Patent Application
20210333758
This application claims priority to European Patent Application No. 20171015.9 filed Apr. 23, 2020, the entire contents of which are incorporated herein by reference.
The invention relates to an escapement mechanism for a timepiece.
The invention also relates to a horological movement comprising such an escapement mechanism.
Finally, the invention relates to a timepiece comprising such a horological movement. The timepiece is for example a watch or a clock.
In the field of horological movements, systems fulfilling the escapement function are known. The escapement is conventionally placed between the energy source of the horological movement and the oscillator of the balance spring type. The purpose of the escapement is to count and maintain the oscillations of the balance spring. Typically, using an escapement of the Swiss pallets type in certain mechanical watches is known. Such an escapement with Swiss pallets comprises an escapement wheel (also referred to as a pallets wheel), pallets provided with entry and exit lifts, and a double plate. The Swiss-pallets escapement transmits the forces from the pallets wheel to the balance through lever effects and sliding inclined planes of the pallets wheel on the pallets. The teeth of the pallets wheel thus fulfil a function of impulse on the pallets lifts. However, such a force transmission principle is also the weak point of this type of escapement. Maintaining the friction conditions on sliding planes in fact involves very tricky lubrication systems that are sensitive to ageing. This constitutes an important factor in the variation of the running and is thus liable to cause running that is unstable in the positions. Furthermore, such an escapement of the Swiss pallets type necessitates having very high amplitudes when new.
In order to remedy these drawbacks, one known solution consists of providing a coaxial escapement system with pallets in the horological mechanism. In addition to the pallets, the system typically comprises a triple coaxial wheel including a first escapement wheel, a second escapement wheel (also referred to as an impulse pinion) and a drive pinion mounted coaxially in this order. The system also comprises an intermediate wheel meshing with the drive pinion; and a balance plate, secured to a balance spring. The balance plate carries a plate peg and a direct impulse pallet stone arranged to cooperate with the first escapement wheel. The pallets include a pallets entry cooperating with the plate peg, an impulse pallet stone arranged to cooperate with the impulse pinion, and support pallet stones arranged to cooperate with the first escapement wheel. The coaxial escapement system with pallets transmits the energy to the balance spring in the clockwise and anticlockwise directions of the oscillations of the balance. An impulse is transmitted in the clockwise direction directly from a tooth of the first escapement wheel to the plate. In the anticlockwise direction is impulse is delivered to the plate via the pallets, or more precisely via the action of a tooth of the impulse pinion on the impulse pallet stone of the pallets, and then of the pallets entry on the plate peg. After the impulses, the first escapement wheel is resting on the support pallet stones and the balance performs its oscillations freely, without interference.
Via its system of tangential transmission of the force, such a coaxial escapement mechanism is not dependent on lubrication for maintaining the operating conditions of the mechanism. This system in fact functions as gears and, for transmission of the force, does not require any lubrication. An important variation factor is consequently eliminated and contributes to a relatively stable running in the movement. Such a coaxial escapement mechanism furthermore allows a transmission of the balance-spring maintenance force that is constant over time, and allows constant maintenance of the amplitude thereof. It is thus no longer necessary, unlike the escapement of the Swiss pallets type, to have very high amplitudes when new. Errors in running in the positions are thus reduced. Finally, this coaxial escape mechanism allows a profitable reduction in the angle of lift of the balance compared with the Swiss pallets escapement. The angle of lift is in fact reduced from 52 degrees for the Swiss pallets escapement to 37 degrees for the coaxial escapement. This ensures less disturbance of the balance at each vibration of the latter, compared with the Swiss pallets escapement. The result is consistency of the qualities of setting of the watch and precision thereof. Such a coaxial escapement mechanism is therefore particularly intended for manufacturing high-precision chronometers.
However, this type of coaxial escapement mechanism is relatively bulky, which is prejudicial to the compactness of the whole. In order to respond to this problem, the patent document EP 1 045 297 A1 proposes a coaxial escapement system with double coaxial wheel. Apart from the pallets, the system described in this document comprises in fact a double coaxial wheel including a first escapement wheel and a second escapement wheel. The system also comprises an intermediate wheel meshing with the second escapement wheel. The pallets include a pallets entry cooperating with the plate peg, an impulse pallet stone arranged to cooperate with the second escapement wheel, and support pallet stones arranged to cooperate with the first escapement wheel. The second escapement wheel fulfils a double function: that of drive pinion meshing with the intermediate wheel and that of escapement wheel cooperating with the impulse pallet stone of the pallets. This makes it possible, by saving on the presence of a component in the coaxial wheel, to reduce the height of the assembly and therefore to improve the compactness thereof. However, one defect with this solution is that the number of teeth on the drive pinion must be identical to the number of teeth on the second escapement wheel. In addition, it is necessary to ensure that the two tooth profiles of the second escapement wheel, the one that meshes with the tooth on the drive pinion, and the one that works with the impulse pallet stone, do not interfere with each other. Optimisation of the two profiles is therefore a constraint. Moreover, a coaxial escapement with triple coaxial wheel necessitates, through its configuration, constraints with regard to the volume of the balance, and therefore with regard to the inertia of the latter. However, limiting the inertia of the balance does not make it possible to obtain optimum quality of isochronism for the horological movement, nor to completely eliminate the variations in running in the movement.
The purpose of the invention is therefore to provide an escapement mechanism for a timepiece that includes a horological movement provided with a balance, making it possible to increase the inertia of the balance while limiting the space requirement and the global volume of the movement, and while keeping the entire latitude of optimisation with regard to the number of teeth and the profile of the drive pinion.
For this purpose, the invention relates to an escapement mechanism of a timepiece, which comprises the features mentioned in independent claim 1.
Particular forms of the escapement mechanism are defined in dependent claims 2 to 5.
By virtue of the particular configuration between the first escapement wheel, the drive pinion and the impulse pinion, or more precisely because these elements are mounted coaxially in this order, the escapement mechanism according to the invention makes it possible to lower the disc of the intermediate wheel (which is typically the seconds wheel for a watch) in the horological movement. This advantageously releases space in the movement, which makes it possible to increase the volume and therefore the inertia of the balance. The quality of the isochronism is consequently improved in the horological movement, and the variations in running reduced, while obtaining a very compact setting for the escapement mechanism.
Advantageously, the impulse pallet stone of the pallets has a height such that said impulse pallet stone extends level with the teeth of the impulse pinion. This allows meshing between the pallets and the impulse pinion.
For this purpose, the invention also concerns a horological movement including the escapement mechanism and which comprises the features mentioned in dependent claim 8.
For this purpose, the invention also concerns a timepiece including the horological movement described above, and which comprises the features mentioned in dependent claim 9.
The aims, advantages and features of the coaxial escapement mechanism for a timepiece according to the invention will appear more clearly in the following description on the basis of at least one non-limitative embodiment illustrated by the drawings, on which:
In the following description, reference is made to a horological movement provided with an escapement mechanism, preferably coaxial, for an oscillator of the balance spring type. The usual components of the horological movement, which are well known to a person skilled in this technical field, are described only in a simplified manner or not described at all. A person skilled in the art will in fact be able to adapt these various components and to make them cooperate for the functioning of the horological movement. In particular, everything that relates to the oscillator of the balance spring type will not be described hereinafter, although such a balance spring can advantageously cooperate with the coaxial escapement mechanism according to the invention.
a, 4b and 5 show a part of a timepiece 1, which comprises a horological movement 2. The timepiece 1 is typically a watch or a clock.
The horological movement 2 includes an oscillator provided with a balance and a balance spring (not shown), an energy source (not shown) and an escapement mechanism 4 placed between the energy source and the oscillator.
The escapement mechanism illustrated in
The triple coaxial wheel 6 includes a first escapement wheel 14, a drive pinion 16 and a second escapement wheel 18 called an impulse pinion. As can be seen in
The intermediate wheel 8 meshes with the drive pinion 16, and transmits the motive force to the latter. The intermediate wheel 8 may be the last wheel in the finishing train driven by the barrel of the horological movement 2, typically the seconds wheel.
The balance plate (which is not shown in the figures) is secured to the oscillator formed by the balance and the balance spring. The balance plate carries a plate peg and a direct impulse pallet stone (neither being shown). Preferably, the plate peg is made from ruby. The direct impulse pallet stone is arranged to cooperate with the teeth of the first escapement wheel 14. Preferably, the direct impulse pallet stone consists of a lift made from ruby.
As illustrated in
The first and second support pallet stones 28a, 28b extend alongside the first escapement wheel 14, and are each arranged to cooperate with the teeth on the first escapement wheel 14. Preferably, the impulse pallet stone 26 and/or the first and second support pallet stones 28a, 28b each consist of a ruby lift. More precisely, as illustrated in
The invention also relates to a horological movement 2 comprising an escapement mechanism 4 as described previously and a balance spring, the balance plate of the coaxial escapement mechanism 4 being secured to the balance spring.
The invention also relates to a timepiece 1 comprising such a horological movement 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20171015.9 | Apr 2020 | EP | regional |
