Electromechanical timepiece movement with gear set for holding display member and with Anti-vibration device

Abstract

To provide an anti-vibration / anti-floating device being easy to mount and mounted in a preparatory stage for mounting a display gear set.SOLUTION: An electromechanical timepiece movement 2 comprises a display gear set 30 including a stem 36 intended to hold a display hand 48, and a brake device coupled to the display gear set 30 and including a brake spring 10 and a washer 8 arranged between the brake spring 10 and the stem 36 of the display gear set 30, where when the display gear set 30 receives rotary drive torque, the brake spring 10 can immediately generate a brake torque on the display gear set 30 via the washer 8 pressed by the brake spring 10, the washer 8 and the brake spring 10 are arranged such that the washer 8 remains stationary and does not rotate during normal operation, and the washer 8 applies overall pressing force towards the stem 36 in order to generate friction force that produces the brake torque between a lateral surface of the washer 8 and a rotating surface of the stem 36.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an electromechanical timepiece movement comprising a gear set that holds a display member, in particular the hands, and equipped with an anti-vibration device (also called anti-float device) formed by a braking device acting on the gear set to prevent the display member from vibrating as it rotates and also to prevent it from floating during intervals and periods when it is stationary. [Background technology]

[0002] Swiss Patent Publication No. 1 discloses a vibration damping device for a timepiece gear set, in particular a chronograph gear set (hereinafter also referred to as a "chrono gear set"). The vibration damping device comprises an axle on which a pinion is mounted, which meshes with a clutch wheel (hereinafter referred to as a "drive wheel") to form a coupling for the chronograph mechanism. Note that an axle on which a pivot that guides rotation is mounted is also called 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 abuts obliquely against the axle, which for this purpose has a frusto-conical shoulder. The wire spring has a support point at the angle formed by the shoulder and a cylindrical section whose diameter corresponds to the minimum diameter of the shoulder, at which point it exerts an oblique force on the axle, so that the teeth of the pinion press against the drive wheel, and the lower annular surface of the axle opposite the shoulder, perpendicular to the axis defined by the axle, presses axially against a bearing on which the chronograph gear set revolves. The spring is designed to be straight when unstressed, and is fixed at one end to the movement frame, while a portion of the second end is under tension and presses against the axle as explained above. For several reasons, this vibration isolation device creates problems with controlling the moment of friction applied to the chronograph gear set, and there is no way to adjust this moment of friction. When the chronograph hand is subsequently removed, the spring is subjected to an axial force that can damage it.

[0003] German Patent Publication No. 2002-2003424 describes a solution for improving the control of the frictional force moment applied to a seconds gear set. According to the document, a wire or band spring is fastened at its first end to a plate by riveting. The plate is suspended by a rivet with a head having a threaded slot located on one side of the bar opposite the plate. The rivet has an intermediate cylindrical portion that is inserted into a hole in the bar by a friction fit, allowing the rivet, plate, and first end of the spring to be subjected to constant rotation using a tool. The second end of the friction spring is free and abuts radially against a plastic washer press-fitted onto the axle of the seconds gear set. The washer has a transverse groove in which the second end of the spring is positioned. This system is very difficult to assemble into a watch movement. First, the friction spring must be fastened to the plate by inserting its first end into a slot and then performing a first riveting operation, forcing material into both ends of the slot. Next, the plate with the friction spring must be brought inside the bar after the rivet is inserted through the hole on the opposite side. A second riveting operation must then be performed to crush the end of the rivet and secure the plate to the rivet. The two consecutive riveting operations pose a high risk of damaging the friction spring at each stage of assembly: first to the plate and then to the bar. Finally, the bar, plate, and friction spring assembly is assembled into the watch movement at approximately the same time as the pivot of the seconds gear set's axle, which holds the grooved washer, is inserted into the bearing located on the corresponding bar. This assembly requires that the spring not be stacked on top of the grooved washer, since the spring is rigidly connected to the bar and the grooved washer, designed to receive the free end of the tensioned spring, is rigidly connected to the axle. Therefore, there is a first assembly / disassembly position for the spring, and a second operating position in which the free end of the spring is placed in the groove of the washer to apply tension to the spring. To move it from one position to the other, the watchmaker must use a tool that acts on the rivet head, which causes the spring tension set when it is removed for maintenance to be lost.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 implement.

[0004] Furthermore, this vibration isolation device does not provide a perfect solution to the problem of adjusting the moment of force applied to the seconds gearset to prevent vibration. This is because the frictional force is determined, in particular, by the shape of the transverse groove in the plastic washer and the shape of the end of the spring inserted into this groove and radially pressing against the washer. This frictional force is difficult to control and reproduce because it depends heavily on the dimensions, shape, and surface finish of the spring and groove. Another problem is that the assembly of an intermediate piece on the axle of the seconds gearset increases the gearset's radial vibration, thereby causing greater fluctuations than would occur without such an intermediate piece, especially when the spring directly presses against a conventional axle with less radial vibration. Furthermore, if the watch is subjected to vibration or shock, the second free end of the spring may come off the grooved washer, making it impossible to guarantee a constant braking torque. Worse yet, if a severe shock is applied, the spring fixing plate, which is held in place by friction alone, may move angularly, changing the braking setting. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Swiss Patent No. 580301 [Patent Document 2] German Utility Model Application Publication No. 6800934 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to solve the above-mentioned problems of the prior art in the case of electromechanical movements which also have vibration / floating problems due to the fact that at least one display gear set intended to hold a display member is not subjected to a holding torque outside the time intervals when it is driven in rotation by a timepiece motor. In particular, the present invention proposes an anti-vibration / anti-floating device for a display gear set driven in rotation by an electromechanical motor, which is easy to install and, in a preferred alternative embodiment, can be installed in preparation for the installation of said display gear set. [Means for solving the problem]

[0007] To this end, the invention relates to an electromechanical timepiece movement comprising an electromechanical motor, an indicator gearset arranged to be driven in rotation by the electric motor and comprising an axle intended to hold an indicator member, and a braking device coupled to the indicator gearset and comprising a brake spring and an intermediate piece arranged between the brake spring and the axle of the indicator gearset. The brake spring is arranged so that it can generate a braking torque on the indicator gearset via the intermediate piece against which it presses as soon as the indicator gearset is subjected to a rotational driving torque. The intermediate piece and the brake spring are arranged so that the intermediate piece remains stationary and non-rotating during normal operation, the intermediate piece having a lateral surface pressing against the rotational surface of the axle and a bearing surface against which the brake spring exerts an overall pressing force towards the axle in order to generate a frictional force between the lateral surface and the rotational surface that generates the braking torque.

[0008] In a preferred alternative general embodiment, the intermediate piece exerts only radial pressure on the axle of the indicator gear set.

[0009] In the main embodiment, the damping spring is a wire or band spring, the longitudinal axis of which lies in a geometric plane parallel to the general plane of the movement.

[0010] In one main embodiment, the movement comprises an eccentric, the axis of rotation of which is perpendicular to said geometric plane and which is arranged to radially press against the damping spring, such that rotation about its axis of rotation makes it possible to vary the overall radial pressing force that the damping spring exerts on the intermediate part. [Brief explanation of the drawings]

[0011] The invention is explained in more detail below using the accompanying drawings, given as non-limiting examples, in which: [Figure 1] 1 is a bottom view of a main embodiment of an electromechanical timepiece movement according to the invention, with parts of the movement removed to better show the braking device according to the invention; FIG. [Figure 2] 2 is an enlarged partial view of the electromechanical timepiece movement of FIG. 1 showing the braking device according to the invention; [Figure 3] FIG. 3 is a perspective view of the braking device of the main embodiment of FIGS. 1 and 2; [Figure 4] FIG. 4 is a horizontal section through the electromechanical timepiece movement through the brake device of FIGS. 2 and 3, in this case in a pre-assembled state following a preparatory step for assembling the brake device, which precedes the assembly of the indicator wheel set to the movement. [Figure 5] FIG. 5 is a partial cross-sectional view of the partially assembled timepiece movement following said preparatory step, taken along section line VV in FIG. 4, the cross-section passing through the central axis of the tube intended to receive part of the axle of the display wheel set. [Figure 6] 6 is a cross-sectional view of the electromechanical timepiece movement of FIG. 1 taken along the section line VI-VI of FIG. 2, the view passing through the axis of rotation of the axle of the indicator gear set and showing the brake device after the indicator gear set has been mounted on the movement. [Figure 7] 1A and 1B show schematic partial views of certain alternative embodiments to the main embodiment; [Figure 8] 8A and 8B show schematic partial views of two advantageous alternative embodiments to the main embodiment. [Figure 9] 1 shows a schematic partial view of another specific alternative embodiment to the main embodiment; [Figure 10] 2 shows a schematic partial view of a second embodiment of the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] A main embodiment of an electromechanical timepiece movement 2 according to the invention will be described below with reference to FIGS.

[0013] Electromechanical watch movement 2 an electromechanical motor 54, in particular of the stepper type, comprising a rotor 56 on which a pinion 58 is mounted; a first gear set 30 forming a display gear set intended to hold a display member 48, in particular a seconds hand, the first gear set 30 being driven in rotation by a second gear set 52 which is driven in rotation via its pinion 58 by a rotor 56 when an electromechanical motor 54 is activated; a braking spring 10 arranged so as to generate on the first gear set 30 a braking torque to prevent oscillation of the indicator member 48 as soon as this first gear set is subjected to a rotational drive torque, and a permanent radial force to maintain the indicator member in a stable position when the indicator member is at rest and between drive pulses, thus preventing it from floating; Equipped with.

[0014] According to the invention, the electromechanical timepiece movement 2 comprises a brake device 6 acting on the indicator gearset 30, the brake device 6 comprising a brake spring 10 and an intermediate piece 8 arranged between the brake spring and the axle 36 of the first gearset 30. The brake spring is arranged so that, as soon as the indicator gearset is subjected to a rotational driving torque, it can generate a braking torque on the indicator gearset via the intermediate piece against which it presses. For this purpose, the intermediate piece has a lateral surface 9 that presses against the rotational surface 35 of the axle and a bearing surface 25 against which the brake spring exerts an overall pressing force in the direction of the axle, so that a frictional force is generated between the lateral surface 9 and the rotational surface 35, which frictional force generates a braking torque. The braking torque is thus applied by the brake spring to the first gearset / indicator gearset via the intermediate piece against which it presses. The intermediate piece 8 and the brake spring 10 are arranged so that the intermediate piece remains stationary and does not rotate during normal operation. The axle 36 and intermediate piece of the first gear set 30 are configured so that the rotating surface 35 of the axle can slide over the flank 9 while being subjected to dynamic friction forces that create a braking torque. Before the rotating surface slides over the flank, static friction forces create a braking torque that keeps the axle stationary.

[0015] Preferably, the intermediate piece 8 exerts only radial pressure on the axle 36 of the first gearset 30. According to an advantageous feature, the damping spring 10 exerts only a radial overall pressing force on the intermediate piece. The bearing surface 25 is opposite the flank 9, i.e., the bearing surface is located on one side of the intermediate piece 8 opposite another side of this intermediate piece that defines the flank 9. This alternative embodiment is advantageous because the damping device abuts on an undercut that varies little in radial runout and therefore provides a constant damping torque for a given friction force between the rolling surface 35 and the flank 9. In the advantageous alternative embodiment shown in the figures, the rolling surface 35 of the axle 36 is cylindrical and axial, and the flank 9 of the intermediate piece is axial, i.e., the cylindrical rolling surface 35 and the flank 9 are oriented along the rotation axis 42 of the first gearset 30, which coincides with the central axis of the axle 36, and therefore the flank 9 and the cylindrical rolling surface 35 are parallel to this rotation axis 42. In an alternative preferred embodiment, the intermediate part 8 and the brake spring 10 are configured in such a way that said pressure remains constant once the indicator wheel set is assembled in the movement and the brake device is fully assembled and adjusted.

[0016] According to a main alternative embodiment, the brake spring 10 is a wire or band spring whose longitudinal axis lies in a geometric plane parallel to the general plane 50 of the electromechanical timepiece movement 2 .

[0017] According to the alternative embodiment shown, the intermediate part 8 is a washer having a central cylindrical opening in which the axle 36 of the first gearset 30 slides and rotates freely without any interaction from the damping spring 10, said side surface 9 of this washer 8 being defined by the cylindrical surface of its central cylindrical opening, which is preferably circular (i.e. the surface of revolution).

[0018] According to a particular alternative embodiment, the washer 8 has a circular groove 24 on its periphery, which defines a bearing surface 25, and into which a portion of the brake spring 10 is at least partially inserted, exerting a radial pressure. In particular, the groove 24 has a generally V-shaped cross section, and the brake spring 10 is a wire spring with a circular cross section, as shown in Figures 5 and 6. This arrangement allows the brake spring to be axially disposed in contact with the washer at its center, and therefore cannot move freely axially.

[0019] As a non-limiting example, in a first alternative embodiment, at least the portion of the washer 8 defining the central cylindrical opening is made of a copper-beryllium (CuBe) alloy while at least the portion of the mandrel defining the surface of rotation 35 is made of steel, or vice versa. This first alternative embodiment provides good tribological results. In a second alternative embodiment, in which the mandrel is made of steel or CuBe, at least the portion of the washer defining the 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 the portion of the washer defining the central cylindrical opening is made of bronze, nickel, or gold, particularly in the case of nickel or gold, or more typically in the case of a metal alloy containing gold or nickel, in the form of a thin layer deposited on a base of another material. In another alternative embodiment, at least the portion of the washer that defines the central cylindrical opening is made of ceramic, particularly ruby ​​or zirconia.

[0020] It should be noted that the material of the brake spring can be selected to optimize the elasticity of this spring and its manufacture, without having to worry about friction or wear problems, given that the washer, and more generally the intermediate part, is intended to remain stationary, i.e., stationary and not rotating, during the normal operation of the electromechanical timepiece movement. In the case of a washer, modifications can be made to the shape of the intermediate part and / or the shape of the brake spring, as will be explained in more detail below, to prevent rotation, or, in the case of a washer in particular, modifications can be made to the material used to make the spring and at least the outer part of the intermediate part that comes into contact with the spring and / or the surface treatment applied to these parts, to obtain a high frictional force between the brake spring and the intermediate part.

[0021] According to another preferred alternative embodiment, the brake spring 10 is arranged in the electromechanical timepiece movement 2 so that a central 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 central portion of the brake spring exerts said pressure on the bearing surface 25 of the intermediate part / washer 8. For this purpose, the two ends of the brake spring, located on either side of the central portion, are stressed by two remote portions 16 and 20 of the timepiece movement so that the central portion exerts a pressure on the bearing surface of the intermediate part / washer 8. This configuration of the brake device is advantageous because it allows the brake spring to constantly press against the bearing surface of the intermediate part / washer. Furthermore, this configuration is less sensitive to vibrations and shocks than a brake spring having a fixed point at one of its ends and a contact point at the other.

[0022] In a particular alternative embodiment, the brake spring 10 is curved in its central portion, and the bearing surface 25 of the intermediate part / washer 8 has a convex curvature in said geometric plane relative to the axle 36 of the first gearset 30, particularly a circular curvature in the case of the washer, followed in the first alternative embodiment by the central portion of the brake spring along the bearing surface. In a second alternative embodiment, the radius of curvature of the central portion is smaller than the average radius of curvature of the bearing surface, so that the brake spring presses on the intermediate part / washer at "two points" on the bearing surface, i.e., at two separate locations. It should be noted that in the case of a substantially V-shaped groove, a spring with a circular cross section presses locally at a pair of axially aligned points. Thus, with such a configuration of groove and brake spring, the spring presses at two pairs of points angularly spaced from one another, each pair of points being axially aligned and therefore "two points" projecting in the general plane of the spring parallel to the general plane 50 of the movement. Finally, these alternative embodiments do not exclude other advantageous alternative embodiments in which the mean radius of curvature of the central portion is greater than the radius of curvature of the bearing surface, so that radial pressure is applied at a "single point" (i.e., a pair of axially aligned points, but at a single point that protrudes in the general plane of the spring / general plane of the movement 50).

[0023] According to an advantageous alternative embodiment, as shown in Figures 2 to 4, the brake spring 10 is not fixed to the movement by a specific part, but is held under tension by two parts 16 and 20 of the movement, which are pressed by two ends of the brake spring located on either side of the center of the brake spring and abutting radially against an intermediate part (specifically washer 8). The direction of the forces exerted on the spring by the two parts 16 and 20 is opposite to the direction of the reaction force of the intermediate part / washer 8 on the center 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, coinciding with the central axis of the axle 36), generate stresses that hold the brake spring in place. To prevent the spring from moving axially / vertically, particularly its central portion, from leaving the groove 24, two portions of the plate 4 are provided on each of the two sides, defining the lower axial stops of the brake spring. On the first side, the plate 4 is provided with an upper groove 14 (analog display side), the bottom of which forms a thin horizontal wall and is positioned so as to define the lower limit of the displacement of the portion of the spring located on the first side. On the second side, the brake spring is partially positioned on a small protrusion 18. The plate 4 is positioned below an intermediate plate 60 of the timepiece movement 2, which defines the general plane 50 of the movement and fixedly supports the base of a tube 44 through which the axle 36 of the display gear set 30 passes, the central axis of which defines the rotation axis 42. The intermediate plate 60 defines the upper axial stop of the spring 10. The base of the tube 44 can support the washer 8 when it is mounted, in particular before the spring is mounted, and thus forms a support for the washer. It should be noted that in another alternative embodiment, the element 44 constitutes a rotatable barrel.

[0024] Various other advantageous alternative embodiments are illustrated in Figures 7, 8A, and 8B. The alternative embodiment shown in Figure 7 features a brake spring 10A having a central portion with two bent portions 71 and 72, separated by a straight portion 70 (without stress) that abuts against the circular washer 8 substantially in its center. This ensures that the brake spring 10A always abuts against the washer 8 at a "single point." The alternative embodiments of Figures 8A-8B feature an intermediate part 68 that is not circular but is formed by a cut washer having a straight zone 80. In the alternative embodiment shown in Figure 8A, the brake spring 10 has a bent portion 74 in its central portion that is arranged facing the straight zone 80 of the cut washer 68. In the alternative embodiment shown in FIG. 8B , the spring 11 is straight and unstressed, and when tension is applied to the spring 11 to press against the intermediate part, the spring 11 bends slightly (concave curvature as viewed from the intermediate part) to press against both ends of the linear zone 80 of this intermediate part. Thus, in the alternative embodiments of FIGS. 8A and 8B , the brake spring 10 or 11 applies two forces F1 and F2, respectively, to both ends of the linear zone 80. The two forces F1 and F2 are generally radial; that is, their sum at the midpoint is radial. However, because each of the two forces exerts a force moment on the intermediate part 68, as the spring moves longitudinally and one of the two forces F1 and F2 decreases relative to the other, the intermediate part 68 automatically undergoes a small rotation to rebalance the moments of the two opposing forces acting on it. The alternative embodiment shown in FIG. 8B is preferred because it reduces the risk of the cut-off washer rotating. This alternative embodiment also allows the desired braking torque to be maintained even if the braking spring undergoes some longitudinal displacement during impact or sudden acceleration. However, the alternative embodiment shown in FIG. 8A using a bending spring is less likely to undergo longitudinal displacement during impact. The alternative embodiment using a cut-off washer is advantageous in preventing the intermediate part from rotating during normal operation, which is important to ensure a constant set braking torque. The alternative embodiments shown in FIGS. 8A and 8B always provide support at "two points" projecting in the geometric plane of the spring.

[0025] A specific alternative embodiment is illustrated in FIG. 9. This alternative embodiment, like the alternative embodiment of FIG. 7, is designed to ensure that the brake spring 10B is always pressed at a "single point" on an intermediate part 78 having a generally square shape with rounded corners. The brake spring 10B has a bend 76, and two straight sections of the spring on either side of the bend are at an angle greater than 90° relative to each other but relatively close to this value, for example, equal to 110°. One of the rounded corners of the intermediate part is located at the bend 76 of the spring, and the spring exerts a substantially radial force F on the intermediate part when the spring and intermediate part 78 are stationary. When the spring 10B moves, particularly as a result of an impact, the direction of the force changes, and the intermediate part is subjected to a force moment and rotated. This ensures that the same corner of the square intermediate part always remains at the bend 76 of the brake spring, and pressure is applied at "one point." Also, during normal operation (when the braking spring is at rest), this alternative embodiment keeps the intermediate part stationary (non-rotating), thereby ensuring a constant, well-defined braking torque on the gear set axle.

[0026] According to a preferred alternative embodiment of the present invention, the brake device 6 comprises an eccentric 20, the rotation axis of which is perpendicular to the general plane 50 and thus parallel to the central axis / rotation axis 42 of the gearset 30. The eccentric 20 is arranged to radially press against the brake spring so that rotation about its rotation axis can vary the radial pressure the brake spring exerts on the intermediate part / washer. In the advantageous alternative embodiment shown in FIGS. 1 and 2, the eccentric 20 constitutes one of two parts that keep the brake spring under tension. Rotating the eccentric 20 therefore varies the stress on this spring, making it possible to adjust the braking torque applied to the first gearset 30 (chronograph gearset) when it is subjected to a rotational driving torque. This configuration is advantageous because it is less sensitive to vibrations and shocks. In another alternative embodiment, a different device for adjusting the radial force is provided, in particular a device equipped with a linearly movable pressure member.

[0027] 10 shows another embodiment of the invention in which the brake spring 11 is straight / linear (unstressed). This spring is rigidly fixed at one of its ends to a fixed part 82 and cannot change its angular position in a geometric plane, thus preventing any unintended or impact-induced displacement. The groove in the fixed part 82 into which the end of the spring 11 is inserted is oriented so that the central zone of the spring exerts a radial pressure force F on the washer 8, the spring having a first convex curvature (as seen from the washer) between the fixed part 82 and the spring's support point on the washer. Preferably, the other end of the spring is provided with an eccentric to adjust the radial force F, which in this embodiment is located on the same side as the brake spring and washer 8, which form an intermediate part between the brake spring and the axle of the gearset in question. Therefore, the brake spring 11 also has a second convex curvature between the 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. 10 defines a structure with a single support point, i.e., a structure in which the brake spring exerts pressure on the washer at a "single point" according to the above definition. Another alternative embodiment of the "two-point" type is provided with a star-shaped intermediate part, for example, with four to six tips, each with a small rounded portion. A slightly convex brake spring always exerts pressure on two tips of the star-shaped intermediate part, thus exerting two forces and creating an overall radial pressure at their center point. In other words, the two forces generate two opposing force moments of equal strength on the intermediate part. It should also be noted that the brake device cannot be disengaged in the event of an impact.

[0028] Figures 4 and 5 show the electromechanical timepiece movement 2 with the brake device 6 pre-assembled in preparation for the assembly of the first gearset 30. This pre-assembly of the brake device 6 is advantageous, in particular because the force exerted by the brake spring is radial and because the washer 8 is provided on the pinion and wheel 32 forming the first gearset. The axle 36 of the first gearset can therefore be mounted from below the timepiece movement through the central opening of the washer 8. Figures 1 to 3 and 6 show the electromechanical timepiece movement 2 and the brake device in operation after the first gearset 30 has been mounted on this movement.

[0029] To allow preliminary assembly of the brake device 6, the washer 8 is placed on the support (the base of the tube 44) at the plate 4, which has an abutment surface 26 around the washer that faces horizontally towards the washer and is located directly opposite said bearing surface 25, so that the washer 8 and the brake spring 10 can be pre-assembled in the electromechanical timepiece movement 2, with the washer abutting against the abutment surface 26, as shown in Figures 4 and 5, before the assembly of the first gearset 30.

[0030] In a preferred alternative embodiment, the abutment surface 26 is arranged so that, after pre-assembly of the washer 8 and the brake spring 10, the central cylindrical opening of the washer has at least one area where it overlaps with the central circular opening of the pipe or tube 44, into which a portion of the axle 36 of the first gearset 30 is inserted, so that when the first gearset is attached to the electromechanical timepiece movement 2, the axle can pass through the two central openings without first exerting a radial force on the washer. As shown in FIG. 5 , in the illustrated alternative embodiment, the central cylindrical opening of the washer 8 does not completely overlap the central circular opening of the tube 44. Preferably, at least a majority of the washer opening overlaps the central opening of the tube. It should be noted that in the illustrated example, the axle 36 of the first gearset 30 is inserted into a stationary tube 44. The upper end of the axle intended to support the seconds hand has a smaller diameter, which makes it easier to insert this axle into the two central openings when assembling the display gear set 30, if the two central openings only partially overlap initially when the brake device is in a pre-assembled state.

[0031] When the first gearset 30 is assembled in the timepiece movement, the washer 8 no longer abuts against the side wall 26 of the plate 4, but rather, through its central cylindrical opening, against the axle 36 of the first gearset, more precisely against the rotation surface 35 of this axle, which is advantageously cylindrical and axial. This first gearset can then be driven in rotation at any time by an electromechanical motor 54 via the second gearset 52, on command.

[0032] Although the invention has been described in detail with respect to the seconds wheel set 30, the braking device of the invention may be provided on other wheel sets of an electromechanical timepiece movement, in particular on the minute wheel set or the chrono wheel set.

[0033] The present invention has several advantages, some of which have already been described. The brake device 6 comprises an eccentric 20 which makes it easy to adjust the radial pressure exerted by the brake spring on the intermediate piece / washer 8 and thus on the axle 36 of the first gearset 30, as well as the moment of friction applied to this first gearset. The eccentric 20 makes it possible to adjust the braking torque after the brake device has been fully mounted on the electromechanical timepiece movement, without having to remove the brake spring in order to slightly change its initial shape. In addition to the fact that the forces involved are intended to be radial, and given the presence of washer 8 between brake spring 10 and axle 36, the mounting of second hand 48 on first gearset 30, and in particular its removal, for example when replacing this hand or cleaning the electromechanical timepiece movement, does not damage the brake spring, which is a delicate element of brake device 6, and washer 8 is able to withstand a certain amount of axial pressure against its support.

[0034] The brake device 6 is protected from stresses that may damage the brake device 6 during the assembly of other parts of the electromechanical timepiece movement, in particular during the assembly of the display gear set 30. When the timepiece movement 2 is removed, in particular when the display gear set is removed, the brake device 6 can remain in place without having to change its setting.

[0035] The braking device according to the invention makes it possible to predetermine the moment of friction force relatively accurately, since the flank 9 of the intermediate part, in particular the washer 8, has a height which is generally much greater than the flank 9 of the braking spring, the material of the intermediate part / washer 8 can be selected, and the diameter of the surface of rotation of the mandrel 36 which defines the cylindrical axial surface against which the intermediate part / washer 8 abuts is precisely determined.

Claims

1. An electromechanical clock movement (2), comprising: an electromechanical motor (54); an indicator gear set (30) arranged to be rotated by said electromechanical motor and comprising an axle (36) intended to carry an indicator member (48); a braking device (6) coupled to the indicator gear set and comprising a braking spring (10, 10A, 10B, 11) and an intermediate part (8, 68, 78) arranged between the braking spring and the axle of the indicator gear set; Equipped with the brake spring is arranged so that, as soon as the indicator gearset is subjected to a rotational drive torque, it can generate a brake torque on the indicator gearset via the intermediate part against which it presses, the intermediate part and the damping spring are arranged so that the intermediate part remains stationary and non-rotating during normal operation; The intermediate part has a side surface (9) that presses against a rotation surface (35) of the axle, and a bearing surface (25) on which the braking spring exerts an overall pressing force towards the axle to generate a friction force between the side surface and the rotation surface that generates the braking torque.

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

3. 2. A timepiece movement according to claim 1, characterized in that said axle defines a central axis (42), said surface of rotation (35) is cylindrical and axial, and said side surface (9) is axial.

4. 4. A timepiece movement according to claim 1, wherein the brake spring (10, 10A, 10B, 11) is a wire or band spring, the longitudinal axis of which lies in a geometric plane parallel to the general plane (50) of the movement.

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

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

7. 6. A timepiece movement according to claim 5, characterized in that the movement comprises an eccentric (20) whose axis of rotation is perpendicular to said geometric plane and which is arranged to press against said brake spring (10, 10A, 10B, 11) in such a way that, by rotating about its axis of rotation, the pressing force exerted by said brake spring on said intermediate part (8, 68, 78) can be varied.

8. 4. A timepiece movement according to claim 1, wherein the intermediate part is a washer (8) having a central opening through which the axle (36) of the indicator wheel set passes, the side surface (9) of this washer being defined by the cylindrical surface of its central opening.

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

10. 4. A timepiece movement according to claim 1, wherein the intermediate part (8) is arranged facing an abutment surface (26) diametrically opposite to the bearing surface (25), so that the intermediate part and the brake spring can be pre-assembled in the electromechanical timepiece movement with the intermediate part abutting against the abutment surface before the indicator wheel set (30) is assembled.

11. 11. The timepiece movement according to claim 10, characterized in that the abutment surface (26) is arranged in such a way that, after pre-assembly of the intermediate part (8) and the brake spring (10), the central cylindrical opening of the intermediate part has at least one area that overlaps with the central cylindrical opening of a rotatable or fixed pipe or tube (44) into which a portion of the axle (36) of the indicator gear set (30) is inserted, so that, when the indicator gear set is mounted on the electromechanical timepiece movement, the axle can pass through the two central circular openings without first exerting a radial force on the intermediate part.

12. 4. A timepiece movement according to claim 1, wherein at least the part of the axle (36) that defines the surface of rotation (35) is made of steel or a copper alloy, and at least the part of the intermediate part (8) that defines the side surfaces (9) is made of a copper alloy or steel, respectively.

13. 4. A timepiece movement according to claim 1, wherein at least the part of the axle (36) that defines the surface of rotation (35) is made of steel or a copper alloy, and at least the part of the intermediate part (8) that defines the side surface (9) is made of a polymer.

14. 4. A timepiece movement according to claim 1, wherein at least the part of the axle (36) that defines the surface of rotation (35) is made of steel or a copper alloy, and at least the part of the intermediate part (8) that defines the side surface (9) is made of ceramic, in particular ruby ​​or zirconia, or of a material that contains gold or nickel and forms an outer layer that at least partially covers the intermediate part.

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