The present invention concerns an alarm control mechanism including a member that triggers a striking mechanism, a rotating hour cam with a radial recess, a cam follower that abuts approximately radially against the hour cam and whose movement can activate the striking mechanism trigger, and manual means for setting the alarm time, arranged for adjusting the relative angular position of the hour cam and the cam follower.
The term “alarm” designates not only the striking system in alarm timepieces, but any device that generates a signal (also called an alarm) at a pre-selected time in any timepiece, particularly a watch.
CH Patent No. 341771 illustrates an example of a mechanism of this type and it includes a rocking lever, one arm of which is pushed by a spring to follow the edge of a rotating spiral-shaped cam with an abrupt radial recess. The cam is friction mounted, so that its angular position can be adjusted to set the alarm time, on a wheel, which is driven by the timepiece movement and completes one revolution in twenty-four hours. The other arm of the lever cooperates with the means triggering the striking mechanism and with a push-button for stopping the striking mechanism. This type of lever occupies a considerable amount of space beside the cam, which can be a drawback, particularly in a large complication watch.
The usual alarm control mechanisms, for example that described in GB Patent No. 1397982, include two coaxial wheels with a frontal cam system between them, so that, at the alarm time, one of the wheels moves axially towards the other and thus triggers the striking mechanism. The main drawbacks of these mechanisms are their relative lack of precision as to the moment the alarm is triggered, and problems to reset the system, so that it strikes again 24 hours later without having to be specially reset by action by the user.
It is an object of the present invention to create an alarm control mechanism that largely avoids the aforementioned drawbacks of the prior art, while limiting the space occupied by the mechanism, for example so that the mechanism can be integrated in the movement of a grand complication watch. It is a particular object to create a type of mechanism that can, if necessary, be associated with a minute cam, in order to determine more precisely the instant that the striking mechanism is triggered. Moreover, a particular embodiment of the invention should allow the alarm to strike a second time, several minutes after the alarm time.
According to a basic concept of the invention, there is provided a mechanism as defined in claim 1.
Thus, the kinematic chain from the alarm hour cam to the trigger wheel is concentrated in a compact group of coaxial wheels, which can be carried by a common arbour and occupy a reduced space in the plane. Since, in order to set the alarm time, it is the programming wheel and not the hour cam that is acted upon, there is no longer a need for the hour cam to be friction mounted, so that the entire mechanism can be a positive drive mechanism.
Moreover, according to an improved embodiment, this group of coaxial wheels can also include an alarm minute cam. This cam is driven so that it makes one revolution per hour, and it includes at least one radial notch. The cam follower includes a second finger for abutting against the minute cam. Thus, the moment at which the striking mechanism is triggered is determined by the conjunction of the respective positions of the minute cam notch and the hour cam notch. Because of this feature, the moment at which the striking mechanism is triggered can be determined more precisely.
Other characteristics and advantages of the present invention will appear from the following description of a preferred embodiment in connection with the annexed drawings.
a shows the normal position of the cam follower.
b and 6c show two other operating positions of the cam follower.
The alarm control mechanism shown in
A lever, carried by a pivot 31, forms a striking mechanism trigger 30. A rack 32, located at one end of trigger 30, meshes on toothing 5 of trigger wheel 4. The part of trigger 30 which includes rack 32 is slightly flexible in its plane, which enables the rack to operate like a click on toothing 5, as will be explained below. Trigger 30 is biased in rotation clockwise by a relatively weak return spring (not shown), which is just strong enough to hold rack 32 slightly abutting against toothing 5. Further, when the striking mechanism is in its triggered state, the force of a winding spring R, which acts more powerfully than the return spring, tends to pivot trigger 30 clockwise to hold it pressed strongly against toothing 5 and thus tending to rotate trigger wheel 4 anticlockwise, as indicated by arrow A. The other end of trigger 30 is provided with special members 34 for controlling the working of the striking mechanism, when the trigger pivots clockwise, and the return movement of the trigger when the striking mechanism stops. These members can be of various known types and do not need to be described in detail here.
Reference will now be made more particularly to
The mechanism operates in the following manner. The user sets the alarm time (with a resolution of the order of one minute) by rotating wheel 26 (see
When the alarm striking mechanism is not set, there is no action by winding spring R. Trigger 30 and the cam follower lever 8 are only biased by their weak return springs, so that pin 40 is only gently pushed against the cams and the surprise-piece. Thus pin 40 cannot enter notches 47 and 48, which are covered by projecting portions 53 and 54 of the surprise-piece, since spring 12 offers sufficient resistance to prevent the pin from rotating. Pin 40 slides over the hour cam and passes over the projecting portions of the surprise-piece by sliding over their bevels 55 and 56. Since lever 8 and its pin 40 move very little on wheel 7, wheel 4 and its pinion 6 remain practically stationary and thus do not move trigger 30.
If the alarm striking mechanism is set, this means that spring R acts on trigger 30 and trigger wheel 4 in the direction indicated by arrows R and A (
Several minutes before the alarm time, recess 44 of the hour cam passes in front of pin 40. The pin can then make a slight radial movement to slide against cylindrical part 46 of minute cam 14, as in the situation illustrated in
If the user stops the striking mechanism then, this stops the action of winding spring R and the force F of lever 8 on pin 40. Pin 40 is pushed back out of notch 47 by the flank thereof, thus allowing the surprise-piece to return to cover the notch, so that the pin cannot go back in. When the second notch 48 of the minute cam arrives in front of pin 40, bevel 56 of projecting portion 54 of surprise-piece 11 resists sufficiently to push back the pin and allow said pin to pass, by sliding over the surface 58 of the surprise-piece. Thus, the pin cannot enter the second notch 48. Once the second notch and projecting portion 54 have passed, pin 40 can go back to abutting against hour cam 3, whose notch 43 has finished passing.
If the user has not stopped the striking mechanism at the alarm time the striking mechanism stops by itself after a predetermined time, owing to a suitable mechanism, which also acts on the rack of members 34 to pivot trigger 30 anticlockwise, against the force of spring R. Pin 40 can therefore come back out of notch 47 as previously indicated in the preceding paragraph. Next, the aforecited mechanism stops pushing back trigger 30; the effect of spring R is to press the pin against surprise-piece 11 again, then onto minute cam 14. The cylindrical surface of the cam then slides against the pin in the situation illustrated in
The construction described above could obviously undergo alterations without losing the essential operating feature, which consists in pivoting the trigger wheel in relation to the programming wheel to trigger the striking mechanism. For example, lever 8 could be replaced by a sliding element. Another variant could consist in replacing the rack transmission 37 and pinion 6 by a permanent system of engaging pin 40 in an oblique slot arranged in trigger wheel 4, such that any radial movement of the pin would cause the wheel to pivot and vice versa.
Moreover, it will be noted that the basic concept of the invention can be applied without reactivating the striking mechanism after a few minutes, and even without using a minute cam, if one is satisfied with less alarm time precision.
Number | Date | Country | Kind |
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07150255.3 | Dec 2007 | EP | regional |