Method for manufacturing sprung balance oscillator for high torque variation balance springs

Abstract

To provide a method for manufacturing an oscillator for a timepiece made of a balance and a balance spring.SOLUTION: The method comprises the steps of: measuring an average moment of inertia of a plurality of balances 2; providing a plurality of pinned up balance springs 3, the balance springs having an excess number of coils forming up to three more turns than the final number of coils; making a first predetermined external cut of the plurality of balance springs with an excess, measuring torque of the balance springs and sorting the plurality of balance springs according to a value of the torque; assembling the balance springs to form an oscillator with an intermediate frequency and to determine a length to be cut to achieve a desired oscillation frequency; making a second external cut of the plurality of balance springs selected to achieve both the oscillation frequency and a target value to obtain an attachment point angle within ±50° of a theoretical value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the general technical field of mechanical oscillators, particularly those used in the watch industry. More particularly, the present invention relates to a method for manufacturing an oscillator including a hairspring and a temple or balance.

Background Art

[0002] Despite the fact that machining operations are extremely precise and highly reproducible, adjustments almost always have to be made during assembly operations, or more frequently during adjustment or fine-tuning operations. In particular, unbalance adjustment and inertia adjustment for movable parts, and frequency adjustment for oscillators must be performed.

[0003] In particular, at the assembly stage, the pairing of certain components must be completed. Although these components are individually within the range of machining tolerances or manufacturing tolerances, they cannot be simply and purely assembled due to operational constraints specific to sub-assemblies or to assemblies once installed.

[0004] This is particularly true for the regulating members of a watch, and more particularly for spring balance assemblies. The adjustment of both static and dynamic unbalance and inertia already appears to be very delicate at the stage of individual components, and these adjustment operations become extremely complex when the components are assembled. Dynamic adjustment in particular is cumbersome to implement. Various techniques are known for adjusting spring balance sub-assemblies, but the two most commonly used are as follows.

[0005] The "omega metric" system consists of · classifying a plurality of hairsprings already cut at their correct mounting positions according to their torque, and · classifying a plurality of balances according to their inertia, and Pairing a balance selected from a specific classification with a hairspring also selected from a specific classification, these classifications being compatible with each other to achieve the selected frequency accuracy.

[0006] This method requires a large component inventory and has many logistics constraints.

[0007] An alternative is a "spirodynamic" system as follows. · Include a pinned hairspring in the balance, · This hairspring is cut to a length that provides a torque adapted to the inertia of the balance. By well controlling the inertia of the balance and the torque distribution of the hairspring, this cut-off point is within the maximum tolerance of ±50° of the theoretical target value.

[0008] This method does not guarantee a high accuracy of the attachment point of the hairspring to the collet outlet, so the chronometer performance can be impaired. This is especially true when the nominal torque distribution of the hairspring is wide.

[0009] The first technique is very expensive, and the second technique has mediocre chronometer performance. Furthermore, these techniques are inappropriate or insufficiently appropriate when there is a very large variation in the torque of the hairspring at the end of the manufacturing process. This makes the combination with the balance and adjustment difficult, and typically affects the chronometer performance of mediocre oscillators. Summary of the Invention

[0010] One object of the present invention is to provide a cost-effective method for assembling an oscillator.

[0011] Specifically, one object of the present invention is to propose a method for manufacturing an oscillator including a hairspring and a balance, and this method is cost-effective even when the torque dispersion of the hairspring is large.

[0012] For this purpose, the present invention relates to a method for manufacturing a timepiece oscillator made from a balance and a hairspring, the method comprising: · measuring the average moment of inertia of a plurality of balances in a batch; · providing a plurality of pinned hairsprings, the hairsprings having an excess number of turns formed up to three turns more than the final number of coils; · performing a first predetermined external cut of the plurality of hairsprings by a defined excess in the length of one to two coils, then measuring the torque of the plurality of hairsprings and sorting the plurality of hairsprings according to the measured torque values; · assembling a plurality of hairsprings corresponding to the plurality of balances measured to form an oscillator having an intermediate frequency; · performing a second external cut of the plurality of hairsprings selected to achieve both a desired oscillation frequency and a target value for an attachment point angle within ±50° of the theoretical value.

[0013] According to another advantageous alternative embodiment of the present invention, · the hairspring is made from a blank of metal or metal alloy, · the blank is covered by a surface layer of ductile material, · the metal or metal alloy is selected from titanium, niobium, zirconium, or a combination of these metals, · the hairspring is formed by drawing and / or roller rolling the blank, alternating with at least one heat treatment step, and the step of winding up the hairspring is performed before the final heat treatment step, · the ductile surface layer is removed after roller rolling and before winding up.

Brief Description of the Drawings

[0014] Other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings. This description is given by way of example and is in no way limiting.

[0015]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0016] The present invention relates to a method for manufacturing an oscillator 1 intended to be equipped in a timepiece movement.

[0017] "Manufacturing" is understood in the broadest sense to mean steps involved in manufacturing the components of the oscillator 1 and steps involved in assembling the components of the oscillator 1.

[0018] During the first step, a plurality of balances 2 of a batch are taken from the production line, and the plurality of balances 2 of the batch are obtained using a process that enables a given inertia for balancing to be obtained. The average inertia of the plurality of balances 2 of the batch is measured to ensure that there is no dispersion that is too large within the batch, and any balance having an inertia that is too far from this average is removed from the batch.

[0019] In the second step, a plurality of pinned hairsprings 3 are supplied. These hairsprings have an excessive number of coils forming up to three additional coils, as shown in FIG. 1. Such an excessive number of coils allows the plurality of hairsprings to be later shortened as part of an adjustment operation.

[0020] These hairsprings are made from blanks made of metal or metal alloy.

[0021] Subsequently, a surface layer of a ductile material is deposited on the alloy blank to facilitate forming into a wire shape. This thickness of ductile material means that the blank can be easily stretched, drawn out, and roller rolled.

[0022] Finally, to form the mustache 3, the blank covered by the ductile surface layer is deformed by roller rolling after wire drawing and undergoes at least one heat treatment step, and finally a winding step is performed to form the mustache 3.

[0023] The deformation step as a whole represents one or more deformation processes that may include drawing and / or roller rolling. Wire drawing requires the use of one or more drawing plates, either in the same deformation step or in different deformation steps as required. Wire drawing is carried out until a wire with a round cross-section is obtained. Roller rolling may be carried out in the same deformation step as wire drawing or in other subsequent deformation steps. Advantageously, the last deformation treatment applied to the alloy is a roller rolling operation, preferably having a rectangular profile that conforms to the inlet cross-section for the winder spindle.

[0024] The addition of the ductile material may be galvanic or mechanical by PVD or CVD, in which case a sleeve or tube of the ductile material is obtained. These are adjusted in the alloy blank and then thinned during one or more steps of deforming the blank.

[0025] The ductile material is removed once all deformation treatment operations have been carried out, i.e., after the final rolling operation and before the winding operation. The wire is stripped of the layer of ductile material, for example, by chemical etching using an acid-based solution.

[0026] At the end of these steps, a mustache 3 with an excess outer length of at least three coils, comprising an alloy core and a ductile shell, is obtained.

[0027] The resulting beard spring 3 therefore has a variable cross-section. This is because the wire forming the beard spring is not an alloy as deformable as copper and thus does not become uniformly regular, and as a result, the cross-section of the wire changes after various deformation steps. That is, there is a high variation in torque among the plurality of beard springs 3 to be manufactured, and in such a case, a "spiro-matic" system cannot be assumed or used.

[0028] As shown in FIG. 2, the method according to the present invention includes a third step in which a first external cutting 30 is performed to obtain a pre-cut beard spring 3. The length of the outer cutting portion 30 is made to extend over one or two coils so that an excessive length remains in the beard spring 3 when adjusting the beard spring 3 at the balance 2.

[0029] Thereafter, in a fourth step, the torque of the beard spring 3 is measured, the beard spring 3 is sorted according to the measured torque value, and a plurality of batches of beard springs having the same measured torque are formed.

[0030] In a fifth step, a plurality of beard springs 3 whose measured torque corresponds to the inertia of the balance 2 are assembled to form an oscillator having an intermediate frequency, and the length to be cut to achieve a desired oscillation frequency is determined.

[0031] Thereafter, in a sixth step, a second external cutting is performed on the selected beard spring 3 to achieve a desired oscillation frequency, and a target value of an angle α formed by the stud of the collet 4 and the attachment point 6 to the outlet 5 of the beard spring 3 after the second external cutting is achieved with a tolerance of plus or minus 50° from the theoretical value. The theoretical value is defined so as to satisfy the product requirements once the curve is formed.

[0032] That is, by such a method, it is allowed to pair a batch of beard springs so that all the beard springs in the batch can be paired with a batch of balances within a tolerance of ±50°.

[0033] In this way, the method of the present invention provides a spring-type balance assembly tuned to a specific frequency with good reliability and accuracy.

Claims

1. A method for manufacturing a timepiece oscillator (1) made of a balance (2) and a hairspring (3), comprising the steps of: - measuring the average moment of inertia of a batch of balances (2); Providing a pinned hairspring (3), the hairspring (3) having an excess number of coils forming up to three turns more than the final number of coils; - performing a first predetermined external cut of the plurality of hairsprings (3) with a defined excess of one to two coils in length, after which the torque of the plurality of hairsprings (3) is measured and the plurality of hairsprings (3) is sorted according to the values ​​of the measured torque; - assembling said plurality of hairsprings (3) whose measured torques correspond to said plurality of balances (2) to form an oscillator having an intermediate frequency; - making a second external cut of the plurality of hairsprings (3) selected to achieve both a desired oscillation frequency and a target value for obtaining an attachment point (6) angle (α) within ±50° of the theoretical value; A method of manufacturing comprising the steps of:

2. 2. A manufacturing method according to claim 1, characterized in that the hairsprings (3) are made from a blank made of metal or metal alloy.

3. 3. A method according to claim 2, characterized in that the blank is covered with a surface layer of ductile material.

4. 3. The method of claim 2, wherein the metal or metal alloy is selected from titanium, niobium, zirconium, or a combination of these metals.

5. 2. The method according to claim 1, wherein the plurality of hairsprings (3) are shaped by drawing and / or rolling the blank, alternating with at least one heat treatment step, and the step of winding and shaping the hairspring is carried out before a final heat treatment step.

6. 4. The method of claim 3, characterized in that the ductile surface layer is removed after rolling and before winding.

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