This application claims priority from European Patent Application No 16151735.4 of Jan. 18, 2016, the entire disclosure of which is hereby incorporated herein by reference.
The invention concerns the field of timepiece movements having an analogue display. It concerns, in particular, the shock resistance of a mechanism driving an analogue indicator, particularly a disc bearing calendar data and in particular a date ring. The invention concerns firstly electromechanical movements provided with an electromagnetic motor as the drive source for the analogue indicator drive mechanism. However, it may also be applied to purely mechanical movements.
In particular, the invention finds a specific application in an electromechanical movement having two analogue indicators driven by the same single motor and arranged such that at least one of the two indicators can be actuated to display its function without the other indicator being driven.
In most known date display devices, the positioning of the date ring in the successive display positions is generally ensured by a jumper spring associated with the date ring toothing. Conventional drive systems do not ensure sufficient retention of the date ring in the event of shocks and therefore generally any locking. Thus, it is the jumper spring that has to ensure this locking function, which is why it has a high elastic constant. It will be noted that, to overcome the elastic force of the jumper spring, a high torque must be provided at the date ring.
However, to overcome the problem of the positioning jumper spring also having an anti-shock function, EP Patent Application 2927756 proposed a date ring drive mechanism including an irreversible transmission system capable of ensuring the anti-shock function while the positioning of the date ring is still ensured by a jumper spring, which then has a lower elastic constant. This document proposes, in particular, one embodiment with a pinion formed of two diametrically opposite pins relative to the axis of rotation of the pinion. In this document, a large play is provided between the pin and the ring toothing to ensure interference-free driving, particularly without locking. As the positioning jumper spring holds or returns the ring in or to a position where the axis of rotation of the pinion substantially intercepts the central axis of the tooth inserted between the pins, the pins penetrate the hollows of the toothing without risk of locking. To ensure this function, the pins are even truncated on the side of the rotational axis. It will be noted that the toothing has hollows with sides that close towards the bottom of the toothing. One problem with the embodiment represented in
Moreover, there is known from U.S. Pat. No. 6,185,158 an electronic watch fitted with an analogue display for several time parameters, in particular the hours, minutes and seconds, by means of three coaxial hands located at the centre of the watch dial. Further, the analogue display includes a chronograph hand, in particular a minute hand for the measured time interval, associated with a circular graduation over 360°, and a date display utilising a date ring, the displayed date appearing in conventional manner through an aperture in the dial. This Patent proposes to actuate the mechanism driving the chronograph hand (hereafter the “first mechanism”) and the mechanism driving the date ring (hereafter the “second mechanism”) via the same single electromechanical motor.
The first mechanism includes an intermediate wheel driven directly by the rotor of the motor and a chronograph wheel that meshes with the intermediate wheel. The second mechanism also includes said intermediate wheel and also an auxiliary wheel meshing with said intermediate wheel. The auxiliary wheel is integral with a wheel set that periodically actuates a wheel driving the date ring, this wheel set having a finger for actuating the drive wheel. The periodic actuation wheel set and the drive wheel together form a Geneva mechanism, known for periodically driving a date ring/disc. On each rotation of the periodic actuation wheel set, the finger drives the date ring drive wheel, which is driven in rotation over an angular distance corresponding to the change from one date to the next in the aperture in the dial provided for the date display. The Geneva mechanism is thus characterized by the periodic driving of the date ring drive wheel, with the periodic actuation wheel set only meshing with the drive wheel over an angular sector of less than 360°, whereas the wheel set locks the drive wheel on the remaining angular sector. Thus, although the periodic actuation wheel set rotates when positioned in the remaining angular sector, the rotational motion of the rotor is not transmitted to the date ring.
U.S. Pat. No. 6,185,158 uses the Geneva mechanism to enable the motor used for driving the date mechanism to perform an additional function, namely driving a chronograph hand. In short, the method consists in driving the chronograph hand when said periodic actuation wheel set is in its area of non-actuation, i.e. in said remaining angular sector, and, at the end of the measured time interval, in performing a reverse reset to return the periodic actuation wheel set to a predefined initial position.
The Geneva mechanism or a similar Maltese cross mechanism are relatively complex for the driving of a date ring. They require low tolerances for such a mechanism to be efficient and there is a risk of locking. Moreover, they are relatively bulky.
It is a first object of the invention to propose a timepiece movement equipped with an analogue display device for an item of information whose value varies periodically or intermittently, and wherein the periodic or intermittent drive mechanism for the indicator of this display device is relatively inexpensive, simple to assemble and limits the space required inside the timepiece movement, while providing an anti-shock function and proper positioning of the indicator in the plurality of discrete positions of the analogue display device.
“Periodic driving” means driving that occurs only periodically, that is to say the driving occurs periodically during a limited time interval and that no driving occurs between the limited time intervals. Likewise, “intermittent driving” means discontinuous driving which stops and starts according to the command of the intermittent drive mechanism without the driving necessarily occurring at regular intervals.
It is a second object of the invention to provide a timepiece movement that satisfies the aforementioned first object and wherein said drive mechanism allows the efficient positioning of the indicator in a plurality of discrete positions without requiring a jumper spring, in particular ensuring such positioning over a certain angular range of a rotating wheel set actuating the indicator, so as to allow a certain tolerance in the assembly of this rotating wheel set relative to its initial angular position and also to ensure proper positioning of the indicator even in case of missed steps during actuation of the drive mechanism by a stepping motor causing a variation in the angular position of the rotating wheel set in its rest positions.
It is a third object of the invention to provide a timepiece movement that satisfies the second aforementioned object and wherein said rotating wheel set has at least a certain dead angle for driving the aforementioned display device indicator, the anti-shock function and the positioning of the indicator being ensured during a rotation of the rotating wheel set in the dead angle zone defined by this dead angle. Such a timepiece movement allows a fourth object of the invention to be satisfied, consisting in arranging a second analogue display, comprising a second indicator kinematically connected to said drive mechanism, such that the second indicator is driven by the drive mechanism to indicate a second item of information, while the rotating wheel set remains in the dead angle zone.
These various objects are achieved by a timepiece movement provided with an analogue display device for an item of information whose value varies periodically or intermittently, this analogue display device including an indicator for said information provided with a toothing and a mechanism for the periodic or intermittent driving of the indicator, this mechanism comprising a rotating wheel set whose pinion, in a meshing relationship with the indicator toothing, is formed of two pins which are diametrically opposite relative to the rotational axis of the pinion, these two pins being configured to alternately penetrate successive hollows in the toothing and to form a self-locking system if the timepiece movement is subjected to shocks, at least when the pinion is in either of the two tangential positions where the two pins are oriented substantially tangentially to the toothing. In a general plane of the toothing perpendicular to the axis of rotation of the rotating wheel set, each of the two pins has a transverse profile having a first outer portion which is substantially in the arc of a circle centred on the axis of rotation of the rotating wheel set. In a particular embodiment, the two pins of the pinion are configured with respect to the indicator toothing such that there is a dead angle (α) for driving the indicator via the pinion in at least one direction of rotation from each of the two tangential positions of the pinion, the dead angle being in a first variant substantially equal to or greater than fifteen degrees (15°=<α), and in a second advantageous variant substantially equal to or greater than twenty-five degrees (25°=<α). In another variant, the arc of a circle of the transverse profile of the two pins extends over an angular distance substantially equal to or greater than the dead angle. In a preferred variant, the arc of a circle of the transverse profile of the two pins extends over an angular distance (β) comprised between 3/2 multiplied by the aforementioned dead angle and substantially two times said dead angle (3α/2<β<2α).
The invention will be described below with reference to the annexed drawings, given by way of non-limiting example, and in which:
Referring to
To hold the date ring in a plurality of distinct positions in which it remains stationary during successive date display periods, a positioning jumper spring 14 is provided. This jumper spring is arranged to be stably inserted between two adjacent teeth of the toothing in each of the plurality of distinct positions of ring 4. This jumper spring is preferably sized to ensure precise positioning of ring 4, given the considerable play between the two pins 22, 23 and toothing 5 and also the relatively large dead angle a for pinion 12 on its rotation from its two tangential positions. However, the jumper spring is not provided here for an anti-shock function so that the elastic constant can be lower than in conventional devices.
Timepiece movement 2 further includes a second indicator 18 kinematically connected to mechanism 8 driving first indicator 4, this second display being arranged such that second indicator 18 can be driven by this drive mechanism to indicate a second item of information, in particular relating to a measured time interval, while rotating wheel set 10 remains in one or other of the two dead angle zones for driving the first indicator. Indeed, the two pins of pinion 12 are configured with respect to date ring toothing 5 such that there is a dead angle α for driving the indicator by the pinion in at least one direction of rotation from each of the two tangential positions of the pinion; the rotating wheel set thus does not drive the date ring in two dead angle zones defined within an angular marker connected to the timepiece movement and centred on the axis of rotation A10 of the rotating wheel set, these two dead angle zones comprising at least the dead angle indicated respectively from the two tangential positions of the pinion. As represented in
Timepiece movement 2 has several advantages, particularly in relation to the driving of two indicators supplying independent items of information (date and measured time interval) by means of the same single drive source and with the anti-shock function obtained via a relatively simple, inexpensive system that is easy to mount inside the timepiece movement. However, this timepiece movement has some drawbacks. Firstly, the pins are relatively small. There is therefore a real risk of them being damaged when the timepiece movement is subjected to a shock, especially of them being permanently deformed by bending under the force exerted by the toothing on the pins during some shocks. Of course, the cross-section of the pins can be slightly increased, but this then reduces the dead angle zones. It is also possible to take a known toothing with hollows having parallel sides, as represented in
To obtain a maximum dead angle α for such a configuration, in the two aforementioned tangential positions, the pins are arranged to leave a relatively small play between the pins and the two teeth defining the outer sides 28 and 29 of two respective hollows facing the two pins, so that the date ring has a relatively small angular play when the pinion is in one or other of the two tangential positions. Thus, with the best adjustment of the dimensions of toothing 5A and of the pins, it would be possible to do without a positioning jumper in these two tangential positions, which is one of the objects of the invention. However, as can be seen in
It will be noted that the pinion is generally arranged to be in one of its two tangential positions in the rest periods when neither the date ring nor the second indicator are driven. These rest positions are preferred since they ensure the best anti-shock protection. It will be noted that the locking torque exerted by the pinion immediately diminishes moving away from said rest positions. Finally, it will be noted that the preferred rest positions are not always those that occur in practice for various reasons; the first arising from the fact that pinion 12A can be initially mounted with an angular position having a certain variation, and the second from the fact that the motor may miss some steps so that the precise angular position of the pinion is not known. Consequently, even when the drive mechanism is inactive in rest periods, the positioning jumper provided in the prior art is required in order to overcome this problem. However, the invention efficiently overcomes these problems by proposing the solution that will be explained below.
Referring to
In
Owing to the profile of the pins according to the invention, by providing a small play in the two tangential positions of the pinion, it is thus possible to obviate the positioning jumper while ensuring proper positioning of the date ring. Other advantages result from this invention. Firstly, for a width L of the hollows of toothing 5A, the pins are more solid than in the case of
Referring to
Next, each pin 46, respectively 56 has a radial dimension R relative to axis of rotation A10 of the rotating wheel set and a tangential dimension T, perpendicular to the radial dimension, the value of this one tangential dimension being substantially equal to two times that of the radial dimension or greater. It will also be noted that dimension L1 is arranged to be greater than radial dimension R and dimension L2 is arranged to be greater than tangential dimension T, otherwise the meshing of the pinion-pin with the toothing of the calendar indicator cannot function since it will quickly lock.
In the variant of
In the variant of
In a similar manner to that explained above with reference to
Number | Date | Country | Kind |
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16151735.4 | Jan 2016 | EP | regional |