HK1162691B - Striking mechanism for a watch with an active damper counter-spring - Google Patents

Description

Striking mechanism with active damping spring for a timepiece

Technical Field

The invention relates to a striking mechanism for a timepiece equipped with an active damping spring. The mechanism comprises at least one hammer arranged for striking at least one gong fixed to the gong-support at a determined moment. The hammer is held away from the gong in idle mode by the damped damper spring. The drive spring for the hammer in the mechanism may be provided in the form of a resilient plate or beam. The drive spring may be strung to drive the hammer against the gong to provide an acoustic signal, for example, for a preset period of time.

Background

In the field of watchmaking, a striking mechanism may be combined with a conventional timepiece movement to act as a minute repeater or to indicate a preset alarm time. Striking mechanisms of this type generally comprise at least one gong made of a metallic material (for example steel, copper, noble metal, metallic glass, sapphire or quartz). The gong may represent, for example, at least a portion of a circle around the timepiece movement within the bezel. The gong is fixed by at least one of its ends to a gong-support, which is then fixed to the watch plate. The striking hammer is rotatably mounted on the bottom plate, for example, near the gong-support, to strike the gong and vibrate it. The sound produced when the hammer strikes the gong is in the audio frequency range from 1kHz to 20 kHz. This sound indicates to the person wearing the watch the exact time, a preset alarm clock or a minute repeater.

As shown in european patent document EP1574917, the striking mechanism of a watch may comprise two gongs, each fixed by one end to the same gong-support, which is then fixed to the bottom plate. Each gong is beatable by a respective hammer. To achieve this, each hammer is driven by its own drive spring which must be pre-wound to drive the hammer to the gong to indicate a minute repeater time or alarm time. Both damping damper springs are arranged to push back the two hammers and hold them away from the gong in idle mode. The damped damper springs may also slow down the fall of each hammer before the hammer strikes the corresponding gong and then pushes the hammer back to the idle position. An eccentric may also be provided for adjusting the operation of the damper spring to prevent each hammer rebounding against its respective gong.

One disadvantage of this type of striking mechanism with a damper spring is that there is a significant loss of kinetic energy when the hammer strikes the respective gong, which reduces the sound level of the striking action. This loss of energy is due in large part to the deceleration each damper spring exerts on the hammer path as it strikes the gong. Moreover, even if the pre-winding of the drive spring is increased, it still involves adjusting the damping spring by means of its eccentric to avoid any bouncing, which is another drawback of this type of striking mechanism.

Reference may also be made to european patent document EP2048548, which mainly discloses a hammer of a timepiece striking mechanism. The hammer comprises two parts hinged to each other and an elastic element fixed to one of the hinged parts. The resilient spring element secures the two parts of the hammer when the hammer is in the stable position, whereas the two parts move away from each other and are returned by the resilient spring element when the hammer is in the striking position. By this arrangement, the kinetic energy lost by the hammer against the damping element is reduced. However, this type of hammer arrangement complicates the machining of the striking mechanism, which is a drawback, in order to avoid the hammer losing energy when it strikes the gong. During the strike, the hammer may also experience an undesirable rebound of the strike against the gong, which is another disadvantage.

Disclosure of Invention

The aim of the present invention is therefore to overcome the above-mentioned drawbacks of the prior art by providing a timepiece striking mechanism comprising means for increasing the sound level of the sound produced by at least one hammer striking at least one gong during striking and avoiding hammer bounce and loss of energy.

The invention therefore relates to a timepiece striking mechanism comprising the features defined in independent claim 1.

Particular embodiments of the timepiece striking mechanism are defined in dependent claims 2 to 11.

One advantage of the striking mechanism according to the invention lies in the fact that it comprises a damped damping spring which is considered "active", that is to say it does not act immediately to push the hammer back towards the idle position when it strikes the gong. Once the hammer strikes the gong, the damping spring can be actuated with a certain delay by the drive spring abutting against a stop element associated with the damping spring.

Advantageously, the drive spring may take the form of a resilient metal sheet or beam fixed to the plate of the watch and having a free end for pushing the pin or shaft of the rotary hammer when it strikes the gong. The hammer is driven to rotate by the drive spring to strike the gong while preserving the entire striking energy without being braked by the damper spring. This ensures that the sound level produced when the gong is struck by the hammer is increased. The drive spring may also be braked by contacting a stop element associated with the damper spring after said hammer has struck the gong. Once the hammer has struck the gong, the damper spring pushes the hammer towards its idle position to prevent the hammer from bouncing towards the gong. In the idle mode, the hammer shaft is held captive between the free end of the drive spring and one end of the damper spring.

Drawings

The objects, advantages and features of the timepiece striking mechanism with an actively damped shock absorbing spring will become more apparent in the following description with particular reference to the drawings, in which:

FIG. 1 shows a three-dimensional view of the arrangement of spring elements of a striking mechanism with an actively damped damping spring in idle mode, according to the invention, an

Figures 2A to 2E show top views of striking mechanism elements in different positions before, during and after the hammer strikes the gong, according to the invention.

Detailed Description

In the following description, all the parts of a timepiece striking mechanism associated with a timepiece movement known in the art will be described only briefly. The emphasis is primarily on the arrangement of the spring element in the striking mechanism comprising an actively damped damping spring. Due to the different spring elements in the striking mechanism, the hammer loses less energy when it strikes the gong and the safety against any rebound of the hammer striking the gong is improved.

Fig. 1 shows a three-dimensional view of a timepiece striking mechanism 1 in detail. Striking mechanism 1 comprises at least one gong, which is fixed at one end to a gong-holder fixed to the bottom plate 15 of the watch. The other end of the gong is generally free to move. The striking mechanism 1 further comprises at least one hammer mounted rotatably on the bottom plate about an axis 7, in particular close to the gong-carrier. The gong, the gong-carrier and the hammer of striking mechanism 1 are not shown in fig. 1, since they are on the other side of bottom plate 15. This allows the spring element shown in fig. 1 to be easily replaced if necessary.

The striking mechanism 1 further comprises a damped damper spring 5 for keeping the hammer 2 away from the gong in idle mode and a drive spring 3 for the hammer. The drive spring 3 may be wound up by the control rod 11 as described below to drive the hammer 2 to strike the gong in gong strike mode to produce a sound. The damped damper spring 5 is defined as active in that it acts on the hammer just after it strikes the gong to return the hammer to the idle position to avoid any energy loss by the hammer when it acts. This also improves the quality of the generated sound.

As can be seen in fig. 1, the hammer drive spring 3 is fixed at one end 3b of its heel shape to a bottom plate 15 of the watch by a bolt 13. From this heel 3b, the drive spring 3 has a metal sheet or beam exhibiting a U-shape. The beam 3 surrounds a stop element 10 in the form of a control rod which, in combination with the damping damper spring 5, causes the damper spring to actively act as described below. This stop element serves in part as a means of actuating the damping spring. The stop element 10 comprises a first prong 12, the free end of which is intended to come into contact with the middle part of the beam of the drive spring 3. The first stop element bifurcation 12 in contact with the intermediate portion of the spring 3 can take place, for example, at a portion of distance equal to half the length of the beam from the end 3b of the beam fixed to the bottom plate 15. In the idle mode, the middle part of the beam of the drive spring 3 is held in direct contact with this end of the stop element 10.

The free end 3a of the beam of the drive spring 3 may be disposed a slight distance from the hammer shaft 6 (not shown) in the idle mode. However, since the stop element 10 is coupled to the damper spring 5, the first end 5a of the damper spring is actively driven by the hammer shaft 6 via the stop element 10 toward the free end 3a of the drive spring in the idle mode. The hammer is thereby held at a distance by the damping spring 5 abutting on the hammer shaft 6, the hammer shaft 6 projecting from the bottom plate 15 on the spring element side.

The damping shock spring 5 is constituted by a substantially rectilinear control rod rotatably mounted to the bottom plate 15 of the watch about a vertical axis 8. In the idle mode, therefore, the first end 5a of the control rod of the damper spring 5 abuts on the hammer shaft 6 to keep it away from the gong. The second end 5b of the control rod of the damping spring 5 is arranged on the opposite side of the first end 5a with respect to the axis of rotation 8. The eccentric part 4 can be rotatably mounted on the bottom plate 15 of the watch to act as a rotation stop element for the control rod of the damping spring 5.

The first end 5a of the metal damper spring 5 may be slightly bent by the force exerted by the drive spring 3 just after the hammer strikes the gong in strike mode, as described below with reference to fig. 2A to 2E. When the hammer strikes the gong, the first end 5a of the damper shock spring 5 is instantaneously released from the hammer shaft 6. This means that the hammer does not lose energy when it is actuated to strike the gong. However, because of the metallic stop element 10 with the bifurcation 12, which is associated with the damping spring 5, this first end 5a of the damping spring 5 pushes the hammer with a certain delay towards its idle position, just after the hammer has struck the gong.

It is to be noted that in this embodiment, in principle, the eccentric member 4 is not used to act as a fulcrum for the control lever of the damping spring 5 so that the latter pushes the hammer towards its idle position after a strike. The eccentric wheel component may even be omitted from the striking mechanism. The eccentric member 4 is constituted by a wheel which can be brought into contact with one surface of the second end 5 b. This wheel of eccentric part 4 is mounted eccentrically on a rotation pin which is arranged in a hole of the bottom plate 15. The freedom of rotation of the damper spring 5 during the operation of the hammer striking the gong can thereby be adjusted by rotating the eccentric member 4.

In the embodiment of fig. 1, a stop element 10 in the form of a control rod is mounted along the axis of rotation 8 of the damper spring 5. The anchor bolts 17 are provided for assembling the stop element 10 and the damping spring 5 on the base plate 15. The anchor bolt comprises at its bottom a disc fixed to the bottom plate 15 and on the disc a tubular portion which is smooth on the outside and threaded on the inside. The control rod type damping spring 5 is first mounted on the anchor bolt 17 to be supported on the disc of the anchor bolt. To achieve this, the damping spring 5 comprises a through-hole at the axis of rotation 8. The diameter of the through hole is equal to the outer diameter of the tubular portion to allow the damper spring to be assembled on the tubular portion, for example, without a gap. The stop element 10 also comprises a through hole in the intermediate portion 10 a. The diameter of this hole in the stop element is equal to the outer diameter of the tubular portion of the anchor bolt 17 to allow a gapless assembly of the stop element on the tubular portion above the damping spring 5. Once the damping spring 5 and the stop element 10 have been placed on the tubular part of the anchor bolt 17, the bolt 18 is screwed into the threaded part of the tubular part. This bolt 18 is screwed into the mouth of the tubular portion, protruding slightly from a hole in the stop element 10 provided for maintaining the freedom of rotation of the damping spring 5 and the stop element 10 on the bottom plate.

The second eccentric part 14 can also be mounted rotatably on the damper spring 5 for adjusting the position of the stop element 10 on the damper spring 5. The eccentric member 14 comprises a pin inserted in a hole of equal diameter formed in the intermediate portion of the damper spring 5 between the axis of rotation 8 and the second end 5b of the damper spring. Above the pin, the second eccentric part 14 has an eccentric portion arranged in another through hole 24 having a specific shape at one end 10b of the second branch of the stop element 10. Which eccentric portion is in contact with the inner surface of the other through hole 24 in the stop element. This allows the free end of the first lever branch 12 of the stop element 10 to be moved further away from or closer to the gong when rotating the second cam part 14. In this case, the middle part of the pre-strung drive spring 3 comes into contact with the free end of the first lever branch 12 of the stop element 10 more or less quickly when the hammer strikes the gong. This also has the effect of adjusting the time-delay action of the damper spring 5 after the hammer strikes the gong for the first time.

The hammer actuated by the drive spring in operation is rapidly pushed towards the gong before the latter actuates the damper spring by contact on the stop element 10 to push the hammer back into its idle position. Depending on the construction of the spring elements and hammers and their material of construction, the delay before the action of the damper spring 5 may be in the order of 2 milliseconds or so.

In the present embodiment, the first and second lever branches of the stop element 10 are arranged substantially opposite one another with a perforated portion between the two branches. The rotation of the free ends of the first branch 12 and the second branch takes place on the same side with respect to the stop element 10 and the axis of rotation 8 of the damping spring 5. On the path of the drive spring 3 when the hammer strikes the gong, the intermediate portion of the spring comes into contact with the free end of the first lever branch 12 of the stop element 10. The second lever branch of the stop element 10 is normally provided for driving the damper spring 5 so that its first end 5a comes into contact with the hammer shaft 6 in the idle mode. The remaining movement of the drive spring 3 after contact with the stop element 10 during the striking operation can be estimated to be between 0.03 and 0.06 mm. This second lever branch 12 of the stop element 10 can also brake the drive spring 3 when it is applied, at the same time activating the damping spring 5 to clamp the hammer shaft 6 and return it to the idle position. This is achieved with a certain delay with respect to the striking of the gong by the hammer.

In one embodiment, not shown, the bottom of the first lever branch 12 of the stop element 10 may be located at the end 10b of the stop element where the second cam part 14 is located. This gives a perforated portion arranged between the two prongs of the stop element in a reverse manner to the embodiment shown in fig. 1. In this case, the contact of the end of the first prong 12 of the stop element 10 with the drive spring 3 may take place at a portion closer to the free end 3a thereof. The stop element 10 may also have a simple projection instead of a lever. The protruding portion may be formed in the same portion between the two through holes in the stopper member to come into contact with the middle portion of the drive spring 3. In addition to the use of the second cam part 14 for adjusting the position of the stop element 10 on the damping spring 5, the elasticity of the first branch 12 can also be used to adjust the time delay before the damping spring 5 acts.

As shown in fig. 1, the operation of the pre-winding drive spring 3 can be effected by the hammer shaft 6 being driven by a lifting element 11, the lifting element 11 being rotatably mounted on the bottom plate 15 along a rotation axis 27. According to another embodiment, not shown, the lifting element 11 can also be mounted on the axis of rotation 7 of the hammer. The lifting element 11 has, in a known manner, teeth 11a actuated by a toothed wheel 16 rotatably mounted on the bottom plate. The teeth 16a of the wheel 16 are set according to the desired striking timing. Thus, the lifting element 11 can be rotated by the gear wheel 16 in strike mode to wind up the drive spring 3 by pushing the hammer shaft 6 towards the free end 3a of the drive spring 3. When the drive spring 3 is in the pre-chordal position as described below, the damper spring 5 is free to rotate while being constrained in rotation by the first cam member 4.

Depending on the type of material constituting the gong, an initial adjustment must be made by means of the second cam member 14 to avoid any bounce when the hammer strikes the gong. With a gold gong, the impact portion of the hammer may be arranged further away from the gong than a steel gong. However, because of the stop element 10, in the case of any type of gong material, the drive spring 3 can be pre-wound strongly to a greater or lesser extent once the initial adjustment has been carried out.

The different positions of the different spring elements before, during and after the hammer strikes the gong will now be described with reference to fig. 2A to 2E. Parts in figures 2A to 2E that are identical to parts in figure 1 are given the same reference numerals. For the sake of simplicity, a complete description of these individual elements of the striking mechanism 1 will not be repeated.

In fig. 2A to 2E, the main plate is purposely removed to enable each element of striking mechanism 1 to be observed in different operating positions (for example when indicating the preset alarm time of a timepiece). Clearly showing hammer 2 and gong 21 rotatably mounted about axis of rotation 7, one end of gong 21 is fixed to gong-support 22. All other elements are similar to those described with reference to fig. 1 and are shown at least in part in fig. 2A to 2E.

To further improve the sound quality of gong 21 when gong 21 is struck by hammer 2, the hammer may be made of a hard material, such as tungsten carbide cobalt (WCCo) or a ceramic or diamond material. At least the portion 2a of hammer 2 that strikes gong 21 should be made of this hard material. Moreover, the material of the hammer 2 may also have a greater density. This allows for increased energy when the hammer strikes the gong at a given hammer strike speed. Since the damper spring 5 only acts after a certain delay to return the hammer to the idle position, the damper spring 5 does not cause any energy loss when the hammer strikes. The damping spring 5 can also be made of hard metal or steel, similar to the stop element 10, while the drive spring 3 can be made of conventional spring steel.

Gong 21 may be made in the shape of at least a portion of a circle or a rectangle. The gong may also be a metal wire, for example of circular or rectangular cross-section, usually made of steel or noble metal or metallic glass. Conventionally, this circular or rectangular portion surrounds a portion of a timepiece movement (not shown).

Fig. 2A shows only a top view of the idle mode striking mechanism 1, as previously described with reference to fig. 1. In this idle position, the free end 3a of the drive spring 3 and the end 5a of the damper spring 5 clamp the shaft 6 of the hammer 2. The end 5a of the damping spring is pushed towards the shaft 6 by the pressure of the drive spring 3 against the first branch 12 of the stop element 10. The striking portion 2a of hammer 2 is kept away from gong 21. Even in the event of a strike on the timepiece equipped with this striking mechanism 1, the hammer 2 is still held at a distance by the damping spring 5 and the drive spring 3.

After the idle mode, the drive spring 3 is pre-wound at the beginning of the striking mode, which is partially shown in fig. 2B. The drive spring 3 is shaped such that it can be pre-wound with a maximum force of around 1N. The operation of the pre-strung drive spring 3 can be effected by means of a hammer shaft 6, the hammer shaft 6 being driven by a lifting element 11 which is rotatably mounted on the bottom plate 15 along the axis of rotation 27. The lifting element 11 is driven in rotation by its teeth 11a, the teeth 11a being actuated by one of the teeth 16a in a toothed wheel 16 rotatably mounted on the plate 15. When the spring is in this pre-winding position, the striking portion 2a of hammer 2, ending in a flange shape, is further away from gong 21. In this position, the damping damper spring 5 and the stop element 10 are no longer in contact with the shaft 6 of the hammer 2 and the drive spring 3.

In fig. 2C, the lifting element 11 is released, which allows the pre-strung drive spring 3 to drive the hammer 2 towards the gong. At this hammer driving stage and under the urging of the drive spring 3, it is noted that the rotational speed of the hammer 2 becomes higher than the rotational speed of the drive spring which comes into slight contact with the first branch 12 of the stopper element. In this case, it is to be noted that in fig. 2C, since the hammer is rotated about its rotational axis faster than the drive spring, the shaft 6 of the hammer 2 is no longer in contact with the free end 3a of the drive spring 3. The damping spring 5 is of course no longer active and does not brake the hammer when it rotates in the direction of the gong 21.

In fig. 2D, the striking portion 2a of the hammer 2 strikes the gong 21 at its fastest speed without being braked by the damper spring 5, which improves the resulting sound quality compared to conventional striking mechanisms. The striking time period of hammer 2 against gong 21 from the pre-winding position of drive spring 3 may be in the order of 0.2 milliseconds. The drive spring 3, which is active and in contact with the stop element 10, actuates the damper spring 5 with a certain time delay with respect to the striking of the hammer 2 against the gong 21. The delay may be around 2 milliseconds. The stop element 10 mounted on the damper spring 5 thus acts as a sensor for triggering the damper spring 5 at the desired moment.

As shown in fig. 2E, once the hammer has struck the gong, the damper spring 5 is actuated by the drive spring 3 in contact with the stop element 10. The actuated damper spring can thus push the hammer 2 towards the idle position through the shaft 6 of the hammer 2. From this point on, the damper spring 5 is coupled to the drive spring 3 to prevent the hammer from rebounding against the gong.

From the description given immediately above, those skilled in the art will be able to devise several variants of a timepiece striking mechanism incorporating an active damping spring without departing from the scope of protection of the invention defined by the claims. The stop element and the damping spring may form a single component. Other means may be provided for actuating the damper spring with a certain time delay after the hammer strikes the gong. The trigger means may force the damper spring back to the retracted position when the drive spring is pre-wound. Once the hammer first strikes the gong, the triggering device releases the damper spring, so that the damper spring pushes the hammer towards the idle position without rebounding against the gong. The hammers may be mounted on the plate to strike the gong along a linear path rather than a rotational path. Several gongs of different lengths may be provided, fixed or integral with the same gong-support mounted on the bottom plate or on a part of the watch case. Each gong is struck by a respective hammer, each of which is driven by its own drive spring. It is therefore necessary to provide each hammer with a damped damper spring in combination with a stop element.

Claims (11)

1. Timepiece striking mechanism (1), said mechanism comprising:

a gong (21) connected to a gong-support (22),

-a hammer (2) mounted on the bottom plate for striking the gong (21) at a predetermined moment, the hammer comprising a shaft (6),

-a damped damping spring (5) for keeping the hammer away from the gong (21) in idle mode, and

-a driving spring (3) for a hammer, comprising a fixed end (3b) and a freely movable end (3a), said driving spring being capable of being wound to drive said hammer (2) to strike a gong (21) in strike mode to emit a sound,

characterized in that the striking mechanism comprises means (10) for actuating the damping spring (5) with a certain delay after the hammer (2) strikes the gong (21) in the striking mode, so that after the hammer strikes the gong, the damping spring pushes the hammer towards the idle position, said damping spring (5) being defined as active to act on the hammer just after the hammer strikes the gong to return the hammer to the idle position in order to avoid any energy loss caused by the hammer when it acts, and said means for actuating the damping spring (5) in the striking mode comprise stop elements (10,12) arranged in the path of the drive spring;

the stop element is in the shape of a lever and comprises a first branch (12) which, when it is applied, brakes the drive spring, while activating the damping spring to clamp the hammer shaft and return it to the idle position.

2. Striking mechanism (1) according to claim 1, characterized in that the free end (3a) of the drive spring is intended to drive the hammer (2) against the gong (21) in the striking mode, and in that the intermediate portion of the drive spring (3) is intended to come into contact with the stop element (10) when active in order to actuate the damping spring after the hammer strikes the gong.

3. Striking mechanism (1) according to claim 1, characterized in that the drive spring is provided in the form of a spring beam or leaf (3) such that the middle part of the pre-wound drive spring comes into contact with the stop element (10) after the hammer strikes the gong to actuate the damped damper spring (5).

4. Striking mechanism (1) according to claim 1, characterized in that the damped damper spring (5) is a lever rotatably mounted on the bottom plate (15) along the axis of rotation (8), a first end (5a) of the lever being intended to push the hammer (2) backwards towards the idle position after the hammer strikes the gong.

5. Striking mechanism (1) according to claim 1, characterized in that the hammer (2) is rotatably mounted on the plate (15) along a rotation axis (7) substantially perpendicular to the plate plane, and in that the shaft (6) is driven by the free end (3a) of said drive spring which is active when the hammer strikes the gong (21).

6. Striking mechanism (1) according to one of claims 4 and 5, characterized in that the lever of the damping shock spring (5) comprises a second straight end (5b) on the opposite side of the first end (5a) with respect to the axis of rotation (8), and in that the first eccentric member (4) is rotatably mounted on the bottom plate (15) as a rotation stop element for the damping shock spring lever second end.

7. Striking mechanism (1) according to claim 1, characterized in that it comprises a lifting element (11) rotatably mounted on the bottom plate along the rotation axis (7) of the hammer (2) or on a rotation axis (27) parallel to the rotation axis of the hammer (2), said lifting element being arranged for pushing the shaft (6) of the hammer (2) through the free end (3a) of the drive spring (3) to arrange the drive spring in the pre-winding position away from the stop element (10), while arranging the damping spring to be freely movable before being able to be actuated after the hammer strikes the gong (21).

8. Striking mechanism (1) according to claim 1, characterized in that the free end of the first branch (12) is arranged to come into contact with the middle part of the drive spring when the hammer strikes the gong, and in that the stop element (10) is mounted on the damped damping spring (5) to actuate it after the hammer strikes the gong.

9. Striking mechanism (1) according to claim 8, characterized in that the intermediate portion (10a) of the stop element (10) is mounted along the axis of rotation (8) of the damping spring (5) in the form of a lever to constitute the base of the first branch (12) of the stop element.

10. Striking mechanism (1) according to claim 9, characterized in that one end (10b) of the second branch of the stop element (10) is connected to the damped damping spring by means of a second cam part (14) to adjust the position of the stop element on the damped damping spring (5).

11. Striking mechanism (1) according to claim 1, characterized in that the stop element (10) and the damping spring (5) constitute a single component.