Friction system for horological movement

Abstract

To provide a friction system that allows transmission of a high torque, that is easy to manufacture, and whose friction repeatability is easy to manage.SOLUTION: A friction system 100 for a horological movement includes: a shaft 1; a first fixed element 2 mounted on the shaft 1; a second fixed element 4 mounted on the shaft 1; a toothed member 3 mounted to rotate freely on the shaft between the first fixed element 2 and the second fixed element 4; a third fixed element 6 mounted on the shaft 1; and a spring 5 mounted on the shaft 1 and arranged between the second fixed element 4 and the third fixed element 6. The spring 5 takes the form of a washer including an inner portion close to the shaft 1 abutting on the third fixed element 6, and an outer peripheral portion of the washer elastically abutting on an annular element of the second fixed element 4. The spring 5 is elastically deformed and forms a kinematic link 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 predetermined friction torque.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of mechanical watch manufacturing. More particularly, it relates to a friction system for a watch movement.

Background Art

[0002] Friction systems are commonly used in watch movements to connect a first member to a second member for rotating the first member together with the second member until a torque limit value is reached. When this limit value is exceeded, the two members are no longer connected to rotate integrally. Usually, this type of system is used in a cannon pinion, especially for driving an indicating hand or an indicating disk, for time and minute indicating means.

[0003] The cannon pinion is usually snap-fitted by indentation to ensure friction between the cannon pinion and the arbor. The indentation consists of applying pressure to the tube contained in the cannon pinion on the opposite side of the shoulder or clearance of the arbor. This pressure is applied manually, and the result is unpredictable because it depends on the skill and sensitivity of the watchmaker. This is unfortunate because the purpose of the indentation is to ensure a certain level of friction between the arbor and the cannon pinion during the normal operation of the watch, but the manual hand setting operation performed by the user applies a torque greater than the frictional torque, so the frictional torque must not be too high.

[0004] Therefore, precise adjustment of the frictional torque requires care. Thus, it is important to accurately control the clamping force applied, and conventional manual indentation cannot obtain this accuracy or the required reproducibility.

[0005] Another drawback is that the friction obtained by indentation cannot withstand high-torque transmission and is sensitive to assembly and disassembly.

[0006] There are also other solutions for obtaining friction, such as metal foils, but it is difficult to guarantee the reproducibility of their manufacture for each batch.

[0007] There are also helical springs, but these take up too much space.

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0008] The main object of the present invention is to overcome various drawbacks of the prior art.

[0009] The present invention also aims to provide a friction system that enables high-torque transmission, is easy to manufacture, and facilitates management of friction reproducibility.

MEANS FOR SOLVING THE PROBLEM

[0010] For this purpose, the present invention is a friction system for a watch movement, comprising: · a shaft intended to be attached to the watch movement; · a first fixed element attached to the shaft; · a second fixed element attached to the shaft; · a toothed member rotatably mounted freely on the shaft between the first fixed element and the second fixed element; · a third fixed element attached to the shaft; · a spring attached to the shaft and disposed between the second fixed element and the third fixed element. The friction system is related to.

[0011] According to the present invention, the spring takes the form of a washer including an inner portion close to the shaft abutting against the third fixed element and an outer peripheral portion of the washer elastically abutting against the annular element of the second fixed element. The spring is elastically deformed to form a chain link both between the first fixed element and the toothed member and between the second fixed element and the toothed member up to a predetermined frictional torque.

[0012] According to another advantageous alternative embodiment of the present invention, · The washer includes at least two catches arranged on its outer periphery, and the catches are arranged to elastically abut against the annular element of the second fixing element. · The first fixing element and the toothed member each have a conical contact surface. · The shaft includes a shoulder intended to cooperate with the flat part of the second fixing element. · The third fixing element takes the form of a ring, and the ring has an over-thickness portion near the hole for attaching the ring to the shaft, and the over-thickness portion is arranged to abut against the spring. · The second fixing element has a conical contact surface with the catch of the spring. · The catches on the outer periphery and the inner part of the spring are in two different planes.

[0013] The present invention further relates to a timepiece movement including a friction system according to the present invention.

Brief Description of the Drawings

[0014] Other features and advantages of the present invention will become apparent from the following detailed description, given by way of example and not in any way limiting, with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] Figure 1 shows a friction system 100 according to the present invention. This system includes a shaft 1 arranged to be attached to a timepiece movement, and this shaft can include portions having sections 10, 11 of different diameters.

[0016] Shaft 1 supports a toothed member 3, in this case a pinion, which is mounted so as to rotate freely on shaft 1. Alternatively, this toothed member 3 may be a wheel. Shaft 1 can also support a plurality of toothed members and can take a number of known shapes depending on the needs of those skilled in the art.

[0017] As shown in Figure 2, the system includes a first fixing element 2, such as a flange, which is pushed onto shaft 1 and extends perpendicular to shaft 1. This flange 2 has a first conical seating surface 20 and functions as a first friction surface between the toothed member 3 and the flange 2.

[0018] System 100 further includes a second fixing element 4, and the toothed element is disposed between the first fixing element 2 and the second fixing element 4 and rotates around shaft 1. The second fixing element 4 takes the form of a collar that includes an annular rib 42 on its surface facing the toothed element 3, and forms an annular seating surface between the toothed element 3 and the second fixing element 4.

[0019] On the other hand, the collar 4 has an annular peripheral portion 40 that forms a skirt and has a void space 43 extending between the annular peripheral portion 40 and the center of the collar 4. As can be seen in Figure 3, the annular peripheral portion 40 is inclined so as to form a conical seating surface.

[0020] Advantageously, shaft 1 includes a shoulder 12 arranged to cooperate with a flat portion 41 of the second fixing element 4. This arrangement allows the second fixing element 41 to slide on the shaft and ensures that it is accurately positioned and held on the shaft after installation.

[0021] The system further includes a third fixing element 6 attached or pushed onto shaft 1. This third fixing element takes the form of a ring 6, and the ring 6 has an excess thickness portion 60 near a hole 61 for attaching the ring 6 to shaft 1. The excess thickness portion 60 has a diameter smaller than the diameter of the ring 6 and forms an annular seating surface 62 for spring 5.

[0022] The spring 5 is mounted so as to be able to move around the shaft 1 or not to move, and is arranged between the second fixed element and the third fixed element.

[0023] The spring 5 takes the form of a flat washer including an inner portion 51 near the shaft 1 that abuts against the third fixed element 6, more precisely against the excess thickness portion 6, and an outer peripheral portion that elastically abuts against the conical surface 40 of the skirt 4.

[0024] At rest, the spring 5 takes the form of a flat washer and elastically deforms when stressed between the second fixed element 4 and the third fixed element 5. The use of a flat washer is particularly advantageous because, for example, reproduction is facilitated by the use of a flat portion, especially as compared to a domed element.

[0025] According to one embodiment of the invention, the spring 5 includes at least two catches 50 arranged on the outer periphery of the washer, and the catches 50 are intended to elastically abut against the conical seating surface 40 of the second fixed element 4. Thus, when all the parts are assembled, the spring 5 is able to form a chain link 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 predetermined frictional torque.

[0026] Preferably, as shown in the figure, the spring 5 has three catches for improving the force distribution and facilitating the deformation of the spring.

[0027] The catches 50 are arranged at the same angular distance on the washer 5 for a good distribution of the supporting force on the annular peripheral portion 40 of the collar 4. In the example shown, the three catches are arranged at 120° to each other. When the number of catches is large, for example in the case of five catches, the catches are arranged at 72° to each other.

[0028] According to a particularly advantageous aspect, the frictional torque can be fully adjusted by accurately pushing the ring 6 onto the shaft 1 against the spring 5, and a very accurate frictional torque can be obtained by the elastic force exerted by the spring 5 on the fixed element 4.

[0029] As shown in Figure 3, when the system is assembled, the catch 50 on the outer periphery and the inner part 51 of the spring 5 are arranged in two different planes, and the assembly bends the spring 5 to apply stress between the ring 6 and the collar 4.

[0030] Thus, the stress of the spring 5 can be changed by moving the ring 6 on the shaft 1 and acting on the distance between the planes of the seating surface 62 and the seating surface 40. As a result, the frictional torque that the system can withstand before the toothed member 3 rotates relative to the shaft 1 can be changed. Such an arrangement can make the adjustment extremely simple and easy to reproduce.

[0031] The present invention further relates to a timepiece movement comprising a friction system according to the present invention.

[0032] The present invention further relates to a method of assembling a friction system according to the present invention, comprising: · a step of providing a shaft 1; · a step of pushing the first fixing element 2 onto the shaft 1 to a predetermined position; · a step of sliding the toothed member 3 on the shaft 1 to the first fixing element 2; · a step of sliding the second fixing element 4 on the shaft 1 while orienting the second fixing element 4 relative to the shaft by means of a flat portion 41 cooperating with a shoulder 12 formed on the shaft 1; · a step of arranging a spring 5 having at least three catches 50 arranged on the outer periphery of the spring 5, the catches 50 abutting against the second fixing element 4; · a step of gradually pushing the third fixing element 6 onto the shaft 1 and compressing the spring 5 between the second fixing element 4 and the third fixing element 6 in order to obtain a chain link both between the first element and the toothed member and between the second fixing element and the toothed member until a predetermined frictional torque is obtained. and relates to a method including the above steps.

[0033] Needless to say, the present invention is not limited to the illustrated embodiments, and various alternative means and modifications will be apparent to those skilled in the art within the scope of the present invention defined by the claims.

Claims

1. A friction system (100) for a watch movement, comprising: - a shaft (1) intended to be attached to a watch movement; - a first fixed element (2) attached to said shaft; - a second fixed element (4) attached to said shaft; - a toothed member (3) mounted on said shaft so as to rotate freely between said first fixed element and said second fixed element; - a third fixed element (6) attached to said shaft; - a spring (5) attached to said shaft and arranged between said second fixed element (4) and said third fixed element (6); wherein said spring (5) is in the form of a flat washer comprising an inner part (51) close to said shaft (1) abutting against said third fixed element (6) and an outer peripheral part of a washer elastically abutting against an annular element of said second fixed element (4); said spring is arranged to be stressed so as to elastically deform between said second fixed element (4) and said third fixed element (6), and is arranged to form a chain link both between said first fixed element (2) and said toothed member (3) and between said second fixed element (4) and said toothed member (3) up to a predetermined frictional torque. A friction system.

2. The system according to claim 1, characterized in that said washer comprises at least two catches (50) arranged on its outer periphery, said catches (50) being arranged to elastically abut against an annular element of said second fixed element (4).

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

4. The system (100) according to claim 1, characterized in that said shaft (1) comprises a shoulder (12) arranged to cooperate with a flat part (41) of said second fixed element.

5. The system (100) according to claim 1, characterized in that said third fixed element (6) is in the form of a ring, said ring having an excess thickness part (60) near a hole (61) for attaching said ring to said shaft (1), said excess thickness part (60) being arranged to abut against said spring (5).

6. The system (100) according to claim 1, characterized in that said second fixed element (4) has a conical contact surface (40) with said catch (50) of said spring (5).

7. The system (100) according to claim 1, characterized in that a catch (50) on the outer periphery of the spring (5) and the inner part (51) are present in two different planes.

8. A method of assembling a friction system according to the present invention, comprising: - providing a shaft (1); - pushing a first fixing element (2) onto the shaft (1) to a predetermined position; - sliding a toothed member (3) on the shaft (1) up to the first fixing element (2); - sliding a second fixing element (4) on the shaft (1) while orienting the second fixing element (4) with respect to the shaft (1) by means of a flat portion (41) cooperating with a shoulder (12) formed on the shaft (1); - arranging a spring (5) on the shaft (1); - gradually pushing a third fixing element (6) onto the shaft (1) in order to obtain a chain link both between the first element and the toothed member and between the second fixing element and the toothed member until a predetermined frictional torque is obtained, and compressing the spring (5) between the second fixing element (4) and the third fixing element (6). A method including the above steps.

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