Patent Application
20110158058
This application claims priority from Swiss Patent Application No. 02002/09 filed Dec. 24, 2009, the entire disclosure of which is incorporated herein by reference.
The invention concerns a strike mechanism for a watch. The mechanism includes at least one hammer arranged for striking at least one gong, secured to a gong-carrier, at determined times. Said hammer is held at a distance from the gong by a damping counterspring in an idle mode. A spring driving the hammer of the mechanism can be configured in the form of a resilient strip or beam. This drive spring can be wound to drive said hammer against the gong to provide an acoustic signal, for example of a programmed time period.
Within the field of watchmaking, a strike mechanism can be combined with a conventional timepiece movement to act as a minute repeater or to indicate a programmed alarm time. This type of strike mechanism generally includes at least one gong made of metallic material, such as steel, bronze, precious metal, metallic glass, sapphire or quartz. This gong may describe, for example, at least one portion of a circle around the timepiece movement in the watch frame. The going is secured via at least one end thereof to a gong-carrier, which is itself integral with a watch plate. A hammer of the mechanism is rotatably mounted on the plate, for example in proximity to the gong-carrier, so as to strike the gong to make it vibrate. The sound produced when the hammer strikes the gong is within the audible frequency range from 1 kHz to 20 kHz. This indicates a well defined time, programmed alarm or minute repeater to the person wearing the watch.
As shown in EP Patent No. 1 574 917, the strike mechanism of a watch may include two gongs secured via one end thereof to the same gong-carrier, which is itself integral with a plate. Each gong can be struck by a respective hammer. To achieve this, each hammer is driven by its own drive spring, which has to be pre-wound, so as to drive the hammer against the gong to indicate a minute repeater or alarm time. Two damping countersprings are provided for pushing back the hammers and holding them at a distance from the gongs in the idle mode. The damping countersprings also slow down the fall of each hammer prior to striking the respective gong before pushing each hammer back into the idle position. Eccentrics are also provided for regulating the operation of the countersprings to prevent each hammer bouncing against the respective gong.
One drawback of this type of strike mechanism structure with countersprings is that there is a significant waste of kinetic energy from the hammer when the respective gong is struck, which reduces the acoustic level of the strike work. Moreover, even if the pre-winding of the drive springs is increased, this means adapting the countersprings via their eccentric to prevent any bouncing, which is another drawback of this type of strike mechanism.
EP Patent No. 2 048 548, which mainly discloses a hammer for a watch strike mechanism, may also be cited. This hammer has two parts hinged to each other and a resilient element secured to one of the hinged parts. When the hammer is in a stable position, the resilient spring element holds the two parts of the hammer, whereas when the hammer is in the strike position, the two parts move away from each other, returned by the resilient spring element. With this arrangement, it is possible to reduce the kinetic energy wasted by the hammer against a damping member. However, in order to be able to prevent the hammer wasting energy when it strikes the gong, this hammer arrangement makes the strike mechanism more complicated to make, which is a drawback. The hammer may bounce against the gong in an undesirable manner during striking, which is another drawback.
It is thus an object of the invention to overcome the drawbacks of the aforementioned prior art by providing a strike mechanism for a watch, which includes means for increasing the acoustic level of the sound produced by at least one gong struck by at least one hammer, while preventing any bouncing and any waste of energy of the hammer during striking.
The invention therefore concerns a strike mechanism for a watch, including:
Particular embodiments of the strike mechanism for a watch are defined in the dependent claims 2 to 13.
One advantage of the strike mechanism according to the present invention lies in the fact that at least one stop member is provided on the path of the hammer drive spring when the hammer strikes the gong. This generates a catapult effect of the hammer against the gong at the moment that an intermediate part of the hammer drive spring comes into contact with the the stop member. To achieve this, the drive spring may take the form of a resilient metal strip or beam secured to the watch plate with one end free to push a catch or shaft of the rotating hammer when the hammer strikes the gong. The rotational speed of the end of the spring, which comes into contact with the hammer shaft to drive it against the gong, thus becomes greater after contact with the stop member, than the rotational speed of the end of the spring prior to contact with the stop member, which generates the catapult effect. There is thus less wasted energy from the hammer prior to striking the gong yet there is an increase in the acoustic level generated by the struck gong.
Another advantage of the strike mechanism lies in the fact that the hammer drive spring can be pre-wound further. This may be achieved without adapting the damping counterspring due to the presence of the stop member on the path of the hammer drive spring when the hammer strikes the gong. The stop member may be connected to the damping counterspring to activate the counterspring with a certain delay compared to the braking of the drive spring upon contact with the stop member. This also makes it easier to move the hammer away after striking the gong to prevent any bouncing.
The objects, advantages and features of the watch strike mechanism will appear more clearly in the following description, made with reference to the annexed drawings, in which:
In the following description, all those parts of the watch strike mechanism combined with the watch movement that are well known in this technical field will be only briefly described. The emphasis is mainly on the arrangement of the spring elements, including the stop member of the strike mechanism. This stop member guarantees an increase in the strike speed of the hammer with less hammer energy waste, and improved security against any hammer bounce against the gong.
Strike mechanism 1 includes at least one hammer 2 rotatably mounted around an arbour 7 on the plate, in particular in proximity to gong-carrier 22. Strike mechanism 1 further includes a damping counterspring 5 for keeping hammer 2 at a distance from gong 21 in an idle mode, and a spring 3 for driving the hammer. This drive spring 3 may be wound to drive hammer 2 against the gong in a strike mode to produce an acoustic sound.
In
According to the invention, strike mechanism 1 also includes a stop member 10 on the path of drive spring 3 of hammer 2. This stop member 10 is only shown symbolically in
However, it is also possible to envisage hammer shaft 6 being held against counterspring 5, and the intermediate part of spring 3 coming back into contact with stop member 10 before the free end 3a of the spring comes into contact with the shaft 6 of hammer 2 to be driven against gong 21. As soon as the intermediate part of spring 3 enters into contact with stop member 10, the rotational speed of end 3a of active drive spring 3 is observed to increase compared to the rotational speed that precedes contact with stop member 10, which produces the catapult effect. This also prevents any significant loss of kinetic energy when the hammer strikes the gong.
After an idle mode, drive spring 3 is pre-wound at the start of the strike mode as shown partly in
Counterspring 5 is formed in a known manner by a lever or pivoting part, which is rotatably mounted around an arbour 8 secured to the watch plate. A first end 5a of the lever of counterspring 5 abuts against shaft 6 of hammer 2 to hold it at a distance from gong 21. This first end 5a of metal counterspring 5 bends in the strike mode against the force applied by the drive spring 3 in action. After the hammer has struck gong 21, the first end 5a of the lever pushes hammer 2 back towards its idle position. A second end 5b of the lever in the form of a cam is arranged on an opposite side of first end 5a relative to axis of rotation 8. This second end 5b is in contact with an eccentric part 4 rotatably mounted on the plate. This eccentric part 4 includes a regulating wheel, on which an off-centre pin 4a is placed. Pin 4a is in direct contact with one surface of second end 5b of the lever in the form of a cam. By rotating eccentric part 4 on the plate, the operation of damping counterspring 5 can be adjusted, particularly to move the impact portion 2a of hammer 2 away from or closer to gong 21 in an idle mode.
The position of stop member 10 can also be adjusted relative to the beam or strip of drive spring 3. Stop member 10 can be moved in a direction along the metal strip or beam of drive spring 3. This allows the location of the point or line of contact of the intermediate part of drive spring 3 in action against stop member 10 to be altered in strike mode. Thus, the strike speed of hammer 2 may increase more or less sharply after spring 3 comes into contact against stop member 10. Stop member 10 may also be moved in the plane of gong 21 in a perpendicular direction to the gong so that drive spring 3 in action enters into contact with stop member 10 more or less quickly. A combination of adjustment between stop member 10 and counterspring 5 may also be envisaged.
Owing to the use of a stop member 10 on the path of spring 3 for driving hammer 2 against gong 21, spring 3 can easily be pre-wound to a greater or lesser extent without having to adjust damping counterspring 5 to prevent any bounce. Thus an absolute increase in the strike energy of the hammer against the gong can be obtained to increase the acoustic level without any effect on counterspring 5.
It is also to be noted that hammer 2 and gong 21 secured to gong-carrier 22 can preferably be fixed on a side of the plate opposite to the side that carries damping counterspring 5, drive spring 3 and stop member 10. In these conditions, counterspring 5, drive spring 3 and stop member 10 can easily be changed without any contact with the other parts on an opposite side of the plate. However, for the sake of simplification, in
To further improve the sound quality of gong 21 struck by hammer 2, the hammer can be made of a hard material, such as cobalt tungsten carbide (WCCo) or a ceramic material or diamond. At least the impact portion 2a of hammer 2 against gong 21 should be made of hard material. Moreover, the material of said hammer 2 may also have significant density to increase the energy when the hammer strikes the gong at a given strike speed of the hammer. Counterspring 5 may also be made of hard metal or steel, like stop member 10, whereas drive spring 3 can be made of conventional spring steel.
It is to be noted in a variant of the strike mechanism shown in
As
Counterspring 5 is formed, as in the first embodiment of
Unlike the eccentric part shown in
Stop member 10 in this embodiment is mounted on the axis of rotation 8 of counterspring 5. A screw foot 17, which includes a disc at the base thereof fixed to plate 15 and on the disc, a tubular part, which is smooth on the outside and threaded on the inside, is provided for mounting stop member 10 and counterspring 5 on plate 15. Counterspring 5, in the form of a lever, is first of all mounted on screw foot 17 to rest on the disc of the screw foot. To achieve this, counterspring 5 includes a through aperture in proximity to axis of rotation 8, whose diameter is equivalent to the external perimeter of the tubular part, enabling it to be assembled on the tubular part with no play. Stop member 10 further includes a through aperture in an intermediate portion 10a. The diameter of this aperture in the stop member is equivalent to the external perimeter of the tubular part of screw foot 17 for mounting the stop member without any play on the tubular part above counterspring 5. Once counterspring 5 and stop member 10 are arranged on the tubular part of screw foot 17, a screw 18 is screwed into the threaded portion of the tubular part. This screw 18 is screwed in as far as the mouth of the tubular part, which slightly projects from the aperture in stop member 10, positioned for keeping counterspring 5 and stop member 10 free to rotate on the plate.
A second eccentric part 14 can also be provided, rotatably mounted on counterspring 5, for adjusting the position of stop member 10 on counterspring 5. This eccentric part 14 includes a pin inserted in a bore of equivalent diameter made in an intermediate portion of counterspring 5 between axis of rotation 8 and the second end 5b of the counterspring. Above the pin, the second eccentric part 14 has an off-centre portion placed in another through aperture 24 with a particular shape at one end 10b of a second branch of stop member 10. In a known manner, this off-centre portion is in contact with an inner surface of the other transverse aperture 24 in the stop member. When the second eccentric part 14 is rotated, this enables the free end of the first lever branch 12 of stop member 10 to be moved closer to or further from the gong. In these conditions, the intermediate part of pre-wound drive spring 3 returns more or less quickly into contact with the free end of first lever branch 12 of stop member 10 when the hammer strikes the gong.
In this embodiment, the first and second lever branches of stop member 10 are arranged approximately opposite each other with a pierced portion between the two branches. The rotation of the free end of first branch 12 and the second branch occurs on the same side relative to axis of rotation 8 of stop member 10 and counterspring 5. On the path of drive spring 3 when the hammer strikes the gong, the intermediate part of the spring comes into contact first of all with the free end of first lever branch 12 of stop member 10. The second lever branch of stop member 10 is designed normally for driving counterspring 5 such that the first end 5a thereof comes into contact with hammer shaft 6 in the idle mode. In these conditions, the counterspring does not apply any return force against hammer shaft 6 given also that the second end 5b thereof is not in contact with the first eccentric part 4. The hammer strike speed is, however, increased as soon as the stop member acts against the intermediate part of active drive spring 3. This may occur in particular when the second end 5b of the counterspring comes into contact with the first eccentric part 4.
The second lever branch 12 of stop member 10 can also brake active drive spring 3 while generating the desired catapult effect of the hammer against the gong. In this operation for braking stop member 10, which is combined with counterspring 5, counterspring 5 is activated with a certain delay without slowing down the hammer as it falls in the direction of the gong.
As indicated above, when strike mechanism 1 is in an idle mode, the free end 3a of drive spring 3 can be at a distance from the hammer shaft 6 held against the first end 5a of damping counterspring 5. However, the intermediate part of drive spring 3 is abutting against the free end of first lever branch 12 of stop member 10. However, according to this embodiment of
As shown in
Depending upon the type of material forming the gong, an initial adjustment must be made by one or other of eccentric parts 4, 14 to prevent any bounce when the hammer strikes the gong. For a gold gong compared to a steel gong, the impact portion of the hammer can be arranged further away from the gong. However, because of stop member 10, drive spring 3 may be pre-wound to a greater or lesser extent with any type of gong material once the initial adjustment has been performed. As a result of this arrangement of the spring elements of strike mechanism 1, a catapult effect is obtained by the hammer against the gong with increased strike speed following contact of pre-wound active drive spring 3 with stop member 10. The acoustic level produced by the struck gong is thus increased.
From the description that has just been given, those skilled in the art can devise several variants of the watch strike mechanism fitted with a stop member, without departing from the scope of the invention defined by the claims. Several gongs of different lengths can be provided, secured to or integral with the same gong-carrier on the plate. Each gong can be struck by a respective hammer, or each hammer can be driven by its own drive spring with contact with a respective stop member on the path of each drive spring.
| Number | Date | Country | Kind |
|---|---|---|---|
| 02002/09 | Dec 2009 | CH | national |
