HK1242428B - Timepiece mechanism comprising a pivoting member provided with magnetic return means - Google Patents

Description

Clockwork comprising a pivoting member provided with a magnetic return device

Technical Field

The invention generally relates to a timepiece mechanism comprising a rotating wheel set, a support, an element mounted to pivot on the support and magnetic return means for returning a portion of the pivoting element against a surface of the rotating wheel set.

Background Art

Clockwork mechanisms are known that include a magnetic device for coupling two elements, in particular a cam and a follower lever. Thus, FIG. 15 of French Patent FR1276734 shows a component of an automatic winding mechanism that converts the rotational motion of a rotating wheel set into the alternating motion of a pivoting lever. In the example shown, the rotating wheel set with which the lever cooperates comprises a three-leaf cam and a return device for returning a portion of the lever to rest against the surface of the rotating wheel set comprising two permanent magnets. The first magnet is a linear magnet fixedly supported by the lever, while the second magnet is attached to the lever support. It will be noted that the first magnet also serves to partially counteract the magnetic return force through its configuration, with its north pole positioned close to the three-leaf cam, which also constitutes a magnetic north pole. Consequently, the magnetic cam is moved away by magnetic repulsion, with the head of the first magnet integral with the lever.

As mentioned above, the present invention therefore relates to a timepiece mechanism in which the restoring mechanism operates not via a spring but via a pair of magnets generating a magnetic restoring force. The use of such a magnetic restoring mechanism offers the particular advantage of avoiding any problems associated with spring fatigue. Indeed, when a spring is repeatedly subjected to repetitive stresses, there is a risk of cracks forming and a resulting reduction in its elastic modulus or even breaking it.

However, clockwork mechanisms incorporating magnetic return devices also have some drawbacks. In practice, the permanent magnets must be positioned close to one another. In these circumstances, the prevailing magnetic interaction forces between the magnets make assembly operations difficult. This also complicates any disassembly (particularly for maintenance) and adjustment of the mechanism.

Summary of the Invention

One object of the present invention is to overcome the disadvantages of the prior art by providing a timepiece mechanism of the type described above, in which the rotating wheel set and the components cooperating therewith can be easily assembled when assembling the mechanism, and subsequently easily removed for inspection, cleaning or repair when disassembling, and finally easily reassembled. The invention achieves this object by providing a timepiece mechanism as described below.

According to the invention, a timepiece mechanism comprises a rotating wheel set, a support, an element pivotally mounted on the support, and return means for returning a portion of the pivoting element to rest against the surface of the rotating wheel set during normal operation. These return means comprise a first magnet carried by the pivoting element and a second magnet carried by a support separate from the pivoting element, the first and second magnets being arranged to respectively occupy, during normal operation, a first position relative to the pivoting element and a second position relative to the support, the first and second positions being arranged such that the interaction of the respective magnetic fields of the first and second magnets generates a first magnetic force that returns the portion of the pivoting element towards the surface of the rotating wheel set. The first or second magnet is associated with a device for changing the position of the first magnet relative to the pivoting element or the position of the second magnet relative to the support so that the first or second magnet can occupy a third position in which the interaction of the respective magnetic fields of the first and second magnets generates a second magnetic force that tends to move the portion of the pivoting element away from the surface of the rotating wheel set. The means for changing the position of the first magnet or the second magnet is arranged such that the change between the respective first position, second position and third position is reversible.

According to an advantageous variant of the invention, the second magnet is arranged so as to cooperate with a tool in order to cause it to rotate and thereby reversibly drive it to rotate between the second and third positions. One advantage of this variant is that it allows the watchmaker to modify the magnetic interactions in the provided magnetic system, and in particular to alter the direction of the magnetic force on the pivoting element, in order to keep it away from the rotating wheel set at all times, thereby facilitating the assembly or disassembly of the timepiece mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention will become apparent on reading the following description, given purely by way of non-limiting example, with reference to the accompanying drawings in which:

- Figure 1 is a plan view of the automatic winding mechanism of a watch constituting a specific embodiment of the timepiece mechanism of the present invention.

FIG. 2 is an enlarged perspective view of the automatic winding mechanism of FIG. 1 , with the oscillating weight omitted.

3A and 3B show a partial plan view of the automatic-winding mechanism of FIGS. 1 and 2 , respectively in its normal operating configuration and in a non-operating configuration for assembling or disassembling said mechanism.

- Figure 4 is a partial view similar to Figure 3, showing a variant embodiment of the automatic winding mechanism for a mechanical watch.

DETAILED DESCRIPTION

Figures 1 and 2 are diagrams of a first specific embodiment of a clockwork mechanism according to the present invention. In the illustrated embodiment, the clockwork mechanism (generally designated 1) is a bidirectional automatic winding mechanism for a clock movement. This mechanism comprises an oscillating weight 3 and an eccentric cam 5 fixedly mounted coaxially to the oscillating weight 3 so that the cam 5 integrally participates in the oscillating motion of the oscillating weight 3. As shown in Figure 1, the cam takes the form of an elliptical disk having a center of symmetry 2 through which its axis of rotation passes. However, it will be understood that the eccentric cam may also take a different form, such as an elliptical or heart-shaped form, in a known manner.

With more particular reference to FIG2 , it can be seen that the mechanism shown comprises a lever 7 pivoted about an arbour 9. An eccentric cam 5 is in contact with the lever via two discs 11, each mounted on an outer stud 13 of the lever. The interaction between the eccentric cam and the two discs has the effect of transmitting the oscillating motion to the lever 7 when the pendulum 3 pivots in one direction or the other.

The lever 7 of the clockwork mechanism 1 carries two pivoting members 15a and 15b, which pivot on the lever about two different spindles 17a and 17b. Each pivoting member takes the form of a first-class lever with an arm extending on either side of the pivot axis. The first arm ends in a beak 19 and is arranged to function as a pawl. In this example, each pivoting member thus defines a pawl. The second arm of each pivoting member then carries a magnet 21 (hereinafter referred to as the first magnet). The first magnet is preferably mounted in a housing 23 provided for this purpose. hereinafter, each of the two pivoting members will be referred to as a "pawl" in view of its function.

With further reference to the figures, it can also be seen that lever 7 carries another magnet 25 (hereinafter referred to as the second magnet), which is mounted separately from the two pivoting members 15a, 15b. In the example shown, the three magnets 21 and 25 are generally aligned and positioned in a plane perpendicular to the axis of rotation 2 of pendulum 3. The second magnet is arranged at a distance from the two first magnets 21 on lever 7. It can also be seen that magnets 21 and 25 are disc-shaped, and their polarization direction generally corresponds to the direction of alignment of the magnets in a plane perpendicular to axis 2.

Clockwork 1 also includes a rotating wheel set 27. In the example shown, this is a ratchet. The ratchet is arranged, in a known manner, to be driven by two pawls 15a and 15b. In the embodiment shown in Figures 1 and 2, the two pawls return to rest against ratchet 27 in opposite directions. Thus, when lever 7 pivots clockwise about arbor 9, pawl 15a is pulled and disengaged from the ratchet tooth profile, while pawl 15b is also pulled and drives the ratchet. Conversely, when lever 7 pivots counterclockwise about arbor 9, pawl 15a is pulled and drives the ratchet, while pawl 15b is also pulled and disengaged from the ratchet tooth profile. The ratchet is arranged, in a conventional manner, to drive the barrel arbor via the gear train to wind the mainspring.

More particularly, referring to Figures 3A and 3B, it can be seen that in normal operation as represented in Figure 3A, the three magnets are arranged alternately with respect to their polarization directions (magnetic axis vectors). In other words, the two first magnets 21 are polarized in the same direction, while the second magnet 25 inserted between the two first magnets is polarized in the opposite direction. In this case, the magnets repel each other and a repulsive magnetic force occurs, which generates magnetic restoring forces FMRa and FMRb on the two pawls, respectively. This generates a magnetic restoring torque applied to the pawl 15a in the counterclockwise direction and a magnetic restoring torque applied to the pawl 15b in the clockwise direction.

According to the invention, at least one of the first and second magnets 21, 25 is arranged to allow the watchmaker to change its polarization direction, or preferably its polarity along the magnets' alignment direction, and thereby to modify the magnetic force acting on each pawl 15a, 15b. In the variant described here, the second magnet 25 is arranged so that it can be reversibly rotated by 180° relative to the lever 7 to which it is mounted, with the aid of a screwdriver. It is thus easy to change the polarity of this second magnet. Thus, starting from the configuration of FIG. 3A , the watchmaker can rotate magnet 25 by half a turn to move it to another configuration, represented in FIG. 3B , i.e., a different angular position corresponding to the assembly or disassembly position of the mechanism. In the assembly/disassembly configuration of FIG. 3B , the interaction of the respective magnetic fields of the first and second magnets generates magnetic forces FMEa, FMEb, respectively, acting on each pawl, which tend to move the beak 19 of each of the two pawls away from the ratchet tooth profile.

It will be noted that the second magnet 25, partially housed in the recess of the lever 7, takes the form of a slotted screw head to allow the watchmaker to rotate the magnet using a screwdriver. According to a variant, the second magnet is mounted in a rotating housing (not shown) housed in the recess of the lever, the housing presenting a device for changing the angular position of the second magnet. An advantage of this variant is that it allows the second magnet to rotate without subjecting it to mechanical stress. For example, the housing will be mounted to rotate with friction in a circular hole in the lever. This friction makes it possible to maintain the second magnet in a first angular position during normal operation of the clockwork. When the watchmaker has rotated the housing, in particular during assembly or disassembly of the clockwork, the friction also makes it possible to maintain the second magnet in a second angular position corresponding to the non-operating configuration.

When the second magnet 25 rotates 180°, the three magnets 21 and 25 are thus polarized in the same direction as shown in Figure 3B. In these cases, magnets 21 and 25 attract each other rather than repel each other. As a result, an attractive magnetic force occurs in the form of a torque applied to pawl 15a in a clockwise direction and a torque applied to pawl 15b in a counterclockwise direction. The two pawls thus move away from the ratchet 27. Due to this feature of the present invention, the components of the clockwork can be easily installed or easily removed for inspection, cleaning or maintenance. In addition, the present invention provides significant advantages for loosening the mainspring of the barrel (for example, to replace the mainspring). In fact, as described above, reversing the polarity of the second magnet makes it possible to keep the two pawls 15a and 15b detached from the ratchet and thus from the mainspring.

The present invention offers another advantage, as the ability to rotate the magnet allows the orientation of its magnetization axis to be varied, and thus its interaction with the other magnet in the associated magnetic system, specifically the strength of the magnetic force between the two magnets. This allows the strength of the magnetic force acting on the pivoting member to be adjusted. Fine-tuning the magnetic force can be crucial for optimizing functionality, particularly the strength of the restoring force exerted on the pivoting member. In a first variant, particularly one employing a pawl or jumper spring, the arrangement of the support member on which the magnet rotates forms a cam, meaning that the magnet is not centered on its axis of rotation. Therefore, changing the angular position of the magnet also moves it closer to or further away from the magnet carried by the rotating member. In a second variant, the magnet does not have a cylindrical or square shape projecting into a generally plane perpendicular to its axis of rotation, but rather a different shape, such as a rectangular or oval. As in the first variant, this configuration allows the force exerted on the associated magnetic system to be varied.

FIG4 is a partial view, similar to FIG3A , of an automatic winding mechanism for a watch constituting a second variant embodiment of the present invention. The mechanism of FIG4 includes a lever 107 (only a portion of which is visible) pivoting about an arbour 109. The lever carries two pivot members 115a and 115b, which pivot on the lever about two different arbours 117a and 117b. It will be noted that, unlike in the first variant, the arrangement of the pivot members in FIG4 is asymmetrical. Pivot member 115a is in the form of a third-class lever, having a single arm extending from pivot arbour 117a, while pivot member 115b is in the form of a first-class lever, having two arms extending on either side of pivot arbour 117b. The first arm of pivot member 115b terminates in a beak 119 and is arranged to function as a detent. The second arm carries a first magnet 121. The pivoting member 115a is also arranged to act as a pawl, its single arm also terminating in a beak 119, and it also carries a first magnet 121, which is arranged between the pivoting spindle 117a and the beak 119. It will be appreciated that it is this intermediate position of the magnets that makes the pivoting member 115a a lever of the third kind.

Referring again to Figure 4 , it can also be seen that lever 107 carries a second magnet 125, which is separate from the two pivot members 115a and 115b. As in the first variant, the three magnets 121 and 125 are generally aligned and positioned in a plane perpendicular to the lever's axis of rotation. Furthermore, the second magnet is positioned on lever 107 between the two magnets 121 and at a distance from them to prevent collision during normal operation of the automatic winding mechanism. Again, its polarization direction generally corresponds to its alignment direction. The first and second magnets 125 mounted on pivot member 115b are polarized in the same direction. Under these conditions, the two magnets attract each other, generating an attractive magnetic force in the form of a restoring torque exerted counterclockwise on pivot member 115b. Similarly, the first magnet mounted on pivot member 115a is polarized in the same direction as the second magnet 125, and is therefore attracted to the second magnet. The attractive magnetic force between the first and second magnets 125 mounted on the pivot member 115a appears as a restoring torque applied to the pivot member 115a in a counterclockwise direction.

It will also be understood that various modifications apparent to those skilled in the art may be made to the variant embodiments forming the subject of this description without departing from the scope of the invention as defined by the appended claims. In particular, the invention is not limited to automatic winding mechanisms. Indeed, those skilled in the art will recognize numerous other watchmaking applications that utilize wheels or rings and pawls or jumper springs. The invention can readily be adapted to each of these applications. Furthermore, pawls and jumper springs are naturally not the only examples of pivoting elements that can be arranged to cooperate with a rotating wheel set. Examples other than pawls include cam-controlled mechanisms, return-to-zero mechanisms using hammers, engaging coupling mechanisms, and lever mechanisms for perpetual calendars.

Claims (7)

1. A watch mechanism comprising a rotating wheel assembly (27), a support, a pivot (15a, 15b; 115a, 115b) mounted on the support, and a return mechanism for returning a portion (19) of the pivot towards a surface of the rotating wheel assembly during normal operation, the return mechanism comprising a first magnet (21; 121) carried by the pivot and a second magnet (25; 125) carried by the support, which is separate from the pivot, the first magnet and the second magnet being arranged to occupy a first position relative to the pivot and a second position relative to the support, respectively, during normal operation, the first position and the second position being arranged such that the interaction of the respective magnetic fields of the first magnet and the second magnet produces A first magnetic force, which causes the portion (19) of the pivot to return toward the surface of the rotating wheel assembly, is characterized in that the first magnet or the second magnet is associated with a device for changing the position of the first magnet relative to the pivot or the position of the second magnet relative to the support, such that the first magnet or the second magnet can occupy a third position in which the interaction of the respective magnetic fields of the first magnet and the second magnet generates a second magnetic force that tends to move the portion (19) of the pivot away from the surface of the rotating wheel assembly, and the device for changing the position of the first magnet or the second magnet is arranged such that the change between the corresponding first position, second position and third position is reversible. 2. The clock mechanism according to claim 1, wherein the means for changing the position of the first magnet or the second magnet is arranged to allow the magnet to rotate on its own. 3. The clock mechanism according to claim 2, wherein the means for changing the position of the first magnet or the second magnet is arranged to allow the magnet to rotate 180° about an axis perpendicular to its polarization axis. 4. The watch mechanism according to claim 2, wherein the magnet associated with the means for changing the position of the magnet is a second magnet (25; 125), and the means for changing the position of the second magnet is configured by rotational friction of the second magnet and constituted by a configuration of the second magnet that allows for cooperation with a tool to rotate the second magnet itself. 5. The watch mechanism according to any one of the preceding claims, characterized in that the rotating wheel pair (27) is a ratchet, and the pivot (15a, 15b; 125a, 125b) defines a pawl. 6. The watch mechanism according to claim 5, characterized in that the watch mechanism is an automatic winding mechanism including a lever (7; 107), the lever (7; 107) constituting the support member, and the pawl pivoting on the lever. 7. The clock mechanism according to claim 6, characterized in that the clock mechanism includes two pawls (15a and 15b; 125a and 125b) mounted on a lever (7; 107) and pivoting about two different spindles (17a and 17b; 117a and 117b), one of the two pawls being provided with the first magnet, and the other of the two pawls being provided with a third magnet, the third magnet being polarized in the same direction as the first magnet.