HK1145206B - Locking mechanism for timepiece drive module - Google Patents

Description

Locking mechanism of clock driving module

Technical Field

The present invention relates to a lock mechanism of a clock drive module. The invention is particularly applicable to electromechanical micromotors for watches.

Background

Stepper motors are well known for converting electrical pulses into rotational mechanical motion. In 1936 Mr. Lavet invented the first stepper motor for the clock making industry; since then, these motors have been used to drive the movement in most quartz watches with hands. Such motors are also commonly used in all devices where it is desirable to control speed or position.

The "Lavet" motor has permanent magnets that can create stable positions between electrical pulses. Therefore, it is desirable that the permanent torque exerted on the rotor (i.e. the rotating part of the motor) prevents any accidental movement of the rotor, even when the watch is subjected to shocks. The purpose of the permanent torque, which is usually chosen to be significantly greater than the motor torque, is also to prevent any increase of more than one step at the same time. However, these detent torques cannot fully lock or incrementally index (index) the engaged wheels; therefore, pawl systems have been proposed to cooperate with these motors to improve the holding and locking function, as exemplified in U.S. patent No. 4647218. In this patent, the Lavet motor drives the wheel through 180 degrees of rotation with each electrical pulse (i.e., per minute); the wheel is mounted at two diametrically opposite ends by plugs engaging in successive radial slots in the minute wheel. Between each pulse, therefore, the two pins engage in two successive radial grooves of the minute wheel and prevent any possible movement of the minute wheel.

Now, other types of stepper motors can be utilized, such as the microelectromechanical motor disclosed by the applicant in european patent No.1921520, which comprises a linear actuator equipped with an active pawl for driving the wheel in rotation and a passive pawl for preventing the rotor from rotating in the opposite direction when the actuator returns during its oscillation. The same locking function and single increment function are also desired for this motor. It is clear, however, that the particular detent mechanism described above for the Lavet motor is unsuitable.

Disclosure of Invention

The object of the present invention is to provide a new mechanism that locks the engaged wheels in a stable indexing position and at the same time prevents any increment of said wheels more than one step.

It is another object of the present invention to provide a locking mechanism that can be adapted to any type of stepper motor and not just "Lavet" type motors.

These aims are achieved in particular by a device for locking and single increment of a driving module 1 of a clockgear train, comprising an actuator 2 equipped with a driving pawl 5 cooperating with a gear wheel 7. The device 1 comprises a first finger 8 and a second finger 9 cooperating with the gear 7, characterized in that:

the first finger 8, when it is engaged in one of the teeth of the toothed wheel 7, completely locks the rotation of the toothed wheel 7; and is

The second finger 9 is arranged between the first stop member 10 and the second stop member 11, the space between the stop members 10 and 11 limiting the angular travel of the gear wheel 7 when said second finger 9 is engaged in one of the teeth of said gear wheel 7.

These objects are also achieved by a locking method using a device according to the main claim, said method comprising the steps of:

- (a) lowering the first finger 8 and releasing the gear 7;

- (B) driving the gear 7 in rotation via the active pawl 5 of the actuator;

- (C) raising the first finger 8 and engaging it in one of the teeth of the toothed wheel 7;

- (D) releasing and returning said active pawl 5 of the actuator 2;

- (E) releasing the second finger and returning it relative to the first stop member 10;

- (F) raising the second finger 9 and engaging it in one of the teeth of said toothed wheel 7.

One advantage of the provided solution is that it can be applied to or associated with any type of stepper motor (including for example the adjustment means of a mechanical watch) and any type of clock drive module.

Another advantage of the solution provided is that permanent magnets for stabilizing the idle or rest position of the motor-driven gear train are no longer required.

A further advantage of the solution provided is that the electromechanical stepper motor no longer requires passive pawls to prevent the rotor from rotating in the opposite direction when the actuator returns during its oscillation.

Furthermore, the locking solution provided is essentially different from the locking system applied to the Lavet motor in that the required power consumption is independent of the motor torque maximum. An important advantage of the solution thus provided is that the power consumption of the locking system can be significantly less than the power consumption of the motor itself.

Drawings

Exemplary embodiments of the invention are described in this specification and illustrated by the accompanying drawings, in which:

fig. 1 illustrates a top view of a known stepper motor of the prior art, which would preferably be associated with a locking mechanism according to the present invention.

Fig. 1b illustrates a cross-sectional view along the motor plane showing a detailed actuation of the rotor gear with active and passive pawls.

FIG. 2 illustrates a cross-sectional view of a locking device according to a preferred embodiment of the present invention idle prior to motor stepping;

fig. 3 illustrates a cross-sectional view of the locking device according to a preferred embodiment of the present invention during the step of lowering the first locking finger.

Fig. 4 illustrates a cross-sectional view of a locking device according to a preferred embodiment of the present invention during motor stepping.

Fig. 5 illustrates a cross-sectional view of the locking device according to a preferred embodiment of the present invention when the second locking finger is stopped.

Fig. 6 illustrates a cross-sectional view of the locking device according to a preferred embodiment of the invention after the first locking finger has been raised and during the return of the actuator and the second locking finger.

Fig. 7 illustrates a cross-sectional view of the locking device according to a preferred embodiment of the invention during idle periods at the end of motor stepping.

Fig. 8 illustrates a state diagram integrating the various states of the locking device and the steps of the preferred embodiment of the locking method according to the present invention.

Detailed Description

Fig. 1 illustrates a drive module 1 for engaging a clock wheel, comprising an electromechanical stepping micromotor of known type. The micromotor is formed by an actuator 2, the actuator 2 comprising a movable stylus 3, the stylus 3 driving the rotor in rotation via a driving pawl 5, the driving pawl 5 cooperating with a gear 7 of the rotor. The term "motor" actuator is also commonly used for the actuator 2, given its active function of driving the rotor 5. The cooperation between the gear 7 and the pawl and the mechanism for driving the rotor in rotation in sequence are clearly illustrated in detail in fig. 1b, which is an enlarged view of fig. 1, showing the gear 7 at the 5 o' clock position in the plane of the motor.

In fig. 1, the actuator 2 is formed of two generally symmetrical parts, the first part comprising an active thrust pawl and the second part comprising an active traction part, so as to improve motor throughput by applying a greater torque. However, those skilled in the art will appreciate that a single thrust pawl and a single traction pawl is sufficient to drive the rotor in rotation. According to the advantageous embodiment shown, each actuator 2 is associated with a passive pawl 6, the passive pawl 6 being elastically held in engagement with the toothed wheel 7, so as to ensure a precise angular positioning during the driving phase when the feeler pin 3 is moved, and also forming a locking mechanism of the toothed wheel 7 to prevent any reverse movement of the toothed wheel 7.

Fig. 1b illustrates the drive and indexing mechanism for the stepper motor of fig. 1, showing a single passive pawl 6 and a single active pawl. The active pawl 5 at the end of the stylus has an oscillating movement in the tangential direction 4 of the gear wheel 7. The indentation of the gear wheel 7 tends to force the gear wheel to move in a counter-clockwise rotational direction during the pulling movement of the stylus 3, while each tooth of the associated passive pawl 6 gives an indexing position for rotating the gear wheel which generally corresponds to one motor step. Furthermore, during the return movement of the stylus 3 in the same tangential direction 4 of the gear wheel 7 (but in the opposite direction), the passive pawl 6 prevents the active pawl 5 from driving the gear wheel 7 in the opposite direction and prevents the active pawl 5 from maintaining the angular position of the gear wheel 7 between each step. However, said locking and indexing mechanism does not prevent an undesired acceleration of the toothed wheel 7 in the counter-clockwise direction, for example in the case of an excessive motor torque exerted by the active pawl 5 when the amplitude of the electric pulse generated by the actuator 2 is excessive, or even in the case of a watchcase containing an electromechanical motor between the motor steps subjected to shocks.

Fig. 2-7 illustrate a preferred embodiment of a locking and indexing mechanism according to the present invention that overcomes these deficiencies of the prior art. Fig. 2-7 all show cross-sectional views in the plane of rotation of the gear wheel 7, the gear wheel 7 being driven by the active pawl 5, the active pawl 5 engaging in a tooth of the gear wheel 7 and moving linearly via an oscillating movement in the tangential direction of the gear wheel 7 in the geared position (gearing level); fig. 2-7 also show the locking means in various positions depending on the state of the mechanism, which locking means are formed by two different locking fingers 8 and 9. According to the preferred embodiment shown, the first locking finger 8 is accommodated between the two stop elements 15, 16 such that it is guided with only a vertical movement and therefore with only one degree of freedom in the direction of translation. However, according to an alternative embodiment, the degree of freedom may also be in the direction of rotation. The function of the first finger is to prevent any rotational movement of the gear wheel when it is engaged in one of the teeth of the gear wheel. The second locking finger 9 is arranged between the two stop members 10 and 11 so that the angular travel of the gear wheel is limited when the finger engages in one of the teeth of the wheel. According to the shown preferred embodiment of the invention, the space between the stop members 10, 11 limits the angular travel of the gear wheel 7 to the movement of a single tooth, corresponding to one motor step. Reference to the stop members 10, 11 and stop elements will be explained in all the following figures 3-7, which figures 3-7 describe the movement of the fingers during the various locking steps, but these references will not be systematically addressed in the description.

Fig. 2 illustrates the locking device according to the invention in an idle or rest state before the motor is stepped. In this state, the two locking fingers 8 and 9 are raised and housed in two consecutive teeth of the toothed wheel 7. The second locking finger 9 is also received against the first stop member 10. In this state of the system, the pawl 5 engages in one of the teeth 71 of the toothed wheel 7 and moves along the linear oscillating movement of the arrow 4 (note: the movable contact pin shown in fig. 1 and 1b is not shown in this or the following figures, as this is not necessary for understanding the locking mechanism described below). All the following fig. 3-7 will describe the reference to the tooth 71 engaged by the active pawl 5, but this reference will not be systematically described in the description.

Fig. 3 illustrates the locking device during the step of lowering the first locking finger 9 (arrow a). According to the preferred embodiment shown, it can be seen that the only degree of freedom of the first locking finger 8 is translation in the radial direction of the gear wheel 7 (i.e. perpendicular to the movement of the actuator and the active pawl 5), as will be seen in the following figures. Once the fingers have been lowered, the gear wheel 7 can be driven in rotation. However, when the system is in this state, the second locking finger 9 is still received against the first stop member 10, but the second locking finger 9 has a translational degree of freedom between the two stop members 10 and 11.

Fig. 4 illustrates the locking device according to the invention (step B illustrated by the corresponding arrow B) during motor stepping (i.e. when the gear wheel 7 is driven in rotation by the active pawl 5). The rotation of the gear wheel 7, in which the locking finger 9 engages in one of the teeth of this gear wheel 7, thus drives the finger 9 to perform the same translational movement along the arrow B as the movement of the pawl in the tangential direction of the wheel and in the direction corresponding to one of the two degrees of freedom of the finger 9. Once the second finger 9 is positioned against the second stop member 11, the gear 7 stops, which prevents any additional movement of the gear.

Fig. 5 illustrates the locking device according to the invention in a state in which the second finger 9 is locked against the stop member 11. Arrow C illustrates the step of lifting the first locking finger 8, the first locking finger 8 then engaging in one of the teeth of the gear and thereby preventing any movement of the gear 7, even in the opposite direction to the direction in which the gear was actuated until then (i.e. clockwise in the illustrated embodiment). Once this step is completed, the device will therefore be in a stable condition again, preventing any rotational movement of the gear, but unlike the case in fig. 2 where the two fingers are housed in two consecutive teeth of the wheel, the two fingers 8, 9 are now separated by two teeth. Thus, in the embodiment shown, the angular travel of the toothed wheel 7 corresponds to at most one tooth of the toothed wheel 7.

Fig. 6 illustrates the locking device after the first locking finger has been lifted and during the return step of the actuator (arrow D) and the second locking finger (arrow E), which has to be lowered beforehand (arrow E1) to be released from the tooth, in order to allow a translational movement in the same direction as the pawl 5. The return steps D and E2 of the active pawl 5 and the second finger 9 can be performed sequentially in any order, independently of each other. However, according to a preferred embodiment of the invention, it is possible to set, for example by programming, an actuator (not shown in the figures, but corresponding to reference number 2 in fig. 1) different from the actuator controlling the active pawl 5 to act on the second finger 9 during the return movement of the active pawl 5, or even by coupling the actuator of the pawl 5 (reference number 2 in fig. 1) to the second finger 9 by means of a stem (not shown), so that any translational movement of the actuator 2 along the actuator oscillation direction (see arrow 4 in fig. 2) and in particular the return direction (arrow D in the present figure) is done by the same translational movement of the second finger 9, which steps can be performed simultaneously. Furthermore, this coupling will allow the pawl 5 and the second finger 9 to be simultaneously released from the teeth that they respectively engage.

Fig. 7 illustrates the locking device according to the invention in an idle state at the end of the motor step (i.e. once the second finger 8 has returned to a stop state against the first stop member 10 and has been lifted into one of the teeth of the gear wheel 7) (step F, shown by the corresponding arrow in the figure). It should be noted that the arrangement of the two locking fingers 8, 9 is the same as the arrangement of fig. 2, and the arrangement of the pawl 5 with respect to the fingers 8, 9 is also the same. But the pawl 5 is now positioned behind the tooth 71 that it engaged before the motor was stepped.

As can be seen by comparing the steps described with reference to the figures, according to a preferred embodiment of the disclosed locking mechanism, the first finger 8 has a translational (vertical in the figures) degree of freedom to enable it to be raised or lowered to engage in or release from one of the teeth of the toothed wheel 7. The second finger 9 has this same degree of translational freedom and an additional degree of freedom (horizontal in the figure) between the stop members 10 and 11 (corresponding to the direction of oscillation 4 of the active pawl 5 and to the tangential direction of the gear wheel 7 where the fingers 9 mesh). It should be observed, however, that the correlation between the degrees of freedom of the two locking fingers 8, 9 and the direction of the translational movement are not necessary to guarantee the proper functioning of the invention, and the direction of the translational movement does not have to be vertical and horizontal, respectively. Furthermore, it has been specified above that the degrees of freedom of the engagement and release teeth may also be not translational but rotational for the first and second fingers 8, 9. Any combination between the degrees of freedom and the types of degrees of freedom of each finger 8, 9 is possible within the scope of the invention.

Fig. 7 also shows a preferably programmable electronic circuit 14 for managing the sequence of movement of the locking fingers 8 and 9. This circuit 14 is added to the figure because it corresponds to a preferred embodiment of the invention according to which the movement of the fingers 8, 9 is controlled by an electrical signal which causes the movement of an electrostatic actuator 12, 13 coupled to each finger 8, 9 respectively. In this figure, the motor actuator 2 is also added to avoid any confusion with the actuators 12, 13 of the fingers 8, 9.

The sequence of movement of the fingers 8, 9 follows the steps described above, which are integrated in the state diagram of fig. 8, in fig. 8 the three numbers describing the state of the locking system represent the following:

the first number: the state of the first finger 8; 0 is lower and 1 is higher;

second number: the state of the second finger 9; 0 is lower and 1 is higher;

the third number: the position of the second finger 9; 0 is lower and 1 is higher.

The first step a is to lower the first finger 8 after the first finger 8 has been released from said gear wheel 7, which causes the system to go from a stable, "idle" or rest state 110 to a state 010 where the gear wheel can be rotated.

The second step B consists in driving the gear wheel 7 in rotation via the active pawl 5 of the actuator 2, which causes the second locking finger 9 of the stop member 10 to move in the system state 010 towards the other stop member 11, the stop member 11 blocking any further travel of the gear wheel and thus bringing the system into the state 011.

The third step C consists in raising said first finger 8 to engage in one of the teeth of the gear 7 to lock the wheel completely again, the system changing from state 011 to stable state 111.

Step D consists in that the release and return of the active pawl 5 of the actuator 2 does not change the state of the locking system. However, the step E of release and return of the second finger with respect to the first stop member 10 can be divided into two sub-steps: e1, wherein the second finger is lowered causing the system to change from state 111 to state 101; and, E2, where the system changes from state 101 to 100. According to a preferred variant embodiment of the locking method, the steps D and E of release and return of the active pawl 5 and of the second finger 9 are carried out simultaneously.

Finally, step F consists in raising the second finger 9 to engage in one of the teeth of the toothed wheel 7, returning the system to the initial condition 110, called "idle" or rest condition, thus ending an incremental cycle of motor steps.

Said sequence, which guarantees that at least one of the two fingers is always engaged in one of the teeth, causes the locking device to remain in a "stable" state, i.e.: in this state, the gear is made completely fixed (with the first finger engaged in the tooth of the wheel 7), the "limited" state being: in this state, the stroke of the gear is limited (with the second finger 9 engaged in the teeth of the wheel 7). The present invention therefore eliminates the need to use magnets to apply detent torque in an idle or stationary state to achieve a steady state; furthermore, the first finger does not require the use of a passive pawl, which is more complex to machine and therefore more expensive. The solution thus provided reduces the overall cost of the locking device, improving its function at the same time, since the angular travel of the gear is always limited at this time. It will also be apparent to those skilled in the art that the pawl 5, which meshes with the gear wheel, is actuated completely independently of the device and locking method, so that the pawl can be applied to electromechanical and purely mechanical clockwork trains.

According to a preferred embodiment shown in fig. 7, the desired sequence is preferably obtained by electronic programming. However, embodiments are contemplated in which at least the finger lowering and raising movements may be cammed.

Furthermore, although the finger actuators are electrostatic according to a preferred embodiment of the invention, it is also conceivable for the implementation of the micromotor locking means in a watch to use hydraulic actuators for other timepiece applications. Similarly, the oblique shape of the teeth shown in the disclosed figures, which tend to rotate the gear anticlockwise, may be changed to a similar shape in the opposite direction, or for example slotted to ensure that the wheel is fully locked even in case of shocks. In fact, this notch shape (not shown) will make it impossible for the teeth to be released via a force external to the system due to the cooperation of the same but inverted notch shape corresponding to the ends of the locking fingers 8, 9. However, the tooth profile shown in the figures is also suitable for meshing gears clockwise, and can therefore be easily associated with a display train with hands, for example.

List of reference numerals

1	Drive module
		2	Motor actuator
3	Movable actuator stylus
		4	Direction of oscillation of the movable stylus
5	Active pawl for actuator
		6	Passive pawl
7	Gear wheel
		8	First locking finger
9	Second locking finger
		10	First stop member of second locking finger
11	Second stop member of second locking finger
		12	First locking finger actuator
13	Second lock finger actuator
		14	Programmable circuit for actuating a lock finger
15	First stop element of first locking finger
		16	Second locking element of first locking finger
A	Step of lowering the first locking finger
		B	Step of driving the gear and the second locking finger
C	Step of raising the first locking finger
		D	Active pawl return step in the opposite direction of gear drive
E1	Step of lowering the second locking finger
		E2	Second locking finger returning step
F	Step of raising the second locking finger
		110	Idle or quiescent state of the system: two fingers rise onto two consecutive teeth, the second finger rising against the first stop member
010	System state allowing increment of one tooth: the first finger is lowered against the first stop member and the second finger is raised against the first stop member
		011	System state after one tooth increment: second finger shape

	The object is raised and abuts the second stop member, the first finger still being lowered
		111	Fully locked system state after one tooth increment: the second finger is raised and abuts the second stop member, the first finger is raised
101	Fully locked system state: the first finger is raised and the second finger is lowered against the second stop member
		100	Fully locked system state: the first finger is raised, the secondThe finger is lowered against the first stop member

Claims (13)

1. A locking and single increment device for a driving module (1) of a clockgear train, said module (1) comprising an actuator (2) equipped with a driving pawl (5) cooperating with a gear wheel (7), said device comprising a first finger (8) and a second finger (9) cooperating with said gear wheel (7), characterized in that:

said first finger (8) completely locking the rotation of said gear wheel (7) when said first finger (8) is engaged in one of the teeth of said gear wheel (7); and is

The second finger (9) is arranged between a first stop member (10) and a second stop member (11), the space between the first stop member (10) and the second stop member (11) limiting the angular travel of the gear wheel (7) when the second finger (9) is engaged in one of the teeth of the gear wheel (7).

2. The device according to claim 1, wherein the maximum angular travel of the gear wheel (7) is one tooth of the gear wheel (7).

3. The device according to claim 1, wherein the first finger (8) has two translational degrees of freedom and the second finger (9) has two translational degrees of freedom.

4. Device according to claim 1, wherein the first finger (8) has a translational degree of freedom along a radius of the gear wheel (7) and the second finger (9) has a translational degree of freedom along the direction of oscillation (4) of the active pawl (5).

5. A device according to claim 3, wherein the second finger (9) has the same degree of freedom as the first finger (8) and an additional degree of freedom.

6. The device according to claim 1, wherein the teeth of the gear (7) and the ends of the first and second fingers (8, 9) have a notch shape.

7. The device according to claim 1, wherein the first finger (8) and the second finger (9) are controlled by electrostatic or hydraulic actuators (13, 14).

8. The device according to claim 1, further comprising programmable electronic circuitry for controlling actuation signals of the first finger (8) and the second finger (9).

9. The device according to claim 1, further comprising a cam for actuating the movement of the first finger (8) and the second finger (9).

10. The device according to claim 1, wherein the second finger (9) is coupled to an actuator (2) actuating the active pawl (5).

11. Method for locking and single incrementing of a driving module (1) of a clockgear train using a device for locking and single incrementing according to any one of the preceding claims, the method comprising the steps of:

-a) lowering the first finger (8) and releasing the gear wheel (7);

-B) driving the gear wheel (7) in rotation via the active pawl (5) of the actuator (2);

-C) raising the first finger (8) and engaging the first finger (8) in one of the teeth of the gear wheel (7);

-D) releasing the active pawl (5) of the actuator (2) and returning it;

-E) releasing the second finger and returning it against the first stop member (10);

-F) raising said second finger (9) and engaging said second finger (9) in one of the teeth of said toothed wheel (7).

12. Method for locking and single increment of a driving module (1) of a gear train of clocks according to claim 11, wherein said step E) comprises: a first sub-step E1) of lowering the second finger (9) and a second sub-step E2) of returning the second finger with respect to the first stop member (10).

13. Method according to claim 11, wherein said steps D) and E) of releasing and returning the active pawl (5) and the second finger (9) of the actuator (2) are simultaneous.