Spiral spring

p00001Spiral spring

Technical scope

p00002The present invention relates to the field of mechanical watchmaking. This concerns, more particularly, a spiral spring designed to equip a mechanical watch regulator.

State of the art

p00003In wall clocks, table clocks and mechanical or electrical wristwatches, there is always a regulatory body that allows, as the name implies, to regulate the progress of the clockwork. In the case of a mechanical watch, the regulating body is constituted by a steering wheel and a spiral spring.

p00004In a traditional way, the spiral is a sheet, generally metallic, of rectangular section wound on a spiral-shaped archimedes. This is fixed, in its center, to the axis of the steering wheel, by a piece called ferrule. The exterior of the spiral is fixed to a steering wheel bridge, called coq, by a piece called python. The python is fixed directly to the foot of the steering wheel, or by means of a mobile carrier.

p00005Such a spiral assembly is not optimal for clock isochronism. In fact, the center of the spiral moves during its unrolling. which induces reaction forces at the level of the pivots of the flywheel shaft. The intensity of the forces exerted on the pivots play an important part in the isochronism that is generally observed.

p00006Watches are known, provided with two spirals mounted on the steering wheel axis, in opposite directions, arranged in different planes. The H. Moser & Cie house proposes an escape provided with two spirals arranged on both sides of the steering wheel, in opposite directions. Document EP2063325 proposes a mechanism according to the preamble of claim 1 and comprising two traditional spirals arranged concentrically and coplanarly. It is known that it is difficult to obtain precise characteristics in spirals performed in a traditional way and that, therefore, two spirals will almost always be different, if only slightly. Thus, in the regulation of such a steering wheel provided with two spirals of different characteristics, the alignment of the forces exerted by the two spirals presents difficulties. In addition, the probable difference between the two spirals makes that the result of the forces exerted at the level of the steering wheel axis is, in most cases, non-zero and difficult to control.

p00007Document EP2151722 was published on February 10, 2010. This, therefore, constitutes a current technique in accordance with Article 54 (3) CBE. This document describes a spiral spring with a clock mechanism, comprising a plurality of co-planar sheets wound one inside the other, the inner ends of each sheet being integral with a single ferrule. This document also describes that the outer extremities of each sheet are joined together by a rigid frame provided with at least a portion to receive a fixing member, said frame, sheets and ferrule being made in a monolithic piece.

p00008Thus, the present invention aims to propose a spiral that allows to improve the isochronism of a clock, while keeping it simple to put into practice.

p00009Disclosure of the invention

p00010More precisely, the invention relates to a spiral spring clock mechanism as defined in claim 1.

p00011Other features of the invention are given in the dependent claims.

p00012Brief description of the drawings

p00013Other features of the present invention will become clearer with the reading of the following description, made referring to the attached drawings, in which Figures 1 to 5 show, in view from above, schematic views of different examples. illustrative to better understand the invention.

p00014Figure 6 shows an embodiment of the invention.

Embodiments of the invention

p00015Figure 1 represents a flat spiral spring 10. This comprises a first inner limb associated with a ferrule 12.

p00016In particular, several sheets are deployed from ferrule 12, two of these drawings illustrating. Thus, there is a first 10a and a second 10b sheets, rolled in the same plane and in the same direction. The sheets 10a and 10b are wound one inside the other, the turns of one between the turns of the other. The first 10a and the second 10b sheets are arranged at 180 ° from each other. The sheets are identical, so that the ends of the sheets are located in a circle and are located 180º from each other.

p00017Advantageously, the outer ends of the sheets are joined together by a rigid frame 14, that is to say that the frame does not contribute (or almost not) to the elastic torque exerted by the spring. The shape of the frame 14 has a circular symmetry with respect to the center of the spiral. Preferably, the frame follows a circular path, concentric with the spiral.

p00018Typically, as the techniques for putting in the form of silicon-type materials allow, ferrule 12 is made by forming the same piece with the rest of the spiral. Advantageously, in order for the sheets to have identical elastic characteristics, the two sheets 10a and 10b, the ferrule 12 and the frame 14 form the same piece, in a monolithic manner. For this, the spiral according to the invention can be made in materials conformable by deep etching techniques, particularly with two spirals based on silicon, especially monocrystalline silicon, possibly covered by a layer of silicon oxide, but also with two spirals made in diamond, obtained by growth and deep engraving, or still with spirals made in DCS (Diamond Coated Silicon), that is diamond coated silicon spirals.

p00019Thanks to the symmetrical arrangement of the two identical sheets 10a and 10b, each of the sheets exerts a force on the steering wheel axis that compensates for the force exerted by the other sheet. Thus, the reactions on the axis are minimal, or almost nil, which allows to improve the isochronism of the oscillator.

p00020The frame 14 is arranged so that it can support a fixing member, preferably a python, for attaching the spiral to a holder attached to the mechanism. In the example of Figure 1, the frame has a width portion adapted to receive a slotted python, known to the person skilled in the art. More precisely, the frame has a wide area 14a and a thinner area 14b to receive the python. The latter is fixed to the frame by an adapted technique, such as bonding or welding, chosen by the specialist in the field.

p00021Figures 2 to 5 propose different executions to make the frame 14. In Figures 2 to 4, the frame 14 is semicircular and joins the two ends of the sheets arranged at 180 °. In Figure 2, the wide areas 14a of the frame are emptied, which makes it possible to lighten the spiral in its outer zone, which is always interesting to limit the stresses in the python in the event of a crash.

p00022In Figure 3, the frame 14 has several fine areas 14b, which allow the python to be placed in several places around the frame, which can give flexibility for the construction of the mechanism.

p00023Figure 4 proposes a frame provided with a hole 16 for receiving a non-slotted python, capable of being housed and fixed inside the hole. The frame 14 of Figure 5 is arranged in the same way, but forms a complete circle joining the outer ends of the sheets on their two sides. The distribution of the masses is thus perfectly symmetrical. It should be noted that, even in the configuration in which the frame was provided with a hole, the frame could be emptied. Various holes may also be arranged in the frame.

p00024Although the figures show only examples in which the spiral spring 10 comprises two sheets, more of these can be provided. In this way, n identical sheets can be had, distributed at 360º / n around the ferrule, the outer extremities being equally distributed at 360º / n. Such an arrangement allows to improve the distribution of the sheets and the forces around the axis of the steering wheel and, therefore, a better compensation.

p00025In this case, with n sheets, a circle-shaped frame 14 defines an angle of 360º / n, or a multiple of this value, according to the choice of the specialist in the field. A complete circular frame is also possible.

p00026By wrapping each sheet between the turns of the other sheets, it is understood that, for a spiral of a given dimension, the increase in the number of sheets implies, on the one hand, the reduction of the active length of each sheet. Thus, with respect to a traditional spiral that occupies a surface S, provided with a single sheet whose active length is L and of thickness e (the thickness being the dimension of the sheet in the plane of the spiral) and of passage between the turns p, in a spiral according to the invention with n sheets of thickness e, of step p for each turn, which occupies the same surface S, each sheet will have an active length of length L / n. This results in increasing the stiffness of the sheet, but this can be compensated by decreasing the thickness of each sheet, which allows to increase the active length and decrease the stiffness. It is thus easy to obtain a desired total torque and in accordance with the pairs obtained with traditional spiral springs. It can also be considered to make turns that occupy a larger surface in order to obtain sheets of desired length. From a practical point of view, spirals of 2, 3 or 4 sheets will be preferred.

p00027Figure 6 proposes a spiral spring 10 according to the invention in which the outer spiral of each sheet is provided with a reinforcement 18 that allows correcting the centering of the spiral and bringing the center of gravity of the active part to the center of action. of the elastic pair, that is to the center of the spiral. Such reinforcement 18 makes it possible to improve the concentricity of the spiral development and further reduce the reactions in the pivot. It will be noted that the reinforcement 18 in itself does not participate in the definition of the elastic torque of the spiral. As Figure 6 shows, the step that separates the last turn and the penultimate turn is constant, that is to say that the last turn is at a constant distance from the penultimate turn, even at the reinforcement level. It could also be considered that the distance between the last turn and the penultimate turn is less than the step that separates the other turns, particularly at the level of the reinforcement.

p000285 The present invention has been given only by way of non-limiting illustration of the invention and the person skilled in the art can still provide various alternatives that come directly from the description given above, without departing from the framework defined by the claims. Especially, the passage of each sheet can be constant as shown in the drawings, but it can also vary. In addition, the python can be replaced by another fixing method, especially a screw to directly support the frame with the foot of

p0002910 steering wheel.