Chronograph mechanism for watch movement and watch equipped with said mechanism

Abstract

To provide a zero-reset mechanism that offers precise zero-resetting of a chronograph second hand positioned exactly opposite a predetermined graduation on a dial.SOLUTION: A chronograph mechanism comprises a zero-reset mechanism 40 for resetting a chronograph counter 22 to zero. A hammer 50 can be moved by a zero-reset control 60 between a rest position, in which the hammer 50 is not in contact with a cam track, and a zero-reset position, in which the hammer 50 is in contact with the cam track and holds a zero-reset member 225 in a reference position. The hammer 50 generates a driving torque on the zero-reset member 225 between the rest position and the zero-reset position. The hammer 50 cooperates with guide members shaped to guide an outward movement of the hammer 50 along a first path between the rest position and the zero-reset position and to guide a return movement of the hammer 50 along a second path between the zero-reset position and the rest position, the first path and the second path of the hammer being non-coincident.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a chronograph mechanism for a timepiece movement.

[0002] More particularly, the present invention relates to a chronograph mechanism that includes a zero reset mechanism.

[0003] The invention further relates to a timepiece including such a chronograph mechanism. [Background technology]

[0004] The chronograph mechanism makes it possible to measure time on demand by means of several chronograph counters, for example a minutes counter and a seconds counter.

[0005] The chronograph mechanism generally includes a zero reset mechanism for resetting the chronograph counter to zero, i.e. for repositioning the chronograph counter to a reference position, so that time can be measured again on demand.

[0006] Conventionally, such a zero-reset mechanism consists of a user-operable zero-reset control, for example by means of a push button or actuation pin accessible from outside the central part in which the watch movement is mounted.

[0007] The zero reset control cooperates directly or indirectly with a zero reset hammer which strikes a zero reset cam carried by the various chronograph counters.

[0008] The chronograph counters and associated hands are reset to zero by a hammer pressing against the surface of a zero reset cam, generating a driving torque that changes the position of the appropriate chronograph counter until the chronograph counter returns to a reference position determined by the geometry of the zero reset hammer and cam.

[0009] Zero reset cams are known to be formed with a single convolution and have an eccentric or "snail" shape that causes the reset to always occur in the same direction. An example of such a prior art zero reset cam is shown in Figure 1.

[0010] These spiral cams lack precision and cannot guarantee that the counter is reset to zero at every angular position of the cam. Indeed, if the spiral cam is in an angular position very close to its nominal position, for example an angular position corresponding to a fraction of a second of hand rotation, the gaps present between the various parts may mean slippage of the hammer on the cam, which may result in a backward movement of the hand visible to the user, instead of driving the hand in the direction in which it is reset to zero.

[0011] To overcome these drawbacks, a heart-shaped zero reset cam was developed, which is characterized by two identical spirals, but arranged in opposite directions, thus giving it a heart shape, as shown in the reference manual "Théorie d'horlogerie" by C.-A. Reymondin et al., Federation des Ecoles Techniques, 2015 edition, p. 238.

[0012] Such a zero reset cam is shown in Figure 2.

[0013] A hammer for resetting such a heart shape to zero includes an arm shaped like a horseshoe (as seen in Figure 2). At the end of the hammer stroke (linear or circular), the arm rests on the double lobe formed by the heart part, ensuring that the counter and the corresponding hand are held in a stable position corresponding to the zero reset position.

[0014] Although this type of zero reset mechanism is widely known, it suffers from several drawbacks.

[0015] First, the positioning of the hands, especially the seconds hand, when returning to zero is often random and lacking in precision, which is particularly detrimental in the case of a jumping seconds hand that is supposed to be in a precise angular position every second to face the scale on the dial.

[0016] Secondly, given the geometrical configuration of the heart piece and the hammer, the frictional forces at their interface are not constant, which results in uneven wear of these parts, adversely affecting the long term reliability of the mechanism.

[0017] Thirdly, in some angular positions of the heart parts, as shown in Figures 11 to 29 of the aforementioned manual, the hammer rubs against the heart parts with sharp edges, thereby increasing stress concentrations, wear and mechanical fatigue of these parts.

[0018] Fourthly, the inertia of the heart parts acquired during their rotation means that they are not immediately locked into a reference position at the end of the hammer stroke, but are left moving in damped oscillations before coming to rest, which undermines the feeling of precision that experienced users expect.

[0019] Thus, there is a need for improved chronograph mechanisms, and in particular the mechanisms for resetting the counters of such chronograph mechanisms to zero. Summary of the Invention [Problem to be solved by the invention]

[0020] In this regard, one of the objects of the present invention is to provide a chronograph mechanism which overcomes at least one of the above problems.

[0021] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to provide a zero reset mechanism that provides an accurate zero reset, particularly of a chronograph seconds hand that is diametrically opposed to a given graduation on a dial.

[0022] One of the objects of the present invention is to provide a reliable and safe zero reset mechanism that enables the chronograph to be reset to zero in its direction of travel while avoiding the phenomenon in which the hands move in the reverse direction when the zero reset hammer hits the zero reset cam. [Means for solving the problem]

[0023] In this regard, the invention relates to a chronograph mechanism for a timepiece movement, comprising: A chronograph counter having a shaft and a hand that rotates integrally with the shaft; a zero reset mechanism for resetting the chronograph counter to zero, the zero reset mechanism comprising: a zero reset member integral with the shaft; and a hammer configured to cooperate with the zero reset member and generate a drive torque under the action of a zero reset control by rotation of the chronograph counter in the forward direction until the zero reset member is located in a reference position; Equipped with the zero reset member being a spiral cam having a cam track spiralling around said shaft of the chronograph counter from a proximal end defining a zone of minimum radius relative to the shaft to a distal end defining a zone of maximum radius relative to the shaft, The hammer can be moved by a zero reset control between a rest position where the hammer does not contact the cam track and a zero reset position where the hammer contacts the cam track to hold the zero reset member at the reference position, and the hammer generates a drive torque to the zero reset member between the rest position and the zero reset position; The present invention relates to a chronograph mechanism, characterized in that the hammer cooperates with a guide member configured to guide the forward movement of the hammer along a first path between a rest position and a zero reset position and to guide the return movement of the hammer along a second path between the zero reset position and the rest position, the first path and the second path of the hammer not coinciding.

[0024] Advantageously, the return path (ie the second path) is different to the outward path (ie the first path), such that the return path is at least substantially offset from the first path.

[0025] The difference between the forward and backward travel of the hammer, especially in the area of ​​contact with the cam track, ensures a sufficient bearing surface on the cam track when the chronograph counter is reset to zero, especially when the counter is stopped at the position corresponding to the start of the timed minute. This ensures that the contact between the hammer and the cam is made on the surface of the scroll and not on the nose of the cam. This ensures that the counter returns to its reference position on the correct side.

[0026] In addition to the features mentioned in the previous paragraph, the chronograph mechanism according to the invention may have one or more of the following complementary features, considered individually or according to any technically possible combination: The guide member is shaped to guide the hammer along a first unidirectional linear path between the rest position and the zero reset position, and along a second multi-directional path having at least two different directions between the zero reset position and the rest position. The guide member is shaped to guide the hammer along a first curved path between the rest position and the zero reset position, and along a second path between the zero reset position and the rest position that is different from the first curved path. The guide member comprises a disengageable guide yoke configured to be inoperative during forward movement of the hammer and to be operative during return movement of the hammer. The disengageable guide yoke comprises a guide cam cooperating with a guide peg integral with the hammer, said guide cam having a first portion shaped to disengage the guide yoke during forward movement of the hammer and a second portion shaped to guide the hammer during return movement of the hammer. The disengageable guide yoke cooperates with a guide yoke spring which is biased to reposition said disengageable yoke to a neutral equilibrium position against the yoke stop. The hammer has at its free end an arm having an inclined surface configured to contact the cam track of the zero reset member and generate a driving torque under the action of the zero reset control until the zero reset member is located in the reference position. The arm has a stop surface configured to provide an angular positioning stop for the zero reset member during a zero reset operation. The arm has an end beak that extends the inclined surface to form a protrusion that projects from the stop surface. The zero reset member has a connection portion connecting the proximal end and the distal end, the connection portion not belonging to the cam track, and the connection portion has a recess forming a gap for receiving and accommodating the end beak when the hammer is in the zero reset position. The second portion of the guide cam is shaped to disengage the end beak from the recess during return movement of the hammer and so that the end beak bypasses the distal end of the zero reset member. The chronograph counter is a seconds counter. The mechanism also comprises a minute counter having a minute counter shaft and a minute hand rotating integrally with the minute counter shaft, the minute counter shaft carrying a second heart-shaped zero reset member. The hammer includes a second arm that cooperates with the second zero reset member, the second arm being configured to generate a drive torque under the action of the zero reset control until the second zero reset member is located in the reference position.

[0027] Another aspect of the invention relates to a timepiece movement including such a chronograph mechanism according to the invention.

[0028] Another aspect of the invention relates to a timepiece including such a timepiece movement according to the invention, which includes a chronograph mechanism according to the invention.

[0029] The timepiece is preferably a wristwatch that includes a watch case configured to receive and house a timepiece movement according to the present invention. [Brief description of the drawings]

[0030] The objects, advantages and features of the present invention will be better understood from the following detailed description taken in conjunction with the following figures. [Figure 1] FIG. 1 is a schematic diagram of a first example of a zero reset cam for a prior art chronograph mechanism, already described in the technical background. [Diagram 2] FIG. 2 is a schematic diagram of a second example of a zero reset cam for a prior art chronograph mechanism, already described in the technical background. [Diagram 3] 1 is a schematic 2D representation of the chronograph mechanism of a timepiece movement according to the invention, the chronograph mechanism being in a neutral rest position. [Figure 4] FIG. 4 is a detailed view of a portion of the chronograph mechanism shown in FIG. 3, in particular showing the first arm of the zero reset hammer. [Diagram 5] 1 is a schematic 2D representation of the chronograph mechanism of a timepiece movement according to the invention, the chronograph mechanism being in the operational zero reset position. [Figure 6] FIG. 6 is a detailed view of a portion of the chronograph mechanism shown in FIG. 5, particularly showing the first arm of the zero reset hammer in contact with the zero reset member. [Figure 7] FIG. 2 is a detailed view showing the end of a disengageable guide yoke of the chronograph mechanism according to the invention, with a guide cam for guiding the hammer. [Figure 8] 6 shows the chronograph mechanism according to the invention in a first intermediate position during the forward movement of the hammer between the neutral rest position shown in FIG. 3 and the operational zero reset position shown in FIG. 5. [Figure 9] 6 shows the chronograph mechanism according to the invention in a first intermediate position during the return movement of the hammer between the operational zero reset position shown in FIG. 5 and the neutral rest position shown in FIG. 3. [Figure 10] 6 shows the chronograph mechanism according to the invention in a second intermediate position during the return movement of the hammer between the operational zero reset position shown in FIG. 5 and the neutral rest position shown in FIG. [Figure 11] 4 shows the return stroke of the hammer in the seconds counter of the chronograph mechanism according to the invention.

[0031] In all figures, common elements are numbered the same unless otherwise indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] FIG. 3 shows a schematic plan view of a chronograph mechanism 10 incorporated in a timepiece movement 1 according to the invention.

[0033] 3 in particular shows the chronograph mechanism 10 in a neutral, i.e. non-operating, position. It should be noted that the chronograph counters are, by way of example, in their reference positions.

[0034] FIG. 5 shows the same chronograph mechanism 10 in an operational zero reset position in which the counters are repositioned to their reference positions regardless of their initial positions.

[0035] The clock movement 1 according to the invention comprises, in a conventional manner, a plate 2 which serves as a support for the various elements of the clock movement 1, in particular for a working train (not shown) dedicated to the division of time, driven by an energy source (not shown).

[0036] Energy source 50 is, for example, a barrel that constitutes a reserve of energy for powering an actuation train.

[0037] Conventionally, the actuation train drives the hands of the time display, in particular the hour hand which cooperates with the hour scale, the minute hand which cooperates with the minute scale and the seconds hand which cooperates with the second scale, i.e. the Trotouse hand.

[0038] The actuation train is conventionally restrained by a restraining member.

[0039] The regulating member conventionally includes an oscillator and an escapement. The oscillator can be an electrical or mechanical oscillator.

[0040] For example, the oscillator is a mechanical spring balance oscillator. Such a spring balance has a vibration frequency of, for example, between 2.5 Hz and 4 Hz.

[0041] For example, the oscillator is a high frequency electrical or mechanical oscillator, ie it vibrates at a frequency above 4 Hz.

[0042] For example, the oscillator is a high frequency electrical or mechanical oscillator, ie it vibrates at a frequency of 5 Hz or higher.

[0043] The chronograph mechanism 10 includes a chronograph train 20 which can be kinematically connected, on demand, to an operating train via a coupling (not shown) controlled by a chronograph on / off control member 30 .

[0044] According to an alternative embodiment, the coupling is a yoke coupling which allows the coupling wheel to pivot.

[0045] According to an alternative embodiment, the coupling is a vertical coupling.

[0046] According to another alternative embodiment, the coupling is a differential coupling cooperating with a coupling yoke controlled by a chronograph start / stop control member to interrupt one of the differential coupling inputs.

[0047] Conventionally, the chronograph train 20 comprises at least one chronograph counter.

[0048] 3 and 5, the chronograph train 20 comprises a first chronograph counter formed by a seconds counter 22 and a second chronograph counter formed by a minutes counter 21.

[0049] The minute counter 21 comprises a minute counter wheel 211 connected to a shaft 213, called the minute counter shaft, which drives a chronograph minute hand 214 (shown in dotted lines in FIG. 3).

[0050] The seconds counter 22 comprises a seconds counter wheel 221 connected to a shaft 223, called the seconds counter shaft, which drives a chronograph seconds hand 224 (shown in dotted line in FIG. 3).

[0051] Preferably, the minute counter wheel 211 is integral with the shaft 213 of the minute counter 21 and the second counter wheel 221 is frictionally mounted on the shaft 223 of the second counter 22. Naturally, the reverse configuration is also possible without departing from the context of the invention.

[0052] According to an alternative embodiment, the minute counter wheel 211 and the second counter wheel 221 are frictionally mounted on their respective shafts 213 , 223 .

[0053] The chronograph train 20 may also include an additional fractional seconds counter (not shown), also known as a fractional seconds counter.

[0054] The chronograph train 20 can include intermediate chronograph wheel sets 23, 24, 25 to obtain the desired ratio between the various counters 21, 22 of the chronograph mechanism 10. The chronograph train 20 can include more intermediate wheel sets depending on the needs and the structure of the movement and the layout of the minute counter 21, the second counter 22 and optionally the second counter on the plate 2 of the watch movement 1.

[0055] The chronograph mechanism 10 also features a mechanism 40 for resetting the minute counter 21 and the second counter 22 to zero, and more specifically the hands 214, 224 associated with these counters 21, 22 to zero.

[0056] The zero reset mechanism 40 comprises zero reset members 215, 225 integral with the shafts 213, 223 of the chronograph counters 21, 22. The zero reset members 215, 225 cooperate with the hammers 50 to place them in a reference position and to reset the hands 214, 224 of the counters 21, 22 to zero.

[0057] The zero reset members 215, 225 of the minute counter 21 and the second counter 22 are zero reset cams, for example in the shape of a snail, a heart, etc., which shape makes it possible to reposition the hands 214, 224 to a reference position at the end of the stroke of the hammer 50.

[0058] 3 to 11, the zero reset member 215 of the chronograph minute counter 21 is, for example, a heart part having two identical spirals arranged in opposite directions. In the following description, the zero reset member 215 of the minute counter 21 is simply referred to as the heart cam 215.

[0059] According to the present invention, the zero reset member 225 of the chronograph second counter 22 is a snail-shaped cam having a single spiral shape. In the following description, the zero reset member 225 of the second counter 22 is simply referred to as the spiral cam 225.

[0060] 4, which shows more precisely the seconds counter 22 and the hammer 50 in a neutral rest position, similar to FIG. 3, the spiral cam 225 defines the boundaries of a cam track 226 which extends radially in a spiral manner around the shaft 223 of the seconds counter 22, from a proximal end 227, which defines a zone of minimum radius of the cam track 226 relative to the shaft 223, to a distal end 228, which defines a zone of maximum radius of the cam track 226 relative to the shaft 223. The cam track 226 defines the outer track of the spiral cam 225 against which the hammer 50 bears to apply a driving torque to the shaft 223.

[0061] The distal end 228 and the proximal end 227 of the cam track 226 are connected by a connecting portion 230 that does not form part of the cam track 226. In the example shown, the connecting portion 230 has a generally S-shaped configuration extending radially relative to the shaft 223 of the seconds counter 22.

[0062] The connecting portion 230 has a recess 232 located near the proximal end 227. The recess 232 provides a clearance suitable for receiving a portion of the hammer 50, specifically the protruding end of the first arm 510, at the end of its stroke (zero reset position).

[0063] The connecting portion 230 may also include an additional bearing surface 231 located near the distal end 228 to extend the area intended to abut the hammer 50 when the spiral cam 225 is reset to zero.

[0064] The zero reset mechanism 40 includes a zero reset control 60 that is user operable, for example, by a push button or actuation pin 61. The zero reset control 60 is rotatable about an axis of rotation 66 and cooperates directly or indirectly with a zero reset hammer 50 which in turn acts on cams 215, 225 to reset the hands 214, 224 of the associated counters 21, 22 to zero.

[0065] 3 and 5, the zero reset control 60 cooperates with a resilient zero reset element 62 configured to reposition the zero reset control 60 to a neutral rest position (FIG. 3) during each user operation. Repositioning the zero reset control 60 under the resilient effect of the resilient element repositions the hammer 50 to the neutral position.

[0066] The zero reset mechanism 40 also includes a retention member 64 that secures the zero reset mechanism 40 and ensures full actuation of the hammer 50 to its zero reset position. The retention member 64 is configured to temporarily hold back actuation of the zero reset control 60, and thus the hammer 50, until a certain force is applied to the zero reset control 60.

[0067] The retaining member 64 is a safety member that prevents the hands 214, 224 of the chronograph mechanism 10 from being unintentionally reset to zero. The retaining member 64 has a dynamic behavior similar to that of a mechanical fuse.

[0068] 2 and 5, the retaining member 64 comprises a portion integral with the plate 2 and a resilient portion arranged to apply a retaining force against actuation of the zero reset control 60. The resilient portion is configured to deform when a force greater than the retaining force is applied to the zero reset control 60, thereby releasing the full movement of the zero reset control 60 and allowing the hammer 50 to move to its zero reset position (FIG. 5). The zero reset control 60 comprises, for example, a stud 65 designed to rest on the resilient portion of the retaining member 64.

[0069] More specifically, the stud 65 rests against a retention notch formed in the free end of the elastic portion of the retention member 64. The retention notch has a retention surface and a tilt point over which the retention member 64 allows rapid and unhindered actuation of the zero reset control 60, thereby allowing the hammer 50 to be fully actuated until it comes into contact with the zero reset cams 215, 225 of the chronograph counters 21, 22 and repositions these cams to their reference positions.

[0070] The hammer 50 comprises at its free end a first arm 510 having an inclined surface 512 forming a first bearing surface arranged for inclined bearing against the cam track 226 of the spiral cam 225 of the seconds counter 22. The first arm 510 of the hammer 50 is shown in more detail in Figures 4 and 5.

[0071] In particular, FIG. 4 shows the first arm 510 of the hammer 50 in its neutral rest position, while FIG. 6 shows the same arm 510 of the hammer 50 in its zero reset position at the end of the stroke of the hammer 50.

[0072] The first arm 510 has a stop surface 513 that forms a positioning stop that serves as a reference for the angular positioning of the spiral cam 225. The stop surface 513 stops the rotation of the spiral cam 225 when the spiral cam is reset to zero when the bearing surface 231 and / or the distal end 228 of the cam track 226 contact the stop surface 513, thereby placing the spiral cam 225 in its reference position.

[0073] The angled surface 512 of the first arm 510 together with the stop surface 513 form an end beak 514. The end beak 514 extends the angled surface 512 to form a protrusion that projects from the stop surface 513.

[0074] The first arm 510 of the hammer 50 therefore has a shape which differs from the horseshoe shape known from the prior art.

[0075] The end beak 514 ensures sufficient overlap between the inclined surface 512 of the arm 510 and the cam track 226 during the zero reset operation, especially when the spiral cam 225 is in a critical position, i.e. already at or very close to its reference position. In fact, in these specific positions, with a conventional horseshoe shaped hammer, the arm 510 may "slip" and push the spiral cam instead of rotating it in the normal zero reset direction. This phenomenon may be perceived by the user as the counter hand moving in the opposite direction instead of rotating in the normal zero reset direction (clockwise in this case).

[0076] Thus, such end beak 514 extends the contact surface of the inclined surface 512, ensuring that the spiral cam 225 operates when the zero reset control 60 of the chronograph mechanism 10 is activated and when the hammer 50 impacts the spiral cam 225, regardless of its angular position.

[0077] The recess 232 in the connecting portion 230 of the volute cam 225 receives and accommodates the end beak 514 of the first arm 510 when the volute cam 225 is in its home position and when the hammer 50 is at the end of its stroke, as shown in FIG.

[0078] When the end beak 514 is received in the recess 232 , the bearing surface 231 of the spiral cam 225 , or at least the distal end 228 of the cam track 226 , abuts against the stop surface 513 of the first arm 510 of the hammer 50 .

[0079] The hammer 50 has a second arm 520 configured to cooperate with the heart cam 215 of the minute counter 21 .

[0080] As shown in FIGS. 3 and 6, the second arm 520 has a bearing surface 521 with two inclined sides forming a V, and the bearing surface 521 is configured to cooperate with the heart cam 215 of the minute counter 21.

[0081] In this way, each inclined surface of the bearing surface 521 can cooperate with one of the two heart-shaped spirals of the heart cam 215 depending on its relative position when the zero reset control unit 60 is activated. The inclination of each inclined surface is configured to generate a driving torque to the shaft 213 integral with the chronograph minute hand 214, repositioning the heart cam 215 to its reference position in a clockwise or counterclockwise direction.

[0082] The heart cam 215 has a notch between the two spirals to receive the tip formed by the two inclined surfaces of the bearing surface 521 in order to keep the heart cam 215, and therefore the chronograph minute hand 214, in a stable position in its zero reset position, thereby avoiding the phenomenon of the hand 214 wobbling.

[0083] Resetting the chronograph mechanism 10, and in particular the hands 214, 224 of the counters 21, 22, to zero is performed as follows.

[0084] When actuated by a user, a force greater than the holding force of the retaining member 64 is applied to the zero reset control 60, the zero reset control is released, allowing the hammer 50 to move quickly and completely to its zero reset position shown in FIG.

[0085] The hammer 50 then moves from its neutral rest position shown in FIG. 3, out of contact with the zero reset members 215, 225 of the counters 21, 22, to the zero reset position shown in FIG. 5, repositioning the zero reset members 215, 225 of the counters 21, 22 to their home positions and holding them in a stable position until the zero reset control 60 is released by the user.

[0086] The hammer 50 cooperates with a guide member 140 configured to guide the hammer 50 when the zero reset control 60 is actuated and when the zero reset control 60 is released by the user, repositioning the zero reset control 60 to a neutral rest position under the action of the resilient zero reset element 62. In this manner, the guide member 140 defines and guides the forward movement of the hammer 50 along a first path and the return movement of the hammer along a second path.

[0087] In particular, the forward movement of the hammer 50 corresponds to the stroke of the hammer 50 from its neutral rest position to its zero reset position, and conversely, the return movement of the hammer 50 corresponds to the stroke of the hammer 50 from its zero reset position to its neutral rest position.

[0088] The return movement of the hammer 50 under the action of the elastic return of the elastic zero reset element 62 has a path different from the path of the forward movement. In particular, this is necessary in order to release the end beak 514 accommodated in the recess 232 in the zero reset position without changing the angular position of the spiral cam 225 during the return movement of the hammer 50. In this way, the resetting of the cam to zero is not affected.

[0089] As an example, the path of the hammer 50 during its forward movement is unidirectional and the path during its return movement is at least bidirectional.

[0090] As an example, the path of the hammer 50 during its forward movement is straight and in one direction, and the path during its return movement is straight and in at least two different directions.

[0091] As an example, the path of the hammer 50 during its forward movement may be circular, and the path during its return movement may be curved such that it has a different path than the forward movement.

[0092] To vary the stroke of the hammer 50 during forward and backward movement, the guide member 140 includes a guide yoke 142 which can be disengaged depending on whether the hammer 50 is moving forward or backward and which cooperates with a guide peg 55 which is integral with the hammer 50 .

[0093] In the illustrated example, the disengageable guide yoke 142 is configured to be disengaged, i.e., inactive, during forward movement of the hammer 50 and to redirect the unidirectional path of the hammer 50 during return movement, in particular to disengage the end beak from the recess 232 and to move the end beak 514 sufficiently away from the spiral cam 225 to avoid contact between the end beak 514 and the distal end 228 of the cam.

[0094] The disengageable guide yoke 142 is rotatable about its axis of rotation 12 in a plane parallel to the plate 2. A guide yoke spring 143 biases the guide yoke 142 to reposition it in its neutral equilibrium position against a fixed yoke stop 144, also limiting the angular play of the guide yoke 142 in a first rotational direction.

[0095] Without any special action by the hammer 50 on the guide yoke 142 , the guide yoke 142 is held in this neutral position abutting against the yoke stop 144 by the guide yoke spring 143 .

[0096] The guide yoke 142 carries a guide cam 145 which cooperates with the guide peg 55 of the hammer 50 .

[0097] The guide cam 145 has a first portion 146 configured to allow disengagement of the guide yoke 142 by moving the guide yoke 142 away from the yoke stop 144 due to the forward movement of the guide peg 55 when the zero reset control 60 is actuated.

[0098] The guide cam 145 has a second portion 147 configured to redirect the path of the hammer 50 when the zero reset control 60 is released.

[0099] 7, which shows the guide cam 145 of the disengageable guide yoke 142 in more detail, the guide cam 145 has an overall shape, for example, of a diamond, with a first portion 146 of the guide cam 145 having a first inclined surface 146a for receiving the guide peg 55 during the forward stroke of the hammer 50. When the guide peg 55 contacts the first inclined surface 146a, the inclination of the first inclined surface 146a allows the disengagement yoke to be disengaged as the hammer 50 advances by rotating the guide yoke 142 about the axis of rotation 12. Disengagement is achieved by applying a force against the guide yoke spring 143.

[0100] The first portion 146 also includes a first flat 146 b of a predetermined length that is configured to hold the disengagement yoke in this disengaged position unless the guide peg 55 passes the guide cam 145 .

[0101] The second portion 147 has a second inclined surface 147a that forms a gentle slope to receive and guide the guide peg during the return movement of the hammer 50. When the guide peg 55 comes into contact with this second inclined surface 147a while the guide yoke 142 is blocked against the yoke stop 144 during the return movement of the hammer 50, the second inclined surface 147a changes the direction of the guide peg 55 and thus the hammer 50 so that the first arm 510 can bypass the spiral cam 225. The second portion 147 also includes a second flat portion 147b of a predetermined length that is configured to hold the hammer 50 away from the spiral cam 225 unless the guide peg 55 passes the guide cam 145 during the return movement of the hammer 50.

[0102] The hammer 50 has an oblong first guide slot 51 which cooperates with a first guide pin 71 integral with the zero reset control 60. The first guide slot 51 is oriented to translate the rotational motion of the zero reset control 60 into a substantially linear motion of the hammer 50 while allowing some angular displacement between the hammer 50 and the zero reset control 60. The first guide slot 51 and the first guide pin 71 belong to a guide member 140. The first slot 51 is located at a first end of the hammer 50.

[0103] The hammer 50 features an oblong second guide slot 52 oriented substantially in the direction of travel of the hammer 50. The second guide slot 52 is located at the end of the hammer 50 opposite the zero reset control 60.

[0104] The second guide slot 52 cooperates with a second guide pin 72 which is stationary and is, for example, integral with the plate 2 .

[0105] The second guide slot 52 and the second guide pin 72 belong to the guide member 140 and form a pivot-slide connection, guiding and enabling translational movement along the oval shape of the second guide slot 52 and rotational movement of the hammer 50 around the pivot formed by the second guide pin 72.

[0106] The hammer 50 also features a third guide slot 53, the outer contour of which defines the extent of angular play of the hammer 50 between forward and backward movement. The third guide slot 53 cooperates with a third guide pin 73, which is stationary and is, for example, integral with the plate 2.

[0107] During the forward stroke of the hammer 50, the zero reset control 60 initiates a linear displacement of the hammer 50. The hammer 50 is guided in translation by both the second guide pin 72 cooperating with the second guide slot 52 and the third guide pin 73 cooperating with the third guide slot 53. A hammer spring can be used to apply a biasing force to hold the hammer 50 against the third guide pin 73 during the forward stroke, such that the third guide pin 73 is held in contact with the lower contour of the third guide slot 73 (as shown in FIG. 3 ).

[0108] Given the inclination of the first inclined surface 146a of the first portion 146 and the constraints imposed by the guide member 140, the displacement of the guide peg 55 (in this case linear) during the forward movement of the hammer 50 changes the angular position of the guide yoke 142 by changing the direction of the guide cam 145 during the straight movement of the guide peg 55. When the guide peg 55 passes the guide cam 55, the disengageable guide yoke 72 returns to its rest position under the action of the guide yoke spring 143.

[0109] During this forward movement of the hammer 50, the two arms 510, 520 collide with the zero reset members 215, 225 and, as described above, impart a driving torque to the respective shafts 213, 223. In this way, the zero reset members 215, 225 are repositioned to their reference positions.

[0110] When the user releases the zero reset yoke 60, under the action of the elastic zero reset element 62, the hammer 50 initially moves along a linear path similar to the forward stroke until the guide peg 55 contacts the second part 147 of the guide cam 145 of the disengageable guide yoke 142.

[0111] Given the inclination of the second inclined surface 147a of the guide cam 145 and the yoke stop 144 preventing rotation of the disengageable guide yoke 72, the guide peg 55, and therefore the hammer 50, is redirected by the guide cam 145 and exerts a force on the hammer spring 50.

[0112] This angular offset of the hammer 50 provided by the shape of the guide cam 145 is made possible in particular by the presence of the third guide slot 53, which gives the hammer 50 an angular degree of freedom about the pivot slide connection formed by the second guide slot 52 and the second guide pin 72.

[0113] By way of example, FIG. 3 shows the chronograph mechanism 10 according to the invention, and in particular the hammer 50, in its neutral rest position, when the zero reset control 60 has not been operated.

[0114] Figure 8 shows the chronograph mechanism 10 according to the invention in an intermediate position between the neutral rest position of the hammer 50 and the zero reset position during its forward movement. In this figure 8, it can be seen that the rotation of the zero reset control 60 has caused the hammer 50 to move linearly towards the counters 21, 22. The guide peg 55 redirects the guide yoke 142 away from the yoke stop 144. The inclined surface 512 of the first arm 510 is in contact with the cam track 226, initiating the zero reset of the spiral cam 225.

[0115] Further movement of the hammer 50 brings it to the position shown in Figure 5 above, where the arms 510, 520 impact the zero reset members and reposition the zero reset members 215, 225 to their home positions.

[0116] 9 and 10 show two intermediate positions of the chronograph mechanism 10 according to the invention, during the return movement of the hammer 50, between the zero reset position of FIG. 5 and the neutral rest position of FIG.

[0117] More specifically, Figure 9 shows the position of the hammer 50 as it is redirected by the inclination of the second inclined surface 147a of the second portion 147 of the guide cam 145. The hammer then follows a path in a first direction t1.

[0118] 10 shows the position of the hammer 50 when it is held apart by the second flat 147b of the second portion 147 of the guide cam 145. From this position, when the guide peg 55 is no longer deflected by the guide cam 145, under the action of the hammer spring (not shown), the hammer 50 returns to abut the third guide pin 73 and moves in the second direction t2 before returning to its original neutral rest position shown in FIG.

[0119] FIG. 11 specifically shows the path of the first arm 510 around the spiral cam 225 during the return stroke of the hammer 50.

[0120] The invention has been particularly described with a hammer that moves along a linear path in one direction during its forward movement and along a linear path in at least two directions during its return movement, however the invention is also applicable to hammers that are configured to cooperate with a zero reset control and a guide member, and that use disengageable guide cams to create an offset in the return movement of the first arm, allowing the hammer to have a circular, curvilinear or complex path during forward and return movements, and a path in multiple directions during the return movement.

[0121] As shown in the various figures, the chronograph mechanism 10 includes a column wheel 63 to control the various movements of various levers that rest against a column or are placed between two columns. The operation of the chronograph mechanism 10 by means of such a column wheel 63 is widely known, so there is no need to further explain how such a wheel works.

[0122] Of course, the chronograph mechanism 10 may be a chronograph mechanism having a cam instead of the column wheel 63 without departing from the scope of the present invention.

[0123] The invention also relates to a timepiece, for example a wristwatch, equipped with such a timepiece movement.

Claims

1. A chronograph mechanism (10) for a timepiece movement (1), comprising: A chronograph counter (22) having a shaft (223) and a hand (224) that rotates integrally with the shaft (223); a zero reset mechanism (40) for resetting the chronograph counter (22) to zero, the zero reset mechanism (40) comprising a zero reset member (225) integral with the shaft (223) and a hammer (50) configured to cooperate with the zero reset member (225) and to generate a driving torque under the action of a zero reset control (60) by rotation of the chronograph counter (22) in the forward direction until the zero reset member (225) is located in a reference position; Equipped with the zero reset member (225) being a spiral cam having a cam track (226) extending spirally around the shaft (223) of the chronograph counter (22) from a proximal end (227) defining a zone of minimum radius relative to the shaft (223) to a distal end (228) defining a zone of maximum radius relative to the shaft (223); The hammer (50) can be moved by the zero reset control unit (60) between a rest position where the hammer (50) does not contact the cam track (226) and a zero reset position where the hammer (50) contacts the cam track (226) to hold the zero reset member (225) at the reference position, and the hammer (50) generates a driving torque to the zero reset member (225) between the rest position and the zero reset position, A chronograph mechanism (10) for a timepiece movement (1), characterized in that the hammer (50) cooperates with a guide member (140) shaped to guide the forward movement of the hammer (50) along a first path between the rest position and the zero reset position and to guide the return movement of the hammer along a second path between the zero reset position and the rest position, the first path and the second path of the hammer (50) not coinciding.

2. 2. The chronograph mechanism (10) for a timepiece movement (1) according to claim 1, characterized in that the guide member (140) is shaped to guide the hammer (50) along a first unidirectional linear path between the rest position and the zero reset position and along a second multidirectional path having at least two different directions between the zero reset position and the rest position.

3. 2. The chronograph mechanism (10) for a timepiece movement (1) according to claim 1, characterized in that the guide member (140) is shaped to guide the hammer (50) along a first curvilinear path between the rest position and the zero reset position and along a second path different from the first path between the zero reset position and the rest position.

4. 2. The chronograph mechanism (10) for a timepiece movement (1) according to claim 1, characterized in that the guide member (140) comprises a disengageable guide yoke (142) configured to be inactive during the forward movement of the hammer (50) and to be active during the return movement of the hammer (50).

5. 5. A chronograph mechanism (10) for a timepiece movement (1) according to claim 4, characterized in that the disengageable guide yoke (142) comprises a guide cam (145) cooperating with a guide peg (55) integral with the hammer (50), the guide cam (145) comprising a first portion (146) shaped to disengage the guide yoke (142) during the forward movement of the hammer (50) and a second portion (147) shaped to guide the hammer (50) during the return movement of the hammer (50).

6. 6. The chronograph mechanism (10) for a timepiece movement (1) according to claim 5, characterized in that the disengageable guide yoke (142) cooperates with a guide yoke spring (143) biased to reposition the disengageable guide yoke (142) to a neutral equilibrium position abutting a yoke stop (144).

7. 2. The chronograph mechanism (10) for the timepiece movement (1) according to claim 1, characterized in that the hammer (50) comprises at its free end an arm (510) having an inclined surface (512) configured to contact a cam track (226) of the zero reset member (225) and generate a driving torque under the action of the zero reset control (60) until the zero reset member (225) is positioned in the reference position.

8. The chronograph mechanism (10) for a timepiece movement (1) according to claim 7, characterized in that the arm (510) has a stop surface (513) configured to form an angular positioning stop for the zero reset member (225) during a zero reset operation.

9. A chronograph mechanism (10) for a clock movement (1) according to claim 8, characterized in that the arm (510) has an end beak (514) which extends the inclined surface (512) to form a protrusion projecting from the stop surface (513).

10. 10. A chronograph mechanism (10) for a timepiece movement (1) according to claim 9, characterized in that the zero reset member (225) comprises a connecting portion (230) connecting the proximal end (227) and the distal end (228), the connecting portion (230) not belonging to the cam track (226), the connecting portion (230) comprising a recess (232) forming a gap for receiving and accommodating the end beak (514) when the hammer (50) is in the zero reset position.

11. The guide member (140) comprises a disengageable guide yoke (142) configured to be inoperative during forward movement of the hammer (50) and to be operative during return movement of the hammer (50), the disengageable guide yoke (142) comprising a guide cam (145) cooperating with a guide peg (55) integral with the hammer (50), the guide cam (145) having a first portion (146) configured to disengage the guide yoke (142) during forward movement of the hammer (50), and and a second portion (147) shaped to guide the hammer (50) during its return movement, the second portion (147) of the guide cam (145) being shaped to disengage the end beak (514) from the recess (232) and such that the end beak (514) bypasses the distal end (228) of the zero reset member (225) during the return movement of the hammer (50).

12. 2. The chronograph mechanism (10) for a timepiece movement (1) according to claim 1, characterized in that the chronograph counter (22) is a seconds counter.

13. 13. The chronograph mechanism (10) for a timepiece movement (1) according to claim 12, characterized in that the chronograph mechanism (10) comprises a minute counter (21) having a minute counter shaft (213) and a minute hand (214) rotating integrally with the minute counter shaft (213), the minute counter shaft (213) carrying a heart-shaped second zero reset member (215).

14. The chronograph mechanism (10) for the timepiece movement (1) according to claim 13, characterized in that the hammer (50) comprises a second arm (520) cooperating with the second zero reset member (215), the second arm (520) being configured to generate a driving torque under the action of the zero reset control portion (60) until the second zero reset member (215) is located in a reference position.

15. A timepiece movement (1) comprising a chronograph mechanism (10) according to claim 1.

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