CH712226A2 - Spiral with reduced space. - Google Patents

Abstract

The invention relates to a single-piece hairspring (1) comprising a single blade (3) wound on itself between an inner turn (SI) and an outer turn (SE), the blade (3) comprising a geometry that allows the hairspring ( 1), when in contraction at a value of 360 degrees, has a substantially constant distance between each turn of the inner turn (SI) to the penultimate turn (SP). Preferably, the turns of an area (A) are of constant section and different from a constant section of the outer turn (S E) in zone (B 2).

Description

Description

FIELD OF THE INVENTION [0001] The invention relates to a spiral with reduced overall dimensions and, more particularly, such a spiral intended to cooperate with a balance to form a resonator.

BACKGROUND OF THE INVENTION [0002] The price of a silicon balance spring is substantially proportional to its surface, that is to say the more it is possible to engrave spirals on the same wafer, the lower the price of silicon. a spiral to the unit.

It is however not possible to reduce the clutter at random because the turns of a hairspring must not touch as well in contraction as expansion. SUMMARY OF THE INVENTION [0004] The object of the present invention is to overcome all or part of the aforementioned drawbacks by proposing a reduced bulk spiral while ensuring that its turns do not touch as well in contraction as in expansion.

For this purpose, the invention relates to a monobloc spring comprising a single blade wound on itself between an inner coil and an outer coil, the blade at rest comprising between the end of the inner coil and the penultimate spire, a first zone in which the pitch between each turn increases continuously so that the spiral, when in contraction at a value of 360 degrees, has a substantially constant distance between each turn of the inner coil to the penultième turn.

Advantageously according to the invention, it is understood that the bulk of the spiral is reduced while ensuring a minimum constant distance between the contraction turns and, optionally, also expanding. We can therefore try to minimize the size of the hairspring, without losing in chronometric properties. Such a spiral optimizes the number of spirals that will be engraved on the same plate to reduce the unit cost.

According to other advantageous variants of the invention: in the first zone, the pitch between each turn increases continuously according to a constant value; the first zone comprises a constant section; - The spiral has a second zone, extending from the first zone and between the beginning of the penultième turn and the end of the outer turn, in which the pitch increases continuously so that the spiral, when expanding to a value of 360 degrees, has a minimum distance between the penultimate turn and the outer turn to avoid contact; in the second zone, the pitch increases continuously according to a constant value; - The second zone comprises a first portion whose section is substantially identical to that of the first zone and a second portion, an extension of the first portion, the section is increased; the section of the blade is constant between the beginning of the second portion of the second zone and the end of the outer coil; the spiral is based on silicon.

The invention also relates to a resonator characterized in that the resonator comprises a balance cooperating with a hairspring according to one of the preceding variants.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] Other features and advantages will become clear from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the accompanying drawings, in which: FIG. 1 is a top view in contraction of a hairspring according to the invention; fig. 2 is a top view at rest of a hairspring according to the invention; fig. 3 is an expanding top view of a hairspring according to the invention; fig. 4 is a graph showing the evolution of the pitch between the turns as a function of the number of turns of the hairspring at rest; fig. 5 is a graph showing the evolution of the thickness of the turns as a function of the number of spiral turns at rest; fig. 6 is a graph showing the evolution of the distance between turns as a function of the number of turns of the spiral and the movement of the spiral.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] The invention relates to a reduced bulk spiral intended to cooperate with a balance to form a spiral balance type resonator for a timepiece.

The development of the present invention was initiated to optimize the number of spirals on the same silicon-based wafer while ensuring that the turns of each spiral do not touch as well in contraction as expansion. However, it is understood that the spiral can not be limited to a silicon-based material. In a nonlimiting manner, it is understood that the same logic is applicable to a spiral formed from a LIGA process, that is to say based on an electrically conductive material or any other material craftable wafer.

The terms based on silicon mean a material comprising monocrystalline silicon, doped monocrystalline silicon, polycrystalline silicon, doped polycrystalline silicon, porous silicon, silicon oxide, quartz, silica, silicon nitride or silicon carbide. Of course, when the silicon-based material is in crystalline phase, any crystalline orientation can be used.

As illustrated in FIG. 2, the invention thus relates to a spiral 1 monobloc having a single blade 3 wound on itself between an inner coil Si and an outer turn SE. According to the invention, the blade 3 of the hairspring 1, in its rest position of FIG. 2, comprises between the end 5 of the inner turn Si and the penultimate turn SP, a first zone A in which the pitch between each turn increases continuously as shown in FIG. 4.

This advantageous configuration allows the hairspring 1, when it is in contraction, that is to say when the end 5 of the inner turn Si has made a rotation of substantially at -360 degrees with respect to the center of the spiral 1, as shown in FIG. 1, has a substantially constant distance between each turn, the internal turn Si to the penultimate turn SP.

[0015] Preferably, as illustrated in FIG. 4, the pitch between each turn increases continuously according to a constant value Δ \ Λ in the first zone A. In addition, as illustrated in FIG. 5, the first zone A comprises, preferably according to the invention, a constant section. Thus, by way of example, the constant section may comprise a constant thickness E-ι of between 10 and 50 μm and a constant height of between 50 μm and 250 μm.

According to an additional optional feature, the spiral 1 comprises, advantageously according to the invention, a second zone B, extending from the first zone A and between the beginning of the penultimate turn SP and the end 7 of the turn external SE. The second zone B has a step, between the penultimate turn SP and the outer turn SE, which increases continuously as illustrated in FIG. 4.

This advantageous configuration allows the hairspring 1, when it is expanding, that is to say when the end 5 of the inner coil Si has made a rotation of substantially +360 degrees with respect to the center of the spiral 1, as shown in FIG. 3, has a minimum distance, that is to say a predefined distance of guaranteed security, between the penultième a turn SP and the external turn SE to avoid the contact in particular between the penultième a turn SP and the external turn SE.

Preferably, as illustrated in FIG. 4, the pitch between each turn increases continuously according to a second constant value ΔV2 in the second zone B. As shown in FIG. 4, the second constant value AM2 of the second zone B is preferably greater than the first constant value Δ \ Λ of the first zone A.

In addition, as shown in FIG. 5, the second zone B comprises, preferably according to the invention, a first part B-ι with a substantially identical section to that of the first area A and a second part B2 in which the section is increased. In a preferred manner, as illustrated in FIG. 5, the section of the blade is constant between the beginning of the second portion B2 of the second zone B and the end 7 of the outer turn SE.

In addition, the section is preferably increased only by the variation of the thickness of the blade 3, that is to say with a constant height. Thus, as shown in FIG. 5, the second constant thickness value of the second portion B2 of the second zone B is preferably greater than the first constant thickness value of the first zone A and the first portion B-1 of the second zone B. Thus by way of example, the constant section of the second portion B2 of the second zone B may comprise a constant thickness of between 25 and 75 μm and a constant height of between 50 μm and 250 μm.

A first graph showing the evolution of the pitch between the turns as a function of the number of turns of the hairspring at rest is shown in FIG. 4. It can be seen that, in the first zone A of the hairspring 1, the second zone A has a constant increase according to the value Δ \ Λ of the pitch to the second zone B. The second zone B comprises a constant increase according to the Δν2 value of the pitch to the end 7 of the external turn SE. As shown in fig. 4, the constant increase AV2 of the pitch of the second zone B is much more pronounced than that AV- of the first zone A.

In a complementary manner, a second graph shown in FIG. 5, shows indirectly the evolution of the section of the blade 3. In fact, the manufacture using a wafer intrinsically inducing a substantially constant height, only the change in the thickness of the turns depending on the number of spiral turn is shown in fig. 5. It can be seen that the first zone A of the spiral 1 has a constant section E-, up to the second zone B. More precisely, the second zone B has a first portion B- whose section remains substantially identical to that Ei of the first zone A and a second portion B2, an extension of the first portion B · ,, whose section is increased.

As shown in FIG. 5, the section E2 of the blade 3 is substantially constant between the beginning of the second portion B2 of the second zone B and the end 7 of the outer coil SE. It can be seen in particular in the example of FIG. 5 that the section E2 of the second portion Bg of the second zone B is almost twice as large as that E, the first zone A and the first portion B1 of the second zone B.

Finally, a graph showing the evolution ΔΡ of the distance between turns as a function of the number of turns of the spiral is shown in FIG. 6. More precisely, the distance ΔΡ of the turns is illustrated for the hairspring in its contracted state in FIG. 1 (curve annotated in square □), in its rest state in FIG. 2 (triangle annotated curve Δ) and, in its expanded state in FIG. 3 (annotated curve in circle O).

Therefore, in the state of expansion annotated in a circle (O), it can be seen that, in the first zone A of the spiral 1, the distance ΔΡ between the turns comprises a distance ΔΡ between the turns which increases continuously until the fixed pinning point of the end 7 reduces the distance between the turns to a minimum value, that is to say a predefined distance of guaranteed safety. In the example of FIG. 6, it can be seen that the predefined safety distance guaranteed is about 50 μm.

Logically, since in its state at rest, the triangle annotated curve Δ in FIG. 6 is identical to the curve of FIG. 2. Finally, in a state of contraction annotated in a square (□), it can be seen that, in the first zone A of the spiral 1, the distance ΔΡ between the turns comprises a distance ΔΡ between the turns which increases continuously according to a slope if weak that the distance ΔΡ can be considered substantially constant in the first zone A. In the example of FIG. 6, it can be seen that the distance ΔΡ in the zone A is approximately 35 μm. It can be noted, then, that the second zone B comprises a continuous increase, more marked than in the first zone A, of the distance ΔΡ between the turns approaching the end 7 of the outer coil Se- [0027] In FIG. 6, we note that the minimum values of the curves circle (O) and square (□) are not identical. However, they could be made geometrically identical.

Similarly, the values described in FIGS. 4-6 are used only as examples. Thus, depending on the configurations of the hairspring and / or the resonator to which it belongs, the minimum value chosen could be different from the 35 micrometers chosen as an example in FIG. 6. It is therefore understood that each minimum value of the curves in circle (O) and in square (□) could be chosen lower or higher than, respectively, 50 and 35 micrometers.

Advantageously according to the invention, however, it is understood that these particular characteristics of the hairspring 1 allow congestion of the hairspring at rest which is reduced while ensuring a minimum constant distance between the contraction turns and, preferably, also expanding. It is therefore possible to minimize the size of the hairspring without losing in chronometric properties. Such a hairspring according to the invention makes it possible to optimize the number of spirals that will be engraved on the same plate in order to reduce the unit cost.

Of course, the present invention is not limited to the example shown but is susceptible to various variations and modifications that will occur to those skilled in the art. In particular, the geometry, that is to say the variations of pitch, section such as, for example, the thickness and the number of turns, may vary according to the intended applications.

By way of example, it could be envisaged additionally to reduce the number of turns to further reduce the bulk of the spiral.

It is also clear that the 360 degree angle contraction or expansion could be lower without departing from the scope of the invention. Indeed, this angle has been chosen because mechanically this angle can theoretically not be exceeded in a resonator -spiral type-balance. However, the importance is not for which angle the distance is minimal but rather to be sure that the minimum distance is never exceeded. It is therefore understandable that the angle could be deliberately chosen lower because, according to the configuration of the movement, it is clear that this angle will not be exceeded in normal operation.

In addition, the values in ordinates of FIG. 4, are in no way limiting. Thus, following the section of the first zone A, the minimum pitch of the first zone A and / or the maximum pitch of the second zone B may vary. It is therefore understood that only the variations of pitch are conserved but not necessarily according to the same minimum and / or maximum values.

Similarly, the ordinate values of FIG. 5, are in no way limiting. Thus, according to the variation of the pitch of the first zone A, the minimum section of the first zone A and / or the maximum section of the second zone B may vary. It is therefore understood that only section variations are maintained but not necessarily according to the same minimum and / or maximum values.

Finally, even if the calculations were made from the variation of the thickness, it is obvious that the variation must be understood as a variation of section, that is to say that the variation s' applies to the height and / or thickness of the spiral blade.

Claims (9)

claims 1. Spiral (1) monobloc comprising a single blade (3) wound on itself between an inner turn (Si) and an outer turn (SE), the blade (3) resting between the end of the inner turn (Si) and the penultimate turn (Sp), a first zone (A) in which the pitch between each turn increases continuously so that the hairspring (1), when in contraction at a value of 360 degrees, has a distance substantially constant between each turn of the inner turn (Si) to the penultimate turn (Sp). 2. Spiral (1) according to the preceding claim, characterized in that, in the first zone (A), the pitch between each turn increases continuously according to a constant value (Δ \ Λ |). 3. Spiral (1) according to claim 1 or 2, characterized in that the first zone (A) has a constant section. 4. Spiral (1) according to one of the preceding claims, characterized in that the spiral (1) comprises a second zone (B), an extension of the first zone (A) and between the beginning of the penultième turn ( Sp) and the end (7) of the outer coil (SE), in which the pitch increases continuously so that the spiral (1), when expanding to a value of 360 degrees, has a minimum distance between the penultimate spire (Sp) and the outer turn (SE) to avoid contact. 5. Spiral (1) according to the preceding claim, characterized in that, in the second zone (B), the pitch increases continuously according to a constant value (AV2). 6. Spiral (1) according to claim 4 or 5, characterized in that the second zone (B) comprises a first portion (B-ι) whose section is substantially identical to that of the first zone (A) and a second part (B2), an extension of the first part (B-ι), whose section is increased. 7. Spiral (1) according to the preceding claim, characterized in that the section of the blade (3) is constant between the beginning of the second portion (B2) of the second zone (B) and the end (7) of the outer turn (SE). 8. Spiral (1) according to one of the preceding claims, characterized in that the spiral (1) is based on silicon. 9. Resonator characterized in that the resonator comprises a rocker cooperating with a hairspring (1) according to one of the preceding claims.