CH711675B1 - Small space spiral with constant section. - Google Patents

Abstract

The invention relates to a single piece spiral (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 allowing the spiral, when in contraction at a value of 360 degrees, has a constant distance between each turn of the inner coil to the penultimate coil (SP).

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, ie the more it is possible to engrave spirals on the same wafer, the lower the price of a spiral to the 'unit.

It is however not possible to reduce the clutter at random because the turns of a spiral must not be touching as well in contraction and 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 second turn, a first zone in which the pitch decreases, a second zone, in extension of the first zone, in which the pitch between each turn increases continuously so that the spiral, when it is in contraction at a value of 360 degrees, has a constant distance between each turn of the inner turn to the penultimate turn.

Advantageously according to the invention, it is understood that the bulk of the spiral is reduced to the maximum 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 second zone, the pitch between each turn increases continuously according to a constant value; the second zone comprises a constant section; the first zone comprises a section which decreases between the end of the inner coil and its junction with the second zone; - The spiral has a third zone, an extension of the second 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 third zone, the pitch increases continuously according to a constant value; - The third zone comprises a first portion whose section is substantially identical to that of the second zone and a second portion, an extension of the first portion, the section increases in approaching the end of the outer coil; the spiral is based on silicon.

In addition, the invention relates to a resonator characterized in that it 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 spiral; fig. 5 is a graph showing the evolution of the thickness of the turns as a function of the number of turns of the spiral; 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 manufacture a maximum 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. Without limitation, 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.

The silicon-based terms 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 coil Si and the second turn S2, a first zone A in which the pitch between the inner coil Si and the second turn S2 decreases.

Advantageously, the hairspring 1 comprises, as an extension of the first zone A, a second zone B, in which the pitch between each turn increases continuously so that the hairspring 1, when it is in contraction, is that is, when the end 5 of the inner coil Si has rotated substantially at -360 degrees to the center of the hairspring 1, as seen in FIG. 1, has a substantially constant distance between each turn of the inner turn Si at the penultimate turn SP.

[0015] Preferably, as illustrated in FIG. 4, the pitch between each turn increases continuously according to a constant value in the second zone B. In addition, preferably according to the invention, the second zone B has a constant section. Thus, by way of example, the constant section may comprise a constant thickness 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 comprises, advantageously according to the invention, a third zone C, extending from the second zone B and between the beginning of the penultimate turn SP and the end 7 of the outer coil. SE, in which the pitch, between the penultimate turn SP and the outer turn SE, increases continuously so that the hairspring 1, when expanding, that is to say when the end 5 of the inner turn Si has rotated substantially +360 degrees from the center of the hairspring 1, as shown in FIG. 3, has a minimal distance 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.

[0017] Preferably, as illustrated in FIG. 4, the pitch between each turn increases continuously according to a second constant value in the third zone C. As shown in FIG. 4, the second constant value is preferably greater than the first constant value of the second zone B. In addition, preferably according to the invention, the third zone C comprises a first portion C1 with a thickness substantially identical to that of the second zone B then a second part C2 in which the thickness increases continuously.

A first graph showing the evolution of the pitch between the turns as a function of the number of turns of the spiral is illustrated in FIG. 4. It can be seen that in the first zone A of the hairspring 1, the pitch decreases substantially substantially until the beginning of the second zone B. In FIG. 4, it can be seen that the second zone B comprises a constant increase of the pitch to the third zone C. The latter C comprises a constant increase of the pitch to the end 7 of the outer turn SE. As shown in fig. 4, the constant increase of the pitch of the third zone C is much more pronounced than that of the zone B.

In a complementary manner, a second graph showing the change in the thickness of the turns as a function of the number of turns of the spiral is illustrated in FIG. 5. It can be seen that in the first zone A of the hairspring 1, the thickness decreases to the beginning of the second zone B. In FIG. 5, it can be seen that the second zone B has a constant thickness up to the third zone C. The latter zone C has a first portion Ct whose thickness remains constant and a second portion C2, an extension of the first portion C · ,, whose thickness increases as it approaches the end 7 of the outer turn SE.

Finally, a graph showing the evolution ΔΡ of the distance between turns as a function of the number of turns of the spiral is illustrated in FIG. 6. More precisely, the spacing ΔΡ of the turns is illustrated for the hairspring in its contracted state of FIG. 1 (curve annotated in square □), in its rest state of FIG. 2 (triangle annotated curve Δ) and, in its expanded state of 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 decreases to the beginning of the second zone B. It will be noted, then, that the second and third zones B and C comprise a distance ΔΡ between the turns which increases continuously until the fixed point of pitting of the end 7 reduces the distance between the turns to a minimum value .

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 the state of contraction annotated in square (c), it can be seen that in the first and second zones A and B of the hairspring 1, the distance ΔΡ between the turns is advantageously constant and equal to a minimum value. It will be noted, then, that the third zone C comprises a continuous increase in the distance ΔΡ between the turns while approaching the end 7 of the outer coil Se.

In FIG. 6, we note that the minimum values of the curves in circle (O) and in 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 20 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 20 micrometers.

Advantageously according to the invention, it is however understood that these particular characteristics of the hairspring 1 allow congestion of the hairspring at rest which is reduced to the maximum while ensuring a minimum constant distance between the contraction turns and, optionally, 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, of section such as 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 was chosen because mechanically this angle can not theoretically be exceeded. 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 second zone B, the maximum pitch of the first zone A and / or the third zone C 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, depending on the thickness of the second zone B, the maximum thickness of the first zone A and / or the third zone C may vary. It is therefore understood that only thickness variations are retained 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, the height and / or or the thickness of the spiral blade.

Claims (9)

claims 1. A single-piece spiral (1) comprising a single blade (3) wound on itself between an inner turn (Si) and an outer turn (SE), the blade (3) at rest comprising, between the end of the turn internal (Si) and the second turn (S2), a first zone (A) in which the pitch decreases, and comprising a second zone (B), in extension of the 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 constant distance 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 second zone (B), the pitch between each turn increases continuously in a constant value. 3. Spiral (1) according to claim 1 or 2, characterized in that the second zone (B) has a constant section. 4. Spiral (1) according to one of the preceding claims, characterized in that the first zone (A) comprises a section which decreases between the end (5) of the inner coil (Si) and its junction with the second zone (B). 5. Spiral (1) according to one of the preceding claims, characterized in that the spiral (1) comprises a third zone (C), an extension of the second zone (B) 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 at a value of 360 degrees, has a minimum distance between the penultimate spire (SP) and outer coil (SE) to avoid contact. 6. Spiral (1) according to the preceding claim, characterized in that, in the third zone (C), the pitch increases continuously according to a constant value. 7. Spiral (1) according to the preceding claim, characterized in that the third zone (C) comprises a first portion (C-ι) whose section is substantially identical to that of the second zone (B) and a second part ( C2), an extension of the first part (C-ι), the section increases in approaching the end (7) of the outer coil (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 spiral (1) according to one of claims 1 to 8.