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] The present invention relates to an electromechanical timepiece movement comprising a wheel set carrying a display member, in particular a hand, and provided with an anti-vibration device (also called an anti-floating device) formed by a braking device acting on this wheel set, in order to prevent the display member from vibrating when rotating and from floating during certain time intervals and periods when the display member is at rest. Background Art

[0002] Swiss Patent Document CH 580301 discloses an anti-vibration device for a timepiece wheel set, in particular a chronograph wheel set (hereinafter also referred to as a "chronograph wheel set"). The device comprises a stem equipped with a pinion that meshes with a clutch wheel (hereinafter also referred to as a "drive wheel"), thereby forming a coupling device for the chronograph mechanism. It should be noted that a stem equipped with a pivot to guide its rotation is also referred to as a "shaft" in the watchmaking industry. The anti-vibration device for the chronograph seconds hand is formed by a friction device comprising a wire spring that bears obliquely against the stem. To this end, the stem has a frustoconical shoulder. The wire spring has a bearing point in the angle formed by this shoulder and an annular cylindrical portion whose diameter corresponds to the smallest diameter of the shoulder. At this point, the spring exerts a tilting force on the stem, causing the teeth of the pinion to press against the drive wheel and the lower annular surface of the stem, opposite the shoulder and orthogonal to the axis defined by the stem, to press axially against a bearing in which the chronograph wheel set pivots. This spring is designed to be straight when not stressed. This spring is fastened to the frame of the movement on one side of a first end, while a portion of the side of a second end is in tension and presses against the stem, as explained above.

[0003] For various reasons, this anti-vibration device poses problems in controlling the torque of the friction force applied to the chronograph wheels. Furthermore, there is no way to adjust the torque of this friction force. Subsequently, when the chronograph hand (chronograph hand) is removed, the spring is subjected to an axial force that could damage it.

[0004] German patent document DE 6800934 U describes a solution for improving the control of the torque applied to the frictional force of the seconds wheel assembly. According to the teachings of this document, a wire spring or leaf spring is fastened at its first end portion to a plate using a riveting technique. The plate is held suspended by a rivet having a head with a screw-like groove, located on the side of the stem opposite the plate. The rivet has a central cylindrical portion that is inserted into a hole in the stem with a friction fit, allowing the rivet, and therefore the plate, and thus the first end portion of the spring, to undergo a certain amount of rotation with the aid of a tool. The second end portion of the friction spring is free and rests radially against a plastic washer that is press-fitted onto the stem of the seconds wheel assembly. This washer has a lateral groove into which the second end portion of the spring rests. This system is difficult to assemble in a timepiece 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 the material onto the two edges of the groove to perform a first riveting operation. After inserting the rivet 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. The end of the rivet must then be crushed, and a second riveting operation must be performed to secure the plate to the rivet. As can be seen, there is a high risk of damaging the friction spring at each stage of assembly, via two consecutive riveting operations, of the friction spring being attached to the plate and then to the rod. Finally, the rod, plate, and friction spring assembly is assembled in the watch movement, while the pivot of the stem carrying the seconds wheel assembly with the grooved washer is simultaneously inserted into a bearing arranged in the relevant rod. This assembly requires that the spring not be stacked on top of the grooved washer, as the spring is rigidly connected to the rod, and the grooved washer, designed to receive the free end of the spring in a tensioned state, is rigidly connected to the stem. Consequently, there are a first assembly / disassembly position for the spring and a second operating position, in which the free end of the spring is brought into the groove in the washer and the spring is tensioned. To adjust the movement from one position to another, the watchmaker must use a tool to act on the rivet heads, causing the spring to lose its set tension when it is removed for maintenance. Consequently, the braking force must be readjusted each time the seconds wheel assembly is assembled. The assembly method described here is difficult and time-consuming to implement.

[0005] Furthermore, this anti-vibration device does not offer a perfect solution to the problem of regulating the torque applied to the seconds wheel assembly to prevent it from vibrating, as the friction force is determined, in particular, by the profile 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 friction force is difficult to control and reproduce, as 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 the intermediate component on the stem of the seconds wheel assembly increases the radial play of the wheel assembly and, therefore, results in greater variations than would be the case without such an intermediate component (particularly if the spring were supported directly on a conventional stem with less radial play). Furthermore, if the watch is subjected to vibrations or shocks, the second free end of the spring may become disengaged from the grooved washer, and a constant braking torque will no longer be guaranteed. Even worse, in the event of a severe impact, the spring retaining plate, held in place only by friction, may shift angularly and alter the braking setting. Summary of the Invention

[0006] The object of the present invention is to overcome the problems of the prior art mentioned above in the case of electromechanical movements, in which at least one display wheel set intended to carry a display member also suffers from vibration / float problems due to the fact that this display wheel set is not subject to a holding torque outside the time intervals during which it is rotatably driven by the timepiece motor. In particular, the present invention proposes an anti-vibration / anti-float device for a display wheel set rotatably driven by an electromechanical motor, which device is easy to install and, in a preferred alternative embodiment, can be installed during a preliminary step in installing the display wheel set in question.

[0007] To this end, the present invention relates to an electromechanical timepiece movement comprising an electromechanical motor, a display wheel set arranged to be rotatably driven by the electromechanical motor and comprising a stem intended to carry a display member, and a braking device associated with the display wheel set and comprising a brake spring and an intermediate component arranged between the brake spring and the stem of the display wheel set. The brake spring is arranged so as to generate a braking torque on the display wheel set via the intermediate component against which the brake spring presses, once the display wheel set is subjected to a rotational drive torque. The intermediate component and the brake spring are arranged so that, during normal operation, the intermediate component remains stationary and does not rotate. The intermediate component has a lateral surface and a bearing surface, the lateral surface pressing against the rotating surface of the stem, the brake spring applying a total pressure force against the stem against the bearing surface to generate a friction force between the lateral surface and the rotating surface, which friction force generates the braking torque.

[0008] In a preferred general alternative embodiment, the middle part exerts an exclusively radial pressure on the stem of the display wheel set.

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

[0010] In a main embodiment, the movement comprises an eccentric whose axis of rotation is perpendicular to said geometrical plane and which is arranged to press radially against the detent spring so as to be able to vary said radial total pressure exerted by the detent spring on the middle part by rotating it about its axis of rotation. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0012] - Figure 1 is a bottom view of a principal embodiment of an electromechanical timepiece movement according to the invention, with certain parts of this movement omitted in order to better illustrate the braking device according to the invention;

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

[0014] - Figure 3 yes Figure 1 and Figure 2 A perspective view of a braking device according to a main embodiment of the present invention;

[0015] - Figure 4 It passes through Figure 2 and Figure 3 a horizontal cross-sectional view of an electromechanical timepiece movement, taken through the braking device in the movement, in this case in a pre-assembled state after a preliminary step of assembling the braking device, which step precedes the assembly of the display wheel in the movement;

[0016] - Figure 5 is a partially assembled watch movement after the preliminary steps described along Figure 4 a partial cross-sectional view taken along the cutting line VV in FIG. 1 , which passes through the central axis of a tube intended to receive a portion of the stem of the display wheel set;

[0017] - Figure 6 yes Figure 1 The electromechanical clock movement in Figure 2 a cross-sectional view taken along the cutting line VI-VI in FIG, which passes through the axis of rotation of the stem of the display wheel set and shows the braking device after the display wheel set has been installed in the movement;

[0018] - Figure 7 diagrammatically showing partial views of certain alternative embodiments to the main embodiment;

[0019] - Figure 8A and Figure 8B diagrammatically showing partial views of two advantageous alternative embodiments of the main embodiment;

[0020] - Figure 9 a partial view diagrammatically showing another specific alternative embodiment to the primary embodiment; and

[0021] - Figure 10 A partial view of a second embodiment of the invention is shown diagrammatically. DETAILED DESCRIPTION

[0022] The following will refer to Figures 1 to 6 A main embodiment of an electromechanical timepiece movement 2 according to the invention is described.

[0023] The electromechanical watch movement 2 comprises:

[0024] an electromechanical motor 54 , in particular a stepper motor, comprising a rotor 56 equipped with a pinion 58 ,

[0025] a first wheel set 30 forming a display wheel set, intended to carry a display member 48 , in particular a seconds hand, and driven in rotation by a second wheel set 52 via a pinion 58 of a rotor 56 when an electromechanical motor 54 is activated,

[0026] a brake spring 10 arranged so as to generate on the first wheel set 30 a braking torque intended to prevent the display member 48 from trembling, as soon as this first wheel set is subjected to a rotational drive torque, and a permanent radial force which holds the display member in a stable position when it is at rest and between drive pulses, and thus prevents this display member from floating.

[0027] According to the invention, the electromechanical timepiece movement 2 includes a braking device 6 acting on the display wheel set 30 and comprising a brake spring 10 and an intermediate component 8 arranged between the brake spring and the stem 36 of the first wheel set 30. The brake spring is arranged so that, once the display wheel set is subjected to a rotational drive torque, it can generate a braking torque on the display wheel set via the intermediate component against which the brake spring is pressed. To this end, the intermediate component has a lateral surface 9 and a bearing surface 25. The lateral surface 9 presses against the rotating surface 35 of the stem. The brake spring exerts a total pressure force against the bearing surface 25 in the direction of the stem, generating a friction force between the lateral surface 9 and the rotating surface 35. This friction force generates the braking torque. The brake spring thus applies a braking torque to the first wheel set / display wheel set via the intermediate component against which the brake spring is pressed. The intermediate component 8 and the brake spring 10 are arranged so that, during normal operation, the intermediate component remains stationary and does not rotate. The stem 36 and the middle part of the first wheel set 30 are configured so that the rotating surface 35 of the stem can slide on the lateral surface 9 while being subjected to dynamic friction forces that generate a braking torque. Before the rotating surface slides on the lateral surface, the static friction forces generate a braking torque and thus keep the stem stationary.

[0028] Preferably, middle part 8 exerts a purely radial pressure on stem 36 of first wheel set 30. According to an advantageous feature, brake spring 10 exerts a purely radial total pressure on the middle part. Bearing surface 25 is opposite lateral surface 9, i.e., it is located on the side of middle part 8 opposite that which defines lateral surface 9. This alternative embodiment is advantageous because the braking device bears against an undercut whose radial play varies minimally, thus providing a constant braking torque for a given frictional force between surface of revolution 35 and lateral surface 9. In the advantageous alternative embodiment shown in the figures, surface of revolution 35 of stem 36 is cylindrical and axial, and lateral surface 9 of the middle part is axial, i.e., cylindrical surface of revolution 35 and lateral surface 9 are oriented along axis of rotation 42 of first wheel set 30, which coincides with the central axis of stem 36, and lateral surface 9 and cylindrical surface of revolution 35 are therefore parallel to this axis of rotation 42. In a preferred alternative embodiment, middle part 8 and brake spring 10 are configured so that the pressing force remains constant once the display wheel set has been assembled in the movement and the braking device is completely assembled and adjusted.

[0029] According to the main alternative embodiment, brake spring 10 is a wire spring or a leaf spring, the longitudinal axis of which lies in a geometric plane parallel to the general plane 50 of electromechanical timepiece movement 2 .

[0030] According to the alternative embodiment shown, intermediate part 8 is a washer having a central cylindrical opening in which stem 36 of first wheel set 30 will be free to slide and rotate without any interaction from brake spring 10, said lateral surface 9 of this washer 8 being defined by the cylindrical surface of its central cylindrical opening, which cylindrical surface is preferably annular (i.e. a surface of revolution).

[0031] According to a particular alternative embodiment, the washer 8 has on its periphery a circular groove 24 which defines a bearing surface 25 and in which a portion of the brake spring 10 which applies the radial compression force is at least partially inserted. In particular, the groove 24 has a substantially 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 This arrangement allows the brake spring to be positioned axially in contact with the washer in its middle portion. Consequently, the spring cannot move freely axially.

[0032] By way of non-limiting example, in a first alternative embodiment, when at least the portion of the arbor defining the surface of revolution 35 is made of steel, at least the portion of the washer 8 defining its central cylindrical opening is made of a copper beryllium (CuBe) alloy, or vice versa. This first alternative embodiment gives good tribological results. In a second alternative embodiment in which the portion of the arbor is made of steel or CuBe, at least the 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 arbor is made of steel or a copper alloy (such as CuBe or brass), at least the portion of the washer defining its central cylindrical opening 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 comprising gold or nickel. In other alternative embodiments, at least the portion of the washer defining its central cylindrical opening is made of ceramic, particularly ruby ​​or zirconium oxide.

[0033] It should be noted that the material of the brake spring can be chosen in such a way as to optimize the elastic properties of this spring and its manufacture without having to worry about problems of friction and wear, since the washer, and more generally the middle part, is intended to be static, that is, stationary and not rotating, during normal operation of the electromechanical timepiece movement. In the case of the washer, in order to prevent its rotation, the shape of the middle part and / or of the brake spring may be modified, as will be explained in more detail below, or, in the case of the washer in particular, the material used to make the spring and at least the outer part of the middle part that comes into contact with the spring, and / or the surface treatment applied to these parts in order to achieve high friction between the brake spring and the middle part, may be modified.

[0034] According to another preferred alternative embodiment, brake spring 10 is arranged in electromechanical timepiece movement 2 in such a manner that its intermediate portion, between its two end portions, presses radially against bearing surface 25 of middle part / washer 8. More specifically, brake spring 10 is arranged so that its intermediate portion exerts the aforementioned compressive force on bearing surface 25 of middle part / washer 8. To this end, its two end portions, located on either side of the intermediate portion, are stressed by two distal portions 16 and 20 of the timepiece movement, causing this intermediate portion to exert a compressive force on the bearing surface of the middle part / washer. This configuration of the braking device is advantageous because it allows the brake spring to be constantly pressed against the bearing surface of the middle part / washer. Furthermore, it is less sensitive to vibrations and shocks than a brake spring having an anchor point at one end and a contact point at the other.

[0035] In a particular alternative embodiment, detent spring 10 is curved in its middle portion, and the bearing surface 25 of middle part / washer 8 has a convex curvature relative to stem 36 of first wheel set 30 in the geometric plane, and in particular, in the case of a washer, a circular curvature. In the first alternative embodiment, the middle portion of the detent spring follows this circular curvature along the bearing surface. In a second alternative embodiment, the radius of curvature of the middle portion is smaller than the average radius of curvature of the bearing surface, so that the detent spring presses against the middle part / washer at "two points" (i.e., at two separate locations) on the bearing surface. It should be noted that, for a generally V-shaped groove, a spring with a circular cross-section compresses locally at a pair of axially aligned points. Thus, in this configuration of groove and detent spring, the spring compresses at two pairs of points angularly spaced apart from one another (where each pair of points is aligned in the axial direction), and thus at "two points" that project 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 average radius of curvature of the intermediate portion is greater than the radius of curvature of the bearing surface, resulting in the radial pressure being exerted at "one point" (i.e. not at a pair of points aligned in the axial direction, but at a single point protruding in the general plane 50 of the spring / movement).

[0036] According to an advantageous alternative embodiment, Figures 2 to 4As shown in FIG, the brake spring 10 is not fastened to the movement by any specific component, but rather is held in tension by two parts 16 and 20 of the movement. The two end portions of the brake spring, located on either side of its central portion, press against these two parts 16 and 20, which in turn bear radially against the middle component, specifically washer 8. The forces exerted on the spring by the two parts 16 and 20 are directed in the opposite direction to the reaction force exerted by the middle component / washer 8 on the spring's central portion. These forces, applied to the brake spring in the geometric plane containing its longitudinal axis (a horizontal plane orthogonal to the axis of rotation 42 of stem 36, which coincides with its central axis), generate a stress that holds the brake spring in place. To prevent the spring from axial / vertical movement, and in particular from its central portion escaping from groove 24, two parts of plate 4 are provided on each of the two side faces, defining the brake spring's lower axial stop. On the first side, an upper recess 14 is provided in plate 4 (on the analog display side). This recess 14 is arranged so that its bottom (forming a thin horizontal wall) provides a lower limit for any possible displacement of the portion of the spring located on this side. On the second side, the brake spring portion is located above the small projection 18. Plate 4 is located below an intermediate plate 60 of timepiece movement 2, which defines the movement's general plane 50 and securely supports the base of tube 44, through which stem 36 of display wheel assembly 30 passes, the central axis of which defines axis of rotation 42. Intermediate plate 60 defines the upper axial stop for spring 10. The base of tube 44 can support washer 8, particularly when it is assembled before the spring is installed, and thus forms a support for it. It should be noted that, in an alternative embodiment, element 44 constitutes a rotatable barrel.

[0037] exist Figure 7 、 Figure 8A and Figure 8B Various other advantageous alternative embodiments are shown diagrammatically in FIG. Figure 7 The alternative embodiment shown in FIG is characterized in that the middle portion of the brake spring 10A has two bends 71 ​​and 72 separated by a straight section 70 (unstressed) which bears substantially in its middle against the circular washer 8. This ensures that the brake spring 10A always bears against the washer 8 at “one point”. Figures 8A to 8B An alternative embodiment of is characterized by an intermediate part 68 which is not circular but is formed by a truncated washer with straight zones 80. Figure 8A In the alternative embodiment shown in , the brake spring 10 has a bend 74 in its middle portion, which is located facing the straight zone 80 of the truncated washer 68. Figure 8BIn the alternative embodiment shown in , the spring 11 is straight / straight when not stressed, and when it is tensioned to press against the intermediate part, it bends slightly (concave curvature when viewed from the intermediate part) so that it presses at the ends of a straight zone 80 of this intermediate part. Figure 8A and Figure 8B In an alternative embodiment, the brake spring 10 or 11 exerts two forces F1 and F2, respectively, at the ends of the straight zone 80. The two forces F1 and F2 are generally radial, i.e., their sum at the midpoint is radial. However, each of these two forces exerts a moment on the intermediate part 68, so that when 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 in order to re-establish the equilibrium between the two opposing moments exerted on it. Figure 8B The alternative embodiment shown in is preferred because the risk of rotation of the truncated washer is smaller. Furthermore, this alternative embodiment allows the desired braking torque to be maintained even when the brake spring undergoes a certain longitudinal displacement in the event of an impact or sudden acceleration. However, Figure 8A The alternative embodiment with a bent spring shown in is less likely to undergo longitudinal displacement in the event of an impact. The alternative embodiment with a truncated washer is advantageous in preventing the intermediate part from rotating during normal operation, which is important for ensuring a constant braking torque is set. Figure 8A and Figure 8B The alternative embodiment shown in always provides support at "two points" that protrude in the geometrical plane of the spring.

[0038] Certain alternative embodiments are shown diagrammatically in Figure 9 In. Like Figure 7 Like the alternative embodiment, this design ensures that brake spring 10B is always compressed at a single point on intermediate component 78, which has an overall square shape with rounded corners. Brake spring 10B has a bend 76, such that two straight sections of the spring, on either side of the bend, make an angle greater than 90°, but relatively close to that value, for example, equal to 110°. One of the rounded corners of the intermediate component is positioned within the spring's bend 76, and when this spring and intermediate component 78 are at rest, the spring exerts a generally radial force F on the intermediate component. If spring 10B moves, particularly due to an impact, the direction of the force changes, subjecting the intermediate component to a torque that causes it to rotate. This ensures that the square intermediate component always maintains the same angle within the brake spring's bend 76, and that the pressure is applied at a single point. Furthermore, during normal operation (when the brake spring is at rest), this alternative embodiment keeps the intermediate component stationary (non-rotating), thereby ensuring a constant, well-defined braking torque on the wheel stem.

[0039] According to a preferred alternative embodiment of the invention, the brake device 6 comprises an eccentric 20, the axis of rotation of which is perpendicular to the general plane 50 and therefore parallel to the central axis / axis of rotation 42 of the wheelset 30, the eccentric 20 being arranged to press radially against the brake spring so as to be able to vary said radial pressing force exerted by the brake spring on the intermediate part / washer by rotating about its axis of rotation. Figure 1 and Figure 2 In the advantageous alternative embodiment shown in , eccentric 20 constitutes one of the two components that maintain the brake spring in a tensioned state. Thus, by rotating eccentric 20, the stress on this spring is varied, thereby adjusting the braking torque applied to first wheel set 30 (chronograph wheel set) when it is subjected to a rotational drive torque. This configuration is advantageous because it is insensitive to vibrations and shocks. In another alternative embodiment, another device for adjusting the radial force is provided, in particular a device equipped with a linearly movable pressure member.

[0040] Figure 10 Another embodiment of the invention is shown in which the brake spring 11 is straight / rectilinear (without stress). This spring is rigidly fastened at one of its two ends in a fixed part 82, without being able to change the angular position of the fixed part 82 in a geometric plane, thus preventing any involuntary displacement or displacement due to impact. The groove in the part 82, into which the end of the spring 11 is inserted, is oriented so that the middle zone of the spring exerts a radial compression force F on the washer 8, the spring then having a first convex curvature between the fastening part 82 and the support point of the spring on the washer. Preferably, at the other end of the spring, an eccentric is provided for adjusting the radial force F, which in this embodiment is located on the same side of the brake spring as the washer 8, which forms the intermediate part between the brake spring and the stem of the associated wheel set. Therefore, the brake spring 11 also has a second convex curvature between the said support point and the eccentric 20, this second curvature being smaller than the first curvature since the radial force F is not zero. It should be noted that Figure 10 The alternative embodiment shown in defines a construction of the type with a single bearing point, i.e., according to the definition given above, the brake spring presses on the washer at "one point." In another alternative embodiment of the "two-point" type, a star-shaped intermediate component is provided, for example with four to six tips, each with a small rounded portion. This slightly convex brake spring always presses on the two tips of the star-shaped intermediate component, thus exerting two forces that create a total radial compressive force at its center. In other words, these two forces generate two opposing moments of equal strength on the intermediate component. It should also be noted that in the event of an impact, the braking system cannot be released.

[0041] Figure 4 and Figure 5An electromechanical timepiece movement 2 is shown in which the brake device 6 is preassembled in a preliminary step before assembling the first wheel set 30. This preliminary assembly of the brake device 6 is advantageous. This is made possible in particular by the fact that the force exerted by the brake spring is radial and that a washer 8 is provided above the pinion and wheel 32 forming the first wheel set. Thus, the stem 36 of the first wheel set can be installed from below the timepiece movement and passed through the central opening in the washer 8. Figures 1 to 3 as well as Figure 6 Electromechanical timepiece movement 2 is shown after first wheel set 30 has been installed in this movement and the braking device is in operation.

[0042] To allow a preliminary assembly of the braking device 6, the washer 8 is arranged on the support 4 (the base of the tube 44), which has, on the periphery of this washer, an abutment surface 26, positioned horizontally facing the washer and diametrically 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 before assembling the first wheel set 30, with the washer abutting against the abutment surface 26, as Figure 4 and Figure 5 As shown in .

[0043] In a preferred alternative embodiment, abutment surfaces 26 are arranged so that, after pre-assembly of washer 8 and brake spring 10, the central cylindrical opening in the washer has at least one zone superimposed on the central circular opening in tube or pipe 44 into which a portion of stem 36 of first wheel set 30 is subsequently inserted, so that when the first wheel set is mounted in electromechanical timepiece movement 2, the stem can penetrate these two central circular openings without initially having to exert a radial force on the washer. Figure 5 As can be seen, in the alternative embodiment shown, the central cylindrical opening in gasket 8 completely overlaps the central circular opening in tube 44. Preferably, at least the majority of the opening in the gasket overlaps the central opening in the tube. In the example shown, it should be noted that stem 36 of first wheel assembly 30 is inserted into tube 44, which does not move. The upper end of the stem, intended to receive the seconds hand, has a smaller diameter, which makes it easier to insert this stem into the two central openings during assembly of display wheel assembly 30, the initial overlap of which is only partial when the brake device is in the pre-assembled state.

[0044] Once first wheel set 30 is assembled in the timepiece movement, washer 8 no longer rests against side wall 26 of plate 4 but, via its central cylindrical opening, against stem 36 of the first wheel set, more precisely against its revolving surface 35, which is advantageously cylindrical and axial. This first wheel set can then be driven in rotation from time to time, on command, by electromechanical motor 54 via second wheel set 52.

[0045] The invention has been described in detail for seconds wheel set 30 , but the braking device of the invention may be provided for other wheel sets of an electromechanical timepiece movement, in particular for a minute wheel set or a chronograph wheel set.

[0046] The present invention offers several advantages, some of which have already been described. Braking device 6 includes an eccentric 20 that facilitates adjustment of the radial compressive force exerted by the brake spring on middle member / washer 8 and, via this radial force applied to stem 36 of first wheel set 30, adjusts the torque of the frictional force applied to this first wheel set. Once the braking device has been fully installed in the electromechanical timepiece movement, eccentric 20 allows adjustment of the braking torque without having to remove the brake spring in order to slightly alter its initial shape. Given the presence of washer 8 between brake spring 10 and stem 36, and in addition to the fact that the forces involved are intended to be radial, the assembly of seconds hand 48 on first wheel set 30, and especially its removal (for example when replacing this hand or when cleaning the electromechanical timepiece movement), does not damage the brake spring (a delicate and delicate element in braking device 6), since washer 8 is more robust and can withstand a certain amount of axial pressure against its support.

[0047] Braking device 6 is protected from stresses that could damage it during the assembly of the other components of the electromechanical timepiece movement, in particular during the assembly of display wheel set 30. When timepiece movement 2, and in particular when display wheel set 30, is removed, braking device 6 can remain in place without changing its setting.

[0048] The braking device according to the invention makes it possible to predetermine the torque of the friction force relatively accurately, since the height of the lateral surface 9 of the intermediate part, in particular the washer 8, is generally much greater than the height of the brake spring, since the material of the intermediate part / washer 8 can be chosen, and since the diameter of the revolving surface of the defined cylindrical and axial surface of the stem 36 against which the intermediate part / washer 8 rests is precisely determined.

Claims

1. An electromechanical timepiece movement (2) 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 a display member (48), and a braking device (6) associated with the display wheel set and comprising a brake spring (10, 10A, 10B, 11) and an intermediate part (8, 68, 78) arranged between the brake spring and the stem of the display wheel set, the brake spring being arranged to brake as soon as this display wheel set is subjected to a rotational drive torque. The brake spring is arranged so that the intermediate component remains stationary and does not rotate during normal operation. The intermediate component has a lateral surface (9) and a support surface (25). The lateral surface (9) is pressed against the rotating surface (35) of the stem. The brake spring applies a total pressing force to the stem against the support surface (25) so as to generate a friction force between the lateral surface and the rotating surface. The friction force generates the braking torque.

2. The watch movement according to claim 1, characterized in that The intermediate part (8, 68, 78) exerts a purely radial pressure on the stem (36) of the display wheel set (30).

3. A timepiece movement according to claim 1 or 2, wherein the stem defines a central axis (42), characterized in that The surface of revolution (35) is cylindrical and axial, and the lateral surface (9) is axial.

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

5. The watch movement according to claim 4, characterized in that The brake spring (10, 10A, 10B, 11) is arranged so that a middle portion of this brake spring exerts the pressing force on the support surface of the middle part (8, 68, 78); and wherein two end portions of the brake spring, respectively located on either side of the middle portion, are pressed by two remote parts (16, 20) of the watch movement so that this middle portion exerts the pressing force on the support surface.

6. The watch movement according to claim 5, characterized in that The brake spring (10, 10A, 10B) is not fastened to the timepiece movement, but is held in tension by the remote part (16, 20) of the timepiece movement, the two end portions of the brake spring pressing against the remote part in two corresponding directions in the geometrical plane.

7. The watch movement according to claim 5 or 6, characterized in that: This movement comprises an eccentric (20) whose axis of rotation is perpendicular to the geometrical plane and which is arranged to press against the brake springs (10, 10A, 10B, 11) so as to be able to vary the pressing force exerted by the brake springs on the middle part (8, 68, 78) by rotating about its axis of rotation.

8. Timepiece movement according to any one of the preceding claims, characterized in that The middle part is a washer (8) having a central opening through which the stem (36) of the display wheel set passes, the lateral surface (9) of this washer being defined by the cylindrical surface of its central opening.

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

10. Timepiece movement according to any one of the preceding claims, characterized in that The middle part (8) is arranged facing an abutment surface (26) diametrically opposite the bearing surface (25), so that the middle part and the brake spring can be preassembled in the electromechanical timepiece movement before assembling the display wheel set (30), with the middle part resting against the abutment surface.

11. The watch movement according to claim 10, characterized in that The abutment surfaces (26) are arranged so that, after pre-assembly of the middle part (8) and the brake spring (10), the central cylindrical opening in the middle part has at least one zone superimposed on the central cylindrical opening in a tube or pipe (44), said tube or pipe (44) being 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 electromechanical timepiece movement, the stem can penetrate the two central circular openings without having to initially exert a radial force on the middle part.

12. Timepiece movement according to any one of the preceding claims, characterized in that At least a portion of the arbor (36) defining the surface of revolution (35) is made of steel or of a copper alloy, and at least a portion of the intermediate part (8) defining the lateral surface (9) is correspondingly made of a copper alloy or of steel.

13. The timepiece movement according to any one of claims 1 to 11, characterized in that At least a portion of the stem (36) defining the surface of revolution (35) is made of steel or of a copper alloy, and at least a portion of the middle part (8) defining the lateral surface (9) is made of a polymer.

14. The timepiece movement according to any one of claims 1 to 11, characterized in that At least a portion of the stem (36) defining the revolving surface (35) is made of steel or of a copper alloy, and at least a portion of the middle part (8) defining the lateral surface (9) is made of ceramic, in particular ruby ​​or zirconium oxide, or of a material containing gold or nickel, and forms an outer layer that at least partially covers the middle part.

Images