Barrel for a timepiece

Abstract

The present invention relates to a barrel (1) for a self-winding watch part comprising a drum (11) with axis AA provided with an inner side wall (12) and a mainspring (2) forming a winding having an outer coil (21) the end (22) of which is friction-coupled with said inner side wall (12) and free to slide against the inner side wall (12) in case of over-tension of the mainspring (2).According to the invention, the end (22) of said outer coil (21) comprises an outer face (23) having two friction surfaces (24, 25) arranged in the upper and lower part of the outer coil (21) and arranged to be in contact with the inner side wall (26) so that the part between the friction surfaces (24, 25), said central part (26), is not in contact with the inner side wall (12), said central part (26) forming a reservoir (27) for a lubricant between the two friction surfaces (24, 25).

Description

Technical field of the invention

[0001] The present invention relates to the field of watchmaking. More specifically, it relates to a barrel intended to equip a self-winding timepiece. It also relates to a timepiece equipped with such a barrel. Technological background

[0002] Barrel springs for self-winding timepieces typically comprise a drum housing a mainspring wound in a spiral around a barrel arbor. To prevent any over-tension of the mainspring, which could cause it to break or damage the gear train of the self-winding device, the mainspring is not fixed to the side wall of the drum, but is frictionally coupled, via its last coil, using an elastic strip called a sliding flange. The friction coupling between the mainspring and the side wall of the drum must be calculated so that beyond a given maximum driving torque, the last coil slides along said wall and thus reduces the tension of the mainspring. The surface condition of the inner side wall of the drum and its lubrication are factors that strongly influence the operation of this friction coupling.Another determining factor concerns the geometry of the inner side wall.

[0003] According to the prior art, the inner side wall of the drum has friction surfaces against which the end of the mainspring rubs, which wears the drum wall. To remedy this problem, a lubricant such as grease is applied to the inner side wall of the drum.

[0004] However, the problem of wear is still present, it increases over time and can lead to significant damage, malfunctions or even the breakage of a part. Indeed, the friction of the end of the last coil of the mainspring tends to scrape and push the grease on the upper and lower edges of the drum. Finally, the end of the outer coil of the spring tears fine particles from the drum wall, and these make the friction even more abrasive, which produces even more particles and accelerates the wear phenomenon. In the long run, the friction coupling between the mainspring and the side wall of the barrel can be seriously affected.

[0005] Therefore, disassembly of the barrel and the addition of grease remains necessary to maintain satisfactory operating conditions.

[0006] An aim of the present invention is therefore to propose a barrel making it possible to remedy this wear problem.

[0007] Documents CH708660A1, JP2016090313A and CH343889A present solutions to this problem. Summary of the invention

[0008] The invention solves the aforementioned drawbacks by proposing a barrel comprising a mainspring whose external coil comprises a configuration providing two friction surfaces arranged in the upper and lower parts of the external coil, the friction surfaces being arranged to be in contact with the inner side wall of the barrel drum.

[0009] To this end, the present invention relates to a barrel for a self-winding timepiece comprising a drum with axis AA provided with an inner side wall and a mainspring forming a winding comprising an outer coil whose end is frictionally coupled with said inner side wall and free to slide against the inner side wall in the event of overtension of the mainspring.

[0010] According to the invention, the end of said outer turn comprises an outer face having two friction surfaces arranged in the upper and lower part of the outer turn and arranged to be in contact with the inner side wall so that the part between the friction surfaces, called the central part, is not in contact with the inner side wall, said central part forming a reservoir for a lubricant between the two friction surfaces and making it possible to channel the lubricant to the center of the outer turn, the friction surfaces being in the form of localized excess thicknesses in the upper and lower part of the outer turn.

[0011] According to other advantageous variants of the invention: the friction surfaces are formed by removing material, over part of the thickness of the outer turn or over the entire thickness, at the middle part of the outer turn; the friction surfaces extend along the length of the outer turn; the thickness of the material removal varies increasingly from the end of the outer turn and along the length of the outer turn; the material removal is in the form of a funnel, a neck, a parabola or a semicircle or any other geometry capable of channeling the grease to the center of the friction track of the blade against the drum.

[0012] The invention also relates to a watch movement comprising a barrel according to the invention.

[0013] The invention also relates to a watch comprising a movement equipped with a barrel according to the invention. Detailed description of the invention

[0014] A barrel according to the invention will now be described in the following with joint reference to: figures 1, 2 And 3a to 3d .

[0015] As illustrated in the figure 2 , the barrel 1 for a self-winding clockwork movement comprises a base 10 secured to a drum 11 with axis AA. A mainspring 2, also illustrated in figure 1 , is wound inside the barrel 1, the inner coil 20 of the mainspring 2 being coupled to a bung 4 arranged around a shaft 5, and the outer coil 20 of the spring 2 being in contact with the inner side wall 12 of the drum 11.

[0016] The spring 2 can be made in one piece and is in the form of a ribbon. The spring can thus be mounted on the bung 4 around the shaft 5 of the barrel.

[0017] The outer coil 21 has an end 22 frictionally coupled with the inner side wall 12 and free to slide against the inner side wall 12 in the event of overtension of the mainspring 2.

[0018] As can be observed in the figure 2 , the driving member 100 has a barrel 1 which comprises a cylindrical drum 11 in which the spring 2 is housed, a barrel shaft 5 and a plug 4 on which the inner coil 20 of the spring 2 is fixed, and a cover 6 which closes the drum 11.

[0019] The drum 4 also has an external toothing 13 which meshes with a pinion of a timer train (not shown).

[0020] According to the invention, the end 22 of the outer turn 21 comprises an outer face 23 having two friction surfaces 24, 25 arranged in the upper and lower parts of the outer turn 21 and arranged to be in contact with the inner side wall 12 so that the part between the friction surfaces 24, 25, called the central part 26, is not in contact with the inner side wall 12.

[0021] Advantageously, the central part 26 forms a reservoir for a lubricant, the reservoir then being located at least partly between the two friction surfaces 24, 25.

[0022] As illustrated, the friction surfaces 24 and 25 are formed by removing material, over a portion of the thickness of the outer turn 21 or over the entire thickness, at the middle portion 26. This removal of material allows only the friction surfaces 24 and 25 to be in contact with the inner side wall 12 of the drum, the lubricant being brought back towards the center thanks to the removal of material when the outer turn 21 slides against the drum.

[0023] According to the invention, the friction surfaces 24, 25 are in the form of localized excess thicknesses on the upper and lower parts of the outer turn 21, the excess thicknesses thus being the only ones to be in contact with the inner side wall 12 of the drum and forming a reservoir for a lubricant at the level of the middle part of the outer turn 21.

[0024] The friction surfaces 24, 25 extend along the length of the outer turn 21, the length obviously being able to vary according to the needs of the person skilled in the art. It is also obvious that the friction surfaces 24, 25 do not extend over the entire length of the outer turn 21 so as not to weaken it or make it too rigid, which would also impair the proper functioning of the barrel.

[0025] According to an embodiment illustrated in the 3d figure , the thickness of the material removal varies increasingly from the end of the outer turn 21 and according to the length of the outer turn. The material removal is in the form of a funnel, a neck, a parabola or a semicircle for example, so as to form a reservoir for the lubricant and guide it towards the center of the inner side wall of the drum.

[0026] Still according to another embodiment illustrated in the Figure 3b, the end 22 of the outer turn 21 is deformed at its outer face 23 so as to form the two friction surfaces 24, 25. Such deformation of the outer turn 21 is obtained, for example, by stamping.

[0027] In addition, such an arrangement of the end of the outer coil allows the lubricant to be distributed evenly from the start of operation of the barrel, and subsequently allows the lubricant to be channeled to the center of the outer coil.

[0028] The invention also relates to a watch movement and a timepiece equipped with a barrel according to the invention.

[0029] Thanks to these different aspects of the invention, a barrel is provided which makes it possible to reduce the wear caused by the friction of the spring on the barrel drum.

[0030] Of course, the present invention is defined by the appended claim 1 and is not limited to the illustrated example and is susceptible of various variations and modifications which will appear to those skilled in the art.

Claims

1. Barrel (1) for self-winding timepiece comprising a drum (11) of axis AA provided with an inner lateral wall (12) and a mainspring (2) forming a winding including an outer coil (21) the end (22) of which is friction coupled with said inner lateral wall (12) and free to slip against the inner lateral wall (12) in the event of overtension of the mainspring (2), in which the end (22) of said outer coil (21) comprises an external face (23) having two friction surfaces (24, 25) disposed in the top and bottom portion of the outer coil (21) and arranged to be in contact with the inner lateral wall (26) in such a way that the portion between the friction surfaces (24, 25), referred to as central portion (26), is not in contact with the inner lateral wall (12), said central portion (26) forming a reservoir (27) for a lubricant between the two friction surfaces (24, 25), characterised in that the friction surfaces (24, 25) are in the form of localised overthicknesses in the top and bottom portion of the outer coil (21).

2. Barrel (1) according to claim 1, characterised in that the friction surfaces (24, 25) are formed by removing material, on one portion of the thickness of the outer coil or on the entire thickness, at the middle portion of the outer coil (21).

3. Barrel (1) according to claim 1 or 2, characterised in that the friction surfaces extend along the length of the outer coil.

4. Barrel (1) according to claim 2, characterised in that the thickness of the material removal varies increasingly from the end of the outer coil and along the length of the outer coil.

5. Barrel (1) according to claim 2, characterised in that the removal of material is in the form of a funnel, of a neck, of a parabola or of a semicircle.

6. Movement comprising a barrel (1) according to one of claims 1 to 5.

7. Timepiece comprising a movement according to claim 6 and / or a barrel (1) according to one of claims 1 to 5.

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