Friction system for a clock movement

Abstract

The invention relates to a friction system (100) for a clock movement comprising: a shaft (1), with longitudinal axis (L), a first fixed element (2), mounted rotationally fixed on the shaft (1); said first fixed element (2) having a first bearing surface (40); a second fixed element (7) mounted rotationally fixed on the shaft (1); a toothed member (3), mounted freely in rotation on the shaft (1) between the first fixed element (2) and the second fixed element (7);characterized in that the toothed member (3) is integral with a sleeve (4) having a second bearing surface (42), and in that the second fixed element (7) comprises a body (72) configured to be rotationally integral with the shaft (1) and elastic tabs (71), projecting from the body (72) extending in the direction of the toothed member (3), said elastic tabs (71) being in elastic contact with said second bearing surface (42) of the sleeve (4), said elastic tabs (71) being arranged to deform elastically under stress from the second bearing surface (42) and to form a kinematic connection both between the first fixed element (2) and the toothed member (3) and between the second fixed element (7) and the sleeve (4) integral with the toothed member (3) up to a predetermined friction torque.

Description

Technical field of the invention

[0001] The invention relates to the field of mechanical watchmaking.

[0002] The invention relates more particularly to a friction system for a clockwork movement, for example for setting the time. Technological background

[0003] Friction systems are commonly used in watch movements. These systems allow a first component to rotate in conjunction with a second component until a torque limit is reached. Once this limit is exceeded, the two components are no longer rotated together. Generally, this type of system is used for hour and minute display mechanisms, particularly in the movement of the hands or display discs.

[0004] Typically, the carriage is fitted with a lantern pin to ensure friction between it and a pivot. This fitting involves pinching a tube within the carriage at a specific point or clearance of the pivot. This pinching is a manual task, and its result depends on the watchmaker's skill and sensitivity, and is therefore unpredictable.

[0005] Correctly adjusting the friction torque is therefore a delicate process. Precise control of the applied clamping force is thus important, and conventional manual adjustment does not allow for this precision or the required reproducibility.

[0006] Another disadvantage is that the lantern frictions cannot withstand the transmission of high torque and are sensitive to assembly / disassembly.

[0007] There are other solutions for obtaining friction such as the use of shims as described in document FR 2394839, but these have manufacturing repeatability that is difficult to guarantee from one batch to another.

[0008] Document CH 712197 describes another solution for achieving friction consisting of using a spiral-shaped friction spring having an inner part bearing on a first annular bearing surface fixed in rotation to a first toothed member, and an outer part bearing on a second annular bearing surface fixed to the second toothed member, the inner and outer parts being connected by at least one elastic spiral-shaped arm.

[0009] However, these solutions are complex to implement, have a significant size which makes certain implementations in watch movements impossible. Summary of the invention

[0010] The present invention aims to remedy at least one of the aforementioned drawbacks.

[0011] The invention also aims to provide a friction system enabling the transmission of high torque, which is easy to manufacture, and whose repeatability of the applied friction torque is easily manageable.

[0012] The invention also makes it possible to provide a friction system with a limited footprint, and whose radial footprint of the system is determined by the footprint of the toothed members and not by the footprint of the friction system.

[0013] To this end, the present invention relates to a friction system for a watch movement comprising: a shaft, with longitudinal axis L, arranged to be mounted in the watch movement; a first fixed element, mounted rotationally fixed on the shaft; said first fixed element having a first bearing surface; a second fixed element mounted rotationally fixed on the shaft; a toothed member, mounted freely in rotation on the shaft between the first fixed element and the second fixed element.

[0014] According to the invention, the toothed member is fixed to a sleeve having a second bearing surface, and in that the second fixed element comprises a body, configured to be rotationally fixed to the shaft, and elastic tabs, projecting from the body and extending towards the toothed member, said elastic tabs being in elastic contact with said second bearing surface of the sleeve, said elastic tabs being arranged to deform elastically under stress from the second bearing surface and to form a kinematic link both between the first fixed element and the toothed member and between the second fixed element and the sleeve fixed to the toothed member up to a predetermined friction torque.

[0015] The architecture of the friction system according to the invention allows the entire length of the shaft to be used while minimizing the overall size of the system in a radial direction. Thus, such a friction system is more easily integrated into watch movements, and particularly into watch movements with numerous complications.

[0016] Thanks to the invention, the friction torque can be perfectly adjusted by axially controlling the displacement of the second fixed element on the shaft; the stress exerted by the elastic deformation of the elastic lugs on the sleeve allows for a more gradual increase in friction torque, which facilitates precise and repeatable adjustment of a predetermined friction torque.

[0017] Furthermore, such a friction system according to the invention is not sensitive to successive and repeated assembly / disassembly.

[0018] In addition to the characteristics mentioned in the preceding paragraph, the friction system according to the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: The elastic legs extend along an axis substantially parallel to the longitudinal axis of the shaft; the second bearing surface is a conical bearing surface; the second bearing surface is an internal bearing surface formed at the level of a bore of the sleeve and having a slope oriented towards the longitudinal axis of the shaft; the second bearing surface is an external conical bearing surface formed at the periphery of the sleeve and having a slope oriented outwards from the sleeve; the elastic legs bear elastically on said second bearing surface of the sleeve at their free end; the free end of the elastic legs has a rounded or beveled shape; the first bearing surface of the first fixed element is flat or conical; the sleeve is machined from the material with the toothed element;The mounting sleeve is an added part fixed to the toothed element; the mounting sleeve is pressed onto a tubular portion that receives the toothed element.

[0019] The invention also relates to a clockwork movement comprising a friction system according to the invention.

[0020] The invention also relates to a method for assembling a friction system according to the invention, the method comprising the following steps: provide a shaft; drive a first fixed element onto the shaft in a predetermined axial position; slide a first toothed element onto the shaft until it reaches the first fixed element so that the first toothed element is in contact with the first fixed element; the first toothed element being attached to a sleeve; progressively drive a second fixed element having elastic tabs directed towards the sleeve on the shaft, so as to compress the elastic tabs against the sleeve, to obtain a kinematic frictional connection both between the first fixed element and the first toothed element, and between the second fixed element and the sleeve attached to the toothed element until a predetermined frictional torque is obtained. Brief description of the figures

[0021] Other features and advantages of the invention will become apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings in which: there figure 1 represents a perspective view of a first example of an embodiment of a friction system according to the invention; the figure 2 represents an exploded view of the friction system illustrated in the figure 1 ; there figure 3 represents a longitudinal cross-sectional view along axis AA of the first example embodiment of the friction system illustrated in the figure 1 ; there figure 4 is a detailed view showing particularly the contact area generating the friction of the friction system illustrated in the figure 1 ; there figure 5 is a detailed view showing the contact area generating the friction of a variant embodiment of a friction system according to the invention; the figure 6represents an exploded view of a second example of an embodiment of a friction system according to the invention; the figure 7 represents a longitudinal cross-sectional view along axis AA of the second example embodiment of the friction system illustrated in the figure 6 ; there figure 8 represents a longitudinal cross-sectional view along axis AA of a third embodiment of the friction system according to the invention; the figure 9 is a schematic representation of a timepiece comprising a clock movement equipped with a friction system according to the invention. Detailed description of the invention

[0022] With reference to the figure 1A first example of the embodiment of a friction system 100 according to the invention is shown. This system comprises a shaft 1 arranged to be mounted in a clockwork movement 200; the shaft 1 extends along a central longitudinal axis L which forms the axis of rotation of the shaft 1. The shaft 1 may comprise portions with cross-sections of different diameters and / or different shapes.

[0023] The shaft 1 carries a first toothed element 3, for example a wheel, mounted freely for rotation on the shaft 1. Alternatively, this first toothed element 3 may be a pinion or another element intended to be mounted with friction on the shaft 1.

[0024] The shaft 1 can also bear several toothed organs attached to the shaft 1, and can take on a large number of known forms according to the needs of the person skilled in the art.

[0025] Tree 1, for example, is a roadway.

[0026] As depicted in the figure 1The shaft 1 has a second fixed toothed element 5, integral with the shaft 1. This second fixed toothed element 5 can be a pinion, as shown, or a gear. In the example shown, the second toothed element 5 is integral with the shaft 1. According to an alternative embodiment, this second toothed element 5 can be pressed onto the shaft 1 so as to be integral with the movements of the shaft 1.

[0027] As depicted in the figure 2 , illustrating an exploded view of the first example of embodiment of the friction system 100 according to the invention, the friction system 100 comprises a first fixed element 2, forming a first support element, such as an annular flange 2, driven onto the shaft 1 so as to be fixed to the movements of the shaft 1.

[0028] This annular flange 2 has a first annular bearing surface 20 serving as the first friction surface between the annular flange 2 and the first toothed member 3. The first toothed member 3 rests on this annular bearing surface 20 via its lower face.

[0029] The friction system 100 also includes a second fixed element 7 mounted by pressing onto the shaft 1. The first toothed element 3 is mounted between the first fixed element 2 and the second fixed element 7. The axial position along the longitudinal axis L of the second fixed element 7 allows a kinematic friction link to be formed and the friction force of the friction system 100 to be adjusted.

[0030] The friction system 100 also includes a fitting sleeve 4, integral with the toothed member 3, having a second bearing surface 42 cooperating with the second fixed element 7. This second bearing surface 42 is intended to receive and cooperate with the second fixed element 7 pressed onto the shaft 1. The second bearing surface 42 therefore forms a second friction surface of the friction system 100 between the first toothed member 3 and the second fixed element 7.

[0031] According to the first example of implementation illustrated in figures 1 to 3 , the sleeve 4 is one piece with the first toothed element 3. In this embodiment example, the sleeve 4 extends in projection relative to the plate of the first toothed element 3, opposite the lower face bearing on the annular bearing surface 20 of the annular flange 2.

[0032] For example, the sleeve 4 has a tapered bore having a tapered internal surface having a slope oriented towards the longitudinal axis L of the shaft 1. The tapered internal surface of the sleeve 4 forms the second bearing surface 42 of the friction system 100 according to the invention.

[0033] Other bore profiles, not necessarily linear, are also possible without departing from the context of the invention insofar as the internal surface of the bore has a profile with a slope oriented towards the longitudinal axis L of the shaft 1. However, a conical profile with a linear slope is preferred.

[0034] The second fixed element 7 of the friction system 100 comprises a body 72 having a central orifice 73, and elastic tabs 71 extending in projection relative to the body 72, at the level of an external peripheral region of the body 72. The elastic tabs 71 extend in a direction substantially parallel to the longitudinal axis L. The body 72 is mounted on the shaft 1 via the central orifice 73, preferably by pressing.

[0035] The elastic legs 71 have a free end 74 configured to cooperate in elastic support on the second bearing surface 42 of the socket 4.

[0036] The free ends 74 of the elastic legs 71 can have variable shapes, for example a rounded shape as illustrated in the figure 4 or even at an angle as illustrated in the figure 5The beveled shape advantageously increases the contact surfaces between the elastic tabs 71 and the second bearing surface 42, preferably conical, of the sleeve 4, and therefore the friction torque of the friction system 100.

[0037] When the Friction System 100 is assembled, as illustrated in the figure 3 , the free ends 74 of the elastic legs 71 are constrained by the geometry of the second bearing surface 42 and are more or less elastically deformed towards the inside of the system, i.e. in the direction of the axis L, depending on the axial position of the fixed element 7 relative to the first toothed member 3. The elastic deformation by bending of the elastic legs 71 is proportional to the stress on the first toothed member 3.

[0038] Thus, the friction torque of the friction system 100 according to the invention is generated as a function of the driving position of the second fixed element 7 on the shaft 1, more or less important, and therefore as a function of the stress exerted by the elastic tabs 71 on the fitting sleeve 4.

[0039] Thanks to the invention, the friction torque can be perfectly adjusted by precisely driving the second fixed element 7 onto the shaft 1. The stress exerted by elastic deformation of the elastic tabs 71 on the sleeve 4 makes it possible to obtain a very precise friction torque, with a progressive and controllable evolution of the friction torque as the second fixed element 7 is driven in. Thus, it is easier to precisely adjust the required friction torque according to the relative position of the second fixed element 7 with respect to the first toothed element 3. Moreover, the adjustment of the friction torque is repeatable because it is relatively independent of the manufacturing tolerances of the various elements of the friction system 100.

[0040] The stress exerted by the elastic legs 71 can therefore be adjusted by acting on the relative gap between the second fixed element 7 and the first toothed element 3, and more particularly between the second fixed element 7 and the second bearing surface 42, preferably conical, of the sleeve 4 along the longitudinal axis L, which makes it possible to adjust the frictional torque that the system can undergo before the first toothed element 3 pivots relative to the shaft 1. Such an arrangement thus allows an extremely simple and easily reproducible adjustment.

[0041] Thus, when the set of parts is assembled, the elastic tabs 71 of the second fixed element 7 form a kinematic link both between the first fixed element 2 and the first toothed member 3, and between the second fixed element 7 and the toothed member 3, via the sleeve 4 up to a predetermined friction torque at the toothed member 3.

[0042] Preferably, the second fixed element 7 has at least three elastic tabs 71 so as to provide a better distribution of forces.

[0043] Preferably, as illustrated on the figures 1 to 3 , the second fixed element 7 has four elastic legs 71.

[0044] Preferably, the elastic tabs 71 are distributed uniformly around the peripheral perimeter of the body 72 with identical angular distances to each other to provide good distribution of the bearing force on the conical bearing surface 42 of the socket 4.

[0045] In the example of implementation illustrated in figures 1 to 3 The four elastic legs 71 are arranged at 90° to each other. In the case where the number of elastic legs is greater, for example six elastic legs, they would be arranged at 60° to each other.

[0046] According to a second example of an embodiment of the invention illustrated in figures 6 to 7 , the sleeve 4 is an added part and is driven directly onto the first toothed member 3, in order to secure the sleeve 4 and the toothed member 3.

[0047] For example, the first toothed element 3 has a male element, for example a boss, tenon, sleeve, tongue, etc. carried by the plate of the toothed element 3, intended to cooperate with a female element, for example a counterbore, mortise, bore, made on the handle sleeve 4.

[0048] Of course, the positions of the male and female organs can be reversed, so that the first toothed organ 3 has the female organ provided on its board and the socket 4 carries the male organ.

[0049] In the example of implementation illustrated in figures 6 and 7, the first toothed member 3 has a tubular receiving portion 31, and the fitting sleeve 4 has a bore 44 configured to cooperate by pressing with the tubular receiving portion 31.

[0050] This second example of implementation allows in particular for more free dimensioning of the diameter of the sleeve 4 and therefore the extent of the second bearing surface 42, without the dimensioning constraints of the board and the teeth of the first toothed element 3 linked to the operation of the clockwork movement 200.

[0051] This second embodiment allows for an increase in the friction torque of such a friction system 100, notably by increasing the diameter of the sleeve 4 and the second fixed element 7. This allows for an increase in the number of elastic tabs 71 on the outer periphery of the body 72 in contact with the second bearing surface 42 to generate friction. Therefore, this embodiment is preferable when a high friction torque is required.

[0052] There figure 8 illustrates an alternative embodiment of the friction system 100 according to the invention. This alternative embodiment is shown with the sleeve 4 pressed onto the first toothed member 3; however, this alternative embodiment is also applicable with a one-piece sleeve 4 with the first toothed member 3 as described previously with reference to the figures 1 to 3 .

[0053] In this embodiment, the socket 4 has an external bearing surface formed at its periphery, which constitutes the second bearing surface 42 of the friction system 100 according to the invention. The external bearing surface has a slope oriented outwards from the socket 4.

[0054] Preferably, the external support surface is a conical surface, but other profiles are possible without departing from the context of the invention.

[0055] Thus, in this variant of the embodiment, the elastic legs 71 come to deform elastically towards the outside of the system 100, that is to say by moving away from the axis L relative to their neutral rest position, during the more or less pronounced pressing of the second fixed element 7 on the shaft 1.

[0056] Such a variant makes it easier to lubricate the bearing surface 42 which is a contact surface with the elastic tabs 71. Such a variant also makes it possible to obtain a multiplying effect of the friction torque as the second fixed element 7 is driven out, since the contact points between the elastic tabs 71 and the bearing surface 42 are radially further and further away from the center of the shaft 1.

[0057] The friction system 100 according to the invention is, for example, a friction system for setting the time of a clock movement 200.

[0058] The invention also relates to a watch movement 200 comprising a friction system 100 according to the invention, as well as a watch part 300 comprising such a watch movement 200.

[0059] The invention also relates to a method for assembling a friction system according to the invention, the method comprising the following steps: provide a shaft 1; drive a first fixed element 2 onto the shaft 1 into a predetermined axial position; slide a first toothed element 3 onto the shaft 1 until the first fixed element 2 so that the first toothed element 3 is in contact with the first fixed element 2; the first toothed element 3 being integral with the sleeve 4; progressively drive a second fixed element 7 having elastic tabs 71 directed towards the sleeve 4 onto the shaft 1, so as to compress the elastic tabs 71 against the sleeve 4, to obtain a kinematic frictional connection both between the first fixed element 2 and the first toothed element 3, and between the third fixed element 7 and the sleeve 4 integral with the toothed element 3 until a predetermined frictional torque is obtained.

[0060] Of course, the present invention is not limited to the illustrated example and is susceptible to various variants and modifications which will appear to a person skilled in the art, without departing from the scope of the invention as defined by the claims.

Claims

1. Friction system (100) for clockwork movement (200) comprising: - a shaft (1), with longitudinal axis (L), arranged to be mounted in the clockwork movement (200); - a first fixed element (2), mounted rotationally fixed on the shaft (1); said first fixed element (2) having a first bearing surface (40); - a second fixed element (7) mounted rotationally fixed on the shaft (1); - a toothed member (3), mounted freely to rotate on the shaft (1) between the first fixed element (2) and the second fixed element (7); characterized in that the toothed member (3) is integral with a socket (4) having a second bearing surface (42), and in thatthe second fixed element (7) comprises a body (72), configured to be rotationally fixed to the shaft (1), and elastic tabs (71), projecting from the body (72) and extending towards the toothed member (3), said elastic tabs (71) being in elastic contact with said second bearing surface (42) of the sleeve (4), said elastic tabs (71) being arranged to deform elastically under stress of the second bearing surface (42) and to form a kinematic link both between the first fixed element (2) and the toothed member (3) and between the second fixed element (7) and the sleeve (4) fixed to the toothed member (3) up to a predetermined friction couple.

2. Friction system (100) for clockwork movement (200) according to the preceding claim, characterized in that the elastic legs (71) extend along an axis substantially parallel to the longitudinal axis (L) of the tree (1).

3. Friction system (100) for clockwork movement (200) according to any one of the preceding claims, characterized in that the second support surface (42) is a conical support surface.

4. Friction system (100) for clockwork movement (200) according to any one of the preceding claims, characterized in that the second bearing surface (42) is an internal bearing surface formed at the level of a bore of the sleeve (4) having a slope oriented towards the longitudinal axis (L) of the shaft (1).

5. Friction system (100) for clockwork movement (200) according to any one of claims 1 to 3, characterized in that the second bearing surface (42) is an external bearing surface formed at the periphery of the fitting sleeve (4) and having a slope oriented outwards from the fitting sleeve (4).

6. Friction system (100) for clockwork movement (200) according to any one of the preceding claims, characterized in thatsaid elastic legs (71) are in elastic support on said second bearing surface (42) of the socket (4) at the level of their free end (74).

7. Friction system (100) for clockwork movement (200) according to the preceding claim characterized in that the free end (74) of the elastic legs (71) has a rounded shape or a beveled shape.

8. Friction system (100) for clockwork movement (200) according to any one of the preceding claims, characterized in that the first bearing surface (40) of the first fixed element (2) is flat or conical.

9. Friction system (100) for a watch movement (200) according to any one of the preceding claims, characterized in that the handle sleeve (4) came from the material with the toothed part (3).

10. Friction system (100) for clockwork movement (200) according to any one of claims 1 to 8, characterized in thatthe handle sleeve (4) is an added part fixed to the toothed member (3).

11. Friction system (100) for clockwork movement (200) according to claim 10, characterized in that the fitting sleeve (4) is driven onto a tubular receiving portion (31) of the toothed member (3).

12. Clock movement (200) comprising a friction system (100) according to any one of the preceding claims.

13. Method for assembling a friction system (100) according to any one of claims 1 to 11, the method comprising the following steps: - providing a shaft (1); - driving a first fixed element (2) onto the shaft (1) into a predetermined axial position; - sliding a first toothed element (3) onto the shaft (1) until it reaches the first fixed element (2) so that the first toothed element (3) is in contact with the first fixed element (2); the first toothed element (3) being integral with a fitting sleeve (4);- progressively drive a second fixed element (7) having elastic tabs (71) directed towards the sleeve (4) on the shaft (1), so as to compress the elastic tabs (71) against the sleeve (4), to obtain a kinematic frictional connection both between the first fixed element (2) and the first toothed member (3), and between the second fixed element (7) and the sleeve (4) integral with the toothed member (3) until a predetermined frictional torque is obtained.;

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