Friction system for a clock movement

Abstract

The invention relates to a friction system (100) for a watch movement comprising: - an axis (1) arranged to be mounted in the watch movement; - a first fixed element (2), mounted on the axis; - a second fixed element (4), mounted on the axis; - a toothed member (3), mounted freely rotatable on the axis between the first fixed element and the second fixed element; - a third fixed element (6), mounted on the axis; - a spring (5) mounted on the axis (1) and arranged between the second fixed element (4) and the third fixed element (6).According to the invention, the spring (5) is in the form of a washer comprising an inner part (51) close to the axis (1) bearing against the third fixed element (6), and an outer peripheral part of the washer resting in elastic support against an annular element of the second fixed element (4), the spring being elastically deformed and forming a kinematic connection both between the first fixed element (2) and the toothed member (3), and between the second fixed element (4) and the toothed member (3) up to a predefined friction torque.

Description

Technical field of the invention

[0001] The invention relates to the field of mechanical watchmaking. It concerns, more particularly, a friction system for a watch movement. Technological background

[0002] Friction systems are commonly used in watch movements. They are used to keep a first component rotating with a second component until a torque limit is reached. Once this limit is exceeded, the two components are no longer rotating together. This type of system is generally used for hour and minute display devices, particularly on cannon-pinion surfaces to drive display hands or display discs.

[0003] Usually, the cannon-pinion is lantern-shaped to ensure friction between the cannon-pinion and a tiger-pinion. Lantern-shaped operation consists of pinching the constriction of a tube in the cannon-pinion opposite a bearing or clearance of the tiger-pinion. This pinching is a manual task, and its result depends on the dexterity and sensitivity of the watchmaker, and is therefore random, which is unfortunate, because the lantern-shaped operation is intended to ensure a certain level of friction between the tiger-pinion and the cannon-pinion during normal operation of the watch, while manual time-setting operations by the user apply a torque greater than that of friction, which friction torque should therefore not be too high.

[0004] Correct adjustment of the friction torque is therefore delicate. Precise control of the applied clamping force is therefore important, and conventional manual lanterning does not allow this precision or the required reproducibility to be achieved.

[0005] Another disadvantage is that lantern frictions do not support the transmission of high torque and are sensitive to assembly / disassembly.

[0006] There are other solutions for obtaining friction such as foils, but the latter have manufacturing repeatability that is difficult to guarantee from one batch to another.

[0007] There are also coil springs, but these are too bulky. Summary of the invention

[0008] The invention aims in particular to overcome the various drawbacks of the prior art.

[0009] The invention also aims to provide a friction system which allows the transmission of high torque, is easy to manufacture, and whose friction repeatability is easily manageable.

[0010] To this end, the present invention relates to a friction system for a watch movement comprising: an axis arranged to be mounted in the watch movement; a first fixed element, mounted on the axis; a second fixed element, mounted on the axis; a toothed member, mounted freely rotatable on the axis between the first fixed element and the second fixed element; a third fixed element, mounted on the axis; a spring mounted on the axis and arranged between the second fixed element and the third fixed element.

[0011] According to the invention, the spring is in the form of a washer comprising an inner part close to the axis bearing against the third fixed element, and an outer peripheral part of the washer resting in elastic support against an annular element of the second fixed element, the spring being elastically deformed and forming a kinematic connection both between the first fixed element and the toothed member, and between the second fixed element and the toothed member up to a predefined friction torque.

[0012] According to other advantageous variants of the invention: the washer comprises at least two lugs arranged at its outer periphery, the lugs being arranged to rest in elastic support against the annular element of the second fixed element; the first fixed element and the toothed member each have a conical contact surface; the axis comprises a bearing surface arranged to cooperate with a flat of the second fixed element; the third fixed element is in the form of a ring, the ring having an excess thickness near the hole by which it is mounted on the axis, the excess thickness being arranged to bear against the spring; the second fixed element has a conical contact surface with the lugs of the spring; the lugs at the outer periphery of the spring and the inner part are in two different planes.

[0013] The invention also relates to a watch movement comprising a friction system in accordance with the invention. Brief description of the figures

[0014] Other characteristics and advantages of the invention will appear on reading the following detailed description given by way of non-limiting example, with reference to the appended drawings in which: there Figure 1 represents a perspective view of a friction system according to the invention; Figure 2 represents an exploded view of a friction system according to the invention; the Figure 3 represents a sectional view along axis AA of a friction system according to the invention. Detailed description of the invention

[0015] In reference to the Figure 1 , a friction system 100 according to the invention is shown. This system comprises an axis 1 arranged to be mounted in a clockwork movement, the axis may comprise parts with sections 10, 11 of different diameters

[0016] The axis 1 carries a toothed member 3, here a pinion, mounted freely in rotation on the axis 1. Alternatively, this toothed member 3 can be a wheel. The axis 1 can also carry several toothed members, and can take a large number of known forms according to the needs of those skilled in the art.

[0017] As shown in the Figure 2 , the system comprises a first fixed element 2, such as a flange, driven onto the axis and extending perpendicular to the axis 1. This flange 2 has a first conical bearing surface 20 and serves as a first friction surface between the toothed member 3 and the flange 2.

[0018] The system 100 also comprises a second fixed element 4, the toothed element being positioned and rotating around the axis 1, between the first fixed element 2 and the second fixed element 4. The second fixed element 4 is in the form of a collar comprising a rib 42 of annular shape on its face oriented towards the toothed element 3 forming an annular bearing surface between the toothed element 3 and the second fixed element 4.

[0019] The collar 4 has on its other face an annular peripheral rim 40 forming a skirt, an empty space 43 thus extending between the annular peripheral rim 40 and the center of the collar 4. As can be seen in Figure 3 , the annular peripheral rim 40 is beveled so as to form a conical bearing surface.

[0020] Advantageously, the axis 1 comprises a bearing surface 12 arranged to cooperate with a flat 41 of the second fixed element 4. Such an arrangement makes it possible to slide the second fixed element 41 onto the axis while guaranteeing its correct position and its correct retention on the axis once mounted.

[0021] The system also comprises a third fixed element 6 which is mounted or driven onto the axis 1. This third fixed element is in the form of a ring 6, the ring 6 having an excess thickness 60 near the hole 61 by which it is mounted onto the axis 1. The excess thickness 60 has a diameter smaller than that of the ring 6 and forms an annular bearing surface 62 for a spring 5.

[0022] The spring 5 is mounted fixed or movable around the axis 1 and is arranged between the second fixed element and the third fixed element.

[0023] The spring 5 is in the form of a flat washer comprising an inner part 51 in the immediate vicinity of the axis 1 which bears against the third fixed element 6, and more precisely bears against the excess thickness 6, and an outer peripheral part bearing elastically against the conical surface 40 of the skirt 4.

[0024] At rest, the spring 5 is in the form of a flat washer, which then deforms elastically when it is stressed between the second fixed element 4 and the third fixed element 5. The use of a flat washer is particularly advantageous because the use of a flat part makes it easier to reproduce the latter, in particular compared to a curved element for example.

[0025] According to one embodiment of the invention, the spring 5 comprises at least two lugs 50 arranged at the outer periphery of the washer and are arranged to rest in elastic support against the conical support surface 40 of the second fixed element 4. Thus, when all of the parts are mounted, the spring 5 makes it possible to form a kinematic connection both between the first fixed element 2 and the toothed member 3, and between the second fixed element 4 and the toothed member 3 up to a predefined friction torque.

[0026] Preferably, and as illustrated in the figures, the spring 5 has three lugs so as to provide better distribution of forces and also facilitate the deformation of the spring.

[0027] The lugs 50 are distributed on the washer 5 at identical angular distances to provide a good distribution of the bearing force on the annular peripheral edge 40 of the collar 4. In the illustrated case, the three lugs are arranged at 120° from each other. In the case where the number of lugs is greater, for example five lugs, the latter would be arranged at 72° from each other.

[0028] According to a particularly advantageous aspect, the friction torque can be perfectly adjusted by precisely driving the ring 6 onto the axis 1 against the spring 5, the elastic force exerted by the spring 5 on the fixed element 4 making it possible to obtain a very precise friction torque.

[0029] When the system is assembled, as shown in the Figure 3, the lugs 50 located on the outer periphery of the spring 5 and the inner part 51 are located in two different planes, the assembly causing the spring 5 to flex in order to constrain it between the ring 6 and the collar 4.

[0030] The stress of the spring 5 can therefore be modified by acting on the gap between the planes of the bearing surfaces 62 and 40, by moving the ring 6 on the axis 1, and consequently the friction torque that the system can undergo before the toothed member 3 pivots relative to the axis 1. Such an arrangement thus allows an extremely simple and easily reproducible adjustment.

[0031] The invention also relates to a watch movement comprising a friction system according to the invention.

[0032] The invention also relates to a method of assembling a friction system according to the invention, the method comprising the following steps: providing an axis 1; driving a first fixed element 2 onto the axis 1 into a predetermined position; sliding a toothed member 3 onto the axis 1 as far as the first fixed element 2; sliding the second fixed element 4 onto the axis 1, orienting the second fixed element 4 relative to the axis by means of a flat 41 cooperating with a bearing surface 12 formed on the axis 1; placing a spring 5 provided with at least three lugs 50 arranged on the outer periphery of the spring 5, the lugs 50 resting against the second fixed element 4; gradually driving a third fixed element 6 onto the axis 1, so as to compress the spring 5 between the second fixed element 4 and the third fixed element 6, to obtain a kinematic connection both between the first element and the toothed member, and between the second fixed element and the toothed member until a predefined friction torque is obtained.

[0033] Of course, the present invention is not limited to the illustrated example and is susceptible to various variants and modifications which will appear to those skilled in the art, without departing from the scope of the invention as defined by the claims.

Claims

1. Friction system (100) for a watch movement comprising: - an axis (1) arranged to be mounted in the watch movement; - a first fixed element (2), mounted on the axis; - a second fixed element (4), mounted on the axis; - a toothed member (3), mounted freely rotatable on the axis between the first fixed element and the second fixed element; - a third fixed element (6), mounted on the axis; - a spring (5) mounted on the axis (1) and arranged between the second fixed element (4) and the third fixed element (6);the spring (5) being in the form of a flat washer comprising an inner part (51) close to the axis (1) bearing against the third fixed element (6), and an outer peripheral part of the washer resting in elastic support against an annular element of the second fixed element (4), the spring being arranged to be placed under stress to deform elastically between the second fixed element (4) and the third fixed element (6), and to form a kinematic connection both between the first fixed element (2) and the toothed member (3), and between the second fixed element (4) and the toothed member (3) up to a predefined friction torque.; 2. System according to claim 1, characterized in that the washer comprises at least two lugs (50) arranged at its outer periphery, the lugs (50) being arranged to rest in elastic support against the annular element of the second fixed element (4).

3. System (100) according to claim 1 or 2, characterized in that the first fixed element (2) and the toothed member (3) each have a conical contact surface (20, 30).

4. System (100) according to one of claims 1 to 3, characterized in that the axis (1) comprises a bearing surface (12) arranged to cooperate with a flat (41) of the second fixed element.

5. System (100) according to one of claims 1 to 4, characterized in that the third fixed element (6) is in the form of a ring, the ring having an excess thickness (60) near the hole (61) by which it is mounted on the axis (1), the excess thickness (60) being arranged to bear against the spring (5).

6. System (100) according to one of claims 1 to 5, characterized in that the second fixed element (4) has a conical contact surface (40) with the lugs (50) of the spring (5).

7. System (100) according to one of claims 1 to 6, characterized in thatthe lugs (50) on the outer periphery of the spring (5) and the inner part (51) are located in two different planes.

8. Method for assembling a friction system according to the invention, the method comprising the following steps: - providing an axle (1); - driving a first fixed element (2) onto the axle (1) into a predetermined position; - sliding a toothed member (3) onto the axle (1) as far as the first fixed element (2); - sliding a second fixed element (4) onto the axle (1), orienting the second fixed element (4) relative to the axle (1) by means of a flat (41) cooperating with a bearing surface (12) formed on the axle (1); - placing a spring (5) onto the axle 1, ; - gradually driving a third fixed element (6) onto the axis (1), so as to compress the spring (5) between the second fixed element (4) and the third fixed element (6), to obtain a kinematic connection both between the first element and the toothed member, and between the second fixed element and the toothed member until a predefined friction torque is obtained.

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