TWI767384B - Timepiece balance - Google Patents

Abstract

The invention relates to a balance for a horological movement, comprising rigid parts consisting of a hub defining the pivot axis of said balance, at least one felloe sector, at least one arm connecting said at least one felloe sector to the hub, and including at least one slot for receiving and gripping an inertia-block in position, said at least one slot being delimited on the one hand by said at least one arm, and on the other hand an elastic arm including a first end integral with the arm, and a second distal end free relative to said hub, to said arm, and to said felloe sector.

Description

Hour hand balance

The present invention relates to a balance wheel for a timepiece movement, comprising a rigid part consisting of a hub defining the pivot axis of the balance wheel, a rim, and at least one arm connecting the rim to the hub, and comprising at least A holding mechanism for receiving and grasping the rod of the inertia-block in place.

The present invention relates to the field of horological oscillators and, more particularly, to the field of balance wheels comprising means for adjusting inertia and/or balance.

Several embodiments of balances are known, which have means for adjusting inertia and/or balance. In particular, it is known to have a balance with an inertia mass locked or driven into an implantation of the rim of the balance. Some achievements have attempted to hold inertia blocks by grasping. Thus, document CH 705238 is known, which discloses a balance wheel comprising at least one groove for receiving and gripping the rod of the inertial mass in positioning, this groove being delimited on the one hand by a rigid part of the balance wheel, and On the other hand, this slot is delimited by a resilient arm permanently returning towards the rigid part of the balance, holding the mass of inertia.

When the inertial mass is inserted, the elastic arm undergoes significant plastic deformation due to its stretching. These plastic deformations create residual stress in the traction on the surface. Since most balance wheels are made of copper alloys, there is a risk of cracking under stress. Consequently, this can adversely affect the reliability of the balance, or even damage the balance, since the inertial mass can no longer be held correctly by the elastic arms and becomes dislodged.

The aim of the present invention is in particular to overcome the various disadvantages of these known techniques.

More specifically, the object of the present invention is to provide a balance wheel that enables the retention of the inertial mass to be ensured by elastic arms with a state of compressive stress at the bottom of the groove, and thus minimising the risk of defects.

Another object of the present invention is to provide a balance wheel with elastic arms having a sufficiently rigid geometry and allowing sufficient bearing forces so that the mass of inertia is held in the position to which the watch is subjected when it is worn.

These and other objects, which will become clearer hereinafter, are achieved according to the present invention by a device for a balance wheel of a timepiece movement as claimed in claim 1 .

Other advantageous variants according to the invention: - The second region is positioned between the first region and the neutral fibre of the elastic arm. - the vertical displacement of the free distal end (5A) of the elastic arm is contained between 1 μm and 100 μm from its rest position; - the elastic arm defines a slope with an elevation angle comprised between 1 and 5 degrees; - When the inertia block is installed, the elastic arm provides a holding force of at least 0.1N; - the arm includes notches for positioning the inertial mass; - at least one elastic arm and balance wheel are made in one piece; - The balance wheel includes several elastic arms, and the elastic arms are set to be centrosymmetric around the center of the balance wheel.

The invention also relates to a timepiece movement comprising a balance spring oscillator system according to the invention.

The invention also relates to a timepiece comprising a timepiece movement according to the invention.

The invention also relates to a method according to the invention for mounting an inertia mass on a balance.

Thus, with the various functional and structural aspects described above, the object of the present invention allows to obtain a more stable balance wheel, in particular due to the disappearance of tensile stresses on the surface at the bottom of the groove for receiving the inertial mass, which The formation of weakened regions is restricted.

A balance wheel according to an exemplary embodiment will now be described below with reference to Figures 1 to 4b in combination.

The present invention concerns a balance wheel 1 for a timepiece movement. The balance wheel comprises a rigid part consisting of a hub 2 whose center defines the pivot axis A of the balance wheel 1 , a rim 3 , and at least one arm 4 connecting the rim 3 to the hub 2 .

The balance wheel is made of copper, or a copper alloy (eg, nickel silver), according to the needs of those skilled in the art. The balance wheel can also be made of aluminium, aluminium alloys, titanium or titanium alloys, gold or gold alloys, platinum or platinum alloys.

The balance wheel 1 further comprises at least one elastic arm 5 comprising a first end 5B integral with the arm 4 of the balance wheel 1, and a second distal end 5A opposite to the hub 2, the at least one arm 4, With the rim sector 3 free, the free end 5A can be deformed in the plane of the rim and clamp the inertia mass 6 on the balance. The balance wheel also has a slot 7 capable of receiving the mass 6 of inertia, which is delimited on the one hand by the elastic arm 5 and, on the other hand, by the balance arm 4 , which is permanently oriented towards the end of the balance wheel 1 . Arm 4 is restored to delimit slot 7 .

Preferably, the resilient arms 5 extend substantially radially with respect to the pivot axis A, or parallel to the radius from the pivot axis A.

According to another embodiment, the spring arm 5 is inclined in the direction of the balance arm 4 such that the horizontal distance between the arm 4 and the spring arm 5 increases between the distal end 5A and the first end 5B integral with the arm 4 . As can be seen in FIG. 1 , the elastic arm 5 defines a slope relative to the arm 4 , this slope having an elevation angle α comprised between 1 and 5 degrees.

The elastic arm 5 is configured to be moved vertically away from its rest position according to the vertical displacement of the elastic arm 5 comprised between 1 μm and 100 μm, to ensure plastic deformation at the bottom of the groove, this vertical displacement also depends on the inertia of the placed The diameter of the foot of the block.

According to the invention, the spring arm 5 is configured to switch from a position called a rest position, in which the spring arm is not subjected to any stress, to a stress position, in which the free distal end 5A of the spring arm 5 is at the edge of the rim. is displaced vertically from its rest position in plane relative to the balance arm 4 to obtain a thickness in the first region 71 at the bottom 70 of the groove 7 that exceeds that contained between 1 μm and 300 μm from the bottom of the groove plastic deformation. The bottom of the groove or groove bottom means the inner joint area between the spring arm 5 and the balance arm 4 .

The displacement of the free distal end 5A of the elastic arm 5 of the spring arm 5 for placing the inertial mass 6 from its rest position to the stress position also results in the displacement of the Elastically deformed, this second area 72 is positioned between the first area 71 and the neutral fiber F of the elastic arm and tends to return the elastic arm 5 to its rest position.

The return of the spring arm 5 from the stressed position to its rest position allows the inertial mass to be grasped and held in place, this return to the rest position also allows to create a surface acting on the bottom of the groove at a thickness comprised between 1 µm and 50 µm compressive stress on.

According to the invention, the vertical displacement of the free distal end 5A of the elastic arm 5 from its rest position is comprised between 1 μm and 5 μm and is sufficient to plastically deform the bottom of the groove 7 .

The inventors have unexpectedly discovered that, by deforming the bottom of the groove in a plastic field, this allows the bottom of the groove to undergo compression and no longer, unlike the habit of those skilled in the art trying to stay within the elastic range. Tighten as is common in the prior art. Its main advantage is that it compensates for defects that can form at the bottom of the grooves, eg microcracks, this region acting under compression and thus becoming less subject to these defects.

The slot 7 has an opening 9 which allows the end 5A of the spring arm to be displaced vertically relative to the balance arm 4 in the plane of the rim and in contact with the inertial mass 6 to clamp it when it is placed in the slot 7 on the balance arm.

In the example shown in Figures 4a and 4b, the inertial mass 6 is equipped with feet 65, the rod 62 is then connected to a head 61, both the head 61 and the feet 65 have a diameter that is larger than that of the rod 62 to attach the inertial mass 6 The travel of the elastic arm 5 is limited in a direction parallel to the pivot axis A, or even fixed in this direction.

The balance arm includes notches 11 to precisely position the inertia mass 6 and hold it in place. The width of the opening 9 is set to be less than the diameter of the inertial mass, or the diameter of the rod of the inertial mass, to hold the inertial mass in place.

The inertial mass 6 comprises a head 61 comprising an adjustment profile 63 arranged to cooperate with the tool. The inertial mass 6 may comprise a rod 62 extending from this head 61 , the head 61 having a diameter that is greater than the diameter of the rod 7 .

The rod 62 of the inertial mass extends along an axis through the centre of the inertial mass 6 around which the mass can be oriented angularly by means of the tool on the adjustment profile 63 once gripped in the clamping mechanism 5 . The inertial mass 6 includes an imbalance about this axis, which is caused, for example, by a flat section 64 made on the head 61 .

When the inertial mass 6 is placed in the notch 11 of the opening 9 , the free end 5A of the elastic arm 5 is displaced perpendicular to the general direction of the radius formed by the rigid arm 4 extending from the hub 2 to the rim 3 .

Obviously, the arm 4 without the notch will hold the inertial mass 6 in position by clamping the elastic arm 5 .

In a preferred embodiment, as seen in Figures 1 and 3, the slot 7 extends radially with respect to the pivot axis A, or parallel to the radius from the pivot axis A. This embodiment is advantageous because it deforms the rim 3 of the balance wheel 1 very little, the deformation when the inertia mass 3 is installed, which is hardly measurable by conventional measuring means.

In this embodiment, the end 5B of the resilient arm 5 is integral with the arm 4 which is arranged substantially radially with respect to the pivot axis A.

Preferably, the distal end 5A is further away from the pivot axis A than the end 5B.

According to the invention, the spring arm is arranged to deform when the inertia mass 6 is assembled to the balance, the free end 5A of the spring arm 5 being able to displace perpendicularly relative to the arm 4 in the plane of the rim.

When the inertial mass is placed by mechanically opening the arm, the plastic deformation of the surface at the bottom of the lip is sufficient to cause the surface of the article at the bottom of the slot to experience compressive forces during elastic recovery of the arm. Furthermore, this elastic return ensures the retention of the inertial mass.

The size and geometry of the spring arm 5 is determined to obtain the minimum desired force for holding the inertial mass, the holding force obtained by the spring arm is less than 0.1 N.

The dimensions of the elastic arm 5 allow significant elastic energy to be stored from the deformation of the arm, the stored deformation energy producing a restoring force on the rod of the inertial mass clamped by the elastic arm 5, This ensures that its forces and torques remain in the notch 11 .

By virtue of the asymmetry of the spring arm 5 , the invention allows to obtain a satisfactory holding force for the inertial mass and overcomes the disadvantages associated with the formation of areas subject to tension when the arm rests on the inertial mass 6 .

The invention also concerns an assembled balance comprising such a balance 1 and at least one inertial mass 6 comprising a rod 62 whose smallest diameter is greater than the width of the groove 7 in the free state and whose largest The diameter is smaller than the width of the groove 7 when the elastic arm 5 is stretched from the rigid part of the balance 1 under the action of the stretching force applied to the elastic arm 5 delimiting the groove 7 .

The invention also relates to a method for mounting an inertial mass on the balance wheel described above. The installation method according to the present invention comprises the following steps: a) Place the balance wheel 1 on the support and hold it in place; b) Extending the spring arm 5 from its rest position, in which the spring arm is not subjected to any stress, to a stress position in which the free distal end 5A of the spring arm 5 is in the plane of the rim relative to the balance arm 4 is displaced vertically to plastically deform the first region 71 at the bottom 70 of the groove 7 beyond a thickness comprised between 1 μm and 300 μm from the bottom 70 of the groove when displacing the free distal end of the elastic arm , and elastically deform the second area 72 contained between the neutral fiber F of the elastic arm 5 and the bottom 70 of the groove; c) Place the inertia block 6 at the notch 11 so that the foot 62 partially rests in the slot 7; d) release the elastic arm 5 so that it returns to its resting position to grip the feet of the inertial mass and create compressive stress on the surface of the bottom of the slot; e) Displace the inertial mass 6 to position it precisely so that the head of the inertial mass is in contact with the upper or lower surface of the elastic arm 5 and the upper or lower surface of the arm 4.

The invention also concerns a balance 1 comprising a plurality of elastic arms 5 each arranged to receive at least one inertial mass 6 .

The invention also relates to a timepiece movement comprising at least one balance 1 of this type as described above.

The invention also relates to a timepiece comprising at least one such movement, which is preferably a wristwatch.

1: balance wheel 2: Wheel hub 3: Rim 4: Arm 5: Elastic arm (clamping mechanism) 5A: Second distal end (free (distal) end) 5B: First End 6: Inertia block 7: Groove 9: Opening 11: Notch 61: Head 62: Rod 63: Adjust the outline 64: Flat section 65: Feet 70: Bottom 71: The first area 72: Second area A: pivot axis F: neutral fiber α: Elevation angle

Other features and advantages of the present invention will become more apparent on reading the following description of specific embodiments of the invention, given by way of simple illustration and non-limiting example, and the accompanying drawings, in which: - [FIG. 1 ] is a top view of the balance according to the invention; - [ FIG. 2 ] is a detail view of the elastic arm of the balance according to the invention in its rest position; - [ FIG. 3 ] is the elastic arm of the balance according to the invention in Detail view of its extended position; and - [Figures 4a and 4b] are schematic views of an inertial mass that can be used with a balance according to the invention.

1: balance wheel

2: Wheel hub

3: Rim

4: Arm

5: Elastic arm (clamping mechanism)

5A: Second distal end (free (distal) end)

5B: First End

6: Inertia block

7: Groove

9: Opening

11: Notch

62: Rod

A: pivot axis

Claims (12)

A balance wheel (1) for a timepiece movement, comprising a rigid part consisting of a hub (2) defining a pivot axis (A) of the balance wheel (1), at least one rim sector (3), the At least one rim sector (3) is connected to at least one arm (4) of the hub (2) and comprises at least one slot (7) for receiving and gripping the inertial mass (6) in position, the At least one slot (7) is bounded on the one hand by the at least one arm (4) and on the other hand by a resilient arm (5) comprising a first end (5B) and a second The distal end (5A), the first end (5B) is integral with the arm (4), the second distal end (5A) is relative to the hub (2), the arm (4), and the rim sector ( 3) Free, characterized in that the resilient arm (5) is configured to switch from a rest position, in which the resilient arm (5) is not subject to any stress, to a stress position, in which the stress position is The free distal end (5A) of the spring arm (5) is displaced vertically relative to the balance arm (4) in the plane of the rim so that upon displacement of the free distal end (5A) of the spring arm, The first region (71) at the bottom (70) of the groove (7) is plastically deformed beyond a thickness comprised between 1 μm and 300 μm from the bottom (70) of the groove and is made to be contained within the groove (70). The second area (72) between the neutral fibers (F) of the elastic arm (5) and the bottom (70) of the groove is elastically deformed and at the bottom of the groove as the elastic arm returns to its rest position compressive stress on the surface. The balance wheel (1) for a timepiece movement as claimed in claim 1, wherein the second region (72) is located between the first region (71) and the neutral fiber (F) of the elastic arm. A balance wheel (1) for a watch movement according to claim 1, Therein, the vertical displacement of the free distal end (5A) of the elastic arm (5) is comprised between 1 μm and 100 μm from its rest position. A balance wheel (1) for a timepiece movement as claimed in claim 1, wherein the elastic arm (5) is inclined in the direction of the balance wheel arm (4) so that the arm (4) and the elastic arm ( 5) The horizontal distance between the distal end (5A) and the first end (5B) increases. A balance wheel (1) as claimed in claim 1, wherein the elastic arm (5) defines a slope having an elevation angle α comprised between 1 and 5 degrees. The balance wheel (1) of claim 1, wherein when the inertia mass is installed, the elastic arm provides a holding force of at least 0.1N. The balance wheel (1) of claim 1, wherein the arm (4) comprises a notch (11) for positioning the inertial mass, the distance between the bottom of the notch (11) and the arm (4) being less than The diameter of the rod of this inertial mass. The balance of claim 1, wherein the at least one elastic arm (5) and the balance (1) are made in one piece. The balance wheel of claim 1, wherein the balance wheel comprises a plurality of elastic arms (5), and the elastic arms are arranged to be centrally symmetric with the center of the balance wheel as the center. A timepiece movement comprising at least one balance wheel (1) as claimed in claim 1. A timepiece comprising at least one timepiece movement as claimed in claim 10, wherein the timepiece is a wristwatch. A method for installing the inertia block (6) in the The method on the balance wheel (1), the installation method comprises the following steps: placing the balance wheel (1) on a support and holding it in position; extending the elastic arm (5) from its rest position to Stress position; placing the inertial mass (6) at the notch (11) of the arm (4) so that the inertial mass partially rests in the slot (7) at the notch (11); and releasing the elasticity arm (5) so that the resilient arm returns to its rest position.

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