HK1216119B - Timepiece movement provided with a drive mechanism for the periodic or intermittent movement of an analogue indicator - Google Patents

Description

Timepiece movement provided with a drive mechanism for the periodic or intermittent movement of an analog indicator

Technical Field

The invention concerns the field of timepiece movements comprising an analogue display of information whose value varies periodically or intermittently between predetermined discrete values, in particular calendar information and/or a function/application selected from a plurality of possible functions/applications. "value" generally refers to a number, calendar information (such as a date, a week, or a month), and one function or application also selected from a plurality of functions or applications, although this list is not exhaustive. The invention relates in particular to a drive mechanism for simulating periodic or intermittent movements of a pointer, and to an impact-resistant mechanism for such a pointer, in addition to the precise positioning of the pointer at each of a plurality of said discrete display positions.

Background

There are three main known mechanisms for driving a calendar indicator, in particular a date ring: continuous mechanisms, traditional semi-instantaneous mechanisms, and instantaneous mechanisms.

In the conventional variant shown in fig. 1, the continuous mechanism 2 is arranged to drive a date ring 4 provided with an internal gear ring 6. The sequential mechanism comprises a maltese cross 8 and a wheel set 12 for actuating it. The maltese cross comprises six branches 9 and is integral with a coaxial pinion 10 which meshes with the toothing 6 of the date ring. The pinion 10 has six teeth. The number of branches of the maltese cross and the number of teeth of the pinion are given here only by way of non-limiting example. There is therefore also a known mechanism of the above-mentioned type with a maltese cross with four branches and a pinion with eight teeth. Preferably, the ratio between the number of teeth and the number of branches is an integer. The actuating wheel set 12 comprises two driving pins 16, 17 and a locking member 14 which cooperates with the branch 9 to lock the maltese cross in a stable position between two successive driving operations performed respectively by the two pins. The actuating wheel set is driven in rotation, for example by a pinion 20. Since the operation of the maltese cross system is well known, it will not be described in more detail here.

The continuous drive mechanism described above is characterized by gears with little or no play and by having no jumper springs. The driving function and the function of positioning the date ring in its display position are therefore both carried out by a pinion cooperating with the maltese cross. Furthermore, since the locking member 14 easily ensures the impact resistance function, which is achieved by the maltese cross system. Timepiece movements with a mechanism of the type described above are expensive to manufacture, since machining and assembly tolerances (manufacturing tolerances) of the mechanism and of the date ring must be minimized to ensure accurate positioning of the annular member at the display position, for example accurate centering of the respective date in a hole provided for the dial of the timepiece movement.

Conventional semi-instantaneous drive mechanisms comprise a drive wheel for a date ring, usually provided with one finger or two fingers, which are periodically inserted into the toothing of the date ring to drive it from one display position to the next. The spaces between the teeth of the ring gear are generally made wide to allow, in particular, the fingers to enter and leave the date ring without the risk of locking; in particular due to manufacturing and centering tolerances of the date ring. Therefore, it is clear that the drive wheel cannot ensure the function of positioning the date ring. Furthermore, the shock-resistant function cannot be ensured, since there is usually no meshing between the ring gear and the respective one of the two fingers within a certain angular range of the drive wheel.

In order to ensure the positioning function and the shock-resistant function, a jumper spring, also called "jumper spring", is provided, which is inserted between two successive teeth of the toothing of the date ring. This is called a semi-instantaneous system, since in the first phase of the change to the next date, the date ring is driven in rotation by the fingers of the drive wheel and the tip of the tooth located downstream of the jumper spring lifts the jumper spring until it rests against the tip of the tooth. Next, the jumper spring exerts a tangential force on the rear flank of the associated tooth and then acquires its next rest position. In a second phase, the jumper rapidly drives the date ring into the next display position, the finger of the drive wheel continuing to rotate at a lower speed than the date ring and thus stopping to apply a torque to the date ring. The space between the teeth is arranged to be large enough so that the successive teeth pushed by the fingers do not abut against the fingers inserted in the ring gear of the date ring. The main drawback of this semi-instantaneous mechanism stems from the fact that: the anti-shock function is achieved by a jumper spring which must therefore be pressed with great force against the date ring in order to exert a sufficiently large locking moment in the event of an impact. Thus, at each change of date, the drive mechanism must provide a large drive torque to overcome the detent torque of the jumper spring; this requires a large amount of energy and a mechanism capable of providing such a drive torque at the date ring gear.

There are several embodiments of the instant drive mechanism. In all cases, a positioning jumper spring is provided which also ensures the shock-resistant function. This mechanism therefore has the same disadvantages as the semi-instantaneous mechanism described above.

Disclosure of Invention

It is an object of the present invention to overcome the problems and disadvantages of the prior art drive mechanisms for the periodic or intermittent movement of an analogue indicator, in particular a date ring.

To this end, the invention relates to a timepiece movement provided with an analog display device for displaying information, the value of which varies periodically or intermittently, the analog display device comprising, on the one hand, an indicator of said information provided with a first toothing, and, on the other hand, a drive mechanism for driving the indicator periodically or intermittently. The drive mechanism is formed by an irreversible transmission system comprising a second toothed ring meshing with the first toothed ring. The display device further comprises an indicator positioning jumper spring which generates a positioning force on the first toothed ring which is sufficient to accurately position the indicator at a plurality of discrete display positions, but insufficient to ensure an impact-resistant function for the indicator. Furthermore, the tangential play between the first and second gear rings is arranged to be sufficiently large such that the first gear ring and the second gear ring do not contact each other when the indicator is in any of the plurality of discrete display positions and the irreversible transmission is in the respective predetermined position. The irreversible transmission system ensures an anti-shock function for the indicator by means of the engagement of the first toothing and the second toothing, at least when the indicator is in any one of a plurality of discrete display positions and the irreversible transmission system is in said respective predetermined position.

"periodic driving" refers to driving that is performed only periodically, that is, driving is performed periodically for a limited time interval and no driving occurs between the limited time intervals. Likewise, "intermittent drive" refers to discontinuous drive that stops and starts according to instructions of the intermittent drive mechanism without having to cause the drive to occur at regular time intervals.

Thanks to the features of the timepiece movement according to the invention, the problems of the continuous mechanism of the maltese cross with drive and positioning of the indicator described above, as well as the problems of the traditional semi-instantaneous or instantaneous mechanism in which the jumper spring ensures the positioning and shock-resistance functions of the indicator, are solved. In a particular embodiment of the invention, the drive mechanism defines a mechanism similar to a semi-instantaneous mechanism having one or more fingers for driving the indicator integral with the maltese cross, said one or more fingers forming the above-mentioned second toothing. In fact, the positioning jumper spring is also commonly used to actuate the pointer in the second phase of changing the pointer from one display position to the next.

According to the invention, the driving function of the indicator and the anti-shock function at least in the first phase of changing the indicator from one display position to the next are ensured by an irreversible transmission system which is capable of exerting a very high locking force. However, the detent function cannot be ensured by this irreversible transmission system as in the prior art, but rather a force sufficient for this function but much less than the prescribed minimum force for locking the indicator in the event of an impact is exerted by the detent jumper.

Thus, on the one hand, the indicator can be driven from one display position to another with a much lower driving torque than prior art embodiments with conventional semi-instantaneous or instantaneous mechanisms in which the jumper spring must be able to exert a large tangential force on the indicator ring gear in the event of an impact. On the other hand, the tolerance and assembly problems of prior art embodiments with a continuous mechanism but without a jumper spring are eliminated.

Other specific features of the invention will be described in the following detailed description of the invention.

Drawings

The invention will be described below with reference to the attached drawings, given by way of non-limiting example, in which:

fig. 1 is a top view of a prior art continuous drive mechanism with a maltese cross system as already described.

Figure 2A is a schematic top view of a first embodiment of a timepiece movement according to the invention.

Fig. 2B is a partial enlarged view of the view of fig. 2A, showing the engagement between the date ring and the maltese cross system of the first embodiment.

Figures 3A and 3B show a partial view and respective perspective and top views of a second embodiment of a timepiece movement according to the invention.

Detailed Description

With reference to fig. 2A and 2B, a first embodiment of a timepiece movement according to the invention will be described below. Timepiece movement 24 is provided with an analogue display device for analogue display of the date, which periodically varies the information and has a plurality of functions F1, F2, etc., which can be selected by the user of a watch provided with such a timepiece movement. The analogue display device comprises an annular member 26 provided with a first gear ring 28 and a drive mechanism 30. A plurality of dates "1" to "31" and names of a plurality of possible functions are printed on the ring member 26. Each date and each function defines a discrete display position of the annular member 26 by means of an aperture provided in the dial mounted on the timepiece movement 24. The driving action is periodic with respect to date and intermittent with respect to selecting a function from a plurality of possible functions.

The drive mechanism 30 is formed by a maltese cross system, which defines an irreversible transmission system. The system includes a drive wheel 32 having a maltese cross 34 surmounted by a pinion 36 having a second ring gear 38 meshing with the first ring gear 28. To periodically or intermittently actuate the drive wheel, the drive mechanism further comprises an actuation wheel 40 driven by a pinion 46, the pinion 46 itself being driven in rotation by an electromagnetic motor (not shown). The actuator wheel comprises two pins 41 and 42 aligned on the diameter of the actuator wheel and a lock 44 centrally located on the (actuator wheel) axis of rotation. The pin is arranged to be inserted between the branches of the maltese cross and allows driving the wheel 32 and thus the independent date ring.

The maltese cross system thus defines an irreversible transmission system, since the actuation wheel can drive the drive wheel in rotation, but not in reverse. The torque transmitted by the drive wheel to the actuator wheel will cause the actuator wheel to rotate at most within a small angular distance, regardless of the angular position of the actuator wheel. This is also referred to as a self-locking drive mechanism, since it prevents the transmission of torque and thus rotation in the direction opposite to the desired direction by design. In the discrete display positions, the locking member 44 is preferably disposed in substantial alignment over the end of one of the legs of the maltese cross (as shown in fig. 2A and 2B), thereby preventing any rotation of the maltese cross (beyond manufacturing tolerances). Thus, at least when the ring 26 is in any one of its plurality of discrete display positions and the maltese cross system is in the respective position defined above, the torque exerted by the ring on the pinion gear 36 will not drive the wheel 40 to rotate.

According to the invention, there is a tangential play between the first ring gear 28 and the second ring gear 38, which is substantially equal to J1+ J2, as shown in fig. 2B. This tangential play is made sufficiently large that the first and second gear rings do not contact each other when the ring 26 is in any of the aforementioned plurality of discrete display positions and the maltese cross is in the respective predetermined position as shown preferably in fig. 2A and 2B. The first and second ring gears are always in mesh regardless of the angular position of the pinion gear 36. Thus, accidental jumping of the independent date ring during impact is by no means possible. In fact, even if the annulus is subjected to an acceleration due to impact when driven by the pinion 36, the tooth 48 will always be in the space 50 provided between two adjacent teeth 51 and 52 of the ring gear 28 once the drive is completed and the maltese cross system returns to the non-driving position defined among the plurality of discrete display positions. Thus, at least when the maltese cross system is in the predetermined non-driving position, the pinion remains stationary if a significant torque is exerted on the pinion 36 by the ring 26. The ring may thus only move in the aforementioned tangential play when it is in any of a number of discrete display positions. The maltese cross system thus ensures an impact-resistant function for the ring 26 by means of the meshing of the first and second ring gears. The "impact resistance function" is not meant to prevent the mechanism from breaking or being damaged during an impact, but to prevent the indicator from changing discrete display positions in a permanent manner under the effect of the impact, which the watch can be subjected to without breaking (according to NIHS 91-10, 91-20, 91-30 and other standards).

In order to accurately position the individual date ring, the display device also comprises a positioning jumper spring 56 for the date ring. The jumper spring (also referred to as a jumper spring) is formed by an arm 58 having a detent tooth 60 at a first end and pivoting about an axis at the other end, and a resilient member 62 that applies a force to the arm to generate a detent force on the first ring gear 28. When the ring moves away from the display position and the jumper leaves the corresponding stable or rest position, the positioning force has a tangential component acting on the ring toothing in order to return the ring to the display position in the absence of a change in discrete display position or in order to move the ring to another predetermined display position during the actuation of the drive of the ring at the end stage. The resilient member 62 is, for example, a curved resilient pin or strip, one portion of which is in the groove 64 and another portion of which rests against the rear side of the arm 58. According to the invention, the positioning force is sufficient to position the ring 26 precisely at the plurality of discrete display positions but insufficient to ensure the shock-resistant function of the ring. The setting force is thus set to be less than the prescribed minimum force for locking the ring during an impact, in order to be able to minimize the energy required for the ring to be driven in rotation and thus change from one display position to another with a lower torque. In a preferred variant, the positioning force is greater than the maximum friction exerted by the timepiece movement on the ring 26 on the one hand and less than three times this maximum friction on the other hand.

By way of non-limiting example, it was observed that a conventional date ring made of brass, having a diameter of 20mm, requires a torque of about 60 μ Nm to overcome the static friction on the ring when the movement is laid flat. To ensure the anti-shock function by means of the jumper spring, as was the case in the previously mentioned prior art movements, the jumper spring must be able to exert a locking torque of about 2000 μ Nm in this example. For an aluminum or plastic ring, the moment of impact resistance will be less than, for example, about 800 μ Nm at lower weights. However, thanks to the invention, in the case of steel annular elements, the elastic element 62 can be dimensioned in a variant such that the jumper spring 56 exerts a moment of 120 to 180 μ Nm. With an aluminum or plastic ring, the torque applied by jumper spring 56 will be, for example, between 80 μ Nm and 120 μ Nm. It has thus been found that the present invention can greatly reduce the torque exerted on the annular member by the jumper spring and thus reduce the required drive torque transmitted by the drive mechanism 30. In particular, the gear reduction ratio in the drive mechanism can be reduced.

According to a preferred variant, the tangential play between the first ring gear and the second ring gear is set to be greater than or substantially equal to twice the accumulated manufacturing tolerances formed at the first ring gear 28 and the second ring gear 38 in the transmission formed by the ring 26 and the maltese cross 32.

In a particular variant, the play between the first toothing and the second toothing is set to be less than a maximum distance at which a jumper spring moved by the movement of the indicator away from a stable rest position corresponding to the display position can return the indicator to this stable rest position by a positioning force exerted by said jumper spring on the indicator toothing. In another variant, half the play plus the accumulated manufacturing tolerances generated in the transmission at the first and second ring gears are smaller than the above-mentioned maximum distance, said transmission consisting of an indicator and an irreversible transmission system. In this variant, the theoretical position of the second ring gear of the irreversible transmission system for the discrete indicator display position is substantially centrally located in the first ring gear of the indicator; that is, the play is distributed substantially in equal parts on both sides of the tooth or teeth of the second ring gear inserted in the first indicator ring gear, as is the case in fig. 2B. It should be noted that the jumper spring may also have some tolerance with respect to the display position, which is defined by its stable rest position in the first toothed ring. This tolerance is advantageously added to the accumulated manufacturing tolerances formed in the aforementioned transmission to define the play provided in the aforementioned variant. In a preferred variant, the position of the jumper spring can be adjusted after the indicator has been assembled, so that the discrete display positions are predefined in a very precise manner and the positioning tolerances of the jumper spring can be disregarded.

Figures 3A and 3B partially show a second embodiment of a timepiece movement according to the invention. The aforementioned different variations that may also be provided in the second embodiment will not be described again here. The second embodiment is characterized by having a drive mechanism of a self-locking pin system in place of the maltese cross system of the first embodiment. In the variant shown, the drive mechanism 64 for the date ring 26A comprises a driving wheel 66 to which two pins 68 and 69 are fixed, which define a second toothing in the transmission formed by the ring 26A and the wheel 66. The drive wheel is driven by a pinion gear 70 associated or coupled to an electromagnetic motor. The two pins are aligned along the diameter of the drive wheel 66. Thus, in the positions shown in fig. 3A and 3B, corresponding to the position of the driving wheel 66 arranged in discrete display positions of the date ring, these two pins ensure the complete locking of the date ring. In fact, the torque exerted by the ring on the wheel 66 will not be able to drive it in rotation; the wheel thus forms an irreversible transmission system by its two pins.

Preferably, the two pins are not cylindrical, but have a substantially semicircular section, so as to obtain a large play between the first ring gear 28A and the second ring gear formed by the two pins, while providing an unlocked transmission. In fact, when the annular element is driven during the day, the individual pins must be able to alternatively exit from the space of the ring gear 28A and then enter another space of the ring gear without abutting against the tips of the teeth. Other features that have been described with reference to the first embodiment will not be repeated here. In particular, a jumper spring similar to that of the first embodiment is arranged to accurately position the date ring at a plurality of discrete display positions.

Finally, it should be pointed out that other embodiments for forming an irreversible transmission system can be proposed by the person skilled in the art. Irreversibility may be considered in the range of torsional forces that may occur in a wheel meshing with an indicator, in particular a date ring toothing, in an impact or violent movement. The irreversibility is therefore sufficient to obtain a maximum torque in the wheel, up to that generated by the indicator in the various situations that the watch provided with the timepiece movement according to the invention may encounter. Certain embodiments relate to an electronic movement that includes an electromagnetic motor arranged to actuate an indicator drive mechanism. In the case of a stepper motor, the stator is arranged to generate a cogging torque applied to the permanent magnet rotor of the motor, which may increase due to short-circuiting of the coils, particularly in the case of a Lavet (Lavet) type motor. This positioning torque holds the rotor in at least one stable rest position (the position assumed in the absence of a power supply). The motor may be configured such that the positioning torque transmitted to the rotor of the wheel in engagement with the indicator defines a locking force higher than the maximum torque force that the indicator can exert on the wheel, particularly during an impact. Preferably, the gear reduction ratio of the kinematic chain of the drive mechanism is relatively high, so that the locking force is sufficiently high. It should be noted that the locking force obtained depends not only on the positioning moment and the damping factor of the kinematic chain, but also on the friction losses in the kinematic chain.

Claims (6)

1. Timepiece movement (24) provided with an analogue display device for displaying information whose value varies periodically or intermittently, comprising, on the one hand, an indicator (26,26A) of said information provided with a first toothing (28,28A), and, on the other hand, a drive mechanism (30,64) for driving said indicator periodically or intermittently, said drive mechanism being formed by an irreversible transmission system comprising a second toothing (38; 68,69) meshing with said first toothing,

characterized in that the analog display device further comprises a positioning jumper (56) for the indicator, which generates a positioning force on the first toothing that is sufficient to position the indicator precisely at a plurality of discrete display positions, but insufficient to ensure an impact-resistant function for the indicator; wherein there is a tangential play (J1+ J2) between the first and second gear rings, the tangential play being arranged to be large enough such that the first and second gear rings do not contact each other when the indicator is in any of the plurality of discrete display positions and the irreversible transmission is in the respective predetermined position; and wherein the irreversible transmission system ensures an anti-shock function for the indicator by engagement of the first and second gear rings at least when the indicator is in any one of the plurality of discrete display positions and the irreversible transmission system is in the respective predetermined position.

2. Timepiece movement according to claim 1, wherein the irreversible transmission system is a maltese cross system (32, 40).

3. Timepiece movement according to claim 1, wherein the irreversible transmission system is a self-locking pin system (66,68, 69).

4. A timepiece movement according to any one of claims 1 to 3, wherein the detent force is higher than the maximum friction force exerted by the timepiece movement on the indicator, and wherein the detent force is lower than three times the maximum friction force.

5. Timepiece movement according to any one of claims 1 to 3, wherein the tangential play (J1+ J2) between the first and second ring gears is greater than or substantially equal to twice the cumulative manufacturing tolerance produced at the first and second ring gears in the transmission formed by the indicator and the irreversible transmission system.

6. A timepiece movement according to any one of claims 1 to 3, wherein the indicator is a date ring (26A).