A mechanical watch movement comprising a wheel set carrying a display member and provided with a braking device

Abstract

To provide a mechanical horological movement comprising a wheel set that carries a display member and comprises a braking device.SOLUTION: A mechanical horological movement includes: a display wheel set 30 intended to carry a display member, particularly a chronograph hand 48, and be driven rotatably by a barrel; and a braking spring 10 arranged to generate a braking torque on the display wheel set 30 when the display wheel set 30 is subjected to a rotary drive torque to prevent trembling of the display member. The mechanical horological movement further includes an intermediate part, particularly a washer 8, located between the braking spring 10 and an arbor 36 of the display wheel set 30, the intermediate part 8 being mounted to rotate freely on the arbor 36. The intermediate part 8 and the braking spring 10 are arranged such that the intermediate part 8 remains stationary and non-rotating in normal operation. The braking spring 10 overall exerts a pressing force on the intermediate part 8 in the direction of the arbor 36 to generate the braking torque.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a mechanical timepiece movement comprising a wheel set that holds a display element, in particular the hands, and that is equipped with an anti-vibration device, also called an anti-vibration device, formed by a braking device acting on the wheel set, in order to prevent the display element from vibrating when rotating and, if necessary, also from floating when at rest. [Background technology]

[0002] Patent Document 1 discloses a vibration-damping device for a timepiece wheel set, particularly a chronograph wheel set, hereinafter also referred to as a "chrono wheel set," which includes an axle fitted to a pinion. This pinion meshes with a clutch wheel, hereinafter referred to as a "drive wheel," which forms a coupling device for the chronograph mechanism. It should be noted that the axle fitted to the pivot to guide the pivot's rotation is also referred to as a "shaft" in watchmaking. The vibration-damping device for the seconds hand of the chronograph function is formed by a friction device with a wire spring that supports obliquely against the axle. For this purpose, the axle has a frustoconical shoulder. The wire spring has a support point at an angle formed by the shoulder and a circular cylindrical section whose diameter corresponds to the minimum diameter of the shoulder, and at this point it exerts an oblique force on the axle. The engagement of the pinion thereby presses against the drive wheel, and the lower annular surface of the axle, facing the aforementioned shoulder and perpendicular to the axis defined by the axle, presses axially against the bearing on which the chronograph wheel set revolves. The spring is designed to be straight in the absence of stress. At its first end, this spring is fastened to the movement frame, while the part at its second end is under tension and presses against the axle as explained above.

[0003] For many reasons, this vibration isolation device has problems with controlling the moment of friction force applied to the chronograph wheel set. Furthermore, there is no way to adjust this moment of friction force. Then, when the chronograph hand (chrono hand) is removed, an axial force is applied to the spring, which can damage the spring.

[0004] Patent Document 2 describes a solution for improving the control of the friction force moment applied to a seconds wheel set. According to the teachings of this document, a wire or strip spring is fastened at its first end to a plate by riveting. The plate is held in a floating state by a rivet with a head with a threaded slot, located on one side of the bar opposite the side on which the plate is located. The rivet has an intervening tubular part that is inserted into the hole in the bar by a friction fit. The friction fit allows the rivet, and thus the plate, and thus the first end of the spring, to undergo a specific rotation with the aid of a tool. The second end of the friction spring is free and radially supports against a plastic washer that is force-fitted / press-fitted onto the axle of the seconds wheel set. This washer has a transverse groove in which the second end of the spring is positioned. This system is very difficult to assemble in a watch movement. First, the friction spring must be fastened to the plate by inserting its first end into the slot and then performing a first riveting operation, pressing the material against the two edges of the slot. The plate with the friction spring must then be brought inside the bar after inserting a rivet into the hole in the bar from the other side. The end of the rivet must then be crushed, and a second riveting operation must be performed to fasten the plate to the rivet. It can be seen that at each stage of assembling the friction spring to the plate and then to the bar through two consecutive riveting operations, there is a high risk of damaging the friction spring. Finally, the assembly of the bar, plate, and friction spring is simultaneously assembled in the watch movement by inserting the pivot of the seconds wheel set, which holds the grooved washer, into the bearing located in the associated bar. Such assembly requires that the spring not be stuck on top of the grooved washer. This is because the spring is rigidly connected to the bar and the grooved washer designed to receive the free end of the spring under tension is rigidly connected to the axle.For this reason, there is a first assembly / disassembly position for the spring and a second operating position in which the free end of the spring is carried into the groove of the washer and the spring is tensioned. To move from one position to the other, the watchmaker must use a tool that acts on the rivet head. This tool causes the spring to lose its set tension when it is removed for maintenance. As a result, the braking moment must be readjusted every time the seconds wheel set is assembled. The assembly method described here is difficult and time-consuming to perform.

[0005] Furthermore, this anti-vibration device does not provide a complete solution to the problem of adjusting the force moment applied to the seconds wheel set to prevent it from vibrating. This is because the friction force is determined, inter alia, by the profile of the transverse groove in the plastic washer and the shape of the end of the spring inserted into this groove and pressing radially against the washer. This friction force is difficult to control and reproduce because it is highly dependent on the dimensions of the spring and the groove, their respective configuration, and their respective surface finish. Another problem arises from the fact that assembling an intervening part on the axle of the seconds wheel set increases the wheel set's radial vibration, which in turn results in greater variations than would occur without such an intervening part, particularly if the spring were directly supported on a conventional axle with less radial vibration. Furthermore, in the event of vibration or shock to the watch, the second free end of the spring may come off the grooved washer and no longer guarantee a constant braking torque. To make matters worse, in the event of a severe impact, the spring clamping plates, which are held in place solely by friction, can move axially and change the brake setting. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Swiss Patent Invention No. 580301 [Patent Document 2] West German Utility Model Publication No. 6800934(U) Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to solve the above-mentioned problems of the prior art and likewise to propose an anti-vibration device for an indicator wheel set arranged outside the gear train from the barrel to the escape wheel set, which anti-vibration device is easy to install and, in a preferred alternative embodiment, can be installed in a preparatory stage before the installation of the wheel set in question. [Means for solving the problem]

[0008] The present invention therefore relates to a mechanical timepiece movement comprising a barrel, an escape wheel set associated with a mechanical resonator, an indicator wheel set with an axle intended to hold a display element, and a braking device associated with the indicator wheel set and comprising a brake spring and an intermediate part arranged between the brake spring and the axle of the indicator wheel set, the indicator wheel set being capable of being driven in rotation by the barrel but not forming part of the toothed wheel train from the barrel to the escape wheel set. The brake spring is arranged so that as soon as the indicator wheel set is subjected to a rotational driving torque, it is able to generate a braking torque on the indicator wheel set via the intermediate part against which it presses. The intermediate part and the brake spring are arranged so that the intermediate part remains stationary and non-rotating in normal operation. The intermediate part has a lateral surface that presses against the rotating surface of the axle and a bearing surface against which the brake spring applies its entire pressing force towards the axle to generate a friction force between the lateral surface and the rotating surface that generates the braking torque.

[0009] According to a first advantageous alternative embodiment, the intermediate part and the brake spring are configured in such a way that the aforementioned pressure remains constant once the indicator wheel set is assembled in the movement and the brake device is fully assembled and adjusted.

[0010] In a preferred and generally alternative embodiment, the intervening piece exerts radial pressure exclusively on the axle of the indicator wheel set.

[0011] In the main embodiment, the damping spring is a wire or strip spring, the longitudinal axis of which lies in a geometric plane parallel to the general plane of the movement.

[0012] In one main embodiment, the movement comprises an eccentric whose axis of rotation is perpendicular to the geometric plane and which is arranged to press radially against the brake spring, thereby making it possible, by rotation about its axis of rotation, to vary the total radial pressure exerted by the brake spring on the intermediate part.

[0013] The invention will be described in more detail below with reference to the accompanying drawings, which are given as non-limiting examples. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a partial perspective view of a main embodiment of a mechanical timepiece movement according to the invention, showing a braking device according to the invention pre-mounted in a preparatory step prior to the assembly of the chronograph wheel set for which the braking device is intended; [Figure 2] FIG. 2 is a plan view of a portion of the mechanical timepiece movement shown in FIG. 1. [Figure 3] 3 is a cross-sectional view taken along the section plane III-III of FIG. 2, passing through the central axis of a tube designed to receive part of the axle of a chronograph wheel set. [Figure 4]FIG. 1 is a bottom view of a mechanical timepiece movement in the main embodiment when fitted with a chronograph wheel set. [Figure 5] FIG. 5 is a partial cross-sectional view of the mechanical timepiece movement taken along the cross section VV of FIG. 4. [Figure 6] 1A-1C are schematic partial views of certain alternative embodiments of the main embodiment; [Figure 7A] FIG. 1 shows a schematic partial view of one advantageous alternative embodiment of the main embodiment. [Figure 7B] FIG. 1 shows a schematic partial view of one advantageous alternative embodiment of the main embodiment. [Figure 8] 1A-1C are schematic partial views of certain alternative embodiments of the main embodiment of the present invention; [Figure 9] FIG. 2 shows a schematic partial view of a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] A main embodiment of a mechanical timepiece movement 2 according to the invention will now be described with reference to FIGS.

[0016] Mechanical watch movement 2 Incense box and an escape wheel set 58 associated with a mechanical resonator (not shown); a first wheel set 30 intended to carry a display member, in particular a hand 48 for displaying the seconds of the chronograph function, forming a display wheel set driven in rotation by a second wheel set 52 incorporated in the gear train from the barrel to the escape wheel set, this first wheel set not being included in this toothed wheel train; and a braking spring 10 arranged so as to be able to generate on the first wheel set 30 a braking torque intended to prevent the display member 48 from vibrating as soon as a rotational driving torque is applied to this first wheel set, and a permanent radial force which maintains the display member in a stationary position when the display member is stationary.

[0017] According to the present invention, the mechanical timepiece movement 2 comprises a braking device 6 acting on the display wheel set and comprising a braking spring 10 and an intervening part 8 arranged between the braking spring and the axle 36 of the first wheel set 30. The braking spring is arranged in such a way that, as soon as the display wheel set is subjected to a rotational drive torque, it is able to generate a braking torque on the display wheel set via the intervening part against which it presses. For this purpose, the intervening part has a lateral surface 9 that presses against the rotating surface 35 of the axle and a bearing surface 25 against which the braking spring applies its entire pressing force in the direction of the axle to generate a friction force between the lateral surface and the rotating surface. This friction force generates a braking torque, which is thus exerted by the braking spring on the first wheel set / display wheel set via the intervening part against which it presses. The intervening part 8 and the braking spring 10 are arranged in such a way that, during normal operation, the intervening part remains stationary and does not rotate. The axle 36 and intervening components of the first wheel set are configured to allow the rolling surface 35 of the axle to slide on the lateral surface 9 while subjected to a kinetic friction force that creates a braking torque. Before the rolling surface slides on the lateral surface, static friction forces create a braking torque, thus keeping the axle stationary.

[0018] Preferably, the intermediate piece 8 exerts a radial pressure exclusively on the axle 36 of the first wheelset 30. According to an advantageous feature, the braking spring 10 exerts a radial pressure exclusively on the intermediate piece. The bearing surface 25 is opposite the lateral surface 9, i.e., the bearing surface is located on one side of the intermediate piece 8 opposite the other side of the intermediate piece that defines the lateral surface 9. This alternative embodiment is advantageous because the braking device is supported against the notches, and the radial oscillations of the notches vary slightly, thus providing a constant braking torque for a given friction force between the rolling surface 35 and the lateral surface 9. In the advantageous alternative embodiment shown in the figures, the rolling surface 35 of the axle 36 is cylindrical and axial, and the lateral surface 9 of the intermediate piece is axial. That is, the cylindrical rolling surface 35 and the lateral surface 9 are oriented along the rotation axis 42 of the first wheelset 30. The axis of rotation 42 of the first wheel set 30 coincides with the central axis of the axle 36, so that the transverse surface 9 and the cylindrical surface of rotation 35 are parallel to this axis of rotation 42. According to a preferred alternative embodiment, the intermediate part 8 and the brake spring 10 are configured in such a way that the aforementioned pressing force remains constant once the indicator wheel set is assembled in the movement and the brake device is fully assembled and adjusted.

[0019] According to a main alternative embodiment, the brake spring 10 is a wire or strip spring, the longitudinal axis of which lies in a geometric plane parallel to the general plane 50 of the mechanical timepiece movement 2 .

[0020] According to the illustrated alternative embodiment, the intervening part 8 is a washer having a central cylindrical opening in which the axle 36 of the first wheel set 30 slides and rotates freely without any interaction from the brake spring 10, the aforementioned lateral surface 9 of this washer 8 being defined by the preferably circular (i.e., rotating) cylindrical surface of its central cylindrical opening.

[0021] According to a particular alternative embodiment, the washer 8 has, on its outer periphery, a circular groove 24 defining a bearing surface 25 into which a portion of the brake spring 10 is at least partially inserted, thereby exerting a radial pressing force. In particular, as shown in Figures 3 and 5, the groove 24 has a V-shaped cross section, and the brake spring 10 is a wire spring with a circular cross section. This arrangement allows the brake spring to be axially positioned at its midpoint in contact with the washer, so that the spring is not free to move axially.

[0022] As a non-limiting example, in a first alternative embodiment, if at least a portion of the mandrel defining the rotation surface 35 is made of steel, at least a portion of the washer 8 defining its central cylindrical opening is made of a beryllium copper (CuBe) alloy, and vice versa. This first alternative embodiment provides good friction results. In a second alternative embodiment, in which the aforementioned portion of the mandrel is made of steel or CuBe, at least a portion of the washer defining its central cylindrical opening is made of a polymer. Preferably, the entire washer is made of a polymer. This second alternative embodiment is particularly advantageous for self-lubrication. In other alternative embodiments in which the mandrel is made of steel or a copper alloy (e.g., CuBe or brass), at least a portion of the washer defining its central cylindrical opening is made in the form of a thin layer deposited on a base of another material, such as bronze, nickel, or gold, particularly in the case of nickel or gold, or more generally, an alloy containing gold or nickel. In another alternative embodiment, at least a portion of the washer defining its central cylindrical opening is formed from ceramic, particularly ruby or zirconia.

[0023] It should be noted that the material of the brake spring can be selected in such a way as to optimize the elastic properties of this spring, and also its manufacture, without having to worry about friction and wear problems, provided that the washer, and more generally the intermediate part, is intended to be stationary, i.e. static and not rotating, during the normal operation of the mechanical timepiece movement. In the case of a washer, changes can be made either to the shape of the intermediate part and / or to the shape of the brake spring, as will be explained in more detail below, in order to prevent the washer from rotating, or, especially in the case of a washer, to the material used to form the spring and to the surface treatment applied to at least the outer part of the intermediate part in contact with the spring and / or to these parts in order to obtain a high friction force between the brake spring and the intermediate part.

[0024] According to another preferred alternative embodiment, the brake spring 10 is arranged in the mechanical timepiece movement 2 in such a way that the intermediate portion between its two ends presses radially against the bearing surface 25 of the intermediate part / washer 8. More specifically, the brake spring 10 is arranged so that the intermediate portion of the brake spring exerts the aforementioned pressing force on the bearing surface 25 of the intermediate part / washer 8. Thus, the two ends of the brake spring, located on either side of the intermediate portion, are stressed by the two remote parts 16 and 20 of the timepiece movement, such that the intermediate portions apply a pressing force to the bearing surface of the intermediate part / washer. This configuration of the brake device is advantageous because it ensures that the brake spring is always pressed against the bearing surface of the intermediate part / washer. Furthermore, this configuration is less sensitive to vibrations and shocks than a brake spring having an anchoring point at one of its ends and a contact point at the other end.

[0025] In certain alternative embodiments, the brake spring 10 is curved at its midsection, so that the bearing surface 25 of the interposer / washer 8 has a convex curvature in the aforementioned geometric plane relative to the axle 36 of the first wheelset 30, specifically a circular curvature in the case of the washer, which in the first alternative embodiment is followed by the midsection of the brake spring along the bearing surface. In a second alternative embodiment, the radius of curvature of the midsection is smaller than the average radius of curvature of the bearing surface, so that the brake spring presses against the interposer / washer at "two points" of the bearing surface, i.e., at two separate locations. It should be noted that a spring with a substantially V-shaped groove and a circular cross section presses locally at a pair of axially aligned points. Thus, in such a configuration of groove and damping spring, the damping spring presses at two pairs of points angularly spaced from each other, with each pair of points axially aligned, and thus projects at "two points" in the general plane of the spring, which is parallel to the general plane of the movement 50. Finally, these alternative embodiments do not exclude other advantageous alternative embodiments in which the average radius of curvature of the intermediate portion is greater than the radius of curvature of the bearing surface, resulting in radial pressure being exerted at "one point" (i.e. at a pair of axially aligned points, rather than at a single point projecting in the general plane of the spring / general plane of the movement 50).

[0026] According to an advantageous alternative embodiment, as shown in Figure 2, the brake spring 10 is not fastened to the movement by a specific part, but is held under tension by two parts 16 and 20 of this movement against which press the two ends of the brake spring, located respectively on either side of the intermediate part of this brake spring that bears radially against an intermediate part, in particular a washer 8. The direction of the forces exerted by the two parts 16 and 20 on the spring is opposite to the direction of the reaction force of the intermediate part / washer 8 on the intermediate part of the spring. These forces, exerted on the brake spring in the geometric plane in which its longitudinal axis lies (a horizontal plane perpendicular to the axis of rotation 42 of the axle 36 that coincides with its central axis), generate stresses that hold the brake spring in place. For this reason, two portions of the support 4 are provided on each of the two aforementioned sides, which define a lower axial stop for the braking spring, in order to prevent the spring from moving axially / vertically, in particular its middle part, from leaving the groove 24. On the first side, a groove 14 is provided in the support 4 (barrel bar) of the braking device, which can support the washer 8, in particular when assembling the washer before installing the spring. The bottom of this groove, which forms a thin horizontal wall, provides a lower limit for any possible displacement of the part of the spring located on this side. On the second side, the braking spring is partially located on a small protrusion 18.

[0027] Various other advantageous alternative embodiments are shown diagrammatically in Figures 6, 7A, and 7B. The alternative embodiment shown in Figure 6 is characterized by a brake spring 10A with a middle portion having two bends 71 and 72. The two bends 71 and 72 are separated by a straight section 70 (when unstressed) that supports the brake spring 10A substantially at its middle portion against a circular washer 8. This ensures that the brake spring 10A always supports the washer 8 at a "single point." The alternative embodiments of Figures 7A and 7B are characterized by an intermediate part 68 that is not circular but is formed by a truncated washer having a straight zone 80. In the alternative embodiment shown in Figure 7A, the brake spring 10 has a bend 74 in its middle portion that is arranged facing the straight zone 80 of the truncated washer 68. In the alternative embodiment shown in Figure 7B, the spring 11 is straight / rectangular in its unstressed state, and when tensioned so that it presses against the intermediate part, the spring 11 curves slightly (concave as seen from the intermediate part), causing the spring 11 to press at the two ends of the linear zone 80 of this intermediate part. Thus, in the alternative embodiments of Figures 7A and 7B, the damping spring 10 or 11, respectively, exerts two forces F1 and F2 at the two ends of the linear zone 80. The two forces F1 and F2 are generally radial, i.e., their sum at the midpoint is radial. However, each of the two forces exerts a force moment on the intervening part 68, such that if the spring moves longitudinally and one of the two forces F1 and F2 decreases relative to the other, the intervening part 68 will automatically rotate slightly, thereby re-establishing balance between the two opposing force moments exerted on the intervening part 68. The alternative embodiment shown in Figure 7B is preferred because there is less risk of the truncated washer rotating. Furthermore, this alternative embodiment allows the desired braking torque to be maintained even when the braking spring undergoes a certain longitudinal displacement in the event of an impact or sudden acceleration.However, in the alternative embodiment shown in Figure 7A, the bent spring is less likely to be subjected to longitudinal displacement in the event of an impact. The alternative embodiment with a truncated washer is advantageous for preventing the intervening part from rotating during normal operation, which is important for ensuring a constant damping torque is set. The alternative embodiment shown in Figures 7A and 7B always provides support at "two points" projecting in the geometric plane of the spring.

[0028] A specific alternative embodiment is shown diagrammatically in FIG. 8. This alternative embodiment, like the alternative embodiment of FIG. 6, is designed to ensure that the brake spring 10B is always pressed at "one point" on the intervening part 78. The intervening part 78 has a generally square shape with rounded corners. The brake spring 10B has a bend 76 such that the two straight parts of the spring on each side of the bend are at an angle greater than 90 degrees relative to each other, but relatively close to this value, e.g., equal angles of 110 degrees. One of the rounded corners of the intervening part is located at the bend 76 of the spring, and the spring exerts a substantially radial force F on the intervening part when the spring and intervening part 78 are stationary. If the spring 10B moves, particularly as a result of an impact, the direction of the force changes such that the intervening part is in turn subjected to a force moment that causes the intervening part to rotate. This ensures that the same corner of the square intervening piece always remains within the bend 76 of the brake spring and that pressure is applied at "one point." Furthermore, in normal operation (when the brake spring is stationary), this alternative embodiment keeps the intervening piece stationary (not rotating), thus ensuring a constant, well-defined braking torque on the wheelset axle.

[0029] According to an alternative preferred embodiment of the present invention, the braking device 6 comprises an eccentric 20. The axis of rotation of this eccentric 20 is perpendicular to the general plane 50 and thus parallel to the axis of rotation 42 of the central shaft / wheel set 30. The eccentric 20 is also arranged to radially press against the braking spring, so that rotation about its axis of rotation makes it possible to vary the aforementioned radial pressure exerted by the braking spring on the intermediate part / washer. In the advantageous alternative embodiment shown in FIGS. 1 and 2, the eccentric 20 constitutes one of the two parts that keep the braking spring under tension. Rotating the eccentric 20 thus varies the stress on this spring, making it possible to adjust the braking torque applied to the first wheel set 30 (chronograph wheel set) when the first wheel set is subjected to a rotational driving torque. This configuration is advantageous because it is less sensitive to vibrations and shocks. In another alternative embodiment, another device for adjusting the radial force is provided, in particular a device fitted to a linearly movable pressing member.

[0030] 9 shows another embodiment of the invention in which the brake spring 11 is straight / rectangular (without stress). At one of its two ends, the spring is rigidly fastened to a fastening part 82, preventing it from changing its angular position in a geometric plane and thus preventing any unintended displacement or displacement due to impact. The grooves in the part 82 into which the ends of the spring 11 are inserted are oriented so that the middle zone of the spring exerts a radial pressure force F on the washer 8, so that the spring has a first convex curvature (as seen from the washer) between the fastening part 82 and the spring's support point on the washer. Preferably, an eccentric is provided at the other end of the spring to adjust the radial force F, which in this embodiment is located on the same side of the brake spring as the washer 8, and which forms an intermediate part between the brake spring and the axle of the wheelset concerned. Therefore, the brake spring 11 also has a second convex curvature between the aforementioned support point and the eccentric 20, which is smaller than the first curvature due to the non-zero radial force F. It should be noted that the alternative embodiment shown in FIG. 9 defines a configuration with a single support point, i.e., a configuration with a brake spring supporting the washer at "one point" according to the above-given definition. Another alternative embodiment of the "two points" type provides a star-shaped interposing element, e.g., an interposing element with four to six vertices, each with a small rounded portion. A slightly convex brake spring always supports two vertices of the star-shaped interposing element, thus exerting two forces at their center point that form the overall radial pressure. In other words, the two forces generate two opposing force moments on the interposing element, of equal strength. It should also be noted that the brake device cannot be released in the event of an impact.

[0031] 1 to 3 show a mechanical timepiece movement 2 in which the brake device 6 has been pre-assembled in a preliminary stage, before the assembly of the first wheel set 30. This pre-assembly of the brake device 6 is advantageous, made possible in particular by the fact that the force exerted by the brake spring is radial and by the fact that washers 8 are provided on the pinions and wheels 32 forming the first wheel set and, in the illustrated embodiment where the first wheel set is a chronograph wheel set, on the reset heart piece 34. Figures 4 and 5 show the mechanical timepiece movement 2 after the first wheel set 30 has been attached to this movement and the brake device has been put into operation.

[0032] To enable the pre-assembly of the braking device 6, the washer 8 is placed on a support 4 (barrel bar) which has on its outer periphery an abutment surface 26 which faces the washer horizontally and which is located diametrically opposite the aforementioned bearing surface 25, so that the washer 8 and the braking spring 10 can be pre-assembled on the mechanical timepiece movement 2, before assembling the first wheel set 30, with the washer supported against the abutment surface 26, as shown in Figures 1 to 3. The abutment surface 26 is defined by a lateral surface of a cavity 12 machined in the support 4, and the washer is placed in this cavity 12 which opens onto the lower side of the movement (by default, with the analog display on top).

[0033] In a preferred alternative embodiment, the abutment surface 26 is arranged such that, following the preliminary assembly of the washer 8 and the brake spring 10, the central cylindrical opening of the washer has at least one zone overlapping the central circular opening in a rotatable or fixed pipe or tube 44 into which a portion of the axle 36 of the first wheel set 30 (chrono wheel set) is then inserted, so that when the first wheel set is installed in the mechanical timepiece movement 2, the axle can pass through the two central circular openings without first having to apply a radial force to the washer. As can be seen in FIG. 3 , in the illustrated alternative embodiment, the central cylindrical opening of the washer 8 is entirely overlapped on the central circular opening in the pipe 44. It should be noted that in the illustrated example, the axle 36 of the first wheel set 30 is inserted into the pipe 44, which holds the display hands and is therefore rotatable, and which is pivoted within the plate 60 and the barrel bar 4. An internal bearing 46 is arranged inside the central opening of the pipe, in which the internal bearing rotates the end 37 of the mandrel 36, on which the chronograph hand 48 is mounted. This end has a maximum diameter that is smaller than the diameter of the rotation surface 35, which is specifically cylindrical and axial and ultimately lies inside the central cylindrical opening 9 within the washer. In particular, this makes it easier to insert the mandrel 36 into the two central circular openings when the chronograph wheel set is assembled, if the initial overlap of the two central circular openings is only partial before the assembly of the chronograph wheel set.

[0034] Once mounted, the first wheel set 30, which in the illustrated embodiment forms the chronograph wheel set, is swiveled by means of the upper bearing 46 and by means of the lower bearing 38 arranged in the opening of the bar 40, so that the washer 8 is no longer supported against the side wall 26 of the cavity 12 of the support 4, but, via its central cylindrical opening, against the axle 36 of the first wheel set, more precisely against the rolling surface 35 of this axle, which is advantageously cylindrical and axial. In the illustrated alternative embodiment, the barrel 30 is supported between the barrel bar 4 and the plate 60, which form the support for the washer 8. It should be noted that the first wheel set is rotated. The first wheel set is in turn driven in rotation by the second wheel set 52, sometimes via a clutch wheel 54 mounted on a lever 56. The lever 56 is customarily controlled by a column wheel or cam (disengagement is indicated by an arrow in FIG. 4). The second wheel set 52 comprises a drive wheel integrated into a gear train from the barrel to the escape wheel 58. This drive wheel here forms the small seconds wheel of the time display of a watch receiving a mechanical timepiece movement 2.

[0035] Although the present invention has been described in detail with respect to the chronograph wheel set 30, the braking device of the present invention can be provided with respect to other wheel sets of a mechanical timepiece movement, in particular with respect to the small seconds wheel set when this wheel set is not included in the tooth wheel train from the barrel to the escape wheel 58.

[0036] The present invention has several advantages, some of which have already been described. The braking device 6 comprises an eccentric 20 that facilitates adjusting the radial pressure exerted by the braking spring on the intermediate part / washer 8 and, through this, the radial force applied to the axle 36 of the first wheel set 30, and thus the moment of friction applied to this first wheel set. The eccentric 20 makes it possible to adjust the braking torque once the braking device is fully mounted on the mechanical timepiece movement, without having to remove the braking spring in order to slightly change its initial shape. In the presence of the washer 8 between the brake spring 10 and the axle 36, and in addition to the fact that the forces involved are intended to be radial, the fitting of the chrono hand 48 on the first wheel set 30, and in particular its removal, for example when changing this hand 48 or cleaning the mechanical timepiece movement, cannot damage the brake spring, which is a delicate element of the brake device 6, and the washer 8 is quite strong and can withstand a certain amount of axial pressure against the support 4.

[0037] The braking device 6 is such that it is protected against stresses that may damage it during the assembly of the other parts of the mechanical timepiece movement, in particular during the assembly of the chrono wheel set 30. When the timepiece movement is removed, in particular when the first wheel set 30 is removed, the braking device 6 can remain in place without changing its settings.

[0038] The braking device according to the invention makes it possible to determine the frictional force moment relatively accurately in advance, since the lateral surfaces 9 of the intermediate piece, in particular the lateral surfaces 9 of the washer 8, have a height that is generally significantly greater than that of the braking spring, allowing the material of the intermediate piece / washer 8 to be selected and the diameter of the surface of revolution that defines the cylindrical and axial surface of the mandrel 36 that it supports to be accurately determined. [Explanation of symbols]

[0039] 2 Mechanical watch movements 4. Support 6 Braking Device 8 Intervening parts, washers 9 Lateral surface 10, 10A, 10B, 11 Brake spring 20 Eccentric 24 groove 25 Support surface 26 Contact surface 30 Display Wheel Set 35 Surface of Revolution 36 Mandrel

Claims

1. an indicator wheel set (30) comprising a barrel, an escape wheel set (58) associated with a mechanical resonator, an axle (36) intended to hold an indicator element (48), and a braking device (6) associated with said indicator wheel set and comprising a braking spring (10, 10A, 10B, 11) and an intermediate part (8, 68, 78) arranged between said braking spring and the axle of said indicator wheel set, said indicator wheel set being capable of being driven in rotation by said barrel but not forming part of a gear train from said barrel to said escape wheel set, said braking spring being adapted to brake said indicator wheel set as soon as said indicator wheel set is subjected to a rotational driving torque; A mechanical timepiece movement (2) arranged so that it is possible to generate a braking torque on the indicator wheel set through the intermediate part against which the braking spring presses, characterized in that the intermediate part and the braking spring are arranged so that the intermediate part remains stationary and does not rotate in normal operation, and the intermediate part has a lateral surface (9) that presses against the rotating surface (35) of the axle, and a bearing surface (25) against which the braking spring exerts its entire pressing force towards the axle to generate a friction force between the lateral surface and the rotating surface that generates the braking torque.

2. 2. A mechanical timepiece movement according to claim 1, characterized in that the intermediate part (8, 68, 78) exerts exclusively radial pressure on the axle (36) of the indicator wheel set (30).

3. 3. A mechanical timepiece movement according to claim 2, characterized in that said axle defines a central axis (42), said surface of revolution (35) is cylindrical and extends axially, and said transverse surfaces (9) extend axially.

4. 3. A mechanical timepiece movement according to claim 2, characterized in that the brake spring (10, 10A, 10B, 11) is a wire or strip spring whose longitudinal axis lies in a geometric plane parallel to the general plane (50) of the movement.

5. 5. A mechanical timepiece movement according to claim 4, characterized in that the brake spring (10, 10A, 10B, 11) is arranged so that a middle part of the brake spring exerts the pressing force on the bearing surface of the intermediate part (8, 68, 78), and that two end parts of the brake spring, located on either side of the middle part, are stressed by two remote parts (16, 20) of the timepiece movement so that the middle part exerts the pressing force on the bearing surface.

6. 6. A mechanical clock movement according to claim 5, characterized in that the brake spring (10, 10A, 10B) is not fastened by the clock movement but is held under tension by the remote parts (16, 20) of the clock movement against which the two ends of the brake spring press in two directions in the geometric plane.

7. 7. A mechanical timepiece movement according to claim 6, characterized in that the intermediate part and the brake spring are configured in such a way that the relative arrangement of the intermediate part and the brake spring does not substantially change over time, even in the event of possible longitudinal displacements of the brake spring as a result of accelerations to which the movement is subjected in its general plane.

8. 8. A mechanical timepiece movement according to any one of claims 5 to 7, characterized in that the movement comprises an eccentric (20) whose axis of rotation is perpendicular to the geometric plane and which is arranged to press against the brake spring (10, 10A, 10B, 11) in order to make it possible, by rotation of its axis of rotation, to vary the pressing force exerted by the brake spring of the intermediate part (8, 68, 78).

9. 8. A mechanical timepiece movement according to any one of claims 1 to 7, characterized in that the intermediate part is a washer (8) having a central opening through which the axle (36) of the indicator wheel set passes, the lateral surface (9) of the washer being defined by the cylindrical surface of its central opening.

10. 9. A mechanical timepiece movement according to claim 8, characterized in that the intermediate part is a washer (8) having a central opening through which the axle (36) of the indicator wheel set passes, the lateral surface (9) of the washer being defined by the cylindrical surface of the central opening.

11. 10. A mechanical timepiece movement according to claim 9, characterized in that the washer (8) has on its periphery a groove (24) which defines the bearing surface (25) and into which a portion of the brake spring (10) is at least partially inserted, exerting the pressing force in the direction of the axle.

12. 11. A mechanical timepiece movement according to claim 10, characterized in that the washer (8) has on its periphery a groove (24) which defines the bearing surface (25) and into which a portion of the brake spring (10) is at least partially inserted, exerting the pressing force in the direction of the axle.

13. 8. A mechanical timepiece movement according to any one of claims 1 to 7, characterized in that the intermediate part (8) is arranged on a support (4) which has, on its outer periphery, an abutment surface (26) which faces the intermediate part horizontally and which is located directly opposite the support surface (25), so that the intermediate part and the brake spring can be pre-assembled in the mechanical timepiece movement before assembling the indicator wheel set (30), with the intermediate part supported against the abutment surface.

14. A mechanical clock movement as described in claim 13, characterized in that the intervening part (8) is a washer (8) having a central cylindrical opening through which the axle (36) of the display wheel set passes, and the abutment surface (26) has at least one zone that overlaps with the central circular opening of a rotatable or fixed pipe (44) into which a portion of the axle (36) of the display wheel set (30) is inserted following the preliminary assembly of the intervening part (8) and the brake spring (10), so that when the display wheel set is mounted in the mechanical clock movement, the axle is arranged in such a way that it can jump out of the central cylindrical opening of the washer (8) and the central circular opening of the pipe (44) without first having to exert a radial force on the intervening part.

15. 8. A mechanical timepiece movement according to any one of claims 1 to 7, characterized in that at least a portion of the axle (36) defining the surface of revolution (35) is made of steel or consists of a copper alloy, and at least a portion of the intermediate parts (8) defining the lateral surfaces (9) is respectively made of a copper alloy or steel.

16. 8. A mechanical timepiece movement according to any one of claims 1 to 7, characterized in that at least a portion of the axle (36) defining the surface of revolution (35) is made of steel or consists of a copper alloy, and at least a portion of the intermediate part (8) defining the lateral surface (9) consists of a polymer.

17. 8. A mechanical timepiece movement according to any one of claims 1 to 7, characterized in that at least a portion of the axle (36) defining the surface of revolution (35) is made of steel or consists of a copper alloy, and at least a portion of the intermediate piece (8) defining the lateral surface (9) is made of ceramic or a material containing gold or nickel and forming an outer layer at least partially covering the intermediate piece.

Images