Mechanical clock movement comprising a mobile bearing a display member and provided with a braking device

Abstract

The mechanical watch movement comprises a mainspring barrel, an escapement wheel associated with a mechanical resonator, a display wheel (30) for carrying a display element, in particular a chronograph hand (48), and driven in rotation by the mainspring barrel, and a braking spring (10) arranged to generate, when the latter is subjected to a rotational driving torque, a braking torque intended to prevent vibration of the display element. The mechanical watch movement further comprises an intermediate component, in particular a washer (8), located between the braking spring and a shaft (36) of the display wheel, this intermediate component being freely mounted for rotation on the shaft. The intermediate component and the braking spring are arranged so that the intermediate component remains stationary and does not rotate during normal operation.The brake spring exerts an overall pressure force on the intermediate part in the direction of said shaft in order to generate said braking torque.

Description

Technical field of the invention

[0001] The present invention relates to a mechanical watch movement comprising a moving part carrying a display element, in particular a hand, and equipped with an anti-shake device, also called an anti-shake device, formed by a braking device acting on the moving part to prevent shaking of the display element in rotation and also fluttering of this element when stopped, if necessary. Technological background

[0002] Document CH 580301 discloses an anti-shake device for a horological movement, specifically a chronograph movement, hereinafter also referred to as a 'chronograph movement', comprising a shaft with a pinion, which meshes with a clutch wheel, referred to herein as a drive wheel, forming a clutch mechanism for a chronograph. It should be noted that a shaft with pivots to guide its rotation is also called an 'axis' in horology.The anti-shake device for the chronograph seconds hand consists of a friction device comprising a wire spring bearing obliquely against the shaft, which has a frustoconical shoulder for this purpose. The wire spring has a pivot point in the angle formed by this shoulder and a circular cylindrical portion, the diameter of which corresponds to the minimum diameter of the shoulder. This cylindrical portion exerts an oblique force on the shaft at this point, causing the pinion teeth to press against the driving wheel and a lower annular surface of the shaft, opposite the shoulder and perpendicular to the axis defined by the shaft, to press axially against a bearing in which the chronograph wheel pivots. The spring is designed to be straight when under no stress.This spring is fixed to the movement frame on one end while part of the other end is under tension and presses against the shaft, as explained above.

[0003] This anti-shake device presents several problems in controlling the frictional force applied to the chronograph movement. Furthermore, there is no way to adjust this frictional force. Additionally, when the chronograph hand is retracted, the mainspring is subjected to an axial force that can damage it.

[0004] Document DE 6800934 U describes a solution for improving the control of the frictional torque applied to a moving part. According to this document, the wire or leaf spring is attached at its first end by riveting to a plate held in suspension by a rivet with a slotted head, similar to a screw, positioned on one side of a bridge opposite the side where the plate is located. The rivet has an intermediate cylindrical section that is inserted into a hole in the bridge with a greasy friction, allowing the rivet, and thus the plate and the first end of the spring, to be rotated using a tool.The second end section of the friction spring is free and radially supported against a press-fit plastic washer mounted onto the seconds wheel arbor. This washer has a lateral groove into which the second end section of the spring is placed. The system is very difficult to install in the watch movement. First, the friction spring must be attached to the plate by inserting its first end section into a slot and then pushing material along both edges of this slot to create an initial rivet. Next, the plate with the friction spring must be brought to one inner side of the bridge after the rivet has been inserted into the hole in the bridge from the other side. Finally, the end of the rivet must be flattened, and a second rivet must be made to secure the plate to the rivet.It is observed that at each stage of assembling the friction spring to the plate and then to the bridge, via two successive rivets, there is a high risk of damaging the friction spring. Finally, the bridge, plate, and friction spring assembly is mounted in the watch movement, presumably simultaneously with the insertion of a pivot for the seconds hand arbor, which carries the grooved washer, into a bearing located in the bridge. Such an assembly requires that the spring not be superimposed on the grooved washer, as the spring is integral with the bridge, and the grooved washer, designed to receive the free end of the spring under tension, is integral with the arbor. Thus, a first mounting / dismounting position is provided for the spring, and a second working position is used in which the free end of the spring is brought into the groove of the washer and the spring is tensioned.To move from one position to the other, the watchmaker must manipulate the rivet head with a tool, which causes the spring to lose its tension, set during disassembly for maintenance. Therefore, each time the seconds hand is reassembled, the braking force must be readjusted. The assembly method described here is difficult to implement and very time-consuming.

[0005] Furthermore, this anti-vibration device only partially solves the problem of adjusting the torque applied to the seconds wheel to prevent vibration, because the friction force is defined, in particular, by the profile of the lateral groove in the plastic washer and the shape of the end of the spring that is inserted into this groove and presses radially against the washer. Such a friction force is difficult to control and reproduce, as it depends heavily on the dimensions of the spring and the groove, their respective configurations, and their respective surface finishes. Another problem arises from the fact that assembling an intermediate part on the seconds wheel shaft will generate an increase in the radial runout of the wheel, and therefore a greater variation than in the absence of such an intermediate part, especially if the spring pressed directly against a conventional shaft, which has less radial runout.Furthermore, if the watch is subjected to vibrations or shocks, the second free end of the spring could detach from the grooved washer, compromising consistent braking torque. Worse still, in the event of a violent impact, the spring retaining plate, held in place solely by friction, could shift angularly and alter the brake setting. Summary of the invention

[0006] The present invention aims to solve the problems of the prior art mentioned above and also to propose an anti-shake device for a display mobile, arranged outside the gear train of the barrel to the escapement mobile, which is easy to mount and which can, in a preferred embodiment, be mounted in a preliminary step to the mounting of the mobile in question.

[0007] To this end, the present invention relates to a mechanical watch movement comprising a mainspring barrel, an escapement wheel associated with a mechanical resonator, a display wheel comprising a shaft for carrying a display element, and a braking device associated with the display wheel and comprising a braking spring and an intermediate piece arranged between the braking spring and the shaft of the display wheel. This display wheel can be driven in rotation by the mainspring barrel but is not part of a gear train from the mainspring barrel to the escapement wheel. The braking spring is arranged so as to generate a braking torque on the display wheel as soon as the latter is subjected to a rotational driving torque, via the intermediate piece against which this braking spring presses.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 has a lateral surface pressing against a surface of revolution of the shaft, and a bearing surface against which the brake spring exerts a total pressure force in the direction of the shaft to generate a friction force between the lateral surface and the surface of revolution, which in turn generates the braking torque.

[0008] According to a first advantageous variant, the intermediate piece and the braking spring are configured so that said pressure force remains constant once the display mobile is mounted in the movement and the braking device is fully mounted and adjusted.

[0009] In a preferred general variant, the intermediate piece exerts exclusively radial pressure on the shaft of the display mobile.

[0010] In a principal embodiment, the braking spring is a wire spring or a leaf spring whose longitudinal axis is located in a geometric plane parallel to a general plane of motion.

[0011] In a main embodiment, the movement includes an eccentric whose axis of rotation is perpendicular to said geometric plane and which is arranged to press radially against the braking spring in order to be able to vary, by a rotation around its axis of rotation, said overall radial pressure force exerted by the braking spring on the intermediate part. Brief description of the figures

[0012] The invention will be described in more detail below with reference to the accompanying drawings, given by way of non-limiting examples, in which: there Figure 1is a partial, perspective view of a principal embodiment of a mechanical watch movement according to the invention, showing a braking device according to the invention previously mounted in a preliminary step before the assembly of the chronograph movement for which the braking device is intended; Figure 2 is a plan view of the part of the mechanical watch movement shown at the Figure 1 ; there Figure 3 is a cross-sectional view, passing through the central axis of a tube designed to receive part of the chronograph's moving part, along the cross-section line III-III of the Figure 2 ; there Figure 4 is a bottom view of the mechanical watch movement of the main embodiment once the chronograph wheel is mounted; the Figure 5 is a partial cross-sectional view of the mechanical watch movement along the VV cutting line of the Figure 4 ; there Figures 6schematically and partially represents a particular variant of the main embodiment; Figures 7A and 7B schematically and partially represent two advantageous variants of the main embodiment; the Figure 8 schematically and partially represents a particular variant of the main embodiment of the invention; and the Figure 9 schematically and partially represents a second embodiment of the invention. Detailed description of the invention

[0013] With reference to Figures 1 to 5 , we will describe below a main embodiment of a mechanical watch movement 2 according to the invention.

[0014] The mechanical watch movement 2 includes: a barrel, an escapement wheel 58 which is associated with a mechanical resonator (not shown in the figures), a first wheel 30, forming a display wheel, intended to carry a display element, in particular a hand 48 of a chronograph function's seconds display, and driven in rotation by a second wheel 52 incorporated in a gear train from the barrel to the escapement wheel, the first wheel not being included in this gear train, a braking spring 10 arranged so as to be able to generate on the first wheel 30, as soon as this first wheel is subjected to a rotational driving torque, a braking torque intended to prevent a shaking of the display element 48 and also a permanent radial force which keeps the display element in a stable position when it is stopped.

[0015] According to the invention, the mechanical watch movement 2 comprises a braking device 6 acting on the display wheel and comprising the braking spring 10 and an intermediate piece 8 arranged between the braking spring and a shaft 36 of the display wheel 30. The braking spring is arranged so as to generate a braking torque on the display wheel as soon as this display wheel is subjected to a rotational driving torque, via the intermediate piece against which this braking spring presses. To this end, the intermediate piece has a lateral surface 9, pressing against a surface of revolution 35 of the shaft, and a bearing surface 25 against which the braking spring exerts an overall pressure force in the direction of the shaft to generate a friction force between the lateral surface and the surface of revolution, this friction force generating the braking torque.Thus, the braking torque is exerted on the first moving part / display moving part by the braking spring via the intermediate piece against which the braking spring presses. The intermediate piece 8 and the braking spring 10 are arranged so that the intermediate piece remains stationary and non-rotating during normal operation. The shaft 36 of the first moving part and the intermediate piece are configured so that the surface of revolution 35 of the shaft can slide on the lateral surface 9, experiencing a dynamic friction force that generates the braking torque. Before the sliding of the surface of revolution on the lateral surface, a static friction force generates the braking torque and thus keeps the shaft stationary.

[0016] Preferably, the intermediate piece 8 exerts a purely radial pressure on the shaft 36 of the first moving part 30. According to an advantageous feature, the braking spring 10 exerts an overall exclusively radial pressure force on the intermediate piece. The bearing surface 25 is opposite the lateral surface 9; that is, the bearing surface is located on one side of the intermediate piece 8 that is opposite another side of this intermediate piece, defining the lateral surface 9. This variant is advantageous because the braking device bears on a machined part whose radial runout varies little, thus providing a constant braking torque for a given friction force between the surface of revolution 35 and the lateral surface 9.In an advantageous embodiment shown in the figures, the surface of revolution 35 of the shaft 36 is cylindrical and axial, and the lateral surface 9 of the intermediate piece is axial; that is to say, the cylindrical surface of revolution 35 and the lateral surface 9 are oriented along the axis of rotation 42 of the first moving part 30, which coincides with the central axis of the shaft 36, the lateral surface 9 and the cylindrical surface of revolution 35 thus being parallel to this axis of rotation 42. In a preferred embodiment, the intermediate piece 8 and the braking spring 10 are configured so that said pressure force remains constant once the display moving part is mounted in the movement and the braking device is fully mounted and adjusted.

[0017] According to one main variant, the braking spring 10 is a wire spring or a leaf spring whose longitudinal axis is located in a geometric plane parallel to a general plane 50 of the mechanical watch movement 2.

[0018] According to the variant shown, the intermediate piece 8 is a washer having a central cylindrical opening in which, without the interaction of the braking spring 10, the shaft 36 of the first mobile 30 would slide and rotate freely, said lateral surface 9 of this washer 8 being defined by the cylindrical surface, preferably circular (i.e. of revolution), of its central cylindrical opening.

[0019] According to a particular variant, the washer 8 has a circular groove 24 around its circumference defining the bearing surface 25 and into which at least part of the brake spring 10 is inserted, which exerts the radial pressure force. In particular, the groove 24 has a V-shaped cross-section and the brake spring 10 is a wire spring with a circular cross-section, as shown in the figures. Figures 3 And 5 This arrangement allows the brake spring to be axially positioned in its central part in contact with the washer. The spring is therefore not free to move axially.

[0020] By way of non-limiting examples, in a first variant, at least the portion of the washer 8 defining its central cylindrical opening is made of a copper-beryllium (CuBe) alloy when at least the portion of the shaft defining the surface of revolution 35 is made of steel, or vice versa. This first variant provides good tribological results. In a second variant, where said portion of the shaft is made of steel or CuBe, at least the portion of the washer defining its central cylindrical opening is made of polymers. Preferably, the entire washer is made of polymers. This second variant offers, in particular, advantageous self-lubrication.In other versions where the shaft is made of steel or a copper alloy (e.g., CuBe or brass), at least the portion of the washer defining its central cylindrical opening is made of bronze, nickel, or gold, particularly as a thin layer deposited on a base of another material in the case of nickel or gold, or more generally of a metallic alloy containing gold or nickel. In other versions, at least the portion of the washer defining its central cylindrical opening is made of ceramic, particularly ruby ​​or zirconia.

[0021] It should be noted that the material of the braking spring can be selected to optimize its elastic characteristics and manufacturing process, without having to worry about friction and wear issues, since the washer, and more generally the intermediate component, is designed to be static—that is, stationary and non-rotating—during normal operation of the mechanical watch movement. In the case of the washer, to prevent its rotation, one can either modify the shape of the intermediate component and / or the shape of the braking spring, as will be explained in more detail later, or, particularly in the case of a washer, modify the materials forming the spring and at least the outer part of the intermediate component in contact with the spring, and / or apply a surface treatment to these components to ensure high friction between the braking spring and the intermediate component.

[0022] According to another preferred variant, the braking spring 10 is arranged in the mechanical watch movement 2 such that a midsection between its two end sections presses radially against the bearing surface 25 of the intermediate piece / washer 8. More precisely, the braking spring 10 is arranged so that a midsection of this braking spring exerts said pressure force on the bearing surface 25 of the intermediate piece / washer 8. To this end, the two end sections of the braking spring, located respectively on either side of said midsection, are constrained by two distant parts 16 and 20 of the watch movement so that this midsection exerts the pressure force on the bearing surface of the intermediate piece / washer. This configuration of the braking device is advantageous because it allows constant pressure of the braking spring on the bearing surface of the intermediate piece / washer.Furthermore, this configuration is less sensitive to vibrations and shocks than if the brake spring had an anchor point at one end and a contact point at the other end.

[0023] In one particular embodiment, the brake spring 10 is curved in its midsection, and the bearing surface 25 of the intermediate piece / washer 8 has a convex curvature in said geometric plane, relative to the shaft 36 of the first moving part 30, and specifically a circular curvature in the case of the washer, which the midsection of the brake spring follows along the bearing surface in a first embodiment. In a second embodiment, the radius of curvature of the midsection is smaller than the average radius of curvature of the bearing surface, so that the brake spring presses on the intermediate piece / washer at two points on the bearing surface, i.e., at two distinct locations. It should be noted that, with a groove substantially in the shape of a V, a spring with a circular cross-section presses locally at a pair of axially aligned points.Thus, in such a configuration of the groove and the brake spring, the latter exerts pressure at two pairs of angularly separated points, with each pair of points aligned along an axial direction. Therefore, it exerts pressure at "two points" in projection onto the general plane of the spring, which is parallel to the general plane of motion. Finally, these variants do not preclude other advantageous variants in which the average radius of curvature of the central portion is provided to be larger than the radius of curvature of the bearing surface. Consequently, the radial pressure is then exerted at "one point" (i.e., at a pair of points aligned along an axial direction, but at a single point in projection onto the general plane of the spring / general plane of motion).

[0024] According to an advantageous variant, as shown in the Figure 2The 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 this movement against which two end portions of the brake spring, located respectively on either side of a median portion of this brake spring, bear radially against the intermediate part, which is in particular the washer 8. The direction of the force applied by the two parts 16 and 20 on the spring is reversed with respect to the direction of the reaction force of the intermediate part / washer 8 on the median portion of the spring. These forces, which act on the brake spring in the geometric plane (horizontal plane orthogonal to the axis of rotation 42 of the shaft 36 coinciding with its central axis) in which its longitudinal axis is located, generate a stress that holds the brake spring in place.Next, to prevent the spring from moving axially / vertically, and in particular to prevent its middle section from coming out of the groove 24, two sections of the support 4 are provided on each of the two sides, defining lower axial stops for the brake spring. On one side, a groove 14 is provided in the support 4 (barrel bridge) of the braking device. This support can hold the washer 8, particularly when the washer is installed before the spring is fitted. The bottom of this groove, forming a thin horizontal wall, limits any possible movement of the spring section located on that side. On the second side, the brake spring is partially positioned above a small protruding section 18.

[0025] Several other advantageous variants are schematically represented in the Figures 6, 7A and 7B The variant of the Figure 6is characterized by a braking spring 10A with a central portion having two bends 71 ​​and 72 separated by a straight section 70 (unconstrained), which bears, substantially at its midpoint, against the circular washer 8. This ensures that the braking spring 10A bears at a single point on the washer 8 at all times. Variants of Figures 7A to 7B are characterized by an intermediate piece 68 which is not circular, but is formed by a truncated washer with a straight area 80. In the variant of the Figure 7A The brake spring 10 has, in its middle part, a bend 74 which is located opposite the straight area 80 of the truncated washer 68. In the variant of the Figure 7BThe spring 11 is straight / rectilinear without constraint and, when energized to press against the intermediate piece, it curves slightly (concave curvature as seen from the intermediate piece) so that it presses at both ends of the straight area 80 of this intermediate piece. Thus, in the variants of Figures 7A and 7B The braking spring 10, respectively 11, exerts two forces F1 and F2 at the two ends of the straight section 80, respectively. The two forces F1 and F2 are globally radial, meaning that their sum at a midpoint is radial. However, each of the two forces exerts a torque on the intermediate piece 68, so that if the spring moves longitudinally and one of the two forces F1 and F2 decreases relative to the other, the intermediate piece 68 automatically undergoes a small rotation to restore equilibrium between the two opposing torques acting on it. The variant of the Figure 7Bis preferable because the risk of rotation of the truncated washer is lower. Furthermore, this variant allows the desired braking torque to be maintained even if the brake spring undergoes some longitudinal displacement during a shock or sudden acceleration. However, the variant of the Figure 7A With a bent spring, it is less likely to undergo longitudinal displacement in the event of an impact. The variant 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 as set. The variants of Figures 7A and 7B ensure at all times a support at "two points" projected into the geometric plane of the spring.

[0026] A particular variant is schematically represented at the Figure 8 This variant, like that of the Figure 6The system is designed to ensure constant pressure from the brake spring 10B at a single point on the intermediate piece 78, which has a generally square shape with rounded corners. The brake spring 10B has a bend 76 such that the two straight sections of the spring on either side of the bend form an angle greater than 90° but relatively close to this value, for example, an angle of 110°. One of the rounded corners of the intermediate piece is positioned within the bend 76 of the spring, which, when the spring and the intermediate piece 78 are stationary, exerts a substantially radial force F on the intermediate piece. If, particularly under the action of an impact, the spring 10B moves, the direction of the force changes, causing the intermediate piece to experience a torque that rotates it.Thus, it is ensured that the same angle of the square intermediate piece remains at all times within the bend 76 of the braking spring, and that pressure is applied at a single point. Furthermore, in normal operation (with the braking spring stationary), this variant keeps the intermediate piece stationary (without rotation), thereby ensuring a constant and well-defined braking torque on the shaft of the moving part.

[0027] According to a preferred embodiment of the invention, the braking device 6 comprises an eccentric 20 whose axis of rotation is perpendicular to the general plane 50, and therefore parallel to the central axis of rotation 42 of the moving part 30, and which is arranged to press radially against the braking spring so as to be able to vary, by a rotation about its axis of rotation, said radial pressure force exerted by the braking spring on the intermediate piece / washer. In the advantageous embodiment described in Figures 1 And 2The eccentric 20 is one of the two parts that maintain tension on the braking spring. Thus, by rotating the eccentric 20, the tension on this spring is varied, allowing adjustment of the braking torque applied to the first moving part 30 (chronograph wheel) when it is subjected to a rotational driving torque. This configuration is advantageous because it is not sensitive to vibrations and shocks. In another variant, a different radial force adjustment device is provided, specifically a device equipped with a pressure element that can be moved linearly.

[0028] There Figure 9This illustrates another embodiment of the invention in which the brake spring 11 is straight (unconstrained). This spring is rigidly fixed at one of its two ends to a fixed part 82, the angular positioning of which in the geometric plane is fixed, thus preventing any unintentional displacement or displacement due to impact. The groove in the part 82, into which the end of the spring 11 is inserted, is oriented such that a median area of ​​the spring exerts a radial pressure force F on the washer 8. This spring then presents, between the fixing part 82 and the point of contact of the spring on the washer, a first convex curvature (as seen from the washer).Preferably, at the other end of the spring, to adjust the radial force F, an eccentric is provided which, in this embodiment, is located on the same side of the brake spring as the washer 8 that forms the intermediate piece between the brake spring and the shaft of the moving part concerned. Thus, the brake spring 11 also has a second convex curvature between said fulcrum and the eccentric 20, this second curvature being less pronounced than the first curvature because the radial force F is not zero. Note that the variant shown in Figure 1... Figure 9This defines a single-point support design, meaning the brake spring bears a single point on the washer, as previously defined. Another variant, the two-point design, incorporates a star-shaped intermediate piece, for example, with four to six points, each slightly rounded. The slightly convex brake spring constantly presses on two points of this intermediate star, exerting two forces that, at their central point, combine to create a single radial pressure force. In other words, the two forces generate two equal and opposite moments of force on the intermediate piece. It should also be noted that the braking system cannot be misaligned in the event of an impact.

[0029] THE Figures 1 to 3The diagram shows the mechanical watch movement 2 with the braking device 6 pre-assembled in a preliminary step before the assembly of the first moving part 30. This preliminary assembly of the braking device 6 is advantageous. It is made possible in particular by the fact that the force exerted by the braking spring is radial and by the fact that the washer 8 is positioned above a pinion and a wheel 32 forming the first moving part and, in the example shown where the first moving part is a chronograph moving part, above a reset heart 34. Figures 4 And 5 show the mechanical watch movement 2 after the assembly of the first mobile 30 in this movement and the braking device in a functional state.

[0030] To allow the preliminary assembly of the braking device 6, the washer 8 is arranged on a support 4 (barrel bridge) which has a horizontally positioned stop surface 26 around the periphery of the washer, opposite the washer and diametrically opposite the bearing surface 25, so that the washer 8 and the braking spring 10 can be pre-assembled in the mechanical watch movement 2, before the assembly of the first moving part 30, with the washer bearing against the stop surface 26, as shown in the diagrams. Figures 1 to 3 The stop surface 26 is defined by a lateral surface of a cavity 12 machined in the support 4, the washer being arranged in this cavity 12 open on the lower side of the movement (by definition, the analog display is on the upper side).

[0031] In a preferred embodiment, the stop surface 26 is arranged so that, following the prior assembly of the washer 8 and the braking spring 10, the central cylindrical opening of the washer has at least one overlapping area with the central circular opening of a barrel or tube 44, into which a portion of the shaft 36 of the first moving part 30 (chronograph moving part) is subsequently inserted, so that the shaft can, during the assembly of the first moving part in the mechanical watch movement 2, enter both central circular openings without initially having to exert a radial force on the washer. As this is visible in the Figure 3In the variant shown, the central cylindrical opening of the washer 8 is entirely superimposed on the central circular opening of the barrel 44. It should be noted that, in the example given, the shaft 36 of the first mobile 30 is inserted into a barrel 44 which carries a display hand and is thus mobile in rotation, this barrel being pivoted in the plate 60 and the barrel bridge 4. Inside the central opening of the barrel is arranged an internal bearing 46 in which is pivoted an end part 37 of the shaft 36 on which the chrono hand 48 is mounted, this end part having a maximum diameter less than the diameter of the surface of revolution 35, in particular cylindrical and axial, which is finally located inside the central cylindrical opening 9 of the washer.This makes it possible in particular to facilitate the introduction of the shaft 36 into the two central circular openings during the assembly of the chronograph mechanism when the initial overlap of the two central circular openings, before the assembly of this chronograph mechanism, is only partial.

[0032] Once mounted, the first moving part 30, forming a chronograph moving part in the embodiment shown, is pivoted by the upper bearing 46 and by a lower bearing 38 arranged in an opening in a bridge 40. The washer 8 is no longer supported against the lateral wall 26 of the cavity 12 of the support 4, but rather, by its central cylindrical opening, it rests against the shaft 36 of the first moving part, more precisely against a surface of revolution 35, advantageously cylindrical and axial, of this shaft. Note that in the variant shown, the barrel is pivoted between the barrel bridge 4, forming the support piece for the washer 8, and the plate 60. The first moving part is driven in rotation intermittently, on command, by a second moving part 52 via a clutch wheel 54 mounted on a rocker 56, which is conventionally driven by a column wheel or a cam (disengagement schematically indicated by an arrow at the Figure 4). The second mobile 52 includes a drive wheel which is incorporated into the gear train from the barrel to the escape wheel 58. This drive wheel here forms a small seconds wheel of the time display of the watch receiving the mechanical watch movement 2.

[0033] The present invention has been described in detail for a chronograph mobile 30, but the braking device of the invention can be provided for other mobiles of a mechanical watch movement, in particular for a small seconds mobile when this mobile is not included in the gear train from the barrel to the escape wheel 58.

[0034] The invention offers several advantages, some of which have already been described. The braking device 6 includes an eccentric 20 that allows for easy adjustment of the radial pressure force exerted by the braking spring on the intermediate piece / washer 8 and, via this washer, the radial force applied to the shaft 36 of the first moving part 30, as well as adjustment of the frictional torque applied to this first moving part. The eccentric 20 allows for adjustment of the braking torque once the braking device is fully mounted in the mechanical watch movement, without having to remove the braking spring to slightly alter its initial shape.Given the presence of the washer 8 between the brake spring 10 and the shaft 36, and in addition to the fact that the forces involved are expected to be radial, the placement of the chrono hand 48 on the first moving part 30 and especially its removal, for example when changing this hand 48 or for cleaning the mechanical watch movement, cannot damage the brake spring which is the delicate element in the braking device 6, the washer 8 being much more robust and able to withstand a certain axial pressure against the support 4.

[0035] The braking device 6 is such that it is protected against stresses which could damage it during the assembly of other parts of the mechanical watch movement, in particular during the assembly of the chrono mobile 30. During disassembly of the watch movement, and in particular of the first mobile 30, the braking device 6 can remain in place without its setting being modified.

[0036] The braking device according to the invention allows the moment of force of the friction to be defined in advance in a relatively precise manner, given that the lateral surface 9 of the intermediate piece, in particular of the washer 8, has a height generally much greater than that of the braking spring, that the material of the intermediate piece / washer 8 can be selected and that the diameter of the surface of revolution, defining a cylindrical and axial surface, of the shaft 36 against which the intermediate piece / washer 8 presses is precisely determined.

Claims

1. Mechanical horological movement (2) comprising a barrel, an escape wheel set (58) associated with a mechanical resonator, a display wheel set (30) comprising an arbor (36) intended to carry a display member (48), and a braking device (6) associated with the display wheel set and comprising a braking spring (10, 10A, 10B, 11) and an intermediate part (8, 68, 78) arranged between the braking spring and the arbor of the display wheel set, this display wheel set being able to be driven rotatably by the barrel but not forming part of a gear train from the barrel to the escape wheel set, the braking spring being arranged so as to be able to generate, via the intermediate part against which this braking spring presses, a braking torque on the display wheel set, as soon as this display wheel set is subjected to a rotary drive torque, characterised in that the intermediate part and the braking spring are arranged so that the intermediate part remains stationary and non-rotating in normal operation; and in that the intermediate part has a lateral surface (9) pressing against a surface of revolution (35) of said arbor, and a bearing surface (25) against which the braking spring exerts an overall pressing force towards said arbor in order to generate a friction force between the lateral surface and the surface of revolution that generates said braking torque.

2. Mechanical horological movement according to claim 1, characterised in that the intermediate part (8, 68, 78) exerts exclusively radial pressure on the arbor (36) of the display wheel set (30).

3. Mechanical horological movement according to claim 1 or 2, wherein the arbor defines a central axis (42), characterised in that said surface of revolution (35) is cylindrical and axial and said lateral surface (9) is axial.

4. Mechanical horological 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 strip spring whose longitudinal axis is located in a geometric plane parallel to a general plane (50) of the movement.

5. Mechanical horological movement according to claim 4, characterised in that the braking spring (10, 10A, 10B, 11) is arranged so that a middle part of this braking spring exerts said pressing force on said bearing surface of the intermediate part (8, 68, 78); and in that two end parts of the braking spring, located respectively on either side of said middle part, are stressed by two distant parts (16, 20) of the horological movement so that this middle part exerts the pressing force on said bearing surface.

6. Mechanical horological movement according to claim 5, characterised in that the braking spring (10, 10A, 10B) is not fastened to the horological movement but is held under tension by said distant parts (16, 20) of this horological movement against which said two end parts of the braking spring press in two directions in said geometric plane.

7. Mechanical horological movement according to claim 6, characterised in that the intermediate part and the braking spring are configured in such a way that their relative positioning substantially does not vary over time, even in the event of a possible longitudinal displacement of the braking spring as the result of an acceleration to which the movement is subjected in its general plane.

8. Mechanical horological movement according to any one of claims 5 to 7, characterised in that this movement comprises an eccentric (20) whose axis of rotation is perpendicular to said geometric plane and which is arranged so as to press against the braking spring (10, 10A, 10B, 11) in order to be able to vary, by rotation about its axis of rotation, said pressing force exerted by the braking spring on the intermediate part (8, 68, 78).

9. Mechanical horological movement according to any one of the preceding claims, characterised in that the intermediate part is a washer (8) having a central opening through which the arbor (36) of the display wheel set passes, said lateral surface (9) of this washer being defined by a cylindrical surface of its central opening.

10. Mechanical horological movement according to claim 9, characterised in that the washer (8) has, on its periphery, a groove (24) defining said bearing surface (25) and into which is inserted at least partially a part of the braking spring (10) exerting said pressing force in the direction of said arbor.

11. Mechanical timepiece movement according to any one of the preceding claims, characterised in that the intermediate part (8) is arranged on a support (4) which has at the periphery of this intermediate part an abutment surface (26) situated horizontally facing the intermediate part and diametrically opposite said bearing surface (25), so that the intermediate part and the braking spring can be preassembled in the mechanical timepiece movement, before assembling the display wheel set (30), with the intermediate part bearing against the abutment surface.

12. Mechanical horological movement according to claim 11, characterised in that the abutment surface (26) is arranged in such a way that, following prior assembly of the intermediate part (8) and of the braking spring (10), the central cylindrical opening in the intermediate part has at least one zone that is superimposed with the central cylindrical opening in a pipe (44) or tube, which is rotatable or fixed, into which part of the arbor (36) of the display wheel set (30) is inserted, so that the arbor can, when the display wheel set is mounted in the mechanical horological movement, penetrate the two central circular openings without initially having to exert a radial force on the intermediate part.

13. Mechanical horological movement according to any one of the preceding claims, characterised in that at least part of the arbor (36) defining said surface of revolution (35) is made of steel or consists of a copper alloy and at least part of the intermediate part (8) defining said lateral surface (9) consists of a copper alloy or steel respectively.

14. Mechanical horological movement according to any one of claims 1 to 12, characterised in that at least part of the arbor (36) defining said surface of revolution (35) is made of steel or consists of a copper alloy and at least part of the intermediate part (8) defining said lateral surface (9) consists of polymers.

15. Mechanical horological movement according to any one of claims 1 to 12, characterised in that at least part of the arbor (36) defining said surface of revolution (35) is made of steel or consists of a copper alloy and at least part of the intermediate part (8) defining said lateral surface (9) consists of a ceramic, in particular ruby or zirconia, or of a material containing gold or nickel and forming an outer layer at least partially covering the intermediate part.

Images