HK1174695B - Striking mechanism for a watch with a hammer locking device - Google Patents

Description

Striking mechanism for a watch provided with a hammer locking device

Technical Field

The invention relates to a striking mechanism for a watch provided with a hammer locking device. 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 kept at a distance from the gong by a damped damper spring in idle mode and is locked by a locking device. The drive spring for the hammer in the mechanism may be provided in the form of an elastic band or rod. The drive spring may be strung to drive the hammer to the gong in a strike mode to provide an acoustic signal, for example, for a preset period of time.

Background

In the field of watch manufacturing, the striking mechanism can be combined with a conventional watch movement to act as a minute repeater or to indicate a preset alarm time. This type of striking mechanism usually comprises at least one gong made of sapphire or quartz or metallic material, such as steel, copper, noble metals, metallic glass. The gong may be described as, for example, at least a portion of a circle within the bezel surrounding the watch movement. The gong is fixed by at least one of its ends to a gong-support, which is in turn fixed to the watch motherboard. A 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 striking the gong with the hammer 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 patent application EP1574917a1, the striking mechanism of a watch may comprise two or more gongs, each one fixed by one end to the same gong-holder, which is in turn fixed to the bottom plate. Each gong can be struck 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 for pushing back the two hammers and keeping them away from the gong in idle mode. In the strike mode, the damping damper spring acts to slow down the fall of each gong with a very high force before it hits the corresponding gong. After striking, these damping springs allow each hammer to be pushed back into its idle position. An eccentric may also be provided for adjusting the operation of the damper spring primarily to prevent each hammer from rebounding against the respective gong.

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

Patent application EP1394637a1 also discloses a striking mechanism equipped with at least one gong and a hammer capable of striking the gong at a determined moment. The striking mechanism further comprises control means which provide, on the one hand, a visual indication of the active or inactive state of the mechanism and, on the other hand, enable locking or unlocking of the hammer by means of a push-button. When the hammer is in the unlocked state in the strike mode, there is no means to avoid the hammer bouncing back towards the gong after the first strike of the hammer towards the gong, which is a disadvantage.

Disclosure of Invention

It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art by providing a watch striking mechanism comprising hammer locking means for avoiding the hammer from bouncing against the gong after the first strike in the striking mode, without significant energy losses when the hammer falls down and strikes the gong.

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

Particular embodiments of the watch striking mechanism are defined in the dependent claims 2 to 15.

One advantage of the dotting mechanism according to the invention lies in the fact that: it comprises a locking device fitted with at least one slider or bolt, which locks the hammer after its first impact against the gong in idle mode or in strike mode. The peg may comprise a hook, dedicated to hooking onto a notch formed on the outer periphery of the rotary hammer. When the drive spring is wound up in the striking mode, the hook of the peg moves away from the outer periphery of the hammer so that it no longer directly locks the hammer. After the spring has been wound, the hammer is driven in the direction of the gong to strike it for the first time, before a peg is applied with a certain delay to the outer periphery of the hammer to lock the hammer. This means that the hammer does not bounce against the gong and the damper spring no longer needs to exert a large force on the hammer to return it to the idle position and keep it at a distance from the gong in idle mode.

Drawings

The objects, advantages and features of the watch striking mechanism will become more apparent from the following description with particular reference to the accompanying drawings, in which:

FIG. 1 shows a simplified three-dimensional view of some parts of a striking mechanism equipped with a hammer locking device according to the present invention, an

Fig. 2a to 2c show enlarged plan views of main elements in the striking mechanism equipped with a hammer lock device according to the present invention at different positions from the idle mode to the striking mode.

Detailed Description

In the following description, all the components of a watch striking mechanism known in the art will be described only briefly. The important point is mainly how the hammer locking device operates in idle mode and striking mode to avoid any rebound of the hammer against the gong after the first strike.

Fig. 1 shows a simplified view of a striking mechanism 1 for a watch. The various components of dotting mechanism 1 are typically mounted on a main board or clamping plate, which is not shown to avoid the plethora of fig. 1. The main board is typically positioned above the various illustrated components of the dotting mechanism, while a portion of the clamping plate is positioned below the illustrated components and is also secured to the main board.

Striking mechanism 1 comprises at least one gong 2, which is fixed at one end to a gong-support 3. The gong-carrier can in principle be fixed to the watch bottom plate (not shown), but also to the watch case internal parts. The other end (not shown) of gong 2 is generally free to move. Gong 2 may be made in the form of at least a portion of a circle or rectangle surrounding the watch movement. The gong may also be a wire, for example of circular or rectangular cross-section, usually made of steel or noble metal or metallic glass or another material.

Striking mechanism 1 further comprises at least one hammer 4 rotatably mounted about a central axis 14 between a bottom plate, not shown, and a clamping plate. The hammer is preferably mounted close to gong-support 3. The striking mechanism 1 further includes a damper spring 5 and a drive spring 6 for the hammer. The damping damper spring 5 keeps the hammer 4 at a distance from the gong 2 in idle mode and pushes the hammer back to the idle position in dotting mode. The damping vibration springs 5 and the drive springs 6 take the form of elastic bands. One end 25 of the damper shock spring 5 and one end 26 of the drive spring 6 are fixed to a cleat or a bottom plate (not shown). The free end of the damper spring 5 is kept at a distance from the gong 2 by a shaft 9, the shaft 9 being fixed through a portion of the hammer between the axis of rotation 14 and the impact portion of the hammer.

Drive spring 6 may be wound to drive the hammer in the direction of gong 2 in striking mode, for the purpose of generating sound. The drive spring 6 is pre-wound by a rod 12, the rod 12 being rotatably mounted on the axis of rotation 14 of the hammer 4. The lever 12 has teeth visible in fig. 1, which are typically actuated by a gear (not shown) rotatably mounted on the bottom plate or cleat. When the lever 12 is driven in rotation by one of the teeth of the gear, the lever 12 drives the shaft 9 of the hammer 4 in rotation about its axis of rotation 14 in the counterclockwise direction in fig. 1.

The hammer 4 further comprises a pin 10, the pin 10 being fixed in a hole in the end of the hammer opposite the impact portion with respect to the axis of rotation 14. The pin 10 is preferably arranged parallel to the axis of rotation 14 and extends mainly only on the bottom side of the hammer. When hammer 4 is rotated anticlockwise by the action of rod 12, pin 10 pushes the free end of drive spring 6 towards its pre-chordal position at the start of the dotting mode. A lever spring 11 in the form of a resilient band and fixed at one end 21 to a cleat or a host plate is also provided for pushing the rod 12 through its free end to keep it in contact with the shaft 9.

According to the present invention, the striking mechanism further comprises hammer locking means. The locking device mainly comprises a bolt 8, as will be described in detail below with particular reference to fig. 2a to 2 c. The peg 8 is rotatably mounted between the plate and the plate along a rotation axis 18, the rotation axis 18 being parallel to the rotation axis 14 of the hammer 4. The peg 8 comprises a first arm 8a which may be arcuate in shape. The free end of the first arm 8a is provided with a hooking element in the form of a hook 28. The hook is intended to hook onto or abut on a hooking means, which is a recess 15 formed on the side of the outer periphery of the end of the hammer 4 opposite the striking portion. When the hook 28 comes into contact with the outer periphery of the hammer, it abuts or hooks onto the recess 15 of the hammer to lock the hammer. This prevents the striking portion of the hammer from rotating clockwise in the direction of the gong after the first striking in the striking mode. The notch 15 may be a flat portion provided at a right angle or an acute angle to the side of the hammer to lock the hammer with the hook 28 of the first arm 8 a.

The peg 8 further comprises a second arm 8b, which second arm 8b may be arranged parallel to the first arm 8a and may also be of the same arcuate shape. The free end of the second arm 8b comprises a ramp-shaped portion on which the auxiliary strip spring 6' of the drive spring 6 abuts. The strip spring 6' is formed integrally with the main strip of the drive spring 6 and is made of spring steel. Preferably, this auxiliary strap spring 6' of the locking device is parallel to the main strap of the drive spring 6, wherein the free end of the auxiliary strap spring is arranged slightly behind the free end of the main strap of the drive spring. When the strip spring 6' is on the slope adjacent the second arm, this pushes the peg 8 so that the first arm 8a abuts on the outer periphery of the hammer to lock it. However, when the drive spring 6 is pre-wound, the strip spring 6' no longer abuts against the inclined surface of the second arm 8 b.

The locking device further comprises a bolt spring 7 in the form of a rod which is rotatably mounted on the clamping plate about a rotational axis 17, and the rotational axis 17 is for example parallel to the rotational axis 14 of the hammer 4. The bolt spring 7 comprises an elastic band, the first free end of which rests on a portion of the drive spring 6 in order to be able to generate a return force in the clockwise direction. Bolt spring 7 further includes a portion of the second end proximate rotational axis 17. When the auxiliary strip spring 6' is no longer in contact with the inclined surface of the second arm 8b, the end edge of the bolt spring 7 acts to push the second arm 8b away from the outer periphery of the hammer. This end pushes the second arm 8b by the force generated by the bending of the strip when it abuts on the drive spring 6. This also moves the hook 28 of the first arm 8a away from the outer periphery of the hammer 4 so that it no longer locks the hammer.

The end of bolt 7 further comprises a recess in the shape of a segment of a circle for receiving pin 10 of hammer 4 when the hammer strikes the gong for the first time. The end of bolt 7 keeps second arm 8b and first arm 8a at a distance from the outer periphery of hammer 4 before the hammer strikes gong 2. In the striking mode, when hammer 4 is driven by drive spring 6 in the direction of gong 2, hook 28 of first arm 8a cannot yet be hooked onto notch 15 of the hammer, since the end of bolt 7 still keeps second arm 8a at a distance. The auxiliary strip spring 6' comes into contact with the inclined surface of the second arm when the hammer is driven, but there is not sufficient force to push the second arm 8b directly in the direction toward the outer periphery of the hammer to lock the hammer. The force also depends on the inclination of the ramp which can be adjusted.

Once the hammer strikes the gong 2 for the first time, the hammer pin 10 enters the circular groove at the end of the bolt 7. By the movement of the pin 10 in said groove, the end of the bolt spring 7 is forced to rotate slightly in the counter-clockwise direction in fig. 1. The first end of the elastic band of the bolt spring 7, which is in contact with the driving spring 6, is then bent. This has the effect of allowing the auxiliary strip spring 6' to contact the inclined surface of the second arm 8b to push the second arm 8b and the first arm 8a in the direction of the outer periphery of the hammer 4. The hook 28 of the first arm 8a thus abuts on the notch 15 of the hammer after the first strike of the gong, at which time the hammer is pushed back into the idle position by the damping spring 5. Once hammer 4 returns to the idle position, the end no longer has sufficient force to push second arm 8b away from the hammer, due to the contact between the tip of auxiliary strip spring 6' and the inclined surface. It is therefore the object of the present invention that the hammer is directly locked after a single strike of the gong without any subsequent bounce.

Due to the hammer locking device, the damper spring 5 no longer requires a large reaction force to return the hammer to the idle position after the gong has been struck. In contrast, according to the present invention equipped with the above-described locking device, the damper spring 5 needs only an action force of the order of 0.1N to return the hammer to the idle position. With conventional striking mechanisms, the damper spring theoretically has to push the hammer back with a force of the order of 3N to avoid any bounce. The pre-strung drive spring typically generates a force in the order of 1N for pushing the hammer towards the gong.

For a better understanding of the locking means in the striking mechanism according to the present invention, reference is made to fig. 2a to 2 c. These figures 2a to 2c show enlarged views of the locking means of the mechanism, the elements of which are shown from below with respect to figure 1. Fig. 2a shows the striking mechanism in the idle position, and the bolt 8 of the locking device, which locks the hammer 4. Fig. 2b shows the initial position of the dotting mode and the pre-wound drive spring. Finally, fig. 2c shows the moment when the hammer 4 strikes the gong for the first time, in which the first arm 8a and the second arm 8b are driven back into contact with the outer periphery of the hammer, but before the hammer is locked.

In fig. 2a, the striking mechanism is in idle mode. The bolt 8 of the locking device keeps the hammer 4 locked. To achieve this, the peg, which is mounted rotatably about a rotation axis 18, preferably perpendicular to the bottom plate, comprises a first arm 8a and a second arm 8b, substantially similar in shape and arranged parallel to the first arm. The first arm 8a comprises a hook 28 at one end, the hook 28 abutting or hooking onto the recess 15 of the hammer 4 in fig. 2 a. The second arm 8b is pushed toward the hammer outer periphery by the auxiliary strip spring 6' contacting the inclined surface 30 of the second arm. The auxiliary strip spring 6' pushes the second arm against the repulsive force generated by the corner 26 of the end of the bolt spring 7 acting on the edge 29 of the end of the second arm 8 b. In this case, the bolt spring 7 cannot generate a sufficient force with respect to the force of the auxiliary strip spring 6' through the corner 26 to push the second arm 8b and the first arm 8a away from the outer periphery of the hammer 4 through the inclined surface 30. In the idle mode, the friction of the auxiliary strip spring 6' on the inclined surface 30 and the inclination of the inclined surface also play a role in keeping the hammer in this locked position.

In the idle mode of the striking mechanism, the ends of the damper springs 5 are theoretically in contact with the hammer shaft 9. A lever 12 rotatably mounted about a rotational axis 14 of the hammer 4 is urged against the shaft 9 by a lever spring, not shown. The free end of the drive spring 6 is not in contact with the pin 10 nor is the pin 10 in contact with the circular recess 27 at the end of the bolt spring 7.

The movement of the elements in the mechanism during the change of the dotting mechanism from idle mode to dotting mode is illustrated by the arrows indicated by the dashed lines. The lever 12 is driven to rotate clockwise by a gear (not shown). This rotation of the lever 12 has the effect of moving the shaft 9 and the pin 10 clockwise relative to the axis of rotation 14 of the hammer 4. Once the pin 10 is in contact with the free end of the drive spring 6, the pin 10 pushes the drive spring 6 to the pre-chordal position as shown in fig. 2b below. The movement of the drive spring means that the auxiliary strip spring 6' is no longer in contact with the ramp 30. This allows the end corner 26 to push the edge 29 of the second arm 8b of the bolt 8 away from the outer periphery of the hammer 4.

Fig. 2b shows the initial dotting mode position and the pre-strung drive spring 6. In this position, the free end of the damper spring 5 is no longer in contact with the shaft 9, since the lever 12 has been rotated via the gear to the maximum position. The pin 10 keeps the drive spring 6 in a pre-wound state. The auxiliary strip spring 6' is no longer in contact with the inclined surface 30 and the corner 26 has pushed the edge 29 of the second arm 8b towards the outside of the outer periphery of the hammer 4. In this case, the force generated by the bending of the elastic band of the bolt spring 7 when it abuts on the drive spring 6 becomes minimal.

Fig. 2c shows the moment when the hammer 4 strikes the gong for the first time, in which the first arm 8a and the second arm 8b are driven back into contact with the outer periphery of the hammer, but before the hammer is locked. Driven by drive spring 6 from its pre-sprung position towards the gong, hammer 4 strikes the gong for the first time. When the striking portion of the hammer comes into contact with the gong, the pin 10 of the hammer 4 comes into contact with the circular groove 27 at the end of the bolt 7. The effect of the contact of the pin 10 in the recess 27 is to rotate the bolt spring 7 clockwise as shown by the arrow shown in dotted lines. Since the hammer is sufficiently heavy, it exerts a large force in the recess 27 to rotate the end of the bolt spring 7 against the bending force of its elastic band abutting on the drive spring 6.

The auxiliary strip spring 6' abuts on the inclined surface 30 to move the bolt 8 in the direction of the outer periphery of the hammer. However, since the hammer has just struck the gong for the first time, the hook 28 of the first arm 8a has not yet had time to hook onto the notch 15 of the hammer. It is the object of the present invention that this hook 28 will hook onto the recess 15 of the hammer to keep it locked only after the hammer 4 has struck the gong for the first time, when the damper spring 5 pushes the hammer back into its idle position.

Thanks to the locking device in the striking mechanism according to the invention, any rebound of the hammer against the gong is avoided. It is not necessary for the striking mechanism to be provided with a damper spring that urges the hammer back to its rest position with a large force. The force of the damper spring can be minimized, which provides the advantage that the kinetic energy loss of the hammer when it strikes the gong is minimized to produce sound of sufficient sound level.

From the description given immediately above, a person skilled in the art will be able to devise several variants of a watch striking mechanism equipped with a locking device without departing from the scope of protection of the invention as defined by the following claims. The auxiliary band spring, once machined, may be bolted or welded to the main band of the drive spring. The bolt spring may be disposed about the rotational axis of the bolt. The bolt may have only one arm with at least one hook at its end and a support element for the auxiliary strip spring and possibly for the bolt spring. The bolt may be set in a locking or unlocking position of the hammer by linear movement. The hammer may be arranged to move in a linear manner to strike the gong. The shaft and/or the pin of the hammer can be made directly in one piece from the material of the hammer.

Claims (15)

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

a gong (2) connected to a gong-support (3),

-a hammer (4) for striking the gong (2) at a predetermined moment,

-a damped damping spring (5) for keeping the hammer at a distance from the gong (2) in idle mode, and

-a driving spring (6) for the hammer, comprising a fixed end and a freely movable end, said driving spring being capable of being wound up to drive said hammer (4) towards the gong (2) in a striking mode to generate sound,

characterised in that the striking mechanism comprises locking means fitted with at least one bolt (8) for locking the hammer (4) in the idle mode and moving away from the hammer when winding the drive spring (6) in the striking mode, the locking means being arranged such that the drive spring drives the hammer to strike the gong for the first time before said bolt locks the hammer in the idle position.

2. Striking mechanism (1) according to claim 1, characterized in that the hammer is rotatably mounted on the watch bottom plate around a rotation axis (14) and in that the hammer comprises an impact portion capable of striking the gong (2) at a predetermined moment and an end portion having hooking means (15) for locking means.

3. Striking mechanism (1) according to claim 2, characterized in that the hooking means comprise a notch (15) formed on the side at the outer periphery of the end of the hammer.

4. Striking mechanism (1) according to claim 3, characterized in that the recess (15) is arranged on the opposite side of the axis of rotation (14) to the impact portion of the hammer (4).

5. Striking mechanism (1) according to claim 1, characterized in that the drive spring (6) and the damping shock spring (5) are provided in the form of strip springs, one end of which is fixed to the bottom plate or bridge of the watch and the other end is free to move.

6. Striking mechanism (1) according to claim 5, characterized in that the hammer (4) comprises a shaft (9) on the striking part side of the hammer in contact with the free end of the damped damper spring (5) to keep the hammer at a distance from the gong in idle mode or to push the hammer back to idle position.

7. Striking mechanism (1) according to claim 5, characterized in that the hammer (4) comprises a pin (10), the pin (10) being arranged in the end of the hammer on the opposite side of the hammer impact portion with respect to the hammer rotation axis (14), and in that the free end of the drive spring (6) is intended to strike the gong (2) by means of the pin (10) driving the impact portion of the hammer when the drive spring is pre-strung in the striking mode.

8. Striking mechanism (1) according to claim 1, characterized in that the bolt (8) of the locking device is rotatably mounted on the bottom plate or bridge of the watch about the axis of rotation (18) and in that the bolt (8) comprises a first arm (8a) provided at its free end with a hooking element in the form of a hook (28) for locking the hammer.

9. Dotting mechanism (1) according to claim 8, characterized in that the hook (28) of the peg is intended to hook onto a recess (15) on the end of the hammer.

10. Striking mechanism (1) according to claim 8, characterized in that the bolt comprises a second arm (8b) on the free end of which an auxiliary strip spring (6') fixed to the drive spring (6) abuts, the auxiliary strip spring (6') being intended to push the second arm in the direction of the outer periphery of the end of the hammer, so that the hook (28) hooks onto the recess (15) of the hammer after the first strike of the hammer against the spring in the idle mode or in the striking mode.

11. Dotting mechanism (1) according to claim 10, characterized in that the auxiliary strip spring (6') is formed integrally with the drive spring (6), arranged substantially parallel to the drive spring and directed towards the free end of the drive spring.

12. Dotting mechanism (1) according to claim 11, characterized in that the free end of the auxiliary strip spring (6') is a ramp (30) for abutting against the free end of the second arm (8 b).

13. Striking mechanism (1) according to claim 10, characterized in that the second arm (8b) of the bolt (8) is pushed by the corner (26) of the first end of the bolt spring (7) in contact with the free end of the second arm (8b) towards a position at a distance from the hammer outer periphery when the auxiliary strip spring (6') is no longer in contact with the free end of the second arm (8b) in the striking mode.

14. Striking mechanism (1) according to claim 13, characterized in that the bolt spring (7) is rotatably mounted around the rotation axis (17) and is in the form of a strip spring, wherein the free second end of the bolt spring is in contact with a part of the drive spring (6) and is thus able to bend and provide a repelling force to a corner (26) at the first end of the bolt spring to push the second arm (8b) away from the outer periphery of the hammer.

15. Striking mechanism (1) according to claim 13, characterized in that the first end of the bolt-spring (7) comprises a circular recess (27) for receiving the pin (10) of the hammer after the first strike of the hammer on the bolt in the striking mode in order to move the corner (26) of the first end of the bolt-spring (7) and to allow the auxiliary strip-spring (6') to push the second arm (8b) in the direction of the outer periphery of the hammer (4) so as to lock the hammer after the first strike of the hammer on the hammer.