Electromechanical timepiece movement comprising wheel set carrying display member and provided with braking device

Abstract

Comprising a wheel set carrying a display member and provided with a braking device. An electromechanical timepiece movement (2) is disclosed comprising an electromechanical motor (54), a display wheel set (30) arranged to be rotated by the electromechanical motor and comprising a stem (36) intended to carry display hands (48), and a braking device associated with the display wheel set and comprising a brake spring (10) and a gasket (8) arranged between the brake spring and the stem of the display wheel set, the brake spring is arranged so as to be able to generate a brake torque on the display wheel set via the washer pressed by the brake spring once the display wheel set is subjected to a rotational drive torque. The washer and the brake spring are arranged such that the washer remains stationary and does not rotate in normal operation. The gasket applies a total compression force to the arbor so as to create a friction force between the lateral surface of the gasket and the revolution surface of the arbor, which generates a braking torque.

Description

Technical Field

[0001] This utility model relates to an electromechanical watch movement, which includes a wheel assembly that carries a display component, particularly a hand, and is provided with an anti-vibration device (also called an anti-floating device) formed by a braking device acting on the wheel assembly to prevent the display component from vibrating when rotating and to prevent the display component from floating during certain time intervals and during periods when the display component is stationary. Background Technology

[0002] Swiss patent document CH 580301 discloses an anti-vibration device for a watch wheel assembly, particularly a chronograph wheel assembly (hereinafter also referred to as a "chronograph wheel assembly"), comprising a stem fitted with a pinion that meshes with a clutch wheel (hereinafter also referred to as a "drive wheel"), thereby forming a connecting device for the chronograph mechanism. It should be noted that the stem fitted with a pivot to guide its rotation is also referred to as a "shaft" in watchmaking. The anti-vibration device for the second hand of the chronograph function is formed by a friction device comprising a spring inclined against the stem. For this purpose, the stem has a truncated conical shoulder, and the spring has a support point at the angle formed by the shoulder and an annular cylindrical portion, the diameter of which corresponds to the minimum diameter of the shoulder. At this point, an inclined force is applied to the stem, causing the teeth of the pinion to press against the drive wheel, and causing the lower annular surface of the stem, opposite the shoulder and orthogonal to the axis defined by the stem, to axially press against a bearing in which the chronograph wheel assembly pivots. The spring is designed to be straight when there is no stress. The spring is fastened to the frame of the movement on one side of the first end, while a portion of one side of the second end is under tension and presses against the stem, as explained above.

[0003] For various reasons, this anti-vibration device causes problems in controlling the torque of the frictional force applied to the timer wheel assembly. Furthermore, there is no way to adjust this frictional torque. Subsequently, when the timer hand (timing pointer) is removed, the spring is subjected to axial force, which may damage the spring.

[0004] German patent document DE 6800934 U describes a solution for improving the control of torque applied to the frictional force of a seconds wheel assembly. According to this document, a spring or leaf spring is fastened to a plate at its first end portion by a riveting technique. This plate is held suspended by a rivet having a head with a screw-like groove, arranged on the side of a rod opposite the side where the plate is located. The rivet has a central cylindrical portion that is inserted into a hole in the rod by means of a friction fit, thereby allowing the rivet, and therefore the plate, and therefore the first end portion of the spring, to undergo a certain rotation with the aid of a tool. The second end portion of the friction spring is free and radially abuts against a plastic washer that is press-fitted / press-fitted onto the shank of the seconds wheel assembly. This washer has a lateral groove in which the second end portion of the spring is placed. This system is difficult to assemble in a watch movement. First, the friction spring must be fastened to the plate by inserting the first end portion of the friction spring into the groove and then pressing material against the two edges of the groove to perform the first riveting operation. After the rivet is inserted into the hole in the rod from the other side, the plate with the friction spring must be brought to the inside of the rod. Then, the end of the rivet must be crushed, and a second riveting operation must be performed to secure the plate to the rivet. It can be seen that there is a high risk of damaging the friction spring at each stage of assembling the friction spring to the plate via two consecutive riveting operations, and then to the rod. Finally, the rod, plate, and friction spring assembly are assembled into the watch movement, simultaneously inserting the pivot of the stem carrying the grooved washer into the bearing arranged in the relevant rod. This assembly requires that the spring not stack on top of the grooved washer, because the spring is rigidly connected to the rod, and because the grooved washer, designed to receive the free end of the tensioned spring, is rigidly connected to the stem. Therefore, there is a first assembly / disassembly position and a second working position for the spring, in which the free end of the spring is brought into the groove in the washer, and the spring is tensioned. To move the movement from one position to another, watchmakers must use tools to work on the rivet heads, causing the springs to lose their set tension when removed for maintenance. Therefore, the braking torque must be readjusted each time the seconds wheel assembly is reassembled. The assembly method described here is difficult and time-consuming to implement.

[0005] Furthermore, this anti-vibration device does not provide a perfect solution to the problem of regulating the torque applied to the seconds wheel assembly to prevent its vibration, because the frictional force is specifically defined by the contour of the lateral groove of 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 is highly dependent on the dimensions of the spring and the groove, their corresponding configuration, and their respective surface finish. Another problem arises from the fact that assembling the intermediate component onto the crown of the seconds wheel assembly will increase the radial wobble of the assembly, and thus cause a greater variation than without this intermediate component (especially when the spring is directly supported on the conventional crown with less radial wobble). In addition, if the watch is subjected to vibration or impact, the second free end of the spring may become detached from the grooved washer, and a constant braking torque will no longer be guaranteed. Worse still, in the event of a severe impact, the spring retainer plate, which is held in place only by friction, may move at an angle and change the braking setting. Utility Model Content

[0006] The purpose of this invention is to overcome the problems of the prior art mentioned above in the case of electromechanical motors, where at least one display wheel assembly intended to support the display components also suffers from a jitter / float problem due to the fact that this display wheel assembly is not subjected to holding torque outside of the time intervals during which it is rotatably driven by a clock motor. In particular, this invention proposes an anti-jitter / anti-float device for display wheel assemblies rotatably driven by an electromechanical motor, which is easy to install and, in a preferred alternative embodiment, can be installed in the preliminary steps of installing the display wheel assembly in question.

[0007] For this purpose, the present invention relates to an electromechanical watch movement comprising an electromechanical motor, a display wheel assembly, and a braking device. The display wheel assembly is arranged to be rotatably driven by the electromechanical motor and includes a stem designed to support display components. The braking device is associated with the display wheel assembly and includes a braking spring and an intermediate component disposed between the braking spring and the stem of the display wheel assembly. The braking spring is arranged such that once the display wheel assembly is subjected to a rotational driving torque, a braking torque is generated on the display wheel assembly via the intermediate component pressed against it. The intermediate component and the braking spring are arranged such that the intermediate component remains stationary and non-rotating during normal operation. This intermediate component has a lateral surface and a supporting surface, the lateral surface pressing against the rotating surface of the stem, and the braking spring applying a total clamping force against the supporting surface to the stem to generate friction between the lateral surface and the rotating surface, which generates the braking torque.

[0008] In a preferred general alternative embodiment, the intermediate component applies exclusively radial pressure to the shank of the display wheel assembly.

[0009] In the primary embodiment, the braking spring is a wire spring or a leaf spring, the longitudinal axis of which lies in a geometric plane parallel to the overall plane of the movement.

[0010] In one primary embodiment, the movement includes an eccentric device whose axis of rotation is perpendicular to the geometric plane, and the eccentric device is arranged to radially press against a brake spring so that the total radial clamping force applied to the intermediate component by the brake spring can be changed by rotating about its axis of rotation. Attached Figure Description

[0011] The present invention will now be described in more detail using the accompanying drawings, which are given by way of example and are in no way limiting, wherein:

[0012] - Figure 1 This is a bottom view of the main embodiment of the electromechanical watch movement according to the present invention, with some parts of the movement omitted in order to better show the braking device according to the present invention;

[0013] - Figure 2 yes Figure 1 An enlarged partial view of the electromechanical movement of a watch, showing the braking device provided according to the present invention;

[0014] - Figure 3 yes Figure 1 and Figure 2 A perspective view of the braking device in the main embodiment;

[0015] - Figure 4 Is it through Figure 2 and Figure 3 The view shows a horizontal cross-sectional view of the electromechanical watch movement taken from the braking device. In this case, the movement is in a pre-assembled state after the initial steps of assembling the braking device, which precede the assembly of the wheelset in the movement.

[0016] - Figure 5 The watch movement is partially assembled after the aforementioned preliminary steps. Figure 4 The partial cross-sectional view is taken by the cutting line VV in the middle, which passes through the central axis of the tube designed to receive a portion of the shank showing the wheel set;

[0017] - Figure 6 yes Figure 1 The electromechanical movement of the watch follows Figure 2 The cross-sectional view cut by line VI-VI passes through the axis of rotation of the shank of the display wheel assembly and shows the braking device after the display wheel assembly has been installed in the movement;

[0018] - Figure 7 Partial views of specific alternative embodiments of the main embodiment are shown in an illustrative manner;

[0019] - Figure 8A and Figure 8B Partial views of two advantageous alternative embodiments of the main embodiment are illustrated in an illustrative manner;

[0020] - Figure 9 A partial view of another specific alternative embodiment of the main embodiment is illustrated in an illustrative manner; and

[0021] - Figure 10 A partial view of the second embodiment of the present invention is shown in an illustrative manner. Detailed Implementation

[0022] The following will refer to Figures 1 to 6 The main embodiments of the electromechanical watch movement 2 according to the present invention are described.

[0023] Electromechanical watch movement 2 includes:

[0024] - Electromechanical motor 54, particularly a stepper motor, which includes a rotor 56 equipped with a pinion 58.

[0025] - The first wheel assembly 30, which forms the display wheel assembly, is designed to support the display component 48, particularly the second hand, and is rotatably driven by the second wheel assembly 52. ​​When the electromechanical motor 54 is activated, the second wheel assembly 52 is rotatably driven by the rotor 56 via the pinion 58 of the rotor 56.

[0026] - A brake spring 10 is arranged to generate a braking torque on the first wheel set 30, which is intended to prevent the display member 48 from trembling, once the first wheel set is subjected to a rotational drive torque, as well as a permanent radial force that holds the display member in a stable position when the display member is stationary and when the display member is between drive pulses, and thus prevents the display member from floating.

[0027] According to this invention, the electromechanical watch movement 2 includes a braking device 6 that acts on a display wheel assembly 30 and includes a braking spring 10 and an intermediate component 8 disposed between the braking spring and the stem 36 of the first wheel assembly 30. The braking spring is arranged such that once the display wheel assembly is subjected to a rotational driving torque, a braking torque is generated on the display wheel assembly via the intermediate component pressed by the braking spring. For this purpose, the intermediate component has a lateral surface 9 and a supporting surface 25. The lateral surface 9 presses against the rotating surface 35 of the stem, and the braking spring applies a total clamping force against the supporting surface 25 in the direction of the stem to generate friction between the lateral surface 9 and the rotating surface 35, which generates a braking torque. Therefore, the braking spring applies a braking torque on the first wheel assembly / display wheel assembly via the intermediate component pressed by the braking spring. The intermediate component 8 and the braking spring 10 are arranged such that the intermediate component remains stationary and does not rotate during normal operation. The shank 36 and intermediate components of the first wheel assembly 30 are configured such that the rotating surface 35 of the shank can slide on the lateral surface 9 while being subjected to dynamic friction that generates braking torque. Static friction generates braking torque before the rotating surface slides on the lateral surface, thus keeping the shank stationary.

[0028] Preferably, the intermediate component 8 applies a fully radial pressure on the shank 36 of the first wheel set 30. According to an advantageous feature, the brake spring 10 applies a fully radial total clamping force on the intermediate component. The support surface 25 is opposite to the lateral surface 9, i.e., the support surface is located on the opposite side of the intermediate component 8 from one side of the defined lateral surface 9 of the intermediate component. This alternative embodiment is advantageous because the braking device abuts against an undercut portion, which exhibits minimal radial wobble variation, and thus provides a constant braking torque for a given frictional force between the rotating surface 35 and the lateral surface 9. In the advantageous alternative embodiment shown in the figures, the rotating surface 35 of the shank 36 is cylindrical and axial, and the lateral surface 9 of the intermediate component is axial, i.e., the cylindrical rotating surface 35 and the lateral surface 9 are oriented along the axis of rotation 42 of the first wheel set 30, which coincides with the central axis of the shank 36; therefore, the lateral surface 9 and the cylindrical rotating surface 35 are parallel to this axis of rotation 42. In a preferred alternative embodiment, the intermediate component 8 and the brake spring 10 are configured such that the clamping force remains constant once the display wheel assembly has been assembled in the movement and the braking device has been fully assembled and adjusted.

[0029] According to the primary alternative embodiment, the braking spring 10 is a wire spring or a spring sheet, the longitudinal axis of which lies in a geometric plane parallel to the general plane 50 of the electromechanical watch movement 2.

[0030] According to the alternative embodiment shown, the intermediate component 8 is a washer with a central cylindrical opening in which the shank 36 of the first wheel assembly 30 will slide and rotate freely without any interaction from the brake spring 10. The lateral surface 9 of this washer 8 is defined by the cylindrical surface of its central cylindrical opening, which is preferably annular (i.e., a rotating surface).

[0031] According to a particular alternative embodiment, the washer 8 has a circular groove 24 on its periphery, the circular groove 24 defining a support surface 25, and a portion of the brake spring 10, which applies radial clamping force, is at least partially inserted into the circular groove 24. Specifically, the groove 24 has a generally V-shaped cross-section, and the brake spring 10 is a wire spring with a circular cross-section, such as... Figure 5 and Figure 6 As shown in the diagram. This arrangement allows the brake spring to be axially positioned in its middle section to contact the washer. Therefore, the spring cannot move freely axially.

[0032] By way of non-limiting example, in a first alternative embodiment, when at least the portion defining the rotating surface 35 of the shank is made of steel, at least the portion defining its central cylindrical opening of the washer 8 is made of a copper-beryllium (CuBe) alloy, and vice versa. This first alternative embodiment provides good tribological results. In a second alternative embodiment in which said portion of the shank is made of steel or CuBe, at least the portion defining its central cylindrical opening of the washer 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 shank is made of steel or a copper alloy (e.g., CuBe or brass), at least the portion defining its central cylindrical opening of the washer is made of bronze, nickel, or gold, particularly in the case of nickel or gold, in the form of a thin layer deposited on a substrate of another material, or more generally of a metal alloy including gold or nickel. In other alternative embodiments, at least the portion defining its central cylindrical opening of the washer is made of ceramic, particularly ruby ​​or zirconium oxide.

[0033] It should be noted that the material of the brake spring can be selected in such a way that the elastic properties of the spring and its manufacture are optimized without concern for friction and wear, because the washer, and more generally the intermediate component, is intended to be static during the normal operation of the electromechanical watch movement, i.e., stationary and non-rotating. In the case of the washer, to prevent its rotation, the shape of the intermediate component and / or the shape of the brake spring can be modified, as will be explained in more detail below, or particularly in the case of the washer, the material used to make the spring and at least the outer parts of the intermediate component that contact the spring and the surface treatment applied to these parts to obtain high friction between the brake spring and the intermediate component can be modified.

[0034] According to another preferred alternative embodiment, the brake spring 10 is arranged in the electromechanical watch movement 2 such that its intermediate portion, between its two end portions, radially presses against the support surface 25 of the intermediate component / washer 8. More specifically, the brake spring 10 is arranged such that the intermediate portion of this brake spring applies the clamping force on the support surface 25 of the intermediate component / washer 8. For this purpose, the two end portions of the brake spring, located on either side of the intermediate portion, are pressurized by two distant portions 16 and 20 of the watch movement, such that the intermediate portion applies a clamping force on the support surface of the intermediate component / washer. This configuration of the braking device is advantageous because it allows the brake spring to continuously press against the support surface of the intermediate component / washer. Furthermore, this configuration is less sensitive to vibration and shock than a case where the brake spring has an anchor point at one end and a contact point at the other end.

[0035] In a particular alternative embodiment, the brake spring 10 is curved in its middle portion, and the support surface 25 of the middle component / washer 8 has a convex curvature relative to the shank 36 of the first wheel assembly 30 in the geometric plane, and particularly a circular curvature in the case of the washer, which, in a first alternative embodiment, the middle portion of the brake spring follows along the support surface. In a second alternative embodiment, the radius of curvature of the middle portion is smaller than the average radius of curvature of the support surface, such that the brake spring presses against the middle component / washer at “two points” (i.e., at two separate locations) on the support surface. It should be noted that for the generally V-shaped groove, the spring with a circular cross-section is locally compressed at a pair of axially aligned points. Thus, in this configuration of the groove and the brake spring, the spring is compressed at two pairs of points angularly spaced apart from each other (where each pair of points is aligned in the axial direction), and therefore at “two points” protruding in the total plane of the spring parallel to the total plane 50 of the movement. 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 support surface, resulting in radial pressure being applied at “one point” (i.e., not at a pair of points aligned in the axial direction, but at a single point protruding in the total plane of the spring / the total plane of the movement 50).

[0036] According to advantageous alternative embodiments, such as Figures 2 to 4As shown, the brake spring 10 is not fastened to the movement by a specific component, but is held taut by two parts 16 and 20 of the movement. Two end portions of the brake spring, located on either side of the middle portion of the brake spring, press against the two parts 16 and 20. The brake spring radially abuts against the middle component, which is specifically the washer 8. The direction of the force exerted on the spring by the two parts 16 and 20 is opposite to the direction of the reaction force of the middle component / washer 8 on the middle portion of the spring. These forces applied to the brake spring in the geometric plane containing the longitudinal axis of the brake spring (a horizontal plane orthogonal to the axis of rotation 42 of the shank 36 coinciding with its central axis) generate stress that holds the brake spring in place. Then, to prevent axial / vertical movement of the spring, and particularly to prevent its middle portion from dislodging from the groove 24, two portions of the plate 4 are provided on each of the two sides, defining a lower axial stop for the brake spring. On the first side, an upper recess 14 (on the analog display side) is provided in plate 4, the upper recess 14 being arranged such that its bottom (forming a thin horizontal wall) provides a lower limit for any possible displacement of the portion of the spring located on that side. On the second side, the brake spring portion is located above the small protrusion 18. Plate 4 is located below the intermediate plate 60 of the watch movement 2, the intermediate plate 60 defining the overall plane 50 of the movement and steadfastly supporting the base of tube 44 through which the stem 36 of the display wheel assembly 30 passes, the central axis of which defines the axis of rotation 42. The intermediate plate 60 defines an upper axial stop for spring 10. The base of tube 44 can support washer 8, particularly when the washer is assembled before the spring is installed, and thus forms a support for the washer. It should be noted that in another alternative embodiment, element 44 constitutes a rotatable mainspring barrel.

[0037] exist Figure 7 , Figure 8A and Figure 8B Various other advantageous alternative embodiments are illustrated in the figure. Figure 7 The alternative embodiment shown is characterized in that the middle portion of the brake spring 10A has two bends 71 ​​and 72, which are separated by a straight section 70 (stress-free) that abuts against a circular washer 8 substantially in its middle. This ensures that the brake spring 10A always abuts against the washer 8 at "one point". Figures 8A to 8B An alternative embodiment is characterized by an intermediate component 68 that is not circular but formed of a truncated washer having a straight band 80. Figure 8A In the alternative embodiment shown, the brake spring 10 has a bend 74 in its middle portion, the bend 74 being positioned facing the straight section 80 of the truncated washer 68. Figure 8BIn the alternative embodiment shown, spring 11 is straight / linear when unstressed, and when tensioned to press against the intermediate member, it bends slightly (a concave curvature when viewed from the intermediate member), pressing against the ends of the straight section 80 of this intermediate member. Therefore, in Figure 8A and Figure 8B In an alternative embodiment, the brake spring 10 or 11 applies two forces F1 and F2 at the two ends of the straight band 80, respectively. The two forces F1 and F2 are radial overall, i.e., their sum at the midpoint is radial. However, each of these two forces applies a torque on the intermediate member 68 such that as the spring moves longitudinally and one of the two forces F1 and F2 decreases relative to the other, the intermediate member 68 automatically undergoes a small rotation to re-establish balance between the two opposing torques applied to it. Figure 8B The alternative embodiment shown is preferred because the risk of rotation of the truncated washer is lower. Furthermore, this alternative embodiment allows the desired braking torque to be maintained, even when the brake spring experiences some longitudinal displacement under impact or sudden acceleration. However, Figure 8A The alternative embodiment with a bending spring shown is less likely to withstand longitudinal displacement under impact. The alternative embodiment with a truncated washer helps prevent rotation of the intermediate components during normal operation, which is important for ensuring a constant braking torque. Figure 8A and Figure 8B The alternative embodiments shown always provide support at “two points” protruding in the geometric plane of the spring.

[0038] Specific alternative embodiments are illustrated in the figure. Figure 9 In the middle. Like Figure 7 Similar to the previous embodiment, this alternative embodiment is designed to ensure that the brake spring 10B is always compressed at "one point" on the intermediate member 78, which has an overall square shape with rounded corners. The brake spring 10B has a bend 76 such that two straight portions of the spring on either side of this bend form an angle greater than 90° relative to each other, but close to that value, for example, an angle equal to 110°. One of the rounded corners of the intermediate member is positioned within the bend 76 of the spring, and when the spring and intermediate member 78 are stationary, the spring applies a generally radial force F to the intermediate member. If the spring 10B moves, particularly due to impact, the direction of the force changes, subjecting the intermediate member to a torque that causes it to rotate. This ensures that the square intermediate member always maintains the same angle within the bend 76 of the brake spring, and that pressure is applied at "one point." Furthermore, during normal operation (when the brake spring is stationary), this alternative embodiment keeps the intermediate member stationary (non-rotating), thus ensuring a constant and well-defined braking torque on the shank of the wheelset.

[0039] According to a preferred alternative embodiment of the present invention, the braking device 6 includes an eccentric device 20, the axis of rotation of which is perpendicular to the overall plane 50 and therefore parallel to the central axis / axis of rotation 42 of the wheel assembly 30. The eccentric device 20 is arranged to radially press against the brake spring so that the radial clamping force applied to the intermediate component / washer by the brake spring can be changed by rotating about its axis of rotation. Figure 1 and Figure 2 In the advantageous alternative embodiment shown, the eccentric device 20 constitutes one of the two components that keep the brake spring under tension. Therefore, by rotating the eccentric device 20, the stress on this spring is changed, thereby adjusting the braking torque applied to the first wheel set 30 (timer wheel set) when it is subjected to a rotational drive torque. This configuration is advantageous because it is insensitive to vibration and shock. In another alternative embodiment, another device for adjusting the radial force is provided, particularly a device equipped with a pressing member capable of linear movement.

[0040] Figure 10 Another embodiment of the present invention is shown, wherein the brake spring 11 is straight / linear (without stress). This spring is rigidly fastened at one of its ends to a fixing member 82, preventing any change in the angular position of the fixing member 82 in the geometric plane, thus preventing any involuntary displacement or displacement due to impact. A groove in member 82 (in which the end of the spring 11 is inserted) is oriented such that the middle section of the spring applies a radial clamping force F to the washer 8, and the spring has a first convex curvature between the fastening member 82 and the spring's support point on the washer. Preferably, at the other end of the spring, an eccentric device is provided for adjusting the radial force F; in this embodiment, the eccentric device is located on the same side of the brake spring as the washer 8, which forms an intermediate part between the brake spring and the shank of the associated wheel assembly. Therefore, the brake spring 11 also has a second convex curvature between the support point and the eccentric device 20, which is less than the first curvature because the radial force F is not zero. It should be noted that... Figure 10 The alternative embodiments shown define a construction with a single support point, i.e., the brake spring presses against the washer at "one point," as defined above. In another alternative embodiment of the "two-point" type, a star-shaped intermediate component is provided, for example, having four to six tips, each with a small rounded portion. This slightly convex brake spring always presses against the two tips of the star-shaped intermediate component, thus applying two forces that form a total radial clamping force at its center point. In other words, these two forces produce two opposing torques of equal strength on the intermediate component. It should also be noted that, in the event of an impact, control of the braking device cannot be released.

[0041] Figure 4 and Figure 5The electromechanical watch movement 2 is shown, in which the braking device 6 is pre-assembled in a preliminary step before the assembly of the first gear train 30. This preliminary assembly of the braking device 6 is advantageous. This is made possible in particular by the fact that the force applied by the braking spring is radial, and that the washer 8 is provided above the pinion and wheel 32 forming the first gear train. Therefore, the shank 36 of the first gear train can be mounted from below the watch movement and passes through the central opening in the washer 8. Figures 1 to 3 as well as Figure 6 The electromechanical watch movement 2 is shown after the first wheel assembly 30 has been installed in the movement and the braking device is in operation.

[0042] To allow for the initial assembly of the braking device 6, a washer 8 is arranged on a support 4 (the base of tube 44), the support 4 having an abutment surface 26 on the periphery of this washer. The abutment surface 26 is positioned horizontally facing the washer and diametrically opposed to the support surface 25, such that the washer 8 and the brake spring 10 can be pre-assembled in the electromechanical watch movement 2 before the assembly of the first wheel assembly 30, wherein the washer abuts against the abutment surface 26, as... Figure 4 and Figure 5 As shown in the image.

[0043] In a preferred alternative embodiment, the adjacent surface 26 is arranged such that, after the pre-assembly of the washer 8 and the brake spring 10, the central cylindrical opening in the washer has at least one zone overlapping with the central circular opening in the tube or pipe 44, a portion of the stem 36 of the first wheel assembly 30 is then inserted into the tube or pipe 44, such that when the first wheel assembly is mounted in the electromechanical watch movement 2, the stem can pass through both central circular openings without initially applying radial force to the washer. Figure 5 As can be seen, in the illustrated alternative embodiment, the central cylindrical opening in the washer 8 completely overlaps the central circular opening in the tube 44. Preferably, at least a majority of the opening in the washer overlaps the central opening in the tube. In the illustrated example, it should be noted that the shank 36 of the first wheel assembly 30 is inserted into the stationary tube 44. The upper end of the shank, intended to receive the second hand, has a smaller diameter, which makes it easier to insert this shank into the two central openings during the assembly of the display wheel assembly 30, where the initial overlap of the two central openings is only partial when the braking device is in a pre-assembled state.

[0044] Once the first gear train 30 is assembled in the watch movement, the washer 8 no longer abuts against the side wall 26 of the plate 4, but rather against the stem 36 of the first gear train via its central cylindrical opening, or more precisely against the rotating surface 35 of this stem, which is advantageously cylindrical and axial. This first gear train can then be rotatably driven from time to time by the electromechanical motor 54 via the second gear train 52, according to a command.

[0045] The present invention has been described in detail with respect to the seconds wheel assembly 30, but the braking device of the present invention can be provided for other wheel assemblies in electromechanical watch movements, particularly for minute wheel assemblies or chronograph wheel assemblies.

[0046] This invention has several advantages, some of which have been described. The braking device 6 includes an eccentric device 20, which facilitates adjustment of the radial clamping force applied by the brake spring on the intermediate component / washer 8, and adjusts the torque of the frictional force applied to the first wheel assembly via this radial force applied to the shank 36 of the first wheel assembly 30. Once the braking device is fully installed in the electromechanical watch movement, the eccentric device 20 allows adjustment of the braking torque without removing the brake spring to slightly alter its initial shape. Given the presence of the washer 8 between the brake spring 10 and the shank 36, and besides the fact that the force involved is intended to be radial, the mounting of the second hand 48 on the first wheel assembly 30, and especially its removal (e.g., when replacing the hand or when cleaning the electromechanical watch movement), does not damage the brake spring (a delicate and vulnerable component in the braking device 6), because the washer 8 is more robust and can withstand a certain amount of axial pressure against its support.

[0047] The braking device 6 is protected from stresses that could damage it during the assembly of other components of the electromechanical watch movement, particularly during the assembly of the display wheel assembly 30. When the watch movement 2 is removed, and especially when the display wheel assembly is removed, the braking device 6 can remain in place without altering its settings.

[0048] The braking device according to this invention allows for the relatively precise pre-determination of the frictional torque because the height of the lateral surface 9 of the intermediate component, particularly the washer 8, is typically much greater than the height of the brake spring. This is because the material of the intermediate component / washer 8 can be selected, and the diameter of the rotating surface of the defined cylindrical and axial surface of the shank 36 against which the intermediate component / washer 8 abuts is precisely determined.

Claims

1. An electromechanical timepiece movement (2) characterized in that, The timepiece movement comprises an electromechanical motor (54), a display wheelset (30) arranged to be rotated by the electromechanical motor and comprising a stem (36) intended to carry a display member (48), a braking device (6) associated with the display wheelset and comprising a braking spring (10, 10A, 10B, 11) and an intermediate part (8, 68, 78) arranged between the braking spring and the stem of the display wheelset, the braking spring being arranged to be able to generate a braking torque on the display wheelset via the intermediate part against which it is pressed once this display wheelset is subjected to a rotational drive torque, the intermediate part and the braking spring being arranged so that the intermediate part remains stationary and non-rotating in normal operation, the intermediate part having a lateral surface (9) which presses against a gyration surface (35) of the stem and a bearing surface (25) against which the braking spring exerts a total compression force on the stem so as to generate a friction force between the lateral surface and the gyration surface, the friction force generating the braking torque.

2. A timepiece movement according to claim 1, characterized in that, The intermediate part (8, 68, 78) exerts a pressure which is entirely radial on the stem (36) of the display wheelset (30).

3. Watch movement according to claim 1 or 2, wherein the arbor defines a central axis (42), characterized in that, The gyration surface (35) is cylindrical and axial and the lateral surface (9) is axial.

4. A watch movement according to any one of the preceding claims, characterised in that, The braking spring (10, 10A, 10B, 11) is a wire spring or a spring leaf, the longitudinal axis of which lies in a geometric plane which is parallel to the general plane (50) of the movement.

5. A timepiece movement according to claim 4, characterised in that, The braking spring (10, 10A, 10B, 11) is arranged so that an intermediate portion of this braking spring exerts the compression force on the bearing surface of the intermediate part (8, 68, 78); and in which two end portions of the braking spring, respectively located on either side of the intermediate portion, are pressurized by two distant portions (16, 20) of the timepiece movement, so that this intermediate portion exerts the compression force on the bearing surface.

6. A timepiece movement according to claim 5, characterized in that, The braking spring (10, 10A, 10B) is not fastened to the timepiece movement but is held in tension by the distant portions (16, 20) of this timepiece movement, the two end portions of the braking spring pressing against the distant portions in two respective directions in the geometric plane.

7. A timepiece movement according to claim 5 or 6, characterised in that, This movement comprises an eccentric device, the rotation axis of which is perpendicular to the geometric plane, and which is arranged to press against the braking spring (10, 10A, 10B, 11) so as to be able to vary the compression force exerted by the braking spring on the intermediate part (8, 68, 78) by rotating around its rotation axis.

8. A watch movement according to any one of the preceding claims, characterised in that, The intermediate part is a washer having a central opening through which the stem (36) of the display wheelset passes, the lateral surface (9) of this washer being defined by a cylindrical surface of its central opening.

9. A timepiece movement according to claim 8, characterised in that, The gasket has a recess (24) on its periphery, which defines the bearing surface (25) and into which a portion of the brake spring (10) exerting the pressing force in the direction of the stem is at least partially inserted.

10. A watch movement according to any one of the preceding claims, characterised in that, The intermediate part (8) is arranged to face an abutment surface (26) diametrically opposite the bearing surface (25), so that the intermediate part and the brake spring can be pre-assembled in the mechanical clock movement before the display wheel set (30) is assembled, with the intermediate part resting against the abutment surface.

11. A timepiece movement according to claim 10, characterized in that, The abutment surface (26) is arranged so that, after pre-assembly of the intermediate part (8) and the brake spring (10), the central cylindrical opening in the intermediate part has at least one zone superimposed with a central cylindrical opening in a tube or pipe (44), which is rotatable or fixed, into which a portion of the stem (36) of the display wheel set (30) is inserted, so that when the display wheel set is mounted in the mechanical clock movement, the stem can pass through the two central circular openings without having to exert a radial force initially on the intermediate part.

12. A watch movement according to any one of the preceding claims, characterised in that, At least a portion of the stem (36) defining the swivel surface (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 correspondingly of a copper alloy or steel.

13. A timepiece movement according to any one of claims 1 to 11, characterized in that, At least a portion of the stem (36) defining the swivel surface (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.

14. A timepiece movement according to any one of claims 1 to 11, characterized in that, At least a portion of the stem (36) defining the swivel surface (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 ceramic, in particular ruby or zirconium oxide, or of a material containing gold or nickel, and forms an outer layer at least partially covering the intermediate part.

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