CH714357B1 - Spiral cam second reset watch mechanism. - Google Patents

Abstract

The invention relates to a clock mechanism (22) for resetting the second to zero, comprising: a seconds tree; a second hand (15); a cam (23) forming a spiral cam path (24) which extends spirally around the seconds shaft from an inner end to an outer end interconnected by a radial abutment surface; a hammer (29) carrying a cam follower (30), mounted in rotation about a hammer axis (A3) between a disengaged position in which the cam follower (30) is spaced from the cam path (24), and an engaged position in which the cam follower (30) bears on the cam path (24); a non-return pawl system comprising a toothed wheel (41) and a pawl (42) which engages the toothed wheel (41).

Description

Technical area

The invention relates to the field of watchmaking. It relates, more precisely, to a horological mechanism for resetting the second to zero, as well as a watch equipped with such a mechanism.

Technological background

We can find a reset mechanism for the second: in most chronograph watches, and in certain watches fitted with a second hand (also called a seconds hand, or more simply a second hand) and whose time adjustment is accompanied by an automatic reset of the second hand.

[0003] Conventionally, such a mechanism comprises (in addition to the second hand and its seconds shaft): a cam integral in rotation with the seconds shaft and a peripheral edge of which forms a cam track; a hammer carrying a cam follower, this hammer being mounted in rotation about a hammer axis between a disengaged position in which the cam follower is moved away from the cam track, and an engaged position in which the cam follower is in pressure on the cam track to produce motor torque on the seconds shaft.

[0004] The cam usually has a heart shape, which is why it is called simply "heart", as it appears in the reference manual of C.-A. Reymondin et al, “Theory of horology”, Federation of Technical Schools, 2015 edition, p.238.

In chronographs, the hammer is a complex part provided with several cam followers which simultaneously strike several respective cams, integral with the hour hand, the minute hand, the seconds hand (and , more occasionally, with a tenths needle).

In watches with automatic reset of the second hand, such as that described in European patent EP2224294 (Glasshütte), the hammer is simpler in shape but the principle is the same.

In all cases, the cam follower is usually formed by one end of the hammer in the form of a horse shoe, which comes, at the end of the stroke (angular or linear), to be applied against a double boss formed on the heart to keep it in a stable position corresponding to resetting the second hand.

This type of mechanism, very widely used, however suffers from several drawbacks.

[0009] First, the position of the second hand when resetting to zero is most often quite random and lacks precision. This is particularly detrimental in the case of a jumping needle, which is assumed to be at each second in a very precise angular position (each angular position being spaced from the next by 6 °).

Second, given the respective geometry of the core and of the hammer, the friction forces at their interface are not constant. This results in non-uniform wear of these parts, which is detrimental in the long term to the reliability of the mechanism.

Third, in certain angular positions of the heart, the hammer rubs against it by a sharp edge, as illustrated in FIG.11.29 of the aforementioned manual, which increases the stress concentration, wear and mechanical fatigue of these rooms.

Fourth, the momentum acquired by the heart during its rotation means that it is not immediately blocked at the end of the stroke by the support of the end of the hammer in the seconds tree, but remains, before coming to a stop, animated by damped oscillations which harm the perception of precision expected by an informed user.

Fifth, the complexity of the known mechanisms makes them heavy and tedious to manufacture.

A first objective is to provide a second reset mechanism which provides a precise position of the second hand, exactly opposite a predetermined graduation of the dial (typically a twelve hour index).

A second objective having greater reliability, and therefore greater longevity.

A third objective is to provide a mechanism for resetting the second of simpler architecture (and therefore less bulky, lighter and easier to manufacture) than the known mechanisms.

Summary of the invention

To achieve all or part of the aforementioned objectives, it is proposed, first of all, a clock mechanism for resetting the second to zero, which comprises: a seconds tree; a second hand rotationally integral with the seconds shaft; a cam integral in rotation with the seconds shaft and a peripheral edge of which forms a cam track; a hammer provided with a cam follower, this hammer being mounted in rotation about a hammer axis between a disengaged position in which the cam follower is moved away from the cam track, and an engaged position in which the cam follower is resting on the cam track to produce a driving torque on the seconds shaft; this mechanism being remarkable: in that the cam is in the form of a spiral, the cam track extending spirally around the seconds shaft from an inner end to an outer end connected to each other by a stop surface which s 'extends substantially radially with respect to the seconds shaft and against which the cam follower abuts in an angular end-of-travel position of the second hand; in that it comprises a non-return pawl system comprising a toothed wheel mounted on the seconds shaft, and a pawl carried by the cam and which attacks the toothed wheel.

Thanks to this architecture, the mechanism remains effective while being quite simple, light and not bulky. When resetting, the seconds hand can find a precise position next to a graduation.

Various additional characteristics can be provided, alone or in combination. So, for example: the mechanism may include a hammer spring provided with a fixed head and an elastic blade which urges the hammer towards its engaged position. the hammer can carry a projecting primary pin, against which the leaf of the spring is in permanent abutment. the mechanism may include an actuator mounted to move between a retaining position in which it places the hammer in its disengaged position, and a release position in which it allows the hammer to occupy its engaged position. the hammer can carry a projecting secondary pin, against which a shoulder formed on the actuator bears in the retaining position thereof. the mechanism may include a non-return pawl system which only allows rotation of the cam in one direction. the ratchet system may include a toothed wheel mounted coaxially with the seconds shaft, and a pawl carried by the cam and which engages the toothed wheel. the hammer axis can be provided with an eccentric whose rotation causes the hammer to debate by adjusting the angular end-of-travel position of the second hand.

Secondly, a watch equipped with such a mechanism is proposed.

According to a preferred embodiment, the watch can be equipped with a dial provided with a graduation including a twelve hour index with which the hand is substantially aligned when it is in the angular end-of-travel position.

Brief description of the figures

Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given below with reference to the accompanying drawings in which: FIG. 1 is a plan view of a watch equipped with a second reset mechanism; FIG. 2 is a detailed perspective view of the second reset mechanism; FIG. 3 is a detailed sectional view of the reset mechanism, according to the section plane III-III of FIG. 1; FIG. 4, FIG. 5, FIG. 6, FIG. 7 and FIG. 8 are detailed plan views, on a larger scale, of the second reset mechanism and illustrating various phases of its operation.

Detailed description of the invention

In FIG.1 is shown a watch 1. This watch 1 comprises a middle part 2, which can be made of metal (eg steel), or a synthetic material (eg in a composite material comprising a polymer matrix loaded with fibers, typically carbon).

The watch 1 may include, for wearing on the wrist, a bracelet 3 (in phantom in FIG.1) which is fixed on the middle part 2 between the lugs 4 formed projecting thereon.

In the example illustrated, the caseband 2 has a circular outline, but this shape is not limiting. In particular, this contour could be rectangular (eg square).

The caseband 2 defines an interior space 5. The watch 1 comprises, to close this interior space 5, a crystal and a back (not shown), fixed on either side of the middle part 2.

The watch 1 is equipped with a dial 6 provided with a graduation 7. According to an embodiment illustrated in the drawings, and more particularly in FIG.1, the graduation 7 comprises indexes 8 for each hour and 9 intermediate indexes for each minute. The intermediate minute markers 9 are preferably smaller than the hour markers 8.

In the example illustrated, the indexes 8 of the hours are not figurative. However, alternatively, the hour markers 8 could be figurative, and be in the form of numerals (eg Roman, Arabic, Gothic, Greek). Be that as it may, the graduation includes an index 10 of the twelve hours, indicating midnight and noon for the hours, and indicating the zero of the minutes and seconds.

The watch 1 comprises a timepiece movement (hereinafter simply referred to as "movement"), which comprises a plate intended to be housed in the middle part 2 by being fixed thereto, eg. by means of screws. The plate forms a support for various mechanisms such as gear train, escapement, transmission, timer, winder (non-exhaustive list).

The movement comprises a mobile timer 11, which includes an hour wheel and a minute wheel (not shown) as well as a second wheel 12. The timer mobile 11 is rotatably mounted about an axis A1.

The timer mobile 11 is rotated by a motor device (not shown). It is preferable that the power source is a barrel spring associated with a spiral balance regulator. However, it would not be outside the scope of the present invention for the energy source to be a battery associated with a quartz regulator.

The watch 1 comprises an hour hand and a minute hand (not shown), respectively for the display of hours and minutes.

The watch is equipped with a time reset mechanism 13, which includes a winder coupled to the hour and minute hands. This winder comprises in particular a crown 14 accessible to the wearer on one side of the caseband 2. The crown 14 is movable between: a retracted position, illustrated in solid lines in FIG. 1 and in which the crown 14 is uncoupled from the hour and minute hands, which remain driven in rotation by the timer mobile 11, and an extended position, illustrated in dotted lines in FIG. 1 and in which the crown 14 is coupled to the hands to allow the time to be reset.

As illustrated, the watch 1 further comprises a seconds hand 15 (also called the "second hand" or more simply "second hand"), coupled to the second wheel 12.

The seconds hand 12 is rotated by the timer mobile 11, around an axis A2 about which it performs a complete revolution in one minute. In the example illustrated, the seconds hand 15 is a large central second hand, its axis A2 of rotation coinciding with the central axis of dial 6.

The seconds hand 15 has a distal end 16 which runs, during the rotation of the hand 15, the dial 6 passing successively to the right of each index 8, 9 of the graduation 7.

The seconds hand 15 is mounted (by being driven, for example) on a seconds shaft 17 which extends along the axis A2. As seen in FIG. 3, the seconds shaft 17 comprises an upper section 18, on which the seconds hand 15 is mounted, and a lower section 19.

On the shaft 17 of the seconds is mounted a pinion 20 which meshes the wheel 12 of the seconds. More precisely, as illustrated in FIG. 3, the pinion 20 is mounted on the lower section 19 of the shaft 17 of the seconds.

As seen in FIG.3, and more particularly in the detail inset at the bottom left, the lower section 19 of the shaft 17 of the seconds is provided with one or more bead (s) 21 of larger diameter, on which (which) the pinion 20 is fitted. This results in a reduction in the interface between the seconds shaft 17 and the pinion 20.

In this way, the shaft 17 of the seconds and the pinion 20 are integral in rotation as the shaft 17 of the seconds is not subjected to any driving torque (or resistance) applied independently of the pinion 20.

Therefore, on the other hand, an engine torque (or resistance) exceeding a predetermined threshold is applied to the shaft 17 of the seconds independently of the pinion 20, the shaft 17 of the seconds can rotate freely relative to the pinion 20 , which remains fixed because it engages the timer mobile 11. In this case, a slip occurs at the interface between the seconds shaft 17 and the pinion 20.

Watch 1 is equipped with a clock mechanism 22 for resetting the second to zero. By this mechanism 22, the second hand 15 is separated from the timer mobile 11 and reset to the right of the index 10 of the twelve hours (that is to say to zero) when a time reset is initiated by the wearer, in particular by pulling on the crown 14.

In addition to the seconds shaft 17 and the seconds hand 15 already mentioned, the second reset mechanism 22 comprises a cam 23 integral in rotation with the seconds shaft 17 and of which a peripheral edge forms a cam track 24.

According to a preferred embodiment illustrated in the drawings, and in particular in FIG.3, the cam 23 is an insert mounted tightly (typically by driving) on the shaft 17 of the seconds.

In the example illustrated in FIG.3, the cam 23 is fitted on the upper section 18 of the shaft 17 of the seconds. Its height position is fixed by a flange 25 formed on the second shaft 17 at the junction between the upper section 18 and the lower section 19, and against which the cam 23 is wedged.

As can be seen clearly in FIG.4 to FIG.8, the cam 23 is in the form of a spiral: the cam path 24 extends in a spiral around the axis A2 (it is that is to say around the shaft 17 of the seconds) from an internal end 26 (close to the axis A2), to an external end 27 (remote from the axis A2). The cam path 24 is smooth, without roughness.

The inner end 26 and the outer end 27 are interconnected by a stop surface 28 which extends substantially radially with respect to the seconds shaft. When seen from the front (that is to say along the axis A2), the contour of the cam 23 is thus similar to the contour of the shell of a marine cephalopod of the nautilus species.

The cam 23 is advantageously a metal part, eg. in steel. It is preferably perforated, in order to be light and to have a low moment of inertia.

The second reset mechanism 22 further comprises a hammer 29 provided with a cam follower 30. This hammer 29 is rotatably mounted around a hammer axis A3 between: a disengaged position (FIG.4, FIG.8) in which the cam follower 30 is moved away from the cam track, and an engaged position (FIG.5, FIG.6, FIG.7) in which the cam follower 30 bears on the cam path 24 to produce a driving torque on the second shaft 17.

The cam follower 30 is for example. in the form of a lug which projects at a free end 31 of the hammer, at a distance from the axis A3 of the hammer. The cam follower 30 is advantageously made of a material with a low coefficient of friction, e.g. in a plastic material (in particular in polytetrafluoroethylene, also known under the names PTFE and Teflon®), or in a precious stone (in particular in ruby). The cam follower 30 is advantageously fixed rigidly (in a non-removable manner) on the hammer 29. Alternatively, the hammer 29 and the cam follower 30 can form a one-piece element, formed from a single machined part.

In normal operation of the watch 1, the hammer 29 is in its disengaged position. In this case, the seconds hand 15 is integral, with the seconds shaft 17, of the pinion 20 which the seconds wheel 12 engages.

When a time reset is initiated by the user, typically by pulling on the crown 14, the hammer 29 is moved to its engaged position to drive in rotation, via the cam follower 30 resting on the cam track 24, the seconds shaft 17 (and with it the 15 seconds hand) - independently of the pinion 20 - until the 15 seconds hand is brought into an angular end-of-travel position where it rests. found substantially to the right of the index 10 of the twelve hours (reset).

The angular end-of-travel position of the second hand 15 (zero position) is determined by the abutment of the cam follower 30 against the abutment surface 28. In this position, illustrated in FIG. 7 (and more particularly in the detail inset at the bottom middle), the rotation of the cam 23 (and therefore of the shaft 17 of the seconds and of the hand 15 of the seconds) is stopped.

The support of the cam follower 30 on the cam path 24 is provided by a lever effect exerted on the hammer 29, which tends to cause it to pivot (here in the clockwise direction) around the axis A3 of hammer.

For this purpose, the mechanism 22 comprises a hammer spring 32. This hammer spring 32 is provided with a fixed head 33 and an elastic blade 34 which urges the hammer 29 towards its engaged position.

According to one embodiment, the hammer 29 carries a protruding primary pin 35, against which the leaf 34 of the spring is in permanent abutment. The leverage exerted on hammer 29 by resilient blade 34 of hammer spring 32 via primary pin 35 is illustrated by the black arrow at the top in FIG. 5.

The induced rotation of the hammer 29 is indicated by the black arrow in the middle of FIG.5. This rotation brings the cam follower 30 into contact with the cam track 24. Since the cam track 24 is smooth, and the cam follower 30 has a low coefficient of friction, the latter can slide freely on the cam track 24.

The leverage applied by the hammer spring 32 on the hammer 29 continuing, the cam follower 30 slides on the cam surface 24 by exerting on it (and therefore on the cam 23) a non-concurrent force with the seconds axis A3, from which there results a motor torque induced on the cam 23 (and therefore on the seconds shaft 17).

The cam 23, the hammer 29 and the hammer spring 32 are configured so that, whatever the angular position of the cam 23, the torque induced thereon by the cam follower 30 is always greater than the threshold Beyond which a slip occurs at the interface between the seconds shaft 17 and the pinion 20.

As a result, the seconds shaft 17, and with it the seconds hand 15, is driven in rotation about the axis A2, as illustrated by the black arrow at the bottom right in FIG.5 , the cam follower 30 sliding on the cam surface 24 until it reaches the stop surface 28, which stops the rotation of the cam 23 (and therefore the seconds hand 15).

According to an embodiment illustrated in the drawings, the second reset mechanism 22 comprises an actuator 36 mounted movably between: a retaining position in which the actuator 36 places the hammer 29 in its disengaged position (FIG.4, FIG.8), and a release position in which the actuator 36 allows the hammer 29 to occupy its engaged position (FIG.5, FIG.6, FIG.7).

In the example illustrated, the actuator 36 is in the form of a rod mounted in translation (but it could be mounted in rotation).

The hammer 29 for its part carries a projecting secondary pin 37, against which a shoulder 38 formed on the actuator 36 bears in the retaining position thereof. This shoulder 38 is eg. defined by a claw 39 protruding from one end of the actuator 36.

The movement of the actuator 36 is controlled by the winder, and more precisely by the crown 14. Thus, in the retracted position of the crown 14, the latter places the actuator 36 in the retaining position, which maintains the hammer 29 in the disengaged position and allows the rotation of the seconds shaft 17 (and with it of the seconds hand 15) induced by the timer mobile 11.

On the other hand, in the extended position of the crown 14, the latter places the actuator 36 in the release position (horizontal black arrow, top left in FIG.5), which allows the hammer spring 32 to exert its leverage on the hammer 29 to apply the cam follower 30 on the cam track 24.

According to a preferred embodiment illustrated in particular in FIG. 4, and more particularly in the detail inset at the bottom left, the mechanism 22 for resetting the second to zero comprises a system 40 with a non-return pawl which only allows rotation of cam 23 in one direction (clockwise in the example shown).

The ratchet system 40 comprises a toothed wheel 41 mounted coaxially with the seconds shaft 17, and a pawl 42 carried by the cam 23 and which attacks the toothed wheel 41.

More specifically, the toothed wheel 41 is integral in rotation with the pinion 20, if necessary (as illustrated in FIG.2) via a doll 43 driven on the pinion 20. According to one embodiment, the doll 43 is integrated into a transmission wheel 44 meshing eg. a ringing mobile (not shown).

According to a preferred embodiment, the toothed wheel 41 is of Breguet type toothing, that is to say that the teeth are triangular and asymmetrical. In the example illustrated, the toothed wheel 41 comprises sixty teeth, which each index, via the pawl 42, a determined position of the seconds hand 15 (which is then called "jumping") corresponding to each of the sixty seconds contained in one minute. In other words, the positions of the second hand are separated from each other by an angle of 6 °.

In the example illustrated in FIG.4, the pawl 42 is biased towards the toothed wheel 41 by means of a leaf 45 also spring carried by the cam 23.

The operation of the second reset mechanism 22 is as follows.

In the retracted position of the crown 14, the latter maintains the actuator 36 in the retaining position, which maintains the hammer 29 (and the cam follower 30) in the disengaged position, away from the cam 23 .

The seconds shaft 17 (and with it the seconds hand 15) is integral in rotation with the pinion 20, which, meshed by the timer mobile 11, drives it in rotation around the axis A2. Under these conditions, the seconds hand 15 plays its role as a second hand and provides the wearer with an indication of the seconds elapsed in the current minute.

In the extended position of the crown 14, the latter places the actuator 36 in the release position, which allows the hammer 29 to move, under the leverage provided by the hammer spring 32, towards its engaged position, in which the cam follower 30 is slidingly bearing against the cam path 24.

The sliding support of the cam follower 30 against the cam track 24 induces, as explained above, the rotation of the cam 23, and with it the shaft 17 of the seconds (which slides at its interface with the pinion 20, which remains fixed in rotation around the axis A2 while remaining meshed by the timing wheel 11).

The rotation of the cam 23 (clockwise) and of the second hand 15, which is integral with it, continues until the cam follower 30 comes to rest against the surface 28 of stop, which stops the rotation of the cam 23 (and therefore of the shaft 17 of the seconds and of the hand 15 of the seconds). The seconds hand 15 is then in its end-of-travel position, and is located substantially to the right of the index 10 of the twelve hours on the graduation 7 of the dial 6. The pawl 42 is positioned between two successive teeth of the toothed wheel 41, and thus blocks any rebound of the needle when it reaches the end of its travel, for the benefit of the precision of the reset.

It may be that the second hand 15, at the end of the stroke, is not exactly in line with the index 10 of the twelve hours.

To allow fine adjustment of the end position of the 15 seconds hand, and to ensure that in this position the 15 seconds hand is located exactly to the right of the twelve hour index, the hammer axis A3 is defined by a shaft 46 provided with an eccentric 47.

The rotation of the eccentric 47 causes the hammer 29 to debate by adjusting the angular end position of the second hand 15 (as suggested by the various positions sketched in dotted lines in FIG.8).

The rotation of the eccentric 47 is eg. performed by manual action, typically by means of a screwdriver. To this end, as illustrated in particular in FIG. 7, one end of the eccentric 47 is shaped as a recess 48 (eg a slot) for a screwdriver. There is illustrated, in the detail inset at the bottom left in FIG. 7, the rotation of the eccentric (double black arrow), and its effect (in dotted lines) on the positioning of the hammer 29.

Once the crown 14 is returned to its retracted position, the actuator 37 is returned to its retaining position (FIG.8). The movement of the actuator 37 exerts a traction on the secondary pin 37 and drives the hammer 29 in rotation against the return force of the spring 32. The rotation of the hammer causes the cam follower 30 to slide along. the abutment surface 28, then release the cam follower 30 from the cam 23. Consequently, no motor or resistive torque is no longer applied to the second shaft 17, including the frictional forces at the interface between the (S) bead (s) 21 and the pinion 20 re-couples it in rotation to the latter.

It follows that the rotation of the pinion 20, meshed by the mobile 11 of the timer (and more precisely by the wheel 12 of the seconds) rotates the shaft 17 of the seconds, and with it the hand 15 of the seconds in ordinary cyclical motion.

The mechanism 22 for resetting the seconds to zero which has just been described has the following advantages.

First, in comparison with known core mechanisms, the present mechanism 22 is of simpler architecture. Hammer 29, in particular, is less complex in shape. The absence of a heel, and the presence of the cam follower 30 which, at the end of the stroke, simply abuts against the stop surface 28, prevents rebounds of the second hand 15, to the benefit of the reliability of the mechanism 22 .

As already mentioned, rebounds are also prevented by the ratchet system 40, which ensures the unidirectional nature of the rotation of the second hand 15 when it is reset to zero.

Being simpler, this mechanism 22 is light, compact, and easy to manufacture.

This results in particular greater reliability, and therefore greater longevity of the mechanism 22 (and therefore of the watch 1).

Claims (10)

1. Clock mechanism (22) for resetting the second to zero, comprising: - a seconds tree (17); - a second hand (15) integral in rotation with the seconds shaft (17); - A cam (23) integral in rotation with the seconds shaft (17) and a peripheral edge of which forms a cam path (24); - a hammer (29) provided with a cam follower (30), this hammer (29) being mounted in rotation about a hammer axis (A3) between a disengaged position in which the cam follower (30) is moved away from the cam path (24), and an engaged position in which the cam follower (30) bears on the cam path (24) to produce a driving torque on the seconds shaft (17); this mechanism (22) being characterized: - in that the cam (23) is in the form of a spiral, the cam path (24) extending spirally around the shaft (17) of the seconds from an end (26) internal to an outer end (27) interconnected by a stop surface (28) which extends substantially radially with respect to the seconds shaft (17) and against which the cam follower (30) abuts in an angular position end of travel for resetting the second hand (15) to zero; - in that it comprises a non-return pawl system comprising a toothed wheel (41) mounted on the seconds shaft (17), and a pawl (42) carried by the cam and which attacks the wheel (41) toothed. 2. Mechanism (22) according to claim 1, characterized in that it comprises a hammer spring (32) provided with a fixed head (33) and a resilient blade (34) which urges the hammer (29). towards its engaged position. 3. Mechanism (22) according to claim 2, characterized in that the hammer (29) carries a protruding primary pin (35), against which the leaf (34) of the spring is in permanent abutment. 4. Mechanism (22) according to claim 2 or 3, characterized in that it comprises an actuator (36) movably mounted between a retaining position in which it places the hammer (29) in its disengaged position, and a position of release in which it allows the hammer (29) to occupy its engaged position. 5. Mechanism (22) according to claim 4, characterized in that the hammer (29) carries a projecting secondary pin (37), against which a shoulder (38) formed on the actuator (36) bears in position. retention of it. 6. Mechanism (22) according to one of the preceding claims, characterized in that the toothed wheel (41) comprises a Breguet type toothing. 7. Mechanism (22) according to claim 6, characterized in that the toothed wheel (41) comprises sixty teeth. 8. Mechanism (22) according to one of the preceding claims, characterized in that the axis (A3) of the hammer is formed by a shaft (46) provided with an eccentric (47) whose rotation makes the hammer debate ( 29) by adjusting the angular end position of the second hand needle (15). 9. Watch (1) equipped with a clock mechanism (22) for resetting the second to zero according to one of claims 1 to 8. 10. Watch (1) according to claim 9, equipped with a dial (6) provided with a graduation (7) including a twelve hour index (10) with which the second hand (15) is substantially aligned when 'it is in the angular position of the reset limit switch.