consequently, the second local softening zone e2 is more flexible (the spiral spring 1 is thinner at zone e2) when the blade includes both the second and fourth local softening zones e2, e4 than when the blade includes only the second local softening zone e2 on the first coils.

[0068] Preferably, said second local softening zone e2 may vary between a zone extending over a spiral segment with an angle Δα2 of approximately 8°, and a thickness h2 of approximately 0.5H2, and a zone extending over a spiral segment with an angle Δα2 of approximately 90°, and a thickness h2 of approximately 0.9H2 and said fourth local softening zone e4 may vary between a zone extending over a spiral segment with an angle Δα4 of approximately 8°, and a thickness h4 of approximately 0.5H4, and a zone extending over a spiral segment with an angle Δα4 of approximately 90°, and a thickness h4 of approximately 0.9H4.

[0069] Preferably, the second local easing zone e2 extends over a spiral segment with an angle Δα2 of approximately 40°, said second zone e2 having a thickness h2 of approximately 2 / 3 H2, and the fourth local easing zone e4 extends over a spiral segment with an angle Δα4 of approximately 33°, said fourth zone e4 having a thickness h4 of approximately 3 / 4 H4, as illustrated in bold on the figure 11 and as depicted on the figure 10 .

[0070] On the figure 11 other possible proportions of the second zone e2 and fourth zone e4 of local softening appear in fine lines, which also allow for further minimization of the displacement of the end 2a of the spiral spring 1 fixed to the ferrule 4. Thus, the second zone e2 and fourth zone e4 of local softening can indifferently be narrower (Δα2 = 14°, h2 = 0.5H2; Δα4 = 18°, h4 = 2 / 3 H4;) or more flared (Δα2 = 90°, h2 = 0.8 H2; Δα4 = 60°, h4 = 0.8 H4).

[0071] The first and third local relaxation zones e1, e3 as described above with reference to figures 8 et 9 can be provided on the last turns of a spiral spring whether the blade has a variable or constant cross-section.

[0072] Preferably, when the blade section is variable, said blade includes at least the first two and second local softening zones e1, e2 as described above in the second embodiment.

[0073] In a particularly preferred manner, said blade comprises at least the first four, second, third and fourth zones e1, e2, e3, e4 of local softening, the pairs e1, e3 being as described above with reference to figures 8 et 9 , and the pairs e2, e4 being as described above with reference to figures 10 et 11 .

[0074] When the cross-section of the blade is constant, said blade comprises at least, and preferably only, the first two and third local softening zones e1, e3 as described above with reference to figures 8 et 9 .

[0075] In another embodiment not shown, the spiral spring blade comprises, as local softening zones, the first local softening zone e1 and optionally the third local softening zone e3 described above, but does not include any local softening zones on its first few turns such as the second and fourth local softening zones e2, e4 described above. In this case, the first inner turn 2 may include a feature selected from a zone of increased stiffness whose cross-section is larger than the cross-section of the blade in the vicinity of said zone of increased stiffness, such as an angle bracket or an internal Grossmann curve.

[0076] In another embodiment not shown, the blade of the spiral spring includes, as a local softening zone, a local softening zone centered about 3 / 4 of a turn from the first inner coil 2 from its free end 2a, and optionally another local softening zone centered about 5 / 4 of a turn from the first inner coil 2 from its free end 2a, each local softening zone having a cross-section smaller than the cross-section of the blade in the vicinity of said local softening zone, said local softening zones being similar to the second and fourth local softening zones e2, e4 described above, but the blade does not include a local softening zone on its last coils, such as the first and third local softening zones e1, e3 described above.In this case, the last outermost turn preferably includes an arrangement chosen from an area of ​​increased stiffness whose cross-section is greater than the cross-section of the blade in the vicinity of said area of ​​increased stiffness, such as an angle iron, or a raised Breguet or Philipps terminal curve.

[0077] Advantageously, in order to guarantee no contact between the coils of the spiral spring 1 during its contraction and expansion, it is possible to slightly modify the first inner coil 2 and / or the last outer coil 6.

[0078] To that end, and with reference to the figure 4 The blade may have, on its last turn, at least two slight bends, namely a bend C0 located approximately 1 / 4 turn from its free end 6a, intended to be fixed to the pin 8, said last outer turn 6 being in its rest position and not yet deformed as shown in thin dashed line, and a bend C1 at the level of the first local flexibility zone e1 obtained by slightly bending the last outer turn 6 at said first zone e1. A new last outer turn 6' is thus obtained, shown in solid line on the figure 4 , whose free end 6a' is intended to be integral with the piton 8', forming a new pitoning point.

[0079] These bends C0, C1 advantageously allow the first local flexing zone e1 to be placed on the last outermost turn 6' thus formed, slightly more than ¾ of a turn from the point of attachment to the pin 8 (= end 6a) of the last outermost turn 6 at rest and undeformed. In the example shown on the figure 4 , the first local softening zone e1 is then centered at an angle α1 equal to approximately 270° + 30° from the free end 6a of the last undeformed outer turn 6.

[0080] In this configuration, the coils of the spiral spring 1 remain at a certain distance from each other during the contractions and expansions of said spiral spring 1.

[0081] When these bends C0 and C1 are provided, the configuration of the first local softening zone e1 can be modified. For example, the first local softening zone e1 can be more open and preferably extend over a spiral segment with an angle Δα1 of approximately 58°, said first zone e1 having a thickness h1 of approximately ¾ H1. This first local softening zone e1 advantageously allows for a minimum displacement of the spiral spring 1 at the new attachment point (end 6a') to the pin 8' during the expansion and contraction of said spiral spring 1. The first local softening zone e1 is thus more flexible when the last outer coil 6 is curved.

[0082] If the third local easing zone e3 is present, at least one other bend C3 (cf. figure 12 ) can be provided at the level of said third local easing zone e3. This requires preferably placing said third local easing zone e3 at a little more than 5 / 4 of a turn from the end 6a of the last undeformed outer loop 6. For example, the third local easing zone e3 can then be centered at an angle α3 equal to approximately 450° + 30° from the free end 6a of the last undeformed outer loop 6.

[0083] Similarly, and with reference to the figure 7 The blade may have, on its first turn, at least two slight bends, namely a bend C5 located approximately 1 / 4 turn from its free end 2a, which is intended to be integral with the ferrule 4, said first internal turn 2 being in its rest position and not yet deformed as shown in thin dashed lines, and a bend C2 at the level of the second local flexibility zone e2 obtained by slightly bending the first internal turn 2 at said second zone e2. This results in a new first internal turn 2', shown in solid lines on the figure 7 , whose free end 2a' is intended to be integral with the ferrule 4', forming a new ferrule attachment point.

[0084] These bends C5, C2 advantageously allow the second local flexibility zone e2 to be placed on the first internal turn 2' thus formed, slightly less than ¾ of a turn from the end 2a of the first internal turn 2 at rest and undeformed. In the example shown on the figure 7 , the second local softening zone e2 is then centered at an angle α2 equal to approximately 270° - 30° from the free end 2a of the first undeformed inner turn 2.

[0085] In this configuration, the coils of the spiral spring 1 remain at a certain distance from each other during the contractions and expansions of said spiral spring 1.

[0086] When these bends C2 and C5 are provided, the configuration of the second local softening zone e2 can be modified. For example, the second local softening zone e2 can be less open and preferably extend over a spiral segment with an angle Δα2 of approximately 35°, said second zone e2 having a thickness h2 of approximately ¾ H2. This second local softening zone e2 advantageously allows for a minimum displacement of the spiral spring 1 at the new end 2a' fixed to the ferrule 4' during the expansion and contraction of said spiral spring 1. The second local softening zone e2 is thus more rigid when the first inner coil 2 is curved.

[0087] If the fourth local easing zone e4 is present, at least one other bend C4 (cf. figure 12 ) can be provided at the level of said fourth local easing zone e4. This requires preferably placing said fourth local easing zone e4 at slightly less than 5 / 4 of a turn from the end 2a of the first undeformed inner turn 2. For example, the fourth local easing zone e4 can then be centered at an angle α4 equal to approximately 450° - 30° from the free end 2a of the first undeformed inner turn 2.

[0088] In the examples shown, the local softening zones are represented with a thickness h which varies in such a way that they correspond to rectangular notches formed in equal parts on either side of the blade of the spiral spring 1.

[0089] It is quite clear that local relaxation zones can take other forms than the rectangular shape.

[0090] More generally, a local softening zone can be defined as a more or less abrupt decrease in the thickness of the blade followed by a substantially constant thickness, and finally a more or less abrupt increase in the thickness until returning to a thickness substantially equal to the initial thickness. The local softening zones thus defined can take, as described above for local softening zones of rectangular shape, a flared shape by extending over a spiral segment of angle Δαx of the order of 90° for a depth of 1 / 10th to 1 / 5th of the total thickness of the blade (which corresponds to a thickness hx of 0.8 Hx to 0.9 Hx where Hx is the thickness of the blade in the vicinity of said x-th local softening zone).These local softening zones can also take a narrower form by extending over a spiral segment with an angle Δαx of at least about 8° to a few tens of degrees for a depth not exceeding half the thickness of the blade (which corresponds to a thickness hx less than Hx / 2).

[0091] Furthermore, the local softening zones can be created indifferently, notably by thinning the blade, symmetrically on both sides of the blade as shown in the figures 2 , 4 , 5 , 7 , 8 , 10 , And 12 , or only on one side or the other of the blade, or even distributed asymmetrically on either side of said blade.

[0092] With reference to the figure 12 , a spiral spring 1 is represented which includes all the elements described above, namely the elbow C0, the first local softening zone e1 and its elbow C1 on the last deformed outer coil 6' of free end 6a' intended to be solid to the pin 8', the third local softening zone e3 and its elbow C3, the fourth local softening zone e4 and its elbow C4, and the second local softening zone e2 and its elbow C2 as well as the elbow C5 on the first inner coil 2' of free end 2a' intended to be solid to the ferrule 4'.

[0093] With reference to the figure 13 The last few turns, including the last outermost turn 6', of the spiral spring are shown in solid lines. figure 12 , and in fine dashed lines the last turns, including the last outer turn 6, of a similar but undeformed spiral spring (without local softening zone or bend).

[0094] With reference to the figure 14 which is an enlargement of the figure 13 The displacement t of the free end 6a' of the last outer loop 6', attached to the pin 8', was calculated and compared to the displacement tc of the free end 6a of the last outer loop 6 attached to the pin 8. figure 14 This shows that the pinned end 6a of an undeformed spiral spring follows the trajectory tc, while the pinned end 6a' of a deformed spiral spring 1 according to the invention follows the trajectory t, which is drastically reduced and resembles a point. The displacement tc is greater than one coil pitch, while the displacement t is significantly less. The effective pinning will therefore result in reduced eccentricity. The development of the spiral spring 1 according to the invention is consequently more concentric.

[0095] Similarly, with reference to the figure 15 The first coils, including the first inner coil 2', of the spiral spring are shown in solid lines. figure 12 , and in fine dashed lines the first turns, including the first inner turn 2, of a similar but undeformed spiral spring (without local softening zone or bend).

[0096] With reference to the figure 16 which is an enlargement of the figure 15 The displacement t' of the free end 2a' of the first inner turn 2', attached to the ferrule 4', was calculated and compared to the displacement tc' of the free end 2a of the first inner turn 2 attached to the ferrule 4. figure 16This shows that the end 2a of the ferrule of an undeformed spiral spring follows the trajectory tc', while the end 2a' of the ferrule of a deformed spiral spring 1 according to the invention follows the trajectory t', which is drastically reduced and resembles a point. The displacement tc' is approximately one coil pitch, while the displacement t is significantly less. The effective ferrule will therefore result in reduced eccentricity. The development of the spiral spring 1 according to the invention is consequently more concentric.

[0097] Furthermore, thanks to the bends, the coils remain apart during the contractions and expansions of the spiral spring 1.

Claims

1. Spiral spring intended to be associated with a balance wheel in a regulating organ of a watch movement and comprising a series of turns formed by a blade wound upon itself between a first inner turn (2) and a last outer turn (6), said blade having a constant or variable cross-section, characterized in that said blade comprises, on at least one of the first inner turn (2) and the last outer turn (6), at least one local flexing zone (e1, e2) centered at approximately ¾ of a turn of said turn (2, 6) from its free end (2a, 6a), said local flexing zone (e1, e2) having a cross-section smaller than the cross-section of the blade in the vicinity of said local flexing zone (e1, e2).

2. Spiral spring according to claim 1, characterized in thatsaid at least one local softening zone is a first local softening zone (e1) centered about ¾ of a turn from the last outermost turn (6) from its free end (6a), said first local softening zone (e1) having a cross-section smaller than the cross-section of the blade in the vicinity of said first local softening zone (e1).

3. Spiral spring according to claim 2, characterized in that said blade includes at least a second local flexing zone (e2) centered about 3 / 4 of a turn from the first internal turn (2) from its free end (2a), said second local flexing zone (e2) having a cross-section smaller than the cross-section of the blade in the vicinity of said second local flexing zone (e2).

4. Spiral spring according to one of claims 2 and 3, characterized in thatsaid blade includes at least a third local flexing zone (e3) centered about 5 / 4 of a turn from the last outermost turn (6) from its free end (6a), said third local flexing zone having a cross-section smaller than the cross-section of the blade in the vicinity of said third local flexing zone (e3).

5. Spiral spring according to any one of claims 2 to 4, characterized in that said blade includes at least a fourth local flexing zone (e4) centered about 5 / 4 of a turn from the first internal turn (2) from its free end (2a), said fourth local flexing zone (e4) having a cross-section smaller than the cross-section of the blade in the vicinity of said fourth local flexing zone (e4).

6. Spiral spring according to claim 5, characterized in that said blade includes at least the first, second, third and fourth zones (e1, e2, e3, e4) of local softening.

7. Spiral spring according to one of claims 2 and 4, dependent on claim 2, characterized in that the blade does not include a local softening zone on its first few turns and in that the first internal turn (2) includes an arrangement selected from an increased stiffness zone whose section is greater than the section of the blade in the vicinity of said increased stiffness zone or an internal Grossmann curve.

8. Spiral spring according to claim 1, characterized in that said at least one local easing zone is a local easing zone (e2) centered approximately ¾ of a turn from the first internal turn (2) starting from its free end (2a), said local easing zone (e2) having a cross-section smaller than the cross-section of the blade in the vicinity of said local easing zone (e2), in that the blade does not include a localized softening zone on its last turns and in thatthe last outermost coil includes an arrangement chosen from an increased stiffness zone whose cross-section is greater than the cross-section of the blade in the vicinity of said increased stiffness zone or a raised Breguet or Philipps terminal curve.

9. Spiral spring according to claim 8, characterized in that the blade includes another local flexing zone (e4) centered about 5 / 4 of a turn from the first internal turn (2) from its free end (2a), said other local flexing zone (e4) having a cross-section smaller than the cross-section of the blade in the vicinity of said other local flexing zone (e4).

10. Spiral spring according to any one of the preceding claims, characterized in thatsaid x-th local easing zone, where x is an integer preferably between 1 and 4, extends over a spiral segment of angle Δα x between about 8° and 100°, and preferably less than about 90°, and more preferably between about 30° and 50°.

11. Spiral spring according to any one of the preceding claims, characterized in that said x-th local softening zone has a thickness hx between 0.5Hx and 0.9Hx, where Hx is the thickness of the blade in the vicinity of said x-th local softening zone.

12. Spiral spring according to any one of the preceding claims, characterized in that said x-th local softening zone varies between a zone extending over a spiral segment with an angle Δαx equal to approximately 8°, and a thickness hx equal to approximately Hx / 2, and a zone extending over a spiral segment with an angle Δαx equal to approximately 90°, and a thickness hx equal to approximately 0.9Hx.

13. Spiral spring according to any one of the preceding claims, characterized in that the blade has at least two bends (C2, C5) provided at approximately 1 / 4 turn from the first internal turn (2) from its free end and at the level of the second local softening zone (e2), and at least one bend (C4) provided at the level of the fourth local softening zone (e4) if it is present.

14. Spiral spring according to any one of the preceding claims, characterized in that the blade has at least two bends (C0, C1) provided at approximately 1 / 4 turn from the last outer turn (6) from its free end and at the level of the first local softening zone (e1), and at least one bend (C3) provided at the level of the third local softening zone (e3) if it is present.

15. Regulator comprising a balance wheel and a spiral spring according to any one of claims 1 to 14.

16. Timepiece comprising a regulating organ according to claim 15 or a spiral spring according to any one of claims 1 to 14.

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